JPH0585723B2 - - 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 supplied to the combustion chamber 5. All of these intake and exhaust valves are driven by a drive cam 8 via a rocker arm 7 in synchronization with engine rotation, but each of these rocker arms 7 has its own mechanism as shown in FIGS. 19 and 20. A deactivation mechanism capable of deactivating the device is provided. This operation stop mechanism has a hydraulic cylinder 9 provided on the back surface of the rocker arm 7, and a fork-shaped stopper 11 connected to the piston rod 10 thereof, one end of which abuts the drive cam 8 and the other end of the rocker arm 7. A plunger 1 is held in a reciprocating manner and abuts against a stem end 12 of an intake/exhaust valve.
3 is locked to the stopper 11 when the cylinder 9 is not in operation, and the swinging of the rocker arm 7 is transmitted to the intake/exhaust valves via the plunger 13, and lubricating oil is supplied to the cylinder chamber 9A by a switching valve (not shown). By causing the piston rod 10 to protrude, the plunger 13 is released from the stopper 11.
Since the plunger 13 is not constrained by the rocking motion of the rocker arm 7, the rocking motion is not transmitted to the intake and exhaust valves. That is, the operation of the cylinder 9 stops the operation of the intake and exhaust valves.

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 low load, the operation of all intake and exhaust valves 1, 2, and 3 is stopped. Only 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 completely controlled. For example, as shown in Fig. 21, the engine's output torque cannot be sufficiently increased in the medium speed range (shaded area in the figure), that is, in the transient operating range. There was a problem that I couldn't do it. In addition, the main and sub-intake valves have one of them set to low-speed operation timing and lift.
Since the other one was designed for high speeds, there was also the problem that the intake air filling efficiency at high speeds could not be sufficiently increased. 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) The present invention includes a variable valve mechanism for each of the intake valve and the exhaust valve to vary the valve opening/closing timing and valve lift amount in stages according to the operating conditions of the engine. In a multi-cylinder internal combustion engine, the intake valve is configured to simultaneously change its valve opening/closing timing and valve lift amount, and the exhaust valve is configured to maintain its valve opening/closing timing constant and change its valve lift amount.

(Function) The multi-cylinder internal combustion engine according to the present invention uses a variable valve mechanism to vary the valve opening/closing timing and valve lift amount of the intake valve and the exhaust valve in stages according to the operating conditions of the engine. In this case, the valve opening/closing timing and valve lift amount of the intake valve are simultaneously changed by the variable valve mechanism, while the valve opening/closing timing of the exhaust valve is kept constant despite changes in operating conditions by the variable valve mechanism. By holding the valve and changing the valve lift amount, it is possible to improve startability by reducing friction loss and to achieve an increase in output torque at high speeds.

(Example) Hereinafter, an example of a multi-cylinder internal combustion engine according to 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, reference numeral 21 indicates a camshaft in an in-line four-cylinder internal combustion engine, and this camshaft 21 is driven and rotated in synchronization with the engine output shaft via a pulley 22 fixed to the shaft end. As shown in FIG. 1, an intake valve drive cam 23 and an exhaust valve drive cam 24 are fixed to the camshaft 21 with a predetermined phase. In the same figure, 25 is the intake port, 2
Reference numeral 6 indicates an intake valve that opens and closes this, 27 indicates an exhaust port, and 28 indicates an exhaust valve that opens and closes this. In addition, in the same figure, 29 indicates the combustion chamber in which both ports 25 and 27 are open, 30 indicates the cylinder head, and 3
Reference numerals 1 and 32 indicate valve springs of the intake and exhaust valves.

The intake valve 26 and the exhaust valve 28 each have variable valve mechanisms 33 and 34 that vary the valve opening/closing timing and valve lift amount in stages according to the operating conditions of the engine.
It is driven to open and close by the drive cams 23 and 24 via the drive cams 23 and 24.

The variable valve mechanism 33 includes a rocker arm 35, a lever 36, and a lift control cam 37, as shown in FIG. One end (right end in the figure) of the rocker arm 35 is provided in contact with the drive cam 23, and the other end is provided in contact with the stem end 26A of the intake valve 26, and its back surface 35A is curved at a predetermined curvature along its longitudinal direction. It is formed as follows. In addition, the rear arm 35 is
5A is in fulcrum contact with the lower surface 36A of the lever 36. That is, the rocker arm 35 is swingably supported by the lever 36. The lower surface 36A of this lever 36 is formed flat along its longitudinal direction. A lift control cam 37 is provided in contact with the upper surface of one end of the lever 36, and a lower spherical portion of a hydraulic pivot 38 is slidably fitted into the recessed portion 36B of the other end. That is, the lever 36 is swingably provided above the rocker arm 35 with a hydraulic pivot 38 as a fulcrum, and its inclination angle is variably controlled by a lift control cam 37. Further, a spring 40 with a small spring constant is compressed between the recess 39A of the support shaft 39 (see FIG. 6) inserted into the longitudinal center of the rocker arm 35 and the groove 36C on the lower surface of the lever 36. , these rocker arms 35 and levers 36 are positioned relative to each other.

Here, the hydraulic pivot 38 is connected to the bracket 4.
1 so that the center of its lower end spherical portion is located on an extension of the axis of the intake valve 26 (L ₁ , which is inclined at a predetermined angle with respect to the vertical plane K including the axis of the camshaft 21). It is set up. Therefore, when one end of the rocker arm 35 is in contact with the base circle of the drive cam 23, the contact point M _I between the lever 36 and the rocker arm 35 is located approximately on the extension line _LI . Note that 42 is an oil hole formed in the bracket 41, and pressurized oil at a predetermined pressure, such as engine lubricating oil, is supplied through this oil hole 42 to the hydraulic chamber built in the hydraulic pivot 38 to maintain the valve clearance at a constant value. Hydraulic pivot 38 has a zero-latch function to maintain the position.

Here, the lift control cam 37 is connected to the cam control shaft 5 via a coil spring 46, as shown in detail in FIG. 4 and FIG. When the rotational force from the cam control shaft 45 through the lever overcomes the reaction force through the lever 36, the valve rotates, for example, when the valve is closed. That is, the lift control cam 37 is loosely fitted to the cam control shaft 45, and the coil spring 46 has one end attached to a boulder 47 screwed to the cam control shaft 45, and the other end attached to the lift control cam 3.
7, respectively. In FIG. 5, reference numeral 48 denotes a stopper pin protruding from the cam control shaft 45, and is provided in the cylindrical portion 37A so as to be able to come into contact with the notch. This prevents excessive force from acting on the coil spring 46. Note that 49 is a cap that rotatably supports the cam control shaft 45.

On the other hand, a variable valve mechanism 34 that drives the exhaust valve 28
The structure is also substantially the same as that of the variable valve mechanism 33 of the intake valve 26. That is, one end of the rocker arm 50 is provided in contact with the drive cam 24, and the other end is provided in contact with the stem end 28A of the exhaust valve 28, respectively. Further, the curved back surface 50A of the rocker arm 50 is in fulcrum contact with the flat lower surface 51A of the lever 51. The lever 51 is slidably supported by a hydraulic pivot 52, and its inclination can be changed by a lift control cam 53. Also,
The lift control cam 53 is connected to the cam control shaft 54 via a coil spring 70.

Here, the center of curvature of the lower spherical portion of the hydraulic pivot 52 is located a predetermined distance closer to the engine center (on the vertical plane K side) than the extension of the axis L _E of the exhaust valve 28 . Note that the axis L _E is provided so as to be symmetrical about the vertical plane K with respect to the above-mentioned axis L _I. Therefore, when the rocker arm 50 is in contact with the base circle of the drive cam 24 (the lift amount is 0), the lever 51 and the rocker arm 5
The contact point M _E with 0 is located a predetermined distance inward (on the vertical plane K side) from the extension line of the axis L _E (Fig. 1).

7 and 8 show the cam profiles of these lift control cams 37 and 53, respectively. As shown in FIG. 7, the lift control cam 37
are five cam surfaces 37a, 37b, which vary the valve lift amount and valve opening/closing timing of the intake valve 26, respectively.
37c, 37d, and 37e. Cam surface 3
7a has a valve lift amount of 2 mm, cam surface 37b has a valve lift amount of 5 mm, cam surface 37c has a valve lift amount of 8 mm,
The cam surface 37d has a valve lift of 9.4 mm.
e corresponds to the valve lift amount of 10.8 mm. In addition, as shown in FIG. 8, the lift control cam 53 has five cam surfaces 53a, 53b, 53c, and 53a, 53a, 53b, 53c, and 53c, which respectively vary the amount of valve lift of the exhaust valve 28.
3d and 53e. The cam surface 53a has a valve lift of 2 mm, and the cam surface 53b has a valve lift of 5 mm.
, the cam surface 53c has a valve lift amount of 8 mm, and the cam surface 53c has a valve lift amount of 8 mm.
3d corresponds to a valve lift amount of 9.4 mm, and the cam surface 53e corresponds to a valve lift amount of 10.8 mm. In this way, the lift control cams 37 and 53 have cam surfaces that can vary the valve lift amount in five stages, and these cams are designed to simultaneously drive the intake and exhaust valves 26 and 28 with the same valve lift amount. The cam control shafts 45 and 54 are provided symmetrically with respect to the middle vertical plane K, respectively.

The cam control shafts 45 and 54 are arranged parallel to the camshaft 21, as shown in FIG. 2, and gears 56 and 57 having different numbers of teeth are fixed to one end of each, as shown in FIG. has been done. Further, these cam control shafts 45 and 54 are driven and rotated by a stepping motor 58 at the same reduction ratio via reduction means. That is, the gear 57 meshes with a drive gear 59 driven by the output shaft of the stepping motor 58, the idler gear 60 meshes with the gear 57, and the gear 56 meshes with the idler gear 60. Therefore, the cam control shafts 45 and 54 are rotated by the stepping motor 58 in the same direction by the same rotation angle. In addition, the stepping motor 58
is driven and controlled by a control means (for example, an on-vehicle microcomputer) not shown, and this control means controls the engine based on various detection signals of the engine input from, for example, a rotation speed sensor, a water temperature sensor, etc. The stepping motor 58 determines the operating conditions and controls the intake/exhaust valves 26 and 28 to have the set valve lift amount and valve opening/closing timing according to the operating conditions.
control the drive.

Next, the operation of this embodiment will be explained.

In this embodiment, as shown in FIG. 9, depending on the engine rotational speed and the engine load (accelerator opening),
The entire operating range of the engine is divided into five ranges () to (), and each lift characteristic of the intake valve 26 and the exhaust valve 28 is changed. In other words, area () represents the idling state of the engine, area () represents the engine's low speed and low load area, area () represents the engine's low speed full-open area and medium speed, low and medium load area, and area () represents the engine's medium speed. The area and area () indicate the high speed area of the engine, respectively. Curves I ₁ and E ₁ in FIG. 10 indicate the lift characteristics of the intake and exhaust valves 26 and 28 in the region ( ). (I ₁ : intake valve, E ₁ : exhaust valve). Similarly I ₂ , E ₂
indicates that of area (), I ₃ , E ₃ indicates that of area (), I ₄ , E ₄ indicates that of area (), I ₅ , E ₅ indicates that of area (), respectively. There is. In addition,
The solid line in FIG. 9 shows the switching value between each region when the rotational speed increases, and the broken line shows the switching value when the rotational speed decreases. In this way, hysteresis is provided in switching the regions, that is, driving the stepping motor 58,
Prevents hunting in the valve train system.

Here, changes in the valve opening/closing timing of the exhaust valve 28 will be explained.

In the variable valve mechanism 34 of the exhaust valve 28, when the rocker arm 50 is in contact with the base circle of the drive cam 24 (when the valve is closed), the contact point _M between the rocker arm 50 and the lever 51 is aligned with the axis of the exhaust valve 28. Since it is located closer to the drive cam 24 than the extension line of L _E , the rocker ratio is not 0. That is, as shown by the curve E _R in FIG. 16, even if the valve lift amount changes, the rocker ratio when the exhaust valve 28 is lifted always starts from a constant value and changes.
This is also because the back surface shape of the rocker arm 50 is formed so that the contact point M _E between the rocker arm 50 and the lever 51 does not move toward the extension line L _E than the hydraulic pivot 52. As a result, even if the lift control cam 53 is rotated, only the valve lift amount of the exhaust valve 28 changes while keeping the valve opening/closing timing constant. (Fig. 10 _E1 to _E5 ).

On the other hand, the variable valve mechanism 33 of the intake valve 26
is the contact point between the rocker arm 35 and the lever 36
Since M _I is placed on the extension line L _I , the Rotzka ratio is approximately 0.
(curve I _R in FIG. 16), the valve opening/closing timing changes in accordance with the change in valve lift amount (I ₁ to I ₅ in FIG. 10).

Each area will be explained below.

During idling (region ()) and when starting the engine, the stepping motor 58 is driven to
53a to push down the levers 36, 51. As a result, one end of each of the levers 36, 51 is located farthest from each one end of the rocker arms 35, 50 and located above (the inclination angle of the levers 36, 51 is maximum),
The rocking fulcrums of the rocker arms 35 and 50 are shifted to the other ends (toward the stem ends 26A and 28A). Therefore, as shown in FIG.
Both the exhaust valves 28 and 28 lift with a minimum valve lift amount of 2 mm, while the exhaust valve 28 opens before bottom dead center and closes after top dead center (E ₁ ), and the intake valve 26 lifts at this top dead center. The valve opens when the valve closes after the point, and closes before the bottom dead center (I ₁ ). As a result, the amount of intake air is appropriate for the operation in question, significantly reducing friction loss in each valve system, improving fuel efficiency, and significantly increasing cranking speed, especially at extremely low temperatures, and starting the engine. Improved performance. In addition, intake/exhaust valve 2
Since the amount of overlap between the combustion chambers 6 and 28 is approximately zero, it is possible to prevent combustion from becoming unstable due to an increase in residual gas in the combustion chamber 29.

Low speed and low load range (region ()) In this operating range, the lift control cams 37, 53 push down the levers 36, 51 with their cam surfaces 37b, 53b. As a result, the inclination of the levers 36, 51 becomes gentler, and the fulcrum contact points of the rocker arms 35, 50 shift to the other ends (towards the drive cams 23, 24). Therefore,
As shown in FIG. 12, the exhaust valve 28 and the intake valve 2
6 has a valve lift of 5 mm, and an exhaust valve of 28
The opening/closing timing of the intake valve 26 does not change, the opening timing of the intake valve 26 advances, and the closing timing of the intake valve 26 delays (E ₁ , I ₂ ). That is, as the valve lift amount increases, the amount of intake air also increases, making it possible to obtain a suitable output torque. Furthermore, since the closing timing of the intake valve 26 is advanced compared to that of a normal fixed valve type, the actual compression ratio is increased and fuel efficiency is improved.

Low speed fully open range and medium speed low medium load range (region ()) In this operating range, the lift control cams 37, 53 push down the levers 36, 51 with the cam surfaces 37c, 53c. As a result, the inclination of the levers 36, 51 also becomes smaller, and the fulcrum contact points of the rocker arms 35, 50 also move further toward the drive cams 23, 24. Therefore, as shown in FIG. 13, the intake valve 26 and the exhaust valve 28 have the same valve lift amount of 8 mm, the valve opening/closing timing of the exhaust valve 28 is the same in the above ranges () and (), and the intake valve 26 has the same valve lift amount of 8 mm. The valve opening timing is advanced to near top dead center, and the valve closing timing is delayed until after bottom dead center. Therefore, the amount of overlap is small. Therefore, a sufficient amount of air-fuel mixture can be sucked in, and the amount of pumping of the air-fuel mixture once sucked is reduced, so-called charging efficiency is improved, and as a result, output torque is improved.

Medium speed full open range, high medium speed/low medium load range (region ()) In this operating range, as a result of further pushing down the levers 36, 51 by the lift control cams 37, 53,
The inclinations of the levers 36 and 51 are further reduced, and the fulcrum contact points of the rocker arms 35 and 50 are also closer to the drive cam 2.
Moving further to the 3rd and 24th sides. Therefore, as shown in FIG. 14, the valve lift amount of the intake/exhaust valves 26 and 28 is 9.4 mm, and the overlap amount also increases. Then,
A sufficient amount of air-fuel mixture can be sucked in, and the output torque can be improved by 3% to 6% compared to the conventional system.

High-speed range (region ()) In this operating range, the levers 36 and 51 are pushed down by the cam surfaces 37e and 53e, and their inclinations are minimized (approximately horizontal). Therefore, the fulcrum contact point of the rocker arms 35, 50 is further connected to the drive cam 2.
Move to the 3rd, 24th side. As a result, as shown in FIG. 15, the opening timings of both the intake valve 26 and the exhaust valve 28 are at their maximum (the amount of overlap is also maximum).
The valve lift amount is also maximum (10.8mm). Therefore, the intake air filling efficiency can be increased in the high speed range, and the output torque can be further improved (an increase of 3% to 6% compared to the conventional model).

(Effects) As explained above, according to the present invention,
The valve lift characteristics of the intake and exhaust valves are controlled in a detailed step-by-step manner according to the engine operating conditions, ensuring optimal output and fuel efficiency according to each operating condition. Particularly at low speeds and low loads, the friction of the valve train can be reduced, improving overall durability against wear.

[Brief explanation of drawings]

1 to 16 show an embodiment of a multi-cylinder internal combustion engine according to the present invention, FIG. 1 is a sectional view showing its variable valve mechanism, FIG. 2 is a plan view thereof,
Fig. 3 is a schematic front view showing the deceleration means, Fig. 4 is an exploded perspective view showing the mounting part of the lift control cam in the valve mechanism, Fig. 5 is a perspective view showing the mounting part, and Fig. 6 7 is a perspective view showing the support shaft of the valve mechanism, FIG. 7 is a front view showing the cam profile of the lift control cam for the intake valve, and FIG. 8 is a cam profile of the lift control cam for the exhaust valve. Front view, Figure 9 is a graph showing the correspondence of the cam surface of each lift control cam to engine operating conditions, Figure 10 is a graph showing changes in the lift characteristics of the intake and exhaust valves, and Figure 11 is the graph at idle. Graph showing the lift characteristics of intake and exhaust valves. Figure 12 is a graph showing it at low speed and low load. Figure 13 is a graph showing it at low speed fully open. Figure 14 is a graph showing it at medium speed. , FIG. 15 is a graph showing that in a high speed range, and FIG. 16 is a graph showing changes in rocker ratios of intake and exhaust valves. 17 to 21 show a conventional multi-cylinder internal combustion engine, in which FIG. 17 is a plan view thereof, FIG. 18 is a front sectional view thereof, and FIG.
Figure 20 is a partially cutaway front view showing the intake/exhaust valve operation stop mechanism, Figure 20 is a sectional view taken along the - arrow in Figure 19, and Figure 21 shows the relationship between engine speed and output shaft torque. It is a graph. 26...Intake valve, 28...Exhaust valve, 33...Variable valve mechanism for intake valve, 34...Variable valve mechanism for exhaust valve.

Claims (1)

[Claims] 1. In a multi-cylinder internal combustion engine equipped with a variable valve mechanism that varies the valve opening/closing timing and valve lift amount in stages according to engine operating conditions for each of the intake valve and exhaust valve, the intake valve is A multi-cylinder internal combustion engine characterized in that the timing and valve lift amount are changed simultaneously, and the valve lift amount of the exhaust valve is changed while maintaining the valve opening/closing timing constant.