Valves and valve actuation – Fluid actuated or retarded – Piston type expansible chamber reciprocating valve actuator
Reexamination Certificate
2002-12-02
2004-10-26
Hirsch, Paul J. (Department: 3754)
Valves and valve actuation
Fluid actuated or retarded
Piston type expansible chamber reciprocating valve actuator
Reexamination Certificate
active
06808158
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German Patent Document DE 101 58 873.9, filed on Nov. 30, 2001, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a hydraulic valve control arrangement with a control line of a control cylinder, said control line being connected to a first oil volume, with a first control piston having a control face A
1
and operatively connected to the first oil volume, and with a plunger piston which is arranged between the first control piston and an outlet valve and has a control face A
2
and which is operatively connected to a second oil volume.
A hydraulic valve control is already known from German Patent Document DE 195 42 561 C1, having preferably two pistons which are separated from one another and act selectively on the valve and which are connected to a high-pressure accumulator. In this case, the piston arrangement is capable of being acted upon by fuel maintained at a different pressure level, and, at the end of the opening operation and during the closing operation, the moved mass can be reduced. To open the valve, the piston arrangement is acted upon by fuel of higher pressure and, for closing, is acted upon by fuel of lower pressure. Two different pressure levels of the pressure accumulator or pressure accumulators are therefore necessary.
In particular British Patent Document GB 2 265 419 A describes a piston arrangement of a compression brake, having a telescopically connected piston arrangement in which a first volume delimited via a plunger piston bearing against a rocker is acted upon by excess pressure. In this case, an actuating force of the actual displacement piston is generated counter to the closing force of the valves, the actuating force ultimately resulting in the opening of the valves. The piston arrangement is integrated at any time into the force flux of the rocker. There is no provision for a gradation of the actuating force.
An aspect of certain preferred embodiments of the invention is to design and arrange a hydraulic valve control device in such a way that different actuating forces are ensured by way of one pressure level.
This aspect can be achieved, according to certain preferred embodiments of the invention, in that a first control edge, switching the first throughflow connection from the first oil volume to the second oil volume operatively connected to a control face A
3
of the first control piston, is provided between the control cylinder and the first control piston. Thereby the second oil volume is cut in by the control edge after a defined displacement S
1
of the control piston and a counterforce F
3
to the current actuating force F
1
is generated according to the arrangement of the control face A
1
and control face A
2
or according to their face ratio. Thus, during the second part of the valve stroke, the valve-opening force decreases according to the control-face ratios, and increased wear on the materials and also an overshoot of the outlet valve are avoided.
For this purpose, it is advantageous that, starting from a neutral position of the first control piston, the first throughflow connection is opened after a displacement S
1
of the first control piston or of the first control edge. It is therefore unimportant whether the control edge or the control piston executes the displacement S
1
so that the throughflow connection is opened.
Furthermore, it is advantageous that the control face A
3
is arranged opposite the control face A
1
and the control face A
2
, opposite control faces being acted upon by oil pressure generating opposed actuating forces. Thus, the control face A
3
generates an actuating force opposed to the control face A
1
and control face A
3
.
Moreover, a solution is achieved in that a first control edge switching the first throughflow connection from the first oil volume to the control face A
1
of the first control piston is provided between the control cylinder and the first control piston or a second control piston. Thereby the control face A
1
is cut in by the first control edge after an initial displacement S
0
. The cut-in control face A
1
also generates a corresponding control force F
1
which then assists the operation of opening the outlet valve.
For this purpose, it is advantageous that the first control piston or a second control piston has a control face A
0
, which is operatively connected to the first oil volume during the displacement S
0
, and the first control edge closing the first oil volume. Consequently, the oil volume is closed with respect to the control face A
1
during the displacement S
0
and is throughflow-connected to the smaller control face A
0
. Accordingly, only a control force F
0
corresponding to the control face A
0
is generated over the initial displacement S
0
and is then increased to F
1
by the operation of opening the control face A
1
.
It is also advantageous, for this purpose that, after the displacement S
0
, the first control edge is in a position opening the first oil volume, a first throughflow connection from the first oil volume to the control face A
1
being provided after the displacement S
0
. After the displacement S
0
, the control face A
1
is acted upon by oil pressure by the first throughflow connection, so that, from this point in time, an increased control force F
1
is available.
Finally, according to a preferred embodiment, there is provision for a second throughflow connection designed as a throttle to be provided between the first oil volume and the control face A
1
. Thus, even before the end of the displacement S
0
, an oil pressure is exerted on the control face A
1
, so that, in this position, an actuating force arises via the control face A
1
according to the throttle cross section or to the prevailing oil pressure.
It is particularly advantageous that the displacement S
0
corresponds to a valve clearance and the displacement S
1
corresponds to an opening displacement of the outlet valve, the opening displacement being between 5% and 50%, in particular between 10% and 20%, of the total valve displacement SG, and the displacement S
2
constituting a displacement which completes the total valve displacement SG. By virtue of the existing pressure-space conditions or of the valve-actuating device, an optimum distribution of the actuating force to the outlet valve can be ensured. The valve-clearance compensating stroke requires a low actuating force, and the first part of the opening stroke of the outlet valve requires the highest actuating force, since the outlet valve has to be opened counter to the highly compressed combustion-space gases. After opening, and over the last part of the opening stroke, a low actuating force is again required, since, at this point in time, the combustion space is already depressurized.
In connection with the design and arrangement according to certain preferred embodiments of the invention, it is advantageous that, after the displacement S
1
, the control face A
0
is operatively connected to the first oil volume, and a second control edge closing the first oil volume via the displacement S
2
is provided. This ensures a reduction of the effective control face A
1
to the control face A
0
, so that the completion stroke S
2
is executed with a lower actuating force.
It is advantageous, furthermore, that the first control piston or the second control piston has the first control edge and/or the second control edge, after the displacement S
0
the first control edge being operatively connected to a first control groove of the control cylinder, and after the displacement S
2
the second control edge being operatively connected to a second control groove of the control cylinder. The control piston can therefore have a one-part or two-part design, the necessary control edges and the control grooves which correspond to them being provided, within the control-piston wall, on the second or on the one control piston.
Moreover, it is advantageous that the second control piston is arranged upstream
Daimler-Chrysler AG
Hirsch Paul J.
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