BRAKE ACTUATOR

Abstract

A brake actuator for brakingly engaging a brake block or pad (9) with a rotating part of a vehicle has spring means (24) creating a linear brake force. An eccentric mechanism (21, 23, 25) is arranged in a brake force transmitting chain from the spring means (24) to the brake block or pad (9), and there is a motor (2) for controlling the angular position of an eccentric (25) in this mechanism and thus the brake force transmitted from the spring means (24).

Claims

1. A brake actuator for brakingly engaging a brake block or pad with a rotating part of a vehicle, said brake actuator comprising: spring means for creating a linear brake force; an eccentric mechanism in a brake force transmitting chain from the spring means to the brake block or pad; and a motor for controlling the angular position of an eccentric in said eccentric mechanism and the brake force transmitting chain from the spring means to the brake block or pad.

2. The brake actuator according to claim 1 for brakingly engaging a brake pad with a brake disc of a vehicle, comprising said spring means for biasing a drive bridge in a brake application direction, said drive bridge being connected to the brake pad and being controlled in its position in this direction by said eccentric, which extends through an opening in the drive bridge and is arranged on a control shaft journalled in relation to a housing of the brake actuator and connected to the motor.

3. The brake actuator according to claim 2, wherein said spring means is supported by a cover of the housing of the brake actuator, and wherein the control shaft is journalled in shaft supports of the cover.

4. The brake actuator according to claim 2, wherein reduction gearing is provided between the electric motor and an outgoing drive pinion thereof.

5. The brake actuator according to claim 4, wherein the reduction gearing comprises a planetary reduction gearing.

6. The brake actuator according to claim 4, wherein said drive pinion is in gear engagement with a gear wheel on the control shaft.

7. The brake actuator according to claim 2, wherein the drive bridge is in connection with a brake head which in turn is connected to the brake pad.

8. The brake actuator according to claim 7, wherein the brake pad is attached to a brake pad holder which is connected to the brake head by a brake lever pivotally attached to a brake disc engaging assembly.

9. The brake actuator according to claim 7, wherein a load cell is arranged between the drive bridge and the brake head.

10. The brake actuator according to claim 7, wherein a slack adjuster device is arranged between the drive bridge and the brake head.

11. The brake actuator according to claim 10, wherein a nut rod provided with an external threaded nut portion is connected to the brake head, the nut portion being in internal thread engagement with a rotatable adjuster tube connected to the drive bridge, and the adjuster tube being arranged to be driven by the electric motor via an electromagnetic clutch, a bevel gear wheel and an adjuster tube gear wheel in splines connection with the adjuster tube.

12. (canceled)

13. The brake actuator according to claim 2, wherein said eccentric comprises a cam.

14. The brake actuator according to claim 2, wherein said motor comprises an electric rotary motor.

15. The brake actuator according to claim 3, wherein said spring means comprise compression springs.

16. The brake actuator according to claim 9, wherein said load cell is configured to sense a transmitted braking force to the brake head.

17. A vehicle comprising: a rotating part; a brake actuator configured for brakingly engaging a brake block or pad with the rotating part, wherein said brake actuator comprises: spring means for creating a linear brake force; an eccentric mechanism in a brake force transmitting chain from the spring means to the brake block or pad; and a motor for controlling the angular position of an eccentric in said eccentric mechanism and the brake force transmitting chain from the spring means to the brake block or pad.

18. A vehicle as claimed in claim 17, wherein the vehicle comprises a rail vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The teachings herein will be described in further detail below with reference to the accompanying drawings, in which

[0029] FIG. 1 is an isometric view of an electromechanical disc brake unit,

[0030] FIG. 2 is a view from above of the same unit with certain portions shown in section, and

[0031] FIG. 3 is a schematical illustration of a block brake unit embodying the same principles as the disc brake unit of FIGS. 1 and 2.

DETAILED DESCRIPTION

[0032] Referring first to FIG. 1, an electromechanical disc brake unit generally comprises a main body 1, in which a mechanism for converting a rotary movement into a longitudinal movement is contained and to which an electric rotary motor 2 is attached.

[0033] As is known in the art, such a brake unit is intended for mounting in an under frame of a vehicle, normally a rail vehicle (not shown), in the vicinity of a brake disc D (dotted lines in FIG. 2) which is mounted to a rotating part, normally a wheel axle of the vehicle and with which the brake unit is to brakingly cooperate.

[0034] A brake disc engaging assembly 3 is connected to the main body 1 in such a manner that minor axial movements of the brake disc D relative to the main body are allowed during service.

[0035] The design for the mounting of the brake unit in the vehicle does not form a part of the concept set forth herein and is not further illustrated and described.

[0036] Referring then mainly to FIG. 2, the main body 1 has a housing 4 and a cover 5 attached thereto. Also the motor 2 is attached thereto.

[0037] A first brake pad holder 6, provided with a replaceable brake pad 7, is part of the brake disc assembly 3. A second brake holder 8, provided with a replaceable brake pad 9, is slidably arranged on guide rods 10 attached to the first brake pad holder 6. A brake lever 11 is pivotally connected at its central part to the brake disc assembly 3. The end to the left in the drawings of the brake lever 11 is pivotally connected to the second brake holder 8, whereas its end to the right in the drawings is pivotally connected to a brake head 12. Return springs 13 are arranged around the guide rods 10 between the two brake holders 6, 8 for biasing them apart.

[0038] By this design, a movement downward in FIG. 10f the brake head 12 will cause the second brake pad holder 8 to move in the direction towards the first brake pad holder 6 for effecting a braking engagement of the brake pads 7 and 9 with the brake disc D rotating between these pads. A return movement will then be effected by the return springs 13.

[0039] The electric motor 2 has an outgoing, rotating shaft 14 (FIG. 2) in gear engagement with rotatable planet wheels 15, which at their outer peripheries are in gear engagement with a fixed ring wheel 16. The planet wheels 15 are journalled in a planet holder 17, preferably journalled by a radial ball bearing 18 in the main body 1. The planet holder 17 is provided with an outgoing drive pinion 19, whose rotational speed is considerably reduced by the described planetary gearing in relation to the rotational speed of the motor 2.

[0040] The reducing gear between the motor 2 and the outgoing drive pinion 19 may however be of various designs.

[0041] A gear wheel 20, preferably with considerably larger diameter than the drive pinion 19, is in gear engagement with the drive pinion 19. A cylindrical control shaft 21 is journalled for rotation in two shaft supports 22 in the cover 5.

[0042] A drive bridge 23 is guided by the housing 4 and the cover 5 for longitudinal movements downwards and upwards in FIG. 2. Powerful compression springs 24 are arranged between the drive bridge 23 and the cover 5 for exertingas will appear more clearly belowa brake applying force downwards in FIG. 2.

[0043] The central portion of the control shaft 21 is formed as an eccentric or cam 25 cooperating with an opening in the drive bridge 23 with such a shape that a rotation of the control shaft 21 with its eccentric 25 from the shown rest position with the drive bridge 23 in its uppermost position and the springs 24 compressed will enable the drive bridge 23 to move slightly downwards in FIG. 2 under the action of the springs 24. As there is a mechanical connection (to be described) between the drive bridge 23 and the brake head 12, such a movement can result in a movement downwards of the brake head 12 and a pivotal movement of the brake lever 11 in a brake applying direction.

[0044] The parts 21, 23, 25 can together be called an eccentric mechanism.

[0045] The brake head 12 is provided with a nut rod 26 extending upwards in FIG. 2. This nut rod 26 is provided with an external threaded nut portion 26 in internal thread engagement with a rotatable adjuster tube 27.

[0046] In an appropriate compartment in the drive bridge 23 there is above the adjuster tube 27 provided a piston 28, a pressure medium 29, and a pressure transducer 30. During operation of the device, the force from the drive bridge 23 is accordingly transmitted to the brake head 12 via the pressure medium 29, the piston 28, the adjuster tube 27, and the nut rod 26 with its nut portion 26. The transmitted force is sensed by the pressure transducer 30 and is used to control the operation of the electric motor 2 for obtaining the desired brake characteristic.

[0047] The parts 28-30 can together be called a load cell.

[0048] The rotatable adjuster tube 27 (in engagement with the nut portion 26 of the nut rod 26) is part of a slack adjuster device now to be described.

[0049] Selectively connected to the drive pinion 19 over an electromagnetic clutch 31 is a bevel gear wheel 32, forming a right angle gear with an adjuster tube gear wheel 33. This letter gear wheel 33 has a splines connection to the adjuster tube 27, so that rotation of the gear wheel 33 will impart a rotation to the adjuster tube 27 but that relative axial movement is allowed. There is a compression spring 34 biasing the gear wheel 33 downwards in FIG. 2.

[0050] When the rotational movement of the eccentric 25 is indicated to be too long in relation to the desired brake force, which is an indication of worn-off brake pads 7, 9, the electromagnetic clutch 31 will engage, so that rotary motion is transmitted from the drive pinion to the adjuster tube 27 over the right angle gear 32, 33, pushing the nut rod 26 and thus the brake head 12 slightly downwards for compensating for the wear of the brake pads 7, 9 and of the brake disc D.

[0051] The parts 26, 26, 27, 31-34 can together be called a slack adjuster device.

[0052] An exemplary block brake unit is schematically shown in FIG. 3. Shown herein is a housing 40 with an ear 40 for the attachment of the brake unit to a rail vehicle to be braked. In the housing 40 an eccentric mechanism 41 is axially movable, acted on by a powerful spring 42. Controlled by the eccentric mechanism 41, as will be described, the force from the spring 42 can be transmitted via a load cell 43 and a slack adjuster device 44 to a brake block 45 to be brakingly applied against a wheel W of the vehicle, on which the brake unit is mounted.

[0053] The eccentric mechanism 41 has a shaft 46, which is journalled for rotation in the housing 40 and can be rotated by a motor (not shown). The eccentric mechanism 41 is provided with open sides or axial long-holes for allowing axial movement thereof. The eccentric is here illustrated as a roller 47 contained in a transverse slot 41 in the eccentric mechanism 41. The roller 47 is connected to a lever 48 which is attached to the shaft 46. By rotating the shaft 46 an angle by means of the motor, the eccentric assembly 41 will be allowed to move forward or to left in the drawing under the action of the spring 42. Also, the roller 47 can itself generate a brake force to the left in the drawing by its engagement with the left side of the slot 41.

[0054] One or more compression springs 24, 42 are used in the two described embodiments, but generally any spring means can be utilized.

[0055] The means for controlling the eccentric mechanism is shown and described as an electric rotary motor, but generally any motor can be utilized.

[0056] The teachings herein have been exemplified by a disc brake unit and a schematic block brake unit, but generally the concept can theoretically be embodied in any brake actuator (without load cell and/or slack adjuster device).

[0057] The electric motor has been described as providing a rotary control movement for the eccentric or cam, but the design is such that the force from the motor can be added as a brake force to the force of the spring means.

[0058] A favorable aspect of the described embodiments is that thanks to the design with the eccentric mechanism near its equilibrium (as is illustrated in FIG. 3) the great forces from the spring means may be controlled by a small motor.