Crankcase Ventilation

Abstract

The crankcase for an internal combustion engine is vented to the fuel-air inlet induction passage via a ventilation valve comprising a tubular valve housing having a comparatively small metering orifice which cooperates with a movable valve element responsive to decreasing pressure in the induction conduit for restricting the orifice. A coil spring yieldingly opposes closing movement of the valve element and is seated on a tubular spring retainer adjustably telescoped into the upstream end of the valve housing to effect a predetermined rate of gas flow through the orifice when a predetermined low pressure differential corresponding to part load operation of the engine is applied across the orifice. Downstream of the orifice, a cylindrical movement limiting plunger extends through an opening in the sidewall of an elbow in the housing and is secured at a position adjusted to engage and limit closing movement of the valve element to effect a predetermined low rate of gas flow through the orifice when a predetermined high pressure differential is applied across the orifice corresponding to engine idling.

Description

BACKGROUND AND SUMMARY OF THE INVENTION

This application relates to improvements in a crankcase ventilating valve of the general type disclosed in the following representative United States patents for regulating the flow of gases from the crankcase of an internal combustion engine to the latter's air inlet system: U.S. Pat. Nos. 2,359,485; 2,716,398; 2,742,057; 3,105,477; 3,241,534; 3,263,699; 3,354,898 and 3,359,960.

In order to reduce the emission of unburned hydrocarbons from the fuel and exhaust systems of an automobile, it is customary to vent the fuel tank and carburetor bowl to the crankcase for storing fuel vapors therein when the engine is not operating, and to ventilate the crankcase during engine operation by controlled conduction of the crankcase gases comprising a mixture of fresh air and engine blow-by products into the usual carburetor inlet induction conduit to supply a portion of the combustion supporting air to the inlet fuel. The carburetor is accordingly adjusted so that when the crankcase gases are added to the customary throttle controlled fuel and air supply, the desired fuel-air ratio for efficient engine operation will result. It is therefore necessary to control the ventilation flow of crankcase gases closely, otherwise inefficient engine operation and the exhausting of excessive incompletely burned fuel will result.

It has been common to provide a pressure responsive flow control valve in the ventilating conduit between the crankcase and induction conduit for controlling the ventilation flow in accordance with the engine operation. Such valves have been costly heretofore because of the close tolerances required for the component parts and the high rate of rejection of assembled valves that do not meet the required standards.

An important object of the present invention is to provide an improved crankcase ventilation valve of the foregoing character that can be economically manufactured by conventional low cost methods, as for example by molding and stamping operations, wherein the valve parts may be readily assembled and adjusted either during or after assembly to compensate for comparatively large dimensional variations in the parts and to avoid the scrapping of costly valve assemblies, yet still meet the exacting standards required for satisfactory engine operation and exhaust emission control. In particular it is an object to provide such a crankcase ventilating valve which is readily susceptible for adjustment at two critical regions of its pressure-flow relationship.

Another and more specific object is to provide such a valve comprising a tubular L-shaped body containing a metering orifice upstream of the elbow or bend of the L-body and having a tubular extension or spring retainer adjustably telescoped into its upstream end. A valve element movable within the housing is responsive to the pressure differential across the orifice for opening or restricting the latter. A coil biasing spring under compression between the valve element and the adjustable retainer or extension opposes movement of the valve element in the direction of orifice closing and urges movement of the valve element in the opposite direction to enable increased flow of crankcase gases during part throttle acceleration as the pressure in the carburetor induction conduit increases.

In the above regard the upstream end of the tubular valve housing comprising the tubular extension is connected to the crankcase. The downstream end of the housing is connected to the carburetor inlet induction conduit at a location downstream of the usual throttle valve and is thus subject to low induction pressure urging the valve element in the closing direction in opposition to the biasing spring. An adjustable movement limiting plunger extends through the sidewall of the housing at the region of the exterior angle of the elbow and coaxially with the orifice and valve element to engage the latter and limit the closing movement at a predetermined position of maximum restriction for the orifice when the engine is idling. A portion of the plunger extends to the exterior of the valve housing and is accessible to facilitate axial adjustment of the plunger.

By virtue of the foregoing, during assembly of the valve parts, a predetermined pressure differential corresponding to part throttle acceleration may be applied across the opposite ends of the housing and the resulting gas flow measured by a meter. The tubular spring retainer is then adjustably telescoped into the upstream end of the housing until the desired gas flow through the housing results. Thus regardless of comparatively loose dimensional tolerances in the valve parts, the desired crankcase ventilation flow into the carburetor induction conduit will result when the aforesaid predetermined pressure differential exists between the induction conduit and crankcase, which latter is vented to atmosphere and maintained approximately at atmospheric pressure at all times.

After adjusting the valve for a predetermined part throttle acceleration condition, the pressure differential across the opposite ends of the valve housing may be increased during assembly to a second predetermined value to simulate engine idle operation. The movement limiting plunger is then adjusted against the valve element until the gas flow through the housing desired for the engine idling condition results, again regardless of comparatively loose production tolerances in the dimensions of the valve components.

The position of the movable valve element with respect to the movement limiting plunger and accordingly the extent of opening of the orifice at any given pressure differential thereacross is determined by the spring rate of the valve biasing spring. Another object is to provide an improved crankcase ventilating valve of the above character wherein the spring rate is readily adjustable either during or after assembly of the valve components.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIG. 1 is a schematic front elevational view of an automobile engine embodying the present invention.

FIG. 2 is an enlarged longitudinal sectional view of the crankcase ventilation valve of FIG. 1, showing in solid lines the position of the valve during engine operation under heavy load and showing in phantom the position of the valve during idle operation.

FIG. 3 is a view similar to FIG. 2 showing the valve prior to calibration and subject to a pressure differential of approximately 9 inches of mercury corresponding to light load.

FIG. 4 is a view similar to FIG. 2, showing the position of the valve after the first calibration.

FIG. 5 is a view similar to FIG. 2, showing the position of the valve subject to a pressure differential of approximately 18 inches of mercury prior to the second calibration.

FIG. 6 is a view similar to FIG. 5 showing the position of the valve after the second calibration step.

FIG. 7 shows the relationship between air flow measured in cubic feet per minute, through the valve the pressure in the inlet induction conduit, measured in inches of mercury and manifold vacuum.

FIGS. 8 and 9 are fragmentary views similar to FIG. 2, showing two different modifications of the movable valve element and the spring retainer.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a V-8 type engine 10 having a fresh air inlet 11, an air cleaner 12 connected by a carburetor induction conduit 13 with the combustion chamber of the engine 10, and a carburetor 14 for supplying fuel to the conduit 13. During normal engine operation, combustion blow-by products comprising a mixture of air, inert gases, and incompletely burned hydrocarbons leak past the engine pistons into the crankcase 15, which is normally maintained at or close to atmospheric pressure by means of a fresh air vent 16 communicating between the air inlet 11 and the crankcase 15 via internal passages not shown within the engine 10. The blow-by gases from the crankcase 15 are recirculated through internal passages not shown within the engine 10 and a crankcase vent line 17 to the induction conduit 13 downstream of the throttle valve 18.

Liquid fuel is supplied via conduit 19 to the carburetor 14 from a fuel tank 20 which is conventionally closed by a vented closure cap 21 that prevents loss of fuel vapors to the atmosphere but enables air flow into the tank 20 to maintain its interior at atmospheric pressure. The upper portion of the tank 20 above the fuel level is vented via conduit 22 to the engine 10 and thence via internal passages not shown to the crankcase 15. Similarly the fuel bowl of the carburetor 14 is vented via conduit 23 to the crankcase 15. The foregoing may be conventional and is accordingly not described in further detail.

In order to control the flow of crankcase gases into the induction conduit 13 during various conditions of engine operation, a pressure responsive ventilation flow control valve 24 is provided in the line 17. As illustrated in detail, see particularly FIGS. 2 and 6, the valve 24 may comprise a molded plastic L-shaped tubular housing 25 having an elbow 26 joining a downstream arm 27 terminating in an annular hose retaining enlargement 27a and an upstream cylindrical arm 28 enlarged at an intermediate region to provide an annular shoulder 29. Upstream of the elbow 26, a coaxial metering orifice 30 is provided by an annular orifice element 31 which may comprise a sheet metal stamping formed with a peripheral flange 31a embedded within the housing 25 at a fluid tight seal.

Telescoped within the upstream end of arm 28 is a coaxial tubular plastic extension or spring retainer 32 having an annular spring retaining flange 33 at its upper end. The flange 33 provides a seat for the upper end of a coil biasing spring 34 which seats at its lower end at an annular seat 35 comprising an enlargement of an axially movable valve element 36. The valve element 36 has a tapered metering portion 37 which terminates upwardly in a cylindrical extension 38 of reduced diameter with respect to the orifice 30. The lower end of spring 34 loosely engages the body of the valve 36 frictionally to damp axial oscillation of the valve 36.

A sheet metal annular seat 39 is embedded coaxially within the lower or upstream end of the extension 32 at a thickened region 32a comprising an annular retainer for a flexible hose. Upstream of the spring seat 35, the valve 36 is tapered conically at 35a to seat at the annular seat 39 and close the opening therethrough upon downward movement of the valve 36, thereby to prevent a reverse flow through the conduit 17 in the event of engine backfire for example. Also extending coaxially with the valve 36 through an opening in the sidewall of the housing 25 at the region of the elbow 26 is a movement limiting plunger 40 adjusted as described below.

During engine idling, the low pressure (or high vacuum) within induction conduit 13 downstream of the throttle 18 induces a comparatively large pressure differential across the valve housing 25 and urges the valve 36 upward against the reaction of spring 34 as illustrated in phantom, FIG. 2, to the limit permitted by plunger 40. The latter is adjusted axially to determine the maximum restriction for the orifice 30 and to permit a predetermined limited flow of crankcase ventilation gases through the valve 24 during idle operation, whereby fresh air is conducted into the crankcase via duct 16 and the mixture of air and blow-by gases are discharged into the conduit 13. As the throttle 18 opens for operation under increasing load, the pressure differential across the housing 25 and urging the valve 36 in the downstream orifice closing direction decreases and the valve 36 urged by spring 34 moves downwardly from the plunger 40 to increase the opening 30 and the flow of crankcase gases.

In order to obtain efficient engine operation during all operating conditions, it is essential to control the crankcase recirculating flow within comparatively narrow limits, so that the flow from the crankcase when admixed with the fuel and air supplied to the conduit 13 from carburetor 14 and air inlet 11 will result in the desired combustible mixture for efficient engine operation with a minimum of unburned hydrocarbons in the exhaust. During engine idling when the air flow through conduit 13 is a minimum, the variations in the crankcase ventilating flow must be narrowly limited because small changes in the ventilating flow will amount to a large percentage change in the idle fuel-air ratio. The relationships between air flow and engine operation as indicated by inlet manifold vacuum is illustrated in FIG. 7, wherein lines 41 and 42 represent the maximum and minimum limits permissible for the ventilating flow through the valve 24, and the dotted line 43 represents the desired or optimum flow.

In order to avoid the excessive costs of maintaining close dimensional tolerances of the valve components within the narrow limits required by the relationships indicated in FIG. 7, the present invention provides a valve which is susceptible of calibration at two important regions of the pressure-flow relationship during or after assembly. Thus the component parts, particularly the housing 25 and extension 32 may be formed by economical mass production molding processes and the orifice member 31 may be formed by economical sheet metal stampings. The valve 37 may comprise either a molded plastic or a formed metal part.

Referring to FIG. 3, the assembled valve 24 is illustrated prior to the final adjustment of the extension 32 within the arm 28 and the plunger 40 within the body 25. The assembly as shown in FIG. 3, with the extension 32 at P1 and the plunger 40 at P3, may be secured in a calibration fixture wherein the arm 27 is connected to a controlled source of low pressure and the extension 32 is connected to atmospheric pressure through a flow meter. A regulated pressure differential is then established across the valve, amounting to for example 9 inches of mercury in a typical situation. At this situation the flow through the valve might amount to about 41/2 CFM (cubic feet per minute) by way of example as illustrated by point F1 of FIG. 7. A sleeve member adapted to fit over the arm 27 and seat at the shoulder 29 may then be forced downwardly against the extension 32, which latter may be maintained in a fixed position, causing the extension 32 to be telescoped into the arm 28 and thereby to adjust the position of the valve 36 with respect to the orifice 30 until the measured air flow through the housing 25 corresponds to point F2, which in the present situation will be slightly less than 3 CFM.

The operating point of the valve 24 will thus be shifted from point F1 to point F2 in FIG. 7 and extension 32 will be shifted from P1, FIG. 3, to P2, FIG. 4. The extension 32 may be maintained at its adjusted position P2 within the arm 28 by friction, or a cement may be applied between the members 32 and 28 prior to the adjustment. The fresh cement will serve to lubricate these members and facilitate the adjustment. When the cement hardens, the members 28 and 32 will be secured against relative movement at a fluid-tight seal.

While the valve 24 is still confined within the calibration fixture, a new pressure differential may be established across the housing 25, which in a typical situation might be 18 inches of mercury corresponding to an idle operating condition. A typical flow at this position might be about 1.5 CFM as indicated by point F4 of FIG. 7, whereby the valve 36 will be shifted to the position P4 of FIG. 5. The upper adjusting plunger 40 is then pushed inwardly against the extension 38 until the measured flow through the valve 24 is increased to the desired value indicated by point F5 in FIG. 7, which is approximately 2.2 CFM. At this condition, the plunger 40 and valve 36 will have been moved to the position P5 in FIG. 6. The plunger 40 may be retained in its adjusted position by a fluid-tight frictional engagement with the sidewall of the valve 25. The excess portion of the plunger 40, may be sheared flush with the exterior of indicated in phantom, FIG. 2, housing 25 and heat sealed to the latter by a hot tool. Likewise a cement may be applied between the plunger 40 and housing 25 prior to the adjustment to lubricate the parts and facilitate the adjustment and to secure the plunger 40 at a fluid-tight seal within the body 25 in its finally adjusted position when the cement hardens.

A final check of the valve may then be made by establishing a new pressure differential amounting to approximately 4 inches of mercury across the valve, FIG. 2. If the resulting flow through the valve as measured by the flow meter falls within the limits determined by lines 41 and 42, as for example at point F6 in FIG. 7, the valve is acceptable and can be packed for shipping. Also as illustrated in FIG. 6 by the portion of line 43 between points F5 and F7, the rate of flow through orifice 30 remains substantially constant and is independent of the pressure differential until the valve extension 38 moves out of contact with the movement limiting plunger 40. This is a well known small orifice phenomena at low pressure and prevails throughout engine idling and coasting at closed throttle conditions by virtue of the small effective orifice 30 when valve 36 is at its position of maximum restriction.

When the throttle valve 18 opens sufficiently with increasing engine load to reduce the vacuum in conduit 13 to below point F7, i.e., as the pressure in conduit 13 downstream of throttle valve 18 increases, the valve 36 will move upstream from the FIG. 6 position of maximum restriction for orifice 30. As the latter opens, the crankcase ventilation flow increases as indicated by the slope of line 43 at the high pressure side of F7, regardless that the pressure differential across orifice 30 actually decreases. Finally at a vacuum of about 4 inches or 5 inches of mercury in conduit 13, the rate of ventilation flow will begin to decrease with decreasing pressure differential across the orifice 30 as may be expected.

As the throttle 18 moves to its wide open position, the ventilation flow through orifice 30 may not equal the blow-by flow past the engine cylinders into the crankcase 15. If this condition arises, the flow through conduit 16 will be reversed and a portion of the crankcase gases will flow upwardly through duct 16 into the air inlet 11 and thence into conduit 13.

In the type of valve shown, after the valve extension 38 moves away from the finally adjusted position P5 of plunger 40, the slope A of line 43 is determined by the spring rate of spring 34 and the taper of the valve metering portion 37. The spring rate may be adjusted as illustrated in FIGS. 8 and 9 by suitably varying the number of effective coils of the spring 34. For example, in FIG. 8, in place of the annular spring retaining flange 33, the upper portion of coil spring 34 is screwed on the internally threaded portion 33b of retainer 32. It is apparent that by adjusting the number of turns of the spring 34 between the valve seat 35 and threaded portion 33b, the effective spring rate may be adjusted to accommodate slight dimensional variations in the production spring 34 and to obtain the desired slope A illustrated in FIG. 7.

FIG. 9 illustrates a similar adjustment wherein the upper portion of the spring 34 frictionally engages the upper portion of the extension or retainer 32 and the lower portion of the spring 34 is adjustably screwed onto a threaded portion 35b of the valve 36, in lieu of seating at the annular retaining flange 35.

Claims

I CLAIM:

1. In a crankcase ventilating device for controlling the flow of gases from the crankcase to the fuel-air inlet induction conduit of an internal combustion engine to effect a predetermined low rate of flow when a large pressure differential exists between said crankcase and conduit corresponding to idle operation of said engine and to effect an increasing rate of flow when said pressure differential decreases within a range of pressures corresponding to part load operation of said engine,

a. a valve housing having a passage for gases extending therethrough and opening at upstream and downstream ends adapted respectively for connection with said crankcase and conduit, said housing comprising upstream and downstream tubular members telescoped one within the other to an adjusted position relative to each other, the passage through said downstream member defining a metering orifice,

b. a valve element movable in said passage axially of said orifice and responsive to an increasing pressure differential thereacross for moving in the axial direction for progressively restricting said orifice,

c. means for limiting the maximum restriction for said orifice,

d. resilient means disposed within said passage and having a portion engaging said valve element for yieldingly opposing axial movement thereof in said direction for restricting said orifice,

e. retaining means on said upstream member engaging another portion of said resilient means to anchor the latter portion relative to said orifice at a position determined by said adjusted position of said upstream and downstream members relative to each other, thereby to determine the force of said resilient means yieldingly opposing said axial movement of said valve element in said direction, said adjusted position effecting a preselected rate of gas flow through said orifice independently of production variations in the dimensions of said device when a preselected pressure differential is maintained between said upstream and downstream ends.

2. In the device according to claim 1, said adjusted position effecting said preselected rate of gas flow from said crankcase and through said orifice when said preselected pressure differential corresponds to said part load operation.

3. In the device according to claim 2, means for adjusting the rate of change in the flow through said orifice with respect to the rate of change of the pressure differential between said upstream and downstream ends comprising a screw threaded portion on at least one of the components comprising said valve element and upstream member, and said resilient means comprising a coil spring having one end adjustably screwed on said threaded portion to adjust the effective length and spring rate of said spring.

4. In the device according to claim 1, said means for limiting the maximum restriction for said passage comprising a movement limiting plunger adjusted to a position within the path of said valve element to engage and limit movement of the latter in said direction opposed by said resilient means to effect a preselected rate of gas flow through said orifice independently of production variations in the dimensions of the components of said device when a preselected pressure differential corresponding to idle operation of said engine is maintained between said upstream and downstream ends.

5. In the device according to claim 4, said downstream tubular member defining an elbow and having a portion downstream of said orifice extending from said elbow angularly with respect to the axis of said orifice, said plunger extending axially of said orifice through the sidewall of said downstream tubular member to the exterior of the latter.

6. In the device according to claim 1, said resilient means comprising a coil spring confined within said upstream tubular member around said valve element, said retaining means comprising a radially inward projection of said upstream member arranged to seat against the downstream end of said spring, said portion of said valve element engaged by said resilient means comprising a radial seat arranged to seat against the upstream end of said spring.

7. In the device according to claim 6, said adjusted position effecting said preselected rate of gas flow from said crankcase and through said orifice when said preselected pressure differential corresponds to said part load operation.