JP2021050636A - Valve structure and internal combustion engine - Google Patents

Abstract

To provide a valve structure capable of inhibiting a sliding surface from being fastened by rust etc., and to provide an internal combustion engine.SOLUTION: A valve structure includes: a poppet valve which opens or closes at least one of an exhaust port and an intake port and has a shaft-like stem; and a valve guide having a guide hole into which the stem is inserted in a manner that the stem can be moved in an axial direction. An outer peripheral wall of the stem has a proximity part located in the proximity of an inner peripheral wall of the guide hole when the poppet valve closes the port. For example, the proximity part has an annular protruding part which extends in an annular shape along an outer peripheral direction of the stem and protrudes to the shaft radial outer side.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to valve structures and internal combustion engines.

Conventionally, a poppet valve having a shaft-shaped stem that opens and closes the exhaust port or the intake port of the cylinder head and a valve guide that is arranged in the cylinder head and has a guide hole that guides the stem so as to be slidable in the axial direction are provided. Internal combustion engines are known (for example, Patent Document 1).

The heat generated in the combustion chamber of the internal combustion engine is transferred to the cylinder head via the stem and valve guide.

Japanese Unexamined Patent Publication No. 63-167070

By the way, water contained in the gas guided to the combustion chamber may condense and adhere to the gap between the outer peripheral wall of the stem and the inner peripheral wall of the guide hole to cause rust. Then, there is a problem that the sliding surface (the outer peripheral wall of the stem and the inner peripheral wall of the guide hole) may be fixed due to rust.

An object of the present disclosure is to provide a valve structure and an internal combustion engine capable of preventing the sliding surface from sticking due to rust or the like.

In order to achieve the above object, the valve structure in the present disclosure is:
A poppet valve with a shaft-shaped stem that opens and closes at least one of the exhaust or intake ports.
A valve guide having a guide hole through which the stem is movably inserted in the axial direction,
With
The outer peripheral wall of the stem has a proximity portion close to the inner peripheral wall of the guide hole when the poppet valve closes the port.

The internal combustion engine in the present disclosure is
It has the above valve structure.

According to the valve structure of the present disclosure, it is possible to prevent the sliding surface from sticking due to rust or the like.

FIG. 1 is a diagram schematically showing a valve structure according to an embodiment of the present disclosure. FIG. 2 is a partially enlarged view of the valve structure. FIG. 3 is a vertical cross-sectional view showing a cross section of a part of the valve structure along the X axis. FIG. 4 is a partial vertical sectional view of the valve structure in the closed state. FIG. 5 is a vertical cross-sectional view showing a cross section of a part of the valve structure according to the first modification along the X axis. FIG. 6 is a partial vertical cross-sectional view of the valve structure in the valve closed state according to the first modification. FIG. 7 is a vertical cross-sectional view showing a cross section of a part of the valve structure according to the modified example 2 along the X axis. FIG. 8 is a partial vertical cross-sectional view of the valve structure in the valve closed state according to the modified example 2. FIG. 9 is a partial vertical cross-sectional view of the valve structure in the valve closed state according to the modified example 3. FIG. 10 is a partial vertical cross-sectional view of the valve structure in the valve closed state according to the modified example 3. FIG. 11 is a partial vertical sectional view of the valve structure in the valve closed state according to the modified example 4. FIG. 12 is a partial vertical cross-sectional view of the valve structure in the valve closed state according to the modified example 4. FIG. 13 is a diagram schematically showing the inner peripheral wall of the guide hole according to the modified example 5. FIG. 14A is a cross-sectional view showing one end side of the groove in the axial direction. FIG. 14B is a cross-sectional view showing the other end side of the groove in the axial direction. FIG. 15A is a cross-sectional view showing another example of the groove. FIG. 15B is a cross-sectional view showing another example of the groove. FIG. 16 is a diagram schematically showing the inner peripheral wall of the guide hole according to the modified example 6. FIG. 17 is a diagram schematically showing the inner peripheral wall of the guide hole according to the modified example 7. FIG. 18 is a diagram schematically showing the inner peripheral wall of the guide hole according to the modified example 7. FIG. 19 is a partially enlarged view of the inner peripheral wall of the guide hole according to the modified example 7. FIG. 20 is a partial cross-sectional view of the inner peripheral wall of the guide hole according to the modified example 8. FIG. 21 is a partial cross-sectional view of the inner peripheral wall of the guide hole according to the modified example 8.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
FIG. 1 is a diagram schematically showing a valve structure 100 according to an embodiment of the present disclosure. FIG. 2 is an enlarged view showing a part of the valve structure 100 shown in FIG. 1 in an enlarged manner. The X-axis and the Y-axis are drawn in FIG. In FIG. 2, the vertical direction is referred to as an axial direction or "X direction", the upward direction is referred to as "+ X direction", and the downward direction is referred to as "-X direction". In FIG. 2, the left-right direction is referred to as the axial radial direction or the "Y direction", and the direction away from the central axis from the direction orthogonal to the central axis of the stem 4 is the outer axial direction or the "+ Y direction", the central axis. The direction close to is referred to as the inside in the axial radial direction or the "-Y direction".

The configuration of the valve structure 100 will be briefly described with reference to FIGS. 1 and 2. As shown in FIGS. 1 and 2, the valve structure 100 includes exhaust and intake ports 2 provided in a cylinder head 1 of an engine (internal combustion engine), a poppet valve 3, a valve guide 6, a coil spring 7, and the like. It is equipped with a cam 8.

A valve seat 21 is fitted and fixed to the opening edge of the port 2.

The poppet valve 3 has a stem 4 and a valve face 5. The stem 4 extends in the axial direction (X direction) from the port 2 side. For example, stainless steel is used as the material of the poppet valve 3. In the following description, in the stem 4, the end closer to the port 2 is referred to as an axial end 41, and the end farther from the port 2 is referred to as an axial other end 42.

The valve face 5 is provided on the axial end 41 side of the stem 4. The valve is closed when the valve face 5 comes into contact with the valve seat 21. Further, the valve face 5 is opened by being separated from the valve seat 21.

The valve guide 6 is press-fitted into the cylinder head 1. The valve guide 6 has a guide hole 61 through which the stem 4 is movably inserted in the axial direction (X direction). As the material of the valve guide 6, for example, a cast iron material is used.

The coil spring 7 is arranged so as to be fitted on the other end 42 side in the axial direction of the stem 4. A sandwiching member 71 is locked to the other end 42 side of the stem 4 in the axial direction. The coil spring 7 is sandwiched between the cylinder head 1 and the sandwiching member 71 in a compressed state. The coil spring 7 urges the poppet valve 3 in the valve closing direction.

The cam 8 is provided on a camshaft (not shown) that rotates in synchronization with the crankshaft (not shown) of the engine so as to synchronize with the engine rotation. The cam 8 is connected to the stem 4 via a rocker arm 81 and a bridge 82 so as to press the poppet valve 3 in the valve opening direction against the urging force of the coil spring 7.

Next, the configuration of the valve structure 100 will be described in detail with reference to FIGS. 3 and 4. FIG. 3 is a vertical cross-sectional view showing a cross section of a part of the valve structure 100 along the X axis. FIG. 4 is a partial vertical sectional view of the valve structure 100 in the closed state. In the stem 4, the end on the port 2 side is referred to as an axial end 41 (see FIG. 2), and the end opposite to the port 2 is referred to as an axial other end 42 (see FIG. 2). Further, in the valve guide 6, the end on the port 2 side is referred to as an axial end 65 (see FIG. 2), and the end opposite to the port 2 is referred to as an axial other end 66 (see FIG. 2). Further, the outer peripheral wall 43 of the stem 4 and the inner peripheral wall 62 of the guide hole 61 are referred to as “sliding surfaces”.

As shown in FIG. 4, the outer peripheral wall 43 of the stem 4 has a proximity portion close to the inner peripheral wall 62 of the guide hole 61 in the valve closed state.

More specifically, the proximity portion has an annular convex portion 47. The annular convex portion 47 extends in an annular shape along the outer peripheral direction of the outer peripheral wall 43. The annular convex portion 47 projects outward in the axial radial direction (+ Y direction). Since the annular convex portion 47 is close to the inner peripheral wall 62 of the guide hole 61 in the valve closed state, the gap between the annular convex portion 47 and the inner peripheral wall 62 of the guide hole 61 becomes smaller (in the valve closed state in FIG. 4). The gap S1 is shown). This makes it difficult for condensed water to enter the gap between the outer peripheral wall 43 of the stem 4 and the inner peripheral wall 62 of the guide hole.

When the annular convex portion 47 comes into contact with the inner peripheral wall 62 of the guide hole 61, sliding resistance is generated. In the present embodiment, the end surface 471 of the annular convex portion 47 on the outer side in the axial direction (+ Y direction) is rounded. As a result, the end face 471 is in line contact with the inner peripheral wall 62 of the guide hole 61. The line contact can suppress the sliding resistance to be smaller than the surface contact when the end face 471 is not rounded.

According to the valve structure 100 according to the embodiment, a poppet valve 3 having an axial stem 4 and a guide through which the stem 4 is movably inserted by opening and closing at least one port 2 of exhaust or intake. A valve guide 6 having a hole 61 is provided, and the outer peripheral wall 43 of the stem 4 has a proximity portion close to the inner peripheral wall 62 of the guide hole 61 in the valve closed state. The proximity portion has an annular convex portion 47 that extends in an annular shape along the outer peripheral direction of the stem 4 and projects outward in the axial direction (+ Y direction).

With the above configuration, in the valve closed state, the condensed water is less likely to enter the gap between the outer peripheral wall 43 of the stem 4 and the inner peripheral wall 62 of the guide hole 61. Further, since the end surface 471 of the annular convex portion 47 is rounded, the contact with the outer peripheral wall 43 of the stem 4 becomes a line contact, and the sliding between the outer peripheral wall 43 of the stem 4 and the inner peripheral wall 62 of the guide hole 61 The dynamic resistance can be suppressed to a small value.

In the above embodiment, one annular convex portion 47 is provided on the outer peripheral wall 43 of the stem 4, but a plurality of annular convex portions 47 may be provided in the axial direction (X direction). In this case, the outer diameter of the annular convex portion 47 on the one end 41 side (−X side) in the axial direction may be larger than the outer diameter of the annular convex portion 47 on the other end 42 side (+ X side) in the axial direction. This makes it difficult for condensed water to enter the gap between the outer peripheral wall 43 of the stem 4 and the inner peripheral wall 62 of the guide hole 61, and makes it easier for the condensed water to be discharged from the gap to the outside of the guide hole 61 (port 2 side). It becomes possible.

(Modification example 1)
Next, a modification 1 of the present embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 is a vertical cross-sectional view showing a cross section of a part of the valve structure according to the first modification along the X axis. FIG. 6 is a partial vertical cross-sectional view of the valve structure in the valve closed state according to the first modification.

In the above embodiment, the size of the inner peripheral wall 62 of the guide hole 61 in the axial radial direction (Y direction) is constant. On the other hand, in the modified example 1, the inner peripheral wall 62 of the guide hole 61 has an inner diameter of one end 65 side in the axial direction (-X side, see FIG. 2) on the other end 66 side in the axial direction (+ X side, FIG. 2). It has a stepped portion 64 larger than the inner diameter of (see). The wall surface 472 on the other end 42 side (+ X side) in the axial direction of the annular convex portion 47 has an inclined surface 48 inclined to one end side (−X side) in the axial direction with respect to the outer side in the axial direction (+ Y direction). In other words, the region including the annular convex portion 47 in the axial direction is a cone having the other end 42 side in the axial direction as the head and the one end side in the axial direction as the bottom surface, and the head surface is a plane parallel to the bottom surface. Here, it is a truncated cone that is the remaining part cut out in a plane orthogonal to the axial direction. The inclined surface 48 is a side surface of the truncated cone. The annular convex portion 47 is arranged at a position corresponding to the step portion 64 in the valve closed state.

With the above configuration, since the inclined surface 48 of the annular convex portion 47 is close to the step portion 64 in the valve closed state, the gap between the inclined surface 48 of the annular convex portion 47 and the step portion 64 becomes small (FIG. 6). Indicates the gap S1 in the valve closed state). This makes it difficult for condensed water to enter the gap. Further, the wall surface 472 on the other end 42 side in the axial direction of the annular convex portion 47 has an inclined surface 48. This makes it easier to discharge the condensed water.

(Modification 2)
Next, a modification 2 of the present embodiment will be described with reference to FIGS. 7 and 8. FIG. 7 is a vertical cross-sectional view showing a cross section of a part of the valve structure according to the modified example 2 along the X axis. FIG. 8 is a partial vertical cross-sectional view of the valve structure in the valve closed state according to the modified example 2.

In the first modification, the annular convex portion 47 has an inclined surface 48. On the other hand, in the modified example 2, the end face on the outer side in the axial direction of the annular convex portion 47 has a rounded semicircular cross-sectional shape as in the above embodiment.

According to the above configuration, since the annular convex portion 47 is close to the step portion 64 in the valve closed state, the gap between the annular convex portion 47 and the step portion 64 becomes small (the gap S1 in the valve closed state is shown in FIG. 8). Shows). This makes it difficult for condensed water to enter the gap.

(Modification example 3)
Next, a modification 3 of the present embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 is a vertical cross-sectional view showing a cross section of a part of the valve structure 100 according to the modified example 3 along the X axis. FIG. 10 is a partial vertical cross-sectional view of the valve structure in the valve closed state according to the modified example 3.

In the second modification of the above embodiment, the annular convex portion 47 has a rounded semicircular cross-sectional shape at the end face on the outer side in the axial direction.

On the other hand, in the modified example 3, the wall surface 472 on the other end 42 side (+ X side) in the axial direction of the annular convex portion 47 is one end side (−X side) in the axial direction with respect to the outer side (+ Y direction) in the axial direction. It has an inclined surface 48A that inclines toward. As shown in FIG. 9, in the valve open state, the end of the inclined surface 48A on the other end 42 side (+ X side) in the axial direction corresponds to the position of the step portion 64. Therefore, the inclined surface 48A approaches the step portion 64 as the valve shifts from the valve open state to the valve closed state.

According to the above configuration, since the inclined surface 48A is close to the step portion 64 in the valve closed state, the gap between the inclined surface 48A and the step portion 64 becomes small (FIG. 10 shows the gap S1 in the valve closed state). ). This makes it difficult for condensed water to enter the gap. Further, the wall surface 472 on the other end 42 side in the axial direction of the annular convex portion 47 has an inclined surface 48A. This makes it possible to easily discharge the condensed water adhering to the gap between the outer peripheral wall 43 of the stem 4 and the inner peripheral wall 62 of the guide hole 61.

(Modification example 4)
Next, the modification 4 will be described with reference to FIGS. 11 and 12. FIG. 11 is a vertical cross-sectional view showing a cross section of a part of the valve structure 100 according to the modified example 4 along the X axis. FIG. 12 is a partial vertical cross-sectional view of the valve structure in the valve closed state according to the modified example 4. In the third modification, the step portion 64 is provided on the inner peripheral wall 62 of the guide hole 61, but in the fourth modification, as shown in FIG. 11, a tapered portion 67 is provided instead of the step portion 64. The tapered portion 67 is inclined outward in the axial direction (+ Y direction) with respect to one end 65 side in the axial direction (−X side, see FIG. 2). The inclination angle of the tapered portion with respect to the axial direction (X direction) is different from the inclination angle of the inclined surface 48A with respect to the axial direction. The tilt angles of the two may be the same.

For example, when the inclination angle of the tapered portion 67 with respect to the axial direction is smaller than the inclination angle of the inclined surface 48A with respect to the axial direction, the inclined surface 48A is closed from the valve open state as compared with the case where both inclination angles are the same. As the valve state shifts, the tapered portion 67 approaches the tapered portion 67, so that the gap between the inclined surface 48A and the tapered portion 67 becomes smaller (FIG. 12 shows the gap S1 in the valve closed state). This makes it more difficult for condensed water to enter the gap. Further, the wall surface 472 on the other end 42 side in the axial direction of the annular convex portion 47 has an inclined surface 48A. This makes it possible to easily discharge the condensed water adhering to the gap between the outer peripheral wall 43 of the stem 4 and the inner peripheral wall 62 of the guide hole 61.

(Modification 5)
Next, the modification 5 will be described with reference to FIGS. 13 to 15B. In the fifth modification, a configuration in which the above-mentioned annular convex portion 47 and the groove 63 are combined will be described. In FIG. 13, the groove 63 provided on the semicircular wall of the inner peripheral wall 62 is shown by a solid line, and the groove 63 provided on the remaining semicircular wall is shown by a dotted line. The groove 63 is briefly shown in FIG.

The inner peripheral wall 62 has a groove 63 extending from one end 65 side in the axial direction to the other end 66 side in the axial direction. The groove 63 is an inclined groove extending in a direction in which it is inclined with respect to the axial direction (X direction).

As shown in FIG. 13, the groove 63 is a spiral groove having a plurality of grooves (here, three grooves). The inclination angle of the groove 63 with respect to the X direction is constant. In FIG. 13, the groove 63 provided on the semicircular wall of the inner peripheral wall 62 is shown by a solid line, and the groove 63 provided on the remaining semicircular wall is shown by a dotted line.

FIG. 14A is a cross-sectional view showing one end 65 side in the axial direction of the groove 63. FIG. 14B is a cross-sectional view showing the other end 66 side in the axial direction of the groove 63. As shown in FIGS. 14A and 14B, the groove 63 (spiral groove) has a triangular cross section. The cross-sectional area S of the groove 63 is increased by increasing the depth d of the groove 63 and increasing the width w of the groove 63. The cross-sectional area S of the groove 63 becomes smaller as the depth d of the groove 63 becomes shallower and the width w of the groove 63 becomes narrower.

The cross-sectional area S1 of the groove 63 on the one end 65 side in the axial direction can be represented by the width w1 and the depth d1. The cross-sectional area S2 of the groove 63 on the other end 66 side in the axial direction can be represented by a width w2 and a depth d2. The cross-sectional area S1 is larger than the cross-sectional area S2 (S1> S2). Specifically, the depth d1 is deeper than the depth d2 (d1> d2). The width w1 is wider than the width w2 (w1> w2). The cross-sectional area S may gradually increase toward one end side in the axial direction (−X direction), or may increase continuously.

In the above modified example 5, the groove 63 has a triangular cross section, but the cross-sectional shape of the groove 63 is not limited to this. For example, the groove 63 may have a rectangular cross section (see FIG. 15A). Further, the groove 63 may have a semicircular cross section (see FIG. 15B). Also in these cross-sectional shapes, the groove 63 can increase the cross-sectional area S by increasing the depth d and increasing the width w.

According to the valve structure 100 according to the modification 5, the poppet valve 3 having the axial stem 4 and the guide hole 61 into which the stem 4 is movably inserted in the axial direction (X direction) by opening and closing the port 2. The inner peripheral wall 62 of the guide hole 61 has a groove 63 extending from the axial one end 65 side, which is the end of the inner peripheral wall 62 on the port 2 side, to the axial other end 66 side. However, the cross-sectional area of the groove 63 on the one end 65 side in the axial direction is larger than the cross-sectional area on the other end 66 side in the axial direction.

With the above configuration, the following effects are obtained.
Condensed water adhering to the gap between the outer peripheral wall 43 of the stem 4 and the inner peripheral wall 62 of the guide hole 61 can be moved to the groove 63. Further, the condensed water that has moved to the groove 63 can be discharged to the outside of the guide hole 61. Further, the contact area between the stem 4 and the valve guide 6 can be reduced, and for example, the sliding resistance can be reduced. Further, since the cross-sectional area of the groove 63 on the one end 65 side in the axial direction is larger than the cross-sectional area of the groove 63 on the other end 66 side in the axial direction, it becomes difficult for condensed water to enter from the one end 65 side in the axial direction to the other end 66 side in the axial direction. Moreover, the condensed water can be easily discharged from the other end 66 side in the axial direction to the one end 65 side in the axial direction. Further, since a plurality of grooves 63 are provided as spiral grooves, the effect of discharging condensed water can be improved. Further, since the structure is such that the annular convex portion 47 and the groove 63 are combined, it is more difficult for the condensed water to enter the gap between the outer peripheral wall 43 of the stem 4 and the inner peripheral wall 62 of the guide hole 61, and the condensed water is further prevented from entering. Can be easily discharged from the gap to the outside of the guide hole.

(Modification 6)
Next, the modification 6 will be described with reference to FIG. FIG. 16 is a diagram schematically showing an inner peripheral wall 62 of the guide hole 61 according to the modified example 6. In FIG. 16, the groove 63 provided on the semicircular wall of the inner peripheral wall 62 is shown by a solid line, and the groove 63 provided on the remaining semicircular wall is shown by a dotted line.

When the groove 63 as a spiral groove is clogged with, for example, carbides, it becomes difficult for the condensed water to be discharged along the groove 63, so that the condensed water may stay and rust may occur.

Therefore, in the modified example 6, as shown in FIG. 16, a plurality of grooves 63 (spiral grooves) are provided on the inner peripheral wall 62 of the guide hole 61 so as to intersect each other. In other words, the inner peripheral wall 62 is provided so that the right-handed three spiral grooves and the left-handed three spiral grooves intersect each other in the + X direction.

When the groove 63 is clogged with carbides or the like due to the intersection of the spiral grooves and the condensed water does not flow, the flow direction of the condensed water is on the upstream side (the other end 66 side in the axial direction) with the groove 63 clogged with the carbides or the like. Since it switches to the other intersecting grooves 63, the condensed water can be reliably discharged. This makes it possible to suppress the occurrence of rust.

(Modification 7)
Next, the modification 7 will be described with reference to FIGS. 17 to 19. In the modified example 7, a configuration in which the annular convex portion 47, the groove 63, and the concave portion 68 are combined will be described. 17 and 18 are views schematically showing the inner peripheral wall 62 of the guide hole 61 according to the modified example 7. FIG. 19 is a partially enlarged view of the inner peripheral wall 62. In FIGS. 17 and 18, the grooves 63 and the recesses 68 provided in the semicircular wall of the inner peripheral wall 62 are shown by solid lines, and the grooves 63 provided in the remaining semicircular wall are shown by dotted lines, and the rest. The recess 68 provided in the semicircular wall of the above is omitted.

FIG. 17 shows an inner peripheral wall 62 provided with a plurality of recesses 68 and a plurality of grooves 63. For example, when a large amount of condensed water is generated, the condensed water may not be sufficiently discharged even by the groove 63 in the above-described modified example. Therefore, in the modified example 7, as shown in FIG. 17, the inner peripheral wall 62 (sliding surface) of the guide hole 61 has a plurality of recesses 68 in the axial radial direction (Y direction). All or part of the plurality of recesses 68 may not be connected to the groove 63 (spiral groove), but are preferably connected to the groove 63. Here, the plurality of recesses 68 are connected to the groove 63.

The recess 68 is, for example, a hemispherical recess. Condensed water escapes into the recess 68 through the gap between the outer peripheral wall 43 of the stem 4 (see FIG. 2) and the inner peripheral wall 62 of the guide hole 61. The recess 68 accommodates the condensed water that has escaped from the gap. Further, the condensed water escapes from the groove 63 to the recess 68. The recess 68 accommodates the condensed water that has escaped from the groove 63.

As described above, even if the condensed water escapes to the recess 68 and rust is generated in the recess 68, the rust is contained in the gap between the recess 68 and the outer peripheral wall 43 of the stem 4 (see FIG. 2). The sliding surface is less likely to stick. Further, since the contact area between the outer peripheral wall 43 of the stem 4 and the inner peripheral wall 62 of the guide hole 61 on the sliding surface can be suppressed to be small by providing the plurality of recesses 68 on the sliding surface, this point as well. The sliding surface is less likely to stick.

18 and 19 show an inner peripheral wall 62 provided with a plurality of recesses 68 and a plurality of grooves 63 (grooves intersecting each other). All or part of the plurality of recesses 68 may not be connected to grooves 63 (spiral grooves) that intersect each other, but are preferably connected to grooves 63, as shown in FIGS. 18 and 19. .. Further, all or a part of the plurality of recesses 68 may be arranged at positions other than the positions where the grooves 63 intersect with each other, but as shown in FIGS. 18 and 19, the positions where the grooves 63 intersect with each other may be arranged. It is more preferable to be arranged in. This makes it possible to further enhance the effect of discharging condensed water. The contact area of the sliding surface can be further reduced. Further, since the recesses 68 are arranged at positions where they intersect with each other, the intersecting positions are less likely to be clogged with carbides and the like, so that the condensed water can be reliably discharged. Further, since the structure is such that the annular convex portion 47, the groove 63, and the concave portion 68 are combined, in addition to the above effects, condensed water is applied to the gap between the outer peripheral wall 43 of the stem 4 and the inner peripheral wall 62 of the guide hole 61. Further, it becomes difficult to invade, and it becomes possible to easily discharge the condensed water from the gap to the outside of the guide hole.

The plurality of recesses 68 do not have to be connected to the groove 63. Even when the plurality of recesses 68 are not connected to the grooves 63, the recesses 68 contain condensed water, so that even if rust occurs, the sliding surface is less likely to stick. Further, since the contact area of the sliding surface can be suppressed to a small size, the sliding surface is less likely to be fixed.

(Modification 8)
Next, the modification 8 will be described with reference to FIGS. 20 and 21. 20 and 21 are partial cross-sectional views of the inner peripheral wall 62 of the guide hole 61. Oil (for example, rust preventive oil) is applied to the sliding surface in order to suppress the occurrence of rust.

As shown in FIG. 20, the groove 63 provided in the inner peripheral wall 62 holds oil. Since the groove 63 improves the oil retention, the oil suppresses the generation of rust. From this point as well, the sliding surface is less likely to stick.

As shown in FIG. 21, the recess 68 provided in the inner peripheral wall 62 holds oil. Since the recess 68 improves the oil retention, the oil suppresses the generation of rust. From this point as well, the sliding surface is less likely to stick.

In addition, the above embodiments are merely examples of embodiment of the present disclosure, and the technical scope of the present disclosure should not be construed in a limited manner by these. .. That is, the present disclosure can be implemented in various forms without departing from its gist or its main features.

In the above embodiment, the groove 63 is provided on the inner peripheral wall 62 of the guide hole 61, but the present disclosure is not limited to this, and for example, the groove 63 may be provided on the outer peripheral wall 43 of the stem 4. Further, the groove 63 may be provided on both the inner peripheral wall 62 of the guide hole 61 and the outer peripheral wall 43 of the stem 4.

In the above embodiment, the recess 68 is provided in the inner peripheral wall 62 of the guide hole 61, but the present disclosure is not limited to this, and for example, the recess 68 may be provided in the outer peripheral wall 43 of the stem 4. Further, the recess 68 may be provided on both the inner peripheral wall 62 of the guide hole 61 and the outer peripheral wall 43 of the stem 4.

Further, in the above embodiment, the groove 63 is an inclined groove extending in a direction inclined with respect to the axial direction (X direction), but the present disclosure is not limited to this, and the groove 63 is along the axial direction (X direction). May be extended.

Further, in the above embodiment, the inclination angle of the groove 63 (spiral groove) is made constant, but the present disclosure is not limited to this. For example, the inclination angle of the groove 63 on one end side in the axial direction and the inclination angle on the other end side in the axial direction may be different so that the condensed water is difficult to enter and is easily discharged. For example, the inclination angle of the groove 63 on one end side in the axial direction may be smaller than the inclination angle on the other end side in the axial direction.

The present disclosure is suitably used for an internal combustion engine having a valve structure that is required to prevent the sliding surface from sticking due to rust or the like.

1 Cylinder head 2 ports 3 Poppet valve 4 Stem 5 Valve face 6 Valve guide 7 Coil spring 8 Cam 21 Valve seat 41 Axial one end 42 Axial other end 43 Outer wall 47 Circular convex 48, 48A Inclined surface 61 Guide hole 62 Inner peripheral wall 63 Groove 64 Step 65 One end in the axial direction 66 The other end in the axial direction 67 Tapered part 68 Recessed part 71 Holding member 81 Rocker arm 82 Bridge 100 Valve structure 471 End face 472 Wall surface

Claims (11)

A poppet valve with a shaft-shaped stem that opens and closes at least one of the exhaust or intake ports.
A valve guide having a guide hole through which the stem is movably inserted in the axial direction,
With
The outer peripheral wall of the stem has a proximity portion close to the inner peripheral wall of the guide hole when the poppet valve closes the port.
Valve structure. The proximity portion has an annular convex portion that extends in an annular shape along the outer peripheral direction of the stem and projects outward in the axial direction.
The valve structure according to claim 1. The end face of the annular convex portion on the outer side in the axial direction is rounded.
The valve structure according to claim 2. The wall surface on the other end side in the axial direction of the annular convex portion has an inclined surface inclined to one end side in the axial direction with respect to the outer side in the axial direction.
The valve structure according to claim 2 or 3. The inner peripheral wall of the guide hole has a stepped portion in which the inner diameter on one end side in the axial direction is larger than the inner diameter on the other end side in the axial direction.
The annular protrusion is arranged at a position corresponding to the step when the poppet valve closes the port.
The valve structure according to claim 4. The inner peripheral wall of the guide hole has a tapered portion that is inclined outward in the axial direction with respect to one end side in the axial direction.
The inclination angle of the inclined surface of the annular convex portion with respect to the axial direction is different from the inclination angle of the tapered portion with respect to the axial direction.
The valve structure according to claim 4. At least one peripheral wall of the inner peripheral wall of the guide hole and the outer peripheral wall of the stem has a groove extending from one end side in the axial direction to the other end side in the axial direction of the peripheral wall.
The valve structure according to any one of claims 1 to 6. The groove allows condensed water adhering to the gap between the inner peripheral wall of the guide hole and the outer peripheral wall of the stem to pass through.
The valve structure according to claim 7. At least one peripheral wall of the inner peripheral wall of the guide hole and the outer peripheral wall of the stem has a plurality of recesses recessed in the axial direction.
The valve structure according to any one of claims 1 to 8. The recess is configured to accommodate condensed water adhering to the gap between the inner peripheral wall of the guide hole and the outer peripheral wall of the stem.
The valve structure according to claim 9. An internal combustion engine having the valve structure according to any one of claims 1 to 10.

Images