Patent Application
20120090098
Laundry treating appliances wash laundry using a treating chemistry, such as a wash liquor. The wash liquor may contain solvents, such as water and surfactants, as well as other agents. The surfactants may reduce the surface tension of water to enhance cleaning action. The reduced surface tension may also result in enhanced foaming of the wash liquor. Excessive foaming or an over-sudsing condition may lead to reduced effect of mechanical energy applied to the laundry for cleaning, such as, for example, the suds may insulate the impact of the laundry on the side of the drum. Detection of an over-sudsing condition may allow for responding to the over-sudsing condition to enable a more effective wash cycle of operation.
One embodiment of the invention is related to a method for determining an over-sudsing condition in a laundry treating appliance comprising multiple components for implementing a washing cycle of operation including a tub for holding liquid, a drum defining a treating chamber rotatably mounted within the tub, a pressure sensor fluidly coupled to the tub and outputting a signal indicative of the amount of water in the tub, and a controller coupled to and controlling the components, including receiving the signal and implementing the cycle of operation. The method comprises rotating the drum while the tub contains a foamable liquid, determining, over time, a fluctuation in the signal from the pressure sensor while the drum is rotating, determining an over-sudsing condition when the fluctuation satisfies a predetermined threshold, and altering the cycle of operation in response to the determination of an over-sudsing condition.
In the drawings:
The present invention relates generally to a laundry treating appliance and detecting an over-sudsing condition (OSC) within the laundry treating appliance. More specifically, the invention is related to detecting an OSC by processing the signal of a pressure sensor measuring the amount of and the pressure of liquid within the laundry treating appliance.
The tub 14 may further contain a sump 46 connected to a recirculation pump 50 via a sump conduit 48. The recirculation pump 50 may selectively pump liquid contained within the sump back in to the tub 14 via a recirculation conduit 54 or to a household drain (not shown) via a drain conduit 52. There may also be a water inlet 40 to the tub 14 for introducing fresh household tap water to the laundry treating appliance 10. There may be water source 32 external to the laundry treating appliance coupled to an inlet valve 34 to actuate the flow of water from the water source 32. A filter conduit 36 downstream of the inlet valve 34 leads to a water filter 38 for removing particulates from water coming from the water source 32. An inlet conduit 40 in fluid communication with the water filter 38 and the tub 14 may provide water to the tub 14 when the inlet valve 34 allows the flow of water from the water source 32.
A laundry treatment agent dispenser 42 accessible from outside the cabinet 12 for holding a laundry treatment agent (not shown) and dispensing the agent in to the tub 14 via laundry treatment agent conduit 44 and may be provided.
A drive system having a shaft 28 attached to the drum 16 and coupled to a motor assembly 30 is provided for rotating the drum 16 when the laundry treating appliance 10 runs a wash cycle of operation.
A pressure sensor 60 for measuring the pressure on the water in the sump 46 may be coupled to the tub, such as at the sump 46, by way of a tube 58, in which may be provided an airlock 56. All of the electronic components of the laundry treatment appliance 10, including the inlet valve 34, the motor 30, the recirculation pump 50, and the pressure sensor 60 may be controlled by a controller 62 with electronic memory 64 that is communicatively coupled to the electronic components via a communications pathway 66.
The pressure sensor 60 may be an analog pressure sensor or a digital pressure sensor. The pressure sensor 60 may output a signal that is indicative of the amount or level of liquid in the tub. The signal may be a voltage or current signal that is related to the amount of water in the tub 14 and the pressure imparted on the water in the tub 14 during a wash cycle of operation. The voltage or current signal of the pressure sensor 60 may further be directly and linearly related to the head pressure of the water in the tub 14 and pressure imparted on the water by the tub 14 and laundry during a wash cycle of operation.
The controller 62 may be a microprocessor, microcontroller, field programmable gate array (FPGA), application specific integrated circuit (ASIC), or any other known electronic controller. The controller 62 may receive the signal from the pressure sensor 60. The controller 62 may further process and store the signal from the pressure sensor 60 in the electronic memory 64. The controller 62 may, for example determine, over time, a fluctuation in the signal from the pressure sensor 60 while the drum 16 is rotating, and compare the fluctuation in the signal to a predetermined threshold to determine an over-sudsing condition in the tub 14. The controller 62 may further alter the cycle of operation in the laundry treating appliance 10 in response to the determination of an over-sudsing condition. The controller 62 may also serve the purpose of controlling the wash cycle of operation of the laundry treating appliance 10. The memory may be a dynamic random access memory (DRAM), static random access memory (SRAM), or any other known type of electronic memory and may be used by the controller 62 to store pressure sensor 60 signals and parameters for various wash cycles of operation.
While the laundry treating appliance 10 of
As is readily seen in both
As currently understood, it is believed that the phenomena is because the pressure sensor signal may be indicative of both the amount of water in the tub, as well as the pressure imparted on the water in the tub from the laundry landing on the water as the drum 16 rotates. When there is excessive foaming, or an OSC within the tub 14, the quantum of force imparted to the surface of the water in the tub 14 may be reduced as a result of the suds damping the velocity and force of the laundry landing on the water in the tub 14. The reduction in force imparted to the surface of the water as the laundry lands thereon may be detected as a reduced fluctuation in the pressure sensor signal. This phenomenon is used in the method disclosed herein to detect an OSC. In brief, the method segments the continuously collected pressure sensor signals into multiple segments and then calculates a mean and range of the pressure sensor signals within each of these segments. The determined series of means and ranges of the segments are used to determine if an OSC exists. If an OSC exists, then a suds handling routine may be run, otherwise the pressure sensor signal continues to be monitored, segmented and analyzed until an OSC is detected or the wash phase ends.
The pressure sensor signal behavior may be easier to see in conjunction with
As seen in
As can be seen from
A method according to the invention is described with reference to
Corrective action in response to an OSC may include, but is not limited to, stopping the cycle of operation, moving to the next wash phase, adding water to the tub 14, draining wash liquor from the tub 14, or any combinations thereof.
The procedure for Mean and Range Calculation of the Current Segment at 102 is shown in greater detail in
Where Current_Mean is the mean up to and considering the present sample within the segment,
Sample_Count is the count of the current sample,
Previous_Current_Mean is the mean up to and considering the previous sample within the segment,
Current_Sample is the current sample pressure sensor 60 value.
Next, it is determined if the Current Sample is greater than the Segment Maximum Value at 120. If it is, then the Segment Maximum Value is set to the Current Sample at 122. If the Current Sample is not greater than the Segment Maximum Value, then it is determined if the Current Sample value is less than the Segment Minimum Value at 124. If it is, then the Segment Minimum Value is set to the Current Segment at 126. If it is not, then it may be determined if the Sample Count is less than the Segment Maximum Count at 128. If the Sample Count is less than the Segment Maximum Count, then the procedure loops back to storing the next pressure sensor sample at 114. If, however, the Sample Count is not less than the Segment Maximum Count, then the last sensor sample for the current segment has been considered in the mean and range of segment calculation at 102. At that point, the Mean of Current Segment is set to Current Mean at 130 and Range of Current Segment is set to the difference of the Segment Maximum Value and the Segment Minimum Value at 132.
The method of Calculating the Mean and Range of the Segment at 102 is a particularly non-memory intensive method, as only the Current Sample value, along with the Current Mean, Segment Maximum Value, and the Segment Minimum Value are stored in memory 64 at any given time to Calculate the Segment Mean and Range at 102. There are however, other ways to determine the Mean and Range of the Segment, such as by loading all of the samples from a particular segment into memory and averaging and comparing within those data points. Such means may be more memory intensive, computationally intensive, or both.
Once the Mean and Range of the present segment is determined at 102, it is determined if an OSC exists in the current segment at 104. The details of 102 are shown in
Basically, 104 is checking if the Current Segment Range is a predetermined fraction of the Previous Segment Range. The predetermined fraction is the Suds Threshold, which may be a scalar quantity between 0 and 1. For example, it may be 0.5. In that case, at 138 a drop of half or more from one segment to the next is checked. Once a drop in the range from one segment to the next by a half is identified, the Range of the Previous Segment is set as the Range Benchmark. Ranges from subsequent segments are then checked to see if they are the predetermined fraction (Suds Threshold) of the Range Benchmark. If it is, then that segment is counted as a low segment, by Incrementing the Low Segment Count at 144. When the Low Segment Count reaches a predetermined count of Low Segment Count Threshold, an OSC is declared. In other words, a low Range of the Current Segment compared to the Range Benchmark must be observed for at least a Low Segment Count Threshold number of segments before an OSC is declared.
Comparing the difference between the Mean of the Current Segment and the Mean of Previous Segment to a Filling Threshold at 134, may prevent a false Low Segment Count increment from being registered while the tub 14 is being filled. During the tub filling process, spurious signals may be obtained from the pressure sensor 60 that is not necessarily indicative of the level of sudsing in the tub 14. Such signals may manifest themselves as a large difference between the Mean of the Current Segment and Mean of the Previous Segment.
The methods for detecting an OSC as described in conjunction with
Suds handling routine at 106 may be any known number of methods to reduce the amount of sudsing in the tub 14, including, but not limited to adding additional water from water source 32, pausing the cycle of operation, or a combination thereof.
The method disclosed herein has used the range within a segment as a measure of the fluctuation of the pressure sensor 60 signal over a segment. There may be other effective methods of representing the fluctuation of the pressure sensor 60 signal within a time segment, including, but not limited to calculating the variance or the standard deviation of all the samples within the segment.
The methods disclosed herein may be implemented with no additional hardware than those present on many standard laundry treating appliances. The method is also not computationally or memory intensive and can be implemented with little or no burden on the controller 62 and the electronic memory 64 of the laundry treating appliance 10.
Washing laundry in a laundry treating appliance 10 may involve chemical, mechanical and thermal means to wash the laundry. The mechanical means require a transfer of mechanical energy from the rotating drum 16 to the laundry as the laundry is partially lifted and dropped back onto the inner surface of the drum 16. If there are too many suds present within the drum, the surface coefficient of static friction of the inside wall of the drum 16 and the baffles 22 disposed therein may be reduced and lift the laundry to a lower height than if there was not excessive sudsing. As such, the clothes may fall from a lower height onto the inner surface of the drum 16 and thereby result in a reduced transfer of mechanical energy from the rotating drum 16. Additionally, if an OSC is present within the drum 16, the falling laundry onto the inside wall of the drum 16 may be damped and thereby provide a second mechanism for reduced mechanical energy transfer from the rotating drum 16 to the laundry. As a result, it is important to know if there are too many suds present in the drum 16, so that the suds can be reduced before proceeding with the wash so that the laundry may be washed properly. The method disclosed herein provides a cost effective means of detecting such an OSC without adding any additional hardware to most typical laundry treating appliances.
While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation. Reasonable variation and modification are possible within the scope of the forgoing disclosure and drawings without departing from the spirit of the invention which is defined in the appended claims.
