Blow-by gas recirculation device

Abstract

To suitably enable warming-up in a crank case and ventilation of the crank case.SOLUTION: A first passage 20 that communicates a portion A downstream of a compressor 15 and upstream of an intercooler 16 in an intake passage 11 and a crank case 18, a second passage 21 that communicates a portion B downstream of the intercooler 16 in the intake passage 11 and the crank case 18 and a third passage 22 that communicates a portion C upstream of the compressor 15 in the intake passage 11 and the crank case 18 are installed in a supercharged engine 10. A blow-by gas recirculation device includes a selector valve 24 for switching between a state where the first passage 20 communicates and the second passage 21 is blocked and a state where the first passage 20 is blocked and the second passage 21 communicates.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a blow-by gas recirculation device that recirculates blow-by gas in a crankcase of a supercharged engine to an intake passage. [Background technology]

[0002] As a blow-by gas recirculation device as described above, a device described in Patent Document 1 is known. This blow-by gas recirculation device ventilates the blow-by gas by introducing intake air pressurized by a compressor into a crankcase. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-46244 A Summary of the Invention [Problem to be solved by the invention]

[0004] When the temperature inside the crankcase is low, the moisture in the blow-by gas condenses, and the condensed water can reduce the lubricating ability of the engine oil. [Means for solving the problem]

[0005] A blow-by gas recirculation device that solves the above-mentioned problems is a blow-by gas recirculation device for a supercharged engine having a compressor installed in an intake passage and an intercooler installed in a portion of the intake passage downstream of the compressor, which recirculates blow-by gas in a crankcase of the supercharged engine to the intake passage, and is provided with a first passage that connects the crankcase to a portion of the intake passage downstream of the compressor and upstream of the intercooler, a second passage that connects the crankcase to a portion of the intake passage downstream of the intercooler, a third passage that connects the crankcase to a portion of the intake passage upstream of the compressor, and a switching mechanism, wherein the switching mechanism switches between a state in which the first passage is connected and the second passage is blocked, and a state in which the first passage is blocked and the second passage is connected. Effect of the Invention

[0006] The blow-by gas recirculation device has the effect of suitably warming the crankcase as well as ventilating the crankcase. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram showing a schematic configuration of an embodiment of a blow-by gas recirculation device; [Diagram 2] 4 is a flowchart of a switching control routine executed by a control unit included in the blow-by gas recirculation device. [Diagram 3] FIG. 4 is a diagram showing a gas flow in the blow-by gas recirculation device during cold supercharging operation. [Figure 4] FIG. 4 is a diagram showing a gas flow in the blow-by gas recirculation device during warm supercharging operation. [Diagram 5] FIG. 4 is a diagram showing a gas flow in the blow-by gas recirculation device when warming up during natural intake operation. [Figure 6] FIG. 10 is a diagram illustrating a configuration of a modified example of a blow-by gas recirculation device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, one embodiment of the blow-by gas recirculation device will be described in detail with reference to Figs. <Configuration of the blow-by gas recirculation device> First, the configuration of a blow-by gas recirculation device of this embodiment will be described with reference to Fig. 1. The blow-by gas recirculation device of this embodiment is installed in a supercharged engine 10 for mounting on a vehicle.

[0009] The supercharged engine 10 is a hydrogen engine that generates power by burning hydrogen. The supercharged engine 10 includes an intake passage 11, a combustion chamber 12, and an exhaust passage 13. Intake air is introduced into the combustion chamber 12 through the intake passage 11. In the combustion chamber 12, a mixture of the intake air and hydrogen is combusted. Exhaust gas generated by the combustion in the combustion chamber 12 is discharged through the exhaust passage 13.

[0010] An air cleaner 14 that filters intake air taken in from the outside is installed in the intake passage 11. A compressor 15, which is a supercharger, is installed in the intake passage 11 downstream of the air cleaner 14. The compressor 15 is operated by the flow of exhaust gas flowing through the exhaust passage 13. An intercooler 16 is installed in the intake passage 11 downstream of the compressor 15. The intercooler 16 cools the intake air that has become hot due to adiabatic compression in the compressor 15. A throttle valve 17 is installed in the intake passage 11 downstream of the intercooler 16. The throttle valve 17 is a valve that adjusts the amount of intake air introduced into the combustion chamber 12 by changing the flow path area of ​​the intake air in the intake passage 11.

[0011] The blow-by gas recirculation device of the present embodiment recirculates the blow-by gas in the crankcase 18 of the supercharged engine 10 into the intake air, thereby ventilating the crankcase 18. Note that engine oil accumulates at the bottom of the crankcase 18.

[0012] The blow-by gas recirculation device of this embodiment includes four passages, a first passage 20, a second passage 21, a third passage 22, and a fourth passage 23, which are passages that communicate between the intake passage 11 and the crankcase 18. The first passage 20 is a passage that communicates between the crankcase 18 and a portion of the intake passage 11 downstream of the compressor 15 and upstream of the intercooler 16. The second passage 21 is a passage that communicates between the crankcase 18 and a portion of the intake passage 11 downstream of the intercooler 16 and upstream of the throttle valve 17. The third passage 22 is a passage that communicates between the crankcase 18 and a portion of the intake passage 11 upstream of the compressor 15 and downstream of the air cleaner 14. The fourth passage 23 is a passage that communicates between the crankcase 18 and a portion of the intake passage 11 downstream of the throttle valve 17. Although not shown, the third passage 22 and the fourth passage 23 are each provided with an oil separator for removing oil in the blow-by gas passing therethrough.

[0013] The blow-by gas recirculation device further includes a switching valve 24, a one-way valve 25, a PCV (Positive Crankcase Ventilation) valve 26, and a control unit 27. The switching valve 24 is an electromagnetic valve that switches between a state in which the first passage 20 is connected and the second passage 21 is blocked, and a state in which the first passage 20 is blocked and the second passage 21 is connected. The one-way valve 25 is a valve that restricts the flow of gas from the crankcase 18 to the intake passage 11 through the first passage 20 and the second passage 21. The PCV valve 26 is a valve that restricts the flow of gas from the intake passage 11 to the crankcase 18 through the fourth passage 23. The control unit 27 is an electronic control device that controls the operation of the switching valve 24. An example of the control unit 27 is an electronic control module (ECM: Engine Control Module) for engine control. A detection signal of an oil temperature sensor 28 that detects an oil temperature THO, which is the temperature of engine oil, is input to the control unit 27.

[0014] 1, the first passage 20 and the second passage 21 are independent of each other on the intake passage 11 side, but are combined into one passage on the crankcase 18 side. The changeover valve 24 is disposed at the junction of the first passage 20 and the second passage 21. The one-way valve 25 is disposed in the first passage 20 and the second passage 21 on the crankcase 18 side of the changeover valve 24.

[0015] In the following description, the pressure of the intake air in the portion of the intake passage 11 downstream of the throttle valve 17 will be referred to as the intake pipe pressure. Furthermore, operation of the supercharged engine 10 in a state where the intake pipe pressure is a negative pressure lower than atmospheric pressure will be referred to as the naturally aspirated operation. Furthermore, operation of the supercharged engine 10 in a state where the intake pipe pressure is a positive pressure higher than atmospheric pressure will be referred to as the supercharged operation.

[0016] The changeover valve 24 in the blow-by gas recirculation device configured as described above has a function of exclusively connecting the following two parts A and B in the intake passage 11 to the crankcase 18. The part A is a part in the intake passage 11 downstream of the compressor 15 and upstream of the intercooler 16. The part B is a part in the intake passage 11 downstream of the intercooler 16 or upstream of the intercooler 16. Intake air that is high in temperature and has a positive pressure due to the supercharging operation of the compressor 15 flows through the part A during the supercharged operation of the supercharged engine 10. In contrast, intake air that is positive in pressure like the part A but is cooled by the intercooler 16 and has a lower temperature than the intake air flowing through the part A flows through the part B during the supercharged operation of the supercharged engine 10. In the case of this embodiment, the changeover valve 24 corresponds to the changeover mechanism.

[0017] Incidentally, the pressure of the intake air in the portion C of the intake passage 11 upstream of the compressor 15 to which the third passage 22 is connected is atmospheric pressure both during supercharged operation and during naturally aspirated operation of the supercharged engine 10. Also, the portion D of the intake passage 11 downstream of the throttle valve 17 to which the fourth passage 23 is connected is subject to negative pressure due to throttling by the throttle valve 17 during naturally aspirated operation of the supercharged engine 10.

[0018] <Switching valve control> Next, the control of the switching valve 24 executed by the control unit 27 will be described with reference to Fig. 2. Fig. 2 is a flowchart of a switching valve control routine executed by the control unit 27 to control the switching valve 24. The control unit 27 repeatedly executes this routine at every predetermined control period while the supercharged engine 10 is in operation. In Fig. 2 and the following description, "S" in S100 to S130 represents a step.

[0019] When the control unit 27 starts this routine, first, in S100, it acquires the oil temperature THO based on the detection signal of the oil temperature sensor 28. Next, in S110, the control unit 27 judges whether the oil temperature THO is less than a predetermined threshold value. If the oil temperature THO is less than the threshold value (YES), the control unit 27 controls the switching valve 24 so that the first passage 20 is in a connected state and the second passage 21 is in a blocked state (S120). On the other hand, if the oil temperature THO is equal to or greater than the threshold value (NO), the control unit 27 controls the switching valve 24 so that the first passage 20 is in a blocked state and the second passage 21 is in a connected state (S130). Then, after the process of S120 or S130, the control unit 27 ends the process of this routine in the current control cycle.

[0020] The threshold value used for the judgment in S110 of FIG. 2 is set in the following manner. The blow-by gas in the crankcase 18 contains moisture generated by the combustion in the combustion chamber 12. When the temperature in the crankcase 18 is low, the moisture in the blow-by gas may condense and mix with the engine oil. The mixed moisture may cause the engine oil to become cloudy, and the lubricating ability of the oil may decrease. When the temperature of the engine oil in the crankcase 18 becomes high beyond a certain level, the temperature in the crankcase 18 also becomes high, making it difficult for condensed water to be generated. The above threshold value is set as a value that is the lower limit of the oil temperature THO at which the amount of condensed water generated in the crankcase 18 is suppressed to a level at which the engine oil does not become cloudy. In other words, when the oil temperature THO is below the threshold value, condensed water is likely to be generated in the crankcase 18.

[0021] <Actions and Effects of the Embodiments> The operation and effects of the blow-by gas recirculation device of this embodiment configured as above will be described.

[0022] The inside of the crankcase 18 immediately after a cold start is in a state where condensation is likely to occur because the temperature is low. At this time, the engine oil is not yet warmed up, so the oil temperature THO is below the threshold. Therefore, the control unit 27 at this time controls the switching valve 24 to open the first passage 20 and close the second passage 21.

[0023] FIG. 3 shows the gas flow in the blow-by gas recirculation device when the supercharged engine 10 is performing supercharging operation with the switching valve 24 controlled as described above. During supercharging operation, the pressure of the intake air is higher than atmospheric pressure in the portions A, B, and D downstream of the compressor 15 in the intake passage 11. On the other hand, the pressure of the intake air in the portion C upstream of the compressor 15 in the intake passage 11 to which the third passage 22 is connected is atmospheric pressure. Therefore, as shown in FIG. 3, the intake air flows into the crankcase 18 through the first passage 20, which is connected by the switching valve 24, out of the first passage 20 and the second passage 21. Then, the blow-by gas in the crankcase 18 is pushed out by the intake air and recirculated through the third passage 22 to the portion C upstream of the compressor 15 in the intake passage 11. The intake air flowing into the crankcase 18 through the first passage 20 at this time is at a high temperature due to adiabatic compression by the compressor 15. The inside of the crankcase 18 is heated by this high-temperature intake air, thereby suppressing the generation of condensation water.

[0024] Thereafter, as the supercharged engine 10 continues to warm up, the oil temperature THO also rises. When the oil temperature THO reaches or exceeds a threshold value, the control unit 27 switches the changeover valve 24 to a state in which the first passage 20 is blocked and the second passage 21 is communicated.

[0025] 4 shows the gas flow in the blow-by gas recirculation device when the supercharged engine 10 is performing supercharged operation with the switching valve 24 controlled as described above. In this case, the intake air flows into the crankcase 18 through the second passage 21, which is connected by the switching valve 24, out of the first passage 20 and the second passage 21. Then, the blow-by gas in the crankcase 18 is pushed out by the flowing intake air and recirculated through the third passage 22 to the portion C of the intake passage 11 upstream of the compressor 15.

[0026] The intake air that flows into the crankcase 18 through the second passage 21 is cooled by the intercooler 16. On the other hand, the density of the intake air increases as the temperature decreases. Therefore, more intake air can be introduced into the crankcase 18 by introducing intake air before it is cooled by the intercooler 16 than by introducing intake air before it is cooled by the intercooler 16. In this way, the ventilation efficiency of the crankcase 18 is improved by controlling the switching valve 24 as described above. At this time, the inside of the crankcase 18 has already warmed up to a state where condensation is unlikely to occur, even if high-temperature intake air does not flow in.

[0027] During natural aspiration operation of the supercharged engine 10, the pressure of the intake air in the portion D of the intake passage 11 downstream of the throttle valve 17, i.e., the intake pipe pressure, becomes a negative pressure lower than atmospheric pressure. Meanwhile, the crankcase 18 communicates with the portion C of the intake passage 11 upstream of the compressor 15 through the third passage 22. Since the portion C of the intake passage 11 upstream of the compressor 15 is at atmospheric pressure, the inside of the crankcase 18 is also at atmospheric pressure. Therefore, the intake air is introduced into the crankcase 18 through the third passage 22 during natural aspiration operation. Moreover, the blow-by gas in the crankcase 18 is sucked into the intake passage 11 through the fourth passage 23 by the intake negative pressure formed by the throttling of the throttle valve 17. In this manner, the crankcase 18 is ventilated during natural aspiration operation.

[0028] According to the blow-by gas recirculation device of the present embodiment described above, the following effects can be achieved. (1) The blow-by gas recirculation device of this embodiment includes a first passage 20, a second passage 21, a third passage 22, and a changeover valve 24. The first passage 20 is a passage that connects a portion A of the intake passage 11 downstream of the compressor 15 and upstream of the intercooler 16 with the crankcase 18. The second passage 21 is a passage that connects a portion B of the intake passage 11 downstream of the intercooler 16 with the crankcase 18. The third passage 22 is a passage that connects a portion C of the intake passage 11 upstream of the compressor 15 with the crankcase 18. The changeover valve 24 is a valve that switches between a state in which the first passage 20 is connected and the second passage 21 is blocked, and a state in which the first passage 20 is blocked and the second passage 21 is connected. In such a blow-by gas recirculation device, the intake air introduced into the crankcase 18 during supercharging operation can be switched between high-temperature intake air before being cooled by the intercooler 16 and low-temperature intake air after being cooled by the intercooler 16. Therefore, it is possible to select whether to introduce high-temperature intake air to promote warming up of the crankcase 18 or to introduce low-temperature intake air to increase the ventilation efficiency of the crankcase 18, depending on the situation. Therefore, the blow-by gas recirculation device of this embodiment has the effect of being able to preferably warm up the inside of the crankcase 18 as well as ventilate the crankcase 18.

[0029] (2) The control unit 27 determines whether or not condensation is likely to occur in the crankcase 18 based on the oil temperature THO. If the control unit 27 determines that condensation is likely to occur in the crankcase 18, it controls the switching valve 24 to open the first passage 20 and close the second passage 21. If the control unit 27 determines that condensation is not likely to occur in the crankcase 18, it controls the switching valve 24 to close the first passage 20 and open the second passage 21. This allows the crankcase 18 to be warmed up effectively.

[0030] (3) The blow-by gas recirculation device of this embodiment includes a fourth passage 23 and a PCV valve 26 described below, in addition to the first passage 20, the second passage 21, the third passage 22, and the switching valve 24. The fourth passage 23 is a passage that connects a portion D of the intake passage 11 downstream of the throttle valve 17 with the crankcase 18. The PCV valve 26 is a valve that restricts the flow of gas from the intake passage 11 to the crankcase 18 through the fourth passage 23. Therefore, the crankcase 18 can be ventilated even during natural aspiration operation.

[0031] (4) The blow-by gas recirculation device of this embodiment is provided with a one-way valve 25 that restricts the flow of gas from the crankcase 18 to the intake passage 11 through the first passage 20 and the second passage 21. Therefore, during natural aspiration operation of the supercharged engine 10 or while the operation is stopped, the blow-by gas in the crankcase 18 is prevented from flowing into the intake passage 11 through the first passage 20 and the second passage 21.

[0032] (5) The blow-by gas recirculation device of this embodiment is applied to a hydrogen engine. Hydrogen becomes water when burned, so the moisture content of the blow-by gas is more likely to be large than in gasoline engines or diesel engines. Therefore, the blow-by gas recirculation device of this embodiment, which can effectively warm the inside of the crankcase 18, is particularly suitable for application to a hydrogen engine.

[0033] (Other embodiments) <Warming up the crankcase during naturally aspirated operation> There are turbochargers that can adjust the supercharging rate of the intake air, such as a variable nozzle turbocharger. When the blow-by gas recirculation device of the above embodiment is applied to a supercharged engine equipped with such a supercharger that can adjust the supercharging rate, it is possible to warm up the crankcase 18 even during natural aspirated operation. In the following description, the pressure of the intake air in the portions A and B downstream of the compressor 15 and upstream of the throttle valve 17 in the intake passage 11 is referred to as the supercharging pressure.

[0034] FIG. 5 shows the gas flow of the blow-by gas recirculation device when warming up the crankcase 18 during natural aspirated operation. The amount of intake air flowing into the combustion chamber 12 of the supercharged engine 10 is determined by the engine speed and the intake pipe pressure. In the case of the supercharged engine 10 equipped with a supercharger capable of adjusting the supercharging rate, the supercharging rate can be increased while the opening of the throttle valve 17 is reduced during natural aspirated operation, thereby increasing the supercharging pressure while maintaining the intake pipe pressure. This allows the supercharging pressure to be a positive pressure higher than the atmospheric pressure even during natural aspirated operation. In this state, when the switching valve 24 is controlled to communicate the first passage 20 and block the second passage 21, high-temperature intake air is introduced into the crankcase 18 through the first passage 20. Then, the blow-by gas in the crankcase 18 is recirculated to the intake passage 11 through the fourth passage 23. Therefore, the crankcase 18 can be ventilated while being warmed up even during natural aspirated operation.

[0035] <How to determine whether or not condensation is likely to occur> In the above embodiment, whether or not the crankcase 18 is in a state where condensation water is likely to occur is determined based on whether or not the oil temperature THO is less than a threshold value. This determination may be performed in a different manner. For example, the following determination method is possible.

[0036] The above determination may be made based on the coolant temperature of the supercharged engine 10 instead of the oil temperature THO. The above judgment may be made based on the elapsed time after the start of the supercharged engine 10. The temperature inside the crankcase 18 after a cold start is approximately the same as the outside air temperature at the time of start, and then increases with the passage of time. Therefore, it can be estimated that the inside of the crankcase 18 is in a low temperature state in which condensation is likely to occur until a certain time has passed after the start of the supercharged engine 10. The same judgment can also be made based on the integrated intake air volume and integrated rotation speed after the start of the supercharged engine 10. Note that the temperature inside the crankcase 18 at the time of start varies depending on the outside air temperature. Therefore, it is desirable to make the judgment based on the elapsed time after start, etc. as described above in a manner that reflects the influence of the outside air temperature. For example, the elapsed time after start, at which it is judged that the state in which condensation is likely to occur has switched to the state in which condensation is unlikely to occur, may be set to a longer time when the outside air temperature is low than when it is high.

[0037] An EGR device that recirculates part of the exhaust gas into the intake air is used as a device for the supercharged engine 10. The exhaust gas (EGR gas) that the EGR device recirculates into the intake air contains moisture. When the EGR gas is introduced into the low-temperature intake air cooled by the intercooler 16, the moisture in the EGR gas may condense. In this case, when the intake air is introduced into the crankcase 18 through the second passage 21, the condensed water generated in the intake passage 11 may flow into the crankcase 18. Therefore, it may be determined that the state is prone to condensed water while the EGR gas is being introduced. Then, depending on the determination, the crankcase 18 is ventilated with the first passage 20 open and the second passage 21 closed, thereby preventing the condensed water generated in the intake passage 11 from flowing into the crankcase 18.

[0038] <Configuration of the blow-by gas recirculation device> A one-way valve 25 may be provided in each of the first passage 20 and the second passage 21 at a position closer to the intake passage 11 than the switching valve 24 is.

[0039] When the switching valve 24 is configured so that both the first passage 20 and the second passage 21 can be shut off, the backflow of blow-by gas into the intake passage 11 can be prevented by controlling the switching valve 24. In this case, the one-way valve 25 can be omitted. Also, there are cases where the backflow of blow-by gas into the intake passage 11 through the first passage 20 and the second passage 21 can be permitted, for example, when an oil separator that removes oil in the blow-by gas is installed in the first passage 20 and the second passage 21. In such a case, the one-way valve 25 can also be omitted.

[0040] As shown in FIG. 6, the first passage 20 and the second passage 21 may be independent passages. In the case of FIG. 6, the first passage 20 and the second passage 21 are provided with changeover valves 24A and 24B, respectively. The control unit 27 controls the two changeover valves 24A and 24B so that only one of the first passage 20 and the second passage 21 is in a communication state. In this case, the changeover mechanism is composed of the two changeover valves 24A and 24B. In the case of FIG. 6, the control unit 27 controls the changeover valves 24A and 24B to be in a blocked state during the naturally aspirated operation or stop of the supercharged engine 10. This suppresses the backflow of blow-by gas from the crankcase 18 to the intake passage 11 through the first passage 20 and the second passage 21. Instead of performing such control, a one-way valve that limits the flow of gas from the crankcase 18 to the intake passage 11 may be provided in each of the first passage 20 and the second passage 21.

[0041] If there is no need to ventilate the crankcase 18 during naturally aspirated operation, the fourth passage 23 and the PCV valve 26 may be omitted. The blow-by gas recirculation device of the above embodiment and modified example can also be applied to supercharged engines other than hydrogen engines, such as gasoline engines and diesel engines. [Explanation of symbols]

[0042] 10. Supercharged Engine 11 Intake passage 12 Combustion chamber 13 Exhaust passage 14 Air cleaner 15 Compressor 16 Intercooler 17 Throttle valve 18 Crankcase 20 1st aisle 21 2nd aisle 22 3rd aisle 23 4th aisle 24, 24A, 24B Switching valve 25 One-way valve 26 PCV valve 27 Control Unit 28 Oil temperature sensor

Claims

1. A blow-by gas recirculation device for a supercharged engine including a compressor installed in an intake passage and an intercooler installed in a portion of the intake passage downstream of the compressor, the blow-by gas recirculation device recirculating blow-by gas in a crankcase of the supercharged engine to the intake passage, a first passage communicating a portion of the intake passage downstream of the compressor and upstream of the intercooler with the crankcase; a second passage communicating a portion of the intake passage downstream of the intercooler with the crankcase; a third passage communicating a portion of the intake passage upstream of the compressor with the crankcase; A switching mechanism; Equipped with The switching mechanism is a mechanism that switches between a state in which the first passage is connected and the second passage is blocked, and a state in which the first passage is blocked and the second passage is connected. Blow-by gas recirculation device.

2. 2. The blow-by gas recirculation device according to claim 1, further comprising a control unit that determines whether or not a state in which condensation is likely to occur in the crankcase is present, and controls the switching mechanism so that, when it is determined that the state in which condensation is likely to occur is present, the first passage is opened and the second passage is closed, whereas, when it is determined that the state in which condensation is not likely to occur is present, the first passage is closed and the second passage is opened.

3. the supercharged engine includes a throttle valve disposed in a portion of the intake passage downstream of the intercooler, The blow-by gas recirculation device according to claim 1, further comprising: a fourth passage connecting a portion of the intake passage downstream of the throttle valve with the crankcase; and a PCV valve restricting the flow of gas from the intake passage to the crankcase through the fourth passage.

4. 2. The blow-by gas recirculation device according to claim 1, further comprising a one-way valve for restricting the flow of gas from the crankcase to the intake passage through the first passage and the second passage.

5. 2. The blow-by gas recirculation device according to claim 1, wherein the supercharged engine is a hydrogen engine.

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