DE102006048356A1 - High-pressure fuel pump and fuel injection system for an internal combustion engine - Google Patents

Abstract

The pump (1) has a drive shaft (35) supported in pump housing by bearings (39, 41), and a pump unit (21), which is arranged radially relative to the drive shaft. A conveying pump (5) e.g. external gear pump, conveys fuel to a fuel inlet (15) and a metering unit (19) regulates conveying amount of the pump unit (21). The metering unit and a pressure regulating valve (20) are supplied with the fuel by a fuel return line (18). A non-return valve (43) is provided downstream to the bearing (39) and another non-return valve (45) is provided downstream to the bearing (41).

Description

State of the art

The The invention is based on a high-pressure fuel pump for a fuel injection system an internal combustion engine, with a pump housing in which a drive shaft is supported by a first bearing and a second bearing, with at least a respect the drive shaft radially arranged pump element, with a fuel inlet, being a prefeed pump Fuel into the fuel feed, with a fuel return, with a metering unit for controlling the flow rate of the pump or the elements and with a pressure control valve.

at this known from the prior art high-pressure fuel pump the pressure regulating valve is used to control the pressure in the low-pressure circuit to regulate the high-pressure fuel pump. At the same time the flow rate becomes the prefeed pump usually in three sub-streams divided up. A first partial flow flows through the metering unit on the suction side of the pump or the elements. The second partial flow flows usually over a lubricating throttle through the pump housing, where it is used for cooling and Lubrication of the pump. From the pump housing this second partial flow passes in the fuel return of the fuel injection system.

One third partial flow flows by the pressure control valve, which can also be designed as a relief valve and also gets into the fuel return.

With increasing injection pressures The mechanical and thermal loads increase as well the drive shaft and the bearing of the drive shaft in the pump housing. this increasing loads are the conventional high-pressure fuel pumps not always grown.

Disclosure of the invention

Of the Invention is based on the object, a high-pressure fuel pump for a Fuel injection system to provide that with respect to thermal and mechanical load capacity known from the prior art Superior to high-pressure fuel pumps is. Furthermore should the high-pressure fuel pump according to the invention simple and inexpensive be produced.

These Task is according to the invention in a High-pressure fuel pump for a fuel injection system of an internal combustion engine, with a pump housing, with a drive shaft, wherein the drive shaft in the pump housing through a first bearing and a second bearing is mounted, with at least a respect the drive shaft radially arranged pump element, with a fuel inlet, being a prefeed pump Fuel into the fuel intake promotes, with a fuel return, with a metering unit for controlling the delivery rate of the pump element or elements, and with a pressure control valve, wherein both the metering unit as also supplies the pressure control valve of the fuel return with fuel be solved by that downstream the first bearing a first check valve is provided, and that downstream of the second bearing a second check valve is provided.

Thereby Is it possible, that the entire flow the pre-feed pump for lubrication and cooling the high-pressure fuel pump can be used. Because the first optional check valve and the second optional check valve only open when an adjustable opening pressure is reached stands in the starting phase of the internal combustion engine, the entire of the prefeed pump funded Fuel flow for the pressure build-up in the pump elements available. This will additionally the Start the engine easier.

Further Benefits during the entire operation of the internal combustion engine are present are first the very big one Cold and Lubricating amounts, since the total amount of fuel delivered by the prefeed pump for cooling and lubrication of the high-pressure fuel pump can be used before part of this flow through the metering unit enters the pump elements of the high-pressure fuel pump.

The excess part from the pre-feed pump funded Fuel flow is over the pressure control valve is returned to the fuel return. This will be a very effective cooling the high-pressure fuel pump allows because of the above Pressure control valve outflowing and heated by the high-pressure fuel pump fuel in the tank of Fuel injection system will be sufficiently cooled before this Fuel again from the pre-supply pump sucked and fed to the high-pressure fuel pump.

Another advantage of the high-pressure fuel pump according to the invention is that at the same load of the prefeed pump in the interior of the high-pressure fuel pump, a relatively high pressure level is reached because there are no throttle points between the prefeed pump and the interior. Thereby, the Kavitationsneigung is reduced in the interior of the high-pressure fuel pump and the amount of fuel flowing through the first bearing and the second bearing fuel is increased. As a result, the load capacity of the first and of the second camp. Since the first bearing and / or the second bearing are usually designed as hydrostatic plain bearings, these bearings benefit particularly from an increased flow rate, since hydrostatic bearings have a higher capacity with increasing flow.

By the increased Cold and Lubricating not only the first and the second bearing, but the entire high-pressure fuel pump are higher pump loads or, at the same loads, pumps with longer service life possible.

at an advantageous embodiment of the invention opens Output of the pressure control valve in the return line. This will Ensures that the entire excess amount of fuel from the pressure control valve get back into the tank and cool it down sufficiently can.

alternative it is also possible that the outlet of the pressure control valve on the suction side or the conveying side the pre-feed pump flows into the fuel inlet. This will indeed find the cooling over the fuel the return line and the tank stops; however, the advantage of the improved lubrication due to higher fuel flow through the interior and the bearings of the high-pressure fuel pump.

A particularly advantageous alternative embodiment of the high-pressure fuel pump according to the invention provides that the pressure control valve in two stages with a first Output and a second output is formed that the first Output in the return line opens and that the second exit opens into the fuel inlet.

Thereby Is it possible, on the one hand the lubrication of the fuel high pressure pump through the entire flow the pre-feed pump to ensure and at the same time a part of the fuel in the fuel supply line recirculate and the remaining part over the return line to return to the tank. So can the advantages of the invention be achieved in full, without the flow rate of the fuel coming from the high-pressure fuel pump into the tank is promoted back, significantly increase.

Brief description of the drawings

1 and 2 Embodiments of high-pressure fuel pumps according to the invention and their integration into a fuel injection system.

Embodiments of the invention

1 shows a first embodiment of a high-pressure fuel pump according to the invention 1 in a block diagram representation.

Embodiments of the invention

The high-pressure fuel pump 1 is part of a fuel injection system that consists essentially of a tank 3 , a prefeed pump 5 with an element for limiting the flow rate 52 , a filter 7 a rail 9 and a pressure relief valve 11 consists. The injectors attached to the rail 9 are connected in 1 not shown.

The element for limiting flow 52 is formed in the embodiments shown in the figures as a throttle, which is directly at the entrance of the feed pump 5 is arranged. The throttle 52 causes the total in the high-pressure fuel pump 1 compressed fuel quantity is limited. Furthermore, this will result in an interior 17 the high-pressure fuel pump 1 resulting pressure corresponding to a characteristic of a pressure regulating valve 20 limited. These effects have a positive effect on the efficiency of the fuel injection system and the mechanical stress of the high-pressure fuel pump 1 out.

The pressure relief valve 11 opens into a return line 13 , in which also the leakage quantities of the injectors, not shown, are discharged. The return line 13 opens in this first embodiment in the tank 3 and drives there a jet pump (without reference numeral).

Inside the high-pressure fuel pump 1 Optionally, a temperature sensor T can be arranged. The high-pressure fuel pump 1 is about a fuel feed 15 , the filter 7 and the prefeed pump 5 hydraulically with the tank 3 connected.

The fuel feed 15 connects a delivery side of the feed pump 1 with an interior 17 the pump housing, so that the entire flow of the feed pump 1 in the interior 17 arrives.

A fuel return 18 Provides a hydraulic connection between the interior 17 the pump housing on the one hand and a metering unit 19 and the return line 13 on the other hand. Between the fuel return 18 and the return line 13 is a pressure control valve 20 arranged.

The metering unit 19 serves to that of pump elements 21 to control the fuel high-pressure pump sucked amount of fuel and thus their flow rate. These are the suction sides of the pump elements 21 via a distribution line 23 with the output of the metering unit 19 hydraulically connected.

The pump elements 21 consist essentially of suction valves 25 , high pressure side check valves 27 and a piston 29 , which oscillates in a cylinder bore (without reference numeral). The pistons 29 the pump elements 21 be about roller tappet 31 of cams 33 a drive shaft 35 driven. The pump elements 21 promote high pressure fuel through a high pressure line 34 in the rail 9 ,

The cams 33 are part of a drive shaft 35 that are on both sides of the cams 33 in a first bearing and in a second bearing in a pump housing (not shown) is rotatably mounted. The drive shaft 35 is in the interior 17 arranged the pump housing. Bearings of a drive shaft 35 are in the block diagram according to 1 shown as throttle point. The first camp has in 1 the reference number 39 while the second bearing with the reference numeral 41 was provided.

At the in 1 shown first embodiment of a high-pressure fuel pump according to the invention is the pressure control valve 20 downstream of the interior 17 the high-pressure fuel pump 1 arranged. The pressure control valve 20 includes a leakage line 57 in the optional throttle 61 can be provided. By the arrangement of the pressure control valve 20 downstream of the interior 17 prevails in the interior 17 almost the same pressure as on the pressure side of the feed pump 5 , As a rule, the overpressure on the pressure side of the prefeed pump 5 and thus of the interior 17 about 3 bar to about 7 bar.

This one in the interior 17 The prevailing pressure leads to a reduction in the cavitation tendency and thus to the suppression of vapor bubbles, especially at high speeds.

In addition, the increased internal pressure in the interior leads 17 the pump housing to that, depending on the in the interior 17 prevailing pressure, the viscosity of the fuel and the flow resistance of the first bearing 39 and the second camp 41 , a defined amount of fuel through the bearings 39 and 41 is pressed. This leads to a significant increase in the capacity of both the first camp 39 , as well as the second camp 41 ,

Because the first camp 39 and the second camp 41 are usually designed as plain bearings, is formed by the forced flow through the camp 39 and 41 in the camps 39 and or 41 a hydrostatic lubricating wedge. This increases the load capacity of the first bearing 39 and the second camp 41 Significantly and at the same time, the heat dissipation from the first bearing 39 and the second camp 41 improved.

So that the pressure build-up within the high-pressure fuel pump 1 and in the rail 9 can be accelerated downstream and in series with the first bearing 39 a first check valve 43 be arranged. Accordingly, downstream and in series with the second bearing 41 a second check valve 45 be arranged. The opening pressure of the check valves 43 and 45 is chosen so that they are closed when starting the engine and only open when the engine is running. In addition, during operation of the internal combustion engine, the flow resistance of the check valves ensures 43 and 45 for that the dispersion of the amount of fuel passing through the bearings 39 and 41 flow, is reduced., The first check valve 43 and the second check valve 45 open into the return line 13 , Alternatively, instead of the first check valve 43 or instead of the second check valve 45 a throttle or aperture are provided.

It has been found in experiments that due to the manufacturing tolerances, for example, on the diameter of the journal (not shown) of the drive shaft 35 for the bearings 39 and 41 and the associated bearing shell (not shown) in the pump housing at an unfavorable tolerance position, the amount of fuel passing through the bearings 39 and 41 flows within a series of high-pressure fuel pumps 1 can significantly scatter. This undesirable effect is, if necessary, through the check valves 43 and 45 reduced to an uncritical level.

The pre-feed pump 5 may be designed as a vane pump, as an internal gear pump, in particular as a gerotor pump, or as an external gear pump. These pumps have a gap between the rotating components and the pump housing that causes leakage losses. This gap is in 3 by the symbol of a throttle (see reference numeral 49 ). The amount of leakage flowing through the gap is through a leakage line 51 dissipated. The leakage line 51 flows in front of the first check valve 43 in the line (not numbered), which by the first camp 39 flowing amount of fuel through the first check valve 43 the return line 13 supplies.

The high-pressure fuel pump according to the invention 1 has among other things the following advantages: By the arrangement of the pressure regulating valve 20 in the fuel return 18 will that be in the interior 17 raised pressure level of the pump housing, which reduces the risk of cavitation and the risk of vapor bubble formation.

In addition, both the first camp 39 as well as the second camp 41 forcibly from Fuel flows through, which significantly increases their capacity, both in terms of mechanical and thermal stresses.

Possibly occurring fluctuations in the flow rate between different copies in series manufactured high-pressure fuel pumps according to the invention 1 can through series-connected check valves 43 . 45 and / or throttles or apertures are reduced.

For lubrication and cooling purposes through the pump housing and bearings 39 and 41 flowing fuel quantity is greatly increased.

A Grease throttle for setting a defined amount of lubricant can omitted. By the big ones Lubricating amounts will eventually be removed from the existing particles Interior washed up.

The Delivery height of the pre-supply pump can often be reduced, reducing the efficiency of the injection system improved.

In 2 a further embodiment of a fuel injection system according to the invention is also shown as a block diagram. Only the essential differences are explained. The same components are provided with the same reference numerals and it is the case with respect to the previous embodiments said accordingly.

In the embodiment according to 2 has the pressure control valve 20 a first exit 53 in the return line 13 empties. Furthermore, the pressure regulating valve has 20 a second exit 55 , which is on the suction side of the pre-feed pump 5 in the fuel feed 15 empties. This allows the excess amount of fuel from the pressure control valve 20 is dissipated, split, leaving a portion of the excess fuel through the return line 13 in the tank 3 flows back where this fuel can be cooled. Another part of the excess fuel will be in the second exit 55 of the pressure control valve 20 directly into the fuel feed 15 recycled. As a result, the full flow rate of the prefeed pump is still 5 used for lubrication of the high-pressure fuel pump, while only a part of this flow rate through the return line 13 the tank 3 is supplied for cooling. In this embodiment of a high-pressure fuel pump according to the invention by the return line 13 flowing amount of fuel about the same size as in conventional fuel injection pumps, although the lubrication of the high-pressure fuel pump according to the invention 1 much more powerful than conventional high-pressure fuel pumps.

Both in the first exit 53 as well as in the leakage line 57 of the pressure control valve 20 can chokes 59 and 61 be provided. With the first throttle 59 It is possible to remove the part of the excess fuel that enters the return line 13 flows, limit. With the second throttle 61 can the movements of the valve piston (without reference numeral) of the pressure control valve 20 be effectively damped. The high pressure delivery and the cooling and lubricating amount are set much more constant.

An alternative arrangement of the throttle 61 in the leakage line 57 is shown in dashed lines. Of course it is also possible at the second exit 55 of the pressure control valve 20 to provide a throttle, not shown, with the help of which directly into the fuel inlet 15 the amount of fuel returned is limited. By a suitable vote of the first throttle 59 , the second choke 61 and optionally the third throttle in the second output 55 of the pressure control valve 20 The desired distribution of excess fuel to the return line 13 and the fuel feed 15 be adjusted according to the requirements.

Claims (15)

High-pressure fuel pump for a fuel injection system of an internal combustion engine, with a pump housing, with a drive shaft ( 35 ), wherein the drive shaft ( 35 ) in the pump housing through a first bearing ( 39 ) and a second warehouse ( 41 ) is mounted, with at least one with respect to the drive shaft ( 35 ) radially arranged pump element ( 21 ), with a fuel feed ( 15 ), whereby a prefeed pump ( 5 ) Fuel in the fuel feed ( 15 ), with a fuel return ( 43 ), with a metering unit ( 19 ) for controlling the delivery rate of the pump element or elements ( 21 ), and with a pressure regulating valve ( 20 ), whereby both the metering unit ( 19 ) as well as the pressure control valve ( 20 ) from the fuel return ( 18 ) are fueled, characterized in that downstream of the first bearing ( 39 ) a first check valve ( 43 ) and that downstream of the second bearing ( 41 ) a second check valve ( 45 ) is provided. High-pressure fuel pump according to claim 1, characterized in that the first bearing ( 39 ) and the second camp ( 41 ) are lubricated by pressurized fuel, and that the first bearing ( 39 ) and the second camp ( 41 ) with both the fuel feed ( 15 ) as well as with a return line ( 13 ) communicates hydraulically. High-pressure fuel pump according to one of the preceding claims, characterized gekennzeich net, that the first camp ( 39 ) and / or the second bearing ( 41 ) is designed as a sliding bearing. High-pressure fuel pump according to one of the preceding claims, characterized in that the fuel connection ( 15 ) in an interior ( 17 ) of the pump housing opens. High-pressure fuel pump according to one of the preceding claims, characterized in that an output of the pressure regulating valve ( 20 ) in the return line ( 13 ) opens. High-pressure fuel pump according to one of claims 1 to 4, characterized in that the output of the pressure regulating valve ( 20 ) on the suction side or the delivery side of the prefeed pump ( 5 ) into the fuel feed ( 15 ) opens. High-pressure fuel pump according to one of claims 1 to 4, characterized in that the pressure regulating valve ( 20 ) is carried out in two stages, with a first output ( 53 ) and a second output ( 55 ), that the first exit ( 53 ) in the return line ( 13 ) and that the second exit ( 55 ) of the pressure regulating valve ( 20 ) on the suction side of the prefeed pump ( 5 ) into the fuel feed ( 15 ) opens. High-pressure fuel pump according to claim 7, characterized in that the second output ( 55 ) of the pressure regulating valve ( 20 ) is only opened when a predeterminable minimum pressure (p _min ) at the inlet of the pressure regulating valve ( 20 ) prevails. High-pressure fuel pump according to claim 7 or 8, characterized in that downstream of the first output ( 53 ) a first throttle ( 59 ) and / or that downstream of the second exit ( 55 ) A throttle is provided. High-pressure fuel pump according to one of the preceding claims, characterized in that at a leakage line ( 57 ) of the pressure regulating valve ( 20 ) a throttle ( 59 ) is provided. High-pressure fuel pump according to one of the preceding claims, characterized in that an opening pressure of the first check valve ( 43 ) and / or an opening pressure of the second check valve ( 45 ) is selected so that the first check valve ( 43 ) and / or the second check valve ( 45 ) are closed during the start of the internal combustion engine and open upon reaching the idling speed of the internal combustion engine. Fuel injection system for an internal combustion engine, with a prefeed pump ( 5 ), with a tank ( 3 ), with a high-pressure fuel pump ( 1 ), with a common rail ( 9 ) and with at least one injector, characterized in that the high-pressure fuel pump ( 1 ) is a high-pressure fuel pump according to one of the preceding claims. Fuel injection system according to claim 12, characterized in that the prefeed pump ( 5 ) is driven by the internal combustion engine or by an electric motor. Fuel injection system according to one of claims 12 or 13, characterized in that the prefeed pump ( 5 ) is designed as a vane pump, as an internal gear pump or as an external gear pump. Fuel injection system according to one of claims 12 to 14, characterized in that the prefeed pump ( 5 ) an element for limiting flow 52 , in particular a throttle and / or a diaphragm.