JPH0598919A - Valve timing switching device for internal combustion engine - Google Patents

Abstract

PURPOSE:To switch the open degree of an intake valve or an exhaust valve automatically, and maintain the stabilized operating condition by providing a hydraulic selective switching means for switching the timing of an intake valve or an exhaust valve between the low speed condition and the high speed condition, and providing a spring means for always energizing a plunger so as to maintain the low speed condition. CONSTITUTION:In a low speed area, the oil pressure from an oil pump is low, and a sliding arm 8 is removed from a high speed cam 3 by energizing of a spring. With the rotation of a cam shaft 1, a locker arm 5 is oscillated by a low speed cam 2, and a valve 6 is pushed to be opened, resisting a spring 7. In a high speed area, when the oil pressure from the oil pump exceeds a predetermined value, the plunger is pushed, resisting the spring, and the sliding arm 8 is engaged between the high speed cam 3 and the locker arm 5. Consequently, the high speed cam 3 oscillates the locker arm 5 through the sliding arm 8 to open the valve 6. Since the timing for opening the valve 6 is set large and a lift quantity thereof is set large by the high speed cam 3, the high output can be obtained.

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 rocked 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, at a low speed with a small intake and exhaust amount, the flow velocity of intake air becomes slow, swirl flow is not possible, combustion efficiency is lowered, and output is lowered. To do. In addition, the intake and exhaust valves overlap each other, which increases the amount of intake air blow-through, 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 high output can be obtained at high speed and low speed.
Use the oil pressure of the oil pump to switch between a low-speed state suitable for low-speed operation and a high-speed state suitable for high-speed operation. If a failure occurs in this oil pump or other related mechanism, it may be switched to a low-speed state by spring force. The present invention has been made for the purpose of providing a valve timing switching device for an internal combustion engine.

[0005]

As a means for solving the above problems, the present invention relates to an intake valve which is biased by a valve spring in a valve closing direction and is opened by a cam of a camshaft which rotates in conjunction with a crankshaft. In an internal combustion engine having an intake / exhaust device equipped with an exhaust valve, an oil pump that interlocks the opening and closing timing of an intake valve or an exhaust valve with a low speed state suitable for low speed operation of the engine and a high speed state suitable for high speed operation of the engine The oil pump has a hydraulic selection switching means for switching by a plunger that operates upon receipt of the hydraulic pressure, and is provided on the opposite side of the hydraulic chamber of the plunger to urge the plunger to keep the plunger at a low speed at all times. When the hydraulic pressure is higher than a predetermined value, the plunger is moved against the spring means to be displaced toward the high speed state. It is characterized in that the.

[0006]

[Operation] During high speed operation, the oil pressure of the oil pump pushes the plunger in the hydraulic chamber against the bias of the spring, so it is in a high speed state. Returned and put in slow speed. When the oil pressure of a predetermined pressure stops acting 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 as in 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 is set to have 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 rocker arm 5 pivotally mounted on 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 sliding arm 8 is slidably and swingably supported on the rocker shaft 4 in the axial direction thereof.
The high speed cam 3 and the side projection 9 of the rocker arm 5 are engaged and disengaged. The sliding arm 8 is connected to a plunger 12 of a hydraulic chamber 11 via a 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 range, the plunger 12 is pushed against the spring 13 and
The sliding arm 8 is engaged between the high speed cam 3 and the side projection 9 of the rocker arm 5. When the hydraulic pressure decreases, the sliding arm 8 is disengaged from the high speed cam 3 by the bias of the spring 13.

Next, the operation will be described.

In the low speed range, the oil pressure from the oil pump is low, and the sliding arm 8 is disengaged from the high speed cam 3 due to the bias of the spring 13 (FIG. 2). The rotation of the cam shaft 1 causes the low speed cam 2 to move the rocker arm. 5 is rocked, and the valve 6 is pushed open against the spring 7. Since the low-speed cam 2 is set such that the valve 6 has a short opening timing and a small lift amount, a high intake velocity can be obtained near the valve 6 even if the intake / exhaust amount is small at a low speed, and a swirling flow is generated in the cylinder. As a result, 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 sliding 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 sliding arm 8 is engaged between the high speed cam 3 and the rocker arm 5 as shown by the chain line in FIG.
Therefore, the high speed cam 3 swings the rocker arm 5 via the sliding 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 region, the rotation of the oil pump causes the oil pressure above the predetermined pressure to move the plunger to the high speed state, and in the low speed region, the oil pressure decreases. The spring bias moves the plunger to a low speed state, and the valve opening is automatically switched according to the rotation of the engine, and the valve timing and lift amount can be adapted to the rotation in the low speed region and the high speed region, respectively. High output at high and low speeds can be obtained, and fuel can be saved. Especially at high speeds, when the hydraulic pump, solenoid valves of the pump circuit, or other hydraulic-related parts fail, or if the hydraulic pressure of the specified pressure stops working due to damage to the piping, the plunger automatically lowers the speed by the spring force. Since the engine is moved to the side and kept in the low speed state, 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 Rocker arm 6 Valve 8 Sliding arm

Claims (1)

[Claims] 1. An internal combustion engine having an intake / exhaust device including an intake valve and an exhaust valve, which are biased by a valve spring in a valve closing direction and opened by a cam of a camshaft which rotates in conjunction with a crankshaft. Alternatively, a hydraulic selection switching means for switching the opening / closing timing of the exhaust valve between a low speed state suitable for low speed operation of the engine and a high speed state suitable for high speed operation by a plunger operated by receiving the oil pressure of the oil pump interlocked with the engine A spring means is provided opposite to the hydraulic chamber of the plunger for constantly urging the plunger so as to keep the plunger at a low speed, and the plunger is moved against the spring means when the oil pressure of the oil pump is a predetermined value or more. Valve timing switching device for an internal combustion engine, characterized in that