Electric vacuum cleaner

Abstract

An electric vacuum cleaner includes a filter, blower, switching element for switching current flowing through the blower, current detecting section, and control section, wherein the control section includes a first control mode in which an amount of airflow flowing through the filter and the blower is restrained and a second control mode in which an applied power to the blower is maintained to a target value, and selects one of the first and second control modes according to the applied power.

1 . An electric vacuum cleaner comprising: 
 a blower for generating an air flow containing dust;    a filter configured to separate dust from the air flow;    a switching element for switching a current flowing through the blower in response to a control signal;    an air-flow-amount sensing section for sensing an amount of the air flowing through the filter to output a first value indicating the sensed result, the air-flow-amount being varied in response to amount of the dust separated by the filter;    a current detecting section for detecting a current flowing through the blower to output a second value indicating the detected current value, the current corresponding to power applied to the blower; and    a control section for selecting, in accordance with power applied to the blower, one of a first control mode in which a suitable output timing of the control signal from the control section to the switching element is determined so that variation in the amount of the air flow is restrained based on the first value and a second control mode in which a suitable output timing of the control signal is determined so that the applied power to the blower is maintained at a prescribed target value based on the second value and for controlling the operation of the switching element with the control signal outputted at the suitable output timing of the selected mode.    
   
   
       2 . The electric vacuum cleaner according to  claim 1 , wherein the air-flow-amount sensing section includes a current sensor for sensing a current flowing through the blower, the current being varied in response to an amount of the air flowing through the filter.  
   
   
       3 . The electric vacuum cleaner according to  claim 1 , wherein the control section selects the first control mode when the power applied to the blower is equal to or less than a prescribed value and otherwise selects the second mode.  
   
   
       4 . The electric vacuum cleaner according to  claim 1 , further comprising a zero-cross detecting section for detecting a zero-cross point of the applied voltage to the blower, wherein the control section outputs the control signal every half period of the applied voltage with reference to the detected zero-cross point.  
   
   
       5 . The electric vacuum cleaner according to  claim 1 , wherein the control section includes a PWM (pulse-width-modulation) signal generation section for outputting a PWM signal to the switching element as the control signal.  
   
   
       6 . The electric vacuum cleaner according to  claim 1 , further comprising a memory for storing a plurality of output timing values and thresholds of the air-flow-amount corresponding to each value of the output timing values,  
     wherein, in the first control mode, the control section compares the thresholds with one of the first value and a value calculated based on the first value, selects one of the plurality of output timing values in accordance with the compared result, and outputs the control signal based on the selected value of the output timing.  
   
   
       7 . The electric vacuum cleaner according to  claim 6 , wherein the memory stores a first switching threshold, and  
     wherein the control section switches the first control mode to the second control mode when the one of the first value and the calculated value exceeds the first switching threshold.  
   
   
       8 . The electric vacuum cleaner according to  claim 1 , further comprising a memory for storing value of a target current and a proportional coefficient, wherein the control section, in the second control mode, calculates an error between the target current value and one of the second value and a current value calculated based on the second value, and determines the suitable output timing according to a value that is obtained by multiplying the error by the proportional coefficient.  
   
   
       9 . The electric vacuum cleaner according to  claim 8 , wherein the memory stores a second switching threshold, and wherein the control section switches the second control mode to the first control mode when the error goes smaller than the second switching threshold.  
   
   
       10 . The electric vacuum cleaner according to  claim 1 , further comprising an informing section for informing that the blower operates in the second mode.