DE10302043A1 - High pressure fuel pump with ball valve in the low pressure inlet - Google Patents

Abstract

A high-pressure fuel pump (10), in particular a radial piston pump, is proposed, in which the suction valves (35) are designed as ball valves, which has an advantageous effect on the efficiency of the high-pressure fuel pump (10). In addition, the manufacture and assembly of the high-pressure fuel pump (10) according to the invention is simplified by the use of ball valves.

Description

The invention is based on one from the German patent DE 101 17 600 Known high-pressure fuel pump for a fuel injection system with a housing, with a low-pressure inlet, with a delivery chamber in which the fuel is compressed, with a suction valve between the delivery chamber and low-pressure inlet, wherein a valve member of the suction valve is supported against a compression spring arranged in the delivery chamber.

With this high pressure fuel pump the valve member of the suction valve is designed as a valve cone.

Advantages of invention

In a high-pressure fuel pump according to the invention for a Fuel injection system, with a housing, with a low pressure inlet, with a funding room, in which the fuel is compressed, with a suction valve between delivery chamber and low pressure inlet, wherein a valve member of the suction valve against one in the production room supports the arranged compression spring, the valve member of the suction valve is designed as a ball.

This will make the High pressure fuel pump simplified because a ball is cheaper to manufacture is as a valve member with a sealing cone and a stem, like it is known from the prior art. It also improves efficiency the high-pressure fuel pump according to the invention improved because a ball together with the sealing seat is an exact defined circular Sealing line forms that despite the inevitable manufacturing tolerances in the manufacture of the valve seat with respect to the valve seat seals very well. If the valve seat cooperating with the ball is round, the suction valve according to the invention seals well, too if the angle or location of the valve seat is not made with the highest precision were.

Furthermore, with the suction valve according to the invention ensures that all suction valves are manufactured in series High pressure fuel pumps have almost identical hydraulic properties and thus the optimization of the high-pressure fuel pump manufactured in series is simplified.

In a variant of the invention it is provided that between the compression spring and ball a spring plate is arranged so that the ball is fixed relative to the sealing seat is improved and also a Buckling of the compression spring is avoided. In addition, the use of a spring plate enables that the diameter of the compression spring and ball can be different. It has proven particularly advantageous when the diameter the ball is smaller than the diameter of the compression spring, because in In this case, the buckling of the compression spring is effectively avoided and the diameter of the ball the hydraulic requirements corresponds to the high-pressure fuel pump in an optimal manner.

In a further embodiment the invention is the valve seat, which cooperates with the ball, in the housing incorporated so that the number of pressurized Sealing surfaces and compared to the number of components the high-pressure fuel pump known from the prior art is reduced. This increases the reliability of the High-pressure fuel pump according to the invention and lowers the manufacturing and assembly costs of the same.

It has proven to be beneficial if the valve seat has a seat angle between 30 ° and 150 °, in particular between 80 ° and 100 °.

As an alternative to that arranged directly in the housing The housing can fit tightly also include a screw, which bore a delivery chamber to the outside closes, and in their promotion room facing end face the valve seat is formed. This variant has the advantage that, for example, the suction valve is installed or replaced in the event of a repair can be done without the high pressure fuel pump completely disassemble since the suction valve is accessible from the outside via the screw.

In a further embodiment of this variant it is provided that the screw has a reduced diameter Area that the reduced diameter with the housing bounded an annulus, and that the annulus with the low pressure inlet hydraulically connected. This ensures in a simple manner that regardless of how far the screw is screwed into the housing, always one hydraulic connection to the low pressure inlet.

The advantages of the invention come naturally in a fuel system with a fuel tank, with an injection valve, which delivers the fuel directly into the combustion chamber of an internal combustion engine injects, with a high pressure fuel pump and with a fuel rail, to which the at least one injector is connected for Wear if the high pressure fuel pump is designed according to one of the preceding claims is.

Other advantages and beneficial Embodiments are the following drawing, its description and the claims removable.

Show it:

1 a first embodiment of a radial piston pump according to the invention,

2 a second embodiment of a radial piston pump according to the invention,

3 an intake valve according to the invention in an enlarged view and

4 is a schematic representation of an internal combustion engine equipped with a high-pressure fuel pump according to the invention.

description the embodiment

1 shows a first embodiment of a high-pressure fuel pump 10 according to the invention in cross section. The high pressure fuel pump 10 is a radial piston pump with three pump elements 11 executed. The pump elements 11 include a piston 13 that is in a cylinder bore 15 to be led. The cylinder bore 15 is in one case 17 the high pressure fuel pump 10 executed as a blind hole. Via manufacturing and assembly holes 19 can the cylinder bore 15 getting produced. After mounting the high-pressure fuel pump according to the invention, the mounting holes 19 by plugging 21 locked.

The pistons are driven 13 from a drive shaft with an eccentric section 22 over a polygon ring 23 with flats 25 , On the flats 25 there is a piston footplate 27 on which the piston 13 in an oscillating motion when the drive shaft is driven and the polygon ring 23 consequently makes a circular movement. The oscillating movement of the pistons 13 is in one of the pump element 11 with a double arrow 29 indicated.

The cylinder bore 15 and the piston 13 limit a funding area 31 per pump element 11 , being the volume of the delivery space 31 depends on the position of the drive shaft. At the in 1 perpendicular. pump element directed upwards 11 whose piston 13 is near its top dead center (TDC) is the volume of the headroom 31 minimal while it is with the other pump elements 11 has almost a maximum. With a compression spring 33 become the piston foot plates 27 and with her the pistons 13 always in contact with the flats 25 of the polygon ring 23 held.

For reasons of clarity, not all pump elements 11 All components are provided with reference symbols. However, they are all three pump elements 11 constructed the same way and have the same components.

The cylinder bore 15 is, as already mentioned, designed as a blind hole. At the end of the cylinder bore 15 is a suction valve 35 with a sealing seat 37 and one with the sealing seat 37 interacting sphere 39 intended. The bullet 39 is over a spring plate 41 from a compression spring 43 that are at the other end on the piston 13 supports against the valve seat 37 pressed.

Here is the compression spring 43 dimensioned so that fuel is not automatically drawn in at bottom dead center. If not shown, on the suction side of the high-pressure fuel pump 10 arranged metering unit is closed, promotes the high-pressure fuel pump 10 no fuel. If the metering unit is opened completely or partially, builds up in front of the suction valve 35 an overpressure generated by a prefeed pump (not shown) due to the fuel against the compression spring 43 in the funding room 31 is pressed. The metering unit has the task of setting the overpressure in front of the suction chamber so that the desired delivery rate from the high-pressure fuel pump 10 is promoted.

If the piston 13 has moved in the direction of its top dead center, the bias of the compression spring takes 33 so strong that the ball 39 against the sealing seat 37 is pressed and thus the connection between the delivery area 31 and low pressure inlet 45 is interrupted. This effect is intensified considerably by the increasingly higher pressure in the delivery chamber 31 ,

Alternatively, the compression spring 43 also be dimensioned so that the ball 39 also at the bottom dead center (UT) of the piston 13 still slightly against the sealing seat 37 is pressed. Only if on the in 1 not shown low pressure side of the high pressure fuel pump 10 sufficient overpressure compared to the pressure in the delivery chamber 31 there is fuel flowing into the delivery chamber 31 on. The pressure on the low pressure side of the high pressure fuel pump 10 , or the suction side of the delivery chamber 31 and thus the delivery rate of the high-pressure fuel pump 10 is replaced by an in 1 Metering unit, not shown, set by a control unit (not shown) as a function of the operating state of the internal combustion engine.

These measures ensure that even when the metering unit, not shown, the fuel flow through the low pressure inlet 45 into the pump elements 11 is throttled, each of the pump element 11 approximately the same amount of fuel is sucked in and thus a uniform torque and power requirement of the high-pressure fuel pump 10 results. This improves the smooth running of the internal combustion engine, especially when idling.

In that the piston 13 not even over its entire length in the cylinder bore at its top dead center 15 there is sufficient "overflow" for honing tools or the like. This overflow facilitates the production of the cylinder bore designed as a blind hole 15 ,

A high pressure outlet and the associated pressure valve are in 1 not shown, since the high pressure outlet and the associated pressure valve are perpendicular to the plane of the drawing behind the pump elements 11 are arranged. The arrangement of these components can be found in the DE-PS 101 17 600 to which reference is hereby made.

By using a spring plate 41 between bullet 39 and compression spring 43 will lead ball 39 improved. In addition, due to the improved contact surface of the compression spring 43 on the spring plate 41 a buckling of the compression spring 43 be prevented. Finally, the diameter of the ball 39 regardless of the diameter of the compression spring 43 be chosen what to optimize the high pressure fuel pump 10 can be beneficial.

However, it is also easily conceivable and possible on the spring plate 41 to do without (not shown) so that the compression spring 43 right on the ball 39 rests.

At the in 1 illustrated first embodiment of a high-pressure fuel pump according to the invention 10 there is only a very small number of high-pressure sealing points. This is especially the sealing seat 37 in connection with the ball 39 as well as the annular gap between pistons 13 and cylinder bore 15 , In many cases, this small number of high-pressure sealing points justifies the somewhat higher manufacturing outlay in the production of the cylinder bore 15 if this is designed as a blind hole.

The specific advantages of a suction valve designed as a ball valve 35 is described below in connection with the 3 still to be discussed in detail.

In 2 is a second embodiment of a high pressure pump according to the invention 10 also shown in section. The same components are provided with the same reference symbols and the same applies with regard to 1 Said accordingly. The main difference from the first embodiment is that the cylinder bore 15 is not designed as a blind hole, but as a through hole. In this embodiment, the cylinder bore 15 by a screw 47 locked. In the screw 47 is the sealing seat 37 of the suction valve 35 incorporated.

In the following, the 3 which an enlarged section A of 2 shows the function of the suction valve 35 explained in more detail.

In 3 the piston 13 is at top dead center. Accordingly, the funding room 31 its minimal volume and the sphere 39 seals the pumping chamber 31 against the low pressure inlet 45 the high pressure fuel pump 10 from. This sealing takes place along a circular sealing line (not shown), which results from the line of contact between the ball 39 and the sealing seat 37 results. The tightness of this suction valve designed as a ball valve 35 is very high as there is only a linear contact between the ball 39 and sealing seat 37 there, which leads to a correspondingly high surface pressure on the sealing line. In addition, the accuracy requirements for the manufacture of a tightly closing ball valve are lower than for cone valves. Depending on the angle α of the sealing seat 37 is selected, the diameter of the sealing line between the ball 39 and sealing seat 37 can be varied with a constant ball diameter. It has been found that sealing angles α between 30 ° and 150 ° are possible and, as a rule, a sealing angle α of 90 ° leads to very good results.

To the sealing seat 37 close an axial bore 48 as well as a cross hole 49 on. Alternatively, several cross holes can be made 49 (not shown) may be provided. The cross hole 49 opens into an annulus 50 which from the housing 17 and a reduced diameter area 50 the screw 47 is limited. On one end 52 the screw 47 is a biting edge 53 formed which the annular space 51 from the delivery room 31 seals.

The annulus 51 stands with the low pressure inlet not visible in this illustration 45 the high pressure fuel pump 10 hydraulically connected. By making the annulus the screw 47 surrounds on all sides, can via the cross hole 49 and the axial bore 48 Fuel into the delivery chamber 31 be sucked in regardless of how deep the screw 47 in the housing 17 was screwed in.

By using a suction valve designed as a ball valve 35 the efficiency of the high pressure fuel pump is increased because the ball 39 releases a large flow cross-section as soon as it leaves the sealing seat 37 takes off so that the fuel can be drawn in quickly and without large flow losses. It is also advantageous if the suction valve is open 35 the annular cross-sectional area between the sealing seat 37 and bullet 39 is up to 20 times larger than the cross-section of the cross hole 49 ,

In addition, because of the good sealing properties of the suction valve designed as a ball valve 35 during the delivery stroke of the piston 13 no fuel from the delivery chamber 31 into the low pressure inlet 45 pushed back.

In 4 is an internal combustion engine 54 shown schematically. It includes a fuel injection system 56 , This in turn has a fuel tank 58 on, out of which an electric low pressure fuel pump 60 Fuel promotes.

The electric low pressure fuel pump 60 delivers fuel to the high pressure fuel pump 10 , which is designed as in the 1 and 2 shown. The high pressure outlet 18 the high pressure fuel pump 10 is with a fuel rail 62 connected. This is generally referred to as a "common rail". To the fuel rail 62 are a total of four injectors 64 connected. These inject the fuel directly into combustion chambers 66 the internal combustion engine 54 on.

Claims (9)

High pressure fuel pump ( 10 ) for a fuel injection system ( 56 ), with a housing ( 17 . 47 ), with a low pressure inlet ( 45 ), with a funding room ( 31 ), in which the fuel is compressed, with a suction valve ( 35 ) between the funding area ( 31 ) and low pressure inlet ( 45 ), a valve member of the suction valve ( 35 ) in the funding room ( 31 ) arranged compression spring ( 43 ) against a piston ( 13 ) and with a high-pressure outlet, characterized in that the valve member of the suction valve ( 35 ) as a ball ( 39 ) is trained. High-pressure fuel pump according to claim 1, characterized in that between the compression spring ( 43 ) and ball ( 39 ) a spring plate ( 41 ) is provided. High-pressure fuel pump according to claim 1 or 2, characterized in that the diameter of the ball ( 39 ) smaller than the diameter of the compression spring ( 43 ) is. High pressure fuel pump ( 10 ) according to one of the preceding claims, characterized in that in the housing ( 17 . 47 ) one with the ball ( 39 ) cooperating sealing seat ( 37 ) is available. High-pressure fuel pump according to claim 4, characterized in that the sealing seat ( 37 ) has a seat angle (α) between 30 ° and 150 °, in particular 90 °. High-pressure fuel pump according to one of the preceding claims, characterized in that the housing ( 17 . 47 ) a screw ( 47 ) which has a cylinder bore ( 31 ) closes to the outside, and that the sealing seat ( 37 ) in a funding room ( 31 ) facing end face ( 52 ) the screw ( 47 ) is trained. High pressure fuel pump ( 10 ) according to claim 6, characterized in that the screw ( 47 ) a reduced diameter area ( 50 ) shows that the reduced diameter area ( 50 ) with the housing ( 17 ) an annulus ( 51 ) and that the annulus ( 51 ) with the low pressure inlet ( 45 ) is hydraulically connected. Fuel injection system ( 56 ) with a fuel tank ( 58 ), with at least one injection valve ( 64 ) which feeds the fuel directly into the combustion chamber ( 66 ) an internal combustion engine ( 54 ) with at least one high pressure fuel pump ( 10 ), and with a fuel rail ( 62 ) to which the at least one injection valve ( 64 ) is connected, characterized in that the high-pressure fuel pump ( 10 ) is designed according to one of claims 1 to 7 ( 4 ). Internal combustion engine ( 54 ) with at least one combustion chamber ( 66 ) into which the fuel is injected directly, characterized in that it has a fuel injection system ( 56 ) according to claim 8 ( 4 ).