Patent Application
20070101953
The present invention relates to coolant systems for internal combustion engines used in automotive applications. More particularly, the present invention relates to an improved de-aeration system for automotive coolant systems.
The coolant used for cooling an internal combustion engine is a liquid which is subject to acquiring suspended air bubbles (i.e., aerated coolant) in the course of its flow through various coolant passages within the engine. Since the presence of air bubbles in the coolant is undesirable, as for example it reduces coolant volume and surface contact area for heat transfer and can impede coolant flow, some mechanism is usually provided to promote removal of the air bubbles from the coolant.
The prior art passive de-aeration system 10 is also a component of the coolant system 18 for removing air bubbles from the coolant. A coolant fill tube 30 is vertically oriented and has at its top end 30a a pressure cap 32 which has a twist fit connection to the fill tube. The fill tube 30 is about 150 mm in length L between its top end 30a and bottom end 30b, and is about 40 mm in diameter D. The pressure cap 32 is of a type well known in the automotive arts, wherein for situations of below a predetermined coolant pressure (for example, around 70 kPa), air escapes through a vent passage 34 in the pressure cap to an overflow nipple 36; however, if pressure exceeds the predetermined pressure, then the internal sealing of the pressure cap is released with respect to an annular cap seal lip 30c of the fill tube and coolant 40 can then travel out via the overflow nipple. The bottom end 30b of the fill tube 30 opens to a highest elevation coolant passage 42a of the plurality of coolant passages 42, as for example at the head 16, such that the fill tube rises vertically at the highest point in the coolant system 18.
In operation, coolant 40 flows (see arrows F) in a coolant passage 42, wherein air bubbles 38 travel in suspension in the coolant and pass below the fill tube 30. Passively, under urge of buoyancy some air bubbles will drift upwardly into the stagnant pool 40a of the coolant 40 situated within the fill tube 30. The air bubbles 38 find the surface and merge with the air A thereabove, whereupon the increased pressure caused thereby is released by air passing-out through the vent passage 34.
While the aforedescribed coolant system and its associated de-aeration system provide removal of air bubbles within the coolant, the passive nature of the de-aeration involving a stagnant coolant pool and the passivity of buoyancy, air bubble movement from the coolant passage and into the prior art passive de-aeration system is at a very slow pace, such that the air bubbles must, on average, make very many circuits of the coolant path before successfully finding the fill tube.
Accordingly, what remains needed in the prior art is an active de-aeration system for an automotive coolant system, wherein coolant is actively freed of suspended air.
The present invention is an active de-aeration system for removing air bubbles in coolant of an automotive coolant system, wherein a portion of the coolant which is most likely laden with a highest density of air bubbles is actively siphoned into the de-aeration system.
The active de-aeration system according to the present invention includes a fill tube and a pressure cap removably connectable thereto, wherein the fill tube further includes a de-aeration baffle therewithin and an externally disposed outlet conduit connected thereto. The outlet conduit is fluidically connected to a sump chamber of the fill tube which is disposed outside a baffled chamber created by the de-aeration baffle. The outlet conduit is also connected to the coolant system externally downstream with respect to the fill tube, most preferably plumbed to the inlet side of the pump.
The de-aeration baffle preferably includes an inverted frustoconical shell situated adjacent the bottom end of the fill tube, and a hollow stem fluidically communicating with a high elevation point of the frustoconical shell. The stem vertically follows, in parallel relation, the fill tube and terminates short of the top end thereof so that coolant may flow thereout and into the sump chamber. Preferably, a baffle orifice is provided in the stem, most preferably at a lower end of the stem, adjacent the frustoconical shell.
In operation, flowing coolant has a portion thereof which is most laden (densely populated) with air bubbles, this being located at a highest elevation of the coolant passage whereat the fill tube openingly interfaces therewith. Since the outlet conduit creates a negative coolant pressure at the bottom end of the fill tube, the pressure differential with respect to the coolant in the coolant passage causes the aforementioned upper layer of coolant in the highest elevation portion of the coolant passage which is most densely populated with air bubbles (most aerated) to be suckingly siphoned into the fill tube. As the siphoned coolant passes through the de-aeration baffle and then passes into the more slowly moving coolant sump, the air bubbles therein buoyantly make their way to the air above the surface of the flowing coolant in the sump chamber, whereupon excess air exits through the vent passage of the pressure cap.
Thus, it is seen that the coolant most laden with air bubbles in the coolant passage is actively drawn into the active de-aeration system, whereafter the air bubbles buoyantly ascend and make their way out of the coolant, whereupon the coolant flowing out the outlet conduit is de-aerated, and whereupon the coolant flowing out of the coolant passage (that proportion of the coolant not going through the de-aeration system) is greatly depopulated of air bubbles.
Accordingly, it is an object of the present invention to provide an active de-aeration system for an automotive coolant system.
This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment.
Referring now to the drawing,
As depicted at
The active de-aeration system 100 serves as a component of the coolant system 102 for removing air bubbles 124 from the coolant 110. A coolant fill tube 126 is vertically oriented and has at its top end 126a a removable pressure cap 128 which has, preferably, a twist fit connection to the fill tube and, via a resiliently biased elastomeric portion 128a thereof, seals on an annular cap seal lip 126c of the fill tube. The fill tube 126 is about 150 mm in length L′ between its bottom end 126b and the cap seal lip 126c, and is about 40 mm in diameter D′.
The pressure cap 128 is preferably conventional and of the type discussed hereinabove with respect to
Referring now additionally to
The de-aeration baffle 140 establishes two separated coolant chambers within the fill tube 126: a baffled chamber 144a and a sump chamber 144b, wherein the baffled chamber is internal to the de-aeration baffle and internal to the fill tube, and wherein the sump chamber is external to the de-aeration baffle and internal to the fill tube. The outlet conduit 142 is connected at its inlet end to the fill tube 126 at the sump chamber 144b, and connected at its outlet end to the coolant system 102 downstream of the fill tube, preferably by plumbing to the inlet side of the pump 122 so as to create a low coolant pressure, for example 35 kPa, at the sump chamber 144b in relation to the nominal coolant pressure, for example 70 kPa, in the coolant passage 112 whereat the bottom end 126b of the fill tube 126 interfaces.
The de-aeration baffle 140 is characterized by an inverted frustoconical shell (i.e., a shell having an inverted funnel shape) 146, situated adjacent the bottom end 126b of the fill tube 126, and a hollow (straw-like) stem 148 of about 6 mm diameter which is sealingly connected with (preferably by being integral therewith), and communicates fluidically with the highest elevation point 146a of the frustoconical shell. The stem 148 vertically follows, in parallel relation, the fill tube 126 and terminates in an open stem top end 148a that is spaced a distance L″ of about 15 mm from the cap seal lip 126c.
A baffle orifice 150 of about 2 mm diameter is provided via a baffle diaphragm 152 (see
In operation, coolant 110 flows (see arrows F′) in a selected highest elevation coolant passage 112a, wherein the coolant is most densely laden with air bubbles 124 at a high-elevation portion layer 110a thereof, and whereat the fill tube openingly interfaces therewith so as to ensure a highest density of aerated coolant is exposed to the opening 126d of the fill tube 126. In this regard, a highest elevation passage is preferably selected for interface with the fill tube. Since the outlet conduit 142 creates a negative coolant pressure at the sump chamber 144b, and as a consequence, at the fill tube opening 126d, the pressure differential thereby established causes the upper layer 110a of the coolant, the most densely aerated portion of the coolant, to be suckingly siphoned into the fill tube. As the aerated coolant passes through the baffled chamber 144a, by metering through the baffle orifice 140, and passes out of the stem 148 at the open stem end 148a into the more slowly moving coolant sump 144b. The air bubbles buoyantly move in the coolant and exit therefrom at its surface S′ so as to thereby mix with the air A′above the surface. Thereupon, excess air exits through the vent passage 130 of the pressure cap 128.
As a result of the active nature of operation of the active de-aeration system 100 according to the present invention, the coolant most laden with air bubbles in the coolant passage is actively drawn into the active de-aeration system, whereafter the air bubbles 124 buoyantly ascend and make their way out of the coolant, whereupon the fraction of the coolant 110b flowing out the outlet conduit 142 is de-aerated, and whereupon the fraction of the coolant 110c flowing out of the coolant passage (the portion of the coolant not going through the de-aeration system) is greatly depopulated of air bubbles.
To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.
