GB1580972A - Fuel feed units - Google Patents

Description

(54) IMPROVEMENTS IN FUEL FEED UNITS (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: This invention relates to fuel feed units and in particular to a fuel feed unit of the type in which a rotary fuel pump is driven by an electric motor.

The invention is based on a fuel feed unit of the type wherein an electric motor and a rotary fuel pump are mounted on a common shaft and are inter-connected by a coupling.

In a known fuel feed unit of this type, either the pump rotor is rigidly connected to the motor rotor or they are coupled to each other via a tube which accommodates a bearing common to the pump rotor and the motor rotor. It follows that the starting forces of the motor rotor, which act in an axial direction are transmitted to the pump rotor and press the same axially against the housing wall of the pump. Because of this pressure and the poor lubricating properties of newer fuels, failure of the pump can occur owing to the progressive wear of its rotor on the housing of the pump, especially in the case of dry running.

Furthermore, because the stress exerted radially on the bearings by the pump rotor is substantially greater than that exerted by the motor rotor, the common bearing of the two rotors is subjected to substantially greater wear than the bearing on the other side of the motor rotor. This non-uniform wear of the bearings has the disadvantage that the motor no longer runs coaxially with the shaft with a resultant increase in axial forces and substantial wear of the coupling.

A feature of the present invention is that it is arranged so that no axial forces can be transmitted from the motor rotor to the pump rotor.

According to the present invention there is provided a fuel feed unit comprising a pump and an electric motor each having a rotor journalled for rotation in a common housing about a common non-rotatable shaft and in rotary connection with each other in such a way as to prevent transmission of axial forces from the motor rotor to the pump rotor, the pump rotor being axially fixed in position relative to the housing by parts of the pump fixed to the housing, and fixing means unassociated with the pump rotor being provided for axially fixing the rotor of the electric motor with respect to the housing.

In a preferred embodiment, the fixing device includes a part arranged on the shaft at each end of the motor rotor.

Advantageously, the fixing device comprises at least one snap ring which is received in a corresponding annular groove in the shaft.

The invention will be further described by way of example, with reference to the drawing which is a longitudinal section of a fuel feed unit in accordance with the present invention.

The fuel feed unit comprises a rotary fuel pump 1 and an electric motor 2. Pump and motor are accommodated in a pot-shaped housing 3, which at one end has a suction connector 4 for a fuel line, and which is closed at its other end by a cover 5 on which are arranged a pressure connecting nipple 6 and a non-return valve 7 which serves as a pressure valve. A seal 8 is arranged between housing 3 and cover 5, the latter being fixed to the housing 3 by a flange 9 at the open end of the housing. In the housing 3 are arranged, viewed from the suction side towards the delivery side, first the fuel pump 1 and then the electric motor 2; with this arrangement the fuel pumped under pressure by the pump 1 flows around and past the electric motor 2, thereby serving to cool it.

The pump 1 has a baseplate 11, an intermediate annular plate 13 and a supporting plate 14 arranged coaxially and held together by bolts 16 so as to enclose a pump rotor 17 having a bearing bush 18 which is journalled for rotation about a fixed shaft 12 received in the baseplate 11. The suction or low pressure side of the working chamber of the pump 1 is connected via openings (not shown) to a chamber 19 which is defined by the base of the housing 3 and by the base plate 11. The delivery or high pressure side of the pump 1, on the other hand, is connected to a chamber 20, in the vicinity of the electric motor 2, the chamber 20 communicating with the pressure nozzle 6.

A pressure controlled relief valve 21 is arranged in an opening between the chamber 20 and the chamber 19. The pump communicates with the chambers 19 and 20 by ports (not shown) controlled by the pump rotor, the ports preferably being open passages. The electric motor 2 comprises a motor rotor 23, a commutator 24 and a magnetic stator member 25.

The motor rotor 23 has bearing bushes 27 which are journalled for rotation about the shaft 12, the bearing bushes being arranged in a supporting tube 28 to which are attached the armature core 29, the armature winding 30 and the commutator hub 31 which are assembled by press fitting.

Because these parts are made of extruded plastics material a good rotational and axial contact is ensured between them. A further part of this kind is a bush 32 which is pressed on the end of the supporting tube 28 adiacent the pump. The bush 32 forms part of a rotary coupling and for this purpose has at least one driving pin 33 which extends axially into a corresponding recess 34 in the pump rotor 17 so that the coupling cannot transmit axial forces from the motor rotor 23 to the pump rotor 17.

Commutator brushes 35 slide on the commutator 24 and are arranged in cages 36 which are electrically connected to terminals (not shown) arranged outside the housing 3.

The magnetic stator member 25 of the electric motor 2 comprises a permanent magnet 38 which is arranged in a sheetmetal tube 39 made of a magnetically permeable material.

Annular grooves 41 are provided in the shaft 12 at each end of the motor rotor to receive snap rings 42. A washer 43 is provided between each snap ring 42 and the corresponding bearing bush 27 of the motor rotor. The snap rings 42 thereby act as fixing means by which the motor rotor 23 is fixed in an axial direction relative to the shaft 12 and thereby relative to the housing 3 and so cannot transmit axial forces, in particular during starting, to the pump rotor.

Given that the radial stresses on the bearing bushes 27 are small, and to provide minimum frictional resistance to axial sliding, even in the event of dry running, bearing bushes 27 with the following layered structure, as viewed in the direction towards the shaft are used, a steel back, a copper layer and a porous tin-bronze layer, whose pores are filled with PTFE and lead.

WHAT WE CLAIM IS: 1. A fuel feed unit comprising a pump and an electric motor each having a rotor journalled for rotation in a common housing about a common non-rotatable shaft and in rotary connection with each other in such a way as to prevent transmission of axial forces from the motor rotor to the pump rotor, the pump rotor being axially fixed in position relative to the housing by parts of the pump fixed to the housing, and fixing means unassociated with the pump rotor being provided for axially fixing the rotor of the electric motor with respect to the housing.

2. A fuel feed unit as claimed in claim 1, in which the shaft is axially fixed in the housing and has at least one annular groove into which the fixing means engages.

3. A fuel feed unit as claimed in claim 2, in which the fixing means comprises at least one snap ring which engages the annular groove.

4. A fuel feed unit as claimed in claim 1, 2 or 3, in which a washer is arranged between fixing means and the motor rotor.

5. A fuel feed unit as claimed in any preceding claim, in which the fixing means includes a part arranged at each end of the motor rotor.

6. A fuel feed unit as claimed in any preceding claim, in which the bearings of pump rotor and motor rotor are arranged on the shaft independently of one another.

7. A fuel feed unit as claimed in claim 6, in which the motor rotor has at least two bearing bushes pressed into its centre bore and which have, proceeding radially inwards of the shaft, the following layered structure; a steel base a copper layer and a porous tin-bronze layer whose pores are filled with PTFE and lead.

8. A fuel feed unit as claimed in claim 7, in which the armature and commutator of the electric motor are arranged on a supporting tube into the ends of which the bearing bushes are pressed.

9. A fuel feed unit as claimed in any preceding claim, in which the rotary connection has at least one driving pin extending substantially in an axial direction from a bush carried by one of the rotors, which pin

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

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. the electric motor 2, thereby serving to cool it. The pump 1 has a baseplate 11, an intermediate annular plate 13 and a supporting plate 14 arranged coaxially and held together by bolts 16 so as to enclose a pump rotor 17 having a bearing bush 18 which is journalled for rotation about a fixed shaft 12 received in the baseplate 11. The suction or low pressure side of the working chamber of the pump 1 is connected via openings (not shown) to a chamber 19 which is defined by the base of the housing 3 and by the base plate 11. The delivery or high pressure side of the pump 1, on the other hand, is connected to a chamber 20, in the vicinity of the electric motor 2, the chamber 20 communicating with the pressure nozzle 6. A pressure controlled relief valve 21 is arranged in an opening between the chamber 20 and the chamber 19. The pump communicates with the chambers 19 and 20 by ports (not shown) controlled by the pump rotor, the ports preferably being open passages. The electric motor 2 comprises a motor rotor 23, a commutator 24 and a magnetic stator member 25. The motor rotor 23 has bearing bushes 27 which are journalled for rotation about the shaft 12, the bearing bushes being arranged in a supporting tube 28 to which are attached the armature core 29, the armature winding 30 and the commutator hub 31 which are assembled by press fitting. Because these parts are made of extruded plastics material a good rotational and axial contact is ensured between them. A further part of this kind is a bush 32 which is pressed on the end of the supporting tube 28 adiacent the pump. The bush 32 forms part of a rotary coupling and for this purpose has at least one driving pin 33 which extends axially into a corresponding recess 34 in the pump rotor 17 so that the coupling cannot transmit axial forces from the motor rotor 23 to the pump rotor 17. Commutator brushes 35 slide on the commutator 24 and are arranged in cages 36 which are electrically connected to terminals (not shown) arranged outside the housing 3. The magnetic stator member 25 of the electric motor 2 comprises a permanent magnet 38 which is arranged in a sheetmetal tube 39 made of a magnetically permeable material. Annular grooves 41 are provided in the shaft 12 at each end of the motor rotor to receive snap rings 42. A washer 43 is provided between each snap ring 42 and the corresponding bearing bush 27 of the motor rotor. The snap rings 42 thereby act as fixing means by which the motor rotor 23 is fixed in an axial direction relative to the shaft 12 and thereby relative to the housing 3 and so cannot transmit axial forces, in particular during starting, to the pump rotor. Given that the radial stresses on the bearing bushes 27 are small, and to provide minimum frictional resistance to axial sliding, even in the event of dry running, bearing bushes 27 with the following layered structure, as viewed in the direction towards the shaft are used, a steel back, a copper layer and a porous tin-bronze layer, whose pores are filled with PTFE and lead. WHAT WE CLAIM IS:

1. A fuel feed unit comprising a pump and an electric motor each having a rotor journalled for rotation in a common housing about a common non-rotatable shaft and in rotary connection with each other in such a way as to prevent transmission of axial forces from the motor rotor to the pump rotor, the pump rotor being axially fixed in position relative to the housing by parts of the pump fixed to the housing, and fixing means unassociated with the pump rotor being provided for axially fixing the rotor of the electric motor with respect to the housing.

2. A fuel feed unit as claimed in claim 1, in which the shaft is axially fixed in the housing and has at least one annular groove into which the fixing means engages.

3. A fuel feed unit as claimed in claim 2, in which the fixing means comprises at least one snap ring which engages the annular groove.

4. A fuel feed unit as claimed in claim 1, 2 or 3, in which a washer is arranged between fixing means and the motor rotor.

5. A fuel feed unit as claimed in any preceding claim, in which the fixing means includes a part arranged at each end of the motor rotor.

6. A fuel feed unit as claimed in any preceding claim, in which the bearings of pump rotor and motor rotor are arranged on the shaft independently of one another.

7. A fuel feed unit as claimed in claim 6, in which the motor rotor has at least two bearing bushes pressed into its centre bore and which have, proceeding radially inwards of the shaft, the following layered structure; a steel base a copper layer and a porous tin-bronze layer whose pores are filled with PTFE and lead.

8. A fuel feed unit as claimed in claim 7, in which the armature and commutator of the electric motor are arranged on a supporting tube into the ends of which the bearing bushes are pressed.

9. A fuel feed unit as claimed in any preceding claim, in which the rotary connection has at least one driving pin extending substantially in an axial direction from a bush carried by one of the rotors, which pin

slidingly engages with play in one or more corresponding recesses formed in the other rotor.

10. A fuel feed unit constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.