Supercharged engine

Abstract

To excellently ventilate blow-by gas in an oil tank in both of natural intake operation and supercharging operation.SOLUTION: The dry sump supercharged engine 10, which circulates lubricating oil between the engine 10 and the oil tank 30, includes the first circulation passage 34, which connects the portion of the intake passage 17 downstream of the throttle valve 22 to the oil tank 30, the second circulation passage 36, which connects the portion of the intake passage 17 upstream of the compressor 20 to the oil tank 30, the first check valve 35, which is arranged in the first circulation passage 34, and the second check valve 37, which is arranged in the second circulation passage 36.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a dry sump type supercharged engine. [Background technology]

[0002] An engine using a dry sump lubrication system includes a scavenge pump for recovering engine oil from the crankcase and an oil tank for storing the recovered engine oil. Patent Document 1 describes a dry sump supercharged engine configured to recirculate blow-by gas from the oil tank to an intake passage. This supercharged engine recirculates blow-by gas from the oil tank to a portion of the intake passage downstream of the throttle valve during naturally aspirated operation, and to a portion of the intake passage upstream of the compressor during supercharged operation. Of the blow-by gas recirculation paths during both naturally aspirated and supercharged operation, this supercharged engine includes a check valve only in the recirculation path during naturally aspirated operation to prevent intake air from flowing back from the intake passage to the oil tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-113820 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional supercharged engines described above, the return path during supercharged operation, which is not equipped with a check valve, remains open even during naturally aspirated operation. Therefore, during naturally aspirated operation, intake air may flow into the oil tank through the return path during supercharged operation. As a result, there is a risk that the ventilation efficiency of the oil tank during naturally aspirated operation may decrease. [Means for solving the problem]

[0005] The supercharged engine that solves the above problem is a dry sump type supercharged engine that circulates lubricating oil between an intake passage, a compressor installed in the intake passage, a throttle valve installed in a portion of the intake passage downstream of the compressor, a first return path that connects the portion of the intake passage downstream of the throttle valve with the oil tank, a second return path that connects the portion of the intake passage upstream of the compressor with the oil tank, a first check valve that limits the flow of intake air from the intake passage toward the oil tank through the first return path, and a second check valve that limits the flow of intake air in the second return path from the intake passage toward the oil tank. [Effects of the Invention]

[0006] The above-described supercharged engine has the advantage that blow-by gas in the oil tank can be well ventilated both during natural aspirated operation and during supercharged operation. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating a configuration of an embodiment of a supercharged engine; [Figure 2] 2 is a diagram showing the ventilation operation of the oil tank during natural aspiration operation in the supercharged engine of FIG. 1. FIG. [Figure 3] 3A and 3B are diagrams illustrating the ventilation operation of the oil tank during supercharged operation in the supercharged engine of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a supercharged engine will be described in detail below with reference to FIGS. <Supercharged engine configuration> The configuration of a supercharged engine 10 of this embodiment will be described with reference to FIG. 1. The supercharged engine 10 includes a cylinder 12 in which a piston 11 is arranged so as to reciprocate. The piston 11 defines a combustion chamber 13 within the cylinder 12, in which an air-fuel mixture is combusted. The piston 11 is connected to a crankshaft 15 via a connecting rod 14. A crankcase 16 accommodating the crankshaft 15 is provided below the cylinder 12 in the drawing of the supercharged engine 10. The supercharged engine 10 actually has multiple cylinders 12, but FIG. 1 shows only one of them. An intake passage 17, which is an intake passage for intake air, and an exhaust passage 18, which is an exhaust passage for exhaust gas, are connected to the combustion chamber 13. An air cleaner 19, a compressor 20, an intercooler 21, a throttle valve 22, and an intake manifold 23 are provided in the intake passage 17. A turbine 24, which rotates due to the exhaust flow, is provided in the exhaust passage 18. The air cleaner 19 is a filter device that filters out dust and other particles from the intake air. The compressor 20 rotates in conjunction with the turbine 24, compressing the intake air that has passed through the air cleaner 19. The intercooler 21 cools the intake air that has been heated by compression in the compressor 20. The throttle valve 22 is a valve for adjusting the flow rate of intake air in the intake passage 17, and is installed in a portion of the intake passage 17 downstream of the intercooler 21. The intake manifold 23 is a branch pipe that distributes the intake air that has passed through the throttle valve 22 to the combustion chambers 13 of each cylinder 12.

[0009] <Configuration of Lubrication System of Supercharged Engine 10> The configuration of a lubrication system for supplying lubricating oil to the lubricated parts 25 of the supercharged engine 10 will be described. The lubricated parts 25 are sliding contact parts of the components of the supercharged engine 10. The supercharged engine 10 has a dry sump type lubrication system. The dry sump type lubrication system includes an oil tank 30 installed outside the supercharged engine 10. The lubrication system is configured to circulate lubricating oil between the oil tank 30 and the lubricated parts 25 of the supercharged engine 10 by a scavenge pump 31 and a supply pump 32. The scavenge pump 31 is a pump that delivers lubricating oil from the crankcase 16 to the oil tank 30. The supply pump 32 is a pump that delivers lubricating oil from the oil tank 30 to the lubricated parts 25 of the supercharged engine 10.

[0010] While the supercharged engine 10 is operating, the lubricating oil stored in the oil tank 30 is supplied to each lubricated part 25 of the supercharged engine 10 by the supply pump 32. After the lubricating oil has been used to lubricate the lubricated parts 25, it is collected in the crankcase 16. The lubricating oil in the crankcase 16 is returned to the oil tank 30 by the scavenge pump 31. In this way, the lubricating oil is circulated between the oil tank 30 and the lubricated parts 25 of the supercharged engine 10.

[0011] <Configuration of the ventilation system for the oil tank 30> The lubricating oil that the scavenge pump 31 delivers to the oil tank 30 is mixed with blow-by gas, which contains combustion gas that has leaked from the combustion chamber 13 into the crankcase 16. The supercharged engine 10 is equipped with a ventilation system that recirculates the blow-by gas that has flowed into the oil tank 30 back into the intake air.

[0012] The ventilation system includes two paths, a first recirculation path 34 and a second recirculation path 36, for recirculating blow-by gas from the oil tank 30 to the intake passage 17. The ventilation system also includes an air introduction path 39.

[0013] The first recirculation path 34 is a recirculation path for blow-by gas that is configured to connect a portion of the intake passage 17 downstream of the throttle valve 22 with the oil tank 30. More specifically, the end of the first recirculation path 34 on the intake passage 17 side is connected to the intake manifold 23. The first recirculation path 34 is made up of piping such as hoses and pipes and a first check valve 35. The first check valve 35 is a valve that limits the flow of intake air from the intake passage 17 toward the oil tank 30 through the first recirculation path 34. In the case of the supercharged engine 10 of this embodiment, the first check valve 35 is installed in the connection portion of the first recirculation path 34 to the oil tank 30.

[0014] The second recirculation path 36 is a recirculation path for blow-by gas that is configured to connect a portion of the intake passage 17 upstream of the compressor 20 with the oil tank 30. More specifically, the end of the second recirculation path 36 on the intake passage 17 side is connected to a portion of the intake passage 17 upstream of the compressor 20 and downstream of the air cleaner 19. The second recirculation path 36 is configured by piping such as hoses and pipes and a second check valve 37. The second check valve 37 is a valve that limits the flow of intake air from the intake passage 17 toward the oil tank 30 through the second recirculation path 36. In the case of the supercharged engine 10 of this embodiment, the second check valve 37 is installed in a connection portion of the second recirculation path 36 to the oil tank 30.

[0015] The air introduction passage 39 is a passage that connects the crankcase 16 to a portion of the intake passage 17 upstream of the compressor 20. More specifically, the end of the air introduction passage 39 on the intake passage 17 side is connected to a portion of the intake passage 17 upstream of the compressor 20 and downstream of the air cleaner 19. The air introduction passage 39 is shown in a simplified manner in FIG. 1. In more detail, the air introduction passage 39 is made up of a pipe that connects the cam chamber of the supercharged engine 10 to the intake passage 17, and a passage that passes through the inside of the cylinder head and cylinder block of the supercharged engine 10 to connect the cam chamber to the crankcase 16. A restrictor 40 is installed in the air introduction passage 39 to limit the flow rate of intake air flowing from the intake passage 17 to the crankcase 16.

[0016] An oil separator 33 that separates oil mist from the blow-by gas is installed in the oil tank 30. The oil tank 30 is configured to send the blow-by gas through the oil separator 33 to a first return path 34 and a second return path 36.

[0017] <Operation of the supercharged engine 10 of this embodiment> Next, the ventilation operation of the oil tank 30 of the supercharged engine 10 of this embodiment will be described with reference to Figures 2 and 3. During operation of the supercharged engine 10, the scavenge pump 31 sends blow-by gas from the crankcase 16 together with lubricating oil to the oil tank 30. When the internal pressure of the crankcase 16 decreases in response to the sending of blow-by gas, intake air is replenished into the crankcase 16 through the air introduction passage 39. In Figures 2 and 3, this flow of intake air is indicated by outline arrows.

[0018] 2, the flow of blow-by gas during naturally aspirated operation of the supercharged engine 10 is indicated by hatched arrows. During naturally aspirated operation, the throttle valve 22 is throttled, causing the internal pressure in the portion of the intake passage 17 downstream of the throttle valve 22 to become negative, lower than atmospheric pressure. The blow-by gas sent together with lubricating oil from the crankcase 16 to the oil tank 30 by the scavenge pump 31 is drawn into the intake manifold 23 through the first return path 34 by this negative pressure.

[0019] 3, the flow of blow-by gas during supercharged operation of the supercharged engine 10 is indicated by hatched arrows. During supercharged operation, the internal pressure in the portion of the intake passage 17 downstream of the compressor 20 becomes a positive pressure higher than atmospheric pressure. At this time, the first recirculation path 34 is closed by the first check valve 35. On the other hand, during supercharged operation, the intake air is drawn in by the compressor 20, and a negative pressure is created in the portion of the intake passage 17 upstream of the compressor 20 and downstream of the air cleaner 19. Due to this negative pressure, the blow-by gas in the oil tank 30 is drawn into the intake passage 17 through the second recirculation path 36.

[0020] <Effects of the supercharged engine 10 of this embodiment> The supercharged engine 10 of this embodiment has the following advantages. (1) The supercharged engine 10 is equipped with a first recirculation path 34 and a second recirculation path 36 as paths for recirculating blow-by gas in the oil tank 30 to the intake passage 17. The first recirculation path 34 is a recirculation path for blow-by gas configured to connect a portion of the intake passage 17 downstream of the throttle valve 22 with the oil tank 30. The second recirculation path 36 is a recirculation path for blow-by gas configured to connect a portion of the intake passage 17 upstream of the compressor 20 with the oil tank 30. During natural aspiration operation of the supercharged engine 10, a negative pressure is created in a portion of the intake passage 17 downstream of the throttle valve 22. This negative pressure causes the blow-by gas in the oil tank 30 to be recirculated to the intake passage 17 via the first recirculation path 34. On the other hand, during supercharged operation of the supercharged engine 10, a negative pressure is created in a portion of the intake passage 17 upstream of the compressor 20. This negative pressure causes the blow-by gas in the oil tank 30 to be recirculated to the intake passage 17 through the second recirculation path 36. Therefore, the blow-by gas in the oil tank 30 can be well ventilated whether the supercharged engine 10 is operating in a naturally aspirated or supercharged state.

[0021] (2) If the internal pressure of the oil tank 30 is positive, blow-by gas in the oil tank 30 is likely to leak to the outside air due to deterioration or holes in the sealing material. Therefore, it is desirable to maintain the internal pressure of the oil tank 30 at a negative pressure while the supercharged engine 10 is operating. In contrast, the supercharged engine 10 of this embodiment is equipped with a first check valve 35 and a second check valve 37 that restrict the flow of intake air from the intake passage 17 toward the oil tank 30 through the first recirculation path 34 and the second recirculation path 36, respectively. These first check valve 35 and second check valve 37 prevent the backflow of intake air from the intake passage 17 to the oil tank 30 through the first recirculation path 34 and the second recirculation path 36. Therefore, the internal pressure of the oil tank 30 is likely to be maintained at a negative pressure both during natural aspirated operation and during supercharged operation.

[0022] (3) If a large amount of blow-by gas flows into the intake passage 17 at one time, the air-fuel ratio of the mixture burning in the combustion chamber 13 may be disturbed. The flow rate of blow-by gas flowing into the intake passage 17 can be limited, for example, by adjusting the flow path areas of the first recirculation path 34 and the second recirculation path 36. However, in such a case, when a large amount of blow-by gas flows from the crankcase 16 into the oil tank 30, it may not be possible to recirculate all of the flowing blow-by gas to the intake passage 17, and the internal pressure of the oil tank 30 may increase. In response to this, the supercharged engine 10 of this embodiment has a restrictor 40 installed in the air introduction path 39 that communicates between the intake passage 17 and the crankcase 16. The restrictor 40 restricts the flow rate of intake air flowing into the crankcase 16 through the air introduction path 39. This restriction also limits the flow rate of blow-by gas that the scavenge pump 31 can draw from the crankcase 16 and send to the oil tank 30, and further limits the flow rate of blow-by gas that is returned from the oil tank 30 to the intake passage 17. Therefore, the flow rate of blow-by gas flowing into the intake passage 17 can also be limited by installing a throttle 40 in the air introduction passage 39. Even if such a throttle 40 is installed, the blow-by gas transport capacity of the first recirculation path 34 and the second recirculation path 36 does not decrease. Therefore, the flow rate of blow-by gas flowing into the intake passage 17 can be limited while suppressing an increase in the internal pressure of the oil tank 30.

[0023] (Other embodiments) The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0024] The locations where the first check valve 35 and the second check valve 37 are installed may be changed. For example, the first check valve 35 and the second check valve 37 may be installed at the connection portions of the first recirculation path 34 and the second recirculation path 36 to the intake passage 17. Furthermore, the first check valve 35 and the second check valve 37 may be installed in intermediate portions of the first recirculation path 34 and the second recirculation path 36.

[0025] The air introduction passage 39 may not be provided with the throttle 40 . The air introduction passage 39 may be omitted, and air may be introduced into the crankcase 16 from a location other than the intake passage 17.

[0026] The configuration of the supercharged engine 10 may be changed as appropriate. For example, the supercharged engine 10 may be configured to employ a supercharger other than an exhaust turbine type, such as a mechanical supercharger that drives the compressor 20 using the power of the supercharged engine 10. [Explanation of symbols]

[0027] 10...Supercharged engine, 16...Crankcase, 17...Intake passage, 20...Compressor, 22...Throttle valve, 30...Oil tank, 34...First return path, 35...First check valve, 36...Second return path, 37...Second check valve, 39...Air introduction path, 40...Throttle.

Claims

1. A dry sump type supercharged engine that circulates lubricating oil between the engine and an oil tank, An intake passage; a compressor installed in the intake passage; a throttle valve disposed in the intake passage downstream of the compressor; a first return path that connects a portion of the intake passage downstream of the throttle valve with the oil tank; a second return path that connects a portion of the intake passage upstream of the compressor with the oil tank; a first check valve that limits the flow of intake air from the intake passage toward the oil tank through the first return path; a second check valve that limits the flow of intake air in the second return path from the intake passage toward the oil tank; Supercharged engine with.

2. an air introduction passage that communicates a portion of the intake passage upstream of the compressor with a crankcase of the supercharged engine; a throttle provided in the air introduction path; 2. The supercharged engine according to claim 1, comprising:

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