JPS6316111A - Tappet mechanism for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve following-up of a tappet mechanism in high speed running of an engine in the above caption, by increasing spring force which make a rocker arm to come into contact with a cam as the engine speed increases in a type of a tappet mechanism in which valve opening timing is controlled in response to the engine speed. CONSTITUTION:An intake valve 1b is opened and closed as rocker arms 5-7 rock around a rocker shaft 8. At the rear faces of said rocker arms 5-7 touches a cam provided with a high speed cam 4 and a low speed cam 3, either of which is brought into contact with said rock arms 5-7 to control valve opening timing in response to the speed of the engine concerned. Said rocker arm 6 is pushed by a spring 16 in the direction for bringing the rocker arm into con tact with said cam 4. A piston 17 supporting the bottom of said spring 16 receives pressurized oil from an oil passage 19. The pressurized oil is increased in its pressure as the engine speed increases and pushes said spring 16 upward, causing the contact of said rocker arm 6 with said cam 4 to become tighter.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a valve mechanism that opens and closes an intake boat or an exhaust boat in synchronization with the rotation of an internal combustion engine. The present invention relates to a valve operating mechanism for an internal combustion engine that includes a variable device for applying a biasing force in the valve closing direction to a valve that is controlled by a valve stop Ill or a valve timing switching mechanism so as to make the timing variable.

<Prior Art> The combustion chamber of a four-stroke engine is equipped with an intake valve and an exhaust valve in order to supply the air-fuel mixture to the combustion chamber and discharge combustion gas according to a predetermined cycle.
Both of these valves are normally biased in the valve closing direction by a valve spring provided so as to surround the valve stem. Furthermore, both of these valves are forcibly operated against the biasing force of the valve springs mentioned above by a cam that is installed on a camshaft that is connected and driven from the engine's crankshaft using a belt or pulley. It can be pushed open.

On the other hand, each cylinder has multiple intake valves or exhaust valves, and during low-speed operation, one intake valve or exhaust valve is operated, and during high-speed operation, all valves are operated, and at the same time, the operation timing of these valves is adjusted according to the engine rotation. A technique for improving the filling efficiency of the air-fuel mixture into the combustion chamber over a wide operating range by changing the speed according to the speed has been proposed in Japanese Patent Laid-Open No. 1991-1991 by the present applicant.

<Problems to be Solved by the Invention> However, in the case of a valve train equipped with a valve operation timing switching device as described above, setting the biasing force of the valve spring that regulates the movement of the valve train is exposed and troublesome. become. In other words, if the biasing force of the valve spring is set to match the high-speed rotation range, the friction in the valve train will increase unnecessarily during low-speed rotation operation, and the pressure applied to the movement of the cam and rocker arm will increase, causing wear and tear. If the spring constant is set low to reduce operating friction, the valve will not be able to follow the rotation of the cam during high-speed rotation, causing a so-called valve jump phenomenon. Also, if you increase the valve lift amount at the same time as changing the valve timing, the blood pressure against the cam will increase.
The width of the cam sliding surface had to be made large, which was one of the factors that hindered weight reduction.

In view of the problems of the prior art, the main object of the present invention is to provide a valve mechanism having a variable valve opening timing device.
It is an object of the present invention to provide a valve train mechanism for an internal combustion engine that can ensure good followability of the valve train over a wide operating range and at the same time suitably suppress cam surface pressure.

<Means for Solving the Problems> According to the present invention, this purpose is achieved by installing a valve in the intake port or exhaust port of the combustion chamber, which is always biased to close by a spring means, and which is synchronized with the crankshaft. A valve operating mechanism for an internal combustion engine, which is driven to open by a rotating cam and whose valve opening timing can be varied according to the rotational speed, and which acts directly or indirectly on the spring means. By doing so, a fluid pressurizing device is provided for changing the spring reaction force of the spring means, and the spring reaction force in the high speed operation range is at least larger than the spring reaction force in the low speed operation range. This is achieved by providing a valve train for an internal combustion engine characterized by φ.

In particular, it is preferable that the second engine rotation speed that changes the spring reaction force is higher than the first engine rotation speed that changes the valve opening timing.

<Operation> In this way, the valve closing biasing force can be set small in the low-speed operating range where the inertial force is relatively low, so that it is possible to reduce the friction as well as the cam surface pressure.

In a high-speed operating range where the inertial force increases, the valve closing biasing force is increased by the fluid pressurizing device, thereby making it possible to further improve the followability of the valve train in the high-speed operating range.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the engine body (not shown) is provided with a pair of intake valves 1a and 1b.
A pair of low-speed cams 3a, 3b and a single high-speed cam 4 having an oval cross section are integrally provided on a camshaft 2 which is synchronously driven at 1/2 speed (not shown), and these cams. The opening/closing operation is performed by working with the first to thirtieth claw arms 5 to 7 as cam followers that engage with the 3a13b and 4 to perform rocking motion. The engine is also equipped with a pair of exhaust valves (not shown), which are driven to open and close in the same manner as the intake valves 1a and 1b described above.

The first to thirtieth lever arms 5 to 7 are pivotally supported adjacent to each other so as to be able to swing freely on a rocker shaft 8 that is fixed below the camshaft 2 in parallel to the camshaft 2. The first and thirtieth lever arms 5.7 have basically the same shape, their bases are pivotally supported by the rocker shaft 8, and their respective play parts extend above the intake valves 1a, 1b. Tappet screws 9a and 9b that abut the upper ends of the intake valves 1a and 1b are screwed into the Tli portions of these double-ended hook arms 5.7 so as to be able to move forward and backward, respectively. It is prevented from loosening.

The 20th claw arm 6 is connected to the first and 30th claw arms 5.
7 and is pivotally supported on the rocker shaft 7. This 20th
The lever arm 6 connects both intake valves 1 from the rocker shaft 8.
a and 1b, and as shown in FIG. 2, there is a high-speed cam 4 on its upper surface.
A cam slipper 6a is formed, and the lower end surface of the cam slipper 6a is in contact with the upper end surface of a lifter 12 of a loading device 11, which will be described later.

As described above, the cam shirt 1 to 2 is rotatably supported above the engine body, and includes low-speed cams 3a and 3b corresponding to the first and 30th claw arms 5.7, and the 20th claw arm 6. A high-speed cam 4 corresponding to the cam 4 is integrally connected. As clearly shown in FIG. 3, the low-speed cams 3a and 3b have a relatively small lift,
It is formed in a cam profile suitable for low-speed operation of the engine, and its outer peripheral surface can be brought into sliding contact with cam slippers 5a and 7a formed on the upper surfaces of the first and thirtieth lever arms 5.7. The high speed cam 4 is the low speed cam 3
Compared to cam slippers 6a and 3b, it is formed with a cam profile suitable for high-speed operation that has a large lifting head that rotates at a wider angle, and its outer peripheral surface is in contact with the cam slipper 6a of the 20th latch arm 6 described above. 1q. Note that the loading device 11 is not shown in FIG. 3.

These 1st to 30th lever arms 5 to 7 are installed in holes drilled through the center of each of the lever arms 5 to 7 in parallel with the rocker shaft 8, as shown in FIGS. 4 and 5. A connecting device 13, which will be described later, is capable of switching between a state in which it can swing integrally and a state in which it can be relatively displaced by 1q.

As clearly shown in FIG. 2, the loading device 11 has two intake valves 1a and 1b (not shown in FIG. 2) installed in the cylinder head 14. A guide hole 15 that is bored approximately parallel to the learning axis, and a lid 12 that slides into the guide hole 15,
a coil spring 16 that constantly biases the lifter 12 upward;
It consists of a piston 17 sandwiched between the lower end of the coil spring 16 and the bottom wall surface of the enlarged diameter portion 15a at the bottom of the guide hole 15.

The piston 17 slides fluid-tightly into the enlarged diameter portion 15a of the guide hole, and is connected to the hydraulic port 1 opened in the bottom wall of the guide hole 15.
8, the expanded diameter portion 15a can be displaced upwardly along the inner circumferential surface of the enlarged diameter portion 15a by the action of pressure oil supplied from an oil pressure generation source (not shown) via an oil passage 19.

On the other hand, a retainer 2 is installed at the top of both intake valves 1a and 1b.
Valve springs 26a and 26b surrounding the stems of both intake valves 1a and 1b are interposed between these retainers 25a and 25b and the engine body. Valve 1a, 1b
is urged in the valve closing direction, that is, upward in FIG.

As clearly shown in FIGS. 4 and 5, a first guide hole 27 that opens toward the 20th claw arm 6 side is bored in the 10th claw arm 5 in parallel with the rocker shaft 8. . A reduced diameter portion 28 is formed on the bottom side of the first guide hole 27, and a stepped portion 29 is formed accordingly.

A second kite hole 30 that communicates with the first guide hole 27 of the tenth claw arm 5 is bored through the 20th claw arm 6 between both sides thereof.

A third guide hole 31 communicating with the second guide hole 30 is bored in the 30th claw arm 7 . The bottom side of the third guide hole 3 (like the first guide hole 27, the stepped portion 32
A small diameter portion 33 is formed, and a small diameter insertion hole 34 passing through the bottom wall of the third guide hole 31 is formed concentrically with the third guide hole 31 .

Inside these first to third guide holes 27, 30, 31 is a first piston 3 that can move between a position where the first and 20th hook arms 5.6 are connected and a position where the connection is released.
5, a second piston 36 that is movable between a position where the second and 30th hook arms 6.7 are connected and a position where the connection is released, a stopper 37 that restricts movement of both pistons 35 and 36, and both pistons. A first coil spring 38 that biases the pistons 35 and 36 toward the connected position, and a second coil spring 39 that biases both pistons 35 and 36 toward the disconnected position with a stronger biasing force than the first coil spring 38. is installed.

The first piston 35 has a first guide hole 27 and a second guide hole 3.
0, and as a result, the bottom surface of the first guide hole 27 and the first
A hydraulic chamber 40 is defined between the end faces of the screws 1 to 35. Further, an oil passage 41 is bored in the rocker shaft 8 and communicates with a hydraulic pressure supply device (not shown).
The rocking state of the tenth lever arm 5 can be controlled via an oil passage 42 drilled in the zero lever arm 5 so as to communicate with the hydraulic chamber 40 and a communication hole 43 bored in the peripheral wall of the rocker shaft 8. Regardless, hydraulic oil is always supplied into the hydraulic chamber 40 and 1q
It is designed to be

The axial dimension of the first piston 35 is such that when one end thereof comes into contact with the stepped portion 29 in the first guide hole 27, the other end does not protrude from the side surface facing the 20th claw arm 6 of the 10th claw arm 5. It is set.

The second piston 36 has an axial dimension equal to the entire length of the second guide hole 30 so that it can slide into the second guide hole 30 and the third guide hole 31.

The stopper 37 has a disk portion 37a formed at one end that fits into the third guide hole 31, and a guide rod 44 inserted into the small diameter hole 34 at the other end. Further, between the disk portion 37a of the stopper 37 and the bottom of the small diameter portion 33 of the third guide hole 31, the second coil spring 3, which surrounds the guide rod 44, is provided.
is interposed.

Next, we will explain the operation of this device explained above.
Ru.

First, referring to FIG. 4.5, in the middle and low speed range of the engine, hydraulic pressure is not supplied to the hydraulic chamber 40 of the coupling device 13, and each piston 35, 36 is operated by the second coil spring 39. The biasing force aligns them within their respective guide holes 27, 30 as shown in FIG. 4, so that each rocker arm 5-7 can be displaced angularly relative to each other.

In such a disconnected state of the coupling device 13, the first and 30th claw arms 5.7 swing according to sliding contact with the low-speed cams 3a and 3b due to the rotational operation of the camshaft 2, Both intake valves 1a and 1b are driven to open and close by retarding their opening timing and advancing their closing timing, and with a reduced lift. At this time, the 20th lever arm 6 swings due to sliding contact with the high-speed cam 4, but this swinging action has no effect on the operation of both intake valves 1a and 1b.

On the other hand, the hydraulic pressure does not act on the piston 17 of the loading device 11, and the compression coil spring 16 compressed in the guide hole 15
Since the initial deflection amount of is also relatively small, the second
Although the zero tension arm 6 is always biased toward the high-speed power arm 4, the friction against the camshaft 2 is suppressed to an extremely small range (FIG. 2).

When the engine is operated at high speed, hydraulic pressure is supplied to the hydraulic chamber 40 of the coupling device 13. As a result, as shown in FIG. 5, the first piston 35 is
The second piston 36 moves toward the 20th lever arm 6 against the biasing force of the piston 9, and the second piston 36 moves toward the 30th
Move to Tsuka arm 7 side. As a result, the first and second pistons 35.36 move together until the disk portion 37a of the stopper 37 comes into contact with the stepped portion 32, and the first piston 35 connects the first and 20th hook arms 5.6. A second piston 36 connects the second and thirtieth claw arms 6.7.

As described above, when the first to thirtieth lever arms 5 to 7 are connected to each other by the coupling device 13, the amount of swing of the 20th lever arm 6, which is in single contact with the high-speed cam 4, is the largest. 1st and 30th Tsuka Arm 5
．． 7 is j-driven together with the 20th lever arm 6. Therefore,
Both the intake valves 1a and 1b are driven to open and close together with their closing timings shifted and delayed according to the cam profile of the high-speed cam 4, and their lift amounts increased.

In the low speed range, the movement speed of the valve and rocker arm is relatively low, and the valve closing force may also be relatively small. However, as the engine speed increases, the first
When the ~30th lever arms 5 to 7 are connected, the movement speed of the valve and rocker arm increases, and the inertial mass of these valve train systems as a whole increases. As a result, in a high speed range, it is necessary to close both intake valves 1a and 1b and at the same time increase the acting force for pushing the first to thirtieth lever arms 5 to 7 upward.

Therefore, according to the present invention, the oil passage 19 is communicated with the oil pressure generation source at a speed higher than a set speed by, for example, a directional solenoid valve that is driven to open and close by a speed signal.

When pressure oil is introduced from the hydraulic port 18, the piston 17 is pushed upward until it comes into contact with the stepped portion 15b formed by expanding the diameter of the guide hole 15a, and the coil spring 16 is compressed accordingly. , the upward biasing force on the 20th hook arm 6 is increased.

FIG. 6 shows the control timing and changes in the surface pressure between the cam and the cam slipper in the above embodiment.

If both valve springs 26a and 26b are set to a spring constant that corresponds to the entire speed range, and only the valve timing is changed at a predetermined rotation speed N1, as shown by the broken line in FIG. It can be seen that as the blood pressure becomes relatively high, friction also increases.

The cam surface pressure decreases as the speed increases, but when the valve refmill amount increases due to valve timing switching, the cam surface pressure also increases rapidly. Since the maximum surface pressure P1 at this time acts on the high speed cam 4 and the 20th latch arm 6, in this case, it is necessary to make the contact area between the cam and the cam slipper relatively large.

In FIG. 6, the solid line shows the change in blood pressure according to this example.

First, by setting the spring constants of both valve springs 1a and 1b to be relatively low so as to correspond only to the medium and low speed range, the cam surface pressure in the low speed range is also suppressed to a low level. Therefore, the maximum surface pressure P2 when switching the valve timing at the first engine rotational speed N1 is also kept relatively low.

Next, when a biasing force is applied to the 20th lever arm 6 by the loading device 11 at the second engine speed N2, the cam surface pressure increases again, but the blood pressure increases compared to the time when the valve timing is switched (N1). can be kept to a low level.

FIG. 7 shows, as a second embodiment, a modification of the first embodiment described above. Below, the same reference numerals are given to the parts corresponding to the first embodiment, and detailed explanation will be omitted.

In this embodiment, instead of the hydraulic pressure applied to the piston 17 in the first embodiment, air pressure is applied to the lick 12 from the lower wall of the guide hole 15 through the passage 20. I have to.

In the case of this embodiment, since air pressure acts as a spring, the spring constant can be changed as appropriate by changing the compression pressure of the air.

FIG. 8 shows a third embodiment based on the present invention. In this embodiment, a cylinder part 50 is formed in the valve spring holding part of the cylinder head 14, and the cylinder part 50 is provided between the lower end of the valve spring 26a (26b) provided surrounding the valve stem 51 and the bottom wall of the cylinder part 50. , cylinder section 50
A spring seat 52 is provided along the axis of the valve stem 51 so as to be freely movable, and hydraulic pressure is applied to the lower surface of the spring seat 52 through an oil passage 19 formed in the cylinder head 14. By doing so, the initial deflection amount of the valve springs 26a (26b) is changed.

In this embodiment, the loading device 11 shown in the first embodiment is also used.
The valve closing biasing force of the intake valve 1a (1b) changes.

FIG. 9 shows a fourth embodiment, in which an upper valve spring retainer 53 is formed in the shape of a piston and slid onto an inner cylindrical surface 54 formed in the cylinder head 14, and is bored in the cylinder head 14. Air pressure is applied to the inner surface of the valve spring retainer 53 through the passage 20, and repulsive force of the compressed air is applied to the valve spring 26a (26b) made of a coil spring in the same manner as in the second embodiment. has been done.

FIG. 10 shows a fifth embodiment, in which air pressure is applied to the inside of the piston-type direct lifter 55 through a passage 20 bored in the lower part of the lifter guide 56.
It is designed to be compatible with direct drive by the camshaft 2. This embodiment also provides the same effects as the fourth embodiment described above.

Note that the present invention is not limited to the type having a plurality of intake valves per cylinder as described in the first embodiment, but can be similarly implemented with a single valve.
In addition to variable valve timing, it can also be implemented in combination with a valve body mechanism. In other words, the same effect as above can be obtained by setting the biasing force of the valve spring on the normally operating side to be weak when one valve is at rest, and set to be strong in the region where both valves are operating together. be.

Further, the switching rotational speed of the valve timing and the switching rotational speed of the valve spring load may be determined as appropriate depending on the operating characteristics of the engine.

<Effects of the Invention> As described above, according to the present invention, the cam surface pressure can be reduced by appropriately switching the valve timing and switching the valve spring biasing force according to the operating speed of the engine. Since it is possible to suppress it to a low level, it is possible to reduce the cam width. Furthermore, it is possible to reduce friction in the low speed range and improve followability of the valve train in the high speed range, which has a great effect on improving the operating characteristics of the engine over a wider range. be.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway top view showing the vicinity of a valve train to which a loading device according to the present invention is applied. FIG. 2 is a sectional view taken along line II-I in FIG. 1. FIG. 3 is a view in the direction of the ■ arrow in FIG. 1. FIG. 4 is a sectional view taken along the line IV--IV in FIG. 3 showing the state of low-speed operation. FIG. 5 is a cross-sectional view similar to FIG. 4 showing the state of high-speed operation. FIG. 6 is a graph showing changes in cam surface pressure. FIG. 7 is a partial sectional view seen from the same position as FIG. 2 showing the second embodiment. 8 to 10 are sectional views of main parts of different embodiments, respectively. 1a, 1b...Intake valve 2...Camshaft 2a...Protuberance 3...Low speed cam 4...High speed cam 5...10th claw arm 6...20th claw arm 5a, 5a, cam slipper 7...30th latch arm 7a...contact surface 8...locker shafts 9a, 9b...tappet screws 10a, 10b...lock nut 11...loading device 12...arm 13...
Connecting device 14... Cylinder head 15... Guide hole 15a... Expanded diameter part 15b... Step part
16...Coil spring 17...Piston 1
8...Hydraulic port l~19...Oil passage 20.
...Passage 25a, 25b...Retainer 26a, 26b...Valve spring 27...First
Guide hole 28...Small diameter part 29...Step part
30...Second guide hole 31...Third guide hole 32
...Stepped portion 33...Small diameter portion 34...Insertion hole 35...First piston 36...Second piston 37
...Stopper 37a...Disk portion 38...First coil spring 39...Second coil spring 40...Hydraulic pressure 41.42...Oil passage 43...Communication hole
44... Guide rod 50... Cylinder part 51.
... Valve stem 52 ... Spring seat 53 ... Piston type valve spring retainer 54 ...
...Inner cylinder surface 55...Direct lifter 56-
...Lifter guide patent applicant Honda Motor Co., Ltd.
Attorney Patent Attorney Yo Oshima -Figure 1Figure 2Figure 4Figure 1AFigure 6Engine rotation speed -m-Figure 7

Claims (6)

[Claims] (1) It is installed at the intake port or exhaust port of the combustion chamber, and is always biased to close by a spring means, and is driven to open by a cam that rotates in synchronization with the crankshaft, and the valve opens according to the rotation speed. A valve operating mechanism for an internal combustion engine having variable timing, the fluid pressurization for changing the spring reaction force of the spring means by acting directly or indirectly on the spring means. What is claimed is: 1. A valve train for an internal combustion engine, comprising a valve mechanism for an internal combustion engine, characterized in that a spring reaction force in a high speed operation range is greater than a spring reaction force in a low speed operation range. (2) The valve-opening timing and the spring reaction force can be changed stepwise, and the second engine speed that changes the spring reaction force is higher than the first engine rotation speed that changes the valve-opening timing. The valve operating mechanism for an internal combustion engine according to claim 1, wherein the engine rotation speed is set higher. (3) The valve operating mechanism includes a valve capable of opening and closing the intake port or exhaust port, a first spring provided directly on the valve, and a second spring provided separately from the first spring. The internal combustion engine according to claim 1 or 2, wherein the internal combustion engine has a spring, and the fluid pressure of the fluid pressurizing device is applied to the second spring. Valve mechanism. (4) The valve mechanism includes a valve having a head portion and a stem portion, and a compression coil spring surrounding the stem portion, and the fluid pressurizing device is attached to one end of the coil spring. The valve operating mechanism for an internal combustion engine according to claim 1 or 2, characterized in that the valve operating mechanism is adapted to apply a fluid pressure of . (5) A valve train mechanism for an internal combustion engine according to any one of claims 1 to 4, wherein the fluid pressure is oil pressure. (6) The valve mechanism for an internal combustion engine according to any one of claims 1 to 4, wherein the fluid pressure is air pressure.