DE102014214095A1 - Actuator for an electro-hydraulic brake system - Google Patents

Abstract

An actuator (2) for an electrohydraulic brake system, which can be controlled to actively build pressure in at least one wheel brake, comprising a housing (38, 160) comprising an electric motor (8) having a rotor (50) and a stator (44) and a hydraulic pressure chamber (78) in which a pressure piston (90) is displaced to build up pressure and a rotational-translation gear, which converts a rotational movement of the rotor (50) into a translational movement of the pressure piston (90), while reducing the axial Space allow an optimized power flow to the hydraulic pressure build-up. For this purpose, the pressure chamber (78) is designed as an annular piston chamber, in which the pressure piston (90) is displaceable.

Description

The invention relates to an actuator for an electrohydraulic brake system, which can be controlled for active pressure buildup in at least one wheel brake, with a housing comprising an electric motor with a rotor and a stator and a hydraulic pressure chamber in which a pressure piston is displaced to build up pressure and a Rotation-translation gear, which converts a rotational movement of the rotor into a translational movement of the pressure piston.

In modern braking systems, in particular electro-hydraulic brake systems with the operating mode "brake by wire", the driver is decoupled from the direct access to the brakes. Upon actuation of the pedal usually a pedal decoupling unit and a simulator are operated, which is detected by a sensor, the braking request of the driver. The pedal simulator, which is usually designed as a master brake cylinder, serves to give the driver as familiar and comfortable a brake pedal feel as possible. The detected braking request leads to the determination of a desired braking torque, from which then the target brake pressure for the brakes is determined. The brake pressure is then actively built up by a pressure-providing device in the brakes. The actual braking thus takes place by active pressure build-up in the brake circuits with the aid of a pressure supply device, which is controlled by a control and regulation unit. As a result of the hydraulic decoupling of the brake pedal actuation from the pressure build-up, many functionalities such as ABS, ESC, TCS, hill-start assist etc. can be comfortably realized for the driver in such brake systems.

In such brake systems, there is usually provided a hydraulic fallback level by which the driver can decelerate or stop the vehicle by muscular force upon actuation of the brake pedal when the "by-wire" mode fails or is disturbed. While in normal operation by a pedal decoupling unit, the above-described hydraulic decoupling between brake pedal operation and brake pressure build-up, this decoupling is canceled in the fallback so that the driver can move brake means directly into the brake circuits.

The pressure supply device in brake systems described above is also referred to as an actuator or hydraulic actuator. In particular, actuators are designed as linear actuators or linear units in which a piston is axially displaced into a hydraulic pressure chamber for pressure build-up, which is built in series with a rotational-translation gear.

From the DE 10 2009 019 209 A1 is a linear unit for applying an axially acting force known with a rotational-translation gear having a threaded spindle and a threaded nut and a brushless electric motor with a rotor and a stator. To build up pressure, a hydraulic piston, which is attached to the threaded spindle, axially displaced in a hydraulic pressure chamber. Another linear unit is from the DE 10 2010 039 916 A1 known.

A disadvantage of such linear actuators is that sufficient space is required in the axial direction and the power flow is limited due to the design.

The invention has for its object to improve such an actuator to the effect that with simultaneous reduction of the axial space for hydraulic pressure build-up an optimized power flow is made possible.

This object is achieved in that the pressure chamber is designed as a piston ring chamber.

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

The invention is based on the consideration that in conventional actuators, the linear design has significant disadvantages. On the one hand, due to the series connection of rotational-translation gear, pressure piston and pressure chamber, the installation space is predetermined in the longitudinal direction. On the other hand, this construction also results in high pressure loads on the spindle during pressure build-up, whereby the maximum force flow is limited due to the bending tendency of the spindle.

As has now been recognized, these disadvantages can be eliminated by an alternative spatial design of the hydraulic pressure chamber. Valuable space can be saved by the pressure chamber is formed as an annular space or annular piston chamber, in which the pressure piston can be moved in the axial direction. That is, the piston is not pushed into a space arranged in the axial direction, but moves within a ring-like space. In this way, the piston can be pulled through the pressure chamber, so that no bending forces act on the spindle.

Advantageously, the annular piston chamber, the rotational translation gear at least partially spatially, whereby the space required in the axial direction can be kept low and is effectively limited only by the length of the spindle.

In a preferred embodiment, the rotor is designed as a hollow rotor and integrates the annular piston chamber in the rotor. The rotor, which is preferably sleeve-shaped in its construction as a hollow rotor, surrounds the annular piston chamber spatially or forms its outer envelope.

The pressure piston is preferably designed as a stepped ring piston. He has to at least two stages or areas with different sized radius. Particularly preferably, the pressure piston has two stages. The annular piston chamber is advantageously designed such that upon displacement of the pressure piston in the annular piston chamber after a predetermined displacement value, the hydraulically effective area is reduced or the hydraulically effective area is switched, whereby a rapid pressure build-up is possible.

The rotation-translation gear is preferably formed as a ball screw (KGT) with a spindle and a rotatably mounted thereon mother, run between the spindle and nut balls in helical, grooved tracks formed between the spindle and nut. In order to keep the mass moment of inertia of the KGT as low as possible, the spindle is preferably driven by the electric motor, in which case the rotor and spindle are connected to one another in a rotationally fixed manner. So that the nut does not rotate during a rotation of the spindle, it is secured against rotation by means of a rotation lock. A rotation of the spindle thus leads to an axial displacement of the nut, which is fixedly coupled to the pressure piston.

The nut is advantageously biased in the axial direction by an elastic element, so that when sucking a disturbing noise can be prevented. The elastic element is preferably designed as a spring, in particular as a compression spring.

The axis of rotation of the motor or electric motor is advantageously arranged perpendicular to a printed circuit board of an electrical control and regulating unit of the electric motor. On the circuit board, a sensor for detecting a signal of an encoder attached to the spindle end can be mounted near the end of the spindle. Due to this short design, a large hole in the circuit board or board can be avoided.

The housing of the actuator is preferably made in one piece with a valve block, whereby material and space can be saved.

If the housing is made of magnetically conductive material, it can represent the standing magnetic return path in a BL (brushless) motor concept with two air gaps, whereby a particularly dynamic motor can be realized.

The advantages of the invention are in particular that due to the formation of the hydraulic pressure chamber as a piston chamber of the piston pressure piston can be pulled by the KGT in load operation, whereby its life is increased and the bending tendency of the spindle, which occurs at high pressure forces, is eliminated. In addition, the actuator is reduced in length and thus its required space when KGT and hydraulic pressure chamber are not connected in series one behind the other, but the KGT is at least partially surrounded by the piston ring space. If the piston ring chamber or the piston ring chamber is integrated in a hollow rotor, a particularly compact design results. Due to the compact design of the actuator can be integrated in a common housing with the valve block. The suction line to the container can be downsized, and the motor housing is less heavily loaded.

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

1 an actuator with an electric motor and a rotational-translation gear and a hydraulic pressure chamber in a preferred embodiment in a pressure build-up position, and

2 the actuator according to 1 in a starting position. Identical parts are provided with the same reference numerals in all figures.

An in 1 illustrated actuator 2 includes an electric motor 8th and a rotational-translation gear, which as a ball screw (KGT) 14 is formed with a about an axis of rotation 20 rotatable threaded spindle or spindle 26 and one rotatable about the spindle 26 stored threaded nut or nut 32 , Between spindle 26 and mother 32 Run several balls in helical paths or grooves on the surface of the spindle 26 ,

The electric motor 8th is in a housing 38 arranged and includes a stator 44 and a rotatable rotor 50 , The rotor 50 is fixed to the spindle 26 connected. An anti-twist device 56 prevents the nut from rotating the spindle 26 rotates. Depending on the direction of rotation of the spindle 26 it moves in the axial direction 62 or, in the opposite direction of rotation, opposite thereto. The rotor 50 is designed as a hollow rotor and comprises a cup-shaped sleeve 68 , on the surface or outside of which permanent magnet segments 74 are arranged.

The actuator 2 is capable of exerting high hydraulic forces while having a compact design in the axial direction 62 , This is not, as in conventional hydraulic actuators, a hydraulic pressure chamber in the axial direction 62 seen - ie in the picture to the right - from the mother 32 or spindle 26 arranged, in which a pressure piston is moved. In the present case, rather, a hydraulic pressure chamber 78 as a ring piston chamber 80 formed in the rotor 50 is spatially integrated or surrounded by it. The ring piston chamber 80 is in the radial direction, that is perpendicular to the axial direction 62 , by an inner stator 86 limited. That is, the inner stator 86 , which provides the magnetic return, is between the piston ring chamber 80 and sleeve 68 arranged and thus at the same time fulfills the function of a high-pressure cylinder.

In the ring piston chamber 80 is one with the mother 32 firmly connected pressure piston 90 arranged, which is designed as an annular piston and at least partially the spindle 26 surrounds. The power flow in the spindle 26 does not lead to a pressure load as in conventional linear units or linear actuators but to a tensile load, whereby the bending tendency of the spindle is eliminated. The power flow can be closed in the cylinder housing, the pressure piston 90 KGT 14 , the rotation lock 56 and a thrust bearing (see below). The pressure piston 90 can by a valve block near force application point of the mother 32 of the KGT 14 on the pressure piston 90 be pulled pulled, whereby wear and shear forces are reduced. The anti-rotation lock of the nut 32 Can be done in the valve block or a separate component.

The annular piston is formed in two stages with a first stage 96 and a second stage 98 , each with gaskets 100 . 102 are provided. The ring piston chamber 80 is correspondingly stepped constructed with a first ring area 108 and a second ring area 110 , If the ring piston in the axial direction 62 , which to some extent also represents the stroke direction, shifted, so are initially both ring areas 108 . 110 available, so that the corresponding large cross-sectional area or effective area of the annular piston is used and the pressure build-up can be done quickly accordingly. Has an annular surface of the annular piston a transition between the first 108 and second ring area 110 achieved, the pressure space is divided, wherein (preferably) the outer chamber is connected via a valve to the container, which eliminates this part of the force on the piston and with a corresponding excess of force, the liquid volume can be displaced from the inner chamber with potentially higher pressure level. This results in a switching of the effective surface of the annular piston, whereby at the beginning of a rapid pressure build-up is possible.

The rotation axis 20 corresponds to the motor axis and is perpendicular to a circuit board 130 or a printed circuit, ie a PCB (Printed Circuit Board) of a control unit (ECU) of the actuator 2 oriented. The circuit board 130 has a sensing area 136 opposite a spindle end 140 which is in a ball bearing 142 is stored on. At the end of the spindle 140 is a magnetic encoder 146 mounted to determine the orientation or rotation of the spindle 26 with a magnetic encoder 146 in the sensing area 136 opposite magnetic sensor 150 cooperates to generate a signal to the spindle position, from which the control unit determines the piston position. By using a magnetic sensor can be dispensed gears for detecting the motor position and corresponding sensors.

The control unit controls pressure requirements via an electrical connection 156 the electric motor 8th at. A housing 160 surrounds the spindle in some areas 26 and the circuit board 130 , Through plug contacts 162 can the circuit board 130 to a power source, not shown, in particular the electrical system, are connected. The housing 38 . 160 is in one piece with a valve block 164 manufactured.

In 2 is the actuator 2 out 1 represented here, wherein here also designed as a spring elastic element 166 to see which, to the bias of the mother 32 used in suction, whereby a disturbing noise can be prevented.

LIST OF REFERENCE NUMBERS

2

 actuator

8th

 electric motor

14

 Ball Screw

20

 axis of rotation

26

 spindle

32

 mother

38

 casing

44

 stator

50

 rotor

56

 twist

62

 axially

68

 shell

74

 Permanent magnet segment

78

 pressure chamber

80

 Ring piston chamber

86

 internal stator

90

 pressure piston

96

 first stage

98

 second step

100

 poetry

102

 poetry

108

 first ring area

110

 second ring area

116

 ring surface

120

 crossing

130

 circuit board

136

 sensing area

140

 spindle end

142

 ball-bearing

146

 magnetic encoder

150

 sensor

156

 electrical connection

160

 casing

162

 plug contact

164

 manifold

166

 elastic element

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

• DE 102009019209 A1 [0005]
• DE 102010039916 A1 [0005]

Claims (10)

Actuator ( 2 ) for an electro-hydraulic brake system, which can be controlled for active pressure build-up in at least one wheel brake, with a housing ( 38 . 160 ) comprising an electric motor ( 8th ) with a rotor ( 50 ) and a stator ( 44 ) and a hydraulic pressure chamber ( 78 ), in which a pressure piston ( 90 ) and a rotational-translation gear, the a rotational movement of the rotor ( 50 ) in a translational movement of the pressure piston ( 90 ), characterized in that the pressure space ( 78 ) is designed as a piston ring chamber. Actuator ( 2 ) according to claim 1, wherein the annular piston chamber the rotation-translation gear ( 14 ) at least partially spatially. Actuator ( 2 ) according to claim 1 or 2, wherein the rotor ( 50 ) is formed as a hollow rotor, and wherein the annular piston chamber in the rotor ( 50 ) is integrated. Actuator ( 2 ) according to one of claims 1 to 3, wherein the pressure piston ( 90 ) is designed as a stepped ring piston. Actuator ( 2 ) according to one of claims 1 to 4, wherein the rotation-translation gear as a ball screw ( 14 ) with a spindle ( 26 ) and a rotatably mounted thereon nut ( 32 ) is trained. Actuator ( 2 ) according to claim 5, wherein the spindle ( 26 ) rotatably with the rotor ( 50 ) connected is. Actuator ( 2 ) according to claim 5 or 6, wherein the nut ( 32 ) in the axial direction by an elastic element ( 166 ) is biased. Actuator ( 2 ) according to one of claims 1 to 7, wherein an axis of rotation ( 20 ) of the electric motor ( 8th ) perpendicular to a printed circuit board ( 130 ) an electrical control unit of the electric motor ( 8th ) is arranged. Actuator ( 2 ) according to one of claims 1 to 8, wherein the housing ( 38 . 160 ) in one piece with a valve block ( 164 ) is executed. Actuator ( 2 ) according to one of claims 1 to 9, wherein the housing ( 38 . 160 ) is formed of magnetically conductive material.

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