Screw pump and a cooling circuit of a vehicle presenting such a pump

Abstract

Screw pump (26), in particular for a cooling circuit (24) of a vehicle, this screw pump comprising: - screws (28, 30) meshed with each other and of which at least one (30) is rotatable about a first axis (B) and configured to force the circulation of liquid from the inlet to the outlet, when the screw rotates about this first axis (B), and - an electric motor (32) for rotating said at least one rotating screw, this motor comprising: - a cylindrical rotor (33) which extends about a second axis (B) as well as about said screws (28, 30), and - electric coils (32a) arranged about the second axis (A) and about said rotor and configured to be electrically supplied in order to drive said rotor in rotation about the second axis (A).

Description

Technical field of the invention

[0001] The invention relates to the field of screw pumps and cooling circuits for vehicles, in particular automobiles. Technical background

[0002] Typically, a cooling circuit for a motor vehicle, such as that shown in Figure 1 , comprises a pump 12 ensuring the circulation of a cooling liquid, such as water, in the cooling circuit.

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

[0004] The element 16 is equipped with a temperature sensor 20 whose signals are transmitted to a unit 18 for controlling a proportional valve 22 making it possible to regulate the flow of coolant leaving the pump 12 and supplying the heat exchanger 14.

[0005] In the current technique, the pump 12 is a centrifugal pump, that is to say it is a pump whose rotor is formed by a vaned impeller configured to suck liquid through the center and to discharge it through its periphery. The flow rate of coolant at the outlet of the pump depends on the rotation speed of the impeller but is not always constant and it is therefore necessary to associate with this type of pump the aforementioned proportional valve 22. Furthermore, there is a latency time between the stopping of a centrifugal pump and the cancellation of the flow rate at the outlet of the pump. In the case where the circuit includes other (auxiliary) pumps, these pumps would also be centrifugal pumps. EP 2 336 590 A2 describes a cooling circuit for a vehicle using a screw pump. DE 37 01 586 A1 shows a screw pump.

[0006] The present invention provides an improvement to this technology. Summary of the invention

[0007] The invention relates to a cooling circuit for a vehicle, in particular a motor vehicle, this circuit comprising a screw pump according to claim 1. This screw pump comprising: a liquid inlet, a liquid outlet, screws meshed with each other and at least one of which is rotatable about a first axis and configured to force the circulation of liquid from the inlet to the outlet, when the screw rotates about this first axis, and an electric motor for rotating said at least one rotating screw, characterized in that the motor comprises: a cylindrical rotor which extends around a second axis as well as around said screws, this rotor being made of ferromagnetic material or comprising elements in this material, and being movable in rotation around the second axis, the first and second axes being parallel, and electrical coils arranged around the second axis and said rotor and configured to be electrically powered in order to rotate said rotor around the second axis, said screws comprising: a fixed screw extending on and along the second axis, in said rotor, and said at least one rotating screw which extends in said rotor and which is rotated around its respective first axis as well as around the second axis, by the rotor which rotates around the second axis and the fixed screw.

[0008] The invention thus provides an optimized screw pump, and in particular one with optimized size. Mounting the screws inside the motor rotor is particularly advantageous for limiting the axial size of the pump (compared to a pump in which the screws would extend in the axial extension of the motor rotor). The screw pump can be used in any application and is particularly advantageous for its use in a motor vehicle, for example to ensure the circulation of a coolant in a cooling circuit.

[0009] One of the advantages of a screw pump is that it provides an output flow proportional to the engine rotation speed and which is cancelled as soon as the pump is stopped. When using this screw pump in a cooling circuit, it is therefore understandable that it would be possible to eliminate the proportional valve required when using a centrifugal pump. Furthermore, another advantage is linked to the small size of a screw pump compared to a centrifugal pump. The power of a screw pump can, for example, be optimized by adapting the length, diameter and / or number of screws, whereas the power of a centrifugal pump can be optimized only by the diameter or thickness of its impeller.It would also be advantageous to use screws in the pump that are not made of metal but rather made of plastic or composite material, in order to reduce the weight of the pump and facilitate the production of these screws, for example by injection molding.

[0010] The number of screws is not limiting and is determined according to the needs in terms of flow rate at the pump outlet in particular.

[0011] The circuit may include one or more of the following features, taken in isolation from each other or in combination with each other: the rotor comprises a body made of ferromagnetic material or comprising elements in this material, as well as two discs fixed respectively to the axial ends of the body; each of the discs comprises housings for mounting and / or guiding axial ends of at least some of said screws; the pump comprises at least two or three rotating screws regularly distributed around the second axis and inside said rotor; the body comprises a central cylindrical housing crossed by said fixed screw, and cylindrical lateral housings communicating with the central housing and crossed respectively by said rotating screws; the rotor is clamped between two flanges, a first of which defines said inlet, and a second of which defines said outlet; said inlet and outlet are coaxial;each of the flanges comprises a first element configured to cooperate with a complementary element of one end of the fixed screw, in order to immobilize the latter in rotation about the second axis; each of the flanges comprises an orifice configured to cooperate by complementary shapes with the corresponding end of the fixed screw, in order to immobilize the latter in rotation about the second axis; the number of driving and driven screws of the pump is between 2 and 16; this number is however not limiting, 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 screws are made of plastic or composite material; the pump is fixed on a coolant reservoir.

[0012] The present invention also relates to a cooling circuit for a vehicle, in particular an automobile, this circuit comprising a screw pump as described above.

[0013] The circuit may further comprise one or more of the members chosen from: a coolant reservoir, a heat exchanger, at least one element to be cooled and a temperature sensor of this equipment, the circuit being devoid of a proportional valve and said pump being configured to be controlled by a control unit according to signals emitted by said temperature sensor.

[0014] The present invention also relates to a vehicle, in particular a motor vehicle, comprising at least one pump or circuit as described above. Brief description of the figures

[0015] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: [ Fig. 1 ] there Figure 1 is a schematic view of a vehicle cooling circuit, [ Fig. 2 ] there Figure 2 is a schematic view of a cooling circuit of a vehicle, according to one embodiment of the invention, [ Fig. 3 ] there Figure 3 is a schematic perspective view of a coolant reservoir equipped with a screw pump, [ Fig. 4 ] there Figure 4 is an exploded perspective schematic view of one embodiment of a screw pump, [ Fig. 5 ] there Figure 5 is a schematic perspective view with partial cutaway of the screw pump of the Figure 4 , [ Fig. 6 ] there Figure 6is another schematic view in perspective and with partial tearing of the screw pump of the Figure 4 , [ Fig. 7 ] there Figure 7 is a schematic axial sectional view of the screw pump of the Figure 4 , And [ Fig. 8 ] there figure 8 is another schematic cross-sectional view of the screw pump of the Figure 4 . Detailed description of the invention

[0016] There Figure 1 has been described in the above.

[0017] There Figure 2 illustrates a cooling circuit 24 within the meaning of the invention. This circuit 24 comprises at least one screw pump 26 which is associated with a coolant reservoir 10 in the example shown.

[0018] 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 top of each other as in the example of the Figure 3 where the pump 26 is fixed directly to the tank 10.

[0019] 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.

[0020] 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, an outlet 14b of which 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.

[0021] The element 16 is equipped with a temperature sensor 20, the signals from which are transmitted to a unit 18 for controlling the screw pump 26 in order to regulate the flow of coolant leaving the pump 12 and supplying the heat exchanger 14.

[0022] A screw pump 26 comprises screws, at least one of which is driven, directly or indirectly, by a motor, the rotating screw(s) being configured to force the circulation of coolant in the circuit 24.

[0023] A screw, whether fixed or rotating, has an elongated shape and a helical thread that extends substantially along its entire length. The screws run alongside and parallel to each other. The screw threads are complementary and mesh with each other, with the threads of rotating screws being configured to force the flow of liquid along the screw. Naturally, the direction of liquid flow depends on the direction of rotation of the screw, which depends on the direction of the motor's supply current.

[0024] The screws 28, 30 are advantageously made of plastic or composite material. They are for example made by injection molding, which makes it possible to have screws of complex shape at a relatively limited cost.

[0025] THE figures 4 to 8 illustrate an embodiment of a screw pump 26 according to the invention.

[0026] The pump 26 comprises a fixed central screw 28 and three rotating lateral screws 30 in the example shown, although these respective numbers are not limiting.

[0027] The pump 26 further comprises an electric motor 32 which is here of the BLDC type (acronym for the English Brushless Direct Current ).

[0028] The motor 32 comprises fixed electric coils 32a and a rotor 33 made of ferromagnetic material or carrying elements 33a in this material.

[0029] The rotor 33 extends along and around an axis A, which is the main axis of the screw pump 26. As seen in the drawings, the inlet 26a and outlet 26b of the pump 26 are coaxial and centered on this axis A.

[0030] The rotor 33 comprises a body 33b as well as two discs 33c fixed respectively to the axial ends of the body 33b.

[0031] The body 33b comprises a central housing 34 of cylindrical shape and axis A. The body 33b further comprises cylindrical lateral housings 36 extending parallel to the axis A. The figure 8 allows us to see that the housings 36 are regularly distributed around the central housing 34 and the axis A, and open into the central housing 34.

[0032] These housings 34, 36 are closed at their axial ends by the discs 33c, which are attached and fixed to the body 33b, for example by screws or the like.

[0033] There Figure 6in particular allows us to see that the body 33b comprises at its external periphery recesses for receiving the ferromagnetic elements 33a. These elements 33a are for example three or more in number and are regularly distributed around the axis A.

[0034] The coils 32a are arranged around the rotor 33 and the axis A. For example, there are three or more of them and they are regularly distributed around the axis A.

[0035] The coils 32a may extend along the axis A over a distance L1 representing at least 80% of the length L2 of the rotor 33.

[0036] According to a characteristic of the invention, the screws 28, 30 are housed in the rotor 33 and pass axially through this rotor 33.

[0037] The screw 28 is fixed and extends on and along the axis A, inside the aforementioned central housing 34.

[0038] The other screws 30 are rotatable and extend parallel to the axis A, inside the lateral housings 36. Each of the rotatable screws 30 has an elongation axis B which is parallel to the axis A and which is an axis of rotation of this rotatable screw 30.

[0039] As can be seen in the figure 8 , the lateral housings 36 have diameters slightly larger than those of the rotary screws 30 and are configured to guide these screws 30 in rotation around the axes B.

[0040] Although the central housing 34 has an external diameter slightly greater than that of the fixed screw 28, this screw 28 is prevented from rotating around the axis A. This rotational blocking is here ensured by flanges 38, 40 attached to the axial ends of the rotor 33 and defining the inlet 26a and the outlet 26b of the pump 26.

[0041] A first 38 flange, located on the left on the Figure 7, defines the inlet 26a (due to the direction of the arrow F1 of circulation of the liquid in the pump 26) and comprises a tubular sleeve 38a centered on the axis A and forming this inlet, and an annular flange 38b for watertight attachment to the other flange 40.

[0042] The second flange 40, located on the right on the Figure 7 , defines the outlet (see arrow F1) and comprises a tubular sleeve 40a centered on the axis A and forming this outlet, and an annular bell 40b for watertight attachment to the other flange 38.

[0043] The bell 40b extends around the rotor 33 with a certain radial clearance so as to allow the rotation of the rotor 33 around the axis A inside this bell. The bell 40 comprises at an axial end opposite the sleeve 40a a flange 40c applied and fixed axially against the flange 38b of the first flange 38. Annular sealing joints 42, for example made of elastomer, can be mounted in the junction plane of the flanges 38b, 40c, as in the example shown.

[0044] As can be seen in the Figure 6 in particular, the pump 26 further comprises a fairing 44 which extends around the flanges 38, 40 and the rotor 33. The bell 40b of the second flange 40 extends inside a cylindrical portion 44a of the fairing 44 and defines with the latter an annular space E for housing the coils 32a.

[0045] In the example shown, the flanges 38b, 40c of the plates 38, 40 have their external peripheries which bear on an internal cylindrical surface 44aa of this cylindrical portion 44a in order to center the flanges 38, 40 in the fairing 44, at one end of this fairing.

[0046] At the opposite end of the fairing 44, the cylindrical portion 44a is connected to an annular rim 44b which extends radially inwards relative to the axis A and bears on a cylindrical rim 40d of the second flange 40 or of its bell 40b.

[0047] The flanges 38, 40 comprise elements for immobilizing the fixed screw 28 in rotation around the axis A. In the example shown, each of the flanges 38, 40 comprises an orifice 38c, 40e configured to receive and cooperate by complementary shapes with a corresponding end 28a of the fixed screw 28, in order to immobilize the latter in rotation around the axis A. Each end 28 may for example be crenellated or serrated and comprise teeth engaged in notches of the orifices 38c, 40e.

[0048] The ends 28a of the screw 28 pass through orifices 33ca of the discs 33c, located at the level of the axis A. The discs 33c further comprise holes 33cb, at the level of the axial ends of the rotating screws 30, which allow the passage of liquid from the inlet to the outlet (arrows F2).

[0049] The invention brings several advantages, including: the reduced cost of a screw pump, in particular through the use of injected plastic screws; a current consumption of the motor 32 which is proportional to the flow rate of the pump 26; which allows energy savings compared to a centrifugal pump when a low flow rate of liquid is required; the screw pump 26 makes it possible to stop the circulation of liquid in the circuit when the motor 32 is not operating; this can, for example, make it possible to eliminate a closing valve from the circuit of the prior art; the flow rate of the pump is directly proportional to the rotation speed of the motor; the pump can be directly controlled as a function of the temperature of the element to be cooled 16; the transfer of liquid can be done in both directions and is a function of the direction of rotation of the motor; whereas it can only pass in one direction in a centrifugal pump; the screw pump has better hydraulic efficiency;that is to say that the current consumption is lower for the same volume of liquid transferred; the screw pump makes it possible to obtain a higher pressure compared to a centrifugal pump, whatever the speed of its rotor; the screw pump provides a liquid flow rate at the outlet proportional to the rotation speed of the motor; there is no cavitation phenomenon in a screw pump; and the screw pump is relatively compact and easily integrated into a coolant tank.;

Claims

1. A cooling circuit (24) for a vehicle, in particular a motor vehicle, this circuit comprising a screw pump (26), this screw pump (26) comprising: - a fluid inlet (26a), - a fluid outlet (26b), - screws (28, 30) meshing with each other, at least one (30) of which is rotatable around a first axis (B), and which are configured to force fluid to flow from the inlet to the outlet when the screw rotates around this first axis (B), and - an electric motor (32) for rotating said at least one rotatable screw, this motor comprising a cylindrical rotor (33) that extends around a second axis (B) as well as around said screws (28, 30), this rotor being made of ferromagnetic material or comprising elements (33a) made of this material, and being rotatable around the second axis (B), the first and second axes (A, B) being parallel, and - electric coils (32a) arranged around the second axis (A) and said rotor and configured to be electrically powered in order to rotate said rotor around the second axis (A), said screws comprising: - a fixed screw (28) extending on and along the second axis (A) in said rotor (33), and - said at least one rotatable screw (30) which extends in said rotor and which is rotated around its respective first axis (B) as well as around the second axis (A) by the rotor (33) that rotates around the second axis (A) and around the fixed screw (28), characterized in that said screws (28, 30) are made of plastic or composite material.

2. The vehicle cooling circuit (24) according to claim 1, characterized in that the rotor (33) comprises a body (33b) made of ferromagnetic material or comprising elements (33a) made of this material, as well as two discs (33c) fastened respectively to the axial ends of the body.

3. The vehicle cooling circuit (24) according to claim 2, characterized in that each of the discs (33c) comprises housings (33ca, 33cb) for mounting axial ends (28a) of at least some of said screws (28) and / or for fluid passage.

4. The vehicle cooling circuit (24) according to any of the preceding claims, characterized in that the screw pump comprises at least two or three rotatable screws (30) regularly spaced around the second axis (A) and inside said rotor (33).

5. The vehicle cooling circuit (24) according to claims 3 and 4, characterized in that the body (33b) comprises a central cylindrical housing (34) traversed by said fixed screw (28), and cylindrical side housings (36) communicating with the central housing and traversed respectively by said rotatable screws (30).

6. The vehicle cooling circuit (24) according to any of the preceding claims, characterized in that the rotor (33) is enclosed between two flanges (38, 40), a first of which defines said inlet (26a) and a second of which defines said outlet (26b).

7. The vehicle cooling circuit (24) according to any of the preceding claims, characterized in that said inlet (26a) and outlet (26b) are coaxial.

8. The vehicle cooling circuit (24) according to any of claims 6 or 7, characterized in that each of the flanges (38, 40) comprises a first element (38c, 40e) configured to cooperate with a complementary element on one end (28a) of the fixed screw (28) to immobilize the latter in rotation around the second axis (A).

9. The vehicle cooling circuit (24) according to claim 8, characterized in that each of the flanges (38, 40) comprises an opening (38c, 40e) configured to cooperate through complementary shapes with the corresponding end (28a) of the fixed screw (28), to immobilize the latter in rotation around the second axis (A).

10. The vehicle cooling circuit (24) according to any of claims 6 to 9, characterized in that the rotor (33) and the flanges (38, 40) are housed in a casing (44) comprising means for electrically connecting the motor (32).

11. The vehicle cooling circuit (24) according to any of the preceding claims, characterized in that it comprises one or more members chosen among: a coolant reservoir (10), a heat exchanger (14), at least one element to be cooled (16) and a temperature sensor (20) for this equipment, the circuit having no proportional valve (22) and said pump (26) being configured to be controlled by a control unit (18) in response to signals emitted by said temperature sensor.

12. A vehicle, in particular a motor vehicle, comprising at least one cooling circuit (24) according to any of claims 1 to 11.

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