Combined shut-off valve and cover for an engine breather system

In prior art engine breather systems, shut off valves that prevent oil from entering the engine induction system have been mounted externally on the engine and require associated external pipework. Both the shut off valve and pipework are prone to damage and leaking. The closed circuit breather apparatus of the present invention includes a cylinder head cover and a shut off valve provided beneath the cylinder head cover. The shut off valve includes an aperture in communication with a blow-by gas inlet passage and a valve float restrained to move between a first position in which the aperture is open and a second position in which the aperture is closed. Preferably the shut off valve is integral with the cylinder head cover. The shut off valve is thus packaged inside the engine valve chamber, making it easy to fit and eliminating leak paths.

TECHNICAL FIELD

This invention relates to breather systems in internal combustion engines which allow the free flow of bypass gases and air movement between chambers of the engine during engine running, and to shut-off valves provided in such breather systems to prevent oil in the breather system from entering the engine induction system, and is particularly but not exclusively applicable to closed circuit breather systems.

BACKGROUND

An internal combustion engine typically has three chambers, the crankcase, the timing case and the top cover. Each of these chambers must be openly connected to allow free flow of bypass gases and air movement during engine running. In a closed breather system blow-by gas escapes past the piston into the crankcase where it mixes with airborne oil droplets and is fed back into the engine induction system. The blow-by gas passes through a woven mesh oil separator that separates the oil from the blow-by gas before allowing the oil to return to the sump under gravity. The blow-by gas then continues through a pressure regulation valve to the induction manifold. The pressure regulation valve typically has a spring-loaded diaphragm that closes when the induction depression overcomes the spring load. Positive crankcase pressure opens the diaphragm and allows blow-by gases to escape into the air intake system. Negative crankcase pressure closes the diaphragm and prevents blow-by gases being drawn back into the engine.

In the known closed circuit breather systems there is a reliance on gravity to ensure that oil in the blow-by gases returns to the sump. Under abnormal operating conditions, such as sump overfill or excessive blow-by of oil arising from a worn engine, there is a risk that oil may not return to the sump, but may be directed to the pressure regulation valve and hence to the engine induction system by gravity, resulting in undesirable engine emissions. If the engine is mounted in a vehicle or machine that is operated at an extreme inclination or rolls over, there is a risk that substantial quantities of oil can flow under gravity and enter the engine induction system. This can cause the engine to run in an ungoverned condition and can result in damage to the engine as well as undesirable engine emissions.

The present invention seeks to provide a shut-off valve for a breather system that overcomes one or more of these problems.

SUMMARY OF THE INVENTION

According to one aspect of this invention, a closed circuit breather apparatus for an engine breather system comprises a cylinder head cover and a shut off valve provided beneath the cylinder head cover. The shut off valve includes an aperture in communication with a ventilation inlet passage and a valve float restrained to move between a first position in which the aperture is open and a second position in which the aperture is closed.

According to another aspect of this invention, a closed circuit breather apparatus for an engine breather system comprises a cylinder head cover adapted to define an engine valve chamber and a shut off valve provided within the engine valve chamber. The shut off valve includes an aperture in communication with a ventilation inlet passage and a valve float restrained to move between a first position in which the aperture is open and a second position in which the aperture is closed.

According to still another aspect of this invention, a cylinder head cover arrangement for an internal combustion engine comprises a cylinder head cover and a ventilation inlet passage integral with the cylinder head cover. A breather shut off valve is integral with the cylinder head cover and in communication with the ventilation inlet passage.

Other features and advantages of this invention will become apparent from the following description and the accompanying drawings.

DETAILED DESCRIPTION

A known closed breather system10is shown inFIGS. 1 and 2. An engine12has a crankcase14, an air filter16and an induction manifold18. Blow-by gas which escapes past the pistons (not shown) into the crankcase14mixes with airborne oil droplets in the crankcase and is fed back to the engine induction system. The gas first passes through the crankcase breather pipe20to a combined filter/separator22that separates the oil from the blow-by gas before allowing the oil to return to the crankcase14under gravity. The blow-by gas then continues through a pressure regulation valve24and along an air intake pipe26to the induction manifold18. The closed breather system shown inFIG. 1does not include a shut-off valve.

The pressure regulation valve24is shown in more detail in FIG.2and has a housing28with a crankcase inlet30connected to the crankcase breather pipe20via the combined filter/separator22and an induction manifold outlet connected to the air intake pipe26. Mounted in the housing28is a spring-loaded diaphragm32that closes when the induction depression overcomes the load in the spring34. Positive crankcase pressure opens the diaphragm32to the position shown inFIG. 2, thereby allowing blow-by gases to escape into the air intake system along the path indicated by the arrows36. Negative crankcase pressure closes the diaphragm32and prevents blow-by gases being drawn back into the engine.

One embodiment of a closed circuit breather apparatus50according to the invention is described with reference toFIGS. 3to6, by way of example only. The closed circuit breather apparatus50includes a pressure regulation valve52similar to the pressure regulation valve24shown inFIG. 2, but it is to be understood that the pressure regulation valve52may be omitted or may be provided separately. The closed circuit breather apparatus50includes a cylinder head cover54, which in use covers the cylinder head56, thereby enclosing the valves (not shown) and valve operating mechanism57within the engine valve chamber58. A gasket59seals the cylinder head cover54to the walls of the cylinder head56. The valve operating mechanism57may be any suitable mechanism, such as a rocker shaft, an electrically operated mechanism or a hydraulically operated mechanism.

The pressure regulation valve52is mounted within the cylinder head cover54and includes a cover plate60beneath which is a spring-loaded diaphragm62which closes when the induction depression overcomes the load in the spring64. Positive crankcase pressure opens the diaphragm62to the position shown inFIG. 4, thereby allowing blow-by gases to pass into the air intake system along the path indicated by the arrows66.

The closed circuit breather apparatus50includes a ventilation inlet passage68and a ventilation outlet passage70, which convey blow-by gases through the pressure regulation valve52. A connecting aperture72connects a shut off valve74to the gas inlet passage68. The shut off valve74includes a valve float76movably held in a guide cage78comprising an upper cylinder80and three lower legs82which project downwardly from the cylinder80. The cylinder80has a valve seat84at its upper end. The connecting aperture72is provided in the valve seat84. The lower legs82are connected at their lower ends to form a seat86that limits the downward travel of the valve float76in the guide cage78.

Screws or other suitable fixings (not shown) pass through apertures88in a flange90connected to the guide cage78, in order to secure the shut off valve74to the cylinder head cover54. Alternatively the guide cage78may be formed integrally with the cylinder head cover54, or fixed by any other suitable means. The form of the guide cage78may vary, for example it may have a different number of legs82, and the legs may extend the full height of the guide cage78. The valve float76has a density less than that of oil, so that it is able to float on any oil92entering the engine valve chamber58. The valve float76may be a ball float, for example a hollow ball of plastic or metal, or any other suitable construction.

The ventilation outlet passage70comprises a tapering outlet passage94, which is formed integrally with the cylinder head cover54. A first portion96of the outlet passage94extends beneath the cylinder head cover54, best seen inFIG. 3in which the rocker shaft57is omitted for clarity. A second portion98of the outlet passage94extends through the side wall99of the cylinder head cover54to an outlet100positioned outside the cylinder head cover54. In the example ofFIGS. 4 and 5a pipe102is connected by a seal104to the outlet100. The pipe102is in communication with the induction chamber (not shown) of the engine. Other forms of connection may be made to the outlet100.

INDUSTRIAL APPLICABILITY

The closed circuit breather apparatus50of the present invention provides a compact structure for preventing any oil passing through the breather system in the event of oil entering the engine valve chamber58, and for reducing the carryover of oil droplets into the breather system.

In normal engine operation the valve float76sits on the seat86in the first position shown inFIG. 4, thereby allowing the passage of blow-by gases up through the vent passages (not shown) from the engine crankcase (not shown), through the connecting aperture72, into the ventilation inlet passage68and along the path indicated by the arrows66. The shut off valve74prevents large oil drops, which are typically greater than 10 microns in size and are present as a result of rocker lever movement in the engine valve chamber58, from entering the ventilation inlet passage68. Blow-by gases follow a tortuous path through the shut off valve74, since they cannot flow straight up through the shut off valve74to the aperture72. As the blow-by gases change direction, oil droplets are deflected onto the guide cage78and valve float76, thereby reducing oil carryover to the engine induction system.

If oil enters the engine valve chamber58, due to abnormal operating conditions such as such as sump overfill, excessive blow-by of oil arising from a worn engine, or operation of the engine on a gradient, the level of oil92will rise. As the level of oil92rises the valve float76rises until it is seated against the valve seat84in a second position shown inFIG. 5, thereby covering the aperture72and preventing the passage of blow-by gases through the connecting aperture72into the ventilation inlet passage68.

If the engine overturns the valve float76will fall under gravity until it is seated against the valve seat84in the second position shown inFIG. 5, even before the engine valve chamber58fills with oil, thereby covering the aperture72and preventing the passage of oil through the connecting aperture72into the ventilation inlet passage68.

The shut off valve74thus prevents oil in the closed circuit breather system from entering the engine induction system, which can cause the engine to run in an ungoverned condition and can result in engine damage.

The closed circuit breather apparatus50of the present invention permits the introduction of a shut off valve74into an engine breather system without increasing the height of the engine or its components, since the shut off valve74is contained within the cylinder head cover54and utilizes space in the engine valve chamber58which would otherwise be unused. The shut off valve is simple to fit, is not positioned outside the engine where it is susceptible to damage, does not require associated external pipework and eliminates potential leak paths.

It is to be understood that the geometric arrangement of the shut off valve74and the inlet and outlet passages68,70may be varied to suit the layout of the engine, as will be apparent to the person skilled in the art. The cylinder head cover54may be a complete cover, a top cover or a part cover. The material of the shut off valve74and the cylinder head cover54can be any suitable material, for example aluminum, alloy, pressed steel, composite material, thermosetting plastic or thermoplastic. The shut off valve74may be formed integrally with the cylinder head cover54, or may be formed separately and then attached to the cylinder head cover54to form an integral unit. Other modifications may be made within the scope of the appended claims.