DE3600383A1 - MIXER THERMOSTAT - Google Patents

Description

Friedrich Grohe Armaturenfabrik GmbH & Co.

K.L.Ellington-H.Heimel-A.S.Lefley 11-2-2

MIXER THERMOSTAT

This invention is concerned with an electronically controlled mixer thermostat such as that used in domestic use Sanitary facilities or industrial manufacturing processes is used.

An electronically controlled mixer thermostat has a temperature sensor - hereinafter referred to as "sensor" - which comes into contact with the mixed water flow and corresponding to the mixed water temperature electrical signal is generated, which is then sent to an electronic circuit, hereinafter referred to as the "control device" is referred to, is forwarded. An electronic or electromechanical operated by the user Setting element - hereinafter referred to as "temperature selector" - generated according to the desired Temperature is another electrical signal, which is then also switched to the control device. To The control device generates a comparison of the two above signals in accordance with a specially defined one functional relationship (e.g .: P, PI or PID) an electrical output signal that corresponds to an electromechanical

Drive element - hereinafter referred to as "motor"
is activated. The motor generates a mechanical position change based on the signal generated by the control device, which is transmitted directly or via any transmission device to a mixing valve, which changes the ratio between the inflowing hot and cold water and thereby regulates the temperature of the mixed water outflow. Such electronic mixer thermostats are (already) known and are described, for example, in German patents DE-PS 24 10 316, DE-OS 30 20 040 and DE-OS 30 30 167.

However, the invention also applies to electronically controlled mixer thermostats in which the "mixing valve" The designated component group consists of two or more structurally separate valve units or in which the "Motor" denoted component group consisting of two or more structurally separate electromechanical drive elements consists, for example, in German patents DE-PS 23 23 841, DE-PS 28 36 698 and DE OS 30 30 716 are described. This invention also applies to mixer thermostats in which the "control device" designated component group not as a simple electronic circuit, but wholly or partially as a computer with

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suitable programming is implemented, this computer, for example, from a microprocessor circuit could exist. Such a system is described in German patent DE-OS 29 25 234, for example.

All the systems described so far have in common that, although they more or less perform the task of keeping the mixed water temperature constant, they do not take any precautions to prevent the adverse effects that can result from technical malfunctions in the relatively complex overall system. It is therefore entirely possible that with an apparatus of the type described, which is used as a shower thermostat, failure of the sensor during showering results in the person showering suddenly being exposed to hot water at the temperature of the hot water inflow, before she has a chance to protect herself. In the same way, mixer thermostats that are used in industrial manufacturing processes can cause considerable material damage by the occurrence of similar errors.

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Other elements of the apparatus in the previously known systems can also lead to malfunctions with dangerous Consequences lead. For example, if a mixer valve that was last used to draw off hot water, is not used for a long time and due to limescale deposits or other foreign bodies in the hot position is blocked, it would dispense hot water at a later time, even if the user would have chosen a lower temperature.

The object of this invention is therefore to provide an electronic mixer thermostat _f in which an electronic safety system prevents the disadvantageous consequences of a technical malfunction by monitoring all critical elements of the apparatus as far as possible and causes a suitable reaction when the error state is detected.

In the present invention, an electronically controlled mixer thermostat has a safety system that is shown in is able to set critical parameters of the control system with regard to compliance with specified safety thresholds to be monitored and, if a monitored parameter exceeds a safety threshold, one or more Initiate security measures.

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In the preferred embodiment of the invention, the mixer thermostat also has a second safety system, that is able to monitor input variables from external setting devices operated by the user and, if these input variables indicate improper use of the setting elements, additional safety measures initiate.

Embodiments of the inventions will now be described with reference to the accompanying drawings.

Figure 1 is a schematic representation of the way in which a security system controls the mixed water temperature monitored depending on the set temperature.

Figure 2 is a block diagram showing the safety systems in a mixer thermostat.

Figure 3 shows a flow diagram of a mixer thermostat with the controller and safety system in microcomputer technology are realized.

Figure 1 is a schematic representation of the operation of a safety system in which the measured value T _{M of} the mixed water temperature (actual

Temperature signal) is recorded as a function of the set temperature T ^. The double diagonal line marks the rule optimum T _M = T ^.

The shaded areas A1, A2, B1, B2 and C1, C2 represent forbidden areas. Every value pair ( ^Τ Μ ' ^Τ ς)> that falls into one of these areas triggers a safety measure. On the other hand, every pair of values (Tm, Τς) that is not on the ideal line _; but also does not fall into a prohibited area, tolerated.

The two horizontal lines T _K and T ,, mark the externally determined temperature of the cold or hot water inflow and thus limit the respective control interval R. During operation, T _K and T _w can be subject to considerable fluctuations, which leads to a narrowing or expansion of the interval R comes.

The points E ^ and E ,, mark the two end positions of the mixing valve. If the control system is working properly, the mixing valve is moved to the cold end position E _K at each set temperature T, - <T ^, in which the cold water inflow is completely open and the hot water inflow is completely closed. the

Mixing temperature then corresponds to T ^. The opposite applies to setting temperature values Τς> Tw and the end position E _y .

Various critical parameters of the control system are monitored with regard to compliance with certain safety thresholds. If one of these safety thresholds is exceeded, a safety measure is triggered immediately or with a delay, depending on the type of disturbance. The safety system is designed in such a way that it automatically detects certain external fault conditions typical of mixed water thermostats, in which a safety reaction would be undesirable, and thus avoids false alarms and self-locking of the device .

The security measure is that:

(a) an interfering signal is generated which can be used, for example, to trigger an alarm device.

(b) a shut-off valve is triggered in the mixed water outlet.

Measure (b) applies to installations where a Shutting off the water supply would have a more adverse effect than exceeding the temperature limit, not for Use. In such cases, the user must find a meaningful use for the alarm signal.

In detail, the following monitoring functions are included accompanying security measures possible:

(1) Monitoring of the set temperature signal J ^ by line S1 (Figure 2) with regard to falling below the minimum value al or exceeding the maximum value a2. If the set temperature signal falls within the forbidden areas A1 or A2, a safety measure is taken immediately.

Purpose: To detect a malfunction in the temperature setting device (especially a circuit break or short circuit). At the upper limit of the forbidden area A1 (Fig.1) on the Setting temperature axis is the minimum value al, which is so is chosen to be slightly below the lowest allowable set temperature value. Analogous to this lies at the upper limit of A2 the maximum value a2, which is slightly above the maximum permissible setting temperature value lies.

(2) Monitoring of the sensor signal T _M (measured temperature) by line S2 with regard to falling below the minimum value b1 or exceeding the maximum value b2. If the sensor signal falls within the forbidden areas B1 or B2, a safety measure is triggered immediately. Purpose:

Detection of a fault in the temperature sensor (in particular Open circuit or short circuit). The forbidden areas B1 and B2 are on the mixed temperature axis determined analogously to A1 and A2.

(3) Monitoring of the temperature _{error signal δ T = T M} - T <by line S3 with regard to falling below a negative minimum value δ 1 and exceeding a positive maximum value δ 2. A safety measure takes place after a delay _τ if δΤ falls into the forbidden areas C1 or C2 . Purpose:

Detection of a fault in the controller or the control system (e.g. engine failure, blocking of the mixing valve) as well as the occurrence of external faults that cannot be corrected quickly enough by the control device. The time constant τ is set dynamically so that the temperature-error-time integral
I / ^τ = δ Tdt does not exceed a critical value I _K (typical value for I _K = 1O ⁰ C see). Through the

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Time delay is achieved so that if the control system is functioning properly, no reaction of the safety system is triggered by external disturbances if the control system is able to cope with these disturbances before the critical value I ^ is reached. The forbidden area C1 has the value d = T <~ + δ1> as the upper limit on the mixed temperature axis, where T ~ stands for the temperature currently selected, and the lower limit is the range B1. Conversely, the area C2 is limited at the bottom by the value c2 = Τς + Δ ζ and at the top by the forbidden area B2.

A monitoring of the water temperature is for example easily possible by using thermocouples.

(4) Monitoring of the valve position with regard to compliance with the control range R using lines S6 and S7. This is achieved, for example, by two limit switches ESw and ES ,, which mark the cold and hot end positions Ew and E "of the valve. When E _K is reached, the forbidden area is deleted. This means that excess temperatures up to range B2 are tolerated. Correspondingly, the area C1 is deleted _{when E w is reached.} Undertemperature until

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Area B1 are therefore tolerated. This does not represent a safety risk, since in the end positions E ^ and E ,, the hot and cold water supply lines are shut off.
Purpose:

(a) Recognition of situations in which the properly functioning control system due to external influences is not able to reach the set mixing temperature without triggering a safety measure.

(b) Avoidance of self-locking of the thermostat system, especially during commissioning.

Self-locking during commissioning can easily occur with a mixer thermostat with a safety system according to (1) to (3) above, if it does not contain an additional override device as described in section (4). Example: assume that T "= 1O ⁰ C, T _w = 6O ⁰ C and T ₅ = 40 ⁰ C. It is also assumed that there is water in the supply line between the hot water source and the mixer _{tap that is at T 'w} = 2O ⁰ C has cooled. When starting up, the mixing valve will immediately move to the end position Ew. However, the mixing temperature will be around 20 C below the set value over a longer period of time and will therefore fall into range C1. If this area were not deleted, the closing of the solenoid valve in the outflow through the

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Safety device means that the influx of fresh amounts of warmer water from the supply line would be prevented. This would remove the safety measure when the installation is switched on again inevitably triggered again.

(5) Monitoring the supply voltages for the sensors and the temperature setting device with the help of lines S4 and S5 in order to exceed predetermined limit values impede. If one of these voltages falls below or exceeds the specified limit values, a Security measure triggered. Purpose:

Avoidance of interfering signals from the sensor or the temperature setting device to the control device or the safety system due to excessive fluctuations in the supply voltages. The supply voltages of the control device and the motor do not need to be specially monitored, since an error that occurs here is recognized by the monitoring system in section (3) above. In the event of a total supply breakdown, the system is safely shut down due to the shut-off by the solenoid valve.

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(6) If the control and / or safety system is implemented digitally: Self-monitoring of the microcomputer. Purpose:

Detection of hardware or program errors in the microcomputer which could have an influence on the safety monitoring described in sections (1) to (5) above . After each work cycle has been completed, the program in the microcomputer sends an OK status message to an external monitoring circuit, which is preferably implemented in the form of a hardware timer. If the OK status message is not repeated periodically after a specified time interval, the monitoring circuit generates a signal that triggers the safety measure.

(7) If the position of the mixing valve is constantly monitored by a position sensor:

(a) Recognition of the end positions E _K and K ,, according to (4) above, by comparing the position signal with the corresponding predetermined limit values. The limit switches ES ^ and ES "can then be omitted.

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(b) Monitoring of the position signal with regard to exceeding certain specified limit values which are outside the limits defined in Section 7 (a) by E _K and Ew and which will definitely not be reached if the system is functioning properly. Purpose: Detection of errors in the position sensor (in particular open circuit or short circuit) which would lead to the incorrect message "Ej, reached" or "E" reached "to the safety system.

If these limit values are exceeded, the safety measure is triggered immediately.

The above security measures are provided by the security system I in Figure 2. Incorrect operation of the mixer thermostat by the user is not taken into account. A second Safety system II monitors the setting devices operated by the user and guides in the event of incorrect operation appropriate security measures.

In general, the user, e.g. B. in a domestic shower facility, only via an on / off switch and a temperature adjuster to exercise control. With the inclusion of a microcomputer in an electronic control there is the possibility of a

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A large number of other safety precautions must be taken. In general, the input variables are the external Control elements are constantly monitored for compliance with certain safety conditions. If the respective Condition is not met, the function selected by the user is replaced by a substitute function, safety guaranteed, replaced.

In detail, the following safety devices and accompanying measures are possible:

(8) Establishing the predetermined starting temperature

("Reset temperature")

Required function: Switching on the installation to provide water without prior temperature selection. Substitute safety function: Switching on the installation to provide water with entry of a safe temperature setting (reset temperature). In the case of sanitary (non-commercial) applications, the reset ^{temperature could be set to 35 °} C., for example. The user can then select any other temperature by operating the temperature setting device (s).

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Purpose:

(a) Installations where the last Temperature value is maintained (e.g. temperature selection via potentiometer):

Prevents the previous user from starting the installation with a dangerous temperature setting and the next user switches on the installation without noticing the set temperature value to have.

(b) Installations where the last Temperature value is not maintained (temperature selection by electronically controlled linear increase):

Avoidance of an undefined initial state

(9) Prevention of unintentional selection of dangerous temperatures (child safety)

Required function: Setting _{temperature T 5} > critical temperature ^T _C rit "Substitute safety function: Setting temperature only as preselected if another control element (e.g. key switch, hidden pressure switch, etc.) is triggered at the same time as the temperature setting element.
Otherwise T _c = T,

crit

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For non-commercial applications, T .. could be

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Example lie at 38 ^{0 C.}

Purpose: To protect young children or careless users from accidentally choosing dangerous temperatures.

(10) Display of the status "temperature unreachable"

Required function: T _c < l _v or T _c > T ₁₁

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Substitute safety function: T ₅ as required, but also display "Temperature unreachable" as soon as the mixing valve reaches one of the end positions E _K , E _w .

Purpose: To inform the user that (due to conditions in the supply line) the set Temperature cannot be reached at the moment, but may be possible at a later point in time if the supply line has stabilized. Through this

(a) Avoid the dangerous situation that due to not reaching the temperature and lack of knowledge the function of the control device an even higher / lower temperature is selected.

(b) the user is saved from the unpleasant surprise of a delayed regulation of the selected temperature.

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(11) Prevention of the selection of an under / over temperature in the '-'Temperature unreachable' state.
Required function: Τς <T "or Τς> T ,,
Substitute safety function: Τς first as required.
As soon as the valve reaches the end position E _K , the option of selecting a lower temperature is inhibited.
As soon as the valve reaches the end position E _w , the possibility of selecting a higher temperature is inhibited.
Purpose: To improve the safety function of (10a) above. This safety function is particularly desirable for mixer thermostats, in which only the actual mixture temperature is displayed, while the set temperature cannot be checked directly.

The present invention can be implemented in several ways, the choice having no influence on the achievement of the functions. Three preferred forms of implementation are listed below:
(1) Control device and safety system through

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electronic analog technology realized.

(2) Control device implemented by electronic analog circuits - safety devices by Realized microcomputer technology.

(3) Control device and safety devices implemented using microcomputer technology.

In Figure 2, an implementation of the invention according to section (1) above is shown as a block diagram. the functional blocks "Sicherheitssystem I" and "Sicherheitssystem II" can preferably by Operational amplifiers can be realized.

In Figure 3 there is shown a flow chart of how it can be implemented in one embodiment of the invention with the use of microcomputer technology.

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Claims (1)

Friedrich Grohe Armaturenfabrik GmbH 8ε Co. GRP - 535 EXPECTATIONS 1. Electronically controlled mixer thermostat for the preparation of temperature-controlled mixed water, characterized in that a safety system is provided is that is capable of critical parameters of the control system with regard to compliance with specified To monitor safety limits and, if a parameter exceeds a safety limit, a or to initiate several security measures. 2. Thermostat according to claim 1, characterized in that that the safety device is able to generate an alarm signal. / 21 3. Thermostat according to claim 2, characterized in that the safety device is able to Shut off mixer outlet. 4. Thermostat according to at least one of claims 1 to 3, characterized in that the monitoring device for monitoring the set temperature is designed so that a malfunction of the temperature setting device it is recognized when the set temperature is either below a predetermined minimum value or is above a predetermined maximum value, whereupon a corresponding safety measure is initiated will. 5. Thermostat according to at least one of claims 1 to * 3, characterized in that the monitoring input * Direction for monitoring the thermostat output tem temperature is designed so that a malfunction of the output temperature sensor it is detected when the output temperature is either below a predetermined minimum value or above a predetermined maximum value is located, whereupon an appropriate security measure is initiated. 6. Thermostat according to at least one of claims 1 to 3, characterized in that the monitoring device for monitoring a temperature error signal is designed so that the difference between the set temperature and the initial temperature is determined to indicate a malfunction of the thermostat control system to recognize, and if the error signal is outside the specified limits, a corresponding one Security measure is initiated. ... / 22 Thermostat according to at least one of Claims 1 to 3, characterized in that the monitoring device for monitoring a mixing valve for a medium with the aid of valve position limit switches is designed, with the output temperatures outside specified limits are permissible without a safety measure is initiated due to the monitoring of the set or output temperature. 8. Thermostat according to at least one of claims 1 to 3, characterized in that the monitoring device is designed to monitor the supply voltages for temperature sensors, with voltages are recognized outside of predetermined limits, whereupon a corresponding security measure is initiated will. Thermostat according to at least one of Claims 1 to 3, characterized in that the electronic Control is realized by a digital microcomputer, which is used to carry out a self-monitoring routine is programmed at specified times and an OK status message is sent to an external Sends monitoring circuit with a timer, whereby a corresponding safety measure is initiated is, if not within a previously set time after a preceding OK status message another OK status message is issued. ./23 10. Thermostat according to claim 6, characterized in that the safety device with a delay works through which the control system corrects the error signal for a certain period of time is possible before a security measure is initiated. 11. Thermostat according to claim 1, characterized in that that another device for monitoring the input variables that are set by the user, is provided, and the device uses substitute manipulated variables when the manipulated variables selected by the user do not meet the specified safety conditions. 12. Thermostat according to claim 11, characterized in that that the monitoring device monitors the setting temperature of the thermostat and, if the set temperature If the temperature exceeds a specified value, a Tiber control triggers to the set temperature to keep the other given value. 13. Thermostat according to claim 12, characterized in that that another separate control element is provided with which the monitoring device can be deactivated can. 14. Thermostat according to claims 12 or 13, characterized in that a further separate control element is provided with which the override is switched off until the setpoint temperature is reached is set back below the specified temperature. ... / 24 -M- 15. Thermostat according to claim 11, characterized in that the monitoring device controls the position of the Mixing valve monitored by valve position limit switch, with an alarm "temperature unreachable" triggered when one of the limit switches is activated. 16. Thermostat according to claim 15, characterized in that the safety device is designed so that if there is a "temperature unreachable" alarm, a temperature setting outside of a pre-determined range prevents up to pre-determined conditions for the hot and cold water supply are fulfilled.