Abstract:
An electronic drive includes an electro-mechanical brake associated with a direct-current motor. A first valve or diode connects one of the terminals of the direct-current motor with the first electrical terminal of the brake in a forward direction. A second valve or diode connects the other terminal of the direct-current motor with the first electrical terminal of the brake. A second electrical terminal of the brake is at least indirectly connected with a reference voltage.

Description:
TECHNICAL FIELD 
     The invention relates to an electronic drive having an electro-mechanical brake. 
     RELATED ART 
     In order to brake the electric motor of an electronic drive, electronically-controllable mechanical brakes (electro-mechanical brakes) can be used, which are controlled by a controller or regulator of the drive using electronics and/or electricity. 
     SUMMARY 
     It is an object of the invention to provide a simplified electronic drive having an electro-mechanical brake associated with the motor of the drive. 
     In one aspect of the present teachings, an electronic drive includes:
         an electronic direct-current motor having a first and a second electrical terminal,   an electro-mechanical brake associated with the direct-current motor and having a first electrical terminal and a second electrical terminal, the latter of which is at least indirectly connected with a reference voltage,   a first valve, which connects the first terminal of the direct-current motor with the first electrical terminal of the brake in the forward direction, and   a second valve, which connects the second terminal of the direct-current motor with the first electrical terminal of the brake in the forward direction.       

     Thus, the electronic drive according to this aspect comprises the direct-current motor and the electro-mechanical brake associated with the direct-current motor; the brake may be embodied, in particular, as a stopping brake. According to the invention, the brake is connected with the terminals of the direct-current motor via the two valves, which can be embodied in particular as diodes. During operation of the electronic drive according to this aspect, the brake is supplied with electric current via the motor windings, i.e. the terminals of the direct-current motor, whereby the brake is driven to its disengaged position. Due to the connection of the valves, an electric current is applied to the brake as long as an electric current is applied at least to one of the terminals of the direct-current motor. The brake is then only current-less, i.e. it only holds the direct-current motor fixed and/or brakes it, when an electric current is applied to neither of the terminals of the direct-current motor. As a result, a relatively simple construction of the electronic drive is made possible. 
     The electronic drive according to this aspect can further include:
         a first controllable switch, which is configured, in a first position, to connect the first terminal of the direct-current motor with a first node, to which an electric direct current is applied during operation of the electronic drive, and, in a second position, to connect the first terminal of the direct-current motor with a second node,   a second controllable switch, which is configured, in a first position, to connect the second terminal of the direct-current motor with the first node and, in a second position, to connect the second terminal of the direct-current motor with the second node, and   a third controllable switch, which is configured, in a first position, to connect the second node at least indirectly with the reference voltage and, in a second position, to decouple the second node from the reference voltage.       

     By using the controllable switches, the electric current can be selectively applied to the first or to the second terminal of the direct-current motor according to the intended rotational direction of the direct-current motor. The other terminal of the direct-current motor can be connected with the reference voltage via the third controllable switch. The reference voltage can have, in particular, the electric potential 0V or can be ground. 
     The first controllable switch can be formed as a first relay, the second controllable switch can be formed as a second relay, and/or the third controllable switch can be formed as semiconductor switch, in particular as a transistor and preferably as a FET (Field-Effect Transistor). 
     The electro-mechanical brake can have an inductance. In order to create a current path for the electrical current of the inductance when the brake is switched-on, i.e. when the applied electric current is switched off to it, a flyback diode can be connected in parallel to the electrical terminals of the brake. 
     The electronic drive according to this aspect can include a controller device, which is configured to control the first controllable switch, the second controllable switch and the third controllable switch. Based on the different control states, the controller device can activate and deactivate the direct-current motor and the brake. 
     According to an embodiment of the inventive electronic drive, the controller device is configured, in a first operational state, to drive the first, the second and the third controllable switches to their second positions. As a result, an electric current is applied to none of the terminals of the direct-current motor and the direct-current motor is short-circuited. As a result, the brake is also current-less and thus holds the direct-current motor fixed. According to this embodiment, the controller device is further configured to subsequently switch either the first or the second controllable switch to its first position. As a result, the electric current of the first node is applied to the terminals of the direct-current motor, whereby an electric current is also applied to the brake, whereby it disengages. However, because the third controllable switch disconnects the second node from the reference voltage, the direct-current motor remains still. According to this embodiment, the controller device is further configured to switch the third controllable switch to its first position with a time delay. As a result, the second node is at least indirectly connected with the reference voltage, whereby the direct-current motor begins to rotate. 
     According to a further variant of the inventive electronic drive, the controller device is configured, in a second operational state, after the third controllable switch has been brought to its first position, to pulse it such that it switches in an alternating manner from its first to its second position. The electrical output of the direct-current motor is thereby adjusted, if necessary regulated, in order to, e.g., control or regulate the speed of the direct-current motor. 
     According to a further embodiment of the inventive electronic drive, the controller device is configured, in a third operational state, to bring the first and the second controllable switches to their first positions and, in necessary, to bring the third controllable switch to its second position. As a result, the direct current is applied to both terminals of the direct-current motor, whereby the direct-current motor is short-circuited and is electronically braked. However, at the same time, an electric current is applied to the brake due to the first and second valve, so that it remains disengaged. According to this embodiment, the controller device is further configured, in a time-delayed manner or after the direct-current motor no longer rotates, to bring the first and the second controllable switch to their second positions. As a result, no voltage is applied to the brake any more, whereby it actuates. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       An exemplary embodiment of the invention is illustrated in an exemplary manner in the appended schematic drawing, and the sole FIGURE shows a block circuit diagram of an electronic drive having a brake for the motor of the electronic drive. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The electronic drive  1  illustrated in the FIGURE includes an electric motor  3  having terminals  5 ,  7 . The electric motor  3  is a direct-current motor, which is embodied, e.g., as a brush-free direct-current motor. 
     In the case of the present exemplary embodiment, the electronic drive  1  includes a controllable first switch, which is embodied in particular as a first relay  9 , and a second controllable switch, which is embodied in particular as a second relay  11 . The two relays  9 ,  11  each comprise a switch element  9   a ,  11   a , which can be switched between two positions by a coil  9   b ,  11   b . One of the terminals of the coils  9   b ,  11   b  is, e.g., connected to earth and/or ground and the other terminal  13 ,  15  is connected with a controller device  25  of the electronic drive  1 . 
     In the case of the present exemplary embodiment, the electronic drive  1  includes a first node  17 , via which the electric motor  3  can be supplied with an electric current, in particular an electric direct-current voltage of, e.g., 24V. A second node  19  of the electronic drive  1  is connected with a third controllable switch, which is embodied, e.g., as a semiconductor switch, in particular as a transistor and preferably as a FET (Field-Effect Transistor)  21 . The drain  21   a  of the FET  21  is connected with the second node  19  and the source  21   b  of the FET  21  is connected with earth and/or ground via a resistor  23 . The FET  21  can be switched between its conducting and its non-conducting state through the gate  21   c  of the FET  21 , which is connected with the controller device  25 . In its conducting state, the second node  19  is connected to earth and/or ground via the resistor  23 . It is possible to provide to the controller device  25  a value of the electric current flowing through the FET  21  by using a current measuring device  27  connected with the controller device  25 . 
     In the case of the present exemplary embodiment, the electronic drive  1  includes an electro-mechanical brake  29  associated with the motor  3 , which brake  29  is embodied as a stopping brake. In particular, the motor  3  can be held fixed in its stationary state by the brake  29 . 
     The brake  29  is situated in its disengaged position when an electric current, in particular, a direct-current voltage, is applied to it. If the brake  29  is without current, i.e. no electric current is being applied to the brake  29 , then the brake  29  is applied or remains applied in order to hold the motor  29  fixed. 
     The brake  29  comprises two electrical terminals  29   a ,  29   b , of which one of the terminals  29   a  is connected with the cathode of a first diode  31  and with the cathode of a second diode  33 . The other terminal  29   b  of the brake  29  is connected to ground. The anode of the first diode  31  is connected with one of the terminals  5  of the motor  3  and the anode of the second diode  33  is connected with the other terminal  7  of the motor  3 . A third diode  35  is connected in parallel to the brake  29  and is provided as a flyback diode. 
     The controller device  25  of the electronic drive  1  can be configured to operate, e.g., as follows: 
     For example, if the motor  3  is still, then the controller device  25  controls the two relays  9 ,  11  such that these are switched so that the two terminals  5 ,  7  of the motor  3  are connected with the second node  19 . This state is shown in the FIGURE. Thus, no electric current flows across the terminals  5 ,  7  of the motor, whereby no electric current is applied to the electro-mechanical brake  29  and thus the brake  29  engages and holds the motor  3  still . Moreover, the FET  21  is biased to its non-conductive state, so that the second node  19  is not connected to ground via the resistor  23 , i.e. it is decoupled from ground. 
     If the motor  3  should be moved, then the controller device  25  switches, according to the intended rotational direction of the motor  3 , either the first relay  9  or the second relay  11  in order to connect the corresponding terminal  5 ,  7  of the motor  3  with the first node  17  and thus to supply the corresponding terminal  5 ,  7  with the electric direct current. For example, if the first relay  9  is switched, then the electric direct current is applied to the terminal  5 , and if the second relay  11  is switched, the direct current is applied to the terminal  7 . Due to the first and second diode  31 ,  33 , the direct current is applied to the brake  29 , independent of which relay  9 ,  11  is switched, whereby the brake  29  is disengaged. 
     Thereafter, the controller device  25  switches the FET  21  with a time delay in order to connect the terminal  5 ,  7  of the motor  3 , which terminal is still connected with the second node  19 , to ground via the resistor  23 . The electric circuit comprising the motor  3  is thereby closed, whereby the motor  3  starts to rotate. The electric output of the motor  3  can be controlled, if necessary also regulated, by the controller device  25  by pulsing the FET  21 , e.g., based on pulse width modulation (PWM). 
     If the motor  3  should be stopped, e.g., in order to change its rotational direction, then in the case of the present exemplary embodiment the controller device  25  switches the respective relay  9 ,  11 , which is not yet switched, so that both relays  9 ,  11  are switched and both terminals  5 ,  7  of the motor  3  are connected with the first node  17 . As a result, the same DC voltage is applied to both terminals  5 ,  7  and the motor  3  is short-circuited. As a result, it stops. Due to the first diode  31  and the second diode  33 , the direct current is applied to the electrical terminal  29   a  of the brake  29  for this operational state, whereby it remains disengaged. The FET  21  is also controlled by the controller device  25  such that it is non-conducting in order to decouple the second node  19  from ground. 
     After a predetermined time or when the motor  3  has come to a standstill, the controller device  25  controls the two relays  9 ,  11  so that these switch into their switched position shown in the FIGURE, i.e. the two terminals  5 ,  7  of the motor  3  connect with the second node  19 . As a result, the motor  3  remains short-circuited and no electric current is applied to the brake  29  anymore, whereby it is applied and thus it holds the motor  3  fixed. Due to the third diode  35 , which is embodied as a flyback diode, electric current stored in an inductance of the brake  29  can flow, if necessary. 
     Reference Number List 
     
         
           1  Electronic drive 
           3  Motor 
           5 ,  7  Terminal 
           9 ,  11  Relay 
           9   a ,  11   a  Switch element 
           9   b ,  11   b  Coil 
           13 ,  15  Terminal 
           17 ,  19  Node 
           21  FET 
           21   a  Drain 
           21   b  Source 
           21   c  Gate 
           23  Resistor 
           25  Controller device 
           29  Brake 
           29   a ,  29   b  Terminal 
           31 ,  33 ,  35  Diode