Crankcase Ventilation

Abstract

An internal combustion engine crankcase ventilation system includes a flow control valve in a line connecting the crankcase with the engine induction system so as to control the flow of crankcase vapors to maintain a proper mixture in the inlet charge. In preferred form, a thermostatic disc valve is provided at one end of the flow control valve to shut off the flow of crankcase vapors under cold engine starting and warmup conditions. When the thermostatic disc is heated to a predetermined point by engine operation, it snaps open to a position which permits a sufficient flow of crankcase vapors to avoid any significant effect on the calibration of the flow control valve with which it is used.

Description

FIELD OF THE INVENTION

This invention relates to crankcase ventilation systems for internal combustion engines and, more particularly, to a crankcase ventilation valve arrangement for controlling the flow of vapors from the crankcase to the induction system of an internal combustion engine.

It is known in the art to provide an internal combustion engine with a crankcase ventilation system wherein crankcase vapors are carried from the engine crankcase to the inlet manifold or some other portion of the engine induction system downstream of the usual throttle valve. Systems of this type provide for the removal of blow-by and other vapors which tend to collect in the engine crankcase by drawing them into the induction system with the vacuum naturally formed by the operation of the engine. Such systems usually also include provision for the addition of fresh air to the crankcase, which mixes with the crankcase vapors and is carried into the induction system therewith.

Because of the wide variation in induction system vacuum over the range of engine operating conditions, the incorporation of a crankcase ventilation flow control valve is necessary to adjust the volume of flow to a desirable level for the various conditions that exist during engine operation. An example of one type of valve which has been extensively used for this purpose is shown in U.S. Pat. No. 3,359,960 Pittsley assigned to the assignee of the present invention. Such spring biased plunger type valves have been satisfactorily used in many commercial applications and are currently in wide use.

The predetermined flow curve of the crankcase ventilation valve is normally matched with the characteristics of the engine carburetor so that under normal operating conditions a properly proportioned mixture of fuel and air is delivered to the engine combustion chambers for burning. During starting and engine warmup under the various ambient temperature conditions in which engines must operate, the engine carburetor, possibly in conjunction with other devices, is usually relied on to make the necessary adjustments in the fuel mixture to provide proper operation under all conditions.

It has been found, however, that in some instances, especially during cold engine starting and warmup, the flow of crankcase vapors into the engine induction system as controlled by a valve properly designed for normal engine operation may be too high to permit adequate control of the mixture by the carburetor with the result that starting or proper operation of the engine during warmup may prove difficult. In such instances, it has been found desirable to shut off the flow of crankcase vapors into the inlet manifold until the temperature of the engine has increased to a point where operational difficulties are not encountered with a normal flow of crankcase vapors.

SUMMARY OF THE INVENTION

The present invention provides a thermostatic valve arrangement which is adapted to cut off the flow of crankcase vapors to the engine induction system below the throttle valve when the engine temperature is below a predetermined desired level. The thermostatic valve is intended for use in combination with, or as a part of, a conventional flow control valve and is arranged so that, when it is open, it is sufficiently unrestrictive of flow as to not significantly disturb or alter the desired flow curve of the flow control valve.

A preferred type of valve which is both simple, yet effective for the purpose, is in the form of a thermostatic snap disc of the bimetallic type which is curved in one direction at low temperatures and snaps to curvature in the opposite direction at higher temperatures. Such a disc is preferably positioned at one end of the flow control valve housing so as to cooperate with a wall of the flow control plunger chamber to either cut off or freely pass the flow of crankcase vapors. A cover and retention member provided for securing the valve disc in place is also designed to protect the disc from inadvertent damage due to mishandling before installation.

These and other features and advantages of the invention will be more clearly understood from the following description of a preferred embodiment of the invention, taken together with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing:

FIG. 1 is a front elevational view of an engine having a crankcase ventilation system with a flow control valve that includes a thermostatic valve according to the invention;

FIG. 2 is a cross-sectional view of the flow control valve incorporating the thermostatic valve of the invention with the thermostatic valve shown in its shutoff position;

FIG. 3 is a cross-sectional view similar to FIG. 2 but showing the thermostatic valve in its open position;

FIG. 4 is an end view of the valve taken generally in the plane indicated by the line 4--4 of FIG. 2 and having portions cut away to show the interior construction of the thermostatic portion of the valve; and

FIG. 5 is a graphic presentation of a desired flow curve for the flow control valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the drawing, FIG. 1 illustrates an internal combustion engine generally indicated by numeral 10 having a crankcase 11 and a plurality of cylinders 12 arranged in a pair of banks angularly displaced with respect to one another. Cylinders 12 have pistons 14 arranged for reciprocation therein and connected by connecting rods 16 with the respective throws of a crankshaft 18.

The engine includes conventional cylinder heads 20 closing the tops of the cylinders and forming in cooperation with the pistons combustion chambers 22. An induction system is provided for introducing a combustible mixture into the combustion chambers and includes inlet ports 24 formed in the cylinder heads, an inlet manifold 26 connecting with the inlet ports, a carburetor 28 mounted on the inlet manifold and an inlet air cleaner 30 carried by the carburetor.

Engine 10 further incorporates a crankcase ventilation system including a conduit 32 extending between the inlet manifold 26 and one of the engine rocker covers 34, the interior of which communicates through internal passages, not shown, with the crankcase 11. A crankcase ventilation flow control valve 36 is mounted on the rocker cover 34 and connects with one end of the conduit 32, thereby providing a flow path for crankcase vapors through valve 36 and conduit 32 into inlet manifold 26 in which the vapors are mixed with the combustible mixture to be introduced into the engine cylinders.

The other rocker cover 38 is connected by means of a second conduit 40 and an inlet fitting 41 with the inlet air cleaner 30 so that fresh air from the air cleaner may be drawn through the rocker compartment and into the crankcase as is commonly done to assist in removal of the crankcase vapors.

In engine operation, a combustible mixture is inducted into each cylinder and is ignited when the piston is near the upper end of its stroke, burning the mixture and causing the crankshaft to rotate. Vacuum created in the inlet manifold due to the restriction of the carburetor throttle valve, not shown, causes a flow of crankcase vapors to be drawn from rocker cover 34 through ventilation valve 36 and conduit 32 into the inlet manifold, the flow being controlled by the valve 36 in a manner to be subsequently described.

In normal operation, the rate of withdrawal of crankcase vapors from the engine is in excess of the amount of blowby gases leaking into the crankcase past the various pistons 14. Accordingly, a reduced pressure is created in the crankcase, which causes a flow of fresh air from the inlet air cleaner 30 through conduit 40 and fitting 41 to the rocker cover 38 and thence to the engine crankcase. If the flow of blowby gases becomes excessive or the normal flow through ventilation valve 36 is cut off, as will be subsequently noted, blowby gases will be removed from the crankcase by flowing in reverse direction through conduit 40 to the inlet air cleaner, where they will be drawn into the engine by way of the carburetor and, hence, will not escape to atmosphere.

The construction of the crankcase ventilation flow control valve 36 is disclosed in FIGS. 2 - 4. The main portion of the valve is of known construction and includes a generally cylindrical housing 42 defining an internal cavity 44 which has a pair of end walls defined in part by insert members 46, 48 having orifice openings 50, 52, respectively.

Within cavity 44 of the housing 42 there is reciprocably disposed a valve plunger 54 having a tapered body portion 56 and a head portion 58. The tapered body portion 56 extends into and cooperates with orifice opening 52 to restrict the flow of crankcase vapors through the valve, the restriction increasing as the head of the plunger is moved toward the orifice 52. When the plunger is moved fully in the opposite direction, the head portion engages insert member 46, closing orifice opening 50.

A compression spring 60 extends between the plunger head and insert member 48 and biases the plunger in a direction away from insert 48, which tends to maintain orifice opening 52 at its largest flow capacity. This tendency is offset by the pressure differential across the valve and the flow of vapors created thereby, which move the plunger against the spring so as to restrict the orifice opening and control flow in a pressure-flow relationship which may be as illustrated in FIG. 5.

As shown in FIG. 2, the head 58 of the valve plunger is spaced slightly from insert member 46, in which position the spring 60 is completely expanded and a flow path for vapors exists through orifice opening 50, cutouts 62 in head portion 58 and orifice opening 52. Crankcase vapors may flow through this path if they are not otherwise blocked as shown in the figure. If, however, flow is cut off through the valve, the valve plunger will normally, when mounted in the position shown, be drawn downwardly by gravity so that the head portion 58 rests against insert member 46, closing the orifice 50.

The foregoing portion of the crankcase ventilation flow control valve structure is of known construction and operates generally in the manner of the valve described in the aforementioned U.S. Pat. No. 3,359,960.

The valve of the present invention, however, incorporates in addition to the above described plunger type valve element, a thermostatic snap disc arranged to act as an on-off control valve for modifying the pattern of crankcase ventilation flow. To this end, valve 36 includes a cover and retainer member 64 which defines adjacent the inlet end 66 of housing 42 a chamber 68 in which a bimetallic disc 70 comprising the thermostatic valve element is retained. Cover member 64 is preferably retained by press fitting on the end of housing 42 but may be retained in any other suitable manner.

Inlet end 66 includes through openings 72 which are divided by a central cross bar 74 for a purpose to be subsequently described. Openings 72 connect with orifice opening 50 of the insert member 46 so as to permit vapor flow through the end wall made up of end portion 66 and insert member 46. Cover member 64, in turn, includes six openings 76 annularly spaced around the periphery of its end portion 78 so as to permit the flow of fluids therethrough, the central part of end portion 78 being left without an opening for a purpose to be subsequently described.

Bimetallic disc 70 is of the type which is curved in one direction when cold and snaps to a curvature in the opposite direction when heated above a certain temperature. As installed, disc 70 has the side which is convex when cold facing the inlet end 66 of housing 42. The disc is sufficiently large so that when its edge is in contact with end 66 it completely surrounds the openings 72, blocking the flow of vapors therethrough as shown in FIG. 2.

In operation, under cold starting and low temperature warmup conditions, disc 70 is curved in the position shown in FIG. 2 and is lifted upwardly by a slight differential in pressure to contact inlet end 66 and prevent the flow of crankcase vapors through the valve to the engine induction system. When due to engine operation, the valve temperature increases to a predetermined level which may be, for example, around 110.degree. F., disc 70 snaps to a curvature in the opposite direction, as shown in FIG. 3. In this position the convex side of disc 70 engages the crossbar 74 of inlet end 66, permitting a flow of vapors to pass through opening 76, around the edges of disc 70, through openings 72 and 50 and through the remainder of the valve in conventional manner.

The diameter of the cover member 64 in relation to the diameter of disc 70 is sufficiently large so that when in the open position of FIG. 3, the cover and disc valve assembly will not substantially restrict flow to the plunger portion of the ventilation valve. In this way, the thermostatic valve disc 70, when open, permits the complete valve assembly to operate on its normal curve of flow versus pressure differential, as shown in FIG. 5, substantially as if the thermostatic disc were no longer present.

The operation of the thermostatic disc in the manner described is of importance since if the valve constituted a restriction to flow when in the open position, the change in the pressure differential across the plunger portion of the valve could cause a substantial increase in flow through the total assembly in the engine idle and low load operating conditions, which might upset the delicate balance of carburetion. The arrangement of this invention avoids this possibility.

Bimetallic discs of the type used for valve disc 70 are subject to damage if they are mechanically deformed by flattening. For this reason, the end portion 78 of cover member 64 is made without a central opening in its end portion 78. In this way, the possibility is lessened that someone will damage the disc in handling by poking at it with a pencil or other foreign object, since the disc is less liable to be deformed by such action at its edges than at its center.

While the invention has been described by reference to a preferred embodiment, it should be understood that numerous variations are possible within the scope of the inventive concepts disclosed. The invention is, accordingly, intended to be limited only by the language of the following claims.

Claims

What is claimed is:

1. In combination,

an internal combustion engine having a crankcase and an induction system connected together by passage defining means for delivery of crankcase vapors to the induction system,

first valve means in said passage means and operative to control the flow of vapors to the induction system in accordance with a predetermined function of pressure differential across said first valve means, and

second valve means in said passage means and operative to control vapor flow therethrough independently of said first valve means, said second valve means having a snap action and being responsive to temperature in a manner to close said passage under predetermined conditions of low temperature and to snap to an open position upon reaching a predetermined higher temperature, said open position being sufficiently non-restrictive of flow through said passage means as not to significantly alter the vapor flow determined by said first valve means and said snap opening avoiding any substantial period of operation at restrictive positions of said second valve means intermediate said closed and open positions.

2. A crankcase ventilation valve for use with an internal combustion engine having an induction system and a crankcase, said ventilation valve being adapted for connection between the crankcase and the induction system to control flow therebetween and comprising

a housing having an internal passage for fluid flow,

a pressure responsive first valve element in said passage and operative to control fluid flow therethrough according to a predetermined relationship dependent upon pressure differential across said valve and,

a temperature responsive second valve element in said passage and operative to control fluid flow therethrough independently of said first valve element, said second valve element being operative to close said passage under predetermined conditions of low temperature and to snap to an open position upon reaching a predetermined higher temperature, said open position being sufficiently non-restrictive of fluid flow as not to significantly alter the pressure differential across said first valve element in its range of operation and said snap opening avoiding any substantial period of operation at restrictive positions of said second valve element intermediate said closed and open positions.

3. A crankcase ventilation valve for use in an internal combustion engine for controlling the flow of vapors from the crankcase to the induction system of such engine, said ventilation valve comprising

a generally cylindrical housing defining a chamber and having an opposed pair of end walls, each including an opening to said chamber,

a pressure responsive valve body movably disposed in said chamber and cooperating with said openings to control fluid flow through said chamber according to a predetermined relationship dependent upon pressure differential across said valve body, said valve body having a head portion engageable with one of said end walls to close its respective opening,

means defining a second chamber separated from the first chamber by said one end wall, and

a bimetallic disc curved in one direction at low temperatures and operative in response to a predetermined higher temperature to snap to a curvature in the opposite direction, said disc being retained in said second chamber so that, when curved in said one direction, its outer edges are engageable with said one end wall so as to surround and close its respective opening, said disc edges being away from said one wall and in an open position to permit flow through said opening when said disc is curved in said opposite direction, said open position being sufficiently non-restrictive of fluid flow as not to significantly alter the pressure differential across said valve body in its range of operation and said snap opening avoiding any substantial period of operation at restrictive positions of said bimetallic disc intermediate said closed and open positions.

4. A crankcase ventilation valve as defined in claim 3 wherein said means defining a second chamber includes a cover member having an end portion arranged to permit the passage of crankcase vapors therethrough but to protect the central portion of said bimetallic disc from being engaged by foreign objects inserted through said cover member, thereby minimizing the possibility of said disc being deformed in handling of said valve.