JPH04175411A - Valve system in internal combustion engine - Google Patents

Abstract

PURPOSE:To simply surely change valve timing or valve lift by providing a contact fulcrum part for a rocker arm shaft in a sub-rocker arm while providing in the rocker arm shaft an eccentric part which can be changed over to make contact with or part from the contact fulcrum part by the rotation of the rocker arm shaft. CONSTITUTION:When an eccentric part 16 is set not to contact a contact fulcrum part 15 of a sub-rocker arm 13 by rotating a rocker arm shaft 8, the sub-rocker arm 13 is swingably pivoted only about a pivot pin 14 for both main rocker arms 12 by a high speed cam 11 without being swingably pivoted about the fulcrum of the rocker arm shaft 8. Thus, the swingable pivoting of the sub-rocker arm 13 is not transmitted to an intake valve 3 and the intake valve 3 is operatively opened and closed by a low speed cam 10. On the other hand, when the eccentric part 16 is set to contact the contact fulcrum part 15, the sub-rocker arm 13 is swingably pivoted about the fulcrum of the rocker arm shaft 8 by the high speed cam 11. The intake valve 3 is operatively opened and closed by the high speed cam 11.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to timing for opening and closing intake valves or exhaust valves in internal combustion engines (so-called valve timing) and/or valve lift. The present invention relates to a valve train that allows changes to be made during the operation of an internal combustion engine.

[Conventional technology]

As a prior art, Japanese Utility Model Application No. 61-58605 proposes the following as a valve train that can change valve timing or valve lift during operation of an internal combustion engine. are doing.

That is, this prior art valve train has a cam profile on the camshaft that is suitable for a low speed rotation range.

A low-speed cam and a high-speed cam with a cam profile suitable for a high-speed rotation range are provided, and a rocker arm shaft disposed parallel to the cam shaft contacts the intake valve or exhaust valve and the low-speed cam. A main rocker arm and a sub-rocker arm that abuts the high-speed cam are pivoted adjacent to each other, and both the main rocker arm and the sub-rocker arm are provided with pin holes parallel to the rocker arm axis. The plunger pin is slidably inserted into one of the two pin holes, and the plunger pin is retracted into one pin hole, and the two pin holes are retracted. When the plunger pin is retracted into one of the pin holes and the two-end hook arms are disconnected, the intake valve or the exhaust valve is moved by the low-speed cam. When the valve timing or valve lift suitable for the low-speed rotation range is used to open and close the valve, and the plunger pin is fitted across both pin holes to connect the two-end hook arms, the intake valve or exhaust valve is not suitable for high-speed rotation. The valve was configured to open and close using a cam with valve timing or valve lift appropriate for the high-speed rotation range.

[Problem to be solved by the invention]

However, this prior art valve train has the following problems.

In other words, when the plunger pin is fitted across both pin holes in the double-ended hook arm to connect the double-ended hook arms, the intake valve or exhaust valve is attached to the plunger pin against its spring. A twisting force acts due to the bending moment and shear load due to the large force required to open the valve (hereinafter referred to as valve opening force), and against this twisting force,
Since the plunger pin has to slide in the axial direction, the inner surfaces of the pin holes into which the plunger pin fits are prone to wear such as fatigue, resulting in low durability.In addition to this low durability, Since the plunger is moved in the axial direction, it lacks quickness, and cannot keep up with the increasing speed of the internal combustion engine.

Furthermore, in the prior art valve train, in order to configure the plunger pin to fit across both pin holes or to be retracted into one pin hole, it is necessary to deviate from the axis of the rocker arm shaft. The distance to the center of the pin hole in the main rocker arm and the distance from the axis of the rocker arm axis to the center of the pin hole in the secondary rocker arm must be configured accurately so that the axes of both pin holes coincide in a straight line. Not only that, but a high level of processing precision is required to process both pin holes, resulting in a significant increase in manufacturing costs.

An object of the present invention is to provide a variable valve timing and/or valve lift type valve operating system that eliminates these problems.

[Means to solve the problem]

To achieve this object, the present invention provides a low-speed cam and a high-speed cam on a camshaft, and also provides an intake valve or an exhaust valve and a low-speed cam on a rocker arm shaft disposed parallel to the camshaft. In the valve train, the main rocker arm is pivotally mounted to contact both the cam and the sub rocker arm is provided to contact the high speed cam, and the sub rocker arm is rotatable by a pin on the main rocker arm. It is pivoted to, and furthermore,
The auxiliary rocker arm is provided with a fulcrum part that abuts against the rocker arm shaft, and the rocker arm shaft has a position where it abuts the fulcrum part and a position where it abuts the fulcrum part by rotating the rocker arm shaft. The eccentric portion is configured to be switchable between a non-contact position and a non-contact position.

[For production]

In this configuration, the eccentric portion of the rocker arm axis is
When the rocker arm shaft is rotated to a position where it does not contact the contact fulcrum of the sub rocker arm, the sub rocker arm is swung by the high speed cam around the pivot pin relative to the main rocker arm. It only pivots, but does not pivot about the rocker arm shaft as a fulcrum (therefore, the pivoting motion of this sub-rocker arm is not transmitted to the intake valve or the exhaust valve, so the intake valve Alternatively, the exhaust five-air valve is configured to adjust the valve timing suitable for the low-speed rotation range at the low-speed cam through the swinging rotation of the main rocker arm that is pivotally mounted on the rocker arm shaft and in contact with the low-speed cam. It is opened and closed by valve lift.

When the eccentric portion of the rocker arm shaft is brought into contact with the contact fulcrum portion of the sub-rocker arm by rotation of the rocker arm shaft, the sub-rocker arm that contacts the high-speed cam is brought into contact with the rocker arm. The high-speed cam swings and rotates about the shaft as a fulcrum, and this swinging rotation is transmitted to the intake valve or exhaust valve via the main rocker arm. A high-speed cam is used to open and close the valve with valve timing or valve lift suitable for the high-speed rotation range.

〔Effect of the invention〕

As described above, the present invention changes the valve timing or valve lift by rotating the rocker arm shaft, and when changing the valve timing, as in the prior art,
No twisting force occurs due to large valve opening force (
Moreover, since it can be operated quickly, it can greatly improve durability and can reliably keep up with the increasing speed of internal combustion engines.Moreover, unlike the prior art mentioned above, it does not require high processing precision. This has the effect of significantly reducing manufacturing costs.

〔Example〕

The following describes the drawings in which the embodiments of the present invention are applied to an intake valve. In the drawings, reference numeral l indicates a cylinder block, and reference numeral 2 indicates a cylinder head fastened to the upper surface of the cylinder block l. Each is shown.

Further, reference numeral 3 indicates an intake valve provided at the opening into the combustion chamber 5 of the intake port 4 formed in the cylinder head 2, and there are two intake valves 3 for the - combustion chambers 5. Both intake valves 3 are provided with valve springs 6 for keeping each intake valve normally closed.

A cam shaft 7 and a rocker arm shaft 8 are disposed parallel to each other on the upper surface of the cylinder head 2, and the bearings provided on the upper surface of the cylinder head 2 are mounted on the cam shaft 7 and the rocker arm shaft 8. A pair of left and right low-speed cams 10 for both the intake valves 3 and one i-speed cam 11 for both the intake valves 3 are integrally supported on the camshaft 8. It is shaped.

The rocker arm shaft 8 is rotatably fitted with the base end boss portions 12a of the pair of left and right main rocker arms 12, and the double rocker arm 12 has a slipper on its upper surface that abuts both the low speed cams IO. The portion 12b is provided with a tappet screw 12c at the other end thereof, which abuts on the upper end of the stem 3a of both the intake valves 3.

Further, between the two main rocker arms 12, a sub-rocker arm 13 is provided which has a slipper portion 13a on its upper surface that comes into contact with the high-speed cam 11.
3 is pivotally connected to both the main rocker arms 12 via a pin 14.

The auxiliary rocker arm 13 is provided with a fulcrum portion 15 that abuts against the rocker arm shaft 8.
On the other hand, an eccentric portion 16 with respect to the axis 8a of the rocker arm shaft 8 is provided at a portion of the rocker arm shaft 8 that corresponds to the contact fulcrum portion 15.
is integrally provided, and by rotating the rocker arm shaft 8, the eccentric part 16 can be moved to a position where it does not abut against the contact fulcrum part 15, as shown in FIG. , the eccentric portion 16 is configured to selectively switch to a position in which it abuts against the abutment fulcrum portion 15 as shown in FIG.

Note that the sub rocker arm 13 is urged upward by a spring 17 provided between it and the cylinder head 2.

In this configuration, the eccentric portion 1 in the rocker arm shaft 8
6 by rotating the rocker arm shaft 8.
As shown in the figure, when the secondary rocker arm 13 is placed in a position where it does not contact the abutment fulcrum 15, the secondary rocker arm 13 is moved around the high-speed cam 11 around the pivot pin 14 for both main rocker arms 12. The auxiliary rocker arm 13 only swings and rotates at , but does not swing and rotate about the rocker arm shaft 8 as a fulcrum, and therefore, the swing and rotation of this sub-rocker arm 13 is not transmitted to both intake valves 3. , both intake valves 3 are adapted to the low speed rotation range by the low speed cam lO through the rocking rotation of both main rocker arms 12 which are pivotally connected to the rocker arm shaft 8 and in contact with the low speed cam lO. It is opened and closed by the valve timing or valve lift.

Then, the eccentric portion l6 in the rocker arm shaft 8 is
By rotating the rocker arm shaft, as shown in FIG. 4, when the sub rocker arm 13 is brought into contact with the abutment fulcrum portion 15 of the sub rocker arm 13, the sub rocker arm 13 that abuts the high speed cam 11 is moved to the position shown in FIG. The high-speed cam 11 swings around the rocker arm shaft 8 as a fulcrum, and this swing is transmitted to both intake valves 3 via the rocker arms 12 on both sides. , the high-speed cam 11 is opened and closed with valve timing or valve lift suitable for the high-speed rotation range.

Therefore, by rotating the rocker arm shaft 8 as described above according to the rotation speed of the internal combustion engine, the valve timing or valve lift of both intake valves 3 is adjusted over both the low speed rotation range and the high speed rotation range. This control can be performed automatically while the internal combustion engine is operating.

Note that, although the above embodiment has been applied to two intake valves 3 provided in one combustion chamber 5, the present invention is not limited to this; Needless to say, this method can be applied not only to intake valves that have been installed, but also to exhaust valves that have one or two installed in one combustion chamber.
Furthermore, the contact fulcrum portion 14 may be configured in a boss-like form.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings show embodiments of the present invention, and FIG. 1 is a diagram illustrating the gist of the present invention, and is a sectional view taken along line II in FIG. 2, a plan view, and FIG. 3. 4 is a cross-sectional view taken along the line ■--■ in FIG. 2. FIG. 4 is a view showing the operating state of FIG. 3, and FIG. 5 is a cross-sectional view taken along the line v--v in FIG. 1000. Cylinder block, 2...Cylinder head, 3...Intake valve, 4...Intake boat, 5...
...Combustion chamber, 6...Valve spring, 7...Camshaft, 8...Rocker arm shaft, 9...Bearing part, 1
0...Low speed cam, 11...High speed cam, 12
...Main rocker arm, 13...Sub-rocker arm, 14...Connection pin, 15...Abutment fulcrum part, 1
6...Eccentric part.

Claims (1)

[Claims] (1) A low-speed cam and a high-speed cam are provided on the camshaft, and both the intake valve or exhaust valve and the low-speed cam are connected to the rocker arm shaft arranged parallel to the camshaft. In the valve train, the secondary rocker arm is rotatably connected to the main rocker arm with a pin, and the secondary rocker arm is rotatably connected to the main rocker arm with a pin; , the secondary rocker arm includes:
while providing an abutting fulcrum portion for the rocker arm shaft;
The rocker arm shaft is provided with an eccentric portion configured to be switchable between a position in which it abuts the abutting fulcrum and a position in which it does not abut the abutting fulcrum by rotating the rocker arm shaft. A valve train for an internal combustion engine characterized by: