WO2004043753A1 - Rotary electromechanical actuator, particularly for a parking brake for a motor vehicle - Google Patents

Rotary electromechanical actuator, particularly for a parking brake for a motor vehicle Download PDF

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Publication number
WO2004043753A1
WO2004043753A1 PCT/EP2003/012549 EP0312549W WO2004043753A1 WO 2004043753 A1 WO2004043753 A1 WO 2004043753A1 EP 0312549 W EP0312549 W EP 0312549W WO 2004043753 A1 WO2004043753 A1 WO 2004043753A1
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WO
WIPO (PCT)
Prior art keywords
gear
speed
central
worm
helical
Prior art date
Application number
PCT/EP2003/012549
Other languages
French (fr)
Other versions
WO2004043753A8 (en
Inventor
Andreas Geyer
Alessandro De Cristofaro
Original Assignee
Aktiebolaget Skf
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aktiebolaget Skf filed Critical Aktiebolaget Skf
Priority to AU2003283383A priority Critical patent/AU2003283383A1/en
Publication of WO2004043753A1 publication Critical patent/WO2004043753A1/en
Publication of WO2004043753A8 publication Critical patent/WO2004043753A8/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T7/00—Brake-action initiating means
    • B60T7/02—Brake-action initiating means for personal initiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/02—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with mechanical assistance or drive

Definitions

  • Rotary electromechanical actuator particularly for a parking brake for a motor vehicle
  • the present invention relates to a rotary electromechanical actuator suitable particularly, but not exclusively, for mounting on motor vehicles for operating, for example, drum- type parking brakes .
  • a rotary electromechanical actuator comprises two speed-reduction stages connected in series.
  • a first speed-reduction stage is a worm gear system with a worm 11 turned by an electric motor 12 and engaging a helical gear 13.
  • a second speed-reduction stage consists of a planetary gear system with a central gear 14 rigidly connected to the helical gear 13, an internally toothed ring gear 15, fixed to stationary casing 16, and a plurality of planet gears 17 distributed about the central gear 14 which engage with the central gear 14 and with the peripheral internal teeth of the ring gear 15.
  • the planet gears 17 are mounted rotatably on pins 18 of a planet carrier 19 which is rigidly connected to or formed integrally with a spool member 20 which is thus turned about an axis perpendicular to that of the operating motor 12, with a total speed-reduction ratio of for example about 1:300.
  • a flexible transmission means (not shown) , generally a Bowden cable whose opposite ends are connected to the levers operating the jaws of two drum brakes to apply a braking action.
  • Automotive manufacturers require to reduce to a minimum the total axial dimensions of the actuator so that it can be mounted easily in a variety of different positions and on a variety of different vehicles, even on vehicles where there is no much space available.
  • Actuators of the type described above have a large total axial dimension because the plane in which the first speed- reduction stage - the worm gear - operates is axially distant from the plane in which the second speed-reduction stage - the epicyclic gear system - operates.
  • Figures 1, 2 and 3 are, respectively, an exploded perspective view, a side view and a cross-sectional view of a rotary electromechanical actuator of known type;
  • Figure 4 is a cross-sectional view, similar to Figure 3, of a rotary electromechanical actuator according to the present invention.
  • Figure 5 is a schematic view looking down in the direction of the arrow V on the actuator seen in Figure 4 ;
  • Figure 6 is an exploded perspective view of the actuator seen in Figures 4 and 5;
  • Figure 7 is a perspective general view of the actuator according to the invention.
  • a rotary electromechanical actuator 10 comprises two speed-reduction stages connected in series, namely a worm-gear first speed-reduction stage and an epicyclic-gear second speed-reduction stage.
  • an electric commutator motor 12 turns a shaft 12a carrying a worm 11.
  • the worm 11 engages with a helical gear 13 rigidly connected to a central gear 14 of the epicyclic-gear second speed-reduction stage.
  • This second stage is essentially conventional and comprises, in addition to the central gear 14, an internally toothed ring gear 15 fixed to a stationary casing 16, and a plurality of planet gears 17 (four in this example) arranged about the central gear 14.
  • the planet gears 17 mesh with the central gear 14 and with the internal peripheral teeth of the fixed ring gear 15.
  • the planet gears 17 rotate on pins 18 attached to a planet carrier 19 which is rigidly connected to or formed integrally with a spool member 20 capable of rotating about the central axis x of the second speed-reduction stage in order to drive a flexible transmission means (not shown) .
  • the reference 21 denotes the whole of a discoidal plate capable of supporting the free ends of the pins 18 in order to keep the planet gears 17 parallel to the central axis and correctly engaged with the central gear 14 and with the ring gear 15.
  • the external peripheral surface 21a of the plate 21 is rounded to define a single line of contact with the internal cylindrical surface 16a of the casing 16.
  • the discoidal plate 21 has circumferentially equidistant recesses or flats (not shown) .
  • the helical gear 13 is essentially coaxial with and located around the second speed- reduction stage, i.e. in radially external position with respect to this stage, in such a way that the mid-plane PI in which the first speed-reduction stage works is close to the mid-plane P2 in which the second speed-reduction stage works, or virtually coincides with it .
  • the helical gear 13 and the central gear 14 are formed as a single part 134, the overall shape of which is that of a cup in which the following portions may be distinguished: a radially external axial cylindrical wall 135 whose upper edge has helical teeth 13 projecting radially outwardly and defining the helical gear; a grooved or toothed central protrusion defining the central gear 14; a radial base wall 136 of discoidal shape rigidly connecting the outer wall 135 to the central protrusion 14 and having in the centre a cylindrical recess or hole 137 for rotatably mounting the part 134 on a central pin formation 16b of the supporting casing 16.
  • the configuration described above places the input shaft 12a and the worm 11 level with the planetary-gear speed-reduction stage, and therefore greatly reduces the maximum axial dimension of supporting casing 16. Overall, the actuator is flatter than in the prior art.
  • the embodiments and the details of construction can be greatly varied in comparison to those described and illustrated purely by way of non-restrictive example, without departing from the scope of the invention as defined in the appended claims.
  • the number and dimensions of the toothed members may vary as a function of requirements in order to achieve the final desired speed-reduction ratio.
  • the helical gear 13 and the central gear 14 could form an assembled subassembly.

Abstract

A rotary electromechanical actuator rotationally drives a spool member (20) for operating a flexible transmission means in a motor vehicle. The actuator comprises two speed-reduction stages connected in series. The first speed-reduction stage is a worm gear system with a worm (11) rotated by an electric motor (12) and a helical gear (13). The second speed-reduction stage is a planetary gear system with a central gear (14) rigidly connected to the helical gear (13), an internally toothed ring gear (15) fixed to a stationary casing (16), a series of planet gears (17) rotating on pins (18) attached to a planet carrier (19) rigidly connected to the spool member (20). The teeth of the helical gear (13) are coaxial and lie around and axially approximately level with the planetary gear system.

Description

Rotary electromechanical actuator, particularly for a parking brake for a motor vehicle
The present invention relates to a rotary electromechanical actuator suitable particularly, but not exclusively, for mounting on motor vehicles for operating, for example, drum- type parking brakes .
In the present-day automotive industry there is a steadily increasing demand for the control of vehicle-mounted devices from a remote position by means of electromechanical actuators connected electrically to control buttons located near the -driver's seat.
In order to enable the prior art and its associated problems to be understood more clearly, a description will first be given of a known type of rotary electromechanical actuator, illustrated in Figures 1, 2 and 3 of the appended drawings.
Referring to Figures 1-3, a rotary electromechanical actuator comprises two speed-reduction stages connected in series. A first speed-reduction stage is a worm gear system with a worm 11 turned by an electric motor 12 and engaging a helical gear 13. A second speed-reduction stage consists of a planetary gear system with a central gear 14 rigidly connected to the helical gear 13, an internally toothed ring gear 15, fixed to stationary casing 16, and a plurality of planet gears 17 distributed about the central gear 14 which engage with the central gear 14 and with the peripheral internal teeth of the ring gear 15. The planet gears 17 are mounted rotatably on pins 18 of a planet carrier 19 which is rigidly connected to or formed integrally with a spool member 20 which is thus turned about an axis perpendicular to that of the operating motor 12, with a total speed-reduction ratio of for example about 1:300.
In its rotational movement, the spool member 20 winds and pulls a flexible transmission means (not shown) , generally a Bowden cable whose opposite ends are connected to the levers operating the jaws of two drum brakes to apply a braking action.
Automotive manufacturers require to reduce to a minimum the total axial dimensions of the actuator so that it can be mounted easily in a variety of different positions and on a variety of different vehicles, even on vehicles where there is no much space available.
Actuators of the type described above have a large total axial dimension because the plane in which the first speed- reduction stage - the worm gear - operates is axially distant from the plane in which the second speed-reduction stage - the epicyclic gear system - operates.
It is therefore an object of the present invention to provide a rotary electromechanical actuator of the type specified above first of all addressing the problem of optimizing and reducing the space between the two speed- eduction stages, and thus produce an actuator with particularly compact axial dimensions .
This and other objects and advantages, which would become clearer herein after, are achieved according to the invention by a rotary electromechanical actuator having the features defined in the appended claims . The structural and functional features of a preferred but non-restrictive embodiment of a rotary electromechanical actuator according to the invention will now be described with reference to the appended drawings, in which:
Figures 1, 2 and 3 are, respectively, an exploded perspective view, a side view and a cross-sectional view of a rotary electromechanical actuator of known type;
Figure 4 is a cross-sectional view, similar to Figure 3, of a rotary electromechanical actuator according to the present invention;
Figure 5 is a schematic view looking down in the direction of the arrow V on the actuator seen in Figure 4 ;
Figure 6 is an exploded perspective view of the actuator seen in Figures 4 and 5; and
Figure 7 is a perspective general view of the actuator according to the invention.
Referring now to Figures 4 to 7, and using, for simplicity sake, the same reference numbers to indicate parts identical or corresponding to those already described in Figures 1 to 3, a rotary electromechanical actuator 10 according to the present invention comprises two speed-reduction stages connected in series, namely a worm-gear first speed-reduction stage and an epicyclic-gear second speed-reduction stage.
In the first speed-reduction stage, an electric commutator motor 12 turns a shaft 12a carrying a worm 11. The worm 11 engages with a helical gear 13 rigidly connected to a central gear 14 of the epicyclic-gear second speed-reduction stage. This second stage is essentially conventional and comprises, in addition to the central gear 14, an internally toothed ring gear 15 fixed to a stationary casing 16, and a plurality of planet gears 17 (four in this example) arranged about the central gear 14. The planet gears 17 mesh with the central gear 14 and with the internal peripheral teeth of the fixed ring gear 15. The planet gears 17 rotate on pins 18 attached to a planet carrier 19 which is rigidly connected to or formed integrally with a spool member 20 capable of rotating about the central axis x of the second speed-reduction stage in order to drive a flexible transmission means (not shown) .
Throughout this description and the following claims, terms and expressions indicating positions and orientations such as "radial" and "axial" refer to the central axis x of the epicyclic-gear speed-reduction stage.
The reference 21 denotes the whole of a discoidal plate capable of supporting the free ends of the pins 18 in order to keep the planet gears 17 parallel to the central axis and correctly engaged with the central gear 14 and with the ring gear 15. The external peripheral surface 21a of the plate 21 is rounded to define a single line of contact with the internal cylindrical surface 16a of the casing 16. To further reduce the area of the sliding surface, the discoidal plate 21 has circumferentially equidistant recesses or flats (not shown) .
According to the present invention, the helical gear 13 is essentially coaxial with and located around the second speed- reduction stage, i.e. in radially external position with respect to this stage, in such a way that the mid-plane PI in which the first speed-reduction stage works is close to the mid-plane P2 in which the second speed-reduction stage works, or virtually coincides with it .
As shown in Figures 4 and 6, in the preferred embodiment of the invention the helical gear 13 and the central gear 14 are formed as a single part 134, the overall shape of which is that of a cup in which the following portions may be distinguished: a radially external axial cylindrical wall 135 whose upper edge has helical teeth 13 projecting radially outwardly and defining the helical gear; a grooved or toothed central protrusion defining the central gear 14; a radial base wall 136 of discoidal shape rigidly connecting the outer wall 135 to the central protrusion 14 and having in the centre a cylindrical recess or hole 137 for rotatably mounting the part 134 on a central pin formation 16b of the supporting casing 16.
As will be appreciated, the configuration described above places the input shaft 12a and the worm 11 level with the planetary-gear speed-reduction stage, and therefore greatly reduces the maximum axial dimension of supporting casing 16. Overall, the actuator is flatter than in the prior art.
Lastly, it can be seen that the reduction in the distance between the planes of action of the two speed-reduction assemblies shortens the lever arm and therefore the bending torque transmitted from the worm to the epicyclic gear system.
Naturally, without departing from the principle of the invention, the embodiments and the details of construction can be greatly varied in comparison to those described and illustrated purely by way of non-restrictive example, without departing from the scope of the invention as defined in the appended claims. In particular, the number and dimensions of the toothed members may vary as a function of requirements in order to achieve the final desired speed-reduction ratio. Also, as an alternative to what was described above, the helical gear 13 and the central gear 14 could form an assembled subassembly.

Claims

1. A rotary electromechanical actuator for rotationally driving a spool member (20) for operating a flexible transmission means in a motor vehicle, of the type in which the actuator comprises two speed-reduction stages connected in series, wherein the first speed-reduction stage is a worm gear system with a worm (11) rotated by an electric motor (12) and a helical gear (13) , the second speed-reduction stage is a planetary gear system with a central gear (14) rigidly connected to the helical gear (13) , a fixed internally toothed ring gear (15) , a plurality of planet gears (17) meshing with the central gear (14) and the ring gear (15) , and a planet carrier (19) forming pins (18) for rotatably supporting the planet gears (17) , the carrier
(19) being rigidly connected to or formed integrally with said spool member (20) , characterized in that the teeth of the helical gear (13) are essentially coaxial and lie around and axially approximately level with the planetary gear system.
2. An actuator according to Claim 1, characterized in that the helical gear (13) and the central gear (14) are formed as a single part (134) or an assembled subassembly, the overall shape of which is that of a cup with: a radially external axial cylindrical wall (135) with helical teeth (13) projecting radially outwardly and defining the helical gear; and a grooved or toothed central protrusion defining the central gear (14) .
3. An actuator according to Claim 2, characterized in that the said single part (134) or assembled subassembly also forms a radial base wall (136) rigidly connecting the outer wall (135) to the central protrusion (14) .
4. An actuator according to Claim 3 , characterized in that the radial base wall (136) is discoidal with a central cylindrical recess or hole (137) for the rotatable mounting of the part (134) on a pin formation (16b) integral with a stationary casing (16) .
5. An actuator according to Claim 1, characterized in that the electric motor (12) and the worm (11) are axially approximately level with the planetary gear system. .
6. An actuator according to any one of the preceding claims, characterized in that the flexible transmission means is a cable connected to levers operating the jaws of two drum brakes to apply a braking action.
PCT/EP2003/012549 2002-11-12 2003-11-11 Rotary electromechanical actuator, particularly for a parking brake for a motor vehicle WO2004043753A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003283383A AU2003283383A1 (en) 2002-11-12 2003-11-11 Rotary electromechanical actuator, particularly for a parking brake for a motor vehicle

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITTO2002A000975 2002-11-12
ITTO20020975 ITTO20020975A1 (en) 2002-11-12 2002-11-12 ELECTROMECHANICAL ROTARY ACTUATOR, IN PARTICULAR FOR

Publications (2)

Publication Number Publication Date
WO2004043753A1 true WO2004043753A1 (en) 2004-05-27
WO2004043753A8 WO2004043753A8 (en) 2004-07-22

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PCT/EP2003/012549 WO2004043753A1 (en) 2002-11-12 2003-11-11 Rotary electromechanical actuator, particularly for a parking brake for a motor vehicle

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AU (1) AU2003283383A1 (en)
IT (1) ITTO20020975A1 (en)
WO (1) WO2004043753A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7014017B2 (en) * 2004-06-30 2006-03-21 Dura Global Technologies, Inc. Electronic parking brake actuating assembly
CN101528519A (en) * 2006-10-18 2009-09-09 卢卡斯汽车股份有限公司 Single-part carrier for an electric parking brake actuator with planetary gear set
CN102072270A (en) * 2011-01-20 2011-05-25 奇瑞汽车股份有限公司 Electric brake
DE102013227045B3 (en) * 2013-12-20 2015-06-18 Automotive Research & Testing Center Transmission device for a vehicle brake

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB110228A (en) * 1916-11-16 1917-10-18 Peter Payne Dean Improvements in Driving Mechanism for Valves and the like.
US4994001A (en) * 1988-03-24 1991-02-19 Limitorque Corporation Valve actuator differential worm planetary gear drive

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB110228A (en) * 1916-11-16 1917-10-18 Peter Payne Dean Improvements in Driving Mechanism for Valves and the like.
US4994001A (en) * 1988-03-24 1991-02-19 Limitorque Corporation Valve actuator differential worm planetary gear drive

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7014017B2 (en) * 2004-06-30 2006-03-21 Dura Global Technologies, Inc. Electronic parking brake actuating assembly
CN101528519A (en) * 2006-10-18 2009-09-09 卢卡斯汽车股份有限公司 Single-part carrier for an electric parking brake actuator with planetary gear set
US8307960B2 (en) 2006-10-18 2012-11-13 Lucas Automotive Gmbh Single-part carrier for an electric parking brake actuator with planetary gear set
CN102072270A (en) * 2011-01-20 2011-05-25 奇瑞汽车股份有限公司 Electric brake
DE102013227045B3 (en) * 2013-12-20 2015-06-18 Automotive Research & Testing Center Transmission device for a vehicle brake

Also Published As

Publication number Publication date
ITTO20020975A1 (en) 2004-05-13
WO2004043753A8 (en) 2004-07-22
AU2003283383A1 (en) 2004-06-03

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