JPH1181924A - Valve system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve system of an internal combustion engine which is capable of suppressing striking sound from a locker shaft and obtaining exact valve lift amount. SOLUTION: A cam cap 8 is provided with an inserting/passing hole 22 of a locker shaft 14. Further, a slitting 30 for this inserting/passing hole 22 is formed. When a bolt 10 fixing the cam cap 8 to a cylinder head 6 is fastened, the moving of the locker shaft 14 within the inserting/passing hole 22 is constrained at this time because the inserting/passing hole 22 is reduced in diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a valve train for an internal combustion engine having a rocker shaft in a valve drive system.

[0002]

[Related Background Art] A valve train of this kind of internal combustion engine is
The rocker shaft is provided with a rocker shaft serving as a rocking fulcrum of the rocker arm. The rocker shaft is usually fastened to the support member by a bolt penetrating the rocker shaft in a state of being inserted through an insertion hole provided in the support member. In addition, an appropriate clearance is secured between the inner peripheral surface of the insertion hole of the rocker shaft and the outer peripheral surface of the rocker shaft in consideration of ease of assembly work.

On the other hand, during operation of the internal combustion engine, the rocker shaft repeatedly receives a reaction force when the intake and exhaust valves are driven, and the rocker shaft moves by the above-described clearance due to the reaction force. A tapping sound may be generated from the shaft. An engine valve gear that suppresses the occurrence of such a tapping sound is disclosed in, for example, Japanese Utility Model Laid-Open Publication No.
No. 15,805. In this known valve gear, a rocker shaft holder is integrally provided on a cam cap, and rocker shaft insertion holes are formed in a plurality of cam caps arranged in the cylinder row direction. The center of the insertion holes is displaced downward with respect to the other insertion holes, and the rocker shaft is inserted into these insertion holes and supported on the cylinder head. It has become.

Therefore, according to the above-described valve train, movement of the rocker shaft with respect to the insertion hole is restricted in a state where the rocker shaft is inserted into the insertion hole, so that the above-described hitting sound is effectively generated during operation of the engine. It is considered that it is suppressed.

[0005]

However, in the above-described known valve train, the restraining force of each of the insertion holes with respect to the rocker shaft is weaker as the position is farther from the center cam cap, and the rocker shaft is weaker. It is difficult to constrain the entirety in each insertion hole. Therefore, it cannot be said that the above-mentioned hitting sound is surely suppressed.

Further, in the above-described valve gear, since the center of the rocker shaft insertion hole is relatively displaced, a slight distortion is generated in the rocker shaft in a state where the rocker shaft is inserted into the insertion hole. Variations occur in the position of the swing fulcrum. In such a situation, accurate operation of the valve train is hindered, and it is no longer possible to obtain a valve lift as designed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent occurrence of a tapping sound from a rocker shaft, and to achieve an accurate lift of an intake / exhaust valve. Is to provide a valve train for an internal combustion engine that can reliably obtain the valve timing.

[0008]

According to a first aspect of the present invention, there is provided a valve gear for an internal combustion engine, wherein a slot is formed in an insertion hole of a rocker shaft provided in a support member, and the rocker shaft is supported by a fastening means. When fastening the member to the cylinder head, the diameter of the insertion hole is reduced while the rocker shaft is inserted.

In other words, according to the first aspect of the present invention, when the rocker shaft is inserted into the insertion hole, an appropriate clearance is provided between the inner peripheral surface of the insertion hole and the outer peripheral surface of the rocker shaft. When the support member is fastened to the cylinder head by the fastening means, the diameter of the insertion hole is reduced by slitting, and the above-mentioned clearance is eliminated. Accordingly, in this state, the rocker shaft is securely fixed to the cylinder head via the support member, so that the rocker shaft does not move in the insertion hole.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a valve gear of an internal combustion engine according to an embodiment of the present invention; FIG. 1 shows an engine 1 to which a valve train of the embodiment is applied. The engine 1 according to this embodiment is, for example, an in-cylinder in-cylinder gasoline engine of an in-line multi-cylinder type. Therefore, in this engine 1, a fuel injector 4 capable of directly injecting fuel into each combustion chamber of the cylinder 2 is provided. It is provided on the cylinder head 6. However, the internal combustion engine to which the valve train of the present invention can be applied is not limited to the engine.

The valve train shown in FIG. 1 is provided with a cam cap 8 as a support member disposed on the upper surface of the cylinder head 6 and a bolt 10 as a fastening means. Also,
As is well known, the elements of the valve train include camshaft 1
2, a rocker shaft 14, a rocker arm 16, an intake valve 18, an exhaust valve 20, and the like. The cam cap 8 is integrally provided with a rocker shaft holder. The cam cap 8 is provided with an insertion hole 22 for the rocker shaft 14 in addition to the bearing of the cam shaft 12. The rocker shaft 12 is inserted into the insertion hole 22.
And is supported by the cam cap 8 in a state where it is inserted through.
The camshaft 12 and the rocker shaft 14 extend over the entire area of the cylinder row, and therefore the cam cap 8
Are arranged at predetermined intervals in the longitudinal direction of the cylinder head 6.

Each cam cap 8 is fastened to the cylinder head 6 by a bolt 10, and this bolt 10 is also provided corresponding to each cam cap 8. In addition,
A reinforcing plate 24 extending in the arrangement direction is provided on the top of the cam cap 8.
Are fastened together with the cam caps 8 by bolts 10. Note that such a reinforcing plate 24 is merely provided as a reinforcement for the cam cap 8, and is not essential for the valve train of the present invention.

Next, referring to FIG.
A part of the cam cap 8 on the side is shown in an enlarged manner, and one of the rocker shaft 14, the insertion hole 22 and the bolt 10 corresponding to the cam cap 8 is also shown. As shown in FIG.
A bolt insertion hole 26 is formed on each of the cam cap 8 and the rocker shaft 14 on the same line, and a bolt hole 28 into which the bolt 10 is screwed is formed in the cylinder head 6. Cam cap 8
Means that the bolt 10 is inserted into the bolt hole 2 through the bolt insertion hole 26.
8 and fastened to the cylinder head 6
In this state, the camshaft 1
2 is pinched. In addition to the bolt 10, the bolt insertion hole 26 and the bolt hole 28 also serve as fastening means. The bolt 10 is, for example, a bolt hole 2
The nut may be tightened on the upper surface of the reinforcing plate 24 with respect to the stud bolt screwed into the nut 8.

Here, the insertion hole 22 of the rocker shaft 14
Will be described in detail. The inner diameter of the insertion hole 22 is set slightly larger than the outer diameter of the rocker shaft 14, and an appropriate clearance (for example, 20 to 20) is provided between the inner peripheral surface of the insertion hole 22 and the outer peripheral surface of the rocker shaft 14. 50μ
m) is secured. Therefore, when assembling the valve gear, the rocker shaft 14 can be easily inserted into the insertion hole 22.

On the other hand, as shown in FIG. 2, the cam cap 8 is formed with a slit 30 for the insertion hole 22. The slot 30 is formed on the outer surface 3 of the cam cap 8.
2 extends into the insertion hole 22, the center line of which is formed perpendicular to the axis of the bolt 10 and toward the axis of the rocker shaft 14. The inner diameter of the insertion hole 22 can be reduced by the slit 30.

Specifically, when the bolt 10 is tightened with the rocker shaft 14 inserted through the insertion hole 22, the cam cap 8 is pressed in the vertical direction by the axial force of the bolt 10. As a result of the cam cap 8 being deformed by the pressing force at this time, the diameter of the insertion hole 22 is reduced by the slot 30, and the above-mentioned clearance is eliminated. Therefore, at this time, the movement of the rocker shaft 14 in the insertion hole 22 is completely restrained.

The cross-sectional shape of the insertion hole 22 is set to match the outer peripheral surface of the rocker shaft 14 in the reduced diameter state at this time. Further, the insertion position of the bolt 10 must be set so that the cam cap 8 can be deformed by the axial force to reliably reduce the diameter of the insertion hole 22. In this embodiment, in consideration of miniaturization and weight reduction of the cam cap 8 and securing space on the side of the slit 30, the insertion position of the bolt 10 is set inside the axis (not shown) of the insertion hole 22 (on the side opposite to the slit 30). ). In this case, it is necessary that at least the flange portion of the bolt 10 wraps around the insertion hole 22 when viewed in the vertical direction of the cam cap 8. Note that the insertion position of the bolt 10 is set outside (with a slit 30) with respect to the axis of the insertion hole 22.
Side), the bolt 10
Need not be wrapped in the insertion hole 22.
The bolt 10 has, for example, a tensile strength of 70 kgf / mm ^2.
The above high tension bolts are suitable.

FIGS. 3 and 4 show the state of the rocker during the operation of the engine during one revolution of the camshaft, that is, until the valve in the closed state is driven to open once and returns to the closed state again. The respective changes in the force vector acting radially on the shaft 14 are shown. 3 and 4, the horizontal axis indicates the vector component Fh in the horizontal direction, and the vertical axis indicates the vector component Fp in the vertical direction, as shown by superimposing the axis of the rocker shaft 14 on the origin of the graph. In this case, the lateral direction is a direction parallel to the upper surface of the cylinder head. Such a force vector is based on the reaction force received by the rocker shaft 14 from the rocker arm when the intake valve or the exhaust valve is driven.

Specifically, the diagrams in FIGS. 3 and 4 show the vector components Fh and Fp at each contact point between the rocker arm and the cam per rotation of the camshaft, and plot the locus of the vector components Fh and Fp. It has become. That is, a vector directed from the origin to each point on the diagram represents a vector of a force acting on the rocker shaft 14 at the position of the contact point at that time. For example, each point P1 to P shown on the diagram
5 is a point P1 at −60 °, a point P2 at −30 °, and a point P3 when the point of contact between the rocker arm 16 and the cam is viewed around the axis of the camshaft and expressed as an angle away from the top of the cam peak. Is 0 °, point P4 is 30 °, and point P5 is 60 °. In addition, these separation angles are positive when increasing in a counterclockwise direction with respect to the axis of the camshaft. In this example, the point P1 indicates the start of opening of the valve, that is, the initial position of the lift, and the point P2 indicates the end of opening, that is, the position of the end of the lift.

FIG. 3 shows a vector change of a force in a low rotation speed region where the engine speed is about 1,000 rotations per minute. As shown in the figure, in the vector of the force acting on the rocker shaft 14, the component in the vertical direction rapidly rises from the state where the magnitude is 0 to the initial stage of the valve lift (point P1), and the maximum value of the valve The peak is reached near the lift position (point P3), and after the end of the valve lift (point P5), it sharply decreases and returns to zero again.

On the other hand, FIG. 4 shows that the engine speed is 6
A vector change in a high rotation range of about 1,000 rotations is shown. In this case, in the force vector, the component in the vertical direction rises sharply near the initial stage of the valve lift (point P1) from the state where the magnitude is 0, and the component in the horizontal direction increases until the point P2. Is at its first peak. Then, the force vector reaches the second peak from the point P4 to the end of the valve lift (point P5), and thereafter, the force vector sharply decreases to zero.

As apparent from FIGS. 3 and 4,
It can be seen that the force acting on the rocker shaft 14 tends to rapidly rise in the vertical direction at the beginning of the valve lift regardless of the level of the engine speed. According to observations made by the inventors, it has been confirmed that the above-described striking sound is significantly generated when such a force acts on the rocker shaft 14 at an early stage of the valve lift. In particular, in the low rotation range of the engine, the tapping sound generated from the rocker shaft 14 is easily heard as mechanical noise.

Further, the present inventors have confirmed that the rocker shaft 14 moves due to the force at this time, and the rocking fulcrum of the rocker arm is displaced, so that the valve lift amount as designed cannot be obtained. . Such a problem of the valve lift has a bad influence on the engine performance particularly in a high rotation speed range. However, according to the valve gear of this embodiment, the rocker shaft 14 is restrained from moving in the insertion hole 22 of the cam cap 8 as shown in FIG. It can be effectively prevented. Moreover, according to the valve train of this embodiment, the slit 30 is provided in the horizontal direction with respect to the insertion hole 22, so that the diameter of the insertion hole 22 is greatly reduced in the vertical direction, and the clearance with the insertion hole 22 is also reduced. Eliminated more reliably in the vertical direction. Therefore, the movement of the rocker shaft 14 due to the vertical force at the beginning of the valve lift can be reliably suppressed.

Further, since the rocker shaft 14 is securely restrained, the intake / exhaust valves 18 and 2 can be adjusted with an accurate lift amount.
0 can be driven, and in particular, the performance of the engine 1 in a high rotation range can be sufficiently exhibited. In this embodiment, in the state where the plurality of cam caps 8 are arranged on the cylinder head 6, all the center lines of the insertion holes 22 provided in each cam cap 8 are provided on the same line. The rocker shaft 14 can be smoothly inserted into the inside 22, and the workability of assembling the valve train does not deteriorate.

Since the bolt 10 is also used as a fixing bolt for the cam cap 8, there is no need to separately provide a locking bolt for the rocker shaft 14, and the number of parts does not increase. Referring now to FIG. 5, a second embodiment of the valve train is shown. In this case, the shape of the slit 30 is different from that of the above-described embodiment, and the cross-sectional shape of the insertion hole 22 is substantially C-shaped. That is,
The slit 30 shown in FIG. 5 is formed on the same plane as the outer surface 32 of the cam cap 8, and therefore, the outer peripheral surface of the rocker shaft 14 is formed by the slit 30 on the outer surface of the cam cap 8. It has a shape that protrudes partially from 32.

After the slit 30 is formed in the cam cap 8, it is not necessary to further process the slit after the insertion hole 22 is formed. That is, if the position of the insertion hole 22 is set so that the peripheral edge thereof protrudes from the outer side surface 32 of the cam cap 8, when the insertion hole 22 is formed, the slot 30 is simultaneously formed.
Will also be formed. According to the valve operating device of the second embodiment, the rocker shaft 14
Can be reliably restrained. Moreover, the slit 30
And the width of the cam cap 8, that is, the length in the direction in which the pair of rocker shafts 14 are arranged can be set short. Therefore, it is more advantageous in terms of workability and weight reduction of the cam cap 8, and interference between the cam cap 8 and other members in the rocker cover can be easily avoided, so that the assembling workability of the valve train is further improved. I do.

The present invention is not limited to the above-described embodiments. For example, as shown in FIG. 6, in addition to the slit 30 of the embodiment, a slit 34 extending toward the inside of the cam cap 8. Can be further provided. In this case, the deformation of the cam cap 8 becomes easier, and the restraining force of the rocker shaft 14 due to the diameter reduction of the insertion hole 22 is further increased.

Further, this valve train is not only an engine whose valve drive system is of the SOHC type as in each embodiment,
It goes without saying that the present invention can be applied to a DOHC type engine.

[0029]

As described above, according to the valve operating device for an internal combustion engine of the first aspect, it is possible to prevent occurrence of a tapping sound during operation and to sufficiently exhibit the power performance of the internal combustion engine. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an engine to which a valve train according to an embodiment is applied.

FIG. 2 is a cross-sectional view showing a mounting state of a cam cap.

FIG. 3 is a graph for explaining a vector of a force acting on a rocker shaft when the engine is running at a low speed.

FIG. 4 is a graph for explaining a vector of a force acting on a rocker shaft when the engine rotates at a high speed.

FIG. 5 is a view showing a cam cap according to a second embodiment.

FIG. 6 is a view showing a modification of the slit.

[Explanation of symbols]

 Reference Signs List 6 Cylinder head 8 Cam cap (support member) 10 Bolt (fastening means) 14 Rocker shaft 22 Insertion hole 26 Bolt insertion hole (fastening means) 28 Bolt hole (fastening means) 30 Slot

Claims (1)

[Claims] A supporting member disposed on a cylinder head and having a through hole for a rocker shaft; a slot formed in the supporting member, the diameter of the through hole being reduced; and a rocker shaft inserted into the through hole. A valve operating device for an internal combustion engine, comprising: fastening means for fastening the support member to the cylinder head with the diameter of the insertion hole being reduced in the inserted state.