GB2131630A

GB2131630A - Permanent-magnet energized generator for vehicles

Info

Publication number: GB2131630A
Application number: GB08332642A
Authority: GB
Inventors: Peter Ahner; Gunther Bergan; Helmut Harer; Siegfried Schustek
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1982-12-08
Filing date: 1983-12-07
Publication date: 1984-06-20
Also published as: DE3245400A1; JPS59113754A; GB8332642D0; GB2131630B; FR2537799A1

Abstract

An electrical generator for vehicles, having a permanent-magnetic rotor whose magnets (1) are in the form of thin prismatic plates which are aligned substantially radially in the rotor.The permanent magnets (1) and the flux conducting pieces (2) are held together by paramagnetic die-cast material (4) with saw-tooth boundary surfaces. <IMAGE>

Description

SPECIFICATION Permanelt-magnet energized generator for vehicles The invention relates to an electric generator, intended for vehicles.

Flywheel magnetosfor motor cycles and small motor vehicles are already known in which the rotor, in the form ofaflywheel, includes at leasttwo, preferablyfouror more, permanent magnets which are polarized in a circumferential direction, such that like poles of two respective magnets following one another in a circumferential direction abut against one of a plurality of soft iron pole shoes which are each disposed between two respective permanent magnets and which are intended to conduct the magnetic flux in a radial direction to fixed armatures provided with windings.

Generators which do not have slip-rings and which therefore require little maintenance, can be inexpenxively manufactured in a known mannerwith permanent-magnet excitation. An object ofthe invention is to provide a permanent-magnet excited generator which operates with small losses even during part load operation.

The invention resides in an electric generator for vehicles, having a multi-pole rotorwhich rotates in the stator bore of a stack ofstator laminations carrying a plurality of alternating current windings and which includes at least two permanent magnets which are polarized tangentially in the circumferential direction ofthe rotorandwhose polefaces abut againstflux conducting pieces from which magnetic lines offlux emerge radially and enterthestackofstator laminations, wherein the permanent magnets are in the form of thin prismatic plates whose broad pole faces are aligned radially or nearly radially.

A particularly inexpensive construction ensues if the permanent magnets are ferrite magnets.

In a further developmet of the invention, very high centrifugal speeds can be obtained in the case of an internal rotor, having permanent magnets, ifthe radially directed planes of symmetry lying in the axis ofthe rotor between two respective laminated flux conducting pieces have cutaway portions provided with saw-toothed-shaped boundary surfaces and which are filled with a paramagnetic cast or pressed materialwhich unitesthe rotorandatthesametime can form the hub ofthe rotor drawn onto the central drive shaft.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axial half-section through the rotor of a permanent-magnet-excited electric generatorfor a motorvehicle, in accordance with the invention, and Figure 2 is a cross section through the rotortaken at right angles to the rotor axis.

The drawings show a rotorofan electric generator, such as a motor vehicle generator, comprising perma- nent magnets 1 which are of thin prismatic shape and whose broad pole faces are plane parallel. The magnets 1 are interposed between laminated flux concentrators 2, acting as a magnetic flux conducting piece, and are positively and firm ly connected to one another and to the rotor shaft 6 by die-cast parts 3,4,5 and 11. The flux conducting pieces 2 have cut-away portions whose boundary surfaces are saw-tooth shaped.The rotor is heldtogetherbythefirtree shaped roots 4 made from paramagnetic die-cast material, bythe closure member3 in the pole gaps and by the annular end caps 11 having integrally cast fan vanes 10.

In a permanent-magnet rotor as described above, with a magnet of adequate thickness, a maximum flux-producing surface area of the magnet is enabled by the position of the magnets on a radius or at an acute angle to the radius. This is particularly important when using the very expensive ferrite magnetic materials having a remnance of 0.4 to 0.44T. The surface area in the air gap ofthe generator is normally adequate for "rare earth" magnets having 0.8 to 1.2 T.

However, in this arrangement, considerable problems with respect two securing the magnets arise in the case of high-speed electric generators.

T is the S.l. unit for induction B. (The old unit was Gauss).

Vs 1T=1OKG=- m Br = 0.4-. 0.44T is an excellentvalueforferrite.

Bands ofglassfibre reinforced plastics material or anti-magnetic steel cylinders are normally used for fixing the parts. In both cases, the air gap is enlarged with a resultant reduction in the flux, despite high manufacturing costs.

The illustrated rotor construction does not have these disadvantages. The laminated flux concentra- tors 2, which can be manufactured in a simple manner as parts stamped from sheet-metal, extend up tithe air gap between the cylindrical circumference ofthe rotor and the bore ofthe stator (not shown) which comprises a stack of stator laminations. If required, the flux concentrators 2 can befinish-turned or finish-g round after die-casting aboutwith aluminium.

The magnetic lines of flux thus emerge radiallyfrom the flux concentrators 2 and enterthe stack of stator laminations.

The flux concentrators as well as the magnets are held by virtue ofthe construction of the fir tree roots 4 and by the intergrally cast caps 11 contiguous to both sides ofthe stack of laminations. The closure members 3, which are also integrally cast, prevent the mechanicallyveryhard magnets from breaking apart even in the event of concealed cracks, thus preventing destruction ofthe entire generator. Advantageously, the vanes 10 for radial fans can be integrally cast on the caps 11 at the same time. The waveform of the electric voltage produced by the generator can be advantageously influenced by suitable construction of the contours ofthe air gaps of the stamped, readily manufacturable flux concentrators. The rotor body is secured to the shaft by means of a milled portion 7 on the shaft 6 and by peened-over portions 9, whereby die-cast material is displaced into the recesses 8 in the shaft 6.

1. An electricgeneratorforvehicles, having a multi-pole rotor which rotates inthe stator bore of a stack of stator laminations carrying a plurality of

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Permanelt-magnet energized generator for vehicles The invention relates to an electric generator, intended for vehicles. Flywheel magnetosfor motor cycles and small motor vehicles are already known in which the rotor, in the form ofaflywheel, includes at leasttwo, preferablyfouror more, permanent magnets which are polarized in a circumferential direction, such that like poles of two respective magnets following one another in a circumferential direction abut against one of a plurality of soft iron pole shoes which are each disposed between two respective permanent magnets and which are intended to conduct the magnetic flux in a radial direction to fixed armatures provided with windings. Generators which do not have slip-rings and which therefore require little maintenance, can be inexpenxively manufactured in a known mannerwith permanent-magnet excitation. An object ofthe invention is to provide a permanent-magnet excited generator which operates with small losses even during part load operation. The invention resides in an electric generator for vehicles, having a multi-pole rotorwhich rotates in the stator bore of a stack ofstator laminations carrying a plurality of alternating current windings and which includes at least two permanent magnets which are polarized tangentially in the circumferential direction ofthe rotorandwhose polefaces abut againstflux conducting pieces from which magnetic lines offlux emerge radially and enterthestackofstator laminations, wherein the permanent magnets are in the form of thin prismatic plates whose broad pole faces are aligned radially or nearly radially. A particularly inexpensive construction ensues if the permanent magnets are ferrite magnets. In a further developmet of the invention, very high centrifugal speeds can be obtained in the case of an internal rotor, having permanent magnets, ifthe radially directed planes of symmetry lying in the axis ofthe rotor between two respective laminated flux conducting pieces have cutaway portions provided with saw-toothed-shaped boundary surfaces and which are filled with a paramagnetic cast or pressed materialwhich unitesthe rotorandatthesametime can form the hub ofthe rotor drawn onto the central drive shaft. The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axial half-section through the rotor of a permanent-magnet-excited electric generatorfor a motorvehicle, in accordance with the invention, and Figure 2 is a cross section through the rotortaken at right angles to the rotor axis. The drawings show a rotorofan electric generator, such as a motor vehicle generator, comprising perma- nent magnets 1 which are of thin prismatic shape and whose broad pole faces are plane parallel. The magnets 1 are interposed between laminated flux concentrators 2, acting as a magnetic flux conducting piece, and are positively and firm ly connected to one another and to the rotor shaft 6 by die-cast parts 3,4,5 and 11. The flux conducting pieces 2 have cut-away portions whose boundary surfaces are saw-tooth shaped.The rotor is heldtogetherbythefirtree shaped roots 4 made from paramagnetic die-cast material, bythe closure member3 in the pole gaps and by the annular end caps 11 having integrally cast fan vanes 10. In a permanent-magnet rotor as described above, with a magnet of adequate thickness, a maximum flux-producing surface area of the magnet is enabled by the position of the magnets on a radius or at an acute angle to the radius. This is particularly important when using the very expensive ferrite magnetic materials having a remnance of 0.4 to 0.44T. The surface area in the air gap ofthe generator is normally adequate for "rare earth" magnets having 0.8 to 1.2 T. However, in this arrangement, considerable problems with respect two securing the magnets arise in the case of high-speed electric generators. T is the S.l. unit for induction B. (The old unit was Gauss). Vs 1T=1OKG=- m Br = 0.4-. 0.44T is an excellentvalueforferrite. Bands ofglassfibre reinforced plastics material or anti-magnetic steel cylinders are normally used for fixing the parts. In both cases, the air gap is enlarged with a resultant reduction in the flux, despite high manufacturing costs. The illustrated rotor construction does not have these disadvantages. The laminated flux concentra- tors 2, which can be manufactured in a simple manner as parts stamped from sheet-metal, extend up tithe air gap between the cylindrical circumference ofthe rotor and the bore ofthe stator (not shown) which comprises a stack of stator laminations. If required, the flux concentrators 2 can befinish-turned or finish-g round after die-casting aboutwith aluminium. The magnetic lines of flux thus emerge radiallyfrom the flux concentrators 2 and enterthe stack of stator laminations. The flux concentrators as well as the magnets are held by virtue ofthe construction of the fir tree roots 4 and by the intergrally cast caps 11 contiguous to both sides ofthe stack of laminations. The closure members 3, which are also integrally cast, prevent the mechanicallyveryhard magnets from breaking apart even in the event of concealed cracks, thus preventing destruction ofthe entire generator. Advantageously, the vanes 10 for radial fans can be integrally cast on the caps 11 at the same time. The waveform of the electric voltage produced by the generator can be advantageously influenced by suitable construction of the contours ofthe air gaps of the stamped, readily manufacturable flux concentrators.The rotor body is secured to the shaft by means of a milled portion 7 on the shaft 6 and by peened-over portions 9, whereby die-cast material is displaced into the recesses 8 in the shaft 6. CLAIMS

1. An electricgeneratorforvehicles, having a multi-pole rotor which rotates inthe stator bore of a stack of stator laminations carrying a plurality of alternating currentwindings and which includes at least two permanent magnets which are polarized tangentially in the circumferential direction of the rotor and whose polefacesabutagainstfluxconduct- ing pieces from which magnetic lines offlux emerge radially and enterthe stack of stator laminations, wherein the permanent magnets are in the form of thin prismatic plates whose broad pole faces are aligned radially or nearly radially.

2. Ageneratorasclaimed in claim 1, wherein the permanent magnets are ferrite magnets.

3. A generator as claimed in claim 1 or 2, wherein the laminated flux conducting pieces include cutaway portions having saw-toothed-shaped boundary surfaces.

4. A generator as claimed in claim 3, wherein the cutaway portions are filled with paramagnetic die-cast material and are connected to the magnets.

5. A generator constructed substantially as herein described with reference to and as illustrated in the accompanying drawings.