A CONTROL METHOD FOR A VACUUM CLEANER

Abstract: A control method for a vacuum cleaner (1) including a control means (7) to perform control algorithms, a motor (6) to drive a fan (8) that provides suction, a dust sensor (2) placed on the dust passageway and including a light emitter (3) and a light receiver (4) to detect dust passing through the dust passageway, and indication means (5) to give an indication to the user when the dust sensor (2) is dirty. The voltage variations pattern is observed at the light receiver (4) output and a series of comparisons are made in order to decide whether the place is dusty or the dust sensor (2) is dirty.

Description: A CONTROL METHOD FORA VACUUM CLEANER This invention relates to a method used in vacuum cleaners to determine the dirtiness of the place to be cleaned and of the dust sensor components. In the prior art, dust sensors formed of optic components namely light emitting and light receiving components are placed on the dust passageway of a vacuum cleaner. Light emitting device is emitting an infrared light beam or the like and light receiving device is receiving the light emitted by the light emitting device. These devices are arranged in a predetermined position on the air passageway. These light emitting and light receiving devices are placed across each other at fixed positions so that the change in light intensity indicates the amount of dust passing through the suction path. When these devices are covered with dust, the light received is decreased so the performance of the dust sensing means is degraded. Under these circumstances, if the light emitted is kept constant then the amount of dust passing through the passageway can be determined when the vacuum cleaner is at its on stage according to the light received by the receiver. The light intensity received by the receiver decreases as the amount of dust passing through the passageway increases. This property is used to increase the motor power as the dust is sensed. Although this is an efficient way of determining dust, as the dust is sucked through the passageway, it covers the surface of the sensors decreasing the amount of light received although there is no dust passing. In EP 0904723 a "sensitivity correction means" is described to solve this problem. The aim of the method described in this patent is to increase the amount of light emitted by the emitter proportional to the reduction of light caused by the adhering of particles on the sensors. The problem with this method is that, if the amount of light emitted is increased when the window members on the sensors are soiled, after a certain period it reaches a limit value, i.e. the emitted light can no longer be increased. In this case the window members on the sensors have to be cleaned manually. The user is informed that soiling of the window members is increased too much that a correction in the intensity of light emitted by the light emitting device reaches its limit value. In US 5152028 another method is described. The surfaces of the sensors are cleaned with the help of a mechanical device so that the light intensity emitted is kept constant. In this patent an upright vacuum cleaner including a dust sensor is introduced. The problem explained above, is solved by a cleaning member that cleans the surface of the window members by the help of the sliding movement of the vacuum cleaner. Since this is an upright vacuum cleaner, the sliding movement is achieved by the movement of the handle. As the handle reaches an angle of 90° the sliding member covers the surface of the sensors. One disadvantage of this method is that when the sliding degree is less than 90° but not big enough to completely move out, the sliding member may partially cover the surface of the sensor thus light intensity may be decreased so the efficiency of the sensitivity means will be decreased as a result. The object of the present invention is to sense whether the place that is being cleaned is dusty or not. Another object of this invention is to determine whether the components of the dust sensor are soiled or not. The present invention is illustrated in the drawings, wherein: Figure 1 - is the shematic view showing an overall arrangement of a vacuum cleaner. Figure 2 - is the circuit diagram of the detection means according to the preferred embodiment of the present invention. Figure 3 - is the light intensity versus time graph when dust sensor components are getting dirty. Figure 4 - is the reference difference value (Dref) versus received light intensity graph. Figure 5 - is the flow chart of the control method. The components shown in the drawings have the following numbers; I- Vacuum cleaner 2- Dust sensor 3- Light emitter 4- Light receiver 5- Indication means 6- Motor 7- Control means 8- Detection means 9- Fan 10- Resistor I I- Detection circuit In the preferred embodiment of this invention, a vacuum cleaner (1) comprises a motor (6) to drive a fan (9) that provides the suction, a detection means (8) to detect the dust, and an indication means (5) either comprising LED's or LCD's to indicate to the user that the dust sensor components are dirty and a control means (7) that controls the motor (6). Detection means (8) comprises a dust sensor (2) placed on the dust passageway to detect the dust passing through and comprising two components namely a light emitter (3) which is preferably a light emitting diode and a light receiver (4) which is preferably a phototransistor to detect dust passing through the dust passageway, a resistor Rl (10) for determining the current to be introduced into the light emitter (3), and a detection circuit (11) to measure the light received by the light receiver (4) in terms of voltage or current depending on its arrangement. The supply voltage (Vx) on the light emitting side of the detection means (8), the resistor Rl (10) is chosen such that the current that is applied to the light emitter (3) is always maximum and it is not changed during the operation of the vacuum cleaner (1) so that the intensity of the emitted light is kept constant during the operation of the vacuum cleaner (1). When the vacuum cleaner (1) is started to clean a surface, the maximum current is applied to the light emitter (3) of the dust sensor (2) (101). This current does not change during the operation of the vacuum cleaner (1). The output from the light receiver (5) is measured for predetermined intervals of time. Each time interval defines a cycle. For a cycle n, as dust passes through the dust passageway, the intensity of the light received by the light receiver (4) fluctuates. It decreases at the moment when the dust passes between the light emitter (3) and the light receiver (4) and it increases at the moment when no dust passes between the light emitter (3) and the light receiver (4). A probable light intensity versus time graph is shown in Figure 3. Depending on the arrangement of the detecting circuit (1 1), the light intensity can be measured in terms of voltage or in terms of current and the measured voltage or current can increase or decrease with the dust passing through the dust passageway i.e. voltage or current measurement is proportional or inversely proportional to the intensity of light received by the light receiver (4). After observing the light intensity during the cycle n, the local maximum values max,(n), max 2 (n), ... maXj(n) and local minimum values min,(n), min 2 (n).... min^n) of the light intensity are found and stored (102). Then, the mean value of the local maximum values (max(n)) and the mean value of the local minimum values (min(n)) of the output data are computed and stored for the cycle n, in the memory of the control means (7). (103). Then, the difference (Delta(n)) between the mean value of the local maximum values (max(n)) and the mean value of the local minimum values (min(n)) is calculated (104). The difference (Delta(n)) is then compared with a predetermined reference difference value (Dref(n)) (106). Preferably the reference difference value (Dref(n)) depends on the mean value of the local minimum values (min(n)). For each probable value of the mean value of the local minimum values of the light intensity, (min(n)), a different reference difference value Dref(n) is kept in the memory of the control means (7). While cleaning the surface, if the surface is dirty and/or if the dust is adhering on the dust sensor (2) components, the mean value of the local minimum values of the light intensity, (min(n)) will decrease, and the fluctuations in the received light intensity will decrease as well. When the fluctuations decrease there is a possibility to have smaller difference (Delta(n)) values therefore (Dref(n)) is chosen as a small value to provide the adaptation to the detection conditions and to be able to detect the presence of dust with a smaller Delta(n) value. The reference difference value (Dref(n)) can also be chosen as a constant value. If the difference (Delta(n)) is greater than the predetermined reference difference value (Dref(n)), then the decision is that; "the place is dusty" and it is decided to increase the motor (6) power. (107). A new cycle n+1 starts with a newly starting time interval, light intensity is observed again and new mean value of the local maximums (max(n+l)) and mean value local minimum values (min(n+l)) are computed and stored. If the difference (Delta(n)) is smaller than the predetermined reference difference value (Dref(n)), i.e if the fluctuations in the output data are not big enough to indicate the presence of dust for the cycle n, two possibilities are considered; The first possibility is that "the place is not dusty" so there will be no need to increase the motor (6) power. The second possibility is that "dust sensor (2) components, the light emitter (3) and/or the light receiver (4) are dirty, and it causes an output without enough fluctuations to reflect the real state of the surface which is being cleaned". To make the decision between these two possibilities the mean value of the local minimum values (min(n)) is compared with a predetermined minimum allowed light intensity value (Dmin), that is a constant value determined experimentally and stored in the memory unit (108). If the mean value of the local minimum values of the light intensity (min(n)) for the cycle n is greater than the predetermined minimum allowed constant light intensity value (Dmin), the decision is that there is no dust in the drawn air i.e. "the place is not dusty" and it is decided to keep the motor (6) power constant (109). The cycle n+1 starts. If the mean value of the local minimum values of the light intensity (min(n)) for the cycle n is smaller than the predetermined minimum allowed light intensity value Dmin and it is started to count the number of consequent cycles where the following conditions occur(l lθ); the difference values (Delta) are smaller than the reference difference values (Dref) and mean values of the local mimimum values (min) are smaller than the predetermined minimum allowed light intensity value (Dmin), i.e the differences (Delta(n), Delta(n+1 ),.... Delta(n+c)) are smaller than the reference difference values (Dref(n), Dref(n+1), Dref(n+c)) respectively and each mean values of the local minimum values (min(n), min(n+l) min(n+c)) are smaller than the predetermined minimum allowed light intensity value (Dmin). Then the number of cycles counted is compared with c (111). If they are equal, i.e. if above conditions exist for c consecutive cycles, it is decided that "the dust sensor components, the light emitter (3) and the light receiver (4) are dirty" and the user is warned via the indication means (5) and the cycle n+c+1 starts. Since a continuous flow of dust can cause during some cycle (but not as long as during cycles c), an output with low fluctuations, i.e with a difference (Delta) smaller than the reference difference value (Dref) and with a mean value of the local minimum values (min(n)) smaller than the predetermined minimum allowed light intensity value (Dmin), it is not decided on the dirtiness of the dust sensor components without being sure that it is caused by continuous dust. If the difference values (Delta(n), Delta(n+1 ),.... Delta(n+c)) are smaller than the reference difference values (Dref(n), Dref(n+1), Dref(n+c)) respectively and each mean values of the local minimum values (min(n), min(n+l) min(n+c)) are smaller than the predetermined minimum allowed light intensity value (Dmin), it is decided that this is caused by the dirtiness of the dust sensor (2) components.

Claims: CLAIMS 1. A control method for a vacuum cleaner (1) including a motor (6) to drive a fan (9) that provides the suction, a detection means (8) comprising a dust sensor (2) placed on the dust passageway having a light emitter (3), a light receiver (4) and a detection circuit (11) to detect the dust passing through the dust passageway, a control means (7) that controls the motor (6) and an indication means (5) either comprising LED's or LCD's to indicate to the user that the dust sensor (2) components are dirty, comprises the steps of starting the vacuum cleaner (1) and applying the maximum current to the light emitter (3) and observing the light intensity at the light receiver (4) for a predetermined period of time that defines a cycle n (101), finding and storing local maximum values (max, (n)... max, (n)) and local minimum values (min,(n) min,(n)) of the light intensity during cycle n (102), then computing the mean value of the local maximum values (max(n)) and the mean value of the local minimum values (min(n)) (103), calculating the difference (Delta(n)) between the mean value of the local maximum values (max(n)) and the mean value of the local minimum values (min(n)) (104), getting a corresponding reference difference value (Dref(n)) which is kept in the memory of the control means (7) (105), comparing the difference value (Delta(n)) with a predetermined reference difference value (Dref(n)) (106), if the difference value (Delta(n)) is greater than the predetermined reference difference value (Dref(n)) deciding that the place is dusty (107) and increasing the motor (6) power accordingly and if the difference value (Delta(n)) is smaller than the predetermined reference value (Dref(n)), determining whether the place is clean or whether the dust sensor components are dirty. 2. A control method for a vacuum cleaner (1) according to Claim 1 characterized in that in order to provide the adaptation to the detection conditions, the predetermined reference difference value (Dref(n)) depends on the mean value of the local minimum values (min(n)) such that reference difference value Dref is decreasing while mean value of the local minimum values; (min) is decreasing, in order to have smaller reference difference value (Dref(n)) when the fluctuations are smaller due to the continuous dust, or due to the adhering of dust on the dust sensor (2) components. 3. A control method for a vacuum cleaner (1) according to Claim 2 characterized in that, if the difference value (Delta(n)) is smaller than the predetermined reference difference value (Dref(n)) for the predetermined period of time, it further comprises the steps of comparing the mean value of the local minimum values (min(n)) with a constant predetermined minimum allowed light intensity value (Dmin) (108), deciding on the "absence of dust in the drawn air" if the mean value of the local minimum values (min(n)) of the light intensity is greater than the predetermined constant value (Dmin) (109) and keeping the motor (4) power constant. 4. A control method for a vacuum cleaner (1) according to Claim 3, characterized in that if the mean value of the local minimum values (min(n)) is smaller than the constant predetermined minimum allowed light intensity value (Dmin), it further comprises the steps of counting the number of consecutive cycles where the following conditions occur (110); the difference values (Delta) are found smaller than the reference difference values (Dref) and the mean values of the local minimum values (min) are found smaller than (Dmin) value, i.e if the difference values (Delta(n), Delta(n+1 ),.... Delta(n+c)) are smaller than the reference difference values (Dref(n), Dref(n+1), Dref(n+c)) respectively and each mean values of the local minimum values (min(n), min(n+l) min(n+c)) are smaller than the predetermined minimum allowed light intensity value (Dmin), then if above conditions exist for c consecutive cycles, deciding that "the dust sensor components, the light emitter (3) and the light receiver (4) are dirty" and warning the user about the dirtiness of the dust sensor (2) by means of the indication means (3). 5. A control method for a vacuum cleaner (1) according to Claim 4, characterized in that the output at the light receiver (4) is measured in terms of voltage or current, and the detection circuit (11) is arranged such that the measured voltage value is (directly or inversely) proportional to the light intensity. 6. A vacuum cleaner that is using a control method according to any of Claim 1 to 5.

Inventors: EFEC K BUELENT, SULAMACI BANU, EFEC K, BUELENT, SULAMACI, BANU
Applicants: ARCELIK AS, EFEC K BUELENT, SULAMACI BANU, ARCELIK A.S., EFEC K, BUELENT, SULAMACI, BANU
Application year: 2000
Main classification: A47L9
IPC codes: A47L9