JPH055408A - Valve drive for internal combustion engine - Google Patents

Abstract

(57) [Abstract] [Purpose] In a valve train of an internal combustion engine, at the time of switching operation of the valve operation switching mechanism, the switching pin of the switching mechanism operates at least when the valve opening lift of the intake valve or the exhaust valve is large. Make sure it does not come out of the guide hole of the corresponding cam follower. [Structure] The first and second switching pins are adapted to engage with the free cam follower and the second drive cam follower at the same time or in advance of the second switching pin when the switching operation is performed in response to the hydraulic action on the hydraulic chamber. Composed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided with a free cam follower which can be free with respect to an intake valve or an exhaust valve, between first and second drive cam followers which are interlocked with and connected to an intake valve or an exhaust valve. A connection switching mechanism that can switch between connecting the cam follower and releasing the connection is slidably fitted to the first drive cam follower with one end facing the hydraulic chamber and can be fitted to the free cam follower. A first switching pin, and a second switch pin which is slidably fitted to the free cam follower by abutting one end coaxially with the other end of the first switching pin and fitted to the second drive cam follower.
The switching pin, the regulation pin that is coaxially abutted to the other end of the second switching pin and slidably fitted to the second drive cam follower, and the regulation pin and the regulation pin for urging each pin toward the hydraulic chamber. The present invention relates to a valve operating system for an internal combustion engine, which includes a return spring provided between two drive cam followers.

[0002]

2. Description of the Related Art Conventionally, such a valve operating device is known, for example, from Japanese Patent Application Laid-Open No. 61-199911.

[0003]

By the way, in such a valve operating system, when the hydraulic pressure is applied to the hydraulic chamber in order to connect the connection switching mechanism, the first switching pin is fitted into the free cam follower secondly. If it is performed prior to the fitting of the switching pin to the second drive cam follower, the first and second switching pins will come out of the free cam follower and the second drive cam follower when the intake valve or the exhaust valve is opened with a high lift. The connection switching mechanism may be damaged. That is, in such a state, the push-back force by the return spring and the push-back force by the valve spring act on the second switching pin, and when the valve opening lift of the intake valve or the exhaust valve is small, the free cam follower of the first switching pin is applied. Since the shearing force of the valve spring and the hydraulic pressure of the hydraulic chamber due to the fitting of the pressure acting on the first switching pin act on the first switching pin, both switching pins will not come off. However, when the valve opening lift of the intake valve or the exhaust valve becomes large, the spring force of the valve spring becomes large, and the push-back force of the valve spring acting on the second switching pin becomes large, and the second connecting pin or Both the first and second connecting pins may come off.

The present invention has been made in view of the above circumstances, and when the valve opening lift amount of at least the intake valve or the exhaust valve is large during the connection operation of the connection switching mechanism, the first and second connection pins come off. It is an object of the present invention to provide a valve operating device for an internal combustion engine that can prevent the occurrence of the above.

[0005]

According to the present invention, when the first and second switching pins are switched in response to the hydraulic action on the hydraulic chamber, the first and second switching pins are provided on the free cam follower and the second drive cam follower simultaneously or on the second drive cam follower. Two switching pins are configured to mate first.

According to the above construction, during the coupling operation of the coupling switching mechanism, the shear force of the valve spring acts on the first switching pin when the tip of at least one of the switching pins starts to be fitted into the corresponding cam follower. Therefore, the switching pin is not prevented from coming off until the valve lift of the intake valve or exhaust valve becomes large, and the intake valve or exhaust valve starts to open when each switching pin is not in the full stroke state. With this, it is possible to prevent the valve from coming off when the valve opening lift amount is small, and to avoid it when the valve opening lift amount becomes large.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, FIGS. 1 and 2 showing an embodiment of the present invention.
In the engine main body E, a pair of intake valves 1a,
Reference numeral 1b denotes a low speed cam 3, 3 and a high speed cam 5 which are integrally provided on a cam shaft 2 which is rotationally driven from a crank shaft of the engine at a speed reduction ratio of 1/2, and a rocker shaft 6 which is parallel to the cam shaft 2. First and second rocker arms 7, 8 as first and second drive cam followers pivotally supported on the third rocker arm 9 as a free cam follower
And the connection switching mechanism 10 provided between the rocker arms 7 to 9 are operated to open and close.

The camshaft 2 is rotatably disposed above the engine main body E, and the low speed cams 3 are integrated with the camshaft 2 at positions corresponding to the intake valves 1a and 1b, respectively, and are fast. The working cam 5 is integrated with the camshaft 2 between the low speed cams 3 and 3. Each of the low speed cams 3 and 3 has a high position 3a having a relatively small protrusion amount along the radial direction of the cam shaft 2.
And a base circle portion 3b. Further, the high-speed cam 5 has a protrusion amount of the camshaft 2 outward in the radial direction larger than that of the high-level portion 3a, and a high-level portion 5a covering a central angle range wider than the high-level portion 3a and a base circular portion 5b. Have and.

The rocker shaft 6 is fixedly arranged below the cam shaft 2. This rocker shaft 6 has
A first rocker arm 7 interlockingly connected to one intake valve 1a, a second rocker arm 8 interlockingly connected to the other intake valve 1b, and a third rocker arm 7 disposed between the first and second rocker arms 7 and 8. The rocker arms 9 are adjacent to each other and are pivotally supported. Further, a cam slipper 11 which is in sliding contact with one of the low speed cams 3 is provided above the first rocker arm 7, and the other low speed cam 3 is provided above the second rocker arm 8.
A cam slipper 12 that is in sliding contact with the cam rocker 12 is provided, and a cam slipper 13 that is in sliding contact with the high speed cam 5 is provided above the third rocker arm 9.

On the other hand, a flange portion 14 is provided above each of the intake valves 1a and 1b, and a valve spring 15 is interposed between the flange portion 14 and the engine body E, so that each intake air The valves 1a and 1b are biased by the valve springs 15 in the valve closing direction, that is, upward. Further, the intake valves 1a and 1b are attached to the tips of the first and second rocker arms 7 and 8.
The tappet screws 16 that come into contact with the upper ends of the first and second rocker arms 7 and 8 are screwed together so as to be able to move forward and backward, thereby interlockingly connecting the first and second rocker arms 7 and 8 to the intake valves 1 and 1b.

Referring also to FIG. 3, the third rocker arm 9 is slightly extended from the rocker shaft 6 toward both intake valves 1a and 1b, and the third rocker arm 9 and the engine body E are connected to each other. The elastically urging means 19 provided therebetween urges elastically in a direction of sliding contact with the high speed cam 5.

The elastically urging means 19 has a bottomed cylindrical lifter 20 whose closed end is in contact with the third rocker arm 9 and a lifter spring 21 which is compressed between the lifter 20 and the engine body E.
The lifter 20 is slidably fitted in a bottomed hole 22 formed in the engine body E.

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

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

The first rocker arm 7 is provided with a bottomed first guide hole 27 opened to the third rocker arm 8 side in parallel with the rocker shaft 6, and the first guide hole 27 is formed.
The first switching pin 23 is slidably fitted in the. 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. Moreover, the first guide hole 27
The closed end of the first switching pin 23 comes into contact with one end of the first switching pin 23 and
A restriction protrusion 29 that restricts the movement of the switching pin 23 toward the hydraulic chamber 28 is provided in a protruding manner. Further, a chamfered portion 23a is provided around the other end of the first switching pin 23 over the entire circumference.

Further, a hydraulic chamber 28 is provided in the first rocker arm 7.
The rocker shaft 6 is provided with a hydraulic passage 31 communicating with the hydraulic pressure supply passage 31 communicating with a hydraulic pressure supply source (not shown). The communication passage 30 and the hydraulic pressure supply passage 31 are connected to each other via the communication hole 32 formed in the side wall of the rocker shaft 6 through the first passage.
Regardless of the rocking state of the rocker arm 7, the rocker arm 7 always communicates.

The first guide hole 2 is formed in the third rocker arm 9.
7, a guide hole 33 having the same diameter is formed in parallel with the rocker shaft 6 between both side surfaces thereof, and the other end of the first switching pin 23 has one end coaxially abutted thereto.
The switching pin 24 is slidably fitted in the guide hole 33. Moreover, the chamfered portion 33a is provided at the opening edge of the guide hole 33 on the side of the first rocker arm 7 over the entire circumference.
A chamfered portion 24a is provided around the entire circumference of the other end of the switching pin 24.

The guide hole 3 is provided in the second rocker arm 8.
A second guide hole 34 having the same diameter and a bottom and corresponding to No. 3 is bored in parallel with the rocker shaft 6 with its open end facing the third rocker arm 9, and the disc-shaped regulating pin 25 is used as the second guide. It is slidably fitted in the hole 34. A shaft portion 35 is coaxially connected to the restriction pin 25, and the shaft portion 35 is movably inserted into a guide hole 36 formed at the closed end of the second guide hole 34. Moreover, the return spring 26 is provided between the closed end of the second guide hole 34 and the regulation pin 25 so as to surround the shaft portion 35, and the return spring 26 causes the pins 23 and 24 to come into coaxial contact with each other. , 25 are urged toward the hydraulic chamber 28. Further, a chamfered portion 34a is provided over the entire circumference at the opening edge of the second guide hole 34 on the third rocker arm 9 side.

In the connection switching mechanism 10, the first and second switching pins 23 and 24 start to be simultaneously fitted into the guide hole 33 and the second guide hole 34 at the time of the connection operation in which the hydraulic pressure is applied to the hydraulic chamber 28. Is composed of. That is, the distance l ₁ between the small diameter ends of the chamfered portions 23a and 33a and the distance l ₂ between the small diameter ends of the chamfered portions 24a and 34a at the time of disconnection are set to be equal.

To explain the operation of this embodiment, the hydraulic pressure in the hydraulic chamber 28 is released during the low speed operation of the engine, and the pins 23 to 25 are moved to the maximum by the spring force of the return spring 26. It has been moved and is in a disconnected state.
In this state, the contact surfaces of the first and second switching pins 23 and 24 are at positions corresponding to the first and third rocker arms 7 and 9, and the contact surfaces of the second switching pin 24 and the restriction pin 25 are It is in a position corresponding to between the third and second rocker arms 9, 8. Therefore, the rocker arms 7 to 9 are in a state where they can be angularly displaced relative to each other.

In the uncoupled state, the first and second rocker arms 7 and 8 swing due to the rotational operation of the cam shaft 2 in accordance with the sliding contact with the low speed cams 3 and 3, and therefore, both intake valves. 1a and 1b are opened and closed at the timing and lift amount according to the shapes of the low speed cams 3 and 3. At this time, the third rocker arm 9 swings in response to the sliding contact with the high speed cam 5, but the swinging motion does not have any influence on the first and second rocker arms 7 and 8.

High hydraulic pressure is supplied to the hydraulic chamber 28 during high-speed operation of the engine. As a result, the first and second switching pins 2
3, 24 and the restriction pin 25 move to the connecting position side against the spring force of the return spring 26, the first switching pin 23 fits into the guide hole 33, and the second switching pin 24 moves to the second position.
The rocker arms 7 to 9 are fitted into the guide holes 34 and are connected to each other. At this time, the rocking amount 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 rock together with the third rocker arm 9, and both intake valves 1a and 1b move at high speed. The opening / closing operation is performed at a timing and a lift amount according to the shape of the working cam 5.

By the way, when the connection switching mechanism 10 is connected, the first and second rocker arms 7 and 8 are brought into sliding contact with the base circle portion 3b of the low speed cams 3 and 3, and the third rocker arm 9 is connected.
Is started in a state of being in sliding contact with the base circle portion 5b of the high speed cam 5. At the start of the coupling operation, the first and second switching pins 23 and 24 may not make a full stroke, and the first and second rocker arms 7 and 8 may start to swing due to the high position portion 3a of the low speed cams 3 and 3. In such a case, the chamfered portion 2 of the first switching pin 23 as shown in FIG.
3a is engaged with the chamfered portion 33a of the guide hole 33, and the chamfered portion 24a of the second switching pin 24 is engaged with the chamfered portion 34a of the second guide hole 34.
The valve opening lift operation may be started. At this time,
While the push-back force of the return spring 26 and the push-back force of the valve spring 15 act on the second switching pin 24, only the hydraulic pressure of the hydraulic chamber 28 acts on the first switching pin 23. The shearing force by the valve spring 15 does not act. Therefore, when the valve opening lift operation of the intake valves 1a, 1b is started in the state of FIG. 5, the force for pushing back the first and second switching pins 23, 24 to the connection position side is stronger than the force for returning them to the connection release position side. Becomes larger and the valve opening lift amount is low, the first and second switching pins 23 and 24 are pushed back to the hydraulic chamber 28 side and come out from the guide hole 33 and the second guide hole 34. Therefore, the state of FIG. 5 does not continue until the valve opening lift amount of the intake valves 1a, 1b becomes large, and if the first and second switching pins 23, 24 may come off during the coupling operation, This is limited to the case where the valve opening lift amount of the intake valves 1a and 1b is small, and it is possible to reliably prevent the valve from coming off after the valve opening lift amount becomes large.

FIGS. 6 and 7 show another embodiment of the present invention, in which parts corresponding to those of the above-mentioned embodiment are designated by the same reference numerals.

A coupling switching mechanism 10 'capable of switching coupling and decoupling of the rocker arms 7, 8 and 9 has a first switching pin 23', a second switching pin 24 ', a regulating pin 25 and a return spring 26. , First and second switching pins 23 ', 2
4'is configured so that the second switching pin 24 'can be fitted into the second guide hole 34 prior to the connection operation. That is,
A small diameter portion 24'b that abuts the first switching pin 23 'is coaxially provided on the first switching pin 23' side of the second switching pin 24 ', and the first switching pin 23' and the small diameter portion 24 'are provided.
The contact surface of b is the second switching pin 24 'and the regulation pin 25.
The contact surface of is in the position corresponding to between the third and second rocker arms 9 and 8 and is in the first guide hole 27 when the connection is released. When the connection is released, the chamfered portion 2 of the first switching pin 23 '
3a ′ and the distance l ₁ ′ between the small diameter ends of the chamfered portion 33a of the guide hole 33 are equal to the chamfered portion 24 of the second switching pin 24 ′.
It is set to be larger than the distance l ₂ ′ between a ′ and the small diameter end of the chamfered portion 34a of the second guide hole 34. In addition, the outer diameter of the small diameter portion 24'b of the second switching pin 24 'is in the first guide hole 27, the first and third rocker arms 7,
It is set so as to form a gap larger than the swing amount difference of 9 with the inner surface of the first guide hole 27.

In such a connection switching mechanism 10 ', when the connection is operated, as shown in FIG.
The chamfered portion 23a 'of 3'is the chamfered portion 33 of the guide hole 33.
The second switching pin 24 'has the second
It fits in the guide hole 34. Therefore, the intake valve 1a,
In the state of FIG. 7 when the valve opening operation of the valve 1b is started, the push-back force by the valve spring 15 and the push-back force by the return spring 26 act on the second switching pin 24 ', while the first switching Only the hydraulic pressure of the hydraulic chamber 28 acts on the pin 23 ', and the first and second switching pins 23', 23 ', in the state where the valve opening lift of the intake valves 1a, 1b is small, as in the previous embodiment.
24 'is missing.

Although the valve operating device for the intake valve has been described in the above embodiments, the present invention is also applicable to the valve operating device for the exhaust valve.

[0028]

As described above, according to the present invention, when the first and second switching pins perform the switching operation according to the hydraulic action on the hydraulic chamber, the first and second switching pins are simultaneously provided to the free cam follower and the second drive cam follower or to the second drive cam follower. Since the two switching pins are configured to be fitted in advance, the shearing force of the valve spring acts on the first switching pin when the first and second switching pins are not in full stroke at the start of the coupling operation. Therefore, it is possible to reliably prevent the disconnection of the switching pin from occurring at the time of high lift.

[Brief description of drawings]

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

FIG. 2 is a sectional view taken along line 2-2 of FIG.

3 is a sectional view taken along line 3-3 of FIG.

FIG. 4 is an enlarged cross-sectional view taken along line 4-4 of FIG. 2 when the connection is released.

FIG. 5 is a cross-sectional view of the main parts of FIG. 4 at the start of the coupling operation.

FIG. 6 is a cross-sectional view corresponding to FIG. 4, showing another embodiment of the present invention.

7 is a cross-sectional view of the main parts of FIG. 6 at the start of the coupling operation.

[Explanation of symbols]

1a, 1b ... Intake valve 7 ... First rocker arm as first drive cam follower 8 ... Second rocker arm as second drive cam follower 9 ... Third rocker arm as free cam follower 10, 10 '... Connection switching mechanism 23, 23'. First switching pin 24, 24 '. Second switching pin 25 ........ Regulating pin 26 .. ..Return spring 28 ........ hydraulic chamber

Claims (1)

Claim: What is claimed is: 1. An intake valve or an exhaust valve between a first drive cam follower and a second drive cam follower, which are interlocked with and connected to an intake valve or an exhaust valve biased in a valve closing direction by a valve spring. A free cam follower, which can be free to the other, is arranged, and a connection switching mechanism that can switch between connecting and disconnecting each cam follower is slidable on the first drive cam follower with one end facing the hydraulic chamber. A first switching pin which is fitted to the free cam follower and is fitted to the free cam follower;
A second switching pin slidably fitted to the free cam follower by coaxially contacting one end with the other end of the switching pin and fittable with the second drive cam follower, and one end to the other end of the second switching pin. It is composed of a restriction pin that is coaxially abutted and slidably fitted in the second drive cam follower, and a return spring provided between the restriction pin and the second drive cam follower to urge the pins toward the hydraulic chamber. In the valve operating system for an internal combustion engine, the first and second switching pins simultaneously or with the second switching pin precede the free cam follower and the second drive cam follower when the first and second switching pins are switched according to the hydraulic action on the hydraulic chamber. A valve train for an internal combustion engine, which is configured to be fitted together.