JPH07224611A - Valve drive for internal combustion engine - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a valve operating system for an internal combustion engine in which a valve mechanism having an outer shim valve lifter is driven by a cam, and an object thereof is to achieve both weight reduction of the cam and prevention of drop of the shim. To do. [Structure] The valve lifter 16 is connected to the end of the valve body 10.
To provide. A valve spring 12 for urging the valve body 10 in a valve closing direction via a valve lifter 16 is provided. The shim 20 is attached to the surface of the valve lifter 16 to adjust the dimensional tolerance. The cam shaft 24 is arranged so that the cam piece 22 contacts the upper surface of the shim 20. Cam piece 22
The base circular portion 22a is made thinner than the cam nose portion 22b to reduce the weight. An oil passage 26 and an oil injection port 28 that open to the side surface on the side of the base circular portion 22a are provided.
An oil supply source 30 for generating a predetermined hydraulic pressure in the oil passage 26
To communicate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating system for an internal combustion engine, and more particularly to a valve operating system for an internal combustion engine in which a valve mechanism having an outer shim valve lifter is driven by a cam.

[0002]

2. Description of the Related Art Conventionally, a cam mechanism has been known as a drive mechanism (also called a valve operating mechanism) for an intake / exhaust valve of an internal combustion engine. An example of this valve mechanism is shown in Japanese Utility Model Laid-Open No. 60-128904. The technique disclosed in this publication aims to reduce the weight of the camshaft without impairing the strength and surface pressure of the campiece by forming the thickness of the base circular portion of the campiece smaller than the thickness of the cam nose portion of the campiece. (See FIG. 3).

A lifter is used in the direct drive type valve mechanism. Shims are also used with this lifter to keep the clearance between the cam and valve lifter appropriate. In this case, in order to facilitate the replacement of the shim, the shim may be arranged between the lifter and the cam. The shims arranged in this way are called outer shims.

It is also conceivable to use the camshaft disclosed in Japanese Utility Model Laid-Open No. 60-128904 in a direct drive type valve mechanism having such an outer shim.

[0005]

However, in the conventional camshaft described above, the configuration shown in FIG. 3 (B) is desirable because the boring of the cam 2 is difficult and the base circular portion 2a is divided into two parts. The total wall thickness required to secure rigidity is thicker than that of the base circular portion 4a shown in FIG. 3 (C),
Further, there are disadvantages such that the serviceability when assembling the outer shim to cancel the dimensional error is inferior to the form shown in FIG. 3 (C).

Therefore, in order to reduce the thickness and weight of the conventional cam, the shape shown in FIG. 3C is actually used, but the cam 4 shown in FIG. 3C is also used. , There were the following problems.

That is, the outer shim is fitted and held in the valve lifter and is sandwiched between the valve lifter and the cam 4, and should be substantially fixed on the valve lifter. However, when the internal combustion engine is operating in a high rotation range, that is, when the valve lifter is moving at high speed, abnormal vibration is transmitted to the outer shim,
In some cases, the substantially fixed state between the outer shim and the valve lifter may be lost.

In particular, when the cam 4 is in the non-lift section, that is, when the base circle portion 4a of the cam 4 is in contact with the outer shim, the clamping force acting between the valve lifter and the cam 4 is small and the outer shim is May lift from the valve lifter. In this case, if the base circular portion 4a has a sufficient thickness with respect to the outer shim, the lifting thereof can be prevented, but when the base circular portion 4a is thinned as in the conventional cam 4 described above, The drag against lifting is clearly reduced. In addition, the outer shim may be tilted when lifted up, the engagement state between the shim and the lifter may be deteriorated, and uneven wear may occur.

Therefore, when a valve train is constructed using the conventional cam 4, it is necessary to secure the wall thickness of the base circular portion 4a to the extent that the outer shim can be prevented from falling off. In the end, there was a problem that the weight could not be sufficiently reduced.

The present invention has been made in view of the above-mentioned points. The cam base circular portion is made thinner than the cam nose portion, and the base circular portion is directed toward the outer shim surface when the base circular portion contacts the outer shim. The purpose is to prevent the outer shim from rising due to the pressure of the injected oil.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a valve operating system for an internal combustion engine in which a valve mechanism having an outer shim valve lifter is driven by a cam, wherein a base circular portion is formed thinner than a cam nose portion. And an oil injection means for injecting oil onto the outer shim surface when at least the base circle of the cam faces the outer shim.

[0012]

In the valve operating system for an internal combustion engine according to the present invention, in the cam, the cam nose portion that abuts the outer shim in the lift section has a sufficient thickness, and thus a sufficient rigidity. In addition, the base circular portion, which only slides on the outer shim in the non-lift section, is made thinner to reduce the weight.

On the other hand, the oil injection means injects oil onto the surface of the outer shim when the outer shim contacts the base circle. The injected oil urges the outer shim toward the valve lifter side and prevents the outer shim from floating.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of a valve train for an internal combustion engine which is an embodiment of the present invention. The valve body 10 in FIG.
Is a valve element that constitutes an intake valve or an exhaust valve of the internal combustion engine, and is provided to control the conduction state of the intake port or the exhaust port by seating on or off a valve seat (not shown).

The valve spring 12 has one end on the cylinder head 14 and the other end on the valve spring retainer 1.
It is in contact with 1. The valve spring retainer 11 is
It is attached to the valve stem via a cotter 13.
The valve lifter 16 is sandwiched between the valve stem and the cam piece 22 of the cam shaft 24, and the lifter bore 18 formed in the cylinder head is slidably arranged as the cam piece 22 rotates.

The valve lifter 16 is provided with a shim 20 corresponding to the outer shim on the upper surface thereof. Sim 20
Is a member that adjusts the positional relationship between the valve lifter 16 and the cam piece 22 by absorbing dimensional tolerances of the valve body 10 and a cam piece 22 described later, and is fitted and held by the valve lifter 16.

The cam piece 22 is provided integrally with a cam shaft 24 which rotates with the rotation of the internal combustion engine, and as shown in a side view of FIG.
2a and cam nose portion 22b.

The base circular portion 22a is formed in a coaxial circular shape with the cam shaft 24, and slides on the surface of the shim 20 when the cam shaft 24 rotates. At this time, the cam piece 22 does not do any substantial work, and the valve lifter 1
6 is held at its upper displacement end as shown in FIG.
The valve body 10 is held in a closed state.

The cam nose portion 22b has a cam shaft 24.
It is formed so that the distance from the center of rotation to the outer shape thereof gradually increases toward the peak point. Therefore, with the cam nose 22b in contact with the shim 20, the camshaft 2
When 4 rotates, the cam piece 22 functions to slide the shim 20 and gradually push down the valve lifter 16 to open the valve body 10.

By the way, in the valve operating system for the internal combustion engine of this embodiment, as shown in FIG. 1, the thickness of the base circular portion 22a is made thinner than the thickness of the cam nose portion 22b. As described above, since the shim 20 and the cam piece 22 hardly receive the reaction force from the valve spring 12 in the base circular portion 22a, the strength equal to that of the cam nose portion 22b is unnecessary, and thus the weight is reduced by reducing the thickness. Is.

However, as described above, it is necessary to consider the prevention of the fall of the shim 20 when the thickness is reduced. That is, in the configuration in which the valve lifter 16 is sandwiched between the cam piece 22 and the valve stem as in the valve operating system of the present embodiment, the internal combustion engine causes the spring constant of the valve spring 12 and the valve lifter 16, the valve body 10, and the valve spring retainer. When the engine rotational speed drives the valve at a speed at which the resonance frequency is determined by the mass of 11, the cotter 13, the shim 20, etc., the valve spring vibrates (resonates) abnormally, causing the valve lifter 16 and the shim 20 to rotate the cam piece 22. It may not follow.

When such abnormal vibration occurs, the vibration is transmitted to the shim 20 through the valve lifter 16 and causes the shim 20 that is originally fitted and held in the valve lifter 16 to float. Such floating of the shim 20 is likely to occur particularly in the non-lift section where the clamping force acting between the cam piece 22 and the valve lifter 16 decreases, and the base circle portion that abuts the shim 20 in the non-lift section as in the present embodiment. With the configuration in which the wall thickness of 22a is made thin, the behavior of the shim 20 attempting to rise cannot be sufficiently regulated by the cam piece 22 alone.

In order to eliminate such an adverse effect, the valve operating system of the present embodiment is constructed such that oil is sprayed onto the surface of the shim 20 at an appropriate pressure when at least the base circular portion 22a contacts the shim 20. It is characterized by the point.

Here, in this embodiment, an oil passage 26 is provided at the center of the camshaft 24, and one end is opened into the oil passage 26 and the other end is the base circular portion 22a.
The above-mentioned function is realized by providing an oil injection port 28 opening to the side surface and communicating the oil passage 26 with an oil supply source (oil pump or the like) that generates a predetermined hydraulic pressure. In the present embodiment, these oil passages 2
6, the oil injection port 28, and the oil supply source 30 correspond to the oil injection means described above.

With this structure, when the camshaft 24 rotates and the base circular portion 22a comes into contact with the shim 20, the oil injection port 28 simultaneously faces the shim 20. Then, the shim 20 has an oil injection port 28.
It is urged toward the valve lifter 16 side by the injection pressure of the oil injected from the base circular portion 22a, so that the base circular portion 22a is prevented from being lifted up even though a sufficient thickness is not secured.

As described above, according to the valve operating system for the internal combustion engine of the present embodiment, the shim 20 is prevented from coming off due to the oil injection pressure, and the shim 20 is prevented from falling even if the regulation by the cam piece 22 is insufficient. It floats up from the ground and never falls off. Therefore, the base circle portion 22a
The thickness can be set in consideration of only the required rigidity, and a great reduction in weight can be realized while ensuring high reliability as compared with the conventional valve operating device.

By the way, since the valve operating system for the internal combustion engine of this embodiment is configured to positively inject oil onto the surface of the shim 20, the sliding portion between the shim 20 and the cam piece 22 is different from the conventional system. Can be cooled more effectively, and the sliding loss caused by the sliding of the two can be more effectively reduced.

Therefore, according to the apparatus of this embodiment, the wear of the shim 20 and the cam piece 22 is suppressed, the durability of both is improved, and the fuel consumption is reduced by improving the output characteristics of the internal combustion engine. Can be achieved.

Further, according to the apparatus of this embodiment, the shim 20
Since the oil is sprayed on the surface of the valve at any time, the oil does not stagnate between the valve lifter 16 and the lifter bore 18, which is effective in preventing the generation of oil sludge.

That is, when the oil is not positively injected onto the surface of the shim 20, the oil may stagnate on the upper surface of the shim 20 depending on the shapes of the valve lifter 16 and the lifter bore 18. When oil stagnates like this,
Stagnation oil may be continuously exposed to high temperature for a long period of time to generate oil sludge. Such oil sludge is not preferable because it causes deterioration of the lubrication characteristics of the oil and also causes clogging of the filter to hinder proper lubrication.

On the other hand, the device of this embodiment does not cause oil stagnation between the valve lifter 16 and the cylinder bore 18 and does not generate oil sludge as described above. As described above, the valve train for an internal combustion engine according to the present embodiment is also effective in improving the reliability and durability of the internal combustion engine from this point of view.

In the above embodiment, the cam piece 2
In order to ensure good workability, the shape of No. 2 is as shown in FIG. 1, that is, the thickness of the base circular portion 22a is reduced from both sides, and the base circular portion 22a is integrally formed near the center of the cam nose portion 22b. However, the shape is not limited to this and may be any shape that does not require boring.

That is, for example, as shown in FIG. 2, the cam 32 having a shape in which the base circular portion 32a is thinned from only one side and the base circular portion 32a is formed so as to be biased to one side of the cam nose portion 32b may be used. Good.

The present invention is not limited to the above-described embodiment, and in particular, when the base circle portion of the cam piece is in contact with the shim of the valve lifter, the force is applied uniformly to the sliding surface of the shim. In consideration of the above, it is possible to select the contact position of the thin cam piece and the position of the oil ejection hole.

[0035]

As described above, according to the present invention, by energizing the outer shim with the oil injection, the wall thickness of the base circular portion can be made sufficiently thin without giving consideration to preventing the outer shim from rising. . Therefore, the valve operating system for an internal combustion engine according to the present invention can ensure higher operational reliability as compared with the conventional valve operating system for an internal combustion engine, and can realize more effective weight reduction. It has features.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a valve train for an internal combustion engine that is an embodiment of the present invention.

FIG. 2 is a configuration diagram of another example of a cam suitable for the valve operating system for the internal combustion engine of the present embodiment.

FIG. 3 is a configuration diagram of a cam used in a conventional valve operating system for an internal combustion engine.

[Explanation of symbols]

 10 valve body 12 valve spring 16 valve lifter 18 cylinder bore 20 shim 22, 32 cam 22a, 32a base circular portion 22b, 32b cam nose portion 24 camshaft 26 oil passage 28 oil injection port 30 oil supply source

Claims (1)

[Claims] 1. A valve operating system for an internal combustion engine in which a valve mechanism having an outer shim valve lifter is driven by a cam, the cam having a base circular portion thinner than a cam nose portion, and at least the base of the cam. A valve operating device for an internal combustion engine, comprising: an oil injection unit that injects oil onto a surface of the outer shim when a circular portion faces the outer shim.