Patent Grant
8820280
1. Field of the Invention
The invention pertains to the field of variable camshaft timing mechanisms. More particularly, the invention pertains to a hydraulic variable camshaft timing mechanism with a default mode.
2. 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). As shown in the figures, vane phasers have a rotor 105 with one or more vanes 104, mounted to the end of the camshaft 126, surrounded by a housing assembly 100 with the vane chambers into which the vanes fit. It is possible to have the vanes 104 mounted to the housing assembly 100, and the chambers in the rotor assembly 105, as well. The housing's outer circumference 101 forms the sprocket, pulley or gear accepting drive force through a chain, belt, or gears, usually from the crankshaft, or possible from another camshaft in a multiple-cam engine.
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, the rotor, 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 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 operates under a similar principle with the exception that it has 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 torque.
The problem with OPA or TA systems 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. 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. This limits the phaser to being able to move in one direction only in the default mode. In the past this was acceptable because at engine shut down and during engine start the VCT phaser would be commanded to lock at one of the extreme travel limits (either full advance or full retard). However, recent calibration work has demonstrated that there is considerable benefit to start the engine with the VCT system in some intermediate position and not at the extreme stops.
In addition with large range of angular motion on a VCT phaser it is necessary to start in the mid travel position because the extreme stops may be positions where the engine will not start or be damaged during an engine start. It is equally desirable that if the engine is shut down and the phaser is not in the optimum mid start position that the phaser is able to move in either direction during engine cranking to get back to the optimum start position somewhere in mid travel. Current OPA and TA VCT systems are not capable of such recovery because by default they exhaust the oil from one of the working chambers (either advance or retard) and therefore render that chamber a non working chamber at shut down, such that the VCT phaser can only move in one direction.
A variable cam timing phaser for an internal combustion engine including a housing assembly, a rotor, and a control valve. The housing assembly has an outer circumference for accepting drive force and the rotor assembly is coaxially located within the housing for connection to a camshaft. The rotor has a plurality of vanes, with one vane separating a chamber formed between the housing and the rotor into an advance chamber and a retard chamber. The control valve directs fluid from a fluid input to and from the advance chamber and the retard chamber through an advance line, a retard line, a common line, and at least one exhaust line. The control valve is movable between a default mode and an oil pressure actuated mode. The oil pressure actuated mode at least includes the control valve being movable to an advance mode in which fluid is routed from the fluid input to the advance chamber and fluid is also routed from the retard chamber to at least one exhaust line, a retard mode in which fluid is routed from the fluid input to the retard chamber and fluid is also routed from the advance chamber to at least one exhaust line, and a holding position in which fluid is routed to both of the chambers. In the default mode, the control valve blocks the at least one exhaust line, retaining fluid within the advance chamber and retard chamber.
The present invention overcomes the limitations of the torsion assist (TA) and oil pressure actuated (OPA) variable camshaft timing (VCT) systems such that as desired, TA or OPA VCT phasers can have one or more working chambers operate in a cam torque actuated (CTA) operating mode. The invention utilizes the control valve in a default mode and a hydraulic default circuit to direct the VCT phaser in either direction, advance or retard, to reach the mid lock position and, if so desired, to engage a locking pin at that mid lock position. The following description and embodiments are described in terms of a torsion assisted (TA) phaser, which has one or more check valves in oil supply lines, but it will be understood that they are also applicable to an oil pressure actuated phaser.
In the present invention, an offset or remote piloted valve is added to a hydraulic circuit of a torsion assist or oil pressure actuated phaser to manage the hydraulic default switching function.
The piloted valve may be controlled with the same hydraulic circuit that engages or releases the lock pin. This shortens the VCT control valve back to two hydraulic circuits (versus three as discussed in the background section), a VCT control circuit and a combined lock pin/hydraulic default control circuit. Movement of the piloted valve to the first position is actively controlled by the remote on/off valve or the control valve of the phaser.
One of the advantages to using the remote piloted valve is that it can have a longer stroke than the control valve, since it is not limited by a solenoid. Therefore, the piloted valve can open up a larger flow passage for the hydraulic default mode and improve actuation rate in the default mode. In addition, the location of the remote piloted valve shortens and simplifies the hydraulic default circuit and thereby increases performance of the VCT default mode or intermediate phase angle position of the phaser.
Referring to
The hydraulic default circuit 133 includes a spring 131 loaded piloted valve 130 and an advance default line 128 that connects the advance chamber 102 to the piloted valve 130 and the common line 114 to check valves 108, 110, and a retard default line 134 that connects the retard chamber 103 to the piloted valve 130 and the common line 114 to check valves 108, 110. The advance default line 128 and the retard default line 134 are a predetermined distance or length from the vane 104. The piloted valve 130 is in the rotor assembly 105 and is fluidly connected to the lock pin circuit 123 and line 119a through line 132. The lock pin circuit 123 includes the lock pin 125, lock pin spring 124, line 132, the piloted valve 130, supply line 119a, and exhaust line 122.
The lock pin 125 is slidably housed in a bore in the rotor assembly 105 and has an end portion that is biased towards and fits into a recess 127 in the housing assembly 100 by a spring 124. Alternatively, the lock pin 125 may be housed in the housing assembly 100 and be spring 124 biased towards a recess 127 in the rotor assembly 105. The opening and closing of the hydraulic default circuit 133 and pressurization of the lock pin circuit 123 are both controlled by the switching/movement of the phase control valve 109.
A control valve 109, preferably a spool valve, includes a spool 111 with cylindrical lands 111a, 111b, 111c, 111d, and 111e slidably received in a sleeve 116 within a bore in the rotor 105 and pilots in the camshaft 126. One end of the spool contacts spring 115 and the opposite end of the spool contacts a pulse width modulated variable force solenoid (VFS) 107. The solenoid 107 may also be linearly controlled by varying current or voltage or other methods as applicable. Additionally, the opposite end of the spool 111 may contact and be influenced by a motor, or other actuators.
The position of the spool 111 is influenced by spring 115 and the solenoid 107 controlled by the ECU 106. Further detail regarding control of the phaser is discussed in detail below. The position of the spool 111 controls the motion (e.g. to move towards the advance position, holding position, or the retard position) of the phaser as well as whether the lock pin circuit 123 and the hydraulic default circuit 133 are open (on) or closed (off). In other words, the position of the spool 111 actively controls the piloted valve. The control valve 109 has an advance mode, a retard mode, a holding position, and a default mode.
In the advance mode, the spool 111 is moved to a position so that fluid may flow from supply S by pump 140 through inlet check valve 118, through line 119b to the advance chamber 102 and fluid from the retard chamber 103 exits through the spool 111 to exhaust line 121. The default valve circuit 133 is off or closed and the lock pin 125 is preferably unlocked.
In the retard mode, the spool 111 is moved to a position so that fluid may flow from supply S by pump 140 through inlet check valve 118, through line 119b to the retard chamber 103 and fluid from the advance chamber 102 exits through the spool 111 to exhaust line 122. The default valve circuit 133 is off and the lock pin 125 is preferably unlocked.
In holding position or null mode, the spool 111 is moved to a position that is partially open to the advance chamber 102 and the retard chamber 103 and allows supply fluid to bleed into the advance and retard chambers 102, 103, applying the same pressure to the advance chamber and retard chamber to hold the vane position. The default valve circuit 133 is off and the lock pin 125 is preferably unlocked.
In the default mode, three functions occur simultaneously:
The first function in the default mode is that the spool 111 moves to a position in which spool lands 111d and 111b blocks the flow of fluid from line 112 and line 113 from exiting the chambers 102, 103 through exhaust lines 121, 122, and only allowing a small amount of pressurized fluid from supply S to enter the advance chamber 102 and the retard chamber 103 to keep the advance and retard chambers 102, 103 full, effectively removing control of the phaser from the control valve 109.
The second function in default mode is to open or turn on the default valve circuit 133. With the default valve is open, one or more of the torsion assist advance and retard chambers 102, 103 are converted to cam torque actuated (CTA) mode. In other words, fluid is allowed to recirculate between the advance chamber and the retard chamber, instead of supply filling one chamber and exhausting the opposite chamber to sump through exhaust lines. The default valve circuit 133 has complete control over the phaser moving to advance or retard, until the vane 104 reaches the intermediate phase angle position.
The third function in the default mode is to vent the lock pin circuit 123, allowing the lock pin 125 to engage the recess 127. The intermediate phase angle position or mid position is when the vane 104 is somewhere between the advance wall 102a and the retard wall 103a defining the chamber between the housing assembly 100 and the rotor assembly 105. The intermediate phase angle position can be anywhere between the advance wall 102a and retard wall 103a and is determined by where the default passages 128 and 134 are relative to the vane 104.
Based on the duty cycle of the pulse width modulated variable force solenoid 107, the spool 111 moves to a corresponding position along its stroke. When the duty cycle of the variable force solenoid 107 is approximately 30%, 50% or 100%, the spool 111 will be moved to positions that correspond with the retard mode, the holding position, and the advance mode, respectively and the piloted valve 130 will be pressurized and move to the second position, the hydraulic default circuit 133 will be closed, and the lock pin 125 will be pressurized and released. When the duty cycle of the variable force solenoid 107 is 0%, the spool 111 is moved to the default mode such that the piloted valve 130 vents and moves to the second position, the hydraulic default circuit 133 will be open, and the lock pin 125 vented and engaged with the recess 127. A duty cycle of 0% was chosen as the extreme position along the spool stroke to open the hydraulic default circuit 133, vent the piloted valve 130, and vent and engage the lock pin 125 with the recess 127, since if power or control is lost, the phaser will default to a locked position. It should be noted that the duty cycle percentages listed above are an example and they may be altered. Furthermore, the hydraulic default circuit 133 may be open, the piloted valve 130 vented, and the lock pin 125 vented and engaged with the recess 127 at 100% duty cycle, if desired.
It should be noted that the duty cycle of the variable force solenoid 107 of approximately 30%, 50%, or 100% may alternatively correspond to the spool 111 being moved to positions that correspond to the advance mode, the holding position, and the retard mode, respectively.
Line 119a leads to the lock pin 125 and branches into line 132 which leads to the piloted valve 130. The pressure of the fluid in line 119a moves through the spool 111 between lands 111d and 111e to bias the lock pin 125 against the spring 124 to a released position, filling the lock pin circuit 123 with fluid. The fluid in line 119a also flows through line 132 and pressurizes the piloted valve 130 against the spring 131, moving the piloted valve 130 to a position where retard default line 134, advance default line 128 and line 129 are blocked as shown in
Line 119a leads to the lock pin 125 and branches into line 132 which leads to the piloted valve 130. The pressure of the fluid in line 119a moves through the spool 111 between lands 111d and 111e to bias the lock pin 125 against the spring 124 to a released position, filling the lock pin circuit 123 with fluid. The fluid in line 119a also flows through line 132 and pressurizes the piloted valve 130 against the spring 131, moving the piloted valve 130 to a position where retard default line 134 and the advance default line 128 are blocked from line 129 and from each other as shown in
Referring to
The ability of the phaser of the present invention to default to a mid position or intermediate phase angle position without using electronic controls allows the phaser to move to the mid position or intermediate phase angle position even during engine cranking when electronic controls are not typically used for controlling the cam phaser position. In addition, since the phaser defaults to the mid position or intermediate phase angle position, it provides a fail safe position, especially if control signals or power is lost, that guarantees that the engine will be able to start and run even without active control over the VCT phaser. Since the phaser has the mid position or intermediate phase angle position upon cranking of the engine, longer travel of the phase of the phaser is possible, providing calibration opportunities. In the prior art, longer travel phasers or a longer phase angle is not possible, since the mid position or intermediate phase angle position is not present upon engine cranking and startup and the engine has difficulty starting at either the extreme advance or retard stops.
When the duty cycle of the variable force solenoid 107 is set to 0%, the force on the VFS on the spool 111 is decreased, and the spring 115 moves the spool 111 to the far right end of the spool's travel to a default position as shown in
Referring to
Referring to
The advance default line 128 and the retard default line 134 are completely closed off or blocked by the rotor assembly 105 from the advance and retard chambers 102, 103 when phaser is in the mid position or intermediate phase angle position, requiring that the lock pin 125 engages the recess 127 at the precise time in which the advance default line 128 or the retard default line 134 are closed off from their respective chambers. Alternatively, the advance default line 128 and the retard default line 134 may be slightly open or partially restricted to the advance and retard chambers 102, 103, in the mid position or intermediate phase angle position to allow the rotor assembly 105 to oscillate slightly, increasing the likelihood the lock pin 125 will pass over the position of the recess 127 so the lock pin 125 can engage the recess 127.
Referring to
The difference between the embodiment shown in
The hydraulic default circuit 433 includes a spring 131 loaded piloted valve 130 connected to a retard default line 134 that connects the retard chamber 103 to the piloted valve 130 and the common line 114 to check valve 110. The retard default line 134 is a predetermined distance or length from the vane 104. The piloted valve 130 is in the rotor assembly 105 and is fluidly connected to the lock pin circuit 123 and line 119a through line 132. The lock pin circuit 123 includes the lock pin 125, lock pin spring 124, line 132, the piloted valve 130, supply line 119a, and exhaust line 122.
In the default mode, the spool 111 moves to a position in which spool lands 111d and 111b blocks the flow of fluid from line 112 and line 113 from exiting the chambers 102, 103 through exhaust lines 121, 122, and only allowing a small amount of pressurized fluid from supply S to enter the advance chamber 102 and the retard chamber 103 to keep the advance and retard chambers 102, 103 full, effectively removing control of the phaser from the control valve 109.
With the default valve circuit 433 on or open, and the default valve open, one or more of the torsion assist advance and retard chambers 102, 103 are converted to cam torque actuated (CTA) mode. In other words, fluid is allowed to recirculate between the advance chamber and the retard chamber, instead of supply filling one chamber and exhausting the opposite chamber to sump through exhaust lines. The default valve circuit 433 has complete control over the phaser moving to advance or retard, until the vane 104 reaches the intermediate phase angle position.
In the default mode the lock pin circuit 123 is vented, allowing the lock pin 125 to engage the recess 127. The intermediate phase angle position or mid position is when the vane 104 is somewhere between the advance wall 102a and the retard wall 103a defining the chamber between the housing assembly 100 and the rotor assembly 105. The intermediate phase angle position can be anywhere between the advance wall 102a and retard wall 103a and is determined by where the retard default passage 134 is relative to the vane 104.
Depending on where the vane 104 was prior to the duty cycle of the variable force solenoid 107 being changed to 0%, fluid from the advance chamber 102 will exit through line 112 and flows into common line 114, through check valve 110 to the retard chamber 103 through line 113. As the retard chamber 103 fills, the retard default line 134 is exposed and fluid in the retard chamber 103 recirculates back to the retard chamber 103 or advance chamber 102 depending on the direction of cam torque through the piloted valve 130. Therefore, in the retard direction, the phaser can freely move until the vane 104 contacts the advance wall 102a.
In the advance direction, when the hydraulic detent circuit is open, the phaser moves until the retard default line 134 is closed off by the housing 100. The retard default line 134 is closed off or blocked by the rotor assembly 105 from the retard chamber 103 when phaser is in the mid position or intermediate phase angle position, requiring that the lock pin 125 engages the recess 127 at the precise time in which the retard default line 134 is closed off from its respective chambers. If the lock pin 125 doesn't engage the recess 127, the rotor 105 and vane 104 oscillates between a detent position where the retard default line 134 is blocked by the housing 100 and full retard stop, (e.g. on the side with the shortest amount of travel between the mid position locking of the lock pin) where vane 104 contacts the advance wall 102a. When the phaser is oscillating, the lock pin 125 will eventually mate with the recess 127, locking the phaser in the mid position.
One of the advantages of only having a default line on one side of the phaser is decreased costs, since only one check valve is needed, not two and less drilling of the phaser is required.
It is preferable to have the check valve and default line on the side of the phaser with the longest travel for the lock pin to engage the recess and not have the check valve and default line with the shortest amount of travel for the lock pin to engage the recess, therefore limiting the amount of oscillation to the side, e.g. between the intermediate phase angle or mid position stop and the extreme stop and therefore the increased oscillation that does occur is on one end of the vane travel.
Alternatively, the check valve and default line on the opposite side, for example check valve 110 and default line 134 may also be removed.
Referring to
Fluid is supplied to the phaser from supply S by pump 140 and enters line 119 through a cam interface 120. Line 119 splits into two lines 119a and 119b. Line 119b leads to inlet check valve 118 and the control valve 109. From the control valve 109, fluid enters lines 112, 113 leading to the TA advance and retard chambers 102, 103, applying the same pressure to the advance chamber 102 as the retard chamber 103, to hold the vane in position.
Line 119a leads to the piloted valve 230. The pressure of the fluid in line 119a moves through the spool 111 between lands 111d and 111e to line 132 to pressurize the piloted valve 230 against the spring 231, moving the piloted valve 230 to a position where retard default line 134, advance default line 128 are blocked and the default circuit is off. Exhaust line 122 is blocked by spool land 111d, preventing the default circuit 233 from venting or opening.
Depending on where the vane 104 was prior to the duty cycle of the variable force solenoid 107 being changed to 0%, either the advance default line 128 or the retard default line 134 will be exposed to the CTA mode advance or retard chamber 202, 203 respectively. In addition, if the engine had an abnormal shut down (e.g. the engine stalled), when the engine is cranking, the duty cycle of the variable force solenoid 107 would be 0% the rotor assembly 105 would move via the default circuit to the mid position or intermediate phase angle position and the lock pin 125 would be engaged in mid position or intermediate phase angle position regardless of what position the vane 104 was in relative to the housing assembly 100 prior to the abnormal shut down of the engine.
The ability of the phaser of the present invention to default to a mid position or intermediate phase angle position without using electronic controls allows the phaser to move to the mid position or intermediate phase angle position even during engine cranking when electronic controls are not typically used for controlling the cam phaser position. In addition, since the phaser defaults to the mid position or intermediate phase angle position, it provides a fail safe position, especially if control signals or power or lost, that guarantees that the engine will be able to start and run even without active control over the VCT phaser. Since the phaser has the mid position or intermediate phase angle position upon cranking of the engine, longer travel of the phase of the phaser is possible, providing calibration opportunities. In the prior art, longer travel phasers or a longer phase angle is not possible, since the mid position or intermediate phase angle position is not present upon engine cranking and startup and the engine has difficulty starting at either the extreme advance or retard stops.
When the duty cycle of the variable force solenoid 107 is set to 0%, the force on the VFS on the spool 111 is decreased, and the spring 115 moves the spool 111 to the far right end of the spool's travel to a default mode as shown in the
Fluid is prevented from flowing through line 119a to the piloted valve 230 by spool land 111e. Since fluid cannot flow to line 119a, the piloted valve 230 vents to exhaust line 122, opening passage between the advance default line 128 and the retard default line 134 through the piloted valve 230 to line 229 and the common line 214, in other words, opening or turning on the hydraulic default circuit 233.
If the vane 104 was positioned within the housing assembly 100 near or in the retard position and the advance default line 128 is exposed to the CTA mode advance chamber 202, then fluid from the CTA mode advance chamber 202 will flow into the advance default line 128 and through the open piloted valve 230 and to line 229 leading to common line 214 as shown in
If the vane 104 was positioned within the housing assembly 100 near or in the advance position and the retard default line 134 is exposed to the CTA mode retard chamber 203, then fluid from the CTA mode retard chamber 203 will flow into the retard default line 134 and through the open piloted valve 230 and to line 229 leading to common line 214. From the common line 214, fluid flows through check valve 208 and into the CTA mode advance chamber 202, moving the vane 104 relative to the housing assembly 100 to close off the retard default line 134 to the CTA mode retard chamber 203. As the rotor assembly 105 closes off line the retard default line 134 from the CTA mode retard chamber 203, the vane 104 is moved to a mid position or intermediate phase angle position within the chamber formed between the housing assembly 100 and the rotor assembly 105.
The advance default line 128 and the retard default line 134 are completely closed off or blocked by the rotor assembly 105 from the CTA mode advance and retard chambers 202, 203 when phaser is in the mid position or intermediate phase angle position, requiring that the lock pin 125 engages the recess 127 at the precise time in which the advance default line 128 or the retard default line 134 are closed off from their respective chambers. Alternatively, the advance default line 128 and the retard default line 134 may be slightly open or partially restricted to the CTA mode advance and retard chambers 202, 203, in the mid position or intermediate phase angle position to allow the rotor assembly 105 to oscillate slightly, increasing the likelihood the lock pin 125 will pass over the position of the recess 127 so the lock pin 125 can engage the recess 127.
The difference between the embodiment shown in
The hydraulic default circuit 533 includes a spring 231 loaded piloted valve 230 and an advance default line 128 that connects the switched TA advance chamber 202 now in CTA mode to the piloted valve 230 and the common line 214 to check valve 208. The advance default line 128 is a predetermined distance or length from the vane 104. The piloted valve 230 is in the rotor assembly 105 and is fluidly connected to the lock pin circuit 123 and line 119a through line 132. The lock pin circuit 123 includes the lock pin 125, lock pin spring 124, line 132, the piloted valve 230, supply line 119a, and exhaust line 122.
Depending on where the vane 104 was prior to the duty cycle of the variable force solenoid 107 being changed to 0%, fluid from the CTA mode retard chamber 203 will exit through line 213 and flow into common line 214, through check valve 208 to the CTA mode advance chamber 202 through line 212. As the CTA mode advance chamber 202 fills, the advance default line 128 is exposed and fluid in the CTA mode advance chamber 202 recirculates back to the CTA mode advance chamber 202 or CTA mode retard chamber 203 depending on the direction of cam torque through the piloted valve 230. Therefore, in the advance direction, the phaser can freely move until the vane 104 contacts the retard wall 203a.
In the default mode, spool land 111b blocks the flow of fluid from line 112 to exhaust line 121 and spool land 111d blocks the flow of fluid from line 113 to exhaust line 122, allowing fluid from supply to openly circulate between the TA advance and retard chambers 102, 103, effectively removing control of the phaser from the control valve 109. At the same time, fluid from supply may flow through line 119 to line 119b and inlet check valve 118 to lines 112, 113 leading to the TA advance and retard chambers 102, 103 as described above and into common line 214, through the piloted valve 230 and through check valve 208 and into the CTA mode advance chamber 202 through line 212 or to the CTA mode retard chamber 203 through line 213.
Fluid is prevented from flowing through line 119a to the piloted valve 230 by spool land 111e. Since fluid cannot flow to line 119a, the piloted valve 230 vents to exhaust line 122, opening passage between the advance default line 128 through the piloted valve 230 to line 229 and the common line 214, in other words, opening or turning on the hydraulic default circuit 533.
In the retard direction, when the hydraulic detent circuit is open, the phaser moves until the advance default line 128 is closed off by the housing 100. The advance default line 128 is closed off or blocked by the rotor assembly 105 from the CTA mode advance chamber 202 when phaser is in the mid position or intermediate phase angle position, requiring that the lock pin 125 engages the recess 127 at the precise time in which the advance default line 128 is closed off from its respective chambers. If the lock pin 125 doesn't engage the recess 127, the rotor 105 and vane 104 oscillates between a detent position where advance default line 128 is blocked by the housing 100 and full advance stop, (e.g. on the side with the shortest amount of travel between the mid position locking of the lock pin) where vane 104 contacts the retard wall 203a. When the phaser is oscillating, the lock pin 125 will eventually mate with the recess 127, locking the phaser in the mid position.
One of the advantages of only having a default line on one side of the phaser is decreased costs, since only one check valve is needed, not two and less drilling of the phaser is required.
It is preferable to have the check valve and default line on the side of the phaser with the longest travel for the lock pin to engage the recess and not have the check valve and default line with the shortest amount of travel for the lock pin to engage the recess, therefore limiting the amount of oscillation to the side, e.g. between the intermediate phase angle or mid position stop and the extreme stop and therefore the increased oscillation that does occur is on one end of the vane travel.
Alternatively, the check valve and default line on the opposite side, for example check valve 208 and advance default line 128 may also be removed.
Referring to
Fluid is supplied to the phaser from supply S by pump 140 and enters line 119 through a cam interface 120. Line 119 splits into two lines 119a and 119b. Line 119b leads to inlet check valve 118 and the control valve 109. Spool lands 111b and 111c are positioned such that fluid may bleed into lines 112 and 113, leading to the advance and retard TA chambers 102, 103, applying the same pressure to the advance chamber 102 as the retard chamber 103, to hold the vane in position.
Line 119a leads to the piloted valve 330. The pressure of the fluid in line 119a moves through the spool 111 between lands 111d and 111e to line 132 to pressurize the piloted valve 330 against the spring 331, moving the piloted valve 330 to a position where retard default line 134, advance default line 128 are blocked and the default circuit is off. Fluid can however move unrestricted and freely between the CTA advance chamber 302 and the CTA retard chamber 303 through the piloted valve 330 when the hydraulic default circuit 333 is off. Exhaust line 122 is blocked by spool land 111d, preventing the default circuit 333 from venting or opening.
Depending on where the vane 104 was prior to the duty cycle of the variable force solenoid 107 being changed to 0%, either the advance default line 128 or the retard default line 134 will be exposed to the CTA mode advance or retard chamber 302, 303 respectively. In addition, if the engine had an abnormal shut down (e.g. the engine stalled), when the engine is cranking, the duty cycle of the variable force solenoid 107 would be 0% the rotor assembly 105 would move via the default circuit to the mid position or intermediate phase angle position and the lock pin 125 would be engaged in mid position or intermediate phase angle position regardless of what position the vane 104 was in relative to the housing assembly 100 prior to the abnormal shut down of the engine.
The ability of the phaser of the present invention to default to a mid position or intermediate phase angle position without using electronic controls allows the phaser to move to the mid position or intermediate phase angle position even during engine cranking when electronic controls are not typically used for controlling the cam phaser position. In addition, since the phaser defaults to the mid position or intermediate phase angle position, it provides a fail safe position, especially if control signals or power or lost, that guarantees that the engine will be able to start and run even without active control over the VCT phaser. Since the phaser has the mid position or intermediate phase angle position upon cranking of the engine, longer travel of the phase of the phaser is possible, providing calibration opportunities. In the prior art, longer travel phasers or a longer phase angle is not possible, since the mid position or intermediate phase angle position is not present upon engine cranking and startup and the engine has difficulty starting at either the extreme advance or retard stops.
When the duty cycle of the variable force solenoid 107 is set to 0%, the force on the VFS on the spool 111 is decreased, and the spring 115 moves the spool 111 to the far right end of the spool's travel to a default mode as shown in the
Fluid is prevented from flowing through line 119a to the piloted valve 330 by spool land 111e. Since fluid cannot flow to line 119a, the piloted valve 330 vents to exhaust line 122, opening passage between the advance default line 128 and the retard default line 134 through the piloted valve 330 to line 329 and the common line 314, in other words, opening or turning on the hydraulic default circuit 333.
If the vane 104 was positioned within the housing assembly 100 near or in the retard position and the advance default line 128 is exposed to the CTA mode advance chamber 302, then fluid from the CTA mode advance chamber 302 will flow into the advance default line 128 and through the open piloted valve 330 and to line 329 leading to common line 314 as shown in
If the vane 104 was positioned within the housing assembly 100 near or in the advance position and the retard default line 134 is exposed to the CTA mode retard chamber 303, then fluid from the CTA mode retard chamber 303 will flow into the retard default line 134 and through the open piloted valve 330 and to line 329 leading to common line 314. From the common line 314, fluid flows through check valve 308 and into the CTA mode advance chamber 302, moving the vane 104 relative to the housing assembly 100 to close off the retard default line 134 to the CTA mode retard chamber 303. As the rotor assembly 105 closes off line the retard default line 134 from the CTA mode retard chamber 303, the vane 104 is moved to a mid position or intermediate phase angle position within the chamber formed between the housing assembly 100 and the rotor assembly 105.
The advance default line 128 and the retard default line 134 are completely closed off or blocked by the rotor assembly 105 from the CTA mode advance and retard chambers 302, 303 when phaser is in the mid position or intermediate phase angle position, requiring that the lock pin 125 engages the recess 127 at the precise time in which the advance default line 128 or the retard default line 134 are closed off from their respective chambers. Alternatively, the advance default line 128 and the retard default line 134 may be slightly open or partially restricted to the CTA mode advance and retard chambers 302, 303, in the mid position or intermediate phase angle position to allow the rotor assembly 105 to oscillate slightly, increasing the likelihood the lock pin 125 will pass over the position of the recess 127 so the lock pin 125 can engage the recess 127.
The difference between the embodiment shown in
The hydraulic default circuit 333 includes a spring 331 loaded piloted valve 330 and an advance default line 128 that connects the CTA mode advance chamber 302 to the piloted valve 330 and the common line 314 to check valve 308. The advance default line 128 is a predetermined distance or length from the vane 104. The piloted valve 330 is in the rotor assembly 105 and is fluidly connected to the lock pin circuit 123 and line 119a through line 132. The lock pin circuit 123 includes the lock pin 125, lock pin spring 124, line 132, the piloted valve 330, supply line 119a, and exhaust line 122.
Depending on where the vane 104 was prior to the duty cycle of the variable force solenoid 107 being changed to 0%, fluid from the CTA mode retard chamber 303 will exit through line 313 and flow into common line 314, through check valve 308 to the CTA mode advance chamber 302 through line 312. As the CTA mode advance chamber 302 fills, the advance default line 128 is exposed and fluid in the CTA mode advance chamber 302 recirculates back to the CTA mode advance chamber 302 or CTA mode retard chamber 303 depending on the direction of cam torque through the piloted valve 230. Therefore, in the advance direction, the phaser can freely move until the vane 104 contacts the retard wall 303a.
In the default mode, spool land 111b blocks the flow of fluid from line 112 to exhaust line 121 and spool land 111d blocks the flow of fluid from line 113 to exhaust line 122, allowing fluid from supply to openly circulate between the TA advance and retard chambers 102, 103, effectively removing control of the phaser from the control valve 109. At the same time, fluid from supply may flow through line 119 to line 119b and inlet check valve 118 to lines 112, 113 leading to the TA advance and retard chambers 102, 103 as described above and into common line 314, through the piloted valve 330 and through a check valve 308 into the CTA mode advance chamber 302 through line 312 and through to the CTA mode retard chamber 302 through line 313.
Fluid is prevented from flowing through line 119a to the piloted valve 330 by spool land 111e. Since fluid cannot flow to line 119a, the piloted valve 330 vents to exhaust line 122, opening passage between the advance default line 128 through the piloted valve 330 to line 329 and the common line 214, in other words, opening or turning on the hydraulic default circuit 633.
In the retard direction, when the hydraulic detent circuit is open, the phaser moves until the advance default line 128 is closed off by the housing 100. The advance default line 128 is closed off or blocked by the rotor assembly 105 from the CTA mode advance chamber 302 when phaser is in the mid position or intermediate phase angle position, requiring that the lock pin 125 engages the recess 127 at the precise time in which the advance default line 128 is closed off from its respective chambers. If the lock pin 125 doesn't engage the recess 127, the rotor 105 and vane 104 oscillates between a detent position where advance default line 128 is blocked by the housing 100 and full advance stop, (e.g. on the side with the shortest amount of travel between the mid position locking of the lock pin) where vane 104 contacts the retard wall 203a. When the phaser is oscillating, the lock pin 125 will eventually mate with the recess 127, locking the phaser in the mid position.
One of the advantages of only having a default line on one side of the phaser is decreased costs, since only one check valve is needed, not two and less drilling of the phaser is required.
It is preferable to have the check valve and default line on the side of the phaser with the longest travel for the lock pin to engage the recess and not have the check valve and default line with the shortest amount of travel for the lock pin to engage the recess, therefore limiting the amount of oscillation to the side, e.g. between the intermediate phase angle or mid position stop and the extreme stop and therefore the increased oscillation that does occur is on one end of the vane travel.
Alternatively, the check valve and default line on the opposite side, for example check valve 308 and advance default line 128 may also be removed.
Referring to
Fluid is supplied to the phaser from supply S by pump 140 and enters line 119 through a cam interface 120. Line 119 splits into two lines 119a and 119b. Line 119b leads to inlet check valve 118 and the control valve 109. From the control valve 109, fluid enters lines 112, 113 leading to the TA advance and retard chambers 102, 103, applying the same pressure to the advance chamber 102 as the retard chamber 103, to hold the vane in position.
Line 119a leads to the piloted valve 330. The pressure of the fluid in line 119a moves through the spool 111 between lands 111d and 111e to line 132 to pressurize the piloted valve 330 against the spring 331, moving the piloted valve 330 to a position where retard default line 134, advance default line 128 are blocked and the default circuit is off. Fluid can however move unrestricted and freely between the CTA advance chamber 302 and the CTA retard chamber 303 through the piloted valve 330 when the hydraulic default circuit 333 is off. Exhaust line 122 is blocked by spool land 111d, preventing the default circuit 333 from venting or opening.
Depending on where the vane 104 was prior to the duty cycle of the variable force solenoid 107 being changed to 0%, either the advance default line 128 or the retard default line 134 will be exposed to the CTA mode advance or retard chamber 302, 303 respectively. In addition, if the engine had an abnormal shut down (e.g. the engine stalled), when the engine is cranking, the duty cycle of the variable force solenoid 107 would be 0% the rotor assembly 105 would move via the default circuit to the mid position or intermediate phase angle position and the lock pin 125 would be engaged in mid position or intermediate phase angle position regardless of what position the vane 104 was in relative to the housing assembly 100 prior to the abnormal shut down of the engine.
The ability of the phaser of the present invention to default to a mid position or intermediate phase angle position without using electronic controls allows the phaser to move to the mid position or intermediate phase angle position even during engine cranking when electronic controls are not typically used for controlling the cam phaser position. In addition, since the phaser defaults to the mid position or intermediate phase angle position, it provides a fail safe position, especially if control signals or power or lost, that guarantees that the engine will be able to start and run even without active control over the VCT phaser. Since the phaser has the mid position or intermediate phase angle position upon cranking of the engine, longer travel of the phase of the phaser is possible, providing calibration opportunities. In the prior art, longer travel phasers or a longer phase angle is not possible, since the mid position or intermediate phase angle position is not present upon engine cranking and startup and the engine has difficulty starting at either the extreme advance or retard stops.
When the duty cycle of the variable force solenoid 107 is just set to 0%, the force on the VFS on the spool 111 is decreased, and the spring 115 moves the spool 111 to the far right end of the spool's travel to a default mode as shown in the
Fluid is prevented from flowing through line 119a to the piloted valve 330 by spool land 111e. Since fluid cannot flow to line 119a, the piloted valve 330 vents to exhaust line 122, opening passage between the advance default line 128 and the retard default line 134 through the piloted valve 330 to line 329 and the common line 314, in other words, opening or turning on the hydraulic default circuit 333.
If the vane 104 was positioned within the housing assembly 100 near or in the retard position and the advance default line 128 is exposed to the CTA mode advance chamber 302, then fluid from the CTA mode advance chamber 302 will flow into the advance default line 128 and through the open piloted valve 330 and to line 329 leading to common line 314 as shown in
If the vane 104 was positioned within the housing assembly 100 near or in the advance position and the retard default line 134 is exposed to the CTA mode retard chamber 303, then fluid from the CTA mode retard chamber 303 will flow into the retard default line 134 and through the open piloted valve 330 and to line 329 leading to common line 314. From the common line 314, fluid flows through check valve 308 and into the CTA mode advance chamber 302, moving the vane 104 relative to the housing assembly 100 to close off the retard default line 134 to the CTA mode retard chamber 303. As the rotor assembly 105 closes off line the retard default line 134 from the CTA mode retard chamber 203, the vane 104 is moved to a mid position or intermediate phase angle position within the chamber formed between the housing assembly 100 and the rotor assembly 105.
The advance default line 128 and the retard default line 134 are completely closed off or blocked by the rotor assembly 105 from the CTA mode advance and retard chambers 302, 303 when phaser is in the mid position or intermediate phase angle position, requiring that the lock pin 125 engages the recess 127 at the precise time in which the advance default line 128 or the retard default line 134 are closed off from their respective chambers. Alternatively, the advance default line 128 and the retard default line 134 may be slightly open or partially restricted to the CTA mode advance and retard chambers 302, 303, in the mid position or intermediate phase angle position to allow the rotor assembly 105 to oscillate slightly, increasing the likelihood the lock pin 125 will pass over the position of the recess 127 so the lock pin 125 can engage the recess 127.
The difference between the embodiment shown in
The hydraulic default circuit 333 includes a spring 331 loaded piloted valve 330 and an advance default line 128 that connects the CTA mode advance chamber 302 to the piloted valve 330 and the common line 314 to check valve 308. The advance default line 128 is a predetermined distance or length from the vane 104. The piloted valve 330 is in the rotor assembly 105 and is fluidly connected to the lock pin circuit 123 and line 119a through line 132. The lock pin circuit 123 includes the lock pin 125, lock pin spring 124, line 132, the piloted valve 330, supply line 119a, and exhaust line 122. With the hydraulic default circuit 733 on or open, fluid from the advance torsion assist chamber 102 and the retard torsion assist chamber 103 empty out to sump through exhaust lines 121 and 122. Therefore, the only set of chambers that has fluid when the spool is fully out or in default mode is the one or more sets of CTA mode advance and retard chambers 302, 303. Fluid from supply S may flow into common line 314 through an annulus (not shown) on the outer diameter of the sleeve 116.
Depending on where the vane 104 was prior to the duty cycle of the variable force solenoid 107 being changed to 0%, fluid from the CTA mode retard chamber 303 will exit through line 313 and flow into common line 314, through check valve 308 to the CTA mode advance chamber 302 through line 312. As the CTA mode advance chamber 302 fills, the advance default line 128 is exposed and fluid in the CTA mode advance chamber 302 recirculates back to the CTA mode advance chamber 302 or CTA mode retard chamber 303 depending on the direction of cam torque through the piloted valve 230. Therefore, in the advance direction, the phaser can freely move until the vane 104 contacts the retard wall 303a.
In the default mode, spool land 111b allows the flow of fluid from line 112 to exhaust line 121 and spool land 111d allows the flow of fluid from line 113 to exhaust line 122, allowing fluid from the TA advance and retard chambers to empty to sump. At the same time, fluid from supply may flow through line 119 to line 119b and inlet check valve 118 to common line 314 and through the piloted valve 330 and through a check valve 308 into the CTA mode advance chamber 302 and through to the CTA mode retard chamber 302 through lines 312, 313.
Fluid is prevented from flowing through line 119a to the piloted valve 330 by spool land 111e. Since fluid cannot flow to line 119a, the piloted valve 330 vents to exhaust line 122, opening passage between the advance default line 128 through the piloted valve 330 to line 329 and the common line 314, in other words, opening or turning on the hydraulic default circuit 733.
In the retard direction, when the hydraulic detent circuit is open, the phaser moves until the advance default line 128 is closed off by the housing 100. The advance default line 128 is closed off or blocked by the rotor assembly 105 from the CTA mode advance chamber 302 when phaser is in the mid position or intermediate phase angle position, requiring that the lock pin 125 engages the recess 127 at the precise time in which the advance default line 128 is closed off from its respective chambers. If the lock pin 125 doesn't engage the recess 127, the rotor 105 and vane 104 oscillates between a detent position where advance default line 128 is blocked by the housing 100 and full advance stop, (e.g. on the side with the shortest amount of travel between the mid position locking of the lock pin) where vane 104 contacts the retard wall 303a. When the phaser is oscillating, the lock pin 125 will eventually mate with the recess 127, locking the phaser in the mid position.
One of the advantages of only having a default line on one side of the phaser is decreased costs, since only one check valve is needed, not two and less drilling of the phaser is required.
It is preferable to have the check valve and default line on the side of the phaser with the longest travel for the lock pin to engage the recess and not have the check valve and default line with the shortest amount of travel for the lock pin to engage the recess, therefore limiting the amount of oscillation to the side, e.g. between the intermediate phase angle or mid position stop and the extreme stop and therefore the increased oscillation that does occur is on one end of the vane travel.
Alternatively, the check valve and default line on the opposite side, for example check valve 308 and advance default line 128 may also be removed.
The housing assembly 100 of the phaser has an outer circumference 101 for accepting drive force. The rotor assembly 105 is connected to the camshaft 126 and is coaxially located within the housing assembly 100. The rotor assembly 105 has a vane 104 separating a chamber 117 formed between the housing assembly 100 and the rotor assembly 105 into an advance chamber 102 and a retard chamber 103. The vane 104 is capable of rotation to shift the relative angular position of the housing assembly 100 and the rotor assembly 105. Additionally, a hydraulic default circuit 133 and a lock pin circuit 123 are also present. The hydraulic default circuit 133 and the lock pin circuit 123 are essentially one circuit as discussed above, but will be discussed separately for simplicity.
The hydraulic default circuit 133 includes a spring 131 loaded piloted valve 130 and an advance default line 128 that connects the advance chamber 102 to the piloted valve 130 and the common line 114 to check valves 108, 110, and a retard default line 134 that connects the retard chamber 103 to the piloted valve 130 and the common line 114 to check valves 108, 110. The advance default line 128 and the retard default line 134 are a predetermined distance or length from the vane 104. The piloted valve 130 is in the rotor assembly 105 and is fluidly connected to the lock pin circuit 123 and line 119a through line 132. The lock pin circuit 123 includes the lock pin 125, line 132, the piloted valve 130, supply line 119a, and exhaust line 122.
The lock pin 125 is slidably housed in a bore in the rotor assembly 105 and has an end portion that is biased towards and fits into a recess 127 in the housing assembly 100 by a spring 124. Alternatively, the lock pin 125 may be housed in the housing assembly 100 and be spring 124 biased towards a recess 127 in the rotor assembly 105. The opening and closing of the hydraulic default circuit 133 and pressurization of the lock pin circuit 123 are both controlled by the switching/movement of the phase control valve 109.
A control valve 409, preferably a spool valve, includes a spool 411 with cylindrical lands 411a, 411b, 411c, 411d, and 411e slidably received in a sleeve 116 within a bore in the rotor 105 and pilots in the camshaft 126. One end of the spool contacts spring 115 and the opposite end of the spool contacts a pulse width modulated variable force solenoid (VFS) 107. The solenoid 107 may also be linearly controlled by varying current or voltage or other methods as applicable. Additionally, the opposite end of the spool 111 may contact and be influenced by a motor, or other actuators.
The position of the spool 411 is influenced by spring 115 and the solenoid 107 controlled by the ECU 106. Further detail regarding control of the phaser is discussed in detail below. The position of the spool 411 controls the motion (e.g. to move towards the advance position, holding position, or the retard position) of the phaser as well as whether the lock pin circuit 123 and the hydraulic default circuit 133 are open (on) or closed (off). In other words, the position of the spool 411 actively controls the piloted valve. The control valve 409 has an advance mode, a retard mode, a holding position, and a default mode.
In the advance mode, the spool 411 is moved to a position so that fluid may flow from supply S by pump 140 through inlet check valve 118, through line 119b to the advance chamber 102 and fluid from the retard chamber 103 exits through the spool 411 to exhaust line 121. The default valve circuit 133 is off or closed and the lock pin 125 is preferably unlocked.
In the retard mode, the spool 411 is moved to a position so that fluid may flow from supply S by pump 140 through inlet check valve 118, through line 119b to the retard chamber 103 and fluid from the advance chamber 102 exits through the spool 411 to exhaust line 122. The default valve circuit 133 is off and the lock pin 125 is preferably unlocked.
In holding position or null mode, the spool 411 is moved to a position that is partially open to the advance chamber 102 and the retard chamber 103 and allows supply fluid to bleed into the advance and retard chambers 102, 103, applying the same pressure to the advance chamber and retard chamber to hold the vane position. The default valve circuit 133 is off and the lock pin 125 is preferably unlocked.
When the duty cycle of the variable force solenoid 107 is 0%, the spool is in default mode, the piloted valve 130 is vented, the hydraulic default circuit 133 is open or on, and the lock pin circuit 123 is off or closed, the lock pin 125 is vented and engages with a recess 127, and the rotor 105 is locked relative to the housing assembly 100 in a mid position or an intermediate phase angle position.
Depending on where the vane 104 was prior to the duty cycle of the variable force solenoid 107 being changed to 0%, either the advance default line 128 or the retard default line 134 will be exposed to the advance or retard chamber 102, 103 respectively. In addition, if the engine had an abnormal shut down (e.g. the engine stalled), when the engine is cranking, the duty cycle of the variable force solenoid 107 would be 0%, the rotor assembly 105 would move via the default circuit 133 to a mid lock position or an intermediate phase angle position and the lock pin 125 would be engaged in mid position or intermediate phase angle position regardless of what position the vane 104 was in relative to the housing assembly 100 prior to the abnormal shut down of the engine. In the present invention, default mode is preferably when the spool is an extreme end of travel. In the examples shown in the present invention, it is when the spool is at an extreme full out position from the bore, although other positions of the spool may be used.
The ability of the phaser of the present invention to default to a mid position or intermediate phase angle position without using electronic controls allows the phaser to move to the mid position or intermediate phase angle position even during engine cranking when electronic controls are not typically used for controlling the cam phaser position. In addition, since the phaser defaults to the mid position or intermediate phase angle position, it provides a fail safe position, especially if control signals or power is lost, that guarantees that the engine will be able to start and run even without active control over the VCT phaser. Since the phaser has the mid position or intermediate phase angle position upon cranking of the engine, longer travel of the phase of the phaser is possible, providing calibration opportunities. In the prior art, longer travel phasers or a longer phase angle is not possible, since the mid position or intermediate phase angle position is not present upon engine cranking and startup and the engine has difficulty starting at either the extreme advance or retard stops.
When the duty cycle of the variable force solenoid 107 is set to 0%, the force on the VFS on the spool 411 is decreased, and the spring 115 moves the spool 411 to the far right end of the spool's travel to a default position as shown in
Fluid from supply flows from line 119b to the control valve 409 between spool lands 411c and 411b to retard line 113 leading to the retard chamber 103. Fluid is prevented from flowing directly to the advance chamber 102 from the control valve 409 and supply pump 140 by spool land 411c. Fluid is also prevented from flowing through line 119a to the lock pin 125 by spool land 411e. Since fluid cannot flow to line 119a, the lock pin 125 is no longer pressurized and vents through the spool 411 between spool land 411d and spool land 411e to exhaust line 122. Similarly, the piloted valve 130 also vents to exhaust line 122, opening passage between the advance default line 128 and the retard default line 134 through the piloted valve 130 to line 129 and the common line 114, in other words opening the hydraulic default circuit 133 and essentially converting all of the torsion assist chambers into cam torque actuated chambers (CTA) or into CTA mode with circulation of fluid being allowed between the advance chamber 102 and the retard chamber 103. Therefore, fluid supplied to the retard chamber 103 from the control valve 409 may flow into the default line 134, through the piloted valve 130 to line 129 and the common line 114, through check valve 108 through line 112 to the advance chamber 102.
If the vane 104 was positioned within the housing assembly 100 near or in the advance position and the retard default line 134 is exposed to the retard chamber 103, then fluid from the retard chamber 103 will flow into the retard default line 134 and through the open piloted valve 130 and to line 129 leading to common line 114. From the common line 114, fluid flows through check valve 108 and into the advance chamber 102, moving the vane 104 relative to the housing assembly 100 to close off the retard default line 134 to the retard chamber 103. As the rotor 105 closes off line the retard default 134 from the retard chamber 103, the vane 104 is moved to an intermediate phase angle position or a mid position within the chamber formed between the housing assembly 100 and the rotor assembly 105, and the lock pin 125 aligns with the recess 127, locking the rotor 105 relative to the housing assembly 100 in a mid position or an intermediate phase angle position.
If the vane 104 was positioned within the housing assembly 100 near or in the retard position and the advance default line 128 is exposed to the advance chamber 102, then fluid from the advance chamber 102 will flow into the advance default line 128 and through the open piloted valve 130 and to line 129 leading to common line 114. From the common line 114, fluid flows through check valve 110 and into the retard chamber 103, moving the vane 104 relative to the housing assembly 100 to close off or block advance default line 128 to the advance chamber 102. As the rotor assembly 105 closes off the advance default line 128 from the advance chamber 102, the vane 104 is moved to an intermediate phase angle position or a mid position within the chamber formed between the housing assembly 100 and the rotor assembly 105, and the lock pin 125 aligns with recess 127, locking the rotor assembly 105 relative to the housing assembly 100 in a mid position or an intermediate phase angle position.
The advance default line 128 and the retard default line 134 are completely closed off or blocked by the rotor assembly 105 from the advance and retard chambers 102, 103 when phaser is in the mid position or intermediate phase angle position, requiring that the lock pin 125 engages the recess 127 at the precise time in which the advance default line 128 or the retard default line 134 are closed off from their respective chambers. Alternatively, the advance default line 128 and the retard default line 134 may be slightly open or partially restricted to the advance and retard chambers 102, 103, in the mid position or intermediate phase angle position to allow the rotor assembly 105 to oscillate slightly, increasing the likelihood the lock pin 125 will pass over the position of the recess 127 so the lock pin 125 can engage the recess 127.
Referring to
The difference between the embodiment shown in
The hydraulic default circuit 833 includes a spring 131 loaded piloted valve 130 connected to an advance default line 128 that connects the advance chamber 102 to the piloted valve 130 and the common line 114 to check valve 108. The advance default line 128 is a predetermined distance or length from the vane 104. The piloted valve 130 is in the rotor assembly 105 and is fluidly connected to the lock pin circuit 123 and line 119a through line 132. The lock pin circuit 123 includes the lock pin 125, lock pin spring 124, line 132, the piloted valve 130, supply line 119a, and exhaust line 122.
In the default mode, the spool 411 moves to a position in which spool lands 411d and 411b blocks the flow of fluid from line 112 and line 113 from exiting the chambers 102, 103 through exhaust lines 121, 122, and only allowing a small amount of pressurized fluid from supply S to enter the retard chamber 102 and the advance chamber 102 to keep the advance and retard chambers 102, 103 full, effectively removing control of the phaser from the control valve 409.
With the default valve circuit on or open and the default valve open, one or more of the torsion assist advance and retard chambers 102, 103 are converted to cam torque actuated (CTA) mode. In other words, fluid is allowed to recirculate between the advance chamber and the retard chamber, instead of supply filling one chamber and exhausting the opposite chamber to sump through exhaust lines. The default valve circuit 833 has complete control over the phaser moving to advance or retard, until the vane 104 reaches the intermediate phase angle position.
In default mode the lock pin circuit 123 is vented, allowing the lock pin 125 to engage the recess 127. The intermediate phase angle position or mid position is when the vane 104 is somewhere between the advance wall 102a and the retard wall 103a defining the chamber between the housing assembly 100 and the rotor assembly 105. The intermediate phase angle position can be anywhere between the advance wall 102a and retard wall 103a and is determined by where the advance default passage 128 is relative to the vane 104.
Depending on where the vane 104 was prior to the duty cycle of the variable force solenoid 107 being changed to 0%, fluid from the retard chamber 103 will exit through line 113 and flows into common line 114, through check valve 108 to the advance chamber 102 through line 112. As the advance chamber 102 fills, the advance default line 128 is exposed and fluid in the advance chamber 102 recirculates back to the advance chamber 102 or retard chamber 103 depending on the direction of cam torque through the piloted valve 130. Therefore, in the advance direction, the phaser can freely move until the vane 104 contacts the retard wall 103a. In the retard direction, when the hydraulic detent circuit is open, the phaser moves until the advance default line 128 is closed off by the housing 100. The advance default line 128 is closed off or blocked by the rotor assembly 105 from the advance chamber 102 when phaser is in the mid position or intermediate phase angle position, requiring that the lock pin 125 engages the recess 127 at the precise time in which the advance default line 128 is closed off from its respective chambers. If the lock pin 125 doesn't engage the recess 127, the rotor 105 and vane 104 oscillates between a detent position where the advance default line 128 is blocked by the housing 100 and full advance stop, (e.g. on the side with the shortest amount of travel between the mid position locking of the lock pin) where vane 104 contacts the retard wall 103a. When the phaser is oscillating, the lock pin 125 will eventually mate with the recess 127, locking the phaser in the mid position.
One of the advantages of only having a default line on one side of the phaser is decreased costs, since only one check valve is needed, not two and less drilling of the phaser is required.
It is preferable to have the check valve and default line on the side of the phaser with the longest travel for the lock pin to engage the recess and not have the check valve and default line with the shortest amount of travel for the lock pin to engage the recess, therefore limiting the amount of oscillation to the side, e.g. between the intermediate phase angle or mid position stop and the extreme stop and therefore the increased oscillation that does occur is on one end of the vane travel.
Alternatively, the check valve and default line on the opposite side, for example check valve 108 and advance default line 128 may also be removed.
In the embodiments shown the control valve in the rotor, it is understood that a person skilled in the art could use a remote control valve as well.
In all of the embodiments, the default mode of the control valve is when the control valve is at an extreme end of travel. The extreme end of travel is preferably when the spool is biased full out from the bore by the spring.
While all embodiments are shown with an inlet check valve, and therefore a torsion assist phaser, a person skilled in the art would be able to apply all of the above embodiments to an oil pressure actuated phaser in which the inlet check valve 118 is removed.
Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.
This application claims one or more inventions which were disclosed in Provisional Application No. 61/389,451, filed Oct. 4, 2010, entitled “VARIABLE CAMSHAFT TIMING MECHANISM WITH A DEFAULT MODE” and Provisional Application No. 61/417,943, filed Nov. 30, 2010, entitled “VARIABLE CAMSHAFT TIMING MECHANISM WITH A DEFAULT MODE”. The benefit under 35 USC §119(e) of the United States provisional applications are hereby claimed, and the aforementioned application is hereby incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2011/054196 | 9/30/2011 | WO | 00 | 3/27/2013 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2012/047748 | 4/12/2012 | WO | A |
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| Number | Date | Country |
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| 2007138744 | Jun 2007 | JP |
| 2009114500 | Sep 2009 | WO |
| Entry |
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| International Search Report for PCT/US2011/054196; Mailed May 7, 2012; 9 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20130180486 A1 | Jul 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61389451 | Oct 2010 | US | |
| 61417943 | Nov 2010 | US |
