JPS6340274B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to fuel injection pumps, and more particularly to fuel injection pumps for diesel-powered internal combustion engines.

Recently, efforts have been made to reduce the consumption of diesel fuel, which has become increasingly expensive.
This applies in particular to high-power diesel engines. One possibility to achieve this is to enhance the formation of internal mixtures by improving the atomization of the fuel. For this purpose the pressure in the fuel injection system must be increased significantly. Components operated at high pressures and subjected to compressive stresses must consequently be designed to withstand continuous pulse pressures and deformations, and to minimize leakage. Therefore, efforts are being made to reduce and minimize the number of critical high pressure sealing surfaces in fuel injection systems. Conditions on fuel injection pumps are particularly problematic in this regard. This is because one or two discharge valves are required between the pump chamber and the input duct for accurate dosing.

German Utility Model No. 1892860 discloses a fuel pump in which the piston guide is provided with a partition wall which delimits the pump chamber in the discharge direction. This compartment wall is followed by a protruding collar with external threads. Holes are drilled in the partition wall and in the collar leading to the free front end surface. The front end face of the collar is flat and polished, preferably lapped. The pressure support rests directly on the flat, precision-finished front end face of this piston guide and is fixed thereto. In this way, the front end face of the piston guide acts as a sealing surface between the piston guide and the pressure support without the need for an additional sealing ring.

In this prior art device, the valve piston of the valve closing body is guided in a bore which communicates from the pump chamber with the pressure support. Therefore, the diameter of this hole is relatively large;
It corresponds approximately to the inner diameter of the piston guide and to the diameter of the pump piston guided through the piston guide. The stability of the wall section delimiting the pump chamber is thereby affected. Furthermore, in this conventional device, the closing body is developed as a valve cone,
The bore in the piston guide has a correspondingly formed valve receiving surface. However, the production of a conical bearing surface for such valves, which must match the shape of the valve cone, is expensive. Furthermore, if a repair is required, the valve receiving surface, in addition to the free front end surface of the piston guide acting as a sealing surface, must also be reworked, which has the disadvantage of further increasing the repair costs.

The invention is therefore based on the problem of improving a fuel injection pump of the above-mentioned type in such a way that it can supply pressures of more than 2000 bar in continuous operation with little technical effort and without fear of leakage. .

This problem is solved by the configuration described in claim 1.

The invention is based on the idea that when the valve closing body is guided in the pressure support, the stability of the compartment wall delimiting the pump chamber in the discharge direction can be significantly improved. In this case, the diameter of the bore in the piston guide can be significantly reduced.
Furthermore, the design is substantially simplified, and the flat precision-finished front end face of the piston guide is used directly as a valve face for the valve closing body, which has a flat sealing surface. This embodiment has the advantage that when overhauling the pump guide, the valve receiving surface is also machined by simply machining the front end face.

In such an embodiment, significant elastic deformations of the piston guide at high pressures can be tolerated without danger. This is because the lateral partition walls defining the pump chamber are stably connected by the front wall. An advantageous development of the invention makes it possible to compress the bush onto the piston guide in order to further improve the stability. The dimensions of this bushing are then calculated in such a way that the stresses occurring in the radial direction compensate or balance the stresses caused by the high internal pressure in the pump chamber.

Compared to conventional devices, the sealing surface between the front end face of the piston guide and the pressure support is improved by being screwed directly onto the piston guide via several screws. This method allows even higher surface pressures to be obtained than with conventional devices.

Further advantageous embodiments of the invention will be described below with reference to the accompanying drawings.

A piston guide 2 is arranged within the pump container 1 . In the illustrated embodiment, this piston guide 2 is provided with a bush 3 crimped on its outside in order to withstand high pressures and increase mechanical stability. The piston 4 is connected to the piston guide 2 as usual.
The pump chamber 5 in the piston guide 2 is delimited in the discharge direction by a partition wall 6. The edge of the partition wall 6 projects laterally from the circumferential surface of the piston guide 2 to form a flange 7. The piston guide 2 is inserted into a hollow cylindrical pump container 1, and the flange 7 is fixed to the pump container 1 by a tension ring 8 and screws 9.

Two boreholes 10 and 11 are perforated in the partition wall 6 which limits the pump chamber in the discharge direction, which open into the free front end face 12 of the piston guide 2 . The hole 10 serves to conduct the fuel supplied by the upward movement of the piston 4, while the hole 11 acts as a fuel return hole. The two holes 10 and 11 are arranged eccentrically with respect to the piston guide axis, and both have diameters that are smaller than the inner diameter of the piston guide body 2. The pump chamber 5 is therefore stably sealed even at pressures of 2000 bar or more.

The front side of the partition wall 6, ie the side 12 of the piston guide 2 facing away from the pump chamber, is designed as a flat, precision-finished sealing surface. Press support 1
3 seats directly on this front face 12 and is attached to the piston guide by several screws. Therefore, a sufficient sealing condition is ensured between the piston guide 2 and the pressing support 13.

Two valves 15 and 16 are located in the pressure support 13.
There is. The closing body 17 of the valve 15 is a pressure spring 1
8 and is substantially formed as a cylindrical body with a pocket hole 19 which communicates with a portion of the output duct 20 of increasing diameter. This cylindrical closure body 1
The end face 21 of 7 is designed as a flat sealing surface, which rests directly on the flat front end face 21 of the piston guide 2 in the rest position. This front end surface 12 thus acts as a flat seating sealing surface. When this front end surface 12 is machined, the valve sealing surface is accordingly also machined.

Via an inclined input duct 22 opening into the jacket surface, the pocket hole 19 in the closure body 17 is connected to an annular duct 23 surrounding the closure body 17, through which the fuel can flow when the valve is opened. It flows into the output duct 20. When valve 15 is opened,
The closing body 17 moves in the same direction as the discharge piston, and the rise of the valve thereby is limited when the closing body 17 collides with the edge 24 of the pressure support 13. The discharged fuel is forced into the bore 25 of the pressure support and further into an injection pipe, which is not shown in detail.

An input duct 26 is connected to the valve 1 from the hole 25 in the pressure support.
It is connected to 6. The input duct 26 in this pressure support 13 is connected to the bore 11 in the partition wall 6 of the piston guide 2 . This second valve 16 opens in a direction opposite to the direction of fuel supply, thus allowing fuel to flow back into the pump chamber. valve 16
has a ball 27 or cone as a sealing means, which has a suitably shaped valve receiving surface 2.
Works in conjunction with 8. A stop bush 29 is inserted into the input duct 26 from the side of the piston guide 2, on whose perforated bottom 30 a valve pressure spring 31 is supported. Stop button 2
9 is pressed onto the front face 12 of the piston guide 2 by this valve pressure spring 31. The opposite free edge 32 limits the lifting of the valve closure.

As clearly shown in the figure, the input duct 26 and the output duct 20 open at a distance A into the bore 25 of the pressure support. 2 ducts 20,2
The wall thickness A between 6 and 6 cannot be substantially reduced further. This is because unacceptable peak stresses are created in the material. This advantageous embodiment therefore has the aim of creating a fuel injection pump which can also withstand high charging pressures without any danger during continuous operation. To further explain the overall structure of the device, the piston guide 2 has two control holes 40 and 41 through which fuel can flow into the pump chamber 5. The piston 4 is provided with two opposite control ends 42, 43, which operate in cooperation with these control holes 40 and 41.

According to the invention, a fuel injection pump has been developed which has only one high-pressure sealing surface on the front side of the piston guide 2 and can therefore withstand high stresses.

Its construction is simple compared to known devices in which this high-pressure sealing surface simultaneously acts as a receiving surface for the valve. This saves time when testing the fuel injection pump is necessary.

[Brief explanation of the drawing]

The figure shows, partially in section, a fuel injection pump according to an embodiment of the present invention. 2... Piston guide body, 3... Button, 4...
... Piston, 5 ... Pump chamber, 6 ... Compartment wall, 7
...Flange, 8...Tension ring, 10,
11... Hole, 12... Front end surface, 13... Pressing support, 15, 16... Valve, 17... Closing body for valve 15, 18... Pressure spring, 19... Pocket hole, 20... Output Duct, 22...Input duct,
23... Annular duct, 26... Input duct, 27
... Ball, 28 ... Surface that receives the valve.

Claims (1)

[Scope of Claims] 1. A piston guide 2 arranged in a pump container 1, which has a partition wall 6 which partitions a pump chamber 5 in the discharge direction. The piston guide 6 is provided with one or more holes 10 communicating with the front end surface 12 thereof, and is further provided with a pressing support 13 which is attached by pressing directly onto the flat front end surface 12 of the piston guide 2. The pressing support 13 has an output duct 20 following the hole 10.
and a closing body 17, which discharge valve 15 is guided in the pressure support 13 and seals the bore 10 in the piston guide 2 in the rest position, said piston guide 2 The front end face 12 of the partition wall 6 is a flat plane with a precision finish, and the closure body 17 has a flat sealing surface 21 which, in the rest position, provides a precision finish of the piston guide body 2. A fuel injection pump characterized in that the fuel injection pump is seated directly on a flat front end surface 12. 2 The guide body 2 has a bush 3 crimped on its outer surface.
and the dimensions of this bush 3 are selected in such a way that the stresses occurring in its radial direction compensate or balance the stresses caused by the high internal pressure in the pump chamber 5. The fuel injection pump according to item 1. 3. Fuel injection pump according to claim 1, characterized in that the pressure support 13 is attached directly to the piston guide 2 by several screws 14. 4 The closing body 17 of the valve 15 is substantially formed as a cylinder provided with a pocket hole 19 for receiving the pressure spring 18 and is guided through the output duct section 20 of enlarged diameter so that the closing body 17 in the oblique direction
The fuel injection pump according to claim 1, characterized in that the pocket hole (19) is connected to an annular duct (23) surrounding the closure body (17) through an input hole (22) which is opened in a side surface of the fuel injection pump. 5 Second hole 11 in partition wall 2 of piston guide 2
is bored, an input duct 26 is provided in the pressure support 13 adjacent to it, a valve 16 which opens in the direction opposite to the discharge direction is arranged in the input duct, a stop bush 29 is inserted into the input duct, The free edge 32 of the stop bush 29 limits the amount of descent of the valve closure body 27, the perforated bottom 30 of this stop bush 29 being pressed against the free front end face 12 of the piston guide 2 by the valve pressure spring. Claims 1 to 4 are characterized in that
A fuel injection pump according to any one of the following paragraphs. 6. The fuel according to claim 5, characterized in that the output duct 20 and the input duct 26 open into the hole 25 of the pressure support 13 at a distance 16 from each other within the pressure support 13. Infusion pump.