JP2007315341A - Exhaust device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of a torque level difference when a flow path selector valve 5 is opened. <P>SOLUTION: In parallel to an upstream side portion of a main passage 3 which has a main catalyst converter 4 on the downstream side, a bypass passage 7 is provided whose cross section area is relatively smaller than the total cross section area of the main passage 3. A bypass catalyst converter 8 is provided in the bypass passage 7, and the flow path selector valve 5 is provided in the upstream side portion of the main passage 3, bypassed by the bypass passage 7, for closing the main passage 3. When the flow path selector valve 5 is changed over from a closed condition into an opened condition, a timing for closing an exhaust valve is quickened. This prevents the occurrence of the torque level difference when the flow path selector valve 5 is opened. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust device for an internal combustion engine.

  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 flow path is provided in parallel with the upstream portion of the main flow path including the main catalytic converter, and another bypass catalytic converter is interposed in the bypass flow path. However, an exhaust device has been conventionally proposed in which exhaust gas is guided to the bypass flow path side immediately after the 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 relatively early, so that exhaust purification can be started from an earlier stage. it can.
JP-A-5-321644

  However, in the configuration as described above, when the changeover valve is switched so that the warm-up of the main catalytic converter is completed and the exhaust flows to the main flow path side, the exhaust does not pass through the bypass catalytic converter that becomes a passage resistance. As a result of the flow, the exhaust pressure rapidly decreases and a torque step (specifically, an increase in torque) occurs.

  Therefore, the present invention is provided with a bypass passage having a relatively small total cross-sectional area relative to the total cross-sectional area of the main passage in parallel with the upstream portion of the main passage provided with the main catalytic converter on the downstream side. An exhaust system for an internal combustion engine, comprising: a bypass catalytic converter in a bypass passage; and a flow path switching valve that closes the main passage in the upstream portion of the main passage that is bypassed by the bypass passage. The exhaust valve closing timing is advanced when the path switching valve switches from the closed state to the open state. This makes it possible to control the amount of residual gas in the cylinder when the flow path switching valve is switched from the closed state to the open state.

  According to the present invention, the residual gas amount in the cylinder is controlled by controlling the closing timing of the exhaust valve, and the residual gas amount when the flow path switching valve is switched from the closed state to the open state is controlled. By suppressing the change and allowing the gradual control of the residual gas amount, generation of a torque step can be prevented.

  Hereinafter, an embodiment in which the present invention is applied as an exhaust device of an in-line four-cylinder internal combustion engine will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory view schematically showing the piping layout of the exhaust device. First, the configuration of the entire exhaust device will be described based on FIG.

  In the cylinder head 1, exhaust ports 2 of the cylinders # 1 to # 4 arranged in series are formed so as to open toward the side surfaces, and a main passage is formed in each of the exhaust ports 2. 3 is connected. The four main passages 3 of the # 1 cylinder to the # 4 cylinder merge into one flow path, and the main catalytic converter 4 is disposed on the downstream side thereof. The main catalytic converter 4 has a large capacity arranged under the floor of the vehicle, and includes, for example, a three-way catalyst and an HC trap catalyst as the catalyst. The main passage 3 and the main catalytic converter 4 constitute a main passage through which exhaust flows during normal operation. In addition, a flow path switching valve 5 that opens and closes the main passages 3 at the same time is provided as a flow path switching means at the junction of the four main paths 3 from each cylinder.

  On the other hand, bypass passages 7 each having a smaller passage sectional area than the main passage 3 are branched from the main passages 3 of the respective cylinders as bypass passages. The branch point 6 that is the upstream end of each bypass passage 7 is set to a position on the upstream side of the main passage 3 as much as possible. The four bypass passages 7 merge into one flow path on the downstream side, and a bypass catalytic converter 8 using a three-way catalyst is interposed immediately after the junction. The bypass catalytic converter 8 has a small capacity as compared with the main catalytic converter 4, and preferably uses a catalyst excellent in low-temperature activity. The downstream end of the bypass passage 7 extending from the outlet side of the bypass catalytic converter 8 is at the junction 12 on the upstream side of the main catalyst converter 4 in the main passage 3 (so that the flow path switching valve 5 is upstream of the junction 12). It is connected.

  Air-fuel ratio sensors 10 and 11 are disposed at the inlet of the main catalytic converter 4 and the inlet of the bypass catalytic converter 8, respectively.

  Further, in the present embodiment, the exhaust valve side valve operating mechanism for driving the exhaust valve includes an exhaust valve side sprocket (not shown) provided at a front end portion of an exhaust valve side camshaft (not shown), An exhaust valve side phase control actuator (not shown) that relatively rotates the exhaust valve side camshaft within a predetermined angle range. That is, the exhaust valve side valve operating mechanism includes a phase varying means. The exhaust valve side sprocket is linked to a crankshaft (not shown) via a timing chain or timing belt (not shown). The exhaust valve side phase control actuator comprises, for example, a hydraulic rotary actuator. By the action of the exhaust valve side phase control actuator, the exhaust valve side sprocket and the exhaust valve side camshaft are relatively rotated, and the lift center angle in the valve lift of the exhaust valve is retarded. In other words, the entire lift angle is retarded without changing the lift characteristic curve itself of the exhaust valve. This change can also be obtained continuously.

  In such a configuration, when the engine temperature or the exhaust gas temperature after the cold start is low, the flow path switching valve 5 is closed via an appropriate actuator, and the main passage 3 is blocked. Therefore, the entire amount of exhaust discharged from each cylinder flows from the branch point 6 to the bypass catalytic converter 8 through the bypass passage 7. The bypass catalytic converter 8 is located upstream of the exhaust system, that is, at a position close to the exhaust port 2 and is small in size, so that it is activated quickly and exhaust purification is started at an early stage.

  On the other hand, when the engine warms up and the engine temperature or the exhaust temperature becomes sufficiently high, the flow path switching valve 5 is opened. Thus, the exhaust discharged from each cylinder mainly passes through the main catalytic converter 4 from the main passage 3. At this time, the bypass passage 7 side is not particularly cut off, but the bypass passage 7 side has a smaller passage cross-sectional area than the main passage 3 side and the bypass catalytic converter 8 is interposed. Due to the difference, most of the exhaust flow passes through the main passage 3 side and hardly flows into the bypass passage 7 side. Therefore, the thermal deterioration of the bypass catalytic converter 8 is sufficiently suppressed.

  Here, when the flow path switching valve 5 opens the main passage 3 as described above, since the passage resistance of the main passage 3 is small, the exhaust pressure rapidly decreases, and the residual gas amount in the cylinder also sharply increases. If it is left as it is, the torque increases instantaneously and a torque step occurs.

  Therefore, in the present invention, when the flow path switching valve 5 is opened, the pressure drop in the main passage 3 is rapidly increased by confining the residual gas in the cylinder by correcting the valve closing timing of the exhaust valve to the advance side. Even if it occurs, a sudden change in the amount of residual gas in the cylinder is suppressed, and an instantaneous torque increase is prevented.

  FIG. 2 is a timing chart for explaining various operations in the first embodiment of the present invention. In the figure, the solid line is the characteristic line in the first embodiment of the present invention, and the broken line is the flow path switching valve 5. This is a characteristic of the first comparative example in which the residual gas amount in the cylinder changes stepwise without correcting the valve closing timing of the exhaust valve to the advance side when switching from fully closed to fully open. The alternate long and short dash line in the generated torque characteristic line of the internal combustion engine indicates that the throttle valve (not shown) arranged in the intake passage is opened when the flow path switching valve 5 is opened in the first embodiment. FIG. 3 shows the characteristics of the generated torque when the degree is corrected large (in comparison with the control of the present invention) in the valve closing direction as indicated by the dotted line in FIG.

  When the warm-up is completed, the control command for the flow path switching valve 5 is switched from a fully closed command to a full open command, and the flow path switching valve 5 starts to open at the timing of this switching. At this time, the valve closing timing of the exhaust valve is corrected to the advance side so that the residual gas amount in the cylinder is kept constant, and the valve opening of the throttle valve is corrected to the valve closing side. In other words, when the flow path switching valve 5 is switched from the fully closed state to the fully open state, the exhaust valve closing timing is corrected to the advance side so that the residual gas amount in the cylinder is maintained constant. Correction of the valve opening of the throttle valve to the valve closing side is performed.

  Thereby, when the flow path switching valve 5 starts to open from the fully closed state, the residual gas amount in the cylinder is maintained, and the generated torque of the internal combustion engine can have a flat characteristic without a torque step. Note that the correction amount of the throttle valve immediately after switching is smaller than that in the case where the closing timing of the exhaust valve is not corrected.

  When the flow path switching valve 5 is fully opened, the valve opening of the throttle valve is gradually changed in the closing direction while returning the closing timing of the exhaust valve corrected to the advance side to the retard side. To do. In other words, the valve timing of the exhaust valve changed to the advance side is returned to the retard side in cooperation with the throttle valve after the flow path switching valve 5 is opened. In this way, by controlling the residual gas amount in the cylinder by the exhaust valve side valve operating mechanism, the change in the residual gas amount in the cylinder can be moderated and the occurrence of a torque step can be prevented. . In other words, the residual gas amount in the cylinder can be controlled without being influenced by the valve opening / closing speed (switching speed) of the flow path switching valve 5, and therefore, for example, a drive system in which the valve opening / closing speed cannot be controlled. An actuator can be employed as the drive source of the flow path switching valve 5, and the degree of freedom in selecting the actuator that becomes the drive source of the flow path switching valve 5 is increased, thereby reducing costs.

  In the first embodiment described above, when the flow path switching valve 5 is opened, the closing timing of the exhaust valve is corrected to the advance side. However, the closing timing of the exhaust valve is corrected to the advance side. Instead of this, even if the valve opening timing of the intake valve is corrected to the advance side, the same effect as in the first embodiment can be obtained. In this case, the intake valve side valve operating mechanism for driving the intake valve is configured to include phase variable means for delaying the lift center angle in the valve lift of the intake valve, and the flow path switching valve 5 is fully opened. Then, the opening timing of the intake valve is returned to the retard side in cooperation with a throttle valve (not shown) arranged in the intake passage. Since the timing when the intake valve is closed affects the in-cylinder intake efficiency, the intake valve is opened while the in-cylinder intake efficiency is not increased to the extent that the torque suppression effect due to residual gas maintenance is negated. Correct the valve timing to the advance side. For example, correct the valve opening timing of the intake valve to the advance side while keeping the angle from the bottom dead center after correction at least as compared with the angle from the bottom dead center before correction. To do.

  Further, when the flow path switching valve 5 is opened, the closing timing of the exhaust valve is corrected to the advance side, and at the same time, the opening timing of the intake valve is corrected to the advance side. The same effect as the form can be obtained. In this case, both the intake valve side valve mechanism for driving the intake valve and the exhaust valve side valve mechanism for driving the exhaust valve are each provided with phase varying means for delaying the lift center angle in the valve lift. When the flow path switching valve 5 is fully opened, both the exhaust valve closing timing and the intake valve opening timing are retarded in cooperation with a throttle valve (not shown) arranged in the intake passage. Will be returned to.

  FIG. 3 is a timing chart for explaining various operations in the second embodiment of the present invention. In the figure, the solid line is the characteristic line in the second embodiment of the present invention, and the broken line is the flow path switching valve 5. 6 is a characteristic line of a second comparative example in which the residual gas amount in the cylinder changes stepwise without correcting the valve closing timing of the exhaust valve to the advance side when switching from fully closed to fully open.

  The second embodiment is controlled in substantially the same manner as the first embodiment described above, but the flow path is switched in consideration of the responsiveness of the exhaust valve side phase control actuator of the exhaust valve side valve operating mechanism. When the control command for the valve 5 is switched from the fully closed command to the fully opened command, the operating duty for the exhaust valve side phase control actuator is increased in advance prior to the actual valve opening operation of the flow path switching valve 5. is there. That is, when the flow path switching valve 5 is opened, the operating duty for the exhaust valve side phase control actuator is increased in advance, so that in addition to the effects of the first embodiment described above, Responsiveness of correction (switching) to the advance side of the valve closing timing can be improved, the change in the residual gas amount in the cylinder is further reduced, and the occurrence of a torque step can be prevented more reliably.

  In the second embodiment, when the flow path switching valve 5 is opened, the closing timing of the exhaust valve is corrected to the advance side. However, the closing timing of the exhaust valve is corrected to the advance side. Instead, even if the valve opening timing of the intake valve is corrected to the advance side, the same effect as the second embodiment can be obtained. In this case, the intake valve side valve operating mechanism for driving the intake valve is configured to include phase variable means for delaying the lift center angle in the valve lift of the intake valve, and the flow path switching valve 5 is fully opened. Then, the opening timing of the intake valve is returned to the retard side in cooperation with a throttle valve (not shown) arranged in the intake passage.

  Further, when the flow path switching valve 5 is opened, the closing timing of the exhaust valve is corrected to the advance side, and at the same time, the opening timing of the intake valve is corrected to the advance side. The same effect as the form can be obtained. In this case, both the intake valve side valve mechanism for driving the intake valve and the exhaust valve side valve mechanism for driving the exhaust valve are each provided with phase varying means for delaying the lift center angle in the valve lift. When the flow path switching valve 5 is fully opened, both the exhaust valve closing timing and the intake valve opening timing are retarded in cooperation with a throttle valve (not shown) disposed in the intake passage. Will be returned to.

  The technical idea of the present invention that can be grasped from the above embodiment will be listed together with the effects thereof.

  (1) A bypass passage having a relatively small total cross-sectional area relative to the total cross-sectional area of the main passage is provided in parallel with the upstream portion of the main passage provided with the main catalytic converter on the downstream side. An exhaust system for an internal combustion engine, comprising: a bypass catalytic converter; and an upstream portion of the main passage that is bypassed by the bypass passage, the passage switching valve closing the main passage. When the valve switches from the closed state to the open state, the exhaust valve closing timing is advanced. This controls the residual gas amount in the cylinder by controlling the closing timing of the exhaust valve, and suppresses the change in the residual gas amount when the flow path switching valve is switched from the closed state to the open state. In addition, it is possible to prevent the occurrence of a torque step by enabling a gradual control of the residual gas amount.

  (2) Specifically, the exhaust system for an internal combustion engine according to the above (1) is a phase variable means for correcting the phase of the center angle of the lift of the exhaust valve to the advance side in order to advance the exhaust valve closing timing. Is provided.

  (3) A bypass passage having a relatively small total cross-sectional area relative to the total cross-sectional area of the main passage is provided in parallel with the upstream portion of the main passage provided with the main catalytic converter on the downstream side. An exhaust system for an internal combustion engine, comprising: a bypass catalytic converter; and an upstream portion of the main passage that is bypassed by the bypass passage, the passage switching valve closing the main passage. When the engine switches from the closed state to the open state, the intake valve opening timing is advanced.

  (4) Specifically, the exhaust system for an internal combustion engine according to (3) described above is a phase variable means for correcting the phase of the center angle of the lift of the intake valve to the advance side in order to advance the opening timing of the intake valve. Is provided.

  (5) A bypass passage having a relatively small total cross-sectional area relative to the total cross-sectional area of the main passage is provided in parallel with the upstream portion of the main passage provided with the main catalytic converter on the downstream side. An exhaust system for an internal combustion engine, comprising: a bypass catalytic converter; and an upstream portion of the main passage bypassed by the bypass passage, the passage switching valve closing the main passage. When the engine is switched from the closed state to the open state, the exhaust valve closing timing and the intake valve opening timing are advanced.

  (6) Specifically, the exhaust system for an internal combustion engine according to (5) described above advances the phase of the central angle of the lift of the exhaust valve and the intake valve in order to advance the exhaust valve closing timing and the intake valve opening timing. Phase variable means for correcting the angle side is provided.

  (7) In the exhaust system for an internal combustion engine according to any one of (2), (4), and (6), a flow path switching valve switching command for switching the flow path switching valve from a closed state to an open state is issued. In this case, prior to the opening operation of the flow path switching valve, the operation duty for the phase variable means is increased in advance. As a result, the responsiveness of switching the exhaust valve closing timing to the advance side can be improved, the change in the residual gas amount in the cylinder can be further reduced, and the occurrence of a torque step can be prevented more reliably. Can do.

  (8) In the exhaust system for an internal combustion engine according to any one of (1) to (7), the valve timing changed to the advance side is the same as that of the throttle valve after the flow path switching valve is opened. It returns to the retarded angle side in cooperation. As a result, the residual gas amount in the cylinder can be controlled without being influenced by the valve opening / closing speed (switching speed) of the flow path switching valve. An actuator can be employed as the drive source of the flow path switching valve 5, and the degree of freedom in selecting the actuator that becomes the drive source of the flow path switching valve is increased, thereby reducing the cost.

BRIEF DESCRIPTION OF THE DRAWINGS The structure explanatory drawing which shows the piping layout of the whole exhaust apparatus of the internal combustion engine which concerns on this invention. The timing chart for demonstrating the various operation | movement in 1st Embodiment of this invention. The timing chart for demonstrating the various operation | movement in 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Main passage 4 ... Main catalytic converter 5 ... Flow path switching valve 6 ... Branch point 7 ... Bypass passage 8 ... Bypass catalytic converter 12 ... Junction point

Claims (8)

A bypass passage having a relatively small total cross-sectional area relative to the total cross-sectional area of the main passage is provided in parallel with the upstream portion of the main passage provided with the main catalytic converter on the downstream side. And an exhaust device for an internal combustion engine comprising a flow path switching valve that closes the main passage at the upstream portion bypassed by the bypass passage among the main passages,
An exhaust system for an internal combustion engine, wherein the exhaust valve closing timing is advanced when the flow path switching valve is switched from a closed state to an open state.   2. An exhaust system for an internal combustion engine according to claim 1, further comprising phase varying means for correcting the phase of the central angle of the lift of the exhaust valve to the advance side in order to advance the closing timing of the exhaust valve. A bypass passage having a relatively small total cross-sectional area relative to the total cross-sectional area of the main passage is provided in parallel with the upstream portion of the main passage provided with the main catalytic converter on the downstream side. And an exhaust device for an internal combustion engine comprising a flow path switching valve that closes the main passage at the upstream portion bypassed by the bypass passage among the main passages,
An exhaust system for an internal combustion engine, wherein the intake valve opening timing is advanced when the flow path switching valve switches from a closed state to an open state.   4. An exhaust system for an internal combustion engine according to claim 3, further comprising phase varying means for correcting the phase of the central angle of the lift of the intake valve to the advance side in order to advance the opening timing of the intake valve. A bypass passage having a relatively small total cross-sectional area relative to the total cross-sectional area of the main passage is provided in parallel with the upstream portion of the main passage provided with the main catalytic converter on the downstream side. And an exhaust device for an internal combustion engine comprising a flow path switching valve that closes the main passage at the upstream portion bypassed by the bypass passage among the main passages,
An exhaust system for an internal combustion engine, wherein the exhaust valve closing timing and the intake valve opening timing are advanced when the flow path switching valve is switched from a closed state to an open state.   6. The phase varying means for correcting the phase of the central angle of the lift of the exhaust valve and the intake valve to the advance side in order to advance the exhaust valve closing timing and the intake valve opening timing. An exhaust system for an internal combustion engine.   When a flow path switching valve switching command for switching the flow path switching valve from the closed state to the open state is issued, the operating duty for the phase variable means is increased in advance prior to the opening operation of the flow path switching valve. An exhaust system for an internal combustion engine according to any one of claims 2, 4, and 6.   8. The valve timing changed to the advance side is returned to the retard side in cooperation with the throttle valve after the flow path switching valve is opened. Exhaust device for internal combustion engine.

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