JPH08284620A - Lash adjuster and internal combustion engine provided with it - Google Patents

Abstract

PURPOSE: To eliminate malfunction generated at using exhaust brake, and enable valve clearance to be correctly adjusted even at a low speed drive. CONSTITUTION: In a hydraulic type lash adjuster interposed in the valve system of an internal combustion engine, it is provided with a check valve 50 allowing oil flow from a reservoir chamber 47 to a pressure chamber 24, when pressure difference over a fixed value is generated between the pressure chamber 24 and the reservoir chamber 47, and a non-return valve 60 opening when the pressure in the pressure chamber 24 is over a fixed value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic lash adjuster installed in a valve train of an internal combustion engine.

[0002]

2. Description of the Related Art As one of valve operating mechanisms, there is an overhead valve type (OHV type) as shown in FIG. This is a system in which a valve 4 is opened and closed via a lash adjuster 3, a push rod 5, a rocker arm 6 from a cam 4 which is rotated in synchronization with the rotation of an engine crankshaft.

Here, as shown in FIG. 2, the lash adjuster 3 has a plunger 9 inside a adjuster body 90.
1, a push rod socket 92, a plunger spring 93, a check valve 94, etc. are housed and configured, and between the pressure chamber 95 formed by the adjuster body 90 and the plunger 91, and between the plunger 91 and the push rod socket 92. Oil is supplied to the reservoir chamber 96 formed in the above, and the valve clearance is automatically adjusted. That is, when the valve is opened, the pressure chamber 95
Since the plunger 91 is held so as not to be lowered by hydraulic pressure because there is oil inside, when the valve is closed, the plunger 91 pushes the plunger 91 upward to push the bottom of the adjuster body 90 in a direction to reduce the valve clearance to zero. Rod socket 9
The distance between the top surface of 2 increases.

[0004]

By the way, when an exhaust brake is used in an OHV type diesel engine having a hydraulic lash adjuster interposed, the back pressure of the exhaust manifold becomes a predetermined value or more, and the compression stroke A phenomenon occurs in which the exhaust valve is pushed down by the back pressure in the initial stage (hereinafter referred to as "pressure adjusting lift"). Then, a gap is created between the stem head 7a of the valve 7 and the rocker arm 6, and the lash adjuster 3 considers that a clearance has been created and works to make the valve clearance zero. That is, the plunger spring 93 extends to fill the gap, and the distance between the top surface of the push rod socket 92 and the bottom surface of the adjuster body 90 (hereinafter, simply referred to as “adjustment length”) becomes longer than a predetermined length. I will end up. If the lash adjuster 3 thus malfunctions and enters the compression stroke, the exhaust valve cannot completely close the exhaust port. Therefore, the exhaust valve is slightly lifted, and when the compression valve reaches the compression top dead center in this state, the exhaust valve is pressed against the valve seat by the strong compression pressure of the piston. Then, an excessive load exceeding the allowable value is applied to the valve operating system such as the push rod 5. Further, when the valve is not completely closed (the valve is lifted) and the exhaust cycle reaches the top dead center of the next cycle, there is a problem that the valve and the piston interfere with each other.

Therefore, as shown in FIG. 2, a small hole 97 having an appropriate passage area is provided at a predetermined position of the plunger 91 so as to connect the pressure chamber 95 and the reservoir chamber 96. This small hole 97 functions to appropriately leak oil from the pressure chamber to the reservoir chamber so that the pressure in the pressure chamber 95 does not rise too much. As a result, measures are taken to make the adjusted length a predetermined length.

However, the range in which the amount of oil leakage can be appropriately controlled by the small holes 97 is determined by the passage area of the small holes 97. Therefore, it cannot cover the entire wide range of driving situations. That is, in the case of the small hole 97 provided to prevent excessive pressure in the high speed region, the leak amount can be correctly controlled when the engine is driven at high speed.
When the rotation speed is low, there is an inconvenience that the amount of oil leak becomes too large. As described above, if the oil leak amount is too large, the adjustment length becomes shorter than a predetermined length, and the valve lift amount decreases.

Therefore, the present invention solves the above problems in the hydraulic lash adjuster, eliminates the erroneous operation that occurs when the exhaust brake is used, and can accurately adjust the valve clearance even at low rotation drive. The purpose is to provide.

[0008]

In order to achieve the above object, according to the present invention, in a hydraulic lash adjuster interposed in a valve train of an internal combustion engine, a bottomed cylindrical adjuster body and the adjuster are provided. A plunger slidably inserted into the body, a pressure chamber formed by the adjuster body including the bottom portion and the plunger, and disposed in the pressure chamber so as to urge the plunger toward the opening side of the adjuster body. A plunger spring, a reservoir chamber that stores oil discharged from the pressure chamber, and a check valve that allows the flow of oil from the reservoir chamber to the pressure chamber when a pressure difference of a predetermined value or more occurs. A leak passage having a check valve that is opened when the pressure in the pressure chamber exceeds a predetermined value. Lash adjuster is provided.

Further, according to the present invention, the exhaust brake means for increasing the engine braking force by blocking the exhaust pipe line when the engine brake is used, and the exhaust valve system in which the hydraulic lash adjuster is interposed. The lash adjuster includes a bottomed cylindrical adjuster body, a plunger slidably inserted into the adjuster body, a pressure chamber formed by the adjuster body including the bottom portion and the plunger, and the plunger. A pressure difference of a predetermined value or more between the plunger spring disposed in the pressure chamber so as to urge the adjuster body toward the opening side and the reservoir chamber for storing the oil discharged from the pressure chamber. A check valve that allows the flow of oil from the reservoir chamber to the pressure chamber, Pressure internal combustion engine, characterized in that it comprises a leakage passage having a check valve which is opened when a predetermined value or more is provided.

[0010]

In the lash adjuster according to the present invention, when the pressure in the pressure chamber exceeds a predetermined value, the check valve opens and the oil in the pressure chamber leaks to the reservoir chamber.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the present invention will be described with reference to the accompanying drawings. The lash adjuster 1 of the present invention is an exhaust valve system of an internal combustion engine, which comprises an exhaust brake means,
As shown in FIG. 1, it is interposed between the cam 4 and the base end of the push rod 5. The exhaust brake means includes a shutoff valve attached to the exhaust pipe, and the shutoff valve shuts off the pipeline of the exhaust pipe. During operation of the exhaust brake, the exhaust gas continuously discharged raises the pressure (back pressure) in the exhaust manifold, increasing the pump work in the exhaust stroke and producing a large braking force.

As shown in FIG. 3, the lash adjuster 1 includes an adjuster body 10, a plunger 20 slidably inserted into the adjuster body, and a plunger spring 30 for urging the plunger toward the opening of the adjuster body 10. And a push rod socket 40 slidably inserted into the adjuster body and disposed on the upper portion of the plunger. Here, a predetermined amount of oil is injected into the lash adjuster 1.

The adjuster body 10 has a cylindrical shape with a bottom, and the inner peripheral surface thereof has a lower portion 10a and an upper portion 10b.
The diameter is appropriately reduced to form a step. Then, on the inner peripheral surface near the opening of the upper portion, grooves are provided over the entire circumference in the circumferential direction. A snap ring 11 for preventing the push rod socket 40, which will be described later, from protruding is fitted into this groove.

The plunger 20 has a disk shape and an outer diameter substantially equal to the inner diameter of the lower portion 10a of the inner peripheral surface of the adjuster body 10. The plunger 20 is axially slidable and rotatable in the lower portion of the adjuster body. Is inserted. Plunger 2
At 0, a peripheral wall 21 extending downward is formed along the periphery of the plunger, and a communication hole 22 is provided at the center position thereof. And the bottom 10 of the adjuster body
pressure chamber 24 between c and the lower end surface 23 of the plunger 20.
Is defined. The opening of the communication hole 22 on the end face 23 side is
The diameter is expanded into a hemispherical shape so that a check ball 51 described later can be seated. In addition, the communication hole 22 in the lower end surface 23
A check ball cage 53, which will be described later, is provided around the periphery of the opening.
The recessed portion 25 into which is fitted is provided in a step shape.

The check valve 50 includes a first check ball 51, a first check ball spring 52, and a check ball cage 53. The check ball cage 53 has a bottomed cylindrical shape (cup shape), has a flange portion 53a that bulges outward at the upper opening end, and has a plurality of through holes 53b through which oil passes on the side surface. . In the check ball cage 53, the flange portion 53a is pressed against the recessed portion 25 of the plunger 20 by the urging force of the plunger spring 30 described later. The first check ball 51 is housed in the check ball cage 53, and the first check ball closes the communication hole 22 by the urging force of the first check ball spring 52. In this way, the check valve 50 is formed, and when a pressure difference of a predetermined value or more is generated between the pressure chamber 24 and a reservoir chamber 47 described later, the oil can be discharged only in the direction from the reservoir chamber 47 to the pressure chamber 24. Work to allow flow.

The plunger 20 includes a check valve 50.
A check valve 60 is provided so as to be biased with respect to. The check valve 60 is formed by accommodating a second check ball 61, a second check ball spring 62, and a retainer plate 63 in a leak passage 29 provided at a predetermined position of the plunger 20 to form a pressure chamber. When the pressure in 24 becomes equal to or higher than a predetermined value, the valve is opened and oil is leaked to the reservoir chamber 47.

The leak passage 29 is formed by the lower end surface 2 of the plunger.
The small-diameter leak hole 27 that opens so as to face 3 and the large-diameter leak hole 28 that opens so as to face above the plunger 20 are concentrically provided through holes. That is, the small-diameter leak hole 27 and the large-diameter leak hole 28 communicate with each other to form a step. Large leak hole 28 of small leak hole 27
The opening facing toward the second check ball 61 is hemispherically expanded toward the large-diameter leak hole 28 so that the second check ball 61 is seated. A groove into which a snap ring 64 for fixing a retainer plate 63, which will be described later, is fitted is provided on the entire inner peripheral surface of the large-diameter leak hole 28 in the vicinity of the upper opening end.

In the leak passage 29, a circular retainer plate 63 having a size substantially equal to that of the large-diameter leak hole 28 is arranged near the upper opening end of the large-diameter leak hole 28. The retainer plate 63 has a snap ring 64 whose upper end surface near the outer periphery is fitted in the groove,
It is arranged so as not to move further upward. Further, the retainer plate 63 has a plurality of holes 6 through which oil is passed.
3a is provided. Then, the retainer plate 63
And the second check ball 61, the second check ball spring 62 is contracted between the second check ball 61 and the second check ball 61.
Is pressed against the small-diameter leak hole 27 side. That is, the second
The check ball 61 is pressed against the seating portion of the small diameter leak hole 27 by the urging force of the second check ball spring 62 to close the small diameter leak hole 27. The second check ball 61 allows the oil to flow only from the pressure chamber 24 toward the reservoir chamber 47, which will be described later.

Here, the second check ball spring 6
2 is contracted when an excessive pressure is generated in the pressure chamber 24 due to the pressure-controlled lift that occurs when the exhaust brake is used, and is not contracted by the pressure in the pressure chamber 24 during normal operation or low rotation driving. In addition, the spring pressure is adjusted. That is, the check valve 60 opens only when an excessive pressure is applied to the pressure chamber 24, and does not open during normal operation or low rotation driving.

The plunger spring 30 is contracted between the lower end surface 23 of the plunger 20 and the bottom portion 10c of the adjuster body, and the flange portion 53a of the check ball cage 53 is pressed against the recessed portion 25 while the plunger 20 is pressed.
Is urged toward the opening of the adjuster body 10, that is, toward the push rod 5. The push rod socket 40 has a disk shape, and has an outer diameter substantially equal to the inner diameter of the inner peripheral surface upper portion 10b of the adjuster body, and is axially slidable and rotatable with respect to the upper portion 10b in the adjuster body. Is inserted. Then, the snap ring 11 is fitted into the groove near the upper end opening of the adjuster body 10, so that the push rod socket 40
However, jumping out of the adjuster body 10 is suppressed.

The push rod socket 40 has a recess 41 at the center of the upper end surface (top surface) which is in sliding contact with the push rod 5.
Is provided, and a cylindrical boss 42 that abuts against the plunger 20 is provided at the center of the lower end surface. And
A skirt wall 43 is integrally formed on the peripheral portion so as to face downward. Here, the concave portion 41 is formed to have a curved surface that is substantially equal to the curved surface of the base end of the push rod 5. Further, the boss 42 has a bottomed hole 44 formed in its axial center, and a plurality of through holes 45 are provided on the side surface thereof so as to be orthogonal to the holes 44. Therefore, the bottomed hole 44 and the reservoir chamber 47 described later are communicated with each other through the through hole 45.

On the outer peripheral surface of the boss 42, the diaphragm seal 46 extends over the entire circumference above the through hole 45.
The inner peripheral end of is fixed in a liquid-tight manner. The outer peripheral end of the diaphragm seal 46 is liquid-tightly fixed to the upper end of the lower inner peripheral surface 10a of the adjuster body over the entire circumference. In this way, the diaphragm seal 46,
Lower part 10a of inner peripheral surface of adjuster body, plunger 2
0, the reservoir chamber 47 is defined by the outer peripheral surface of the boss 42 of the push rod socket 40.

In the internal combustion engine equipped with the exhaust brake means in which the lash adjuster 1 as described above is interposed in the exhaust valve system, the operation when the exhaust brake is operated will be described below. When the exhaust brake is operated during the operation of the internal combustion engine, the back pressure of the exhaust manifold becomes equal to or higher than a predetermined value, and a so-called pressure regulation lift occurs in which the exhaust valve is pushed down by the back pressure at the beginning of the compression stroke. Then, a gap is created between the stem head of the valve and the rocker arm, so that the lash adjuster 1 operates so that the valve clearance becomes zero. That is, in the lash adjuster 1, the plunger spring 30 extends to fill the gap and pushes up the plunger 20 and the push rod socket 40 that is in contact with the plunger. Then, the volume in the pressure chamber 24 increases and the pressure in the pressure chamber 24 decreases, so that the first check ball 51 lowers and the oil flows from the reservoir chamber 47 toward the pressure chamber 24. Then, the valve clearance is kept at 0. At this time, the adjustment length is longer than the predetermined length.

In this case, since the lash adjuster 1 is in an improper operating state, the exhaust valve cannot completely close the exhaust port. Therefore, the exhaust valve is slightly lifted up even at the compression top dead center. But,
At the compression top dead center, the strong compression pressure by the piston is applied to the exhaust valve, so that the exhaust valve is forcibly pressed against the valve seat. Then, a load larger than the load during normal operation is about to be applied to the push rod 5, but the plunger 20 is also pushed in the direction of arrow A via the push rod socket 40, and the pressure in the pressure chamber 24 is reduced. To rise. Then, when the pressure in the pressure chamber 24 becomes equal to or higher than a predetermined value, the second check ball spring 62 of the check valve 60 contracts and the second check ball 61 is pushed up, whereby the pressure chamber 24 moves toward the reservoir chamber 47. As a result, excess oil is leaked and excessive pressure rise is prevented. Thus, the adjusted length returns to the predetermined length, and the lift of the exhaust valve is eliminated.

Check valve 60 in lash adjuster 1
The second check ball spring 62 has its spring pressure adjusted so as to contract only when a predetermined pressure or more is applied. Therefore, the check valve 60 is not opened when the exhaust brake is not operated and the engine is driven at low speed. Therefore, the oil is not excessively leaked at the time of low rotation driving, and the reduction of the valve lift at the time of low rotation driving is prevented.

Next, a second embodiment of the present invention will be described with reference to the attached drawings. As shown in FIG. 4, the lash adjuster 2 of the present invention is the same as the lash adjuster 1 of the first embodiment except that the check valve 70 uses a valve spring 71 having a flat bottom. Take a different configuration. Therefore, the same members are denoted by the same reference numerals and detailed description thereof will be omitted.

Like the plunger 20, the plunger 80 of the lash adjuster 2 has a disk shape, and has an outer diameter substantially equal to the inner diameter of the inner peripheral surface lower portion 10a of the adjuster body 10, and the lower portion inside the adjuster body 10 has the same outer diameter. It is inserted into 10a so as to be slidable and rotatable in the axial direction.
The plunger 80 has a peripheral wall 81 similar to the plunger 20.
And a communication hole 82. And the plunger 80
An annular recessed groove 84 having a predetermined depth is provided on the upper surface of the above so as to be concentric with the communication hole 82 over the entire circumference.

At the bottom of the groove 84, a plurality of through holes 85 for passing oil are provided. Further, a groove 86 is provided on the side surface near the upper opening of the concave groove 84 over the entire circumference, and in this groove 86, the donut-shaped plate 7 is formed.
2 is inset. The valve spring 71 is compressed between the bottom of the groove 84 and the plate 72.

The valve spring 71 is a spring in which the wire diameter is gradually reduced from the lower part to the upper part, and the lowermost part is processed to be flat so that the wire has a substantially semicircular cross section. Therefore, the through hole 8 is formed by the flat portion at the lower end.
5 (leak passage) can be closed. Further, by adjusting the spring pressure of the valve spring 71 itself to a predetermined value, when excessive pressure is applied to the pressure chamber 24, the valve spring 71 contracts and the through hole 85 can be opened.

As described above, the lash adjuster 2 is formed by using the valve spring 71 as the check valve. Further, in the internal combustion engine equipped with the exhaust brake means in which the lash adjuster 2 is interposed in the exhaust valve system, when the exhaust brake is operated, the exhaust is caused by the pressure adjustment lift as in the case of the first embodiment. Even if the valve floats and an excessive load is applied to the push rod, when the pressure in the pressure chamber exceeds a predetermined value, the valve spring 71 contracts, the through hole 85 (leak passage) is opened, and excess oil leaks. Therefore, the lift of the exhaust valve is suppressed, and the inconvenience associated therewith is eliminated.

Here, as the valve spring 71, one having a flat lower end and a gradually changing wire diameter is used, but a donut-shaped washer is used to close the through hole 85 (leak passage), The washer may be biased by a normal spring having a constant wire diameter. Although the structure of the closed hydraulic lash adjuster is shown in the embodiment of the present invention, the configuration of the present invention can be applied to a generally used externally supplied hydraulic lash adjuster.

[0032]

The lash adjuster of claim 1 opens the check valve and leaks excess oil when an excessive load is applied to the push rod due to the pressure-controlled lift that occurs when the exhaust brake is used. Then, the normal state can be immediately restored. Therefore, it is possible to prevent an excessive load from being applied to the push rod and the valve mechanism, and it is possible to suppress the interference between the exhaust valve and the piston. Therefore, it can be suitably used for an internal combustion engine with an exhaust brake. Further, the check valve of the lash adjuster opens only when a pressure equal to or higher than a predetermined value is applied, so that the valve clearance is accurately adjusted during normal operation. Therefore, the oil does not leak excessively when the engine is driven at a low speed. Therefore, it is possible to prevent the valve lift from decreasing during low rotation driving.

Since the internal combustion engine of claim 2 is provided with a lash adjuster having a check valve that opens when a pressure equal to or higher than a predetermined value is applied, the exhaust valve due to the pressure regulating lift that has occurred when the exhaust brake is used. Can be prevented from rising. Therefore, it is possible to avoid a situation in which an excessive load is applied to the push rod or the valve mechanism or the exhaust valve and the piston interfere with each other. Therefore, the occurrence of failures is extremely small. In addition, the lash adjuster used here does not excessively leak oil when the engine is running at low speed, so it is possible to prevent the valve lift from decreasing when driving at low speed, and it is good even at low speed. You can drive

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an OHV type valve mechanism.

FIG. 2 is a sectional view showing a schematic configuration of a conventional hydraulic lash adjuster.

FIG. 3 is a sectional view showing a schematic configuration of a lash adjuster of the first embodiment.

FIG. 4 is a sectional view showing a schematic configuration of a lash adjuster of a second embodiment.

[Explanation of symbols]

 1, 2 lash adjuster (present invention) 3 lash adjuster (conventional example) 10 adjuster body 20 plunger 24 pressure chamber 30 plunger spring 47 reservoir chamber 50 check valve 60 check valve 70 check valve 80 checker

Claims (2)

[Claims] 1. A hydraulic lash adjuster interposed in a valve train of an internal combustion engine, including a bottomed cylindrical adjuster body, a plunger slidably inserted in the adjuster body, and the bottom portion. A pressure chamber formed by the adjuster body and the plunger, a plunger spring arranged in the pressure chamber so as to urge the plunger toward the opening side of the adjuster body, and an oil discharged from the pressure chamber. A check valve that allows the flow of oil from the reservoir chamber to the pressure chamber when there is a pressure difference of a predetermined value or more with the reservoir chamber that stores the fluid, and opens when the pressure of the pressure chamber exceeds a predetermined value. A lash adjuster having a leak passage having a check valve configured as described above. 2. An exhaust valve means for increasing the engine braking force by shutting off the exhaust pipe when the engine brake is used, and an exhaust valve system in which a hydraulic lash adjuster is interposed. A lash adjuster has a bottomed cylindrical adjuster body, a plunger slidably inserted into the adjuster body, a pressure chamber formed by the adjuster body including the bottom portion and the plunger, and the plunger with the adjuster body. The plunger spring disposed in the pressure chamber so as to urge it toward the opening side of the reservoir chamber and the reservoir chamber that stores the oil discharged from the pressure chamber, and the reservoir when the pressure difference exceeds a predetermined value. Check valve that allows the flow of oil from the chamber to the pressure chamber, and the pressure in the pressure chamber is above a specified value And a leak passage having a check valve that is opened when the internal combustion engine is opened.