JPH0346644B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multi-cylinder internal combustion engine, for example a multi-cylinder internal combustion engine mounted on a vehicle.

(Prior Art) Conventionally, multi-cylinder internal combustion engines for achieving high engine output and low fuel consumption have been developed, for example, as shown in FIGS.
The one shown in Figure 1 is known (Japanese Patent Application Laid-open No. 1983-
Publication No. 25537).

As shown in these figures, this internal combustion engine has 4
Each cylinder has two intake valves, a main intake valve 1 and a sub-intake valve 2, and an exhaust valve 3. Here, the main intake port 4, which is opened and closed by the main intake valve 1, is arranged so that a swirl is formed in the combustion chamber 5 by the intake air flow, and the auxiliary intake port 6, which is opened and closed by the sub-intake valve 2, is
has a flow passage area larger than that of the main intake port 4 so that a large amount of intake air can be delivered to the combustion chamber 5. These intake and exhaust valves are all driven by a drive cam 8 via a rocker arm 7 in synchronization with the engine rotation, but each rocker arm 7 has a A deactivation mechanism capable of deactivating the device is provided.
This operation stop mechanism has a hydraulic cylinder 8A provided on the back surface of the rocker arm 7, and a fork-shaped stopper 10 connected to the piston rod 9. A plunger 1 is held at the end so as to be able to reciprocate and abuts against the stem end 11 of the intake/exhaust valve.
2 is locked to the stopper 10 when the cylinder 8A is not in operation, and the rocker arm 7 is prevented from swinging by the plunger 12.
At the same time, lubricating oil is supplied to the cylinder chamber 13 by a switching valve (not shown) to cause the piston rod 9 to protrude, thereby releasing the locking of the plunger 12 by the stopper 10.
Since the plunger 12 is not constrained by the rocking motion of the rocker arm 7, the rocking motion is not transmitted to the intake/exhaust valves. That is, the operation of the intake and exhaust valves is stopped by the operation of the cylinder 8A.

Further, this operation stop mechanism is driven by the control means 14 according to the operating state of the engine, and at low speed and low load, the operation of all intake and exhaust valves 1, 2, and 3 is stopped, and at low speed and high load, the operation of all intake and exhaust valves 1, 2, and 3 is stopped. Control is performed so that only the operation of the intake valve 2 is stopped.

(Problems to be Solved by the Invention) However, in such conventional multi-cylinder internal combustion engines, the valve opening/closing timing and valve lift amount of the intake and exhaust valves are not variable, but the operation is completely controlled. For example, as shown in Figure 21, the engine's output torque cannot be sufficiently increased in the medium speed range (shaded in the figure) between the low speed range and the high speed range, that is, in the excessive operation range. There was a problem that I couldn't do it. In addition, because the two main and sub intake valves were configured with one for low-speed operation timing and lift, and the other for high-speed operation, there was a problem in that the intake air filling efficiency at high speeds could not be sufficiently increased. It also had points. Furthermore, since the configuration stops the operation of one intake valve under specific operating conditions, a two-system fuel supply system is required, which poses the problem of complicating the system, especially in systems that supply fuel to each cylinder. Was.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a multi-cylinder internal combustion engine having two intake valves per cylinder. Equipped with a variable valve mechanism that changes the lift amount in stages according to engine operating conditions, these two
A phase difference is provided between the lift center angles of the two intake valves, and the closing timings of the two intake valves are made to match when the engine is running at low speeds, and the opening timings of the two intake valves are made to match when the engine is running at high speeds. .

(Function) In the multi-cylinder internal combustion engine according to the present invention, the valve opening/closing timing and valve lift amount of each of the two intake valves are made variable by the variable operation valve mechanism according to the operating conditions of the engine. A phase difference is provided between the lift center angles of the two intake valves to match the closing timings of the two intake valves when the engine is running at low speed and to match the opening timings of the two intake valves when the engine is running at high speed.
Therefore, when the engine is running at low speed, there is no throttling loss upstream or downstream of the intake valve due to a delay in closing one intake valve, the combustion state is stabilized, and pumping loss is reduced. In addition, when the engine is running at high speed, deterioration of engine stability and knocking due to excessive valve overlap are prevented, and a reduction in intake air volume during the initial intake stroke due to insufficient valve overlap is prevented. Engine output increases stably and smoothly over the entire rotation range.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

1 to 16 show an embodiment of the present invention.

First, the configuration will be explained.

In FIG. 2, 21 is a camshaft in an in-line four-cylinder internal combustion engine, which is driven and rotated in synchronization with the engine output shaft. Further, 22 is a rocker arm of the exhaust valve, which is rotatably supported by a rocker shaft 23. As shown in FIG. 3, the combustion chamber 24 of each cylinder has two main and sub intake ports 2.
5, 26 and one exhaust port 27 are open. 28 is a spark plug. Both the main intake port 25 and the auxiliary intake port 26 extend linearly, making it possible to inhale a large amount of air-fuel mixture.
Further, the main intake port 25 opens away from the spark plug 28 and has a smaller diameter (also flow path area) than the sub intake port 26 that opens toward the spark plug 28.

The main and auxiliary intake valves 29, 30 and the exhaust valve 31, which open and close the main and auxiliary intake ports 25, 26 and the exhaust port 27, respectively, are driven by a drive cam 34 through rocker arms 32, 33, 22, respectively. Ru. As shown in FIG.
A variable valve mechanism is attached to the rocker arm 32, and a similar variable operation valve mechanism is attached to the sub-intake valve 30, although not shown.
9 and 30, the valve opening/closing timing and valve lift amount are variable. Specifically, the engine of this embodiment is controlled so that the closing timings of both intake valves 29 and 30 coincide at low speeds, and so that the opening timings of both intake valves 29 and 30 coincide at high speeds. . Note that the exhaust valve 31 is driven to open and close at a constant valve opening/closing timing and valve lift amount via a fixed valve operating mechanism.

The variable operation valve mechanism 35 has a rocker arm 32, one end of which contacts the drive cam 34 and the other end of which contacts the stem end of the main intake valve 29. The lever 36 is in fulcrum contact (line contact) with a lower surface 36A formed flat along the longitudinal direction of the lever 36. That is, the rocker arm 32 is swingably supported by the lever 36. A lift control cam 37 is in contact with the upper surface of one end of the lever 36, and a hydraulic pivot 39 supported by a bracket 38 is slidably fitted into the recess 36B at the other end. That is, the lever 36 is provided so as to be swingable about the hydraulic pivot 39. Note that the bracket 38 is fixed to the cylinder head 40. Further, a support shaft 42 (see FIG. 6) inserted through the center of the rocker arm 32 is fitted into the groove 41 of the lever 36, and there is a space between the support shaft 42 and the bottom wall of the groove 41. A spring 43 is compressed. Note that the spring constant of this spring 43 is set to be considerably smaller than that of the valve spring 44. 38A is an oil passage formed in the bracket 38, which supplies pressure oil to the hydraulic pivot 39 to maintain the valve clearance at a constant value.

Further, as shown in FIGS. 4 and 5, the lift control cam 37 is loosely fitted to the cam control shaft 45, and the holder 46 fixed to the cam control shaft 45 and the cylindrical portion 37A of the lift control cam 37 are connected to each other. These are connected via a coil spring 47 contracted between them. Furthermore, as shown in FIG. 5, a stopper pin 48 is provided protrudingly from the cam control shaft 45, and this stopper pin 48 is able to come into contact with a notch in the cylindrical portion 37A of the lift control cam 37. This prevents any force from acting on it. In addition, in FIG. 4, 49 is a cap that rotatably supports the cam control shaft 45.

7 and 8 show the cam profiles of the lift control cams 37 and 50 of the main intake valve 29 and the sub-intake valve 30, respectively. As shown in the figure,
The lift control cam 37 has five cam surfaces 37 that vary the valve lift amount and valve opening/closing timing of the main intake valve 29.
a, 37b, 37c, 37d, and 37e, and the lift control cam 50 has five cam surfaces 5 that vary the valve lift amount and valve opening/closing timing of the sub-intake valve 30.
It has 0a, 50b, 50c, 50d, and 50e. The cam surface 37a corresponds to a valve lift amount of 1 mm of the main intake valve 29, the cam surface 37b corresponds to 4.5 mm, and the cam surfaces 37c to 37e correspond to 8 mm. In addition, the cam surface 50a has a valve lift amount of 0.5 mm of the sub-intake valve 30, and the cam surface 50b has a valve lift amount of 3 mm.
The cam surface 50c is also 8 mm, the cam surface 50d is 9.4 mm, and the cam surface 50e is 10.8 mm.
Each corresponds to the other. Furthermore, these lift control cams 37 and 50 have respective cam surfaces formed with profiles so that their valve lift center angles (maximum lift indicated by crank angle) are different from each other. Each cam surface is formed to the above dimensions so that the closing timings of both intake valves 29 and 30 coincide at low speeds, and so that the opening timings of both intake valves 29 and 30 coincide at high speeds. Needless to say. Further, as shown in FIG. 2, a stepping motor 52 is connected to one end of a cam control shaft 45 that supports these lift control cams 37 and 50 via a speed reduction mechanism 51. Note that this stepping motor 52 is driven by a control means (for example, an on-vehicle microcomputer) not shown, and this control means operates based on various detection signals input from a rotation speed sensor, a water temperature sensor, etc. The operating condition of the engine is determined and the motor 52 is driven according to the operating condition.

Next, the operation of this embodiment will be explained.

First, when the engine is idling and starting, the stepping motor 52 drives and rotates the cam control shaft 45 to control each lift control cam 37 and 50 so that the cam surfaces 37a and 50a are connected to the main and sub intake valves 2, respectively.
It rotates so as to come into contact with each lever 36 of 9 and 30. As a result, each lever 36 has one end (first
The end on the drive cam 34 side in the figure) is the rocker arm 32.
The swinging fulcrum (fulcrum contact point) of the rocker arm 32 is located above and away from the main intake valve 29 (sub-intake valve 3).
0 also moves to the ) side. Therefore, the main intake valve 29
and the auxiliary intake valve 30, as shown in FIG. ), the lift center angle of the main intake valve 29 shifts to the leading side (toward the top dead center) and the lift center angle of the auxiliary intake valve 30 shifts to the lag side (towards the bottom dead center) at the minimum valve lift amount. do. Therefore, the closing timings of both intake valves 29 and 30 coincide before bottom dead center,
Valve overlap between intake and exhaust valves is eliminated,
The residual gas in the combustion chamber 24 is reduced, and the combustion state is stabilized (idling is stabilized). Also, especially
Since the closing timings of both intake valves 29 and 30 coincide before the bottom dead center, as shown in Fig. 16, the difference in the mixture pressure when the mixture expands in the cylinder after the valves are closed and is compressed again. becomes smaller, and both intake valves 29, 30
Both intake valves 29,
30 upstream and downstream throttling losses are eliminated, and engine pumping losses are also significantly reduced.

It should be noted that the opening timing of the main intake valve 29 is determined by the auxiliary intake valve 30.
Since the timing is earlier than the valve opening timing of the valve, pumping loss especially associated with suction is also reduced.

Next, when the engine is operating at low speed and low load, the cam control shaft 45 is rotated to push down one end of the lever 36 with the cam surfaces 37b, 50b of the lift control cams 37, 50. As a result, the fulcrum contact point of the rocker arm 32 moves to the drive cam 34 side, and the main intake valve 29 and the auxiliary intake valve 30 are driven at different lift center angles with a small valve lift amount, as shown in FIG. . Therefore, although the closing timing of the intake valves 29 and 30 is shifted toward the bottom dead center side compared to when the engine is idling, the pumping loss of the engine is reduced in the same way as when idling, and the effect of reducing fuel consumption can be obtained.

Next, when the engine is fully open at low speed, the lift control cam 3
One end of the lever 36 is further pushed down using the cam surfaces 37c and 50c of 7 and 50. As a result, the fulcrum contact point of the rocker arm 32 further shifts to the left in FIG. 1, and the lift characteristics of both the main and auxiliary intake valves 29, 30 increase in valve lift amount, as shown in FIG. 12. Therefore, the valve closing timing is also near the bottom dead center,
The amount of intake air increases and the output torque improves.

Also, as the engine speed increases further, the cam surface 3
At 7d and 50d, the lever 36 is further pushed down, and the lift amount and opening/closing timing of the main intake valve 29 do not change, but the valve lift amount of the auxiliary intake valve 30 increases, and the valve closing timing is further delayed from bottom dead center. At this time, the opening timings of both intake valves 29 and 30 come to substantially coincide before top dead center so that the valve overlap does not become so large. FIG. 13 shows the lift characteristics in this case. As a result,
This prevents the deterioration of engine stability and knocking caused by excessive valve overlap, and also prevents the intake air amount from decreasing in the initial intake stroke due to too little valve overlap, increasing the intake air amount. Output torque is improved. The reason why the valve lift amount and opening/closing timing of the main intake valve 29 are not changed is to prevent fresh air from blowing through due to an excessive overlap amount.

Furthermore, when the engine speed increases, the lever 36 is further pushed down by the cam surfaces 37e and 50e, and the valve lift amount of the sub-intake valve 30 increases.
Its opening timing is the same as that of the main intake valve 29 so that the valve overlap does not become large.
FIG. 14 shows the lift characteristics in this case.
As a result, the amount of intake air is further increased and the output torque is further improved.

FIG. 9 shows changes in the lift characteristics of both the main and auxiliary intake valves 29, 30 as described above. In the figure, the curve
X ₁ , X ₂ , X ₃ represent the lift characteristics of the main intake valve 29, curves Y ₁ , Y ₂ , Y ₃ , Y ₄ , Y ₅ represent those of the auxiliary intake valve 30, and curve Z represents the lift characteristics of the exhaust valve. 31 is shown. In the figure, _W1 indicates the lift center angle of the main intake valve, and _W2 indicates that of the sub-intake valve.

Further, FIG. 15 shows changes in the cam surfaces of the lift control cams 37 and 50 in relation to the engine rotational speed (horizontal axis) and the engine load (accelerator opening, vertical axis). In other words, when idling as indicated by point P in the figure, the cam surfaces 37a and 50a, when the area Q in the figure is low speed and low load, the cam surfaces 37b and 50b, when the area R is low speed and fully open, the cam surfaces 37c and 50c, and the area S. When the speed is medium, the cam surfaces 37d and 50d correspond to the cam surfaces 37d and 50d, and when the speed is high in the region T, the cam surfaces 37e and 50e correspond to the cam surfaces 37e and 50e, respectively. Note that the solid lines and broken lines in the figure indicate the switching conditions for each region, and the switching condition value when the rotation speed and load decrease, shown by the broken line, is lower than when the rotation speed and load increase, shown by the solid line, to provide hysteresis and improve the mechanism. Prevents hunting.

In the above embodiment, the lift control cam performs five-stage control, but it is needless to say that the present invention is not limited to this. Furthermore, in addition to the five-stage control described above, the engine air-fuel ratio can also be changed as appropriate.

(Effects) As explained above, according to the present invention, it is possible to strengthen the swirl at low speeds and reduce pumping loss, so fuel consumption can be reduced.
In addition, the output can be smoothly increased over the entire rotation range at high speeds, and as a result, the engine performance can be sufficiently improved over the entire operating range of the engine. Also,
Since there is only one fuel supply device, it is possible to prevent the device from becoming complicated.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a multi-cylinder internal combustion engine according to the present invention, FIG. 2 is a plan view thereof, FIG. 3 is a schematic diagram showing the layout of its intake and exhaust ports, and FIG. An exploded perspective view showing the mounting part of the lift control cam, FIG. 5 is a perspective view showing the mounting part of the lift control cam, FIG. 6 is a perspective view showing its support shaft, and FIG. 7 is a perspective view showing the main intake valve. Figure 8 is a front view showing the cam profile of the lift control cam for the sub-intake valve, Figure 9 is a front view showing the cam profile of the lift control cam for the sub-intake valve, and Fig. 9 shows the lift characteristics of the exhaust valve for both the main and sub-intake valves. Graph showing relationships, No. 10
Figures 1 to 14 are graphs showing the lift characteristics corresponding to each cam surface of the lift control cam, Figure 15 is a graph showing the correspondence between engine speed, accelerator opening, and each cam surface, and Figure 16 is a graph showing the correspondence between engine speed, accelerator opening, and each cam surface. FIG. 3 is a PV diagram during idling in this embodiment. 17 to 21 show a conventional multi-cylinder internal combustion engine. FIG. 17 is a plan view thereof, FIG. 18 is a front sectional view thereof, and FIG. 19 is a partially cutaway front view showing its operation stop mechanism. Figure 20 is the figure 19 -
The cross-sectional view taken in the direction of arrows, FIG. 21, is a graph showing the relationship between the engine speed and the output torque. 29...Main intake valve, 30...Sub-intake valve, 35...
...Variable valve mechanism.

Claims (1)

[Claims] 1. In a multi-cylinder internal combustion engine equipped with two intake valves for each cylinder, a variable valve that varies the valve opening/closing timing and valve lift amount of each of these two intake valves in stages according to engine operating conditions. It is equipped with a mechanism that provides a phase difference between the lift center angles of these two intake valves, matches the closing timing of the two intake valves when the engine is running at low speed, and adjusts the closing timing of the two intake valves to match when the engine is running at high speed.
A multi-cylinder internal combustion engine characterized in that the opening timings of two intake valves are made to coincide with each other.