GB2491554A

GB2491554A - An Actuator Assembly for a Turbocharger Wastegate Valve Assembly

Info

Publication number: GB2491554A
Application number: GB1105689.2A
Authority: GB
Inventors: Nitin Kumar Khanna
Original assignee: Cummins Ltd
Current assignee: Cummins Ltd
Priority date: 2011-04-02
Filing date: 2011-04-02
Publication date: 2012-12-12
Anticipated expiration: 2031-04-02
Also published as: GB2491554B; GB201105689D0

Abstract

An actuator assembly for a turbocharger wastegate valve assembly comprises an actuator 15 coupled to an elongate actuator rod 16. The actuator or connecting rod 16 has an elongate axis and is arranged for translation substantially in the direction of the axis. The rod has a first end for coupling to the wastegate valve assembly to control the position thereof and a second end with a connecting element, the connecting element being arranged for coupling to the wastegate valve. The rod is an elongate hollow member which may deformed, crimped or swaged to define at least one flange 32 or 35 by which the actuator 15 or the connecting element, such as a nut 33, is supported against axial movement in one direction along the rod.

Description

I

AN ACTUATOR ASSEMBLY FOR A TURBOCHARGER WASTEGATE

The present invention relates to an actuator assembly for a turbocharger wastegate, a method for manufacturing the same, and to a turbocharger incorporating such an assembly.

Turbochargers are well-known devices for supplying air to the intake of an internal combustion engine at pressures above atmospheric (boost pressures). A conventional turbocharger essentially comprises an exhaust gas driven turbine wheel mounted on a rotatable shaft within a turbine housing. Rotation of the turbine wheel rotates a compressor wheel mounted on the other end of the shaft within a compressor housing.

The compressor wheel delivers compressed air to the intake manifold of the engine, thereby increasing engine power. The turbocharger shaft is conventionally supported by journal and thrust bearings, including appropriate lubricating systems, located within a central bearing housing connected between the turbine and compressor wheel housing.

It is known to allow some of the exhaust gas to bypass the turbine and proceed directly from the exhaust manifold to the exhaust outlet. This is achieved using a wastegate valve in a bypass passageway between the exhaust inlet and exhaust outlet portions of the turbine housing. The valve is controlled to open the passageway when the pressure level of the boost air increases to a predetermined level, thus allowing some of the exhaust gas to bypass the turbine wheel preventing the boost pressure from rising further. The wastegate valve is generally actuated by a pneumatic actuator operated by boost air pressure delivered from the compressor. The position of the wastegate valve, and thus the amount of exhaust gas permitted to bypass the turbine wheel, is thus controlled in direct response to variations in the boost pressure.

A conventional pneumatic actuator comprises a spring-loaded diaphragm or sliding seal housed within a canister (referred to as the wastegate actuator can) which is typically mounted on the compressor housing. The diaphragm seal acts on a connecting rod which in turn actuates the wastegate valve.

The actuator can is connected to the compressor outlet via a hose to deliver boost air to the can which acts on the diaphragm (or sliding seal) to oppose the spring bias. The spring is selected, and the actuator and wastegate valve initially set, so that under low boost conditions the wastegate valve remains closed. However, when the boost pressure reaches a predetermined maximum the diaphragm seal is moved against the action of the spring and operates to open the wastegate valve (via the connecting actuator rod) thereby allowing some exhaust gas to bypass the turbine wheel.

In conventional arrangements the wastegate valve is supported on a valve stem which extends through the turbine housing and which is rotated to open and close the valve.

Rotation of the valve stem is achieved by the reciprocal axial movement of the connecting rod via a lever arm which links the end of the rod to the valve stem. To accommodate the motion of the rod there is a pivotable joint between the lever arm and the rod, the opposite end of the lever arm being secured (typically by welding) to the end of the valve stem.

It is essential to ensure that the wastegate valve begins to open at the correct exhaust gas pressure. The actuator assembly has to be fitted carefully to the wastegate valve to ensure it opens at the correct point. The precise actuator can pressure at which the diaphragm begins to move is dependent on the preload of the spring used.

Unfortunately, this can vary from spring to spring owing to manufacturing tolerances and thus it is necessary to set the valve opening point individually. The rod is of adjustable length in order to ensure that the spring is compressed to apply a valve closing force that is equivalent to the force applied by the pressure at which the valve begins to open. Two aligned portions of the rod are movable axially relative to each other, by means of a threaded connection, in order to lengthen or shorten the rod. The desired pressure at which the wastegate valve begins to open is this set by adjusting the length of the rod during assembly. This can be a time consuming and relatively complex operation.

It is one object of the present invention to provide an actuating assembly for a turbocharger wastegate which obviate or mitigate the aforementioned disadvantages. It is also an object to provide for an improved actuating assembly.

According to a first aspect of the present invention there is provided an actuator assembly for a turbocharger wastegate valve assembly, the actuator assembly comprising an actuator coupled to an elongate actuator rod, the actuator rod having an elongate axis and being arranged for translation substantially in the direction the axis, the actuator rod having a first end for coupling to the wastegate valve assembly to control the position thereof, wherein the rod is an elongate hollow member.

The elongate hollow member may comprise a wall surrounding a hollow interior. The wall may be outwardly deformed to define at least one radially outwards extending flange. The flange may be for preventing axial movement of at least one component along the rod in one direction. The component may, for example, be part of the actuator or a connecting element by which the rod is directly or indirectly coupled to the wastegate control valve assembly The at least one flange may be defined by a crimped formation, whereby the wall of the rod is for example folded by pressing or pinching such that it is outwardly deformed.

The at least one flange may abut part of the actuator on the rod so as to retain it on the rod against axial movement in at least one direction. There may be more than one flange. There may be a flange disposed at opposite ends of the rod.

The at least one flange may retain a connecting element on the rod against axial movement in one direction. The connecting element may be arranged for coupling to the wastegate valve. In one embodiment the connecting element is coupled to the wastegate valve assembly by means of a link arm. The link arm may be arranged for coupling to a lever arm of the wastegate valve assembly. The lever arm may be disposed for pivotal movement and connected to a valve stem of a valve member of the valve assembly.

The connecting element may be disposed at the first end of the rod. The actuator may be disposed at a second end of the rod.

At least one of the first and second ends may be outwardly deformed, the outwardly deformed end serving to retain at least one component on the rod. The outwardly deformed end may be axially spaced from the at least one flange. An actuator may be retained on the rod between a flange and the outwardly deformed second end. The connecting element may be retained on the rod between a flange and the outwardly deformed first end. The first and or second ends may be open and the deformation provided by outwards flaring of the end.

The connecting element may be a nut. It may be rotatably disposed on the rod and it may have flats defined on its outer surface for connection to the link arm. The link arm may have a socket for receiving the nut.

The actuator may be coupled to the rod at a second end. The rod may be deformed outwardly at the second end. The deformed second end of the rod may serve to retain at least one component of the actuator on the rod.

The actuator may be a pneumatic actuator which may comprise a variable volume air chamber with a sliding piston and/or diaphragm. The rod may be biased into a first position by a biasing member of the actuator.

According to a second aspect of the present invention there is provided a turbocharger comprising an exhaust gas drive turbine that drives a compressor, a wastegate valve assembly for opening and closing a bypass passage between a turbine inlet and a turbine outlet, and an actuator assembly as defined above.

According to a third aspect of the present invention there is provided a method for manufacturing an actuator assembly for a turbocharger wastegate valve assembly, the method comprising: deforming an elongate hollow rod to define at least one radially outward flange along its length, coupling an actuator to the rod at or near a first end, supporting a connecting element at or near a second end such that at least one of the actuator or the connecting element abuts the at least one radially outward flange, and deforming the first and second end radially outwards to increase its diameter so as to retain the actuator or the connecting element on the rod.

The at least one flange may be formed by a crimping operation.

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an axial cross section through a turbocharger to which the actuator assembly of the present invention may be fitted; Figure 2 is a perspective view of a conventional turbocharger wastegate valve actuator assembly shown partly cut-away; Figure 3 is a sectioned perspective view of part of a first embodiment of an actuator assembly for a turbocharger wasteg ate valve; Figure 4 is a sectioned perspective view of part of a second embodiment of an actuator assembly for a turbocharger wasteg ate valve; Figure 5 illustrates the steps in fabricating a connecting rod and nut of the actuator assembly of figures 3 and 4; and Figure 6 is a schematic plan view of the actuator assembly of figures 3 and 4 fitted to a wastegate valve of a turbocharger.

Referring now to figure 1 of the drawings, the turbocharger comprises a turbine 1 joined to compressor 2 via a central bearing housing 3. The turbine I comprises a turbine housing 4 which houses a turbine wheel 5. Similarly1 the compressor 2 comprises a compressor housing 6 that houses a compressor impeller wheel 7. The turbine wheel 5 and compressor impeller wheel 7 are mounted on opposite ends of a common rotary shaft 8 which is supported on bearing assemblies 9 within the bearing housing 3.

The turbine is provided with an exhaust gas inlet 10, which receives exhaust gas from an engine outlet manifold, and an exhaust gas outlet 11. The inlet 10 directs the incoming exhaust gas to an annular inlet chamber 12 which forms a volute surrounding the turbine wheel 5. The exhaust gas flows through the turbine I and into the outlet 11 via a circular outlet opening which is coaxial with the turbine wheel 5. This causes the turbine wheel and shaft 8 to rotate and drive the compressor impeller 7 in rotation such that air is compressed and delivered to an internal combustion engine intake manifold.

Referring now to figure 2, a conventional wastegate valve and actuator (not visible in figure 1) are fitted to the turbine 1. The turbine housing 4 is provided with a bypass passageway (not shown) which allows gas to flow between the exhaust inlet 10 and the exhaust outlet 11 without passing through the turbine wheel 5. The bypass passageway communicates with the exhaust inlet 10 via a circular opening (not shown) which is opened and closed by a valve member 13a of a wastegate valve 13 provided for controlling the flow therethrough. In figure 2 the part of the turbine housing 4 defining the inlet 10 is shown partially cut away to reveal details of the wastegate valve 13 which is operated by rotation of a valve stem 14 which extends through a bush 14a in the turbine housing 5.

Rotation of the valve stem 14, and thus actuation of the wastegate valve 13, is effected by an actuator assembly mounted on the outside of the turbocharger. The assembly comprises a spring-loaded pneumatic actuator 15 which is linked to the valve stem 14 S via a connecting rod 16 and actuating lever 17. The actuator has a housing 18 (often referred to as the "can") which receives pressurised air from the compressor 2 and is thus conventionally mounted on the outside of the compressor housing 6 by an appropriate bracket (not shown).

The actuator 15 comprises a sliding piston or diaphragm disposed within the cylindrical can that is moveable under the influence of the air pressure delivered to the can from the compressor. The connecting rod 16, which is machined from solid bar, has a first end fixed to the piston or diaphragm inside the can and an opposite second end pivotally coupled to the actuating lever 17. In figure 2 the actuator can is shown cut away to reveal a coil spring 19 acting between the diaphragm/piston (not shown) and the front end wall of the can 18. The coil spring 19 thus biases the actuator rod towards the rear of the actuator can 18.

In operation the wastegate valve 13 will be held closed at low pressures (low boost) by the action of the spring 19. However, once the pressure in the compressor outlet reaches a predetermined limit, the pressurised air transmitted to the interior of the can forces the diaphragm/piston to move against the force of the spring 19 thereby extending the rod, pivoting the lever 17, rotating the valve stem 14 and opening the wastegate 13 to allow inlet exhaust gas to bypass the turbine 1. In this manner the maximum boost pressure produced by the turbocharger can be controlled and limited.

Figure 3 illustrates an embodiment of the actuator 15 and connecting rod 16 in accordance with the present invention. Components which are unchanged from those of figure 2 and given the same reference numerals as their counterparts. The wastegate valve 13, valve stem 14 and lever arm 17 are not shown in this figure but are substantially identical to those shown in figure 2.

The actuator housing ("can") 18 defines a generally cylindrical chamber 20 in which a diaphragm 21 and a piston 22 are received along with the spring 19. The can 18 is formed from two parts that are joined by a crimped joint I 8a, each part defining an end wall of the can. A first end wall 23 has an inlet opening 24 to which a spigot 25 is connected for the supply of air from the compressor 2. The opposite second end wall 26 is penetrated by the connecting rod 16 that passes through a seal 27 in the wall 26 and two fixing members 28 by which the can 18 is supported on the turbocharger. The diaphragm 21 is a flexible membrane whose outer periphery is fixed in the crimped joint 18a and effectively divides the chamber 20 into first and second variable volume chambers 20a, 20b. The second chamber 20b is occupied by the coil spring 19 that acts between a first spring seat 29 disposed adjacent to diaphragm and a second spring seat 30 fixed to the second end wall 26 so as to force the piston 22 towards the first end wall 23. The second spring seat 30 also serves to hold the seal 27 in place.

The first variable volume chamber 20a receives pressurised air from the compressor 2 through the inlet opening 24 which acts on the facing surface of the piston 22. The force applied to the piston 22 acts against the force of the spring 19 and, if sufficient to overcome the spring force, will cause the piston to move towards the second end wall 26, the diaphragm 21 deforming in the process.

The piston 22 is fixed on the connecting rod 16 between a pair of washers 31 so that as it moves within the confines of the can 16, the rod 16 is guided to reciprocate in an axial direction to operate the wastegate valve 13 as described above.

The connecting rod 16 is hollow as compared to the solid version described in figure 2.

Not only does this render the actuator assembly lighter but also it simplifies the manufacturing and assembly processes. It may be manufactured from any suitable material such as, for example, steel. The ends of the rod are open.

Figure 5 illustrates the steps in fabricating the connecting rod 16 from a plain hollow tube of metal (fig 5a). The first stage is the formation of two integral annular flanges 32 (see fig 5b), 35 that extend radially outwards and are spaced apart along the axial length of the rod 16. These flanges 31, 32 are produced by any suitable deformation technique such as, for example, crimping or swaging using a suitable punch and die, whereby the wall of the rod is folded to define the flange. A first flange 32 is disposed adjacent a first end of the rod 16 on which a nut 33 is mounted (fig Sc). The flange 32 prevents the nut 33 from moving axially in a direction towards the other end of the rod 16. The first end of the rod 16 is deformed outwardly at 34 by flaring or crimping in order to retain the nut 33 on the rod 16 (see fig Sd). A similar flaring deformation may be applied to the second end once the piston 22 has been fitted. This may be achieved by inserting a suitable deforming tool in the open end of the rod.

The second flange 35 is disposed adjacent a second end of the rod 16 and is intended to retain the first spring seat 29 against movement relative to the rod in one direction.

Figure 4 shows an alternative actuator assembly embodiment in which the only difference is that the hollow rod 16 is not deformed to define the second flange so as to leave the nut 33 free to translate along the rod 16 in the direction towards the can 18 until such time as it is fixed to the lever arm 17.

In both embodiments (figures 3 and 4) the connecting rod 16 is fixed to the lever arm 17 by means of a link arm 36 as shown in figure 6. One end of the link arm 36 is fixed to the lever arm 17 in the usual manner whereas the opposite end defines a socket with an internal thread that is secured to threads defined on the external surface of the nut 33. The socket has a series of flats 36 for that may be crimped against flats defined on the external surface of the nut 33.

The rod 16 may be coated in a suitable corrosion resistant material such as, for

example, copper.

The operation of the actuator assembly of figures 3, 4 and 6 is identical to that described in relation to figure 2.

The provision of a hollow connecting rod for the actuator renders the assembly easier to manufacture and install. Moreover, since there are no significant bending or twisting forces during operation of the actuator, the structural rigidity of the assembly is not compromised. A lighter rod also reduces the risk of noise and vibration since the reduction in mass increases the resonant frequency of the assembly. Furthermore the amount of heat transferred from the relatively hot areas of the turbocharger along the rod to the actuator is reduced thus lowering the risk of thermal fatigue failure.

Claims

CLAIMS1. An actuator assembly for a turbocharger wastegate valve assembly, the actuator assembly comprising an actuator coupled to an elongate actuator rod, the actuator rod having an elongate axis and being arranged for translation substantially in the direction the axis, the actuator rod having a first end for coupling to the wastegate valve assembly to control the position thereof, wherein the rod is an elongate hollow member.
2. An actuator assembly according to claim 1, wherein the elongate hollow member has a wall surrounding a hollow interior and the wall is outwardly deformed to define at least one radially outwards extending flange for preventing axial movement of at least one component along the rod in one direction.
3. An actuator assembly according to claim 2, wherein the at least one flange is defined by a crimped formation.
4. An actuator assembly according to claim 2 or 3, wherein the at least one flange abuts part of the actuator on the rod.
5. An actuator assembly according to claim 2 or 3, wherein the at least one flange retains a connecting element on the rod against axial movement in one direction, the connecting element being arranged for coupling to the wastegate valve.
6. An actuator assembly according to claim 5, wherein the connecting element is coupled to the wastegate valve assembly by means of a link arm, the link arm being arranged for coupling to a lever arm of the wastegate valve assembly.
7. An actuator assembly according to claim 5 or 6, wherein the connecting element is disposed at the first end of the rod.
8. An actuator assembly according to any preceding claim, wherein the rod has a second end and at least one of the first and second ends is outwardly deformed, the outwardly deformed end serving to retain at least one component on the rod.
9. An actuator assembly according to claim 5, 6, or 7, wherein the first end of the actuator rod is outwardly deformed, the connecting element being retained on the rod between the at least one flange and the deformed first end.
10. An actuator assembly according to any one of claims 5 to 7 or 9, wherein the connecting element is a nut.
11. An actuator assembly according to any one of claims 2 to 7, 9 or 10, wherein the actuator is coupled to the rod at a second end, the rod being deformed outwardly at the second end, the deformed second end serving to retain at least one component of the actuator on the rod.
12. An actuator assembly according to any preceding claim wherein the actuator is a pneumatic actuator.
13. A turbocharger comprising an exhaust gas drive turbine that drives a compressor, a wastegate valve assembly for opening and closing a bypass passage between a turbine inlet and a turbine outlet, and an actuator assembly according to any one of claims I to 12.
14. A method for manufacturing an actuator assembly for a turbocharger wastegate valve assembly, the method comprising: deforming an elongate hollow rod todefine at least one radially outward flange along its length, coupling an actuator to the rod at or near a first end, supporting a connecting element at or near a second end such that at least one of the actuator or the connecting element abuts the at least one radially outward flange, and deforming the first and second end radially outwards to increase its diameter so as to retain the actuator or the connecting element on the rod.
15. A method according to claim 14, wherein the flange is formed by a crimping operation.
16. A method according to claim 14 or 15, further comprising connecting a link arm to the connecting element, the link arm being fixed to the wastegate valve assembly.