AN INTERNAL COMBUSTION ENGINE VALVE ROCKER COMPARTMENT COVER, WITH A LUBRICATING OIL ANTI-SUCKING DEVICE

Abstract: A cover for the valve rocker compartment of internal combustion engines comprises a hollow shaped casing (9) for closing the compartment containing the rockers (6) which operate the engine intake and exhaust valves (22; 33), and a duct system which connects said shaped casing to the engine air intake manifold (2). The duct system is intercepted by a valving member (31) which is kept in the open position by an elastic member of predetermined load, but closes said duct system when the vacuum in the manifold reaches an undesirable value.

Description: This invention relates to improvements in the cover for the valve rocker compartment of internal combustion engines in general. As is well known, in internal combustion engines the rockers which open and close the intake and exhaust valves are located on the cylinder head in a compartment closed by a cover, which is fixed in a sealed manner onto the cylinder head. The space between said cylinder head and cover is connected to the engine crankcase by way of the aperture through which the rocker operating rods pass, so that the vapour generated when the lubricating oil contained in the crankcase increases in temperature seeps into said compartment to place it under slight pressure. To prevent overpressure in the compartment containing the valve rockers, its cover either comprises an outwardly directed vent or, to prevent pollution, is connected by a tube to the air filter. Whether this connection is made upstream or downstream of the filter cartridge, it creates difficulties. In this respect, in the first case said vapour causes early clogging of the filter elements in the air filter. In the second case, if a large negative pressure arises in the intake manifold due to clogging of the air filter, it is transmitted to the compartment containing the valve rockers with the result that the lubricating oil can be drawn up from the crankcase and sucked into the engine cylinder (or cylinders), so feeding the combustion and progressively drying the sump, so resulting in danger to persons and damage to the engine. Instead to be connected to the air filter downstream of the filter cartridge, the compartment containing the valve rockers may be connected to air intake manifold directly. US-A-4602607 discloses a valve rocker compartment cover of an internal combustion engine, consisting of a hollow shaped casing for containing the rocker which operates the engine intake valve. The cover comprises a duct system communicating with the air intake manifold and connecting the inner space of the cover to the air intake manifold. The duct system is intercepted by a valving member controlling the passage of the crankcase vapors to the intake manifold. The solution above does not prevent the lubricating oil to be drawn up from the crankcase and sucked into the engine cylinder when the vacuum value in the intake manifold increases over an undersirable value due, for example, to the air filter clogging. The main object of the present the present invention is to provide an arrangement which obviates the aforesaid within the context of a simple, reliable and low-cost construction. According to the invention, the proposed cover comprises a duct system which extends from the valve spring retainer to the engine intake manifold and contains a valving member arranged to close said duct system only when the vacuum in the manifold reaches undesirable values for any reason, for example because of clogging of the air filter. This can be achieved for example by elastic means having a predetermined preload, ie able to retain the valving member in its open position with a force which is able to oppose the suction action due to the usual range of vacuum in the manifold. In other words, the valving member is insensitive to the vacuum which is produced by normal air intake conditions, whereas said valving member closes said duct system when the vacuum increases and approaches the limiting value which would result in oil being drawn up from the engine crankcase. These and further merits and characteristics of the invention will be more apparent from the detailed description given hereinafter with reference to the accompanying figures which illustrate a preferred embodiment thereof by way of non-limiting example only. Figure 1 shows the invention associated with a single-cylinder engine, in a sectional view taken on the line I-I of Figure 2. Figure 2 is a view of the cover taken from below. Said figures, and in particular Figure 1, show the cylinder head 1 of an engine block, which in the illustrated case is of single-cylinder type. This is in no way to be considered a limiting factore as the characteristic elements of the invention are suitable for any type of single or multi-cylinder internal combustion engine of the diesel or otto cycle with its cylinders either in line or not in line. In said cylinder head 1 there are provided an intake duct 2 and an exhaust duct 3, the former connected to a usual air filter 4 (of which only part is shown), and the latter connected to an exhaust pipe (not shown). As is usual, said two ducts 2 and 3 open into the corresponding explosion chamber by way of suitable valves 22 and 23, namely the intake valve and exhaust valve respectively. In addition, the valve stems 5 emerge from the cylinder head 1 to rest against respective rockers 6, contact between said stems 5 and rockers 6 being ensured by compression springs 7 lying between the cylinder head 1 and respective valve spring retainers 8 associated with said stems 5 (Figure 1). Again, although not shown, it should be noted that the opposing ends of the rockers are subjected to the action of push rods which extend towards the engine crankcase where the corresponding camshaft is located. No further cylinder head constructional details will be described as these are of the usual type well known to experts of the art. The engine crankcase, and thus the zone containing the lubricating oil, communicates with the top of the cylinder head 1 by way of the aperture in which said push rods are contained, this aperture located in correspondence with the aperture indicated diagrammatically at 66 in Figure 2. As is usual, a hollow shaped cover 9 is placed on the top of the cylinder head 1 to close the compartment containing said rockers 6 and the upper mouth of the aperture 66 (Figure 2). The cover 9 is provided with holes 10 for its fixing to the cylinder head 1 (see Figure 2) and a cap 11 positioned on the aperture 66 to allow lubricating oil to be fed into the engine crankcase. In addition, said cover 9 comprises a duct system which connects the inner space of the cover 9 to a bore 13 (Figure 1) which opens into the air intake manifold 2. Said duct system comprises a first chamber 14 situated within the cover 9, and a second chamber 15 situated external thereto, said chambers being connected together by a circumferential series of equidistant holes 16 (Figure 2). The first chamber 14 is closed by a base 17 fixed at 18 (Figure 2), and communicates with the interior of the cover 9 through a side aperture 19 and two opposing end openings 170. Furthermore, in said first chamber 14 there is housed a filtering layer 20 covering the passageways through said aperture 19 and said openings 170. The second chamber 15 is closed by a plate 21 which is fixed to the cover 9 at 22 and comprises a central stem 23 which acts as a travel limiter for the lifting of a disc valve 24 which simply rests against the upper mouths of the holes 16. Said chamber 15 opens by way of a duct 240 into a cylindrical housing 25 which is aligned with said bore 13 and contains as a free sliding fit a piston 26 which lies between two springs 27 and 28. When in the operating position shown in Figure 1, the piston 26 is completely raised and keeps the upper spring 27 compressed by the effect of the thrust produced by the lower spring 28. When in said raised position, the piston is completely free of the communication port between the duct 240 and the housing 25. The space containing the spring 27 opens to the outside through a hole 29 provided in the plate 21. It should also be noted that said two springs 27 and 28 are sized such that the piston 26 is urged upwards with a force sufficient to oppose the lowering of the piston when there is the usual vacuum in the intake manifold 2, ie a vacuum deriving from normal engine operation. More specifically, the piston 26 is subjected to a thrust which is at least slightly less than the force in the opposite direction which would act on said piston if in the intake manifold 2 a vacuum was created sufficient to draw lubricating oil up from the engine crankcase. This will be apparent hereinafter. Finally, returning to Figure 1 it can be seen that the lower spring 28 rests against a shoulder 30 which is provided at the lower end of the housing 25 to act as the valve seat for a valving member 31, this latter consisting of a push rod fixed to the piston 26. During normal or regular engine operation the piston 26 remains raised by the spring 28, and the vapour due to the heating of the lubricating oil reaches the cover 9, facilitated in this by the effect of the vacuum induced in it via the duct system communicating with the intake manifold 2. That part of the vapour which condenses within the cover 9 returns to the crankcase through the aperture opposite the aperture 66, whereas the remainder flows towards said air intake manifold 2 after passing through the filtering layer 20. This latter retains most of the droplets transported in the passing flow, so that they combine into a fluid mass which is then discharged through the openings 170 (Figure 2) to return to the engine crankcase. The invention operates as stated while the vacuum within the air intake manifold 2 and thus in the housing 25 is of a value lying within the range for normal engine operation. In contrast, if for example because of clogging of the air filter there occurs in the manifold 2 a considerable vacuum of such a value as to suck lubricating oil up from the crankcase, the piston 26 lowers to interrupt communication between the duct 240 and the housing 25, the valving member 31 resting against the seat 30 to prevent said sucking action. Under these operating conditions, the oil vapour present in the crankcase still escapes to the outside through the duct 240 and the hole 29, so allowing the engine to operate.

Claims: 1. An internal combustion engine valve rocker compartment cover, of the type consisting of a hollow shaped casing (9) for containing the rockers (6) which operate the engine intake and exhaust valves (22), (23), where the cover comprises a duct system (240, 25, 13) communicating with the air intake manifold (2) and connecting the inner space of the casing (9) to the intake air manifold (2) intercepted by a valving member, characterized in that the valving member (31) is elastically urged towards its open position with a force which exceeds the maximum pulling force exerted on the valving member (31) by the vacuum in the manifold (2) during normal engine operation, but which is less than the pulling force exerted on said valving member by a vacuum of such a value as to draw up lubrificating oil from the crankcase. 2. A cover as claimed in claim 1, characterised in that said valving member (31) is fixed to a piston (26) slidingly housed in a cylindrical seat which is provided with a valve seat (30) for the valving member and has one end connected to the outside environment, whereas its other end communicates with said duct system and houses an elastic thrust member (28) of predetermined load for said piston (26). 3. A cover as claimed in the preceding claims, characterised in that said duct system comprises upstream of said valving member a chamber (14) containing a filtering layer (20) and provided with at least one opening (170) to allow the oil retained by said layer (20) to drain. 4. A cover as claimed in the preceding claims, characterised in that between said filter chamber (14) and valving member (31) there is provided a disc valve (24) the valve seat (16) of which is situated on the same side as said chamber.

Inventors: CASTELLARI, ANGELO
Applicants: LOMBARDINI FABBRICA ITALIANA MOTORI S.P.A.
Application year: 1989
Main classification: F01M13
IPC codes: F02F7, F01M13