JP3473212B2 - Valve train for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a valve train for an internal combustion engine, and more particularly, to a camshaft journal and a support member surrounding the journal. The present invention relates to a valve gear for an internal combustion engine having a clearance provided therebetween. 2. Description of the Related Art Conventionally, as this kind of technology, for example, a technology disclosed in Japanese Patent Application Laid-Open No. Hei 6-193420 is known. In general, a direct-acting type valve train including this technique is configured as follows, for example. That is, as shown in FIG. 6A, an intake valve 52 (or an exhaust valve) is provided in a cylinder head 51. A camshaft 5 for opening and closing each intake port and the like is formed on the upper portion by periodically pushing down (lifting) the intake valve 52.
3 are provided. The cam shaft 53 has a journal 54 and a cam 55 at a position corresponding to the valve 52. And the journal unit 54
Is rotatably supported in the concave portion 56 above the cylinder head 51. A cam journal cap 57 having a recess 58 is mounted and fixed on the upper portion of the cylinder head 51. Therefore, the journal portion 54 is supported in a state of being surrounded by the concave portion 56 at the upper portion of the cylinder head 51 and the concave portion 58 at the lower portion of the cam journal cap 57. When the camshaft 53 rotates, first, as shown in FIG. 6 (b), the valve 52 resists the reaction force of a valve spring (not shown) by the cam nose 59 of the cam 55. And the intake port and the like are opened. Further, with further rotation, the valve 52
Is pushed up by the reaction force of a valve spring (not shown), and the intake port and the like are closed. In order to smoothly rotate the camshaft 53, conventionally, between the cylinder head 51 and the journal portion 54, and between the cylinder head 51 and the cam journal cap 5,
As shown in FIG. 6A, a fixed clearance 61 was provided between the journal 7 and the journal portion 54, respectively. The clearance 61 includes the camshaft 5.
The lubricating oil is supplied from the third oil holes 62 and 63, thereby further smoothing the rotation of the camshaft 53. [0007] However, the above prior art has the following problems. That is, when the valve 52 is lifted, the camshaft 53 receives the reaction force of the valve spring upward in the drawing.
At this time, the clearance 6 conventionally provided between the cam journal cap 57 and the journal portion 54
Due to the presence of 1, there is a possibility that the cam shaft 53 moves upward as shown in FIG. Therefore, each time the journal portion 54 hits the cam journal cap 57, there is a possibility that a tapping sound is generated. On the other hand, in order to solve the above problem, it is conceivable that the diameter of the journal portion 54 having a perfect circular cross section is maximized and the clearance 61 is set to substantially "0".
However, in such a case, the friction between the journal portion 54, the cam journal cap 57, and the cylinder head 51 increases, which hinders the rotation of the cam shaft 53. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to suppress the generation of a tapping sound associated with the rotation of a camshaft without inhibiting the rotation of the camshaft. It is an object of the present invention to provide a possible valve train for an internal combustion engine. In order to achieve the above object, according to the present invention, there is provided a cam for opening and closing at least one of an intake valve and an exhaust valve of an internal combustion engine.
A camshaft rotatably provided, and a support for supporting the journal of the camshaft so as to surround the journal, between the journal and the support, reducing friction between the two. In a valve gear for an internal combustion engine provided with a clearance for ensuring rotation of the camshaft, the cross-sectional shape of the journal portion may be changed to an egg shape.
By setting the shape, when at least one of the intake valve and the exhaust valve is opened by the cam, only the portion on the opposite side to the cam nose is minimized. This is the gist. According to the above configuration, the camshaft is supported by the support so that the journal portion is surrounded. When the camshaft rotates, the cam also rotates integrally, and the cam nose pushes down at least one of the intake valve and the exhaust valve of the internal combustion engine.
As a result, intake air is introduced into the internal combustion engine, and exhaust gas is discharged from the internal combustion engine. When the camshaft rotates, friction between the journal and the support is reduced due to the clearance provided between the journal and the support. For this reason, smooth rotation of the camshaft can be ensured. According to the present invention, the disconnection of the journal portion is performed.
By making the surface shape an egg shape, it is configured such that, when at least one of the intake valve and the exhaust valve is opened by the cam, only the portion of the clearance opposite to the cam nose is minimized. You. Here, when at least one of the intake valve and the exhaust valve is opened, the camshaft receives a reaction force from a spring for the intake valve, the exhaust valve or the like, and tends to move in the direction of the reaction force. However, at this time, since the distance in the moving direction among the clearances between the support and the journal portion is small, even if the journal portion hits the support, it is difficult for the tapping sound to occur at that time. [0013] Further, in a portion where the clearance is not minimum, friction between the journal portion and the support is unlikely to occur. Therefore, the rotation of the camshaft as a whole hardly causes any trouble. In addition, the clearance is opposite to the cam nose
It is configured so that only the side part is minimized
Therefore, friction can be further reduced.
Further smooth camshaft rotation can be achieved.
You. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying a valve train for an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. FIG. 2 is a schematic sectional view showing the valve train of a twin-cam direct-hit engine mounted on a vehicle in the present embodiment. An intake port 4 communicating with a combustion chamber 3 for each cylinder is formed in a cylinder head 2 of an engine 1 as an internal combustion engine. An annular valve seat 5 is attached to an opening of the intake port 4 in each combustion chamber 3. An intake valve 6 for periodically opening and closing each intake port 4 is attached to the cylinder head 2. Each intake valve 6 is composed of a stem 6a extending substantially vertically in a slightly inclined state and slidably inserted into the cylinder head, and an umbrella 6b formed at the lower end of the stem 6a. I have. Then, when each intake valve 6 moves upward and the umbrella portion 6b comes into contact with the valve seat 5, the intake port 4 is closed. When each intake valve 6 moves down and the umbrella portion 6b separates from the valve seat 5, the intake port 4 is opened. A guide hole 7 is provided in the cylinder head 2 so as to correspond to the intake valve 6, and a valve lifter 8 is slidably inserted therein. A shim 9 is fitted on the upper part of each valve lifter 8. The upper end of each stem portion 6a is in contact with the inner wall surface of the valve lifter 8. A valve spring retainer 12 is mounted on the upper end of each stem 6a via a cotter (not shown). A valve spring 13 is mounted between each retainer 12 and the support surface 2a in the cylinder head 2 in a compressed state. Each of the springs 13 urges the intake valve 6 upward, which is a direction in which the intake port 4 is closed. Above the valve lifter 8, a mechanism for opening and closing each intake port 4 by periodically pushing down (lifting) each intake valve 6 against the urging force of the valve spring 13 is provided. Have been. That is, as shown in FIGS. 2 and 3, the camshaft 14 is rotatably supported in the supporting recess 2 b at the upper part of the cylinder head 2. The camshaft 14 includes a shaft body 15 having a journal portion 15a.
5a, the camshaft 14 is supported by the cylinder head 2. A cam journal cap 16 is attached to the cylinder head 2 so as to cover the journal portion 15a from above. Accordingly, the journal portion 15a is supported in a state surrounded by the concave portion 2b of the cylinder head 2 and the concave portion 16a below the cam journal cap 16, that is, in a circular space surrounded by the concave portions 2b and 16. Thus, in the present embodiment, the cylinder head 2 and the cam journal cap 16
Constitutes a support. In the shaft body 15, a cam 17 is provided at a position corresponding to each intake valve 6 so as to be integrally rotatable. The cam 17 may be formed integrally with the shaft main body 15 or may be fixed thereto. The cam 17 includes a buffer portion 17a and a cam nose 17b. In the cam 17, when the buffer portion 17a is in contact with the shim 9, no downward force acts on the intake valve 6. Also, the cam 17 rotates,
When the contact portion with the shim 9 shifts from the buffer portion 17a to the cam nose 17b, a pressing force starts to act on the intake valve 6, and the lift of the valve 6 starts, and the cam 17
The lift amount of the intake valve 6 changes according to the rotation (FIG. 4B). Then, when the contact portion with the shim 9 shifts from the cam nose 17b to the buffer portion 17a, there is no longer any pushing force on the intake valve, and the lift of the intake valve 6 is terminated. As shown in FIG. 1, in the present embodiment, a clearance C is provided between the journal 15a and the recesses 2b, 16a in order to smooth the rotation of the cam 17. In addition, the shaft body 15 includes
Oil holes 18 and 19 are formed, and the oil holes 18 and 19 are formed.
Communicates with the clearance C. For this reason, lubricating oil is supplied to the clearance C from the oil holes 18 and 19 of the shaft body 15, thereby further smoothing the rotation of the camshaft 14. As shown in FIG. 2, an exhaust port 21 communicating with the combustion chamber 3 for each cylinder is formed in the cylinder head 2 of the engine 1 similarly to the intake port 4. A valve seat 22 is also mounted on the opening of the exhaust port 21. An exhaust valve 23 for periodically opening and closing each exhaust port 21 is attached to the cylinder head 2.
Is periodically provided (lifted) to open and close each exhaust port 21.
However, since this mechanism is exactly the same as that of the above-described intake valve 6, further description is omitted here. Next, features of the present embodiment will be described. As shown in FIG. 1, the cross-sectional shape of the journal 15a in the present embodiment is not a perfect circle,
The cam nose 17b is formed in an oval shape along the extending direction. Therefore, of the clearance C,
When the intake valve 6 is opened (at the time of lift), the clearance "C1" on the side opposite to the cam nose 17b.
However, it is designed to be minimum compared to other parts. Next, the operation and effect of the embodiment constructed as described above will be described. When the camshaft 14 rotates, the cam 17 also rotates integrally. Then, as shown in FIG. 4B, when the contact portion with the shim 9 shifts from the buffer portion 17a to the cam nose 17b, the cam nose 17b pushes down the intake valve 6. And the contact part with the shim 9 is the cam nose 17.
When shifting from b to the buffer section 17a, the pushing force on the intake valve disappears, and the lift of the intake valve 6 ends. Therefore, the intake valve 6 is, for example, as shown in FIG.
As shown in (1), it is pushed up by the urging force of the valve spring 13. By a series of these operations, the intake air is introduced into the combustion chamber 3 of the engine 1 or not. When the camshaft 14 rotates,
Existence of clearance C provided between journal portion 15a and each of recesses 2b and 16a, and clearance C
The friction between the two is reduced by supplying lubricating oil to the two. For this reason, basically, smooth rotation of the camshaft 14 can be ensured. According to this embodiment, the cross-sectional shape of the journal portion 15a of the camshaft body 15 is formed into an elliptical shape, so that the cam nose 17b of the clearance C at the time of valve lift by the cam 17 is formed. The clearance “C” on the opposite side (the upper part in FIGS. 1 and 4)
1 "is minimized. Here, when the intake valve 6 is lifted, the camshaft 14 receives the reaction force of the valve spring 13 and tends to move in the direction of the reaction force (upward in FIGS. 1 and 4). However, at this time, of the clearance C, the distance in the moving direction is small (“C
1 "), even if the journal portion 15a hits the concave portion 16a of the cam journal cap 16, the tapping sound is less likely to occur at that time. That is, according to the present embodiment, it is possible to suppress the generation of a tapping sound due to the rotation of the camshaft 14. On the other hand, a portion of the clearance C where the clearance C is not minimum has a sufficient distance, and the gap between the journal portion 15a and the concave portion 2b of the cylinder head 2 is large. Part 15a
And the recess 16a of the cam journal cap 16 are less likely to cause friction. Therefore, the rotation of the camshaft 14 as a whole is hardly supported, and as a result, the smooth rotation of the camshaft 14 can be sufficiently ensured. Further, in the present embodiment, the above-described operation and effect can be sufficiently exerted simply by making the cross-sectional shape of the journal portion 15a of the camshaft 14 oval. Therefore, the processing of the camshaft 14 can be performed relatively easily, and the increase in cost can be suppressed. Although not described in detail in the above text, the same can be said of the camshaft on the exhaust valve 23 side as well as the camshaft 14 on the intake valve 6 side. The present invention is not limited to the above embodiment, and may be configured as follows, for example. (1) In the above embodiment, the concave portions 2b, 1
By making the accommodation space formed by 6a a perfect circular cross section and making the cross section of the journal portion 15a of the camshaft main body 15 an elliptical shape, the clearance C is opposite to the cam nose 17b at the time of valve lift. Although the clearance “C1” of the side portion is configured to be the minimum, it may be configured as follows, for example.
That is, as shown in FIG. 5, the cross-sectional shape of the journal portion 15b of the camshaft main body 15 is made oval (the half journal portion 15b on the cam nose 17b side is formed in an arc shape as in the related art), so that the clearance C home,
At the time of valve lift, the clearance "C1" of only the portion opposite to the cam nose 17b may be minimized. With such a configuration, the friction can be further reduced, and the rotation of the camshaft 14 can be further smoothed. (2) Conversely, the cross-sectional shape of the journal portion 15a of the camshaft body 15 is made to be a perfect circular shape as in the past, and the concave portions 2b,
By making the accommodation space formed by 16a a non-circular cross section, the clearance "C1" on the side opposite to the cam nose 17b during valve lift may be minimized. (3) In the above-described embodiment, the valve gear of the twin cam direct hit type engine 1 has been embodied. However, the embodiment can be embodied in the case where the number of the camshafts 15 is one. Further, the present invention can be applied to only one of the intake valve 6 and the exhaust valve 23. Further, the present invention can be applied to a rocker arm type valve operating device. The technical ideas which are not described in the claims and can be grasped from the above embodiment will be described below together with their effects. (A) At least the intake and exhaust valves of the internal combustion engine
Also has a cam for opening and closing one side and is rotatably provided
And a jar of the camshaft
A support for surrounding the nut portion.
Between the internal part and the support.
To reduce rotation and ensure rotation of the camshaft.
In a valve train for an internal combustion engine provided with a clearance , the cam section of the camshaft opens at least one of the intake valve and the exhaust valve by making the cross-sectional shape of the journal portion of the camshaft an elliptical shape. In this case, the portion on the side opposite to the cam nose is minimized. With the above configuration, the processing of the camshaft can be performed relatively easily, and the increase in cost can be suppressed. As described in detail above, according to the valve train for an internal combustion engine of the present invention, the hitting sound accompanying the rotation of the camshaft is generated without obstructing the rotation of the camshaft. This has an excellent effect that it is possible to suppress the generation of

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged sectional view showing a shape of a journal portion of a camshaft according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a valve train of the engine according to the embodiment. FIG. 3 is a cross-sectional view showing the valve operating device at a position different from FIG. 2; FIGS. 4A and 4B are schematic views of a valve train showing the operation of an embodiment. FIG. 5 is an enlarged sectional view showing a shape of a journal portion according to another embodiment. FIGS. 6A and 6B are schematic diagrams showing the operation of a valve train according to the related art. DESCRIPTION OF SYMBOLS 1 ... Engine as internal combustion engine, 2 ... Cylinder head constituting support, 6 ... Intake valve, 14 ... Camshaft, 15a ... Journal, 17 ... Cam, 17b ... Cam nose, 23 ... Exhaust valve , C ... clearance.

Claims (1)

(57) Claims: 1. A camshaft having a cam for opening and closing at least one of an intake valve and an exhaust valve of an internal combustion engine and rotatably provided; A support that surrounds the journal, and a clearance is provided between the journal and the support to reduce friction between the two and ensure rotation of the camshaft. In the valve train for an internal combustion engine, the cross-sectional shape of the journal portion is an oval shape.
Ri, of the clearance, the valve operating in at least one of the time to be opened, an internal combustion engine, characterized in that as a minimum only the portion opposite to the cam nose of the intake and exhaust valves by the cam apparatus.