JP4926148B2 - Insulated oil pan structure - Google Patents

Description

  The present invention relates to an oil pan structure of an automobile, and more particularly to a structure of a heat insulating oil pan excellent in heat retention of lubricating oil.

  Oil pans are widely used as devices for storing lubricating oil for internal combustion engines. Lubricating oil stored in an oil pan (hereinafter referred to as oil) is pumped up through a strainer by an oil pump during operation of the internal combustion engine, and after foreign matter is removed by an oil filter, lubrication of various contact portions of the internal combustion engine or Used for cooling. The used oil returns to the oil pan and is stored in the oil pan until it is pumped again.

  Since conventional oil pans do not place importance on heat retention, the oil temperature rapidly decreases after the internal combustion engine is stopped. When the oil temperature decreases, the fluidity of the oil decreases due to an increase in viscosity, so when the internal combustion engine is operated again, the flow resistance increases and the friction loss increases, the load on the starter motor increases, and the fuel efficiency deteriorates. There was a problem to do.

  Japanese Patent Laid-Open No. 2000-199416 proposes a two-part oil pan structure in which a baffle plate is disposed between an upper side main body and a lower side main body attached to a crankcase lower. The baffle plate is formed with an oil introduction hole and an oil outlet hole. The oil introduction hole is provided with an openable / closable heat retaining cover, and the oil outlet hole is closed with a strainer. Therefore, according to this structure, the inside of the lower-side main body can be a sealed structure, and the heat retaining property of oil is improved.

  However, in this oil pan structure, since the upper side main body is fixed below the crankcase lower, there is a problem in that the amount of protrusion from the crankcase lower becomes large and the space restriction is large. Moreover, although the said gazette does not have description about the material of an upper side main body and a lower side main body, since it is high in heat conductivity, it is inferior to heat insulation.

  On the other hand, Japanese Utility Model Laid-Open No. 04-132445 describes a resin oil pan. However, the resin oil pan has insufficient strength against the collision of stepping stones during traveling. Moreover, since the upper part of an oil pan is opening, heat retention is low.

  Japanese Patent Laid-Open No. 2001-152824 discloses a first oil storage chamber provided with an oil passage for supplying oil to an oil pump, and a second oil storage chamber that can communicate with the first oil storage chamber via a communication hole. And a control valve that opens the communication hole to connect the first oil storage chamber and the second oil storage chamber when the oil storage amount of the first oil storage chamber is smaller than a predetermined amount. Has been. It is also described that a float valve that opens and closes according to the oil flow rate is used as the control valve.

  With this configuration, when the amount of oil stored is greater than a certain level, the control valve closes the communication hole and prevents the oil from flowing between the two oil storage chambers. A small amount of oil is supplied to each part of the engine via the oil passage, and the increase in the oil temperature during the engine warm-up operation can be promoted.

However, the above publication describes that the partition plate (21) is provided with an air vent hole (32). Therefore, even if the control valve is closed to promote an increase in the temperature of the oil, there is a problem that the heat dissipation of the oil proceeds through the air vent hole.
JP 2000-199416 Japanese Utility Model Publication No. 04-132445 Japanese Patent Laid-Open No. 2001-152824

  This invention is made | formed in view of the said situation, and makes it the problem which should be solved to further improve the heat retention of the oil stored by the oil pan.

The heat insulating oil pan structure of the present invention that solves the above problems is characterized in that a crankcase lower, an oil pan fixed to the lower part of the crankcase lower, and a reverse container shape opening in the lower part are housed in the crankcase lower. A heat insulating oil pan structure in which a closed space is formed between the upper member and the oil pan. The heat insulating oil pan is formed between the upper member and the oil pan. Because
The upper member has an oil introduction hole for introducing lubricating oil into the closed space, an oil outlet hole for extracting the lubricating oil from the closed space, and an air vent hole communicating the closed space with the outside. Formed in the side wall of the member, the air vent hole is formed in the upper bottom portion of the upper member, a valve member comprising a float and a valve body is arranged in the upper member, and according to the amount of lubricating oil stored in the closed space The valve main body opens and closes the oil introduction hole and the float opens and closes the air vent hole.

  According to the heat insulating oil pan structure of the present invention, the resin upper member having a lower thermal conductivity than the metal is disposed between the crankcase lower and the oil pan, and oil is stored between the upper member and the oil pan. A closed space is formed. When a predetermined amount of oil is stored in the closed space when the internal combustion engine is stopped, the oil introduction hole is closed by the valve member, so that the communication between the closed space and the crankcase is blocked. As a result, the oil stored in the closed space can be substantially sealed, and heat dissipation from the oil is suppressed. Therefore, when the internal combustion engine is stopped, the oil stored in the closed space has a high heat retaining property, and the oil having a high temperature is circulated at the next start, so that the friction loss can be reduced.

  Since the upper member is accommodated in the crankcase lower, the oil does not become bulky and the oil introduction hole is formed in the side wall of the upper member, so that the oil between the upper member and the crankcase lower is also moved to the closed space. Can lead.

  By the way, when the oil flows into the closed space, if the oil level is above the oil introduction hole, there is no escape space for the air in the closed space, and it becomes difficult for the oil to flow further. Therefore, it is desirable to provide an air vent hole that communicates between the closed space and the outside in the upper part of the upper member. However, if the air hole is always opened, the heat retaining property of the oil stored by heat radiation from the air hole is lowered.

  Therefore, in the heat insulating oil pan structure of the present invention, a valve member composed of a float and a valve main body is disposed on the upper member. The valve member includes a float and a valve body, and the valve body opens and closes the oil introduction hole, and the float opens and closes the air vent hole. When the liquid level of the oil stored in the closed space reaches a predetermined height, the float closes the air vent hole, so that the heat retaining property of the stored oil is further improved.

By opening and closing the oil introduction hole and opening and closing the air vent hole with one valve member, the opening and closing of both holes can be linked easily and reliably. Moreover, since this interlock can be performed only with the buoyancy of the float, the drive source is unnecessary and the cost can be reduced.
Furthermore, it is desirable to provide an urging member that urges the float in a direction to close the air vent hole, and the urging member is configured to exert an urging force at a predetermined temperature or higher. By doing in this way, even when the amount of oil in the oil pan is small, the air vent hole and the oil introduction hole can be closed according to the temperature of the oil, and heat radiation can be suppressed. In addition, since the oil introduction hole is closed immediately after the engine is stopped, the heat retaining property of the oil in the oil pan is improved.

  If the oil pan is composed of the upper member and the resin lower member, and the closed space is formed between the lower member and the upper member, the entire oil pan has low thermal conductivity. Since it is formed from resin, the heat dissipation of the stored oil can be further suppressed.

  At least the upper member desirably has an air layer in the peripheral wall. By comprising in this way, an air layer functions as a heat insulation layer and the heat retention of the stored oil further improves.

  It is desirable to place a strainer on the oil pan and close the oil outlet hole with the strainer. By comprising in this way, the airtightness of closed space increases further and the heat retention of the stored oil improves further.

  A crankcase of a general automobile engine is composed of a crankcase upper and a crankcase lower, and is arranged at the lower part of the cylinder block. A relatively large space facing the oil pan is generally formed in the lower part of the crankcase lower. In the present invention, this space is also used as a part of the oil pan.

  In the heat insulating oil pan structure of the present invention, the resin upper member is sandwiched between the crankcase lower and the oil pan, and the upper member enters the space formed in the lower portion of the crankcase lower, and the upper member It is partitioned from the oil pan. The upper member can be formed by injection molding from polyamide, polyacetal, polypropylene, polyphenylene sulfide or the like.

  Since the upper member is sandwiched between the crankcase lower and the oil pan, a closed space in which oil is stored is formed between the upper member and the oil pan. The upper member has an oil introduction hole for introducing oil into the closed space and an oil outlet hole for extracting oil from the closed space.

  That is, the oil used for lubrication or cooling falls into the crankcase lower, flows after adhering to the upper member, and flows into the closed space from the oil introduction hole. The oil stored in the closed space is pumped up from the oil outlet hole by the oil pump. Therefore, it is desirable to form an oil passage toward the oil introduction hole on the upper surface of the upper member or the inner peripheral surface of the crankcase lower. Further, it is desirable to form a collective flow path where oil collects and flows between the upper member and the crankcase lower, and to form an oil introduction hole in the lowermost portion of the collective flow path.

  The upper member is provided with a valve member that closes the oil introduction hole when a predetermined amount of oil is stored in the closed space. The valve member opens the oil introduction hole until the oil stored in the closed space reaches a predetermined amount, and closes the oil introduction hole when the predetermined amount is reached when the internal combustion engine is stopped. That is, when the internal combustion engine is stopped, the oil pump is also stopped, so that most of the oil is stored in the closed space. When a predetermined amount of oil is stored in the closed space, the valve member functions and the oil introduction hole is closed. As a result, communication between the closed space and the inside of the crankcase lower is blocked. Therefore, the oil stored in the closed space can be substantially sealed, and the heat retention is improved because heat dissipation from the oil is suppressed.

  The valve member includes a float and a valve body, and is configured such that the float opens and closes the air vent hole and the valve body opens and closes the oil introduction hole according to the vertical movement of the oil level. When the liquid level of the oil stored in the closed space reaches a predetermined height, the float closes the air vent hole, so that the heat retaining property of the stored oil is further improved. Further, the oil level in the closed space can be set up to near the upper bottom surface of the upper member, and the float can have both the function of detecting the liquid level and the function of opening and closing the air vent hole.

  It is desirable to place a strainer on the oil pan and close the oil outlet hole with the strainer. With this configuration, the communication between the closed space and the inside of the crankcase can be further shielded, so that the airtightness of the closed space is increased and the heat retaining property of the stored oil is further improved.

  An oil pan is constituted by a resin-made lower member that is open at the top and has a container shape capable of storing lubricating oil, and a metal oil pan cover that covers the lower member from below, and the lower member is fixed to the upper member. It is desirable to form a closed space between the lower member and the upper member. By covering the entire closed space with resin, the heat dissipation of the stored oil can be further suppressed.

  The lower member and the upper member are fixed so that the openings face each other to form a closed space. For example, the opening of the lower member and the upper member can have the same shape as each other, but the end surfaces of the openings can be brought into contact with each other by welding or the like. It is desirable to fix the member and the upper member so as to be separable. In order to do this, it is possible to form flange portions on the peripheral edges of the opening of the lower member and the upper member, and to join both the flange portions together with a bolt or the like. In this case, it is desirable to interpose a sealing material such as a liquid gasket (FIPG) between the two flange portions.

  At least the upper member desirably has an air layer in the peripheral wall. The heat insulation is further improved by the air layer. Although it is possible to form an air layer by forming the peripheral wall from foamed resin, there are cases where the oil is impregnated into the bubbles or the strength is lowered. Therefore, it is desirable to form the peripheral wall from at least two resin plates and to form an air layer between the resin plates.

  To do this, at least the upper member is composed of a container-shaped inner member and a container-shaped outer member that is slightly larger than the inner member, and the inner member and the outer member are joined together, It is desirable to form an air layer in between.

  When an air layer is formed at least in the peripheral wall of the upper member where the flange portion is formed, the air layer can be easily formed as follows. That is, at least the upper member is composed of a container-shaped inner member and a container-shaped outer member that is slightly larger than the inner member, the flange portion is formed on the inner member, and the opening end surface of the outer member is joined to the flange portion by welding or the like. The air layer can be easily formed simply by doing so. In this way, since the number of flange portions is reduced, the number of steps for interposing the sealing material is reduced. Then, by sandwiching the flange portion between the crankcase lower and the oil pan, at least the upper member can be fixed between the crankcase lower and the oil pan.

  In the case of a heat insulating oil pan structure provided with a lower member, it is desirable to form an air layer on the lower member as well as the upper member.

  Hereinafter, the present invention will be described specifically by way of examples.

Example 1
FIG. 1 shows a heat insulating oil pan structure according to this embodiment, and FIG. This heat insulating oil pan structure is used in automobiles, and is made of an aluminum alloy crankcase lower 1, a stainless steel oil pan 2 fixed to the lower surface of the crankcase lower 1, and a polyamide resin reinforced with glass fiber. The upper member 3, the valve member 4, and the strainer 5 are configured. The upper member 3 is sandwiched between the crankcase lower 1 and the oil pan 2.

  The crankcase lower 1 is conventionally used, and a relatively large space 10 is formed in a portion facing the oil pan 2 inside thereof. A plurality of boss portions 11 for fixing the oil pan 2 with bolts are formed at the lower portion.

  The oil pan 2 is formed in a container shape corresponding to a conventional oil pan, and a pan flange 20 is formed at the periphery of the opening. Further, a boss 22 (see FIG. 9) into which the drain bolt 21 is screwed protrudes from the bottom.

  The upper member 3 has an inverted container shape and is formed into a shape that can be accommodated in the space 10 of the crankcase lower 1 from below. A part of the outer peripheral surface of the upper member 3 has a shape corresponding to a part of the inner peripheral surface of the crankcase lower 1 and is arranged in close contact with a part of the inner peripheral surface of the crankcase lower 1. It is configured. An upper flange 30 is formed at the opening peripheral edge of the upper member 3, and an oil introduction hole 31 (see FIG. 3) that opens in the lateral direction, an oil lead-out hole 32 that opens in the upward direction, and an air vent hole 33 are formed. Has been.

  The valve member 4 includes a valve body 40, a rod 41 extending from the valve body 40, and a float 42 to which the other end of the rod 41 is fixed. A leg 43 projects from the valve body 40. As shown in FIG. 3, the bracket 44 is fixed to the upper member 3, and the valve main body 40 is pivotally supported by the bracket 44 so as to be swingable. That is, the valve body 40 opens and closes the oil introduction hole 31 of the upper member 3 by swinging. Further, the float 42 closes the air vent hole 33 when the valve body 40 closes the oil introduction hole 31.

  The strainer 5 is a flange formed at a position slightly away from the resin base portion 50, the mesh 51, the lid portion 52, the cylindrical portion 53 extending from the lid portion 52, and the tip 54 of the cylindrical portion 53. The base part 50 and the lid part 52 communicate with each other via a mesh 51.

  In order to assemble the heat insulating oil pan structure of this embodiment, first, the flange portion 55 of the strainer 5 is welded and fixed around the oil outlet hole 32 of the upper member 3. Then, the whole is placed in the oil pan 2. In this state, the upper member 3 is inserted into the space 10 of the crankcase lower 1. At this time, the tip 54 of the strainer 5 protruding from the oil outlet hole 32 is fitted into the opening of the oil pump suction passage formed in the crankcase lower 1.

  Then, the crankcase lower 1, the pan flange 20, and the upper flange 30 are integrally fixed with bolts (not shown). Thereby, a closed space 100 is formed between the upper member 3 and the oil pan 2. Between the crankcase lower 1 and the upper member 3, a groove portion 12 for temporarily storing the oil that has flowed down is formed as shown in FIG. 8, and an oil introduction hole 31 is opened below the groove portion 12. Therefore, the oil that has flowed down can be reliably stored in the closed space 100. Further, a connection portion to an oil pump (not shown) is fixed around the oil outlet hole 32 in a liquid-tight manner. A flange portion formed at the tip of a suction cylinder portion of an oil pump (not shown) is fixed in a liquid-tight manner.

  The operation of the valve member 4 will be described below. The float 42 floats on the oil stored in the closed space 100 and moves together with the oil level. When the oil level is less than a predetermined height, as shown in FIGS. 3 and 4, the float 42 moves downward due to its own weight, and the valve body 40 opens the oil introduction hole 31. Further, excessive swinging of the valve main body 40 is restricted by the leg portion 43 coming into contact with the inner peripheral surface of the oil pan 2.

  As the oil level rises, the float 42 moves upward, and accordingly, the valve body 40 swings in a direction to close the oil introduction hole 31. Even when the oil level is above the oil introduction hole 31, the inflow of oil into the closed space 100 is continued because the air vent hole 33 is open. When the oil level reaches a predetermined height, the float 42 closes the air vent hole 33 and the valve body 40 closes the oil introduction hole 31 as shown in FIG. As a result, the closed space 100 is sealed. Therefore, the heat radiation from the stored oil can be further suppressed, and the heat retention is further improved.

  Therefore, according to the heat insulating oil pan structure of the present embodiment, most of the oil that has flowed down flows from the oil introduction hole 31 and is stored in the closed space 100 when the engine is stopped. The upper surface of the closed space 100 is covered with a resin upper member 3 having a high heat insulating property, and the opening of the oil introduction hole 31 and the air vent hole 33 are closed by the valve member 4. Therefore, heat dissipation from the stored oil is suppressed and heat retention is excellent, so that friction loss at the next start-up can be greatly reduced.

(Example 2)
The heat insulating oil pan structure of this example is shown in FIG. In the oil pan structure, an oil pan body 8 including an upper member 6 and a lower member 7 is disposed between a crankcase lower 1 and an oil pan 2. Inside the oil pan main body 8, a valve member 4 and a strainer 5 similar to those in the first embodiment are arranged. Parts having the same shape as in the first embodiment and having the same functions will be described with the same reference numerals as in the first embodiment.

  The structure of the oil pan body 8 is shown in FIG. The upper member 6 includes an outer container 60 having an inverted container shape and an inner member 61 having an inverted container shape. The outer member 60 is formed in a shape that is accommodated in the space 10 of the crankcase lower 1. Further, a part of the outer peripheral surface of the outer member 60 has a shape corresponding to a part of the inner peripheral surface of the crankcase lower 1 and is arranged in close contact with a part of the inner peripheral surface of the crankcase lower 1. It is configured. The outer member 60 is formed with an oil introduction hole 31 similar to that of the first embodiment, an oil outlet hole 32 that opens upward, and an air vent hole 33.

  The inner member 61 is formed in a shape that is slightly smaller than the outer member 60, and an upper flange 62 is formed at the periphery of the opening. Further, a through cylinder part 63 (see FIG. 8) that opens in the lateral direction, and a through cylinder part 64 and a through cylinder part 65 that open in the upward direction are formed.

  The inner member 61 is overlapped with the outer member 60, and the ribs 66 formed on the inner peripheral surface of the outer member 60 abut against the outer peripheral surface of the inner member 61, thereby positioning the both. The open end surface of the outer member 60 is welded to the upper surface of the upper flange 62, and the outer member 60 and the inner member 61 are integrated to form the upper member 6. An air layer 200 having a thickness corresponding to the height of the rib 66 is formed between the outer member 60 and the inner member 61. Then, the tip of the through cylinder part 63 is joined to the peripheral part of the oil introduction hole 31, and the tips of the through cylinder part 64 and the through cylinder part 65 are joined to the peripheral parts of the oil outlet hole 32 and the air vent hole 33, so that the air Layer 200 is sealed.

  The lower member 7 includes a container-shaped outer member 70 and a container-shaped inner member 71. The outer peripheral surface of the outer member 70 has a shape corresponding to the inner peripheral surface of the oil pan 2 and is configured to be in close contact with the inner peripheral surface of the oil pan 2. A through hole 72 (see FIG. 9) is formed at the bottom of the outer member 70.

  The inner member 71 is formed in a shape that is slightly smaller than the outer member 70, and a lower flange 73 is formed at the periphery of the opening. A plurality of ribs 74 are formed on the outer peripheral surface. A through cylinder portion 75 (see FIG. 9) with which the boss 22 of the oil pan 2 is engaged is formed at the bottom.

  The inner member 71 is overlapped with the outer member 70, the rib 74 is in contact with the inner peripheral surface of the outer member 70, the through tube portion 75 is engaged with the through hole 72, and the boss 22 is engaged with the through tube portion 75. Thus, both are positioned. The open end surface 76 of the outer member 70 is welded to the lower surface of the lower flange 73, and the outer member 70 and the inner member 71 are integrated to form the lower member 7. As shown in FIG. 8, an air layer 300 having a thickness corresponding to the height of the rib 74 is formed between the outer member 70 and the inner member 71.

  In order to assemble the heat insulating oil pan structure of this embodiment, first, the valve member 4 is attached to the upper member 6, and the flange portion 55 of the strainer 5 is passed through the through cylinder portion 64 of the inner member 61 of the upper member 6. And fixed around the oil outlet hole 33. Then, the lower member 7 and the upper member 6 are temporarily assembled. At this time, the lower flange 73 and the upper flange 62 are overlapped. FIPG is interposed in advance between the lower flange 73 and the upper flange 62.

  Next, the whole is placed in the oil pan 2. At this time, as shown in FIG. 9, the positioning and sealing of the arrangement can be easily performed by inserting the boss 22 into the through cylinder part 75 via the O-ring 23. In this state, the upper member 6 is inserted into the space 10 of the crankcase lower 1. At this time, the tip 54 of the strainer 5 protruding from the oil outlet hole 32 is fitted into the opening of the oil pump suction passage 13 formed in the crankcase lower 1.

  Then, the crankcase lower 1, the pan flange 20, the lower flange 73, and the upper flange 62 are fixed integrally with a bolt (not shown). As a result, a tank-shaped oil pan body 8 having a closed space 100 between the lower member 7 and the upper member 6 is formed. As shown in FIG. 8, a groove 12 for temporarily storing the oil that has flowed down is formed between the crankcase lower 1 and the oil pan body 8, and an oil introduction hole 31 is opened below the groove 12. . Therefore, the oil that has flowed down can be reliably stored in the closed space 100 of the oil pan body 8. The oil outlet hole 32 is closed by the tip 64 of the strainer 6 and the oil pump suction passage 13.

  Therefore, according to the heat insulating oil pan structure of the present embodiment, most of the oil that has flowed down flows from the oil introduction hole 31 and is stored in the closed space 100 of the oil pan body 8 when the engine is stopped. The closed space 100 is entirely surrounded by highly heat-insulating resin having air layers 200 and 300, the oil introduction hole 31 is closed by the valve body 40 from the closed space 100 side, and the oil outlet hole 32 is the tip 54 of the strainer 6. And the oil pump suction passage 13, and the air vent hole 33 is closed by the float 42 from the closed space 100 side. Therefore, since the closed space 100 is in a sealed state, heat dissipation from the stored oil is suppressed and heat retention is excellent, so that the friction loss at the next start-up can be greatly reduced.

(Example 3)
As shown in FIGS. 10 and 11, the heat insulating oil pan structure of the present embodiment is the same as that of the first embodiment except that the float 42 is supported on the upper bottom of the upper member 3 by a spring-like member 45 made of a shape memory alloy. It is the same. The spring-like member 45 has one end fixed to the upper base of the upper member 3 and the other end fixed to the rod 41. The spring-like member 45 is easily plastically deformed with the movement of the float 42 below the predetermined temperature, and becomes a coil spring shape as shown in FIG. 11 above the predetermined temperature to urge the float 42 upward.

  Therefore, according to the heat insulating oil pan structure of this embodiment, even when the amount of oil in the oil pan is small, the air vent hole 33 and the oil introduction hole 31 can be closed according to the temperature of the oil, and heat radiation can be suppressed. It becomes. Further, since the air vent hole 33 and the oil introduction hole 31 can be closed immediately after the engine is stopped, the heat retaining property of the oil in the oil pan is improved.

It is a perspective view which shows the oil pan structure which concerns on one Example of this invention. 1 is an exploded perspective view of an oil pan structure according to an embodiment of the present invention. It is principal part sectional drawing of the oil pan structure which concerns on one Example of this invention. It is the perspective view which looked at the oil pan structure concerning one example of the present invention from the oil pan main part inside side. It is the perspective view which looked at the oil pan structure concerning one example of the present invention from the oil pan main part inside side. It is a disassembled perspective view of the oil pan structure concerning the 2nd example of the present invention. It is a disassembled perspective view of the oil pan main body used for the oil pan structure which concerns on the 2nd Example of this invention. It is sectional drawing of the oil pan structure which concerns on the 2nd Example of this invention. It is principal part sectional drawing of the oil pan structure which concerns on the 2nd Example of this invention. It is the perspective view which looked at the oil pan structure concerning the 3rd example of the present invention from the oil pan main part inside side. It is the perspective view which looked at the oil pan structure concerning the 3rd example of the present invention from the oil pan main part inside side.

Explanation of symbols

1: Crankcase lower 2: Oil pan 3: Upper member 4: Valve member 5: Strainer 6: Upper member 7: Lower member 8: Oil pan body
31: Oil introduction hole 33: Air vent hole
40: Valve body 42: Float

Claims (7)

A crankcase lower, an oil pan fixed to the lower portion of the crankcase lower, and a resin upper member having a reverse container shape opened to the lower portion and housed in the crankcase lower. A heat insulating oil pan structure sandwiched between the crankcase lower and the oil pan and having a closed space in which lubricating oil is stored between the upper member and the oil pan;
The upper member has an oil introduction hole for introducing lubricating oil into the closed space, an oil outlet hole for extracting lubricating oil from the closed space, and an air vent hole communicating the closed space with the outside, The oil introduction hole is formed in the side wall of the upper member, the air vent hole is formed in the upper bottom portion of the upper member,
A valve member comprising a float and a valve body is disposed on the upper member, and the valve body opens and closes the oil introduction hole according to the amount of lubricating oil stored in the closed space, and the float opens the air. A heat-insulating oil pan structure characterized by opening and closing holes.   The heat insulating oil pan structure according to claim 1, further comprising an urging member that urges the float in a direction to close the air vent hole, wherein the urging member exhibits an urging force at a predetermined temperature or higher.   The heat insulating oil pan structure according to claim 2, wherein the biasing member is a spring made of a shape memory alloy and generates a spring force at the predetermined temperature or higher.   The oil pan is composed of a resin-made lower member that opens in the upper part and has a container shape capable of storing lubricating oil, and a metal oil pan cover that covers the lower member from below, and the lower member is the upper member The heat insulation oil pan structure according to claim 1, wherein the closed space is formed between the lower member and the upper member.   The heat insulation oil pan structure according to any one of claims 1 to 4, wherein a strainer is disposed in the closed space, and the oil outlet hole is closed by the strainer.   The heat insulating oil pan structure according to claim 1, wherein at least the upper member has an air layer in a peripheral wall.   The said lower member and the said upper member have a flange part in the opening periphery, and both flange parts are clamped and fixed between the said crankcase lower and the said oil pan cover. Insulated oil pan structure as described.

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