WO2018113988A1

WO2018113988A1 - An internal combustion engine

Info

Publication number: WO2018113988A1
Application number: PCT/EP2016/082473
Authority: WO
Inventors: Björn LUNDSTEDT
Original assignee: Volvo Truck Corporation
Priority date: 2016-12-22
Filing date: 2016-12-22
Publication date: 2018-06-28

Abstract

The invention provides an internal combustion engine (2) comprising a fuel system (5) and an air inlet duct (4) arranged to guide air towards at least one cylinder (301) of the engine, the cylinder being arranged to compress air from the air inlet duct, and the fuel system (5) being arranged to inject fuel into the air compressed in the cylinder, the air inlet duct (4) comprises a first conduit (401) and a second conduit (402) arranged to provide parallel air flows, the air inlet duct (4) being arranged to merge the parallel air flows upstream of the cylinder, a first valve (411) being arranged to control the flow through the first conduit (401) and a second valve (412) being arranged to control the flow through the second conduit (402).

Description

An internal combustion engine

TECHNICAL FIELD The invention relates to an internal combustion engine and a heavy duty vehicle comprising an internal combustion engine.

The invention can be applied in heavy-duty vehicles, such as trucks, buses and construction equipment, such as wheel loaders, haulers and excavators.

BACKGROUND

Heavy duty vehicles usually use diesel engines due to their high efficiency and power density. As is known in a diesel engine operation presents a diesel cycle in which air is compressed in the engine cylinders, upon which fuel injected into the compressed air. The fuel may be of any suitable type, such as diesel fuel, biodiesel, or natural gas.

A diesel engine may be provided with an air inlet throttle valve, e.g. to allow an increase of an exhaust gas recirculation (EGR) flow, or to provide a decreased air flow at low load conditions. A diesel engine may also be equipped with a heater in the air intake manifold to assist the engine operation during cold start conditions.

Diesel engines for heavy duty vehicles varies in size depending on the operational characteristics of the vehicles. As the demand for large heavy duty vehicles increase, so does the demand for large engines. Large diesel engines for heavy duty vehicles such as trucks may reach sizes above 15 litres and may present maximum power levels of more than 800 hk, e.g. 1000 hk. Such engines require large components. For example, the air intake for large diesel engines present large cross-sections. A large air intake entails an intake throttle valve which is large in size. As a result, the throttle valve body will present a high inertia which means that a high torque is needed for the valve actuation. (The inertia is proportional to the square of the valve diameter.) Thereby, the valve actuator needs to be relatively powerful, which contributes to a high cost of the engine. Also, the valve itself will be expensive to manufacture due to its size. Also a large air intake entails a preheater which is large in size. As a result, a large amount of energy is needed to activate the heater. Also, the heater will be expensive to manufacture due to its size.

SUMMARY

An object of the invention is to facilitate the operation of air intake components of large heavy duty diesel engines. An object of the invention is to facilitate the manufacturing of air intake components of large heavy duty diesel engines.

The objects are achieved by an internal combustion engine according to claim 1 . Hence the invention provides an internal combustion engine comprising a fuel system and an air inlet duct arranged to guide air towards at least one cylinder of the engine, the cylinder being arranged to compress air from the air inlet duct, and the fuel system being arranged to inject fuel into the air compressed in the cylinder, characterized in that the air inlet duct comprises a first conduit and a second conduit arranged to provide parallel air flows, the air inlet duct being arranged to merge the parallel air flows upstream of the cylinder, a first valve being arranged to control the flow through the first conduit and a second valve being arranged to control the flow through the second conduit.

It is understood that the fuel system is arranged to inject fuel into air which has been compressed in the cylinder. The invention is applicable to engines with any number of cylinders. Also the cylinders may be arranged in any configuration, e.g. in an inline configuration or a V-configuration. It is understood that the air inlet duct may be arranged to guide air towards all cylinders or towards a subset of the cylinders. In the latter case, a further air inlet duct may be provided to guide air towards the remaining cylinders; e.g. each air inlet duct may be arranged to serve a respective of two cylinder banks in a V- configuration engine. It is further understood that the first valve may be located in the first conduit and the second valve may be located in the second conduit.

The air inlet duct may comprise an inlet manifold arranged to guide air to each of a plurality of cylinders. Thereby the first and second conduits may be arranged to merge the parallel air flows upstream of the inlet manifold. Alternatively the first and second conduits may be arranged such that the parallel air flows are merged in the inlet manifold. The first and second conduits with the first and second valves provide a number of advantages for large diesel engines. The first and second valves may replace a single valve for a single large air intake. Thereby the throttle valve size may be considerably reduced with a substantial reduction of the inertia of the throttle valve bodies, and an equally substantial reduction of the torque is needed for the valve actuation. Thereby, the operation of the valves will be facilitated since less powerful valve actuators may be needed, which contributes to reducing the cost of the engine. In addition, the

manufacturing cost of the valves will be reduced. Also valves available for smaller engines may be used, which allows valve designs to be shared between different engine sizes; this simplifies the overall manufacturing setup for various engine types, in turn reducing cost.

Further, the invention provides for allowing an air intake a preheater which is considerably reduced in size. This will reduce the amount of energy needed to activate the heater whereby the operation of the heater will be facilitated. Also, the heater will simpler and cheaper to manufacture due to its relatively small size.

Preferably, the second valve is arranged to control the flow through the second conduit independently of the control of the first valve. Thereby, advantageous control possibilities are provided. For example, the engine further may comprise a heater in the first conduit. The heater may be an electrical heater. The heater may be located downstream of the first valve. Thereby, the heater may be arranged to heat the air flowing through the first conduit. During cranking, e.g. in cold conditions, most or all of the inlet air may be sucked through the heater by throttling or closing the second valve. At engine cranking and starting, the intake air flow may be less than 10% of the maximum air flow, due to a low engine speed and a lack of boost pressure. By embodiments of the invention, an electrical heater can be made narrower and more efficient for heating the relatively low air flow. During normal operation both valves may be open. It should be noted that the invention is also applicable where there is a heater in the first conduit, which is of another type than electrical. For example, the heater may be a burner, e.g. arranged to burn diesel fuel.

Also for large engine sizes, heaters available for smaller engines may be used, which allows the heater design to be shared between different engine sizes; this simplifies the overall manufacturing setup for various engine types, in turn reducing cost. In addition, an air intake heater is typically used only a few seconds at engine start. A relatively small heater being allowed provides for less current to be used since there is less heater wire to heat. I.e., the heated mass will be lower. Once the use of the heater is no longer needed upon engine start, the less energy is wasted since the heated mass is small.

Preferably, at least one of the first and second valves is a throttle valve. The throttle valve may be arranged to assume a fully open position, a fully closed position, or any of a plurality of positions between a position in which the throttle valve is fully closed and a position in which the throttle valve is 40% open. A throttle valve may advantageously provide for all desired intermediate flows to be obtained in the positions between the fully closed position and the 40% open position. Thereby, only relatively small movements will be required in the valve actuation, whereby the valve control may be simplified. It should be noted that in some embodiments, the throttle valve may be arranged to assume a fully open position, a fully closed position, or any of a plurality of positions between a position in which the throttle valve is fully closed and a position in which the throttle valve is fully open. Advantageously, the first and second valves are identical or of mirrored design. Thereby, manufacturing planning and handling will be simplified.

In some embodiments, at least one of the first and second valves is arranged to assume either a fully open position or a fully closed position. This valve may be a binary open- shut, on/off valve. Thus, one of the valves can be a simple on/off valve. The binary valve may be provided without a position sensor for a closed loop control, and thereby, the cost for the engine may be reduced. The binary valve may be of a simple mechanical design, such as a spring loaded throttle. Alternatively it may be software controlled. Preferably, one of the first and second valves is a throttle valve, and the other of the first and second valves is arranged to assume either a fully open position or a fully closed. Hence, one of the valves may be a throttle valve allowing any flow between fully open and closed positions, and the other valve may be a binary open-shut valve. Thereby, from a condition where both valves are fully open, the throttle valve may be used to gradually decrease the flow. When the throttle valve has been fully closed, and a further decrease in the total flow is desired, the binary valve may be fully closed and the throttle valve may be simultaneously fully opened, upon which the throttle valve may be used to gradually reduce the total flow further. Where the engine comprises a heater in the first conduit the throttle valve may be provided in the second conduit and the binary valve may be provided in the first conduit, or vice versa.

Preferably, the engine comprises a first sensor being arranged to detect values of a parameter indicative of the temperature, the air mass flow and/or the pressure in the first conduit, and a second sensor being arranged to detect values of a parameter indicative of the temperature, the air mass flow and/or the pressure in the second conduit.

Advantageously the first and second sensors are hot wire mass airflow sensors. As is known per se a hot wire mass airflow sensor works by heating a wire exposed to the air stream, with an electric current through the wire. The wire's electrical resistance increases as the wire's temperature increases, which varies the electrical current through the wire. Thereby, variations in the air temperature, and hence variations in the air density, may be detected.

By providing for large engine sizes hot wire mass airflow sensors in each of the first and second conduits, hot wire mass airflow sensors available for smaller engines may be used, which allows the sensor design to be shared between different engine sizes. This simplifies the overall manufacturing setup for various engine types, in turn reducing cost.

It should be noted that in alternative embodiments, the first and second sensors may be of some other suitable type, for example pressure sensors.

The air mass flow may be controlled by the first and second valves by means of a control unit as exemplified below. The control unit may be arranged to control the first and second valves based on data from the first and second sensors described above. Thereby, the air mass flow may be controlled based on values of a parameter indicative of the

temperature, the air mass flow and/or the pressure in the first and second conduits.

Preferably, where the engine comprises an exhaust duct arranged to guide exhaust gases from at least one cylinder of the engine, the engine comprises an exhaust gas

recirculation (EGR) conduit arranged to guide exhaust gases from the exhaust duct to the second conduit. This is advantageous, in particular where the engine further comprises a heater, e.g. an electrical heater, in the first conduit, as described above. More specifically, the EGR gases are not guided past the heater, whereby depositions on the heater from EGR gases may be avoided, so that smoke generation from the heater may be avoided. It is understood that the exhaust duct may be arranged to guide the exhaust gases towards an exhaust after treatment system (EATS).

The EGR conduit may be arranged to merge with the second conduit downstream of the second valve. Where the engine further comprises a heater, e.g. an electrical heater, in the first conduit, as described above, the first and second valves may be controlled in a way that is advantageously suited for the functions of the heater and the EGR conduit. For example, the second conduit may be throttled by means of the second valve while the first valve is moved to a closed position, to support the flow through the EGR conduit. It should be noted however, that in some embodiments, the EGR conduit may be arranged to guide exhaust gases from the exhaust duct to the first conduit. Where a heater is provided in the first conduit, as described above, the EGR conduit may be arranged to merge with the first conduit upstream or downstream of the heater. In further embodiments, where the engine comprises an exhaust duct arranged to guide exhaust gases from at least one cylinder of the engine, and an exhaust gas recirculation (EGR) conduit arranged to guide exhaust gases from the exhaust duct to the air inlet duct, the EGR conduit presents a first branch and a second branch, the first branch merging with the first conduit, and the second branch merging with the second conduit. Thereby, the engine may comprise a heater, e.g. an electrical heater, arranged in the first conduit, the first branch merging with the first conduit downstream of the heater. Thereby, by means of the first and second valves, a variety of flow control alternatives are available for affecting the flow through the EGR conduit. By the first branch merging with the first conduit downstream of the heater, depositions on the heater from the EGR gases, and an entailing smoke generation, may be avoided.

Preferably, where an air compressor is provided in the air inlet duct, the air compressor is provided upstream of the first and second conduits. Thereby, an intercooler may be provided in the air inlet duct, between the compressor and the first and second conduits. In some embodiments, the intercooler may be provided downstream of the first and second conduits.

The objects are also reached with a heavy duty vehicle according to claim 19.

Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

In the drawings:

Fig. 1 is a side view of a vehicle in the form of a truck comprising an internal combustion engine with an exhaust gas treatment system,

Fig. 2 depicts the engine in the vehicle in fig. 1 .

Fig. 3 - fig. 4 depict engines according to alternative embodiments of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION Fig. 1 shows a vehicle 1 in the form of a truck in a partly cut side view. The vehicle 1 has an internal combustion engine 2 in the form of a diesel engine for the propulsion of the vehicle 1 .

As can be seen in fig. 2, the engine 2 comprises six cylinders 301 in an inline configuration. Each cylinder includes a reciprocating piston arranged to contribute to the torque of a crankshaft (not shown).

The engine further comprises a fuel system 5 with a fuel container 501 and a fuel pump 502 arranged to pump fuel from the fuel container 501 . The fuel system also comprises injectors 505 arranged to receive fuel from the fuel pump 502, and each arranged to inject fuel directly into a respective of the cylinders 301 .

An air inlet duct 4 is arranged to guide air towards the cylinders 301 . The air inlet duct 4 comprises an inlet manifold 407 arranged to guide air to each of the cylinders. The engine being a diesel engine, the cylinders are arranged to compress air from the air inlet duct, and the fuel system 5 is arranged to inject fuel into the air compressed in the cylinders.

A portion of the air inlet duct 4 is branched so that the air inlet duct 4 comprises a first conduit 401 and a second conduit 402 arranged to provide parallel air flows. The air inlet duct 4 is arranged to merge the parallel air flows upstream of the inlet manifold 407.

Alternatively the first and second conduits 401 , 402 may extend up to the inlet manifold 407 so as for the parallel air flows to be merged in the inlet manifold. A first valve 41 1 is arranged to control the flow through the first conduit 401 and a second valve 412 is arranged to control the flow through the second conduit 402. The first and second valves 401 , 402 are actuatable by means of actuators, such as stepper motors (not shown). Further, the actuation of the first and second valves 401 , 402 are controllable by a control unit 9 described further below. Thereby the second valve 412 is arranged to control the flow through the second conduit 402 independently of the control of the first valve 41 1 .

The engine further comprises an electrical heater 406 in the first conduit 401 . The heater 406 is located downstream of the first valve 41 1 . The heater 406 is provided in the form of an electric wire arranged to conduct an electric current supplied by an electric power source 405, whereby the wire 406 is heated due to its resistance.

The second valve 412 is a throttle valve, arranged to assume a fully open position, a fully closed position, or any of a plurality of positions between a position in which the throttle valve is fully closed and a position in which the throttle valve is 40% open. Thereby, as suggested above, the throttle valve 412 will be able to provide a smooth change of the flow in the second conduit 402 in the entire range from a maximum flow to a zero flow. The first valve 41 1 is what is herein referred to as a binary valve, arranged to assume either a fully open position or a fully closed position. By the combination of the binary valve 41 1 and the throttle valve 412 advantages will be provided as suggested above.

5 In alternative embodiments, the first as well as the second valve 41 1 , 412 are throttle valves. Thereby, the first and second valves 41 1 , 412 may be identical or of mirrored design.

A first hot wire mass airflow sensor 421 is arranged to detect the air mass flow in the first 10 conduit 401 , and a second hot wire mass airflow sensor 422 is arranged to detect the air mass flow in the second conduit 402. The control unit 9 is arranged to control the first and second valves 41 1 , 412 based on data from the first and second sensors 421 , 422. Thereby, the air mass flow may be controlled based on feedback from the sensors 421 , 422.

15

It should be noted that in alternative embodiments, the first and second sensors 421 , 422 may be of some other type suitable for detecting values of a parameter indicative of the temperature, the air mass flow and/or the pressure in the first and second conduits 401 , 402. For example the first and second sensors may be pressure sensors for determining 20 the boost pressure in the first and second conduits 401 , 402.

The engine further comprises an exhaust duct 7 arranged to guide exhaust gases from the cylinders 301 . An exhaust gas recirculation (EGR) conduit 8 arranged to guide exhaust gases from the exhaust duct 7 to the second conduit 402. The EGR conduit 8 is 25 arranged to merge with the second conduit 402 downstream of the second valve 412.

Advantages with such an arrangement have been described above.

Further, the engine comprises a turbo charger 6. The turbo charger 6 comprises an air compressor 601 provided in the air inlet duct 4, upstream of the first and second conduits 30 401 , 402. An intercooler 403 is provided in the air inlet duct 4, between the compressor 601 and the first and second conduits 401 , 402. The compressor is arranged to be driven by a turbine 602 provided in the exhaust duct 7. As mentioned, in some embodiments, the EGR conduit 8 may be arranged to guide exhaust gases from the exhaust duct 7 to the first conduit 401 . Thereby, the EGR conduit 8 is preferably arranged to merge with the first conduit 401 downstream of the heater 406. Reference is made to fig. 3 showing an engine 2 according to an alternative embodiment. The engine in fig. 3 is similar to the engine in fig. 2, with the following exception: The EGR conduit 8 presents a first branch 801 and a second branch 802. The first branch 801 merges with the first conduit 401 , downstream of the heater 406. The second branch 802 merges with the second conduit 402. Advantages with such embodiments have been discussed above.

Reference is made to fig. 4 showing an engine according to another embodiment. The engine comprises a fuel system 5 and an air inlet duct 4 arranged to guide air towards cylinders 301 of the engine. The cylinders are arranged to compress air from the air inlet duct, and the fuel system 5 is arranged to inject fuel into the air compressed in the cylinder. The air inlet duct 4 comprises a first conduit 401 and a second conduit 402 arranged to provide parallel air flows. The air inlet duct 4 is arranged to merge the parallel air flows upstream of the cylinders. A first valve 41 1 is arranged to control the flow through the first conduit 401 and a second valve 412 is arranged to control the flow through the second conduit 402.

It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

Claims

1 . An internal combustion engine (2) comprising a fuel system (5) and an air inlet duct (4) arranged to guide air towards at least one cylinder (301 ) of the engine, the cylinder being arranged to compress air from the air inlet duct, and the fuel system

(5) being arranged to inject fuel into the air compressed in the cylinder, characterized in that the air inlet duct (4) comprises a first conduit (401 ) and a second conduit (402) arranged to provide parallel air flows, the air inlet duct (4) being arranged to merge the parallel air flows upstream of the cylinder, a first valve (41 1 ) being arranged to control the flow through the first conduit (401 ) and a second valve (412) being arranged to control the flow through the second conduit (402).

2. An engine according to claim 1 , characterized in that the second valve (412) is arranged to control the flow through the second conduit (402) independently of the control of the first valve (41 1 ).

3. An engine according to any one of the preceding claims, characterized in that the engine further comprises a heater (406) in the first conduit (401 ).

4. An engine according to claim 3, characterized in that the heater is an electrical heater (406).

5. An engine according to any one of claims 3-4, characterized in that the heater (406) is located downstream of the first valve (41 1 ).

6. An engine according to any one of the preceding claims, characterized in that at least one of the first and second valves (41 1 , 412) is a throttle valve.

7. An engine according to claim 6, characterized in that the throttle valve (41 1 , 412) is arranged to assume a fully open position, a fully closed position, or any of a plurality of positions between a position in which the throttle valve is fully closed and a position in which the throttle valve is 40% open.

8. An engine according to any one of the preceding claims, characterized in that the first and second valves (41 1 , 412) are identical or of mirrored design.

9. An engine according to any one of the preceding claims, characterized in that at least one of the first and second valves (41 1 , 412) is arranged to assume either a fully open position or a fully closed position.

10. An engine according to any one of the preceding claims, characterized in that one of the first and second valves (41 1 , 412) is a throttle valve, and the other of the first and second valves (41 1 , 412) is arranged to assume either a fully open position or a fully closed position.

1 1 . An engine according to any one of the preceding claims, characterized in that the engine comprises a first sensor (421 ) being arranged to detect values of a parameter indicative of the temperature, the air mass flow and/or the pressure in the first conduit (401 ), and a second sensor (422) being arranged to detect values of a parameter indicative of the temperature, the air mass flow and/or the pressure in the second conduit (402).

12. An engine according to claim 1 1 , characterized in that the first and second sensors (421 , 422) are hot wire mass airflow sensors.

3. An engine according to any one of the preceding claims, characterized in that the engine comprises an exhaust duct (7) arranged to guide exhaust gases from at least one cylinder (301 ) of the engine, and an exhaust gas recirculation (EGR) conduit (8) arranged to guide exhaust gases from the exhaust duct (7) to the second conduit (402).

4. An engine according to claim 13, characterized in that the EGR conduit (8) is arranged to merge with the second conduit (402) downstream of the second valve (412).

15. An engine according to any one of the preceding claims, characterized in that the engine comprises an exhaust duct (7) arranged to guide exhaust gases from at least one cylinder (301 ) of the engine, and an exhaust gas recirculation (EGR) conduit (8) arranged to guide exhaust gases from the exhaust duct (7) to the air inlet duct (4), the EGR conduit (8) presenting a first branch (801 ) and a second branch (802), the first branch merging with the first conduit (401 ), and the second branch merging with the second conduit (402).

16. An engine according to claim 15, characterized in that the engine comprises a heater (406) arranged in the first conduit (401 ), the first branch merging with the first conduit (401 ) downstream of the heater (406).

17. An engine according to any one of the preceding claims, characterized in that an air compressor (601 ) is provided in the air inlet duct (4), upstream of the first and second conduits (401 , 402).

8. An engine according to claim 17, characterized in that an intercooler (403) is provided in the air inlet duct (4), between the compressor (601 ) and the first and second conduits (401 , 402).

9. A heavy duty vehicle comprising an engine according to any one of the preceding claims.