Condensed-water treatment method for internal combustion engine and device therefor

Abstract

In the present invention, an internal combustion engine (2) for driving a power-generation motor generator (1) in a series hybrid vehicle has a turbocharger (12). A water-cooled intercooler (26) for cooling supercharged intake air is disposed downstream of a throttle valve (22). If it was determined that condensed water has accumulated in the intercooler (26), the degree of opening of the throttle valve (22) is reduced, according to the temperature in the intercooler (26), to a target throttle-valve opening degree at which reduced-pressure boiling can occur, and motoring is carried out by the power-generation motor generator (1). The reduced-pressure boiling of the condensed water occurs as a result of the reduced-pressure treatment, and the amount of condensed water is thereby reduced.

Description

Method and device for treating condensed water from an internal combustion engine

[0001] The present invention relates to a method and apparatus for treating condensed water accumulated in an intercooler that cools the intake air of an internal combustion engine.

[0002] In an intercooler, which cools the intake air of an internal combustion engine by exchanging heat with coolant or outside air, condensation can occur and accumulate inside the intercooler as the temperature of the intake air containing water vapor drops. For example, when the internal combustion engine suddenly accelerates, excessive amounts of condensed water that has accumulated inside the intercooler can flow into the combustion chamber, causing deterioration of combustion.

[0003] Patent Document 1 discloses a configuration in which condensed water introduction passages are provided to guide condensed water collected at the bottom of an intercooler to each cylinder so that the condensed water is evenly distributed among the cylinders.

[0004] However, the technology of Patent Document 1 merely distributes condensed water evenly among a plurality of cylinders, and does not attempt to reduce the amount of condensed water as much as possible.

[0005] JP 2016-84716 A

[0006] This invention is a method for treating condensed water in an internal combustion engine that is equipped with an intercooler downstream of a throttle valve and is used to drive a generator in a hybrid vehicle that runs on motor output, and which determines whether condensed water has formed in the intercooler, and when it is determined that condensed water has formed, obtains the temperature of the intercooler, calculates a target intercooler pressure at which the intercooler temperature will exceed the boiling point of water, controls the opening of the throttle valve to an opening corresponding to this target intercooler pressure, and performs pressure reduction treatment by rotating the internal combustion engine.

[0007] In a configuration where an intercooler is located downstream of a throttle valve, the pressure drop caused by narrowing the throttle valve opening affects the condensed water inside the intercooler. Furthermore, in a hybrid vehicle, the throttle valve opening can be narrowed regardless of the vehicle's driving conditions. Therefore, when condensed water forms in the intercooler, narrowing the throttle valve opening reduces the pressure inside the intercooler, promoting the boiling and evaporation of the condensed water.

[0008] In this way, according to the present invention, the condensed water inside the intercooler can be treated by reducing the pressure by reducing the opening of the throttle valve.

[0009] The present invention relates to a series hybrid vehicle, an internal combustion engine, and a method for manufacturing the same.

[0010] An embodiment of the present invention will now be described in detail with reference to the drawings. FIG. 1 schematically illustrates the configuration of a series hybrid vehicle as an example to which the present invention is applied. The series hybrid vehicle includes a power-generating motor / generator 1 that operates primarily as a generator, an internal combustion engine 2 that serves as a power-generating internal combustion engine and drives the power-generating motor / generator 1 in response to a power demand, a traction motor / generator 4 that operates primarily as a motor to drive drive wheels 3, and a battery 5 that stores the generated power. The power obtained by the internal combustion engine 2 driving the power-generating motor / generator 1 is stored in the battery 5 via an inverter device (not shown). The traction motor / generator 4 is driven and controlled using the power from the battery 5. The power generated by the traction motor / generator 4 during regeneration is stored in the battery 5 via an inverter device (not shown).

[0011] The operation of the motor generators 1 and 4, the charging and discharging of the battery 5, and the operation of the internal combustion engine 2 are controlled by a controller 6. The controller 6 is composed of multiple controllers connected to each other so that they can communicate with each other, such as a motor controller 7 that controls the motor generators 1 and 4, an engine controller 8 that controls the internal combustion engine 2, and a battery controller 9 that manages the battery 5. Information such as the accelerator pedal position and vehicle speed (not shown) is input to the controller 6. The battery controller 9 also calculates the SOC of the battery 5 based on the voltage and current of the battery 5. When the SOC drops to a predetermined lower limit level, the internal combustion engine 2 is started via the engine controller 8 to generate electricity. Such a series hybrid vehicle has two driving modes: an EV mode in which the vehicle runs on power from the battery 5 without combustion operation of the internal combustion engine 2, and an HEV mode in which the vehicle runs while generating electricity through combustion operation of the internal combustion engine 2.

[0012] 2 shows the system configuration of an internal combustion engine 2. This internal combustion engine 2 is a four-stroke, spark-ignition internal combustion engine (a so-called gasoline engine) equipped with a turbocharger 12. A pair of intake valves 14 and a pair of exhaust valves 15 are disposed on the ceiling wall of each cylinder 13, and an ignition plug 16 is disposed in the center surrounded by these intake valves 14 and exhaust valves 15. A fuel injection valve 17 is disposed below the intake valve 14 to supply fuel into the cylinder 13. The ignition timing of the spark plug 16 and the injection timing and injection amount of fuel by the fuel injection valve 17 are controlled by an engine controller 8. A combustion chamber 10 is formed by a piston 11 that slides up and down within the cylinder 13. Note that the internal combustion engine 2 may be configured as a port injection type in which fuel is injected toward an intake port.

[0013] An electronically controlled throttle valve 22, the opening of which is controlled by a control signal from the engine controller 8, is provided in the intake passage 21. The compressor 12a of the turbocharger 12 is located upstream of the throttle valve 22, and an air flow meter 24 that detects the amount of intake air and an air cleaner 25 are disposed upstream of the compressor 12a. A recirculation valve 27 is also provided to communicate the discharge side and intake side of the compressor 12a.

[0014] A water-cooled intercooler 26 is provided in the intake passage 21 downstream of the compressor 12a to cool the high-temperature, high-pressure intake air. In particular, the intercooler 26 is located downstream of the throttle valve 22. In one embodiment, the intercooler 26 is elongated in the cylinder row direction and is substantially integrated with the intake air collector. Coolant flows through the intercooler 26 via a coolant inlet passage 28 and a coolant outlet passage 29, exchanging heat with the high-temperature, high-pressure intake air. An intercooler water temperature sensor 30 is provided in the coolant inlet passage 28 to detect the temperature of the coolant introduced into the intercooler 26. An intake air temperature sensor 31 and an intake air pressure sensor 32 are provided in the intake passage 21 on the outlet side of the intercooler 26 to detect the temperature and pressure of the intake air after passing through the intercooler 26, respectively.

[0015] The cooling water flowing through the intercooler 26 may be part of a cooling water system that flows through a water jacket in the main body of the internal combustion engine 2, or may be in a cooling water system separate from the cooling water that flows through the water jacket.

[0016] The turbine 12b of the turbocharger 12 is located in the exhaust passage 40, and a pre-catalytic device 41 and a main catalytic device 42 for purifying exhaust gas are disposed downstream of the turbine 12b. The pre-catalytic device 41 is disposed at the outlet of the turbine 12b, and the main catalytic device 42 is disposed under the floor of the vehicle. An air-fuel ratio sensor 43 for detecting the air-fuel ratio is disposed upstream of the turbine 12b in the exhaust passage 40. The turbine 12b is equipped with a wastegate valve 44 that bypasses a portion of the exhaust gas in accordance with the boost pressure in order to control the boost pressure. The wastegate valve 44 is, for example, an electrically operated valve whose opening is controlled by the engine controller 8.

[0017] The exhaust gas recirculation system includes an exhaust gas recirculation passage 45 that recirculates exhaust gas as EGR gas from downstream of the turbine 12b to a position upstream of the compressor 12a, an EGR gas cooler 47 that cools the EGR gas, for example, a water-cooled type, and an EGR valve 48 that controls the EGR gas flow rate (in other words, the EGR rate), as an exhaust gas recirculation device that recirculates a portion of the exhaust gas from the exhaust passage 40 to the intake passage 21. Note that a high-pressure exhaust gas recirculation system that recirculates exhaust gas from upstream of the turbine 12b to a position downstream of the compressor 12a may also be provided.

[0018] The engine controller 8 receives detection signals from sensors (none of which are shown), such as the air flow meter 24, intercooler water temperature sensor 30, intake air temperature sensor 31, intake air pressure sensor 32, and air-fuel ratio sensor 43, as well as a crank angle sensor for detecting engine speed, a water temperature sensor for detecting the temperature of the cooling water flowing through the water jacket, an outside air temperature sensor for detecting the outside air temperature, and a humidity sensor for detecting the outside air humidity. Based on these detection signals and requests from the other controllers 7 and 9, the engine controller 8 optimally controls the fuel injection amount and injection timing, ignition timing, throttle valve 22 opening, boost pressure, etc.

[0019] The internal combustion engine 2 is basically started when the SOC of the battery 5 drops to a predetermined lower limit SOC value, and is stopped when the SOC recovers to a predetermined level. That is, the internal combustion engine 2 drives the power generation motor generator 1 to generate electricity. The generated electricity is consumed by the traction motor generator 4, and surplus electricity is stored in the battery 5. Furthermore, when the vehicle is decelerating or going downhill, the traction motor generator 4 is controlled to regenerate, and the obtained electricity is recovered in the battery 5. The internal combustion engine 2 is started by motoring (in other words, cranking) the internal combustion engine 2 using the power generation motor generator 1, which is mechanically linked to the internal combustion engine 2.

[0020] Next, we will explain condensed water treatment, a key feature of the present invention. In the intercooler 26, which cools the high-temperature, high-pressure intake air, water vapor originally contained in the fresh air (outside air) and water vapor contained in the EGR gas condense as the intake air cools, becoming condensed water and accumulating at the bottom of the intercooler 26. FIG. 4 shows the boiling point characteristics of water, with the horizontal axis representing the intake air pressure in the intercooler 26 and the vertical axis representing the intake air temperature in the intercooler 26. In region A above the solid line L1 (i.e., the high-temperature side), which indicates the boiling point, water vapor remains in the gas phase, and the condensed water collected in the intercooler 26 decreases. On the other hand, in region B below the solid line L1 (i.e., the low-temperature side), water vapor and liquid water exist, creating conditions that could increase the amount of condensed water accumulating at the bottom of the intercooler 26. If this accumulated condensed water were to suddenly flow into the combustion chamber 10, it would undesirably deteriorate combustion. Therefore, in this embodiment, when it is estimated that a predetermined amount of condensed water has accumulated, motoring is performed by powering the power generating motor generator 1 with the throttle valve 22 opening reduced, thereby reducing the pressure inside the intercooler 26 and promoting the boiling and evaporation of the condensed water.

[0021] 3 is a flowchart showing the flow of a condensed water treatment process according to one embodiment, which is executed by the engine controller 8. The routine shown in this flowchart is repeatedly executed while the internal combustion engine 2 is in operation.

[0022] In the first step 1, it is determined whether a predetermined amount of condensed water has accumulated in the intercooler 26. For example, the amount of condensed water per unit time is calculated from conditions such as the outside air temperature, outside air humidity, EGR rate, the temperature of the coolant introduced into the intercooler 26 (the temperature detected by the intercooler water temperature sensor 30), the intake air temperature after passing through the intercooler 26 (the temperature detected by the intake air temperature sensor 31), and the intake air pressure inside the intercooler 26 (the pressure detected by the intake air pressure sensor 32), and the amount of condensed water accumulated in the intercooler 26 is estimated by integrating this amount. Then, this estimated value is compared with a threshold value to determine whether the predetermined amount has accumulated. If the determination in step 1 is NO, the routine ends.

[0023] If the determination in step 1 is YES, the process proceeds to step 2, where information on the intake pressure and intake temperature in the intercooler 26 is obtained. In one embodiment, the pressure detected by the intake pressure sensor 32 located at the outlet of the intercooler 26 is considered to be the intake pressure in the intercooler 26. Also, the temperature detected by the intake temperature sensor 31 located at the outlet of the intercooler 26 is considered to be the intake temperature of the intercooler 26. Alternatively, the temperature of the coolant introduced into the intercooler 26 (the temperature detected by the intercooler water temperature sensor 30) may be considered to be the temperature of the intercooler 26, i.e., the intake temperature in the intercooler 26.

[0024] Next, in step 3, it is determined whether these intake pressure and intake temperature conditions in the intercooler 26 are within region B in Fig. 4. If NO, that is, if they are within region A, this means that the condensed water can naturally decrease, so the routine is terminated without actively performing pressure reduction processing.

[0025] If it is determined in step 3 that the intake air temperature is within region B, the process proceeds to step 4 and subsequent steps, where a pressure reduction process is performed to reduce the pressure and boil the condensed water. In step 4, the boiling point characteristics in FIG. 4 are referenced, and a target intercooler pressure at which the intake air temperature in the intercooler 26 will exceed the boiling point is calculated based on the intake air temperature in the intercooler 26 at that time. Specifically, as shown by dashed line L2 in FIG. 4, a target characteristic is pre-defined that allows for a suitable margin on the high-temperature side of the solid line L1, which indicates the boiling point. The target intercooler pressure is then determined in accordance with the target characteristic of dashed line L2. For example, if the current intake air temperature in the intercooler 26 is T1 and the intake air pressure in the intercooler 26 is P1, the target intercooler pressure is calculated as P2 so that an intersection is obtained on dashed line L2.

[0026] In step 5, a target throttle valve opening corresponding to this target intercooler pressure is calculated. For example, a target throttle valve opening that can reduce the pressure to the target intercooler pressure is calculated based on the rotational speed of motoring by the power-generating motor / generator 1. The target throttle valve opening is a relatively small opening. Note that the target throttle valve opening may be any opening that can achieve a pressure equal to or lower than the target intercooler pressure, and may be set to the fully closed position, for example.

[0027] Next, the process proceeds to step 6, where pressure reduction processing is executed. Specifically, after the internal combustion engine 2 is stopped, the opening of the throttle valve 22 is controlled to the target throttle valve opening, and motoring is performed using the power-generating motor-generator 1 for a predetermined time.

[0028] By motoring with the throttle valve 22 at a small opening in this manner, the pressure downstream of the throttle valve 22, including the intercooler 26, decreases, causing the condensed water accumulated inside the intercooler 26 to boil under reduced pressure. This causes the accumulated condensed water to disappear or decrease. The predetermined time for motoring described above is set appropriately according to the threshold value for the amount of condensed water used to start the process in step 1, but it does not necessarily have to be a fixed value and may be a variable value according to some parameter such as the temperature condition of the entire internal combustion engine 2.

[0029] When power generation by the internal combustion engine 2 is to be resumed after the pressure reduction process for condensed water treatment has been performed, motoring can be continued as is and fuel injection and ignition can be resumed, thereby starting the internal combustion engine 2.

[0030] Thus, according to the above embodiment, the condensed water inside the intercooler 26 can be treated by utilizing the negative pressure generated by reducing the opening of the throttle valve 22, without requiring any additional device for treating the condensed water.

[0031] In the above embodiment, the internal combustion engine 2 is stopped and pressure reduction processing is performed when it is determined that condensed water has accumulated. However, instead of performing such a forced stop, pressure reduction processing may be performed immediately before the next start of the internal combustion engine 2 according to normal power generation control. In other words, in a series hybrid vehicle, the internal combustion engine 2 is started and stopped relatively frequently in response to power generation demands. Therefore, when it is determined that condensed water has accumulated while the internal combustion engine 2 is operating, pressure reduction processing may be performed by waiting until the next time the internal combustion engine 2 is started. This can be achieved by performing pressure reduction processing by motoring for a predetermined time before the start of fuel injection and ignition for startup. This method allows normal power generation control to be continued in response to power demands.

[0032] Furthermore, the pressure reduction process may be performed by the combustion operation of the internal combustion engine 2, rather than by motoring using the power-generating motor generator 1. In other words, a similar pressure reduction process can be achieved by performing the combustion operation with the opening of the throttle valve 22 set to the target throttle valve opening.

[0033] The present invention is not limited to the series hybrid vehicle described above, but can be applied to any hybrid vehicle in which the throttle valve opening of the internal combustion engine can be reduced independently of the output required for running.

Claims

1. A method for treating condensation water in an internal combustion engine that is equipped with an intercooler downstream of a throttle valve and is used to drive a generator in a hybrid vehicle that runs on motor output, comprising the steps of: determining whether condensation water has formed in the intercooler; obtaining the temperature of the intercooler when it is determined that condensation water has formed; determining a target intercooler pressure at which the intercooler temperature will exceed the boiling point of water; controlling the opening of the throttle valve to an opening corresponding to the target intercooler pressure; and performing pressure reduction treatment by rotating the internal combustion engine.

2. The method for treating condensed water in an internal combustion engine according to claim 1, wherein the intercooler is a water-cooled intercooler, and the temperature of the cooling water supplied to the intercooler is regarded as the temperature of the intercooler.

3. The condensed water treatment method for an internal combustion engine according to claim 1, wherein the temperature of the intake air having passed through the intercooler is regarded as the temperature of the intercooler.

4. The method for treating condensed water in an internal combustion engine according to claim 1, wherein the hybrid vehicle is a series hybrid vehicle, and the pressure reduction treatment is performed by motoring the internal combustion engine through powering of the generator.

5. The method for treating condensed water in an internal combustion engine according to claim 1, wherein the pressure reduction treatment is performed by a combustion operation of the internal combustion engine.

6. A condensation water treatment method for an internal combustion engine as described in claim 1, wherein, when it is determined that condensation has occurred, the temperature of the intercooler is acquired, and the intake pressure downstream of the throttle valve is acquired, and if the temperature of the intercooler exceeds the boiling point of water corresponding to the intake pressure, pressure reduction treatment is not performed.

7. A condensation water treatment device for an internal combustion engine comprising: an internal combustion engine equipped with an intercooler downstream of a throttle valve and used to drive a generator in a hybrid vehicle that runs on motor output; a controller for controlling the operation of the internal combustion engine; and a temperature sensor for directly or indirectly detecting the temperature of the intercooler, wherein the controller determines whether or not condensation has occurred in the intercooler, and when it is determined that condensation has occurred, obtains the temperature of the intercooler using the temperature sensor, determines a target intercooler pressure at which the temperature of the intercooler will exceed the boiling point of water, controls the opening of the throttle valve to an opening corresponding to the target intercooler pressure, and performs pressure reduction treatment by rotating the internal combustion engine.

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