Throttle valve and method of producing the same

A throttle assembly including a first throttle component that is formed of a plastic material including a conductive additive substantially homogeneously dispersed within the plastic material, and a second throttle component is axially aligned with the first throttle component and movable relative to the first throttle component between a first position and a second position to selectively vary a flow through the throttle assembly. A terminal is coupled to the first throttle component such that electricity may be provided to the first throttle component, thereby resistively heating the first throttle component via the conductive additive and a flow window is defined in one of the first throttle component and the second throttle component.

BACKGROUND

The invention relates to throttle valves and a method of producing throttle valves. Particularly, the invention relates to throttle bodies for automotive applications, and a method of manufacturing a set of mating cones for a conical throttle assembly or other throttling devices. U.S. Pat. No. 6,782,912 discloses a generally conically shaped throttle valve and is incorporated by reference in its entirety herein.

Typically, throttle valves (i.e., throttle bodies, throttle assemblies) include multiple machined components that are assembled using fasteners. The tolerancing of machined parts often leads to slight variation in parts. Machining mating parts with very small or tight tolerances is expensive and time-consuming. In addition to manufacturing limitations, close fitting parts must include additional tolerance due to climatic and environmental condition changes such as humidity and thermal expansion. These additional tolerance requirements may compromise the function of the part over a wide operating range.

SUMMARY

The current machining technology makes the repeatable production of parts with tight tolerances expensive and unrealistic. The invention provides an improved throttle valve formed with precise mating surfaces, repeatably, and at an acceptable cost. In one embodiment, a two shot injection or compression molding technique is utilized (e.g., over-molding or transfer molding).

The material used is a composite thermoset plastic that can include release agents, shrink modifiers, and other additives, as desired. Due to the inherent nature of the materials selected and the tool design, any deviation in one mating part will be reflected in the other mating part. So long as the parts remain as a mating set, there will be no issue with tolerance shift. This process may be used to produce various parts of the throttle valve including matching cone sets, cams, gears, shafts, and/or other parts, thereby reducing the number of parts, the machining required, and assembly processes.

In one embodiment, the invention provides a throttle assembly including a first throttle component that is formed of a plastic material including a conductive additive substantially homogeneously dispersed within the plastic material, and a second throttle component axially aligned with the first throttle component and movable relative to the first throttle component between a first position and a second position to selectively vary a flow through the throttle assembly. A terminal is coupled to the first throttle component such that electricity may be provided to the first throttle component, thereby resistively heating the first throttle component via the conductive additive. A flow window is defined in one of the first throttle component and the second throttle component.

In another embodiment the invention provides a method of producing a throttle assembly. The method includes inserting a first core into a mold portion to form a first throttle component cavity between the first core and the mold portion, providing a first thermoset plastic material into the first throttle component cavity to form a first throttle component, removing the first core from the mold portion while maintaining the first throttle component positioned within the mold portion, inserting a second core into the mold portion to form a second throttle component cavity between the mold portion, the first throttle component, and the second core, providing a second thermoset plastic material into the second throttle component cavity to form a second throttle component, removing the second core from the mold portion, removing the first throttle component and the second throttle component from the mold portion, and at least partially separating the first throttle component from the second throttle component.

DETAILED DESCRIPTION

The below detailed description uses several terms known in the art. For example, components of a throttle body or throttle valve are often referred to as cones (e.g., a first throttle cone and a second throttle cone). While the illustrated cones or throttle components may be generally cone shaped, they are not strictly geometrically cone shaped and include features that vary from a geometric cone. Furthermore, the cones may be non-conical in nature, as desired. The throttle components could be any suitable shape for a throttle body or throttle valve, as desired.

FIGS. 1 and 2show an air intake throttle assembly or throttle valve10for a vehicle. In other embodiments, the throttle valve10could be used for beverage dispensing, air conditioning systems, high volume fluid flow throttling, other fluid throttling/valving applications. The illustrated throttle valve10is generally conical and includes a first throttle component in the form of a first throttle cone14and a second throttle component in the form of a second throttle cone18. Throttle assemblies or throttle valves are commonly referred to in the art as throttle bodies. In the illustrated embodiment, the first cone14is an outer cone and the second cone18is an inner cone. In other embodiments, the cones14,18may be arranged differently or may have a different shape or geometry, as desired.

The first throttle cone14is generally hollow, frustoconically shaped, and defines a first distal end22of the first throttle cone14. The first distal end22has an outer diameter A and a face26(FIG. 2) that defines a plane B (FIG. 1).

A wall portion30extends from the first distal end22in the direction of an axis C and reduces in diameter as it moves away from the first distal end22to define a generally frustoconical shape. The wall portion30has a generally consistent cross sectional thickness as it extends along the axis C.

An end wall or rim34is defined at the end of the frustoconically shaped wall portion30opposite the first distal end22, and defines a flat surface38(FIG. 2). The interior of the rim34defines a rim sealing surface42between the flat surface38and the wall portion30. Two guide cams or tabs46are formed on the flat surface38and project in the direction of the axis C toward the first distal end22. The two tabs46are positioned on the rim34one-hundred-eighty degrees from one another with respect to the axis C. In other embodiments, the two tabs46are positioned at a different angle relative to one another and the axis C. Additionally, more or less tabs46may be utilized, as desired.

A first window50and a second window54are formed in the wall portion30one-hundred-eighty degrees apart with respect to the axis C. The first and second windows50,54are spaced axially an equal distance from the first distal end22such that a support portion56exists between the first and second windows50,54and the first distal end22. The first and second windows50,54are generally wedge-shaped to follow the wall portion30and to increase flow area, and define a sealing seat58along three edges of the first and second windows50,54. Each illustrated sealing seat58is a beveled surface. A fourth edge of the first and second windows50,54is defined by the flat surface38of the rim34.

In the illustrated embodiment, the throttle valve10is a heated throttle valve. Details of the heating features will be discussed below. The heating feature is optional and can be eliminated such that the throttle valve10is not heated. The illustrated first throttle cone14(with heating features) includes first and second protrusions62,66that extend from the wall portion30. The first protrusion62includes a flat surface70that is substantially parallel to the face26of the first distal end22. A locating bump74protrudes from the flat surface70of the first protrusion62and provides a locating feature to aid in the proper orientation of the throttle valve10when installed in the vehicle. Alternatively, the locating bump may be used for orienting an electrical connector (not shown).

The second protrusion66is the same as the first protrusion62but does not include a locating bump74. The first and second protrusions62,66are approximately one-hundred-eighty degrees from each other relative to the axis C and are positioned between the windows50,54. In the illustrated embodiment, the protrusions62,66are integrally formed with the wall portion30.

In the illustrated embodiment, a terminal in the form of two electrodes78is molded into the first and second protrusions62,66(i.e., one electrode78in each protrusion62,66). The electrodes78are a conductive material (e.g., a ferrous metal, copper, etc.), and are directly connected to the throttle valve10via the first and second protrusions62,66. Again, the protrusions62,66and the terminal are optional and may be eliminated from the throttle valve10, as desired. For example, in a temperate or tropical location where freezing temperatures are not expected, a heating throttle valve10is not necessary and the heated features may be eliminated. Alternatively, the insert molded electrodes78may be replaced with cavities to accept a separately-attached, external terminal. In another embodiment, the electrodes78may be replaced by molding out protrusions as part of the first throttle cone14to accept a separate mating clip or connector of comparative geometry.

The first throttle cone14also includes a generally cylindrical portion82that extends along the axis C from the rim34, away from the first distal end22, and to a second distal end84. The cylindrical portion82is substantially hollow and defines a cutout area86that extends over approximately ninety degrees of the cylindrical portion82. An aperture90extends concentric with the axis C through the rim34and into communication with the interior of the cylindrical portion82and defines a bearing surface. In the illustrated embodiment, the cutout area86is at the second distal end84. In other embodiments, the cutout area86could be an enclosed aperture90formed in the cylindrical portion82. The function and purpose of the cutout area86will be discussed further below.

In the illustrated embodiment, the first throttle cone14may be molded from a thermoset plastic such as a bulk molding compound (BMC) material that includes a conductive additive (e.g., graphite). The conductive additive is dispersed substantially homogeneously throughout the BMC material such that the first throttle cone14is conductive to provide resistance-heating capabilities as will be discussed in greater detail below. The illustrated BMC material is available from Bulk Molding Compounds, Inc. located in West Chicago, Ill. as Product No. BMC 945-17510 and will be discussed in detail below with regard to the method of forming the throttle valve10. Other materials with similar properties may also be used, as desired.

The second throttle cone18is sized and configured to fit into the substantially hollow center of the first throttle cone14and selectively mate and nest therewith. The second throttle cone18includes a circular disk portion94substantially parallel to the plane B and sized to mate with the flat surface38of the rim34. The circular disk portion94includes a sealing edge98that substantially matches the rim sealing surface42to selectively form a seal therebetween. Two depressions102(FIG. 2a) are formed in the circular disk portion94and are sized to receive the two tabs46of the rim34as discussed further below. In another embodiment, the tabs46are formed on the second throttle cone18and the depressions102are formed on the first throttle cone14to be selectively received within the first throttle cone14. Additionally, any number of tabs46and depressions102may be utilized.

An actuating rod106is molded to the circular disk portion94and extends along the axis C. The actuating rod106is received through the aperture90, and supported on the bearing surface, in the first throttle cone14to allow controlled axial and rotational movement of the second throttle cone18with respect to the first throttle cone14. The illustrated actuating rod106includes a first portion110with a first diameter, a second portion114with a second smaller diameter, an aperture118formed in the first portion110perpendicular to the axis C, and a notch122formed in the distal end of the second portion114. The illustrated notch122is used for alignment during the molding process, as described below. Alternatively, the aperture118may also be used to align the actuating rod106during the molding process. In one embodiment, an end of the actuating rod106opposite the notch122includes a knurled or notched end (not shown) to facilitate bonding when molded into the second throttle cone18. Alternatively, the actuating rod106may be integrally formed from the thermoset plastic material during the forming of the second throttle cone18or may be eliminated. An optional sealing arrangement may be positioned within the cylindrical portion82to form a seal between the actuating rod106and the first throttle cone14.

The second throttle cone18also includes a first cover portion126and a second cover portion130. The first and second cover portions126,130extend away from the circular disk portion94in a direction opposite the actuating rod106. The first and second cover portions126,130are shaped to correspond with the first and second windows50,54, respectively, and each includes a sealing surface134along three edges. The sealing surfaces134of the first and second cover portions126,130selectively seal against the respective sealing seats58of the first and second windows50,54. The illustrated sealing surfaces134are beveled to match the sealing seats58. Additionally, the first and second cover portions126,130each extend to a distal end138of the second throttle cone18.

The first cover portion126and the second cover portion130are separated by two voids140such that the distal end138does not form a continuous circle or perimeter. The voids140allow fluid flow through the throttle valve10as will be described below.

A spine142is formed between and interconnects the first cover portion126, the second cover portion130, and the circular disk portion94to provide rigidity to the second throttle cone18. The illustrated spine142extends from the circular disk portion94almost to the distal end138and bisects each of the first and second cover portions126,130. The spine142may vary in shape and depth toward the distal end138to provide a desirable rigidity and to provide desirable flow characteristics (e.g., flow separation) with respect to the first and second flow windows46,50.

In operation, the throttle valve10is positioned in the air intake of a vehicle engine (not shown). The first throttle cone14is mounted to the engine and the electrodes78are connected to an electrical system via suitable connectors (not shown). The actuating rod106is engaged by an actuating system (not shown) via the aperture118.

The second throttle cone18is moveable between a first position wherein the first and second cover portions126,130inhibit air flow through the throttle valve10by sealing the sealing surfaces134against the sealing seats58of the first and second windows50,54, respectively, and a second position where the first and second cover portions126,130allow air to flow through the throttle valve10. The second throttle cone18is moved axially and rotationally relative to the first throttle cone14to open the first and second windows50,54.

In the illustrated embodiment, tabs46and depressions102include camming surfaces rounded portions146that are designed such that the radii of the rounded portions146provide a desirable movement profile. The cutout area86also has camming surfaces or rounded portions150that provide a desirable movement profile. A pin (not shown) that is inserted through the aperture118is sized to cooperate with the rounded portions150of the cutout area86. As the second throttle cone18moves between the first position and the second position, the interplay between the rounded portions146of the tabs46and the depressions102, and the interplay between the rounded portions150of the cutout86and the pin inserted in the aperture118, provide a desired movement path axially and/or rotationally for the second throttle cone18relative to the first throttle cone14. During a portion of the movement between the first position and the second position, the second throttle cone18is moving both axially and rotationally relative to the first throttle cone14as guided by the rounded portions146,150. The operation described above is achieved through the use of a specially designed gear drive (not shown) engaging the first and second portions110,114and the pin installed into aperture118.

When the second throttle cone18is in the first position, the distal end138intersects the plane B and is adjacent the first distal end22of the first throttle cone14. When in the second position, the second throttle cone18is moved axially in the direction of the axis C such that the tabs46are no longer disposed within the depressions102and the second throttle cone18is rotated about the axis C about ninety degrees such that air may flow through the windows50,54. The actuator system moves the second throttle cone18between the first and second position to selectively control the flow of air to a combustion chamber (not shown) of the engine. At positions between the first position and the second position (i.e., an infinite number of possible positions between the first and second positions), the throttle valve10allows a variable amount of air or fluid to flow therethrough and may be used to control the combustion characteristics of the engine. When the second throttle cone18is not in the first position, the first throttle cone14and the second throttle cone18are at least partially separated such that a desired portion of air or fluid may flow through the windows50,54.

In a cold environment (e.g., winter in a northern climate), the throttle valve10may have a tendency to become cold and freeze, thereby causing the first and second throttle components14,18to stick and resist relative movement between the first and second positions. In such cases, the heating features are utilized and electricity may be provided to the electrodes78. When a current is applied to the electrodes78, energy flows through the conductive additive throughout the first throttle cone14and resistively heats the throttle valve10. The addition of the conductive additive provides a valve heating solution without the addition of complicated heaters, metallic coils, or other costly and less reliable systems typically employed such as engine coolant passages. The heating features may be activated any time before, during, and/or after operation of the throttle valve10to release ice build up and/or to prevent ice from accumulating through the thermodynamic refrigeration phenomena known as expansion. Additionally, a mechanical ice breaking operation may be used wherein the second throttle cone18moves axially between the first and second positions to dislodge and break ice away from the throttle valve10with the use of the specially designed gear drive and by taking advantage of mechanical leverage.

Described hereafter with respect toFIGS. 3 and 4is an apparatus and method for producing a throttle valve10as described above. The apparatus includes a mold portion200, a first core204, and a second core208.

The mold portion200includes a generally frustoconical depression212that includes mold features for forming the first distal end22, the wall portion30, the rim34, the cylindrical portion82, and the protrusions62,66of the first throttle cone14. Some geometry of the first and second windows50,54and first and second cover portions126,130are also formed by the mold portion200as will become apparent below. Any other features on the external surface of the throttle valve10are also formed in the mold portion200, as desired. A pneumatic ejection port214is formed in the mold portion200for ejecting the throttle valve from the frustoconical depression212.

In the illustrated embodiment, the mold portion200also includes holding geometry in the form of recesses216to hold the electrodes78and the actuating rod106in place such that they may be molded into the first and second throttle cones14,18, respectively.

The first core204(FIG. 3) includes a generally frustoconically shaped protrusion228that includes mold features for forming the first and second windows50,54, the tabs46, the first distal end22, the rim34, and other features of the first throttle cone14.

A first resin flow path220is formed in the first core204(e.g., defined by a conduit and a bore) and provides a flow path for molten resin (e.g., BMC material) through the first core204. The illustrated first resin flow path220includes four outlets224(three are visible inFIG. 3) positioned to inject molten resin into the generally frustoconical depression212, although more or fewer outlets are contemplated and any number of outlets may be utilized, as desired.

The second core208(FIG. 4) includes a generally frustoconically shaped protrusion232that includes mold features for forming the first and second cover portions126,130, the spine142, the circular disk portion94, and other features of the second throttle cone18. The illustrated first and second cores204,208includes features for forming the first and second flow windows50,54and the first and second cover portions126,130such that the size and configuration may be changed. For example, the first and second cores204,208may be changed to produce larger or smaller flow windows46,50and covers126,130or flow windows46,50and covers126,130with a different geometry, as desired.

A second resin flow path236(FIG. 4) is formed in the second core208(e.g., defined by a conduit and a bore) and provides a flow path for molten resin (e.g., BMC material) through the second core208. The illustrated second resin flow path236includes four outlets240(three are visible inFIG. 4) positioned to inject molten resin into the generally frustoconical depression212, although more or fewer outlets are contemplated and any number of outlets may be utilized, as desired.

In the illustrated embodiment, the first core204is held by a first core holding tool244and the second core208is held by a second core holding tool248. The first and second core holding tools244,248include pneumatic ejection ports252similar to the ejection port214for ejecting the throttle valve10from the first and second cores204,208. In another embodiment, the first core holding tool244and the second core holding tool248are the same component and the first core204and the second core208are both held by a single holding tool. In yet another embodiment, a single holding tool is utilized but only holds either the first core204or the second core208at any one time, such that the first core204and the second core208must be interchanged during a forming operation. Other core holding arrangements may be realized to optimize the speed, efficiency, or other factors, as desired.

In operation, the two electrodes78and the actuating rod106are positioned in the holding geometry216of the mold portion200, and the first core204is moved into the mold portion200and held in place to form a first mold cavity between the mold portion200and the first core204. Then, a first shot of molten resin (e.g., including the conductive additive) is pushed into the first mold cavity via the first resin flow path220to form the first throttle cone14including the first and second windows50,54, the sealing seats58, the tabs46, the apertures90, and all the other features of the first throttle cone14. In the illustrated embodiment, the actuating rod106is used as a part of the first mold cavity to form the aperture90and the bearing surface. This allows for a substantially perfect mating and bearing surface between the bearing surface of the aperture90and the actuating rod106. The first shot of molten resin fills the first mold cavity such that substantially no pockets exist. After the first shot of molten resin sets and cures satisfactorily, the first core204is removed. In the illustrated embodiment, the molten resin is raised to an elevated temperature and pressure while in the first mold cavity to set the thermoplastic resin. The elevated temperature and pressure are maintained for a predetermined amount of time to allow the thermoplastic to cure. The temperature and pressure may be varied to produce desirable results. For example, a controlled cooling cycle may be used to cure the first throttle cone14.

After the first core204is removed, with the first throttle cone14and the actuating rod106still positioned in the mold portion200, the second core208is positioned within the mold portion200such that a second mold cavity is formed between the mold portion200, the first throttle cone14, and the second core208. Then, a second shot of molten resin is pushed into the second mold cavity via the second resin flow path236to form the second throttle cone18including the cover portions126,130, the sealing surface134, the depressions102, and the other features of the second throttle cone18. The second shot of molten resin fills the second mold cavity such that substantially no pockets exist and the second throttle cone18is formed substantially completely to the first throttle cone14. The mating surfaces of the second throttle cone18are formed directly to the first throttle cone14. For example, the sealing seats58of the first throttle cone14act as the portions of the second mold cavity that form the respective sealing surfaces134of the second throttle cone18such that the mating relationship between the sealing seats58and the sealing surfaces134is substantially perfect. After the second shot of molten resin sets and cures satisfactorily, the second core208is removed from the mold portion200. In the illustrated embodiment, the molten resin is raised to an elevated temperature and pressure while in the second mold cavity to set the thermoset plastic resin. The elevated temperature and pressure are maintained for a predetermined amount of time to allow the thermoset plastic to cure. The temperature and pressure may be varied to produce desirable results. For example, a controlled cooling cycle may be used to cure the second throttle cone18. In addition, the setting and curing parameters may be different for the first throttle cone14and the second throttle cone18, as desired.

The throttle valve10may then be removed from the mold portion200as a unit. The first throttle cone14and the second throttle cone18are a mated pair with matching features due to being formed together (i.e., the second throttle cone18molded directly to the first throttle cone14). Additionally, the first and second throttle cones14,18may be removed from the mold portion200separately while maintaining an association between the first throttle cone14and the second throttle cone18(e.g., color coding, labeling, organized stacking/boxing, or nesting of parts, etc.). In one embodiment, the first throttle cone14and the second throttle cone18are at least partially separated from one another either during or after removal from the mold portion200. The actuating rod106remains disposed within the aperture90while the first throttle cone14and the second throttle cone18are at least partially separated (i.e., mating features of the first and second throttle cones14,18are spaced apart from one another). Additionally, the first throttle cone14and the second throttle cone18may be completely separated (i.e., with the actuating rod106completely removed from the aperture90). Partial or complete separation may be used for cleaning, polishing, flashing removal, or other finishing and processing operations, as desired.

In an alternate embodiment, a compression molding process is utilized wherein pre-measured composite billets or slugs are placed into the mold portion200and compressed by the first and second cores204,208to form the throttle components in generally the same sequence and manner as described above. For example, a first plastic billet is positioned within mold portion200before the first core204is brought into the mold portion200. The first core204then compresses the billet within the mold portion200such that the billet fills the first throttle component cavity and forms the first throttle cone14.

After the first throttle cone14cures (similar to the injection molding process described above), the first core204is removed from the mold portion200and a second plastic billet is provided into the mold portion200with the first throttle cone14still in place. The second core18is then brought into the mold portion200to compress the second billet and fill the second throttle component cavity to form the second throttle cone18. The second throttle cone18then cures within the second throttle component cavity and the second core208is removed. In other embodiments, a combination of injection and compression molding process may be utilized, as desired.

The first and second billets are made of materials comparable to those used in the injection molding process described above and produce similar parts. In other embodiments, different materials may be used, as desired. Additionally, the billets may be warmed or softened before being provided to the mold portion200.

In the above examples, the material used for the first throttle cone14is a BMC material that is a thermoset plastic. Further, the conductive additive provides a resistive heating ability to the plastic. Various additives create a plastic that can be used in the above method such that the throttle valve10has sufficient rigidity and moldability, and such that the first and second cones14,18may be separated from one another after the two shot molding process. The BMC material used by the Assignee to form the first throttle cone14is produced by and available from Bulk Molding Compounds, Inc. located in West Chicago, Ill. as Product No. BMC 945-17510. Other materials with similar properties may be used.

The illustrated second throttle cone18is formed of a second BMC material without the conductive additive. The second BMC material is designed to separate cleanly from the first throttle cone14after the two shot molding process and is produced by and available from Bulk Molding Compounds, Inc. located in West Chicago, Ill. as Product No. BMC 304-17202. In other embodiments, other materials may be used, or the second throttle cone18may be formed of a conductive material similar to or the same as the first throttle cone14. Additionally, the first throttle cone14may be unheated and the second throttle cone18can include heating features. Furthermore, both the first and the second throttle cones14,18may be formed of a BMC material without a conductive filler such that the throttle valve10is not heated.

In other embodiments, the throttle assembly may vary such that the first throttle component is an inner cone, and the second throttle component is an outer cone. Furthermore, the throttle valve may be shaped differently and may include more components (e.g., cams, gears, shafts, etc.) that may be formed with or without the described method, as desired.