Information
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Patent Grant
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6321702
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Patent Number
6,321,702
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Date Filed
Thursday, May 11, 200024 years ago
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Date Issued
Tuesday, November 27, 200123 years ago
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Inventors
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Original Assignees
-
Examiners
Agents
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CPC
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US Classifications
Field of Search
US
- 123 9012
- 123 9013
- 123 9015
- 123 198 C
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International Classifications
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Abstract
A system for controlling a gas exchange valve for internal combustion engines, comprising a movable valve member in a housing which, on an end close to the combustion chamber, has a valve sealing face that cooperate with a valve seat in order to control an inlet or outlet cross section at the combustion chamber of the engine. On an end remote from the combustion chamber a working piston defines at least one hydraulic working chamber, whose alternating filling and discharging with a pressure fluid can be used to move the valve member in the opening and closing direction. The supply pressure of the pressure fluid supplied for the actuation of the gas exchange valve member is adjusted step wise as a function of current operating parameters of the engine.
Description
PRIOR ART
The invention is based on a process for controlling a gas exchange valve for internal combustion engines. In a device of this kind, which has been disclosed by DE 195 11 320 and is for controlling a gas exchange valve, the gas exchange valve has an axially movable valve member which, on its end close to the combustion chamber, has a valve sealing face that it uses to cooperate with a stationary valve seat in order to control an inlet or outlet cross section at the combustion chamber of the engine. On its end remote from the combustion chamber, the valve member of the gas exchange valve has a working piston which, with its axial end faces, defines two hydraulic working chambers, of which an upper working chamber further from the combustion chamber can be alternatingly filled with a pressure fluid and discharged, and which consequently acts on the valve member of the gas exchange valve in the opening or closing direction counter to a constant closing force acting on the underside of the piston. The constant closing force on the valve member piston is assured through the fact that the lower working chamber close to the combustion chamber constantly communicates with a high pressure fluid source.
The known control device, however, has the disadvantage that it is operated with a constant pressure fluid supply pressure. This supply pressure must thereby be chosen to be at least high enough to achieve the necessary valve adjusting dynamics at the maximum speed and load of the engine as well as at low temperatures and consequently a low viscosity of the hydraulic fluid. These operating states in the engine to be fed, however, only occur temporarily in actual vehicle operation so that most of the time, an unnecessarily high pressure fluid supply pressure has to be maintained. However, since this pressure contributes directly to the power consumption of the overall vehicle system, it also impairs the overall efficiency of the engine to be fed.
Advantages of the Invention
The process according to the invention for controlling a gas exchange valve for internal combustion engines has the advantage over the prior art that the supply pressure of the valve control device is only brought to the maximum level required for the extreme boundary conditions when such a high supply pressure is actually required by the current operating parameters of the engine to be fed. The pressure fluid supply pressure produced to actuate the gas exchange valve member advantageously changes and adjusts as a function of the current operating parameters of the engine to be fed during its operation. In this manner, over broad operating cycles of the engine to be fed, it is possible to operate the valve control device with a reduced pressure that is sufficient for the normal everyday operation of vehicle engines. In this everyday operation, vehicle engines are for the most part operated at an operating temperature and in an average speed and load range in which the demands on the dynamics of the hydraulic valve control system are significantly lower than in high-stress operating states, e.g. at high speed, high load, and low temperatures. In this connection, however, the continuous variable adjustment of the supply pressure of the valve control system also assures the reliable operation of the valve control device even in the high-stress operating states of the engine that require a high pressure fluid supply pressure.
Since the supply pressure to be supplied by the high pressure pump for the valve control system contributes directly to the power consumption of the engine, a pressure reduction that is dependent on the current operating state of the engine leads directly to an energy savings in comparison to the known valve control system that has a constant supply pressure.
In this connection, the variable changing of the supply pressure level is alternatively possible by means of two strategies, wherein with a first strategy, the valve control system pressure is changed smoothly as a function of the operating parameters of the engine, e.g. the temperature, speed, and load. In this connection, it is particularly advantageous to execute the adjustment of the supply pressure level by way of a characteristic diagram stored in an electric control unit.
A second alternative strategy for the variable control of the supply pressure level is the smooth switching between different pressure levels as a function of the temperature, speed, and load of the engine to be fed. The number of pressure stages in this connection is initially variable, but an optimal design must be adapted to the respective engine. It is particularly advantageous to provide two pressure level stages, the first of which covers the lower to middle operating state of the engine and the second covers the high pressure level for the high-stress operating states. In order to prevent an excessively frequent switching back and forth between adjacent pressure levels, a hysteresis function is provided in their boundary regions.
A high pressure pump that can be regulated is advantageously used as a pressure supply device and this pump can be driven directly by the engine and at a speed synchronous to the engine so that the delivery volume of the pump already increases automatically with the speed of the engine. Alternatively, however, it is also possible to execute the regulation of the high pressure pump on the suction side, for example, by means of an adjustable suction throttle, or on the pressure side by means of corresponding pressure valves.
The valve control device advantageously has a hydraulic adjuster in which a piston connected to the gas exchange valve defines at least one hydraulic working chamber. This hydraulic working chamber can be alternately filled with a highly pressurized pressure fluid and discharged, wherein the filling and discharging of the working chamber takes place by means of control valves in a supply line or discharge line, as a function of operating parameters of the engine. The adjusting force acting on the piston of the hydraulic adjuster from the side of the hydraulic working chamber is counteracted by a constant opposing force directed in the closing direction of the gas exchange valve member. This constantly present closing force can be produced hydraulically or mechanically. The mechanical production of this force takes place by means of springs, while the hydraulic opposing force is produced through the provision of a second hydraulic working chamber which engages the adjusting piston of the gas exchange valve member in opposition to the first hydraulic working chamber. In the exemplary embodiment described, this second hydraulic working chamber that acts in the closing direction advantageously communicates continuously with the high pressure fluid supply line so that the high pressure of the hydraulic adjusting medium continuously prevails in this chamber. Alternatively, it is also possible to produce the adjusting motion in the piston of the gas exchange valve member by means of alternately filling the two hydraulic working chambers in the adjusting piston with a pressure fluid.
Other advantages and advantageous embodiments of the subject of the invention can be inferred from the specification, the claims, and the drawing.
BRIEF DESCRIPTION OF THE DRAWING
An exemplary embodiment of a device for executing the process according to the invention for controlling a gas exchange valve for internal combustion engines is shown in the drawing and will be explained in detail in the description that follows.
The sole FIGURE shows a schematic diagram of a system and device for actuating a gas exchange valve for internal combustion engines, in which the hydraulic adjusting piston of the gas exchange valve member defines two hydraulic working chambers that function in opposition to each other, wherein the hydraulic pressure fluid is supplied by a high pressure pump that can be regulated.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
In the device shown in
FIG. 1
for controlling a gas exchange valve for internal combustion engines, a piston-shaped valve member
3
of the gas exchange valve is guided so that the valve member can move axially in the housing
1
. On its lower end oriented toward the combustion chamber, the gas exchange valve member
3
has a valve disk
5
, whose upper end face constitutes a valve sealing face
7
. With this valve sealing face
7
, the valve member
3
cooperates with a stationary valve seat
9
on the housing
1
and thus controls an inlet or outlet cross section of the housing
1
at the combustion chamber of the engine to be fed, which is not shown in detail. On its upper end remote from the combustion chamber, the valve member
3
has a cross-sectionally enlarged hydraulic adjusting piston
11
, which is guided so that its cylindrical circumference wall surface slides in a sealed fashion in a cylinder
13
. With its lower annular end face
15
oriented toward the combustion chamber, the piston
11
defines a lower hydraulic working chamber
17
, and with its entire upper piston end face
19
, the piston
11
defines an upper hydraulic working chamber
21
. The hydraulic working pressure present in the lower working chamber
17
thereby acts on the piston
11
in the closing direction of the valve member
3
by way of the lower annular end face
15
, while the pressure in the upper working chamber
21
acts on the piston
11
in the opening direction of the valve member
3
by way of the upper piston end face
19
.
The hydraulic pressure fluid that actuates the hydraulic valve adjuster is supplied by a high pressure pump
23
that can be regulated, which aspirates the pressure fluid, preferably hydraulic oil or motor oil, from a reservoir
25
and supplies the oil to the cylinder
13
by way of a pressure fluid supply line
27
. In this connection, the pressure fluid supply line
27
feeds with its main branch into the upper hydraulic working chamber
21
, wherein a branch line
29
leads from the pressure fluid supply line
27
and for its part feeds into the lower hydraulic working chamber
17
. In order to control the pressure fluid supply into the upper working chamber, an electric control valve
31
is inserted into the pressure fluid supply line
27
downstream of the split into the branch line
29
and just before the infeed into the upper working chamber
21
. In addition, in order to maintain a standing pressure, a first check valve
33
is inserted into the pressure fluid supply line
27
in the flow direction upstream of the split into the branch line
29
. In order to relieve pressure in the upper hydraulic working chamber
21
of the valve control device, a discharge line
35
also leads from the upper working chamber
21
and feeds into the reservoir
25
; this discharge line
35
also has an electric control valve
37
inserted into the line, which can open or close the discharge line
35
. A second check valve
38
is provided in the discharge line
35
, downstream of the control valve
37
.
For the control according to the invention of the gas exchange actuation device, an electric control unit
41
is also provided, which processes various current operating parameters of the engine to be fed, such as temperature, speed, and load as input values. The regulatable high pressure pump
23
and the electric control valves
31
and
37
are then controlled as a function of these current input values, preferably in a characteristic diagram-controlled manner.
The above-described actuation device for a gas exchange valve for internal combustion engines functions in the following manner. With the beginning of the operation of the internal combustion engine to be fed, the high pressure pump
23
is also driven, preferably with a speed synchronous to that of the engine and thus supplies the pressure fluid from the reservoir
25
under pressure to the pressure supply line
27
. In this connection, pressurized pressure fluid travels via the branch line
29
into the lower working chamber
17
that continuously communicates with the pressure supply line
27
. In the lower working chamber
17
, the high pressure acts on the piston
11
via the annular end face
15
in the closing direction of the valve member
3
so that this valve member
3
is held with its valve sealing face
7
in contact with the stationary valve seat
9
. The check valve
33
disposed in the pressure fluid supply line
27
thus assures the maintenance of a particular standing pressure in the branch line
29
and the lower working chamber
17
so that the valve member
3
is held in the closed position even when the engine is switched off. The control valve
31
disposed in the pressure fluid supply line
27
thereby remains in the initial position, i.e. when the gas exchange valve is closed, the infeed of the pressure fluid supply line
27
into the upper working chamber
21
is closed. At the same time, the electric control valve
37
in the discharge line
35
keeps this line open so that a possible high pressure in the upper working chamber
21
can escape into the reservoir
25
and in the rest position, this reservoir
25
is pressure relieved. Here, too, a check valve
38
in the line
35
maintains a particular residual pressure in the upper working chamber
21
and in the line
35
, which should prevent an excessively long dead time due to a complete emptying of the upper working chamber
21
. In order to open the gas exchange valve, the electric control valves
31
and
37
are triggered in such a way that the control valve
31
now permits the pressure fluid flow into the upper working chamber
21
while the control valve
37
closes the discharge line
35
. As a result, the same high pressure of the pressure fluid builds up in the upper working chamber
21
as in the lower working chamber
17
, wherein the compressive force acting on the piston
11
in the opening direction of the valve member
3
exceeds the closing force of the lower working chamber
17
due to the larger effective pressure engagement area on the piston
11
and thus permits the valve member
3
to lift off from the valve seat
9
with its valve sealing face in the downward direction. An opening cross section between the valve sealing face
7
and the valve seat
9
at the combustion chamber of the engine to be fed is then opened, via which an inlet or outlet cross section is opened. A corresponding triggering of the control valves
31
and
37
permits all valve member opening positions to be variably adjusted and maintained. The opening of the gas exchange valve is ended by virtue of the fact that the control valves
31
and
37
are triggered again by the electric control unit
41
in such a way that the infeed of the pressure fluid supply line into the upper working chamber
21
is closed and the discharge line
35
leading from it is opened again. As a result, the high pressure in the upper working chamber
21
escapes into the reservoir
25
and the closing force in the lower working chamber
17
acting on the piston
11
of the valve member
3
via the annular end face
15
once more slides the valve member
3
into sealed contact with its valve sealing face
7
against the valve seat
9
.
In order to then prevent unnecessarily high pressures of the pressure fluid of the valve control device during particular operating conditions of the engine, the high pressure pump
23
is regulated in such a way that the supply pressure of the pressure fluid is adjusted as a function of current operating parameters of the engine to be fed during its operation. To that end, the high pressure pump can be operated at a motor-synchronous speed, e.g. throttled on the suction side. The control of the various pressure levels can be smoothly changed and is preferably also carried out in a characteristic diagram-controlled manner by means of the electric control unit
41
. The smooth adjustment of various supply pressure levels represents another variant of the adjustment of the supply pressure of the valve control device during the operation of the engine. To that end, a number of pressure stages are provided, wherein preferably, even two supply pressure level stages are sufficient. A first lower pressure level stage covers the operating range of the engine in which the engine is operated at low or mid-range speed, load, and temperature. The second pressure level is only adjusted in the high pressure pump
23
when the engine is operated under extreme operating conditions. These extreme operating conditions, for example, are a very low ambient temperature, high speeds, and high loads. In this instance, high restoring forces act on the valve member
3
of the gas exchange valve, which also require high adjusting forces of the hydraulic pressure fluid. In order to prevent an excessively frequent switching back and forth between the individual pressure levels in their boundary regions, a hysteresis function is interposed between the pressure levels in these boundary regions. For example, with a changeover boundary between the pressure levels at a speed of 5000 rpm, this hysteresis function results in the fact that the switching up into the high pressure level only occurs at a speed of approx. 5500 rpm. In contrast to this, the switching down from the high pressure level into the lower pressure level only occurs at a speed of approx. 4500 rpm so that no changeovers occur in an approx. 1000 rpm speed range and consequently, a constant jumping back and forth between the two pressure level stages can be reliably prevented.
With the process according to the invention for controlling a gas exchange valve for internal combustion engines, in particular through the operating point-dependent adaptation of the supply pressure of the pressure fluid of the hydraulic valve adjuster, it is consequently possible to achieve a considerable energy savings in the most frequently used operating range of the engine to be fed. This energy savings is achieved by means of a corresponding reduction in the pressure fluid supply pressure level so that the power consumption of the high pressure pump can be correspondingly reduced, which considerably improves the total energy balance of the engine.
The foregoing relates to a preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.
Claims
- 1. A system for controlling a gas exchange valve for internal combustion engines, which system comprises:a housing, a movable valve member (3) in said housing, which, on an end close to a combustion chamber of the engine, has a valve sealing face (7), said valve sealing face cooperates with a valve seat (9) in order to control an inlet or outlet cross section to or from the combustion chamber of the engine and on an end remote from the combustion chamber said movable valve has a working piston (11) which defines at least one hydraulic working chamber (21) which is alternatingly filled with a pressure fluid and discharged of said fluid to move the valve member (3) in an opening and closing direction, whereby the supply pressure of the pressure fluid supplied for the actuation of the gas exchange valve member (3) is adjusted as a function of current operating parameters of the engine during the operation of the engine, wherein the supply pressure of the valve control device is adjusted step wise during the operation of the engine as a function of engine operating parameters.
- 2. The system according to claim 1, in which the supply pressure of the valve control device is smoothly changed during an operation of the engine as a function of engine operating parameters.
- 3. The system according to claim 2, in which an adjustment of the supply pressure takes place in a characteristic diagram-controlled manner.
- 4. The system according to claim 1, in which two pressure level stages are provided in said housing.
- 5. The system according to claim 4, in which a hysteresis function is provided between a changeover between the individual pressure level stages, in a boundary region between the pressure stages.
- 6. The system according to claim 2, in which a supply pressure of the valve control device is adjusted as a function of the temperature, load, and speed of the engine.
- 7. The system according to claim 1, in which a supply pressure of the valve control device is adjusted as a function of the temperature, load, and speed of the engine.
- 8. The system according to claim 1, in which the supply pressure of the valve control device is produced by a regulatable pump (23).
- 9. The system according to claim 8, in which the pump (23) is regulated on a pressure side.
- 10. The system according to claim 9, in which the pump is regulated on a suction side.
- 11. The system according to claim 1, in which a constantly present opposing force engages a lower piston end face (15) disposed opposite from the upper piston end face (19) that defines a working chamber (21) that is alternatingly filled with pressure fluid and discharged, and this opposing force counteracts an opening compressive force against the upper piston end face (19) of the gas exchange valve member (3) and holds the gas exchange valve member (3) in a closed position when the hydraulic pressure chamber (21) is not pressurized.
- 12. The system according to claim 11, in which the constantly present opposing force in the closing direction is embodied as a hydraulic compressive force that is produced in a second hydraulic working chamber (17).
- 13. The system according to claim 12, in which the supply high pressure of the pressure fluid constantly prevails in the second hydraulic working chamber (17) that acts on the gas exchange valve member (3) in the closing direction.
- 14. A system for controlling a gas exchange valve for internal combustion engines, which system comprises:a housing, a movable valve member (3) in said housing which, on an end close to a combustion chamber of the engine, has a valve sealing face (7), said valve sealing face cooperates with a valve seat (9) in order to control an inlet or an outlet to or from the combustion chamber of the engine and on an end remote from the combustion chamber said movable valve has a working piston (11) which defines at least one hydraulic working chamber (21) which is alternatingly filled with a pressure fluid and discharged of said fluid to move the valve member (3) in an opening and closing direction, said fluid being supplied from a single pressure reservoir which is pressurized in a step wise fashion according to current operating parameters of the engine, so that the working piston is acted on by fluid at step wise varied pressures to open or close the valve with varied force according to the current operating parameters of the engine.
Priority Claims (1)
Number |
Date |
Country |
Kind |
198 26 045 |
Jun 1998 |
DE |
|
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
102e Date |
371c Date |
PCT/DE99/00424 |
|
WO |
00 |
5/11/2000 |
5/11/2000 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO99/66178 |
12/23/1999 |
WO |
A |
US Referenced Citations (4)
Foreign Referenced Citations (1)
Number |
Date |
Country |
05-202712 |
Aug 1993 |
JP |