METHOD AND APPARATUS FOR OPERATING VACUUM CLEANER

Abstract: Method and apparatus for operating a vacuum cleaner in which by detecting a rotational speed of a variable speed fan motor (8) adapted to give a suction force to the cleaner (1) and its change range, the choking state of the filter (6) and the state of the cleaned surface are discriminated, and a speed command of the fan motor (8) is corrected on the basis of the result of the discrimination, and the comfortable cleaning can be performed by the optimum suction force.

Description: The present invention relates to a vacuum cleaner and, more particularly, to method and apparatus for operating a vacuum cleaner which is operated in the optimum condition in accordance with the state of the cleaning surface and the choking state of the cleaner. In general vacuum cleaners, an input is set to a constant value irrespective of the state of the cleaning surface. Therefore, the suction force is too strong or too weak for the cleaning surface or an object to be cleaned, so that the optimum control which is comfortable to the user cannot be performed. To solve this problem, such an optimum control can be realized by, for example, controlling the input and adjusting a suction amount of the cleaner in accordance with the cleaning surface. As a method of adjusting the suction amount of the cleaner, a method whereby the rotational speed of the drive motor is variably set is first considered. As a method of changing the rotational speed of the motor, there have been known a method whereby the phase is controlled using a thyristor and a method whereby the rotational speed is controlled by an inverter. A vacuum cleaner disclosed in JP-A-60-242827 relates to the latter method. Namely, this cleaner uses a brushless motor which is driven by an inverter. Although the motor which is driven by the inverter is disclosed in the foregoing official gazette, nothing is taught with respect to the technical subject for allowing the motor to be automatically operated in the optimum condition in accordance with the state of the cleaning surface or the choking state of the filter. In addition, means for solving this technical subject is not shown. Prior art document US 4 601 082 discloses a vacuum cleaner comprising a variable speed electric motor. The motor power is controlled in accordance with an electric signal derived from an optical sensor disposed in the suction pose. The sensor provides a signal indicative of the dust quantity being sucked into the cleaner. This system however will not respond to different operating conditions caused by different cleaning surfaces and by an increasing choking state of the filter. Suction performance is therefore reduced. It is the first object of the present invention to provide method and apparatus for operating a vacuum cleaner in which a suction amount is controlled in the optimum condition in accordance with the state of the cleaning surface and the choking state of the filter. This object is solved in accordance with the features set out in the independent claims. Dependent claims are directed on preferred embodiments of the present invention. It is the first feature of the present invention that in a vacuum cleaner having a filter to collect dusts and a variable speed fan motor adapted to give a suction force to the cleaner, the rotational speed of the fan motor is sequentially detected at short periods during the cleaning, the state of the cleaning surface or an object to be cleaned is presumed from the fluctuation mode based on a change in rotational speed which was detected within a predetermined sampling time, and then the input of the fan motor is automatically adjusted to set the rotational speed of the motor into the speed which is suitable for the presumed state of the cleaning surface or the like. Hereinunder refering to the Figures single embodiments of the present invention will be described in detail. Fig. 1 is a schematic constitutional diagram of a vacuum cleaner according to an embodiment of the present invention; Fig. 2 is a whole constitutional diagram of a speed control unit comprising a brushless DC motor and an inverter control unit; Fig. 3 is a diagram showing performance curves of the vacuum cleaner; Figs. 4A and 4B are diagrams showing fluctuations in rotational speed due to the choking state of a filter; Fig. 5 is a diagram showing a fluctuation in rotational speed in the case where the cleaning surface and the choking state of the filter are considered; Fig. 6 is a diagram showing the differences of the fluctuation modes in rotational speed for the cleaning surfaces; Fig. 7 is a diagram showing a function table in accordance with the cleaning surface; Fig. 8 is a diagram showing the processing contents which are executed by a microcomputer; Fig. 9 is a control block diagram of an apparatus to drive the vacuum cleaner showing an embodiment of the invention; Fig. 10 is a diagram showing performance curves in dependence on the presence or absence of the choke of the filter; Fig. 11 is a diagram showing performance curves to the cleaning surface; Fig. 12 is a control block diagram showing another embodiment (1) of the present invention. An embodiment of the present invention will be described in detail hereinbelow with reference to Figs. 1 to 11. The invention is constituted on the assumption that a variable speed motor is used as a drive source of a vacuum cleaner (fan motor). As a variable speed motor, it is considered to use an AC commutator motor whose speed is changed by controlling the input, a phase controlled motor, an induction motor which is driven by an inverter, a reactance motor, a brushless motor which is driven by an inverter, or the like. This embodiment will be explained with respect to an example in which a brushless DC motor having no mechanical brush in which the life is long and the control response speed is high is used. Fig. 1 is a schematic constitutional diagram of a vacuum cleaner according an embodiment of the invention. In the diagram, reference numeral 1 denotes a vacuum cleaner main body; 2 is a hose; 3 and 4 wheels; 5 a power supply cord; 6 and 7 filters; 8 a fan; 9 a brushless DC motor; and 10 an inverter control unit. When an electric blower consisting of the fan 8 and brushless DC motor 9 is driven by the inverter control unit 10, the wind inhaled by the hose 2 passes along the path consisting of the filter 6, fan 8, and filter 7 as indicated by arrows and is discharged from the vacuum cleaner main body 1. Thus, the fine particles of the abraded powder of the brush are not discharged from the vacuum cleaner and at the same time, the smell due to the sparks of the brush is not generated. Therefore, there is an effect such that the user can perform the cleaning operation in the clean circumstances. Fig. 2 shows a whole constitution of a speed control unit consisting of the brushless DC motor and inverter control unit of the invention. In the diagram, reference numeral 10 denotes the inverter control unit. An AC power source 14 is rectified by a rectifier 15 and smoothed by a capacitor 16, so that a DC voltage E d is supplied to an inverter 20. The inverter 20 is the inverter having a conducting period of angle 120° comprising transistors TR₁ to TR₆ and flywheel diodes D₁ to D₆ connected thereto. The transistors TR₁ to TR₃ constitute a positive arm. The transistors TR₄ to TR₆ constitute a negative arm. The current supplying period of time (i.e. conducting period of angle) of each arm corresponds to the electric angle of 120° and is pulse width modulated (PWM). A resister R₁ of a relatively low resistance is commonly connected between the emitter of each of the transistors TR₄ to TR₆ constituting the negative arm and the anode terminal of each of the flywheel diodes D₄ to D₆. The brushless DC motor 9 comprises a rotor 9b using permanent magnets of two poles as fields and a stator 9a into which armature windings U, V, and W are inserted. Since winding currents flowing through the armature windings U, V, and W also flow through the low resistor R₁, a load current I D of the motor 9 can be detected by the voltage drop of the low resistor R₁. The speed control circuit of the brushless DC motor 9 mainly comprises: a magnetic pole position detecting circuit 12 to detect the position of the magnetic pole of the rotor R by a hall device 11 or the like; a current detecting circuit 17 of the load current I D ; a base driver 19 to drive the transistors TR₁ to TR₆; and a microcomputer 13 to drive the base driver 19 on the basis of detection signals obtained from the detecting circuits 12 and 17. Numeral 18 denotes an operation switch which is operated by the actual user. The magnetic pole position detecting circuit 12 receives a signal from the hall device 11 and produces a position detection signal 125 of the rotor 9b. The position detection signal 12S is used to switch the currents of the armature windings U, V, and W and is also used as the signal to detect the rotational speed. The microcomputer 13 obtains the speed by counting the number of position detection signals 12S within a predetermined sampling time. The current detecting circuit 17 detects the voltage drop of the resistor R₁ to obtain the load current I D , and a current detection signal 17S is obtained by an A/D converter (not shown). The microcomputer 13 comprises: a central processing unit (CPU) 13a; a read only memory (ROM) 13b; and a random access memory (RAM) 13c. Although not shown, these components are mutually connected by an address bus, a data bus, a control bus, etc. The programs necessary to drive the motor 9, for example, the programs for the process to calculate the speed, the process to fetch a speed command, the process to control the speed, etc. are stored in the ROM 13b. On the other hand, a function table 22 in which various kinds of arbitrary speed control patterns are stored is provided in the ROM 13b. The RAM 13c comprises: a memory section to read and write various kinds of data necessary to execute the foregoing various kinds of processing programs; and a memory section in which a speed pattern data relative to the value of the winding current to be supplied every position of the rotor is stored. The transistors TR₁ to TR₆ are respectively driven by the base driver 9 in response to an ignition signal 13S which was processed and produced by the microcomputer 13. A voltage command circuit 21 produces a chopper signal, which will be explained hereinafter. Since the winding currents flowing through the armature windings U, V, and W of the motor 9 correspond to the output torque of the motor 9, the output torque can be varied by changing the winding currents. Namely, by adjusting the load current I D , the output torque can be continuously arbitrarily changed. In addition, by changing the driving frequency of the inverter 20, the rotational speed can be freely changed. The characteristic of the vacuum cleaner is as shown in Fig. 3. In Fig. 3, an axis of abscissa denotes the wind amount Q (m³/min) of the vacuum cleaner and an axis of ordinate indicates the suction power P out representative of the suction performance, the rotational speed N of the motor, and the load current I D . The region surrounded by two alternate long and two short dashes lines indicates the actual operating range. When the filter is hardly choked, the wind amount Q is maximum and the rotational speed N is minimum. As the degree of choking state progresses, the operating point gradually moves to the left and when the filter is completely choked, the wind amount Q is minimum and the rotational speed N is maximum and the operating point reaches the minimum point. The suction power P out decreases irrespective of the choking amount of the filter in the ranges before and after the maximum suction power P max as a turning point. Therefore, by controlling the rotational speed of the motor to the optimum speed in accordance with the choking amount of the filter, it is possible to provide the vacuum cleaner which can improve the suction power P out . A method of detecting the state or kind of cleaning surface will now be described. In this embodiment, an attention is paid to the fact that the minimum or maximum rotational speed, the average rotational speed, or the fluctuating state of the rotational speed varies in dependence on the cleaning surface. The cleaning surface is presumed from the rotational speed, thereby controlling the motor to perform the optimum operation according to the presumed state of the cleaning surface. Figs. 4A and 4B show fluctuations in rotational speed of the motor in the case of cleaning a tatami mat. (Japanese straw matting). These diagrams show the fluctuations in rotational speed which were actually confirmed by the experiments. Fig. 4A shows the case where the wind amount Q is large in the state in which the filter is not choked. Fig. 4B shows the case where the wind amount Q is small in the state in which the filter was choked. As will be obvious from these diagrams, when the cleaning was, performed by the cleaner whose wind amount is large, the rotational speed of the motor changes from the minimum speed N₁₁ to the maximum speed N₁₂. On the other hand, when the cleaning was performed by the cleaner in the choking state, the rotational speed of the motor changes from the minimum speed N₁₃ to the maximum speed N₁₄. As will be clearly understood from the comparison between them, in the case of the cleaner in the choking state, the minimum speed N₁₃ is higher than the minimum speed N₁₁ when the filter is not choked. Likewise, the maximum speed N₁₄ is also higher than the maximum speed N₁₂. Therefore, for example, if the minimum speed N₁₁ is stored in the ROM 13b or RAM 13c and compared with the minimum speed N₁₃ when the cleaner was actually operated, the choking state of the filter can be detected. A reference value of the rotational speed which is stored in the ROM 13b or RAM 13c is not limited to only the value of N₁₁ but may be set to N₁₂, N₁₃, or N₁₄. If the degree of the choking state is high, the difference between the rotational speeds is large. Therefore, by increasing the input so as to raise the rotational speed in accordance with this difference, a desired suction force of the cleaner can be obtained and the suction power P out can be also improved. As explained above, although the rotational speed of the motor of the cleaner varies in dependence on the choking state of the filter, it is actually largely influenced by the state of the cleaning surface. Since the cleaning surface is instantaneously changed during a single cleaning operation in a manner such that it is changed from the floor to a carpet or from a tatami mat to a curtain, a fluctuation in rotational speed occurs due to the change in cleaning surface, i.e., during a single cleaning operation when considering the time cycle. However, by properly deciding the sampling time, the change in cleaning surface can be also detected. This state is shown in Fig. 5. In Fig. 5, an axis of abscissa denotes the surface or object to be cleaned and an axis of ordinate indicates the rotational speed. Although there are various kinds of cleaning surfaces and objects to be cleaned, typical four kinds of cleaning surfaces and objects such as tatami mat, carpet, sofa, and curtain are shown in this diagram. In the diagram, a solid line shows the rotating state in the case where the filter is not choked and a broken line indicates the rotating state in the case where the filter is choked. Namely, the rotational speed is the lowest in the case of tatami mat and sequentially increases in accordance with the order of carpet, sofa, and curtain. This tendency is derived irrespective of the choking state of the filter. However, as the choking state progresses, there is a tendency such that the difference between the rotational speeds decreases even when the kind of cleaning surface changed. Although the rotational speeds N₁ to N₄ for the respective cleaning surfaces vary even when they are cleaned, respectively, each of those speeds represents the minimum rotational speed or average rotational speed. When the vacuum cleaner is operated for a long time in the closed room, the air is not circulated in the room and the heat cannot be radiated, so that the temperature increases and there is a fear of burning of the motor. To avoid this, a bypass passage is provided for the main air passage. In general, the bypass passage takes the outside air from the portions other than the suction port and feeds the cooling wind to the electric blower. The inside of the cleaner is cooled by this cooling wind and thereafter, the cooling wind is discharged to the outside. The indication of the operation of a bypass valve in Fig. 5 indicates the position at which the valve is made operative to open the bypass passage when the suction port was completely closed. The bypass valve functions as what is called a protecting apparatus to prevent that the rotational speed rises to a value which is equal to or higher than the speed indicated by the position of the bypass valve operation in Fig. 5. As explained above, when the cleaning surface and object to be cleaned change and when the choking state fluctuates, the rotational speed varies. Therefore, in addition to accurately detect the choking state, it is also necessary to detect the cleaning surface and object in order to perform the optimum operation of the cleaner in accordance with the cleaning surface and object. Fig. 6 shows the fluctuation modes of the rotational speed every cleaning surface and every object in the case where the cleaning operation was executed by use of the cleaner having a filter which is not choked. Namely, similarly to Fig. 5, in Fig. 6, an axis of abscissa indicates the cleaning surface and an axis of ordinate represents the rotational speed. In particular, each of the fluctuation modes M₁ to M₄ shown in the circles indicates a change in rotational speed during the cleaning operation for each cleaning surface. An axis of abscissa denotes a time. As is obvious from this diagram, when the cleaning surface is a tatami mat, the minimum speed is N₁₁ and the maximum speed is N₁₂ and a fluctuation in rotational speed is small within a predetermined sampling time. The minimum rotational speed at this time is N₁ shown in Fig. 5. In the case of a carpet, the minimum speed is N₂₁ and the maximum speed is N₂₂ and the difference between the minimum and maximum speeds within the same sampling time as that mentioned above is larger than that in the case of the tatami mat. The minimum speed at this time is N₂. The waveforms of vibration in the fluctuation modes of the rotational speeds in the cases of the tatami mat and carpet are similar although the fluctuation differences between the minimum and maximum speeds of the average rotational speeds are different. In the case of a sofa, the minimum speed is N₃₁ and the maximum speed is N₃₂. The difference between them within the same sampling time is further larger than that in the case of the carpet. At this time, the minimum speed is N₃. The waveform in the fluctuation mode in the case of the sofa is similar to a square wave. In the case of a curtain, the minimum speed is N₄₁ and the maximum speed is N₄₂ and the difference between them within the same sampling time is still larger than that in the case of the sofa. The minimum speed is N₄. The waveform in the fluctuation mode in the case of the curtain is also similar to a square wave similarly to the case of the sofa. It can be considered that each of the minimum rotational speeds N₁₁, N₂₁, N₃₁, and N₄₁ corresponds to the open state in which the suction port was removed from the cleaning surface. However, the average rotational speed can be also used in place of the minimum rotational speed. As is obvious from the above explanation, it will be understood that the surface or object which is actually being cleaned can be detected from the average or minimum rotational speed and the fluctuation modes M₁ to M₄ of the motor of the cleaner and that the choking state can be also detected. On the other hand, when considering the cleaning surface or object to be cleaned, it is the curtain that it is most difficult to fetch dusts. Therefore, when it has been decided that the cleaning surface is a carpet or an object similar to a carpet, it is desirable to set the rotational speed into the highest speed. Next, it is preferable to sequentially set the rotational speed in accordance with the tatami mat, sofa, and curtain so as to gradually decrease. Namely, it was desirable to assume the rotational speeds as mentioned above in consideration of the easiness in fetching of dusts and a phenomenon and state in which the suction port is attracted to the cleaning surface or the like. Namely, since the cleaning surface or object or the choking state can be detected from Fig. 6 and the like, by setting the optimum rotational speed in accordance with the choking state detected, the cleaning operation can be performed in accordance with the cleaning surface. Practical control means will now be explained. Fig. 7 shows control patterns stored in the ROM 13b in the microcomputer 13. Practically speaking, these patterns are stored as the function tables 22 corresponding to the respective cleaning surfaces. In this diagram, an axis of abscissa denotes a degree of the choking state and an axis of ordinate indicates a speed command N * . The rotational speed is set from the foregoing necessary rotational speeds in accordance with the order of carpet, tatami mat, sofa, and curtain and is set so as to increase as the choking state progresses. Due to this, the function in the function table 22 is automatically set in accordance with the cleaning surface. The cleaning surface such as a carpet or the like is not limited to the carpet. It is also possible to consider in a manner such that the function for a carpet is used in the case of the cleaning surface having a characteristic similar to that of the carpet. The same shall also apply to the cases of tatami mat, sofa, and curtain. Further, by calculating the speed command N * in accordance with the degree of choking state, the speed command N * corresponding to not only the presumed cleaning surface but also the degree of choking state is derived and the optimum control can be accomplished. Fig. 8 shows the content of the processes which are executed by the microcomputer 13. This diagram shows a procedure to obtain the speed command N * in accordance with the cleaning surface and the degree of choking state. In the process I, the rotational speed of the motor 9 which changes with an elapse of time is calculated using the position detection signal 12S. In the process II, the maximum speed N max and the minimum speed N min within a sampling time T are detected. In the process III, the mode of the rotational vibration, namely, the vibration frequency and the value of amplitude within the sampling time are compared with the vibration mode (fluctuation mode of the speed) which has previously been stored in the ROM 13b, thereby presuming the cleaning surface and deciding the degree of choking state from the rotational speeds N max and N min . In the process IV, a predetermined value corresponding to the choking state is selected from the function table 22 selected on the basis of the cleaning surface and the degree of choking state, thereby obtaining the speed command N * in accordance with this value. A control circuit to realize this processing method will now be explained with reference to Fig. 9. Various kinds of speed control systems such as ASR, ACR, and the like are considered. In Fig. 9, the voltage controlled system of a closed loop is shown. In the diagram, when the user of the cleaner turns on the operation switch 18, an operation command is fetched to start the brushless DC motor 9. When the rotational speed rises to a predetermined speed, the activating process is finished. Thereafter, the processes to presume the cleaning surface and to detect the degree of choking state are executed. The microcomputer 13 shown in Figs. 2 and 9 receives the position detection signal 12S from the magnetic pole position detecting circuit 12 and calculates the rotational speed in the process I in Fig. 6. In the next process II, the maximum speed N max and the minimum speed N min are detected. Further, the microcomputer 13 presumes the cleaning surface and decides the choking state in the process III on the basis of the detected maximum and minimum speeds. Subsequently, in the process IV, a predetermined function table 22 is selected by a switch 23 in accordance with the cleaning surface and choking state. The speed command N * is obtained on the basis of a predetermined speed command value in the function table 22 selected in accordance with the degree of choking state of the filter. The speed command N * is converted into a voltage command V * by a gain K. The voltage command V * is input to a D/A converter. An output of the D/A converter is compared with an output of a triangular wave generator, which is provided separately from the D/A converter, by a comparator provided at the post stage. An output corresponding to the difference between those outputs is supplied to the base driver 19. The base driver 19 applies the voltage based on the voltage command which was determined at the front stage to the motor 9. In this manner, the motor 9 is rotated at the speed in response to the speed command N * according to the cleaning surface and the degree of choking state. Fig. 10 shows performance curves of a cleaner (electric blower) using the motor 9 which is controlled as explained above as the motor to drive the vacuum cleaner. Fig. 10 is simimar to that described in Fig. 3. In Fig. 10, broken lines indicate the case where the filter is not choked and solid lines represent the case where the filter is choked. As is obvious from this diagram, as the choking state of the filter progresses, by detecting this choking state and by increasing the rotational speed in accordance with the degree of choking state, the suction power P out which was reduced due to the choke can be raised as shown by the solid lines, so that the vacuum cleaner of a high efficiency can be obtained. Fig. 11 similarly shows a change in performance to the cleaning surface. This diagram shows changes in suction power P out , rotational speed N, and load current I D which are necessary in accordance with the cleaning surface. The optimum rotational speed N * is given in accordance with the characteristic responsive to the choking state on the basis of the function table 22 corresponding to the cleaning surface. Although the control of the cleaner has been accomplished by only the brushless DC motor 9, it can be also attained by the variable speed motor. Fig. 12 shows another embodiment (1) of the invention. In the diagram, a phase controlled AC commutator motor 24 comprises a field winding 24A and an armature 24B. The motor 24 is connected to the AC power source 14 through a phase control unit 25 including a control device such as triac, FLS, thyristor, or the like. An ignition angle of a gate of the control device of the phase control unit 25 is controlled by a driver 27 similar to the base driver 19 shown in Fig. 2. The microcomputer 13 also has the processing function similar to that mentioned above. Namely, the microcomputer 13 Presumes the cleaning surface on the basis of the maximum speed N max and the minimum speed N min within the sampling time on the basis of the rotation information (mainly, rotational speed information) derived from a rotation detector 26, thereby producing a gate signal of the control device by further considering the choking state. The content of the practical processes which are executed by the microcomputer is similar to that shown in Fig. 8. In this embodiment (1), it is also possible to provide the cleaner having the optimum suction state according to the presumed cleaning surface and choking state and the cleaning efficiency does not deteriorate. According to the foregoing embodiment, it is possible to obtain the cleaner having the optimum suction performance in accordance with the cleaning surface and the choking state of the filter. However, since the cleaning surface is presumed from the rotational speed, when it has been presumed that the cleaning surface is the tatami mat, this surface is not always the tatami mat. In other words, this presumed cleaning surface is the surface having the same surface as that of the tatami mat or the cleaning surface in the state similar to the tatami mat. In any cases, the rotational speed is controlled in accordance with the state of the cleaning surface or controlled so as to compensate the suction performance which was deteriorated due to the choke. Thus, the optimum control of the cleaner can be automatically performed. As is obvious from the above description, the rotational speed can be detected by directly using the signal of the hall device 11 in the magnetic pole position detecting circuit 12 which is generally used in, for example, the brushless DC motor 9, so that what is called a sensorless vacuum cleaner is derived.

Claims: A method of operating a vacuum cleaner having a filter (6) to collect dusts and a variable speed fan motor (8) to give a suction force to a cleaner (1),characterized by comprising the steps of: sequentially detecting a rotational speed of said fan motor (8) at a short period of time during the cleaning; presuming the state of a cleaning surface or an object to be cleaned from a fluctuation mode based on a change in said detected rotational speed within a predetermined sampling time; and automatically adjusting an input of the fan motor (8) to set the rotational speed to a speed suitable for said presumed state of the cleaning surface or the like. A method according to claim 1, characterized in that the state of the cleaning surface or object to be cleaned is presumed in a manner such that an actual speed fluctuation mode is compared with a plurality of fluctuation modes which have previously been stored and one of the fluctuation modes stored which is coincident with or similar to the actual speed fluctuation mode is selected. A method according to claim 2,characterized in that a choking state of said filter (6) is detected by comparing the value of the rotational speed in the actual operation with a predetermined value. A method according to claim 1, characterized in that the presumption of the state of the cleaning surface or object to be cleaned or the presumption of a choking state of the filter (6) is performed on the basis of the value of the rotational speed and the fluctuation in rotational speed. A method according to claim 1, characterized in that said fan motor (8) is driven by a brushless motor (9). A method according to claim 5, characterized in that an original signal to detect the speed is obtained by a magnetic pole position detecting circuit (12) of a brushless motor (9). A method according to claim 1, characterized in that said automatical adjusting step includes controlling an input of the fan motor (8) along a function table (22) which is selected in accordance with the presumed state of the cleaning surface, said selected function table (22) being corrected in accordance with a choking state of the filter (6). A method according to claim 1, characterized in that said automatical adjusting step includes giving a speed command to the fan motor (8) on the basis of the value of the detected rotational speed in accordance with a cleaning surface or an object to be cleaned and a choking state of said filter (6), wherein said speed command is obtained by the following processes: process I ... a rotational speed N is obtained by calculation; process II ... the maximum rotational speed N max and the minimum rotational speed N min are obtained within the sampling time; process III ... the cleaning surface is presumed and the degree of choking state of the filter (6) is obtained on the basis of the maximum and minimum rotational speeds N max and N min ; and process IV ... one function table is selected from a plurality of function tables (22) and the speed command N * is output by said selected function table. A method according to claim 8, characterized in that said speed command is a voltage command (V * ) or a current command. An apparatus for operating a vacuum cleaner having a filter (6) to collect dusts and a fan motor (8) to give a suction force to a cleaner (1), comprising: a circuit to apply an electric power to said fan motor (8); a circuit (12) to detect an actual rotational speed of the fan motor (8); and a base driver (19) to control the electric power which is applied to the fan motor (8), characterized in that the value of the rotational speed derived by said circuit (12) to detect the rotational speed is input to a microcomputer (13), and said microcomputer (13) compares the value of the input rotational speed with a pattern of a speed command which has previously been stored in the microcomputer (13) and gives a new speed command to said base driver (19) on the basis of said comparison value. An apparatus according to claim 10, characterized in that said pattern of the speed command is a plurality of function tables (22) suitable for a plurality of cleaning surfaces, said function tables have previously been stored in an ROM in said microcomputer (13), and one of the function tables is selected on the basis of the value of said actually detected rotational speed and a fluctuation in said rotational speed, thereby obtaining said speed command from the selected function table. An apparatus according to claim 10, characterized in that said speed detecting circuit is a magnetic pole position detecting circuit (12) to detect the position of the magnetic pole of said motor (9). An apparatus according to claim 11, characterized in that said selected function table is corrected in accordance with a choking state of said filter (6).

Inventors: ENDO, TSUNEHIRO, HISHI, WAKICHIRO, ISHII, YOSHITARO, JYORAKU, FUMIO, KOHARAGI, HARUO, MIYASHITA, KUNIO, SAITO, KOHICHI, TAHARA, KAZUO, TOYOSHIMA, HISANORI, WATANABE, SYUJI, YAMASHITA, KOUJIROU
Applicants: HITACHI, LTD.
Application year: 1987
Main classification: H02P6
IPC codes: H02P23, H02P6, A47L9