Patent Application
20140311433
Not applicable.
The present invention relates to a device and method for the actuation of a valve of a combustion chamber of an internal combustion engine, independently of mechanical movement within the engine and without a camshaft.
The majority of existing internal combustion engine designs rely on mechanical means to open and close intake and exhaust valves. Other types of actuators have been proposed for years based on the concept that variable valve actuation independent of engine operation could overcome inherent compromises and inefficiencies in cam driven (mechanical) operation. The present invention addresses these compromises in engine operations and offers increased flexibility for the engine designer and increased efficiency in operation.
Inherent inflexibility in valve train operation has usually meant that completely different parts had to be installed to change engine valve operation. Some benefits of variable valve timing and lift are seen in mechanical designs that provide variable mechanical actuation determined by load or engine speed. These have become popular but still present a very limited option (usually 2 or 3 configurations) compared to actuating the valves independent of engine operation. The present invention provides a broader selection of operating parameters approaching a continuously variable design.
Other inventions in the field include electromechanical, hydraulic and pneumatic systems, although these have usually been supplemented by mechanical return springs which retain many of the other limitations of the primarily mechanical designs. These limitations include high stresses at low rpm in order to meet high rpm needs, inherent harmonic oscillations that can cause valve ‘float’ under some conditions, elastic failure in which springs ‘relax’ over time and perform less well with age—regardless of usage. A pneumatic valve return system was adopted for Formula I racing cars which still relied on mechanical (cam) valve activation and suffered from failure modes not seen in other systems. The present invention addresses these limitations while providing unique upgrade and customization paths.
The present invention is directed to a valve actuator for controlling the movement of a valve of an internal combustion engine, the actuation device comprising: a double acting actuator piston or diaphragm, contained within a cylinder closed at each end so as to form two chambers of inversely variable volume, mechanically affixed to the valve stem so as to control the position of the valve via chamber-pressure differential, directly or through a lever arm, and an electronically controlled fluid circuit for controlling the inlet and outlet of pressurized fluid to both chambers formed by the actuator piston or diaphragm and cylinder. The method for controlling the movement of the actuator piston by controlling the pressures and timing of the pressure changes will permit variable valve actuation: timing, duration, and lift. The method of controlling valve actuation with programmable variables will permit engine designers and tuners to tailor engine performance specifications while providing a convenient method for maintenance upgrades. These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and claims.
Further characteristic features and advantages of the invention are set out in the following detailed description, given purely by way of non-limiting example and made with reference to the accompanying drawings, in which:
In referring to the diagrams, the following terms will be used for brevity and clarity but are not meant to limit the scope of the claims: fluid is a liquid or gas such as hydraulic fluid or air, a spool is a flow control device such as a poppet valve or pneumatic spool or hydraulic spool for communicating fluid flow and pressure, a check valve is a one-way check valve or an adjustable pressure regulating device in combination with a one-way check valve, a piston is a piston or a diaphragm, a valve is an intake or exhaust valve of a combustion chamber of an internal combustion engine.
Referring to
The double acting actuator piston 11 is displaceably arranged within an actuator cylinder 12 so as to separate chambers 13 & 14, and is manufactured such that leakage between the opposing chambers 13 & 14 can be controlled (sealed) while allowing the necessary movement to double-actuate (open and close) the valve 15. The actuator piston 11 is mechanically attached, primarily directly or alternately through a lever arm (commonly known as a rocker arm), to the valve stem 15a so as to move the valve 15 within the valve guide 16.
In construction, the actuator cylinder 12 and chambers 13 & 14 are formed in a housing that may be a cast-in-place part of the engine head or mechanically fastened in place. The housing has an inlet 16 and an outlet 17 for the upper chamber 13 and an inlet 18 and an outlet 19 for the lower chamber 14 either as part of the housing, within end-cap 10, or a combination. In addition, the housing and/or end cap(s) may provide for mounting pressure and/or flow control devices as described below, and connecting supply 20b and exhaust 21b manifolds. In an alternate embodiment, the chambers are connected to auxiliary chambers or manifolds to provide for pressure storage.
The upper chamber inlet 16 pressure control consists of two spools 20, which function as an ‘and gate’, actuated independently by bistable electronically controlled solenoids 20a. As a alternate embodiments, the upper chamber inlet 16 pressure control can be of the spring return type and/or a single spool actuated by an electronically controlled solenoid. The upper chamber inlet pressure is supplied from a pressure regulated supply manifold 20b in the preferred embodiment.
The upper chamber outlet 17 pressure relief consists of a single spool 21 moved by an electronically actuated solenoid 21a. Alternately, the upper chamber outlet 17 pressure relief can be two spools, which function as an ‘and gate’, actuated independently by bistable electronically controlled solenoids. The upper chamber outlet pressure is exhausted to a pressure regulated exhaust manifold 21b in the preferred embodiment.
The lower chamber inlet 18 pressure control consists of a check valve 22, connected to the pressure regulated supply manifold 22b (alternately, a separate pressure regulator and/or manifold may be used). Alternately, the lower chamber inlet 18 pressure control can be a single spool actuated by an electronically controlled solenoid (not shown).
The lower chamber outlet 19 pressure relief consists of a check valve 23, connected to the pressure regulated exhaust manifold 23b, to the atmosphere, or to other suitable outlet. Alternately, the lower chamber outlet 19 pressure relief can be a single valve or spool actuated by an electronically controlled solenoid.
As shown in
The bistable solenoids 20a and 21 a are triggered by an electronic control circuit consisting of a microprocessor, various inputs and sensors, shift registers (optional for small systems), H-bridge controller circuits or ICs and the connectors, power supplies, switches, relays, and the necessary circuitry and parts to connect, regulate, and protect these components. To implement the interactive features of a programmable system, additional interface connections (OBDII, USB, or equivalent, or wireless) are required, as is a program to allow programming, configuring, and I/O with, the microprocessor.
Referring to
Referring to
More specifically, the upper chamber inlet spools 20 can be controlled through an ‘and gate’ of two independently operated bistable solenoids 20a to independently and variably control valve 15 timing, duration and lift, using the following preferred method: Valve 15 timing and duration are controlled by the timing of the triggering of the inlet solenoid (pair) 20a and outlet solenoid 21a of the upper chamber 13. Signal processing and inertial movement delays within the system—typically on the order of a few milliseconds, as well as engine crankshaft angle and rotational speed, are used to calculate solenoid 20a & 20b control trigger signal generation. Discrete signals to the pair of inlet solenoids 20a control charge-pulse duration (therefore volume and pressure) and offset signal timing can control valve 15 lift. For required charge-pulse durations equal to or longer than solenoid movement duration (on the order of 5 ms), the primary solenoid 20a (currently ‘closed’) is triggered with or prior to the secondary solenoid 20a (currently ‘open’). For shorter required charge-pulse durations (and lower valve 15 lift), the secondary solenoid 20a is triggered prior to the primary solenoid 20a, thus allowing shortening of the charge-pulse duration to as short as the signal switching repeatability limits (on the order of 0.5 ms). In the preferred embodiment the upper chamber outlet spool 21 can be accurately controlled by a single solenoid 21a since the outlet 17 bleed-pulse duration is not as critical as the inlet 16 charge-pulse duration and the outlet pressure is suitably controlled by the exhaust manifold 21b, valve 15 closure ‘lift’ being constant 0.
The adjustment to the lower chamber low pressure is through a one-way check valve 22, in which supply pressure can pass through the one-way check valve 22 when the lower chamber low pressure falls below a determined level. The adjustment to the lower chamber high pressure is through a one-way check valve 23 when the lower chamber high pressure exceeds a determined level. The preferred embodiment is for both of the one-way check valves 22 & 23 to be attached to pressure adjustable manifolds, thereby allowing dynamic adjustment during engine operation.
The timing of valve 15 operation can be altered to enable smooth low rpm operation (later intake pulse and decreased valve overlap) and efficient high rpm operation (earlier intake pulse and increased valve overlap) with an almost continuous transition. The duration and lift of valve 15 operation can be altered to meet low demand (short duration, small lift) and high demand (long duration, large lift) with an almost continuous transition. In addition, unique combinations are available with this system: some valves 15 (and thereby, combined with temporary fuel and possibly ignition spark cutout, some combustion chambers) can be temporarily non-actuated, allowing the engine to behave as one of smaller displacement operating at increased air-flow (higher efficiency during low demand operation); some valves 15 timing can be staggered within an engine cylinder to promote fuel-air swirl; some valves 15 can be actuated or non-actuated to allow engine cylinders to behave as two valve 15 or four valve 15 arrangements to meet varying operating parameters. An increase in efficiency is expected due to removal of the throttle plate, varying valve duration and lift to control fuel-air induction, thereby reducing pumping losses through the engine.
An orifice restricted upper chamber exhaust muffler (not shown) may be incorporated to provide a ‘soft seat’ for valve 15 closure. Mechanical methods of softening the impact (so called ‘bump stops’) at piston 11 travel limits may be used as well. Although the primary embodiment uses both of these braking methods to reduce noise and mechanical wear, some (or all) applications may function normally without this ‘braking’ or may use a substitute method.
Referring to
The preferred embodiment uses a continuously replenished pneumatic (air) supply and exhaust system for speed of operation and low cost construction. One alternate embodiment could use hydraulic fluid as the upper chamber 13 circuit fluid, although this would require changes to the seals and pressure system, and the use of a recovery and storage system.
A limitation of the present invention is leak-down over time. Although some leak-down is unavoidable and easily dealt with, a seal failure or engine start after a long delay could lead to engine damage due to piston-valve interference. There are two strategies for dealing with this potential: Primarily, the device can be restricted to use in non-interference engines. The decrease in power and efficiency can be more than recouped by turbo-charging the engine intake system. Since this is common and inherently increases efficiency it is the preferred embodiment. Secondly, the system can incorporate safety pumps and latches to prevent piston-valve strike under normal operation, including startup. For system reliability it is anticipated that some form of monitoring system, most likely one or more pressure sensors, will be incorporated into the electronic and/or fluid circuits. For non-interference engines, a maintenance mode may be programmed that when selected will allow the valves to operate as if the crankshaft was turning in order to check for proper operation.
The present invention may provide all or some of the benefits described above, depending on the specifications (both mechanical and electronic) as implemented. Not all of the benefits will be realized for all applications and failure to provide a desired benefit in any particular application or combination of applications should not be interpreted to limit the scope of the claims made.
Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, it is understood that other alternates and equivalents of each of the above embodiments are within the scope of the invention. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained therein. Accordingly, all such modifications are intended to be included within the scope of the invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.
Provisional application No. 61/637,207 filed Apr. 23, 2012.
