Fluid handling – Self-proportioning or correlating systems – Self-controlled branched flow systems
Reexamination Certificate
2000-01-31
2001-04-24
Hepperle, Stephen M. (Department: 3753)
Fluid handling
Self-proportioning or correlating systems
Self-controlled branched flow systems
C417S159000, C417S188000, C417S189000, C417S191000
Reexamination Certificate
active
06220271
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a checkvalve unit which is generally used to connect an operating system, e.g. the braking force amplifier of a vehicle braking system or the servomotor of the power steering system, of a vehicle requiring negative pressure to a suction system which produces negative pressure, e.g. the suction pipe or aspiration channel of a combustion engine. The checkvalve unit is to ensure that a negative pressure produced in an operating system is maintained, even when the pressure in the suction system rises or when the negativepressure production in the suction system is completely interrupted. The latter is the case for example when the vehicle engine is stopped.
A checkvalve unit comprises an inlet and an outlet connected to each other via a main air channel. In the assembled state or in case of utilization, the inlet is connected to the operating system and the outlet to the suction system. A first checkvalve is located in the main air channel. This prevents the negative pressure from escaping once it has been produced in the operating system in case that pressure rises in the suction system. Furthermore, one single outlet channel which branches off from the main air channel downstream of the first checkvalve and lets out into the atmosphere is provided with the checkvalve unit in question. A venturi pipe or a narrowing of the cross-section is provided in this outer-air channel. This narrowing of the cross-section is connected via a channel, hereinafter the venturi channel, to the main air channel at a point located upstream of the first checkvalve.
Such a checkvalve unit, hereinafter the valve unit, is described in U.S. Pat. No. 5,291,916; DE 43 44 624 A1 and DE 43 10 761 C2. In the known valve units, it is a disadvantage that air is constantly sucked in through the outer-air channel. This is especially detrimental with combustion engines where the air mass flowing through the choke valve of the air suction pipe is used for engine control or to optimize the combustion process. In a valve unit described in U.S. Pat. No. 3,754,841 the outer-air channel containing the venturi pipe can be closed off by a sliding valve when the system pressure of the operating system has reached its target value. The sliding valve is controlled by differential pressure. In addition, a membrane holding a plunger which actuates the sliding valve is subjected on the one hand to the system pressure and on the other hand to a reference pressure. To produce the reference pressure, a venturi pipe is installed in a second outer-air channel letting out into the atmosphere and connected to the suction pipe of the engine. A connecting channel branches off from the narrowing point of the venturi pipe and influences the above-mentioned membrane from one side. The second outer-air channel is permanently open, so that a stream of wrong air is constantly aspired by the suction pipe. Furthermore this valve unit can only be produced at high manufacturing and assembly costs.
OBJECTS AND SUMMARY OF THE INVENTION
Based on this, it is a principal object of the present invention to propose a valve unit which is simple in design and with which constant suction of outside air is prevented.
According to the present invention, a cut-off valve is installed before or after the narrowing of the cross-section of the venturi pipe in the single outer-air channel, said cut-off valve being actuated as a function of the system pressure prevailing in the operating system in such a manner that the connection to the atmosphere is opened when a predetermined target pressure is exceeded and is interrupted when this pressure is not reached. The connection to the outer air is thus open only when the system pressure exceeds a predetermined target pressure. As soon as the system pressure has dropped back to its target pressure, the outer-air channel is again shut off. An adulteration of the air mass flowing through the checkvalve is thereby substantially prevented. As a seat valve, the checkvalve is made with two defined switching positions, i.e. one open and one closed position. Such a valve is easy to produce and is also less prone to failure than a sliding valve, in which a suitably sized valve bore must be precisely made.
In an example of an embodiment of the invention, the shutoff valve is an electromagnetically actuated 2-way valve which is actuated by a control device which senses the system pressure by means of a pressure sensor. In this embodiment, it is first of all advantageous that the duration of the outer air arrival or of the open state of the outer-air channel can be kept very short thanks to the electrical control. Generally speaking, opening the outer-air channel with a valve unit according to the invention is only rarely needed, e.g. with repeated braking, after a long stoppage or with rpm ranges of the engine which are rarely reached. An additional advantage of the electrical controls consists in the fact that analog electrical signals for other electrical or electromechanical control functions can be utilized for the actual negative pressure in the braking force amplifier.
The shut-off valve may be a pneumatic shut-off valve which is actuated by the difference in pressure between the system pressure and the atmospheric pressure. Such a checkvalve unit is simple in design if for no other reason than that the pressure difference is not between the system pressure and a separately produced reference pressure, but that the reference pressure used is the atmospheric pressure. Advantageous embodiments of the valve unit are characterized in particular by simple and compact construction.
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patent: 3333566A1 (1984-03-01), None
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patent: 4310761A1 (1994-10-01), None
Buratowski Thaddaus
Emmerich Ulf
Alfmeier Prazision AG Baugruppen und Systemlosungen
Dority & Manning
Hepperle Stephen M.
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