JP6591798B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine capable of executing cylinder deactivation control.

  2. Description of the Related Art Conventionally, as a technique for controlling an internal combustion engine mounted on a vehicle or the like, cylinder deactivation control for stopping combustion in some of a plurality of cylinders is known. The cylinder deactivation control is a control that is executed when the required torque of the internal combustion engine is relatively small. During the cylinder deactivation operation, the intake valves and exhaust valves of some cylinders are maintained in a closed state, fuel injection into the cylinders is stopped, and output torque is obtained by the remaining cylinders. At this time, in order to obtain the same output torque as when all cylinders are operated by the remaining cylinders, the opening degree of the intake throttle valve is increased, so that the pumping loss (intake loss) is reduced and the fuel consumption characteristics are improved. .

  Here, in an intake system of an internal combustion engine, pressure pulsation (hereinafter, this pulsation is also referred to as “intake pulsation”) is generated by intake of each cylinder. For example, in a four-cylinder internal combustion engine, when two cylinders are deactivated, the number of intakes during two revolutions of the crankshaft is halved, so the period of intake pulsation is also halved. As a result, the mode of vibration generated by the intake air pulsation of the internal combustion engine changes from the secondary to the primary, and the low-frequency intake sound becomes larger than that in the four-cylinder operation. In general, the cylinder deactivation control is executed in an operation region where the required torque of the internal combustion engine is small. Therefore, the low frequency component of the intake sound during the cylinder deactivation operation is easily felt as noise.

  On the other hand, there is an internal combustion engine having a silencer in the intake system. For example, Patent Document 1 discloses an internal combustion engine that can reduce intake noise during all-cylinder operation and cylinder deactivation operation without increasing the size of the resonator. The internal combustion engine includes a first resonator, and includes a first intake passage that communicates with a cylinder of one cylinder bank, a second intake passage that includes a second resonator and communicates with a cylinder of the other cylinder bank, a first intake passage, A bypass passage communicating with the second intake passage, and an open / close valve provided on the upstream side of the second resonator in the second intake passage. The on-off valve is opened during all cylinder operation and closed during cylinder deactivation operation. Thereby, at the time of cylinder deactivation operation, since the intake passage is configured to include two resonators, low-frequency noise can be reduced.

  Patent Document 2 discloses an intake noise reduction device for reducing noise during cylinder deactivation in an internal combustion engine having an independent intake system for each of a plurality of cylinder groups. The internal combustion engine includes a communication unit that communicates the upstream side of the throttle valve provided in the intake system of the cylinder group to be deactivated with the intake system of the cylinder group to be activated during the cylinder deactivation operation. In such an internal combustion engine, the air cleaner provided in the intake system of the cylinder for which the operation is suspended functions as a resonator for the operated cylinder, and noise can be reduced.

JP 2010-163945 A JP-A-8-3030312

  However, the internal combustion engines described in Patent Documents 1 and 2 are each an internal combustion engine provided with an intake throttle valve and a resonator or an air cleaner in each of two intake systems branched from an intake passage for taking in fresh air to each cylinder bank. In addition to being intended for an engine, a communication path connecting two intake systems is provided, which makes the configuration complicated.

  Further, in order to reduce low frequency sound, a large capacity or long silencer is required, and installation is often difficult due to the layout in the engine room of the vehicle. Therefore, it is desirable to be able to reduce low-frequency sound without newly adding a silencer or newly providing a communication path as described in Patent Documents 1 and 2.

  The present invention has been made in view of the above problems, and an object of the present invention includes a plurality of connection pipes branched from an intake passage provided with an intake throttle valve and connected to a plurality of cylinders. Another object of the present invention is to provide an internal combustion engine capable of reducing noise during cylinder deactivation operation of the internal combustion engine.

In order to solve the above problems, according to an aspect of the present invention, a plurality of cylinders each provided with an intake valve and an exhaust valve and a plurality of cylinders branched from an intake passage provided with an intake throttle valve are divided into the plurality of cylinders. A plurality of connecting pipes connected to each other, and a cylinder deactivation mechanism that maintains the intake valves and the exhaust valves of some cylinders of the plurality of cylinders in a closed state, and deactivates some of the cylinders. An internal combustion engine in which a length of the connection pipe connected to the part of the cylinders to be deactivated among the plurality of connection pipes is set according to a frequency band of intake pulsation that occurs during cylinder deactivation operation. An institution is provided.

  The part that is provided with at least one silencer for reducing the sound of a predetermined frequency in the intake passage, and pauses so as to reduce the sound having a frequency different from the frequency of the sound reduced by the silencer. The length of the connecting pipe connected to the cylinder may be set.

  The silencer provided in the intake passage reduces the noise in the frequency band of intake pulsation generated during all cylinder operation, and the connection pipe connected to the part of the cylinders to be deactivated is generated during cylinder deactivation operation. The sound in the frequency band of the intake pulsation may be reduced.

  There may be a plurality of the partial cylinders to be deactivated, and the lengths of the plurality of connection pipes connected to the plurality of cylinders to be deactivated may be different depending on the frequency of the sound to be reduced.

  The intake passage includes a collector portion at a branch position of the connection pipe, and the collector according to an anti-resonance frequency from the connection pipe connected to the some cylinders when the some cylinders are stopped The volume of the part may be set.

  ADVANTAGE OF THE INVENTION According to this invention, the noise at the time of cylinder deactivation operation of the internal combustion engine provided with the some connection pipe branched from the intake passage provided with the intake throttle valve and connected to a some cylinder can be reduced.

1 is a schematic diagram showing a schematic configuration of an internal combustion engine according to an embodiment of the present invention. It is a schematic diagram which shows the structural example of the intake system of an internal combustion engine. It is explanatory drawing which shows the intake pulsation which generate | occur | produces in the intake system of an internal combustion engine. It is explanatory drawing which shows the vibration noise of an internal combustion engine. It is explanatory drawing which shows the muffling function of a connecting pipe. It is explanatory drawing which shows the resonance frequency of each of the silencer function of a connection pipe, and a silencer. It is explanatory drawing which shows the insertion loss of a connecting pipe. It is explanatory drawing which shows the insertion loss of a collector part.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol. In addition, components having substantially the same functional configuration may be distinguished by adding different alphabets to the end of the same symbol.

<1. Configuration of Internal Combustion Engine>
(1-1. Overall configuration)
First, an example of the overall configuration of the internal combustion engine according to the present embodiment will be described. FIG. 1 is a schematic diagram schematically showing a configuration example of the internal combustion engine 100. FIG. 1 is an explanatory diagram showing a configuration of a horizontally opposed internal combustion engine 100. In the internal combustion engine 100 shown in FIG. 1, cylinders # 1 and # 2 are located on the front side of the vehicle.

  The internal combustion engine 100 includes a cylinder block 101a, a cylinder head 101b, a piston 104, a connecting rod 106, a spark plug 108, an intake valve 110a, an exhaust valve 110b, a cam mechanism 111, and a crankshaft 115. A plurality of cylinders # 1, # 2, # 3, and # 4 are provided in the cylinder block 101a. In the example of FIG. 1, four cylinders # 1, # 2, # 3, and # 4 are provided in the cylinder block 101a. Of these, two cylinders # 1 and # 3 constitute a cylinder group in the right bank, and the remaining two cylinders # 2 and # 4 constitute a cylinder group in the left bank.

  Cylinder head 101b closes the ends opposite to crankshaft 115 among the axial ends of cylinders # 1, # 3 (# 2, # 4) in each of the right bank and the left bank. Provided. In each cylinder # 1, # 2, # 3, # 4, a piston 104 is held so as to be able to move forward and backward. A combustion chamber C is defined by the cylinder head 101b and the crown surface of the piston 104 at the top dead center. The piston 104 performs a linear reciprocating motion by the combustion of fuel in the combustion chamber C. The linear reciprocating motion is transmitted as a rotational motion to the crankshaft 115 via the connecting rod 106.

  The internal combustion engine 100 is connected to an intake system 200 and an exhaust system (not shown). The intake system 200 supplies intake air to the cylinders # 1, # 2, # 3, and # 4. The intake system 200 includes an intake passage 202 provided with an intake throttle valve 210, a collector portion 204 connected to the intake passage 202, and branches from the collector portion 204 to each cylinder # 1, # 2, # 3, # 4. A plurality of connecting pipes 206a, 206b, 206c, and 206d connected to each other. The exhaust system discharges combustion gas from each cylinder # 1, # 2, # 3, # 4. The cylinder head 101b is provided with an intake valve 110a and an exhaust valve 110b for each cylinder # 1, # 2, # 3, and # 4.

  The intake valve 110a opens and closes an intake port between the intake system 200 and each combustion chamber C. In the intake stroke, intake valve 110a is opened, and intake air is taken into each combustion chamber C through the intake port. The exhaust valve 110b opens and closes an exhaust port between the exhaust system and each combustion chamber C. In the exhaust stroke, the exhaust valve 110b is opened so that the combustion gas is discharged from each combustion chamber C via the exhaust port. The opening and closing operations of the intake valve 110a and the exhaust valve 110b are performed by the cam mechanism 111.

  The cam mechanism 111 includes a cam shaft 112 and a cam 114 fixed to the cam shaft 112. The camshaft 112 is connected to a crankshaft 115 of the internal combustion engine via a gear (not shown), and rotates as the crankshaft 115 rotates. The intake valve 110a and the exhaust valve 110b include a return spring (not shown). As the camshaft 112 rotates, the cam 114 rotates, and the cam crest of the cam 114 directly or indirectly pushes the intake valve 110a and the exhaust valve 110b, thereby opening the intake valve 110a and the exhaust valve 110b.

  In the internal combustion engine 100 shown in FIG. 1, the rocker arm 30 is provided between the cam 114 and the intake valve 110a and the exhaust valve 110b. The intake valve 110 a and the exhaust valve 110 b are pushed by the cam 114 via the rocker arm 30. Further, when the intake valve 110a and the exhaust valve 110b are released from the pushing of the intake valve 110a and the exhaust valve 110b by the cam 114, they are returned to their original positions by the return spring.

  The cylinders # 1 and # 2 are provided with a cylinder deactivation mechanism 60 for preventing the pushing operation of the rocker arm 30 by the cam 114 from being transmitted to the intake valve 110a and the exhaust valve 110b. The cylinder deactivation mechanism 60 is configured using, for example, a hydraulic circuit. Specifically, a cylinder deactivation mechanism capable of switching engagement and disengagement between a pressed portion pressed by the cam 114 and a pressing portion pressing the intake valve 110a and the exhaust valve 110b by supplying and discharging hydraulic pressure. can do. However, the cylinder deactivation mechanism 60 may be a mechanism other than this configuration.

  The number of intake valves 110a and exhaust valves 110b provided in each cylinder # 1, # 2, # 3, # 4 can be set as appropriate. In the present embodiment, two intake valves 110a and two exhaust valves 110b are provided for each of the cylinders # 1, # 2, # 3, and # 4, and each of the intake valves 110a and the exhaust valves 110b is an intake port or an exhaust. Open and close the port. In FIG. 1, each cylinder # 1, # 2, # 3, and # 4 shows a set of intake valves 110a.

  Each cylinder # 1, # 2, # 3, # 4 is provided with a fuel injection valve (not shown) so as to face the combustion chamber C. The fuel injection valve is fixed to the wall surface of the cylinder head 101b, for example. The fuel injection valve is driven and controlled by a control device (not shown) and injects fuel into the combustion chamber C. As a result, an air-fuel mixture of intake air and fuel is formed in the combustion chamber C. Further, during the cylinder deactivation operation, fuel injection to the cylinder to be deactivated is not performed. The fuel injection valve is not limited to a type that directly injects fuel into the combustion chamber C. A fuel injection valve may be provided upstream of the intake port, and a previously formed air-fuel mixture may be introduced into the combustion chamber C from the intake port.

  A spark plug 108 is provided in the cylinder head 101b so as to face the combustion chamber C of each cylinder # 1, # 2, # 3, # 4. The spark plug 108 is driven and controlled by a control device (not shown) and ignites the air-fuel mixture formed in each combustion chamber C. As a result, combustion occurs in the combustion chamber C, the piston 104 is pushed down, and the crankshaft 115 rotates. In this specification, the rising of the piston 104 means that the piston 104 moves to the combustion chamber C side, and the lowering of the piston 104 means that the piston 104 moves to the crankshaft 115 side.

  The crankshaft 115 includes a crankpin 116, a crank journal 118, and a crank arm 120 connected thereto. The crankpin 116 is connected to the connecting rod 106. The crank arm 120 is rotated by the linear reciprocation of the piston 104, and the crank journal 118 is rotated by the rotation of the crank arm 120. The crankshaft 115 is connected to a drive transmission device (not shown), and the output torque of the internal combustion engine 100 is transmitted to the drive transmission device.

(1-2. Configuration of intake system)
FIG. 2 is a schematic diagram showing the intake system 200 of the internal combustion engine 100. FIG. 2 shows an intake system 200 of one cylinder # 1.

  The intake system 200 includes an intake passage 202, a collector unit 204, and a connecting pipe 206a. The intake passage 202 includes an air cleaner 208, an intake throttle valve 210, a side branch type silencer 212, and a Helmholtz type silencer 214. Note that connecting pipes 206b, 206c, and 206d connected to the other cylinders # 2, # 3, and # 4 are connected to the collector unit 204. Intake system 200 guides fresh air taken from intake opening 202a to cylinder # 1. An exhaust system 250 is connected to the cylinder # 1.

  The intake throttle valve 210 is controlled by a control device (not shown) to adjust the flow rate of fresh air passing through the intake passage 202. The intake throttle valve 210 is provided in the intake passage 202, and the opening degree of the intake throttle valve 210 changes as the intake throttle valve 210 rotates by an electric motor or the like. Thereby, the passage area of the intake passage 202 changes, and the flow rate of fresh air is adjusted. The opening degree of the intake throttle valve 210 is determined based on the required torque and the rotational speed of the internal combustion engine 100 with reference to a previously created opening degree map.

  Further, the opening degree of the intake throttle valve 210 is different between the four-cylinder operation and the cylinder deactivation operation. The opening degree of the intake throttle valve 210 during the cylinder deactivation operation is made larger than the opening degree of the intake throttle valve 210 during the 4-cylinder operation in order to output the same torque as the torque during the 4-cylinder operation from the internal combustion engine 100. . As a result, during cylinder deactivation, the amount of intake charge per cylinder increases, and the torque generated per cylinder increases.

  The air cleaner 208 collects foreign substances contained in the introduced fresh air. An air flow meter (not shown) for measuring the flow rate of fresh air is provided on the downstream side of the air cleaner 208. Further, an EGR (Exhaust Gas Recirculation) passage for returning a part of the exhaust to the intake system 200 may be connected to the intake passage 202 upstream of the intake throttle valve 210. In this case, an EGR valve is provided in the middle of the EGR passage, and the flow rate of EGR gas recirculated from the exhaust system 250 to the intake system 200 is adjusted.

  The collector unit 204 has a function of temporarily storing intake air and uniformly distributing the intake air to the cylinders # 1, # 2, # 3, and # 4. The connecting pipe 206a branches from the collector unit 204 and is connected to the cylinder # 1, and guides intake air in the collector unit 204 to the cylinder # 1. An intake port 220 is interposed between the connecting pipe 206a and the cylinder # 1, and the intake port 220 is opened and closed by the intake valve 110a. By opening the intake valve 110a during the period in which the piston 104 of the cylinder # 1 descends, intake air is sucked into the cylinder # 1.

  The side branch-type silencer 212 and the Helmholtz-type silencer 214 provided in the intake passage 202 reduce intake noise of a predetermined frequency. The side branch type silencer 212 is a tubular member whose open end is connected to the intake passage 202 and whose other end is closed, and the length is set according to the frequency component to be reduced. The side branch type silencer 212 reduces the sound of the frequency component by causing the specific frequency component of the sound generated in the intake passage 202 to resonate within the side branch type silencer 212. The side-branch silencer 212 is identified by the fact that when a specific frequency component enters the side-branch silencer 212, the air vibrates vigorously and the sound energy is lost due to friction loss with the side wall. Reduce frequency sound. The relationship between the length Ls of the side branch silencer 212 and the resonance frequency fn can be expressed by the following formula (1).

ｆｎ：共鳴周波数
Ｌｓ：消音器の長さ
ｎ：次数（ｎ＝１，２，・・・）
Ｃ：音速

fn: resonance frequency Ls: silencer length n: order (n = 1, 2,...)
C: Speed of sound

  Further, the Helmholtz type silencer 214 is a resonator in which an opening end of a tubular portion is connected to the intake passage 202 and an expansion chamber (resonance chamber) is provided on the other end side, and the tubular portion according to a frequency component to be reduced. The length, the cross-sectional area, or the volume of the expansion chamber is set. The Helmholtz silencer 214 is configured to vibrate the air in the tubular portion vigorously when a specific frequency component of the sound generated in the intake passage 202 enters the Helmholtz silencer 214. The sound energy is lost due to frictional loss with the side wall, thereby reducing the sound of a specific frequency. The relationship between the length Lh of the tubular portion in the Helmholtz silencer 214 and the resonance frequency fn can be expressed by the following formula (2).

ｆｎ：共鳴周波数
Ｌｈ：管状部の長さ
Ｓｈ：管状部の断面積
Ｖ：拡張室の容積
ｎ：次数（ｎ＝１，２，・・・）
Ｃ：音速

fn: resonance frequency Lh: length of the tubular portion Sh: cross-sectional area of the tubular portion V: volume of the expansion chamber n: order (n = 1, 2,...)
C: Speed of sound

  The side branch type silencer 212 and the Helmholtz type silencer 214 attenuate pulsations of different frequency components. Further, a plurality of side branch type silencers 212 and Helmholtz type silencers 214 may be provided in accordance with the frequency components to be attenuated. However, the lower the frequency of the sound to be silenced by the side branch silencer 212 and the Helmholtz silencer 214, the longer or larger capacity the silencer must be. is there.

<2. Intake noise>
Next, intake noise generated in the intake system 200 will be described. FIG. 3 is a diagram showing a standing wave when the intake system 200 is viewed as a pipe line with one end closed and one end open.

  The upper diagram of FIG. 3 shows a standing wave when the vibration mode is second order. When the order is secondary, the intake opening 202a serving as an opening end is a node, and the end on the cylinder # 1 (# 2, # 3, # 4) side where intake is performed is abdomen. A standing wave having a wavelength of 4/3 is generated. In contrast, the lower diagram of FIG. 3 shows a standing wave when the mode of vibration is the first order. When the order is primary, the intake opening 202a serving as the opening end is connected, and the end on the cylinder # 1 (# 2, # 3, # 4) side where intake is performed is abdomen. A standing wave having a double wavelength, that is, a standing wave having a frequency lower than that of the second order is generated.

  Here, the basic order of the internal combustion engine 100 varies depending on the number of cylinders to be operated (intake timing). That is, the frequency of the intake pulsation generated in the intake system 200 by the vibration force generated by the intake air varies depending on the number of cylinders to be operated. Specifically, the basic order at the time of four-cylinder operation is secondary, whereas the basic order at the time of cylinder deactivation (two-cylinder operation) is primary, and the frequency of intake pulsation during cylinder deactivation is 1/2 of the frequency during 4-cylinder operation. For example, when the rotational speed of the internal combustion engine 100 is 1800 rpm, the frequencies when the basic order is the second order and the first order are 60 Hz and 30 Hz, respectively.

  Thus, the frequency of the intake pulsation during the four-cylinder operation of the internal combustion engine 100 is dominant when the basic order is second order, and the frequency of the intake pulsation during the cylinder deactivation operation is the first order of the basic order. In this case, the frequency becomes dominant. Therefore, when the intake system 200 is designed with the basic idea of reducing intake noise during four-cylinder operation, the sound in the frequency range when the basic order is secondary is reduced, while the basic order is primary. In this case, the sensitivity to the sound in the frequency range increases, and the intake noise in the low frequency range increases.

  FIG. 4 is a conceptual diagram showing the intensity of vibration noise generated from the internal combustion engine 100 during four-cylinder operation and cylinder deactivation operation (two-cylinder operation). When the internal combustion engine 100 is switched from the four-cylinder operation to the two-cylinder operation, the low-frequency sound due to the intake pulsation increases, so the intensity of the low-frequency vibration noise becomes relatively large. In order to attenuate low-frequency sound generated during 2-cylinder operation with a side-branch silencer or a Helmholtz silencer externally attached to the intake passage 202, it is necessary to use a long or large-capacity silencer. Therefore, it is difficult to realize the layout in the engine room.

<3. Silencer function for connecting pipes>
FIG. 5 is a view for explaining the muffling function of the connecting pipe 206a connected to the idle cylinder # 1 in the internal combustion engine 100 according to the present embodiment. As described above, the connecting pipes 206a, 206b, 206c, and 206d connected to the cylinders # 1, # 2, # 3, and # 4 branch from the collector unit 204. The collector unit 204 is positioned near the end point with respect to the entire length of the intake system 200 with the intake opening 202a as a base point. That is, the collector unit 204 is located at a position close to the antinode of the intake pulsation that occurs during cylinder deactivation operation.

  The connection pipes 206a and 206b connected to the idle cylinders # 1 and # 2 that are maintained in a state where the intake valve 110a is closed during the cylinder idle operation can function as a side branch type silencer. In particular, the connecting pipes 206a and 206b can be regarded as silencers provided at positions close to the antinodes of intake pulsation that occurs during cylinder deactivation operation. Focusing on this point, in the internal combustion engine 100 according to the present embodiment, the length L of the connecting pipes 206a and 206b connected to the idle cylinders # 1 and # 2 is set according to the frequency of the low frequency sound to be reduced. Has been.

  Since the connecting pipes 206a and 206b can function as a side branch type silencer, the length L thereof can be set by the above equation (1). Since the connection pipes 206a and 206b are originally longer than the side branch type silencer 212 externally attached to the intake passage 202, the silencers having a relatively long length Ls can be obtained. That is, the low frequency component of the noise generated during the cylinder deactivation operation can be reduced by the silencing function of the connecting pipes 206a and 206b.

  Further, the number of external silencers installed in the intake passage 202 can be reduced by using the connection pipes 206a and 206b connected to the idle cylinders # 1 and # 2 as silencers that can reduce the sound of a specific frequency component. Can be reduced. Also by this, the internal combustion engine 100 according to the present embodiment is advantageous in terms of the layout of the internal combustion engine 100 in the engine compartment.

  It is preferable that the frequency of the sound reduced by the silencing function of the connecting pipes 206a and 206b is different from the frequency of the sound reduced by the side branch type silencer 212 and the Helmholtz type silencer 214 attached to the intake passage 202. As a result, the side branch type silencer 212 and the Helmholtz type silencer 214 that are externally attached to the intake passage 202 have a function of reducing noise generated during four-cylinder operation, while in the cylinder idle operation, Low-frequency noise can be reduced by the silencing function of the connecting pipes 206a and 206b connected to # 2.

  FIG. 6 shows the frequency components reduced by the side branch silencer 212 and the Helmholtz silencer 214 attached to the intake passage 202, and the silence function of the connecting pipes 206a and 206b connected to the idle cylinders # 1 and # 2. It is explanatory drawing which shows the frequency component reduced. In the example shown in FIG. 6, the side branch type silencer 212 and the Helmholtz type silencer 214 attached to the intake passage 202 reduce sound in the middle frequency range (for example, 400 to 1000 Hz) during four-cylinder operation. On the other hand, the noise in the connecting pipes 206a and 206b connected to the deactivated cylinders # 1 and # 2 reduces noise in a low frequency range (for example, 200 to 350 Hz) that is less likely to be noticed during four-cylinder operation. .

  The frequency of the sound reduced by the silencing function of the connecting pipe 206a connected to the cylinder # 1 may be different from the frequency of the sound reduced by the silencing function of the connecting pipe 206b connected to the cylinder # 2. That is, the length L of the connecting pipe 206a and the length L of the connecting pipe 206b may be made different according to the frequency of the sound to be reduced. Thereby, the sound of a some frequency can be reduced among the low frequency components of the sound generated at the time of cylinder deactivation operation.

  In this way, by setting the length L of the connecting pipes 206a and 206b connected to the deactivated cylinders # 1 and # 2, the sound generated during the cylinder deactivated operation without increasing the silencer attached to the intake passage 202 is obtained. Can be reduced.

  Further, in the internal combustion engine 100 according to the present embodiment, the volume Vc of the collector unit 204 is set in order to reduce the influence of anti-resonance that occurs when the connection pipes 206a and 206b are used as a silencer. At this time, the collector unit 204 and the connecting pipes 206a and 206b function as an expansion silencer that attenuates the frequency component of the anti-resonance that occurs. The expansion-type silencer attenuates pulsations of a specific frequency by reflecting sound waves at a place where the pipe line expands or shrinks rapidly and causing sound wave interference in the expansion chamber or the pipe line.

  FIG. 7 is an explanatory diagram showing insertion loss (IL) of the connecting pipe 206a (206b) when the connecting pipe 206a (206b) connected to the idle cylinder # 1 (# 2) is caused to function as a side branch type silencer. It is. FIG. 8 is an explanatory diagram showing the insertion loss (IL) of the collector unit 204 when the collector unit 204 is caused to function as an expansion silencer.

  First, as shown in FIG. 7, when the connection pipe 206a (206b) is used as a silencer for reducing the sound of the low resonance frequency f1, the insertion loss of the resonance frequency component f1 increases, while the connection pipe 206a (206b). ) Causes an anti-resonance due to reflection pulsation. Therefore, the sound of the anti-resonance frequency component f1 ′ surrounded by the broken line may be easily heard.

  On the other hand, as shown in FIG. 8, the volume Vc of the collector part 204 is set so as to satisfy a predetermined condition, thereby suppressing a reduction in insertion loss of the collector part 204 with respect to the anti-resonance frequency f1 ′. Can do. Therefore, by setting the volume Vc of the collector part 204 according to the antiresonance frequency f1 ′ generated when the connecting pipe 206a (206b) functions as a side branch type silencer, the sound of the antiresonance frequency component f1 ′ is obtained. Can be suppressed.

  The expansion silencer configured by the collector unit 204 and the connecting pipe 206a (206b) has a frequency component and a silencing effect that are reduced by the length and cross-sectional area of the pipe line of the collector unit 204 and the connecting pipe 206a (206b). Determined. Therefore, the length and the cross-sectional area of the collector unit 204 are set according to the anti-resonance frequency component generated when the connecting pipe 206a (206b) functions as a silencer. Thereby, the sound of anti-resonance frequency component f1 'can be reduced.

<4. Effect>
As described above, in the internal combustion engine 100 according to the present embodiment, the length L of the connection pipes 206a and 206b connected to the deactivated cylinders # 1 and # 2 has a desired frequency to be reduced during the cylinder deactivated operation. It is set according to the sound. Therefore, the internal combustion engine 100 according to the present embodiment can reduce the sound having a desired frequency without increasing the number of silencers attached to the intake passage 202. Alternatively, the internal combustion engine 100 according to the present embodiment can omit a part of the silencer attached to the intake passage 202. As a result, the layout of the internal combustion engine 100 in the engine compartment is also advantageous.

  In the present embodiment, the length L of the connecting pipes 206a and 206b is set so as to reduce the low frequency component of the sound generated during the cylinder deactivation operation. Therefore, the silencer attached to the intake passage 202 only needs to have a function of reducing a relatively high frequency sound generated during the four-cylinder operation, and the number of silencers that reduce the low frequency sound can be reduced. it can. Alternatively, a silencer that reduces low frequency sound is not required. As a result, the layout of the internal combustion engine 100 in the engine compartment is also advantageous.

  In the present embodiment, the connecting pipes 206a and 206b function as side branch type silencers, and the collector unit 204 functions as an expansion type silencer that reduces the anti-resonance frequency sound from the connecting pipes 206a and 206b. . Therefore, the internal combustion engine 100 according to the present embodiment can further reduce low frequency sound.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can make various modifications or application examples within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above embodiment, the description has been given by taking the four-cylinder horizontally opposed internal combustion engine 100 as an example, but the configuration of the internal combustion engine is not limited to the above example. The internal combustion engine may be an internal combustion engine having various numbers of cylinders such as 6 cylinders, 8 cylinders, and 12 cylinders. Further, the internal combustion engine is not limited to the horizontally opposed type, and may be a V-type internal combustion engine or an in-line internal combustion engine as long as it has a connection pipe branched from the intake passage through the intake manifold and connected to each cylinder. It may be an institution.

60 Cylinder deactivation mechanism 100 Internal combustion engine 110a Intake valve 110b Exhaust valve 200 Intake system 202 Intake passage 202a Intake opening 204 Collector section 206a, 206b, 206c, 206d Connection pipe 208 Air cleaner 210 Intake throttle valve 212 Side branch type silencer 214 Helmholtz type silencer 220 Inlet port 250 Exhaust system

Claims (5)

A plurality of cylinders each provided with an intake valve and an exhaust valve;
A plurality of connecting pipes branched from an intake passage provided with an intake throttle valve and connected to the plurality of cylinders;
A cylinder deactivation mechanism that maintains the intake valve and the exhaust valve of some cylinders of the plurality of cylinders in a closed state, and deactivates some of the cylinders;
An internal combustion engine in which a length of the connection pipe connected to the some cylinders to be deactivated among the plurality of connection pipes is set in accordance with a frequency band of intake pulsation generated during cylinder deactivation operation . The intake passage is provided with at least one silencer for reducing sound of a predetermined frequency,
2. The length of the connection pipe connected to the some cylinders to be paused is set so as to reduce a sound having a frequency different from a frequency of the sound reduced by the silencer. Internal combustion engine. The silencer provided in the intake passage reduces the noise in the frequency band of intake pulsation that occurs during all cylinder operation,
3. The internal combustion engine according to claim 2, wherein the connection pipe connected to the part of the cylinders that are stopped reduces noise in a frequency band of intake pulsation that occurs during cylinder stop operation. There are a plurality of the partial cylinders to be deactivated,
The internal combustion engine according to any one of claims 1 to 3, wherein lengths of the plurality of connection pipes connected to the plurality of cylinders to be stopped differ according to a frequency of sound to be reduced. The intake passage includes a collector portion at a branch position of the connection pipe,
The volume of the said collector part is set according to the frequency of the antiresonance from the said connection pipe connected to the said some cylinder at the time of the said some cylinder's deactivation. The internal combustion engine according to item.

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