FI80328B - Sealing arrangement - Google Patents

Description

80328

SEALING ARRANGEMENT - TÄTNINGSARRANGEMANG

The invention relates to a sealing structure according to the preamble of claim 1 in the fuel jet pump lifter of an internal combustion engine, in particular a large diesel engine.

The diesel engine injection pump is a single-acting piston pump-5 pu, in which the piston is moved by means of a roller lifter and a cam; the camshaft pushes the piston up and the spring down. The reciprocating cylindrical plunger is rotatable about its longitudinal axis so that the volume of fluid compressed by the pump per stroke can be varied by adjusting the relative angular position of this piston.

The side wall of such a piston has a partially annular or helical section (guide edge) which forms an intermediate part of the piston having a cross-section smaller than the diameter of the rest of the piston. This cut or chute thus divides the piston into two parts, namely the upper part, i.e. the adjusting amount adjusting part, and the lower part, i.e. the actual pressing part. Attached to the lower part of the piston is a cylindrical lifter large in relation to the diameter of the submersible piston, which cooperates with the camshaft and is guided by a cylindrical surface formed in the lower part of the injection pump.

The operating principle of an injection pump according to the current state of such technology is presented, for example, in Finnish patent application no. 763180.

The clearance between the submersible piston and the cylinder of the injection pump is only a few thousandths of a millimeter, which achieves good tightness even at high pressures and low rotational speeds. In the case of a hoist, the clearance is considerably greater. Likewise, the lubricant requirement of the sliding surface of the hoist is considerably higher than the lubricant consumption of the plunger.

30 The cylinder part of the injection pump has one or more radial bores through which the fuel enters the pressure chamber from the suction chamber. At the end of the pump stroke, the 2 80328 fuel in the pressure space flows back into the intake space along the longitudinal groove of the piston. However, between the lower part of the plunger and its cylindrical surface, there is some leakage of fuel downwards into the working space of the lifter and further into the crankcase. 5 Fuel in the lubricant naturally significantly impairs the lubricating properties of the lubricant.

To prevent such leakage, a leakage barrier consisting of heavy oil in the form of an oil groove is provided in the cylinder wall of the lower part of the plunger in the prior art. However, such an oil groove tends to become coking, as the temperature in the area of the oil groove is of the order of 140 ° C. The coking oil groove is no longer able to prevent fuel from leaking down.

The object of the invention is to provide an injection pump sealing-15 arrangement which avoids the disadvantages of the prior art and can effectively prevent fuel leaks into the oil sump or crankcase.

The object of the invention is achieved by arranging the characterizing part of claim 1. By arranging the lift of the injection piston 20 into a separate member, which is even narrower in shape and whose support is located in a cylindrical part below the spring and the spring support, a structure is obtained which can be reliably sealed by a sliding-0 ring and an oil groove. In such a structure, in which the sealing point 25 is moved to a lower part of the structure, the temperature prevailing at the sealing point is considerably lower than in the region of the plunger. Thus, it is possible to use, for example, a sealing Teflon-coated O-ring, the sealing of which is ensured by an oil groove, the risk of coking of which is also avoided due to the lower temperature.

In the arrangement according to the invention, the spring restoring the plunger and its support are located in a closed space where no lubricant is present. Thus, a combustion leakage connection for the combustion can be provided in this space, and the actual sealing arrangements can be arranged in connection with the hoist located below. Structurally, this requires the arrangement of a sealing flange in the lower part of the pump, in which flange a cylindrical opening 5 is formed for the pump lifter.

The invention will now be described in more detail with reference to the accompanying drawing, in which Figure 1 shows an injection pump according to the prior art, and Figure 10 shows the lower part of an injection pump according to the invention with sealing arrangements.

In Figure 1, reference 6 denotes the upper part of the submersible piston of the injection pump and reference 7 denotes the lower part of the piston. Reference 10 is a piston lifter which receives its Sweat from a camshaft 11 via a lifter 15 10. The spring 8 located in the spring support 9 provides a return movement of the piston. In this known arrangement, in which the submersible piston lifter 10 is an integrated part of the injection pump, the entire lower part of the pump where the spring 8, the spring support 9 and the lifter 10 are located is a space lubricated with heavy oil. 20 Thus, sealing arrangements are provided in connection with the lower part 7 of the plunger to prevent excess fuel from entering the space of the hoist. The high temperature at this point prevents the use of a slip-0 ring, and the only option is to use a sealing oil groove 25. As stated earlier, the proper functioning of such an oil groove is disturbed by the coking of the oil in the oil groove.

In the structure according to the invention, the return spring 8 'and the spring support 9' are located separately from the lift. There is no contact between the spring support 9 'and the pump wall 30, and thus there is no need for lubrication. Reference 4 refers to the actual hoist cooperating with the camshaft (not shown). The sealing flange 5 closes the lower part of the injection pump and has an opening for the lifter 4, which is a 35 pin-shaped member. Reference 3 is a drain connection for an additional 4 80328 fuel that has leaked into the lower space past the lower part of the plunger.

In this way, the fuel leak sealing arrangements are connected to the hoist 4. The sealing arrangements comprise a sliding O-ring 1 and an oil groove 2, which preferably simultaneously takes care of the lubrication of the hoist. The hoist 4, in cooperation with the sealing flange 5, provides the necessary control for the movement of the hoist.

The sealing members in connection with the hoist 4 can be provided 10 using several different methods known in the art. Most important in the invention is the fact that the sealing arrangements of the fuel leaks are placed in connection with the circumference of the hoist, which achieves advantages obvious to a person skilled in the art over the prior art. The small amounts of oil used to lubricate the plunger 15 are mixed with the excess fuel in the new arrangement; however, the amounts of fuel used are so small that they are insignificant in terms of fuel composition.

The invention is not limited to the embodiment shown, but several variations are conceivable within the scope of the appended claims.

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Claims (5)

1. Sealing arrangement of a pre-combustion engine, in particular a large diesel engine injection pump, with which arrangement excess fuel is prevented from leaking into the lubricant space 5 of the lifting plunger of the pump and / or of the pump's lubricating sump or the crankcase of the pump, is a pin-shaped member, adjacent to which said sealing arrangement (1,2) is arranged, that the lower part of the pump housing 10 comprises a sealing flange (5), through whose opening the lifting member (4) extends to the interior space of the injection pump and that in the interior space of the injection pump , which is located above the sealing flange (5), is provided with an excess duct (3) for excess fuel leaking past the plunger of the injection pump (6,7). Sealing arrangement according to claim 1, characterized in that said arrangement (1,2) is located between the lifting member (4) and the opening of the sealing flange (5). Sealing arrangement according to any one of the preceding claims, characterized in that the diameter of the lifting member (4) is substantially smaller than the diameter of the internal space of the injection pump within the area of the sealing flange (5). Sealing arrangement according to any of the preceding claims, characterized in that said sealing arrangement comprises a preferably Teflon-coated slide-O-ring (1) and in the direction of any leakage of a sealing oil barrier (2) arranged beyond this. Sealing arrangement according to any of the preceding claims, characterized in that the return spring (8 ') and spring support (9') of the injection pump 30 are located inside the pump in a space above the sealing flange (5).