Control method for a resonant linear compressor and an electronic control system for a resonant linear compressor applied to a cooling system

Abstract

A control method and system for a resonant linear compressor applied for controlling the capacity of a cooling system. The method includes: a) reading a reference operation power (P.sub.ref) of the motor of the compressor; b) measuring an operation current (i.sub.MED); c) measuring an operation voltage of a control module of the compressor; d) calculating an input power (P.sub.MED) of the motor as a function of the operation current (i.sub.MED) and of the operation voltage; e) comparing the input power (P.sub.MED) with the reference operation power (P.sub.ref); f) if the reference operation power (P.sub.ref) is higher than the input power (P.sub.MED), then increase an operation voltage of the compressor (UC); g) if the reference operation power (P.sub.ref) is lower than the input power (P.sub.MED), then decrease the operation voltage of the compressor (UC).

Claims

1. A control method for a resonant linear compressor (100), applied to a cooling system, the method comprising: reading a reference operation power (P.sub.ref) of the compressor (100), wherein said step of reading the reference operation power (P.sub.ref) comprises one of: (i) reading input from a user that indicates said reference operation power (P.sub.ref); (ii) reading a temperature signal from a thermostat that indicates a temperature of the cooling system and calculating the reference operation power (P.sub.ref) as a function of the temperature signal; measuring an operation current (i.sub.MED) of the motor of the compressor (100); measuring an operation voltage of a control module of the compressor (100); calculating an input power (P.sub.MED) of the motor of the compressor (100) as a function of the operation current (i.sub.MED) and of the operation voltage; detecting a piston displacement value (D.sub.pis) of the compressor (100); comparing the piston displacement value (D.sub.pis) with a maximum displacement value (D.sub.Pmax); if the piston displacement value (D.sub.pis) is higher than the maximum displacement value (D.sub.Pmax), then decrease the operation voltage of the compressor (UC) using an electronic power device (300); if the piston displacement value (D.sub.pis) is lower than the maximum displacement value (D.sub.Pmax), then carrying out a sequence of steps comprising: comparing the input power (P.sub.MED) with the reference operation power (P.sub.ref); if the reference operation power (P.sub.ref) is higher than the input power (P.sub.MED), then increase an operation voltage of the compressor (UC) using the electronic power device (300); if the reference operation power (P.sub.ref) is lower than the input power (P.sub.MED), then decrease the operation voltage of the compressor (UC) using the electronic power device (300).

2. The control method according to claim 1, wherein the measurement of operation current (i.sub.MED) of the compressor motor (100) and the calculation of the input power (P.sub.MED) are carried out on a processing electronic device (200).

3. The control method according to claim 1, wherein the electronic power device (300) used to increase and decrease the operation voltage (UC) of the compressor comprises one of the inverter and a TRIAC.

4. An electronic control system for a resonant linear compressor (100), applied to a cooling system, the resonant linear compressor (100) comprising an electric motor and a displacement piston, the system comprising a processing electronic device (200) configured for input of a reference operation power (P.sub.ref) and an operation current (i.sub.MED) of the electric motor of the compressor (100), wherein said electronic device (200) is configured for input of said reference operation power (P.sub.ref) by one of: (i) reading user input that indicates said reference operation power (P.sub.ref); (ii) reading a temperature signal from a thermostat that indicates a temperature of the cooling system and calculating the reference operation power (P.sub.ref) as a function of the temperature signal, the processing electronic device (200) being configured for measuring an operation voltage of the compressor (100) and providing an input power (P.sub.MED) of the compressor (100) as a function of the measured operation voltage and operation current (i.sub.MED) of the motor, the processing electronic device (200) being further configured for comparing the input power (P.sub.MED) with the reference operation power (P.sub.ref) and, the processing electronic device (200) being further configured for comparing a piston displacement value (D.sub.pis) with a maximum displacement value (D.sub.Pmax) such that: if the piston displacement value (D.sub.pis) is higher than the maximum displacement value (D.sub.Pmax), then decrease the operation voltage of the compressor (UC), otherwise if the piston displacement value (D.sub.pis) is lower than the maximum displacement value (D.sub.Pmax), then: comparing the input power (P.sub.MED) with the reference operation power (P.sub.ref); increasing the operation voltage of the compressor (UC) if the reference operation power (P.sub.ref) is higher than the input power (P.sub.MED); and decreasing the operation voltage of the compressor (UC) if the reference operation power (P.sub.ref) is lower than the input power (P.sub.MED).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will now be described in greater detail with reference to the attached drawings, in which:

(2) FIG. 1 is a schematic view of a resonant linear compressor;

(3) FIG. 2 shows a block diagram of the control of the cooling system of the present invention;

(4) FIG. 3 shows a simplified block diagram of the electronic control of the present invention;

(5) FIG. 4 shows block diagram of the control with actuation by inverter, according to the teachings of the present invention;

(6) FIG. 5 shows a block diagram of the control with actuation by TRIAC-type device;

(7) FIG. 6 shows a flow chart of the control system of the present invention; and

(8) FIG. 7 shows the wave forms of the discharge pressure, identifying the power and the maximum piston displacement for control by power versus control by stroke, according to the present invention.

DETAILED DESCRIPTION OF THE FIGURES

(9) As mentioned before, most solutions employed for controlling capacity combines the known measuring techniques, or stroke estimation, with a system of controlling maximum piston displacement, adjusting this displacement to act at the cooling capacity of the system.

(10) Additionally, such techniques take into account, in many cases, the use of position sensors, in order to measure the piston stroke, thus causing a considerable increase in cost for the final product.

(11) On the other hand, the solutions without position sensor do not have good accuracy or operation stability, and sometimes it is necessary to use additional devices, such as temperature sensors and accelerometers for impact detection. This construction implies a piece of equipment of higher cost and longer maintenance time.

(12) The present invention employs innovatory method and system for controlling a resonant linear compressor 100, such a compressor being illustrated in FIG. 1. Said control method is preferably applied to a cooling system, being intended to operate according to the following steps:

(13) a) reading a reference operation power P.sub.ref of the compressor 100;

(14) b) measuring an operation current i.sub.MED of the compressor 100 motor;

(15) c) measuring an operation voltage of a control module of the compressor 100;

(16) d) calculating an input power P.sub.MED of the compressor 100 motor as a function of the operation current i.sub.MED measured in step b) and of the operation voltage obtained in step c);

(17) e) comparing the input power P.sub.MED calculated in the preceding step with the reference operation power P.sub.ref,

(18) f) if the reference operation power P.sub.ref is higher than the input power P.sub.MED, then increase an operation voltage of the compressor UC;

(19) g) if the reference operation power P.sub.ref is lower than the input power P.sub.MED, then decrease the operation voltage of the compressor UC.

(20) Said reference operation power P.sub.ref is read or presented to the present system via operator or user of the final equipment. Otherwise, the operation power P.sub.ref is calculated as a function of a signal from the electronic thermostat of the cooling system, as shown in FIG. 2.

(21) The same figure shows a block diagram of control of the cooling system, pointing out its main blocks, or operational steps, necessary to the correct functioning of the presently proposed object.

(22) FIG. 3, in turn, shows a more simplified block diagram, pointing out the essential steps of the claimed system.

(23) It should be pointed out that the present control method further comprises, in an alternative manner, the following steps:

(24) h) detecting a piston displacement value D.sub.pis of the compressor 100;

(25) i) comparing the piston displacement D.sub.pis with a maximum displacement value D.sub.Pmax;

(26) j) checking whether the piston displacement value D.sub.pis is higher than the maximum displacement value D.sub.Pmax, and, if not, carrying out the sequence of preceding steps “d”, “e” and “f”; and

(27) k) checking whether the piston displacement value D.sub.pis is lower than the maximum displacement value D.sub.Pmax, and, if not, then decrease the operation voltage of the compressor UC.

(28) FIG. 6 shows, by means of a flow chart, the main steps involved in the proposed control method.

(29) Steps “j” and “k” are employed so as to foresee a system for protecting or detecting the piston-stroke limit, thus preventing impact of the piston with its stroke end. For the present application, it is important to evaluate whether the stroke has reached the maximum limit for protection of the system or not, rather than necessarily intermediate displacement values.

(30) In the scope of the present invention, one further foresees measuring the operation current i.sub.MED of the compressor 100 and calculating the input power P.sub.MED through a processing electronic device 200.

(31) Said electronic device 200, in conjunction with a control module, or electronic power device 300, operates the electric motor of the resonant linear compressor 100 within the teachings of the present invention.

(32) More particularly, the operation voltage of the compressor UC is increased or decreased from the electronic power device 300, the latter being of the inverter or TRIAC type. FIGS. 4 and 5 shows the two possible embodiments for the power step for the present method.

(33) FIG. 7, in turn, shows a flow chart of the whole control method, embracing the essential steps for capacity control of a cooling system.

(34) The presently claimed object further foresees an electronic control system for the resonant linear compressor 100, especially applied to a cooling system.

(35) Said system take into account the fact that the resonant linear compressor 100 comprises an electric motor and a displacement piston, so that the electric motor of the compressor 100 will be actuated from an operation voltage of the compressor UC.

(36) In a more broad manner, the proposed system operates according to the steps of the method already described before.

(37) It should be pointed out that said system comprises a processing electronic device 200, configured for measuring an operation current of the electric motor of the compressor 100.

(38) On the other hand, the processing device 200 is configured for providing an input power P.sub.MED of the compressor 100 as a function of motor operation current measured, and comparing this input power P.sub.MED with a reference operation power P.sub.ref value.

(39) In line with the method developed, the present system is configured for increasing or decreasing the operation voltage of the compressor UC from a power difference D.sub.ifpot calculated between the input power P.sub.MED and the reference operation power P.sub.ref.

(40) The operation voltage of the compressor UC is increased or decreased from a electronic power device 300 of the inverter or TRIAC type, as shown in FIGS. 4 and 5.

(41) Preferably, the processing electronic device 200 is configured for digital control of the whole system.

(42) Once again, it should be pointed out that the adjustment of the operation voltage of the compressor UC is given from the comparison of the reference operation power P.sub.ref with the input power P.sub.MED.

(43) In greater detail, it should be pointed out that the operation voltage of the compressor UC is increased when a reference operation voltage value P.sub.ref is higher than the input power P.sub.MED. Similarly, the operation voltage of the compressor UC is decreased in the condition that a reference operation power P.sub.ref value is lower than the input power P.sub.MED.

(44) Still more preferably, the operation voltage of the compressor UC is increased or decreased from a pulse width modulation control PWM. However, other types of control signal may be employed without detriment to the functioning of the whole system, according to the teachings of the present invention.

(45) In the face of the foregoing, the presently claimed object achieves the objectives by means of a control method and system for a resonant linear compressor, capable of eliminating the need for sensors or complex methods for estimating the piston stroke for wide ranges displacement amplitude.

(46) Additionally, it should be pointed out that the present invention, besides reducing the cost of the compressor as compared with presently available solutions, further enables one to reduce possible noise peaks of the compressor, as well as improving the operation stability thereof. Such stability is achieved the same power is kept constant for the same reference.

(47) Finally, it should be further mentioned that the pressure peaks during the starting of the compressor are reduced, according to the teachings of the present invention, while the power is kept constant, unlike the stroke-control technique that was usually employed before, which generates a consumption peak and an “overshot” in the discharge pressure, as shown in FIG. 7. It should be mentioned that, in order to further reduce pressure peaks, which may contribute to generating high noises during the start, it is possible to introduce a ramp for the power, according to the teachings of the present invention, further limiting the “overshot” in the pressure.

(48) A preferred embodiment example having been described, one should understand that the scope of the present invention embraces other possible variations, being limited only by the contents of the accompanying claims, which include the possible equivalents.