Ventilation system of supercharged engine

Abstract

The invention provides a ventilation system of a supercharged engine. The first passage communicates the downstream intake part with the crankcase in order to ventilate the crankcase. A second passage communicates the upstream intake portion with the crankcase. The oil separator is provided in the second passage. A third passage communicates the downstream intake portion with the oil separator. The one-way valve restricts the flow of gas through the third passage from the oil separator toward the downstream intake portion.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority from Japanese patent application No. 2024-049828, filed on March 26, 2024, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to a breathing system for a supercharged engine. Background Art

[0004] A blowby ventilation system described in Japanese Patent Application Laid-Open No. 2008-111422 is known. This blowby ventilation system includes a first passage and a second passage. The first passage connects a downstream portion of the intake passage, downstream of the intercooler, to the crankcase. The second passage connects an upstream portion of the intake passage, upstream of the compressor, to the crankcase.

[0005] In the ventilation system, during supercharged operation of the supercharged engine, intake air pressurized by the compressor is introduced into the crankcase through the first passage. The pressure of the introduced intake air displaces blowby gas from the crankcase and returns to the intake passage through the second passage, thereby ventilating the crankcase. An oil separator is provided in the second passage of the ventilation system. The oil separator separates oil from the blowby gas that returns to the intake passage. Summary of the Invention

[0006] According to one aspect of the present disclosure, a ventilation system for a supercharged engine is provided. The ventilation system includes a first passage connecting the intake passage of the supercharged engine with a crankcase. The supercharged engine includes a compressor arranged in the intake passage. The intake passage includes an upstream intake portion located upstream relative to the compressor and a downstream intake portion located downstream relative to the compressor. A throttle valve is arranged in the downstream intake portion. The first passage connects the downstream intake portion with the crankcase in order to ventilate the crankcase. A second passage connects the upstream intake portion with the crankcase. An oil separator is arranged in the second passage. A third passage connects the downstream intake portion with the oil separator. A one-way valve restricts the flow of gas from the oil separator toward the downstream intake portion through the third passage.

[0007] The ventilation system of the supercharged engine has the effect of suppressing the generation of emulsion.

[0008] Blow-by gas in the crankcase contains water. In typical ventilation systems, if water in the blow-by gas mixes with the oil during oil separation in the oil separator, it can create an emulsion. The above structure prevents this possibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a diagram schematically showing the structure of an embodiment of a ventilation system for a supercharged engine.

[0010] Figure 2 Yes Figure 1 Diagram showing the flow of gas in the ventilation system of a supercharged engine during natural aspiration operation.

[0011] Figure 3 Yes Figure 1 A diagram showing the flow of gas in the ventilation system of a supercharged engine during supercharged operation.

[0012] Figure 4 It is a diagram schematically showing a modified example of the ventilation system of a supercharged engine. DETAILED DESCRIPTION

[0013] In this specification, “at least one of A and B” should be understood to mean “only A”, “only B” or “both A and B”.

[0014] Figures 1 to 3 An embodiment of a ventilation system for a supercharged engine will be described in detail.

[0015] <Structure of Supercharged Engine 10>

[0016] Reference Figure 1 The structure of the supercharged engine 10 will be described. The supercharged engine 10 adopts the ventilation system of this embodiment. Figure 1 The supercharged engine 10 shown is a hydrogen engine that uses hydrogen as fuel. In a hydrogen engine, blowby gas may contain combustible hydrogen. Therefore, the ventilation performance of the blowby gas of a hydrogen engine is required to be higher than that of the blowby gas of a gasoline engine or a diesel engine.

[0017] The supercharged engine 10 includes a cylinder block 11. A plurality of cylinders 12 are formed inside the cylinder block 11. Figure 1 In the figure, only one of the multiple cylinders 12 is shown. A piston 13 is housed in each cylinder 12 in a freely reciprocating manner. A combustion chamber 17 for burning hydrogen is formed in the portion of the cylinder 12 above the piston 13 in the figure. An oil pan 14 for storing oil is mounted at the lower portion of the cylinder block 11. A crankcase 15 is formed in the cylinder block 11 below the cylinder 12. A cylinder head 16 is mounted on the upper portion of the cylinder block 11. Inside the cylinder head 16, a separate intake port 18 and exhaust port 19 are formed for each cylinder 12. A cylinder head cover 16A is mounted on the upper portion of the cylinder head 16. A valve chamber 20 for accommodating the valve mechanism is formed in the upper portion of the cylinder head 16 covered by the cylinder head cover 16A.

[0018] The supercharged engine 10 includes an intake passage 21, which serves as an air intake path for the combustion chamber 17, and an exhaust passage 22, which serves as an exhaust path for the exhaust gas from the combustion chamber 17. An air filter 23 is provided in the intake passage 21 to filter dust and other particles from the air. A compressor 24 is provided in the downstream portion of the intake passage 21, downstream of the air filter 23. A turbine 25 is provided in the exhaust passage 22. The compressor 24 and turbine 25 together constitute a turbocharger. Specifically, the intake passage 21 includes an upstream intake section 21a, upstream of the compressor 24, and a downstream intake section 21b, downstream of the compressor 24. An intercooler 26 is provided in the downstream intake section 21b. The intercooler 26 is a heat exchanger used to cool the air heated by the compression of the compressor 24. A throttle valve 27 is provided in the downstream portion of the intake passage 21, downstream of the intercooler 26. The throttle valve 27 adjusts the flow rate of air delivered to the combustion chamber 17 through the intake passage 21. An intake manifold 28 is provided downstream of the throttle valve 27. The intake passage 21 branches off at the intake manifold 28 for each cylinder 12. The intake manifold 28 is connected to each combustion chamber 17 via an intake port 18.

[0019] The supercharged engine 10 includes an injector 29, a hydrogen tank 30, and a pressure regulating device 31. The pressure regulating device 31 regulates the pressure of hydrogen in the hydrogen tank 30 and supplies the hydrogen to the injector 29. The injector 29 injects hydrogen into the air used for combustion in the combustion chamber 17. Figure 1 The injector 29 is provided so as to inject hydrogen into the intake port 18. The present invention is not limited thereto, and the injector 29 may be provided so as to inject hydrogen into the combustion chamber 17.

[0020] <About the structure of the ventilation system>

[0021] Next, the structure of the ventilation system of this embodiment applied to the supercharged engine 10 will be described. This ventilation system is configured to ventilate the blowby gas in the crankcase 15 by releasing the blowby gas into the intake air. The ventilation system of this embodiment includes a first passage R1, a second passage R2, a third passage R3, and a fourth passage R4.

[0022] The first passage R1 connects the downstream intake portion 21b with the interior of the crankcase 15. In the ventilation system of this embodiment, the connection portion of the first passage R1 connected to the intake passage 21 is connected to the intake manifold 28. The first passage R1 includes a first PCV hose 45 and a first PCV valve 46. The first PCV hose 45 connects the crankcase 15 to the intake manifold 28. The first PCV valve 46 allows gas to flow from the intake passage 21 to the interior of the crankcase 15 through the first passage R1. On the other hand, the first PCV valve 46 restricts the flow of gas from the crankcase 15 to the intake passage 21 through the first passage R1. The first PCV valve 46 is provided at the connection portion of the first PCV hose 45 connected to the crankcase 15.

[0023] The second passage R2 connects the upstream intake section 21a with the interior of the crankcase 15. The second passage R2 includes an oil return passage 47, the valve operating chamber 20, a first oil separator 48, and a second PCV hose 49. The oil return passage 47 passes through the interior of the cylinder block 11 and cylinder head 16, connecting the valve operating chamber 20 with the crankcase 15. The oil return passage 47 serves as a passage for returning oil from the valve operating chamber 20 to the oil pan 14. Furthermore, the oil return passage 47 also functions as a passage for circulating gas between the valve operating chamber 20 and the crankcase 15. The first oil separator 48 separates oil mist from the blowby gas flowing through the second passage R2. The first oil separator 48 is located inside the cylinder head cover 16A. In this embodiment, the first oil separator 48 corresponds to the oil separator provided in the second passage R2. The second PCV hose 49 connects the downstream portion of the upstream intake section 21a, downstream of the air cleaner 23, to the first oil separator 48.

[0024] The third passage R3 connects the downstream intake section 21b with the first oil separator 48. In the ventilation system of this embodiment, the connection portion of the third passage R3 to the intake passage 21 is connected to the upstream portion of the downstream intake section 21b, upstream of the intercooler 26. The third passage R3 is formed by a hose, a tube, or the like. A check valve 50 is provided in the third passage R3. The check valve 50 restricts the flow of gas from the first oil separator 48 to the intake passage 21.

[0025] The fourth passage R4 connects the downstream portion of the intake passage 21, downstream of the throttle valve 27, with the interior of the crankcase 15. The fourth passage R4 includes a blow-by gas passage 40, a second oil separator 41, a second PCV valve 42, a third PCV hose 43, and a third oil separator 44. The second and third oil separators 41 and 44 separate oil mist from the blow-by gas flowing through the fourth passage R4. The second oil separator 41 is mounted inside the cylinder head cover 16A. The blow-by gas passage 40 passes through the interiors of the cylinder block 11 and cylinder head 16, connecting the interior of the crankcase 15 to the second oil separator 41. The third oil separator 44 is provided in the cylinder block 11 within the blow-by gas passage 40. The third PCV hose 43 connects the second oil separator 41 to the intake manifold 28. The second PCV valve 42 restricts the flow of gas from the intake passage 21 to the crankcase 15 through the fourth passage R4. The second PCV valve 42 is provided at a connection portion of a third PCV hose 43 connected to the second oil separator 41 .

[0026] In the ventilation system of this embodiment, the minimum flow path area S1 of the first passage R1 is larger than the minimum flow path area S3 of the third passage R3 (S1>S3). The minimum flow path area S2 of the second passage R2 is larger than the minimum flow path area S1 of the first passage R1 (S2>S1). These minimum flow path areas represent the flow path areas of the portions of each passage where the gas flow path area is the smallest. This relationship between the minimum flow path areas S1, S2, and S3 (S2>S1>S3) can be achieved by varying the inner diameter of the hoses that constitute each passage. Furthermore, the aforementioned relationship between the minimum flow path areas S1, S2, and S3 can be achieved by providing throttling sections within each passage (R1, R2, R3).

[0027] <Functions and Effects of Implementation Methods>

[0028] The operation and effects of the ventilation system of the supercharged engine 10 according to the present embodiment will be described.

[0029] Figure 2 The flow of gas in the ventilation system during the naturally aspirated operation of the supercharged engine 10 is shown. Figure 2 and Figure 3The hollow arrows shown indicate the direction of air flow within the ventilation system. The hatched arrows indicate the direction of blowby gas flow within the ventilation system. During natural intake operation, the downstream portion of the intake passage 21, which is located downstream of the throttle valve 27, becomes negative pressure due to the throttling of the throttle valve 27. Therefore, for example, the pressure within the intake manifold 28 is lower than atmospheric pressure. The crankcase 15 is connected to the negative-pressure intake manifold 28 via the fourth passage R4. The second PCV valve 42 provided in the fourth passage R4 allows the flow of gas from the crankcase 15 toward the intake passage 21. Therefore, the blowby gas within the crankcase 15 is drawn into the intake manifold 28 via the fourth passage R4. Air is introduced into the crankcase 15 via the second passage R2 and the third passage R3.

[0030] Figure 3 This figure shows the flow of gas within the ventilation system during supercharged operation of the supercharged engine 10. During supercharged operation, the downstream intake section 21b is at a positive pressure. That is, the pressure in the downstream intake section 21b is higher than atmospheric pressure. Air is introduced from the positive-pressure intake manifold 28 into the crankcase 15 via the first passage R1. Blow-by gas within the crankcase 15 is transported by the introduced air through the second passage R2 to the upstream intake section 21a.

[0031] As blow-by gas is delivered to the upstream intake portion 21a through the second passage R2, oil is separated from the blow-by gas in the first oil separator 48 of the second passage R2. If the temperature inside the first oil separator 48 is low, moisture in the blow-by gas may mix with the oil separated by the first oil separator 48, potentially forming an emulsion.

[0032] In contrast, the ventilation system of this embodiment is provided with a third passage R3. The third passage R3 connects the downstream air intake section 21b with the first oil separator 48. In the downstream air intake section 21b during supercharging operation, high-temperature air exists due to the adiabatic compression of the compressor 24. This high-temperature air is introduced into the first oil separator 48 through the third passage R3, thereby increasing the temperature inside the first oil separator 48. The higher the ambient temperature, the more difficult it is to form an emulsion. In addition, the higher the ambient temperature, the lower the viscosity of the emulsion that has been formed. Moreover, by introducing air into the first oil separator 48 through the third passage R3, the water vapor partial pressure of the blowby gas introduced into the first oil separator 48 is reduced. When the water vapor partial pressure of the blowby gas is reduced, the dew point is lowered. Therefore, the generation of condensed water in the first oil separator 48 can be suppressed. Therefore, the generation of emulsion is suppressed.

[0033] According to the ventilation system of the supercharged engine 10 of the present embodiment described above, the following effects can be achieved.

[0034] (1) The ventilation system of this embodiment includes the following: a first passage R1, a second passage R2, a third passage R3, and a check valve 50. The first passage R1 connects the downstream intake section 21b to the crankcase 15. The second passage R2 connects the upstream intake section 21a to the crankcase 15. The third passage R3 connects the downstream intake section 21b to the first oil separator 48 provided in the second passage R2. The check valve 50 restricts the flow of gas from the first oil separator 48 to the intake passage 21 through the third passage R3. In this ventilation system, air compressed by the compressor 24 and heated to a high temperature is introduced into the first oil separator 48 during supercharging operation. The introduction of the high-temperature air heats the first oil separator 48. Therefore, the formation of emulsion within the first oil separator 48 can be suppressed. Therefore, the ventilation system of this embodiment suppresses the formation of emulsion.

[0035] (2) The third passage R3 connects the upstream portion of the downstream air intake section 21b, which is upstream of the intercooler 26, to the first oil separator 48. Therefore, compared to, for example, the case where air from the downstream portion of the downstream air intake section 21b, which is downstream of the intercooler 26, is introduced into the first oil separator 48, it is possible to introduce high-temperature air into the first oil separator 48. Consequently, the effect of suppressing emulsion formation is enhanced.

[0036] (3) The minimum flow area S1 of the first passage R1 is larger than the minimum flow area S3 of the third passage R3 (S1>S3). Furthermore, the minimum flow area S2 of the second passage R2 is larger than the minimum flow area S1 of the first passage R1 (S2>S1). If, during supercharged operation of the supercharged engine 10, the flow rate of gas flowing into the crankcase 15 through the first passage R1 continues to be greater than the flow rate of gas discharged from the crankcase 15 through the second passage R2, the following situation may occur. That is, the internal pressure of the crankcase 15 may increase. In contrast, by setting the minimum flow area of ​​each passage as described above, the increase in the internal pressure of the crankcase 15 can be suppressed.

[0037] (Other Implementation Methods)

[0038] The above-mentioned embodiment can be implemented by modifying as follows: The above-mentioned embodiment and the following modification examples can be implemented by combining with each other within the scope of no technical contradiction.

[0039] <About the Third Path R3>

[0040] exist Figures 1 to 3In the ventilation system of the above-described embodiment, the third passage R3 is connected to the upstream portion of the downstream intake portion 21b, which is upstream of the intercooler 26. This is not limiting, and the connecting portion of the third passage R3 connected to the intake passage 21 may be connected to the downstream intake portion 21b. Therefore, the connecting portion of the third passage R3 connected to the intake passage 21 may also be connected to the downstream portion of the downstream intake portion 21b, which is downstream of the intercooler 26. Figure 4 An example is shown. In this modified example, air that has passed through the intercooler 26 is introduced into the first oil separator 48 during supercharging operation. Although this introduced air is cooled by the intercooler 26, its temperature is higher than that of the outside air. Therefore, the first oil separator 48 can be heated.

[0041] You can also Figure 4 The third path R3 is formed as shown. Figure 4 In the ventilation system shown, the third passage R3 branches off from the first passage R1. Specifically, the third passage R3 communicates with the downstream portion of the downstream intake section 21b, downstream of the intercooler 26, via the first passage R1. The first passage R1 branches off from the third passage R3 at a branching point B1. Specifically, the third passage R3 extends from the downstream intake section 21b along the first passage R1 and, after branching off from the first passage R1 at the branching point B1, connects to the first oil separator 48. Figure 4 The one-way valve 51 of the ventilation system is provided in the first passage R1 between the branch point B1 and the intake passage 21. Figure 4 In the ventilation system, a single one-way valve 51 is responsible for Figures 1 to 3 The functions of the two valves in the ventilation system. Figure 4 The one-way valve 51 bears Figures 1 to 3 The functions of both the one-way valve 50 and the first PCV valve 46 are realized.

[0042] <Other>

[0043] The first oil separator 48 may be provided at a location different from that in the valve operating chamber 20 .

[0044] The size relationship among the minimum flow passage areas S1, S2, and S3 of the first passage R1, the second passage R2, and the third passage R3 may be changed as appropriate.

[0045] When ventilation of the crankcase 15 is not required during the naturally aspirated operation, the fourth passage R4 , the second PCV valve 42 , the second oil separator 41 , the third oil separator 44 , and the like may be omitted.

[0046] The ventilation system of the above-described embodiment and its modified examples can also be applied to a supercharged engine using a fuel other than hydrogen.

Claims

1. A ventilation system for a supercharged engine, wherein: The ventilation system comprises: a first passage connecting an intake passage of the supercharged engine with a crankcase, wherein the supercharged engine includes a compressor disposed in the intake passage, the intake passage includes an upstream intake portion located upstream of the compressor and a downstream intake portion located downstream of the compressor, a throttle valve being disposed in the downstream intake portion, and the first passage connecting the downstream intake portion with the crankcase for ventilating the crankcase; a second passage connecting the upstream air intake portion with the crankcase; an oil separator, disposed in the second passage; a third passage connecting the downstream air intake portion and the oil separator; and A one-way valve restricts the flow of gas from the oil separator toward the downstream intake portion through the third passage.

2. The ventilation system for a supercharged engine according to claim 1, The minimum flow path area of ​​the first passage is configured to be larger than the minimum flow path area of ​​the third passage. The minimum flow path area of ​​the second passage is configured to be larger than the minimum flow path area of ​​the first passage.

3. The ventilation system for a supercharged engine according to claim 1 or 2, The supercharged engine includes an intercooler provided at an upstream portion of the downstream intake portion that is upstream of the throttle valve. The third passage is connected to an upstream portion of the downstream intake portion that is upstream of the intercooler.

4. The ventilation system for a supercharged engine according to any one of claims 1 to 3, The third passage is connected to the downstream intake portion through the first passage, the first passage has a branching position from the third passage, and the third passage is configured to be connected to the oil separator after branching from the first passage at the branching position. The one-way valve is provided in the vicinity of the intake passage relative to the branch position.

5. The ventilation system for a supercharged engine according to any one of claims 1 to 4, The fuel for the supercharged engine is hydrogen.

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