GB1595540A

GB1595540A - Fuel feed pump assembly

Info

Publication number: GB1595540A
Application number: GB2033278A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1977-08-09
Filing date: 1978-05-18
Publication date: 1981-08-12
Also published as: DE2735759C2; DE2735759A1

Description

(54) FUEL FEED PUMP ASSEMBLY (71) We, ROBERT BOSCH GMBH, a German company of Postfach 50, 7 Stuttgart 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a fuel feed pump assembly for an internal combustion engine, and more particularly to one in which a two-stage pump system is serially connected to an electric driving motor.

Preferably, both pump stages of the twostage pump system are arranged on one side of the electric driving motor remote from the commutator.

In order to facilitate radial and axial adjustment of the elements of a pump relative to one another and to the other components of the overall arrangement, a known pump has a hollow-shafted armature in the driving motor. This permits the necessary adjustments to be effected more easily owing to the fact that the hollow armature shaft is rotatably supported on a stationary axle. This form of armature is disadvantageous and relatively complicated, however. In particular, in the known form of construction incorporating a hollowshafted armature, the problem arises in a two-stage embodiment of the pump of driving both stages from the armature and at the same time effecting accurate axial and radial adjustment of the system. This is of material importance when using either a rotary positive displacement pump or a side-channel pump as the elements of the pump system.

In accordance with this invention there is provided a fuel feed pump assembly for an internal combustion engine, the assembly having a housing in which are contained two pump stages and an electric drive motor whose shaft is journalled in bearings, the assembly also having an intermediate baseplate between the pump stages, a hollow axle press-fitted in the baseplate and extending beyond the baseplate at at least one side thereof to rotatably support the rotor of the pump stage at that side, and an auxiliary shaft extending through the hollow axle, the motor shaft being rotatably coupled to one end of the auxiliary shaft and to the rotor of the adjoining pump stage and the rotor of the other pump stage at the side of the baseplate remote from the motor being rotatably driven by the auxiliary shaft.

In contrast with the known construction an advantage of a fuel feed pump in accordance with this invention is that, owing to the hollow axle, the adjustment of play, in particular adjustment of the axial clearance between the intermediate baseplate and the rotor of the pump stage adjoining the motor may be effected easily and with great accuracy. Precise axial positioning of the rotor of the pump stage on the remote side of the baseplate is effected in a corresponding manner, the rotor concerned in the case of the preferred embodiment of the invention being the rotor of a side-channel pump.

Such a construction enables the armature of the respective electric motor to be mounted on a solid shaft rotating in suitable bearings, so that, notwithstanding substantial improvements, such a fuel feed pump assembly is relatively inexpensive to manufacture. The present invention combines the advantages with regard to play adjustment and close tolerances, due to the use of a stationary hollow axle, with the advantages provided by the solid rotary shaft with regard to support of the armature.

Owing to the deteriorating quality of fuel, faults in the operation of a roller-cell pump may occur to an increasing degree when feeding petrol at high temperatures. This may be prevented by feeding the fuel at a pressure slightly above atmospheric pressure. In this way failure of the pump because of a substantial increase in vapour formation may be eliminated. Generation of the primary pressure may be effected by means of a hydrodynamic pump having a venting arrangement, which may be either connected upstream as a separate electrical fuel pump or be integrated as a primary stage in the region of the roller-cell pump.

In addition to generation of the primary pressure by means of a first stage built into the housing adjacent a second stage, the present invention enables the cost advantages of a motor shaft supported in cap-type bearings to be combined with the advantages with regard to assembly and operation due to mounting the pump on a stationary axle. The transmission of the driving torque from the motor rotor is effected simultaneously to both stages of the pump.

Furthermore, suitable sealing can be provided between the different pump stages with their different levels of pressure, a suitable small amount of axial play being provided especially for when the pump is started up.

In a preferred embodiment of this invention a particular advantage may be gained if a driving element drivingly engages in an end bore in the motor shaft and engages, via a dog-type extension, in a corresponding recess in the pump rotor of the adjoining pump stage. The driving element is preferably made from a plastics material and may be either injection moulded onto the auxiliary shaft or merely be provided with a flat in a bore for an angularly rigid entrainment of the auxiliary shaft.

This form of construction solves the problem of the coupling of the primary-stage pump rotor through the baseplate, and associated sealing problems. Owing to the auxiliary shaft, which. in a first embodiment, alone supports the rotor of the primary-stage pump (the auxiliary shaft being supported inside the hollow axle) an excellent seal is effected between the separate stages of the pump system; accurate axial adjustment of the rotor of the first stage pump may be effected by means of locking rings and spacing collars which act upon the auxiliary shaft.

The invention is further described hereinafter, by way of example only, with reference to the accompanying drawings. in which: Figure I is a longitudinal section of a first embodiment of a fuel feed pump assembly according to this invention; and Figure 2 is a partial section of the relevant region of a second embodiment of this invention.

The fuel feed pump assembly shown in Figure 1 comprises a fuel pump region 1 and an electric motor 2. Since the region comprising the electric motor 2 is the same in both of the illustrated embodiments, the electric motor is not shown in Figure 2.

The region 1 of the fuel feed pump, and the electric motor 2, are accommodated in a cup-shaped housing 3, which, at its end adjacent to the pump, is provided with a suction connection 4 for connection of a fuel hose (not shown), and which at its opposite end is sealed by a cover 5, on which a pressure-connecting nipple 6 and a nonreturn valve 7 are arranged. A seal 8 is arranged between the housing 3 and the cover 5; the cover 5 is attached to the housing 3 by means of a flange 9 on the open end of the housing 3.

In the housing 3, when viewed from the suction side in a direction towards the compression side, are, first, the pump region 1 and then the electric motor 2, the pressurised fuel delivered by the pump also flowing through the electric motor 2 in order to cool it.

The pump region 1 contains two pump stages which are driven by a motor shaft 11, which is supported in bearings such as so-called cap-type bearings 10a and 10b.

The shaft 11 is a solid shaft, in order to provide an inexpensive form of construction of the electric-motor region, and carries an armature or motor rotor 12, which is fixedly attached to the shaft. Current is supplied to the windings of the motor rotor 12 via a commutator 13 on the shaft 11, upon which commutator brushes, mounted in cages 14, slide. The commutator brushes are connected to terminals (not shown) arranged externally of the housing 3. To complete the electric motor 2, a magnetic element 15, comprising permanent magnets 16, is arranged in a sheet-metal tube 17 which is manufactured from magnetically permeable material. The components of the pump system are clamped by the cover 5 in the housing 3 via the sheet-metal cylinder or tube 17, which serves as a general retaining member; this feature is discussed further hereinafter.

The cap-bearings 10a and 10b for the shaft 11 are supported axially and radially, namely, in the case of the cap bearing lOb, at the end remote from the pump region 1 by the cover 5 itself, while at the other end support is provided by a stationary supporting or retaining plate 18, which, as shown, is shaped in the form of a cone 19 to receive the cap bearing 10b. This supporting plate 18, owing to its being supported against a shoulder 20 on the sheet-metal retaining tube 17, at the same time provides a means for rigidly clamping and securely supporting the components forming the pump region.

In particular, the pump system 1 comprises a first-primary-stage pump 25, which acts directly upon the suction connection 4, and a second stage pump 26 serially connected to the primary-stage pump. In a preferred embodiment of the invention, the primarystage pump 25 is a side-channel pump (which, for example, builds up a pressure of about 0.3 bar in the region between the two pumps) while the second pump stage 26 is a rotary positive displacement pump (which provides a final fuel pressure of, for example, about 6 bar). This latter pressure prevails in the pressure chamber 27. However, the two serially-connected pumps forming the two pump stages may be of any desired type, the only essential provision being that each pump shall have a driven member, whose rotary motion is provided by the shaft 11 of the electric motor 2.Thus, in so far as this is possible within the general technical framework, the two pump stages may be any form of hydraulic pump, such as gear pumps, side-channel pumps, roller-cell pumps etc. Moreover, both stages may comprise the same type of pump.

In the following description of the preferred embodiment of the invention it is assumed that the first pump stage 25 is a side-channel pump having a rotor 28, while the second pump stage 26 is a roller-cell pump having a pump rotor in the form of a slotted disc 29. The primary-stage pump 25 is provided with a stationary baseplate 30, which is retained in the housing 3 via an intermediate seal 31 and associated conical surfaces 32, 33 on the baseplate 30 and the base of the housing respectively, and which co-operates with the rotor 28 of the primarystage pump. The specific construction and method of operation of the individual pumps are, however, discussed hereinafter only in so far as is necessary in order to understand the invention, since these pumps are basically known and do not require detailed explanation.On its other side the baseplate 30 also forms the retaining-plate region or baseplate region for the adjacent second stage pump 26, so that the baseplate lies between the pump stages. The second stage pump 26, when viewed in axial sequence starting from the baseplate 30, comprises an intermediate plate 35 and also the already mentioned supporting plate 18. The baseplate 30, the intermediate plate 35 and the supporting plate 18 are clamped together by means of screws 36, and include between them the pump rotor or slotted disc 29 of the roller-cell pump. At least one duct-like connection 37 is provided in the baseplate 30 between the compression side of the first stage pump 25 and the suction side of the adjacent second stage pump 26.

A stationary hollow axle 39, inside which there is journalled an auxiliary shaft 41, for example, by means of bearings 40, is pressfitted in a central bore 38 in the baseplate 30 and forms a drive connection between the output end of the shaft 11 of the electric motor 2 and the rotor 28 of the side-channel pump 25.

In a particularly advantageous and simple manner the hollow axle 39, press-fitted in the baseplate 30, permits radial and axial adjustment of play in the individual components of the pump. For this purpose, the slotted disc 29 of the roller-cell pump is supported via a bearing 43 on a reduceddiameter portion 42 of the hollow axle 39 extending beyond the baseplate 30. Since the rotor 29 of the roller-cell pump is supported on a stationary axle, tolerances can be closer than would otherwise be the case in order to provide for the necessary running clearances.

In the embodiment shown in Figure 1, the rotor 28 of the side-channel pump is arranged and supported on an end 45 of the shaft 41 which extends outwardly of the hollow axle 39; the axial adjustment of play is effected by means of shims 46a, 46b between the rotor 28 and the hollow axle 39 at one end, and between a locking ring 48, which engages with a groove 47 in the auxiliary shaft 41, and the hollow axle 39 at the other end.

A driving element 50 is provided for transmitting rotation of the motor shaft 11 to the slotted disc 29 and, via the auxiliary shaft 41, to the rotor 28. This driving element 50 is positively connected on the one hand to the shaft 11 of the electric motor 2, and, on the other hand, forms part of a coupling, by means of which the slotted disc 29 and also the end 51 of the auxiliary shaft 41 extending beyond the groove 47 are rotatably engaged.

In the preferred embodiment of the invention, the driving element 50 comprises a member made from a plastics material, which engages in a bore 52 in the end of the rotor shaft 11 and in which there is a groove (not shown), so as to provide a positive fit about the auxiliary shaft end 51. On the other hand, in order to support the end 51 of the auxiliary shaft 41 with zero angular movement in the plastics material of the driving element 50, the shaft end 51 may be provided with a flat portion 53. A driving dog 54, originating from the region of the main body of the driving element 50, engages in a corresponding recess 55 in the slotted disc 29.

It can be seen that, although at least one rotatable pump member is mounted on the stationary hollow axle 39 for better sealing purposes, and so that adjustment of play may be more easily and accurately effected the motor rotor itself is mounted on a rotating shaft 11. Such an arrangement can be manufactured more easily.

In the embodiment of Figure 1 the auxili ary shaft 41 is simply rotatably connected to the driving element 50 at its end 51, while at its end 45, the shaft 41 positively retains, supports and transmits drive to the rotor 28.

However, the special connection of the auxiliary shaft 41' to the driving element 50' is the opposite of this in the embodiment shown in Figure 2. In this embodiment, the auxiliary shaft 41' is carried by the driving element 50', but it extends further into the driving element 50' and is preferably attached to the latter by injection-moulding of the driving element onto the auxiliary shaft 41'. As distinct from the embodiment of Figure 1, in the embodiment of Figure 2 the auxiliary shaft 41' is not supported by means of bearings inside the hollow axle 39', but extends freely through it and serves in this embodiment purely for the transmission of torque from the shaft 11 of the electric motor, to the rotor 28' of the primary-stage pump.Also in this embodiment, the primary-stage pump comprises a side-channel pump; however, the construction of the rotor 28' differs in so far as it is operatively connected to an additional plate 60 in front of the rotor 28', which additional plate 60 is stationary in the housing 3'. The rotor 28' is supported, for example by means of two bearings 62, on an end 61 of the hollow axle 39' extending from the baseplate 30 in a direction towards the front end. For this purpose, the rotor 28' is provided with a central cup-shaped enlargement or hub 63 in the form of a hollow cylinder sealed at its base. As indicated by the numeral 64, this cup-shaped hub 63 extends beyond the axle end 61 and has a base 65.

Since the additional plate 60, supported via a chamfered annular flange 66 against an inwardly extending annular, chamfered flange 67 on the housing 3', is provided on the suction side in this embodiment, the outer housing cover is here unnecessary.

Accordingly, as indicated by the numeral 68, the housing is open; into this open region, starting from the additional plate 60, there extend the off-centre suction connection 4', which is integrally formed on the additional plate 60, and a central hollow boss 69 on the additional plate, whose shape is complementary to the hub 63, 64, 65 on the rotor 28' and which retains the latter in a predetermined axially adjusted position in order to achieve correspondingly close clearances due to the provision of one or more shims 71 between the base 65 of the hub 63 and the interior 70 of the base of the hollow boss 69 on the additional plate 60.

Radial location and support are effected by means of the bearings 62 at the end 61 of the hollow axle 39'.

For axial support and retention of the adjusted working clearance with respect to the pump region formed by the additional plate 60, there is provided a spring 72, one of whose ends abuts the inside of the base of the hub 63, 64, 65 and whose other end abuts a shoulder 74 on the auxiliary shaft 41', which, as already mentioned above, is supported and retained axially and radially at its other end by the driving element 50' attached to it, or a washer 73 resting against the shoulder 74. The driving element is itself correspondingly axially and radially supported via the motor shaft 11 and in the cap bearing 10a abutting the supporting plate 18'.Therefore, connection of the end 45' of the auxiliary shaft 41' to the hub 63 of the rotor 28' is advantageously not rigid nor positive, as is the case in the embodiment of Figure 1 in which the shaft end 45 effectively retains and supports the rotor 28. In this second embodiment the connection is only rotationally rigid so that axial adjustment of the rotor 28' is not dependent upon the necessarily more widely toleranced position and mobility of the cap bearings 10a, 10b of the motor shaft 11. Moreover, in order to prevent radial displacement, support is provided by the hollow axle 39'. In this embodiment of Figure 2 also, the hollow axle 39' is press-fitted at 75 in the central bore of the baseplate 30'.The baseplate 30', the intermediate plate 35' and the supporting plate 18' are again clamped together by means of screws 36; one or more further screws 76 clamp the baseplate 30' to the intermediate plate 35'. The outer additional plate 60 is retained via an intervening seal 77 by means of a projecting rim 78 on the baseplate 30', which rim 78 engages with a shoulder 79 on the additional plate 60. A further seal 80 is provided in the gap between the intermediate plate 35' and the supporting plate 18', which is itself retained by the tubular supporting plate 17 pertaining to the magnetic region of the electric motor 2. ln this embodiment also, the slotted disc 29 of the roller-cell pump is supported on a projecting end of the hollow axle 39'.

Axial displacement of the shaft 11 of the electric motor 2, which shaft is supported in cap bearings 10a and lob, is prevented by locking arrangements 85a, 85b which engage in annular grooves at both ends of the shaft 11, the locking ring arrangements 85a, 85b being supported against stationary projections 84 on the supporting plate 18, 18' of the pump system or on corresponding projections on the cover 5, and at the same time also preventing axial displacement of the cap bearings.

WHAT WE CLAIM IS: 1. A fuel feed pump assembly for an internal combustion engine, the assembly having a housing in which are contained two pump stages and an electric drive motor whose shaft is journalled in bearings, the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. ary shaft 41 is simply rotatably connected to the driving element 50 at its end 51, while at its end 45, the shaft 41 positively retains, supports and transmits drive to the rotor 28. However, the special connection of the auxiliary shaft 41' to the driving element 50' is the opposite of this in the embodiment shown in Figure 2. In this embodiment, the auxiliary shaft 41' is carried by the driving element 50', but it extends further into the driving element 50' and is preferably attached to the latter by injection-moulding of the driving element onto the auxiliary shaft 41'. As distinct from the embodiment of Figure 1, in the embodiment of Figure 2 the auxiliary shaft 41' is not supported by means of bearings inside the hollow axle 39', but extends freely through it and serves in this embodiment purely for the transmission of torque from the shaft 11 of the electric motor, to the rotor 28' of the primary-stage pump.Also in this embodiment, the primary-stage pump comprises a side-channel pump; however, the construction of the rotor 28' differs in so far as it is operatively connected to an additional plate 60 in front of the rotor 28', which additional plate 60 is stationary in the housing 3'. The rotor 28' is supported, for example by means of two bearings 62, on an end 61 of the hollow axle 39' extending from the baseplate 30 in a direction towards the front end. For this purpose, the rotor 28' is provided with a central cup-shaped enlargement or hub 63 in the form of a hollow cylinder sealed at its base. As indicated by the numeral 64, this cup-shaped hub 63 extends beyond the axle end 61 and has a base 65. Since the additional plate 60, supported via a chamfered annular flange 66 against an inwardly extending annular, chamfered flange 67 on the housing 3', is provided on the suction side in this embodiment, the outer housing cover is here unnecessary. Accordingly, as indicated by the numeral 68, the housing is open; into this open region, starting from the additional plate 60, there extend the off-centre suction connection 4', which is integrally formed on the additional plate 60, and a central hollow boss 69 on the additional plate, whose shape is complementary to the hub 63, 64, 65 on the rotor 28' and which retains the latter in a predetermined axially adjusted position in order to achieve correspondingly close clearances due to the provision of one or more shims 71 between the base 65 of the hub 63 and the interior 70 of the base of the hollow boss 69 on the additional plate 60. Radial location and support are effected by means of the bearings 62 at the end 61 of the hollow axle 39'. For axial support and retention of the adjusted working clearance with respect to the pump region formed by the additional plate 60, there is provided a spring 72, one of whose ends abuts the inside of the base of the hub 63, 64, 65 and whose other end abuts a shoulder 74 on the auxiliary shaft 41', which, as already mentioned above, is supported and retained axially and radially at its other end by the driving element 50' attached to it, or a washer 73 resting against the shoulder 74. The driving element is itself correspondingly axially and radially supported via the motor shaft 11 and in the cap bearing 10a abutting the supporting plate 18'.Therefore, connection of the end 45' of the auxiliary shaft 41' to the hub 63 of the rotor 28' is advantageously not rigid nor positive, as is the case in the embodiment of Figure 1 in which the shaft end 45 effectively retains and supports the rotor 28. In this second embodiment the connection is only rotationally rigid so that axial adjustment of the rotor 28' is not dependent upon the necessarily more widely toleranced position and mobility of the cap bearings 10a, 10b of the motor shaft 11. Moreover, in order to prevent radial displacement, support is provided by the hollow axle 39'. In this embodiment of Figure 2 also, the hollow axle 39' is press-fitted at 75 in the central bore of the baseplate 30'.The baseplate 30', the intermediate plate 35' and the supporting plate 18' are again clamped together by means of screws 36; one or more further screws 76 clamp the baseplate 30' to the intermediate plate 35'. The outer additional plate 60 is retained via an intervening seal 77 by means of a projecting rim 78 on the baseplate 30', which rim 78 engages with a shoulder 79 on the additional plate 60. A further seal 80 is provided in the gap between the intermediate plate 35' and the supporting plate 18', which is itself retained by the tubular supporting plate 17 pertaining to the magnetic region of the electric motor 2. ln this embodiment also, the slotted disc 29 of the roller-cell pump is supported on a projecting end of the hollow axle 39'. Axial displacement of the shaft 11 of the electric motor 2, which shaft is supported in cap bearings 10a and lob, is prevented by locking arrangements 85a, 85b which engage in annular grooves at both ends of the shaft 11, the locking ring arrangements 85a, 85b being supported against stationary projections 84 on the supporting plate 18, 18' of the pump system or on corresponding projections on the cover 5, and at the same time also preventing axial displacement of the cap bearings. WHAT WE CLAIM IS:

1. A fuel feed pump assembly for an internal combustion engine, the assembly having a housing in which are contained two pump stages and an electric drive motor whose shaft is journalled in bearings, the

assembly also having an intermediate baseplate between the pump stages, a hollow axle press-fitted in the baseplate and extending beyond the baseplate at at least one side thereof to rotatably support the rotor of the pump stage at that side, and an auxiliary shaft extending through the hollow axle, the motor shaft being rotatably coupled to one end of the auxiliary shaft and to the rotor of the adjoining pump stage and the rotor of the other pump stage at the side of the baseplate remote from the motor being rotatably driven by the auxiliary shaft.

2. A fuel feed pump assembly as claimed in claim 1, in which the auxiliary shaft is journalled in bearings in the hollow axle.

3. A fuel feed pump assembly as claimed in claim 2, in which the rotor of the pump stage at the side of the baseplate remote from the motor is mounted on and supported by the auxiliary shaft and the motor shaft is non-relatively rotatably but axially displaceably coupled to the auxiliary shaft.

4. A fuel feed pump assembly as claimed in claim 1, 2 or 3, in which the intermediate baseplate co-operates with the rotor of the pump stage at the side remote from the motor and forms a part of that pump stage.

5. A fuel feed pump assembly as claimed in claim 4, in which the housing comprising a cup-shaped housing member whose closed end encloses the remote pump stage and has a fluid connection to that pump stage.

6. A fuel feed pump assembly as claimed in claim 5, in which the fluid connector extends co-axially with the shafts.

7. A fuel feed pump assembly as claimed in claim 1, in which the rotor of the pump stage at the side of the intermediate baseplate remote from the motor is rotatably supported on a portion of the hollow axle extending from the baseplate and the intermediate shaft is so coupled to such rotor and to the motor shaft as to allow relative axial displacement therebetween.

8. A fuel feed pump assembly as claimed in any preceding claim, in which the motor shaft is coupled to the adjoining pump stage rotor and to the auxiliary shaft by means of a driving element which is secured, at least non-relatively rotatably to the end of the motor shaft and which is in engagement with both the adjoining pump stage rotor and the adjoining end of the auxiliary shaft.

9. A fuel feed pump assembly as claimed in claim 8, in which the driving element is formed from a plastics material.

10. A fuel feed pump assembly as claimed in claim 8 or 9, in which the driving element is received in a grooved end bore in the motor shaft.

11. A fuel feed pump assembly as claimed in claim 8, 9 or 10, in which the driving element has an off-centre dog which non-relatively rotatably but relatively axially displaceably engages the rotor of the adjoining pump stage.

12. A fuel feed pump assembly as claimed in any one of claims 8 to 11, when appendant to claim 7, in which the auxiliary shaft is fixed to and supported at one end by the driving element.

13. A fuel feed pump assembly as claimed in claim 7 or 12 in which the auxiliary shaft is non-relatively rotatably but axially displaceably supported at its other end by the rotor of the remote pump stage.

14. A fuel feed pump assembly as claimed in claim 7, 12 or 13, in which the rotor of the remote stage pump has a closed cup-shaped hub by which it is journalled via bearings on the corresponding extended end of the hollow axle.

15. A fuel feed pump assembly as claimed in claim 1,7,12,13 or 14, in which an additional baseplate co-operating with the rotor of said remote pump stage to form part of the latter and has an off-centre fluid connector to that pump stage.

16. A fuel feed pump assembly as claimed in claim 15, when appendant to claim 14, in which the closed hub is axially located against the inside of a hollow central boss formed on the additional baseplate.

17. A fuel feed pump assembly as claimed in claim 16, in which a coil spring is disposed about the auxiliary shaft and acts between the latter and the cup-shaped hub to press the latter into axial location against the hollow central boss.

18. A fuel feed pump assembly as claimed in any preceding claim, in which the rotor of the pump stage adjoining the motor is rotatably supported on an extended portion of the hollow axle.

19. A fuel feed pump assembly as claimed in any preceding claim. in which the intermediate baseplate co-operates with the rotor of the pump stage adjoining the motor to form part of that pump stage.

20. A fuel feed pump assembly as claimed in any preceding claim, in which the end of the motor shaft facing the pump stages is journalled in a supporting plate located between the motor and the adjoining pump stage.

21. A fuel feed pump assembly as claimed in claim 20, when appendant to claim 19, in which the supporting plate and the intermediate baseplate are secured to one another by screws to form a pump unit.

22. A fuel feed pump assembly as claimed in claim 20 or 21, in which said facing end of the motor shaft is journalled in a bearing supported by projections on the supporting plate.

23. A fuel feed pump assembly as claimed in any preceding claim in which the end of the motor shaft remote from the pump stages is journalled in a bearing supported by an end plate closing the housing and having a connecting nipple which communicates via the motor interior with the adjoining pump stage.

24. A fuel feed pump assembly as claimed in any preceding claim in which the pump stage at the side of the intermediate baseplate remote from the motor is the first or primary pump stage.

25. A fuel feed pump assembly as claimed in any preceding claim, in which the first or primary pump stage is a side channel pump.

26. A fuel feed pump assembly as claimed in any preceding claim, in which the second pump stage is a rotary positive displacement pump.

27. A fuel feed pump assembly as claimed in claim 26, in which the second pump stage is a roller-cell pump.

28. A fuel feed pump assembly, constructed and adapted to operate substantially as herein described with reference to and as illustrated in Figure 1 of the accompanying drawings.

29. A fuel feed pump assembly constructed and adapted to operate substantially as herein described with reference to and as illustrated in Figure 2 of the accompanying drawings.