JPH0511285Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a valve stem seal, and particularly to a valve stem seal for sealing intake and exhaust valves, etc. disposed in the cylinder head of an engine.

[Conventional technology]

This type of valve stem seal is used to seal the valve stems that open and close the intake valve that supplies a mixture of gasoline and air to the combustion chamber of an engine, and the exhaust valve that discharges exhaust gas from the combustion chamber after combustion. It is used.

FIG. 5 shows an example of the conventional engine. A cylinder head 1 is attached to the top of the engine, and a combustion chamber 2 located at the top of the cylinder of the engine body is formed in the cylinder head 1. ing. This combustion chamber 2 is communicated with an intake passage 3 that supplies a mixture of gasoline and air from a carburetor, a combustion injection device, etc., and an exhaust passage 4 that discharges exhaust gas after combustion. An intake valve 5 and an exhaust valve 6 are provided between the exhaust passage 4 and the combustion chamber 2, respectively.
is arranged so that it can be opened and closed freely. The valve stem 7 of each of these valves 5 and 6 is slidably inserted into a cylindrical guide 8 that is fitted by shrink fitting or the like so as to pass through the cylinder head 1. A valve stem seal 9 is fitted to the valve stem seal 9.

Further, a valve spring 18 is attached to the upper end of the valve stem 7 of each of the valves 5 and 6, respectively, for biasing each valve 5 and 6 upward (in the direction of closing the valve). Further, a cam 19 connected by a chain or the like to a crankshaft which is rotated by the vertical movement of the piston is in contact with the upper end of the valve stem 7 of the valves 5 and 6. The accompanying rotation of the cam 19 opens and closes the valves 5 and 6 at desired timings.

As shown in FIG. 6, this valve stem seal 9 is a seal made of an elastic material such as rubber, inside a substantially cylindrical outer shell member 10 having an inner flange 11 formed at its upper end. It is constructed by baking and integrating the materials 12. The sealing material 12 includes a main body 13 provided inside the outer shell member 10 and a seal cylinder 14 connected to the main body 13 so as to come out above the outer shell member 10.
The guide 8 is attached to the guide 8 by fitting an engagement protrusion 15 formed on the inner peripheral surface of the lower part of the guide 8 into an annular engagement groove 16 at the upper end of the guide 8. The valve stem 7 is slidably inserted into the seal cylinder 14, and a seal lip 17 having an annular tip 17a is formed protruding from the inner surface of the seal cylinder 14, as shown in an enlarged view of FIG. Furthermore, a tightening spring 20, which is a coil spring formed into an annular shape, is fitted to the outer circumference of the seal tube 14, and the diameter of the seal tube 14 is reduced by the tightening force of the tightening spring 20, so that the seal lip 17 and its diameter are reduced. The peripheral portion is in close contact with the outer peripheral surface of the valve stem 7 to form a seal.

The valve stem seal 9 formed in this manner has the lip tip 17a of the seal lip 17 when the valve stem 7 is reciprocating in the axial direction.
A thin oil film is formed between the valve stem 7 and the outer peripheral surface of the valve stem 7, and the lubricating oil is passed through the oil film to the valve stem 7.
The sealing is performed while being supplied to the sliding portion between the guide 8 and the guide 8.

The amount of oil leaked by the valve stem seal 9 needs to be controlled within an appropriate range in relation to the slidability of the valve stem 7 within the guide 8.
, the curvature of its tip 17a, and the tightening position of the tightening spring 20, that is, the seal lip 1.
This is done by changing the offset position of the tightening spring 20 with respect to the tip 17a of the spring 7.

[The problem that the idea aims to solve]

However, when the conventional valve stem seal 9 reduces the amount of oil leakage, the valve stem 7
If the amount of circulating oil supplied to the sliding parts between the valve stem and the guide 8 decreases, and the engine rotates at high speed or is operated for a long period of time, the valve stem 7 may seize on the guide 8, causing engine trouble. Ta. For this reason, as mentioned above, the amount of oil leakage is adjusted, but adjustment is troublesome because it is necessary to change various factors such as the angle of the seal lip, the curvature of its tip, and the offset position of the tightening spring 17. I was getting used to it. Therefore, in the past, in order to ensure safety, it was necessary to set the amount of oil leakage higher than necessary.

The present invention was developed in consideration of these points, and even if the amount of oil leakage is reduced, an appropriate amount of oil can be supplied to the sliding part between the valve stem and the guide.
It is an object of the present invention to provide a valve stem seal that can prevent a valve stem from seizing on a guide and, therefore, can easily adjust the amount of oil leakage.

[Means to solve the problem]

In order to achieve the above object, the valve stem seal of the present invention is a valve stem seal that is fitted to the end of a guide that guides the sliding of a valve stem inserted in the axial direction to perform a seal. a seal cylinder that is movably inserted, a seal lip that has an annular tip that contacts the outer surface of the valve stem and projects from the inner surface of the seal cylinder, and a seal lip that is attached to the outer periphery of the seal lip to form a seal. A tightening spring that applies a tightening force to reduce the diameter of the cylinder is provided, and the radius of the annular tip of the seal lip is made non-uniform in the circumferential direction, so that the tip has a non-uniform distribution of surface pressure in the circumferential direction. It is characterized by being molded into a shape that closely fits the outer surface of the stem.

[Effect]

According to the valve stem seal of the present invention, the annular tip of the seal lip is in close contact with the outer peripheral surface of the valve stem with uneven surface pressure in the circumferential direction. A portion with a smaller amount of oil leakage is formed, and the amount of oil leakage necessary to prevent seizure of the valve stem can be secured than the portion with a larger amount of oil leakage.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4. In addition, in these figures, the same parts as in the prior art are given the same reference numerals.

The valve stem seal 9a of this embodiment is constructed by integrating an outer shell member 10 and a sealing material 12, as shown in FIG. The outer shell member 10 is formed into a substantially cylindrical shape with an inner flange 11 formed at the upper end, and the sealing material 12 is baked into the outer shell member 10 so as to be integrated with the outer shell member 10. There is. The sealing material 12 is entirely made of an elastic member such as rubber, and has a main body part 13 fitted into the guide 8 and a seal cylinder 14 connected above the main body part 13. An engaging annular groove 16 for the guide 8 is provided at the lower part of the inner surface of the main body 13.
(See Figure 6)
It is formed in steps. The seal cylinder 14 is the outer shell member 1
0, and the valve stem 7 is slidably inserted therethrough. A seal lip 21 is formed on the inner peripheral surface of the seal cylinder 14 and projects inwardly in a tapered shape. This seal lip 21 seals the valve stem 7 by closely contacting the valve stem 7 inserted into the seal cylinder 14, and the most protruding part is an annular tip 22a having a predetermined curvature. . Further, a tightening spring 20, which is a ring-shaped coil spring, is fitted onto the outer peripheral surface of the seal cylinder 14.

In the above configuration, the annular tip 22 of the seal lip 21 is formed into a shape in which arcuate portions 22a and linear portions 22b are alternately continuous, as shown in FIGS. 2 and 3. They are formed at predetermined intervals on a circular locus of radius R by cutting out a circle with the same radius R as the circular arc portion 22a at a predetermined angle, and the straight portion 22b is formed by linearly connecting the cut portions of this circle. has been done. Therefore, the radial positions of both are such that the straight portion 22b is located on the inside and the circular arc portion 22a is located on the outside. When the valve stem 7 is inserted into the seal cylinder 14, the straight portion 22b is placed under a large contact pressure. abuts against the outer peripheral surface of the valve stem 7,
The arcuate portion 22a makes contact with a smaller contact pressure than this. Due to this contact with the valve stem 7, the straight portion 22b having a large contact pressure is greatly deformed. Along with this deformation, the straight portion 22b and the circular arc portion 2
The contact portion 22c, which is the contact point with the valve stem 2a, contacts the valve stem 7 with the smallest contact pressure. In this embodiment, the arcuate portion 22a is formed to have a predetermined length in the axial direction of the inner surface of the seal cylinder 14, as shown in FIG. Rather, a straight portion 22b and an arcuate portion 22a are formed continuously in the axial direction over the inner surface of the seal lip 21 and the seal cylinder 14.

Figure 4 shows the seal lip 2 formed in this way.
The surface pressure distribution of the annular tip 22 of No. 1 to the valve stem 7 is shown, and the maximum surface pressure (surface pressure of the straight portion 22b) and minimum surface pressure (the surface pressure of the contact portion 22b) are
c) appear alternately, and an intermediate surface pressure (the surface pressure of the circular arc portion 22a) appears between the maximum and minimum surface pressures, and the surface pressure distribution in the circumferential direction is uneven as a whole. It's summery.

Next, the operation of this embodiment will be explained.

In this embodiment, since the contact pressure distribution in the circumferential direction at the contact area between the tip 22 of the seal lip 21 and the valve stem 7 is uneven, the amount of lubricating oil leaking from the area where the contact pressure is small is reduced. It becomes larger than that from areas with large surface pressure. When the valve stem 7 reciprocates, leakage of lubricating oil is promoted mainly from the portions where the surface pressure is small, and the valve stem 7 reciprocates in a sufficiently lubricated state. Therefore, when the valve stem 7 slides back and forth within the guide 8, the lubricating oil provides a sufficient lubrication effect, so that the valve stem 7 does not seize on the guide 8. Therefore, even if the amount of oil leaked from the valve stem seal 9a is reduced, a sufficient amount of oil to prevent seizure can always be ensured, and furthermore, it can be easily adjusted.

The shape of the annular tip of the seal lip that enables non-uniform surface pressure distribution in the circumferential direction may be a polygon, or may be a series of alternating arcuate portions with different radii. .

Note that the present invention is not limited to the above-mentioned embodiments, and can be modified as necessary.

[Effect of idea]

Since the valve stem seal of the present invention is constructed and operates in this manner, it is necessary to ensure a sufficient amount of oil leakage from the bottom of the circumferential surface pressure of the seal lip to prevent seizure of the valve stem. Since the valve stem slides within the guide in this state, seizure of the valve stem can be reliably prevented, and the amount of oil leakage can be easily adjusted.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the valve stem seal of the present invention, Fig. 2 is an enlarged sectional view of the seal lip, Fig. 3 is an enlarged plan view showing the shape of the seal lip, and Fig. 4 is an enlarged sectional view of the seal lip. A characteristic diagram showing the surface pressure distribution in the circumferential direction of the sliding contact area with the valve stem. Figure 5 is a cross-sectional view of the engine head section equipped with a conventional valve stem seal. Figure 6 is a cross-sectional view of the conventional valve stem seal. , FIG. 7 is an enlarged view of a portion of FIG. 6. 7... Valve stem, 8... Guide, 9a...
Valve stem seal, 14...Seal tube, 21...
...Seal lip, 22...Tightening spring.

Claims (1)

[Scope of utility model registration request] A valve stem seal that is fitted to the end of a guide that guides the sliding of a valve stem inserted in the axial direction to perform sealing includes a seal cylinder through which the valve stem is slidably inserted; a seal lip that has an annular tip that contacts the outer surface in an annular shape and projects from the inner surface of the seal tube; and a tightening spring that is attached to the outer periphery of the seal lip and applies a tightening force that reduces the diameter of the seal tube. The annular tip of the seal lip is shaped to have a non-uniform radius in the circumferential direction so that the tip comes into close contact with the outer surface of the valve stem with a non-uniform surface pressure distribution in the circumferential direction. and valve stem seals.