SYSTEM FOR ENERGY RECOVERY IN ELECTRIC FANS FOR CAR RADIATORS

Abstract: A system for energy recovery in electric fans of car radiators, which comprises at least one power supply (B), which is connected to an electronic control device (CM), operated by a pilot electronic-box (CC) and coupled to an electric machine (M), able to start at least one cooling fan (V); a pilot circuit being placed between said electronic control device (CM) and said electric machine (M) so that the electric machine (M) may be configured like a motor for the fan of like a controlled generator operated by the fan itself, said electric machine (M) being controlled by an application program for computers able to control the electric machine (M) in function of sizes or parameters inside the system and/or commands outside the system.

Description: SYSTEM FOR ENERGY RECOVERY IN ELECTRIC FANS FOR CAR RADIATORS DESCRIPTION The aim of the present invention is a system for energy recovery in electric fans for car radiators . There is a currently a well-known tendency in the automobile industry to opt for technological solutions which aim at reducing consumption. The aim of the present invention is to use the electric fan group of the radiator to generate electrical energy during the phase in which the electric fan itself is not in use so, on the other hand, the fan is turned by the fluid dynamic energy of the air flow inducted by the engine of the vehicle . Normally, the above-mentioned energy is not used; therefore the fan, when it is not supplied by the electric motor, turns at an extremely fast rate to reach the speed at which is dynamically in equilibrium with the speed of the air. This situation occurs whenever the airflow generated by the vehicle's engine is in itself sufficient to cool the radiator. Even if the amount of energy recuperated is in the order of a few dozen watts, it should be borne in mind that in the context of the overall amount of energy these watts must be multiplied by approximately two in that otherwise said energy will be supplied by the aboard alternator, with an efficiency rate equal to about 50%. The present invention is particularly relevant and interesting when considered in the context of electric fans which are electronically controlled in speed, in that said invention can achieve the aim described above at practically no additional cost, the only addition necessary being to add a management logic function to the control logic function of the machine itself in such a way that it can be made to function as a generator. Toward the attainment of these and additional objects and advantages, which will be better understood later, the invention provides a system for energy recovery in electric fans of radiators, the system comprising at least a power supply, which is connected to an electronic control device, operated by a pilot electronic-box and coupled to an electric machine, able to start at least one cooling fan; the system being characterised by the fact that a pilot circuit is placed between said electronic control device and said electric machine so that the electric machine may be configured like a motor for the fan of like a controlled generator operated by the fan itself, said electric machine being controlled by an application program for computers able to conduct the electric machine in function of sizes or parameters inside the system and/or commands outside the system. The system according to the present invention will now be described in detail with reference to the attached drawings, in which: FIGURE 1 is s block diagram of an electric fan group for a car; FIGURES 2 - 6 are wiring diagrams and diagrams cf the system according to the invention as applied to an electric fan group for a car. Figure 1 illustrates a block diagram of the functional aspects of an electric fan group for a car radiator. A indicates the air flow, v indicates the fan, M indicates the electric machine (motor/generator) , CM indicates the electronic control for the latter, F indicates an electric filter placed between CM and the battery, which is indicated by B, so as to smooth the harmonics of the current, and CC indicates a control unit outside the motor which, acccrdinc to RECTIFIED SHEET (RULE 91) ISA/EP the variables imposed by different car manufacturers (such as air temperature, vehicle speed etc) sends input to CM to control the functions of the fan (ON, OFF, rotation speed etc) . The system configured in Figure 1, where the machine M is operated by CM as a motor only, is one of the well-known systems which is normally in use nowadays. As has previously been explained, with regard to cost, the present invention does not substantially alter the functional blocks shown in Figure 1, but is applied only the form of the block CM which provides for a "bridge" command structure. The present invention provides for, in particular: a) integrating the system with an input logic which permits the transformation of the electric machine generator; b) adding management software for the machine as a generator in the block CM which can, in accordance with the needs of various clients, control the generator at the required speed and limit current flow either to maximum fixed levels or in accordance with the voltage of the battery. RECTIFIED SHEET (RULE 91) ISA/EP It is possible to obtain, by means of this alternative, the automatic control management of the whole of the "braking phenomenon" exercised on the fan turned by the air flow, in such a way as to guarantee maximum energy transference from fluid dynamics to electricity (recharging of the battery) . In the interests of simplicity of description, let us now refer to a motor which functions by electronic switching, the simplest form of which is a single-phase structure. This reference is made solely in the interests of describing the operating principle, taking into account that in reality these kinds of motors would in fact generally be two phase, three phase or five phase. The operating principle described according to the single-phase alternative, however, provides a full explanation of how other machines with more phases function according to current well-known techniques. The basic circuit usually starts from a bridge structure as indicated in Figure 2. The bridge structure provides, in a single phase structure, for four power switches ? x , P 2 , ? 3 , ? 4 , which are fixed to the ends of the supply wires which place a filter CF between the bridge itself and the battery 3, in its simplest form the filter is just a condenser. RECTIFIED SHEET (RULE 91) ISA/EP Inside the bridge is the winding of the machine which as an equivalent network can be expressed as an electromotive force E, a winding resistance Ra and a winding inductance La. When the machine functions as a motor, the control unit CC, which controls the above-mentioned switches, operates according to well-known techniques by switching alternately between two half waves SI and S2 (see Figure 2A) of the electromotive force E, in such a way that, as the voltage supply is unipolar, the sides of the bridge P lf P 4 switch alternately by one half wave, or the sides of the bridge P 2 , P 3 switch alternately when the other half wave is in operation so that one pair in the machine is always active. These components, which in the embodiment in question are normally obtained with Mos, comprise a parasitic component in parallel which is traditionally a diode; in Figure 1 each diode is illustrated in association with a switch indicated by D lf D 2 , D 3 , D 4 . When this machine is used as a generator the switches P x and P 2 are no longer necessary and are in fact turned off by the control unit CC, so that the circuit becomes like the one shown in Figure 3, that is to say that it is simplified into a structure of this kind. There are two upper diodes D x and D 2 , two switches P 3 and P 4 and two other diodes D 3 and D 4 but as we shall see the latter two do not function normally for which reason they could even be omitted from the illustration as they do not take part in the overall operation of the machine. In order to understand what happens, it is sufficient to consider that on the half wave SI, where, for example, the battery voltage is positive, the switch P 3 remains closed during the entire period in which the electromotive force E is positive; during this half period, the node J being earthed, (see Figures 2 and 3) , the diode D x is not in operation, so that it seems that it does not exist. In order to further simplify the functioning on one half wave (it is useless to explain the functioning on the other because it is exactly the same as in this case) , the circuit can be further simplified, we can make reference here to the circuit shown in Figure 4, which provides an immediate visual explanation of what happens. The motor is now shown with the electromotive force E, the inductance La, the resistance Ra, the diode D 2 (the diode D x is not shown because it is no longer of any use) and with the switch P 3 closed (it is shown completely closed, because it remains completely closed throughout the functioning of the half wave) . What happens instead is that the other switch P 4 works by impulse modulation, that is to say that it opens and closes according to a certain duty cycle. The diode D2 acts first on the condenser CF which, in turn, acts on the battery B. What in fact happens during this impulse modulation? The point of the question is how, in fact, the battery B can be charged even though the general electromotive force E of the machine is lower than the battery voltage; for example, at the speed at which the fan is turning, let us assume that the voltage generated inside the electric machine is three volts lower than that of the battery. If the voltage is three times lower, what happens is that when the switch P 4 is closed the voltage will make a current pass into the motor, in its inductance La and its resistance Ra, and this current will charge the inductance with a certain amount of energy which corresponds to the impulse at the level of the current. Figures 5 and 5a illustrate the form of this current 1, according to variations of the charge CB of the battery B, during the ON period Tl and the OFF period T2 respectively. When the switch P is opened, the current that has accumulated energy equivalent to Lai 2 in the inductance La of the machine continues to try and maintain its flow. When the switch P 4 is opened, during the OFF period, the current from the circuit of the switches is set to zero (because it can no longer circulate in this circuit) but it continues to flow during the OFF phase of the circuit regarding the battery. During the period that P 4 is OFF the current which has reached this level suddenly appears via the diode D 2 , according to the well-known function diagram of a step up, and will then appear in the battery circuit. It is obvious that this inductance, over a certain period of time, will tend to reduce the current towards the battery, but at a certain point the switch P 4 will close again; the current in the battery will be reset at zero and from this point the current will reappear in this circuit, which will continue to recharge it . What happens next is that, notwithstanding the fact that there is voltage at the beginning of the generator, a certain average current "levelled" by the condenser of the filter CF is supplied to the battery B. Starting from the loss in the circuit, in principle, the product El at the input, that is to say the average value of the current which is circulating in the generator at four volts, multiplied four times, will be equal to the value of the voltage of the battery multiplied by the average voltage of the current supplied by the battery, less the loss in the circuit. In order that this transferred current can reach maximum level, there is a shunt resistance s (a current sensor) in the battery's return circuit towards the control system, from where the value of the current is taken and integrated via a circuit RC to give the average value IB. Practically, the average value of the current in the battery is obtained, this average value goes to the micro switch which calculates, moment by moment, the average value of the current going to charge the battery in function of the condition of the fan. Figure 4 illustrates, purely as an example, an electrical circuit R r , C j _ of the type RC, via which the values of the currents are integrated over time RECTIFIED SHEET (RULE 91) ISA/EP with the aim of obtaining an average value IB, which is then transferred as input to said electronic control device CM. When the first half wave is finished the Hall sensor, or any other type of Rs sensor which can transmit to the machine that the other half wave is beginning, moves the function to the other half of the machine, which is to say that on the other half wave it will be P 4 which remains closed and P 3 which functions in Pwm, while D 2 will not function any more and D x , instead, will be active in the circuit. As can be seen from the embodiment, the bridge structure is absolutely fundamental so that the machine may effectively function as a generator as well as an electric motor using exactly the same components . In fact, thanks to this structure, no additional power components are added and nothing has been done other than to change the piloting logic of the electric switches. A different software management is, therefore, sufficient so that it can carry out the management of the switching of the machine in such a way that it looks to either the speed of the machine, or the value of the current, and limits it; that is to say, it applies a logic which causes the machine to function as a generator. The machine, instead of being of the single- phase type, can also be a two-phase bridge structure, a three-phase bridge structure, or a five- phase bridge structure. In the case of permanent magnet electronically controlled direct current brush motors (not brushless motors, as have been dealt with up till now) , the same considerations hold good as for the single phase brushless structure with circuit simplification which, being without an alternated F.E.M., only need a semi-bridge structure to achieve the above- mentioned aims, (see Figure 6). In this case when the machine is functioning as a motor P x is impulse controlled while P 2 is OFF, when the machine is functioning as a generator V 1 is OFF and P 2 is impulse controlled. In both cases the loss of voltage on Rf transmits information to the control motor CM concerning the current in the motor for the same reasons as those mentioned above. It should also be mentioned, in conclusion, that the functions of the diodes (D x , D 2 ) can also be carried out by the same switches (P x , P 2 ) being set to the ON position during the time in which it is foreseen that they will act as conductors for the diodes .

Claims: CLAIMS 1. System for energy recovery in electric fans of radiators, the system comprising at least a power supply (B) , which is connected to an electronic control device (CM) , operated by a pilot electronic- box (CC) and coupled to an electric machine (M) , able to start at least one cooling fan (V) ; the system being characterised by the fact that a pilot circuit is placed between said electronic control device (CM) and said electric machine (M) so that the electric machine (M) may be configured like a motor for the fan of like a controlled generator operated by the fan itself, said electric machine (M) being controlled by an application program for computers able to conduct the electric machine (M) in function of sizes or parameters inside the system and/or commands outside the system. 2. System for energy recovery as claimed in Claim 1, characterised by the fact that said pilot circuit has a bridge configuration or semi-bridge configuration comprising at least two electronic power switches (P 3 , P 4 ) and at least two diodes (D x , D 2 ) , said switches (P 3 , P 4 ) and said diodes (O l t D 2 ) being electrically connected to a winding (E, Ra, La) of said electric machine (M) . 3. System for energy recovery as claimed in Claim 2, characterised by the fact that the function of the diodes (D lf D 2 ) can be fulfilled by the same switches (P 1# P 2 ) maintained in the ON position during the time-lag, in which the diodes are estimated to function as conductors . 4. System for energy recovery as claimed in Claim 2, characterised by the fact that said power supply (B) comprises a storage battery, to which at least one filter (CF) is electrically connected in parallel. 5. System for energy recovery as claimed in Claim 4 , characterised by the fact that said filter (CF) is defined by a capacitor. 6. System for energy recovery as claimed in Claim 2, characterised by the fact that, during a first condition of functioning, a first electronic power switch (P lf P 3 ) is closed and a second electronic power switch (P 2 , P 4 ) functions in pulse modulation, said winding (E, Ra, La) being connected to a single electronic parasitic component (D 2 ) . 7. System for energy recovery as claimed in Claims 4 and 6, characterised by the fact that a current sensor device (Rs, Rf) is arranged in sequenze to an impedance defined by a connection parallel to said filter (CF) with said power supply (B) , in such a way that said sensor device (Rs, Rf) can take values of current circulating during the time. 8. System for energy recovery as claimed in Claim 7, characterised by the fact that said values of current are integrated during the time by an electric circuit (R 1# C^ of RC-type, so as to obtain an average value (IB) , said average value (IB) being transferred as input to said electronic control device (CM) . 9. System for energy recovery as claimed in Claim 2 , characterised by the fact that during a second condition of functioning, said first electronic power switch (P x , P 3 ) functions in pulse modulation and said second electronic power switch (P 2 , P 4 ) is closed, said winding (E, Ra, La) being connected to a single electronic parasitic component (D x ) . 10. System for energy recovery as claimed in Claim 2, characterised by the fact that said first and second conditions of functioning are related to relevant positive and/or negative half waves of an electromotive force signal (E) of said electric machine (M) , said conditions being revealed by an electronic sensor, for example a Hall sensor. 11. System for energy recovery as claimed in Claim 1, characterised by the fact that said electric machine (M) is single-phase electronic switching machine, or a two-phase bridge machine, or a three- phase bridge machine, or a five-phase bridge machine. 12. System for energy recovery as claimed in Claim 1, characterised by the fact that said electric machine (M) is defined by a single-phase brushless motor. 13. System for energy recovery as claimed in Claim 1, characterised by the fact that said electric machine (M) is defined by a direct current brush motor with electronically controlled permanent magnets.

Inventors: DE FILIPPIS PIETRO, DEL FAVERO ANGELO, DE FILIPPIS, PIETRO, DEL FAVERO, ANGELO
Applicants: BITRON SPA, DEL FAVERO ANGELO, FILIPPIS PIETRO DE, BITRON S.P.A., DE FILIPPIS, PIETRO, DEL FAVERO, ANGELO
Application year: 1999
Main classification: B60K25
IPC codes: B60K11, B60K25, F01P5, F04D27, H02J7, H02P9