Lubricating structure of engine

Abstract

The invention provides a lubrication structure of an engine, which can increase oil pressure of a variable valve device without increasing discharge amount of an oil pump. The engine is equipped with a variable valve device (12) capable of changing valve operation. The lubrication structure of the engine is provided with a discharge valve (21) for adjusting the oil pressure of oil discharged from an oil pump (16), a main oil passage (19) for supplying oil as lubricating oil to engine components (13a-13c), and an oil control valve (18) for controlling the oil pressure of a variable valve device. Oil on the downstream side of a bleed hole of the bleed valve is supplied to the main oil passage, and oil on the upstream side of the bleed hole is supplied to the oil control valve.

Description

Technical Field

[0001] This invention relates to a lubrication structure for an engine. Background Technology

[0002] Conventionally, as a lubrication system for engines, a device is known that utilizes oil from an oil pump to operate a variable valve timing device (see, for example, Patent Document 1). In the lubrication system described in Patent Document 1, oil is drawn from an oil pan by an oil pump and supplied to an oil control valve through an oil filter and a main oil passage. The oil pressure for the variable valve timing device is controlled by the oil control valve, and the variable valve timing device operates using oil from the oil control valve. Additionally, lubricating oil is also supplied from the main oil passage to various engine components.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2023-154209

[0006] The technical problem to be solved by the invention

[0007] As mentioned above, oil is also used for lubricating engine components, therefore, sometimes the oil pressure required to operate the variable valve timing system is insufficient. Although oil pressure can be increased by increasing the pump's discharge rate, this results in a larger pump size and a larger engine. In addition, the mechanical losses during pump operation increase, raising concerns about reduced engine output and fuel economy. Summary of the Invention

[0008] The present invention was made in view of this, and its object is to provide a lubrication structure for an engine that can increase the oil pressure for a variable valve timing device without increasing the discharge of the oil pump.

[0009] Technical means for solving problems

[0010] One aspect of the present invention provides a lubrication structure for an engine equipped with a variable valve timing device capable of changing valve actuation. The structure includes: a bleed valve that adjusts the oil pressure of oil discharged from an oil pump; a main oil passage for supplying oil as lubricant to engine components; and an oil control valve that controls the oil pressure for the variable valve timing device. Oil downstream of the bleed orifice of the bleed valve is supplied to the main oil passage, and oil upstream of the bleed orifice is supplied to the oil control valve, thereby solving the aforementioned technical problem.

[0011] Invention Effects

[0012] According to one aspect of the lubrication structure of the engine of the present invention, the oil pressure upstream of the drain hole is increased and supplied to the oil control valve until the drain hole of the drain valve is opened. Therefore, even at extremely low engine speeds immediately after engine startup, oil can be preferentially supplied to the oil control valve to activate the variable valve timing device. When the oil pressure is sufficiently increased to open the drain hole, working oil is supplied to the oil control valve, and lubricating oil is also supplied to various engine components through the main oil passage. Since it is not necessary to increase the discharge capacity of the oil pump, mechanical losses during pump operation can be reduced, improving engine output and fuel economy. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the lubrication structure of the engine in the first embodiment.

[0014] Figure 2 This is a schematic diagram of the lubrication structure of the engine in the second embodiment.

[0015] Figure 3 This is a schematic diagram of the lubrication structure of the engine in the third embodiment.

[0016] Figure 4 This is a schematic diagram of the lubrication structure of the engine in the fourth embodiment.

[0017] Figure 5 This is a schematic diagram of the lubrication structure of a comparative engine.

[0018] Symbol Explanation

[0019] 12, 32, 52, 72: Variable valve timing system

[0020] 16, 36, 56, 76: Oil pump

[0021] 17, 37, 57, 77: Oil filters

[0022] 18, 38, 58, 78: Oil control valves

[0023] 19, 39, 59, 79: Main oil passage

[0024] 21, 41a, 61, 81a: Relief valves

[0025] 24, 44a, 64, 84a: Drainage holes

[0026] 41b, 81b: Other relief valves

[0027] 69, 89: Bypass pathways. Detailed Implementation

[0028] One aspect of the present invention provides an engine equipped with a variable valve timing device capable of altering valve actuation. In the engine's lubrication system, a bleed valve adjusts the oil pressure discharged from the oil pump. Oil downstream of the bleed valve's bleed orifice is supplied to the main oil passage, where it is used as lubricant to engine components. Oil upstream of the bleed orifice is supplied to an oil control valve, which controls the oil pressure for the variable valve timing device. The oil pressure upstream of the bleed orifice is increased and supplied to the oil control valve until the bleed valve's bleed orifice opens. Therefore, even at extremely low engine speeds immediately after engine startup, oil can be preferentially supplied to the oil control valve to activate the variable valve timing device. When the oil pressure is sufficiently increased and the bleed orifice is open, working oil is supplied to the oil control valve, and lubricant is also supplied to various engine components via the main oil passage. Since it is not necessary to increase the oil pump's discharge rate, mechanical losses during pump operation are reduced, improving engine output and fuel economy.

[0029]

Example

[0030] Generally, motorcycle engines contain variable valve timing (VVT) and variable valve lift (VVL) mechanisms. Oil is drawn from an oil pan and supplied to the variable valve mechanism via an oil control valve. Oil pressure is used to activate the variable valve mechanism, adjusting valve timing, valve lift, and other parameters. In such motorcycles, oil is also supplied for lubricating engine components such as pistons or crankshafts, including ball bearings, metal bearings, and piston cooling injectors.

[0031] In such engines, due to factors such as the large area of ​​the oil supply orifice open to the atmosphere for lubricating components like pistons and crankshafts, or the relatively small discharge volume of the oil pump, sufficient oil pressure may not be obtained to enable the variable valve timing mechanism to operate. If ball bearings are used in the crankshaft bearings of a small scooter, ball bearings require more oil for lubrication than metal bearings, and the oil supply orifice for lubrication is left largely unused, much like a nozzle. Furthermore, the small oil pump in a single-cylinder engine cannot provide sufficient oil discharge.

[0032] Specifically, such as Figure 5As shown, in the comparative example engine, a small oil pump 92 draws oil from the oil pan 91, and the oil passes through the oil filter 93 before being sent to the main oil passage 94. The main oil passage 94 is connected to the variable valve timing device 96 via the oil control valve 95, and also to the oil passages of engine components 97a-97c, which are connected to various engine parts such as ball bearings. Oil for the operation of the variable valve timing device 96 is supplied from the main oil passage 94 to the oil control valve 95, and lubricating oil is supplied from the main oil passage 94 to the engine components 97a-97c.

[0033] A bleed valve 98 is connected midway through the oil passage from oil pump 92 to oil filter 93. When the oil pressure of the oil discharged from oil pump 92 increases due to an increase in engine speed, the remaining oil is discharged from bleed valve 98 to oil pan 91, thereby maintaining a constant oil pressure from oil filter 93 to main oil passage 94. Supply holes for lubricating engine components 97a-97c are formed at the front end of main oil passage 94. Due to the increased area of ​​the multiple supply holes, the oil pressure in main oil passage 94 decreases, resulting in insufficient oil pressure for the operation of variable valve timing device 96.

[0034] Therefore, in the lubrication structure of the engine in the first embodiment, an oil passage for the operation of the variable valve timing device and an oil passage for the lubrication of the engine components are respectively formed. Taking the bleed orifice of the bleed valve as a boundary, the oil passage upstream of the bleed orifice is connected to the variable valve timing device via an oil control valve, and the oil passage downstream of the bleed orifice is connected to the engine components via the main oil passage. The higher pressure oil upstream of the bleed orifice is supplied to the variable valve timing device through the oil control valve, while the oil discharged from the bleed valve is supplied to the engine components through the main oil passage.

[0035] <First Embodiment>

[0036] The following is for reference Figure 1 The lubrication structure of the engine in the first embodiment will be described. Figure 1 This is a schematic diagram of the lubrication structure of the engine according to the first embodiment. Furthermore, the following describes an example of applying the engine lubrication structure to a single-cylinder engine of a small scooter.

[0037] like Figure 1 As shown, in the engine's lubrication structure, oil passages 14a-14f extend from the oil pan 11 toward engine components 13a-13c, such as the VVT ​​or VVL mechanism and ball bearings. An oil coarse filter 15 is installed at the upstream end of oil passage 14a, and the oil enters the oil pan 11. An oil pump 16 is installed downstream of the oil coarse filter 15, drawing oil from the oil pan 11. An oil filter 17 is installed midway through oil passage 14b downstream of the oil pump 16, filtering the oil discharged from the oil pump 16.

[0038] Downstream of the oil filter 17, an oil passage 14c branches off from the oil passage 14b and connects to the drain valve 21. The drain valve 21 has an inlet 23 and a drain hole 24 formed in its valve body 22. The inlet 23 of the drain valve 21 is connected to the oil passage 14c, and the drain hole 24 is connected to the oil passage 14d. Inside the valve body 22, a valve spring 25 presses the plunger 26 towards the closed position of the drain hole 24. The expansion and contraction of the valve spring 25 opens and closes the drain hole 24, adjusting the oil pressure discharged from the oil pump 16.

[0039] Additionally, downstream of the oil filter 17, an oil passage 14e branches off from the oil passage 14b and connects to the oil control valve 18. Oil filtered by the oil filter 17 is supplied to the variable valve timing device 12 via the oil control valve 18. The oil control valve 18 houses a valve core (not shown), and the movement of the valve core controls the oil pressure on the variable valve timing device 12, thus activating it. Immediately after engine startup, the vent valve 21 closes, preferentially supplying higher pressure oil to the oil control valve 18, thereby actuating the variable valve timing device 12.

[0040] The bleed orifice 24 of the bleed valve 21 is connected to the main oil passage 19 via oil passages 14d and 14f. Oil, as lubricating oil, is supplied from the main oil passage 19 to the engine components 13a-13c. The oil passage 14e, which directs oil upstream of the bleed orifice 24 to the oil control valve 18, is formed smaller than the oil passage 14d, which directs oil downstream of the bleed orifice 24 to the main oil passage 19. Although the variable valve timing device 12 requires high oil pressure, it does not require a large amount of oil. Therefore, by reducing the cross-sectional area of ​​the oil passage 14e, the amount of oil supplied to the engine components 13a-13c through the main oil passage 19 is sufficiently ensured.

[0041] At extremely low engine speeds immediately after engine startup, the amount of oil discharged from oil pump 16 to oil passage 14b is minimal. Oil flows from oil passage 14b through oil passage 14c into inlet 23 of bleed valve 21, but the rebound force of valve spring 25 is greater than the oil pressure at inlet 23 of bleed valve 21. Plunger 26 is not pushed in by the oil pressure at inlet 23, and bleed orifice 24 is closed by plunger 26. Because oil is not discharged from bleed orifice 24, oil is not supplied to engine components 13a-13c via oil passages 14d, 14f, and main oil passage 19.

[0042] Furthermore, by closing the drain hole 24, the oil pressure upstream of the drain hole 24 increases. Consequently, higher pressure oil is supplied from oil passage 14b to oil control valve 18 via oil passage 14e. As described above, although the oil discharge from oil pump 16 is small, the oil control valve 18 and variable valve timing device 12 require a small amount of oil, allowing the variable valve timing device 12 to operate with a small amount of oil via oil control valve 18. The operation of the variable valve timing device 12 is used to adjust valve timing and valve lift.

[0043] As engine speed increases and the amount of oil discharged from oil pump 16 to oil passage 14b increases, the amount of oil entering oil passage 14c from oil passage 14b also increases, causing the oil pressure at inlet 23 of bleed valve 21 to rise. The oil pressure at inlet 23 becomes greater than the rebound force of valve spring 25, overcoming the rebound force of valve spring 25 and pushing plunger 26 in, thus opening bleed hole 24. Oil is discharged from bleed hole 24 through oil passages 14d and 14f to main oil passage 19, adjusting the pressure in oil passage 14b. Additionally, lubricating oil is supplied from main oil passage 19 to each engine component 13a-13c.

[0044] Additionally, oil is supplied from oil passage 14b to oil control valve 18 via oil passage 14e to activate variable valve timing device 12. In this case, oil control valve 18 is connected to main oil passage 19 via oil passages 14b to 14f, thereby reducing the overall oil pressure in the oil passages. On the other hand, the engine speed increases, increasing the overall oil pressure in the oil passages, thus ensuring the oil pressure required to activate variable valve timing device 12. In this way, oil downstream of drain hole 24 is supplied to main oil passage 19, and oil upstream of drain hole 24 is supplied to oil control valve 18.

[0045] According to the lubrication structure of the engine in the first embodiment, the oil pressure upstream of the drain hole 24 is increased and supplied to the oil control valve 18 until the drain hole 24 of the drain valve 21 is opened. Therefore, even at extremely low engine speeds immediately after engine startup, oil can be preferentially supplied to the oil control valve 18 to enable the variable valve device 12 to operate. When the oil pressure is sufficiently increased to open the drain hole 24, working oil is supplied to the oil control valve 18, and lubricating oil is also supplied to the engine components 13a to 13c of each part of the engine through the main oil passage 19. Since it is not necessary to increase the discharge volume of the oil pump 16, mechanical losses during pump operation are reduced, and engine output and fuel economy are improved.

[0046] <Second Embodiment>

[0047] Next, the lubrication structure of the engine in the second embodiment will be described. Figure 2This is a schematic diagram of the lubrication structure of the engine according to the second embodiment. The lubrication structure of the engine in the second embodiment differs from that of the engine in the first embodiment in that an additional drain valve is provided downstream of the drain orifice of the drain valve. Therefore, for the second embodiment, descriptions of structures identical to those in the first embodiment are omitted.

[0048] like Figure 2 As shown, in the lubrication structure of the engine in the second embodiment, similar to the lubrication structure of the engine in the first embodiment, oil passages 34a to 34f extend from the oil pan 31 toward the variable valve device 32 and engine components 33a to 33c. Oil is drawn from the oil pan 31 by the oil pump 36 through the oil coarse filter 35, and the oil discharged from the oil pump 36 is filtered by the oil filter 37. Downstream of the oil filter 37, oil passage 34c, branching from oil passage 34b, is connected to the drain valve 41a, and oil passage 34e, branching from oil passage 34b, is connected to the oil control valve 38.

[0049] The drain orifice 44a of the drain valve 41a is connected to the main oil passage 39 via oil passages 34d and 34f, supplying oil from the main oil passage 39 to engine components 33a-33c. A drain valve (another drain valve) 41b with a higher opening pressure than the drain valve 41a is connected midway through oil passage 34d. The drain valve 41b has the same structure as the drain valve 41a, but its drain orifice 44b is open to the atmosphere above the oil pan 31. By discharging oil from the drain orifice 44b into the oil pan 31, the oil pressure in the oil passages 34d and 34f, located downstream of the drain orifice 44a, is adjusted.

[0050] In the lubrication structure of this engine, at extremely low engine speeds immediately after engine startup, the amount of oil discharged from the oil pump 36 to the oil passage 34b is relatively small. The rebound force of the valve spring 45a is greater than the oil pressure at the inlet 43a of the bleed valve 41a, and the bleed orifice 44a is closed by the plunger 46a. The oil pressure upstream of the bleed orifice 44a increases, supplying higher pressure oil from the oil passage 34e to the oil control valve 38, which then activates the variable valve timing device 32. Thus, similar to the first embodiment, oil is preferentially supplied to the variable valve timing device 32 at extremely low engine speeds.

[0051] When the engine speed increases and the amount of oil discharged from the oil pump 36 to the oil passage 34b increases, the oil pressure at the inlet 43a becomes greater than the rebound force of the valve spring 45a, pushing the plunger 46a in and opening the drain hole 44a. Oil is discharged from the drain hole 44a through the oil passages 34d and 34f to the main oil passage 39, and oil is supplied from the main oil passage 39 to each engine component 33a-33c. Although the oil pressure in the oil passage 34b is adjusted below the specified pressure, it is above the operating pressure of the variable valve timing device 32. Therefore, oil is also supplied to the oil control valve 38 through the oil passage 34e to activate the variable valve timing device 32.

[0052] Furthermore, at high engine speeds, the amount of oil discharged from the oil pump 36 to the oil passage 14b increases, and more oil is discharged from the drain hole 44a of the bleed valve 41a into the oil passage 34d. The amount of oil entering the inlet 43b of the bleed valve 41b from the oil passage 34d increases, and the oil pressure at the inlet 43b becomes higher. The oil pressure at the inlet 43b becomes greater than the rebound force of the valve spring 45b, pushing the plunger 46b in and opening the drain hole 44b. The remaining oil returns to the oil pan 31 from the drain hole 44b, adjusting the oil pressure in each oil passage and the main oil passage 39.

[0053] In the lubrication structure of the engine in the second embodiment, oil is preferentially supplied to the oil control valve 38 to activate the variable valve timing device 32. Furthermore, since there is no need to increase the discharge volume of the oil pump 36, mechanical losses during pump operation are reduced, improving engine output and fuel economy. Moreover, at high engine speeds, excess oil is discharged from the drain valve 41b, stabilizing the oil pressure of the oil discharged from the drain valve 41a toward the main oil passage 39.

[0054] <Third Embodiment>

[0055] Next, the lubrication structure of the engine in the third embodiment will be described. Figure 3 This is a schematic diagram of the lubrication structure of the engine according to the third embodiment. The difference between the lubrication structure of the engine in the third embodiment and that in the first embodiment is that the upstream and downstream sides of the bleed valve's bleed hole are connected through a bypass passage. Therefore, for the third embodiment, the same structure as in the first embodiment is omitted from the description.

[0056] like Figure 3 As shown, in the lubrication structure of the engine in the third embodiment, similar to the lubrication structure of the engine in the first embodiment, oil passages 54a to 54f extend from the oil pan 51 toward the variable valve device 52 and engine components 53a to 53c. Oil is drawn from the oil pan 51 by the oil pump 56 through the oil coarse filter 55, and the oil discharged from the oil pump 56 is filtered by the oil filter 57. Downstream of the oil filter 57, oil passage 54c, branching from oil passage 54b, is connected to the drain valve 61, and oil passage 54e, branching from oil passage 54b, is connected to the oil control valve 58.

[0057] The bleed orifice 64 of the bleed valve 61 is connected to the main oil passage 59 via oil passages 54d and 54f, supplying oil from the main oil passage 59 toward engine components 53a to 53c. The oil passage 54b upstream of the bleed orifice 64 and the oil passage 54f downstream of the bleed orifice 64 are connected via a bypass passage 69. The bypass passage 69 serves as an injection orifice, and its cross-sectional area is smaller than that of the oil passage 54b that directs oil from the oil pump 56 to the bleed valve 61. Even when the bleed valve 61 is closed, oil is supplied to the main oil passage 59 via the bypass passage 69.

[0058] In the lubrication structure of this engine, at extremely low engine speeds immediately after engine startup, the amount of oil discharged from the oil pump 56 to the oil passage 54b is relatively small. The rebound force of the valve spring 65 is greater than the oil pressure at the inlet 63 of the bleed valve 61, so the bleed orifice 64 is closed by the plunger 66, but oil is supplied little by little to the main oil passage 59 through the bypass passage 69. Even at extremely low engine speeds when the bleed valve 61 is closed, oil is supplied to engine components 53a-53c. The oil pressure upstream of the bleed orifice 64 increases, supplying higher pressure oil from the oil passage 54e to the oil control valve 58, which then activates the variable valve timing device 52.

[0059] As engine speed increases and the amount of oil discharged from oil pump 56 into oil passage 54b increases, the oil pressure at inlet 63 becomes greater than the rebound force of valve spring 65, pushing plunger 66 in and opening drain hole 64. Oil is discharged from drain hole 64 through oil passages 54d and 54f into main oil passage 59, and oil is supplied from main oil passage 59 to each engine component 53a-53c. Although the oil pressure in oil passage 54b is adjusted below the specified pressure, it is above the operating pressure of variable valve timing device 52. Therefore, oil is also supplied to oil control valve 58 through oil passage 54e to activate variable valve timing device 52.

[0060] In the lubrication structure of the engine in the third embodiment, oil is preferentially supplied to the oil control valve 58 to activate the variable valve timing device 52. Furthermore, since it is not necessary to increase the discharge volume of the oil pump 56, mechanical losses during pump operation are reduced, improving engine output and fuel economy. Moreover, even at extremely low engine speeds when the blow-off valve 61 is closed, oil is supplied from the oil pump 56 to engine components 53a-53c via the bypass passage 69 and the main oil passage 59.

[0061] <Fourth Embodiment>

[0062] Next, the lubrication structure of the engine in the fourth embodiment will be described. Figure 4This is a schematic diagram of the lubrication structure of the engine according to the fourth embodiment. The lubrication structure of the engine in the fourth embodiment differs from that of the engine in the first embodiment in that the upstream and downstream sides of the bleed valve's bleed hole are connected via a bypass passage, and another bleed valve is provided downstream of the bleed valve's bleed hole. Therefore, for the fourth embodiment, descriptions of structures identical to those in the first embodiment are omitted.

[0063] like Figure 4 As shown, in the lubrication structure of the engine in the fourth embodiment, similar to the lubrication structure of the engine in the first embodiment, oil passages 74a to 74f extend from the oil pan 71 toward the variable valve device 72 and engine components 73a to 73c. ​​Oil is drawn from the oil pan 71 by the oil pump 76 through the oil coarse filter 75, and the oil discharged from the oil pump 76 is filtered by the oil filter 77. Downstream of the oil filter 77, oil passage 74c, branching from oil passage 74b, is connected to the drain valve 81a, and oil passage 74e, branching from oil passage 74b, is connected to the oil control valve 78.

[0064] The drain orifice 84a of the drain valve 81a is connected to the main oil passage 79 via oil passages 74d and 74f, supplying oil from the main oil passage 79 to engine components 73a-73c. A drain valve (another drain valve) 81b with a higher opening pressure than the drain valve 81a is connected midway through oil passage 74d. The drain valve 81b has the same structure as the drain valve 81a, but its drain orifice 84b is open to the atmosphere above the oil pan 71. By discharging oil from the drain orifice 84b into the oil pan 71, the oil pressure in the oil passages 74d and 74f, located downstream of the drain orifice 84a, is adjusted.

[0065] The oil passage 74b upstream of the drain orifice 84a and the oil passage 74f downstream of the drain orifice 84a are connected by a bypass passage 89. Oil passage 74f is located on the main oil passage 79 side compared to the drain valve 81b, and the bypass passage 89 is formed to bypass both drain valves 81a and 81b. The bypass passage 89 serves as an injection orifice, and its cross-sectional area is smaller than that of the oil passage 74b. Even when the drain valve 81a is closed, oil is supplied to the main oil passage 79 through the bypass passage 89.

[0066] In the lubrication structure of this engine, at extremely low engine speeds immediately after engine startup, the amount of oil discharged from the oil pump 76 to the oil passage 74b is relatively small. The rebound force of the valve spring 85a is greater than the oil pressure at the inlet 83a of the bleed valve 81a, so the bleed orifice 84a is closed by the plunger 86a, but oil is supplied little by little to the main oil passage 79 through the bypass passage 89. Even at extremely low engine speeds when the bleed valve 81a is closed, oil is supplied to engine components 73a-73c. The oil pressure upstream of the bleed orifice 84a increases, supplying higher pressure oil from the oil passage 74e to the oil control valve 78, which then activates the variable valve timing device 72.

[0067] When the engine speed increases and the amount of oil discharged from the oil pump 76 to the oil passage 74b increases, the oil pressure at the inlet 83a becomes greater than the rebound force of the valve spring 85a, pushing the plunger 86a in and opening the drain hole 84a. Oil is discharged from the drain hole 84a through oil passages 74d and 74f to the main oil passage 79, and oil is supplied from the main oil passage 79 to each engine component 73a-73c. Although the oil pressure in the oil passage 74b is adjusted below the specified pressure, it is above the operating pressure of the variable valve timing device 72. Therefore, oil is also supplied to the oil control valve 78 through the oil passage 74e to activate the variable valve timing device 72.

[0068] Furthermore, at high engine speeds, the amount of oil discharged from the oil pump 76 to the oil passage 74b increases, and more oil is discharged from the drain hole 84a of the bleed valve 81a into the oil passage 74d. The amount of oil entering the inlet 83b of the bleed valve 81b from the oil passage 74d increases, and the oil pressure at the inlet 83b becomes higher. The oil pressure at the inlet 83b becomes greater than the rebound force of the valve spring 85b, pushing the plunger 86b in and opening the drain hole 84b. The remaining oil returns to the oil pan 71 from the drain hole 84b, adjusting the oil pressure in each oil passage and the main oil passage 79.

[0069] According to the lubrication structure of the engine in the fourth embodiment, oil is preferentially supplied to the oil control valve 78 to activate the variable valve timing device 72. Furthermore, since it is not necessary to increase the discharge volume of the oil pump 76, mechanical losses during pump operation are reduced, improving engine output and fuel economy. Moreover, even at extremely low engine speeds when the blow-off valves 81a and 81b are not open, oil is supplied from the oil pump 76 to engine components 73a to 73c via the bypass passage 89 and the main oil passage 79.

[0070] Furthermore, in various embodiments, an oil passage extending from the oil filter branches off towards the oil control valve at a location farther from the oil filter than the relief valve, but this structure is not limited to this. Alternatively, an oil passage extending downstream from the oil filter branches off towards the oil control valve at a location closer to the oil filter than the relief valve.

[0071] Furthermore, in the second and fourth embodiments, the oil passage extending from the bleed orifice of the bleed valve is connected to other bleed valves, but this structure is not limited to that. Other bleed valves only need to be connected to the oil passage between the bleed orifice of the bleed valve and the main oil passage.

[0072] In addition, in the third and fourth embodiments, the oil passage extending from the oil filter and connected to the main oil passage are connected by a bypass passage, but this structure is not limited to this. The bypass passage only needs to be able to connect the upstream side and the downstream side of the drain hole.

[0073] Furthermore, the lubrication structure of the engine in this embodiment is not limited to small scooters, but can also be used in other types of riding vehicles or other vehicles.

[0074] As described above, the first approach is a lubrication structure for an engine equipped with variable valve timing devices 12, 32, 52, and 72 capable of changing valve actuation. This structure includes: relief valves 21, 41a, 61, and 81a that adjust the oil pressure of oil discharged from oil pumps 16, 36, 56, and 76; main oil passages 19, 39, 59, and 79 for supplying oil as lubricant to engine components; and oil control valves 18, 38, 58, and 78 that control the oil pressure for the variable valve timing devices. Oil downstream of the relief orifices 24, 44a, 64, and 84a of the relief valves is supplied to the main oil passages, while oil upstream of the relief orifices is supplied to the oil control valves. According to this structure, the oil pressure upstream of the relief orifices is increased and supplied to the oil control valves until the relief orifices of the relief valves are open. Therefore, even at extremely low engine speeds immediately after engine startup, oil is preferentially supplied to the oil control valve to activate the variable valve timing system. When the oil pressure is sufficiently increased to open the vent, working oil is supplied to the oil control valve, and lubricating oil is also supplied to various engine components via the main oil passage. Since there is no need to increase the oil pump's discharge rate, mechanical losses during pump operation are reduced, improving engine output and fuel economy.

[0075] The second method, as in the first method, involves a bleed valve located downstream of oil filters 17, 37, 57, and 77, supplying oil from the downstream side of the filters to the oil control valve. With this configuration, oil filtered by the filters can be supplied to the variable valve mechanism via the oil control valve.

[0076] The third approach, as in the first or second approach, involves shaping the cross-sectional areas of the oil passages 14e, 34e, 54e, and 74e of the oil-directing control valve upstream of the bleed hole to be smaller than the cross-sectional areas of the oil passages 14d, 34d, 54d, and 74d of the oil-directing main oil passage downstream of the bleed hole. According to this structure, the variable valve timing device requires high oil pressure but not a large quantity of oil. Therefore, by reducing the cross-sectional area of ​​the oil passages directing the oil to the oil-directing control valve, the amount of oil supplied to the engine components through the main oil passage can be adequately ensured.

[0077] The fourth method involves, in any of the first to third methods, an additional bleed valve 41b whose opening pressure is set to be greater than that of the bleed valve. This additional bleed valve adjusts the oil pressure downstream of the bleed valve's bleed orifice. According to this structure, at high engine speeds, residual oil is discharged from the additional bleed valve, stabilizing the oil pressure of the oil discharged from the bleed valve toward the main oil passage.

[0078] The fifth method involves, in any of the first to third methods, forming a bypass passage 69 or 89 connecting the upstream and downstream sides of the drain hole. The cross-sectional area of ​​the bypass passage is smaller than the cross-sectional area of ​​the oil passage that directs oil from the oil pump to the drain valve. According to this structure, even at extremely low engine speeds when the drain valve is not open, oil can be supplied from the oil pump to engine components through the bypass passage and the main oil passage.

[0079] The sixth method, as in the fifth method, includes another relief valve 81b whose opening pressure is set higher than that of the relief valve. This other relief valve adjusts the oil pressure downstream of the relief orifice. A bypass passage connects the oil passage 74b upstream of the relief orifice to the oil passage 74f on the main oil passage side of the other relief valves. According to this structure, even at extremely low engine speeds when the relief valves and other relief valves are not open, oil can be supplied to engine components from the oil pump through the bypass passage and the main oil passage.

[0080] Furthermore, although this embodiment has been described, other embodiments may also be created by combining the above embodiments and variations in whole or in part.

[0081] Furthermore, the technology of the present invention is not limited to the above embodiments, and various changes, substitutions, and modifications can be made without departing from the spirit of the technical concept. Moreover, as long as the technical concept can be realized by other methods through technological advancements or derived technologies, this method can also be used for implementation. Therefore, the scope of protection sought covers all implementation methods that can be included within the scope of the technical concept.

Claims

1. A lubrication structure for an engine, the engine being equipped with a variable valve timing device capable of changing valve actuation, characterized in that, have: A relief valve that adjusts the oil pressure of the oil discharged from the oil pump; The main oil passage, which supplies oil as lubricant to engine components; and An oil control valve controls the oil pressure for the variable valve timing device. Oil downstream of the drain orifice of the drain valve is supplied to the main oil passage, and oil upstream of the drain orifice is supplied to the oil control valve.

2. The lubrication structure of the engine according to claim 1, characterized in that, The drain valve is located on the downstream side of the oil filter, and the oil on the downstream side of the oil filter is supplied to the oil control valve.

3. The lubrication structure of the engine according to claim 1 or 2, characterized in that, The cross-sectional area of ​​the oil passage leading from the upstream side of the drain hole to the oil control valve is formed to be smaller than the cross-sectional area of ​​the oil passage leading from the downstream side of the drain hole to the main oil passage.

4. The lubrication structure of the engine according to claim 1 or 2, characterized in that, Other relief valves are available with an opening pressure set higher than that of the aforementioned relief valve. The other relief valves adjust the oil pressure on the downstream side of the relief valve's relief orifice.

5. The lubrication structure of the engine according to claim 1 or 2, characterized in that, A bypass passage is formed that connects the upstream side and the downstream side of the drain hole. The cross-sectional area of ​​the bypass passage is formed to be smaller than the cross-sectional area of ​​the oil passage that directs oil from the oil pump to the relief valve.

6. The lubrication structure of the engine according to claim 5, characterized in that, Other relief valves are available with an opening pressure set higher than that of the aforementioned relief valve. The other bleed valves adjust the oil pressure on the downstream side of the bleed orifice. The bypass passage connects the oil passage upstream of the bleed hole to the oil passage on the side closer to the main oil passage than the other bleed valves.

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