Valve stem seal

Abstract

 To provide a valve stem seal 1 of the structure which is excellent in mechanical strength in response to the high output of an internal combustion engine without causing difficulty of manufacture. A valve stem seal includes a mounting ring 11 arranged so as to surround the outer periphery of a valve guide 3 protruding from a cylinder head 2, a seal lip 12 integrally provided at one end of the mounting ring 11 and slidably brought into close contact with the outer peripheral surface of a valve stem 4 which is inserted through the valve guide 3 and biased in the axial direction by a valve spring 5, a spring receiving ring 14 arranged at the outer periphery of the mounting ring 11 and pushed against the cylinder head 2 by the valve spring 5. The spring receiving ring 14 has a rigidity higher than the mounting ring 11, and has an internal diameter portion locked to a locking groove 11c formed at the outer peripheral surface of the mounting ring 11, and, a groove shoulder of the locking groove 11c on the side of the seal lip 12 is formed with a deformable projecting portion 11e having a diameter larger than the internal diameter of the mounting ring 11 and permitting the internal diameter portion of the spring receiving ring 14 to axially pass therethrough.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to a valve stem seal capable of sealing a valve stem of an intake/exhaust valve of an internal combustion engine and a valve guide supporting the valve stem in an axially movable manner.

Description of the Related Art

[0002] The gap between the valve stem of an intake/exhaust valve of an internal combustion engine and the valve guide supporting the valve stem in an axially movable manner is sealed by a valve stem seal. Fig. 5 is a half cross-sectional view illustrating a valve of an internal combustion engine which is provided with a valve stem seal of a related art, and Fig. 6 is a half cross-sectional view illustrating the mounted state of a valve stem seal of a related art.

[0003] In Fig. 5, reference numeral 101 denotes a cylinder head, reference numeral 102 denotes an exhaust port formed in the cylinder head 101, reference numeral 103 denotes a valve for opening and closing an intake port (or exhaust port) 102, reference numeral 104 denotes a valve stem extending from the valve 103, reference numeral 105 denotes a valve guide penetrating the cylinder head 101 and supporting the valve stem 104 in an axially movable manner, reference numeral 106 denotes a valve spring for biasing the valve 103 in a valve closing direction via the valve stem 144, and reference numeral 107 denotes a cam bringing into contact with a lifter 108 installed at an upper end of the valve stem 104 and pushing the valve 103 in a valve opening direction against a biasing force of the valve spring 106 whenever the cam is rotated once by a camshaft 107a. A valve stem seal 110 is mounted on the valve guide 105.

[0004] More specifically, the valve stem seal 110 includes, as shown in Fig. 6, a valve guide seal portion 111 brought into close contact with an upper outer peripheral surface of the valve guide 105, a seal lip 112 extending from an upper end of the valve guide seal portion and slidably brought into close contact with the outer peripheral surface of the valve stem 104, and a mount ring 113 of a metal material buried in the valve guide seal portion 111. The valve stem seal prevents engine oil in an oil chamber O formed in an upper portion of the valve guide 105 from leaking from a gap G between the valve stem 104 and the valve guide 105. A flange 113a is installed at one end of the mounting ring 113 and abuts against the cylinder head 101.

[0005] The flange 113a installed at the mounting ring 113 serves as a base receiving a load of the valve spring 106 and fixing the valve stem seal 110 by using the load of the valve spring 106. That is, by a pressing force of the valve spring 106 toward the flange 113a, it is possible to prevent movement or detachment of the valve stem seal 110 from the valve guide 105 in a release direction due to the pressure which is applied to a space S behind the seal lip 112 via the gap G between the valve stem 104 and the valve guide 105 from a combustion chamber in the cylinder. In this instance, a valve stem seal having the configuration similar to that in Fig. 6 is disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-249200 and Japanese Patent Application Laid-Open No. 09-177522.

SUMMARY OF THE INVENTION

[0006] However, there has recently been a tendency towards increase of the load on the valve spring 106 accompanying the increasing power of the internal combustion engine. In the valve stem seal of the related art shown in Fig. 6 or disclosed in the above-described publications, since the flange 113a formed on the mounting ring 113 is made of a soft metal plate which can be formed by press molding, there is are concerns about deficiency in the strength thereof. Accordingly, the idea of using a hard metal material having high strength as the mounting ring 113 so as to reinforce the insufficient strength has been considered. In this instance, however, there is a problem in that machining or press forming of the mounting ring 113 becomes difficult to impossible.

[0007] In view of the above-mentioned problem, an object of the invention is to provide a valve stem seal of a configuration which does result in fabrication problems and increases the mechanical strength thereof so as to cope with a higher power internal combustion engine.

[0008] As a means for effectively solving the above-mentioned object, the valve stem seal of the invention according to claim 1 includes a mounting ring arranged so as to surround the outer periphery of a tubular valve guide protruding from a cylinder head; a seal lip integrally provided at one end of the mounting ring and slidably brought into close contact with the outer peripheral surface of a valve stem which is inserted through the valve guide and biased in the axial direction by a valve spring; and a spring receiving ring arranged at the outer periphery of the mounting ring and pushed against the cylinder head by the valve spring, wherein the spring receiving ring has rigidity higher than the mounting ring, and has an internal diameter portion locked to a locking groove formed at the outer peripheral surface of the mounting ring, and a groove shoulder of the locking groove on the side of the seal lip is formed with a deformable projecting portion having a diameter larger than the internal diameter of the mounting ring and permitting the internal diameter portion of the spring receiving ring to axially pass therethrough. The projecting portion is easily deformed by the interference of the internal diameter portion of the spring receiving ring in a process of inserting the spring receiving ring onto the mounting ring from the end of the seal lip side, thereby permitting the internal diameter portion to pass through the locking groove side. After the spring receiving ring is locked to the locking groove, the axial movement of the spring receiving ring is restricted.

[0009] In the valve stem seal according to claim 2, a plurality of the projecting portions is formed at predetermined intervals in a peripheral direction in the configuration according to claim 1.

[0010] With the valve stem seal according to claim 1, since the spring receiving ring is fabricated of a material different from the mounting ring, the spring receiving ring can have strength higher than that of the mounting ring. For this reason, durability of the spring receiving ring can be increased against the load from the valve spring, and it is possible to easily assemble the spring receiving ring to the locking groove of the mounting ring.

[0011] With the valve stem seal according to claim 2, in addition to the effect obtained by the invention of claim 1, the assembly of the spring receiving ring can be further easily performed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] 

Fig. 1 is a half cross-sectional view illustrating a mounting state of a valve stem seal according to a preferred embodiment of the invention.

Fig. 2 is a side view taken along a half of a valve stem seal according to a preferred embodiment of the invention to illustrate a state before a spring receiving ring is assembled to a mounting ring.

Fig. 3 is a half cross-sectional view illustrating a process of assembling a spring receiving ring to a mounting ring in a valve stem seal according to a preferred embodiment of the invention.

Fig. 4 is a half cross-sectional view illustrating a state in which a spring receiving ring is assembled to a mounting ring in a valve stem seal according to a preferred embodiment of the invention.

Fig. 5 is a half cross-sectional view illustrating a valve of an internal combustion engine which is provided with a valve stem seal of a related art.

Fig. 6 is a half cross-sectional view illustrating the mounting state of a valve stem seal of a related art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, a valve stem seal according to a preferred embodiment of the invention will be described with reference to the accompanying drawings.

[0014] First, in Fig. 1, reference numeral 1 denotes a valve stem seal according to the invention, reference numeral 2 denotes a cylinder head of an internal combustion engine, reference numeral 3 denotes a valve guide penetrating the cylinder head 2 made of a cylindrical sintered metal and having an upper portion protruding from the cylinder head 2, reference numeral 4 denotes a valve stem inserted into the valve guide 3 and having a valve (not shown) formed at a lower end thereof, and 5 denotes a valve spring for biasing the valve (valve stem 4) in a valve closing direction (upward side on the figure) with respect to an axial direction via the valve stem 4.

[0015] The valve stem seal 1 includes a mounting ring 11 arranged so as to surround the outer periphery of the valve guide 3 protruding from the cylinder head 2, a seal lip 12 integrally provided at one end of the mounting ring 11 and slidably brought into close contact with the outer peripheral surface of the valve stem 4, a valve guide seal portion 13 installed on the inter peripheral surface of the mounting ring 11 and brought into close contact with the outer peripheral surface of the valve guide 3, a spring receiving ring 14 locked to the outer periphery of the end of the cylinder head 2 side in the mounting ring 11 and pushed against the cylinder head 2 side by the valve spring 5, and a garter spring 15 mounted onto the outer periphery of the seal lip 12. The seal lip 12 and the valve guide seal portion 13 are formed in succession, and are integrally formed with the mounting ring 11 of a metal material by a rubber-type elastic material (e.g., rubber material or synthetic resin material having rubber-like elasticity).

[0016] In the valve stem seal 1, the mounting ring 11 is fabricated by plastic working such as press forming of metal. The mounting ring has an axial length longer than a projecting distance of the valve guide 3 from the cylinder head 2. The mounting ring 11 has a body portion 11 a and an inward flange portion 11 b bent and formed at an upper end of the body portion. The outer peripheral surface of the mounting ring is provided with a locking groove 11c at a lower end thereof, and the locking groove extends in the peripheral direction. In the locking groove 11c, the groove shoulder opposite to the seal lip 12 is constituted of an outward flange portion 11 d bent and formed at an end of the cylinder head 2 side of the mounting ring 11. In the locking groove 11c, the groove shoulder of the seal lip 12 side is constituted of a projecting portion 11e.

[0017] In the valve stem seal 1, the seal lip 12 is integrally cure-adhered to the inward flange portion 11b so that a base portion thereof encloses the inward flange portion 11b of the mounting ring 11. The seal lip extends therefrom in an upward direction, so that the internal diameter portion in the vicinity of a distal end (upper end) is slidably brought into close contact with the outer peripheral surface of the valve stem 4 protruding from the upper end opening of the valve guide 3.

[0018] In the valve stem seal 1, the valve guide seal portion 13 is integrally cure-adhered to the inner peripheral surface of the body portion 11 a of the mounting ring 11, and is provided with a plurality of seal bosses 13a in a peripheral direction at regular intervals. The plurality of seal bosses 13a are brought into close contact with the outer peripheral surface of the valve guide 3 with appropriate tolerance for interference.

[0019] In the valve stem seal 1, the spring receiving ring 14 is formed in a washer shape by a hard metal material having rigidity higher than the mounting ring 11. The internal diameter portion of the spring receiving ring is provided with projecting portions 14a to be locked and stepped concave portions 14b beneath the projecting portions 14a at regular intervals in a peripheral direction. The projecting portion 14a to be locked is locked to the locking groove 11c of the mounting ring 11, and the outward flange portion 11d of the mounting ring 11 is loose-fitted into the stepped concave portion 14b.

[0020] The portion of the mounting ring 11 which extends from the projecting portion 11e to the outward flange portion 11d is separated in a peripheral direction by a plurality of slits 11f, as shown in Fig. 2. For this reason, the mounting ring 11 has an appropriate spring property. Each of the projecting portions 11e has an external diameter slightly larger than an internal diameter of the projecting portion 14a to be locked of the spring receiving ring 14, and a surface facing a side (seal lip 12 side) opposite to the locking groove 11c is formed in a gentle inclined surface 11g. The external diameter portion of the projecting portion 11e is formed to be elastically deformed so that it permits the internal diameter portion of the projecting portion 14a to be locked to pass therethrough in an axial direction under a relatively small axial load.

[0021] The garter spring 15 is formed by connecting coil springs of metal in a circular form, and, as shown in Fig. 2, is removably fitted in the circular groove 12a formed on the outer peripheral surface in the vicinity of the distal end (upper end) in the seal lip 12 to compensate a fastening force of the seal lip 12 with respect to the outer peripheral surface of the valve stem 4.

[0022] With the valve stem seal 1 having the above configuration, the mounting ring 11 integrally formed with the seal lip 12 and the valve guide seal portion 13 is assembled with the spring receiving ring 14 which is made as a member different from the mounting ring.

[0023] In the assembly of the spring receiving ring 14 to the mounting ring 11, as shown in Fig. 3, when the spring receiving ring 14 is inserted onto the end of the seal lip 12 side in the mounting ring 11 and is moved toward the locking groove 11c, the projecting portion 14a to be locked of the internal diameter portion of the spring receiving ring 14 interferes with the vicinity of the external diameter portion of the projecting portion 11e formed on the mounting ring 11, in which the projecting portion 11e has a diameter slightly larger than the internal diameter of the projecting portion 14a to be locked. However, since the portion of the mounting ring extending from the projecting portion 11e to the outward flange portion 11d is separated in a peripheral direction by the plurality of slits 11f, the portion is easily deformed in an internal diameter side by the relative mounting of the projecting portion 14a to be locked onto the inclined surface 11g due to the pressing load applied to the spring receiving ring 14 in an insertion direction, thereby permitting the projecting portion 14a to be locked to pass therethrough toward the locking groove 11c. Accordingly, as shown in Fig. 4, the spring receiving ring 14 is locked to the locking groove 11c of the mounting ring 11 even by a relatively light force.

[0024] After the spring receiving ring 14 is locked to the locking groove 11c, the axial movement of the spring receiving ring is restricted by the interference of the outward flange portion 11d forming the groove shoulder of the locking groove 11c or the projecting portion 11e, thereby preventing the release of the spring receiving ring 14. Consequently, it is possible to easily treat the valve stem seal in a step before it is mounted on the valve shown in Fig. 1.

[0025] Further, in the mounting state shown in Fig. 1, since the valve guide seal portion 13 comes into close contact with the outer peripheral surface of the valve guide 3 protruding from the cylinder head 2 with appropriate tolerance for interference and the seal lip 12 is slidably brought into contact with the outer peripheral surface of the valve stem 4 at the upper portion of the valve guide 3, the valve stem seal 1 having the above configuration suppresses leakage of engine oil from an oil chamber of the upper portion of the cylinder head 2 via the gap G between the outer peripheral surface of the valve stem 4 and the inner peripheral surface of the valve guide 3.

[0026] In the spring receiving ring 14 which is pressed against the cylinder head 2 by the valve spring 5 biasing the valve stem 4 in the valve closing direction (upward direction), the projecting portion 14a to be locked of the internal diameter portion of the spring receiving ring 14 is locked to the locking groove 11c of the mounting ring 11. For this reason, for example, even though a load is applied to the valve stem seal 1 from the valve guide 3 in a release direction by the pressure applied to the space S behind the seal lip 12 from a combustion chamber side (not shown) in the cylinder via the gap G between the valve stem 4 and the valve guide 3, the groove shoulder (outward flange portion 11d) opposite to the seal lip 12 is prevented from released from the locking groove 11c of the mounting ring 11 by the interference of the projecting portion 14a to be locked of the spring receiving ring 14. In other words, in the valve stem seal 1, the mounting ring 11 is pushed by the valve spring 5 via the spring receiving ring 14. Accordingly, it is possible to reliably fix the valve stem seal 1, without depending upon the tolerance for interference of the valve guide seal portion 13 with respect to the outer peripheral surface of the valve guide 3.

[0027] In addition, since the spring receiving ring 14 is fabricated differently from the mounting ring 11 which is formed by plastic working, the spring receiving ring 14 can be made of a material having strength higher than that of the mounting ring 11. For this reason, it is possible to sufficiently increase the mechanical strength of the spring receiving ring 14 against the load of the valve spring 5 and the load of a release direction due to the pressure applied to the space S behind the seal lip 12 via the gap G between the valve stem 4 and the valve guide 3.

Claims

1. A valve stem seal comprising:

a mounting ring arranged so as to surround the outer periphery of a tubular valve guide protruding from a cylinder head;

a seal lip integrally provided at one end of the mounting ring and slidably brought into close contact with the outer peripheral surface of a valve stem which is inserted through the valve guide and biased in the axial direction by a valve spring; and

a spring receiving ring arranged at the outer periphery of the mounting ring and pushed against the cylinder head by the valve spring,

wherein the spring receiving ring has rigidity higher than the mounting ring, and has an internal diameter portion locked to a locking groove formed at the outer peripheral surface of the mounting ring, and
a groove shoulder of the locking groove on the side of the seal lip is formed with a deformable projecting portion having a diameter larger than the internal diameter of the mounting ring and permitting the internal diameter portion of the spring receiving ring to axially pass therethrough.

2. The valve stem seal as claimed in claim 1, wherein a plurality of the projecting portions is formed at predetermined intervals in a peripheral direction.

Drawing