AN OIL PRESSURE RUSH ADJUSTER OF A DIRECTLY ACTING TYPE

Abstract: A sealing device (60) is provided on the outer circumference of an oil pressure unit (1), or on the partitioning wall (21) of a sub-reservoir (20) surrounding the oil pressure unit (1), or therebetween so as to provide a sealing between said partitioning wall (21) and said outer circumference of the oil pressure unit (1) while an engine stops and allow a part of an oil to leak therebetween while the engine drives. Since the oil is perfectly prevented, while the engine stops, from leaking between the outer circumference of the oil pressure unit and the partitioning wall of the sub-reservoir, the oil amount may be enough secured in the reservoirs though not supplied from the cylinder head, and the air cannot be absorbed into the high pressure chamber.

Description: The invention relates to a hydraulic valve lash adjuster of the bucket type according to the preamble of claim 1. Such a hydraulic valve lash adjuster is known from EP-A-187 217, wherein a partitioning wall surrounding a hydraulic lash adjusting unit is fitted closely on the outer side of an oil pressure unit of the hydraulic lash adjusting unit, so that there is no leakage of oil between the partitioning wall and the oil pressure unit. By every movement of the hydraulic valve lash adjuster a friction force between the broad contact surface of the partitioning wall and the oil pressure unit occures. A valve actuating mechanism used in an internal combustion engine is subject to influences of wear or thermal expansion, whereby a space or a clearance formed at the valve is deformed during the operation, thus influencing the output badly and making noise. Therefore, a valve lash adjuster is used to rectify the deformed space. A valve actuating mechanism has been composed to be light in weight for a cam to directly strike a shaft end of a valve, and such a mechanism has also been employed with the valve lash adjuster as shown in Fig. 8. The valve lash adjuster is composed of a bucket X and the oil pressure unit Y housed therein, and is placed between a cam 300 and the shaft end of a valve 400. The oil pressure unit Y is slidably mounted on the outer circumference of a plunger 101 shaped in cylinder form and having an oil hole 104 at its bottom. The unit Y comprises a body 100 of cylinder shape defining a high pressure chamber 102 in relation with the bottom of the body 100; an elastic member 105 provided in the high pressure chamber 102 and biasing the body 100 downward; a check valve 106 disposed in the high pressure chamber for opening and closing the oil hole 104; and a valve spring 107 supporting the check valve 106 and a check valve cage 108 in the high pressure chamber 102. The oil pressure unit Y is housed in the bucket X, defining a main reservoir 103 as an oil storage between the rear side of a face disc 202 and the hollow portion of the plunger 101 as well as a sub-reservoir 200 communicating, via an overflow recess 203, with the main reservoir 103 partitioned with the circumferential wall of the plunger 101, the sub reservoir 200 being supplied with the actuating oil through an oil feed hole 500 of a cylinder head and an oil hole 510 of the bucket X. On the other hand, the cam 300 is in contact with the face disc 202 of the bucket X, while the shaft end of the valve 400 is in contact with the closed face of the body 100, so that the cam 300 strikes the shaft end of the valve 400 via the valve lash adjuster. The valve lash, adjuster makes use of the imcompressibility of the actuating oil effected when exerting pressure to the actuating oil filled in the high pressure chamber 102, and a repulsion wherein the elastic member 105 expands in the chamber when releasing the pressure so as to rectify the space to be zero which has been thermally deformed in the valve actuating mechanism. A part of the oil to be supplied to the sub-reservoir 200 leaks via a space between the outer circumference of the oil pressure unit Y (the outer circumference of the body 100 in the drawing) and the sleeve 201 forming a partition of the sub-reservoir 200. No special problems arise if the oil leaks while the engine drives, because the actuating oil is supplied into the sub-reservoir 200 from an oil field hole 500 of a cylinder head and an oil hole of the bucket X. But if the engine stops, the oil is not supplied any longer from the cylinder head until the engine is re-started. Especially when the engine stops under an oblique state, or when the stopped engine is furnished with a lash adjuster in an oblique state, the oil cannot be sufficiently secured in the reservoirs 103, 200 due to the oil leaking. When the engine re-starts, air may be absorbed together with the actuating oil from the reservoir 103 into the high pressure chamber 102. When the internal combustion engine is stopped while a cam nose 301 keeps pressing the face disc 202 of the bucket X, the oil pressure unit Y is compressed as shown in Fig. 9, that is, it is most shortened or pressed to a maximum. If the engine is re-started under this condition, the sliding stroke between the plunger 101 and the body 100 is a maximum, and the oil is absorbed into the high pressure chamber 102. Because the oil is not supplied thereinto from a cylinder head, as said above while the engine is stopped, the oil amount is reduced in the main and sub-reservoir. Therefore air is absorbed into the high pressure chamber 102, and the incompressibility of the actuating oil is lost, so that the space of the valve cannot be rectified. This is called a "sponge" condition). SUMMARY OF THE INVENTION In view of the above-stated problems of the prior art the present invention has been devised, and it is an object of the invention to prevent the leakage of oil while the engine is at rest although part of the oil is allowed to leak while the engine is driven. This object is achieved by the features in the characterising part of claim 1. Since the oil is perfectly prevented from leaking between the outer circumference of the oil pressure unit and the inner flange of the sub-reservoir while the engine is stopped, the oil amount may be secured enough in the reservoirs though there isn't any oil supplied from the cylinder head, and the air cannot be absorbed into the high pressure chamber. On the other hand, since the actuating oil is supplied from the cylinder head. while the engine is driven, and if there weren't any leakage between the outer circumference of the oil pressure unit and the inner flange of the sub-reservoir, the oil would be hindered from circulating. Thus, the present sealing device allows a part of the oil leaking therebetween while the engine is driven so that the oil may circulate. However, the leaking amount is naturally smaller in comparison with the case of having no sealing device. Depending upon such a structure, if the actuating oil is mixed with air going into the high pressure chamber, it is possible to exhaust it outside as a leaking amount. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 is a cross-sectional view showing the valve lash adjuster exemplified in the invention in connection with a valve actuating mechanism of a directly actuating type; Fig.2 is an explanatory view showing a maximally pressed ion of the oil pressure unit when the cam contacts the face disc of the bucket with its cam nose; Fig.3 is an explanatory view showing another embodiment; Fig.4 is a partially cross-sectional view showing another embodiment; Fig.5 is a cross-sectional view showing a further embodiment; Fig.6 is a partially cross-sectional view showing another embodiment; Fig.7 is a partially cross-sectional view showing another embodiment; Fig.8 is a cross-sectional view showing a conventional example of a valve-actuating mechanism of the bucket type; and Fig.9 is an explanatory view showing when the oil pressure unit is maximally pressed and stopped with the cam nose. In the drawings, 1,Y are oil pressure units; 10,100 are bodies; 11,101 are plunger; 12,102 are high pressure chambers 13,103 are main reservoirs; 14,104 are oil holes; 20,200 are sub-reservoirs; 21 is an inner flange or a partitioning wall; 201 is a sleeve; 22,202 are face discs; 3,303 are cams; 30,301 are cam noses; 60,61,62,63,64,65 are sealing members. DETAILED DESCRIPTION OF THE INVENTION Actual embodiments of the invention will be explained in reference to the attached drawings. Figs.1 and 2 of the drawings show one example of the invention. In the drawings, the reference numeral 1 is an oil pressure unit; 10 is a body composing the unit 1; 11 is a plunger also composing the unit 1; 12 is a high pressure chamber defined between the body 10 and the plunger 11; 13 is a main reservoir defined in the plunger 11; 14 is an oil hole communicating between the high pressure chamber 12 and the main reservoir 13; 2 is a bucket; 20 is a sub-reservoir defined by a partitioning wall furnished within the bucket 2; 3 is a cam; 4 is a valve; and 5 is a valve spring. In the present embodiment, a sealing member 60 of a circular shape is attached to the bottom of a partitioning wall 21 of the sub-reservoir 20 so that an inner circumferential rim respectively edge 60a of the sealing member 60 is in contact with an outer circumference of a closed side of a body 10 reduced in diameter, wherein said sealing member becomes smaller in thickness as extending to the inner side. The inner circumferential edge 60a of this sealing member 60 contacts the outer circumference of the closed side of the body 10 when the engine stops, so as to seal a space between the body 10 and the partitioning wall 21 and to prevent the oil leaking from the sub-reservoir, irrespective of the case that the cam 3 is in contact with a face disc 22 of a bucket 2 at its circular base as shown in Figs.1 and 2, and of the case of contacting it at its cam nose 30. It is assumed that the oil leaks nostly when the rush adjuster is tilted as shown in Fig.2. The oil leaks also mostly when the engine stops in a state that the cam 3 contacts the face disc 22 with its cam nose 30 (i.e., morsinnally pressed condition), but the leakage of the oil is avoided, and the oil may be sufficiently stored in the reservoirs 13, 20 though the oil is not supplied from the cylinder head, and the air can be avoided from going into the high pressure chamber 12 when the engine is re-started. During driving of the engine, the inner circumferential edge 60a of the sealing member 60 is deformed due to the pressure of the actuating oil sent from the cylinder,head, and a space or clearance is created in relation with the outer circumference of the closed side of the body 10, and the oil partially leaks therefrom. Although the actuating oil circulates from the cylinder head to the reservoirs 13, 20 and oil mixed with air flows in, it may be exhausted from the space. By closing the space between the outer circumference of the body 10 and the partitioning wall 21 of the sub-reservoir 20, it is made difficult for the actuating oil stored in the main reservoir 13 and the sub-reservoir 20 to flow out from the oil hole of the bucket 2. Fig.3 shows another embodiment in which a ring-shaped sealing material 61 is attached with a patch 70, as seen in the preceeding embodiment, to the lower end of a vertical side of the partitioning wall 21 of the sub-reservoir 20, and the inner circumferential thin edge 61a is in contact with the outer circumference of the closed side of the body 10. Figs.4 and 5 show, contrary to the above embodiment, that ring-shaped sealing members 62,63 are attached directly or with a patch 71 to the outer circumference of the closed side of the body 10, and the thin rims 62a,63a are in contact with the lower sides of the partitioning wall 21 of the sub-reservoir 20. Figs.6 and 7 show that a vertical face of the partitioning wall 21 of the sub-reservoir 20 is extended downward, and flat sealing parts 64,65 of ring shape are secured directly or with the patch 72 to the outer circumference of the closed side, and rims 64a,65a of the sealing members 64,65 are in contact with said vertical face of the partitioning wall 21. In the embodiments shown in Figs. 6 and 7, if the body 10 and the partitioning wall 21 slide vertically in relation to one another, the end parts 64a,65a of the sealing members 64,65 are always in contact with the vertical face of the partitioning wall 21. But the end parts 64a,65a are deformed during the operation of the engine and a space is made in relation with the vertical wall 21 so that a part of the oil is allowed to flow out. According to the invention, since the sealing device prevents the oil leakage between the outer circumference of the oil pressure unit and the partitioning wall of the sub-reservoir, and if the oil pressure unit is maximally pressed and the engine is stopped, the oil is sufficiently secured in the reservoirs, so that air will not be absorbed into the high pressure chamber when the engine is re-started. The oil is allowed to leak partially during the operation of the engine, and thereby the supply of oil from the cylinder head is not disturbed. The leaking amount of this case is smaller than in the case without an sealing device, so that an exhausting amount of an oil pump may be small and a path for an oil return from the cylinder may be small. Since the oil leaking amount is restrained as said above and if the oil mixed with air is supplied into the reservoirs, the air is prevented from accumulation therein. In addition, when the oil supply force increases, the partial leakage is allowed, and since the oil pressure within the reservoirs increases in comparison to the case without the sealing, and even if the air is mixed, the coil does not miss its incompressibility.

Claims: Hydraulic valve lash adjuster of the bucket type placed between a driving cam (3) and the shaft end of a driven valve (4), comprising an oil pressure unit (1,10) within a bucket (2), a main reservoir (13) within the oil pressure unit (1,10), a subreservoir (20) surrounding the oil pressure unit (1,10) within the bucket (2) for supplying oil fed from a cylinder head to the main reservoir (13), and an inner flange (21) fixed to the inside face of the bucket (2) defining the subreservoir (20) and comprising a cylindrical part surrounding and guiding the oil pressure unit (1,10), wherein a space is provided between the outer circumference of the oil pressure unit (1,10) and said cylindrical part of the flange (21), through which space oil can leak from the subreservoir (20), characterized in that a sealing element (60) extends across said space between the outer circumference of the oil pressure unit (1,10) and the inner flange (21), wherein the sealing element (60) is deformable, so that, when the engine is driven, the sealing element is deformed due to the oil pressure for opening said space through which oil can leak from the subreservoir (20), whereas the space is closed by the sealing element (60), when the engine is stopped. Hydraulic valve lash adjuster according to claim 1, characterized in that the sealing element (62;63) is with one rim attached to the circumference of the oil pressure unit (1,10) and the other rim (62a;63a) is in contact with the lower side of the partitioning wall (21). Hydraulic valve lash adjuster according to claim 1, characterized in that the sealing element (64;65) is attached with one rim to the circumference of the oil pressure unit (1,10) and the other rim (64a;65a) is in contact with the vertical face of the partitioning wall (21). Hydraulic valve lash adjuster according to one of the proceeding claims, characterized in that the sealing element (60) becomes thinner as extending to the other rim (60a). Hydraulic valve lash adjuster according to one of the proceeding claims, characterized in that the sealing element (61;62;64) is attached with a patch (70;71;72).

Inventors: HOSAKA, AKIHIKO
Applicants: NITTAN VALVE CO., LTD.
Application year: 1990
Main classification: F01L1
IPC codes: F01L1