JP2003343226A - Valve train of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure rigidity in a power-transmission point and a lift of a valve in a valve train which changes opening/closing timing for an engine valve by a member operating in contact and linking with a piston in the valve train of an internal combustion engine. <P>SOLUTION: The valve train comprises 1st rocker arms 33, 34, a 2nd rocker arm 35, a piston 151, and a locking protrusion 35a. The rocker arms 33, 34 are supported by a rocker-shaft 32 in a freely swingable manner, and driven by the 1st cam to operate the intake valve. The 2nd rocker-arm 35 is supported by the rocker shaft 32 in a freely swingable manner adjacently to the 1st rocker arm 33, 34, and driven by the 2nd cam. The piston 151 is placed in either one cylinder 150 in linking with the 1st and the 2nd rocker arms, and biassed by a return spring 152. The locking protrusion 35a is placed in the other part of the 1st and the 2nd rocker arms, and puts both rocker-arms in sequential motion by coming into contact with the piston 151. A return spring 152 is placed eccentrically relative to the piston 151 in the direction apart from the piston 151. <P>COPYRIGHT: (C)2004,JPO

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, which can open and close an intake valve and an exhaust valve of the internal combustion engine at different drive timings depending on the operating state of the engine.

[0002]

2. Description of the Related Art In recent years, operating characteristics (opening / closing timing and opening) of an intake valve and an exhaust valve (hereinafter collectively referred to as an engine valve or simply a valve) provided in a reciprocating internal combustion engine (hereinafter referred to as an engine) A valve operating device (also referred to as a variable valve operating mechanism) that can switch the period) to an optimum one according to the load condition and speed condition of the engine has been developed and put into practical use.

As one of the mechanisms for switching the operating characteristics in such a valve operating device, for example, a low speed cam having a cam profile suitable for low-speed engine rotation and a high speed having a cam profile suitable for high-speed engine rotation are provided. The engine cam is selectively used according to the rotation state of the engine to open and close the engine valve.

For example, in the technique disclosed in Japanese Patent Application Laid-Open No. 63-170513, a drive rocker arm that basically swings by a low speed cam to drive an engine valve and a cam including a low speed cam. It is provided with a free rocker arm that is swung by a high speed cam having a profile, and a connection switching mechanism provided between the drive rocker arm and the free rocker arm. When the connection switching mechanism is disconnected, the free rocker arm swings freely, and the drive rocker arm swings by the low speed cam to drive the engine valve with a characteristic according to the cam profile of the low speed cam. When the connection switching mechanism is set to the connected state, the free rocker arm and the drive rocker arm swing together, and the drive rocker arm drives the engine valve with a characteristic according to the cam profile of the high speed cam.

For the connection switching mechanism in this case, various techniques such as the one disclosed in Japanese Patent No. 2586163 have been proposed in addition to the one disclosed in the above publication.

[0006]

[Problems to be Solved by the Invention]
Shows the structure of a valve train proposed in the process of devising the present invention. As shown in FIGS. 4 and 5, the cylinder head 10 above each cylinder of the engine is provided with two intake valves 11 and 12 and two exhaust valves 21 and 22 for each cylinder. Intake valves 11, 12 and exhaust valves 21, 22
A valve train 30 is equipped to drive the engine.

The valve train 30 is divided into an intake valve drive system that drives the intake valves 11 and 12, and an exhaust valve drive system that drives the exhaust valves 21 and 22. The intake valve drive system includes a cam shaft 31 and a cam 31 fixed to the cam shaft 31.
a to 31c, a rocker shaft 32, and rocker arms 33 to 35 swingably supported by the rocker shaft 32 and rocked by respective cams 31a to 31c.
The exhaust valve drive system includes a camshaft 31 that is also used as an intake system,
Cams 31d and 31e fixed to the camshaft 31,
The rocker shaft 36 and rocker arms 37 and 38 (not shown in FIG. 5) swingably supported by the rocker shaft 36 and swung by the cams 31d and 31e are provided.

A variable valve mechanism 40 having a connection switching mechanism 41 is provided in the intake valve drive system portion of the valve operating device 30. That is, the rocker arm 3 for driving the intake valve
Of the rocker arms 33 and 34, the adjusting screws 33a and 34a at one end are brought into contact with the stem ends of the intake valves 11 and 12, and the intake valve 11 is the rocker arm 3 to 35.
3, the intake valve 12 is opened and closed according to the rocking of the rocker arm 3
It is adapted to open and close in accordance with the swing of 4.

The rocker arm 33 has a roller 33b at the other end.
Is brought into contact with the low speed cam 31a formed in the low speed cam profile corresponding to the low speed rotation of the engine,
When the intake valve 11 is swung according to the low speed cam 31a, the intake valve 11 is opened with the characteristic shown by the alternate long and short dash line in FIG. The rocker arm 34 includes a roller 34b at the other end.
Is brought into contact with the low speed cam 31b formed on the low speed cam profile corresponding to the low speed rotation of the engine,
When swung in accordance with the low speed cam 31b, the intake valve 11 is opened with the characteristic shown by the solid line in FIG. 8 (a).

On the other hand, the rocker arm 35 has an engagement projection 35a at one end which can be engaged with the rocker arms 33 and 34, and a roller 35b provided at the other end is a high speed cam profile for high speed engine rotation. It is in contact with the high speed cam 31c formed on the. Rocker arm 33,
A cylinder 50 having an opening 53 is formed at a portion on the 34 side where one end of the rocker arm 35 can abut, and a piston 51 is built in the cylinder 50.

A rocker shaft 32 is provided in the cylinder 50.
When the hydraulic pressure in the cylinder 50 is increased as shown in FIG. 6 (b), hydraulic oil (here, lubricating oil is also used) is supplied from the side through the oil passages 32a and 32b. The piston 51 receives hydraulic pressure at one end and the opening 53
It is driven so as to project to a position that closes. Also,
When the hydraulic pressure in the cylinder 50 is weakened, as shown in FIG. 6A, the piston 51 is driven by the urging force of the return spring 52 so as to be retracted from the opening 53.

A piston 51 in such a cylinder 50
And a hydraulic pressure adjusting device 42 for adjusting the hydraulic pressure in the cylinder 50.
And a connection switching mechanism 41 for switching the connection state between the rocker arms 33, 34 and the rocker arm 35.
The variable valve mechanism 40 is composed of the connection switching mechanism 41 and the intake valve drive system. The hydraulic pressure adjusting device 42 is
As shown in FIG. 7, lubricating oils 42a to 42c for supplying lubricating oil pumped up from the oil pan (not shown) at the lower part of the engine to the cylinder block 10 to the oil passage 32a in the rocker shaft 32, and the lubricating oil. An oil control valve 42d interposed in the middle of the supply path 42c and a controller (not shown) that controls the opening degree of the oil control valve 42d.

FIG. 7 shows a state in which a small-diameter oil passage for supplying lubricating oil to the oil control valve 42d is in communication. When a hydraulic pressure should be applied to the pistons 33e and 34e, a large-diameter oil passage (not shown) is in communication. To be driven. A filter 42e is provided on the lubricating oil supply paths 42a and 42b.
Is installed, and after filtering the lubricating oil, the cylinder 33d,
It is designed to be supplied into 34d.

Therefore, when the oil pressure in the cylinder 50 is weakened by the oil pressure adjusting device 42, the piston 51 is buried and brought into the disengaged state (see FIG. 6A), and the cylinder 5
A space is formed in the opening 53 of the rocker arm 3
When the rocking arm 5 swings, the engaging projection 3 at one end of the rocker arm 35
5a appears and disappears in this space, but rocker arms 33, 3
4 does not touch itself. This enables the rocker arm 3
3, 34 swing according to the corresponding cams 31a, 31b,
The intake valves 11 and 12 are opened and closed.

On the other hand, when the hydraulic pressure in the cylinder 50 is increased by the hydraulic pressure adjusting device 42, the piston 51 is brought into a projecting engagement state (see FIG. 6B), and the piston 51 exists in the opening 53 of the cylinder 50. As a result, when the rocker arm 35 swings, the engagement protrusion 35a at one end of the rocker arm 35 has the side surface (engagement surface) 5 of the piston 51.
4, the rocker arm 33 via the piston 51,
34 is rocked. At this time, the rocker arms 33, 34
8 is driven by the rocker arm 35 and swings according to the high speed cam 31c while being separated from the corresponding cams 31a and 31b, and the intake valves 11 and 12 are made to correspond to the high speed rotation of the engine. Open with the characteristics shown by the solid line in b).

Therefore, the hydraulic pressure adjusting device 42 is a piston position switching device for switching the position of the piston 51 between an engaging position where the engaging protrusion 35a engages and a non-engaging position where the engaging protrusion 35a does not engage. Function. By the way, in such a valve operating device, the piston 51 in the cylinder 50 is
Considering the arrangement of the coil-shaped return spring 52 for urging the clutch to the non-engagement position, for example, Japanese Patent Laid-Open No. 06-00251.
As disclosed in Japanese Patent No. 8, the return spring 52 is generally arranged on the same axis as the piston 51 and the cylinder 50.

That is, as shown in FIGS. 9 (a) to 9 (c), the piston 51 has a shaft center portion on one end side (here, the upper surface side) in which the one end (here, the lower end) of the return spring 52 is housed. A circular recess 51a is formed concentrically with the cylindrical outer peripheral surface of the piston 51 (that is, concentric with the cylindrical outer peripheral surface of the cylinder 50), and also on one end surface (here, the upper end surface) of the cylinder 50. A circular recess 50a for housing the other end (here, the upper end) of the return spring 52 is formed concentrically with the cylindrical outer peripheral surface of the cylinder 50. As a result, the return spring 52 is arranged on the same axis as the piston 51 and the cylinder 50.

In this case, even when the piston 51 is in the disengaged position (see FIG. 9 (a)), since the return spring 52 is located deep inside the opening 53, the engagement projection 35a has the return spring 52. It can only be operated within a range that avoids interference with. Therefore, the piston 51
To the engagement position (see FIG. 9 (b)).
Therefore, it becomes difficult to secure a sufficient valve lift amount when operating the rocker arms 33, 34 according to the high speed cam 31c.

Further, the hollow portion of the piston 51 having the return spring 52 inside has a thin wall portion,
Since the engagement projections 35a serve as the engagement surfaces 54 to be engaged, when pressed by the engagement projections 35a and a valve lift load acts, the parts of the engagement surfaces 54 may be deformed. If the rigidity of the power transmission portion of the valve train is reduced, the valve cannot be driven according to the cam profile, and the original performance of the valve train cannot be achieved.

Of course, if the hollow portion of the piston 51 is made thicker, the rigidity of the power transmission portion of the valve train can be prevented from being lowered, and the operating range of the engagement projection 35a can be prevented from interfering with the return spring 52. Can be enlarged to secure the valve lift amount, but for this purpose, it is necessary to increase the outer diameter of the piston 51 itself or decrease the diameter of the return spring 52. If the outer diameter of the piston 51 is increased, the size of the piston is increased, the size of the device is increased, and the weight is increased. Further, the driving force for switching the position of the piston (here Then, it is necessary to increase the hydraulic pressure) or increase the elastic force of the return spring 52. Further, there is a limit to reducing the diameter of the return spring 52 from the viewpoint of securing elastic force.

The present invention has been devised in view of the above-mentioned problems, and the opening / closing timing of the engine valve is switched by a piston having a return spring and capable of switching the position, and a member which abuts on the piston and can be linked with each other. An object of the present invention is to provide a valve operating device for an internal combustion engine, which is capable of ensuring rigidity of a power transmission portion of a valve operating system and securing a valve lift amount in a valve operating device without increasing the size of a relevant portion. To do.

[0022]

Therefore, in the valve operating system for an internal combustion engine according to the present invention (claim 1), the tip end is linked to one of the intake valve and the exhaust valve and is rockably supported by the rocker shaft. A first rocker arm driven by a first cam and a rocker shaft swingably supported by the rocker shaft and disposed adjacent to the first rocker arm.
Second rocker arm driven by a second cam having a cam shape different from that of the cam, a cylinder formed on one of the first and second rocker arms, and slidably mounted in the cylinder. A piston, an engagement protrusion that is provided on the other of the first and second rocker arms and is engageable with an engagement portion formed on the piston, and an engagement that engages the piston with the engagement protrusion. And a piston position switching device for switching between a position and a non-engaging position where the engaging projection is not engaged.

Therefore, when the piston is brought into the engagement position by the piston position switching device, the engagement protrusion formed on the other of the first and second rocker arms engages with the engagement portion formed on the piston. As a result, the first rocker arm and the second rocker arm swing together to open and close one of the intake valve and the exhaust valve according to the cam profile of the second cam.
Further, when the piston is brought into the disengaged position by the piston position switching device, the first rocker arm and the second rocker arm swing independently, and one of the first and second rocker arms moves to the first rocker arm. One of the intake valve and the exhaust valve is opened and closed according to the cam profile of the cam.

The piston position switching device has a return spring for urging the piston to the non-engagement position, and the return spring is eccentrically arranged with respect to the piston in a direction away from the engagement protrusion. Therefore, it is easy to secure a movable stroke within the range where the engagement projection does not interfere with the return spring, and even when the return spring is arranged inside the engagement portion formed on the piston, the thickness of this engagement portion is large. It becomes easy to secure.

A recess for accommodating one end side of the return spring is formed in the piston, and a thick wall portion having the engagement portion is provided on the engagement projection side around the recess of the piston. Preferably, the thick-walled portion is located outside the cylinder when the piston is in the engagement position, and is housed in the cylinder when the piston is in the non-engagement position (claim). Item 2).

The piston has a cylindrical portion, the thick portion is formed in the cylindrical portion, and the engaging portion provided in the thick portion is formed in a cylindrical surface shape, and the engaging projection is formed. It is preferable that a portion of the contacting portion with the engaging portion is formed in a concave shape along the engaging portion (claim 3).

The return spring is arranged on the extension of the swing locus of the engagement projection relative to the piston side, and at the engagement projection side of the piston,
It is preferable that a spring guard portion is provided on the extension of the swing locus of the engaging projection when the piston is in the non-engaging position so as to cover the return spring (claim 4). The relative swing locus of the engagement protrusion with respect to the piston is not only the swing locus when the rocker arm provided with the engagement protrusion moves toward the piston, but also the rocker arm with the piston engaged. It also includes a swing locus when it moves toward the protrusion. It is preferable that the spring guard portion is formed in a cylindrical surface shape along the concave surface of the engagement protrusion (claim 5).

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIGS. 1 and 2 show a valve operating system for an internal combustion engine as a first embodiment of the present invention, and FIG. 1 is a schematic cross-sectional view showing a main part (piston position switching device) thereof. FIG. 2 is a schematic side view of the inside of the cylinder head. Note that, in FIGS. 1 and 2, the same reference numerals as those in FIGS. 4 to 7 denote the same components. Also, some of them are shown in Figs.
This will be described with reference to FIG.

This valve operating device is characterized by a piston position switching device. Except for this portion, it is the same as the one devised in the process of devising the present invention already described with reference to FIGS. Is configured. That is, as shown in FIGS. 4 and 2, in the cylinder head 10 above each cylinder of the engine,
Two intake valves 11 and 12 and two exhaust valves 2 for each cylinder
1, 22 and the intake valves 11, 1
2. A valve train 30 is installed to drive the exhaust valves 21 and 22.

The valve operating device 30 is divided into an intake valve drive system that drives the intake valves 11 and 12, and an exhaust valve drive system that drives the exhaust valves 21 and 22. The intake valve drive system includes a cam shaft 31 and a cam 31 fixed to the cam shaft 31.
a to 31c, an intake rocker shaft 32, and cams 31a to 3c that are swingably supported by the rocker shaft 32.
The rocker arms 33 to 35 swinging by 1c are provided.

The exhaust valve drive system includes a camshaft 31 that is also used as an intake system, and a cam 31 fixed to the camshaft 31.
d, 31e, the exhaust rocker shaft 36, and the cams 31d, 3 that are swingably supported by the rocker shaft 36.
The rocker arms 37 and 38 (not shown in FIG. 1) swinging by 1e are provided. A variable valve mechanism 40 having a connection switching mechanism 41 is provided in the intake valve drive system of the valve operating device 30.

That is, the rocker arm 33 for driving the intake valve
Rocker arm (first rocker arm) out of 35 3
3, 34 have adjustment screws 33a, 34a at one end abutting on the stem ends of the intake valves 11, 12, the intake valve 11 opens and closes in response to rocking of the rocker arm 33, and the intake valve 12 of the rocker arm 34 moves. It opens and closes in response to rocking.

The rocker arm 33 has a roller 33b at the other end.
Is brought into contact with a low speed cam (first cam) 31a formed in a low speed cam profile corresponding to the low speed rotation of the engine, and swings in accordance with the low speed cam 31a,
The intake valve 11 is opened with the characteristic shown by the alternate long and short dash line in FIG. The rocker arm 34 brings the roller 34b at the other end into contact with a low speed cam (first cam) 31b formed on a low speed cam profile corresponding to the low speed rotation of the engine. When swinging, the intake valve 11 is opened with the characteristic shown by the solid line in FIG. Note that FIG.
In (a), the valve lift phases of the two low speed cams 31a and 31b are shifted and described, but this is an example, and the phases of both low speed cams 31a and 31b may be the same.

On the other hand, the rocker arm (second rocker arm) 35 has an engagement projection 35a projecting from one end which can be engaged with the rocker arms 33 and 34, and a roller 35b provided on the other end to the engine. High-speed cam formed on the high-speed cam profile that corresponds to the high-speed rotation of the
Cam) 31c. Rocker arm 33,3
A cylinder 150 having an opening 153 is formed at a portion on the fourth side with which one end of the rocker arm 35 can abut, and a piston 151 is incorporated in the cylinder 150. The opening 153 is not limited to the shape of this embodiment, and may have any shape as long as it can secure a space in which the engagement protrusion 35a can swing.

The cylinder 150 is supplied with working oil (here, the lubricating oil is also used) from the rocker shaft 32 side through the oil passages 32a and 32b, so that the hydraulic pressure in the cylinder 150 is increased. Then, as shown in FIG.
As shown in (b), the piston 151 receives a hydraulic pressure at one end and is driven so as to project to a position where the opening 153 is closed.

When the hydraulic pressure in the cylinder 150 is weakened, the piston 151 is driven by the urging force of the return spring 152 so as to be retracted from the opening 153 as shown in FIG. 9A. . The piston 151 in the cylinder 150 and the hydraulic pressure adjustment device 42 for adjusting the hydraulic pressure in the cylinder 150 constitute a connection switching mechanism 41 for switching the connection state between the rocker arms 33, 34 and the rocker arm 35. Mechanism 4
The variable valve mechanism 40 is composed of 1 and the intake valve drive system.

As shown in FIG. 7, the hydraulic pressure adjusting device 42 supplies the lubricating oil pumped up from the oil pan (not shown) at the lower part of the engine to the cylinder block 10 to the oil passage 32a in the rocker shaft 32. Lubricating oil supply path 42
a to 42c, an oil control valve 42d interposed in the middle of the lubricating oil supply passage 42c, and a controller (not shown) that controls the opening degree of the oil control valve 42d. Lubricating oil supply paths 42a, 4
A filter 42e is interposed in 2b, and the lubricating oil is filtered and then supplied into the cylinder 150.

Therefore, when the hydraulic pressure in the cylinder 150 is weakened by the hydraulic pressure adjusting device 42, the piston 151 is buried (see FIG. 9A), and a space is formed in the opening 153 of the cylinder 150, and the rocker arm 35 is formed.
When the rocking of the rocker arm 35
a appears and disappears in this space, but rocker arms 33, 34
Do not touch itself. This enables the rocker arm 3
3, 34 swing according to the corresponding cams 31a, 31b,
The intake valves 11 and 12 are opened with the characteristics shown by the alternate long and short dash line or the solid line in FIG.

On the other hand, when the hydraulic pressure in the cylinder 150 is increased by the hydraulic pressure adjusting device 42, the piston 151 is in a protruding state (see FIG. 9B), and the piston 151 is present in the opening 153 of the cylinder 150. When the rocker arm 35 swings, the engagement protrusion 35a at one end of the rocker arm 35 abuts on the piston 151 and swings the rocker arms 33 and 34 via the piston 151. At this time, the rocker arms 33 and 34 are driven by the rocker arm 35 and swing according to the high-speed cam 31c while being separated from the corresponding cams 31a and 31b, so that the intake valves 11 and 12 rotate at high speeds of the engine. Corresponding to the occasion, it is opened with the characteristic shown by the solid line in FIG.

Therefore, the hydraulic pressure adjusting device 42 is a piston position switching device for switching the position of the piston 151 between an engaging position where the engaging protrusion 35a engages and a non-engaging position where the engaging protrusion 35a does not engage. Function. by the way,
In this valve operating device, the coil-shaped return spring 152 that biases the piston 151 to the unlocked position is
51 and the cylinder 150 are eccentrically arranged in a direction away from the engagement protrusion 35a.

That is, as shown in FIGS. 1 (a) to 1 (c), the piston 151 has one end side (upper surface in this case).
At one end (here, the lower end) of the return spring 152
Is formed in a circular recess 151a in a front view, and a circular recess 150a in a front view that accommodates the other end (an upper end here) of the return spring 152 is provided on one end side (here, a downward surface of an upper portion) of the cylinder 150. The recesses 151a and 150a are formed so as to be eccentric in the direction away from the engagement protrusion 35a with respect to the axial center lines of the piston 151 and the cylinder 150. Therefore, the return springs 152 whose both ends are locked by the recesses 151a and 150a are also eccentrically arranged in the direction away from the engagement protrusion 35a.

Due to this eccentric arrangement, the portion of the side surface of the piston 151 around the recess 151a on the side (engagement surface) 154 on which the engagement projection 35a of the piston 151 is engaged has a large thickness. When the piston 151 is in the engagement position, the engagement surface 154 having a large thickness is located in the opening 153 of the cylinder 150, and the engagement projection 35a comes into contact with the engagement surface 154. There is.
When the piston 151 is in the non-engagement position, the piston 151 retracts (is buried) and is housed in the cylinder 150, and the thick engagement surface 154 is disengaged from the opening 153 of the cylinder 150.

Further, the engaging projection 3 on the piston 151
A spring guard portion 155 is provided on the side of the 5a side closer to the tip than the engagement surface 154. When the piston 151 is in the non-engagement position, the spring guard portion 155 has an extension line of the movement locus of the engagement protrusion 35a.
That is, the rocker arms 33 and 34 or the rocker arm 3 are located in the opening 153 of the cylinder 150 and normally do not contact the engagement protrusions 35a, but when the connection switching mechanism 41 is inoperative.
5 corresponds to the corresponding cam 31a, 31b, 31c
It may be considered that an abnormal state in which the engagement projection 35a and the piston 151 change due to the following is not driven, and the engagement projection 35a enters the return spring 152 side in the piston 151. . In such a case, since the spring guard portion 155 protects the return spring 152, the engagement protrusion 35a does not come into contact with the return spring 152, and damage to the return spring 152 due to such contact can be avoided. You can do it.

That is, the rocker arms 33, 34, 35
When the piston 151 is in the disengaged position in a normal state in which the cam is driven following the cams 31a, 31b, 31c, respectively, the piston 151 and the return spring 152 inside the piston 151 do not interfere with the engagement protrusion 35a. Is set to. In this embodiment, the piston 151
Since the spring guard portion 155 is provided to protect the internal return spring 152, damage to the return spring 152 can be avoided even in the above-mentioned abnormal state.

The piston 15 including the engaging surface 154
As shown in FIG. 1 (c), the outer periphery of No. 1 is formed of a cylindrical surface excluding the spring guard portion 155, and the surface of the spring guard portion 155 itself is a convex surface eccentric to the axial center of the piston 151. It is composed of a partially cylindrical surface. Further, a rotation stop pin 156 is interposed between the piston 151 and the cylinder 150 so that the piston 151 does not rotate in the cylinder 150. That is, one of the piston 151 and the cylinder 150 is provided with a rotation stop pin 156.
Is provided so as to project, and an engagement groove with which the detent pin 156 is engaged is bored on the other side to restrict the piston 151 from rotating within the cylinder 150 while allowing the piston 151 to move in the axial direction.

On the other hand, the engaging projection 35a, which abuts the engaging surface 154 formed of a convex cylindrical surface, has a tip end surface contacting the engaging surface 154 corresponding to the engaging surface 154 (however, It is configured by a concave cylindrical surface having a diameter slightly larger than that of the mating surface 154, and is configured so as to surely make a line contact with the engagement surface 154. The rocker arms (first rocker arms) 33 and 34 are urged by return springs (not shown) provided to the intake valves 11 and 12 so as not to separate from the corresponding cams 31a and 31b. (Second rocker arm) 3
Since such a biasing force is not acting on 5,
As shown in FIG. 3, the arm spring 43 serves as a biasing member that keeps the rocker arm 35 from separating from the cam 31c.
Is installed.

The arm spring 43 comprises a spring body 43a and a casing 43b containing the spring body 43a, and the biasing force of the spring body 43a is transmitted to the rocker arm 35 via the casing 43b. The arm spring 43 is mounted in a recess 144 a formed in one end of the holder 144 and supported by the holder 144. The holder 144 has a rocker shaft 36 supporting the exhaust rocker arms 37 and 38 inserted through a shaft hole 144b formed in an intermediate portion, and is rotatably supported by the rocker shaft 36, and the other end 144c is attached to the cylinder head. The rib 145 as a supporting member that is erected upward from 10 is abutted.

That is, since the holder 144 is rotatably supported by the rocker shaft 36, the holder 144 will rotate if the arm spring 43 is attempted to be supported as it is, but the rib 145 and the holder 144 that abuts the rib 145.
The other end 144c of the holder 144 forms a locking structure 146 for stopping the rotation of the holder 144 around the rocker shaft 36. The locking structure 146 restricts the rotation of the holder 144 so as to support the arm spring 43. .

Since the valve operating system for the internal combustion engine according to the first embodiment of the present invention is constructed as described above, the hydraulic pressure adjusting device (piston position switching device) 42 increases the hydraulic pressure in the cylinder 150 to increase the piston 151. Is in a protruding state (engagement position) (see FIG. 1B), the engagement surface 154 of the piston 151 is located in the opening 153 of the cylinder 150, and the rocker arm 35 swings when the rocker arm 35 swings. The engagement projection 35a at one end of 35 abuts on the engagement surface 154 of the piston 151 to swing the rocker arms 33, 34 via the piston 51. That is, the connection switching mechanism 41 is in the connected state, the intake rocker arms 33, 34 swing together with the rocker arm 35, and open / close the intake valves 11, 12 according to the cam profile of the high-speed cam 31c.

Hydraulic pressure adjusting device (piston position switching device) 4
2 weakens the hydraulic pressure in the cylinder 150 and the piston 15
When 1 is in a buried state (non-engagement position) (see FIG. 1A), a space is formed in the opening 153 of the cylinder 150, and the rocker arm 35 rocks when the rocker arm 35 swings.
The engagement projection 35a at one end of the rocker protrudes and retracts in this space and does not contact the rocker arms 33 and 34 themselves. As a result, the connection switching mechanism 41 is disconnected, the intake rocker arms 33, 34 swing without being affected by the rocker arm 35, and the low speed cam 31a or the low speed cam 3 is swung.
The intake valves 11 and 12 are opened and closed according to the cam profile of 1b.

In this device, the return spring 152 in the piston 151 is arranged at a position biased away from the engagement projection 35a side, so that the movable range of the engagement projection 35a that does not interfere with the return spring 152 can be widened. , Rocker arm 33 through rocker arm 35,
A sufficient valve lift amount can be secured when the 34 is operated according to the high speed cam 31c.

Further, due to the eccentric arrangement of the return spring 152, since the engagement surface 154 of the piston 151 with which the engagement protrusion 35a of the rocker arm 35 abuts is formed to have a large thickness, it is pressed by the engagement protrusion 35a. Even when a valve lift load is applied to the engagement surface 154, the engagement surface 154 is unlikely to be deformed, and the rigidity of the power transmission portion of the valve train can be sufficiently secured. Therefore, the valve can be driven according to the cam profile, and the original performance of the valve train can be reliably exhibited.

A torsion spring may be used as the return spring 152 for urging the piston 151 to the non-engagement position. However, when the torsion spring is used, the torsion spring may come into contact with the rocker arm side to cause abrasion damage. is there. In this respect, if the return spring 152 is composed of a coil-shaped spring as in the present embodiment, it is possible to prevent wear and damage of the spring from occurring.

Further, even if the engagement projection 35a enters the return spring 152 side in the piston 151, the spring guard portion 155 protects the return spring 152, so that the engagement projection 35a is attached to the return spring 152. The turn spring 152 is prevented from being damaged without contact. The engagement surface 154 on the outer periphery of the piston 151 is formed of a convex cylindrical surface.
The tip end surface of the engaging projection 35 a that abuts on the engaging surface 54 is the engaging surface 15
4 and a concave cylindrical surface having a diameter slightly smaller than that of the engaging surface 154, the engaging projection 35a can be reliably brought into line contact with the engaging surface 154. The rocker arms 33 and 34 can be reliably and properly interlocked with the rocker arm 35. Further, since the surface of the spring guard portion 155 is also formed of a convex cylindrical surface, there is an advantage that the movable range of the engagement protrusion 35a is expanded.

[Second Embodiment] FIG. 3 is a schematic developed sectional view (corresponding to FIG. 2) showing a valve train for an internal combustion engine according to a second embodiment of the present invention. Note that, in FIG. 3, the same reference numerals as those in FIGS. 1, 2, and 4 to 7 indicate the same parts.

In this embodiment, both the intake valve side and the exhaust valve side are constructed as variable valve actuation mechanisms. That is, on the rocker shaft 32 for intake, a rocker arm (first rocker arm) 133 that rocks by the low speed cam 31b and a rocker arm (second rocker arm) 135 that rocks by the high speed cam 31c are rockable. It is pivotally supported. A first connection switching mechanism 41a similar to that of the first embodiment is interposed between the rocker arm 133 and the rocker arm 135.

One end of the rocker arm 133 is bifurcated, and each end drives the intake valves 11 and 12, respectively. When the first connection switching mechanism 41a is in the disconnected state, the rocker arm 133 is not affected by the movement of the rocker arm 135 and the low speed cam 31 is not affected.
The intake valves 11, 1 swing by corresponding to the cam profile of b.
2 is opened / closed at a low speed as shown by the solid line in FIG. When the connection switching mechanism 41a is in the connected state, the rocker arm 133 is integrated with the rocker arm 135 through the engagement protrusion 135a of the rocker arm 135.
The intake valve 11, 1 swings corresponding to the cam profile of c.
2 is opened and closed at high speed as shown by the solid line in FIG.

On the other hand, on the rocker shaft 36 for exhaust,
A rocker arm 137 swinging by a low speed cam 31f corresponding to the low speed of the engine and a rocker arm 139 swinging by a high speed cam 31g are pivotally supported. A second connection switching mechanism 41b similar to that of the first embodiment is provided between the rocker arm 137 and the rocker arm 139.
Is installed.

One end of the rocker arm 137 is bifurcated and each end drives the exhaust valves 21 and 22, respectively. When the second connection switching mechanism 41b is in the disconnected state, the rocker arm 137 is not affected by the movement of the rocker arm 139, and the low speed cam 31 is not affected.
The exhaust valves 21 and 2 are swung corresponding to the cam profile of f.
Open and close 2 according to the low speed operation of the engine. When the connection switching mechanism 41b is in the connected state, the rocker arm 13
Rocker arm 137 through the engagement protrusion 139a of
Oscillates integrally with the rocker arm 139 corresponding to the cam profile of the high speed cam 31g, and opens and closes the exhaust valves 21 and 22 corresponding to the high speed operation of the engine.

As shown in FIG. 3, the rocker arms (second rocker arms) 135 and the rocker arms 139 are provided with the rocker arms 135 and 139 and the cams 31c and 31, respectively.
Arm springs 43A and 43B are installed as the first and second biasing members so as not to separate from g. In the hydraulic pressure adjusting device (piston position switching device) 42 of each connection switching mechanism 41a, 41b, the first
Similar to the embodiment, the return spring 152 for urging the piston 151 to the non-locking position has the piston 15
1 and the cylinder 150 are arranged eccentrically in the direction away from the engagement protrusion 35a, and the engagement surface 1 of the piston 151
54 is formed to be thick, and the spring guard portion 155 is formed to be thinner than the engaging surface 154 by being recessed.

Since the valve operating system for the internal combustion engine as the second embodiment of the present invention is configured as described above, it does not interfere with the return spring 152 due to the bias of the return spring 152 as in the first embodiment. Engagement protrusion 35
It is possible to secure a sufficient valve lift amount when the rocker arm 33 and 34 are operated according to the high-speed cam 31c through the rocker arm 35, and the wall thickness of the engaging surface 154 is large. Since the valve is formed large, there is an advantage that the rigidity of the power transmission portion of the valve operating system can be sufficiently secured and the original performance of the valve operating device can be reliably exhibited.

As described above, while obtaining the same advantages as those of the first embodiment, it is possible to suppress the enlargement of the piston, the enlargement of the device, the increase in weight, and the increase in the driving force required for switching the position of the piston. The elastic force of the return spring can also be secured. Furthermore, in the unlikely event that the engaging projection 35
Even when “a” enters the return spring 152 side in the piston 151, the spring guard portion 155 protects the return spring 152 and the turn spring 15
2 damage is prevented.

[Others] Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and various modifications can be made without departing from the spirit of the present invention. . For example, although the spring guard portion 155 is provided in the above embodiment, the engagement protrusion 35a
The spring guard portion 155 may be omitted as long as there is no risk of contacting the return spring 152 in the piston 151. In this case, the movable range of the engagement protrusion 35a that does not interfere with the return spring 152 can be increased.

Further, in the above first and second embodiments, the rocker arms 33 and 3 driven by the low speed cam.
Cylinders, pistons and openings are provided at 4, 133, and rocker arms 35, 135 driven by the high speed cam are provided with engaging projections. On the contrary, the rocker arms 33, 34, 133 are provided with engaging projections. Provided, rocker arm 3
Although the cylinder, the piston, and the opening are provided in 5,135, the cylinder, the piston, and the opening may be provided.

[0065]

As described in detail above, according to the valve operating system for an internal combustion engine of the present invention, since the return spring is eccentrically arranged with respect to the piston in the direction away from the engaging projection, the engagement is improved. The movable range of the engagement protrusion of the second rocker arm can be increased while avoiding the interference between the protrusion and the return spring, and the valve lift amount when operating the first rocker arm according to the second high speed cam. Can be sufficiently secured (Claim 1).

Further, since the engaging portion which is located in the opening portion when the piston is in the engaging position and which is disengaged from the opening portion when the piston is in the non-engaging position is provided in the thick portion of the piston, this engaging Even when a valve lift load is applied to the surface, this engagement surface is difficult to deform, and the rigidity of the power transmission portion of the valve system can be sufficiently secured, and the original performance of the valve operating device can be reliably exhibited. (Claim 2).

In particular, the eccentric arrangement of the return spring makes it possible to partially increase the wall thickness of the engaging surface and its vicinity, without increasing the size of the piston.
Further, the rigidity of the power transmission portion of the valve train can be secured without excessively downsizing the return spring (claim 2). By forming the engagement surface in a cylindrical shape and forming the contact portion of the engagement projection with the engagement surface in a concave shape along the engagement surface, the engagement projection is reliably contacted with the engagement surface. They can be brought into contact with each other, and the first rocker arm and the second rocker arm can be reliably and properly interlocked with each other through the engagement projection and the piston (claim 3).

Further, even if the engaging projection 5a enters the return spring in the piston, the spring guard protects the return spring, so that the engaging projection does not come into contact with the return spring and the turn spring is protected. Is prevented (claim 4). If the spring guard portion is formed in a cylindrical surface along the concave surface of the engaging protrusion, the concave surface of the engaging protrusion largely enters the spring guard portion side when contacting the surface of the spring guard portion. And then come into contact with each other, and there is an advantage that the movable range of the engagement protrusion can be expanded correspondingly, and the lift amount of the second rocker arm can be increased (claim 5).

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a main part (piston position switching device) of a valve train for an internal combustion engine according to a first embodiment of the present invention. FIG. 1 (a) shows a piston in a disengaged position. 1B is a vertical cross-sectional view when the piston is at the engagement position, and FIG. 1C is a horizontal cross-sectional view when the piston is at the engagement position (arrow AA in FIG. 1B). FIG.

FIG. 2 is a schematic side view inside the cylinder head showing the valve operating system for the internal combustion engine according to the first embodiment of the present invention.

FIG. 3 is a schematic developed cross-sectional view (corresponding to FIG. 4) inside a cylinder head showing a valve operating system for an internal combustion engine according to a second embodiment of the present invention.

FIG. 4 is a schematic developed cross-sectional view in a cylinder head showing the valve operating device for an internal combustion engine devised in the process of devising the present invention and the valve operating device for an internal combustion engine according to the first embodiment of the present invention (FIG. 5 is a cross-sectional view taken along the line BB of FIG. 5).

FIG. 5 is a schematic side view of the inside of a cylinder head showing a valve operating system of an internal combustion engine devised in the devising process of the present invention.

FIG. 6 is a schematic cross-sectional view showing a piston position switching device in a valve operating system for an internal combustion engine, which was devised in the devising process of the present invention, in which (a) shows a non-connected state and (b) shows The connected state is shown.

FIG. 7 is a schematic cross-sectional view showing a valve operating device of an internal combustion engine devised in the process of devising the present invention and a hydraulic pressure adjusting mechanism of a connection switching mechanism in the valve operating device of the internal combustion engine according to each embodiment of the present invention. Is.

FIG. 8 is a graph showing valve operating characteristics of an internal combustion engine valve operating device devised in the process of devising the present invention and an internal combustion engine valve operating device according to each embodiment of the present invention. The characteristics at low speed are shown, and (b) shows the characteristics at high speed.

FIG. 9 is a schematic cross-sectional view showing a piston position switching device in a valve operating system of an internal combustion engine devised in the devising process of the present invention, and FIG. 9 (a) is a vertical cross section when a piston is in a non-engaging position. FIG. 9B is a vertical cross-sectional view when the piston is in the engagement position, and FIG. 9C is a cross-sectional view when the piston is in the engagement position (a cross-sectional view taken along the line CC in FIG. 9B). ).

[Explanation of symbols]

11,12 intake valve 21,22 exhaust valve 31a, 31b Low speed cam (first cam) 31c High-speed cam (second cam) 32 Intake-side rocker shaft (first rocker shaft) 33,34,133 1st rocker arm 35,135 Second rocker arm 35a, 135a, 139a Engagement protrusion 36 Intake side rocker shaft (second rocker shaft) 41 Connection switching mechanism 41a First connection switching mechanism 41b Second connection switching mechanism 42 Hydraulic adjustment device (piston position switching device) 150 cylinders 151 piston 152 Return spring 153 opening 154 Side surface of piston 151 (engagement portion) 155 Spring guard part 156 Detent pin

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3G016 AA08 AA19 BA03 BA06 BA18                       BA28 BB12 CA27 CA28 CA29                       DA08 DA22 GA00                 3G018 AA05 AB05 AB17 BA07 BA13                       CA19 CB03 DA14 DA18 DA19                       DA24 DA28 DA51 DA83 EA04                       EA24 EA35 FA03 FA06 FA07                       GA00 GA03

Claims (5)

[Claims] 1. A first rocker arm, the tip of which is linked to one of an intake valve and an exhaust valve, is rockably supported by a rocker shaft and is driven by a first cam, and is rockable by the rocker shaft. A second bearing supported and arranged adjacent to the first rocker arm and driven by a second cam having a cam shape different from that of the first cam.
Rocker arm, a cylinder formed on one of the first and second rocker arms, a piston slidably mounted in the cylinder, and a protrusion provided on the other of the first and second rocker arms. Between an engagement protrusion engageable with an engagement portion formed on the piston and an engagement position where the piston engages the piston and a non-engagement position where the engagement protrusion does not engage the piston. A piston position switching device for switching between the piston position switching device and the piston position switching device, the piston position switching device including a return spring for urging the piston to the non-engaging position, the return spring being away from the engaging projection with respect to the piston. A valve operating device for an internal combustion engine, wherein the valve operating device is eccentrically arranged. 2. The piston is formed with a recess for accommodating one end side of the return spring, and the thick portion having the engagement portion is provided on the engagement protrusion side around the recess of the piston. And the thick portion is located outside the cylinder when the piston is in the engagement position, and is housed in the cylinder when the piston is in the non-engagement position. Item 1. A valve train for an internal combustion engine according to Item 1. 3. The piston has a cylindrical portion, the thick portion is formed in the cylindrical portion, and the engaging portion provided in the thick portion is formed in a cylindrical surface shape. The valve operating device for an internal combustion engine according to claim 1 or 2, wherein a contact portion of the fitting protrusion with the engaging portion is formed in a concave shape along the engaging portion. 4. The return spring is arranged on an extension of a swing locus of the engagement protrusion relative to the piston side, and the piston is not engaged with the engagement protrusion side of the piston. 4. The spring guard portion, which is located so as to cover the return spring, is provided on the extension of the swing locus of the engagement projection when the position is in the position, and the spring guard portion is provided. A valve train for an internal combustion engine as set forth in. 5. The valve operating system for an internal combustion engine according to claim 4, wherein the spring guard portion is formed into a cylindrical surface along the concave surface of the engaging projection.