JPH0712643Y2 - Valve drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a valve operating system in which a ceramic intake / exhaust valve and a valve spring retainer are integrally fixed via a cotter.

[Conventional technology]

In recent years, internal combustion engines have become high-speed and high-power, and valves for intake and exhaust of the combustion chamber of the engine are placed in a more severe environment both mechanically and thermally. It is proposed to use a ceramic having excellent heat resistance. By the way, generally, in a valve train in which a valve spring retainer is locked to a valve stem via a cotter, the valve spring resonates when the engine is over-rotating, and the retainer and the cotter tend to make oscillating motions other than the normal vertical motion. It is in. As a result, a bending load acts on the stem portion of the valve, and the local contact between the stem portion and the cotter causes stress to concentrate on that portion. Therefore, as described above, the valve operating device in which the valve itself is made of ceramic has a problem that the ceramic valve having low fatigue strength is damaged. To solve such a problem, for example, in Japanese Utility Model Laid-Open No. 61-101604, a hollow ring that relieves stress from the cotter is provided at the locking portion between the cotter and the stem portion, and the cotter and the valve lifter are engaged. Let
A valve operating system is disclosed in which a driving force of a camshaft indirectly acts on a valve body via a valve lifter and a cotter to prevent a large load from being applied to a ceramic valve. In addition, in Japanese Utility Model Publication No. 63-19012,
A valve train that tries to reduce local stress concentration by forming a heat-resistant stress buffer layer such as Cu, Ni metal or fluorine-based heat-resistant plastic on one of the contact surfaces between the stem and the cotter. Is disclosed.

[Problems to be solved by the device]

In the above-mentioned valve operating device in which the cotter and the valve lifter are engaged, although the stress from the cotter is relieved to some extent by the hollow ring, the motion of the cotter is restrained by the valve lifter, so when the engine is running at excessive speed, If the inertial force of the valve train becomes larger than the spring load of the valve spring, a gap will be created between the inner surface of the valve spring retainer and the outer periphery of the cotter, and stress will concentrate on the contact area between the retainer and the cotter. There is a problem of impairing the durability of. Further, in the valve gear having the heat-resistant stress buffer layer formed, since the coating itself of Cu, Ni metal or fluorine-based heat-resistant plastic does not have wear resistance,
During engine overspeed operation, if a slight slip occurs between the outer circumference of the stem and the inner circumference of the cotter, the stress buffer layer wears and eventually the stem and the base material of the cotter come into contact with each other. A crack may occur in the part. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a valve operating device that does not damage the retainer and the cotter and does not damage the valve stem portion even during engine overspeed operation. .

[Means for Solving the Problems]

According to the present invention for the above purpose, the valve spring retainer is locked to the stem part of the ceramic intake / exhaust valve through the cotter, and at least one of the contact surfaces of the cotter and the stem part is wear-resistant. And a stress buffer layer having a two-layer structure of a PTFE (polytetrafluoroethylene) layer and a Ni-P alloy layer in which PTFE fine particles are dispersed, and ,
There is provided a valve operating device in which the PTFE layer is arranged on a contact surface side with a mating member and the Ni—P alloy layer is arranged on a base material side.

[Action]

The stress buffer layer has a low friction coefficient on the contact surface side with the mating member.
With a two-layer structure in which a PTFE layer is arranged and a Ni-P alloy layer with high hardness is arranged on the base metal side, it is possible to obtain a stress buffer layer with a low coefficient of friction and high hardness, and the stress buffer The wear resistance of the layer is significantly improved. In addition, PT is used for the Ni-P layer.
Since the FE fine particles are dispersed, the elasticity of the Ni-P layer is improved. Therefore, even if a slight slip occurs between the cotter and the stem portion during overspeed operation of the engine, the stress buffer layer does not wear due to wear resistance, and contact between the base materials is avoided. . Further, since the cotter is provided between the valve spring retainer and the stem portion of the valve and is not restrained by the valve lifter, the cotter and the retainer move up and down as a unit, and there is no gap between the cotter and the retainer.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

In the first embodiment shown in FIG. 1, 1 is a valve for intake or exhaust of an engine, and this valve 1 is made of ceramic and comprises a valve body portion 1a and a cylindrical stem portion 1b. . An annular groove 2 is formed in the stem 1b of the valve 1 near the upper end. Reference numeral 3 denotes a metal cotter, which has a plurality (for example, two) of split wrapping type and has a substantially cylindrical shape when assembled. Such a cotter 3 is mounted on the stem 1b of the valve 1 and has a ridge 3a having a semicircular cross section which engages with the groove 2 on the inner peripheral surface.
Are integrally formed along the circumferential direction. 4 is a cotter 3
Is a valve spring retainer fitted to the outer peripheral surface of, which is composed of an annular portion 4a having a mounting hole inside and a collar portion 4b,
The inner peripheral surface of the annular portion 4a is tapered in the opposite direction to the outer peripheral surface of the cotter 3. Reference numeral 5 denotes a valve spring provided between the valve 1 and a cylinder head (not shown), which moves the valve 1 axially upward via the valve spring retainer 4 and the cotter 3 when the valve is closed. is there. Reference numeral 6 is a valve lifter provided when the present invention is applied to a direct-type engine, and 7 is a cam shaft for driving the valve 1.

When the present invention is applied to an engine that indirectly drives a valve via a rocker arm (not shown), the valve lifter is not normally provided and the rocker arm directly contacts the top of the valve stem. .

According to the present embodiment, in the valve operating device configured as described above, the stress buffer layer 8 having wear resistance is formed on the outer surface of the cotter 3. The stress buffer layer 8 is formed by electroless plating a Ni-P alloy containing PTFE (polytetrafluoroethylene) fine particles on a metal base material forming the cotter 3,
After that, it is obtained by hardening the plated surface by heat treatment (age hardening treatment) (“Nyflow” product name), and its structure is, as shown in FIG. 2, PTFE extending over a thickness of several μm from the surface. Layer part 8a and Ni-P containing PTFE particles
It is composed of the alloy layer portion 8b and (the total thickness of the tank 8 is 10
It is preferably at least μm. ). As a result, the layer portion 8a has a small friction coefficient (0.04 to 0.08) due to the PTFE layer and the layer portion 8b has
The Ni-P alloy makes it possible to increase the hardness (HV 820), which ensures the wear resistance of the layer itself, and the layer portion 8b is configured as an elastic layer that relieves stress due to the elasticity of the mixed PTFE fine particles. It becomes possible to do. The layer portion 8a may be eliminated if only the relaxation of stress is taken into consideration. Hereinafter, the operation of the valve gear according to the present embodiment and the operation of the stress buffer layer 8 will be described.

When the engine is operating, the valve 1 moves up and down in the axial direction
The exhaust passage (not shown) is opened and closed, but at this time, the cotter 3 firmly contacts the stem portion 1b by the wedge action with the retainer 4. At this time, the stress buffer layer 8 is appropriately deformed between the cotter 3 and the stem portion 1b in accordance with the outer peripheral shape of the stem portion 1b to avoid local contact between the cotter 3 and the stem portion 1b, and to make a wide contact. The stem portion 1b is supported by its area.
In addition, the valve spring retainer 4 is
Even if the cotter 3 swings, the stress buffer layer 8 follows this movement and is deformed so that the contact area between the valve stem portion 1b and the cotter 3 is as large as possible. Stress concentration is relieved and ceramic valve 1
The bending load on the steel is reduced and fatigue failure does not occur.

In addition, in this embodiment, since the hardened layer portion 8a of the stress buffer layer 8 ensures the wear resistance of the layer itself, a slight slip occurs between the valve stem portion 1b and the cotter 3 during engine overspeed operation. However, the layer 8 will not be worn away, and the problem of breakage of the valve 1 due to contact between the base materials and the resulting stress concentration will be solved. According to the present embodiment, the cotter 3 does not engage with the valve lifter 6 as shown in FIG. 1, but the driving force transmitted from the camshaft 7 to the valve lifter 6 is
(Stem part 1b), cotter 3, retainer 4 transmitted in order,
Since the cotter 3 and the retainer 4 integrally move due to the wedge action of the valve spring 5 in combination with the upward biasing force, there is no gap between the cotter and the retainer, and the durability thereof is not impaired. .

FIG. 3 shows a second embodiment according to the present invention. In this figure, the same elements as those in FIG. 1 are designated by the same reference numerals.

According to this embodiment, an annular groove 3b is formed on the inner peripheral surface of the cotter 3 ', similar to the groove 2 of the stem portion 1b, and an elastically deformable hollow ring is formed in the space defined by the grooves 2 and 3b. 9 is fitted. As a result, the hollow ring 9 relaxes the tightening force on the stem portion 1b due to the wedge action between the cotter 3'and the retainer 4 and the bending load from the cotter 3'generated during engine operation, and the relaxed stress. The degree of concentration is further alleviated by the stress buffer layer 8 interposed between the stem portion 1b and the cotter 3 ', and the contact area between the two is expanded to further reduce local stress concentration on the stem portion 1b. .

FIG. 4 shows a third embodiment of the present invention in relation to the embodiment shown in FIG. 3. According to this embodiment, the most stress is applied to the contact portion between the cotter 3'and the stem portion 1b. The stress buffer layer 8 having wear resistance is formed in an annular shape on the portion where concentration is easy, that is, on the outer periphery of the stem portion 1b in contact with the lower end portion of the cotter 3. That is, also in this embodiment, the action is to prevent the valve stem portion 1b from being cut off by further relaxing the tightening force and bending load relaxed by the hollow ring 9 by the stress buffer layer 8. Although not shown in connection with the present embodiment, the stress buffer layer 8 may be formed over the cotter contact region of the stem portion 1b including the groove 2.

As described above with reference to the respective embodiments, the present invention relaxes the rigidity of the cotter and the stem portion by interposing the stress buffer layer between the stem portion and the cotter, and avoids local stress concentration on the stem portion. It is intended to prevent cutting damage. Further, by providing the stress buffer layer with abrasion resistance, it is ensured that the layer itself continues to exist and the stress buffer action is not impaired due to engine operating conditions and long-term use.

[Effect of device]

As described above, according to the present invention, the PTFE layer and the Ni-P alloy layer in which the PTFE fine particles are dispersed are provided on at least one of the contact surfaces of the cotter and the valve stem that constitute the valve gear.
By forming a wear-resistant stress buffer layer consisting of a layered structure, stress concentration exerted on the stem part by the cotter during engine operation is relieved, and the wear resistance of the buffer layer itself causes the cotter It will not wear out due to slippage. In addition, according to the present invention, since the cotter is structured to be supported by the stem portion and the valve spring retainer, it is possible to reduce noise in the valve train without generating a gap between the cotter and the retainer during engine operation. it can. In addition, in the conventional valve operating system, the upper limit of the engine speed was suppressed in order to secure the durability of the stem portion, whereas according to the present invention, the maximum engine speed is increased by improving the durability of the valve. Can be set.

[Brief description of drawings]

1 is a sectional view of a valve operating device according to a first embodiment of the present invention; FIG. 2 is a sectional view of a pressure buffer layer according to the present invention; and FIG. 3 is a valve operating device of a second embodiment according to the present invention. Sectional view; FIG. 4 is a sectional view of a valve operating system according to a third embodiment of the present invention. 1 ... Intake (exhaust) valve, 1b ... Stem part, 3, 3 '...
Cotter, 4 ... Valve spring retainer, 5 ... Valve spring, 8 ... Stress buffer layer.

Front page continuation (72) Inventor Hiroshi Ueda 3-65 Midorigaoka, Toyota City, Aichi Otoyo Kogyo Co., Ltd. (56) Bibliography 63-19012 (JP, U) , U) Actually open 63-52904 (JP, U) Actually open 2-67012 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A stress buffer layer having a valve spring retainer locked to a stem part of a ceramic intake / exhaust valve via a cotter and having wear resistance on at least one of contact surfaces of the cotter and the stem part. A valve operating device in which the stress buffer layer has a two-layer structure of a PTFE (polytetrafluoroethylene) layer and a Ni-P alloy layer in which PTFE fine particles are dispersed, and the PTFE layer A valve train, wherein the Ni-P alloy layer is arranged on the base material side on the contact surface side with the mating member.