Exhaust pipe of an internal combustion engine

Abstract

To provide an exhaust pipe of an internal combustion engine capable of suppressing intrusion of an exhaust gas to the neighborhood of an addition valve with a simple structure.SOLUTION: An exhaust pipe 1 is provided with a fuel addition valve 4 and an addition valve holding portion 2. An inner peripheral face 2a of the addition valve holding portion 2 configures an injection passage 2b in which spray 4b injected into the exhaust pipe 1 from the fuel addition valve 4 passes. On a position near the fuel addition valve 4 in the injection passage 2b, a swirl flow folding-back member 3 for changing inflow swirl flow advancing along the inner peripheral face 2a of the addition valve holding portion 2 configuring the injection passage 2b, to outflow swirl flow separating from the addition valve while swirling, is disposed. The swirl flow holding-back member 3 configures a truncated-cone side face portion 3a at an outer peripheral face and a cavity portion 3b at an inner peripheral face, and the truncated cone side face portion 3a has a diameter D1 at a side near the fuel addition valve 4, substantially same as an inner diameter D2 of the injection passage 2b and is inclined so that its diameter is reduced to separate from the inner peripheral face 2a as going away from the fuel addition valve 4.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an exhaust pipe of an internal combustion engine that guides exhaust gas discharged from the internal combustion engine to an exhaust gas purification device.

Background Art

[0002] Conventionally, in the exhaust system of a diesel engine, a DPF regeneration process has been carried out. For DPF regeneration, that is, incineration of PM deposited on the DPF, it is necessary to raise the temperature of the exhaust gas flowing into the DPF. As one of the exhaust gas temperature raising techniques, fuel is directly injected into the exhaust pipe from a fuel addition valve, and an oxidation reaction occurs in a DOC arranged downstream of the fuel addition valve and upstream of the DPF to raise the temperature of the exhaust gas.

[0003] By the way, exhaust gas contains soot, and when the soot mixes with the fuel injected from the fuel addition valve, it deposits and adheres to the injection port of the fuel addition valve or the inner wall of the exhaust pipe. In particular, when deposits adhere to the injection port, problems such as nozzle clogging where an appropriate amount of fuel is not injected, or the spray shape not being appropriate occur. As a result, the temperature of the exhaust gas may not be raised, and the DPF regeneration process may not function.

[0004] For example, in Patent Document 1, a cylindrical side wall that forms an injection passage through which the fuel injected from the fuel addition valve passes and is arranged between the exhaust pipe and the fuel addition valve so that the exhaust gas does not reach and hit the fuel addition valve is usually formed in a simple cylindrical shape, but is disclosed as being bulged in the radial direction to form a curved shape.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, since the side wall described in Patent Document 1 has a complicated shape, it is difficult to design and manufacture, and the productivity is not good. At present, while maintaining a simple shape (for example, a cylindrical shape) often used in the injection passage, it is required to have a simpler structure so that the exhaust gas does not hit the fuel addition valve.

[0007] The present invention was devised in view of such points, and an object thereof is to provide an exhaust pipe for an internal combustion engine that can suppress the intrusion of exhaust gas into the vicinity of the addition valve with a simpler structure.

Means for Solving the Problems

[0008] In order to solve the above problems, an exhaust pipe for an internal combustion engine according to the present disclosure is an exhaust pipe of an internal combustion engine that guides exhaust gas discharged from the internal combustion engine to an exhaust gas purification device. In the exhaust pipe, an addition valve that injects a reaction liquid to be reacted in the exhaust gas purification device into the exhaust pipe, and a cylindrical addition valve holding portion that holds the addition valve at an end are provided. The inner peripheral surface of the addition valve holding portion forms an injection passage through which the spray of the reaction liquid injected from the addition valve into the exhaust pipe passes. At a position close to the addition valve in the injection passage, a swirling flow turning member is provided that forms an inflow swirling flow that approaches the addition valve while swirling along the inner peripheral surface of the addition valve holding portion forming the injection passage into an outflow swirling flow that moves away from the addition valve while swirling. The swirling flow turning member is cylindrical, and an outer peripheral surface forms a frustum-shaped side surface portion that is a side surface of a frustum of a cone, and an inner peripheral surface forms a cavity portion through which the spray injected from the addition valve passes. The frustum-shaped side surface portion has an outer diameter on the side close to the addition valve that is substantially the same as the inner diameter of the injection passage, and is inclined so that the outer diameter becomes smaller as it moves away from the addition valve and is separated from the inner peripheral surface of the addition valve holding portion forming the injection passage.

[0009] According to this, even if the inflowing swirling flow approaches the addition valve along the inner peripheral surface of the addition valve holding portion forming the injection passage, the conical side surface portion of the swirling flow turning member serves as a wall to prevent the inflowing swirling flow from entering the addition valve side. Moreover, due to the inclination of the conical side surface portion, the inflowing swirling flow is blocked and at the same time turned back, and along the inclined conical side surface portion, it separates from the addition valve as an outflowing swirling flow without interfering with the inflowing swirling flow. In this way, by installing the swirling flow turning member with respect to the addition valve holding portion, it is possible to suppress the intrusion of exhaust gas into the vicinity of the addition valve with a simpler structure.

[0010] In the exhaust pipe of the internal combustion engine, a dispersion plate is provided in the exhaust pipe so as to face the addition valve with the injection passage therebetween, and the spray injected into the exhaust pipe from the injection port of the addition valve may collide with the dispersion plate and be dispersed.

[0011] According to this, the reaction liquid is atomized when the spray of the reaction liquid collides with the dispersion plate. On the other hand, the installation of the dispersion plate itself can also be a factor in the generation of the inflowing swirling flow. However, regardless of the installation of the dispersion plate, the swirling flow turning member still functions to turn the inflowing swirling flow into an outflowing swirling flow. Therefore, as an exhaust pipe that guides the exhaust gas discharged from the internal combustion engine to the exhaust gas purification device, it is more suitable compared to an exhaust pipe without a dispersion plate.

[0012] In the exhaust pipe of the internal combustion engine, a dispersion space surrounded by the inner wall of the exhaust pipe and the dispersion plate and communicating with the injection passage is formed in the exhaust pipe at the location where the dispersion plate is provided, and the inlet of the exhaust gas in the dispersion space may be arranged upstream of the injection passage in the exhaust gas flow path in the exhaust pipe.

[0013] According to this, for example, by changing the shape of the inlet of the exhaust gas in the dispersion space, it is possible to introduce exhaust gas that allows the atomized reaction liquid to diffuse more. On the other hand, the change in the shape of the inlet itself can also be a factor in the generation of the inflow swirling flow. However, regardless of the shape of the inlet, the swirling flow turning member still functions to turn the inflow swirling flow into an outflow swirling flow. Therefore, it is more suitable as an exhaust pipe that guides the exhaust gas discharged from the internal combustion engine to the exhaust gas purification device.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0015] ●[Structure of the exhaust pipe according to the embodiment (FIGS. 1 to 3)] Embodiments of the exhaust pipe of the internal combustion engine according to the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a plan view of the exhaust pipe of the internal combustion engine according to the embodiment. FIG. 2 is a sectional view taken along line II-II of FIG. 1 as viewed in the arrow direction. FIG. 3 is a sectional view taken along line III-III of FIG. 1 as viewed in the arrow direction. In the figures where the X-axis, Y-axis, and Z-axis are shown, the X-axis, Y-axis, and Z-axis are orthogonal to each other.

[0016] As shown in FIG. 1, the exhaust pipe 1 forms a part of the exhaust passage that guides the exhaust gas discharged from the internal combustion engine to the exhaust gas purification device. Downstream of the exhaust pipe 1, for example, an oxidation catalyst and a DPF are arranged as the exhaust gas purification device. The exhaust gas flowing out from the exhaust pipe 1 flows and is purified in the order of the oxidation catalyst and the DPF, and then flows further downstream. The oxidation catalyst oxidizes and purifies carbon monoxide (CO), hydrocarbons (HC), etc. contained in the exhaust gas. The DPF collects particulate matter (PM) contained in the exhaust gas.

[0017] The exhaust pipe 1 has a curved portion. The exhaust pipe 1 has an additive valve holding portion 2 at the curved portion. The additive valve holding portion 2 extends in the Z-axis direction from the exhaust pipe 1 and is formed in a cylindrical shape. The additive valve holding portion 2 has a holding mechanism for holding the fuel injection valve 4 at the tip portion in the Z-axis direction.

[0018] As shown in FIG. 2, the fuel injection valve 4 is attached to the additive valve holding portion 2. The attachment side of the fuel injection valve 4 has a cylindrical shape corresponding to the additive valve holding portion 2, and has an injection port 4a on its central axis. The fuel injection valve 4 injects fuel to be oxidized by the oxidation catalyst into the exhaust pipe 1 from the injection port 4a at the timing when DPF regeneration is required. Note that the fuel is oxidized by the oxygen remaining in the exhaust gas by the oxidation catalyst. Then, the temperature of the exhaust gas rises due to the heat generated by the oxidation, and the exhaust gas becomes hot. When the floor temperature of the DPF rises due to this hot exhaust gas and the floor temperature becomes equal to or higher than a predetermined temperature (for example, 590 [°C] or higher), the particulate matter (PM) deposited in the DPF burns and is incinerated, and the collection function of the DPF is restored (regenerated).

[0019] Inside the additive valve holding portion 2, an injection passage 2b, which is a cylindrical cavity, is formed. That is, the inner peripheral surface 2a of the additive valve holding portion 2 forms the injection passage 2b. When the fuel injection valve 4 is attached to the additive valve holding portion 2, the central axes of the fuel injection valve 4 and the injection passage 2b are set to coincide with each other. Therefore, the spray 4b injected from the injection port 4a of the fuel injection valve 4 passes through the center of the injection passage 2b and enters the exhaust pipe 1.

[0020] The exhaust pipe 1 has a dispersion plate 5. The dispersion plate 5 is provided at a portion of the exhaust pipe 1 facing the fuel addition valve 4 with the injection passage 2b interposed therebetween. The dispersion plate 5 has a collision surface 5a against which the spray 4b collides, and is formed so as to divide the exhaust flow path in the curved portion of the exhaust pipe 1 where the addition valve holding portion 2 is provided into a dispersion space 1a and a main flow path 1b. The dispersion space 1a is surrounded by the inner wall of the exhaust pipe 1 and the collision surface 5a of the dispersion plate 5 and communicates with the injection passage 2b. The inlet 5b through which the exhaust gas flows into the dispersion space 1a opens on the upstream side in the exhaust gas flow path of the exhaust pipe 1 with respect to the injection passage 2b (the position where the addition valve holding portion 2 is provided). The outlet 5c through which the exhaust gas flows out of the dispersion space 1a opens on the downstream side in the exhaust gas flow path of the exhaust pipe 1 with respect to the injection passage 2b (the position where the addition valve holding portion 2 is provided).

[0021] The collision surface 5a of the dispersion plate 5 collides with the spray 4b that has entered the exhaust pipe 1 through the injection passage 2b. The spray 4b that has collided with the collision surface 5a is atomized and diffused by the exhaust gas flowing into the dispersion space 1a from the inlet 5b, and flows out from the outlet 5c.

[0022] Part of the exhaust gas flowing in from the inlet 5b does not flow out from the outlet 5c and instead heads towards the injection passage 2b of the additive valve holding portion 2. The exhaust gas heading towards the injection passage 2b travels in the Z-axis direction while swirling along the inner peripheral surface 2a of the additive valve holding portion 2 that forms the injection passage 2b. In order to suppress the generation of such a swirling flow, for example, the shape of the upstream side of the dispersion plate 5 can be changed to narrow the inlet 5b, or a substantially triangular prism-shaped flow direction adjusting member 6 for adjusting the flow direction of the exhaust gas can be provided on the inflow side of the exhaust gas in the dispersion space 1a. Alternatively, adjustment of the inner diameter D2 of the injection passage 2b is also conceivable. However, when multiple factors such as the curvature of the exhaust pipe 1, the shape of the dispersion plate 5, and the installation situation overlap, exhaust gas may inevitably enter the injection passage 2b and a swirling flow may occur. Ahead in the advancing direction (Z-axis direction) of the swirling flow, there is the fuel injection valve 4. The exhaust gas (swirling flow) contains soot, and when the soot mixes with the fuel injected from the fuel injection valve 4, it deposits and adheres to the injection port 4a of the fuel injection valve 4, which is not good.

[0023] Therefore, the additive valve holding portion 2 has a swirling flow turning member 3 at a position close to the fuel injection valve 4 in the injection passage 2b. The swirling flow turning member 3 is cylindrical, with its outer peripheral surface forming a frustum of a cone side surface portion 3a and its inner peripheral surface forming a cavity portion 3b. That is, the swirling flow turning member 3 has a frustum of a cone side surface portion 3a that is the side surface of a frustum of a cone shape and a cavity portion 3b through which the spray 4b injected from the fuel injection valve 4 passes.

[0024] The frustum of a cone side surface portion 3a formed by the outer peripheral surface of the swirling flow turning member 3 has a diameter D1 on the side close to the fuel injection valve 4 that is approximately the same as the inner diameter D2 of the injection passage 2b and continues with the inner peripheral surface 2a of the additive valve holding portion 2 that forms the injection passage 2b. The frustum of a cone side surface portion 3a is inclined such that the diameter decreases as it moves away from the fuel injection valve 4 and it moves away from the inner peripheral surface 2a.

[0025] The swirling flow turning member 3 turns back the inflow swirling flow that approaches the fuel injection valve 4 while swirling along the inner peripheral surface 2a of the additive valve holding portion 2 that forms the injection passage 2b, and forms an outflow swirling flow that moves away from the fuel injection valve 4 while swirling in the same direction. ●[Function and Effect of the Swirl Flow Reversing Member (Figs. 4 to 6)]

[0026] In FIGS. 4 and 5, the structures of the exhaust pipe 1 and the additive valve holding portion 2 are omitted, and only the space surrounded by the inner peripheral surface 2a of the additive valve holding portion 2 forming the injection passage 2b and the conical frustum side surface portion 3a formed by the outer peripheral surface of the swirl flow reversing member 3 is drawn, and attention is paid to the swirl flow flowing in the space. As shown in FIG. 4, the inflow swirl flow 7 advances in the Z-axis direction while swirling along the inner peripheral surface 2a of the additive valve holding portion 2 forming the injection passage 2b. Although there is a fuel additive valve 4 at the tip in the Z-axis direction (see FIG. 2), the inner peripheral surface 2a ends at the conical frustum side surface portion 3a. Therefore, the inflow swirl flow 7 has to turn back and go in the opposite direction of the Z-axis direction.

[0027] As shown in FIG. 5, the inflow swirl flow 7 is turned back by the conical frustum side surface portion 3a to become an outflow swirl flow 8, and then advances in the opposite direction of the Z-axis direction while swirling in the same direction along the conical frustum side surface portion 3a. The conical frustum side surface portion 3a is inclined so as to move away from the inner peripheral surface 2a of the additive valve holding portion 2 forming the injection passage 2b. Moreover, while a strong inflow swirl flow 7 is generated on the inner peripheral surface 2a (outer side), there is a space inside the injection passage 2b that is not affected by either the inflow swirl flow 7 or the flow of the spray 4b. Therefore, the outflow swirl flow 8 goes in the opposite direction of the Z-axis direction while swirling inside the inflow swirl flow 7 without interfering with the inflow swirl flow 7.

[0028] In FIGS. 4 and 5, for the sake of convenience, the inflow swirl flow 7 and the outflow swirl flow 8 are separately drawn and explained. However, as shown in FIG. 6, the inflow swirl flow 7 and the outflow swirl flow 8 actually flow continuously.

[0029] Thus, even if the inflow swirl flow 7 approaches the fuel additive valve 4 along the inner peripheral surface 2a of the additive valve holding portion 2 forming the injection passage 2b, the conical frustum side surface portion 3a formed by the outer peripheral surface of the swirl flow reversing member 3 serves as a wall to prevent the inflow swirl flow 7 from entering the fuel additive valve 4 side. Therefore, the exhaust gas does not reach the fuel additive valve 4 and hit it, and the soot in the exhaust gas does not mix with the fuel. As a result, it does not adhere as a deposit to the injection port 4a of the fuel additive valve 4 or the inner wall of the exhaust pipe 1.

[0030] The exhaust pipe of the internal combustion engine of the present invention is not limited to the appearance, configuration, structure, etc. described in this embodiment, and various changes, additions, and deletions are possible without changing the gist of the present invention. For example, in this embodiment, the dispersion plate 5 is provided in the exhaust pipe 1, but an exhaust pipe without the dispersion plate 5 may also be used. Further, even if the dispersion plate 5 is provided, as long as it has a collision surface 5a for colliding the spray 4b, the shape of the dispersion space 1a and the position of the inlet 5b are not limited to those described in this embodiment, and any shape may be used.

[0031] In this embodiment, the fuel addition valve 4 is held by the addition valve holding portion 2, and fuel is injected toward the oxidation catalyst installed on the downstream side. However, the object for suppressing the intrusion of exhaust gas is not limited to the fuel addition valve 4, and for example, an aqueous urea addition valve may be used. The aqueous urea addition valve is an addition valve that injects aqueous urea (reaction liquid) into the exhaust gas toward a selective reduction catalyst (exhaust gas purification device) installed on the downstream side.

[0032] In this embodiment, an example in which the inside of the conical frustum side surface portion 3a of the swirling flow turning member 3 is thick and the cavity portion 3b is cylindrical has been described. However, the cavity portion 3b formed by the inner peripheral surface of the swirling flow turning member 3 only needs to allow the spray 4b to pass through. For example, as shown in FIG. 7, the swirling flow turning member 23 may have a thin inner side of the conical frustum side surface portion 3a and a conical frustum-shaped cavity portion 23b.

Description of Reference Numerals

[0033] 1 Exhaust pipe 1a Dispersion space 1b Main flow path 2 Addition valve holding portion 2a Inner peripheral surface 2b Injection passage 3, 23 Swirling flow turning member 3a Conical frustum side surface portion 3b, 23b Cavity portion 4 Fuel addition valve 4a Injection port 4b Spray 5 Dispersion plate 5a Collision surface 5b Inlet 5c Outlet 6 Direction adjustment member 7 Inflow swirling flow 8 Outflow swirling flow

Claims

1. An exhaust pipe of an internal combustion engine that guides exhaust gas discharged from the internal combustion engine to an exhaust gas purification device, wherein the exhaust pipe is provided with an addition valve that injects fuel, which is a reaction liquid to be subjected to an oxidation reaction by an oxidation catalyst included in the exhaust gas purification device, into the exhaust pipe, and a cylindrical addition valve holding portion that holds the addition valve at an end portion thereof, an inner peripheral surface of the addition valve holding portion forms an injection passage through which the spray of the reaction liquid injected from the addition valve into the exhaust pipe passes, at a position in the injection passage close to the addition valve, a swirling flow turning member is provided that forms an inflow swirling flow that approaches the addition valve while swirling along the inner peripheral surface of the addition valve holding portion forming the injection passage, and forms an outflow swirling flow that moves away from the addition valve while swirling, the swirling flow turning member is cylindrical, an outer peripheral surface forms a frustoconical side surface portion having a frustoconical shape, and an inner peripheral surface forms a cavity portion through which the spray injected from the addition valve passes, the frustoconical side surface portion has an outer diameter on the side close to the addition valve that is substantially the same as the inner diameter of the injection passage, and is inclined so that the outer diameter decreases as it moves away from the addition valve and moves away from the inner peripheral surface of the addition valve holding portion forming the injection passage, An exhaust pipe of an internal combustion engine.

2. An exhaust pipe of an internal combustion engine according to Claim 1, wherein a dispersion plate is provided in the exhaust pipe so as to face the addition valve with the injection passage interposed therebetween, the spray injected into the exhaust pipe from the injection port of the addition valve collides with the dispersion plate and is dispersed, An exhaust pipe of an internal combustion engine.

3. An exhaust pipe of an internal combustion engine according to Claim 2, wherein a dispersion space surrounded by the inner wall of the exhaust pipe and the dispersion plate and communicating with the injection passage is formed in the exhaust pipe at the location where the dispersion plate is provided, an inlet for exhaust gas in the dispersion space is arranged on the upstream side in the exhaust gas flow path rather than the injection passage in the exhaust pipe, An exhaust pipe of an internal combustion engine.

Images