JP2010038073A - Intake air control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intake air control device for an internal combustion engine, suitable for improving fuel consumption and reducing emissions. <P>SOLUTION: An intake chamber 61 is provided to communicate with an intake passage 71B downstream of a throttle valve 51 when the throttle valve 51 has a predetermined opening or less and the engine 10 is rotated at low load and low speed. The volume of the intake chamber 61 is so set that at least the total volume with the volume of an intake pipe downstream of the throttle valve 51 is ≥60% of stroke volume. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

The intake pipe of a vehicle engine (internal combustion engine) is an independent intake pipe type having an independent throttle valve for each cylinder of the engine, and an intake manifold having a throttle valve in an intake manifold having a branched shape connected to a plurality of cylinders There are some of them.
The independent intake pipe system can reduce the intake volume between the intake valve and the throttle valve of the engine compared to the intake manifold system, so it is used in motorcycle engines that require throttle response and high specific output performance. The tendency is especially strong for high-speed and high-power engines. For example, an independent intake pipe type motorcycle engine has an intake volume of about 1/5 to 1/10 as compared to a four-wheeled vehicle engine of the same displacement employing an intake manifold system.
In addition, in this type of motorcycle engine, an intake chamber is connected to an intake passage of the engine, and a rotary valve is provided at a connection portion between the intake chamber and the intake passage to change the pressure of the air-fuel mixture in the intake passage. Has been proposed to improve the intake efficiency by improving the intake efficiency and improve the engine output and the engine response (see, for example, Patent Document 1).
JP-A-8-338253

By the way, in recent years, demands for improving fuel consumption and reducing emissions have increased.
However, in a conventional motorcycle engine with a small intake volume, it is necessary to increase the concentration of the air-fuel mixture in order to perform stable idling, which is disadvantageous for improving fuel efficiency and purifying exhaust gas in post-processing. Requires a secondary air introduction device for introducing secondary air.
In addition, the configuration described in Patent Document 1 increases the intake volume in order to improve engine output and engine response, and does not improve fuel consumption and reduce emissions. In addition, the configuration of Patent Document 1 has a problem in that the configuration and control become complicated due to the valve control.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an intake control device for an internal combustion engine suitable for improving fuel consumption and reducing emissions.

In order to solve the above-mentioned problems, the present invention provides an intake control device for an internal combustion engine in which an intake throttle valve is provided in an intake passage communicating with a combustion chamber. An intake chamber is provided in the downstream intake passage so that the internal combustion engine communicates at low load and low rotation. The intake chamber has a volume that is at least the sum of the intake pipe volume downstream of the intake throttle valve and a stroke volume. % Of the volume or more.
According to this configuration, when the intake throttle valve is equal to or smaller than the predetermined opening, the intake chamber is provided in the downstream intake passage of the intake throttle valve so that the internal combustion engine communicates at low load and low rotation. Since the combined volume with at least the intake pipe volume downstream of the intake throttle valve is 60% or more of the stroke volume, the combustion of the lean air-fuel mixture can be improved to the extent that the secondary air introduction device can be abolished, and the fuel efficiency can be improved. And reduce emissions.

  In the above configuration, the volume of the intake chamber may have a volume that is at least one time larger than the intake pipe volume downstream of the intake throttle valve. According to this configuration, even when the intake passage of the engine is reduced as in the case of a conventional motorcycle engine, the volume of the intake chamber, at least the sum of the intake pipe volume downstream of the intake throttle valve, is 60% of the stroke volume. % Or more.

  Further, in the above configuration, a switching valve is provided that connects the intake passage and an intake passage that communicates with a cylinder other than the cylinder that communicates with the intake passage at the time of low load and low rotation of the internal combustion engine. An intake passage of the other cylinder communicated with the intake chamber may be substituted for the intake chamber. According to this configuration, the intake passage on the cylinder side that is not the intake stroke can be substituted for the intake chamber, and the size can be reduced as compared with the case where the intake chamber is separately provided.

  In the above configuration, the intake chamber may be communicated with an intake passage downstream of the intake throttle valve via an opening / closing passage that is opened and closed by the intake throttle valve. According to this configuration, the intake throttle valve can also be used as an intake chamber opening / closing mechanism, and the number of parts can be reduced.

  In the present invention, when the intake throttle valve is below a predetermined opening, an intake chamber is provided in the intake passage downstream of the intake throttle valve so as to communicate with the internal combustion engine during low load and low rotation, and the volume of the intake chamber is at least Since the combined volume with the intake pipe volume downstream of the intake throttle valve is a volume that is 60% or more of the stroke volume, it is possible to improve fuel consumption and reduce emissions.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
<First embodiment>
FIG. 1 is a view showing a motorcycle engine according to a first embodiment of the present invention together with an intake system. In FIG. 1, reference numeral 10 denotes a motorcycle engine (internal combustion engine). The motorcycle engine (hereinafter simply referred to as an engine) 10 includes a crankcase 11, a cylinder block 12, a cylinder head 13, and a head cover 14, and the cylinder block 12 includes one cylinder chamber (cylinder) 12A. This is a 4-cycle single cylinder engine.
A piston 21 is slidably accommodated in the cylinder chamber 12A of the cylinder block 12, and a crankshaft 23 connected to the piston 21 via a connecting rod 22 is rotatably supported in the crankcase 11. . The crankcase 11 houses a clutch mechanism, a transmission mechanism, an output shaft of the engine 10 and the like, although not shown.

The cylinder head 13 is formed with a recess 13A that forms the combustion chamber 15 together with the cylinder chamber 12A and the piston 21, and an intake port 13C extending from the intake port 13B of the cylinder head 13 is communicated with the combustion chamber 15 in the recess 13A. An intake side opening 25 and an exhaust side opening 26 for communicating an exhaust port 13E extending from the exhaust port 13D of the cylinder head 13 with the combustion chamber 15 are formed. The cylinder head 13 is also provided with an intake valve 27 for opening and closing the intake side opening 25, an exhaust valve 28 for opening and closing the exhaust side opening 26, and a valve mechanism 29 for driving the valves 27 and 28. Established.
The valve mechanism 29 drives the valves 27 and 28 in accordance with the rotation of the crankshaft 23 so as to perform four cycles of an intake process, a compression process, a combustion process, and an exhaust process. And a camshaft 29A rotatably supported between the exhaust valve 28, and intake and exhaust side rocker arms 29D and 29E respectively swung by cams 29B and 29C provided on the camshaft 29A. ing. The valve mechanism 29 is not limited to this rocker arm system, and other configurations such as a direct motion system in which the valves 27 and 28 are directly pushed by a cam may be applied.
An ignition plug (not shown) is attached to the cylinder head 13 with its tip facing the combustion chamber 15, and this ignition plug is controlled to ignite via an ignition device (ignition coil) (not shown).

A throttle body 31 is connected to the intake port 13 </ b> B of the engine 10 via an intake pipe 30, and an air cleaner 32 is connected to the upstream side (air intake port side) of the throttle body 31.
The throttle body 31 forms an intake passage to the engine 10 together with the intake pipe 30. In this configuration, the intake pipe 30 is formed integrally with the throttle body 31. The throttle body 31 includes a throttle valve (intake throttle valve) 51 therein, and the throttle valve 51 is rotated about a rotation shaft 52 to open and close the intake passage, whereby the air cleaner 32 is opened. The amount of intake air supplied from the engine to the engine 10 is varied.
Further, an injector mounting portion 53 for mounting an injector (fuel injection device) 33 is provided downstream of the throttle valve 51 of the throttle body 31, and the injector 33 has its tip directed to the intake port 13C toward the injector mounting portion 53. Inserted and fixed. Fuel in a fuel tank mounted on the motorcycle is supplied to the injector 33 by a fuel pump, and the fuel is injected under the control of a control device (not shown). As a result, an air-fuel mixture obtained by mixing fuel and air is supplied from the throttle body 31 toward the engine 10.

FIG. 2 shows the throttle body 31 together with the peripheral configuration. As shown in this figure, the throttle body 31 is provided with a box-shaped intake chamber 61 that can communicate with an intake passage (corresponding to the intake pipe 30) to the engine 10 via a throttle valve 51.
More specifically, the throttle body 31 is integrally formed with a pipe portion (open / close passage) 31B protruding from a throttle body case (hereinafter referred to as a case) 31A that forms an intake passage to the engine 10, and this pipe portion. An intake chamber 61 having a predetermined spatial volume is connected to the tip of 31B.
Further, the throttle valve 51 is arranged so that the opening of the end portion 31C of the pipe portion 31B can be freely opened and closed. Specifically, the throttle valve 51 is provided with a valve body 51A having a substantially half-moon cross section in a side view, and the valve body 51A is rotatably supported with a rotation shaft 52 as a fulcrum. Here, in FIG. 2, the movement trajectory of the outer peripheral surface 51B of the valve body 51A is indicated by symbol α, and the inner peripheral surface of the end portion 31C on the case 31A side of the pipe portion 31B is indicated by the symbol α. It is formed in a curved surface along the movement locus of 51A. That is, the valve body 51A rotates while contacting the inner peripheral surface of the end 31C of the pipe portion 31B, so that the contact portion between the valve body 51A and the pipe portion 31B maintains a contact state with almost no gap. It is configured as follows.

The throttle valve 51 rotates from the position shown in FIG. 2 to the position shown in FIG. 3 according to the accelerator operation by the driver. More specifically, FIG. 2 shows a state in which the throttle valve 51 is closed (an idle state in which operation is continued without load), and FIG. 3 shows a state in which the throttle valve 51 is opened (a fully open state). .
That is, when the throttle valve 51 is closed, as shown in FIG. 2, the valve body 51A of the throttle valve 51 is positioned upstream of the rotating shaft 52 so as to substantially close the intake passage to the engine 10, The air from the air cleaner 32 is suppressed to the minimum amount that can maintain idling. In this case, the valve body 51A closes the gap between the intake chamber 61 and an intake passage upstream of the throttle valve 51 (hereinafter referred to as upstream intake passage) 71A, but the intake chamber 61 and the throttle valve 51 downstream side. The intake passage (hereinafter referred to as the downstream intake passage) 71B is in communication.
As a result, when the throttle valve 51 is closed and the engine 10 is under low load and low rotation, the intake volume on the downstream side of the throttle valve 51 is increased by the volume of the intake chamber 61, that is, the volume of the downstream intake passage 71B. The volume of the (intake pipe volume) and the volume of the intake chamber 61 are increased.

On the other hand, when the throttle valve 51 is fully open, as shown in FIG. 3, the valve body 51A of the throttle valve 51 moves to the pipe portion 31B side so that the upstream side intake passage 71A and the downstream side intake passage 71B have a large opening. Communicate. In this case, the valve body 51A contacts the entire circumference of the inner peripheral surface of the end portion 31C of the pipe portion 31B to completely close the pipe portion 31B, and between the intake chamber 61 and the intake passage to the engine 10. Block communication completely. Further, the valve body 51A completely enters the pipe portion 31B, and the inner peripheral surface 51C of the valve body 51A has a step between the upstream intake passage 71A and the downstream intake passage 71B of the throttle valve 51. Since it is formed in a three-dimensional shape that communicates without unevenness, it can be a large-open intake passage with reduced intake resistance from the upstream intake passage 71A to the downstream intake passage 71B.
In this way, when the throttle valve 51 is opened (fully opened), the intake chamber 61 can be disconnected by the throttle valve 51 and the downstream intake volume of the throttle valve 51 can be reduced.

Next, the intake volume of the engine 10 will be described.
In general, a motorcycle engine is required to have a throttle response and a high specific output performance, and therefore has a smaller intake volume than a four-wheeled vehicle engine.
However, according to the study by the inventors, when the intake volume is small, the negative pressure in the intake passage does not sufficiently increase (the gas density in the intake passage is large) at low load and low rotation, and the same mass of fresh air is generated. The intake valve passing speed when inhaling is lowered.
An engine having a small intake volume because the kinetic energy of the intake flow that forms the source of the flow of the air-fuel mixture in the combustion chamber 15 such as tumble / swirl (that is, in-cylinder turbulence) is proportional to the product of the inflow mass and the square of the velocity. Then, it is considered that the in-cylinder turbulence becomes extremely weak at the time of low load and low rotation, the ignition delay is increased, and the combustion speed is remarkably reduced.

A simulation was performed on this point. FIG. 4 is a diagram for explaining a simulation model, and FIGS. 5 and 6 show simulation results. In FIG. 4, reference numeral 71 </ b> C indicates a downstream side intake passage of the throttle valve 51.
In this simulation, the case where the downstream side intake passage 71C has a small volume (equivalent to a conventional motorcycle (0.25L (liter))) and the case of a large volume (1.25L in this example) were compared and examined. Other conditions are an engine speed Ne of 1000 rpm / min, an air-fuel ratio of ideal air-fuel ratio (stoichiometry), an average effective pressure IMEP of 150 kPa, and a single cylinder of 650 cc.

FIG. 5 shows changes in the in-cylinder pressure Pc during the intake stroke and the compression stroke. Here, the vertical axis in FIG. 5 represents the in-cylinder pressure Pc, and the horizontal axis represents the volume ratio Vs of the combustion chamber 15 (volume Vs1 / stroke volume Vc of the combustion chamber 15).
As shown in FIG. 5, compared to the case where the downstream side intake passage 71C has a large volume (see the characteristic curve f1A shown by a solid line), the case where the downstream side intake passage 71C has a small volume (see the characteristic curve f2A shown by a two-dot chain line). Thus, it can be seen that the in-cylinder pressure Pc is low from the beginning of the intake stroke, and the amount of fluctuation of the in-cylinder pressure Pc until the end of the intake stroke is reduced. That is, it can be seen that the average pressure of the intake stroke is lowered.
FIG. 6 shows a change in the intake air flow velocity Ui in the intake stroke. Here, the vertical axis in FIG. 6 indicates the intake air flow velocity Ui, and the horizontal axis indicates the crank angle (ADTC (angle after piston top dead center)). As shown in this figure, when the downstream side intake passage 71C has a large volume (see the characteristic curve f1B shown by a solid line), when the downstream side intake passage 71C has a small volume (see the characteristic curve f2B shown by a two-dot chain line). It can be seen that the intake flow velocity Ui is higher than that of the intake stroke, and the average flow velocity of the intake stroke is increased.

  According to FIGS. 5 and 6, the cylinder intake pressure Pc in the intake stroke can be reduced by increasing the downstream intake passage 71C, and the negative pressure (intake air) can be reduced by reducing the cylinder pressure Pc. It is apparent that the negative pressure in the passage) can be increased (the gas density is lowered) and the intake flow velocity Ui (corresponding to the intake valve passage speed) can be increased. Accordingly, in-cylinder turbulence such as tumble / swirl can be appropriately generated, and the charging efficiency of the air-fuel mixture into the combustion chamber 15 can also be increased. This is apparent from the fact that the cylinder pressure Pc is higher during the compression stroke when the downstream intake passage 71C has a larger volume, as shown in FIG.

FIG. 7 shows the change characteristic of the in-cylinder pressure Pc in the entire stroke, and FIG. 8 shows the combustion characteristic of the combustion process. The vertical axis and horizontal axis in FIG. 7 are the same as those in FIG. 5, the vertical axis in FIG. 8 indicates the amount of heat Q (corresponding to work amount J), and the horizontal axis indicates the crank of ADTC (after piston top dead center). Shows the angle.
As shown in FIG. 7, it is compared with the case where the downstream side intake passage 71C has a large volume (see the characteristic curve f1C shown by a solid line) and the case where the downstream side intake passage 71C has a small volume (see the characteristic curve f2C shown by a two-dot chain line). Thus, it can be seen that the in-cylinder pressure Pc increases from the beginning of the combustion stroke, and the amount of fluctuation of the in-cylinder pressure Pc until the end of the combustion stroke also decreases, that is, the average pressure of the combustion stroke increases.
Here, FIG. 8 corresponds to the start of the combustion stroke shown in FIG. As shown in FIG. 8, when the downstream side intake passage 71C has a large volume (see the characteristic curve f1D shown by a solid line), the combustion time T1 required for the heat quantity Q (work amount J) to reach 10% to 90% is It can be seen that the combustion time T2 required when the downstream intake passage 71C has a small volume (see the characteristic curve f2D indicated by the two-dot chain line) is significantly shorter.
This indicates that the combustion time is shortened by increasing the volume of the downstream side intake passage 71C, that is, it is understood that the ignition delay can be suppressed and the combustion speed can be increased.

As indicated by the characteristic curves f2A to f2D described above, in an engine having a small intake volume, the ignition delay increases and the combustion speed is significantly reduced. Therefore, (1) thermal efficiency is poor due to delayed combustion, (2) stable combustion does not occur unless a rich mixture (rich air / fuel ratio (equivalent ratio φ is 1.2 or more)) is given, (3) exhaust Problems such as a large amount of unburned HC (hydrocarbon) in the interior will occur.
This not only deteriorates the fuel consumption, but also the catalyst activity is low immediately after the engine is started. Therefore, if there is a large amount of unburned HC, etc., the catalyst capacity will increase and the exhaust will be exhausted due to the rich air-fuel ratio. The oxygen concentration inside becomes low, and a secondary air introducing device for purifying the exhaust gas in the post-treatment becomes necessary. For this reason, it is difficult to improve fuel consumption and reduce emissions, and the cost of countermeasures such as secondary air introduction devices will increase.

Therefore, in the present embodiment, as described above, when the engine 10 is in a low load and low rotation state, the downstream intake volume of the throttle valve 51 corresponding to the volume of the downstream intake passage 71C at that time is set as the intake chamber 61. By increasing the volume, the deterioration of combustion at low load and low rotation (ignition delay and reduction in combustion speed) is improved.
On the other hand, when the engine 10 is not under low load and low rotation, the intake volume is reduced by the volume of the intake chamber 61, so that the throttle response and high specific output performance requirements are satisfied, as in the case of a conventional engine having a small intake volume. Specifically, the output performance when the throttle is fully opened is ensured, and the deterioration of the response when the throttle is suddenly opened is avoided.

In addition, the inventors have studied the intake volume that can achieve the combustion improvement effect (especially the improvement of the robustness of the combustion with respect to the lean air-fuel mixture) that can eliminate the secondary air introduction device. Has been decided. That is, the intake volume that ensures stable combustion at the stoichiometric air-fuel ratio even in the idle state with the lowest load is examined, and the volume of the intake chamber 61 is determined so as to be the intake volume.
Specifically, the inventors define intake air specific volume ξ = intake volume Vi / stroke volume Vc as a measure of the intake volume, and represents the robustness of combustion by the variation rate COV of the average effective pressure IMEP. The characteristics of the rate of change COV with respect to the air-fuel ratio (equivalent ratio φ) when the intake specific volume ξ was changed were obtained by experiments. The stroke volume Vc is the volume of the cylinder chamber 12A, and corresponds to the displacement in the case of a single cylinder engine.

FIG. 9 is a diagram showing experimental results. In this experiment, the engine speed Ne is 1200 rpm / min, and the average effective pressure IMEP is 70 kPa. Also, in the figure, the symbol COVmax is an upper limit value of the rate of change COV that can be regarded as a stable idle for a motorcycle engine.
For example, in a conventional motorcycle engine, the intake specific volume ξ is set to about 30%. In this case, a dense air-fuel mixture with an equivalent ratio φ of 1.2 or more is required for stable idling. It can be seen that secondary air must be introduced to purify the exhaust gas in the treatment.

As shown in FIG. 9, the region where the variation rate COV exceeds the upper limit value COVmax is shifted to the lean air-fuel mixture side as the intake specific volume ξ increases, and the theoretical air-fuel ratio (equivalent ratio φ = It turned out to be a sparser side than 1).
That is, according to the results of this experiment, an increase in intake volume such that the intake specific volume ξ is less than 60% does not reduce the emission reduction to the extent that the secondary air introduction device can be eliminated, and the intake specific volume ξ is set to 60%. It has been found that by increasing the intake volume as described above, it is possible to obtain an emission reduction effect that can eliminate the secondary air introduction device.

Therefore, by setting the volume of the intake chamber 61 to the volume of the downstream intake passage 71B of the throttle valve 51 so that the intake specific volume ξ is 60% or more, the equivalent ratio φ of the air-fuel mixture can be reduced. It was found that combustion was stable even at 1.0 or less, fuel consumption could be improved and emissions could be reduced, and the secondary air introduction device could be eliminated.
In this case, for example, as in the conventional motorcycle engine, when the intake specific volume ξ of the intake volume not including the intake chamber 61 (corresponding to the downstream intake passage 71B) is about 30%, the intake chamber 61 is By setting the volume of the downstream intake passage 71B to at least one time or more, the total intake volume can be increased to twice or more, and the intake specific volume ξ can be set to 60% or more.

  In the present embodiment, the fuel injection amount is controlled by the injector 33 so that the equivalence ratio φ of the air-fuel mixture becomes 1.0 or less at least when the engine 10 is under low load and low speed. In this case, control with an emphasis on fuel consumption may be performed so that the equivalence ratio φ is always 1.0 or less, or control with emphasis on running performance may be performed by variably controlling the mixing ratio. When the mixture ratio is variably controlled, the fuel injection amount is adjusted so that the equivalent mixture ratio φ is greater than 1.0 when the throttle valve 51 is opened at a predetermined opening or higher and in a high load state or a high rotation state. It is preferable to control.

As described above, according to the present embodiment, when the throttle valve 51 is closed to a predetermined opening or less and the engine 10 is under a low load and low rotation, the throttle valve 51 communicates with the downstream intake passage 71B of the throttle valve 51. Since the intake chamber 61 is provided, it is possible to improve combustion deterioration (ignition delay and decrease in combustion speed) at low load and low rotation. Therefore, it is possible to improve the situation such as (1) poor thermal efficiency due to delayed combustion, (2) stable combustion without giving a rich mixture, and (3) a large amount of unburned HC (hydrocarbon) in the exhaust. it can.
Moreover, in this configuration, the volume of the intake chamber 61 is set so that the intake specific volume ξ is 60% or more, that is, at least the combined volume with the downstream intake passage 71B of the throttle valve 51 (corresponding to the intake volume Vi). Since the volume is set to 60% or more of the stroke volume Vc, the combustibility with respect to the lean air-fuel mixture can be improved to such an extent that the secondary air introduction device can be reliably abolished. This makes it possible to achieve both improved fuel efficiency and reduced emissions without complicating configuration and control.

Further, in this configuration, the volume of the intake chamber 61 is at least one volume larger than that of the downstream intake passage 71B of the throttle valve 51, so that the intake passage (downstream intake passage) is the same as that of a conventional motorcycle engine. Even when the volume (corresponding to the volume of 71B) is reduced, the intake specific volume ξ can be reliably set to 60% or more. For this reason, the application to the conventional motorcycle is easy.
In this configuration, the intake chamber 61 is communicated with the intake passage 71B on the downstream side of the throttle valve 51 via the pipe portion (open / close passage) 31 that is opened and closed by the throttle valve 51. Therefore, the throttle valve 51 is connected to the intake chamber 61. It can also be used as an opening / closing mechanism. Therefore, the number of parts can be reduced and the size can be reduced as compared with the case where this kind of opening / closing mechanism and control mechanism are separately provided, and this also makes it possible to avoid complications in configuration and control.
Further, in this configuration, when the throttle valve 51 is fully open, the valve body 51A of the throttle valve 51 is accommodated in the pipe portion 31B, so that the upstream intake passage 71A and the downstream intake passage 71B of the throttle valve 51 Can be communicated with a large opening, and deterioration of output performance when the throttle is fully opened can be minimized.

<Second embodiment>
10 and 11 show a second embodiment. In the second embodiment, the engine 10 is a four-cycle two-cylinder engine in which the ignition intervals of the cylinders are unequal, and the throttle body 31 of the engine 10 has two intakes as shown in FIG. It is connected to the engine 10 via the pipes 30 and 30. Here, FIG. 10 is a diagram functionally showing the throttle body 31 and its peripheral configuration, and FIG. 11 shows an actual external view.

  As shown in FIG. 10, the throttle body 31 includes throttle valves 51, 51 corresponding to the intake pipes 30, 30, and these throttle valves 51, 51 are integrally opened and closed according to the accelerator operation. In addition, pipe portions (open / close passages) 31B and 31B that are opened and closed by throttle valves 51 and 51 are integrally formed in the case 31A of the throttle body 31, and the pipe portions 31B and 31B are formed as communication passage forming bodies 81. It is designed to communicate with each other. As shown in FIG. 11, the communication path forming body 81 is formed in a small cover shape that allows the pipe portions 31B and 31B to communicate with each other at the shortest distance, and is simply connected to the case 31A of the throttle body 31 via a plurality of bolts 82. Fixed.

In this embodiment, when the throttle valves 51 and 51 are closed, as shown in FIG. 10, both the pipe portions 31B and 31B communicate with the intake pipes 30 and 30 (corresponding to the downstream intake passages 71B and 71B). The downstream intake passages 71B and 71B can be communicated with each other by the communication passage forming body 81 that communicates the pipe portions 31B and 31B. In this case, when one of the cylinders is in the intake stroke, the other cylinder is not in the intake stroke, so that the intake volume that contributes to the intake of one of the cylinders is reduced in the downstream intake passage 71B of the other cylinder. The volume can be doubled.
Since the intake volume can be easily doubled in this way, the intake specific volume ξ of each intake volume of the downstream side intake passages 71B and 71B can be set to about 30% as in the conventional motorcycle engine. Thus, it is possible to easily satisfy the intake specific volume ξ = 60% or more.

Thus, in the two-cylinder engine 10 with unequal ignition intervals, when the throttle valve 51 is closed to a predetermined opening or less and the engine 10 is under low load and low rotation, the downstream side intake passage 71B communicated with one cylinder. And the downstream side intake passage 71B communicating with the other cylinder, the intake volume provided for the intake stroke can be increased without separately providing the intake chamber 61 of the first embodiment. In other words, the intake passage on the cylinder side that is not in the intake stroke is substituted for the intake chamber 61, whereby the intake volume can be easily increased.
Moreover, since the intake volume can be doubled, even if the intake specific volume ξ of the intake volume of each of the downstream intake passages 71B and 71B is made small as in the conventional motorcycle engine, the intake specific volume ξ is reduced. It can be easily and reliably about 60%.
Thus, in this embodiment, in addition to the various effects described in the first embodiment, the other intake passage is replaced with the intake chamber 61, thereby reducing the size and reducing the size of the dedicated intake chamber. The number of parts can be reduced.

As mentioned above, although this invention was demonstrated based on one Embodiment, this invention is not limited to this, A various design deformation | transformation can be performed. For example, in the above-described embodiment, the case where the throttle valve 51 is also used as a switching valve that communicates with the intake chamber 61 (including the intake passage of another cylinder) has been described. A valve may be provided separately.
In the second embodiment described above, the case where the present invention is applied to the intake control device of an independent intake pipe type two-cylinder engine has been described. However, the present invention is not limited to this, and an intake volume such as an independent intake pipe type is small. It can be widely applied to cylinder engines.
Furthermore, the present invention is not limited to being applied to an intake control device for a motorcycle engine, but can be widely applied to an intake control device for an engine having a small intake volume, for example, classified as ATV (rough terrain vehicle). The present invention is applicable to intake control devices for other vehicle engines such as three-wheel vehicles and four-wheel vehicles.

1 is a view showing a motorcycle engine according to a first embodiment of the present invention together with an intake system. FIG. It is a figure which shows the throttle body with a surrounding structure with a throttle valve closed. It is a figure which shows the throttle body with a surrounding structure with a throttle valve open. It is a figure explaining a simulation model. It is a characteristic curve figure which shows the change of the cylinder pressure of an intake stroke and a compression stroke. It is a characteristic curve figure which shows the change of the intake flow velocity of an intake stroke. It is a characteristic curve figure which shows the change of the cylinder pressure of the whole stroke | process. It is a figure which shows the combustion characteristic of a combustion process. It is a characteristic curve figure which shows the relationship between an intake specific volume and an equivalence ratio. It is a figure which shows the intake system of 2nd embodiment functionally. It is an external view of the intake system of 2nd embodiment.

Explanation of symbols

10 Engine (Internal combustion engine)
11 Crankcase 12 Cylinder block 12A Cylinder chamber (cylinder)
13 Cylinder Head 14 Head Cover 15 Combustion Chamber 21 Piston 23 Crankshaft 30 Intake Pipe 31 Throttle Body 31A Throttle Body Case 31B Pipe Portion (Open / Close Path)
32 Air cleaner 33 Injector (fuel injection device)
51 Throttle valve (intake throttle valve)
61 Intake chamber 71A Upstream intake passage 71B, 71C Downstream intake passage

Claims (4)

In an intake control device for an internal combustion engine in which an intake throttle valve is provided in an intake passage communicating with a combustion chamber,
When the intake throttle valve has a predetermined opening or less, an intake chamber is provided in the intake passage downstream of the intake throttle valve so as to communicate with the internal combustion engine at low load and low rotation, and the volume of the intake chamber is at least An intake control device for an internal combustion engine, characterized in that a combined volume with an intake pipe volume downstream of the intake throttle valve is a volume that is 60% or more of a stroke volume. The intake control apparatus for an internal combustion engine according to claim 1,
The intake control device for an internal combustion engine, wherein the intake chamber has a volume that is at least one time larger than an intake pipe volume downstream of the intake throttle valve. The intake control device for an internal combustion engine according to claim 1 or 2,
There is provided a switching valve that communicates the intake passage and an intake passage that communicates with a cylinder other than the cylinder that communicates with the intake passage at the time of low load and low rotation of the internal combustion engine, and communicates via the switching valve. An intake control device for an internal combustion engine, characterized in that an intake passage of another cylinder is substituted for the intake chamber. The intake control apparatus for an internal combustion engine according to any one of claims 1 to 3,
The intake control device for an internal combustion engine, wherein the intake chamber communicates with an intake passage downstream of the intake throttle valve through an open / close passage opened and closed by the intake throttle valve.

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