EP1353071A2 - Fuel pump with capacity control - Google Patents

Abstract

The pump has at least two pump elements (3) for delivering fuel into a high-pressure connection (25) and at least one controlable hydraulic connection (29) between two pump elements. The hydraulic connection is controled by at least one control valve, especially a 2/2-way valve. Several control valves can be arranged in parallel and operated by an actuator, especially an electromagnetic actuator or a piezoelectric actuator.

Description

State of the art

The invention relates to a high-pressure fuel pump for an injection system of internal combustion engines, with at least two pump elements for delivery to delivery of fuel into a high pressure connection.

Such high-pressure fuel pumps are, for example, as Axial piston pumps, radial piston pumps or Series injection pumps are known.

It is known to regulate the delivery rate, either via an intake throttling with the help of a so-called Metering unit that is sucked in by the pump elements Limit fuel to the desired delivery rate. The disadvantage of this flow control is that complex metering unit and high throttling losses, which differs when the fuel is drawn in as Throttle metering unit result. In addition, at this flow control cavitation in the Pump elements occur.

It is also known to regulate the flow of High pressure fuel pumps on their high pressure side provided. Disadvantages of this flow control are the high dissipation losses since the fuel initially is brought to a high pressure level and then the excess fuel in a pressure control valve is relaxed.

The invention has for its object a Provide high-pressure fuel pump, its delivery rate is easy to regulate. In addition, the efficiency of the High-pressure fuel pump according to the invention in all Load points should be approximately the same.

This task is for a high pressure fuel pump for an injection system of internal combustion engines, with at least two pump elements to promote Solved fuel in a high pressure connection in that A controllable one at least between two pump elements hydraulic connection is provided.

Advantages of the invention

The controllable hydraulic connection between the Pump elements ensures that in partial load operation Pump element, which is in the delivery stroke, one Partial quantity in the pump element promotes itself in the Suction stroke is located. This reduces the required Pump work and it only gets the amount of fuel needed brought to the injection pressure. This is the Efficiency of the high-pressure fuel pump according to the invention Relatively good even in the partial load range.

Alternatively, the hydraulic connection through at least one switching valve or at least one control valve be controlled controlled. When using Switching valves, the efficiency of the invention High pressure fuel pump further increased as the hydraulic connection with the switching valve open has low flow resistance.

If the hydraulic connection through a control valve is controlled, it is ensured that no pressure surges in the Low pressure or in the high pressure range of High pressure fuel pump occur and thus overall the loads on the high-pressure fuel pump Reduce minimum.

It turned out to be advantageous if that Control valve a longitudinal slide in a housing has control slots in the housing are hydraulically connected to the pump elements stand, and that the overlap of longitudinal slide and Control slots is adjustable so that the desired throttle effect in the control valve on simple and effective way.

Alternatively, it can also be provided that the control valve has a longitudinal slide guided in a housing, that control grooves are formed in the longitudinal slide, that in the housing holes that are with the pump elements are hydraulically connected, are in place, and that the hydraulic connection between the holes the longitudinal slide is adjustable.

Another alternative embodiment of a High-pressure fuel pump according to the invention provides that the control valve is in sync with the pump elements driven rotary valve that in the Rotary valve a hydraulic connection is provided that the hydraulic connection has one at each end Tax groove shows that the tax grooves with Control slots in a housing of the control valve interact that the control slots with the Pump elements are hydraulically connected, and that the coverage of control grooves and control slots is adjustable. In this embodiment, the Adjust the delivery rate particularly sensitively. this applies especially when the phase shift of the Control grooves and the control slots and the Phase shift of the pump elements of the High pressure fuel pump match.

In a further addition to the invention, the High pressure fuel pump a first membrane on each Have pump element that have a delivery chamber Pump elements limited, and the controllable hydraulic Connection connect the delivery areas of the pump elements. In this embodiment of the invention, the Advantages of a diaphragm pump known per se also for one High pressure fuel pump according to the invention made usable become.

Further advantages arise if the High pressure fuel pump a second membrane on each Has pump element, the second membrane each one Pressure chamber delimited from the pumping chambers of the pump elements and the controllable hydraulic connection the pressure rooms the pump elements connects. In the pressure rooms one can Pressure fluid, especially an oil, as the working medium be present and the piston of the pump elements through the second membranes on the pressure fluid in the pressure rooms Act. This measure is only in the Delivery chambers fuel, so that in the pressure chamber and in the pump elements, in particular between the piston and Cylinder of the pump elements, a suitable pressure fluid, which preferably has good lubricating properties and not prone to cavitation, present.

The high-pressure fuel pump according to the invention can advantageously also in connection with a common rail be used. Especially with common rail fuel injection systems is the regulation of Delivery volume and thus also the pressure in the common rail of of great importance, so that the advantages of the invention are particularly positive in such injection systems to make noticable.

Further advantages and advantageous configurations of the Invention are the following drawing, the Description and the patent claims.

drawing

Fig. 1:

einen Längsschnitt durch ein erstes Ausführungsbeispiel einer als Axialkolbenpumpe ausgeführten erfindungsgemäßen Kraftstoffhochdruckpumpe;

Fig. 2:

einen Querschnitt durch das Ausführungsbeispiel gemäß Fig. 1;

Fig. 3:

einen Längsschnitt entlang der Linie A-B durch ein Regelventil gemäß dem ersten Ausführungsbeispiel;

Fig. 4 und 5:

Ausführungsbeispiele weiterer Regelventile;

Fig. 6:

eine Radialkolbenpumpe nach dem Stand der Technik;

Fig. 7:

eine schematische Darstellung einer erfindungsgemäßen Radialkolbenpumpe;

Fig. 8:

ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Radialkolbenpumpe; und

Fig. 9:

ein Ausführungsbeispiel für ein Schalt- oder Regelventil zur Fördermengenregelung der Radialkolbenpumpe gemäß Fig. 7 und 8.

Show it:

Fig. 1:

a longitudinal section through a first embodiment of an inventive high-pressure fuel pump designed as an axial piston pump;

Fig. 2:

a cross section through the embodiment of FIG. 1;

Fig. 3:

a longitudinal section along the line AB through a control valve according to the first embodiment;

4 and 5:

Exemplary embodiments of further control valves;

Fig. 6:

a radial piston pump according to the prior art;

Fig. 7:

a schematic representation of a radial piston pump according to the invention;

Fig. 8:

a further embodiment of a radial piston pump according to the invention; and

Fig. 9:

an embodiment of a switching or control valve for controlling the delivery rate of the radial piston pump according to FIGS. 7 and 8.

Description of the embodiments

In Fig. 1 is a first embodiment High-pressure fuel pump according to the invention for a Injection system of internal combustion engines schematically shown. In this embodiment, the High-pressure fuel pump 1 as an axial piston pump educated. In the longitudinal section according to FIG. 1 there are two Pump elements 3 recognizable, which are from a swash plate 5 are driven in a manner known per se. The Swash plate 5 in turn is driven by a drive shaft 7 driven.

The pump elements 3 essentially consist of a Pump piston 9, which is guided in a cylinder bore 11 is. On the end facing away from the swash plate 5 the pump piston 9 are a first membrane 13 and a second membrane 15 arranged. The first membrane 13 separates one filled with fuel (not shown) Delivery chamber 17 from the rest of the pump element 3.

The delivery rooms are connected via a low pressure connection 19 17 during the suction stroke of the pump piston 9 with fuel filled. To ensure a backflow of fuel during the Preventing delivery strokes of the pump elements 3 is in the Low pressure connection per pump element 3 a first Check valve 21 arranged. The one from the pump elements 3 funded during the delivery stroke from the delivery rooms 17 Fuel enters via second check valves 23 a high pressure connection 25. Via the high pressure connection 25 can, for example, a common rail, not shown or injectors (also not shown) with under High-pressure fuel can be supplied.

Limit the first membrane 13 and the second membrane 15 a pressure chamber 27. The pressure chambers 27 can with a Pressure fluid (not shown), especially oil, filled his. The use of a special pressure fluid can because of its favorable tribological properties and low tendency to cavitation may be advantageous. Also the Pump piston 9 can be of pressure fluid, especially oil, be surrounded so that the lubrication of the pump piston 9 in the cylinder bore 11 and the swash plate 5 always is guaranteed.

To the delivery rate of the invention To be able to continuously control high-pressure fuel pump 1 a hydraulic connection 29 between the pressure chambers 27a and 27b of the pump elements 3 are provided. The hydraulic connection 29 can in the embodiment 1 as a bore in a housing 31 of the High-pressure fuel pump 1 may be formed. In the hydraulic connection 29 is a control valve 33 arranged. Alternatively, the control valve 33 can also be used as Switch valve to be formed. Through the control valve 33 can the hydraulic connection 29 completely if necessary be closed, so that the invention High-pressure fuel pump 1 like one from the prior art Technology known axial piston pump works. Alternatively, you can the control valve 33 the hydraulic connection 29 also more or less release, so that the pressure difference in the Pressure spaces 27a and 27b is limited.

When the control valve 33 is fully open, takes place an almost complete pressure equalization between the Print rooms 27a and 27b instead. This means that too none of the pump elements 3 during the delivery stroke significant pressure increase in the associated pressure chamber 27 and takes place in the funding room 17. As a result, none Fuel from the delivery chamber 17 into the high pressure connection 25 funded. Thus, in this operating state Zero funding stopped.

When the control valve 33 is in an intermediate position between is fully open and fully closed there is a certain pressure build-up in the high pressure space 27a and 27b adjust when the associated pump piston 9 is in Delivery stroke is located. This pressure is about the first Transfer membrane 13 to the associated delivery chamber 17. As soon as the pressure in the delivery chamber 17 is greater than in High-pressure connection 25, the associated second opens Check valve 23 and it becomes a certain one Amount of fuel from the delivery chamber 17 in the High pressure connection 25 promoted. In this operating state the delivery rate of the high-pressure fuel pump 1 is larger than zero and less than the flow rate when the valve is closed Control valve 33. Depending on the position of the control valve 33 can the delivery rate can be set between 0 and 100%.

Alternatively, the control valve 33 can also be used as a switching valve be carried out (not shown). In this case the flow control by opening and closing the Switch valve made. If the desired delivery rate was promoted by the pump elements 3, the Switch valve opened so that a pressure equalization between the pressure rooms 27a and 27b takes place and as a result no further fuel in the high pressure connection 25 is promoted. The larger the hydraulic cross sections the hydraulic connection 29 and the switching valve, the lower the loss, this type of flow control can be respectively. If the flow rate regulation by opening the Switch valve after reaching the desired flow rate takes place, the pressure surges in the low pressure range and in High-pressure area of high-pressure fuel pump 1 minimized. This flow rate regulation is particularly advantageous.

In Fig. 2, a second embodiment is one High-pressure fuel pump according to the invention in the form of a Cross section of axial piston pump greatly simplified shown. In this illustration, three are at 120 ° Pump elements 3 offset from one another hinted at. The high pressure connection and the Low pressure connection are not in this illustration shown, as well as the swashplate. Regarding this Details and also the formation of pressure room and Delivery space is based on the exemplary embodiment according to FIG. 1 directed.

In Fig. 2 the hydraulic connection 29 is also between the pump elements 3 shown. In the middle of hydraulic connection 29 arranged in a star shape a control valve 33 is arranged, which with reference to FIG. 3, which is a section along the line A-B in Fig. 2nd represents, is explained in more detail below.

In a housing 31 of the high-pressure fuel pump 1 is a Hole 35 recessed. In this bore 35 is a Rotary slide valve 37 is arranged, which via a shaft 39 in Rotation is offset. The speed and phase of the Rotary valve 37 agree with the speed and the Phase position of the swash plate (not shown in FIG. 2 and 3) the axial piston pump. The rotation of the shaft 39 is a groove 41 in the rotary valve 37 and a sliding block 43 from the shaft 39 to the rotary valve 37 transmitted. The hydraulic connection 29 settles in Rotary valve 37 continues. Where the hydraulic connection 29 ends in the rotary valve, control grooves 45 are provided. The hydraulic connections 29 in the housing 31 open into a control slot 47. The control slots 47 open into the bore 35 in the housing 31.

The rotary valve 37 is in via an actuator 49 Longitudinal direction, indicated by the double arrows 51, displaceable. Depending on the coverage of control slots 47 and control grooves 45, the hydraulic connection 29 becomes more or less opened and thus the desired delivery rate set. This type of flow rate regulation was already explained in detail with reference to FIG. 1, and it to avoid repetitions on this Explanations referenced.

4 and 5 are further embodiments of Control valves 33 shown. The configuration of this Control valves 33 in an axial piston pump corresponds that of the embodiment of FIG. 3. In the 4 lead to the hydraulic Connections in the housing 31 in control slots 47. An actuator 49 actuates a longitudinal slide 53 in the direction of Double arrow 51. Depending on the position of the Longitudinal slide 53 covers the control edge 55 of the Longitudinal slide 53 the control slots 47 completely, partially or not at all. 4 is a position of the longitudinal slide 53, in which the Control slots 47 almost completely from the longitudinal slide 53 are covered. This means that only a small one Pressure equalization between the pressure rooms 27 (not shown) via the hydraulic connections 29 can be done. As a result, it does not promote either High-pressure fuel pump 1 shown almost the full Delivery. If the longitudinal slide 53 in Fig. 4 by the Actuator 49 is shifted further to the right is a better pressure balance between those not shown Pressure rooms 27 possible, so that the flow rate drops.

5 is another embodiment of a Control valve 33 shown, in which the hydraulic Connections 29 in the housing 31 directly into the bore 35 lead. In the longitudinal slide 53 is a circumferential Control groove 45 incorporated. In the shown in Fig. 5 Position of the longitudinal slide 53 closes the hydraulic connections 29 so that no pressure equalization between the pump elements (not shown) can take place and thus promoted the full funding becomes. If the longitudinal slide 53 in Fig. 5 to the left is shifted, the control groove 45 allows one Connection of the hydraulic connections 29 so that a partial or full pressure equalization between the not shown pressure rooms takes place and thus the Flow rate is reduced.

Alternatively, the second membrane 15 can also be dispensed with become. In this case, the hydraulic connection 29 the delivery spaces 17 of the pump elements 3 with each other connect. In this case, the pressure equalization does not take place between the pressure rooms, but between the delivery rooms 17 instead, which affects the flow rate in the same way affects the high-pressure fuel pump according to the invention. The advantage of this embodiment is the lower one Construction effort and space requirements.

6 is a radial piston pump according to the state of the Technology shown schematically. After this Embodiment, the three pump elements 3 are radial arranged to a drive shaft 9 and are from a eccentric section 57 of the drive shaft 9 driven. This high-pressure fuel pump is on everyone Low pressure connection 19, a switching valve 59 is provided. In the position of the switching valves shown in Fig. 6 can the fuel during the delivery stroke of the pump elements 3 flow back into the low pressure connection 19, see above that there is zero funding. If the Switching valves 59 in the second, in Fig. 6 not Switch position shown are brought Switching valves 59 the function of the first check valves 21 (see Fig. 1), so that the pump elements 3 in the Promote high pressure connection 25. Depending on which When the switching valves 59 are actuated, the Flow rate of the radial piston pump can be set. However, the control of the switching valves 59 must be very done exactly and there are three complex switching valves 59 required.

7, a first embodiment of a High-pressure fuel pump according to the invention, which as Radial piston pump is formed, shown. By doing 7 connects the hydraulic Connection 29 to the delivery rooms 17a, 17b and 17c of three Pump elements 3, not shown Radial piston pump as described in FIG. 6 together. There is one for each delivery chamber 17a, 17b and 17c Control valve 33 provided. The control valves 33 are controlled together.

In Fig. 8, another embodiment is as Radial piston pump high-pressure fuel pump 1 shown. The three pump elements 3, which of one Drive shaft 7 are driven, each have one Low pressure connection 19 with a first check valve 21 and a high pressure connection 25 with a second Check valve 23 on. From the delivery rooms 17a, 17b and 17c of the three pump elements 3 each carry one hydraulic connection 29 to a switching valve 61. About the switching valve 61 can be a hydraulic connection of the Conveying spaces 17a, 17b and 17c made with each other become. When this hydraulic connection is closed, the radial piston pump delivers the full flow. If the connection is fully open, a Zero funding. By appropriately controlling the Switch valve 61 can between any desired flow rate 0% and 100% can be set.

9 is an embodiment of a switching valve 61 shown in longitudinal section. With this switching valve 61 are the hydraulic connections 29 by a Longitudinal slide 53 closed or more or less open. Depending on the position of the longitudinal slide 53 can thus a more or less large pressure balance between the Delivery spaces 17a, 17b or 17c of the high-pressure fuel pump or the pressure chambers 27a or 27b (see FIG. 1).

All in the drawing, its description and the Features disclosed claims can be both individually as well as in any combination with each other be essential to the invention.

Claims (14)

High-pressure fuel pump for an injection system of internal combustion engines, with at least two pump elements (3) for delivering fuel into a high-pressure connection (25), characterized in that a controllable hydraulic connection (29) is provided at least between two pump elements (3). High-pressure fuel pump according to claim 1, characterized in that the hydraulic connection (29) is controlled by at least one switching valve (61), in particular a 2/2 switching valve. High-pressure fuel pump according to Claim 2, characterized in that a plurality of switching valves (61) are arranged parallel to one another, and in that the plurality of switching valves (61) are actuated by an actuator (49), in particular an electromagnetic actuator or a piezoelectric actuator. High-pressure fuel pump according to claim 1, characterized in that the hydraulic connection (29) is controlled by at least one control valve (33). High-pressure fuel pump according to claim 4, characterized in that the control valve (3) has a longitudinal slide (53) guided in a housing (31), that in the housing (31) there are control slots (47) which are hydraulic with the pump elements (3) are connected, and that the overlap of the longitudinal slide (53) and control slots (47) is adjustable. High-pressure fuel pump according to claim 4, characterized in that the control valve (33) has a longitudinal slide (53) guided in a housing (31) , that control grooves (45) are formed in the longitudinal slide (53), that bores in the housing (31) which are hydraulically connected to the pump elements (3), and that the hydraulic connection (29) between the bores can be adjusted by means of the longitudinal slide (53). High-pressure fuel pump according to Claim 4, characterized in that the control valve (33) has a rotary slide valve (37) which is driven synchronously with the pump elements (3), that a hydraulic connection (29) is provided in the rotary slide valve (37) such that the hydraulic connection ( 29) has at each end a control groove (45) that the control grooves (45) interact with control slots (47) in a housing (31) of the control valve (33), that the control slots (47) with the pump elements (3) hydraulically are connected, and that the overlap of control grooves (45) and control slots (47) is adjustable. High-pressure fuel pump according to claim 7, characterized in that the phase shift of the control grooves (45) and the control slots (47) and the phase shift of the pump elements (3) match. High-pressure fuel pump according to claim 2 or 4, characterized in that the switching valve (61) or the control valve (33) is designed as a longitudinal slide valve. High-pressure fuel pump according to one of the preceding claims, characterized in that the high-pressure fuel pump (1) has a first membrane (13) on each pump element (3), that the first membrane (13) delimits a delivery chamber (17) of the pump elements (3), and that the delivery spaces (17) of the pump elements (3) can be connected by the controllable hydraulic connection (29). High-pressure fuel pump according to claim 10, characterized in that the high-pressure fuel pump has a second membrane (15) on each pump element (3), that the second membrane (15) delimits a pressure chamber (27) from the delivery chambers (17) of the pump elements (3) , and that the pressure chambers (27) of the pump elements (3) can be connected by the controllable hydraulic connection (29). High-pressure fuel pump according to Claim 11, characterized in that the pressure spaces (27) are filled with a pressure fluid, in particular oil, and in that the pump piston (9) of the pump elements (3) through the second membranes (15) onto the pressure fluid in the pressure spaces (27 ) Act. High-pressure fuel pump according to one of the preceding claims, characterized in that the high-pressure fuel pump is designed as an axial piston pump, as a radial piston pump or as a series pump. High-pressure fuel pump according to one of the preceding claims, characterized in that the high-pressure connection (25) is hydraulically connected to a common rail.

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