JP2017025725A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine which can efficiently discharge heat of a refrigerant enclosed in an engine valve to a valve guide while suppressing the thermal deformation of a stem seal.SOLUTION: An internal combustion engine comprises a valve guide 20 supported on a cylinder head 14, an exhaust valve 50, and a stem seal 25 which is provided at the second end 22 of the valve guide 20. The exhaust valve 50 is provided with an internal space 54, in which metallic sodium is received, to span over a head part 511 and a stem part 53. The stem part 53 of the exhaust valve 50 is configured such that the diameter of a portion of the internal space 54 in the stem part 53, which is on the far side from the head part 511, is larger than the diameter of a portion of the internal space 54 in the stem part 53, which is on the near side to the head part 511.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an internal combustion engine including an engine valve in which a refrigerant is sealed.

  Patent Document 1 describes an example of an exhaust valve in which metallic sodium is sealed as a refrigerant. The exhaust valve is supported by a valve guide extending in the axial direction. The shaft portion of the exhaust valve described in Patent Document 1 is connected to the lower shaft portion in which one end in the axial direction is connected to the umbrella portion and the other end in the axial direction of the lower shaft portion. And an upper shaft portion connected to the blocking member. During engine operation, the lower shaft portion close to the blocking member and the upper shaft portion close to the blocking member slide along the inner peripheral surface of the valve guide. It has become.

  Further, an internal space is formed in such an exhaust valve so as to straddle the umbrella portion and the lower shaft portion. Specifically, the inner space opens at the end of the lower shaft portion far from the umbrella portion, and the blocking member closes the opening of the inner space. Metal sodium is accommodated in such an internal space, and heat received by the umbrella portion is transmitted to the metal sodium accommodated in the internal space.

  During engine operation, the exhaust valve is repeatedly moved back and forth, so that molten metallic sodium moves in the internal space of the exhaust valve. Therefore, the metallic sodium that has received heat from the umbrella and has reached a high temperature comes into contact with the inner surface of the lower shaft portion on the side close to the upper shaft portion. Then, the heat of metallic sodium is discharged to the valve guide through the lower shaft portion. Then, the heat transmitted to the valve guide is transmitted to the cylinder head supporting the valve guide, and is recovered by the cooling water flowing in the water jacket of the cylinder head.

  In addition, a stem seal is provided at the end of the valve guide farther from the umbrella portion for oil-tightness between the valve guide and the shaft portion of the exhaust valve. When the exhaust valve moves forward and backward during engine operation, the upper shaft portion of the exhaust valve slides relative to the stem seal, but the lower shaft portion does not reach the position where the stem seal is disposed.

  If the stem seal is deformed, the oil tightness between the valve guide and the shaft portion of the exhaust valve may be reduced. In this regard, in the exhaust valve described in Patent Document 1, a blocking member is interposed between the lower shaft portion and the upper shaft portion. Therefore, during engine operation, the exhaust valve repeats forward and backward movement within a range in which the state where the internal space is located near the exhaust port rather than the stem seal is maintained. As a result, the transmission of heat of metallic sodium to the stem seal via the upper shaft portion is suppressed, and thermal deformation of the stem seal is suppressed.

JP 2012-97627 A

  By the way, in the exhaust valve described above, in order to suppress thermal deformation of the stem seal, the length of the internal space in the axial direction is limited, and the exhaust heat efficiency from the metallic sodium to the valve guide is reduced. It will be.

Such a problem can occur not only in the exhaust valve but also in an intake valve in which a refrigerant such as metallic sodium is sealed.
An object of the present invention is to provide an internal combustion engine that can efficiently discharge heat of a refrigerant sealed in an engine valve to a valve guide while suppressing thermal deformation of a stem seal.

  An internal combustion engine for solving the above-mentioned problems is an engine valve having a valve guide supported by a cylinder head, a shaft portion that slides along an inner surface of the valve guide, and an umbrella portion connected to the shaft portion. When the end facing the port is the first end and the end different from the first end is the second end of the both ends of the valve guide, the second end of the valve guide A stem seal provided at the end. The engine valve is provided with an internal space in which the refrigerant is accommodated so as to straddle the umbrella portion and the shaft portion. During engine operation, the engine valve repeats forward and backward movement within a range in which the state where the internal space is located closer to the port than the second end is maintained. In the internal combustion engine based on such a configuration, the shaft portion of the engine valve has a diameter of a portion of the shaft portion on the side far from the umbrella portion of the internal space, and a portion of the shaft portion on the side close to the umbrella portion of the internal space. It has a configuration that is larger than the diameter.

  The efficiency of discharging heat from the refrigerant sealed in the engine valve to the valve guide is likely to increase as the area of the inner surface of the shaft portion that can come into contact with the refrigerant increases. Therefore, in the above configuration, in the shaft portion of the engine valve, the diameter of the portion of the internal space far from the umbrella portion is larger than the diameter of the portion near the umbrella portion. Thereby, compared with the case where the diameter of the part far from the umbrella part of the internal space is equal to the diameter of the part near the umbrella part, the area of the inner surface of the part far from the umbrella part in the shaft part is reduced. Can be wide. As a result, even if the internal space is not extended to the position where the stem seal is disposed, the heat received by the refrigerant is easily discharged to the valve guide through the shaft portion. Therefore, the heat of the refrigerant sealed in the engine valve can be efficiently discharged to the valve guide while suppressing the thermal deformation of the stem seal.

  In order to increase the area of the inner side surface of the shaft portion and increase the efficiency of exhaust heat from the refrigerant to the valve guide, it is conceivable to increase the overall diameter of the internal space. In this case, the diameter of the portion of the internal space closer to the umbrella portion is also enlarged, and the thickness of the side wall of the shaft portion near the umbrella portion is reduced. However, the part may be near the umbrella part, and is likely to be heated to a high temperature. For this reason, if the side wall of the portion is made too thin, the rigidity of the engine valve is lowered due to the temperature rise of the portion accompanying engine operation.

  On the other hand, in the above configuration, the diameter of the portion of the shaft portion closer to the umbrella portion of the inner space is smaller than the diameter of the portion of the shaft portion farther from the umbrella portion of the inner space. It is suppressed that the side wall of the near part becomes too thin. Therefore, even if the temperature of the portion near the umbrella portion in the shaft portion rises during engine operation, the rigidity of the engine valve is unlikely to decrease. That is, according to the above configuration, the exhaust heat efficiency from the refrigerant to the valve guide can be increased while ensuring the rigidity of the engine valve.

Sectional drawing which shows a part of internal combustion engine of embodiment. Sectional drawing which shows the exhaust valve of the internal combustion engine. The sectional view which decomposed the exhaust valve. Sectional drawing which shows the relationship between the exhaust valve and its peripheral member. Sectional drawing which shows a mode that the exhaust valve is moving forward and backward. Sectional drawing which shows the exhaust valve in the internal combustion engine of another embodiment. Sectional drawing which shows the exhaust valve in the internal combustion engine of other another embodiment.

Hereinafter, an embodiment embodying an internal combustion engine will be described with reference to FIGS.
As shown in FIG. 1, a cylinder 12 is formed in a cylinder block 11 of the internal combustion engine 10, and a piston 13 is slidably accommodated in the cylinder 12. A cylinder head 14 is assembled to the upper part of the cylinder block 11 in the drawing, and a combustion chamber 15 is defined by an inner peripheral surface of the cylinder 12, an upper surface of the piston 13 in the drawing, and a lower surface of the cylinder head 14 in the drawing. Yes.

  An ignition plug 16 is provided at the upper portion of the cylinder head 14 in the figure of the combustion chamber 15 so as to face the piston 13. The cylinder head 14 is formed with an intake port 17 and an exhaust port 18 that communicate with the combustion chamber 15. The cylinder head 14 is an example of an engine valve that communicates and blocks the intake port 17 and the combustion chamber 15, and an engine valve that communicates and blocks the exhaust port 18 and the combustion chamber 15. An exhaust valve 50 is provided. Each valve 40, 50 is inserted through a valve guide 20 fixed to the cylinder head 14.

  Assuming that the extending direction of the tubular valve guide 20 is the axial direction, the end facing the ports 17 and 18 among the both ends in the axial direction of the valve guide 20 is defined as the first end 21, and the first end The end portion on the opposite side of the portion 21 is referred to as a second end portion 22. At this time, the second end 22 of the valve guide 20 is provided with a stem seal 25 for oil tightness between the valve guide 20 and the valves 40 and 50.

  A retainer 26 is fixed to the upper ends of the valves 40 and 50 in the figure, and a valve spring 27 is compressed between the cylinder head 14 and the retainer 26. Thereby, each valve 40 and 50 is each urged | biased in the valve closing direction by the urging | biasing force of the valve spring 27, respectively.

  A lash adjuster 30 is provided inside the cylinder head 14 so as to correspond to the valves 40 and 50, respectively. A rocker arm 31 is installed between the lash adjuster 30 and the valves 40 and 50. One end of the rocker arm 31 is supported by the lash adjuster 30 from below in the figure, and the other end of the rocker arm 31 is in contact with the upper end of the valves 40 and 50 in the figure. During engine operation, the rocker arm 31 swings around the portion supported by the lash adjuster 30 so that the valves 40 and 50 are lifted in the valve opening direction by the rocker arm 31.

A water jacket 19 through which cooling water flows is provided around the intake port 17 and the exhaust port 18 in the cylinder head 14.
Next, the configuration of the exhaust valve 50 will be described with reference to FIGS.

  As shown in FIGS. 2 and 3, the exhaust valve 50 includes a first member 51 located on the lower side in FIG. 2 and a second member 52 extending in the vertical direction in the drawing that matches the axial direction of the valve guide 20. And. The first member 51 is provided with an umbrella portion 511 that blocks communication between the exhaust port 18 and the combustion chamber 15, and a first shaft portion 512 that extends upward from the umbrella portion 511 in the drawing. Then, one end (that is, the lower end in the drawing) of the second member 52 is joined to the tip of the first shaft portion 512 (that is, the upper end in the drawing) by welding or the like. That is, the shaft portion 53 that slides along the inner surface 20 </ b> A of the valve guide 20 in the exhaust valve 50 includes the first shaft portion 512 and the second member 52. And the outer diameter of this axial part 53 is constant.

  In addition, the first member 51 is provided with a recess 513 that opens to the front end surface (that is, the upper surface in the drawing). The bottom surface of the recess 513 is located in the umbrella portion 511. Then, by closing the opening of the concave portion 513 with the second member 52, an internal space 54 that extends over the umbrella portion 511 and the shaft portion 53 is formed. In the internal space 54, metallic sodium is accommodated. This metallic sodium is an example of a refrigerant, and the amount of metallic sodium accommodated in the internal space 54 is about half of the volume of the internal space 54.

  Since the melting point of metallic sodium is higher than normal temperature, metallic sodium may not melt in the internal space 54 when the engine is stopped. In this case, when the engine operation is started and the heat generated in the internal combustion engine 10 is transferred to the metallic sodium through the exhaust valve 50, the metallic sodium is melted. Then, the molten metal sodium moves in the internal space 54 upward and downward in FIG.

  As shown in FIG. 2, the diameter of the inner space 54 of the distal end side portion 512 </ b> B, which is the portion far from the umbrella portion 511 in the first shaft portion 512, is closer to the umbrella portion 511 in the first shaft portion 512. It is larger than the diameter of the internal space 54 of the proximal end side portion 512 </ b> A that is a portion. Specifically, the diameter of the internal space 54 is constant in the proximal end portion 512A, whereas the diameter of the internal space 54 is farther from the umbrella portion 511 in the distal end portion 512B. It is getting bigger gradually. Therefore, the shaft portion 53 of the exhaust valve 50 has a diameter of a portion of the inner space 54 farther from the umbrella portion 511 in the shaft portion 53 than a portion of the inner space 54 in the shaft portion 53 closer to the umbrella portion 511. The configuration is larger than the diameter.

  And, since the inner space 54 is configured in this manner in the first shaft portion 512, the thickness of the side wall of the proximal end side portion 512A is constant, while the thickness of the side wall of the distal end side portion 512B is The distance from 511 gradually decreases.

  FIG. 4 illustrates a state in which such an exhaust valve 50 is provided in the cylinder head 14. As shown in FIG. 4, when the communication between the exhaust port 18 and the combustion chamber 15 is blocked by the umbrella portion 511 of the exhaust valve 50, the proximal end portion 512 </ b> A of the first shaft portion 512 is While projecting into the exhaust port 18 from the first end portion 21, most of the distal end side portion 512 </ b> B of the first shaft portion 512 is located inside the valve guide 20.

  Further, the exhaust valve 50 moves back and forth in the vertical direction in the figure during engine operation. Then, as shown in FIG. 5, in the internal space 54, the molten metal sodium moves upward or downward in the figure. That is, during engine operation, the sodium metal touches the inner surface of the tip side portion 512B of the first shaft portion 512 as well. In this way, when the sodium metal touches the inner surface of the tip side portion 512B, heat exchange is performed between the metal sodium and the valve guide 20 via the side wall of the tip side portion 512B. During such engine operation, the exhaust valve 50 does not move upward in the figure than the state shown in FIGS. That is, when the exhaust valve 50 is moved forward and backward, the second member 52 of the exhaust valve 50 slides with respect to the stem seal 25 and more than the second end 22 to which the stem seal 25 is attached. The state where the internal space 54 is located near the exhaust port 18 is maintained.

Next, the operation of the internal combustion engine 10 of the present embodiment will be described with reference to FIG.
During engine operation, hot exhaust gas is discharged from the combustion chamber 15 into the exhaust port 18. That is, the proximal end portion 512A of the umbrella portion 511 and the first shaft portion 512 in the exhaust valve 50 is exposed to high-temperature exhaust gas. Therefore, as shown by an arrow in FIG. 5, the umbrella portion 511 and the base end side portion 512 </ b> A receive heat from the exhaust gas, and the heat is transmitted to the metallic sodium in the internal space 54.

  During such engine operation, the exhaust valve 50 repeats forward and backward movement, so that molten metallic sodium moves in the internal space 54. That is, the metallic sodium that has received heat from the umbrella portion 511 or the like and has reached a high temperature moves upward in the internal space 54 and touches the inner side surface of the tip side portion 512B of the first shaft portion 512.

  Here, since the water jacket 19 is provided near the valve guide 20 in the cylinder head 14, the valve guide 20 is cooled by the cooling water flowing in the water jacket 19. Therefore, the distal end portion 512 </ b> B of the first shaft portion 512 that slides with respect to the valve guide 20 in the exhaust valve 50 can be cooled through the valve guide 20 by the cooling water flowing in the water jacket 19. Therefore, the temperature of the side wall of the tip side portion 512B tends to be lower than the temperature of metallic sodium that receives heat from the umbrella portion 511 or the like.

  Therefore, when the high-temperature metallic sodium touches the inner surface of the tip-side portion 512B of the first shaft portion 512, the heat of the metal sodium is changed to the side wall of the first shaft portion 512 as shown by the arrow in FIG. In particular, it is discharged to the valve guide 20 through the side wall of the tip side portion 512B. Thereby, since the temperature of metallic sodium falls, the heat reception from the umbrella part 511 etc. by metallic sodium is accelerated | stimulated.

  Incidentally, the amount of heat “Q” transferred from the metallic sodium to the valve guide 20 through the first shaft portion 512 can be expressed by the following relational expression (formula 1). The greater the amount of heat “Q”, the higher the efficiency of exhaust heat from the metallic sodium to the valve guide 20. In the relational expression (formula 1), “q” is the amount of heat (ie, heat flow rate) that crosses the unit area in unit time, and “A” is the area through which heat passes (ie, heat passage area).

In view of the above relational expression (formula 1), by increasing the heat passage area “A” and the heat flow rate “q”, the amount of heat “Q” increases, and the exhaust heat efficiency from the metallic sodium to the valve guide 20 increases. can do.

  The heat passage area “A” is the area of the peripheral surface surrounding the internal space 54 in which metallic sodium is accommodated, that is, the inner side of the tip portion 512B that can be accommodated in the valve guide 20 even on the inner surface of the shaft portion 53. It can be regarded as the side area. As described above, the proximal end portion 512A of the shaft portion 53 is not accommodated in the valve guide 20 during engine operation. Therefore, the area of the inner side surface of the tip side portion 512B can be regarded as the heat passage area “A”. In the present embodiment, the diameter of the internal space 54 in the distal end side portion 512B of the first shaft portion 512 is larger than the diameter of the internal space 54 in the proximal end side portion 512A. As a result, the area of the inner surface of the shaft portion 53 is larger than when the diameter of the internal space 54 in the distal end side portion 512B is equal to the diameter of the internal space 54 in the proximal end side portion 512A. That is, the exhaust valve 50 has a configuration in which the heat passage area “A” is larger than the case where the diameter of the internal space 54 in the distal end side portion 512B is equal to the diameter of the internal space 54 in the proximal end portion 512A. Can do.

  Moreover, said heat flow rate "q" can be represented by the following relational expression (Formula 2). In the relational expression (Formula 2), “Ta” is the temperature of metallic sodium, and “Tb” is the temperature of the valve guide 20. “H1” is a heat transfer coefficient between the metal sodium and the exhaust valve 50, and “h2” is a heat transfer coefficient between the exhaust valve 50 and the valve guide 20. “B” is the thickness of the side wall of the shaft portion 53 of the exhaust valve 50, and “λ” is the thermal conductivity of the valve material that is a material constituting the exhaust valve 50.

“H1”, “h2”, and “λ” in the relational expression (Expression 2) are parameters determined by the material constituting each component. On the other hand, “b” is a parameter corresponding to the thickness of the side wall of the shaft portion 53 of the exhaust valve 50. In the exhaust valve 50, the diameter of the internal space 54 in the distal end side portion 512B of the first shaft portion 512 is larger than the diameter of the internal space 54 in the proximal end side portion 512A. Therefore, compared with the case where the diameter of the internal space 54 in the front end side part 512B is equal to the diameter of the internal space 54 in the base end side part 512A, the thickness of the side wall of the front end side part 512B is thinner. That is, in the present exhaust valve 50, the heat flow rate “q” can be reduced by reducing “b” compared to the case where the diameter of the internal space 54 in the distal end side portion 512B is equal to the diameter of the internal space 54 in the proximal end portion 512A. It is getting bigger.

  As described above, in the present exhaust valve 50, the sodium metal in the internal space 54 has received more than the case where the diameter of the internal space 54 in the distal end portion 512B is equal to the diameter of the internal space 54 in the proximal end portion 512A. Heat is efficiently discharged to the valve guide 20. As a result, the heat of the exhaust received by the umbrella portion 511 and the proximal end portion 512A of the exhaust valve 50 is efficiently released to the cooling water flowing in the water jacket 19 of the cylinder head 14.

As mentioned above, according to the said structure and effect | action, the effect shown below can be acquired.
(1) In the exhaust valve 50, the diameter of the internal space 54 in the distal end side portion 512B is larger than the diameter of the internal space 54 in the proximal end side portion 512A. Thereby, compared with the case where the diameter of the internal space 54 in the distal end side portion 512B is equal to the diameter of the internal space 54 in the proximal end side portion 512A, the area of the inner side surface of the distal end side portion 512B can be increased. it can. As a result, even if the internal space 54 is not extended to the position where the stem seal 25 is disposed, the heat received by the metallic sodium is easily discharged to the valve guide 20 through the shaft portion 53. Therefore, the heat of the metallic sodium sealed in the exhaust valve 50 can be efficiently discharged to the valve guide 20 while suppressing thermal deformation of the stem seal 25 for the exhaust valve.

  (2) In order to increase the area of the inner surface of the shaft portion 53 and increase the efficiency of exhaust heat from the sodium metal to the valve guide 20, not only the diameter of the internal space 54 in the distal end portion 512B but also the proximal end portion 512A It is also conceivable to increase the diameter of the internal space 54. In this case, the thickness of the side wall of the base end portion 512A is reduced by increasing the diameter of the internal space 54 in the base end portion 512A. However, the proximal end portion 512A may be near the umbrella portion 511 and is likely to be heated to a high temperature. For this reason, if the side wall of the base end side portion 512A is made too thin, the rigidity of the exhaust valve 50 is lowered due to the temperature rise of the base end side portion 512A accompanying the engine operation.

  On the other hand, in the exhaust valve 50, since the diameter of the internal space 54 in the proximal end portion 512A is smaller than the diameter of the internal space 54 in the distal end portion 512B, the side wall of the proximal end portion 512A becomes too thin. Is suppressed. Therefore, even if the temperature of the base end side portion 512A rises during engine operation, the rigidity of the exhaust valve 50 is unlikely to decrease. That is, the exhaust heat efficiency from the metallic sodium to the valve guide 20 can be increased while suppressing the decrease in rigidity of the exhaust valve 50.

In addition, the said embodiment may be changed as follows and you may make it implement in another embodiment.
If the diameter of the portion of the internal space 54 far from the umbrella portion 511 is larger than the diameter of the portion near the umbrella portion 511, the first shaft portion 512 of the exhaust valve 50 is used in the above embodiment. It is good also as another structure different from. For example, as shown in FIG. 6, when the diameter of the internal space 54 of the portion close to the umbrella portion 511 in the first shaft portion 512 is the first diameter D1 and the portion is the small diameter portion 60A, A large-diameter portion 60B having a second diameter D2 larger than the first diameter D1 may be provided in a portion facing the second member 52 in one shaft portion 512. Even if it is such a structure, the effect equivalent to said (1) and (2) can be acquired.

  Further, as shown in FIG. 7, the internal space 54 may be configured to straddle the second member 52. In this case, the diameter of the internal space 54 in the second member 52 is increased, and the diameter of the internal space 54 in the upper portion of the first member 51 in the drawing is gradually increased as the second member 52 is approached. It may be. Even in such a configuration, the shaft portion 53 of the exhaust valve 50 is configured such that the diameter of the portion of the shaft portion 53 far from the umbrella portion 511 of the inner space 54 is closer to the umbrella portion 511 of the inner space 54 of the shaft portion 53. It can be set as the structure larger than the diameter of the part. If the state in which the internal space 54 is located closer to the exhaust port 18 than the second end 22 of the valve guide 20 during the forward and backward movement of the exhaust valve 50 is maintained, the internal space 54 is set to the stem seal 25. Even if it does not extend to the arrangement position, the heat received by the metallic sodium is easily discharged to the valve guide 20 through the shaft portion 53. Therefore, the same effect as the above (1) and (2) can be obtained.

The exhaust valve 50 may have a configuration in which a shielding member is interposed between the first member 51 and the second member 52 as long as the internal space 54 does not straddle the second member 52. .
The exhaust valve 50 may be configured such that the diameter of the internal space 54 in the umbrella portion 511 is larger than the diameter of the internal space 54 in the shaft portion 53. Thereby, the heat receiving efficiency by metallic sodium can be improved.

  The intake valve 40 may be an engine valve in which a refrigerant such as metallic sodium is enclosed. Even in such an intake valve 40, the diameter of the portion of the internal space far from the umbrella portion is made larger than the diameter of the portion near the umbrella portion, thereby suppressing thermal deformation of the stem seal 25 for the intake valve. However, the heat of the refrigerant sealed in the intake valve 40 can be efficiently discharged to the valve guide 20.

  -The refrigerant | coolant enclosed with an engine valve may be other refrigerant | coolants other than metallic sodium, as long as it moves in internal space by the advancing / retreating movement of an engine valve.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 14 ... Cylinder head, 17 ... Intake port, 18 ... Exhaust port, 20 ... Valve guide, 20A ... Inner side surface, 21 ... First end, 22 ... Second end, 25 ... Stem seal , 40 ... intake valve, 50 ... exhaust valve, 511 ... umbrella, 53 ... shaft, 54 ... internal space.

Claims (1)

A valve guide supported by the cylinder head;
An engine valve having a shaft portion that slides along the inner surface of the valve guide and an umbrella portion connected to the shaft portion;
Of the both ends of the valve guide, when the end facing the port is the first end and the end different from the first end is the second end, the second end of the valve guide A stem seal provided at the end of the
The engine valve is provided with an internal space in which refrigerant is accommodated so as to straddle the umbrella portion and the shaft portion,
In engine operation, in the internal combustion engine in which the engine valve repeats forward and backward movement within a range in which the state where the internal space is located near the port than the second end is maintained,
The shaft portion of the engine valve has a diameter of a portion of the shaft portion on the side farther from the umbrella portion than the diameter of a portion of the shaft portion on the side close to the umbrella portion. An internal combustion engine characterized by being configured.