This application relates to Venturi devices for producing vacuum using the Venturi effect, more particularly to such devices that employ a fletch insert in the motive section.
Engines, for example vehicle engines, are being downsized and boosted, which is reducing the available vacuum from the engine. This vacuum has many potential uses, including use by the vehicle brake booster.
One solution to this vacuum shortfall is to install a vacuum pump. Vacuum pumps, however, have a significant cost and weight penalty to the engine, their electric power consumption can require additional alternator capacity, and their inefficiency can hinder fuel economy improvement actions.
Another solution is an aspirator or ejector that generates vacuum by creating an engine air flow path that is parallel to the throttle, referred to as an intake leak. This leak flow passes through a Venturi having a fletch in the motive section that generates a suction vacuum. The problem with current fletches is that the abrupt change in shape near the motive exit causes flow losses.
An evacuator is a device which creates a low pressure for drawing a vacuum that acts on a device directly or acts indirectly on the other device via a vacuum reservoir. Such an evacuator may be used, for example, in vehicles to create a vacuum for brake systems, turbocharged engines and heating and ventilations systems. According to prior art known from, for example, applicant's co-owned prior applications US 2016/0061160 and U.S. Ser. No. 17/001,6414 and prior provisional patent application No. 62/042,569, the contents of which incorporated herein by reference in their entirety, it is known to use a fletch insert to reduce the amount of motive flow required by the evacuator to supply a specific amount of vacuum when compared to an evacuator that does not include the fletch insert.
Known fletch inserts are susceptible to vibrations caused by slight differentials in pressure on one side or the other of the fletch insert. This causes the tip of the fletch insert to oscillate, resulting in an undesirable audible noise.
It is an object of the invention to provide an improved fletch insert which eliminates the noise of known fletch inserts. It is a further object of the invention to provide a fletch insert that not only minimizes noise, but does so with minimal interference with motive flow, thereby increasing the suction of the evacuator.
A need exists for improved fletch designs within a Venturi device that generate increased suction flow while minimizing flow losses.
The above and other objects are achieved by the invention, wherein in one embodiment there is provided a device for producing a vacuum, comprising: a housing defining a suction chamber, a motive passageway having an entrance adapted to be connected to a fluid source and an exit in fluid communication with the suction chamber, the motive passageway including a tapering portion with a cross section that tapers toward the exit of the motive passageway, the housing further defining a discharge passageway having an entrance in fluid communication with the suction chamber and a cross section that expands in a direction away from the suction chamber; and a fletch insert disposed in the motive passageway and extending in a longitudinal direction of the motive passageway, the fletch insert including a first section proximate the exit of the motive passageway, a second section proximate the entrance of the motive passageway and a third section between and integral with the first and second sections; wherein the first section includes a region that expands in cross section toward the exit of the motive passageway to form a circumferential opening at the exit of the motive passageway between the first section of the fletch insert and an inner surface of the housing defining the motive passageway; wherein the second section of the fletch insert comprises a partition wall having a length extending in the longitudinal direction of the motive passageway and having a height extending in a direction perpendicular to the longitudinal direction of the motive passageway that extends across a full diameter of the motive passageway, and including partition wall ends connected to an inner surface of the motive passageway; and wherein the third section extends in the longitudinal direction of the motive passageway and tapers in the longitudinal direction from the second section to the first section, the third section having a first cross section that is the same as a cross section of the second section where the second and third sections meet and which transitions to a cross section of the first section where the third section meets the first section.
In an embodiment, the second of the fletch insert has a first width and the third section has a second width extending in the same direction as, and equal to, the first width.
According to another embodiment, the opening at the exit of the motive passageway is a continuous opening in the circumferential direction.
In another embodiment, the first section of the fletch insert is positioned in the tapering portion of the motive passageway.
In a further embodiment, the tapering portion of the motive passageway is conic in shape.
In yet another embodiment, the of the evacuator is configured to employ the Venturi effect, and the motive passageway is aligned with and spaced apart from the entrance of the discharge passageway to define a Venturi gap within the suction chamber.
According to another embodiment, the first section of the fletch insert has a polygonal cross section, in particular has a rectangular cross section, and more particularly has a square cross section.
In another embodiment, the fletch insert extends along a central axis of symmetry of the housing.
According to another embodiment, the fletch insert is only connected to the inner surface of the housing forming the motive passageway via the partition wall of the second section of the fletch insert, whereby the fluid flows around at least the entire circumference of the first section when exiting the motive exit.
FIG. bis a side, longitudinal cross-sectional, perspective view of another embodiment of a Venturi device having a solid fletch.
The following detailed description will illustrate the general principles of the invention, examples of which are additionally illustrated in the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements.
As used herein, “fluid” means any liquid, suspension, colloid, gas, plasma, or combinations thereof.
The device requiring vacuum 102 may be a vehicle brake boost device, fuel vapor purge system, positive crankcase ventilation system, a hydraulic and/or pneumatic valve, automatic transmission, air conditioner, or any other engine system or component in need of vacuum.
The Venturi device 100 includes a housing 101, which as illustrated is formed of an upper housing 104 and a lower housing 106 sealingly connected to one another. The designations of upper and lower portions are relative to the drawings as oriented on the page, for descriptive purposes, and are not limited to the illustrated orientation when utilized in an engine system. Preferably, upper housing portion 104 is joined to lower housing portion 106 by sonic welding, heating, or other conventional methods for forming an airtight seal therebetween. The Venturi device includes a first check valve 111 and a second check valve 120 and has a cap 174 closing an auxiliary port.
As shown representatively in
As shown in
Referring again to
The upper housing 104 includes upper valve seats 125, 127. Each upper valve seat 125, 127 is defined by continuous outer wall 160, 161 and bottom wall 162, 163. Both upper valve seats 125, 127 may include a pin 164, 165 extending downwardly from the bottom walls 162, 163, respectively, toward the lower housing 106. The pins 164, 165 are guides for translation of the sealing members 136, 137 within the cavities 166, 167 defined by the mated upper valve seat 125 with the lower valve seat 124 and defined by the mated upper valve seat 127 with the lower valve seat 126. Accordingly, each sealing member 136, 137 includes a bore therethrough sized and positioned therein for receipt of the pin 164, 165 within its respective cavity 166, 167.
The passageway 144 in the lower housing portion 106 has an inner dimension along a central longitudinal axis that includes a first tapering portion 182 (also referred to herein as the motive cone) in the motive section 180 of the lower housing 106 coupled to a second tapering portion 183 (also referred to herein as the discharge cone) in the discharge section 181 of the lower housing 106. Here, the first tapering portion 182 and the second tapering portion 183 are aligned end to end (outlet end 184 of the motive section 180 to inlet end 186 of the discharge section 181). The inlet ends 188, 186 and the outlet end 184, 189 may be any circular shape, elliptical shape, or some other polygonal form and the gradually, continuously tapering inner dimension extending therefrom may define, but is not limited to, a hyperboloid or a cone. Some example configurations for the outlet end 184 of the motive section 180 and inlet end 186 of the discharge section 181 are presented in co-pending U.S. Pat. No. 9,827,963, incorporated by reference herein in its entirety.
As seen in
When the Venturi device 100 is connected into an engine system, the check valves 111 and 120 functions as follows: as the engine operates, the intake manifold 172 draws air into the motive port 180, through passageway 144 and out the discharge port 112. This creates a partial vacuum in the check valve 111 and passageway 146 to draw seal 136 downward against the plurality of fingers 134, 135. Due to the spacing of fingers 134, 135, fluid flow from passageway 144 to passageway 146 is allowed. The partial vacuum created by the operation of the engine serves in the vacuum assistance of at least the operation of the device requiring vacuum 102. Then as pressure differential change, the first check valve 111 closes and the second check valve 120 opens to allow fluid flow to bypass the Venturi gap 160.
Referring now to
The housing 201 defines a suction chamber 207. The suction chamber may have different configurations, but the one illustrated has cylindrical wall 222 with an enclosed bottom, closed by a cap 218. In another embodiment, the suction chamber when viewed in a transverse cross-section may be generally pear-shaped, as disclosed in co-owned U.S. Pat. No. 10,443,627 having opposing ends walls oriented transverse to a central longitudinal axis of passageway 244.
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As best seen in
The fletch 220 serves to block motive flow within the motive passageway 209 at the center of the motive passageway because flow at this position does not provide any suction. It is more effective to concentrate all the flow along the interior walls defining the motive passageway because this flow produces suction as it passes through the Venturi gap into the discharge passageway. The fletch 220 has a first solid body section 280 positioned centrally within the motive passageway 209 and defining a first end 282 at the motive exit 236 (flush therewith) as shown in
As shown in
In the embodiment of
In the embodiment of
Referring again to
The outer support 570 may be an annular ring that is circular, but the outer support may be oval or may be a polygonal-shaped ring or any other shaped needed to be seatable within the suction chamber at a desired position. The inner annular ring 574 is typically circular or oval in shape. In one embodiment, the upper surface 575 is a continuous surface in one plane perpendicular to the central longitudinal axis C. In another embodiments, the upper surface 575 undulates with two opposing troughs 579. In yet another embodiment, the upper surface 575 is angled downward and radially outward toward the outer support 570 over a minor arc extending 20 degrees up to 170 degrees along the inner annular ring 574, thereby defining an inclined surface portion of the upper surface.
In operation, the device 200, in particular the suction port 210, is connected to a device requiring vacuum (see
Referring now to
The fletch 320 is a solid fletch, in contrast with a hollow fletch of co-pending U.S. application Ser. No. 17/645,827, filed on the same day as this pending application, that serves to block motive flow within the motive passageway 209 at the center of the motive passageway because flow at this position does not provide any suction. The fletch 320 has a first end 322 terminating proximate or at the motive exit 236 as discussed above. The first end 322 has an exterior shape matching the interior shape of the motive passageway 209 but of smaller dimensions, also as explained above. In
Extending from the second end 324 of the fletch 320 in the upstream direction is a partition 340. The partition 340 is seated within the first portion 211 of the motive port 208 with opposing first sides 342, 344, which define the width W2 of the partition 340, against or integrally molded as part of the interior surface of the first portion 211, thereby dividing the first portion 211 into two flow paths along opposing second sides 346, 348, which extend between the opposing first sides 342, 344. The opposing second sides 346, 348 define a height H2 of the partition 340. The height H2 of the partition 340 tapers proximate the fletch 320 to reduce H2 to H1 while maintaining the width, i.e., W2=W1 at the transition of the partition 340 to the fletch 320.
The lower housing 306 and the fletch-partition unit 310 may both be made of plastic. These parts may be made by an injection molding process or an infusion molding process, so that the partition 340 of the fletch-partition unit 310 is integral with the housing by virtue of the connection of opposing first sides 342, 344 to the inner surface of the first portion 211 of the passageway 244. Alternatively, the opposing first sides 342, 344 may be fixed to the inner surface of the first portion 211 by an adhesive. The lower housing 306 and fletch-partition unit 310 may be made of other materials, such as metal and the attachment may be accomplished by other methods, as will be appreciated by those skilled in the art. Importantly, the fletch-partition unit 310 is made of a stiff material and its shape and attachment via the partition 340 eliminate vibration and/or oscillations of the fletch-partition unit 310 which could be caused by slight differentials in pressure on opposite sides of the fletch 320 as fluid flows through the motive passage 209, thereby defining a quiet fletch 320. In other words, no audible noise is emitted during the flow of fluid through passageway 244 as a result of the presence of the letch-partition unit 310.
The transition of the partition 340 to the tapering quadrilateral frustum shaped fletch 320, preferably square or rectangular in cross-section, gives the fletch-partition unit 310 a rigid construction when installed in the passageway 244 as discussed above. Because of the firm connection of the partition 340 within the lower body 306, as well as the light and stiff construction of the fletch-partition unit 310, the fletch 320 has a relatively high natural frequency which is measured by the formula (K/M)0.2, where K is the stiffness of the part, and M is the mass. As a result, the relatively low, noise generating, frequencies are eliminated during operation of the evacuator employing the fletch insert as herein described. Furthermore, the presence of the fletch-partition unit 310 provides minimal interference with the motive flow through the passageway 244 while still providing an increase in the suction flow.
In operation, fluid enters the motive entrance 332 is divided into partial paths on opposite sides of the partition 340. The fluid flows in the longitudinal direction of the passageway 244 and the two partial flows merge together at the beginning of the motive passageway 209 where the fletch 320 begins to divergingly taper toward the Venturi gap 260. Because there is a clearance around the entire exterior surface of the fletch 320 within the motive passageway 209, there will be a circumferentially continuous flow of fluid around the fletch 320 therein. The result is minimal interference with the fluid flow entering and exiting the motive passageway, in particular entering the Venturi gap 260.
Discharge passageway 312 has a discharge entrance 352 in the suction chamber 307 and divergingly tapers away from the Venturi gap 260 toward a motive exit 336. Each of the motive exit 336 and discharge entrance 352 may be rectangularly shaped, interior profile and exterior profile, and may each transition to a circular cross section in a direction extending away from the suction chamber 307.
Although the invention is shown and described with respect to certain embodiments, it is obvious that modifications will occur to those skilled in the art upon reading and understanding the specification, and the present invention includes all such modifications.
This application claims the benefit of U.S. Provisional Application No. 63/130,458, filed Dec. 24, 2020, the entirety of which is incorporated herein by reference.
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