DESCRIPTION

Technical Field

The present invention relates to a rotary pump for fluids, and more specifically it concerns a lubricated rotary vacuum pump, applied to an electric motor.

Preferably, but not exclusively, the invention is applied in vacuum pumps intended to be interfaced with a thermal engine, and the following description will mainly refer to such a preferred application.

Prior Art

In the field of lubricated rotary vacuum pumps it is known to use electric pumps, for instance intended to operate in connection with a thermal engine of a motor vehicle and lubricated by the oil of the thermal engine.

An example of pumps of this kind, known to the skilled in the art, is a lubricated rotary pump made in 1976 by firm D. Bonaldi & C. and employed on car Fiat Dino (equipped with Ferrari engine).

Generally, electric rotary vacuum pumps, unlike mechanical pumps, are not connected to the engine shaft in order to rotate with it, but they are on the contrary used according to a discontinuous operation for reasons of energy saving and are subjected to be repeatedly turned on and off.

Yet, vacuum pumps of the above-specified kind have some drawbacks.

A drawback is that, in the periods in which said prior art vacuum pump is off and the thermal engine is operating, oil from the lubrication circuit of the thermal engine accumulates inside the pump and generates a pressure, in particular in the area of the vacuum chamber between the vane and the tangency point, thereby affecting the area of the suction valve, which could cause oil to flow back towards the utilisation devices with consequent considerable damages.

A further drawback is that, even if a non-return valve is used as a suction valve having a high sealing quality, there is anyway a high risk that oil flows back for instance towards the servo-brake.

Summary of the invention

It is an object of the present invention to provide a lubricated rotary pump for fluids, which is capable of preventing oil from flowing back towards the suction valve when the thermal engine is running and the electric pump is off. The above and other objects are achieved by the present invention by providing a lubricated rotary pump for fluids as claimed in the appended claims.

It is to be intended that the claims are integral part of the technical teachings herein provided in the present description in respect of the invention.

Brief Description of the Figures

Further features and advantages of the present invention will become apparent from the following detailed description, given by way of non limiting example only, with reference to the accompanying drawings, in which:

- Fig. 1 is a front view of a first embodiment of a rotary pump for fluids according to the present invention;

- Fig. 2 is a sectional view of the first embodiment of the rotary pump for fluids according to the present invention;

- Fig. 3 is a schematic view of a detail of the first embodiment of the rotary pump for fluids according to the present invention;

- Fig. 4 is a schematic view of a detail of a second embodiment of the rotary pump for fluids according to the present invention; and

- Fig. 5 is a schematic view of a detail of a third embodiment of the rotary pump for fluids according to the present invention.

Description of a Preferred Embodiment

Referring to the Figures, there is shown an exemplary embodiment of a rotary electric pump for fluids, e. g. a vacuum pump 10, according to the present invention, to which reference will be made hereinafter.

Vacuum pump 10 includes a hollow body 11 and is for instance a single-vane electric pump including a rotor and a vane of known type, not shown in the drawings. The pump is intended to be interfaced with a thermal engine equipped with a lubrication circuit, known per se. In accordance with other embodiments, the rotary electric pump is a multiple-vane pump.

Body 11 is a housing defining a substantially cylindrical cavity 25 in which the rotor and the vane are mounted in known manner and in which there are provided parts 125 to be lubricated, at least one suction chamber 126 and at least one discharge chamber 127.

Said body 11 has at least a first inlet port 112 and an outlet port 115, shown in Fig. 1, and preferably an electric connector 14. Preferably, body 11 has a second inlet port 113.

A primary vacuum inlet valve 12 and a secondary vacuum inlet valve 13 are mounted on inlet ports 112 and 113, respectively, each valve being connected with a respective suction channel for the inflow of a fluid into cavity 25. Outlet port 115 is in turn connected with a discharge duct and a non-return discharge reed valve 15 allowing fluid outflow from cavity 25.

Body 11 is preferably made of a metallic material, more preferably of aluminium alloy, or even of a thermoplastic, thermosetting or composite material.

More particularly, body 11 is closed in fluid-tight manner, for instance through a seal, by a lid 106, so as to define cavity 25.

Lubrication oil is sent under pressure into cavity 25 through a bore 118 formed in body 11 and through suitable first and second ducts for lubrication under pressure (lubrication ducts) 120, 20. Such oil, after having lubricated the pump, by becoming mixed with sucked air, will form a mixture that will be discharged into the engine through non-return discharge reed valve 15.

According to a first embodiment of the invention, shown in Figs. 2 and 3, vacuum pump 10 includes a non-return drain valve (closing valve) 16 of the reed type, consisting of a resilient plate (reed) 18 and a stop plate 28 secured to body 11 for instance by means of a screw 19 associated with a washer. Reed 18 is arranged to close both the second lubrication duct 20, through which pressurised oil arrives into cavity 25, and a connecting duct 21.

The second lubrication duct 20, made for instance of two ducts 20', 20", is connected through the first lubrication duct 120 to bore 118 through which oil inflows into the pump, and it establishes communication of the lubrication circuit of the thermal engine with pump parts to be lubricated 125.

Connecting duct 21 is permanently connected with pump suction chamber 126 and it has a mouth 26 connected selectively and in controlled manner with the pump outside at a pressure close to atmospheric pressure, corresponding to a low-pressure region of the thermal engine. Mouth 26 has, towards the outside, a section with a larger area than the section of lubrication duct 20.

According to a second embodiment of the invention, shown in Fig. 4, vacuum pump

10 includes a non-return drain valve (closing valve) 16a of the reed type that, besides the components described above for closing valve 16 of the first embodiment of the invention, includes a shutter valve 22 located inside the second lubrication duct 20' and a spring 23 connected to shutter valve 22. Shutter valve 22 further has an annular passageway 27 allowing oil to pass from the first lubrication duct 120 to the second lubrication duct 20" when the passageway is at the level of said first lubrication duct 120. According to a third embodiment of the invention, shown in Fig. 5, vacuum pump

10 includes a non -return drain valve 16b (closing valve) of the reed type that, besides the components described above for closing valves 16, 16a of the first and second embodiments of the invention, includes a sucker seal 24 placed in abutment against a step formed between mouth 26 and connecting duct 21.

The operation of electric rotary vacuum pump 10 according to the invention is as follows.

As known, lubricated electric rotary vacuum pumps are used according to a discontinuous operation and are subjected to be repeatedly turned on and off.

Since said pumps are lubricated with the oil of the thermal engine, in the periods in which the pump is off, oil from the first lubrication duct 120 and the second lubrication duct 20 of the lubrication circuit of the thermal engine accumulates inside pump cavity 25 and generates a pressure, in particular in the region of suction chamber 126 between the vane and the tangency point, thereby affecting the region of suction valves 13 and 12, which could make oil flow back towards the utilisation devices, thereby causing considerable damages to such utilisation devices.

Vacuum pump 10 according to the first embodiment of the invention, shown in Figs. 2 and 3, when it is on, generates a vacuum in suction chamber 126 and such a vacuum, by acting on reed 18 through connecting duct 21, generates a force proportional to the area of mouth 26 and to the vacuum in suction chamber 126.

Such a force, besides ensuring closure of connecting duct 21 itself, also closes the mouth of the first lubrication duct 20' by means of reed 18, thereby allowing pressurised lubrication oil to enter the pump and to perform in known manner the lubrication and liquid seal functions.

On the contrary, when the pump is turned off, oil continues arriving from the first lubrication duct 120. The second lubrication duct 20 and connecting duct 21 cooperate in order to make drain valve 16 open. This occurs thanks to the inflow of lubrication oil into cavity 25 through the second lubrication duct 20, what causes the reduction of the vacuum inside the pump and creates a pressure acting onto discharge valve 15 and, through connecting duct 21, onto drain valve 16. Thanks to the high flexibility of the reeds and to the areas onto which the pressure acts, such a pressure becomes close to atmospheric pressure and lubrication oil is advantageously drained to the pump outside, corresponding to the low-pressure region of the thermal engine.

Vacuum pump 10 according to the second embodiment of the invention, shown in Fig. 4, when it is on, generates a vacuum in suction chamber 126 and such a vacuum, by acting on reed 18 through connecting duct 21, generates a force proportional to the area of mouth 26 and to the vacuum in suction chamber 126. Such a force, besides ensuring closure of connecting duct 21 itself, operates shutter valve 22 by overcoming the force exerted thereon by spring 23, and shifts the shutter valve downwards and makes annular passageway 27 arrive at the level of the first lubrication duct 120. In this manner, pressurised oil can enter the pump and perform in known manner the lubrication and liquid seal functions.

On the contrary, when the pump is turned off, oil continues arriving from the first lubrication duct 120. Hence, the second lubrication duct 20 and connecting duct 21 thus cooperate in order to make drain valve 16a open. This occurs thanks to the inflow of lubrication oil into cavity 25 through the second lubrication duct 20, what causes the reduction of the vacuum inside the pump and creates a pressure acting onto discharge valve 15 and, through connecting duct 21, onto closing valve 16a. Thanks to the high flexibility of the reeds and to the areas onto which the pressure acts, such a pressure becomes close to atmospheric pressure and, jointly with the thrust exerted by spring 23, allows shutter valve 22 to close the first lubrication duct 120 establishing connection with the source of pressurised oil. This advantageously solves the problem of the possible oil flow back into the pump, besides producing an energy saving since no use of oil occurs for the whole period during which the pump remains off.

Vacuum pump 10 according to the third embodiment of the invention, shown in Fig. 5, when it is on, generates a vacuum in suction chamber 126 and such a vacuum, by acting on reed 18 through connecting duct 21, generates, with the help of the flow of air initially sucked and licking sucker seal 24, a force proportional to the area of mouth 26 and to the vacuum in suction chamber 126. Such a force, besides ensuring closure of connecting duct 21 itself, operates shutter valve 22 by overcoming the force exerted thereon by spring 23, and shifts the shutter valve downwards and makes annular passageway 27 arrive at the level of the first lubrication duct 120. In this manner, pressurised oil can enter the pump and perform in known manner the lubrication and liquid seal functions.

On the contrary, when the pump is turned off, oil continues arriving from the first lubrication duct 120. Hence, the second lubrication duct 20 and connecting duct 21 cooperate to make drain valve 16b open. This occurs thanks to the inflow of lubrication oil into cavity 25, through the second lubrication duct 20, what causes the reduction of the vacuum inside the pump and creates a pressure acting onto discharge valve 15 and, through connecting duct 21, onto closing valve 16b. Thanks to the high flexibility of the reeds and to the areas onto which the pressure acts, such a pressure becomes close to atmospheric pressure and, jointly with the thrust exerted by spring 23, allows shutter valve 22 to close the first lubrication duct 120 establishing connection with the source of pressurised oil: this advantageously solves the problem of the possible oil flow back into the pump, besides producing an energy saving since no use of oil occurs for the whole period during which the pump remains off.

Of course, the embodiments and the construction details can be widely changed with respect to what has been described and shown by way of non limiting example only, without thereby departing from the scope of the invention as defined in the appended claims.