JP2004225542A - Continuously variable valve timing mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuously variable valve timing mechanism for improving responsiveness of control, and securing sure follow-up performance of a rocker arm. <P>SOLUTION: This continuously variable valve timing mechanism is constituted so as to move the rocker arm in the axial direction of a camshaft according to an engine speed or a load by opening-closing a valve by pivotally moving an intake/exhaust valve by the rocker arm for rocking by slidingly contacting with a three-dimensional cam formed on the rotating camshaft. The rocker arm 3 is pivotally moved by rotational control of a shaft of a motor 11 threadedly engaging with a rocker shaft 6. Since there is no need to move the three-dimensional cam in the axial direction, a control space is not required, and a degree of freedom of design is also enhanced. Since rotation and the axial directional movement can be separated, the valve timing can be highly accurately changed. Moreover, the responsiveness is improved by quickly performing these controls by rotational control of the shaft of the motor 11. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a continuously variable valve timing mechanism that can change the opening / closing timing of intake / exhaust valves in an internal combustion engine or the like according to the engine speed or load.
[0002]
[Prior art]
In recent years, fossil fuel depletion has been called for, and research on energy saving has been actively conducted in various fields.In internal combustion engines, etc., strict exhaust gas control measures with low fuel consumption while ensuring high output are required. I have. As a method for achieving low fuel consumption, a Miller cycle is attracting attention as an effective means, and a hybrid engine or a stationary engine combining an internal combustion engine and an electric motor has been put to practical use. However, since the compression ratio and the expansion ratio are different, a remarkable reduction in fuel consumption can be obtained at a partial load, but the solution is always expected because the maximum output is reduced in principle. By the way, in order to secure high torque in a wide range of rotation in an internal combustion engine, it is necessary to delay the intake valve closing timing in proportion to the rotation speed. As a method to realize this, a variable valve timing mechanism has been studied, and when the intake valve closing timing is delayed in proportion to the rotation speed and the valve timing is optimally set according to the rotation speed or load, the effective compression ratio can be reduced. An increase in fuel consumption and an increase in volumetric efficiency can achieve both low fuel consumption and high torque.
[0003]
As described above, it has been confirmed that, when the valve lift and the timing are changed in accordance with the load and the engine speed, the expansion of the torque band and the improvement of the fuel efficiency can be expected by improving the volumetric efficiency (see Non-Patent Document 1 below). . Research on a continuously variable valve timing mechanism includes a method of moving a camshaft (see Non-Patent Document 2 below), a method using pneumatics (see Non-Patent Document 3 below), and a method using unequal velocity (see Non-Patent Document 2 below). 4) and a method using an oscillating cam (see Non-Patent Document 5 below), but none of them have reached the practical range yet. Recently, a system in which the valve lift and the camshaft phase are continuously and independently variable has been put to practical use, and the effect of improving fuel efficiency has been shown (see Non-Patent Document 6 below).
[0004]
[Non-patent document 1]
Hidetaka Nohira, Trend of Fuel Efficiency Improvement Technology in Europe, Automotive Technology, vol. 56, 2002.
[Non-patent document 2]
Titolo A MTZ, "Variable valve control from Fit" May 1986, pages 185-188.
[Non-Patent Document 3]
Geringer B, "Calculation and development of an electrically and and hydraulically controlled variable available timing for S.Eng., 4th International, 7th International, 7th International.
[Non-patent document 4]
Nohara et al., JSAE Paper 200005493.
[Non-Patent Document 5]
Yamada et al., JSAE Paper20015065.
[Non-Patent Document 6]
Manabu Kumano, "BMW's" Valvetronic "System," CAR GRAPHIC August, 2001.
[Patent Document 1]
Japanese Patent Application No. 11-254449 (JP-A-2001-82117)
[0005]
[Problems to be solved by the invention]
However, in these conventional continuously variable valve timing mechanisms, the intake / exhaust valve is positioned at a low lift position, a medium lift position, and a high lift position on the three-dimensional cam by moving the camshaft itself in the axial direction. And the lift of the intake / exhaust valve with respect to the rotation angle of the camshaft, that is, the timing of opening and closing the valve, may be disadvantageously increased. The degree of freedom of design is limited due to the possibility of being hindered by the design, and it is difficult to design an ideal cam. In addition, when the cam is used in a multi-cylinder engine, any one of the valves is operated while the camshaft is axially moved. However, since the power unit is in operation, a certain amount of power is required for the movement of the camshaft, and the power unit is inevitably increased in size, and its control system is complicated. In addition, the lift of these conventional three-dimensional cams does not change its apex position in either the low lift or the high lift as shown in the lift curve of FIG. Causes malfunction. Therefore, a camshaft phase control device using a hydraulic pressure or the like is required separately.
[0006]
For this reason, the inventor of the present invention has a configuration in which the rocker arm is moved in the axial direction of the camshaft according to the engine speed or load, instead of moving the camshaft, although the detailed principle and the like will be described later. A novel and innovative variable valve timing mechanism has been proposed (see Patent Document 1). As a result, the three-dimensional cam having the lift surface itself does not move, so that the required control space can be reduced, the degree of freedom in design is high, the rotation and the axial movement can be separated, and the valve timing can be changed with high accuracy. The volume efficiency has been improved over a wide range of revolutions to secure a high torque range, and the fuel efficiency has been improved by optimally setting the valve timing according to the load.
[0007]
The present invention further improves the continuously variable valve timing mechanism proposed by the inventor of the present invention, so that the control space is less restricted, the load on the control system is reduced even when adopted in a multi-cylinder engine, and the precision is improved. It is an object of the present invention to provide a continuously variable valve timing mechanism which can change the valve timing, and further, can improve control responsiveness and ensure reliable followability of the rocker arm.
[0008]
[Means for Solving the Problems]
For this reason, the present invention is a valve timing mechanism in which an intake / exhaust valve pivots by a rocker arm that swings by slidingly contacting a three-dimensional cam formed on a rotating camshaft. In a continuously variable valve timing mechanism configured to move in the axial direction of a camshaft according to an engine speed or a load, the axial movement of the rocker arm is controlled by rotation control of a motor shaft screwed to the rocker shaft. It is characterized by comprising. Further, the present invention is characterized in that the three-dimensional cam shape is provided with a phase that is twisted so as to change the valve lift linearly and to change the valve opening / closing timing along the cam axis direction. Further, the present invention is characterized in that the valve lift amount and the valve opening / closing timing are changed with different characteristics between intake and exhaust. The present invention also provides a rocker arm having a tappet interposed between the rocker arm and a three-dimensional cam and slidably contacting the three-dimensional cam, and a spherical bearing for supporting the tappet with a spherical surface. Of the three-dimensional cams are installed at an inclination angle of about 1/2 of the inclination angle of the three-dimensional cam, and these are used as means for solving the problem.
[0009]
Embodiment
Hereinafter, an embodiment of a continuously variable valve timing mechanism according to the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 9, the basic configuration of the present invention is that the intake / exhaust valve 5 is pivoted by the rocker arm 3 which swings by slidingly contacting the three-dimensional cam 1 formed on the rotating camshaft 12. A continuously variable valve timing mechanism for moving the rocker arm 3 in the axial direction of the camshaft 12 according to the engine speed or the load. Is performed by rotation control of a shaft of a motor 11 screwed to a rocker shaft (rocker arm shaft) 6.
[0010]
Hereinafter, the continuously variable valve timing mechanism of the present invention will be described in detail, including a description of principles and engine performance based on experimental results. This system is applied to a 4-cylinder gasoline engine, and a prototype of a simple variable valve timing mechanism having a simple structure according to the present invention using a combination of a three-dimensional cam, a swinging tappet, and a moving rocker arm is mounted on a trial basis. It is clear.
[0011]
<Concept of continuously variable valve timing mechanism>
In order to obtain high performance by operating the engine under the optimal conditions commensurate with the stroke volume, a continuously variable intake / exhaust valve timing mechanism that changes the valve timing and the lift amount according to the operating conditions such as the rotation speed and load is effective. It is one of the means. In the low-speed range, the intake valve closes early to prevent backflow of intake air, and in the high-speed range, the intake valve is closed slowly to increase the opening time area of the suction valve section to increase intake air due to inertia. Not only is the volume efficiency increased and the torque band is expanded, but also the effective compression ratio is increased and the thermal efficiency is improved. 1 includes a basic structure proposed by the present inventor as Patent Document 1 in order to realize these, and a continuous suction unit which is a combination of a three-dimensional cam 1 and a movable rocker arm 3 is shown in FIG. This is an exhaust variable valve timing mechanism.
[0012]
<Operation principle>
The mechanism comprises a three-dimensional cam 1 formed on a camshaft 12, a swing tappet (pillow) 2 that makes linear contact along the cam surface, and a movable rocker arm 3 having a spherical bearing 4 for receiving the same. You. The movable rocker arm 3 is supported by a rocker shaft 6. The free end of the movable rocker arm 3 is abutted to press the head of the valve 5 urged back by the valve spring 7. The shape of the three-dimensional cam 1 is given a twisted phase so that the valve lift changes linearly and the valve opening / closing timing can be changed along the camshaft 12 direction. This provides a valve time area and an optimal valve timing corresponding to the number of revolutions.
[0013]
FIG. 2 shows variable valve timing by the movable rocker arm 3. The movable rocker arm 3 is arranged parallel to the camshaft 12, and the swinging tappet 2 has a low cam position (a) at a low lift, a medium cam position (b) at a medium lift, and a high cam height at a high lift. The contact is made at the position (c). As described above, if the movable rocker arm 3 is moved in parallel with the three-dimensional camshaft 12 in accordance with the load and the number of revolutions of the engine, the lift and the phase as indicated by the arrow of the valve lift curve shown in FIG. And can be controlled continuously. The opening timing of the intake valve is set to be advanced as the lift is increased, and the valve closing timing is set to be delayed as the lift is advanced. By making such a change, the high torque range is expanded from a low speed to a high speed. In addition, when the exhaust valve is opened in a low speed range and at a low load, the valve opening timing is delayed at a low lift to increase the expansion work in the cylinder and increase the work on the piston. On the other hand, at the time of a high speed range and a high load, the valve is advanced by a high lift, the valve opening time area is increased, and the exhaust is sufficiently performed, thereby improving the exhaust efficiency. When the exhaust valve is closed at low speeds and low load, the valve close timing is advanced with a low lift to reduce overlap, improve idle stability and reduce backflow of the intake air-fuel mixture, and improve fuel efficiency. Can be. On the other hand, in a high-speed range and a high load, the valve closing timing is delayed at a high lift, the overlap is increased, and the exhaust is sufficiently performed to improve the exhaust efficiency. FIG. 4 is a valve timing diagram in which the intake and exhaust valve timing is set to be continuously variable over a wide range.
[0014]
<Valve lift and acceleration characteristics>
FIG. 5 shows a valve lift curve and an acceleration curve when the valve lift amount is changed. As shown in the figure, the curve a is the maximum lift curve and acceleration of the intake valve, and the curve b is the minimum lift curve and acceleration. Similarly, curve c is the maximum lift curve and acceleration of the exhaust valve, and curve d is the minimum lift curve and acceleration. In designing a low lift cam curve, if the number of swings is set to be one in one round by entering the inside of the high lift cam curve, the angular acceleration change of the swing tappet will be small, and the cam durability will be reduced. It is advantageous for performance and reliability.
[0015]
<Prototype continuously variable intake and exhaust valve timing mechanism>
The specifications of the gasoline engine used in the experiment are shown below.
4-cylinder, displacement 1,795 cc, borestoke 82 × 85, compression ratio 11.5, EFI fuel supply system, DOHC 4 type valve, Pent proof type combustion chamber.
[0016]
FIG. 6 shows valve train components constituting the valve timing mechanism. These components constitute a valve train by a three-dimensional cam, a swing tappet in linear contact with the three-dimensional cam, and a rocker arm that transmits reciprocating motion to the valve in conjunction with the tappet. The prototype camshaft is manufactured by cutting, and the material is selected SCM415 in consideration of the severe operating environment and workability of the camshaft. After cutting, the entire surface is carburized and quenched to add surface hardness. did. In order to avoid stress concentration due to thermal strain in a high temperature environment, the three-dimensional cam surface was polished. When the tappet spherical bearing is provided parallel to the rocker shaft, there is a risk that the tappet may come off when a force is applied from the cam to the tappet due to a small contact area of the bearing portion.
[0017]
Therefore, as clearly shown in FIGS. 1 and 2, the spherical bearing 4 of the swing tappet 2 of the movable rocker arm 3 is given a 12-degree inclination angle. This inclination angle is set to about 1/2 of the maximum inclination angle of the three-dimensional cam 1, and when a load is applied from the three-dimensional cam 1 to the swing tappet 2, it can be sufficiently received by the tappet spherical bearing 4. , The swing tappet 2 is less likely to come off. Further, the problem of interference between the swing tappet 2 and the movable rocker arm 3 was solved.
[0018]
FIG. 7 shows the basic configuration of a continuously variable valve timing system. A rocker shaft 6 penetrates through a support shaft hole of the moving rocker arm 3 for intake and exhaust, and an elliptical hole is formed in the rocker arm 3 to allow the rocker to swing. Fix it. Therefore, when the rocker shaft 6 is moved, the rocker arm 3 can move in parallel with the three-dimensional cam shaft 12 in a swinging motion. This series of operations constitutes a continuously variable valve timing. As these mechanical components, a continuously variable valve timing can be constituted by a simple mechanism having a very small number of components, including the three-dimensional cam 1, the swing tappet 2, and the movable rocker arm 3. FIG. 8 shows a variable valve timing mechanism assembled to the cylinder head.
[0019]
<Variable valve timing control by DC motor>
・ Variable valve timing control method
FIG. 9 shows a control method of the variable valve timing mechanism proposed in the present invention. The control method is as follows. The male screw 8 fixed to the rotating shaft of the geared DC motor 11 is screwed into the female screw in the rocker shaft 6, and the motor 11 is rotated so that the rocker shaft 6 enters and exits in the axial direction, and is connected thereto. The movable rocker arm 3 is displaced in parallel with the cam shaft. When the geared DC motor 11 is rotated in the counterclockwise direction, the male screw 8 fixed to the motor output shaft rotates in the female screw of the rocker shaft 6 and a thrust in the XL direction acts to move the movable rocker arm 3. . When the geared DC motor 11 is rotated clockwise, the rocker shaft 6 is displaced in the XR direction. The rocker shaft 6 is provided with a groove J, into which a pin P is inserted from the outer casing to restrain the rocker shaft 6 from rotating during movement.
[0020]
FIG. 10 shows the periphery of the control geared motor 11 mounted on the engine. While the valve is operating, a large force acts on the rocker arm to hinder the movement of the rocker arm, and especially when the rocker arm is moved by the motor in a high lift direction, a large torque is required for the motor. However, this mechanism selects a DC motor that is easy to control and can obtain a large torque at startup, selects a geared type motor with a large reduction ratio (about 75), and uses a screw type variable mechanism. Thus, the variable control can be performed quickly, easily and accurately even during the operation of the valve with a large load.
[0021]
<Variable valve timing control circuit>
FIG. 11 shows a block diagram of an example of a DC motor drive circuit used in this mechanism. The motor specification is a rated 12V geared type, the number of revolutions at no load is 394 rpm, the torque at the maximum efficiency after deceleration is 0.735 N · m (at 4.054 A / 330 rpm), and the current when the motor is locked is 20 A. FIG. 12 shows an example of a motor control circuit based on an H-bridge using a MOS-FET. In the figure, in the case of normal rotation, AD of the MOS-FET is turned ON and BC is turned OFF, and in the case of reverse rotation, AD is turned OFF and BC is turned ON. In the case of a brake, if BD is turned ON and AC is turned OFF, both terminals of the motor are short-circuited to ground. Four sets of diodes were connected to each MOS-FET for output protection. A photocoupler was connected to the H-bridge input terminal to reduce switching noise.
[0022]
For detecting the movement of the rocker arm, a non-contact displacement meter 9 (see FIG. 9, the same applies hereinafter) in which a coil is wound around a resin bobbin is inserted into the rocker shaft 6, and the inductance change is measured using a frequency F-voltage V converter. The displacement of the rocker arm 3 was measured by measuring the output voltage value. The drive control of the DC motor is performed by a rotation angle and rotation direction control signal transmitted from the PC. When the motor control circuit receives the rotation start signal from the personal computer, the motor control logic circuit switches the FET, and the motor rotates. When the rocker arm moves, the voltage output from the FV transducer changes. The output voltage is input to the microcomputer via the A / D converter, is compared with the set voltage transmitted from the personal computer, and when the set voltage is reached, a stop (braking) instruction is transmitted to the motor. This circuit can perform forward / reverse rotation and brake control, and the braking ability under no load condition stops at a screw angle of about 30 degrees after transmitting the braking signal.
[0023]
<Motoring experiment>
The intake air amount is affected by the intake valve opening time area represented by the lift amount and the opening time of the intake valve. Therefore, in the three-dimensional cam, at a low speed, the intake start timing is delayed, the valve lift is reduced, and the closing timing is set earlier. At high speeds, the suction start timing was earlier, the valve lift was higher, and the closing timing was set later. If the intake air temperature is constant, the maximum pressure in the cylinder increases in proportion to the intake air amount. Therefore, the optimum valve timing at each rotation speed can be obtained by measuring the maximum cylinder pressure. Therefore, the closing timing of the intake valve was changed under a constant rotation speed by the motoring operation, and the pressure in the cylinder at each valve closing timing was measured. Then, the intake valve closing timing at which the maximum pressure in the cylinder becomes maximum was determined. FIG. 13 shows the maximum cylinder pressure Pmax with respect to the intake valve closing timing at each rotation speed, and the maximum valve lift at that time. As shown in the figure, there is an intake valve closing timing at which the maximum pressure in the cylinder becomes maximum at each rotation speed. This is the optimum intake valve closing timing at that engine speed. Also, it can be seen that the intake valve closing timing is delayed and the lift amount is increased as the speed is increased.
[0024]
<Ignition driving experiment>
In FIG. 13, the optimal intake valve closing timing for each rotation speed was determined. In this experiment, the torque caused by the ignition operation is measured, and the intake valve closing timing at which the shaft average effective pressure at each engine speed becomes maximum is obtained. FIG. 14 shows the shaft average effective pressure BMEP when the valve timing is changed for each engine speed when the throttle is fully open. At each rotation speed, the intake valve closing timing indicating the maximum value of the shaft average effective pressure was almost the same value as the optimal intake valve closing timing indicating the maximum value of the maximum cylinder pressure in the motoring experiment shown in FIG. .
[0025]
FIG. 15 shows the maximum shaft average effective pressure and the net fuel consumption rate with respect to the engine speed, the maximum valve lift at that time, and the optimal valve closing timing. In the experiment of the normal engine, the rotation was changed while the cam phase at which the optimum valve timing was obtained was fixed at 3500 rpm. Compared with the normal engine, the shaft average effective pressure of the prototype engine according to the present invention improved at lower speeds at 2500 rpm or less, and showed an improvement effect of about 17% at 1000 rpm. In the high-speed range, the output increased as the speed became higher at 4000 rpm, and the output was improved by about 4% at 5000 rpm. The net fuel consumption rate was improved between 2000 rpm and 3000 rpm compared to the normal engine, and a fuel efficiency improvement effect of about 7.5% was shown at 2500 rpm. As for the intake valve timing, as the engine speed increases, the optimal valve closing timing is delayed, and the maximum lift amount also increases.
[0026]
From these results, it can be seen that by setting the optimal valve timing for the engine speed, fuel efficiency is improved in the middle and low speed range, and output performance superior to the normal engine over a wide rotation range from low speed to high speed. Demonstrated by experiments. As described above, we proposed and prototyped a simple and continuously variable valve timing mechanism with a combination of a three-dimensional cam and a moving rocker arm, applied it to a four-cylinder gasoline engine, and conducted motoring and ignition driving experiments. The following results were obtained.
[0027]
(1) Compared to the normal engine, the improvement in fuel efficiency in the middle to low speed range was recognized, and the fuel consumption rate was 221.7 g / (kw · h) at 2500 rpm, and an extremely high fuel efficiency reduction effect was realized.
(2) It has been demonstrated that the output performance is superior to that of a normal engine over a wide rotation range from a low speed range to a high speed range.
(3) There is an optimal intake valve closing timing indicating the maximum value of the maximum pressure in the cylinder from the motoring operation.
(4) In the ignition operation, the maximum shaft average effective pressure was obtained at the optimal intake valve closing timing at each engine speed.
(5) The optimum intake valve closing timing obtained by the maximum cylinder maximum pressure in the motoring operation and the optimal intake valve closing timing indicating the maximum value of the shaft average effective pressure in the ignition operation showed almost the same value.
(6) The prototype valve timing lift mechanism using the combination of the three-dimensional cam, the swing tappet, and the movable rocker arm demonstrated stable operation with an extremely simple structure.
(7) The variable valve timing control system in which the rocker arm is displaced by rotating the screw by the DC motor was able to perform high responsiveness and stable control.
(8) Since the spherical bearing is installed at an inclination angle of about 1/2 of the inclination angle of the three-dimensional cam, even if a load from the three-dimensional cam is applied to the swing tappet, it can be sufficiently applied by the tappet spherical bearing. The rocking tappet does not interfere with the moving rocker arm, and the rocking tappet does not easily come off.Simple structure enables reliable control of the rocker arm and operation with stable control It was proved that it was.
[0028]
The embodiments of the present invention have been described above. However, within the scope of the present invention, the shape of the three-dimensional cam (twisted shape, that is, the three-dimensional cam that determines the relationship between the axial stroke of the movable rocker arm and the valve lift). , Rocking tappet shape, moving rocker arm shape and related configuration between them, rocker shaft shape and rocker arm pivotal support to the shaft, motor type, motor shaft and rocker shaft Screw type, rotation control type with rocker shaft axial movement according to engine speed or load by motor, rocking tappet on a spherical bearing, and spherical bearing on rocker arm Can be appropriately selected. In addition, the specifications of the experimental apparatus are illustrative, and should not be construed as limiting.
[0029]
【The invention's effect】
As described above in detail, the present invention employs a valve timing mechanism in which a suction / exhaust valve pivots by a rocker arm that swings in sliding contact with a three-dimensional cam formed on a rotating camshaft to open and close. In the continuously variable valve timing mechanism configured to move the rocker arm in the axial direction of the camshaft according to the engine speed or the load, a motor shaft for screwing the axial movement of the rocker arm to the rocker shaft is provided. Since the three-dimensional cam does not need to be moved in the axial direction, it is not necessary to move the three-dimensional cam in the axial direction, so there is no need for control space, and the degree of freedom in design is increased. In addition, rotation and axial movement are separated. The valve timing can be changed with high accuracy. In addition, these controls are quickly performed by the rotation control of the motor shaft, and the responsiveness is improved.
[0030]
In addition, when the three-dimensional cam shape is provided with a valve lift linearly changing along the cam axis direction and a phase twisted so as to change the valve opening / closing timing, the lift and the phase are continuous. High torque range from low speed to high speed is expanded by controlling and changing the valve opening timing to be advanced as the lift increases and the valve closing timing to be delayed as the lift is advanced. . Further, when the valve lift amount and the valve opening / closing timing are changed with different characteristics between the intake and the exhaust, the closing timing of the intake valve is delayed in proportion to the rotation speed, and the volumetric efficiency is widened. Fuel economy can be improved by improving the rotation range to secure a high torque range by expanding it, or by setting the intake valve closing timing optimally according to the load. Further, by increasing the opening timing of the exhaust valve in proportion to the increase in the rotation speed and the load, the exhaust efficiency is improved, and the pressure is effectively applied to the piston, so that the fuel efficiency can be improved.
[0031]
Still further, a tappet interposed between the rocker arm and the three-dimensional cam and slidably contacting the three-dimensional cam, and a spherical bearing for supporting the tappet with a spherical surface are provided on the rocker arm, and the spherical bearing is provided on the rocker arm. In the case where the three-dimensional cam is installed at an inclination angle of about 1/2 of the inclination angle of the three-dimensional cam, even if a load from the three-dimensional cam is applied to the swing tappet, it can be sufficiently received by the tappet spherical bearing. In addition, there is no problem of interference between the swing tappet and the movable rocker arm, the swing tappet is hardly disengaged, and the simple structure enables the rocker arm to reliably follow and maintain stable control for operation. Thus, there is little restriction on the control space, there is little burden on the control system even when adopted in a multi-cylinder engine, and it is possible to change the valve timing with high accuracy, as well as to improve control responsiveness. Provided is a continuously variable valve timing mechanism capable of ensuring the followability of a rocker arm.
[Brief description of the drawings]
FIG. 1 is a view showing one embodiment of a variable valve timing mechanism of the present invention, and is an explanatory view showing a behavior of a swing tappet on a three-dimensional cam.
FIG. 2 is an explanatory diagram of a variable valve timing showing a behavior of a swing tappet on a three-dimensional cam when the movable rocker arm is moved.
FIG. 3 is a valve lift curve diagram, which is a comparison diagram between the present invention and a conventional one.
FIG. 4 is a valve timing diagram of the variable valve timing mechanism of the present invention.
FIG. 5 is a diagram showing a valve lift curve and an acceleration curve accompanying a change in the valve lift amount.
FIG. 6 shows the valve operating system components of the variable valve timing mechanism.
FIG. 7 is a basic component diagram.
FIG. 8 shows a variable valve timing mechanism assembled to the cylinder head.
FIG. 9 is an explanatory diagram showing a method of controlling valve timing.
FIG. 10 is a diagram showing the periphery of a control geared motor mounted on the engine.
FIG. 11 is a block diagram of a DC motor drive circuit.
FIG. 12 shows a motor control circuit using an H-bridge.
FIG. 13 is a diagram showing the maximum pressure in the cylinder with respect to the intake valve closing timing for each rotation speed and the maximum valve lift at that time.
FIG. 14 is a diagram showing the shaft average effective pressure when the valve timing is changed for each engine speed when the throttle is fully opened.
FIG. 15 is a diagram showing a maximum shaft average effective pressure and a net fuel consumption rate with respect to an engine speed, a maximum valve lift amount at that time, and an optimal valve closing timing.
[Explanation of symbols]
1 3D cam
2 Swing tappet
3 Moving rocker arm
4 Spherical bearing
5 Intake and exhaust valves
6 Rocker shaft (rocker arm axis)
7 Valve spring
8 Screw
9 coils
10 pin
11 DC motor
12 3D camshaft

Claims (4)

A valve timing mechanism in which an intake / exhaust valve pivots by a rocker arm that swings by slidingly contacting a three-dimensional cam formed on a rotating camshaft, wherein the rocker arm is driven by an engine speed or a load. A continuously variable valve timing mechanism configured to move the rocker arm in the axial direction of the cam shaft in response to the rotation of a motor shaft screwed to the rocker shaft. Continuously variable valve timing mechanism. 2. The three-dimensional cam shape according to claim 1, wherein the valve lift is linearly changed along a cam axis direction, and a phase twisted so as to change a valve opening / closing timing is provided. 3. Continuously variable valve timing mechanism. 3. The continuously variable valve timing mechanism according to claim 2, wherein the valve lift amount and the valve opening / closing timing are changed with different characteristics between intake and exhaust. A tappet interposed between the rocker arm and the three-dimensional cam and slidably in contact with the three-dimensional cam, and a spherical bearing for supporting the tappet with a spherical surface are provided on the rocker arm, and the spherical bearing is provided on the three-dimensional cam. The continuously variable valve timing mechanism according to any one of claims 1 to 3, wherein the tilt angle is set to be approximately 1/2 of the tilt angle of (i).

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