JPH0478807B2 - - Google Patents

Description

Detailed Description of the Invention A. Purpose of the Invention (1) Industrial Field of Application The present invention provides a first and second drive cam follower interlocked with and connected to an intake valve or an exhaust valve. A free cam follower that can be made free is arranged, and a connection switching mechanism that can switch between connecting and disengaging each cam follower has a guide hole drilled in each cam follower and a hydraulic chamber at one end. a first switching pin that is slidably fitted into the guide hole of the first driving cam follower while facing the guide hole of the free cam follower, and one end of which is brought into contact with the other end of the first switching pin. a second switching pin that is slidably fitted into the guide hole of the free cam follower and fitable into the guide hole of the second drive cam follower; A valve train for an internal combustion engine, comprising: a regulation pin slidably fitted into a guide hole; and a return spring provided between the regulation pin and the second drive cam follower to urge each pin toward the hydraulic chamber. Regarding equipment.

(2) Conventional technology Conventionally, such a valve train has been developed, for example, by
It is publicly known from Publication No. 19911 and the like.

(3) Problems to be solved by the invention By the way, in such a valve train, when hydraulic pressure is applied to the hydraulic chamber to connect and operate the connection switching mechanism, the first switching pin does not fit into the free cam follower. If this is done prior to the fitting of the second switching pin to the second drive cam follower, the first and second switching pins will slip out of the free cam follower and the second drive cam follower when the intake valve or exhaust valve is opened at a high lift. Otherwise, the connection switching mechanism may be damaged. In other words, in such a state, the second
The push-back force by the return spring and the push-back force by the valve spring act on the switching pin, and when the valve opening lift amount of the intake valve or exhaust valve is small, the shearing by the valve spring due to the fitting of the free cam follower of the first switching pin Since the force and the hydraulic pressure in the hydraulic chamber act on the first switching pin, both switching pins will not come off. However, when the opening lift amount of the intake valve or the exhaust valve becomes large, the spring force of the valve spring becomes large, and the pushing back force of the valve spring acting on the second switching pin becomes large, and the second connecting pin or If the first and second connecting pins suddenly come out when the intake valve or exhaust valve is opened with a high lift, the cam follower may collide with the cam surface, or the intake valve etc. may impactly sit on the valve seat, causing damage to various parts and noise. There is a risk of causing an outbreak.

In order to solve this problem, it is conceivable to fit the first and second switching pins into the respective guide holes of the free cam follower and the second drive cam follower at the same time, but in that case, as described in the above publication, If the structure is such that there is no space between the opposing surfaces of adjacent cam followers, the opposing surfaces in a close state and the mutual contact surfaces of the pins in the disconnected state should be set flush with each other with high precision. If each switching pin slides even slightly due to vibration, oil pressure fluctuation, etc. when each cam follower is disconnected, it may fit into the guide hole of the adjacent cam follower and cause the cam follower to malfunction, or During the fitting process, the valve comes out of the guide hole, causing problems such as the intake valve being seated on the valve seat with an impact as described above.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a valve train for an internal combustion engine that can solve all of the above problems.

B. Structure of the Invention (1) Means for Solving the Problems According to the present invention, in order to achieve the above object, there is a gap between the opposing surfaces of the first drive cam follower and the free cam follower when the two cam followers are connected. A first gap that separates opposing opening edges of the guide hole from each other in the pin sliding direction is also provided between the opposing surfaces of the second drive cam follower and the free cam follower when the two cam followers are connected. A second gap is provided to separate opposing opening edges of the guide hole from each other in the pin sliding direction, and the first and second switching pins are switched in response to hydraulic action on the hydraulic chamber. Free cam follower and second
At the same time, the contact surfaces of the first and second switching pins are in the first space, and the contact surfaces of the second switching pin and the regulating pin are in contact with each other. the second surface
They are arranged so that they are respectively located within the interval 〓.

(2) Effect According to the above-mentioned special provision, when each cam follower is in the disconnected state, each switching pin will vibrate and
Even if it slides slightly due to oil pressure fluctuations, there is no risk of it fitting into the guide hole of an adjacent cam follower by mistake, which is effective in preventing malfunction of the cam follower.

Furthermore, during the connection operation of the connection switching mechanism, when the tip of at least one of the switching pins is beginning to fit into the guide hole of the corresponding cam follower, the shearing force by the valve spring does not act on the first switching pin. There is no risk that the switching pins will be restricted from coming out due to the shearing force until the valve opening lift amount of the intake valve or exhaust valve becomes large. Alternatively, when the exhaust valve starts to open, it is possible to prevent the exhaust valve from falling out when the valve opening lift amount is small, and from falling out when the valve opening lift amount becomes large.

(3) Embodiments Below, embodiments of the present invention will be described with reference to the drawings. First, in FIGS. 1 and 2 showing an embodiment of the present invention, a pair of intake valves 1a and 1b provided in the engine body E are shown. is 1/2 from the engine crankshaft
A low-speed cam 3, 3 and a high-speed cam 5 are provided integrally with the camshaft 2, which is rotationally driven at a reduction ratio of
first and second rocker arms 7, 8 as first and second drive cam followers and a third rocker arm 9 as free cam follower pivoted to
and the connection switching mechanism 10 provided between each rocker arm 7 to 9 to open and close.

The camshaft 2 is rotatably disposed above the engine body E, and the low-speed cams 3, 3 are integrated into the camshaft 2 at positions corresponding to the respective intake valves 1a, 1b, and the high-speed cam 5 is a low-speed cam. It is integrated into the camshaft 2 between the cams 3 and 3. Each of the low-speed cams 3, 3 has a high portion 3a having a relatively small amount of protrusion along the radial direction of the shaft 2, and a base circular portion 3b. In addition, the high-speed cam 5 is arranged such that the amount of radially outward protrusion of the camshaft 2 is adjusted to
It has a high part 5a which is larger than the above and covers a wider center angle range than the high part 3a, and a base circular part 5b.

The rocker shaft 6 is fixedly arranged below the camshaft 2. The locking shaft 6 includes a first locking arm 7 which is interlocked and connected to one intake valve 1a, a second locking arm 8 which is interlocked and connected to the other intake valve 1b, and a locking arm 7 between the first and second locking arms 7 and 8. and the third rocker arms 9 disposed adjacent to each other are pivotally supported. Further, a cam slipper 11 is provided at the top of the first rocker arm 7 to slide against one of the low-speed cams 3, and a cam slipper 11 is provided at the top of the second rocker arm 8 to slide against the other low-speed cam 3.
A cam slipper 12 is provided in sliding contact with the third rocker arm 9, and a cam slipper 13 is provided in the upper part of the third rocker arm 9 in sliding contact with the high speed cam 5.

On the other hand, a flange 14 is provided at the upper part of both intake valves 1a and 1b.
A valve spring 15 is interposed between each of these flanges 14 and the engine body E, and each intake valve 1a, 1b is rotated in the valve closing direction, that is, upward, by the valve spring 15. Each is energized. Tappet screws 16 that abut the upper ends of the intake valves 1a, 1b are screwed into the tips of the first and second rocker arms 7, 8 so that they can move forward and backward, respectively.
As a result, the first and second rocker arms 7, 8 are interlocked and connected to the intake valves 1, 1b.

Referring also to FIG. 3, the third rocker arm 9
The third locker arm 9 extends slightly from the locker shaft 6 toward both intake valves 1a and 1b, and this third locker arm 9 is slid onto the high-speed cam 5 by an elastic biasing means 19 provided between the locker shaft 6 and the engine body E. It is elastically biased in the direction of contact.

The spring biasing means 19 includes a bottomed cylindrical lifter 20 whose closed end is in contact with the third rocker arm 9, and a lifter spring 21 that is compressed between the lifter 20 and the engine body E. is slidably fitted into a bottomed hole 22 bored in the engine body E.

In FIG. 4, a connection switching mechanism 10 is provided between each rocker arm 7 to 9 for switching between connection and disconnection.

The connection switching mechanism 10 includes a first switching pin 23 that can connect the first and third rocker arms 7 and 9;
A second switching pin 24 that can connect the third and second rocker arms 9 and 8, a regulation pin 25 that restricts the movement of the first and second switching pins 23 and 24, and each pin 23 to 25 on the connection release side. A return spring 26 is provided.

The first locking arm 7 has a third locking arm 8.
A first guide hole 27 with a bottom and open to the side is bored parallel to the rocker shaft 6, and the first switching pin 23 is slidably fitted into the first guide hole 27. A hydraulic chamber 28 is defined between the closed end of the first guide hole 27 and the first switching pin 23, so that the hydraulic chamber 28 faces one end of the first switching pin 23. Furthermore, a restriction protrusion 29 is provided at the closed end of the first guide hole 27 to abut one end of the first switching pin 23 and restrict the movement of the first switching pin 26 toward the hydraulic chamber 28 . Further, a chamfered portion 23a is provided at the other end peripheral portion of the first switching pin 23 over the entire circumference.

Furthermore, a communication passage 30 communicating with the hydraulic chamber 28 is bored in the first rocker arm 7, and the rocker shaft 6
A hydraulic pressure supply path 31 communicating with a hydraulic pressure supply source (not shown) is provided inside. The communication passage 30 and the hydraulic pressure supply passage 31 are always in communication through a communication hole 32 formed in the side wall of the rocker shaft 6 regardless of the swinging state of the first rocker arm 7.

In the third rocker arm 9, a guide hole 33 having the same diameter corresponding to the first guide hole 27 is bored parallel to the rocker shaft 6 between both sides of the third rocker arm 9. The second switching pin 24, one end of which coaxially abuts, is slidably fitted into the guide hole 33. In addition, a chamfered portion 33a is provided on the opening edge of the guide hole 33 on the first rocker arm 7 side, and a chamfered portion 24a is provided on the other end of the second switching pin 24. .

The second rocker arm 8 has a second guide hole 34 with the same diameter and a bottom corresponding to the guide hole 33.
is drilled parallel to the rocker shaft 6 with its open end facing the third rocker arm 9 side, and the disc-shaped regulation pin 25 is slidably fitted into the second guide hole 34 . A shaft portion 35 is coaxially connected to the regulating pin 25, and the shaft portion 35 is movably inserted into a guide hole 36 bored at the closed end of the second guide hole 34. Moreover, the second guide hole 34 surrounds the shaft portion 35.
A return spring 26 is installed between the closed end of the hydraulic chamber 2 and the regulating pin 25, and the return spring 26 causes the pins 23, 24, and 25, which are coaxially in contact with each other, to move toward the hydraulic chamber 2.
8 side. Also, the third guide hole 34
A chamfered portion 34a is provided on the opening edge on the rocker arm 9 side.
are provided around the entire circumference.

As is clear from FIG. 4, between the opposing surfaces of the first rocker arm 7 and the third rocker arm 9, when the two cam followers 7, 9 are connected, the opposing opening edges of the guide holes 27, 33 of the two cam followers 7, 9 are formed. A first gap s ₁ that separates them from each other in the pin sliding direction is provided, and a guide hole 34 is provided between the opposing surfaces of the second rocker arm 8 and the third rocker arm 9 when the two cam followers 8 and 9 are connected. , 33, which separates the opposing opening edges from each other in the pin sliding direction.
s ₂ are provided, and between them 〓s ₁ ,
According to the special provision of _s2 , when the locking arms 7, 8, and 9 are in the disconnected state (see Fig. 4), the switching pins 23 and 24 will not move even if they slide slightly due to vibrations, oil pressure fluctuations, etc. Since there is no risk of the locking arms 9, 8 being accidentally fitted into the guide holes 33, 34 of the adjacent rocker arms 9, 8, this is effective in preventing malfunctions of the rocker arms 7, 8, 9.

Further, in the connection switching mechanism 10, the first and second switching pins 23 and 24 are configured so that they start fitting into the guide holes 33 and 34 at the same time during a connection operation when hydraulic pressure is applied to the hydraulic chamber 28, That is, the chamfered portions 23a, 33a when disconnecting
The distance l1 between the small diameter ends of the chamfered portions 24a, 34
The distance l2 between the small diameter ends of a is set to be equal.
Moreover, in the disconnected state of each cam follower 7, 8, 9, the contact surfaces _f1 between the first and second switching pins 23, ₂₄ are within the first gap s1, and the second switching pin 24 and the regulating The contact surface f ₂ of the pins 25 is the second
They are set to be located within s ₂ respectively.

Next, the operation of this embodiment will be explained. When the engine is operated at low speed, the hydraulic pressure in the hydraulic chamber 28 is released, and each pin 23 to 25 is connected to the hydraulic chamber 28 side by the spring force of the return spring 26 and moved to the maximum extent. It is in a released state. In this state, the abutment surfaces f ₁ of the first and second switching pins 23, 24 are within the first gap s ₁ between the opposing surfaces of the first and third rocker arms 7, 9, and the second Switching pin 24 and regulation pin 2
The contact surface f ₂ of 5 is the third and second rocker arm 9,
s ₂ between the opposing surfaces of 8. Therefore, each of the rocker arms 7 to 9 is in a state in which relative angular displacement is possible with respect to each other.

In such a disconnected state, the first and second rocker arms 7, 8 swing according to the sliding contact with the low-speed cams 3, 3 due to the rotational operation of the camshaft 2, and therefore both intake valves 1a, 1b opens and closes at a timing and lift amount depending on the shape of the low-speed cams 3, 3. At this time, the third rocker arm 9 swings in response to sliding contact with the high-speed cam 5, but the swinging action does not have any effect on the first and second rocker arms 7, 8.

When the engine is operating at high speed, high oil pressure is supplied to the hydraulic chamber 28. As a result, the first and second switching pins 2
3, 24 and the regulating pin 25 move toward the connection position against the spring force of the return spring 26, and the first switching pin 23 fits into the guide hole 33 and the second switching pin 23 moves toward the connecting position.
The switching pin 24 fits into the second guide hole 34, and each rocker arm 7-9 is connected. At this time, the amount of swing of the third rocker arm 9 that is in sliding contact with the high-speed cam 5 is the largest, so the first and second rocker arms 7 and 8 swing together with the third rocker arm 9,
Both intake valves 1a and 1b are opened and closed at timings and lift amounts according to the shape of the high-speed cam 5.

By the way, the connection operation of the connection switching mechanism 10 is as follows:
Start with the first and second rocker arms 7, 8 in sliding contact with the base circular portion 3b of the low-speed cams 3, 3, and the third rocker arm 9 in sliding contact with the high-speed cam 5 on the base circular portion 5b. It is. At the start of the connection operation, the first and second switching pins 23, 24
The first and second rocker arms 7, 8 are moved by the high portions 3a of the low-speed cams 3, 3 without making a full stroke.
may begin to swing, and in such a case, the chamfered portion 2 of the first switching pin 23 as shown in FIG.
3a hangs over the chamfered portion 33a of the guide hole 33,
Further, when the chamfered portion 24a of the second switching pin 24 is engaged with the chamfered portion 34a of the second guide hole 34, the opening lift operation of the intake valves 1a and 1b may be started. At this time, each switching pin 23, 24
, only the push-back forces from the return spring 26 and the valve spring 15 and the hydraulic pressure of the hydraulic chamber 28 act, and no shearing force from the valve spring 15 acts. Therefore, when the valve opening lift operation of the intake valves 1a and 1b starts in the state shown in FIG. The power is greater,
When the valve opening lift amount is low, the first and second switching pins 23 and 24 are pushed back toward the hydraulic chamber 28 and come out of the guide hole 33 and the second guide hole 34. Therefore, the state shown in FIG. 5 will not be maintained until the opening lift amount of the intake valves 1a and 1b becomes large, and the first and second switching pins 23 and 24 may come off during the connection operation. Then, this is only when the opening lift amount of the intake valves 1a and 1b is small,
Dislodgement can be reliably prevented when the valve opening lift amount becomes large.

In the above embodiments, a valve operating system for an intake valve has been described, but the present invention is also applicable to a valve operating system for an exhaust valve.

C. Effects of the Invention As described above, according to the present invention, between the opposing surfaces of the first drive cam follower and the free cam follower, when the two cam followers are connected, the opposing opening edges of the guide holes of the two cam followers are slid together with a pin. The first gap spaced apart in the moving direction is also between the opposing surfaces of the second drive cam follower and the free cam follower. Since a second gap is provided to separate the switching pins in the direction, even if each switching pin slides slightly due to vibration, oil pressure fluctuation, etc. in the disconnected state of each cam follower, the guide hole of the adjacent cam follower There is no risk of the cam follower fitting in error, and is therefore effective in preventing malfunctions caused by the vibrations and oil pressure fluctuations of the cam follower.

Further, the first and second switching pins simultaneously fit into the free cam follower and the second drive cam follower when switching in response to the hydraulic pressure applied to the hydraulic chamber, and when each cam follower is in a disconnected state, the first and second switching pins The contact surfaces of the switching pins are within the first gap,
In addition, since the contact surfaces of the second switching pin and the regulating pin are respectively located within the second gap, when the connection switching mechanism starts the connection operation, the first
Also, it is possible to reliably prevent the switching pin from coming off at high lift by avoiding the shearing force caused by the valve spring acting on the first switching pin when the second switching pin is not fully stroked. can.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the present invention, FIG. 1 is a plan view, FIG. 2 is a cross-sectional view taken along the line -- in FIG. 1, and FIG. 4 is an enlarged sectional view taken along the line in FIG. 2 when the connection is released, and FIG. 5 is a sectional view of the main part of FIG. 4 when the connection operation is started. f ₁ , f ₂ ... contact surface, s ₁ , s ₂ ... first and second air valves, 1a, 1b ... intake valve, 7 ... first rocker arm as first drive cam follower, 8 ... …Second
second rocker arm as drive cam follower, 9
...Third rocker arm as free cam follower, 10,10'...Connection switching mechanism, 23,2
3'...First switching pin, 24, 24'...Second switching pin, 25...Restriction pin, 26...Return spring, 2
8... Hydraulic chamber.

Claims (1)

[Claims] 1 between the first and second driving cam followers 7, 8 which are interlocked and connected to the intake valves 1a, 1b or the exhaust valves which are biased in the valve closing direction by the valve spring 15;
A free cam follower 9 that can be free with respect to an intake valve or an exhaust valve is disposed, and a connection switching mechanism 10 that can switch between a state in which each cam follower 7, 8, and 9 is connected and a state in which the connection is released is provided for each cam follower 7. . a first switching pin 23 that can be fitted into a guide hole 38;
A second switching pin whose one end is brought into contact with the other end of the first switching pin 23 and is slidably fitted into the guide hole 33 of the free cam follower 9 and also fitable into the guide hole 34 of the second drive cam follower 8. A pin 24, a regulating pin 25 whose one end abuts the other end of the second switching pin 24 and is slidably fitted into the guide hole 34 of the second drive cam follower 8, and each of the pins 23, 2.
4 and 25 toward the hydraulic chamber 28 side.
5 and a return spring 26 provided between the second drive cam follower 8. In the valve operating system for an internal combustion engine, the first drive cam follower 7 and the free cam follower 9 are provided with a return spring 26 between the opposing surfaces of the first drive cam follower 7 and the free cam follower 9. When connecting the two guide holes 27, 3
A first space S ₁ that separates the opposing opening edges of 3 in the pin sliding direction, and between the opposing surfaces of the second drive cam follower 8 and the free cam follower 9,
When the two cam followers 8, 9 are connected, a second gap _s2 is provided to separate the opposing opening edges of the guide holes 34, 33 from each other in the pin sliding direction. Switching pins 23, 24
is fitted into the free cam follower 9 and the second drive cam follower 8 at the same time when switching in response to the hydraulic action on the hydraulic chamber 28, and when the respective cam followers 7, 8, 9 are in a disconnected state, the first and second cam followers are connected to each other. The contact surfaces _f1 between the switching pins 23 and 24 are in the first space.
s ₁ , and the second switching pin and regulation pin 24, 2
5.The mutual contact surfaces _f2 are located within the second space _s2 ,
Valve gear for internal combustion engines.