Patent Application
20070289289
Other objects, features, and advantages will become more apparent from the following detailed description made with reference to the accompanying drawings, in which like parts are designated by like reference numbers and in which:
Various embodiments according to the present disclosure will be described below with reference to the accompanying drawings. In these embodiments, structural components that are substantially the same are designated by the same reference numerals and repetitive description is omitted.
The exhaust system 60 guides exhaust gases from the engine 11 to an area outside of the engine 11. The exhaust system 60 has an exhaust pipe 61 that forms an exhaust passage 62. The exhaust gases emitted from the engine 11 flow through the exhaust passage 62 to the outside. The exhaust passage 62 defined by the exhaust pipe 61 is fluidly coupled to the engine 11 and an exhaust port 63. The purification unit 20 provided in the exhaust system and is operatively coupled to the exhaust pipe 61. Specifically, the purification unit 20 is disposed between the engine 11 and the exhaust port 63 in the exhaust system 60.
The intake system 70 supplies intake air to the engine 11 from an area outside the engine 11. The intake system 70 has an intake pipe 71 that defines an intake passage 72. The intake air introduced from an intake port 73 flows through an intake passage 72 into the engine 11. The intake passage 72 defined by the intake pipe 71 is fluidly coupled to the intake port 73 and the engine 11. A throttle 74 is disposed in the intake passage 72 for adjusting a flow rate of the intake air.
The purification unit 20 is disposed in the exhaust system 60. In the embodiment shown, the purification unit 20 has a DPE 21, a NOx reduction catalyst 22 and an oxidation catalyst 23. The DPE 21 collects particulate matter (PM) included in the exhaust gases. The NOx reduction catalyst 22 reduces NOx included in the exhaust gases in cooperation with, for example, fuel, such as light oil, and urea as the additive. As a result, the NOx included in the exhaust gases is reduced to N2, CO2, and H2O which are less harmful. The oxidation catalyst 23 oxidizes PM included in the exhaust gases. The first embodiment describes an example of the purification unit 20 provided with the DPF 21, the NOx reduction catalyst 22 and the oxidation catalyst 23. However, it will be appreciated that any suitable purification unit 20 may be provided. For instance, in one embodiment, the NOx reduction catalyst 22 and either the DPF 21 or the oxidation catalyst 23 is provided. In another embodiment, the purification unit 20 is provided with a filter and a catalyst in place of the DPF 21, the NOx reduction catalyst 22, or the oxidation catalyst 23 which are exemplified above.
The additive feeder unit 32 is operatively coupled to the exhaust system 60 at a position between the engine 11 and the purification unit 20 for providing an additive to the exhaust gases flowing in the exhaust system 60. In the embodiment shown, the additive feeder unit 32 includes an additive injection valve 30 that is in fluid communication with the exhaust system 60 between the engine 11 and the purification unit 20. In other words, the injection valve 30 is closer to the engine 11 than the distance between the purification unit 20 and the engine 11.
As will be described below, air from the pressurized air introducer unit 50 allows the injection valve 30 to feed additive into the exhaust system 60. The additive injection valve 30 injects the additive into the exhaust gases flowing in the exhaust passage 62. The additive comprises substances performing the functions of the DPF 21, the NOx reduction catalyst 22 and the oxidation catalyst 23 of the purification unit 20.
For example, the DPF 21 collects the PM included in the exhaust gases. Therefore, when the DPF 21 collects more than a predetermined amount of PM, the DPF 21 can become clogged, resulting in a reduction in function of the DPF 21. To avoid this, the additive injection valve 30 injects, for example, fuel such as light oil as the additive, to burn off the PM collected by the DPF 21. As a result, the clogging of the DPF 21 is reduced, so that the DPF 21 is regenerated.
Also, the NOx reduction catalyst 22 absorbs the NOx included in the exhaust gases. Therefore, when the NOx reduction catalyst 22 absorbs more than a predetermined amount of NOx, the absorption capacity is saturated, resulting in a reduction in function of the NOx reduction catalyst 22. To avoid this, the additive injection valve 30 injects, for example, fuel such as light oil or urea which is an additive serving as a reducer, to thereby reduce the NOx absorbed in the NOx reduction catalyst 22. As a result, the NOx reduction catalyst 22 is regenerated.
Moreover, the oxidation catalyst 23 burns off the PM included in the exhaust gases. Therefore, fuel is required to burn off the PM. For this purpose, the additive injection valve 30 injects, for example, fuel such as light oil as the additive, so that the PM is burned off in the oxidation catalyst 23. As a result, the PM included in the exhaust gases burns, resulting in a reduction in exhaust emission to the outside.
In this manner, by feeding the additive from the additive injection valve 30 to the purification unit 20, the DPF 21, the NOx reduction catalyst 22 and the oxidation catalyst 23 constituting the purification unit 20 perform their functions.
The additive injection vale 30 injects light oil which is the fuel for the engine 11, urea and/or the like as the additive as described above into the exhaust gases flowing in the exhaust passage 62. For this purpose, the additive injection valve 30 is connected to an additive tank 31 such as a fuel tank. The additive is supplied from the additive tank 31 to the additive injection valve 30.
The turbocharger 40 has a turbine 41 disposed in the exhaust system 60, and a compressor 42 disposed in the intake system 70. The turbine 41 is disposed in the exhaust passage 62 between the engine 11 and the additive injection valve 30. In other words, the turbine 41 is closer to the engine 11 than the distance between the injection valve 30 and the engine 11. The compressor 42 is disposed in the intake passage 72 between the intake port 73 and the throttle 74. In other words, the compressor 42 is closer to the intake port 73 than the distance between the intake port 73 and the throttle 74.
The turbine 41 is rotatably driven by the high-pressure exhaust gases flowing in the exhaust passage 62. The turbine 41 and the compressor 42 are rotatably coupled to each other by a shaft 43. For this reason, when the turbine 41 is driven by the flow of the exhaust gases, the compressor 42 is rotated together with the turbine 41. This allows the compressor 42 to pressurize and transport the air flowing in the intake passage 72 toward the engine 11. As a result, the intake air is compressed and sent to the engine 11.
The pressurized air introducer 50 is fluidly and operatively coupled to the intake system 70 and the additive injection valve 30. One end of the pressurized air introducer 50 is fluidly coupled to the intake system 70 at a position between the engine 11 and the compressor 42. In other words, this end of the pressurized air introducer 50 is closer to the engine 11 than the distance between the compressor 42 and the engine 11. The other end of the pressurized air introducer 50 is fluidly coupled to the additive injection valve 30, which injects the additive into the exhaust passage 62. As such, the compressor 42 pressurizes air in the intake passage 72, the pressurized air introducer 50 receives at least a portion of the air pressurized by the compressor 42, and the pressurized air introducer 50 delivers the pressurized air to the additive injection valve 30. Then, the additive injection valve 30 injects the additive into the exhaust system 50 along with the high-pressure air introduced from the pressurized air introducer 50. As a result, the additive ejected from the additive injection valve 30 is formed into a fine spray at least partly due to injection of the high-pressure air introduced from the pressurized air introducer 50.
The additive ejected from the additive injection valve 30 has preferably a smaller drop-diameter, in order for the additive to promote the regeneration of and the burning in the purification unit 20 so that the purification unit 20 can perform its function. As shown in
In this manner, in the first embodiment, highly pressurized air is introduced to the additive injection valve 30 from a position between the compressor 42 of the turbocharger 40. Thereby, when the additive is ejected from the additive injection valve 30, the high-pressure air is ejected along with the additive. This decreases the drop-diameter of the droplets of the additive ejected from the additive injection valve 30 to promote the formation into a fine spray and the reduction in drop-diameter of the additive. As a consequence, it is possible to exert the function of the purification unit 20 with high effectiveness and precision, and therefore to reduce the substances, such as PM and NOx, included in the exhaust gases.
Furthermore, in the case of the engine 11 equipped with the turbocharger 40, the high-pressure air can be provided to the injection valve 30 even without an additional high-pressure air supply source, such as a mechanical compressor, for example. Thus, a large sized high-pressure air supply source is not required, resulting in reduction of the spatial constraints of the system.
As illustrated in
On the other hand, for example, the regeneration of the NOx reduction catalyst 22 is started at the time when the amount of stored NOx, which increases with increased operation time of the engine 11, reaches a predetermined upper limit value M as shown in
To avoid this, the check valve 51 is provided. As a result, even when the boost pressure varies as shown by the broken line in
In the second embodiment, by providing the check valve 51, the pressure of the air supplied from the pressurized air introducer 50 to the additive injection valve 30 is maintained at the maximum value produced in the intake passage 72 until the injection of the additive. This makes possible the constant supply of the high-pressure air to the additive injection valve 30 irrespective of the operation conditions of the engine 11, thus promoting the spray formation of the additive injected.
The check valve 51 may be placed in any position in the pressurized air between the intake passage 72 and the additive injection valve 30. However, if the check valve 51 is disposed at the end of the pressurize air introducer 50 adjoining the intake passage 72, the volume of the pressurized air introducer 50 is increased, thus increasing the capacity of the high-pressure air. In addition, the second embodiment has described the case when the NOx reduction catalyst 22 is regenerated, as an example, but likewise, the DPF 21 is regenerated when the amount of PM collected reaches a predetermined amount.
When the high-pressure air is ejected along with the additive from the additive injection valve 30 for exerting the function of the purification unit 20, it is preferable that the high-pressure air is supplied continuously in accordance with the additive injection period. For this purpose, in the third embodiment, the reservoir 52 is provided for increasing the volume of the pressurized air introducer 50. Thus, the high-pressure air introduced from the intake passage 72 is stored in the reservoir 52 in addition to the pressurized air introducer 50. As a consequence, in the third embodiment, the high-pressure air stored in the reservoir 52 is supplied when the additive is ejected, to thereby continuously promote the atomization of the additive irrespective of the operation conditions of the engine 11.
In the case of the fourth embodiment shown in
For example, if the pressurized air introducer 50 is damaged and an air leak occurs in the pressurized air introducer 50, the air introduced from the intake passage 72 is emitted from the pressurized air introducer 50 to the outside. For this reason, the intake air pressurized by the turbocharger 40 is not supplied to the engine 11, resulting in a reduction in boost pressure of the turbocharger 40. As a result, the engine 11 is unlikely to achieve a predetermined output.
To avoid this condition, in the fourth embodiment, when the flow rate of intake air introduced from the intake passage 72 to the pressurized air introducer 50 becomes excessively high, the air introduction is blocked. Thus, a reduction in boost pressure produced by the turbocharger 40 is less likely and the output of the engine 11 can be stably sustained.
While only the selected example embodiments have been chosen to illustrate the present disclosure, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made therein without departing from the scope of the disclosure as defined in the appended claims. Furthermore, the foregoing description of the example embodiments according to the present disclosure is provided for illustration only, and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-167126 | Jun 2006 | JP | national |
