阅读说明：本技术 内燃机 (Internal combustion engine ) 是由 高桥教悦 百濑好二 于 2020-03-12 设计创作，主要内容包括：具备：进气管(11B),其具有折弯的弯曲部分(71),且弯曲部分(71)的下游侧的进气出口部(71B)与进气歧管(11C)连接；节气门(47A),其在比弯曲部分(71)的上游侧的进气入口部(71A)靠上游侧的附近位置配置；和EGR配管(13),其与弯曲部分(71)连接,节气门(47A)的转动轴(48)设置为与第1平面(75)垂直,上述第1平面(75)包括在进气入口部(71A)穿过的入口侧进气管轴线(72A)和在进气出口部(71B)穿过的出口侧进气管轴线(72B),弯曲部分(71)的第1平面(75)上的外侧的面由与入口侧进气管轴线(72A)平行地向折弯侧延出的第1侧壁面(73A)、与出口侧进气管轴线(72B)平行地向折弯侧延出的第2侧壁面(73B)、将第1侧壁面(73A)与第2侧壁面(73B)的折弯侧端部连接起来的规定曲率半径的外侧曲面(73C)形成。(The disclosed device is provided with: an intake pipe (11B) having a bent curved portion (71), and an intake outlet portion (71B) on the downstream side of the curved portion (71) being connected to an intake manifold (11C); a throttle valve (47A) disposed in the vicinity of the upstream side of the intake inlet (71A) on the upstream side of the curved portion (71); and an EGR pipe (13) connected to the curved portion (71), wherein a rotation axis (48) of the throttle valve (47A) is provided so as to be perpendicular to a 1 st plane (75), the 1 st plane (75) includes an inlet-side intake pipe axis (72A) passing through the inlet portion (71A) and an outlet-side intake pipe axis (72B) passing through the inlet portion (71B), and an outer surface of the 1 st plane (75) of the curved portion (71) is formed by a 1 st side wall surface (73A) extending toward the bent side in parallel to the inlet-side intake pipe axis (72A), a 2 nd side wall surface (73B) extending toward the bent side in parallel to the outlet-side intake pipe axis (72B), and an outer curved surface (73C) having a predetermined radius of curvature connecting the bent side ends of the 1 st side wall surface (73A) and the 2 nd side wall surface (73B).)

1. An internal combustion engine, characterized by comprising:

an intake pipe having a bent curved portion, and an intake outlet portion on a downstream side of the curved portion being connected to an upstream side of an intake manifold;

a throttle valve disposed upstream of an intake inlet on an upstream side of the curved portion and in a vicinity of the intake inlet, the throttle valve being capable of adjusting an opening degree of the intake pipe; and

an EGR pipe connected to the bent portion,

the rotation axis of the throttle valve is disposed perpendicular to a 1 st plane, the 1 st plane including an inlet-side intake pipe axis passing through the intake inlet portion and an outlet-side intake pipe axis passing through the intake outlet portion,

the outer surface of the curved portion on the 1 st plane is composed of a 1 st side wall surface, a 2 nd side wall surface, and an outer curved surface having a predetermined curvature radius,

the 1 st side wall surface extends from the outer end of the intake inlet portion to a bent side in parallel with the axis of the intake pipe on the inlet side,

the 2 nd side wall surface extends from an outer end of the intake outlet portion to a bent side in parallel with the outlet-side intake pipe axis,

the outer curved surface having the predetermined radius of curvature connects the bent side end portions of the 1 st and 2 nd side wall surfaces.

2. The internal combustion engine according to claim 1,

as for the throttle valve, in the case of the throttle valve,

an inner facing portion facing an inner side of the curved portion is rotated toward a downstream side by a predetermined angle around the rotation shaft from a closed position orthogonal to an inlet-side inlet pipe axis of the inlet portion,

an outer facing portion facing an outer side of the curved portion is rotated toward an upstream side by the predetermined angle around the rotation shaft from the closed position orthogonal to the inlet-side inlet pipe axis of the inlet portion,

the intake air flows into the downstream side from gaps between the intake pipe and both side edge portions of the throttle valve in the direction orthogonal to the rotation axis.

3. The internal combustion engine according to claim 1 or 2,

as for an extension line of an EGR pipe axis line of the EGR pipe at the connection port,

the extension line is arranged substantially perpendicular to the 1 st plane and on the opposite side of the intake inlet portion with a 2 nd plane including the outlet side intake pipe axis at the intake outlet portion and orthogonal to the 1 st plane interposed therebetween,

the extension line is disposed closer to the outer curved surface of the curved portion than an intersection between the inlet-side intake pipe axis and the outlet-side intake pipe axis on the 1 st plane.

4. The internal combustion engine according to claim 1 or 2,

as for an extension line of the EGR pipe axis line at the connection port of the EGR pipe,

the extension line is arranged in parallel to the outlet-side intake pipe axis of the intake outlet portion of the bent portion on the 1 st plane,

the extension line is disposed on the side opposite to the intake port portion with a 2 nd plane including the outlet side intake pipe axis and orthogonal to the 1 st plane interposed therebetween.

Technical Field

The present invention relates to an internal combustion engine having an Exhaust Gas Recirculation (EGR) device.

Background

Conventionally, various techniques have been proposed for returning a part of exhaust gas to an intake pipe via an EGR device, mixing the exhaust gas with intake air, and supplying the mixture to an intake manifold. For example, an intake manifold disclosed in japanese patent application laid-open No. 2000-45880 includes: a gas collecting part which is provided with a plurality of connecting ports connected with each cylinder; and a mixing chamber communicating with the gas collector via a communication port. An intake air inlet and an EGR gas inlet are connected to one end of the mixing chamber in the longitudinal direction, and a communication port is provided at the other end of the mixing chamber in the longitudinal direction.

The intake air inlet is opened in a side wall in the longitudinal direction of the mixing chamber, and the throttle valve is disposed in the intake air inlet with its rotation axis aligned in the longitudinal direction of the mixing chamber. In this configuration, the intake air flows from the intake air inlet portion into the mixing chamber through the throttle valve, and flows along the side wall of the mixing chamber toward the communication port as a swirling flow around the longitudinal central axis. The EGR gas inlet port is open toward the center of the swirling flow, and is configured to suck and mix EGR gas in a negative pressure region formed in the center of the swirling flow.

However, since the intake air flowing into the mixing chamber from the intake air inlet portion flows toward the communication port as a swirling flow around the central axis of the mixing chamber in the longitudinal direction, there is a possibility that the ratio of the EGR gas sucked into the vicinity of the central axis of the swirling flow and the EGR gas sucked into the outer peripheral side of the swirling flow, that is, the side wall side of the mixing chamber may be inconsistent in the mixing between the EGR gas and the intake air. As a result, if the amount of EGR gas supplied to each cylinder of the internal combustion engine varies between cylinders, there is a problem as follows: the combustion of each cylinder is not uniform, and the combustion sound is not uniform, which gives an unpleasant impression to the driver.

Disclosure of Invention

Accordingly, the disclosed technology, as one aspect, aims to provide an internal combustion engine capable of suppressing the variation in the amount of EGR gas between cylinders, making the combustion of each cylinder constant, and suppressing the variation in combustion noise.

In order to solve the above problem, one aspect of the present disclosure is an internal combustion engine including: an intake pipe having a bent portion, and an intake outlet portion on a downstream side of the bent portion being connected to an upstream side of an intake manifold; a throttle valve disposed upstream of an intake inlet on an upstream side of the curved portion and in a vicinity of the intake inlet, the throttle valve being capable of adjusting an opening degree of the intake pipe; and an EGR pipe connected to the bent portion, wherein a rotation axis of the throttle valve is arranged to be perpendicular to a 1 st plane, the 1 st plane includes an inlet-side intake pipe axis passing through the intake inlet portion and an outlet-side intake pipe axis passing through the intake outlet portion, the outer surface of the curved portion on the 1 st plane is composed of a 1 st sidewall surface, a 2 nd sidewall surface, and an outer curved surface having a predetermined radius of curvature, the 1 st side wall surface extends from the outer end of the intake inlet to a bent side in parallel with the axis of the intake pipe on the inlet side, the 2 nd side wall surface extends from the outer end of the intake outlet port portion to a bent side in parallel with the outlet-side intake pipe axis, the outer curved surface having the predetermined radius of curvature connects the bent side end portions of the 1 st and 2 nd side wall surfaces.

According to the above disclosure, the throttle valve is rotated by a predetermined angle around the rotation axis from a position orthogonal to the inlet-side intake pipe axis of the intake inlet portion, so that the intake air flows in from the gaps between the intake pipe and both side edge portions of the throttle valve in the direction orthogonal to the rotation axis along the outer surface and the inner surface of the curved portion on the downstream side. The outer surface of the curved portion is formed by a 1 st sidewall surface and a 2 nd sidewall surface which are bent and extended from the outer end of each of the intake inlet portion and the intake outlet portion of the curved portion in parallel to the intake inlet pipe axis and the outlet side intake pipe axis on a 1 st plane including the intake inlet pipe axis passing through the intake inlet portion and the outlet side intake pipe axis passing through the intake outlet portion, and an outer curved surface having a predetermined radius of curvature connecting bent side ends of the 1 st sidewall surface and the 2 nd sidewall surface.

As a result, as one aspect, among the intake air flowing along the 1 st sidewall surface on the upstream side of the curved portion toward the outer curved surface, there are intake air flowing while swirling toward the upstream side while hitting against the outer curved surface, and intake air flowing from the outer curved surface toward the downstream side while swirling along the 2 nd sidewall surface on the downstream side of the curved portion. The intake air that flows while swirling to the upstream side flows along the inner curved surface of the curved portion while hitting the throttle valve and again swirling to the downstream side. On the other hand, among the intake air flowing along the pipe wall toward the inner curved surface of the curved portion, there are intake air flowing while swirling along the inner curved surface of the curved portion and intake air flowing while swirling from the outer curved surface of the curved portion along the 2 nd sidewall surface on the downstream side of the curved portion. Then, by these swirling flows, two swirls swirling in mutually opposite directions in the intake pipe from the intake outlet portion of the curved portion toward the downstream side are generated across the outlet-side intake pipe axis.

Accordingly, the EGR gas flowing in from the connection port of the EGR pipe connected to the bent portion is entrained into the intake air that becomes two vortices, is efficiently mixed, and flows into the intake manifold. Therefore, the intake air obtained by sufficiently mixing the EGR gas by the two swirl flows is supplied to each cylinder via the intake manifold, so that it is possible to suppress the variation in the amount of EGR gas between the cylinders, to make the combustion in each cylinder constant, and to suppress the variation in the combustion noise.

Next, another aspect of the present disclosure is an internal combustion engine, wherein in the throttle valve, an inner facing portion facing an inner side of the curved portion is turned to a downstream side by a predetermined angle around the turning axis from a closed position orthogonal to an axis of the intake pipe on an inlet side of the intake port portion, an outer facing portion facing an outer side of the curved portion is turned to an upstream side by the predetermined angle around the turning axis from the closed position orthogonal to the axis of the intake pipe on the inlet side of the intake port portion, and intake air flows into the downstream side from a gap between both side edge portions of the throttle valve in a direction orthogonal to the turning axis and the intake pipe.

According to the above disclosure, the inner opposing portion facing the inside of the curved portion of the throttle valve is rotated by a predetermined angle toward the downstream side from the closed position orthogonal to the inlet-side intake pipe axis of the intake inlet portion around the rotation shaft. The outer facing portion facing the outside of the curved portion of the throttle valve is rotated by a predetermined angle toward the upstream side from a closed position orthogonal to the inlet-side intake pipe axis of the intake inlet portion around the rotation shaft. Therefore, most of the intake air that collides with the upstream side surface of the throttle valve flows toward the inner curved surface of the curved portion, and flows downstream along the gap between the side edge portion of the throttle valve on the inner facing portion side and the intake pipe.

As a result, as one aspect, the flow velocity of the intake air flowing along the gap between the side edge portion on the inner facing portion side of the throttle valve and the intake pipe can be made larger than the flow velocity of the intake air flowing along the gap between the side edge portion on the outer facing portion side of the throttle valve and the intake pipe. Thus, compared to the case where the inner facing portion of the throttle valve is rotated by a predetermined angle toward the upstream side from the closed position about the rotation axis, the swirling speeds of the two vortices generated in the intake pipe on the downstream side from the intake outlet portion of the curved portion can be increased. As a result, the EGR gas flowing from the connection port of the EGR pipe into the bent portion can be more uniformly mixed with the intake air and supplied to the intake manifold. Therefore, it is possible to further suppress the variation in the amount of EGR gas between the cylinders, to make the combustion in each cylinder constant, and to further suppress the variation in combustion noise.

Next, another aspect of the present disclosure is an internal combustion engine, wherein an extension line of an EGR pipe axis line at a connection port of the EGR pipe is arranged substantially perpendicular to the 1 st plane, is arranged on a side opposite to the intake port portion with a 2 nd plane including the outlet-side intake pipe axis line at the intake port portion and orthogonal to the 1 st plane interposed therebetween, and is arranged closer to the outer curved surface of the curved portion than an intersection point between the inlet-side intake pipe axis line and the outlet-side intake pipe axis line on the 1 st plane.

According to the above disclosure, an extension line of an EGR pipe axis line at a connection port of the EGR pipe is arranged substantially perpendicular to a 1 st plane including an inlet side intake pipe axis line passing through the intake inlet portion and an outlet side intake pipe axis line passing through the intake outlet portion, and is arranged on a side opposite to the intake inlet portion with a 2 nd plane including the outlet side intake pipe axis line of the intake outlet portion and orthogonal to the 1 st plane. Further, an extension line of the EGR pipe axis line at the connection port of the EGR pipe is disposed closer to the outer curved surface of the curved portion than an intersection point between the inlet side intake pipe axis line and the outlet side intake pipe axis line on the 1 st plane.

Accordingly, as one side surface, the EGR gas can be introduced from the lateral direction at a position close to the outer curved surface with respect to the intake air that flows upstream by colliding with the outer curved surface of the curved portion. As a result, the EGR gas can be caused to flow into the front side where the two swirls swirling in the opposite directions to each other are generated in the intake pipe on the downstream side of the curved portion, and the EGR gas can be caused to flow substantially uniformly into the intake air that becomes the two swirls. As a result, the EGR gas is substantially uniformly entrained into the intake air that becomes the two swirl flows, and therefore, the EGR gas and the intake air can be more uniformly mixed and supplied to the intake manifold.

Next, another aspect of the present disclosure is an internal combustion engine, wherein an extension line of an EGR pipe axis line at a connection port of the EGR pipe is disposed in parallel with the outlet-side intake pipe axis line of the intake air outlet portion of the bent portion on the 1 st plane, and the extension line is disposed on a side opposite to the intake air inlet portion with a 2 nd plane including the outlet-side intake pipe axis line and orthogonal to the 1 st plane interposed therebetween.

According to the above disclosure, an extension line of an EGR pipe axis line at a connection port of an EGR pipe is arranged in parallel with an outlet side intake pipe axis line of an intake outlet portion of a bent portion on a 1 st plane including an inlet side intake pipe axis line passing through an intake inlet portion and an outlet side intake pipe axis line passing through an intake outlet portion, and the extension line is arranged on a side opposite to the intake inlet portion with a 2 nd plane including the outlet side intake pipe axis line and orthogonal to the 1 st plane interposed therebetween. Thus, as one side surface, the EGR gas can be caused to flow into the near side where the two swirls swirling in the opposite directions to each other are generated in the intake pipe on the downstream side of the curved portion, and the EGR gas can be caused to flow substantially uniformly into the intake air that becomes the two swirls. As a result, the EGR gas is substantially uniformly entrained into the intake air that becomes the two swirl flows, and therefore, the EGR gas can be more uniformly mixed with the intake air and supplied to the intake manifold.

Drawings

Fig. 1 is a diagram illustrating a schematic configuration of an internal combustion engine according to embodiment 1.

Fig. 2 is a perspective view showing an example of a connection structure between an intake pipe and an outflow side of an EGR pipe according to embodiment 1.

Fig. 3 is a view showing a cross section including an inlet side intake pipe axis and an outlet side intake pipe axis of a bent portion of the intake pipe of fig. 2.

Fig. 4 is a diagram illustrating the arrangement positions of the throttle valve and the EGR pipe as viewed from IV in fig. 3.

Fig. 5 is a diagram illustrating generation of two vortices at a curved portion of the intake pipe of fig. 3.

Fig. 6 is a view showing an example of two vortices in the VI-VI view section of fig. 5.

Fig. 7 is a diagram showing an example of a relationship between a distance L from the center of the EGR pipe to the outer curved surface of fig. 3 and a difference between EGR cylinders.

Fig. 8 is a diagram showing an example of a relationship between the ratio of the 1 st radius of curvature of the outer curved surface to the pipe diameter of the intake pipe in fig. 3 and the difference between the EGR cylinders.

Fig. 9 is a cross-sectional view including an inlet-side intake pipe axis and an outlet-side intake pipe axis, showing a connection structure between an intake pipe and an outlet side of an EGR pipe according to embodiment 2.

Fig. 10 is a diagram illustrating the positions of the throttle valve and the EGR pipe as viewed from the X direction in fig. 9.

Fig. 11 is a diagram illustrating generation of two vortices at a curved portion of the intake pipe of fig. 9.

Fig. 12 is a view showing an example of two vortexes in a section taken along the direction XII-XII in fig. 11.

Fig. 13 is a view showing an example of a state in which the rotation direction of the throttle valve in fig. 3 and 9 is changed.

Fig. 14 is a view showing a 1 st comparative example in which the outer side of the bent portion of the intake pipe of fig. 9 is bulged in the axial direction of the intake pipe facing the outlet side of the intake outlet portion, and a 2 nd comparative example in which the intake pipe on the downstream side from the bent portion is deformed into a substantially quadrangular shape in cross section.

FIG. 15 is a view from the direction of XV in FIG. 14 (D-1).

Fig. 16 is a diagram showing an example of an analysis result of the difference between the EGR cylinders for each combination of the connection structure of the intake pipe and the EGR pipe and the rotation state of the throttle valve shown in fig. 13 and 14.

Detailed Description

Hereinafter, the internal combustion engine according to the present invention will be described in detail based on embodiment 1 and embodiment 2, which embody the same with reference to the drawings. First, a schematic configuration of an internal combustion engine 10 according to embodiment 1 of the present invention will be described with reference to fig. 1. In the description of embodiment 1, a diesel engine mounted on a vehicle, for example, is used as an example of the internal combustion engine 10.

[ embodiment 1 ]

Hereinafter, the internal combustion engine 10 according to embodiment 1 will be described in order from the intake side to the exhaust side. As shown in fig. 1, an intake flow rate detection device 21 (e.g., an intake flow rate sensor) is provided on the inflow side of the intake pipe 11A. The intake air flow rate detection device 21 outputs a detection signal corresponding to the flow rate of air taken in by the internal combustion engine 10 to the control device 50. An intake air temperature detection device 28A (e.g., an intake air temperature sensor) is provided in the intake air flow rate detection device 21. The intake air temperature detection device 28A outputs a detection signal corresponding to the temperature of the intake air passing through the intake air flow rate detection device 21 to the control device 50.

The outflow side of the intake pipe 11A is connected to the inflow side of the compressor 35, and the outflow side of the compressor 35 is connected to the inflow side of the intake pipe 11B. The turbocharger 30 includes: a compressor 35 having a compressor wheel 35A and a turbine 36 having a turbine wheel 36A. The compressor impeller 35A is rotationally driven by the turbine impeller 36A rotationally driven by the exhaust gas, and the intake air flowing in from the intake pipe 11A is pressure-fed to the intake pipe 11B, thereby performing supercharging.

A compressor upstream pressure detection device 24A is provided in the intake pipe 11A on the upstream side of the compressor 35. The compressor upstream pressure detecting device 24A is, for example, a pressure sensor, and outputs a detection signal corresponding to the pressure in the intake pipe 11A on the upstream side of the compressor 35 to the control device 50. A compressor downstream pressure detection device 24B is provided in the intake pipe 11B on the downstream side of the compressor 35 (at a position between the compressor 35 and the intercooler 16 in the intake pipe 11B). The compressor downstream pressure detection device 24B is, for example, a pressure sensor, and outputs a detection signal corresponding to the pressure in the intake pipe 11B on the downstream side of the compressor 35 to the control device 50.

The intake pipe 11B has an intercooler 16 disposed on an upstream side, and a throttle device 47 disposed on a downstream side of the intercooler 16. The intercooler 16 is disposed downstream of the compressor downstream pressure detection device 24B, and reduces the temperature of the intake air supercharged by the compressor 35. An intake air temperature detection device 28B (e.g., an intake air temperature sensor) is provided between the intercooler 16 and the throttle device 47. The intake air temperature detection device 28B outputs a detection signal corresponding to the temperature of the intake air that has been lowered in temperature by the intercooler 16 to the control device 50.

The throttle device 47 drives a throttle valve 47A that adjusts the opening degree of the intake pipe 11B based on a control signal from the control device 50, and is capable of adjusting the intake air flow rate. The controller 50 is capable of outputting a control signal to the throttle device 47 and adjusting the opening degree of the throttle valve 47A provided in the intake pipe 11B based on a detection signal from the throttle opening degree detection device 47S (for example, a throttle opening degree sensor) and the target throttle opening degree. The control device 50 obtains a target throttle opening degree from the depression amount of the accelerator pedal detected based on the detection signal from the accelerator pedal depression amount detection device 25 and the operating state of the internal combustion engine 10.

The accelerator pedal depression amount detection device 25 is, for example, an accelerator pedal depression angle sensor, and is provided in the accelerator pedal. The control device 50 can detect the amount of depression of the accelerator pedal by the driver based on the detection signal from the accelerator pedal depression amount detection device 25.

A pressure detection device 24C is provided in the intake pipe 11B downstream of the throttle device 47, and the outflow side of the EGR pipe 13 is connected thereto. The outflow side of the intake pipe 11B is connected to the inflow side of the intake manifold 11C, and the outflow side of the intake manifold 11C is connected to the inflow side of the internal combustion engine 10. The pressure detection device 24C is, for example, a pressure sensor, and outputs a detection signal corresponding to the pressure of intake air immediately before the intake air flows into the intake manifold 11C to the control device 50. Further, the EGR gas that has flowed in from the inflow side of the EGR pipe 13 (the connection portion with the exhaust pipe 12B) is discharged into the intake pipe 11B from the outflow side of the EGR pipe 13 (the connection portion with the intake pipe 11B). The path formed by the EGR pipe 13 through which the EGR gas flows corresponds to an EGR path.

The internal combustion engine 10 has a plurality of cylinders 45A to 45D, and injectors 43A to 43D are provided for the respective cylinders. The injectors 43A to 43D are supplied with fuel via the common rail 41 and the fuel pipes 42A to 42D, and the injectors 43A to 43D are driven by a control signal from the control device 50 to inject the fuel into the respective cylinders 45A to 45D.

The internal combustion engine 10 is provided with a rotation detection device 22, a coolant temperature detection device 28C, and the like. The rotation detecting device 22 is, for example, a rotation sensor, and outputs a detection signal corresponding to the rotation speed of the crankshaft of the internal combustion engine 10 (i.e., the engine rotation speed) to the control device 50. The coolant temperature detection device 28C is, for example, a temperature sensor, detects the temperature of the coolant circulating in the internal combustion engine 10, and outputs a detection signal corresponding to the detected temperature to the control device 50.

An inflow side of an exhaust manifold 12A is connected to an exhaust side of the internal combustion engine 10, and an inflow side of an exhaust pipe 12B is connected to an outflow side of the exhaust manifold 12A. The outflow side of the exhaust pipe 12B is connected to the inflow side of the turbine 36, and the outflow side of the turbine 36 is connected to the inflow side of the exhaust pipe 12C.

The exhaust pipe 12B is connected to an inflow side of the EGR pipe 13. The EGR pipe 13 communicates the exhaust pipe 12B with the intake pipe 11B, and can recirculate a part of the exhaust gas in the exhaust pipe 12B (corresponding to an exhaust path) to the intake pipe 11B (corresponding to an intake path). The EGR pipe 13 is provided with a path switching device 14A, a bypass pipe 13B, EGR cooler 15, and an EGR valve 14B. The path formed by the bypass pipe 13B corresponds to a bypass path.

The path switching device 14A is a path switching valve that switches the EGR gas flowing from the exhaust pipe 12B to the EGR pipe 13 between an EGR cooler path that returns to the intake path via the EGR cooler 15 and a bypass path that bypasses the EGR cooler 15 via the bypass pipe 13B and returns to the intake pipe 11B, based on a control signal from the control device 50. The bypass pipe 13B is provided to bypass the EGR cooler 15, and is connected to the route switching device 14A on the inflow side and to the EGR pipe 13 between the EGR valve 14B and the EGR cooler 15 on the outflow side.

The EGR valve 14B is provided on the EGR pipe 13 on the downstream side of the EGR cooler 15, and is provided on the downstream side of a merging portion of the EGR pipe 13 and the bypass pipe 13B. The EGR valve 14B adjusts the opening degree of the EGR pipe 13 based on a control signal from the control device 50, thereby adjusting the flow rate of the EGR gas flowing through the EGR pipe 13.

The EGR cooler 15 is provided in the EGR pipe 13 between the route switching device 14A and a junction where the EGR pipe 13 and the bypass pipe 13B join each other. The EGR cooler 15 is a so-called heat exchanger, and is supplied with a coolant for cooling, cools the EGR gas flowing in, and discharges the cooled EGR gas.

An exhaust temperature detection device 29 is provided in the exhaust pipe 12B. The exhaust temperature detection device 29 is, for example, an exhaust temperature sensor, and outputs a detection signal corresponding to the exhaust temperature to the control device 50. The control device 50 can estimate the temperature of the EGR gas flowing into the intake pipe 11B via the EGR pipe 13, the EGR cooler 15 (or the bypass pipe 13B), and the EGR valve 14B based on the exhaust gas temperature detected using the exhaust gas temperature detection device 29, the control state of the EGR valve 14B, the operating state of the internal combustion engine 10, and the like.

The outflow side of the exhaust pipe 12B is connected to the inflow side of the turbine 36, and the outflow side of the turbine 36 is connected to the inflow side of the exhaust pipe 12C. The turbine 36 is provided with a variable nozzle 33 capable of controlling the flow rate of the exhaust gas introduced into the turbine impeller 36A, and the opening degree of the variable nozzle 33 is adjusted by the nozzle drive device 31. The control device 50 is capable of adjusting the opening degree of the variable mouth 33 by outputting a control signal to the mouth driving device 31 based on a detection signal from the mouth opening degree detecting device 32 (e.g., a mouth opening degree sensor) and a target mouth opening degree.

A turbine upstream pressure detection device 26A is provided in the exhaust pipe 12B on the upstream side of the turbine 36. The turbine upstream pressure detection device 26A is, for example, a pressure sensor, and outputs a detection signal corresponding to the pressure in the exhaust pipe 12B on the upstream side of the turbine 36 to the control device 50. A turbine downstream pressure detection device 26B is provided in the exhaust pipe 12C on the downstream side of the turbine 36. The turbine downstream pressure detection device 26B is, for example, a pressure sensor, and outputs a detection signal corresponding to the pressure in the exhaust pipe 12C on the downstream side of the turbine 36 to the control device 50.

An exhaust gas purification device 61 is connected to the outflow side of the exhaust pipe 12C. For example, when the internal combustion engine 10 is a diesel engine, the exhaust gas purification device 61 includes an oxidation catalyst, a particulate filter, a selective reduction catalyst, and the like.

The Control Unit (ECU) 50 includes at least a processor 51(CPU, MPU (Micro-Processing Unit), etc.) and a storage device 53(DRAM, ROM, EEPROM, SRAM, hard disk, etc.). The control unit 50(ECU) detects the operating state of the internal combustion engine 10 based on detection signals from various detection devices including the above-described detection device, and controls various actuators including the above-described injectors 43A to 43D, EGR, the valve 14B, the path switching device 14A, the mouth driving device 31, and the throttle device 47. The detection means for the control device 50 to detect the operation state is not limited to the detection means shown in fig. 1, and the actuator controlled by the control device 50 is not limited to the actuator shown in fig. 1. The storage device 53 stores, for example, programs, parameters, and the like for executing various processes.

The atmospheric pressure detection device 23 is, for example, an atmospheric pressure sensor, and is provided in the control device 50. The atmospheric pressure detection device 23 outputs a detection signal corresponding to the atmospheric pressure around the control device 50 to the control device 50. The vehicle speed detection device 27 is, for example, a vehicle speed detection sensor, and is provided on a wheel or the like of the vehicle. The vehicle speed detection device 27 outputs a detection signal corresponding to the rotational speed of the wheels of the vehicle to the control device 50.

Next, a connection structure 70 between the intake pipe 11B of the internal combustion engine 10 and the outflow side of the EGR pipe 13 configured as described above will be described with reference to fig. 2 to 8. As shown in fig. 2, in the connection structure 70, the outflow side of the EGR pipe 13 is connected to a bent portion 71 of the intake pipe 11B having a substantially circular cross section with a pipe diameter D1 (for example, a pipe diameter of about 55mm to 65mm) bent toward the intake manifold 11C. The bent portion 71 is bent from above toward the lateral direction at a substantially right angle (for example, an angle of about 80 degrees to about 95 degrees) when viewed from the side. The intake pipe 11B on the downstream side of the bent portion 71 is connected to the upstream side of the intake manifold 11C.

In detail, as shown in fig. 3, the curved portion 71 has: an intake inlet portion 71A on the upstream side into which intake air flows and an intake outlet portion 71B on the downstream side from which intake air flows out. As shown in fig. 3 and 4, in the curved portion 71, an inlet-side intake pipe axis 72A passing through the center of the cross section of the inlet portion 71A on the upstream side and an outlet-side intake pipe axis 72B passing through the center of the cross section of the inlet portion 71B on the downstream side intersect in a substantially central portion of the curved portion 71.

As shown in fig. 3 and 4, a throttle valve 47A having a substantially circular shape in plan view, which is capable of adjusting the opening degree of the intake pipe 11B, is rotatably disposed at a position upstream of the intake inlet 71A and near the intake inlet 71A on the upstream side of the curved portion 71. As shown in fig. 3, the rotational shaft 48 of the throttle valve 47A is disposed perpendicular to the 1 st plane 75 including the inlet-side intake pipe axis 72A and the outlet-side intake pipe axis 72B.

As shown in fig. 3, on the 1 st plane 75, the outer surface of the curved portion 71 is formed by a 1 st side wall surface 73A, a 2 nd side wall surface 73B, and an outer curved surface 73C having a 1 st radius of curvature R1 (for example, a radius of curvature of about 42mm to 30mm) connecting the bent side end portions of the 1 st side wall surface 73A and the 2 nd side wall surface 73B. The 1 st side wall surface 73A extends from the outer end of the upstream intake inlet 71A to a bent side in parallel with the inlet-side intake pipe axis 72A, and the 2 nd side wall surface 73B extends from the outer end of the downstream intake outlet 71B to a bent side in parallel with the outlet-side intake pipe axis 72B. The 1 st radius of curvature R1 corresponds to the prescribed radius of curvature of the present disclosure. Further, on the 1 st plane 75, the inner surface of the curved portion 71 is formed by an inner curved surface 74 having a 2 nd radius of curvature R2 (for example, a radius of curvature of about 3mm to 7 mm).

As shown in fig. 3 and 4, an extension 78A of the EGR pipe axis 78 at the connection port 77 of the EGR pipe 13 is disposed substantially perpendicular to the 1 st plane 75, and is disposed on the opposite side of the intake inlet 71A with a 2 nd plane 79 (see fig. 4) including the outlet-side intake pipe axis 72B at the intake outlet 71B and orthogonal to the 1 st plane 75 interposed therebetween. An extension 78A of the EGR pipe axis 78 at the connection port 77 of the EGR pipe 13 is disposed closer to the outer curved surface 73C in fig. 3 than an intersection 72C between the inlet-side intake pipe axis 72A and the outlet-side intake pipe axis 72B on the 1 st plane 75. Therefore, an extension 78A of the EGR pipe axis 78 is disposed on the lower side in fig. 3 than the outlet-side intake pipe axis 72B passing through the intake outlet portion 71B and on the deeper side (left side in fig. 3) than the intersection 72C between the inlet-side intake pipe axis 72A and the outlet-side intake pipe axis 72B.

As shown in fig. 3 and 4, the throttle valve 47A is rotated by a predetermined angle θ 1 (for example, about 20 degrees) toward the downstream side about the rotation shaft 48 from the closed position orthogonal to the inlet-side intake pipe axis 72A of the intake inlet 71A by the throttle device 47, the inner opposing portion 81A opposing the inside of the curved portion 71. Therefore, the throttle valve 47A rotates the outer facing portion 81B facing the outside of the curved portion 71 by a predetermined angle θ 1 (for example, about 20 degrees) toward the upstream side from the closed position orthogonal to the inlet-side intake pipe axis 72A of the intake inlet portion 71A around the rotation shaft 48 by the throttle device 47. As a result, intake air flows into the downstream side from gaps between the intake pipe 11B and both side edges of the throttle valve 47A in the direction perpendicular to the rotation shaft 48 (see fig. 5).

Next, the flow of intake air flowing into the curved portion 71 is explained based on fig. 5 and 6. As shown in fig. 5, the intake air 83A flowing from the gap between the side edge portion (left side edge portion in fig. 5) of the throttle valve 47A on the outer facing portion 81B side and the intake pipe 11B toward the outer curved surface 73C along the 1 st side wall surface 73A on the upstream side of the curved portion 71 includes the intake air 83B flowing while swirling upstream side while colliding with the outer curved surface 73C and the intake air 83C flowing from the outer curved surface 73C toward the downstream side while swirling along the 2 nd side wall surface 73B on the downstream side of the curved portion 71. The intake air 83B flowing while swirling to the upstream side hits the throttle valve 47A, and flows along the inner curved surface 74 of the curved portion 71 while swirling again to the downstream side.

On the other hand, the intake air 86A flowing along the pipe wall 85 from the gap between the side edge portion of the throttle valve 47A on the side of the inner facing portion 81A (the right side edge portion in fig. 5) and the intake pipe 11B toward the inner curved surface 74 of the curved portion 71 includes the intake air 86B flowing while swirling along the inner curved surface 74 of the curved portion 71 and the intake air 86C flowing while swirling along the 2 nd side wall surface 73B extending from the outer side end portion of the intake air outlet portion 71B of the curved portion 71 toward the folded side.

As shown in fig. 6, two swirls 87A and 87B of substantially the same size are generated by the swirling flows of the intake air 83A to 83C, 86A to 86C, and the like, swirling in opposite directions to each other in the intake pipe 11B from the intake air outlet portion 71B of the bent portion 71 to the downstream side with the outlet-side intake pipe axis 72B interposed therebetween. For example, vortex 87A swirls counterclockwise in the downstream direction, and vortex 87B swirls clockwise in the downstream direction.

Further, the throttle valve 47A rotates the inner opposing portion 81A side from the closed position to the downstream side by a predetermined angle θ 1 (for example, about 20 degrees) around the rotation shaft 48 from the closed position orthogonal to the inlet-side intake pipe axis 72A of the intake inlet portion 71A. Therefore, most of the intake air that has collided with the surface on the upstream side of the throttle valve 47A flows toward the inner curved surface 74 of the curved portion 71, and flows downstream along the gap between the side edge portion of the throttle valve 47A on the side of the inner facing portion 81A and the intake pipe 11B.

As a result, the flow velocity of the intake air flowing along the gap between the side edge portion of the throttle valve 47A on the side closer to the inner facing portion 81A and the intake pipe 11B can be made larger than the flow velocity of the intake air flowing along the gap between the side edge portion of the throttle valve 47A on the side closer to the outer facing portion 81B and the intake pipe 11B. Thus, compared to the case where the side edge portion of the throttle valve 47A on the side of the inner facing portion 81A is rotated by a predetermined angle θ 1 (for example, about 20 degrees) from the closed position toward the upstream side (the counterclockwise direction in fig. 5) about the rotation shaft 48, the swirling speeds of the two swirls 87A and 87B generated from the intake outlet portion 71B of the curved portion 71 into the intake pipe 11B on the downstream side can be increased.

Accordingly, the EGR gas flowing into the curved portion 71 from the connection port 77 of the EGR pipe 13 connected to the curved portion 71 is entrained into the intake air that becomes the two swirls 87A and 87B formed in the intake pipe 11B on the downstream side of the intake air outlet portion 71B, is efficiently mixed, and enters the intake manifold 11C. Therefore, since the intake air in which the EGR gas is sufficiently mixed by the two swirls 87A and 87B is supplied to the cylinders 45A to 45D via the intake manifold 11C, it is possible to suppress the variation in the amount of EGR gas between the cylinders 45A to 45D, to make the combustion in the cylinders 45A to 45D constant, and to suppress the variation in combustion noise.

Next, an example of analysis results of the cae (computer Aided engineering) of the "EGR cylinder difference (%)" will be described based on fig. 7, in a case where the position of the extension 78A of the EGR pipe axis 78 at the connection port 77 of the EGR pipe 13 is located at the intersection 72C between the inlet-side intake pipe axis 72A and the outlet-side intake pipe axis 72B in the 1 st plane 75 shown in fig. 3, and in a case where the position of the extension 78A is shifted by about 10mm in the curvature radius direction toward the outer curved surface 73C of the curved portion 71 with respect to the intersection 72C.

The pipe diameter D1 (see fig. 3) of the intake pipe 11B having a circular cross section is set to 62 mm. The inlet-side intake pipe axis 72A and the outlet-side intake pipe axis 72B intersect at right angles on the 1 st plane 75 of the bent portion 71. When the extension 78A is positioned at the intersection 72C between the inlet-side intake pipe axis 72A and the outlet-side intake pipe axis 72B, the radial distance L (see fig. 3) from the extension 78A to the outer curved surface 73C is set to 42 mm.

When the position of the extension 78A is shifted by about 10mm in the curvature radius direction from the intersection 72C between the inlet-side intake pipe axis 72A and the outlet-side intake pipe axis 72B toward the outer curved surface 73C, the distance L (see fig. 3) in the curvature radius direction from the extension 78A to the outer curved surface 73C is set to 30 mm. The pipe diameter of the connection port 77 of the EGR pipe 13 was set to 28 mm. The 1 st radius of curvature R1 (see FIG. 3) of the outer curved surface 73C is 30mm, and the 2 nd radius of curvature R2 (see FIG. 3) of the inner curved surface 74 is 5 mm. The inner facing portion 81A of the throttle valve 47A is rotated 20 degrees toward the downstream side from the closed position about the rotating shaft 48.

Here, the "inter-EGR-cylinder difference (%)" is a percentage of a value obtained by subtracting the "minimum amount" from the "maximum amount" of the amount of EGR gas supplied to each of the cylinders 45A to 45D, divided by the "average value" of the amount of EGR gas supplied to each of the cylinders 45A to 45D. If the "EGR cylinder difference (%)" is equal to or less than the upper limit "M1" (%), it is determined that the combustion in each of the cylinders 45A to 45D is constant, and the combustion noise is suppressed from being inconsistent, so that the driver is not given an unpleasant impression. Further, as the "EGR cylinder difference (%)" becomes higher than the upper limit "M1" (%), it is determined that the combustion noise non-uniformity is more suppressed.

As shown in fig. 7, when the distance L in the curvature radius direction from the extension 78A to the outer curved surface 73C is 42mm, in other words, when the position of the extension 78A is located at the intersection 72C between the inlet-side intake pipe axis 72A and the outlet-side intake pipe axis 72B, "EGR cylinder difference (%)" is "M2" (%) (M2 < M1 × 0.6) which is less than the upper limit "M1" (%). In addition, when the distance L in the curvature radius direction from the extension 78A to the outer curved surface 73C is 30mm, in other words, when the position of the extension 78A is close to about 10mm in the curvature radius direction from the intersection 72C to the outer curved surface 73C side, "EGR cylinder difference (%)" is "M3" (%) (M3 < M1 × 0.1) smaller than "M2" (%).

Therefore, in fig. 3, the position of the extension 78A of the EGR pipe axis 78 at the connection port 77 of the EGR pipe 13 is arranged on the 1 st plane 75 at a position lower in fig. 3 than the intersection 72C between the inlet-side intake pipe axis 72A and the outlet-side intake pipe axis 72B and closer to the outer curved surface 73C than the intersection 72C, so that the EGR gas can be introduced from the lateral direction at a position closer to the outer curved surface 73C than the intake air that flows upstream while colliding with the outer curved surface 73C of the curved portion 71. As a result, the EGR gas can be caused to flow into the intake pipe 11B on the downstream side of the curved portion 71, and two swirling flows 87A and 87B (see fig. 6) swirling in opposite directions can be generated on the front side.

As a result, it is considered that the EGR gas can be made to flow substantially uniformly into the intake air which becomes the two swirls 87A, 87B. Further, the EGR gas is substantially uniformly entrained in the intake air which becomes the two swirls 87A and 87B, and therefore, the EGR gas can be more uniformly mixed with the intake air and supplied to the intake manifold 11C. This makes it possible to keep the combustion in each of the cylinders 45A to 45D constant, and to further suppress the variation in combustion noise.

Next, an example of the analysis result of cae (computer air engineering) of the "EGR cylinder difference (%)" will be described based on fig. 8 in the case where the 1 st curvature radius R1 of the outer curved surface of the curved portion 71 is set to "0.9 times", "0.54 times", and "0.5 times" the pipe diameter D1 of the intake pipe 11B in the 1 st plane 75 shown in fig. 3.

The pipe diameter D1 (see fig. 3) of the intake pipe 11B having a circular cross section is set to 62 mm. The inlet-side intake pipe axis 72A and the outlet-side intake pipe axis 72B intersect at right angles on the 1 st plane 75 of the bent portion 71. The extension 78A is positioned at the intersection 72C between the inlet-side intake pipe axis 72A and the outlet-side intake pipe axis 72B, and the distance L (see fig. 3) in the curvature radius direction from the extension 78A to the outer curved surface 73C is 40 mm.

The pipe diameter at the connection port 77 of the EGR pipe 13 was set to 28 mm. The 1 st radius of curvature R1 (see fig. 3) of the outer curved surface 73C is set to "0.9 times", "0.54 times", and "0.5 times" of the tube diameter D1 of the intake tube 11B, in other words, "55.8 mm", "33.5 mm", and "31 mm". The 2 nd radius of curvature R2 (see fig. 3) of the inner curved surface 74 is set to 5 mm. The inner facing portion 81A of the throttle valve 47A is rotated 20 degrees toward the downstream side from the closed position about the rotating shaft 48.

As shown in fig. 8, when the 1 st curvature radius R1 (see fig. 3) of the outer curved surface 73C is set to "0.9 times" or, in other words, "55.8 mm" of the pipe diameter D1 of the intake pipe 11B, the "EGR cylinder difference (%)" is "M5" (%) (M5 > M1 × 1.3) which is larger than the upper limit "M1" (%). When the 1 st curvature radius R1 (see fig. 3) of the outer curved surface 73C is set to "0.54 times" or in other words "33.5 mm" of the pipe diameter D1 of the intake pipe 11B, the "EGR cylinder difference (%)" is "M6" (%) (M6 < M1 × 0.7) which is smaller than the upper limit "M1" (%). When the 1 st curvature radius R1 (see fig. 3) of the outer curved surface 73C is set to "0.5 times" or in other words "31 mm" of the tube diameter D1 of the intake pipe 11B, the "EGR cylinder difference (%)" is "M7" (%) (M7 < M1 × 0.5) which is smaller than "M6" (%).

From the above, as shown in fig. 8, in order to make the "EGR cylinder difference (%)" to be the upper limit of "M1" (%) or less, it is considered that the 1 st curvature radius R1 (see fig. 3) of the outer curved surface 73C may be set to "0.73 times or less" or, in other words, "45.3 mm or less" of the pipe diameter D1 of the intake pipe 11B. Therefore, the 1 st radius of curvature R1 of the outer curved surface 73C of the curved portion 71 is set to be "0.73 or less" with respect to the pipe diameter D1 of the intake air inlet 71A on the upstream side of the curved portion 71, whereby the amount of intake air 83B (see fig. 5) that flows while swirling to the upstream side while colliding with the outer curved surface 73C can be increased. As a result, it is considered that the two swirls 87A and 87B (see fig. 6) which swirl in opposite directions to each other and are generated in the intake pipe 11B on the downstream side of the curved portion 71 can be made substantially the same size.

Accordingly, the EGR gas flowing from the connection port 77 of the EGR pipe 13 into the curved portion 71 is substantially uniformly entrained into the intake air which becomes the two swirls 87A and 87B (see fig. 6), is efficiently mixed, and flows into the intake manifold 11C. Therefore, intake air in which EGR gas is sufficiently mixed by the two swirls 87A and 87B (see fig. 6) is supplied to the cylinders 45A to 45D via the intake manifold 11C. As a result, it is considered that the variation in the amount of EGR gas between the cylinders 45A to 45D can be suppressed, the combustion in the cylinders 45A to 45D can be made constant, and the variation in the combustion noise can be suppressed.

[ 2 nd embodiment ]

Next, a connection structure 90 between the intake pipe 11B and the outflow side of the EGR pipe 13 according to embodiment 2 will be described with reference to fig. 9 to 12. In the following description, the same reference numerals as those used for the structure of the internal combustion engine 10 according to embodiment 1 denote the same or corresponding parts as those used for the structure of the internal combustion engine 10 according to embodiment 1.

The connection structure 90 between the intake pipe 11B and the outflow side of the EGR pipe 13 according to embodiment 2 is substantially the same as the connection structure 70 between the intake pipe 11B and the outflow side of the EGR pipe 13 according to embodiment 1. As shown in fig. 9 and 10, in the connection structure 90 between the intake pipe 11B and the outflow side of the EGR pipe 13 according to embodiment 2, the connection position of the outflow side of the EGR pipe 13 to the bent portion 71 of the intake pipe 11B is different.

As shown in fig. 9 and 10, an extension 78A of the EGR pipe axis 78 of the connection port 91 of the EGR pipe 13 is disposed on the 1 st plane 75 in parallel with the outlet-side intake pipe axis 72B of the intake outlet portion 71B of the bent portion 71, and is disposed on the opposite side of the intake inlet portion 71A with a 2 nd plane 79 (see fig. 10) including the outlet-side intake pipe axis 72B at the intake outlet portion 71B and orthogonal to the 1 st plane 75 interposed therebetween. Therefore, an extension 78A of the EGR pipe axis 78 is disposed lower in fig. 9 than the outlet-side intake pipe axis 72B passing through the intake outlet portion 71B. The connection port 91 of the EGR pipe 13 is connected to the 1 st side wall surface 73A and the outer curved surface 73C facing the intake air outlet portion 71B of the bent portion 71.

The throttle valve 47A rotates the inner facing portion 81A facing the inside of the curved portion 71 by a predetermined angle θ 1 (for example, about 20 degrees) toward the downstream side about the rotation shaft 48 from the closed position orthogonal to the inlet-side intake pipe axis 72A of the intake inlet portion 71A by the throttle device 47. Therefore, the throttle valve 47A rotates the outer facing portion 81B facing the outside of the curved portion 71 by a predetermined angle θ 1 (for example, about 20 degrees) toward the upstream side from the closed position orthogonal to the inlet-side intake pipe axis 72A of the intake inlet portion 71A around the rotation shaft 48 by the throttle device 47. Therefore, the intake air flows into the downstream side from the gaps between the intake pipe 11B and both side edge portions in the direction perpendicular to the rotation axis 48 of the throttle valve 47A (see fig. 11).

Next, the flow of intake air flowing into the curved portion 71 is explained based on fig. 11 and 12. As shown in fig. 11, the intake air 83A flowing from the gap between the side edge portion on the outer facing portion 81B side of the throttle valve 47A (the left side edge portion in fig. 11) and the intake pipe 11B along the 1 st side wall surface 73A on the upstream side of the curved portion 71 toward the outer curved surface 73C has an intake air 83B flowing while swirling to the upstream side while colliding with the outer curved surface 73C and an intake air 83C flowing from the outer curved surface 73C to the downstream side while swirling along the 2 nd side wall surface 73B on the downstream side of the curved portion 71. The intake air 83B flowing while swirling to the upstream side collides with the throttle valve 47A, and flows along the inner curved surface 74 of the curved portion 71 while swirling to the downstream side again.

On the other hand, the intake air 86A flowing from the gap between the side edge portion on the inner facing portion 81A side of the throttle valve 47A (the right side edge portion in fig. 11) and the intake pipe 11B along the pipe wall 85 toward the inner curved surface 74 of the curved portion 71 includes the intake air 86B flowing while swirling along the inner curved surface 74 of the curved portion 71 and the intake air 86C flowing while swirling along the 2 nd side wall surface 73B extending from the outer end portion of the intake air outlet portion 71B of the curved portion 71 toward the folded side.

As shown in fig. 12, two swirls 87A and 87B of substantially the same size that swirl in opposite directions to each other in the intake pipe 11B with the outlet-side intake pipe axis 72B therebetween are generated from the intake air outlet portion 71B of the bent portion 71 toward the downstream side by the swirling flows of the intake air 83A to 83C, 86A to 86C, and the like. For example, vortex 87A swirls counterclockwise in the downstream direction, and vortex 87B swirls clockwise in the downstream direction.

Further, the throttle valve 47A is rotated by a predetermined angle θ 1 (for example, about 20 degrees) toward the downstream side about the rotation shaft 48 from the closed position orthogonal to the inlet-side intake pipe axis 72A of the intake port 71A. Therefore, most of the intake air that has collided with the surface on the upstream side of the throttle valve 47A flows toward the inner curved surface 74 of the curved portion 71, and flows downstream along the gap between the side edge portion of the throttle valve 47A on the side of the inner facing portion 81A and the intake pipe 11B.

As a result, the flow velocity of the intake air flowing along the gap between the side edge portion of the throttle valve 47A on the side of the inner facing portion 81A and the intake pipe 11B can be made larger than the flow velocity of the intake air flowing along the gap between the side edge portion of the throttle valve 47A on the side of the outer facing portion 81B and the intake pipe 11B. Thus, compared to the case where the throttle valve 47A is rotated by a predetermined angle θ 1 (for example, about 20 degrees) from the closed position to the opposite side (counterclockwise in fig. 11) about the rotation shaft 48 (see (a-1) of fig. 13), the swirling speeds of the two swirls 87A and 87B generated from the intake outlet portion 71B of the curved portion 71 into the intake pipe 11B on the downstream side can be increased.

Accordingly, the EGR gas flowing into the intake outlet portion 71B from the connection port 91 of the EGR pipe 13 connected to the bent portion 71 is entrained into the intake air that becomes the two swirls 87A and 87B formed in the intake pipe 11B on the downstream side of the intake outlet portion 71B, is effectively mixed, and flows into the intake manifold 11C. Therefore, the intake air in which the EGR gas is sufficiently mixed by the two swirls 87A and 87B is supplied to the cylinders 45A to 45D via the intake manifold 11C, so that the amount of EGR gas can be suppressed from being inconsistent among the cylinders 45A to 45D, the combustion in each cylinder can be made constant, and the combustion noise can be suppressed from being inconsistent.

[ example of CAE analysis result of EGR Cylinder to Cylinder Difference ]

Next, an example of the analysis result of the cae (computer air Aided engineering) of the "difference (%) between EGR cylinders" in the connection structure 70 between the intake pipe 11B and the EGR pipe 13 according to embodiment 1 and the connection structure 90 between the intake pipe 11B and the outflow side of the EGR pipe 13 according to embodiment 2 will be described based on fig. 13 and 16.

"a-1" in fig. 16 shows the CAE analysis result of the EGR cylinder difference in the rotational state of the throttle valve 47A of the connection structure 70 shown in (a-1) in fig. 13. "a-2" in fig. 16 shows the CAE analysis result of the EGR cylinder difference in the rotational state of the throttle valve 47A of the connection structure 70 shown in (a-2) in fig. 13. "B-1" in fig. 16 shows the CAE analysis result of the EGR cylinder difference in the rotational state of the throttle valve 47A in the connection structure 90 shown in (B-1) in fig. 13. "B-2" in fig. 16 shows the CAE analysis result of the EGR cylinder difference in the rotational state of the throttle valve 47A in the connection structure 90 shown in (B-2) in fig. 13.

As shown by "a-1" in fig. 16, in the connection structure 70, when the side of the inner opposing portion 81A of the throttle valve 47A is rotated by a predetermined angle θ 1 (for example, about 20 degrees) from the closed position toward the upstream side around the rotation shaft 48, the EGR cylinder difference is "X1" (%). As shown in "a-2" of fig. 16, in the connection structure 70, when the side of the inner opposing portion 81A of the throttle valve 47A is rotated by a predetermined angle θ 1 (for example, about 20 degrees) from the closed position to the downstream side around the rotation shaft 48, the EGR cylinder difference is "X1/6" (%).

As shown in "B-1" of fig. 16, in the connecting structure 90, when the inner opposing portion 81A side of the throttle valve 47A is rotated by a predetermined angle θ 1 (for example, about 20 degrees) from the closed position toward the upstream side around the rotating shaft 48, the EGR cylinder difference is "X2" (%) (X2 > X1). As shown in "B-2" of fig. 16, in the connection structure 90, when the inner opposing portion 81A side of the throttle valve 47A is rotated by a predetermined angle θ 1 (for example, about 20 degrees) from the closed position to the downstream side about the rotation shaft 48, the EGR cylinder difference is "X2/4" (%) (X2/4 > X1/6).

Therefore, in each of the connection structures 70 and 90 between the intake pipe 11B and the outflow side of the EGR pipe 13, it is considered that the "EGR cylinder difference (%)" can be significantly reduced by rotating the inner opposing portion 81A side of the throttle valve 47A by the predetermined angle θ 1 (for example, about 20 degrees) from the closed position toward the downstream side, as compared with the case where the inner opposing portion 81A side of the throttle valve 47A is rotated by the predetermined angle θ 1 (for example, about 20 degrees) from the closed position toward the upstream side.

That is, it is considered that the swirl velocities of the two swirls 87A and 87B generated in the intake pipe 11B on the downstream side from the intake outlet portion 71B of the bent portion 71 are increased by rotating the inner opposing portion 81A side of the throttle valve 47A by the predetermined angle θ 1 (for example, about 20 degrees) from the closed position toward the downstream side about the rotation shaft 48, and the intake air in which the EGR gas is sufficiently mixed is supplied to the cylinders 45A to 45D via the intake manifold 11C. As a result, it is considered that the variation in the amount of EGR gas between the cylinders 45A to 45D can be suppressed, the combustion in the cylinders 45A to 45D can be made constant, and the variation in the combustion noise can be suppressed remarkably.

In the connection structure between the intake pipe 11B and the outflow side of the EGR pipe 13, it is considered that the "EGR cylinder difference (%)" can be reduced in the case of the connection structure 70 in which the extension 78A of the EGR pipe axis 78 is arranged orthogonal to the outlet-side intake pipe axis 72B, compared to the case of the connection structure 90 in which the extension 78A of the EGR pipe axis 78 is arranged parallel to the outlet-side intake pipe axis 72B.

That is, it is considered that, in the connection structure 70 between the intake pipe 11B and the outflow side of the EGR pipe 13, the EGR gas flowing from the connection port 77 of the EGR pipe 13 into the bent portion 71 is more effectively mixed with the intake air that becomes the two swirls 87A and 87B (see fig. 6) than in the case of the connection structure 90, and is supplied to the cylinders 45A to 45D via the intake manifold 11C. As a result, the connecting structure 70 can suppress the variation in the amount of EGR gas between the cylinders 45A to 45D compared to the connecting structure 90, and can suppress the variation in combustion noise by making the combustion in the cylinders 45A to 45D constant.

[ 1 st comparative example ]

Next, an example of analysis results of the "cam (computer Aided engineering) of the" EGR cylinder difference (%) "at the connection structure 100 between the intake pipe 11B and the outflow side of the EGR pipe 13 according to comparative example 1 will be described based on fig. 14 (C-1) and fig. 16. Fig. 14 (C-1) is a diagram showing a connection structure 100 between the intake pipe 11B and the outflow side of the EGR pipe 13 according to comparative example 1. "C-1" in fig. 16 shows the CAE analysis result of the EGR cylinder difference in the rotation state of the throttle valve 47A in the connection structure 100 shown in (C-1) in fig. 14. In the following description, the same reference numerals as those used for the structure of the connection structure 90 according to embodiment 2 denote the same or corresponding portions as those used for the structure of the connection structure 90 according to embodiment 2.

As shown in FIG. 14 (C-1), the connection structure 100 between the intake pipe 11B and the outflow side of the EGR pipe 13 is substantially the same as the connection structure 90 between the intake pipe 11B and the outflow side of the EGR pipe 13 shown in FIG. 13 (B-2). In this case, a bent portion 101 is provided instead of the bent portion 71. The bent portion 101 has substantially the same configuration as the bent portion 71, but is provided with a bottomed cylindrical bulging portion 102 which bulges outward (leftward in fig. 14 (C-1)) in the axial direction of the outlet-side intake pipe axis 72B on the outer side facing the intake outlet portion 71B by a depth L11 (for example, a depth of about 10mm to 20 mm).

Further, the EGR pipe 13 connected to the bulging portion 102 is provided such that an extension 78A of the EGR pipe axis 78 at the connection port 91 of the EGR pipe 13 is coaxial with the outlet-side intake pipe axis 72B passing through the intake air outlet portion 71B. Further, the throttle valve 47A is rotated by a predetermined angle θ 1 (for example, about 20 degrees) toward the downstream side about the rotation shaft 48 from the closed position orthogonal to the inlet-side intake pipe axis 72A by the inner opposing portion 81A facing the inside of the curved portion 101.

In the connection structure 100 thus configured, as shown in "C-1" of fig. 16, the inter-EGR-cylinder difference is "X3" (%) (X3 > X2), and the variation in combustion sound of the cylinders 45A to 45D is a substantially upper limit inter-EGR-cylinder difference that does not give an unpleasant impression to the driver. In other words, the variation in the amount of EGR gas between the cylinders 45A to 45D of the connecting structure 100 shown in FIG. 14 (C-1) is larger than the variation in the amount of EGR gas between the cylinders 45A to 45D of the connecting structure 90 shown in FIG. 13 (B-2).

This is considered to be because, in the connection structure 100, the intake air that flows while swirling upstream while colliding with the bulging portion 102 of the curved portion 101 decreases, the difference in the magnitude of the two swirls 87A and 87B (see fig. 12) that flow while swirling downstream from the intake air outlet portion 71B increases, and the mixture of the EGR gas and the intake air slightly decreases. Therefore, it is considered that in the connection structure 100 in which the bottomed cylindrical bulging portion 102 bulging outward in the intake pipe axial direction by the depth L11 is formed on the outer surface of the curved portion 101 facing the intake air outlet portion 71B, the disagreement of the combustion sound of each of the cylinders 45A to 45D may give an unpleasant impression to the driver.

[ comparative example 2 ]

Next, an example of the analysis result of the cae (computer Aided engineering) of the "EGR cylinder difference (%)" at the connection structure 110 between the intake pipe 11B and the outflow side of the EGR pipe 13 according to the comparative example 2 will be described with reference to (D-1), (D-2) and fig. 15 and 16 of fig. 14. Fig. 14(D-1) and (D-2) are views showing a connection structure 110 between the intake pipe 11B and the outflow side of the EGR pipe 13 according to comparative example 2. FIG. 15 is a view from the direction of XV in (D-1) of FIG. 14.

"D-1" in FIG. 16 shows the CAE analysis result of the EGR cylinder-to-cylinder difference in the rotational state of the throttle valve 47A in the connection structure 110 shown in FIG. 14 (D-1). "D-2" in FIG. 16 shows the CAE analysis result of the EGR-cylinder difference in the rotation state of the throttle valve 47A in the connection structure 110 shown in (D-2) in FIG. 14. In the following description, the same reference numerals as those used for the structure and the like of the connection structure 100 according to comparative example 1 denote the same or corresponding portions as those used for the structure and the like of the connection structure 100 according to comparative example 1.

As shown in FIG. 14(D-1) and FIG. 15, the connection structure 110 between the intake pipe 11B and the outflow side of the EGR pipe 13 is substantially the same as the connection structure 100 between the intake pipe 11B and the outflow side of the EGR pipe 13 shown in FIG. 14 (C-1). However, the present invention differs from the case where the bent portion 111 is provided in place of the bent portion 101, and the intake pipe 113 is provided in place of the intake pipe 11B on the downstream side of the bent portion 101. Specifically, the curved portion 111 and the intake pipe 113 are different in that the cross section is formed in a substantially quadrangular shape circumscribed with a circular tube of a pipe diameter D1 (refer to fig. 9). Therefore, the bent portion 111 is provided with a bottomed quadrangular cylindrical bulging portion 112, which bulges to a depth L11 (for example, a depth of about 10mm to 20mm) outward in the axial direction of the outlet-side intake pipe axis 72B on the outer side facing the intake outlet portion 71B, in place of the bulging portion 102.

Further, the EGR pipe 13 connected to the bulging portion 112 is provided such that an extension 78A of the EGR pipe axis 78 at the connection port 91 of the EGR pipe 13 is coaxial with the outlet-side intake pipe axis 72B passing through the intake air outlet portion 71B. Further, in the throttle valve 47A shown in fig. 14(D-1), the inner facing portion 81A facing the inside of the curved portion 111 is rotated toward the downstream side by a predetermined angle θ 1 (for example, about 20 degrees) around the rotation shaft 48 from the closed position orthogonal to the inlet-side intake pipe axis 72A.

In the connection structure 110 configured as described above, as shown in "D-1" of fig. 16, the inter-EGR-cylinder difference becomes "X4" (%) (X4 > X3 × 1.3), and the variation in the combustion sound of each of the cylinders 45A to 45D is an inter-EGR-cylinder difference giving an unpleasant impression to the driver.

In the connection structure 110 shown in fig. 14 (D-2), the throttle valve 47A is rotated by a predetermined angle θ 1 (for example, about 20 degrees) toward the upstream side about the rotation shaft 48 from the closed position orthogonal to the inlet-side intake pipe axis 72A by the inner opposing portion 81A opposing the inside of the curved portion 111. As a result, in the connection structure 110 configured as described above, as shown in "D-2" of fig. 16, the EGR cylinder difference becomes "X5" (%) (X5 > X4 × 1.3), and the variation in the combustion sound of each of the cylinders 45A to 45D is an EGR cylinder difference that gives a more unpleasant impression to the driver.

Therefore, it is considered that when the cross section of the curved portion 111 and the intake pipe 113 on the downstream side of the curved portion 111 is formed in a substantially quadrangular shape, the mixing between the EGR gas and the intake air is decreased and the variation in combustion noise among the cylinders 45A to 45D becomes large, as compared with the case where the cross section is formed in a circular shape. Further, it is considered that when the inner facing portion 81A side of the throttle valve 47A is rotated by a predetermined angle θ 1 (for example, about 20 degrees) toward the upstream side from the closed position around the rotation shaft 48, the mixture between the EGR gas and the intake air is further decreased, and the variation in the combustion sound of each of the cylinders 45A to 45D is further increased.

It is to be understood that the present invention is not limited to the above-described embodiment 1 and embodiment 2, and various improvements, modifications, additions, and deletions can be made within the scope not departing from the spirit of the invention. For example, the following may be used. In the following description, the same reference numerals as those of the internal combustion engine 10 according to embodiment 1 of fig. 1 to 8 denote the same or corresponding portions as those of the internal combustion engine 10 according to embodiment 1.

(A) For example, as shown in fig. 4, the EGR pipe 13 is connected to the left side wall portion from the outer curved surface 73C of the curved portion 71 toward the downstream side, but the EGR pipe 13 may be connected to the right side wall portion from the outer curved surface 73C of the curved portion 71 toward the downstream side. This enables the EGR gas to flow substantially uniformly into the intake air that becomes the two swirls 87A and 87B (see fig. 6), thereby making the combustion in each of the cylinders 45A to 45D constant and suppressing the combustion noise from being inconsistent.

(B) For example, the outflow side of the EGR pipe 13 may be connected to the side wall portion of the bent portion 71 at an arbitrary position on the opposite side of the intake inlet portion 71A with the 2 nd plane 79 (see fig. 10) therebetween in a section from the position of the connection port 77 shown in fig. 3 to the position of the connection port 91 shown in fig. 9. The outflow side of the EGR pipe 13 may be connected to the side wall portion of the bent portion 71 at an arbitrary position on the opposite side of the intake inlet 71A with the 2 nd plane 79 (see fig. 10) therebetween in a section from the position on the opposite side of the 1 st plane of the connection port 77 shown in fig. 3 of the bent portion 71 to the position of the connection port 91 shown in fig. 9. This enables the EGR gas to flow substantially uniformly into the intake air that becomes the two swirls 87A and 87B (see fig. 6), thereby making the combustion in each of the cylinders 45A to 45D constant and suppressing the combustion noise from being inconsistent.

(C) The numerical values used in the description of embodiment 1 and embodiment 2 are examples, and are not limited to these numerical values. In addition, the above (≧ equal to), below (≦), greater than (>), less than (<), etc. may or may not include an equal sign.