JP2007205326A - Exhaust bypass device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust bypass device of an internal combustion engine in which the mal-function of an opening and closing means is easily detected. <P>SOLUTION: A bypass passage 25 is connected to a main passage 21 in which a first catalyst 31 is installed. A bypass valve 40 is installed in the bypass passage 25. A floor temperature detection sensor 51 is fitted to the first catalyst 31. When the bypass valve 40 is controlled to open during the operation of the internal combustion engine 1, a change ΔT in floor temperature is calculated based on the floor temperature T of the first catalyst 31 detected by the floor temperature detection sensor 51. The change ΔT in floor temperature is compared with a determination reference temperature t. By this comparison, the bypass valve 40 is determined whether it is defective or not. Since one floor temperature detection sensor 51 is installed as the detection means for detecting a change in the state when the bypass valve 40 is opened and closed, the mal-function of the bypass valve 40 can be detected by only the floor temperature T detected by the floor temperature detection sensor 51. Consequently, the mal-function of the bypass valve 40 as the opening and closing means can be easily detected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas bypass device for an internal combustion engine. In particular, the present invention relates to an exhaust gas bypass device for an internal combustion engine that can detect a malfunction in an operating portion.

  In some conventional internal combustion engines, two exhaust gas purification means are provided in the exhaust gas passage, and the two catalysts are selectively used according to the exhaust temperature. In this case, a main passage and a bypass passage are provided in the exhaust gas passage, and one catalyst is provided in the main passage. The other catalyst is provided downstream of the exhaust gas passage where the bypass passage is provided. Furthermore, a switching valve is provided at a branch portion between the main passage and the bypass passage, and the switching valve is switched according to the operating state of the internal combustion engine, whereby exhaust gas can be passed through either the main passage or the bypass passage. Thereby, according to the driving | running condition, the passage of the catalyst provided in a main channel | path and non-passage can be switched.

  Specifically, because the catalyst provided in the main passage is close to the internal combustion engine, the temperature is likely to rise. Therefore, when the internal combustion engine is operating at a low rotation and low load, the catalyst provided in the main passage Pass through. In addition, when the internal combustion engine is operating at a high rotation and high load, the temperature of the catalyst provided in the main passage may become too high, so the switching valve is switched and the exhaust gas passes through the bypass passage. The catalyst inside is not allowed to pass, and only the catalyst located on the downstream side of the bypass passage is allowed to pass. As a result, the exhaust gas purification performance by the catalyst can be improved.

  However, since the exhaust gas flows through the main passage or the bypass passage by switching the switching valve, if a malfunction occurs in the switching valve, the exhaust gas cannot flow through the desired passage, causing various problems. May occur. The cause of the malfunction of the switching valve is, for example, the switching valve sticking due to thermal deformation, the inclusion of foreign matter due to carbon or muddy water, the abnormality of the operating means that operates the switching valve, etc. There is a risk of malfunction of the valve. When exhaust gas can only flow through the main passage due to such a malfunction of the switching valve, a catalyst provided in the main passage when the internal combustion engine is operating at a high rotation and high load. There is a possibility that the temperature becomes too high and heat deterioration occurs. In addition, when exhaust gas can only flow through the bypass passage due to a malfunction of the switching valve, the exhaust gas causes the catalyst in the main passage to pass through when the internal combustion engine is operating at a low rotation and low load. Since it does not pass, there is a possibility that exhaust gas cannot be sufficiently purified, and in this case, there is a possibility that emission may deteriorate.

  For this reason, some conventional exhaust bypass devices detect a malfunction of the switching valve. For example, in the exhaust bypass device described in Patent Document 1, exhaust temperature sensors are provided on the downstream side of the bypass passage and the portion where the bypass passage is provided. When switching the passage through which the exhaust gas flows by switching the switching valve, the temperature difference between the exhaust gas temperatures detected by the two exhaust temperature sensors differs depending on whether the exhaust gas flows through the main passage or the bypass passage. . Therefore, by comparing the temperature difference with the instruction for the switching valve, it is possible to detect the malfunction of the switching valve, and it is possible to detect the malfunction of the switching valve without using special parts.

JP 2005-248736 A

  However, in the case of using the exhaust temperature sensor, it is necessary to provide two exhaust temperature sensors as in the exhaust bypass device described in Patent Document 1, which increases the number of parts and the manufacturing process. There is a risk of an increase. Further, when two exhaust temperature sensors are provided, it is necessary to process two types of exhaust temperatures detected by the respective exhaust temperature sensors, which may make control difficult.

  The present invention has been made in view of the above, and an object of the present invention is to provide an exhaust bypass device for an internal combustion engine that can easily detect a malfunction of an opening / closing means.

  In order to solve the above-described problems and achieve the object, an exhaust bypass device for an internal combustion engine according to the present invention has a first passage through which exhaust gas of the internal combustion engine flows, and further, the exhaust gas flows at both ends. An exhaust passage having a second passage connected to the first passage, a purification means disposed in the first passage and purifying the exhaust gas, and a bed temperature which is a temperature of the purification means is detected. A bed temperature detecting means, an opening / closing means disposed in the second passage and capable of opening and closing in the second passage, and being connected to the opening / closing means and controlling opening / closing of the opening / closing means. And a change in the bed temperature when the control means controls the opening / closing means from a closed state to an open state is greater than a judgment reference temperature that is a criterion for whether the opening / closing means is abnormal. Before Closing means, characterized in that it comprises, an abnormality determination means for determining is abnormal.

  In the present invention, a change in the bed temperature when the bed temperature detecting means for detecting the bed temperature, which is the temperature of the purifying means disposed in the first passage, is provided and the opening / closing means is controlled from the closed state to the open state is provided. Is greater than the determination reference temperature, it is determined that the opening / closing means is abnormal. That is, as a detecting means for detecting a change in state when the opening / closing means is opened / closed, one bed temperature detecting means is provided, and the abnormality of the opening / closing means is determined based on the bed temperature detected by the bed temperature detecting means. Therefore, the malfunction of the opening / closing means is detected only by the bed temperature detected by one bed temperature detecting means. As a result, it is possible to easily detect a malfunction of the opening / closing means.

  In the exhaust gas bypass device for an internal combustion engine according to the present invention, the internal combustion engine further includes fuel supply means for supplying fuel to the internal combustion engine, and the control means is fuel supplied by the fuel supply means. Control is performed to open the opening / closing means when supply is stopped.

  In the present invention, the opening / closing means is controlled to be opened when the fuel supply by the fuel supply means is stopped. The exhaust gas flows into the first passage when the opening / closing means is closed, and flows into the second passage when the opening / closing means is opened. The lean gas, which is the exhaust gas when the fuel is stopped, flows into the first passage, and the lean gas is the first. If the purification means provided in the passage is passed, the purification means may be deteriorated. For this reason, when the fuel supply is stopped, the opening / closing means can be opened to allow the lean gas to flow into the second passage, thereby suppressing the deterioration of the purification means, and the malfunction of the opening / closing means when the fuel supply is stopped is detected. By doing so, deterioration of the purifying means can be suppressed more reliably. As a result, it is possible to easily detect a malfunction of the opening / closing means and to more reliably suppress the deterioration of the purification means.

  The exhaust gas bypass device for an internal combustion engine according to the present invention is characterized in that the control means controls the opening / closing means to be opened when the internal combustion engine is operating at a high rotational speed and a high load.

  In the present invention, the opening / closing means is controlled to be opened when the internal combustion engine is operating at a high rotation and high load. When the internal combustion engine is operated at a high rotational speed and a high load, the exhaust gas becomes high temperature. However, if this high-temperature exhaust gas passes through the purification means provided in the first passage, the purification means may be deteriorated by heat. There is. For this reason, when the internal combustion engine is operated at a high rotation and high load, the deterioration of the purification means can be suppressed by opening the opening / closing means and allowing the high-temperature exhaust gas to flow through the second passage. By detecting a malfunction of the opening / closing means during operation at a high rotational load, it is possible to more reliably suppress deterioration of the purification means. As a result, it is possible to easily detect a malfunction of the opening / closing means and to more reliably suppress the deterioration of the purification means.

  Moreover, the exhaust gas bypass device for an internal combustion engine according to the present invention is characterized in that the determination reference temperature changes according to an operating state of the internal combustion engine.

  In this invention, since the temperature of the exhaust gas discharged from the internal combustion engine changes according to the operating state of the internal combustion engine, the determination reference temperature is changed according to the operating state of the internal combustion engine. That is, the abnormality determination means determines that the opening / closing means is abnormal when the change in the bed temperature when the opening / closing means is controlled from the closed state to the open state is larger than the determination reference temperature. The change may vary depending on the bed temperature when the opening / closing means is closed. For this reason, it is possible to more accurately determine the abnormality of the opening / closing means by changing the determination reference temperature according to the operating state of the internal combustion engine. As a result, it is possible to detect the malfunction of the opening / closing means more reliably.

  The exhaust gas bypass device for an internal combustion engine according to the present invention has an effect that an operation failure of the opening / closing means can be easily detected.

  Embodiments of an exhaust gas bypass device for an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  FIG. 1 is a schematic view of an internal combustion engine provided with an exhaust bypass device according to an embodiment of the present invention. An internal combustion engine 1 shown in FIG. 1 has a cylinder head 2 and a cylinder block 3 in which a combustion chamber 5 is formed. The cylinder block 3 is provided in a reciprocating manner in the cylinder block 3. A piston 4 is provided. The combustion chamber 5 is located on the top dead center side of the piston 4, and an intake pipe 10 that is an intake passage and an exhaust pipe 11 that is an exhaust passage are connected to the combustion chamber 5. Among these, an intake valve 12 is provided at a connection portion between the intake pipe 10 and the combustion chamber 5, and an exhaust valve 13 is provided at a connection portion between the exhaust pipe 11 and the combustion chamber 5. The combustion chamber 5 is provided with a spark plug 6.

  Further, the exhaust pipe 11 constitutes a part of the exhaust bypass device 15, and the exhaust pipe 11 is in the same manner as the main passage 21 that is a first passage through which exhaust gas during operation of the internal combustion engine 1 flows. And a bypass passage 25 that is a second passage through which exhaust gas flows when the engine 1 is operated. The main passage 21 and the bypass passage 25 are further connected to each other after the exhaust pipe 11 branches at a predetermined position from the internal combustion engine 1 in the downstream direction of the exhaust gas. Specifically, the bypass passage 25 is connected to the main passage 21 at both ends thereof, and the end portion of the both ends located on the upstream side of the flow of exhaust gas flowing through the main passage 21 is the upstream connection portion 26. Thus, the end located on the downstream side of the flow of the exhaust gas flowing in the main passage 21 becomes the downstream connection portion 27, and the upstream connection portion 26 and the downstream connection portion 27 are connected to the main passage 21.

  In other words, the upstream connection portion 26 and the downstream connection portion 27 are in the direction in which the main passage 21 is formed or the direction of the exhaust gas flowing through the main passage 21, and the upstream connection portion 26 is the downstream connection portion 27. The downstream connection part 27 is located farther from the internal combustion engine 1 than the upstream connection part 26.

  The bypass passage 25 is provided with a bypass valve 40 which is an opening / closing means. The bypass valve 40 is provided in the bypass passage 25, and is more downstream in the flow direction of the exhaust gas than the upstream connection portion 26 in the bypass passage 25 and more exhaust gas than the downstream connection portion 27. It is provided upstream in the flow direction. The bypass valve 40 is connected to an actuator 41 that operates by changing the internal pressure. The bypass valve 40 can be operated by the actuator 41. Further, the bypass valve 40 is provided so as to be able to open and close the bypass passage 25 by being operated by the actuator 41 in this way.

  In this way, the actuator 41 connected to the bypass valve 40 is connected to a control tube 46 that is a tube through which air passes, and is located on the side of the control tube 46 that is connected to the actuator 41. A VSV (Vacuum Switching Valve) 42 is connected to the end opposite to the end. The VSV 42 is connected to a negative pressure tank 43 provided so that the inner air pressure can be kept lower than the atmospheric pressure. The negative pressure tank 43 is connected to the intake pipe 10 by a negative pressure tube 47. Yes. Thus, since the negative pressure tank 43 is connected to the intake pipe 10, the inner air pressure becomes the same level as the air pressure in the intake pipe 10. The VSV 42 is provided so as to be able to switch between communication between the control tube 46 and the negative pressure tank 43, or communication between the control tube 46 and the outside air, that is, the atmosphere.

  The exhaust pipe 11 is provided with a catalyst 30 which is a purifying means for purifying exhaust gas on the inner side. Of these, the main passage 21 is provided with a catalyst 30 for purifying exhaust gas on the inner side. A first catalyst 31 is disposed. Specifically, the first catalyst 31 is located between the upstream connection portion 26 and the downstream connection portion 27 in the main passage 21. Further, the second catalyst 32 of the catalyst 30 is disposed in the exhaust pipe 11 on the downstream side of the downstream connection portion 27 in the flow direction of the exhaust gas flowing through the exhaust pipe 11. The first catalyst 31 and the second catalyst 32 are so-called removing three substances of hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) at the same time by an oxidation / reduction reaction. It is a three-way catalyst. The first catalyst 31 and the second catalyst 32 have the same purification temperature, but the exhaust gas dissipates heat in the flow direction and has a temperature gradient, so that the flow of exhaust gas is higher than that of the second catalyst 32. The first catalyst 31 located on the upstream side in the direction is exposed to a high temperature.

  In this way, the first catalyst 31 disposed in the main passage 21 is provided with a bed temperature detection sensor 51 which is a bed temperature detection means for detecting the bed temperature which is the temperature of the first catalyst 31. The intake pipe 10 is provided with an injector 50 which is a fuel supply means for injecting fuel into the intake pipe 10. The injector 50 injects fuel into the intake pipe 10 to thereby cause an internal combustion engine. 1 is provided so that fuel can be supplied.

  The bed temperature detection sensor 51, the injector 50, and the VSV 42 are all connected to an ECU (Electronic Control Unit) 60 that controls each part of a vehicle (not shown) on which the internal combustion engine 1 is mounted.

  The ECU 60 is provided with a processing unit 61, a storage unit 67, and an input / output unit 68, which are connected to each other and can exchange signals with each other. The bed temperature detection sensor 51, the injector 50, and the VSV 42 connected to the ECU 60 are connected to an input / output unit 68. The input / output unit 68 inputs and outputs signals to and from these sensors and the like. . The storage unit 67 stores a computer program for controlling the exhaust bypass device 15 of the internal combustion engine 1 according to the present invention. The storage unit 67 is a hard disk device, a magneto-optical disk device, a non-volatile memory such as a flash memory (a storage medium that can be read only such as a CD-ROM), or a RAM (Random Access Memory). A volatile memory or a combination thereof can be used.

  The processing unit 61 includes a memory and a CPU (Central Processing Unit), and at least the bed temperature acquisition unit 62 that acquires the bed temperature of the first catalyst 31 and the bed temperature earned by the bed temperature acquisition unit 62. A bed temperature change calculation unit 63 that calculates the change in the temperature of the gas flow, and an abnormality determination unit 64 that is an abnormality determination unit that determines whether or not the bypass valve 40 is abnormal.

  The control of the bypass valve 40 of the exhaust bypass device 15 is performed by the processing unit 61 using the computer program to execute the computer program based on the detection results by sensors (not shown) provided in each part of the vehicle such as the bed temperature detection sensor 51. The bypass valve 40 is controlled by reading into the memory incorporated in the 61 and calculating and operating the VSV 42 according to the calculation result. At that time, the processing unit 61 appropriately stores a numerical value in the middle of the calculation in the storage unit 67 and takes out the stored numerical value to execute the calculation. In addition, when controlling the exhaust bypass device 15 in this way, it may be controlled by dedicated hardware different from the ECU 60 instead of the computer program. The ECU 60, the VSV 42 connected to the ECU 60, and the actuator 41 connected to the bypass valve 40 are provided as control means for controlling the opening and closing of the bypass valve 40 and operating the bypass valve 40.

  The exhaust gas bypass device 15 of the internal combustion engine 1 according to this embodiment is configured as described above, and the operation thereof will be described below. When the internal combustion engine 1 is operated, fuel is injected into the intake pipe 10 from an injector 50 provided in the intake pipe 10, whereby the air and fuel flowing in the intake pipe 10 are mixed, and the fuel and the fuel are mixed in the intake pipe 10. A mixture with air is created. This air-fuel mixture enters the combustion chamber 5 from the intake pipe 10 when the intake valve 12 is opened. The air-fuel mixture that has entered the combustion chamber 5 is ignited when the ignition plug 6 is ignited, and burns in the combustion chamber 5. Thus, the internal combustion engine 1 is operated by burning the fuel in the combustion chamber 5 and pushing down the piston 4. The gas after combustion of the fuel becomes exhaust gas, flows in the direction of the exhaust pipe 11 when the exhaust valve 13 is opened, and is discharged from the combustion chamber 5.

  Further, when the internal combustion engine 1 is operated in this way, since the air-fuel mixture is sucked into the combustion chamber 5 from the intake pipe 10, the air pressure in the intake pipe 10 becomes lower than the atmospheric pressure. That is, the inside of the intake pipe 10 has a negative pressure. Therefore, the air in the negative pressure tank 43 connected to the intake pipe 10 by the negative pressure tube 47 flows in the direction of the intake pipe 10, and the air pressure in the negative pressure tank 43 is about the same as the pressure in the intake pipe 10. Pressure. Thereby, the negative pressure tank 43 has a negative pressure. Further, the negative pressure tank 43 is connected to the VSV 42, but the VSV 42 can switch between communicating the control tube 46 and the negative pressure tank 43, or communicating the control tube 46 and the atmosphere. It is provided as follows.

  Since this control tube 46 is connected to the actuator 41, the atmospheric pressure or the negative pressure can be transmitted to the actuator 41 by switching the VSV 42. That is, when the VSV 42 is switched so that the control tube 46 communicates with the inside of the negative pressure tank 43, the negative pressure can be transmitted to the actuator 41, and the VSV 42 is switched so that the control tube 46 communicates with the atmosphere. If this happens, the atmospheric pressure can be transmitted to the actuator 41. Thus, by transmitting atmospheric pressure or negative pressure, the actuator 41 operates, and the bypass valve 40 connected to the actuator 41 also operates. That is, the bypass valve 40 can be operated by switching the VSV 42.

  During operation of the internal combustion engine 1, exhaust gas flows through the exhaust pipe 11, but immediately after the internal combustion engine 1 is started or when the internal combustion engine 1 is operated at a low rotation and low load, a signal is sent from the ECU 60 to the VSV 42, The bypass valve 40 is closed by switching the VSV 42. Thereby, the inside of the bypass passage 25 is closed, but in this state, the exhaust gas does not flow into the bypass passage 25 but flows into the main passage 21 from the vicinity of the upstream connection portion 26. Since the first catalyst 31 is provided in the main passage 21, the exhaust gas flowing in the main passage 21 passes through the first catalyst 31, and the exhaust gas is purified by the first catalyst 31. The exhaust gas that has passed through the first catalyst 31 further flows in the direction of the second catalyst 32 that is located downstream of the downstream connection portion 27 in the flow direction of the exhaust gas. For this reason, the exhaust gas passes through the second catalyst 32 and is purified by the second catalyst 32. In the state where the bypass valve 40 is closed, the exhaust gas flows in the main passage 21 in this way, but the temperature of the exhaust gas is low during the warm-up operation of the internal combustion engine 1 or during a low rotation and low load. Therefore, by closing the bypass valve 40, the temperature of the exhaust gas is lowered even when the exhaust gas passes through the first catalyst 31 that is provided in the main passage 21 and is easily exposed to high-temperature exhaust gas. Therefore, it can suppress that the temperature of the 1st catalyst 31 becomes high too much.

  Further, when the internal combustion engine 1 is operated at a high rotation and high load, a signal is sent from the ECU 60 to the VSV 42 to switch the VSV 42 and open the bypass valve 40. When the inside of the bypass passage 25 is opened by opening the bypass valve 40, the exhaust gas flows into the bypass passage 25 from the vicinity of the upstream connection portion 26. In this case, almost all the exhaust gas flowing in the exhaust pipe 11 flows into the bypass passage 25, and therefore does not flow into the main passage 21. Thus, in a state where the bypass valve 40 is opened, the exhaust gas does not flow into the main passage 21, so the exhaust gas flows in the direction of the second catalyst 32 without passing through the first catalyst 31, and the second catalyst 32. And is purified only by the second catalyst 32. Further, when the internal combustion engine 1 is operated at a high rotation and high load, the temperature of the exhaust gas becomes high, but the exhaust gas flows in the downstream direction while dissipating heat, and the second catalyst 32 is in the direction of the exhaust gas flow. It is located downstream of the first catalyst 31. For this reason, when the high-temperature exhaust gas passes through the second catalyst 32, the temperature of the exhaust gas is lowered, so that the temperature of the second catalyst 32 is suppressed from becoming too high.

  As described above, the internal combustion engine 1 is operated at a low rotation speed or a high rotation speed. In this process, that is, at the time of acceleration or deceleration, the amount of fuel injected from the injector 50 into the intake pipe 10 is changed. . Specifically, when the internal combustion engine 1 is accelerated, the amount of fuel injected from the injector 50 is increased. As a result, the amount of fuel sucked into the internal combustion engine 1 increases, and the force that pushes down the piston 4 during combustion of the fuel increases, so the internal combustion engine 1 accelerates.

  On the other hand, when the internal combustion engine 1 is decelerated, the fuel injected from the injector 50 is reduced or the fuel injection is stopped. As a result, the fuel sucked into the internal combustion engine 1 is reduced or no fuel is supplied to the internal combustion engine 1, so that the force for pushing down the piston 4 is reduced, and the internal combustion engine 1 is decelerated.

  As described above, when the internal combustion engine 1 is decelerated, the fuel injected from the injector 50 is reduced or the fuel injection is stopped, but the internal combustion engine 1 is operated in a state where the rotational speed of the internal combustion engine 1 is higher than a predetermined rotational speed. When decelerating, the fuel injection by the injector 50 is stopped. That is, the injector 50 is in a state where the supply of fuel to the internal combustion engine 1 is stopped, and is in a so-called fuel cut state.

  During operation of the internal combustion engine 1, the fuel cut is performed in this way at the time of deceleration in a state where the rotational speed is high, but when performing the fuel cut, the bypass valve 40 is opened. Specifically, when the internal combustion engine 1 is decelerated and fuel cut is performed with the bypass valve 40 closed, a signal is sent from the ECU 60 to the VSV 42 to switch the VSV 42 and open the bypass valve 40. When the fuel cut is performed in this way, only air is sucked into the combustion chamber 5 and discharged, so that the lean gas, which is an exhaust gas having a high oxygen content, flows through the exhaust pipe 11, but the bypass valve 40 is opened. Thus, this lean gas flows through the bypass passage 25 and does not flow into the main passage 21. For this reason, the periphery of the first catalyst 31 in the main passage 21 does not become a lean atmosphere.

  Further, when the fuel cut is performed at the time of deceleration of the internal combustion engine 1 and the bypass valve 40 is opened, the bed temperature T of the first catalyst 31 when the control means such as the ECU 60 performs the control to open the bypass valve 40, This is detected by the bed temperature detection sensor 51. The bed temperature T is continuously detected while a predetermined time elapses after the control to open the bypass valve 40, and the ECU 60 calculates a bed temperature change ΔT that is a change in the bed temperature T at the predetermined time. Further, in the ECU 60, when the bed temperature change ΔT is higher than a determination reference temperature t that is a reference for determining whether or not the bypass valve 40 has an abnormality, the bypass valve 40 has an abnormality such as a malfunction. judge. The determination reference temperature t is stored in the storage unit 67 of the ECU 60.

  FIG. 2 is a flowchart showing a processing procedure of the exhaust bypass device control method according to the embodiment of the present invention. Next, a method for controlling the exhaust bypass device 15 according to the embodiment, that is, a processing procedure of the exhaust bypass device 15 will be described in detail. When the internal combustion engine 1 is operating at a low rotation and low load during operation of the internal combustion engine 1, the bypass valve 40 is closed. When the internal combustion engine 1 is decelerated in this state, the fuel cut is turned on (step ST101). Thereby, the fuel supply to the internal combustion engine 1 by the injector 50 is stopped. Next, control is performed to open the bypass valve 40 (step ST102). That is, a signal for opening the bypass valve 40 is sent from the ECU 60 to the VSV 42, and the VSV 42 is switched to open the bypass valve 40.

  Next, the bed temperature T of the first catalyst 31 in a state where the bypass valve 40 is opened is detected by the bed temperature detection sensor 51, and the detected bed temperature T is transmitted to the ECU 60 by an electric signal, and the bed temperature possessed by the ECU 60 is acquired. Obtained by the unit 62 (step ST103). As the bed temperature T, the bed temperature T in a predetermined time with the fuel cut turned on is acquired. Next, from the acquired bed temperature T, the bed temperature change calculation unit 63 included in the ECU 60 calculates a bed temperature change ΔT that is the amount of change in the bed temperature T during the acquired predetermined time (step ST104).

  Next, the abnormality determination unit 64 of the ECU 60 stores the determination reference temperature t that is stored in the storage unit 67 and serves as a reference for determining whether there is an abnormality in the bypass valve 40 and the calculated bed temperature change ΔT. Compare (step ST105). According to this comparison, when the bed temperature change ΔT is larger than the determination reference temperature t, that is, when (the determination reference temperature t <the bed temperature change ΔT), the abnormality determination unit 64 does not open the bypass valve 40. It is determined that the bypass valve 40 has a malfunction. That is, the abnormality determination unit 64 determines abnormality of the bypass valve 40 (step ST106).

  FIG. 3 is an explanatory diagram showing the relationship between the bed temperature and time when fuel cut is performed. In other words, the temperature of the exhaust gas in the fuel cut state is low because the fuel is not burned, but when the fuel valve is cut and the bypass valve 40 is opened, the low temperature exhaust gas is bypassed. Since it flows through the passage 25, it is difficult to affect the first catalyst 31. That is, by opening the bypass passage 25, the exhaust gas having a low temperature does not flow through the main passage 21, so that the first catalyst 31 is not cooled by the exhaust gas but gradually radiates heat. For this reason, as indicated by the bypass valve opening line 71 in FIG. 3, the bed temperature T of the first catalyst 31 in a state where the fuel cut is performed and the bypass valve 40 is opened gradually decreases with time.

  On the other hand, when the bypass valve 40 does not open because the bypass valve 40 is fixed while closed, the exhaust gas flows through the main passage 21 provided with the first catalyst 31, but the fuel is cut. When the exhaust gas having a low temperature flows through the main passage 21, the first catalyst 31 dissipates a large amount of heat to the exhaust gas having a low temperature, and the bed temperature T of the first catalyst 31 rapidly decreases. For this reason, as indicated by the bypass valve closing time line 72 in FIG. 3, the bed temperature T of the first catalyst 31 in a state where the fuel cut is performed and the bypass valve 40 is closed rapidly decreases as time passes.

  Accordingly, when the bed temperature T of the first catalyst 31 in the fuel cut state is significantly reduced, it can be determined that the bypass valve 40 is closed, and thus the amount of change in the bed temperature T during a predetermined time. When the bed temperature change ΔT is larger, it can be determined that the bypass valve 40 is closed. Therefore, when the control for opening the bypass valve 40 is being performed, the bed temperature change ΔT becomes large, and if (the determination reference temperature t <the bed temperature change ΔT), the bypass valve 40 has a malfunction. Can be determined. In this case, the abnormality determination unit determines abnormality of the bypass valve.

  On the other hand, when the abnormality determination unit 64 compares the determination reference temperature t with the bed temperature change ΔT, if the bed temperature change ΔT is equal to or less than the determination reference temperature t, that is, (determination reference temperature t ≧ bed temperature change ΔT ), The abnormality determination unit 64 determines that the bypass valve 40 is normal (FIG. 2, step ST107).

  The exhaust bypass device 15 of the internal combustion engine 1 described above is provided with the bed temperature detection sensor 51 that detects the bed temperature T, which is the temperature of the first catalyst 31 disposed in the main passage 21, and the bypass valve 40 is closed. The bed temperature T in the case of controlling to an open state is detected. Further, when the bed temperature change ΔT, which is a change in the bed temperature T during a predetermined time, is larger than the determination reference temperature t, the abnormality determination unit 64 determines that the bypass valve 40 is abnormal. That is, as a detecting means for detecting a change in state when the bypass valve 40 is opened and closed, one bed temperature detection sensor 51 is provided, and an abnormality of the bypass valve 40 is determined from the bed temperature T detected by the bed temperature detection sensor 51. is doing. Accordingly, the malfunction of the bypass valve 40 is detected only by the bed temperature T detected by one bed temperature detection sensor 51. As a result, it is possible to easily detect a malfunction of the bypass valve 40 which is an opening / closing means.

  Further, the bypass valve 40 is controlled to be opened when the fuel supply by the injector 50 is stopped, that is, when the fuel is cut. The exhaust gas flows into the main passage 21 when the bypass valve 40 is closed, and flows into the bypass passage 25 when the bypass valve 40 is opened. However, the lean gas that is the exhaust gas at the time of fuel cut flows into the main passage 21 and the lean gas is generated. If the first catalyst 31 provided in the main passage 21 is passed, the first catalyst 31 may be deteriorated. Specifically, the lean gas at the time of fuel cut has a high oxygen content in the exhaust gas because the fuel is not burned. For this reason, when this lean gas flows into the main passage 21 and the periphery of the first catalyst 31 is in a lean atmosphere, the first catalyst 31 may be sintered due to oxygen in the lean gas. The first catalyst 31 may be deteriorated. For this reason, at the time of fuel cut, the deterioration of the first catalyst 31 can be suppressed by opening the bypass valve 40 and flowing the lean gas into the bypass passage 25. Further, by detecting the malfunction of the bypass valve 40 at the time of fuel cut, it is possible to prevent the lean gas from continuing to flow into the main passage 21 and the atmosphere around the first catalyst 31 from becoming a lean atmosphere. Deterioration of the catalyst 31 can be suppressed. As a result, the malfunction of the bypass valve 40 can be easily detected, and the deterioration of the first catalyst 31 can be more reliably suppressed.

  FIG. 4 is an explanatory view according to a modification of the exhaust bypass device according to the embodiment, and is an explanatory view showing a relationship between the bed temperature and time at the time of high rotation and high load. In the exhaust bypass device 15 described above, the bed temperature T of the first catalyst 31 at the time of fuel cut is detected, and the bed temperature change ΔT of the bed temperature T is compared with the judgment reference temperature t. The bed temperature T compared with the temperature t may be a bed temperature T other than during fuel cut. For example, the bed temperature change ΔT compared with the determination reference temperature t is the bed temperature T of the first catalyst 31 when the bypass valve 40 is controlled to open when the internal combustion engine 1 is operated at a high rotation and high load. May be detected, and the bed temperature change ΔT of the bed temperature T may be compared with the determination reference temperature t. That is, the control means such as the ECU 60 controls the bypass valve 40 to be opened when the internal combustion engine 1 is operating at a high rotation and high load, and the bed temperature change ΔT of the bed temperature T of the first catalyst 31 at that time. And the determination reference temperature t may be compared.

  Specifically, the exhaust gas in a state where the internal combustion engine 1 is operated at a high rotation and a high load has a high temperature. However, when the bypass valve 40 is opened in this operation state, the exhaust gas having a high temperature is 25, the first catalyst 31 is hardly affected. That is, since the exhaust gas having a high temperature does not flow through the main passage 21 by opening the bypass passage 25, the first catalyst 31 performs only heat transfer by convection from the upstream connection portion 26 or the downstream connection portion 27. Become. For this reason, as shown by the bypass valve opening time line 76 in FIG. 4, the bed temperature T of the first catalyst 31 in a state where the internal combustion engine 1 is operated at a high rotation and high load and the bypass valve 40 is opened is a passage of time. It rises gradually with it.

  On the other hand, when the bypass valve 40 is closed and cannot be opened, the exhaust gas flows in the main passage 21 provided with the first catalyst 31, but the internal combustion engine 1 is operated at a high rotational speed and a high temperature. When high exhaust gas flows through the main passage 21, the first catalyst 31 is heated by the high exhaust gas, and the bed temperature T of the first catalyst 31 rises rapidly. For this reason, as shown by the bypass valve closing time line 77 in FIG. 4, the bed temperature T of the first catalyst 31 in a state where the internal combustion engine 1 is operated at a high rotation and high load and the bypass valve 40 is closed is time-lapsed. It rises rapidly as you go.

  As a result, when the bed temperature T of the first catalyst 31 in a state where the internal combustion engine 1 is operated at a high rotational speed and a high load is significantly increased, it can be determined that the bypass valve 40 is closed. When the bed temperature change ΔT, which is the amount of change in the bed temperature T, increases, it can be determined that the bypass valve 40 is closed. Therefore, when the control for opening the bypass valve 40 is being performed, the bed temperature change ΔT becomes large, and if (the determination reference temperature t <the bed temperature change ΔT), the bypass valve 40 has a malfunction. Can be determined. In this case, the abnormality determination unit 64 determines abnormality of the bypass valve 40. On the other hand, when the abnormality determination unit 64 compares the determination reference temperature t with the bed temperature change ΔT, if the bed temperature change ΔT is equal to or less than the determination reference temperature t, that is, (determination reference temperature t ≧ bed temperature change ΔT ), The abnormality determination unit 64 determines that the bypass valve 40 is normal as in the fuel cut.

  As described above, even when the internal combustion engine 1 is controlled to open the bypass valve 40 when operating at a high rotation and high load, it is possible to easily detect the malfunction of the bypass valve 40 and more reliably. Deterioration of the first catalyst 31 can be suppressed. That is, the exhaust gas flows into the main passage 21 when the bypass valve 40 is closed, and flows into the bypass passage 25 when the bypass valve 40 is opened. However, the exhaust gas when the internal combustion engine 1 is operating at a high rotation and high load. When the high-temperature exhaust gas is flowing into the main passage 21 and passes through the first catalyst 31 provided in the main passage 21, the temperature of the first catalyst 31 becomes too high, and there is a risk that thermal degradation will occur. For this reason, when the internal combustion engine 1 is operated at a high rotation and high load, the deterioration of the first catalyst 31 can be suppressed by opening the bypass valve 40 and allowing the high-temperature exhaust gas to flow through the bypass passage 25. Further, by detecting a malfunction of the bypass valve 40 when the internal combustion engine 1 is operating at a high rotational speed and a high load, the high temperature exhaust gas continues to flow into the main passage 21 and the first catalyst 31 is at a high temperature. Therefore, it is possible to suppress the deterioration of the first catalyst 31 more reliably. As a result, the malfunction of the bypass valve 40 can be easily detected, and the deterioration of the first catalyst 31 can be more reliably suppressed.

  Further, in the exhaust bypass device 15 described above, the determination reference temperature t is stored in the storage unit 67 in advance, but the determination reference temperature t may be changed according to the operating state of the internal combustion engine 1. That is, since the temperature of the exhaust gas discharged from the internal combustion engine 1 changes according to the operating state of the internal combustion engine 1, the determination reference temperature t may be changed according to the operating state of the internal combustion engine 1. In the abnormality determination unit 64, when the change in the bed temperature T of the first catalyst 31 when the bypass valve 40 is controlled from the closed state to the open state is larger than the determination reference temperature t, the bypass valve 40 is abnormal. Although it is determined that there is a change, the change in the bed temperature T may vary depending on the bed temperature T in a state before the bypass valve 40 is opened.

  That is, when the bed temperature T is high before the bypass valve 40 is opened, the temperature drop due to heat radiation in a state where the exhaust gas does not flow in the main passage 21 is likely to be larger than when the bed temperature T is low. . For this reason, when the determination reference temperature t is constant, the determination of the operation of the bypass valve 40 is likely to be an abnormality determination when the bed temperature T is high, and is not likely to be an abnormality determination when the bed temperature T is low. Become. For this reason, it becomes difficult to accurately determine the abnormality of the bypass valve 40. Therefore, by changing the determination reference temperature t according to the bed temperature T before the bypass valve 40 is opened, that is, according to the operating state of the internal combustion engine 1, the determination of the bypass valve 40 can be performed more accurately. Abnormality can be determined. As a result, the malfunction of the bypass valve 40 can be detected more reliably.

  In the exhaust bypass device 15 described above, the bypass valve 40 is operated using the actuator 41 or the like, but the operation of the bypass valve 40 may be performed by other than the actuator 41 or the like. Any device other than the actuator 41 or the like may be used as long as the operation of the bypass valve 40 can be reliably performed during the operation of the internal combustion engine 1.

  The first catalyst 31 provided in the main passage 21 as the purification means and the second catalyst 32 provided in the bypass passage 25 are both three-way catalysts, but the purification means is other than the three-way catalyst. But you can. For example, an adsorption means for adsorbing hydrocarbons (HC) may be used as the purification means. Even when a purification means other than the three-way catalyst is used in the main passage 21 and the bypass passage 25 of the exhaust bypass device described above, the exhaust gas can be flowed to the necessary purification means more reliably. As a result, the exhaust gas can be purified more reliably.

  As described above, the exhaust gas bypass device for an internal combustion engine according to the present invention is useful when the exhaust pipe has a bypass passage, and is particularly suitable when the exhaust pipe has a mechanism for bypassing the catalyst. .

1 is a schematic view of an internal combustion engine provided with an exhaust bypass device according to an embodiment of the present invention. It is a flowchart which shows the process sequence of the control method of the exhaust gas bypass apparatus based on the Example of this invention. It is explanatory drawing which shows the relationship between the bed temperature at the time of carrying out a fuel cut, and time. It is explanatory drawing which concerns on the modification of the exhaust_gas | exhaustion bypass apparatus which concerns on an Example, and is explanatory drawing which shows the relationship between bed temperature and time at the time of high rotation high load.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder head 3 Cylinder block 4 Piston 5 Combustion chamber 6 Spark plug 10 Intake pipe 11 Exhaust pipe 12 Intake valve 13 Exhaust valve 15 Exhaust bypass device 21 Main passage 25 Bypass path 26 Upstream connection part 27 Downstream side connection part 30 Catalyst 31 First catalyst 32 Second catalyst 40 Bypass valve 41 Actuator 42 VSV
43 Negative pressure tank 46 Control tube 47 Negative pressure tube 50 Injector 51 Bed temperature detection sensor 60 ECU
61 Processing Unit 62 Bed Temperature Acquisition Unit 63 Bed Temperature Change Calculation Unit 64 Abnormality Determination Unit 67 Storage Unit 68 Input / Output Units 71, 76 Bypass Valve Open Line 72, 77 Bypass Valve Close Line

Claims (4)

An exhaust passage having a first passage through which exhaust gas of the internal combustion engine flows, and further having a second passage through which the exhaust gas flows and connected to the first passage at both ends;
Purification means disposed in the first passage and purifying the exhaust gas;
A bed temperature detecting means for detecting a bed temperature which is the temperature of the purifying means;
An opening / closing means disposed in the second passage and provided to be capable of opening and closing the second passage;
Control means connected to the opening and closing means and controlling opening and closing of the opening and closing means;
The switching means when the change in the bed temperature when the control means is controlled from the closed state to the open state is larger than a determination reference temperature that is a criterion for whether the opening / closing means is abnormal. An abnormality determining means for determining that is abnormal;
An exhaust gas bypass device for an internal combustion engine, comprising: Furthermore, the internal combustion engine includes fuel supply means for supplying fuel to the internal combustion engine,
2. The exhaust gas bypass device for an internal combustion engine according to claim 1, wherein the control unit performs control so that the opening / closing unit is opened when fuel supply by the fuel supply unit is stopped.   3. The exhaust gas bypass device for an internal combustion engine according to claim 1, wherein the control means controls the opening / closing means to be opened when the internal combustion engine is operating at a high rotational speed and a high load.   The exhaust gas bypass device for an internal combustion engine according to any one of claims 1 to 3, wherein the determination reference temperature changes according to an operating state of the internal combustion engine.

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