JP2018062915A - Engine condensate water prevention device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a compressor of a turbocharger from risks of corrosion and damage in a manner that prevents condensate water from being generated along with operation of a low pressure loop EGR device.SOLUTION: A condensate water prevention device of an engine 1 comprises: an EGR device 12 which extracts exhaust gas 8 from an exhaust pipe 10 at a downstream side of a turbine 2b of a turbocharger 2 as low pressure EGR gas 8a and circulates the same into an intake pipe 5 at an upstream side of a compressor 2a of the turbocharger 2; and a water-cooled intercooler 6 which cools intake air 4 supercharged by the compressor 2a. A housing of the compressor 2a has a water jacket 26 and at least cooling water 22, passing through the intercooler 6 when a low pressure loop EGR device 12 is operated, is circulated through the water jacket 26.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine condensate suppression device.

  Conventionally, in an automobile engine or the like, a part of exhaust gas is extracted from the exhaust side and returned to the intake side, and combustion of fuel in the engine is suppressed by the exhaust gas returned to the intake side to lower the combustion temperature. So-called exhaust gas recirculation (EGR) is performed to reduce the generation of NOx (nitrogen oxide), and when this type of exhaust gas recirculation is performed, an exhaust manifold is used. An appropriate position of the exhaust passage extending from the exhaust pipe to the exhaust pipe and an appropriate position of the intake passage extending from the intake pipe to the intake manifold are connected by an EGR pipe, and the exhaust gas is recirculated through the EGR pipe.

  In general, in an engine equipped with a turbocharger, a high-temperature and high-pressure exhaust gas extracted from the exhaust manifold and recirculated to the inlet of the intake manifold is called a high-pressure loop EGR device, and the exhaust pipe downstream of the turbocharger turbine. A low-pressure loop EGR device that extracts low-temperature and low-pressure exhaust gas from the exhaust gas and recirculates it to the intake pipe upstream of the compressor of the turbocharger is called a low-pressure loop EGR device.

  In both the high-pressure loop and low-pressure loop EGR devices, a water-cooled EGR cooler is installed in the middle of the EGR pipe to cool the exhaust gas, and thus the exhaust gas is water-cooled and recirculated. Then, the temperature of the exhaust gas is lowered and the volume thereof is reduced, so that the combustion temperature can be lowered and the generation of NOx can be effectively reduced without significantly reducing the output of the engine.

  In addition, as prior art document information related to this type of engine condensate suppression device, there is the following Patent Document 1 or the like.

Japanese Patent Application Laid-Open No. 2014-231762

  However, in the EGR device of the low pressure loop as described above, the particulate filter is located near the outlet of the exhaust pipe so that the pressure is greatly reduced by driving the turbine, and the intake passage is not contaminated with soot or the like. Since the exhaust pipe is returned to the intake pipe upstream of the compressor through a long EGR pipe, the temperature of the exhaust gas is likely to drop significantly before the exhaust pipe is returned to the intake pipe. If the temperature drops to the following, or if the wall temperature in contact with the recirculated exhaust gas is lower than the dew point, condensed water is generated due to condensation, which may cause corrosion of the turbocharger compressor and housing. There is a risk that the blades of the compressor may be damaged by suction of ice pieces formed by freezing the condensed water.

  The present invention has been made in view of the above circumstances, and aims to protect the turbocharger compressor from the possibility of corrosion and damage by suppressing the generation of condensed water caused by the operation of the EGR device of the low pressure loop. To do.

  The present invention cools the intake air supercharged by the compressor and the low pressure loop EGR device that extracts exhaust gas from the exhaust pipe downstream of the turbine of the turbocharger and recirculates it to the intake pipe upstream of the compressor of the turbocharger. An apparatus for suppressing condensed water of an engine comprising a water-cooled intercooler, wherein a water jacket is provided in a housing of the compressor, and at least when the EGR device of the low-pressure loop is operated, cooling water passing through the intercooler is supplied to the water jacket It is characterized by being configured to circulate via

  Thus, in this way, at least in a state where the EGR device of the low-pressure loop is operating, the cooling water that has passed through the intercooler circulates through the water jacket, so that the compressor housing is moderately separated from the intercooler. The wall surface temperature in the housing is maintained higher than the dew point and the generation of condensed water is suppressed.

  Here, the water-cooled intercooler has a dedicated water-cooling system that is independent from the engine water-cooling system, and the temperature of the cooling water that has passed through the water-cooled intercooler is the temperature of the cooling water that has passed through the engine. The temperature is about 45 to 50 ° C., which is significantly lower than (about 80 to 85 ° C.), which is sufficiently higher than the dew point of water vapor in the recirculated exhaust gas, but not higher than necessary. Therefore, there is no need to exert an adverse effect that causes a significant decrease in compressor efficiency.

  Further, since the water jacket itself in the compressor housing has a heat retaining effect, the possibility that condensed water is generated from the exhaust gas remaining in the compressor while the vehicle is stopped is greatly suppressed.

  Further, in carrying out the present invention more specifically, a switching valve is provided in the middle of a path for leading the cooling water from the intercooler to the sub-radiator, and the flow of the cooling water toward the sub-radiator is flowed toward the water jacket by the switching valve. Further, it is preferable that the EGR device of the low-pressure loop is in an operating state and the cooling water directed to the sub-radiator is switched by the switching valve when it is determined that the compressor inlet wall temperature is lower than the set temperature. It is preferable to provide a control device for switching the flow to the flow toward the water jacket.

  According to the condensed water suppression device for an engine of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the first aspect of the present invention, since the generation of condensed water due to the operation of the EGR device in the low pressure loop can be suppressed, the corrosion of the compressor and the housing of the turbocharger due to the condensed water. In addition, it is possible to avoid damage to the compressor blades and the like due to suction of ice pieces formed by freezing of condensed water, and it is possible to avoid excessive heating of the compressor housing. Further, by providing the water jacket itself with a heat retaining effect, the possibility that condensed water is generated from the exhaust gas remaining in the compressor during stopping can be greatly suppressed.

  (II) According to the second and third aspects of the present invention, the switching valve is switched at least under the condition that the EGR device of the low-pressure loop is operating, and the cooling water is circulated to the water jacket. When the engine is warmed up and the EGR device in the low-pressure loop is deactivated, the cooling water is directly flowed from the intercooler to the sub-radiator. Driving loss can be reduced.

It is the schematic which shows an example of the form which implements this invention. It is a flowchart which shows the specific control procedure in the control apparatus of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an example of an embodiment for carrying out the present invention. In the example shown here, an engine 1 includes a turbocharger 2, and intake air 4 guided from an air cleaner 3 passes through an intake pipe 5. The intake air 4 sent to the compressor 2 a of the turbocharger 2 and pressurized by the compressor 2 a is sent to the intercooler 6 to be cooled, and the intake air 4 is further guided from the intercooler 6 to the intake manifold 7. The engine 1 is distributed to each cylinder.

  Further, the exhaust gas 8 discharged from each cylinder of the engine 1 is sent to the turbine 2b of the turbocharger 2 through the exhaust manifold 9, and the exhaust gas 8 driving the turbine 2b goes out of the vehicle through the exhaust pipe 10. In the middle of the exhaust pipe 10, a particulate filter 11 that collects particulates (Particulate Matter) while passing the exhaust gas 8 is provided.

  In the engine 1, a part of the exhaust gas 8 is extracted as low-pressure EGR gas 8 a from the downstream side of the particulate filter 11 and recirculated to the intake pipe 5 upstream of the compressor 2 a of the turbocharger 2. A low-pressure loop EGR device 12 and a high-pressure loop EGR device 13 that extracts a part of the exhaust gas 8 from the exhaust manifold 9 as a high-pressure EGR gas 8 b and recirculates in the vicinity of the inlet of the intake manifold 7 are provided.

  Each of the low-pressure loop EGR device 12 and the high-pressure loop EGR device 13 includes EGR valves 14 and 15 for adjusting the recirculation amount of the exhaust gas 8, low-pressure EGR gas 8a and high-pressure EGR gas to be recirculated. EGR coolers 16 and 17 for cooling 8b are provided, and the EGR coolers 16 and 17 exchange heat between the cooling water, the low-pressure EGR gas 8a, and the high-pressure EGR gas 8b, thereby reducing the low-pressure EGR gas 8a and the high-pressure EGR gas. By reducing the temperature of 8b and reducing its volume, the combustion temperature can be lowered and the generation of NOx can be effectively reduced without significantly reducing the output of the engine 1.

  The opening degree of each of the EGR valves 14 and 15 is controlled by opening degree command signals 14a and 15a from a control device 18 constituting an engine control computer (ECU: Electronic Control Unit). Appropriate control is executed so that an effective NOx reduction rate can be obtained within a range that does not cause a combustion failure based on the operation state grasped from the load, the rotational speed, and the like.

  Here, in this embodiment, a water-cooled type is adopted for the intercooler 6, and the intercooler 6 and a dedicated sub-radiator 19 are interposed between the feed pipe 20 and the return pipe 21. A cooling water 22 is circulated, a thermostat 23 is provided in the middle of the feed pipe 20, a water pump 24 is provided in the middle of the return pipe 21, and the temperature of the cooling water 22 is a specified water temperature. In the following cases, the cooling water 22 can be guided to the inlet side of the water pump 24 by bypassing the sub radiator 19 via the bypass pipe 25 by the action of the thermostat 23.

  Moreover, a water jacket 26 is provided in the housing of the compressor 2 a of the turbocharger 2, and a connection pipe 28 is provided between the switching valve 27 provided on the upstream side of the thermostat 23 in the feed pipe 20 and the water jacket 26. The switching valve 27 can switch the flow of the cooling water 22 toward the sub-radiator 19 to the flow toward the water jacket 26.

  Further, the switching valve 27 and the thermostat 23 in the feed pipe 20 are connected by a communication pipe 29, and the cooling water 22 passing through the water jacket 26 is connected to the switching valve 27 via the communication pipe 29. It is returned between the thermostat 23.

  The water jacket 26 provided in the housing of the compressor 2a may be integrally formed in the housing of the compressor 2a, or may be assembled as a separate part on the outer periphery of the housing of the compressor 2a.

  The switching operation of the switching valve 27 is controlled by the control device 18 via a control signal 27a. In the control device 18, the switching operation is performed according to the control procedure shown in the flowchart of FIG. The valve 27 is switched to either the compressor 2a side or the sub-radiator 19 side.

  That is, when the control of the switching valve 27 is started, first in step S1, it is determined whether or not the temperature of the cooling water (not shown) of the engine 1 monitored by the control device 18 exceeds the specified water temperature. The determination is repeated and the determination is repeated via step S2 until the temperature of the cooling water of the engine 1 exceeds the specified water temperature, and the switching valve 27 is switched to the compressor 2a side.

  And when it determines with the temperature of the cooling water (not shown) of the engine 1 exceeding the regulation water temperature by step S1, it progresses to step S3 and the EGR apparatus 12 of a low voltage | pressure loop is in an operation state. Only when the EGR device 12 in the low-pressure loop is in an operating state, the routine proceeds to step S4, where it is determined whether or not the inlet wall temperature of the compressor 2a is below the set temperature. When the inlet wall temperature is below the set temperature, the routine proceeds to step S5, where the switching valve 27 is switched to the compressor 2a side.

  Here, since the control device 18 is responsible for controlling the opening degree of the EGR valve 14 in the EGR device 12 in the low pressure loop, the EGR device 12 in the low pressure loop is operated unless the EGR valve 14 is controlled to be closed. The inlet wall temperature of the compressor 2a can be estimated thermodynamically by actually measuring the inlet intake temperature and the intake flow rate of the compressor 2a (other methods can also be used) ).

  On the other hand, if it is determined in step S3 that the EGR device 12 in the low-pressure loop is not in operation, or if it is determined in step S4 that the inlet wall temperature of the compressor 2a is not below the set temperature, Proceeding to step S6, the switching valve 27 is switched to the sub-radiator 19 side.

  Here, the set temperature used in step S4 may basically be set near the dew point temperature, but may be corrected as appropriate in consideration of the EGR rate, atmospheric conditions, intake air temperature and pressure, and the like. good.

  Note that the determination in step S1 is to determine whether or not the current engine 1 is in a situation where priority should be given to warm-up. Sometimes, the cooling water 22 is circulated through the bypass pipe 25 without passing through the sub-radiator 19 by the action of the thermostat 23, thereby warming the cooling water 22 at an early stage and using the warmed cooling water 22 to the water of the compressor 2a. It circulates to the jacket 26 so that the warm-up of the engine 1 is accelerated.

  Generally, when the engine 1 is in a situation where priority should be given to warm-up, the low-pressure loop EGR device 12 will be maintained in an inactive state. It is possible to operate the EGR device 12 earlier, and it is possible to contribute to the improvement of NOx reduction performance.

  Thus, in this way, the cooling water 22 that has passed through the intercooler 6 circulates through the water jacket 26 in a state where the warm-up of the engine 1 is completed and the EGR device 12 of the low-pressure loop is operating. As a result, the housing of the compressor 2a is warmed by the cooling water 22 having an appropriate temperature from the intercooler 6, the wall surface temperature in the housing is maintained higher than the dew point, and the generation of condensed water is suppressed.

  Here, the water-cooled intercooler 6 is independently provided with a dedicated water-cooling system different from the water-cooling system of the engine 1, and the temperature of the cooling water 22 that has passed through the water-cooled intercooler 6 depends on the temperature of the engine 1. The temperature is about 45 to 50 ° C., which is significantly lower than the temperature of the cooling water 22 that has passed (about 80 to 85 ° C.), and is higher than the dew point of water vapor in the recirculated exhaust gas 8 (low pressure EGR gas 8a). Although it is sufficiently high but at a moderate temperature that is not higher than necessary, it does not have to have an adverse effect that causes a significant reduction in compressor efficiency.

  Further, in carrying out the present invention more specifically, a switching valve 27 is provided in the middle of a path for guiding the cooling water 22 from the intercooler 6 to the sub-radiator 19, and the cooling water 22 directed toward the sub-radiator 19 by the switching valve 27 is provided. The flow may be switched to the flow toward the water jacket 26, and it is further determined that the EGR device 12 of the low-pressure loop is in an operating state and the inlet wall temperature of the compressor 2a is lower than the set temperature. It is preferable to provide a control device 18 that switches the flow of the cooling water 22 toward the sub-radiator 19 to the flow toward the water jacket 26 from time to time by the switching valve 27.

  Therefore, according to the above embodiment, since the generation of condensed water due to the operation of the EGR device 12 in the low-pressure loop can be suppressed, corrosion of the compressor 2a and the housing of the turbocharger 2 due to the condensed water and the condensed water are prevented. Damage to the blades and the like of the compressor 2a due to suction of ice pieces that have been frozen can be avoided as much as possible, and a significant reduction in compressor efficiency can also be avoided.

  In addition, the switching valve 27 is switched to circulate the cooling water 22 to the water jacket 26 only under the condition that the EGR device 12 of the low-pressure loop is operating, and the housing of the compressor 2a is warmed to suppress the generation of condensed water. Under the condition that the low pressure loop EGR device 12 is inactive after the warm-up of the engine 1 is completed, the cooling water 22 is directly flowed from the intercooler 6 to the sub radiator 19 to reduce the driving loss of the water pump 24. be able to.

  It should be noted that the condensate water suppression device for an engine of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

2 Turbocharger 2a Compressor 2b Turbine 4 Intake 5 Intake pipe 6 Intercooler 8 Exhaust gas 10 Exhaust pipe 12 Low pressure loop EGR device 18 Control device 19 Sub-radiator 22 Cooling water 26 Water jacket 27 Switching valve

Claims (3)

  A low-pressure loop EGR device that extracts exhaust gas from an exhaust pipe downstream from a turbocharger turbine and recirculates the exhaust gas to an intake pipe upstream from the turbocharger compressor, and a water-cooled intercooler that cools the intake air supercharged by the compressor. A condensate suppression device for an engine comprising a cooler, wherein a water jacket is provided in a housing of the compressor, and at least when the EGR device of the low-pressure loop is operated, cooling water that has passed through the intercooler passes through the water jacket. A condensate water suppression device for an engine characterized by being configured to circulate.   A switching valve is provided in the middle of a path for leading the cooling water from the intercooler to the sub-radiator, and the switching valve is configured to be able to switch the flow of the cooling water toward the sub-radiator to the flow toward the water jacket. The condensed water suppression device for an engine according to 1.   A control device that switches the flow of cooling water toward the sub-radiator to the flow toward the water jacket by a switching valve when it is determined that the EGR device of the low-pressure loop is in an operating state and the inlet wall temperature of the compressor is below the set temperature. The condensed water suppression device for an engine according to claim 2, comprising:

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