JP2016217249A - Intake device for supercharged engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress moisture which is contained in back-flowed intake air condensing in upstream of a connection part in an EGR passage when an air by-pass valve is opened and the intake air containing an EGR gas flows back in an intake passage.SOLUTION: An intake device for supercharged engine includes condensation suppression means for suppressing moisture which is contained in an EGR gas condensing in an intake passage 10, by increasing the inner wall surface temperature of the intake passage 10. The condensation suppression means is constituted in such a manner that, by supplying heat to a pipe wall from the outside of the intake passage 10, the inner wall surface temperature in a first section from a compressor 52 to a connection part 106 in an EGR passage 62, and the inner wall surface temperature of a second section from the connection part 106 to a boundary position located in upstream of the connection part 106 are higher than the inner wall surface temperature of a third section in upstream of the boundary position. The boundary position is located in upstream of a maximum reach point which the intake air containing the EGR gas flows back in the intake passage 10 to reach when an air by-pass valve 56 is opened.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an intake device for a supercharged engine.

  The supercharged engine is provided with an air bypass passage that bypasses the compressor and an air bypass valve that opens / closes the air bypass passage. During deceleration, the throttle valve is closed, and the boost pressure, which is the pressure upstream of the throttle valve, increases. At this time, by opening the air bypass valve, the air is returned from the upstream to the downstream of the compressor, the supercharging pressure is lowered, and the occurrence of a surge in the compressor can be prevented.

  In a supercharged engine including a low-pressure EGR device, a portion of the exhaust passage downstream of the turbine and a portion of the intake passage upstream of the turbine are connected by an EGR passage. For example, as shown in FIG. 1 of Patent Document 1 below, generally, the connection portion where the EGR passage is connected to the intake passage is an air bypass passage (represented as a recirculation passage in Patent Document 1). It is located upstream of the connecting portion connected to the intake passage.

  When the air bypass valve is opened, intake air including EGR gas flows into the intake passage from the air bypass passage, and flows back through the intake passage upstream. Japanese Patent Application Laid-Open No. 2004-133830 discloses a volume portion for allowing the backflowed intake air to flow upstream from the connection portion of the EGR passage in the intake passage in order to prevent the air flow meter from being polluted by the EGR gas component contained in the intake air flowing back through the intake passage. It is described to provide.

JP 2013-007268 A JP 2009-174444 A International Publication No. 2011/111171 JP 2002-047959 A JP 2004-019589 A

  By the way, EGR gas contains a lot of moisture (water vapor) generated by the combustion of fuel. When the moisture contained in the EGR gas is introduced into the intake passage through the EGR valve, it mixes with fresh air having a relatively low temperature, and touches the inner wall surface of the relatively low temperature intake passage. , May condense into condensed water. Condensation of moisture contained in the EGR gas is likely to occur downstream of the connection portion of the EGR passage through which the EGR gas constantly flows. However, when the air bypass valve is opened along with the deceleration of the supercharged engine, the intake air including the EGR gas flows backward through the intake passage to the upstream side. For this reason, in a steady state, the generation of condensed water can also occur on the upstream side of the connection portion of the EGR passage where no EGR gas flows. If the generated condensed water flows into the compressor together with the intake air, the compressor impeller may be damaged or eroded.

  However, although the above-mentioned patent document 1 discloses the backflow of the intake air containing EGR gas to the upstream side of the intake passage, moisture contained in the backflowed intake air is condensed upstream of the connection portion of the EGR passage. This is not disclosed. Moreover, said patent document 1 is not disclosing at all about the countermeasure with respect to the condensation in the intake passage of the water | moisture content contained in EGR gas.

  A technique for suppressing condensation of moisture contained in the EGR gas in the intake passage is described in, for example, Patent Document 2 described above. Patent Document 2 discloses that an intake heater is disposed upstream of the connection portion of the EGR passage, and fresh air is heated by the intake heater, thereby suppressing generation of condensed water when EGR gas merges with fresh air. doing. However, Patent Document 2 does not disclose an air bypass passage and an air bypass valve. Therefore, Patent Document 2 does not discuss a problem in the case where the intake air including EGR gas flows into the intake passage from the air bypass passage and the intake air including EGR gas flows back through the intake passage.

  Assuming that the supercharged engine described in Patent Document 2 includes an air bypass passage and an air bypass valve, when the air bypass valve opens, intake air that flows backward from the air bypass passage and EGR introduced from the EGR passage Moisture contained in the gas is condensed in the intake passage, and the generated condensed water flows into the compressor. This is because no matter how much the intake air can be heated by the intake heater, the heat given by the intake heater cannot be transferred downstream of the intake passage in the situation where the intake air flows backward from the compressor side in the intake passage. is there. That is, the method of heating the fresh air and raising the temperature of the intake air including the EGR gas is effective only when the fresh air flows downstream, and is effective when the intake air is flowing backward in the intake passage. Absent.

  The present invention has been made in view of the above-described problems, and the moisture contained in the EGR gas is condensed in the intake passage. In particular, the air bypass valve is opened and the intake air containing the EGR gas flows back through the intake passage. An object of the present invention is to provide an intake device for a supercharged engine that can prevent moisture contained in backflowed intake air from condensing upstream of a connection portion of an EGR passage.

  An intake device for a supercharged engine according to the present invention includes an intake passage, a compressor disposed in the intake passage, an air bypass passage that bypasses the compressor, and an EGR passage that introduces EGR gas into the intake passage. An air bypass valve is disposed in the air bypass passage. The air bypass valve is opened at the time of deceleration, for example, more preferably, when a surge is predicted from the relationship between the flow rate of intake air passing through the compressor and the pressure ratio of the compressor. The EGR passage is an EGR passage of a so-called low pressure EGR device, and the connection portion where the EGR passage is connected to the intake passage is located upstream of the connection portion where the air bypass passage is connected to the intake passage.

  An intake device for a supercharged engine according to the present invention includes condensation suppression means for suppressing moisture contained in EGR gas from condensing in an intake passage. The condensation suppression means is configured to suppress moisture condensation by increasing the inner wall surface temperature of the intake passage. Here, the section from the compressor to the connection part of the EGR passage is the first section of the intake passage (the connection part of the EGR passage is included in the first section), and the connection part of the EGR passage is upstream of the connection part of the EGR passage. Is defined as a second section of the intake passage, and a section upstream of the boundary position is defined as a third section of the intake passage. According to such a definition, in more detail, the condensation suppression means supplies heat from the outside of the intake passage to the pipe wall of the intake passage, so that the inner wall surface temperature of the first section and the inner section of the second section are increased. The wall surface temperature is configured to be higher than the inner wall surface temperature of the third section.

  The first section is a section in which EGR gas introduced from the EGR passage to the intake passage steadily flows in the steady state of the supercharged engine. The second section is a section in which EGR gas does not normally flow, but when the air bypass valve is opened, intake air containing EGR gas is likely to flow backward beyond the first section. is there. According to the present invention, the inner wall surface temperature in these sections is increased by the heat supplied to the pipe wall from the outside of the intake passage, so that the moisture contained in the backflowing intake air (intake air including EGR gas) is increased. Condensation on the wall is suppressed. According to the heat supply to the pipe wall from the outside of the intake passage, the inner wall surface is reliably ensured even in a situation where the intake air flows backward, compared to a method in which fresh air is heated by the intake heater and the inner wall surface is heated from the inside of the intake passage. The temperature can be kept high.

  Whether the intake air including EGR gas reaches the third section beyond the second section depends on the setting of the boundary position between the second section and the third section. In the present invention, the boundary position between the second section and the third section is set upstream of the maximum reaching point where the intake air including the EGR gas flows back through the intake passage when the air bypass valve is opened. ing. Therefore, since the intake air containing EGR gas does not flow back to the third section basically, the inner wall surface temperature of the third section is equal to the inner wall surface temperature of the first section or the second section. It may be relatively low as compared. By doing so, the amount of heat applied to the tube wall from the outside of the intake passage can be suppressed. Note that the maximum reaching point where the intake air containing EGR gas flows back through the intake passage when the air bypass valve is opened can be predicted in advance from the specifications of the supercharged engine, or confirmed experimentally. You can also. Preferably, a boundary position between the second section and the third section is set at the maximum reaching point. According to this, the inner wall surface temperature in the section where the intake air flows back can be kept high without wasting the amount of heat given to the tube wall from the outside of the intake passage.

  As a more detailed configuration of the condensation suppression means, the section including at least the first section is a high temperature section where the inner wall temperature is substantially uniformly high, and the inner wall temperature from the upstream end of the high temperature section to the boundary position is directed upstream. You may make it fall gradually. In the steady state of the supercharged engine, EGR gas flows through the first section and does not flow upstream from the first section. At this time, the dew point temperature of the intake air including the EGR gas is determined by the EGR rate, and the dew point temperature becomes the highest at the design maximum EGR rate. On the other hand, since the EGR rate during high load operation where the air bypass valve opens during deceleration is generally lower than the maximum EGR rate, the dew point temperature of the intake air flowing backward from the air bypass passage is generally Specifically, it is lower than the dew point temperature at the maximum EGR rate. Further, as the backflowed intake air proceeds upstream of the intake passage, dilution with fresh air proceeds and the dew point temperature of the intake air gradually decreases. Therefore, in order to prevent dew condensation on the inner wall surface, at least the first section needs to have a high inner wall surface temperature corresponding to the maximum EGR rate, but in the upstream, it is far from the first section to the upstream side. The inner wall surface temperature may be gradually lowered as the time goes on. If the inner wall surface temperature can be lowered, the amount of heat applied to the tube wall from the outside of the intake passage can be reduced accordingly. Therefore, according to said structure, it can suppress that the water | moisture content contained in the backflowed intake air | moisture condenses on the inner wall surface upstream from the connection part of an EGR channel | path by supply of less heat quantity.

  As another example of a more detailed configuration of the condensation suppression means, all the sections from the first section to the second section may be high-temperature sections in which the inner wall surface temperature is substantially uniform. This is because the EGR rate when the air bypass valve opens may be the maximum design EGR rate. By setting the inner wall surface temperature in all the sections from the first section to the second section to be substantially uniformly high corresponding to the maximum EGR rate, the inner wall surface upstream of the connection portion of the EGR passage Condensation can be suppressed more reliably.

  Condensation suppression means includes a tube wall of the first section and the second section formed of metal, a tube wall of the third section formed of a material having a lower thermal conductivity than the metal, and a tube of the high temperature section. And a heating device that heats the wall. The tube walls of the first section and the second section are formed of a metal having a high thermal conductivity, and the tube wall of the third section is formed of a material having a lower thermal conductivity than that of the metal. The heated heat can be efficiently used to increase the inner wall surface temperature in the first section and the second section. The high temperature section may be a partial section including at least the first section of the first section and the second section, or may be the entire section from the first section to the second section.

  The condensation suppression means may further include a heat insulating material that keeps the tube walls of the first section and the second section from the outside. By suppressing heat dissipation to the outside of the intake passage by the heat insulating material, the inner wall surfaces of the first section and the second section can be warmed more efficiently.

  The heating device may be configured to heat the pipe wall in the high temperature section with engine cooling water heated by the supercharged engine. According to this, the waste heat of the engine can be effectively utilized. In this case, at least the pipe wall in the high temperature section may be constituted by a double pipe, and the engine coolant may be passed through the double pipe.

  Further, the heating device may be configured to heat the tube wall in the high temperature section with an electric heater. According to this, it is easy to adjust the inner wall surface temperature to an appropriate temperature.

  As described above, according to the present invention, when the air bypass valve is opened and the intake air containing EGR gas flows back through the intake passage, the moisture contained in the back-flowed intake air is condensed upstream of the connection portion of the EGR passage. Can be suppressed.

It is a figure which shows typically the structure of the supercharged engine of each embodiment of this invention. It is a figure which shows typically the structure of the intake device of Embodiment 1 of this invention. It is a figure which shows the temperature distribution of the inner wall face of an intake passage in the direction of the flow of an intake passage by Embodiment 1 of this invention. It is a figure which shows typically the flow of the gas in an intake passage at the time of steady operation. It is a figure which shows typically the flow of the gas in an intake passage at the time of valve opening of an air bypass valve. It is a figure which shows typically the structure of the intake device of Embodiment 2 of this invention. It is a figure which shows the temperature distribution of the inner wall face of the intake passage in the direction of the flow of the intake passage by Embodiment 2 of this invention. It is a figure which shows typically the structure of the intake device of Embodiment 3 of this invention. It is a figure which shows the temperature distribution of the inner wall face of the intake passage in the direction of the flow of the intake passage by Embodiment 3 of this invention. It is a figure which shows typically the structure of the intake device of Embodiment 4 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. However, in the embodiment shown below, when referring to the number of each element, quantity, quantity, range, etc., unless otherwise specified or clearly specified in principle, the reference However, the present invention is not limited to this number. The structures and the like described in the following embodiments are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

[Configuration of turbocharged engine]
First, a configuration of a supercharged engine common to the embodiments of the present invention will be described with reference to FIG. The supercharged engine 2 according to the embodiment includes an engine body 4 configured as a spark ignition type 4-stroke reciprocating engine.

  An intake manifold 12 connected to the intake port of each cylinder is connected to the engine body 4. The intake manifold 12 is connected to a surge tank 14 integrated with a water-cooled intercooler 16. An intake passage 10 is connected to the intercooler 16.

  An air cleaner 20 is attached to the inlet of the intake passage 10. An air flow meter 22 that outputs a signal corresponding to the flow rate of fresh air sucked into the intake passage 10 is attached to the intake passage 10 downstream of the air cleaner 20. A throttle valve 24 for adjusting the intake air amount is disposed downstream of the air flow meter 22 in the intake passage 10.

  A compressor 52 of the turbocharger 50 is arranged between the air flow meter 22 and the throttle valve 24 in the intake passage 10. In the intake passage 10, an air bypass passage 54 that bypasses the compressor 52 is provided. An air bypass valve 56 that controls blocking / communication of the air bypass passage 54 is disposed in the air bypass passage 54.

  The air bypass valve 56 is controlled by the control device 200. The control device 200 predicts a surge of the compressor 52 based on the pressure ratio of the supercharging pressure (downstream pressure) to the upstream pressure of the compressor 52 and the flow rate of the compressor 52. When the occurrence of a surge is predicted, the control device opens the air bypass valve 56 and reduces the supercharging pressure by returning the intake air from the downstream of the compressor 52 to the upstream via the air bypass passage 54.

  An exhaust manifold 32 connected to the exhaust port of each cylinder is connected to the engine body 4. A turbine 58 of the turbocharger 50 is arranged in the exhaust manifold 32. A three-way catalyst 40 is disposed at the outlet of the turbine 58, and the exhaust passage 30 is connected to the three-way catalyst 40. A silencer 42 is disposed in the exhaust passage 30.

  The supercharged engine 2 includes a low pressure EGR device 60 that recirculates part of the exhaust gas from the exhaust passage 30 to the intake passage 10. The low pressure EGR device 60 includes an EGR passage 62 that branches from the exhaust passage 30 downstream of the three-way catalyst 40 and connects to the intake passage 10 upstream of the compressor 52. In the EGR passage 62, an EGR cooler 64 is disposed on the upstream side of the flow of EGR gas, and an EGR valve 66 is disposed on the downstream side. The connection portion where the EGR passage 62 connects to the intake passage 10 is located upstream of the intake passage 10 than the connection portion where the air bypass passage 54 connects to the intake passage 10.

  The EGR valve 66 is controlled by the control device 200. The control device 200 determines a target EGR rate with reference to a map in which the EGR rate is associated with the engine rotation speed and the engine load, and controls the opening degree of the EGR valve 66 according to the target EGR rate. Note that, among the gas passages shown in FIG. 1, a passage indicated by a solid line is a passage through which EGR gas flows in the steady state of the supercharged engine 2.

[Intake Device of Embodiment 1]
The intake device of Embodiment 1 of the present invention is applied to the supercharged engine 2 having the above configuration. The intake device is a device that supplies intake air to the engine body 4. In the configuration shown in FIG. 1, at least the intake passage 10, the compressor 52, the air bypass passage 54, and the EGR passage 62 are included in the components of the intake device.

  FIG. 2 is a diagram schematically showing the configuration of the intake device 6A according to Embodiment 1 of the present invention. As shown in FIG. 2, the section upstream of the compressor 52 in the intake passage 10 is divided into three sections.

  The first section is a section from the inlet of the compressor 52 to the connection portion of the EGR passage 62. An outlet 106 of the EGR passage 62 is formed at the connection portion of the EGR passage 62. The outlet 106 of the EGR passage 62 is a junction where fresh air and EGR gas merge. The outlet 106 of the EGR passage 62 is included in the first section. In the first section, the outlet 104 of the air bypass passage 54 (see FIG. 1) is formed downstream of the outlet 106 of the EGR passage 62.

  The second section is a section from the connection portion of the EGR passage 62 to the maximum backflow reaching point. The maximum reverse flow reaching point is the most upstream point where the intake air including the EGR gas reaches the upstream side through the intake passage 10 when the air bypass valve 56 (see FIG. 1) is opened. The maximum reverse flow point can be predicted in advance from the conditions for opening the air bypass valve 56 and the hardware specifications of the supercharged engine 2. For example, Patent Document 1 described above describes a method of calculating the volume of gas flowing into the intake passage 10 from the air bypass passage outlet 104 when the air bypass valve 56 is opened. Further, the maximum backflow point can be experimentally confirmed using the actual engine of the supercharged engine 2.

  The third section is a section upstream from the maximum backflow reaching point that is the boundary position. The air flow meter 22 (see FIG. 1) is included in the third section.

  The intake device 6A is characterized by the structure of the intake passage 10. The first section of the intake passage 10 is composed of a metal double pipe 100 having a high thermal conductivity. Inside the double pipe 100 is a cooling water flow path 102 through which engine cooling water flows.

  The second section of the intake passage 10 includes a metal pipe (single pipe) 110 having a high thermal conductivity. A heat insulating material 120 for keeping the inside warm is wound around the outer periphery of the first section and the second section of the intake passage 10.

  The third section of the intake passage 10 is composed of a rubber or resin pipe (single pipe) 130 having a lower thermal conductivity than metal, that is, a heat insulating property.

  The EGR passage 62 connected to the intake passage 10 includes a metal double pipe 140 at least in the section from the EGR valve 66 to the connecting portion. Inside the double pipe 140 is a cooling water flow path 142 through which engine cooling water flows. The heat insulating material 120 is also wound around the outer periphery of the EGR passage 62.

  The cooling water flow path 102 in the first section of the intake passage 10 and the cooling water flow path 142 of the EGR passage 62 are connected to the engine body 4 via a cooling water introduction pipe 82 and a cooling water discharge pipe 84. These pipes 82 and 84 are part of an engine cooling system 80 that cools the engine body 4. By opening the valve 86 provided in the cooling water introduction pipe 82, the high-temperature engine cooling water that has passed through the engine body 4 flows into the cooling water flow paths 102 and 142. In the intake device 6 </ b> A, the cooling water passage 102 functions as a heating device that heats the pipe wall of the intake passage 10. By being heated from the outside of the pipe wall by the high-temperature engine cooling water, the inner wall surface temperature of the first section of the intake passage 10 and the inner wall surface temperature of the EGR passage 62 are kept high.

  FIG. 3 is a diagram showing the temperature distribution of the inner wall surface of the intake passage 10 in the direction of the flow of the intake passage 10, which is realized by the configuration of the intake device 6A. By heating the pipe wall of the double pipe 100 with the engine cooling water, the inner wall surface temperature in the section (first section) from the compressor inlet to the confluence of fresh air and EGR gas is almost uniformly high. Retained. A section where the inner wall surface temperature is almost uniformly high is called a high temperature section. Since the section (second section) from the confluence of fresh air and EGR gas to the maximum point of backflow is heated by heat conduction from the double pipe 100 to the pipe 110, the inner wall surface temperature in that section is the upstream side. It gradually decreases toward In the section upstream of the maximum reverse flow reaching point (third section), the pipe wall is formed of a highly heat-insulating material, so there is almost no heat transfer from the pipe 110. For this reason, the inner wall surface temperature greatly decreases on the upstream side with the maximum backflow point as a boundary.

  The inner wall surface temperature of the first section, which is a high temperature section, is set to a temperature higher than the dew point temperature T1 at the design maximum EGR rate. In the steady state of the supercharged engine 2, the EGR gas flows in the first section. At this time, the dew point temperature of the intake air including the EGR gas is determined by the EGR rate, and the dew point temperature becomes the highest at the design maximum EGR rate. Therefore, if the inner wall surface temperature is set higher than the dew point temperature T1 at the maximum EGR rate, condensation on the inner wall surface of the first section can be prevented. The dew point temperature T1 of the intake air at the maximum EGR rate can be obtained by calculation from the operating conditions at the maximum EGR rate. For example, assuming that the maximum EGR rate is 25%, the dew point temperature is about 37 ° C. depending on the conditions. The inner wall surface temperature can be controlled by adjusting the temperature of the engine coolant supplied to the coolant channel 102.

  The inner wall surface temperature in the second section is lowest at the maximum backflow point. The thickness of the tube 110 and the thickness of the heat insulating material 120 in the second section are designed such that the inner wall surface temperature at the maximum point of backflow reaches a temperature higher than the backflow dew point temperature T2. The backflow dew point temperature T2 is a dew point temperature determined from an EGR rate (for example, about 15%) when the air bypass valve 56 is opened. Since the EGR rate at the time of high load operation where the air bypass valve 56 is opened is set lower than the maximum EGR rate, the backflow dew point temperature T2 is lower than the dew point temperature T1 at the maximum EGR rate. Note that, as the backflowed intake air proceeds upstream of the intake passage 10, dilution with fresh air proceeds and the dew point temperature of the intake air gradually decreases. Therefore, the actual dew point temperature at the maximum backflow point is calculated from the EGR rate. It is thought that it is lower than the dew point temperature T2 during backflow.

  The configuration of the intake device 6A described above functions as a condensation suppression unit that suppresses the condensation of moisture contained in the EGR gas in the intake passage 10 by increasing the inner wall surface temperature of the intake passage 10.

  FIG. 4 is a diagram schematically showing the flow of gas in the intake passage 10 during steady operation. In the steady state, the intake air including the EGR gas flows downstream in the first section. Although the EGR rate of the intake air flowing through the first section varies depending on the operating state of the supercharged engine 2, the inner wall temperature is increased almost uniformly in the first section assuming the maximum EGR rate. Even when the rate fluctuates, condensation on the inner wall surface can be suppressed.

  FIG. 5 is a diagram schematically illustrating the flow of gas in the intake passage 10 when the air bypass valve 56 is opened. When the air bypass valve 56 is opened, the intake air (intake including EGR gas) that flows into the intake passage 10 from the air bypass passage outlet 104 uses the intake air (intake including EGR gas) accumulated in the first section as the intake passage. 10 is pushed up to the upstream side. The backflowing intake air rises in the second section of the intake passage 10 while pushing back the fresh air in the intake passage 10, and reaches the maximum reverse flow reaching point when it travels the most. The inner wall surface temperature in the second section decreases as it goes upstream, but is at a temperature higher than the backflow dew point temperature T2 even at the lowest backflow maximum reaching point. Therefore, it is possible to suppress the intake air that flows backward in the second section from condensing on the inner wall surface.

  As described above, according to the intake device 6A of the present embodiment, when the air bypass valve 56 is opened and the intake air containing EGR gas flows back through the intake passage 10, the moisture contained in the back-flowed intake air flows into the EGR passage. Condensation upstream of the connecting portion 62 can be suppressed.

[Intake Device of Embodiment 2]
FIG. 6 is a diagram schematically showing the configuration of an intake device 6B according to Embodiment 2 of the present invention. In FIG. 6, elements common to the intake device 6A of the first embodiment shown in FIG.

  In the intake device 6B of the present embodiment, not only the first section, but also a part of the second section that is continuous with the first section is configured by the double pipe 100. The double pipe 100 is formed with a cooling water flow path 102 through which engine cooling water flows close to the upstream end thereof. A metal pipe 110 is used in a section from the upstream end of the double pipe 100 to the maximum backflow point. A heat insulating material 120 for keeping the inside warm is wound around the outer periphery of the double pipe 100 and the pipe 110.

  FIG. 7 is a diagram showing the temperature distribution on the inner wall surface of the intake passage 10 in the direction of the flow of the intake passage 10, which is realized by the configuration of the intake device 6B. The double pipe 100 through which the engine cooling water flows is extended to the upstream side of the outlet 106 of the EGR passage 62, so that the middle part of the second section is a high temperature section in addition to the first section. Since the remaining part of the second section is heated by heat conduction from the double pipe 100 to the pipe 110, the inner wall surface temperature of the section gradually decreases toward the upstream side. However, since the pipe 110 is short, the temperature decrease is small, and the inner wall surface temperature at the maximum point of backflow is sufficiently higher than the backflow dew point temperature T2.

[Intake Device of Embodiment 3]
FIG. 8 is a diagram schematically showing the configuration of an intake device 6C according to Embodiment 3 of the present invention. In FIG. 8, elements common to the intake device 6A of the first embodiment shown in FIG.

  In the intake device 6 </ b> C of the present embodiment, the entire section from the first section to the second section of the intake passage 10 is configured by the double pipe 100. The double pipe 100 is formed with a cooling water flow path 102 through which engine cooling water flows close to the upstream end thereof. A heat insulating material 120 for keeping the inside warm is wound around the outer periphery of the double tube 100.

  FIG. 9 is a diagram illustrating a temperature distribution on the inner wall surface of the intake passage 10 in the direction of the flow of the intake passage 10, which is realized by the configuration of the intake device 6 </ b> C. By setting the entire section from the first section to the second section as the double pipe 100 through which the engine coolant flows, the entire section from the first section to the second section is a high temperature section. In this way, the inner wall surface temperature of all the sections from the first section to the second section is set to be substantially higher than the dew point temperature T1 at the maximum EGR rate, thereby connecting the EGR passage 62. Condensation on the inner wall surface upstream of the portion can be more reliably suppressed.

[Intake Device of Embodiment 4]
FIG. 10 is a diagram schematically showing a configuration of an intake device 6D according to the fourth embodiment of the present invention. In FIG. 10, elements common to the intake device 6 </ b> A of the first embodiment shown in FIG.

  In the intake device 6D of the present embodiment, the entire section from the first section to the second section of the intake passage 10 is configured by a single metal pipe 150. An electric heater 152 as a heating device is wound around the outer periphery of the portion corresponding to the first section of the single tube 150. A heat insulating material 170 for keeping the inside warm is wound around the outer periphery of the first section and the second section of the intake passage 10. The third section of the intake passage 10 is composed of a rubber or resin tube 130 with high heat insulation.

  The EGR passage 62 connected to the intake passage 10 is composed of a single metal pipe 160 at least in the section from the EGR valve 66 to the connecting portion. An electric heater 162 is wound around the outer periphery of the portion corresponding to the first section of the single tube 160. The heat insulating material 170 is also wound around the outer periphery of the EGR passage 62.

  The electric heater 152 in the intake passage 10 and the electric heater 162 in the EGR passage 62 are connected to the power supply device 90. By supplying electric power from the power supply device 90 to the electric heaters 152 and 162 and heating the tube wall by the electric heaters 152 and 162, the inner wall surface temperature of the first section of the intake passage 10 and the inner wall surface temperature of the EGR passage 62 Is held high.

  Note that the use of an electric heater instead of engine cooling water can also be applied to the intake devices of the second and third embodiments.

2 Supercharged engine 4 Engine body 10 Intake passage 22 Air flow meter 52 Compressor 54 Air bypass passage 56 Air bypass valve 62 EGR passage 66 EGR valve 100 Metal double pipe 102 Cooling water passage 104 Air bypass passage outlet 106 EGR passage outlet 110 Metal pipe 120 Heat insulation material 130 Resin or rubber pipe 150 Metal pipe 152 Electric heater

Claims (7)

An intake passage,
A compressor disposed in the intake passage;
An air bypass passage around which the air bypass valve is disposed to bypass the compressor;
An EGR passage for introducing EGR gas into the intake passage,
In the intake device for a supercharged engine, the connection portion where the EGR passage is connected to the intake passage is located upstream of the connection portion where the air bypass passage is connected to the intake passage.
Condensation suppression means that suppresses the moisture contained in the EGR gas from condensing in the intake passage by increasing the inner wall surface temperature of the intake passage,
The condensation suppression means supplies heat to the pipe wall of the intake passage from the outside of the intake passage, thereby causing the inner wall surface temperature of the first section of the intake passage from the compressor to the connection portion of the EGR passage. And the inner wall surface temperature of the second section of the intake passage from the connection portion of the EGR passage to the boundary position set upstream of the connection portion of the EGR passage, and the intake passage upstream of the boundary position. Configured to be higher than the inner wall surface temperature of the third section of
The supercharged engine intake air is characterized in that the boundary position is set upstream of a maximum reaching point where intake air including EGR gas flows back through the intake passage when the air bypass valve is opened. apparatus.   The condensation suppression means sets a section including at least the first section as a high temperature section in which the inner wall temperature is substantially uniformly high, and directs the inner wall temperature from the upstream end of the high temperature section to the boundary position toward the upstream side. The supercharged engine intake device according to claim 1, wherein the intake device is configured to be gradually lowered.   The said condensation suppression means is comprised so that the whole area from the said 1st area to the said 2nd area may be made into the high temperature area where an inner wall surface temperature is high uniformly. The intake system for the supercharged engine described. The condensation suppression means is
A tube wall of the first section and the second section formed of metal;
The tube wall of the third section formed of a material having a lower thermal conductivity than metal;
The supercharged engine intake device according to claim 2, further comprising: a heating device that heats a pipe wall in the high-temperature section.   5. The supercharged engine according to claim 4, wherein the condensation suppression unit further includes a heat insulating material that keeps the tube walls of the first section and the second section from the outside. Intake device.   The supercharged engine intake air according to claim 4 or 5, wherein the heating device is configured to heat a pipe wall of the high temperature section with engine cooling water heated by the supercharged engine. apparatus.   The supercharging engine intake device according to claim 4 or 5, wherein the heating device is configured to heat a tube wall of the high temperature section by an electric heater.

Images