Positive displacement machine with speed sensor

Abstract

A positive displacement machine interacting with an operating fluid, said machine being a pump or a motor and comprising: - means (2) interacting with the operating fluid; - a first shaft (4) operatively associated with the means (2) interacting with the operating fluid; said first shaft (4) being rotatable about a first axis (210) of rotation; - a casing (3) that houses said means (2) interacting with the operating fluid and at least a part of said first shaft (4); said casing (3) extending between a first and a second end (31, 32) along a direction parallel to the first axis (210) of rotation; said casing (3) comprising a first bottom (30) placed at said first end (31); - means (5) for measuring a parameter associated with a rotation speed of said first shaft (4). The means (5) for measuring said parameter comprises an angular sensor (50) that determines an angular position of the first shaft (4); said angular sensor (50) comprising a sensitive element (52) that is associated with said first bottom (30).

Description

[0001] DESCRIPTION

[0002] POSITIVE DISPLACEMENT MACHINE WITH SPEED SENSOR

[0003] Technical field

[0004] The present invention relates to a positive displacement machine interacting with an operating fluid. The machine is a pump or a motor that interacts with an operating fluid.

[0005] Background art

[0006] Gear pumps are known comprising a first and a second toothed wheel keyed on corresponding rotation shafts and meshing with each other.

[0007] The first and the second wheel are placed in a pressurised casing inside which the operating fluid passes.

[0008] It is known to measure the rotation speed of one of such shafts to have information on the operation of the pump. In this regard, an opening is specially made on such a casing in which an inductive sensor is placed which measures the rotation speed of the shaft. Such a sensor is arranged radially with respect to the first toothed wheel and faces the teeth. The measurement is made by counting the gear teeth that pass in front of the sensor in the unit of time.

[0009] A drawback of such a solution is that the creation of an ad hoc opening on the pressurised casing weakens the structural strength thereof. In fact, the pump casing, containing pressurised oil therein, is normally subject to structural stresses, whereby it is designed to ensure adequate performance (in particular the maximum allowable pressure) and an adequate duration. Therefore, drilling the casing causes a weakening thereof and thus a reduction in performance and / or life.

[0010] Furthermore, since each displacement value corresponds to a different length of the gear, it is necessary to use a different perforated casing for each displacement value.

[0011] A solution is also known in which, to avoid weakening of the casing, the shaft is prolonged in a chamber outside the pressurised casing and an auxiliary toothed wheel is keyed thereon. In such a chamber (which is at low pressure), a sensor is positioned which radially faces the auxiliary toothed wheel. The sensor counts the number of teeth that pass in front of it in the unit of time. Thereby, it is able to understand the rotation speed of the shaft.

[0012] A drawback of such a solution is related to the greater construction complexity, as there are a plurality of additional components (auxiliary toothed wheel, chamber outside the casing, etc.). Therefore, there are additional costs and a larger footprint.

[0013] Disclosure of the invention

[0014] The object of the present invention is to provide a more compact and economical positive displacement machine without penalising performance.

[0015] The stated technical task and specified objects are substantially achieved by a positive displacement machine comprising the technical features disclosed in one or more of the appended claims.

[0016] Brief description of drawings

[0017] Further features and advantages of the present invention will become more apparent from the following indicative, and hence non-limiting, description of a preferred, but not exclusive, embodiment of a positive displacement machine as illustrated in the appended drawings, in which:

[0018] - figure 1 shows a sectional view of a positive displacement machine according to the present invention;

[0019] - figure 2 shows an enlarged detail of figure 1 .

[0020] Detailed description of preferred embodiments of the invention

[0021] In the appended figures, reference number 1 denotes a positive displacement machine interacting with an operating fluid. The machine 1 is a pump or a motor. The machine 1 comprises means 2 interacting with the operating fluid. The operating fluid is an incompressible fluid, typically oil. The machine 1 comprises a first shaft 4 operatively associated with the means 2 interacting with the operating fluid. The first shaft 4 is rotatable about a first axis 210 of rotation. The means 2 interacting with the operating fluid comprises first means 20 rotatable about the first axis 210 of rotation. In particular, the first shaft 4 is integral with the first rotatable means 20. For example, the first rotatable means 20 can comprise a first toothed wheel 21 (in a gear pump or motor) or a vane-carrier wheel (in a vane machine or motor).

[0022] For example, in the exemplary solution illustrated in figure 1 , the machine 1 is a gear pump or an external gear motor; in such a case, the means 2 interacting with the fluid also comprises second means 200 rotatable about a second axis of rotation. The first and the second axis of rotation are appropriately parallel. The first and the second rotatable means 20, 200 mesh with each other. The means 2 interacting with the operating fluid comprises at least the first and a second toothed wheel 21 , 22 mutually associated (the second wheel 22 is part of the second rotatable means 200). The first toothed wheel 21 can be a driving gear (as in figure 1 ) or a driven gear. If the first wheel 21 is a driving gear, the second wheel 22 is a driven gear and vice versa. The first and the second toothed wheel 21 , 22 are externally meshing.

[0023] The machine 1 comprises a casing 3 which houses therein the means 2 interacting with the operating fluid. The casing 3 houses at least one part of the first shaft 4 therein. The casing 3 extends between a first and a second end 31 , 32 along a direction parallel to the first axis 210 of rotation. The casing 3 comprises a first bottom 30 placed at said first end 31 .

[0024] The casing 3 comprises a body 310 which envelops the means 2 interacting with the fluid (in particular envelops the first and the second toothed wheel 21 , 22). The first bottom 30 can be a cover for access inside the casing 3. Typically, the first bottom 30 is a rear cover. Appropriately it is located at the opposite end with respect to that of entry of a shaft in the casing 3. Therefore the cover 310 is removably connected to the first bottom 30. In an alternative solution not illustrated, the first bottom 30 is integrated with the body 310 (to form a single body and not an assembly). Appropriately, the casing 3 comprises a second bottom 320. The body 310 which envelops the means 2 interacting with the fluid is interposed between the second bottom 320 and the first bottom 30. Appropriately, the second bottom 320 is placed at the second end 32. Appropriately, the second bottom is a removable cover, typically a front cover.

[0025] The first shaft 4 supports one between the first and the second toothed wheel 21 , 22. In particular, the first shaft 4 supports the first toothed wheel 21. The machine 1 comprises a second shaft 400 which supports the second toothed wheel 22. As exemplified in figure 1 , the first shaft 4 is a single body and moves integrally with the first toothed wheel 20.

[0026] The machine 1 comprises means 5 for measuring a parameter associated with a rotation speed of said first shaft 4.

[0027] The means 5 for measuring said parameter comprises an angular sensor 50 that determines an angular position of the first shaft 4. By determining the angular position of the first shaft 4 over time, it is possible to obtain both the rotation speed and the rotation direction of the first shaft 4. Appropriately the first shaft 4 crosses said second bottom 320.

[0028] The angular sensor 50 (in particular the sensitive element 52) is associated with the first bottom 30. Appropriately, the angular sensor 50 (in particular the sensitive element 52) is embedded in the first bottom 30. The angular sensor 50 (in particular the sensitive element 52) is therefore placed inside the first bottom 30. Appropriately the angular sensor 50 is constrained to the first bottom 30. The angular sensor 50 appropriately comprises a connector 500 which is reachable from the outside of the first bottom 30 (and more generally from the outside of the machine 1 ). Such a connector 500 allows to connect the sensor 50 to an external apparatus for powering the sensor 50 itself and for sending the measured signal. Appropriately the connector 500 protrudes from the first bottom 30. Appropriately, the sensor 50 comprises an electronic board 51 connected to the sensitive element 52. The electronic board 51 conditions the signal detected by the sensitive element 52. The board 51 is integrated in the first bottom 30.

[0029] Appropriately, the first shaft 4 comprises magnetic means 41 integral therewith intended to interact with the angular sensor 50 (in particular with the sensitive element 52). Typically the magnetic means 41 comprises at least one body made of magnetic material.

[0030] Preferably the magnetic means 41 is annular and defines a passage hole 410. The first shaft 4 defines a duct 40 which protrudes inside the first shaft 4. The passage hole 410 is aligned with the duct 40, in particular it is coaxial. The passage hole 410 is therefore located at an end of the duct 40. Such a duct can be used to dispose of the drainage of the machine 1 ; appropriately this occurs if the first wheel 21 is driven.

[0031] Preferably the magnetic means 41 comprises several polar pairs. This allows to increase the accuracy of the angular sensor 50 at low speeds.

[0032] The magnetic means could have a non-axially symmetrical shape. This allows to ensure a better fixing of the magnetic means 41 to the first shaft 4, in particular with respect to the rotation. In particular, the non-axially symmetrical shape allows a shape coupling with the first shaft 4. As exemplified in figure 2, the first bottom 30 comprises a wall 300 interposed between the sensitive element 52 and said first shaft 4 (in particular between the sensitive element 52 and the magnetic means 41 ). In a particular solution, such a wall 300 could also be absent. In such a case the sensitive element 52 associated with the first bottom 30 directly faces the first shaft 4 (although in this case a fluid-dynamic seal between the first bottom 30 and the sensitive element 52 would be necessary). It is appropriate for the distance between the magnetic means 41 and the sensitive element 52 to be less than 1 centimetre, in particular less than 5 millimetres. This allows the magnetic field detected by the sensor 50 to be sufficiently intense and thus the measurement accurate. Since the sensitive element 52 is placed at an area of the casing 1 not subject to high pressure, it is possible that the wall 300 has a limited thickness, for example less than 3 millimetres. Advantageously the wall 300 prevents the operating fluid from coming into contact with the angular sensor 50. No specific fluid-dynamic seals are required.

[0033] Preferably the angular sensor 50 is a Hall effect sensor. However, it could also be another type of sensor, in particular a sensor which detects the angular position in the absence of contact with the first shaft 4.

[0034] Appropriately, the first bottom 30 comprises a single body separating the angular sensor 50 from the magnetic means 41 and which also defines a housing in which the angular sensor 50 is internally positioned. The single body also defines a cavity in which the magnetic means 41 placed on the first shaft 4 protrudes. Such a cavity can also accommodate a portion of the first shaft 4. Such a single body is also directly accessible from the outside of the positive displacement machine 1 . An opening of the housing is occluded by a cap which allows the transit of the connector 500 for powering the angular sensor 50. Such a cap can be inserted / extracted according to a transverse direction (or rather orthogonal) with respect to the first axis 210 of rotation.

[0035] The first shaft 4 has an end 40 facing an area of the first bottom 30 in which said sensitive element 52 (or more generally said angular sensor 50) is obtained.

[0036] The angular sensor 50 is therefore not placed radially to the first toothed wheel 21 , but is located behind it in an area which is not subject to oil pressure and thus where there are no high stresses. The sensitive element 52 (in particular the angular sensor 50) is placed in a position not stressed by high pressures; therefore, the presence of the sensor 50 does not reduce the performance (in particular the maximum allowable pressure) of the machine 1. Appropriately the magnetic means 41 is arranged at an end of the first shaft 4. The magnetic means 41 is partially recessed in the first shaft 4. The magnetic means 41 protrudes partially outside the first shaft 4 (at said end of the first shaft 4).

[0037] Optionally, the machine 1 can comprise an additional angular sensor, for example an additional Hall effect sensor. Such an additional angular sensor is placed at the angular sensor 50 (which can therefore be defined as a first angular sensor 50). Appropriately, it is therefore located at the first bottom 30. The wall 300 fluid-dynamically separates the magnetic means 41 from the additional angular sensor. The combination of the angular sensor 50 and the additional angular sensor allows to determine the rotation direction of the first shaft 4.

[0038] The machine can also house (at least in part) one or more additional valves in the first bottom 30. In particular, such an additional valve can comprise a proportional valve for adjusting the motor speed. Thereby it is possible to obtain a closed loop adjustment of the speed, for example to adjust the rotation speed of a cooling fan.

[0039] The present invention achieves important advantages.

[0040] Firstly, the particular positioning of the angular sensor 50 allows to obtain a very compact solution. It also allows not to penalise the performance (in particular the maximum pressure) of the machine 1 .

[0041] A further advantage is linked to the fact that the same removable cover 30 provided with angular sensor 50 can be used independently of the displacement of the machine 1 .

[0042] The invention thus conceived is susceptible to numerous modifications and variants, all falling within the scope of the inventive concept that characterises it. Furthermore, all the details may be replaced with other technically equivalent elements. All the materials used, as well as the dimensions, may in practice be any whatsoever according to needs.

Claims

CLAIMS1. A positive displacement machine interacting with an operating fluid, said machine being a pump or a motor and comprising:- means (2) interacting with the operating fluid;- a first shaft (4) operatively associated with the means (2) interacting with the operating fluid; the first shaft (4) being rotatable about a first axis (210) of rotation;- a casing (3) that houses said means (2) interacting with the operating fluid and at least a part of said first shaft (4); said casing (3) extending between a first and a second end (31 , 32) along a direction parallel to the first axis (210) of rotation; said casing (3) comprising a first bottom (30) placed at said first end (31 );- means (5) for measuring a parameter associated with a rotation speed of said first shaft (4); characterized in that the means (5) for measuring said parameter comprises an angular sensor (50) that determines an angular position of the first shaft (4); said angular sensor (50) comprising a sensitive element (52) that is associated with said first bottom (30).

2. The machine according to claim 1 , characterized in that said first bottom (30) comprises a wall (300) interposed between said sensitive element (52) and said first shaft (4); said wall (300) preventing the operating fluid from coming into contact with the sensitive element (52).

3. The machine according to claim 1 or 2, characterized in that said sensitive element (52) is placed inside the first bottom (30) and constrained thereto.

4. The machine according to any one of the preceding claims, characterized in that said angular sensor (50) is a Hall effect sensor.

5. The machine according to any one of the preceding claims, characterized in that said first shaft (4) has an end (40) facing an area of the first bottom (30) in which said sensitive element (52) is formed.

6. The machine according to any one of the preceding claims, characterized in that said first shaft (4) comprises magnetic means (41 ) integral therewith that is intended to interact with the sensitive element (52).

7. The machine according to claim 6, characterized in that said magnetic means (41 ) is annular and defines a passage hole (410); said first shaft (4) defines a duct (40) which protrudes into the first shaft (4); said passage hole (410) is located at one end of the duct (40).

8. The machine according to claim 6 or 7, characterized in that the magnetic means (41 ) comprises several polar pairs.

9. The machine according to any one of claims 6 to 8, characterized in that the magnetic means (41 ) has a non-axially symmetrical shape.

10. The machine according to any one of the preceding claims, characterized in that it is a gear pump or a gear motor; said means (2) interacting with the fluid comprising at least a first and a second mutually associated toothed wheel (21 , 22); said first shaft (4) supporting one of the first and the second toothed wheel (21 , 22).

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