JP7690917B2 - Exhaust pipe of an internal combustion engine - Google Patents

Description

The present invention relates to an exhaust pipe for an internal combustion engine that guides exhaust gas emitted from the internal combustion engine to an exhaust purification device.

Conventionally, DPF regeneration processing has been performed in the exhaust system of diesel engines. DPF regeneration, that is, incineration of PM accumulated in the DPF, requires that the exhaust gas flowing into the DPF be heated to a high temperature. One technique for raising the temperature of exhaust gas is known to involve injecting fuel directly into the exhaust pipe from a fuel addition valve, causing an oxidation reaction in a DOC located downstream of the fuel addition valve and upstream of the DPF, thereby raising the temperature of the exhaust gas.

However, exhaust gas contains soot, and when this soot mixes with the fuel injected from the fuel addition valve, it forms deposits on the fuel addition valve's nozzle and the inner walls of the exhaust pipe. In particular, when deposits form on the nozzle, the nozzle becomes clogged, preventing the appropriate amount of fuel from being injected, or causing problems such as an inappropriate spray shape. As a result, the exhaust gas does not heat up, and the DPF regeneration process may not function properly.

For example, Patent Document 1 discloses that the cylindrical side wall that is disposed between the exhaust pipe and the fuel addition valve to prevent exhaust gas from reaching and hitting the fuel addition valve and that forms the injection passage through which the fuel injected from the fuel addition valve passes is usually formed in a simple cylindrical shape, but is instead bulged radially to form a curved shape.

JP 2021-127749 A

However, the side wall described in Patent Document 1 has a complex shape, which makes it difficult to design and manufacture, and reduces productivity. Currently, there is a demand for a simpler structure that prevents exhaust gas from hitting the fuel addition valve while maintaining the simple shape (e.g., cylindrical shape) that is commonly used for injection passages.

The present invention was devised in light of these points, and aims to provide an exhaust pipe for an internal combustion engine that has a simpler structure and can suppress the intrusion of exhaust gas into the vicinity of the additive valve.

In order to solve the above problems, the exhaust pipe of 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 purification device, and the exhaust pipe is provided with an additive valve that injects a reaction liquid to be reacted in the exhaust purification device into the exhaust pipe, and a cylindrical additive valve holder that holds the additive valve at an end, and the inner circumferential surface of the additive valve holder forms an injection passage through which a spray of the reaction liquid injected from the additive valve into the exhaust pipe passes, and at a position in the injection passage close to the additive valve, a nozzle that does not rotate along the inner circumferential surface of the additive valve holder that forms the injection passage is provided. A swirling flow turning member is provided to turn the inflow swirling flow approaching the addition valve into an outflow swirling flow moving away from the addition valve while swirling, and the swirling flow turning member is cylindrical, with an outer peripheral surface forming a truncated cone side portion that is a side surface of a truncated cone shape, and an inner peripheral surface forming a cavity portion that passes the spray injected from the addition valve, and the outer diameter of the truncated cone side portion on the side closer to the addition valve is approximately the same as the inner diameter of the injection passage, and the outer diameter becomes smaller as it moves away from the addition valve, and is inclined so as to move away from the inner peripheral surface of the addition valve holding portion that forms the injection passage.

With this, even if the inflow swirling flow approaches the addition valve along the inner circumferential surface of the addition valve holding portion that forms the injection passage, the truncated cone side portion of the swirling flow turning member acts as a wall to prevent the inflow swirling flow from entering the addition valve side. Moreover, due to the inclination of the truncated cone side portion, the inflow swirling flow is blocked and simultaneously turned back, and moves away from the addition valve as an outflow swirling flow along the inclined truncated cone side portion without interfering with the inflow swirling flow. In this way, the inflow of exhaust gas near the addition valve can be suppressed with a simple structure, namely the installation of a swirling flow turning member on the addition valve holding portion.

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

In this way, the reaction liquid is atomized by the collision of the spray with the dispersion plate. On the other hand, the installation of the dispersion plate itself can be a factor in the generation of an inflow swirling flow. However, regardless of whether the dispersion plate is installed or not, the swirling flow turning member still functions to turn the inflow swirling flow as an outflow swirling flow. Therefore, compared to an exhaust pipe without a dispersion plate, this is more suitable as an exhaust pipe that leads exhaust gas discharged from an internal combustion engine to an exhaust purification device.

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

For example, by changing the shape of the exhaust gas inlet in the dispersion space, exhaust gas can be introduced so as to further disperse the atomized reaction liquid. On the other hand, changing the shape of the inlet itself can be a factor in the generation of an inflow swirling flow. However, regardless of the shape of the inlet, the swirling flow turning member still functions to turn the inflow swirling flow as an outflow swirling flow. Therefore, it is more suitable as an exhaust pipe that leads exhaust gas discharged from an internal combustion engine to an exhaust purification device.

FIG. 2 is a plan view of an exhaust pipe of the internal combustion engine according to the embodiment. 2 is a cross-sectional view taken along line II-II of FIG. 1. 3 is a cross-sectional view taken along line III-III in FIG. 1. FIG. 4 is a diagram showing an inflow swirling flow swirling along the inner circumferential surface of an addition valve holding portion that forms an injection passage. 11 is a diagram showing an outflow swirling flow turned back by a swirling flow turning member; FIG. FIG. 2 is a diagram showing successive inflow and outflow swirling flows. 13A and 13B are diagrams illustrating a swirl flow turning member of an exhaust pipe according to another embodiment.

[Structure of the exhaust pipe according to the embodiment (FIGS. 1 to 3)]
An embodiment of an exhaust pipe for an internal combustion engine according to the present invention will be described with reference to Figures 1 to 3. Figure 1 is a plan view of an exhaust pipe for an internal combustion engine according to the embodiment. Figure 2 is a cross-sectional view taken along line II-II in Figure 1. Figure 3 is a cross-sectional view taken along line III-III in Figure 1. In addition, in the figures in which the X-axis, Y-axis, and Z-axis are depicted, the X-axis, Y-axis, and Z-axis are mutually orthogonal.

As shown in FIG. 1, the exhaust pipe 1 forms part of an exhaust passage that leads exhaust gas emitted from an internal combustion engine to an exhaust purification device. An oxidation catalyst or DPF, for example, is arranged downstream of the exhaust pipe 1 as an exhaust purification device, and exhaust gas flowing out from the exhaust pipe 1 flows through the oxidation catalyst and then the DPF, where it is purified, before flowing further downstream. The oxidation catalyst oxidizes and purifies carbon monoxide (CO) and hydrocarbons (HC) contained in the exhaust gas. The DPF collects particulate matter (PM) contained in the exhaust gas.

The exhaust pipe 1 has a curved portion. The exhaust pipe 1 has an additive valve holder 2 at the curved portion. The additive valve holder 2 extends from the exhaust pipe 1 in the Z-axis direction and is formed in a cylindrical shape. The additive valve holder 2 has a holding mechanism that holds the fuel additive valve 4 at its tip in the Z-axis direction.

As shown in FIG. 2, the fuel addition valve 4 is attached to the addition valve holder 2. The attachment side of the fuel addition valve 4 is cylindrical in shape corresponding to the addition valve holder 2, and has an injection port 4a on its central axis. The fuel addition valve 4 injects fuel into the exhaust pipe 1 from the injection port 4a to be oxidized by the oxidation catalyst at the timing when DPF regeneration is required. The fuel is oxidized by the oxygen remaining in the exhaust gas in the oxidation catalyst. The heat generated by the oxidation increases the exhaust gas temperature, and the exhaust gas becomes hot. The high-temperature exhaust gas increases the bed temperature of the DPF, and when the bed temperature reaches a predetermined temperature or higher (for example, 590°C or higher), the particulate matter (PM) accumulated in the DPF is burned and incinerated, and the collection function of the DPF is restored (regenerated).

Inside the additive valve holder 2, an injection passage 2b, which is a cylindrical cavity, is formed. In other words, the inner circumferential surface 2a of the additive valve holder 2 forms the injection passage 2b. When the fuel additive valve 4 is attached to the additive valve holder 2, the central axes of the fuel additive valve 4 and the injection passage 2b are set to align. Therefore, the spray 4b injected from the injection port 4a of the fuel additive valve 4 passes through the center of the injection passage 2b and enters the exhaust pipe 1.

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 across the injection passage 2b. 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 of the curved portion in 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. In the dispersion space 1a, the inlet 5b through which the exhaust gas flows is opened upstream of the injection passage 2b (where the addition valve holding portion 2 is provided) in the exhaust pipe 1. In the dispersion space 1a, the outlet 5c through which the exhaust gas flows out is opened downstream of the injection passage 2b (where the addition valve holding portion 2 is provided) in the exhaust pipe 1.

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

Some of the exhaust gas flowing in from the inlet 5b does not flow out from the outlet 5c, but heads toward the injection passage 2b of the additive valve holder 2. The exhaust gas heading toward the injection passage 2b heads in the Z-axis direction while swirling along the inner circumferential surface 2a of the additive valve holder 2 that forms the injection passage 2b. In order to suppress the generation of such a swirling flow, for example, the upstream shape of the dispersion plate 5 may be changed to narrow the inlet 5b, or a flow direction adjustment member 6 having a substantially triangular prism shape that adjusts the flow direction of the exhaust gas may be provided on the exhaust gas inflow side in the dispersion space 1a. Alternatively, the inner diameter D2 of the injection passage 2b may be adjusted. However, if multiple factors such as the curvature of the exhaust pipe 1, the shape of the dispersion plate 5, and the installation conditions overlap, the exhaust gas may inevitably enter the injection passage 2b, causing a swirling flow. The fuel addition valve 4 is located at the end of the swirling flow (Z-axis direction). The exhaust gas (swirling flow) contains soot, and when this soot mixes with the fuel injected from the fuel addition valve 4, it forms deposits that adhere to the injection port 4a of the fuel addition valve 4, which is undesirable.

The addition valve holding portion 2 has a swirling flow turning member 3 at a position close to the fuel addition valve 4 in the injection passage 2b. The swirling flow turning member 3 is cylindrical, with its outer peripheral surface forming a truncated cone side portion 3a and its inner peripheral surface forming a hollow portion 3b. In other words, the swirling flow turning member 3 has the truncated cone side portion 3a, which is the side surface of the truncated cone shape, and the hollow portion 3b that allows the spray 4b injected from the fuel addition valve 4 to pass through.

The truncated cone side portion 3a formed by the outer peripheral surface of the swirl flow turning member 3 has a diameter D1 on the side closer to the fuel addition valve 4 that is approximately the same as the inner diameter D2 of the injection passage 2b, and continues to the inner peripheral surface 2a of the addition valve holding portion 2 that forms the injection passage 2b. The truncated cone side portion 3a is inclined so that the diameter becomes smaller as it moves away from the fuel addition valve 4 and moves away from the inner peripheral surface 2a.

The swirling flow turning member 3 turns back the inflow swirling flow approaching the fuel addition valve 4 while swirling along the inner circumferential surface 2a of the addition valve holding portion 2 forming the injection passage 2b, and turns it into an outflow swirling flow moving away from the fuel addition valve 4 while swirling in the same direction.
● [Action and effect of swirl flow return members (Figs. 4 to 6)]

In Figures 4 and 5, the structure of the exhaust pipe 1 and the additive valve holder 2 is omitted, and only the space surrounded by the inner circumferential surface 2a of the additive valve holder 2 forming the injection passage 2b and the truncated cone side portion 3a formed by the outer circumferential surface of the swirl flow turning member 3 is depicted, focusing on the swirling flow flowing within the space. As shown in Figure 4, the incoming swirling flow 7 advances in the Z-axis direction while swirling along the inner circumferential surface 2a of the additive valve holder 2 forming the injection passage 2b. At the end of the Z-axis direction is the fuel addition valve 4 (see Figure 2), but the inner circumferential surface 2a is a dead end due to the truncated cone side portion 3a. Therefore, the incoming swirling flow 7 has no choice but to turn around and head in the opposite direction of the Z-axis.

As shown in FIG. 5, the inflow swirling flow 7 is turned around by the truncated cone side portion 3a to become the outflow swirling flow 8, which then travels in the opposite direction along the Z axis while swirling in the same direction along the truncated cone side portion 3a. The truncated cone side portion 3a is inclined away from the inner circumferential surface 2a of the addition valve holder 2 that forms the injection passage 2b. Moreover, while a strong inflow swirling flow 7 is generated on the inner circumferential surface 2a (outside), there is a space inside the injection passage 2b that is not affected by either the inflow swirling flow 7 or the flow of spray 4b. Therefore, the outflow swirling flow 8 travels in the opposite direction along the Z axis while swirling inside the inflow swirling flow 7 without interfering with the inflow swirling flow 7.

In addition, in Figures 4 and 5, for convenience, the inflow swirling flow 7 and the outflow swirling flow 8 are illustrated separately. However, as shown in Figure 6, the inflow swirling flow 7 and the outflow swirling flow 8 actually flow continuously.

In this way, even if the incoming swirling flow 7 approaches the fuel addition valve 4 along the inner circumferential surface 2a of the addition valve holder 2 forming the injection passage 2b, the truncated cone side portion 3a formed by the outer circumferential surface of the swirling flow turning member 3 acts as a wall to prevent the incoming swirling flow 7 from entering the fuel addition valve 4. Therefore, the exhaust gas does not reach and hit the fuel addition valve 4, 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 addition valve 4 or the inner wall of the exhaust pipe 1.

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 modifications, additions, and deletions are possible within the scope of the present invention. For example, in this embodiment, the exhaust pipe 1 is described as being provided with a dispersion plate 5, but the exhaust pipe may not be provided with a dispersion plate 5. Furthermore, even if a dispersion plate 5 is provided, the shape of the dispersion space 1a and the position of the inlet 5b are not limited to those described in this embodiment and may be any shape as long as it has a collision surface 5a against which the spray 4b collides.

In the present embodiment, the fuel addition valve 4 is held in the addition valve holding section 2, and fuel is injected toward an oxidation catalyst installed downstream. However, the target for suppressing the intrusion of exhaust gas is not limited to the fuel addition valve 4, and may be, for example, a urea water addition valve. The urea water addition valve is an addition valve that injects urea water (reaction liquid) into the exhaust gas toward a selective reduction catalyst (exhaust gas purification device) installed downstream.

In the present embodiment, the swirling flow turning member 3 has a thick inner wall of the truncated cone side portion 3a and a cylindrical hollow portion 3b. However, the hollow 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 truncated cone-shaped hollow portion 23b with the inner wall of the truncated cone side portion 3a thinned.

1 Exhaust pipe 1a Dispersion space 1b Main flow path 2 Addition valve holding part 2a Inner circumferential surface 2b Injection passages 3, 23 Swirl flow folding member 3a truncated conical side surface 3b, 23b Cavity 4 Fuel addition valve 4a Injection port 4b Spray 5 Dispersion plate 5a Collision surface 5b Inflow port 5c Outflow port 6 Direction adjustment member 7 Inflow swirl flow 8 Outflow swirl flow

Claims (3)

An exhaust pipe for an internal combustion engine that guides exhaust gas discharged from the internal combustion engine to an exhaust purification device,
the exhaust pipe is provided with an addition valve that injects fuel, which is a reaction liquid that is oxidized by an oxidation catalyst included in the exhaust purification device, into the exhaust pipe, and a cylindrical addition valve holding portion that holds the addition valve at an end portion,
an inner circumferential surface of the addition valve holding portion forms an injection passage through which a spray of the reaction liquid injected from the addition valve into the exhaust pipe passes,
a swirling flow turning member is provided at a position in the injection passage close to the adding valve, which turns an inflow swirling flow approaching the adding valve while swirling along the inner circumferential surface of the adding valve holding portion that forms the injection passage into an outflow swirling flow moving away from the adding valve while swirling,
the swirl flow turning back member is cylindrical, its outer peripheral surface forms a truncated cone side portion which is a side surface of a truncated cone shape, and its inner peripheral surface forms a hollow portion which allows the spray injected from the addition valve to pass through,
the truncated cone side portion has an outer diameter on a side closer to the addition valve that is substantially the same as an inner diameter of the injection passage, and the outer diameter becomes smaller as it goes away from the addition valve, and is inclined so as to move away from the inner circumferential surface of the addition valve holding portion that forms the injection passage.
Exhaust pipe of an internal combustion engine. 2. An exhaust pipe for an internal combustion engine according to claim 1,
a dispersion plate is provided in the exhaust pipe so as to face the addition valve across the injection passage,
The spray injected from the injection port of the addition valve into the exhaust pipe collides with the dispersion plate and is dispersed.
Exhaust pipe of an internal combustion engine. 3. An exhaust pipe for an internal combustion engine according to claim 2,
a dispersion space is formed in the exhaust pipe at a portion where the dispersion plate is provided, the dispersion space being surrounded by an inner wall of the exhaust pipe and the dispersion plate and communicating with the injection passage,
An exhaust gas inlet in the dispersion space is disposed upstream of the injection passage in the exhaust pipe in a flow path of the exhaust gas.
Exhaust pipe of an internal combustion engine.

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