ES2587267T3 - Method for controlling the speed of a rotating drum of a horizontal axis laundry machine and washing machine using such a method - Google Patents

Abstract

Method for controlling the rotation speed of a rotating drum of a horizontal axis laundry machine, comprising a step of assessing the weight of the laundry load for washing, a determining stage, for the weight of the evaluated load, of a drum speed that maximizes the mechanical action on the laundry for washing and / or a drum speed corresponding to the highest motor efficiency, in which the drum speed is calculated as a weighted average between the speed value corresponding to the highest mechanical action and the speed value corresponding to the highest engine efficiency.

Description

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DESCRIPTION

Method for controlling the speed of a rotating drum of a horizontal axis laundry machine and washing machine using such a method

The present invention relates to a method for controlling the speed of a rotating drum of a horizontal axis laundry machine comprising a stage in which the laundry load is estimated or measured. The present invention also relates to a horizontal laundry machine adapted to carry out a method as such. With the term "horizontal axis laundry machine" it refers to each apparatus in which the rotating drum is mounted with a substantially horizontal axis; therefore, laundry machines with an inclined rotation axis are included in the previous definition.

Currently, laundry machines are typically controlled with a unique speed profile for each wash cycle. JP 2004236704 discloses a laundry machine in which the drum is rotated slowly to carry out the soaking when the wash water is present in the drum, and at high speed to carry out the rotation when the water is drained Wash from the drum.

EP 1441055 B1 discloses a method for controlling the dehydration rate of a washing machine in which the efficiency of the engine is calculated for each predetermined speed.

EP 2080832 A1 discloses a washing machine in which the mechanical work on the clothes to be washed is maximized during a renovation procedure.

The need is well known in the art, either to reduce the duration of the washing cycle, or to increase the energy efficiency of the apparatus.

It is an objective of the present invention to propose a method for controlling the motor of a laundry machine according to which the total cycle time can be reduced and energy efficiency can be increased.

According to the invention, an objective as such is achieved thanks to the characteristics listed in the independent claims 1 and 6 attached.

One of the most relevant characteristics of the method according to the invention is to increase the efficiency during the washing phase of the washing process in a horizontal axis washing machine by dynamically changing the reference speed of the drum.

The main benefits of the invention are a greater mechanical action and, thus, a reduced time (and energy) for washing, and a maximization of motor efficiency, having an equal mechanical action and time but saving energy.

The adaptive speed control has the objective of considering two main metrics, that is, the mechanical action exerted on the load and the efficiency of the engine.

Advantages and additional features according to the present invention will become apparent from the following detailed description, with reference to the attached drawings, in which:

- Figure 1 is a typical simple basic wash cycle of a horizontal axis laundry machine;

- Figure 2 shows different diagrams for different loads that show how the mechanical power transferred to the laundry load changes with the speed of rotation of the drum;

- Figure 3 shows diagrams similar to those of Figure 2 in which, for different loads, it is shown how the electric power of the motor changes with the speed of rotation of the drum;

- Figure 4 shows a flow chart of a control algorithm according to the invention;

- Figure 5 shows how the drum speed changes as a function of time when the algorithm of Figure 4 is implemented;

- Figure 6 shows the variation of speed of figure 5 as a function of time; Y

- Figure 7 is a diagram showing a comparison between a known standard wash cycle and an adaptable cycle according to the invention, as far as energy consumption is concerned.

With reference to Figure 1, the output of the control logic is the magnitude A of the reference speed signal of a basic simple wash cycle, in which in a first part of the cycle the speed of the drum A makes sense of turning the hands of the clock and, in a second part of a cycle as such, the speed A has a direction of rotation against the hands of the clock (or vice versa).

Figure 2 shows the different relationships between mechanical power and washing speed depending on the load size. In a first approach, the friction of the motors and washing machine can be considered a deviation in such a way that the mechanical action on the clothes to be washed can be considered proportional to the mechanical power.

5 Mechanical power can be estimated or measured from the engine in different ways. On a universal motor, typically used in washing machines, the tripping angle or motor current can be converted into torque and then mechanical power using a search or observer table.

Depending on the size of the load, the curve of the mechanical action has a different shape. For example, for a full load (8 kg), the value of the mechanical action that can be generated is quite small, whatever the speed chosen. On the contrary, for a small load, the variation of the mechanical action can be very important for a small change in the speed of rotation.

Figure 3 shows a similar analysis made for the electrical power of the motor required as a function of the speed and size of the load. Typically, the higher the speed, the greater the efficiency of the engine. The graphs in Figure 3 show curves for a universal motor used in an 8 kg machine with different loads. By comparing Figures 2 and 3, it is clear how the electric power curve is different than the mechanical power curve. This means that, in general, the speed that can be selected to optimize mechanical action does not optimize energy efficiency.

In order to maximize cycle performance, the applicant has discovered that the following control strategy can guarantee the best performance of a horizontal axis laundry machine, either in terms of the duration of the cycle or of the energy efficiency :

• Maximize mechanical action with an algorithm capable of finding speed with the highest mechanical action.

• Obtain the best compromise between mechanical action and motor efficiency.

The algorithm according to the invention begins by choosing an initial turning speed by using a mass of 25 planned or calculated laundry loads and a search table. The search table is obtained by maximizing the following Performance Index:

Performance index = a x mechanical power (w) + (1 - a) x electric power (w)

where:

a = 1 will lead to a cycle that maximizes mechanical action (faster cycle)

30 0 <a <1 will lead to a cycle that reaches a compromise between mechanical action and motor efficiency (cycle of

efficiency)

From the example carried out by the applicant with reference to an 8 kg commercial clothes washer, the following speed suggestion table can be obtained:

 Load size

 Mass range (kg) Speed (rpm)

 Little

 m <3 45

 Half

 3 <m <6 50

 Big

 m> 6 60

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In order to improve the algorithm, considering the noise variation due to the load estimation sensor and the process itself, it is possible to dynamically adjust the speed during the wash cycle following the algorithm shown in Figure 4.

Initially a dummy value is given to the Performance Index (typically 0) and the speed variation (i.e. 40 Aw (0) = 3 rpm). During each simple wash cycle, the average mechanical and electrical power is estimated or measured, and the Performance Index is calculated according to the previous formula. The value to this in relation to the user's choice (through a user interface) whether it prefers the shortest wash cycle or the lowest energy consumption of the motor. In this way, the user can set the level of compromise between the speed value corresponding to the greater mechanical action and the speed value corresponding to the greater efficiency of the motor. 45 Of course, a value of a as such by the manufacturer of the apparatus can also be predetermined as a

Good compromise between the duration of the wash cycle and the energy efficiency of the engine. The Performance Index is compared with the value calculated in the previous cycle.

If the Performance Index increases, the rotation speed is modified (increases or decreases) in the same direction as the previous moment; on the other hand, the address is reversed.

5 An alternative way of adapting the cycle is given by adapting the speed, according to the following equation:

, s A mechanical power (t) A electrical power (t)

Aw (t) = yffrn ----------—------ r ---------- + -

Aw (t - 1)

Aw (t - 1)

where:

pm, pe are coefficients that make the two gradients comparable and that allow a balance between a more effective cycle in mechanical action or more efficient in energy consumption.

The magnitude of the reference speed of the rotation phase of the wash cycle using adaptive control logic according to the present invention is shown in Figure 5. The speed value converges rapidly to a stable value (plus or minus 58 rpm).

Figure 6 shows the increase in speed that the control logic produces over the reference speed over the sample example in Figure 5.

The benefits due to the speed variation are shown in Figure 7. More in detail, the energy consumption of two different tests with the same configuration for all parameters is illustrated. The first refers to the standard control logic, that is, with a fixed turning speed, while the second refers to the adaptive logic according to the invention.

If a standard cycle with 3 hours of cycle duration is considered, there is an energy saving of approximately 15% between the two logics. The same benefits can also extend to time savings.

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Claims (6)

5 10 fifteen twenty 25 30 35 40 1. Method for controlling the speed of rotation of a rotating drum of a horizontal axis laundry machine, comprising a stage for evaluating the weight of the laundry load, a determination stage, for the weight of the load evaluated, of a drum speed that maximizes the mechanical action on the laundry and / or a drum speed that corresponds to the highest motor efficiency, in which the drum speed is calculated as a weighted average between the value of speed corresponding to the greater mechanical action and the speed value corresponding to the highest efficiency of the motor. 2. Method according to claim 1, in which the drum speed is calculated as the value that maximizes a Performance Index that is calculated taking into consideration both the electric power and the mechanical action. 3. Method according to claim 2, in which the calculation of said Performance Index is carried out according to the following formula: The following Performance Index: Performance index = a x mechanical power (w) + (1 - a) x electric power (w) where: a = 1 will lead to a cycle that maximizes mechanical action (faster cycle) 0 <a <1 will lead to a cycle that reaches a compromise between mechanical action and motor efficiency (efficiency cycle) 4. Method according to claim 2 or 3 comprising the following steps: - drum rotation start at a predetermined start value; - based on the assessed load of laundry to be washed, determination of mechanical power and electrical power; - calculation of said Performance Index; - comparison of the Performance Index calculated with a predetermined Performance Index of Start or with a Performance Index calculated at a previous stage; - if the Performance Index increases, change of the drum speed in the same direction of the previous stage, on the other hand, change of direction; Y - if the Performance Index remains substantially the same, interrupt the speed change. 5. Horizontal axis laundry machine comprising a rotating drum, a motor and a control unit for driving the motor, said control unit being adapted to evaluate the load of laundry for washing in the drum, characterized in that the circuit of control is adapted to determine, for the evaluated load, a speed of rotation of the drum corresponding to a mechanical action on the laundry for maximized washing and / or a speed of the drum corresponding to the highest efficiency of the motor, in which the unit of control is adapted to calculate a speed of rotation of the drum that is a weighted average between the speed value corresponding to the greater mechanical action and the speed value corresponding to the highest efficiency of the motor. 6. Horizontal axis laundry machine according to claim 5, in which a user interface is provided on which the user can set a value that sets the level of said weighted average between the speed value corresponding to the mechanical action higher and the speed value corresponding to the highest engine efficiency.