TECHNICAL FIELD

This application relates to a crankcase ventilation breach detection system having a constant restriction of flow in the normal flow direction and free flow in the opposite direction, more particularly, to such a system achieving the same with a tuned orifice and at least one check valve in a parallel configuration.

BACKGROUND

In automotive engines, on/off operation of a vacuum generator and/or accessory is frequently controlled by a gate valve in which a rigid gate is deployed across a conduit to stop the flow of a fluid (in this exemplary application, air) through the valve. Within automated or “commanded” valves, the gate is typically actuated by a solenoid and opened or closed in response to an electrical current applied to the solenoid coil. These solenoid-powered gate valves also tend to include a coil spring, diaphragm, or other biasing element which biases the gate towards an unpowered, ‘normally open’ or ‘normally closed’ position.

The pressure in an engine crankcase is ideally maintained near atmospheric pressure (ATM pressure+/−5 kPa). Furthermore, it is desirable to be able to detect any leak in the crankcase ventilation system (path from fresh air to the manifold, including all flow passageways and passageway connections) to ensure crankcase gasses are appropriately managed to avoid excessive pollutants being discharged into the atmosphere. In order to achieve these conditions, free flow (minimal restriction) of air into the crankcase is needed, which can be switched to a restricted opening, in order to conduct a pressure integrity check (and not create an excessively negative pressure in the crankcase). The gate valve approach while successful, is more expensive, heavier, and takes up engine space. A more cost effective and compact system to enable the pressure integrity check of the crankcase ventilation system is desirable, especially one as disclosed herein that does not require any electrical connections to move an actuator, such as a solenoid, to operate a valve.

SUMMARY

In all aspects, a breach detection system for an internal combustion engine having a crankcase, an intake manifold, a positive crankcase ventilation valve, a crankcase ventilation tube with a flow control system therein, and a pressure sensor between the flow control system and the crankcase is disclosed. The flow control system subdivides the crankcase ventilation tube into a plurality of parallel conduits—a first conduit having a normally closed check valve that opens under a first preselected pressure drop in a first direction from the air intake to the crankcase, and a second conduit having either a second check valve that opens under a second preselected pressure drop in a second direction opposite the first direction or a restriction profile having a third preselected pressure drop that is the same in both the first and second direction. When the pressure sensor detects no pressure drop there is a breach in the system.

In one embodiment, the flow control system comprises the restriction profile in the second conduit, and the internal combustion engine is a naturally aspirated engine, and the first preselected pressure drop is greater than the third preselected pressure drop.

In another embodiment, the internal combustion engine has a turbocharger and the crankcase ventilation tube connects upstream of the compressor of turbocharger. The flow control system comprises the second check valve in the second conduit, and the second preselected pressure drop is the same or lower than the first preselected pressure drop.

In yet another embodiment, the flow control system comprises the second check valve in the second conduit and further comprises a third conduit parallel to the first and second conduits, the third conduit has a restriction profile having a third preselected pressure drop that is the same in both the first direction and second direction of flow. Here, the first preselected pressure drop is greater than the third pressure drop, and the second pressure drop is the same or less than the third pressure drop.

In all aspects, the normally closed check valve defines an internal cavity in which an elastically flexible disk is seated and is held in the closed position against a first seat by a plurality of fingers extending into the internal cavity, wherein a pressure drop across the elastically flexible disk from the first seat to the plurality of fingers flexes the elastically flexible disk into an open position, or defines an internal cavity in which a hemispherical poppet sealing member is seated and is held in the closed position against an annular seat. The annular seat of the hemispherical poppet check valve, in a longitudinal cross-section through the check valve, defines a convex spherical radius and, in the closed position, a convex surface of the hemispherical poppet sealing member is sealing engaged with the convex spherical radius of the annular seat. In this variation, one or both of the annular seat and the hemispherical poppet sealing member include a ring of elastomeric sealing material to define the convex spherical radius of the annular seat or the portion of the convex surface of the hemispherical poppet sealing member that engages the annular seat in the closed position.

In all aspects, the second check valve defines an internal cavity in which a sealing disk floats and translates between an open position and a closed position based on pressure drops in the system. The second check valve is a normally neutral check valve.

In one embodiment, the breach detection system for an internal combustion engine has a crankcase, an intake manifold, a positive crankcase ventilation valve, a crankcase ventilation tube with a flow control system therein, and a pressure sensor between the flow control system and the crankcase. The crankcase ventilation tube having a first flow direction from the air intake to the crankcase and a second flow direction opposite thereof and subdividing into a flow control system. The flow control system subdivides the crankcase ventilation tube into a plurality of parallel conduits—a first conduit having a normally closed check valve that opens under a first preselected pressure differential in the first flow direction, and a second conduit having a second check valve that opens under a second preselected pressure differential in a second direction opposite the first direction, and a third conduit having a restriction orifice allowing flow in both the first and second flow direction at pressure differentials below the first preselected pressure differential. When the pressure sensor detects no pressure drop there is a breach in the system. In all aspects of this embodiment, the first check valve is a normally neutral check valve.

In all aspects, the internal combustion engine has a turbocharger and the crankcase ventilation tube connects upstream of the compressor of turbocharger.

The normally closed check valve defines an internal cavity in which an elastically flexible disk is seated and is held in the closed position against a first seat by a plurality of fingers extending into the internal cavity, wherein a pressure drop across the elastically flexible disk from the first seat to the plurality of fingers flexes the elastically flexible disk into an open position, or in which a hemispherical poppet sealing member is seated and is held in the closed position against an annular seat. The annular seat, in a longitudinal cross-section through the check valve, defines a convex spherical radius and, in the closed position, a convex surface of the hemispherical poppet sealing member is sealing engaged with the convex spherical radius of the annular seat. In the first embodiment, the first valve defines an internal cavity in which a sealing disk floats and translates between an open position and a closed position based solely on pressure drops in the system. In the second embodiment, one or both of the annular seat and the hemispherical poppet sealing member include a ring of elastomeric sealing material to define the convex spherical radius of the annular seat or the portion of the convex surface of the hemispherical poppet sealing member that engages the annular seat in the closed position. In all embodiments, the second check valve is a normally neutral check valve and defines an internal cavity in which a sealing disk floats and translates between an open position and a closed position based on pressure drops in the system.

In all aspects, the third of the three parallel conduits has a symmetrical restrictor profile such that flow through the restrictor in the first and the second direction occurs under the same pressure differential, and the second preselected pressure differential is lower than the first preselected pressure differential.

