The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
There are known internal combustion engines for motor vehicles comprising a head bearing one or more cylinders, within which the work cycle is carried out, and which are placed in communication with respective combustion chambers of the engine itself. On the above mentioned head, there are further obtained appropriate seats intended to let the combustion chamber communicate with ducts adapted to supply a mixture of unburnt fuel and air to said chamber (“suction ducts”), and discharge the burnt gases from said combustion chamber (“discharge ducts”).
The flows from and to each combustion chamber are controlled by appropriate valves operating on the mentioned seats. Specifically, each valve generally comprises a guide element fixed within a cavity of the engine head and a slidingly displaceable rod in opposite directions within a through seat defined by the guide element and bearing, at one end, a clogging section to close the connection between the relative suction or discharge duct and the corresponding combustion chamber.
The opposite end of the rod of the valve axially protrudes from the relative guide element and is adapted to receive driving forces from a relative control device.
On the valves of the above described type, there are normally mounted seal gaskets for the lubricating oil normally circulating in the engines. Such gaskets, in one of the most commonly known forms, comprise a support or reinforcing element having a substantially tubular configuration, generally made of a metal material, and an element made of elastomeric material interposed between the support element and the valve.
Specifically, the elastomeric element typically comprises a first portion adapted to cooperate by means of its inner surface with the outer surface of the upper portion of the guide element, and a second portion adapted to directly cooperate with the rod of the valve.
The gaskets of the above described type are widely used in all internal combustion engines to control the amount of lubricating oil that flows from the distribution area towards the combustion chambers. An excessive flow of lubricating oil causes a deterioration in efficiency of the engine and a drop in the performance of the motor vehicle catalytic converter as well as an evident excessive consumption of the oil itself. On the other hand, an insufficient flow determines an increase in the wear and the noise of the valves together with the occurrence of local temperature peaks. These phenomena may determine a premature damage of the valves following the seizure of the rod of the valves themselves within the guide element.
The known gaskets allow the construction of a static-type seal by means of the first portion of the elastomeric element operating on the guide element of the relative valve, and the construction of a dynamic-type seal by means of the second portion of the elastomeric element cooperating with the rod. Specifically, the static seal must ensure a certain degree of radial compression on the guide element in order to avoid the throttling of the lubricating oil to the combustion chambers and at the same time maintain the gasket itself in position, whereas the dynamic seal is designed to allow the minimum flow of oil required for the lubrication of the coupling between rod and guide element.
The support element comprises a first substantially cylindrical portion and a second discoidal annular portion, extending from an axial end of the first portion towards the valve in a transversal direction with respect to the axis of the first portion itself; such a second portion is partially drowned in the elastomeric element.
There are known gaskets of the above described type, in which the elastomeric element is further provided with an annular gas tight seal lip, commonly known as “gas lip”, which is normally arranged in a position interposed between the mentioned first and second portions and cooperates with the rod of the relative valve.
Such a lip serves to counteract the positive pressures of the gases which in some applications occur at the seats on which the valves operate; it protrudes towards the rod of the relative valve from the inner circumferential surface of the elastomeric element and displays an annular frustoconical configuration having a decreasing section in opposite direction to the direction of the pressure forces of the gases ascending along the valves from the relative seats on which such valves operate.
The gas tight seal lip is connected to the remaining part of the elastomeric element at its part displaying a section having a greater diameter and along its radially outermost peripheral edge; in this manner, a sort of virtual hinge between the gas tight seal lip and the inner circumferential surface of the elastomeric element is made.
In the presence of pressure forces ascending along the valve from the seat controlled by such a valve, the gas tight seal lip normally tends to be rotated towards the rod of the valve itself so as to increase the sealing effect. However, in the case in which the pressures involved are especially high, the seal lip could be rotated with respect to the circumferential line which connects it to the inner surface of the elastomeric element by an angle such that it reverses the orientation of its conicalness; in practice, the gas tight seal lip would be arranged with decreasing sections in the direction of the pressure forces it should counteract, therefore losing any counteracting ability.
To overcome such a drawback, it would be required to increase the resistance of the gas tight seal lip so as to make it virtually rigid with respect to high gas pressure values. Such a solution would although be at the expense of the flexibility which such a lip should in any case maintain to allow to restore, during assembly, possible concentricity errors between the gasket and the rod of the valve.
The present disclosure provides a gasket for a valve in an internal combustion engine, which allows to overcome the drawbacks related to the gaskets of the known and above specified type in a simple and cost-effective manner.
The present disclosure refers to a gasket for a valve in an internal combustion engine, said valve comprising a guide element defining a through seat, and a slidingly displaceable rod in such a seat, said gasket comprising a first elastically deformable portion adapted to cooperate with the rod of said valve; a second elastically deformable portion adapted to cooperate with the outer surface of said guide element; and a third elastically deformable portion interposed between said first and second elastically deformable portions and bearing a cantilevered gas tight seal lip adapted to cooperate with said rod of said valve; said lip displaying a frustoconical configuration having a decreasing section in opposite direction to the pressure forces directed in use towards said first elastically deformable portion and being connected to said third elastically deformable portion at its greater section part; wherein said lip is connected, on the side exposed to said pressure forces, to said third elastically deformable portion by a surface bearing one or more waves.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.