Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
2001-10-12
2003-04-08
Denion, Thomas (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C415S030000, C137S527000
Reexamination Certificate
active
06543228
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to turbochargers having valves operable to cause the exhaust gases to by-pass the turbocharger.
2. Description of the Related Art
It is known in the field of internal combustion engines that catalytic converters, which are extensively used in the automobile industry to reduce engine emissions, operate with significantly reduced efficiency during cold start and engine warm-up conditions, resulting in higher than normal exhaust emissions during these periods. It is therefore recognised that thermal inertia within the exhaust system of such an engine should be kept to a minimum during cold start conditions in order to maximise the heat delivered to the catalytic converter from the engine, thereby promoting light off of the catalyst and so minimising the time during which emissions are at an unacceptable level.
Turbochargers are now commonly used to increase the power delivered by an engine by utilising the waste energy of the exhaust gases to power a turbine which compresses the intake air delivered to the combustion chamber. However, the provision of a turbocharger in the exhaust system of the engine imposes extra thermal inertia on the system, which delays catalytic converter light off in such engines and so increasing the time during which engine emissions exceed an acceptable level. In order to overcome this problem, turbochargers have been developed which have two separate ducts at the turbine inlet flange, one duct directing the exhaust gas to the turbine volute and the other providing a bypass for the turbine volute. A valve is provided in each duct to control the flow of exhaust gases therethrough. During normal engine operating conditions, the valve in the turbine volute duct is fully open, allowing exhaust gas to power the turbocharger, whilst the valve in the bypass duct operates to vary the through-flow in the bypass duct so as to provide standard wastegate control of the pressure in the turbine volute in order to prevent over-pressuring. During cold start conditions, however, the turbine volute valve is closed and the bypass valve opened so that the exhaust gases bypass the turbine and are instead directed to the catalytic converter with minimum heat loss, thereby promoting rapid light-off of the catalyst. Conventional such systems have the problem, however, that they require two separate actuators, one for each valve, due to the different range and sequence of movement required for each valve, and this increases the complexity and hence cost of the turbocharger system as well as increasing its overall size.
There is hence a need for a turbocharger which includes a system to enable exhaust gases to bypass the turbine during cold start conditions and instead to be fed to the catalyst with minimal heat loss so as to promote catalytic converter light-off, whilst being of reduced size and complexity as compared with existing turbochargers.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a turbocharger assembly comprising a turbine bypass duct having a first valve disposed therein, and a turbine feed duct having a second valve disposed therein, characterised in that the first and second valves are coupled to a link member, the first valve being operatively attached to said link member so as to be constrained for movement therewith throughout the full range of operative movement of the link member, and the second valve having a lost motion coupling with the link member so as to be constrained for movement therewith through only a part of the full range of operative movement of the link member , wherein upon movement of said link member between a start position and an intermediate position, operative movement of the first valve only is effected and upon movement of the link member between said intermediate position and an end position, operative movement of the first and second valves occurs.
A turbocharger assembly in accordance with the invention has the advantage that it requires just a single actuator to control the valves in the turbine feed and turbine bypass ducts so as to provide wastegate operation during normal operating conditions of the turbocharger in order to prevent over-pressuring, as well as exhaust gas bypass of the turbine during cold start conditions in order to promote rapid catalytic converter light-off using, thereby reducing cost. It also has the advantage that the system is much more compact since space is required for just a single actuator.
In a preferred embodiment of the invention, the lost motion coupling between the second valve and the link member is effected by means of an elongated channel formed in the link member in which an actuating pin of the second valve engages. During movement of the link member between its start position and the intermediate position, the actuating pin of the second valve travels along the channel without moving relative to the turbine volute inlet duct, and upon movement of the link member from its intermediate position to its end position, the actuating pin moves with the link member through engagement with a surface of the channel, moving the actuating pin relative to the turbine volute inlet duct and hence closing the second valve.
The elongated channel is advantageously formed with two distinct sections, a first section along which the actuating pin of the second valve moves upon movement of the link member between the start position and the intermediate position, and a second section which imparts a camming action to the actuating member of the second valve as it moves therealong upon movement of the link member between said intermediate position and the end position. By suitable choice of the shape of the first and second sections, not only can movement of the second valve be eliminated during movement of the link member between said start position and said intermediate position, but also the speed and sensitivity of the movement of the second valve during movement of the link member between said intermediate and end positions can also be controlled.
In one embodiment of the invention, the link member is mounted for pivotal movement in the turbocharger assembly and the second valve is a rotary valve. The elongated channel is then formed such that the first section subtends an arc centred on the axis of rotation of the link member and the second section subtends an arc centred on a point offset from the axis of rotation of the link member, the offset of the centre of the arc of the second section from the axis of rotation of the link member and the radius of curvature of the second arc being used to vary the sensitivity of the second valve to the movement of the link member and hence the range of angular movement of the link member. It is particularly advantageous if the second valve takes the form of a butterfly valve having an actuating pin offset from the axis of rotation of the valve such that movement of the actuating member about the axis of the valve effects operative movement of the valve between an open and a closed position. Since butterfly valves are essentially balanced devices, they only required a relatively small amount of torque for full range movement and power consumption for operation of the turbocharger assembly is therefore reduced. The link member may alternatively be mounted for translational movement.
Preferably the valves are aerodynamically balanced, that is the gas forces developed on the valves are balanced, for example are disposed equally on either side of the pivot axis in a rotary valve or do not have a resultant component in the slide direction in the case of slide valves. In this way, the forces required to operate the valves are kept small and, more importantly, relatively constant during operation, which has the advantage of reducing the power requirements of an actuator utilised to operate the link member.
The first and second valves are preferably realised as rotary valves whose axes are parallel to each other, the first valve being a swing valve and the sec
Borg-Warner
Denion Thomas
Dziegielewski Greg
Pendorf & Cutliff
Trieu Thai-Ba
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