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 reflux device that refluxes blow-by gas in the crankcase of a supercharged engine to an intake passage.

Background Art

[0002] As such a blow-by gas reflux device, the device described in Patent Document 1 is known. This blow-by gas reflux device ventilates blow-by gas by introducing intake air pressurized by a compressor into the crankcase.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the temperature in the crankcase is low, moisture in the blow-by gas condenses. And due to the mixing of condensed water, the lubricating ability of the engine oil may decrease.

Means for Solving the Problems

[0005] A blow-by gas recirculation device for solving the above problems is a blow-by gas recirculation device for a supercharged engine that includes a compressor installed in the intake passage and an intercooler installed in the intake passage downstream of the compressor, which recirculates blow-by gas in the crankcase to the intake passage, and comprises: a first passage that connects the portion of the intake passage downstream of the compressor and upstream of the intercooler with the crankcase; a second passage that connects the portion of the intake passage downstream of the intercooler with the crankcase; a third passage that connects the portion of the intake passage upstream of the compressor with the crankcase; and a switching mechanism, the switching mechanism being a mechanism that switches between a state in which the first passage is open and the second passage is closed, and a state in which the first passage is closed and the second passage is open. [Effects of the Invention]

[0006] The blow-by gas recirculation device described above has the effect of providing ventilation to the crankcase and effectively warming the air inside the crankcase. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram schematically shows the configuration of one embodiment of a blow-by gas recirculation device. [Figure 2] This is a flowchart of the switching control routine executed by the control unit of the blow-by gas recirculation device described above. [Figure 3] This diagram shows the gas flow in the blow-by gas recirculation device during cold supercharging operation. [Figure 4] This diagram shows the gas flow of the blow-by gas recirculation device during hot turbocharging operation. [Figure 5] This diagram shows the gas flow of the blow-by gas recirculation device when warming up the engine during natural aspiration operation. [Figure 6] This diagram schematically shows a modified configuration of a blow-by gas recirculation device. [Modes for carrying out the invention]

[0008] Below, one embodiment of a blow-by gas recirculation device will be described in detail with reference to Figures 1 to 5. <Configuration of blow-by gas recirculation system> First, the configuration of the blow-by gas recirculation device of this embodiment will be described with reference to Figure 1. The blow-by gas recirculation device of this embodiment is installed on a vehicle-mounted supercharged engine 10.

[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 intake air and hydrogen is burned. The exhaust gas produced by the combustion in the combustion chamber 12 is discharged through the exhaust passage 13.

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

[0011] The blow-by gas recirculation device of this embodiment ventilates the crankcase 18 of the supercharged engine 10 by recirculating the blow-by gas in the crankcase 18 into the intake air. Engine oil is present 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 connect the intake passage 11 and the crankcase 18. The first passage 20 is a passage that connects the portion of the intake passage 11 downstream of the compressor 15 and upstream of the intercooler 16 to the crankcase 18. The second passage 21 is a passage that connects the portion of the intake passage 11 downstream of the intercooler 16 and upstream of the throttle valve 17 to the crankcase 18. The third passage 22 is a passage that connects the portion of the intake passage 11 upstream of the compressor 15 and downstream of the air cleaner 14 to the crankcase 18. The fourth passage 23 is a passage that connects the portion of the intake passage 11 downstream of the throttle valve 17 to the crankcase 18. Although not shown in the diagram, the third passage 22 and the fourth passage 23 are each equipped with oil separators to remove oil from the blow-by gas passing through them.

[0013] Furthermore, the blow-by gas recirculation device 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 a solenoid valve that switches between a state in which the first passage 20 is open and the second passage 21 is closed, and a state in which the first passage 20 is closed and the second passage 21 is open. 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. The control unit 27 receives a detection signal from an oil temperature sensor 28 that detects the oil temperature THO, which is the temperature of the engine oil.

[0014] In Figure 1, the first passage 20 and the second passage 21 are separate passages on the intake passage 11 side, but the parts on the crankcase 18 side are combined into a single passage. The switching valve 24 is installed at the junction of the first passage 20 and the second passage 21. The one-way valve 25 is installed in the parts of the first passage 20 and the second passage 21 that are closer to the crankcase 18 than the switching valve 24.

[0015] In the following explanation, the intake pressure in the intake passage 11 downstream of the throttle valve 17 will be referred to as the intake manifold pressure. Furthermore, operation of the turbocharged engine 10 when the intake manifold pressure is a negative pressure (below atmospheric pressure) will be referred to as naturally aspirated operation. In addition, operation of the turbocharged engine 10 when the intake manifold pressure is a positive pressure (above atmospheric pressure) will be referred to as turbocharged operation.

[0016] As described above, the switching valve 24 in the blow-by gas recirculation device has the function of exclusively connecting the following two parts A and B of the intake passage 11 to the crankcase 18. Part A is the part of the intake passage 11 downstream of the compressor 15 and upstream of the intercooler 16. Part B is the part of the intake passage 11 either downstream of the intercooler 16 or upstream of the intercooler 16. During supercharging operation of the supercharged engine 10, intake air that has become hot and positively pressurized due to the supercharging operation of the compressor 15 flows through part A. In contrast, during supercharging operation of the supercharged engine 10, intake air that is positively pressurized like part A flows through part B, but is cooler than the intake air flowing through part A due to cooling by the intercooler 16. In this embodiment, such a switching valve 24 corresponds to a switching mechanism.

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

[0018] <Control of the switching valve> Next, referring to FIG. 2, the control of the switching valve 24 executed by the control unit 27 will be described. FIG. 2 is a flowchart of a switching valve control routine executed by the control unit 27 for controlling the switching valve 24. The control unit 27 repeatedly executes this routine at every predetermined control cycle during the operation of the supercharged engine 10. In FIG. 2 and the following description, "S" in S100 to S130 represents a step.

[0019] When starting this routine, the control unit 27 first obtains the oil temperature THO based on the detection signal of the oil temperature sensor 28 at S100. Next, at S110, the control unit 27 determines whether the oil temperature THO is less than a predetermined threshold value. When 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 communicating state and the second passage 21 is in a blocked state (S120). On the other hand, when the oil temperature THO is greater than or equal to 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 communicating state (S130). Then, after the processing of S120 or S130, the control unit 27 ends the processing of this routine in the current control cycle.

[0020] The threshold value used for the determination at S110 in FIG. 2 is set in the following manner. The blow-by gas in the crankcase 18 contains moisture generated by combustion in the combustion chamber 12. When the inside of the crankcase 18 is at a low temperature, the moisture in the blow-by gas may condense and mix into the engine oil. Then, 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 exceeds a certain level and becomes high, the temperature inside the crankcase 18 also becomes high, and it becomes difficult for condensed water to be generated. The above threshold value is set as the temperature 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 such an extent that the engine oil does not become cloudy. That is, when the oil temperature THO is less than the threshold value, the crankcase 18 is in a state where condensed water is likely to be generated.

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

[0022] Immediately after a cold start, the inside of the crankcase 18 is at a low temperature, making it prone to condensation. At this time, the engine oil has not yet warmed up, so the oil temperature THO is below the threshold. Therefore, the control unit 27 controls the switching valve 24 to open the first passage 20 and block the second passage 21.

[0023] Figure 3 shows the gas flow in the blow-by gas recirculation device when the turbocharged engine 10 is operating under turbocharging conditions with the switching valve 24 controlled as described above. During turbocharging, the intake pressure in sections A, B, and D of the intake passage 11 downstream of the compressor 15 is higher than atmospheric pressure. On the other hand, the intake pressure in section C of the intake passage 11 upstream of the compressor 15, to which the third passage 22 is connected, is atmospheric pressure. Therefore, as shown in Figure 3, intake air flows into the crankcase 18 through the first passage 20, which is connected to the second passage 21 by the switching valve 24. The blow-by gas in the crankcase 18 is then recirculated through the third passage 22 to section C of the intake passage 11 upstream of the compressor 15, pushed out by the incoming intake air. At this time, the intake air flowing into the crankcase 18 through the first passage 20 is at a high temperature due to adiabatic compression by the compressor 15. Because the inside of the crankcase 18 is heated by this high-temperature intake air, the generation of condensation is suppressed.

[0024] Subsequently, as the supercharged engine 10 warms up, the oil temperature THO also rises. When the oil temperature THO exceeds a threshold, the control unit 27 switches the switching valve 24 to a state where the first passage 20 is blocked and the second passage 21 is opened.

[0025] Figure 4 shows the gas flow in the blow-by gas recirculation device when the supercharged engine 10 is operating under supercharged conditions with the switching valve 24 controlled as described above. At this time, intake air flows into the crankcase 18 through the second passage 21, which is connected to the first passage 20 by the switching valve 24. The blow-by gas in the crankcase 18 is then recirculated through the third passage 22 to the portion C upstream of the compressor 15 in the intake passage 11, pushed out by the incoming intake air.

[0026] The intake air flowing into the crankcase 18 through the second passage 21 is cooled by the intercooler 16. On the other hand, the density of 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 increased by controlling the switching valve 24 as described above. At this time, the inside of the crankcase 18 is warmed to a state where condensation is unlikely to occur even without the inflow of high-temperature intake air.

[0027] During naturally aspirated operation of the turbocharged engine 10, the intake pressure in the intake passage 11 downstream of the throttle valve 17, i.e., the intake manifold pressure, is a negative pressure lower than atmospheric pressure. On the other hand, the crankcase 18 is in communication with the intake passage 11 upstream of the compressor 15 through a third passage 22. Since 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, intake air is introduced into the crankcase 18 through the third passage 22 during naturally aspirated operation. In addition, blow-by gas in the crankcase 18 is drawn into the intake passage 11 through a fourth passage 23 by the intake negative pressure created by the throttling of the throttle valve 17. As a result, the crankcase 18 is ventilated during naturally aspirated operation.

[0028] The blow-by gas recirculation device of this embodiment described above can achieve the following effects. (1) The blow-by gas recirculation device of this embodiment comprises a first passage 20, a second passage 21, a third passage 22, and a switching valve 24. The first passage 20 is a passage that connects the crankcase 18 to a portion A of the intake passage 11 that is downstream of the compressor 15 and upstream of the intercooler 16. The second passage 21 is a passage that connects the crankcase 18 to a portion B of the intake passage 11 that is downstream of the intercooler 16. The third passage 22 is a passage that connects the crankcase 18 to a portion C of the intake passage 11 that is upstream of the compressor 15. The switching valve 24 is a valve that switches between a state in which the first passage 20 is open and the second passage 21 is closed, and a state in which the first passage 20 is closed and the second passage 21 is open. In this 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 it is cooled by the intercooler 16 and low-temperature intake air after it has been cooled by the intercooler 16. Therefore, it is possible to select, depending on the situation, whether to introduce high-temperature intake air to promote warming of the crankcase 18 or to introduce low-temperature intake air to improve the ventilation efficiency of the crankcase 18. Thus, the blow-by gas recirculation device of this embodiment has the effect of effectively warming the inside of the crankcase 18 along with ventilating the crankcase 18.

[0029] (2) The control unit 27 determines whether conditions are favorable for condensation to occur in the crankcase 18 based on the oil temperature THO. If the control unit 27 determines that conditions are favorable for condensation to occur, it controls the switching valve 24 so that the first passage 20 is open and the second passage 21 is closed. If the control unit 27 determines that conditions are not favorable for condensation to occur, it controls the switching valve 24 so that the first passage 20 is closed and the second passage 21 is open. As a result, the crankcase 18 can be warmed up effectively.

[0030] (3) In addition to the first passage 20, second passage 21, third passage 22, and switching valve 24, the blow-by gas recirculation device of this embodiment is equipped with the following fourth passage 23 and PCV valve 26. The fourth passage 23 is a passage that connects the portion D downstream of the throttle valve 17 in the intake passage 11 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 equipped 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, when the supercharged engine 10 is operating in natural aspiration mode or when it is stopped, the flow of blow-by gas from the crankcase 18 into the intake passage 11 through the first passage 20 and the second passage 21 is suppressed.

[0032] (5) The blow-by gas recirculation device of this embodiment is applied to hydrogen engines. Since hydrogen turns into water when it burns, the amount of moisture in the blow-by gas tends to be higher than in gasoline or diesel engines. For this reason, the blow-by gas recirculation device of this embodiment, which can suitably warm up the crankcase 18, is particularly suitable for application to hydrogen engines.

[0033] (Other embodiments) <Crankcase warm-up during naturally aspirated operation> Some superchargers, such as variable nozzle turbochargers, allow for adjustment of the intake boost rate. When the blow-by gas recirculation device of the above embodiment is applied to a supercharged engine equipped with such a supercharger that allows for adjustment of the boost rate, it is possible to warm up the crankcase 18 even during naturally aspirated operation. In the following description, the intake pressure in portions A and B of the intake passage 11 downstream of the compressor 15 and upstream of the throttle valve 17 will be referred to as the boost pressure.

[0034] Figure 5 shows the gas flow in the blow-by gas recirculation device when warming up the crankcase 18 during naturally aspirated operation. The amount of intake air flowing into the combustion chamber 12 of the turbocharged engine 10 is determined by the engine speed and intake manifold pressure. In the case of a turbocharged engine 10 equipped with a turbocharger with an adjustable boost rate, during naturally aspirated operation, the boost pressure can be increased while maintaining the intake manifold pressure by increasing the boost rate while reducing the opening of the throttle valve 17. This makes it possible to set the boost pressure to a positive pressure higher than atmospheric pressure even during naturally aspirated operation. In this state, when the switching valve 24 is controlled to open the first passage 20 and close the second passage 21, high-temperature intake air is introduced into the crankcase 18 through the first passage 20. Then, the blow-by gas from the crankcase 18 is recirculated to the intake passage 11 through the fourth passage 23. Therefore, even during naturally aspirated operation, the crankcase 18 can be ventilated while warming up.

[0035] <Determining whether conditions are conducive to condensation> In the above embodiment, whether or not condensation is likely to occur in the crankcase 18 was determined by whether or not the oil temperature THO was below a threshold. This determination may be performed by other methods. For example, the following determination method can be considered.

[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 determination may also be made based on the elapsed time since the start of the supercharged engine 10. The temperature inside the crankcase 18 after a cold start is about the same as the ambient temperature at the time of starting, and then rises over time. Therefore, it can be estimated that the inside of the crankcase 18 is at a low temperature and prone to condensation until a certain amount of time has passed since the start of the supercharged engine 10. A similar determination can also be made based on the cumulative intake air volume and cumulative rotational speed after the start of the supercharged engine 10. Note that the temperature inside the crankcase 18 at the time of starting changes depending on the ambient temperature. Therefore, it is desirable to perform the determination based on the elapsed time since starting, etc., as described above, in a way that reflects the influence of the ambient temperature. For example, the elapsed time since starting at which it is determined that the system has switched from a state where condensation is easily formed to a state where it is not easily formed should be longer when the ambient temperature is low than when it is high.

[0037] One device applicable to the supercharged engine 10 is an EGR (Exhaust Gas Recirculation) system that recirculates a portion of the exhaust gas into the intake air. The exhaust gas (EGR gas) that the EGR system recirculates into the intake air contains moisture. When EGR gas is introduced into the low-temperature intake air cooled by the intercooler 16, the moisture in the EGR gas may condense. At this time, if 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 possible to determine that conditions are favorable for condensation generation while EGR gas is being introduced. Then, in accordance with this determination, the crankcase 18 can be ventilated with the first passage 20 open and the second passage 21 closed, thereby suppressing the inflow of condensed water generated in the intake passage 11 into the crankcase 18.

[0038] <Regarding the configuration of the blow-by gas recirculation system> One-way valves 25 may be individually provided in the portions of the first passage 20 and the second passage 21 that are closer to the intake passage 11 than the switching valve 24.

[0039] If the switching valve 24 is configured to shut off both the first passage 20 and the second passage 21, 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. In addition, there are cases where backflow of blow-by gas into the intake passage 11 through the first passage 20 and the second passage 21 can be permitted, such as when an oil separator to remove oil from the blow-by gas is installed in the first passage 20 and the second passage 21. In such cases, the one-way valve 25 can also be omitted.

[0040] As shown in Figure 6, the first passage 20 and the second passage 21 may be configured as independent passages. In Figure 6, switching valves 24A and 24B are installed in the first passage 20 and the second passage 21, respectively. The control unit 27 controls the two switching valves 24A and 24B so that only one of the first passage 20 or the second passage 21 is connected. In this case, the switching mechanism consists of the two switching valves 24A and 24B. In Figure 6, when the supercharged engine 10 is operating naturally or stopped, the control unit 27 controls both switching valves 24A and 24B to be shut off. 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 this control, one-way valves that restrict the flow of gas from the crankcase 18 to the intake passage 11 may be installed in the first passage 20 and the second passage 21, respectively.

[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 devices of the above embodiments and modified examples are also applicable 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 selector valve 25 One-way valve 26 PCV valves 27 Control Unit 28 Oil temperature sensor

Claims

1. A blow-by gas recirculation device for a supercharged engine, comprising a supercharger having a compressor installed in the intake passage and capable of adjusting the supercharging rate of the intake air, an intercooler installed in the intake passage downstream of the compressor, and a throttle valve installed in the intake passage downstream of the intercooler, recirculates blow-by gas from the crankcase to the intake passage, A first passage connects the portion of the intake passage downstream of the compressor and upstream of the intercooler with the crankcase, A second passage connects the portion of the intake passage downstream of the intercooler with the crankcase, A third passage connecting the portion of the intake passage upstream of the compressor and the crankcase, Switching mechanism, The supercharger, the switching mechanism, and the control unit that controls the throttle valve, It is equipped with, The switching mechanism is a mechanism that switches between a state in which the first passage is open and the second passage is closed, and a state in which the first passage is closed and the second passage is open. The control unit increases the supercharging rate of the supercharger and reduces the opening of the throttle valve, thereby making the intake manifold pressure, which is the intake pressure downstream of the throttle valve in the intake passage, below atmospheric pressure, while making the supercharging pressure, which is the intake pressure downstream of the compressor and upstream of the throttle valve in the intake passage, higher than atmospheric pressure. In this state, the control unit controls the switching mechanism so that the first passage is open and the second passage is closed. Blow-by gas recirculation device.

2. The blow-by gas recirculation device according to Claim 1, wherein the control unit determines whether or not the crankcase is in a state where condensate is likely to be generated, and controls the switching mechanism such that the first passage is open and the second passage is closed if it is determined that the crankcase is in a state where condensate is likely to be generated, and the first passage is closed and the second passage is open if it is determined that the crankcase is not in a state where condensate is likely to be generated.

3. The blow-by gas recirculation device according to claim 1, further comprising: a fourth passage connecting the portion of the intake passage downstream of the throttle valve to the crankcase; and a PCV valve that restricts the flow of gas from the intake passage to the crankcase through the fourth passage.

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

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

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