JPH07107362B2 - Valve timing switching device for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing switching device for a 4-cycle internal combustion engine.

[0002]

2. Description of the Related Art In a four-cycle internal combustion engine, a rocker arm is swung by the rotation of a cam of a camshaft which is interlocked with a crankshaft, and each umbrella valve for intake and exhaust is pushed down against a spring. I am trying to open it.
Therefore, the valve opening / closing timing and the lift amount, which is the valve opening amount, are determined by the shape of the cam. In an engine that requires high output at high speed, the valve timing is increased, the lift amount is increased, and when the intake / exhaust amount is high at high speed, the intake / exhaust efficiency is increased to increase the output.

[0003]

However, when the cam is set in this way, the flow velocity of intake air becomes slow at low speeds with a small intake and exhaust amount, swirling is not possible, combustion efficiency is reduced, and output is reduced. To do. In addition, the intake and exhaust valves overlap each other, which increases the amount of blow-through of intake air, resulting in an increase in fuel consumption.

In view of the above point, the present invention prepares a low speed cam and a high speed cam, and uses a low speed cam and a low speed cam by a sliding arm so that a high output can be obtained in both high speed and low speed.
An object of the present invention is to provide a valve timing switching device for an internal combustion engine, which switches between a low speed state suitable for low speed operation and a high speed state suitable for high speed operation by utilizing the oil pressure of an oil pump.

[0005]

SUMMARY OF THE INVENTION As a means for solving the above problems, the present invention provides a rocker shaft which can be freely rotated by a cam of a cam shaft which is constantly urged to be closed by a spring means and which rotates in conjunction with a crankshaft. In an intake or exhaust valve of an internal combustion engine that is driven to open by a rocker arm that is pivotally supported, a low speed cam and a high speed cam are provided side by side on the cam shaft, and when the engine is operating at a low speed, the low speed cam is operated at a high speed. A switching device for selectively switching a high-speed cam during operation, which opens and closes a valve by means of a cam surface of the rocker shaft which is pivotally supported by the rocker shaft and is centered on the rocker shaft pivotal support portion and an end valve pressing portion. No. 1 rocker arm and the high-speed cam that is pivotally supported by the rocker shaft adjacent to the first rocker arm at high speed A second rocker arm which abuts,
An arm portion extending from the rocker shaft pivotal support portion of the first rocker arm to the cam sliding contact portion, and a connection switching portion of the first and second rocker arms provided adjacent to the cam sliding contact portion, The connection switching unit has a hydraulic pressure selection switching unit that switches and moves the second rocker arm by a plunger that operates by receiving the hydraulic pressure of an oil pump that interlocks with the engine, and the plunger is always provided on the side opposite to the hydraulic chamber of the plunger. A spring means for urging the bear to keep the low speed bear, and when the oil pressure of the oil pump is higher than a predetermined value, the plunger is actuated against the spring means during high speed operation,
The rocker arm of the second rocker arm is switched to the high speed side, the first and second rocker arms are integrally connected by the connection switching portion, and the second rocker arm is slidably contacted to the high speed cam and pivotally supported by the rocker shaft. It is characterized in that the valve is opened / closed via the first rocker arm.

[0006]

In the high speed operation, the oil pressure of the oil pump pushes the plunger in the hydraulic chamber against the urging of the spring, so that the second rocker arm moves to the high speed side and the first and second rocker arms are switched. And the valve is opened and closed by the second rocker arm via the first rocker arm. During low speed operation, the oil pressure of the oil pump is low, so the second rocker arm of the plunger is returned by the biasing of the spring, the connection switching part is separated, and the first rocker arm is operated by the low speed cam, and the low speed state is reached. Get burned. When the oil pressure of a predetermined pressure is not applied even during high speed operation due to a failure of the oil pump or the like, the spring is switched to the low speed state similarly to the low speed operation, and the engine is stabilized.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in the drawings.

A low speed cam 2 and a high speed cam 3 are arranged in parallel on a cam shaft 1 which is interlocked with the crank shaft by a chain or the like. The low speed cam 2 has a shape in which the valve opening timing is short and the lift amount is small.
Is designed to have a long valve opening timing and a large lift amount.

The first rocker arm 5 pivotally attached to the rocker shaft 4 is adapted to push and open an umbrella-shaped valve 6 for intake or exhaust air against a spring 7 by its swinging. It is located below the low speed cam 2.

The second rocker arm 8 is axially slidably and swingably supported on the rocker shaft 4, and has a high-speed cam 3 and side projections 9 of the first rocker arm 5. It is adapted to be engaged and disengaged between and, and constitutes a connection switching unit. The second rocker arm 8 is connected to the plunger 12 of the hydraulic chamber 11 via the lever 10. A hydraulic pipe 14 of an oil pump interlocking with the engine is connected to the hydraulic chamber 11, and when the hydraulic pressure becomes high in a high speed region, the plunger 12 is pushed against the spring 13 and
The second rocker arm 8 is engaged between the high-speed cam 3 and the side projection 9 of the first rocker arm 5 to establish a connected state. When the hydraulic pressure is reduced, the second rocker arm 8 is disengaged from the high speed cam 3 by the biasing force of the spring 13. These constitute a hydraulic pressure selection switching means.

Next, the operation will be described.

In the low speed range, the oil pressure from the oil pump is low, the second rocker arm 8 is disengaged from the high speed cam 3 by the bias of the spring 13 (FIG. 2), and the rotation of the cam shaft 1 causes the low speed cam 2 to move. The first rocker arm 5 is swung, and the valve 6 is pushed open against the spring 7. Low speed cam 2
The valve 6 has a short opening timing and a small lift amount, so even if the intake and exhaust amounts are low at a low speed, a high flow velocity of intake air can be obtained near the valve 6 and swirl can be generated in the cylinder. Combustion efficiency is increased and high output is obtained.
Further, there is no blow-by of intake air, and fuel consumption can be reduced.
At this time, since the second rocker arm 8 is disengaged, the high speed cam 3 is idle.

When the hydraulic pressure from the oil pump becomes higher than a predetermined value in the high speed range, the plunger 12 moves to the spring 13
The second rocker arm 8 is pushed against the high speed cam 3
And the rocker arm 5 are engaged with each other as shown by a chain line in FIG. Therefore, the high-speed cam 3 swings the first rocker arm 5 via the second rocker arm 8 to open the valve 6. Since the high-speed cam 3 has a large opening timing of the valve 6 and a large lift amount, the intake / exhaust efficiency can be increased and the output can be increased even if the intake / exhaust amount increases at high speed. At this time, the low speed cam 2 is playing.

[0014]

As described above, according to the present invention, in the high speed range, the rotation of the plunger causes the plunger to shift to the high speed state by the hydraulic pressure above the predetermined pressure generated in the oil pump, and in the low speed range, the hydraulic pressure decreases. By moving the plunger to a low speed bear by the spring bias, the valve opening is automatically switched according to the rotation of the engine, and the valve timing and lift amount are adapted to the rotation in the low speed region and the high speed region respectively. It is possible to obtain high output at high speed and low speed, and save fuel. When the hydraulic pump, solenoid valve of the pump circuit, or other hydraulic-related parts fail at high speed, or when the hydraulic pressure of the specified pressure stops working due to damage to the piping, the plunger automatically moves to the low speed side due to spring bias. Since the low speed bear is moved to, the engine can be kept operating smoothly at high speed without any trouble.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of the present invention.

FIG. 2 is a view on arrow in FIG. 1A-A.

[Explanation of symbols]

 1 camshaft 2 low speed cam 3 high speed cam 5 first rocker arm 6 valve 8 second rocker arm

Claims (1)

[Claims] 1. An internal combustion engine in which valve opening is driven via a rocker arm that is rotatably supported by a rocker shaft by a cam of a cam shaft that is urged to always close the valve by spring means and that rotates in conjunction with a crankshaft. In the intake or exhaust valve of the above, a switching device for providing a low speed cam and a high speed cam together on the cam shaft, and selectively switching the low speed cam during low speed operation of the engine and the high speed cam during high speed operation, A first rocker arm that is pivotally supported by the rocker shaft and that opens and closes a valve by a cam surface of the cam shaft centering around the rocker shaft pivotal portion through a valve pressing portion at an end, and adjacent to the first rocker arm. A second rocker arm pivotally supported by the rocker shaft and contacting the high speed cam at a high speed; and a first rocker arm. An arm portion extending from the rocker shaft pivotal support portion to the cam sliding contact portion, and a coupling switching portion for the first and second rocker arms provided adjacent to the cam sliding contact portion, the coupling switching portion being provided to an engine. There is provided a hydraulic pressure selection switching means for switching and moving the second rocker arm by a plunger that operates by receiving the hydraulic pressure of an interlocking oil pump, and is provided on the side opposite to the hydraulic chamber of the plunger so that the plunger is always kept in a low speed state. A spring means for urging is provided, and the plunger is operated against the spring means at the time of high-speed operation when the oil pressure of the oil pump becomes equal to or higher than a predetermined value, and the second rocker arm of the previous period is switched to the high-speed side. A second rocker arm integrally connected by the connection switching portion, slidably contacting a high speed cam, and pivotally supported by the rocker shaft.
A valve timing switching device for an internal combustion engine, characterized in that the valve is opened / closed by the rocker arm via the first rocker arm.