Lubrication systems for internal combustion engines

Abstract

To suppress excessive decrease of an oil amount in an oil tank.SOLUTION: A lubrication system for an internal combustion engine includes: a first passage 61 connecting inside of the internal combustion engine 20 and inside of an oil tank 50; a feed pump 71 provided in the first passage 61 and pressure-feeding oil from the oil tank 50 to the internal combustion engine 20; a second passage 62 connecting inside of the internal combustion engine 20 and inside of the oil tank 50; a scavenging pump 72 provided in the second passage 62 and pressure-feeding oil from the internal combustion engine 20 to the oil tank 50; a third passage 63 connecting a portion on the internal combustion engine 20 side viewed from the feed pump 71 and the second passage 62 in the first passage 61; a selector valve 73 for opening / closing the third passage 63; and a control device 90 for controlling the selector valve 73. When an amount of oil in the oil tank 50 is lowered to less than a prescribed value, the control device 90 switches the selector valve 73 to an open state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to lubrication systems for internal combustion engines. [Background technology]

[0002] The lubrication system of the internal combustion engine disclosed in Patent Document 1 employs a so-called dry sump type lubrication method. That is, the lubrication system includes an internal combustion engine, an oil tank, a first passage, a second passage, a feed pump, and a scavenging pump. The oil tank is separate from the internal combustion engine. The oil tank stores oil. The first passage connects the oil tank to the internal combustion engine. The second passage also connects the oil tank to the internal combustion engine. The feed pump is located in the middle of the first passage. The feed pump pumps oil in the oil tank to the internal combustion engine. On the other hand, the scavenging pump is located in the middle of the second passage. The scavenging pump pumps oil to the oil tank after lubricating various parts of the internal combustion engine. When this type of lubrication method is adopted, the oil storage volume at the bottom of the internal combustion engine can be reduced, so that the internal combustion engine can be made smaller. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-064168 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an internal combustion engine such as that described in Patent Document 1, the level of the oil pooled at the bottom of the internal combustion engine may fluctuate or tilt depending on the driving conditions, such as acceleration and turning, of the vehicle on which the internal combustion engine is mounted. If the connection between the second passage and the internal combustion engine becomes exposed above the oil level, the oil cannot be returned to the oil tank via the second passage. In this case, the amount of oil inside the oil tank decreases, which makes it easier for problems such as air intake to occur in the feed pump. [Means for solving the problem]

[0005] a control device that controls the switching valve, wherein the control device switches the switching valve from a closed state to an open state when the amount of oil in the oil tank falls below a predetermined specified value.

[0006] In the above configuration, the control device opens the switching valve when the amount of oil inside the oil tank decreases. When the switching valve is opened, a portion of the oil pumped from the feed pump flows to the third passage without passing through the internal combustion engine. In other words, a circulation path for the oil that bypasses the internal combustion engine is created. By returning a portion of the oil inside the oil tank through this circulation path to the oil tank, the amount of oil that remains inside the internal combustion engine and cannot be collected in the oil tank can be reduced. As a result, an excessive decrease in the amount of oil inside the oil tank can be suppressed. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a lubrication system for an internal combustion engine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of a lubrication system for an internal combustion engine will be described with reference to the drawings. As shown in Fig. 1, a vehicle 100 has an internal combustion engine 20. The internal combustion engine 20 is a drive source of the vehicle 100. The internal combustion engine 20 has a plurality of cylinders 21, a plurality of pistons 22, a plurality of connecting rods 23, a crankshaft 24, and a crank chamber 25. Note that Fig. 1 shows only one of the plurality of cylinders 21. The same applies to the pistons 22 and the connecting rods 23.

[0009] The cylinder 21 is a space for burning fuel. Although not shown, the cylinder 21 is connected to an intake passage that introduces intake air and an exhaust passage that discharges exhaust gas. The crank chamber 25 is a space located below the cylinder 21 and connected to all the cylinders 21. A piston 22 and a connecting rod 23 are provided for each cylinder 21. The piston 22 is located in the cylinder 21. The piston 22 reciprocates in response to the combustion of fuel in the cylinder 21. The piston 22 is connected to the crankshaft 24 via the connecting rod 23. The crankshaft 24 is located in the crank chamber 25. The crankshaft 24 rotates in response to the operation of the piston 22. Note that blow-by gas, which is gas leaking from the cylinder 21 to the crank chamber 25, is present in the crank chamber 25.

[0010] The internal combustion engine 20 has an oil passage 27 through which oil flows. The oil passage 27 is connected to various parts of the internal combustion engine 20 that require lubrication. After lubricating the various parts, the oil accumulates at the bottom of the crank chamber 25. In FIG. 1, the oil passage 27 is diagrammatically illustrated by an arrow.

[0011] The vehicle 100 has a lubrication system 10 for an internal combustion engine 20. The lubrication system 10 for the internal combustion engine 20 includes the above-described internal combustion engine 20. The lubrication system 10 for the internal combustion engine 20 has an oil tank 50, a gas-liquid separation mechanism 51, and an oil level sensor 52.

[0012] The oil tank 50 is separate from the internal combustion engine 20. The oil tank 50 is hollow. Oil is stored inside the oil tank 50. The gas-liquid separation mechanism 51 is located inside the oil tank 50. The gas-liquid separation mechanism 51 separates liquid and gas. The gas-liquid separation mechanism 51 is connected to a gas discharge passage (not shown). The gas discharge passage leads from the inside of the oil tank 50 to the outside. The gas discharge passage is connected to the intake passage. The gas discharge passage is a passage for discharging the gas separated by the gas-liquid separation mechanism 51. The inside of the gas-liquid separation mechanism 51 is also connected to the inside of the oil tank 50. The oil, which is the liquid separated by the gas-liquid separation mechanism 51, flows into the inside of the oil tank 50.

[0013] The oil level sensor 52 is located inside the oil tank 50. The oil level sensor 52 detects the position LD of the oil level. In this embodiment, the oil level sensor 52 is of an ultrasonic type. That is, the oil level sensor 52 detects the position LD of the oil level based on the period from when an ultrasonic wave is emitted until the ultrasonic wave returns.

[0014] The lubrication system 10 of the internal combustion engine 20 includes a first passage 61 , a second passage 62 , a third passage 63 , a feed pump 71 , a scavenging pump 72 , and a switching valve 73 . The first passage 61 extends from the oil tank 50 to the internal combustion engine 20. A first end of the first passage 61 is located at an opening provided at the bottom of the oil tank 50. A second end of the first passage 61 is located inside the internal combustion engine 20 and is connected to the oil passage 27 of the internal combustion engine 20. As a result, the first passage 61 connects the inside of the oil tank 50 and the inside of the internal combustion engine 20.

[0015] The feed pump 71 is located midway through the first passage 61. The feed pump 71 is connected to the crankshaft 24 via a power transmission mechanism (not shown). The feed pump 71 operates in conjunction with the rotation of the crankshaft 24. In other words, the feed pump 71 is a mechanical pump driven by the crankshaft 24. The feed pump 71 pressure-feeds oil from the oil tank 50 to the internal combustion engine 20.

[0016] The second passage 62 extends from the internal combustion engine 20 to the oil tank 50. A first end of the second passage 62 is located in an opening provided in the bottom of the internal combustion engine 20. A second end of the second passage 62 is located in an opening provided in the upper part of the oil tank 50. As a result, the second passage 62 connects the crank chamber 25 of the internal combustion engine 20 and the interior of the oil tank 50.

[0017] The scavenging pump 72 is located midway through the second passage 62. The scavenging pump 72 is connected to the crankshaft 24 via a power transmission mechanism (not shown). The scavenging pump 72 operates in conjunction with the rotation of the crankshaft 24. In other words, the scavenging pump 72 is a mechanical pump driven by the crankshaft 24. The scavenging pump 72 pumps oil from the internal combustion engine 20 to the oil tank 50. When the scavenging pump 72 sucks oil from the internal combustion engine 20, it also sucks blow-by gas contained in the oil as air bubbles. The scavenging pump 72 pumps the blow-by gas together with the oil to the oil tank 50.

[0018] The third passage 63 extends from the first passage 61 to the second passage 62. The third passage 63 connects a portion of the first passage 61 on the internal combustion engine 20 side as viewed from the feed pump 71 to a portion of the second passage 62 on the oil tank 50 side as viewed from the scavenging pump 72.

[0019] The switching valve 73 is located midway through the third passage 63. Although not shown, the switching valve 73 has a solenoid and a valve body. The valve body opens and closes the third passage 63 depending on whether or not electricity is applied to the solenoid. When the valve body is in an open state, the valve body allows the flow of oil. When the valve body is in a closed state, the valve body blocks the flow of oil.

[0020] The lubrication system 10 of the internal combustion engine 20 has a fourth passage 64 and a check valve 74. The fourth passage 64 extends from the internal combustion engine 20 to the oil tank 50. A first end of the fourth passage 64 is located in an opening provided in a lower portion of the internal combustion engine 20. A second end of the fourth passage 64 is located in an opening provided in an upper portion of the oil tank 50. As a result, the fourth passage 64 connects the crank chamber 25 of the internal combustion engine 20 and the interior of the oil tank 50.

[0021] The check valve 74 is located in the middle of the fourth passage 64. Although not shown, the check valve 74 has a coil spring and a valve body. The coil spring biases the valve body from the oil tank 50 side toward the internal combustion engine 20 side. The valve body opens and closes the fourth passage 64 according to the pressure difference between the pressure on the internal combustion engine 20 side and the pressure on the oil tank 50 side. The valve body opens when the pressure on the internal combustion engine 20 side is higher than the pressure on the oil tank 50 side by a certain amount. At this time, the valve body allows the blow-by gas to flow from the crank chamber 25 of the internal combustion engine 20 to the oil tank 50. On the other hand, the valve body closes when the relationship between the pressure on the internal combustion engine 20 side and the pressure on the oil tank 50 side does not satisfy the above-mentioned condition for the open state. At this time, the valve body blocks the flow of blow-by gas from the crank chamber 25 toward the oil tank 50. The valve body always blocks the flow of gas from the oil tank 50 side toward the internal combustion engine 20 side.

[0022] Here, the pressure acting on the valve body from the internal combustion engine 20 side is equal to the pressure in the crank chamber 25. The pressure in the crank chamber 25 pulsates in response to the operation of the piston 22. With respect to the transition of pressure over a time scale sufficiently longer than one period of the pressure pulsation, the average value of the pressure in the transition is called the average pressure. The average pressure can be determined, for example, by an experiment. On the other hand, the pressure acting on the valve body from the oil tank 50 side is approximately atmospheric pressure. In this embodiment, the spring constant of the coil spring of the check valve 74 is determined so that the valve body of the check valve 74 is in an open state when the pressure acting on the valve body from the internal combustion engine 20 side becomes the average pressure.

[0023] The lubrication system 10 of the internal combustion engine 20 includes a control device 90. The control device 90 may be configured as one or more processors that execute various processes according to a computer program (software). The control device 90 may be configured as one or more dedicated hardware circuits, such as an application specific integrated circuit (ASIC), that execute at least a part of the various processes, or a circuit including a combination thereof. The processor includes a CPU and memory, such as a RAM and a ROM. The memory stores program codes or instructions that are configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer.

[0024] The control device 90 repeatedly receives a signal related to the liquid level position LD detected by the oil level sensor 52 at every predetermined control period. When the control device 90 receives the signal related to the liquid level position LD, the control device 90 converts the liquid level position LD into the amount of oil present inside the oil tank 50 (hereinafter referred to as the tank oil amount) LS. In other words, the oil level sensor 52 essentially functions as a sensor that detects the tank oil amount LS. The control device 90 stores a conversion map in advance. The conversion map represents the relationship between the liquid level position LD and the tank oil amount LS. The conversion map is created in advance based on the volume of the oil tank 50, etc. The control device 90 refers to this conversion map when converting the liquid level position LD into the tank oil amount LS.

[0025] The control device 90 controls the switching valve 73. That is, the control device 90 turns on or off the power supply to the solenoid of the switching valve 73. In this way, the control device 90 switches the valve body of the switching valve 73 to an open state or a closed state. In the following, the open state and the closed state of the valve body of the switching valve 73 are simply referred to as the open state and the closed state of the switching valve 73.

[0026] The control device 90 executes a switching process during the operation of the internal combustion engine 20. In the switching process, when the tank oil amount LS falls below the specified value Z, the control device 90 switches the switching valve 73 from the closed state to the open state. On the other hand, in the switching process, when the tank oil amount LS increases to or exceeds the specified value Z, the control device 90 switches the switching valve 73 from the open state to the closed state. As a specific embodiment of the switching process, the control device 90 repeatedly refers to the latest tank oil amount LS, the tank oil amount LS at the immediately previous timing, and the specified value Z. Then, when a first condition is satisfied that the latest tank oil amount LS is less than the specified value Z and the tank oil amount LS at the immediately previous timing is equal to or greater than the specified value Z, the control device 90 switches the switching valve 73 to the open state. On the other hand, when a second condition is satisfied that the latest tank oil amount LS is equal to or greater than the specified value Z and the tank oil amount LS at the immediately previous timing is less than the specified value Z, the control device 90 switches the switching valve 73 to the closed state. The control device 90 stores the specified value Z in advance. The specified value Z will be described in detail later.

[0027] <Operation of the embodiment> (A) Oil circulation path During operation of the internal combustion engine 20, both the feed pump 71 and the scavenging pump 72 are driven in accordance with the rotation of the crankshaft 24. When these pumps are driven, a circulation path is formed for the oil that leaves the oil tank 50, flows through each passage, and then returns to the oil tank 50. There are two circulation paths: a normal path M and a bypass path N. The normal path M is a path that always exists regardless of the open / close state of the switching valve 73. Specifically, the normal path M is a path that leads to the internal combustion engine 20 through the first passage 61 and returns to the oil tank 50 through the second passage 62. The bypass path N is a path that can only be formed when the switching valve 73 is in an open state. Specifically, the bypass path N is a path that leads from the first passage 61 to the third passage 63, and returns to the oil tank 50 from the third passage 63 via the second passage 62. That is, the bypass path N is a path that bypasses the internal combustion engine 20. In addition, in detail, the bypass route N is a route that is formed when the switching valve 73 is in an open state under the following predetermined circumstances.

[0028] The predetermined situation is a situation in which air suction occurs in the scavenging pump 72. That is, the oil level K of the oil stored in the crank chamber 25 of the internal combustion engine 20 may tilt as the vehicle 100 accelerates, turns, etc. In FIG. 1, the state in which the oil level K is tilted is shown by a two-dot chain line. Also, as the vehicle 100 accelerates, turns, etc., the oil present in various places in the internal combustion engine 20 may not return to the crank chamber 25, and the oil level K may drop. When the oil level K of the oil in the crank chamber 25 tilts or drops in this way, a part or the entirety of the intake port, which is the first end of the second passage 62, is exposed from the oil. In this case, air suction occurs in the scavenging pump 72. Then, the amount of oil pumped by the scavenging pump 72 decreases. On the other hand, the amount of oil pumped by the feed pump 71 does not change. When such a large-small relationship of the oil pumped amount is established, the amount of oil in the oil tank 50 decreases.

[0029] (B) Standard values If the above-mentioned predetermined situation continues, there is a risk that the tank oil amount LS will decrease excessively. The specified value Z is a threshold value for switching between opening and closing the switching valve 73 to prevent the tank oil amount LS from decreasing excessively in the predetermined situation.

[0030] Here, when the scavenging pump 72 is not sucking air, the tank oil amount LS is always maintained at a substantially constant value. This constant value is referred to as the normal value. When the scavenging pump 72 starts to suck air as the vehicle 100 accelerates or turns, the tank oil amount LS decreases from the normal value. The specified value Z is a value at which it can be determined that the scavenging pump 72 has started to suck air, and is determined in advance, for example, through experiments or simulations.

[0031] (C) Oil flow during switching process Now, assume that the vehicle 100 is moving straight on a flat road at a constant speed. At this time, the oil level K in the crank chamber 25 of the internal combustion engine 20 is approximately horizontal. In this case, the suction port of the second passage 62 is filled with oil. Therefore, the scavenging pump 72 pumps the oil in the crank chamber 25 to the oil tank 50 without air suction. In this case, the oil after lubricating the internal combustion engine 20 quickly returns to the oil tank 50. In this situation, a sufficient amount of oil is collected in the oil tank 50, so that the tank oil amount LS is equal to or greater than the specified value Z. While the tank oil amount LS remains equal to or greater than the specified value Z, the control device 90 closes the switching valve 73. That is, the oil circulates only through the normal route M without passing through the bypass route N.

[0032] Now, suppose that the vehicle 100, which had been traveling at a constant speed, accelerates. As a result, the oil level K in the crank chamber 25 of the internal combustion engine 20 tilts or drops, and a part of the intake port of the second passage 62 is exposed from the oil. In other words, suppose that a predetermined situation occurs in which air is sucked in by the scavenging pump 72. In this case, since there is oil remaining in various places of the internal combustion engine 20 and in the crank chamber 25 without returning to the oil tank 50, the amount of oil returning to the oil tank 50 decreases. As a result, suppose that the tank oil amount LS becomes less than the specified value Z. Then, the control device 90 switches the switching valve 73 to an open state. In this case, a part of the oil pumped by the feed pump 71 returns to the oil tank 50 through the above-mentioned bypass path N. By circulating the oil through the bypass path N, the amount of oil that remains in various places of the internal combustion engine 20 and in the crank chamber 25 and cannot be collected in the oil tank 50 is reduced.

[0033] After that, suppose that the vehicle 100 finishes accelerating and returns to constant speed running. Then, the oil that had been remaining in various parts of the internal combustion engine 20 flows down into the crank chamber 25. Also, the oil level K in the crank chamber 25 returns to approximately horizontal. At the same time, the intake port of the second passage 62 is filled with oil again. Then, the scavenging pump 72 stops sucking air, and the amount of oil returned from the crank chamber 25 to the oil tank 50 is restored. When the tank oil amount LS eventually returns to or exceeds the specified value Z, the control device 90 switches the switching valve 73 to the closed state.

[0034] (D) Discharge of blow-by gas from the crankcase There are two paths for discharging blow-by gas from the crank chamber 25. The first discharge path is a path passing through the second passage 62. Specifically, the scavenging pump 72 pumps the sucked blow-by gas together with the oil through the second passage 62 to the oil tank 50. The blow-by gas that flows into the oil tank 50 reaches the gas-liquid separation mechanism 51 together with the oil. The gas-liquid separation mechanism 51 separates the blow-by gas from the oil. Of the blow-by gas and the oil, the gas-liquid separation mechanism 51 leaves the oil inside the oil tank 50 and discharges the blow-by gas to the intake passage through the gas discharge passage.

[0035] The second discharge path is a path passing through the fourth passage 64. Here, pressure pulsates in the crank chamber 25 of the internal combustion engine 20. In response to this pressure pulsation, the valve body of the check valve 74 in the fourth passage 64 opens or closes. That is, when the pressure in the crank chamber 25 is relatively low during the transition of the pressure, the valve body is in a closed state. On the other hand, when the gas pressure is relatively high, the valve body is in an open state. When the valve body is in an open state, the blow-by gas flows from the crank chamber 25 to the oil tank 50 through the fourth passage 64. The blow-by gas that flows into the oil tank 50 reaches the gas-liquid separation mechanism 51. The gas-liquid separation mechanism 51 discharges the blow-by gas to the intake passage through the gas discharge passage.

[0036] <Effects of the embodiment> (1) In this embodiment, the control device 90 switches the switching valve 73 to an open state when the tank oil amount LS decreases. When the switching valve 73 is opened, a portion of the oil pumped from the feed pump 71 returns to the oil tank 50 via a bypass path N that bypasses the internal combustion engine 20. By circulating through this bypass path N, the amount of oil that remains inside the internal combustion engine 20 and cannot be recovered in the oil tank 50 can be reduced. As a result, an excessive decrease in the tank oil amount LS can be suppressed. Therefore, air suction by the feed pump 71 and a decrease in the amount of oil pumped to the internal combustion engine 20 can be prevented.

[0037] (2) In this embodiment, the fourth passage 64 is provided as a passage dedicated to discharging the blow-by gas from the crank chamber 25. By providing the fourth passage 64 in this manner, even if a situation arises in which the blow-by gas cannot be discharged by the scavenging pump 72, the blow-by gas can be discharged from the crank chamber 25 before it accumulates excessively in the crank chamber 25. In addition, a check valve 74 is provided in the fourth passage 64. Therefore, even if the pressure in the crank chamber 25 is low, gas does not flow back from the oil tank 50 side.

[0038] In addition, as in this embodiment, by providing a dedicated passage for discharging the blow-by gas from the crank chamber 25 and an associated check valve 74, it is possible to prevent the blow-by gas from accumulating excessively even if the discharge capacity of the scavenging pump 72 is reduced. In other words, a small-sized scavenging pump 72 can be used. This contributes to making the entire lubrication system 10 of the internal combustion engine 20 more compact and reducing costs.

[0039] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0040] The method of determining the specified value Z is not limited to the example of the embodiment. The specified value Z may be a value that allows the switching valve 73 to be switched to the open state in advance so that the feed pump 71 does not cause air suction under a situation in which the amount of oil recovered is temporarily reduced due to air suction by the scavenging pump 72. Here, in the above embodiment, the situation in which the scavenging pump 72 causes air suction is exemplified as the time of acceleration and turning of the vehicle 100. However, the situation in which the scavenging pump 72 causes air suction is not limited to this. Depending on the arrangement of the suction port of the second passage 62, the scavenging pump 72 may cause air suction when the vehicle 100 is decelerating. In addition, the scavenging pump 72 may cause air suction when the vehicle 100 runs on a slope. In this way, there are various situations in which the scavenging pump 72 causes air suction. Taking these various situations into consideration, the specified value Z may be determined so as to avoid a reduction in the tank oil amount LS caused by air suction by the scavenging pump 72.

[0041] The configuration of the feed pump 71 is not limited to the example of the above embodiment. For example, the feed pump 71 may be an electric type. The feed pump 71 only needs to be able to pump oil from the oil tank 50 to the internal combustion engine 20. The same can be said about the scavenging pump 72. That is, the scavenging pump 72 only needs to be able to pump oil from the internal combustion engine 20 to the oil tank 50.

[0042] The manner in which the first passage 61 connects the inside of the oil tank 50 and the inside of the internal combustion engine 20 is not limited to the example of the above embodiment. For example, the first end of the first passage 61 may be located inside the oil tank 50. As long as the inside of the oil tank 50 and the inside of the internal combustion engine 20 can be connected, the manner of connection is not important. The same can be said about the second passage 62 and the fourth passage 64.

[0043] The location of connection of the third passage 63 with the second passage 62 is not limited to the example in the above embodiment. That is, the third passage 63 may be connected to a location on the internal combustion engine 20 side of the second passage 62 when viewed from the scavenging pump 72.

[0044] The configuration of the switching valve 73 is not limited to the example of the above embodiment. That is, the switching valve 73 does not have to be an electromagnetic type. For example, the switching valve 73 may be a type in which a valve body is operated by air pressure. The switching valve 73 may be configured to open and close the third passage 63.

[0045] The configuration of the oil level sensor 52 is not limited to the example of the above embodiment. For example, the oil level sensor 52 may be a type that detects the position of a float floating on the oil surface. The oil level sensor 52 may be configured in any way as long as it can appropriately detect the amount of oil inside the oil tank 50.

[0046] It is not essential to provide the gas-liquid separation mechanism 51. For example, in consideration of the blow-by gas discharge capacity of the scavenging pump 72, the blow-by gas discharge path may be the second discharge path via the fourth passage 64. In this case, the fourth passage 64 may be directly connected to the intake passage. Additionally, the gas-liquid separation mechanism 51 may be omitted from the oil tank 50.

[0047] The spring constant of the coil spring in the check valve 74 is not limited to the example in the above embodiment. The spring constant may be any value that can discharge the blow-by gas from the crank chamber 25 before the blow-by gas accumulates excessively in the crank chamber 25.

[0048] The configuration of the check valve 74 is not limited to the example of the above embodiment. That is, the check valve 74 is not limited to one that utilizes the elastic force of a coil spring. The check valve 74 may be configured to allow the flow of blow-by gas from the internal combustion engine 20 side toward the oil tank 50 side and to always block the flow of gas from the oil tank 50 side toward the internal combustion engine 20 side.

[0049] The fourth passage 64 and the check valve 74 may be omitted. Even in this case, the blow-by gas can be discharged from the crank chamber 25 through the second passage 62 by the scavenging pump 72. [Explanation of symbols]

[0050] 10. Lubrication system 20…Internal combustion engine 50…Oil tank 52...Oil level sensor 61...1st aisle 62…Second aisle 63…3rd aisle 71...Feed pump 72…Scavenging pump 73...Switch valve 90...Control device

Claims

[Claim 1] An internal combustion engine; an oil tank provided separately from the internal combustion engine and capable of storing oil therein; a first passage connecting an interior of the internal combustion engine and an interior of the oil tank; a feed pump provided in the first passage and configured to pump oil from the oil tank to the internal combustion engine; a second passage connecting the inside of the internal combustion engine and the inside of the oil tank; a scavenging pump provided in the second passage and configured to pump oil from the internal combustion engine to the oil tank; a third passage connecting a portion of the first passage that is on the internal combustion engine side as viewed from the feed pump and the second passage; A switching valve that opens and closes the third passage; an oil level sensor for detecting an amount of oil inside the oil tank; a fourth passage connecting the inside of the internal combustion engine and the inside of the oil tank; a check valve provided in the fourth passage and opened only when the pressure on the internal combustion engine side is higher than the pressure on the oil tank side; a gas-liquid separation mechanism located inside the oil tank and configured to separate liquid from gas; A control device for controlling the switching valve, The control device switches the switching valve from a closed state to an open state when the amount of oil inside the oil tank falls below a predetermined specified value. Lubrication system of an internal combustion engine.

Images