JP4730366B2 - Exhaust gas recirculation device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

A cyclone type collection device is provided in the EGR passage for collecting a part of the exhaust gas from the exhaust passage of the internal combustion engine as EGR gas and recirculating the EGR gas to the intake passage of the internal combustion engine. A technique is disclosed (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 2002-130058 JP 2000-170608 A JP 2005-155559 A JP 07-158420 A

  When the EGR gas flow rate is increased and the EGR gas flow rate is increased, the cyclone type collection device provided in the EGR passage can also collect foreign matters having a smaller particle diameter. However, when the EGR gas flow rate increases, the pressure loss when the EGR gas passes through the cyclone-type collecting device increases. When this pressure loss increases, a desired amount of EGR gas is not supplied to the internal combustion engine, and the EGR gas becomes insufficient, leading to deterioration of exhaust emission. As described above, when the pressure loss in the cyclone type collecting device is large, various adverse effects may occur.

  This invention is made | formed in view of the said situation, The place made into the objective is providing the technique which reduces the pressure loss in a cyclone type collection device in the exhaust gas recirculation apparatus of an internal combustion engine.

In the present invention, the following configuration is adopted. That is, the present invention
A turbocharger having a turbine disposed in an exhaust passage of an internal combustion engine and a compressor disposed in an intake passage of the internal combustion engine;
A low pressure EGR passage that takes in a part of exhaust gas as low pressure EGR gas from the exhaust passage downstream from the turbine and recirculates the low pressure EGR gas to the intake passage upstream from the compressor;
A cyclonic collector that is disposed in the low pressure EGR passage and collects foreign matter in the low pressure EGR gas;
A flow rate adjusting path for allowing the low pressure EGR gas to flow out from the foreign matter collecting portion of the cyclone type collecting device to the exhaust passage downstream of the connection portion with the low pressure EGR passage;
A flow rate adjusting valve that is disposed in the flow rate adjusting path and adjusts the flow rate of the low pressure EGR gas flowing through the flow rate adjusting path;
First control means for controlling the opening and closing of the flow rate adjusting valve according to a pressure loss when the low pressure EGR gas flowing through the low pressure EGR passage passes through the cyclone type collection device;
An exhaust gas recirculation device for an internal combustion engine.

The cyclone-type collection device provided in the low-pressure EGR passage can also collect foreign substances having a smaller particle diameter when the low-pressure EGR gas flow rate increases and the low-pressure EGR gas flow rate increases. However, when the low-pressure EGR gas flow rate increases, the pressure loss when the low-pressure EGR gas passes through the cyclone-type collection device increases. When this pressure loss increases, a desired amount of the low-pressure EGR gas is not supplied to the internal combustion engine, and the low-pressure EGR gas becomes insufficient, leading to deterioration of exhaust emission.

  According to the present invention, the flow regulating valve is controlled to open and close according to the pressure loss when the low-pressure EGR gas passes through the cyclone type collection device. Therefore, when the pressure loss increases, that is, when the low-pressure EGR gas flow rate increases, the flow rate adjustment valve can be opened. As a result, the low pressure EGR gas is caused to flow from the cyclone type collector to the flow rate adjusting path, and the low pressure EGR gas remaining in the cyclone type collector is reduced. Then, the pressure loss when the low-pressure EGR gas passes through the cyclone type collector is reduced, so that a desired amount of the low-pressure EGR gas can be supplied to the internal combustion engine, and the exhaust emission is deteriorated due to the shortage of the low-pressure EGR gas. Can be suppressed.

  Moreover, when low-pressure EGR gas is caused to flow from the cyclone-type collector to the flow rate adjustment path as in the present invention, the flow rate of the low-pressure EGR gas passing through the cyclone-type collector becomes slow, and the cyclone-type collector has a small particle diameter. Foreign matter cannot be collected. However, even in this case, it is only necessary that the cyclone-type collecting device can collect foreign matters having a particle size larger than the particle size that affects the intake system of the internal combustion engine. In this way, if a foreign substance having a particle diameter larger than the particle diameter that affects the intake system of the internal combustion engine can be collected by the cyclone type collection device, the intake system of the internal combustion engine is affected by the inclusion of the foreign substance. Absent.

  The first control means is configured such that the pressure at which the low-pressure EGR gas passes through the cyclone-type collecting device is less than the flow rate of the low-pressure EGR gas flowing through the low-pressure EGR passage is collected by the cyclone-type collecting device. When the flow rate is less than the first predetermined flow rate, which is a threshold for giving priority to loss reduction, the flow rate adjustment valve is closed, and the flow rate of the low pressure EGR gas flowing through the low pressure EGR passage is equal to or higher than the first predetermined flow rate. The flow rate adjusting valve may be opened at an opening in a range in which the cyclone type collecting device can collect foreign matters having a particle size larger than the particle size that affects the intake system of the internal combustion engine.

  Here, if the first predetermined flow rate is a flow rate higher than that, the pressure loss when the low-pressure EGR gas passes through the cyclone-type collection device can be reduced rather than collecting the foreign matter by the cyclone-type collection device. This is a low-pressure EGR gas flow rate that is a priority threshold.

  According to the present invention, when the low-pressure EGR gas flow rate is higher than the first predetermined flow rate, the flow rate adjustment valve is opened, and the pressure loss when the low-pressure EGR gas passes through the cyclone type collection device can be reduced. Further, when opening the flow rate adjusting valve, the cyclone type collecting device can collect foreign matters having a particle diameter larger than the particle diameter that affects the intake system of the internal combustion engine.

In the present invention, the following configuration is adopted. That is, the present invention
A turbocharger having a turbine disposed in an exhaust passage of an internal combustion engine and a compressor disposed in an intake passage of the internal combustion engine;
A catalyst that is disposed in the exhaust passage downstream of the turbine and that is hot when activated;
A cyclone-type collecting device that is disposed in the exhaust passage immediately downstream of the catalyst and collects foreign matter in the exhaust;
A low-pressure EGR passage that takes a part of the exhaust gas as low-pressure EGR gas from the exhaust passage downstream from the cyclonic collector, and recirculates the low-pressure EGR gas to the intake passage upstream from the compressor;
A flow rate adjusting path for exhausting the exhaust gas from the foreign matter collecting portion of the cyclone type collecting device to the exhaust passage downstream of the connection portion with the low pressure EGR passage;
A flow rate adjusting valve that is disposed in the flow rate adjusting path and adjusts an exhaust flow rate flowing through the flow rate adjusting path;
A second control means for controlling the opening and closing of the flow rate adjusting valve according to a pressure loss when the exhaust gas flowing through the exhaust passage passes through the cyclone type collecting device;
An exhaust gas recirculation device for an internal combustion engine.

  The cyclone-type collection device provided in the exhaust passage can also collect foreign matters having a smaller particle diameter when the exhaust flow rate increases and the exhaust flow velocity increases. However, when the exhaust gas flow rate increases, the pressure loss when the exhaust gas passes through the cyclone type collecting device increases. When this pressure loss increases, the output of the internal combustion engine is reduced and the fuel consumption is deteriorated.

  According to the present invention, the opening degree of the flow rate adjustment valve is controlled according to the pressure loss when the exhaust gas passes through the cyclone type collecting device. Therefore, when the pressure loss increases, that is, when the exhaust flow rate increases, the flow rate adjustment valve can be opened. As a result, the exhaust gas is allowed to flow from the cyclone type collecting device to the flow rate adjusting path, and the exhaust gas remaining in the cyclone type collecting device is reduced. As a result, the pressure loss when the exhaust gas passes through the cyclone-type collection device is reduced, so that it is possible to suppress a decrease in the output of the internal combustion engine and a deterioration in fuel consumption.

  In addition, when exhaust gas flows from the cyclone type collector to the flow rate adjustment path as in the present invention, the flow velocity of exhaust gas passing through the cyclone type collector becomes slow, and the cyclone type collector collects foreign substances having a small particle diameter. Can not do it. However, even in this case, it is only necessary that the cyclone-type collecting device can collect foreign matters having a particle size larger than the particle size that affects the intake system of the internal combustion engine. In this way, if a foreign substance having a particle diameter larger than the particle diameter that affects the intake system of the internal combustion engine can be collected by the cyclone type collection device, the intake system of the internal combustion engine is affected by the inclusion of the foreign substance. Absent.

  Furthermore, when a cyclone type collector is arranged immediately downstream of the catalyst as in the present invention, the exhaust takes heat away from the catalyst that is at a high temperature when activated, and the exhaust is warmed in a state where the exhaust is warmed. Flows into the collector. For this reason, since exhaust_gas | exhaustion is high temperature in a cyclone-type collection apparatus, the saturated vapor | steam amount of exhaust_gas | exhaustion does not reduce, and it can suppress generating condensed water from exhaust_gas | exhaustion in a cyclone-type collection apparatus. Therefore, it can suppress affecting the corrosion reliability of the intake / exhaust piping resulting from the generation of condensed water.

  The second control means prioritizes the reduction of pressure loss when the exhaust gas passes through the cyclone collector rather than the exhaust gas flow through the exhaust passage collecting foreign matter by the cyclone collector. When the flow rate is less than a second predetermined flow rate, which is a threshold value, the flow rate adjustment valve is closed, and when the exhaust flow rate flowing through the exhaust passage is equal to or higher than the second predetermined flow rate, the cyclone type collecting device is The flow rate adjusting valve may be opened at an opening within a range in which foreign matter having a particle size larger than the particle size that affects the intake system of the internal combustion engine can be collected.

  Here, when the second predetermined flow rate is a flow rate higher than that, priority is given to reduction of pressure loss when exhaust passes through the cyclone-type collection device rather than collecting foreign matter by the cyclone-type collection device. This is the exhaust flow rate that is a threshold value.

  According to the present invention, when the exhaust gas flow rate is higher than the second predetermined flow rate, the flow rate adjustment valve is opened, and the pressure loss when the exhaust gas passes through the cyclone collecting device can be reduced. Further, when opening the flow rate adjusting valve, the cyclone type collecting device can collect foreign matters having a particle diameter larger than the particle diameter that affects the intake system of the internal combustion engine.

In the present invention, the following configuration is adopted. That is, the present invention
A turbocharger having a turbine disposed in an exhaust passage of an internal combustion engine and a compressor disposed in an intake passage of the internal combustion engine;
Low pressure EG that takes in a part of exhaust gas as low pressure EGR gas from the exhaust passage downstream from the turbine and recirculates the low pressure EGR gas to the intake passage upstream from the compressor.
R passage,
A cyclonic collector that is disposed in the low pressure EGR passage and collects foreign matter in the low pressure EGR gas;
A bypass passage for bypassing the cyclone collector in the low pressure EGR gas in the low pressure EGR passage;
A bypass valve for opening and closing the bypass passage;
The flow rate of the low-pressure EGR gas flowing through the low-pressure EGR passage is less than a third predetermined flow rate that is a threshold for preventing foreign matter from reaching the compressor, and the rotation speed of the turbocharger cannot be collected by the cyclone-type collection device. Third control means for opening the bypass valve when a foreign matter having a small particle diameter reaches the compressor and is lower than a predetermined rotational speed that is a threshold value that does not damage the compressor;
An exhaust gas recirculation device for an internal combustion engine.

  Here, the third predetermined flow rate means a low-pressure EGR gas flow rate that is a threshold value that prevents foreign matter from reaching the compressor if the flow rate is smaller than that. In addition, when the predetermined rotational speed is a lower rotational speed, a turbocharger that is a threshold value that does not damage the compressor even when a foreign substance having a small particle size that cannot be collected by the cyclone-type collecting device reaches the compressor. The number of revolutions.

  According to the present invention, the flow rate of the low-pressure EGR gas flowing through the low-pressure EGR passage is less than the third predetermined flow rate that does not allow foreign matter to reach the compressor, and the turbocharger rotation speed cannot be collected by the cyclone-type collection device. The bypass valve is opened when the diameter is lower than a predetermined rotational speed that does not damage the compressor even if the foreign matter reaches the compressor. Accordingly, the cyclone collecting device is bypassed by the low pressure EGR gas flowing through the low pressure EGR passage, and the low pressure EGR gas flows through the bypass passage. For this reason, the pressure loss at the time of low-pressure EGR gas passing a cyclone type collection device is lost. Therefore, since the pressure loss on the path of the low pressure EGR passage is reduced, a desired amount of the low pressure EGR gas can be supplied to the internal combustion engine, and the deterioration of the exhaust emission due to the shortage of the low pressure EGR gas can be suppressed.

  According to the present invention, in an exhaust gas recirculation device for an internal combustion engine, pressure loss in a cyclone type collecting device can be reduced.

  Specific examples of the present invention will be described below.

<Example 1>
FIG. 1 is a diagram illustrating a schematic configuration of an internal combustion engine to which an exhaust gas recirculation apparatus for an internal combustion engine according to the present embodiment is applied and an intake / exhaust system thereof. An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-stroke cycle diesel engine having four cylinders 2 that form a combustion chamber together with a piston. The internal combustion engine 1 is mounted on a vehicle. An intake passage 3 and an exhaust passage 4 are connected to the internal combustion engine 1.

  In the middle of the intake passage 3 connected to the internal combustion engine 1, a compressor 5a of a turbocharger 5 that operates using exhaust energy as a drive source is disposed.

  A throttle valve 6 for adjusting the flow rate of intake air flowing through the intake passage 3 is disposed in the intake passage 3 upstream of the compressor 5a. The throttle valve 6 is opened and closed by an electric actuator. An air flow meter 7 that outputs a signal corresponding to the flow rate of fresh air flowing through the intake passage 3 is disposed in the intake passage 3 upstream of the throttle valve 6. The air flow meter 7 measures the intake air amount (fresh air amount) of the internal combustion engine 1.

  An intercooler 8 that performs heat exchange between the intake air and the outside air is arranged in the intake passage 3 downstream of the compressor 5a.

  On the other hand, a turbine 5 b of a turbocharger 5 is arranged in the middle of the exhaust passage 4 connected to the internal combustion engine 1. An exhaust purification device 9 is disposed in the exhaust passage 4 downstream of the turbine 5b.

  The exhaust emission control device 9 includes an oxidation catalyst and a particulate filter (hereinafter simply referred to as a filter) arranged at the subsequent stage of the oxidation catalyst. The filter may support an NOx storage reduction catalyst (hereinafter simply referred to as NOx catalyst). The exhaust purification device 9 becomes high temperature when the oxidation catalyst or NOx catalyst is activated, and each catalyst performs its function. The oxidation catalyst and NOx catalyst used in the exhaust purification device 9 correspond to the catalyst of the present invention.

  Further, an exhaust throttle valve 10 for adjusting the flow rate of the exhaust gas flowing through the exhaust passage 4 is provided in the exhaust passage 4 downstream of the exhaust purification device 9. The exhaust throttle valve 10 is opened and closed by an electric actuator.

  The internal combustion engine 1 is provided with a low pressure EGR device 30 that recirculates (recirculates) part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 at a low pressure. The low pressure EGR device 30 includes a low pressure EGR passage 31, a low pressure EGR valve 32, and a low pressure EGR cooler 33.

  The low pressure EGR passage 31 connects the exhaust passage 4 downstream of the exhaust purification device 9 and upstream of the exhaust throttle valve 10 and the intake passage 3 upstream of the compressor 5a and downstream of the throttle valve 6. ing. Exhaust gas is fed into the internal combustion engine 1 at low pressure through the low pressure EGR passage 31. In this embodiment, the exhaust gas recirculated through the low pressure EGR passage 31 is referred to as low pressure EGR gas.

  The low pressure EGR valve 32 adjusts the amount of the low pressure EGR gas flowing through the low pressure EGR passage 31 by adjusting the passage sectional area of the low pressure EGR passage 31. The low pressure EGR valve 32 is opened and closed by an electric actuator. The adjustment of the low pressure EGR gas amount can be performed by a method other than the adjustment of the opening degree of the low pressure EGR valve 32. For example, by adjusting the opening degree of the throttle valve 6 or by adjusting the opening degree of the exhaust throttle valve 10, the differential pressure between the upstream and downstream of the low pressure EGR passage 31 is changed. The amount can be adjusted.

  The low pressure EGR cooler 33 exchanges heat between the low pressure EGR gas passing through the low pressure EGR cooler 33 and the engine cooling water of the internal combustion engine 1 to lower the temperature of the low pressure EGR gas.

  Here, in the present embodiment, the cyclonic collection device 11 is arranged in the low pressure EGR passage 31 downstream of the low pressure EGR cooler 33. In the cyclone-type collection device 11, when low-pressure EGR gas containing foreign matter flows into the cyclone-type collection device 11, the low-pressure EGR gas rotates along a cylindrical inner wall whose diameter is smaller at the lower side of the cyclone-type collection device 11. During this time, centrifugal force acts on the foreign matter, and the foreign matter moves in the direction of the wall and is separated from the low-pressure EGR gas. The low-pressure EGR gas from which the foreign matter is separated flows in the direction of the center of the cyclone-type collection device 11 and flows out from the discharge port at the top of the cyclone-type collection device 11. On the other hand, the foreign matter separated from the low-pressure EGR gas descends after being separated from the low-pressure EGR gas and is collected in the foreign matter collecting portion at the lower part of the cyclone type collecting device 11.

  In the present embodiment, a flow rate adjusting path 12 is provided that connects the foreign matter collecting portion at the lower part of the cyclone type collecting device 11 and the exhaust passage 4 downstream from the connection portion of the low pressure EGR passage 31. The flow rate adjusting path 12 causes the low-pressure EGR gas to flow out from the foreign matter collecting part of the cyclone type collecting device 11 to the exhaust passage 4 together with the foreign matter.

  A flow rate adjustment valve 13 is disposed in the flow rate adjustment path 12. The flow rate adjustment valve 13 adjusts the flow rate of the low pressure EGR gas flowing through the flow rate adjustment path 12. The flow rate adjusting valve 13 is opened and closed by an electric actuator.

  The internal combustion engine 1 configured as described above is provided with an ECU 14 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 14 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  The ECU 14 is connected to an air flow meter 7 and a crank position sensor 15 for detecting the engine rotational speed via electric wiring, and output signals from these various sensors are input to the ECU 14.

  On the other hand, the actuators of the throttle valve 6, the exhaust throttle valve 10, the low pressure EGR valve 32, and the flow rate adjusting valve 13 are connected to the ECU 14 through electric wiring, and these devices are controlled by the ECU 14.

  In this embodiment, the low pressure EGR gas flow rate is controlled using the low pressure EGR valve 32 in accordance with the operating state of the internal combustion engine 1. As a result, the internal combustion engine 1 is operated in a state in which the low-pressure EGR gas is contained in the intake air sucked into the internal combustion engine 1, so that the oxygen concentration of the intake air is reduced to reduce the combustion temperature and the combustion speed. Thus, the effect of reducing NOx generated during combustion is exhibited.

  FIG. 2 shows the low-pressure EGR gas flow rate required according to the operating state of the internal combustion engine 1. The horizontal axis in FIG. 2 indicates the engine load of the internal combustion engine 1, and the vertical axis indicates the low-pressure EGR gas flow rate. In the two characteristic curves in FIG. 2, the upper characteristic curve is a characteristic curve when the engine speed of the internal combustion engine 1 is high, and the lower characteristic curve is a case where the engine speed of the internal combustion engine 1 is low. It is a characteristic curve. As shown in FIG. 2, as the operating state of the internal combustion engine 1, the low-pressure EGR gas flow rate required for the internal combustion engine 1 tends to increase as the engine load is light / medium load and the engine speed is high. is there. A map as shown in FIG. 2 is used to supply a low-pressure EGR gas flow rate required according to the operating state of the internal combustion engine 1.

  By the way, in the present embodiment, the cyclonic collecting device 11 is disposed in the low pressure EGR passage 31. The cyclone-type collection device 11 provided in the low-pressure EGR passage 31 can also collect foreign matters having a smaller particle diameter when the low-pressure EGR gas flow rate increases and the low-pressure EGR gas flow rate increases. However, when the low-pressure EGR gas flow rate increases, the pressure loss when the low-pressure EGR gas passes through the cyclone-type collection device 11 increases. When this pressure loss increases, a desired amount of the low-pressure EGR gas is not supplied to the internal combustion engine 1, and the low-pressure EGR gas becomes insufficient. For this reason, due to the shortage of low-pressure EGR gas, the oxygen concentration of the intake air does not decrease, the combustion temperature and the combustion speed do not decrease, NOx is generated during combustion, and exhaust emission deteriorates.

  Further, if the exhaust throttle valve 10 is controlled to be closed in order to supply the insufficient low pressure EGR gas, the pressure loss when the low pressure EGR gas passes through the cyclone type collector 11 is further increased, and the flow of the exhaust gas is also increased. The stagnation and the pumping loss increase, leading to a decrease in output of the internal combustion engine 1 and a deterioration in fuel consumption.

  Therefore, in this embodiment, the flow rate adjustment valve 13 is controlled to open and close according to the pressure loss when the low-pressure EGR gas flowing through the low-pressure EGR passage 31 passes through the cyclone type collection device 11.

  Here, the pressure loss when the low-pressure EGR gas passes through the cyclone-type collection device 11 is correlated with the low-pressure EGR gas flow rate flowing into the cyclone-type collection device 11, and as the low-pressure EGR gas flow rate increases, Pressure loss also increases. For this reason, as the actual control of the flow rate adjusting valve 13, the low pressure EGR gas flow rate that has been previously correlated with the pressure loss is calculated, and the flow rate adjusting valve 13 is controlled to open and close according to the calculated low pressure EGR gas flow rate. To do.

  Specifically, the flow rate of the low-pressure EGR gas flowing through the low-pressure EGR passage 31 is less than the pressure loss when the low-pressure EGR gas passes through the cyclone-type collection device 11 than when the foreign matter is collected by the cyclone-type collection device 11. When the flow rate is less than the first predetermined flow rate, which is a threshold for giving priority to reduction, the flow rate adjustment valve 13 is closed.

  On the other hand, when the low-pressure EGR gas flow rate is equal to or higher than the first predetermined flow rate, the flow rate adjustment valve 13 is opened. The opening when the flow rate adjusting valve 13 is opened is a range in which the cyclone collecting device 11 can collect foreign matters having a particle size larger than the particle size that affects the intake system of the internal combustion engine 1. Stipulated in

  If the first predetermined flow rate is a flow rate higher than that, the pressure loss when the low-pressure EGR gas passes through the cyclone-type collection device 11 is lower than when the cyclone-type collection device 11 collects foreign matter. Is a low-pressure EGR gas flow rate that is a threshold value that prioritizes.

  According to this embodiment, when the pressure loss when the low-pressure EGR gas passes through the cyclone-type collection device 11 increases, that is, when the flow rate of the low-pressure EGR gas flowing into the cyclone-type collection device 11 increases, the flow rate is adjusted. The valve 13 is opened. As a result, when the low-pressure EGR gas flow rate is increased, the low-pressure EGR gas is caused to flow from the cyclone-type collection device 11 to the flow rate adjustment path 12, and the low-pressure EGR gas remaining in the cyclone-type collection device 11 is reduced. Then, the pressure loss when the low-pressure EGR gas passes through the cyclone type collection device 11 is reduced.

  FIG. 3 is a diagram illustrating a relationship between the flow rate of the low-pressure EGR gas flowing into the cyclone-type collection device 11 and the pressure loss when the low-pressure EGR gas passes through the cyclone-type collection device 11. In FIG. 3, the first characteristic curve shows the relationship between the low pressure EGR gas flow rate and the pressure loss when the flow rate adjustment valve 13 is closed, and the second characteristic curve is when the flow rate adjustment valve 13 is opened. The relationship between the low pressure EGR gas flow rate and the pressure loss is shown. As shown in FIG. 3, by opening the flow rate adjustment valve 13, the position shifts from the position A of the first characteristic curve to the position B of the second characteristic curve, and the pressure loss with respect to the low pressure EGR gas flow rate becomes small.

  Since the pressure loss is reduced in this way, a desired amount of the low-pressure EGR gas can be supplied to the internal combustion engine 1, and the low-pressure EGR gas supplied to the internal combustion engine 1 is not insufficient. Accordingly, sufficient low-pressure EGR gas is supplied, the oxygen concentration in the intake air is lowered, the combustion temperature and the combustion speed are lowered, NOx generated during combustion can be reduced, and deterioration of exhaust emission can be suppressed.

  Further, it is not necessary to control the exhaust throttle valve 10 to the closed side in order to supply the insufficient low-pressure EGR gas, so that the pressure loss when the low-pressure EGR gas passes through the cyclone type collecting device 11 does not further increase. Moreover, the flow of exhaust gas does not stagnate, the pumping loss does not increase, and the output reduction and deterioration of fuel consumption of the internal combustion engine 1 can be suppressed.

  Here, when the low pressure EGR gas is caused to flow from the cyclone type collection device 11 to the flow rate adjusting path 12, the flow rate of the low pressure EGR gas passing through the cyclone type collection device 11 becomes slow, and the cyclone type collection device 11 has a small particle diameter. Foreign matter cannot be collected, and the collection efficiency of foreign matter having a small particle diameter is reduced. However, in the present embodiment, the flow rate adjusting valve is limited to a range in which the cyclone type collection device 11 can collect foreign matters having a particle size larger than the particle size that affects the intake system of the internal combustion engine 1. The opening of 13 is controlled to the opening side. For this reason, the cyclone-type collection device 11 can collect foreign matters having a particle diameter larger than the particle diameter that affects the intake system of the internal combustion engine 1.

  FIG. 4 is a diagram showing the relationship between the particle size of the foreign matter and the foreign matter collection efficiency in the cyclone type collecting device 11. 4A shows the foreign matter collection efficiency at the position A of the first characteristic curve when the flow rate adjusting valve 13 used in FIG. 3 is closed, and B shows the flow rate adjusting valve 13 used in FIG. The foreign material collection efficiency in the B position of the 2nd characteristic curve at the time of valve opening is shown. C indicates the foreign matter collection efficiency at the C position when the low pressure EGR gas flow rate of the first characteristic curve is small when the flow rate adjustment valve 13 of FIG. 3 is closed. Further, the hatched portion indicates a range (NG region) where the particle diameter of the foreign matter is larger than the particle diameter that affects the intake system of the internal combustion engine 1. As shown in FIG. 4, by opening the flow rate adjustment valve 13, the foreign matter collection efficiency of A is shifted from the foreign matter collection efficiency of A to B, and the foreign matter collection efficiency of foreign matter having a small particle diameter is reduced. Foreign matter having a particle size larger than the particle size that affects the intake system of the internal combustion engine 1 in the NG region can be collected.

  Therefore, in the case of the present embodiment, the inclusion of foreign matter that cannot be collected by the cyclonic collection device 11 affects the intake system of the internal combustion engine such that the foreign matter reaches the compressor 5a and damages the compressor 5a. There is no.

  Next, a control routine for the low-pressure EGR gas flow rate according to this embodiment will be described. FIG. 5 is a flowchart showing a control routine for the low-pressure EGR gas flow rate according to this embodiment. This routine is repeatedly executed every predetermined time. The ECU 14 that executes this routine corresponds to the first control means of the present invention.

  In step S101, the ECU 14 reads the output signals of various sensors and detects the operating state of the internal combustion engine 1.

  In step S102, the ECU 14 determines whether or not it is necessary to introduce low-pressure EGR gas into the internal combustion engine 1 from the operating state of the internal combustion engine 1 detected in step S101.

  It is determined that it is necessary to introduce low-pressure EGR gas to the internal combustion engine 1 when it is necessary to reduce the NOx generated during combustion by reducing the intake oxygen concentration to reduce the combustion temperature and the combustion speed.

  If it is determined in step S102 that the low pressure EGR gas needs to be introduced into the internal combustion engine 1, the process proceeds to step S103. If it is determined in step S102 that it is not necessary to introduce the low pressure EGR gas into the internal combustion engine 1, the process proceeds to step S106.

  In step S103, the ECU 14 calculates a low-pressure EGR gas flow rate to be introduced from the operating state of the internal combustion engine 1 detected in step S101.

  The low-pressure EGR gas flow rate can be calculated by obtaining a map as shown in FIG. 2 in advance and taking in the engine load and engine speed of the internal combustion engine 1 in this map.

In step S104, the ECU 14 calculates the opening degree of the flow rate adjustment valve 13 from the low pressure EGR gas flow rate calculated in step S103.

  When the low-pressure EGR gas flow rate calculated in step S103 is smaller than the first predetermined flow rate, priority is given to collecting foreign matter with the cyclone-type collection device 11, and therefore the opening of the flow rate adjustment valve 13 is zero (valve closed) State). When the calculated low-pressure EGR gas flow rate is equal to or higher than the first predetermined flow rate, the low-pressure EGR gas flow rate is taken into a map as shown in FIG. 3 or FIG. The opening degree of the flow regulating valve 13 is calculated within a range in which foreign matters having a particle size larger than the particle size that affects the intake system of the engine 1 can be collected. This opening is a value larger than zero. Note that the greater the low-pressure EGR gas flow rate, the greater the pressure loss when the low-pressure EGR gas passes through the cyclone collection device 11. From this, as the low-pressure EGR gas flow rate increases, the opening degree of the flow rate adjustment valve 13 is preferably opened to reduce the pressure loss.

  In step S105, the ECU 14 controls the opening degree of the flow rate adjustment valve 13 to the value calculated in step S104.

  On the other hand, in step S106, the ECU 14 closes the flow rate adjustment valve 13 to fully close it.

  In step S107, when the low pressure EGR gas is introduced into the internal combustion engine 1, the ECU 14 actually introduces the low pressure EGR gas having the flow rate of the low pressure EGR gas calculated in step S103 and performs the EGR operation. At this time, high-pressure EGR gas or internal EGR gas may be introduced. On the other hand, when the low pressure EGR gas is not introduced into the internal combustion engine 1, the EGR operation is performed by introducing only the high pressure EGR gas or the internal EGR gas. After the processing of this step, this routine is once ended.

  By executing the above control routine, the pressure loss when the low-pressure EGR gas passes through the cyclone type collection device 11 can be reduced.

<Example 2>
Next, Example 2 will be described. Here, a configuration different from the above-described embodiment will be described, and description of the same configuration will be omitted.

  FIG. 6 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas recirculation apparatus for an internal combustion engine according to this embodiment is applied, and an intake / exhaust system thereof.

  In the present embodiment, a cyclone type collecting device 11 is arranged directly downstream of the exhaust purification device 9 and integrated with the exhaust purification device 9. Also in the present embodiment, the flow rate adjusting path 12 is provided that connects the foreign matter collecting portion at the lower part of the cyclone type collecting device 11 and the exhaust passage 4 downstream from the connection portion of the low pressure EGR passage 31. A flow rate adjustment valve 13 is disposed in the flow rate adjustment path 12.

  The low-pressure EGR passage 31 includes an exhaust passage 4 downstream of the cyclone type collection device 11 and upstream of a connection portion with the flow rate adjustment passage 12, and an intake passage upstream of the compressor 5a and downstream of the throttle valve 6. 3 are connected.

  A three-way valve 16 is disposed at a connection site where the low pressure EGR passage 31 is connected to the upstream exhaust passage 4 and the downstream exhaust passage 4. The three-way valve 16 is operated by an electric actuator. The actuator of the three-way valve 16 is connected to the ECU 14 via electric wiring, and the three-way valve 16 is controlled by the ECU 14.

  FIG. 7 is a diagram illustrating the three-way valve 16 according to the present embodiment. The three-way valve 16 shown in FIG. 7 connects the upstream exhaust passage 4 upstream of the three-way valve 16 shown in FIG. 7A and the downstream exhaust passage 4 downstream of the three-way valve 16 to provide a low-pressure EGR passage. 31 is a state in which low pressure EGR gas is turned off, and a state in which the upstream side exhaust passage 4, the downstream side exhaust passage 4 and the low pressure EGR passage 31 are connected as shown in FIG. 7B (low pressure EGR gas ON state), The state can be changed to a state where all the passages are blocked (all passage blocking state) shown in FIG.

  In the low-pressure EGR gas OFF state shown in FIG. 7A and the low-pressure EGR gas ON state shown in FIG. 7B, the three-way valve 16 is disconnected at the boundary portion between the upstream exhaust passage 4 and the downstream exhaust passage 4. By adjusting the area, the amount of exhaust flowing to the downstream side exhaust passage 4 can be adjusted, and it can serve as an exhaust throttle valve. In the low-pressure EGR gas ON state shown in FIG. 7B, the three-way valve 16 adjusts the passage cross-sectional area at the boundary with the low-pressure EGR passage 31, thereby reducing the amount of low-pressure EGR gas flowing through the low-pressure EGR passage 31. Can be adjusted and can act as a low pressure EGR valve. In the state where all the passages shown in FIG. 7C are blocked, all the exhaust gas is circulated to the flow rate adjusting passage 12, and the foreign matter accumulated in the foreign matter collecting portion at the lower part of the cyclone type collecting device 11 is sent to the exhaust passage 4. Can be discharged.

  By the way, in the present embodiment, a cyclone type collecting device 11 is arranged in the exhaust passage 4. The cyclone-type collection device 11 provided in the exhaust passage 4 can also collect foreign matters having a smaller particle diameter when the exhaust flow rate increases and the exhaust flow velocity increases. However, when the exhaust gas flow rate increases, the pressure loss when the exhaust gas passes through the cyclone type collecting device 11 increases. When this pressure loss increases, the pumping loss increases, leading to a decrease in the output of the internal combustion engine 1 and a deterioration in fuel consumption.

  Therefore, in this embodiment, the flow rate adjustment valve 13 is controlled to open and close according to the pressure loss when the exhaust gas flowing through the exhaust passage 4 passes through the cyclone type collection device 11.

  Here, the pressure loss when the exhaust gas passes through the cyclone-type collection device 11 is correlated with the exhaust flow rate flowing into the cyclone-type collection device 11, and the pressure loss increases as the exhaust flow rate increases. For this reason, as an actual control of the flow rate adjusting valve 13, an exhaust flow rate that has been previously correlated with the pressure loss is calculated, and the flow rate adjusting valve 13 is controlled to open and close according to the calculated exhaust flow rate.

  Specifically, the exhaust flow rate through the exhaust passage 4 is a threshold value that prioritizes the reduction of pressure loss when the exhaust passes through the cyclone-type collection device 11 rather than collecting foreign matter by the cyclone-type collection device 11. When the flow rate is smaller than the second predetermined flow rate, the flow rate adjustment valve 13 is closed.

  On the other hand, when the exhaust flow rate is equal to or higher than the second predetermined flow rate, the flow rate adjustment valve 13 is opened. The opening degree of the flow rate adjusting valve 13 is within a range in which the cyclone type collecting device 11 can collect foreign matters having a particle size larger than the particle size that affects the intake system of the internal combustion engine 1. Determine.

  Note that when the second predetermined flow rate is a flow rate higher than that, priority is given to reducing pressure loss when exhaust passes through the cyclone-type collection device 11 rather than collecting foreign matter with the cyclone-type collection device 11. It is the exhaust gas flow rate which becomes a threshold value.

According to this embodiment, the flow rate adjustment valve 13 is opened when the pressure loss when the exhaust gas passes through the cyclonic collector 11 increases, that is, when the exhaust gas flow into the cyclone collector 11 increases. I speak. As a result, when the exhaust gas flow rate increases, the exhaust gas is caused to flow from the cyclone type collecting device 11 to the flow rate adjusting path 12, and the exhaust gas remaining in the cyclone type collecting device 11 is reduced. Then, the pressure loss when the exhaust gas passes through the cyclone type collecting device 11 is reduced.

  The relationship between the flow rate of exhaust gas flowing into the cyclone-type collection device 11 and the pressure loss when the exhaust gas passes through the cyclone-type collection device 11 is the same as the flow rate of low-pressure EGR gas flowing into the cyclone-type collection device 11 shown in FIG. This is the same as the relationship with the pressure loss when the low-pressure EGR gas passes through the cyclone type collection device 11. Therefore, as shown in FIG. 3, by opening the flow rate adjustment valve 13, the position shifts from the A position of the first characteristic curve to the B position of the second characteristic curve, and the pressure loss with respect to the exhaust flow rate becomes small.

  Since the pressure loss is reduced in this way, the pumping loss can be reduced, and the decrease in the output of the internal combustion engine 1 and the deterioration in fuel consumption can be suppressed.

  Here, when the exhaust gas is caused to flow from the cyclone type collecting device 11 to the flow rate adjusting path 12, the flow velocity of the exhaust gas passing through the cyclone type collecting device 11 becomes slow, and the cyclone type collecting device 11 collects foreign matters having a small particle diameter. It cannot be performed, and the collection efficiency of foreign matters having a small particle size is reduced. However, in the present embodiment, the flow rate adjusting valve is limited to a range in which the cyclone type collection device 11 can collect foreign matters having a particle size larger than the particle size that affects the intake system of the internal combustion engine 1. The opening of 13 is controlled to the opening side. For this reason, the cyclone-type collection device 11 can collect foreign matters having a particle diameter larger than the particle diameter that affects the intake system of the internal combustion engine 1.

  Also in the case of the present embodiment, the relationship between the particle diameter of the foreign matter and the foreign matter collecting efficiency in the cyclone type collecting device 11 is as shown in FIG. For this reason, as shown in FIG. 4, by opening the flow rate adjusting valve 13, the foreign matter collecting efficiency of A is shifted to the foreign matter collecting efficiency of B, and the foreign matter collecting efficiency of the foreign matter having a small particle diameter is lowered. However, foreign matters having a particle size larger than the particle size that affects the intake system of the internal combustion engine 1 can be collected.

  Therefore, in the case of the present embodiment, the internal combustion engine in which the foreign matter passes through the low pressure EGR passage 31 and reaches the compressor 5a due to the inclusion of the foreign matter that cannot be collected by the cyclone type collecting device 11, and the compressor 5a is damaged. The intake system of 1 is not affected.

  Here, in the present embodiment, a cyclone type collecting device 11 is disposed directly downstream of the exhaust purification device 9 and integrated with the exhaust purification device 9. For this reason, heat is taken away from the exhaust purification device 9 having an oxidation catalyst or NOx catalyst that is at a high temperature when the exhaust is active, and the exhaust flows into the cyclone-type collection device 11 in a warmed state.

  FIG. 8 is a graph showing the characteristics of the exhaust temperature and the water vapor amount. The horizontal axis in FIG. 8 indicates the exhaust temperature, and the vertical axis indicates the water vapor amount. As shown in FIG. 8, if the exhaust gas is hot in the cyclone type collector 11 as in the present embodiment, the total water vapor amount enters the steam side with respect to the boundary line between water and steam, and condensed water is generated. do not do. On the other hand, as shown by the broken line, if the exhaust gas is at a low temperature, the amount of water vapor protrudes toward the water side with respect to the boundary line between water and steam, and the amount of protrusion is condensed water. Thus, in this embodiment, since the exhaust gas is hot in the cyclone-type collection device 11, the saturated vapor amount of the exhaust does not decrease, and condensed water is generated from the exhaust gas in the cyclone-type collection device 11. Can be suppressed.

  Therefore, it can suppress affecting the corrosion reliability of the intake / exhaust piping resulting from the generation of condensed water.

Next, an exhaust flow rate control routine according to this embodiment will be described. FIG. 9 is a flowchart showing an exhaust flow rate control routine according to this embodiment. This routine is repeatedly executed every predetermined time. The ECU 14 that executes this routine corresponds to the second control means of the present invention.

  In step S <b> 201, the ECU 14 reads output signals from various sensors and detects the operating state of the internal combustion engine 1.

  In step S202, the ECU 14 calculates the exhaust gas flow rate from the operating state of the internal combustion engine 1 detected in step S201.

  In step S203, the ECU 14 calculates the opening degree of the flow rate adjustment valve 13 from the exhaust flow rate calculated in step S202.

  When the exhaust gas flow rate calculated in step S202 is smaller than the second predetermined flow rate, priority is given to collecting foreign matter by the cyclone type collecting device 11, and therefore the opening of the flow rate adjusting valve 13 is zero (closed state). It is. When the calculated exhaust flow rate is equal to or higher than the second predetermined flow rate, the exhaust flow rate is taken into a map similar to FIG. 3 or FIG. 4 corresponding to the exhaust flow rate obtained in advance, and the cyclone collecting device 11 The opening degree of the flow regulating valve 13 is calculated within a range in which foreign matters having a particle size larger than the particle size that affects the intake system of the engine 1 can be collected. This opening is a value larger than zero. Note that the greater the exhaust gas flow rate, the greater the pressure loss when the exhaust gas passes through the cyclone type collector 11. From this, it is preferable that the opening degree of the flow rate adjustment valve 13 is opened more in order to reduce the pressure loss as the exhaust flow rate increases.

  In step S204, the ECU 14 controls the opening degree of the flow rate adjustment valve 13 to the value calculated in step S203. After the processing of this step, this routine is once ended.

  By executing the above control routine, it is possible to reduce the pressure loss when the exhaust gas passes through the cyclone type collector 11.

  In the present embodiment, the cyclonic collection device 11 is integrally provided immediately downstream of the exhaust purification device 9. However, the present invention is not limited to this, and the exhaust gas flowing into the cyclone collection device 11 is exhausted. The cyclone collector 11 may be separated away from the exhaust gas purification device 9 as long as it takes away the amount of heat from 9 and becomes high temperature and the exhaust does not generate condensed water in the cyclone collector 11. .

<Example 3>
Next, Example 3 will be described. Here, a configuration different from the above-described embodiment will be described, and description of the same configuration will be omitted.

  FIG. 10 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas recirculation apparatus for an internal combustion engine according to this embodiment is applied, and an intake / exhaust system thereof.

  In the present embodiment, a bypass passage 17 is provided in the low-pressure EGR passage 31 for bypassing the cyclone collecting device 11 to the low-pressure EGR gas.

  The bypass passage 17 is provided with a bypass valve 18 that is opened to allow the low-pressure EGR gas to flow through the bypass passage 17 and is closed to block the flow of the low-pressure EGR gas through the bypass passage 17. The bypass valve 18 is opened and closed by an electric actuator. An actuator of a bypass valve 18 is connected to the ECU 14 via an electrical wiring, and the bypass valve 18 is controlled by the ECU 14.

By the way, in the present embodiment, the cyclonic collecting device 11 is disposed in the low pressure EGR passage 31. When the low-pressure EGR gas passes through the cyclone-type collection device 11, a pressure loss is caused. When this pressure loss increases, a desired amount of low-pressure EGR gas is not supplied to the internal combustion engine, and the low-pressure EGR gas becomes insufficient. For this reason, due to the shortage of low-pressure EGR gas, the oxygen concentration of the intake air does not decrease, the combustion temperature and the combustion speed do not decrease, NOx is generated during combustion, and exhaust emission deteriorates.

  Further, if the exhaust throttle valve 10 is controlled to be closed in order to supply the insufficient low pressure EGR gas, the pressure loss when the low pressure EGR gas passes through the cyclone type collector 11 is further increased, and the flow of the exhaust gas is also increased. The stagnation and the pumping loss increase, leading to a decrease in output of the internal combustion engine 1 and a deterioration in fuel consumption.

  Therefore, in this embodiment, the flow rate of the low-pressure EGR gas flowing through the low-pressure EGR passage 31 is less than a third predetermined flow rate that is a threshold value that prevents foreign matter riding on the low-pressure EGR gas from reaching the compressor 5a, and the rotation of the turbocharger 5 When the number is lower than a predetermined rotational speed that is a threshold value that does not damage the compressor 5a even if foreign matter having a small particle size that cannot be collected by the cyclone type collection device 11 reaches the compressor 5a, the bypass valve 18 is opened. I tried to do it.

  Note that the third predetermined flow rate is a low-pressure EGR gas flow rate that is a threshold value that prevents foreign matter riding on the low-pressure EGR gas from reaching the compressor 5a when the flow rate is smaller than that. Further, when the predetermined rotational speed is a lower rotational speed, it becomes a threshold value that does not damage the compressor 5a even if a foreign substance having a small particle size that cannot be collected by the cyclone-type collecting device 11 reaches the compressor 5a. This is the rotational speed of the turbocharger 5.

  FIG. 11 is a view showing a region where the bypass valve 18 is opened according to the operating state of the internal combustion engine 1. The horizontal axis in FIG. 11 is the engine speed of the internal combustion engine 1, and the vertical axis is the engine load of the internal combustion engine 1. In FIG. 11, a plurality of solid characteristic curves indicate the low-pressure EGR gas flow rate required according to the operating state of the internal combustion engine 1, and the engine load is light / medium load and the engine speed is high. The lower the EGR gas flow rate required for the internal combustion engine is, the more it tends to increase. The plurality of broken characteristic curves indicate the rotational speed of the turbocharger 5 required in accordance with the operating state of the internal combustion engine. The higher the engine load and the higher the engine speed, the higher the internal combustion engine. The rotational speed of the turbocharger 5 required for 1 tends to be high. The shaded area indicates a region where the condition for opening the bypass valve 18 is satisfied (bypass valve opening region). The shaded portion that is the bypass valve opening region is a region where the low-pressure EGR gas flow rate is lower than the third predetermined flow rate and the turbocharger speed is lower than the predetermined speed.

  According to the present embodiment, the bypass valve 18 is opened when the operating state of the internal combustion engine 1 is in the bypass valve opening region of the shaded portion in FIG. Then, the low pressure EGR gas flowing through the low pressure EGR passage 31 is caused to bypass the cyclone collecting device 11, and the low pressure EGR gas flows through the bypass passage 17. For this reason, there is no pressure loss when the low-pressure EGR gas passes through the cyclone type collection device 11. Therefore, the pressure loss on the low-pressure EGR passage 31 is reduced.

  FIG. 12 is a diagram showing the relationship between the low-pressure EGR gas flow rate and the pressure loss on the low-pressure EGR passage 31. In FIG. 12, the broken line characteristic curve indicates the pressure loss when the low pressure EGR gas passes through the cyclone type collector 11 with respect to the low pressure EGR gas flow rate, and the solid line characteristic curve indicates that the low pressure EGR gas with respect to the low pressure EGR gas flow rate is the bypass passage. The pressure loss when passing through 17 is shown. As shown in FIG. 12, when the bypass valve 18 is opened and the low-pressure EGR gas passes through the bypass passage 17, the pressure loss is reduced.

Thus, since the pressure loss on the path of the low pressure EGR passage 31 is reduced, a desired amount of the low pressure EGR gas can be supplied to the internal combustion engine 1, and the low pressure EGR gas supplied to the internal combustion engine 1 is not insufficient. Accordingly, sufficient low-pressure EGR gas is supplied, the oxygen concentration in the intake air is lowered, the combustion temperature and the combustion speed are lowered, NOx generated during combustion can be reduced, and deterioration of exhaust emission can be suppressed.

  Further, it is not necessary to control the exhaust throttle valve 10 to the closed side in order to supply the insufficient low-pressure EGR gas, so that the pressure loss when the low-pressure EGR gas passes through the cyclone type collecting device 11 does not further increase. Moreover, the flow of exhaust gas does not stagnate, the pumping loss does not increase, and the output reduction and deterioration of fuel consumption of the internal combustion engine 1 can be suppressed.

  Here, when the low-pressure EGR gas is caused to flow into the bypass passage 17, the low-pressure EGR gas does not pass through the cyclone-type collection device 11, and the cyclone-type collection device 11 cannot collect foreign matter. However, in this embodiment, the flow rate of the low-pressure EGR gas flowing through the low-pressure EGR passage 31 is less than the third predetermined flow rate, which is a threshold value that prevents foreign matter riding on the low-pressure EGR gas from reaching the compressor 5a, and the rotation of the turbocharger 5 When the number is lower than a predetermined rotational speed that is a threshold value that does not damage the compressor 5a even if foreign matter having a small particle size that cannot be collected by the cyclone type collection device 11 reaches the compressor 5a, the bypass valve 18 is opened. To do. For this reason, even if the foreign matter has not been collected by the cyclone type collection device 11, the foreign matter riding on the low pressure EGR gas does not reach the compressor 5a, or the small particle size that cannot be collected by the cyclone type collection device 11 Even if the foreign matter reaches the compressor 5a, the compressor 5a is not damaged. Therefore, it is possible to suppress adverse effects caused by foreign matter mixed into the intake system of the internal combustion engine 1.

  Next, a control routine for the bypass valve 18 according to this embodiment will be described. FIG. 13 is a flowchart showing a control routine of the bypass valve 18 according to this embodiment. This routine is repeatedly executed every predetermined time. The ECU 14 that executes this routine corresponds to the third control means of the present invention.

  In step S301, the ECU 14 reads the output signals of various sensors and detects the operating state of the internal combustion engine 1. Here, the rotational speed of the turbocharger 5 is also detected by a compressor rotational speed sensor disposed adjacent to the compressor 5a.

  In step S302, the ECU 14 determines whether low-pressure EGR gas needs to be introduced into the internal combustion engine 1 from the operating state of the internal combustion engine 1 detected in step S301.

  If it is determined in step S302 that the low pressure EGR gas needs to be introduced into the internal combustion engine 1, the process proceeds to step S303. If it is determined in step S302 that it is not necessary to introduce the low pressure EGR gas into the internal combustion engine 1, the process proceeds to step S307.

  In step S303, the ECU 14 calculates the low-pressure EGR gas flow rate to be introduced from the operating state of the internal combustion engine 1 detected in step S301.

  In step S304, the ECU 14 determines whether or not the low pressure EGR gas flow rate calculated in step S303 is smaller than a third predetermined flow rate.

  If it is determined in step S304 that the low-pressure EGR gas flow rate is smaller than the third predetermined flow rate, the process proceeds to step S305. If it is determined in step S304 that the low-pressure EGR gas flow rate is greater than or equal to the third predetermined flow rate, the process proceeds to step S307.

  In step S305, the ECU 14 determines whether or not the rotational speed of the turbocharger 5 detected in step S301 is lower than a predetermined rotational speed.

  If it is determined in step S305 that the rotational speed of the turbocharger 5 is lower than the predetermined rotational speed, the process proceeds to step S306. If it is determined in step S305 that the rotational speed of the turbocharger 5 is equal to or higher than the predetermined rotational speed, the process proceeds to step S307.

  In step S306, the ECU 14 opens the bypass valve 18. After the processing of this step, this routine is once ended.

  On the other hand, in step S307, the ECU 14 closes the bypass valve 18. After the processing of this step, this routine is once ended.

  By executing the above control routine, the cyclone collecting device 11 can be bypassed by the low pressure EGR gas, and the pressure loss on the path of the low pressure EGR passage 31 can be reduced.

  The exhaust gas recirculation apparatus for an internal combustion engine according to the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention.

1 is a diagram illustrating a schematic configuration of an internal combustion engine and an intake / exhaust system thereof according to Embodiment 1. FIG. It is a figure which shows the low pressure EGR gas flow volume requested | required according to the driving | running state of the internal combustion engine which concerns on Example 1. FIG. It is a figure which shows the relationship between the pressure loss at the time of the low pressure EGR gas flow inflowing into the cyclone type collection device which concerns on Example 1, and low pressure EGR gas passes a cyclone type collection device. It is a figure which shows the relationship between the particle diameter of the foreign material which concerns on Example 1, and the foreign material collection efficiency in a cyclone type collection apparatus. 3 is a flowchart illustrating a control routine for a low-pressure EGR gas flow rate according to the first embodiment. It is a figure which shows schematic structure of the internal combustion engine which concerns on Example 2, and its intake / exhaust system. It is a figure which shows the state which the three-way valve which concerns on Example 2 can take. It is a figure which shows the characteristic of the exhaust temperature which concerns on Example 2, and the amount of water vapor | steam. 7 is a flowchart illustrating an exhaust flow rate control routine according to a second embodiment. It is a figure which shows schematic structure of the internal combustion engine which concerns on Example 3, and its intake-exhaust system. FIG. 6 is a diagram illustrating a region where a bypass valve is opened according to an operating state of an internal combustion engine according to a third embodiment. It is a figure which shows the relationship between the low pressure EGR gas flow volume concerning Example 3, and the pressure loss on the path | route of a low pressure EGR channel | path. 10 is a flowchart illustrating a control routine for a bypass valve according to a third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Intake passage 4 Exhaust passage 5 Turbocharger 5a Compressor 5b Turbine 6 Throttle valve 7 Air flow meter 8 Intercooler 9 Exhaust purification device 10 Exhaust throttle valve 11 Cyclone collection device 12 Flow rate adjustment path 13 Flow rate adjustment valve 14 ECU
15 Crank position sensor 16 Three-way valve 17 Bypass passage 18 Bypass valve 30 Low pressure EGR device 31 Low pressure EGR passage 32 Low pressure EGR valve 33 Low pressure EGR cooler

Claims (4)

A turbocharger having a turbine disposed in an exhaust passage of an internal combustion engine and a compressor disposed in an intake passage of the internal combustion engine;
A low pressure EGR passage that takes in a part of exhaust gas as low pressure EGR gas from the exhaust passage downstream from the turbine and recirculates the low pressure EGR gas to the intake passage upstream from the compressor;
A cyclonic collector that is disposed in the low pressure EGR passage and collects foreign matter in the low pressure EGR gas;
A flow rate adjusting path for allowing the low pressure EGR gas to flow out from the foreign matter collecting portion of the cyclone type collecting device to the exhaust passage downstream of the connection portion with the low pressure EGR passage;
A flow rate adjusting valve that is disposed in the flow rate adjusting path and adjusts the flow rate of the low pressure EGR gas flowing through the flow rate adjusting path;
First control means for controlling the opening and closing of the flow rate adjusting valve according to a pressure loss when the low pressure EGR gas flowing through the low pressure EGR passage passes through the cyclone type collection device;
An exhaust gas recirculation device for an internal combustion engine, comprising: The first control means includes
Threshold for giving priority to the reduction of pressure loss when the low-pressure EGR gas passes through the cyclone-type collecting device rather than the low-pressure EGR gas flow rate flowing through the low-pressure EGR passage through the cyclone-type collecting device. When the flow rate is less than the first predetermined flow rate, the flow rate adjustment valve is closed,
When the flow rate of the low-pressure EGR gas flowing through the low-pressure EGR passage is equal to or higher than the first predetermined flow rate, the cyclone-type trapping device removes foreign matters having a particle size larger than the particle size that affects the intake system of the internal combustion engine. 2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the flow rate adjusting valve is opened at an opening within a range in which collection is possible. A turbocharger having a turbine disposed in an exhaust passage of an internal combustion engine and a compressor disposed in an intake passage of the internal combustion engine;
A catalyst that is disposed in the exhaust passage downstream of the turbine and that is hot when activated;
A cyclone-type collecting device that is disposed in the exhaust passage immediately downstream of the catalyst and collects foreign matter in the exhaust;
A low-pressure EGR passage that takes a part of the exhaust gas as low-pressure EGR gas from the exhaust passage downstream from the cyclonic collector, and recirculates the low-pressure EGR gas to the intake passage upstream from the compressor;
A flow rate adjusting path for exhausting the exhaust gas from the foreign matter collecting portion of the cyclone type collecting device to the exhaust passage downstream of the connection portion with the low pressure EGR passage;
A flow rate adjusting valve that is disposed in the flow rate adjusting path and adjusts an exhaust flow rate flowing through the flow rate adjusting path;
A second control means for controlling the opening and closing of the flow rate adjusting valve according to a pressure loss when the exhaust gas flowing through the exhaust passage passes through the cyclone type collecting device;
An exhaust gas recirculation device for an internal combustion engine, comprising: The second control means includes
A second predetermined flow rate at which the exhaust flow rate through the exhaust passage is a threshold value that prioritizes the reduction of pressure loss when exhaust passes through the cyclone collection device rather than collecting foreign matter with the cyclone collection device. If less, close the flow control valve,
When the exhaust flow rate flowing through the exhaust passage is equal to or higher than the second predetermined flow rate, the cyclone type collecting device collects foreign matters having a particle size larger than the particle size that affects the intake system of the internal combustion engine. 4. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 3, wherein the flow rate adjustment valve is opened at an opening within a range in which the internal combustion engine can be operated.

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