JP2010196617A - Exhaust device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent damage to a turbine of an internal combustion engine provided with the turbine rotated by energy of exhaust gas. <P>SOLUTION: This exhaust device includes a catalyst 8 and a catalyst carrying filter 9 in an exhaust gas passage 7a provided with a turbine 4b, and a cooling gas introduction inlet 15 introducing cooling gas of which temperature is lower than exhaust gas at a downstream of the catalyst and an upstream side of the turbine. Since the catalyst is disposed at the upstream side of the turbine in the exhaust gas passage, time for raising temperature of the catalyst to activating temperature is shortened, especially in low temperature start. Also, temperature of exhaust gas flowing into the turbine is reduced by introducing cooling gas from an outside of the exhaust gas passage, temperature of exhaust gas discharged from the catalyst is prevented from rising to high temperature damaging the turbine under a condition where normal purification is being done after the temperature reaches activating temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust device for an internal combustion engine including a turbine provided in an exhaust passage and driven by exhaust gas.

  Conventionally, there is an internal combustion engine (for example, a diesel engine) provided with a supercharger and a catalyst (oxidation catalyst) for purifying the exhaust gas is provided upstream of the turbine. By providing the catalyst upstream of the turbine, the temperature of the catalyst can be quickly increased and activated quickly, and the exhaust gas can be quickly purified at the time of starting.

  In the structure where the catalyst is provided upstream of the turbine as described above, it is considered that the turbine is damaged due to chipping or peeling of the catalyst. Therefore, a foreign substance separation device (separator) is provided downstream of the catalyst and upstream of the turbine. (For example, Patent Document 1). On the other hand, in order to eliminate the possibility of an increase in turbine inlet temperature due to lack of oxygen during full-open acceleration, air is supplied upstream of the catalyst to promote the oxidation reaction of the catalyst and increase the catalyst outlet temperature, that is, the turbine inlet temperature. In some cases, the inlet pressure of the turbine is increased (for example, Patent Document 2).

JP 11-1332036 A JP-A-61-108822

  However, when a catalyst is disposed on the upstream side of the turbine, the catalyst outlet temperature rises as described above, which may result in operating conditions exceeding the allowable temperature of the turbine. May damage the turbine. On the other hand, in each of the above-mentioned Patent Documents 1 and 2, it is assumed that the temperature of the turbine inlet is raised, and it is impossible to avoid damage to the turbine when the temperature is raised excessively. There is.

  In order to solve such problems and prevent damage to the turbine in an internal combustion engine provided with a turbine that is rotated by the energy of the exhaust gas, in the present invention, the engine is rotated by the energy of the exhaust gas of the internal combustion engine. A turbine (4b) provided in the exhaust passage (7a) and a catalyst (8) provided on the upstream side of the turbine (4b) in the exhaust passage (7a) to purify the exhaust gas. In the exhaust system for an internal combustion engine, a cooling gas introduction port for introducing a cooling gas having a temperature lower than that of the exhaust gas to the downstream side of the catalyst (8) and the upstream side of the turbine (4b) in the exhaust passage (7a) ( 15) is provided.

  According to this, since the catalyst is arranged on the upstream side of the turbine in the exhaust passage, the catalyst quickly rises to a predetermined activation temperature especially at the time of low temperature start. The temperature of exhaust gas flowing into the turbine can be reduced by introducing.

  In particular, exhaust gas temperature detection means (17) for detecting the exhaust gas temperature in the turbine, and when the exhaust gas temperature detected by the exhaust gas temperature detection means exceeds a predetermined value, the cooling gas is introduced into the cooling gas. It is preferable to have cooling gas introduction control means (V7) to be introduced into the mouth.

  According to this, the cooling gas can be introduced only when the temperature of the exhaust gas to the turbine is detected and there is a risk of turbine damage, and an efficient operation can be performed.

  In addition, a foreign matter removing device (18) for removing foreign matter mixed in the exhaust gas may be provided on the exhaust passage downstream of the catalyst and upstream of the turbine.

  According to this, since the foreign substance removing device is provided between the catalyst and the turbine, it is possible to prevent the missing parts of the catalyst from entering the turbine and damaging the turbine.

  Further, it is preferable that an air cleaner (3) provided in the intake passage of the internal combustion engine is provided, and the downstream side of the air cleaner in the intake passage and the cooling gas introduction port communicate with each other.

  According to this, it is possible to introduce the cooling gas through the air cleaner, and it is possible to introduce clean cooling gas from which dust in the atmosphere has been removed.

  In addition, a compressor that compresses intake air by rotating integrally with the turbine is provided in the intake passage of the internal combustion engine, and a cooler that cools the compressed intake air downstream of the compressor in the intake passage. It is preferable that the cooling gas is taken out from the downstream side of the cooler in the intake passage.

  According to this, in a compressor having a compressor integrated with a turbine, the compressed air is introduced as a cooling gas after being cooled by a cooler. Therefore, the cooling gas is introduced by the differential pressure between the supercharging pressure and the exhaust pressure by the compressor. Since it becomes easy and it cools, the cooling effect can be improved further.

  Moreover, it is good to provide the auxiliary compressor which pumps the said cooling gas to the said cooling gas inlet.

  According to this, the cooling gas can be pumped by the auxiliary compressor, the cooling gas can be easily introduced even in an operation state where the exhaust pressure is high, and the cooling effect is increased.

  And an exhaust gas recirculation passage that communicates the downstream side of the catalyst and the upstream side of the turbine in the exhaust passage and the intake passage of the internal combustion engine to recirculate the exhaust gas to the intake passage. The introduction port may be provided on the downstream side of the connection port with the exhaust gas recirculation passage in the exhaust passage.

  According to this, by recirculating the purified exhaust gas in the exhaust gas recirculation passage provided, it is possible to prevent deposits and the like from adhering to the exhaust gas recirculation passage, and to prevent the exhaust gas recirculation passage in the exhaust passage. By providing the cooling gas introduction port on the downstream side, it is possible to prevent the cooling gas containing a large amount of the active gas component from flowing into the exhaust gas recirculation passage and to prevent the EGR function from being lowered.

  As described above, according to the present invention, the catalyst is arranged on the upstream side of the turbine in the exhaust passage, so that the catalyst rises quickly to a predetermined activation temperature particularly at low temperature start, and the cooling gas from the outside of the exhaust passage. Since the temperature of the exhaust gas flowing into the turbine can be lowered by introducing the exhaust gas, the exhaust gas discharged from the catalyst in the state where the normal purification after reaching the predetermined activation temperature is performed is the turbine. It is possible to prevent the temperature from rising to a high temperature at which damage can occur.

It is an intake-exhaust path | route figure of the internal combustion engine with a supercharger which shows the 1st, 2nd embodiment based on this invention. It is a figure corresponding to FIG. 1 which shows 3rd Embodiment. It is a figure corresponding to FIG. 1 which shows 4th Embodiment. It is a figure corresponding to FIG. 1 which shows 5th and 6th embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an intake / exhaust path diagram of an internal combustion engine with a supercharger according to the present invention. In this embodiment, the internal combustion engine is described as a diesel engine. However, the present invention is not limited to a diesel engine, and may be a gasoline engine.

  In the figure, an intake manifold 2 is connected to the intake side of the engine body 1 to collect upstream portions of the branched intake passages communicating with the cylinders. In the intake passage 2a extended upstream from the intake manifold 2, an air cleaner 3, a compressor 4a of a turbocharger 4, an intercooler valve V1, and an intercooler 5 are arranged in this order from the upstream side. Air entering from the air cleaner 3 enters the compressor 4 a of the turbocharger 4, is compressed by the compressor 4 a, is then cooled by the intercooler 5, and is sent to the intake manifold 2. An intercooler bypass passage 6 that bypasses the intercooler 5 is provided, and an intercooler bypass valve V2 is provided in the intercooler bypass passage 6.

  An exhaust manifold 7 is provided on the exhaust side of the engine body 1 to collect downstream portions of the branch exhaust passages communicating with the cylinders. In the exhaust passage 7a extending downstream from the exhaust manifold 7, an (oxidation) catalyst (DOC: Diesel Oxidation Catalyst) 8, a catalyst support filter (DPF) 9, and a turbocharger are arranged in the exhaust flow direction. 4 turbines 4b are arranged in this order. Here, the catalyst-carrying filter 9 is one in which a catalyst is carried on a filter that collects particulates, and in order to burn and remove the collected particulates, the combustion is promoted by the catalyst. It is a thing. Thus, the catalyst 8 and the catalyst-carrying filter 9 constitute an exhaust purification device that includes the catalyst. The exhaust gas discharged from the exhaust manifold 7 is exhausted through the muffler 10 after rotating the turbine 4b by the exhaust energy.

  This diesel engine with a turbocharger (turbocharger 4) is provided with an exhaust gas recirculation device. The exhaust gas recirculation device includes a high-pressure exhaust gas recirculation passage 11 that branches from a location downstream of the catalyst-carrying filter 9 and upstream of the turbine 4b in the exhaust passage 7a and reaches the intake manifold 2, and a downstream of the turbine 4b (in the illustrated example, the muffler 10). ) To the upstream side of the compressor 4a in the intake passage 2a (downstream of the air cleaner 3 in the illustrated example).

  A high pressure EGR cooler 13 and a high pressure EGR valve V3 are arranged in this order from the upstream side in the high pressure exhaust gas recirculation passage 11. The low-pressure exhaust gas recirculation passage 12 is provided with a low-pressure EGR cooler 14 and a low-pressure EGR bypass passage 12a in parallel with each other, and a low-pressure EGR valve V4 is provided downstream of the low-pressure EGR cooler 14. The low pressure EGR bypass passage 12a is provided with a low pressure EGR cooler bypass valve V5. The low pressure exhaust gas recirculation passage 12 returns to one passage downstream of the valves V4 and V5, and is connected to the upstream side of the compressor 4a in the intake passage 2a via the low pressure EGR valve V6.

  A cold air introduction port 15 is provided upstream of the turbine 4b and downstream of the catalyst 8 (catalyst carrying filter 9), and a cold air introduction valve V7 as a cooling gas introduction control means is connected to the cold air introduction port 15. Has been. By opening the cold air introduction valve V7, for example, outside air in the engine room can be introduced into the turbine 4b, and the amount of cooling gas introduced can be adjusted by adjusting the opening. In order to introduce atmospheric air into the turbine 4b, for example, a nozzle and a one-way valve (not shown) facing the flow direction of exhaust gas from the catalyst-carrying filter 9 to the turbine 4b are provided in the cold air inlet 15, It can be introduced by the drawing force generated by the exhaust flow.

  A control unit (ECU) 16 is provided for performing opening / closing control (full opening, full closing or intermediate opening control) of the valves V1 to V7. In addition, the intake and exhaust passages are not limited to the above-described configuration, and well-known components used for engine control and exhaust purification are disposed at appropriate positions and controlled by the control unit 16, but these are illustrated and described. Omitted.

  Thus, the exhaust system of the internal combustion engine to which the present invention is applied is configured. Next, the action of the exhaust gas on the turbine 4b in the exhaust purification apparatus including the catalyst described above will be described. In the exhaust gas discharged from the exhaust manifold 7, HC is first purified by the catalyst 8, and particulates are removed by the next catalyst-carrying filter 9. Further, the exhaust gas becomes a high temperature due to the oxidizing action of the catalyst 8, and combustion is promoted by the catalyst-carrying filter 9, so that the particulates collected by the catalyst-carrying filter 9 are burned. The exhaust gas thus purified is sent to the turbine 4b.

  Further, the exhaust gas consumes energy by driving the turbine 4b, and there is a temperature drop in the turbine 4b due to heat radiation to the housing of the supercharger 4, but a catalyst 8 is disposed upstream of the turbine 4b. Therefore, it passes through the catalyst 8 in a high temperature state before entering the turbine 4b. As a result, the catalyst 8 can reach the predetermined activation temperature at an early stage particularly at the time of starting at a low temperature, so that a high purification ability is exhibited at an early stage.

  Further, by opening the high-pressure EGR valve V3 to perform exhaust gas recirculation, the exhaust gas purified by the catalyst 8 and the catalyst-carrying filter 9 is recirculated to the intake manifold 2 and NOx is reduced. Since the high-pressure exhaust gas recirculation passage 11 is provided with the high-pressure EGR cooler 13, the EGR gas is cooled, and NOx can be further reduced. At this time, when the EGR gas is cooled to near the atmospheric temperature by the high pressure EGR cooler 13, there is a problem that deposits or the like (for example, HC) adhere to the high pressure EGR cooler 13 and the cooler performance deteriorates. This can be dealt with by purifying HC and the like before the exhaust gas flows into the high-pressure exhaust gas recirculation passage 11 because the catalyst 8 is disposed upstream of the high-pressure exhaust gas recirculation passage 11. NOx can be reduced without degrading performance. The catalyst 8 for purifying the exhaust gas sent to the turbine 4b and the catalyst-carrying filter 9 are disposed before (upstream) the branch to the high-pressure exhaust gas recirculation passage 11 in the exhaust passage 7a. Since it is not necessary to separately provide an EGR catalyst and a particulate filter in the recirculation passage 11, the structure of the exhaust gas purification device can be simplified.

  Further, since heat is generated by the catalytic reaction in the catalyst 8 provided upstream of the turbine 4b, it is assumed that the exhaust gas temperature flowing into the turbine 4b exceeds the allowable temperature of the turbine 4b. In that case, for example, the operating state is estimated based on the engine speed and the vehicle speed, and when it is determined that the exhaust gas temperature exceeds the allowable temperature based on the estimated operating state, the cold air introduction valve V7 is opened. As a result, the cooling gas (outside air) is mixed into the exhaust gas, so that the temperature of the exhaust gas flowing into the turbine 4b can be suppressed from being increased, and thermal damage to the turbine 7b can be prevented. The outside air as the cooling gas contains a large amount of active gas components, but the connection port of the cold air inlet 15 is located downstream of the branch port of the high pressure exhaust gas recirculation passage 11, and the high pressure exhaust gas recirculation passage 11. It is possible to prevent the cooling gas containing a large amount of the active gas component from flowing in, and to prevent the EGR function (inert gas recirculation) from decreasing. In addition, instead of constantly introducing cool air into the turbine 4b, the cool air is always introduced by introducing cool air only when the temperature of the exhaust gas entering the turbine 4b rises to a temperature that may damage the turbine 4b. This can minimize the loss of turbine output.

  In the above embodiment, the low-pressure exhaust gas recirculation passage 12 is provided, and NOx can be further reduced. Depending on the combination of opening and closing of the valves V4 and V5, the high-temperature exhaust gas can be cooled and recirculated, or can be recirculated as it is when cooling is not necessary. If exhaust gas recirculation through the low pressure exhaust gas recirculation passage 12 is not required, the low pressure EGR valve V6 may be closed. Thereby, the effect of EGR can be exhibited to the maximum according to the operating state, and NOx discharged from the engine can be reduced as much as possible.

  The present invention is not limited to the above embodiment, and other embodiments will be described below. In the second embodiment, instead of determining that the exhaust gas temperature exceeds the allowable temperature based on the above-described estimation of the operation state, the exhaust gas flow to the turbine 4b as shown by the two-dot chain line in FIG. A temperature sensor 17 as exhaust gas temperature detection means is provided at or near the inlet 4c to directly detect the exhaust gas temperature. The temperature sensor 17 detects the inlet temperature (exhaust gas temperature) of the turbine 4b, and transmits the detected value to the control unit 16. When the exhaust gas temperature exceeds a predetermined value, the control unit 16 turns the cold air introduction valve V7 on. open. The predetermined value is, for example, a temperature that may damage the turbine 4b.

  As a result, as in the first embodiment, instead of constantly introducing cool air into the turbine 4b, the temperature of the exhaust gas entering the turbine 4b has been raised to a temperature that may damage the turbine 4b. Since cold air is introduced only when it is detected, the loss of turbine output due to constant introduction of cold air can be minimized. Although the inlet temperature of the turbine 4b is detected as the exhaust gas temperature, the temperature is not limited to the turbine inlet temperature, and may be, for example, the outlet temperature of the turbine 4b or the temperature of the turbine 4b itself (for example, a housing). .

  Next, a third embodiment will be described with reference to FIG. In FIG. 2, the same parts as those described above are denoted by the same reference numerals, and detailed description thereof is omitted (the same applies to the following embodiments). In the drawing, a dust separator 18 as a foreign matter removing device is disposed at a location downstream of the catalyst carrying filter 9 downstream of the catalyst 8 and upstream of the turbine 4b. The dust separator 18 may be a cyclone separator using a gas flow, for example. In addition, the separator integrated with the housing of the turbine 4b may be sufficient.

  In the case where the catalyst 8 and the catalyst-carrying filter 9 are provided on the upstream side of the turbine 4b as in the present embodiment, when fragments or the like are missing from the catalyst 8 and the catalyst-carrying filter 9, the turbine 4b flows into the turbine 4b. However, by providing the dust separator 18, foreign matter such as debris can be removed before the exhaust gas flows into the turbine 4b. Can be prevented. Moreover, as shown by the solid line in the figure, by providing the cold air inlet 15 upstream of the dust separator 18, the dust separator 18 can be cooled, and thermal damage to the dust separator 18 can be suppressed.

  If there is no need to consider heat damage to the dust separator 18, a cold air introduction passage may be provided as shown by a two-dot chain line in the figure, and the cold air introduction port 15 may be provided on the downstream side of the dust separator 18. good. Thereby, since cold air is directly introduced into the turbine 4b, the cooling capacity by cold air can be increased.

  The fourth embodiment will be described with reference to FIG. In the fourth embodiment, an intake throttle valve V8 is provided downstream of the air cleaner 3 and upstream of the compressor 4a, and a cold air introduction path 19 extending from the upstream side of the intake throttle valve V8 to the downstream of the catalyst 8 and the catalyst-carrying filter 9 is provided. Is provided. As a result, the cold air mixed into the exhaust gas entering the turbine 4b becomes through the air cleaner 3, and it is possible to prevent dust and the like in the air, which can be considered when directly introducing the air, from being mixed. The connection position of the cold air introduction path 19 to the exhaust passage 7a may be upstream of the separator 18 as shown by the solid line in FIG. 3, but the cold air introduction path as shown by the two-dot chain line in the figure. 19 may be extended to the downstream side of the separator 18.

  Further, as a fifth embodiment, as shown in FIG. 4, it is preferable to provide an intake air introduction path 21 from the intake port of the intake manifold 2 to the intake air introduction valve V7. Note that the intake port of the intake manifold 2 is on the downstream side of the intercooler 5 when the intake air passes through the intercooler 5, and is simply on the downstream side of the compressor 4 a when the intake air passes through the intercooler bypass passage 6.

  Thereby, it can replace with the external air introduction in 1st Embodiment, and can introduce into the turbine 4b the compressed air compressed with the compressor 4a as cold air. The intake pressure is increased by the compressor 4a, and the cooling gas can be easily introduced into the turbine 4b due to the pressure difference between the intake pressure and the exhaust pressure. Furthermore, when the intake air is passed through the intercooler 5, the intake air is cooled, so that the cooling capacity can be improved.

  Furthermore, a sixth embodiment will be described with reference to FIG. In the sixth embodiment, an auxiliary compressor 22 as an auxiliary compressor is provided in the middle of the intake air introduction passage 21 as shown by a two-dot chain line in the figure. The auxiliary compressor 22 may be an electric motor, for example. Thereby, even in the case of an engine having a high exhaust pressure, cold air having a pressure higher than that can be introduced, and the exhaust gas temperature can be further effectively reduced.

  Although the temperature sensor 17 in the second embodiment is not shown in the drawings of the first, third, fourth, fifth, and sixth embodiments, the introduction of cold air is controlled based on the exhaust gas temperature. Needless to say, the temperature sensor 17 can also be provided in each embodiment.

  In the above embodiment, the turbocharger turbine has been described. However, the turbine to which the present invention is applied is not limited to the turbocharger turbine, and the turbo compound that transmits the output of the turbine to the crankshaft or the turbine It can also be applied to structures that transmit output to a generator.

4b Turbine 7a Exhaust passage 8 Catalyst 15 Cooling gas introduction port 17 Exhaust gas temperature detection means V7 Cooling gas introduction control means 18 Foreign matter removal device 3 Air cleaner

Claims (7)

Exhaust gas of an internal combustion engine having a turbine provided in an exhaust passage so as to be rotated by energy of exhaust gas of the internal combustion engine, and a catalyst provided upstream of the turbine in the exhaust passage to purify the exhaust gas In the device
An exhaust system for an internal combustion engine, characterized in that a cooling gas introduction port for introducing a cooling gas having a temperature lower than that of the exhaust gas is provided downstream of the catalyst and upstream of the turbine in the exhaust passage.   Exhaust gas temperature detecting means for detecting an exhaust gas temperature in the turbine, and cooling for introducing the cooling gas into the cooling gas inlet when the exhaust gas temperature detected by the exhaust gas temperature detecting means exceeds a predetermined value The exhaust system for an internal combustion engine according to claim 1, further comprising gas introduction control means.   3. The foreign matter removing device for removing the foreign matter mixed in the exhaust gas is provided on the downstream side of the catalyst and the upstream side of the turbine in the exhaust passage. Exhaust device for internal combustion engine. An air cleaner provided in an intake passage of the internal combustion engine;
The exhaust system for an internal combustion engine according to any one of claims 1 to 3, wherein a downstream side of the air cleaner in the intake passage communicates with the cooling gas introduction port. A compressor that compresses intake air by rotating integrally with the turbine is provided in the intake passage of the internal combustion engine,
A cooler for cooling the compressed intake air is provided on the downstream side of the compressor in the intake passage,
The exhaust device for an internal combustion engine according to any one of claims 1 to 4, wherein the cooling gas is taken out from a downstream side of the cooler in the intake passage.   The exhaust device for an internal combustion engine according to any one of claims 1 to 5, further comprising an auxiliary compressor that pumps the cooling gas to the cooling gas introduction port. An exhaust gas recirculation passage for recirculating the exhaust gas to the intake passage by communicating the downstream side of the catalyst in the exhaust passage and the upstream side of the turbine and the intake passage of the internal combustion engine;
The exhaust gas of an internal combustion engine according to any one of claims 1 to 6, wherein the cooling gas introduction port is provided on the downstream side of the connection port with the exhaust gas recirculation passage in the exhaust passage. apparatus.

Images