Electromagnetic-positioning system for gas exchange valves

An improved actuator assembly for an electromagnetically-actuated spring-loaded positioning system in displacement machines, such as for lifting valves in internal combustion engines. The positioning mechanism has a spring system and two electrically-operated, opposed actuating solenoids, by means of which the actuator may be moved between, and held at, two discrete, mutually-opposite operating positions. The improved actuator assembly of the invention comprises an actuator anchor plate secured to a guide rod which reciprocatingly engages a guide sleeve. The guide rod is moved back and forth by solenoids acting on the anchor plate, and comes into contact with a separate valve stem, by means of which the valve is opened and closed. The required tolerances for (a) the guideway for the valve stem, and (b) the guideway for the guide rod operating inside the electromagnetic unit, may thus be separately evaluated and selected. The separate guide rod and valve stem arrangement permits precise adjustment of valve travel. The entire positioning system is constructed as an easily replaceable module in its own housing unit.

FIELD 
The invention concerns an improved actuator assembly for 
electromagnetically-actuated positioning systems for spring-loaded 
reciprocating actuators in displacement machines, such as for lifting 
valves of internal combustion engines. The positioning mechanism has a 
spring system and two electrically-operated, opposed actuating solenoids, 
by means of which the actuator may be moved between, and held at, two 
discrete, mutually-opposite operating positions, valve open and valve 
closed. The improved actuator assembly of the invention comprises an 
actuator anchor plate secured to a guide rod which reciprocatingly engages 
a guide sleeve. The guide rod carries a tappet member that contacts the 
end of the valve stem rod. The valve stem end is spaced apart from the 
guide rod in the valve closed position. The guide rod is axially 
adjustable, thereby permitting precise control of valve travel. 
BACKGROUND 
A similar system is known from DE-OS No. 30 24 109. 
This known device shows a gas exchange valve for an internal combustion 
engine, the stem of which is joined to the valve disk and has an anchor 
plate which is alternatingly attracted to two actuating solenoids, causing 
the valve to open or close. This anchor plate is directly attached to the 
valve stem. 
As the accuracy of anchor plate guidance between the solenoids must be 
relatively high, precise guidance of the valve stem is necessary. Problems 
may be encountered in this regard, particularly with the exhaust valves of 
internal combustion engines, as said exhaust valves are simultaneously 
subject to severe thermal stress. 
Furthermore, assembly of this known device is relatively problematic. 
In the normal operating RPM range of modern engines, the valve actuators 
must change positions frequently, at precise intervals, and their stroke 
must be the full length of intended travel. At the high temperatures and 
frequency of movement, friction due to even slight misalignment or thermal 
expansion of the parts can delay properly timed valve opening and closing, 
increase or reduce valve opening, or hinder complete closing, thereby 
causing reduced engine performance. There is thus a significant need for 
improved valve actuator assembly systems which permit precise valve travel 
adjustment. 
THE INVENTION 
Objects 
It is among the objects of the invention to provide a type-conformable 
device offering relative ease of assembly. 
It is another object of this invention to provide an improved valve 
actuator assembly which is separate from the valve disc and valve stem 
assembly. 
It is another object of the invention to provide an improved system for 
accurately guiding actuator rods of spring-loaded reciprocating actuator 
assemblies in displacement machines, such as are used in conjunction with 
lifting valves of internal combustion engines. 
It is another object of the invention to provide an improved valve actuator 
assembly in which the valve actuator does not come into contact with the 
valve stem in the valve "closed" position. 
It is another object of this invention to provide an improved valve 
actuator assembly which includes actuating and adjusting assemblies in a 
separate housing which is preassembled for ease of mounting over the valve 
stem, and which permits precise and simple adjustment of the valve stroke. 
Still other objects will be evident from the following specification, 
drawing and claims.

Summary 
The objects of the invention are achieved by providing an actuator assembly 
comprising a guide assembly having a guide rod carrying an anchor plate, 
which actuator assembly is not integrally joined to the gas exchange 
valve. Rather, one end of the actuator assembly guide rod acts upon the 
valve stem, from which it is separate, and causes the valve disk to lift 
due to pressure on the valve stem 
Preferred embodiments include: the actuator assembly intermittently moving 
out of contact with the valve stem, particularly when the valve is in the 
closed position; the guide rod being guided with greater accuracy than the 
valve stem; the valve stem being lubricated while the guide rod slides in 
a dry bearing; the entire assembly of actuating and adjusting solenoids, 
spring system and actuator assembly are contained in a preassembled unit 
which slips over the valve stem and is so mounted (by shims or rings 
around bolts) to permit simple adjustment thereof for precise adjustment 
of valve travel; employment of rotatable shim stacks to adjust the valve 
travel; and providing a larger bore for the spring system than for the 
guide sleeve. To permit operation with the lowest possible power 
consumption, the two rods (i.e., guide rod and valve stem) should be 
coaxially mounted. 
The actuator assembly of the invention is particularly suited for 
electromagnetically-actuated positioning mechanisms for spring-loaded 
valve actuator assemblies in displacement machines, such as are used with 
lifting valves of internal combustion engines. The overall positioning 
mechanism has a spring system and two electrically-operated, opposed 
actuating solenoids. By alternately energizing the solenoids, the actuator 
assembly may be moved between, and held (for a predetermined desired 
length of time) at two discrete, mutually-opposite operating positions, 
e.g., valve open and valve closed positions. The positioning mechanism 
also includes an adjusting solenoid which serves to shift the locus of the 
spring system equilibrium from a point centered between operating 
positions to a non-central point. This is accomplished by the adjusting 
solenoid shifting a support which acts as one seat of the spring system. 
The spring support is preferably secured to the guide assembly, either 
guide rod or sleeve. 
The actuator assembly comprises a guide rod and a ferromagnetic anchor 
plate which is positioned between the core faces of the two actuating 
solenoids. One end of the guide rod may be adapted with a tappet member 
which may include a slightly pointed face to contact the valve stem end. 
The other end may be secured to the ferromagnetic anchor plate of the 
adjusting solenoid assembly. For further details of the overall actuator 
system see my copending applications Nos. 532.4004, 532.0006, and 
532.0007, and that of Josef Buchl No. 532.0008, all filed of even date 
hereof, the disclosures of which are incorporated by reference herein. 
In one operating position, the gas exchange valve is preferably fully 
opened by pressure on the valve stem by the actuator assembly guide rod, 
whereas in the other operating position, corresponding to the "closed" 
position of the gas exchange valve, the guide rod is slightly raised away 
from the valve stem, so that the mechanism operates with a slight 
clearance. This ensures a reliably positive closure of the gas exchange 
valve under all conditions of tolerance, including a given amount of 
valve-disk or valve-seat pitting or wear, and lengthening of the valve 
stem by expansion from engine operation heat. 
The system pursuant to the invention also shows particular advantages 
inasmuch as the guideway for the guide rod is separate from the guideway 
for the valve shaft. Allowance is thus provided for the fact that the 
guide sleeve requires extremely accurate guidance, whereas the valve stem 
may be guided with a lower degree of precision and under broader 
tolerances. Deliberately providing overly large tolerances for the 
valve-stem guideway is helpful in engine design precisely due to the fact 
that valves in internal-combustion engines--and particularly exhaust 
valves--are subject to extreme temperature variations. Thus cold play is 
needed to compensate for heat expansion, but this adversely affects 
precise valve adjustment. Pursuant to the invention, the 
necessarily-accurate guide-rod guidance can be ensured independently of 
the valve-stem loose tolerance requirements. 
It is thereby possible to provide oil lubrication for the valve stem, while 
the guide rod travels in a dry bearing. 
A valve actuator assembly unit (composed of a portion of the spring system, 
actuating solenoids, guide rod and guide sleeve) is particularly easy to 
assemble. This system may be installed in a housing forming the actuator 
unit module, and, as required, repair is accomplished by module 
replacement. For assembly, the gas exchange valves and the valve portion 
of the spring system are installed in the cylinder head, uponn which the 
preassembled, complete housing, containing the required components, may be 
directly mounted and bolt-fastened. The complicated assembly of the 
valve-actuating mechanism directly on the engine may thus be eliminated. 
In a preferred embodiment, the annular actuating solenoids form a 
cylindrical cavity or bore housing the spring system. The guide rod 
follows an axial path in the direction opposite the valve disk. The upper 
end of the guide rod fits into a guide sleeve housed in a bore surrounded 
by an adjusting solenoid. The adjusting solenoid acts to shift the 
position of equilibrium of the spring system, which may be as described in 
DE-OS No. 30 24 109. As the bore diameter is smaller in the region of the 
adjusting solenoid than in the region of the actuating solenoid, 
adjusting-solenoid construction may be wider in diameter, thereby reducing 
the height of the overall unit. 
Valve travel is adjustable in a simple manner by displacing the height of 
the module housing (containing the adjusting solenoid, one actuating 
solenoid, guide rod and guide sleeve) relative to the cylinder head. To 
this end, appropriate shims may be inserted under the bolts at those 
points where the positioning system module is bolted to the cylinder head. 
In some cases this creates a hazard of tilting the positioning system, so 
that the valve stem and the guide rod-anchor plate assembly are no longer 
coaxial. To prevent this tilting, it is preferred to provide an axially 
adjustable ring assembly circumferentially surrounding the entire housing, 
whereby tilt-free mounting of the unit is ensured. 
Instead of a single ring, the adjusting system may comprise one or more 
rings whereby at least two rings present oblique mating surfaces such 
that, when rotated relative to one another, their overall height increases 
or decreases. Valve travel can thus be easily and continuously adjustable 
merely by rotating the rings relative to one another. One example is 
matingly engaging threaded cylinders or rings. 
Detailed Description of the Best Mode of the Invention 
The following detailed description of the best mode of carrying out the 
invention makes reference to the figures, and is by way of example and not 
by way of limitation of the principles of the invention. 
FIG. 1 illustrates a cross-section from the engine block of an internal 
combustion engine. Item 10 indicates the cylinder head. An intake port 12, 
which may be selectively closed with an intake valve 18, leads into 
cylinder bore 16. An exhaust port 14, which may be selectively closed with 
an exhaust valve 20, leads out of cylinder bore 16. Valves 18 and 20 are 
actuated by an electromagnetic positioning system situated in housing 22. 
The unit situated in housing 22 is preferably identical for both intake 
and exhaust valves, in order to reduce the range of parts required. 
Nonetheless, it is possible to match intake and exhaust valve 
characteristics to specific design requirements. It may thus be observed 
in FIG. 1 that the disk of exhaust valve 20 is larger than the disk of 
intake valve 18. 
As there is no theoretical difference between intake and exhaust valve 
construction, the following discussion will refer to the exhaust valve 
only. 
Valve disk 20 is integral with valve stem 24 which slides in valve guide 
26, inserted in cylinder head 10. The end of valve stem 24, indicated as 
Item 28, has a bearing surface which contacts a tappet 40, to be described 
below. 
A flange 30 is circumferentially mounted on the end of valve stem 24 
opposite valve disk 20. Flange 30 acts as a seat for a spring system 
consisting of a large spiral spring 32 and a small spiral spring 34. Both 
spiral springs 32 and 34 are coaxially installed. The opposite spring seat 
36 is formed by a bearing surface in the cylinder head. Valve stem 24 may 
be actuated in valve guide 26 against the loading of springs 32 and 34, 
causing valve disk 20 to rise off its seat and open exhaust port 14. 
An unconnected axial extension to valve stem 24 is formed by actuator rod 
38, the lower end of which is fitted with tappet 40, which makes contact 
with valve stem 26. To open valve 20, tappet 40 contacts end 28 of valve 
stem 26, pushing valve stem 26 to the "open" position of valve disk 20. 
Rod 38 may be in the form of a tubular sleeve 37, which is guided by a 
shaft or tube 39 situated (disposed) in this sleeve. This embodiment is 
illustrated in FIG. 1. Alternatively, as shown in FIG. 2, rod 39 may be a 
shaft or tube guided in a sleeve 70. An annular anchor plate 46, made of 
ferromagnetic material, is joined to actuator rod 38 in the region of 
tappet 40. This anchor plate also supports a spring system consisting of a 
large sprial spring 42 and small spiral spring 44, which are also coaxial 
to one another and to rod 38. 
The seat for this spring system 42 and 44 is formed by a support 48, to be 
described in greater detail below. 
A magnet core 68 having a U-shaped cross-section to form a cup magnet, is 
annularly installed with the axis of the annulus coinciding with the axis 
of valve stem 24. A coil 66 is situated inside magnet core 68. The open 
side (face) of U-sectioned magnet core 68 faces in the direction of anchor 
plate 46. 
Actuator rod 38 is likewise surrounded by a similarly shaped magnet core 
64, inside of which is a coil 62. Depending on energizing solenoids 62 and 
66, anchor plate 46 moves from a contact face on magnet core 64 to a 
contact face on magnet core 68, and back again. 
Also provided is an adjusting solenoid consisting of a magnet core 58 and a 
coil 60. Energizing coil 60 attracts ferromagnetic component 56, which is 
joined to part 54. This movement, caused by energizing adjusting solenoid 
coil 60 and acting on part 54, is transmitted by means of pin 50, placed 
in a cover plate 52, to the spring-system seat formed by support 48, 
whereby energizing adjusting solenoid coil 60 shifts the seat of springs 
42 and 44. 
Pursuant to the invention, a separation is provided between guide rod 
assembly 38, the rod (or tube) 39 of which can slide in a central bore in 
cover plate 52 (FIG. 1), or rod 38 itself slides in sleeve 70 (FIG. 2), 
and valve stem 24, which slides in valve guide 26. As exhaust valve 20 is 
relatively highly heated by escaping, burnt exhaust gases, high demands 
will be placed on the heat resistance of valve guide 26; oil lubrication 
may be provided for the valve guide as needed. 
The demands on the guide sleeve for guide rod 38 are of a different nature. 
Particular attention must be paid to the fact that anchor plate 46 must be 
very accurately guided, as only slight tilting caused by inaccurate 
guidance would impede sliding travel, leading to time lags. At high engine 
speeds, however, the actuating events caused by action of solenoids 62 and 
66 on anchor plate 46 must take place very rapidly, so that the guidance 
for anchor plate 46, determined by guide rod 38 and guide sleeve 52, is 
absolutely critical. 
Pursuant to the invention, both demands may be reconciled by a separation 
of guide rod and valve stem. 
FIG. 2 shows a variant form for guide rod 38, sliding in guide sleeve 70. 
The index numbers refer to the same items as in FIG. 1, but FIG. 2 differs 
in that core 64 of actuating solenoid 62 is separated from core 58 of 
adjusting solenoid 60 by a magnetic gap 72. The term "magnetic gap" 
signifies that said gap 72 presents a magnetic field with the same 
properties as an air gap, and this shows no ferromagnetic properties. The 
gap also presents a resistance to eddy currents. It is therefore not 
necessary for gap 72 to be air-filled, and it may be composed of other 
materials, such as paramagnetic or diamagnetic materials. In order to 
preserve single-piece construction for adjusting-solenoid core 58 and 
actuating solenoid core 64, however, both of these cores may be joined at 
point 74, e.g., by electron beam welding. By comparison, a large-area 
joint without magnetic gap would result in undesired field effects of 
solenoid 60 on core 64 and solenoid 62 on core 58. For more details of 
this construction see my copending application Ser. No. 850,939, not 
assigned. 
Upon application of current to core 58, adjusting solenoid 60 attracts 
ferromagnetic component 56, which is joined to guide sleeve 70, causing 
guide sleeve 70 to move downward. Guide sleeve 70 has a circumferential 
flange 48 which acts as a seat for the spring system consisting of springs 
42 and 44. The movement of guide sleeve 70 to its operating position upon 
energizing solenoid 60 establishes the locus of equilibrium of the spring 
system midway between actuating solenoids 62 and 66. 
Bore 76, a cylindrical cavity completely surrounded by magnet core 64 
and/or 58, is provided to house the spring systems, guide sleeve 70 and 
guide rod 38. The diameter of bore 76 is adjusted to match the space 
requirements of spring system 42 and 44 and support 48. 
It is to be noted that the diameter of the extension of the guide rod 
running from the anchor plate into guide sleeve 70 is smaller than that of 
bore 76, such that cylindrical space 78, which is bounded by solenoids, 
has a smaller internal diamter than bore 76 in this region. The additional 
space thus gained for adjusting solenoid 60, filled by core 58, makes it 
possible to reduce the physical height of adjusting solenoid 60. 
The entire unit shown in FIG. 2 may be preassembled into 
assembly/replacement modules as follows. Assembly is essentially performed 
such that guide sleeve 70 is inserted from underneath into the cuplike 
assembly of core 64 and core 58. Ferromagnetic anchor plate component 56 
is slipped over the upper end of sleeve 70, which is then joined with said 
ferromagnetic component 56, e.g., by nut 71. Springs 44 and 42, followed 
by guide rod 38 which is joined to anchor plate 46, may then be installed. 
A self-contained unit is formed with subsequent attachment of core 68. 
During engine assembly, valve 20 is installed in the customary manner. 
Springs 32 and 34 are threaded on valve stem 24, after which support 30 
for springs 32 and 34 is attached. All that remains is for the complete 
unit described above to be mounted over the stem of the installed valve, 
and housing 22 bolted to cylinder head 10 (See FIG. 3). 
FIG. 3 indicates that housing 22 is provided with a circumferential flange 
80, containing boreholes for passage of bolts 82, which engage cylinder 
head 10. Item number 84 refers to shims for adjustment of the height of 
housing 22 relative to cylinder head 10, and thus relative to the valve 
seat, whereby valve travel is also adjustable. 
Shims 84 may be replaced by a ring, circumferentially surrounding housing 
22 and positioned between flange 80 and cylinder head 10. This arrangement 
guarantees the accurate alignment of the positioning mechanism relative to 
the cylinder head and the valve stem. 
An appropriately threaded shim or ring construction, or oblique (tapered) 
frontal surfaces upon which the shims bear against one another, provide a 
simple valve adjustment mechanism, as the clearance between flange 80 and 
cylinder head 10 can be adjusted by simple rotation of the shims or ring 
system. 
It should be understood that various modifications within the scope of this 
invention can be made by one of ordinary skill in the art without 
departing from the spirit thereof. I therefore wish my invention to be 
defined by the scope of the appended claims as broadly as the prior art 
will permit, and in view of this apecification if need by.