VARIABLE DISPLACEMENT OIL PUMP

Abstract

A variable displacement oil pump is described. The oil pump has pump body connected to an intake channel and to a delivery channel, a rotor capable of rotating inside the pump body about a rotation axis and provided with a plurality of vanes. The oil pump has an oscillating stator arranged in an eccentric position around the rotor and pivoted inside the pump body at a rotation pin. The oil pump has adjustment means for adjusting the displacement of the oil pump which acts on the oscillating stator to displace it with respect to the rotor and position it in at least one predetermined operative position. The adjustment means has first thrusting means configured to exert a first thrusting action on a first outer surface portion of the oscillating stator arranged on a substantially opposite side with respect to the rotation pin taking as a reference the rotor.

Claims

1. A variable displacement oil pump, comprising: a pump body connected to an intake channel and to a delivery channel, a rotor capable of rotating inside the pump body about a rotation axis and provided with a plurality of vanes, an oscillating stator arranged in an eccentric position around the rotor and pivoted inside the pump body at a rotation pin, and adjustment means for adjusting the displacement of the oil pump which acts on the oscillating stator to displace it with respect to the rotor and position it in at least one predetermined operative position, wherein said adjustment means comprise first thrusting means configured to exert a first thrusting action on a first outer surface portion of the oscillating stator arranged on a substantially opposite side with respect to the rotation pin taking as a reference the rotor, and at least one thrusting chamber defined between the pump body and a second outer surface portion of the oscillating stator arranged between the rotation pin and said first outer surface portion, said at least one thrusting chamber being configured to be filled with a predetermined amount of a pressurised fluid to exert on the oscillating stator a second thrusting action opposite to said first thrusting action and suitable for displacing the oscillating stator to bring it to said at least one predetermined operative position, wherein said at least one thrusting chamber is fluid-dynamically insulated with respect to the rotation pin by two opposite sealing gaskets, and wherein said oil pump comprises an insulation chamber arranged between said at least one thrusting chamber and the rotation pin and connected to an intake conduit.

2. The oil pump according to claim 1, wherein said intake conduit is connected to said intake channel.

3. The oil pump according to claim 1, wherein the insulation chamber is defined between the rotation pin and a first gasket of said two opposite sealing gaskets, and said at least one thrusting chamber is defined between the first gasket and a second gasket of said two opposite sealing gaskets.

4. The oil pump according to claim 3, wherein said first gasket is angularly spaced from the rotation pin by an angle lower than 90° with respect to said rotation axis.

5. The oil pump according to claim 3, wherein said second gasket is angularly spaced from the first gasket by an angle greater than 90° with respect to said rotation axis.

6. The oil pump according to claim 3, wherein said at least one thrusting chamber comprises a first thrusting chamber arranged between the first gasket and a further sealing gasket arranged between the first gasket and the second gasket, and at least one second thrusting chamber arranged between said further sealing gasket and the second gasket, wherein said first and second thrusting chambers are each configured to be filled, simultaneously or alternatively, with a respective predetermined amount of pressurised fluid.

7. The oil pump according to claim 1, wherein said at least two opposite sealing gaskets are housed in respective seats formed in the oscillating stator.

Description

[0026] Further characteristics and advantages of the present invention will become clearer from the following detailed description of a preferred embodiment thereof, made with reference to the attached drawings and given for indicating and not limiting purposes. In such drawings:

[0027] FIG. 1 schematically shows a cross section of a variable displacement oil pump made according to the prior art and described above;

[0028] FIG. 2 schematically shows a cross section of a variable displacement oil pump made according to the invention.

[0029] With reference to FIG. 2, a variable displacement oil pump in accordance with the present invention is shown. Such an oil pump is indicated with 110.

[0030] The oil pump 110 is suitable for being used in an automobile engine.

[0031] The pump 110 comprises a pump body 112 in which a rotor 114 rotates. The rotor 114 is provided with radial cavities 116 inside which vanes 118 slide. For the sake of clarity of illustration, reference numerals 116 and 118 are associated with only one of the radial cavities and with only one of the vanes shown.

[0032] The pump body 112 is connected to an intake channel 112a and to a delivery channel 112b.

[0033] The radially outer ends 120 of the vanes 118 contact the inner surface 121 of an oscillating stator 122 arranged in an eccentric position around the rotor 114. The vanes 118, the oscillating stator 122 and the rotor 114 define a plurality of chambers 124 inside the pump body 112. For the sake of clarity of illustration, reference numeral 124 is associated with only one of the chambers shown.

[0034] During the rotation of the rotor 114 the volume inside the chambers 124 in which oil has been fed by the intake channel 112a reduces, obtaining an increase in pressure of the oil until each chamber 124 reaches the delivery channel 112b, through which the pressurised oil is fed to the engine.

[0035] The oscillating stator 122 is pivoted inside the pump body 112 at a rotation pin 123 and is able to move with respect to the rotor 114 between a first position in which the eccentricity between rotation axis O of the rotor 114 and centre of the oscillating stator 122 is at the minimum and a second position in which the eccentricity between rotation axis O of the rotor 114 and centre of the oscillating stator 122 is at the maximum (in FIG. 2 a condition of maximum eccentricity is shown). The aforementioned variation in eccentricity determines a variation of the volume of the chambers 124 and, consequently, a variation of the flow rate (or displacement) of the oil pump 110.

[0036] The rotation pin 123 can be integrated in the oscillating stator 122 and housed in a seat formed in the pump body 112, or alternatively it can be integrated in the pump body 112 and housed in a seat formed in the oscillating stator 122, or alternatively it can be a distinct element from the pump body 112 and from the oscillating stator 122 and housed in seats formed on the pump body 112 and the oscillating stator 122.

[0037] The oil pump 110 comprises a helical spring 130, of the compression type, which is associated, at a first free end thereof, with the pump body 112 and which exerts a pushing action, at the opposite free end thereof, on a first outer surface portion 122a of the oscillating stator 122 arranged on the opposite side to the rotation pin 123 with reference to the rotor 114.

[0038] The oil pump 110 further comprises a thrusting chamber 128 defined between the pump body 112 and a second outer surface portion 122b of the oscillating stator 122. Such a thrusting chamber 128 is connected to the intake channel 112a and is delimited by two opposite sealing gaskets 132, 133 housed in respective seats 132a, 133a formed on the oscillating stator 122.

[0039] The eccentricity between rotation axis O of the rotor 114 and centre of the oscillating stator 122 is determined by the balance between the thrusting action exerted by the helical spring 130 on the first outer surface portion 122a of the oscillating stator 122 and the opposite thrusting action exerted on the second outer surface portion 122b of the oscillating stator 122 by a predetermined amount of pressurised fluid (typically oil) fed into the thrusting chamber 128.

[0040] Both of the gaskets 132, 133 are arranged between the rotation pin 123 and the aforementioned first outer surface portion 122a of the oscillating stator 122, the gasket 132 being closer to the rotation pin 123 and the gasket 133 being closer to the helical spring 130. The aforementioned gaskets 132, 133 ensure that the thrusting chamber 128 is fluid-dynamically insulated with respect to the rotation pin 123.

[0041] An insulation chamber 134 is arranged between the rotation pin 123 and the thrusting chamber 128. Such an insulation chamber 134 thus structurally separates the thrusting chamber 128 from the rotation pin 123, preventing undesired leakages of the pressurised fluid present in the thrusting chamber 128 to occur at the rotation pin 123.

[0042] The insulation chamber 134 is thus defined between the rotation pin 123 and the gasket 132.

[0043] The gasket 132 is angularly spaced from the rotation pin 123 by an angle lower than 90° with reference to the rotation axis O of the rotor 114, whereas the gasket 133 is angularly spaced from the gasket 132 by an angle greater than 90° with reference to the aforementioned rotation axis O.

[0044] The fluid-dynamic insulation of the rotation pin 123 from the thrusting chamber 128 is ensured, also in the case of leakage of pressurised oil from the thrusting chamber 128 into the insulation chamber 134, by the fact that the insulation chamber 134 is connected to the intake conduit 112c, which ensures the evacuation by suction of possible pressurised oil present in the insulation chamber 134.

[0045] Preferably, the intake conduit 112c is connected to the suction channel of the pump 100.

[0046] Alternatively, the intake conduit 112c is connected to a distinct suction pump.

[0047] Alternatively, the intake conduit 112c is connected to the outside of the pump body 112 or at an area having a pressure lower than that of the insulation chamber 134.

[0048] The helical spring 130 and the thrusting chamber 128, when filled with pressurised fluid, define adjustment means 126 for adjusting the eccentricity between rotation axis O of the rotor 114 and centre of the oscillating stator 122, i.e. adjustment means 126 for adjusting the displacement of the oil pump 110.

[0049] In operation, a predetermined amount of a pressurised fluid is fed into the thrusting chamber 128 to move the oscillating stator 122 with respect to the rotor 114, overcoming the thrusting action exerted by the helical spring 130, and to position the oscillating stator 122 in a predetermined operative position defined as a function of the required displacement or flow rate. A change in the amount of fluid fed into the thrusting chamber 128 produces a change in the eccentricity between centre of the oscillating stator 122 and rotation axis O of the rotor 114 and, therefore, a change in the displacement or flow rate of the oil pump 110. Oil is fed into the chambers 124, said oil being pressurised as a consequence of the decrease of the volume of the chambers 124 upon rotation of the rotor 114. The pressurised oil is then fed to the parts of the engine that need to be lubricated.

[0050] In order to satisfy specific and contingent requirements, those skilled in the art can bring numerous modifications and changes to the oil pump 110 described above with reference to FIG. 2, all of these modifications and changes being in any case covered by the scope of protection of the present invention as defined by the following claims.

[0051] For example, in some solutions (not shown) it is possible to foresee two or more thrusting chambers, a first thrusting chamber being structurally separated from the rotation pin 123 by the aforementioned insulation chamber 134 and the other thrusting chamber(s) being arranged, with reference to the aforementioned first thrusting chamber, on the opposite side to the insulation chamber 134.

[0052] It is also possible to foresee further solutions (also not shown) in which the aforementioned insulation chamber 134 is positioned on the opposite side to the thrusting chamber 128, taking the rotation pin 123 as reference, or in which the insulation chamber 134 houses the rotation pin 123, or in which the insulation chamber 134 is not present. In this last case, the thrusting chamber 128 (or one of the two or more thrusting chambers possibly foreseen) is adjacent to the rotation pin 123 and, in order to avoid fluid leakage at the rotation pin 123, the latter is insulated from the aforementioned thrusting chamber 128 through a suitable sealing gasket.