FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION A Novel Waste Gate System For Turbocharged Engine
APPLICANTS


TATA MOTORS LIMITED, an Indian Company
having its registered office at Bombay House,
24 Homi Mody Street, flu tat ma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTORS
Mr. Dattatraya R. Katkar, Mr. Deepak S. Kulkarni And Mr. G. Sathya Narayanan
All are Indian Nationals
of TATA MOTORS LIMITED,
an Indian company having its registered office
at Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India

PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner
in which it is to be performed


FIELD OF INVENTION
This invention relates to a waste gate system for a small sized turbocharged engine. More particularly it relates to an external waste gate system that relieves the back pressure on the engine at low load conditions where turbo boost is not necessary and combined with a diaphragm loaded internal waste gate system for restricting Max Boost pressure. So it results in significant reduction of pumping losses of the engine by bypassing exhaust gases at part loads.
BACKGROUND OF INVENTION
For the development of Turbocharged engine of lower cubic capacity, more challenges are to be faced in matching the fuel consumption characteristics similar to a naturally aspirated engine along with higher Power - Torque requirements. Most essential is the exact matching of the Turbocharger with Engine. Turbocharger matching is not complex in case of Multi-cylinder higher cubic capacity engines, where the exhaust flow rates are quite high and pressure pulses are better. Whereas, in lower cubic capacity engines, the pressure energy of gases and exhaust flow rates are minimal. Boost pressure requirement of engine at all operating speeds and loads can be met with fine tuning of the waste gate system, Higher the requirement of boost pressure requires higher the exhaust gas pressure before turbine to drive turbine wheel at higher speeds, The boost requirement varies with engine operating speed and load conditions. The waste gate system can be either internal or external. This invention discloses an external waste gate system with novel method of actuation for reducing part load pumping losses.
PRIOR ART
Considerable amount of work has been done in the past for waste gate control in Turbocharged diesel engines,
2

US 4,492,519 teach about a Turbocharger having a by-pass system for selectively by¬passing exhaust gases from the turbine rotor. The exhaust gases are diverted around the turbine section by the by-pass system containing a by-pass port, passage and valve within the turbine housing. The cross-sectional area of the by-pass system is less than exhaust gas inlet but of sufficient area wherein exhaust gas by-passing does not create back pressure detrimental to the engine performance. By-pass port and valve are of quarter moon shape to minimize the angular movement of the valve plate required to fully uncover the by-pass port. Control device for actuating the by-pass valve is remote from the turbocharger for reducing the cost of control elements.
US 5, 755,101 teach about the turbocharger waste gate control system having electrical control for controlling the position of a waste gate valve positioned within a exhaust bypass conduit of the turbocharger. The control system comprises of air pressure control device having an inlet port receiving boost pressure from intake manifold, an outlet port providing waste gate pressure to waste gate actuator and vent to atmosphere. Air control switches were used to electrical control signals to control the level of boost pressures and vented air to thereby provide a plurality of discrete waste gate air pressures levels to the waste gate actuator. The control system includes an electrically controllable waste gate actuator responsive to boost air pressure and electrical control signals to modulate the position of the waste gate actuator plunger.
US 6,976, 359 B2 teach about the usage of the swing type valve for actuating the waste gate which is separate from the turbocharger. The swing valve has a pivot point that lies outside the path of the exhaust gases. The passage has a recess therein that receives a portion of the swing valve in its open position to improve the flow of exhaust gases through the passage. The passage forms a ninety degree bend. While comparing to the integral waste gate system in the turbocharger this external waste gate system can be removed and replaced without removing the turbocharger, which makes repairs easier, its performance can also be adjusted easily and control actions are more sensitive. When the remote waste gate valve is in the open position the swing
3

valve forms forty five degree with respect to any of the legs of the exhaust bypass passage.
It is worthwhile to note at this point that, even though the above mechanisms claims the use of the external waste gate system was to provide wide area for gases to follow, longer life of the waste gate valves, serviceability ease of waste gate and to limit the Max boost by compressor, it does not call for any role in the fuel efficiency view point. So considering the importance of developing fuel efficient engines, the external waste gate system was designed in order to increase the fuel efficiency at part loads combined with regular internal waste gate system for restricting the max boost pressure.
OBJECTS OF INVENTION
• The main objective of this invention is to satisfy the turbo boost requirement of engine at various operating conditions.
• Yet another objective of this invention is to bypassing the exhaust gases where there is no turbo boost requirement.
• Yet another objective of this invention is to reduce the pumping losses resulting by to easy flushing of exhaust gases by exhaust gas bypass at part load conditions, there by increasing the fuel efficiency.
• Yet another objective of this invention is to restrict the boost pressure limit by usage of internal waste gate on the turbocharger for safety purposes.
SUMMARY OF INVENTION
The present invention relates to usage of external bypass system for a turbocharged
4

engine along with diaphragm loaded internal waste gate system. The waste gate control system comprises of following components,
• Waste gate controller
• Electrically controlled butterfly valves
• FIP throttle lever position sensor
• Engine speed sensor
• Air mass flow sensor
• Throttle body
In the fuel efficiency point of view, part load fuel consumption plays a major role. At part load condition, say, below lower loads, there is no requirement of compressor to provide engine with denser air. Under such circumstances the entire turbine unit (turbine housing and turbine wheel) provides restriction for the exhaust gas to pass by. So it makes engine to act as a pump to push out the exhaust gases, which contributes to the pumping losses. By eliminating these losses the fuel efficiency can be better. In the earlier inventions, the external waste gate was used to bypass the exhaust gases once the compressor achieved the desired boost pressure. The use of the external waste gate system was to provide wide area for gases to follow, longer life of the waste gate valves and the serviceability ease of waste gate. In those prior art systems spring loaded valves were used to open the bypass way open desired boost pressure is reached.
This novel waste gate system will operate the engine in the following two modes for better fuel efficiency,
• Turbocharger active mode
• Turbocharger inactive mode
When the engine operates on higher loads, the turbocharger should be kept active to deliver required power at a certain speeds and turbocharger can be made inactive at part loads. To achieve this functionality FIP throttle lever position sensor on Fuel
5

injection pump (FIP), crank speed sensor and Waste gate controller should be used. The engine operating information like load and speed can be obtained by FIP throttle lever position sensor and Crank speed sensor. Turbocharger active zone should be decided and operating map of turbocharger w. r. to engine load and engine speed should be fed into the waste gate controller. This map will decide the operation of the electrically controlled waste gate valves (Stepper motor or D.C motor controlled).
Accordingly, the present invention relates to a turbocharged engine with a waste gate control system, comprising a turbocharger connected to an intake manifold and an exhaust manifold, said intake manifold being connected to a compressor unit through an intercooler and said exhaust manifold being connected to a turbine unit; wherein said waste gate control system comprises: a waste gate controller for obtaining load/speed data from respective sensors; a bypass passage connecting a turbine inlet and a turbine outlet and interconnected with a main exhaust flow passage; a first control valve for controlling exhaust flow rate in said main exhaust flow passage prior to the turbine inlet and a second control valve for controlling exhaust flow rate in said bypass passage, such that, exhaust gases from main exhaust flow area or bypass passage is adapted to pass through to a silencer based on active or inactive mode of said turbocharger.
STATEMENT OF INVENTION
This invention relates to a turbocharged engine with a waste gate control system, comprising a turbocharger connected to an intake manifold and an exhaust manifold, said intake manifold being connected to a compressor unit through an intercooler and said exhaust manifold being connected to a turbine unit; wherein-said waste gate control system comprises; a waste gate controller for obtaining load/speed data from respective sensors; a bypass passage connecting a turbine inlet and a turbine outlet and interconnected with a main exhaust flow passage; a first control valve for controlling exhaust flow rate in said main exhaust flow passage prior to the turbine inlet and a second control valve for controlling exhaust flow rate in said bypass
6

passage, such that, exhaust gases from main exhaust flow area or bypass passage is adapted to pass through to a silencer based on active or inactive mode of said turbocharger.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 shows the details of novel waste gate system
Fig. 2 shows the waste gate system with addition of Throttle body (16) and air mass flowsensor(17).
DETAILED DESCRIPTION OF INVENTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same. The sketches showing details of the components of the novel waste gate system are given herewith
Referring to the figure no. 1 & 2
The turbocharged engine (1) is connected to the intake manifold (2) and exhaust manifold (5). The fuel injection pump (3) is directly driven by engine with the drive ratio 0.5. Fuel injection pump is equipped with FIP throttle position sensor (4) that provides the load data to the waste gate controller (8). Filtered air is supplied to the compressor unit (9) by the air filter (13). Compressor unit (9) is connected to the intake manifold through intercooler (14) and hoses (15). Turbine unit (10) is connected to the exhaust manifold (5) and bypass passage connects the turbine inlet and turbine outlet, where the electrically controlled valve (6) is controlling exhaust flow prior to the turbine unit (10). Similarly electrically controlled valve (7) controls the exhaust flow rate in the bypass passage. Main exhaust flow area and bypass flow area are connected and the exhaust gas passes through silencer (12) through catalytic converter (11). In addition to the external waste gate system, the turbocharger unit has
7

diaphragm loaded waste gate flap valve for limiting the max pressure generated by turbocharger.
In addition to the external waste gate system show in fig. 1 an intake throttle (16) is added. For EGR usage the intake throttle (16) can be used and for sensing intake manifold vacuum, air mass flow sensor (17) can be used for metering the air quantity and to fine tune the EGR admission points.
TURBOCHARGER ACTIVE MODE
Under higher load conditions specifically above 50% load of the engine, the electrically controlled waste gate valve (6) will be kept open by recognizing load through FIP throttle lever position sensor (4). Alternatively waste gate valve (7) will be kept close to avoid bypass of the exhaust gas. Since the actuation of both electrically controlled valves (6) (7) are opposite to each other, the coordination of the valve open - close should be proper to prevent exhaust braking. Turbocharger active in the high load conditions gives sufficient boost pressure to the engine. The internal waste gate system with diaphragm loaded flap valve will limit the max boost pressure. At these higher load operations, specific fuel consumption will be better since engine will be delivering more power and effect of pumping losses will be minor.
TURBOCHARGER INACTIVE MODE
When fuel throttle lever travel will be below 50% of its maximum travel, the fuel lever position sensor provide input to the waste gate controller (8) to run engine in turbocharger inactive mode. Under part load condition specifically below 50% load, the electrically controlled valve (6) will be kept completely closed and the waste gate valve (7) will be kept wide open to bypass the exhaust gas thereby reducing the pumping losses of the engine considerably. The interference of the turbine wheel on exhaust gas flow is completely prevented and exhaust gas are not flowing through lesser cross - sectional area of turbine housing, which reduces the pumping work of
8

the engine at part load condition significantly. The reduction in the pumping losses will make engine to consume less fuel to deliver the same power. Thus fuel efficiency improves significantly at part load conditions.
Considering engine operations at lower speeds, where even below 75% of the full load condition there is no generation of boost pressure generated due to weak pressure pulses at lower speeds. So at those points the turbocharger can be made inactive to reduce pumping losses. Since the effect of pumping losses in fuel consumption becomes predominant factor at low engine speeds, the turbocharger active map should be formed with respect to engine speed and engine load i.e fuel throttle lever position. This map can be fed into the waste gate controller (8) for more efficient operations. So irrespective of engine load throughout all engine speeds, if we create a map which tells waste gate controller (8) to bypass the exhaust gases completely where there is no necessity of boosted air fuel efficiency benefits from this novel external waste gate system will be more.
On the emission point for reducing NOx emission if EGR becomes necessary, then the above mentioned system can be changed as per fig. no 2. Since the waste gate system keeps the turbocharger inactive at part loads, exhaust gas pressure drops and introduction of EGR inside intake manifold becomes difficult. To overcome this difficulty, intake throttling should be provided with addition of throttle body on the intake manifold. Air mass flow sensor can also be added with the existing system for metering the air quantity and to fine tune the EGR admission points.
The demerit of the external waste gate system is the addition in restriction to the fresh air by compressor wheel at turbocharger inactive mode. Intake depression offered by idle compressor blades in the Turbocharger inactive mode at Part loads can slightly affect fuel efficiency. The intake depression offered by compressor will be minimal considering the pumping losses offered by the turbine blades. So there will be net gain in fuel consumption perspective when such a system is used.
9

The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.
10

WE CLAIM
1. A turbocharged engine with a waste gate control system, comprising a
turbocharger connected to an intake manifold and an exhaust manifold, said intake
manifold being connected to a compressor unit through an intercooler and said
exhaust manifold being connected to a turbine unit; wherein said waste gate control
system comprises;
a waste gate controller for obtaining load/speed data from respective sensors;
a bypass passage connecting a turbine inlet and a turbine outlet and interconnected with a main exhaust flow passage;
a first control valve for controlling exhaust flow rate in said main exhaust flow passage prior to the turbine inlet and a second control valve for controlling exhaust flow rate in said bypass passage, such that, exhaust gases from main exhaust flow area or bypass passage is adapted to pass through to a silencer based on active or inactive mode of said turbocharger.
2. The turbocharged engine as claimed in claim 1, wherein said first and second control valves are electrically controlled butterfly valves.
3. The turbocharged engine as claimed in claim 1, wherein said turbocharger has a diaphragm loaded waste gate flap valve for limiting the maximum pressure generated by said turbocharger.
4. The turbocharged engine as claimed in claim 1, wherein an intake throttle is connected to said intake manifold.
5. The turbocharged engine as claimed in claim 4, wherein an air mass flow sensor is provided for sensing intake manifold vacuum and for metering the air quantity.
11

6. The turbocharged engine as claimed in claim 1, wherein said first control valve is configured to be opened and said second control valve is configured to be closed to avoid bypass of the exhaust gas during higher loads and speeds of the engine.
7. The turbocharged engine as claimed in claim 1, wherein said first control valve is configured to be closed and said second control valve is configured to be opened during lower loads and speeds of said engine to bypass the exhaust gas to reduce the pumping losses of the engine.
8. The turbocharged engine as claimed in claim 1. wherein a map formed with respect to engine speed and engine load (fuel throttle lever position) is inputted into said waste gate controller.
9. The turbocharged engine as claimed in claim 1, wherein filtered air is supplied to said compressor unit by an air filter.
10. The turbocharged engine as claimed in claim 1, wherein exhaust gases is adapted to pass to said silencer through a catalytic converter.
11. A turbocharged engine comprising a waste gate control system substantially as hereinabove described with reference to the accompanying drawings.
12
Dated this 23rd day of March 2009