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1. WO2020115639 - APPAREIL ET PROCÉDÉ DE COMMANDE D'UN ÉTAT DE LUBRIFICATION D'ENSEMBLE COMPRESSEUR ET MACHINE RÉFRIGÉRANTE COMPRENANT LEDIT APPAREIL

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

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CLAIMS

1. Process for controlling the lubrication of a compressor unit (15) of a refrigerating machine which is equipped with an expansion valve (17) which has an adjustable degree of opening and which has an inlet (18) and an outlet (19) and which is in fluid communication with a casing (15a) of said compressor unit (15) to be passed through by a flow tapped from the latter; within said casing (15a), refrigerant fluid and lubricating oil for lubricating said compressor unit (15) being present; the outlet (19) of said expansion valve (17) being connected to an intake duct (23) of said compressor (15) so as to replenish the latter with said tapped flow;

said process comprises a check procedure which comprises:

- a tapping operation which involves drawing a flow from said compressor and passing it through said expansion valve (17), so as to expand it;

- a measurement operation which involves measuring a temperature difference which said fluid has between the inlet (18) and the outlet (19) of said expansion valve (17);

- a verification operation which is positive if the modulus of the measured temperature difference, in said measurement operation, exceeds a threshold value;

- a replenishment operation which involves the introduction of lubricating oil into said compressor (15); said replenishment operation being carried out when said verification operation is positive.

2. Process according to claim 1 which, at the beginning of said tapping operation, involves a heating step which involves setting the degree of opening of said expansion valve (17) to a start-up level which corresponds to the maximum opening of said expansion valve (17), so as to obtain fast heating, by the fluid tapped from said compressor, of the inlet (18) and of the outlet (19) of said expansion valve (17).

3. Process according to claim 2, wherein said tapping operation involves, after said heating step, a check step which involves setting said degree of opening to a check level at which the degree of opening of said expansion valve (17) is less than that of said start-up level.

4. Process according to claim 3, wherein said check procedure involves starting said check step and said verification operation not before the temperature of said inlet (18) is equal to the temperature of the oil contained in said compressor unit (15) or a predefined fraction thereof.

5. Process according to one of the claims 3 and 4, wherein said check step comprises a plurality of check sub-steps which are started in succession starting from a first one of said check sub-steps up to an n-th one of said check sub-steps; each i-th check sub-step of said check steps, where i varies from 1 to n, involves partially closing said expansion valve (17) so that the degree of opening of said expansion valve (17) is less than the degree of opening of said expansion valve (17) in the directly preceding check step, i.e. in an (i+l)-th step of said check sub-steps, the degree of opening of said expansion valve (17) is less than that of the i-th check sub-step which directly precedes said (i+l)th check sub-step.

6. Process according to claim 5, wherein during or following each of said check sub-steps, said verification operation is carried out and each (i+l)-th check sub-step is performed only if the verification operation which is carried out in the i-th check sub-step has a positive result; said replenishment operation being performed only if the verification operation, carried out during or following the n-th check sub-step, is positive.

7. Process according to claim 6, wherein said verification operation is performed cyclically during said replenishment operation and said replenishment operation is terminated following a negative result of said verification operation.

8. Process according to one of the preceding claims, wherein said threshold value is equal to the modulus of a modelled temperature difference, or to a fraction of the latter, where said modelled temperature difference corresponds to the temperature difference that would be measured in said measurement operation if the flow tapped in said tapping operation consisted exclusively of said cooling fluid.

9. Process according to claim 8, wherein said modelled temperature difference is equal to the difference between the temperature of said inlet (18), measured in said measurement operation, and a theoretical temperature of said outlet (19), which is calculated as a function of the pressure and temperature of said inlet (18) and the pressure of said flow in said outlet (19), which is assumed to be equal to the intake pressure of said compressor, where it is assumed that, across said expansion valve (17), said flow undergoes an isoenthalpic transformation.

10. Process according to one of the preceding claims, wherein said check procedure is performed cyclically, each cycle being terminated following a negative result of said verification operation.

11. Process according to claim 10, which comprises an estimation procedure suitable for estimating a drainage index which represents the amount of said lubricating oil which is removed from said compressor unit (15) during the operation of said refrigerating machine (10); said check procedure being started when said drainage index exceeds a limit index.

12. Process according to claim 10 or 11, which involves calculating an operating time of said compressor, where said check procedure is started when said operating time exceeds a limit time.

13. Process according to one of the claims 11 or 12, wherein said drainage index is calculated cyclically and the value of said drainage index in a calculation cycle is defined by a function of the intake and delivery pressures of said compressor (15) and the speed of rotation of the drive motor of said compressor (15).

14. Process according to claim 13, wherein said drainage index is calculated cyclically and the value of said drainage index in a calculation cycle is defined by a function of the following parameters:

- flow rate and speed of rotation of the compressor, in said calculation cycle;

- reference flow rate and speed of rotation of the compressor;

- time elapsed between a said calculation cycle and the calculation cycle d irectly preceding said calculation cycle;

- value assumed by said drainage index in said preceding calculation cycle.

15. Process according to claim 14, wherein said flow rate in the current calculation cycle is derived by means of linear regression from flow rates calculated at a predetermined number of revolutions of the motor of said compressor unit (15) by means of a polynomial formula which is a function of the evaporation temperature of said refrigerating machine (10) and of the absolute discharge pressure of said compressor unit (15), with polynomial parameters characteristic of said compressor unit (15) defined as a function of the speed of rotation of the motor rotor of said compressor unit (15).

16. Process according to one of the claims 11-15, wherein said estimation procedure is performed only when the speed of rotation of the rotor of said compressor unit (15) reaches or exceeds a minimum speed value or when said compressor (15) is active.

17. Process according to one of the preceding claims, wherein said compressor unit (15) comprises a plurality of compressors (151, 152, 153), each provided with a control apparatus (16) and said replenishment operation comprises an equalization operation which is started when said verification operation is positive for at least one of said compressors (151, 152, 153); said equalization operation involving the opening of the expansion valves (17) of all said control apparatus (16) until the level of oil in said compressors (151, 152, 153) is equalized.

18. Process according to claim 17, wherein said replenishment operation involves replenishment of oil from an external tank or a separator (30) located downstream of said compressor unit (15) if said verification operation has a positive result for all said compressors (151, 152, 153).

19. Process according to one of the preceding claims, wherein as a result of said replenishment operation, at least one of said verification operations for verifying the effectiveness of replenishment of the lubricating oil in said compressor unit (15) is performed.

20. Apparatus for controlling the lubrication of a compressor unit (15) of a refrigerating machine (10) comprising :

- an expansion valve (17) having an adjustable opening, an inlet

(18) and an outlet (19) and configured to expand a refrigerating fluid contained in a flow which, during use, passes through said expansion valve (17); said inlet (18) being designed to be placed in fluid communication with a refrigerating machine compressor casing (15a) so as to receive a fluid flow therefrom;

- a first temperature sensor (20) thermally connected to said inlet (18) and a second temperature sensor (21) thermally connected to said outlet (19);

- a control device (22) connected to said temperature sensors and to said expansion valve (17), so as to drive it, said control device (22) being programmed to perform a process according to one of claims 1 to 19.