EP3983682A1

EP3983682A1 - Displacement machine

Info

Publication number: EP3983682A1
Application number: EP20732913.7A
Authority: EP
Inventors: Patrizia Domenica CILIBERTI; Nicola FILIPPI; Leonardo Cadeddu; Lillo TERRANOVA
Original assignee: VHIT SpA
Current assignee: VHIT SpA
Priority date: 2019-06-17
Filing date: 2020-06-17
Publication date: 2022-04-20
Also published as: WO2020254387A1; IT201900009213A1

Abstract

Displacement machine acting on an operating fluid passing therethrough and including: - a rotary rotor (3), - a stator (2) that forms a housing chamber (20) for the rotor (3), - a first discharge (21) for a fluid from said housing chamber (20), - a first check valve (4) that enables the fluid to flow out of the first discharge (21). In an operating mode in which the rotor (3) is stopped and no operating fluid is being expelled from the housing chamber (20) through said first discharge (21), the first valve (4) spontaneously assumes an idle configuration closing said first discharge (21).

Description

DESCRIPTION

Displacement machine

The present invention relates to a displacement machine acting on an operating fluid flowing therethrough. Said machine is in particular a pump able to generate/maintain a pressure drop on the suction side (vacuum pump). The displacement machine acts on a gaseous operating fluid.

Vacuum vane pumps with two discharges that enable the fluid to be discharged from a stator forming a chamber containing the rotor with the vanes are known. The fluid coming out of the discharges is collected in a shared chamber formed by a flexible sleeve arranged immediately downstream of the chamber. The sleeve has a single central duct for draining the fluid in the shared chamber.

This causes the accumulation of the volume of air in the shared chamber behind the chamber. This does not facilitate the elimination of heat. Furthermore, pumps of this type are noisy.

When the vane pump stops running as a result of the pressure drop created in the chamber, the flexible cap is moved back towards a plate that delimits the chamber containing the rotor. This closes the mouth of the central duct, which is pressed against said plate. The air also tends to enter the chamber through the imperfect seals of a shaft driving the rotor in rotation. This, in combination with the natural elastic return of the cap, causes the mouth of the central duct to move away from the plate, suddenly reopening the connection between the chamber and the zone downstream of the central duct. The spring effect caused by the cap causes said connection to open before pressure stabilization. This results in a significant backflow of air into the chamber from the discharge, potentially resulting in the ingress of impurities.

The present invention is intended to provide a displacement machine that precludes the ingress of impurities when the machine is stopped. A further significant advantage is related to optimal heat dissipation. An additional advantage is related to reduced noise. In particular, the present invention is intended to overcome the aforementioned technical drawbacks.

The technical brief and objectives specified are substantially achieved by a displacement machine having the technical features set out in one or more of the attached claims.

Further features and advantages of the present invention are set out more clearly in the description, which is illustrative and therefore not limiting, of a displacement machine illustrated in the attached drawings, in which:

- Figure 1 is a perspective view of a displacement machine according to the present invention,

- Figure 2 is a plan view of the machine in Figure 1 ,

- Figure 3 is a view of the section plane shown in Figure 2,

- Figure 4 shows a detail from Figure 3 in two different operating configurations,

- Figure 5 shows the machine in Figure 1 with some portions removed to better show other portions,

- Figure 6 shows an internal component of the machine in Figure 1 ,

- Figure 7 is a view of the section plane shown in Figure 6,

- Figures 8, 9 and 10 show the route of the fluid inside the machine in Figure

1,

- Figure 11 shows a detail from Figure 10.

In the attached figures, reference sign 1 indicates a displacement machine acting on operating fluid passing therethrough.

The machine can naturally be used as an aspirator or a compressor. The machine is preferably a vacuum displacement machine (pump) that is therefore designed to generate a pressure drop on the suction side. Advantageously, the machine 1 operates dry. The machine uses a gas such as air as operating fluid. The operating fluid is not a liquid.

For example, the displacement machine 1 can be used by the hydraulic pressure booster of the braking system of electric, hybrid or heat-engine vehicles. This assembly comprises an electric motor that can be a direct- current motor with or without brushes and with or without a drive engine control unit (ECU).

Advantageously, the machine 1 includes:

- a rotary rotor 3,

- a stator 2 that forms a housing chamber 20 for the rotary rotor 3.

This rotor 3 is also known as an impeller. This rotor 3 is advantageously carried by a rotary shaft 300. The rotor 3 can therefore rotate about an axis 301 of rotation. By way of non-limiting example, the housing chamber 20 is elliptical or substantially elliptical in a section orthogonal to the axis 301 of rotation. Advantageously, the machine 1 is a vane displacement machine. The rotor 3 has vanes 30 extending towards the stator 2 (see Figure 5). The rotor 3 has seats for the vanes 30. Each vane 30 is at least partially inserted into a corresponding seat. During rotation of the rotor 3, these vanes tend to move outwards, coming into contact with the stator 2. The vanes therefore move between a position closer to an axis 301 of rotation of the rotor 3 and a position further away from an axis 301 of rotation of the rotor 3.

A space is left between two contiguous vanes 30 to contain the operating fluid. Each space undergoes two compressions and two aspirations with each rotation. Advantageously, the stator 2 therefore has two aspirations and two discharges, as explained in greater detail below.

Consequently, there are 16 compressions and 16 aspirations with each rotation of the rotor 3, in the preferred non-binding embodiment shown,. This fractioning helps to reduce peaks of drag torque and to separate the phases between spaces, with the resulting improvement in volumetric efficiency, at the expense of aspiration and discharge noise.

Furthermore, being a dry machine 1 that is therefore not lubricated, the only fluid enabling a heat exchange with the outside is the aspirated operating fluid, which is more rarefied the greater the value of the vacuum generated. Advantageously, the machine 1 has a first discharge 21 for a fluid from the housing chamber 20. The first discharge 21 has a first hole 201 that traverses a cover 200 that helps to delimit said housing chamber 20 containing the rotor 3. The flow area is reduced through the hole 201. The cover 200 of the housing chamber 20 is transversal (preferably orthogonal) to an axis 301 of rotation of the rotor 3. The cover 200 can also be a closing plate of the pump unit or of the housing chamber 20.

The machine 1 has a first check valve 4 that enables the fluid to flow out of the first discharge 21.

In an operating mode in which the rotor 3 is stopped and no operating fluid is being expelled from the housing chamber 20 through said first discharge 21 , the first valve 4 spontaneously assumes an idle configuration closing said first discharge 21. The first valve 4 is controlled by the upstream/downstream pressure difference.

The first valve 4 can therefore be understood to be a one-way valve.

The first valve 4 is arranged on top of the first discharge 21 , both in the idle configuration and when the fluid is coming out of the housing chamber 20 through the first discharge 21.

Advantageously, the machine 1 has a cap 5 arranged downstream of the first discharge 21. This cap 5 forces the fluid coming out of the housing chamber 20 to effect a plurality of changes of direction. This cap 5 can be made of flexible or rigid material, or partially of flexible material and partially of rigid material. The cap 5 can act as acoustic barrier, which helps to reduce the noise of the machine 1.

Advantageously, the machine 1 has a cover 8 for the cap 5. The cap 5 is therefore interposed between the cover 8 and the housing chamber 20. The cover 8 therefore envelops the cap 5.

Advantageously, the cover 8 has a crown 81 from which a side wall 82 extends. This side wall 82 extends from the crown 81 towards the housing chamber 20.

Advantageously, the first check valve 4 is at least partially (and preferably entirely) built into said cap 5. In particular, said valve is built into a portion of the cap 5 that is closer to the housing space 20 and/or the cover 200 that helps to delimit the chamber 20.

In particular, the first check valve 4 is a single member integral with said cap 5. In an alternative solution (not shown), said valve could be assembled with said cap, for example by gluing, welding or mechanical fastening. Advantageously, the first check valve 4 is made of an elastomeric material, such as rubber. Said elastomeric material is able to withstand high temperatures.

The first check valve 4 advantageously comprises a membrane valve 400. The membrane of the valve is cantilevered and, in said idle configuration, prevents the fluid from flowing through said first discharge 21 , and, in an operating configuration assumed while the operating fluid is coming out of the housing chamber 20 through said first discharge 21 , is at least partially further away from said first discharge 21. In the idle configuration, the membrane valve 400 therefore provides a fluid dynamic seal on the first discharge 21.

In the preferred solution, the membrane valve 400 is arranged at one end of the first discharge 21 (in a specific non-limiting embodiment, said valve is arranged vertically above the first discharge 21).

The machine 1 (or rather the cap 5) has a first path 6 extending immediately downstream of said first valve 4. The first valve 4 is arranged at a first end 61 of the first path 6. The first end 61 is behind the first discharge 21.

The first valve 4 is arranged across the first path 6. In particular, the first valve 4 is integral with the first path 6.

Advantageously, the machine 1 has a second discharge 22 for the fluid from said housing chamber 20.

The machine 1 has a second check valve 40 that enables the fluid to flow out of the second discharge 22.

In an operating mode in which the rotor 3 is stopped and no operating fluid is being expelled from the housing chamber 20 through said second discharge 22, the second valve 40 spontaneously assumes an idle position closing said second discharge 22. The second valve 40 is controlled by the upstream/downstream pressure difference.

Advantageously, the description of the first valve 4 and/or the interaction thereof with the remaining portions of the machine 1 also apply to the second valve 40 and to the interaction thereof with the remaining portions of the machine 1.

In particular, the second valve 40 is advantageously arranged on top of the second discharge 22.

The second discharge 22 has a hole 202 that traverses the cover 200 that helps to delimit said housing chamber 20 containing the rotor 3.

The second check valve 40 is at least partially built into the cap 5.

Preferably, the second check valve 40 is a single member integral with the cap 5.

Advantageously, the first and second valves 4, 40 are built into the cap 5 as a single member.

The second check valve 40 comprises a membrane valve. The membrane of the second valve 40 is cantilevered and, in said idle position, prevents the fluid from flowing through said second discharge 22, and, in an operating position assumed while the operating fluid is coming out of the housing chamber 20 through said second discharge 22, is at least partially further away from said second discharge 22.

The membrane valve 40 is arranged vertically above the second discharge 22.

The stator 2 has two discharges only {the first and second discharges 21 , 22), both of which can be closed by a check valve (the first and second valves 4, 40).

The machine 1 (or rather the cap 5) advantageously includes a second path 60. This path advantageously extends immediately downstream of the second valve 40. The second valve 40 is arranged at a first end 610 of said second path 60, said first end 610 being behind said second discharge 22. Advantageously, the second valve 40 is arranged across the second path 60.

The first path 6 and/or the second path 60 are advantageously integral with the cap 5.

Downstream of the first and second discharges 21 , 22, the cap 5 and the cover 8 together define at least two alternative fluid routes. These alternative routes join together along the lengths thereof to define shared sections, and branch away from one another (defining separate sections). Said two alternative routes are of different lengths (the branching and asymmetry of the routes helps to better dampen the sound waves).

The first and second paths 6, 60 are separate from one another. Advantageously, said paths define two distinct routes for the operating fluid. Furthermore, the first and second paths 6, 60 operate fluid dynamically in parallel, i.e. the operating fluid on the first path 6 does not also flow on the second path 60, and vice versa. Said paths extend respectively downstream of the first and second discharges 21 , 22 away from said housing chamber 20 and towards said cover 8. The first and second paths 6, 60 convey the fluid coming out of the first and second valves 4, 40 respectively.

The first and second paths 6, 60 flow into a first expansion chamber 91 and a second expansion chamber 910 respectively. Advantageously, the first and second paths 6, 60 flow out at diametrically opposite points in relation to the axis 301 of rotation of the rotor 3.

Advantageously, the first and second expansion chambers 91 , 910 are behind the cover 8. In particular, the fluid in the first and second expansion chambers 91 , 910 is in contact with an inner surface of the cover 8. Advantageously, the fluid is in contact with the crown 81 of the cover 8. Advantageously, the first and second chambers 91 , 910 overlap the crown 81 of the cover 8 by between 15% and 50%. This facilitates the heat exchange with the outside. The first and second expansion chambers 91 , 910 define mutually asymmetrical routes. In particular, both the first chamber 91 and the second chamber 910 define a curved route. The route formed by the first chamber 91 is however not the same length as the route formed by the second chamber 910.

Advantageously, the machine 1 has a first channel 92 and a second channel 920 that convey the fluid towards a theoretical plane that is orthogonal to the axis 301 of rotation and that passes through the cover 200 or through the chamber 20 (the fluid will not however return to the chamber 20). In practice, the fluid is inverted compared to the route in the first and second paths 6, 60. In the first and second paths, the fluid moves upwards away from the housing chamber 20. In the first and second channels, the fluid moves downwards towards the housing chamber 20. The first and second channels 92, 920 extend respectively from the first and second expansion chambers 91 , 910. The direction of the fluid in the first and second channels 92, 920 is the opposite of the direction of the fluid on the first and second paths 6, 60. The first and second channels 92, 920 advantageously extend parallel to one another. The first and second channels 92, 920 flow into a shared chamber 93 in which the fluid coming from the first and second channels 92, 920 is mixed together. The shared chamber 93 has at least one portion with an irregular lateral surface. This irregular surface constitutes means affecting sound proofing and heat exchange.

Advantageously, the cap 5 has a third path 94 running from said shared chamber 93 to said cover 8. The third path 94 runs away from the housing chamber 20, therefore running upwards. Advantageously, the third path 94 runs parallel to the first and second paths 6, 60. The third path 94 is substantially in the centre of the shared chamber 93.

The third path 94 advantageously has at least two inlets 941 , 942 in said shared chamber 93. The two inlets 941 , 942 constitute a restriction of the flow area. The two inlets 941 , 942 define a radial passage between the outside and the inside of the third path 94. Advantageously, said inlets are in two opposite positions of the third path 94. In particular, said inlets are in diametrically opposite positions. The fluid in the third path moves away from the housing chamber 20, preferably in a direction parallel to the direction of conveyance of the first and second paths 6, 60.

The machine 1 also has an annular passage 96 interposed between the cap 5 and the cover 8 into which said fluid flows. This annular passage 96 is advantageously downstream of the third path 94. Advantageously, said annular passage 96 can have fins to improve heat exchange and sound proofing. Advantageously, said fins are arranged on the cover 8.

Advantageously, the machine 1 includes an outlet 962 for the fluid in said annular passage 96. The outlet 962 is in a position of the cap 5 opposite (preferably diametrically opposite) an inlet 961 for the fluid in said annular passage 96.

The machine 1 also includes a substantially radial duct 95 (see Figure 11) that links an outlet 940 of the third path 94 and the annular passage 96.

In said outlet 940, the machine 1 defines another reduction of the flow area. The machine 1 therefore includes a discharge pipe 99. Downstream of said outlet 940 and immediately before the discharge pipe 99, there is also a double direction inversion 943, 944 (the fluid flowing first upwards, then downwards).

Advantageously, downstream of the housing chamber 20, the fluid is conveyed along at least one first section away from the housing chamber 20 (advantageously upwards), along a second section towards a theoretical plane that is orthogonal to the axis 301 of rotation of the rotor 3 and that passes through said housing chamber 20, a third section away from the housing chamber 20, and a fourth section towards said theoretical plane. Advantageously, the first, second, third and fourth sections extend over more than 70% of the height of the sleeve 5, measured parallel to the axis 301 of rotation. The first section concerns the first and second paths 6, 60. The second section concerns the first and second channels 92, 920. The third section concerns the third path 94. The fourth section concerns the annular passage 96. In the annular passage, in addition to moving about the sleeve 5, the fluid also has an axial component (parallel to the axis 301 of rotation).

Advantageously, the machine 1 has a support 85 to which the electric motor that drives the rotor 3 is attached. The suction pipe 98 and the discharge pipe 99 are formed in and/or mounted on said support 85.

Said support 85 is also linked to vibration-damping elements 86 for connection to the vehicle (not shown). The support 85 is also usually designed to carry, directly or via the electric motor, the electric cables 87 and related power connectors (not shown). The drive shaft 300 of the rotor 3 also passes through the support 85.

The present invention also relates to an operating method of a displacement machine acting on an operating fluid flowing therethrough. Advantageously, the displacement machine 1 has one or more of the technical features described above. Advantageously, the method includes phases that are implemented using the machine 1.

The method includes the phase of closing the first discharge 21 when the rotor 3 of the machine 1 stops. This is determined by the fact that the pressure drop that occurs in the housing chamber 20 when the rotor 3 stops moves the first valve 4 back, closing the first discharge 21.

As the pressure difference drops, the first valve 4 remains closed.

Advantageously, the method includes the phase of conveying the fluid coming out of the housing chamber 20 through the first and second discharges 21 , 22 respectively along the first and second paths 6, 60. Advantageously, the phase of conveying the fluid coming out of the housing chamber 20 includes the fluid flowing through the first and second valves 4, 40 (see Figures 3 and 4).

Advantageously, the method includes the phase of expanding the fluid in said first and second expansion chambers 91 , 910 (see Figure 8).

The method advantageously includes the phase of conveying the fluid from the first and second expansion chambers 91 , 910 respectively along a first channel 92 and a second channel 920 to a shared chamber 93 (see Figures 8 and 10). Moving from the first and second expansion chambers 91 , 910 to the first and second channels 92, 920 involves an abrupt variation in the flow area (shape and/or size).

In the shared chamber 93, the fluid taken through the first path 6 and the fluid taken through the second path 60 are mixed back together (see Figure 10).

The passage of the fluid from the first and second channels 92, 920 to the shared chamber 93 is associated with an increase in the flow area of the fluid.

The method also includes the phase of laminating the fluid by injecting said fluid into a third path 94 (see Figure 10). This is carried out using at least two inlets 941 , 942 in the shared chamber 93 (see Figure 11). This third path conveys the fluid away from the housing chamber 20 (to the crown 81 of the cover 8).

Advantageously, the method includes the phase of conveying said fluid to an annular passage 96 interposed between the cap 5 and the cover 8.

As shown by way of example in Figure 10, the phase of conveying said fluid to an annular passage 96 interposed between the cap 5 and the cover 8 includes the following phases:

- injecting the fluid into an inlet 961 of said annular passage 96,

- draining the fluid through an outlet 962 in said annular passage (96),

- splitting the fluid flowing from the inlet 961 to the outlet 962 of the annular passage 96 into a first flow and a second flow, one of which moves in a clockwise direction and the other of which moves in an anti-clockwise direction, in contact with opposite sides of the cap 5.

The method also includes the phase of draining the fluid from said machine 1 through an outlet duct 97 arranged downstream of said annular passage 96.

The present invention brings important advantages.

Firstly, the invention enables the check valve on the discharge to be kept closed for the entire time that the displacement machine 1 is turned off. Another advantage relates to the creation of a virtuous route for the discharge fluid coming out of the housing chamber 20. This makes it possible to separate the sound waves from the discharge channels, differentiating the flows thereof in terms of tortuosity and route. The asymmetrical routes make it possible to phase-shift the sound waves caused by the discharges, as well as enabling lamination and volumetric variations (abrupt expansions or reductions in flow area reduce sound levels). Furthermore, the tortuous route comes into contact with an external zone and helps to maximize heat exchange, improving the heat exchange coefficient between the inside and the outside of the machine 1.

The invention thus designed can undergo numerous modifications and variations within the scope of the inventive concept characterizing the invention. Furthermore, all of the details may be replaced by other technically equivalent elements. In practice, any materials and dimensions may be used, as required.

Claims

1. Displacement machine acting on an operating fluid passing therethrough and including:

- a rotary rotor (3),

- a stator (2) that forms a housing space (20) for the rotary rotor (3),

- a first discharge (21) for a fluid from said housing chamber 20,

- a first check valve (4) that enables the fluid to flow out of the first discharge

(21),

characterized in that, in an operating mode in which the rotor (3) is stopped and no operating fluid is being expelled from the housing chamber (20) through said first discharge (21), said first valve (4) spontaneously assumes an idle configuration closing said first discharge (21);

said displacement machine (1) having a second discharge (22) for the fluid from said housing chamber 20 and a second check valve (40) that enables the fluid to flow out of the second discharge (22);

when the rotor (3) is stopped and no operating fluid is being expelled from the housing chamber (20) through said second discharge (22), the second valve (40) spontaneously assumes an idle position closing said second discharge (22).

2. Machine according to Claim 1 , characterized in that said first valve (4) faces said first discharge (21), said first discharge (21) having a first hole (201) that traverses a cover (200) that helps to delimit said housing chamber (20) containing the rotor (3).

3. Machine according to Claim 1 or 2, characterized in that it includes a cap (5) arranged downstream of the first discharge (21) that forces the fluid coming out of said housing chamber (20) to effect a plurality of changes of direction.

4. Machine according to Claim 3, characterized in that at least said first check valve (4) is at least partially built into said cap (5).

5. Machine according to Claim 3 or 4, characterized in that said first check valve (4) is a single member integral with said cap (5). 4M

6. Machine according to any one of the preceding claims, characterized in that said first check valve (4) comprises a cantilevered membrane valve (400) that:

- prevents the fluid from flowing through the first discharge (21) in said idle configuration of the first valve (4),

- in an operating configuration assumed while the operating fluid is coming out of the housing chamber 20 through said first discharge (21), is at least partially further away from said first discharge (21) compared to said idle configuration

7. Machine according to Claim 6, characterized in that said membrane valve

(400) is arranged vertically above the first discharge (21).

8. Machine according to any one of the preceding claims, characterized in that it includes a first path (6) immediately downstream of said first valve (4), said first valve (4) being arranged at a first end (61) of said first path (6), said first end (61) being behind said first discharge (21).

9. Machine according to Claim 8, characterized in that said first valve (4) is arranged across the first path (6).

10. Machine according to any one of the preceding claims, characterized in that it is a dry vane vacuum pump, said rotor (3) including vanes (30) that extend towards the stator (2).