JPH09133012A - Valve gear for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust energizing force of a spring making a rocker arm follow up to a cam interlocking with its switching. SOLUTION: This valve gear is provided with a subspring 10 pressing a subrocker arm 2 to a high speed cam 22, at operation time using it with the high speed cam 22 concerned in opening/closing action of an intake valve 9, and a lever releasing energizing force of the subspring 10 pressing the subrocker arm 2 to the high speed cam 22, at operation time using a low speed cam 21 when it is concerned in opening/closing action of the intake valve 9.

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 Conventionally, the lift characteristic of an intake valve or an exhaust valve is made different according to the operating state for the purpose of achieving both torque during low-medium speed operation and improvement of output during high-speed operation. Alternatively, it is known to control the intake / exhaust amount (see, for example, JP-A-2-78721).

This type of valve operating device includes a valve spring for urging the intake / exhaust valve in a valve closing direction, a main rocker arm for opening / closing the intake / exhaust valve by following a low speed cam having a relatively small profile, A sub-rocker arm that follows a high-speed cam having a relatively large profile and a cam switching mechanism that can lock the relative displacement of the sub-rocker arm with respect to the main rocker arm according to engine operating conditions are provided.

In the high engine speed range, when the relative displacement of the sub rocker arm with respect to the main rocker arm is locked by the cam switching mechanism, the main rocker arm swings integrally with the sub rocker arm and follows the high speed cam. Open and close the intake and exhaust valves.

In the low and medium engine speed range of the engine, the sub rocker arm is displaced relative to the main rocker arm by the cam switching mechanism, and the main rocker arm follows the low speed cam to open and close the intake and exhaust valves.

[0006]

However, in such a conventional valve operating system for an internal combustion engine, the main rocker arm and the sub-rocker arm are connected to the high speed cam in a high rotational speed range where the high speed cam opens and closes the intake and exhaust valves. If the urging force of the valve spring is increased so that the
There is a problem in that the load that the main rocker arm is pressed against the low-speed cam becomes excessive in the low to medium speed range in which the exhaust valve is opened and closed, resulting in an increase in friction.

Further, if the urging force of the valve spring is set to be small corresponding to the low and medium speed range in which the low speed cam opens and closes the intake and exhaust valves, the high speed cam is mainly used in the high speed range in which the intake and exhaust valves are opened and closed. This causes a so-called valve jump phenomenon in which the rocker arm and the sub-rocker arm cannot follow the high speed cam.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a valve operating system for an internal combustion engine which adjusts the urging force of a spring that causes a rocker arm to follow a cam in association with switching of the cam.

[0009]

According to a first aspect of the present invention, there is provided a valve operating system for an internal combustion engine, which follows a valve spring for urging an intake / exhaust valve in a valve closing direction and a low speed cam having a relatively small profile. A main rocker arm that opens and closes the intake and exhaust valves, a sub-rocker arm that follows a high-speed cam with a relatively large profile, and a cam switching mechanism that can lock the relative displacement of the sub-rocker arm with respect to the main rocker arm according to engine operating conditions. The high-speed cam is used to open and close the intake / exhaust valve.The sub-spring that presses the sub-rocker arm against the high-speed cam during operation using the high-speed cam and the low-speed cam uses the low-speed cam that engages opening / closing the intake / exhaust valve to operate the sub-rocker arm at high speed. An urging force releasing mechanism for releasing the urging force of the sub spring pressed against the cam.

A valve operating system for an internal combustion engine according to claim 2 is
In the invention according to claim 1, a claw portion that cooperates with a sub-rocker arm is formed in a prop that is swingably connected to a main rocker arm as the cam switching mechanism, and the prop can cooperate with the sub-spring as an urging force releasing mechanism. Form the lever.

A valve operating system for an internal combustion engine according to claim 3 is
In the invention according to claim 2, a lifter that responds to the expansion and contraction of the sub-spring is connected to the engine body, and the lifter is arranged so as to cooperate with the lever during operation using a high speed cam.

A valve operating system for an internal combustion engine according to claim 4 is
In the invention according to claim 2, the lifter that responds to the expansion and contraction of the sub-spring is coupled to the lever, and the lifter is arranged so as to cooperate with the engine body side during the operation using the high speed cam.

A valve operating system for an internal combustion engine according to claim 5 is
In the invention according to any one of claims 1 to 4,
The spring load is set such that the ratio of the biasing force of the valve spring and the sub spring to the biasing force of the valve spring is substantially equal to the ratio of the masses of the main rocker arm and the sub rocker arm to the mass of the main rocker arm.

A valve operating system for an internal combustion engine according to claim 6 is
A valve spring that biases the intake and exhaust valves in the closing direction,
A main rocker arm that drives an intake / exhaust valve to open and close by following a low-speed cam with a relatively small profile, a sub-follower that is rotatably connected to the main rocker arm and can follow a high-speed cam with a relatively large profile, and a sub-follower. The cam switching mechanism that rotates between the cooperation position where the high speed cam follows the high speed cam and the non-cooperation position where it disengages from the high speed cam, and the high speed cam engages the opening / closing operation of the intake / exhaust valve. A sub spring and a biasing force releasing mechanism that releases the biasing force of the sub spring that pushes the sub follower against the high speed cam during operation using the low speed cam in which the low speed cam is involved in opening and closing the intake / exhaust valve.

A valve operating system for an internal combustion engine according to claim 7 is
In the invention according to claim 6, a lever capable of cooperating with the sub spring is formed in the sub follower as the biasing force releasing mechanism.

A valve operating system for an internal combustion engine according to claim 8 is
In the invention according to claim 7, a lifter that responds to the expansion and contraction of the sub-spring is connected to the engine body, and the lifter is arranged so as to cooperate with the lever during operation using a high speed cam.

A valve operating system for an internal combustion engine according to claim 9 is
In the invention according to claim 7, a lifter that responds to the expansion and contraction of the sub-spring is coupled to a lever, and the lifter is arranged so as to cooperate with the engine body side during high-speed cam operation.

According to a tenth aspect of the present invention, in the valve operating system for an internal combustion engine according to any one of the sixth to ninth aspects, the ratio of the biasing force of the valve spring and the sub-spring to the biasing force of the valve spring. , The spring load is set so that the ratio of the mass of the main rocker arm and the mass of the sub-follower to the mass of the main rocker arm is approximately equal.

[0019]

In the valve operating system for the internal combustion engine according to claim 1, when the high speed cam is used for opening / closing the intake / exhaust valve, the high speed cam is operated by both the urging force of the valve spring and the urging force of the sub spring. Since the rocker arm is pressed against the high-speed cam, the main rocker arm and the sub-rocker arm follow the high-speed cam up to a high rotation speed range,
It is possible to prevent the valve jump phenomenon. As a result, the engine can be rotated at a high speed and the output can be increased.

During operation of the low speed cam in which the low speed cam is involved in opening / closing the intake / exhaust valve, the urging force of the sub spring that presses the sub rocker arm against the high speed cam is released, and the main rocker arm is moved to the low speed cam only by the urging force of each valve spring. Since it is pressed against, it is possible to reduce friction. As a result, wear of the low speed cam and the main rocker arm can be suppressed, and the fuel consumption of the engine can be reduced.

In a valve operating system for an internal combustion engine according to a second aspect of the present invention, a cam is switched using a single prop by a structure in which a claw part that cooperates with the sub-rocker arm and a lever that can cooperate with the sub-spring are formed in the prop. Both the mechanism and the urging force releasing mechanism can be driven, and the structure can be simplified.

According to a third aspect of the present invention, in the valve operating system for an internal combustion engine, the structure in which the lifter that responds to the expansion and contraction of the sub-spring is connected to the engine body causes the lever to lift when the prop moves to rotate when the high speed cam is used. The elastic force of the sub spring is transmitted to the sub rocker arm via the lifter and lever in cooperation with the.

In the valve operating system for the internal combustion engine according to the fourth aspect, the structure in which the lifter that responds to the expansion and contraction of the sub-spring is coupled to the lever causes the lever to move when the high speed cam is used and the prop rotates to move the lever to the engine body. The sub spring is expanded and contracted in cooperation with the side, and the urging force of the sub spring is transmitted to the sub rocker arm via the lifter and lever.

By coupling the sub spring and the lifter to the prop, these can be unitized together with the main rocker arm to enhance the productivity.

In the valve operating system of the internal combustion engine according to claim 5, the ratio of the biasing force of the valve spring and the sub spring to the biasing force of the valve spring is equal to the ratio of the mass of the main rocker arm and the sub rocker arm to the mass of the main rocker arm. By setting the spring load to be approximately equal, the surface pressure acting on each cam is kept substantially constant in response to the increase in the inertial mass of the valve train that occurs as the sub-rocker arm cooperates with the main rocker arm. It is possible to minimize friction.

In the valve operating system for the internal combustion engine according to claim 6, the sub-follower is actuated by both the biasing force of the valve spring and the biasing force of the sub-spring during the operation using the high-speed cam in which the high-speed cam is involved in opening and closing the intake and exhaust valves. Since it is pressed against the high speed cam, the main rocker arm and the sub follower can follow the high speed cam up to the high speed range, and the valve jump phenomenon can be prevented. As a result, the engine can be rotated at a high speed and the output can be increased.

Since the sub-follower is rotatably connected to the main rocker arm, a lost motion mechanism for causing the sub-follower to follow the low-speed cam when operating with a high-speed cam is not required, which simplifies the structure and reduces friction. It can be reduced.

During operation of the low-speed cam in which the low-speed cam is involved in opening / closing the intake / exhaust valve, the urging force of the sub-spring that presses the sub-follower against the high-speed cam is released, and the main rocker arm becomes the low-speed cam only by the urging force of each valve spring. Since it is pressed against, friction can be reduced. As a result, wear of the low speed cam and the main rocker arm can be suppressed, and the fuel consumption of the engine can be reduced.

In the valve operating system for the internal combustion engine according to the seventh aspect, the cam switching mechanism using a single sub-follower has a structure in which the sub-follower has a sliding contact portion for the high-speed cam and a lever capable of cooperating with the sub-spring. Both the urging force releasing mechanism and the urging force releasing mechanism can be driven, and the structure can be simplified.

In the valve operating system of the internal combustion engine according to the present invention, the structure in which the lifter that responds to the expansion and contraction of the sub spring is connected to the engine body causes the lever to lift when the sub follower rotates when the high speed cam is used. The sub spring is expanded and contracted in cooperation with and the urging force of the sub spring is transmitted to the sub follower via the lifter and the lever.

In the valve operating system of the internal combustion engine according to claim 9, the structure in which the lifter that responds to the expansion and contraction of the sub spring is coupled to the lever causes the lever to move when the high-speed cam is used and the sub follower rotates to move the lever to the engine body. The sub spring is expanded and contracted in cooperation with the side, and the biasing force of the sub spring is transmitted to the sub follower via the lifter and the lever.

By connecting the sub spring and the lifter to the sub follower, these can be unitized together with the main rocker arm, and the productivity can be improved.

In the valve operating system for an internal combustion engine according to claim 10, the ratio of the biasing force of the valve spring and the sub spring to the biasing force of the valve spring is substantially equal to the ratio of the masses of the main rocker arm and the sub follower to the mass of the main rocker arm. By setting the spring loads so that they are equal, the surface pressure acting on each cam is kept approximately constant in response to the increase in the inertial mass of the valve train that occurs as the sub-follower cooperates with the main rocker arm, and friction is reduced. It can be minimized.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 2, the 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 cam shaft 20, and the high speed cam 22 operates at a low speed so as to satisfy the valve lift characteristics required at low engine speed and high engine speed. Compared to the cam 21, it has a profile that increases both the valve lift amount and the valve opening period.

Each cylinder is provided with a single main rocker arm 1 corresponding to two intake valves 9. A 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 the intake valve 9 is opened and closed while the valve spring 8 is expanded and contracted as the main rocker arm 1 swings.

The main rocker arm 1 is provided with a pair of sliding contact portions 14 which are in sliding contact with the pair of low speed cams 21, and a single sub-rocker arm 2 is provided between each sliding contact portion 14.

As shown in FIG. 3, the base end of the sub-rocker arm 2 is rotatably connected to the main rocker arm 1 via the sub-rocker shaft 16. 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, and rings 19 are fitted to both ends of the sub-rocker shaft 16 to prevent the sub-rocker shaft 16 from coming off. .

The sub-rocker arm 2 does not have a portion that comes into contact with the intake valve 9, and a sliding contact portion 23 that slidably contacts the high speed cam 22 is formed at the tip of the sub-rocker arm 2 so as 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 accommodated in the sub-rocker arm 2 is provided, and the sub-rocker arm is in contact with the main rocker arm 1 via the lifter 41. A lost motion spring 25 that presses 2 against the high speed cam 22 is interposed.

Between the main rocker arm 1 and the sub-rocker arm 2, the relative rotation of the two is locked and the cams involved in the opening / closing operation of each intake valve 9 are the low speed cam 21 to the high speed cam 22.
A cam switching mechanism for switching to is provided.

As this 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 engages with the lower end of the sub-rocker arm 2 at one end thereof to lock 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 is provided that rotates the sub-rocker arm 2 to the locking position against the spring 33.

The spring 33 and the pin 34 are slidably accommodated in a hole formed in the main rocker arm 1, and the pin 34 abuts on 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. 1, the main rocker arm 1
A hydraulic piston 30 is slidably fitted to the hydraulic piston 30, and a hydraulic chamber 37 is formed behind the hydraulic piston 30.

A hydraulic passage for guiding the working hydraulic pressure to the hydraulic chamber 37 is provided through the insides of the main rocker arm 1 and the rocker shaft 3. The discharge hydraulic pressure of the oil pump is introduced into the hydraulic passage through a switching valve during a predetermined high speed operation. The control unit that electronically controls the operation of the switching valve inputs the engine rotation signal, the cooling water temperature signal, the lubricating oil temperature signal, the intake supercharging pressure signal by the supercharger, the throttle valve opening signal, etc. Based on the detected value, the low speed cam 21 and the high speed cam 2 are controlled while suppressing the rapid change of the engine torque.
It is designed to smoothly switch between the two.

During operation using the low speed cam, the main rocker arm 1 swings in accordance with the profile of the low speed cam 21, and opens and closes 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 the non-locking position where it does not engage with the sub-rocker arm 2, so that the movement of the main rocker arm 1 is not hindered.

When the operating hydraulic pressure is introduced into the hydraulic chamber 37 through the hydraulic passage 38 during the operation using the high speed cam, the hydraulic piston 30 locks the prop 31 against the spring 33 as shown by the broken line in FIG. By moving to the position and engaging one end of the prop 31 with the main rocker arm 1, the two rocker arms 1 and 2 swing integrally. Since the high-speed cam 22 is formed so that the valve opening angle and the lift amount are both larger than the low-speed cam 21, the low-speed cam 21 is integrated with the sub-rocker arm 2 and the low-speed cam 21 becomes the main rocker arm. Lifted from the sliding contact portion 14 of 1,
Each intake valve 9 is opened and closed according to the profile of the high-speed cam 22, so that both the opening angle and the lift amount of the valve become large. When the operation using the high-speed cam is changed to the operation using the low-speed cam again, the hydraulic pressure introduced to the hydraulic chamber 37 is lowered by the operation of the switching valve, and as shown by the solid line in FIG. Moves to the non-locking position, and the restraint of the sub-rocker arm 2 is released.

By the way, when the biasing force of the valve spring 8 is increased so that the main rocker arm 1 and the sub-rocker arm 2 follow the high speed cam 22 in the high rotational speed range where the high speed cam operation of the engine is performed, the low speed cam operation is performed. Main rocker arm 1 on low-speed cam 21 in low and medium rpm range
There is a problem in that the load that is pressed against becomes excessive and causes an increase in friction.

If the urging force of the valve spring 8 is set to be small in response to the low speed cam operation, the main rocker arm 1 and the sub rocker arm 2 cannot follow the high speed cam 22 during the high speed cam operation, so-called valve jump. Cause a phenomenon.

In response to this, the present invention allows the sub-rocker arm 2 to move the high-speed cam 22 when the high-speed cam is used in which the sub-rocker arm 2 swings integrally with the main rocker arm 1.
A sub-spring 10 is provided to apply a biasing force to the. The sub spring 10 that pushes the sub rocker arm 2 against the high speed cam 22 during operation using the low speed cam
An urging force releasing mechanism is provided for releasing the urging force of the.

In the present embodiment, the cylinder head 4 is coupled with the lifter 42 that responds to the expansion and contraction of the sub spring 10. The cylinder head 4 has a cylindrical guide member 47.
Are located under the prop 31 and are coupled to each other. A lifter 42 having a bottomed cylindrical shape is slidably disposed inside the guide member 47. A coiled sub spring 10 is interposed between the lifter 42 and the cylinder head 4 in a compressed state.

As a biasing force releasing mechanism, a lever 43 that cooperates with the lifter 42 is formed on the prop 31 so as to project therefrom.

The prop 31 has a claw portion 44 projecting upward from the shaft 32 serving as a swing fulcrum, a sliding contact portion 46 projecting from the shaft 32 toward the hydraulic piston 30, and a lever 43 projecting downward from the shaft 32. Are integrally formed.

As a result, by using the single hydraulic piston 30 and the single prop 31, the cam switching mechanism for switching the cam involved in the opening / closing operation of each intake valve 9 from the low speed cam 21 to the high speed cam 22, and the low speed cam. Sub spring 10 that presses the sub rocker arm 2 against the high speed cam 22 during operation
Both of the urging force releasing mechanisms for releasing the urging force of are driven to simplify the structure.

During operation using a high-speed cam in which the claw portion 44 of the prop 31 engages with the lower end of the sub-rocker arm 2 to lock the relative rotation of the sub-rocker arm 2 with respect to the main rocker arm 1, the lever 43 cooperates with the lifter 42, It is arranged so that the biasing force of the sub spring 10 is transmitted to the sub rocker arm 2 via the prop 31.

During operation using a low speed cam in which the claw portion 44 of the prop 31 is disengaged from the lower end of the sub rocker arm 2 and the sub rocker arm 2 is rotated relative to the main rocker arm 1, the lever 43 is disengaged from the lifter 42 and the sub spring 10 of the sub spring 10 is rotated. The urging force is arranged so as not to be transmitted to the sub rocker arm 2 via the prop 31.

The urging force of the valve spring 8 for pressing the main rocker arm 1 against the low speed cam 21 during the operation using the low speed cam, and the urging force of the valve spring 8 and the sub spring 10 for pressing the sub rocker arm 2 against the high speed cam 22 during the operation using the high speed cam. The spring loads of the springs 8 and 10 are set so that the ratio becomes substantially equal to the ratio of the mass of the main rocker arm 1 to the mass of the main rocker arm 1 and the sub rocker arm 2.

With the above construction, the lever 43 cooperates with the lifter 42 to expand and contract the sub-spring 10 during a high-speed cam operation in which the high-speed cam 22 is involved in opening and closing the intake valve 9. In this way, the sub-rocker arm 2 is pressed against the high-speed cam 22 by both the urging force of each valve spring 8 and the sub-spring 10, so that the main rocker arm 1 and the sub-rocker arm 2 follow the high-speed cam 22 up to a high rotational speed range, and the valve It is possible to prevent the jump phenomenon from occurring. As a result, the engine can be rotated at a high speed and the output can be increased.

When the low speed cam 21 is in operation for opening and closing the intake valve 9, the lever 43 is disengaged from the lifter 42 and the biasing force of the sub spring 10 is released. In this way, the sub-rocker arm 2 is pressed against the high-speed cam 22 only by the urging force of each valve spring 8. Therefore, it is possible to suppress an excessive load of pressing the main rocker arm 1 against the low-speed cam 21 and reduce friction. As a result, wear of the low speed cam 21 and the sliding contact portion 14 can be suppressed, and the fuel consumption of the engine can be reduced.

Each spring is adjusted so that the ratio of the biasing force of the valve spring 8 to the biasing force of the valve spring 8 and the sub spring 10 is substantially equal to the ratio of the mass of the main rocker arm 1 to the mass of the main rocker arm 1 and the sub rocker arm 2. By setting the spring load of 8 and 10, the sub rocker arm 2 becomes the main rocker arm 1
The surface pressure acting on each of the cams 21 and 22 is kept substantially constant in response to the increase in the inertial mass of the valve train caused by the cooperation with
It is possible to minimize friction.

Next, the embodiment shown in FIG. 4 will be described. The parts corresponding to those in FIG. 1 are designated by the same reference numerals.

As a biasing force releasing mechanism, the lever 43 protruding from the prop 31 is coupled with the lifter 42 which responds to the expansion and contraction of the sub spring 10, while the sliding contact member 49 which cooperates with the lifter 42 is fixed to the cylinder head 4. .

A cylindrical guide member 48 is coupled to the lower end of the lever 43, and the lifter 42 is slidably interposed in the guide member 48. A coiled sub spring 10 is interposed between the lifter 42 and the cylinder head 4 in a compressed state.

In this case, the claw portion 44 of the prop 31 engages with the lower end of the sub-rocker arm 2 and the main rocker arm 1
During operation using a high-speed cam that locks the relative rotation of the sub-rocker arm 2 with respect to, the lifter 42 coupled to the lever 43 cooperates with the sliding contact member 49 on the cylinder head 4 to apply the urging force of the sub-spring 10 via the prop 31. And tell Sablocka Arm 2.

During operation using a low speed cam in which the claw portion 44 of the prop 31 disengages from the lower end of the sub-rocker arm 2 and the sub-rocker arm 2 rotates relative to the main rocker arm 1, the lifter 42 connected to the lever 43 moves above the cylinder head 4. It comes off from the sliding contact member 49 of the sub spring 10
The urging force of No. 1 is not transmitted to the sub rocker arm 2 via the prop 31.

By providing the sub spring 10 and the lifter 42 on the prop 31, these can be unitized together with the main rocker arm 1 and the productivity can be improved.

Next, the embodiment shown in FIG. 5 will be described. The parts corresponding to those in FIG. 1 are designated by the same reference numerals.

The main rocker arm 1 is provided with a pair of slidable contact portions 14 slidably contacting the pair of low speed cams 21, and a single sub-follower 50 is slidably contacted with the high speed cam 22 between the slidable contact portions 14. . The middle of the sub follower 50 is rotatably connected to the main rocker arm 1 via a shaft 56.

The sub-follower 50 does not have a portion that comes into contact with the intake valve 9, and a sliding contact portion 53 that comes into sliding contact with the high speed cam 22 is formed in an arcuate shape at its upper end.

The sub-follower 50 rotates between a cooperative position where it slides on the high speed cam 22 as shown by the broken line in the figure and a non-cooperative position where it does not slide on the high speed cam 22 as shown by the solid line in the figure.

A return spring (not shown) for urging the sub follower 50 to the non-cooperative position is interposed and
By driving the sub-follower 50 to the cooperation position, the cams involved in opening and closing the intake valves 9 are moved from the low speed cam 21 to the high speed cam 22.
A cam switching mechanism for switching to is provided.

As this cam switching mechanism, a hydraulic piston 30 for rotating the sub-follower 50 to the cooperative position against the return spring is provided. A hydraulic piston 30 is slidably fitted to the main rocker arm 1, and a hydraulic chamber 37 is formed behind the hydraulic piston 30. Hydraulic chamber 3
A hydraulic passage for guiding the operating hydraulic pressure to 7 is provided through the insides of the main rocker arm 1 and the rocker shaft 3. The discharge hydraulic pressure of the oil pump is introduced into the hydraulic passage through a switching valve during a predetermined high speed operation.

During operation using the low speed cam, the main rocker arm 1 swings in accordance with the profile of the low speed cam 21, and opens and closes each intake valve 9 against the valve spring 8. At this time, the sub-follower 50 is disengaged from the high speed cam 22 and does not hinder the movement of the main rocker arm 1.

When the operating hydraulic pressure is introduced into the hydraulic chamber 37 through the hydraulic passage 38 during the operation using the high speed cam, the hydraulic piston 3
0 moves the sub follower 50 to the cooperation position against the return spring, and the sliding contact portion 53 of the sub follower 50 slides on the high speed cam 22. Since the high-speed cam 22 is formed so that the valve opening angle and the lift amount are both larger than the low-speed cam 21, the low-speed cam 21 is the main when the sub-follower 50 is in sliding contact with the high-speed cam 22. The intake valve 9 is lifted up from the sliding contact portion 14 of the rocker arm 1 and is opened / closed according to the profile of the high-speed cam 22, so that both the opening angle and the lift amount of the valve increase. When shifting from the high speed cam use operation to the low speed cam use operation again, the hydraulic pressure introduced to the hydraulic chamber 37 is lowered by the operation of the switching valve, and the elastic follower restoring force of the return spring causes the sub-follower 50 to rotate to the non-cooperative position. , Comes off the high speed cam 22.

The sub-follower 50 is the main rocker arm 1.
A sub-spring 10 is provided to apply a biasing force that pushes the sub-follower 50 against the high-speed cam 22 during operation using the high-speed cam that swings together with the high-speed cam. Further, an urging force releasing mechanism for releasing the urging force of the sub spring 10 that presses the sub follower 50 against the high speed cam 22 during the operation using the low speed cam is provided.

Ratio of the biasing force of the valve spring 8 that pushes the main rocker arm 1 against the low speed cam 21 during the operation using the low speed cam and the biasing force of the valve spring 8 and the sub spring 10 that pushes the sub follower 50 against the high speed cam 22 during the operation using the high speed cam. But the main rocker arm 1
Mass and main rocker arm 1 and sub follower 50
Each spring 8, so that it is almost equal to the mass ratio of
Set a spring load of 10.

In the present embodiment, the cylinder head 4 is coupled with the lifter 42 that responds to the expansion and contraction of the sub spring 10. The cylinder head 4 has a cylindrical guide member 47.
Are located under the prop 31 and are coupled to each other. A lifter 42 having a bottomed cylindrical shape is slidably disposed inside the guide member 47. A coiled sub spring 10 is interposed between the lifter 42 and the cylinder head 4 in a compressed state.

As a biasing force releasing mechanism, a lever 55 that cooperates with the lifter 42 is formed on the sub follower 50 so as to project.

The sub-follower 50 has a sliding contact portion 53 projecting upward from a shaft 56 serving as a rotation fulcrum, and a sliding contact portion 56 projecting from the shaft 32 toward the hydraulic piston 30.
Then, a lever 55 protruding downward from the shaft 32 is integrally formed.

As a result, by using the single hydraulic piston 30 and the single sub-follower 50, the cam switching mechanism for switching the cam involved in the opening / closing operation of each intake valve 9 from the low speed cam 21 to the high speed cam 22, and the low speed cam. Sub spring 1 that presses the sub follower 50 against the high speed cam 22 during operation
Drives both the urging force releasing mechanism for releasing the urging force of 0,
The structure can be simplified.

With the above construction, the lever 55 cooperates with the lifter 42 to expand and contract the sub-spring 10 during the high-speed cam use operation in which the high-speed cam 22 is involved in opening and closing the intake valve 9. Thus, the sub-follower 50 is pressed against the high-speed cam 22 by the urging force of each valve spring 8 and the sub-spring 10, so that the main rocker arm 1 and the sub-follower 50 follow the high-speed cam 22 up to a high rotation speed range. It is possible to prevent the jump phenomenon from occurring. As a result, the engine can be rotated at a high speed and the output can be increased.

The sub-follower 50 is the main rocker arm 1.
Since the structure is rotatably connected with respect to each other, a lost motion mechanism for causing the sub-follower 50 to follow the low speed cam 21 during the operation using the high speed cam is unnecessary, and the structure can be simplified and the friction can be reduced. .

When the low speed cam 21 is in operation for opening and closing the intake valve 9, the lever 55 is disengaged from the lifter 42 and the urging force of the sub spring 10 is released. As a result, the sub-follower 50 is pressed against the high-speed cam 22 only by the urging force of each valve spring 8. Therefore, it is possible to prevent the load for pressing the main rocker arm 1 against the low-speed cam 21 from becoming excessive and reduce the friction. As a result, wear of the low speed cam 21 and the sliding contact portion 14 can be suppressed, and the fuel consumption of the engine can be reduced.

Each spring 8 is adjusted so that the ratio of the urging force of the valve spring 8 to the urging force of the valve spring 8 and the sub spring 10 is substantially equal to the ratio of the mass of the main rocker arm 1 to the mass of the main rocker arm 1 and the sub follower 50. , 10 by setting the spring loads, the surface pressures acting on the cams 21 and 22 are made substantially constant in response to the increase in the inertial mass of the valve train that occurs as the sub-follower 50 cooperates with the main rocker arm 1. It is possible to maintain and minimize friction.

Next, the embodiment shown in FIG. 6 will be described. Parts corresponding to those in FIG. 5 are denoted by the same reference numerals.

As a biasing force releasing mechanism, a sub follower 50
While the lifter 42 protruding from the lever 55 is coupled to the lifter 42 that responds to the expansion and contraction of the sub spring 10, the sliding contact member 49 that cooperates with the lifter 42 is fixed to the cylinder head 4.

A tubular guide member 48 is connected to the lower end of the lever 55, and the lifter 42 is slidably interposed in the guide member 48. A coiled sub spring 10 is interposed between the lifter 42 and the cylinder head 4 in a compressed state.

In this case, the lifter 42 connected to the lever 55 is slidably contacted by the lifter 42 connected to the lever 55 during a high speed cam operation in which the slidable contact portion 53 of the sub-follower 50 is slidably contacted with the high speed cam 22 as shown by the broken line in the figure. The urging force of the sub-spring 10 is transmitted to the main rocker arm 1 via the sub-follower 50 in cooperation with.

The sliding contact portion 53 of the sub-follower 50 is disengaged from the high speed cam 22. During operation using a low speed cam, the lifter 42 connected to the lever 55 causes the slide contact member 4 on the cylinder head 4 to move.
9, the biasing force of the sub spring 10 is not transmitted to the main rocker arm 1 via the sub follower 50.

By providing the sub-spring 10 and the lifter 42 on the sub-follower 50, these can be unitized with the main rocker arm 1 and the productivity can be improved.

[0094]

As described above, the valve operating system for the internal combustion engine according to claim 1 presses the sub-rocker arm against the high-speed cam by the urging force of the valve spring and the urging force of the sub-spring when the high-speed cam is used. The main rocker arm and the sub rocker arm are made to follow the high-speed cam up to a high rotation speed range, and the valve jump phenomenon is prevented to achieve high output. On the other hand, the urging force of the sub spring that presses the sub-rocker arm against the high-speed cam is released during operation using the low-speed cam, and the main rocker arm is pressed against the low-speed cam only by the urging force of each valve spring.
It is possible to suppress wear of the low-speed cam and the main rocker arm in the low to medium speed range and reduce fuel consumption of the engine.

A valve operating system for an internal combustion engine according to claim 2 is
Due to the structure in which the prop has a claw that cooperates with the sub-rocker arm and a lever that can cooperate with the sub-spring, it is possible to drive both the cam switching mechanism and the biasing force release mechanism using a single prop. Can be simplified.

A valve operating system for an internal combustion engine according to claim 3 is
Due to the structure in which the lifter that responds to the expansion and contraction of the sub spring is coupled to the engine body, the sub spring can prevent the inertial mass of the valve train from increasing, and the engine speed can be increased.

A valve operating system for an internal combustion engine according to claim 4 is
Due to the structure in which the lifter that responds to the expansion and contraction of the sub spring is connected to the lever, the sub spring, lifter, and prop are unitized together with the main rocker arm to improve productivity.

A valve operating system for an internal combustion engine according to claim 5 is
By setting the spring load so that the ratio of the biasing force of the valve spring and the sub spring to the biasing force of the valve spring is approximately equal to the ratio of the mass of the main rocker arm and the sub rocker arm to the mass of the main rocker arm, the sub rocker arm is It is possible to keep the surface pressure acting on each cam substantially constant in response to an increase in the inertial mass of the valve operating system caused by the cooperation with the rocker arm, and to minimize the friction.

A valve operating system for an internal combustion engine according to claim 6 is
The lost motion mechanism that causes the sub-follower to follow the low speed cam during the operation using the high speed cam is not required, and the structure can be simplified and the friction can be reduced. During operation using a high-speed cam, the sub-follower is pressed against the high-speed cam by the biasing force of both the valve spring and the sub-spring, causing the main rocker arm and sub-follower to follow the high-speed cam up to a high rotational speed range to prevent the valve jump phenomenon. Output can be achieved. On the other hand, the biasing force of the sub-spring that presses the sub-follower against the high-speed cam is released during operation using the low-speed cam, and the main rocker arm is pressed against the low-speed cam only by the biasing force of each valve spring. Wear of the engine can be suppressed and the fuel efficiency of the engine can be reduced.

A valve operating system for an internal combustion engine according to claim 7 is
With the structure that forms the sliding contact part for the high-speed cam and the lever that can cooperate with the sub-spring on the sub-follower,
It is possible to drive both the cam switching mechanism and the urging force releasing mechanism using a single sub-follower, which simplifies the structure.

A valve operating system for an internal combustion engine according to claim 8 is
Due to the structure in which the lifter that responds to the expansion and contraction of the sub spring is coupled to the engine body, the sub spring can prevent the inertial mass of the valve train from increasing, and the engine speed can be increased.

A valve operating system for an internal combustion engine according to claim 9 is
Due to the structure in which the lifter that responds to the expansion and contraction of the sub-spring is connected to the lever, the sub-spring, lifter and sub-follower can be unitized with the main rocker arm to enhance productivity.

In the valve operating system for the internal combustion engine according to the tenth aspect, the ratio of the biasing force of the valve spring and the sub spring to the biasing force of the valve spring is substantially equal to the ratio of the masses of the main rocker arm and the sub follower to the mass of the main rocker arm. By setting the spring loads so that they are equal, the surface pressure acting on each cam is kept approximately constant in response to the increase in the inertial mass of the valve train that occurs as the sub-follower cooperates with the main rocker arm, and friction is reduced. It can be minimized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of the present invention.

FIG. 2 is a side view of the same.

FIG. 3 is an exploded perspective view of the same.

FIG. 4 is a cross-sectional view illustrating another embodiment.

FIG. 5 is a sectional view showing still another embodiment.

FIG. 6 is a sectional view showing still another embodiment.

[Explanation of symbols]

 1 Main Rocker Arm 2 Sub Rocker Arm 4 Cylinder Head 8 Valve Spring 9 Intake Valve 10 Sub Spring 20 Cam Shaft 21 Low Speed Cam 22 High Speed Cam 30 Hydraulic Piston 31 Prop 42 Lifter 43 Lever 44 Claw 50 Sub Follower 55 Lever

Claims (10)

[Claims] 1. A valve spring for urging an intake / exhaust valve in a closing direction, a main rocker arm for opening / closing the intake / exhaust valve driven by a low speed cam with a relatively small profile, and a high speed with a relatively large profile. A sub-rocker arm that follows the cam, a cam switching mechanism that can lock the relative displacement of the sub-rocker arm with respect to the main rocker arm according to the engine operating conditions, and a high-speed cam that is involved in opening and closing the intake and exhaust valves. A sub-spring that pushes the sub-rocker arm against the high-speed cam, and a biasing force release mechanism that releases the biasing force of the sub-spring that pushes the sub-rocker arm against the high-speed cam during operation when the low-speed cam is used to open and close the intake and exhaust valves. A valve operating device for an internal combustion engine, comprising: 2. A prop that is swingably connected to a main rocker arm is formed with a pawl portion that cooperates with a sub-rocker arm as the cam switching mechanism, and a lever that is capable of cooperating with the sub-spring is formed with the prop as an urging force releasing mechanism. The valve operating system for an internal combustion engine according to claim 1, wherein: 3. The internal combustion engine according to claim 2, wherein a lifter that responds to the expansion and contraction of the sub-spring is connected to an engine body, and the lifter is arranged so as to cooperate with a lever during operation using a high speed cam. Valve drive. 4. The internal combustion engine according to claim 2, wherein a lifter that responds to expansion and contraction of the sub-spring is coupled to a lever, and the lifter is arranged so as to cooperate with the engine body side during operation using a high speed cam. Valve device. 5. The spring load is set such that the ratio of the biasing force of the valve spring and the sub spring to the biasing force of the valve spring is substantially equal to the ratio of the mass of the main rocker arm and the sub rocker arm to the mass of the main rocker arm. Claim 1 characterized by the above-mentioned.
5. A valve train for an internal combustion engine according to any one of items 1 to 4. 6. A valve spring for urging the intake / exhaust valve in a closing direction, a main rocker arm for opening / closing the intake / exhaust valve by following a low speed cam having a relatively small profile, and a main rocker arm for rotating the main rocker arm. A sub-follower that is movably connected and can follow a high-speed cam with a relatively large profile, a cam switching mechanism that rotates the sub-follower between a cooperative position that follows the high-speed cam and a non-cooperative position that separates from the high-speed cam, and a high-speed cam Is a sub-spring that presses the sub-follower against the high-speed cam during operation using the high-speed cam that is involved in opening and closing the intake and exhaust valves, and a sub-spring that presses the sub-follower against the high-speed cam during operation when the low-speed cam is involved in opening and closing the intake and exhaust valves. A valve operating device for an internal combustion engine, comprising: a biasing force releasing mechanism that releases the biasing force of the internal combustion engine. 7. The valve operating system for an internal combustion engine according to claim 6, wherein a lever capable of cooperating with a sub spring is formed in the sub follower as the urging force releasing mechanism. 8. The internal combustion engine according to claim 7, wherein a lifter that responds to expansion and contraction of the sub-spring is connected to an engine body, and the lifter is arranged so as to cooperate with a lever during operation using a high speed cam. Valve drive. 9. The internal combustion engine according to claim 7, wherein a lifter that responds to expansion and contraction of the sub-spring is connected to a lever, and the lifter is arranged so as to cooperate with the engine body side during operation using a high speed cam. Valve device. 10. The spring load is set such that the ratio of the biasing force of the valve spring and the sub spring to the biasing force of the valve spring is substantially equal to the ratio of the mass of the main rocker arm and the sub follower to the mass of the main rocker arm. The valve operating system for an internal combustion engine according to any one of claims 6 to 9, characterized in that.