Vacuum cleaner and method for operating the same

Abstract: An output of an electric driven blower (2) in a cleaner main body (1) is controlled in response to a detection value of a pressure sensor (12) which detects an operation condition in the cleaner main body (1). A change-over level setting value (C₁ , C 1′ ) is provided as an control value for the sensor (12) so as to form a judgement point for changing over a control condition of the blower. A return level setting value (C R′ C 2′ ) is provided as a control value for the sensor so as to form a judgement point for returning to a previous control condition of the blower (2) from a changed-over condition of the blower. When the detection value of the sensor (12) is more than the change-over level setting value, the return level setting value is set higher than the change-over setting value, thereby the output of the blower (2) is increased, or the return level setting value is set a lower than the change-over level setting value, thereby the output of the blower is decreased.

Description: BACKGROUND OF THE INVENTION: The present invention relates to a vacuum cleaner having a detection sensor for detecting an operation condition of the vacuum cleaner in a cleaner main body and a method for operating a vacuum cleaner. The present invention relates to a vacuum cleaner and a method for operating the same, the vacuum cleaner comprising a detection sensor for detecting an operation condition in the vacuum cleaner and having an electric driven blower and a control unit for controlling the electric driven blower in response to a detection value of the detection sensor. Such a vacuum cleaner is described, for example in DE-A-1 920 640. The above stated vacuum cleaner comprises the pressure sensor for detecting the operation condition of the electric driven blower and a control portion for controlling the electric driven blower in response to the detection value of the pressure sensor. In the above stated conventional vacuum cleaner, the following can be carried out: i) a method for decreasing an output of the electric driven blower at the operation range in a region of high air flow rate, as shown in the characteristic curve in Fig. 2, ii) or a method for decreasing the output of the electric driven blower at an operation range in a region of low air flow rate, as shown in the characteristic curve in Fig. 3. However, if it is attempted to save electric power or reduce noise by decreasing the output of the electric driven blower at both the high and low air flow rates which are positioned respectively outside of the practical cleaner operation ranges, the following problem arises. At low flow rates, if a given pressure value is exceeded, the output of the electric blower must be reduced. Conversely, if pressure drops below the given value, the output of the blower is increased. At high flow rates, on the other hand, the output of the blower is to be reduced when pressure drops below a given level. Such a control is difficult to achieve with only one pressure sensor, as the airflow cannot be determined with sufficient certainty from the pressure detected by this sensor alone. Short time fluctuations of pressure may induce erroneous control, that is, the control intended actually for high flow rates is performed when the flow rate is low and vice versa. EP-A-0 264 728 teaches how to control a vacuum cleaner by detecting from the rotational speed and current input to the electric blower and from fluctuations thereof the nature of the surface being cleaned and setting operating conditions accordingly. Therefore, it is necessary to have a combination of a plurality of pressure sensors or different kinds of pressure sensors, thereby making the vacuum cleaner main body construction particularly complicated. Furthermore, this cannot be practically adopted in the case of a negative gradient control as regards to the characteristics of an air flow rate and a static pressure with respect to the electric driven blower, which is shown at portion (A) in the characteristic curve in Fig. 4 because it causes a circulation control or a chattering phenomenon which involves an increase in the static pressure over a change-over setting point (or a move toward the small air flow rate), a lowering control for the output of the electric driven blower, a decrease in the static pressure below the change-over setting point, and a control for returning to a previous control condition. In the conventional vacuum cleaner, in case of an output decrease of the electric driven blower, the return level and the change-over level have nearly the same value. Also, the change-over level setting point and the new operating point vary along the same load curve line. Accordingly, a chattering phenomenon is caused in the conventional vacuum cleaner. Further, due to a method for detecting a pressure value, control change-over points are different depending on whether the air flow rate is increasing or decreasing to, so that a hysteresis phenomenon arises. It is therefore difficult to carry out the control of the output of the electric driven blower with a high degree of accuracy. Namely, in the conventional method for operating the vacuum cleaner, in case of an output increase of the electric driven blower, unless it returns to a return point which has the same pressure value as the change-over level setting point, it does not return to the previous control condition. The air flow rate at the change-over level setting point in the forth passage differs from the air flow rate at the return point in the back passage, accordingly the hysteresis phenomenon arises in the conventional vacuum cleaner. Further, in the conventional vacuum cleaner, the electric driven blower generates a negative pressure according to a centrifugal fan rotating at a high speed by an electric motor and creating a suction force. In an aerodynamic characteristic of the electric driven blower in the cleaner main body as motion curves in Fig. 5 show, in case that it is driven by an electric motor having a series characteristic such a commutator motor, since the load thereof becomes light at a small air flow rate, a rotation number N rises, also a static pressure H rises. Besides, the electric power consumption W decreases. Further, even when the electric driven blower is driven at a constant speed with a synchronous motor or an induction motor, as shown in motion curves in Fig. 6, at the small air flow rate similar characteristics to those of Fig. 5, for the static pressure (H) and power consumption are obtained. Namely, when the above stated rotation number N is constant, at small air flow rates, the rate of change of the static pressure H with the air flow rate Q is larger so that a reduction of the air flow rate leads to a large reduction of motor torque and load. Accordingly, the decrease rates in the electric power consumption W and electric current I become large. In the case of an inverter motor operated at a variable speed, characteristic curves as shown in Fig. 7, may be obtained by combining pieces of characteristic curves at constant speed control. As motion curves shown in Fig. 8, by the operation of each portion (1), (2), (3) and (4) which is shown in the bold lines of a plurality of the constant speed characteristic curves, is changed over selectively, therefore the characteristic curves shown in Fig. 7 can be realized. Now, as characteristic curves in Fig 9 show, the above stated various characteristics have in common that each rate of amounts ΔH, ΔN, ΔW etc., which is respectively a variation of the amount of the static pressure H, the rotation number N, or the electric power consumption W with respect to the air flow variation amount ΔQ differs for large air flow rates and for small air flow rates, respectively. When ΔH/ΔQ, ΔN/ΔQ, ΔW/ΔQ, and the combinations of those are detected using the pressure sensor, then a predetermined control for the vacuum cleaner is carried out. In case that the detection sensitivity of the pressure sensor is made same, error judgment and error control may be carried out. However, in the conventional vacuum cleaner, no considerations are provided about these variation rates and their control. Summary of the Invention: An object of the present invention is to provide a vacuum cleaner and a method for operating the same wherein an electric driven blower installed in a cleaner main body can be operated with an optimum characteristic. Another object of the present invention is to provide a vacuum cleaner and a method for operating the same wherein an output of an electric driven blower installed in a cleaner main body can be decreased at both large air flow rates and small air flow rates. A further object of the present invention is to provide a vacuum cleaner and a method for operating the same wherein an output of an electric driven blower installed in a cleaner main body can be decreased using one detection sensor for detecting an operation condition of the vacuum cleaner. A further object of the present invention is to provide a vacuum cleaner and a method for operating the same wherein a hysteresis phenomenon in an electric driven blower installed in a cleaner main body can be prevented. A further object of the present invention is to provide a vacuum cleaner and a method for operating the same wherein a hysteresis amount in an electric driven blower installed in a cleaner main body can be adjusted. A further object of the present invention is to provide a vacuum cleaner and a method for operating the same wherein a chattering phenomenon in an electric driven blower installed in a cleaner main body can be prevented. A further object of the present invention is to provide a vacuum cleaner and a method for operating the same wherein an output of an electric driven blower installed in a cleaner main body can be controlled accurately in response to a cleaning condition of the vacuum cleaner. A further object of the present invention is to provide a vacuum cleaner and a method for operating the same wherein, an erroneous control for an electric driven blower installed in a cleaner main body, which is caused by varying the rate of variation of a static pressure, a rotation number, an electric power consumption, or an electric current etc. with respect to the rate of variation of an air flow at a large air flow rate side and also at a small air flow rate, may be prevented. According to the present invention, in a vacuum cleaner comprising a cleaner main body having a filter for catching dusts and an electric driven blower within a main case, a detection sensor for detecting an operation condition in the cleaner main body, and a control apparatus for controlling an output of the electric driven blower in response to a detection value of the detection sensor, in which as control values in accordance with the detection value of the detection sensor, a change-over level setting value for forming a judgment point for changing over a control condition of the electric driven blower and a return level setting value for forming a judgment point for returning to a previous control condition of the electric driven blower from a changed-over control condition of the electric driven blower, and an output of the electric driven blower is controlled by the change-over level setting value and the return level setting value. When the detection value of the detection sensor is above the change-over level setting value and the output of the electric driven blower is increased, the return level setting value is set higher than the change-over level setting value. When the detection value of the detection sensor is above the change-over level setting value and the output of the electric driven blower is decreased, the return level setting value is set a lower than the change-over level setting value. According to the present invention, in a vacuum cleaner comprising a sensor for detecting an operating condition in a cleaner main body having an electric driven blower, and a control portion for controlling the electric driven blower in response to a detection value of the detection sensor, the detection sensitivity of the detection sensor is varied in response to a suction air flow rate. According to the present invention, in controlling the output of the electric driven blower, since the return level setting value can be set to a predetermined return value in response to a newly changed-over control condition, it is possible to return to an operating point which is close to an operating point at change-over time; so it is possible to control the output of the electric driven blower at same or substantially same air flow range, thereby the hysteresis phenomenon in the electric driven blower can be prevented. According to the present invention, a detection sensitivity of the detection sensor is varied in response to a suction air flow rate, and a detection output having substantially same level in the electric driven blower can be obtained at all air flow rates. When a condition of a suction portion of the vacuum cleaner according to a fluctuation width and a variation pattern of the detection amount by the detection sensor is judged and an output control for the electric driven blower is carried out corresponding to this judgment, it is possible to judge accurately by using a judgment apparatus which uses the same judgment and control circuit or a small number of judgment and control circuits, or judgment programs. Accordingly, an erroneous control caused by the rate of variation of the various parameters, which is respectively a variation in the amount of the static pressure, the rotation number, the electric power consumption, or the electric current with respect to the variation in the air flow variation amount at the large air flow range and at the small air flow range is avoided, and an erroneous control of the electric driven blower due to the incorrect judgment is also prevented and further an output control for the electric driven blower can be carried out accurately in response to the condition of the surface to be cleaned. Brief Description of the Drawings: Fig. 1 is a vertical cross-sectional view showing one embodiment of an internal structure of a vacuum cleaner having an electric driven blower and a pressure sensor according to the present invention; Fig. 2 is a characteristic view showing a suction performance in a vacuum cleaner in which an output of an electric driven blower is decreased at high air flow rates; Fig. 3 is a characteristic view showing a suction performance in a conventional vacuum cleaner in which an output of an electric driven blower is decreased at small air flow rates; Fig. 4 is a characteristic view showing a suction performance in a conventional vacuum cleaner in which a negative gradient control for an output of an electric driven blower is carried out with respect to an electric driven blower characteristic; Fig. 5 is a characteristic view showing an aerodynamic performance in a vacuum cleaner in which an electric driven blower is driven by a commutator motor; Fig. 6 is a characteristic view showing an aerodynamic performance in a vacuum cleaner in which an electric driven blower is driven by a synchronous motor or an induction motor; Fig. 7 is a characteristic view showing aerodynamic performances in a vacuum cleaner in which an electric driven blower is driven by an inverter motor; Fig. 8 is a characteristic view showing aerodynamic performances in a vacuum cleaner according to various motion curves in which an electric driven blower is driven by an inverter motor; Fig. 9 is a characteristic view showing aerodynamic performance curves in a vacuum cleaner in which each rate of variation of the amounts of static pressure, rotation number, and electric power consumption with respect to a variation in the air flow rate is indicated; Fig. 10 is a characteristic view showing suction performances in one embodiment of a vacuum cleaner according to the present invention; Fig. 11 is a characteristic view showing suction performances in another embodiment of a vacuum cleaner according to the present invention; Fig. 12 is a characteristic view showing a suction performance in a further embodiment of a vacuum cleaner according to the present invention; Fig. 13 is a characteristic view showing aerodynamic performance curves in a further embodiment of a vacuum cleaner according to the present invention; Fig. 14 is a characteristic view showing a relationship between a detection value of a static pressure by a pressure sensor and a time period at an operating range of a large air flow rate; and Fig. 15 is a characteristic view showing a relationship between a detection value of a static pressure by a pressure sensor and a time period at an operating range of a small air flow rate. Description of the Invention: Hereinafter, one embodiment of a vacuum cleaner according to the present invention will be explained referring to the drawings. In Fig. 1, a cleaner main body 1 of a vacuum cleaner comprises a main case 3 having an electric driven blower 2 installed in it, and a dust case 5 having a filter 4 for catching dusts installed in it, and the cleaner main body 1 is connected to a hose 6, an extension pipe 7, and a suction nozzle 8. The suction nozzle 8 is a general one for use on a floor, a suction nozzle 9 for use in clearance, and a suction nozzle 10 for use on a shelf, each connected to the cleaner main body 1 as attachment parts. A control apparatus 11 in the cleaner main body 1 is constructed of electronic circuits including a central execution processing apparatus such as electric circuits or a microcomputer and the control apparatus 11 controls an output of the electric driven blower 2 in response to a detection value of a pressure sensor 12. The pressure sensor 12 detects an operating condition of the vacuum cleaner. A setting location of the pressure sensor 12 is positioned at a downstream portion of the filter 4 as shown in figure, however the pressure sensor 12 may be suitably provided in the dust case 5 or at an upstream portion of a side of the suction nozzle 8 for use in floor cleaning. In the vacuum cleaner of the embodiment according to the present invention, a control sequence route is shown in Fig. 10. In Fig. 10, the horizontal axis shows an air flow amount Q and the vertical axis shows a static pressure H of each portion of the vacuum cleaner. Fig. 10 shows a method for increasing the output of the electric driven blower 2. A motion curve B in Fig. 10 shows a static pressure characteristic at a portion of the suction nozzle 8 for use on a floor. A characteristic curve C shows a static pressure characteristic detected by the pressure sensor 12 and has pressure values higher than those of the motion curve line B by the sum of the pressure losses in each of the portions at the filter 4, the dust case 5, the hose 6, and the extension pipe 7. Herein, when the suction nozzle 8 for use in floor is covered by the floor surface and the static pressure H rises over a value H₁ of a change-over level setting point C₁, in case of a control for increasing an output of the electric driven blower 2, the characteristic curve B and the characteristic curve C change over to characteristic curve B' and to characteristic curve C', respectively. A new operating point occurs at an intersection point C'₁ with the load curve shown in the curve D which is the sum of the above stated pressure loss and the static pressure assumes a value H'₁. After this, the operating point moves along the characteristic curve C'. However, in the conventional method for operating the vacuum cleaner, unless the operating point reaches a return point C'₂ which has the same pressure value H₁ as the change-over level setting point C₁, the blower motor does not return to the previous control condition. The air flow rate Q₁ at the change-over level setting point C₁ in the forth transition differs from the air flow rate Q₂ at the return point C'₂ in the return transition, accordingly the hysteresis occurs in the conventional vacuum cleaner. In the embodiment of the present invention, a return point C' R is set with an approximate value H' R a little smaller than the value H'₁. When the return transition carried out, it is possible to carry out the control sequence route almost without hysteresis. At the return point C' R , the air flow rate has a value Q R . As a concrete return control method for operating the vacuum cleaner, a comparator for setting the change-over level and a comparator for setting the return level may be provided and a logic construction using both comparators may be made. Alternatively, one comparator may be provided and a logic construction may be made in which, after the change-over motion the judgment value is replaced by the return level setting value. Needless to say, using a central execution processing apparatus, the judgment function may be carried out by a program. Fig. 11 shows a method for realizing the negative gradient characteristic against the characteristic of the electric driven blower 2, namely a method for decreasing the output of the electric driven blower 2. The references of each characteristic curve B, C, B'', and C'' are the same ones as those shown in Fig. 10. When the static pressure H₃ at the change-over level setting point C₃ is exceeded, and a control for decreasing the output of the electric driven blower 2 is carried out, then the characteristic curves B and C are shifted over to characteristic curves B'' and C'', respectively. Similarly to the above stated description, a new operating point C''₃ is reached and the value of the static pressure becomes H''₃. When the control is left as it is, a control for returning to the previous motion curve line C may be carried out. However in this embodiment of the present invention, at the return level setting point C'' R , the pressure value is set at a lower value H'' R from a predetermined value than H''₃, so that it is possible to carry out the motion on the motion curve C''. Naturally, when the adhesion of the surface to be cleaned to the suction nozzle 8 etc. is released and the air flow rate Q increases, the cleaner returns to the previous motion curve line C or a control sequence route. By the combination of the above stated operations, it is possible to realize the characteristic shown in Fig. 4 by using only one pressure sensor. In a further embodiment of the present invention, it is possible to realize a complicated control sequence route shown in Fig. 12. In Fig 12, dashed line E shows a maximum output line of the electric driven blower 2. Namely, a range R₁ in Fig. 12 shows a practical range for the suction nozzle 8 for use in floor and an optimum control for the vacuum cleaner is carried out. In a range R₂ in which the suction nozzle 9, for use in clearance, is connected to the cleaner main body 1, even when only the suction nozzle 9 is connected, the air flow amount Q may decrease, the static pressure H may rise also. In the conventional vacuum cleaner control, even when no cleaning is carried out, the electric driven blower 2, is operated at maximum output which is undesirable from the point of view of electric power saving and noise reduction. However, when the suction nozzle 9 is moved away from the area to be cleaned, the output of the electric driven blower 2 is lowered and it is possible to control the electric driven blower 2 so that the maximum output thereof is in accordance with the cleaning loading condition of the suction nozzle 9. This greatly improves operativeness by saving electric power saving, reducing noise, and preventing adhesion of the suction nozzle 9. Further, since the cleaner control responds to the load condition of the above stated suction nozzle 9, when the suction nozzle 9 is rapidly and repeatedly moved to and released from the cleaning surface, the output of the electric driven blower 2 rises to maximum when the suction nozzle 9 returns to the surface. Accordingly it is possible to prevent the defect of the suction nozzle 9 adhering and causing an incorrect operation during the cleaning operation of the vacuum cleaner. The pressure in the portion of the pressure sensor 12 can respond in the integrated style to the pressure fluctuation due to adhesion and release of the suction nozzle portion, because of a time delay in the detection of a rise of total pressure due to a volume of the passage portion between the suction nozzle portion and the sensor. Accordingly, the issue of an unnecessarily rapid output variation command to the electric blower motor is avoided, thus preventing the above stated chattering problem. By the provision of an orifice having a small hole to the portion of the pressure sensor 12 which acts as a dashpot, not shown in figure, and by the optimizing the response speed, the above stated operation can be utilized positively. When the suction nozzle 9 is operated slowly, it can operate with a high output condition as stated above, therefore it is possible to carry out a new use in which the suction force can be adjusted according to the operation speed of the suction nozzle 9. Further, a range R₃ corresponds to a nearly closed condition of the nozzle and lies outside the practical range. As in this range the output of the electric driven blower 2 is lowered as shown in Fig. 12, it is possible to prevent the suction nozzle 9 for use in clearance from adhering. When the adhesion is released, high output operation is automatically resumed. A characteristic curve shown in Fig. 12, the details of which are enlarged is realized by combining a very large number of the basic motions or control sequence routes shown in Fig. 10 and Fig. 11, however if the number of the combined basic motions is small, a smooth motion curve line cannot obtained. Practically, the motion curve can be realised with a plurality of the electric circuits, however an ideal characteristic motion curve is easily realized by executing a program in the central execution processing apparatus of the microcomputer. In this case, each change-over level setting point or each return level setting point is stored as a table in the microcomputer, and a successive write-in renewal method for operating the vacuum cleaner can be realized with a small sized apparatus. According to the above stated embodiment of the present invention, there occur the following effects: It is possible to carry out the output control for the electric driven blower 2 without the hysteresis on the forth passage and the back passage by the setting of the change-over level setting point and the return level setting point. Further, it is possible during the output control in the electric driven blower 2 to adjust the amount of the hysteresis. Despite the fact that the detection value is detected by only one pressure sensor 12, it is possible to realize the characteristic for the electric driven blower 2 having a negative gradient characteristic. By the combination of the positive gradient characteristic and the negative gradient characteristic, it is possible to achieve the optimum characteristic for the output control of the electric driven blower 2 by matching to the kinds of suction nozzles and their operating conditions. It is possible to set large number of the setting points for the change-over level and the return level in the output control for the electric driven blower 2 by the combination of the central execution processing apparatus, accordingly it is possible to achieve the optimum characteristic for operating the vacuum cleaner. A basic motion or a control sequence route of the vacuum cleaner is shown in Fig. 13 taking into account various pressure losses. The horizontal axis in Fig. 13 shows an air flow amount Q, and the vertical axis shows a static pressure H at each portion of the vacuum cleaner. A motion curve line A₁ shows a static pressure characteristic in each portion of the suction nozzle 8 for use on floor. A characteristic curve B₁ shows a static pressure characteristic detected by the pressure sensor 12. The characteristic curve B₁ has a pressure value which is higher than that of the motion curve line A₁ by the sum of a pressure loss at the suction nozzle 8 portion, a pressure loss at the filter 4, a pressure loss at the dust case 5, a pressure loss at the hose 6, and a pressure loss at the extension pipe 7. The pressure sensor 12 detects the pressure value on the characteristic curve line B₁. Herein, during the cleaning operation of the vacuum cleaner, when the suction nozzle 8 for use on a floor is moved back and forth on the surface of the item to be cleaned or is lifted away from said item, the flow resistance of the suction nozzle 8 fluctuates, and the pressure varies between the motion curve line B₁ and the motion curve line C₁ (Fig. 13). As the fluctuation width of the suction nozzle 8 varies at this time, a difference between a point D₁ and a point E₁ is detected. Moreover, in the case that the filter 4 in the cleaner main body 1 is clogged and consequently the motion point shifts toward the small air flow rate, the pressure fluctuation between a point F₁ and a point G₁ in Fig. 13 is detected. The reason is that, at the large air flow rate, the fluctuation width at each condition is large, namely the air flow variation amount ΔQ and the pressure variation amount ΔH are large, because the air flow amount Q is large and the opening area of the suction nozzle 8 varies. Moreover, at the small air flow rate, the absolute value of the pressure loss of the suction nozzle 8 portion is small and the fluctuation width becomes small because the air flow amount Q is small. Further, as explained in Fig. 9, the fluctuation width becomes small at the small air flow rate due to the aerodynamic characteristics of the electric driven blower 2. Herein, in the use condition at the large air flow rate, an example of the variation of the pressure detection value ΔH₁ in a time period T, which is detected by the pressure sensor 12, is shown in Fig. 14. Further, in the use condition at the small air flow rate, an example of the variation of the pressure detection value ΔH₂ in a time period T, which is detected by the pressure sensor 12, is shown in Fig. 15. As shown in Fig. 14, at large air flow rates, the steady pressure value H₁ is small, and the fluctuation pressure value ΔH₁ becomes large. The steady pressure value H₁ is obtained in the case when the suction nozzle 8 for use on a floor is lifted up in the air so that the fluid resistance is small and therefore no fluctuation with time occurs. In this way, the fluctuation width and the variation time interval (variation pattern) of the pressure are detected by the pressure sensor 12, they are multiplied at a predetermined level and are sent to the control apparatus 11. The control apparatus 11, due to the combination of the microcomputer and the judgment program, judges the kinds of the suction nozzles, the condition of the surface of the item to be cleaned, and the existence of the cleaning operation (the operation is carried out when the suction nozzle 9 is used in clearance or not). The control apparatus 11 controls the output of the electric driven blower 2 so as to suit the cleaning condition of the vacuum cleaner and also to obtain the optimum operation condition for the vacuum cleaner. For example, when the cleaning is carried out by lifting up the suction nozzle 8 from a floor to the air, the output of the electric driven blower 2 is lowered, therefore, the low noise structure and the electric power saving can be achieved. At the small air flow rate, as shown in Fig. 15, the steady pressure value H₂ is made large by the clogging of the filter 4 etc., and the fluctuation pressure value ΔH₂ becomes small. As stated above, when the cleaning condition is judged by the fluctuation width and the variation pattern of the pressure, the variation width of the pressure is very small and the judgment is difficult or becomes impossible. Further, at small air flow rates, erroneous judgment may occur or the judgment according to, the judgment value of the judgment program at large air flow rates may be impossible. As a countermeasure to this, the judgment program may be prepared in response to each air flow range, however the number of programs corresponding to each aerodynamic characteristic becomes enormous, therefore this is not a practical solution. Namely, as shown in the embodiment in Fig. 8, after the operation control, it is necessary to have the judgment (value) programs in response to each air flow amount Q of each motion curve line corresponding to the aerodynamic characteristic curve lines (1), (2), (3), and (4). However, in order to carry out a highly accurate control, it is necessary to increase this number of the programs. In this embodiment of the present invention, each of the characteristic groups (as shown in the above stated Fig. 8), turning an attention to the rate ΔH/ΔQ of the pressure amount variation ΔH in respect with the air flow amount variation ΔQ at the large air flow rate and at the small air flow rate, show the same tendency, namely the detection sensitivity of the pressure sensor 12 varies at the small air flow rate. The pressure variation ΔH, the air flow amount variation ΔQ, each of which has substantially same level, or the fluctuation width of the variation rate ΔH/ΔQ having substantially same level at all air flow amount area can be obtained by varying the detection sensitivity of the pressure sensor 12. In this case, the fluctuation width of the output of the pressure sensor 12 at the small air flow rates is made to have substantially the same fluctuation width as the output in the pressure sensor 12 at the large air flow rates. In other words, the detection sensitivity of the pressure sensor 12 is varied in accordance to the suction air flow rate. Therefore a detection output having substantially the same level of the pressure sensor 12 can be obtained at all air flow ranges. When the condition of the suction opening area of the vacuum cleaner is judged according to the fluctuation width of the detection amount and the variation pattern of pressure, and when the output control in the electric driven blower 2 is carried out in response to the judgment, it is possible to judge accurately by using a judgment apparatus which uses sane or small number of judgment and control circuit or judgment programs. An erroneous control in the electric driven blower 2 due to an incorrect judgment and judgment impossibility is prevented and also an output control for the electric driven blower 2 is carried out accurately in response to the cleaning condition of the vacuum cleaner. As a concrete embodiment of the present invention, in a comparison with Fig. 14 and Fig. 15, it is attained by varying the detection sensitivity of the pressure sensor 12 at the small air flow rates (in this example, increasing the detection sensitivity, so as to obtain the fluctuation pressure width ΔH₂ in the small air flow rates which corresponds to the fluctuation pressure width ΔH₁ in the large air flow rates. The above stated detection sensitivity variation of the pressure sensor 12 is attained by detecting a predetermined air flow rate point, and corresponding to this, by varying the gain of the amplifier, which is included in the pressure sensor 12. It is possible to carry out the detection sensitivity change-over operation for the pressure sensor 12 by the electric circuits constituting the change-over judgment circuit, or by the command in the microcomputer. Further, by the detection sensitivity variation in the pressure sensor 12, the steady pressure value part H₂ is amplified, however it is possible to process the execution by the electric circuits or the microcomputer, by taking out the fluctuation pressure value part from the remaining the steady pressure value part. As stated above, according to this embodiment of the present invention, the detection sensitivity of the detection sensor is varied in response to a suction air flow rate, and a detection output having substantially the same level for the detection sensor can be obtained at all air flow rates. When a condition of a suction opening face of the vacuum cleaner according to a variation width and a variation pattern of the detection amount is judged and a control is carried out corresponding to this judgment, it is possible to judge accurately by using a judgment apparatus which uses same or small number of judgment and control circuits or judgment programs. An erroneous control of the electric driven blower 2 due to the incorrect judgment and the judgment impossibility is prevented and an output control for the electric driven blower 2 is carried out accurately in response to the cleaning condition. Further, in this embodiment of the present invention, the detection of the pressure variation by the pressure sensor 12 is given as example, however in place of this detection the air flow rate variation may be detected by using the air flow rate detection sensor. Further, in case that the control is carried out by detecting the variation amount of the operation conditions in respect to the rotation number variation, the electric power consumption variation, and the electric current variation etc., by the difference in the variation rate at the large air flow rates and at the small air flow rates is equalized and detected, the same effects as those in the above stated embodiment of the present invention can be obtained. According to this embodiment of the present invention, a detection sensitivity of the detection sensor is varied in response to a suction air flow rate, and a detection output having substantially the same level can be obtained at all air flow rates. Further, only by the provision of the same and small number of the judgment and control circuit and the judgment programs, since it is possible to carry out the control in response to the cleaning condition having the large range, circuit structure and program structure can be remarkably simplified and a reduction in the part cost and the program making costs, can be achieved, resulting in great economic advantages.

Claims: A vacuum cleaner comprising a cleaner main body (1) having a filter (4) for catching dusts and an electric driven blower (2) within a main ease (3), a detection sensor (12) for detecting an operation condition in said cleaner main body (1), and a control unit (11) provided in said cleaner main body (1) for controlling an output of said electric driven blower (2) in response to a detection value of said detection sensor (12) characterized in that the following control values in accordance with said detection value of said detection sensor (12) are set: a change-over level setting value (H₁, H₃) for forming a judgment point for changing over a control condition of said electric driven blower (2), a return level setting value (H R ', H R '') for forming a judgment point for returning to a previous control condition of said electric driven blower (2) from a changed-over control condition of said electric driven blower (2), an output of said electric driven blower (2) being controlled by said obtained change-over level setting value (H₁, H₃) and said obtained return level setting value (H R ', H R ''). A vacuum cleaner according to claim 1, characterized in that when said detection value of said detection sensor (12) is above said change-over level setting value (H₁), the output of said electric driven blower (2) is increased and said return level setting value (H R ') is set at a higher value than said change-over level setting value (H₁). A vacuum cleaner according to claim 1, characterized in that when the detection value of said detection sensor (12) is above said change-over level setting value (H₃), the output of said electric driven blower (2) is decreased and said return level setting value (H R '') is set at a lower value than said change-over level setting value (H₃). A vacuum cleaner according to claim 1, characterized in that when the detection value of said detection sensor (12) is above said change over level setting value (H₁, H₃), the output of the electric driven blower and the return level setting value are changed, a control unit (11) being provided for determining whether the output of the electric driven blower (2) is increased and the return level setting value is set higher than the change-over level setting value or the output of the electric driven blower (2) is decreased and the return level setting value is set lower than the change-over level setting value, according to a suction air flow rate. A vacuum cleaner according to any of claims 1 to 4, characterized by said control unit (11) being a central execution processing unit, said change-over level setting value (H₁, H₃) and said return level setting value (H R ', H R '') being stored in said central execution processing unit, said electric driven blower (2) being controlled by resetting one or both of said change-over level setting value (H₁, H₃ ) and said return level setting value (H₁ ', H R '') to a predetermined value. A vacuum cleaner according to claim 5, characterized in that said central execution processing unit is a microcomputer. A vacuum cleaner according to claim 5, characterized in that said output of said electric driven blower (2) is controlled by said central execution processing unit. A vacuum cleaner according to any of claims 1 - 7, wherein said detection sensor (12) is a pressure sensor for detecting a pressure in said cleaner main body (1). Method for operating a vacuum cleaner comprising a sensor for detecting an operation condition in a cleaner main body (1) having a filter (4) and an electric driven blower (2), and a control portion (11) provided in said cleaner main body (1) for controlling said electric driven blower in response to a detection value of a detection sensor (12), characterized in that a detection sensitivity of said detection sensor (12) is varied in response to a suction air flow rate, said detection sensitivity of said detection sensor (12) being higher, the lower the suction air flow rate is.

Inventors: ISHII YOSHITARO, JYOURAKU FUMIO, KOHARAGI HARUO, SUKA HISAO, TAHARA KAZUO, ISHII, YOSHITARO, JYOURAKU, FUMIO, KOHARAGI, HARUO, SUKA, HISAO, TAHARA, KAZUO
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1989
Main classification: A47L9
IPC codes: A47L9