WO2014199442A1

WO2014199442A1 - Condensed water treating apparatus for internal combustion engine

Info

Publication number: WO2014199442A1
Application number: PCT/JP2013/066095
Authority: WO
Inventors: 倫行高田; 橋詰　剛
Original assignee: トヨタ自動車株式会社
Priority date: 2013-06-11
Filing date: 2013-06-11
Publication date: 2014-12-18

Abstract

A condensed water treating apparatus is configured such that the lower the pH of condensed water generated by the exhaust system of an internal combustion engine, the more the amount of condensed water supplied to the intake system of the internal combustion engine is reduced, and such that the lower the engine rotational speed of the internal combustion engine given a constant pH of condensed water, the more the amount of supplied condensed water is reduced.

Description

Condensate treatment device for internal combustion engine

The present invention relates to a condensate treatment apparatus for an internal combustion engine that supplies condensate generated in an exhaust system of the internal combustion engine to an intake system.

As a condensate treatment device for an internal combustion engine, condensate generated by an EGR cooler included in the exhaust system is stored in a condensate water tank, and when the amount of water stored in the condensate water tank reaches a predetermined amount, the condensate is injected into the intake passage Is known (Patent Document 1). As a result of the condensed water supplied to the intake passage being led into the cylinder together with the intake and being vaporized, the combustion temperature is suppressed. As a result, the generation amount of NOx accompanying the combustion is suppressed. In addition, there is Patent Document 2 as a prior art document related to the present invention.

Japanese Patent Laid-Open No. 10-318049 JP 2008-196368 A

Since the condensed water generated in the exhaust system of the internal combustion engine is acidic, if the location where the condensed water is supplied is made of metal, there is a risk that corrosion will occur at that location.

Therefore, an object of the present invention is to provide a condensate treatment apparatus for an internal combustion engine that can suppress the corrosion of the intake system caused by the condensed water supplied to the intake system.

An apparatus for treating condensed water of an internal combustion engine according to the present invention supplies a condensed water tank that stores condensed water generated in an exhaust system of the internal combustion engine, and supplies condensed water stored in the condensed water tank to an intake system of the internal combustion engine. When the pH of the condensed water decreases, the amount of condensed water supplied to the intake system decreases, and when the pH of the condensed water is the same, the condensed water decreases as the engine speed of the internal combustion engine decreases. And a condensate supply control means for controlling the condensate supply mechanism so that the supply amount of the condensate decreases.

The ease of corrosion of the intake system due to the supply of condensed water affects the pH of the condensed water supplied to the intake system and the amount of condensed water remaining in the intake system. That is, since the acidity becomes stronger as the pH of the condensed water is lower, the intake system is easily corroded. Further, the larger the amount of condensed water stayed, the more easily the intake system corrodes. Therefore, in order to suppress corrosion of the intake system, it is desirable to reduce the amount of condensate remaining in the intake system when the pH of the condensed water is low. The lower the engine speed of the internal combustion engine, the lower the flow velocity and flow rate of the intake air flowing through the intake system, and the condensate tends to stay in the intake system.

According to the condensed water treatment apparatus of the present invention, the smaller the pH of the condensed water stored in the condensed water tank, the lower the amount of condensed water supplied. Reduced condensate supply. Therefore, compared with the case where the supply amount of the condensed water having the same pH is not changed according to the engine rotation speed, it is possible to suppress an increase in the retention amount of the condensed water accompanying the decrease in the engine rotation speed. In particular, in a situation where the pH of the condensed water is small and the intake system is likely to corrode, it is possible to suppress an increase in the amount of condensate water retention due to a decrease in the engine rotation speed, and thus corrosion of the intake system can be suppressed.

As one aspect of the condensed water treatment apparatus of the present invention, the condensed water supply control means prohibits the supply of condensed water to the intake system when the pH of the condensed water stored in the condensed water tank is below a lower limit value. The condensed water supply mechanism may be controlled as described above. According to this aspect, it is possible to avoid the corrosion of the intake system from being accelerated by supplying the condensed water to the intake system in a situation where the acidity of the condensed water is so high that it cannot be dealt with by adjusting the supply amount of the condensed water.

As one aspect of the condensate treatment apparatus of the present invention, the exhaust system of the internal combustion engine includes an EGR device that introduces EGR gas that is part of exhaust gas into the intake system, and the internal combustion engine includes An EGR control means may be provided for changing the amount of EGR gas introduced into the intake system according to the amount of condensed water supplied to the intake system. The supply of EGR gas to the intake system is common to the supply of condensed water to the intake system in that the combustion temperature of the internal combustion engine is suppressed. According to this aspect, the effect of suppressing the combustion temperature of the internal combustion engine can be controlled by changing the amount of EGR gas introduced according to the amount of condensed water supplied.

In this aspect, the EGR control means adjusts the amount of condensed water supplied to the intake system such that the smaller the amount of condensed water supplied to the intake system, the larger the amount of EGR gas introduced into the intake system. Accordingly, the amount of EGR gas introduced into the intake system may be changed. In this case, since the amount of EGR gas introduced increases as the amount of condensed water supplied decreases, it is possible to suppress an excess or deficiency in the suppression effect of the combustion temperature of the internal combustion engine. Thereby, since the fluctuation | variation of the production amount of NOx is suppressed, the stable exhaust performance is realizable.

The figure which showed the whole structure of the internal combustion engine to which the condensed water processing apparatus which concerns on one form of this invention was applied. 6 is a flowchart illustrating an example of a control routine according to an embodiment of the present invention. The conceptual diagram which showed the structure of the calculation map which calculates the amount of condensed water supply, and the amount of EGR.

As shown in FIG. 1, the internal combustion engine 1 is configured as an in-line four-cylinder type diesel engine in which four cylinders 2 are arranged in one direction. The internal combustion engine 1 is mounted, for example, as a driving power source for automobiles. In the internal combustion engine 1, a fuel injection valve 3 is provided for each cylinder 2 in order to supply fuel into each cylinder 2. Each fuel injection valve 3 is connected to a common rail 5 to which fuel is pumped, and fuel is supplied to each fuel injection valve 3 via the common rail 5. An intake passage 10 and an exhaust passage 11 are connected to each cylinder 2. The air guided to the intake passage 10 is filled in each cylinder 2 in the intake stroke. The fuel injected from the fuel injection valve 3 into the cylinder 2 is self-ignited and combusted in the compression stroke. The exhaust after combustion is guided to the exhaust passage 11. The exhaust gas led to the exhaust passage 11 is purified by the NOx occlusion reduction type exhaust gas purification device 12 and then released to the atmosphere. A turbine 15 a of the turbocharger 15 is provided upstream of the exhaust purification device 12. The intake passage 10 is provided with a compressor 15b of the turbocharger 15, an intercooler 16 that cools the air pressurized by the compressor 15b, and a throttle valve 17 that adjusts the flow rate of the intake air.

As shown in FIG. 1, the internal combustion engine 1 is provided with an EGR device 20 that performs EGR (Exhaust Gas Recirculation) to recirculate a part of the exhaust to the intake system in order to reduce nitrogen oxides (NOx) and improve fuel efficiency. ing. The EGR device 20 adjusts the flow rate of an EGR passage 21 that connects the exhaust passage 11 and the intake passage 10, an EGR cooler 22 that cools the exhaust gas in the EGR passage 21, and the exhaust gas (EGR gas) that is led to the intake passage 10. EGR valve 23 is provided. The EGR passage 21 has an end on the exhaust side that opens to the downstream side of the exhaust purification device 12, and an end on the intake side that opens to the upstream side of the compressor 15b. As is well known, the EGR cooler 22 uses the cooling water of the engine 1 as a refrigerant, and lowers the temperature of the exhaust gas (EGR gas) by exchanging heat between the refrigerant and the warm exhaust gas. Since the water contained in the EGR gas condenses as the temperature of the EGR gas decreases, condensed water is generated in the EGR cooler 22.

As shown in FIG. 1, a condensate treatment device 30 is provided in the internal combustion engine 1 in order to collect and treat the condensate generated by the EGR cooler 22. The condensed water treatment device 30 includes a condensed water tank 31 that stores condensed water CW, and a condensed water supply mechanism 32 that supplies the condensed water CW stored in the condensed water tank 31 to the intake system of the internal combustion engine 1. . The condensed water tank 31 is provided with a pH sensor 34 that outputs a signal corresponding to the pH of the stored condensed water CW. The condensed water supply mechanism 32 has a condensed water passage 35 that connects the condensed water tank 31 and the intake passage 10. The condensed water passage 35 is provided with an electric pump 36 and an injection valve 37 for injecting and supplying condensed water pressurized by the pump 36 into the intake passage 10. By controlling the valve opening period of the injection valve 37, the supply amount of condensed water can be controlled.

The internal combustion engine 1 is provided with an engine control unit (ECU) 40 configured as a computer for controlling each part of the internal combustion engine 1. The ECU 40 is used for controlling the EGR device 20 and the condensed water treatment device 30 in addition to performing the main operation control for controlling the fuel injection amount and the injection timing by the fuel injection valve 3. The ECU 40 receives signals from a number of sensors that detect various physical quantities in order to grasp the operating state of the internal combustion engine 1. For example, as a sensor related to the present invention, a crank angle sensor 41 that outputs a signal corresponding to the crank angle of the engine 1 and a signal corresponding to the depression amount (accelerator opening) of an accelerator pedal 38 provided in the engine 1 are used. An accelerator opening sensor 42 and the like for output are provided in the engine 1, and output signals from these sensors are input to the ECU 40. The output signal of the pH sensor 34 described above is also input to the ECU 40.

2 is held in the ECU 40, read out in a timely manner, and repeatedly executed at a predetermined calculation interval. In step S <b> 1, the ECU 40 acquires the engine rotation speed of the internal combustion engine 1 based on the output signal of the crank angle sensor 41. In step S <b> 2, the ECU 40 acquires the pH of the condensed water CW stored in the condensed water tank 31 based on the output signal of the pH sensor 34.

In step S3, the ECU 30 determines whether the pH of the condensed water is equal to or lower than the lower limit value. This lower limit value is set to 2, for example, as a value having a strong acidity that cannot be dealt with by adjusting the supply amount of condensed water. If the pH of the condensed water exceeds the lower limit value, the process proceeds to step S4. If the pH of the condensed water is equal to or lower than the lower limit value, the process proceeds to step S6, and the ECU 40 prohibits the supply of the condensed water to the intake system.

In step S4, the ECU 40 calculates the amount of condensed water supplied to the intake system of the internal combustion engine 1. The condensed water supply amount is calculated based on the pH of the condensed water and the engine speed. Specifically, as shown in FIG. 3, a calculation map M <b> 1 that gives the condensed water supply amount with the pH of the condensed water and the engine rotation speed as variables is stored in the ECU 40 in advance. Then, the ECU 40 refers to the calculation map M1, and the condensed water supply amount is calculated by specifying the condensed water supply amount corresponding to the engine rotation speed acquired in step S1 and the condensed water pH acquired in step S2. The The calculation map M1 indicates that the condensed water supply amount, pH, and engine rotation are such that the condensed water supply amount decreases as the condensed water pH decreases, and the condensed pH supply amount decreases as the engine rotational speed decreases. Speed correlation is set. In FIG. 3, a calculation map M2 for calculating the EGR amount so as to correspond to the calculation map M1 is shown for convenience, and a detailed description of the calculation map M2 will be described later. In step S5, the ECU 40 controls the valve opening period of the injection valve 37 so that the condensed water corresponding to the condensed water supply amount calculated in step S4 is injected into the intake passage 10.

In step S7, the ECU 40 calculates an EGR amount that is an amount of EGR gas introduced into the internal combustion engine 1. The EGR amount is calculated according to the condensed water supply amount. Specifically, based on the calculation map M2 of FIG. 3, the ECU 40 calculates the EGR amount so that the EGR amount increases as the condensed water supply amount decreases. The supply of EGR gas to the intake system is common to the supply of condensed water to the intake system in that the combustion temperature of the internal combustion engine 1 is suppressed. Therefore, the ECU 40 calculates the condensed water supply amount and the EGR amount based on the two calculation maps M1 and M2 shown in FIG. Fluctuation can be suppressed. In step S8, the ECU 40 controls the valve opening period of the EGR valve 23 so that EGR gas corresponding to the EGR amount calculated in step S7 is introduced into the intake system.

As shown in FIG. 3, the region A having a pH of 7 or more is neutral, and there is no possibility of accelerating corrosion of the intake system by supplying condensed water. For this reason, it is possible to actively supply condensed water while minimizing the amount of EGR. The region B having a pH of 4 to 7 is acidic but not at a level that promotes corrosion, so that condensed water can be actively supplied. However, since the influence on corrosion increases as the pH decreases, the amount of condensed water supplied decreases as the pH decreases. In this case, the EGR amount is increased as the condensed water supply amount decreases in order to maintain the NOx generation suppressing effect. Even in the region C where the pH is 4 to the lower limit value x, the amount of condensed water supplied decreases as the pH decreases. However, since the region C is strongly acidic, if the condensed water injected into the intake passage 10 stays in the intake passage 10, corrosion of the intake system may be promoted. Therefore, when the engine rotation speed that can reduce the condensate retention amount is high even at a pH showing strong acidity, the condensate supply amount is increased. In other words, when the engine speed is low, the amount of condensed water staying increases and corrosion of the intake system may be promoted. Therefore, in the strongly acidic region C, the lower the engine speed, the more condensed water is supplied. Reduce the amount. In the region D where the pH is lower than the lower limit value x, the supply of condensed water to the intake system is prohibited, and the generation of NOx is suppressed only by EGR.

According to the above control routine, it is possible to suppress an increase in the amount of condensate water retention due to a decrease in engine rotation speed in a situation where the pH of the condensate water is small and the intake system is easily corroded as in the region C of FIG. Therefore, corrosion of the intake system can be suppressed. The ECU 40 functions as the condensed water supply control means and the EGR control means according to the present invention by executing the control routine of FIG.

The present invention is not limited to the above embodiment, and can be implemented in various forms within the scope of the gist of the present invention. Although the condensed water produced | generated by the EGR cooler is processed, it is also possible to implement this invention for the treatment of the condensed water produced | generated by the exhaust passage. That is, the present invention can be used to treat condensed water generated in any of the exhaust systems of an internal combustion engine.

In the above embodiment, the pH of the condensed water is obtained by measuring the pH of the condensed water using a pH sensor provided in the condensed water tank, but using the pH sensor is merely an example of obtaining the pH of the condensed water. For example, the NOx concentration in the exhaust gas can be estimated from the operating conditions of the internal combustion engine, and the pH of the condensed water can be estimated and acquired based on the NOx concentration. The pH used for the control is not limited to the pH of the condensed water stored in the condensed water tank. If the condensed water generated in the exhaust system is present in the path until the condensed water is supplied to the intake system, it can be used for control. For example, the pH of the condensed water in the condensed water passage 35 shown in FIG. 1 may be used for control.

Although the internal combustion engine 1 of the said form is comprised as a diesel engine, the engine used as the application object of this invention is not restricted to a diesel engine. Therefore, the present invention can be implemented in a spark ignition type internal combustion engine. Further, application of the present invention is not affected by the presence or absence of the turbocharger. Therefore, the present invention can also be applied to a naturally aspirated internal combustion engine. When the present invention is applied to a naturally aspirated internal combustion engine, the condensed water can be supplied to the intake system using the negative pressure in the intake passage, so that the pump for pressurizing the condensed water as in the above embodiment can be omitted.

Claims

A condensed water tank for storing condensed water generated in the exhaust system of the internal combustion engine;
A condensed water supply mechanism for supplying condensed water stored in the condensed water tank to an intake system of the internal combustion engine;
As the condensed water pH decreases, the amount of condensed water supplied to the intake system decreases, and when the condensed water has the same pH, the amount of condensed water decreases as the engine speed of the internal combustion engine decreases. And condensate supply control means for controlling the condensate supply mechanism,
An apparatus for treating condensed water of an internal combustion engine.
The condensed water supply control means controls the condensed water supply mechanism so that the supply of condensed water to the intake system is prohibited when the pH of the condensed water stored in the condensed water tank is below a lower limit value. The condensed water treatment apparatus according to claim 1.
The exhaust system of the internal combustion engine includes an EGR device that introduces EGR gas, which is part of exhaust gas, into the intake system.
The condensed water treatment apparatus according to claim 1 or 2, wherein the internal combustion engine is provided with an EGR control means for changing an introduction amount of EGR gas into the intake system in accordance with a supply amount of condensed water to the intake system. .
The EGR control means determines the intake air in accordance with the amount of condensed water supplied to the intake system such that the smaller the amount of condensed water supplied to the intake system, the larger the amount of EGR gas introduced into the intake system. The condensate treatment apparatus according to claim 3, wherein the amount of EGR gas introduced into the system is changed.