Patent Application
20110215269
The present invention relates to spool-type valves; and more particularly, to such valves as are commonly employed for switching and controlling flow of activation and lubrication fluids to various components of internal combustion engines; and most particularly, to switchable oil control valves having a spool for regulating oil pressure and for switching between high pressure mode and pressure relief mode.
Spool-type valves for controllably diverting the flow of fluids are well known. In a typical spool valve, a piston or “spool,” having a plurality of annular grooves in the spool wall is slidably disposed within a cylindrical body that is also provided with a plurality of internal annular grooves and radial ports extending through the body wall. The spool is variably positionable axially within the body to cause selected ports in the spool to align with grooves and ports in the body, thereby permitting flow of fluid from outside the body through first aligned ports into the interior of the spool and out through second aligned ports. A plurality of different flow paths typically is created by positioning the spool at a plurality of different axial positions within the body. Typically, the spool is connected to a linear solenoid actuator, whereby the spool may be axially positioned by signals from a controller such as a computerized engine control module, although other actuators such as pneumatic and hydraulic actuators can be used.
A common usage for an oil-control spool valve is to variably actuate engine control subsystems such as camshaft phasers, variable valve activation (VVA) mechanisms, and multi-step or valve deactivation mechanisms. In a two step valve mechanism, for example, the mechanism selects the engine intake valve lift profile (low or high) of an intake valve camshaft using a hydraulically activated roller finger follower (RFF).
In a simple configuration of this example, a spool valve supplies high pressure oil, typically from an engine-driven oil pump, to activate the RFF, and shuts off the oil supply to deactivate and drain pressure from the RFF. However, it is desirable that in RFF-deactivation mode the oil supply not be completely shut off, as other components of the valve train, such as camshaft lobes and rocker arms, continue to require flow of oil for lubrication.
U.S. Pat. No. 6,904,937 discloses a piloted spool-type valve that is switchable not simply between on and off modes but also between a pressure high enough for RFF activation and a controlled pressure sufficient for lubrication but insufficient for RFF activation. A piloted spool-type valve requires two spools to function; a regulating spool and a pilot spool. The regulating spool controls a relatively high flow of working fluid through the valve by being axially displaced in the valve. A high force is required to axially displace the regulating spool because of the high hydraulic force acting on the regulating spool as a result of the high flow of working fluid being directed by the regulating spool. The force required to axially displace the regulating spool is higher than can practically be supplied by a mechanical actuator. The pilot spool is therefore provided to be axially displaced in the valve in order to direct a low flow of working fluid which in turn axially displaces the regulating spool. A mechanical actuator can provide the force needed to axially displace the pilot spool in the valve since the pilot spool is subjected to a smaller hydraulic force from the working fluid because of the low flow of working fluid being directed. While a piloted spool-type valve works well in an application with a relatively high flow requirement, a piloted spool-type valve adds unnecessary complexity and expense when used in an application that has lower flow requirements and thus produces lower hydraulic forces on the regulating spool.
What is needed is a simpler, direct-acting, i.e. non-piloted, oil control valve assembly that is switchable not simply between on and off modes but also between a pressure high enough for RFF activation and a controlled pressure low enough for lubrication but insufficient for RFF activation.
Briefly described, the present invention provides a valve assembly having a housing with a longitudinal bore. The bore receives working fluid from a working fluid source through a supply port, sends working fluid to and from a working device through a control port, and returns working fluid to the working fluid source through a vent port. A spool slideably disposed in the longitudinal bore controls the flow of working fluid between the supply port and the control port and between the control port and the vent port. An actuator assembly moves the spool axially within the longitudinal bore in order to select the desired valve mode of high pressure mode, pressure relief mode, or pressure regulating mode. A solenoid of the actuator assembly produces linear motion and a connecting rod structurally separate from the spool mechanically transmits linear motion from the solenoid to the spool when switching from at least one of the valve modes to another of the valve modes. A pressure regulating spring may be provided to bias the spool away from the actuator assembly.
When high pressure mode is selected, the spool is positioned in the longitudinal bore such that the control port is not in fluid communication with the vent port while the supply port is in fluid communication with the control port. High pressure mode allows full pressure from the working fluid source to be applied to the control port.
When pressure relief mode is selected, the spool is positioned in the longitudinal bore such that the supply port is not in fluid communication with the control port while the control port is in fluid communication with the vent port. Pressure relief mode causes pressure to be relieved from the control port. When this happens, the working fluid is allowed to flow to the vent port and back to the working fluid source.
When pressure regulating mode is selected, the spool is positioned in the longitudinal bore such that the control port is not in fluid communication with the vent port while the supply port is in fluid communication with the control port such that fluid at the control port is regulated to a pressure that is less than pressure at the supply port.
Further features and advantages of the invention will appear more clearly on a reading of the following detail description of the preferred embodiment of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings.
This invention will be further described with reference to the accompanying drawings in which:
In accordance with a preferred embodiment of this invention and referring to
Spool 30 is slideably disposed in longitudinal bore 18 for controlling the flow of working fluid between supply port 20 and control port 24, the flow of working fluid between control port 24 and vent port 28, and the pressure at control port 24. Actuator assembly 14 is used to selectively alter the axial position of spool 30 in longitudinal bore 18 in order to achieve a valve mode selected from the group of high pressure mode (
Pressure regulating spring 36 is provided to bias spool 30 away from actuator assembly 14. Pressure regulating spring 36 is grounded by pressure regulating spring stop 38 and is disposed between spool 30 and pressure regulating spring stop 38. In a first embodiment, as shown in
Return spring 40 may be provided to bias connecting rod 34 away from spool 30. Return spring 40 is disposed between pressure regulating spring stop 38 which is fixed to housing 16 and return spring stop 42 which is fixed to connecting rod 34. Return spring 40 will be discussed further when the operation of valve assembly 10 is described.
Spool 30 is provided with vent land 44 which is dimensioned to be in close running tolerance with first end 46 of longitudinal bore 18. Vent land 44 substantially prevents working fluid from being communicated directly to vent port 28. An insignificant amount of working fluid may leak past vent land 44 from supply port 20 to vent port 28 while still considering vent land 44 to substantially prevent working fluid from being communicated directly to vent port 28.
Spool 30 is further provided with inlet annulus 48 which is adjacent vent land 44 and which is in fluid communication with supply port 20. Inlet annulus 48 is dimensioned to be smaller in diameter than vent land 44.
Spool 30 is further provided with intermediate land 50 which is adjacent inlet annulus 48 and which is dimensioned to be in close running tolerance with intermediate portion 52 of longitudinal bore 18. Intermediate land 50 substantially prevents working fluid from being communicated from supply port 20 to control port 24 when in pressure relief mode (
Spool 30 is further provided with spool metering edge 51 which is formed by inlet annulus 48 and intermediate land 50. More specifically, spool metering edge 51 is the intersection of intermediate land 50 and the surface connecting the dissimilar diameters of inlet annulus 48 and intermediate land 50.
Spool 30 is further provided with pressure regulating annulus 54 which is adjacent intermediate land 50. Pressure regulating annulus 54 is dimensioned to be smaller in diameter than intermediate land 50.
Spool 30 is further provided with pressure regulating shoulder 55 which is formed by intermediate land 50 and pressure regulating annulus 54. More specifically, pressure regulating shoulder 55 is the surface connecting the dissimilar diameters of intermediate land 50 and pressure regulating annulus 54.
Spool 30 is further provided with pressure relief land 56 which is adjacent pressure regulating annulus 54 and is dimensioned to be larger in diameter than pressure regulating annulus 54 and in close running tolerance with second end 58 of longitudinal bore 18. The function of the various elements of spool 30 will be discussed further when the operation of valve assembly 10 is described.
Longitudinal bore 18 is provided with working annulus 60 formed by enlarged portion 62 of longitudinal bore 18. Working annulus 60 is located between first end 46 of longitudinal bore 18 and second end 58 of longitudinal bore 18.
Longitudinal bore 18 is further provided with bore metering edge 64 of longitudinal bore 18 which is formed by intermediate portion 52 of longitudinal bore 18 and working annulus 60. More specifically, bore metering edge 64 is formed by the intersection of intermediate portion 52 and the surface connecting the dissimilar diameters of working annulus 60 and intermediate portion 52.
Longitudinal bore 18 is further provided with high pressure shoulder 66 which is formed by working annulus 60 of longitudinal bore 18 and second end 58 of longitudinal bore 18. More specifically, high pressure shoulder 66 is the surface connecting the dissimilar diameters of working annulus 60 and second end 58. The function of the various elements of longitudinal bore 18 will be discussed further when the operation of valve assembly 10 is described.
In operation, and now referring to
In operation, and now referring to
In operation, and now referring to
Pressure regulating spring 36 is selected to provide a spring force that will regulate the pressure at control port 24 to a desired level. As working fluid is used to lubricate working device 26, the pressure at control port 24 decreases. This decrease in pressure at control port 24 allows spool 30 to be displaced further away from actuator assembly 14 under the force of pressure regulating spring 36. As spool 30 is displaced, the distance between spool metering edge 51 of spool 30 and bore metering edge 64 of longitudinal bore 18 becomes greater and therefore provides a smaller pressure differential between supply port 20 and control port 24. However, as the pressure increases at control port 24 due to the smaller pressure differential, working fluid will react against pressure regulating shoulder 55 to counteract the force of pressure regulating spring 36 to prevent spool 30 from being displaced too far and thereby preventing too great of a pressure at control port 24. In this way, pressure is regulated at control port 24.
In accordance with a second preferred embodiment of this invention, and now referring to
While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.
