METHOD FOR DETERMINING DESIGN PARAMETERS OF AN ELECTROMECHANICAL BRAKE, AND ELECTROMECHANICAL BRAKE

Abstract

A method for determining design parameters of an electromechanical brake is provided. The brake comprises an electric motor connected to a brake lining by a transmission. The brake lining can be pressed against a friction lining movable relative to the brake lining. The electric motor is connected to the brake lining by a transmission that has a transmission ratio which is not constant over an actuation stroke. A reliable and economical brake is achieved in that an electric motor, a brake lining and a friction lining are selected, whereupon the transmission ratio is selected on the basis of the counter-torque acting over the actuation stroke, which counter-torque acts on the transmission. The transmission ratio is selected in such a way that the electric motor is operated at an optimal operating point, in particular at an operating point of maximum power, substantially over the entire actuation stroke.

Claims

1-15. (canceled)

16. A method for determining design parameters of an electromechanical brake, the brake comprising an electric motor connected to a brake lining by a transmission, the brake lining adapted to press against a friction lining movable relative to the brake lining, the transmission having a transmission ratio which is not constant over an actuation stroke, comprising: selecting an electric motor; selecting a brake lining; selecting a friction lining; and selecting the transmission ratio based on a counter-torque acting over the actuation stroke, the counter-torque adapted to act on the transmission on account of the selected electric motor, the selected brake lining, the selected friction lining and a mechanical connection of these elements, the transmission ratio being selected so the electric motor is operated at an optimal operating point substantially over the entire actuation stroke.

17. The method according to claim 16, wherein the transmission ratio is selected so the electric motor is operated at a maximum power substantially over the entire actuation stroke.

18. The method according to claim 16, further comprising: determining the counter-torque mathematically; wherein the transmission ratio is a variable ratio.

19. The method according to claim 18, wherein the counter-torque is determined based on at least one of tolerances, an air gap between the brake lining and the friction lining when the brake is open, friction losses in the transmission, and possible thermal expansions.

20. The method according to claim 16, further comprising determining the counter-torque by a numerical simulation.

21. The method according to claim 16, wherein: the transmission ratio is a variable ratio; the transmission ratio being determined based on at least one of a reduction in a motor torque caused by a demagnetization at an end of a planned service life, an increased temperature, manufacturing tolerances, and a reduction in a supply voltage down to a lower limit at which a function of the brake still has to be guaranteed.

22. A method for producing an electromechanical brake, wherein the electromechanical brake is produced according to design parameters determined in a method according to claim 16.

23. An electromechanical brake, comprising: an electric motor; a brake lining; and a friction lining arranged to be movable relative to the brake lining; wherein the brake lining is adapted to press against the friction lining by means of the electric motor to convert mechanical energy into thermal energy by the friction between the brake lining and friction lining; wherein the electric motor is connected to the brake lining by a transmission with an actuating stroke and a variable transmission ratio; and wherein the electromechanical brake is produced by a method according to claim 22.

24. The electromechanical brake according to claim 23, wherein the variable transmission ratio is selected on a basis of the actuation stroke so the electric motor, when actuated, can be operated over the actuation stroke at an optimal operating point.

25. The electromechanical brake according to claim 24, wherein the variable transmission ratio is selected so the electric motor is operated at a maximum power substantially over the entire actuation stroke.

26. The electromechanical brake according to claim 23, wherein: the transmission comprises two disks rotatable about an axis of rotation, the two disk being connected by at least one ball arranged in a ball ramp; and the variable transmission ratio is at least partially formed by the ball ramp.

27. The electromechanical brake according to claim 23, wherein: the transmission comprises at least one non-circular cam rotatably arranged about an axis of rotation; and the variable transmission ratio is at least partially formed by the the non-circular cam.

28. The electromechanical brake according to claim 23, wherein the transmission comprises one of: a control disk attached to a shaft, a center of the control disk being outside a shaft axis; and a lever to implement the variable transmission ratio.

29. The electromechanical brake according to claim 23, wherein the transmission comprises at least one of: a cam transmission; a cam disk; a connecting rod; and a coupling mechanism.

30. The electromechanical brake according to claim 23, wherein the transmission is designed so that the variable transmission ratio has both positive and negative values over the actuation stroke.

31. The electromechanical brake according to claim 23, wherein the transmission is designed such that the variable transmission ratio is zero at least over a segment of the actuation stroke, a movement of the electric motor in the segment not causing a movement of the brake lining relative to the friction lining.

32. The electromechanical brake according to claim 23, wherein a cable connection is provided so that the brake lining can be pressed against the friction lining by pulling on a cable attached to the cable connection.

33. A vehicle with an electromechanical brake, wherein the electromechanical brake is designed according to claim 23.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Further features, advantages and effects of the invention can be derived from the embodiments presented below. The drawings, to which reference is made, show the following:

[0054] FIG. 1 is a schematic representation of an electromechanical brake according to the invention;

[0055] FIG. 2 is a schematic representation of a method for producing a brake according to the invention;

[0056] FIG. 3 depicts different elasticity curves of a brake;

[0057] FIG. 4 is a detail representation of an embodiment of a brake according to the invention;

[0058] FIG. 5 is a schematic detail representation of a further embodiment of a brake according to the invention;

[0059] FIG. 6 is a detail representation of a brake according to the invention;

[0060] FIG. 7 is a schematic detail representation of a further embodiment of a brake according to the invention;

[0061] FIG. 8 is a schematic representation of a further embodiment of a brake according to the invention; and

[0062] FIG. 10 shows a ninth preferred embodiment of the vertical member in plan view.

DETAILED DESCRIPTION

[0063] FIG. 1 shows a brake 1 according to the invention in a schematic representation. As can be seen, a transmission 3 is provided between an electric motor 2 and a brake lining 4, which, in a closing direction 6, can be pressed against a friction lining 5. The friction lining 5 can be formed, for example, by a brake disk of a motor vehicle, in particular a car, which is arranged to rotate with a wheel of the motor vehicle.

[0064] The brake lining 4 can be formed by brake shoes which are not connected to the motor vehicle in a rotating manner with a wheel of the motor vehicle. In order to achieve a small size, low weight and low cost, the invention provides that the transmission 3 has a variable transmission ratio over an actuation stroke which the brake lining 4 can execute between an open position of the brake 1 and a closed position of the brake 1. Usually the transmission ratio at the beginning of a stroke is greater than at an end of the actuation stroke since at the beginning of the actuation stroke an air gap 7 between the brake lining 4 and the friction lining 5 has to be overcome while at an end of the actuation stroke, the brake lining 4 rests on the friction lining 5 so that the electric motor 2 is subjected to a high counter-torque.

[0065] FIG. 2 shows a method according to the invention for producing a brake 1. In a first step 8, an electric motor 2, a brake lining 4, a friction lining 5 and a mechanical connection of these elements are selected, whereupon, in a second step 9, the brake lining 4, the friction lining 5, the mechanical connection, the electric motor 2 and, if necessary, other components acting against the counter-torque are determined. Then, in a third step 10, a transmission ratio of the transmission 3 is selected depending on the actuation stroke, such that the electric motor 2 is always operated at an optimal operating point over an actuation stroke when the electric motor 2 is actuated to operate the brake 1.

[0066] This is largely an operating point at which the electric motor 2 has maximum power so that the brake lining 4 is moved very quickly in the closing direction 6 over the air gap 7, with a transmission ratio usually being high, whereupon the brake lining 4 rests on the friction lining 5, whereupon the brake lining 4 is pressed further against the friction lining 5, with the transmission ratio usually being low.

[0067] In this regard, tolerances are usually taken into account within which the individual components of the brake 1 can exist so that an actuation is reliably possible even if the tolerances of the individual components of the brake 1 add up in the most unfavorable manner. In particular, manufacturing tolerances, friction losses in the transmission 3 and possible thermal expansions are calculated and taken into account. Furthermore, the transmission ratio is selected such that a reliable actuation is possible at an optimal operating point when the electric motor 2 is no longer able to generate a reduced motor torque due to a demagnetization at an end of a planned service life of the brake 1, due to increased temperature during operation, due to manufacturing tolerances and/or due to a reduction of a supply voltage only suitable for applying a reduced motor torque.

[0068] In addition, when designing the transmission ratio, which is not constant over the actuation stroke, it is taken into account that the elasticity of the friction lining 5 and the brake lining 4 can change due to the wear of the friction lining 5 and the brake lining 4 so that a reliable actuation is guaranteed even at a correspondingly increased rigidity.

[0069] FIG. 3 shows a counter-torque over the actuation stroke of a brake 1 with a new friction lining 5 in a solid line 11 and, for comparison purposes, a dash-dotted line 12 shows a counter-torque of a brake 1 with a worn friction lining 5 and a worn brake lining 4. As can be seen, the brake 1, in which the friction lining 5 and brake lining 4 are worn after a certain stroke in which the brake lining 4 passes the air gap 7, has a stronger increasing counter-torque, which is taken into account when configuring the transmission ratio of the transmission 3 in such a way that the engine torque is always greater than the counter-torque acting on the electric motor 2 on account of the transmission 3. As a result, the brake 1 can be reliably actuated even with aging, and the electric motor 2 can be operated at an optimal operating point.

[0070] FIG. 4 shows part of a transmission 3 of a brake 1 according to the invention, which comprises a ball ramp 14 for the structural implementation of the transmission ratio which is not constant over the actuation stroke. Two disks 13 are provided in the transmission 3, at least one of which is formed with such ball ramps 14. By rotating a disk 13, the balls are caused to roll in the ball ramps 14 such that a minimum axial distance between the two disks 13 is defined by the ball ramps 14. As a result, the brake lining 4 connected to a disk 13 on the output side can be moved in the axial direction by rotating the electric motor 2 connected to a disk 13 on the output side. A transmission ratio of the transmission 3 thus formed by the ball ramps 14 depends on a gradient of the ball ramp 14 at a respective angular position and can be configured in a simple manner as desired by means of the actuation stroke. The disk 13 can be driven directly by means of the electric motor 2 or by means of a further transmission connected to the electric motor 2, which in turn can have a linear or a non-linear transmission ratio. Furthermore, a spring can, of course, also be provided in order to support the actuation of the brake 1 and/or the release of the brake 1.

[0071] FIG. 5 shows a detail of a further embodiment of a transmission 3 of a brake 1 according to the invention in which the brake lining 4 is pressed against the friction lining 5 by means of a cam 16 or a cam disk. The cam 16 or cam disk has, on an outer contour, a variable distance from a cam axis 18 about which it is rotated by the electric motor 2. The cam 16 can be driven by the electric motor 2 by means of a gear pair 21, a pinion 20, a cam 25 rotatably mounted about a point of rotation 26, a connecting rod 24 or the like. In FIG. 5, the gear pair 21, the pinion 20, the cam 25 mounted about the point of rotation 26 and the connecting rod 24 are shown as examples of the connection between the electric motor 2 and the cam disk or the cam 16. The cam 16 can also be designed as a control disk mounted on a shaft, the center of which is located outside the shaft axis, or as a lever. The cam 16 can be actuated directly by means of the electric motor 2 or by means of a transmission connected to the electric motor 2, which in turn can have a linear or a non-linear transmission ratio.

[0072] On account of the contour of the cam 16 or the cam disk thus having a different distance from the cam axis 18, the brake lining 4 is moved or pressed in the direction of the friction lining 5 such that any transmission ratio adjustable by means of the actuation stroke can be achieved by means of the distance of the outer contour of the cam 16 or the cam disk of the cam axis 18, which is variable over a circumference of the cam 16 or the cam disk. As a result, a force applied by the electric motor 2 is translated into a pressing force 19 of different magnitudes on the basis of an actuation stroke of the brake 1. An actuating spring 22 and/or a reversing spring 23 can be provided in parallel to the electric motor 2 in order to assist with the actuation of the brake 1 and/or release of the brake 1.

[0073] Of course, other types of transmissions 3 known from the prior art can also be used as an alternative in order to achieve a transmission ratio which is not constant over the actuation stroke.

[0074] A brake 1 according to the invention can be designed not only as a disk brake but also as a drum brake. Furthermore, the brake lining 4 and the friction lining 5 can also be formed merely from components that move in a translatory manner, for example for linear displacement or up and down movements. Furthermore, the brake 1 according to the invention can be used in a motor vehicle both as a parking brake and as a driving brake.

[0075] FIG. 6 shows a detail of a transmission 3 of a brake 1 according to the invention, which comprises a control element 38 with a contour 35 for the structural implementation of the transmission ratio that can be changed over the actuation stroke, which control element 38 can be moved along a drive direction 32 by means of the electric motor 2, not shown. The drive direction 32 can, of course, also be designed as a circular path, for example, about an axis of rotation 15 of the electric motor 2. The following considerations apply analogously for a rotatably mounted cam 16, a control disk by means of which the actuation takes place or the like.

[0076] A first contact position 33 and a second contact position 34 on the contour 35 are shown by way of example, at which contact positions 33, 34 an element connected to the brake pad 4 can slide in order to actuate the brake pad 4 by means of the electric motor 2 connected to the control element 38 in the closing direction 6. A local gradient of the contour 35 results in a transmission ratio from a movement of the contour 35 in the drive direction 32 to a movement of the brake lining 4 in the output direction or in the closing direction 6. The transmission ratio is consequently higher in the first contact position 33 than in the second contact position 34. In order to achieve a required closing force, however, a resulting supporting force 37 in the first contact position 33 perpendicular to the closing direction 6, which can lead to self-locking even at a low friction, is significantly higher than in the second contact position 34. In parallel to the closing force with which the brake lining is pressed against the friction lining, the closing reaction force 36 acts on the contour as shown. In order to prevent self-locking, the invention provides that, when determining the transmission ratio at the contour 35, the friction that occurs is taken into account in such a way that self-locking is avoided even in the event of friction that occurs in the worst case. This avoids a gradient of the contour 35, which is mathematically required to achieve a very high transmission ratio that is necessary, for example, for overcoming the air gap 7 but that would not be practically feasible due to the friction occurring on account of the self-locking.

[0077] FIG. 7 schematically shows a brake 1 designed according to the invention, which can be actuated both by means of the electric motor 2 and the transmission 3 and by means of a cable attached to a cable connection 28. The transmission 3, not shown here, to which the electric motor 2 is connected, acts on an actuating part 31 to which the brake lining 4 is connected. A transmission element 30, which comprises the cable connection 28, is also connected to the actuating part 31 so that the actuation part 31 can be actuated both by means of the cable connection 28 and by means of the electric motor 2. As can be seen, the transmission element 30 is rotatably mounted about the axis of rotation 15 of the actuating part 31 in the housing 27 of the transmission 3. The actuating part 31 with the transmission element 30 is rotatably mounted by means of a driver 29. The driver 29 can be connected to the actuating part 31 in such a way that a movement of the driver 29 is transmitted to the actuating part 31, but a movement of the actuating part 31, which can be caused by the electric motor 2, does not cause a movement of the transmission element 30 or the cable connection 28. As a result, a corresponding brake 1 can easily be used both as a driving brake and as a parking brake in a motor vehicle. Due to the sealed mounting of the transmission element 30 in the transmission 3 and the cable connection 28 arranged outside the transmission 3, the cable can remain outside the transmission 3 so that sealing problems that would arise if a moving cable were to pass through the housing 27 of the transmission 3 are avoided.

[0078] FIG. 8 shows a brake 1 according to the invention designed as a floating caliper brake. As can be seen, brake linings 4 are arranged on both sides of a friction lining 5, which is usually formed by a brake disk and which can be actuated by mechanically connected cams 16, which can be moved synchronously in opposite directions. The transmission ratio between an electric motor 2 (not shown) actuating the cams 16, which can be changed by means of the actuation stroke, and the movement of the brake linings 4 is realized here by means of the cams 16. Ball ramps 14 or other transmissions 3 could be used here as well. Furthermore, a spring 23 can also be provided here, as shown by way of example, in order to assist with the actuation or the opening of the brake 1. The electric motor 2 (not shown) can apply an actuating force 41 on the cams 16 by means of a lever, as shown, or also directly, of course. Alternatively, the electric motor 2 can also act on the cams 16 by means of an actuating cam 40, which is also shown for the purpose of illustration. As can be seen, the cams 16 are connected by means of a connecting element 39 such that the cams 16 move synchronously.

[0079] The brake 1 shown in FIG. 8 can be used for an elevator and arranged vertically in the elevator shaft, for example, by connecting the brake linings 4 to an elevator car and forming the friction lining with an element connected to the elevator shaft. The components of the brake 1 shown in FIG. 8 are thus generally arranged on the elevator car. The electric motor 2, not shown in FIG. 8, which acts on the cams 16, is generally arranged on the elevator car as well. When actuated, the brake 1 is centered by a horizontal movement of the elevator car such that both brake linings 4 rest equally on the friction lining 5 that is rigidly connected to the elevator shaft. Alternatively, the brake 1 shown in FIG. 7 can also be designed as a fixed caliper brake.