JPH03202602A - Intake device for multiple valve type engine - Google Patents

Abstract

PURPOSE:To change the opening term of an intake valve by providing a first cam shaft for driving one intake valve, and a second cam shaft for driving two intake valves, and providing a phase changing means onto one side cam shaft, in a device provided with three intake valves per one cylinder. CONSTITUTION:Three intake ports 11 to 13 and two exhaust ports 14, 15 are formed on a cylinder head 2, and the intake ports 11 to 13 are opened/closed by intake valves 21 to 23. In this state, three lines l1 to l3 are assumed in parallel with a crank shaft, and a central intake valve 21 is arranged on the line l1, and also two side intake valves 22, 23 are arranged on the line l2. Moreover, a first to a third cam shafts 31 to 33 are arranged on a cylinder head 2 opposing to respective lines l1 to l3, and the central intake valve 21 is opened/closed by the first cam shaft 31, on the other hand, side intake valves 22, 23 are opened/closed by the second cam shaft 32. Subsequently a phase changing mechanism (not shown in figure) for changing the opening/closing timing in response to the rotating position of the crank shaft, is provided in relation to the second cam shaft 32.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for a multi-valve engine that changes the opening and closing timing of an intake valve with respect to the rotational position of a crankshaft.

(Prior art) In order to increase output and efficiency, recent engines are
There are many so-called multi-valve engines in which a plurality of intake valves are provided for one cylinder.

By the way, the timing of opening and closing the intake valve has a great effect on the performance of the engine. From this point of view, as shown in Japanese Patent Publication No. 61-1.614, a phase changing means for changing the opening/closing timing of the intake valve with respect to the rotational position of the crankshaft is provided on the camshaft for driving the intake valve. There is something. This phase change means is operated according to predetermined conditions, and for example, the phase change means is controlled according to the engine speed, and the opening/closing timing of the intake valve is set at low engine speeds to prevent intake air from blowing back. At high speeds, the intake valve opening/closing timing is changed to improve filling efficiency to ensure low-speed torque.

(Object of the Invention) However, in an engine having a conventional phase change means, there is only one camshaft for driving the intake valve, so even if the opening/closing timing of the intake valve can be changed, the opening period of the intake valve I couldn't change that.

Therefore, an object of the present invention is to provide a multi-valve engine that can change the open period of the intake valves using a phase change means, based on the premise that the engine is a multi-valve engine having three intake valves in one cylinder. The purpose is to provide an intake device for

(Structure and operation of the invention) In order to achieve the above object, the present invention has the following structure. That is, in an engine equipped with three intake valves in one cylinder, the camshafts driving the three intake valves described in iii. According to the present invention, the first camshaft drives a predetermined one of the three intake valves, and the second camshaft drives the remaining two intake valves, and both of the camshafts One of the intake valves is provided with phase changing means for changing the opening/closing timing of the intake valve relative to the rotational position of the crankshaft.

When three intake valves are provided in one cylinder, if you try to obtain an ideal combustion chamber shape based on the cross-sectional shape of the cylinder, the shape of the intake valve, etc., it is inevitable that two predetermined intake valves will be located at the center of the cylinder. The remaining one intake valve is located between the two intake valves and is provided spaced apart in the crankshaft direction (hereinafter, these two intake valves are referred to as side intake valves).
The center intake valve is located radially outward of the cylinder than the two intake valves (hereinafter, this one intake valve will be referred to as a central intake valve). This means that the camshaft for driving the intake valves, which is disposed extending in the direction of the crankshaft, has two camshafts: a first camshaft for driving the central intake valve, and a second camshaft for driving the two side intake valves. This means that the book is provided.

By providing a phase change means on one of the two intake valve driving camshafts, for example, the second camshaft, the opening/closing timing of the central intake valve can be maintained as it is, while the opening and closing timing of the two side intake valves can be changed. By changing the opening/closing timing, the open period of the intake valve as a whole is changed. Of course, a phase changing means may be provided on the first camshaft to change the opening/closing timing of the central intake valve.

(Effects of the Invention) As described above, according to the present invention, the conventionally known phase t = p
By effectively utilizing the means, the open period of the intake valve can be substantially changed, and the opening period of the intake valve can be set more preferably in accordance with the operating state of the engine.

(Example) Examples of the present invention will be described below based on the attached drawings.

In Fig. 1, the cylinder head 2 is placed above the cylinder l.
A combustion chamber 4 is defined by the cylinder 1, the cylinder head 2, and the piston 3 slidably inserted into the cylinder 1.

As shown in FIG. 3, the cylinder head 2 includes three intake boats 11, 12, 13 and two exhaust boats 14.
5 is formed. This intake boat 11. +2.13
are opened and closed by intake valves 21, 22 or 23,
The exhaust boats 14, 15 are opened and closed by exhaust valves 24 or 25.

Each of the above boats 11 to 13, that is, intake valves 21 to 23,
The positional relationship of the exhaust boat 14.15, that is, the exhaust valve 24.25, with respect to the combustion chamber 4 will be explained with reference to FIG. First, the vertical direction in FIG. 3 is the crankshaft direction, and three lines from Ql to flood 3 are assumed to be parallel to this crankshaft. This line A2 passes through the position closest to the center of the combustion chamber 4, and is slightly offset from the center of the combustion chamber 4 to the right side in FIG. Further, the line flll is offset to the right side in FIG. 3 from the line flll 2. The line I23 is offset from the center of the combustion chamber 4 to the left side in FIG.

Above line I! , one central intake valve 21 is arranged so as to be located at one end. Also, the line i! is located on the line flood 2 and the line i! , 2 axially spaced apart from each other, 2
Two side intake valves 22,23 are arranged. Two exhaust valves 24 and 25 are positioned above the line C3 and spaced apart in the axial direction of the line C3.

Due to the arrangement of the valves 21 to 25, the shape of the combustion chamber 4 is an ideal pent roof type, and the spark plug 5 is disposed approximately at the center thereof.

As shown in FIGS. 1 and 2, the cylinder head 2 includes:
Three camshafts 31, 32, and 33, first to third, are rotatably arranged. Each camshaft 31.3
2.33 are offset from each other in a direction orthogonal to the crankshaft, corresponding to the offset of the lines C1 to I23. That is, the first camshaft 31 corresponds to the line 21 and drives the central intake valve 21. A second camshaft 32 corresponds to line I22 and drives the two lateral intake valves 22,23. A third camshaft 33 corresponds to the line 23 and is used to drive the two exhaust valves 24 and 25.

As shown in FIG. 2, a pulley 41 or 42 is fixed to the first camshaft 31 and the third camshaft 33, and the timing of rotation of the pulley 41, 42 in synchronization with the crankshaft is A belt 43 is wound around it. The distance between the second camshaft 31 and the second camshaft 32 is small.
are linked together using. Then, a phase change mechanism 4 as shown in the above publication is provided for the second camshaft 32.
7 is provided. As a result, the first camshaft 3
The opening and closing timings of the central intake valve 21 driven by the central intake valve 21 and the exhaust valves 24 and 25 driven by the third camshaft 33 are respectively fixed with respect to the rotational position of the crankshaft. On the other hand, the second camshaft 3
The two side intake valves 22,23 driven by
The phase change mechanism 47 changes the opening/closing timing with respect to the rotational position of the crankshaft.

FIG. 4 and FIG. 5 show an intake valve 21 using a phase change mechanism.
This shows the opening/closing timing of ~23.

FIG. 4 shows a state in which the phase change mechanism 47 is not activated. In this case, the intake valves 21 to 23 all have the same opening and closing timing, and the intake period is slightly larger than the crank angle of 180 degrees. ing. FIG. 5 shows the state when the 1-phase change mechanism 47 is activated. At this time, the opening/closing timing of the side intake valves 22, 23 is shifted to the later intake closing side. As a result, each intake valve 21 to 23
The actual intake period is changed to a value considerably larger than the crank angle of 180 degrees. The basic opening/closing timing shown in FIG. 4 is such that sufficient scavenging can be performed while preventing intake air from blowing back when the engine is running at low speed. Further, the intake period, particularly the closing timing, of the side intake valves 22 and 23 shown in FIG. 5 is set to ensure output so that sufficient intake air can be taken in when the engine is at high speed and under high load.

Various conditions can be set for operating the phase change mechanism 47, but in this embodiment, the conditions are high rotation and high load as shown in region A in FIG. Note that if the phase mechanism 47 is operated even in the operating region shown as region B in FIG. 6, it is possible to reduce the pumping loss due to late intake closing. In addition, U in FIG. 1 is a control unit for controlling the phase change mechanism 47, and this control unit U receives a signal from a sensor 51 that detects the engine load and a signal from a sensor 52 that detects the engine speed. is input.

Although the embodiment has been described above, the phase change mechanism 47 may be provided on the first camshaft 31 to change the opening/closing timing of the central intake valve 21. In this case, the pulley 41 may be provided on the second camshaft 32. However, when the pulley 41 is provided on the first camshaft 31, the phase change mechanism 47 is also provided on the second camshaft 32, and the phase of the second camshaft 32 is changed by the phase change of the first camshaft 4I. It may be possible to return the .

[Brief explanation of drawings]

FIG. 1 is a front sectional view showing one embodiment of the present invention. FIG. 2 is a top view of the cylinder head. Figure 3 is a diagram of the cylinder head viewed from the combustion chamber side. FIG. 4 and FIG. 5 are diagrams showing how the open period of the intake valve is changed by the phase change mechanism. FIG. 6 is a diagram showing an example of setting the region in which the phase change mechanism is activated. 2 cylinder head 3: piston 4: [burning chamber 21: central intake valve 22: side intake valve 23: square intake valve 31: first camshaft 32: second camshaft 41.42: pulley 43: timing belt 45 .46: Interlocking gear 47: Phase change mechanism 1: Cylinder Figure 4 DC DC Figure 5 Figure 6

Claims (1)

[Claims] (1) In an engine equipped with three intake valves in one cylinder, the camshafts that drive the three intake valves are composed of two camshafts, a first camshaft and a second camshaft, which are arranged parallel to the crankshaft. According to the present invention, the first camshaft drives a predetermined one of the three intake valves, and the second camshaft drives the remaining two intake valves, and both of the camshafts An intake system for a multi-valve engine, characterized in that one of the intake valves is provided with phase changing means for changing the opening and closing timing of the intake valve with respect to the rotational position of the crankshaft.