Field of application

The present invention is generally applicable to the technical field of compressors, and in particular has as object a frequency changer assembly for a compressor as well as a compressor comprising such assembly. State of the art

Compressors of known type, especially of refrigeration type, are generally controlled by means of a frequency changer, commonly called inverter, which controls the power supply current in order to regulate the operating speed of the compressor.

Typically, inverters are housed in an electrical cabinet that is distant from the compressor. Such configuration nevertheless has various critical conditions, due to the difficulty of connection to the compressor as well as with the costs, since such inverters generally have relatively large size.

In order to overcome such drawbacks, the same Applicant made a compressor having an inverter integrated in its casing, such inverter being connected to a cooling plate.

Such compressor, disclosed in the patent application WO2009136277, even if achieving lower size, since the direct cooling of the inverter allows reducing the size thereof, nevertheless requires that the compressor be modified in its typical configuration in order to be able to house the group constituted by a plate and an inverter.

Presentation of the invention The object of the present invention is to overcome the above drawbacks by realizing a frequency changer assembly for controlling a compressor which is particularly effective and inexpensive.

One particular object is to realize a frequency changer assembly for compressors which can be applied to any compressor type, without requiring substantial modifications of the compressor.

Still another object is to realize a frequency changer assembly for compressors which also allows the use of compressors not especially designed for receiving an inverter thereinside.

Not the least object of the present invention is to realize a compressor provided with such assembly and which is not necessarily designed to receive an inverter at its interior, nevertheless conferring high compactness to the compressor.

Such objects, as well as others which will be clearer below, are achieved by a frequency changer assembly for compressors in accordance with claim 1 . Due to this combination of features, it will be possible to use an inverter directly connected with a cooling member without it being necessary to especially design the compressor to receive a group constituted by an inverter and a cooling member at its interior. In this manner, the compressor thus assembled will be considerably less expensive and more compact with respect to known solutions. According to a further aspect of the invention, a compressor is provided for, in accordance with claim 10, comprising an assembly according to the invention.

Advantageous embodiments are obtained in accordance with the dependent claims.

Brief description of the drawings

Further characteristics and advantages of the invention will be clearer in light of the detailed description of several preferred but not exclusive embodiments of an assembly and a compressor according to the invention, illustrated as a non-limiting example with the aid of the drawing table set, in which:

FIGG. 1 and 2 are section views of an assembly according to the invention applied to a known compressor, with its cover open in order to allow the view at its inside;

FIG. 3 is a top view of an assembly according to the invention applied to a known compressor and having the cover open in order to allow the view of its interior;

FIGG. 4 to 7 are side and front views of a compressor provided with the assembly according to the invention. Detailed description of a preferred embodiment

With reference to the mentioned figures, an assembly is illustrated according to the invention, indicated overall with 1 , coupled to a compressor 2 provided with an external casing 3 to which the assembly 1 is fixed.

The compressor 2 will preferably be a refrigeration compressor, as a non- limiting example a semi-hermetic twin-screw compressor, designed to be inserted in a cooling circuit, not illustrated, operating with a compressible working fluid. The casing 3 will be composed of at least one first and one second portions 3', 3" housing motor means 4 for the compressor 2, e.g. a common electric motor not shown in the figures, and at least part of the compression means belonging to the compressor 2, not visible since they are contained in the casing 3 and which will not be described in detail since they are of known type.

In a merely exemplifying manner, both the motor means 4 and the compression means can be of the type described in the abovementioned patent application WO2009136277.

In a known manner, the two portions 3', 3" will comprise respective coupling flanges 5', 5" mutually joined by means of screw means 6 or the like, e.g. bolts, stud bolts or the like. The frequency changer assembly 1 will comprise a containment shell 7 which encloses an inverter or frequency changer 8 at its interior, electrically connectable to the electric motor in order to adjust its operation speed.

In the shell 7, a cooling member 9 is also housed, arranged in thermal contact with the inverter 8 for its cooling by means of a refrigerant fluid, e.g. air drawn from the outside via a fan device, or water or another liquid, or a suitable gas for the refrigeration which flows inside the cooling member 9. For example, the cooling member 9 will comprise a cooling plate 10 crossed by the refrigerant fluid; such plate will allow interfacing the inverter 8 with the compressor 2. The inverter 8 and the cooling member 9 will be stably joined in a possibly removable manner, by means of suitable connection means 16, in order to define a unitary group. According to one particular feature of the invention, the unitary group formed by the inverter 8 and the cooling member 9 will be provided with anchoring means 1 1 designed for removably anchoring such group to the casing 3 of the compressor 2. In a first embodiment variant, not illustrated, the assembly 1 will comprise a protection cover designed to be placed on top of the casing 3 of the compressor 2, which may have a suitable seat for receiving the unitary group. In the configuration illustrated in the figures, the assembly 1 will comprise a protective shell 7 which encloses the inverter-cooling member group 8, 9 and which has the means 1 1 for the removable anchoring to the casing 3 of the compressor 2, on the outside of the casing 3. In particular, the anchoring means 1 1 will be designed for stably anchoring the shell 7, and consequently the inverter 8 and the cooling member 9, to any one compressor 2 of known type - not especially designed for housing an inverter inside its casing 3. The shell 7 can be of the type configured for enclosing all the electrical and electronic components associated with the inverter 8 and the cooling member 8, in such a manner to obtain an IP54 protection level.

A special painting inside the protective shell 7 can also be provided for, suitable for reducing the outward magnetic emissions of the inverter 8, permitting compliance with electromagnetic compatibility laws. The shell 7 can also be provided with an openable cover 12, in order to allow access to its interior for control or maintenance operations. In particular, the anchoring means 1 1 will comprise a coupling member 13 solidal with the shell 7 and outside the same and designed to be anchored to the portions 3', 3" of the casing 3 at their coupling flanges 5', 5", by means of the same screw means 6 which achieve the stable joining thereof. Preferably, the shell 7 will extend along a predetermined longitudinal direction X and the coupling member 13 will comprise a pair of anchoring brackets 14, 15 projecting transversely from opposite longitudinal ends of the shell 7. Each of the brackets 14, 15 will have substantially longitudinal, coupling through holes engageable by the screw means 6 of the compressor 2.

The latter will preferably have a casing 3 comprising two end portions 3', 3"' and one central portion 3" extending along a longitudinal axis L substantially parallel to the extension direction X of the shell 7, in assembled condition.

The central portion 3" will also be provided with a pair of end flanges 5", 5"' joined with respective flanges 5', 5 ^IV of the lateral portions 3', 3"' by means of respective screw means 6, 6', in order to define mutually coupled flange pairs 5', 5"; 5"', 5 ^iv .

The anchoring brackets 14, 15 will thus be anchored to respective flange pairs 5', 5"; 5"', 5 ^IV by means of the same screw means 6 which achieve the joining of the flanges 5', 5", 5"', 5 ^iv . The anchoring means 1 1 can comprise anti-vibration members, e.g. made of rubber, not visible in the figures. Such anti-vibration members are adapted for being interposed between the shell 7 and the casing 3, so as to be able to arrange the inverter 4 on the casing 3 of the compressor 2 by means of a damped fixing system which prevents the transmission of the vibrations of the operating compressor 2 to the electronic parts.

In both of the described configurations, the means 16 for connecting the inverter 8 to the cooling member can be constituted by a fixing support, which in the first case can also define the anchoring means 1 1 , which support ensures the suitable protection level and avoids accidental contact with the power-supplied components, complying with the relevant safety laws. The fixing system 16 can be provided with anchorage screws 17.

Such screws 17 will be tightened on the support 16, which in turn will be made solidal with the compressor 2 by means of brackets with high thickness which have the object of supporting the inverter 8, providing it with a solid support base that does not allow electronic part bending. All the screws 17 are removable, allowing the assembly 1 to be disassembled for maintenance or substitution. The cooling member 9 will comprise a heat exchanger 18 which encloses a refrigeration duct at its interior, not visible since it is inside the exchanger, from which a refrigerant fluid will be drawn.

In particular, the refrigeration duct will be connectable to the same feed circuit for the refrigerant fluid intended to be compressed by the compressor, by arranging a suitable derivation of the same.

The refrigerant fluid will thus cross through the exchanger 18, which is provided with a cooling plate 19 arranged in thermal contact with the duct and the inverter 8. Inside the exchanger 18, the evaporation of the refrigerant fluid will thus be obtained; such evaporation is suitable for causing the cooling of the electronic components placed in contact with the plate 19, which in practice will define the support for the inverter 8.

The evaporated gas will be advantageously driven to the compressor 2 by utilizing a drawing port of the same, open on the compression chamber of the compression means; such drawing port will have a pressure greater than the drawing pressure.

The use of the additional port will allow increasing the surface temperature of the cooling plate 19, significantly reducing the risk of condensate formation inside the electronic module. By means of a small fan 20 placed in the shell 7, the recirculation of air will be facilitated, and a greater uniformity of the temperature inside the shell will be ensured. In such a manner, the risk of formation of areas with high humidity will be reduced, which could be potentially damaging for the components.

The entire cooling plate 19 can be insulated in the areas not dedicated to the exchange with the electronic components, in order to limit any formation of condensate that could increase the risk of electrical malfunctioning.

The connection between the inverter 8 and the electric motor will be directly carried out by means of rigid members (not visible in the figures), preferably made of a material with high conductivity. In an exemplifying and non-limiting manner, such material could be copper rods, exiting from the shell, which reduce installation problems and maintain the correct protection level of the assembly 1 .

The inverter-compressor group can communicate by means of a management software which detects all the operative parameters and monitors them, respecting the application limits of the system thus composed. In a particular manner, the software will control - instant-by- instant - the temperature of the motor and the circuit boards and the electrical absorption, preserving the life of the system.

The temperature of the inverter 8 can be automatically controlled by means of two temperature probes, and its cooling will be arranged only if it is necessary, upon reaching two temperature levels.

In particular, the inflow of the refrigerant fluid inside the refrigerant duct of the exchanger 18 can be controlled by two solenoid valves.

When the temperature exceeds a predetermined value, e.g. comprised between 25 °C and 45 °C and preferably close to 35 °C, the first solenoid valve is opened. If the evaporation of the fluid quantity which passes after the opening of the first solenoid valve is not sufficient, and the temperature of the inverter 8 reaches a higher temperature, e.g. comprised between 35 °C and 55 °C and preferably close to 45 °C, the second valve will also be opened in order to obtain a greater heat removal.

According to a further aspect of the finding, a compressor 2 is provided for refrigeration plants having a cooling circuit for the circulation of a work fluid, in which the compressor has an external casing 3, to which an assembly 1 of the above-described type is removably and stably coupled.

In a typical manner, the compressor 2 will comprise an external casing 3 which encloses a drawing chamber for the work fluid at its interior. Such chamber has an inlet port 21 connectable to the cooling circuit, compression means for the drawn fluid and a delivery chamber for the compressed fluid having an outlet port 22 connectable to the cooling circuit. In the casing 3, motor means 4 are also housed, e.g. an electric motor with suitable torque, supplied with electrical power and operatively coupled to the compression means in order to drive them with predetermined adjustable speed.

The containment shell 7 will be removably anchored on the outside of the casing 3 and will enclose an inverter 8 therein that is electrically connected to the motor means 4 and connectable to a voltage source in order to supply electrical power to the motor means 4, regulating the drive speed thereof, according to known functioning modes.

The casing 3 will comprise two end portions 3', 3"' respectively housing the drawing chamber and the delivery chamber and a central portion 3" extending along the longitudinal axis L and housing both the motor means 4 and at least part of the compression means.

The latter can be at least in part housed in one of the two lateral portions. The central portion 3" will be provided with a pair of end flanges 5", 5"' joined to respective flanges 5', 5 ^IV of the lateral portions 3', 3" by means of screw means 6, 6', in order to define mutually coupled flange pairs 5', 5"; 5"', 5 ^IV .

The coupling member 13 of the shell 7 will comprise a pair of anchoring brackets 15, 16 projecting transversely from opposite longitudinal ends of the shell 7 and anchored to respective flange pairs 5', 5"; 5"', 5 ^IV by means of the screw means 6, 6'.

Advantageously, the casing 3 will have a drawing port fluidically connected to the outlet of the internal duct of the cooling member 9 in order to receive the evaporated fluid from the same. From that stated above, it is clear that the invention attains the pre- established objects and in particular that of providing a changer assembly for compressors which allows applying an inverter directly associated with a cooling member even to compressors that are not especially designed for receiving an inverter, obtaining a compressor with high compactness.

The assembly and the compressor according to the finding are susceptible to numerous modifications and variants, all falling within the inventive concept expressed in the enclosed claims. All details can be substituted by other technically equivalent elements, and the materials can be different as required, without departing from the scope of the finding.

Even if the assembly and the compressor were described with particular reference to the enclosed figures, the reference numbers used in the description and in the claims are used for improving the comprehension of the finding and do not constitute any limitation of the claimed protective scope.