Engine

Abstract

To suppress insufficient supply of lubricating oil when an engine is started.SOLUTION: A first negative pressure path 34 and a second negative pressure path 36 connected to a negative pressure source for generating negative pressure during operation of an engine 10 are connected to an oil tank 30 in addition to a recovery path 26 and an oil feed path 27 which are circulation paths of lubricating oil between a lubrication part 25 of the engine 10 and the oil tank 30. By providing a first check valve 35 and a second check valve 37 for closing the first negative pressure passage 34 and the second negative pressure passage 36 when the engine 10 is stopped, a negative pressure state inside the oil tank 30 is maintained even after the engine is stopped.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A dry sump engine such as that disclosed in Patent Document 1 includes a scavenge pump for recovering engine oil in the crankcase, and an oil tank for storing the recovered engine oil. [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 low-temperature environments, the viscosity of the lubricating oil increases, which hinders the scavenge pump from collecting the lubricating oil. As a result, the engine may be stopped before a sufficient amount of lubricating oil has been collected in the oil tank. In such cases, there is a risk that the supply of lubricating oil will be insufficient the next time the engine is started. [Means for solving the problem]

[0005] The engine that solves the above problem is a dry sump engine that stores lubricating oil in an oil tank installed outside the crankcase, and the oil tank is connected to multiple paths, including a negative pressure path connected to a negative pressure source that generates negative pressure while the engine is operating, and a lubricating oil circulation path between the lubricating parts of the engine and the oil tank, and the engine is equipped with a closing mechanism that closes all paths connected to the oil tank except for the circulation path when the engine is stopped. [Effects of the Invention]

[0006] The engine has the effect of suppressing shortage of lubricating oil supply when the engine is started. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating a schematic configuration of an embodiment of an engine. FIG. [Figure 2] 2 is a diagram showing the ventilation operation of the oil tank in the engine of FIG. 1 during natural aspiration operation. FIG. [Figure 3] 3A and 3B are diagrams illustrating ventilation of the oil tank during supercharged operation in the engine of FIG. 1. [Figure 4] 1. FIG. 4 is a diagram showing the operation of recovering lubricating oil after the engine of FIG. 1 is stopped. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of the engine will be described in detail below with reference to Figures 1 to 4. The engine of this embodiment has a dry sump type circulation system and is configured as a supercharged engine equipped with an exhaust turbine type supercharger.

[0009] <Engine 10 Configuration> The configuration of an engine 10 of this embodiment will be described with reference to Figure 1. The engine 10 has a cylinder 12 in which a piston 11 is arranged so as to be able to reciprocate freely. Inside the cylinder 12, a combustion chamber 13 in which an air-fuel mixture is burned is defined by the piston 11. The piston 11 is connected to a crankshaft 15 via a connecting rod 14. A crankcase 16 that houses the crankshaft 15 is provided below the cylinder 12 of the engine 10 in the drawing. The engine 10 actually has multiple cylinders 12, but Figure 1 shows only one of them.

[0010] The combustion chamber 13 is connected to 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. The intake passage 17 is provided with an air cleaner 19, a compressor 20, an intercooler 21, a throttle valve 22, and an intake manifold 23. The exhaust passage 18 is provided with a turbine 24 that rotates due to the exhaust flow. 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 by 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 provided 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.

[0011] <Configuration of the lubrication system of the engine 10> The configuration of a lubrication system for supplying lubricating oil to lubricating parts 25 of engine 10 will be described. Lubricating parts 25 are sliding contact parts of components of engine 10, etc. Engine 10 is equipped with an oil tank 30 installed outside crankcase 16. Oil tank 30 is connected to crankcase 16 through a recovery path 26. Oil tank 30 is also connected to lubricating parts 25 of engine 10 through an oil supply path 27. A scavenge pump 31 is installed in recovery path 26, and a supply pump 32 is installed in oil supply path 27. The scavenge pump 31 is a pump that delivers lubricating oil from crankcase 16 to oil tank 30. The supply pump 32 is a pump that delivers lubricating oil from oil tank 30 to lubricating parts 25 of engine 10.

[0012] While the engine 10 is operating, the lubricating oil stored in the oil tank 30 is supplied by the supply pump 32 to each lubricated part 25 of the engine 10. 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 manner, the lubricating oil is circulated between the oil tank 30 and the lubricated parts 25 of the engine 10. In the case of the engine 10 of this embodiment, the recovery path 26 and the oil supply path 27 correspond to the lubricating oil circulation path between the lubricated parts 25 of the engine 10 and the oil tank 30.

[0013] <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 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.

[0014] The ventilation system includes two paths, a first negative pressure path 34 and a second negative pressure path 36, for returning blow-by gas from the oil tank 30 to the intake passage 17. The ventilation system also includes an air introduction path 39.

[0015] The first negative pressure path 34 is a path that connects the portion of the intake passage 17 downstream of the throttle valve 22 with the oil tank 30. More specifically, the end of the first negative pressure path 34 on the intake passage 17 side is connected to the intake manifold 23. The first negative pressure 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 restricts the flow of intake air from the intake passage 17 toward the oil tank 30 through the first negative pressure path 34. In the case of the engine 10 of this embodiment, the first check valve 35 is installed in the first negative pressure path 34 at a connection portion to the oil tank 30.

[0016] The second negative pressure path 36 is a path that connects a portion of the intake passage 17 upstream of the compressor 20 with the oil tank 30. More specifically, the end of the second negative pressure 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 negative pressure path 36 is made up of piping such as hoses and pipes and a second check valve 37. The second check valve 37 is a valve that restricts the flow of intake air from the intake passage 17 toward the oil tank 30 through the second negative pressure path 36. In the case of the engine 10 of this embodiment, the second check valve 37 is installed in a connection portion of the second negative pressure path 36 to the oil tank 30.

[0017] The air introduction passage 39 is a passage that connects the crankcase 16 to a portion of the intake passage 17 that is 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 that is 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 engine 10 to the intake passage 17, a passage that passes through the inside of the cylinder head and cylinder block of the engine 10 to connect the cam chamber to the crankcase 16, and the like. 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.

[0018] 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 the first negative pressure path 34 and the second negative pressure path 36.

[0019] <Operation of the embodiment> While the engine 10 is running, 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 the 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 the outline arrows.

[0020] 2, the flow of blow-by gas during naturally aspirated operation of the 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 a negative pressure 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 sucked into the intake manifold 23 through the first negative pressure path 34 by this negative pressure.

[0021] 3, the flow of blow-by gas during supercharged operation of the 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 negative pressure 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 negative pressure path 36.

[0022] In the case of the engine 10 of this embodiment, the following two portions correspond to negative pressure sources that generate negative pressure during operation of the engine 10. One is a portion of the intake passage 17 downstream of the throttle valve 22 where negative pressure is generated during natural aspiration operation. The other is a portion of the intake passage 17 upstream of the compressor 20 where negative pressure is generated during supercharging operation. The first negative pressure path 34 and the second negative pressure path 36 connected to these negative pressure sources correspond to negative pressure paths.

[0023] In this way, in the engine 10 of this embodiment, whether in naturally aspirated operation or supercharged operation, the oil tank 30 is ventilated by drawing in blow-by gas using the negative pressure generated in the intake passage 17. Therefore, the inside of the oil tank 30 is under negative pressure while the engine 10 is operating. The inside of the oil tank 30 is also under negative pressure when the engine 10 stops operating.

[0024] FIG. 4 shows the state immediately after the engine 10 is stopped. Here, a case where the inside of the oil tank 30 is under negative pressure when the engine is stopped will be described. When the engine 10 is stopped, the entire intake passage 17 becomes atmospheric pressure. However, at this time, the first negative pressure path 34 and the second negative pressure path 36 are closed by the first check valve 35 and the second check valve 37. Therefore, of the paths connected to the oil tank 30, only two paths, the recovery path 26 and the oil supply path 27, which constitute the lubricating oil circulation path, are open. Therefore, the inside of the oil tank 30 is maintained under negative pressure for a while after the engine is stopped.

[0025] When the engine 10 stops and the scavenge pump 31 stops pumping lubricating oil, the inside of the crankcase 16 becomes atmospheric pressure due to the introduction of air through the air inlet passage 39. Meanwhile, as described above, the inside of the oil tank 30 is under negative pressure when the engine is stopped. Therefore, the lubricating oil remaining in the crankcase 16 is sucked into the oil tank 30.

[0026] If the engine 10 is started when the amount of lubricating oil in the oil tank 30 is less than a certain level, it may not be possible to immediately supply lubricating oil to the lubrication unit 25 due to air entering the oil supply path 27, etc. In particular, in a low-temperature environment, the viscosity of the lubricating oil is high, which hinders the scavenge pump 31 from recovering the lubricating oil from the crankcase 16, and therefore the lubricating oil shortage after the engine starts may continue for a long time. In contrast, in this embodiment, even if the amount of lubricating oil in the oil tank 30 is small when the engine is stopped, the negative pressure in the oil tank 30 allows the lubricating oil to be recovered from the crankcase 16 after the engine is stopped. Therefore, it is unlikely that the lubricating oil shortage will occur when the engine is started.

[0027] In the case of the engine 10 of this embodiment, four paths are connected to the oil tank 30: the recovery path 26 and the oil supply path 27, which are lubricating oil circulation paths, the first negative pressure path 34, and the second negative pressure path 36. Therefore, of the paths connected to the oil tank 30, all paths except the circulation path are two paths: the first negative pressure path 34 and the second negative pressure path 36. In this embodiment, a closing mechanism that closes all paths connected to the oil tank 30 except the circulation path when the engine 10 is stopped is composed of the first check valve 35 and the second check valve 37.

[0028] <Effects of the embodiment> The engine 10 of this embodiment has the following advantages. (1) After the engine is stopped, a negative pressure state is maintained inside the oil tank 30. This negative pressure allows lubricating oil remaining in the crankcase 16 to be recovered into the oil tank 30. This makes it easier to ensure that there is enough lubricating oil in the oil tank 30 when the engine is started. Therefore, the engine 10 of this embodiment has the effect of preventing a shortage of lubricating oil when the engine is started.

[0029] (2) The oil tank 30 is connected to a portion of the intake passage 17 downstream of the throttle valve 22 through the first negative pressure path 34, and is connected to a portion of the intake passage 17 upstream of the compressor 20 through the second negative pressure path 36. Therefore, the inside of the oil tank 30 can be made negative pressure during both natural aspirated operation and supercharged operation. This also allows blow-by gas inside the oil tank 30 to be effectively ventilated.

[0030] (3) The negative pressure generating portion of the intake passage 17 is used as a negative pressure source. That is, the negative pressure generated in the intake passage 17 while the engine is running is used to create a negative pressure inside the oil tank 30. Therefore, the inside of the oil tank 30 can be created as a negative pressure when the engine is stopped without adding a negative pressure generating device such as a vacuum pump to the engine 10.

[0031] (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.

[0032] A mechanical supercharger that drives the compressor 20 using the power of the engine 10 may be used. 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 negative pressure path 34 and the second negative pressure 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 negative pressure path 34 and the second negative pressure path 36.

[0033] 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.

[0034] Either the first negative pressure path 34 or the second negative pressure path 36 may be omitted. The lubrication system and ventilation system of the above embodiment may be applied to a naturally aspirated engine that does not have a turbocharger. In this case, the second vacuum path 36 and the second check valve 37 are not necessary.

[0035] Instead of the first check valve 35 and the second check valve 37, other closing mechanisms such as solenoid valves may be used to close the first negative pressure path 34 and the second negative pressure path 36 when the engine is stopped. A negative pressure generating device such as a vacuum pump may be used as a negative pressure source for generating the negative pressure introduced into the oil tank 30.

[0036] In addition to the lubricating oil circulation path and the negative pressure path connected to the negative pressure source, other paths may be connected to the oil tank 30. In this case, the closing mechanism is configured to close all paths connected to the oil tank 30 except for the circulation path when the engine 10 is stopped. [Explanation of symbols]

[0037] 10...engine, 16...crankcase, 17...intake passage, 20...compressor, 22...throttle valve, 25...lubrication section, 26...recovery path (lubricating oil circulation path), 27...oil supply path (lubricating oil circulation path), 30...oil tank, 34...first vacuum path, 35...first check valve (closing mechanism), 36...second vacuum path, 37...second check valve (closing mechanism).

Claims

1. A dry sump engine in which lubricating oil is stored in an oil tank installed outside the crankcase, The oil tank is connected to a plurality of paths, including a negative pressure path connected to a negative pressure source that generates negative pressure while the engine is running, and a lubricating oil circulation path between a lubricating part of the engine and the oil tank, The engine is provided with a closing mechanism that closes all of the paths connected to the oil tank except for the circulation path when the engine is stopped. engine.

2. 2. The engine according to claim 1, wherein the closing mechanism includes a check valve that restricts the flow of gas from the negative pressure source through the negative pressure path toward the oil tank.

3. 2. The engine according to claim 1, wherein the negative pressure source is a portion of the intake passage of the engine downstream of a throttle valve.

4. 2. The engine according to claim 1, wherein the engine is a supercharged engine having a compressor installed in an intake passage, and the negative pressure source is a portion of the intake passage upstream of the compressor.

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