JP2007224790A - Catalyst bypass device - Google Patents

Abstract

A catalyst bypass device capable of suppressing the frequency of opening and closing a valve is provided.
SOLUTION: A first exhaust passage 2 that communicates an internal combustion engine 100 and a main catalyst 120, a second exhaust passage 3 that has both end portions 31 and 32 communicate with the first exhaust passage 2, and a second exhaust passage 3. An auxiliary catalyst 4 that is disposed and purifies the exhaust gas that has flowed into the second exhaust passage 3, and is disposed in the first exhaust passage 2, and passes through the first exhaust passage 2 by closing the first exhaust passage 2. A valve 5 for causing the exhaust gas to flow into the second exhaust passage 3, an actuator 6 as a valve opening / closing means for opening and closing the valve 5, a temperature sensor 7 as a temperature detection means for detecting the temperature of the auxiliary catalyst 4, and detection When the detected temperature is equal to or higher than the valve opening temperature, the valve 6 is opened by the actuator 6. When the detected temperature is lower than the valve closing temperature that is a predetermined temperature lower than the valve opening temperature, the valve 6 is closed by the actuator 6. Valve open And a is a control unit ECU 8.
[Selection] Figure 1

Description

  The present invention relates to a catalyst bypass device, and more particularly to a catalyst bypass device that purifies exhaust gas exhausted from an internal combustion engine by an auxiliary catalyst when the purification capability of a main catalyst is low.

Exhaust gas exhausted from internal combustion engines such as gasoline engines and diesel engines mounted on vehicles such as passenger cars and trucks contains various harmful substances. This harmful substance is mainly carbon monoxide (CO), unburned hydrocarbon (HC), nitrided oxide (NO _x ) and the like. Release of these harmful substances to the atmosphere will adversely affect the human body and pollute the natural environment, and the amount of harmful substances that can be released to the atmosphere is regulated by a certain amount. In general, the amount of harmful substances contained in the exhaust gas exhausted from the internal combustion engine is reduced to the atmosphere by purifying the exhaust gas by a catalyst disposed in the exhaust path of the internal combustion engine.

  Conventionally, as shown in Patent Document 1, there is one in which an exhaust bypass device (catalyst bypass device) is provided in an exhaust path of an internal combustion engine. This exhaust bypass device is disposed between an internal combustion engine and a rear catalyst (main catalyst) through which exhaust gas always passes. The exhaust bypass device includes a front catalyst (auxiliary catalyst) through which exhaust gas passes according to the operating state of the internal combustion engine, a switching valve (valve), and an actuator (valve opening / closing means) that operates the switching valve. In this exhaust bypass device, when the switching valve opens the bypass passage and closes the front catalyst side passage by the actuator, the exhaust gas exhausted from the internal combustion engine flows directly into the rear catalyst. On the other hand, when the switching valve closes the bypass passage and opens the passage on the front catalyst side by the actuator, this exhaust gas flows into the rear catalyst via the front catalyst.

  Here, in the conventional exhaust bypass device shown in Patent Document 1, when the temperature of the exhaust gas is low and the purification capacity of the rear catalyst is low, the exhaust gas is caused to flow into the front catalyst and purified to some extent by the front catalyst. Let it flow into the rear catalyst. Further, this exhaust bypass device allows the exhaust gas to flow directly into the rear catalyst without passing through the front catalyst when the internal combustion engine is operating at a high rotation and high load.

Japanese Patent Laid-Open No. 10-8945

  By the way, in the conventional catalyst bypass device including the above-mentioned Patent Document 1, the operation of the valve, that is, the opening / closing timing is usually performed based on the temperature of the auxiliary catalyst. For example, a temperature sensor that detects the temperature of the auxiliary catalyst is provided, and when the temperature of the auxiliary catalyst detected by the temperature sensor exceeds a predetermined temperature (for example, 700 °), the valve is opened by the valve opening / closing means. The exhaust gas is caused to flow directly into the main catalyst without passing through the auxiliary catalyst. That is, the valve is opened when the temperature is higher than the predetermined temperature, and the valve is closed when the temperature is lower than the predetermined temperature.

  However, as described above, when the opening / closing operation of the valve is performed at a predetermined temperature, that is, the threshold value, the opening / closing frequency of the valve increases when the temperature of the auxiliary catalyst rises and falls across the predetermined temperature. Therefore, the opening / closing operation of the valve by the valve opening / closing means becomes frequent, and there is a possibility that a delay occurs in the opening / closing operation of the valve by the bubble opening / closing means. Further, when the valve opening / closing means performs the valve opening / closing operation with negative pressure as described above, the negative pressure is consumed every time the valve opening / closing operation is performed. There is a possibility that the opening / closing operation of the valve by the opening / closing means cannot be performed.

  Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a catalyst bypass device that can suppress the frequency of opening and closing of the valve.

  In order to solve the above-described problems and achieve the object, in the present invention, a first exhaust passage that communicates an internal combustion engine and a main catalyst that purifies exhaust gas exhausted from the internal combustion engine, and both end portions thereof are the first exhaust passage. A second exhaust passage communicating with one exhaust passage, an auxiliary catalyst disposed in the second exhaust passage for purifying exhaust gas flowing into the second exhaust passage, disposed in the first exhaust passage, and the first exhaust passage. By closing the exhaust passage, a valve for allowing the exhaust gas passing through the first exhaust passage to flow into the second exhaust passage, valve opening / closing means for opening / closing the valve, and temperature detection for detecting the temperature of the auxiliary catalyst And when the detected temperature is equal to or higher than the valve opening temperature, the valve is opened by the valve opening / closing means, and when the detected temperature is equal to or lower than the valve closing temperature which is lower than the valve opening temperature by a predetermined temperature, Valve opening / closing Characterized in that it and a valve opening and closing control means for closing the valve by the step.

  According to this invention, the valve opening temperature that is the threshold value for opening the valve by the valve opening and closing means is different from the valve closing temperature that is the threshold value for closing the valve by the valve opening and closing means. In other words, after the detected temperature of the auxiliary catalyst becomes equal to or higher than the valve opening temperature and the valve is opened by the valve opening / closing means, the valve is opened until the temperature of the auxiliary catalyst reaches a valve closing temperature lower than the valve opening temperature by a predetermined temperature. The valve state is maintained. Therefore, the valve opening / closing frequency can be suppressed as compared with the case where the valve opening / closing means performs the valve opening / closing operation using one temperature as a threshold value. Thereby, generation | occurrence | production of the delay of valve | bulb opening / closing operation | movement can be suppressed.

  In the present invention, the first exhaust passage that communicates the internal combustion engine and the main catalyst that purifies the exhaust gas exhausted from the internal combustion engine, the second exhaust passage that both ends communicate with the first exhaust passage, An auxiliary catalyst that is disposed in the second exhaust passage and purifies exhaust gas that has flowed into the second exhaust passage, and is disposed in the first exhaust passage and closes the first exhaust passage, thereby closing the first exhaust. A valve for allowing the exhaust gas passing through the passage to flow into the second exhaust passage, a valve opening / closing means for opening / closing the valve, a temperature detection means for detecting the temperature of the auxiliary catalyst, and the detected temperature being a valve opening temperature Valve opening / closing control means for opening the valve by the valve opening / closing means as described above, and closing the valve by the valve opening / closing means when the temperature detected again after a predetermined time is less than the valve opening temperature , Characterized in that it comprises a.

  According to the present invention, when the detected temperature of the auxiliary catalyst becomes equal to or higher than the valve opening temperature, the valve is opened by the valve opening / closing means, and when the temperature of the auxiliary catalyst detected again becomes lower than the valve opening temperature, the valve is opened by the bubble opening / closing means. The auxiliary catalyst temperature detected again is the temperature of the auxiliary catalyst detected after a predetermined time. Therefore, the frequency of opening and closing of the valve can be suppressed as compared with the case where the detected temperature of the auxiliary catalyst is always compared with the valve opening temperature and the valve opening and closing means performs the valve opening and closing operation. Thereby, generation | occurrence | production of the delay of valve | bulb opening / closing operation | movement can be suppressed.

  In the present invention, the valve opening / closing means opens the valve using a negative pressure generated by the internal combustion engine.

  According to this invention, the frequency of opening and closing of the valve by the valve opening and closing means can be suppressed, so that consumption of negative pressure used by the valve opening and closing means can be suppressed. Thereby, the opening / closing operation | movement of a valve can be performed reliably.

  The catalyst bypass device according to the present invention can suppress the opening and closing frequency of the valve.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following examples. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or that are substantially the same. Here, the catalyst bypass device described below is disposed in an exhaust path of an internal combustion engine such as a gasoline engine or a diesel engine mounted on a vehicle such as a passenger car or a truck.

  FIG. 1 is a diagram showing a configuration example of a catalyst bypass device according to the present invention. The catalyst bypass device 1-1 according to the present invention is disposed in the exhaust path 110 of the internal combustion engine 100. The catalyst bypass device 1 is disposed between the internal combustion engine 100 and a main catalyst 120 that purifies exhaust gas exhausted from the internal combustion engine 100 in the exhaust path 110. The catalyst bypass device 1-1 includes a first exhaust passage 2, a second exhaust passage 3, an auxiliary catalyst 4, a valve 5, an actuator 6, a temperature sensor 7, and an ECU 8. The main catalyst 120 is a catalyst that purifies harmful substances in the exhaust gas, such as a three-way catalyst, and exhibits a predetermined purification ability at an activation temperature or higher.

  The first exhaust passage 2 communicates a combustion chamber (not shown) of the internal combustion engine 100 and the main catalyst 120. A valve 5 that can close the first exhaust passage 2 is disposed in the first exhaust passage 2.

  The second exhaust passage 3 is disposed so that both end portions 31 and 32 thereof communicate with the first exhaust passage 2 so as to bypass the middle of the first exhaust passage 2. Here, the both end portions 31 and 32 communicate with the first exhaust passage 2 so as to sandwich the valve 5 disposed in the first exhaust passage 2. An auxiliary catalyst 4 is disposed in the second exhaust passage 3. The second exhaust passage 3 communicates with the first exhaust passage 2 so that the unpurified exhaust gas passing through the first exhaust passage 2 hardly flows when the valve 5 is opened. .

  The auxiliary catalyst 4 purifies the unpurified exhaust gas that has flowed into the second exhaust passage 3. The auxiliary catalyst 4 is disposed in the middle of the second exhaust passage 3, and is a purification catalyst such as a three-way catalyst, for example, like the main catalyst 120, and is a catalyst that exhibits a predetermined purification ability at an activation temperature or higher. .

  The valve 5 closes the first exhaust passage 2 so that unpurified exhaust gas passing through the first exhaust passage flows into the second exhaust passage 3. The valve 5 is supported in the middle of the first exhaust passage 2 so as to be rotatable with respect to the first exhaust passage. The valve 5 opens the first exhaust passage 2 by opening the valve, and closes the first exhaust passage 2 by closing the valve.

  The actuator 6 is a valve opening / closing means and opens and closes the valve 5. That is, the actuator 6 opens and closes the valve 5. The actuator 6 opens the valve 5 using the negative pressure generated by the internal combustion engine 100. The actuator 6 includes a diaphragm actuator 61, a VSV (Vacuum Switching Valve) 62, and a negative pressure tank 63. Reference numeral 64 denotes a connecting member that connects the diaphragm actuator 61 and the valve 5. Reference numeral 65 denotes a check valve that only allows air to flow from the negative pressure tank 63 to the intake passage 130. Reference numerals 66 to 69 denote tubes connected to the respective components constituting the actuator 6.

  The diaphragm actuator 61 is operated by negative pressure and opens the valve 5. The diaphragm actuator 61 is a diaphragm actuator, and is connected to the VSV 62 via a tube 66. The operation of the diaphragm actuator 61 is transmitted to the connecting member 64, and the opening / closing operation of the valve 5 is performed by the operation of the diaphragm actuator 61 transmitted to the connecting member 64.

  The VSV 62 introduces negative pressure or atmospheric pressure to the diaphragm actuator 61. Three tubes 66 to 68 are connected to the VSV 62, respectively. The VSV 62 is connected to the diaphragm actuator 61 by a tube 66, connected to the negative pressure tank 63 by a tube 67, and connected to the atmosphere by a tube 68. That is, the VSV 62 introduces either the negative pressure introduced through the tube 67 or the atmospheric pressure introduced through the tube 68 to the diaphragm actuator 61 through the tube 66. Here, when a negative pressure is introduced by the VSV 62, the diaphragm actuator 61 opens the valve 5 via the connecting member 64. Further, when the atmospheric pressure is introduced by the VSV 62 from the state in which the valve 5 is opened, the diaphragm actuator 61 performs an operation opposite to that in the case where the negative pressure is introduced, and is opened via the connecting member 64. Valve 5 is closed. The VSV 62 is controlled by the ECU 8, and either negative pressure or atmospheric pressure is introduced into the diaphragm actuator 61 by a control signal output from the ECU 8.

  The negative pressure tank 63 stores negative pressure generated in the intake passage 130 of the internal combustion engine 100. The negative pressure tank 63 is connected to the VSV 62 by the tube 67 and is connected to the intake path 130 by the tube 69. In the negative pressure tank 63, when a negative pressure is generated in the intake path 130 via the tube 69, the air in the negative pressure tank 63 is supplied to the intake path 130 via the check valve 65 and the negative pressure is stored. The The negative pressure tank 63 introduces the stored negative pressure into the diaphragm actuator 61 via the tube 67 and the VSV 62.

  The temperature sensor 7 measures and detects the temperature of the auxiliary catalyst 4, in this embodiment, the bed temperature of the auxiliary catalyst 4. The detected temperature T of the auxiliary catalyst 4 is output to the ECU 8.

  The ECU (Engine Control Unit) 8 controls the operation of the internal combustion engine 100 and is valve opening / closing control means. The EUC 8 controls the opening and closing of the valve 5 by controlling the VSV 62. Here, the ECU 8 includes an input / output port (I / O) (not shown), a processing unit, and a storage unit. Input / output ports (not shown) include, for example, the temperature sensor 7, a throttle opening sensor that detects the opening of a throttle valve (not shown) that adjusts the amount of intake air taken into the internal combustion engine 100, VSV 62, and other operation controls for the internal combustion engine 100. It is connected to various sensors necessary for the above and the above various devices. Therefore, the ECU 8 inputs data output from the temperature sensor 7, the throttle opening sensor, and other various sensors to the ECU 8. The ECU 8 outputs control signals to the VSV 62 and other various devices based on the input data and various maps stored in a storage unit (not shown). A processing unit (not shown) includes a RAM (Random Access Memory) and a CPU (Central Processing Unit). This processing unit is realized by loading a program based on a catalyst bypass device control method for controlling the catalyst bypass device, that is, a valve opening / closing control method into, for example, a RAM and executing the program. In addition, a storage unit (not shown) is configured by a ROM (Read Only Memory), a RAM, or a combination thereof. In this embodiment, the ECU 8 is used as the valve opening / closing control means, but the present invention is not limited to this. For example, a catalyst bypass device control method for controlling the catalyst bypass device, that is, a valve opening / closing control method, may be realized by a control device different from the ECU 8.

  Next, operation | movement of the catalyst bypass apparatus 1-1 concerning this Example 1 is demonstrated. FIG. 2 is an operation flowchart of the catalyst bypass device according to the first embodiment. Here, the operation until the valve 5 that is normally closed is opened and then closed again will be described.

  First, the ECU 8 acquires the temperature T of the auxiliary catalyst 4 (step ST101). Here, the ECU 8 acquires the temperature T of the auxiliary catalyst 4 detected by the temperature sensor 7.

  Next, the ECU 8 determines whether or not the temperature T of the auxiliary catalyst 4 acquired, that is, detected, is equal to or higher than the valve opening temperature T1 (step ST102). The valve opening temperature T1 is a threshold value at which the valve 5 is opened by the actuator 6, and is a temperature reached when unpurified exhaust gas flows into the auxiliary catalyst 4 when the internal combustion engine is in a high speed and high load operation state. The temperature at which the thermal deterioration of the auxiliary catalyst 4 cannot be suppressed. For example, the valve opening temperature is about 700 °. When the detected temperature T of the auxiliary catalyst 4 is lower than the valve opening temperature T1, the ECU 8 detects the temperature of the auxiliary catalyst 4 detected until the detected temperature T of the auxiliary catalyst 4 becomes equal to or higher than the valve opening temperature T1. Repeat the acquisition of T.

  Next, when the ECU 8 determines that the detected temperature T of the auxiliary catalyst 4 is equal to or higher than the valve opening temperature T1, the ECU 8 opens the valve 5 (step ST103). Here, the ECU 8 outputs a control signal to the VSV 62. The VSV 62 introduces the negative pressure stored in the negative pressure tank 63 to the diaphragm actuator 61 via the tube 67, VSV 62, and tube 66 by this control signal. The diaphragm actuator 61 opens the valve 5 that has been closed via the connecting member 64 by the introduced negative pressure. That is, when the ECU 8 determines that the detected temperature T of the auxiliary catalyst 4 is equal to or higher than the valve opening temperature T <b> 1, the ECU 6 opens the valve 5.

  When the valve 5 is opened, as shown in FIG. 1, the unpurified exhaust gas exhausted from the combustion chamber (not shown) of the internal combustion engine 100 to the exhaust path 110 becomes the first exhaust as shown by an arrow A. It passes through the passage 2 and flows into the main catalyst 120. That is, when the internal combustion engine 100 is operating at a high speed and a high load, the valve 5 is opened so that unpurified exhaust gas does not pass through the second exhaust passage 3, that is, flows into the auxiliary catalyst 4. Instead, it flows directly into the main catalyst 120 by passing through the first exhaust passage 2. Therefore, the thermal degradation of the auxiliary catalyst 4 due to the high temperature unpurified exhaust gas flowing into the auxiliary catalyst 4 is suppressed, and the pressure loss due to the unpurified exhaust gas passing through the auxiliary catalyst 4 is reduced. A decrease in the output of the internal combustion engine 100 can be suppressed.

  Here, the valve 5 remains closed until it is determined that the temperature T of the auxiliary catalyst 4 detected by the ECU 8 is equal to or higher than the valve opening temperature T1. Therefore, when the valve 5 is kept closed, as shown in the figure, the unpurified exhaust gas exhausted from the combustion chamber (not shown) of the internal combustion engine 100 to the exhaust path 110 is indicated by an arrow B (same figure). As shown by the dotted line), the air flows from the first exhaust passage 2 into the second exhaust passage 3 through the end portion 31. Then, it flows into the auxiliary catalyst 4, passes through the auxiliary catalyst 4, returns to the first exhaust passage 2 again through the end portion 32, and flows into the main catalyst 120. That is, since the temperature of the unpurified exhaust gas exhausted from the internal combustion engine 100 to the exhaust path 110 is low, the temperature of the main catalyst 120 does not increase, and the purification performance of the main catalyst 120 is low. Exhaust gas flows into the auxiliary catalyst 4. As a result, the exhaust gas flows into the auxiliary catalyst 4 before the exhaust gas flows into the main catalyst 120 having a low purification capacity, so that the unpurified exhaust gas can be purified to some extent by the auxiliary catalyst 4. Even if the purification capability of the catalyst 120 is low, the exhaust gas exhausted to the exhaust passage 110 can be sufficiently purified.

  Next, as shown in FIG. 2, the ECU 8 determines whether or not the internal combustion engine 100 is in a fuel cut state (step ST104). Here, the ECU 8 determines whether or not a fuel cut state, that is, a state in which no fuel is supplied to the internal combustion engine 100, based on a throttle valve opening obtained by a throttle opening sensor (not shown) in the first embodiment. To do. For example, the ECU 8 determines whether or not the throttle valve opening is 0, that is, whether or not the throttle valve is closed. Here, when the internal combustion engine 100 is in the fuel cut state, the air taken into the internal combustion engine 100 from the intake passage 130 to the exhaust passage 110 is exhausted as it is. Therefore, when the internal combustion engine 100 is in the fuel cut state and the valve 5 is in the closed state, the air exhausted into the exhaust passage 110 flows into the auxiliary catalyst 4, and the auxiliary catalyst 4 may be excessively oxygen and deteriorate. is there. However, if the ECU 8 determines that the internal combustion engine 100 is in the fuel cut state, the ECU 8 repeats acquisition of the throttle valve opening again and maintains the valve 5 opened until it is determined that the internal combustion engine 100 is not in the fuel cut state. Therefore, deterioration of the auxiliary catalyst 4 due to excessive oxygen can be suppressed.

  Next, when determining that the internal combustion engine 100 is not in the fuel cut state, the ECU 8 acquires the temperature T of the auxiliary catalyst 4 again (step ST105). Here, the ECU 8 acquires the temperature T of the auxiliary catalyst 4 detected by the temperature sensor 7 again.

  Next, the ECU 8 determines whether or not the temperature T of the auxiliary catalyst 4 acquired again, that is, detected again, is equal to or lower than the valve closing temperature T2 (step ST106). The valve closing temperature T2 is a threshold value for closing the valve 5 by the actuator 6, and is different from the valve opening temperature T1 and is lower than the valve opening temperature T1. The valve closing temperature T2 is a temperature lower by a predetermined temperature than the valve opening temperature T1. This predetermined temperature is, for example, about 30 °. When the detected temperature T of the auxiliary catalyst 4 exceeds the valve closing temperature T2, the ECU 8 keeps the internal combustion engine 100 in the fuel cut state until the detected temperature T of the auxiliary catalyst 4 becomes equal to or lower than the valve closing temperature T2. It is determined whether or not there is, and acquisition of the temperature T of the auxiliary catalyst 4 detected again is repeated.

  Next, when the ECU 8 determines that the detected temperature T of the auxiliary catalyst 4 is equal to or lower than the valve closing temperature T2, the ECU 8 closes the valve 5 in the valve open state (step ST107). Here, the ECU 8 outputs a control signal to the VSV 62. The VSV 62 introduces atmospheric pressure to the diaphragm actuator 61 via the tube 68, VSV 62, and tube 66 according to this control signal. The diaphragm actuator 61 closes the valve 5 that has been opened via the connecting member 64 due to the introduced atmospheric pressure. That is, when the ECU 8 determines that the detected temperature T of the auxiliary catalyst 4 is equal to or lower than the valve closing temperature T2, the ECU 6 closes the valve 5 by the actuator 6.

  As described above, the valve 5 is closed after the detected temperature T of the auxiliary catalyst 4 becomes equal to or higher than the valve opening temperature T1 and is opened by the actuator 6, and then the temperature of the auxiliary catalyst 4 is lower than the valve opening temperature T1 by a predetermined temperature. The valve open state is maintained until the valve temperature T2 is reached. Therefore, the opening / closing frequency of the valve 5 can be suppressed as compared with the case where the actuator 6 performs the opening / closing operation of the valve 5 using one temperature as a threshold value. Thereby, generation | occurrence | production of the delay of valve | bulb opening / closing operation | movement can be suppressed. Moreover, since the frequency | count of opening / closing of the valve 5 can be suppressed, the fall of the reliability of the opening / closing operation | movement of the valve 5 can be suppressed. Moreover, since the opening / closing frequency of the valve 5 by the actuator 6 can be suppressed, consumption of the negative pressure used by the actuator 6 can be suppressed. Therefore, when it is desired to open the valve 5, it is possible to suppress the negative pressure introduced into the negative pressure tank 63 from being small and making it difficult to open the valve 5. Thereby, the opening / closing operation | movement of the progress valve 5 can be performed reliably.

  Next, the catalyst bypass device 1-2 according to Embodiment 2 of the present invention will be described. The difference between the catalyst bypass device 1-2 according to the second embodiment and the catalyst bypass device 1-1 according to the first embodiment is that the opening / closing operation of the valve 5 is such that the temperature T of the auxiliary catalyst 4 is one threshold value. Depending on whether the valve opening temperature is equal to or higher than T1, the valve 5 is closed only after a predetermined time has elapsed after the valve 5 is opened. The basic configuration of the catalyst bypass device 1-2 according to the second embodiment is substantially the same as the basic configuration of the catalyst bypass device 1-1 according to the first embodiment, and the description thereof is omitted (see FIG. 1). ).

  Next, operation | movement of the catalyst bypass apparatus 1-2 concerning Example 2 is demonstrated. FIG. 3 is an operation flowchart of the catalyst bypass device according to the second embodiment. In addition, in operation | movement of the catalyst bypass apparatus 1-2 concerning this Example 2, the part same as operation | movement of the catalyst bypass apparatus 1-1 concerning Example 1 is abbreviate | omitted or simplified and demonstrated.

  First, the ECU 8 acquires the temperature T of the auxiliary catalyst 4 (step ST201). Next, the ECU 8 determines whether or not the temperature T of the auxiliary catalyst 4 acquired, that is, detected, is equal to or higher than the valve opening temperature T3 (step ST202). The valve opening temperature T3 is the same as the valve opening temperature T1 of the first embodiment, and is reached when unpurified exhaust gas flows into the auxiliary catalyst 4 when the internal combustion engine is operating at high speed and high load. The temperature at which the auxiliary catalyst 4 cannot be suppressed. For example, the valve opening temperature T3 is about 700 °. When the detected temperature T of the auxiliary catalyst 4 is lower than the valve opening temperature T3, the ECU 8 detects the temperature of the auxiliary catalyst 4 detected until the detected temperature T of the auxiliary catalyst 4 becomes equal to or higher than the valve opening temperature T3. Repeat the acquisition of T.

  Next, when the ECU 8 determines that the detected temperature T of the auxiliary catalyst 4 is equal to or higher than the valve opening temperature T3, the ECU 8 opens the valve 5 (step ST203). That is, when the ECU 8 determines that the detected temperature T of the auxiliary catalyst 4 is equal to or higher than the valve opening temperature T3, the valve 6 is opened by the actuator 6. Thereby, as shown in FIG. 1, unpurified exhaust gas exhausted from the combustion chamber (not shown) of the internal combustion engine 100 to the exhaust path 110 passes through the first exhaust passage 2 as shown by an arrow A, It flows into the main catalyst 120. The valve 5 is kept closed until it is determined that the temperature T of the auxiliary catalyst 4 detected by the ECU 8 is equal to or higher than the valve opening temperature T3. Therefore, as shown in the figure, the unpurified exhaust gas exhausted from the combustion chamber (not shown) of the internal combustion engine 100 to the exhaust path 110 is the first exhaust passage 2 as shown by an arrow B (dotted line in the figure). Flows into the second exhaust passage 3 through the end portion 31, flows into the auxiliary catalyst 4, passes through the auxiliary catalyst 4, returns to the first exhaust passage 2 again through the end portion 32, and returns to the main catalyst 120. Inflow.

  Next, as shown in FIG. 3, when the valve 5 is opened, the ECU 8 starts to accumulate elapsed time (step ST204). Here, the ECU 8 starts counting by a counter (not shown) configured in the ECU 8, for example.

  Next, the ECU 8 determines whether or not the internal combustion engine 100 is in a fuel cut state (step ST205). Here, the ECU 8 determines whether or not the throttle valve opening is 0, that is, whether or not the throttle valve is closed.

  Next, when determining that the internal combustion engine 100 is not in the fuel cut state, the ECU 8 determines whether or not a predetermined time has elapsed after the valve 5 is opened (step ST206). ). The predetermined time refers to a time during which the operation state of the internal combustion engine 100 is continued at a high rotation and high load in the normal operation state of the internal combustion engine 100. For example, the predetermined time is about 3 seconds.

  Next, when the ECU 8 determines that the elapsed time of starting integration after the opening of the valve 5 has passed a predetermined time, the ECU 8 acquires the temperature T of the auxiliary catalyst 4 again (step ST207).

  Next, the ECU 8 determines whether or not the temperature T of the auxiliary catalyst 4 acquired again, that is, detected again, is lower than the valve opening temperature T3 (step ST208). When the detected temperature T of the auxiliary catalyst 4 is equal to or higher than the valve opening temperature T3, the ECU 8 keeps the internal combustion engine 100 in the fuel cut state until the detected temperature T of the auxiliary catalyst 4 becomes lower than the valve opening temperature T3. And after the valve 5 is opened, it is determined whether or not a predetermined time has elapsed after the valve 5 is opened, and the temperature T of the auxiliary catalyst 4 detected again is acquired. repeat.

  Next, when the ECU 8 determines that the detected temperature T of the auxiliary catalyst 4 is lower than the valve opening temperature T3, the ECU 8 closes the valve 5 in the valve open state (step ST209). Here, when the ECU 8 determines that the detected temperature T of the auxiliary catalyst 4 is lower than the valve opening temperature T3, the valve 6 is closed by the actuator 6.

  As described above, after the valve 5 is opened by the actuator 6 after the detected temperature T of the auxiliary catalyst 4 becomes equal to or higher than the valve opening temperature T3, the detected temperature of the auxiliary catalyst 4 is opened again after a predetermined time has elapsed. When the temperature becomes lower than the valve temperature T3, the valve 5 is closed by the actuator 6. The detected temperature T of the auxiliary catalyst 4 and the valve opening temperature T3 are always compared, and the opening / closing frequency of the valve 5 can be suppressed as compared with the case where the actuator 6 performs the opening / closing operation of the valve 5. Thereby, generation | occurrence | production of the delay of valve | bulb opening / closing operation | movement can be suppressed. Moreover, since the frequency | count of opening / closing of the valve 5 can be suppressed, the fall of the reliability of the opening / closing operation | movement of the valve 5 can be suppressed. Moreover, since the opening / closing frequency of the valve 5 by the actuator 6 can be suppressed, consumption of the negative pressure used by the actuator 6 can be suppressed. Therefore, when it is desired to open the valve 5, it is possible to suppress the negative pressure introduced into the negative pressure tank 63 from being small and making it difficult to open the valve 5. Thereby, the opening / closing operation | movement of the progress valve 5 can be performed reliably.

  INDUSTRIAL APPLICABILITY The catalyst bypass device according to the present invention is useful for a catalyst bypass device that purifies exhaust gas exhausted from an internal combustion engine by an auxiliary catalyst when the purification capacity of the main catalyst is low. Suitable for

It is a figure which shows the structural example of the catalyst bypass apparatus concerning this invention. It is an operation | movement flowchart of the catalyst bypass apparatus concerning Example 1. FIG. It is an operation | movement flowchart of the catalyst bypass apparatus concerning Example 2. FIG.

Explanation of symbols

1-1, 1-2 Catalyst bypass device 2 First exhaust passage 3 Second exhaust passage 31 End portion 32 End portion 4 Auxiliary catalyst 5 Valve 6 Actuator (valve opening / closing means)
61 Diaphragm actuator 62 VSV
63 Negative pressure tank 64 Connecting member 65 Check valve 66-69 Tube 7 Temperature sensor (temperature detection means)
8 ECU (valve open / close control means)
DESCRIPTION OF SYMBOLS 100 Internal combustion engine 110 Exhaust path 120 Main catalyst 130 Intake path

Claims (3)

A first exhaust passage communicating the internal combustion engine and a main catalyst for purifying exhaust gas exhausted from the internal combustion engine;
A second exhaust passage whose both ends communicate with the first exhaust passage;
An auxiliary catalyst disposed in the second exhaust passage and purifying exhaust gas flowing into the second exhaust passage;
A valve that is disposed in the first exhaust passage and closes the first exhaust passage so that exhaust gas passing through the first exhaust passage flows into the second exhaust passage;
Valve opening and closing means for opening and closing the valve;
Temperature detecting means for detecting the temperature of the auxiliary catalyst;
When the detected temperature is equal to or higher than the valve opening temperature, the valve is opened by the valve opening / closing means, and when the detected temperature is equal to or lower than the valve closing temperature lower than the valve opening temperature, the valve opening / closing means is opened. Valve opening / closing control means for closing the valve by
A catalyst bypass device comprising: A first exhaust passage communicating the internal combustion engine and a main catalyst for purifying exhaust gas exhausted from the internal combustion engine;
A second exhaust passage whose both ends communicate with the first exhaust passage;
An auxiliary catalyst disposed in the second exhaust passage and purifying exhaust gas flowing into the second exhaust passage;
A valve that is disposed in the first exhaust passage and closes the first exhaust passage so that exhaust gas passing through the first exhaust passage flows into the second exhaust passage;
Valve opening and closing means for opening and closing the valve;
Temperature detecting means for detecting the temperature of the auxiliary catalyst;
When the detected temperature is equal to or higher than the valve opening temperature, the valve is opened by the valve opening / closing means. When the temperature detected again after a predetermined time has passed is less than the valve opening temperature, the valve opening / closing means opens the valve. Valve opening / closing control means for closing the valve;
A catalyst bypass device comprising:   The catalyst bypass device according to claim 1 or 2, wherein the valve opening / closing means opens the valve using a negative pressure generated by the internal combustion engine.

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