A method for controlling a timing of a camshaft in an internal combustion engine comprising a variable cam timing phaser arrangement, comprising:
- a rotor having at least one rotor vane, the rotor arranged to be connected to a camshaft;
- a stator co-axially surrounding the rotor, having at least one stator recess for receiving the at least one rotor vane and allowing rotational movement of the rotor with respect to the stator, the stator having an outer circumference arranged for accepting drive force,
- wherein the at least one rotor vane divides the at least one stator recess into a first phasing chamber and a second phasing chamber, the first phasing chamber and the second phasing chamber being arranged to receive hydraulic fluid under pressure, wherein an introduction of the hydraulic fluid into the first phasing chamber causes the rotor to move in a first rotational direction relative to the stator and an introduction of the hydraulic fluid into the second phasing chamber causes the rotor to move in a second rotational direction relative to the stator, the second rotational direction being opposite the first rotational direction;
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- a control assembly for regulating hydraulic fluid flow from the first phasing chamber to the second phasing chamber or vice-versa, wherein the control assembly comprises:
- a control valve comprising:
- a cylindrical valve body comprising an outer wall, a first end and a second end, wherein the first end has a recess configured for receiving a rotational shuttle element and allowing rotational movement of the rotational shuttle element with respect to the valve body,
- wherein the rotational shuttle element coaxially located within the recess of the valve body,
- wherein the recess and rotational shuttle element together define a signalling chamber and a flow chamber,
- wherein the recess comprises a vane dividing the signalling chamber into a first signalling chamber on a first side of the vane and a second signalling chamber on a second side of the vane,
- wherein the rotational shuttle element is arranged to rotate between at least three positions in response to fluid pressure variations in the first and second signalling chambers;
- a first position fully rotated in a first rotational direction so that a size of the first signalling chamber relative to the second signalling chamber is maximized, a second position fully rotated in a second rotational direction so that a size of the second signalling chamber relative to the first signalling chamber is maximized, and an intermediate position wherein a size of the first and second signalling chambers are substantially equal,
- wherein an actuable blocking pin is configured in the control valve and the rotational shuttle element is configured with two corresponding holes for receiving the actuable blocking pin, a first hole arranged to block the rotational shuttle element from moving to the first position upon receiving the actuable blocking pin and a second hole arranged to block the rotational shuttle element from moving to the second position upon receiving the actuable blocking pin,
- wherein the recess comprises a first fluid groove arranged in fluid communication with the first signalling chamber at one end, and arranged to be in fluid communication with the flow chamber at an other end whenever the rotational shuttle element is in the second or intermediate positions, and arranged to be prevented from fluid communication with the flow chamber whenever the rotational shuttle element is in the first position,
- wherein the recess comprises a second fluid groove arranged in fluid communication with the second signalling chamber at one end, and arranged to be in fluid communication with the flow chamber at an other end whenever the rotational shuttle element is in the first or intermediate positions, and arranged to be prevented from fluid communication with the flow chamber whenever the rotational shuttle element is in the second position,
- wherein the valve body has a first trough running parallel to the first end and second end around a circumference of the outer wall at a position between the first end and the second end of the valve body, and a second trough running parallel to the first trough around the circumference of the outer wall at a position between the first trough and the second end of the valve body,
- wherein a first channel through the valve body connects the first fluid groove to the first trough,
- wherein a second channel through the valve body connects the second fluid groove to the second trough, and
- wherein said control valve is centrally mounted in the rotor and/or camshaft, wherein the first trough of the control valve is arranged in fluid communication with the first phasing chamber and the second trough of the control valve is arranged in fluid communication with the second phasing chamber;
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- an actuating device for actuating the actuable blocking pin,
- the method comprising:
- i. providing the variable cam timing phaser arrangement having the actuable blocking pin in a disengaged position, thereby preventing fluid communication between the first phasing chamber and the second phasing chamber;
- ii. deploying the actuable blocking pin at a time to coincide with the rotational shuttle element being in the first position, thereby engaging the actuable blocking pin to block the second position of the rotational shuttle element;
- or deploying the actuable blocking pin at a time to coincide with the rotational shuttle element being in the second position thereby engaging the actuable blocking pin to block the first position;
- iii. maintaining the deployment of the actuable blocking pin thereby allowing fluid to periodically flow in a single direction between the first phasing chamber and the second phasing chamber due to camshaft torque, and preventing fluid flow in an opposite direction, thus rotating the rotor relative to the stator in a chosen direction;
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- iv. once a desired rotation of the rotor relative to the stator is obtained, disengaging the actuable blocking pin, thereby preventing further fluid communication between the first phasing chamber and the second phasing chamber.