DE102018203769A1 - Fuel delivery device for cryogenic fuels - Google Patents

Abstract

The invention relates to a fuel delivery device for cryogenic fuels, comprising a piston pump (1) for conveying the cryogenic fuel to high pressure, wherein the piston pump (1) has a reciprocating pump piston (2) with a drive piston (3) in a cylinder bore (4) of a housing part (5) is received and in the cylinder bore (4) defines a drive space (6) which can be acted upon by a hydraulic pressure medium, so that the pump piston (2) is hydraulically driven. According to the invention, the drive piston (3) and the housing part (5) act together to form a slide valve (8), wherein the inlet of the hydraulic pressure medium into the drive chamber (6) and / or the outlet of the hydraulic pressure medium from the drive space are by means of the slide valve (8) (6) is controllable in dependence on the axial position of the pump piston (2) or are.

Description

The invention relates to a fuel delivery device for cryogenic fuels having the features of the preamble of claim 1.

The cryogenic fuel may in particular be natural gas (NG) stored on board a motor vehicle for operating a liquefied natural gas (LNG) in a specially designed tank.

State of the art

From the EP 2 541 062 A1 is a piston pump for cryogenic fuels, especially for natural gas, known with a reciprocating pump piston. The pump piston defines a pump working space, which can be filled with liquid natural gas, so that in the pump working space existing liquid natural gas can be acted upon by a lifting movement of the pump piston with high pressure. At the other end of the pump piston limits a drive space which can be filled with a hydraulic pressure medium to drive the pump piston in a reciprocating motion. Alternatively, an electric, pneumatic or mechanical drive is proposed.

Based on the above-mentioned prior art, the present invention has the object to provide a fuel delivery device for cryogenic fuels with a designed as a piston pump high-pressure fuel pump, which is hydraulically driven and has high dynamics at the same time increased robustness.

To solve the problem, the fuel delivery device with the features of claim 1 is proposed. Advantageous developments of the invention can be found in the dependent claims.

Disclosure of the invention

The proposed fuel delivery device for cryogenic fuels comprises a piston pump for delivering the cryogenic fuel to high pressure, the piston pump having a reciprocating pump piston with a drive piston received in a cylinder bore of a housing part and defining a drive space in the cylinder bore. The drive space is acted upon by a hydraulic pressure medium, so that the pump piston is hydraulically driven. According to the invention, the drive piston and the housing part cooperate to form a slide valve. By means of the slide valve is or are the inlet of the hydraulic pressure medium in the drive space and / or the flow of the hydraulic pressure medium from the drive chamber in dependence on the axial position of the pump piston controllable. That is, by means of the slide valve, the hydraulic pressure prevailing in the drive chamber and consequently a hydraulic pressure force acting on the pump piston can be set exactly. The reciprocating movements of the pump piston are thus precisely controlled. In particular, pressure conditions can be created that lead to improved dynamics.

Furthermore, the volume flow of the hydraulic pressure medium in the inlet direction and / or in the outlet direction can be controlled via the at least one slide valve. That is, depending on the axial position of the pump piston, the inlet in the drive space and / or the outlet from the drive space varies, in particular throttled, can be, for example, to achieve a cushioning of the pump piston. In this way, the robustness of the piston pump can be increased.

The provision of the pump piston can be effected mechanically, in particular by means of a spring or also hydraulically.

To bring about the provision of the pump piston also hydraulically, it is proposed in a further development of the invention that the drive piston separates the drive space from another in the cylinder bore and acted upon by the hydraulic pressure medium drive space.

Furthermore, it is proposed that the drive piston and the housing part cooperating form a further slide valve and by means of the further slide valve, the inlet of the hydraulic pressure medium in the further drive space and / or the flow of the hydraulic pressure medium from the further drive space in dependence on the axial position of the pump piston is controllable. The reciprocating movements of the pump piston can thus be controlled even more precisely. Furthermore, the dynamics of the piston pump can be further increased.

The two drive spaces are preferably acted upon alternately with the hydraulic pressure medium. While the one drive space is acted upon by the hydraulic pressure medium, the other drive space is relieved. The reciprocating movements of the pump piston are therefore controlled by the voltage applied to the drive piston pressure conditions. This means that the drive of the piston pump is effected purely hydraulically, so that a mechanical spring for returning the pump piston is dispensable.

Preferably, at least one inlet channel for the hydraulic pressure medium is formed in the housing part, which is aligned substantially radially with respect to the cylinder bore and / or opens into an annular bore extending the cylinder bore. The inlet channel is assigned to a drive space, so that hereby the inlet in this drive space is controllable. To act on both drive spaces alternately with the hydraulic pressure medium, preferably at least two inlet channels formed in the housing part are provided. The substantially radial orientation of the at least one inlet channel with respect to the cylinder bore formed in the housing part has the advantage that the inlet channel is controllable via the drive piston in dependence on the axial position of the pump piston. This means that, depending on the axial position of the pump piston, a connection of the inlet channel with the respective drive space is established or at least partially interrupted in order for example to throttle the feed into the drive space or to stop it entirely. If the inlet channel opens into an annular channel formed in the housing part, this has the advantage that the inlet in the respective drive chamber can be controlled independently of the angular position of the drive piston with respect to the housing part.

Furthermore, the inlet channel and / or the annular channel is / are preferably connected to a drive space via at least one connecting channel formed in the drive piston or can be connected to a drive space as a function of the axial position of the pump piston. Accordingly, via the inlet channel and / or the annular channel tapered hydraulic pressure fluid can be supplied to the drive space via the at least one connecting channel formed in the drive piston. For this purpose, the connection channel can be designed as an oblique bore, which is guided from radially outside to an end face of the drive piston. Alternatively or additionally, the at least one connecting channel can be designed as a radial bore passing through the drive piston, which is connected to the respective drive space via at least one further connecting channel designed as an axial bore or oblique bore.

In a further development of the invention, it is proposed that the at least one connecting channel formed in the drive piston of the pump piston opens into a circumferential annular groove which, depending on the axial position of the pump piston, can at least partially overlap with the inlet channel and / or annular channel formed in the housing part. The annular groove ensures that, irrespective of the angular position of the pump piston with respect to the housing part, a connection of the at least one inlet channel formed in the housing part to the at least one connecting channel formed in the drive piston can be produced. The annular groove formed in the drive piston may be provided as an alternative or in addition to an annular channel formed in the housing part.

It is also proposed that the at least one annular channel formed in the housing part and / or the at least one annular groove formed in the drive piston has or have a geometry deviating from a rectangular cross-sectional shape. For example, the annular channel and / or the annular groove can have a trapezoidal cross-section. A deviating from a rectangular cross-sectional geometry has the advantage that in the case of an achievable throttling of the inlet of hydraulic pressure medium in a drive space, a throttle gap can be created which varies depending on the axial position of the pump piston in both the axial and in the radial direction , In this way, the throttle characteristic can be influenced.

According to a preferred embodiment of the invention, the at least one inlet channel forms at least in sections at the same time a drainage channel, via which the respective drive space can be relieved. This means that the inlet channel replaces a separate outlet channel, which simplifies the production of the piston pump. Furthermore, the connection costs are reduced.

Preferably, the at least one inlet channel via a directional control valve is alternately connected to a high-pressure line and a low-pressure line for the hydraulic pressure medium, so that flows through the hydraulic pressure medium in response to the switching position of the directional control valve of the inlet channel in the inlet direction or in the drain direction. Preferably, the directional control valve is designed as a 3/2-way valve or as a 4/2-way valve. Both drive spaces can be alternately connected to the high-pressure line or the low-pressure line for the hydraulic pressure medium via the 4/2-way valve. The two drive spaces are thus alternately acted upon by the hydraulic pressure medium, so that each pressurizes a drive space and the other drive space is relieved. In the conveying operation of the piston pump, the first drive space is acted upon by the hydraulic pressure medium, while the second drive space is relieved. In the suction operation of the piston pump, it behaves vice versa, wherein the pump piston is returned to its original position.

In order to achieve a quick return of the pump piston to its initial position, it is proposed as a further development measure that at least one drainage channel is formed in the drive piston of the pump piston and / or in the housing part. The drainage channel increases the discharge the respective drive space available flow cross-section, so that the discharge is accelerated. As a result, the dynamics of the pump piston can be further increased. Preferably, a check valve opening in the direction of flow is integrated into the drainage channel.

This ensures that no hydraulic pressure medium can flow through the drainage channel, but rather an inlet throttling is achieved. Further preferably, the at least one flow channel via the at least one slide valve and can be switched off.

Preferably, the second drive space is designed as an annular space, which is bounded radially inwardly by a piston portion of the pump piston, which has a reduced outer diameter relative to the drive piston. Further preferably, the admission of the second drive space with the hydraulic pressure medium via a plurality of connecting channels, which are designed in the drive piston as oblique holes. In this way, the most uniform possible application of the annular space with the hydraulic pressure medium can be effected.

In addition, preferably, the drive piston at its end facing the first drive space on a preferably radially outwardly disposed, annular stop edge. This ensures that stopping of the drive piston maintains a minimum hydraulic volume in the first drive space, which counteracts hydraulic adhesive effects. This measure also contributes to increasing the dynamics.

• 1 einen schematischen Längsschnitt durch eine erfindungsgemäße Kraftstofffördereinrichtung mit Kolbenpumpe,
• 2a, b jeweils einen vergrößerten Ausschnitt der 1 im Bereich des Antriebs der Kolbenpumpe, a) zu Beginn eines Förderhubs und b) während eines Förderhubs,
• 3a, b jeweils einen vergrößerten Ausschnitt der 1 im Bereich des Antriebs der Kolbenpumpe, a) zu Beginn eines Saughubs und b) während eines Saughubs,
• 4 einen vergrößerten Ausschnitt der 2b,
• 5 einen vergrößerten Ausschnitt der 2b mit modifiziertem Antriebskolben,
• 6a, b jeweils einen schematischen Längsschnitt durch eine Kolbenpumpe einer weiteren erfindungsgemäßen Kraftstofffördereinrichtung im Bereich des Antriebs, a) zu Beginn eines Förderhubs und b) während eines Förderhubs,
• 7a, b jeweils einen schematischen Längsschnitt durch die Kolbenpumpe der weiteren erfindungsgemäßen Kraftstofffördereinrichtung im Bereich des Antriebs, a) zu Beginn eines Saughubs und b) während eines Saughubs,
• 8 einen schematischen Längsschnitt durch eine Kolbenpumpe einer Kraftstofffördereinrichtung gemäß einer dritten bevorzugten Ausführungsform,
• 9 einen schematischen Längsschnitt durch eine Kolbenpumpe einer Kraftstofffördereinrichtung gemäß einer vierten bevorzugten Ausführungsform, und
• 10 einen schematischen Längsschnitt durch eine Kolbenpumpe einer Kraftstofffördereinrichtung gemäß einer fünften bevorzugten Ausführungsform.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. These show:

• 1 a schematic longitudinal section through a fuel delivery device according to the invention with piston pump,
• 2a, b each an enlarged section of the 1 in the region of the drive of the piston pump, a) at the beginning of a delivery stroke and b) during a delivery stroke,
• 3a, b each an enlarged section of the 1 in the region of the drive of the piston pump, a) at the beginning of a suction stroke and b) during a suction stroke,
• 4 an enlarged section of the 2 B .
• 5 an enlarged section of the 2 B with modified drive piston,
• 6a, b in each case a schematic longitudinal section through a piston pump of a further fuel delivery device according to the invention in the region of the drive, a) at the beginning of a delivery stroke and b) during a delivery stroke,
• 7a, b in each case a schematic longitudinal section through the piston pump of the further fuel delivery device according to the invention in the region of the drive, a) at the beginning of a suction stroke and b) during a suction stroke,
• 8th a schematic longitudinal section through a piston pump of a fuel delivery device according to a third preferred embodiment,
• 9 a schematic longitudinal section through a piston pump of a fuel delivery device according to a fourth preferred embodiment, and
• 10 a schematic longitudinal section through a piston pump of a fuel delivery device according to a fifth preferred embodiment.

Detailed description of the drawings

The in the 1 represented fuel delivery device according to the invention serves to supply an internal combustion engine (not shown) of a motor vehicle with a cryogenic fuel, which may in particular be natural gas. The cryogenic fuel is in a tank 27 Stored in which a pump 28 is received, by means of which the cryogenic fuel of a piston pump 1 to promote the cryogenic fuel to high pressure can be supplied.

The piston pump 1 to promote the cryogenic fuel to high pressure has a reciprocating pump piston 2 on, one end a compression room 22 limited, in which the fuel is subjected to high pressure. The compression room 22 is over an inlet 23 with integrated inlet valve 24 filled with the cryogenic fuel. The high-pressure cryogenic fuel leaves the compression chamber 22 via an outlet 25 in a check valve 26 is integrated.

The pump piston 2 the piston pump 1 at the other end has a drive piston 3 up in a cylinder bore 4 a housing part 5 is included and inside the cylinder bore 4 a first drive space 6 and a second drive space 7 limited. The second drive room 7 is designed as an annular space, the radially inward of a piston section 18 of the pump piston 2 is limited, the opposite to the drive piston 3 has a reduced outer diameter.

The first drive room 6 and the second drive space 7 are via a directional valve 13 alternately acted upon by a hydraulic pressure medium, while the other drive space 7 . 6 is relieved, so that, depending on the respectively on the drive piston 3 adjacent hydraulic pressure conditions of the pump piston 2 performs a delivery stroke or a suction stroke. To pressurize or discharge a drive space 6 . 7 to effect this is via the directional control valve 13 optionally with a high-pressure line 14 or a low pressure line 15 connectable to the hydraulic pressure medium. The connection is via at least one in the housing part 5 trained inlet channel 9 . 9 ' and at least one in the drive piston 3 trained connection channel 11 . 11 ' produced, which can be brought into overlap depending on the axial position of the pump piston.

As in the illustrated embodiment, both drive spaces 6 . 7 via the directional valve 13 can be acted upon by the hydraulic pressure medium is each drive space 6 . 7 an inlet channel 9 . 9 ' and at least one connecting channel 11 . 11 ' assigned. The inlet channels 9 . 9 ' each lead into one in the housing part 5 trained annular channel 10 . 10 ' , so that a connection of the inlet channel 9 . 9 ' with the associated connection channel 11 . 11 ' each independent of the angular position of the pump piston 2 with respect to the housing part 5 can be produced. The in the drive piston 3 trained connection channels 11 . 11 ' also open in ring grooves 12 . 12 ' , which depends on the axial position of the pump piston 2 in overlap with the ring channels 10 . 10 ' can be brought. In this way, the drive piston forms 3 together with the housing part 5 a first slide valve 8th and a second slide valve 8th' for controlling the inlet of the hydraulic pressure medium in the respective drive space 6 . 7 out. About the slide valves 8th . 8th' In particular, the inlet of the hydraulic pressure medium in the respective drive space 6 . 7 be throttled, for example, to achieve cushioning.

The 2a and 2 B is in each case a representation of the drive side of the piston pump 1 in the conveying operation. The directional valve 13 is located for this purpose in a first switching position, in which the first drive space 6 assigned inlet channel 9 with the high pressure line 14 is connected while the second drive space 7 assigned inlet channel 9 ' via the directional valve 13 with the low pressure line 15 connected is. That means that the first drive space 6 can be acted upon by the hydraulic pressure medium, while the second drive space 7 is relieved. The pump piston 2 moves downwards (see arrow). Depending on the switching position of the two slide valves 8th . 8th' However, the supply of hydraulic pressure medium in the first drive space 6 and / or the flow of hydraulic pressure fluid from the second drive space 7 be throttled.

Again 2a can be seen, is located at the beginning of the delivery stroke of the pump piston 2 in the drive piston 3 trained annular groove 12 at the height of the housing part 5 trained annular channel 10 , so that the inflow of hydraulic pressure fluid into the first drive space 6 unthrottled takes place. That means that the first drive space 6 quickly filled with hydraulic pressure fluid, so that the drive piston 3 including the ring groove 12 move down. This reduces the coverage area of the annular groove 12 with the ring channel 10 , so that the inlet of the hydraulic pressure medium in the first drive space 6 first throttled and finally interrupted (see 2 B) , As a result, the movement of the pump piston 2 is slowed down. The throttled inlet into the first drive space thus leads to a cushioning.

Alternatively or additionally, for end cushioning, the second slide valve 8th' be set so that shortly before reaching the end position of the flow of hydraulic pressure fluid from the second drive space 7 is throttled or prevented, so that in the second drive space 7 a the movement of the drive piston 3 decelerating pressure pad is formed.

To reset the pump piston 2 becomes the directional valve 13 transferred to a second switching position (see 3a and 3b) , so that now the second drive space 7 assigned inlet channel 9 ' with the high pressure line 14 is connected while the first drive space 6 assigned inlet channel 9 with the low pressure line 15 connected is. The second drive room 7 can now be acted upon by the hydraulic pressure medium. At the same time, a relief of the first drive space 6 be effected.

At the beginning of the suction stroke of the pump piston 2 is a far-reaching overlap of the drive piston 3 trained annular groove 12 ' with the in the housing part 5 trained annular channel 10 ' made (see 3a) , so that the second drive space 7 quickly filled with hydraulic pressure medium. This has the consequence that the pump piston 2 moved upwards (see arrow). With increasing stroke, the common overlap area decreases, so that the inlet of the hydraulic pressure medium in the second drive space 7 first throttled and finally interrupted (see 3b) , In this way, the movement of the pump piston 2 braked again and reached a cushioning.

Like that 3a and 3b can be seen, the drive piston 3 at its the first drive room 6 facing the end of a radially outer annular stop edge 19 on, with which the drive piston 3 for installation on the housing part 5 arrives. The stop edge 19 counteracts hydraulic adhesive effects.

As exemplified in the 4 shown, the throttling of the inlet of hydraulic pressure medium in at least one of the two drive spaces 6 . 7 through the geometry of the ring channel 10 . 10 ' and / or the geometry of the annular groove 12 . 12 ' to be influenced. In the 4 has the ring channel 10 a trapezoidal cross-section with sloping channel side walls 20 so that, depending on the axial position of the pump piston 2 between the drive piston 3 and the housing part 5 a throttle gap is formed, which is variable in the axial and radial directions. In this way, an optimal throttle characteristic can be set. The upper groove flank of the annular groove 12 is with a chamfer 21 provided that the immersion of the drive piston 3 in one to the ring channel 10 adjoining area of the cylinder bore 4 should facilitate.

In the 5 is an alternative embodiment of a drive piston 3 shown. In contrast to the drive piston 3 the piston pump the 1 to 4 , points in the 5 illustrated drive piston 3 no ring groove 12 on, which overlap with the annular channel 10 can be brought. That is, the connection channel 11 , which is designed as a radial bore, in overlap with the annular channel 10 must be brought to the inflow of hydraulic pressure medium in the first drive space 6 to enable.

Another preferred embodiment of a piston pump 1 for a fuel delivery device according to the invention is the 6a and 6b and 7a and 7b. For faster relief of the first and the second drive space 6 . 7 are those in the drive piston 3 trained connection channels 11 . 11 ' each with one in the housing part 5 trained additional drainage channel 16 . 16 ' connectable. So through the additional drainage channels 16 . 16 ' the intended for cushioning inlet throttling is not canceled, is in each drain channel 16 . 16 ' a check valve 17 . 17 ' integrated, which only opens in drain direction. The drainage channels 16 . 16 ' are also dependent on the axial position of the pump piston 2 over the slide valves 8th . 8th' can be switched on and off. In the conveying mode of the piston pump 1 This ensures that only the second drive space 7 over the drainage channel 16 ' is additionally relieved, while the drainage channel 16 is switched off (see 6a) , When the drive piston approaches 3 its end position, is in support of the slide valve 8th caused cushioning the drain channel 16 ' switched off (see 6b) , In suction mode of the piston pump 1 it behaves the other way around. Here is the drainage channel at the beginning of the suction stroke 16 over the slide valve 8th switched on, allowing a faster discharge of the first drive space 6 is effected (see 7a) , When the drive piston approaches 3 its end position, is in support of the slide valve 8th' caused cushioning the drain channel 16 switched off (see 7b) ,

Of the 8th is a simplified embodiment of a piston pump 1 for a fuel delivery device according to the invention. The pump piston 2 is again driven purely hydraulically. The pressurization and discharge of the first drive space 6 takes place analogously to the embodiments described above.

The second drive room 7 is via an inlet channel 9 ' , which also serves as a drainage channel, depending on the switching position of the directional control valve 13 pressurized or relieved. The directional valve 13 is designed as a 4/2-way valve. As the drive piston 3 shortened, may be an end face 31 of the drive piston 3 be used as a control edge, so that in the drive piston 3 trained connection channels 11 ' and / or annular grooves 12 ' are dispensable.

A modification of the embodiment of the 8th is in the 9 shown. The drive room 7 is here with a pressure accumulator 29 connected to effect pressurization and / or discharge. Accordingly, the directional control valve 13 be designed as a 3/2-way valve.

Of the 10 In addition, an embodiment of a piston pump for a fuel delivery device according to the invention can be seen, which is driven hydraulically only in the conveying direction, in analogy to the embodiments described above. The return of the pump piston 2 on the other hand is mechanically by means of a spring 30 causes.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2541062 A1 [0003]

Claims (13)

A fuel delivery device for cryogenic fuels, comprising a piston pump (1) for delivering the cryogenic fuel to high pressure, said piston pump (1) having a reciprocating pump piston (2) with a drive piston (3) in a cylinder bore (4) of a Housing part (5) is received and in the cylinder bore (4) defines a drive space (6) which can be acted upon by a hydraulic pressure medium, so that the pump piston (2) is hydraulically driven, characterized in that the drive piston (3) and the Housing part (5) a slide valve (8) forming cooperate and by means of the slide valve (8) the inlet of the hydraulic pressure medium in the drive chamber (6) and / or the flow of the hydraulic pressure medium from the drive chamber (6) in dependence on the axial position of the Pump piston (2) is controllable or are. Fuel delivery after Claim 1 , characterized in that the drive piston (3) the drive space (6) of a further in the cylinder bore (4) formed and acted upon by the hydraulic pressure medium drive space (7) separates. Fuel delivery after Claim 2 , characterized in that the drive piston (3) and the housing part (5) cooperating forming a further slide valve (8 ') and by means of the further slide valve (8') of the inlet of the hydraulic pressure medium in the further drive space (7) and / or the Drain of the hydraulic pressure medium from the other drive space (7) in dependence on the axial position of the pump piston (2) is controllable. Fuel delivery device according to one of the preceding claims, characterized in that in the housing part (5) at least one inlet channel (9, 9 ') is formed for the hydraulic pressure medium, which is aligned substantially radially with respect to the cylinder bore (4) and / or in a cylinder bore (4) widening annular channel (10, 10 ') opens. Fuel delivery after Claim 4 , characterized in that the inlet channel (9, 9 ') and / or the annular channel (10, 10') via at least one in the drive piston (3) formed connecting channel (11, 11 ') connected to a drive space (6, 7) or Depending on the axial position of the pump piston (2) with a drive space (6, 7) is connectable or are. Fuel delivery after Claim 5 , characterized in that the at least one in the drive piston (3) of the pump piston (2) formed connecting channel (11, 11 ') in a circumferential annular groove (12, 12') opens, which depends on the axial position of the pump piston (2) at least in sections overlapping with the inlet channel (9, 9 ') formed in the housing part (5) and / or annular channel (10, 10') can be brought. Fuel delivery device according to one of Claims 4 to 6 , characterized in that the at least one in the housing part (5) formed annular channel (10, 10 ') and / or the at least one in the drive piston (3) formed annular groove (12, 12') has a deviating from a rectangular cross-sectional geometry or have. Fuel delivery device according to one of Claims 4 to 7 , characterized in that the inlet channel (9, 9 ') at least in sections at the same time forms a drainage channel, via which the respective drive space (6, 7) is relieved. Fuel delivery device according to one of Claims 4 to 8th , characterized in that the inlet channel (9, 9 ') via a directional control valve (13), preferably a 3/2-way valve or a 4/2-way valve, alternately with a high pressure line (14) and a low pressure line (15) for the hydraulic pressure medium is connectable. Fuel delivery device according to one of the preceding claims, characterized in that at least one outflow channel (16, 16 ') is formed in the drive piston (3) and / or in the housing part (5), in which preferably a non-return valve (17, 17') opening in the direction of flow is formed. is integrated. Fuel delivery after Claim 10 , characterized in that the flow channel (16, 16 ') via the at least one slide valve (8, 8') switched on and off. Fuel delivery device according to one of Claims 2 to 11 , characterized in that the second drive space (7) is designed as an annular space which is bounded radially inwardly by a piston portion (18) of the pump piston (2) which has a reduced outer diameter relative to the drive piston (3). Fuel delivery device according to one of the preceding claims, characterized in that the drive piston (3) at its end facing the first drive space (6) has a preferably radially outwardly disposed, annular stop edge (19).

Images