MXPA99006095A - Cleaning system and method with starting your - Google Patents

Abstract

The present invention relates to a floor cleaning apparatus is operated by a change reluctance actuator that is gently started to avoid any reaction of the transient torque that unbalances the body of the cleaner the soft start occurs when profiling the current demand of the system actuator as a function of rotor speed. The profile is typically done with a continuous function, a series of steps or a value pair

Description

APPLIANCE L IMPACTOR AND METHOD WITH SOFT START Field of the Invention This invention relates to floor and vacuum cleaners that are controlled by electronic controllers. In particular, this relates to the cleaners where the speed of the apparatus is controlled during a starting period.

Vacuum cleaners fall broadly into two broad categories. The first one is the one in which every cleaner moves through the surface that will be cleaned: these cleaners are usually referred to as "vertical" cleaners. The second are those where the main body of the cleaner is connected by means of a flexible hose to a cleaning nozzle that moves through the surface to be cleaned: these cleaners are usually classified as "cylindrical" cleaners. A variation of Ref .: 30567 this second category has a static body and a system of ducts and hoses centrally placed to provide local cleaning. In each of the cases, the cleaning action is partly provided by the suction that is produced by a ventilation unit driven by an electric motor.

Background of the Invention Traditionally, the electric motor used in vacuum cleaners is a motor commuted in series with a coiled armature and a coil that is supplied with power or a permanent magnetic field. These motors are well documented in the art, for example in "Electric Motors and Drives", Hughes, Heinemann Newnes, 1980. Figure 1 shows a typical characteristic of torque vs. speed of this type of engine in which it can be seen that The torque is relatively high when the motor is initially connected to the power supply decreases while the speed increases. Also shown in Figure 1 is a typical torque vs. speed curve for a vacuum cleaner with fan, which shows that the load presented by the fan is low at low speed but increases rapidly with speed. The difference between the two curves represents the acceleration torque that is available at any speed to accelerate the load. Therefore, the fan will accelerate rapidly when the motor is initially connected to the power supply but the acceleration will decrease while the curves are together and the motor will run stably at the speed where the curves cross.

Because the acceleration torque is high when stopping, and because there is a significant inertia associated with the motor rotor and the ventilation unit, there is a considerable reaction of torque at start-up. While this is not a big problem with vertical cleaners (because mechanical planning generally fits reasonably well with torque reaction), this is more difficult in cylindrical cleaners since torque reaction causes the body of the Cleaner shakes strongly while the engine starts. This can be at least one cause of user discomfort or a source of damage or danger to the user if the cleaner is flipped over. This is becoming a big problem, with the increase in suction requirements in cleaners, and therefore more powerful engines.

Similar problems occur in rotating floor cleaners where a rotating brush or scouring pad is used to clean or polish a floor surface. The reaction of the transient torque produced can be a nuisance or even be dangerous for the user because the machine can spin out of control when it is started.

Rudimentary forms for speed control of cleaning devices have been available for several years and are generally in the form of thyristor or bidirectional thyristor which are used for the phase control of the alternating power supply over a limited range. Typically these will allow the user to reduce the speed of 100%. at a lower level, for example 70%. However, because of a large inherent starting torque of the motor, these forms for speed control are not particularly effective in controlling the transient start.

An adopted solution for rotary floor cleaners has been to replace the motor in series with a 3-phase induction motor driven by an inverter, for example as described by Ku aki in US Patent 4992718. In order to avoid a high current Starting point taken, Kumaki proposes a complex method to reduce the starting current for a given period of time using a microprocessor. In addition this proposal to produce will have the incidental effect of reducing the starting torque, the system has no means to measure the speed and therefore no control over the speed where the torque of the motor is varied.

Therefore, there is a need for a simple system for starting an apparatus for cleaning the floor so that the transient torque is reduced to an acceptable level over the speed range from stopping to working speed.

Brief description of the invention According to the present invention, there is provided a floor cleaning apparatus comprising the means for cleaning, an interchanged reluctance actuator having a rotor for actuating the cleaning means, a controller for controlling the power supply of the actuator and the means to determine the speed of the rotor of the actuator and to feed a signal indicating the speed of the rotor to the controller when the apparatus is changed the controller is changed if it is operable to vary the power supply of the actuator as a function of the measured rotor speed from a first value to a second higher value, therefore controlling the torque produced by the engine during start-up.

The controller may be operable to vary the power supply slightly from the first to the second value. For example, the controller may be operable to vary the level of the power supply according to the following relationship: a + b where E is the level of power supply demanded, m is the rotor speed, a is an empirical constant, n is an index that describes the shape of the fan torque curve and b is a constant that represents the required value of the power supply level at zero speed. The controller may be operable to vary the power supply in the steps between the first value and the second value. The steps are stored in an estimation table.

The level of power supply of the actuator can vary from the first level to the level of operation in a single step. In order to achieve this, the controller may comprise a first resistor connected to a reference voltage, a second resistor connected to the first resistor, a third resistor connected to the second resistor and another voltage, a microprocessor connected between the first and second resistors. and an output between the first and second resistors for supplying a control signal to the actuator, the microprocessor is operable to set its output impedance to substantially zero when the apparatus is changed and substantially sets its impedance to a higher value when the speed of the rotor reaches a certain value. In this way when the microprocessor has its fixed impedance at substantially zero the controller provides a relatively low level of the output signal and thus produces the first value of the power supply, and when the impedance of the microprocessor is set to a higher value, it is provides a sufficient control signal to produce the second value of the power supply of the actuator.

Preferably the controller is operable to vary the level of the power supply by varying the current demand of the actuator.

Preferably, the apparatus is a vacuum cleaner. Typically, the cleaning means comprises a fan to create suction and the means operably connected to the fan to remove debris from a surface that is cleaned.

Alternatively, the apparatus may be a floor polisher. Typically, the cleaning means comprises a cleaning pad or a brush-shaped head or a scouring head.

According to another aspect of the invention, there is provided a method for operating a floor cleaning apparatus having means actuated by an interchanged reluctance actuator having a rotor operably connected to the cleaning means, the method comprising: supplying the actuator with a first level of power supply to operate the apparatus at a first speed when the apparatus is turned on, measure the speed of the rotor, and increase the level of the power supply supplied to the actuator as a function of the measured rotor speed.

The level of the power supply may vary slightly as a function of the measured rotor speed. The level of the energy supply can be increased according to the following relationship: E = a wn + b where E is the energy supply level demanded, vs is the rotor speed, a is an empirical constant, n is an index that describes the shape of the fan torque curve and b is a constant that represents the required value of the level of the power supply at zero speed.

The method may involve increasing the level of energy supply in stages. This may comprise reading from an estimation table containing information at the power supply level as a function of the rotor speed.

The level of the power supply can be increased from a simple stage from its initial value to that required to operate the device up to its full speed of operation.

Preferably the level of the power supply by varying the current demand of the actuator.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows typical torque vs. speed curves for a series commutator motor and for a vacuum cleaner ventilation unit; Figure 2 shows a schematic diagram of a vacuum cleaner having an interchanged reluctance actuator coupled to a ventilation unit; Figure 3 shows a torque vs. speed curve and a current versus speed demand curve for a reluctance actuator changed for use in a floor cleaning apparatus where the invention is projected; Figure 4 shows a torque vs. speed curve and a current versus speed demand curve for another reluctance actuator changed for use in a floor cleaning apparatus where the invention is projected; Figure 5 shows a torque vs. speed curve and a current versus speed demand curve for another reluctance actuator changed for use in a floor cleaning apparatus where the invention is projected; Y Figure 6 shows a comparator circuit that can be used in an apparatus where the invention is projected.

Detailed description of the invention Figure 2 shows, schematically, a vacuum cleaner ventilation unit 19 driven by the rotor 18 of an exchange reluctance motor 12. A flexible hose 21 with a cleaning nozzle 23 at its end is connected to the ventilation unit. In use, the cleaning nozzle 23 moves through the surface to be cleaned.

Power is supplied to the motor 12 by means of a DC power supply 11 which can be a rectified and filtered AC battery or cables. The DC voltage provided by the power supply 11 is changed through the phase winding 16 of the motor 12 by an energy converter 13 under the control of the electronic control unit 14. For proper operation of the actuator the change must be made correctly synchronized to the rotation angle of the rotor. A detector 15 of rotor position is typically used to supply signals corresponding to the angular position of the rotor. The output of the rotor position detector 15 can also be used to generate a velocity feedback signal.

The rotor position detector 15 can have various shapes. For example, this may be in the form of a programming device, as shown schematically in FIG. 2, or of a programming algorithm that calculates the position of other monitored parameters of the actuator system, as described in the EP-A- Patent. 0573198 (Ray). In some systems the rotor position detector 15 may comprise a rotor position transducer which provides for the output signals to change state each time the rotor rotates to a position where an arrangement of a different gear change is required. the energy converter 13.

The power supply of the in-phase windings in an exchange reluctance machine depends not only on the detection of the angular position of the rotor but also on the level of current demanded in the phase winding during the driving period. Typically, one or more current sensors detect current current and power in the phase winding and return the information to the electronic controller. This is shown schematically in Figure 2 by the current sensor 17 which detects the current in a phase winding 16 and supplies the information to the electronic controller 14. The current phase current, which is determined by the current sensor, can then to be compared with the desired phase current and the appropriate control action can be taken by the controller 14 to operate the switches in the power converter 13. In some actuators the current demand, and hence the level of the power supply, it will be constant in the period of excitement; in others, the current demand will be adjusted during a driving period (so called "current profile"). In both cases, the level of current demand is used as a measure of the torque that is being developed by the motor. The voltage applied to the windings is turned on and off to achieve the desired current level. The characteristics and operation of the reluctance machines with change are well known in the art and are described in, "The Characteristics, Disign and Application of Switched Reluctance Motors and Drives" by Stephenson and Blake, PCIM'93, Nürnberg, 21-24 June 1993, incorporated here as a reference.

Whether or not the current profile is used in a driving period is typically the case that the maximum value of the current demand remains constant while the speed of the actuator is increased from zero to its total load. This would give an increase to a large acceleration torque at a low speed and consequently a great reaction to the transient torque in the body of the cleaner. The inventors have recognized that by modifying the current demand as a function of the speed the acceleration torque can be reduced to a controlled amount over the speed range up to the total load. This is shown in Figure 3 where the current demand has been set so that only a small torque is available at low speed and the acceleration torque is maintained at a level that will give a more gradual acceleration of the fan at its speed. job. This has the benefit of reducing the effort on the motor, reducing the reaction torque in the body of the cleaner, reducing the transient stress on the same ventilation unit, and possibly reducing the ratio of the power switches. The greater of these benefits will be , the more gradual acceleration. Eventually, there is a point at which a change is reached with the reduced speed of motor response to a start command.

Since the exchange reluctance actuators operate by continuous monitoring of the position (and therefore the speed) of the rotor, several methods are available to produce the current demand, and therefore the voltage and torque developed depend on speed. The appropriate values can be calculated in real time using a simple algorithm, in the form aan + b (1 Where Id is the demand of current a is the rotor speed n is an index related to the curve of the torque of the fan and the saturation level of the magnetic circuits of the motor, typically around 2 a is an empirical constant b is a constant which represents the required value of current at zero speed.

A relation of this general formula will give a slight change in current demand, and thus, with the speed of the rotor.

Depending on the ability of the cleaner to withstand the reaction of transient torque without overturning or showing other undesirable characteristics, it will be possible to absorb the gentle curve of the current flow through a series of steps. Figure 4 shows a series of stages. The values of the current demand, and the rotor speeds where they change, can be stored in a simple estimation table and give access by using the measured speed of the rotor as a parameter.

In some application, especially where the cost is important, the series of stages can be reduced to two values, as shown in Figure 5. The current demand can be stored again as a function of the speed in a stimulation table or, in a particular modality effective in cost, it can be produced as follows: It should be noted in Figures 4 and 5 that, for simplicity, the diagrams have been drawn on the basis that the constant current demand will produce a constant torque. Those skilled in the art will recognize this as a simplification commonly used for the more complex relationships that exist in practical machines.

Figure 6 shows part of an exchange reluctance actuator control system that includes a microprocessor 40 and could be included in the controller 14 of Figure 2. An output 41 of the microprocessor is connected to a resistor chain Rl, R2 and R3 which act as voltage dividers for a reference voltage Vrßf. The signal Vcr of the junction of Rl and R2 is supplied to the comparator 42 to represent a reference of the desired current. The second input to the comparator 42 is a feedback signal of the current 44 representative of the current in the phase winding of the motor. The signal 44 can be taken from a current transducer as shown in Figure 2 or it can be produced by an algorithm that predicts or deduces the winding current in phase. The output 45 of the comparator 42 is used to control the discharge of the switches in the power converter 13 of Figure 2. This is done in a conventional manner, for example when the phase winding current increases above the corresponding level - to the reference current Vcr, the comparator will disable the change of the energy converter until the current falls below the required level. The cycle is then repeated as long as it is required to supply power to the winding in phase.

When the actuator is started, the microprocessor detects that the speed is at or near zero and is programmed to make the signal 41 be at or near zero volts. This R3 is shorted and reduces the Vcr which causes the actuator to start with a low reference current and therefore reduces the torque level. As the speed of the actuator increases, it reaches a predetermined threshold where the microprocessor sets the output 41 to a high impedance. The junction of R2 and R3 is not brought to zero volts and increases to a steady state value determined only by Vrßf and Rl, R2 and R3. The Vcr then increases to an adequate level to run at a steady state at the required current and torque levels.

This method provides a simple and cost-effective implementation of the invention where the apparatus on which the actuator is installed is capable of coupling with the torque stage associated with the sudden change in the reference level of the current at the point of change . A simple modification to this technique includes a capacitor connected through, R2 or R2 and R3. It will be apparent to a person skilled in the art, this will have the effect of changing the stage in the current demand on a ramp which thus softens the abrupt transition between the two levels of current demand.

It is important to realize that, in all the described modes, the current demand, and therefore the developed torque, varies as a function of the rotor speed and is not a function of time. Thus, if for any reason the load on the fan varies, for example due to the accumulation of dust in a filter or suction hole and the time it takes to reach a particular speed varies, the system will continue to operate correctly. In contrast, if the demand was a function of time, the development of the system would vary as the load on the fan varied.

The person skilled in the art will appreciate that variations of the arrangements discussed are possible without departing from the invention. Although the specific description has been based on a cylindrical vacuum cleaner, it will be apparent that the invention can equally be applied to other types of vacuum cleaners and to floor polishers and cleaners. Accordingly, the above description of various modalities is made as a means of example and not for purposes of limitation.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present invention.

Having described the invention as above, the content of the following is claimed as property.

Claims (20)

Claims

1. A floor cleaning apparatus, characterized in that it comprises the cleaning means, an exchange reluctance actuator having a rotor for driving the cleaning means, a controller for determining the speed of the actuator rotor, when the apparatus is initially changed the controller is operable to vary the power supply of the actuator as a function of the rotor speed from a first value to a second higher value, by means of controlling the torque produced by the motor during start-up.

2. An apparatus for cleaning the floor as claimed in claim 1, characterized in that the controller is operable to vary the power supply of the actuator slightly from the first value to the second value.

3. An apparatus for cleaning the floor as claimed in claim 2, characterized in that the controller is operable to vary the power supply of the actuator according to the following relationship E = a ts11 + b where E is the power supply of the actuator, you is the rotor speed, a is an empirical constant, n is an index and b is a constant that represents the power supply at zero speed.

4. An apparatus for cleaning the floor as claimed in claim 1, characterized in that the controller is operable to vary the energy supply in stages between the first value and the second value.

5. An apparatus for cleaning the floor as claimed in claim 4, characterized in that the speeds of the rotor to which the power supply is varied are stored in an estimation table.

6. An apparatus for cleaning the floor as claimed in claim 4 or 5, characterized in that the controller is operable to vary the power supply from the first value to the second value in a single stage.

7. An apparatus for cleaning the floor as claimed in claim 6, characterized in that the controller comprises a first resistor connected to a reference voltage, a second resistor connected to the first resistor, and a third resistor connected to the second resistor and another voltage , a microprocessor connected between the second and the third resistor and an output between the first and second resistors to supply a control signal to the actuator, the microprocessor that is operable sets its output impedance to substantially zero when the apparatus is turned on and subsequently sets its output impedance to a higher value when the rotor speed reaches a predetermined value.

8. An apparatus for cleaning the floor as claimed in any of the preceding claims, characterized in that the controller varies the power supply by varying a signal of the current demand.

9. An apparatus for cleaning the floor as claimed in any of the preceding claims, characterized in that the apparatus is a vacuum cleaner.

10. an apparatus that cleans the floor as claimed in claim 9, characterized in that the cleaning means comprises a fan to create suction and the means, operably connected with the fan, to remove debris from a surface to be cleaned.

11. An apparatus for cleaning floors as claimed in any of claims 1 to 8, characterized in that the apparatus is a floor polisher.

12. An apparatus for cleaning floors as claimed in claim 11, characterized in that the cleaning means comprises any of a polishing pad, a brush-shaped head and a scouring head.

13. A method for operating a "floor cleaning apparatus having cleaning means actuated by a change reluctance actuator having a rotor operably connected to the cleaning means, characterized in that the method comprises: supplying power to the actuator at a first level to drive at a first speed when the device is turned on, measure the speed of the rotor, and vary the energy supply as a function of the measurement of the rotor speed at which the rotor is driven.

14. A method as claimed in claim 13, characterized in that it comprises slightly varying the level of the power supply as a function of the measured rotor speed.

15. A method as claimed in claim 14, characterized in that the level of the energy supply is varied according to the following relationship: E = a sn + b where E is the energy supply level, ts is the rotor speed, a is an empirical constant, n is an index and b is a constant that represents the level of the energy supply at zero speed.

16. A method as claimed in claim 13, characterized in that it includes increasing the level of energy supply in one or more stages.

17. A method as claimed in claim 16, characterized in that it includes reading from an estimation table containing values of the rotor speed at which the steps take place.

A method as claimed in any of claims 13 to 17, characterized in that the step of varying the power supply is dependent on a signal of the current demand.

19. A method as claimed in any of claims 13 to 18, characterized in that the apparatus is a vacuum cleaner.

20. A method as claimed in any of claims 13 to 18, characterized in that the apparatus is a floor polisher.