JPS6245960A - Tappet valve mechanism of internal combustion engine - Google Patents

Abstract

PURPOSE:To avoid the application of an excessive load onto a valve system by installing a revolution limitter for regulating the max. engine speed each time when the opening/closing timing of an intake/exhaust value is switched by a valve-timing varying mechanism. CONSTITUTION:A valve-timing varying mechanism slides a cam by the operation of an actuator 6, and engages one among two kinds of control surfaces for high-speed revolution and low-speed revolution which are installed onto the outer peripheral surface of the cam with a locker arm and opens and closes an intake/exhaust value in the timing corresponding to the shape of each control surface. The actuator 6 is operated by controlling a solenoid value 5 by a valve timing controller 3 according to the output of an engine speed sensor 4. In this case, the max. revolution speed at the valve-timing setting position is regulated by a revolution limitter built in an ignition control device 7, according to the output of a valve-timing detection sensor and the revolution speed sensor 4 which are built in the actuator 6.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to a valve train for an internal combustion engine equipped with a variable valve timing mechanism that changes the opening and closing timing of an intake valve, an exhaust valve, or both, depending on the rotational speed of the internal combustion engine. It is about the mechanism.

"Prior Art" The optimal opening angle of the intake and exhaust valves of an internal combustion engine changes as the engine speed changes. For this reason, if you try to control the operation of these valves with a single cam, when the engine is in a predetermined rotation speed range, the valve will operate ideally and high output will be obtained, but the engine If it deviates from this range, the valve will not be able to perform its ideal operation and the output will drop.

Therefore, the technique described in Japanese Patent Publication No. 44-26485 was proposed. This technology prepares multiple cam control surfaces for each predetermined rotational speed range of the engine to operate the intake or exhaust valves, and selects the optimal cam control surface that matches the engine rotational speed from among these multiple cam control surfaces. The purpose is to selectively function the valves depending on the engine speed, and to optimize the valve opening/closing timing no matter what speed range the engine is in, thereby increasing the engine's output. In Fig. 1, A1 and A2 indicate the lift curve of the cam control surface for high rotations and its acceleration coefficient change, and BISB indicates the lift curve of the cam control surface for low rotations and its acceleration coefficient change. .

"Problem to be Solved by the Invention" By the way, in an internal combustion engine, the limit engine speed at which the intake and exhaust valves can move accurately along the cam control surface is determined by the inertial weight of the valve system and the load characteristics of the valve spring. , as well as the acceleration coefficient of the valve lift curve.

As mentioned above, this is a type of system that changes the valve opening/closing timing by selectively using any one of several different shaped cam control surfaces without changing the inertial weight of the valve system or the load characteristics of the valve spring. In an internal combustion engine equipped with a variable valve timing mechanism, when the valve timing is switched to narrow the opening angle, the maximum lift amount of the valve is simultaneously reduced. This is because, if this is not done, the acceleration coefficient of the valve lift curve will increase, and the limit rotational speed at which the valve can move accurately along the cam control surface will decrease.

In fact, since the valve opening angle is set to become narrower when the engine speed decreases, it seems as if no problems will occur. However, if the throttle opening is suddenly increased during idling with no load, the engine will reach a high rotation range before the variable valve timing mechanism switches, and the engine rotation speed will be lower than the acceleration of the valve lift curve. There are cases where the rotational speed exceeds the limit determined by the coefficient, etc., at which the valve can move accurately along the cam control surface. At this time, there is a risk that problems such as excessive load being applied to the valve system may occur.

For this reason, in conventional systems equipped with the aforementioned variable valve timing mechanism, the maximum lift amount is lowered in advance when the valve opening angle is narrow (as shown in Figure 1) to prevent excessive load from being applied to the valve system. (not shown), the actual situation is that the acceleration coefficient of the valve lift curve is set to be approximately equal to that when the valve opening angle is wide.

However, while this setting has the advantage that no excessive load is applied to the valve system under any circumstances, it also reduces the lift amount when the valve opening angle is narrow.
It also has the disadvantage that the output in the low rotation range is lower than the ideal power.

``Object of the Invention'' The present invention was made in view of the above circumstances, and there is no risk of excessive load being applied to the valve system, and even when the valve opening angle is narrow, a large valve lift can be achieved. An object of the present invention is to provide a valve mechanism for an internal combustion engine that can obtain high output even in a low speed rotation range.

"Means for Solving the Problems" In order to achieve the object, the present invention provides an internal combustion engine equipped with a variable valve timing mechanism that changes the opening/closing timing of an intake valve, an exhaust valve, or both according to the rotational speed of the internal combustion engine. In this configuration, a rotation limiter is provided for regulating the maximum rotation speed of the internal combustion engine at each predetermined state switched by the variable valve timing mechanism.

According to the above-mentioned valve train mechanism, when the variable valve timing mechanism switches to a predetermined state, the maximum rotation speed is regulated by the rotation limiter, so when determining each valve lift curve at the design stage, It is only necessary to set the valve so that it can move accurately along the cam control surface within the maximum rotation speed range regulated by the rotation limiter, and for this reason, it is possible to have a larger valve lift a compared to the conventional one. became.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 2 to 7.

FIG. 2 is a diagram of the operating system of the valve mechanism according to the present invention, in which reference numeral 1 indicates the engine body and 2 indicates the spark plug. Further, 3 indicates a valve timing controller, and this controller 3 is connected to a sensor 4 that detects the engine speed, and when the engine speed exceeds a predetermined value or falls below a predetermined value, the solenoid valve is activated. The actuator 6 is switched by sending a signal to the actuator 5.

The actuator 6 slides a cam connected to the actuator 6 using hydraulic pressure, and controls any one of two types of control surfaces for high-speed rotation and low-speed rotation provided on the outer circumferential surface of the cam via a rocker arm. The valve opening/closing timing is optimally matched to the engine speed at that time by bringing the intake valve or exhaust valve into engagement. The actuator 6 also has a sensor ( (not shown)
is built in, and the signal emitted from the sensor is sent to the ignition control device 7.

Here, the sensor 4, the valve timing controller 3,
The solenoid valve 5 and the actuator 6 constitute part of a variable valve timing mechanism that changes the opening and closing timing of the valve according to the engine speed.

The ignition control device 7 performs the normal function of supplying electrical energy for ignition to the plug 2, and also performs the following functions based on signals sent from the rotation speed detection sensor 4 and the valve timing detection sensor built into the actuator 6. The built-in rotation limiter also functions to regulate the maximum engine speed at the valve timing setting position by thinning out the ignition, etc., depending on the valve timing setting position. Specifically speaking about the latter function, when the valve opening angle is narrow, the engine rotation speed is set to a predetermined rotation speed device that is set slightly higher than the rotation speed when the variable valve timing mechanism switches. Also, when the valve opening angle is wide, the engine speed is set higher than the above-mentioned predetermined speed.
Regulate the second party. Note that O in FIG. 2 indicates an oil passage.

On the other hand, FIGS. 3 to 6 show specific examples of the variable valve timing mechanism. In the figure, reference numeral II is a cylinder head, 12 is a head cover, and 13 is a camshaft. The camshaft 13 is connected to the crankshaft of an internal combustion engine via a sprocket 14 and a chain (not shown), and is synchronized with the crankshaft. Therefore, the speed is reduced to 1/2 and rotated.

=7- The camshaft I3 is composed of a camshaft main body 15 and a cam cylinder 16 fitted around the outer periphery of the camshaft main body 15. The cam cylinder I6 has an inner circumference i%i18 fitted to a pin 17 implanted in the camshaft main body I5, so that it can move freely in the axial direction with respect to the camshaft main body 15 and rotate integrally therewith. It has become. As shown in FIG. 5, the cam cylinder 16 is formed with one low-speed rotation cam lobe and one high-speed rotation cam lobe 20 aligned in the axial direction.

2I is a rocker arm support shaft, and the rocker arm 22 swingably supported by this shaft 2I has its cam engaging portion 22a connected to the cam lobe 19, 20 as shown in FIG.
(FIG. 3 shows a state in which it is pressed by the high-speed rotation cam lobe 20)
(or exhaust valve). The cam cylinder 16 is moved relative to the camshaft main body 15 in the direction A-B in FIG. 3 by the cam switching mechanism 24 according to the rotational speed of the engine.
The portion that engages with the rocker arm 22 can be switched.

To explain the switching mechanism 24, a first piston 26 is fitted into a first cylinder 25 formed in the head cover 12. A second piston 27 is fixed to the outer periphery of the protruding end of the first piston 26 by means such as press fitting. This second piston 27 is fitted into a second cylinder 28 provided in the head cover I2. and,
The first and second pistons 26 and 27 are connected to the first cylinder 2
By introducing pressure oil into the camshaft 5 or the second cylinder 28, they are moved together in parallel to the axial direction of the camshaft 13 (in the directions A and B in FIG. 3). That is,
The cylinder 25, 28 and piston 26, 27 constitute the actuator 6 described with reference to FIG. 2 above.

Cam slide fork 2 is located between both pistons 26 and 27.
9 is provided so as to be movable relative to the pistons 26, 27 in the AB direction by the gap formed therebetween. The arm 29a of the cam slide fork 29 engages with a groove 16a formed in the center of the cam cylinder 6, and moves integrally with the cam cylinder 16 in the direction AB. Further, the cam slide fork 29 is biased toward the first piston 26 by a spring 30 provided between the cam slide fork 29 and the first piston 26 .

On the other hand, numeral 31 in FIG. 4 is a trigger lever support shaft disposed parallel to the camshaft 13, and a trigger lever 32 is swingably supported on this shaft 3I. Trigger lever 3
One end of the trigger lever 32 is engaged with a trigger cam 33 formed integrally with the camshaft 13, and the other end of the trigger lever 32 is connected to the outer periphery of the first piston 26 on the left end side in FIG. It can be fitted into the formed narrow groove 34 or the groove 35. Further, the trigger lever 32 receives a force such that it rotates in the direction C in FIG.
3.

Here, the trigger cam 33 is connected to the rocker arm 22.
Immediately after the cam engaging portion 22a of the cam lobe I9.20 comes into contact with the valve lift portion of the cam lobe I9.20, the trigger lever 32 is rotated in the direction in FIG.
The shape is such that the engagement with 6 can be removed. Also,
The positions and widths of the narrow groove 34 and the groove 35 are the same as those of the cam lobe 19.
20 individual widths and the whole of them, that is, cam cylinder 1
It is determined by the width of 6, etc.

Further, numeral 36 in FIG. 3 indicates an oil pump, and the discharge side of this oil pump 36 is connected to the solenoid valve 5 via a conduit 37. The solenoid valve 5 changes the pipe route depending on the rotational speed of the engine; when the engine rotates at low speed, the pipe line 37 is connected to the pipe line 39 leading to the first cylinder 25, and when the engine rotates at high speed, the pipe line 37 is connected to the pipe line 39 connected to the first cylinder 25. When doing so, the conduit 37 is connected to the conduit 40 leading to the second cylinder 28. The solenoid valve 5 is switched based on the engine speed by the valve controller 3 as described above.

Next, the operation of the valve train having the above configuration will be explained.

When the engine rotates at low speed, the solenoid valve 5 controlled by the valve timing controller 3 is in a negative state (for example, in an excited state), and the oil pump 3
6 is introduced into the first cylinder 25 via line 37.39. Also, in this state, the cam cylinder 16
The cam lobe 19 for low speed rotation is engaged with the rocker arm 22 (see FIG. 6).

Here, the operating position of the actuator 6 is sent to the ignition control device 7 as an electric signal by a sensor built into the actuator 6.

Based on the signal sent from the actuator 6, the ignition control device 7 uses a built-in rotation limiter to regulate the engine rotation speed so that it does not exceed a predetermined rotation speed.

Therefore, when the actuator 6 is in this state, that is, when the low-speed cam lobe 19 is engaged with the rocker arm 22, even if the accelerator opening is suddenly increased,
The number of revolutions of the engine does not exceed a predetermined number of revolutions.

When the rotation of the engine increases from this state and exceeds a predetermined rotation speed, the solenoid valve 5 is switched by the valve controller 3 to enter a different state compared to the above, and the pipe 37 is connected to the pipe 40. Ru. Along with this, the second
Hydraulic pressure is applied to the cylinder 28, which attempts to move the second piston 27 in the 36 direction in FIG.

However, even if hydraulic pressure is applied to the second cylinder 28 as described above, the trigger lever 32 does not move toward the first piston 2.
As long as the first piston 26, the cam slide fork 29, the cam cylinder 16, etc. are engaged with the narrow groove 34 of the trigger lever 32, their movement is restrained by the trigger lever 32, and the first piston 26, the cam slide fork 29, the cam cylinder 16, etc. do not move.

Thereafter, at the same time as the intake valve 23 is lifted, the trigger lever 32 is slightly rotated by the trigger cam 33 in the direction toward the center of FIG. 4, and the engagement between the trigger lever 32 and the narrow groove 34 is released. Immediately thereafter, the first piston 26 is pushed by the spring 30 and moved in the B direction, and at the same time the narrow groove 34 is displaced from the engagement position with the trigger lever 32.

Subsequently, while the cam engaging portion 22a of the rocker arm 22 is in contact with the base interior θ''2 of the low-speed rotation cam lobe I9, the second piston 27 and the cam slide fork 29
, the cam cylinder 16, etc. are moved in the direction B by the hydraulic pressure applied to the second cylinder 28.

As a result, the rocker arm 22 has a cam lobe 2 for high speed rotation.
0, and the trigger lever 32 is inserted into the lever 35 (see FIG. 3).

In this state, the actuator 6 is in the operating position (first
1 second piston 26, 27 is moving in direction B as shown in FIG.
Based on this sent signal, the ignition control device 7 regulates the upper limit of the engine speed at that time using a built-in rotation limiter.

In addition, when the engine speed decreases from this state, the variable valve timing mechanism is activated and the cam lobe 1 for low speed rotation is activated again.
9 is brought into engagement with the rocker arm 22. Thereafter, the variable valve timing mechanism is operated in a similar manner according to the engine rotation speed, and the cam lobe suitable for the rotation speed at that time engages with the rocker arm 22.

According to the dual valve mechanism, the rotation limiter built into the actuator 6 determines the operating position of the actuator 6, in other words, which of the two cam lobes is engaged with the rocker arm 22. Therefore, if you take this into consideration in advance when designing the cam lobe 19 for low-speed rotation, the valve lift amount can be controlled within a range that does not apply excessive load to the valve system. The cam lobe 20 can be made to the same extent as the high-speed rotation cam lobe 20, and as a result, the output direction during low-speed rotation can be increased as shown in FIG. In addition, in the figure, X indicates the output characteristics of the engine when switching to the low-speed rotation cam lobe I9 in the second embodiment, and Y indicates the engine output characteristic when switching to the high-speed rotation cam lobe 20. Z indicates the output characteristic of the engine when switching to the low-speed rotation cam lobe with a small valve lift a, as explained in the conventional example.

In addition, in the dual embodiment, the cam engaging portion 2 of the rocker arm 22 is controlled by the trigger cam 33 and trigger lever 32.
Cam lobe switching is performed only when 2a is engaged with the inside θ of the cam base, and this is designed to prevent excessive impact force from being applied to the valve mechanism components when switching the cam lobe. .

In addition, in the second embodiment, two types of cam lobes are used, but the present invention is not limited to this, and can also be applied to a case where three or more types of cam lobes are provided and the valve timing is changed in two steps of three or more. Of course, the present invention can also be applied to the case where the valve timing is changed continuously.

In addition, in the above embodiment, as a method of changing the opening/closing timing of the valve according to the engine speed, two types of cam lobes are prepared, and one of them is selectively engaged with the rocker arm according to the engine speed. However, the present invention is not limited to this; for example, as described in Japanese Patent Application No. 6 G-42338, the cam is aligned at a predetermined angle with respect to the cam shaft supporting it. It is also applicable to a method in which the cam can be switched between a mode in which the cam can swing freely within a range and a mode in which the cam is fixed to the camshaft so that it cannot swing.

"Effects of the Invention" As explained above, according to the present invention, in an internal combustion engine equipped with a variable valve timing mechanism that changes the opening and closing timing of an intake valve, an exhaust valve, or both, according to the rotational speed of the internal combustion engine, the valve timing Since a rotation limiter is provided that regulates the maximum rotation speed of the internal combustion engine at each predetermined state switched by the variable valve timing mechanism, when determining each valve lift curve at the design stage, It is only necessary to set the value so that excessive load is not applied to the valve system within the maximum rotation speed range regulated by the rotation limiter. This makes it possible to avoid applying heavy loads. Therefore, the output can be improved compared to the conventional one, especially in the low speed rotation range.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a valve lift curve and acceleration coefficient using a cam lobe for low-speed rotation and high-speed rotation switched by a conventional variable valve timing mechanism, and Fig. 2 to 7 show an example of the present invention. Fig. 2 is an overall system diagram, Fig. 3 is a sectional view of the upper part of the engine showing the variable valve timing mechanism, Fig. 4 is a vertical side view thereof, Fig. 5 is a perspective view of the cam cylinder, and Fig. 6 is a sectional view of the upper part of the engine showing the variable valve timing mechanism. FIG. 7, which is a sectional view showing another state of the variable valve timing mechanism, is an output diagram of the internal combustion engine of the above embodiment. l... Engine body, 3... Valve timing controller, 5... Solenoid valve, 6... Actuator, 7... Ignition control device, 11... ... Norinda head, 12 ... Head cover, I3 ... Camshaft, 19 ... Cam lobe for low speed rotation, 20 - Cam lobe for high speed rotation, 22 ... Rocker arm, 23...Intake valve, 24...Cam switching mechanism, 29...Cam slide fork, 32...Trigger lever, 33...Trigger cam, 36...Oil pump . Figure 1 Figure 2 Figure 4 -ai'q- Figure 6

Claims (1)

[Claims] In an internal combustion engine equipped with a variable valve timing mechanism that changes the opening/closing timing of an intake valve and/or exhaust valve according to the rotational speed of the internal combustion engine, the maximum rotational speed of the internal combustion engine at that time for each predetermined state switched by the variable valve timing mechanism. A valve mechanism for an internal combustion engine, characterized by being provided with a rotation limiter that regulates the rotation of the engine.