EP0240394A1 - Water or bath gas burner - Google Patents

Abstract

A water heater of the instantaneous gas type without a permanent pilot light includes: a small turbo-alternator through which the water drawn off passes; an arrangement for using the current from the turbo-alternator for lighting a main pilot light; a valve arrangement for using the flow of water drawn off to admit the gas to the main pilot light and a differential pneumatic valve for controlling the intake of gas to the burner. This differential pneumatic valve is itself actuated by a venting, at the level of an auxiliary pilot light, controlled by an electrovalve fed with the current i. The electrovalve is energized by the positive half waves of the current, chosen so that the cycles of its openings and closings can follow one another at a high rate and the durations of its openings are regulated by modifying the amplitude of the half waves by resistance responsive to the temperature of the drawn off water.

Description

The invention relates to instantaneous gas water heaters or bath heaters of the type without permanent pilot light operating without batteries and without connection to the electrical network, in which the presence of a small hydraulic turbo-alternator rotated by water which passes through the water heater for the entire duration of a hot water drawing, allows, in conjunction with a small solenoid valve driving a gas valve with differential membrane, automatic production, each time a drawing tap is opened d 'hot water, successive and known following operations: ignition of the gas in the pilot, check of the existence of the flame at the head of this pilot, then control the arrival of the gas in the burner.

Such an apparatus has been described in French patent No. 1,215,731 filed on November 7, 1958.

However, it has not been able to give rise to practical achievements for multiple reasons and in particular because until now there has not been a solution which is both sufficiently economical and sufficiently reliable to control the solenoid valve from the current developed by the turbo-alternator, so as to ensure thermostatic regulation of the water drawn by automatic slaving of the gas flow at the temperature of this water drawn.

The object of the invention is, above all, to propose such a solution.

To this end, the devices of the type in question according to the invention also comprise, in a manner known per se, a small turbo-alternator crossed by the tap water and suitable for generating an alternating current i as a function of this crossing. , means for exploiting this current i for the purpose of lighting a main pilot, means for exploiting the circulation of water of drawing so as to admit the gas on the one hand to the main pilot and on the other hand into a gas inlet chamber, a pneumatic valve for controlling the supply of gas to the burner, valve including the diaphragm valve sealingly divides the gas inlet chamber into two compartments, the opening of this valve being controlled by partial venting, at the level of an auxiliary pilot, of one of the two compartments of the chamber , a solenoid valve to ensure this venting and means for exploiting the current i for the purpose of electrical supply to the solenoid valve so as to control the opening of this solenoid valve only when the main pilot is on, and they are characterized in that the solenoid valve is chosen of a type such that its opening and closing cycles can follow one another at a high frequency, of the order of a few tens of Hz, and that its openings are slaved to exceeding d '' a threshold given I _n by a amplitude of its supply current and in that the control means of this solenoid valve comprise means for adjusting at each instant the amplitude of the successive sinusoidal half-alternations of the current i before applying them to the solenoid valve, adjustment being made as a function of the difference D between a temperature setpoint T and the actual temperature of the water drawn at said instant so that the opening times of the solenoid valve, and therefore those of the diaphragm valve , vary in the same direction as this difference D.

• - les moyens de réglage comprennent une résistance sensible à la température de l'eau puisée, résistance du type à coefficient de température positif (CTP) pour laquelle la valeur ohmique croît rapidement dès que la température atteint et dépasse la valeur de consigne T,
• - le chauffe-eau comprend des moyens pour redresser les alternances sinusoïdales du courant i avant de les appliquer sur l'électrovalve, ces moyens étant de préférence constitués par un pont de diodes,
• - le chauffe-eau comprend des moyens pour amplifier les demi-alternances sinusoïdales successives du courant i avant de les appliquer sur l'électrovalve,
• - l'électrovalve est du type "inverseuse", propre à faire communiquer alternativement le compartiment qu'elle contrôle avec l'admission du gaz ou avec l'atmosphère, et la section de la buse contrôlée qui communique avec l'atmosphère est plus grande que la section de l'autre buse.

In preferred embodiments, use is also made of one and / or the other of the following arrangements:

• the adjustment means comprise a resistance sensitive to the temperature of the drawn water, resistance of the type with positive temperature coefficient (PTC) for which the ohmic value increases rapidly as soon as the temperature reaches and exceeds the setpoint T,
• the water heater comprises means for rectifying the sinusoidal alternations of the current i before applying them to the solenoid valve, these means preferably being constituted by a diode bridge,
• the water heater comprises means for amplifying the successive sinusoidal half-waves of the current i before applying them to the solenoid valve,
• - the solenoid valve is of the "inverting" type, suitable for alternately communicating the compartment which it controls with the gas inlet or with the atmosphere, and the section of the controlled nozzle which communicates with the atmosphere is larger than the section of the other nozzle.

The invention includes, apart from these main provisions, certain other provisions which are preferably used at the same time and which will be more explicitly discussed below.

In what follows, a preferred embodiment of the invention will be described with reference to the accompanying drawings in a manner which is of course not limiting.

• FIG. 1, of this drawing, very schematically shows an instantaneous gas water heater established according to the invention.
• FIGS. 2 to 5 respectively show four pairs of half-alternations of the current i rectified, having decreasing amplitudes.
• Figures 6 and 7 show two explanatory curves.

We see in 1 a section of cold water pipe fitted with a water flow limiting valve 3 just upstream of a chamber 2 delimited by a membrane differential 4 of the “water shortage safety valve” type, loaded by a spring 36.

Downstream of the chamber 2, the water is sent in parallel to a relief valve 5 calibrated by a spring 6 and to the turbine 8 of a small turbo-alternator 9,10, these two paths being combined at the same outlet. 7.

This outlet 7 is placed in communication with the second chamber 41 delimited by the differential membrane 4 and it communicates successively with a water pipe which passes through the heating body (not shown), which pipe is itself extended by the tubing of drawing hot water controlled by a tap (not shown).

The 8-10 turbo-alternator is advantageously of the type which has been described in French patent No. 84 04890 filed on March 29, 1984.

The turbine 8 is chosen so that the pressure drop of the water passing through it is equal to the pressure difference applied to the membrane 4 when the flow of this water has its minimum value allowing the device to operate.

This pressure difference is slightly lower than that which causes the opening of the valve 5 to start.

38 shows a fuel gas inlet pipe to the burner 43.

This admission is successively controlled by a gas valve 37 mounted on a rod 42 linked to the center of the membrane 4, then by a differential pneumatic valve 44.

A second gas valve 39, also mounted on the rod 42, controls the admission of gas to a main pilot 22 through a pipe 25.

The differential pneumatic valve 44 comprises a gas chamber divided into two compartments, one upper 34 and the other lower 35, by a membrane 33 whose central portion forming a valve is applied by a spring 31 against a seat 32 secured to the burner 43.

The compartment 34 communicates with the downstream zone of the valve 37.

The compartment 35 communicates either with the upstream zone of the valve 37 by a tube 45, or with the atmosphere by a tube 24 terminating in an auxiliary pilot 23, according to a "reversing" lining 27, located in the chamber 35, is applied against an outlet nozzle 26 of the tube 45 or against an inlet nozzle 28 of the tube 24.

This lining 27 is constituted by the central portion of a vibrating membrane with very low inertia and with almost instantaneous response, as is known in the field of loudspeakers.

It is here joined to a very light mobile coil 29 capable of moving in the air gap of an electromagnet 46. The frequency of the beats of the mobile assembly is of the order of a few tens of Hz, being more generally between 15 and 100 Hz, and the electric power necessary to generate these beats is very low, being generally less than 80 mW (with a current intensity generally between 50 and 100 mA).

The solenoid valve 30 formed by the assembly of the coil 29, the electromagnet 46, the lining 27 and the nozzles 26 and 28 cooperating with the latter is advantageously constituted in the manner described in French patent n ° 85 08544 filed June 6, 1985.

The electrical winding of the electromagnet 46 is connected to the stator winding 10 of the turbo-generator 8-10 by an electronic circuit comprising a diode bridge 11, a photoresistor 16 sensitive to the ignition of the pilot light 22, a temperature sensor 40 sensitive to the temperature of the drawn water, a transistor or other amplification member 15 and electrical connection wires 17 and 18.

The stator winding 10 is also connected, by means of a rectifying circuit (diode 12) and filtering (capacitor 13) and a high voltage igniter 14 with recurrent sparks suitable for lighting the pilot light 22.

A black body 20 disposed in the vicinity of the top of the blue cone of the flame of this pilot light 22 and constituted in particular by a single very fine platinum wire, is brought, as soon as this pilot light is lit, to a temperature corresponding to a radiation of yellow color corresponding to the maximum spectral sensitivity of photoresistor 16, for example to cadmium sulfide.

A small light guide 19, constituted in particular by a simple glass rod, is provided for transmitting to the photoresistor 16 the radiation emitted by the small black body 20.

The operation of the device thus described is as follows.

As long as the flow of water drawn following the opening of a drawing tap remains below a given threshold, this water circulates in the turbine 8 at a speed insufficient to cause anything, the various valves of the device remaining all closed.

As soon as the flow of water drawn exceeds the minimum threshold for operating the device, all of the following consequences are observed.

The water valve 5 opens little by little, bypassing the turbine 8.

The gas valves 37 and 39 also open, which supplies gas, in addition to compartment 35, compartment 34 and the main pilot 22.

The turbo-generator generates electric current, which has the effect of exciting the electrode 21 of the igniter 14 and lighting the main pilot 22.

The transmission of the bright light of the black body 20, by the guide 19, to the photoresistor 16, has the effect of causing the ohmic value of the latter to drop in a considerable ratio, in particular of the order of 100 to 1: amplitude of the current which appears at the base of the transistor 15 during the production of each half-wave rectified current by the diode bridge 11, increases in the same proportion and is found on the collector of said transistor in a ratio further amplified by the gain of this transistor.

This diode bridge 11 has the effect of rectifying one of the two half-alternations of each alternation of the alter-native current i generated by the stator winding 10 and letting the other half pass unmodified. half-wave, and the half-waves obtained, all of the same polarity (assumed to be positive in this specification) are applied to the voice coil 29, one of the connection wires 18 of which is connected to the collector of the transistor 15, its other connection wire 17 being connected to the positive output of the diode bridge 11; the base of transistor 15 is also connected to the positive output of this same bridge 11 in series with on the one hand, the photoresist cell 16, and on the other hand the temperature sensor 40.

The latter is preferably constituted by a resistance with a positive temperature coefficient, called PTC, having the known characteristic of exhibiting, from a certain temperature, a very rapid and very significant increase in its ohmic value.

Each time, during the passage of a half-wave of positive current in the voice coil 29, the instantaneous value of this current exceeds a certain threshold value 1 (see FIGS. 2 to 5) from which said moving coil lifts, the lining 27 which is integral with this coil comes to be applied, by its upper face, against the small nozzle 26 which it closes, while its lower face takes off from the small nozzle 28 which it closed at rest, thus putting the chamber 35 located under the membrane 33 in communication with the atmosphere through the tubing 24 and the second pilot 23 which is there only to burn the small volume of gas then escaping from the chamber 35.

It is easily understood that at each half-wave current flow, during the period of time during which the current in the voice coil 29 exceeds the threshold 1 which causes the said coil to rise, the gas leakage which results therefrom. the pilot 23 causes a progressive drop in the pressure of the gas in the chamber 35, that is to say under the membrane 33 and, as the pressure in the chamber 34 above this same membrane is constant and substantially equal to the gas supply pressure of the device, the gas pressure differential on either side of the membrane increases and this increase is substantially proportional to the ratio between the duration A, of each half-wave, during which the current in the voice coil exceeds the threshold value I _n , and the total duration B of each half-wave, that is to say at the rate of modulation of the width of the slots of operation of the solenoid valve 30.

As can be seen in FIGS. 2 to 5, this modulation rate, which is expressed by the A / B ratio, increases itself as a function of the amplitude of the half-waves of current from the moment when the value of this amplitude exceeds the threshold current value I _n .

Since, in addition, this amplitude is linked, to the current gain near transistor 15, to the value of the current in the base of this same transistor and that the latter is linked, by Ohm's law, to the ohmic value of the sensor resistive 40, it is understood that, each time the temperature of the hot water produced approaches the temperature T from which the ohmic value of the sensor 40 increases very quickly, the base current of the transistor also decreases very quickly, causing the same rapid decrease in the amplitude of the half-vibrations in the voice coil and, consequently, such a rapid decrease in the modulation rate of the micro-solenoid valve, which results in a decrease in the differential pressure acting on the membrane 33 , which finally lifts towards the seat 32, thereby reducing the gas flow rate to the burner 43.

This value T is given the setpoint of the temperature at which one wishes to draw water.

In the opposite case, when the temperature of the hot water produced drops, the sequence of the operating sequences described above is the reverse of the previous one.

The curve of FIG. 6 shows the variations of the differential pressure P ₁ -P ₂ applied to the membrane 33 (P ₁ being the pressure of the gas in the upper compartment 34 and P ₂ the pressure of the gas in the lower compartment 35) in function of the A / B ratio between the duration of opening A of the solenoid valve 30 and the duration B of each half-wave of current.

On a second abscissa, the corresponding values of the amplitudes of the half-waves of current applied to the solenoid valve are plotted.

The point C of the curve corresponding to the maximum amplitude I _m is that beyond which a further increase in the amplitude, resulting in a further increase in the differential pressure P ₁ -P _{2 '} remains without effect on the gas flow , the latter then having reached its maximum value, corresponding to the maximum lifting of the differential membrane.

The value of the A / B ratio corresponding to this point C is here equal to 4/5.

Point C in question corresponds to the situation shown schematically in Figure 2 while point D (for which the A / B ratio is equal to 1/3) corresponds to the situation shown schematically in Figure 4 and that point E (for which the A / B ratio is zero) corresponds to the situation shown diagrammatically in FIG. 5.

This curve shows that, for the whole range of amplitudes between the threshold value 1 and the maximum value I _m , the differential pressure P ₁ -P ₂ is substantially proportional to the ratio A / B.

It is substantially the same for the flow rate of gas to the burner, as shown by the curve in FIG. 7: on this curve, we have plotted on the ordinate this flow rate of gas Q and on the abscissa the amplitude I of the half-wave alternations applied to the solenoid valve.

The simple regulation of the amplitudes I described above as a function of the temperature of the water drawn therefore leads to that of the gas flow rate by regulating the relative widths A / B of the "slots" of current or the "rate of modulation "of this current: the calorific power generated by the burner is therefore higher the lower the temperature of the water drawn.

This regulation is extremely simple, reliable and economical.

It should be noted that, to a certain extent, said calorific power is also regulated as a function of the flow rate of the drawn water since the amplitudes of the alternations of the current i generated by the turbo-alternator are substantially proportional to this flow rate, at least as long as the bypass valve 5 is not fully open.

• - celles où le pont de diodes 11 serait remplacé par une diode unique, ce qui reviendrait à supprimer purement et simplement l'une des deux demi-alternances de chaque alternance du courant i, savoir l'alternance négative dans l'exemple décrit ci-dessus,
• - celles où le pont de diodes serait supprimé purement et simplement, seules les demi-alternances de polarité utile du courant i étant alors exploitées pour exciter l'électrovalve (cette formule réduit certes l'étendue de la gamme de réglage possible pour le taux de modulation, mais elle est particulièrement économique et permet d'éviter la légère chute de tension observable lors de toute traversée d'un redresseur par un courant),
• - celles où l'organe amplificateur de courant serait autre qu'un transistor, cet organe étant par exemple constitué par un amplificateur opérationnel,
• - celles où l'électrovalve 30 ne serait pas "inverseuse" mais simple et propre uniquement à contrôler la mise à l'air libre du compartiment 35,
• - et celles où ladite électrovalve serait encore "inverseuse", mais où les deux buses 26 et 28 contrôlées par elle présenteraient des sections différentes, de façon notamment à augmenter la gamme de réglage possible du taux de modulation ci-dessus lorsqu'on exploite une seule des deux demi-alternances de chaque alternance du courant i, cas dans lequel c'est la section de la buse 28 qui est la plus grande.

As it goes without saying, and as already follows from the above, the invention is not limited in no way to those of its modes of application and embodiments which have been more especially envisaged; on the contrary, it embraces all variants, in particular:

• - those where the diode bridge 11 would be replaced by a single diode, which would amount to simply eliminating one of the two half-vibrations of each half-wave of current i, namely the negative half-wave in the example described here- above,
• - those where the diode bridge would be eliminated purely and simply, only the half-vibrations of useful polarity of the current i then being exploited to excite the solenoid valve (this formula certainly reduces the extent of the range of possible adjustment for the rate of modulation, but it is particularly economical and makes it possible to avoid the slight drop in voltage observable during any crossing of a rectifier by a current),
• - those where the current amplifier member would be other than a transistor, this member being for example constituted by an operational amplifier,
• - those where the solenoid valve 30 is not "inverting" but simple and suitable only for controlling the venting of the compartment 35,
• - And those where said solenoid valve is still "inverting", but where the two nozzles 26 and 28 controlled by it would have different sections, so as in particular to increase the range of possible adjustment of the modulation rate above when operating a only one of the two half-waves of each half-wave of current i, in which case the section of nozzle 28 is the largest.

Claims (6)

1. Instantaneous gas water heater of the type without permanent pilot light, comprising a small turbo-alternator (8-10) traversed by the draw-off water and suitable for generating an alternating current i depending on this crossing, means (12 -14) to exploit this current i for the purpose of lighting a main pilot (22), means (4) for exploiting the circulation of the draw-off water so as to admit the gas on the one hand to the pilot main and secondly in a gas inlet chamber, a pneumatic valve (31-35) for controlling the supply of gas to the burner, a valve whose diaphragm valve (33) divides the chamber gas inlet in two compartments (34 and 35), the opening of this valve being controlled by partial venting, at the level of an auxiliary pilot (23), of one of the two compartments (35) of the chamber, an electrovalve (30) to ensure this venting and means for exploiting the current i for the purpose of electrical supply e of the solenoid valve so as to control the opening of this solenoid valve only when the main pilot is lit, characterized in that the solenoid valve (30) is chosen of a type such that its openings and closings can succeed one another high frequency, of the order of a few tens of Hz and that its openings are slaved to exceeding a given threshold 1 by the amplitude of its supply current and in that the control means of this solenoid valve comprise means (40) to adjust at each instant the amplitude of the successive sinusoidal half-waves of the current i before applying them to the solenoid valve, this adjustment being carried out as a function of the difference D between a setpoint value T of the temperature and the actual temperature of the water drawn from said instant so that the durations opening of the solenoid valve, and therefore those of the diaphragm valve (33), vary in the same direction as this difference D. 2. Water heater according to claim 1, characterized in that the modulation means comprise a resistor (40) sensitive to the temperature of the water drawn, resistance of the type with positive temperature coefficient (PTC) for which the ohmic value increases rapidly as soon as the temperature reaches and exceeds the setpoint T. 3. Water heater according to any one of claims 1 and 2, characterized in that it comprises means (11) for rectifying the sinusoidal alternations of the current i before applying them to the solenoid valve (30). 4. Water heater according to claim 3, characterized in that the rectifying means consist of a diode bridge (11). 5. Water heater according to any one of the preceding claims, characterized in that it comprises means (15) for amplifying the successive sinusoidal half-waves of the current i before applying them to the solenoid valve (30). 6. Water heater according to any one of the preceding claims, characterized in that the solenoid valve (30) is of the "inverting" type, capable of alternately communicating the compartment (35) which it controls with the admission of the gas. (45) or with the atmosphere (23,24), and in that the section of the controlled nozzle (28) which communicates with the atmosphere is larger than the section of the other nozzle (26).

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