IT201700010437A1 - VOLUMETRIC MACHINE - Google Patents

Description

"Volumetric machine"

The present invention relates to a volumetric machine acting on an operating fluid, typically oil. This volumetric machine can be a pump or a motor or a machine which alternatively allows operation as a pump and as a motor.

Volumetric gear pumps are known comprising two counter-rotating toothed wheels which mesh with each other.

They are housed in a pump body closed on two opposite faces by two distinct shims that develop orthogonally to the rotation axis of the two toothed wheels.

The casing and the gears define a plurality of compartments for receiving an operating fluid that necessarily move together with the toothed wheels that help define them.

The need to have high volumetric and hydromechanical yields requires knowing how to accurately control the law of pressurization of the oil compartment during the rotation of the gear wheels. In this regard, circumferential machining, called pressurization drains, is used on the surfaces of the shims.

They allow to convey oil from the high pressure environment to a compartment in a position defined by the designer. It is thus sure that when the pump rotation speed varies, the axial balance of forces acting on the shims remains constant, avoiding seizure (in the event that the shim is excessively pushed towards the toothed wheels) or in conditions of low efficiency. volumetric (in the event that the toothed wheels move away from the shim).

After setting the pressure values at the suction and delivery, the pressure differential imposed on the pump is known. As the pressure differential increases, there is a strong erosion that particularly affects the outlet end of the pressurization exhaust. This is linked to the fact that the speed of the oil jet exiting the pressurization exhaust increases as the pressure differential increases and this favors the onset of local cavitation phenomena. In practice, there is the formation of gas bubbles dissolved in the oil (and possibly oil vapor) which then implode due to the sudden pressurization inside the compartment (interposed between two teeth of the toothed wheel) which receives the outgoing fluid . All this causes erosion which in a short time compromises the efficiency as well as the functionality of the pump.

In this context, the technical task underlying the present invention is to propose a volumetric machine which overcomes the aforementioned drawbacks of the known art.

In particular, it is an object of the present invention to provide a volumetric machine capable of eliminating / minimizing erosive phenomena.

The specified technical task and the specified purposes are substantially achieved by a volumetric machine comprising the technical characteristics set out in one or more of the appended claims.

Further characteristics and advantages of the present invention will become clearer from the indicative, and therefore non-limiting, description of a preferred but not exclusive embodiment of a volumetric machine, as illustrated in the accompanying drawings in which:

figure 1 shows a simplified exploded view of a volumetric machine according to the present invention;

figure 2 shows a view of a volumetric machine according to the present invention;

figure 3 shows an enlargement of a detail of figure 2;

figure 4 shows a sectional view of a detail of a volumetric machine according to the present invention;

figure 5 shows a comparative graph;

figure 6 shows a volumetric machine according to the present invention and alternative to that of figure 2;

figure 7 shows a volumetric machine according to the present invention and alternative to that of figure 2 or 6;

figure 8 shows portions of a volumetric machine according to the present invention as an alternative to that of figure 2 or 6 or 7.

In the accompanying figures, the reference number 1 indicates a volumetric machine acting on an operating fluid.

Typically the operating fluid is oil. Volumetric machine 1 is a pump or motor. Eventually it is a machine that can operate alternately as a motor or a pump.

The volumetric machine 1 comprises a first toothed wheel 21.

The first toothed wheel 21 comprises a first group 210 of teeth which identify, between them, a first plurality 201 of compartments for the operating fluid. Conveniently, the first group 210 of teeth comprises all the teeth of the first wheel 21 (in Figure 2 for simplicity of illustration only a part of the teeth of the first group have been indicated with 210). They develop around the circumference.

The machine 1 comprises a second toothed wheel 22 comprising a second group 220 of teeth intended to mesh with the teeth of the first group 210. The teeth of the second group 220 are all the teeth of the second wheel 22 (in figure 2 for illustrative simplicity they have been indicated with 220 only a part of the teeth of the second group). In the course of the present discussion, what has been described with reference to the first wheel 21 can also be repeated for the second wheel 22. The axis of rotation of the first wheel 21 is parallel and distinct from that of the second wheel 22. The first and second wheel 21 , 22 are external to each other (they partially interpenetrate in correspondence with the meshing teeth). Conveniently, the machine 1 comprises a casing 3 which defines a housing 30 for positioning the first toothed wheel 21. This housing 30 also accommodates the second toothed wheel 22. The casing 3 is for example made of an aluminum alloy or cast iron.

The machine 1 comprises a path 4 which extends along a portion of said casing 3. The path 4 can be a groove, for example a chamfer. The path 4 places at least two compartments of said first plurality 201 in fluid communication. In particular the path 4 places more than two compartments of the first plurality 201 in communication. Conveniently the path 4 defines a sort of whisker. Preferably the path 4 develops along an arc of circumference. Path 4 in the case of a pump is called a pressurization drain. Path 4 in the case of an engine is known as a depressurization exhaust.

The envelope 3 comprises at least a first channel 51 distinct from said path 4.

At least in a predetermined configuration assumed by the first wheel 21:

- the first channel 51 places in fluid communication a first and a second compartment 211, 212 of said first plurality 201 which are consecutive and at least partially delimited by the same tooth of the first group 210 (the first channel 51 allows a by-pass of the tooth in said predetermined configuration);

- at least the first compartment 211 of the first plurality 201 is distinguished from (all) the compartments of the first plurality 201 lapped by said path 4 (i.e. the compartments facing the path 4; for example with reference to Figure 7 they are the compartments 90c, 90d, 90e, 90f, 90g); in other words, the first compartment 211 is not directly lapped by the path 4;

- the second compartment 212 is instead lapped by the path 4;

- the first compartment 211 is located upstream of the second compartment 212 and of the compartments of the first plurality 201 lapped by the path 4.

This predetermined configuration photographs the situation at a particular angle of rotation of the first toothed wheel 21 (for example Figures 2, 3, 4, 6, 7).

In the course of the present discussion, a compartment is defined upstream of another compartment if in the path that goes from a mouth 28 for the fluid inlet in the machine 1 to an outlet 29 for the fluid from the machine 1 it is located closer to the mouth 28 input. For example, in figure 7 the compartment 90a (assuming that it is located in correspondence with the entrance mouth 28) will be located upstream of the compartment 90b which in turn will be upstream of the compartment 90c which in turn will be upstream of the compartment 90d which in turn will be found upstream of compartment 90e which in turn will be upstream of compartment 90f which in turn will be upstream of compartment 90g. For example, in the case of figure 2, the clockwise rotation direction of the first toothed wheel 21 has been fixed, the inlet mouth 28 will be at the bottom and the outlet mouth 29 will be at the top (regardless of motor or pump operation). So in the case of pump operation, the high and low pressure environment will be respectively at the top and bottom, while in the case of motor operation they will be reversed.

In technical jargon, in the case of a pump, the inlet port 28 and the outlet port 29 are respectively defined as intake and delivery, while in the case of an engine they are normally defined as inlet and outlet.

Also for the second wheel 22 a path similar to the path 4 and a passage similar to the first channel 51 will be available (in Figure 2 they have been indicated respectively by the references 95 and 96). Also for the second wheel 22 what indicated for the compartments of the first wheel 21 and their interaction with the path 95 and / or the passage 96 can be repeated. The predetermined configuration of the first wheel 21 could however not be contemporary to a configuration of the second wheel 22 in which the passage 96 places two consecutive compartments in fluid communication (just as illustrated in Figure 2).

The casing 3 comprises a first shim 300. The first shim 300 defines at least one cylindrical seat for housing a shaft of the first or second toothed wheel 21, 22.

Conveniently, the first shim 300 comprises a surface which extends along a transverse plane (preferably orthogonal) to an axis of rotation of the first toothed wheel 21. Similarly, the casing 3 includes a second shim 9. The first wheel 21 is axially interposed between the first and second shim 300, 9. The path 95 is suitably obtained on the first shim 9.

The casing 3 also includes a lateral body 91 which axially surrounds the first wheel 21. The lateral body, the first and the second shim 91, 300, 9 define stator elements. In pumps, the lateral body 91 is commonly defined as the pump body or motor body depending on whether the machine 1 is a pump or a fluid-dynamic motor. As exemplified in figures 2, 3, 4, 6, 7 the first channel 51 is obtained on the first shim 300. Also the path 4 is advantageously obtained on the first shim 300. Possibly the additional passage 96 is advantageously obtained on the first shim 300. described with reference to the first channel 51 can also be repeated for the additional passage 96.

Advantageously, elements analogous to the first channel 51 and / or to the path 4 and / or to the path 95 and / or to the passage 96 can also be present on the second shim 9.

As exemplified in Figure 8, the first channel 51 can be obtained on the lateral body 91. Also in this case at least one additional channel may be present (for example on the first shim 300).

If the volumetric machine 1 were a pump then the first channel 51 would allow to partially pressurize the first compartment 211 before it overlaps the outlet of the path 4. In this way, when this overlap occurs, the pressure in the first compartment 211 will be increased in absolute value and therefore the difference in pressure to which the fluid will be subjected at the outlet end of the path 4 will be smaller, thus reducing erosive phenomena.

Alternatively, if the volumetric machine 1 were a motor, the first channel 51 (see figure 2) would allow the first compartment 211 to be partially depressurized before it overlaps the inlet of path 4 (everything connected to path 4 is connected to low pressure environment). In this way, when the first compartment 211 overlaps the path 4, the lower the pressure difference between the fluid present in the first compartment 211 and the fluid present in the path 4 and therefore the erosion at the mouth of the route 4.

In a particular constructive solution, the machine 1 allows reversible operation, that is, it allows correct operation in both directions of rotation of the first wheel 21 (for example see Figure 6).

In this regard, the casing 3 includes a second channel 52 (see Figure 6). In this case the first channel 51 is useful during operation during a first direction of rotation of the first wheel 21 (the clockwise one in figure 6) and the second channel 52 is useful during operation during a second opposite direction of rotation of the first wheel 21 to the first (the counterclockwise one in figure 6).

In a predetermined configuration which may or may not coincide with the predetermined configuration above:

- the second channel 52 places in fluid-dynamic connection a third and a fourth compartments 213, 214 of said first plurality 201 of compartments;

- the fourth compartment 214 is distinct from the compartments of the first plurality 201 lapped by the path 4 (the third compartment 213 is instead lapped by the path 4);

- the path 4 is interposed between the first and the second channel 51, 52.

If the predetermined configuration coincides with the predetermined one (as in the case of figure 6) the path 4 is interposed between the first and fourth compartment 211, 214.

In the solution exemplified in Figure 7, the first channel 51 is part of a first pair 50 of side-by-side channels which in said predetermined configuration place the first and second compartment 211, 212 in fluid communication.

The first channel 51 places the first and second compartment 211, 212 in fluid communication for a rotation of the first toothed wheel 21 of less than 10 ° (for example the first channel 51 could place the first and second compartment 211 in fluid communication , 212 for a rotation of less than half an angular pitch of the first wheel 21). In fact, the time period in which the first channel 51 allows fluid communication between the first and the second compartment 211, 212 must be relatively limited. Alternatively, the pressures of the two compartments would be adjusted, largely nullifying the advantages offered by the present invention.

For similar reasons, the passage section of the first channel 51 is relatively small.

Typically, the first channel 51 has a depth of less than 1.5 millimeters. For example, in a first constructive solution the path 4 develops for an amplitude between 60 ° and 70 ° and the depth of the first channel 51 is less than 0.5 millimeters. In a second exemplary constructive solution the path 4 develops for an amplitude comprised between 30 ° and 40 ° and the depth of the first channel is comprised between 0.7 and 1.5 millimeters.

Conveniently, the first channel 51 is a pocket and has a preponderant development direction 510 of less than 20 millimeters.

To reach said predetermined configuration, the fluid communication between the second compartment 212 and the path 4 starts in phase with or in advance of the fluid communication between the second compartment 212 and the first compartment 211.

For example, to reach said predetermined configuration, the second compartment 212 is placed in fluid communication with the path 4 in advance of the fluid communication between the second compartment 212 and the first compartment 211 (this advance could be between 2 ° and 8 ° ). This is for example the case of the first solution described above.

Alternatively, the second compartment 212 is placed in fluid communication with the first compartment 211 in phase with the path 4.

As previously indicated, machine 1 can be a pump (or in any case it can work as a pump). In this case the path 4 comprises a pressurization groove of the second compartment 212. It increases the pressure of the second compartment 212 putting it in communication with a compartment of the first plurality 201 located downstream of said second compartment 212. The machine 1 can be an engine o be able to function both as a motor and as a pump. With reference to Figure 2, in the case of engine operation, the path 4 comprises a depressurization groove of the second compartment 212. The path 4 therefore allows to reduce the pressure in the second compartment 212 by placing it in contact with a compartment located downstream (which it is at a lower pressure, that is to say the pressure available at the outlet mouth 29 of the volumetric machine 1). The object of the present invention is also an operating method of a volumetric machine having one or more of the characteristics described above.

The method comprises the step of rotating the first and second toothed wheels 21, 22. In this way the fluid flows into the first plurality 201 of compartments and is moved between the inlet mouth 28 and the outlet mouth 29. Similarly, the fluid is moved by the second toothed wheel 22. This occurs in a similar manner to what occurs in the first wheel 21. The first and second wheels 21, 22 are counter-rotating.

In the predetermined configuration described above, the method comprises the steps of:

- bringing the pressure of the second compartment 212 closer to that of one of the compartments of said first plurality 201 located downstream of the second compartment 212 by means of said path 4 (this step could however take place or at least start before reaching said predetermined configuration); - approach the pressure of the first compartment 211 to that of the second compartment 212 by means of said first channel 51 so that the pressure in the first compartment 211 becomes intermediate between the pressure in the second compartment 212 and the pressure of the inlet mouth 28. Conveniently (at the end of the step of bringing the pressure of the first compartment 211 closer to that of the second compartment 212 by means of said first channel 51) the absolute value of the pressure difference between a point of the first compartment 211 and a point of the machine inlet 28 1 can be between 30% and 70% of the absolute value of the pressure variation between the inlet port 28 and the fluid outlet port 29.

In figure 5 the ordinates show the relationship between the pressure in the first compartment 211 and the pressure at the outlet mouth 29 as a function of the angle of rotation of the first wheel 21. This graph, in the case of a pump, is to be read from left to right. In the case of motor operation, it should be read from right to left.

Curve A shows the pressure increase in the case of a machine 1 operating as a pump and integrating the present invention. The other curves, on the other hand, relate to a machine outside the present invention. Curves B and C show the pressure profile if path 4 is absent. Curve D shows the pressure profile if path 4 is present, but the first channel 51 is absent and therefore It is possible to establish in advance when the compartment will be pressurized.

The invention achieves important advantages.

In particular, it allows to eliminate or in any case reduce the erosive phenomena that occur at one of the two ends of the path 4. With reference to Figure 2 this is achieved by means of a first channel 51 which allows the pressure passage to be divided into two steps from the inlet port 28 to the outlet port 29. It can therefore be defined as a pre-pressurization pocket (in the case of a pump) or a pre-depressurization pocket (in the case of an engine).

The invention thus conceived is susceptible of numerous modifications and variations, all falling within the scope of the inventive concept that characterizes it. Furthermore, all the details can be replaced by other technically equivalent elements. In practice, all the materials used, as well as the dimensions, may be any according to requirements.

Claims (10)

CLAIMS 1. Volumetric machine acting on an operating fluid comprising: - a first toothed wheel (21) comprising a first group (210) of teeth which identify interposed between them a first plurality (201) of compartments for the operating fluid; - a second toothed wheel (22) comprising a second group (220) of teeth intended to mesh with the teeth of the first group (210); - a casing (3) which defines a housing (30) for positioning the first and second toothed wheels (21, 22); -a path (4) which extends along a portion of said casing (3) and which places at least two compartments of said first plurality (201) in fluid communication; said volumetric machine being a pump and / or a fluid-dynamic motor; characterized by the fact that the casing (3) includes at least a first channel (51) distinct from said path (4); at least in a predetermined configuration assumed by the first wheel (21): - the first channel (51) places in fluid communication a first and a second compartment (211, 212) of said first plurality (201) which are consecutive and at least partially delimited by the same tooth of the first group (210); - at least the first compartment (211) of the first plurality (201) being distinct from the compartments of the first plurality (201) lapped by said path (4); - said second compartment (212) being lapped by the path (4); - said first compartment (211) being placed upstream of the second compartment (212) and of the compartments of the first plurality (201) lapped by said path (4). 2. Machine according to claim 1, characterized by the fact that the casing (3) comprises a first shim (300) on which said first channel (51) is obtained. 3. Machine according to claim 1 or 2, characterized in that said first channel (51) has a depth of less than 1.5 millimeters. 4. Machine according to any one of the preceding claims, characterized in that the path (4) develops along an arc of circumference. 5. Machine according to any one of the preceding claims, characterized in that to allow reversible operation in both directions of rotation of the first toothed wheel (21), said casing (3) comprising a second channel (52); in a predetermined configuration which may or may not coincide with said predetermined configuration: - the second channel (52) places in fluid-dynamic connection a third and a fourth compartment (213, 214) of said first plurality (201) of compartments; - the fourth compartment (214) is distinct from the compartments of the first plurality (201) lapped by the path (4); - the path (4) is interposed between the first and the second channel (51, 52). 6. Machine according to any one of the preceding claims, characterized in that the first channel (51) is part of a first pair (50) of side by side channels which, in the predetermined configuration, place the first and second compartment (211, 212) in fluid communication ). 7. Machine according to any one of the preceding claims, characterized in that the first channel (51) places the first and the second compartment (211, 212) in fluid communication for a rotation of the first toothed wheel (21) less than 10 ° . 8. Machine according to any one of the preceding claims, characterized in that it is: -a pump, said path (4) comprising a pressurization groove of the second compartment (212) which increases the pressure of the second compartment (212) by placing it in communication with a compartment of the first plurality (201) located downstream of said second compartment ( 212); or -a motor, said path (4) comprising a depressurization groove of the second compartment (212) which therefore allows to reduce the pressure in the second compartment (212) by placing it in contact with a compartment of the first plurality located downstream and located at lower pressure. Machine according to any one of the preceding claims, characterized in that the first channel (51) is a pocket and has a preponderant development direction (510) of less than 20 millimeters. 10. Method of operation of a volumetric machine according to any one of claims 1 to 9, comprising the step of rotating the first and second toothed wheels (21, 22) making the fluid flow in the first plurality (201) of compartments and moving it between an inlet (28) for entering the machine (1) and an outlet (29) for leaving the machine (1); in said predetermined configuration the method comprises the step of bringing the pressure of the first compartment (211) closer to that of the second compartment (212) by means of said first channel (51), so that the pressure in the first compartment (211) becomes intermediate between the pressure in the second compartment (212) and the pressure of the inlet port (28).