|Publication number||USRE40439 E1|
|Application number||US 11/583,382|
|Publication date||Jul 22, 2008|
|Filing date||Oct 18, 2006|
|Priority date||Nov 2, 2001|
|Also published as||US6805079|
|Publication number||11583382, 583382, US RE40439 E1, US RE40439E1, US-E1-RE40439, USRE40439 E1, USRE40439E1|
|Inventors||Diana D. Brehob, Eric Warren Curtis, William Francis Stockhausen|
|Original Assignee||Ford Global Technologies, Llc|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (2), Classifications (11), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention relates generally to a method for controlling electromechanical valves in an internal combustion engine.
2. Background of the Invention
An electromechanically operated poppet valve in the cylinder head of an internal combustion, as disclosed in U.S. Pat. No. 4,455,543, is actuated by energizing and de-energizing electromagnets acting upon an armature coupled to the poppet valve. Because the actuation of the electromagnets is controlled by an electronic control unit, valve opening and closing events occur independently of engine rotation. In conventional engines with camshaft actuated valves, which have timings based on engine rotation, air delivery to the cylinders is controlled by a throttle valve placed in the inlet duct of the engine. In contrast, electromechanical valves are capable of controlling air delivery based on valve timing, thereby providing a thermal efficiency improvement over throttled operation of a conventional engine.
However, a drawback to electromechanical valves is the amount of electrical energy consumed in actuating them. The inventors of the present invention have recognized a method to operate electromechanical valves in a manner which consumes less electrical energy than prior methods.
Disadvantages of prior methods are overcome by a method for actuating an intake valve disposed in a cylinder head of an internal combustion engine by an electromagnetic valve apparatus. The apparatus has a valve closing electromagnet capable of exhibiting an electromagnetic force for attracting the armature to close the valve, a valve opening electromagnet capable of exhibiting an electromagnetic force for attracting the armature to open the valve, a valve opening spring for biasing the armature in a direction to open the valve, and a valve closing spring for biasing the armature in a direction to close the valve. The method includes the steps of actuating the valve according to a first mode when a first set of engine operating conditions are detected and actuating the valve according to a second mode when a second set of engine operating conditions are detected. The first mode further includes the steps of de-energizing the valve closing electromagnet, maintaining the valve closing electromagnet in the de-energized state for a first predetermined time enabling the valve to oscillate by force of the valve opening spring and the valve closing spring, and energizing the valve closing electromagnet after the first predetermined time to close the valve. The second mode further includes the steps of de-energizing the valve closing electromagnet to allow the valve to open, energizing the valve opening electromagnet in response to said de-energizing step to attract the armature to the valve opening electromagnet thereby causing the valve to open, de-energizing the opening electromagnet after a second predetermined time has elapsed since the valve opening electromagnet has been energized, and energizing the valve closing electromagnet in response to the de-energizing step of the valve opening electromagnet to attract the armature to the valve closing electromagnet thereby causing the valve to close.
An electromagnetic valve apparatus for actuating a valve disposed in a cylinder head of a multi-cylinder internal combustion engine is disclosed which has an armature operatively connected to the valve, a valve closing electromagnet capable of exhibiting an electromagnetic force for attracting said armature to close the valve, a valve opening spring coupled to the armature for biasing the armature in a direction to open the valve, a valve closing spring coupled to the valve for biasing the valve to a closed position, and an electronic control unit operably connected to the valve closing electromagnet. The electronic control unit de-energizes the valve closing electromagnet allowing the valve to oscillate by force of the valve opening spring and the valve closing spring and maintains the valve closing electromagnet in the de-energized state at least until the valve travels to a nearly open position and returns to a nearly closed position. The predetermined time is based on dynamic characteristics of the valve and the electromagnetic valve apparatus. The valve is an intake valve of the engine. Intake air flows past an oscillating intake valve.
A primary advantage of the present invention is that the amount of energy utilized in actuating a valve is approximately half of prior art actuation methods.
According to an aspect of the present invention, the valve may be opened for a period of time over which the valve oscillates between a nearly open position and a nearly closed position. Compared with prior methods in which the valve is maintained in a fully open position for the entire duration of opening, the present invention provides more intake turbulence to the incoming air stream by virtue of the air being inducted past an intake valve which is at a half open position, on average.
The advantages described herein will be more fully understood by reading an example of an embodiment in which the invention is used to advantage, referred to herein as the Detailed Description, with reference to the drawings wherein:
Continuing to refer to
Continuing to refer to
Before discussing aspects of the present invention, an example of prior art control of an electromechanical valve is described. Typically, a valve, whether an intake or exhaust valve, of an internal combustion engine is normally closed, i.e., the valve is in the closed position for more of the time than the open position. Thus, the description of valve opening begins with a closed valve, i.e., with a holding current be applied to valve closing electromagnet 32. Actuating the valve proceeds by: de-energizing valve closing electromagnet 32 which causes the valve to open under the influence of valve opening spring 36; applying a peak current to valve opening electromagnet 28 to grab armature 30 when it is near its fully open position; applying a holding current to valve opening electromagnet 28 after armature 30 is attracted to valve opening electromagnet 28); applying holding current for as long as the desired open duration of the valve; de-energizing valve opening electromagnet 28 which causes the valve to close under the influence of valve spring 24; and, applying a peak current to valve opening electromagnet 32 to grab armature 30 when it is near its fully closed position. The terms peak current and holding current are concepts known to those skilled in the art and refer to a higher current level (peak current) used to catch a moving armature 30 and a lesser current (holding current) used to prevent a stationary armature 30 from moving.
The neutral position, i.e., the position that valve 20 attains when both electromagnets 28 and 34 are de-energized, is about halfway between the fully closed position,
As mentioned above, the power consumption in performing a valve catching, i.e., applying the peak current, is the predominant energy consuming function. In performing one cycle of valve open and close, prior art methods perform two such valve catching events:
valve grabbing near the fully open position and valve grabbing near the fully closed position. The present invention, in contrast, performs only one valve catching event, valve grabbing near the closed position. As a consequence, about a 50% electrical energy savings in electromechanical valve actuations is realized by practicing the present invention.
The valve lift profiles and open duration provided by prior art are quite different from the present invention and are illustrated in FIG. 5. In the upper graph of
Comparing the valve profile of prior art, upper graph in
When intake valve 20 is operated according to prior art approaches, the amount of air inducted can be determined by controlling the opening and closing time of the valve, as shown in the upper graph of FIG. 5. According to an aspect of the present invention, intake valve 20 is opened at any time; however, the closing occurs at predetermined intervals only. In the example shown in
According to an aspect of the present invention discussed above, closing of the valve occurs based on a number of valve periods or oscillations of the valve, i.e., based on a time. Alternatively, if the valve apparatus is equipped with a valve position sensor, such as a LVDT as shown in
A method of operating an engine according to an aspect of the present invention is shown in FIG. 7. The procedure begins in step 100. Control passes to step 102 in which it is determined how much air, Ma, should be trapped in the cylinder. This is based on driver demand for power. Control passes to step 104 in which it is determined whether the desired amount of air, Ma, can be provided by practicing the present invention. If not, control passes to step 120, in which prior art methods are used. The valve trajectory of prior art is shown in the upper half of FIG. 5 and is described above. From step 120, control returns to step 100, where a determination of valve procedure is determined for the next valve opening cycle. If a positive result in step 104, control passes to step 106 in which the minimum number of valve oscillations that can be used to provide Ma is determined. The minimum number is an integral number and is less than the number of oscillations in which the trajectory of armature 30 fails to attain the minimum valve grabbing distance. Control passes to step 108 in which the timing to initiate valve opening is determined. Constraints placed on the initiation time are that the number of oscillations is that which was found in step 106 and Ma is to be provided to the cylinder. Control is passed to step 110 in which the valve is opened starting at the initiation time found in block 108 and is open for the minimum number of oscillations. Control then returns to block 100.
In the above discussion of determining a valve opening time in step 108, the constraints discussed are the number of valve periods or oscillations over which the valve is open and providing the desired air, Ma.
Alternatively, the opening time could be constrained by a desired turbulence level of the inducted gases or a desired level of exhaust gases to trap in the cylinder. These alternative constraints could preferably be used in lean burn engines, that is, engines in which the amount of air delivered to the cylinder is more than that for fully combusting the fuel that is supplied to the cylinder.
While several modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize alternative designs and embodiments for practicing the invention. The above-described embodiments are intended to be illustrative of the invention, which may be modified within the scope of the following claims.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|US8985074||Apr 22, 2013||Mar 24, 2015||Eaton Corporation||Sensing and control of a variable valve actuation system|
|US20130312506 *||Apr 22, 2013||Nov 28, 2013||Eaton Corporation||Systems, methods, and devices for valve stem position sensing|
|U.S. Classification||123/90.11, 123/90.15, 251/129.07, 123/90.24|
|International Classification||F01L9/04, F02B1/12|
|Cooperative Classification||F01L2009/0436, F02B1/12, F01L2009/0469, F01L9/04|