Shading device

Abstract

The invention relates to a shading system (1) with a blind (2) which can be moved upwards or downwards by means of an electric drive. The electric drive is designed as an AC motor (5). A control unit (7) is provided, which controls the AC motor (5) with pulse-width modulation. A brake unit (6) is associated with the AC motor (5).

Description

[0001] The invention relates to a shading system according to the preamble of claim 1.

[0002] Such a shading system generally includes a curtain which can be moved upwards or downwards by means of an electric drive, so that the curtain can be moved between an upper and lower end position.

[0003] The term "shading system" generally encompasses sun protection and privacy screens. For example, a shading system can consist of a roller shutter, a blind, a zip curtain, or similar devices.

[0004] Commonly used shading systems employ two-phase induction motors with an auxiliary capacitor. These induction motors rotate at a fixed speed, which is directly linked to the mains frequency of the power supply; therefore, speed adjustment is not possible with such electric drives.

[0005] It is also known to use electric drives in shading systems, where electronic speed control can be achieved via phase-angle control. However, a disadvantage of this is that phase-angle control reduces the efficiency of the electric drive, leading to faster heating of the drive. Furthermore, electric drives controlled by phase-angle control generate a clearly audible humming noise, typically in the range of approximately 100 Hz. This is perceived as extremely annoying by the user.

[0006] EP 1 503 472 A2 relates to a drive device for an positioning system with a drive which is supplied with an alternating voltage forming a supply voltage, with a control unit and associated switching means by means of which a phase-sensitive switching of the supply voltage to the drive can be carried out depending on the speed of the drive.

[0007] The invention is based on the objective of providing a shading system of the type mentioned above, which has a high level of functionality despite its simple design.

[0008] The features of claim 1 are provided to solve this problem. Advantageous embodiments and expedient further developments of the invention are described in the dependent claims.

[0009] The invention relates to a shading system with a blind that can be moved upwards or downwards by means of an electric drive. The electric drive is designed as an AC motor. A control unit is provided that controls the AC motor using pulse-width modulation. A braking unit is associated with the AC motor. The frequencies of the pulse-width modulation are in the kHz range.

[0010] The combination according to the invention of an electric drive designed in the form of an alternating current motor, which is controlled with pulse width modulation, and the brake unit associated with the electric drive achieves a high level of functionality of the shading system in a structurally simple manner.

[0011] A key advantage of the invention is that pulse-width modulation enables high-frequency control of the AC motor. This allows for high control frequencies that depend directly on the switching frequency of the pulse-width modulation. This, in turn, allows for high resolution in the control processes, resulting in smooth operation of the AC motor.

[0012] Furthermore, pulse-width modulation makes it possible to achieve slow speeds of the AC motor and thus of the blind over longer periods, thereby increasing the user-friendliness of the shading system.

[0013] Another significant advantage of the invention is that the pulse-width modulation of the AC motor achieves a considerable reduction in noise compared to known drive systems for shading systems. This is due to the fact that the control with pulse-width modulation is high-frequency, with the pulse-width modulation frequency advantageously being above the frequency range audible to humans.

[0014] According to the invention, the frequencies of the pulse width modulation are in the kHz range, in particular in the range of 15 - 20 kHz.

[0015] Annoying humming noises from the AC motor are thus completely eliminated by the pulse-width modulation according to the invention.

[0016] Preferably, pulse-width modulation can be used to control the speed of the AC motor, which offers further advantages for the shading system according to the invention.

[0017] A user-related advantage arises particularly when multiple shading systems are used in an application, for example on a building. The inventive speed control of the AC motor by means of pulse-width modulation enables precise synchronous operation of the blinds of the individual shading systems, which leads to a particularly good overall visual impression when several blinds are arranged side by side, for example on a track wall.

[0018] Another advantage of speed control is that the operation of the shading system is largely independent of the input voltage. This makes it possible, in particular, to meet the standard requirement that the operation of the AC motor be independent of fluctuations in the mains voltage within a range of ±10% of the nominal value. In principle, it is even possible, through pulse-width modulation, to use the AC motor and thus the shading system in countries where completely different mains voltages are available.

[0019] Furthermore, it is already possible to avoid heat generation in the AC motor through pulse width modulation.

[0020] This effect is enhanced in a surprisingly simple way by adding a braking unit to the AC motor. When the braking unit is activated, the AC motor pushes the blind against the braking force of the brake, especially when the blind is moving downwards. The braking unit is designed so that energy is supplied to the AC motor during this downward movement of the blind. This, in turn, means that the AC motor does not generate heat; that is, no separate resistors are needed to dissipate energy generated in the AC motor.

[0021] Energy-optimized operation of the shading system is ensured in particular if the braking unit is only activated during the downward movement of the blind, but is deactivated or only partially activated during the upward movement of the blind.

[0022] A particular advantage is that the braking unit is continuously activated, meaning it is engaged during both the raising and lowering of the blind. This allows for a particularly simple design of the overall system. Specifically, no separate control devices are required for time-dependent control of the braking unit.

[0023] According to an advantageous embodiment, the AC motor is designed as a single-phase asynchronous motor with an auxiliary capacitor.

[0024] Furthermore, the braking unit advantageously consists of a hysteresis brake, in particular a magnetic hysteresis brake.

[0025] In general, the present application is also applicable to a horizontal shading system in which the fabric can be moved, at least approximately, horizontally between a closed and an open position. An example of this is an awning.

[0026] The invention will be explained below with reference to the drawings. The drawings show: Figure 1: Schematic representation of an embodiment of the shading system according to the invention. Figure 2: Circuit diagram of the control of the electric drive. Figure 3: Diagram of a pulse-width modulation for controlling the electric drive according to Figure 2 Figure 4a - c: Diagram of a phase-angle control of the electric drive according to the state of the art.

[0027] Figure 1 Figure 1 shows a highly schematic embodiment of the shading system 1 according to the invention. The shading system 1, as defined by the invention, includes sun protection and privacy screens of all kinds. For example, the shading system 1 can be designed in the form of a roller shutter, a Venetian blind, or a ZIP curtain.

[0028] The shading system 1 comprises a curtain 2 which can be moved upwards or downwards by means of a drive unit 3 and can thus be moved between an upper and lower end position. Figure 1 shows the curtain 2 in the lower end position.

[0029] The drive unit 3 sets a shaft 4 into a rotary motion. Depending on the direction of rotation of the shaft 4, the curtain 2 is wound up or unwound onto the shaft 4.

[0030] The drive unit 3 comprises an electric drive in the form of an AC motor 5, a brake unit 6 and a control unit 7.

[0031] In the present case, the AC motor 5 is formed by a single-phase asynchronous motor with an auxiliary capacitor. A second phase is generated by the auxiliary capacitor in a known manner, so that two phases are available to generate a rotating magnetic field.

[0032] The brake unit 6 advantageously consists of a hysteresis brake, in this case a magnetic hysteresis brake.

[0033] The control unit 7 consists of a processor or the like. In this case, the control unit 7 is integrated into the drive unit 3. Alternatively, the control unit 7 can also be located outside the drive unit 3 and connected to the drive unit 3 by a cable connection or the like.

[0034] Figure 2Figure 1 shows the control of the AC motor 5 of the drive unit 3. The AC motor 5 is integrated into an AC circuit 8. The AC motor 5 is controlled in a known manner by a push-pull controller 9, which is part of the control unit 7. The push-pull controller 9 controls a switching element 10 in a freewheeling circuit 11, thereby enabling controlled switching on and off of the AC motor 5 and thus commutation of the AC motor 5.

[0035] According to the invention, the AC motor 5 is controlled by pulse-width modulation. For this purpose, the control unit 7 has a generator 12 which generates a control signal for the pulse-width modulation via a line 13, which is output to a power stage 14 of the pulse-width modulation. Furthermore, the push-pull controller 9 outputs a synchronization signal to the power stage 14 via line 15. The power stage 14 consists of a switch or the like.

[0036] The principle of pulse-width modulation shows Figure 3 In the time diagram of Figure 3 Figure 3 shows one period of the voltage for the AC motor 5. Using pulse-width modulation, this period is divided into a large number of control sections, one of which is designated by the reference numeral a in Figure 3.

[0037] By selecting the number and size of the control sections, the voltage supplied to the AC motor 5 can be set very quickly and precisely. This allows for fast and accurate control of the AC motor 5, and in particular, enables slow operation of the AC motor 5 over extended periods.

[0038] Such pulse-width modulation allows for significantly faster and more precise control of the AC motor 5 than would be possible with a known phase-angle control. Such phase-angle control is shown in the timing diagrams of the Figures 4a - c shown. There are only two control sections per phase of the voltage of the AC motor 5 (in the Figures 4b, 4c (labelled b).

[0039] In comparison, pulse-width modulation allows for much faster and more precise control of the AC motor 5, since each phase of the voltage for the AC motor 5 can be divided into a large number of control sections a.

[0040] Pulse-width modulation (PWM) allows the AC motor 5 to be controlled in the kHz range, a frequency above the range of human hearing. This eliminates any disturbing humming noises audible to humans when controlling the AC motor 5.

[0041] Furthermore, by controlling the AC motor 5 using pulse-width modulation, unwanted heat generation in the AC motor 5 can be reduced.

[0042] The heat generation of the AC motor 5 is also reduced in particular by the brake unit 6 associated with the AC motor 5, which in this case is designed in the form of a magnetic hysteresis brake.

[0043] In the present case, the brake unit 6 is designed to be permanently activated, that is, both during the upward and downward movements of the blind 2.

[0044] During downward movement, the activated braking unit 6 continuously supplies energy to the AC motor 5, which means that no potential energy of the curtain 2 needs to be dissipated during the downward movement. This eliminates the need for additional resistors and the like to dissipate this potential energy.

[0045] In principle, the shading system 1 can also be designed so that the brake unit 6 is fully activated only during the downward movements of the blind 2, but is deactivated or only activated to a limited extent during the upward movements.

[0046] Advantageously, the AC motor 5 is provided with speed control, which is carried out via the control unit 7. This enables the AC motor 5 to operate independently of the mains voltage. Reference symbol list

[0047] (1) Shading system (2) Blind (3) Drive unit (4) Shaft (5) AC motor (6) Brake unit (7) Control unit (8) AC circuit (9) Push-pull control (10) Switching element (11) Freewheeling circuit (12) Generator (13) Cable (14) Power stage (15) Cable aControl section bControl section

Claims

1. Shading device (1) with a curtain (2), which can be moved up or down by means of an electric drive, wherein the electric drive is designed as an alternating current motor (5), wherein a control unit (7) is provided which controls the alternating current motor (5) with pulse width modulation, and wherein a brake unit (6) is assigned to the alternating current motor (5), characterised in that the frequencies of the pulse width modulation are in the kHz range.

2. Shading system (1) according to claim 1, characterised in that the control unit (7) is used to control the speed of the alternating current motor (5).

3. Shading system (1) according to one of claims 1 or 2, characterised in that the brake unit (6) is activated at least during the downward movements of the curtain (2).

4. Shading system (1) according to one of claims 1-3, characterised in that the brake unit (6) is activated during the upward and downward movements of the blind (2).

5. Shading system (1) according to one of claims 1-4, characterised in that the frequency of the pulse width modulation is above the frequency range audible to humans.

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