EP-4283857-B1 - ELECTRONIC BRAKING SYSTEM FOR AN ELECTRIC MOTOR IN THE ABSENCE OF AN ELECTRICAL SUPPLY

Inventors

• TURCHETTI, Claudio

Dates

Publication Date

20260506

Application Date

20230526

Claims (7)

1. Electronic braking system for an electric motor (2) for an automatic swing door sector in the absence of an electrical supply comprising • • a braking circuit (6), • • a control circuit (5) comprising a microcontroller (51) which controls said braking circuit, • • an enabling switch (9) that connects said control circuit (5) and braking circuit (6) to the electrical connections of the motor when power (7) is removed from it, wherein the braking circuit carries out a PWM modulation of the induced voltage signal generated by the motor in rotation, when the power supply is removed from it and said control circuit controls the "duty cycle" of said modulation, characterised in that the control circuit comprises a voltage regulator circuit (52) which takes the voltage induced by the motor stabilizes it and supplies it as a power supply to said microcontroller (51) only when the enabling switch connects the control circuit and braking circuit to the electrical connections of the motor (2) when power (7) is removed from it.
2. System according to claim 1, wherein said braking circuit comprises a PWM modulated MOSFET, the PWM being generated by the microcontroller of the control circuit (5).
3. System according to claim 1, comprising a position sensor (8) of the rotation of a crankshaft, the microcontroller receiving the signal from the position sensor, so as to activate the braking circuit when a predefined angular position of the shaft is reached.
4. System according to claim 3, wherein the control circuit comprises a selector (55) which allows to select a minimum or maximum braking speed.
5. System according to claim 1, comprising a unidirectional element (4) designed to prevent the intervention of the braking system during normal use of the motor.
6. System according to claim 1, wherein a control circuit comprises a circuit (53) for detecting the speed of rotation of the motor.
7. System according to claim 1, in which the motor (2) is associated with the leaf of an automatic swing door.

Description

The present invention relates to an electronic braking system for an electric motor in the absence of an electrical supply. In particular, the present invention relates to an electronic braking system for an electric motor in which the rotation is to be slowed down (until the rotation of the crankshaft stops) when it is without power supply voltage. Such a system is used, for example, in the automatic swing door sector. A typical application is the one related to a door leaf, which is opened manually, in the absence of power supply, by overcoming the force of a spring that is loaded during such opening. The leaf automatically closes again due to the force of the preloaded spring, the leaf returns to the closed position. In such cases, the last part of the movement is desired to be faster than the first part, and therefore the motor is required to be used as a braking device for the leaf movement. In these cases it is desired to release the brake in the last fraction of the movement in order to, for example, trigger a lock. Another example occurs in the opposite situation, wherein the closure of a door is motor driven, while its opening is adjusted by a spring, and the motor has to act as a brake; such a situation occurs in escape routes or in smoke evacuation. In these cases, but not exclusively, a slowdown is desirable to prevent the leaf from hitting against an end-of-stroke device, or against a wall. There are many products, in the market segment of the swing door driving devices that use circuits that, in the event of a power supply failure or electrical failure, slow down the speed of the door. Many examples may be found that use passive components or linear circuits. For example, when the power supply voltage in the motor is interrupted, it operates like a dynamo, generating electrical energy. Such energy is dissipated by a dissipation circuit that comprises one or more dissipation resistors. These solutions generally cause heating problems in the printed circuit board due to the dissipation of linear elements (e.g. the resistor(s)). JP H11 128587 A discloses an electromagnetic brake system, comprising a regenerative brake, a discharge brake and a short circuit brake, for damping a 3 phase brush less motor which actuates a rotation tank and an agitator. The present invention proposes an electronic braking system for an electric motor in the absence of an electrical supply that solves such problems. One aspect of the present invention relates to an electronic braking system for an electric motor having the characteristics of the attached claim 1. Further features of the present invention are contained in the dependent claims. The characteristics and advantages of the present invention will become more apparent from the following description of an embodiment of the invention, provided by way of non-limiting example, with reference to the schematic attached drawings, wherein: Figure 1 shows a block diagram of a general electric braking system applied to an electric motor;Figure 2 shows a block diagram of the electric braking system applied to the motor of a door leaf according to an embodiment of the invention. With reference to the above-mentioned figures, the braking system according to the present invention is applied to an electric motor 2 in order to slow down and then stop rotation thereof when the power supply to that motor has been interrupted. In the embodiment shown in Figure 3, the motor 2 moves a door leaf, allowing it to be opened. The door leaf closes again thanks to the counteracting action of a spring 3 that is loaded when the leaf is opened, returns its compression force to the leaf when the power source is disconnected, allowing it to close again. The braking system according to the present invention allows, alternatively, either to release the brake to increase the speed, or to slow down, in the last part of the leaf movement, by braking or releasing the rotation of the motor against the spring action. Obviously the present invention may be applied to any application where it is required to brake the rotation of an electric motor when the electrical supply has been removed from it, either because of a fault or due to a determined choice. The principle underlying the system is that of exploiting the counter-electromotive force that is generated in an electric motor when the power supply is removed from it, which behaves in such conditions, like an electric generator. Such an electromotive force is supplied to the braking circuit, which dissipates it, thus braking the rotation (see, e.g. Figure 1 showing such principle). The system generally comprises a unidirectional element 4 designed to prevent the intervention of the braking system in the manually controlled direction of rotation, a control circuit 5 which manages the intervention of a braking circuit 6, designed to dissipate the induced counter-electromotive force, when the rotating motor is disconnected from its normal power supply