Permanentmagnetretarder

Abstract

Permanent magnet retarder 1.1 with a rotor (1) rotating about an axis of rotation (10) and a stator (2), one of which carries a plurality of permanent magnets (3) arranged in a circumferential direction above the axis of rotation (10) with alternating polarity and the other comprising at least one or more areas of magnetizable material facing the permanent magnets (3); 1.2 with a switching element (4) between the permanent magnets (3) and the at least one area of ​​magnetizable material, wherein 1.3 the switching element (4) extends in a disk-shaped, ring-shaped or ring-segment-shaped circumferential direction over the axis of rotation (10) between the rotor (1) and the stator (2) such that magnetizable return elements (5) alternate with non-magnetizable intermediate elements (6) of the switching element (4) in the circumferential direction; and 1.4 with at least one actuator (7) by means of which the permanent magnets (3) relative to the switching element (4) and / or the switching element (4) relative to the permanent magnets (3) can be rotated reciprocally in the circumferential direction in order to position the return elements (5) opposite the permanent magnets (3) in a first position and the intermediate elements (6) opposite the permanent magnets (3) in a second position; wherein 1.5 the force to be applied by the actuator (7) during its actuation to return the permanent magnets (3) and / or the switching element (4) from the first position to the second position is smaller at a comparatively high rotational speed of the rotor (1) than at a comparatively lower rotational speed; 1.6 The actuator (7) comprises an elastic restoring element (13) which exerts a restoring force on the permanent magnets (3) and / or the switching element (4) in the sense of rotating the permanent magnets (3) and / or the switching element (4) into the second position; characterized in that 1.7 the elastic restoring element (13) has a spring stiffness that is greater than the force required to restore the permanent magnets (3) and / or the switching element (4) at the comparatively high rotational speed of the rotor (1) and less than the force required to restore the permanent magnets (3) and / or the switching element (4) at the comparatively lower rotational speed.

Description

[0001] The present invention relates to a permanent magnet retarder, in particular with the features according to the preamble of claim 1.

[0002] A generic permanent magnet retarder is described, for example, in the published patent applications JP 2003-209 965 A and JP 2003-209 966 A. These published patent applications disclose the circumferential displacement of the permanent magnets, which are held by a circular magnet carrier, relative to a switching element radially surrounding the magnet carrier between the permanent magnets and the rotor by means of a double-acting cylinder, in order to switch the permanent magnet retarder on and off. To enable the permanent magnet retarder to be switched off even if the compressed air control of the double-acting cylinder fails, a compression spring is arranged in one of the two cylinder chambers. This spring exerts a force on the piston of the cylinder and thus on the magnet carrier, thereby returning it to the off position.According to the two published patent applications, this spring has a non-linear spring characteristic or spring stiffness, with a first range, starting from the maximum compression state and moving toward the relaxed state, exhibiting a particularly high spring stiffness, followed by a second range with a comparatively lower spring stiffness. In this first range of spring travel, the compression spring is capable of generating such a high restoring force on the magnet carrier that it is reliably reset by the compression spring, even at low rotor speeds, where the resistance force or moment of resistance of the magnet carrier with respect to this reset is particularly high, up to half the reset travel.

[0003] A disadvantage of the described design is that this very high spring force must be overcome by operating the actuator in the form of a double-acting cylinder when the permanent magnet retarder is to be activated, by rotating the magnet carrier against this spring force. This means that the double-acting cylinder must be designed to be comparatively robust, and the actuation pressures are correspondingly high.

[0004] The present invention is based on the object of specifying a permanent magnet retarder in which a safe switching off is achieved even in the event of failure of the control of an actuator and at the same time the force required for switching on is comparatively low.

[0005] The object of the invention is achieved by a permanent magnet retarder having the features of claim 1. Advantageous and particularly useful embodiments of the invention are specified in the dependent claims.

[0006] The permanent magnet retarder according to the invention comprises a rotor rotating about a rotational axis and a stator. The rotor or the stator carries a plurality of permanent magnets arranged one behind the other in the circumferential direction about the rotational axis and aligned with alternating polarity. The other component (the rotor if the stator carries the permanent magnets, and the stator if the rotor carries the permanent magnets) comprises at least one region facing the permanent magnets made of a magnetizable material or a plurality of such regions facing the permanent magnets made of a magnetizable material. According to a favorable embodiment in which the stator carries the permanent magnets, the entire rotor, or an entire ring of the rotor opposite the stator, is made of such a magnetizable material, for example iron or steel.

[0007] In order to enable the switching on and off of the permanent magnet retarder, which is in particular free of magnetic coils for generating the braking torque, a switching element is provided between the permanent magnets and the at least one region made of magnetizable material, in particular the rotor. For example, the stator can carry the plurality of permanent magnets by means of a magnet carrier, wherein the magnet carrier is then designed in particular in a ring-shaped manner, and the rotor can enclose the stator or the magnet carrier with the permanent magnets in a ring-shaped manner radially from the inside or radially from the outside. The switching element is then arranged between the rotor and the magnet carrier or the permanent magnets, wherein in particular the magnet carrier, the switching element and the rotor are positioned concentrically to one another.

[0008] The switching element extends in a disk-shaped, ring-shaped, or ring-segment-shaped manner in the circumferential direction over the rotational axis of the rotor and between the rotor and the stator, such that magnetizable return elements of the switching element alternate with non-magnetizable intermediate elements of the switching element in the circumferential direction. Thus, by a relative rotation between the switching element and the permanent magnets, it is now possible to position the return elements opposite the permanent magnets in a first position, in particular in the radial direction, and to position the intermediate elements opposite the permanent magnets in a second position, in particular in the radial direction.This adjustment of the switching element and / or the permanent magnets, the latter in particular via the magnet carrier, by means of a rotation, in particular a limited rotation of the adjustable element in the circumferential direction, is effected by means of an actuator that can effect both a rotation from the first position to the second position and from the second position to the first position. Of course, it is also possible to provide a first actuator for the rotation from the second position to the first position and a second actuator for the rotation from the first position to the second position. A plurality of such actuators can also be provided, either for alternating rotation or for respective rotation in only one direction.

[0009] In the first position, when the return elements face the permanent magnets, a magnetic field is generated from the stator via the return elements into the rotor and back into the stator. When the rotor rotates or is driven by a drive train, particularly a vehicle such as a passenger car, truck, or rail vehicle, the rotor and thus the drive train are decelerated due to the magnetic field(s).If, however, the intermediate elements are positioned opposite the permanent magnets in the second position, the return elements short-circuit two permanent magnets arranged adjacent to each other in the circumferential direction with opposite polarity, so that only a "small" magnetic circuit or circular magnetic field is established between the permanent magnets and the return elements. This magnetic circuit does not extend beyond the system boundary between the rotor and stator and thus does not flow through both the rotor and the stator. Accordingly, the rotor can rotate freely relative to the stator or essentially without being decelerated by a magnetic field; the permanent magnet retarder is deactivated.

[0010] As those skilled in the art will know, the force required by the actuator during its actuation, particularly by means of a pressure control device, to return the permanent magnets and / or the switching element from the first position to the second position, i.e., to deactivate the permanent magnet retarder, is smaller at a comparatively high rotor speed than at a comparatively lower rotor speed. This means that below a predetermined limit of the rotational speed, a comparatively greater force must be applied for the return or deactivation than at a rotational speed above the predetermined limit.

[0011] In order to enable the permanent magnet retarder to be reset or switched off even in the event of a failure of the "normal" control of the actuator, also referred to as active control, the actuator comprises an elastic reset element which can be provided locally inside the actuator or outside the actuator, assigned to it, which exerts a restoring force on the permanent magnets and / or the switching element, depending on which component is rotatable in the circumferential direction, in the sense of rotating the permanent magnets and / or the switching element into the second position, i.e. in the sense of switching off the permanent magnet retarder.According to the invention, this elastic return element has a spring stiffness which is greater than the force to be applied to return the permanent magnets and / or the switching elements at the comparatively high speed of the rotor, but at the same time smaller than the force to be applied to return the permanent magnets and / or the switching element at the comparatively lower speed of the rotor.

[0012] The inventive design is based on the finding that a reliable reset or deactivation of the permanent magnet retarder can be achieved even when the spring stiffness or elastic force of the elastic reset element is insufficient to effect reset in all operating situations, namely at lower rotor speeds. These lower speeds are followed by higher speeds, at which the required reset force is reduced, and which the elastic reset element can then overcome. At the same time, at lower speeds with the comparatively large required reset force, there is no risk of excessive heating of the permanent magnet retarder due to the low rotor speed.Only at higher speeds, when the risk of overheating increases, does the elastic return element engage and automatically or independently switches off the permanent magnet retarder.

[0013] However, the reduced elastic force or spring stiffness of the elastic return element also has the advantage that when the permanent magnet retarder is switched on or when the permanent magnets and / or the switching element are rotated from the second position to the first position, a lower force must be applied by the usual control of the actuator in order to overcome the force of the elastic return element.

[0014] It is advantageous if the at least one actuator comprises a double-acting pressure cylinder, with a first cylinder chamber to which a control pressure medium can be applied, and a second cylinder chamber to which a control pressure medium can be applied. The first cylinder chamber is separated from the second cylinder chamber by a piston in a pressure-tight or control pressure-medium-tight manner. The piston is displaceable in such a way that, in a first direction of displacement, it enlarges the first cylinder chamber and reduces the second cylinder chamber, and in a second, opposite direction of displacement, it reduces the first cylinder chamber and enlarges the second cylinder chamber. A piston rod or an equivalent element is connected to the piston, via which the rotation of the permanent magnets, in particular of the magnet carrier carrying the permanent magnets, and / or of the switching element is effected directly or indirectly.Accordingly, the piston rod or the corresponding element is directly or indirectly connected to the permanent magnet or the magnet carrier and / or the switching element.

[0015] It is advantageous if the elastic return element applies the return force to the piston and / or the piston rod. For example, the elastic return element can be positioned in the first or the second cylinder chamber and, in particular, can be supported with a first axial end on the piston and with its second axial end on a wall of the cylinder chamber. For example, the elastic return element can be designed as a compression spring, the first end of which is supported on the piston and the second end of which is supported inside on the end face of the housing of the pressure cylinder. It is advantageous if the elastic return element is always supported on the piston and on the wall or end face of the housing, so that no play occurs between the elastic return element and the piston or at the opposite axial end of the wall.

[0016] The elastic return element can have a linear spring stiffness over the spring travel.

[0017] Furthermore, the elastic return element can be designed in one part or in several parts, whereby it is advantageous if the elastic return element is the only elastic return element of the permanent magnet retarder, which exerts a return force on the switching element and / or the permanent magnets, in particular held in the magnet carrier.

[0018] According to the invention, a pressure control device can be provided that alternately fills the first cylinder chamber and the second cylinder chamber with control pressure medium, usually via a control pressure medium connection in each cylinder chamber. This alternate filling serves the previously described "normal" control of the actuator to switch the permanent magnet retarder on and off.

[0019] Although not further described here, one or more single-acting cylinders or multiple double-acting cylinders can be used instead of a double-acting cylinder. Other actuators, such as electrically or magnetically driven actuators, are also possible.

[0020] The invention will be described below using an exemplary embodiment.

[0021] They show: Fig. 1 shows a cut-out area of ​​an axial section through a permanent magnet retarder designed according to the invention in a schematic representation in the switched-on state; Fig. 2 the corresponding area of Fig. 1 when switched off.

[0022] In the Fig. In the embodiment shown in Figure 1, the rotor 1 surrounds the stator 2 in the circumferential direction. The rotor 1 rotates about the rotational axis 10 and is arranged concentrically with the stator 2.

[0023] The stator 2 has an annular magnet carrier 18 that is circumferentially displaceable relative to a radially inner, fixed core region 2.1, which carries a plurality of permanent magnets 3. The permanent magnets 3 are arranged one behind the other in the circumferential direction above the rotation axis 10 with alternating polarity, i.e., all permanent magnets 3 in the sequence with an even position number have a radially outer north pole and a radially inner south pole, and all permanent magnets 3 with an odd position number have a radially outer south pole and a radially inner north pole.

[0024] Arranged radially between the rotor 1 and the permanent magnets 3 is a switching element 4, which can be designed in a stationary manner, for example, as a housing shell of the stator 2. The switching element 4 has a ring shape, and in the circumferential direction, magnetizable return elements 5 alternate with non-magnetizable intermediate elements 6. The return elements 5 are made, for example, of steel or iron, and the non-magnetizable intermediate elements 6 are made of aluminum.

[0025] If now, as in the Fig. 1, the return elements 5 are opposite the permanent magnets 3 in the radial direction, in particular are aligned with one another, a magnetic field can be formed which extends from the stator 2 into the rotor 1 and back. As shown, for example, the outer magnetic flux lines of the magnetic field extend from a first permanent magnet 3 through the opposite first return element 5 into the rotor 1, which is made in particular of steel or iron, in the circumferential direction along the rotor 1, back through a second return element 5 radially inwards through a second permanent magnet 3 and back in the opposite circumferential direction as in the rotor 1 through the magnet carrier 18, which can accordingly also be made of steel or iron, again into the first magnet 3. If, however, as in the Fig. 2, the intermediate elements 6 are opposite the permanent magnets 3 in the radial direction, so a return element 5 bridges two permanent magnets 3 arranged adjacent to one another, whereby a smaller magnetic field is achieved which does not reach into the rotor 1.

[0026] Accordingly, the position in the Fig. 1, which is referred to here as the first position, the stator 2 exerts a braking effect on the rotor 1 by means of the magnetic fields, whereas in the position referred to here as the second position according to the Fig. 2 no braking torque is exerted by a magnetic field on the rotor 1. In the first position, the permanent magnet retarder is therefore switched on, and in the second position, the permanent magnet retarder is switched off.

[0027] For the limited displacement of the magnet carrier 18 in the circumferential direction, an actuator 7 is connected to it, which is formed by a double-acting pressure cylinder 8. The pressure cylinder 8 has a first piston chamber 9, which includes a control pressure connection 14, via which a control pressure medium can be introduced into the first cylinder chamber 9 in order to thereby displace the piston 10 in the sense of extending the piston rod 12. On the side of the piston 10 facing away from the first cylinder chamber 9, a second cylinder chamber 11 is provided, also with a control pressure connection 15. By introducing the control pressure medium via the control pressure connection 15 into the second cylinder chamber 11, the piston 10 is displaced in the sense of retracting the piston rod 12.

[0028] By extending the piston rod 12, the magnet carrier 18 is moved to the first position and the permanent magnet retarder is activated. By retracting the piston rod 12, the magnet carrier 18 is moved to the second position and the permanent magnet retarder is deactivated.

[0029] Positioned in the second cylinder chamber 11 is an elastic return element 13 in the form of a compression spring, which is clamped between a wall, here the end face of the housing of the pressure cylinder 8, and the piston 10 and exerts a force on the piston 10 in the sense of retracting the piston rod 12. Accordingly, the elastic return element 13 exerts a return force in the sense of deactivating the permanent magnet retarder.

[0030] According to the invention, the restoring force of the elastic restoring element is in any state such that it is smaller than the force required to return the magnet carrier 18 to the second position when the rotor 1 rotates at a comparatively low speed. However, when the rotor 1 rotates at a comparatively high speed, the restoring force of the elastic restoring element 13 is sufficient to return the magnet carrier 18 to the position specified in the Fig. 2 shown second position.

Claims

[1] Permanent magnet retarder 1.1 with a rotor (1) rotating about an axis of rotation (10) and a stator (2), one of which carries a plurality of permanent magnets (3) arranged one behind the other in the circumferential direction about the axis of rotation (10) with alternating polarity and the other of which comprises at least one or more regions of magnetizable material facing the permanent magnets (3); 1.2 with a switching element (4) between the permanent magnets (3) and the at least one area of ​​magnetizable material, wherein 1.3 the switching element (4) extends in a disc-shaped, annular or ring-segment-shaped manner in the circumferential direction over the axis of rotation (10) between the rotor (1) and the stator (2) such that magnetizable return elements (5) alternate with non-magnetizable intermediate elements (6) of the switching element (4) in the circumferential direction; and 1.4 with at least one actuator (7), by means of which the permanent magnets (3) can be rotated in the circumferential direction relative to the switching element (4) and / or the switching element (4) relative to the permanent magnets (3) in order to position the return elements (5) opposite the permanent magnets (3) in a first position and to position the intermediate elements (6) opposite the permanent magnets (3) in a second position; wherein 1.5 the force to be applied by the actuator (7) during its actuation to return the permanent magnets (3) and / or the switching element (4) from the first position to the second position is smaller at a comparatively high speed of the rotor (1) than at a comparatively lower speed; 1.6 the actuator (7) comprises an elastic return element (13) which exerts a return force on the permanent magnets (3) and / or the switching element (4) in the sense of a rotation of the permanent magnets (3) and / or the switching element (4) into the second position; characterized by , that 1.7 the elastic return element (13) has a spring stiffness which is greater than the force to be applied to return the permanent magnets (3) and / or the switching element (4) at the comparatively high speed of the rotor (1) and is smaller than the force to be applied to return the permanent magnets (3) and / or the switching element (4) at the comparatively lower speed. [2] Permanent magnet retarder according to claim 1, characterized byin that the actuator (7) comprises a double-acting pressure cylinder (8), comprising a first cylinder chamber (9) to which a control pressure medium can be applied, and a second cylinder chamber (11) which is pressure-tightly separated from the first cylinder chamber (9) by a displaceable piston (10), wherein the piston (10) is at least indirectly connected to the switching element (4) via a piston rod (12) or the like for rotating the permanent magnets (3) and / or the switching element (4), and the elastic restoring element (13) applies the restoring force, in particular to the piston (10) or the piston rod (12). [3] Permanent magnet retarder according to claim 2, characterized by that each cylinder chamber (9, 11) has at least one control pressure connection (14, 15) for introducing the control pressure medium. [4] Permanent magnet retarder according to one of claims 2 or 3, characterized bythat the elastic return element (13) is positioned in the first or the second cylinder chamber (9, 11) and in particular is always supported with a first axial end on the piston (10) and with a second axial end on a wall of the cylinder chamber (9, 11). [5] Permanent magnet retarder according to one of claims 1 to 4, characterized by that the elastic return element (13) is designed as a compression spring or tension spring, in particular with a linear spring stiffness over the spring travel. [6] Permanent magnet retarder according to one of claims 2 to 5, characterized by that a pressure control device is provided which alternately fills the first cylinder chamber (9) and the second cylinder chamber (11) with the control pressure medium for the controlled actuation of the actuator (7). [7] Permanent magnet retarder according to one of claims 1 to 6, characterized bythat the elastic return element (13) is designed in one part or in several parts, but is the only elastic return element (13) of the permanent magnet retarder which exerts a return force on the permanent magnets (3) and / or the switching element (4). [8] Permanent magnet retarder according to one of claims 1 to 7, characterized by that the rotor (1) extends in a ring shape outside the stator (2) around the latter, the switching element (4) encloses the permanent magnets (3) radially from the outside, the permanent magnets (3) are rotatable to a limited extent in the circumferential direction and the switching element (4) is held stationary.

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