WO1999028620A1

WO1999028620A1 - Quick-start of a high pressure pump by means of a pressure intensifier piston

Info

Publication number: WO1999028620A1
Application number: PCT/EP1998/007582
Authority: WO
Inventors: Franz Pawellek
Original assignee: Mannesmann Rexroth Ag
Priority date: 1997-11-29
Filing date: 1998-11-24
Publication date: 1999-06-10
Also published as: DE19753155A1

Abstract

The invention relates to a fuel supply system for an internal combustion engine. The system comprises a high pressure pump which takes in fuel from a low pressure area and supplies it to one of a number of cylinders of the internal combustion engine having a high pressure area. The system also comprises a presupply pump which is driven by an electric motor. The pump feeds fuel under a presupply pressure to the low pressure area. The aim of the invention is to generate a high pressure in the high pressure area as quickly as possible during the starting operation of the internal combustion engine. According to the invention, this is achieved by means of a pressure intensifier with a pressure intensifier piston which has a large active surface and a small active surface. A first pressure chamber which is fluid connected to the low pressure area borders said large active surface, and a second pressure chamber which is fluid connected to the high pressure area borders said small active surface. As a result, a high pressure can be generated in the high pressure area via the pressure intensifier when the presupply pump is already running, however, the high pressure pump however remains idling.

Description

description

QUICK START OF A HIGH PRESSURE PUMP BY PRESSURE TRANSLATION PISTON

The invention is based first of all on a fuel supply system for an internal combustion engine, which according to the preamble of claim 1 is a high-pressure pump that draws fuel from a low-pressure area and delivers it into a high-pressure area common to a plurality of cylinders of the internal-combustion engine, and has a pre-pump driven by an electric motor Feeds fuel under a pre-pressure into the low pressure range. The invention also relates directly to the high-pressure pump, which, according to the preamble of claim 6, has a housing which preferably accommodates a plurality of delivery units which deliver fuel from the low-pressure region under a pre-pressure to the common high-pressure region.

Both a fuel supply system and a high-pressure pump of the type described are known from DE 42 16 877 C2. The high-pressure pump there is a radial piston pump with three delivery pistons which are arranged essentially radially and at equal angular intervals with respect to the axis of a drive shaft and are kept in contact with an eccentric which sits on the drive shaft and is located in a crank chamber of the housing. In the suction stroke, during which the working area increases on a delivery piston, fuel flows from the low-pressure area into the working area. In the working stroke, the fuel is displaced by the delivery pistons into the common high-pressure area. From this, the fuel is injected directly into the cylinders of the internal combustion engine with precise timing and quantity control. One speaks of a common rail direct injection. This type of fuel supply has recently been implemented in a type of car equipped with a diesel engine,

The aim is to use common rail direct injection in gasoline engines, too, and it is hoped that this will result in considerable fuel savings. One obstacle to the success of this technology is that the high pollutant emissions in the exhaust gas have not yet been controlled. In particular, the starting process does not yet meet the requirements in this regard.

If a high-pressure pump mechanically driven via the camshaft is used for a gasoline engine with common rail direct injection, a few revolutions of the drive shaft of the high-pressure pump are generally required during the starting of the internal combustion engine until a sufficient injection pressure is built up in the high-pressure range. Until the sufficient injection pressure is reached, injection must be carried out into the suction stroke of the cylinders of the internal combustion engine with an excessively low pressure, at the beginning even with the pre-pressure that is built up by the delivery of the pre-pump in the low-pressure range when the ignition switch is actuated. However, a good mixture composition cannot be achieved at these low pressures, so that relatively many unburned hydrocarbons get into the exhaust gas.

In order to increase the pressure in the high-pressure area more quickly, there is the consideration of using a high-pressure pump that has a larger stroke volume, which means that it pumps a lot of fuel per revolution of the drive shaft.

This, on the one hand, increases the power consumption of the pump and, on the other hand, increases the heat input into the fuel due to the reduced excess amount. The aim of the invention is to develop a fuel supply system with the features from the preamble of claim 1 in such a way that even when a high-pressure pump with a stroke volume matched to the fuel consumption during normal operation of the internal combustion engine is used, the internal combustion engine starts quickly a high pressure is reached in the high pressure range. In particular, the pressure should already be high within a period of a few tenths of a second, which is when the ignition key is actuated between the switching on of the ignition and the start of the rotation of the starter motor.

This goal is achieved by a fuel supply system which, in addition to the features from the preamble of claim 1 according to the characterizing part of this claim, has a pressure booster with a pressure booster piston, which has a large effective area, adjacent to which a first pressure chamber is fluidly connected to the low pressure region is connected, and has a small effective area, which is adjoined by a second pressure chamber which is fluidly connected to the high pressure region. During the starting process, the electric motor of the pre-pump is immediately energized when the ignition is switched on and starts to turn. In the low-pressure range, the pre-pressure builds up quickly, from which the pressure booster piston acts on the large effective area. In accordance with the area ratio between the large effective area and the small effective area, the fuel located in the high pressure area is compressed to a high pressure. If the area ratio is, for example, 12.5, a pressure of 50 bar can be generated with a preliminary pressure of 4 bar on the high pressure side. In any case, it is possible to generate a pressure on the high-pressure side that meets the requirements for fuel injection. Advantageous refinements of a fuel supply system according to the invention can be found in subclaims 2 to 6.

In order to keep the line expenditure low and to require little additional installation space for the pressure intensifier, this is preferably integrated in the high pressure pump according to claim 3.

It is conceivable that the high pressure area is not completely filled with fuel at the start of a starting process. In order to enable rapid filling regardless of a movement of the pressure booster piston, an additional fluid path is provided between the low pressure area and the high pressure area, in which a check valve is arranged, which opens from the low pressure area to the high pressure area and blocks the other way round. In principle, if the high-pressure pump contains suction and pressure valves, the high-pressure area can also be filled by the preliminary pump via these valves. However, the fluid path through these valves may be long and has many deflections. Furthermore, the suction and pressure valves can be biased relatively high in the closing direction. Overall, there could be a pressure drop between the high-pressure area and the low-pressure area, which allows the pressure booster piston to move even before the high-pressure area is completely filled. The closing element of the check valve in the additional fluid path is only very slightly or not at all biased in the closing direction, so that the pressure difference between the low-pressure area and the high-pressure area is only very small during the filling of the latter. The friction on the seals for the pressure booster piston is therefore sufficient to keep the pressure booster piston in its initial position until the filling of the high pressure area. Again in order to save installation space, the additional fluid path advantageously runs through the pressure booster piston on which the check valve is also located. A latching in the starting position ensures that the pressure booster piston assumes the starting position at the beginning of the starting process and only moves between the low-pressure side and the high-pressure side at a certain pressure difference. After a short distance, the locking force disappears, so that a high pressure ratio is achieved.

Claims 7 to 12 are directed to a high-pressure pump which is intended for use in a fuel supply system according to one of Claims 1 to 6 and has a housing in which not only the delivery units which deliver fuel from the low-pressure region to the common high-pressure region, but also the pressure booster piston is housed. Little additional installation space is then required for the pressure booster piston.

If the high-pressure pump is a radial piston pump with a plurality of delivery pistons arranged essentially radially and at equal angular distances from one another, the pressure booster piston is advantageously likewise arranged approximately in the radial direction and is accommodated between two delivery pistons in the housing.

The fluidic connection between the first pressure chamber on the pressure booster piston and the low-pressure region can be established in a simple manner by an opening in the housing if the crank chamber of the housing, which receives the eccentric that drives the delivery pistons, is in the low-pressure region.

The measures from claims 10, 11 and 12 are also advantageous with regard to a simple and compact design.

An embodiment of a fuel supply system according to the invention and an embodiment of a high pressure pump used in such a fuel supply system with integrated pressure intensifier are shown in the drawings. The invention will now be explained in more detail with reference to these drawings.

Show it

1 shows the fuel supply system in terms of circuitry,

Figure 2 shows a cross section through the high-pressure pump designed as a radial piston pump in the area of the radial piston and the integrated pressure intensifier and

FIG. 3 shows a longitudinal section through the high-pressure pump according to line III-III from FIG. 2.

The fuel supply system according to FIG. 1 has a preliminary pump 11 which is driven by an electric motor 10 and which, together with the electric motor, forms a structural unit which is located within a fuel tank 12 of a motor vehicle. The unit also includes a pressure relief valve 13, the input of which is connected to the pressure outlet of the preliminary pump 11 and by means of which a pressure of, for example, 4 bar can be set at the pressure outlet. From the pressure output of the pre-pump 11, a pre-delivery line 14 is led out of the tank 12 and with the interposition of a fuel filter 15 to a high-pressure pump 16. As can be seen in more detail from FIGS. 2 and 3, this is a radial piston pump with a housing 17 in which three delivery units 18 are accommodated. The pre-delivery line 14 opens into a cavity 19 of the housing 17, which is indicated by a line in FIG. 1 and from which fuel can get into the working space of a delivery unit via a suction valve 20 constructed in the manner of a check valve. The entire line section between the outlet of the pre-pump 11 and the suction valves 20 can be referred to as the low-pressure range, in which, apart from the low throttle losses in the lines and in the fuel filter 15, the pre-pressure set at the pressure relief valve 13 prevails. Every working space of the high pressure pump is over a pressure valve designed as a check valve blocking it with it is connected to a channel running in the housing 17. All channels run together within the housing 17 and are guided in a single channel to a pressure outlet 22 of the high-pressure pump. This will be explained in more detail when looking at FIGS. 2 and 3. A high-pressure line 23, which is common to all cylinders of the internal combustion engine to be supplied with fuel, is connected to the pressure outlet 22. The entire line tract between the pressure valves 21 and the cylinders of the internal combustion engine can be referred to as a high pressure area.

In the high-pressure pump 16, a pressure intensifier 30 with a pressure intensifier piston 31 is installed, which is composed of a primary-side part piston 32 of large diameter and a secondary-side part piston 33 of small diameter. A pressure chamber 35 adjoins the active surface 34 of the primary-side partial piston 32 facing away from the partial piston 33 and is fluidly connected to the cavity 19 of the housing 17, that is to say to the low-pressure region of the fuel supply system. A pressure chamber 37 adjoins the active surface 36, which is substantially smaller than the active surface 34, of the secondary piston 33, which is fluidly connected to the high-pressure region of the fuel supply system.

A detent groove 25 runs around the partial piston 33 on the side of a high-pressure seal 24 facing away from the high pressure, into which a detent ball 26 which is under spring load can snap. The pressure booster piston 31 is thereby secured in an initial position.

A bore 38 leads through the pressure booster piston 31 centrally and axially, in which a check valve 39 is arranged at the mouth into the pressure chamber 37 and blocks in the direction from the second pressure chamber 37 to the first pressure chamber 35. The closing member 40 of the check valve 39 is in the closing direction loaded by a weakly preloaded compression spring 41. The preload is in a range which allows the check valve to be opened when the pressure difference between the first pressure chamber 35 and the second pressure chamber 37 is in the range below 0.1 bar.

The high-pressure pump is driven by the internal combustion engine via the camshaft 42 schematically indicated in FIG.

A pressure relief valve 45 is connected to the high pressure area, which is electromagnetically adjustable and with the aid of which the optimum high pressure in the high pressure area is set. A line 46 leads from the pressure relief valve back to the fuel tank 12. The annular space on one side of the partial piston 32 of the pressure booster 30 is also connected to this line.

It is now assumed that a motor vehicle equipped with the fuel supply system according to FIG. 1 is stationary when the internal combustion engine is not running and that all fuel lines are filled with fuel under atmospheric pressure. During the starting process, the ignition switch is actuated and first reaches a switch position "ignition on", in which the electric motor 10 is already energized while the starter is still disconnected from the vehicle electrical system. The electric motor 10 drives the pre-pump 11, whereupon this fuel flows into promotes the low pressure area, so that a pressure of 4 bar builds up there. Even with a small pressure difference between the pressure spaces 35 and 37, the locking force of the locking ball 26 is overcome and the pressure booster piston 31 begins to move, so that in the high pressure area an Pressure builds up ratio of surface 34 to surface 36 on the pressure booster piston in a very short time before the ignition starter switch reaches a position in which the starter is also energized and the internal combustion engine begins and with it the camshaft and to drive the delivery units of the high pressure pump 16. Fuel can therefore be injected into the cylinders of the internal combustion engine under high pressure right from the start.

During the starting process, fuel delivered by the preliminary pump 11 can reach the high-pressure region via the suction valves 20 and the pressure valves 21, as long as the pressure there is lower than the preliminary pressure by a pressure difference, which is equivalent to the sum of the preloading forces of a suction valve 20 and a pressure valve 21 . If each valve 20 and 21 is 0.1 bar, for example, fuel can flow from the low pressure area into the high pressure area as long as the pressure in the high pressure area is below 3.8 bar. Basically, it is conceivable to fill the high-pressure area via the suction valves 20 and pressure valves 21 before the pressure booster piston 31 moves, if it is not completely filled at the start of a starting process of the internal combustion engine. The filling then does not have to take place with the aid of the pressure booster piston 31, so that its path can be limited. Without the locking ball, however, the friction between the pressure booster piston and its guide would then have to be so great that the pressure booster piston does not move during the filling process via the suction and pressure valves 20 and 21 due to the pressure difference between the low pressure area and the high pressure area. On the other hand, the friction on the pressure intensifier should be as small as possible so that the force generated by the preliminary pressure on the large active surface 34 is used to the greatest possible extent for the pressure translation. Such utilization to a large extent enables the pressure booster piston to be locked in its initial position and the additional fluid path 38 leading via the pressure booster piston from the low pressure area to the high pressure area with the check valve 40 arranged therein, the closing spring 41 of which is much weaker than, for example, biased to 0.05 bar than the respective closing spring of the suction and pressure valves 20 and 21. Because of the weaker preload of the pressure spring 41 and because only one in the additional fluid path Check valve is arranged, during the initial filling process of the high-pressure area, the pressure difference between the low-pressure area and the high-pressure area is substantially smaller than when filling only via the suction and pressure valves 20 and 21, so that a low cogging force between the pressure booster piston 31 and the locking ball is sufficient to to hold the pressure booster piston in its initial position shown in FIG. 1 during the filling process. After filling the high-pressure area, the pressure there rises above 1 bar and the difference in opposing pressure forces quickly becomes so great at the pressure intensifier 31 that, viewed in FIG. 1, it moves to the right and puts the fuel under high pressure in the high-pressure area.

When the high-pressure pump then works, the pressure in the high-pressure region rises above the maximum pressure that can be achieved with the pressure intensifier, so that the pressure intensifier moves back into the position shown in FIG. 1 and remains there. The check valve 40 prevents fuel from flowing back from the high pressure area into the low pressure area via the additional fluid path 38.

When the internal combustion engine is switched off, care is taken to ensure that the high-pressure region is not relieved via the pressure-limiting valve 45 until the electric motor 10 and thus the preliminary pump 11 have come to a standstill and the preliminary pressure has decreased to tank pressure. The pressure booster piston then remains securely in its initial position shown in FIG. 1 and can be effective again the next time the engine is started.

For a numerical example it is assumed that a common pre-pump delivers 120 1 / h at a pre-pressure of 4 bar. The time difference between the switching on of the electric motor 10 and the starter is 300 ms. During this time, the pre-pump 11 delivers 10 cm ³ . If 10 mm ^{3 are} required per injection into the cylinder of an internal combustion engine, then for the first 20 injections 200 mm ^{3 of} fuel consumed. Assuming a required minimum pressure for injection of 50 bar, neglecting friction on the pressure booster piston results in an area ratio of 50 bar to 4 bar = 12.5. In order to maintain this area ratio, the secondary part of the pressure intensifier had a diameter of 10 mm and the primary part of the piston had a diameter of 35 mm. Due to the delivery of the preliminary pump in the amount of 120 1 / h and the size of the first effective surface 34, a maximum stroke of the pressure booster piston of 10 mm is possible in 300 ms. The stroke to provide the necessary injection quantity of 200 mm ³ is 2.5 mm. The stroke difference between 10 mm and 2.5 mm is available to increase the pressure of the fuel in the high pressure area and for other losses.

Pushing the pressure booster piston back into its starting position takes about 30 pump revolutions in common high-pressure pumps and means a temporary restriction of the pressure dynamics in the high-pressure range. However, this is hardly noticeable when starting. As soon as the pressure booster piston has reached its starting position again, the pressure control between start pressure, e.g. 50 bar, and maximum pressure, e.g. 120 bar, possible.

The radial piston pump 16 shown in FIGS. 2 and 3 has a one-piece pump housing 17 in which an axial bore 54 is formed for receiving a drive shaft 55. This is provided for coupling to the camshaft of an internal combustion engine. The drive shaft is assigned three conveyor units 18, which are distributed evenly over the circumference and are installed in a respective cylinder receiving space 57 of the pump housing 17.

As can be seen from FIG. 3, the drive shaft 55 is in the axial bore 54 of the pump housing by means of a roller bearing 58 17 stored. The drive shaft 55 has a radially projecting radial collar 59 which separates a bearing section 60 of the drive shaft 55 from an eccentric 61 which is produced in one piece with the drive shaft. The eccentric 61 is offset by the eccentricity e from the shaft axis of rotation 62. On the outer circumference, the eccentric 61 carries a slide bush 63 on which an eccentric ring 64 is mounted. The axial length of the eccentric ring 64 is somewhat larger than that of the sliding bush

63 chosen so that the full length of the eccentric ring

64 is covered.

The right end face of the eccentric ring 64 in FIG. 3 is supported on a radial shoulder 66 of the axial bore 54 via a perforated disk 65. The perforated disk 65 is fixed in the radial direction via an annular groove 67 which is formed in the radial shoulder 66 and into which the perforated disk 65 is partially immersed.

On the other end face of the eccentric ring 64 there is a shaft sealing device with a slide ring 68 and with a support ring 69, via which the eccentric or crank chamber 70 delimited by the eccentric ring 64 and the adjacent circumference of the axial bore 54 is sealed off from the roller bearing 58. The eccentric ring 64 is also acted upon by the adjacent end face of the radial collar 59 of the drive shaft 55 in the axial direction, so that it is pressed in the direction of the perforated disk 65. If, despite the shaft sealing device with the slide ring 68 and the support ring 69, leakage occurs from the crank chamber 70 to the roller bearing 58, this leakage is made via a circumferential groove 75 formed in the wall of the axial bore 54 and a leakage connection 76 connected thereto, which is only shown schematically in FIG is shown, returned to the fuel tank 12.

As can be seen from FIG. 2, the eccentric ring 64 is provided with three flats 77 distributed uniformly over its circumference. see, on each of which a slide shoe 78 of a conveyor unit 18 is supported. The eccentric ring 64 performs a wobble movement which, in addition to a lifting movement, leads to a lateral displacement of each flat 77 with respect to the axis of each conveyor unit 18. Each conveyor unit 18 has a cylinder 79 with a cylinder bore 80 into which the sliding block 78 is inserted. The sliding shoe 78 dips into the cylinder bore 80 with a hub-shaped projection. Recesses 81 in the surface of a slide shoe 78 abutting a flat 77 provide a connection from the crank chamber 70 to an axial through-bore 82 of the slide shoe, at the mouth of which is directed into the interior of the respective cylinder, a plate valve is arranged as a suction valve 20 of the respective delivery unit 18. When the suction valve is open, fuel can flow into the cylinder bore 80 from the crank chamber 70, which is to be connected to the pre-delivery line 14 via a connecting nib 83. The cylinder 79 is biased by a compression spring 84 in the direction of a flat 77, the compression spring 84 being supported on the one hand on a radial shoulder of the cylinder 79 and on the other hand on a screw part 85 which closes a receiving bore 57 of the housing 17 for a delivery unit 18 is screwed into the housing 17.

The end section of a circular-cylindrical piston 87 is pressed into a central blind bore of the screw part 85, the freely projecting section of which plunges into the cylinder bore 80 and which, together with the cylinder 79 and the sliding block 78, limits a variable working space of a delivery unit 18. The piston 87 has an axially extending piston bore 88, in which a pressure valve 21 is installed. On the output side of the pressure valve 21, a radial bore 89 is formed in the wall of the piston 87, which opens into an annular groove running around the outside of the piston 87, towards which an oblique bore 90 of the screw part 70 is also open. The oblique bore in turn opens into an annular channel 91 between the screw part 70 and a shoulder of a cylinder receiving bore 57. From the annular space 91, a bore 92 extends obliquely through the housing 17 and opens into an annular channel 93, between the wall of a central bore 94 located in the extension of the axial bore 54 in the housing 17 and one into the bore 94 screwed plug 95 is formed. Corresponding to the three existing conveyor units 18, there are three bores 92 in the housing 17, all of which open into the annular channel 93. From this, a common manifold 96 leads through the housing 17 to the pressure connection 22. All channels and bores downstream of the pressure valves 21 are in the high pressure range.

Between two of the conveyor units 18, which are each installed in approximately radially projecting domes of the housing 17, a further material projection is formed on the housing 17, in which there is an outwardly open, circular-cylindrical recess 101, the diameter of which corresponds to the diameter of the primary partial piston 32 of the pressure booster piston 31 is matched. The recess 101 is closed to the outside by a cover 102 which is screwed onto the housing 17 and which has a central blind bore 103 coaxial with the recess 101, the diameter of which is matched to the diameter of the secondary part piston 33 of the pressure booster piston 31. The pressure booster piston 31 is located in the recess 101 and in the blind bore 103. The free space between the partial piston 32 and the bottom of the recess 101 forms the first pressure chamber 35, which is connected via a bore 104 to the crank chamber 70, that is to say to the low-pressure region of the pump is. The space between the partial piston 33 and the bottom of the blind bore 103 is to be regarded as a second pressure space 37. This is connected via a radial bore 105 to the pressure connection 22 formed in the cover 102, that is to say to the high-pressure region of the pump. The annular space between the cover 102 and the primary piston 32 is to be connected to the return line 46 (see FIG. 1) via a bore 106 running axially in the cover 102. Several sets of seals provide a seal between the Pressure chamber 35 and the annular space just mentioned, between this annular space and the second pressure space 37 and between the annular space and the outside of the housing 17 and the cover 102. As already described when considering FIG. 1, a bore 38 leads through the pressure booster piston 31 , into which the check valve 39 is inserted from the end face of the partial piston 33. On the other side of the pressure booster piston 31 there is a connection between the crank chamber 70 and the bore 38 even when the pressure booster piston 31 is supported on the bottom of the recess 101, so that in this position of the pressure booster piston 31 fuel from the crank chamber 70 through the bore 38 can flow through to the pressure connection 22.

The latching of the pressure booster piston is not shown in FIGS. 2 and 3. However, a transfer from FIG. 1 is easily possible, the housing and / or cover and the partial piston 33 being to be extended in the axial direction of the pressure booster piston compared to the embodiment according to FIGS. 2 and 3.

The mode of operation of the high-pressure pump and the pressure intensifier has already been described with reference to FIG. 1 and can also be easily understood with reference to FIGS. 2 and 3, so that further explanations regarding the function of the specific exemplary embodiment according to FIGS. 2 and 3 are unnecessary.

Claims

claims

1.Fuel supply system for an internal combustion engine with a high-pressure pump (16) which draws fuel from a low-pressure area (14, 19) and delivers it into a high-pressure area (22, 23, 96) common to a plurality of cylinders of the internal combustion engine, and with one by an electric motor (10 ) driven pre-pump (11), which feeds fuel under a pre-pressure into the low-pressure area (14, 19), characterized by a pressure booster (30) with a pressure booster piston (31), which has a large effective area (34) to which a fluid with the The first pressure chamber (35) connected to the low pressure region (14, 19) adjoins, and has a small effective area (36) to which a second pressure chamber (37) fluidly connected to the high pressure region (22, 23, 96) adjoins.

2. Fuel supply system according to claim 1, characterized in that the size ratio of the large effective area (34) to the small effective area (36) is in the range between ten and fifteen.

3. Fuel supply system according to claim 1 or 2, characterized in that the pressure intensifier (30) with the high pressure pump (16) combined to form a structural unit, in particular integrated in the high pressure pump (16).

4. Fuel supply system according to one of the preceding claims, characterized in that a non-return valve (40) is arranged in an additional fluid path (38) between the low-pressure region (14, 19) and the high-pressure region (22, 23, 96) , 16) to the high pressure area (22, 23, 96) and vice versa.

5. Fuel supply system according to claim 4, characterized in that the additional fluid path (38) through the Pressure booster piston (31) runs through and the check valve (40) sits on the pressure booster piston (31).

6. Fuel supply system according to one of the preceding claims, characterized in that the pressure booster piston (31) is locked in the starting position.

7. High-pressure pump for use in a fuel supply system according to one of the preceding claims, which sucks fuel from a low-pressure region (14, 19) and delivers it to a common high-pressure region (22, 23, 96) of an internal combustion engine, characterized in that it and a pressure intensifier (30) with a pressure booster piston (31), which has a large effective area (34), to which a first pressure chamber (35) fluidically connected to the low pressure area (14, 19), and a small effective area (36), to which a second pressure chamber (37) fluidly connected to the high pressure region (22, 23, 96) forms a structural unit.

8. High-pressure pump according to claim 7 and with a housing (17) which preferably accommodates a plurality of delivery units (18) which deliver fuel from a low-pressure region (19) under a pre-pressure pressure into a common high-pressure region (96), characterized in that in the Housing (17) has a pressure booster piston (31) with a large effective area (34), to which a first pressure chamber (35) fluidically connected to the low pressure region (19) is adjacent, and with a small effective area (36), to which a fluidic area is connected the second pressure chamber (37) connected to the high pressure region (96) is accommodated.

9. High-pressure pump according to claim 8, characterized in that this is a radial piston pump (16) with a drive shaft (55) and with a plurality with respect to the drive shaft (55) arranged substantially radially and at equal angular intervals from one another Conveyor units (18) and that the pressure booster piston (31) is at least approximately in the radial direction between two conveyor units (18) housed in the housing (17).

10. High-pressure pump according to claim 9, characterized in that one of the delivery pistons (79) of the delivery units (18) driving eccentric (61) receiving crank chamber (30) of the housing (17) is in the low pressure region and that the first pressure chamber (35) on Pressure booster piston (31) is fluidly connected to the crank chamber (30) via an opening (104) in the housing (17).

11. High-pressure pump according to claim 8, 9 or 10, characterized in that the housing (17) has an outwardly open recess (101) in which the pressure booster piston (31) is located and that the recess (101) through a cover ( 102) is closed, which has a recess (103) into which the pressure booster piston (31) with its secondary part piston (33) is immersed.

12. High-pressure pump according to claim 11, characterized in that the pressure booster piston (31) with its primary part piston (32) from the recess (101) in the housing (17) is received directly.

13. High pressure pump according to one of claims 7 to 12, characterized in that the second pressure chamber (37) on the pressure booster piston (31) and the high pressure region (96) within the housing (17) are fluidly connected to one another.