JPH02225848A - Chain tension automatic regulator - Google Patents

Abstract

PURPOSE:To prevent the generation of the vibration of a chain caused by the intake of the air immediately after a start by opening one end of an orifice passage in an oil sump chamber of the tip of a plunger, ans eccentrically arranging a working chamber opening end and the oil sump chamber opening end respectively upper and lower of the center line of the plunger. CONSTITUTION:Immediately after an engine start, even if a backing plunger 36 projects suddenly, the lubricating oil in an oil sump chamber 48 is sucked into a working chamber 37 to eliminate the danger that the air is sucked from the outside into the working chamber 37. Especially, an opening end of the oil sump chamber 48 of an orifice passage 52 is positioned in the lower of the oil sump chamber 48 to secure a distance in vertical direction to the oil surface of the oil sump chamber 48, namely, an air exhaust hole 49, and the air intake is prevented more surely. Since the working chamber 37 side opening end of the passage 52 is positioned upper than a center line l of the plunger 36, namely, it is positioned in the more upper part of the working chamber 37, the capacity of the air remaining in the upper part is greatly reduced, and the air exhaust is performed more surely.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an automatic chain tension adjustment device used in a valve train of an internal combustion engine.

BACKGROUND OF THE INVENTION FIG. 5 shows an example of the configuration of a transmission mechanism in a valve train for an internal combustion engine. In the figure, l is a crank sprocket attached to the front end of the crankshaft, 2 is a cam sprocket attached to the front end of the camshaft, and a timing chain 3 is wound around both. A swingable chain guide 4 is provided on the slack side of the timing chain 3 that operates in the direction of the arrow in the figure, and an automatic chain tension adjustment device 5 is provided on the back of this chain guide 4. Appropriate tension is applied to the timing chain 3 (Utility Model No. 58-207)
Publication No. 55).

FIG. 6 shows the configuration of a conventional chain tension automatic adjustment device 5, and this chain tension automatic adjustment device gj1
5. (A body 7 in which a cylindrical cylinder 6 is recessed,
It is generally composed of a plunger 8 that fits into the cylinder 6 and is slidable in the tension direction of the timing chain 3, and a check valve 9 attached to one end of the body 7. A working chamber IO is defined within the cylinder 6 by the plunger 8, and this working chamber I
A tension spring 11 that biases the plunger 8 in the projecting direction is housed in the housing. The check valve 9 includes a substantially cylindrical seat member 12, a check ball 13, a relief spring 14, and a check ball 1.
3 and a retainer 1 that holds the relief spring 14.
5, and is located between the working chamber 10 and the oil supply hole 167 to prevent backflow of oil. A stopper 17 for regulating the most retracted position of the plunger 8 is attached to the tip of the plunger 8 together with a damper I8 made of an elastic body.
is in contact with boss l519 on the back of chain guide 4. Further, a plug 21 having a spiral orifice passage 20 formed on its outer periphery is press-fitted into the tip of the plunger 8 equipped with the stobbar summer 7, and the working chamber 10 communicates with the outside through the orifice passage 20. . The automatic chain tension adjustment device 5 is normally installed at an angle with respect to a horizontal plane with the tip end of the plunger 8 facing upward as shown in the figure, when in operation, for example, when mounted on a vehicle. The passage 20 also functions as a discharge passage for air accumulated in the upper part of the working chamber 10, that is, on the tip side.

The automatic chain tension adjustment device 5 configured as described above includes tension springs 1. The chain guide 4 is pressed by the biasing force of I and the oil pressure of the oil supplied into the working chamber 10, and appropriate tension is applied to the timing chain 3. A suitable amount of oil always flows out from the orifice passage 20, and the pressure in the working chamber 10 is kept approximately constant. However, when the chain 3 is pulled excessively during sudden acceleration, oil flows out from the orifice passage 20. When pushed out, the plunger 8 temporarily retreats, and the impact can be buffered. That is, the vibrations of the chain 3 are quickly damped. Furthermore, the air mixed with the lubricating oil and flowing into the working chamber is naturally discharged to the outside through the orifice passage 20, as described above.

Problems to be Solved by the Invention In the conventional automatic chain tension adjustment device 5 as described above, for example, the plunger 8 is
If the engine is stopped while being strongly pressed, the lubricating oil in the working chamber 10 will be pushed out while the engine is stopped, and the plunger 8 will be in a retracted state. Then, when the engine starts and the pressing force from the timing chain 3 is released,
The plunger 8 tries to protrude suddenly due to the tension spring 11, but the supply oil pressure is low immediately after starting and the oil supply hole! Since lubricating oil is not supplied smoothly from 6, air may be sucked into the oil chamber 10 through the orifice passage 20. Furthermore, air is likely to be sucked in even if the plunger 8 is greatly retracted or protruded due to a change in the tension of the timing chain 3 immediately after starting. As a result, the desired damping characteristics cannot be obtained, and the timing chain 3 vibrates until the air that has been sucked in is exhausted.

Moreover, in the above configuration, the working chamber 10 of the orifice passage 20
A considerably large space (shaded area indicated by symbol A in FIG. 6) is created at 611 from the side open end, and since the air accumulated in this area cannot be discharged, the characteristics tend to become unstable.

Means for Solving the Problem) In order to solve the two problems, the automatic chain tension adjustment device according to the present invention is slidably fitted to the cylinder,
and a plunger which is biased in the projecting direction by a tension spring and is inclined with respect to a horizontal plane so that the tip side faces upward, and a cylinder is defined by the plunger, and oil is supplied through a check valve. an oil reservoir chamber that is defined at the tip of the plunger and communicates with the outside from the top; and an oil reservoir chamber that communicates with the oil reservoir chamber described in 2. The orifice passage is located eccentrically above the center line, and the opening end on the oil reservoir side is eccentrically located below the plunger center line.

Effect The orifice passage provided at the tip side of the working chamber has one end opening into the oil reservoir chamber at the tip of the plunger.

Therefore, when the plunger suddenly protrudes and the working chamber becomes negative pressure, the oil in the oil reservoir chamber is sucked through the orifice passage, thereby preventing air from entering. Furthermore, since the opening end of the orifice passage on the working chamber side is eccentric above the plunger center line, the volume of the space remaining above this opening end is smaller. Since the opening end on the opposite side of the oil reservoir chamber is eccentrically downward from the center line of the plunger, a relatively large depth from the oil surface of the oil reservoir chamber is ensured.

Embodiment Hereinafter, one embodiment of an automatic chain tension adjustment device 5 according to the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1, reference numeral 31 denotes a body attached to the front end surface of the internal combustion engine, and the body 31 has a cylindrical cylinder 32 with an open end recessed along an oblique direction. A reservoir chamber 33 whose top surface is open is formed above. The reservoir chamber 33 has an upper opening closed by a cap 34, and has an oil supply hole 3 in a relatively upper portion communicating with the engine lubricating oil passage.
5 is formed with an opening.

A bottomed cylindrical plunger 36 is slidably fitted into the cylinder 32, thereby defining an operating chamber 37. The plunger 36 is always urged in the projecting direction by a tension spring 38 housed in the working chamber 37. Here, as shown in the figure, the body 31 is attached to the internal combustion engine in an inclined state with respect to the horizontal direction so that the front end side of the plunger 36 faces upward.

Further, a check valve 43 is attached to the bottom of the cylinder 32. The check valve 43 includes a belt member 39, a check ball 40, a relief spring 41, and a retainer 42 for holding the check ball 40 and the relief spring 41. This check valve 43 is located between the oil supply passage 44 extending from the reservoir chamber 33 and the working chamber 37, and only allows oil to flow into the working chamber 37.

Furthermore, the bottom side of the cylinder 32 and the reservoir chamber 33
A spiral damping orifice 45 is provided on the outer peripheral surface between the
A cylindrical plug 46 with a cylindrical shape is press-fitted therein. The damping orifice 45 has one end communicating with the lower part of the reservoir chamber 33 and the other end communicating with the working chamber 37.

On the other hand, a substantially disk-shaped stopper 47 is fitted and fixed to the tip cylindrical portion 36a of the plunger 36, and an oil reservoir chamber 48 is defined therein.

An air exhaust hole 49 is formed through the stopper 47 so as to communicate with the top of the oil reservoir chamber 48 .

Incidentally, a gunpa 50 made of an elastic body is disposed on the contact surface of the stopper 47 with the body 31.

The oil reservoir chamber 48 and the working chamber 37 communicate with each other through an orifice passage 52 provided in a cylindrical orifice member 51 press-fitted into the plunger 36 . The orifice passage 52 is connected to the working chamber 37, as shown in detail in FIG.
passage holes 52a and 52b drilled with their tips sealed from the side and the oil reservoir chamber 48 side, and a circumferential groove 5 recessed all around the outer periphery of the orifice member 51;
2c, the passage holes 52a, 52b, and the circumference 'Itlt.
It is composed of small holes 52d and 52e that communicate with 52c. Here, the working chamber 3 of the orifice passage 52 is
As shown in FIG. 2, the passage hole 52a, which is the open end on the 7 side, opens eccentrically above the center line Q of the plunger 36. The passage hole 52b, which is the opening end on the opposite side of the oil reservoir chamber 4g, opens eccentrically below the centerline i of the plunger 36.

The stopper 47 presses the chain guide 4 when the recess 147a on its front surface is fitted into the chain guide 4 (see FIG. 5). Therefore, the posture of the plunger 36 integrated with the stopper 47 in the rotational direction is regulated by the chain guide 4.
Always kept in the state shown.

Now, according to the above configuration, from the reservoir chamber 33 to the working chamber 3
The lubricating oil that is sequentially fed into the lubricant 7 is discharged in appropriate amounts to the oil reservoir chamber 48 side through the orifice passage 52 at the tip, and finally overflows to the outside from the air discharge hole 49. Therefore, the oil reservoir chamber 48 is always filled with lubricating oil, and the oil is retained even when the engine is stopped. Therefore, even if the plunger 36 that had been retracted suddenly protrudes immediately after the engine is started, the lubricating oil in the oil reservoir chamber 48 will be sucked into the working chamber 37, and air will flow into the working chamber 37 from the outside. There is no risk of inhaling it.

In particular, in the L structure, the oil sump chamber 48 of the orifice passage 52
The side opening end is located at the lower part of the oil reservoir chamber 48, and a sufficiently large distance in the L downward direction to the curved surface of the oil reservoir chamber 48, that is, the air exhaust hole 49, can be secured, so that air is not sucked. This can be prevented even more reliably.

In contrast, the opening end of the orifice passage 52 on the working chamber 37 side is located above the center line g of the plunger 36, that is, it opens further above the working chamber 37. On the other hand, the remaining air volume becomes very small. Therefore, the air can be reliably discharged from the -layer.

In the above configuration, when the plunger 36 is pushed in by the timing chain 3, the oil is discharged through the orifice passage 52, and some of the oil is pushed back into the reservoir chamber 33 through the damping orifice 45. A large mounting effect can be obtained.

Next, FIG. 3 shows an embodiment in which an orifice passage 52 is formed in a straight line inside an orifice member 51. The orifice member 5! of the orifice passage 52 has both ends opened at positions 180° different from each other. The opening end on the working chamber 37 side is located eccentrically above the center line a of the plunger 36, and the opening on the oil reservoir chamber 48 side is drilled obliquely with respect to the axis of The end is located eccentrically below the center line e.

In the embodiment shown in FIG. 4, an orifice passage 52 is formed by carving a spiral groove on the outer peripheral surface of an orifice member 51. In this case as well, the pitch of the spiral is determined so that both ends are opened at 180' different positions, and the opening end on the working chamber 37 side is upward with respect to the center line Q of the plunger 36, and the opening end on the oil reservoir chamber 48 side is The open end is located at the bottom.

Effects of the Invention As is clear from the above explanation, the automatic chain tension adjustment device according to the present invention prevents air from being sucked in from the orifice passage on the tip side of the working chamber when the plunger suddenly protrudes. In addition, air mixed with oil and flowing into the working chamber can be quickly and sufficiently discharged.

Therefore, the chain does not vibrate due to air intake immediately after starting or the like.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of an automatic chain tension adjustment device according to the present invention, and FIG. 2 is an enlarged sectional view of the main parts thereof.
FIG. 3 is an enlarged cross-sectional view of a main part showing a different embodiment of the present invention, FIG. 4 is an enlarged cross-sectional view of a main part showing a further different embodiment of the present invention, and FIG. FIG. 6, which is an explanatory diagram of the entire structure of the transmission mechanism of the valve device, is a sectional view of a conventional chain tension automatic adjustment device. 32...Cylinder, 36...Plunger, 37...
・Working chamber, 38... Tension spring, 43...
- Check valve, 48...oil reservoir chamber, 52...orifice passage. 32 - Cylinder 36 - Plunger 37 - Working chamber 38 - Tension spring 43 - Check valve 48 - Oil reservoir chamber 52 - Orifice passage diagram

Claims (1)

[Claims] (1) A plunger that is slidably fitted into the cylinder, is biased in the protruding direction by a tension spring, and is inclined with respect to the horizontal plane so that the tip side faces upward;
an operating chamber defined in the cylinder by the plunger and to which oil is supplied via a check valve; an oil reservoir chamber defined at the tip of the plunger and whose upper portion communicates with the outside; An orifice that communicates between the chamber and the oil reservoir chamber, and has an opening end on the working chamber side eccentrically located above the center line of the plunger, and an opening end facing the oil reservoir chamber side located eccentrically below the center line of the plunger. An automatic chain tension adjustment device comprising a passageway.