AU2022201961A1 - Valve Stem Seal Structure - Google Patents

Abstract

OF THE DISCLOSURE A valve stem seal structure according to the present disclosure includes a valve guide (50) and a stem seal (10). The valve guide (50) has a notch (52) recessed from an outer peripheral surface of the valve guide (50), and the notch (52) is provided on a 5 side of a lubricating oil chamber (70) in a length direction of the valve guide (50). The stem seal (10) includes a reinforcing member (20) and a rubbery elastic member (30) provided integrally with the reinforcing member (20). The rubbery elastic member (30) includes a first seal (34) located between a lubricating oil chamber (70) side end and the notch (52) and a second seal (36) located between a port (80) side end 10 and the notch (52). 1/4 FIG.1 43 48 6 662 424

Description

1/4

FIG.1 6 48 43

662

Valve Stem Seal Structure

This nonprovisional application is based on Japanese Patent Application No. 2021-062693 filed on April, 1, 2021 with the Japan Patent Office, the entire contents of which are hereby incorporated by reference. BACKGROUND Field The present disclosure relates to a valve stem seal structure, and more particularly to a valve stem seal structure including a valve guide and a stem seal. Description of the Background Art An intake valve and an exhaust valve are disposed in an intake port and an exhaust port, respectively, of an internal combustion engine such as a gasoline engine and a diesel engine. The intake valve and the exhaust valve include a valve stem extending from a valve head toward a lubricating oil chamber side of the engine. The valve stem is held by a valve guide so as to be reciprocable in an axial direction. A stem seal is provided on the lubricating oil chamber side of the valve guide. The stem seal controls the amount of lubricating oil flowing between the valve stem and the valve guide. Accordingly, the valve stem and the valve guide can be appropriately lubricated. In addition, the stem seal prevents gas in a port that has passed through a gap between the valve stem and the valve guide from leaking to the lubricating oil chamber side. WO 2017/099045, Japanese Patent Laying-Open No. 2019-143684, and Utility Model Laying-Open No. 60-3206 disclose a valve stem seal structure including a valve guide and a stem seal. In order to determine the direction when the valve guide is assembled to a cylinder head, there is a valve guide in which a notch is provided on the lubricating oil chamber side of the valve guide. The notch is formed as a groove that goes around an outer peripheral surface of the cylindrical valve guide. Sometimes the notch is also used to fix the stem seal to the valve guide. For example, as illustrated in Fig. 4, a fixing rib 112 that fits into a notch 152 of a valve guide 150 is provided in a stem seal 110. The fixing rib 112 is fitted in the notch 152 to prevent the stem seal 110 from being detached from the valve guide 150 upward in Fig. 4. A valve guide made of a porous sintered body is known. When the valve guide is made of the porous sintered body, a small amount of lubricating oil can be impregnated into the valve guide. The lubricating oil contained in the valve guide provides better lubrication between the valve guide and the valve stem. At this point, while the valve guide made of the porous sintered body can be impregnated with the lubricating oil, there is a problem in that gas on a port side passes through pores of the porous sintered body. In order to prevent the gas on the port side from passing through, treatment for sealing the gas is performed on the outer peripheral surface of the valve guide. In this gas sealing, for example, the outer peripheral surface of the valve guide is subjected to grinding treatment to close the pores exposed on the outer peripheral surface. The gas sealing can prevent the gas from flowing out from the outer peripheral surface of the valve guide. The outer peripheral surface of the valve guide subjected to the treatment of gas-sealing the valve guide is cut when the notch is provided in the valve guide made of the porous sintered body. When the groove is formed by cutting, the pores are exposed on the inner wall surface of the groove. In order to prevent the outflow of the gas from the pores exposed on the inner wall surface of the groove, sealing treatment for closing the pores is further required. As the sealing treatment, for example, shot blasting may be performed on the inner wall surface of the groove. The shot blasting is treatment of processing a surface of a workpiece by causing particles to collide with the workpiece. When the sealing treatment such as shot blasting is performed on the inner wall surface of the groove, a new process is added, and productivity is degraded. SUMMARY The present disclosure has been made to solve the above problems, and an object of the present disclosure is to provide a valve stem seal structure capable of preventing the gas from flowing out to the lubricating oil chamber side without degrading the productivity even when the porous-sintered-body valve guide provided with the notch is used. A valve stem seal structure according to the present disclosure includes: a valve guide in which a valve stem penetrates an inside of the valve guide, the valve guide being disposed between a lubricating oil chamber and a port; and a stem seal provided on a lubricating oil chamber side of the valve guide. The valve guide is a porous sintered body formed in a cylindrical shape. At least an outer peripheral surface of the valve guide is gas-sealed. The valve guide includes: a through-hole through which the valve stem penetrates, the through-hole extending in a longitudinal direction; and a notch recessed from the outer peripheral surface of the valve guide, and the notch is provided on the lubricating oil chamber side in a length direction of the valve guide. The stem seal includes: a reinforcing member including a cylindrical main body; and a rubbery elastic member provided integrally with the reinforcing member. The rubbery elastic member includes: a first seal located between a lubricating oil chamber side end and the notch, the first seal protruding to an inner peripheral side of the main body of the reinforcing member toward the outer peripheral surface of the valve guide, the first seal being in contact with the outer peripheral surface of the valve guide; and a second seal located between a port side end and the notch, the second seal protruding to the inner peripheral side of the main body of the reinforcing member toward the outer peripheral surface of the valve guide, the second seal being in contact with the outer peripheral surface of the valve guide. According to the valve stem seal structure of the present disclosure, it is possible to provide the valve stem seal structure capable of preventing the gas from flowing out to the lubricating oil chamber side without degrading the productivity even when the porous-sintered-body valve guide provided with the notch is used. The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a longitudinal sectional view illustrating a valve stem seal structure according to a first embodiment. Fig. 2 is a partially enlarged longitudinal sectional view illustrating the valve stem seal structure of the first embodiment. Fig. 3 is a longitudinal sectional view illustrating a valve stem seal structure according to a second embodiment. Fig. 4 is a longitudinal sectional view illustrating a conventional valve stem seal structure. DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings, a valve stem seal structure according to each embodiment of the present disclosure will be described below. In each embodiment described below, the same component or equivalent component is denoted by the same reference numeral, and overlapping description may not be repeated. (First embodiment) With reference to Figs. 1 and 2, a first embodiment of the present disclosure will be described below. Fig. 1 is a longitudinal sectional view illustrating a valve stem seal structure of the first embodiment. Fig. 2 is a partially enlarged longitudinal sectional view illustrating the valve stem seal structure. An internal combustion engine to which the valve stem seal structure of the present disclosure is applied includes a cylinder head 90. The cylinder head 90 is disposed above a cylinder (not illustrated). A piston (not illustrated) is disposed inside the cylinder so as to be able to reciprocate. An intake port and an exhaust port (not illustrated) are provided in the cylinder head 90. An intake valve and an exhaust valve are provided in the intake port and the exhaust port, respectively. The valve stem seal structure of the present disclosure can be applied to both a valve stem of the intake valve and a valve stem of the exhaust valve. The valve stem seal structure of the first embodiment includes a valve guide 50 in which a valve stem 60 penetrates, the valve guide 50 being disposed between a lubricating oil chamber 70 and a port 80, and a stem seal 10 provided on a side of the lubricating oil chamber 70 of the valve guide 50. The valve guide 50 is formed in a cylindrical shape. The valve guide 50 is made of a porous sintered body. The sintered body is a member obtained by baking a powdered metal at a temperature lower than a melting point of metal. Pores (voids) continuous with each other are formed inside the sintered body by baking the powdered metal at the temperature lower than the melting point of the metal. At least an outer peripheral surface is gas-sealed in the valve guide 50 of the first embodiment. For example, the gas sealing is performed by grinding a surface of the valve guide made of the sintered body. The pores exposed on the surface of the valve guide 50 can be closed when the surface of the valve guide 50 is ground by a grinding stone. The valve guide 50 is disposed between the lubricating oil chamber 70 and the port 80 of the engine. A notch 52 is provided on the outer peripheral surface of the valve guide 50. The notch 52 is provided on the side of the lubricating oil chamber 70 in a length direction of the valve guide 50. The notch 52 is provided near an end of the valve guide 50 on the side of the lubricating oil chamber 70. The notch 52 is a groove that goes around the outer periphery of the valve guide 50 in the first embodiment. When the notch 52 is the groove, the notch 52 can be easily formed by grinding the valve guide 50 while rotating the valve guide 50 with the longitudinal direction of the valve guide 50 as a rotation center axis. The notch 52 is formed as a groove having a rectangular section. The section of the groove constituting the notch 52 may have a shape other than a rectangle. For example, the sectional shape of the groove may be a trapezoid or a triangle. In addition, although the productivity is poor, the notch 52 can be configured by a groove other than the groove that goes around the outer peripheral surface of the valve guide 50. For example, a recess may be intermittently provided on the outer peripheral surface of the valve guide 50.

Sealing treatment is not performed on the inner wall surface of the notch 52. Accordingly, the number of process due to the sealing treatment is not increased in manufacturing the valve guide 50. Because the notch 52 is not subjected to the sealing treatment, there is a possibility that the gas of the port flows out from the inner wall surface of the notch 52. However, the stem seal 10 described later can prevent the gas from flowing out to the side of the lubricating oil chamber 70. The notch 52 is provided on the side of the lubricating oil chamber 70. A failure of an assembling direction can be prevented because the notch 52 is used as a mark when the valve guide 50 is assembled to the cylinder head 90. The valve guide 50 is held by the cylinder head 90. The lower end of the valve guide 50 is fitted into a hole made in the cylinder head 90. In assembling the valve guide 50, the end side where the notch 52 of the valve guide 50 is provided is held, and the opposite end is inserted into the hole of the cylinder head 90. A through-hole 54 is made inside the valve guide 50. The through-hole 54 has a cylindrical shape. The valve stem 60 passes through the through-hole 54. The valve stem 60 has a columnar shape. A valve head (not illustrated) is provided at an end on the side of the port 80 of the valve stem 60. The valve stem 60 is held by the valve guide 50 so as to be reciprocable in the axial direction of the valve stem 60. The inner peripheral surface of the through-hole 54 of the valve guide 50 and the outer peripheral surface of the valve stem 60 slide on each other. Because the valve guide 50 is formed of the porous sintered body, the valve guide 50 is impregnated with the lubricating oil stored in the lubricating oil chamber 70. This lubricating oil can suitably lubricate the valve guide 50 and the valve stem 60 that slide with each other. The stem seal 10 is provided on the side of the lubricating oil chamber 70 of the valve guide 50. The stem seal 10 controls the amount of lubricating oil flowing between the valve stem 60 and the valve guide 50. Accordingly, the valve stem 60 and the valve guide 50 can be appropriately lubricated. In addition, the stem seal 10 prevents the gas in the port 80 from leaking to the side of the lubricating oil chamber 70 from between the valve stem 60 and the valve guide 50. The stem seal 10 includes a reinforcing member 20 including a cylindrical main body 22 and a rubbery elastic member 30 provided integrally with the reinforcing member 20. The rubbery elastic member 30 is integrally formed with the reinforcing member 20 by vulcanization molding. The reinforcing member 20 includes a spring seat 24 extending from the end on the side of the port 80 of the cylindrical main body 22 toward an outer peripheral direction. A coil spring 65 is provided outside the stem seal 10. The coil spring 65 biases a valve including the valve stem 60 and the valve head in a direction from the port 80 toward the lubricating oil chamber 70. The end on the side of the cylinder head 90 of the coil spring 65 gives biasing force that is reaction force toward the cylinder head 90 to the spring seat 24. The spring seat 24 is biased toward the cylinder head 90 by the reaction force of the coil spring65. The stem seal 10 can be pressed against the cylinder head 90 by the coil spring65. The stem seal 10 is pressed by the coil spring 65, and fixed to the cylinder head 90. The reinforcing member 20 includes an inner flange 26 extending from the end on the side of the lubricating oil chamber 70 of the cylindrical main body 22 toward an inner peripheral direction. For example, the rubbery elastic member 30 is made of an elastomer. The rubbery elastic member 30 includes a large diameter portion 32 and a small diameter portion 42. The large diameter portion 32 is disposed on a radial outside of the valve guide 50. The small diameter portion 42 is disposed on the radial outside of the valve stem 60. The small diameter portion 42 of the rubbery elastic member 30 is located on a distal end side of the inner flange 26 of the reinforcing member 20. The small diameter portion 42 is held by the inner flange 26. The large diameter portion 32 and the small diameter portion 42 are both held by the reinforcing member 20 and are continuous with each other. The inner peripheral side of the small diameter portion 42 of the rubbery elastic member 30 is in contact with the outer peripheral surface of the valve stem 60. A first lip 44, a second lip 46, and a third lip 48 are provided on the inner peripheral surface of the small diameter portion 42. The first lip 44, the second lip 46, and the third lip 48 extend along the outer peripheral surface of the valve stem 60 and are in contact with the outer peripheral surface of the valve stem 60. The inner peripheral surface of the small diameter portion 42 other than the first lip 44, the second lip 46, and the third lip 48 is not in contact with the outer peripheral surface of the valve stem 60. The first lip 44 prevents excessive deformation of the third lip 48 due to back pressure from the gap between the valve stem 60 and the valve guide 50. The third lip 48 mainly prevents the lubricating oil in the lubricating oil chamber 70 from excessively flowing into the valve guide 50. The second lip 46 helps the first lip 44 and the third lip 48 to come into contact with the valve stem 60 at uniform contact pressure in the state where the stem seal 10 is assembled to the valve guide 50. An engagement groove 43 is provided on the outer peripheral surface of the small diameter portion 42. The engagement groove 43 goes around the outer peripheral surface of the small diameter portion 42. A garter spring 67 is provided in the engagement groove 43. The garter spring 67 is an annular spring that expands and contracts in the circumferential direction. The garter spring 67 biases the small diameter portion 42 in the inner diameter direction. In particular, the third lip 48 of the small diameter portion 42 is pressed against the valve stem 60 by the garter spring 67. A first seal 34, a second seal 36, and a third seal 38 are provided on the inner peripheral surface of the large diameter portion 32 of the rubbery elastic member 30. The first seal 34, the second seal 36, and the third seal 38 extend along the outer peripheral surface of the valve guide 50 and are in contact with the outer peripheral surface of the valve guide 50. The inner peripheral surface of the large diameter portion 32 other than the first seal 34, the second seal 36, and the third seal 38 is not in contact with the outer peripheral surface of the valve guide 50. The first seal 34 protrudes from the inner peripheral surface of the large diameter portion 32 toward the outer peripheral surface of the valve guide 50. The first seal 34 is located on the inner peripheral side of the main body 22 of the reinforcing member 20. The first seal 34 is located between the lubricating oil chamber 70 side end and the notch 52 (the first seal 34 is located opposite to the port 80 side end). The second seal 36 protrudes from the inner peripheral surface of the large diameter portion 32 toward the outer peripheral surface of the valve guide 50. The second seal 36 is located on the inner peripheral side of the main body 22 of the reinforcing member 20. The second seal 36 is located between the port 80 side end and the notch 52. The third seal 38 protrudes from the inner peripheral surface of the large diameter portion 32 toward the outer peripheral surface of the valve guide 50. The third seal 38 is located on the inner peripheral side of the main body 22 of the reinforcing member 20. The third seal 38 is located between the port 80 side end and the second seal 36. The notch 52 is located between the first seal 34 and the second seal 36. Because the inner wall surface of the notch 52 is not subjected to the sealing treatment, there is a possibility that the gas flows out from the notch 52. A space between the first seal 34 and the second seal 36 is sealed by the first seal 34 and the second seal 36, so that the gas flowing out from the notch 52 does not flow out to the side of the lubricating oil chamber 70. In addition, the gas flowing out from the notch 52 is blocked by the first seal 34 and the second seal 36, so that the gas does not flow into a sliding portion between the valve guide 50 and the valve stem 60. Accordingly, the valve guide 50 and the valve stem 60 can be prevented from being fixed to each other. The center (the center in the vertical direction in Fig. 1) in the length direction of the notch 52 is closer to the first seal 34 than to the second seal 36 in the length direction of the valve guide 50. In other words, a distance A between the center of the first seal 34 and the center of the notch 52 illustrated in Fig. 1 is smaller than a distance B between the center of the notch 52 and the center of the second seal 36.

Inclination of the stem seal 10 with respect to the valve guide 50 can be prevented by providing the third seal 38. The third seal 38 is located between the lubricating oil chamber 70 side end and a position of 1/3 from the port 80 side end of an entire lengthL of the stem seal 10. In other words, a distance C from the side of the port 80 of the entire length of the stem seal 10 to the third seal 38 illustrated in Fig. 1 is largerthan 1/3 of entire length L of the stem seal 10. Thus, a portion having a relatively large inner diameter is formed from the side of the port 80 over a length of at least 1/3 of entire length L of the stem seal 10. The portion having the relatively large inner diameter can be temporarily inserted into the valve guide 50, so that assembly of the stem seal 10 and the valve guide 50 is simplified. The valve stem seal structure of the first embodiment has the above-described structure. The lubricating oil can be held in the pores by configuring the valve guide 50 with the porous sintered body. The lubrication between the valve stem 60 and the valve guide 50 can be suitably performed by the lubricating oil held in the pores. In addition, because the valve guide 50 is made of the porous sintered body, there is the possibility that the gas from the port 80 flows out from the notch 52. However, the first seal 34 and the second seal 36 are provided so as to sandwich the notch 52, so that the gas can be prevented from flowing out to the side of the lubricating oil chamber 70 and the sliding portion between the valve guide 50 and the valve stem 60 by sealing the notch 52 with the first seal 34 and the second seal 36. As described above, according to the valve stem seal structure of the first embodiment, even when the valve guide 50 made of the porous sintered body in which the notch 52 is provided is used, the gas can be prevented from flowing out to the side of the lubricating oil chamber 70 and the sliding portion between the valve guide 50 and the valve stem 60 without degrading the productivity. (Second embodiment) With reference to Fig. 3, a second embodiment of the present disclosure will be described below. Fig. 3 is a longitudinal sectional view illustrating a valve stem seal structure of the second embodiment.

In the valve stem seal structure of the second embodiment, unlike the first embodiment, a fixing protrusion 41 fitted into the notch 52 is provided in the large diameter portion 32 of the rubbery elastic member 30. The sectional shape of the fixing protrusion 41 is substantially the same as the sectional shape of the groove constituting the notch 52. The fixing protrusion 41 is provided integrally with the large diameter portion 32 and the reinforcing member 20. The stem seal 10 canbe fixed to the valve guide 50 by fitting the fixing protrusion 41 into the notch 52. In the stem seal 10 of the second embodiment, the large diameter portion 32 and the reinforcing member 20 are disconnected near the side of the port 80 of the second seal 36. Accordingly, the third seal 38 and the spring seat 24 provided in the stem seal 10 in the first embodiment are not provided. In the second embodiment, a spring seat 69 separate from the stem seal 10 is provided. Also in the valve stem seal structure of the second embodiment, the first seal 34 and the second seal 36 are provided so as to sandwich the notch 52. Thegascanbe prevented from flowing out to the side of the lubricating oil chamber 70 and the sliding portion between the valve guide 50 and the valve stem 60 by sealing the notch 52 with the first seal 34 and the second seal 36. Other structures and operational effects are the same as those of the first embodiment. Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being interpreted by the terms of the appended claims.

Claims (5)

WHAT IS CLAIMED IS:

1. A valve stem seal structure comprising: a valve guide in which a valve stem penetrates an inside of the valve guide, the valve guide being disposed between a lubricating oil chamber and a port; and a stem seal provided on a lubricating oil chamber side of the valve guide, wherein the valve guide is a porous sintered body formed in a cylindrical shape, at least an outer peripheral surface of the valve guide is gas-sealed, the valve guide includes a through-hole through which the valve stem penetrates, the through hole extending in a longitudinal direction, and a notch recessed from the outer peripheral surface of the valve guide, the notch is provided on the lubricating oil chamber side in a length direction of the valve guide, the stem seal includes a reinforcing member including a cylindrical main body, and a rubbery elastic member provided integrally with the reinforcing member, and the rubbery elastic member includes a first seal located between a lubricating oil chamber side end and the notch, the first seal protruding to an inner peripheral side of the main body of the reinforcing member toward the outer peripheral surface of the valve guide, the first seal being in contact with the outer peripheral surface of the valve guide, and a second seal located between a port side end and the notch, the second seal protruding to the inner peripheral side of the main body of the reinforcing member toward the outer peripheral surface of the valve guide, the second seal being in contact with the outer peripheral surface of the valve guide.

2. The valve stem seal structure according to claim 1, wherein the reinforcing member further includes a spring seat that is continuous to a port side end of the main body and extends from the main body toward an outer peripheral direction.

3. The valve stem seal structure according to claim 1 or 2, wherein the rubbery elastic member further includes a fixing protrusion fitted to the notch.

4. The valve stem seal structure according to any one of claims 1 to 3, wherein a center in the length direction of the notch is closer to the first seal than to the second seal in the length direction of the valve guide.

5. The valve stem seal structure according to claim 1, 2, or 4, wherein the rubbery elastic member further includes a third seal located between the port side end and the second seal, the third seal protruding to the inner peripheral side of the main body of the reinforcing member toward the outer peripheral surface of the valve guide, the third seal being in contact with the outer peripheral surface of the valve guide, and the third seal is located between the lubricating oil chamber side end and a position of 1/3 from a port side end of an entire length of the stem seal.