JPS623113A - Multi-cylinder internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve output torque for a multi-cylinder internal combustion engine with two suction valves on each cylinder by providing a variable dynamic valve mechanism for making variable the operation cycle of each suction valve and the lift thereof, and forming a phase difference for the lift center angles of the two suction valves. CONSTITUTION:In an engine wherein main and sub-suction valves 29 and 30 for opening and closing main and sub-suction ports 25 and 26 open to the combustion chamber 24 of each cylinder are operated by the rotation of a drive cam 34 via a rocker arm 32, a variable dynamic valve mechanism 35 is fitted to each rocker arm 32. This mechanism 35 makes the curved top face 32A of the rocker arm 32 as fulcrum supported on the lower flat surface 36A of a lever 36. Also, a lift control cam 37 is made in contact with the top of one end of the lever 36 and a hydraulic pivot 39 as supported on a bracket 38 is coupled to the concave part 36B of the other end. And the control cam 37 for each lift related to the main and sub-suction valves 29 and 30 is so formed that the center angles of the lifts of said valves will be different from each other.

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, as a multi-cylinder internal combustion engine for achieving high engine output and low fuel consumption, the ones shown in FIGS. Public bulletin).

As shown in these figures, this internal combustion engine has a main intake valve 1 and a sub-intake valve 2 for each of the four cylinders.
It has two intake valves and three exhaust valves. Here,
The main intake boat 4, which the main intake valve 1 opens and closes, sends a large amount of intake air to the combustion chamber 5 so that a swirl is formed in the combustion chamber 5 by the intake air flow, and the sub-intake boat 6, which the sub-intake valve 2 opens and closes, sends a large amount of intake air to the combustion chamber 5. It has a flow passage area larger than that of the main intake boat 4 so that air can be supplied.

These intake and exhaust valves are all driven by a drive cam 8 via a rocker arm 7 in synchronization with engine rotation.
As shown in FIGS. 19 and 20, each of these rocker arms 7 is provided with an operation stopping mechanism capable of stopping its operation. This operation stop mechanism includes a hydraulic cylinder 8A provided on the back of the rocker arm 7, a fork-shaped stopper 10 connected to the piston rod 9,
A plunger 12, which is held reciprocatingly at the other end of the rocker arm 7 whose one end abuts the drive cam 8 and abuts the stem end 11 of the intake/exhaust valve, is connected to the cylinder 8.
A When not in operation, the rocker arm 7 is locked by the stopper 10 and the swinging motion of the rocker arm 7 is transmitted to the intake/exhaust valves via the plunger 12, and lubricating oil is supplied to the cylinder chamber 13 by a switching valve (not shown). By protruding the piston loft 9, the locking of the plunger 12 by the stopper IO is released and the plunger 12 is not restrained against the rocking motion of the rocker arm 7, so that the rocking motion is not transmitted to the intake/exhaust valves. I have to. That is, the operation of the intake and exhaust valves is stopped by the operation of the cylinder 8A.

In addition, 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, all suction and
The operation of the exhaust valves 1.2.3 is stopped, and at low speed and high load, only the operation of the auxiliary intake valve 2 is controlled to be 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 not completely controlled. For example, as shown in Figure 21, the engine's output torque cannot be sufficiently increased in the medium speed range (hatched in the figure), that is, in the transient operating range, as shown in Figure 21. The problem was that it couldn't be done. 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) A multi-cylinder internal combustion engine according to the present invention has two intake valves for each cylinder, and the valve opening/closing timing and valve lift amount of each of these two intake valves is controlled by the engine. This configuration includes a variable valve mechanism that is variable in stages according to operating conditions, and uses this variable valve mechanism to provide a phase difference between the lift center angles of these two intake valves.

(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 valve mechanism according to the operating conditions of the engine. By setting a phase difference between the lift center angles of the two intake valves and making the closing times of the main and sub-intake valves coincide at low speeds, it is possible to strengthen the swirl at low speeds and reduce pumping loss, and at the same time to increase the swirl at low speeds and reduce pumping loss. This improves output by matching the opening timing of the intake valves.

(Example) Embodiments of the present invention will be described below 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, two main and sub intake boats 25, 26 and one exhaust port 27 are opened in the combustion chamber 24 of each cylinder. 28 is a spark plug. Both the main intake boat 25 and the sub-intake boat 26 extend in a straight line, and are capable of inhaling a large amount of air-fuel mixture. Further, the main intake boat 25 opens away from the spark plug 28 and has a smaller diameter (also flow path area) than the sub intake boat 26 that opens toward the spark plug 28.

These main bodies, the main bodies that open and close the graphic picture intake port 25.26 and the exhaust port 27, the graphic picture intake valve 29.30 and the exhaust valve 31, respectively, are connected to rocker arms 32, 33, and 22, respectively.
is driven by a drive cam 34 via. As shown in FIG. 1, the rocker arm 32 of the main intake valve 29 is equipped with a variable valve mechanism, and the sub-intake valve 30 is also equipped with a similar variable valve mechanism, although not shown. Both intake valves 2
9.30 has variable valve opening/closing timing and valve lift amount. 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 valve mechanism 35 has a rocker arm 32, which has one end abutting the drive cam 34 and the other end abutting the stem end of the main intake valve 29, and the back surface 32A of the rocker arm 32 is curved along the longitudinal direction. 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 connected to the lever 3
6 is swingably supported. Further, 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 concave portion 36B at the other end. That is, the lever 36 is provided so as to be swingable around the hydraulic pivot 39. Note that the bracket 38 is fixed to the cylinder head 40. Also, lever 3
A support shaft 42 (see FIG. 6) inserted through the center of the rocker arm 32 is fitted into the groove 41 of No. 6, and a spring 43 is inserted between the support shaft 42 and the bottom wall of the groove 41. It has been reduced. 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. Further, as shown in FIG. 5, a stopper pin 48 is provided protruding from the cam control shaft 45, and this stopper pin 48 can come into contact with a notch in the cylindrical portion 37A of the lift control cam 37, and the coil spring 4
7 to prevent excessive force from acting on it. In addition, the fourth
In the figure, 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.
It shows the direction. As shown in the figure, the lift control cam 37 has five cam surfaces 37a, 37b, 37 that vary the valve lift amount and valve opening/closing timing of the main intake valve 29.
c37d, 3713, lift control cam 50
are five cam surfaces 50a150b150cs 50d15 that vary the valve lift amount and valve opening/closing timing of the sub-intake valve 30.
It has 0e. The cam surface 37a has a valve lift fi l tm of the main intake valve 29, and the cam surface 37b has the same <4.5n.
The cam surfaces 37c to 37e respectively correspond to the same <8 m. Also, the cam surface 50a has the same valve lift amount of 0.5fi of the sub-intake valve 30, the cam surface 50b has the same <3 m, the cam surface 50C has the same 8 cranes, and the cam surface 50d has the same <9.
4fl and the cam surface 50e correspond to the same <10.8 mm. Furthermore, these lift control cams 37, 50 have respective cam surface profiles formed so that their valve lift center angles (maximum lift indicated by crank angle) are different from each other. 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 deceleration mechanism 51.

Note that this stepping motor 52 is controlled by a control means (not shown) (
This control means determines the operating conditions of the engine based on various detection signals input from the rotation speed sensor, water temperature sensor, etc., and adjusts the engine according to the operating conditions. It drives the motor 52 mentioned above.

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 levers 36 of the main and comic intake valves 29 and 30, respectively. Rotate so that they touch. As a result, one end of each lever 36 (the end on the drive cam 34 side in FIG. Similarly, the sub-intake valve 30 also moves to the ) side. Therefore, the main intake valve 29 and the sub-intake valve 3
0, as shown in FIG.

(The solid line X shows the lift characteristic of the main intake valve 29, the broken line Y shows that of the auxiliary intake valve 30, and the solid line 2 shows that of the exhaust valve 31.) With the minimum valve lift amount, the main intake valve The lift center angle of valve 29 is on the leading side (towards top dead center), and the lift center angle of sub-intake valve 30 is on the lag side.

(towards bottom dead center). Therefore, there is no valve overlap between the intake and exhaust valves, the residual gas in the combustion chamber 24 is reduced, and the combustion state is stabilized (idling is stabilized).
do. Furthermore, as the main and dramatic intake valves 29 and 30 both close at a time before bottom dead center, the pumping loss of the engine is significantly reduced, as shown in the p-v diagram in this case in Fig. 16. Ru.

Next, during low-speed, low-load operation of the engine, the cam control shaft 45 is rotated so that the cam surface 37b150 of the lift control cam 37.50
Push down one end of the lever 36 with b. As a result, the fulcrum contact point of the rocker arm 32 moves to the drive cam 34 side,
As shown in FIG. 11, the main intake valve 29 and the sub-intake valve 30 are driven at different lift center angles with a small valve lift amount. Therefore, although the timing of closing the intake valves 29 and 30 is closer to the bottom dead center than when the engine is idle, the pumping loss of the engine is reduced, and the effect of reducing fuel consumption can be obtained.

Next, when the engine is fully open at low speed, the lift control cam is 37.50
One end of the lever 36 is further pushed down using the cam surfaces 37c and 50c. As a result, the fulcrum contact point of the rocker arm 32 moves further to the left in FIG.
In the lift characteristic of No. 30, as shown in FIG. 12, the valve lift amount increases. Therefore, the valve closing timing is also near the bottom dead center, and the amount of intake air increases and the output torque improves.

Furthermore, when the engine speed increases further, the cam surfaces 37d, 5
At 0d, the lever 36 is pushed all the way 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. FIG. 13 shows the lift characteristics in this case. As a result, the amount of intake air increases and the output torque improves. 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 rotation speed is increased, the cam surface 37e,
50e, the lever 36 is further pushed down, the valve lift amount of the sub-intake valve 30 increases, and its closing timing becomes the same as that of the main intake valve 29. 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 the main/dramatic intake valves 29 and 30 as described above. In the figure, curves XI, X2, X3
is the lift characteristic of the main intake valve 29, and the curves Y+ and Y
z −Y:+ −Y4 , Y5 represents that of the sub-intake valve 30, and curve Z represents that of the exhaust valve 31. In the figure, WI indicates the lift center angle of the main intake valve, and W2 indicates that of the auxiliary intake valve.

Further, FIG. 15 shows changes in the cam surface of the lift control cam 37.50 in relation to the engine rotational speed (lK axis) and the engine load (accelerator opening, vertical axis).

That is, at idle as indicated by point P in the figure, the cam surface 37a,
5Qa, at low speed and low load in region Q in the figure, cam surface 37b,
50b, cams 37c and 50c correspond to cams 37c and 50c when fully open at low speed in region R, cam surfaces 37d and 50d during medium speed in region S, and cam surfaces 37e and 50e during high speed in region T, 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 described above, according to the present invention, the output torque can be sufficiently increased in the entire operating range of the engine, and fuel consumption can be reduced. Moreover, a single fuel supply device is sufficient, and the complexity of the device can be prevented. Furthermore, the effect can be obtained that the output, especially when the engine is fully open, can be smoothly improved over the entire rotation range.

[Brief explanation of the drawing]

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. Fig. 8 is a front view showing the cam profile of the lift control cam for the sub-intake valve, Fig. 9 is a front view showing the cam profile of the lift control cam for the sub-intake valve, and Fig. 9 shows the relationship between the lift characteristics of the exhaust valve of the main/gekigai intake valve. Figures 10 to 14 are graphs showing the lift characteristics corresponding to each cam surface of the lift control cam, and Figure 15 shows the correspondence between engine speed, accelerator opening, and each cam surface. The graph in FIG. 16 is a P-Vfi diagram at idle 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,
Figure 20 is a sectional view taken along the line xx-xx in Figure 19, and the second
FIG. 1 is a graph showing the relationship between engine speed and output torque. 29...Main intake valve, 30...Sub-intake valve, 35...Variable valve mechanism.

Claims (1)

[Claims] In a multi-cylinder internal combustion engine equipped with two intake valves per cylinder, a variable valve mechanism that changes the valve opening/closing timing and valve lift amount of each of these two intake valves in stages according to engine operating conditions. A multi-cylinder internal combustion engine characterized in that a phase difference is provided between lift center angles of these two intake valves.