DE102013221158A1 - Electric drive - Google Patents

Abstract

An electric drive (2) with a stationary outer stator (20) and inner stator (96) and a rotor (50) comprising a ferromagnetic rotor sleeve (56) on which on the side facing the outer stator (20), permanent magnets (62) are mounted, and with a rotation-translation gear (78) comprising a rotatable with the rotor (50) spindle (80) and a relative to the spindle (80) rotatable nut (86), should have the lowest possible moment of inertia and Simultaneously easy to be in production. For this purpose, it is provided that the inner stator comprises an anti-twist device for the nut (86).

Description

The invention relates to an electric drive with a fixed outer stator and an inner stator and a rotor comprising a ferromagnetic rotor sleeve, are mounted on the side facing the outer stator side permanent magnets, and with a rotation-translation gear, comprising one with the rotor co-rotating spindle and a nut rotatable relative to the spindle.

Such electric drives are used in a variety of technical fields. Thus, for example, they are used as linear actuators in which an actuator element is to be linearly moved back and forth by electronic control.

A typical field of application are "active" brake systems for motor vehicles, in which brake pressure can be built up in the brake circuits without the driver's muscle power. Such braking systems are usually operated in a "brake-by-wire" mode in which the driver is decoupled from direct access to the brakes by means of a pedal decoupling unit. A pedal simulator gives him as comfortable and familiar a brake feel as he pushes brake fluid in a simulator when pressing the brake pedal. By a displacement sensor, which may include, for example, a displacement and / or angle sensor, a measure of the operation of the brake pedal is determined, from which then the driver's braking request is determined. From this, a desired braking torque or a desired braking pressure is then determined in a control and regulation unit, which is then adjusted by means of a pressure-providing device in the brakes. For this purpose, a pressure piston is pushed into a hydraulic pressure chamber by means of an electric drive, comprising an electric motor and a downstream rotation-translation gear, whereby brake fluid is conveyed into the brakes.

In the braking systems described above, safety programs such as ABS, TCS and comfort programs such as HSA can be comfortably realized for the driver. The safety programs usually require fast control processes in which pressure has to be built up and taken down quickly on individual brakes. For this, the piston has to be driven quickly back and forth, d. H. also be reversed quickly. In this fast to be performed adjusting movement, the moment of inertia of the rotor is decisive.

From the WO 2007/022833 A1 An electric drive with an external stator and an internal stator is known, wherein the internal stator does not rotate with the rotor, which has at least one pot-shaped part, and thus does not contribute to its moment of inertia. The disadvantage of such a configuration is the complex production.

The invention is therefore based on the object to improve an electric drive to the effect that it has the lowest possible moment of inertia and at the same time is easy to manufacture.

This object is achieved in that the inner stator comprises a rotation for the mother.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is based on the consideration that in many conventional electric drives a large contribution to the moment of inertia comes from the iron yoke. However, a significant reduction in the moment of inertia of the rotor can be achieved if the iron yoke is not involved in the rotation of the rotor. This can be achieved by the formation of an inner stator, which is arranged inside the rotor and serves as iron yoke, so that the outer part of the rotor, which is provided with permanent magnets, rotates between the inner stator and the outer stator.

As has now been recognized, the fact that the inner stator does not rotate with the rotor adds another function to the inner stator. In order for the electric drive to function as a linear actuator in which the rotational movement of the rotor or the spindle is converted into a linear movement, the nut must be secured against rotation, that is, it must be provided against rotation for the mother. Since now the inner stator is disposed within the rotor and, so to speak, adjacent to the mother, it can be used because of its rigid spatial arrangement as anti-rotation device for the mother. The inner stator thus has a double function. In this way can be dispensed with additional components for a rotation of the mother, so that the production of the drive is simplified.

Advantageously, the rotation is formed by a groove extending in the inner stator and an integrally formed on the nut engagement element which runs in the axial direction when turning the spindle in the groove. The rotation thus comprises the groove in the inner stator and the engagement element on the nut, which is preferably designed in the manner of a cam, block or wedge and runs at a rotation of the spindle with the least possible play in the groove, so that reversals of the spindle rotation as directly as possible to Reversing the linear movements of the mother. In an exemplary alternative embodiment, a groove is formed in the nut, which comprises a radially projecting from the inner stator inwardly projecting elongate cam or comb, so that the rotation of the nut is prevented.

The inner stator is preferably designed as an inner stator sleeve arranged inside the rotor shell. That is, it is formed as a hollow cylinder whose wall thickness is small compared to its length in the axial direction. Due to its sleeve-like design, the assembly spindle / nut, inner stator, rotor in the radial direction can be built very narrow and space-saving.

In order to realize a particularly reliable material connection with low thermal distortion, the inner stator sleeve is advantageously connected by laser welding to an element of the drive, in particular a bearing element. As a result, a precise positioning and alignment of the inner stator sleeve can be realized. This makes it possible to arrange this sleeve in the radial direction as closely as possible to the rotation-translation gear and as close as possible to the rotor, so that the air gap between the inner stator and the rotor can be made small.

The inner stator sleeve is preferably supported axially on a bearing of the electric drive and is oriented thereon. In this way, a precise arrangement and alignment of the sleeve is possible, so that taking into account the corresponding tolerances, a narrow design of the air gap between the inner stator and the rotor sleeve is made possible.

In a preferred embodiment, the nut is designed as an inner stator. The rotation is effected here by one or more grooves in the nut and a component which corresponds to the inner stator with large recesses introduced. That is, the mother takes over a second function, namely that of the inner stator or iron yoke. It is preferably made of ferromagnetic material. Due to the dual function of the nut can be dispensed with a separate inner stator or a separate iron yoke. The rotor sleeve is preferably formed ungestufted, d. H. in the axial direction, the rotor sleeve always has the same diameter.

The permanent magnets are preferably fastened to the rotor with at least one fixing sleeve, which has beads, so that a particularly robust and reliable fastening of the permanent magnets is made possible. As a result, the expansion of the permanent magnets in the radial direction is very precisely controlled, so that the air gap between the rotor and the outer stator can be kept very small.

The respective fixing sleeve is preferably fixed by laser welding to the rotor sleeve, so that only slight thermal deformations of the fixing sleeve and rotor sleeve occur during the welding process, as a result of which the air gap between rotor and outer stator can be determined very precisely.

The respective fixing sleeve preferably engages over the permanent magnets outside the active air gap. As a result, the air gap can be small and the efficiency of the engine can be kept high.

The advantages of the invention are, in particular, that the provision of an anti-rotation device for the mother by the inner stator, the production of the electric drive over known drives is significantly simplified. A sleeve-like inner stator forms a particularly space-saving training. Together with a sleeve-like rotor, these two components can be arranged in the radial direction very close to the rotation-translation gear.

Several embodiments of the invention will be explained in more detail with reference to a drawing. In it show in a highly schematic representation:

1 an electric drive with an external stator, a rotor and an internal stator in a first preferred embodiment in a longitudinal section,

2 the electric drive according to 1 in an alternative representation in a longitudinal section,

3 an electric drive in a second preferred embodiment in a longitudinal section, and

4 an electric drive in a third preferred embodiment in a longitudinal section.

Identical parts are provided with the same reference numerals in all figures.

An in 1 shown electric drive 2 is designed as a brushless electric motor, which is designed for the active pressure build-up in an electro-hydraulic brake system. He is in a housing 4 arranged or installed and includes an electromechanical component 8th on which a hydraulic component 14 is attached. Its electromechanical component 8th includes an external stator with two excitation coils 26 . 32 and one in two ball bearings 36 . 44 mounted rotor 50 , The rotor 50 comprises a ferromagnetic, sleeve-like magnet carrier or a rotor sleeve 56 on which a number of permanent magnets 62 attached or attached. The magnet carrier or the rotor sleeve 56 is designed as ungestufte or continuous sleeve, that is, its diameter is constant in the axial direction.

The rotor 50 is by laser welding to an annular weld area 70 with a bearing element 76 which is in the ball bearing 44 is stored, rigidly connected or flanged. The electric drive 2 includes a rotational-translation gear 78 comprising a spindle 80 and a mother 86 through which the rotational movement of the rotor 50 in a translatory movement of the mother 86 is converted.

With the bearing element 76 is the spindle 80 rigidly connected, resulting in rotation of the rotor 50 turns with him. The spindle 80 is from the mother 86 surrounded, which on an external thread 92 the spindle 80 relative to the spindle 80 circulates.

The electric drive 2 is designed to minimize the moment of inertia of the rotor 50 while being easy to manufacture. For this purpose, the iron yoke is first formed as a component or a component that is not with the rotor 50 co-rotates and thus does not contribute to its moment of inertia. The iron yoke is as an inner stator 96 in the form of a sleeve 98 educated. He has a groove 104 on, which is designed as a longitudinal groove and in the axial direction 68 in the sleeve 98 runs and in the one to the mother 86 molded cam 110 engages such that upon rotation of the spindle 80 the rotation of the mother 86 is prevented. The mother 86 moves in this way during a rotation of the spindle 80 in the axial direction 68 or opposite.

The mother 86 is rigid with a pressure piston 120 connected. In this embodiment, the connection is made by caulking. The pressure piston 120 is used to build up pressure in the axial direction 68 in a hydraulic pressure chamber 126 pushed or moved. A pressure reduction is possible by moving the plunger 120 in the opposite direction. The pressure room 126 is with a brake fluid reservoir 132 If necessary, hydraulically connectable to suck in a suction cycle braking means. The hydraulic component 14 further comprises a valve block 136 , Also marked are a capacitor 140 , a tandem master cylinder 146 , an inductive displacement sensor 152 , a power plug 158 and a press-fit pin 160 ,

In the present embodiment, the electric drive 2 the hydraulic component 14 which makes it suitable for use in an electro-hydraulic brake system. This component 14 but is not necessarily part of the drive 2 , In other embodiments, the component 14 be missing or replaced by another.

In representation of the electric drive in 2 is the ball bearing 44 clearly visible on the left side.

At the in 3 shown embodiment of the electric drive 2 the inner stator is supported 96 or the sleeve 98 in a storage area 170 at the ball bearing 36 from. The sleeve 98 is in this area in the axial direction 68 seen twice angled 90 ° outwards, creating a sort of collar 176 is formed. Such a construction allows a stable attachment and beyond a precise alignment of the sleeve 98 parallel to the sleeve-shaped rotor 50 , The sleeve 98 and the rotor 50 should be as parallel as possible, since the air gap formed between them should be as low as possible and still the tolerances of the two components must be taken into account in their dimensioning in the radial direction. By the in 3 illustrated alignment of the inner stator is thus enables the formation of a very narrow air gap.

An electric drive 2 in a further preferred embodiment is finally in 4 shown. In this embodiment, the mother takes over 86 the function of the iron yoke or inner stator 96 , Because of their mobility in the axial direction 68 it forms one in the axial direction 68 sliding inner stator. The mother 86 contributes during rotation of the rotor 50 not to its moment of inertia, so that also in this embodiment, a low-inertia actuator is realized.

The anti-rotation lock of the nut 86 is executed in the present embodiment as described above. As in the examples above, the sleeve 98 of the rotor 8th with the bearing element 76 rigidly connected by laser welding.

LIST OF REFERENCE NUMBERS

2

 electric drive

4

 casing

8th

 electromechanical component

14

 hydraulic component

20

 outer stator

26

 excitation coil

32

 excitation coil

36

 ball-bearing

44

 ball-bearing

50

 rotor

56

 rotor sleeve

62

 permanent magnet

68

 axial direction

70

 welding area

76

 bearing element

78

 Rotation-translation gear

80

 spindle

86

 mother

92

 external thread

96

 internal stator

98

 shell

104

 groove

110

 cam

120

 pressure piston

126

 pressure chamber

132

 Brake fluid reservoir

140

 capacitor

146

 Tandem master cylinder

152

 Inductive displacement sensor

158

 Power plug

160

 Einpresskontaktpin

170

 storage area

176

 collar

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

• WO 2007/022833 A1 [0005]

Claims (10)

Electric drive ( 2 ) with a fixed external stator ( 20 ) and an inner stator ( 96 ) and a rotor ( 50 ), which is a ferromagnetic rotor sleeve ( 56 ) at the on the outer stator ( 20 ) facing side permanent magnets ( 62 ) and with a rotation-translation gear ( 78 ), comprising one with the rotor ( 50 ) co-rotating spindle ( 80 ) and one opposite the spindle ( 80 ) rotatable nut ( 86 ), characterized in that the inner stator ( 96 ) an anti-twist device for the nut ( 86 ). Electric drive ( 2 ) according to claim 1, wherein the anti-twist device is secured by a in the inner stator ( 96 ) running groove ( 104 ) and one at the mother ( 86 ) molded engaging element ( 110 ) is formed, which when turning the spindle ( 80 ) in the groove in the axial direction ( 68 ) running. Electric drive ( 2 ) according to claim 1 or 2, wherein the inner stator ( 96 ) than within the rotor sleeve ( 56 ) arranged inner stator sleeve ( 98 ) is trained. Electric drive ( 2 ) according to claim 3, wherein the inner stator sleeve ( 98 ) by welding, preferably laser welding, with an element of the drive, in particular a bearing element ( 76 ), connected is. Electric drive ( 2 ) according to claim 3 or 4, wherein the inner stator sleeve ( 98 ) axially on a bearing of the electric drive ( 2 ) and aligns. Electric drive ( 2 ) according to claim 1, wherein the mother is 86 ) Inner stator is formed. Electric drive ( 2 ) according to one of the preceding claims, wherein the rotor sleeve ( 56 ) is designed ungraded. Electric drive ( 2 ) according to one of the preceding claims, wherein the permanent magnets ( 62 ) with at least one fixing sleeve, which has beads, on the rotor ( 50 ) are mounted torque transmitting. Electric drive ( 2 ) according to claim 8, wherein the respective fixing sleeve by welding, preferably laser welding, on the rotor sleeve ( 56 ) is attached. Electric drive ( 2 ) according to claim 8 or 9, wherein the respective fixing sleeve, the permanent magnets ( 62 ) overlaps outside the active air gap.

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