Abstract:
The invention relates to an electromechanical brake applying device, especially for a rail vehicle brake, comprising a) an operating brake unit for producing a load-corrected and/or a skid-controlled brake force, b) an accumulation brake unit having an energy accumulator for storing and supplying energy for applying the brake, and c) an unlockable locking device for the energy accumulator. According to the invention, at least one control and monitoring device is provided for monitoring the brake function of the brake applying device. When the brake applying device is intact, a signal for keeping the locking device locked can be produced by said control and monitoring device, and in the event of safety braking and/or park braking, the operating brake unit can be activated in order to apply the brake.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
   The invention is based on an electromechanical brake application device, particularly for a rail vehicle brake. 
   Currently, three types of wheel braking systems are essentially used in the rail vehicle field: Pneumatic or electro-pneumatic braking systems, hydraulic or electro-hydraulic braking systems as well as mechanical or electromechanical braking systems. The wheel braking system may be constructed as an active or passive braking system, depending on whether the power of the brake actuator has to be applied for the engaging (active braking system) or for the releasing of the brake (passive braking system). In case of operating disturbances, energy is stored in air brake reservoirs if pneumatic systems are used; energy is stored in hydraulic reservoirs if hydraulic systems are used; and energy is accumulated in the form of accumulator-type springs when electromechanical systems are used. 
   From the prior art, electromechanical brake application devices are known which have a service-type brake unit as well as an accumulator-type brake unit which has an energy accumulator. The service-type brake unit contains a braking power generator for the application and/or release of the brake; for example, in the form of an electric-motor drive which can be controlled by a control device for slip-controlled or load-corrected braking. The accumulator-type brake unit comprises at least one energy accumulator for the storage and supply of energy for the application of the brake as a service-type emergency brake during a safety braking demand; as a parking brake; or a safety braking level, in the event of a failure of the service-type brake unit. 
   A power converter provides a conversion of the energy supplied by the braking power generator and/or by the energy accumulator to a brake application movement and comprises, for example, a brake spindle driven by the electric-motor drive. 
   For activating the energy accumulator, a locking device is provided which can be unlocked upon a safety braking and/or parking braking demand signal. The accumulator-type brake unit is generally constructed as a spring brake, the accumulator-type spring being held in the tensioned condition by the locking device. Upon the safety braking demand signal, which is controlled, for example, by a safety loop of the rail vehicle into the locking device, the locking device is released and the power of the accumulator-type spring can be transmitted by the power converter to brake shoes. 
   However, it is a disadvantage that, while the brake application device is intact, no non-skid-controlled or load-corrected feeding of the braking power can be achieved in order to permit a certain braking comfort during safety and parking braking. 
   In view of the above, the present invention is based on further developing an electromechanical brake application device such that, also during a safety braking and/or parking braking, a braking can take place in a non-skid-controlled and/or load-corrected manner. 
   When the safety braking or parking braking is demanded, while the brake application device is intact, a braking can take place in complete comfort, that is, in a load-corrected and or slip—or non-skid-controlled manner, by the service-type brake unit. The controlling-in of the braking power is monitored by the control and monitoring device. When the controlling-in of the braking power is correct (brake application device is intact), this control and monitoring device prevents the opening of the locking device and thus, in the event of a safety braking, the brake slip of the wheels of the rail vehicles which is frequently observed when the accumulator-type brake unit is triggered. As a result of this measure, the driving comfort can be improved, and the mechanical loads and the wear of the brake system can be reduced. 
   As a result of additional measures, advantageous further developments and improvements of the electro-mechanical brake application device can be achieved. 
   According to a particularly preferable measure, in the case of an intact brake application device, a feeding of the safety braking and/or parking braking signal to the locking device can be prevented by a switching device. The switching device can be controlled by the control and monitoring device, and instead a signal for maintaining the locked condition can be controlled in. 
   The locking device preferably has an electromagnetically operable construction, can be locked when energized and can be unlocked when not energized. The safety braking demand signal is formed by a currentless condition which can be controlled in by a safety loop of the rail vehicle. 
   The switching device contains at least one relay which, upon the safety braking demand signal and when the brake application device is intact, connects the locking device with a voltage source. An unlocking of the accumulator-type brake unit will then be reliably prevented by means of simple devices. 
   As an alternative, the locking device may have several locking elements, of which at least one locking element is sufficient for keeping the locking device locked. Thus, when the brake application device is intact, the control and monitoring device can output to this at least one locking element the signal for keeping the locking device locked. 
   The locking device may be electromagnetically operable and contains several solenoid coils as the locking elements for generating magnetic forces which lock or unlock the locking device. The magnetic force of at least one solenoid coil controllable by the control and monitoring device is sufficient for keeping the locking device locked. When the locking device is constructed with a double or multiple coil, a separate control of the individual coils can be implemented in mutually separated electric circuits, for example, by the control and monitoring device, on the one hand, and by a safety loop of the rail vehicle, on the other hand. Solenoid coils are identical parts; one or two additional solenoid coil(s) take up only a little more space. For this reason, the described solution requires little space and can be implemented in a cost-effective manner. Furthermore, solenoid coils are unsusceptible with respect to shock loads or vibration loads and have a long service life. 
   These and other aspects of the present invention will become apparent from the following detailed description of the invention, when considered in conjunction with accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a very schematic representation of a preferred embodiment of a brake application device according to the invention. 
       FIG. 2  is a sectional view of a locking device according to another embodiment of the brake application device. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A preferred embodiment of an electromechanical brake application device of a rail vehicle marked by reference number  1  in  FIG. 1  contains a service-type brake unit with a brake actuator  2  which comprises a brake spindle  6  which can be driven by and electric servo motor  4 . The brake spindle  6  is surrounded by a nut/spindle constructional unit  8  which preferably can be constructed as a roller thread drive, such as a circulating ball spindle, a roller thread drive, a thread roller screw drive or as a planetary roller thread drive. Therefore, during rotations of the brake spindle  6 , a nut  10  of the nut/spindle constructional unit  8  is translatorily guided along the brake spindle  6  and, in the process, acts upon swivellably linked caliper levers  12 . The swivelling movements of the caliper levers  12  are converted to essentially translatory brake application movements of brake linings in the direction of a brake disk axis which is not shown. 
   The service-type brake unit is constructed for generating load-corrected and/or slip-controlled braking powers. A load-corrected braking power is a braking power which is essentially adapted to the respectively present weight of the rail vehicle, and a slip-controlled braking power is a braking power by which the braking takes place with no wheel slip or only a little wheel slip. For this purpose, a control device  16  is provided by a signal line  18 , a signal for the actual braking power value from a first power sensor  20  and can be compared there with a desired braking power value for determining a control difference. The desired braking power value definition is preferably oriented according to the reaching of a demanded braking power in a time period that is as short as possible. 
   The control device  16  controls the operating current for the servo motor  4  by a power part  22 , as a function of the computer control difference between the actual current and a control current measured by a current sensor  24  and transmitted by a signal line  26  to the control device  16 . The build-up of the braking power starts only after any lining play has taken place. A rotational speed sensor  28  is used as a position sensor or as a angle-of-rotation generator for a correct control of the motor by the control device  16 . 
   Furthermore, the brake application device  1  contains an accumulator-type brake unit with an energy accumulator for storing and supplying energy for the application of the brake in the event of a safety braking or an emergency braking. The energy accumulator is preferably an accumulator-type spring  30  which is constructed as a coil spring, is coaxial with respect to the brake spindle and is tensioned in the brake release position. The spring  30  is supported by its end facing the servo motor  4  on a housing of the brake actuator  2  and, by means of its other end, on a sliding sleeve, which is not shown for reasons of scale. The spring  30  can be displaced coaxially with respect to the brake spindle  6 , acts upon the caliper levers  12  and can be held in the release position by a locking device  32 . 
   The locking device  32  is connected by electric line  34  with a safety loop  36  of the rail vehicle, on which a safety braking demand signal is present as a result of the operating of an emergency button or an emergency brake lever. A switching device  38  is arranged between the safety loop  36  and the locking device  32 . The switching device  38  preferably comprises two series-connected relays—a first relay  40  and a second relay  42 . As an alternative, any other type of switching element can be used, such as semiconductors, particularly transistors. 
   A control input  44  of the first relay  40  is connected by an electric control line  46  with the control and monitoring device  48  integrated in the control device  16 . The control input  50  of the second relay  42  is connected by another control line  52  to another redundant control and monitoring device  54  which can communicate with the one control and monitoring device  48 . Both relays  40 ,  42  are connected with their respective power inputs  56 ,  58  with a voltage source  60 . Another power input  62  of the second relay  42  is connected with the safety loop  36 , and its output  64  is connected with the additional power input  66  of the first relay  40 . An output  68  of the first relay  40  is connected by the electric line  34  with the locking device  32 . When they are not energized, both relays  40 ,  42  connect the electric line  34  between the locking device  32  and the safety loop  36 , as illustrated in  FIG. 1 . The two control and monitoring devices  48 ,  54  can receive signals of the safety loop  36  by electric lines  70 . Braking demand signals of a brake signal generator arrive by interface  72  at the control device  16 . In addition, a system diagnosis can take place by way of the interface; furthermore, the interface represents a connection to a higher-ranking control. 
   A second power sensor  74  is connected by a signal line  76  with the redundant control and monitoring device  54 . The output signals of the two power sensors  20 ,  74 , as input signals for the control and monitoring devices  48 ,  54  and the control device  16 , in addition to forming actual braking power values required for the computing of the control difference, also form criteria for the operability of the brake application device  1 . The function test of the brake application device  1  preferably takes place online and continuously by the two control and monitoring devices  48 ,  54 . Instead of directly measuring the braking power, sensors may also be provided for measuring physical quantities, from which the braking power can be derived. 
   The locking device  32  preferably has an electromagnetically operable construction and comprises a locking piston  78  which, when the locking device  32  is energized, locks the accumulator-type spring  30  in its tensioned position and, when the locking device  32  is not energized, unlocks the accumulator-type spring  30 , so that the relaxing accumulator-type spring  30  can cause a brake application movement of the brake linings  14 . 
   The servo motor  4  forms a braking power generator; the other elements of the power transmission path from the servo motor  4  to the brake linings  14  form a braking power converter. With this background, the brake application device  1  has the following function: 
   In the release position of the brake actuator  2 , the accumulator-type spring  30  is tensioned. The two relays  40 ,  42  are in the switching position illustrated in  FIG. 1 , in which the locking device  32  is electrically connected with the safety loop  36 . Since the safety loop  36  is energized in the normal operation, the locking device  32  is in the locked position. The force of the tensioned accumulator-type spring  30  can then be suppressed by the locking device  32 . 
   During the transition from the release position to the service-type braking position, the control device  16  receives a braking demand signal by way of its interface  72 , whereupon the servo motor  4  is driven by the power part  22  and the brake spindle  6  is caused to rotate. The nut  10  of the nut/spindle constructional unit  8  is screwed along the brake spindle  6  and the caliper levers  12  are spread. The accumulator-type spring  30  does not participate in the generating of the service-type braking power and remains in the tensioned condition because it is locked by the still energized locking device  32 . 
   When an emergency button or an emergency brake lever of the rail vehicle is operated, a safety braking demand signal is generated in the safety loop  36 , which safety braking demand signal is preferably generated by switching the safety loop  36  currentless or by removal of current. If it was determined by one or both control and monitoring devices  48 ,  54  that the brake application device  1  is without any defect, for example, by the braking power time courses of preceding brakings, the two relays  40 ,  42  are switched over such that the locking device  32  is energized by the voltage source  60 . As a result, the locking device  32  remains locked despite the presence of the safety braking demand signal on the safety loop  36 , and the accumulator-type spring  30  cannot relax. The safety braking demand signal generated by switching the safety loop  36  currentless, is therefore overwritten by the current supply of the locking device  32  generated by the control and monitoring devices  48 ,  54 . Simultaneously, a service braking is triggered by the two control and monitoring devices  48 ,  54  switched currentless by way of the safety loop  36  on the control input side, during which service braking, by means of the servo motor  4 , a slip-controlled and/or load corrected braking power is generated on the brake linings  14 . If one of the two control and monitoring devices  48 ,  54  fails, its function can in each case be taken over by the other. In particular, the two relays  40 ,  42  are also switched such that, if one relay  40 ,  42  fails, the respective other relay  40 ,  42  can still provide an electric connection between the locking device  32  and the voltage source  60 . 
   However, if one or both control and monitoring devices  48 ,  54  detect a defect in the brake application device  1 , the two relays  40 ,  42  receive no switch-over signals from the control and monitoring devices  48 ,  54  and remain in their conduction position illustrated in  FIG. 1 . Because of the safety loop  36  switched currentless by the operation of the emergency button, the locking device  32  also receives no more current so that it unlocks the accumulator-type spring  30 . The braking by the accumulator-type brake unit will then take place without slip control and without load correction. 
     FIG. 2  shows a locking device  80  according to another embodiment of the brake application device  1  according to the invention. The remaining components of the brake application device  1  are identical or analogous with the components described above. The following explanations relate to the construction of the locking device  80 . 
   In an actuator housing  82  of the brake actuator  2 , an annulus  84  is constructed in which a ring gear  90  is arranged which is in a driving connection with a locking nut  86  by a slipping clutch  88 . The locking nut  86  can be rotated by a non-self-locking thread  92  with respect to a sliding sleeve  94 . The locking thread  92  is displaceable in the direction of the brake spindle and on which the accumulator-type spring  30  is supported. The translatory moving-out movement of the locking thread  92  causes a swivelling of the caliper lever  12  in the brake application direction. The locking device  80  has a housing  96  which is flanged to a radial opening of the annulus  84 . In addition, the locking device  80  comprises a shaft  98 , on whose radial interior end, a bevel gear  100  is arranged and, on whose opposite radially exterior end, a cylindrical inertia disk  102  is arranged. The bevel gear  100  meshes with the toothing of the ring gear  90  and, together with it, forms a bevel gear pair which preferably has a relatively high transmission ratio. The shaft  98  is rotatably disposed in the housing  96  of the locking device  80  by deep groove ball bearings  104 . The shaft  98  arranged perpendicular with respect to the brake spindle  6 . 
   On its face pointing to the brake spindle  6 , the inertia disk  102  has a ring recess  106  for a ring  108  which is arranged coaxial to the shaft  98  and is displaceably received along pins  110  extending in the axial direction, whereby it is non-rotatably connected with the inertia disk  102 . In addition, the ring  108  has a radially external gear rim  112  on its face pointing away from the inertia disk  102 . The gear rim  112  is situated opposite another gear rim  114  supported on the housing  96  of the locking device  80  and is pushed away from that gear rim  114  as a result of the effect of pressure springs  116 . Furthermore, several, preferably two solenoid coils  118 ,  120  are arranged behind one another in the axial direction in the housing  96  of the locking device  80  and are situated opposite the ring  108 . The solenoid coils  118 ,  120  can be individually energized by electric connections  122 , for example. Together, the ring  108 , the two gear rims  112 ,  114  and the two solenoid coils  118 ,  120  form a solenoid cogwheel brake  124 . 
   In the case of at least one energized solenoid coil  118 ,  120 , magnetic attraction powers or fields are generated which move the ring  108  against the effect of the pressure springs  116  along the pins  110  in the axial direction toward the solenoid coils  118 ,  120 , the gear rim  112  of the ring  108  comes to engage with the gear rim  114  held on the housing  96  of the locking device  80  and thus enters into a non-rotatable connection therewith. Then, a torque acting from the accumulator-type spring  30  upon the sliding sleeve  94  and introduced by the locking nut  86  and the ring gear  90  into the locking device  80  can be supported on the housing  96  of the locking device  80 . The flux of force extends through the bevel gear  100 , the shaft  98  and the inertia disk  102 . The solenoid coils  118 ,  120  act magnetically in the same direction and are designed such that the magnetic force of a single solenoid coil  118 ,  120  is sufficient for keeping the solenoid cogwheel brake  124  closed. 
   The solenoid coil  120 , which is situated farther away from the ring  108 , is in an electrically conductive connection by the connections  122  with the control and monitoring devices  48 ,  54  illustrated in  FIG. 1  and receives current from this connection. The solenoid coil  118  situated closer to the ring  108  is connected to the safety loop  36 . As an alternative, a reverse assignment is conceivable. Thus, if the safety loop  36  is switched currentless or no current, the solenoid coil  118  receives no current during a safety braking and therefore also generates no magnetic forces for locking the solenoid cogwheel brake  124 . However, in the case of an intact brake application device, the safety brake demand signal generated during the switching to the currentless condition is overwritten in that the other solenoid coil  120  continues to be energized by the control and monitoring devices  48 ,  54 . The resulting magnetic forces are sufficient for keeping the solenoid cogwheel brake  124  and thus the locking device  80  locked, so that the accumulator-type spring  30  cannot relax. In this case, as in the case of a service-type braking, the safety braking power will then be generated by the servo motor  4  controlled by the control device  16 . 
   In addition or as an alternative, while the brake application device  1  is intact, at least one of the solenoid coils of the solenoid cogwheel brake  124  is energized by the control and monitoring devices  48 ,  54  or, as a result of the latter, remains in the energized condition if another solenoid coil is switched currentless because of the presence of a parking brake demand signal. Also in this case, the parking brake power, as in the case of a service braking, is generated by the servo motor  4  controlled by the control device  16 . 
   In order to achieved a reduction of the power loss, the solenoid coil  120  controlled by the control and monitoring devices  48 ,  54  is operated by a holding current which is just high enough for holding the solenoid cogwheel brake  124  closed. As a result, the current consumption as well as the internal heating of the brake application device  1  is reduced. 
   If, however, the brake application device  1  should have a defect, the solenoid coil  120  is also switched currentless so that the gear rim  112  of the ring  108 , as a result of the pressure springs  116 , disengages from the gear rim  114  held at the housing  96  of the locking device  80  and, for this reason, the ring gear  90 , together with the bevel gear  100 , the shaft  98  and the inertia disk  102  can rotate freely with respect to the housing  96  of the locking device  80 . As a result, the locking nut  86  can rotate along the non-self-locking thread  92  on the sliding sleeve  94  which is forced into the brake application position by the accumulator-type spring  30 . As in the case of the above-described embodiment, the safety braking triggered by the accumulator-type spring  30  takes place without any slip control and without any load correction. 
   The inertia disk  102 , the ring  108 , the shaft  98  and the bevel gear  100 , together, form an inertia weight  126  which can be rotated perpendicular to the brake spindle  6  and, relative to the slipping clutch  88 , is arranged on the other side of the locking nut  86 . Because of its radius, the inertia disk  102  is the largest portion of the mass moment of inertia of the inertia weight  126 . During the brake application movement, the rotation of the locking nut  86  is translated by the bevel gear pair  90 ,  100  into a rotation of the inertia weight  126  which takes place at a higher rotational speed. Thus a large portion of the potential energy of the relaxing accumulator-type spring  30  is converted to rotational energy. 
   When the braking position has been reached, the rotation of the locking nut  86  will stop. The slipping clutch  88  between the locking nut  86  and the ring gear  90  is designed such that the upper limit torque, starting at which a relative rotation can take place between the radial serrations  128  of the ring gear  90  and of the locking nut  86 , is exceeded by the torque from the product of the mass moment of inertia of the inertia weight  126  and of the deceleration in the braking end position existing after passing through the brake application stroke. Thus, after the braking end position has been reached, the inertia weight  126  can first continue to rotate and, essentially as a result of the friction taking place between the radial serrations  128  of the ring gear  90  and of the locking nut  86 , is slowly caused to come to a stop. As a result, a gradual reduction of the rotational energy accumulated in the inertia weight  126  can take place. 
   For engaging the parking brake by the accumulator-type brake unit, all solenoid coils  118 ,  120  can be switched currentless by suitable measures in order to release the locking device  80 . As an alternative and as a result of the reversal of the current flow in one or in both solenoid coils  118 ,  120 , the direction of the magnetic forces can be reversed and thus the solenoid cogwheel brake  124  can be opened. Furthermore, another solenoid coil can be used which can be energized directly by a control line assigned to the parking brake and generates magnetic forces which counteract the magnetic forces of the two solenoid coils  118 ,  120 . 
   Although the present invention has been described and illustrated in detail, it is to be clearly understood that this is done by way of illustration and example only and is not to be taken by way of limitation. The scope of the present invention is to be limited only by the terms of the appended claims.