JP6299277B2 - Engine valve structure - Google Patents

Description

  The present invention relates to an engine valve structure that opens and closes intake and exhaust valves.

  Conventionally, there is a structure using a tappet as a valve structure of an intake / exhaust valve of an engine.

  In general, as the valve body of the intake / exhaust valve, a valve (hereinafter referred to as a “valve member”) in which an umbrella part which is a valve body part is provided at one end of a shaft-like valve stem is used. The valve member is urged by a valve spring in a direction in which the umbrella portion closes the valve hole. The intake / exhaust valve opens and closes when the umbrella portion contacts and separates from the valve hole.

  The tappet is disposed at the other end of the valve stem, that is, the end opposite to the side where the umbrella portion is provided (hereinafter referred to as “stem end”). The shape is a cup shape having a circular end wall portion in plan view and a cylindrical peripheral wall portion that rises from the periphery of the end wall portion toward the valve member.

  The tappet fits into a guide hole formed in the cylinder head and slides on the inner surface of the guide hole. The stem end is in contact with the inner surface of the end wall of the tappet, and the cam that rotates with the rotation of the crankshaft of the engine is in contact with the outer surface of the end wall.

  If the other end of the valve stem is pressed against the urging force of the valve spring through the tappet by the action of the cam, the intake valve and the exhaust valve are opened. Further, if the pressure due to the action of the cam is weakened, the valve member is moved by the urging force of the valve spring, and the intake valve and the exhaust valve are closed (see, for example, Patent Document 1).

JP 2008-128121 A

  By the way, when the cam is in sliding contact with the outer surface of the end wall of the tappet, the stress acting on the end wall varies depending on the degree of elastic deformation of the tappet at each location. For this reason, the elastic deformation is easily suppressed in the vicinity of the axial center where the other end of the valve stem contacts, and the stress acting on the end wall portion may increase.

  If the stress varies depending on the location, uneven surface pressure tends to occur at the sliding contact portion between the cam and the tappet. Non-uniform surface pressure leads to non-uniform wear, which is not desirable for improving the durability of the member and the accuracy of valve operation.

  Accordingly, an object of the present invention is to make the surface pressure more uniform in the sliding contact portion between the cam and the tappet.

  In order to solve the above-described problems, the present invention provides a valve member in which an umbrella portion that is in contact with and away from a valve hole of a valve is provided at one end of a shaft-shaped valve stem, and an end wall portion in which the other end of the valve stem abuts A tappet comprising a peripheral wall portion rising from the peripheral edge of the end wall portion toward the umbrella portion, a cam slidably contacting an outer surface of the end wall portion of the tappet, and an input adjusting portion provided on the cam or the tappet or both The input adjustment unit includes a member that is assumed to be generated in each part of the end wall of the tappet when a certain pressing force is applied to the end wall of the tappet. The pressing force from the cam to the tappet to the portion where the displacement is relatively small is set to be smaller than the pressing force from the cam to the tappet to the portion where the displacement is relatively large. about Employing a valve structure characterized.

  Here, the input adjusting portion can be configured by a concave portion provided on the cam surface of the cam, the outer surface of the end wall portion of the tappet, or both.

  In this configuration, in the end wall portion of the tappet, the axial center portion with which the other end of the valve stem abuts is a portion in which the amount of displacement is relatively smaller than the other portions, and the concave portion is It can provide in the position which opposes the said axial center part among the cam surfaces of a cam.

  Further, in the case where the end wall portion of the tappet includes an annular portion in which the displacement is relatively likely to occur toward the outer diameter side in the radially outer region from the axial center portion, the concave portion is a cam of the cam It can provide so that it may oppose the part near the internal diameter of the said annular part among surfaces.

  It is desirable that the recess and the cam surface around the recess are smoothly connected with a curved surface having a continuous curvature.

  In the case where a concave portion is provided on the cam surface as the input adjustment portion, the end wall portion of the tappet includes a stiffness adjustment portion that gradually increases in thickness toward the outer diameter side of the member in the axial direction. Can be adopted.

  According to the present invention, the cam or the tappet or both has a relative pressing force to a portion with a relatively small displacement amount in accordance with the difference in the displacement amount in the axial direction of the member assumed in the end wall portion. Since the input adjusting unit is set so as to be smaller than the pressing force to the large portion, the surface pressure can be made more uniform in the sliding contact portion between the cam and the tappet.

It is front sectional drawing showing the valve structure of the engine of one Embodiment of this invention. The principal part of the embodiment is shown, (a) is a perspective view, (b) is a front sectional view. It is front sectional drawing and surface pressure distribution map which show other embodiment. (A) (b) is front sectional drawing of the tappet which shows further another embodiment, respectively. (A) (b) is explanatory drawing which shows the relationship between a load and a displacement amount. It is explanatory drawing which shows the state with which force was applied to the tappet from the cam, (a) is sectional drawing of a tappet, (b) is a graph figure which shows the rigidity of the up-down direction of the end wall part of a tappet, (c) is The graph which shows the deflection | deviation of the end wall part of a tappet, (d) is a graph figure which shows distribution of the surface pressure which arises in the end wall part of a tappet.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. This embodiment is a valve structure of an automobile engine. In the drawings, only members and means directly related to the present invention are shown, and other members and the like are not shown. Although only one cylinder 1 is shown in the drawings, the engine may be a single cylinder or a multi-cylinder having a plurality of cylinders 1.

  As shown in FIG. 1, the cylinder 1 is provided with a port 3 communicating with the combustion chamber 2 and a valve 5 (hereinafter referred to as “valve member 5”) for opening and closing the valve hole 4 of the port 3. Port 3 has an intake port and an exhaust port. A fuel injection device (not shown) for injecting fuel into the intake port is provided in the intake port, and fuel is injected into the intake air in the intake port to form an air-fuel mixture. Hereinafter, the valve structure of the engine will be described by taking this intake port as an example, but the same structure can be adopted also in the exhaust port. The engine is not limited to the fuel injection device provided in the intake port, but is provided in the combustion chamber 2 and injects fuel into the intake air in the combustion chamber 2 to form an air-fuel mixture. It may be an expression engine.

  As shown in FIG. 1, the valve structure includes a valve member 5 and an elastic member 6 (hereinafter referred to as “valve spring 6”) that urges the valve member 5 in the valve closing direction of the valve hole 4. . The valve member 5 includes a shaft-shaped valve stem 5b and an umbrella portion 5a that contacts and separates from the valve hole 4 of the valve at one end of the valve stem 5b. The valve stem 5 b is inserted into a valve insertion hole formed in the cylinder 1 through a cylindrical valve stem guide 7, and can advance and retract in the axial direction with respect to the cylinder 1.

  The lower end of the valve spring 6, that is, the end close to the combustion chamber 2 is supported by the cylinder 1 via the valve spring seat, and the upper end, that is, the end on the cylinder head side, is the retainer 8 and the cotter 9. Is fixed to the valve stem 5b. The retainer 8 is an annular member, and supports the upper end of the valve spring 6 at its outer periphery. A valve stem 5 b is inserted into the inner peripheral portion of the retainer 8 through a cotter 9.

  The cotter 9 is a split collet that is divided into two pieces, in which the outer peripheral surface 9b is a conical surface. The cotter 9 comes into surface contact with the inner peripheral surface 8b of the retainer 8 and the outer peripheral surface of the valve stem 5b, which are also formed of conical surfaces, and fixes the valve stem 5b and the retainer 8. At this time, a retaining protrusion 9a is provided on the inner surface of the cotter 9, and the retaining protrusion 9a enters the retaining recess 5d formed on the outer peripheral surface of the valve stem 5b to provide a retaining function in the axial direction. Demonstrate.

  On the other end side of the valve stem 5b, a tappet 11 with which the end surface of the other end (stem end) of the valve stem 5b abuts is disposed. The tappet 11 is a cup-shaped member having an end wall portion 11a that is circular in plan view and a cylindrical peripheral wall portion 11b that rises toward the valve member 5 from the periphery of the end wall portion 11a. The axis c of the valve stem 5b coincides with the axis c of the tappet 11 arranged in a downward cup shape.

  The tappet 11 is fitted into a guide hole formed in the cylinder head and slides on the inner surface of the guide hole. The stem end is in contact with the inner surface of the end wall portion 11a of the tappet 11, and the cam 20 rotating with the rotation of the crankshaft of the engine is in contact with the outer surface of the end wall portion 11a.

  When the stem end of the valve stem 5 b is pressed against the urging force of the valve spring 6 through the tappet 11 by the action of the cam 20, the valve member 5 is lowered to open the valve hole 4. When the pressing force due to the action of the cam 20 is weakened, the valve member 5 is raised by the elastic force of the valve spring 6 and closes the valve hole 4. Thus, the valve member 5 opens and closes the intake port at a predetermined timing by the rotation of the cam 20.

  Transmission of power to the camshaft provided with the cam 20 is performed by connecting a sprocket provided on the camshaft side and a sprocket provided on the crankshaft side by a timing chain or the like.

  In this embodiment, the end wall portion 11a includes a convex portion 11c that protrudes toward the valve stem 5b and contacts the stem end of the valve stem 5b.

  Moreover, the convex part 11c of this embodiment is a truncated cone shape provided with a top part with which the stem end abuts and an inclined surface 11d whose height in the projecting direction decreases toward the outer side in the radial direction on the outer periphery of the top part. .

  The top part of the convex part 11c is a flat surface where the flat end surface of the stem end comes into surface contact. For this reason, the flat surface of the top portion has a surface direction orthogonal to the axis c along with the flat end surface of the stem end. Further, the inclined surface 11d is a conical surface formed on the entire outer periphery of the top portion, and is a convex portion 11c that protrudes in the shape of a truncated cone as a whole. Of the end wall portion 11a of the tappet 11, a portion where the convex portion 11c including the inclined surface 11d is interposed is referred to as an axial portion a (see FIG. 2B).

  In addition, a donut-shaped range in a plan view from the skirt portion of the inclined surface 11d to the skirt portion of the peripheral wall portion 11b in the radially outer region from the axial center portion a is referred to as an annular portion b (also FIG. 2B). reference).

  By the way, in general, the annular portion b is formed in the axial direction of a member assumed to be generated in each portion of the end wall portion 11a of the tappet 11 when a certain pressing force is applied to the end wall portion 11a of the tappet 11. There is a tendency that the amount of displacement increases gradually toward the outer diameter side.

  Explaining this point, for example, as shown in FIGS. 5A and 5B, the member of the annular portion b of the end wall portion 11a of the tappet 11 is supported by the valve stem at the shaft center portion a (axis c). Suppose that it looks like a cantilever beam.

  It is assumed that the thickness of the member of the annular portion b of the end wall portion 11a is constant, and the member of the cantilever has a constant shape of the beam axis orthogonal section along the length direction of the beam. Here, when a certain pressing force is applied to the cantilever (end wall portion 11a), that is, an evenly distributed load indicated by p in the figure, the displacement amount of the member in the downward direction in the axial direction is outside. There is a tendency to gradually increase toward the radial side. This is the same not only when a certain pressing force is an evenly distributed load but also when it is a concentrated load acting on a specific location.

  Further, when a part of the cam surface 20a around the entire rotation center of the cam 20 presses the outer surface of the end wall portion 11a, the contact portion between the cam 20 and the end wall portion 11a is on the outer surface of the end wall portion 11a. Move along. Here, it is assumed that a uniform load as shown in FIG. 6A acts on the outer surface of the end wall portion 11a of the tappet 11. As shown in FIG. 6B, the rigidity of the tappet 11 is high at the shaft center portion a supported by the valve stem and the peripheral wall portion 11b where the member rises in the axial direction, and decreases at the annular portion b therebetween. As shown in FIG. 6C, the amount of axial downward displacement of the member in the end wall portion 11a gradually increases from the inner diameter side toward the outer diameter side. At this time, as shown in FIG. 6D, the surface pressure generated in the end wall portion 11a tends to be particularly large in the shaft center portion a supported by the valve stem 5b and small in the outer region of the shaft center portion a. is there.

  Therefore, in this embodiment, as shown in FIGS. 1 and 2, the thickness of the member in the axial direction in the annular portion b of the end wall portion 11 a of the tappet 11 gradually increases as it goes to the outer diameter side. A rigidity adjusting portion 11e is provided.

  The rigidity adjusting portion 11e is inclined in a direction gradually approaching the valve member 5 side from the skirt portion of the inclined surface 11d to the skirt portion of the peripheral wall portion 11b over the entire circumference of the end wall portion 11a. The whole is an umbrella type. The rigidity adjusting portion 11e increases the rigidity of the annular portion b. In particular, in the annular portion b, the portion closer to the outer diameter is more rigid with respect to the pressing force in the axial direction than the portion closer to the inner diameter. For this reason, the amount of displacement of the member in the annular portion b in the axial direction downward can be made to approach uniformly from the inner diameter side to the outer diameter side.

  If the amount of displacement approaches a certain value, it is possible to prevent the pressing force from the cam 20 from escaping due to the deformation of the member of the end wall portion 11a, particularly in the portion near the outer diameter. For this reason, the surface pressure which arises in the end wall part 11a can be approached more uniformly between the axial center part a and the annular part b which is the outer side area | region. If the surface pressure is made nearly uniform, wear of the tappet 11 can be suppressed, and the durability of the member and the accuracy of the valve operation can be improved. This is because high surface pressure can be avoided from being concentrated in one place.

  Further, in this embodiment, assuming that the surface pressure generated in the end wall portion 11a is particularly large at the shaft center portion a supported by the valve stem, the cam 20 is provided with the input adjusting portion 10.

  The input adjustment unit 10 is a displacement amount of a member in the axial direction of a member that is assumed to be generated in each part of the end wall 11a of the tappet 11 when a certain pressing force is applied to the end wall 11a of the tappet 11. Is set so that the pressing force from the cam 20 to the tappet 11 to a relatively small portion is smaller than the pressing force from the cam 20 to the tappet 11 to a portion having a relatively large displacement. The tendency of the magnitude of the displacement is the same regardless of whether a certain pressing force is an evenly distributed load or a concentrated load in the description of FIG.

  Specifically, the input adjustment unit 10 includes a recess 10 a provided on the cam surface 20 a of the cam 20.

  Here, as described above, of the end wall portion 11a of the tappet 11, the axial center portion a with which the other end of the valve stem 5b abuts has a relative displacement amount of the member in the axial direction relative to other portions. It is a small part. For this reason, the recessed part 10a is provided in the cam surface 20a of the cam 20 in the position facing the axial center part a of the end wall part 11a of the tappet 11. A recess 10a is provided in the vicinity of the center of the entire width of the cam 20 with respect to the rotation center line direction of the camshaft supporting the cam 20.

  The recess 10a can be provided over the entire circumference of the rotation center of the cam 20, but as shown in FIG. 2, the cam surface 20a over the entire circumference is relatively far from the rotation center of the cam 20. It is sufficient to provide the recess 10a only in the direction in which the cam surface 20a exists at the position. Thereby, the high surface pressure in the axial center part vicinity can be relieved.

  Further, in the annular portion b of the end wall portion 11a of the tappet 11, this portion is a portion where the amount of displacement gradually increases toward the outer diameter side. That is, in the annular portion b, the portion closer to the inner diameter has a relatively smaller displacement than the portion on the outer diameter side, so that the surface pressure of the portion closer to the inner diameter is larger than the surface pressure of the portion on the outer diameter side. May also be relatively high (see FIGS. 6C and 6D).

  Therefore, in such a case, the input adjusting portion 10 is provided not only in the portion facing the shaft center portion a but also in the portion near the inner diameter of the annular portion b with respect to the rotation center line direction of the camshaft. This is effective for uniforming the surface pressure.

  Further, as shown in FIG. 3, the recess 10a of the input adjustment unit 10 and the cam surface 20a around the recess 10a may be smoothly connected with a curved surface having a continuous curvature.

  If the recess 10a and the surrounding cam surface 20a are smoothly connected, the distribution of the input from the cam 20 to the tappet 11, that is, the distribution of the pressing force from the cam 20 to the tappet 11 is unlikely to be discontinuous. It is further preferable that the distribution of the pressing force from the cam 20 to the tappet 11 is continuous over the entire sliding contact range in order to make the surface pressure generated in the tappet 11 uniform.

  In this embodiment, the cam 20 is provided with the recess 10a as the input adjustment unit 10, but a configuration in which the tappet 11 is provided with the recess 10a as the input adjustment unit 10 is also conceivable. For example, the structure which provides the recessed part 10a only in the axial center part a among the outer surfaces of the end wall part 11a, and reduces the pressing force from the cam 20 in the axial center part a can be considered.

  The effect of making the surface pressure uniform by providing the input adjustment unit 10 is effective in any case when the rigidity adjustment unit 11e is not provided when the rigidity adjustment unit 11e is provided on the tappet 11 side. When the concave portion 10a and the cam surface 20a around the concave portion 10a are smoothly connected, the rigidity adjusting portion 11e can be omitted as shown in FIG. In this example, the outer region of the shaft center portion a is a flat surface having a surface direction perpendicular to the shaft center c of the valve stem 5b from the skirt portion of the convex portion 10c to the skirt portion of the peripheral wall portion 11b. .

  Thus, by omitting the rigidity adjusting portion 11e, the surface pressure of the annular portion b, which has been conventionally low, can be adjusted so as not to be too high.

  Another embodiment is shown in FIGS. 4 (a) and 4 (b).

  In FIG. 4A, the rigidity adjusting portion 11e is provided only in the portion near the outer diameter of the annular portion b. In this embodiment, although installation of the convex part 11c of the axial center part a is abbreviate | omitted, the aspect which provided the convex part 11c in the axial center part a is also considered. 4 (b) shows a configuration in which the rigidity adjusting portion 11e is provided on the entire annular portion b as in the embodiment of FIGS. 1 and 2, but the installation of the convex portion 11c of the axial center portion a is performed. Omitted. In any embodiment, the installation of the convex portion 11c can be selective. Further, the installation of the inclined surface 11d around the convex portion 11c may be omitted, and the convex portion 11c may have a shape protruding in a columnar shape.

1 Cylinder 2 Combustion chamber 3 Port 4 Valve hole 5 Valve member (valve)
5a Umbrella 5b Valve stem 5c Stem end 5d Retaining recess 6 Valve spring 7 Valve stem guide 8 Retainer 8a Base 8b Inner peripheral surface 8c Overhang 9 Cutter 9a Retaining protrusion 9b Outer peripheral surface 10 Input adjusting unit 10a Recess 11 Tappet 11a End Wall portion 11b Peripheral wall portion 11c Protruding portion 11d Inclined surface 11e Rigidity adjusting portion 20 Cam 20a Cam surface

Claims (4)

A valve member provided with an umbrella part that contacts and separates from the valve hole of the valve at one end of the shaft-shaped valve stem;
A tappet consisting of an end wall part with which the other end of the valve stem abuts and a peripheral wall part rising from the periphery of the end wall part to the umbrella part side;
A cam slidingly contacting the outer surface of the end wall of the tappet;
An input adjusting portion provided on the cam ;
With
The input adjusting unit has a displacement amount of a member in an axial direction of the valve stem that is assumed to be generated in each part of the end wall part of the tappet when a certain pressing force is applied to the end wall part of the tappet. The pressing force from the cam to the tappet to a relatively small portion is set to be smaller than the pressing force from the cam to the tappet to the portion where the displacement amount is relatively large. The end wall portion includes a frustoconical convex portion with which the other end of the valve stem abuts, and an annular portion extending from the hem portion of the convex portion to the hem portion of the peripheral wall portion, and the member in the axial direction is provided. Bei give a rigidity adjusting section gradually becomes thicker as the thickness toward the outer diameter side to the annular portion,
Of the end wall portion of the tappet, the axial center portion with which the other end of the valve stem abuts is a portion where the amount of displacement is relatively smaller than other portions, and the input adjustment portion is a cam surface of the cam. Among these, the valve structure is a concave portion provided at a position facing the shaft center portion . The end wall portion of the tappet includes an annular portion in which the displacement is relatively likely to occur toward an outer diameter side in a radially outer region than the axial center portion, and the concave portion includes the cam surface of the cam. The valve structure according to claim 1 , wherein the valve structure is provided so as to face a portion near the inner diameter of the annular portion. The valve structure according to claim 1 or 2 , wherein the concave portion and the cam surface around the concave portion are smoothly connected with a curved surface having a continuous curvature. The valve structure according to any one of claims 1 to 3 , wherein the rigidity adjusting portion is provided only in a portion near the outer diameter of the annular portion.

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