JP4940979B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an improvement in an exhaust gas purification apparatus for an internal combustion engine that performs exhaust gas purification using a catalytic converter.

  As conventionally known, in a configuration in which the main catalytic converter is disposed relatively downstream of the exhaust system such as under the floor of a vehicle, the temperature of the catalytic converter rises and is activated after a cold start of the internal combustion engine. In the meantime, a sufficient exhaust purification action cannot be expected. On the other hand, the closer the catalytic converter is to the upstream side of the exhaust system, that is, the internal combustion engine side, the lower the durability due to thermal degradation of the catalyst.

  Therefore, as disclosed in Patent Document 1, a bypass passage is provided in parallel with the upstream portion of the main passage including the main catalytic converter, and another bypass catalytic converter is interposed in the bypass passage. Conventionally, an exhaust device has been proposed in which exhaust gas is guided to the bypass passage side immediately after cold start by a switching valve for switching between the two. In this configuration, the bypass catalytic converter is positioned relatively upstream of the main catalytic converter in the exhaust system and is activated early, so that exhaust gas purification can be started from an earlier stage.

A switching valve installed in a conventional exhaust purification device is generally opened and closed by an electric motor or a negative pressure actuator. In such a switching valve, one of the opening and closing is opened and closed using the biasing force of the spring.
Japanese Patent Laid-Open No. 2005-351088

  However, when shifting from one of the open / closed states maintained by the biasing force of the spring to the other state, it is necessary to open / close the switching valve against the biasing force of the spring. May fall.

  Therefore, an object of the present invention is to provide an exhaust emission control device for an internal combustion engine that improves the opening / closing speed of a switching valve that switches the flow of exhaust gas between a main passage and a bypass passage.

The present invention relates to a main passage through which exhaust gas from an internal combustion engine flows, a main catalytic converter installed in the main passage, a part of the main passage, and connected to the main passage on the upstream side of the main catalytic converter. A bypass passage, a bypass catalytic converter installed in the bypass passage, a switching valve that controls the flow of exhaust gas discharged from the internal combustion engine to the main passage, a controller that controls opening and closing of the switching valve, In the exhaust gas purification apparatus for an internal combustion engine, the switching valve includes a negative pressure actuator and a motor as one drive source of the opening / closing operation, and the controller acts on the negative pressure actuator to depending on the negative pressure causing a driving force, the driving source of the switching valve of the negative pressure actuator Or an exhaust purifying apparatus for an internal combustion engine and controlling any combination of the negative pressure actuator and said motor.

  According to the present invention, when the negative pressure acting on the negative pressure actuator is insufficient when shifting from one of the open / closed states to the other state, the switching valve is driven to open / close by the negative pressure actuator and the motor. The opening / closing speed of the switching valve does not decrease.

  FIG. 1 is an explanatory view schematically showing the layout of an exhaust gas purification apparatus for an internal combustion engine to which the present invention is applied.

  The exhaust purification device includes a main catalytic converter 8 disposed under the floor of a vehicle room and a bypass catalytic converter 18 disposed upstream thereof. The main catalytic converter 8 includes an upstream main passage 2 connected to each cylinder of the internal combustion engine and a downstream main passage of main passages 2, 3, 7 including a downstream middle passage main passage 3 and a downstream main passage 7. 7 is installed. The bypass catalytic converter 18 branches from the upstream main passage 2 of the main passage, bypasses the middle flow main passage 3 and connects to the upstream end of the downstream main passage 7, and connects the upstream, downstream bypass passage 11, The bypass passages 11 and 14 are provided in the downstream bypass passage 14.

  The upstream main passage 2 is connected to each cylinder 1 of the # 1 cylinder to # 4 cylinder of the internal combustion engine at the upstream side, and the downstream end portions are gathered, and each upstream main passage 2 is opened and closed at the gathered portion. A switching valve 4 is provided for each passage 2. The switching valve 4 is configured as a switching valve unit 5, and the four upstream main passages 2 are integrated in the switching valve unit 5, and are configured as one passage on the downstream side of each switching valve 4. Connect to. Each switching valve 4 of the switching valve unit 5 is closed when the internal combustion engine is cold, and when closed, the communication between the upstream main passage 2 and the midstream main passage 3 is cut off, and the exhaust is bypassed by the bypass passages 11 and 14. In the open state, the upstream main passage 2 and the midstream side main passage 3 are connected to each other, and exhaust gas is introduced into the midstream side main passage 3. Here, as the passage length or passage volume of the upstream main passage 2 upstream of the switching valve 4 is smaller, the exhaust temperature on the bypass passage side immediately after the cold start is more likely to rise.

  A downstream main passage 7 is connected to the downstream side of the middle flow side main passage 3, and a downstream bypass passage 14 described later joins a connecting portion 7 a between the middle flow side main passage 3 and the downstream main passage 7. A main catalytic converter 8 is installed in the downstream main passage 7. As the catalyst in the main catalytic converter 8, a three-way catalyst and an HC trap catalyst are provided.

  As the bypass passages 11 and 14, the upstream bypass passage 11 is branched from each of the upstream main passages 2, and the upstream bypass passage 11 is a passage having a sufficiently smaller passage cross-sectional area than the upstream main passage 2. . A branch point 2 a with the upstream main passage 2 serving as the upstream end of the upstream bypass passage 11 is set at a position as upstream as possible of the upstream main passage 2. The upstream bypass passages 11 are gathered and connected to one downstream bypass passage 14. As described above, the downstream side of the downstream bypass passage 14 joins the connecting portion 7 a between the midstream main passage 3 and the downstream main passage 7. In FIG. 1 schematically showing each passage, each upstream bypass passage 11 is drawn relatively long, but in practice it is as short as possible. In other words, it merges with the downstream bypass passage 14 with the shortest distance.

  A bypass catalytic converter 18 using a three-way catalyst is installed in the downstream bypass passage 14 in the middle thereof. The bypass catalytic converter 18 is disposed as upstream as possible in the bypass passage 14. That is, the downstream bypass passage 14 is as short as possible. The bypass catalytic converter 18 is a small one having a smaller capacity than the main catalytic converter 8, and preferably a catalyst having excellent low-temperature activity is used. The downstream bypass passage 14 joins the connecting portion 7 a between the midstream main passage 3 and the downstream main passage 7, and introduces the exhaust gas purified by the bypass catalytic converter 18 into the downstream main passage 7.

  An intake passage 21 that communicates with each cylinder 1 via an intake manifold is provided, and a throttle valve 22 is provided in the intake passage 21. Connected to the intake passage 21 is a negative pressure passage 23 connecting the downstream of the throttle valve 22 of the intake passage 21 and the switching valve 4 positioned at the upper end of the middle flow side main passage 3.

  The negative pressure passage 23 opens and closes the negative pressure actuator 24 and the negative pressure passage 23 from the middle flow side main passage 3 side, and a solenoid valve 25 for controlling the negative pressure acting on the negative pressure actuator 24, A pressure sensor 26 for detecting pressure (negative pressure), a negative pressure tank 27 for accumulating negative pressure acting on the negative pressure actuator 24, and a check valve 28 for prohibiting the flow of exhaust gas from the intake passage 21 side are installed in this order. Is done.

  A switching valve 4 is installed at the junction of the middle flow side main passage 3 and the negative pressure passage 23, and the flow of exhaust gas is switched between the upstream side main passage 2 and the upstream side bypass passage 11 by its open / closed state. The switching valve 4 is controlled to be opened and closed by the controller 30.

  This switching valve 4 is installed in each upstream main passage 2 communicating with each cylinder 1 and is controlled to open and close according to the negative pressure of the negative pressure actuator 24 and the electric driving force of the electric motor 29. It opens and closes only by the negative pressure actuator 24 and by the cooperation of the negative pressure actuator 24 and the electric motor 29. In this embodiment, the switching valve 4 uses the aforementioned negative pressure or the like as an acting force for switching from the closed state to the open state by using a biasing force on a spring (not shown) in order to maintain the closed state. However, in order to maintain the open state, a biasing force may be used for a spring (not shown), and the above-described negative pressure or the like may be used as an action force for switching from the open state to the closed state.

  FIG. 2 shows the switching valve 4 and its typical drive system. The switching valve 4 is installed in each upstream main passage communicating with each cylinder 1 as described above, and the driving system for opening and closing the switching valve 4 is different. In addition, although the two switching valves 4 are described in the figure, this is shown schematically and is not limited to this.

  In FIG. 2A, a switching valve 4 is provided for each upstream main passage 2 communicating with each cylinder 1, and each switching valve 4 is driven by a pair of electric control motor 29 and negative pressure actuator 24. It is. For example, each switching valve 4 is configured to be opened by a pair of electric motor 29 and negative pressure actuator 24 using a link mechanism (not shown). In this way, since a plurality of switching valves 4 can be opened by one electric motor 29 and one negative pressure actuator 24 using a link mechanism or the like, cost reduction and wiring and piping layout are easy. There is an effect of becoming.

  FIG. 2 (b) shows a switching valve 4 installed in each upstream main passage 2 communicating with each cylinder 1, and an open / close driving source corresponding to each switching valve 4, that is, an electric control motor 29 and a negative. In this system, a pressure actuator 24 is provided. In this system, the size of the electric motor 29 and the negative pressure actuator 24 installed in each switching valve 4 can be reduced, and the layout is improved. Moreover, since opening / closing control can be performed for each switching valve 4, there is an effect that there is no need to consider variation between the switching valves 4.

  FIG. 2C has a configuration in which a negative pressure pump 31 is added to FIG. When the negative pressure pump 31 is provided, the negative pressure that is deficient in the negative pressure actuator 24 is compensated by the negative pressure generated by the negative pressure pump 31, and the negative pressure is insufficient even if the negative pressure is supplemented by the negative pressure pump 31. Further supplementation by the electric motor 29 is provided. By adopting such a method, the driving force for the opening operation by the negative pressure actuator 24 can be increased, while the required performance of the electric motor 29 can be reduced, and the electric motor 29 can be reduced in size and cost. Can be achieved.

  FIG. 3 is a flowchart for explaining opening / closing control of the switching valve 4 by the controller 30 that controls the switching valve 4 and the negative pressure actuator 24 and the electric motor 29 as its driving source. This control is based on the premise that the switching valve 4 is opened by the negative pressure actuator 24 and the electric control motor 29 and the switching valve 4 is closed by a biasing force of a spring (not shown).

  First, in step S1, the switching valve 4 for switching the flow of exhaust is opened, and it is determined whether or not the opening control of the switching valve 4 can be terminated. When the process ends, the process proceeds to step S2, and it is determined whether or not the negative pressure necessary for maintaining the open state of the switching valve 4 can be secured. Here, the determination of securing the negative pressure is performed using the detection value of the pressure sensor 26 installed in the negative pressure passage 23. The negative pressure required to maintain the switching valve 4 in the open state is a negative pressure required to press the valve body 4a (see FIG. 2) of the switching valve 4 against the counterpart member.

  If the negative pressure required to maintain the open state can be secured, the process proceeds to step S3, where the solenoid valve 25 is opened and the negative pressure is applied to the negative pressure actuator 24 to maintain the switching valve 4 in the open state.

  On the other hand, if the necessary negative pressure cannot be secured in step S2, that is, if the open state of the switching valve 4 cannot be maintained only by the negative pressure, the process proceeds to step S4, where the solenoid valve 25 is opened and the negative pressure is transferred to the negative pressure actuator 24. The switching valve 4 is controlled to maintain the open state by a combination of the negative pressure of the negative pressure actuator 24 and the driving force (torque) of the electric control motor 29. Therefore, in the case of step S4, since the negative pressure applied to the negative pressure actuator 24 is not sufficient, the switching valve 4 is maintained in the open state by the negative pressure actuator 24 and the electric motor 29.

  If the opening control of the switching valve 4 is not completed in step S1, the process proceeds to step S5, the active state of the main catalytic converter 8 is determined, and it is determined whether or not the switching valve 4 is opened. The active state of the main catalytic converter 8 is determined based on the detected temperature, for example, by providing a temperature sensor (not shown) in the main catalytic converter 8 to detect the catalyst temperature in the main catalytic converter 8. When the main catalytic converter 8 is in an active state, the switching valve 4 may be opened to introduce exhaust into the main catalytic converter 8, so that the process proceeds to step S6, the output value of the pressure sensor 26 is read, and the detected negative pressure is detected. Is a negative pressure sufficient to open the switching valve 4. Here, the sufficient negative pressure is a negative pressure required to open the switching valve 4 at a predetermined opening / closing speed against the urging force of a spring (not shown) acting in the closing direction of the switching valve 4. Yes, this is different from the negative pressure required to keep the switching valve 4 in step S2 open. The necessary negative pressure is set in advance as a predetermined negative pressure, and if it is lower than the predetermined negative pressure, the negative pressure is sufficient. If the negative pressure is sufficient, the process proceeds to step S7, where the solenoid valve 25 is opened and the negative pressure is applied to the negative pressure actuator 24 to open the switching valve 4. On the other hand, if the negative pressure is insufficient, the process proceeds to step S8, and the switching valve 4 is controlled to be opened by the negative pressure actuator 24 and the electric motor 29.

  If the main catalytic converter 8 has not reached the active state and it is not necessary to open the switching valve 4 in step S5, the process proceeds to step S9, where the switching valve 4 is opened from the operating state of the vehicle on which the internal combustion engine is mounted. Determine whether it is necessary. For example, if there is a request for opening the switching valve 4 due to a high load request during sudden acceleration or traveling on an uphill road, the flow proceeds to step S10, the negative pressure is read, it is determined whether the required negative pressure can be supplied, and the opening request is If not, the process returns to step S1. The required negative pressure here may be the same required negative pressure as in step S6.

  If it is determined in step S10 that the necessary negative pressure is ensured, the process proceeds to step S11, the solenoid valve 25 is opened, the negative pressure is applied to the negative pressure actuator 24, and the switching valve 4 is controlled to the open state. On the other hand, if it is determined that the required negative pressure is not secured, the process proceeds to step S12, and the negative pressure actuator 24 and the electric motor 29 are cooperatively driven to control the switching valve 4 to the open state.

  The switching valve 4 is controlled to be opened by steps S7, S8, S11 and step S12, and each step subsequently proceeds to step S13. When the switching valve 4 is opened, the valve body 4a of the switching valve 4 is seated on the mating member. The control which suppresses the seating sound which arises at the time is performed.

  The seating sound is more likely to be generated when the valve body 4a of the switching valve 4 is seated by the action of negative pressure or the driving force of the electric motor 29. Therefore, the seating sound can be suppressed by suppressing the seating sound. It is effective to suppress the speed of. Therefore, immediately before the valve body 4a of the switching valve 4 is seated on the mating member, the opening speed of the valve body 4a is decreased to control the seating sound. Here, in order to change the opening speed of the valve body 4a, it is appropriate to control and change the electric motor 29 having a quick response speed at the time of control. The switching valve is operated by the electric motor 29 as in step S8. Not only when opening 4 but also when the switching valve 4 is opened by the negative pressure actuator 24 as in step S7, immediately before sitting, the driving force of the electric motor 29 is applied to slow down the opening speed and the seating sound. Reduce. Further, when the switching valve 4 is seated, the valve body 4a is controlled to be pressed against the mating member, thereby chattering sound when the valve body 4a sits on the mating member (the valve body 4a is mated with the mating member). Sound generated by moving to and away from the camera can be prevented.

  Specifically, in step S13, the output value of the positioning sensor 33 that detects the position of the valve body 4a of the switching valve 4 is read to detect the position of the valve body 4a. When the valve body 4a reaches a predetermined position, the process proceeds to step S14, and the electric motor 29 is controlled so that the opening speed of the valve body 4a becomes a predetermined speed. Then, sit on the mating member and finish the control.

  As described above, the present invention includes the main passages 2, 3, 7 through which the exhaust gas from the internal combustion engine flows, the main catalytic converter 8 installed in the main passages 2, 3, 7, and a part of the main passages 2, 3. And bypass passages 11, 14 connected to the main passage 7 upstream of the main catalytic converter 8, a bypass catalytic converter 18 installed in the bypass passages 11, 14, and the internal combustion engine. In an exhaust gas purification apparatus for an internal combustion engine, comprising: a switching valve 4 that controls the flow of exhaust gas to the main passages 2, 3, and 7; and a controller 30 that controls opening and closing of the switching valve 4. One of the opening / closing operations is driven by the negative pressure actuator 24 or a combination of the negative pressure actuator 24 and a motor 29. Therefore, for example, even when the closing operation of the switching valve 4 is driven by the biasing force of the spring, the opening operation is performed against the biasing force of the spring against the negative pressure actuator 24 or the negative pressure. Since it is driven by the combination of the actuator 24 and the electric motor 29, it can be suppressed that the speed of the opening operation is slow.

  The present invention can be variously modified and changed within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

It is explanatory drawing which showed typically the layout of the exhaust gas purification apparatus which concerns on this invention. It is a block diagram of a switching valve. It is a flowchart explaining opening and closing control of a switching valve.

Explanation of symbols

2: upstream main passage 3: middle flow main passage 4: switching valve 5: valve unit 7: downstream main passage 8: main catalytic converter 11: upstream bypass passage 14: downstream bypass passage 18: bypass catalytic converter 24: Negative pressure actuator 25: Solenoid valve 26: Pressure sensor 27: Negative pressure tank 28: Check valve 29: Electric control motor 30: Controller 31: Negative pressure pump

Claims (9)

A main passage through which the exhaust of the internal combustion engine flows;
A main catalytic converter installed in the main passage;
A bypass passage that bypasses a portion of the main passage and connects to the main passage on the upstream side of the main catalytic converter;
A bypass catalytic converter installed in the bypass passage;
A switching valve for controlling the flow of the exhaust discharged from the internal combustion engine to the main passage;
A controller for controlling opening and closing of the switching valve;
In an exhaust gas purification apparatus for an internal combustion engine comprising:
The switching valve includes a negative pressure actuator and a motor as one drive source for the opening / closing operation,
The controller controls only the negative pressure actuator or the negative pressure actuator and the motor according to a negative pressure that acts on the negative pressure actuator to generate a driving force in the negative pressure actuator. An exhaust emission control device for an internal combustion engine, which is controlled to any one of the combinations.   The exhaust purification device for an internal combustion engine according to claim 1, wherein the controller controls an opening / closing speed of the switching valve by the motor.   3. The exhaust gas purification apparatus for an internal combustion engine according to claim 2, wherein the controller switches the opening / closing speed of the switching valve by the motor so that the opening / closing speed when the switching valve is seated on a mating member is slowed down. .   The controller drives the motor if the negative pressure acting on the negative pressure actuator is less than the negative pressure required to maintain the state when the switching valve is maintained in the open or closed state. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein control is performed so as to maintain the state of the switching valve. The switching valve, according to a plurality of said main passage when each composed to that the valve opening and closing, to claim 1, characterized in that placing said negative pressure actuator and said motor to each valve body An exhaust purification device for an internal combustion engine. The switching valve, when constituted a plurality of the main passage from the respective opening and closing to that the valve body, characterized by installing a pair of the negative pressure actuator for opening and closing the respective valve body and said motor The exhaust emission control device for an internal combustion engine according to claim 1. The exhaust purification device for an internal combustion engine according to claim 6, wherein the negative pressure actuator communicates with a negative pressure pump. When the negative pressure acting on the negative pressure actuator is lower than the negative pressure required to operate the switching valve at a predetermined opening / closing speed against the biasing force acting on the switching valve, the controller The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the switching valve is driven by a negative pressure actuator and the motor.   2. The exhaust emission control device for an internal combustion engine according to claim 1, wherein the other opening / closing operation of the switching valve is driven by a biasing force of a spring.

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