Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-09-05
2002-07-30
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S337000, C123S347000, C123S348000, C123S184560, C123S403000
Reexamination Certificate
active
06425356
ABSTRACT:
DESCRIPTION
In motor vehicles having piston-type internal-combustion engines in which the load control is effected by way of a controllable throttle device in the air-supply conduit, it is known to utilize the vacuum forming behind the throttle device—seen in the air flow direction—in specific operating states when the device is only partially open in order to act appropriately on “vacuum consumers” in the vehicle. The term “vacuum consumers” in the sense of the present invention encompasses, for example, an exhaust-gas recirculation system, a power brake unit, a backwash active-charcoal filter of a fuel-tank ventilation system, etc. . . .
Systems for piston-type internal-combustion engines of this type, in which a bypass conduit is provided for bridging the region of the throttling device, the conduit having a bottleneck that is embodied in the manner of a Venturi tube, are known from DE-B-27 17 685 and DE-A-195 03 568. A vacuum line, which is connected to the vacuum consumer, terminates in the region of the bottleneck. Due to the pressure difference between the region of the air-supply conduit in front of the throttling device, where the pressure is high, and the region of the air-supply conduit behind the throttling device, where the pressure is low, an air current is forcibly created in the bypass conduit, which leads to a drop in the static pressure due to the increase in speed in the region of the bottleneck; this condition can then be utilized by the vacuum consumer.
In piston-type internal-combustion engines in which the load control is effected by way of a variable actuation of the cylinder valves or a regulation of the mixture quality, that is, a regulation of the mixture composition, or in which the fuel is injected directly into the cylinders, the absence of a throttle valve in the air-supply conduit means that an inadequate vacuum is available to the vacuum consumers of a motor vehicle over the entire load range of the piston-type internal-combustion engine, the consumers being indispensable for the operation of the engine. To provide these vacuum consumers with a sufficient vacuum, it has been necessary to this point to generate the vacuum externally via additional vacuum pumps.
Because such additional aggregates are relatively costly, and require corresponding, additional drive energy, it is the object of the invention to embody a piston-type internal-combustion engine with a throttle-free load control such that vacuum generators consuming additional drive energy can be omitted.
According to the invention, this object is accomplished by a piston-type internal-combustion engine having cylinder valves that are completely variably actuatable via a valve timing, and are connected to an air-supply conduit that is provided with a device for generating a vacuum by utilizing energy components of the air flowing through the air-supply conduit, the device being equipped with controllable elements for adaptation to changes in the flow energy as dictated by operating conditions, and being connected by way of at least one vacuum line to at least one vacuum consumer. With this measure, the energy components inherent in the air flow in the air-supply conduit can be directly incorporated into the generation of the vacuum.
In this device, the energy components that are utilized are, on the one hand, the flow speed of the air flowing through the air-supply conduit, which is specifically utilized through an increase in the flow speed, which correspondingly leads to a drop in the static pressure, and/or through the utilization of pulse-like pressure fluctuations that occur in the air flow in the air-supply conduit due to the periodic opening of the gas intake valves. Depending on the conditions, these fluctuations cause the pressure to exceed and fall below the ambient pressure by a “zero level.” This principle of the invention can be realized in different embodiments.
In a first embodiment of the invention, it is provided that the device includes an air-supply conduit, through which air flows, and which has at least one cross-sectional bottleneck that is formed in the region of the termination of the vacuum line, and that controllable elements are provided for setting different cross-sectional bottlenecks. With such a cross-sectional bottleneck, which should have a flow contour that keeps flow losses as low as possible, and should accordingly be embodied in the manner of a Venturi tube, the speed of the air flowing in the air-supply conduit increases, which causes a drop in the static pressure in the air flow relative to the ambient pressure of the air-supply conduit. Thus, it becomes possible to make available the vacuum that is necessary, for example, for a power brake unit, with low pressure losses in the air-supply conduit, or to generate the pressure drop that is necessary for exhaust-gas recirculation and/or the backwash of an active-charcoal filter of a fuel-tank ventilation system for suctioning exhaust gas and/or fuel-containing air into the air-supply conduit via the active-charcoal filter.
If the cross-sectional bottleneck is designed such that a sufficient vacuum can be generated in the air-supply conduit at low rpms, and thus with low mass currents, large flow resistances and therefore drops in power occur in the air-supply conduit at high rpms and with large mass currents. To counteract this, the cross-sectional bottleneck has a variable free flow cross section; controllable elements, which can be actuated, for example, via the valve timing, effect an adaptation to the respective operating state; and the flow resistance can be kept low for the different operating states, i.e., the different rpm ranges.
One embodiment of the invention provides that the air-conduit region has at least two parallel conduits, each with a cross-sectional bottleneck, which are connected at least on the exhaust side to the air-supply conduit. The cross-sectional bottlenecks vary in size, and a controllable actuating element is provided for selective guidance of the air flow through the parallel conduits. Thus, a simple adaptation is possible for at least two different rpm ranges. For the lower rpm range, the actuating element is correspondingly actuated, and the parallel conduit having the cross-sectional bottleneck with the small flow cross section is opened, and for the upper rpm range, the parallel conduit having the cross-sectional bottleneck with the larger free flow cross section is opened, so an appropriate drop in the static pressure is assured in the region of the termination of the vacuum line for both rpm ranges, yet the flow resistances dictated by the cross-sectional bottleneck are minimized.
The actuating element can be formed by a throttle valve disposed in front of the branch of the parallel conduits; this valve selectively enables one of the two parallel conduits for the air flow, but can also be set such that air flows through both parallel conduits, so three rpm ranges can be covered with two parallel conduits. For the low rpm range, the parallel conduit having the smaller flow cross section in the region of the cross-sectional bottleneck is enabled; for a middle rpm range, the other parallel conduit with the larger free flow cross section is enabled; and for an upper rpm range, the throttle valve is set such that both parallel conduits are enabled, so air can flow through them. The effected increase in the air resistance, and the associated loss of power, are maintained within acceptable limits.
In another embodiment of the invention, it is provided that the air-conduit region having a cross-sectional bottleneck has at least one movable wall region in the region of the termination of the vacuum line for changing the free flow cross section of the cross-sectional bottleneck. The movable wall region is connected to controllable actuating elements. With this arrangement, it is possible to precisely adapt the free flow cross section in the region of the cross-sectional bottleneck, with the aid of the valve timing, for example, to the respective air-mass current flowing thro
Duesmann Markus
Lohse Enno
Pischinger Martin
Salber Wolfgang
Schebitz Michael
Corrigan Jaime
Denion Thomas
FEV Motorentechnik GmbH
Kelemen Gabor J.
Venable
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