FR3059716A1 - SYSTEM AND METHOD FOR CIRCULATING AN AUXILIARY ACTUATOR FLUID - Google Patents

Abstract

The invention relates to a fluid circulation system comprising an auxiliary actuator adapted to rotate about an axis of rotation (3), the fluid flowing in a complementary circuit of a motor vehicle equipped with an internal combustion engine equipped with a crankshaft (11) for power transmission. This system also comprises the crankshaft (11), a means for rotating (2P) the actuator in a variable drive ratio, this driving means being connected to the crankshaft (11) by a distribution link ( 34). In addition, the circulation system includes a drive ratio selector (16) between the crankshaft and the drive means of the actuator, and a tensioner (17) of the distribution link (34).

Description

Holder (s): PEUGEOT CITROEN AUTOMOBILES SA Société anonyme.

Extension request (s)

Agent (s): PEUGEOT CITROEN AUTOMOBILES SA Public limited company.

{04 / SYSTEM AND METHOD FOR CIRCULATING AN AUXILIARY ACTUATOR FLUID.

FR 3 059 716 - A1 _ The invention relates to a fluid circulation system comprising an auxiliary actuator able to rotate about an axis of rotation (3), the fluid circulating in a complementary circuit of a motor vehicle equipped with an internal combustion engine provided with a power transmission crankshaft (11). This system also comprises this crankshaft (11), a means of rotation drive (2P) of the actuator according to a variable drive ratio, this drive means being connected to the crankshaft (11) by a distribution link ( 34). In addition, the circulation system includes a selector (16) of drive ratio between the crankshaft and the actuator drive means, as well as a tensioner (17) of the distribution link (34).

SYSTEM AND METHOD FOR CIRCULATING AN AUXILIARY ACTUATOR FLUID The invention relates to a system for circulating a fluid by an auxiliary actuator of an internal combustion engine of a motor vehicle, such an actuator generating circulation of a fluid (liquid or gas) in complementary circuits, in particular for lubrication and cooling of the engine. The invention also relates to a fluid drive method using such an actuator.

In the field of complementary circuits of motor vehicles with thermal engine, it is conventional to provide for this engine one or more cooling circuits, air conditioning, lubrication, etc. These complementary circuits put a fluid in circulation generally by activation of an auxiliary actuator: a water or oil pump, a cooling fan for the engine or the passenger compartment of the vehicle, a vacuum pump, an alternator, etc.

The speed of action of these complementary circuits is thus made independent of the speed of rotation of the engine to be adapted to the management of engine components in temperature, pressure or lubrication.

[0004] Thus, in the case of the lubrication of a heat engine, the need for oil pressure of different components fitted to this heat engine is all the higher as the speed of rotation of said engine increases, up to a predefined level. Beyond this level, the components no longer require an additional pressure increase. It is known to provide the oil pump of combustion engines with a pressostatic valve in order to overcome a higher oil pressure than necessary, so as not to harm the reliability of the combustion engine but also d '' maintain fuel consumption.

Similarly, in the case of cooling the heat engine by a heat transfer circuit, the water pump driven in rotation by the engine speed is not an optimal solution because the flow in the heat transfer circuit is then linked to this regime engine and is therefore generally greater than the need required by the heat engine. It is therefore known that the cooling water circulates by means of a water pump driven by an auxiliary motor, making it possible to make the speed of this pump independent of that of the heat engine.

Better control of the temperature, of the pressure or of the lubrication of the components of the heat engine makes it possible to improve the friction as well as the internal combustion, and therefore the efficiency of the engine as well as, consequently, the consumption in fuel. Structures of complementary circuits have therefore been developed, generally based on more complex technologies: oversized and / or hybrid electric pumps with low energy balance (cascade efficiency including electromechanical conversion), variable displacement pumps, multi-channel valves of the heat transfer circuit, solenoid valves or stepper motor, deactivation of internal coolant circulation, continuously variable speed cooling fan, especially with brushless electric motor, etc.

Among the improvements made to these complementary circuits, the document DE 3007640 proposes a water cooling pump for a heat engine, having a conduit with adjustable flow rate. The regulating device comprises an extensible material which, by its variation in volume, controls the spacing of a pulley driving the water pump by belt, which accelerates the flow of water when the temperature of the cooling water increases.

Another document, GB 2003 15700, describes a cooling system driving the water pump independently of the rotation speed of the heat engine. The speed of this water pump, controlled by the crankshaft, includes a clutch fitted with an electronic control module. This module controls clutch engagement based on engine sensor data and is equipped with an auxiliary engine to allow rapid rotation of the water pump if the engine slows down. In particular, if the speed of the heat engine exceeds a certain threshold, the clutch of the water pump partially disengages and the engine of this pump does not rotate above a given value.

Furthermore, document US 2005 090351 describes a system for regulating the speed of the coolant pump of a heat engine, this fluid being driven, via actuators, by a belt and a pulley whose diameter training is variable. The control is done by a fluid temperature sensor and two actuators to accelerate the speed of the fluid if necessary. For example, if the coolant temperature is above a predetermined threshold, the drive diameter of the pulley is reduced, which accelerates the circulation of the coolant.

However, these solutions provide complexity and space, which makes them unreliable and difficult to implement under all covers or in a pre-established engine architecture.

The invention aims to overcome these drawbacks by minimizing the number of equipment, and by making the best use of the functionality of existing equipment. To do this, the invention provides for directly driving the auxiliary actuators by the crankshaft of a heat engine with a suitable drive ratio.

More specifically, the present invention relates to a fluid circulation system comprising at least one auxiliary actuator able to rotate about an axis of rotation, the fluid flowing in a complementary circuit of a motor vehicle equipped with an internal combustion engine fitted with a power transmission crankshaft. This system also comprises this crankshaft and a means for driving the actuator in rotation according to a variable drive ratio, this drive means being connected to the crankshaft by a distribution link. In addition, the circulation system includes a drive ratio selector between the crankshaft and the actuator drive means, as well as a timing link tensioner.

In a preferred embodiment, the internal combustion engine comprising intake and exhaust camshafts provided with connecting pulleys driven by the distribution link which then constitutes a so-called main distribution, the means of actuator drive is connected to the crankshaft and the camshaft connecting pulleys by the main distribution.

According to advantageous embodiments:

the actuator drive means is chosen from a set of at least two integral, coaxial pulleys arranged on the axis of rotation of the actuator, a variable spacing pulley, an epicyclic train, and a variator mechanical speed of toroidal type, disc, friction, roller or equivalent;

- The pulleys of the set of drive pulleys are chosen between toothed pulleys and notched pulleys, these pulleys cooperating with the chosen distribution link between a chain and a belt;

- alternatively, the set of drive pulleys comprises at least two smooth pulleys cooperating with a distribution link constituted by a belt;

the selector comprises an electromechanical converter slaved to information supplied by a data processing unit relating to the operating state of said engine and of the vehicle, the state of the passenger compartment and of additional circuits of the motor vehicle, in particular to a cabin air conditioning system in the case where the vehicle is equipped with such an air conditioning system, and in particular data relating to the thermal state of the powertrain (comprising the engine and its main equipment: power supply, exhaust, cooling, ignition);

the tensioner comprises a idler wheel and an arm of adaptable or fixed length, the idler wheel being driven in rotation by the crankshaft around an axis of rotation, and the arm extending between a first end secured to the axis of rotation of the idler wheel and a second end, this second end can be fixed, in this case the arm has an adaptable length by the integration of at least one return means, or integral with a return means in the case where the arm has a fixed length;

- the arm of adaptable length lengthens, respectively contracts, so as to maintain constant the tension of the chain / timing belt when changing the actuator drive pulley from a given diameter to a diameter lower, respectively upper;

- the arm of adaptable length is a telescopic arm made up of two coaxial cylindrical parts translating one into the other against at least one return spring.

The invention also relates to a motor vehicle equipped with at least one fluid circulation system as defined above.

The invention also relates to a fluid circulation method implementing the fluid circulation system defined above in a motor vehicle, according to the following steps: command this system to carry out a fluid circulation action in a given additional circuit of the vehicle via an auxiliary actuator; determine the value of the adapted training report based on information provided by the processing unit; set the training medium according to the determined training ratio; tension the distribution link, and activate the drive means to circulate the fluid in the complementary circuit at a speed determined by the drive ratio determined for a determined period.

In the present text, identical elements exercising the same function are identified by the same reference sign which refers to the passage (s) of the text which describes it.

Other data, characteristics and advantages of the present invention will appear on reading the following non-limited description, with reference to the appended figures which represent, respectively:

- Figure 1a, a front view of a set of two coaxial drive pulleys along the axis of rotation of an auxiliary actuator, the pulleys having relatively higher and lower diameters, this set of pulleys being part of a circulation system according to the invention;

- Figure 1b, a sectional view of the pulley assembly according to the plane I I of Figure 1a;

- Figure 2a, a schematic front view of an example of a circulation system according to the invention comprising a main timing chain of the crankshaft driving two pulleys of camshafts and the pulley of larger diameter of the set of pulleys according to Figure 1a;

- Figure 2b, the diagram of the circulation system according to Figure 2a in which the main timing chain drives the pulley of smaller diameter of the set of pulleys according to Figure 1a;

- Figure 3, a sectional view of an example of a tensioner arm of adaptable length to maintain the tension of the timing chains of the examples of circulation system of the previous figures;

- Figure 4a, a schematic front view of another example of a circulation system according to the invention comprising a secondary timing chain of the crankshaft driving the pulley of larger diameter of the set of pulleys;

- Figure 4b, the diagram of the system of Figure 4a in which the secondary timing chain drives the pulley of smaller diameter of the set of pulleys, and

- Figure 5, a flow diagram illustrating an example of implementation of the fluid circulation method according to the invention by an actuator driven by the circulation system according to the invention.

Referring to the front view of a set "2P" of two coaxial pulleys 1 and 2 of Figure 1a, these pulleys have an axis of rotation 3 which coincides with the axis of rotation of an actuator , here a pump in an example of a circulation system according to the invention of a coolant for engine cooling. These drive pulleys 1 and 2 are integral and provided with teeth 10 for use with a timing chain. Alternatively, the pulleys 1 and 2 are notched or smooth for use with a timing belt.

Figure 1b shows a sectional view of the pulleys of Figure 1a in the perpendicular plane ll of Figure 1a, this plane containing the axis of rotation 3. This Figure 1b shows that the rotation of the two pulleys 1 and 2 drives that of a pump wheel 5 whose vanes 6 move the fluid in the complementary engine cooling circuit “C”. This rotation is modulated by the value of the drive ratio deduced from the use of one or the other of the drive pulleys 1 and 2 in the circulation setting system, as is apparent from the alternatives described below.

An example of a cooling fluid circulation system 20 in a complementary circuit of a heat engine is presented with reference to the schematic front view of FIG. 2a. This circulation system 20 comprises a crankshaft 11 - the crankshaft of the heat engine - which drives two camshaft pulleys 12 and 13 as well as the pulley 1 of larger diameter of the assembly 2P via a main distribution chain 14. Advantageously in this example, a tensioner roller 15 is also provided on the main distribution chain 14.

In addition, this system 20 comprises, in addition to the set of pulleys 2P, a selector 16 and a tensioner 17. The selector 16 and the tensioner 17 cooperate to put in operational position the drive pulley to be used depending on the adapted reduction value. To this end, the selector 16 is an actuator of the mechanical or electromechanical type, an electromechanical converter in this example, slaved to different information received and processed by a data processing unit (not shown). This information is representative of the state of use of the heat engine and of the vehicle, for the performance of certain services, for example a need for defrosting / demisting or passenger compartment heating, or even the thermal management of the internal combustion engine or more. largely from the powertrain.

This selector 16 includes a movable fork (not shown) through which the distribution chain 14 passes. The selector fork 16 moves laterally to guide the distribution chain 14 from one drive pulley to the other 2P pulley assembly. The selector is of the speed selector type of two wheels, motorcycle, scooter or bicycle.

The timing chain 14 passes from the larger diameter drive pulley 1 of Figure 2a to the smaller diameter drive pulley 2, as shown in the sectional view of Figure 2b. This FIG. 2b takes up the view of FIG. 2a with the tension of the timing chain 14 being maintained, the length of the chain being constant, by the intervention of the variable length arm 19 of the tensioner 17.

The axis 3 of the pulleys 1 and 2 then rotates faster than in the case of Figure 2a. And when the timing chain 14 returns from the driving pulley of smaller diameter 2 to the driving pulley of larger diameter 1, the selector 16 controls the fork so as to return to the configuration of FIG. 2a.

The tensioner 17 is provided with a idler gear 18 of the free wheel type (or a smooth or notched idler wheel, in the case of use with a timing belt) called, driven in rotation by the timing chain 14. A first end of the arm 19 is connected to the axis of rotation Ax of the idler wheel 18, while its second end is fixed, for example secured to the engine block in the exemplary embodiment.

An example of a variable length tensioner arm 19 of the "telescopic" type is illustrated by the sectional view of FIG. 3. The arm 19 consists of a piston 41, internally hollow, moving within and outside a body 42 against a first return spring 43. The internal faces of the body 42 and of the piston 41 delimit in the internal volume a chamber "H" in which there is a pressure, an oil pressure of lubrication in the example illustrated. The control of the arm 19 is then of the hydraulic type. The first end E1 of the arm 19, on the side of the piston 41, carries the idler wheel 18 (cf. FIGS. 2a and 2b). The second end E2 of the arm 19 is fixed and connected to a lubrication duct 44 intended to supply this arm 19 with lubricating oil.

A non-return valve consisting of a ball 45 blocks the lubrication duct 44 by means of a second spring 46. In the event of wear of the timing chain 14, or of micro-detents due to a drop of the torque to be transmitted, or when the device transits from the meshing of the pulley 1 of larger diameter to the pulley 2 of smaller diameter, the piston 41 leaves the body 42: the chamber "H" is then slightly depression, which causes the non-return valve 45 to rise, and the internal volume “H” is then filled with an additional oil. If the chain 14 (cf. FIGS. 2a and 2b) undergoes a microtension or when the circulation system transits from the meshing of the drive pulley of smaller diameter 2 to that of larger diameter 1, the piston 41 is folded within of the body 42 against the return spring 43 and the non-return valve 45, pressed against the opening of the lubrication duct 44, prevents the return of oil in the lubrication circuit of the arm 17.

In this case of operation, and in order to overcome an excessive pressure within the chamber "H", a pressostatic valve can be advantageously located either in the body 42, for example arranged in parallel with the valve non-return 45, or at the piston 41, for example at its end connected to the axis of rotation Ax of the idler wheel 18. Whatever one or the other of the locations, this pressostatic valve allows to release the passage to oil when the pressure in the chamber "H" exceeds a given threshold.

According to an alternative embodiment, the tensioner arm comprises a body of fixed length extended by a return spring and connected to the idler wheel 18. The tensioner 17 then acts passively when the selector switches from the selection of one pulley to another.

Figure 4a shows a schematic front view of another example of a fluid circulation system 30 according to the invention. In this system 30, the engine crankshaft 11 rotates the pulley 1 of larger diameter of the assembly 2P via a belt (or alternatively a chain) of secondary distribution 34, the crankshaft 11 driving the camshafts 12 and 13 via the timing belt or chain 14 as in the previous embodiment example. The selector 16 and the tensioner 17 also function as in the first embodiment (cf. FIGS. 2a and 2b) by applying here to the secondary distribution chain 34 and not to the main distribution chain 14.

Figure 4b shows the schematic view of Figure 4a in which the secondary timing chain 34 drives the pulley of smaller diameter 2 after intervention of the selector 16. In this case, the axis 3 rotates faster than in the case where the pulley of greater diameter 1 is driven (cf. FIG. 4a) and, the length of the belt or of the secondary timing chain 34 being constant, the arm 19 of the tensioner 17 lengthens to keep the chain tension constant secondary distribution 34. The change of drive pulley is of course reversible by the intervention of the selector 16 according to an inverted kinematics. The chain tension is adapted by a return of the tensioner arm 19 according to a reduced length conforming to that of FIG. 4a.

The flow diagram of FIG. 5 illustrates an implementation of the method according to the invention of circulation of a fluid of a circuit complementary to a heat engine of a motor vehicle. Circulation is carried out using a fluid circulation system according to the invention such as those described above, for example system 30.

This method is then implemented according to the following steps. Following the information provided by the electromechanical converter, an "activation" command is carried out in step 50 by the processing unit "U" to the circulation system 30 to activate a circulation of fluid in the complementary circuit "C> > (see Figure 1b) of the vehicle via an auxiliary actuator, an engine cooling pump in the example.

The next step 51 relates to the determination of the value “R _o ” of the drive ratio (cf. FIG. 4a) corresponding to the speed of the fluid established by the processing unit from the information provided. The value "R _o " covers the value "0" for cutting the fluid flow corresponding to the stopping of the drive by the actuator, regardless of the circulation system 20 or 30.

Then, step 52 consists in adjusting "ADJUST" the drive means corresponding to this drive ratio, for example the drive pulley chosen between the pulley 1 or the pulley 2 (cf. FIG. 4a or 4b) using the selector 16. Then step 53 "TENSION" consists in activating the tensioner 17 so that the distribution link 34 (cf. FIG. 4a) is kept taut.

Step 54 relates to the activation of the drive pulley selected by the crankshaft 11 via the distribution link 34 during a training period "DELAY". this duration corresponds to the duration of circulation of the fluid in the complementary circuit "C" at the speed determined from the drive ratio "Ro". The duration is counted down upon activation (step 50) and a deactivation command (arrow "DISABLED") is transmitted to the processing unit "U" as soon as this duration has expired.

The invention is not limited to the embodiments described and shown.

For example, the selector 16 can be advantageously controlled by any type of information representative of the use of the heat engine (speed, load, operation in the EGR exhaust gas recirculation zone requiring cooling of the exchanger and the associated valve, etc.) and the vehicle (speed, position and position variation of the accelerator pedal, information representative of the driver's desire / start-up state couple: first start or restart, etc.).

Thus, in the case where the auxiliary actuator is a coolant pump of the heat engine, the circulation of liquid within the engine and its heat transfer circuit is deactivated, whenever possible, in phase temperature rise of the powertrain and in particular of the heat engine.

Then, the circulation of coolant within the heat engine and its heat transfer circuit is preferably restored, depending on the operating point requested, characterized in rotation and load of the heat engine, driving the pulley more large diameter in order to achieve the lowest drive ratio and thus reduce, at a given engine speed, the speed of the pump, the flow rate and the pressure jump it provides, at least for one predetermined minimum duration in particular in order to homogenize the circulation of heat-transfer fluid within the whole of the cooling circuit then implemented and to make the fluid temperature measurements robust.

The minimum drive ratio is advantageously maintained as long as the need for thermal management of the powertrain is satisfied (water and engine oil cooling, passenger compartment heating, EGR gas cooling, thermal management of the transmission oil, etc. .). In the opposite case (for example in the event of insufficient interior heating or cooling of the EGR gases, or of significant stress in speed and under load of the heat engine), the device adopts one or more higher drive ratios to then increase , at a given engine rotation speed, the rotation speed of the pump and thus the flow of coolant it provides.

In the case where the auxiliary actuator is a coolant pump for the heat engine, generally a water pump, the advantages associated with temporarily cutting off the circulation of coolant within the internal combustion engine and of its heat transfer circuit are known. In the context of the present invention, the deactivation of the water pump can be carried out by means of its drive by the heat engine in several ways, described below.

Referring to Figures 1b and 4a, the water pump 5 is equipped with an additional pulley mounted coaxially with the axis 3 of the pump 5 but not causing it: this additional pulley is thus mounted idle on the axis 3 of the water pump 5. The latter then not being driven by the secondary distribution chain 34, the circulation of coolant within the engine and its coolant circuit is inhibited when the selector 16 positions the timing chain 34 on this pulley.

According to an alternative, a clutch is disposed between the axis 3 of the water pump 5 and one of the pulleys 1 or 2, or between the crankshaft 11 and the pulley which is associated with it. When this clutch (hydraulic, pneumatic, electric or electromagnetic) is open, the water pump is not rotated: the circulation of coolant within the heat engine and its coolant circuit is then inhibited. Closing the clutch establishes the mechanical connection between the pulley 1 or 2 and the axis 3 of the water pump 5: the circulation of coolant is then restored within the heat engine and its coolant circuit.

In addition, it is possible to provide more than two pulleys in order to increase the number of drive reports while also containing the impacts of the space required.

Furthermore, it is possible to associate an additional toothed (or toothed) wheel with the crankshaft in order to enrich the number of possible drive reports for the actuator.

These additional toothed or toothed wheels are arranged both coaxially with the crankshaft 11 and coaxially with the auxiliary actuator. Thus, if N is the number of wheels arranged coaxially to the crankshaft 11 and M the number of wheels arranged coaxially to the auxiliary actuator, are thus available up to NxM drive ratios between the crankshaft 11 and the auxiliary actuator.

Another alternative to increase the number of drive ratios is to make it continuously variable by replacing the set of 2P pulleys for example by a pulley having two opposite conical grooves called "variable spacing" to accommodate a link distribution constituted by a belt.

Another alternative consists of a toroidal speed variator instead of a belt or a secondary distribution chain 34, movable rollers being pressed between two coaxial discs drawing a torus, or disc type friction or roller.

It is also possible to use a speed variator with planetary gear, for example with biconical rollers or balls, or a set of drive pinions to achieve a variable drive ratio. With these other drive means, the selector acts on the distance between the rollers or sets the train to the desired speed.

The implementation of a variable speed drive thus allows an infinite number of drive ratios between the rotation regimes of the heat engine and of the auxiliary actuator, thus making it possible to continuously optimize the operating point of the actuator (for example, in the case of a pump, characterized in flow and pressure jump) as a function of that of the heat engine (in particular characterized by its rotation speed) while remaining independent thereof. As a variant, the drive ratio can also take a defined number of predetermined discrete values, for example by causing the drive actuator to take the associated fixed positions.

Furthermore, the adaptable arm 19 of the tensioner 17 has a fixed end and a free end so that the arm 19 rotates around the fixed end against a spiral return spring. According to another alternative, the arm 19 has a fixed length and its end which is not linked to the idler 18 is no longer fixed. Thus, it is then possible for the arm 19 to turn around this end against a helical return spring, for the same purpose of maintaining the tension of the chain or of the timing belt.

In addition, the control of the length variation of the arm can be pneumatic, in this case via the vacuum network supplied by the mechanical vacuum pump (then coupled to the heat engine and driven by its rotation), or electric. In addition, the idler wheel 18 can be replaced by a roller or by a guide.

Claims (10)

1. Fluid circulation system (20, 30) comprising at least one auxiliary actuator able to rotate about an axis of rotation (3), the fluid circulating in a complementary circuit (C) of a motor vehicle equipped with an internal combustion engine provided with a power transmission crankshaft (11), characterized in that this system also comprises this engine power transmission crankshaft (11), a means of rotation drive (2P) of the actuator according to a variable drive ratio, this drive means being connected to the crankshaft (11) by a distribution link (14, 34), a selector (16) of drive ratio between the crankshaft (11) and the actuator drive means, as well as a tensioner (17) of the distribution link (14, 34). 2. Fluid circulation system according to claim 1, in which the internal combustion engine comprising intake and exhaust camshafts provided with connection pulleys (12, 13) driven by the distribution link (14 ) which then constitutes a so-called main distribution, the actuator drive means is connected to the crankshaft (11) and to the connecting pulleys (12, 13) by the main distribution. 3. Fluid circulation system according to any one of the preceding claims, in which the drive means is chosen from an assembly (2P) of at least two integral pulleys (1,2), coaxial and arranged on the axis of rotation of the actuator (3), a pulley with variable spacing, a planetary gear and a mechanical speed variator. 4. Fluid circulation system according to claim 3, in which the pulleys of the drive pulley assembly (2P) are chosen between toothed pulleys and notched pulleys (1,2), these pulleys cooperating with the link. distribution (14, 34) chosen between a chain and a belt. 5. Fluid circulation system according to claim 3, in which the set of drive pulleys (2P) comprises at least two smooth pulleys cooperating with a distribution link (14, 34) constituted by a belt. 6. Fluid circulation system according to any one of the preceding claims, in which the selector (16) comprises an electromechanical converter slaved to information supplied by a data processing unit relating to the operating state of said engine and of the vehicle, in the state of the passenger compartment and of additional circuits of the motor vehicle. 7. Fluid circulation system according to any one of the preceding claims, in which the tensioner (17) comprises a idler wheel (18) and an arm of adaptable length (19) by the integration of at least one means of reminder (43), the idler wheel (18) being rotated by the crankshaft (11) about an axis of rotation (Ax), and the arm extending between a first end (E1) integral with the axis of rotation (Ax) of the idler wheel (18) and a second fixed end (E2). 8. Fluid circulation system according to any one of claims 1 to 6, in which the tensioner (17) comprises a idler wheel (18) and an arm of fixed length, the idler wheel (18) being rotated by the crankshaft (11) around an axis of rotation (Ax), and the arm extending between a first end (E1) secured to the axis of rotation (Ax) of the idler wheel (18) and a second end (E2) secured to a return means. 9. Motor vehicle, characterized in that it comprises at least one fluid circulation system according to any one of the preceding claims. 10. A method of circulating fluid in a motor vehicle implementing the fluid circulation system as defined according to any one of claims 1 to 8, characterized in that it comprises the following steps: ordering (step 50) to this system a fluid circulation action in a given complementary circuit of the vehicle via an auxiliary actuator; determining (step 51) the value (R _o ) of the adapted drive ratio as a function of information supplied by the processing unit (U); adjust the drive means (P2) (step 52) according to the determined drive ratio (R _o ); tension (step 53) the distribution link (14, 34), and activate (step 54) the drive means (P2) to circulate the fluid in the circuit 5 complementary to a speed determined by the determined drive ratio (R _o ) for a determined duration. E2 45 46