Zero pressure unlocking system for a phaser

Using existing phaser control valve and a solenoid to create a pumping chamber which provides enough oil pressure to disengage a locking pin at all conditions.

BACKGROUND

The invention pertains to the field of variable cam timing phasers. More particularly, the invention pertains to a zero pressure unlocking system for a variable cam timing phaser.

DESCRIPTION OF RELATED ART

Internal combustion engines have employed various mechanisms to vary the relative timing between the camshaft and the crankshaft for improved engine performance or reduced emissions. The majority of these variable camshaft timing (VCT) mechanisms use one or more “vane phasers” on the engine camshaft, (or camshafts, in a multiple-camshaft engine). Vane phasers have a rotor with one or more vanes, mounted to the end of the camshaft, surrounded by a housing assembly with the vane chambers into which the vanes fit. It is possible to have the vanes mounted to the housing assembly, and the chambers in the rotor assembly, as well. The housing's outer circumference forms the sprocket, pulley or gear accepting drive force through a chain, belt, or gears, usually from the crankshaft, or possibly from another camshaft in a multiple-cam engine.

In cam torque actuated (CTA) variable camshaft timing (VCT) systems, cam torques from the engine are used to move the one or more vanes and fluid is recirculated between the working chambers without exhausting the fluid to sump. A lock pin for locking and unlocking the movement between the housing assembly and the rotor assembly can be controlled by a control valve. During engine shutdown, the control valve is moved to a position such that fluid is maintained within the chambers via recirculation, and any fluid feeding to the lock pin is vented from the circuit through the control valve.

During engine cranking or shortly thereafter, there may not be sufficient oil pressure to release the lock pin because the engine's oil passages, including those leading to the phaser may have drained. Time is required for the oil pump, which is driven by the rotation of the engine, to re-till and build pressure in the engine's oil circuit.

Apart from the camshaft torque actuated (CTA) variable camshaft timing (VCT) systems, the majority of hydraulic VCT systems operate under two principles, oil pressure actuation (OPA) or torsional assist (TA). In the oil pressure actuated. VCT systems, an oil control valve (OCV) directs engine oil pressure to one working chamber in the VCT phaser while simultaneously venting the opposing working chamber defined by the housing assembly, the rotor assembly, and the vane. This creates a pressure differential across one or more of the vanes to hydraulically push the VCT phaser in one direction or the other. Neutralizing or moving the oil control valve to a null position puts equal pressure on opposite sides of the vane and holds the phaser in any intermediate position. If the phaser is moving in a direction such that valves will open or close sooner, the phaser is said to be advancing and if the phaser is moving in a direction such that valves will open or close later, the phaser is said to be retarding.

The torsional assist (TA) systems operate under a similar principle with the exception that they have one or more check valves to prevent the VCT phaser from moving in a direction opposite than being commanded, should it incur an opposing force such as a torque impulse caused by cam operation.

The problem with OPA or TA systems in executing the operations discussed above is that the oil control valve defaults to a position that exhausts all the oil from either the advance or retard working chambers and fills the opposing chamber. In this mode, the phaser defaults to moving in one direction to an extreme stop where the lock pin engages. A bias spring may be used to preferentially guide the phaser to a desired position. The OPA or TA systems are unable to direct the VCT phaser to any other position during the engine start cycle when the engine is not developing any oil pressure and cannot unlock the lock pin.

Some vehicles can use a “stop-start mode” which automatically stops and automatically restarts the internal combustion engine to reduce the amount of time the engine spends idling when the vehicle is stopped, for example at a stop light or while sitting in traffic. This mode reduces emissions and increases fuel efficiency. This stopping of the engine is different than a “key-off” position or manual stop via deactivation of the ignition switch in which the user of the vehicle shuts the engine down or puts the car in park and shuts the vehicle off. In “stop-start mode,” the engine stops as the vehicle is stopped, then automatically restarts in a manner that is nearly undetectable to the user of the vehicle. During “stop-start,” it has been determined that the full retard phaser position reduces the energy required to start the engine and reduces the engine Noise Vibration and Harshness (NVH) during a hot engine restart. Other strategies may be developed that require a different lock position than described.

The problem with an intake camshaft phaser design that has an extended range of authority and the ability to lock at the full retard stop is that if the engine is shut down with the intake camshaft phaser locked at or near the retard stop and the engine is allowed to cool down, then the engine may not be able to accomplish a successful cold start with the phaser locked near the retard stop. During engine cranking there may not be sufficient engine oil pressure to release the lock pin.

SUMMARY OF THE INVENTION

Using an existing phaser control valve and a solenoid to create a pumping chamber which provides enough oil pressure to disengage a locking pin at all conditions.

DETAILED DESCRIPTION

FIGS. 1-10Bshow the operating modes the VCT phaser depending on the spool valve position. The positions shown in the figures define the direction in which the VCT phaser is moving. It is understood that the phase control valve has an infinite number of intermediate positions, so that the control valve not only controls the direction in which the VCT phaser moves but, depending on the discrete spool position, controls the rate at which the VCT phaser changes positions. Therefore, it is understood that the phase control valve can also operate in infinite intermediate positions, and is not limited to the positions shown in the Figures.

Referring toFIG. 5, the housing assembly100of the phaser has an outer circumference101for accepting a drive force. The housing assembly100of the phaser includes an inner face plate100aand an outer face plate100b. The rotor assembly105is connected to the camshaft (not shown) and is coaxially located within the housing assembly100. The rotor assembly105has at least one vane104separating a chamber117formed between the housing assembly100and the rotor assembly105into working chambers such as an advance chamber102and a retard chamber103. The vane104is capable of rotation to shift the relative angular position of the housing assembly100and the rotor assembly105.

The inner face plate100aof the housing, assembly100may include an end plate pocket155connected to a vent128leading to sump. The rotor assembly105has a corresponding rotor pocket157, which when aligned with the end plate pocket155, allows the venting of a control valve109, preventing lock up. The vent128is shown inFIGS. 9A, 9B, 10A and 10Bas an orifice, however, the vent128can be a worm trail or other restricted orifice.

A lock pin125is slidably housed in a bore122in the rotor assembly105and has an end portion125athat is biased towards and fits into a recess127in the inner plate100bof the housing assembly100by a spring124, for example as shown inFIG. 6. Alternatively, the lock pin125may be housed in the housing assembly100and be spring124biased towards a recess127in the rotor assembly105. The outer end plate100bmay include a vent129, for example a worm trail or other restricted orifice which allows the lock pin125to vent and prevents hydraulic lock of the lock pin125.

The lock pin125has a first, unlocked position in which the end portion125aof the lock pin125does not engage the recess127and a second, locked position in which the end portion125aof the lock pin125engages the recess127, locking the relative movement of the rotor assembly105relative to the housing assembly100. The recess127is in fluid communication with the phase control valve109via a pilot valve130. The pressurization of the lock pin125is controlled by the switching/movement of the phase control valve109and the pilot valve130.

Referring toFIGS. 1-4 and 5-8, a phase control valve109, preferably a spool valve, includes a spool111with at least one cylindrical land111ais slidably received in a sleeve116within a bore in the rotor assembly105and pilots in the camshaft (not shown). The phase control valve109may be located remotely from the phaser, within a bore in the rotor assembly105which pilots in the camshaft, or in a center bolt of the phaser. One end of the spool contacts spring115and the opposite end of the spool contacts a pulse width modulated variable force solenoid (VFS)107. The solenoid107may also be linearly controlled by varying current or voltage or other methods as applicable. Additionally, the opposite end of the spool111may contact and be influenced by a motor, or other actuators. Between the end of the spool111which contacts the spring115and the inner diameter116aof the sleeve116is formed a pump chamber150. The pump chamber150stores supply oil and the pressure of the oil in this chamber150is pumped up or increased in pressure by the movement of the pilot valve130and the spool111.

The position of the phase control valve109is controlled by an engine control unit (ECU)106which controls the duty cycle of the variable force solenoid107. The ECU106preferably includes a central processing unit (CPU) which runs various computational processes for controlling the engine, memory, and input and output; ports used to exchange data with external devices and sensors.

The position of the spool111is influenced by spring115and the solenoid107controlled by the ECU106. Further detail regarding control of the phaser is discussed in detail below. The position of the spool111controls the motion (e.g. to move towards the advance position, holding position, or the retard position) of the phaser as well as what fluid is used to lock or unlock the lock pin.

A pilot valve130, preferably a spool valve, includes a spool131with cylindrical lands131a,131b,131c,131dslidably received in a sleeve132within a bore in the rotor assembly105. A through passage134is present between lands131aand131b. The pilot valve130may be located remotely from the phaser, or within a bore in the rotor assembly105which pilots in the camshaft (not shown). One end of the spool131contacts spring133and the opposite end of the spool131is in fluid communication with supply S through line118. The supply line118may contain an inlet check valve119allowing for the flow of fluid into supply line118and preventing the flow of fluid out of supply line118. The pilot valve130is in fluid communication with the phase control valve109through lines141and142as well as with the recess127of the housing assembly100through line140. The pilot valve130additionally is in fluid communication with a supply line144. Supply line144is preferably in fluid communication with supply S. Supply144could be in fluid communication directly with line118or in communication selectively through the spool valve109. Alternatively, supply144could be controlled by the advance chamber102or the retard chamber103. A vent port145is also present within the sleeve132.

The position of the spool131is influenced by spring115and the variable force solenoid107. The position of the spool111controls what fluid is used to unlock or lock the lock pin125and whether supply oil is provided to a pump chamber150present between the spool111and the sleeve116. The pilot valve130has two positions. In a first position of the pilot valve130, spool land131dblocks the flow of supply line144and in a second position in which supply line144is open to supply S and line141is blocked by spool land131a.

A spool controlled lock pin circuit is comprised of a supply line144in fluid communication with the pilot valve130, the pilot valve130, line140in fluid communication with the recess127of the housing assembly100and the lock pin125. When the engine is oft the lock pin125is in the locked position.

A pump chamber circuit is comprised of a supply line118in fluid communication with the pilot valve130, the pilot valve130, line141in fluid communication with the pilot valve130and the pump chamber150, line142in fluid communication with pump chamber150and the pilot valve130. The pump chamber150fills by decaying oil pressure and fluid venting from the lock pin125until either the pressure is no longer sufficient to force fluid into the pump chamber150or the pump chamber150is full. Therefore, the pump chamber150is filled as engine oil pressure drops.

The pump chamber circuit is filled during engine off. All fluid present in the phaser itself, with the exceptions of the advance and retard chambers of a CTA phaser, drain back into the pump chamber150. Residual pressure from the oil system fills the pump chamber circuit until either the pressure is no longer sufficient to force fluid into the pump chamber150or the pump chamber150is full.

Typically, during engine cranking, after an engine shutdown, there is no oil pressure present to unlock the lock pin125and no phasing can begin until after the lock pin125has been pressure biased to an unlocked position. In the present invention, during engine cranking and/or start-up, after engine shutdown, the lock pin125is moved to an unlocked position when the pump chamber circuit is in fluid communication with the spool controlled lock pin circuit. In other words, when fluid moves from the pump chamber150, through line142, between spool lands131cand131dof the pilot valve130to the recess127through line140, the lock pin125is moved against the force of the spring124, such that the end125aof the lock pin125no longer engages the recess127.

Once the end125aof the lock pin125has disengaged from the recess127, the rotor assembly105can be moved relative to the housing assembly100and the phaser can be phased, for example to a retard position, an intermediate position, an advance position and in some phasers a detent position. Fluid is supplied to the recess127of the lock pin125to maintain the lock pin125in the unlocked position from supply line144when supply pressure is present and the phaser is phasing. At this point, no fluid is being maintained in the pump chamber150. Should the pump circuit not be used to unlock the phaser the spool111can perform its normal function of unlocking the phaser after oil pressure reaches an operating level because the pilot valve130will have moved up to vent the pump chamber150and connect passage144to passage140.

Based on the duty cycle of the pulse width modulated variable force solenoid107, the spool111moves to a corresponding position along its stroke. When the duty cycle of the variable force solenoid107is approximately 40%, 60% or 80%, the spool111will be moved to positions that correspond with the retard mode, the null mode, and the advance mode, respectively and the pilot valve130will be pressurized and move to the second position, and the lock pin125will be pressurized and released.

Referring toFIG. 1, when the duty cycle of the variable force solenoid107is 0%, the spool111of the phase control valve109is moved to a position by the spring115, such that the pump chamber150receives any fluid present in the supply line118through the pilot valve130between lands131aand131bvia line141. Since the pressure of the fluid from supply S is below a threshold, due to engine shutdown, spring133biases the spool131of the pilot valve130to a position such that the supply144is blocked from supplying fluid to the lock pin125via line140. Any fluid present in line140can drain to the pump chamber150via the pilot valve130and line142. Due to the absence of fluid pressure in line140, the lock pin125is biased by spring124to engage recess127and lock the relative movement of rotor assembly105relative to the housing assembly100. The filling of the pump chamber150is essentially priming the phase control valve109to act as a pump. The volume of fluid, which aggregates in the fluid chamber150, is preferably a volume in which would be required to unlock the lock pin125, with provisions for leakage. The rotor pocket157is not aligned with the end plate pocket155and vent128is blocked.

FIG. 2shows a schematic of a variable cam timing phaser of an embodiment during operation of the spool pump at engine cranking. During engine cranking there is very little to no pressure present due to the lack of supply oil pressure. Since no supply pressure is present both from supply line118and from line144, there is no pressure present to unlock the lock pin125and thus phase the phaser soon after engine or during engine cranking.

During engine cranking, the spool111of the phase control valve109is moved to a position by the VFS107, against the force of the spring115, such that the spool111blocks the flow of fluid to the pump chamber150via line141. During engine cranking, in order to pump the fluid from the pump chamber150, the duty cycle starts at 0% and moves to 100%, to force the phase control valve109to expel the fluid present in the pump chamber150and exhaust from the pump chamber150into line142, since line141is blocked. The movement of the spool by the VFS107against the force of the spring115creates pressure in the pump chamber150, pumping or forcing the fluid into line142at a high pressure. From line142, fluid flows between lands131cand131dof the pilot valve130to line140in fluid communication with the recess127in the housing assembly100, biasing the lock pin125against the spring124toward an unlocked position. The rotor pocket157is not aligned with the end plate pocket155and vent128is blocked.

FIG. 3shows the phaser during engine cranking, but after the lock pin125has been moved to an unlocked position. It should be noted that the duty cycle is moved to whatever cycle is necessary for a target phasing of the variable cam timing phaser. After the lock pin125has been unlocked and no longer engages the recess127of the housing assembly100, the rotor assembly105is free to rotate. Fluid exiting the pump chamber150exhausts to line143in communication with the vent128, as the rotor pocket157is aligned with the end plate pocket155, allowing the spool111to move and prevent lockup and allow the phaser to phase. Supply144is blocked from supplying fluid to the lock pin125by land131dof the pilot valve130and so that fluid is not allowed to travel back to supply144. It should be noted that supply144is blocked, as the fluid pressure in supply line118is not adequate to bias the pilot valve130to a second position against spring133(e.g. the oil pressure has not reached a threshold).

FIG. 4shows a schematic of a variable cam timing phaser of an embodiment during normal operation once the engine is running and oil pressure has reached a threshold. Once the oil pressure in line118reaches a pressure in which it can bias the spool131against the spring133, the spool131is moved to a second position in which spool land131ablocks line141. Any fluid present in the pump chamber150of the phase control valve109is incidental and vents through vent145of the pilot valve130. Fluid is also supplied from supply144, through the pilot valve130between spool lands131cand131dto line140, maintaining the lock pin125in an unlocked position and biasing the lock pin125against the spring124. It should be noted that the lock pin125may remain in an unlocked state without fluid from supply144until the lock pin125is aligned with the recess127. Normal engine operation may take place and the lock pin125may be moved to an unlocked position, and a locked position per engine operation conditions. Furthermore, the rotor pocket157is aligned with the end plate pocket155and vent128is open.

FIG. 11is a graph of an example of pressure versus position. During normal engine phaser operation, for example as shown inFIG. 4, the oil pressure at the lock pin125may be approximately 5 bar. As then engine shuts down, as shown inFIG. 1, engine oil pressure at the lock pin125begins to decay, or drops, for example to approximately 1.25 bar. The lock pin125is locked or is engaged with the recess127and cannot be disengaged or unlocked below approximately 0.8 bar (i.e. the spring124has a force that is greater than the force of the pressure on the lock pin125). The pilot valve130moves to enable the pump chamber150to fill at approximately 0.4 bar. When the oil pressure at the lock pin125is at zero bar, no additional oil is supplied to the pump chamber150.

During engine cranking on restart, the spool111is moved by the VFS107, such that the volume of oil in the pump chamber150is pressurized to greater than 0.8 bar and expelled to activate and pressurize the spool controlled lock pin circuit, as shown inFIG. 2. It should be rioted that the pressures given inFIG. 11are for example purposes and may vary during engine operation.

While the embodiments described above contain a single pilot valve130of a length, the pilot valve130can be split into at least two pilot valves of a length that is less than the length of the single pilot valve130, reducing the axial package space required for the phaser.

FIGS. 12-18show the operating modes the VCT phaser based on different engine operating conditions. The positions shown in the figures define the direction in which the VCT phaser is moving. It is understood that the phase control valve has an infinite number of intermediate positions, so that the control valve not only controls the direction in which the VCT phaser moves but, depending on the discrete spool position, controls the rate at which the VCT phaser changes positions. Therefore, it is understood that the phase control valve can also operate in infinite intermediate positions, and is not limited to the positions shown in the Figures.

Referring toFIGS. 12-18, a phase control valve109, preferably a spool valve, includes a spool111with at least one cylindrical land111ais slidably received in a sleeve116within a bore in the rotor assembly105and pilots in the camshaft (not shown). The phase control valve109may be located remotely from the phaser, within a bore in the rotor assembly105which pilots in the camshaft, or in a center bolt of the phaser. One end of the spool contacts spring115and the opposite end of the spool contacts a pulse width modulated variable force solenoid (VFS)107. The solenoid107may also be linearly controlled by varying current or voltage or other methods as applicable. Additionally, the opposite end of the spool111may contact and be influenced by a motor, or other actuators. Between the end of the spool111which contacts the spring115and the inner diameter116aof the sleeve116is formed a pump chamber150. The pump chamber150stores supply oil and the pressure of the oil in this chamber150is increased in pressure by the movement of the spool111.

The position of the phase control valve109is controlled by an engine control unit (ECU)106which controls the duty cycle of the variable force solenoid107. The ECU106preferably includes a central processing unit (CPU) which runs various computational processes for controlling the engine, memory, and input and output ports used to exchange data with external devices and sensors.

The position of the spool111is influenced by spring115and the solenoid107controlled by the ECU106. Further detail regarding control of the phaser is discussed in detail below. The position of the spool111controls the motion (e.g. to move towards the advance position, holding position, or the retard position) of the phaser.

A first pilot valve230, preferably a spool valve, includes a spool231with cylindrical lands231a,231bslidably received in a sleeve232within a bore in the rotor assembly105. The first pilot valve230may be located remotely from the phaser, or within a bore in the rotor assembly105, which pilots in the camshaft (not shown). One end of the spool231contacts spring233and the opposite end of the spool231is in fluid communication with supply S through line118. The supply line11may contain an inlet check valve119allowing for the flow of fluid into supply line118and preventing the flow of fluid out of supply line118. The first pilot valve230is in fluid communication with the phase control valve109through lines236and142as well as with the recess127of the housing assembly100through line140. The first pilot valve230additionally is in fluid communication with a supply line234. Supply line234is preferably in fluid communication with supply S. Supply234could also be in fluid communication directly with line118or in communication selectively through the spool valve109, such as a spool controlled lock pin circuit described in further detail below. Alternatively, supply234could be controlled by the advance chamber102or the retard chamber103. A vent port235is also present within the sleeve232of the first pilot valve230. The position of the first pilot valve230determines which circuit is connected to the lock pin: spool controlled lock pin circuit or the pump chamber circuit. In other words, the first pilot valve230determines which of the two lock pin control circuits is connected to the lock pin.

A second pilot valve240, preferably a spool valve, includes a spool241with cylindrical lands241a,241bslidably received in a sleeve242within a bore in the rotor assembly105. The second pilot valve240may be located remotely from the phaser, or within a bore in the rotor assembly105, which pilots in the camshaft (not shown). One end of the spool241contacts spring243and the opposite end of the spool241is in fluid communication with supply S through line118. The second pilot valve240is in fluid communication with the phase control valve109through lines246and142. The second pilot valve240additionally is in fluid communication with a vent244. Supply line118is preferably in fluid communication with line245of the second pilot valve240and directly with line118. A vent port247is also present within the sleeve242of the second pilot valve240. The second pilot valve is not in direct fluid communication with the lock pin125.

The position of the spool111is influenced by spring115and the variable force solenoid107. The position of the spool111controls the spool controlled lock pin circuit and whether supply oil is provided to a pump chamber150present between the spool and the sleeve116with the second pilot valve240. The first pilot valve230and the second pilot valve240each have two positions.

In a first position of the first pilot valve230, spool land231bblocks the flow of fluid from supply line234and in a second position, supply line234is open to receiving fluid from a supply, preferably from the spool controlled lock pin circuit and line236is blocked by spool land231a. In the first position of the second pilot valve240, spool land241bblocks vent244. In a second position of the second pilot valve240, vent244is open and spool land241ablocks supply line245.

A spool controlled lock pin circuit is comprised of a supply line234in fluid communication with the first pilot valve230, the first pilot valve230, line140in fluid communication with the recess127of the housing assembly100and the lock pin125. When the engine is off the lock pin125is in the locked position.

A pump chamber circuit is comprised of a supply line118in fluid communication with the first pilot valve230and the second pilot valve240, the first pilot valve230and the second pilot valve240, line246in fluid communication with, line142and the second pilot valve240, line236in fluid communication with line142and the first pilot valve230, the pump chamber150, and line142in fluid communication with pump chamber150and the first and second pilot valves230,240. The pump chamber150fills by decaying oil pressure and fluid venting from the lock pin125and the first and second pilot valves230,240until either the pressure is no longer sufficient to force fluid into the pump chamber150or the pump chamber150is full. Therefore, the pump chamber150is filled as engine oil pressure drops.

The pump chamber circuit is filled during engine off. Some of the fluid present in the phaser itself, with the exceptions of the advance and retard chambers of a CTA phaser, may drain back into the pump chamber150. The primary method for filling of the pump chamber is the residual oil pressure Residual pressure from the oil system fills the pump chamber circuit until either the pressure is no longer sufficient to force fluid into the pump chamber150or the pump chamber150is full.

Typically, during engine cranking, after an engine shutdown, there is no oil pressure present to unlock the lock pin125and no phasing can begin until after the lock pin125has been pressure biased to an unlocked position. In the present invention, during engine cranking and/or start-up, after engine shutdown, the lock pin125is moved to an unlocked position when the pump chamber is in fluid communication with the lock pin125and the spool111is stroked. In other words, when fluid moves from the pump chamber150, through line142, between spool lands231aand231bof the first pilot valve230to the recess127through line140, the lock pin125is moved against the force of the spring124, such that the end125aof the lock pin125no longer engages the recess127.

Once the end125aof the lock pin125has disengaged from the recess127, the rotor assembly105can be moved relative to the housing assembly100and the phaser can be phased, for example to a retard position, an intermediate position, an advance position and in some phasers, a detent position. Fluid is supplied to the recess127of the lock pin125to maintain the lock pin125in the unlocked position from supply line234of the first pilot valve230when supply pressure is present and the phaser is phasing. At this point, no fluid is being, maintained in the pump chamber150. Should the pump chamber circuit not be used to unlock the phaser the spool111can perform its normal function of unlocking the phaser after oil pressure reaches an operating level because the first pilot valve230will have moved up to vent the pump chamber150and connect passage234to passage140. The second pilot valve240controls when supply oil S is connected to the pump chamber150to fill and when the pump chamber150is vented to allow the spool valve109to move freely.

Based on the duty cycle of the pulse width modulated variable force solenoid107, the spool111moves to a corresponding position along its stroke. When the duty cycle of the variable force solenoid107is approximately 40%, 60% or 80%, the spool111will be moved to positions that correspond with the retard mode, the null mode, and the advance mode, respectively. The first and second pilot valves230,240are pressurized and move to the second position when supply pressure is adequate, and the lock pin125will be pressurized and released.

Referring toFIG. 12, when the duty cycle of the variable force solenoid107is 0%, the spool111of the phase control valve109is moved to a position by the spring115, such that the pump chamber150receives any fluid present in the supply line118by passing through the second pilot valve240between lands241aand241bvia line245to line246and the lock pin125can be pressurized and released via spool controlled lock pin circuit. From line246, fluid flows to line142and to the pump chamber150. Since the pressure of the fluid from supply S is below a threshold, due to engine shutdown, spring233biases the spool231of the first pilot valve230to a position such that the supply234is blocked from supplying fluid to the lock pin125via line140. At the same time, due to the passage of fluid between lands241aand241bof the second pilot valve240and the spring force of spring243, vent244is additionally blocked. Any fluid present in line140can drain to the pump chamber150via the first pilot valve130by passing through the first pilot valve230to line236and line142. Due to the absence of fluid pressure in line140, the lock pin125is biased by spring124to engage recess127and lock the relative movement of rotor assembly105relative to the housing assembly100. The filling of the pump chamber150is essentially priming the phase control valve109to act as a pump. The volume of fluid, which aggregates in the fluid chamber150, is preferably a volume in which would be required to unlock the lock pin125, with provisions for leakage. The rotor pocket157is not aligned with the end plate pocket155and vent128is blocked.

FIG. 13shows a schematic of a variable cam timing phaser of another embodiment during operation of the spool pump at engine cranking. During engine cranking there is very little to no pressure present due to the lack of supply oil pressure. Since no supply pressure is present both from supply line118and from line234, there is no pressure present to unlock the lock pin125and thus phase the phaser soon after engine or during engine cranking.

During engine cranking, the spool111of the phase control valve109is moved to a position, by the VFS107, against the force of the spring115. During engine cranking, in order to pump the fluid from the pump chamber150, the duty cycle starts at 0% and moves to 100%, to force the phase control valve109to expel the fluid present in the pump chamber150and exhaust from the pump chamber150into line142. The movement of the spool by the VFS107against the three of the spring115creates pressure in the pump chamber150, pumping or forcing the fluid into line142at a high pressure. From line142, fluid flows between lands231aand231bof the first pilot valve230to line140in fluid communication with the recess127in the housing assembly100, biasing the lock pin125against the spring124toward an unlocked position. The rotor pocket157is not aligned with the end plate pocket155and vent128is blocked.

FIG. 14shows the phaser during engine cranking, but after the lock pin125has been moved to an unlocked position. It should be noted that the duty cycle is moved to whatever cycle is necessary for a target phasing of the variable cam timing phaser. After the lock pin125has been unlocked and no longer engages the recess127of the housing assembly100, the rotor assembly105is free to rotate. Fluid exiting the pump chamber150exhausts to line143in communication with the vent128, as the rotor pocket157is aligned with the end plate pocket155, allowing the spool111to move and prevent lockup and allow the phaser to phase. Supply234is blocked from supplying fluid to the lock pin125by land231bof the first pilot valve230and so that fluid is not allowed to travel back to supply234. It should be noted that supply234is blocked, as the fluid pressure in supply line118is not adequate to bias the first pilot valve230(nor the second pilot valve240) to a second position against spring233,243(e.g. the oil pressure has not reached a threshold).

FIG. 15shows a schematic of a variable cam timing phaser of an embodiment during normal operation once the engine is running and oil pressure has reached a threshold. Once the oil pressure in line118reaches a pressure in which it can bias the spools231,241of the first and second pilot valves230,240against the spring233,243the spools231,241are moved to a second position in which spool land231ablocks line236and spool land241ablocks line245. Any fluid present in the pump chamber150of the phase control valve109is incidental and vents through vent244of the second pilot valve240. Fluid is also supplied from supply234, through the first pilot valve230between spool lands231aand231bto line140, maintaining the lock pin125in an unlocked position and biasing the lock pin125against the spring124. It should be noted that the lock pin125may remain in an unlocked state without fluid from supply234until the lock pin125is aligned with the recess127. Normal engine operation may take place and the lock pin125may be moved to an unlocked position and a locked position per engine operation conditions. Furthermore, the rotor pocket157is aligned with the end plate pocket155and vent128is open.