Patent Description:
Turbochargers are well known devices used in all forms of vehicles for supplying air to the intake of an internal combustion engine at pressures above atmospheric pressure ("boost pressures"). A conventional turbocharger includes a turbine rotor or wheel with a plurality of fins or blades inside a volute turbine housing. The turbine rotor is rotated by exhaust gases from the engine which impinge upon the turbine blades. The rotor, via a connecting shaft, provides the driving torque to a compressor. Ambient air fed to the compressor creates a boost pressure that is fed to the intake manifold of the engine.

The flow capacity of the exhaust turbine is a function of the housing volute areas and the passage of the exhaust gases as it strikes the turbine blades. The flow of exhaust gas has to be regulated to control the compressor speed to create the desired boost in manifold pressure. A typical centrifugal compressor includes an impeller driven at high speed by the turbine rotor. A diffuser surrounding the impeller causes the ambient air to increase in pressure which is directed to the intake manifold.

One particular goal with any turbocharger is the need for a quick response, i.e., prevent "turbo lag," a delay between the time when high power output is first demanded of the engine by setting the throttle to a wide-open position and the time when a boost in the inlet manifold air pressure is delivered by the compressor. In some instances, turbo lag could result in a dangerous driving situation when substantially instantaneous response is desired. If the turbocharger is large enough to provide the maximum horsepower for an internal combustion engine, then it will have excessive and potentially unsafe lag when the throttle is increased. If the turbocharger is reduced in size to minimize turbo lag, then efficiency is lost at higher engine rpms.

Some early turbocharger designs sought to solve the problem of turbo lag within a certain range of low engine speeds, such as when the engine is idling, by adding a regulated air supply to increase the mass of air entering the turbocharger intake and being forced into the engine manifold. At idle speed, the engine exhaust is insufficient to maintain the speed and charging-air output of the compressor section of the turbocharger, causing the turbocharger to "lag behind" the engine in performance. To maintain the speed of the turbocharger, a pair of nozzles penetrates the housing in opposite directions and injects air generally tangentially to the outer tips of the rotor blades. The air pressure provided by the nozzles acts as a "jet assist" in the turbocharger compressor when the engine is at idling speed (see <CIT>, and <CIT>). Another design positions nozzles at preselected points about the turbine rotor and directs air through the nozzles to impinge the blades and, in addition to providing a jet assist, prevent resonant vibration conditions in the rotor for its entire rotational speed range (see <CIT>).

The air-assisted designs do not operate to minimize turbo lag when the turbocharger is already in a spun-up condition and the engine is at normal operating speed but requires additional horsepower. Furthermore, the air-assisted designs require a waste gate to handle the total exhaust flow at maximum horsepower.

Other designs have proposed variable volute turbines; variable geometry turbines; electrically driven turbines; moveable or pivoting vanes, gates and walls for guiding, dividing, or changing the direction the exhaust gases relative to the turbine rotor and thereby control its rotational speed.

Variable volute turbines make use of a sliding or flexible dividing wall to change the geometry of the volute and, therefore, the flow of exhaust gas into the turbine wheel. One example of a variable volute design is <CIT>. The design can be slow in responding to sudden changes, is used solely as a braking application, and its performance can be negatively affected by debris build-up on the sliding wall surfaces. Another example is <CIT>. This design makes use of a flexible dividing wall that moves along a path to vary the discharge area into the turbine wheel. The design is complicated and failure-prone because the chain and bearing mechanism used to move the wall are in the path of the hot exhaust flow.

Variable geometry turbochargers use adjustable guide vanes arranged about the turbine wheel in order to control exhaust gas flow to the wheel. These designs require a large number of expensive components along with sophisticated software and controls.

Electrically driven turbines essentially turn the shaft of the turbine rotor into an armature. Because the armature must be disengaged once the turbine rotor spins up to a certain speed, these designs entail complicated electro-mechanical structures.

A moveable wall design for a variable geometry turbocharger is disclosed in <CIT>. ("the Watson publication"). A pivoting wall located along the upper wall of the housing pivots about a point located upstream of the housing tongue and near the entry to the housing (compare <CIT> showing a pivoting wall located far downstream of the tongue). As the wall pivots away from the upper wall, the wall reduces the volume of exhaust gas flowing into the volute. Alternatively, a rotating wedge segment can be located along the upper wall of the housing and moved downstream to alter the cross section of the volute. However, neither the wall nor the wedge can prevent exhaust air from flowing into the turbine wheel even when fully closed or deployed, nor can either one alter or extend the end of the housing tongue. Additionally, an equal amount of exhaust cannot flow over and under of the pivoting wall or wedge because there is no neutral position. <CIT> discloses a turbocharger with a volute slot and primary and secondary vanes.

A moveable or variable vane design, which is intended to minimize the occurrence of turbo lag, is described in <CIT> and incorporated by reference herein ("Blaylock"). A flow control gate is positioned in the center of the inlet to the housing on the exhaust side of the turbocharger and adapted, from a command, to momentarily rotate or pivot downstream about a transverse hinge from a neutral first position to a second position toward the blades of the turbine rotor. (There is no open position above the neutral position. ) In the second position, the control gate reduces the volume of exhaust gas flowing along an inner flow path toward the turbine rotor and increases the air velocity and pressure upon the turbine rotor. This causes the turbocharger to reach optimal operating speed to substantially reduce or eliminate harmful emissions while increasing initial engine takeoff power and reducing lag time from when speedup was first signaled by the operator. Once the turbine is spun up, the control gate returns to a neutral position. When in the neutral position, the operation of the turbocharger is as a standard turbocharger. The typical time for the gate action is a very small part of a second before returning to the neutral position. A properly sized turbocharger could eliminate the need for a waste gate and the turbocharger could be large enough to handle the total exhaust flow at maximum horsepower.

Still others have mechanically coupled the turbocharger to the engine. This type of arrangement, called "turbocompounding,' is described in the September <NUM>, North American edition of the trade magazine, Diesel Progress (see "Could SuperTurbocharger Become the Hero on Fuel Economy?"). The turbocharger adds a small additional horsepower boost through the combination of the turbocharger and its transmission. However, turbocompounding entails complexity and involves additional production cost all in hopes of achieving at most a <NUM>% fuel savings on diesel engines.

A flow control gate which momentarily alters the A/R (Area/Radius) ratio of a turbocharger in order to eliminate turbo lag is desirable (compare <CIT> which discloses a gate that lies along the outer wall of the housing and outside the inlet or throat section and, therefore, cannot alter the A/R ratio of the housing). It is well known in the art that the A/R ratio is the inlet cross sectional area dived by the radius from the turbo centerline to the centroid of that area. The inlet (or throat section) of a turbocharger extends between the end of the housing which mounts to the exhaust manifold and the tip or end of the tongue of the housing.

To calculate the A/R ratio,
the area of the turbine housing is measured in square inches of a cutting plane line that passes through the turbine's gas passage at the tip of the tongue, divided by the radius from the center of the turbine wheel's axis of rotation, to the centroid of the volute. The tongue tip is the entry point of the turbine housing where exhaust gas flow begins to reach the turbine wheel inducer. (see <NPL>)).

The ability to alter the area of the inlet is important. For example, reducing the throat cross-section results in higher boost pressures. Turbocharger housings are designed with different A/R ratios along with complicated means (e.g., variable geometry turbines) to achieve the desired performance. Other than Blaylock's flow control gate which attempts to adjust the throat, the A/R ratio in prior art pivoting vane designs remains fixed because, absent making a new housing, there is no way for those designs to alter either the throat area or the radius from the center of the turbine wheel. However, Blaylock cannot alter where the tongue tip or tongue end of the housing begins and ends in real time and, because of the location of the pivot point (at about the center of the vane), cannot close flow completely.

<CIT>, incorporated by reference herein, discloses a turbocharger with a progressively variable A/R ratio that extends the inlet throat area to close flow to the turbine wheel until inlet exhaust gas passes the downstream end of the vane. The turbocharger includes a pivoting vane of fixed length aligned with the volute slot and located at a downstream end of the inlet throat area. When the vane is in its fully closed position, the inlet exhaust gas is prevented from flowing into the slot and, therefore, the turbine wheel, until the inlet exhaust gas passes the end of the vane. The A/R ratio of the housing progressively varies as the vane pivots between the fully opened and fully closed positions. The length of the vane can be any length that provides a desired A/R ratio when the vane is in the fully closed position yet still clear the turbine wheel when moving into the fully opened position, with shorter lengths being less effective than longer lengths. The vane could extend slightly past <NUM>° of the turbine wheel housing but anything more than <NUM>° would require additional means to pivot the vane away when moving toward the open position and still clear the turbine wheel housing.

Embodiments of a turbocharger of this disclosure comprise a housing including a volute containing an inlet throat section and a volute slot; and a dual vane co-aligned with the volute slot, an upstream end of the dual vane located in proximity to a downstream end of the inlet throat section. The dual vane includes a primary vane and a secondary vane, the secondary vane disposed on an upper surface of the primary vane and shaped complementary to the primary vane, the primary vane configured to pivot away from and toward the volute slot between a fully opened position and a fully closed position, the secondary vane configured to slide between a fully retracted position and a fully extended position. The secondary vane is in the fully retracted position when the primary vane pivots between the fully opened and closed positions. An area/radius (A/R) ratio of the housing varies as the primary vane pivots between the fully opened and closed positions. The A/R ratio of the housing also varies as the secondary vane slides between the fully extended and retracted positions.

When in the fully closed position, a portion of the volute slot lying opposite the dual vane is blocked and the secondary vane may extend from the fully retracted position. The dual vane essentially extends the inlet throat by preventing inlet exhaust gas flowing over the vane from entering the volute slot until the exhaust gas passes the far end of the vane. When the secondary vane is extended, an additional portion of the volute slot lying opposite the dual vane is blocked. In a fully closed and fully extended position, the dual vane may block up to <NUM>° of the volute slot, effectively functioning as an exhaust brake.

The primary vane may include a hole at its upstream end that receives a cross shaft. In some embodiments, the primary vane includes a channel located on its upper surface, with at least a portion of the secondary vane located within the channel, extendable from and retractable into the channel. A downstream end of the secondary vane may include a stop configured to prevent the secondary vane from entering the volute slot during extension and retraction.

Embodiments may include a push rod having one end pivotally connected to the secondary vane and another end located outside of the housing. An "ear" may be added to the housing to accommodate the push rod. The push rod may be configured to pivot the primary vane between the fully opened and closed positions and, when the primary vane is in the fully closed position, extend and retract the secondary vane. The dual vane may further include an upstream stop and a downstream stop. When the push rod contacts the upstream stop, the primary vane is permitted to pivot between the fully opened and closed positions. When the push rod moves between the upstream and downstream stops, the secondary vane is permitted to slide between the fully extended and retracted positions, the fully extended position being when the push rod contacts the downstream stop, the fully retracted position being when the push rod contacts the upstream stop. The upstream and downstream stops may be spaced according to a predetermined length of arc depending, in part, on the amount of full extension desired.

A method for progressively varying an area/radius ratio of a turbocharger housing includes pivoting the primary vane between the fully opened and fully closed positions, wherein during the pivoting the secondary vane remains in the fully retracted position; and sliding the secondary vane between the fully retracted and fully extended positions when the primary vane is in the fully closed position; wherein a portion of the volute slot lying opposite the primary vane is blocked when the primary vane is in the fully closed position; and wherein an additional portion of the volute slot is lying opposite the secondary vane is blocked when the secondary vane slides toward the fully extended position.

Objectives of this disclosure are to provide a dual vane configured for use in a turbocharger, the dual vane (<NUM>) is simple in its design and control; (<NUM>) can be retrofitted to existing turbocharger designs; (<NUM>) "spins up" the turbine wheel quickly; (<NUM>) progressively varies the A/R ratio past <NUM>° or <NUM>° of the volute slot; (<NUM>) does not create turbulence when varying the A/R ratio; (<NUM>) does not create backpressure in the inlet throat area; (<NUM>) eliminates the need for a waste gate and other complicated structures intended to control back pressure; and (<NUM>) may provide an exhaust brake.

A turbocharger of this disclosure includes a dual or two-part vane located at or near a downstream end of the initial inlet throat area of the turbocharger housing, with one of the vanes configured to pivot toward and away from the turbocharger wheel and the other vane configured to slide about the wheel and prevent inlet exhaust gas from entering the wheel. The dual vane may be provided separate from the turbocharger or turbocharger housing and installed in the housing with associated control means. The turbocharger housing may be a radial inflow housing, meaning that the housing as a volute that continuously decreases in area and cross section to help maintain even pressure all the way around the turbine wheel. In embodiments, the dual vane is configured to block inlet exhaust gas flowing over the vane from entering the volute slot, and therefore the turbine wheel, located below that portion of the vane.

The pivoting or primary vane pivots toward and away from the turbine wheel between a fully opened and a fully closed position, there being intermediate positions in between. In the fully closed position, inlet exhaust gas flowing over the dual vane is prevented from entering the volute slot lying opposite the vane until it passes the far end of the dual vane. That portion of the volute slot is essentially blocked. In the fully opened position, the primary vane reaches its end of movement toward the housing wall opposite the turbine wheel. In some embodiments, in the fully opened position at least a portion of the dual vane is in contact with or in close proximity to the wall of opposite the volute, with inlet exhaust gas unevenly over and under the dual vane.

The sliding or secondary vane, which is shaped complementary to the primary vane and rides on top of the primary vane in sliding relationship to it, is configured to extend and retract from the far end of the primary vane. When in a fully extended position, the secondary vane reaches its end of travel around the turbine wheel. In embodiments, the secondary vane may be contained within a slot or channel located along an upper surface of the primary vane and sized to accommodate the secondary vane. The primary and secondary vanes may be sized to have a width equal to or greater than a width of the volute slot adjacent the turbine wheel.

A push rod connected to the secondary vane may be used to pivot the primary vane about is pivot point as well as extend and retract the secondary vane. Computerized control means may be configured to actuate and control the push rod and, therefore, the pivot and extension of the vanes. Changing the location of the primary vane's pivot point or the push rod's connecting point (or both points) affects the amount of pivot and extension. For example, the primary vane may pivot to a fully opened position in which a portion of the dual vane lies in contact with, or in close proximity to, an opposing wall surface of the volute. Or, the fully opened position may be a neutral position, the dual vane lying about equidistant from the opposing wall and the volute slot adjacent the turbine wheel.

During a pivot of the primary vane to a fully closed position from the fully opened position, the secondary vane remains in its fully retracted position. When the primary vane pivots into this fully closed position, the dual vane blocks a first portion of the volute slot and the secondary may vane may be extended to block an additional second portion of the volute slot. A stop may be placed on the secondary vane to prevent it from entering into the volute slot during extension and retraction When the secondary vane is retracted back to its fully retracted position and the primary vane is in its fully closed position, the primary vane may then pivot back to the fully open position.

In embodiments, the first portion of the volute slot blocked by the dual vane may be equal to the length of the primary vane, length being measured in degrees of arc. The additional portion blocked by the dual vane may be equal to the length of the secondary vane when fully extended. In a fully closed and fully extended position, the dual vane may block a portion of the volute slot in a range of about <NUM>° to <NUM>° of the volute slot. Or, in a fully closed and fully extended position, the dual vane blocks a portion of the volute slot in a range of about <NUM>° to <NUM>° of the volute slot. Generally speaking, the length of the dual vane, when the secondary vane is fully retracted, is no greater than about <NUM>° of the turbine wheel to avoid additional mechanisms or linkages to clear the turbine wheel). See e.g. Tables 1A and 1B. "About" as used here means plus (where appropriate) or minus <NUM>% to the nearest degree. For example, about <NUM>° means <NUM>° to <NUM>°, about <NUM>° means <NUM>° to <NUM>°, about <NUM>° mean <NUM>° to <NUM>°, and about <NUM>° means <NUM>° to <NUM>° (there being no plus side).

In some embodiments, the downstream end of the secondary vane when in the fully retracted position may be even with that of the primary vane. In other embodiments, the downstream end of the secondary vane may extend farther downstream than that of the primary vane (essentially becoming the far end of the dual vane). This arrangement effectively extends the amount of the volute slot blocked by the primary vane when fully closed past that provided by the length of the primary vane (with the secondary vane still in the fully retracted position).

By way of a non-limiting example, the downstream end of the secondary vane may extend about <NUM>°, <NUM>°, <NUM>°, <NUM>°, <NUM>°, or some other amount past that of the primary vane when the secondary vane is in the fully retracted position, the maximum full length of the dual vane when the secondary vane is fully retracted being no greater than about <NUM>°. For example, if the primary vane's length is <NUM>° of the turbine wheel, the secondary vane's length may be in a range of <NUM>° to <NUM>° of the turbine wheel, there being in both cases <NUM>° of overlapping length with the primary vane and, respectively, <NUM>° to <NUM>° of non-overlapping length (when fully retracted). Continuing with this example, when the primary vane is fully closed and the secondary vane is fully extended, the dual vane blocks, respectively, about <NUM>° to <NUM>° of the volute slot.

The A/R (Area/Radius) ratio of the housing progressively varies as the primary vane pivots between the fully opened and fully closed positions and continues to vary as the secondary vane extends to, and retracts from, its fully extended position. Regardless of the vanes' position, when the volute slot blocker is in its fully closed position inlet exhaust gas is prevented from flowing into the volute slot (and therefore the turbine wheel) until the gas passes the far end of the blocker. When the pivoting vane is in the fully opened position, the initial (first) inlet throat area may remain unaltered and, therefore, so does the AIR ratio of the housing. When the pivoting vane is in the fully closed position, the inlet throat area changes to a first revised inlet throat area having a reduced cross-sectional area. When the vane extends to the fully extended position, the inlet throat area changes, with each degree of extension, to a second revised inlet throat area having a reduced cross-sectional area.

Referring to the drawings, a turbocharger "T" of this disclosure include a housing <NUM> containing an inlet or throat section <NUM> that ends at a downstream end <NUM> of the tongue <NUM>; a volute <NUM> that may continuously decrease in area and cross section from an initial cross section <NUM> of the throat <NUM>; a volute slot <NUM> located along a midline <NUM> of the volute <NUM> into which inlet exhaust gas entering the throat <NUM> can flow; and a turbine inducer or wheel area <NUM> exposed to the volute slot <NUM> and, therefore, the inlet exhaust gas flow. In embodiments of this disclosure, the housing <NUM> includes a dual or two-part vane <NUM> that effectively extends the inlet throat area farther downstream and, therefore, varies the A/R ratio of the housing <NUM>. A single dual vane <NUM> services the volute <NUM>. The vane <NUM> is configured such that, when fully closed and when fully closed and extended, inlet exhaust gas flowing over the vane <NUM> is blocked or prevented from entering the volute slot <NUM> and, therefore, the wheel area <NUM>, until it passes the vane <NUM>.

The dual vane <NUM> is comprised of two complementary vanes: a primary vane <NUM> which pivots and a secondary vane <NUM> that slides. When in an assembled state within the housing <NUM>, a longitudinal centerline <NUM> of the dual vane <NUM> is aligned with a vertical centerline <NUM> of the volute slot <NUM>. The dual vane <NUM> may be sized widthwise such that it can be received by the volute slot <NUM> yet still block flow into the slot <NUM> or can be sized wider than the slot <NUM>. Making the vane <NUM> wider than slot <NUM> serves to raise the dual vane <NUM> higher in the volute <NUM>, thereby decreasing the cross-sectional area above the vane <NUM>. When the dual vane <NUM> pivots to a fully closed position, a first portion α1 of the volute slot <NUM> is blocked. This first portion α1 may be equal to the length of the primary vane <NUM> plus a length of any non-overlapping portion <NUM> of the secondary vane <NUM> when in the fully retracted position. When the secondary vane <NUM> is extended, a second additional portion α2 of the volute slot is blocked. This second portion α2 may be equal to the length of the secondary vane when extended less the length of the non-overlapping portion <NUM> (when fully retracted). The first and second portions α1, α2 may be equal to the overall length of the vanes <NUM>, <NUM>, respectively.

The primary or pivoting vane <NUM> may be located within the housing <NUM> at, or proximal to, the downstream end <NUM> of the tongue <NUM>. The primary vane <NUM> effectively extends the throat <NUM> farther downstream in the volute <NUM> to provide an extended throat <NUM> having reduced cross-section area 23A (and therefore a different A/R ratio. The primary vane <NUM> may include a hole <NUM> at its upstream end <NUM> that receives a pin or cross shaft <NUM>, permitting the vane <NUM> to pivot between a fully opened position "O" and a fully closed position "C". Or, the shaft <NUM> may be the upstream end <NUM> of the vane <NUM>. The cross shaft <NUM> may be located so that it does not affect, or has a negligible effect on, the inlet cross section area <NUM>. In embodiments, the cross shaft <NUM> may be located at the horizontal centerline <NUM> of the inlet or throat <NUM> or below the horizontal centerline <NUM>. In some embodiments, the shaft <NUM> is aligned with the downstream end <NUM> of the tongue <NUM>. The vane <NUM> may be configured to extend up to about <NUM>°, <NUM>°, or <NUM>° of the turbine volute slot <NUM> or turbine wheel <NUM>, the center rotational axis <NUM> of the wheel <NUM> defining the center point of the vane arc or length. Lengths past <NUM>° may be used - alone or in combination with the secondary vane <NUM> - but involve more complicated linkages to ensure the vane <NUM> clears the wheel <NUM>.

The secondary or sliding vane <NUM> rides on top of the primary vane <NUM> in sliding relation to the primary vane <NUM>. The vane <NUM> may be contained in a crosspiece <NUM>. The vanes <NUM>, <NUM> are shaped complementary to one another, with the secondary vane <NUM> sliding between a fully retracted position "R" and a fully extended position "E. " In some embodiments, secondary vane <NUM> may reside in a slot or channel <NUM> located along a top surface <NUM> of the primary vane <NUM>. Channel <NUM> may be an exposed channel, meaning that a portion <NUM> of the top surface <NUM> of the vane <NUM> is exposed when in the channel <NUM>. The downstream end <NUM> of the secondary vane <NUM> may extend past the downstream end <NUM> of the primary vane <NUM>, effectively serving as the downstream end <NUM> of the dual vane <NUM>. As the secondary vane <NUM> extends, the throat section <NUM> extends even farther downstream in the volute <NUM> - that is, past a downstream end <NUM> of the primary vane <NUM> up to its fully extended position E - to provide another, further reduced cross-section area 23B during its extension. The secondary vane <NUM> may be configured to extend from the downstream end <NUM> of the primary vane up to about <NUM>° of the turbine wheel <NUM> or up to about <NUM>°, therefore functioning as an exhaust brake. A stop <NUM>, arranged perpendicular to the longitudinal centerline <NUM> of the dual vane <NUM>, may be provided to prevent the secondary vane <NUM> from entering the volute slot <NUM> during extension and retraction.

To actuate the dual vane <NUM>, a push rod <NUM> may be connected to the secondary vane <NUM>. In some embodiments, the connection to secondary vane <NUM> may be a pivotal connection <NUM>, for example, with push rod <NUM> connected at one end <NUM> to a pin or shaft <NUM>. As the rod <NUM> moves axially, it pivots the primary vane <NUM> about its cross shaft <NUM> and the push rod's end <NUM> pivots about it shaft <NUM>. When the primary vane <NUM> reaches its end of pivoting movement or travel toward the volute slot <NUM>, the push rod <NUM> may continue its axial movement, extending the second vane <NUM> farther downstream. An ear <NUM> may be added to the housing <NUM> to accommodate the push rod <NUM>, with one end <NUM> of the push rod <NUM> lying outside of the ear <NUM> or housing <NUM>.

The dual vane <NUM> may further include a first stop <NUM> and a second stop <NUM>. The stops <NUM>, <NUM> may be wider than the volute slot <NUM> and may be configured to contact the push rod connection <NUM>. When the push rod <NUM> contacts the upstream first stop <NUM>, the primary vane <NUM> is permitted to pivot between the fully opened and closed positions O, C as well as intermediate positions. With the vane <NUM> fully closed, the secondary vane <NUM> is permitted to slide into the fully extended position E and block additional portions α2 of the slot <NUM> as the rod <NUM> moves toward the downstream stop <NUM>. The first and second stops <NUM>, <NUM> may be spaced according to a predetermined length of arc depending, in part, on the amount of full extension desired.

Computerized control means may be configured to actuate and control the push rod <NUM> and, therefore, pivot and slide the vanes <NUM>, <NUM>. Changing the location of the primary vane's pivot point <NUM> or the push rod's connecting point <NUM> (or both points) affects the amount of pivot and extension. The fully opened position O occurs when the dual vane <NUM> reaches an end of its pivoting movement or travel toward the outer wall <NUM> of the volute <NUM>. When in this position, the flow of the inlet exhaust gas may be unevenly distributed, with more flow under rather than over the dual vane <NUM>. In some embodiments, in the fully opened position O a portion <NUM> of the dual vane <NUM> may contact the wall <NUM> of the volute <NUM>. In other embodiments, in the fully opened position O, or in a partially opened position C, the dual vane <NUM> may lie between a horizontal centerline <NUM> of the volute <NUM> and the wall <NUM>, the centerline <NUM> representing a neutral position. Pivot positions between the centerline <NUM> and the volute slot <NUM> may represent partially closed positions. A neutral position essentially splits or defines volute <NUM> into an upper and lower half, with an equal volume of exhaust flowing over and under the vane <NUM>. The fully closed position C occurs when the dual vane <NUM> reaches an end of its pivoting movement or travel toward the volute slot <NUM>.

Claim 1:
A turbocharger comprising:
a housing (<NUM>) including a volute (<NUM>) containing an inlet throat section (<NUM>) and a volute slot (<NUM>);
a dual vane (<NUM>) co-aligned with the volute slot (<NUM>), an upstream end of the dual vane located in proximity to a downstream end of the inlet throat section;
the dual vane including a primary vane (<NUM>) and a secondary vane (<NUM>), the secondary vane disposed on a volute wall-facing surface of the primary vane and shaped complementary to the primary vane, the primary vane configured to pivot away from and toward the volute slot (<NUM>) between a fully opened position and a fully closed position, the secondary vane configured to slide between a fully retracted position and a fully extended position;
characterised in that the secondary vane (<NUM>) is in the fully retracted position when the primary vane (<NUM>) pivots between the fully opened and closed positions;
wherein in the fully closed position, a portion of the volute slot (<NUM>) is blocked and the secondary vane (<NUM>) may extend from the fully retracted position;
wherein when the secondary vane (<NUM>) is extended, an additional portion of the volute slot (<NUM>) is blocked.