JPH10121916A - Valve system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance efficiency of a shim replacing operation by moving a rocker arm 1 in the thrust direction of a rocker shaft while being lifted up so that a thrust fin is contact on an engine. SOLUTION: A thrust fin 51 which protrudes radially from a rocker arm 1 is formed and a guide groove 52 is formed to control a movement of the rocker arm 1 in the thrust direction of a rocker shaft 3, being engaged with the thrust fin 51. The rocker arm 1 is so designed as to be lifted and moved in the thrust direction of the rocker shaft 3 when valve clearance adjustment is done.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a valve train for an internal combustion engine.

[0002]

2. Description of the Related Art As a conventional valve train of an internal combustion engine, a rocker arm is rotatably supported via a rocker shaft.
There is a cam provided with a cam that opens and closes a valve by swinging a rocker arm, and a shim is interposed between the rocker arm and the valve to adjust a valve clearance.

[0003] By adjusting the thickness of the shim during the production or maintenance of the engine, the valve clearance between the cam and the rocker arm is properly maintained.

[0004]

To adjust the valve clearance, the rocker arm is lifted while the camshaft is removed from the cylinder head, and the shim interposed on the stem top of the intake / exhaust valve is replaced. .

However, when replacing the shim, it is necessary to perform the operation while the operator lifts the rocker arm with one hand, which may cause a problem of poor workability.

An object of the present invention is to improve the workability of replacing a shim in a valve train of an internal combustion engine, focusing on the above problems.

[0007]

According to a first aspect of the present invention, there is provided a valve operating device for an internal combustion engine, which rotatably supports a rocker arm via a rocker shaft, and swings the rocker arm to open and close a valve. In a valve operating device for an internal combustion engine in which a shim is interposed between a rocker arm and a valve to adjust a valve clearance, a thrust fin protruding from the rocker arm in a rotational radial direction is formed and engaged with the thrust fin. A guide groove is formed in the engine body to restrict the rocker arm from moving in the thrust direction of the rocker shaft, and the thrust fin abuts on the engine body by lifting the rocker arm and moving it in the thrust direction of the rocker shaft when adjusting valve clearance. Then, the rocker arm is held in a raised state.

According to a second aspect of the present invention, there is provided a valve train for an internal combustion engine.
The invention according to claim 1 includes a plurality of cams having different profiles, and a cam switching mechanism for switching a cam to be followed by a rocker arm in response to oil pressure.

According to a third aspect of the present invention, there is provided a valve train for an internal combustion engine.
3. The invention according to claim 1, wherein a boss portion for supporting the rocker shaft is formed on the engine body, a bearing side surface facing the boss portion with a gap is formed on the rocker arm, and the bearing side surface is slid on the cam. The cam follower is formed so as to be offset from the end of the cam follower so as to be away from the boss.

According to a fourth aspect of the present invention, there is provided a valve train for an internal combustion engine.
The internal combustion engine has a rocker arm rotatably supported via a rocker shaft, a cam that opens and closes a valve by swinging the rocker arm, and a shim interposed between the rocker arm and the valve to adjust valve clearance. In the valve gear, a boss portion for supporting the rocker shaft is formed on the engine body, a bearing side surface facing the boss portion with a gap is formed on the rocker arm, and a convex portion protruding from the bearing side surface toward the boss portion. The boss portion is formed with a concave portion that engages with the convex portion, and the rocker arm is lifted by engaging the convex portion with the concave portion when adjusting valve clearance.

According to a fifth aspect of the present invention, there is provided a valve train for an internal combustion engine.
In the invention described in claim 4, the side surface of the convex portion is formed so as to be offset from the boss portion with respect to the end of the cam follower that slides on the cam.

[0012]

According to the first aspect of the present invention, the thrust fin is brought into contact with the engine body by lifting the rocker arm and moving the rocker shaft in the thrust direction of the rocker shaft when adjusting the valve clearance. Thus, the rocker arm is held in a state of being lifted via the thrust fin. For this reason, the operator can use both hands freely, and can easily perform the work of changing the shim and adjusting the valve clearance.

According to the second aspect of the present invention, the rocker arm is positioned with high accuracy in the thrust direction of the rocker shaft, and the flow of hydraulic oil guided from the hydraulic passage to the cam switching mechanism is reduced. Without being
Deterioration of the cam switching response can be prevented.

According to the third aspect of the invention, the side surface of the bearing is formed so as to be offset from the end of the cam follower so as to be away from the boss portion.
A gap can be provided between the side surface of the bearing and the boss portion without increasing the interval between the boss portions, thereby avoiding an increase in the size of the engine body.

According to the valve gear of the internal combustion engine according to the fourth aspect, the convex portion is engaged with the concave portion by moving in the thrust direction of the rocker shaft with the rocker arm raised when adjusting the valve clearance. The rocker arm is held in a state where the rocker arm is lifted up through the projection. For this reason, the operator can use both hands freely, and can easily perform the work of changing the shim and adjusting the valve clearance.

According to the fifth aspect of the present invention, the side surface of the convex portion is formed so as to be offset from the end of the cam follower so as to be away from the boss portion.
A gap can be provided between the side surface of the bearing and the boss portion without increasing the interval between the boss portions, thereby avoiding an increase in the size of the engine body.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an engine having two intake valves and two exhaust valves for one cylinder will be described with reference to the accompanying drawings.

As shown in FIG. 4, the intake camshaft 20
Has a pair of low speed cams 21 and a high speed cam 22 located between the low speed cams 21. The low-speed cam 21 and the high-speed cam 22 adjacent thereto are integrally formed on a common camshaft 20, and the high-speed cam 22 is driven at a low speed so as to satisfy the valve lift characteristics required when the engine is running at a low speed and at a high speed. Compared to the cam 21, it has a profile that increases both the valve lift and the valve opening period.

As shown in FIG. 3, each cylinder is provided with a single rocker arm 1 corresponding to two intake valves 9. The base end of the rocker arm 1 is a rocker shaft 3 common to each cylinder.
And is swingably supported by the cylinder head 4 via the. The tip of the rocker arm 1 is in sliding contact with the stem top of each intake valve 9, and is driven to open and close while expanding and contracting the valve spring 8 as the rocker arm 1 swings.

The rocker arm 1 is provided with a pair of cam followers 14 slidably in contact with a pair of low-speed cams 21, and a single sub rocker arm 2 is provided between the cam followers 14.

As shown in FIG. 5, the base end of the sub rocker arm 2 is connected to the rocker arm 1 via a sub rocker shaft 3 so as to be relatively rotatable. Sub rocker shaft 16
Are slidably fitted respectively in a hole 17 formed in the sub rocker arm 2 and a hole 18 formed in the rocker arm 1, and rings 19 are fitted at both ends thereof to prevent falling off.

The sub rocker arm 2 does not have a portion that comes into contact with the intake valve, and a cam follower portion 23 that comes into sliding contact with the high-speed cam 22 is formed at the tip of the sub rocker arm 2 to project in an arc shape.

As a lost motion mechanism for causing the sub rocker arm 2 to follow the high speed cam 22, a lifter 41 slidably housed in the sub rocker arm 2 is provided, and the sub rocker arm 2 is Is pressed against the high-speed cam 22.

Between the rocker arm 1 and the sub rocker arm 2, there is provided a cam switching mechanism for locking the relative rotation of the two and switching the cam involved in the opening and closing operation of each intake valve 9 from the low speed cam 21 to the high speed cam 22. Can be

As a cam switching mechanism, a prop 31 is rotatably connected to the rocker arm 1 via a shaft 32. The prop 31 is relatively rotated between a locked position where one end is engaged with the lower end of the sub rocker arm 2 and a non-locked position where one end is disengaged from the lower end of the sub rocker arm 2.

The prop 31 has one end engaged with the lower end of the sub rocker arm 2 so as to stop the relative rotation of the sub rocker arm 2 with respect to the rocker arm 1.

In order to switch the prop 31 between the unlocked position and the locked position, a spring 3 for urging the prop 31 to the unlocked position is provided between the prop 31 and the rocker arm 1.
And a hydraulic piston 3 for rotating the sub rocker arm 2 to a locking position against a spring 33.
0 is provided.

The spring 33 and the pin 34 are slidably housed in a hole formed in the rocker arm 1, and the pin 34 comes into contact with one end of the prop 31.

The spring 33 and the pin 34 are provided offset with respect to the sub rocker arm 2. The prop 31 is formed with an arm 35 to which the pin 34 contacts in a lateral direction.

As shown in FIG. 6, a hole 36 for slidably fitting the hydraulic piston 30 is formed in the rocker arm 1, and a hydraulic chamber 37 is formed behind the hydraulic piston 30.

Hydraulic passage 38 for guiding hydraulic pressure to hydraulic chamber 37
Is provided through the inside of the rocker arm 1 and the rocker shaft 3. The rocker arm 1 has a through hole 42 having one end opened to the hydraulic chamber 37 and the other end opened to a bearing 39 for the rocker shaft 3. An oil gallery 43 is formed in the rocker shaft 3 in the thrust direction, and communicates with the through hole 42 of the rocker arm 1 through a through hole 44.

The oil pressure of the oil pump is guided to the oil gallery 43 via a switching valve (not shown) during a predetermined high-speed operation. The control unit that electronically controls the operation of the switching valve inputs the engine rotation signal, cooling water temperature signal, lubricating oil temperature signal, supercharging pressure signal of intake air by the turbocharger, throttle valve opening signal, etc. The switching between the low-speed cam 21 and the high-speed cam 22 is smoothly performed while suppressing a sudden change in the engine torque based on the detected value.

During low-speed operation of the engine, the rocker arm 1 swings according to the profile of the low-speed cam 21 to open and close each intake valve 9 against the valve spring 8. At this time,
Although the sub rocker arm 2 is swung by the high-speed cam 22, the prop 31 is held at a non-locking position where the prop 31 does not engage with the sub rocker arm 2.
Does not hinder the movement of

When the engine is running at high speed, the operating oil pressure is
When the hydraulic piston 30 is guided to the hydraulic chamber 37 through the position 8, the hydraulic piston 30 moves the prop 31 to the locking position against the spring 33, and one end of the prop 31 engages the rocker arm 1, as shown in FIG. Accordingly, the two rocker arms 1 and 2 swing together. The high-speed cam 22 is formed so that both the valve opening angle and the lift amount are larger than the low-speed cam 21, so that when the swing is integrated with the sub rocker arm 2, the low-speed cam 21 is moved to the main rocker arm. The intake valves 9 are lifted up from the first cam follower 14, and each intake valve 9 is driven to open and close according to the profile of the high-speed cam 22, so that both the opening angle and the lift amount of the valve are increased. On the other hand, when the operation range of the engine shifts from the high rotation range to the low rotation range again, the hydraulic pressure guided to the hydraulic chamber 37 decreases by the operation of the switching valve, and the prop 31
Pivots to the unlocked position, and the restraint of the sub rocker arm 2 is released.

By the way, the mounting position of the rocker arm 1 is shifted with respect to the thrust direction of the rocker shaft 3, and the passage cross-sectional area in which the through hole 44 of the rocker shaft 3 and the through hole 42 of the rocker arm 1 that constitute the hydraulic passage 38 engage. Is smaller, the flow of the hydraulic oil guided to the hydraulic chamber 37 is reduced in this portion, and the switching response of the cams 21 and 22 deteriorates. In order to prevent this, the rocker arm 1 is required to have high mounting accuracy in the thrust direction of the rocker shaft 3.

To cope with this, as shown in FIG. 7, a thrust fin 51 projecting from the rocker arm 1 in the rotational radial direction is provided.
1 is provided with a guide groove 52 to be engaged.

The thrust fin 51 is integrally formed so as to protrude from a lower portion of the rocker arm 1. While being connected to a boss portion 57 to which the rocker shaft 3 is fitted, and being connected to a boss portion 58 to which the hydraulic piston 30 is fitted,
The rocker arm 1 is formed to protrude.

The rocker arm 1 is positioned with high accuracy in the thrust direction of the rocker shaft 3 by the engagement of the thrust fin 51 with the guide groove 52. As a result, the mounting position of the rocker arm 1 is shifted with respect to the thrust direction of the rocker shaft 3, and a hydraulic chamber is formed in a passage portion where the through hole 44 of the rocker shaft 3 and the through hole 42 of the rocker arm 1 that constitute the hydraulic passage 38 engage. The flow of the hydraulic oil guided to 37 is not restricted, so that the switching response of the cams 21 and 22 can be prevented from deteriorating.

The thrust fin 51 is connected to the rocker shaft 3.
Has a pair of thrust receiving surfaces 53 that are orthogonal to the central axis. When the rocker arm 1 is in a single state, the thrust receiving surface 53
Is finished with predetermined accuracy by machining.

The guide groove 52 has a pair of thrust surfaces 55 orthogonal to the central axis of the rocker shaft 3. The thrust receiving surface 55 is finished with predetermined accuracy by machining.

The cylinder head 4 is inclined below the rocker arm 1 so that the upper deck 56 defining the valve operating chamber descends toward the center of the cylinder head 4 to move the camshaft 20 and the like. The oil flowing down on the upper deck 56 after lubrication is collected in an oil drop hole (not shown) opened on the upper deck 56.

The guide groove 52 is opened at a predetermined depth in the vertical direction with respect to the upper deck 56, and defines an oil storage chamber 61 for storing a predetermined amount of oil inside the guide groove 52.

In order to supply lubricating oil to the oil reservoir 61, the oil reservoir 61 is opened immediately below the opening edge of the hole 36 for the rocker arm 1 into which the hydraulic piston 30 is fitted. The oil leaking from the gap 36 falls into the oil reservoir 61.

A disk-shaped shim 5 is interposed between the top of the stem of each intake valve 9 and the tip of the rocker arm 1, and the thickness of the shim 5 is adjusted so that the gap between each low-speed cam 21 and the rocker arm 1 is increased. Valve clearance is maintained properly. In order to adjust the valve clearance, the rocker arm 1 is lifted up as shown by a two-dot chain line in FIG. 3 while the camshaft 20 is detached from the cylinder head 4, and is mounted on the stem top of the intake valve 9. Sim 5
Exchange.

However, when the shim 5 is replaced during the production or maintenance of the engine, it is necessary to replace the shim 5 while the operator lifts the rocker arm 1 with one hand, resulting in poor workability. Can be considered.

According to the present invention, when the shim 5 is replaced, the rocker arm 1 is moved in the thrust direction while the rocker arm 1 is lifted, and the thrust fin 51 is moved to the upper deck 56 of the cylinder head 4 when the shim 5 is replaced. The rocker arm 1 is held in a state of being lifted up through the thrust fin 51 by being brought into contact with the upper side.

As shown in FIG. 1, a boss 45 is formed in the cylinder head 4 so as to penetrate the rocker shaft 3. The boss 45 is formed so as to sandwich the rocker arm 1. Each boss portion 45 has a boss side surface 46 facing the rocker arm 1.

As shown in FIG. 2, the rocker arm 1 has both sides thereof removed to define a gap 47 between the boss side surfaces 46. By providing the gap 47, the rocker arm 1 can be moved in the thrust direction while the operator lifts the rocker arm 1 when the shim 5 is replaced.

The opening width of the gap 47 is such that the rocker arm 1 can be moved in the thrust direction while the rocker arm 1 is lifted up when the shim 5 is replaced, and the thrust fin 51 comes off the guide groove 52 and abuts on the upper deck 56. Distance. For this reason, the opening width of the gap 47 is set to a sufficient size so that the thrust fins 51 do not come off from above the upper deck 56 when the shim 5 is replaced.

Even if the gap 47 is provided, the rocker arm 1 is positioned in the thrust direction of the rocker shaft 3 by the engagement of the thrust fin 51 with the guide groove 52 during operation of the engine as described above.

The rocker arm 1 has a bearing side surface 26 facing the boss side surface 46 of the cylinder head 4. Bearing side 2
6 is formed so as to be offset from the boss 45 with respect to the end 28 of the cam follower 14. Bearing side 2
A step 29 is formed between the cam follower 6 and the cam follower end 28. By providing the step 29, the gap 47 can be provided without increasing the interval between the boss side surfaces 46 of the cylinder head 4, and the cylinder head 4 can be prevented from being enlarged.

The step 29 prevents the side of the rocker arm 1 from interfering with the boss portion 45 when the rocker arm 1 is lifted and moved in the thrust direction when the shim 5 is replaced.
It is formed at a predetermined position. As a result, as described above, the opening width of the gap 47 is set so that the thrust fin 51 is
From the upper deck 56.

The exhaust valve 10 is provided with the same valve gear as the intake valve 9.

The configuration is as described above. Next, the operation will be described.

When the shim 5 is replaced, the rocker arm 1 is moved in the thrust direction within the gap 47 while the rocker arm 1 is lifted by the operator. When the rocker arm 1 is moved until the bearing side surface 26 contacts the boss side surface 46 of the cylinder head 4, a part of the thrust fin 51 faces the upper deck 56 of the cylinder head 4. From this state, by contacting the thrust fin 51 with the upper deck 56 of the cylinder head 4, the rocker arm 1 is held in a state of being lifted via the thrust fin 51. Thereby, the operator can use both hands freely, and can easily perform the operation of replacing the shim 5 and adjusting the valve clearance.

After the replacement of the shim 5 is completed, the rocker arm 1 is positioned in the thrust direction of the rocker shaft 3 by engaging the thrust fin 51 with the guide groove 52. By assembling the camshaft 20 to the cylinder head 4, the thrust fin 51 does not come off the guide groove 52.

Next, the embodiment shown in FIG. 8 will be described. The parts corresponding to those in FIG. 1 are denoted by the same reference numerals.

A gap 67 is defined between the rocker arm 1 and the boss side surface 46 of the cylinder head 4, and a projection 71 projecting from the bearing side surface 26 toward the boss portion 45 is formed.

The rocker arm 1 is restricted from moving to the right in the drawing in the thrust direction by the side surface 73 of the projection 71 slidingly contacting the boss side surface 46. Further, the rocker arm 1 is restricted from moving to the left in the thrust direction in the figure by the side surface 75 slidingly contacting the boss side surface 46.

The cylinder head 4 has a concave portion 72 which is concavely formed on the boss side surface 46. The concave portion 72 engages with the convex portion 71 by moving to the right side in the figure with the camshaft 20 removed and the rocker arm 1 raised.

The side surface 73 of the projection 71 is formed so as not to protrude in the thrust direction with respect to the end surface 28 of the cam follower 14. Thereby, the boss side surface 46 of the cylinder head 4 is formed.
The protrusions 71 can be provided without increasing the distance between the cylinder heads 4, and the cylinder head 4 can be prevented from increasing in size.

The configuration is as described above. Next, the operation will be described.

When the shim 5 is replaced, the worker moves in the thrust direction with the rocker arm 1 lifted, and
1 is engaged with the concave portion 72, so that the rocker arm 1 is
Is held in a state of being lifted through the convex portion 71.
This allows workers to use both hands freely,
The work of adjusting the valve clearance by replacing the shim 5 can be easily performed.

After the replacement of the shim 5 is completed, the engagement between the convex portion 71 and the concave portion 72 is released, so that the side surface 26 and the convex side surface 73 of the rocker arm 1 slide on the respective boss side surfaces 46 of the cylinder head 4. In contact therewith, positioning is performed in the thrust direction of the rocker arm 1.

[Brief description of the drawings]

FIG. 1 is a plan view of a valve train showing an embodiment of the present invention.

FIG. 2 is a side view of the valve gear.

FIG. 3 is a longitudinal sectional view of the engine.

FIG. 4 is a side view of the valve gear.

FIG. 5 is an exploded perspective view of the valve gear.

FIG. 6 is a cross-sectional view of a rocker arm and the like.

FIG. 7 is a front view of the valve gear.

FIG. 8 is a plan view of a valve train according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rocker arm 2 Sub rocker arm 3 Rocker shaft 4 Cylinder head 9 Intake valve 14 Cam follower 30 Hydraulic piston 37 Hydraulic chamber 38 Hydraulic passage 51 Thrust fin 52 Guide groove 26 Bearing side surface 28 Cam follower end portion 29 Step 45 Boss portion 46 Boss side surface 47 Gap 67 Gap 71 convex portion 72 concave portion 73 convex side surface

Claims (5)

[Claims] A rocker arm is rotatably supported via a rocker shaft, a cam is provided for opening and closing a valve by swinging the rocker arm, and a shim is provided between the rocker arm and the valve to adjust a valve clearance. In a valve train for an internal combustion engine to be mounted, a thrust fin protruding from a rocker arm in a radial direction of the rocker arm is formed, and a guide groove for engaging with the thrust fin and restricting the rocker arm from moving in the thrust direction of the rocker shaft is provided in the engine. The rocker arm is lifted up and moved in the thrust direction of the rocker shaft when adjusting the valve clearance, so that the thrust fin abuts on the engine body and the rocker arm is held in a raised state. A valve train for an internal combustion engine. 2. A valve operating apparatus for an internal combustion engine according to claim 1, further comprising: a plurality of cams having different profiles; and a cam switching mechanism for switching a cam to be followed by a rocker arm in response to a hydraulic pressure. . 3. A boss portion for supporting the rocker shaft is formed on the engine main body, a bearing side surface facing the boss portion with a gap is formed on the rocker arm, and the bearing side surface is provided at an end of a cam follower slidingly contacting the cam. 3. The valve train for an internal combustion engine according to claim 1, wherein the valve train is formed so as to be offset from the boss. 4. A rocker arm rotatably supported via a rocker shaft, a cam for opening and closing a valve by swinging the rocker arm, and a shim between the rocker arm and the valve for adjusting valve clearance. In the valve gear of an internal combustion engine to be mounted, a boss portion for supporting the rocker shaft is formed in the engine body, a bearing side surface facing the boss portion with a gap is formed in the rocker arm, and the bearing side faces the boss portion. A projecting projection formed on the boss, a recess engaging with the projection is formed on the boss, and the rocker arm is lifted by engaging the projection with the recess when adjusting the valve clearance. Valve device. 5. A valve train for an internal combustion engine according to claim 4, wherein the side surface of said convex portion is formed so as to be offset from a boss portion with respect to an end of a cam follower slidingly contacting a cam. .