Oil circulation device for engine

Abstract

To early and efficiently circulate oil in two tanks to an engine when an operation state of the engine is switched.SOLUTION: The oil pan 16 includes the first tank 32 and the second tank 34 partitioned from each other, the first tank strainer 22 provided in the first tank 32 and the second tank strainer 24 provided in the second tank 34 are connected to the oil suction passage 18 via the switching valve 26, and the check valve 30 that suppresses the inflow of the oil 2 from the second tank 34 to the first tank 32 is provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an oil circulation device for an engine. [Background technology]

[0002] 2. Description of the Related Art An engine mounted on a vehicle is provided with an engine oil circulation device that circulates oil (lubricating oil) in an oil pan to the engine through an oil suction passage. Patent Document 1 discloses an oil circulation device in which an oil pan is composed of a first tank and a second tank separated horizontally, and a side plate separating the first and second tanks is provided with a one-way valve that allows oil to flow from the first tank to the second tank and prohibits oil from flowing from the second tank to the first tank, a strainer (suction port) connected to an oil suction passage is provided in the first tank, and an opening / closing valve is provided in a top plate that closes the top of the second tank to allow or prohibit the flow of oil dripping from the engine. In this oil circulation device, when the engine is cold, the on-off valve of the second tank is closed and oil is circulated to the engine from the strainer of the first tank through the oil suction passage, so that the oil level in the first tank is lower than the oil level in the second tank.The one-way valve is closed due to the differential pressure between the oil in the first and second tanks, and the oil in the first tank is heated by the engine, allowing the engine to warm up quickly. When the engine is warm, the open / close valve of the second tank is opened, allowing the heated oil that has circulated through the engine to return to both the first and second tanks, causing the oil level in the second tank to rise, and the oil from the second tank flows into the first tank through a communication hole provided in the upper part of the side plate separating the first and second tanks, causing the oil level in the first tank to rise. This reverses the differential oil pressure between the first and second tanks from when the engine is cold, opening the one-way valve and allowing oil to circulate from the first tank to the second tank. Therefore, when the engine is cold, a small amount of oil is circulated through the engine, allowing the engine to warm up quickly, and when the engine is warm, a sufficient amount of oil is available to provide good lubrication for the engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-275675 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional technology, when switching from cold to warm operation, oil flowing down from the engine flows into the second tank through the open on-off valve, and only when the liquid level in the second tank rises to the level of the communication hole does the oil flow from the second tank into the first tank. In other words, since oil does not flow from the second tank into the first tank until the liquid level in the second tank rises to the position of the communication hole, there is a time lag before the oil in the second tank flows into the first tank, and there is room for improvement in circulating the oil from both the first and second tanks through the engine quickly and efficiently when the engine is warm. The present invention has been made in consideration of the above circumstances, and its purpose is to provide an engine oil circulation device that is advantageous in circulating oil from two tanks to the engine quickly and efficiently when the engine's operating state is switched. [Means for solving the problem]

[0005] In order to achieve the above object, one embodiment of the present invention is an oil circulation device for an engine that circulates oil in an oil pan to the engine through an oil suction passage, wherein the oil pan is composed of a first tank and a second tank that are partitioned from each other, and a first tank-side connecting pipe of a first tank strainer provided in the first tank and a second tank-side connecting pipe of a second tank strainer provided in the second tank are connected to the oil suction passage via a switching valve, and a backflow suppression unit is provided to suppress oil from flowing from the second tank to the first tank. In addition, one embodiment of the present invention is characterized in that the first tank and the second tank are arranged one above the other with the first tank positioned above the second tank, and the backflow suppression unit is provided in a portion of the first tank that is positioned below the first tank side suction port of the first tank strainer. In one embodiment of the present invention, the first tank and the second tank each have a bottom wall, and a communication passage is provided that extends from a portion of the bottom wall of the first tank that is located below the first tank-side suction port toward the bottom wall of the second tank, and whose lower end is located at the same height as the second tank-side suction port of the second tank strainer and communicates with the first tank, and the backflow suppression unit is provided in the communication passage. In one embodiment of the present invention, the first tank includes a peripheral wall that rises from the periphery of the bottom wall of the first tank, the second tank includes a peripheral wall that rises from the periphery of the bottom wall of the second tank, the first tank is arranged inside the second tank, the peripheral wall of the first tank is arranged inside the peripheral wall of the second tank at a distance from the peripheral wall of the second tank, and the oil contained in the second tank is interposed between the peripheral wall of the first tank and the peripheral wall of the second tank. In one embodiment of the present invention, the switching valve is a thermostatic valve that connects the first tank side communication passage of the first tank strainer to the oil suction passage when the temperature of the oil flowing through the switching valve is below a threshold value, and connects the second tank side communication passage of the second tank strainer to the oil suction passage when the temperature of the oil is equal to or higher than the threshold value. [Effects of the Invention]

[0006] According to one embodiment of the present invention, the oil supplied to the oil suction passage can be switched from the first tank to the second tank without a time lag by the switching valve connected to the first tank strainer and the second tank strainer. In addition, a backflow suppression unit is provided that suppresses the flow of oil from the second tank to the first tank and allows the flow of oil from the first tank to the second tank. This makes it possible to select between supplying oil only from the first tank and supplying oil from both the first and second tanks, and therefore to use the oil from the first tank and the second tank appropriately depending on the operating state of the engine. Furthermore, if the first and second tanks are arranged one above the other with the first tank positioned above the second tank and a backflow suppression unit is installed in the first tank located below the strainer for the first tank, the negative pressure caused by the oil suction from the strainer for the first tank will act effectively on the backflow suppression unit, thereby ensuring that the backflow suppression unit can maintain a state in which it prevents oil from flowing from the second tank into the first tank when the first tank is in use, which is advantageous for efficiently circulating the oil in the first tank to the lubricated parts of the engine. Furthermore, if a connecting passage is provided that extends from a portion of the bottom wall located below the first tank strainer toward the bottom wall of the second tank, with its lower end located at the same height as the second tank side suction port of the second tank strainer, communicates with the first tank, and has a backflow suppression section, when the second tank is in use, the negative pressure caused by oil suction by the second tank strainer will effectively act on the lower end opening of the connecting passage, opening the backflow suppression section and promoting the flow of oil from the first tank to the second tank via the connecting passage, which is advantageous for efficiently circulating oil from the first and second tanks to the lubricated parts of the engine. Furthermore, if oil is interposed between the first tank side peripheral wall and the second tank side peripheral wall, the oil in the second tank insulates the oil in the first tank, which is advantageous in preventing the temperature of the oil in the first tank from dropping due to outside air or wind from driving, and is advantageous in warming up the engine quickly. Furthermore, when the switching valve is configured as a thermostatic valve, it requires less maintenance effort than when the switching valve is configured as a solenoid valve, and no electricity is required to drive the switching valve, which is advantageous in terms of saving energy. [Brief explanation of the drawings]

[0007] [Figure 1] 1A and 1B are explanatory diagrams showing the configuration of an oil circulation device for an engine according to a first embodiment, in which (A) shows the state when the engine is cold, and (B) shows the state when the engine is warm. [Figure 2] 10A and 10B are explanatory diagrams showing the configuration of an oil circulation device for an engine according to a second embodiment, in which (A) shows the state when the engine is cold, and (B) shows the state when the engine is warm. DETAILED DESCRIPTION OF THE INVENTION

[0008] (First embodiment) Next, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1(A), the engine 10 includes an engine body 12 and an oil circulation device 14 provided below the engine body 12. The engine body 12 accommodates lubricated members such as a crankshaft lubricated with oil 2, a cam mechanism for opening and closing intake and exhaust valves, and pistons, none of which are shown. The oil circulation device 14 is composed of an oil pan 16, an oil suction passage 18, an oil pump 20, a first tank strainer 22, a second tank strainer 24, a switching valve 26, a connecting passage 28, and a check valve 30 (backflow suppression section).

[0009] The oil pan 16 is a portion that contains the oil 2 that lubricates the members to be lubricated, is connected to the bottom of the cylinder block or crankcase, and is made of metal or synthetic resin. The oil pan 16 is composed of a first tank 32 and a second tank 34 that are separated from each other. In this embodiment, the first tank 32 is provided inside and above the second tank 34, and the first tank 32 is supported by the second tank 34 via a bracket (not shown). The first tank 32 and the second tank 34 both contain oil 2. In detail, the second tank 34 comprises a second tank side bottom wall 3402, a second tank side peripheral wall 3404 that stands up from the periphery of the second tank side bottom wall 3402, and a flange 3406 that extends outward from the upper end of the second tank side peripheral wall 3404 and is attached to the lower part of the engine body 12, and is open at the top. The first tank 32 has a first tank side bottom wall 3202 having an outline slightly smaller than that of the second tank side bottom wall 3402, and a first tank side peripheral wall 3204 standing up from the periphery of the first tank side bottom wall 3202, and is open at the top. The first tank side bottom wall 3202 is located above and spaced from the second tank side bottom wall 3402 . The first tank side peripheral wall 3204 is positioned inside the second tank side peripheral wall 3404 with a gap S between it and the second tank side peripheral wall 3404, and oil 2 contained in the second tank 34 is interposed between the first tank side bottom wall 3202 and the second tank side bottom wall 3402, and between the first tank side peripheral wall 3204 and the second tank side peripheral wall 3404. The upper end of the gap S forms an air vent hole for smoothly discharging the oil 2 contained in the second tank 34 by removing a drain plug from a drain hole (not shown) provided in the bottom wall 3402 on the second tank side during oil change. The height of the liquid surface of the oil 2 in the first tank 32 and the height of the liquid surface of the oil 2 in the second tank 34 are approximately the same, and the depth of the oil 2 in the first tank 32 is shallower than the depth of the oil 2 in the second tank 34.

[0010] The oil suction passage 18 guides the oil 2 contained in the oil pan 16 to the oil pump 20 . The oil pump 20 is provided in the oil suction passage 18, and supplies the oil 2 sucked through the oil suction passage 18 to the member to be lubricated, thereby lubricating the member. The oil pump 20 operates when the engine 10 is operating and stops when the engine 10 is stopped. The oil pump 20 may be one that is driven by the rotation of the crankshaft of the engine 10, or may be an electric pump.

[0011] The first tank strainer 22 includes a first tank side suction port 2202 provided near the first tank side bottom wall 3202 and a first tank side communication pipe 2204 communicating with the first tank side suction port 2202. The second tank strainer 24 includes a second tank side suction port 2402 provided near the second tank side bottom wall 3402 and a second tank side communication pipe 2404 communicating with the second tank side suction port 2402. The downstream end of the first tank side communicating pipe 2204 and the downstream end of the second tank side communicating pipe 2404 are connected to the oil suction passage 18 via a switching valve 26 . The switching valve 26 is configured to be switchable between a first switching state in which the oil suction passage 18 communicates with the first tank side connecting pipe 2204, as shown in Figure 1(A), and a second switching state in which the oil suction passage 18 communicates with the second tank side connecting pipe 2404, as shown in Figure 1(B).

[0012] In this embodiment, the switching valve 26 is placed in the oil 2 contained in the first tank 32, and the switching valve 26 is configured as a thermostatic valve that switches to a first switching state when the temperature of the oil 2 flowing through the switching valve 26 is below a threshold value, connecting the first tank strainer 22 and the oil suction passage 18, and switches to a second switching state when the temperature of the oil 2 is above the threshold value, connecting the second tank strainer 24 and the oil suction passage 18. Generally, the viscosity of oil increases significantly when the oil temperature is below 40 degrees, but does not change significantly above 40 degrees. Therefore, if the oil temperature threshold at which the thermostat valve operates is set to approximately 40 degrees or close to 40 degrees, the sudden change in oil viscosity that accompanies switching of the thermostat valve from the first switching state to the second switching state can be suppressed, which is preferable in terms of ensuring the power performance of the engine 10.

[0013] The communication passage 28 extends from the first tank side bottom wall 3202 located below the first tank strainer 22 toward the second tank side bottom wall 3402, with its upper end opening 2802 communicating with the first tank 32 and its lower end opening 2804 located at the same height as the second tank strainer 24. The check valve 30 prevents the oil 2 from flowing from the second tank 34 into the first tank 32. In this embodiment, the check valve 30 is provided in the communication passage 28 at the first tank 32 located below the strainer 22 for the first tank. More specifically, the communication passage 28 extends along the axis of the first tank strainer 22, and the check valve 30 is located on the axis of the first tank strainer 22. In this embodiment, the check valve 30 has been described as having a structure in which a general valve body operates, but it is also possible to use a structure that does not use a valve body, such as a Tesla valve, as long as it has the function of suppressing backflow. The use of a Tesla valve is advantageous in improving the durability of the backflow prevention section because it does not use a valve body.

[0014] Next, the operation of the oil circulation device 14 will be described. As shown in FIG. 1(A), it is assumed that the engine 10 is cold, the temperature of the oil 2 is below the threshold value, and the switching valve 26 is in the first switching state. When the engine 10 is operating, the oil pump 20 is driven, and the oil 2 in the first tank 32 is sucked into the oil suction passage 18 from the first tank strainer 22 via the switching valve 26, and is then circulated to the lubricated members from the oil pump 20. After lubricating the lubricated members, the oil 2 is heated by the engine 10 and flows down from the engine 10 into the first tank 32 below, where it is collected. The recovered oil 2 is circulated to the lubricated members again through the same route as above, and this circulation of the oil 2 is repeated. On the other hand, the check valve 30 prevents the oil 2 in the second tank 34 from flowing into the first tank 32 . In this embodiment, the check valve 30 is provided in the communicating passage 28 at the first tank 32 located below the first tank strainer 22. Therefore, the oil 2 on the first tank 32 side above the check valve 30 is at a low pressure, and a pressure difference occurs between the oil 2 on the first tank 32 side above the check valve 30 and the oil 2 on the second tank 34 side below the check valve 30. This ensures that the check valve 30 is closed, thereby reliably preventing the oil 2 from the second tank 34 from flowing into the first tank 32.

[0015] Therefore, when the engine 10 is cold, the lubricated members of the engine body 12 are lubricated by the small amount of oil 2 in the first tank 32, and as time passes, the circulating oil 2 does not mix with the oil 2 in the second tank 34, so the temperature of the circulating oil 2 rises quickly, and the engine 10 is warmed up quickly. When the temperature of the oil 2 flowing through the switching valve 26 eventually reaches a threshold value or higher, the thermostat valve constituting the switching valve 26 operates, and the switching state changes from the first switching state to the second switching state as shown in FIG. 1(B). In other words, when the engine 10 is warm, the first switching state is changed to the second switching state. When the engine 10 is warm, the oil 2 in the second tank 34 is sucked into the oil suction passage 18 through the second tank strainer 24 and the switching valve 26, and is circulated to the lubricated members from the oil pump 20. After lubricating the lubricated members, the oil 2 is heated by the engine 10 and flows down from the engine body 12 into the first tank 32 below, where it is collected. Furthermore, since the suction force of the second tank strainer 24 acts on the lower end opening 2804 of the communicating passage 28, the pressure of the oil 2 located near the lower end opening 2804 of the communicating passage 28 becomes lower than the pressure of the oil 2 located near the upper end opening 2802 of the communicating passage 28, the check valve 30 opens, and the oil 2 in the second tank 34 is allowed to flow into the first tank 32. Therefore, both the oil 2 in the first tank 32 and the oil 2 in the second tank 34 are circulated to the lubricated members, and a larger amount of oil 2 is circulated to the lubricated members, which not only ensures good lubrication of the lubricated members, but also reduces the temperature of the oil 2, making it possible to cool the engine 10 with the oil 2, and suppressing deterioration of the oil 2.

[0016] According to this embodiment, the oil pan 16 is composed of a first tank 32 and a second tank 34 that are separated from each other, and the first tank strainer 22 provided in the first tank 32 and the second tank strainer 24 provided in the second tank 34 are connected to the oil suction passage 18 via a switching valve 26, and a check valve 30 is provided to prevent the oil 2 from flowing from the second tank 34 to the first tank 32. Therefore, when the engine 10 is cold, the oil 2 in the first tank 32 is circulated to the lubricated parts of the engine 10 via the switching valve 26, thereby quickly raising the temperature of the oil 2 and accelerating the warming up of the engine 10. In addition, the viscosity of the oil 2 can be reduced quickly by raising the temperature of the oil 2, which is advantageous in ensuring the power performance of the engine 10. Furthermore, as the engine 10 changes from cold to warm, the oil 2 supplied to the oil suction passage 18 can be switched from the first tank 32 to the second tank 34 by the switching valve 26 without any time lag. Therefore, when the engine 10 is warm, the oil 2 in the second tank 34 and the first tank 32 can be circulated to the engine 10 quickly and efficiently. This allows a larger amount of oil 2 to be circulated to the lubricated parts, thereby providing good lubrication to the lubricated parts and suppressing deterioration of the oil 2, which is advantageous in reducing the frequency of oil changes and easing the burden on the user. In other words, by providing a backflow prevention section (switching valve 26) that prevents oil 2 from flowing from the second tank 34 to the first tank 32 and allows oil 2 to flow from the first tank 32 to the second tank 34, it is possible to select between supplying oil 2 only from the first tank 32 and supplying oil 2 from both the first tank 32 and the second tank 34 when the engine operating state switches, and therefore it is possible to use the oil 2 from the first tank 32 and the second tank 34 depending on the engine operating state.

[0017] In this embodiment, the first tank 32 and the second tank 34 are arranged one above the other so that the first tank 32 is located above the second tank 34, and the check valve 30 is provided in the first tank 32 at a position below the first tank strainer 22. Therefore, the negative pressure caused by the oil suction by the first tank strainer 22 acts effectively on the check valve 30, so that the check valve 30 can be reliably maintained in a closed state when the engine 10 is cold. This prevents the oil 2 from escaping from the first tank 32 to the second tank 34 via the check valve 30, which is advantageous for efficiently circulating the oil 2 in the first tank 32 to the lubricated members of the engine 10 when the engine 10 is cold. In this case, if the communicating passage 28 is extended along the extension of the axis of the first tank side suction port 2202 of the first tank strainer 22 or along the vicinity of the extension of the axis of the first tank side suction port 2202 of the first tank strainer 22, the negative pressure caused by the oil suction of the first tank strainer 22 can be effectively applied to the upper end of the communicating passage 28 and the oil 2 on the first tank side bottom wall 3202 near the upper end opening 2802 of the communicating passage 28, which is more advantageous in closing the check valve 30 and efficiently circulating the oil 2 in the first tank 32 to the lubricated parts of the engine 10 when the engine 10 is cold. Furthermore, if the check valve 30 is provided on the extension of the axis of the first tank side suction port 2202 of the first tank strainer 22 or near the extension of the axis of the first tank side suction port 2202 of the first tank strainer 22, even if the connecting passage 28 is omitted and the check valve 30 is provided on the first tank side bottom wall 3202, the negative pressure caused by the oil suction of the first tank strainer 22 can be effectively applied to the oil 2 above the check valve 30, which is more advantageous when the engine 10 is cold in that it closes the check valve 30 and efficiently circulates the oil 2 in the first tank 32 to the lubricated parts of the engine 10.

[0018] In addition, in this embodiment, the first tank 32 and the second tank 34 each have a first tank-side bottom wall 3202 and a second tank-side lower wall 3204, and are provided with a communication passage 28 having a check valve 30, which extends from a portion of the first tank-side bottom wall 3202 located below the first tank-side suction port 2202 of the first tank strainer 22 toward the second tank-side bottom wall 3402, with its lower end located at the same height as the second tank-side suction port 2402 of the second tank strainer 24, and which communicates with the first tank 32. Therefore, when the engine 10 is warm, the negative pressure caused by the oil suction of the second tank strainer 24 is effectively applied to the lower end opening 2804 of the connecting passage 28, opening the check valve 30 and promoting the flow of oil 2 from the first tank 32 to the second tank 34 via the connecting passage 28, which is advantageous in efficiently circulating the oil 2 in the first tank 32 and the second tank 34 to the lubricated components of the engine 10.

[0019] In addition, in this embodiment, oil 2 is interposed between the first tank side bottom wall 3202 and the second tank side bottom wall 3402, and between the first tank side peripheral wall 3204 and the second tank side peripheral wall 3404, so that the oil 2 in the first tank 32 is insulated by the oil 2 in the second tank 34. Therefore, for example, when the engine 10 is stopped by an idle stop, or when the engine 10 is stopped while running on battery power in a hybrid vehicle, the operation of the oil pump 20 is stopped. This is advantageous in preventing the temperature of the oil 2 in the first tank 32 from decreasing due to the outside air or wind from traveling, and is advantageous in warming up the engine 10 quickly when the engine 10 is restarted.

[0020] In addition, in this embodiment, the switching valve 26 is configured as a thermostat valve that connects the first tank strainer 22 to the oil suction passage 18 when the temperature of the oil 2 flowing through the switching valve 26 is below a threshold value, and connects the second tank strainer 24 to the oil suction passage 18 when the temperature of the oil 2 is above the threshold value. Therefore, compared to when the switching valve 26 is configured as a solenoid valve, maintenance work is less and, since no power is required to drive the switching valve 26, it is also advantageous in terms of saving power.

[0021] (Second embodiment) Next, a second embodiment will be described with reference to FIG. In the following embodiments, parts and members similar to those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted, and the description will focus on the differences. In the first embodiment, the first tank 32 is provided inside and above the second tank 34, whereas in the second embodiment, the first tank 32 and the second tank 34 are provided side by side in the horizontal direction. As shown in FIG. 2(A), the oil pan 16 is composed of a first tank 32 and a second tank 34 that are separated from each other. In detail, the oil pan 16 has a bottom wall 1602, a peripheral wall 1604 that stands up from the periphery of the bottom wall 1602, and a flange 1606 that extends outward from the upper end of the peripheral wall 1604 and is attached to the lower part of the engine body 12, and is open at the top. Furthermore, a partition wall 1608 is provided standing from the bottom wall 1602, and an upper wall 1610 is provided at the upper end of the partition wall 1608, connecting the upper end of the partition wall 1608 and the peripheral wall 1604.

[0022] The second tank 34 is formed by a space defined by a bottom wall 1602 , a peripheral wall 1604 , a partition wall 1608 , and an upper wall 1610 . The first tank 32 is located on the bottom wall 1602 and inside the peripheral wall 1604, with the upper part open except for the second tank 34, and the liquid level of the oil 2 contained in the first tank 32 is located above the upper wall 1610. The partition wall 1608 is provided with a check valve 30 (backflow prevention portion) that prevents the oil 2 from flowing from the second tank 34 into the first tank 32. The partition wall 1608 is provided with a communication passage 28 that connects the first tank 32 and the second tank 34, and the check valve 30 is provided in this communication passage 28. The communication passage 28 also extends along the top of the bottom wall 1602, and the communication passage 28 protrudes from the partition wall 1608 into the inside of the first tank 32 and the inside of the second tank 34, respectively.

[0023] The first tank side connecting pipe 2204 of the first tank strainer 22 is provided toward the bottom wall 1602 of the first tank 32 at a location away from the partition wall 1608, and the first tank side suction port 2202 of the first tank strainer 22 is provided at the same height as the connecting passage 28. The second tank side connecting pipe 2404 of the second tank strainer 24 is provided at a location away from the partition wall 1608, penetrating the upper wall 1610 toward the bottom wall 1602, and the second tank side suction port 2402 of the second tank strainer 24 is provided at the same height as the connecting passage 28. In the drawing, reference numeral 36 denotes a drain hole provided in the bottom wall 1602 located on the second tank 34 side. By removing a drain plug (not shown) from the drain hole 36, the oil 2 contained in the second tank 34 is drained, and the oil 2 contained in the first tank 32 is smoothly drained via the communicating passage 28, the check valve 30, and the second tank 34.

[0024] According to the second embodiment, the first tank strainer 22 provided in the first tank 32 and the second tank strainer 24 provided in the second tank 34 are connected to the oil suction passage 18 via a switching valve 26, and a check valve 30 (backflow suppression unit) is provided to suppress the flow of oil 2 from the second tank 34 to the first tank 32. Therefore, when the engine 10 is cold, as shown in FIG. 2(A), the oil 2 in the first tank 32 is circulated to the lubricated components of the engine 10 via the switching valve 26, thereby quickly raising the temperature of the oil 2 and promoting the warm-up of the engine 10, which is advantageous in ensuring the power performance of the engine 10. Furthermore, as the engine 10 changes from cold to warm, as shown in FIG. 2(B), the oil 2 supplied to the oil suction passage 18 can be switched from the first tank 32 to the second tank 34 by the switching valve 26 without any time lag, so that a larger amount of oil 2 is circulated to the lubricated members when the engine 10 is warm, which improves the lubrication of the lubricated members and is advantageous in suppressing deterioration of the oil 2.

[0025] In this embodiment, the first tank side suction port 2202 of the first tank strainer 22 is provided at the same height as the communication passage . Therefore, the negative pressure caused by oil suction by the first tank strainer 22 acts effectively on the check valve 30, so that the check valve 30 can be reliably maintained in a closed state when the engine 10 is cold, which is advantageous for efficiently circulating the oil 2 in the first tank 32 to the lubricated parts of the engine 10 when the engine 10 is cold. In addition, in this embodiment, the communication passage 28 having the check valve 30 is provided at the same height as the second tank side suction port 2402 of the second tank strainer 24, but it does not have to be at the same height as long as negative pressure can be generated by strainer suction on the first tank 32 side of the communication passage. However, if they are at the same height, they can be easily positioned close to each other, and when the engine 10 is warm, the negative pressure caused by oil suction by the second tank strainer 24 can be effectively applied to the lower end opening 2804 of the connecting passage 28, opening the check valve 30 and promoting the flow of oil 2 from the first tank 32 to the second tank 34 via the connecting passage 28, which is advantageous for efficiently circulating the oil 2 in the first tank 32 and the second tank 34 to the lubricated parts of the engine 10. In the above-described embodiments, the oil 2 in the first tank 32 is circulated when the engine is cold, and both the oil 2 in the first tank 32 and the oil 2 in the second tank 34 are circulated when the engine is warm. However, depending on the operating state of the engine, it is possible to switch between circulating the oil 2 in the first tank 32 and circulating the oil 2 in both the first tank 32 and the second tank 34. [Explanation of symbols]

[0026] 2. Oil 10 Engine 12 Engine body 14 Oil circulation device 16 Oil pan 1602 bottom wall 1604 Peripheral wall 1606 flange 1608 Bulkhead 1610 Upper wall 18 Oil suction passage 20 Oil pump 22 Strainer for first tank 2202 First tank side suction port 2204 1st tank side communication pipe 24 Strainer for second tank 2402 Second tank side suction port 2404 2nd tank side communication pipe 26 Switching valve 28 Communication path 2802 Top opening 2804 Bottom opening 30 Check valve (backflow prevention part) 32 Tank 1 3202 1st tank side bottom wall 3204 1st tank side peripheral wall 34 Tank 2 3402 Second tank side bottom wall 3404 Second tank side peripheral wall 3406 flange 36 Drain hole

Claims

1. An oil circulation device for an engine that circulates oil in an oil pan to the engine through an oil suction passage, The oil pan is composed of a first tank and a second tank that are separated from each other, a first tank-side communicating pipe of a first tank strainer provided in the first tank and a second tank-side communicating pipe of a second tank strainer provided in the second tank are connected to the oil suction passage via a switching valve; a backflow prevention unit that prevents oil from flowing from the second tank to the first tank; An oil circulation device for an engine.

2. The first tank and the second tank are arranged vertically such that the first tank is located above the second tank; The check valve is provided at a location of the first tank below the first tank side suction port of the first tank strainer.

2. The oil circulation device for an engine according to claim 1.

3. The first tank and the second tank each have a bottom wall; a communication passage extending from a portion of the bottom wall of the first tank that is located below the first tank-side suction port toward the bottom wall of the second tank, with its lower end located at the same height as the second tank-side suction port of the second tank strainer and communicating with the first tank; The check valve is provided in the communication passage.

3. The oil circulation device for an engine according to claim 2.

4. the first tank includes a peripheral wall that stands up from the periphery of the bottom wall of the first tank, the second tank includes a peripheral wall that stands up from the periphery of the bottom wall of the second tank, The first tank is disposed inside the second tank, the peripheral wall of the first tank is disposed inside the peripheral wall of the second tank at a distance from the peripheral wall of the second tank, The oil contained in the second tank is interposed between the peripheral wall of the first tank and the peripheral wall of the second tank.

3. The oil circulation device for an engine according to claim 2.

5. the switching valve is configured as a thermostat valve that connects the first tank side communication passage of the first tank strainer to the oil suction passage when the temperature of the oil flowing through the switching valve is below a threshold value, and connects the second tank side communication passage of the second tank strainer to the oil suction passage when the temperature of the oil is equal to or higher than the threshold value.

5. The oil circulation device for an engine according to claim 1, wherein the oil circulation device is a valve for circulating oil in a cylinder of the engine.

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