EP1375915B1 - Radial piston pump with improved efficiency for high pressure fuel supply in injection systems of internal combustion engines - Google Patents

Description

State of the art

The invention relates to a radial piston pump for high-pressure fuel supply in fuel injection systems of internal combustion engines, especially in common rail injection systems, preferably with a plurality of respect to a mounted in a pump housing drive shaft radially arranged pump elements, wherein the pump elements are actuated by the drive shaft and each have a suction side and a high pressure side and with high pressure channels in the pump housing, each connecting the high pressure side of a pump element to a high pressure port in the pump housing.

Such radial piston pumps are for example for high pressure generation in internal combustion engines with gasoline direct injection known. The pump is operated unregulated. The pressure control required in common-rail injection systems is achieved via a pressure control valve on the common rail. This means that in part-load operation, a considerable part of the pump work performed by the radial piston pump is subsequently dissipated again in the pressure regulating valve, which results in a low degree of utilization of the fuel injection system. In addition, the efficiency of this radial piston pump is not yet satisfactory.

From the DE 198 30 302 A1 is a radial piston pump for internal combustion engines known in which the pump elements are supported outwardly against a circumferential eccentric ring. In this case, each pump element has a suction line and a pressure line. For flow control, a common arranged on the pressure side Magentventil is provided.

Advantages of the invention

In a radial piston pump according to the invention for high-pressure fuel supply in fuel injection systems of internal combustion engines, especially in common-rail injection systems, preferably with a plurality of relative to a mounted in a pump housing drive shaft radially arranged pump elements, wherein the pump elements are actuated by the drive shaft and each have a suction side and a high pressure side and with high-pressure channels in the pump housing, which each connect the high-pressure side of a pump element with a high pressure port in the pump housing, a quantity control valve is provided, which in the open state, a hydraulic connection between the high-pressure channels and the suction sides the pump elements produces, and are provided between the quantity control valve and the suction sides of the pump elements, a storage volume and a throttle.

By the pressure-side flow control valve, the flow rate of the radial piston pump can be controlled in a wide range. The regulation takes place via a suitable Control of the fast switching quantity control valve, so that unnecessary pumping work is prevented and thus the efficiency of the fuel injection system is increased. By the storage volume and a cooperating with the storage volume throttle prevents the pressure surges occurring when opening the flow control valve fully penetrate the suction side of the radial piston pump and can lead to unacceptably high pressure loads and undesirable dynamic disturbances.

In a variant of the invention, it is provided that each high-pressure channel hydraulically connects the high-pressure sides of two pump elements by the shortest path, that the number of high-pressure channels is smaller by 1 than the number of pump elements, and that a high-pressure port branches off from a high-pressure channel. These features minimize the number of high pressure channels and also minimize the volume of these high pressure channels. Thus, the harmful volume is minimized on the high pressure side of the radial piston pump according to the invention, which leads to a further increase of the pump efficiency in all operating conditions. The quantity control valve is hydraulically connected to one of the high pressure channels.

In an advantageous embodiment of the radial piston pump according to the invention, the storage volume is limited by a puncture in the pump housing and a sleeve sealed against the pump housing, so that the desired storage volume can be manufactured easily manufactured. It has also proved to be advantageous if a throttle is provided in the sleeve, which is arranged between the storage volume and the suction side of the pump elements.

Alternatively, it is also possible to carry out the pump housing in two parts and to limit the storage volume of a first housing part and a second housing part. As a result, the sleeve can be dispensed with, which further reduces the assembly effort.

To further improve the pump efficiency, it is provided that each pump element has a piston, a cylinder bore and a cylinder head, that the piston oscillates in the cylinder bore and delimits a delivery space, that a first check valve is arranged on the suction side, that the first check valve in the piston is integrated, and that on the high pressure side, a second check valve is arranged.

The load capacity of the radial piston pump according to the invention, whose drive shaft is mounted in the pump housing of the journal bearing, is further increased when the sliding bearing is forcibly traversed by fuel, in particular by the flowing through the fuel port cool fuel. As a result, a cooling and / or lubrication of the sliding bearing is made, which increases its capacity and durability. The cooling of the sliding bearing can be further improved if a plurality of holes are provided in the drive shaft or a bearing shell of the sliding bearing, which are flowed through by fuel. It is not important for the effect according to the invention, whether the holes are mounted directly in the drive shaft or arranged in a sleeve applied to the drive shaft.

In a further supplement of the invention it is provided that the Kolbenfußplatte is articulated mounted on the piston, and that the lifting movement of the eccentric portion of the drive shaft is transmitted via a polygon ring on the Kolbenfußplatte. It has been found in simulation calculations that reduced in this embodiment, the mechanical stress on the components involved and the friction losses are reduced.

Further advantages and advantageous embodiments of the invention are the following drawings, the description and the claims removable.

drawing

Fig. 1:

ein Schaltbild eines ersten Ausführungsbeispiels einer erfindungsgemäßen Radialkolbenpumpe;

Fig. 2:

ein Ausführungsbeispiel einer erfindungsgemäßen Radialkolbenpumpe im Längs- und Querschnitt;

Fig. 3:

ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Radialkolbenpumpe im Längsschnitt sowie

Fig. 4 u. 5:

Ausführungsbeispiele einer erfindungsgemäßen Kühlung des Gleitlagers der Radialkolbenpumpe.

Show it:

Fig. 1:

a circuit diagram of a first embodiment of a radial piston pump according to the invention;

Fig. 2:

an embodiment of a radial piston pump according to the invention in longitudinal and cross-section;

3:

a further embodiment of a radial piston pump according to the invention in longitudinal section and

Fig. 4 u. 5:

Embodiments of a cooling according to the invention of the sliding bearing of the radial piston pump.

Description of the embodiments

In Fig. 1 is a block diagram of a radial piston pump 1 according to the invention is shown. The radial piston pump 1 has a suction side 3 and a (high) -Pruckseite 5, the over a third check valve 7 communicates with a common rail 9. The pressure control in the common rail 9 via a pressure control valve 11 which directs excess fuel from the common rail 9 in a fuel return line 13. The fuel return line 13 opens into the suction side 3 of the radial piston pump 1. The suction side 3 is supplied with fuel by a fuel tank, not shown here.

Between the pressure side 5 and fuel return 13, which in turn is hydraulically connected to the suction side 3, a quantity control valve 15 is provided. If the quantity control valve 15, as shown in Fig. 1, is opened, no pressure build-up can take place on the pressure side 5 of the radial piston pump 1, since a hydraulic connection via the fuel return line 13 with the suction side 3 is. In this state, the radial piston pump 1 promotes no fuel in the common rail 9, since the pressure in the common rail 9 is much higher than the pressure on the suction side 3 of the radial piston pump 1. If the quantity control valve 15 is closed, the hydraulic connection between the suction side 3 and pressure side 5 is interrupted via the fuel return 13, so that a pressure build-up in the pump elements 17 of the radial piston pump 1 can take place. In this state, the radial piston pump 1 promotes fuel in the common rail 9 as soon as the pressure built up by the pump elements 17 is greater than the pressure prevailing in the common rail 9 pressure. By this type of flow control, the pumping work to be applied by the radial piston pump 1 can be minimized and thus the degree of utilization of the fuel injection system according to the invention can be improved.

So that when opening the quantity control valve 15th occurring pressure surges in the fuel return 13 and on the suction side 3 are minimized, in the fuel return 13, a memory 19 and downstream of the memory 19, a throttle 21 is provided. The memory 19 and the throttle 21 reduce and attenuate the resulting pressure on the opening of the quantity control valve pressure peaks to an acceptable level. As a result, first impermissibly high compressive stresses on the suction side 3 are avoided. Second, the suction of fuel by the pump elements 17 is no longer affected by the muted pressure surges.

2 shows an embodiment of a radial piston pump 1 according to the invention in a longitudinal section (2a) and a cross section along the section line B-B (2b).

The radial piston pump 1 consists of a pump housing 23, which is designed in two parts. The pump housing 23 thus consists of a first housing part 23a and a second housing part 23b. In the second housing part 23b, a recess 25 is incorporated, which forms the memory 19 in the assembled state together with the first housing part 23a. Between the memory 19 and the suction side 3, the throttle 21 is arranged.

In the pump housing 23, a drive shaft 27 is rotatably mounted. The drive shaft 27 has an eccentric portion 29 with a polygonal ring 31. The eccentric portion 29 engages over the polygon ring 31 freely distributed over the circumference pump elements 17, of which in Fig. 2a, only one is visible.

Each pump element 17 has a piston 33 which in a cylinder bore 35 is guided and a delivery chamber 37 limited. The pump elements 17 are inserted radially from the outside into the pump housing 23 and clamped to the pump housing 23 via a fastening screw 39. In the piston 33, a first check valve 41 is provided, which allows the suction of fuel into the delivery chamber 37. Via a transverse bore 41 in the piston 33, the hydraulic connection between the first check valve 41 and the suction side 3 is produced. The fuel drawn in by the tank, not shown, flows on the suction side 3 of the radial piston pump 1 and then flows through a sliding bearing 45 of the drive shaft 27, before it is sucked by the pump elements 17.

In Fig. 2b, the same embodiment along the section line B-B is shown. It is clear from this representation that a second check valve 49 is provided in a cylinder head 47 of the pump elements 17, through which the high-pressure fuel pushed out of the delivery chamber 37 by the piston 33 passes into high-pressure channels 51a and 51b. The high pressure passages 51a and 51b are part of the pressure side indicated by 5 in FIG.

The high pressure passages 51a and 51b connect the three pumping elements 17 by the shortest route, that is, in this case, the high pressure passages 51a and 51b are made straight. In the embodiment shown here, there are three pump elements 17 and two high-pressure channels 51a and 51b. Transferred to radial piston pumps with a different number m of pump elements 17 applies to the number n of the high-pressure channels $$\mathrm{n}\mathrm{=}\mathrm{m}\mathrm{-}\mathrm{1}$$

To the high pressure passage 51 a, the quantity control valve 15 is connected. If the quantity control valve 15 is opened, as mentioned in connection with FIG. 1, a not visible in Fig. 2b hydraulic connection between the high-pressure channels 51 a and 51 b on the one hand and the suction side 3 on the other hand made.

From the high pressure passage 51b, a high pressure port 53 branches off. In the connecting piece 55, the third check valve 7 is integrated.

From Fig. 2b it can be seen that the piston 33 rest with a Kolbenfußplatte 57 on the polygon ring 31. The Kolbenfußplatte 57 is connected via a ball joint 59 with the piston 33, so that the Kolbenfußplatte 57 optimally rests on the polygon ring 31. 'Optimal' means in this context that no local load peaks occur and depending on the dynamic load and the lubricity state between Kolbenfußplatte 57 and polygon ring 31, the Kolbenfußplatte 57 always rests on a large area on the polygon ring 31.

Because of the ball joint 59, the Kolbenfußplatte 57 can take a caused by the axial and radial forces skew. As a result, a "Aufkanten" of the Kolbenfußplatte 57 on the polygon ring 31 are counteracted. As a result, reduce the piston lateral forces in the cylinder guide, the mechanical efficiency improves and durability or resilience of the high-pressure fuel pump can be improved.

In Fig. 3 is another embodiment of a Radial piston pump 1 according to the invention shown in longitudinal section. Identical components are provided with the same reference numerals, and the same applies with regard to an exemplary embodiment for the other exemplary embodiments. In this embodiment, the housing 23 is made in one piece. The memory 19 is formed by a recess 61 in the pump housing 23. This puncture is sealed by a sleeve 63, which hydraulically separates the storage volume of the accumulator 19 from the suction side 3. In the sleeve 63, the throttle 21 is arranged. Thus, the memory 19 according to the invention can be used without major change to the pump housing 23 both in radial piston pumps 1 with one-piece pump housing 23 or two-part pump housing 23a and 23b.

The sealing of the memory 19 to the suction side can be done in the embodiments of FIGS. 2 and 3 by O-rings, metal sealing rings or Beißkanten.

4 and 5 show the slide bearing 45 along a section line II and a section line JJ (see Fig. 2a) in detail. From Fig. 4 it is seen that on the drive shaft 27, a sleeve 65 has been pressed, are incorporated in the longitudinal grooves 67. The sleeve 65 is rotatably mounted in a bearing shell 69, which is pressed in the first housing part 23a. The grooves 67 are, as is apparent from Fig. 2a in conjunction with Fig. 4, flows through the sucked from the fuel tank cool fuel. As a result, the sleeve 65 and the bearing shell 69 are cooled, which is very helpful in particular when using the radial piston pump according to the invention in internal combustion engines with gasoline direct injection. For the invention, it is without Meaning whether the fuel flows through grooves 67 or in the drive shaft 27 incorporated holes (not shown). It is essential that the cool fuel from the fuel tank for cooling the sliding bearing 45 is used.

From Fig. 5 it is seen that the sliding bearing 45 is designed so that at the transition of the drive shaft 27 to the eccentric portion 29 in the bearing shell 69 channels 71 are provided through which the fuel which has flowed through the grooves 67, can flow freely in order to guide the largest possible portion of the sucked fuel through the grooves 67. As a result, the cooling effect is further improved.

Claims (9)

1. Radial piston pump for high-pressure fuel supply in fuel injection systems of internal combustion engines, especially in common-rail injection systems, with preferably a plurality of pump elements (17) arranged radially with respect to a driveshaft (27) mounted in a pump casing (23), the pump elements (17) being actuated by the driveshaft (27) and each having a suction side (3) and a high-pressure side (5) and with high-pressure ducts (51a, 51b) in the pump casing (23) which in each case connect the high-pressure side (5) of a pump element (17) to a high-pressure connection (53) in the pump casing (23), a quantity control valve (15) being provided which, in the open state, makes a hydraulic connection between the high-pressure ducts (51a, 51b) and the suction sides (3) of the pump elements (17), characterized in that an accumulator (19) and a throttle (21) are provided between the quantity control valve (15) and the suction sides (3) of the pump elements (17).
2. Radial piston pump according to Claim 1, characterized in that each high-pressure duct (51a, 51b) connects the high-pressure sides of two pump elements (17) hydraulically to one another along the shortest path, in that the number (n) of high-pressure ducts (51a, 51b) is lower by 1 than the number (m) of the pump elements (17), and in that a high-pressure connection (53) branches off from a high-pressure duct (51b).
3. Radial piston pump according to one of the preceding claims, characterized in that the accumulator (19) is delimited by an indentation (61) in the pump casing (23) and by a sleeve (63) sealed off with respect to the pump casing (23).
4. Radial piston pump according to Claim 3, characterized in that the throttle (21) is arranged in the sleeve (63).
5. Radial piston pump according to one of the preceding claims, characterized in that the pump casing (23) is of two-part design and consists of a first casing part (23a) and of a second casing part (23b), and in that the accumulator (19) is delimited by the first and the second housing part (23a, 23b).
6. Radial piston pump according to one of the preceding claims, characterized in that each pump element (17) has a piston (33), a cylinder bore (35) and a cylinder head (47), in that the piston (33) oscillates in the cylinder bore (35) and delimits a conveying space (37), in that a first non-return valve (41) is arranged on the suction side (3), in that the first non-return valve (41) is integrated into the piston (33), and in that a second non-return valve (49) is arranged on the high-pressure side (5).
7. Radial piston pump according to Claim 5, characterized in that the driveshaft (27) is mounted in the pump casing (23) by means of a plain bearing (45), and in that fuel, in particular the fuel flowing through a fuel connection, flows necessarily through the plain bearing (45).
8. Radial piston pump according to one of the preceding claims, characterized in that one or more bores or grooves (67) are provided in the driveshaft (27) or a bearing shell (69) of the plain bearing (45), and in that fuel flows through these bores or grooves (67).
9. Radial piston pump according to one of the preceding claims, characterized in that the piston footplate (57) is mounted on the piston (33) in an articulated manner, and in that the lifting movement of the eccentric portion (29) of the driveshaft (27) is transmitted to the piston footplate (57) via a polygonal ring (31).

Images