JPH0315765Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a variable valve timing device for an internal combustion engine, and more specifically to a valve operating type in which two types of valve operating cams are selectively operated for one on-off valve (intake valve or exhaust valve). The present invention relates to a variable valve timing device for an internal combustion engine, which operates smoothly, is highly durable, and has no fear of generating blowback noise in an intake system.

In order to operate with high efficiency in both high and low rotation ranges, a valve train for an internal combustion engine has been developed that switches between two types of valve train cams for one on-off valve. A conventional valve train of this type as described in Publication No. 26485 is
When switching two types of valve train cams arranged on the same axis to one rocker arm and operating them, one of the valve train cams is forced to face the rocker arm without considering the phases of the two types. ,
When one valve train cam moves, the other valve train interferes with the rocker arm, or when one valve train cam is lifting the on-off valve, the valve train cam moves and the other valve train cam interferes with the locker arm. When the base diameter portion of the valve drive cam faces the rocker arm, the valve suddenly closes, causing damage or wear to the valve body or valve seat. Furthermore, the intake valve opens when the internal cylinder pressure of the engine is higher than atmospheric pressure.
When the air inside the cylinder flows back into the intake system as pressure waves, problems such as extremely unpleasant blowback noise occur in the intake system.

Both of the above problems are caused by moving the two types of valve train cams without considering their phases, so an attempt was made to electrically detect the phase of the valve train cams and synchronize the movement timing. However,
Since the solenoid valve opens and closes the working fluid passage for the movement of the valve cam, the response delay of the solenoid valve to the valve opening timing tolerance time and variations in the product accuracy of the solenoid valve have a large effect, resulting in low speed It is difficult to establish a system over a wide rotation range from low to high speed.

In addition, to improve the response of a solenoid valve, it is required to place the solenoid valve near the cylinder, but the vicinity of the cylinder is high temperature and has large vibrations, which significantly reduces the durability of the solenoid valve. . moreover,
It was necessary to provide a high-performance solenoid valve for each cylinder, which caused problems such as being extremely uneconomical.

Furthermore, a variable valve timing mechanism that includes a selective switching device for each on-off valve, such as the variable valve timing mechanism described in JP-A No. 58-91317, requires a large number of parts and requires a significant increase in installation space. However, there is a problem in that it is difficult to implement this method in a multi-cylinder internal combustion engine in which an intake valve and an exhaust valve as opening/closing valves are disposed very close to each other.

The purpose of the present invention is to provide a variable valve timing device for an internal combustion engine that eliminates all of the above-mentioned problems. A cam with a plurality of ridges provided on the same axis, an actuator that moves the cam in the axial direction using fluid pressure, and is synchronized with the rotation of the cam, and all of the cams contact the rocker arm at the base diameter part. A feature of the present invention is that the object is achieved by including a fluid pressure supply/discharge control means for supplying/discharging fluid pressure to/from the actuator only when the actuator is in the position.

Embodiments of the apparatus of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the device of the present invention in a longitudinal sectional side view, and FIG. 2 shows a timing valve portion and an exhaust valve valve operating cam portion in a longitudinal sectional front view. A cam unit 2 spline-fitted to the camshaft 1 can freely switch between two types of valve drive cams 4 and 5, which can be switched to a rocker arm 3 for opening and closing intake valves, and a rocker arm 6 for opening and closing exhaust valves. Two types of valve drive cams 7 and 8,
It has a circumferential groove 10 that engages a fork 9 for moving the cam unit 2 in the axial direction, and a circumferential groove 12 that engages a bracket 11 for supporting the camshaft. The cam unit 2 is provided for each cylinder of the internal combustion engine. The fork 9 is fixed to a rod member 13 parallel to the camshaft 1 using a pin 14. The rod member 13 is attached to the bracket 11.
A piston 16 inserted into a cylindrical portion 15 formed in
A control shaft portion 19 is provided protruding from the center of the piston 16 to be inserted into a hole 18 of an actuator 17 formed in the upper part of the bracket 11. The actuator 17 is provided with valve holes 20 and 21 whose axes are orthogonal to the hole 18. The valve hole 20 is a valve hole for the main valve 22, and the valve hole 20 is a valve hole for the main valve 22.
1 is a valve hole for the timing valve 23. The control shaft portion 19 is provided with circumferential grooves 24 and 25 at its base portion near the piston 16 and at its tip portion, respectively. The circumferential grooves 24 and 25 are the balls 2 that are sunk into the valve hole 20.
6 is a groove in which a part of the ball 26 is indented, and the indentation of the ball 26 determines the maximum position of the axial movement of the rod member 13, and the ball 26 is moved only while the rod member 13 moves between the limit positions as shown in FIG. As shown in the circumferential groove 2
4.25 outside. The main valve 22 and the timing valve 23 are biased by springs 27 and 28, respectively, to close the valve holes 20 and 21. As shown in the enlarged longitudinal cross-sectional view in FIG.
8 to form a fluid passage a.

On the other hand, the main valve 22 and the timing valve 2
As shown in the enlarged horizontal sectional view of FIG. 5, the shaft portion 3 has a cross-section shaft and forms a fluid passage b. The valve hole 21 that is opened and closed by the timing valve 23 forms a first path of a fluid pressure supply path that moves the rod member 13 from the two extreme stop positions, and the timing valve 23 that opens and closes this first path is It is opened and closed by a timing cam 29 formed on the cam unit 2. Further, the valve hole 20 that is opened and closed by the main valve 22 forms a second path that opens when the rod member is at an intermediate position between the two extremes. The first system path and the second system constitute a fluid pressure supply device.

The first and second systems communicate with each other in an air chamber 30 of the actuator 17, and this air chamber 30 communicates with a pipe 32 connected to a high-pressure tank 31, and a solenoid valve 33 for switching supply and exhaust pressure is installed in the middle of this pipe. is provided. The solenoid valve 33 is switched open and closed by a signal from a control unit 34, and the control unit 34 also receives detection signals such as engine speed, engine load, accelerator pedal on/off, clutch pedal on/off, vehicle speed, exhaust brake signal, etc. A signal resulting from the input, comparison, and calculation is output to the electromagnetic valve 33.

In the figure, reference numeral 35 is a compression coil spring acting on the rod member 13, 36 is an air passage, and 37 is an exhaust valve stem.

In the device of the present invention having the above-mentioned configuration, the solenoid valve 33 is switched in response to a signal from the control unit 34, and the camshaft 1 is operated while the high-pressure fluid (for example, air) from the high-pressure tank 31 reaches the air chamber 30. When the timing cam 29 pushes up the timing valve 23 due to rotation, the high pressure air in the air chamber 30 enters the fluid passage a in the hole 18 through the fluid passage b in the valve hole 21 and pushes the piston 16.

When the piston 16 is pushed, the rod member 13, of which the piston is a part, moves to the left from the state shown in FIG. 1 against the compression coil spring 35.

In the state shown in FIG. 1, the ball 26 is attached to the rod member 1.
3, and holds the rod member 13 at one extreme position. Now, when the rod member 13 is moved to the left, The ball 26 is pushed up into the valve hole 20 and the third
As shown in the figure, it contacts the peripheral surface of the control shaft portion 19 and pushes up the main valve 22 against the spring 27. When the main valve 22 is pushed up, the high pressure air in the air chamber 30 enters the fluid passage b of the valve hole 20, reaches the inside of the cylindrical part 15 through the ventilation passage 36, and pushes the piston 16. When the main valve 22 is opened, the rod member 13 having the piston 16 pushed by the high-pressure air eventually reaches the other extreme position, and at this time the ball 26 sinks into the circumferential groove 25 to prevent the rod member 13 from moving.
During this time, the main valve 22 is in the open state, but the timing cam 29 returns to the state in which it does not push up the timing valve 23 before the ball 26 enters the circumferential groove 25. This indicates that the high pressure pushing the piston 16 Air is supplied into the cylindrical portion 15 by opening the main valve 22.

The rocker arm 3 is moved by the movement of the rod member 13.
The valve train cam facing the rocker arm 6 changes from 4 to 5, and the valve train cam facing the rocker arm 6 changes from 7 to 8. That is, if the valve train cams 4 and 7 have a profile that makes the intake and exhaust timing in the most desirable state at low speeds, and the valve train cams 5 and 8 have profiles that make the intake and exhaust timing in the most desirable state at high speeds. For example, the timing at which the electromagnetic valve 33 is switched to the state of providing high-pressure air to the air chamber 30 is while the switched state is continued when the valve operating cam is switched.

Next, in order to return to the state shown in FIG. 1, that is, the state in which the valve drive cam 4 faces the rocker arm 3 and the valve drive cam 7 faces the rocker arm 6, the solenoid valve 33 is first switched by a signal from the control unit 34. , the inside of the air chamber 30 becomes atmospheric pressure. When the timing valve 23 is pushed up by the timing cam 29 with the air chamber 30 at atmospheric pressure, the cylindrical portion 1
5, the high pressure air that was pushing the piston 16 flows from the fluid passage a of the hole 18 to the fluid passage b of the valve hole 21.
The air flows through the air chamber 30 and is further radiated to the outside from the solenoid valve 33. That is, since the high-pressure air that had been pushing the piston 16 disappears, the rod member 13 is pushed by the compression coil spring 35 and moves, pushing the ball 26 that had fallen into the circumferential groove 25 out of the circumferential groove. After opening the valve 22, it stops at a position where the circumferential groove 24 faces the ball 26. In this state, the ball 26 is recessed into the circumferential groove 24, and unless the electromagnetic valve 33 is switched, the valve drive cam 4 operates on the rocker arm 3, and the valve drive cam 7 operates on the rocker arm 6. It can be done.

As described above, two types of valve drive cams are switched and used, and the switching operation is performed by the first system having a timing valve that opens and closes in synchronization with the rotational phase of the camshaft 1, and the first system having a timing valve that opens and closes in synchronization with the rotational phase of the camshaft 1. The fluid pressure supply system consists of a second system with a main valve that opens and closes in synchronization with the axial movement, and the valve operating cam is switched by a solenoid valve in response to a signal from the control unit. There is no risk of interference between the rocker arm and the two types of valve drive cams, and it is possible to always have the valve drive cam facing the rocker arm at the base diameter portion.

In the second embodiment, in which the actuator 17 portion is shown in a vertical side view in FIG. When the valve holes 21 and 20 are opened, high pressure air in the air chamber 30 flows from the valve hole 21 to the hole 4 that communicates the valve holes 21 and 20.
The difference from the first embodiment is that the air enters the valve hole 20 through the air passage 36, reaches the cylindrical portion 15 through the air passage 36, and pushes the piston 16.

Note that in order to return the rod member 13 to the state shown in FIG. 6, the solenoid valve (indicated by reference numeral 33 in FIG. 1) is switched to bring the inside of the air chamber 30 to atmospheric pressure. Control unit 3 shown inside
According to the signal from 4.

The third embodiment, shown in FIG. 7 as a vertical side view of the actuator 17, and in FIG. 8 as a sectional view taken in the direction of the arrows in FIG. A branch path 42 from the ventilation path 41 is bored in the center of the camshaft 1.
This embodiment differs from the first embodiment in that the valve operating cam is switched in synchronization with the rotational phase of the camshaft by supplying and discharging the valve each time it matches the groove 43 on the bracket 11 side. It is assumed that both the ventilation path 41 and the air chamber 30 can be supplied and exhausted by the solenoid valve 33 shown in FIG.

In the fourth embodiment, the actuator 17 portion is also shown in a vertical sectional view in FIG. In this example, the notch 45 provided in the control shaft portion 19 of the rod member 13 is actuated by the piston 16 in the rod member 15 as a synchronization means based on the rotational phase of the camshaft 1. or 4
Bushing rod 4 with pin 47 coming out from 6
8, and this bushing rod pushes up the check ball valve 44 to supply and exhaust high pressure air acting on the piston 16, which is different from the previous embodiments.

As is clear from the above explanation, the device of the present invention can switch the valve train cam in complete synchronization with the rotational phase and axial movement of the camshaft, so that the valve train cam and the locker arm can be It has excellent advantages such as being able to avoid interference and withstanding long-term use without the risk of noise generation. Further, in the device of the present invention, all of the cams that are synchronized with the rotation of the cam and act on each on-off valve provided for each cylinder via the rocker arm are located at a position where the base diameter portion contacts the rocker arm. Since it is equipped with a fluid pressure supply/discharge control means that supplies and discharges fluid pressure to the actuator only when the actuator is in use, all on-off valves provided for each cylinder can be moved simultaneously by the single fluid pressure supply/discharge control means. This has the advantage of being optimal for multi-cylinder internal combustion engines in which a plurality of on-off valves are arranged very close to each other.

[Brief explanation of drawings]

Fig. 1 is a vertical side view showing the first embodiment of the device of the present invention, Fig. 2 is a longitudinal front view showing the timing valve and the valve operating cam portion for the exhaust valve, and Fig. 3 is the actuator portion during the switching operation. Fig. 4 is an enlarged longitudinal sectional front view of the control shaft section;
Fig. 5 is an enlarged horizontal sectional view showing the shafts of the main valve and timing valve, Fig. 6 is a longitudinal sectional side view showing the actuator part of the second embodiment, and Fig. 7 is the actuator part and camshaft of the third embodiment. 8 is a vertical sectional view showing the structure of FIG. 7, FIG. 9 is a vertical sectional side view showing the actuator portion of the fourth embodiment, and FIG. It is a diagram. 1...Cam shaft, 2...Cam unit, 3, 6...
...Lotsuka arm, 4, 5, 7, 8... Valve cam,
9...fork, 10, 12...circumferential groove, 13...
Rod member, 17... Actuator, 18... Hole,
19... Control shaft portion, 20, 21... Valve hole, 22...
...Main valve, 23...Timing valve, 2
4, 25... Circumferential groove, 26... Ball, 27, 28
... Spring, 29 ... Timing cam, 30 ... Air chamber, 31 ... High pressure tank, 32 ... Piping, 33 ...
... Solenoid valve, 34 ... Control unit, 35
... Compression coil spring, 36 ... Air passage, 38,3
9...Check ball valve, 40...hole, 41...
Ventilation path, 42...branch path, 43...groove, 44...
Check ball valve, 45, 46...notch, 47...
...Pin, 48... Butsuzurotsudo.

Claims (1)

[Scope of utility model registration request] A cam provided with a plurality of cam ridges on the same axis that act on each on-off valve provided for each cylinder of an internal combustion engine via a rocker arm, and an actuator that moves the cam in the axial direction using fluid pressure; variable valve timing, which is synchronized with the rotation of the cam and supplies and discharges fluid pressure to and from the actuator only when all of the cams are in a position where the base diameter portion contacts the rocker arm; Device.