DESCRIPTION

TECHNICAL FIELD

[0001] The invention relates to the field of cooling circuits for vehicles, in particular motor vehicles.

TECHNICAL BACKGROUND

[0002] Conventionally, a cooling circuit for a motor vehicle, such as that shown in figure 1, comprises in particular at least one pump 12 ensuring the circulation of a cooling liquid, such as water, in the cooling circuit.

[0003] A cooling circuit may also comprise a reservoir 10 of cooling liquid, a heat exchanger 14 and at least one element 16 to be cooled, such as an engine of the vehicle.

[0004] The element 16 is equipped with a temperature sensor 20 of which the signals are transmitted to a control unit 18 for controlling a proportional valve 22 that makes it possible to regulate the flow rate of cooling liquid leaving the pump 12 and supplying the heat exchanger 14.

[0005] In the current state of the art, the pump 12 is a centrifugal pump, meaning that it is a pump of which the rotor is formed by a bladed impeller that is configured to draw liquid in via the center and deliver it via its periphery. The flow rate of cooling liquid at the outlet of the pump depends on the speed of rotation of the impeller but is not always constant, and it is therefore necessary to combine the proportional valve 22 mentioned above with this type of pump. Furthermore, there is a period of latency between a centrifugal pump being stopped and the flow rate at the outlet of the pump becoming zero. In the case in which the circuit comprises other (auxiliary) pumps, these pumps are also centrifugal pumps.

[0006] The present invention proposes a refinement to this technology. SUMMARY

[0007] The invention relates to a cooling circuit for a vehicle, in particular a motor vehicle, this circuit having a pump having at least one rotor that is driven in rotation by a motor and configured to force the circulation of cooling liquid in the circuit, characterized in that said at least one rotor comprises at least one driving screw that is driven by said motor, and at least one driven screw that is driven by said at least one driving screw, the driving screw(s) and driven screw(s) being configured to force the circulation of cooling liquid in the circuit.

[0008] One of the advantages of a screw pump is that it makes it possible to provide a flow rate at the outlet that is proportional to the speed of rotation of the motor and becomes zero as soon as the pump is stopped. In the context of the use of a screw pump in a cooling circuit, it is therefore understood that it would be conceivable to omit the proportional valve that is necessary when using a centrifugal pump. Furthermore, another advantage is linked to the small bulk of a screw pump relative to a centrifugal pump. The power of a screw pump can for example be optimized by adapting the length, the diameter and/or the number of the screws, whereas the power of a centrifugal pump can be optimized only by the diameter and the thickness of its impeller. It would furthermore be advantageous to use in the pump screws that are not made of metal but are rather made of plastic or composite material, in order to reduce the weight of the pump and make these screws easier to produce, for example by injection molding.

[0009] The number of driving screws and driven screws is nonlimiting and is determined in accordance with the requirements in terms of flow rate at the outlet of the pump in particular.

[0010] The circuit may comprise one or more of the following features, taken in isolation from one another or in combination with one another:

- the circuit comprises one driving screw that is aligned with a shaft of the motor, and one or more driven screw(s) that extend parallel to the driving screw and are meshed with this driving screw, - the circuit comprises two driving screws that are parallel to a shaft of the motor and driven by the latter by means of a gear train, and driven screws that extend parallel to the driving screws and are meshed with these driving screws,

- the number of driving screw(s) and driven screw(s) of the pump is between 2 and 16; however this number is nonlimiting, the number of driving screws is for example between 1 and 4 and the number of driven screws is for example between 1 and 4 for each of the driving screws,

- the driving screw(s) and driven screw(s) are mounted and guided in rotation in cylindrical recesses of a single fixed body of the pump,

- the fixed body is mounted at one end of the motor,

- the screws are made of plastic or composite material,

- the pump is fastened to a reservoir of cooling liquid,

- the circuit has a heat exchanger, at least one element to be cooled and a temperature sensor for this device, the circuit having no proportional valve and said pump being configured so as to be controlled by a control unit in accordance with signals emitted by said temperature sensor.

[0011] The present invention also relates to a vehicle, in particular a motor vehicle, having at least one circuit as described above.

BRIEF DESCRIPTION OF THE FIGURES

[0012] Other features and advantages of the invention will become apparent while reading the following detailed description, for the understanding of which reference will be made to the appended drawings, in which:

[0013] Figure 1 is a schematic view of a vehicle cooling circuit,

[0014] Figure 2 is a schematic view of a vehicle cooling circuit, according to one embodiment of the invention, [0015] Figure 3 is a schematic perspective view of a reservoir of cooling liquid equipped with a screw pump,

[0016] Figure 4 is an exploded schematic perspective view of a first embodiment of a screw pump,

[0017] Figure 5 is an exploded schematic perspective view of a second embodiment of a screw pump,

[0018] Figure 6 is an exploded schematic perspective view of a third embodiment of a screw pump.

DETAILED DESCRIPTION

[0019] Figure 1 has been described above.

[0020] Figure 2 illustrates a cooling circuit 24 within the meaning of the invention. This circuit 24 comprises at least one screw pump 26. The circuit 24 also comprises a reservoir 10 of cooling liquid.

[0021] The screw pump 26 and the reservoir 10 may be two separate elements connected by at least one pipe, or they may be mounted on one another as in the example in figure 3 in which the pump 26 is fastened directly to the reservoir 10.

[0022] It is understood that the pump 26 comprises an inlet 26a connected to the reservoir 10 or opening into this reservoir, and an outlet 26b.

[0023] The screw pump 26 is connected to a heat exchanger 14 and to an element 16 to be cooled. The outlet 26b of the pump 26 is connected to an inlet 14a of the exchanger 14 of which an outlet 14b is connected to an inlet 16a of the element 16. This element 16 comprises an outlet 16b connected to the inlet 26a of the pump 26 or to the reservoir 10.

[0024] The element 16 is equipped with a temperature sensor 20 of which the signals are transmitted to a control unit 18 for controlling the screw pump 26 in order to regulate the flow rate of cooling liquid leaving the pump 26 and supplying the heat exchanger 14. [0025] A screw pump 26 comprises at least one driving screw that is driven by a motor, and at least one driven screw that is driven by the driving screw(s), the driving screw(s) and driven screw(s) being configured to force the circulation of cooling liquid in the circuit.

[0026] Figures 4 to 6 illustrate exemplary embodiments of a screw pump 26.

[0027] In the embodiment in figure 4, the pump 26 comprises one driving screw 28 and one driven screw 30. The driving screw 28 has an elongate shape and comprises an end connected to a drive shaft 32 of the motor 33, which is for example an electric motor.

[0028] The screw 28 comprises a helicoidal thread that extends substantially over its entire length. The screw 28 is housed in a central first recess 34 of a cylindrical body 36 of the pump 26.

[0029] The driven screw 30 has an elongate shape and extends alongside the driving screw 28, parallel thereto. The screw 30 comprises a helicoidal thread that extends substantially over its entire length and is complementary to that of the screw 28, so that the screws are meshed and the screw 30 is driven in rotation by the screw 28, which is itself driven in rotation by the shaft 32.

[0030] The screw 30 is housed in a lateral second recess 38 of the body 36. The recesses 34, 38 communicate with one another, as illustrated in the drawing.

[0031] The body 36 is fastened to one end of the motor 33, and comprises for example at one axial end an annular fastening flange 36a.

[0032] In the embodiment in figure 5, the pump 26 comprises one driving screw 28 and three driven screws 30. The driving screw 28 has an elongate shape and comprises an end connected to the drive shaft 32 of the motor.

[0033] The screw 28 comprises a helicoidal thread that extends substantially over its entire length. The screw 28 is housed in a central first recess 34 of a cylindrical body 36 of the pump 26. [0034] The driven screws 30 each have an elongate shape and extend alongside the driving screw 28, parallel thereto. They are regularly spaced apart from one another around the screw 28. Each screw 30 comprises a helicoidal thread that extends substantially over its entire length and is complementary to that of the screw 28, so that the screws are meshed and so that each screw 30 is driven in rotation by the screw 28, which is itself driven in rotation by the shaft 32.

[0035] The screws 30 are housed in lateral recesses 38 of the body 36. The recesses 34, 38 communicate with one another, as illustrated in the drawing.

[0036] The body 36 is fastened in a cowling 40 that is fastened to one end of the motor. This cowling 40 defines the inlet 26a and the outlet 26b of the pump 26.

[0037] In the embodiment in figure 6, the pump 26 comprises two driving screws 28 and two driven screws 30. Each driving screw 28 has an elongate shape and comprises a helicoidal thread that extends substantially over its entire length. The driving screws 28 are disposed in parallel and side by side, and are housed in first recesses 34 of the body 36.

[0038] Each screw 28 bears a pinion 42 at one axial end. A toothed wheel 44 is disposed between the pinions 42 that are secured to the screws 28, and is meshed with these pinions so as to form a gear train. The toothed wheel 44 is mounted on the drive shaft of the motor (not visible) and drives the screws 28 by means of the pinions 42.

[0039] The driven screws 30 each have an elongate shape and extend alongside the driving screws 28, parallel thereto. The axes of rotation of the screws 28, 30 are parallel and are situated for example at four comers of a parallelepiped.

[0040] Each screw 30 comprises a helicoidal thread that extends substantially over its entire length and is complementary to that of the screw 28, so that the screws are meshed and so that each screw 30 is driven in rotation by one of the screws 28.

[0041] The screws 30 are housed in lateral recesses 38 of the body 36. The recesses 34, 38 communicate with one another, as illustrated in the drawing. [0042] As in the preceding embodiment, the body 36 is mounted in a cowling 40 that is fastened to one end of the motor. This cowling 40 defines the inlet and the outlet 26b of the pump 26.

[0043] In the various embodiments described above, the screws 28, 30 are advantageously made from plastic or composite material. They are for example produced by injection molding, which makes it possible to have screws with complex shapes at a relatively limited cost.

[0044] The invention affords a number of advantages, such as one or more of the following:

- the reduced cost of a screw pump, in particular by using inj ected-plastic screws;

- a current consumption of the motor 33 that is proportional to the flow rate of the pump 26; this allows energy to be saved relative to a centrifugal pump when a low flow rate of liquid is necessary;

- the screw pump 26 allows the circulation of liquid in the circuit to be stopped when the motor 33 is not in operation; this may for example allow a valve for closing the circuit of the prior art to be omitted;

- the flow rate of the pump is directly proportional to the speed of rotation of the motor; the pump can be directly controlled in accordance with the temperature of the element to be cooled 16;

- the transfer of liquid can take place in both directions and depends on the direction of rotation of the motor; whereas in a centrifugal pump the liquid can only travel in one direction;

- the screw pump has a better hydraulic efficiency; this means that the current consumption is lower for the same volume of liquid transferred;

- the screw pump allows a higher pressure to be obtained relative to a centrifugal pump, regardless of the speed of its rotor; - the screw pump provides a flow rate of liquid at the outlet that is proportional to the speed of rotation of the motor;

- there is no cavitation phenomenon in a screw pump; and

- the screw pump is relatively compact and is easy to incorporate into a reservoir of cooling liquid.