Operational status checking system of alternative compressor valve and method for checking operational status of alternative compressor valve

Abstract

The present invention refers to a system and method for checking the operational status of alternative compressor valve and more particularly for checking operational status of electrically commanded valves, provided in alternative compressors used in refrigeration systems. In accordance with the present invention, said operational checking system of alternative compressor valve comprises a data processing core (5) capable of estimating one among two possible operations statuses of said metal valve (1) by varying at least one electric parameter provided by said sensor (4), wherein said step of estimating one among two possible operational statuses of said metal valve (1) is effected on the basis of the results from the comparison between said signal of electric parameter from sensor (4) and the predetermined range of data analogous to the electric parameter.

Claims

1. A method for checking an operational status of an alternative compressor valve included in an operational status checking system, the operational status checking system comprising at least one metal valve disposed in at least one compression cylinder of an alternative compressor, at least one inductive component, at least one sensor, and at least one data processing core, wherein the at least one metal valve is configured to switch between at least two operational statuses, wherein the at least one inductive component is fed by a continuous current signal having an amplitude, the method comprising: obtaining an electric parameter signal from the at least one sensor; measuring a voltage value of the at least one inductive component from the electric parameter signal received from the at least one sensor; comparing the voltage value of the at least one inductive component to an experimentally obtained predefined value; determining a valve opened operational status of the at least one metal valve if the voltage value is lower than the experimentally obtained predefined value; and stopping feeding of a valve coil associated with the at least one metal valve if the valve opened operational status is determined to be open due to an elevated pressure differential when the valve opened operational status should be closed.

2. A method for checking an operational status of an alternative compressor valve included in an operational status checking system, the operational status checking system comprising at least one metal valve disposed in at least one compression cylinder of an alternative compressor, at least one inductive component, at least one sensor, and at least one data processing core, wherein the at least one metal valve is configured to switch between at least two operational statuses, wherein the at least one inductive component is fed by a continuous current signal having an amplitude, a switching period, and a switching time, the method comprising: obtaining an electric parameter signal from the at least one sensor; measuring an electric current value of the at least one inductive component from the electric parameter signal received from the at least one sensor; comparing the electric current value of the at least one inductive component to an experimentally obtained predefined value; determining a valve opened operational status of the at least one metal valve if the electric current value is greater than the experimentally obtained predefined value; and stopping feeding of a valve coil associated with the at least one metal valve if the valve opened operational status is determined to be open due to an elevated pressure differential when the valve opened operational status should be closed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will be described in detail based on figures listed below, wherein:

(2) FIG. 1 illustrated a schematic arrangement of the operational status checking system of alternative compressor valve in accordance with the present invention;

(3) FIG. 2 illustrates an equivalent electric model for a valve coil to be monitored;

(4) FIG. 3 illustrates a preferential option of the processing logics of the operation status checking method of alternative compressor valve; and

(5) FIG. 4 illustrates an option of detecting undue opening of the valve when its coil is voltage-fed;

(6) FIG. 5 illustrates an option of detecting undue opening of the valve when its coil is current-fed.

DETAILED DESCRIPTION OF THE INVENTION

(7) As known by a person skilled in the art, and in accordance with Faraday's Induction Law, it is known that a variable magnetic field in an inductive component induces a voltage in the terminals thereof.

(8) In this context, it is verified that a magnetic field may undergo variations stimulated by several electromagnetic factors.

(9) An energized coil, for example, may present variations in its magnetic field by simple proximity interaction with a metal body. In this example, it is further verified that variation of said magnetic field is substantially proportional to the proximity of the metal body.

(10) As described in the embodiments of BR P11105379-8, for example, a magnetic field generated by a coil is responsible for altering the initial operational status of a metal valve. That is, a valve whose initial operational status is normal closed tends to be switched to the opened operational status. In this sense, BR P11105379-8 achieves all the proposed objectives.

(11) Nevertheless, said embodiments do not comprise means capable of checking if a valve, after the switching stimulation, has its operational status switched or not.

(12) In BR P11105379-8, actuation coils (or magnetic field-generating elements) only has active actuation, i.e. they only comprise the function of generating a magnetic field. Therefore, there is no function related to calculation and/or capturing of magnetic field originated from other sources, as to say.

(13) It occurs that, in accordance with the above-mentioned Faraday's Induction Law, movement (or non-movement) of a metal valve tends to generate at least a measurable alteration in the magnetic field of said coil. Therefore, it is observed that if said coil has a passive performance it is possible to estimatewithin a proper logicswhich is the operational status of said metal valve. Relying on this premise the present invention was developed.

(14) From FIG. 1 that depicts a scheme of the operation status checking system of alternative compressor valve in accordance with the present invention, it is observed that there are two metal valves (one is a suction valve and the other is a discharge valve), which are functionally disposed in a compressor cylinder 2 of a conventional alternative compressor. Said operational status checking system of alternative compressor valve further comprises an inductive component 3, a sensor 4 and a data processing core 5.

(15) Valve metals 1 comprise pallet-type valves, which are widely known by a person skilled in the art.

(16) This means that said metal valves 1 comprise binary valves which assume only two operational statuses: opened status (allowing for the passage of fluid through an orifice) and closed status (blocking an orifice and any fluid flow).

(17) Preferably, but not limiting, said metal valves 1 can eventually be integrated in a semi-commanded assembly as described in the above-mentioned document BR PI1105379-8. Nevertheless, said metal valves 1 may also be totally automatic, where switching between their operation statuses depends only on differential pressures of compression cycles, and on the strength of the material to produce valves.

(18) Compressor cylinder 2 essentially comprises a conventional compression cylinder, which is widely known by a person skilled in the art.

(19) Inductive component 3, in accordance with the preferred embodiment of the present invention, comprises a coil and, more specifically, an already preexisting coil, which is used as a semi-command source for metal valves 1 (see BR PI1105379-8).

(20) Sensor 4 comprises an amperemeter and, more particularly, an amperemeter previously existing in one of the modules of data processing core 5. Optionally, said sensor 4 could be capable of reading different electric parameters generated by the inductive component 3 (when exposed to a positioning variation of the metal valves 1).

(21) Said data processing core 5 can comprise a microcontroller (or a microprocessor) previously existing in an alternative compressor and it is used to manage actuation and functioning thereof. As formerly said, it is preferred that said data processing core 5 comprises at least one amperemeter module.

(22) According to basic and essential concepts of the present invention, it is verified that inductive component 3 is capable of inducing electromagnetic field whose intensity varies in accordance with the relative proximity of metal valves 1. To this connection, said inductive component 3 has an inductance which value depends on the opening to the moving gap (metal valves 1).

(23) Sensor 4 is electrically associated with inductive component 3, wherein said sensor 4 is capable of converting the intensity variation of the electromagnetic field induced by the inductive component 3 to electric current of proportionally variable amplitude.

(24) A signal provided by sensor 4 is sent to the data processing core 4, which is capable of estimating, based on determined processing logics, one among two possible operational statuses of said metal valves 1, wherein said estimate derives from said amplitude variation of electric current from the sensor 4.

(25) FIG. 2 illustrates equivalent electric circuit 42 of valve 1. Such circuit is constituted by electric resistance R of the valve, inductance L depending on the valve gap and voltage 43 (E=i.Math.dL/dt), induced by inductance variation during valve movement. Coil feeding signal 6 can be a voltage source or a current source.

(26) FIG. 3 illustrates, in a simplified form, one of the procedures for estimating valve status.

(27) According to this figure, it is depicted signal 6 from the inductive component actuation preferably in the form of a modulated voltage with amplitude V, a switching period PC, and a pulse width having a conduction time t.sub.c. Said switching period PC is substantially lower than the period of compression cycle and also substantially lower than the coil electric constant, which value is given by (=L/R).

(28) Hence, it can also illustrated in this figure signal 41, resulting from the application of signal 6 and read by sensor 4 as each switching period PC is used for estimating the coil inductance value by equation

(29) $\begin{array}{cc}\left(Ln\frac{V{t}_c}{di}\right),& \left[\mathrm{SCSG2}\right]\end{array}$
wherein V is the voltage application to the coil and di is the current variation within time tc.

(30) When the estimate value of inductance fulfills the expression: (L.sub.n>k1.Math.L.sub.), k1>1 is a constant which dependents on design of a valve and La is inductance valve when said valve is open, then valve 1 can be considered as closed (closed operational status).

(31) From this configuration, there can be determined the moment from which said valve 1 was really closed.

(32) The same methodology can then be used to determine the time that the valve opens. In this case, the inductance value Ln is computed by means of the same equation

(33) $\left(L_n\frac{V{t}_c}{di}\right),$
when the value fulfills the expression (Ln>k2.Math.L), wherein k2>1 and k2<k1, K1 is also a constant depending on a valve design, and then valve 1 can be considered open (opened operational status).

(34) The method illustrated in FIG. 3 can also be used for merely detecting undue opening of valve 1, such as when subjected to elevated pressure differential and then the valve coil current shall be immediately stopped to avoid striking of the valve which would may cause excessive wear and it may break.

(35) Another more simplified method to determine the valve status is illustrated in FIG. 4.

(36) This method is allowed to determine only one change from closed status to opened status, and it can be used for protecting the valve by blocking coil feeding as soon as opening is detected.

(37) In this method, the valve coil is fed with a signal 6 in the form of a constant voltage of amplitude V to maintain the valve in the closed status. Consequently, said coil will have a constant current of value I, which value will be equal to the applied voltage V divided by the coil resistance R (Ohm Law), as illustrated in the circuit of FIG. 2. Since the valve under this condition is in the closed status, inductance variation will not occur and term 43 will be null. In the case where the valve is subjected to an elevated pressure differential which causes undue opening thereof, a negative inductance variation, caused by the opening thereof, will lead to the rise of an negative induced voltage due to term 43. Hence, an increase of current I will suddenly occur, resulting in a current peak 44.

(38) Detection of this peak is made by comparing the current value I with a superior Imax limit.

(39) Another variation of the detecting opening of the valve is illustrated in FIG. 5.

(40) This method can also only determine a change in the closed-to-opened status, and it may be used for protecting the valve by stopping the coil feeding as soon as the opening is detected.

(41) In this case, said valve coil is fed with a signal 6 in the forma a current constant I. As a result, the coil will have a constant voltage V, which value is equal to the current I multiplied by the coil resistant R (Ohm Law). Since the valve under this condition is in the closed status, inductance variation will not occur and the induced voltage given by the term 43 will have a null value. If the valve is subjected to an elevated pressure differential which will unduly open the valve, the negative variation inductance will cause a sudden reduction in voltage V on the coil which will result in a negative peak 54.

(42) Detection of this peak is effected by comparing voltage V with a lower limit Vmin.

(43) Methods of detecting the opening of the valve as illustrated in FIGS. 4 and 5 are very easily implemented, since to do so there will only be required a circuit for comparing current or voltage values having maximum and minimum limits, respectively. To this effect, only an analogical circuit with a comparator is needed, thereby eliminating the need to use a microprocessor or microcontroller.

(44) Disclosed examples of the preferred embodiment of the present invention shall lead to the interpretation that the scope thereof contemplates other possible variations, which are only limited by the contents of claims, included therein the possible equivalent means.