JP2002303164A - Exhaust noise reducer for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress exhaust noises generated during early warm-up control of a catalyst. SOLUTION: A variable valve timing device 27 is provided for varying the opening/closing timing for an exhaust valve 26 for an engine 11. During executing the early warm-up control of the catalyst (ignition timing delay control), the opening timing for the exhaust valve 26 is advanced or delayed at a predetermined crank angle from a peak timing for a usual cylinder pressure, Thus, the cylinder pressure during opening the exhaust valve 26 can be properly lowered than the usual peak cylinder pressure and the (exhaust) pressure of a cylinder combustion gas to be exhaust from the engine 11 into an exhaust pipe 22 during the early warm-up control of the catalyst, resulting in suppressed exhaust noises.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust noise reduction device for an internal combustion engine that performs early catalyst warm-up control during cold start.

[0002]

2. Description of the Related Art In recent years, an internal combustion engine mounted on a vehicle carries out early catalyst warm-up control at a cold start in order to quickly warm up a catalyst for purifying exhaust gas to an activation temperature at a cold start. I am trying to do it. In the catalyst early warm-up control, generally, the warm-up of the catalyst is promoted by retarding the ignition timing to increase the temperature of the exhaust gas.

[0003]

However, during execution of the catalyst early warm-up control (ignition timing retard control), as shown in FIG. The rise time of the internal pressure also shifts in the retard direction. Thereby, the timing when the in-cylinder pressure reaches a peak approaches the valve opening timing of the exhaust valve (see the broken line in FIG. 3). As a result, during the early catalyst warm-up control, the in-cylinder combustion gas having a higher pressure than in the normal idling state is discharged into the exhaust pipe, and the gas pressure (exhaust pressure) in the exhaust pipe increases. growing. In vehicles that have been quieted in recent years, there is a problem that the exhaust sound during the catalyst early warm-up control is heard as noise by the driver.

The present invention has been made in view of such circumstances, and an object thereof is to reduce exhaust noise generated during early catalyst warm-up control and improve quietness. An object of the present invention is to provide a device for reducing exhaust noise of an internal combustion engine that can be used.

[0005]

To achieve the above object, an exhaust noise reduction device for an internal combustion engine according to claim 1 of the present invention is provided.
A variable valve timing device for varying the opening / closing timing of the exhaust valve is provided.During early catalyst warm-up control, the exhaust valve control means advances the valve opening timing of the exhaust valve in a direction away from the normal in-cylinder pressure peak timing or It is intended to be retarded.

In this case, if the opening timing of the exhaust valve is advanced from the peak timing of the normal in-cylinder pressure, the exhaust valve can be opened while the in-cylinder pressure is increasing. Further, if the opening timing of the exhaust valve is retarded from the peak timing of the normal in-cylinder pressure, the exhaust valve can be opened after the in-cylinder pressure starts to decrease from the peak pressure. Therefore, if the advance amount or the retard amount of the valve opening timing of the exhaust valve is set appropriately during the catalyst early warm-up control,
The in-cylinder pressure at the time of opening the exhaust valve can be reduced appropriately from the peak pressure of the normal in-cylinder pressure, and the in-cylinder combustion gas discharged from the internal combustion engine into the exhaust passage during the catalyst early warm-up control can be reduced. The pressure (exhaust pressure) can be made lower than before, and exhaust noise can be reduced.

[0007] Further, the flow path volume expansion means may increase the flow path volume of the exhaust passage upstream of the catalyst during the early catalyst warm-up control. With this configuration, even if the in-cylinder pressure at the time of opening the exhaust valve increases due to the catalyst early warm-up control, the gas pressure in the exhaust passage can be increased by increasing the flow path volume in the upstream portion of the exhaust passage. (Exhaust pressure) can be reduced, and exhaust noise can be reduced.

According to a third aspect of the present invention, a bypass passage is provided in a portion of the exhaust passage upstream of the catalyst, and an opening / closing means for opening / closing the bypass passage is provided. By releasing the means, the exhaust gas of the internal combustion engine is divided into the exhaust passage and the bypass passage, and the phase of the exhaust pressure pulsation of both passages is shifted by about a half wavelength (half cycle) at the junction on the downstream side of both passages. You may comprise so that it may join. With this configuration, when the exhaust pressure pulsation wave of one passage has a peak at the junction of the exhaust passage and the bypass passage, the exhaust pressure pulsation wave of the other passage becomes a valley, so that both exhaust pressure pulsations cancel each other. As a result, exhaust pressure pulsation can be effectively attenuated and exhaust noise can be reduced.

According to a fourth aspect of the present invention, there is provided an exhaust manifold length changing means for changing the length of the exhaust manifold of at least some of the cylinders. By changing the length of the manifold, the phase of the exhaust pressure pulsation of each cylinder may be merged at the junction of the exhaust manifold of each cylinder with a shift of approximately half a wavelength. In this way, the exhaust pressure pulsation of each cylinder cancels out at the junction of the exhaust manifold, whereby the exhaust pressure pulsation of each cylinder can be effectively attenuated to reduce the exhaust noise.

[0010]

[Embodiment (1)] An embodiment (1) of the present invention will be described below with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of an intake pipe 12 of an engine 11 which is an internal combustion engine, and an air flow meter 14 for detecting an intake air amount is provided downstream of the air cleaner 13. Downstream of the air flow meter 14, a throttle valve 15 and a throttle opening sensor 16 for detecting a throttle opening are provided.

Further, a surge tank 17 is provided downstream of the throttle valve 15.
7, an intake pipe pressure sensor 18 for detecting an intake pipe pressure is provided. Further, the surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached near an intake port of the intake manifold 19 of each cylinder. I have. An ignition plug 21 is attached to the cylinder head of the engine 11 for each cylinder, and the mixture in the cylinder is ignited by spark discharge of each ignition plug 21.

An intake valve 25 and an exhaust valve 26 of the engine 11 are each driven by a camshaft (not shown), and a variable valve timing of a hydraulic type for changing the opening / closing timing of the exhaust valve 26 is provided on a camshaft on the exhaust side. Device 27
Is provided. This variable valve timing device 27
Is controlled by a hydraulic control valve 28. Note that a variable valve timing device that varies the valve timing of the intake valve 25 may also be provided on the camshaft on the intake side. Further, the variable valve timing device 27 may be driven by an electromagnetic actuator.

On the other hand, a catalyst 24 such as a three-way catalyst for reducing CO, HC, NOx and the like in the exhaust gas is provided in an exhaust pipe 22 (exhaust passage) of the engine 11, and the exhaust gas is provided upstream of the catalyst 24. An air-fuel ratio sensor 23 (linear A / F sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or lean / rich of the gas is provided. A cooling water temperature sensor 29 for detecting a cooling water temperature is provided in a cylinder block of the engine 11.
And a crank angle sensor 30 for detecting the engine speed.
Is attached.

These various sensor outputs are input to an engine control circuit (hereinafter referred to as "ECU") 31.
The ECU 31 is mainly composed of a microcomputer, and executes various control programs stored in a built-in ROM (storage medium) to thereby control a fuel injection amount and an ignition amount of the fuel injection valve 20 according to an engine operating state. The ignition timing of the plug 21 is controlled.

The ECU 31 executes the exhaust valve control program shown in FIG. 2 stored in the ROM, thereby controlling the valve opening timing of the exhaust valve 26 during execution of the catalyst early warm-up control (ignition retard control). By advancing (or retarding) the direction away from the peak timing of the normal in-cylinder pressure, the exhaust pressure at the time of early catalyst warm-up control is reduced as compared with the conventional case, and the exhaust noise is reduced.

Hereinafter, the specific processing contents of the exhaust valve control program of FIG. 2 will be described. This program is repeatedly executed at every predetermined time or every predetermined crank angle, and plays a role as an exhaust valve control means referred to in the claims. When this program is started, first, in step 10
In step 1, it is determined whether or not the catalyst early warm-up execution condition is satisfied, for example, based on whether or not the engine is cold started (the cooling water temperature at the time of starting is equal to or lower than a predetermined temperature). If the catalyst early warm-up execution condition is not satisfied, the routine proceeds to step 105, in which normal control is performed to control the ignition timing of the ignition plug 21 to the target ignition timing for normal control, and the exhaust valve 2
6 is controlled to the target valve opening timing for normal control.

On the other hand, if the catalyst early warm-up execution condition is satisfied (at the time of cold start), the routine proceeds to step 102, where the ignition timing is retarded, and the ignition timing of the spark plug 22 is reduced. It retards to the target ignition timing for warm-up. As a result, the temperature of the exhaust gas is increased, and the warm-up (temperature rise) of the catalyst is promoted.

Thereafter, the routine proceeds to step 103, where the opening timing of the exhaust valve 26 is advanced to the target advance position VT1 for early catalyst warm-up control, as indicated by the dashed line in FIG. This target advance position VT1 for early catalyst warm-up control
Is set at a position advanced by a predetermined crank angle (for example, 20 ° C.) from the peak timing of the normal in-cylinder pressure so that the in-cylinder pressure when the exhaust valve 26 is opened becomes equal to or less than a predetermined value. ing. Thus, the opening timing of the exhaust valve 26 during the early catalyst warm-up control is advanced by a predetermined crank angle (for example, 20 ° C.) from the peak timing of the normal cylinder pressure, and the cylinder pressure is being increased. To open the exhaust valve 26. The peak timing of the normal in-cylinder pressure may be estimated from the ignition timing at the time of early catalyst warm-up control, or measured by an actual machine test, or calculated by simulation.

Thereafter, the routine proceeds to step 104, where it is determined whether or not the condition for terminating the catalyst early warm-up is satisfied, for example, whether or not a predetermined time has elapsed from the start, whether or not the idling operation has been completed. Until the catalyst early warm-up termination condition is satisfied, the ignition timing retard control is continued, and the valve opening timing of the exhaust valve 26 is held at the target advance position VT1 for catalyst early warm-up control (steps 102 to 102). 10
4).

Thereafter, when the catalyst early warm-up termination condition is satisfied, the routine proceeds to step 105, where the routine proceeds to normal control, and
The ignition timing of the ignition plug 21 is returned to the target ignition timing for normal control, and the opening timing of the exhaust valve 26 is
Return to target valve opening timing for normal control.

In the embodiment (1) described above, during the early catalyst warm-up control, the valve opening timing of the exhaust valve 26 is advanced by a predetermined crank angle from the peak timing of the normal cylinder pressure. Since the exhaust valve 26 is opened while the in-cylinder pressure is rising, the in-cylinder pressure at the time of opening the exhaust valve 26 can be appropriately reduced from the normal peak pressure of the in-cylinder pressure. The pressure (exhaust pressure) of the in-cylinder combustion gas discharged from the engine 11 into the exhaust pipe 22 during the early catalyst warm-up control can be reduced as compared with the conventional case, and the exhaust noise can be reduced. Thus, noise (exhaust sound) during early catalyst warm-up control can be reduced and silence can be improved.

In this embodiment (1), during the early catalyst warm-up control, the opening timing of the exhaust valve 26 is advanced by a predetermined crank angle from the peak timing of the normal cylinder pressure. However, as shown by a two-dot chain line in FIG. 3, during the early catalyst warm-up control, the valve opening timing of the exhaust valve 26 is delayed by a predetermined crank angle from the peak timing of the normal in-cylinder pressure. Is also good. In this case, after the in-cylinder pressure has been appropriately reduced from the peak pressure, the exhaust valve 26
Is opened, the in-cylinder pressure at the time of opening the exhaust valve 26 is appropriately reduced from the normal peak pressure of the in-cylinder pressure as in the case where the valve opening timing of the exhaust valve 26 is advanced. And exhaust noise can be reduced.

The exhaust valve 26 at the time of early catalyst warm-up control
The advance amount or the retard amount of the valve opening timing may be fixed to a constant value for simplification of the calculation process, but the increase in the in-cylinder pressure based on the engine operating conditions during the early catalyst warm-up control is performed. The characteristics may be predicted, and the advance amount or the retard amount of the valve opening timing of the exhaust valve 26 may be calculated so that the in-cylinder pressure when the exhaust valve 26 opens is equal to or less than a predetermined value.

[Embodiment (2)] Next, an embodiment (2) of the present invention will be described with reference to FIG. In the present embodiment (2), a volume expansion chamber 34 is formed at the junction of the exhaust manifold 33 of each cylinder in the exhaust pipe 32 (exhaust passage), and a motor, a solenoid, and the like are provided upstream of the volume expansion chamber 34. Is provided with a switching valve 35 that is driven by the motor. When the switching valve 35 is switched to the closed position shown by the solid line in FIG.
The inlet of the volume expansion chamber 34 is closed by the switching valve 35.

On the other hand, when the switching valve 35 is switched to the volume expansion position indicated by the dotted line in FIG. 4, the inlet of the volume expansion chamber 34 is opened, and the exhaust gas flowing out of the exhaust manifold 33 of each cylinder is discharged. And the flow volume at the junction of the exhaust manifold 33 is increased.
The volume expansion chamber 34 and the switching valve 35 play a role corresponding to a flow channel volume expansion means described in the claims.

Normally, the ECU 31 holds the switching valve 35 at the closed position shown by the solid line in FIG. 4 to close the inlet of the volume expansion chamber 34 and reduce the flow volume at the junction of the exhaust manifold 33. To hold. Then, during execution of the catalyst early warm-up control (ignition timing retard control), the switching valve 35 is switched to the volume expansion position shown by the dotted line in FIG. Is maintained in an expanded state.

In the embodiment (2) described above, since the flow passage volume at the junction of the exhaust manifold 33 is increased during the early catalyst warm-up control, the early catalyst warm-up control (ignition timing retard control) is performed. ), The gas pressure (exhaust pressure) at the junction of the exhaust manifold 33 is reduced by expanding the flow volume at the junction of the exhaust manifold 33 even when the in-cylinder pressure when the exhaust valve 26 is opened increases. Exhaust noise can be reduced.

[Embodiment (3)] In the embodiment (2) described above, the exhaust manifold 3 during the catalyst early warm-up control is controlled.
In the embodiment (3) of the present invention shown in FIG. 5, the exhaust gas from the junction of the exhaust manifold 37 to the catalyst 24 is controlled during the early catalyst warm-up control. The channel volume of the tube section 38 is expanded as follows.

In the collective exhaust pipe section 38, a main exhaust flow path 40 and an enlarged flow path 41 are formed by a partition wall 39, and the inlet of the expanded flow path 41 is driven by a motor, a solenoid, or the like. A switching valve 42 is provided. When the switching valve 42 is switched to the closed position shown by the solid line in FIG. 5, the inlet of the enlarged flow passage 41 is closed by the switching valve 42, and the exhaust gas flows only through the main exhaust passage 40.

On the other hand, when the switching valve 42 is switched to the volume expansion position indicated by the dotted line in FIG. 5, the inlet of the expansion channel 41 is opened, and the exhaust gas passes through both the main exhaust channel 40 and the expansion channel 41. As a result, the flow capacity of the collective exhaust pipe portion 38 is increased. The enlarged flow path 41 and the switching valve 42 play a role corresponding to a flow path volume expanding means referred to in the claims.

Normally, the ECU 31 holds the switching valve 42 in the closed position shown by the solid line in FIG. 5, closes the inlet of the enlarged flow passage 41, and reduces the flow volume of the collective exhaust pipe 38. To hold. Then, during execution of the catalyst early warm-up control (ignition timing retard control), the switching valve 42 is switched to the volume expansion position indicated by a dotted line in FIG. The flow volume of the portion 38 is maintained in an enlarged state.

In the embodiment (3) described above, during the early catalyst warm-up control, the exhaust pipe section 3 upstream of the catalyst 24 is controlled.
8, the flow rate of the exhaust pipe section 38 is increased even when the in-cylinder pressure at the time of opening the exhaust valve 26 increases due to the catalyst early warm-up control (ignition timing retard control). By expanding the passage volume, the gas pressure (exhaust pressure) in the collective exhaust pipe section 38 can be reduced, and the exhaust noise can be reduced.

The method of expanding the volume of the exhaust passage is not limited to the above-described embodiments (2) and (3).
The present invention may be implemented with appropriate changes. Further, during the catalyst early warm-up control, the intake pressure pulsation may be reduced by increasing the flow volume of the intake pipe to reduce the intake noise.

[Embodiment (4)] In the embodiment (4) of the present invention, as shown in FIG. 6, a bypass passage 44 is provided in the exhaust pipe 43 (exhaust passage) on the upstream side of the catalyst 24. I have. The length of the bypass passage 44 and the exhaust pipe 43 from the branch to the confluence is set to substantially half wavelength (or an odd multiple of half wavelength) of the exhaust pressure pulsation during the early catalyst warm-up control.
The structure is shifted. Further, a switching valve 45 (opening / closing means) is provided at the entrance of the bypass passage 44. When the switching valve 45 is switched to the closed position shown by the solid line in FIG. 6, the inlet of the bypass passage 44 is closed by the switching valve 45, and the exhaust gas flows only through the exhaust pipe 43.
On the other hand, when the switching valve 45 is switched to the bypass passage opening position indicated by the dotted line in FIG. 6, the inlet of the bypass passage 44 is opened, and the exhaust gas flows through both the exhaust pipe 43 and the bypass passage 44.

The ECU 31 normally holds the switching valve 45 in the closed position shown by the solid line in FIG.
4 is kept closed. During the execution of the catalyst early warm-up control (ignition timing retard control), the switching valve 4
5 is switched to the bypass passage opening position indicated by the dotted line in FIG. As a result, during the early catalyst warm-up control, the exhaust gas flows to both the exhaust pipe 43 and the bypass passage 44, and the exhaust pipe 4
3 and the bypass passage 44, the exhaust pressure pulsations of the two passages 43 and 44 are merged with a phase shift of substantially a half wavelength (half a cycle).

In the embodiment (4) described above, the phase of the exhaust pressure pulsation in the two passages 43 and 44 is shifted by about a half wavelength at the junction of the exhaust pipe 43 and the bypass passage 44 during the early catalyst warm-up control. When the exhaust pressure pulsation wave of one of the passages has a peak at the junction of the exhaust pipe 43 and the bypass passage 44, the exhaust pressure pulsation wave of the other passage becomes a valley, and the exhaust pressure pulsations of the two cancel each other. The exhaust pressure pulsation can be effectively attenuated and exhaust noise can be reduced.

[Embodiment (5)] In the embodiment (4) described above, the exhaust pressure pulsation is canceled out and attenuated by the collective exhaust pipe portion of the exhaust pipe 43, but the present invention shown in FIG. In the embodiment (5), the exhaust pressure pulsation of each cylinder is canceled out and attenuated at the junction of the exhaust manifold 47 of each cylinder in the exhaust pipe 46 (exhaust passage) as follows.

The exhaust port of each cylinder of the engine 11 has:
A normal exhaust manifold 47 is connected to each. Further, for a half of all the cylinders (for example, two cylinders in a four-cylinder engine), the catalyst warm-up exhaust manifold 48 having a different length from the normal exhaust manifold 47 is replaced with the normal exhaust manifold 47. Switching valves 49 are connected in parallel, and are provided at the inlets of the exhaust manifolds 48 when the catalysts are warmed up. In this case, a cylinder not provided with the catalyst warm-up exhaust manifold 48 may be located next to the cylinder provided with the catalyst warm-up exhaust manifold 48.
The cylinder provided with 8 may be changed as appropriate.

At normal times, the switching valve 49 is switched to the normal position shown by the solid line in FIG. 7 to close the inlet of the exhaust manifold 48 when the catalyst is warmed up, and to open the inlet of the normal exhaust manifold 47 to release the exhaust gas. The normal exhaust manifold 4
Pour into 7.

On the other hand, during early catalyst warm-up control, the switching valve 4
9 is switched to the catalyst warm-up position indicated by the dotted line in FIG. 7 to close the inlet portion of the normal exhaust manifold 47 and open the inlet portion of the catalyst warm-up exhaust manifold 48. Thus, during the early catalyst warm-up control, the catalyst warm-up exhaust manifold 48 having a different length from the normal exhaust manifold 47 is used.
Flow exhaust gas through.

In this case, the catalyst warm-up exhaust manifold 4
8 and the normal exhaust manifold 4 of the adjacent cylinder
7, the length of the exhaust manifold 48 at the time of catalyst warm-up is set such that the phases of the exhaust pressure pulsations of the respective cylinders are shifted by about a half wavelength (half cycle). The exhaust manifold 48 and the switching valve 49 at the time of catalyst warm-up play a role corresponding to an exhaust manifold length changing means referred to in the claims.

In the above-described embodiment (5), during the early catalyst warm-up control, the switching valves 49 of half of the cylinders are switched to the catalyst warm-up position indicated by the dotted line in FIG. The inlet is closed and the inlet of the exhaust manifold 48 is opened when the catalyst is warmed up. Thus, during the early catalyst warm-up control, the catalyst exhaust manifold 48 having a different length from the normal exhaust manifold 47 in half the number of cylinders is used.
The exhaust gas flows into the cylinder, and at the junction with the normal exhaust manifold 47 of the adjacent cylinder, the phases of the exhaust pressure pulsations of the respective cylinders are shifted by substantially a half wavelength (half a cycle) to cancel each other. become. As a result, the exhaust pressure pulsation of each cylinder can be effectively attenuated to reduce the exhaust noise.

In the present embodiment (5), the catalyst warm-up exhaust manifold 48 is provided in half of the cylinders. However, the present invention is not limited to this. For example, the exhaust manifold 48 may be provided in less than half of the cylinders. Even in this case, the exhaust noise can be reduced as compared with the related art. In addition, each of the above-described embodiments (1)
A plurality of embodiments from (5) to (5) may be appropriately combined and implemented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment (1) of the present invention.

FIG. 2 is a flowchart showing a flow of processing of an exhaust valve control program.

FIG. 3 is a diagram showing a behavior of a valve operating characteristic and an in-cylinder pressure;

FIG. 4 is a cross-sectional view of a main part on the engine exhaust side showing the embodiment (2).

FIG. 5 is a cross-sectional view of a main part on the engine exhaust side showing the embodiment (3).

FIG. 6 is a cross-sectional view of a main part on the engine exhaust side showing the embodiment (4).

FIG. 7 is a cross-sectional view of a main part on the engine exhaust side showing the embodiment (5).

[Explanation of symbols]

11: Engine (internal combustion engine), 22: Exhaust pipe (exhaust passage), 24: Catalyst, 26: Exhaust valve, 27: Variable valve timing device, 28: Hydraulic control valve, 31: ECU
(Exhaust valve control means), 32 ... exhaust pipe (exhaust passage),
33: exhaust manifold, 34: volume expansion chamber (flow path volume expansion means), 35 ... switching valve (flow path volume expansion means), 37
... exhaust manifold, 38 ... collective exhaust pipe section, 39 ... partition wall, 40 ... main exhaust flow path, 41 ... expanded flow path (flow path volume expanding means), 42 ... switching valve (flow path volume expanding means), 43 ... Exhaust pipe (exhaust passage), 44 ... Bypass passage, 45 ... Switching valve (opening / closing means), 46 ... Exhaust pipe (exhaust passage), 47 ... Normal exhaust manifold, 48 ... Exhaust manifold when catalyst is warmed up (Exhaust manifold length) Changing means), 49 ... switching valve (exhaust manifold length changing means).

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/24 F01N 3/24 R 7/08 7/08 B F term (Reference) 3G004 AA01 BA01 BA06 BA12 CA12 DA03 DA24 DA25 EA01 FA04 3G091 AA02 AA28 AB03 BA00 BA03 BA14 BA15 BA19 BA32. DA01 DA02 DA06 DA07 DA08 DA09 DA10 DC15 DE01S DF02 DF09 DG05 DG07 EA01 EA02 EA03 EA04 EA06 EA11 EA16 EA21 EA28 EA29 EC01 FA14 FA17 FA18 FA31 FA42 GA01 GA02 GA04 HA01Z HA05Z HA06Z HA11X HD05Z HD08 HEX

Claims (4)

[Claims] 1. An internal combustion engine that performs early catalyst warm-up control for quickly warming up a catalyst provided in an exhaust passage during a cold start, a variable valve timing device that varies opening and closing timing of an exhaust valve of the internal combustion engine. An internal combustion engine comprising: exhaust valve control means for advancing or retarding the valve opening timing of the exhaust valve in a direction away from a normal peak pressure of the in-cylinder pressure during the early catalyst warm-up control. Exhaust noise reduction device. 2. An internal combustion engine that performs early catalyst warm-up control for quickly warming up a catalyst provided in an exhaust passage during a cold start, wherein the catalyst in the exhaust passage is reduced during the early catalyst warm-up control. An exhaust noise reduction device for an internal combustion engine, further comprising a channel volume expanding means for expanding a channel volume of an upstream portion. 3. An internal combustion engine for performing early catalyst warm-up control for quickly warming up a catalyst provided in an exhaust passage during a cold start, wherein a bypass passage is provided in a portion of the exhaust passage upstream of the catalyst. And an opening / closing means for opening / closing the bypass passage.Opening the opening / closing means during the early catalyst warm-up control to divide exhaust gas of the internal combustion engine into the exhaust passage and the bypass passage. An exhaust noise reduction device for an internal combustion engine, wherein a phase of exhaust pressure pulsations of both passages is merged at a downstream merging portion with a phase shift of substantially a half wavelength. 4. An exhaust manifold for changing the length of an exhaust manifold of at least some of the cylinders in an internal combustion engine that performs early catalyst warm-up control for quickly warming up a catalyst provided in an exhaust passage during a cold start. By changing the length of the at least a part of the exhaust manifold during the early catalyst warm-up control, the phase of the exhaust pressure pulsation of each cylinder at the junction of the exhaust manifold of each cylinder is substantially half a wavelength. An exhaust noise reduction device for an internal combustion engine, which is configured to merge at different times.