WO2007116698A1

WO2007116698A1 - Exhaust gas purifier for diesel engine

Info

Publication number: WO2007116698A1
Application number: PCT/JP2007/056244
Authority: WO
Inventors: Manabu Sudo; Daisuke Yamagishi
Original assignee: Depro Corporation
Priority date: 2006-03-27
Filing date: 2007-03-26
Publication date: 2007-10-18
Also published as: JP2007262933A

Abstract

A highly reliable exhaust gas purifier which can be manufactured at low cost by simplifying the structure. An exhaust gas purifier for diesel engine has a first DPF (36) for capturing and treating a particulate matter contained in the exhaust gas from a diesel engine, and a bypath (37) juxtaposed to the first DPF (36), wherein the first DPF (36) has a pressure loss for conducting the majority of the exhaust gas to the first DPF (36) when the engine is under light load and passing the majority of exhaust gas through the bypath (37) when the engine is under heavy load.

Description

Specification

Diesel engine exhaust purification system

Technical field

[0001] The present invention relates to an exhaust emission control device for a diesel engine. Specifically, the present invention relates to an exhaust emission control device for a diesel engine that reduces emission of particulate matter (PM) mainly composed of carbon.

Background art

[0002] In recent years, reduction of harmful substances such as particulate matter (PM) and nitrogen oxides (Nx) discharged from diesel engines has been a challenge. In particular, reducing particulate emissions is a major challenge, and exhaust purification devices such as diesel particulate filters (DPFs) have been developed.

[0003] As an exhaust emission control device for a diesel engine using DPF, for example, (Patent Document 1) includes a first continuous regeneration type DPF disposed in an exhaust passage of the engine, and the first continuous regeneration type DPF. A second continuous regeneration type DPF configured to have a capacity smaller than that of the first continuous regeneration type DPF and disposed in the upstream exhaust passage, and a bypass passage disposed so as to surround the outer periphery of the second continuous regeneration type DPF. A control valve for opening and closing the bypass passage, and a control means for controlling the control valve to close the bypass passage when the exhaust temperature region of the engine is a low temperature region lower than a predetermined temperature. An exhaust emission control device for a configured diesel engine is disclosed.

Patent Document 1: Japanese Patent Application Laid-Open No. 2003-3830

Disclosure of the invention

Problems to be solved by the invention

[0005] However, the exhaust purification apparatus as described above has problems such as a complicated apparatus structure and high cost.

[0006] In view of the above-described conventional situation, an object of the present invention is to provide an exhaust emission control device that has a simplified device structure, can be manufactured at low cost, and is highly reliable. . Means for solving the problem

[0007] An exhaust emission control device for a diesel engine according to the present invention includes a first DPF that collects and processes particulate matter contained in exhaust gas of a diesel engine, and a bypass passage that is provided in parallel with the first DPF. The first DPF is a pressure that allows most of the exhaust gas to flow through the first DPF when the engine is under a low load and also allows the exhaust gas to flow through the bypass passage when the engine is under a high load. Characterized by having a loss

[0008] According to the above configuration, the first DPF distributes most of the exhaust gas to the first DPF when the engine is under a low load, and passes the exhaust gas into the bypass passage when the engine is under a high load. Since it has a pressure loss to circulate, the exhaust gas can be circulated through the first DPF or bypass passage at an appropriate rate according to the engine load.

[0009] Further, in the exhaust purification system for a diesel engine of the present invention described above, the first DPF distributes 55 to 75 vol% of the total exhaust gas flow rate to the first DPF when the engine is under a low load, It is characterized by having a pressure loss that causes 65 to 85 vol% of the total exhaust gas flow rate to flow through the bypass passage at high loads.

[0010] According to the above configuration, the ratio of the exhaust gas flowing through the first DPF or the bypass passage is optimized in accordance with the load state of the engine.

[0011] Further, in the exhaust gas purification apparatus for a diesel engine of the present invention described above, the first DPF is provided inside a casing, and a bypass passage is formed between the casing and the first DPF. It is characterized by that.

[0012] According to the above configuration, since the first DPF is arranged in the casing, the surface area of the entire apparatus is reduced, and heat conduction between the apparatus and the outside air is suppressed. In addition, since the first DPF and bypass passage are arranged and integrated in the casing, the entire apparatus is reduced in size.

[0013] Further, in the above-described diesel engine exhaust gas purification apparatus of the present invention, the first DPF is arranged on the flow path center axis of the exhaust gas inlet of the casing.

[0014] According to the above configuration, a larger amount of exhaust gas flowing into the casing can be passed through the first DPF. The ratio of exhaust gas flowing into the first DPF can be increased especially when the flow rate of exhaust gas is low, such as when the engine is under low load. [0015] Further, in the exhaust purification device for a diesel engine according to any one of the above-described present inventions, an exhaust pipe connecting the first DPF and the diesel engine is covered with a heat insulating material.

[0016] According to the above configuration, since the exhaust pipe from the diesel engine to the first DPF is covered with the heat insulating material, the cooling of the exhaust gas is reduced, and the temperature of the exhaust gas at the first DPF inlet is reduced. Can be kept high.

[0017] Further, in the above-described diesel engine exhaust gas purification apparatus of the present invention, a second DPF is provided downstream of the first DPF.

[0018] According to the above configuration, since the second DPF is provided downstream of the first DPF, PM contained in the exhaust gas of the diesel engine can be reliably collected and processed. Furthermore, combustion heat is generated when a part of the exhaust gas PM is oxidized, and the temperature of the first DPF rises. Therefore, the exhaust gas that has passed through the first DPF is also in the second DPF. PM is maintained at a temperature where it can be oxidized.

[0019] Further, in the above-described diesel engine exhaust gas purification apparatus of the present invention, the first DPF is provided at a position closer to the second DPF than the diesel engine.

[0020] According to the above configuration, since the first DPF is provided at a position away from the diesel engine, the temperature of the first DPF is higher than the temperature of the exhaust gas discharged from the diesel engine and the diesel engine. Sensitive tracking is suppressed. In addition, the exhaust gas cooling in the exhaust pipe from the first DPF to the second DPF is reduced, and the temperature of the exhaust gas at the second DPF inlet can be kept high.

[0021] Further, in the above-described diesel engine exhaust gas purification apparatus of the present invention, the DPF unit is arranged such that the central axis of the exhaust gas outlet of the DPF unit is collinear with the central axis of the flow path of the second DPF. It is characterized by that.

[0022] According to the above configuration, the exhaust gas flow path from the DPF unit to the second DPF is close to a straight line, so the exhaust gas passage resistance is reduced and the deterioration of engine performance is suppressed. it can.

The invention's effect [0023] According to the exhaust emission control device for a diesel engine of the present invention, the exhaust gas is allowed to flow through the first DPF and the bypass passage at an appropriate ratio according to the flow rate of the exhaust gas without using a switching valve or the like. Is possible. Specifically, when the exhaust gas flow rate is low and the exhaust gas temperature is low, a large amount of exhaust gas is oxidized with the first DPF, while the exhaust gas flow rate is high and the exhaust gas temperature is high. Can pass the exhaust gas through the bypass passage and oxidize it with the second DPF, so that the exhaust gas can be distributed between the first DPF and the bypass passage at an appropriate ratio without using a switching valve. Become.

[0024] Further, since there is no need to provide a switching valve, an actuator for operating the switching valve, a control device for controlling the switching valve, etc., the device structure can be greatly simplified and manufactured at a low cost. Work and maintenance work become easy. Further, since the device associated with the switching valve is omitted, the entire device is miniaturized, so that it can be mounted on many vehicle types.

Brief Description of Drawings

FIG. 1 is a perspective view showing an overall configuration of an exhaust emission control device for a diesel engine according to an embodiment (1).

FIG. 2 is a diagram showing an overall configuration of an exhaust emission control device for a diesel engine according to an embodiment (1).

FIG. 3 is a longitudinal sectional view of a DPF unit according to Embodiment (1).

FIG. 4 is a cross-sectional view taken along line AA in FIG.

FIG. 5 is a graph showing the relationship between the engine speed and the flow rate ratio R to the first DPF.

First DPF

Explanation of symbols

[0026] 10 diesel engine

11 Exhaust pipe

11A Upstream exhaust pipe

11B Downstream exhaust pipe

12 Intake manifold hold

14 Exhaust manifold hold

21 External EGR piping 30 DPF unit

31 Casing

32 Inlet connection member

33 outer cylinder

34 Outlet connection member

35 Mounting member

36 First DPF

37 Bypass passage

38 Enclosure

60 second DPF

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described in detail. FIGS .: to 5 are views showing an embodiment (1) of an exhaust emission control device for a diesel engine according to the present invention.

[0028] As shown in Figs. 1 and 2, the exhaust purification device for a diesel engine includes a diesel engine 10 for purifying exhaust, and a DPF unit 30 connected to the diesel engine 10 via an exhaust pipe 11A 30 And a second DPF 60 connected via the DPF unit 30 and the exhaust pipe 11B.

[0029] The diesel engine 10 is provided with an intake manifold 12 for introducing fresh air into each cylinder of the diesel engine 10 and an exhaust manifold 14 through which exhaust gas after combustion discharged from each cylinder is passed. An exhaust pipe 11A on the upstream side is connected to the exhaust manifold 14, and the exhaust gas is exhausted to the DPF unit 30 through the exhaust pipe 11A on the upstream side. The upstream exhaust pipe 11A is covered with a heat insulating material so that the exhaust gas exhausted from the diesel engine 10 is not cooled. In addition, the exhaust purification system for diesel engines is provided with an external EGR pipe 21 for cooling the exhaust gas obtained from the exhaust manifold 14 etc. and returning it to the intake manifold 12 etc. The gas flow rate is configured to be adjusted by the external EGR valve 21.

[0030] As shown in FIGS. 3 and 4, the DPF unit 30 includes a cylindrical outer cylinder 33 and an outer cylinder 33. A casing 31 provided at both ends and provided with an inlet side connecting member 32 and an outlet side connecting member 34 for connecting to the exhaust pipes 11A and 1IB, respectively, and a cylinder provided inside the casing 31 via a mounting member 35 And a first DPF 36 having a shape. The first DPF 36 is disposed on the flow path central axis of the casing 31, and a bypass passage 37 is formed between the casing 31 and the first DPF 36.

[0031] The first DPF 36 is a small CR-DP F that collects PM contained in a small amount of exhaust discharged mainly during diesel engine at low to medium or low loads or during medium loads and continuously regenerates it. is there. In combination with the first DPF36, CO, HC and NO are oxidized to CO, H 2 O and

twenty two

An oxidation catalyst for conversion to NO may be provided. On the outer periphery of the first DPF36, the first DP

2

A housing 38 for protecting F36 is provided. As a material of the casing 38, a force capable of using various materials such as a metal and a resin is usually used.

[0032] The first DPF 36 has a pressure loss. The pressure loss causes most of the exhaust gas to flow to the first DPF 36 when the engine is under a low load, and the exhaust gas when the engine is under a high load. It is preferable to have a pressure loss that causes a large amount to flow through the bypass passage 37. Specifically, as shown in Fig. 5, 55 to 75 vol% of the total exhaust gas flow is distributed to the first DPF 36 when the engine is under low load, and 65 to 85 vol% of the total exhaust gas flow is bypassed when the engine is under high load. It is preferable to have a pressure loss flowing through the passage 37. Note that R shown in Fig. 5 is the exhaust gas flowing into the first DPF 36 as shown in the following equation.

First DPF

Flow rate ratio

Represents a rate.

R = F / ¥ = F / (F + F)

1st DPF 1st DPF TOTAL 1st DPF 1st DPF BYPASS

(Where F is the flow rate of the exhaust gas flowing into the first DPF 36 and F is the bypass passage.

First DPF BYPASS

Exhaust gas flow rate through passage 37, F represents total exhaust gas flow rate)

TOTAL

[0033] Also, when the engine is under low load, the exhaust gas total flow rate is 55 to 75 vol. / ₀ is distributed to the first DPF36, and the exhaust gas total flow is 65 to 85 vol at high engine load. /. Specifically, the first DPF36 that has a pressure loss that circulates through the bypass passage 37 has a pressure loss of 2.5kPa to 5kPa when air is flowed at a flow rate of 4.15m3 / min. Preferably, it has a pressure loss of 3 kPa to 4 kPa. Also, when the engine is under low load In general, it means that the engine speed is 500 rpm to 1100 rpm, and when the engine is at a high load, it means that the engine speed is generally 2400 rpm to 2900 i "pm.

[0034] The bypass passage 37 is disposed so as to surround the first DPF 36, and the exhaust gas that has passed through the bypass passage 37 is exhausted to the exhaust pipe 11B on the downstream side through the exhaust gas outlet 34a. Is done.

In addition, the second DPF 60 is provided in the exhaust pipe 11B on the downstream side of the exhaust gas flow path, and the exhaust gas that has passed through the DPF unit 30 flows in. The second DPF60 oxidizes C0, HC and N0 contained in a large amount of exhaust gas discharged at high loads and high speeds of diesel engine to convert them into CO, H0 and NO and PM. The continuous oxidation treatment

2 2 2

Large CR—DPF

[0036] It should be noted that the DPF unit 30 is provided at a position closer to the second DPF 60 than the diesel engine 10 is not provided immediately below the diesel engine 10 so that heat conduction from the diesel engine 10 is suppressed. . Specifically, the downstream exhaust pipe 11B is shorter than the upstream exhaust pipe 11A. In addition, the DPF unit 30 has a central axial force at the exhaust gas outlet 34a of the DPF unit 30, a flow path central axis of the second DPF 60, and a flow path center of the exhaust pipe 11B connecting the second DPF 60 and the DPF unit 30. It is arranged so that it is on the same line as the axis. As a result, the exhaust gas flow path from the DPF unit 30 to the second DPF 60 becomes almost a straight line, so it is possible to suppress the deterioration of the engine performance with a small exhaust gas passage resistance.

[0037] Hereinafter, a case where the above-described diesel engine exhaust gas purification apparatus is actually used will be described.

[0038] First, the exhaust gas exhausted by 10 forces of the diesel engine flows into the DPF unit 30 from the exhaust gas inlet 32a through the exhaust pipe 11A. As shown in FIG. 5, the exhaust gas flowing into the DPF unit 30 has a pressure loss of the first DPF 36 in the bypass passage 37, for example, when the engine speed is 2500 rpm and the engine load is high. Therefore, most of the exhaust gas passes through the bypass passage 37, and the PM in the exhaust gas is continuously oxidized in the second DPF 60. When the engine speed is high and the load is high, the exhaust gas temperature is high, so the exhaust gas that has passed through the bypass passage 37 It can be oxidized with a second DPF. Part of the exhaust gas also flows to the first DPF 36, and similarly PM in the exhaust gas is continuously oxidized. In this way, the temperature of the first DPF 36 can be maintained at a predetermined temperature by continuing to flow a small amount of exhaust gas through the first DPF 36 even when the second DPF 60 is used. For this reason, the first DPF 36 can continuously process PM even when the load is reduced depending on the operating status, and it is possible to continuously regenerate PM even when the operating status changes suddenly. .

[0039] Subsequently, during constant speed running or the like where the engine speed is 1500 rpm, the exhaust gas flows into the first DPF 36 and the bypass passage 37 almost evenly. Therefore, a part of PM contained in the exhaust gas is continuously oxidized in the exhaust gas flowing into the first DPF36. On the other hand, the exhaust gas flowing into the no-pass passage 37 passes through the first DPF 36 at the exhaust gas outlet 34a and is mixed with the exhaust gas subjected to the continuous oxidation treatment and flows into the second DPF 60. Then, continuous oxidation treatment is performed in the second DPF60. At this time, since almost half of the exhaust gas is oxidized in the first DPF 36, the amount of exhaust gas oxidized in the second DPF 60 can be reduced.

[0040] Subsequently, most of the exhaust gas flows into the first DPF3 6 when idling such that the engine speed is 500 rpm, during long downhill driving, or when decelerating from high speed driving. The remaining exhaust gas passes through the bypass passage 37. In this case, since the first DPF 36 is provided at a position closer to the engine than the second DPF 60, it is possible to introduce the exhaust gas at a temperature capable of being oxidized before being cooled. In particular, combustion heat is generated when a part of the exhaust gas PM is oxidized, so the temperature of the exhaust gas that has passed through the first DPF 36 is maintained, and the second DPF 60 is also oxidized. It becomes possible.

[0041] Also, when idling, long downhill running, deceleration from high speed running, etc. continues for a long time, and the exhaust gas temperature is lower than the temperature at which the first DPF36 can be oxidized. In this case, PM collected by the first DPF36 cannot be burned and removed, resulting in clogging, and the pressure loss of the first DPF36 increases. Therefore, in this case, a large amount of exhaust gas flows into the bypass passage 37. This prevents the first DPF 36 from being damaged due to clogging. [0042] According to the exhaust purification system for a diesel engine of the above embodiment (1), the ratio suitable for the first DPF 36 and the bypass passage 37 according to the flow rate of the exhaust gas without using a switching valve or the like. It becomes possible to flow exhaust gas. Specifically, the exhaust gas flow rate is low. When the exhaust gas temperature is low, it is possible to oxidize a large amount of exhaust gas with the first DPF 36, while the exhaust gas flow rate is high. When the temperature is high, a lot of exhaust gas can pass through the bypass passage and be oxidized by the second DPF60.

[0043] Also, if the engine is under low load for a long time, such as when the engine is started, idling while the vehicle is stopped, or when driving at a low speed during traffic jams, the PM collected by the first DPF 36 is burned. It cannot be burned off and the first DPF36 will become clogged. According to the exhaust purification system of the above embodiment (1), even when the first DPF 36 is clogged and as a result the resistance of the exhaust flow increases, most of the exhaust gas is automatically passed through the bypass passage. This prevents the first DPF 36 from being damaged by clogging.

[0044] Further, since there is no need to provide a switching valve, an actuator for operating the switching valve, a control device for controlling the switching valve, etc., the device structure can be greatly simplified and manufactured at low cost. Furthermore, since the device associated with the switching valve is omitted, the entire device is miniaturized, so that it can be mounted on many vehicle types. In addition, since the first DPF 36 is housed in the casing 31 and has a compact shape, the exhaust gas passing through the first DPF 36 and the bypass passage 37 is not It is possible to prevent the device from being thermally detrimental.

[0045] In addition, the exhaust emission control device of the present invention is preferably used particularly for a medium truck having a standard load capacity of 4 t or more. Compared to small trucks, medium trucks tend to reach a temperature at which PM can be continuously regenerated, as the exhaust temperature rises more rapidly when starting. In addition, even when shifting from normal constant speed driving to idling, low speed driving, deceleration from high speed driving, etc., the exhaust gas is kept at a high temperature for a relatively long time, so PM is continuously regenerated. The ability to process S is possible. In this way, in the medium-sized truck, the exhaust gas temperature is always lower than the temperature at which PM can be continuously regenerated, so that the exhaust gas is always in the first DPF as in the exhaust purification device of the present invention. Should also be used in case of inflow Can do.

Industrial applicability

The present invention can be used for the purpose of reducing emission of particulate matter (PM) containing carbon as a main component in a diesel engine.

Claims

The scope of the claims

[1] It has a first DPF that collects and processes particulate matter contained in exhaust gas of a diesel engine, and a bypass passage arranged in parallel with the first DPF,

The first DPF is a diesel engine having a pressure loss that distributes most of the exhaust gas to the first DPF when the engine is under low load and distributes most of the exhaust gas into the bypass passage when the engine is under high load. Exhaust purification device.

[2] In the exhaust emission control device for a diesel engine according to claim 1, the first DPF allows 55 to 75 vol% of the total exhaust gas flow rate to flow through the first DPF when the engine is under a low load, and the engine An exhaust purification device for a diesel engine, characterized by having a pressure loss that causes 65 to 85 vol% of the total exhaust gas flow rate to flow through the bypass passage when the load is high.

[3] In the exhaust purification apparatus for a diesel engine according to claim 1 or 2, the first DPF is provided inside a casing to constitute a DPF unit, and is disposed between the casing and the first DPF. An exhaust emission control device for a diesel engine, characterized in that a bypass passage is formed in the space.

[4] The exhaust emission control device for a diesel engine according to claim 3, wherein the first DPF is disposed on a flow path central axis of the exhaust gas inlet of the casing.

[5] An exhaust emission control device for a diesel engine according to claim 3, wherein an exhaust pipe connecting the first DPF and the diesel engine is covered with a heat insulating material.

[6] In the exhaust gas purification device for a diesel engine according to any one of claims 1, 2, and 4, the exhaust pipe connecting the first DPF and the diesel engine is covered with a heat insulating material. Diesel engine exhaust purification system.

[7] The diesel engine exhaust gas purification apparatus according to any one of claims 1, 2, 4, and 5, wherein the second DPF is provided downstream of the first DPF. Engine exhaust purification system.

[8] In the exhaust emission control device for a diesel engine according to claim 3, the first DPF A diesel engine exhaust purification system, characterized in that a second DPF is installed on the downstream side.

The diesel engine exhaust gas purification apparatus according to claim 6, wherein the second DPF is provided downstream of the first DPF.

8. The exhaust emission control device for a diesel engine according to claim 7, wherein the first DPF is provided closer to the second DPF than the diesel engine.

The exhaust emission control device for a diesel engine according to claim 8 or 9, wherein the first DPF is provided at a position closer to the second DPF than the diesel engine.

In the exhaust emission control device for a diesel engine according to claim 7, the DPF unit is arranged so that the central axis of the exhaust gas outlet of the DPF unit is collinear with the central axis of the flow path of the second DPF. Diesel engine exhaust gas purification device. In the exhaust purification system for a diesel engine according to claim 8 or 9, the DPF unit is disposed so that the central axis of the exhaust gas outlet of the DPF unit is collinear with the central axis of the flow path of the second DPF. An exhaust gas purification system for diesel engines.

In the exhaust emission control device for a diesel engine according to claim 10, the DPF unit is arranged so that the central axis of the exhaust gas outlet of the DPF unit is collinear with the central axis of the flow path of the second DPF. Diesel engine exhaust gas purification device. In the exhaust emission control device for a diesel engine according to claim 11, the DPF unit is disposed so that the central axis of the exhaust gas outlet of the DPF unit is collinear with the central axis of the flow path of the second DPF. Diesel engine exhaust gas purification device.