GB2090435A

GB2090435A - Control system for clothes drier

Info

Publication number: GB2090435A
Application number: GB8138626A
Authority: GB
Original assignee: Carpano and Pons SA
Current assignee: Carpano and Pons SA
Priority date: 1980-12-30
Filing date: 1981-12-22
Publication date: 1982-07-07
Also published as: GB2090435B; FR2497243A1; FR2497243B1; DE3150617A1; DE3150617C2

Abstract

The present invention relates to a control system for a clothes drier. The system comprises a device for detecting a certain predetermined intermediate rate of humidity, said device being based on measurement of the conductivity of the clothes, associated with which is a time-lag device intended to obtain the desired final rate of humidity and a selector for this final rate of humidity desired by the user. It also comprises a device for measuring successive rates of humidity existing before the predetermined intermediate rate of humidity is reached, a device for determining the slope of the curve of evolution of the conductivity of the clothes, as a function of time, a device for memorizing said slope and means for determining the time still required to obtain the desired final rate of humidity, as a function of said slope. <IMAGE>

Description

SPECIFICATION A control system for clothes driers The present invention relates to control systems for clothes driers, the driers comprising a rotary drum containing the clothes and a pulsating hot air device.

These control systems comprise a device for detecting a certain predetermined intermediate rate of humidity, which device is based on the measurement of the conductivity of the clothes, with which a time-lag device is associated, which is intended to obtain the desired final rate of humidity and a selector for this final rate of humidity desired by the user.

In known control systems of this type, such as that described in French Patent No. 2 091 558, the time-lag selected by the user in orderto obtain the desired final rate of humidity begins when the predetermined intermediate rate of humidity is reached and is interrupted automatically at the end of the time-lag, without taking into account the nature and quantity of the clothes contained in the drum, thus without taking into account the drying speed of the clothes. This constitutes a drawback, since the desired final rate of humidity, which was selected by the user, is not obtained in all cases. It may vary by approximately 5%.

It has been proposed to extend the drying time depending on the time taken to reach a certain intermediate rate (US Patent No. 3762 064). However, this extension proportional to the time elapsed does not take into account the characteristic of the drying curve, but considers it as a straight line, whereas the characteristic of this curve, i.e. its slope at the point corresponding to the intermediate rate may vary considerably. It is the precise object of the invention to take into account the characteristic of the drying curve in order to extrapolate it and thus reach the desired final rate of humidity with greater accuracy.

The control system according to the invention is characterised in that it comprises a device for measuring successive rates of humidity, respectively successive temperatures, existing before the predetermined intermediate rate of humidity is reached and a device for determining the slope of the curve of the evolution of conductivity of the clothes, respectively of the evolution of the temperature of the clothes, as a function of time. The control system also comprises a device for memorising said slope and means for determining the time still required in order to obtain the desired final rate of humidity, as a function of said slope.

One advantageous variation can be used in the case where the control system comprises a device for measuring successive rates of humidity existing before the predetermined intermediate rate of humidity is reached and a device for determining the slope of the curve of the evolution of conductivity of the clothes as a function of time. In this case, the device for memorising said slope and the means for determining the time still required to obtain the desired final rate of humidity, as a function of said slope, are constituted by a capacitor supplied across a current generator arrangement controlled by two detectors for voltage thresholds, the inputs of which detectors are connected to two wipers constantly in contact with the clothes. One of the detectors is regulated in order to detect one threshold of conductivity lowerthan the other.The first is provided in order to control the charging of the capacitor, the second in order to interrupt this charge and to position an input of a third threshold detector, provided in order to control the stoppage of the drying when the voltage of the capacitor discharged across at least one resistor of the selector for the final rate of humidity, is less than a predetermined voltage threshold.

The control system according to the invention is proposed in particular for obviating the drawbacks of the prior act. It makes it possible to obtain the final rate of humidity of the clothes desired by the user accurately, by taking into account the nature and quantity of clothes.

The accompanying drawings illustrate, by way of example, embodiments according to the present invention.

Figure 1 is an electric wiring diagram of the first and third embodiments.

Figure 2 is a flow diagram of the programme for managing sensors, in the first embodiment.

Figure 3 is an electrical wiring diagram of a second embodiment.

Figure 4 shows graphically the evolution of the voltage at the terminals of the wipers, during drying of the clothes, as a function of time, in the same second embodiment.

FigureS shows graphically the evolution, during the same time, of the voltage Uc.

Figure 6 is a flow diagram of the programme for managing sensors, in the third embodiment.

Figure 7 is a flow diagram of a sub-programme for managing the temperature, in the same third embodiment.

As illustrated in Figure 1, the control system comprises an integrated circuit 1, which in our example is a TMS1000 microprocessor of Texas Instruments Incorporated, which has four inputs K1, K2, K4 and K8 and outputs S1, S2, S3, S4, S5, S6 ....

S11. The integrated circuit comprises an instruction address register 3 connected to a ROM memory 9.

Which contains a certain number of cells in which are memorised the sequences of instructions corresponding to the programme which is to be carried out by the integrated circuit 1.

The ROM memory mainly comprises three distinct programmes: the programme 19 for managing the keyboard and the display, the programme 20 for managing time and the programme 21 for checking temperatures and measuring humidity. These three programmes use the functions of an analog demultiplexer 14 and an analog-to-digital converter 13.

A RAM memory 8 with read and write capabilities, used for storing the data temporarily, is also connected to the instruction decoder register 4 and to the addressing register 3. Furthermore, in this integrated circuit 1, the addressing registers 3 are connected to an output system 6 and to an arithmetic and logic unit 5 capable of carrying out the operations required by the instructions and of controlling the linking of the various cycles required by these instructions. The arithmetic and logic unit 5 is also capable of reading the logic levels of the inputs K1, K2, K4 and K8. The output system 6 is connected to the outputs S1, S2 and to the groups of outputs S3-S6,57-S11 of the microprocessor. This output system 6 is constituted by the switching circuits allowing the outputs S1 to S11 to assume logic levels zero or one.

A clock 7 is connected to the memory 8, to the instruction address register 3, to the instruction decoder register 4, to the arithmetic and logic unit 5 and to the output system 6. It synchronizes the operation of these various components and the transmissions therebetween.

The output S1 is connected to switches t1 and t2 and to a display circuit 10. The output S2 is connected to switches t3 and t4 and to the display circuit 11. The switches t1 and t4 are connected to the input K2, the switches t2 and t3 to the input K1.

The switches tl to t4 constitute the means for controlling the selectorforthe final rate of humidity.

The input K8 is connected to the power supply 2. The outputs S7 to S11 are connected by means of a system interface 12, to the parts of the machine intended to be controlled.

The output S3 is connected to the analog demultiplexer 14. The analog-to-digital converter 13 is itself also connected to the input K4 of the integrated circuit 1 and to the analog demultiplexer 14. The outputs S5 - S6 are also connected to the analog-todigital converter 13. The inputs 11,12 and 13 of the analog demultiplexer 14 are respectively connected to temperature probes 16 and 17 and to the capacitor 18 which is in turn also connected to the wipers 15 of the drum.

A D.C. supply unit 2 connected to the mains supplies the integrated circuit 1, the interface block 12, the display circuits 10 and 11, the analog-todigital converter 13 and the analog demultiplexer 14.

The RAM memory 8 comprises a "conversion code" register 22, a time-lag counter 23, a zone for memorizing instantaneous data 24 and a zone for memorizing "averaged" data.

The components 125,126,127,128 shown in broken line in Figure 1 relate solely to the third embodiment described hereafter.

As shown diagrammatically in Figure 2, the programme for managing sensors comprises several sub-programmes 25 to 37. The conversion subprogramme 25 comprises the instructions whereof the last precedes the first instruction of subprogramme 26 for incrementing the conversion code. The last instruction of this sub-programme 26 precedes the first instruction of sub-programme 27 for testing the code for conversion to zero, whereof the last instruction is a conditional call instruction to the address of the first instruction of subprogramme 36 for managing the temperature probe 16 or to the address of the first instruction of sub-programme 28 for testing the code for conversion to one.

The last instruction of sub-programme 28 is also a conditional call instruction to the address of the first instruction of sub-programme 37 for managing the temperature probe 17 or to the address of the first instruction of sub-programme 29 for memorizing the result of the conversion. The last instruction of sub-programme 29 precedes the first instruction of sub-programme 30 for testing the current address at 8.

The last instruction of sub-programme 30 is a conditional call instruction to the address of the first instruction of sub-programme 26 or to the address of the first instruction of sub-programme 31 for calculating the mean value. The last instruction of subprogramme 31 precedes the first instruction of sub-programme 32 for memorization according to the principle of a FIFO register of the mean value calculated in sub-programme 31. The last instruction of sub-programme 32 precedes the first instruction of sub-programme 33 for testing the mean value.

The last instruction of sub-programme 33 is a conditional call instruction to the address of the first instruction of sub-programme 26 or to the address of the first instruction of sub-programme 34 for calculating the time-lag, necessary in order to obtain the selected rate of humidity.

The last instruction of sub-programme 34 precedes the first instruction of sub-programme 35 for implementing the time-lag. The last instructions of sub-programmes 36 and 37 are branch instructions to the address of the first instruction of subprogramme 26.

During the operation of the control system, the programme contained in the memory 9 of the integrated circuit 1 successively manages the time by using the mains signal, rectified and smoothed (signal present at the input K8), the keys, i.e. the switches t1 to t4, the logic information coming from the analog-to-digital converter 13 and the control of the lights 10 and 11 which indicate to the user the state of automatism. The integrated circuit 1, across the interface block 12, controls the components of the clothes drier such as the motor for driving the drum and the blower, the heating resistance and the electro-magnetic valve for supplying water, if the drier is of the condensation type.

From the commands given by the user by means of the switches t1 to t4, the integrated circuit 1 uses the sub-programmes described by the flow chart (Figure 2) for checking the temperature in the drier by means of probes 16 and 17 and for checking the humidity with the wipers 15 located on the drier drum. The integrated circuit 1 controls the analog-todigital converter 13 by means of sub-programme 25 in order to obtain a binary number corresponding to the analog value of the signal present at the input of the converter. In this example, the conversion programme lastsfortwo seconds. According to the conversion code, the integrated circuit 1 controls the analog demultiplexer 14 (by its outputs S3 and S4) in order that the voltage at the terminals of the probe 16 (conversion code = zero), at the terminals of the probe 17 (conversion code = one) or at the terminals of the wipers 15 (conversion code = two), is present at the input of the analog converter 13.

As described in the flow chart (Figure 2), the integrated circuit 1 successively checks the tempera ture recorded by the probe 16, then the temperature recorded by the probe 17 and the voltage at the terminals of the wipers 15. Since the conversion programme lasts for two seconds, a measurement of the voltage at the wipers 15 takes place every six seconds.

When using an analog-to-digital converter of the TL 507 type of Texas Instruments, this measurement is memorized in the form of seven bits (capacity of the converter) in the RAM8 of the integrated circuit 1.

These measurements of the voltage of the wipers 15 are memorized in 8 successive addresses (the current address varying from zero to seven) corresponding to the memory zone 24. When 8 measurements have been memorized, the integrated circuit 1, by means of sub-programme 31, calculates the mean value of these 8 measurements and memorizes this value in a FIFO register (first in, first out) where the mean valves are stored in succession.

When the FIFO register is full, for each new datum to be memorized, the oldest mean value is lost. The reason why the measurements are arranged in groups, then "averaged" is that the information transmitted by the wipers 15 is far from being perfect and fluctuates incessantly depending on the position of the clothes in the drum. This technique makes it possible to obtain reliable information regarding the conductivity of the clothes in the drum.

When the mean value calculated corresponds to the maximum value which can be measured by this principle of measuring conductivity, the subprogramme 34 of the integrated circuit 1 determines the time necessary for reaching the selected degree of humidity, by means of the data memorized in the FIFO register. More precisely, this sub-programme 34 adds together the differences between the mean values recorded in the FIFO register and the maximum value which can be measured. This sum in fact represents the evolution of humidity of the clothes in the drum and the integrated circuit 1 compares this sum with a table in order to determine the final time-lag.

Subsequently, with the sub-programme 35, the integrated circuit 1 implements this time-lag. At the end of this chosen time-lag, the clothes have a rate of humidity corresponding to that selected previously.

In the second embodiment of the invention, illustrated in Figure 3, the control system is supplied with D.C. current by a circuit 51 and it comprises two threshold detectors 59 and 64 which control a charging circuit 69 for a capacitor 70, another threshold detector 76 and a device 80 for controlling the advance of the drier programmer.

The resistor 56, shown in broken line, represents the variable resistance of the clothes between two wipers 54 and 55. These wipers 54 and 55 are connected to the terminals of a capacitor 53. The wiper 55 is connected to the negative terminal of the supply 51 and the wiper 54 is connected to the positive terminal of the supply 51 by means of a resistor 52. The wiper 54 is also connected to the positive input of the threshold detector 59, whereof the negative input is connected to a bridge of resistors 57 and 58, which fixes the potential U1 of this input. The output of the threshold detector 59 is connected to the resistor 66 and to a Zener diode 68 of the charging control circuit 69.The wiper 54 is also connected to the positive input of the threshold detector 64, whereof the negative input is connected to a bridge of resistors 62 and 63, which fixes the voltage U2 of this input. The output of this threshold detector 64 is connected, across a resistor 65, to the base of a transistor 67 of the charging circuit 69. This transistor 67 is connected, by its base to the Zener diode 68, by its emitter to the resistor 66 and by its collector to the capacitor 70, to a resistor 74 and to the input of the threshold detector 76. The capacitor 70 and the resistor 74 are also connected to the negative terminal of the power supply 51.

The selector 85 for the final rate of humidity is constituted by the resistor 74 and two push button switches 81 and 82 connected on the one hand to the capacitor 70 and to the collector of the transistor 67 and on the other hand to the negative terminal of the power supply 51 respectively across resistors 83 and 84.

The positive input of the threshold detector 76 is connected to a bridge of resistors 72 and 73, which fixes the voltage U3 of the latter. This bridge of resistors is supplied by the output of the threshold detector 64. The output of the threshold detector 76 is connected, across a resistor 78, to the base of a transistor 79, whereof the emitter is connected to the negative terminal of the power supply 51 and the collector, to the coil of the relay 80, which is also connected to the positive terminal of the power supply 51.

In order to understand the operation of this control system, reference should be made to Figures 3,4 and 5. The user actuates the push button switches 81 and 82 of the selector 85 for the final rate of humidity, in order to choose the desired final rate of humidity, for example from 5% to 20%. During operation, the capacitor 53 charges across the resistor 52 and discharges into the resistor 56 which represents the variable resistance of the clothes. When the clothes are very damp, the voltage at the terminals of the capacitor 53 is low, then as drying proceeds, the voltage at the terminals of this capacitor 53 increases as shown in Figure 4.When the level of the voltage at the terminals of the capacitor 53 reaches the value of the potential U1, the voltage of the output of the threshold detector 59 becomes similar to that of the positive terminal of the power supply 51. The threshold detector 59 supplies the device 69 for charging the capacitor 70. As long as the voltage at the terminals of the capacitor 53 is less than the voltage U2, the voltage of the output of the threshold detector 64 is close to zero (or that of the negative terminal of the power supply 51) and the transistor 67 is conductive. The connection of this transistor 67 to the resistor 66 and the Zener diode 68 ensures the generation of a constant current for charging of the capacitor 70.

As soon as the voltage at the terminals of the capacitor 53 reaches the voltage U2 fixed by the bridge of resistors 62 and 63, the output of the threshold detector 64 becomes similar to the positive terminal of the power supply 51 and causes blocking of the charging circuit 69.

The capacitor 70 thus discharges into at least one of the resistors 74,83,84 of the selector 85. The threshold detector 76 controls the relay 80 through the intermediary of the transistor 79, when the potential of the capacitor 70 becomes less than the voltage U3 fixed by the bridge of resistors 72 and 73.

After the detection of the voltage U2 corresponding to the maximum limit voltage recorded bythe wipers 54 and 56, the capacitor 53 and the resistor 52, this method makes it possible to obtain a time-lag whereof the duration depends on the time elapsed between detecting the voltage levels U1 and U2, thus consequently on the drying speed of the clothes.

In this embodiment, measurements of successive rates of humidity are in practice reduced by the resistor 52 and the capacitor 53 to measurements of voltage effected by the threshold detectors 59 and 64. The second of the successive rates of humidity measured corresponds to the voltage U2 which also corresponds to the predetermined intermediate rate of humidity.

In the third embodiment, illustrated in Figures 6,7, the control system has, on the one hand, the same structure as that previously described with reference to Figure 1, in the first embodiment. This Figure 1 therefore remains valid. Only four components have been added to the structure illustrated in Figure 1: a register 125 for memorizing a slope, a register 126 indicating memorization of the slope, a register 127 for memorizing the present temperature and a register 128 for memorizing the past temperature, contained in the RAM memory 8. They are illustrated in broken line in Figure 1.

As shown diagrammatically in Figures 6 and 7, the programme for managing sensors comprises several sub-programmes 25 to 31,35 and 37 identical to those of the first embodiment. Furthermore, the management programme comprises sub programmes 132, 133, 134, 135 and 137. The conversion sub-programme 25 comprises instructions whereof the last precedes the first instruction of sub-programme 26 for incrementing the conversion code.The last instruction of this sub-programme 26 precedes the first instruction of sub-programme 27 for testing the code for conversion to zero, whereof the last instruction is a conditional call instruction to the address of the first instruction of sub programme 137 for calculating the slope of increas ing temperatures measured with the probe 16, orto the address of the first instruction of sub programme 28 for testing the code for conversion to one. The last instruction of sub-programme 28 is also a conditional call instruction to the address of the first instruction of sub-programme 37 for manag ing the temperature probe 17 or to the address of the first instruction of sub-programme 29 for memoriz ing the result of the conversion.The last instruction of sub-programme 29 precedes the first instruction of sub-programme 30 for testing the current address at 8. The last instruction of sub-programme 30 is a conditional call instruction to the address of the first instruction of sub-programme 26 or to the address of the first instruction of sub-programme 31 for calculating the mean value. The last instruction of subprogramme 31 precedes the first instruction of sub-programme 132 for testing the mean value with respect to a predetermined value. The last instruction of sub-programme 132 is a conditional call instruction to the address of the first instruction of sub-programme 26 or to the address of the first instruction of sub-programme 133 for setting the indicator 126 for memorizing a slope to the value one.The last instruction of sub-programme 133 precedes the first of sub-programme 134 for testing the mean value. The last instruction of subprogramme 134 is a conditional call instruction to the address of the first instruction of subprogramme 26 or to the address of the first instruction of sub-programme 135 for calculating the time-lag necessary for obtaining the selected rate of humidity.

The last instruction of sub-programme 135 precedes the first instruction of sub-programme 35 for implementing the time-lag. The last instructions of sub-programmes 137 and 37 are branch instructions to the address of the first instruction of subprogramme 26.

Sub-programme 137, shown in detail in Figure 7, comprises several sub-programmes 39 to 43. This sub-programme 137 begins by a sub-programme 39 for the transfer of information from the register 127 for memorizing the present temperature to the register 128 for memorizing the past temperature.

The last instruction of sub-programme 39 precedes the first instruction of sub-programme 40 for memorizing the result of the analog-to-digital conversion in the register 127 for memorizing the present temperature. The last instruction of subprogramme 40 precedes the first instruction of sub-programme 41 for calculating the slope (speed of evolution of the temperature). The last instruction of sub-programme 41 precedes the first instruction of sub-programme 42 for testing the register 126 indicating memorization of the slope. The last instruction of sub-programme 42 is a conditional call instruction to the address of the first instruction of sub-programme 26 or to the first instruction of the sub-programme 43 for transferring the result of calculation of the slope into the register 125 for memorizing the slope. The last instruction of sub programme 43 is a branch instruction to the address of the first instruction of sub-programme 26.

The operation of the third embodiment of the control system is identical to that of the first afore-described embodiment (Figures 1 to 5), until the time when sub-programme 31 calculates the mean value of the eight measurements memorized in the memory 24.

After each measurement of the analog-to-digital converter 13 and by means of the values contained in the registers 127 and 128, the sub-programme 137 determines the slope of the curve of evolution of temperature of the clothes as a function of time and memorizes this slope in the register 125 for memor izing the slope.

When the mean value calculated in sub programme 31 corresponds to a predetermined value, the programme 33 positions the register 126 indicating the memorization of a slope, in order that by means of sub-programme 42, the slope of the temperature rise remains memorized in the register 125 for memorizing a slope.

Without diverging from the scope of the present invention, memorization of the slope of the temperature rise could be effected at another instant, for example when a predetermined temperature is reached. The method of calculating the slope of the temperature rise could also be effected in a different manner.

When the mean value calculated corresponds to the maximum value which can be measured by this principle of measuring conductivity, the subprogramme 35 of the integrated circuit 1, determines the time necessary for reaching the selected rate of humidity by means of the datum memorized in the register 125 for memorizing a slope. Then, with the sub-programme 36, the integrated circuit 1 implements this time-lag.

Claims

1. Control system for a clothes drier, said drier comprising a rotary drum containing the clothes and a pulsating hot air device, said control system comprising a device for detecting a certain predetermined intermediate rate of humidity, this device being based on measuring the conductivity of the clothes, with which is associated a time-lag device intended to obtain the desired final rate of humidity and a selector for this final rate of humidity desired by the user, characterised in that it comprises a device for measuring successive rates of humidity, respectively successive temperatures, existing before the predetermined intermediate rate of humidity is reached, a device for determining the slope of the curve of evolution of conductivity of the clothes, respectively of evolution of the temperature of the clothes, as a function of time, a device for memorizing said slope and means for determining the time still required to obtain the desired final rate of humidity, as a function of said slope.

2. Control system according to claim 1, comprising a device for measuring successive rates of humidity existing before the predetermined intermediate rate of humidity is reached and a device for determining the slope of the curve of evolution of the conductivity of the clothes as a function of time, characterised in that the device for memorizing said slope and the means for determining the time still required to obtain the desired final rate of humidity, as a function of said slope, are constituted by a capacitor supplied across a current generator arrangement controlled by two voltage threshold detectors detectors whereof the inputs are connected to two wipers constantly in contact with the clothes, a first detector being regulated in order to detect a threshold of conductivity lower than the other the first being provided in order to control charging of the capacitor, the second in order to interrupt this charge and in order to position an input of a third threshold detector, provided for controlling stoppage of the drying when the voltage of the capacitor discharged across at least one resistor of the selector for the final rate of humidity, is less than a predetermined voltage threshold.

3. A control system substantially as hereinbefore described with reference to the accompanying drawings.