Crankcase ventilating device for reciprocating piston internal combustion engine

A crankcase ventilating device for reciprocating piston internal combustion engines, in which a connecting line between the crankcase and the intake conduit is controlled by a control valve including a spring-loaded control piston, which piston is axially displaceable and has one of its end faces adapted to be actuated upon by the pressure in the crankcase whereas its other end face is adapted to be actuated upon an ambient pressure. The control piston is acted upon by the ambient pressure through a throttle opening ahead of which, when looking in the direction of flow of ambient air through the throttle opening to the control piston, there is arranged a separating chamber having an inlet opening communicating with ambient air.

The present invention relates to a ventilation for a crankcase housing for 
piston internal combustion engines according to which a connecting line 
between the crankcase and the intake conduit is controlled by a control 
valve with a spring loaded control piston axially displaceable in a 
housing while one end face of said control piston is acted upon by the 
pressure in the crankcase, and the other end face of said control piston 
is acted upon by the ambient pressure. 
In view of the laws governing ecology, especially the keeping clean of the 
air, the gases of the crankcase must not any longer be discharged into the 
open air. Generally they are conveyed to the intake air. In order to 
obtain a disturbance-free operation of the internal combustion engine, a 
control valve has to be utilized which controls the pressure in the 
crankcase independently of the obtained quantity of gas and of the intake 
underpressure in the intake pipe is controlled to have a constant pressure 
of approximately from 10 to 25 mm water column. 
U.S. Pat. No. 2,080,588 discloses an arrangement in which the connecting 
line is controlled by a piston connected to a diaphragm. The diaphragm on 
one side thereof is acted upon by the pressure of the crankcase and on the 
other side is acted upon by the ambient pressure so that the valve opens 
as soon as the pressure of the crankcase exceeds the ambient pressure. 
When the valve has opened, the pressure between the crankcase and the 
intake conduit equalizes. The total pressure previously acting upon the 
diaphragm is divided in a dynamic pressure and a static pressure of the 
flowing gas while only the static pressure acts upon the diaphragm. 
Therefore, the valve will close prior to the pressure in the crankcase 
dropping to the environmental pressure. This brings about an unstable 
control in which the valve during a control operation opens and closes in 
a pulsating or oscillating manner. 
German Gebrauchsmuster No. 70 32 571 discloses a ventilation of a crankcase 
according to which a control piston is provided with a longitudinal bore 
and by rolling diaphragms (Rollmembranen) is at the inner and outer 
circumference connected to a housing, is furthermore guided by webs in 
axial direction, and on one end face has a closing seat engaging the 
housing while the covered up area equals the surface inclosed by the 
effective line of the inner rolling diaphragm. The housing part which is 
closed off by the closing seat toward the intake line in non-throttled 
condition communicates with the crankcase. The non-throttled connection 
between the crankcase and the control piston brings about that also with 
the closing seat in open position, the actual overpressure in the 
crankcase in unchanged manner acts upon the control piston. Furthermore, 
in view of the arrangement of the inner rolling diaphragm and the 
longitudinal bore in the control piston, the pressure forces in the 
interior region of the closing seat cancel each other out or act against 
the housing. As a result thereof, the control piston is acted upon only by 
the overpressure in the crankcase and by the ambient pressure so that the 
control is effected independently of the pressure in the intake conduit. 
When the pressure pulsates or oscillates in the crankcase, there exists 
the danger that the control piston of the quickly responsive control valve 
pulsates. 
It is, therefore, an object of the present invention, by simple, safe 
operational means to prevent the control piston from pulsating.

The ventilation system according to the invention is characterized 
primarily in that the control piston is acted upon by the ambient pressure 
through a throttling area in front of which there is arranged a separating 
chamber with an inlet opening. 
Fundamentally it is known to dampen the movements of control members by 
throttling areas in a flowing medium. The arrangement of a throttle at the 
side of the crankcase would be very effective but would affect the control 
because in view of the reduction in the cross section, the ratio of 
dynamic pressure relative to the static pressure would change in an 
unfavorable manner at the control piston when the control valve is open. 
In contrast thereto, with the arrangement of the throttling area according 
to the invention between the surrounding and the control piston, merely 
the pulsation of the piston is avoided, whereas the control operation 
itself is not affected because at this area no continuous flow-through 
exists. In view of the small air volumina which during the actuation of 
the control piston pass through the throttle areas, it is necessary to 
keep the throttle area very narrow. This brings about that the throttle 
area could easily be clogged up by soil particles. This factor is taken 
into consideration according to the invention by the fact that the 
throttle area is preceded by a separating chamber with an inlet opening 
the ambient air quiets down in said separating chamber, and the soil 
particles are separated without passing into the throttle area itself. 
According to a further development of the invention, it is suggested that 
the intake opening is directed downwardly. In this way it is possible that 
the separated soil particles drop again toward the outside through the 
inlet opening. This action with reciprocating piston internal combustion 
engines is aided by the vibration of the engine housing. The extent to 
which such separation is effected can be improved by the arrangement of a 
screen or filter in the separating chamber. 
Referring now to the drawing in detail, the arrangement according to the 
invention comprises a housing 1 of a control valve in which a hollow 
control piston 3 with a longitudinal cavity or bore 4. The control piston 
is preloaded by a weak spring 2 which surrounds a projection extending out 
from an end wall of the housing and into the cavity of the piston. The 
control piston 3 at its outer and inner circumference is connected by 
means of rolling diaphragms 5 and 6 relation to the housing 1 and is 
guided in axial direction by webs 7. At its end face, the control piston 3 
forms with the housing 1 a closing seat 8. The connecting conduit to the 
crankcase not shown in detail is designated with the reference numeral 9. 
The connecting line to the likewise not illustrated intake conduit is 
designated with the reference numeral 10. The control surface 11 which 
pertains to the control piston 3 and which is located opposite the closing 
seat is acted upon by the ambient pressure through the throttle area 12. 
Arranged in front of the throttle area 12 is a separating chamber 13 with 
a screen or filter 15 and a downwardly directed inlet opening 14. 
The diaphragm 5 separates the opening defined by the throttle 12 from the 
opening 9 connected to the crankcase while the diaphragm 6 separates the 
throttle 12 from the opening 10 connected to the engine air intake. The 
space between the end wall abutted by the coil spring 2 and the piston 
forms an ambient air chamber. 
It is, of course, to be understood that the present invention is by no 
means limited to the specific showing in the drawing, but also comprises 
any modifications within the scope of the appended claims.