JPS63253107A - Intake-exhaust valve lift timing variable device - Google Patents

Abstract

PURPOSE:To improve intake-exhaust efficiency over all engine speed areas by forming a cam for low engine speeds and a cam for high engine speeds on a cam shaft, and eaxially moving the cam shaft. CONSTITUTION:A cam 1 consisting of a cam-geometry la for low engine speeds and a cam-geometry 1b for high engine speeds is formed on a cam shaft 2. When a cam shaft moving cam 6 is driven in accordance with engine speed, the cam shaft moves axially. The optimum lift timing of intake-exhaust valves can therefore be constantly ensured and the intake-exhaust efficiency can also be improved over all engine speed areas.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a variable intake/exhaust valve lift timing device for an internal combustion engine that variably controls the lift timing of intake/exhaust valves according to engine operating conditions.

<11th technology> As a device for variable control of the lift characteristics (opening/closing timing and lift amount) of the intake/exhaust vents so that the fresh air filling efficiency and exhaust efficiency of the internal combustion engine are always optimally set, 1, for example, Nissan Motor Co., Ltd. There is an invention (published patent publication Sho 6O-22490)
9) This device requires the use of a rocker arm, but modern internal combustion engines for high-end automobiles use a cam direct-drive valve tappet that does not use a rocker arm.
Furthermore, the current situation is that there is a shift to a DOHC system with four valves per cylinder. It is also installed in the Nissan Bird Altima released in 1986. VG30
The DE engine is a DOHC 1-cylinder 4-valve engine that uses a cam direct drive valve tappet, but the intake valve ref 1-timing control device used in this engine has a constant profile of the intake valve drive cam. This is a device that changes the intake valve lift timing in two stages by changing the phase between the camshaft and a timing pulley driven by a timing belt from the crankshaft. This will be explained using Figure 3.

Curve +1 is the intake valve lift timing in the high-speed range, low-medium speed, and low-load range.Curve 1 is the intake-valve lift timing in the low-medium-speed and high-load range. The lift timing of the exhaust valve is constant. In other words, this device uses the lift timing curve for the low and medium speed range only in the high load range. The reason for this is that the working angle of the intake valve actuating cam of this device (the rotation angle from when the cam starts opening until it finishes closing during one revolution of the cam) is constant, so the intake valve closes quickly when the engine is running at low speed. When changing the valve lift timing from high-speed rotation (curve a in Figure 3) to low-speed rotation (curve 3 b), the intake valve opening timing advances, but at this time the exhaust valve lift timing remains constant. Therefore, the bulb over lamp becomes large. (18→32) In other words, at low engine speeds and low loads when both the exhaust and intake valves remain open for a long time, the exhaust pipe is under positive pressure and the intake pipe is under negative pressure. Combustion gas flows back into the intake pipe, reducing the efficiency of fresh air intake.

The valve lift timing for low-speed rotation (curve mb in Figure 3) cannot be changed only at low-medium speeds and high loads (at this time, the pressure in the intake pipe is close to atmospheric, so there is no backflow from the exhaust pipe). It is. However, in normal operation, high-load operation is rare, so this device is unlikely to operate.

<Purpose of the Invention> The present invention was made to solve these conventional problems, and it is possible to obtain ideal intake/exhaust valve lift timing according to engine operating conditions, and to It is an object of the present invention to provide a variable intake/exhaust valve lift timing device for an internal combustion engine that can be used for such intake/exhaust valve operating devices.

<Summary of the Invention> Therefore, 1 the present invention is to form a cam for operating the intake/exhaust valves so as to obtain the required valve lift timing from low-speed engine rotation to high-speed engine rotation, and to move the camshaft in the axial direction to perform the intake/exhaust valve operation.・The contact point between the exhaust valve tappet and the cam has been changed.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. In FIG. 1 showing an embodiment, the shape of the cam 1 that rotates in synchronization with the engine rotation is a low-speed cam profile in which the valve opening timing is the latest at the 18th section and the valve closing timing is the earliest; The lift characteristics of a curved opening can be obtained. The lb section has a high-speed cam profile with the earliest valve opening timing and the latest valve closing timing. The valve tappet 3 in contact with the cam 1 is the other end of a set of roller tappets that rotates as the cam 1 rotates. This is to avoid wear since the cam 1 and the valve tappet 3 are in point contact. Cam 6 for moving the camshaft for operating the intake/exhaust button (hereinafter referred to as cam 6)
shall be. ) is lt! The coil spring 7 is rotated by a dynamic motor or the like according to the engine operating conditions, moves the camshaft, and compresses the coil spring 7. The contact plate 5, which is in contact with the cam 6, is held by the camshaft 2 with a ball bearing, and even if the camshaft 2 rotates, it does not rotate because it is in contact with the cam 6.The coil spring 7 always keeps the camshaft 2 It is pressed against cam 6. The stopper 88 is connected to the camshaft 2, and the stopper 8b is held by the ball bearing 8a, so even if the camshafts 2 and 88 rotate, the stopper 88 does not rotate and does not transmit rotational force to the coil spring 7. ,
The camshaft bracket 9 is connected to the cylinder head 11 and automatically holds the camshaft 2 in rotation and movement.First, the operation of this embodiment will be explained below. In FIG. 1, a portion 6a of the cam 6 is in contact with the contact plate 5.

Cam profile 18 for low speed of cam 1 is valve tappet 3
, the valve 4 is operated, and the low-speed lift timing at the curve opening in FIG. 2 is obtained. From this state, the engine speed is
As the valve rises, the cam 6 rotates to the left, and when the camshaft 2 is moved, the contact point between the cam 1 and the valve tab -3 moves toward the 1b section, changing from the low-speed lift timing to the high-speed lift timing. When the 6b portion of the cam 6 is in contact with the contact plate 5, the tappet 3 is in contact with the 1b portion of the cam 1, actuating the valve 4 and achieving the high-speed lift timing shown in FIG. 2A.

At this time, the coil spring 7 is in its most compressed state.

When the engine speed decreases from this high speed engine speed, the cam 6 rotates clockwise, and the coil spring 7 moves the camshaft 2 along the shape of the cam roller, resulting in low speed riff 1 timing.

<Effects of the Invention> As described above, according to the present invention, ideal intake/exhaust valve lift timing can always be obtained according to the operating conditions of the internal combustion engine, so intake/exhaust efficiency is improved over the entire engine rotation range. However, effects such as improved shaft torque and fuel efficiency can be obtained. It can also be used with any type of intake/exhaust valve operating device. Especially in recent years.

Do 1, which is produced in large numbers as a high-efficiency engine
-IC It can be applied to engines with 4 valves per cylinder, and its effects can be expected.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing one embodiment of the present invention, and Fig. 2 is a graph showing the valve lift characteristics of the same embodiment (the Y axis is the valve lift amount, the X axis is the crank angle). A graph showing the valve lift characteristics of the VG30DE engine installed in the Leopard automobile (Y# is the valve lift amount,
X axis is crank angle)

Claims (1)

[Claims] The shape of the cam that opens and closes the intake and exhaust valves of an internal combustion engine is shaped so that the required intake and exhaust valve lift timing can be obtained from low to high engine speeds, and by moving the camshaft in the axial direction, the intake and exhaust valves can be opened and closed. This variable intake/exhaust valve lift timing device for an internal combustion engine is characterized by variable control of valve lift timing by moving a contact point between an exhaust valve tappet and a cam.