Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-10-19
2001-11-13
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090430, C123S19800E
Reexamination Certificate
active
06314927
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a support element for a finger lever of a valve train of an internal combustion engine having the following features:
the support element comprises a housing which is installed or can be installed in a reception of a cylinder head, a pressure piston biased toward the finger lever by a spring means being inserted into a bore of the housing;
the pressure piston extends beyond the reception of the cylinder head and possesses a head that serves as a support for the finger lever;
the support element can be switched to a high and a low or a zero lift for at least one gas exchange valve associated to the finger lever and comprises a switching means for switching to the lifts,
the switching means comprises a coupling means and an actuating means for the coupling means, whereby for achieving the high lift, the housing can be connected to the pressure piston by the coupling means in an axially distant relative position, and for achieving the low or zero lift, the housing and the pressure piston can be disconnected from the intervention of the coupling means.
CRITICISM OF PRIOR ART
A support element of the pre-cited type is disclosed in DE-OS 195 00 575. A drawback of this support element is that locking and unlocking is realized by transversely displaceable pistons that are actuated at least in one of their directions of movement by a hydraulic medium. This hydraulic actuation is accompanied by a number of disadvantages, one of which, for example, is that the time required for switching the pistons depends on the viscosity of the hydraulic medium used. Another disadvantage is that complicated additional hydraulic medium ducts have to be provided in the neighboring area of the cylinder head and further, that impurities contained in the hydraulic medium can lead to a clamping of the pistons. Since the hydraulic medium column in front of the pistons is subject to undesired pressure fluctuations, these can lead, in the worst case, to a displacement of the pistons when this is not desired. Still another drawback of this prior art support element is its relatively large design space requirement.
SUMMARY OF THE INVENTION
The object of the invention is therefore to create a support element of the pre-cited type in which the mentioned drawbacks are eliminated, and in which, particularly, an economic and reliable displacement of the coupling means is assured.
The above object is achieved according to the invention through the features of:
an outer peripheral surface of the pressure piston comprises, preferably outside of the reception of the cylinder head, at least one flat portion whose axial dimension corresponds at least to a length of a stroke of the pressure piston relative to the housing in a separated state of the pressure piston and the housing;
the outer peripheral surface is surrounded in a region of the flat portion by a bore of a lever serving as the coupling means, said bore comprising an unrecessed section on the side of flat portion and of complementary shape to the flat portion;
the lever extends generally perpendicularly away from an axial line of the support element and is displaceable in rotating direction by the actuating means;
in the axially distant relative position of the housing and the pressure piston, the pressure piston comprises, as seen in peripheral direction, an annular groove starting from the flat portion and extending on one or both sides thereof, a depth of the annular groove corresponding at least to the depth of the unrecessed section;
to achieve the low lift or the zero lift, the lever can be rotated by the actuating means so that the unrecessed section of the lever and the flat portion of the pressure piston come to be situated directly opposite each other, and for achieving the high lift, the lever can be rotated by the actuating means so that at least a part of the unrecessed section of the lever extends within the annular groove of the pressure piston, and
an anti-rotation device is arranged between the pressure piston and the housing.
The disadvantages discussed above are eliminated by the switching means as described above in combination with the actuating means (
32
) can be displaced in a first direction of displacement by an electromagnetic or electrohydraulic actuator (
33
), a displacement of the actuating means (
32
) in a direction opposite to the first direction of displacement being accomplished either by a mechanical setting means (
34
) such as at least one compression spring (
35
), or likewise by the actuator (
33
). The lever guarantees a reliable and very rapid connection and separation of the pressure piston and the housing for achieving the different lifts. The scope of the invention also extends to a solution in which the support element is not completely switched off so that the gas exchange valve concerned still undergoes a partial lift through the action of the cam-contacted finger lever of the support element.
Although it is proposed to configure at least one flat portion and one section on the pressure piston and the housing, two such configurations situated diametrically opposite each other are particularly advantageous.
In a further development of the invention, the support element is configured as a hydraulic clearance compensation element. In this way, complicated mechanical measures for clearance adjustment can be dispensed with.
It is also within the scope of the invention to configure the flat portion on the pressure piston with a length that corresponds at least to the displacement of the pressure piston relative to the housing in the switched-off state. This flat portion extends up to a head-proximate end of the pressure piston. This measure is particularly favorable from the manufacturing point of view.
According to a further feature of the invention, the reception-proximate surface of the lever is supported on a shoulder formed by the flat portion of the pressure piston. In this way, no additional support means are required for the lever on the support element.
It is understood that means similar to those provided by the invention can also be used to fix the pressure piston in its retracted state in the housing (separation from cam lift). This further reduces friction in the valve train because the pressure piston then no longer executes a movement relative to the housing (zero lift) when the cam rotates. A re-setting is advantageously effected in the run-off flank phase of the cam.
Since the invention requires a positioning of the flat portion relative to the section, a simple-to-manufacture anti-rotation device is proposed that prevents a rotation of the pressure piston relative to the housing. This device can be in the form of a rivet or the like that extends radially inward through the housing and into a longitudinal recess in the outer peripheral surface of the pressure piston. However, it is also conceivable to arrange this rivet in the pressure piston and have it extend radially outward into a corresponding recess of the housing.
In accordance with the invention, the actuating means for the lever can be configured as a rod, or similar to a rod, and be arranged in the cylinder head parallel to the longitudinal axis thereof. The levers for a row of identically operating gas exchange valves can then be connected to each rod.
An electromagnetic actuator is preferably proposed as a simple actuating means for the rod, or an electrohydraulic actuator may also be used. The control of such an actuator is technically relatively simple and has the advantage over a hydraulic actuation of the coupling means of being extremely reliable. At the same time, it is also possible to implement very high speeds of displacement.
It is possible to realize an alternating switching-off operation simply by a special manner of fixing the lever on the rod. At the same time, a third position of switching is provided in which the pressure pistons and housings of all the support elements are connected for achieving a complete cam lift.
The invention further provides means which guarantee an emerge
Bierman, Muserlian and Lucas
Ina Walzlager Schaeffler OHG
Lo Weilun
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