JP2010185378A - Internal combustion engine with supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine with a supercharger wherein degradation of a catalyst is restrained, and which is advantageous in cost reduction. <P>SOLUTION: The internal combustion engine 1 includes: a turbocharger 5 by which exhaust energy is recovered by a turbine 5b in an exhaust passage 4 to drive a compressor 5a in an intake passage 3; and an exhaust-gas purifying catalyst 6 provided in a section downstream of the turbine 5b in the exhaust passage 4 to purify the exhaust. In the internal combustion engine 1, a bypass passage 8 and a bypass exhaust-gas purifying catalyst 9 are provided. The bypass passage 8 is provided to make a detour around the turbine 5b and the exhaust-gas purifying catalyst 6, and connect the section upstream of the turbine 5b in the exhaust passage 4 to the section downstream of the exhaust-gas purifying catalyst 6. The bypass exhaust-gas purifying catalyst 9 which is placed in the bypass passage 8 to purify the exhaust gas. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal combustion engine in which a turbine of a turbocharger and an exhaust purification catalyst are provided in an exhaust passage.

  There is known an internal combustion engine in which a turbocharger turbine is provided in an exhaust passage and an exhaust purification catalyst is provided downstream of the turbine. In such an internal combustion engine, the internal combustion engine includes a bypass passage that bypasses the turbine, and a second catalyst that is disposed in the bypass passage and has a smaller heat capacity than the first catalyst for exhaust purification provided in the exhaust passage. There is known one that selectively switches the tip of the first catalyst to either a bypass passage or a turbine in accordance with the operation state (see Patent Document 1). In addition, there is Patent Document 2 as a prior art document related to the present invention.

JP 2001-50038 A JP-A-5-321643

  As is well known, the exhaust gas that has passed through the catalyst has a high temperature due to the heat of reaction at the catalyst. On the other hand, since the exhaust gas that has passed through the turbine is cooled by the turbine, the temperature is lowered. For this reason, in the internal combustion engine of Patent Document 1, when the connection destination of the catalyst provided in the exhaust passage is switched, the temperature of the exhaust gas flowing into the catalyst may change suddenly. In this case, since the catalyst is suddenly heated or cooled, the catalyst is easily deteriorated. Further, in the internal combustion engine of Patent Document 1, since exhaust gas heated by the catalyst in the bypass passage is introduced into the catalyst in the exhaust passage, it is necessary to provide a catalyst that can withstand high-temperature exhaust in the exhaust passage. In general, the heat resistance of the catalyst improves as the amount of noble metal supported increases. For this reason, in the internal combustion engine of Patent Document 1, it is necessary to dispose a catalyst having a large amount of noble metal carried in the exhaust passage, which increases the cost.

  Accordingly, an object of the present invention is to provide a supercharged internal combustion engine that can suppress deterioration of a catalyst and is advantageous for cost reduction.

  An internal combustion engine with a supercharger according to the present invention is provided in a section downstream of the turbine in the exhaust passage and a turbocharger that recovers exhaust energy by a turbine in the exhaust passage and drives a compressor in the intake passage. In an internal combustion engine comprising an exhaust purification catalyst for purifying exhaust, a section of the exhaust passage upstream of the turbine and downstream of the exhaust purification catalyst bypasses the turbine and the exhaust purification catalyst. A bypass passage connecting the sections and a bypass exhaust purification catalyst provided in the bypass passage for purifying exhaust gas are provided.

  According to the internal combustion engine with a supercharger of the present invention, the bypass passage is connected to a section downstream of the exhaust purification catalyst in the exhaust passage, so that the exhaust gas that has passed through the bypass exhaust purification catalyst is placed downstream of the exhaust purification catalyst. Can lead. Therefore, only the exhaust gas that has passed through the turbine is guided to the exhaust purification catalyst, and only the exhaust gas that has not passed through the turbine is guided to the bypass exhaust purification catalyst. Thereby, since it can suppress that the temperature of the exhaust_gas | exhaustion which flows into each exhaust gas purification catalyst changes suddenly, degradation of each exhaust gas purification catalyst can be suppressed. In addition, since only the exhaust gas that has passed through the turbine flows into the exhaust purification catalyst in this way, it is possible to prevent high temperature exhaust gas from flowing into the exhaust purification catalyst. Therefore, the heat resistant temperature of the exhaust purification catalyst can be lowered. Therefore, the cost can be reduced. On the other hand, since the exhaust before flowing into the turbine is guided to the bypass exhaust purification catalyst, the temperature of the bypass exhaust purification catalyst can be quickly increased by this exhaust. Therefore, exhaust purification by the bypass exhaust purification catalyst can be started quickly.

  In one form of the supercharger-equipped internal combustion engine of the present invention, the exhaust passage is provided in a section between the bypass valve for opening and closing the bypass passage and the turbine and the exhaust purification catalyst in the exhaust passage. And an exhaust control valve for controlling the bypass valve and the exhaust control valve based on an operating state of the internal combustion engine, respectively. In this case, the exhaust gas can be selectively guided to either the turbine or the bypass passage by opening and closing the bypass valve and the exhaust control valve as appropriate.

  In this embodiment, the control means may close the exhaust control valve and open the bypass valve when the internal combustion engine is in a warm-up operation after a cold start (Claim 3). By closing the exhaust control valve and opening the bypass valve in this way, the entire amount of exhaust can be guided to the bypass passage, so that the temperature of the bypass exhaust purification catalyst can be quickly raised by this exhaust. Therefore, the temperature of the bypass exhaust purification catalyst can be quickly raised to a temperature range suitable for exhaust purification, and the exhaust can be purified by the bypass exhaust purification catalyst after the temperature rise. Therefore, exhaust emission when the internal combustion engine is warming up can be improved.

  The control means opens the exhaust control valve and closes the bypass valve when the rotational speed of the internal combustion engine is less than or equal to a predetermined determination value, and the rotational speed of the internal combustion engine is greater than the predetermined determination value. If it is high, both the exhaust control valve and the bypass valve may be opened (Claim 4). In this way, by controlling the exhaust control valve and the bypass valve according to the rotational speed of the internal combustion engine, it is possible to appropriately perform supercharging of the internal combustion engine according to the operating state of the internal combustion engine. Further, when the rotational speed of the internal combustion engine is higher than the determination value, the flow rate of the exhaust gas guided to the exhaust gas purification catalyst is reduced by opening the bypass valve, so that the exhaust gas purification catalyst can be prevented from being excessively heated by the exhaust gas.

  In one form of the internal combustion engine with a supercharger of the present invention, the exhaust purification catalyst and the bypass exhaust purification catalyst each carry a noble metal, and the amount of the noble metal carried on the exhaust purification catalyst is: The amount may be smaller than the amount of noble metal supported on the bypass exhaust purification catalyst. As described above, only the exhaust gas that has passed through the turbine is guided to the exhaust gas purification catalyst. Therefore, the amount of the noble metal supported in this way can be made smaller than that of the bypass exhaust purification catalyst. Moreover, the cost of the exhaust purification catalyst can be reduced by reducing the amount of noble metal in this way.

  As described above, according to the supercharged internal combustion engine of the present invention, the bypass passage is connected to the section downstream of the exhaust purification catalyst in the exhaust passage, so that the exhaust purification catalyst passes through the turbine. Only the exhaust gas that has passed through the turbine is guided to the bypass exhaust gas purification catalyst. Thereby, since it can suppress that the temperature of the exhaust_gas | exhaustion which flows into each exhaust gas purification catalyst changes suddenly, degradation of each exhaust gas purification catalyst can be suppressed. Moreover, since the heat-resistant temperature of the exhaust purification catalyst can be lowered, the cost can be reduced.

1 is a diagram schematically showing an internal combustion engine according to an embodiment of the present invention. The flowchart which shows the exhaust control routine which ECU performs. The figure which shows the relationship between the driving | running state of an engine, and the state of a waste gate valve and an exhaust control valve. The figure which shows an example of the relationship between the heat-resistant temperature of a catalyst, and the amount of noble metals which should be carry | supported by the catalyst.

  FIG. 1 schematically shows an internal combustion engine according to an embodiment of the present invention. An internal combustion engine (hereinafter sometimes referred to as an engine) 1 is a diesel engine mounted on a vehicle as a driving power source, and includes an engine body 2 provided with a plurality of cylinders (not shown), and each cylinder. Are provided with an intake passage 3 and an exhaust passage 4, respectively. The intake passage 3 is provided with a compressor 5 a of a turbocharger 5. In the exhaust passage 4, a turbine 5 b of the turbocharger 5 and an exhaust purification catalyst 6 are provided. An exhaust control valve 7 that opens and closes the exhaust passage 4 is provided in a section of the exhaust passage 4 between the turbine 5 b and the exhaust purification catalyst 6. The exhaust purification catalyst 6 is disposed close to the turbine 5b so that the distance to the turbine 5b is shortened.

  Further, the exhaust passage 4 is provided with a bypass passage 8 that connects a section upstream of the turbine 5 b of the exhaust passage 4 and a section downstream of the exhaust purification catalyst 6. By providing the bypass passage 8 in this manner, the exhaust discharged from the cylinder can be guided to the exhaust passage 4 downstream of the exhaust purification catalyst 6 by bypassing the turbine 5 b and the exhaust purification catalyst 6. The bypass passage 8 is provided with a bypass exhaust purification catalyst 9 for purifying the exhaust. The exhaust purification catalyst 6 and the bypass exhaust purification catalyst 9 each carry a noble metal. As this noble metal, platinum, palladium, rhodium or the like is supported, for example. The capacity of the exhaust purification catalyst 6 is larger than the capacity of the bypass exhaust purification catalyst 9. On the other hand, the amount of the noble metal carried on the exhaust purification catalyst 6 is smaller than the amount of the noble metal carried on the bypass exhaust purification catalyst 9. A waste gate valve 10 as a bypass valve that opens and closes the bypass passage 8 is provided at a connection position between the bypass passage 8 and a section upstream of the turbine 5 b of the exhaust passage 4.

  The operations of the exhaust control valve 7 and the waste gate valve 10 are respectively controlled by an engine control unit (ECU) 20 as a control means. The ECU 20 is configured as a well-known computer unit including a microprocessor and peripheral devices such as a RAM and a ROM necessary for its operation, and determines the operating state of the engine 1 based on output signals of various sensors provided in the engine 1. It is a well-known thing to control. The ECU 20 includes a crank angle sensor 21 that outputs a signal corresponding to the engine rotation speed (rotation speed) of the engine 1 as a sensor for detecting the operating state of the engine 1, and a signal corresponding to the coolant temperature of the engine 1. Is connected to a water temperature sensor 22 or the like. In addition to this, various sensors are connected to the ECU 20, but they are not shown.

  FIG. 2 shows an exhaust control routine that the ECU 20 repeatedly executes at a predetermined cycle during operation of the engine 1 in order to control the operations of the exhaust control valve 7 and the waste gate valve 10. In this control routine, the ECU 20 first acquires the operating state of the engine 1 in step S11. As the operating state of the engine 1, for example, the rotational speed of the engine 1, the temperature of the cooling water of the engine 1, and the like are acquired. In the next step S12, the ECU 20 determines whether or not the engine 1 is in a warm-up operation after a cold start which is a start in a state where the engine temperature is low, that is, whether or not it is in a fast idle. This determination may be made based on, for example, the temperature of the coolant of the engine 1 and the rotational speed of the engine 1. For example, when the temperature of the cooling water of the engine 1 is equal to or lower than a preset determination temperature and the rotational speed of the engine 1 is within a predetermined idling rotational speed range, it is determined that the engine 1 is in a fast idle. If it is determined that the engine 1 is in the first idle state, the process proceeds to step S13, where the ECU 20 opens the waste gate valve 10 and closes the exhaust control valve 7. Thereafter, the current control routine is terminated.

  On the other hand, if it is determined that the engine is not in the fast idle state, the process proceeds to step S14, where the ECU 20 determines whether the engine 1 is operating at a low speed. This determination may be made based on the rotational speed of the engine 1. For example, when the rotational speed of the engine 1 is equal to or less than a predetermined determination value set in advance, it is determined that the engine 1 is operating at a low speed. The determination value is set to a rotational speed that is a criterion for determining whether or not the engine 1 is operating at a low speed, and is set to a value higher than the upper limit value of the idling rotational speed range of the engine 1. When it is determined that the engine 1 is operating at low speed, the process proceeds to step S15, where the ECU 20 closes the waste gate valve 10 and opens the exhaust control valve 7. Thereafter, the current control routine is terminated.

  On the other hand, if it is determined that the engine 1 is operating at a medium or high speed, the process proceeds to step S16, where the ECU 20 opens both the waste gate valve 10 and the exhaust control valve 7. Thereafter, the current control routine is terminated.

  FIG. 3 shows the relationship between the operating state of the engine 1 and the states of the waste gate valve 10 and the exhaust control valve 7. FIG. 3 also shows an exhaust purification catalyst to which exhaust gas is guided in each operation state. As shown in this figure, in the engine 1, the exhaust is guided only to the bypass exhaust purification catalyst 9 during the first idle, and the exhaust is guided only to the exhaust purification catalyst 6 during the low speed operation. During the middle / high speed operation of the engine 1, the exhaust is guided to both the exhaust purification catalyst 6 and the bypass exhaust purification catalyst 9.

  According to the engine 1 of this embodiment, since the bypass passage 8 is connected to the section downstream of the exhaust purification catalyst 6 in the exhaust passage 4, the exhaust gas that has passed through the bypass exhaust purification catalyst 9 is downstream of the exhaust purification catalyst 6. Led. Therefore, only the exhaust gas that has passed through the turbine 5b can be guided to the exhaust purification catalyst 6, and only the exhaust gas that has not passed through the turbine 5b can be guided to the bypass exhaust purification catalyst 9. Thereby, since it can suppress that the temperature of the exhaust gas which flows into each exhaust purification catalyst 6 and 9 changes suddenly, degradation of each exhaust purification catalyst 6 and 9 can be suppressed.

  In the engine 1 of this embodiment, only the exhaust gas that has passed through the turbine 5b is guided to the exhaust purification catalyst 6. Therefore, the heat resistance temperature of the exhaust purification catalyst 6 can be made lower than the heat resistance temperature of the bypass exhaust purification catalyst 9. FIG. 4 shows an example of the relationship between the heat resistant temperature of the catalyst and the amount of noble metal to be supported on the catalyst. 4 represents the heat resistance temperature of the exhaust purification catalyst 6, and the temperature T2 represents the heat resistance temperature of the bypass exhaust purification catalyst 9. As shown in this figure, in order to increase the heat-resistant temperature of the catalyst, it is necessary to carry more noble metal. Therefore, the higher the heat-resistant temperature, the higher the cost. As described above, the heat resistance temperature of the exhaust purification catalyst 6 can be lower than the heat resistance temperature of the bypass exhaust purification catalyst 9. Therefore, the amount of noble metal to be carried on the exhaust purification catalyst 6 can be reduced as compared with the bypass exhaust purification catalyst 9. Therefore, the cost can be reduced.

  Further, according to the engine 1 of this embodiment, the exhaust control valve 7 is closed and the waste gate valve 10 is opened during the first idle, so that almost the entire amount of exhaust discharged from the cylinder is guided to the bypass exhaust purification catalyst 9. . Therefore, the bypass exhaust purification catalyst 9 can be quickly heated and activated by high-temperature exhaust. As a result, exhaust emission during the first idle can be improved. On the other hand, since the exhaust control valve 7 is opened and the waste gate valve 10 is closed during low-speed operation, almost the entire amount of exhaust discharged from the cylinder can be introduced into the turbine 5b. Therefore, exhaust energy can be sufficiently recovered, and the engine 1 can be appropriately supercharged with this exhaust energy. Further, during the middle / high speed operation, both the exhaust control valve 7 and the waste gate valve 10 are opened, so that the exhaust can be purified using both the exhaust purification catalyst 6 and the bypass exhaust purification catalyst 9.

  The present invention is not limited to the above-described form and can be implemented in various forms. For example, the internal combustion engine to which the present invention is applied is not limited to a diesel engine, but may be various internal combustion engines using gasoline or other fuels. Whether or not the internal combustion engine is in the first idle state may be determined by referring to the temperature of the oil instead of the temperature of the cooling water.

  The exhaust control valve and the waste gate valve may be provided with a valve whose opening degree can be adjusted. In this case, the opening degree of the exhaust control valve and the waste gate valve may be appropriately adjusted according to the operating state of the engine. For example, after the end of the first idle operation, the opening degree of these valves is adjusted so that the exhaust control valve is gradually opened and the waste gate valve is gradually closed. By adjusting the opening degree in this way, for example, the rotational speed of the turbine can be gradually increased, so that fluctuations in the rotational speed of the internal combustion engine can be suppressed.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Intake passage 4 Exhaust passage 5 Turbocharger 5a Compressor 5b Turbine 6 Exhaust purification catalyst 7 Exhaust control valve 8 Bypass passage 9 Bypass exhaust purification catalyst 10 Waste gate valve (bypass valve)
20 Engine control unit (control means)

Claims (5)

A turbocharger that recovers exhaust energy by a turbine in the exhaust passage and drives a compressor in the intake passage; and an exhaust purification catalyst that is provided in a section downstream of the turbine in the exhaust passage and purifies the exhaust. In internal combustion engines
A bypass passage that bypasses the turbine and the exhaust purification catalyst and connects a section upstream of the turbine and a section downstream of the exhaust purification catalyst in the exhaust passage, and is provided in the bypass passage. An internal combustion engine with a supercharger, comprising: a bypass exhaust purification catalyst that purifies exhaust gas.   Based on a bypass valve that opens and closes the bypass passage, an exhaust control valve that is provided in a section of the exhaust passage between the turbine and the exhaust purification catalyst, and that opens and closes the exhaust passage, and an operating state of the internal combustion engine The supercharged internal combustion engine according to claim 1, further comprising control means for controlling the bypass valve and the exhaust control valve, respectively.   The internal combustion engine with a supercharger according to claim 2, wherein the control means closes the exhaust control valve and opens the bypass valve when the internal combustion engine is in a warm-up operation after a cold start.   The control means opens the exhaust control valve and closes the bypass valve when the rotational speed of the internal combustion engine is less than or equal to a predetermined determination value, and when the rotational speed of the internal combustion engine is higher than the predetermined determination value The internal combustion engine with a supercharger according to claim 2 or 3, wherein both the exhaust control valve and the bypass valve are opened. The exhaust purification catalyst and the bypass exhaust purification catalyst each carry a noble metal,
The internal combustion engine with a supercharger according to any one of claims 1 to 4, wherein an amount of the noble metal carried on the exhaust purification catalyst is smaller than an amount of the noble metal carried on the bypass exhaust purification catalyst.

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