JP7374571B2 - internal combustion engine - Google Patents

Description

The present invention relates to an internal combustion engine equipped with an exhaust turbocharger.

The energy contained in the exhaust gas discharged from the cylinders of the internal combustion engine is used to rotate the exhaust turbine (turbine wheel), which transmits the rotation to the compressor impeller (compressor wheel) to pressurize and compress the intake air (supercharging). ) and sends the exhaust gas to the cylinders.

There is also an external EGR device that connects the exhaust passage and intake passage of an internal combustion engine through an EGR (Exhaust Gas Recirculation) passage, and recirculates part of the exhaust gas to the intake passage via the EGR passage to mix with the intake air. Widely adopted. With EGR, it is possible to lower the combustion temperature in the cylinder and reduce the amount of harmful substances NO _x emitted, while also reducing pumping loss (see the following patent documents).

Japanese Patent Application Publication No. 2013-155686

Dramatically increase the EGR rate, which is the proportion of EGR gas in the intake air (e.g., over 30%), or make the air-fuel ratio leaner than the stoichiometric air-fuel ratio (e.g., air-fuel ratio λ≧2) to reduce fuel consumption. When attempting to reduce this, the temperature of the gas discharged from the cylinder decreases significantly. The temperature of the exhaust gas may be below 350°C.

If the amount of thermal energy contained in the exhaust gas supplied to the turbine of the exhaust turbo supercharger is small, the efficiency of the supercharger will be reduced and the work of supercharging intake air will be reduced. Furthermore, the exhaust gas, which has become even cooler due to the thermal energy carried away during the process of passing through the turbine, flows into the three-way catalyst, causing a temperature drop in the catalyst, which removes the harmful substances HC, CO, and NO _x contained in the exhaust gas. There also arises a concern that oxidation/reduction reactions may be inhibited.

The purpose of the present invention is to enable an exhaust turbo supercharger to sufficiently perform the task of supercharging intake air, and to maintain high efficiency in purifying harmful substances in exhaust gas by a three-way catalyst.

The present invention is an internal combustion engine equipped with an exhaust turbo supercharger, and includes an exhaust purifying catalyst and a supercharger disposed downstream of the catalyst on the exhaust passage through which exhaust gas discharged from the cylinders flows. A turbine and a return flow path connected downstream of the turbine and guiding the exhaust gas that has passed through the turbine to a location close to the catalyst are provided, and the return flow path passes through the inside of the catalyst or An internal combustion engine was constructed in which the annular return flow path was provided adjacent to or close to the outer periphery .

Preferably, the catalyst and the turbine are arranged adjacent to each other on a side surface of the internal combustion engine.

According to the present invention, the exhaust turbo supercharger attached to the internal combustion engine can sufficiently perform the task of supercharging intake air, and the efficiency of purifying harmful substances in the exhaust gas by the three-way catalyst can be maintained at a high level.

1 is a side view of an internal combustion engine according to an embodiment of the present invention. FIG. 3 is a perspective view showing the external appearance of an exhaust turbo supercharger and a catalyst case of the internal combustion engine of the same embodiment. FIG. 3 is a front view showing the external appearance of an exhaust turbo supercharger and a catalyst case of the internal combustion engine of the same embodiment. FIG. 3 is a sectional view taken along line AA of the catalyst case of the internal combustion engine of the same embodiment. FIG. 3 is a sectional view taken along line BB of the catalyst case of the internal combustion engine of the same embodiment.

An embodiment of the present invention will be described with reference to the drawings. The internal combustion engine 0 of this embodiment is a four-stroke reciprocating engine having multiple cylinders (for example, three cylinders). FIG. 1 shows an internal combustion engine 0 of this embodiment viewed from the side. The cylinders of the internal combustion engine 0 are arranged in parallel along the left-right direction in FIG. 1, and the crankshaft, which is the output shaft of the internal combustion engine 0, extends along the left-right direction in FIG.

Exhaust gas generated by burning fuel in each cylinder of the internal combustion engine 0 is exhausted to the outside of the internal combustion engine 0 through an exhaust port provided in the cylinder head. Exhaust ports communicating with each cylinder open toward the front in FIG. These exhaust ports are also arranged along the left and right direction in FIG.

An exhaust manifold, which is a collecting pipe, is connected to each exhaust port, and the exhaust gases discharged from each cylinder are combined at the exhaust manifold. The outlet of the exhaust manifold is connected to the inlet 12 of a catalyst case 11 containing a three-way catalyst for exhaust purification. That is, the exhaust gas that has passed through the exhaust manifold flows into the catalyst case 11 from the inlet 12. As a supplement, the reason why the exhaust manifold is not shown is because the exhaust manifold exists on the back side of the catalyst case 11 in FIG. 1 and is hidden by the catalyst case 11.

As shown in FIGS. 2 to 5, the catalyst case 11 is a cylindrical body extending parallel or substantially parallel to the direction in which the cylinders of the internal combustion engine 0 and their intake ports are lined up, in other words, the direction in which the crankshaft extends. be. The inlet 12 of the catalyst case 11 is located on one end side of the catalyst case 11, that is, on the right end side in FIGS. 1, 4, and 5. The inlet 12 of the catalyst case 11 protrudes in a direction perpendicular or substantially perpendicular to the extending direction of the catalyst case 11 and is connected to an outlet of the exhaust manifold.

The three-way catalyst for exhaust purification mounted in the catalyst case 11 is similar to known catalysts, and is made by supporting a noble metal such as platinum, palladium, or rhodium on a ceramic carrier 13 coated with alumina or the like. It is. The carrier 13 expands along a direction parallel or substantially parallel to the extending direction of the catalyst case 11. Numerous small holes are formed inside the exhaust gas in the same direction to allow exhaust gas to flow therethrough.

In this embodiment, a large-diameter axial hole is bored in the center of the carrier 13 of the catalyst 1, passing through the carrier 13 in a direction parallel or substantially parallel to the extending direction of the catalyst case 11. That is, the carrier 13 has a donut-like or Baumkuchen-like shape. A return flow path 3, which will be described later, is provided in this shaft hole.

As indicated by arrows in FIG. 4, exhaust gas that has flowed into the catalyst case 11 from the exhaust manifold flows through the carrier 13 of the catalyst 1. At this time, the oxidation/reduction reactions of harmful substances HC, CO, and NO _x contained in the exhaust gas are promoted, and the harmful substances are changed into harmless substances, that is, the exhaust gas is purified.

A turbine of an exhaust turbo supercharger 2 is connected to the other end of the catalyst case 11, the left end in FIGS. 1, 4, and 5. The exhaust gas that has passed through the catalyst 1 flows directly into this turbine.

The exhaust turbo supercharger 2 uses the energy of the exhaust gas to rotate a turbine, transmits the rotation to the impeller of the compressor, and uses the compressor to pressurize and compress the intake air flowing through the intake passage, that is, to supercharge it. This is well known in this field.

As indicated by the arrow in FIG. 5, the exhaust gas that has passed through the turbine of the exhaust turbo supercharger 2 flows into the return flow path 3 that is piped to penetrate inside the carrier 13 of the catalyst 1. Along this return flow path 3, it flows in the opposite direction to the direction when flowing through the catalyst 1. The carrier 13 of the catalyst 1 is in contact with or very close to the outer periphery of the piping of the return flow path 3 . Finally, the exhaust gas heads to the muffler from the exit of the return flow path 3 and is discharged to the outside.

In this embodiment, an internal combustion engine 0 equipped with an exhaust turbo supercharger 2 includes an exhaust gas purifying catalyst 1 disposed downstream of the catalyst 1 on an exhaust passage through which exhaust gas discharged from the cylinders flows. A turbine of the supercharger 2 is provided, and a return passage 3 is connected downstream of the turbine and guides the exhaust gas that has passed through the turbine to a location close to the catalyst 1.

By arranging the exhaust gas purifying catalyst 1 downstream of the exhaust manifold and upstream of the exhaust turbo supercharger 2, it is possible to prevent extremely low temperature gas from flowing into the catalyst 1. As a result, the temperature drop of the catalyst 1 can be suppressed, the activity of the catalyst 1 can be maintained, and the purification efficiency of harmful substances in the exhaust gas can be kept high. Even when the temperature of the catalyst 1 is low, such as during a cold start of the internal combustion engine 0, the temperature can be increased quickly.

In addition, a return flow path 3 through which the exhaust gas that has passed through the catalyst 1 and the turbine flows is provided in a location close to or adjacent to the catalyst 1. Even though the exhaust gas flows down from the turbine, its temperature is never as cold as the outside temperature (ordinary temperature), and it still has a high temperature above a certain level. By flowing this near the catalyst 1, the temperature of the catalyst 1 is maintained, and the amount of heat taken by the catalyst 1 from the exhaust gas that passes through the catalyst 1 and flows into the turbine is reduced, reducing the efficiency of the supercharger 2. This can increase the work of supercharging intake air.

In this embodiment, the catalyst 1 and the turbine are arranged adjacent to each other on the side surface of the internal combustion engine 0. By directly connecting the exhaust manifold immediately upstream of the catalyst case 11 and directly connecting the turbine immediately downstream of the catalyst case 11, it is possible to reduce the amount of thermal energy that the exhaust gas has before flowing into the turbine escapes, and the supercharger 2 can further enhance the work of supercharging. In addition, the exhaust passage can be made more compact and unnecessary members can be eliminated.

The catalyst case 11 and the return flow path 3 each extend parallel or substantially parallel to the direction in which the exhaust ports of each cylinder are lined up. The catalyst case 11 and the return flow path 3 are close to the exhaust manifold and the upper side of the cylinder head and/or cylinder block of the internal combustion engine 0. While the internal combustion engine 0 is operating, the exhaust manifold, cylinder head, and cylinder block are naturally at high temperatures, and by bringing the catalyst case 11 closer to them, the catalyst 1 will receive heat from them, making the heat retention effect of the catalyst 1 even more effective. It increases even more.

Overall, even if the EGR rate of the intake air is increased or lean burn is performed by making the air-fuel ratio leaner, the supercharger 2 can sufficiently perform the task of supercharging the intake air, and the catalyst 1 can eliminate harmful substances in the exhaust gas. It is also possible to maintain high purification efficiency.

Note that the present invention is not limited to the embodiments detailed above. For example, in the embodiment described above, the carrier 13 of the catalyst 1 has a cylindrical shape, and the return flow passage 3 passes through the carrier 13, but the inside and outside of the catalyst and the return flow passage may be reversed. That is, an annular return flow path may be provided adjacent to or close to the outer periphery of the catalyst. In any case, the gist of the present invention is to keep the catalyst warm with the residual heat of the exhaust gas flowing through the return flow path.

In addition, the specific configuration of each part can be variously modified without departing from the spirit of the present invention.

INDUSTRIAL APPLICATION This invention is applicable to the internal combustion engine mounted in a vehicle etc.

0...Internal combustion engine 1...Catalyst 2...Exhaust turbo supercharger 3...Return passage

Claims (2)

An internal combustion engine equipped with an exhaust turbocharger,
On the exhaust passage through which the exhaust gas discharged from the cylinders flows, there is an exhaust purification catalyst, a turbocharger turbine placed downstream of this catalyst, and a turbocharger turbine connected downstream of the turbine to direct the exhaust gas that has passed through the turbine close to the catalyst. A return flow path is provided that leads to the point where the
An internal combustion engine in which the return passage passes through the catalyst, or the annular return passage is provided adjacent to or close to the outer periphery of the catalyst. The internal combustion engine according to claim 1, wherein the catalyst and the turbine are arranged adjacent to each other on a side surface of the internal combustion engine.

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