DEVICE AND METHOD FOR CONTROLLING THE RECOVERY OF VAPORS IN FUEL DISTRIBUTION COLUMNS
The present invention relates to the columns of fuel distributors, in particular columns that are provided by a system for the recovery of the vapors emitted during the operations of the supply to vehicles. In the fuel distributors, and in particular in the street distributors for the supply to vehicles, the norms for the safety and protection of the environment require that the vapor phase, consisting of a mixture of air and fuel vapors, and discharge from the tanks of the vehicles as they are being supplied, do not disperse in the environment. This emission is caused substantially by the effect of displacement by the fluid admitted to the tank, which reduces the volume above its level, and expels an equivalent level of vapor phase. According to the known technique, this air / vapor phase is absorbed by providing the fuel dispensing guns both with fuel distribution nozzles and with suction bottles, which are connected to volumetric pumps. The distributor gun is connected to the column by pipe for the distribution of the liquid fuel, which is supplied by a pumping unit with a variable flow rate, as well as by suction pipe that is connected to a volumetric pump by suction of the vapors , which is triggered by a flow check that is closely correlated, moment by moment, to the fuel distribution flow rate. According to the known technique, several systems have been proposed for the recovery of the vapors, that is, in the air / vapor phase, which is discharged from the tanks of the vehicles as they are being supplied, for example, in the US5 , 038, 838; WO 98/00641, WO 96/06038 and DE 4200803. In order to clarify the technical problems are associated with the recovery of the vapors in the columns, reference is made to the diagram in Figure 1, which refers to a column distributor that is provided with an individual dispensing gun. The column 10 is provided with a box-shaped support structure 11, which contains and supports its units. The content is contained in a buried tank, not shown in the figure, from which the fuel is obtained by means of the suction line, which consists of the bed 12, the pumping unit 13, which is connected to the distributing gun 18 and the meter 14, which measures the amount of fuel distributed, before transporting it via the tube 15 to the separator 16, from which the flexible tube 17 of the dispensing gun 18 extends. A pulse generator 20 is connected to the meter 14, that generates an electrical impulse for each fuel unit distributed, for example, for each centiliter; this pulse signal has a frequency that is proportional to the flow rate, and is transmitted to the indicator head 21, which, based on the number of pulses, calculates and indicates the distributed amount and the corresponding weight of the supply. The same signal is transmitted to the electronic control unit 22, which controls and directs the vapor recovery system. The tube 17 of the dispenser gun 18 contains both a fuel distribution tube 23, which is the extension of the distribution tube 15 such as the dispensing nozzle and the return tube 24, which is connected to a suction nozzle located at the vicinity of the distributor nozzle. This nozzle absorbs the vapors that are expelled from the tank that is filling; this return pipe 24 is connected in the separator 16 to a pipe 25, which is connected to the volumetric pump 26 for suction of the vapors, which is driven by a motor 27, which is directed by the electronic control unit 22 in a number of revolutions, which is in relation, moment by moment, to the frequency of the impulse signal of the generator 20, such as to correlate the revolutions of the pump 26, and thus the suction flow velocity, volumetric, at the fuel distribution flow rate. The distribution of the volumetric pump 26 is readmitted via the tube 28 in the buried tank of the distributor, from which the fuel is obtained; in general, the volumetric relationship between the distributed fuel and the gaseous phase that is absorbed is adjusted and maintained with a range of values that are close to the unit value; this adjustment can be varied according to the type of fuel and the environmental conditions. The fuel is typically distributed with a variable flow rate, which is regulated by the operator by means of the pressure exerted on the lever 30 for regulating the gun, while the suction flow rate must follow moment by moment the development of the distribution flow rate. In practice, a sequence of the impulses faithfully represents the situation, moment by moment, of the distribution of the liquid that takes place, with the number of impulses corresponding to the distributed quantity and the frequency of the impulses corresponding to the velocity of the instantaneous flow; however, the direction of the volumetric suction pump that takes place by modulating its instantaneous speed, that is, its number of revolutions per minute, based on the instantaneous frequency of the meter pulses, is not exactly the same in the final result to obtain a constant relationship between the volumetric flow velocities of the liquid distributed and the vapor absorbed. Actually, the most common types of volumetric pumps used for vapor recovery in fuel distributors are vane pumps, roller pumps, or alternative types of pumps, and have a characteristic flow rate / speed curve that does not It is completely linear, and therefore it is not possible to obtain a constant relationship between the flow velocities of the distributed liquid and the absorbed vapor, if the operation takes place based on the frequency of the meter / generator impulses, when the speed of distribution is varied and the revolutions / minute of the volumetric pump are regulated accordingly linearly. Figures 2A and 2B show indicatively the typical developments of the characteristic curves (flow velocity / velocity) for these types of volumetric pumps operating in a vapor recovery system. In particular, Figure 2A shows the development of the characteristic curve of a vane or roller pump, while Figure 2B qualitatively illustrates the development and a characteristic curve of an alternative pump. Actually, these characteristic curves show the development of the pump / circuit system under constant load loss conditions P and P2 (P2> P). The technical problem is further complicated in the most recently designed distribution systems in which each column is provided with a plurality of dispensing guns, each of which is connected to a different buried fuel tank, for example, super leaded gasoline. , unleaded petrol of various qualities, diesel and so on. In this case, in fact, for each group of guns 18 on the same side of the column 10, only one single dispensing gun can operate at the same time in order to supply the vehicle that is parked in front of the column, while each Gun group 18 on each side is provided by a volumetric suction pump 26. Current below the volumetric pump 26, in the case of the distribution guns 18, the distribution pipes for the vapors absorbed in the corresponding buried tanks are sub-divided into several tubes 28, and in each of these a system of change comprising a series of non-return valves, one of which is shown schematically in Figure 1, and is indicated generally as 31, downstream of the pump 26. There is also the problem that any in equilibrium in the losses of load can occur in the ramifications of the system, as a result of the different calibrations of the valves, the different lengths of the various branches and so on, so that each branch for the distribution of the vapors to the tank does not operate with the same head loss, but according to a different flow velocity / characteristic speed curves, as indicated in Figures 2A and 2B. In this way, depending on the cases, the volumetric pump 26 is operated in vapors with different densities, depending on the type of fuel, at different temperatures, and with different pressure valves downstream. From the above information, it is clear that the operation with linear correlation between the frequency of the generator pulses 20 and the revolution speed of the motor 27 of the pump 26, does not guarantee a constant relationship between the flow rates of the distributed liquid phase and the vapor phase absorbed, but rather, substantial divergences of this constant ratio occur. The object of the present invention is to indicate in this way a method for controlling the recovery of the vapors in fuel distribution columns, which takes into account the actual operating conditions, and makes it possible to comply with the requirement of establishing and maintaining a predetermined relationship in volume terms, between the flow rates of the liquid distributed and the vapor absorbed, both when the flow velocity of the liquid distributed is varied and when the fuel or associated conditions are varied. According to the present invention, the technical object required is that of imparting to the vapor recovery system, the ability to obtain a relation between the predetermined and required flow rates, both during the initial calibration phase and that of periodic control, simply by means of a modulation operation of the revolution speed of the electric motor that is connected to the volumetric pump. A method according to the present invention is defined in the subsequent claim 1. The method according to the invention makes it possible to obtain linear proportionality between the quantity of vapors recovered and the quantity of the product distributed, by means of an electronic control unit, that adequately controls the speed variation of the vapor suction pump; the number of revolutions of the pump varies according to the signal obtained from a pulse generator, via an electronic head. The features and advantages of the method according to the present invention will become more apparent from the following description and a typical embodiment, provided by way of non-limiting example, with reference to the attached schematic drawings, in which: Figure 1 is a schematic representation of a distribution column with a dispensing gun, with the recovery of the vapor phase; Figures 2A, 2B are two Cartesian diagrams showing qualitatively the developments of the characteristic flow rate / speed curve, which relate respectively to a system with a vane or roller pump, and a system with an alternative pump. in particular, Figures 1, 2A and 2B illustrate the technical problem to which the present invention relates; Figure 3 is a block diagram of a control device for the recovery of the vapors, according to the present invention; Figures 4A, 4B, 4C, 4D show a first embodiment of a wiring diagram of the vapor recovery control device according to the present invention; Figure 5 refers to a second embodiment of a wiring diagram of the control device, according to the present invention; Figure 6 shows a Cartesian diagram illustrating the qualitative development of the V / L ratio, when the flow rate varies in a vapor recovery system that is provided with a proportional valve, with a pump, with a fixed number of revolutions , which is controlled mechanically by the motor of the pumping unit, or by an independent motor; Figure 7 shows a Cartesian diagram illustrating the qualitative development of the V / L ratio when the flow rate varies in a vapor recovery system with a variable speed pump, which is controlled electronically; and Figure 8 shows a Cartesian diagram illustrating the qualitative development of the corrective value curve, when the operating point is varied, and that it can be used in the vapor recovery system according to the control device in accordance with the invention . With reference herein to Figure 3, the same components that are already present in Figure 1 are indicated by the same references, while 35 indicates schmatics between a block that refers to the actual vapor recovery system, which allows the recovery of gasoline vapors that are discharged from the tank by the vehicles so much that they are being re-supplied with fuel, as already previously described in detail, and 33 indicates a connection block for the signals obtained from the pulse generator 20 the head 21. The system 35 comprises the volumetric suction pump 26, which is connected to its previous electric motor 27, and has an adequate level of protection for establishment in a hazardous area, and an electronic control unit 22, which is establishes in a non-dangerous area. The volume of the vapor recovered depends on the flow rate of the distributed fuel, in order to be able to carry out this regulation, the control unit 22 detects the pulses obtained from the electronic head 21, or directly from the pulse generator 20, and it acts on the speed of the motor 27 of the pump 26. The recovered steam is transported to the fuel storage tank via the flexible hose 24, which is coaxial with respect to the distribution pipe 24 for fuel distribution.
The vapor recovery system 35 can be used for the suction of normal, super and super unleaded gasoline vapors. According to a preferred but not limiting embodiment of the present invention, the electronic unit 22 controls the speed of the brushless type motor 27, and is supplied with single-phase alternating current, thus ensuring satisfactory operation for an equivalent supply voltage. at 230 volts (nominal value) and a supply voltage frequency of 50 Hz. In practice, the electronic control unit 22 receives as input a series of reference signals, which are processed accordingly, such as to return linear virtually the function that associates the volume of steam recovered by the system 35 with the volume of the distributed fuel, which currently functions following a non-linear development. For this reason, it is necessary to introduce a compensation curve that, for some values (determined by means of previous calibration of values that can be established in a real suction pump 26) of a speed reference signal transmitted to the intake of the control unit 22, determines the actual speed of the suction pump 26; the speed reference input of the unit 22 is directed by a square wave signal with a frequency between 0 and 200 Hz, which is normally supplied by the electronic head 21, via the pulse generator 20. The control unit 22 has a regulator, such that it can adapt to the different amplitudes (typically + 5V to + 12V, or + 12V to + 35V) of the signal obtained from the pulse generator 20, such that it can be interconnected with the pulse generators that are currently very commonly available on the market, the output storage of which may be open NPN corrector, open collector PNP, totem pole, or pull-push type. The speed coefficients of the compensation curve are obtained by means of a device that makes it possible to determine these values automatically at the various distribution flow rates; alternatively, these coefficients can be calculated by means of an application program that is installed in an electronic processor, which makes it possible to store up to 100 coefficients in a frequency range of the speed reference that varies from 0 to 100 Hz. compensation can be further modified by adding or subtracting a constant value obtained from a reminder, by means of a coefficient that can be adjusted by means of the processor; the range of speed regulation is within 20%, while the direction of revolution of the motor 27 can be adjusted by means of a submerged switch, or by means of the processor itself. The electronic control unit 22 also has an input for connection to a temperature sensor, which is accommodated within the motor 27; When the temperature of the windings exceeds a predetermined value, the energy distribution is interrupted until the temperature falls below this limit. Under these conditions, an LED, showing the operating status, indicates normality when switching intermittently; After a predetermined number of blocks and re-start (which can be adjusted, within a specific period of time (which can be adjusted), the vapor recovery system is definitively defined.A censor to measure the ambient temperature can be connect as an alternative to the motor temperature sensor 27. The power stage of the control unit 22 is provided with a sensor which measures the temperature, such as, when the temperature exceeds the value of about 85 ° C, the distribution of energy to motor 27 is stopped, and the LED indicating the operating state lights up, this condition continues until the temperature falls below this limit.In addition to the thermal protection, there is also protection that refers to the maximum current, which operates when a predetermined value of the current intensity is exceeded, thus interrupting the distribution of energy to the motor 27 and this distribution is then automatically restored after several attempts that can be programmed from a minimum of 1 to a maximum of 8. The control unit 22 also has a serial communication gate of the RS485 type for interfacing with an electronic processor and with a device for the calibration and diagnosis of the system; in particular, according to a preferred, but not limiting, modality, there is an asynchronous serial / duplex interface of the RS485 type, with 1200 baud, 8 data bits, 1 stop bit and no parity. In order to communicate with the electronic unit 22, it is necessary to have an electronic processor (personal computer), the minimum configuration of which is as follows: microprocessor 486, 4 megabytes of RAM, operating system Windows 3.1 or later, interface device RS232-RS485; and the following parameters can be established via the processor: - resolution of the input pulses generated by the pulse generator (100/200 pulses per liter of fuel); - resolution of the motor encoder 27 (2/4/8 pulses per revolution); - motor revolution direction 27 (clockwise / counterclockwise) - pump speed control field 26 (± 20%, from 5 to 60 liters) fuel per minute) - manual speed regulation - fixed revolution speed mode for motor 27 - speed control field of pump 26 with fixed speed (from 5 to 60 liters per minute) - selection of variable or fixed revolution mode, - number of compensation coefficients, - assignment of the address for serial operation communication, and - selection of the serial communication gate The main parameters that can be indicated are (in coefficients between 0 and 127), ambient temperature or temperature of the motor windings 27;
- temperature of the power stage of unit 22; - frequency of the input pulses (from 0 to 200); - frequency of the pulses obtained from the motor encoder 27 (from 0 to 200); partial totalization of the distributed fuel (from 0 to 9,999 liters); - correlation coefficients (from 0 to 120); - deviation of the compensation curve (from 0 to
127, where the zero is determined by the number 64); - position of the regulation trimmer; - intensity of the current flowing in the motor 27; and - error code (from 1 to 8). According to the present invention, the electric motor 27 controls the revolution of the vapor suction pump 26, at a speed that depends on the control received from the unit 22, and they are converted into corresponding voltage signals that are going away. to supply to the engine 27; in practice, the speed at which the motor 27 causes the pump 26 to rotate and in this way the amount of steam is recovered, depends on the voltage supplied to the motor 27. It has already been seen that in order to obtain the maximum efficiency of the recovery system 35, the control unit 22 must control the pump 26, such that the vapor phase is recovered at a rate such that it corresponds to the volume of the instantaneous vapor that is generated during a filling operation of the fuel tank. The unit 22 then determines an optimum instantaneous speed value for the suction pump 26. thus providing a non-linear objection with several variables, which in turn depend on a set of independent variables, which are responsible for the variations in the volume of the vapors generated during the introduction of fuel into the tank, that is to say when searching the corresponding values in a matrix that is processed in a microprocessor. The independent variables consist of the speed of distribution of the fuel, the volume distributed, the duration of the distribution, the ambient temperature, the temperature of the fuel and any constriction within the return tube 24 of the vapor phase. Other independent variables can be taken into consideration during the control procedure. In order to determine the corresponding speed of the suction pump 26, the values of the independent variables must be measured instantaneously, by means of a series of sensors and transducers, and the corresponding signals that are related to the dependent variables must be transmit to control unit 22. In particular, there is the point construction of the flow rate / curve (velocity p / v) which refers to the suction pump 26 used, taking into account all the variables included; and in this way, for example, a transducer for the fuel flow transmits a signal proportional to the distributed flow, to the control unit 22, while the temperature transducers measure the ambient temperature and the temperature of the fuel, and transmit instantaneously The signal proportional to the unit 22. An initial calibration of the steam recovery system 35 is carried out by means of a sample pump 26 and the pressure associating the variables of the vapor flow rate V
(recovery) / liquid flow rate L
(distributed fuel) is determined instantaneously by a microprocessor, in order, accordingly to regulate the optimum speed of the motor 27, with respect to the variation of all the variables comprised during the supply operation that provides a non-linearity of the function V / In particular, the mode of the wiring diagram illustrated in Figures 4A-4D which refers to the control device according to the invention, the connecting pins of eight connectors used in an electronic card of a system for the vapor recovery, which is indicated generally by reference 35 in Figure 3. Figure 4? shows the electrical conditions to the poles or pins Pl-1, Pl-2, Pl-3, Pl-6, Pl-7, Pl-8, Pl-9, Pl-10, Pl-11, Pl-12 of the connector Pl of the card, which allows the transmission of signals electrically from and to the pulse generator (pulse generator) 20 or the CPU board of the electronic processor, the LED signaling diode, the temperature sensor and the motor encoder 27 without a brush. In preferred embodiments, non-limiting bolt, the 12-pin Pl connector is of the male, vertical type, for example an MSTBVA 2.5 / 12-G-5, 08. The poles Pl-1 and Pl-2 allow connection with the pulse generator 20 (input signal, negative and positive pole, respectively), while a supply (14.3 V, 100 mA) of the external pulse generator 20 is available in the pin Pl-3.; in addition, the poles Pl-8, Pl-9 and Pl-10 allow the flow at the input of the card, of the signals that are related to the encoder of the motor 27 (according to three spatial coordinates X, Y and Z, respectively , while the pole Pl-11 is connected to the positive pole (6.2 V) of the supply of the brushless motor 27, and the pole Pl-12 represents a voltage reference of 0 V. The poles Pl-6 and Pl-7 refer to available inputs and a voltage reference of 0 V, while pins Jl-4 and Jl-6 refer to a 6-pole vertical pole connector Jl male type, for example, AMP MODUl 280372-2 , and respectively constitute an output pole for a signal from the pulse generator, isolated to the interface card (used if there is a vapor recovery system 35 for a multi-product distributor ie for a column 10 with several distributing guns 18 for different products), and a pole that refers to an input dis wearable Figure 4A also shows the connections to the pins P5-1, P5-2, P5-3, P5-4 of the 4-pole connector P5 of the electronic vapor recovery board; in particular, the connector P5 of the vertical male type, for example, an AMP M0DU2 280371-2, allows the flow of electrical signals from and to the interface of the type RS485 or RS422, or the programming terminal. In this way, for example, the pole P5-1 is connected to the positive supply (5 v) of the interface, the poles P5-2 and P5-3 to the input and output are connected to two lines in which signals are transmitted from and to the interface, while the pole P5-4 is reserved for the connection with the reference of 0 V. Figure 4B illustrates the connections of the card to the pins P2-1, P2-2, P2-3, from the connector P2, of the male type, vertical of 3 poles, for example an MSTBVA 2.5 / 3-G-5, 08 and to the pins Pl-4 and Pl-5 of the connector Pl; the poles P2-1, P2-2, P2-3 allow the output of the electrical signals to reach the motor 27 without brush, refer to the various phases of this electric motor 27, while the poles Pl-4 and pl -5 allow the output of an electrical signal that refers to the supply (positive pole and negative pole) of a LED visual signal diode. Jl-5 pin of connector Jl refers to a default output signal. Figure 4C shows the connections to the poles
P3-1, P3-2, P3-3, P3-6, P3-7, P3-8, P3-9, P3-10, P3-11, P3-12 of connector P3 (which is of the same type, and it has the same functions as the connector Pl), and of the poles J2-4 and J2-6 of the connector J2 (which is of the same type, and has the same functions as the connector Jl). Finally, Figure 4D shows the connections to the pins P3-4, P3-5 of the connector P3, the connections to the pins Jl-1, Jl-2, Jl-3 of the connector Jl, the connections to the pins J2-1 , J2-2, J2-3, J3-5 of connector J2, the connections to pins J3-1, J3-2 of connector J3 (of the vertical male type of 2 poles, for example an AMP MODUl 280609-2, which allows the transmission of the signals to and from the Jl connector and the 36 V supply of the electronic board for the vapor recovery), and the connections to the pins P4-1, P4-2, P4-3 of a connector P4 of the vertical male type of 3 poles, for example, an MSTBVA 2, 5/3-G-5, 0.8 that allows the connection to the output to the electric motor 27, since the signal output controls the phase. Figure 5, which refers to a control wiring diagram for a digital brushless motor, shows the pins Pl-1, Pl-2, (which refers to the inputs of the pulse generator 20), Pl-3 , Pl-4 (which refers to the outputs of the signaling LED), Pl-5, Pl-6 (which refers to the connection of the temperature sensor), Pl-7, Pl-8, Pl-9 (which refers to other connections of sensing devices), and Pl-10, Pl-11, P4-1, P4-2 (which refer to the main direct current supply connection). In addition, pins P2-1, P2-2 and P2-3 refer to connections to the brushless stator phases, while poles P3-1, P3-1, P3-3, P3-4 guarantee the connections to the RS485 serial line. In order to determine the function that associates the volume of the recovered vapor (V) with the volume of the liquid distributed (L), based on a series of experimental data calculated by means of the steam recovery system with a sample suction pump and the pre-adjustment, the microprocessor 40 creates a table of values that refer to the dependent variables, which are stored in an individual or multidimensional matrix (contained in non-volatile memories) according to the number of independent variables on which the function V = f (L) to be determined. The range of values that each independent variable can assume can be selected such as to cover an appropriate measurement interval during the complete supply operation; in addition, the microprocessor 40 uses the same table of values, and updates them for each successive operation of the fuel supply. The independent variables may be selected such as to best stimulate the conventional operating conditions of a vapor recovery system, during the filling stage of a fuel tank. For this purpose, it is also necessary to provide appropriate characteristics of the capacity of the non-volatile memories used. The determination of the function V = f (L), which becomes linear, is thus used to generate a signal to control the speed of a suction pump 26; finally, in order to provide more accurate control, the motor 27 is connected to the microprocessor 40 of the unit 22 by means of a feedback unit, such that, in this case, the feedback signal is transmitted from the motor 27 to the microprocessor 40, and the latter can generate the appropriate control signals for the determination of the instantaneous velocity of the pump 26, taking into account the feedback. In practice, during a filling operation with fuel by a user, the vapor recovery system 35 is monitored as variables the ambient temperature and the volume of the fuel distributed. The ambient temperature is measured directly by a temperature transducer, and a corresponding signal is transmitted to the microprocessor 40 of the electronic unit 22, while the distributed volume is determined by means of the flow, by means of a specific transducer, in reality, during the distribution, the generator or pulse generator 20 transmits a series of pulses via the head 21, to the microprocessor 40, which stores in its memory the number of pulses that have been counted in the term of the supply operation to the vehicle, and calculates the volume of fuel distributed based on this number. The microprocessor 40 also continues to receive the signal fed back by the motor 27, in order to obtain a first exact speed control of the form 26, and compensate for the lack of linearity. The microprocessor 40 of the electronic control unit 22 may also include a timer device, which measures the time interval that elapses between two successive supplies such that, if this time interval is greater than a specific, predetermined value, and from this way the stored data
(dependent variables) that refer to the experimental results, and are adjusted in the V / L curve are not very accurate, are measured experimentally and store new values of the variables in the electronic unit. As an alternative to the solution previously described, according to one embodiment, the additional limitation of the present invention, it is possible to store in the electronic unit 22 with a microprocessor 40, a table or matrix with 120 lines and two columns, wherein the first column contains the values that refer to the input frequency (in a frequency range between 0 and 100 Hz), which corresponds to the signal obtained from the pulse generator '20, and the second column contains a series of values of output frequency, which corresponds to the number of revolutions at which the steam recovery pump 26 must function in its function. 120 lines of the matrix are provided, that is, 20 more than the frequency range 0-100 Hz, in order to be able to obtain a reasonable margin of regulation. A regulation system of this type makes it possible to correct the characteristic curve of the suction pump 26, and the V / L ratio of the complete recovery system 35 for the vapors, if there is a different head downstream of the system 35. The matrix is It inserts into a corresponding non-volatile memory element (for example, AEEPROM memory, integrated into the microprocessor 40, which makes it possible to preserve the data even when the energy is absent and is also capable of modifying the data at any time. determines by a series of experimentally obtained data from a sample assembly of the suction pumps 26, such that the compensation curve is obtained by interpolation (a process that is carried out by an associated electronic microprocessor), and some points in the which the complete vapor recovery system 35 is tested.The interpolation takes place by means of an electronic calibration system, c or corresponding, which can transfer the results obtained to the control unit 22 of the recovery system 35. The vapor recovery system 35 in question can be regulated by means of a potentiometer (trimmer) present on the electronic board of the system 35, which makes it possible to translate a curve or provision stored in the microprocessor 40, ie, which makes it possible, by means of the translation of this curve by means of the transmission of a data to the serial gate present in the electronic card of the recovery system 35, to exclude the trimming function, and to allow a recording with the same functions as the trimmer. By means of an external calibration device that is connected to a meter, it is also possible to simulate a series of distributors with various flow rates, the results of which are interposed in order to obtain the characteristic curve, which is available directly in the electronic control unit 22. The use of the electronic control device according to the invention in this way can limit the variation of the critical value required (ratio V / L), when there is variation in the possible operating conditions of the vapor recovery system; in fact, the main variation of the operating condition is caused by variation of the flow velocity, which, for a monobloc distributor with a capacity of 50 liters / minute, can be considered variable between approximately 50 and 5 liter / minute. It will be appreciated that a qualitative measurement of the value of the vapor recovery system is provided by the fact that the V / L or L / V curve is as constant as possible within the field of operation, satisfaction consists of higher or lower processing of the V / L parameter, that is:? V / L = V / L max - V / L min. The experimental results obtained have shown complete validity according to the present invention; in fact, in addition to a vapor recovery system according to the invention, two conventional systems have been taken into account, for the purpose of a clear quick comparison of the data, that is, a system for recovering vapors by a pump with variable revolutions, which is controlled electronically (where the number of revolutions of the pump is provided at the rate of distributed flow, according to a constant of proportionality), and a system with a pump with fixed revolutions, which is controlled mechanically by the engine, and is provided with a proportional valve (where the number of revolutions of the pump is proportional to the number of revolutions made by the engine, according to a constant of proportionality). The Cartesian graph in Figure 6 refers to the experimental data for the V / L ratio (with a percentage) according to a series of values of the flow velocities (in liters / minutes), which were obtained with a system of use in the pump with fixed revolutions, mechanically controlled. The Cartesian graph in Figure 7 additionally samples the experimental data of the V / L ratio (as a percentage), according to a series of flow velocity values (in liters / minutes), which were obtained by means of a system that uses a pump with variable revolutions, electronically controlled. When the graphs are compared, although it is obvious that in the case of a system that uses a pump with variable revolutions, controlled electronically, a better performance is obtained in the case of a system that uses a pump with fixed revolutions, mechanically controlled, it is can see, in terms of the constancy of the V / L ratio, it is not possible by means of this system to completely eliminate the variation of V / L in the field of operation, as shown by the curve averaged to the experimental values obtained in Figure 7. However, this last curve makes it possible to obtain a curve of corrective calibration values that are to be used in the vapor recovery system according to the present invention, in order to linearize the response of the system. Actually, the graph in Figure 8 shows the curve of the corrective factors, where there is variation of the operating point or flow velocity Q, - which can be used in the recovery system according to the invention. In this case, the number of revolutions of the pump used depends on the distributed flow velocity. The large number of points at which the curve can be evaluated (approximately 100) allows the virtually continuous linearization of the system, thereby providing close control of the V / L or L / V ratio throughout the entire field of operation; On the one hand, it can be seen that both conventional recovery systems have serious limits at the extremes of the field of operation (see Figures 6 and 7), limits that can not be corrected under any circumstances except when using a control system of one type non-linear, as previously described. The description provided makes evident the characteristics of the device and method for controlling the recovery of the vapors in fuel distribution columns and makes it clear that the device and method according to the invention have considerable advantages compared to the known technique; at least the following of these deserve mention: - speed of execution; - maximum accuracy of the results; - lower costs, in terms of use, according to the known technique, as a result of the obtained advantages; and - adjustment speed in the solution of the control functions.