JP4672567B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that purifies exhaust gas discharged from the internal combustion engine with a catalyst.

  Conventionally, as this type of technology, for example, devices described in Patent Documents 1 to 3 below are known. In particular, the device described in Patent Document 1 is an exhaust gas purification device in which a catalytic converter is connected to an exhaust pipe, and is exhausted through the exhaust pipe to a connecting portion between the exhaust pipe and the catalytic converter. There is provided swirling flow generating means for generating swirling flow in the exhaust gas. As a swirl flow generating means, a spiral member having a shape formed by twisting a belt-shaped plate or a swirl blade bent inward with respect to the tube wall at the end of the exhaust pipe is provided. By causing the swirl flow to occur in the exhaust gas by the swirl flow generating means, the exhaust gas is evenly distributed over the entire passage section of the catalytic converter, thereby improving the exhaust gas purification efficiency. In particular, when the internal combustion engine is cold-started (when the catalyst is inactive), it is necessary to warm up the catalyst at an early stage. By generating a swirling flow in the exhaust gas introduced into the catalytic converter, the passage of the catalyst The exhaust gas can be evenly distributed over the entire cross section to promote warming up of the catalyst.

Japanese Utility Model Publication No. 6-69318 Japanese Patent Laid-Open No. 10-89055 JP-A-8-21231

  However, in the apparatus described in Patent Document 1, since the swirl flow generating means always has a ventilation resistance in the exhaust pipe, warming up of the catalytic converter is promoted when the internal combustion engine is cold started (when the catalyst is inactive). Even when the internal combustion engine functions effectively, when the internal combustion engine operates at a high load, that is, when the displacement becomes large, the swirl flow generating means becomes a large ventilation resistance, and the back pressure of the internal combustion engine increases and the pressure loss increases. As a result, there is a concern that the performance of the internal combustion engine may be reduced.

The present invention was made in view of the above circumstances, and its object is touched during inactive the medium by uniformly spread the exhaust in passage section throughout the catalyst achieving warm-up promotion of the catalyst, upon deactivation of the catalyst It is another object of the present invention to provide an exhaust gas purification apparatus for an internal combustion engine that can purify exhaust gas with a catalyst without increasing the ventilation resistance of the exhaust passage.

In order to achieve the above object , an invention according to claim 1 is an exhaust purification device for an internal combustion engine in which a catalyst is provided in an exhaust passage of the internal combustion engine, and a bypass passage provided in the exhaust passage upstream of the catalyst; The bypass passage is connected to the exhaust passage so as to generate a swirling flow in the exhaust flow flowing into the exhaust passage immediately before the catalyst via the bypass passage, and a closed position for opening the exhaust passage and an open position for opening the exhaust passage. The exhaust flow from the internal combustion engine to the catalyst is switched to the bypass flow via the bypass passage by being arranged at the closed position, and from the internal combustion engine by being arranged at the open position. Exhaust flow switching means for switching the exhaust flow toward the catalyst mainly to the main flow via only the exhaust passage, and switching the exhaust flow switching means to the closed position when the catalyst is inactive, and when the catalyst is inactive When the outside and spirit that a control means for switching the exhaust flow switching means in the open position.

  According to the configuration of the present invention, when the catalyst is inactive, the exhaust flow switching means is switched to the closed position by the control means, so that the exhaust flow from the internal combustion engine to the catalyst is switched to the bypass flow via the bypass passage. It is done. Therefore, when the catalyst is inactive, a swirling flow is generated in the exhaust flow flowing from the bypass passage into the exhaust passage immediately before the catalyst, the exhaust is diffused and hits the entire end face of the catalyst, and the exhaust is uniformly distributed over the entire cross section of the catalyst passage. Go around. On the other hand, when the catalyst is not inactive, the exhaust flow switching means is switched to the open position by the control means so that the exhaust flow from the internal combustion engine to the catalyst is switched to the main flow mainly via only the exhaust passage. . Therefore, exhaust gas is introduced straight into the catalyst when the catalyst is not inactive. At this time, since the exhaust flow switching means is disposed in the open position, an increase in ventilation resistance in the exhaust passage is suppressed.

In order to achieve the above object , the invention according to claim 2 is characterized in that, in the invention according to claim 1 , the bypass passage has a smaller passage cross-sectional area than the exhaust passage.

According to the configuration of the above invention, in addition to the action of the invention according to the first aspect, the flow rate of the bypass flow is increased and the flow rate of the exhaust gas flowing into the catalyst is increased.

To achieve the above object, according to a third aspect of the present invention, in the first or second aspect of the present invention, the downstream end of the bypass passage is connected so as to join the exhaust passage from a tangential direction. Intended to be

According to the configuration of the invention described above, in addition to the operation of the invention described in claim 1 or 2, the bypass flow flowing into the exhaust passage easily turns along the inner wall of the exhaust passage.

According to the first aspect of the present invention, when the catalyst is inactive, the exhaust can be evenly distributed over the entire passage cross section of the catalyst to promote catalyst warm-up. When the catalyst is not inactive, the exhaust is exhausted. The exhaust gas can be purified by the catalyst without increasing the ventilation resistance of the passage.

According to the invention described in claim 2, in addition to the effect of the invention described in claim 1 , the exhaust gas can be spread over the entire passage section of the catalyst when the swirling flow is generated.

According to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or 2, it is possible to easily generate a swirling flow, and exhaust can be quickly distributed over the entire passage section of the catalyst. it can.

[First Embodiment]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A detailed description will be given below of a first embodiment of an internal combustion engine exhaust gas purification apparatus according to the present invention with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an exhaust gas purification apparatus for an internal combustion engine in this embodiment. This exhaust purification apparatus includes a catalytic converter 3 provided in an exhaust passage 2 of a gasoline engine (hereinafter referred to as “engine”) 1 as an internal combustion engine of the present invention. The catalytic converter 3 includes a casing 4 and a catalyst 5 stored in the casing 4. In the casing 4, the inlet side and the outlet side are tapered, and the tapered portions 4 a and 4 b are an inlet space 6 and an outlet space 7. The catalyst 5 is composed of, for example, a three-way catalyst and has a cylindrical shape with a honeycomb structure. The casing 4 constitutes a part of a series of exhaust passages 2 together with an exhaust pipe constituting the exhaust passage 2.

  A bypass passage 8 is provided in the exhaust passage 2 upstream of the catalytic converter 3. The bypass passage 8 is configured to generate a swirl as a swirling flow in the exhaust flow flowing into the exhaust passage 2 (inlet space 6 of the casing 4) immediately before the catalytic converter 3 via the bypass passage 8. Connected to. This swirl is a flow swirling around the axis of the catalyst 5. FIG. 2 is a schematic view showing the relationship between the exhaust passage 2, the casing 4, and the bypass passage 8 in FIG. The bypass passage 8 protrudes in the radial direction from the exhaust passage 2 and extends curvedly downward. The downstream end 8 a of the bypass passage 8 is connected to the exhaust passage 2 from the tangential direction at the upper end of the tapered portion 4 a of the casing 4. As a result, the exhaust diameter flowing out from the bypass passage 8 is swung along the inner wall of the taper portion 4a so that the swirl diameter gradually increases. In this embodiment, the bypass passage 8 has a smaller passage cross-sectional area than the exhaust passage 2. For example, in this embodiment, the passage diameter of the exhaust passage 2 is 60 mm, and the passage diameter of the bypass passage 8 is 15 mm.

  Between the upstream end 8b and the downstream end 8a of the bypass passage 8, an exhaust switching valve 9 made of a heat-resistant material is provided in the exhaust passage 2. The exhaust switching valve 9 is provided so as to be selectively switched between a closed position where the exhaust passage 2 is fully closed as shown in FIG. 4 and an open position where the exhaust passage 2 is fully opened as shown in FIG. . The exhaust gas switching valve 9 is driven to open and close by an electric actuator 10. In this embodiment, the exhaust gas switching valve 9 and the actuator 10 constitute exhaust gas switching means of the present invention. Then, the exhaust gas switching valve 9 is arranged at the closed position by the actuator 10 so that the exhaust flow from the engine 1 toward the catalytic converter 3 is switched to the bypass flow via the bypass passage 8 as shown in FIG. ing. Further, the exhaust switching valve 9 is disposed at the open position by the actuator 10 so that the exhaust flow from the engine 1 toward the catalytic converter 3 is switched to the main flow mainly via only the exhaust passage 2 as shown in FIG. It has become.

  The exhaust emission control device of this embodiment includes a controller 21 as control means of the present invention in order to control the opening and closing of the exhaust gas switching valve 9. In addition, the exhaust purification device includes a throttle sensor 22 for detecting an opening degree (throttle opening degree) TA of a throttle valve (not shown) provided in the intake passage 11 as an operating state of the engine 1, and a rotational speed of the engine 1. (Engine rotation speed) A rotation speed sensor 23 for detecting NE is provided. As is well known, the throttle valve is opened and closed according to the operation of the accelerator pedal by the driver. Further, the exhaust purification device includes a catalyst temperature sensor 24 for detecting the temperature (catalyst temperature) CT of the catalyst 5. These sensors 22 to 24 and the actuator 10 are connected to the controller 21. The controller 21 selectively opens and closes the exhaust gas switching valve 9 by controlling the actuator 10 based on detection signals from the sensors 22 to 24. That is, the controller 21 switches the exhaust switching valve 9 to the closed position by controlling the actuator 10 when the catalyst 5 is inactive, such as during cold start of the engine 1, and when the catalyst 5 is not inactive, The exhaust gas switching valve 9 is switched to the open position by controlling the actuator 10.

  FIG. 3 is a flowchart showing the control content executed by the controller 21. When the process proceeds to this routine, the controller 21 first reads the throttle opening degree TA, the engine rotational speed NE, and the catalyst temperature CT in accordance with the detection signals from the sensors 22 to 24 in step 100, respectively.

  Next, in step 110, the controller 21 determines whether or not the engine 1 is in idle operation based on the read throttle opening TA and engine rotational speed NE. That is, when the throttle opening degree TA indicates the fully closed position and the engine rotational speed NE indicates the idle rotational speed, the controller 21 determines that the idling operation is being performed. When the determination result is affirmative, the controller 21 proceeds to step 120, and when the determination result is negative, the controller 21 proceeds to step 140.

  In step 120, the controller 21 determines whether or not the catalyst 5 is inactive based on the catalyst temperature CT. For example, when the catalyst temperature CT is 350 ° C. or lower, the controller 21 determines that the catalyst 5 is inactive. When the determination result is affirmative, the controller 21 proceeds to step 130, and when the determination result is negative, the controller 21 proceeds to step 140.

  That is, when the determination results in steps 110 and 120 are both affirmative, the controller 21 shifts the process to step 130 on the assumption that the catalyst 5 is inactive when the engine 1 is started. In step 130, the controller 21 controls the actuator 10 to place the exhaust gas switching valve 9 in the closed position.

  On the other hand, if any of the determination results of steps 110 and 120 is negative, the controller 21 proceeds to step 140 assuming that the catalyst 5 is not in an inactive state. In step 140, the controller 21 controls the actuator 10 to place the exhaust gas switching valve 9 in the open position.

  According to the exhaust gas purification apparatus of this embodiment described above, the exhaust gas is discharged from the engine 1 to the exhaust passage 2 during operation of the engine 1, that is, in this embodiment, when the catalyst 5 is inactive. As shown in FIG. 4, the exhaust gas switching valve 9 is switched to the closed position. At this time, the exhaust flow from the engine 1 toward the catalyst 5 of the catalytic converter 3 is switched to the bypass flow via the bypass passage 8. Therefore, as shown in FIGS. 4 and 5, swirl is generated in the exhaust flow flowing from the bypass passage 8 into the exhaust passage 2 (inlet space 6 of the casing 4) immediately before the catalyst 5, and the exhaust gas is diffused to diffuse the catalyst 5. Exhaust gas spreads uniformly over the entire cross-section of the passage of the catalyst 5. Thereby, warming-up of the catalyst 5 when the catalyst 5 is inactive can be promoted, and the exhaust purification function by the catalyst 5 can be exhibited at an early stage immediately after startup.

  On the other hand, similarly, when the catalyst 5 is not inactive, the exhaust gas switching valve 9 is switched to the open position as shown in FIG. At this time, the exhaust flow from the engine 1 toward the catalyst 5 is switched to the main flow mainly through only the exhaust passage 2. Therefore, as shown in FIG. 6, exhaust gas is introduced straight to the catalyst 5, and the exhaust switching valve 9 is disposed at the open position in the fully open state, so that an increase in ventilation resistance in the exhaust passage 2 is suppressed. It is done.

  For this reason, according to this exhaust purification apparatus, the exhaust can be evenly distributed over the entire passage cross section of the catalyst 5 and the exhaust can be purified by the catalyst 5 without increasing the ventilation resistance of the exhaust passage 2. It is possible to selectively switch between possible states. At the same time, when the catalyst 5 is inactive, the exhaust can be evenly distributed over the entire cross-section of the passage of the catalyst 5, and warm-up of the catalyst 5 can be promoted. When the catalyst 5 is not inactive, the exhaust gas can be purified by the catalyst 5 without increasing the ventilation resistance of the exhaust passage 2. For example, when the engine 1 is operating at a high load, that is, when the exhaust amount increases, the exhaust switching valve 9 is disposed in the open position, so that the exhaust switching valve 9 does not become a large ventilation resistance in the exhaust passage 2. . For this reason, an increase in the back pressure of the engine 1 can be suppressed, an increase in pressure loss can be suppressed, and the output performance of the engine 1 can be ensured.

  Further, according to the exhaust gas purification apparatus of this embodiment, since the bypass passage 8 has a smaller passage cross-sectional area than the exhaust passage 2, the flow velocity of the exhaust gas flowing into the catalyst 5 via the bypass passage 8 is relatively high. Therefore, the increase in the catalyst temperature TC is further promoted. Further, when the swirl is generated, the exhaust gas can be spread over the entire passage section of the catalyst 5. For this reason, warm-up of the catalyst 5 can be further promoted.

  Furthermore, according to the exhaust gas purification apparatus of this embodiment, the downstream end 8a of the bypass passage 8 is connected so as to join the exhaust passage 2 from the tangential direction, so that it flows into the exhaust passage 2 immediately before the catalyst 5. The bypass flow easily turns along the inner wall of the exhaust passage 2. For this reason, it is possible to easily generate a swirl, and the exhaust gas can be quickly distributed over the entire passage section of the catalyst 5. In this sense, warming up of the catalyst 5 can be promoted.

[Second Embodiment]
Next, a second embodiment in which the exhaust gas purification apparatus for an internal combustion engine according to the present invention is embodied will be described in detail with reference to the drawings. In each of the following embodiments including this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted, and different points will be mainly described below.

  FIG. 7 shows a schematic diagram similar to FIG. FIG. 8 shows a schematic view similar to FIG. In this embodiment, the connection position of the downstream end 8a of the bypass passage 8 is different from that of the first embodiment. That is, in this embodiment, as shown in FIGS. 7 and 8, the downstream end 8 a of the bypass passage 8 joins from the tangential direction to the outer periphery of the exhaust passage 2 (casing 4) at the lower end of the tapered portion 4 a of the casing 4. To be connected. In this embodiment, as shown in FIG. 8, the exhaust flow flowing out from the bypass passage 8 turns along the inner wall of the casing 4 and diffuses. In this embodiment, the configuration is different from that of the first embodiment.

  Therefore, the same effect as that of the first embodiment can be obtained also by the exhaust emission control device of this embodiment.

[Third Embodiment]
Next, a third embodiment of the internal combustion engine exhaust gas purification apparatus according to the present invention will be described in detail with reference to the drawings.

  FIG. 9 is a schematic configuration diagram showing an exhaust emission control device for an internal combustion engine in this embodiment. In this embodiment, the exhaust gas switching valve 9 is opened and closed by a negative pressure actuator 12. The actuator 12 is driven by receiving an operating pressure. In this embodiment, a negative pressure or an atmospheric pressure is selectively supplied to the actuator 12 via the electric three-way valve 13. It has become. As the negative pressure, for example, a vacuum pump is used, or a negative pressure generated downstream of the throttle valve in the intake passage 11 is supplied. In this embodiment, the exhaust gas switching valve 9, the actuator 12 and the three-way valve 13 constitute the exhaust flow switching means of the present invention.

  In this embodiment, instead of the rotation speed sensor 23 and the catalyst temperature sensor 24 in the first and second embodiments, the engine 1 has a water temperature sensor for detecting the temperature of the cooling water (cooling water temperature) THW. 25 is provided. This water temperature sensor 25 is connected to the controller 21.

  In this embodiment, the controller 21 switches the exhaust switching valve 9 to the closed position by controlling the three-way valve 13 when the catalyst 5 is inactive, such as when the engine 1 is cold started, and when the catalyst 5 is inactive. In other cases, the exhaust switching valve 9 is switched to the open position by controlling the three-way valve 13. When the catalyst 5 is inactive, the controller 21 supplies negative pressure to the actuator 12 and switches the exhaust gas switching valve 9 to the closed position.

  FIG. 10 is a flowchart showing the control contents executed by the controller 21. When the processing shifts to this routine, the controller 21 first reads the throttle opening degree TA and the cooling water temperature THW by the detection signals from the throttle sensor 22 and the water temperature sensor 25 in step 200, respectively.

  Next, in step 210, the controller 21 determines whether or not the engine 1 is idling based on the read throttle opening TA. That is, when the throttle opening degree TA indicates the fully closed position, the controller 21 determines that the idling operation is being performed. When the determination result is affirmative, the controller 21 proceeds to step 220, and when the determination result is negative, the controller 21 proceeds to step 240.

  In step 220, the controller 21 determines whether or not the catalyst 5 is inactive based on the coolant temperature THW. For example, when the coolant temperature THW is 70 ° C. or lower, the controller 21 determines that the catalyst 5 is inactive. If the determination result is affirmative, the controller 21 proceeds to step 230. If the determination result is negative, the controller 21 proceeds to step 240.

  That is, if the determination results in steps 210 and 220 are both affirmative, the controller 21 determines that the catalyst 5 is inactive when the engine 1 is started, and the controller 21 proceeds to step 230. In step 230, the controller 21 controls the three-way valve 13 to place the exhaust gas switching valve 9 in the closed position by the actuator 12.

  On the other hand, if any of the determination results in steps 210 and 220 is negative, the controller 21 proceeds to step 240 assuming that the catalyst 5 is not in an inactive state. In step 240, the controller 21 controls the three-way valve 13 to place the exhaust gas switching valve 9 in the open position by the actuator 12.

  Therefore, the same effect as that of the first embodiment can be obtained also by the exhaust emission control device of this embodiment.

  The present invention is not limited to the embodiments described above, and can be implemented as follows by appropriately changing a part of the configuration without departing from the spirit of the invention.

  (1) In each of the above embodiments, the swirl is generated as a swirling flow by the exhaust flow flowing into the exhaust passage 2 (the inlet space 6 of the casing 4) via the bypass passage 8, but the shaft center of the catalyst You may make it generate the tumble which turns so that it may become substantially parallel as a turning flow.

  (2) Although the shut-off valve is not provided in the middle of the bypass passage 8 in each of the above embodiments, the shut-off valve is provided in the middle of the bypass passage, and the shut-off valve is closed when the exhaust gas switching valve is disposed in the open position. When the exhaust switching valve is disposed at the closed position, the shutoff valve may be opened. According to this configuration, by closing the shutoff valve when the exhaust gas switching valve is disposed at the open position, it is possible to prevent a part of the exhaust gas mainly flowing through the exhaust passage from being released to the bypass passage.

The schematic block diagram which shows an exhaust gas purification apparatus. Schematic which shows the relationship between the exhaust passage of FIG. 1, a bypass passage, etc. by planar view. The flowchart which shows the control content of a controller. Schematic which shows the effect | action of an exhaust gas purification apparatus by a front view. Schematic which shows the effect | action of an exhaust gas purification apparatus by planar view. Schematic which shows the effect | action of an exhaust gas purification apparatus by a front view. Schematic according to FIG. Schematic according to FIG. The schematic block diagram which shows an exhaust gas purification apparatus. The flowchart which shows the control content of a controller.

1 engine (internal combustion engine)
2 Exhaust passage 5 Catalyst 8 Bypass passage 8a Downstream end 9 Exhaust switching valve (exhaust flow switching means)
10 Electric actuator (exhaust flow switching means)
12 Negative pressure actuator (exhaust flow switching means)
13 Electric three-way valve (exhaust flow switching means)
21 Controller (control means)

Claims (3)

In an exhaust gas purification apparatus for an internal combustion engine in which a catalyst is provided in an exhaust passage of the internal combustion engine,
A bypass passage provided in the exhaust passage upstream of the catalyst;
The bypass passage is connected to the exhaust passage so as to generate a swirling flow in the exhaust flow flowing into the exhaust passage immediately before the catalyst via the bypass passage;
The exhaust passage is provided so that it can be selectively switched between a closed position for closing the exhaust passage and an open position for opening the exhaust passage. An exhaust flow switching means for switching the exhaust flow from the internal combustion engine toward the catalyst to the main flow mainly via only the exhaust passage by switching to the flow and being arranged at the open position;
An internal combustion engine comprising: control means for switching the exhaust flow switching means to the closed position when the catalyst is inactive, and for switching the exhaust flow switching means to the open position when the catalyst is not inactive. Engine exhaust purification system. The exhaust purification device of an internal combustion engine according to claim 1, wherein the bypass passage has a passage cross-sectional area smaller than that of the exhaust passage. 3. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein a downstream end of the bypass passage is connected so as to join the exhaust passage from a tangential direction. 4.

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