GB2043771A - I.C. engine turbocharger turbine bypass valves - Google Patents

Abstract

The valve 72 controlling communication between a turbine inlet passage 90, 92 and a bypass 94 is operated by at least one diaphragm 58 subject to compressor outlet pressure. A plate 78 adjacent the diaphragm 58 deflects exhaust gas flowing along the valve stem 70 to the housing outlets 158. A further diaphragm 136 is subject to the pressure in a venturi, or downstream of a throttle valve, upstream of the charger turbine. One of the diaphragms may be connected to a piston responsive to the position of the throttle valve. <IMAGE>

Description

SPECIFICATION Reverse actuated wastegate for boost control of turbocharged engines This invention relatestoturbochargersand, more specifically, to a differential pressure control system for controlling inlet pressures offluidsto internal combustion engines and wherein that intake is controlled in a predetermined manner over a wide range of engine speeds, all consistent with the most efficient and beneficial operation of that engine.

As is generally known in the art, the operation of an internal combustion engine over a wide range of engine speeds may have its operating characteristics enhanced by increasing the supply of air or air and fuel mixture under pressure to the engine intake manifold. In order to provide an internal combustion engine with an adequate supply of air having a predetermined pressure range, a turbocharger consisting of a compressor unit driven by a turbine which, in turn, utilizes engine exhaust gases to power same, provides a supply of compressed air or compressed air-fuel mixture to the engine.

Under some conditions, it is undesirable during operation of the internal combustion engine to provide increased charges to the intake of the engine.

Thus, to supply compressed air or compressed airfuel mixture to the intake of the engine where that compression is obtained from a compressor driven by the exhaust gases of the engine, it becomes necessary to divert exhaust gases from the turbine inlet of the turbocharger.

This invention, therefore, relates to a diaphragmoperated wastegate control forturbo-supercharged engines wherein adequate control of compression for the intake fluid is obtained. In the ordinary, conventional, diaphragm-operated waste-gate control valve, the control valve will divert or dump exhaust gases from the engine into a waste conduit or overflow so as to reduce the quantity of the gases from entering into the turbine inlet, thereby decreasing the amount of compression imparted to the fluid to the engine intake. In the conventional, wastegate control design, a pressurized actuator is utilized to lift a valve off its seat and then, as a result, requires a sealing configuration for the valve stem or shaft of the valve which passes through the pressurized chamber within which the control fluid is contained.

The sealing is required to preclude loss of control fluid from the pressurized chamber which would greatly affect the operation of the valve and/or create a safety hazard as, for example, in the case of gasoline engines wherein the source-sensing fluid could be air containing fuel vapor. Additionally, because of the prior art configurations, the seals frequently precipitate failure of the device, not only due to the potential leakage aforedescribed, but also by reason of the fact that foreign material or matter may conglomerate on the valve stem in proximity to the seal clearances, thereby causing sticking of the valve. The foreign material could be the result of exhaust by-product accumulation, corrosion or other sources.

The herein disclosed invention operates in a manner reverse of that heretofore described with respect to the prior art in that the valve is in the normally closed position and does not expose the valve stem to the control fluid, thereby obviating the need for extensive sealing. The unique design also permits the use of conventional, automotive-style valve configurations and employs a cartridge valve seat design which permits modular application of a wastegate control member totally independent of its installed configuration.

Another feature of an embodiment of the invention employs a hot fluid deflector to protect the diaphragm element of the inventive device so as to discharge same into the ambient atmosphere so as to decrease the likelihood of deterioration of the material of which the diaphragm is constructed.

Additionally, the inventive device, in another embodiment, provides for a second diaphragm member to be utilized in conjunction with a first diaphragm member and thereby permitting selective positioning of the wastegate valve at partthrottle, full throttle conditions and at preset manifold pressure conditions. In another embodiment, the inventive design utilizes hydraulic fluid pressure control responsive to engine requirements and demands for increased engine operation and efficiency.

An important object of the invention is to provide a control system for a turbocharger which produces high pressure fluids supplied to an internal combustion engine.

Another object of the invention is to provide a control device for furnishing fluids to a turbine of a tur bochargerso as to regulate the compressed air over a range of pressures supplied to an engine intake and to control said fluid supplies over a wide range of engine speeds in a selective and controlled manner.

It is a further object of the invention to provide a control system which will insure that a turbocharger compressor unit will supply fluid to an engine intake manifold at a predetermined pressure range above atmospheric pressure under a wide range of engine throttle conditions.

It is another object of the invention to provide a wastegate control system for a turbocharger in conjunction with internal combustion engines wherein the amount of exhaust gases furnished to the turbine intake of said turbocharger is selectively controlled.

It is another object of the invention to provide a wastegate control valve for use with a turbocharger for supercharging internal combustion engines wherein the wastegate control valve is in the normally closed position and wherein a control pressure actuates valve movement to operate said valve to divert exhaust gases away from the turbine inlet of said turbocharger.

It is another object of the invention to provide a reverse acting wastegate control valve for use in tur bochargers wherein at least one diaphragm member is utilized to act upon a valve member which is normally biased into the closed position and wherein the stem of the control valve is normally inhibited from coming in contact with the control fluids utilized to actuate the valve.

It is another object of the invention to provide a gas flow control device for association with a gas flow conduit having communication to a disposal conduit wherein a reverse acting valve member is associated with a diaphragm or movable wall means in response to a control fluid and wherein the valve member is biased to a normal closed position to seal off the disposal conduit from the gas flow conduit.

It is still another important object of the invention to provide a wastegate control device which is easily manufactured of unique design wherein at least one diaphragm or movable wall member is associated in an operable manner with a valve member having a stem end and a valve closing end wherein the valve closing end is disposed for opening and closing an exhaust gas communication between a disposal conduit and a gas inlet conduit to a turbine of a turbocharger for utilization with an internal combustion engine.

In an exemplary embodiment, the invention is directed to a gas flow control device for association with a gas flow conduit having communication to a disposal conduit comprising a body member defining a major portion of an enclosed chamber having a communication adapted to be connected to a source of control fluid. A movable wall member is secured to the body member and defines the remaining portion of the enclosed chamber. A retaining means is associated with the movable wall member for retaining a valve member and being movable with said movable wall member along a fluid metering path into open, intermediate and closed positions.A valve member is operatively associated with said retaining means and movable therewith, having a metering end portion adapted to open and close said communication to said disposal conduit and a biasing means for normally maintaining the valve member in the closed position.

In other embodiments another movable wall member may be utilized in order to achieve specific other selected functions for selective gas flow control. These and other objects of the invention will become apparent from the hereinafter following commentary taken in conjunction with the drawings, wherein:: Fig. lisa schematic of one embodiment of the disclosed invention illustrating its association with an internal combustion engine utilizing a turbocharger; Fig. 2 is a cross-sectional view of one embodiment of the waste control device of this invention; Fig. 3 is a cross-sectional view of another embodiment of the device of this invention, the same being schematically illustrated in Fig. 1; Fig. 4 is a cross-sectional elevational view of still another embodiment of the invention utilizing hyd raulic fluid pressure as the control for the wastegate valve; and Fig:5 schematically illustrates the application of the invention to a diesel-fueled engine regarding the part throttle open wastegate embodiment of the invention.

Referring to the various figures of drawings wherein like numerals of reference will designate like elements throughout, and referring specifically to Fig. 1, the general concept of the invention will generally become apparent.

In Fig. 1 there is schematically illustrated a system utilizing one embodiment of the inventive device. In the system shown, the compressor 2 and turbine 4 comprise a turbocharger generally designated 6 communicating with a fluid supply conduit 8 having a butterfly control valve 10. Intake manifold 12 communicates with one cylinder 14 of an internal combustion engine (not shown) which, in turn, communicates via exhaust manifold 16 to turbine inlet 18 and thence to exhaust conduit 20.

In exhaust manifold conduit 16 is disposed a wastegate conduit communication 22 which com municates to waste conduit 24 emptying into exhaust conduit 20. Positioned adjacent orifice 22 is one inventive embodiment of the invention device 26, having valve member 28 disposed for movement along the metering path generally adjacent orifice or seat 22 so as to be able to divert exhaust gases from exhaust manifold 16, either to the turbine inlet 18 or to dump or waste conduit 24.

Wastegate control device 26, in this instance, generally comprises a first movable wall or diaphragm member 30 being operatively associated with valve member 28 having a valve metering end 32, and wherein the valve member 28 is normally biased by means of spring 34 into the closed position. It will be noted that the first diaphragm member 30 forms a chamber 36 which communicates via control fluid conduit 38 to intake manifold 12.

Another diaphragm member 40 is positioned so as to form another chamber 42 responsive to a second control fluid via conduit 44, which communicates to compressor inlet 9, as seen.

In operation of the device shown, which will be more fully elaborated upon in description of Fig. 3, the wastegate control device 26 senses various fluid pressures, and, consequently, fluid demands that the internal combustion engine has, depending upon full or part throttle operation, so as to either allow more or something less than maximum exhaust gas flow to turbine inlet 18. The specific operation of the device 26 will be more fully disclosed hereinafter, it sufficing for the time being to note that the control fluids made available to the device 26 via conduits 38 and 44 do not substantially impinge upon the shaft of valve 28. It will also be noted that the valve 28 is disposed for reverse actuation in comparison to conventional wastegate control devices, and which will be more fully elaborated upon as the description proceeds herein.

Referring now to Fig. 2, one embodiment of the device of the invention is illustrated. Herein the reverse actuated wastegate control device 50 comprises a first generally annular housing member 52, having an inlet communication 54to a control pressure source, not shown, but generally connected via a conduit, not shown, so as to permit intake fluid communication to the chamber 56 formed by the interior wall of housing member 52 cooperating with movable wall or diaphragm 58. A lower housing member 60 is of depending, skirt-like configuration having a plurality of radially spaced apertures 62 vented to the ambient atmosphere and being rigidly secured to upper housing member 52 via screws 64, having diaphragm 58 secured thereby along its periphery or circumferential edge, or by other known means.

An upper retaining member 66, dish-like in config uration in conjunction with an identical reversibly positioned member 68, operatively retains shaft 70 of valve member 72. Shaft 70 has a threaded end 74 and is secured to retaining members 66 and 68 by retaining nut 76. As indicated and as shown, the movable wall member or diaphragm 58 is sandwiched or secured between retaining members 66 and 68 to thereby cause coordinated movement of the movable wall or diaphragm 58 and, thus, the valve 72.

Disposed adjacent the lower interior wall of retaining member 68 is skirt-like, combination radiation shield and deflector plate 78, which is cooperatively secured in sandwich fashion by reason of shoulder 71 on shaft 72 as shown. Thus, to this end, the retaining members 66 and 68, the diaphragm 58 and the deflector plate 78 are provided with a central bore to allow disposition of the threaded shaft end 74 therethrough for retention as shown in Fig. 2. The member78 not only prevents undue heat from reaching the diaphragm member, but also prevents or deflects hot gases therefrom.

Biasing means or spring 80 acts against the upper, inside surface of deflector plate 78, thereby urging the diaphragm assemblage into the upward position as shown in Fig. 2. The lower portion of the spring 80 acts against the spring retaining member 82 so that the metering end 84 of valve 72 seats in the closed position at the orifice 86 of exhaust manifold 88, the portion 90 being in communication from the exhaust manifold of the engine, not shown, while the end 92 communicates to a turbine inlet of a turbocharger while the conduit 94 communicates to the exhaust of the engine to thereby bypass the turbine inlet 92 so as to divert exhaust gases in the exhaust conduit 88 through the orifice 86 and, thus, into bypass or dump conduit 94.

As illustrated in Fig. 2, the device 50 has the valve member 72 normally in the closed or non-wastegate operating position. It will be noted thatthe valve member 72 is of the conventional, automotive valve configuration and seats against annular seat member 100 threadably secured in the bore or aperture 102 in the exhaust manifold 88. Likewise, the outer wall or housing of the gas dump conduit 94 is provided with a threaded bore 104 so as to receive in threadablefashion mounting member 106 of device 50.

It will be noted that the shaft 70 of valve member 72 is not provided with complex sealing members, nor are they required since, in the usual operation of the device 50, fluid pressure within chamber 56 will act upon movable wall or diaphragm 58 to thereby cause the valve member 72 to move along a valve metering path to allow more or less exhaust gases to be dumped or diverted from the turbine inlet depending upon the power demands of the engine.

Thus, under normal starting conditions, where the engine is at rest, the valve 72 will be in the normally closed position as illustrated in Fig. 2, so as to permit full exhaust gas communication to the turbine inlet of the turbocharger.

In operation, as the pressure of the intake increases, this will cause movement of the diaphragm assembly and, hence, valve 72 into the exhaust gas diversion position to thereby allow exhaust gas being dumped through bypass 94, so as to decrease the amount of fluid flow to the turbine inlet. Any seeppage or leakage that may occur between the close tolerance fit of the stem 70 of valve 72 will be kept from deleteriously affecting the diaphragm 58 (normally made of elastomeric material, as is known in the art) by means of deflector plate 78 so that the leaked exhaust gas will be harmlessly diverted to the ambient atmosphere by means of the spaced apertures 62.

Referring now to Fig. 3, there is illustrated another embodiment of the invention wherein the device provides for maintaining the wastegate valve in selected position responsive to part throttle operation. In this instance, the device 120 comprises a first housing member 122 in shallow dish-like configuration, having an aperture 124 vented to the ambient atmosphere and defining in conjunction with a movable wall or diaphragm, as will be described, a chamber 126. A lower housing member 128 forms and defines a second chamber 130 having a nozzle or conduit communication 132 to compressor inlet pressure. Upper housing member 122 is secured to lower housing portion 128 by means of screws 134, or the like.Disposed in the chamber 130 and formed in cooperation with the interior walls of housing 128 is first diaphragm member 136, having retainer plates 138 and 140 on either side and being of annu larconfiguration and secured by means of valve actuator member 142 having a threaded end portion 144 disposed through aligned bores or holes in retainers 138 and 140 and first diaphragm 136. The valve actuator 142 has a lower depending end 146 passing through a boss 148 of lower housing member 128, and having a central bore 150 which thereby receives an end portion of the valve closing member, as will be hereinafter made apparent.

The chamber 130 is isolated from atmosphere and, as previously indicated, allows fluid from the compressor inlet to act upon the confines thereof to thereby move movable wall member or first diaphragm 136 in response to the fluid pressures thereof.

The lower housing member 128 is of such configuration as to form a lower pressure chamber 152 communicating via aperture 154 to the intake manifold of the engine and, consequently, to the compressor outlet of the turbocharger. A lowermost housing member 156 is secured to housing member 128 by means of screws 64 and has a depending skirt-like configuration similar two member 60 of device 50, previously described. Consequently, the member 156 is also provided with apertures 158 open to atmosphere. The remaining elements of the device 120 are identical to that heretofore described with respect to device 50 of Fig. 2 and, thus, will not be gone into in detail except where differences are to be found.

The chamber 152 is equivalent to the chamber 56 of the device 50 previously described.

The lower diaphragm member 58 is positioned as before between retaining members 66 and 68, hav ing radiation deflector plate 78 and biasing means 80 acting in the same manner as in the Fig. 2, or device 50, embodiment.

However, in the Fig. 3 embodiment, the device 120 allows for wastegate valve control during partthrot tle operation so as to maintain the valve 72 in a partially op,,en position selectively responsive to the engine demands with which the device is utilized.

The wastegate valve of this invention will also act as a safety device. For example, referring to Fig. 1, the pressure drop in conduit 9 will, even at wide open throttle conditions of throttle 10, at extremely high engine speeds, be great enough to open the wastegate valve, although the intake manifold pressure is below the preselected value. This can prevent the engine from being supercharged at extremely high engine speeds.

The fig. 3 device causes the valve 72 to be open at part throttle, closed at full throttle and open again at a preset manifold pressure, depending upon end results desired.

Referring now to Fig. 4, an alternative embodiment of the inventive device is illustrated, which is identical in partial element configuration with the devices previously described and has an end function of holding the wastegate valve in the open position at part throttle, being responsive to the internal combustion engine requirements under part throttle conditions.

Specifically, the device 170 employs an upper body housing 172 having threaded connector 174 adapted for connection to an actuator, solenoid or source of actuating fluid, e.g., hydraulic oil, compressed gas, etc., which is directly responsive to a throttle position and hence, fluid requirements of the internal combustion engine.

The upper housing 172 is flanged as at 176 connecting with intermediate body portion 173 and the lower, depending skirt-like body member 178, having radially spaced apertures 180 open to the ambient atmosphere. Upper body member 172, and intermediate body member 173 are secured to lower body member 178 by means of bolts 182 or other means. The upper portion of body member 172 is configured to form an interior cylinder chamber 184 separated from main, upper body chamber 186 by means of a movable wall member or diaphragm 188, being retained between upper retaining plate 190 and lower retaining plate 192 in the position shown in Fig. 4 to form a fluid-tight chamber 186, having vent opening 192 for connection to an air cleaner.

Disposed within cylinder 184 is piston member 194 having upper O-ring seal 196 and having lower actuator portion 198 for purposes of acting upon the stem of the valve member as will become apparent and as will be described.

The cylinder 194 is reciprocally mounted within chamber 184 and is responsive to fluid pressure within chamber 184, introduced through fluid connector source 174 and moves in unison with diaphragm or movable wall member 188 in response to that fluid pressure, which as indicated is the actuating pressure responsive to open or close the wastegate valve at partthrottle conditions.

The chamber formed beneath diaphragm member 188 and specifically the chamber 200 is formed by reason of lower diaphragm member 202, again retained between upper and lower retainers 204 and 206, each of the members having a central aperture for receiving the threaded stem 208 of valve member 210 so that the same may be securely retained in cooperative and operative relationship by means of nut 212. As in previous embodiments, the skirt-like, depending deflector plate 211 is also retained within - the assemblage.

The chamber 200 has a fluid connector 214 in communication with the intake manifold and thus the chamber 200 is responsive to intake manifold pressure.

As in the embodiments previously described, the valve member 210 is of the conventional automotive type and has a lower valve metering portion 216 disposed in the conduit and bypass pipe as previously described.

In this particular instance, in operation under part throttle conditions, the piston 194, movable wall member or diaphragm 188 and valve actuator 198 will move upwardly and downwardly as pictured in Fig. 4 by reason of fluid pressure in the chamber or cylinder 184. If the pressure is sufficiently high, the cooperative assemblage will move downwardly so that the actuator 198 will abut the end 218 of valve member 210 to thereby cause the valve member 210 to open. As previously described, the valve member 210 is normally in the closed position by reason of biasing means or spring 220.

Alternately, the registration of intake manifold pressure in chamber 200 will cause fluid pressure to act upon the surface area of movable wall member 202 to cause the assemblage of valve member 210 and upper and lower retaining members as well as diaphragm 202 to move downwardly to thereby open the waste bypass as previously described.

Referring now to Fig. 5, application of the invention specifically to diesel engines will now be described. In this instance, the conduit 44' is positioned for communication to the venturi throat V between the intake 8' and the compressor inlet 9' leading to compressor 2'.

The venturi V will be of a configuration such that the pressure drop at low engine speeds will not be great enough to overcome the spring biasing means, for example, spring 34 (Fig. 1). However, at high engine speeds, where high intake manifold pressure is not desirable, such as on a high torque rise engine commonly used in highway vehicles, the pressure drop through venturi V will be great enough to cause the wastegate valve to open thereby reducing the intake manifold pressure without increasing the exhaust manifold pressure.

Thus, there has been described a wastegate valve of the reverse acting-type employing a unique design wherein a conventional, automotive valve member is utilized not requiring high sealing requirements about the stem thereof. The reverse actuating wastegate forturbochargers of the various embodiments disclosed herein is easy to adapt to existing engines in modular form and may be combined to achieve selected end results all in a manner which is economical, not requiring highly sophisticated elements and/or mechanisms to achieve selective, desired end results.

While the various embodiments of the invention have been described with with some particularity, those of ordinary skill in the art will at once see various modifications and changes that may be made to adaptthe hereindisclosed invention to various forms, but all such changes and modifications will not depart from the spirit and essence of the invention as disclosed herein and all of which are intended to be covered by the appended claims.

Claims (32)

1. A gas flow control device for association with a gas flow conduit having communication to a disposal conduit comprising: a body member defining a major portion of an enclosed chamber having a communication adapted to be connected to a source of control fluid; a movable wall member secured to said body member and defining the remaining portion of said enclosed chamber; retaining means associated with said movable wall member for retaining a valve member and being movable with said movable wall member along a fluid metering path into open, intermediate and closed positions; a valve member operatively associated with said retaining means and movable therewith having a metering end portion adapted to open and close said communication to said disposal conduit; and biasing means for normally maintaining said valve member in the closed position.

2. The device in accordance with claim 1 wherein a deflector plate member is positioned adjacent to said retaining member in super-position to said metering end portion of said valve member.

3. The device in accordance with claim 2 wherein said valve member is of the conventional, automotive-type having an elongated shank portion and the lower metering end portion flares outwardly into an annular configuration.

4. The device in accordance with claim 2 including a lower, depending skirt-like body member secured to said body member and having a sidewall having spaced apertures adapted to be open to the ambient atmosphere.

5. The device in accordance with claim 4 including an adapter support member operatively secured to said lower, skirt-like body member and having a bore within which is disposed a portion of said valve member, the lowermost portion of said adapter member being adapted forsecurementto a manifold housing.

6. The device in accordance with claim 5 wherein said biasing means is positioned between said deflector plate member and the lower inside wall of said depending, skirt-like body member and is in encircling relationship to the end portion of said valve member.

7. The device in accordance with claim 6 wherein said biasing means is a helical spring and said valve member has an elongated shaft and has a configuration of the conventional, automotive-type valve.

8. The device in accordance with claim 7 wherein said retaining means comprises annular, recessed members having a central aperture; said movable wall member being intermediate said retaining members and also having a central aperture and wherein said deflector plate member has a central aperture whereby, in alignment, an end of said shaft of said valve member is disposed through said aligned apertures and secured for operative movement in unison with said movable wall member, retaining members and deflector plate.

9. The device in accordance with claim 8 wherein said movable wall member is rigidly retained about the peripheral edge thereof between said upper body member and said lower body member.

10. The device in accordance with claim 9 wherein same is utilized in conjunction with a turbocharger for an internal combustion engine and wherein said enclosed chamber is in communication to the compressor inlet of said turbocharger.

11. A control system for a turbocharger of the type having a compressor driven by a turbine comprising the combination: a first diaphragm member defining a first chamber and being responsive to compressor inlet pressure and operatively and selectively associated to exert opening forces on a normally closed valve member for altering the flow of fluid supplied to the turbine so as to vary the pressure of fluid discharged from the compressor; a second diaphragm member defining a second chamber and being responsive to compressor outlet pressure and being operatively connected with said normally closed valve member; a valve member having a metering end portion adapted to meter fluid and being operatively associated with a disposal conduit to selectively dispose of unwanted fluid; and biasing means to bias said valve member into the normally closed position and exert a predetermined force thereon.

12. The system in accordance with claim 11 wherein said first diaphragm member is a larger surface area than said second diaphragm member.

13. The control system in accordance with claim 12 wherein first and second retaining members are positioned on either side of said first diaphragm member and are cooperatively secured therewith for coordinated movement with said first diaphragm member.

14. The control system in accordance with claim 13 wherein said second diaphragm member has recessed dish-like retaining members positioned on either side thereof and are in mirror image place mentwith respectto each other with said second diaphragm member being intermediate thereof.

15. The control system in accordance with claim 14 wherein said first and second diaphragm members are secured about their peripheral edges.

16. The control system in accordance with claim 15 including an upper body member which cooperates with said first diaphragm member to form a first chamber adapted to be in communication to the compressor inlet of said compressor and wherein a second chamber is formed by said body member in cooperation with said second diaphragm, said sec ond chamber being adapted to communicate to the intake manifold or compressor outlet of said compressor and including a lower, skirt-depending member having radially spaced apertures adapted for communication to the ambient atmosphere and being secured to the lower portion of said body member.

17. The control system in accordance with claim 16 wherein a valve actuator member is in depending relationship to said first diaphragm member and wherein same is adapted to abut the upper surface of said retaining member adjacently disposed thereto and being operatively associated with said second diaphragm member.

18. The control system in accordance with claim 17 wherein a deflector plate member is secured in super position to the metering end portion of said valve member and wherein said valve member is of the conventional, automotive-type configuration having an elongated shaft.

19. The control system in accordance with claim 18 wherein said biasing means is a helical spring positioned between said deflector plate member and the lower portion of the depending skirt member.

20. The control system in accordance with claim 19 wherein the upper body member forms a chamber with respect to the upper surface of said diaphragm member and wherein said chamber is vented to ambient atmosphere.

21. A control system for a turbocharger of the type having a compressor driven by a turbine comprising the combination: a first diaphragm member being responsive to a first control fluid pressure and movable in response thereto and defining in cooperation with a second diaphragm member a chamber communicating to a second control fluid pressure source; a second diaphragm member cooperatively supported and operatively associated with a normally closed valve member movable along a valve metering path and adapted to divert exhaust gases from said turbine in response to preselected control pressures; and a biasing means operatively associated with said valve member in the exhaust gas non-diverting position.

22. The control system in accordance with claim 21 wherein first and second retaining members are positioned on either side of said first diaphragm member and are cooperatively secured therewith for coordinated movement with said first diaphragm member.

23. The control system in accordance with claim 22 wherein said second diaphragm member is of smaller surface area than said first diaphragm member and including retaining members positioned on either side of said diaphragm members and movable therewith and wherein said first and second diaphragm members are secured about their peripheries.

24. The control system in accordance with claim 23 including an upper body member coacting with said first diaphragm member to form a first chamber adapted to be in communication to the compressor inlet of said compressor and wherein a second chamber is formed by said body member in cooperation with said second diaphragm, said second chamber being adapted to communicate to the intake manifold or compressor outlet of said compressor.

25. The control system in accordance with claim 24 including a deflector member positioned in juxtaposition to said valve member to deflect escaped fluid away from said second diaphragm member.

26. Acontrol system foraturbochargerofthe type having a compressor driven by a turbine comprising the combination: a body member defining a first cylinder chamber and a second diaphragm chamber, said cylinder chamber communicating to a source of control fluid; a piston member reciprocally mounted in said cylinder chamber and having a lower end portion communicating to said second diaphragm chamber; a first diaphragm member cooperatively difining said second diaphragm chamber with said body member operatively associated with said piston member, said piston and first diaphragm being responsive to control fluid pressure to exert opening forces on a normally closed valve member for altering the flow of fluid supplied to the turbine so as to vary the pressure of fluid discharged from the compressor; a second diaphragm member defining a second diaphragm chamber and being responsive to compressor outlet pressure and being operatively connected with said normally closed valve member; a valve member having a metering end portion adapted to meterfluid and being operatively associated with a disposal conduit to selectively dispose of unwanted fluid; and biasing means to bias said valve member into the normally closed position and exert a predetermined force thereon.

27. The system in accordance with claim 26 wherein said first diaphragm member is of the same surface area as said second diaphragm member.

28. The control system in accordance with claim 27 wherein first and second retaining members are positioned on either side of said diaphragm members and cooperatively secured therewith for coordinated movement therewith.

29. The control system in accordance with claim 28 wherein said first and second diaphragm members are secured about their peripheral edges and including a lower, skirt-depending member having radially spaced apertures adapted for communication to the ambient atmosphere secured to the lower portion of said body member.

30. The control system in accordance with claim 29 wherein said lower end portion of said piston member is in depending relationship to said first diaphragm member and wherein same is adapted to exert opening forces on said valve member.

31. The control system in accordance with claim 30 wherein a deflector plate member is secured in super position to the metering end portion of said valve member and wherein said valve member is of the conventional, automotive-type configuration having an elongated shaft.

32. The invention substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

32. The control system in accordance with claim 31 wherein said biasing means is a helical spring positioned between said deflector plate member and the lower portion of said depending skirt member.