JP2019007469A - Engine, valve guide, and manufacturing method for the valve guide - Google Patents

Abstract

To provide an engine capable of suppressing the agglutination of a valve stem into a valve guide, and to provide the valve guide, and a manufacturing method for the valve guide.SOLUTION: A slide guide surface 3a includes an in-tip guide face 6a provided in a tip 6 out of the tip 6 on the side of a port 1 of a valve guide 3, a base end 8 on the opposite side thereto and an intermediate 7 therebetween, an in-intermediate guide face 7a provided in the intermediate 7, and an in-base-end guide face 8a provided in the base end 8. An in-guide recessed part 3b includes an in-intermediate recessed portion 7b provided in the intermediate 7. The in-intermediate recessed portion 7b is formed by a spiral groove in the intermediate 7 of the valve guide 3. The in-intermediate guide face 7a is formed by the inner peripheral face of the intermediate 7 excluding the in-intermediate recessed portion 7b.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine, and more particularly to an engine, a valve guide, and a method for manufacturing the valve guide that can suppress sticking of a valve shaft in the valve guide.

  Conventionally, there is an engine including a poppet valve that opens and closes a valve port of an exhaust port and a cylindrical valve guide that guides the reciprocation of the poppet valve (see Patent Document 1).

  This type of engine has an advantage that the reciprocating motion of the poppet valve can be smoothly guided by the valve guide.

  In the invention of Patent Document 1, the inner periphery of the valve guide is provided with an inner guide surface in the distal end portion that guides the valve shaft of the poppet valve in the distal end portion on the port side of the valve guide.

Japanese Utility Model Publication No. 58-86411 (see drawing)

<Problem> There is a risk that the valve stem will stick in the valve guide.
In the invention of Patent Document 1, if the carbide of the fuel in the exhaust is formed in the tip portion of the valve guide, the carbide may be caught in the guide surface in the tip portion and the valve shaft may be stuck in the valve guide.

  The subject of this invention is providing the manufacturing method of the engine which can suppress the sticking of the valve shaft in a valve guide, a valve guide, and a valve guide.

(Invention-specific matters of the invention of claim 1)
As illustrated in FIG. 1A, a poppet valve (2) that opens and closes a valve port (1a) of at least one of the exhaust and intake ports (1) and the reciprocation of the poppet valve (2) are guided. An engine comprising a cylindrical valve guide (3), a guide insertion hole (4) into which the valve guide (3) is inserted, and a cylinder head (5) having the port (1).
As illustrated in FIG. 1 (A), the valve guide (3) has a sliding guide surface (3a) for guiding the valve shaft (2a) of the poppet valve (2) on its inner periphery, and this sliding guide. A guide indentation (3b) that is recessed radially outward of the valve guide (3) from the surface (3a),
The sliding guide surface (3a) includes a distal end portion (6) on the port (1) side of the valve guide (3), a proximal end portion (8) on the opposite side, and an intermediate portion (7) between them. A guide surface (6a) provided at the distal end portion (6), an inner guide surface (7a) provided at the intermediate portion (7), and a proximal end portion provided at the proximal end portion (8). It has a guide surface (8a)
The guide recessed portion (3b) includes an intermediate recessed portion (7b) provided in the intermediate portion (7).
As illustrated in FIG. 1 (B), the intermediate inner recessed portion (7b) is formed by a spiral groove in the intermediate portion (7) of the valve guide (3), and the intermediate inner guide surface (7a) is formed in the intermediate portion. An engine comprising the inner peripheral surface of the intermediate portion (7) excluding the recessed portion (7b).

(Invention specific matter of invention of claim 10)
A valve guide used for an engine according to any one of claims 1 to 9, wherein the valve guide (3) is configured as described in claim 1. .

(Invention specific matter of invention of claim 11)
A method for manufacturing a valve guide according to claim 10,
As illustrated in FIG. 2, in manufacturing the valve guide (3) by sintering metal powder (9),
Using the resin core (10) that forms the inner periphery of the valve guide (3) during the molding of the metal powder (9), the resin core (10) is removed by the heat during sintering of the metal powder (9). A method for producing a valve guide, wherein the resin core (10) is removed from the sintered product of the valve guide (3) by melting or thermal decomposition.

(Invention according to Claim 1 or Claim 10)
The invention according to claim 1 or claim 10 has the following effects.
<< Effect >> Sticking of the valve shaft (2a) in the valve guide (3) can be suppressed.
As illustrated in FIG. 1 (A), even if the unburned fuel in the exhaust, the blow-by gas in the intake air, or the component of the EGR gas becomes carbide in the tip portion (6) of the valve guide (3), this carbide Is discharged into the plurality of intermediate inner recesses (7b), and the carbide is difficult to bite into the tip inner guide surface (6a) or the intermediate inner guide surface (7a), and the valve shaft (2a in the valve guide (3)). ) Can be suppressed.

<< Effect >> Sticking of the valve shaft (2a) in the valve guide (3) can be suppressed.
As illustrated in FIG. 1 (A), the surface of the valve shaft (2a), even if the unburned fuel in the exhaust, the blowby gas in the intake air, or the EGR gas component becomes a carbide on the surface of the valve shaft (2a). The carbide adhered to the inner surface is scraped off at the edge of the inner recessed portion (7b) by the rotation of the valve shaft (2a), and the carbide accumulated in the inner recessed portion (7b) is removed from the valve shaft (2a). Depending on the direction of rotation of the spiral groove and the turning direction of the spiral groove constituting the intermediate inner recessed portion (7b), the intermediate recessed portion (7b) is pushed back toward the tip (6) side of the valve guide (3), or the intermediate recessed portion The insertion portion (7b) is moved to the base end portion (8) side and dispersed throughout the intermediate portion indentation portion (7b), and the carbide is difficult to bite into the intermediate portion inner guide surface (7a). Sticking of the valve shaft (2a) can be suppressed.

<Effect> Heat dissipation of the valve shaft (2a) is promoted.
As illustrated in FIG. 1A, the sliding heat of the valve shaft (2a) generated in the valve guide (3) is generated in the distal end guide surface (6a), the intermediate guide surface (7a), and the proximal end portion. Heat is efficiently radiated from the valve guide (3) to the cylinder head (5) through a wide heat radiating area composed of the guide surface (8a), and heat radiation of the valve shaft (2a) is promoted.

(Invention of Claim 11)
The invention according to claim 11 has the following effects.
<Effect> The resin core (10) having a convex portion on the outer periphery can be easily removed.
As illustrated in FIG. 2, the resin core (10) having a convex portion on the outer periphery is easily removed from the sintered product of the valve guide (3).

1A and 1B are diagrams illustrating an engine according to an embodiment of the present invention, in which FIG. 1A is a longitudinal sectional view of a main part of the engine, FIG. 1B is a sectional view taken along line BB in FIG. (C) is the CC sectional view taken on the line of FIG. It is a figure explaining embodiment of the manufacturing method of the valve guide used with the engine of FIG.

  FIG. 1 is a diagram illustrating a method of manufacturing a valve guide used in the engine of the present invention, and FIG. 2 is a diagram for explaining a method of manufacturing a valve guide used in the engine of FIG. 1. In each embodiment, a vertical diesel engine and a valve guide used in the engine are manufactured. A method will be described.

First, the engine according to the embodiment will be described.
As shown in FIG. 1A, this vertical diesel engine includes a poppet valve (2) for opening and closing a valve port (1a) of an exhaust (and intake) port (1), and a poppet valve (2). A valve guide (3) that guides reciprocation, a guide insertion hole (4) into which the valve guide (3) is inserted, and a cylinder head (5) having the port (1) are provided.
This type of engine has an advantage that the reciprocating motion of the poppet valve (2) can be smoothly guided by the valve guide (3).
In this embodiment, the exhaust port and the intake port have the same structure. In the following description, unless otherwise specified, the port (1) means both the exhaust port and the intake port.

As shown in FIG. 1A, the poppet valve (2) includes a valve shaft (2a) and a valve head (2c).
An annular valve seat (1f) is fitted into the open end of the port (1), and a valve port (1a) is opened in the valve seat (1f).
This engine includes a spring retainer (11) attached to a valve shaft (2a) of a poppet valve (2), and a valve disposed between the spring retainer (11) and a spring seat (5b) of a cylinder head (5). A spring (12), a rocker arm (13) in contact with the valve shaft (2a), and a valve shaft seal (14) externally fitted to the proximal end (8b) of the valve guide (3) are provided. 12) With the urging force of 12), the valve face (2d) of the valve head (2c) is seated on the valve seat (1f), and the urging force of the valve spring (12) is resisted by the pressing force of the rocker arm (13). The poppet valve (2) is lowered and the poppet valve (2) is opened.

The configuration of the valve guide (3) is as follows.
As shown in FIG. 1 (A), the valve guide (3) has, on its inner periphery, a sliding guide surface (3a) for guiding the valve shaft (2a) of the poppet valve (2), and this sliding guide surface. An in-guide recess (3b) is provided that is recessed radially outward of the valve guide (3) relative to (3a).
The sliding guide surface (3a) includes a distal end portion (6) on the port (1) side of the valve guide (3), a proximal end portion (8) on the opposite side, and an intermediate portion (7) between them. A guide surface (6a) provided at the distal end portion (6), an inner guide surface (7a) provided at the intermediate portion (7), and a proximal end portion provided at the proximal end portion (8). A guide surface (8a) is provided.

The guide recessed portion (3b) includes an intermediate recessed portion (7b) provided in the intermediate portion (7).
As shown in FIG. 1 (B), the intermediate inner recessed portion (7b) is formed by a spiral groove in the intermediate portion (7) of the valve guide (3), and the intermediate inner guide surface (7a) is formed in the intermediate inner recessed portion. It is comprised by the internal peripheral surface of the intermediate part (7) except an entrance part (7b).

  For this reason, in this embodiment, as shown in FIG. 1 (A), the components of unburned fuel in exhaust, blowby gas and EGR gas in intake air in the tip (6) of the valve guide (3) are carbides. Even in this case, the carbide is discharged to the plurality of intermediate inner recessed portions (7b), and the carbide is difficult to bite into the distal end inner guide surface (6a) and the intermediate inner guide surface (7a). The sticking of the valve shaft (2a) is suppressed.

  Further, as shown in FIG. 1 (A), even if unburned fuel in exhaust, blowby gas or EGR gas in intake air becomes carbide on the surface of the valve shaft (2a), the valve shaft (2a) The carbide adhered to the surface is scraped off at the edge of the intermediate inner recessed portion (7b) by the rotation of the valve shaft (2a), and the carbide accumulated in the intermediate inner recessed portion (7b) is removed from the valve shaft (2a). ) And the turning direction of the spiral groove constituting the intermediate recessed portion (7b) is pushed back from the recessed portion (7b) in the intermediate portion toward the tip (6) side of the valve guide (3), or in the intermediate portion. The recessed portion (7b) is moved to the base end portion (8) side and dispersed throughout the recessed portion (7b) in the intermediate portion, and carbide is difficult to bite into the inner guide surface (7a), and within the valve guide (3). The sticking of the valve shaft (2a) can be suppressed.

  Further, as shown in FIG. 1 (A), the sliding heat of the valve shaft (2a) generated in the valve guide (3) is caused by the inner guide surface (6a) in the distal end portion, the inner guide surface (7a) in the intermediate portion, and the proximal end. Heat is efficiently radiated from the valve guide (3) to the cylinder head (5) through a wide heat radiation area composed of the internal guide surface (8a), and heat radiation of the valve shaft (2a) is promoted.

  Further, as shown in FIG. 1 (A), the carbide that floats up from the tip portion (6) of the valve guide (3) along the guide surface (6a) in the tip portion is formed in the rotational direction of the valve shaft (2a) and in the intermediate portion. According to the turning direction of the spiral groove constituting the recessed portion (7b), the intermediate portion moves from the recessed portion (7b) in the intermediate portion to the base end (8) side, and is dispersed and accumulated in the entire recessed portion (7b) in the intermediate portion. The carbide load that accumulates in the recessed portion (7b) is not hindered from rising of the carbide along the guide surface (6a) in the tip portion, and the discharge of the carbide to the recessed portion (7b) in the intermediate portion is promoted.

As shown in FIG. 1 (A), the distal end inner guide surface (6a) and the proximal end inner guide surface (8a) both guide the entire circumference of the valve shaft (2a). The distal end and the proximal end of the intermediate recessed portions (7b) and (7b) are respectively closed by the wall surfaces of the distal end inner guide surface (6a) and the proximal end inner guide surface (8a).
The axial direction of the valve guide (3) is directed in the vertical direction, the upper side is the base end (8) of the valve guide (3), and the lower side is the front end (6) of the valve guide (3). Yes.

As shown in FIG. 1 (A), the intermediate part (7) in which the intermediate part indentation part (7b) is provided is fitted in the guide insertion hole (4).
For this reason, in this embodiment, as shown in FIGS. 1 (A) and 1 (B), the heat of carbide in the recessed portion (7b) in the intermediate portion that receives the sliding heat of the valve shaft (2a) is transferred to the intermediate portion ( The heat is radiated to the cylinder head (5) through 7), and the heat radiation of the carbide is promoted.

As shown in FIG. 1 (A), the intermediate part (7) in which the intermediate part recessed part (7b) is provided is in close contact with the inner peripheral surface of the guide insertion hole (4).
For this reason, in this embodiment, as shown in FIG. 1 (A), the heat of the carbide in the recessed portion (7b) in the intermediate portion is transferred from the outer peripheral surface of the intermediate portion (7) to the inner periphery of the guide insertion hole (4). Heat is radiated to the cylinder head (5) through the surface, and the heat dissipation efficiency of the carbide is high.

As shown in FIG. 1 (A), the cylinder head (5) includes a water jacket (5a) that allows engine coolant to pass therethrough.
For this reason, in this embodiment, as shown in FIG. 1 (A), the heat of the carbide in the intermediate recessed portion (7b) is strongly cooled by the engine coolant passing through the water jacket (5a). Heat is released to the cylinder head (5), and the heat dissipation efficiency of carbide is high.

  As shown in FIG. 1 (A), the recessed portion (3b) in the guide includes a recessed portion (6b) in the distal end portion provided in the distal end portion (6) of the valve guide (3). 6b) is provided closer to the tip (6c) side than the guide surface (6a) in the tip, and is open toward the port (1).

  Therefore, in this embodiment, as shown in FIG. 1 (A), even if the sliding heat of the valve shaft (2a) is radiated to the exhaust or intake air in the recessed portion (6b) in the tip, Exhaust or intake air that has become hot is replaced by relatively low temperature exhaust or intake air in the port (1) by convection, and heat dissipation of the valve shaft (2a) is promoted.

As shown in FIG. 1 (A), the sliding guide surface (3a) is provided with an innermost guide portion (6α) provided closer to the distal end (6c) than the inner guide surface (6a) in the distal end portion. A plurality of recessed portions (6b) are arranged in the circumferential direction in the valve guide (3) with a predetermined interval, and the innermost guide portion (6α) is adjacent to the recessed portion (6b) in the distal end adjacent in the circumferential direction. -It is provided between (6b), and a plurality are arranged in the circumferential direction.
The indented portion (6b) in the tip end portion may be an annular one that is continuous in the circumferential direction in the valve guide (3).

  For this reason, in this embodiment, as shown in FIG. 1A, even if the components of the unburned fuel in the exhaust, the blowby gas in the intake air, and the EGR gas become carbide on the surface of the valve shaft (2a), The carbide on the surface of the valve shaft (2a) is scraped off at the edge of the tip (6c) of the valve guide (3) by sliding the valve shaft (2a) in the valve closing direction, and the valve shaft (2a). Is scraped off at the edge of the recessed portion (6b) in the distal end portion, and the carbide is difficult to bite into the inner guide surface (6a) and the innermost guide surface (6α) in the distal end portion, and in the valve guide (3). Sticking of the valve shaft (2a) can be suppressed.

  As shown in FIG. 1 (A), the sliding heat of the valve shaft (2a) generated in the valve guide (3) is caused by a plurality of guide portions (6α) in the most distal portion and guide surfaces (6a) in the tip portion. The heat is efficiently radiated from the valve guide (3) to the cylinder head (5) through a wide heat radiating area composed of the inner guide surface (7a) and the intermediate guide surface (8a), and the valve shaft (2a) is radiated. Promoted.

  The input from the rocker arm to the valve shaft (2a) is made at a position offset from the central axis of the valve shaft (2a), and the poppet valve (2) rotates when the rocker arm swings.

  As shown in FIG. 1 (A), the tip (6) of the valve guide (3) is fitted into the guide insertion hole (4), and the inner peripheral surface of the guide insertion hole (4) and the valve guide (3). Between the outer peripheral surfaces of the front end portion (6), an outer end end clearance (4a) that opens toward the port (1) is formed.

  Therefore, in this embodiment, as shown in FIG. 1 (A), the sliding heat of the valve shaft (2a) is radiated to the exhaust and intake air in the outer clearance (4a) at the tip end portion via the valve guide (3). Even so, exhaust and intake air that have become hot due to heat dissipation are replaced by relatively low temperature exhaust and intake air in the port (1) by convection, and heat dissipation of the valve shaft (2a) is promoted.

As shown in FIG. 1A, the outer peripheral surface of the exposed valve shaft portion (2b) of the poppet valve (2) exposed in the port (1) when the poppet valve (2) is fully opened is formed without a step. .
The outer peripheral surface of the exposed valve shaft portion (2b) of the poppet valve (2) has a single diameter.

  For this reason, in this embodiment, when the poppet valve (2) is fully opened, it is formed on the outer peripheral surface of the exposed valve shaft portion (2b) of the poppet valve (2) that receives collision of exhaust or intake air that passes through the port (1) at high speed. In addition, a corner portion due to a step that causes stress concentration or a heat point is not formed, and damage to the poppet valve (2) due to collision of exhaust or intake air is suppressed.

  As shown in FIG. 1 (A), the port (1) has an in-port recessed portion (1c) in which the port inner surface (1b) is recessed toward the port side opening (4b) of the guide insertion hole (4). The tip (6c) of the valve guide (3) faces the recessed portion (1c) in the port.

  For this reason, in this embodiment, as shown in FIG. 1 (A), the exhaust or intake air that passes through the port (1) hardly collides with the tip (6) of the valve guide (3), and the valve guide (3). Generation of carbide in the tip portion (6) of the steel is suppressed.

As shown in FIG. 1 (A), the tip (6c) of the valve guide (3) faces the recessed portion (1c) in the port from the inside of the guide insertion hole (4).
For this reason, in this embodiment, as shown in FIG. 1 (A), the exhaust or intake air that passes through the port (1) is less likely to collide with the tip (6) of the valve guide (3).

As shown in FIG. 1 (A), the port (1) has a boss (1e) protruding into the port (1) from the inner peripheral surface (1d) of the port wall at a position where the guide insertion hole (4) is provided. And an in-port recessed portion (1c) into which the protruding end surface (1g) of the boss (1e) is recessed.
For this reason, in this embodiment, as shown in FIG. 1A, exhaust and intake air flowing in the port (1) along the inner peripheral surface (1d) of the port wall are guided by the outer peripheral surface of the boss (1e). The exhaust and intake air move away from the tip (6) of the valve guide (3).

As shown in FIG. 1A, the port (1) includes a tangential intake port, and the in-port recessed portion (1c) is provided in the tangential intake port.
A tangential intake port refers to an intake port oriented in the tangential direction of the cylinder when viewed in a direction parallel to the cylinder central axis.

  Compared with the swirl port, the tangential port with a large intake flow rate at the center of the port has a large amount of intake air including blowby gas and EGR gas passing through the tip (6) of the valve guide (3). Although there is a tendency that carbide is likely to be generated in the distal end portion (6), in this embodiment, a structure in which intake air does not easily collide with the distal end portion (6) of the valve guide (3) is adopted. The generation of carbides is significantly reduced, and the function of suppressing the generation of carbides in the tip (6) of the valve guide (3) becomes obvious.

  The configuration of the valve guide (3) used in the engine according to the embodiment shown in FIG. 1 is as described above.

Next, an embodiment of a method for manufacturing the valve guide (3) used in the engine according to the embodiment shown in FIG. 1 will be described.
As shown in FIG. 2, in this manufacturing method, when the valve guide (3) is manufactured by sintering the metal powder (9), the inner periphery of the valve guide (3) is formed when the metal powder (9) is formed. A resin core (10) is used.
Next, the resin core (10) is melted or thermally decomposed by heat during sintering of the metal powder (9), and the resin core (10) is removed from the sintered product of the valve guide (3). .

  For this reason, in this embodiment, as shown in FIG. 2, the resin core (10) having a convex portion on the outer periphery is easily removed from the sintered product of the valve guide (3).

An iron-based sintered metal material is used for the metal powder (9).
The metal powder (9) is molded by press molding using a mold (15). The die (15) includes a die (15c) having a cavity (15a) for filling the metal powder (9), a supply port (15b) for supplying the metal powder (9) to the cavity (15a), and a die (15c). The upper and lower punches (15d) and (15e) move up and down inside.
For the resin core (10), a thermoplastic resin such as nylon or a thermosetting resin such as phenol resin can be used.
When a thermoplastic resin is used for the resin core (10), the resin core (10) is removed from the sintered product of the valve guide (3) by melting.
When a thermosetting resin is used for the resin core (10), the resin core (10) is removed from the sintered product of the valve guide (3) by thermal decomposition.
A resin core (10) reinforced with fibers such as glass fibers is used.
On the outer periphery of the resin core (10), in the order from the distal end side, a recessed portion (6b) in the distal end portion, a guide surface in the distal end portion (6a), a recessed portion in the intermediate portion (7b), and a guide surface in the proximal end portion (8a) Concavities and convexities for forming are formed.

(1) ... Port, (1a) ... Valve, (1b) ... Port inner surface, (1c) ... Recessed portion in port, (1d) ... Port wall inner peripheral surface, (1e) ... Boss, (1g) ... Projection End face, (2) ... Poppet valve, (3) ... Valve guide, (3a) ... Sliding guide face, (3b) ... Guide recess in guide, (4) ... Guide insertion hole, (4a) ... Gap outside tip , (5) ... Cylinder head, (6) ... Tip, (6a) ... Guide surface in tip, (6b) ... Recessed in tip, (6c) ... Tip, (7) ... Intermediate, (7a) ... Intermediate part guide surface, (7b) ... Middle part indented part, (8) ... Base end part, (8a) ... Base end part guide surface, (8b) ... Base end, (9) ... Metal powder, (10) ... Resin core.

Claims (11)

A poppet valve (2) for opening and closing the valve port (1a) of at least one of the exhaust and intake ports (1), a cylindrical valve guide (3) for guiding the reciprocating motion of the poppet valve (2), In an engine comprising a guide insertion hole (4) into which a valve guide (3) is inserted and a cylinder head (5) having the port (1),
The valve guide (3) has a sliding guide surface (3a) for guiding the valve shaft (2a) of the poppet valve (2) on the inner periphery thereof, and the valve guide (3) than the sliding guide surface (3a). A guide recessed portion (3b) recessed radially outward of the guide,
The sliding guide surface (3a) includes a distal end portion (6) on the port (1) side of the valve guide (3), a proximal end portion (8) on the opposite side, and an intermediate portion (7) between them. A guide surface (6a) provided at the distal end portion (6), an inner guide surface (7a) provided at the intermediate portion (7), and a proximal end portion provided at the proximal end portion (8). It has a guide surface (8a)
The guide recessed portion (3b) includes an intermediate recessed portion (7b) provided in the intermediate portion (7).
The intermediate inner recessed portion (7b) is formed by a spiral groove in the intermediate portion (7) of the valve guide (3), and the intermediate inner guide surface (7a) is an intermediate portion (7) excluding the intermediate inner recessed portion (7b). The engine characterized by comprising the inner peripheral surface of). The engine according to claim 1,
The engine characterized in that the intermediate portion (7) in which the intermediate portion inner recessed portion (7b) is provided is fitted in the guide insertion hole (4). The engine according to claim 1 or 2,
The recessed portion (3b) in the guide includes a recessed portion (6b) in the distal end portion provided in the distal end portion (6) of the valve guide (3), and the recessed portion in the distal end portion (6b) is a guide surface (6a in the distal end portion). ), Which is provided closer to the tip (6c) side and is open toward the port (1). The engine according to any one of claims 1 to 3,
The distal end portion (6) of the valve guide (3) is fitted into the guide insertion hole (4), and the inner peripheral surface of the guide insertion hole (4) and the outer peripheral surface of the distal end portion (6) of the valve guide (3). An engine characterized in that an outer clearance (4a) at the front end that opens toward the port (1) is formed therebetween. The engine according to any one of claims 1 to 4, wherein
An engine characterized in that the outer peripheral surface of the exposed valve shaft portion (2b) of the poppet valve (2) exposed in the port (1) when the poppet valve (2) is fully opened is formed without a step. The engine according to any one of claims 1 to 5,
The port (1) includes an in-port recessed portion (1c) in which the inner surface (1b) of the port is recessed toward the port side opening (4b) of the guide insertion hole (4), and the tip of the valve guide (3) ( An engine characterized in that 6c) faces into a recessed portion (1c) in the port. The engine according to claim 6, wherein
The engine characterized in that the tip (6c) of the valve guide (3) faces the recessed portion (1c) in the port from the inside of the guide insertion hole (4). The engine according to claim 6 or 7,
The port (1) is provided with a boss (1e) projecting into the port (1) from the inner peripheral surface (1d) of the port wall at a position where the guide insertion hole (4) is provided, and a projecting end surface ( An engine comprising an in-port recessed portion (1c) into which 1g) is recessed. The engine according to any one of claims 6 to 8,
The engine characterized in that the port (1) includes a tangential intake port, and the in-port recessed portion (1c) is provided in the tangential intake port. A valve guide for use in the engine according to claim 1 or 2,
The valve guide (3) has a sliding guide surface (3a) for guiding the valve shaft (2a) of the poppet valve (2) on the inner periphery thereof, and the valve guide (3) than the sliding guide surface (3a). A guide recessed portion (3b) recessed radially outward of the guide,
The sliding guide surface (3a) includes a distal end portion (6) on the port (1) side of the valve guide (3), a proximal end portion (8) on the opposite side, and an intermediate portion (7) between them. A guide surface (6a) provided at the distal end portion (6), an inner guide surface (7a) provided at the intermediate portion (7), and a proximal end portion provided at the proximal end portion (8). It has a guide surface (8a)
The guide recessed portion (3b) includes an intermediate recessed portion (7b) provided in the intermediate portion (7).
The intermediate inner recessed portion (7b) is formed by a spiral groove in the intermediate portion (7) of the valve guide (3), and the intermediate inner guide surface (7a) is an intermediate portion (7) excluding the intermediate inner recessed portion (7b). The valve guide is characterized by comprising an inner peripheral surface of). A method for manufacturing a valve guide according to claim 10,
In producing the valve guide (3) by sintering metal powder (9),
Using the resin core (10) that forms the inner periphery of the valve guide (3) during the molding of the metal powder (9), the resin core (10) is removed by the heat during sintering of the metal powder (9). A method for producing a valve guide, wherein the resin core (10) is removed from the sintered product of the valve guide (3) by melting or pyrolyzing.

Images