DE19605412A1 - Electrodynamic DC linear motor with active braking device - Google Patents

Abstract

The braking device is an active piezoelectric, magnetostrictive or shape memory element (5) which positions the body (6) of the "rotor" with its coil (2) opposite the fixed magnetic circuit comprising a flux guide (3) and permanent magnet (4) in the housing (1) of the stator. The brake is released automatically as soon as current passes through the motor to generate movement. It reshapes the direction of expansion with transmission of force or motion, and is applied within a very short time of attainment of standstill.

Description

The invention relates to a direct current linear motor according to the electrodynamic effect principle. This motor uses the force on moving loads of an energized conductor wick in a magnetic field. The magnetic field can either be from a permanent magnets or generated by a second current-carrying conductor winding. For Use of the relative force acting between the two subsystems is one of the two subsystems (e.g. the energized conductor winding) stationary and thus stator, and that other subsystem (in the example the permanent magnet or a second conductor winding) represents the moving output of the arrangement so the rotor.

Motors of this design are not self-locking. A position can be based on its Can only be reached under load by an active control loop with measuring system. Actuator and Regulator are held. This means that even when the drive is at a standstill a load-dependent electrical power must be supplied to the conductor winding. At standstill, the electrical energy supplied is completely converted into thermal Power loss implemented. This leads to the heating of the engine and because of the be limit permissible overtemperature of the motor ultimately also to limit the maximum holding force of the drive.

DC linear motors are known which enable currentless holding by in the two end positions permanent magnetic fields (DT AS 2229332) or stray fields (DT AS 2118101) can be used. A currentless stop in any position is with not possible with these motors. Within the end positions, i.e. in the normal position nierbetrieb, holding the position is here only via an active control loop with the mentioned disadvantages realizable.

On the other hand, clamping devices made of stepper motors with mechanical ones are known Clamping (DD AP 91857) and so-called inchworm motors. They serve the Support of the feed movement on the clamping point and the position fixation. For Performing a movement step requires two clamping processes. The ge The entire movement process contrasts with the continuous movement a series of electrodynamic direct current linear motors of single steps.

Due to the technically feasible step size, the feed movement of  Stepper drives with clamping very slow and for highly dynamic positioning tasks not suitable. They also have each because of the high number of clamping operations Movement process only short downtimes.

The object of the solution according to the invention is to maintain the high dynamic Mix movements very advantageous DC linear motor principle a powerless or extremely poor performance after completing complete movements to enable in any position with high holding forces.

This problem becomes linear with the electrodynamic direct current linear according to the invention motor with active clamping by those listed in claim 1 and following Features resolved.

The basic idea of the solution according to the invention is the installation of a switchable brake, through which the movable rotor can be fixed relative to the fixed stator. On very quickly responsive component in this brake allows, after completing the Movement to hinder the movement until a new change of position or to block completely.

There is an advantageous embodiment of the DC linear motor according to the invention according to claim 2 in that the energization of the motor for movement generation simultaneously releases the brake, and in the de-energized state Brake is set.

A direct current linear motor according to the invention exists according to claims 3 and 4 for example from a first subsystem with a coil attached to it and one second subsystem with a magnetic circuit of at least one permanent magnets, a magnetic yoke and a housing, between which there are am small air gap, and each of these subsystems the moving output and so that the runner can form, the other subsystem then the fixed one Represents stator.

The brake contains according to claims 5 and 6 for fixing the rotor for example a piezoelectric or magnetostrictive element or an element from a shape memory alloy, the expansion or contraction of the piezoelectric trical or magnetostrictive element or the element from shape memory alloy tion (hereinafter referred to as the active element) at a standstill within a very short time one by frictional or positive locking of the runner relative to the location fixed stator in any position without power or with reduced power.  

During blocking by positive locking, for example by moving effective undercuts can only be done in discrete intervals or steps, the position attainable is not affected by a clamping by flat friction flows. The clamping can directly according to the embodiment of claim 7 by stretching or contraction of an active element perpendicular to the contact surface So in the direction of the surface normal or according to the design according to An say 8 and 9 by reshaping the direction of expansion and additional force or Path translation can be realized.

There is a further embodiment of the direct current linear motor according to the invention according to claim 10 in that an active element made of magnetostrictive material is so integrated in the drive coil of the DC linear motor that the magnetic field of the energized drive coils themselves causes the expansion of the active element and the Clamping the moving part to the stationary part during the movement thereby releases and in the de-energized state the clamp inevitably closes again.

Further advantageous refinements of the direct current linear motor according to the invention exist in accordance with claim 11 in the use of actuating current or voltage to control the active element of the clamp by suitable connection to the Drive coil over a rectifier bridge, so that regardless of the current direction in the drive coil always loosened the clamp with current flow and always without current flow closed is. This inevitably releases the downforce during the movement ben and inevitably fixed again after completion of the movement.

This additional temporary active clamping device inside the motor thus enables any position even under load without or with reduced Holding power loss and generating high holding forces.

Embodiments of the arrangements are described in more detail in the accompanying drawings ( FIGS. 1 to 6). They represent:

Fig. 1 shows a rotationally symmetrical DC linear motor with a piezoelectric tube for clamping the moving inner part. The enlargement of the inner tube diameter is exploited by the expansion of the piezo material in the circumferential direction.

Fig. 2 shows a rotationally symmetrical DC linear motor with a piezoelectric tube for clamping the moving inner part. The expansion of the piezo tube in the axial direction, which clamps the inner part via an elastically deformable element, is used.

Fig. 3 is a rotationally symmetrical DC linear motor with a tube made of magnetostrictive material in the homogeneous field area of the drive coil.

Fig. 4 enlarged view of a design of the intermediate element for mechanical rectification of a signed elongation, for example, a biased magnetostrictive material.

Fig. 5 is a block diagram of the control circuit of the drive coil and the control of the clamping device with a piezoelectric active element.

Fig. 6 is a block diagram of the control circuit of the drive coil and the control of the clamping device with an active element made of a shape memory alloy.

The three illustrated embodiment variants according to FIGS. 1 to 4 consist of two subsystems which are movable relative to one another, the relative movement of which can be prevented or hindered by differently designed clamping points according to patent claims 6 to 9. In the exemplary embodiments shown, the motor is driven via the moving subsystem 1 (inner part rotor) consisting of the body ( 6 ) and the coil ( 2 ). The fixed subsystem 2 (outer parts stator) of the motor is stationary. The body ( 6 ) of the rotor is a component which is elongated in the direction of movement of the motor, the cross section of which is perpendicular to the axis of movement and is tapered on the output side beyond the length of movement of the motor in the examples shown.

At the opposite end, the body ( 6 ) has a groove extending in the direction of movement over the range of movement of the motor for receiving a solenoid-shaped coil ( 2 ). Between the groove and the end face of the body ( 6 ) facing away from the driven side, a narrow collar remains for fixing the coil in the direction of movement. The outer contour of the coil inserted into the groove is minimally set back from the maximum extension of the body ( 6 ) perpendicular to the axis of movement. On the coil side, the body ( 6 ) has an end-side bore which is made coaxially with the coil-slot geometry and whose depth is greater than the slot width, including the collar which remains on the front side. The wall between the hole and the bottom of the groove is very thin.

The area of the maximum cross section of the body ( 6 ) forms the contour of the guide surface to the subsystem 2nd The cross section of the body ( 6 ) remains constant over the range of motion.

In the exemplary embodiments according to FIGS. 1 and 2, the cross section of the body ( 6 ) is identical to the inner contour of the guiding and active element ( 5 ). The length of the guide area of ( 6 ) is at least the length of part ( 5 ) plus the maximum engine stroke.

The element ( 5 ), which is either a guide and active element as in the exemplary embodiment according to FIG. 1 or only an active element as shown in FIG. 2, is permanently installed in the housing ( 1 ). The housing serves as a carrier element of the components of the second subsystem and consists of magnetically non-conductive material. It encloses the motor on all sides with the exception of the driven side, on which the body ( 6 ) has a reduced cross section. The inner shape of the housing ( 1 ) corresponds to the outer contour of the guide and active element ( 5 ). On the driven side opposite lying side of the housing ( 1 ) there is a cup-shaped flux guide ( 3 ) which extends in the longitudinal direction over the entire coil area. The Flußleit piece ( 3 ) consists of magnetically good conductive material and serves to guide the flow. Together with the permanent magnets ( 4 ) protruding into the bore of the body ( 6 ) and a pole piece placed in the direction of the base of the bore, the flux guide ( 3 ) forms a permanently excited magnetic circuit. There is a small air gap between the flux guide ( 3 ) and the coil ( 2 ) or the body so that there is no contact.

In the embodiment of the clamp according to Fig. 1 is located between the Flußleit piece (3) and the guiding and active element (5) has a spacer sleeve (8) having a certain resilience, which can also take over management tasks. The three components ( 8 ), ( 5 ) and ( 3 ) are preloaded in the housing ( 1 ) via a clamping nut ( 7 ) in the direction of the axis of movement. Contact with the body ( 6 ) takes place on the inner surface of the guiding and active element ( 5 ) and on other parts with guiding tasks, such as the spacer sleeve ( 8 ). The guide and active element ( 5 ) in this variant of the clamping consists of a piezoelectric tube with front electrodes. By applying a voltage to the correspondingly polarized and axially pre-stressed piezo material, a volume change takes place which, as a transverse effect, leads to the expansion of the inner shape and thereby to the release of the frictional engagement with the body ( 6 ). When the voltage is applied, the subsystem 1 can be installed or moved relative to the subsystem 2 consisting of the components ( 1 ), ( 3 ), ( 4 ), ( 5 ), ( 7 ) and ( 8 ). The tension remains applied until the end of the movement process. After switching off the voltage, the inner shape contracts again to the original dimension, whereby the subsystem 1 is clamped in the guide or active element ( 5 ). Clamping therefore takes place in the electrically voltage-free state of the active element and thus free of energy.

In Fig. 2, a deformation body ( 9 ) is installed between the active element ( 5 ) and the flux guide ( 3 ) instead of the spacer sleeve ( 8 ). This deformation body also takes on additional management tasks. Due to the biasing force applied in the direction of movement, on the one hand the active piezoelectric element ( 5 ) is mechanically pre-tensioned, on the other hand the deformation body ( 9 ) is elastically deformed and thereby expands perpendicular to the direction of movement. Subsystem 1 is thus clamped. Applying a correspondingly polarized voltage to the piezoelectric active element ( 5 ) now leads to a contraction of the active element ( 5 ) in the direction of movement with correct polarity. This relieves the deformation body ( 9 ) and releases the clamping. The active piezoelectric element ( 5 ) is used either with regard to the transverse effect, in this case the electrodes on the cylinder surfaces outside and inside, so that the inner surface does not take on any additional management tasks. On the other hand, the active piezoelectric element ( 5 ) can also be used with regard to its longitudinal effect; the electrodes are then arranged on the end face.

Necessary isolations are generally not shown in the pictures, they have to be removed corresponding to the potentials permitted in the respective applications be introduced.

In the embodiment according to Fig. 3 and 4, the subsystem 1 is guided by means of a Gleitführungsbuchse (10). This sliding guide bush ( 10 ) is pressed into the housing ( 1 ). A hollow cylinder made of magnetostrictive material ( 13 ) is used as the active element of the clamping. The hollow cylinder is biased in the direction of movement in the bore of the body ( 6 ). Between the bottom of the bore and the hollow cylinder ( 13 ) there is a spacer sleeve ( 12 ) and on the other side of the hollow cylinder there is a switching sleeve ( 14 ) with an internal cam geometry that runs perpendicular to the axis of movement and is designed as a wedge that acts on both sides. The power flow is closed via a plate spring assembly ( 15 ) which adjoins in the direction of movement and a screwed clamping nut ( 11 ). The clamping nut ( 11 ) has a clamping collar which protrudes into the switching sleeve ( 14 ) and which is widened in the form of a lens in the area of the switching cam, so that contact to the switching cam and contact to subsystem 2 take place from the inside. The geometry of the switching cam and the clamping collar is designed so that in the position in which the lenticular widening of the clamping collar is located at the highest point of the cam, the clamping collar is deformed inwards perpendicular to the direction of movement, and clamping between subsystem 1 and 2 takes place.

By applying a voltage and driving a current through the coil ( 2 ), the magnetostrictive hollow cylinder ( 13 ) will expand or contract in the direction of movement depending on the direction of the field if the coil is dimensioned accordingly. In both deformations, the position of the switching sleeve changes so that the clamping collar on the clamping nut ( 11 ) springs open and the clamping is released. The above-mentioned voltage or current represents the voltage or current which provides for the motor movement, that is to say no additional control voltage or additional control current. The release of the clamping takes place automatically only during the movement. After the coil current has been switched off, clamping is carried out again immediately. The clamping is energy-free.

Instead of the magnetostrictive material, the active element ( 13 ) could also consist of piezoelectric material in this embodiment, which is so polarized that the same strains occur as with the magnetostrictive material when a voltage is applied.

The solutions according to FIGS. 1 to 4 can be operated both with separately controlled Klemmvor direction and with the clamping current controlled via the coil current. When operating via the coil current, a configuration of the arrangement that is independent of the current direction must be provided. This can be done either by the design of the mechanical components according to FIGS. 3 and 4, which releases the clamping both when stretching and when contracting the piezoelectric or magnetostrictive material and only clamps in the de-energized state, or in the case of piezoelectric clamping also by interposing rectifiers (e.g. A Graetz rectifier stage) between the coil and the piezo element.

Instead of the piezoelectric active elements ( 5 ) or the magnetostrictive active element ( 13 ) it is also possible to use active elements on a thermal basis, for example active elements made of shape memory alloy, which change their shape very quickly when the switching temperatures are exceeded or fallen below. This change in shape is then used in the same way with the same structure for realizing the clamping.

FIGS. 5 and 6 show embodiments for the control of the Klemmelemen te to the illustrated and above-described embodiments, as a block diagram.

In Fig. 5 an embodiment for controlling the clamping with piezoelectric active elements is shown. In order to realize a clamping at standstill and a release of the clamping device when the motor coil is energized, a control of the motor coil with a pulse-width-modulated servo is proposed more strongly in this variant.

The pulse width modulated output voltage of the servo amplifier becomes one of the Motor coil supplied and the other a rectifier bridge, for. B. a Graetz Circuit. This converts the AC voltage into a DC voltage. The one here generated by direct voltage is directly on the piezo element. Since the AC chip voltage amplitude of the servo amplifier is constant, stands above the rectification and a Smoothing always a constant DC voltage to control the clamping device to disposal. The capacitance of the piezo element acts as a smoothing capacitor. The ripple voltage component can be further increased by connecting capacitors in parallel decrease, but at the same time the dynamic properties of the Clamping device.

With 4-quadrant pulse adjusters that operate asymmetrically, the pulse width modul has voltage only one polarity to ground, i. H. it is either positive or negative direction, and the integral value of the AC voltage corresponds to that Amount of DC voltage. The servo amplifier output is without additional measures voltage is therefore zero in the idle state and this pulse regulator variant without on restriction usable.

If a 4-quadrant pulse controller with symmetrical pulse width modulation is used, there is a pulse width modulated AC voltage that is symmetrical to the ground supply, the integral value of a positive or negative effective DC voltage corresponds. In this case it must be ensured that the AC output voltage when the motor system is at a standstill, for example by switching off the servo amplifier in the target position.  

An embodiment of a control of a thermally operating active elemen tes, for. B. from shape memory alloy, shows Fig. 6, wherein an actuator is used as an analog servo amplifier.

The thermally working active element is, for example, directly as an electrical Resistor (R1 or R2) is connected to the motor circuit and heats up directly through the coil current. Indirect heating via heating wires, which then the represent electrical resistances and are switched into the motor circuit also possible. The heating wires could, for example, around the active element from a Shape memory alloy can be wrapped.

Claims (11)

1. Electrodynamic direct current linear motor with active clamping with a fixed stator and a movable rotor, characterized in that the movable rotor can be fixed relative to the fixed stator by a switchable brake. 2. Electrodynamic direct current linear motor with active clamping according to patent Claim 1, characterized in that the energization of the motor for movement generation simultaneously causes the brake to be released, and in the de-energized state Condition the brake is locked. 3. Electrodynamic DC linear motor with active clamping according to claim 1, characterized in that the DC motor from a first subsystem with a body ( 6 ) and attached coil ( 2 ) and a second subsystem with a magnetic circuit from at least one permanent magnet ( 4th ), a flux guide ( 3 ) as a magnetic yoke and a housing ( 1 ). 4. Electrodynamic direct current linear motor with active clamping according to patent Claim 1 and 3 characterized in that between the subsystems there is little air gap, and each of these subsystems the moving output and so that the runner can form, the other subsystem then the fixed one Represents stator. 5. Electrodynamic direct current linear motor with active clamping according to claims 1 and 4, characterized in that the brake for fixing the rotor contains a piezoelectric ( 5 ) or magnetostrictive ( 13 ) active element or an element made of a shape memory alloy, which contains both guide as well as an active element. 6. Electrodynamic direct current linear motor with active clamping according to claims 1 and 5, characterized in that the expansion or contraction of the piezoelectric ( 5 ) or magnetostrictive ( 13 ) active element or the ele ment of shape memory alloy (hereinafter referred to as the active element ) at a standstill within a very short time a friction-free or form-fitting clamping of the rotor relative to the stationary stator in any position without performance or with reduced performance. 7. Electrodynamic direct current linear motor with active clamping according to claims 1 and 6, characterized in that the active element directly to the body moved relative to the active element ( 6 ) has a contact surface which by expansion or contraction of the active element in the direction of Flat norm paint the clamping realized. 8. Electrodynamic direct current linear motor with active clamping according to claims 1 and 6, characterized in that one or more mechanical components ( 9 or 11 and 14 ) are installed between the active element ( 5 or 13 ) and the components moving relative thereto convert an extension of the active element not directed in the direction of the surface normal of the clamping point into a movement in the direction of the surface normal of the contact surfaces. 9. Electrodynamic direct current linear motor with active clamping according to claims 1 and 8, characterized in that one or more mechanical components ( 9 or 11 and 14 ) are installed between the active element ( 5 or 13 ) and the components moving relative thereto, the effect a force or path translation according to their design. 10. Electrodynamic direct current linear motor with active clamping according to claims 1 to 6 and 7 or 8, characterized in that an active element made of magnetostrictive material ( 13 ) is integrated into the drive coil ( 2 ) of the direct current linear motor so that the magnetic field is energized Drive coils ( 2 ) itself causes the expansion of the active element ( 13 ) and thereby releases the clamping of the moving part to the stationary part during the movement and in the currentless state inevitably closes the clamping again. 11. Electrodynamic direct current linear motor with active clamping according to patent Claim 1 and 2, characterized in that the active element of the brake, the serves for clamping, electrically to the drive coil via a rectifier bridge is connected that regardless of the direction of current in the drive coil Current flow the clamp is always released and is always closed without current flow.