FIELD OF THE INVENTION

[0001] This invention relates to internal combustion engines, including but not limited to control and operation of a turbocharger, EGR system and engine braking for an internal combustion engine.

BACKGROUND OF THE INVENTION

[0002] Adequate and reliable braking for vehicles, particularly large tractor-trailer vehicles, is desirable. While drum or disc wheel brakes are capable of absorbing a large amount of energy over a short period of time, the absorbed energy is transformed into heat in the braking mechanism. An engine braking system can be used to assist in braking the vehicle.

[0003] Multi-cylinder internal combustion engines, particularly diesel engines for large tractor-trailer trucks, may include an exhaust-gas turbocharger. The turbocharger includes a turbine that drives a compressor via a shaft, which generates an increased intake air pressure in the intake duct during normal operation.

[0004] Braking systems are known which include exhaust brakes which inhibit the flow of exhaust gases through the exhaust system, and compression release systems wherein the energy required to compress the intake air during the compression stroke of the engine is dissipated by exhausting the compressed air through the exhaust system.

[0005] One method disclosed in U.S. Patent No. 4,395,884 includes employing a turbocharged engine equipped with a double entry turbine and a compression release engine retarder in combination with a diverter valve. During engine braking, the diverter valve directs the flow of gas through one scroll of the divided volute of the turbine. When engine braking is employed, the turbine speed is maximized, and the inlet manifold pressure is also maximized, thereby maximizing braking horsepower developed by the engine. [0006] Other methods employ a variable geometry turbocharger (VGT). When engine braking is commanded, the variable geometry turbocharger is "clamped down" which means the turbine vanes are closed and used to generate both high exhaust manifold pressure and high turbine speeds, resulting in high compressor speeds. Increasing the turbocharger speed in turn increases the engine airflow and available engine brake power. The method disclosed in U.S. Patent No. 6,594,996 includes controlling the geometry of the turbocharger for engine braking as a function of engine speed and pressure (exhaust or intake, preferably exhaust). U.S. Patent 6,148,793 describes a brake control for an engine having a variable geometry turbocharger which is controllable to vary intake manifold pressure. The engine is operable in a braking mode using a turbocharger geometry actuator for varying turbocharger geometry, and using an exhaust valve actuator for opening an exhaust valve of the engine.

[0007] Other methods of using turbochargers for engine braking are disclosed in U.S. Patent Nos. 6,223,534 and 4,474,006.

[0008] Engine brakes require exhaust backpressure to create a pumping loss and develop retarding power. Some braking systems close a butterfly flap valve in the exhaust outlet housing downstream of the turbochargers to create the backpressure. However, with the valve in this location, mass air flow through the turbochargers can be choked off during high backpressure conditions which results in a loss of compressed air into the cylinders because the compressor wheel does not spin effectively.

[0009] In order to achieve a high engine-braking action, a brake valve in the exhaust line upstream of the turbine may be closed during braking, and excess pressure is built up in the exhaust line upstream of the brake valve. The built-up exhaust gas flows at high velocity into the turbine and acts on the turbine rotor, whereupon the driven compressor increases pressure in the air intake duct. The cylinders are subjected to an increased charging pressure. In the exhaust system, an excess pressure develops between the cylinder outlet and the brake valve and counteracts the discharge of the air compressed in the cylinder into the exhaust tract via the exhaust valves. During braking, the piston performs compression work against the high excess pressure in the exhaust tract, with the result that a strong braking action is achieved. Patents which disclose valves upstream of the turbine include US 7,523,736 and US 4,395,884.

[0010] The present inventors have recognized the need for an efficient engine braking system which allows backpressure to build while also allowing exhaust gas to flow to the turbine without needing to divert the flow of exhaust gas.

SUMMARY OF THE INVENTION

[0011] According to an exemplary embodiment of the present invention, brake valves are located in the exhaust system upstream of a turbine of the engine turbocharger. For exhaust systems utilizing a divided exhaust manifold system with a divided turbocharger turbine inlet, a brake valve is present in each gas flow passageway. The brake valves can be knife edge flap valves or D-shaped valves which rotate about a horizontal axis to adjust the amount of exhaust gas supplied to the turbine, and the amount of gas restricted to generate sufficient back pressure for engine braking.

[0012] By using adjustable backpressure break valves upstream of the turbocharger, the system is capable of generating high levels of backpressure. By adjusting the valves such that a gap remains between the flaps and the exhaust manifold which allows some exhaust gas to flow through, the turbine and the compressor continue to spin, the engine mass flow is not choked off, and improved engine brake performance will result.

[0013] Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic diagram of an engine system that includes a turbocharger and an engine braking system in accordance with an exemplary embodiment of the invention; [0015] Figure 2 is a schematic vertical side sectional diagram of a valve assembly useful in an engine braking system, taken generally along line 2-2 of Figure 1.

[0016] Figure 3 is a schematic plan view of the valve assembly of Figure 2, with a top wall portion removed to view underlying components.

[0017] Figure 3 A is a view along line 3 A - 3 A of Figure 3.

[0018] Figure 4 is a schematic front vertical sectional diagram of an alternate valve assembly useful in an engine braking system, taken generally along line 4-4 of Figure 1.

[0019] Figure 5 is a schematic vertical side sectional diagram of the valve assembly shown in Figure 4, taken generally along line 2-2 of Figure 1.

DETAILED DESCRIPTION

[0020] While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated.

[0021] An engine 100 is shown schematically in FIG. 1. The engine 100 has a block 101 that includes a plurality of cylinders. The cylinders in the block 101 are fluidly connected to an intake system 103 and to an exhaust system 105. The exhaust system includes a first pipe 105 a from cylinders 1, 2 and 3 of one bank of cylinders and a second pipe 105b from cylinders 4, 5 and 6. Although an inline arrangement of six cylinders is illustrated, inline or V- arrangements or other arrangements of plural cylinders of any number of cylinders are also encompassed by the invention.

[0022] A turbocharger 107 includes a turbine 109. The turbine 109 shown has a dual turbine inlet port 113 connected to the exhaust system 105. The turbocharger 107 includes a compressor 111 connected to the intake system 103 through an inlet air passage 115. The turbine can be a divided housing turbine. [0023] During operation of the engine 100, air may enter the compressor 111 through an air inlet 117. Compressed air may exit the compressor 111 through a discharge nozzle 207, pass through the inlet air passage 115, and pass through an optional charge air cooler 119 and an optional inlet throttle 120 before entering an intake air mixer 121 and an intake air manifold 122 of the intake system 103. The compressed air enters the engine cylinders 1-6.

[0024] A stream of exhaust gas from the exhaust system 105 may be routed through an EGR passage or conduit 124, through an exhaust gas recirculation (EGR) valve 125, through an exhaust gas recirculation (EGR) cooler 126 and pass through a further EGR conduit 127 before meeting and mixing with air from the inlet throttle 120 at the mixer 121.

[0025] The inlet port 113 of the turbine 109 may be connected to the exhaust pipes 105a, 105b in a manner that forms a divided exhaust manifold 129. Exhaust gas passing through the turbine 109 may exit the engine 100 through a tailpipe 134. Emissions and sound treating components can be arranged to receive the exhaust gas from the tailpipe, before exhausting to atmosphere, as is known.

[0026] At times when the EGR valve 125 is at least partially open, exhaust gas flows through pipes 105a, 105b, through the conduit 124, through the EGR valve 125, through the EGR cooler 126, through the further conduit 127 and into the mixer 121 where it mixes with air from the inlet throttle 120. An amount of exhaust gas being re- circulated through the EGR valve 125 may depend on a controlled opening percentage of the EGR valve 125.

[0027] A brake valve 133 (Figure 1) is arranged within the exhaust manifold 129. The brake valve 133 includes valve elements 136a that are adjustable between a closed position, shown in solid, for engine braking operation, and an open position, shown in dashed (Figure 2). During a normally operating, non engine braking operation, the valve is moved to a horizontal position, as illustrated by dashed lines in Figure 2, parallel to the direction of exhaust gas flow, to allow exhaust gas to pass through the passage with minimal restriction. [0028] During engine braking, the valve elements 136a are adjusted from their open position to a position which restricts at least a portion of the exhaust gas flow, shown in solid lines (Figure 2). Exhaust gas which passes through the exhaust manifold 129 reaches the turbocharger to maintain turbine speed to maintain a high volume of compressed air from the compressor 111 into the intake system 103.

[0029] A more complete description of engine braking can be found in U.S. Patent Nos. 6,594,996; 6,223,534; 6,148,793; 4,474,006 and 4,395,884; all herein incorporated by reference.

[0030] As shown in Figures 2 and 3, brake valve elements can be knife edge flap valve elements 136a which are hinged at the top 138 to a horizontal shaft 248 in a divided manifold system. The valve elements 136a pivot with respect to each channel of the divided manifold allowing gas to enter a divided turbocharger turbine inlet 113. As illustrated in Figure 2, the knife edge flap valve in its open position is tucked in a recessed portion of the exhaust manifold 129 to minimize the restriction of air flow through the exhaust manifold 129.

[0031] The shaft 248 penetrates the manifold 129 through a top thereof and is sealed within the penetration. As illustrated in Figures 3 and 3A, a crank 252 is fixed to an end of the shaft 248 at a base end 254 of the crank 252 and is pivotally connected at a distal end 256 to a linear actuator 260. The actuator 260 can be an electric solenoid powered actuator for reciprocal movement of an actuator arm 262 into, and out of, an actuator body 264. The distal end 256 of the crank is pivotally connected to a ball joint or pivotal joint 266 of the arm 262. The actuator 260 is pivotally connected at a base end 268 thereof to a support plate 272 mounted on the manifold 129. The pivotal connection of the actuator 260 allows a small degree of pivoting of the actuator 260 as the arm 262 is moved into, or out of, the body 264. As the arm 262 moves with respect to the body 264, the crank 252 is turned and the valves 136a open or close.

[0032] As alternatives to an electrical solenoid powered actuator, a pneumatic cylinder actuator, a hydraulic oil powered actuator, other types of electrical powered actuators, or other known actuators are possible. [0033] As illustrated in Figure 2, knife edge flap valve elements 136a have a bottom edge 135 which is angled. The angled bottom edge 135 allows for exhaust gas not restricted by the valves in its closed position to flow around the bottom edge 135 towards the turbine inlet in direction A. Without wishing to be bound by any particular theory, it is believed that by blocking flow to the upper half of the turbine housing, and directing flow towards the bottom of the turbine, the expansion of gas as it passes into the turbine housing is minimized and the flow of exhaust gas flow is directed into an area of the turbine housing where flow velocity is most effectively maintained.

[0034] The knife edge flap valve element 136a in Figure 2 is show in its substantially closed position in solid lines. The closed position can be defined by a stop mechanism situated near shaft 248 to prevent the knife flap valve element 136a from further rotating in a counterclockwise position. Alternatively, the closed position can be defined by the actuator by only allowing the shaft to rotate up to a certain degree of rotation from the open position.

[0035] In another embodiment, as illustrated in Figures 4 and 5, a brake valve 133a has D-shaped valve elements 136b to accommodate circular, divided exhaust passages 300, separated by a dividing wall 128. D-shaped valve elements 136b pivot about a shaft 248a passing through the center of each D-shaped valve at its widest region, allowing the D-shaped valve element 136b to rotate between a closed position, shown dashed in Figure 5, and an open position, shown solid in Figure 5. The shaft 284a may be rotated by an actuator 260 attached, and operated as described with respect to Figures 3 and 3 A. The D-shaped valve elements 136b have a bottom edge 135a which has been truncated so as to allow greater exhaust gas flow at the bottom region 137a of the passage compared to the exhaust gas flow that would flow through the bottom region 137 of the valve in its open position without the truncated bottom edge 135a. The truncated bottom edge 135a allows for more exhaust gas flow from the bottom of the passageway towards the turbine when the valve is adjusted to one of its opened positions. In an alternative embodiment, D-shape valves without the truncated bottom edge 135a can also be used. [0036] The valves 133, 133a can be adjusted to any position within a range between a closed position, where maximum restriction of flow occurs, and an open position, where minimum flow restriction occurs, depending on engine operating conditions and desired breaking conditions.

[0037] In another embodiment, valves 133, 133a could be a separate assembly that can be attached upstream of the turbocharger, and not as part of the exhaust manifold.

[0038] The optimal position of the adjustable valves 133, 133a can be calibrated and optimized according to various operating conditions to which the engine is subjected.

[0039] In addition to adjusting valves 133, 133a to any position ranging between open and closed positions, one or more exhaust valves of the engine can be opened, as described in U.S. Patents 6,594,996; 6,148,793; 6,779,506; 6,772,742 or 6,705,282, herein incorporated by reference, to maximizing braking horsepower developed by the engine.

[0040] In addition to providing a simple, efficient system for engine braking, the valves 133, 133a disclosed can also be closed to promote engine warm up during light loads or cold start conditions. The valves 133, 133a can also be closed to drive EGR during EGR cycles.

[0041] Parts List

100 engine

101 block

103 intake system 105 exhaust system 105 a first exhaust pipe 105b second exhaust pipe 107 turbocharger 109 turbine 111 compressor 115 inlet air passage 119 optional charge air cooler

120 optional inlet throttle

121 inlet air mixer

122 intake manifold

124 EGR conduit

125 EGR valve

126 cooler

127 further conduit

128 dividing wall

129 divided exhaust manifold 132 divided turbine inlet 133, 133a brake valve

134 tailpipe

135 bottom edge of knife edge flap valves 135a bottom edge of D-shaped valves 136a knife edge flap valve element

136b D-shaped valve element

137 gas flow path at the bottom region of flow passage 137a gas flow path at the bottom region of flow passage

138 top region of knife edge flap valve 201 compressor housing

248 shaft 252 crank

254 base end of crank 256 distal end of crank 260 linear actuator 262 actuator arm 264 actuator body 266 pivotal joint 268 base end of body 264 272 support plate

[0042] From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred.