Patent Application
20210262420
The present invention relates to an air intake device for an engine.
Patent Literature 1 discloses that a supercharger raising a pressure of air introduced into engine combustion chambers is arranged in an intake passage of a multi-cylinder engine, a bypass passage bypassing the supercharger is provided in the intake passage, a bypass valve adjusting an opening of the bypass passage is provided in the bypass passage, and an EGR valve is provided in an EGR passage connecting the intake passage with an exhaust passage.
Patent Literature 1: Japanese Patent Laid-Open No. 2003-322039
In a case of a multi-cylinder engine causing EGR gas to return, when EGR amounts become non-uniform among cylinders, stable combustion may not be performed in all of the cylinders. The inventor has investigated non-uniformity of the EGR amounts among the cylinders. Then, it has been found that one factor in the non-uniformity is that the EGR gas returned to an intake passage and fresh air flowing through the intake passage are not sufficiently mixed together before those are distributed from the intake passage to each of the cylinders.
In
In
An important problem is that in accordance with an operation state of an engine (for example, an engine speed), not only an uneven state of a fresh air flow in the intake passage (the bypass passage in the example of
Accordingly, an object of the present invention is to efficiently mix fresh air and EGR gas.
To solve the above problem, in the present invention, an expanding portion in which a passage cross-sectional area expands and which lowers a flow speed of EGR gas flowing into an intake passage is provided in a position close to a connection port of an EGR passage to the intake passage.
An air intake device for an engine disclosed herein, includes:
an intake passage leading intake air to combustion chambers of a multi-cylinder engine;
an exhaust passage discharging exhaust gas from the combustion chambers; and
an EGR passage connecting the intake passage with the exhaust passage and returning a portion of the exhaust gas as EGR gas from the exhaust passage to the intake passage, and is characterized in that
the EGR passage includes, in a position close to a connection port to the intake passage, an expanding portion in which a passage cross-sectional area expands and which lowers a flow speed of the EGR gas so as to reduce an uneven flow, in the connection port, of the EGR gas flowing, into the intake passage.
Accordingly, the flow speed of the EGR gas in the EGR passage is lowered in a position close to the connection port to the intake passage, and the uneven flow of the EGR gas in the connection port is thereby reduced. That is, the extent of the uneven flow becomes low, and the EGR gas easily flows into the intake passage along a whole circumference of the connection port. As a result, even if a flow of fresh air flowing through the intake passage is slightly uneven, the EGR gas is likely to collide with the fresh air, that is, mixing of the fresh air and the EGR gas easily progresses, and non-uniformity of EGR amounts among the cylinders is reduced. Consequently, an advantage in securing combustion stability of the engine is obtained.
In one embodiment, the EGR passage includes a passage portion extending toward the connection port and in a direction intersecting with the intake passage and intersecting with a center line of the connection port and a direction-changing portion starting from the passage portion, changing a direction to the direction of the center line of the connection port, and reaching the connection port, and the expanding portion is provided in the direction-changing portion.
In a case where the direction-changing portion in which a flow direction of the EGR gas changes is present in a position close to the connection port to the intake passage in the EGR passage, unevenness of the flow of the EGR gas is likely to occur, but the expanding portion is provided in the direction-changing portion, and the unevenness is thereby reduced.
In one embodiment, the intake passage includes a supercharging passage in which a supercharger raising a pressure of the intake air introduced into the combustion chambers is arranged and a bypass passage connecting an upstream. side with a downstream side of the supercharger and leading the intake air to the combustion chambers while bypassing the supercharger, and the EGR passage is connected with the bypass passage of the intake passage.
When the fresh air is led from the bypass passage to the combustion chambers without going through the supercharger, mixing of the fresh air and the EGR gas by the supercharger is not expected. However, even in this case, as described above, the expanding portion is provided in the EGR passage, mixing of the fresh air and the EGR gas thereby easily progresses in the bypass passage, and non-uniformity of the EGR amounts among the cylinders is reduced.
In one embodiment, an EGR valve of a poppet type is included, the EGR valve being provided to the connection port and adjusting a returning amount of the EGR gas, and a valve shaft of the EGR valve passes through the bypass passage. Accordingly, in a portion around the valve shaft, collision between the fresh air flowing while bypassing the valve shaft and the EGR gas flowing along the valve shaft is caused, and mixing of the fresh air and the EGR gas thereby easily progresses.
In one embodiment, a bypass valve is included, the bypass valve being provided in the bypass passage and adjusting a supercharging pressure of the intake air by the supercharger, and the connection port opens on an upstream side of the bypass valve in the bypass passage. Accordingly, because the flows of the fresh air and the EGR gas are disturbed when those pass through the bypass valve, mixing of the fresh. air and the EGR gas easily progresses.
In one embodiment, the expanding portion includes a divergent portion in which a passage cross-sectional area gradually expands toward the connection port. Accordingly, when the EGR gas passes through the divergent portion, the EGR gas is easily spread in the whole expanding portion while its flow speed is gradually lowered toward the connection port. Thus, unevenness of the flow of the EGR gas can be reduced without excessively disturbing the flow of the EGR gas.
In the present invention, an EGR passage includes, in a position close to a connection port to an intake passage, an expanding portion in which a passage cross-sectional area expands and which lowers a flow speed of EGR gas so as to reduce an uneven flow of the EGR gas in the connection port. Thus, the EGR gas flowing into the intake passage is likely to collide with fresh air, and consequently, mixing of the fresh air and the EGR gas easily progresses. As a result, non-uniformity of EGR amounts among cylinders reduced, and an advantage in securing combustion stability of an engine is thus obtained.
A form for carrying out the present invention will hereinafter be described based on drawings. The description of a preferable embodiment is substantially only exemplification and is not intended to restrict the present invention, applications thereof, or uses thereof.
<General Configuration of Engine>
In a vehicle-installed engine system illustrated in
The engine 1 is an in-line four-cylinder compression ignition engine.
The intake passage 2 includes an intake manifold (not illustrated) for introducing intake air into the combustion chambers 10 of the cylinders in a branched manner. In the intake passage 2, in order from an upstream side to a downstream side, an air cleaner 21, a throttle valve 22 adjusting an introduction amount of fresh air into the combustion chambers 10, a supercharger raising a pressure of gas introduced into the combustion chambers 10, and an intercooler 24 cooling the gas introduced into the combustion chambers 10 by a supercharger 3 are disposed. Further, in the intake passage 2, a bypass passage 25 connecting an upstream side of the supercharger 23 with a downstream side of the intercooler 24 is provided on a downstream side of the throttle valve 22.
That is, the intake passage 2 includes a supercharging passage in which the supercharger 23 raising a pressure of the intake air introduced into the combustion chambers 10 is arranged and the bypass passage 25 leading the intake air to the combustion chambers 10 while bypassing the supercharger 23. In the bypass passage 25, a bypass valve 26 is provided which adjusts a flow amount of gas flowing through the bypass passage 25.
The supercharger 23 of this embodiment is a mechanical supercharger driven via a belt by a crankshaft of the engine 1. A supercharger 44 of a mechanical type may be of a Roots type, a Lysholm type, a vane type, or a centrifugal type, for example. Note that instead of a mechanical supercharger, an electric supercharger, or a turbocharger driven by exhaust energy may be employed.
The supercharger 23 is connected with the crankshaft of the engine 1 via an electromagnetic clutch 27. Transmission and disconnection of motive power from the engine 1 to the supercharger are performed by connection and disconnection of the electromagnetic clutch 27.
When the electromagnetic clutch 27 is set to a disconnected state (when the supercharger 23 is not acting), the bypass valve 26 is fully opened. Accordingly, the intake air is introduced into the combustion chambers 10 of the engine 1 by the bypass passage 25 without going through the supercharger 23. That is, the engine 1 is operated in a naturally aspirated (non-supercharging) state.
When the electromagnetic clutch 27 is set to a connected state (when the supercharger 23 is acting), a supercharging pressure is adjusted to a desired pressure by control of the bypass valve 26. That is, when the bypass valve 26 is opened, a portion of the intake air passing through the supercharger 23 goes through the bypass passage 25 and reversely flows to an upstream side of the supercharger 23. Because a reverse flow amount of the intake air changes in accordance with the opening of the bypass valve 26, the supercharging pressure of the intake air introduced into the combustion chambers 10 can be controlled.
The exhaust passage 3 includes an exhaust manifold 31 for gathering and discharging exhaust gas of the cylinders. In the exhaust passage 3 on a downstream side of the exhaust manifold 31, two catalytic converters purifying the exhaust gas are provided. The catalytic converter on an upstream side has a three-way catalyst 32 and a GPF (gasoline particulate filter) 33 and is disposed in an engine room of a vehicle. The catalytic converter on a downstream side has a three-way catalyst 34 and is disposed on the outside of the engine room. An exhaust shutter valve 35 is provided to each branch pipe of the exhaust manifold 31.
The intake passage 2 and the exhaust passage 3 are connected together by an EGR passage 6 returning a portion of the exhaust gas as EGR gas to the intake passage 2. An upstream end of the EGR passage 6 is connected with a portion in the exhaust passage 3 between the upstream catalytic converter and the downstream catalytic converter. A downstream end of the EGR passage 6 is connected with an intermediate portion of the bypass passage 25 so as to supply the EGR gas to a portion in the intake passage 2 on a downstream side of the throttle valve 22 and on an upstream side of the supercharger 23. The EGR gas enters an upstream side of the supercharger 23 in the intake passage 2 without going through the bypass valve 26 of the bypass passage 25. In the EGR passage 6, an EGR cooler 61 cooling the EGR gas and an EGR valve 62 adjusting a returning amount of the EGR gas are disposed.
Note that although
The fuel tank 4 is connected with the fuel injection valves 11 by a fuel supply passage 41. An upstream end of the fuel supply passage 41 is connected with a fuel strainer 40 in the fuel tank 4. In the fuel supply passage 41, a fuel pump 42 and a common rail 43 are provided. The fuel pump 42 pumps fuel into the common rail 43. The common rail 43 stores the fuel pumped from the fuel pump 42 at a high fuel pressure. When the fuel injection valve 11 is opened, the fuel stored in the common rail 43 is injected from an injection hole of the fuel injection valve 11 into the combustion chamber 10.
The evaporated fuel treatment device 5 includes canisters 51 causing the evaporated fuel produced in the fuel tank 4 to be adsorbed onto activated carbon. The fuel tank 4 and the canisters are connected together by a tank-side passage 52, and the canisters 51 and the intake passage 2 are connected together by a purge passage 53. An outside air introduction passage 54 having an atmospheric opening is connected with the canisters 51. A purge valve 55 opening and closing the purge passage 53 is provided to the purge passage 53. The purge valve 55 opens when a predetermined purge condition is satisfied, for example, in a state where an air-fuel ratio of the engine 1 can properly be controlled by control of a fuel injection amount by the fuel injection valves 11.
When a negative pressure is generated on a downstream side of the throttle valve 22 in the intake passage 2 in a state where the purge valve 55 is open, the evaporated fuel collected in the canisters 51 is purged. That is, together with air introduced from the outside air introduction passage 54 into the canisters 51, the evaporated fuel is purged from the purge passage 53 to a downstream side of the throttle valve 22 in an intake passage 21. The purged evaporated fuel is supplied to the combustion chambers of the engine 1 through the supercharger 23 or the bypass passage 25 and is combusted together with the fuel supplied from the fuel injection valves 11.
The engine system includes a blowby gas returning device. The blowby gas returning device includes a blowby passage 57 and an air introduction passage 58. One end of the blowby passage 57 is connected with a crankcase 1a of the engine 1, and the other end is connected with a portion of the intake passage 2 on a downstream side of the throttle valve 22 and on an upstream side of the supercharger 23. A PCV (positive crankcase ventilation) valve 59 is provided to the blowby passage 57.
The PCV valve 59 allows only gas in a direction from the crankcase 1a side to the intake passage 2 side to pass through. In a negative pressure state where the pressure on the downstream side of the throttle valve 22 in the intake passage 2 is lower than the pressure of the crankcase 1a, the opening of the PCV valve 59 changes in accordance with the extent of the negative pressure. That is, a blowby gas flow amount from the crankcase 1a to the intake passage 2 is adjusted to an appropriate amount in accordance with the negative pressure.
One end of the air introduction passage 58 is connected with the crankcase 1a via a cylinder head 1b of the engine 1, and the other end is connected with a portion of the intake passage 2 between the air cleaner 21 and the throttle valve 22. In the air introduction passage 58, a check valve 60 is provided which allows only air in a direction from the intake passage 2 side to the crankcase 1a side to pass through.
When blowby gas is released from the crankcase 1a to the intake passage 2 through the blowby passage 57, air filtered by the air cleaner 21 is introduced from the air introduction passage 58 into the crankcase 1a. Accordingly, the crankcase 1a is ventilated.
In the intake passage 2, an air flow sensor 63 detecting an intake air amount, a pressure sensor 64 detecting an intake pressure on a downstream side of the throttle valve 22 (an upstream side of the supercharger 23), a temperature sensor 65 detecting the temperature of the intake air ejected from the supercharger 23, and a pressure sensor 66 detecting the intake pressure on a downstream side of the intercooler 24 are provided, the sensors being for controlling the engine 1. In the exhaust passage 3, a linear O2 sensor 67 detecting an oxygen concentration in the exhaust gas on an upstream side of the three-way catalyst 32 and a lambda O2 sensor 68 detecting the oxygen concentration in the exhaust gas on a downstream side of the three-way catalyst 32 are provided.
<Structures of Engine System Configuration Elements>
As illustrated in
An upstream end of an ejection duct 76 for leading pressurized intake air to a surge tank (reference sign 75 in
As illustrated in
On a downstream side of the connection port 79 of the bypass passage 25, the upstream intake pipe 71 forms a passage expanding portion 2b in which a passage cross-sectional area expands toward the supercharger 3, and an expanding end thereof is connected with the supercharger 3.
The bypass pipe 78 has a folded portion 78a that is continuous with the above-described oblique rising portion and is folded, in a curved manner, toward a downstream side of the upstream intake pipe 71. The bypass pipe 78 is continuous with the folded portion 78a and extends toward a central side of the surge tank 75 in the cylinder array direction above the supercharger 23. An EGR pipe (not illustrated in
As illustrated in
As illustrated in
As illustrated in
As illustrated in
An expanding portion 95 in which a passage cross-sectional area expands compared to the passage portion 92 (a passage portion with a circular cross section on a downstream side of the flexible portion 84) is formed in the direction-changing portion 94. The expanding portion 95 includes a divergent portion 96 in which the passage cross-sectional area gradually expands from a downstream end of the passage portion 92 toward the connection port 69. The passage cross-sectional area of the expanding portion 95 is larger than the passage cross-sectional area of the connection port 69. The direction-changing portion 94 includes a portion in which the passage cross-sectional area shrinks and which is continuous with the expanding portion 95 and reaches the connection port 69, and a valve seat 97 of the EGR valve 62 opening and closing the connection port 69 is formed in the shrinking portion.
The EGR valve 62 of a poppet type, a valve shaft 98 thereof passes through the bypass passage 25 and extends in the direction of the center line 8) of the connection port 69. That is, the valve shaft 98 crosses an inside of the bypass passage 25 in the direction of the center line D of the connection port 69. The valve shaft 98 moves forward and backward by being driven by a solenoid-type EGR valve drive part 85 illustrated in
Note that in
<Mixing of EGR Gas and Fresh Air>
In the above embodiment, in a case where the supercharger 23 is not acting, the case being illustrated in
As illustrated in
As described above, when the flow direction of the EGR gas changes in the direction-changing portion 94, in related art, in accordance with an operation state of the engine, that is, in accordance with the flow speed of the EGR gas, unevenness occurs to a flow of the EGR gas in the direction-changing portion 94. For example, as the ow speed becomes higher, the EGR gas is more likely to flow unevenly along an upper half circumferential side of the direction-changing portion 94 and to flow from an upper side of the EGR valve 62 into the bypass passage 25 through the connection port 69. In this case, because the EGR gas moves obliquely downward from the upper side of the EGR valve 62 toward the connection port 69 and as a result flows into a lower half circumferential side of the bypass passage 25, as illustrated in
On the other hand, in the above embodiment, because the expanding portion 95 of the passage cross-sectional area is formed in the direction-changing portion 94, the flow speed. of the EGR gas flowing through the passage portion 92 is lowered in the expanding, portion 95. This lowering of the flow speed reduces unevenness of the EGR gas in the direction-changing portion 94, and the EGR gas flows from the portion around the EGR valve 62 into the bypass passage 25 while comparatively evenly going through the connection port 69. As a result, in the bypass passage 25, the EGR gas is likely to contact with the flow of the fresh air from a lateral side, and the fresh air and the EGR gas are thus easily mixed together.
Furthermore, in the above embodiment, because an upstream side of the expanding portion 95 is formed as the divergent portion 96, when the EGR gas passes through the divergent portion 96, the EGR gas is easily spread in the whole expanding portion while its flow speed is gradually lowered. Thus, this is advantageous to reduction of unevenness of the flow of the EGR gas.
Further, in the above embodiment, because the valve shaft 98 of the EGR valve 62 crosses the bypass passage 25, the fresh air moving while bypassing the valve shaft 98 collides with the EGR gas flowing along the valve shaft 98, and the fresh air and the EGR gas are easily mixed together. In addition, because when the fresh air and the EGR gas pass through the bypass valve 26, the flows of those are disturbed by the bypass valve 26, mixing easily progresses.
As described above, unevenness of the flow of the EGR gas passing through the connection port 69 is reduced, and mixing of the fresh air and the EGR gas in the bypass passage 25 easily progresses. As a result, non-uniformity of EGR amounts among cylinders is reduced, and an advantage in securing combustion stability of the engine is consequently obtained.
Note that the EGR valve 62 of the above embodiment is of a poppet type; however, a butterfly type EGR valve can also reduce unevenness of the flow of the EGR gas passing through the connection port 69 by providing an expanding portion as described above in the vicinity of the connection port on a downstream side of the EGR valve.
1 engine
2 intake passage
3 exhaust passage
6 EGR passage
10 combustion chamber
23 supercharger
25 bypass passage
26 bypass valve
62 EGR valve
69 connection port
92 passage portion
94 direction-changing portion
95 expanding portion
96 divergent portion
98 valve shaft
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-138348 | Jul 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/025515 | 6/27/2019 | WO | 00 |
