DE3932802A1 - Brushless high speed DC vacuum cleaner motor - has electronic commutation for hazardous applications using Hall-effect sensors in permanent magnet rotor with in-built stator current limit - Google Patents

Abstract

A brushless electronically commutated DC vacuum cleaner motor (1) with permanent magnet rotor (5) has a two-stage turbine fan (10,11) and a speed characteristic which results in rotor acceleration when the intake orifice (29) is obstructed. The motor drive employs an alternating stator field under the control of hall-effect sensors (26) and push-pull transistor output stages to produce an efficient unit capable of high speeds with high power/weight ratio. Logic circuitry determines appropriate stator current with overload limitation provided by thermal unit (35). A fixed direction of rotation is ensured by the asymmetric airgap. USE/ADVANTAGE - Particularly in areas where spark ignition of combustible dust cloud may cause explosion. Has efficient operating level at high powers and speeds, low inductance and high power/weight ratio. Vacuum increase to clear intake obstruction due to automatic increase in RPM. No commodator to cause sparking at sudden load change. Less expensive than digitally controlled alternatives.

Description

The invention relates to a vacuum cleaner motor consisting of a Stator with excitation winding and a rotor with a turbine for Generation of negative pressure is coupled, with the engine on Has speed behavior, such that when closing the Suction opening of the vacuum cleaner the speed of the motor runs up and down sets an increased suction pressure.

So far, it has been the case with vacuum cleaners with the speed behavior shown known to use a collector motor. Such one The collector motor also runs when the suction opening is closed automatically up in speed, which is desirable in order to to achieve a higher suction pressure when the suction nozzle is loaded. However, a disadvantage occurs with these universal motors of the type Collector motors on a brush fire, so that the equipped Vacuum cleaners are not to be used in potentially explosive areas can. Otherwise correspond to those with collector motors Equipped vacuum cleaners do not meet the safety requirements for dust explosion-proof industrial vacuum cleaners type 1 (Ignition source free design).

They are already connected to a frequency converter Asynchronous motors are known which are used for vacuum cleaners. Such asynchronous motors have the vacuum cleaner Disadvantage that they have a stable speed behavior, so that too with closed vacuum cleaner opening no increase in Speed. Only fixed vacuum values of reached about 130 to 140 mbar. In the event of a run-on or run-up of the However, speed becomes a pressure of about 230 mbar for an increased suction pressure needed.  

To in known motors which are arranged in vacuum cleaners, at Load to increase the speed are already additional devices known, in particular within the vacuum cleaner with a sensor the vacuum is picked up by means of a membrane pressure switch or an electrical pressure sensor. The signal from the diaphragm pressure switch or pressure sensor is a control electronics or a Frequency converter fed, causing the motor to jump on its Maximum speed of approximately 25,000 revolutions per minute is increased, which corresponds to a frequency of approx. 400 Hz.

In another known embodiment, the current of the motor tapped and fed to a control electronics, with increasing the Vacuum by reducing the intake opening of the engine draws less current and then this frequency becomes the frequency pushed. With such a modulation, the current of the Vacuum cleaner motor achieved with known AD modulators. The However, known solutions are relatively complex and prone to failure.

The object of the present invention is therefore a Vacuum cleaner motor of the type mentioned so that in structurally simple manner with relatively little effort Brushless, high-speed, high-performance DC motor created which runs up in speed when the suction opening is reduced and is particularly suitable for explosive areas. The The present invention is particularly concerned with the creation of a Motor, neglecting the starting torque with high Power works at high speeds and only rotates in one direction and especially with a low level of iron saturation high efficiency, d. H. a very high power volume ratio having. The vacuum cleaner motor like a brushless one DC motor with a frequency superimposed DC voltage is also operated - to keep disruptions to a minimum - a very have low inductance.  

To solve the problem, the characteristics of the characterizing part of the Claim 1 provided.

The essence of the invention is that the motor with one frequency-superimposed direct current is operated, whereby starting from Stator is a trapezoidal magnetic field that changes with frequency is achieved, which acts on permanent magnets of the rotor and so the motor rotates with high efficiency. The Frequency readjustment takes place here via Hall generators which Permanent magnets, which are arranged in the area of the rotor shaft, can be controlled, whereby the motor is regulated in frequency, until a desired maximum speed is reached. In connection with the Frequency control of the motor is also a current limitation provided, frequency control and current limitation via gates are linked together so as not to overload the motor. The The motor itself is controlled by output stages, with push-pull switched transistors provided in connection with a diode bridge are, wherein a direct current is generated to control the motor, the is superimposed with the control frequency in the manner of a sawtooth pattern. By controlling the motor in push-pull a particularly high one Efficiency achieved, in connection with the frequency control the engine turns up particularly quickly, in about 1 second, and in a very high speed of over 30,000 revolutions per minute is achieved.

The speed is limited by the air pressure set in the two-stage turbine and additionally through the ventilation wheel for the Winding cooling.

In an advantageous embodiment, it is provided that the switching pulses of the Hall sensors symmetrically at the inputs of the control logic are routed via Schmitt triggers and further AND gates be forwarded where a link with a flip-flop regarding the circuit is started and an additional connection is made via  additional AND gate is provided where a link to the Current control of the output stages takes place in such a way that the transistors be switched through so that a with the control frequency of Hall sensors fluctuating DC current within the Excitation winding arises. In this regard, the transistors of the Power amplifiers switched on or off with increasing current and in cycles the control frequency, so that in the field of excitation winding sawtooth-shaped, fluctuating current curve arises. This will a trapezoidal magnetic field is generated with the stator advantageously steep rising edges, the magnetic field on the ring-shaped permanent magnets of the rotor acts and such in Clock of the control frequency rotates the rotor.

In a further advantageous embodiment it is provided that in Starting time of the motor delays the activation of the output stages an RC element and an additional switching stage, which is in the another flip-flop that switches with its output AND gate for the control with the Hall sensors releases, causing the motor is started.

After switching on the supply voltage, the motor or the Excitation winding initially decelerates with an increasing current branch applied, whereby the rotor is rotated slightly and then the Hall sensors come into effect via the control logic and in further adjust the frequency of the output stages. This will start with an increasing current load starting from the point at which the motor is switched on reached while under the influence of the frequency readjustment via the Hall sensors then at the apex of the power branch the current drops until to an adjustable value and then rising again and so on according to the control voltage of the Hall sensors.

The power amplifiers are also advantageous via a thermal switch Motors controlled, the thermal switch in connection with a Switching element controls the error input of the output stages.  

The Hall sensors themselves are advantageous in the area of the rotor shaft arranged opposite magnets rotating with the rotor shaft.

In an advantageous embodiment, the excitation winding is divided into four poles trained, the excitation winding in the same number of poles ring-shaped Face the permanent magnets of the stator in the manner of a ring shell.

In a further advantageous embodiment it is provided that in Area of the field winding of the air gap towards the stator accordingly the number of poles is narrowed asymmetrically, such that towards the respective narrowing of the air gap predetermined starting direction of the motor results.

With the narrowing of the air gap between the stator and rotor, in a constructively simple way, always the same starting direction of the engine reached, with the asymmetrically arranged in a ring Air gap arrangement avoided saturation of the rotor or stator laminations becomes.

The invention is explained in more detail below with reference to drawings described, and from the description still further for the invention substantial benefits emerge.

Show it:

Partly in section Fig. 1 is a view of the vacuum cleaner motor with a flanged turbine,

Fig. 2 is a longitudinal section through the engine in a schematic representation;

Fig. 3 shows a cross section through the motor in a schematic representation;

Fig. 4, the control circuit for the motor with the control logic circuit for controlling the frequency and power characteristics of the engine,

Fig. 5, the course of the driving current for the vacuum cleaner motor to the output of the circuit according to Fig. 4,

Fig. 6 shows the current profile in the field winding, depending on the number of revolutions of the motor.

In Fig. 1, the vacuum cleaner motor 1 is shown with flange-mounted turbine 10 , wherein the motor 1 consists of stator 2 with excitation winding 3 and the rotor 5 . The rotor 5 is arranged on a continuous rotor shaft 8 , on which the turbine 10 with the turbine wheel 11 with individual fan blades is also attached.

From Fig. 1 it can be seen that the rotor 5 opposite the stator 2 has permanent magnets 7 which are held together laterally by means of bearing shells via clamping screws 23 .

The motor 1 furthermore itself has a fan wheel 9 , suction slits 29 and outlet slits 16 being provided in order to cool the motor 1 .

The motor 1 is covered in the exemplary embodiment by a cover 32 in connection with a bearing of the motor (not shown in more detail) in a bearing plate, the turbine wheel 11 advantageously also being mounted in the same place as the motor in the bearing plate, so that this results in advantageous cooling of the Storage results.

On the circumference of the turbine 10 , the outlet openings 17 can be seen, which furthermore, with corresponding air channels in the vacuum cleaner itself, bring about the negative pressure in the suction pipe of the vacuum cleaner.

Schematic representation of Figure 1 is shown in Fig. Can also be seen that on the rotor shaft 8 on the outer side of the cover 32 sensors 26, preferably two Hall sensors 26 are provided, which rotating permanent magnets are 25 opposite, whereby the time necessary for the drive circuit of FIG. 4 Frequency is concerned to control the speed of the vacuum cleaner motor.

In Fig. 2, the motor 2 is shown in longitudinal section, it being apparent that rotor plates 6 of the rotor are arranged on the rotor shaft, the permanent magnets 7 being arranged in a schematic representation on the circumference of the rotor plates 6 in the manner of an annular shell. Starting from the stator 2 and the excitation winding 3, these permanent magnets 7 are acted upon by a preferably trapezoidal magnetic field, as a result of which the permanent magnets 7 are triggered in alternation of the frequency and the rotor 5 is thus set in rotation.

Between the rotor 5 and the stator 2 , an air gap 4 can also be seen, which, according to FIG. 3, has a narrowing 24 in accordance with the number of poles in an annular arrangement, so that the air gap 4 as a whole runs asymmetrically from the excitation winding 3 to the next excitation winding 3 . In this way it is achieved that the motor 1 always rotates with a preferred starting direction.

From Fig. 2, the Hall sensors 26 are clearly recognizable in a schematic representation with the permanent magnets 25 rotatingly arranged on the rotor shaft 8 , which cause a likewise trapezoidal voltage potential in the Hall sensors 26 , which further serves for frequency control with regard to the circuit according to FIG. 4.

From Fig. 3 it can be seen that the excitation winding 3 is formed according to a four-pole arrangement, which is opposed by an annular shell 18 - formed from permanent magnets 7 - the permanent magnets 7 also being arranged in a four-pole arrangement on the rotor shaft 8 . The rotor 5 is accordingly formed by rotor plates 6 , which are arranged in a nested arrangement in the manner of a package on the rotor shaft 8 , the annular shell 18 , formed by the permanent magnets 7 , being arranged on the circumference of the rotor plates 6 .

In the area of an excitation winding 3 according to FIG. 3 there is further arranged a thermal switch THS 1 , which has its input connected to the circuit according to FIG. 4, the output stages being controlled via a Schmitt trigger in order to prevent the motor from overheating in the area the fault input of the output stages to ensure a current shutdown.

From Fig. 3 it can be seen that the permanent magnets 7 of the rotor 5 are provided in a ring-shaped series connection in a north-south arrangement, the excitation windings 3 of the stator in conjunction with the current curve according to FIG. 5 and the frequency curve shown form an alternating field, which is shown schematically in the area of the excitation windings 3 of the stator 2 . Via this preferably trapezoidal alternating field, the permanent magnets 7 of the rotor 5 are triggered in time with the frequency, starting from the Hall generators 26 , which causes the circuit to oscillate and the motor to reach its maximum speed of over 20 in a very short time of about 1 second Revs up 000 revolutions per minute.

The speed itself is not limited when the engine is cranked up. Only a current limitation of the field winding 3 of the motor is provided according to FIG. 6 in connection with the control logic according to FIG. 4. The motor can therefore reach speeds between 20,000 and 30,000 revolutions per minute, whereby the speed limitation only in the mechanical property of the Turbine wheels of the turbine and the fan wheel is justified.

In FIG. 4 the manner of a block circuit diagram illustrating the control for the field windings 3 of the engine 1.

The motor 1 is connected with its excitation winding 3 to the outputs K 1 , K 2 (Mot B, Mot A). The further outputs K 3 and K 4 (+ U _M , -U _M ) of the circuit according to FIG. 4 are connected to an operating voltage of preferably 270 volts DC, which is generated in a power supply unit, not shown here.

The circuit outputs K 5 and K 6 lead to ground or to 15 volts DC voltage to supply the control logic according to FIG. 4, the supply voltage also being generated in a power supply unit, not shown, with stabilizing devices.

The other outputs K 7/1 to K 7/5 of the circuit lead to the motor or its control board. The output K 7/1 supplies the control board of the motor and the circuit arranged on it with a control voltage of 15 volts DC. The K 7/5 output is connected to ground.

The outputs K 7/2 and K 7/3 of the circuit according to FIG. 4 lead to the Hall sensors 26 or HS 1 and HS 2 . The output K 7/4 leads to the thermal switch 35 of the motor or to the switch THS Mot.

In the circuit of Fig. 4, the two amplifiers 28 as integrated circuits IV 1 and IV 2 are shown at the outputs of the transistors T 1, T 2 and T 3, T 4 in conjunction with a diode bridge D 1 and D 2 are connected , the outputs K 1 , K 2 for connecting the excitation winding 3 of the motor starting from a bridge branch of the diode bridge D 1 and D 2 .

The output stages 28 , which act as frequency converters 27 , are controlled by a control logic, the supply voltage of 15 volts DC voltage being first applied to a Schmitt trigger IV 6 / C via the RC elements R 8 and C 7 . The output of the Schmitt trigger IV 6 / C controls a flip-flop IV 6 / A and IV 6 / B, whereby the input circuit in the area of the Hall sensors 26 is started with the output of the flip-flop.

The Hall sensors 26 - here at the outputs HS 1 and HS 2 - are on the one hand via the Schmitt trigger IV 4 / C and IV 4 / D directly at the frequency input trip 1 of the output stages 28 and on the other hand are the Hall generators 26 with one frequency - and current control linked.

This link serves to limit the motor with respect to a certain current strength of the excitation windings 3 and on the other hand to impose a frequency on the current of the excitation windings with which the transistors T 1 , T 4 or T 2 and T 3 in connection with the diode bridge D Switch through 1 , D 2 . This frequency originates from the Hall sensors 26 according to FIG. 2, where in connection with the rotating magnets 25 a preferably trapezoidal frequency pattern is generated, which is further linked in the control logic according to FIG. 4 together with the current control, in order in this way to the excitation windings or to obtain a current profile according to FIG. 5 at the output of the circuit according to FIG. 4.

According to Fig. 5 it can be seen that the current I - starting from the zero point - rises rapidly and then the transistors T 1 , T 4 or T 2 , T 3 turn on at the apex, whereby the output current is sawtooth-shaped with a frequency mixture, starting from the Hall sensors 26 is modulated.

In connection with this, according to FIG. 6, there is a current limitation at approximately 10 amperes, this current of the excitation winding 3 remaining limited even at higher speeds of over 20,000 revolutions per minute.

To associate the frequency with the current limit, the outputs of the Hall sensors are shown in FIG. 4 performed 26 Schmitt trigger IV 4 / A and IV 4 / B, which with their outputs to AND gates IV 3 / A and abut IV 3 / B . At the other inputs of these AND gates IV 3 / A and IV 3 / B is the start signal for the motor - starting from the flip-flop IV 6 / A and IV 6 / B.

The output of the AND gates IV 3 / A and IV 3 / B is led as an input to further AND gates IV 3 / C and IV 3 / D, which are further connected to the supply voltage and an amplifier IV 5 / B for current limitation are linked. The frequency mixture from the Hall sensors 26 is present at an input of the amplifier IV 5 / B, which is used to limit the current, and this is then passed to the frequency input of the output stages 28 .

At the output of the link, starting from the AND gates IV3 / C and IV 3 / D, there is an input TOP of the output stage 28 , as a result of which a current limitation is achieved in connection with the control frequency.

Furthermore, after the circuit of Fig. 4 or the terminal of a thermal switch 35 and THS 1 is provided via the input H 7/4 said thermal switch 6 / D is fed to the error input of the power amplifiers via a schmitt trigger IV and is also present at the input of the flip-flop IV 6 / A in order to connect the control logic to start, for example when the engine overheats, and thus to interrupt the engine 1 .

The circuit according to FIG. 4 works as follows:
At the input of the circuit, the operating voltage of approximately 250 volts DC is initially present via the connections K 3 and K 4 , the transistors T 1 to T 4 being connected to the base with resistors R 1 to R 4 to ensure that when switching off the voltage supply immediately drops to zero.

For the supply voltage of 15 volts DC regarding the Control logic is - not shown here - a transformer in Connection provided with a rectifier, the voltage in in a known manner with an additional voltage stabilizer is stabilized.  

So if the mains voltage is 220 volts AC is created, the power supply to supply the power amplifiers and the motor has a voltage of about 270 volts DC and another 15 volts for the control logic.

After a delay via the RC element R 8 and C 7 , a negative pulse arises at the output of IV 6 / C, which resets the flip-flop IV 6 / A and IV 6 / B.

Now the output 4 of this flip-flop reaches a higher voltage level, whereby the AND gates IV 3 / A and IV 3 / B are activated.

The signal from the Hall sensors 26 or HS 1 and HS 2 now reaches the Schmitt triggers IV 4 / C and IV 4 / D, whereby the motor starts with the signals generated.

The engine 1 reaches its maximum number of revolutions in about 1 second.

The Schmitt triggers IV 4 / C and IV 4 / D are used to convert the frequency signal of the Hall sensors 26 into a voltage signal. In this regard, a dependence of the number of revolutions on the current is achieved in the manner of a limitation according to FIG. 6.

If the rotor of the motor z. B. is stopped mechanically, so according to FIG. 6 only three amperes flow through the excitation winding 3 , so that the motor is not overheated.

However, a motor switch THS 1 or THS Mot is also provided via input K 7/4 , which is switched between the motor windings, which causes the switch THS 1 to open and the Schmitt trigger IV 6 / D to zero when the temperature rises sets, which also resets the flip-flop IV 6 / A and IV 6 / B, whereby the output stages 28 are switched off electronically by the supply voltage.

In connection with FIG. 5, when the control logic is turned on, the transistors T 1 and T 4 or T 3 and T 2 turn on after a few fractions of a second, as a result of which the excitation winding is energized and the motor turns.

The maximum current level of the excitation windings 3 is regulated by the amplifier IV 5 / B. As soon as the current reaches the maximum level, the output 7 of the amplifier IV 5 / B switches to zero, as a result of which the AND gates IV 3 / C and IV 3 / D are blocked. As a result, the input 22 (top) of the output stages 28 approaches zero, so that the transistors T 1 or T 2 are closed. Furthermore, the current now flows through the diode D 2 and the transistor T 4 or T 2 , as a result of which the current profile according to FIG. 5 is modulated in a sawtooth shape in accordance with the frequency applied. At this frequency, the motor is forcibly steered upwards, and in connection with the Hall sensors 26 , the motor starts to oscillate in terms of speed in the manner of a feedback, as a result of which the motor starts up very quickly and very high speeds can reach up to 100,000 revolutions per minute when idling , depending on the mechanical strength of the moving parts and depending on the pneumatic properties of the turbine.

Drawing legend

1 engine
2 stator 32 cover
3 excitation winding
4 air gap
5 Rotor 35 THS 1 thermal switch
6 rotor plate
7 permanent magnet
8 rotor shaft
9 fan wheel
10 turbine
11 turbine wheel

16 outlet slot
17 outlet opening
18 ring bowl

23 clamping screw
24 narrowing
25 permanent magnet
26 Hall sensor
27 frequency converters
28 power amplifier
29 suction slot

Claims (7)

1. Vacuum cleaner motor, consisting of a stator with excitation winding and a rotor, which is coupled to a turbine for generating the negative pressure, the motor having a speed behavior, such that when the suction opening of the vacuum cleaner closes, the speed increases and an increased suction pressure is established , characterized in that a brushless DC motor ( 1 ) is provided in the manner of an electronically commutated motor, the excitation winding ( 3 ) of the motor being the push-pull of transistors T 1 (T 3 ) and T 4 (T 2 ) in connection with a diode bridge D 1 , D 2 is frequency and current controlled via two output stages IV 1 and IV 2 , which in turn are connected to a control logic IV 3 C, IV 3 D and IV 5 B for current limitation, with control pulses from Hall sensors ( 26 ) the inputs HS 1 and HS 2 of another control logic IV 4 C, IV 4 D readjust the output stages IV 1 and IV 2 in frequency, so that out Before the current superimposed with a sawtooth-shaped frequency in the excitation winding ( 3 ), an alternating, trapezoidal magnetic field is generated, which acts on ring-shaped permanent magnets ( 7 ) of the rotor ( 5 ). 2. Vacuum cleaner motor according to claim 1, characterized in that the switching pulses of the Hall sensors ( 26 ) are first guided symmetrically at the inputs HS 1 , HS 2 via Schmitt trigger IV 4 A, IV 4 B and further to AND gates IV 3 A, IV 3 B, where a link to a flip-flop IV 6 A, IV 6 b takes place regarding the start of the circuit and additionally a connection via AND gates IV 3 C, IV 3 D is provided, where a link to the Current control of the output stages IV 1 , IV 2 takes place in such a way that the transistors T 1 and T 4 or T 2 and T 3 are switched so that a current profile fluctuating within the excitation winding ( 3 ) with the control frequency of the Hall sensors ( 26 ) is generated becomes. 3. Vacuum cleaner motor according to claim 1, characterized in that the activation of the final stages IV 1 , IV 2 is delayed with an RC element via a switching stage IV 6 C, which in the further a flip-flop IV 6 A, IV 6 B switches, which releases the AND gates IV 3 A, IV 3 B with its output for control with the Hall sensors ( 26 ) and the engine is started in this way. 4. Vacuum cleaner motor according to claim 1, characterized in that the output stages IV 1 , IV 2 are additionally controlled via a thermal switch THS 1 of the motor, a switching element IV 6 D controlling the error input of the output stages IV 1 , IV 2 . 5. Vacuum cleaner motor according to claim 1, characterized in that the Hall sensors ( 26 ) in the region of the rotor shaft ( 8 ) opposite to the rotor shaft ( 8 ) rotating magnets ( 25 ) are arranged. 6. Vacuum cleaner motor according to claim 1, characterized in that the excitation winding ( 3 ) has a four-pole design, the excitation winding ( 3 ) having the same number of poles facing annular permanent magnets ( 7 ) of the stator in the manner of an annular shell ( 18 ). 7. Vacuum cleaner motor according to claim 1, characterized in that in the region of the excitation winding ( 3 ) the air gap ( 4 ) to the stator ( 2 ) is formed asymmetrically in accordance with the number of poles, such that in the direction of the respective narrowing ( 24 ) of the Air gap ( 4 ) results in a predetermined starting direction of the motor ( 1 ).