Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
  • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
  • F04C18/30—Rotary-piston pumps specially adapted for elastic fluids having the characteristics covered by two or more of groups F04C18/02, F04C18/08, F04C18/22, F04C18/24, F04C18/48, or having the characteristics covered by one of these groups together with some other type of movement between co-operating members
  • F04C18/34—Rotary-piston pumps specially adapted for elastic fluids having the characteristics covered by two or more of groups F04C18/02, F04C18/08, F04C18/22, F04C18/24, F04C18/48, or having the characteristics covered by one of these groups together with some other type of movement between co-operating members having the movement defined in group F04C18/08 or F04C18/22 and relative reciprocation between the co-operating members
  • F04C18/344—Rotary-piston pumps specially adapted for elastic fluids having the characteristics covered by two or more of groups F04C18/02, F04C18/08, F04C18/22, F04C18/24, F04C18/48, or having the characteristics covered by one of these groups together with some other type of movement between co-operating members having the movement defined in group F04C18/08 or F04C18/22 and relative reciprocation between the co-operating members with vanes reciprocating with respect to the inner member
  • F04C18/3441—Rotary-piston pumps specially adapted for elastic fluids having the characteristics covered by two or more of groups F04C18/02, F04C18/08, F04C18/22, F04C18/24, F04C18/48, or having the characteristics covered by one of these groups together with some other type of movement between co-operating members having the movement defined in group F04C18/08 or F04C18/22 and relative reciprocation between the co-operating members with vanes reciprocating with respect to the inner member the inner and outer member being in contact along one line or continuous surface substantially parallel to the axis of rotation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
  • F01C21/00—Component parts, details or accessories not provided for in groups F01C1/00 - F01C20/00
  • F01C21/08—Rotary pistons
  • F01C21/0809—Construction of vanes or vane holders
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
  • F04C25/00—Adaptations of pumps for special use of pumps for elastic fluids
  • F04C25/02—Adaptations of pumps for special use of pumps for elastic fluids for producing high vacuum
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
  • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
  • F04C28/06—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids specially adapted for stopping, starting, idling or no-load operation

Definitions

• the present invention relates to vacuum pumps, in particular for the automotive field.
• a depression for operating An example is the servo braking system, which is a pneumatic servomotor using depression as a source of energy.
• the depression can be generated in the intake manifold thanks to the inlet choking created by the butterfly valve when the accelerator is released.
• depression is on the contrary obtained by means of a vacuum pump.
• many petrol-fuelled engines have a reduced depression level at the manifold, which level is no longer sufficient to supply the servo braking system. Hence a vacuum pump is used also in these engines.
• the operation of the vacuum pump serves for compensating vacuum consumption by the utilising devices and losses. Since such devices are not permanently operating and losses are limited, time periods, even of considerable duration, exist in which pump operation is not necessary. Yet, usually, vacuum pumps in motor vehicles are permanently operated by the engine. This results in an unnecessary power absorption and in a certain increase in fuel consumption, as well as in a useless wear of the pump components.
• the vanes are associated with a respective counterweight that, when the rotational speed of the motor is below a given threshold, keeps the vane in contact with the chamber wall due to the thrust exerted by a spring.
• the centrifugal force overcomes the force applied by the spring and the counterweight retracts the vane, thereby disengaging it from the wall and turning the pump off.
• the invention provides a pump where the rotor comprises at least one pumping element arranged to move in a first direction to turn the pump on in case of deceleration of a motor driving the pump, and in a second direction to turn the pump off in case of acceleration.
• the pump allows generating vacuum during deceleration and recovering kinetic energy during engine deceleration.
• the invention also provides a method of controlling said pump, as claimed in claim
• Fig. 1 is a schematic radial cross-sectional view of a first embodiment of the invention
• Figs. 2A to 2D are diagrams illustrating the operation of the pump shown in Fig. 1;
• Fig. 3 is a schematic radial cross-sectional view of a second embodiment of the invention.
• a rotary vacuum pump 1 according to a first embodiment of the invention comprises a cylindrical hollow body 2 inside which rotor 3 eccentrically rotates.
• the rotor too is cylindrical and its external wall 3 A is tangent to internal surface 2 A of hollow body 2 along a stationary tangency line 4.
• rotor 3 rotates clockwise (arrow Rl) and its rotation axis is denoted by A.
• the suction and exhaust ports 6 and 7 are located at both sides of tangency line 4, at the left and the right of said line, respectively, with the rotation direction indicated.
• rotor 3 is hollow and has a central bulkhead 5 connected to internal wall 3B of rotor 3 by means of radial partitions 9, for instance two partitions arranged in a diametric plane of rotor 3, dividing the internal cavity of rotor 3 into a plurality of chambers 8.
• Partitions 9 may have a shorter axial extension than rotor 3 and bulkhead 5 in order to allow communication between adjacent chambers 8.
• rotor 3 can be made of plastics, by moulding techniques, for instance injection moulding.
• Cavities 10 are open at one end in correspondence of external surface 3 A of the rotor and are closed at the opposite end.
• Each cavity 10 houses a vane 11 that is radially slidable between a first position, which is taken by the vane when pump 1 is operating and in which the vane forward end (with reference to the rotation direction) is in contact with internal surface 2A of body 2, and a second position, which is taken by the vane when pump 1 is not operating and in which the vane is retracted within cavity 10, so that its forward end is not in contact with surface 2A.
• This second position is shown in dashed line for the left vane.
• the two positions will also be referred to as “operating position” and “idle position”, respectively.
• the vanes are received in cavities 10 with a sufficient clearance to allow their sliding, taking into account the manufacture tolerances.
• the vane sliding will be made easier by lubricating oil, e.g. directly supplied by the engine.
• barycentre B of the vane is located between the middle point of cavity 10 and the bottom of the same cavity.
• vanes 11 In the operating position, vanes 11 will define, in the cavity of body 2, the suction and exhaust chambers communicating with ports 6, 7.
• Vanes 11 move to the idle position during the acceleration phases of the engine, and move to the operating position in case of deceleration.
• the vanes When the engine is rotating at constant speed, the vanes will be in the operating or the idle position, depending on whether the constant speed condition has been attained after a deceleration or an acceleration.
• Cavities 10 are mutually connected by a passageway 12 opening at or near the bottom of the cavities themselves. Still at or near their bottom, cavities 10 communicate with adjacent chambers 8 through passageways 13. Communication of cavities 10 with each other and with chambers 8 allows wholly discharging air possibly present in the cavities, whereby the retraction of vanes 11 is not hindered, and, together with communication between chambers 8, it allows passage of the lubricant oil.
• the profile of cavities 10 and vanes 11 may be arc-shaped, as shown in the Figure, with the concavity directed forward with reference to the rotation direction, or it may be rectilinear.
• FIGs. 2A to 2D show the forces acting on vane 11 in conditions of constant speed, acceleration and deceleration, respectively, and show a situation in which the open end of cavity 10 is up, so that in the operating position vane 11 projects into the cavity of body 2.
• Fig. 2D shows the forces acting on vane 11 in conditions of acceleration, when the open end of cavity 10 is substantially located in correspondence of the line of tangency 4, so that vane 11 is retracted within cavity 10 also in the operating position.
• the Figures are intended to show only the direction of the forces, and the lengths of the vectors are not be intended as being representative of the actual intensities of the forces themselves.
• vane 11 is obviously subjected to the centrifugal force, which is directed along a line joining the centre of rotation A of rotor 3 with the barycentre of vane 11.
• Reference symbols Bl and B2 denote the barycentre in the operating and idle position of the vane, respectively, and reference symbols Fl and F2 denote the centrifugal force in the two conditions.
• Force Fl, F2 has a component, denoted FI N , F2 N , normal to vane 11 in the barycentre, and a tangential component F1 T , F2 T .
• the normal component which is the only component in the position depicted in fig.
• vane 11 is subjected to the action of the centrifugal force only. If vane 11 is in the operating position (i.e. the constant speed condition has been attained after a deceleration), tangential component F1 T of the centrifugal force tends to make the vane slide towards the outside, and hence the vane remains in operating position. This occurs whatever the position of the rotor in the cycle may be. Similarly, if vane 11 is in the idle position (i.e. the constant speed condition has been attained after an acceleration), tangential component F2 T will tend to push vane 11 towards the bottom of cavity 10, provided barycentre B2 is located between the middle point and the bottom of the cavity.
• Fig. 3 shows a second embodiment of the pump according to the invention, denoted 101. Elements corresponding to those shown in Fig. 1 are denoted by corresponding reference numerals, increased by 100.
• central bulkhead 105 is formed by a hollow cylindrical member, coaxial with rotor 103, and has diametric partition 120, for instance substantially normal to partitions 109.
• two pairs of chambers 108 are formed, an "outer” pair between the external surface of bulkhead 105 and the internal surface 103B of rotor 103, and an “inner” pair inside the cavity of bulkhead 105.
• partitions 109 may have a shorter axial extension than rotor 103 and bulkhead 105 in order to allow communication between outer chambers 108.
• Vanes 111 which in this embodiment are flat, are arranged at both sides of partition 120 and are slidable within slots 110 extending through the walls of both bulkhead 105 and rotor 103 at least at one end of partition 120 and, preferably, at both ends thereof.
• the through slots have similar functions to passageways 12, 13 in Fig. 1.
• vanes 111 will move to the idle position in case of engine acceleration and to the operating position in case of deceleration.
• Each vane 111 has on its forward face (with reference to the rotation direction of the rotor, which in this embodiment has been supposed to be the counterclockwise direction, as shown by arrow R2), near its forward end intended to engage wall 102A of body 102, a recess 121 which can be engaged by one end of an anchoring element 122, intended to hold the vane in the retracted position.
• a similar recess is provided also on the rearward face of the vane, near the rearward end, and both ends of elements 122 are so shaped that they can engage recesses 121. This assists in an error-proof mounting.
• Both anchoring elements 122 are slidably mounted in a respective outer chamber 108, in the region defined by the forward face of vane 111 and the closest partition 109, and are symmetrically arranged.
• Elements 122 have an arched shape, corresponding to the shape of the chambers, and they may have a substantially circular cross section.
• anchoring elements 122 In case of acceleration, due to the effect of inertia and the relevant inertia force (inertial force), anchoring elements 122 will be in contact with the surface of vanes 111 and, when the latter are retracted in rotor 103, such elements will engage recesses 121 thereby locking vanes 111. In case of deceleration, always due to the effect of inertia and the relevant inertia force (inertial force), anchoring elements 122 will disengage from recesses 121 and vanes 111 will be free to move out of the rotor, due to the effects of the centrifugal force, and into contact with internal surface 102A of body 102. As before, at constant speed, the vanes will remain in the idle position (and hence they will be locked by anchoring elements 122) or in the operating position, depending on whether the constant speed has been attained after an acceleration or a deceleration.
• the invention achieves the aim indicated above. Since the turning on of the pump depends on the deceleration and not on the speed, the possible risk or damage situations are eliminated. Moreover, the forces present because of rotation are directly exploited in order to bring the pump to the operating or the idle position: thus, there is no need for counterweights and springs or external devices, such as valves, so that the structure is simpler, less expensive and less prone to possible failures.
• the pump according to the invention in the various embodiments, comprises pumping elements directly operated by forces generate internally of the rotor because of acceleration or deceleration of the same rotor.
• the invention also implements a method of controlling a vacuum pump, in order to automatically turn the pump on or off at the occurrence of first or second operating conditions, respectively, of a motor driving the same pump.
• a method of controlling a vacuum pump includes the following steps:
• the pump may have a single vane.
• the pump when it is operating, sucks and compresses, at each revolution, a volume of fluid equal to the volume comprised between the internal surface of the body and the external surface of the rotor, less the vane volume.
• the two-vane embodiment is preferable, in that it allows doubling the displacement, with the same size, since the two phases are separated.
• vanes 111 having a recess 121 on each face, at opposite ends, have been shown in Fig. 3. It is also possible to provide opposing recesses 121 on both faces and at both ends of each vane. In this way, vanes 111 may be mounted with any orientation. Further, anchoring elements 122 could be mounted at one end of respective arms or spokes pivotally connected, at the opposite end, in correspondence of rotation axis A of rotor 103.
• Elements 122 instead of having circular cross-section, could be shaped so that each of them engages an elongated recess or a plurality or recesses, for instance aligned recesses: the configuration must be such that the axial extension of elements 122 is shorter than that of vanes 111 , to allow air/oil to flow through slots 110.
• the pumps as shown in the embodiments considered as preferable can be used also in conjunction with electric control motors.
• the electric control motor is directly supplied with the deceleration or the acceleration or is supplied with a suitable signal causing a corresponding deceleration or acceleration of the pump.
• the invention can be applied to any rotary pump in which a pumping element is displaceable in the rotor between an operating position and idle position.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Rotary Pumps (AREA)
• Valves And Accessory Devices For Braking Systems (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=43743108

Family Applications (1)

Country Status (3)

Families Citing this family (3)

Family Cites Families (8)

• 2010
  • 2010-11-29 IT ITTO2010A000945A patent/IT1403001B1/it active
• 2011
  • 2011-11-25 WO PCT/IB2011/055301 patent/WO2012073165A2/en unknown
  • 2011-11-25 EP EP11805599.5A patent/EP2646655A2/de not_active Withdrawn

Non-Patent Citations (1)

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