Brushless Dc-Motor

• US 20090009115A1
• Filed: 06/03/2005
• Published: 01/08/2009
• Est. Priority Date: 06/04/2004
• Status: Active Grant

• Current Assignee: Belimo Holding AG
• Original Assignee: Belimo Holding AG
• Inventors: Grogg, Silvio, Staheli, Curdin, Ochsenbein, Martin
• Granted Patent: US 8,314,580 B2
• Time in Patent Office: Days
• US Class Current: 318/400.340
• CPC Class Codes: H02P 6/182 using back-emf in windings
• CPC Class Codes: H02P 6/21 Open loop start
• CPC Class Codes: H02P 6/24 Arrangements for stopping

Abstract

According to the invention, a DC-motor (46) actuates a highly reduced reduction gear of an actuating drive for a flap or for a valve in order to regulate a gas or liquid volume flow, in particular in the field of heating/ventilation/climatisation, or fire or room protection. The electric flow of current in the stator coils (A, B, C) is commutated in a program-controlled manner without integrated position sensors. The rotations of the rotor (54) of the DC-motor (46) can be counted by means of special algorithms. Problems related to the principle of motor rotation speed of less than approximately 200 rpm are prevented. The DC-motor (46) comprises a stator (44) which comprises three stator coils (A, B, C) which extend over 3n stator poles (52), and an annular-shaped permanent magnet rotor (54) having 2m permanent magnet segments with alternating polarity (N, S), a coaxial cup-shaped external rotor (110) and a coaxial drive shaft (108), whereby n and m are whole multiplication factor numbers (1, 2, 3, 4) and are different from each other. The drive shaft (112) comprises, preferably, a spring (120) for the automatic return in case of an interruption in current.

Claims

1. Method for controlling a brushless DC motor (46) comprising a stator (44) and rotor (54), which has a highly reduced reduction gear of an actuating drive for a flap or valve in order to regulate a gas or liquid volume flow, in particular in the field of heating, ventilation and climatisation (HLK), fire and room protection, characterised in that the electrical current flow in the stator coils (A, B, C) is commutated under programme control without integral position sensors.

2. Method according to claim 1, characterised in that the polarities of the zero crossings of the phase voltages (DRA, DRB, DRC) are checked with BEMF comparators (12), each polarity change is allocated to a rotor position and the next commutation determined.

3. Method according to claim 2, characterised in that the valid zero crossings of three phase voltages (DRA, DRB, DRC) are detected and the generated BEMF signals (13) control the switch between the three phase voltages (DRA, DRB, DRC).

4. Method according to claim 3, characterised in that the valid zero crossings (56) are detected by means of a ZERO detector (14) and ZERO pulses (18) are generated.

5. Method according to any of claims 1 to 4, characterised in that from the BEMF signals (13) which on valid zero crossings cause ZERO pulses (18), a period counter (20) calculates the next commutation time and a corresponding control signal, a NEXT pulse (22), is emitted.

6. Method according to any of claims 2 to 5, characterised in that the direction of rotation of the rotor (54) is determined by means of the BEMF comparators (12) in that the BEMF comparator thresholds (58), depending on polarity of the expected zero crossing, are located just above or below the zero line (S) of the phase voltages (DRA, DRB, DRC).

7. Method according to claim 6, characterised in that the direction of rotation of the rotor (54) in the high impedance commutation gaps (L) of the phase voltages (DRA, DRB, DRC) is determined at low speeds preferably at the end of the commutation gap and at high speeds at the end of the passive PWM phase.

8. Method according to any of claims 1 to 7, characterised in that the DC motor (46) commutates the end stages on start up and their current limit (102) is increased for an accelerated start, preferably by 10 to 50%, in particular by around 20%, until valid BEMF signals are reached, after which commutation of the next phase is located between two zero crossings.

9. Method according to claim 8, characterised in that after an unsuccessful powering of the first end stage, a logic commutates in steps the current supply of the next end stage until a starting position which is favourable for the rotor (54) is reached.

10. Method according to claim 8 or 9, characterised in that on lack of detection of a zero crossing of a phase voltage, after a first commutation the rotor oscillates with its resonant frequency into the zero position and by these zero crossings, valid BEMF signals are achieved.

11. Method according to any of claims 1 to 10, characterised in that the logic detects a wrong direction of rotation of the rotor (54) from the wrong polarity of the BEMF signals (13) and corrects this by increasing the counter state of the cycle counter (24) by two steps.

12. Method according to any of claims 1 to 11, characterised in that the rotor (54) in a first step for braking and holding first by short circuit switches all stator coils (A, B, C) powerless under continuing commutation, after reaching a pre-set threshold value of preferably maximum around 400 rpm in a second step, with a greatly increased current pulse (65) leading to block, changes from the next to the last commutation state, and in a third step again by short circuit switches the stator coils (A, B, C) of rotor (54) powerless or inhibits them with low pulse width modulation (PWM).

13. Method according to claim 12, characterised in that the rotor (54) in the first step is switched actively in the opposite direction.

14. Method according to claim 12 or 13, characterised in that to achieve and hold a high contact pressure by the reduction gear in the stop position of the flap or valve, the DC motor (46) which is stalled by the stop, because of the rotor inertia torque continues to rotate uncontrolled for a few revolutions, the rotor position is detected by an immediately subsequent brief acceleration in the opposite direction by means of BEMF signals (13), and the rotor (54) is braked under control and held.

15. Method according to claim 14, characterised in that acceleration in the opposite direction takes place only after relaxation of the reduction gear.

16. Method according to any of claims 1 to 15, characterised in that the process algorithms are stored retrievably.

17. Method according to any of claims 1 to 16, characterised in that the electronics count the revolutions of the rotor (54) of the DC motor (46), where preferably each motor commutation is detected and supplied to a counter with special algorithms.

18. Method according to claim 17, characterised in that algorithms for start and stop cause motor speeds below around 200 rpm to be passed quickly and without the occurrence of counting errors.

19. Method according to any of claims 1 to 18 for an actuating drive with a pre-tensioned spring (120), in particular a coil spring (120), characterised in that on a power failure two of the three individually moveable bridge switches (a, b, c) of a switch group (50) short-circuit two of the three stator coils (A, B, C) of the DC motor (46) to earth when the speed falls below an adjustable limit speed of the rotor (54).

20. Method according to claim 19, characterised in that a bridge switch pair (a and b, a and c, b and c) is activated by way of a pulse width modulated control signal from the allocated transistors, preferably with increasing time intervals.

21. Brushless DC motor (46) without position sensors for performance of the method according to any of claims 1 to 20, characterised in that it comprises a stator (44) with three stator coils (A, B, C) which extend over 3n stator poles (52) and an annular permanent magnet rotor (54) with 2m permanent magnet segments of alternating polarity (N, S), a coaxial cup-shaped external rotor (110) and a coaxial drive shaft (108), where n and m are whole multiplication factors 1, 2, 3, 4 . . . independent of each other.

22. DC motor (46) according to claim 21, characterised in that n=1 and m=1 or n=3 and m=6.