EP3803124B1

EP3803124B1 - Rotary volumetric pump

Info

Publication number: EP3803124B1
Application number: EP19726704.0A
Authority: EP
Inventors: Leonardo Cadeddu
Original assignee: VHIT SpA
Current assignee: VHIT SpA
Priority date: 2018-05-30
Filing date: 2019-05-29
Publication date: 2022-03-30
Anticipated expiration: 2039-05-29
Also published as: WO2019229106A1; IT201800005866A1; CN112543845A; EP3803124A1

Description

The present invention relates to a rotary volumetric pump, in particular a vane pump, used to generate pneumatic pressure and/or vacuum, especially in dry vacuum pumps, i.e. vacuum pumps not lubricated by a fluid.
Vane pumps of the type comprising a rotary shaft to which a rotor may be connected by means of a drive coupling are known in the prior art. This coupling is connected to the shaft in such a way as to avoid relative rotation. It has a ring from which two arms, that are engaged in corresponding seats afforded in the rotor, extend.
According to a first structural solution, said arms have a substantially circular cross section and a conical longitudinal section, due to deformation by stamping. According to a second structural solution, the side wall of each of the arms has two opposite surfaces that are reciprocally domed and intended to come into contact with the flat surfaces of the corresponding rotor seats.
Said couplings are obtained by precision casting and the piece thus obtained is subjected to several machining operations by machine tools (typically on the inside of the hole of the annular coupling). This obviously slows down the production process, while requiring successive machining operations that increase costs.
Documents WO 2017/093073 A1 , DE 10 2007 019283 A1 , DE 10 2010 001240 A1 disclose couplings known in the prior art.
One aim of the present invention is to provide a pump that allows optimisation of costs as well as distribution of the pressures acting on the surfaces.
A further aim is to reduce wear and maintain good centring. The technical problem described and the aims specified are substantially achieved by a pump comprising the technical features defined in one or more of the attached claims.
Further features and advantages of the present invention will become clearer from the non-limiting description provided, for information, of a pump as shown in the attached drawings, in which:

figure 1 shows a view of a shaft/rotor/coupling sub-assembly of a pump according to the present invention; said sub-assembly is identified by the reference sign 1;
figure 2 shows a perspective view of a part of the sub-assembly of the pump of figure 1;
figures 3, 4 and 5 show, respectively, a perspective view, a front view and a view in section of a rotor with a vane, which is a component of the solution shown in figure 1;
figure 6 shows a further component of the solution shown in figure 1.

The present invention relates to a rotary volumetric pump, preferably a vane pump (it may also possibly be a gear pump or other type of pump). Typically, the pump is a dry pump. Conveniently, it is a vacuum pump. For example, it may be used in vehicle braking systems. In the preferred solution, the pump is driven by an electric motor. The pump comprises:

a shaft 2 suitable for rotating about an axis of rotation;
a rotor 3. The rotor 3 is a member that allows movement of the working fluid processed by the pump. The rotor 3 thus comes into contact with the working fluid.

In the preferred solution in which the pump is a vane pump, the rotor 3 houses the vanes 4 at least partially.
In this regard, the rotor 3 has cavities 300 for housing the vanes 4. Each of said cavities 300 extends between an inner radial position and an outer radial position. Advantageously, said cavities 300 are inclined with respect to a purely radial direction. The cavities 300 preferably pass completely through the rotor 3 in the axial direction.
Figure 4 shows a single one of said vanes 4, although each cavity 300 houses one.
Advantageously, the rotor 3 is made of carbon-graphite. Conveniently, the rotor 3 is a discoidal element. The rotor 3 is preferably coaxial with the shaft 2.
The pump comprises a stator element, not shown in the attached figures, which defines an opening in which the rotor 3 is housed. The rotor 3 thus rotates inside the opening. Depending on the position of each, said vanes 4 project from the rotor 3 to a greater or lesser degree. Externally, the vanes 4 are touched by the stator element.
The pump further comprises means 5 for transmitting torque from the shaft 2 to the rotor 3. In the solution shown in figures 1, 2 and 6, the transmission means 5 comprise/coincide with a transmission coupling.
The rotor 3 comprises a first seat 31. The first seat 31 comprises a side wall 310 (see figure 3). The side wall 310 comprises a first flat portion 311 (shown in figure 4). The side wall 310 advantageously also comprises a second flat portion 312, opposite the first flat portion 311, and advantageously two connection zones located at opposite ends of the first seat 31. The first seat 31 advantageously comprises an end wall 313. The first portion 311 lies in a first plane, and the second portion 312 lies in a second plane parallel to the first plane.
The transmission means 5 comprise an annular structure 50. The annular structure 50 is preferably obtained from a sheet of stainless steel. It is applied to the shaft 2. In particular, the shaft 2 is engaged in (and through) a hole 59 defined by the annular structure 50. Conveniently, the shaft 2 and the annular structure 50 are coupled by interference. The torque is thus transmitted by the shaft 2 to the annular structure 50, which in turn transmits the torque to the rotor 3. The annular structure 50 is removably connected to said rotor 3. The annular structure 50 in turn comprises at least one first projecting tab 51 that at least in one operating configuration of the pump is engaged in said first seat 31 of the rotor 3. Said projecting tab 51 is for transmitting the movement of the annular structure 50 to the rotor 3.
The first tab 51 comprises at least one first flat surface 510. The first tab 51 has a mainly longitudinal direction of extension. The longitudinal direction of the first tab 51 extends in an axial direction. The first tab 51 comprises a second flat surface 511 which is positioned on the opposite side to the first flat surface 510.
In a section orthogonal to said main direction of extension, the first tab 51 has a rectangular section. At the two vertices 55 of said orthogonal section (on the side opposite that on which there may be cutting burrs), the corner does not have any burrs, as a result of the actual cutting process. Conveniently, in this section, the two vertices 55 are at the ends of the first surface 510.
In the operating configuration, the first flat surface 510 is a surface that pushes the rotor 3 and is in contact with said first flat portion 311 of said wall 310 of the first seat 31. The direction of rotation of the shaft 2 is such as to bring the first surface 510 to press against the first portion 311. Conveniently, the second flat surface 511, in the operating configuration, faces the second portion 312 of the side wall 310.
This first surface 510 is a zone of contact with the rotor 3. The first surface 510 has a mainly longitudinal extension that extends parallel to the axis of rotation of the shaft 2.
Similarly, the first surface 510 has a larger radial extension component than a tangential extension component (said tangential component may even be zero). The radial extension is evaluated with respect to the axis of rotation of the shaft 2. The tangential component is evaluated tangentially to circumferences centred on the axis of rotation of the shaft 2. This orientation makes it possible to transfer torque to the rotor 3, reducing localised stresses and improving specific pressure spikes (by virtue of the increased areas of contact).
Conveniently, the first surface 510 lies in a plane that also contains the axis of rotation of the shaft 2.
In the preferred solution, the first tab 51 is a portion of sheet less than 1.5 millimetres thick. The first tab 51, for example, extends longitudinally over a length of between 5 and 9 millimetres. Preferably, the first tab 51 has a width of between 2 and 4 millimetres.
The annular structure 50 comprises a central crown 500 from which there extends an L-shaped structure 501, which defines said first tab 51.
Conveniently, the annular structure 50 comprises a second projecting tab 52 which, in the operating configuration, is engaged in a second seat 32 afforded in the rotor 3. The first and second tabs 51, 52 are advantageously in diametrally opposite positions.
The description provided with reference to the first tab 51 may be repeated for the second tab 52. Likewise, the description provided with reference to the first seat 31 may be repeated for the second seat 32. In particular, the description provided with reference to the first tab 51 and the interaction thereof with the first seat 31 may be repeated for the second tab 52 and the interaction thereof with the second seat 32. For example, the second tab 52 may comprise a thrust surface 520. Said thrust surface 520 is flat. It is contained entirely in the plane containing the first surface 510 and the axis of rotation of the shaft 2.
There may also be further tabs projecting from the crown 500, engaged in corresponding seats afforded in the rotor 3.
The rotor 3 preferably comprises a housing 30 in which, in said operating configuration, said central crown 500 is completely inserted. Said first seat 31, in which the first tab 51 is engaged, extends from said housing 30, parallel to the axis of rotation of the shaft 2.
Conveniently, the rotor 3 comprises an axial portion 56 in correspondence with which the radial play with the shaft 2 is minimal. The first tab 51 extends internally inside the first seat 31 only (or at least for 90%) in correspondence with said axial portion 56 in correspondence with which the radial play is minimal. The same may be said of the second tab 52 which extends inside the second seat 32. The purpose of these arrangements is to ensure that the transmission of torque to the rotor 3 by the means 5 (the coupling) takes place in a zone where the rotor 3 is well guided by the shaft 2 so as to prevent small errors of shape leading to misalignments.
The present invention also relates to a method for realising a pump. Conveniently, said pump comprises one or more of the features described above.
The method comprises the step of realising the annular structure 50. This advantageously takes place in a progressive stamping die, which works on a "sheet strip", in which a series of operations take place in succession. When the part leaves the progressive stamping die, no machining is performed to remove additional shavings from the annular structure 50. This renders production more rapid and less costly. The step of realising the annular structure 50 comprises the step of shaping a sheet (which is conveniently at least initially flat) by cutting and drawing to form a central crown 500 from which at least one lateral arm 501 extends. At least in this step, the central crown 500 advantageously remains connected to the surrounding sheet by means of at least one connection point which, in this step, is not cut (this happens only later). The drawing determines a thickening of the central crown 500 whose thickness becomes greater than that of the initial sheet. This facilitates transmission of the torque from the shaft 2.
The step of realising the annular structure 50 comprises bending the lateral arm 501 to define the first tab 51. This involves bending the arm 501 by an angle of between 70° and 110°, preferably 90°.
Conveniently, the longitudinal extension of the lateral arm 501 has two curves (see figure 6):

a first curve 504 indicating the passage from a radial extension to a substantially tangential extension;
a second curve 505 that determines the passage from a substantially tangential extension to an extension parallel to the axis of rotation of the shaft 2. Conveniently, the step of realising the annular structure 50 further comprises the step of bending (typically by 90°) the at least one additional arm 502 that extends from the central crown 500. This additional arm defines the second tab 52. Detachment from the "sheet strip" takes place in a successive realisation step.

The method further comprises the step of inserting the shaft 2 into the hole 59 of said annular structure 50. This takes place after the annular structure 50 is complete. The shaft 2 and the annular structure 50 are normally connected by interference.
The method further comprises the step of inserting the shaft 2 into the rotor 3 (connecting the annular structure 50 and the rotor 3). This comprises the step of inserting the first tab 51 into the first seat 31 of the rotor 3 (and, advantageously, the second tab 52 is also inserted into the second seat 32).
The present invention affords significant advantages.
First of all, it makes it possible to limit production costs by realising the coupling by stamping sheet metal without additional machining. Moreover, there are improved areas of contact with the consequent reduction in specific pressures (which are considerable especially in the case in which the rotor is made of carbon-graphite, a material which has optimal temperature resistance but mechanical properties that are inferior to steel).
A further significant advantage relates to the good centring between the rotor 3 and the shaft 2 thanks to coupling with reduced play which allows sufficient dynamic oscillation to make up for the errors in orthogonality from production, while limiting wear; this is also thanks to the abovementioned configuration of the coupling 5.
Moreover, all the details may be substituted by other technically equivalent elements. In practice, all the materials used, and the dimensions, may be whatever is required.

Claims

A volumetric pump comprising:
- a shaft (2) suitable for rotating about an axis of rotation;

- a rotor (3);

- a means (5) for transmitting torque from the shaft (2) to the rotor (3);
said rotor (3) comprising a first seat (31) comprising a side wall (310) comprising a first flat (311) portion;
the transmission means (5) comprising an annular structure (50) solidly constrained to the shaft (2) and connected to said rotor (3); said annular structure (50) in turn comprising at least one first projecting tab (51) that at least in one operating configuration of the pump is engaged in said first seat (31) of the rotor (3); said first tab (51) comprising at least one first flat surface (510);

characterised in that in said operating configuration said first flat surface (510) is a thrust surface and is in contact with said first flat portion (311) of the side wall (310) of the first seat (31);

said first tab (51) having a larger radial extension component than a tangential extension component, said radial extension being evaluated with respect to the axis of rotation of the shaft (2), said tangential component being evaluated tangentially to circumferences centred on the axis of rotation of the shaft (2).
The pump according to claim 1, characterised in that it comprises at least one second projecting tab (52) which in said operating configuration is engaged in a second seat (32) afforded in the rotor (3).
The pump according to claim 1 or 2, characterised in that said first tab (51) is a portion of sheet less than 1.5 millimetres thick.
The pump according to any one of the preceding claims, characterised in that said rotor (3) is made of carbon-graphite, said annular structure (50) is obtained from a sheet of stainless steel.
The pump according to any one of the preceding claims, characterised in that said annular structure (50) comprises a central crown (500) from which the first tab (51) extends.
The pump according to claim 5, characterised in that the first tab (51) is integrated in an L-shaped structure (501) that extends from the central crown (500).
The pump according to claim 5 or 6, characterised in that said rotor (3) comprises a housing (30) in which in said operating configuration said central crown (500) is completely inserted; said first seat (31) in which the first tab (51) is engaged extending parallel to the axis of rotation of the shaft (2) from said housing (30).
A method for realising a pump according to claim 5 or 6 or 7,
characterised in that it comprises the steps of:
a) realising said annular structure (50), which comprises the steps of:
- shaping a sheet by cutting and drawing to form a central crown (500) from which at least one lateral arm (501) extends;

- bending the lateral arm (501) to define said first tab (51);

b) inserting said shaft (2) into a hole (59) of said annular structure (50);

c) inserting said first tab (51) into the first seat (31) of said rotor (3).
The method according to claim 8, characterised in that said drawing determines a thickening of the central crown (500) whose thickness becomes greater than that of the initial sheet.