Electromechanical brake applying device

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.

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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of an electromechanical brake application device of a rail vehicle marked by reference number1inFIG. 1contains a service-type brake unit with a brake actuator2which comprises a brake spindle6which can be driven by and electric servo motor4. The brake spindle6is surrounded by a nut/spindle constructional unit8which 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 spindle6, a nut10of the nut/spindle constructional unit8is translatorily guided along the brake spindle6and, in the process, acts upon swivellably linked caliper levers12. The swivelling movements of the caliper levers12are 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 device16is provided by a signal line18, a signal for the actual braking power value from a first power sensor20and 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 device16controls the operating current for the servo motor4by a power part22, as a function of the computer control difference between the actual current and a control current measured by a current sensor24and transmitted by a signal line26to the control device16. The build-up of the braking power starts only after any lining play has taken place. A rotational speed sensor28is used as a position sensor or as a angle-of-rotation generator for a correct control of the motor by the control device16.

Furthermore, the brake application device1contains 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 spring30which is constructed as a coil spring, is coaxial with respect to the brake spindle and is tensioned in the brake release position. The spring30is supported by its end facing the servo motor4on a housing of the brake actuator2and, by means of its other end, on a sliding sleeve, which is not shown for reasons of scale. The spring30can be displaced coaxially with respect to the brake spindle6, acts upon the caliper levers12and can be held in the release position by a locking device32.

The locking device32is connected by electric line34with a safety loop36of 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 device38is arranged between the safety loop36and the locking device32. The switching device38preferably comprises two series-connected relays—a first relay40and a second relay42. As an alternative, any other type of switching element can be used, such as semiconductors, particularly transistors.

A control input44of the first relay40is connected by an electric control line46with the control and monitoring device48integrated in the control device16. The control input50of the second relay42is connected by another control line52to another redundant control and monitoring device54which can communicate with the one control and monitoring device48. Both relays40,42are connected with their respective power inputs56,58with a voltage source60. Another power input62of the second relay42is connected with the safety loop36, and its output64is connected with the additional power input66of the first relay40. An output68of the first relay40is connected by the electric line34with the locking device32. When they are not energized, both relays40,42connect the electric line34between the locking device32and the safety loop36, as illustrated inFIG. 1. The two control and monitoring devices48,54can receive signals of the safety loop36by electric lines70. Braking demand signals of a brake signal generator arrive by interface72at the control device16. 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 sensor74is connected by a signal line76with the redundant control and monitoring device54. The output signals of the two power sensors20,74, as input signals for the control and monitoring devices48,54and the control device16, 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 device1. The function test of the brake application device1preferably takes place online and continuously by the two control and monitoring devices48,54. 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 device32preferably has an electromagnetically operable construction and comprises a locking piston78which, when the locking device32is energized, locks the accumulator-type spring30in its tensioned position and, when the locking device32is not energized, unlocks the accumulator-type spring30, so that the relaxing accumulator-type spring30can cause a brake application movement of the brake linings14.

The servo motor4forms a braking power generator; the other elements of the power transmission path from the servo motor4to the brake linings14form a braking power converter. With this background, the brake application device1has the following function:

In the release position of the brake actuator2, the accumulator-type spring30is tensioned. The two relays40,42are in the switching position illustrated inFIG. 1, in which the locking device32is electrically connected with the safety loop36. Since the safety loop36is energized in the normal operation, the locking device32is in the locked position. The force of the tensioned accumulator-type spring30can then be suppressed by the locking device32.

During the transition from the release position to the service-type braking position, the control device16receives a braking demand signal by way of its interface72, whereupon the servo motor4is driven by the power part22and the brake spindle6is caused to rotate. The nut10of the nut/spindle constructional unit8is screwed along the brake spindle6and the caliper levers12are spread. The accumulator-type spring30does 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 device32.

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 loop36, which safety braking demand signal is preferably generated by switching the safety loop36currentless or by removal of current. If it was determined by one or both control and monitoring devices48,54that the brake application device1is without any defect, for example, by the braking power time courses of preceding brakings, the two relays40,42are switched over such that the locking device32is energized by the voltage source60. As a result, the locking device32remains locked despite the presence of the safety braking demand signal on the safety loop36, and the accumulator-type spring30cannot relax. The safety braking demand signal generated by switching the safety loop36currentless, is therefore overwritten by the current supply of the locking device32generated by the control and monitoring devices48,54. Simultaneously, a service braking is triggered by the two control and monitoring devices48,54switched currentless by way of the safety loop36on the control input side, during which service braking, by means of the servo motor4, a slip-controlled and/or load corrected braking power is generated on the brake linings14. If one of the two control and monitoring devices48,54fails, its function can in each case be taken over by the other. In particular, the two relays40,42are also switched such that, if one relay40,42fails, the respective other relay40,42can still provide an electric connection between the locking device32and the voltage source60.

However, if one or both control and monitoring devices48,54detect a defect in the brake application device1, the two relays40,42receive no switch-over signals from the control and monitoring devices48,54and remain in their conduction position illustrated inFIG. 1. Because of the safety loop36switched currentless by the operation of the emergency button, the locking device32also receives no more current so that it unlocks the accumulator-type spring30. The braking by the accumulator-type brake unit will then take place without slip control and without load correction.

FIG. 2shows a locking device80according to another embodiment of the brake application device1according to the invention. The remaining components of the brake application device1are identical or analogous with the components described above. The following explanations relate to the construction of the locking device80.

In an actuator housing82of the brake actuator2, an annulus84is constructed in which a ring gear90is arranged which is in a driving connection with a locking nut86by a slipping clutch88. The locking nut86can be rotated by a non-self-locking thread92with respect to a sliding sleeve94. The locking thread92is displaceable in the direction of the brake spindle and on which the accumulator-type spring30is supported. The translatory moving-out movement of the locking thread92causes a swivelling of the caliper lever12in the brake application direction. The locking device80has a housing96which is flanged to a radial opening of the annulus84. In addition, the locking device80comprises a shaft98, on whose radial interior end, a bevel gear100is arranged and, on whose opposite radially exterior end, a cylindrical inertia disk102is arranged. The bevel gear100meshes with the toothing of the ring gear90and, together with it, forms a bevel gear pair which preferably has a relatively high transmission ratio. The shaft98is rotatably disposed in the housing96of the locking device80by deep groove ball bearings104. The shaft98arranged perpendicular with respect to the brake spindle6.

On its face pointing to the brake spindle6, the inertia disk102has a ring recess106for a ring108which is arranged coaxial to the shaft98and is displaceably received along pins110extending in the axial direction, whereby it is non-rotatably connected with the inertia disk102. In addition, the ring108has a radially external gear rim112on its face pointing away from the inertia disk102. The gear rim112is situated opposite another gear rim114supported on the housing96of the locking device80and is pushed away from that gear rim114as a result of the effect of pressure springs116. Furthermore, several, preferably two solenoid coils118,120are arranged behind one another in the axial direction in the housing96of the locking device80and are situated opposite the ring108. The solenoid coils118,120can be individually energized by electric connections122, for example. Together, the ring108, the two gear rims112,114and the two solenoid coils118,120form a solenoid cogwheel brake124.

In the case of at least one energized solenoid coil118,120, magnetic attraction powers or fields are generated which move the ring108against the effect of the pressure springs116along the pins110in the axial direction toward the solenoid coils118,120, the gear rim112of the ring108comes to engage with the gear rim114held on the housing96of the locking device80and thus enters into a non-rotatable connection therewith. Then, a torque acting from the accumulator-type spring30upon the sliding sleeve94and introduced by the locking nut86and the ring gear90into the locking device80can be supported on the housing96of the locking device80. The flux of force extends through the bevel gear100, the shaft98and the inertia disk102. The solenoid coils118,120act magnetically in the same direction and are designed such that the magnetic force of a single solenoid coil118,120is sufficient for keeping the solenoid cogwheel brake124closed.

The solenoid coil120, which is situated farther away from the ring108, is in an electrically conductive connection by the connections122with the control and monitoring devices48,54illustrated inFIG. 1and receives current from this connection. The solenoid coil118situated closer to the ring108is connected to the safety loop36. As an alternative, a reverse assignment is conceivable. Thus, if the safety loop36is switched currentless or no current, the solenoid coil118receives no current during a safety braking and therefore also generates no magnetic forces for locking the solenoid cogwheel brake124. 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 coil120continues to be energized by the control and monitoring devices48,54. The resulting magnetic forces are sufficient for keeping the solenoid cogwheel brake124and thus the locking device80locked, so that the accumulator-type spring30cannot relax. In this case, as in the case of a service-type braking, the safety braking power will then be generated by the servo motor4controlled by the control device16.

In addition or as an alternative, while the brake application device1is intact, at least one of the solenoid coils of the solenoid cogwheel brake124is energized by the control and monitoring devices48,54or, 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 motor4controlled by the control device16.

In order to achieved a reduction of the power loss, the solenoid coil120controlled by the control and monitoring devices48,54is operated by a holding current which is just high enough for holding the solenoid cogwheel brake124closed. As a result, the current consumption as well as the internal heating of the brake application device1is reduced.

If, however, the brake application device1should have a defect, the solenoid coil120is also switched currentless so that the gear rim112of the ring108, as a result of the pressure springs116, disengages from the gear rim114held at the housing96of the locking device80and, for this reason, the ring gear90, together with the bevel gear100, the shaft98and the inertia disk102can rotate freely with respect to the housing96of the locking device80. As a result, the locking nut86can rotate along the non-self-locking thread92on the sliding sleeve94which is forced into the brake application position by the accumulator-type spring30. As in the case of the above-described embodiment, the safety braking triggered by the accumulator-type spring30takes place without any slip control and without any load correction.

The inertia disk102, the ring108, the shaft98and the bevel gear100, together, form an inertia weight126which can be rotated perpendicular to the brake spindle6and, relative to the slipping clutch88, is arranged on the other side of the locking nut86. Because of its radius, the inertia disk102is the largest portion of the mass moment of inertia of the inertia weight126. During the brake application movement, the rotation of the locking nut86is translated by the bevel gear pair90,100into a rotation of the inertia weight126which takes place at a higher rotational speed. Thus a large portion of the potential energy of the relaxing accumulator-type spring30is converted to rotational energy.

When the braking position has been reached, the rotation of the locking nut86will stop. The slipping clutch88between the locking nut86and the ring gear90is designed such that the upper limit torque, starting at which a relative rotation can take place between the radial serrations128of the ring gear90and of the locking nut86, is exceeded by the torque from the product of the mass moment of inertia of the inertia weight126and 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 weight126can first continue to rotate and, essentially as a result of the friction taking place between the radial serrations128of the ring gear90and of the locking nut86, is slowly caused to come to a stop. As a result, a gradual reduction of the rotational energy accumulated in the inertia weight126can take place.

For engaging the parking brake by the accumulator-type brake unit, all solenoid coils118,120can be switched currentless by suitable measures in order to release the locking device80. As an alternative and as a result of the reversal of the current flow in one or in both solenoid coils118,120, the direction of the magnetic forces can be reversed and thus the solenoid cogwheel brake124can 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 coils118,120.

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.