MOTOR VEHICLE OIL PUMP

Abstract

A motor vehicle oil pump, including: a pump body, an external rotor having a first plurality of lobes, an internal rotor having a second plurality of lobes configured to engage the first plurality of lobes of the external rotor, and a driving body rotatable with respect to the pump body about a first axis of rotation. The external rotor is constrained to the driving body. An idle shaft is rotatably connected to the pump body about a second axis of rotation parallel and eccentric to the first axis of rotation. The external rotor rotates about the first axis of rotation and is rotated by the driving body. The driving body is rotated by a motor. The internal rotor is fitted onto the idle shaft for rotating about the second axis of rotation and is rotated by the external rotor.

Claims

1.-10. (canceled)

11. A motor vehicle oil pump, comprising: a pump body; an external rotor having a radially internal surface forming a first plurality of lobes; an internal rotor having a radially external surface forming a second plurality of lobes configured to engage the first plurality of lobes of the external rotor, wherein the number of lobes of the first plurality of lobes is equal to the number of lobes of the second plurality plus one; a driving body rotatable with respect to the pump body about a first axis of rotation, wherein the external rotor is constrained to the driving body; and an idle shaft rotatably connected to the pump body about a second axis of rotation parallel and eccentric to the first axis of rotation, wherein: the external rotor is rotatable about said first axis of rotation and is configured to be rotated by the driving body; the driving body is configured to be rotated by a motor; said internal rotor is fitted onto said idle shaft for rotating about said second axis of rotation; and said internal rotor is configured to be rotated by the external rotor.

12. The motor vehicle oil pump according to claim 11, comprising a guide shaft rotatable about the first axis of rotation, said guide shaft cooperating with the driving body during rotation of the driving body about said first axis of rotation.

13. The motor vehicle oil pump according to claim 11, comprising a bearing directly connected to the pump body for enabling rotation of the driving body with respect to the pump body about the first axis of rotation.

14. The motor vehicle oil pump according to claim 12, comprising a bearing directly connected to the pump body for enabling the rotation of the driving body with respect to the pump body about the first axis of rotation.

15. The motor vehicle oil pump according to claim 14, wherein said guide shaft is constrained to the driving body and wherein said bearing directly acts on said guide shaft so that the external rotor, the driving body and the guide shaft form a rotating assembly rotatably connected to the pump body through said bearing.

16. The motor vehicle oil pump according to claim 13, wherein said bearing directly acts between said driving body and said pump body.

17. The motor vehicle oil pump according to claim 14, wherein said bearing directly acts between said driving body and said pump body.

18. The motor vehicle oil pump according to claim 17, wherein the driving body comprises a cylindrical portion crossed in an axial direction by the guide shaft, said cylindrical portion being press-fitted on the bearing.

19. The motor vehicle oil pump according to claim 11, wherein said driving body comprises a base wall and a side wall extending axially away from the base wall for defining an internal cavity of the driving body, said external rotor being inserted into said internal cavity and being constrained to said side wall.

20. The motor vehicle oil pump according to claim 11, comprising an electric motor having a rotor and a stator, said driving body being operatively connected to said rotor of the electric motor.

21. The motor vehicle oil pump according to claim 12, comprising an electric motor having a rotor and a stator, said driving body being operatively connected to said rotor of the electric motor.

22. The motor vehicle oil pump according to claim 21, wherein said rotor of the electric motor is constrained to said guide shaft for rotating the guide shaft.

23. The motor vehicle oil pump according to claim 20, wherein said rotor of the electric motor is directly constrained to the driving body.

Description

[0050] Further characteristics and advantages of the present invention will become clearer from the following detailed description of the preferred embodiments thereof, with reference to the appended drawings and provided by way of indicative and non-limiting example. In such drawings:

[0051] FIG. 1 represents a perspective view of a motor vehicle oil pump according to a first embodiment of the present invention;

[0052] FIG. 2 represents a perspective view of a motor vehicle oil pump according to a second embodiment of the present invention;

[0053] FIG. 3 schematically represents a section according to plane III-III of the oil pump of FIG. 1;

[0054] FIG. 4 schematically represents a section according to plane Iv-Iv of the oil pump of FIG. 1; and

[0055] FIG. 5 schematically represents a section according to plane V-V of the oil pump of FIG. 2.

[0056] With reference to FIGS. 1 to 5, some preferred embodiments of a motor vehicle oil pump 10 in accordance with the present invention are shown. Identical reference numbers refer to identical characteristics of each embodiment, the differences between them will become more apparent below.

[0057] The oil pump 10 comprises a pump body 11 closed by a cover 12. Two openings are made on the cover 12, which define a delivery opening 13 and a suction opening 14 for oil, respectively. The oil enters the pump body 11 through the suction opening 14 and the oil leaves the pump body 11 through the discharge opening 13. Preferably, the pump body 11 is made of a metallic material, preferably of aluminium or its alloys, or of steel or its alloys.

[0058] FIG. 3 essentially shows the oil pump 10 of FIG. 1 in a top view with the cover 12 removed. This figure may also represent, for the purposes of this description and net of differences which will appear below, the oil pump 10 of FIG. 2 in a view from above with the cover 12 removed.

[0059] As shown in FIG. 3, the oil pump 10 comprises an external rotor 15 and an internal rotor 16.

[0060] The external rotor 15 comprises a substantially cylindrical radially external surface 17 and a radially internal surface 18. The radially internal surface 18 is shaped to define a first plurality of lobes 19. In the illustrated embodiment, there are six lobes 19 of the first plurality of lobes, but there could be more or less than six.

[0061] The internal rotor 16 comprises a radially outer surface 20 shaped to define a second plurality of lobes 21. In the illustrated embodiment, there are five lobes 21 of the second plurality of lobes. In any case, irrespective of the number of lobes 19 of the first plurality of lobes, the lobes 21 of the second plurality of lobes 21 are equal in number to the lobes 19 of the first plurality of lobes less one.

[0062] The external rotor 15 is rotatably mounted inside the pump body 11 about a first axis of rotation R1 and the internal rotor 16 is rotatably mounted with respect to the external rotor 15 (and thus with respect to the pump body 11) about a second axis of rotation R2 parallel to and offset from the first axis of rotation R1, so that the internal rotor 16 rotates eccentrically with respect to the external rotor 15.

[0063] The internal rotor 16 is inserted inside the external rotor 15 and is rotated by the external rotor 15. The lobes 21 of the internal rotor 16 engage cyclically with the lobes 19 of the external rotor 15 during the rotation of the external rotor 15 and the internal rotor 16.

[0064] The mutual rotation between the internal rotor 16 and the external rotor 15 defines, by the engagement of the respective lobes 21, 19, a plurality of compression chambers 22 within which the oil is pressurised. The pressurised oil is discharged through the delivery opening 13. Each compression chamber 22 moves circumferentially (by the rotation of the internal rotor 16 and the external rotor 15) from a first position in which oil is introduced into the compression chamber 22 to a second position in which oil is expelled from the compression chamber 22. In the first position, the compression chamber is placed in correspondence and in fluid communication with the suction opening 14. In the second position, the compression chamber is placed in correspondence and in fluid communication with the delivery opening 13. During the movement of each compression chamber 22 from the first to the second position, the volume of the compression chamber 22 decreases by increasing the pressure of the oil contained therein. Once the oil has been expelled, the compression chamber 22, due to the relative rotation between the internal rotor 16 and the external rotor 15, returns from the second to the first position, increasing its volume. Once the first position has been reached, a new compression cycle begins.

[0065] Advantageously, the internal rotor 16 is driven in rotation by the external rotor 15, i.e. the rotation of the lobes 19 of the external rotor 15 puts the internal rotor 16 into rotation through the engagement of the lobes 19 with the lobes 21 of the internal rotor 16.

[0066] In this regard, the external rotor 15 is constrained radially and axially in rotation to a driving body 26 (FIGS. 4 and 5) which rotates about the first axis of rotation R1 and which is configured to be operated by a motor 100. The internal rotor 16 is guided in rotation about the second axis of rotation R2 by an idle shaft 24 coaxial with the second axis of rotation R2. As illustrated in FIGS. 4 and 5, the idle shaft 24 is integral with the internal rotor 16 (for example, it is press-fitted into the internal rotor 16 or is coupled thereto by means of a coupling flange), emerges axially from the internal rotor 16 and is rotatably inserted into a guide seat 25 obtained in the cover 12 of the oil pump 10.

[0067] The driving body 26 also has the function of housing the external rotor 15 and is guided in rotation about the first axis of rotation R1 or is assisted in rotation about the first axis of rotation R1 by a guide shaft 23.

[0068] As shown in FIGS. 4 and 5, the driving body 26 comprises a base wall 27 and a side wall 28 which develops axially away from the base wall 27. The base wall 27 and the side wall 28 are integral with each other. The side wall 28 is substantially annular and cylindrical in shape and is counter-shaped to the radially external wall 17 of the external rotor 15. The driving body 26 comprises an internal cavity having a closed end. The internal cavity is delimited by the side wall 28 and, at said closed end, by the base wall 27. The external rotor 15 is inserted into the internal cavity of the driving body 26 in contact with the side wall 28 of the driving body 26. In particular, the external rotor 15 is inserted into the internal cavity of the driving body 26 with the radially external wall 17 in contact with the side wall 28. The internal rotor 16 rotates inside the driving body 26. Preferably, the internal rotor 16 is in sliding contact with the base wall 27 of the driving body 25. The compression chambers 22 are therefore bounded in the axial direction by the base wall 27 of the driving body 26. The compression chambers 22 are further delimited in the axial direction, on the opposite side with respect to the base wall 27 of the driving body 26, by the cover 12 of the pump body 11. The external rotor 15 is integral with the driving body 26, preferably press-fitted into the internal cavity of the driving body 26. The external rotor 15 has no radial or axial clearance with respect to the driving body 26.

[0069] The driving body 26 and with it the external rotor 15 rotate in the pump body 11 due to the effect of a single bearing 30. This bearing 30 comprises a radially external washer 31 directly connected to the pump body 11 and a radially internal washer 32.

[0070] In the embodiment illustrated in FIG. 4, the guide shaft 23 has the function of rotating the driving body 26. The guide shaft 23 is coupled to the base wall 27 of the driving body 26 and extends axially away from the base wall 27 on the opposite side with respect to the side wall 28. For this purpose, the base wall 27 comprises a housing seat 29 located in the centre of the base wall 27. The housing seat 29 can be made from a hole or a cavity which is open in the direction of the guide shaft 23 and closed in the direction of the side wall 28. The guide shaft 23 can be press-fitted into the housing seat 29 or made integral with it in some other way.

[0071] The rotating assembly comprising guide shaft 23, driving body 26, external rotor 15 and internal rotor 16 rotates inside the pump body 11 supported by the bearing 30. In other words, the only element which acts as an interface between (i.e. which connects) the rotating assembly which rotates in the pump body 11 (and which consists of guide shaft 23, driving body 26, external rotor 15 and internal rotor 16) and the pump body 11 is the bearing 30.

[0072] In the embodiment illustrated in FIG. 4, the radially internal washer 32 of the bearing 30 is directly connected to the guide shaft 23. The guide shaft 23 is press-fitted into the bearing 30 in such a way that there is no radial or axial clearance with respect to the pump body 11.

[0073] In the embodiment shown in FIG. 5, the driving body 26 is rotatable with respect to the guide shaft 23 and the latter has the function of helping the driving body to rotate about the first axis of rotation R1. In this respect, the guide shaft 23 is rotatably inserted into the base wall 27 of the driving body 26 and extends axially away from the base wall 27 on the opposite side with respect to the side wall 28. The driving body 26 comprises a cylindrical portion 33 extending axially away from the base wall 27 of the driving body 26 on the opposite side with respect to the side wall 28. The guide shaft 23 is rotatably inserted into the cylindrical portion 33 and the cylindrical portion 33 has an internal diameter greater than the diameter of the guide shaft 23. A bearing or bushing 38 may be provided between the guide shaft 23 and the cylindrical portion 33, which rotatably couples the guide shaft to the driving body 26. The pump body 11 includes a housing 34 for constraining and retaining the end of the guide shaft 23 (opposite the end rotatably inserted into the base wall 27 of the driving body 26) to the pump body 11.

[0074] In this embodiment, the cylindrical portion 33 is press-fitted into the bearing 30. In particular, the cylindrical portion 33 is in direct contact with the radially internal washer 32 of the bearing 30. The rotating assembly comprising driving body 26, external rotor 15 and internal rotor 16 rotates inside the pump body 11 supported by the bearing 30. In other words, the only element which acts as an interface between (i.e. which connects) the rotating assembly which rotates in the pump body 11 (and which consists of driving body 26, external rotor 15 and internal rotor 16) and the pump body 11 is the bearing 30.

[0075] In both embodiments of the invention, the motor 100 rotating the driving body 26 is an electric motor. The electric motor 100 comprises a rotor 101 and a stator 102. The stator 102 is integral with the pump body 11 and contained inside the pump body 11. The electric motor 100 is driven by a control unit 103 preferably contained in the pump body 11 and electrically connected to the electric motor 100. The control unit 103 is configured to limit the speed of the electric motor to 1800 rpm.

[0076] In the embodiment illustrated in FIG. 4, the rotor 101 of the electric motor 100 is directly connected to the guide shaft 23 and transmits to it a driving torque which sets the guide shaft 23 in rotation.

[0077] In this embodiment, the driving body 26 is inserted into a cavity 35 of the pump body 11 extending axially from the cover 12 to an area axially below the base wall 27 of the driving body 26, so that the cavity 35 can axially contain the driving body 26. The cavity 35 has a radial extension greater than the radial extension of the driving body 26. The cavity 35 is crossed by the guide shaft 23 and is in fluid communication with a portion of the pump body 11 housing the electric motor 100, preferably through a hole 39. A gap 36 having dimensions of not less than 5 millimetres, more preferably not less than 2 millimetres, is formed between the containment body 26 and the wall of the pump body 11 delimiting the cavity 35. In other words, the containment body 26 is inserted into the cavity 35 and is spaced both radially and axially from walls of the cavity 35 by distances of not less than 5 millimetres, more preferably not less than 2 millimetres. The gap 36 is filled with oil (the same oil on which the pump 10 operates) which enters through the suction opening 14 and which, through the hole 39, reaches the electric motor to cool it during operation.

[0078] In the embodiment illustrated in FIG. 5, the rotor 101 of the electric motor 100 is directly connected to the driving body 26 and transmits a driving torque thereto which sets it in rotation (and which consequently sets the guide shaft 23 in rotation). The rotor 101 is constrained to the side wall 28 of the driving body. As illustrated in FIG. 5, the rotor 101 is constrained to a radially external surface 37 of the side wall 28.

[0079] In order to satisfy specific and contingent requirements, a person skilled in the art will be able to make numerous modifications and variations to the motor vehicle oil pump described above with reference to the appended figures, all of which are included in the scope of protection of the present invention as defined by the following claims.