JP5296594B2 - Exhaust poppet valve for internal combustion engines - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a poppet valve for exhaust in which the whole area of a valve shank facing inner peripheral surface of a valve guide is formed in a taper shape and the valve shank and the valve guide do not interfere with each other. <P>SOLUTION: In an exhaust valve 20 in which a valve umbrella portion 27 is formed integrally to the valve shank 22 via a skirt-shape transition area 28, the whole sliding area of the shank 22 with respect to a cylindrical guide 30 is tapered toward the umbrella portion 27 side. A gap S1 between the valve and the guide at the umbrella portion 27 side is large as compared with the case where the shank 22 has an equal diameter, so that the shrank 22 and the guide 30 do not interfere even when the gap S1 is narrowed by heat of exhaust gas. An inflection point (origin of a tapered portion) of an outside convex is not within the guide 30, thus, when the valve 20 slides, the inflection point does not interfere with the inner peripheral surface of the guide, the valve 20 smoothly slides, vibration and noise are not generated, and the valve 20 is not broken. No metal powder is generated on a relative sliding portion, so that engine oil is not made dirty and an exhaust passage 3 is not narrowed. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  In the present invention, a valve shaft portion, which is a portion that is slidably supported in the axial direction by a cylindrical valve guide, and a conical seat contact surface corresponding to the valve seat on the exhaust port side are formed on the outer periphery thereof. A valve umbrella part that is a part for opening and closing the exhaust port and an exhaust poppet valve for an internal combustion engine that is integrally formed through a skirt-like transition region, in particular, the valve umbrella part side of the valve shaft part The present invention relates to an exhaust poppet valve configured such that a region facing the inner peripheral surface of the valve guide opening end portion is tapered toward the valve umbrella side.

  An exhaust poppet valve that constitutes a valve mechanism for an internal combustion engine such as an automobile is a valve shaft portion that is slidably guided by a cylindrical valve guide and a portion that acts to open and close an exhaust port. The valve umbrella is integrally formed with the skirt transition region. As shown in FIG. 1, the poppet valve is disposed so that the valve shaft portion passes through the valve guide fixed to the cylinder head and the valve umbrella portion crosses the exhaust passage. The valve (shaft) slides in the valve guide in the axial direction in synchronization with the rotation of the cam), so that the conical seat abutment surface on the outer periphery of the valve umbrella is brought into contact with the valve seat on the periphery of the exhaust port. The valve is configured to change from a closed state in which the exhaust port is closed by pressure contact to an open state in which the valve umbrella (seat contact surface) is separated from the valve seat and opens the exhaust port.

  In addition, because of the configuration of the valve mechanism, the sliding operation in the axial direction of the valve involves a slight swing, so that the valve can smoothly slide along the valve guide even if the valve swings slightly. A predetermined clearance is provided between the valve shaft portion having a uniform outer diameter and the valve guide having a uniform inner diameter, and the engine oil penetrates into the clearance.

  Both the valve and the valve guide expand due to the influence of the heat of the exhaust gas at a high temperature, whereas the valve guide radiates heat through the cylinder head, whereas the valve The amount of thermal expansion in the radial direction of the valve is larger than that of the valve guide. For this reason, in particular, the valve-guide clearance at the valve guide opening on the side where the valve umbrella extends (the side close to the exhaust port) is narrowed. And the inner periphery of the valve guide opening end interfere with smooth sliding movement of the valve, wear the interference area, increase the clearance between the valve and guide, and generate vibration and noise. Or the valve may be broken. In addition, the metal powder scraped by the interference may cause problems such as reducing the life of the engine oil or sintering and adhering in the exhaust passage to narrow the exhaust passage.

  Therefore, in Patent Document 1 below, as shown in FIG. 6, the opening end of the valve guide c (the opening end of the valve guide c on the side where the valve umbrella portion b2 extends) in the shaft portion b1 of the valve b is provided. By providing a tapered portion b3 in the facing area and preliminarily increasing the valve-guide clearance s at the opening end of the valve guide c, the valve-guide clearance s is narrowed by the heat of the exhaust gas. Even so, a structure has been proposed in which interference between the valve shaft portion b1 and the opening end portion of the valve guide c is avoided, and the above problem is solved.

US Pat. No. 5,592,913

  In Patent Document 1, interference between the valve shaft b1 and the valve guide c opening end is surely avoided by providing the tapered portion b3 on the shaft b1 of the valve b. However, since the inflection point (starting point of the taper portion) b4 that protrudes from the region where the outer diameter of the valve shaft portion b1 is uniform to the taper portion b3 is in the sliding region with the valve guide c, the valve When b slides, an outwardly inflection point (starting point of the tapered portion) b4 interferes with the inner peripheral surface of the valve guide c.

  For this reason, the smooth sliding movement of the valve is hindered, the interference area between the valve and guide is worn, the clearance between the valve and guide is expanded, vibration and noise may occur, and the valve may be broken. The above-mentioned various problems such as the fact that the metal powder shaved in the interference region reduces the life of the engine oil or sinters and adheres to the exhaust passage narrows the exhaust passage. It has not been improved.

  The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to configure the entire sliding region of the valve shaft portion with the valve guide in a tapered shape, thereby enabling the valve to slide. An object of the present invention is to provide an exhaust poppet valve for an internal combustion engine in which a valve shaft portion and a valve guide do not reliably interfere with each other.

In order to achieve the above object, in the exhaust poppet valve for an internal combustion engine according to claim 1, a valve shaft portion which is a portion slidably supported in the axial direction by a cylindrical valve guide, A conical seat contact surface corresponding to the valve seat on the exhaust port side is formed at the periphery, and a valve umbrella portion that is a part that opens and closes the exhaust port is integrally formed via a skirt-like transition region In an exhaust poppet valve for an internal combustion engine,
At least the entire sliding area of the valve shaft portion with the valve guide is configured to be tapered toward the valve umbrella side.

  (Operation) Since the entire sliding region of the valve shaft portion with the valve guide is formed in a tapered shape (small diameter) toward the valve umbrella portion side, the following operations are exhibited.

  First, the clearance between the inner peripheral surface of the opening end of the valve guide (the valve guide opening end on the side where the valve umbrella portion extends) and the valve shaft portion forms the valve shaft in a tapered shape. Since the structure is larger than the conventional structure (conventional structure in which the entire length of the valve shaft is made uniform), even if the clearance between the valve and the guide is reduced due to the heat of exhaust gas, the valve shaft and valve Interference with the inner peripheral surface of the guide opening end is avoided.

  Second, an outwardly inflection point (starting point of the taper portion) that transitions from the uniform outer diameter region to the tapered portion in the valve shaft portion is outside the sliding region with the valve guide (the inflection point is Therefore, when the valve slides, the inflection point that protrudes outward (starting point of the taper portion) interferes with the inner peripheral surface of the valve guide. It is impossible to do.

  The exhaust poppet valve for an internal combustion engine according to claim 1, wherein a taper angle θ of the tapered portion of the valve shaft portion is set as a sliding region of the valve shaft portion with the valve guide. The length of the sliding taper portion (hereinafter referred to as the sliding taper portion) is L, the minimum radius of the sliding taper portion is r, the inner radius of the valve guide is R, the linear expansion coefficient of the valve shaft portion is α, and the linear expansion coefficient of the valve guide is β, where t is the temperature at the minimum radius position of the sliding taper portion, and T is the temperature of the valve guide corresponding to the minimum radius position of the sliding taper portion, r (αt + 1) <R (βT + 1) and L · tan θ <R− It was configured to satisfy the conditional expression r.

  (Operation) While the valve mechanism is being driven, the valve and the valve guide are thermally expanded on the side of the exhaust port (close to) under the influence of the heat of the high-temperature exhaust gas. The thermal expansion is negligible because Therefore, if the valve-guide clearance is configured to be constant in the valve axial direction when the valve mechanism is not driven, the valve-guide clearance during driving of the valve mechanism will However, in the second aspect, the taper angle θ of the sliding region (taper portion) of the valve shaft portion with the valve guide is r (αt + 1) <R ( βt + 1) and the condition that L · tan θ <R−r is satisfied, and between the valve and the guide when the valve is driven (the valve and the valve guide are thermally expanded under the influence of the exhaust gas heat) The clearance is substantially constant in the longitudinal direction, and the valve can slide smoothly in the axial direction.

According to a third aspect of the present invention, in the exhaust poppet valve for an internal combustion engine according to the first or second aspect, the valve is a valve shaft member made of a first material, and is more heat resistant than the first material. The valve umbrella member including the skirt-like transition region, which is made of the second material excellent in the above, is configured to be joined and integrated.

  (Operation) When the entire valve is made of a material having excellent toughness such as austenitic heat-resisting steel containing nickel, post-treatment is required to increase the high temperature creep strength in the valve umbrella including the skirt-like transition region. .

  On the other hand, when the entire valve is made of a material excellent in heat resistance (high temperature creep strength) such as a nickel-based heat-resistant alloy (for example, NCF80A, NCF751), the manufacturing process is equivalent to the high valve processing temperature by hot forging. Is troublesome. Further, after finishing forging, a post-treatment for increasing the toughness in the valve shaft portion is necessary.

  However, in claim 3, the valve shaft portion that is required to have strength against axial tensile stress or bending stress due to a change in the spring force (axial tensile force) or torque of the return spring acting in the valve closing direction is applied. Since the valve shaft portion is made of a material having excellent toughness such as austenitic heat-resistant steel containing nickel, the durability (abrasion resistance) is excellent. On the other hand, a valve umbrella portion including a skirt-like transition region that is always exposed to high-temperature exhaust gas is a part that particularly requires heat-resistant creep strength, but for example, heat resistance (high-temperature creep strength) such as a nickel-based heat-resistant alloy is particularly required. Because it is made of excellent materials, it has excellent heat resistance.

  According to a fourth aspect of the present invention, in the exhaust poppet valve for an internal combustion engine according to any one of the first to third aspects, an inner portion of the valve guide is disposed inside the valve guide opening end on the side where the valve umbrella portion extends. It was comprised so that the enlarged diameter part which expands a surrounding surface to radial direction outer side might be provided.

  (Operation) A diameter-enlarged portion provided inside the valve guide opening end on the side where the valve umbrella portion extends (specifically, a stepped portion, a tapered surface, an arc surface, etc. can be considered). However, since the clearance between the valve and the guide near the opening end portion of the valve guide (the valve guide opening end portion on the side where the valve umbrella portion extends) is enlarged, the taper angle of the taper portion of the valve shaft portion can be reduced.

  As is apparent from the above description, according to the first aspect, even if the clearance between the valve and the guide is narrowed due to the heat of the exhaust gas, the valve (valve shaft portion) slides along the inner peripheral surface of the valve guide. During dynamic operation, interference between the valve shaft and the inner peripheral surface of the valve guide opening end is of course avoided, and interference between the valve shaft and the entire length of the inner peripheral surface of the valve guide is surely avoided. Is done.

  First, a smooth sliding operation of the exhaust valve is ensured, and an accurate opening / closing operation of the exhaust port is ensured for a long period of time.

  Second, there is no possibility that vibration or noise occurs or the exhaust valve breaks during the sliding operation of the exhaust valve.

  Third, since metal powder is not generated in the relative sliding portion between the exhaust valve and the valve guide, the life of the engine oil is extended and there are no problems such as a narrow exhaust passage.

  According to claim 2, the clearance between the valve and the guide becomes substantially constant in the longitudinal direction, and the smooth sliding operation of the exhaust valve is further ensured, and the accurate opening / closing operation of the exhaust port is ensured for a longer period of time. The

  Further, the desired taper angle of the sliding region (sliding taper portion) with the valve guide of the valve shaft portion is set such that the length L of the sliding taper portion, the minimum radius r of the sliding taper portion, the inner radius R of the valve guide, The linear expansion coefficient α of the valve shaft portion, the linear expansion coefficient β of the valve guide, the temperature t at the minimum radius position of the sliding taper portion, and the temperature T of the valve guide corresponding to the minimum radius position of the taper portion can be easily obtained. Therefore, the dimension design of the taper portion formed in the valve shaft portion is simplified.

  According to the third aspect, it is possible to provide an exhaust poppet valve that is excellent in both heat resistance (high temperature creep strength) in the valve umbrella portion including the skirt-shaped transition region and toughness in the valve shaft portion.

  According to the fourth aspect, since the taper angle of the taper portion provided in the valve shaft portion can be reduced, the taper processing of the valve shaft portion is facilitated accordingly.

It is sectional drawing of the valve mechanism which opens and closes the exhaust port of the internal combustion engine for motor vehicles. 1 is a cross-sectional view showing a first embodiment of an exhaust poppet valve according to the present invention. It is explanatory drawing explaining the detail of the taper part provided in the valve shaft part. It is sectional drawing which shows 2nd Example of the poppet valve for exhaust_gas | exhaustion which concerns on this invention. It is sectional drawing which shows 3rd Example of the poppet valve for exhaust gas based on this invention. It is principal part sectional drawing of patent document 1. FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a valve operating mechanism for opening and closing an exhaust port of an internal combustion engine, FIG. 2 is a sectional view showing a first embodiment of an exhaust poppet valve according to the present invention, and FIG. It is explanatory drawing explaining the detail of the taper part.

  In FIG. 1, a valve operating mechanism 1 on the side of an exhaust port 4 of an automobile engine is configured as a mechanism for opening and closing an exhaust port 4 of an exhaust passage 3 that opens to a combustion chamber 6, and rotates in synchronization with the rotation of the engine. A cam 12 fixed to the camshaft 10 to be driven and an exhaust passage disposed in the vertical direction so as to cross the exhaust passage 3 provided in the cylinder head 2 and spring-biased in a direction to close the exhaust port 4 A poppet valve (hereinafter referred to as an exhaust valve) 20, a rocker arm 16 slidably disposed between the cam 12 and the shaft end of the exhaust valve 20, and a hydraulic type disposed at a position that serves as a fulcrum of the rocker arm 16 A lash adjuster 18 is provided.

  Reference numeral 30 denotes a cylindrical valve guide that slidably supports the valve shaft portion 22 of the valve 20, and is fitted and fixed to the upper and lower through holes 2 a provided in the cylinder head 2 so as to intersect the exhaust passage 3. . Reference numeral 34 denotes a disk-shaped retainer fixed to the shaft end of the valve 20. The exhaust valve 20 is urged upward (the valve closing direction) between the retainer 34 and the seat surface 2 b around the upper and lower through holes 2 a. A compression coil spring 36 is interposed. Reference numeral 5 denotes a conical valve seat provided at the peripheral edge of the exhaust port 4. The exhaust port 4 is closed with the seat contact surface 27 a on the exhaust valve 20 side being in pressure contact with the valve seat 5. The exhaust port 4 is configured to open in a state where the seat contact surface 27 a on the side is separated from the valve seat 5.

  The camshaft 10 (cam 12) is rotated by the driving force accompanying the driving of the engine. The rocker arm 16 swings up and down around the hydraulic lash adjuster 18 as the cam 12 rotates, and the rocker arm of the cam 12 is rotated. The exhaust valve 20 slides up and down in synchronization with the timing of pressing 16 (synchronized with the rotation of the cam 12) to open and close the exhaust port 4.

  Next, the structure of the exhaust valve 20 will be described in detail with reference to FIG.

  The exhaust valve 20 includes a valve shaft portion 22 that is a portion that is slidably supported in the axial direction by a cylindrical valve guide 30, and a conical seat contact surface 27a corresponding to the valve seat 5 on the exhaust port 4 side. Is formed on the outer peripheral edge, and the valve umbrella portion 27 which is a portion for opening and closing the exhaust port 4 is integrally formed through the skirt-like transition region 28, so that the whole has heat resistance and toughness. It consists of austenitic heat-resistant steel containing excellent nickel. On the other hand, the valve guide 30 is made of a sintered material containing graphite and having excellent lubricity.

  In addition, the valve guide 30 is configured in a cylindrical shape whose inner diameter is constant in the axial direction, while the valve shaft portion 22 (region excluding the region from the valve umbrella portion 27 to the skirt transition region 28). A region indicated by a length L1 including a sliding region (shown by a length L) with the valve guide 30 is configured in a tapered shape that becomes narrower toward the umbrella portion 27 side. Hereinafter, the tapered region 22c indicated by the length L1 is referred to as a tapered portion.

  Then, the taper angle θ of the taper portion 22c of the valve shaft portion 22 is configured to a predetermined value satisfying the conditional expression r (αt + 1) <R (βt + 1) and L · tanθ <R−r. The valve-guide clearance S in the state in which the valve 20 and the valve guide 30 are thermally expanded under the influence of gas heat becomes substantially constant in the axial direction of the valve guide 30, and the valve 20 slides smoothly in the axial direction. It is configured to be able to move.

  Hereinafter, the taper portion 22c (taper angle θ) of the exhaust valve 20 will be described in detail with reference to FIG.

  While the valve mechanism is being driven, the valve 20 and the valve guide 30 are thermally expanded on the exhaust port 4 side due to the influence of the high-temperature exhaust gas, but on the opposite side to the exhaust port 4 side, the heat of the exhaust gas. The thermal expansion is negligible because For this reason, the valve-guide clearance S1 on the exhaust port 4 side in a state where the valve operating mechanism is driven (a state narrowed due to the heat of the exhaust gas) is larger than 0, and the influence of the heat of the exhaust gas. If the valve-to-guide clearance S2 on the opposite side of the exhaust port 4 side that can be ignored is also greater than 0, the valve-to-guide clearance S is substantially constant in the valve axial direction, and the valve 20 slides smoothly in the axial direction. It is considered possible.

  For this purpose, when the valve shaft portion 22 is formed in a tapered shape (taper angle θ), the clearance S1 between the valve and the guide on the exhaust port 4 side which is narrowed by the influence of the heat of the exhaust gas, and the exhaust gas. What is necessary is just to obtain the taper angle θ at which the valve-guide clearance S2 on the opposite side to the exhaust port 4 side where the influence of the heat can be ignored is positive (greater than 0).

That is, of the tapered portion 22c, the length of the sliding region (sliding tapered portion 24) with the valve guide 30 is L, the taper angle of the sliding tapered portion 23 is θ, and the minimum radius of the sliding tapered portion 24 is r. The inner radius of the valve guide 30 is R, the linear expansion coefficient of the exhaust valve 20 (valve shaft portion 22) is α, and the linear expansion coefficient of the valve guide 30 is β. The temperatures of the exhaust valve 20 and the valve guide 30 rise due to the heat of the exhaust gas. The rising temperature at the minimum radius position P1 of the sliding taper portion 23 is t, and the tapered portion 22c (sliding taper) in the valve guide 30 is obtained. Assuming that the rising temperature of the position P2 corresponding to the minimum radius position P1 of the portion 24) is T (<t), when the valve 20 is driven, P1 → P1 ′ and P2 → P2 ′ due to thermal expansion. That is, the radius r at the minimum radius position P1 of the sliding taper portion 24 becomes the radius r ′ = r (1 + αt) at the P1 ′ position due to the heat of the exhaust gas. Further, the inner radius R of the position P2 corresponding to the minimum radius position P1 of the sliding taper portion 23 in the valve guide 30 becomes the inner radius R ′ = R (1 + βT) at the position P2 ′ due to the heat of the exhaust gas. Therefore, the clearance S1 at the minimum radius position P1 of the sliding taper portion 24 is
S1 = R′−r ′ = R (1 + βT) −r (1 + αt) (1).

On the other hand, since the influence of heat on the clearance S2 on the side opposite to the exhaust port 4 side (the position P4 corresponding to the maximum radius position P3 of the sliding taper portion 24 and P3 of the valve guide 30) can be ignored, the sliding taper portion 23 The clearance S2 at the maximum radial position P3 is
S2 = R− (r + L · tan θ) (2)

  In order for both S1 and S2 to be positive (greater than 0), it is necessary to satisfy the conditional expression (3) where r (αt + 1) <R (βT + 1) and L · tanθ <R−r.

Further, the valve shaft portion 22 and the valve umbrella portion region 23 are integrally formed through continuous cylindrical straight portions 22a and 23a having a predetermined length.
The valve shaft portion 22 includes a straight portion 22d on the end side where a groove 34a for fixing the retainer 34 is formed, a tapered portion 22c formed with a taper that narrows toward the valve umbrella region 23, and the tapered portion 22c and the straight portion. It is comprised by the reverse taper part 22b formed between 22a.

  As described above, in this embodiment, the conditional expression (3) is such that the sliding region (sliding region indicated by reference numeral 24) of at least the valve shaft portion 22 with the valve guide 30 becomes narrower toward the valve umbrella portion 27 side. Therefore, the following actions and effects are achieved.

  First, the valve-guide clearance S1 on the side where the valve umbrella portion 27 extends is larger than the clearance in the conventional structure in which the valve shaft portion 22 is configured to have a uniform diameter. Even if the clearance S1 between the valve and the guide is narrowed due to the influence of heat, interference between the valve shaft portion 22 and the inner peripheral surface of the opening end portion of the valve guide 30 is avoided, and a smooth sliding operation of the exhaust valve 20 is ensured. Thus, an accurate opening / closing operation of the exhaust port 4 is ensured for a long period of time.

  Second, an outwardly inflection point (starting point of the taper portion) that transitions from the uniform outer diameter region of the valve shaft portion 22 to the taper portion 24 is outside the sliding region with the valve guide 30 (change). Therefore, when the exhaust valve 20 is slid, the inflection point (starting point of the taper portion) that protrudes outward is disclosed in Patent Document 1. There is no interference with the inner peripheral surface of the guide 30, and there is no possibility that vibration or noise occurs during the operation of the exhaust valve 20 or the exhaust valve 20 is broken. Further, since metal powder is not generated at the relative sliding portion between the exhaust valve 20 and the valve guide 30, the life of the engine oil is extended and there is no problem such as the exhaust passage 3 being narrowed.

  FIG. 4 is a sectional view showing a second embodiment of the exhaust poppet valve according to the present invention.

  In the first embodiment, the exhaust valve 20 is made of a single material (austenitic heat-resistant steel containing nickel), but in this second embodiment, the exhaust valve 20A has improved heat resistance and toughness. A valve shaft member 22A made of excellent austenitic heat-resistant steel containing nickel (linear expansion coefficient α) and a skirt shape made of nickel-based heat-resistant alloy (linear expansion coefficient α1) particularly excellent in heat resistance (high temperature creep resistance) An umbrella area component 23A including the transition area 28 and the valve umbrella 27 is joined and integrated in the axial direction. Reference symbol X indicates a joint position between the valve shaft member 22A and the umbrella region component 23A.

That is, the valve shaft portion 22A, which requires a spring force (axial tensile force) and torque fluctuations of the return spring 36 acting in the valve closing direction and requires strength against axial tensile stress and bending stress, contains nickel. Since it is composed of a material having excellent toughness (linear expansion coefficient α) such as austenitic heat-resistant steel, it is excellent in durability (wear resistance). On the other hand, the valve umbrella region 23A including the skirt-like transition region 28 that is always exposed to high-temperature exhaust gas is a part that particularly requires heat-resistant creep strength, but particularly heat-resistant (high-temperature creep, such as a nickel-based heat-resistant alloy). Since it is made of a material (linear expansion coefficient α ₁ ) excellent in strength), it has excellent heat resistance.

  When the entire valve 20 is made of a material having excellent toughness such as austenitic heat-resistant steel containing nickel as in the first embodiment, in the valve umbrella portion 27 including the skirt-shaped transition region 28. In this second embodiment, the valve shaft portion 22A and the valve umbrella portion region 23A are both made of a metal having desirable characteristics for each function. Therefore, as in the first embodiment, no post-treatment is required to increase the high temperature creep strength in the valve umbrella region 23A.

  Similarly to the first embodiment, the taper angle θ of the taper portion 22c (sliding taper portion 24) of the valve shaft portion (valve shaft member) 22A is r (αt + 1) <R (βT + 1) and L · tan θ. It is configured to a predetermined value that satisfies the conditional expression R−r, and interference between the valve shaft portion 22 and the inner peripheral surface of the opening end portion of the valve guide 30 is avoided to ensure a smooth sliding operation of the exhaust valve 20A. Has been.

  Further, in the second embodiment, an enlarged diameter portion that expands the inner peripheral surface of the valve guide 30 outward in the radial direction is provided inside the opening end portion 30a of the valve guide 30 on the side where the valve umbrella portion 27 extends. A certain stepped portion 32 is provided around.

  For this reason, the step 32 provided inside the valve guide opening end 30a further expands the clearance s1 between the valve and the guide as compared with the structure in which the step 32 is not provided. Even if the valve-guide clearance S1 is narrowed, interference between the valve shaft portion 22 and the inner peripheral surface of the valve guide opening end portion 30a is further avoided as compared with the first embodiment.

  Further, since the stepped portion 32 provided inside the valve guide opening end portion 30a increases the valve-guide clearance S1, the taper angle θ of the tapered portion 24 provided in the valve shaft portion 22A can be reduced. The taper processing of the portion 22A becomes easy.

  In addition, as the diameter-expanded portion that expands the inner peripheral surface of the valve guide 30 outward in the radial direction, instead of the stepped portion 32, a tapered portion or a circular arc portion having a larger inner diameter on the opening side (projected inward or recessed inward) Of the circular arc surface).

  Others are the same as in the first embodiment described above, and therefore, the same reference numerals are given and the redundant description is omitted.

  FIG. 5 is a sectional view showing a third embodiment of the exhaust poppet valve according to the present invention.

  In the first and second embodiments, the exhaust valves 20 and 20A are both made of solid material. However, the third embodiment is characterized in that the exhaust valve 20B is made of a hollow body. is there.

That is, the valve shaft member 22B made of a material (linear expansion coefficient α) such as austenitic heat-resistant steel containing nickel excellent in heat resistance and toughness, which is composed of a hollow body that opens downward, and a hollow body that also opens upward A valve umbrella region region constituting member 23B including a part of the valve shaft portion and made of a material (linear expansion coefficient α ₁ ) such as a nickel-based heat-resistant alloy particularly excellent in heat resistance (high temperature creep resistance), , And are joined and integrated in the axial direction at the position indicated by X. A refrigerant such as sodium is accommodated in the hollow portion of the valve 20B as necessary.

The taper angle θ of the taper portion 22c (sliding taper portion 24) of the valve shaft portion 22 is a predetermined value satisfying the conditional expression r (α ₁ t + 1) <R (βT + 1) and L · tan θ <R−r. Thus, interference between the valve shaft portion 22 and the inner peripheral surface of the opening end portion of the valve guide 30 is avoided, and a smooth sliding operation of the exhaust valve 20B is ensured.

  Others are the same as in the first embodiment described above, and therefore, the same reference numerals are given and the redundant description is omitted.

  In each of the first to third embodiments described above, the valve shaft portion 22 is almost entirely tapered, but at least the region of the valve shaft portion 22 that slides with the valve guide 30 is tapered. What is necessary is just to comprise.

  In the above-described embodiment, the cam 12 and the shaft end of the exhaust valve 20 are connected via the rocker arm 16, but a direct acting lash adjuster is provided between the cam 12 and the shaft end of the exhaust valve 20. The structure which intervened may be sufficient.

DESCRIPTION OF SYMBOLS 1 Valve mechanism 2 Cylinder head 3 Exhaust passage 4 Exhaust port 5 Valve seat 6 Combustion chamber 10 Cam shaft 12 Cam 16 Rocker arm 18 Hydraulic lash adjuster 20, 20A, 20B Exhaust poppet valve (exhaust valve)
22 Valve shaft portion 22A, 22B Valve shaft member 22c Taper portion 23 Valve umbrella region 23A, 23B Valve umbrella region component 24 Sliding taper 27 Valve umbrella 27a Seat contact surface 28 Skirt transition region 30 Valve guide 36 Compression coil spring r Sliding taper portion minimum radius L Sliding taper portion length θ Sliding taper portion taper angle R Valve guide inner radius

Claims (4)

A valve shaft portion, which is a portion that is slidably supported in the axial direction by a cylindrical valve guide, and a conical seat contact surface corresponding to the valve seat on the exhaust port side are formed on the outer peripheral edge thereof. In an exhaust poppet valve for an internal combustion engine in which a valve umbrella part which is a part for opening and closing a port is integrally formed via a skirt-like transition region,
An exhaust poppet valve for an internal combustion engine, wherein at least the entire sliding region of the valve shaft portion with the valve guide is tapered toward the valve umbrella side.   The taper taper angle θ of the valve is such that the length of the sliding region of the valve shaft portion with the valve guide (hereinafter referred to as a sliding taper portion) is L, and the minimum radius of the sliding taper portion is r. The inner radius of the valve guide is R, the linear expansion coefficient of the valve shaft is α, the linear expansion coefficient of the valve guide is β, the temperature at the minimum radial position of the sliding taper is t, and the minimum radial position of the sliding taper is 2. The internal combustion engine according to claim 1, wherein the temperature of the corresponding valve guide is T, and the conditional expression r (αt + 1) <R (βT + 1) and L · tanθ <R−r is satisfied. Exhaust poppet valve for engine. The valve includes a valve shaft member made of a first material, and a valve umbrella member including the skirt-like transition region, made of a second material that is more heat resistant than the first material. The exhaust poppet valve for an internal combustion engine according to claim 1, wherein the two are joined and integrated.   The diameter increasing part which expands the inner peripheral surface of a valve guide to a radial direction outer side was provided in the valve guide opening end part inside the side where the said valve umbrella part is extended, The surroundings were provided. 4. An exhaust poppet valve for an internal combustion engine according to any one of 3 above.

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