Added motion hydraulic circuit with proportional valve

A hydraulic circuit comprises a temperature sensor, an added motion valve system, and a valve. The temperature sensor detects operating temperature of fluid in the hydraulic circuit. The added motion valve system includes a valve body having an actuator fluid volume. The valve adjusts flow rate quantity of fluid to the actuator fluid volume as a function of the operating temperature of the fluid. A method for controlling the hydraulic circuit is also disclosed.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to a system that provides a delayed closing movement for an engine valve of an internal combustion engine, including a system that provides controlled engine valve seating and controlled added motion closing movement for a valve over a wide range of fluid temperatures/viscosities.

BACKGROUND

It is known in the art that a cam system, which may include, for example, a cam shaft and rocker arm, can be employed to open and close a valve of an internal combustion (IC) engine. An example of a standard cam profile engine valve opening/closing curve300ais generally shown inFIG. 3.

The timing of engine valve closure during an IC engine's induction stroke may be varied to, among other things, optimize the performance of the engine. Variable valve timing in the closing of the engine valve can be accomplished by, for example, employing a hydraulic force actuator that counteracts the closing force of the valve spring. As generally illustrated inFIG. 3, the delayed closing movement of the engine valve (generally represented in the Figure by301) is often referred to as an “added motion.”

Although current added motion systems can provide a desired delayed closing movement of a valve, temperature and viscosity variations of an associated fluid, such as, for example, engine oil, may result in an inconsistency in the timing of the closing of the engine valve.FIG. 3generally illustrates a seating variation (shown generally by segment403).

Accordingly, a need exists to provide an added motion system that can provide controlled engine valve seating and controlled added motion closing movement to a valve over a wide range of fluid temperatures and/or viscosities.

DETAILED DESCRIPTION

FIG. 1generally illustrates an embodiment of the invention with a hydraulic circuit10in fluid communication with a plurality of added motion valve systems100. The hydraulic circuit10includes a sump12associated with fluid11; a pump14; a fluid temperature sensor16; one or more check valves18; one or more main valves20; a proportional valve22including valve flow orifices24; and a controller26. The main valve20and proportional valve22may comprise a solenoid valve and, in the illustrated embodiment, such valves are shown including springs28,30and single solenoids32,34. While the valves20,22are shown as spring-offset single-solenoid valves, it will be appreciated that the valves20,22may take on other desirable valve configurations. For example, the valves20,22may instead comprise a dual-solenoid having any desirable fluid flow path, such as, for example, a single flow path or a parallel flow path. A pressure regulator is shown generally at50. The pressure regulator50controls the pressure of the fluid11to the circuit10as provided by the pump14.

An embodiment of an added motion valve system100, including a cam system75, is generally illustrated inFIG. 2. The illustrated cam system75generally includes a camshaft77, rocker arm79, and rocker arm roller81. The valve system100is generally shown to include, among other things, an added motion valve body102having a bore104; a piston106; an engine valve108; an engine valve spring110; and an actuator112, which is generally defined by a first port36, a second port38, the valve body102, and piston106. The actuator112permits movement of fluid11from the valves20,22of the hydraulic circuit10(FIG. 1) to an actuator fluid volume114of the bore104.

Referring toFIG. 1, the proportional valve22may be controlled by applying current to an associated solenoid34. If the current is less than the amount of current needed to operate the solenoid34, the current may be amplified by an amplifier card (not shown). If included, such an amplifier card can be mounted on, or, instead may be located remotely from the proportional valve22. As current flows through a coil (not shown), an electromotive force is developed, causing an associated armature or push pin (not shown) to move, which, in turn, inputs a force to a valve spool (not shown), thereby causing the valve spool to travel. With such a configuration, the valve spool will typically continue in motion until the solenoid force is balanced by a return spring force. Accordingly, valve spool travel can be made relative (i.e., proportional) to the amount of current passing through the coil of the solenoid34.

Referring toFIGS. 1 and 2, the operation of an added motion valve systems100is discussed in connection with a hydraulic circuit10. In operation, the valves20,22of the hydraulic circuit10can improve operation of the added motion valve system100over a wide range of temperatures/viscosities associated with fluid11. In the illustrated embodiment, fluid11is fed by pump14to valves18,20, and22when the valve system100is opened. When the valve system100is closed, fluid11is returned to sump12. For purposes of simplicity, the fluid feed line is generally shown designated as P and the fluid return line is generally shown designated as T.

InFIG. 1, the temperature of fluid11from a pump14is sensed by a fluid temperature sensor16. The fluid11is delivered to a main valve20over a fluid passage13,15. The main valve20feeds fluid11to a first port36through a fluid passage17,19. The temperature of fluid11from the pump14is sensed by fluid temperature sensor16. The fluid is then passed to a proportional valve22over a fluid passage21. The proportional valve22feeds fluid11to a second port38through a fluid passage23,25. Fluid11from the pump14is also sensed by the fluid temperature sensor16as it passes to a check valve18over a fluid passage27,29. The check valve18feeds fluid11to the second port38through a fluid passage31,33.

According to an embodiment, the proportional valve22serves as a seating valve for seating an engine valve108when fluid11is being pumped out of actuator volume114at a second port38. The check valves18can feed fluid11to the second port38when the main valve20is in a closed position. Accordingly, the primary purpose of the check valves18is to more easily fill the actuator volume114, especially at low engine operating temperatures. Thus, in operation, the first port36is closed off when an engine valve108is in the closed position or when the engine valve is seated as the second port38is always exposed to the actuator volume114.

In such an arrangement, when the proportional valve22seats the engine valve108, the proportional valve22may function as a slow speed valve (i.e., the valve22doesn't have to respond for every cycle of the cam mechanism), for example, one having a 10-to-20 milli-second closing rate. If desired, a valve flow orifice24may be adjusted to compensate, at least in part, for different oil viscosities resulting from different fluid operating temperatures to provide more consistent seating303and delayed movement/locking401of an engine valve108. For example, in Winter, a vehicle may be called upon to start when the ambient temperature is −40° F. Accordingly, the fluid temperature sensor16may detect the operating temperature of the fluid11from the pump14, which is then provided to the controller26(e.g., over communication line35). For instance, the controller26can then provide a signal to the proportional valve22over communication line37to increase the opening of the orifice24to compensate for a decreased flow rate quantity Qfof fluid11(i.e., due to low fluid viscosity) from a second port38. As the temperature of fluid11rises (i.e., as the viscosity of the fluid11rises), the temperature sensor16provides a temperature signal to the controller26(e.g., over communication line35) so that the controller26may command the proportional valve22(over line37) to decrease the opening of the orifice24to, at least in part, compensate for a increased flow rate quantity Qfof fluid11from a second port38. Accordingly, the temperature sensor16can function as a feedback link in a closed-loop control system for controlling the fluid11delivered to the valve system100in view of changes in operation temperature/viscosity associated with fluid11.

The main valve20can be designed as a high speed valve (i.e., the valve20may have to operate for every cycle of the cam mechanism) that may default to an open state, but, given a directional control of fluid from the check valve18, main valve20may be closed during or prior to an engine valve108opening stroke. The open state of the main valve20can, among other things, provide a fail-safe feature to the operation of the valve system100. If the main valve20is moved from an open state to a closed state, the movement to the closed state can be accomplished gradually (e.g., to one having a closing rate of 10-to-15 milli-seconds), and, when the valve is returned to the open state, the opening rate can be sped up (e.g., to a time of 1-to-2 milli-seconds).

An added-motion engine valve opening/closing curve300baccording to an embodiment is shown generally as300binFIG. 3. A main valve20is primarily responsible for the control of the flow of fluid11from one or more actuators112for delaying the closing movement of one or more associated engine valves (e.g., as shown generally at segment301of the added-motion curve300b). A proportional valve22is primarily responsible for the control of the flow of fluid11from one or more actuators112for seating an engine valve (e.g., as shown generally at segment303) during the closing movement of such valve. The main valve20, as explained above, may be closed (at any time during the time period generally designated as T1) but can be configured to open quickly (at any time during the time period generally designated as T2) to provide a controlled location for a closing movement associated with an engine valve (e.g., which is shown generally designated as segment302). If a main valve20is closed during the opening movement of an associated engine valve, which is shown generally designated as segment304, the check valve can then provide flow of fluid11to second port38.

Accordingly, because the temperature may affect the viscosity of the fluid11, a valve flow orifice24of a proportional valve22may be varied accordingly in view of the sensed operating temperature of the fluid11detected by a temperature sensor16. As such, variations of the viscosity of the fluid11that could result in an inconsistency of the seating403and/or an inconsistency with a delayed closing movement401of an engine valve can be reduced or eliminated.

The present invention has been particularly shown and described with reference to the foregoing embodiments, which are merely illustrative of the best mode or modes for carrying out the invention. It should be understood by those skilled in the art that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention without departing from the spirit and scope of the invention as defined in the following claims. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.