JP4661792B2 - Exhaust noise suppression device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust noise suppression device for an internal combustion engine that includes an exhaust purification catalyst in an exhaust system.

  In general, in an internal combustion engine, if an exhaust system is equipped with a catalyst for exhaust purification, it is known that after the engine is cold, the catalyst has not been warmed up and its processing capacity is not sufficient. It has been. That is, when the warming-up of the catalyst is not completed, unburned HC, which is likely to be generated when the engine is cold, is discharged without being processed, and the emission may be deteriorated. In order to reduce such deterioration of emissions, it is required to reduce the generation of unburned HC in the engine itself as well as to warm up the catalyst early.

  In order to satisfy such demands, a technique has been proposed in which the exhaust gas temperature is increased by retarding the ignition timing immediately after the cold start so as to quickly warm up the exhaust gas purification catalyst disposed in the exhaust system. (See, for example, Patent Document 1).

  Further, Patent Document 2 discloses a stratified charge combustion in an in-cylinder injection type spark ignition internal combustion engine in which the ignition timing is retarded and the exhaust gas temperature is increased to perform stratified charge combustion by internal exhaust gas recirculation. Technology that delays the exhaust valve opening timing during stratified combustion without increasing the valve overlap period by a variable valve timing mechanism in order to further increase the exhaust gas temperature without causing instability Is disclosed.

JP 11-324765 A JP 2005-105874 A

  By the way, as described above, when exhaust gas temperature rise control is performed by retarding the ignition timing after the engine is cold, combustion in the combustion chamber is exhausted by the retarded ignition timing. As a result of approaching the valve opening timing, the in-cylinder pressure at the opening timing of the exhaust valve becomes higher than that due to combustion at the normal ignition timing. In other words, the pressure difference in the front and back flow of the exhaust valve in the closed state becomes large. As a result, the exhaust gas in the combustion chamber suddenly flows into the exhaust passage downstream of the exhaust valve at the moment when the exhaust valve is opened, and the exhaust pulsation that causes exhaust noise also increases. As a result, there is a problem in that the excitation force to the exhaust pipe increases, the wave tends to be shocking, and abnormal noise is generated.

  The present invention has been made in view of such circumstances, and an object of the present invention is to reduce the occurrence of abnormal noise in an internal combustion engine that can suppress the occurrence of abnormal noise even when the ignition timing is retarded in order to perform early catalyst warm-up. The object is to provide a sound suppression device.

  An exhaust noise suppression device for an internal combustion engine according to an aspect of the present invention that achieves the above object includes an ignition timing that includes a catalyst disposed in an exhaust passage and retards the ignition timing by a predetermined amount for warming up the catalyst. In an internal combustion engine having a retard control means, when the ignition timing is retarded by the ignition timing retard control means, the opening timing of the exhaust valve is changed in accordance with the in-cylinder pressure resulting from the retarded ignition timing. An exhaust valve opening timing changing means is provided.

  Here, the exhaust valve opening timing changing means is caused by the in-cylinder pressure resulting from the ignition timing when the ignition timing is in a normal advance state and the ignition timing retarded by the ignition timing retarding control means. It is preferable to change the opening timing of the exhaust valve at a timing at which the in-cylinder pressure becomes substantially equal.

  According to the exhaust noise suppression apparatus for an internal combustion engine according to an aspect of the present invention, when the ignition timing is retarded by the ignition timing retard control means, the in-cylinder pressure caused by the retarded ignition timing is made to correspond. Thus, the exhaust valve opening timing is changed by the exhaust valve opening timing changing means. Therefore, since the opening timing of the exhaust valve is changed corresponding to this in-cylinder pressure, the occurrence of abnormal noise is suppressed by opening the exhaust valve at a timing when the pressure difference in the upstream and downstream flow of the exhaust valve becomes small. Can do.

  Further, the exhaust valve opening timing changing means includes a cylinder pressure caused by the ignition timing when the ignition timing is in a normal advance state, and a cylinder caused by the ignition timing retarded by the ignition timing retard control means. According to the mode in which the opening timing of the exhaust valve is changed at the timing when the internal pressure becomes substantially equal, even when the ignition timing is retarded, compared with when the ignition timing is retarded, the exhaust timing is The generation of exhaust noise can be reliably suppressed without increasing the excitation force to the pipe.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, referring to FIGS. 1 and 2, reference numeral 10 denotes an engine body, which is connected to an intake pipe 2 via an intake manifold 1 and connected to an exhaust pipe 4 via an exhaust manifold 3. The intake pipe 2 is provided with a so-called electric throttle valve 5 that is driven by a motor (not shown) independently of the amount of depression of the accelerator pedal and whose opening degree can be controlled by an electronic control unit (ECU) 50 described later. Has been. An air flow meter 6 is provided upstream of the intake pipe 2 and further communicated with an air cleaner. Also. An exhaust purification catalyst, for example, a three-way catalyst 7 is disposed in the exhaust pipe 4 forming the exhaust passage. Further, an expansion chamber 8 is communicated with the exhaust pipe 4 upstream of the three-way catalyst 7 via an on-off valve 9.

  The engine body 10 includes a cylinder block 12, a piston 14 that reciprocates within the cylinder block 12, and a cylinder head 16 attached to the cylinder block 12. The cylinder head 16 is provided with a spark plug 18. A plurality of (three in this embodiment) combustion chambers 22 defined by the cylinder block 12, the piston 14, and the cylinder head 16 are formed in the engine body 10.

  Each combustion chamber 22 communicates with an intake port 24 and an exhaust port 26 formed in the cylinder head 16. An intake valve 28 is disposed between the combustion chamber 22 and the intake port 24, and the intake valve 28 opens and closes the flow path between the combustion chamber 22 and the intake port 24. On the other hand, an exhaust valve 30 is disposed between the combustion chamber 22 and the exhaust port 26, and the exhaust valve 30 opens and closes a flow path between the combustion chamber 22 and the exhaust port 26. In the present embodiment, the cylinder head 16 is provided with a fuel injection valve 32 for supplying fuel directly to the combustion chamber 22.

  The intake valve 28 and the exhaust valve 30 are linked to an intake valve variable valve mechanism 34 and an exhaust valve variable valve mechanism 36, respectively. The intake valve variable valve mechanism 34 and the exhaust valve variable valve mechanism 36 are respectively an intake cam that drives the intake valve 28 and the exhaust valve 30 to move forward and backward, an intake camshaft in which an exhaust cam is formed, and rotation of the exhaust camshaft relative to the crankshaft. The phase can be changed by a hydraulic drive mechanism (not shown), and the opening / closing timing of the intake valve 28 and the exhaust valve 30 can be arbitrarily controlled based on a signal from the ECU 50. Therefore, for example, when the intake valve variable valve mechanism 34 and / or the exhaust valve variable valve mechanism 36 are operated based on a signal from the ECU 50, the opening / closing timing of the intake valve 28 and / or the exhaust valve 30 is changed from the reference angular position. The advance angle and / or the retard angle are controlled. Since the structures of the intake valve variable valve mechanism 34 and the exhaust valve variable valve mechanism 36 are well known, detailed description thereof is omitted. Here, in the initial state in which no hydraulic pressure is supplied, the hydraulic drive mechanism is fixed by a lock pin at the most retarded angle position for the intake valve 28 and at the most advanced angle position for the exhaust valve 30, and this position is the initial reference angle. A hydraulic drive mechanism is configured as the position. In this way, the structure and control are simplified. The intake valve variable valve mechanism 34 and the exhaust valve variable valve mechanism 36 are also mapped and stored in advance in the ROM of the ECU 50 according to the operating state.

  The ECU 50 includes a microcomputer having a known configuration in which a read only memory (ROM), a random access memory (RAM), a microprocessor (CPU), an input port, and an output port are connected to each other via a bidirectional bus. In addition to the coolant temperature sensor 21 and the air flow meter 6 of the engine 10, the ECU 50 includes an accelerator opening sensor, a throttle opening sensor, and a crankshaft (not shown) that generate an output voltage proportional to the amount of depression of the accelerator pedal at a predetermined angle. Various sensors such as a crank angle sensor that generates an output pulse each time it rotates and an air-fuel ratio sensor for detecting the air-fuel ratio of combustion gas are connected.

  Further, the electric throttle valve 5, the on-off valve 9, the spark plug 18, the fuel injection valve 32, the intake valve variable valve mechanism 34, the exhaust valve variable valve mechanism 36, and the like are also connected to the ECU 50, and the operation thereof is performed. Be controlled. In the present embodiment, the opening degree of the throttle valve 5 can be changed regardless of the accelerator depression amount, and the intake pressure is controlled by adjusting the throttle valve opening degree. In the ROM of the ECU 50, the reference value of the fuel injection amount and ignition timing set according to the operating state and the engine cooling are set based on the engine load and the engine speed obtained by the accelerator opening sensor and the crank angle sensor. Correction values and the like based on the water temperature are mapped and stored in advance.

  Here, an example of the control procedure of the present embodiment configured as described above will be described with reference to the flowchart of FIG. First, when control is started, it is determined in step S301 whether or not ignition timing retard control for warming up the catalyst 7 is being executed. When the ignition timing retarding control for warm-up is not being executed, this control is terminated.

  The ignition timing retarding control for warming up the catalyst 7 is read at a predetermined cycle in a control routine executed separately from the flowchart of FIG. 3, for example, the engine speed Ne and the engine cooling. This is performed based on the water temperature Thw. That is, when the engine cooling water temperature Thw is equal to or lower than a predetermined value, it is estimated that the warm-up of the catalyst 7 is not completed, and is obtained in advance by experiments or the like according to the height of the engine cooling water temperature Thw and stored in the ROM of the ECU 50. The retard amount stored in the map is added to the reference value, and the ignition timing is retarded.

  Therefore, if it is determined in step S301 that the ignition timing retardation control is being executed, the process proceeds to step S302, and the retardation amount Ad at that time is confirmed. In the next step S303, it is determined whether or not the opening timing of the exhaust valve 30 corresponds to the confirmed retardation amount Ad. In other words, it is determined whether or not the exhaust valve 30 is opened at the opening timing corresponding to the in-cylinder pressure caused by the ignition timing retarded by the retard amount Ad. If it is determined in step S303 that the opening timing of the exhaust valve 30 does not correspond to the retard amount Ad, the process proceeds to step S304, and the opening timing of the exhaust valve 30 is changed by the exhaust valve opening timing changing means. Is done. That is, the hydraulic drive mechanism of the exhaust valve variable valve mechanism 36 is controlled, and the opening timing of the exhaust valve 30 is changed. If it is determined in step S303 that the opening timing of the exhaust valve 30 corresponds to the retard amount Ad, the process returns to step S301 and the above control procedure is repeated.

  As for the opening timing of the exhaust valve 30, the relationship between the retard amount and the in-cylinder pressure is experimentally obtained in advance and stored in a map as described above, and the exhaust valve 30 is opened at a predetermined in-cylinder pressure. May be opened. Although not shown, the in-cylinder pressure is detected using an in-cylinder pressure sensor, and feedback control is performed so that the exhaust valve 30 is opened at the opening timing at which the detected in-cylinder pressure becomes a predetermined in-cylinder pressure. May be.

  Here, the content of the above-described control will be described in more detail with reference to FIG. 4 and FIG. FIG. 4 shows the in-cylinder pressure resulting from the ignition timing when the ignition timing is in the normal advance state when the horizontal axis is the crank angle (° CA) and the exhaust valve 30 is opened at the predetermined crank angle EVOn. 5 is a time chart showing a state of change in the in-cylinder pressure caused by the ignition timing retarded by the retard amount Ad by the ignition timing retard control means, and a state of change in the exhaust pulsation pressure caused by these. In FIG. 4, the upper graph shows how the in-cylinder pressure (MPa) changes, and the lower graph shows how the exhaust pulsation pressure changes, and curve A shows the ignition timing in a normal advance state. When curve B is at the retarded ignition timing. The in-cylinder pressure caused by the ignition timing in the normal advance state is approximately 60 ° CA after the top dead center (TDC), whereas the cylinder pressure caused by the retarded ignition timing. It can be seen that the internal pressure has a peak around 80 ° CA after top dead center (TDC).

  FIG. 5 is a time chart showing an enlarged area surrounded by a broken line in FIG. As is apparent from curve A and curve B of this time chart, when the exhaust valve 30 is opened at a predetermined crank angle EVOn and the ignition timing is in a normal advance state (curve A), the in-cylinder pressure is MPan. In contrast, when the exhaust valve 30 is opened at a predetermined crank angle EVOn and the ignition timing is retarded (curve B), the in-cylinder pressure becomes MAd. Therefore, in the present embodiment, the exhaust valve opening timing changing means has the in-cylinder pressure MPan resulting from the ignition timing when the ignition timing is in the normal advance angle state, and the ignition retarded by the ignition timing retard control means. The opening timing of the exhaust valve 30 is delayed by d and changed to the timing EVOd at which the in-cylinder pressure due to the timing becomes substantially equal.

  As a result, even when the ignition timing is retarded due to warm-up of the catalyst 7, the in-cylinder pressure MPan resulting from the ignition timing when the ignition timing is in the normal advance state, in other words, the exhaust valve Since the exhaust valve 30 is opened at a timing when the pressure difference between the upstream and downstream flows becomes small, the generation of exhaust noise is suppressed.

  In the present embodiment, when the ignition timing is retarded due to the warm-up of the catalyst 7 described above, the on-off valve 9 is opened, and the exhaust pipe 4 and the expansion chamber 8 upstream of the three-way catalyst 7 To increase the capacity. In this way, even when the control of the exhaust valve 30 is not sufficient to suppress the noise, the increase in the capacity of the exhaust pipe 4 including the exhaust manifold 3 immediately after the exhaust valve 30 causes the increase in capacity. Since the exhaust pulsation that causes exhaust noise and the excitation force to the exhaust pipe 4 are attenuated, the generation of abnormal exhaust noise can be reliably suppressed. The opening / closing valve 9 may control the opening degree so as to be optimal in relation to the exhaust noise and the performance after the warm-up of the catalyst 7 is completed and the retard control of the ignition timing is completed. .

1 is a schematic plan view showing an outline of an exhaust noise suppression device for an internal combustion engine according to the present invention. 1 is a schematic side sectional view showing an outline of an abnormal noise suppression apparatus for an internal combustion engine according to the present invention. It is a flowchart which shows an example of the control procedure of the exhaust noise suppression apparatus of the internal combustion engine which concerns on this invention. When the exhaust valve is opened at a predetermined crank angle, the cylinder pressure caused by the ignition timing when the ignition timing is in the normal advance angle state and the cylinder caused by the ignition timing retarded by the ignition timing retard control means It is a time chart which shows the mode of a change of internal pressure, and the mode of a change of exhaust pulsation pressure resulting from these. 5 is an enlarged time chart showing a region surrounded by a broken line in FIG.

Explanation of symbols

4 Exhaust pipe 7 Three-way catalyst 8 Expansion chamber 9 Open / close valve 10 Engine body 18 Spark plug 30 Exhaust valve 32 Fuel injection valve 36 Exhaust valve variable valve mechanism 50 ECU

Claims (1)

In an internal combustion engine that includes a catalyst disposed in an exhaust passage and includes an ignition timing retard control means that retards an ignition timing by a predetermined amount for warming up the catalyst.
When the ignition timing is retarded by the ignition timing retard control means, the exhaust valve opening timing changing means for changing the opening timing of the exhaust valve in response to the in-cylinder pressure resulting from the retarded ignition timing,
The exhaust valve opening timing changing means includes an in-cylinder pressure resulting from the ignition timing when the ignition timing is in a normal advance angle state, and an in-cylinder pressure resulting from the ignition timing retarded by the ignition timing retard control means. An exhaust noise suppression device for an internal combustion engine, characterized in that the opening timing of the exhaust valve is changed at a timing when becomes substantially equal .

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