JP2588362B2 - Multi-cylinder internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-cylinder internal combustion engine, for example, a multi-cylinder internal combustion engine mounted on a vehicle.

[0002]

2. Description of the Related Art Conventionally, as a multi-cylinder internal combustion engine for achieving high output and low fuel consumption of an engine, for example, the one shown in FIGS. 17 to 21 is known (Japanese Patent Application Laid-Open No. 58-25537). . As shown in these figures, this internal combustion engine has an intake air 2 between a main intake valve 1 and a sub intake valve 2 for each of four cylinders.
It has a valve and an exhaust valve 3. Here, the main intake valve 1
The main intake port 4 that opens and closes forms a swirl in the combustion chamber 5 by the intake air flow, and the sub intake port 6 that opens and closes the sub intake valve 2 mainly supplies a large amount of intake air to the combustion chamber 5. It has a passage area larger than the passage area of the intake port 4. These intake and exhaust valves are all rocker arms 7
The rocker arms 7 are driven in synchronism with the rotation of the engine via a drive cam 8. These rocker arms 7 are provided with operation stop mechanisms capable of stopping the operation thereof, as shown in FIGS. 19 and 20. . The operation stopping mechanism includes a hydraulic cylinder 8A provided on the back surface of the rocker arm 7, a fork-shaped stopper 10 connected to the piston rod 9,
A plunger 12 that is held reciprocally at the other end of the rocker arm 7 that abuts the drive cam 8 and abuts the stem end 11 of the intake / exhaust valve .
The plunger 12 is engaged with the stopper 10 to transmit the swing of the rocker arm 7 to the intake / exhaust valve via the plunger 12 . Further, by supplying lubricating oil to the cylinder chamber 13 by a switching valve (not shown) to cause the piston rod 9 to protrude ,
The locking of the plunger 12 by the stopper 10 is released, and the plunger 12 is not restrained against the swing of the rocker arm 7, so that the swing is not transmitted to the intake / exhaust valve. That is, the operation of the intake / exhaust valve is stopped by the operation of the cylinder 8A.

The operation stop mechanism is driven by the control means 14 in accordance with the operating state of the engine. At low speed and low load, all the intake and exhaust valves 1, 2, and 3 are stopped, and at low speed and high load. Is controlled so that only the operation of the sub intake valve 2 is stopped.

[0004]

However, in such a conventional multi-cylinder internal combustion engine, since the operation of the intake and exhaust valves is completely stopped, for example, as shown in FIG. There is a problem that the output torque of the engine cannot be sufficiently increased in the middle speed range (the hatched area in the figure) between the high speed range and the high speed range.

In addition, since the two main and sub intake valves are configured such that one of them is operated at a low speed and the other is operated at a high speed, it is not easy to generate a desired swirl at a low speed, and it is not easy at a high speed. Knocking is likely to occur due to the intake swirl, making it difficult to improve the combustion stability and durability of the engine. Therefore, the present invention operates both intake valves from low speed to high speed.
The valve opening / closing timing, valve opening period and lift amount
Variably controlled in a mutual relationship according to the engine operating conditions
Accordingly , it is an object to improve the combustion stability and durability of the engine by improving the output torque, strengthening the swirl at low speed and preventing knocking at high speed.

[0006]

Because of the problem-solving means for the above problems solved, the present invention provides a multi-cylinder internal combustion engine having two intake valves per cylinder, each of the valve timing of the two intake valves, opening period and equipped with a variable valve mechanism for varying in accordance with the lift amount to the operating conditions of the engine, movable variable valve mechanism, drive
Abuts on the moving cam, and
The rocker arm that abuts and the rocking state of the rocker arm
Rocking state varying means that varies according to the operating conditions of the engine.
To change the rocking state of the rocker arm.
Therefore, when the engine is running at a low speed , both of the two intake valves operate.
Substantially matched the intake valves of the varying the opening timing and closing timing to together while, on the other hand, increase than low speed each open period and the lift amount of the two intake valves at the time of high speed of the engine In addition, the valve opening timings of both intake valves are configured to be substantially the same.

[0007]

According to the present invention, the drive cam and the two intake valves come into contact with each other.
Rocker arm swings depending on engine operating conditions.
This causes the two intake valves to twin at low engine speeds.
Both valves open at different opening times and both intake valves are closed
The periods are controlled so that they substantially coincide. Therefore, a strong swath
Cause a delay in closing one intake valve.
There is no problem that the swirl is weakened. further,
Even at low speeds, both intake valves operate
From this, it is possible to efficiently inhale an appropriate amount of air-fuel mixture,
An appropriate output torque is obtained according to the operating conditions. Also,
When the engine is running at high speed, the opening timings of the two intake valves are almost the same.
The intake valve has a wider opening period than at low speed and
Operating with the shift amount,
Can efficiently inhale a large amount of air-fuel mixture
The torque can be improved and the intake
To prevent knocking and reduce engine
Durability can be increased.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 16 show an embodiment of the present invention. First, the configuration will be described. 1 and 2, reference numeral 21 denotes a camshaft in an in-line four-cylinder internal combustion engine, which is driven and rotated in synchronization with an engine output shaft. Reference numeral 22 denotes a rocker arm of an exhaust valve, which is rotatably supported on a rocker shaft 23. Here, as shown in FIG.
, Two main and sub intake ports 25 and 26 and one exhaust port 27 are open. 28 is a spark plug. Both the main intake port 25 and the sub intake port 26 extend linearly so that a large amount of air-fuel mixture can be sucked. Also,
The main intake port 25 opens away from the ignition plug 28,
The diameter (and the flow path area) of the auxiliary intake port 26 that opens toward the ignition plug 28 is smaller than that of the auxiliary intake port 26.

The main and sub intake valves 29, 30 and the exhaust valve 31, which open and close the main and sub intake ports 25, 26 and the exhaust port 27, respectively, are driven by a drive cam 34 via rocker arms 32, 33, 22 respectively. Driven by As shown in FIG. 1, a variable valve mechanism is mounted on the rocker arm 32 of the main intake valve 29, and a similar variable valve mechanism (not shown) is mounted on the sub intake valve 30. The intake valves 29 and 30 have variable valve opening / closing timings and valve lift amounts. Then, the engine of the present embodiment is controlled such that the closing timings of the intake valves 29 and 30 coincide at a low speed, and the opening timings of the intake valves 29 and 30 coincide at a high speed ( Details will be described later). The exhaust valve 31 is driven to open and close at a fixed valve opening / closing timing and a valve lift through a fixed valve operating mechanism.

The variable valve mechanism 35 has a rocker arm 32 having one end abutting on the drive cam 34 and the other end abutting on the stem end of the main intake valve 29, and is formed to be curved along the longitudinal direction of the rocker arm 32. The back surface 32A is fulcrum contact (line contact) with the lower surface 36A formed flat along the longitudinal direction of the lever 36.
doing. That is, the rocker arm 32 is swingably supported by the lever 36. A rotatable lift control cam 37 abuts on the upper surface of one end of the lever 36, and a hydraulic pivot 39 supported by a bracket 38 is slidably fitted in a concave portion 36B of the other end. ing. That is, the lever 36 Contact engage swingably hydraulic pivot 39
When the lift control cam 37 rotates, the hydraulic pivot 39
The lever 36 swings as a swing center, and the rocker arm 32 is supported.
So that the point contact portion moves along the lower surface 36A of the lever 36
Has become. Furthermore, the rocking state of the rocker arm 32 is changed.
The rotation position of the lift control cam 37 depends on the operating conditions of the engine.
(Described later).
The lever 36 and the lift control cam 37 are
Rocker arm 32 with hydraulic pivot 39
Means for changing the swing state according to the operating conditions of the engine.
Make up. The other lock corresponding to the auxiliary intake valve 30
For the arm 33, a lift that replaces the lift control cam 37
Control cam 50, lever 36 and hydraulic pivot 39
Needless to say, the same swing state changing means is provided.
Nor. The bracket 38 is fixed to the cylinder head 40. A support shaft 42 (see FIG. 6) inserted through the center of the rocker arm 32 is fitted in the groove 41 of the lever 36. A spring is provided between the support shaft 42 and the bottom wall of the groove 41. 43 have been reduced. The spring constant of the spring 43 is set to be much smaller than that of the valve spring 44. Reference numeral 38A denotes 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.

As shown in FIGS. 4 and 5, the lift control cam 37 is loosely fitted on 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. These are connected via a coil spring 47 contracted between the two. Further, as shown in FIG. 5, a stopper pin 48 protrudes from the cam control shaft 45. The stopper pin 48 can be brought into contact with the notch of the cylindrical portion 37A of the lift control cam 37. Excessive force is prevented from acting. In FIG. 4, reference numeral 49 denotes a cam control shaft 45.
Is a cap that rotatably supports.

FIGS. 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 FIG.
Vary the valve lift and valve opening / closing timing of the main intake valve 29 5
The lift control cam 50 has five cam surfaces 50a, 50b, 50c for changing the valve lift amount and the valve opening / closing timing of the auxiliary intake valve 30. The cam surfaces 37a, 37b, 37c, 37d, 37e
It has 50d and 50e. The cam surface 37a has a valve lift of 1 mm for the main intake valve 20 and the cam surface 37b has a valve lift of 4.5 mm.
The cam surfaces 37c to 37e also correspond to 8 mm, respectively. Further, the cam surface 50a has a valve lift amount of the sub intake valve 30 of 0.
The cam surface 50b corresponds to 5 mm, the cam surface 50b corresponds to 3 mm, the cam surface 50c corresponds to 8 mm, the cam surface 50d also corresponds to 9.4 mm, and the cam surface 50e corresponds to 10.8 mm. Further, these lift control cams 37 and 50 are provided with the valve lift center angle (the maximum lift is indicated by the crank angle ).
Are formed so as to be different from each other.

Incidentally, each cam surface is provided with both intake valves 29,
Needless to say, the dimensions are formed so that the valve closing timing of the valve 30 coincides and the valve opening timing of the intake valves 29 and 30 coincide at high speed. As shown in FIG. 2, one end of a cam control shaft 45 supporting these lift control cams 37 and 50 is provided with a stepping motor via a speed reduction mechanism 51.
52 are connected. This stepping motor 52
Is driven by a control means (for example, a microcomputer mounted on a vehicle) which is not shown. The control means determines operating conditions of the engine based on various detection signals input from a rotation speed sensor, a water temperature sensor, and the like. The motor 52 is driven according to the operating conditions.

FIG. 9 shows the lift characteristics of the main and sub intake valves 29, 30.
It is a figure which shows a sex change. As shown in FIG.
Lift center angle W of main intake valve 29 that opens and closes port 25₁Is the leading side
(Top dead center side), a secondary suction port that opens and closes the large-diameter secondary suction port 26
Lift center angle W of air valve 30_TwoAre on the lag side (bottom dead center side)
Are set with a phase difference
W₁, W_TwoAnd phase difference are basic even if lift characteristics are changed
It keeps a constant value. Riff of main intake valve 29
The characteristic is indicated by the curve X in the figure.₁, X_Two, X_Three3 as shown
At this stage, the lift characteristic of the sub intake valve 30 is represented by a curve Y₁, Y_Two,
Y _Three, Y_Four, Y_FiveIs variably controlled in five stages as shown in
On the other hand, the lift characteristic of the exhaust valve 31 is constant as shown by the curve Z.
And is not variable. The timing for opening and closing the valve
It changes as follows according to the valve lift amount. In other words,
The larger the shift length, the longer the period during which the valve is open.
When the valve lift is larger, the valve timing is more advanced.
The larger the lift, the more the delay changes.
become.

FIG. 15 shows changes in the cam surfaces of the lift control cams 37 and 50, that is, changes in the lift characteristics, in relation to the engine speed (horizontal axis) and the engine load (accelerator opening, vertical axis). It is. In the figure, at the time of idling indicated by the point P, the cam surfaces 37a, lift characteristics of the main intake valve 29 is controlled to 50a are X _1, lift characteristics of the auxiliary intake valve 30 is Y _1, and the 2
The intake valves 29, 30 and the exhaust valve 31 are each driven to open and close as shown in FIG. In addition, at the time of low speed and low load in the region Q, the main and sub intake valves 29 are controlled by the cam surfaces 37b and 50b.
The lift characteristics of 30 become X ₂ and Y ₂ respectively, and two intake valves
The 29, 30 and one exhaust valve 31 are driven to open and close as shown in FIG. When the region R is fully opened at a low speed, the lift characteristics of the main and sub intake valves 30 are controlled by the cam surfaces 37c and 50c to be X ₃ and Y ₃ , and the two intake valves and one exhaust valve are shown in FIG. It is driven to open and close as shown. At medium speed in the region S, the cam surface 37d,
Lift characteristic of being controlled main and auxiliary intake valves 29, 30 to 50d each X _3, Y _4, and the exhaust valves 31 of the two intake valves 29 and 30 and one is opening and closing, as shown in FIG. 13 Is done. Further, at the time of high speed in the region T, the cam surfaces 37e and 50e are controlled by the main
The lift characteristics of the auxiliary intake valves 29 and 30 are X ₃ and Y ₅ , respectively, and the two intake valves 29 and 30 and the one exhaust valve 31 are driven to open and close as shown in FIG. Note that the solid line and the broken line in FIG. 15 show the switching condition of each area, but the switching condition value at the time of the decrease shown by the broken line is reduced from that at the time of the increase of the rotation speed and the load shown by the solid line, and hysteresis is provided. Hunting of the mechanism is prevented.

Next, the operation in each of the operating ranges P, Q, R, S and T in FIG. 15 will be described in detail. First, when the engine is idling and starting (point P in FIG. 15), a stepping motor is used.
Each lift control cam is driven by rotating the cam control shaft 45 by 52.
Cam surfaces 37a and 50a are both main and sub intake valves for 37 and 50
It rotates so as to contact each lever 36 of 29 and 30. As a result, each lever 36 has one end (the end on the side of the drive cam 34 in FIG. 1) above and separated from the rocker arm 32, and the rocking fulcrum (fulcrum contact point) of the rocker arm 32 is connected to the main intake valve 29 (the auxiliary fulcrum). The intake valve 30 also shifts to the side). Therefore, the main intake valve 29 and the auxiliary intake valve 30, as shown in FIG. 10 (a solid line X ₁ is the main intake valve 29
The lift characteristics, a broken line Y ₁ is its auxiliary intake valve 30, it solid Z is the exhaust valve 31, respectively) driven to open and close at the narrowest opening valve period and the minimum valve lift amount, respectively. Therefore, each valve opening period is very short, and when paying attention to the valve opening timing, it is the most delayed side compared to the state where the lift amount is large, and it is later than the piston reaches the top dead center. The valve overlap between the two intake valves 29, 30 and one exhaust valve 31 is eliminated. In addition, the main intake valve
The combination of the fact that the lift amount and the valve opening period of the valve 29 are larger and longer than those of the sub intake valve, and that the central angle of the lift characteristic of the main intake valve is set to be more advanced than that of the sub intake valve. Therefore, the opening timing of the main intake valve is located much more advanced than that of the sub intake valve. On the other hand, focusing on the valve closing timing, the closing timings of the two intake valves are both earlier than when the pistons reach the bottom dead center, similarly to the valve opening timings. The valve closing timings coincide.

By shifting the opening timings of the two intake valves 29 and 30 as described above, the so-called residual gas in which the burned gas remains in the combustion chamber 24 is reduced, and further, the intake valve having a small lift amount is reduced. The air-fuel mixture whose velocity has been increased like a jet is sucked into the combustion chamber 24 only from the main intake port 25 at the beginning of the intake stroke, so that a strong swirl is generated, the combustion state is improved, and the startability and Idle stability is improved. Further, by making the closing timings of the two intake valves 29 and 30 coincide with each other as described above, the difference between the opening periods of the two intake valves 29 and 30 can all be given as the difference between the opening timings. Can increase the swirl of the
Since the sub intake valve 30 is opened until later than the main intake valve 29, it is possible to prevent a reverse swirl from occurring and weakening the swirl formed at the beginning of the intake stroke.
In addition, since the valve closing timing is before the bottom dead center of the piston, the intake air sucked while the piston descends toward the bottom dead center is discharged while the piston rises past the bottom dead center. Wasteful work such as
As shown in FIG. 16, the pumping loss of the engine can be reduced.

Next, during low-speed low-load operation of the engine (region Q in FIG. 15), the cam control shaft 45 is rotated to push down one end of the lever 36 with the cam surfaces 37b and 50b of the lift control cam 37. As a result, the fulcrum contact points of the rocker arm 32 is shifted to the side driving cam 34, the main intake valve 29 and the auxiliary intake valve 30, FIG. 11X ₂ and Y
_As shown by ₂ , each is driven with the second smallest valve lift and the second narrowest valve opening period, respectively. Therefore, the closing timing of the intake valves 29 and 30 shifts to the lower dead center side from the start and idle times, and the valve opening timing shifts to the upper dead center side.

As described above, by setting a larger lift amount and a wider valve opening period than at the time of starting and idling,
A large amount of intake air can be taken in more efficiently than at the time of starting and idling, an output suitable for low-speed, low-load operation can be obtained, and the residual gas in the combustion chamber 24 as in the starting and idling. , The combustion is stabilized by the strong swirl, and the pumping loss can be reduced.

Next, when the engine is fully opened at low speed (region R in FIG. 15).
Are levers on the cam surfaces 37c and 50c of the lift control cams 37 and 50.
Push down one end of 36 further. As a result, the fulcrum contact points of the rocker arm 32 is further moves to the left in FIG. 1, the lift characteristics of the main-auxiliary intake valves 29 and 30, as indicated by X ₃ and Y ₃ in FIG. 12, the valve lift amount As the valve opening period increases, the valve opening timing is near top dead center and the valve closing timing is near bottom dead center.
As described above, the increase in the valve lift amount and the valve opening period increases the intake air amount, thereby improving the output torque.

When the engine speed further increases (FIG. 15)
In the region S), the lever 36 is pushed down by the cam surfaces 37d and 50d, and the lift amount and opening / closing timing of the main intake valve 29 do not change, but the valve lift amount and the valve opening period of the auxiliary intake valve 30 increase. Figure 13 shows the lift characteristics of the case in X ₃ and Y _4, closing timing of the auxiliary intake valve 30 is beyond the bottom dead center of the piston, it will be delayed from that of the main intake valve 29, whereas, vice The opening timing of the intake valve 30 approaches that of the main intake valve 29. The reason why the valve lift amount and the opening / closing timing of the main intake valve 29 are not changed is to prevent the amount of overlap from becoming excessive and the occurrence of blow-by of fresh air. With this opening / closing characteristic, the intake air amount can be appropriately increased according to the rotation speed and the load, and the output torque is improved.

Further, when the engine speed is increased (see FIG.
In region T) of 15), the lever 36 is pushed down by the cam surfaces 37e and 50e, so that the valve lift amount and the valve opening period of the auxiliary intake valve 30 increase. FIG. 14 shows the lift characteristics in this case as X ₃ and Y ₅ . The closing timing of the sub intake valve 30 is further delayed beyond the bottom dead center, while the opening timing of the sub intake valve 30 is further advanced and coincides with the opening timing of the main intake valve 29. As described above, by setting a large lift amount and a wide valve opening period, the intake air amount is further increased in the high-speed rotation region, and the output torque is improved. Also, since the opening timings of the two intake valves 29 and 30 are the same,
No swirl is generated, and heat transfer from the wall surface of the combustion chamber 24 to the air-fuel mixture can be suppressed, so that knocking can be prevented and the durability of the engine can be improved.

In the above embodiment, the five-step control is performed by the lift control cam. However, it is needless to say that the present invention is not limited to this. Further, in addition to the above five-stage control, the engine air-fuel ratio can be appropriately changed.

[0024]

As described above, according to the present invention, both intake valves are operated while both intake valves are operated at a low speed.
By making the valve opening timing different,
When a strong swirl is generated in the combustion chamber from the intake port of
In both cases, the closing timings of these two intake valves are substantially matched.
To prevent the strong swirl from being weakened
Can be. In addition, both intake valves are operated at low speed.
, An appropriate amount of air-fuel mixture according to the operating conditions of the engine
Inhalation can be performed efficiently, and appropriate
Output torque can be obtained. Also, two at high speed
The opening timings of the intake valves match, and both intake valves are low.
Larger valve opening period than at high speed and larger lift at low speed
Large amount of mixing according to the operating conditions of the engine
Air can be inhaled efficiently and output torque is improved.
And prevent the occurrence of intake swirl.
To prevent knocking and increase engine durability.
Can be.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a multi-cylinder internal combustion engine according to the present invention.

FIG. 2 is a plan view showing the embodiment.

FIG. 3 is a schematic diagram showing a layout of the intake / exhaust ports.

FIG. 4 is an exploded perspective view showing a mounting portion of the lift control cam.

FIG. 5 is a perspective view showing a mounting portion of the lift control cam.

FIG. 6 is a perspective view showing the support shaft.

FIG. 7 is a front view showing a cam profile of the lift control cam for the main intake valve.

FIG. 8 is a front view showing a cam profile of the lift control cam for the auxiliary intake valve.

FIG. 9 is a graph showing the relationship between lift characteristics of both main and sub intake valves and exhaust valves.

FIG. 10 is a graph showing lift characteristics at the time of idling and at the time of starting of the engine.

FIG. 11 is a graph showing lift characteristics during low-speed low-load operation.

FIG. 12 is a graph showing lift characteristics at the time of low-speed full opening.

FIG. 13 is a graph showing a lift characteristic when the vehicle speed is slightly higher.

FIG. 14 is a graph showing lift characteristics at a high speed.

FIG. 15 is a graph showing a correspondence relationship between an engine speed, an accelerator opening, and each cam surface.

FIG. 16 is a PV diagram during idling in the present embodiment.

FIG. 17 is a plan view showing a conventional multi-cylinder internal combustion engine.

FIG. 18 is a front sectional view of the conventional example.

FIG. 19 is a partially cutaway front view showing a conventional operation stop mechanism.

20 is a sectional view taken along the line AA in FIG. 19;

FIG. 21 is a graph showing a relationship between an engine speed and an output torque in a conventional example.

[Explanation of symbols]

 29 Main intake valve 30 Secondary intake valve 35 Variable valve mechanism

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-138720 (JP, A) JP-A-59-46308 (JP, A) JP-A-59-96431 (JP, A) JP-A 51-964 57322 (JP, A) Actually open sho 56-122707 (JP, U)

Claims (1)

(57) [Claims] 1. A first cylinder multi-cylinder internal combustion engine having two intake valves for each of the valve timing of the two intake valves, contact opening period
And a variable valve mechanism that varies the lift amount according to the operating conditions of the engine. The variable valve mechanism contacts the drive cam and controls the two intake valves respectively.
The rocker arm in contact with and the rocking state of the rocker arm
Means for changing the swing state according to the operating conditions of the engine.
By changing the rocking state of the rocker arm, both of the two intake valves are operated when the engine is running at a low speed.
Increase One with varying the opening timing of the intake valves substantially matched the closing timing, whereas, than low speed each <br/> open period and the lift amount of the two intake valves at the time of high speed of the engine A multi-cylinder internal combustion engine characterized in that the opening timings of both intake valves are made substantially the same.