JP2002122011A - Valve system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve system for an internal combustion engine which can secure position precision of a rocker arm. SOLUTION: This valve system is provided with a main rocker arm 2, a hydraulic piston 30 for making the main rocker arm 2 operate the cam-switching mechanism and an upper deck 56 on a lower side of the main rocker arm 2. The valve system is provided with a thrust fin 51 projected and formed in the rotary radial direction from the main rocker arm 2 and a guide groove 52, which is engaged to the thrust fin 51 and defines an oil reservoir chamber 61 for storing oil from the hydraulic piston 30. The main rocker arm 2 is provided with a boss part 57, for fitting the rocker shaft and a boss part 58, for fitting the hydraulic piston 30. The thrust fin 51 is projected and formed on the main rocker arm 2, so as to connect with the boss part 57 for fitting the rocker shaft and connected with the boss part 58 for fitting the hydraulic piston 30. The guide groove 52 opens with a prescribed depth with respect to the upper deck 56.

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 operating device for an internal combustion engine, there is, for example, one shown in FIG.
Publication No.).

[0003] To explain this, two rocker arms 102 and 103 are swingably supported via a rocker shaft 103. Above the rocker arm 102,
A cam (not shown) that rotates in synchronization with engine rotation is provided. Each rocker arm 102, 103 swings following the cam to open and close the two valves 109 respectively.

[0004] Between the rocker arms 102 and 103,
A cam switching mechanism 108 that connects the two in response to oil pressure is provided. With the respective rocker arms 102 and 103 connected, the two valves 109 are opened and closed in synchronization.
With the rocker arms 102 and 103 disconnected, one of the valves 109 stops opening and closing operations.

[0005] A hydraulic passage 107 is provided across the rocker shaft 103 and the rocker arm 102. An operating oil pressure is guided to a cam switching mechanism 108 through a hydraulic passage 107.

The end faces 110 of the bearings of the rocker arms 102 and 103 are connected to the end faces 111 of the boss of the cylinder head 105.
The rocker arms 102 and 103 are brought into sliding contact with each other.
Is restricted from moving in the axial direction of the rocker shaft 103.

[0007]

Since the hydraulic passage 107 for guiding the operating oil pressure to the cam switching mechanism 108 is provided over the rocker shaft 103 and the rocker arm 102, the hydraulic passage 107 is disposed in the axial direction of the rocker shaft 103. When the mounting position of the rocker arm 102 is shifted, the flow of the hydraulic oil guided to the cam switching mechanism 108 is reduced, and the operation responsiveness of the cam switching mechanism 108 is deteriorated. To prevent this, the rocker arm 102 has a rocker shaft 1
High positional accuracy is required in the axial direction of 03.

However, in such a conventional valve train for an internal combustion engine, it is necessary to cut the end face 111 of the boss portion of the cylinder head 105 on the side face of the end mill, so that sufficient finishing accuracy can be ensured. It is difficult, and moreover, the number of steps required for the finishing process is increased, which may cause a problem of low productivity.

An object of the present invention is to provide a valve train for an internal combustion engine that can easily secure the positional accuracy of a rocker arm, focusing on the above problems.

[0010]

According to a first aspect of the present invention, there is provided a valve train for an internal combustion engine, comprising a plurality of cams having different profiles.
A main rocker arm that is swingably supported via a rocker shaft and that opens and closes a valve by swinging following the cam; a cam switching mechanism for switching the cam that the main rocker arm follows; and a main rocker arm A valve piston for actuating the cam switching mechanism, and a cylinder head that swingably supports the main rocker arm and has an upper deck positioned below the main rocker arm. A thrust fin protruding from the rocker arm in the radial direction of rotation thereof; and a thrust fin engaged with the thrust fin to prevent the main rocker arm from moving in the axial direction of the rocker shaft, and oil leaking from the hydraulic piston. A guide groove defining an oil reservoir for storing oil, The rocker arm includes a boss for fitting the rocker shaft and a boss for fitting the hydraulic piston, and the thrust fin is connected to the boss for fitting the rocker shaft, and The main rocker arm is formed to protrude from the main rocker arm so as to be connected to the boss portion into which a piston is fitted, and the guide groove opens to the upper deck with a predetermined depth.

According to a second aspect of the present invention, there is provided a valve train for an internal combustion engine.
2. The valve train for an internal combustion engine according to claim 1, wherein the upper deck is inclined so as to descend toward a central portion of the cylinder head.

According to a third aspect of the invention, there is provided a valve train for an internal combustion engine.
3. The invention according to claim 1, wherein a center of the main rocker arm in a direction opposite to a center of mass of the cam switching mechanism interposed in the main rocker arm with respect to an axial center of a bearing portion fitted to the rocker shaft. Offset the center of mass of the thrust fin.

[0013]

The thrust fin protruding from the rocker arm in the rotation radial direction is characterized in that:
By engaging with the guide groove, the rocker arm is positioned with high accuracy in the axial direction of the rocker shaft.

As a result, when the hydraulic passage for guiding the operating oil pressure to the cam switching mechanism is provided across the rocker shaft and the rocker arm, the mounting position of the rocker arm is shifted with respect to the axial direction of the rocker shaft, and the cam switching from the hydraulic passage is performed. It is possible to prevent the flow of the hydraulic oil guided to the mechanism from being restricted, and to prevent the switching response of the cam from being deteriorated.

The guide groove can be formed in a cylinder head or the like by drilling, so that the number of steps required for finishing is small, and productivity can be improved. By storing the oil leaked from the gap of the hydraulic piston in the oil reservoir defined by the guide groove, the sliding portion between the thrust fin and the guide groove is lubricated, and the friction can be reduced.

According to a second aspect of the present invention, there is provided a valve train for an internal combustion engine.
The upper deck is tilted so as to descend toward the center of the cylinder head, so that oil leaked from the gap between the hydraulic pistons is efficiently stored in the oil storage chamber. Friction with the sliding contact portion can be reduced.

According to a third aspect of the present invention, there is provided a valve train for an internal combustion engine.
By offsetting the center of mass of the thrust fin in the direction opposite to the center of mass of the cam switching mechanism interposed in the main rocker arm with respect to the axial center of the bearing fitted to the rocker shaft of the main rocker arm, The inertia force acting on the swinging object integrally with the cam switching mechanism and the like approaches the center of the bearing portion of the main rocker arm, the surface pressure generated in the bearing portion of the main rocker arm is made uniform, and the friction can be reduced.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, two intake valves and two intake valves for one cylinder will be described.
An embodiment in which the present invention is applied to an engine having the exhaust valve 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 to the low-speed cam 21 are integrally formed on a common camshaft 20, respectively, so that the high-speed cam 22 and the high-speed cam 22 can satisfy the valve lift characteristics required at low engine speed and high engine speed.
Has a profile that increases both the valve lift and the valve opening period as compared with the low-speed cam 21.

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

The main rocker arm 1 is provided with a pair of cam followers 14 which are in sliding contact with a pair of low speed cams 21.
A single sub rocker arm 2 between each cam follower section 14
Is provided.

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

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 so as to protrude 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 is brought into contact with the main rocker arm 1 via the lifter 41. A lost motion spring 25 that presses the high speed cam 2 against the high speed cam 22 is interposed.

Between the main rocker arm 1 and the sub rocker arm 2, the relative rotation between them is locked, and the cams involved in opening and closing the intake valves 9 are changed from the low speed cam 21 to the high speed cam 22.
A cam switching mechanism is provided for switching to a cam.

As a cam switching mechanism, a prop 31 is rotatably connected to the main 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 main rocker arm 1.

In order to switch the prop 31 between the unlocked position and the locked position, a spring 33 for urging the prop 32 to the unlocked position is interposed between the prop 31 and the main rocker arm 1. A hydraulic piston 30 that rotates the sub rocker arm 2 to the locking position against the spring 33 is provided.

The spring 33 and the pin 34 are slidably housed in a hole formed in the main 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 from 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. 1, the main rocker arm 1
Is formed with a hole 36 for slidably fitting the hydraulic piston 30, and a hydraulic chamber 37 is formed behind the hydraulic piston 30.

A hydraulic passage 38 for guiding the working oil pressure to the hydraulic chamber 37
Is provided through the inside of the main rocker arm 1 and the rocker shaft 3. The main rocker arm 1 is formed with 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 inside of the rocker shaft 3 in the axial direction.
Through the through-hole 42 of the main rocker arm 1.

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 receives the engine rotation signal, cooling water temperature signal, lubricating oil temperature signal, supercharging pressure signal of the intake air by the supercharger, throttle valve opening signal, etc. The switching between the low-speed cam 21 and the high-speed cam 22 is performed smoothly while suppressing a rapid change in the engine torque based on the detected value.

During low-speed operation of the engine, the main 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 main rocker arm 1 does not engage with the main rocker arm 1.

When the operating oil pressure is introduced into the oil pressure chamber 37 through the oil pressure passage 38 during the high-speed operation of the engine, the hydraulic piston 30 moves the prop 31 against the spring 33 to the locking position as shown in FIG. The two rocker arms 1 and 2 swing together as one end of the prop 31 engages with the main rocker arm 1. High speed cam 2
2 is formed such that the valve opening angle and the lift amount are both larger than those of the low-speed cam 21, so that the low-speed cam 21 rotates the main rocker arm 1 when swinging integrally with the sub rocker arm 2. Each intake valve 9 is lifted up from the cam follower section 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 of the valve and the lift amount increase. On the other hand, when the engine shifts from the high rotation range to the low rotation range again, the hydraulic pressure guided to the hydraulic chamber 37 is reduced by the operation of the switching valve, and the prop 31 is rotated to the unlocked position by the elastic restoring force of the spring 33. Thus, the restraint of the sub rocker arm 2 is released.

The mounting position of the main rocker arm 1 is shifted with respect to the axial direction of the rocker shaft 3 so that the through hole 44 of the rocker shaft 3 and the through hole 42 of the main rocker arm 1 that constitute the hydraulic passage 38 engage. When the cross-sectional area becomes small, the flow of the hydraulic oil guided to the hydraulic chamber 37 is reduced at this portion, and the switching response of the cams 21 and 22 deteriorates. In order to prevent this, the main rocker arm 1 is required to have high mounting accuracy in the axial direction of the rocker shaft 3.

To cope with this, a thrust fin 51 protruding from the main rocker arm 1 in the radial direction of rotation is provided, and a guide groove 52 engaging with the thrust fin 51 is provided in the cylinder head 4.

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

The main rocker arm 1 is formed substantially symmetrically with respect to the center of the sub rocker arm 2, but the thrust fin 51 is opposite to the arm 35, the spring 33 and the pin 34 with respect to the center of mass of the main rocker arm 1. The main rocker arm 1 is configured so that the center of mass is located at the center of the main rocker arm 1 in a state where the sub rocker arm 2 is assembled to the main rocker arm 1. As a result, the surface pressure generated between the bearing hole 39 of the main rocker arm 1 and the rocker shaft 3 is made uniform, and the friction is reduced.

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. With the main rocker arm 1 alone, the thrust receiving surface 53 is finished with a predetermined accuracy by machining.

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

The cylinder head 4 is located below the main rocker arm 1 and defines an upper deck 5 defining a valve operating chamber.
6 is inclined so as to descend toward the center of the cylinder head 4 so that oil flowing down onto the upper deck 56 after lubricating the camshafts 20 and the like is transferred to the upper deck 56.
The oil is collected in an oil drop hole (not shown) that opens upward.

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 just below the opening edge of the hole 36 with respect to the main rocker arm 1 into which the hydraulic piston 30 is fitted. Oil leaking from the gap of the hole 36 falls into the oil reservoir 61.

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

The operation will be described below.

The thrust fins 51 projecting from the main rocker arm 1 in the radial direction of rotation engage with the guide grooves 52 opened in the cylinder head 4, so that the main rocker arm 1 is highly accurate in the axial direction of the rocker shaft 3. Positioned.

As a result, the mounting position of the main rocker arm 1 is shifted with respect to the axial direction of the rocker shaft 3, and the through hole 44 of the rocker shaft 3 and the through hole 42 of the main rocker arm 1 that constitute the hydraulic passage 38 are engaged. The flow of the hydraulic oil guided to the hydraulic chamber 37 in the passage portion is not restricted,
It is possible to prevent the switching response of the cams 21 and 22 from deteriorating.

The thrust receiving surface 53 of the thrust fin 51
However, the area of the guide groove 52 in sliding contact with the thrust surface 55 is:
Since the end face of the boss portion of the main rocker arm is considerably smaller than that of the conventional structure in which the main rocker arm slides on the cylinder head side, the friction accompanying the swing of the main rocker arm 1 can be reduced.

The guide groove 52 has a rectangular cross section and is concavely recessed in the upper deck 56 of the cylinder head 4. Therefore, the guide groove 52 can be formed by drilling. Enhanced.

The thrust fins 51 are formed so as to be connected to a boss portion 57 for fitting the rocker shaft 3 of the main rocker arm 1 and a boss portion 58 for fitting the hydraulic piston 30, so that the housing rigidity of the main rocker arm 1 is increased. And the weight of the main rocker arm 1 can be reduced.

The thrust fin 51 is offset in the direction opposite to the arm 35 with respect to the center of mass of the main rocker arm 1, and the center of mass is shifted to the main rocker arm 1 with the sub rocker arm 2 assembled to the main rocker arm 1.
Of the main rocker arm 1 and the sub-rocker arm 2 and the like, the inertia force acting on the swinging object acting integrally with the main rocker arm 1 and the sub-rocker arm 2 acts on the center of the bearing hole 39 of the main rocker arm 1. Thus, the surface pressure generated in the bearing portion of the main rocker arm 1 is made uniform, and the friction is reduced.

Oil reservoir 6 defined by guide groove 52
1 is a main rocker arm 1 to which the hydraulic piston 30 is fitted
The oil leaking from the gap between the hydraulic piston 30 and the hole 36 from the hydraulic chamber 37 is shaken off from the main rocker arm 1 and is Accumulate. By supplying the oil to the guide groove 52 in this manner, the sliding contact portion with the thrust fin 51 is lubricated, and the friction is reduced.

[0054]

As described above, the valve gear of the internal combustion engine according to the first aspect of the present invention is supported swingably via a plurality of cams having different profiles and a rocker shaft, and follows the cams. A main rocker arm that drives the valve to open and close by swinging, a cam switching mechanism that switches the cam that the main rocker arm follows, a hydraulic piston that operates the cam switching mechanism with the main rocker arm, and swings the main rocker arm. Support as possible,
In a valve train for an internal combustion engine including a cylinder head having an upper deck positioned below the main rocker arm, a thrust fin protruding from the main rocker arm in a radial direction of rotation and engaging with the thrust fin. The main rocker arm restricts movement of the main rocker arm in the axial direction of the rocker shaft, and a guide groove defining an oil reservoir for storing oil leaked from the hydraulic piston, and the main rocker arm is fitted with the rocker shaft. A boss portion for fitting the hydraulic piston, and a boss portion for fitting the hydraulic piston, wherein the thrust fin is connected to the boss portion for fitting the rocker shaft, and is connected to the boss portion for fitting the hydraulic piston. Projecting from the main rocker arm so as to be connected,
Since the guide groove is opened with a predetermined depth with respect to the upper deck, the rocker arm is positioned with high accuracy in the axial direction of the rocker shaft. Further, the guide groove can be formed in the cylinder head or the like by drilling, so that the number of steps required for finishing is reduced, and the productivity is improved.

According to a second aspect of the invention, there is provided a valve train for an internal combustion engine.
In the invention described in claim 1, the upper deck is
By inclining so as to descend toward the center of the cylinder head, oil leaked from the gap between the hydraulic pistons is efficiently stored in the oil storage chamber, and a small amount of oil is used for sliding contact between the thrust fin and the guide groove. And the friction between them.

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 center of the main rocker arm in a direction opposite to a center of mass of the cam switching mechanism interposed in the main rocker arm with respect to an axial center of a bearing portion fitted to the rocker shaft. By offsetting the center of mass of the thrust fin, the main rocker arm and the cam switching mechanism etc. are integrated into one body, so that the inertial force acting on the swinging object approaches the center of the main rocker arm bearing portion, and the main rocker arm has a bearing portion. The generated surface pressure is made uniform, and friction can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main rocker arm and the like showing an embodiment of the present invention.

FIG. 2 is a front 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 sectional view of a rocker arm and the like showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main rocker arm 2 Sub rocker arm 3 Rocker shaft 4 Cylinder head 9 Intake valve 30 Hydraulic piston 37 Hydraulic chamber 38 Hydraulic passage 51 Thrust fin 52 Guide groove 61 Oil storage chamber

Continued on front page F term (reference) 3G016 AA08 AA19 BA18 BA28 BA36 BB12 BB21 BB25 CA04 CA06 CA11 CA16 CA21 CA25 CA27 CA29 CA31 CA44 CA45 CA50 CA51 CA57 DA06 DA08 DA22 FA12 FA38 GA02 GA08 GA09 3G018 AB04 AB17 BA03 BA06 BA12 BA17 BA36 CA19 DA08 DA15 DA69 DA85 EA02 EA03 EA04 EA11 EA17 FA03 FA06 GA02 GA23 GA25

Claims (3)

[Claims] A plurality of cams having different profiles, a main rocker arm supported to be swingable via a rocker shaft, and opening and closing a valve by swinging following the cam; A cam switching mechanism for switching the cam, a hydraulic piston for operating the cam switching mechanism on the main rocker arm, and an upper deck that swingably supports the main rocker arm and is located below the main rocker arm. And a thrust fin protruding from the main rocker arm in the radial direction of rotation thereof; and engaging the thrust fin to move the main rocker arm in the axial direction of the rocker shaft. And restrict leakage from the hydraulic piston. A guide groove defining an oil storage chamber for storing the discharged oil, the main rocker arm includes a boss for fitting the rocker shaft, and a boss for fitting the hydraulic piston. A guide groove formed on the main rocker arm so as to be connected to the boss portion to which the rocker shaft is fitted and to be connected to the boss portion to be fitted with the hydraulic piston; A valve train for an internal combustion engine, characterized in that it opens with a depth. 2. The valve train for an internal combustion engine according to claim 1, wherein the upper deck is inclined so as to descend toward the center of the cylinder head. 3. A mass of the thrust fin in a direction opposite to a center of mass of the cam switching mechanism interposed in the main rocker arm with respect to an axial center of a bearing portion of the main rocker arm fitted to the rocker shaft. 3. The valve train for an internal combustion engine according to claim 1, wherein the center is offset.