DEVICE, BRAKE SYSTEM AND METHOD FOR FORCE-GRADIENT CONTROL OF A PASSIVE BRAKE DEVICE

Description

[0001] The present invention relates to a device, a braking system and a method for force gradient-based control of a passive braking device, in particular an electromechanical braking device. State of the art

[0002] In practice, it is known that electromechanical brakes currently available on the market are generally designed as active brakes, meaning the braking force is directly controlled by a motor. The brake force generator typically uses pneumatic, hydraulic, or spring-force controls, which create an equilibrium between the brake pad and the brake disc based on the applied braking force. The position of the pad relative to the disc is thus a result of the applied forces. A return spring is used to separate the brake pad from the disc; its spring force lifts the brake pad away from the disc, thereby creating an air gap between the two components.

[0003] For the implementation of a passive brake, in which a motor works against a force generator such as a spring, the problem arises that a (strong) dynamic is inevitably generated by the interaction between the motor and the spring. This dynamic is further exacerbated by the fact that the typically high spring forces are not damped. Therefore, vibrations and natural frequencies are evident in the operating range of a passive brake, which have a detrimental effect on the braking process.

[0004] To control these vibrations / natural frequencies and the dynamics within the braking system, friction could optionally be increased. However, this directly contradicts the requirement for minimal friction in passive brakes. Therefore, using an electric motor as a generator seems more advisable, enabling reliable and safe brake activation while simultaneously controlling the dynamics. In this scenario, a circuit between the motor windings acts like a speed control via self-induction.

[0005] Up to now, brushed motors have been predominantly used in electromechanical brakes. However, these have components subject to wear and are therefore unsuitable for longer maintenance cycles or low-maintenance operation. As an alternative, brushless motors could be used, which are inexpensive and easy to maintain and manufacture, or stepper motors, even though their speed range is limited.

[0006] For example, in the rail vehicle industry, passive brakes or brake actuators based on the principle of spring force are widely used. They are particularly common in trams, where they serve as a fail-safe and parking brake for extended periods of vehicle standstill. Hydraulically or pneumatically based systems dominate the current rail vehicle market, although electromechanical brakes or brake actuators appear to be an interesting alternative due to their greater modularity and lower maintenance costs. A technical challenge for electromechanical braking systems is fail-safe brake actuation; that is, in the event of a failure, the braking force should be applied by switching off the electrical power to the actuator, and the energy of the springs should then generate the braking force.Even with this passive application, the braking force gradient should be controlled to avoid excessive jerking in the vehicle and flat spots due to wheel slippage. In fluid-based systems, such as hydraulic or pneumatic systems, the braking force gradient is controlled by a series of passive elements that limit the fluid velocity, e.g., a nozzle.

[0007] Examples from the prior art are described, for instance, in DE 10 2017 215289 A1 and WO 2021 / 198994 A1, with DE 10 2017 215289 A1 in particular relating to a brake actuator for a rail vehicle, comprising a housing; a pressure element configured to be pressed against a brake disc; a means for moving the pressure element; a logic unit in or on the housing configured to control the means for moving the pressure element; a control connection on the housing; a supply connection on the housing for supplying the brake actuator with energy; and power electronics with energy storage arranged in or on the housing and assigned only to the one brake actuator. Task

[0008] It is therefore an object of the present invention to provide a device and a method for force gradient-based control of a passive braking device. Disclosure of the invention

[0009] This problem is solved according to the invention by a device with the features of claim 1. According to this claim, a device for force gradient-based control of a passive braking device is provided, wherein the device comprises the following: an electric motor for releasing the passive braking device against a spring force, a motor control unit for controlling the electric motor, which is at least electrically connected to the electric motor, at least one passive electronic element with an electrical resistance, which is connected to the electric motor and the motor control unit, and at least one contact circuit, which is connected to the electric motor, the motor control unit and the at least one passive electronic element, wherein the at least one contact circuit is switchable between a first, electrically non-conductive switching state and a second, electrically conductive switching state, wherein the device can be short-circuited by the first switching state to the counter-induction of the electric motor, and wherein a braking force gradient of the passive braking device can be controlled by the electrical resistance.

[0010] The device is in particular a device for force gradient-based control of a passive electromechanical braking system.

[0011] The invention is based on the fundamental idea that the rotational speed profile of the electric motor can be influenced via passive electronic components or elements, such as a resistor, an inductor, and / or a capacitor. This allows for more precise and improved design of braking gradients and braking application times of the braking system. Furthermore, it enables a more flexible design of the motor and gearbox, as well as the transformation between rotation and translation.

[0012] The electric motor is operated to release the braking device against a spring force, whereby the electric motor is mechanically activated without self-locking. To ensure that the braking device's brake is applied at specific intervals using the electric motor, a defined spring force and a corresponding mechanical transmission are employed.

[0013] The electric motor only "works" when the brake mechanism is actually released. In the released state, the electric motor merely maintains a certain force against the spring force. This holding force is less than the force required to release the brake, because in the released state, mechanical friction and inertia make it easier to maintain the position of the brake pads.

[0014] Since docking must be guaranteed even without an electric motor or in the event of its failure, the spring tension and mechanics are designed so that the braking movement can be carried out under all conditions. This is important to provide sufficient safety certification even without electronics.

[0015] After the braking motion is initiated, the brake pads accelerate towards the brake discs because the electric motor no longer holds the brake pads against the spring force. This generally results in very high application speeds and a strong impact of the brake pads against the respective brake disc.

[0016] In a safety situation, the motor windings of the electric motor are short-circuited with passive components such as resistors or capacitors. The gradient for brake force build-up can be adjusted by appropriately dimensioning these components. Thus, in a safety situation, the electric motor is used as a generator for braking. The motor control and the windings of the electric motor are short-circuited. This prevents the brake mechanism from engaging too quickly and simultaneously ensures the desired application time.

[0017] However, the electric motor can also be used to accelerate the braking process if necessary, by acting in the same direction as the spring force. The use of stepper motors as electric motors is possible in this case, since their speed disadvantages when the braking device is engaged can be compensated for by the prevailing spring force.

[0018] Further details and advantages of the invention will now be explained in more detail with reference to an exemplary embodiment shown in the drawing.

[0019] They show: Fig. 1 shows a circuit diagram of an exemplary embodiment of a brake control system for a passive electromechanical brake; Fig. 2 shows the application behavior of a passive electromechanical brake according to Fig. 1 at different resistances; Fig. 3 a circuit diagram of a further embodiment of a brake control of a passive electromechanical brake; and Fig. 4 an application behavior of a passive electromechanical brake according to Fig. 3 at different resistances.

[0020] The device V in Fig. 1 includes an electric motor M, a motor control C, a first, second and third normally-closed contact NC1, NC2, NC3, a first, second and third resistor W1, W2, W3 and a relay R.

[0021] The electric motor M is electrically connected to the motor control C.

[0022] The first resistor W1 and the second resistor W2 form a series circuit, and the series circuit of the first and the second resistor W1, W2 is in a parallel circuit P with the third resistor W3.

[0023] The parallel circuit P is arranged between the motor control C and the electric motor M.

[0024] The first resistor W1 can be connected via the first normally closed contact NC1, the second resistor W2 can be connected via the second normally closed contact NC2 and the third resistor W3 can be connected via the third normally closed contact NC3 in the parallel circuit P.

[0025] In Fig. 1 A relay R on the train SZ's safety loop holds the normally closed contacts NC1 to NC3 open until an emergency brake application is requested. Upon request, relay R switches to its de-energized state, causing the normally closed contacts NC1 to NC3 to close. This allows current to flow between the windings, resulting in back-induction in the electric motor M and thus braking the motor. The braking of the electric motor M counteracts the spring force of the passive braking device when it is engaged.

[0026] In the diagram in Fig. 2 The braking force F (in kN) is plotted against time (in s).

[0027] The diagram shows the braking force curves for different resistances (in Ω), starting at a braking force F of 0 kN, i.e. the brake is completely released, and rising to a plateau value of approximately 11 kN, which essentially represents the state of a fully braked vehicle.

[0028] For the in Fig. 2 The following resistances have been used in a device according to the invention in the braking force curves shown: 2 Ω, 4 Ω, 6 Ω, 8 Ω, 10 Ω and 12 Ω.

[0029] In the diagram according to Fig. 2 It can be seen that when using a 2-Ω resistor, the braking force increases after approximately 0.41 s and only reaches the plateau value significantly after 0.8 s, whereby the gradient of the braking force increase decreases or flattens out with increasing time and the curve consequently approaches the plateau value almost asymptotically.

[0030] When using a 4-Ω resistor, the braking force increases at approximately 0.405 s with a significantly steeper gradient, so that the plateau value is reached at approximately 0.55 s. In the 4-Ω curve, only a slight decrease in the gradient is observed after reaching a braking force of approximately 6 kN.

[0031] When using a 6-Ω resistor, the braking force increases sharply and almost linearly from about 0.33 s, which is why the plateau value is reached after about 0.12 s.

[0032] A similar behavior occurs when using an 8-Ω resistor, where the braking force increases almost as early as with a 6-Ω resistor, namely after approximately 0.34 s. The curve of the 8-Ω resistor reaches the plateau value at approximately the same time as the 6-Ω curve, which is why the gradient of the nearly linear increase is slightly greater than that of the 6-Ω curve.

[0033] It is noticeable that when using an even larger resistance of 10 Ω, the braking force only increases later, after approximately 0.38 s, and then runs almost parallel to the 8 Ω curve, reaching the plateau value after approximately 0.106 s, i.e., at approximately 0.486 s. In the further course of the curve, an oscillation around the plateau value occurs from approximately 0.674 s, with a maximum undershoot of the plateau value of approximately 0.6 kN being observed.

[0034] According to the curve for the use of a 12-Ω resistor, the braking force only begins to increase from approximately 0.446 s, and does so almost parallel to the 8-Ω and 10-Ω curves. The 12-Ω curve reaches its plateau value at approximately 0.54 s and oscillates again around this plateau value from approximately 0.717 s, with a maximum undershoot of the plateau value of approximately 1 kN occurring.

[0035] In summary, it can be seen that increasing the resistance value from 2 Ω to 4 Ω to 6 Ω shifts the increase in the braking force F towards an earlier time and also increases the gradient of the braking force F.

[0036] However, a further increase to 8 Ω shifts the increase in the braking force F towards a later time, without the gradient being significantly increased further.

[0037] The same applies to resistance values ​​of 10 Ω and 12 Ω, whereby it is noticeable in the corresponding curves of these two resistance values ​​that after reaching the plateau value, there is a time-delayed oscillation around the plateau value, which, according to the curve profiles, is strongly damped.

[0038] The device V in Fig. 3 is essentially the same as device V in Fig. 1 , so that only differences will be described below.

[0039] Furthermore, in Fig. 3 A braking system BS is shown in which the said device V is installed.

[0040] In other words, the said device V is configured to be set up and / or operable or operated in a braking system BS.

[0041] Alternatively or additionally, a braking system BS has at least the aforementioned device V.

[0042] As in Fig. 3 As shown, the braking system BS further includes one or more discs, in particular brake discs, and for each disc a pair of pads, in particular brake pads, are assigned and / or the braking system BS comprises such.

[0043] The respective brake discs are configured to be pressed against or to be pressed against the brake disc in order to initiate or maintain braking, in particular by means of a spring which is included in and / or associated with the brake system BS.

[0044] In other words, a braking force can be generated by pressing the two brake pads against the rotating brake disc, in particular by means of a spring which is included in and / or associated with the brake system BS.

[0045] A wear adjuster or wear adjuster, which is included in and / or assigned to the brake system BS, is operatively connected to the said spring and the brake pads and / or the brake disc, in particular arranged between them.

[0046] The wear adjuster prevents the spring force of the spring from being reduced by wear of the pads and disc.

[0047] The BS braking system also includes a rotary-to-linear converter for converting torque into force.

[0048] By means of the rotary-to-linear converter, a torque that can be generated or produced by the electric motor M can be converted into a force that acts and / or can act against the spring (or the spring force of the spring).

[0049] In the present embodiment, the braking system BS further comprises a gearbox which is connected between and / or arranged between the electric motor M and the rotary-to-linear converter.

[0050] The gearbox enables an increase in the motor torque of the electric motor M, which may be required in the present application of the brake system BS.

[0051] It is also conceivable that the BS braking system is configured without such a gearbox.

[0052] As already mentioned in connection with Fig. 1 As explained, the device V comprises the electric motor M, a motor control C, a first, second and third normally-closed contact NC1, NC2, NC3, a first, second and third resistor W1, W2, W3 and a relay R.

[0053] The electric motor M is electrically connected to the motor control C, which includes a power phase.

[0054] The first, second and third resistors W1, W2, W3 form a parallel circuit P.

[0055] Each resistor W1, W2, W3 is associated with a capacitor C1, C2, C3, in particular connected in parallel.

[0056] The aforementioned parallel circuit P is arranged between the motor control C and the electric motor M.

[0057] In particular, each resistor-capacitor pair is assigned to an electric motor winding.

[0058] In other words, the parallel circuit P forms a ballast circuit, with the first, second and third resistors W1, W2, W3 forming a ballast resistor and the respective capacitors C1, C2, C3 forming a ballast capacitor.

[0059] The ballast resistance allows the engine speed to be reduced according to the principle of the rheostatic brake.

[0060] By means of the ballast capacitor, which can be charged by the counter-electromotive force of the electric motor M, the shape of the force gradient can be changed.

[0061] In other words, the ballast circuit includes a ballast resistor (R_BALLAST) that reduces the motor speed according to the principle of the rheostatic brake, and a ballast capacitor (C_BALLAST) that can be charged by the back electromotive force of the motor to change the shape of the force gradient.

[0062] The first resistor W1 can be connected via the first normally closed contact NC1, the second resistor W2 can be connected via the second normally closed contact NC2 and the third resistor W3 can be connected via the third normally closed contact NC3 in the parallel circuit P.

[0063] In Fig. 3 A switch SW3 keeps the normally closed contacts NC1 to NC3 open until an emergency stop is requested.

[0064] The switch SW3 can be controlled by the relay R Fig. 1 on the safety loop of the train SZ and / or function as such.

[0065] Switch SW3 is assigned to and / or connected in front of another capacitor C_SW3 to increase the delay time of the force application.

[0066] The switch SW3 is connected to a position controller of the brake system BS, in particular via the additional capacitor C_SW3.

[0067] The position controller is connected to the electric motor M via a signal connection and configured to receive position feedback.

[0068] Furthermore, the position controller is connected to the power phase.

[0069] The BS braking system also includes a brake control unit, which is connected to the train control unit and the position controller via signal transmission. Furthermore, force feedback can be received via the brake control unit, particularly from the wear adjuster and / or the brake pads.

[0070] Furthermore, each train control unit and brake control unit are assigned a switch SW1 and SW2, respectively, by means of which a power supply to the position controller and / or the power phase can be switched. Specifically, the train control unit has a first switch SW1 and the brake control unit has a second switch SW2. The first and / or second switch SW1, SW2 are part of and / or assigned to the brake system BS.

[0071] During the braking functions of service braking and emergency braking of the braking system BS, the electric motor M is controllable by the position controller via the power phase of the motor control C. A required position is calculated by the brake control unit based on force feedback and the requirements of the train control system. The parking brake function is achieved by completely de-energizing the system.

[0072] In this case, for emergency braking, a limitation of the gradient of the spring force application can be achieved by means of the ballast circuit, which includes the passive electronic element.

[0073] In particular, the ballast circuit can be triggered by means of the train control, especially via a current cut-off of the first switch SW1.

[0074] Additionally or alternatively, the ballast circuit can be triggered by means of the brake control unit, in particular by switching off the current of the second switch SW2.

[0075] Additionally or alternatively, the ballast circuit can be triggered by means of the position controller, in particular by switching off the current of switch SW3.

[0076] In other words, when a demand is placed, switch SW3 switches to its unenergized state, causing the normally closed contacts NC1 to NC3 to close and a current to flow between the windings, resulting in a back induction in the electric motor M and thus a braking of the electric motor M.

[0077] The braking of the electric motor M counteracts the spring force of the passive braking device during clamping, in particular via the gearbox and / or the rotary-to-linear converter.

[0078] The SW3 switch is of the normally open type, therefore in the event of full energization of the system, e.g. due to a backflow in the power grid, the ballast circuit may also be triggered.

[0079] In Fig. 4 A diagram is shown which is essentially the same as the diagram of Fig. 2 corresponds to the diagram in Fig. 4 The braking force F (in kN) is plotted against time (in s).

[0080] The diagram shows the braking force curves for different resistances, starting at a braking force F of 0 kN, i.e. the brake is completely released, and rising to a plateau value, which essentially represents the state of a fully braked vehicle.

[0081] For the in Fig. 4 The following ballast resistances have been used in a device V and / or a braking system BS according to the invention, as shown in the braking force curves: R1, R2 and R3, wherein R1 > R2 > R3 are related to each other.

[0082] In the diagram according to Fig. 4 It can be seen that when using an R3 resistor, the braking force initially increases gradually compared to R1 and R2, and reaches the plateau value last compared to R1 and R2, with the gradient of the braking force increase decreasing or flattening over time and the curve consequently approaching the plateau value almost asymptotically.

[0083] When using an R2 resistor, the braking force increases later in time compared to an R3 resistor, and with a significantly steeper gradient, so that the plateau value is reached more quickly compared to the R3 resistor. The R2 curve shows only a slight decrease in the gradient.

[0084] It is noticeable that when using an even larger resistance, i.e., an R1 resistance, the braking force increases later compared to the R2 and / or R3 resistances, and with a significantly steeper gradient. This means the plateau value is reached most quickly compared to the R2 and / or R3 resistances. In the R1 curve, there is almost no decrease in the gradient.

[0085] In other words, the greater the ballast resistance, the shorter the braking force build-up time, for example, the braking force build-up time to achieve 90% of a maximum braking force and / or the force required for complete braking.

[0086] In other words, the smaller the ballast resistance, the sooner a braking force will build up within a delay time, which can last up to a braking force value of 10% of a maximum braking force and / or the force required for complete braking. REFERENCE MARK LIST

[0087] C Motor control F Braking force NC1 First normally closed contact NC2 Second normally closed contact NC3 Third normally closed contact M Electric motor P Parallel circuit R Relay SZ Train safety loop V Device W1 First resistor W2 Second resistor W3 Third resistor BS Braking system C1 First capacitor C2 Second capacitor C3 Third capacitor R Ballast Ballast resistor C Ballast Ballast capacitor SW1 First switch SW2 Second switch SW3 Device switch

Claims

1. Device (V) for controlling a passive brake apparatus, in particular a passive electromechanical brake apparatus, based on a force gradient, the device (V) comprising: - an electric motor (M) for releasing the passive brake apparatus against a spring force, and - a motor control system (C) for controlling the electric motor (M), which is at least mono-electrically connected to the electric motor (M), characterized in that the device (V) further comprises the following: - at least one passive electronic element (W1, W2, W3) with an electrical resistance, which is connected to the electric motor (M) and the motor control system (C), and - at least one contact circuit (NC1, NC2, NC3), which is connected to the electric motor (M), the motor control system (C) and the at least one passive electronic element (W1, W2, W3), wherein the at least one contact circuit (NC1, NC2, NC3) can be switched between a first, electrically non-conductive switching state and a second, electrically conductive switching state, wherein the device (V) can be short-circuited by the first switching state for counter-induction of the electric motor (M), and wherein a braking force gradient of the passive brake apparatus can be controlled by the electrical resistance of the at least one passive electronic element (W1, W2, W3).

2. Device (V) according to claim 1, characterized in that the device (V) further has at least one relay (R), with which the at least one contact circuit (NC1, NC2, NC3) can be switched between the first and the second switching state, wherein the relay (R) has a first, energized state and a second non-energized state.

3. Device (V) according to claim 2, characterized in that the at least one contact circuit (NC1, NC2, NC3) is a normally-closed contact circuit, wherein the normally-closed contact circuit can be maintained in the first switching state by the at least one relay (R), which has the first state.

4. Braking system (BS) for controlling a passive brake apparatus, in particular a passive electromechanical brake apparatus, based on a force gradient, wherein the braking system (BS) has at least one device (V) according to claims 1 to 3.

5. Method for controlling a brake apparatus, in particular a passive electromechanical brake apparatus, based on a force gradient, wherein the method can be implemented by a device (V) according to claims 1 to 3 or a braking system according to claim 4, and wherein the method comprises the following steps: - Switching the at least one contact circuit (NC1, NC2, NC3) from the first switching state into the second switching state.