Valve unit and refrigeration system including such a valve unit

Abstract

Refrigeration system comprising a refrigerant circuit comprising an inlet flow control valve (28) configured to control the flow of refrigerant from the condenser heat exchanger (52, 54) to the evaporator heat exchanger (58), and an outlet flow control valve (29) configured to control the flow of refrigerant from the evaporator heat exchanger (58) to the compressor (51). The inlet and outlet flow control valves (28, 29) are fluid driven without electrical connections and can be operationally associated with a mechanical impact sensor (8) comprising an inertial body.

Description

[0001] Valve unit and refrigeration system including such a valve unit

[0002] Technical field

[0003] The present invention relates to valve unit and a refrigeration system, in particular a transport refrigeration system, which comprises said valve unit. The invention moreover relates to a method for controlling said refrigeration system.

[0004] Background of the invention

[0005] With the Montreal Protocol, ozone-depleting substances such as chlorofluorocarbons (CFCs), which had until then been widely used in refrigeration systems, were regulated and subsequently replaced by hydrofluorocarbons (HFCs). However, HFCs have been found to have a very high global warming potential and have been limited by the Kigali Amendment to the Montreal Protocol and, in Europe, by the Ell Regulation on F-gases (fluorinated greenhouse gases). In response, hydrofluoroolefins (HFOs) were developed, which have low ozone-depleting potential and low global warming potential. However, growing scientific evidence seems to indicate that trifluoroacetic acid (TFA), which is a degradation product of some HFOs, harms the environment and human health, for example, through its accumulation in lakes, groundwater, oceans and finally in drinking water (see, for example,

[0006] Therefore, regulation of the use of HFOs is to be expected and less environmentally harmful refrigerants for use in refrigeration systems should be considered. Liquefied natural gases, such as propane (also known as R290), are suitable alternative refrigerants. However, propane and other suitable refrigerant candidates such as, for example, 2,3,3,3-Tetrafluoropropene (also known as R1234yf) and R452 are highly flammable and explosive substances. Other suitable refrigerant candidates such as carbon dioxide (CO2, also known as R744) are toxic, at least at high concentrations. It is therefore necessary to take safety measures.

[0007] For example, in a refrigerated cargo truck comprising a transport refrigeration system (see, for example, US-11 , 565, 568B2), it must be ensured that, in the event of an accident, no or only a limited amount of flammable or toxic refrigerant escapes from the refrigeration system and in the cargo compartment, thus ensuring that the concentration of flammable or toxic refrigerant within the compartment remains below a tolerable limit. Leaked flammable refrigerant could easily be ignited by a spark or the like, causing an explosion or at least a fire. Toxic refrigerant can, for example, spoil perishable foods and harm dispensers and service personnel.

[0008] In motorized and non-motorized gas-heated caravans, safety regulations prescribe that there should be no gas leaks into the passenger compartment when using gas heating while driving. Caravans are therefore equipped with crash sensors as described, for example, in EP-2096340B1, EP-3822524B1, EP- 3822525B1. The impact sensors comprise an inertial body as a trigger that is moved from its resting position if a horizontal force greater than a predefined limit is applied. The principle is similar to that used in earthquake-activated gas valves described, for example, in document IIS-4, 799, 505A and to block the flow of fuel from the tank of a vehicle in the event of a traffic accident as described in document US-4,960, 145A. All these impact sensors are non-electric, specifically to ensure that the respective sensors continue to work even in the absence of electricity, for example, when the cables of a car battery are interrupted.

[0009] In contrast, in a refrigerated truck the cooling of the cargo, for example, of perishable food, must be guaranteed even in the event of an accident, since the deterioration of the perishable food would lead to a financial loss for the food distribution company.

[0010] Furthermore, additional fault detection and surveillance measures must be integrated into a transport refrigeration system which requires electricity. For example, it must be detected if a door in the refrigerated cargo hold of the truck has been left open, accidentally or intentionally, for example, to load or unload goods or during repairs or maintenance. Components of the refrigeration system, such as the evaporator heat exchanger or refrigerant piping, could be damaged during loading or unloading of cargo, for example, due to a collision with a forklift or pallet, so as to cause potentially dangerous refrigerant leaks.

[0011] Summary of the invention

[0012] A task of the present invention is to provide a valve unit with an impact sensor that is in particular suitable for use in a refrigeration system, in particular a transport refrigeration system, in which flammable and / or toxic refrigerants may be used.

[0013] A further task of the present invention is to provide a refrigeration system, in particular a transport refrigeration system, in which flammable and / or toxic refrigerants may safely be used. Yet a further task of the present invention is to provide a method for controlling said refrigeration system.

[0014] To achieve these and other tasks of the invention, which will become more easily evident as the description proceeds, a valve unit with the features of claim 1 , a refrigeration system with the features of claim 6, and a method with the features of claim 9 are provided.

[0015] The impact sensor of the invention is associated with a valve unit having at least one shutter displaceable by means of a fluid pressure, from a closed position to an open position, comprising a movable rod along which the shutter slides axially between a first stop of the movable rod corresponding to said closing position and a second stop of the movable rod corresponding to said open position. The impact sensor comprises:

[0016] - an inner slide cooperating with one end of said movable rod and moveable transversally thereto, the inner slide (6) being displaceable between a first position in which it prevents the displacement of the movable rod and a second position in which the displacement of the movable rod is permitted in order to cause said second stop to move forward so as to bring said shutter from the open position to the closed position, the first position corresponding to a set-back position and the second position corresponding to a forward position,

[0017] - an inner slide activation element, movable between a non-operational position and an operational position to move the inner slide from the set-back position to the forward position

[0018] - an inertial body cooperating with the activation element to permit, in the event of an impact, the displacement of said activation element from the non- operational position to the operational position and the consequent displacement of the inner slide from the first forward position to the second forward position.

[0019] A significant advantage of the impact sensor according to the invention consists in the fact that it comprises only mechanical components and therefore does not require electrical connections which could, in the event of an accident, be interrupted rendering the impact sensor non-operational, or vice versa constitute a source of ignition for a flammable refrigerant.

[0020] The inertial body typically comprises a movable ball in a travel space, the travel space comprising a rigid seat with a conical surface tilted upwards, the ball laying at rest on the deepest part of the conical surface of the rigid seat in a resting position, and the activation element of said inner slide rests against the ball to maintain the activation element in the non-operational position, disengaging from the ball when this moves from the resting position to permit movement of the activation element in its operational position. the inner slide is conveniently formed a with tilted plane on which said end of the rod slides when the inner slide moves from the set-back position to the forward position. This end of the rod is advantageously in rolling contact with the inner slide.

[0021] In a further aspect of the invention, a refrigeration system is provided to control the temperature of a compartment or hold. The refrigeration system is, in particular, a transport refrigeration system used, for example, in a refrigerated cargo truck, in a refrigerated tractor trailer or in a cargo container (as used, for example, on ships, airplanes or trains), wherein the cargo is transported in a compartment of the truck, tractor trailer or container. The refrigeration system according to the invention can also be used, for example, as a climate control system in a car, wherein the "cargo" in this case consists of human beings and the passenger compartment, from the inside of the vehicle. Likewise, the refrigeration system can be used as an air conditioning system in a truck transporting livestock. Depending on the outside temperature, the refrigeration system of the invention can also function as a heat pump system when the desired temperature inside the compartment is higher than the ambient temperature.

[0022] The refrigeration system of the invention comprises a refrigeration circuit comprising, for example:

[0023] - a compressor configured to compress a refrigerant;

[0024] - a condenser heat exchanger operationally coupled to the compressor;

[0025] - an evaporator heat exchanger operationally coupled to the compressor;

[0026] -expansion means for reducing the refrigerant pressure, the expansion means arranged between the condenser heat exchanger and the evaporator heat exchanger;

[0027] - an inlet flow control valve arranged between the condenser heat exchanger and the expansion means and configured to control the flow of refrigerant from the condenser heat exchanger to the evaporator heat exchanger;

[0028] - an outlet flow control valve arranged between the evaporator heat exchanger and the compressor and configured to control the flow of refrigerant from the evaporator heat exchanger to the compressor, - a control unit configured to control the compressor, wherein said inlet and outlet flow control valves (28, 29) are fluid driven without electrical connections.

[0029] According to one aspect of the invention, the valve unit is operationally associated with an impact sensor of the type defined above.

[0030] The refrigerant circuit works as follows: the refrigerant gas enters the compressor. In the compressor, the refrigerant pressure increases leading to an increase in temperature. This high-temperature, high-pressure gaseous refrigerant enters the condenser heat exchanger located downstream of the compressor. In the condenser heat exchanger, the gaseous refrigerant condenses, turning into a liquid refrigerant at high pressure. In the condenser heat exchanger, the heat of the refrigerant is transferred to the medium conducted through the condenser heat exchanger, for example, air blown through the condenser heat exchanger by a fan assigned to the condenser heat exchanger (also called condenser fan). After leaving the condenser heat exchanger, the now liquid refrigerant enters the expansion means arranged downstream of the condenser heat exchanger. The expansion means comprise, for example, an expansion valve, in particular a thermostatic expansion valve. Expansion means a reduction in refrigerant pressure, resulting in a decrease in temperature. Due to the pressure drop, the liquid refrigerant begins to turn into gas, in particular vapor. Downstream of the expansion means the refrigerant enters the evaporator heat exchanger. A relatively warm medium of the hold is conducted through the evaporator heat exchanger, for example, warm air blown through the evaporator heat exchanger by a fan associated with it (also called evaporator heat exchanger). By means of the heat transfer, the refrigerant is completely vaporized, whereas the fluid conducted through the evaporator heat exchanger is cooled. This leads to the cooling of the hold and, therefore, of the cargo inside the hold. After passing through the evaporator heat exchanger, the now gaseous refrigerant is sucked into the compressor and the refrigeration cycle begins again.

[0031] To effectively cool the hold, the evaporator heat exchanger is preferably arranged inside the hold or in its immediate vicinity. If the evaporator heat exchanger is arranged outside but in the immediate vicinity of the hold, the evaporator heat exchanger is preferably arranged in an insulating chamber whose insulating walls are connected to a connecting (external) wall of the hold. An opening is provided in the connecting wall of the hold for the passage of the fluid (in particular air flow) from the evaporator heat exchanger arranged in the insulating chamber in the hold. The expansion means are preferably arranged near the evaporator heat exchanger within the hold, inside the insulating chamber in the event in which the evaporator heat exchanger is provided in an insulating chamber separate from the hold, or outside of both the hold and the insulating chamber. The compressor and condenser heat exchanger are preferably arranged in another part of a refrigerated truck outside the hold and outside the insulation chamber, if provided. The inlet flow control valve and / or the outlet flow control valve can preferably also be arranged in or close to the insulating walls of the insulating chamber. If an insulating chamber is provided to receive the evaporator heat exchanger, the inlet flow control valve and / or the outlet flow control valve may also be arranged in or near the insulating walls of the insulating chamber.

[0032] As described above, there are trends to replace refrigerants such as hydrofluoroolefins (HFOs) with more environmentally friendly refrigerants, for example, liquefied natural gases, such as propane, which are, however, often highly flammable and therefore explosive. Alternatively, carbon dioxide can be used, which however is toxic at higher concentrations. Therefore, safety measures must be taken to protect people and cargo.

[0033] In potentially dangerous situations that could lead to the release of flammable substances and / or refrigerants, the control unit is therefore preferably configured to perform an insulation of the hold by switching off the compressor.

[0034] In this event, it is also necessary to provide for the closing of the inlet flow control valve, so as to prevent a further flow of refrigerant to the expansion means and to the evaporator heat exchanger and, therefore, to the corresponding parts of the refrigeration circuit inside of the hold and also to the insulation chamber, if the evaporator heat exchanger and / or expansion means are arranged in an insulation chamber separate from the hold. By also closing the outlet flow control valve, those parts of the refrigeration circuit that are inside of or in the vicinity (that is, in the aforementioned insulating chamber) of the hold (also called: parts of the hold or temperature-controlled parts of the refrigeration circuit) are insulated from those parts of the refrigeration circuit located outside the hold and also outside the optional insulating chamber, if provided, (also called: parts outside the hold or parts of the refrigeration circuit at uncontrolled temperatures). In other words, an insulation of the parts of the refrigeration circuit hold is carried out (also called: hold insulation). Shutting off the compressor also deactivates a potential ignition source for the flammable refrigerant.

[0035] According to a preferred embodiment, the refrigeration system of the invention comprises the impact sensor of the invention. If the impact sensor has been activated, in particular in the event of an accident with horizontal acceleration, the inlet and outlet flow control valves are closed without intervention of the control unit and without the need for an electrical power supply. Since an accident could result in a refrigerant leak, it is preferable that the inlet flow control valve and the outlet flow control valve are closed simultaneously, turning off the compressor at the same time.

[0036] With the refrigeration system equipped with the impact sensor of the invention, the insulation of the hold is performed if the impact sensor is in an activated state. In addition, or alternatively, it is possible to insulate the compartment if at least one of the following elements is detected: a) the temperature of the hold is equal to or lower than the set temperature of the hold; b) an access door to the hold is open; c) the compressor pressure exceeds a predefined pressure threshold; d) the compressor temperature exceeds a predefined temperature threshold; e) a gas concentration inside the hold exceeds a predefined gas concentration threshold; or f) a leakage in the refrigeration circuit is detected.

[0037] For further details, and to avoid repetition, please refer to the previous description of the refrigeration system and its preferred embodiments, including the description of the situations indicated above, which applies similarly to the method of the invention.

[0038] Brief description of the drawings

[0039] Further advantageous features and applications of the invention can be found in the dependent claims as well as in the following description of the drawings illustrating the invention. In the drawings, similar reference signs designate the same or similar elements in the various figures of wherein:

[0040] Fig. 1 shows a schematic sectional view of an impact sensor of the invention associated with a valve unit, in a deactivated state and with the valve unit in a closed condition, Fig. 2 shows a schematic sectional view of the impact sensor shown in Fig. 1 , in a deactivated state but with the valve unit in an open condition;

[0041] Fig. 3 shows a schematic sectional view of the impact sensor shown in Fig. 1 in an activated state and with the valve unit in a closed condition,

[0042] Fig. 4 schematically shows an example of a transport refrigeration system according to the invention;

[0043] Fig. 5 is a diagram showing a control unit of the refrigeration system example of Fig. 4; and

[0044] Fig. 6 schematically shows an example of a refrigerated cargo truck with an example of a transport refrigeration system according to the invention.

[0045] Description of preferred embodiments

[0046] Fig. 1 to Fig. 3 show an impact sensor 8 according to the invention, associated with a valve unit 2 formed, in the case in the example shown, by a body 3 for two valves 28, 29 which, as will be seen, can consist respectively of the inlet flow control valve and of the outlet flow control valve of a refrigeration circuit which will be discussed in detail later.

[0047] It should be noted that the impact sensor according to the invention is generally applicable even in the event where the valve unit comprises a single valve.

[0048] Each valve 28, 29 comprises a respective shutter 4, 10 generally in the shape of a hollow piston displaceable by means of a fluid pressure from a closed position (Fig. 1 and Fig. 3) to an open position (Fig. 2). Each shutter 4, 10 slides axially along a respective rod 39, 9 between a first stop 30, 33 corresponding to the closed position, and a second stop 31, 34 of the rod corresponding to the open position. The shutter 4 controls the communication between an input A and an output B and the shutter 10 controls the communication between an input C and an output D of the body 3 of the valve unit 2.

[0049] References 20, 23 and 17, 35 indicate sealing gaskets between the shutters 4, 10 and the corresponding internal surfaces of the body 2. References 22 and 18 indicate sealing gaskets between the shutters 4, 10 and the respective rods 39, 9 and references 1 and 19 indicate balancing pistons of the shutters 4, 10 of the valves 28 and 29, with the relative sealing gaskets 24 and 19.

[0050] The two rods 39 and 9 which, in the case of the example shown, are side-by- side and parallel to each other but could also have different orientations, are normally stationary and bear respective stops 30, 31 and 33, 34 which define the closing and open positions of the shutters 4, 10.

[0051] The shutters 4, 10 are stressed in the closed position, one against the stop 30 and the other against the stop 33, by respective thrust springs 14 and 13 reacting against one side of the stops 31 and 34. Thrust springs 15, 25 are placed between the other side of the stops 31 , 34 and the body 3 of the valve unit 2. the rods 39, 9 have free ends conveniently equipped with respective ball rolling elements 5 cooperating with an impact sensor indicated as a whole with 8.

[0052] The impact sensor 8 comprises:

[0053] - an enclosure 8 within which an inner slide 6 is displaceable, transversally to the rods 39, 9 (that is, vertically) between a set-back (that is, raised) position in which it blocks the axial displacement of the rods 39, 9 (Fig. 1 and Fig. 2) and a forward (that is, lowered) position in which the axial displacement of the rods 39, 9 is permitted (Fig. 3) in order to cause the stops 31, 34 to move forward, as will be seen in order to bring the shutters 4, 10 from the open position to the closing position,

[0054] - appendages 27 borne by the inner slide 6 and formed with respective tilted planes with which the balls 5 borne at the ends of the rods 39, 9 cooperate

[0055] - an activation element 7 of the inner slide 6, coupled with this and movable between a non-operational position (that is, raised - Fig. 1 and Fig. 2) and an operational position (that is, lowered - Fig. 3) to move the inner slide 6 from the set-back position to the forward position; a spring 16 tends to press the activation element 7 towards the operational position, the inner slide 6 is inserted within a seat of the activation element 7 with a certain reciprocal play in their direction of displacement,

[0056] - an inertial body 12 against which an appendage 7B of the activation element 7 rests, under the action of the spring 16. The inertial body 12 cooperates with the activation element 7 to permit, in the event of an impact, the displacement of the activation element 7 from the non-operational position to the operational position and the consequent displacement of the inner slide 6 from the set-back position to the forward position.

[0057] The inertial body 12 consists typically of a movable ball in a travel space delimited by a rigid seat 11 with a conical surface 32 tilted upwards. At rest, the ball 12 rests on the deepest part of the conical surface 32 of the seat 11 in a resting position, the activation element 7 of the inner slide 6 rests against the ball 12 to maintain the activation element 7 in the non-operational position. When the ball 12 moves from its resting position as a result of an impact, or a sudden deceleration of the valve unit 2, it frees the movement of the activation element 7 which can thus move into its operational position by drawing the inner slide 6 towards its lowered position. In this way the balls 5 roll on the tilted planes of the appendages 27 of the inner slide 6, permitting the rods 39, 9 to translate from the position shown in Fig. 1 and Fig. 2 to that represented in Fig. 3.

[0058] It should be noted that, instead of being linearly movable, the inner slide 6 could be rotatable between a first and a second position, for example, about a central axis of the two valves 28 and 29, and in this case the two rods 39, 9 could also have different orientations from the one shown.

[0059] Fig. 1 shows the closed condition of the valve group 2: the shutters 4, 10 of the two valves 28, 29 are arranged against the respective stops 30, 33, so that the flow between inlet A and outlet B and between input C and output D is interrupted.

[0060] Fig. 2 shows the opened condition of the valve group 2: the shutters 4, 10 of the two valves 28, 29 are arranged against the respective stops 31, 34, so that the flow between inlet A and outlet B and between inlet C and outlet D is open.

[0061] In both cases the impact sensor 8 is non-operational.

[0062] The operation of the valve unit 2, associated with the cooling system which will be described in detail below, is as follows.

[0063] In the closed condition represented in Fig. 1 (corresponding to the off condition of the cooling system compressor) all the pressure inside the refrigeration circuit will be the same and will depend on the temperature of the refrigerant. In this condition the force acting on the two sides of the shutter 4 of the valve 28 (pressure A on the left side and pressure D on the right side) will be the same, including because of the presence of the balancing piston 28, therefore the force of the spring 14 will move the shutter against the stop 30, closing the gasket 20.

[0064] The same situation occurs on the two sides of the shutter 10 of the valve 29 (the pressure A on the left side and the pressure D on the right side is the same, also because of the presence of the balancing piston 19, therefore the spring 13 moves the shutter 10 against the left stop 33 closing the gasket 35.

[0065] In the condition represented in Fig. 2, corresponding to the activation of the compressor of the cooling system, the pressure in the part of the refrigeration circuit from the compressor to the evaporator valve will be higher than the pressure in the return to the compressor from the evaporator.

[0066] In this condition, the force acting on the two sides of the piston of the shutter 4 of the valve 28 (the pressure A on the left side will be greater than the pressure D on the right side) prevails over the force of the spring 14, moving the shutter 4 towards the stop 31 opening the gasket 20 and permitting the flow of the refrigerant.

[0067] The same situation is also found on the two sides of the shutter 10 of the valve 29: the pressure A on the left side will be higher than the pressure D on the right side so that the force generated will prevail over the force of the spring 13, moving the shutter 10 against the stop 34, opening the seal 35 and permitting the refrigerant to flow.

[0068] The operation described above is independent of the presence or absence of the impact sensor 8.

[0069] In the event of intervention of the impact sensor 8, in the manner described above, the axial displacement of the rods 39, 9 causes the translation of the stops 31, 34, returning the shutters 4, 10 of the two valves 28, 29 to the closed position.

[0070] In the event that the two valves 28, 29 consist respectively of the inlet flow control valve and the outlet flow control valve of a refrigeration system, their closure operated by the impact sensor 8 permits the refrigerant circuit to be insulated from the evaporator side.

[0071] Since the activation element 8 is stressed in the activation position and therefore cannot return by itself to the deactivation position once the inertial body 12 has been moved from its resting position, for example, during an impact, resetting means are provided to bring the activation element 7 back from its activation position to its deactivation position, rearming the impact sensor 8. The rearming is carried out, for example, manually, or even with the aid of a possible electromagnetic auxiliary device, by moving the activation element 7 in the raised position, through its appendage 7A accessible through a slot in the enclosure 6 and against the action of the spring 16, to bring it back to rest on the ball 12 repositioned at rest in the deep part of the conical surface of the seat 32.

[0072] Fig. 4 and Fig. 5 show an example of a refrigeration system of the invention in the form of a transport refrigeration system 200 (Fig. 6). The present invention, however, is not limited to transport refrigeration systems, but also applies to stationary refrigeration systems. The transport refrigeration system 200 shown in Fig. 4 and Fig. 5 may for example be provided in a refrigerated cargo truck 300 as shown in Fig. 6. Alternatively, the transport refrigeration system can be used as an air conditioning system, for example, in a passenger vehicle.

[0073] Fig. 5 shows the control unit 68 of the transport refrigeration system 200 which is not illustrated in Fig. 4 and Fig. 6 for reasons of clarity. In Fig. 4 the reference signs in the dashed boxes denote signals, in particular measurement signals or activation signals / control signals, and the arrows with dashed beginning or end in Fig. 4 and Fig. 5 indicate the transmission of the respective signal to or from the control unit 68.

[0074] The transport refrigeration system 200 comprises a refrigerant circuit with a compressor 51 and a condenser heat exchanger 52 arranged downstream and operationally coupled to the compressor 51 by means of refrigerant piping. To improve efficiency, an additional condenser heat exchanger 54 may be present provided it is coupled in series with the (first) condenser heat exchanger 52. An accumulator 53 may be assigned to one or both condenser heat exchangers 52, 54 to remove and return refrigerant from the refrigeration circuit, if deemed necessary.

[0075] The refrigeration circuit moreover comprises an evaporator heat exchanger 58 and expansion means 57 (for example, a thermostatic expansion valve) upstream of the evaporator heat exchanger 58. The evaporator heat exchanger 58 is operationally coupled to the compressor 51. Refrigerant piping is provided to connect an evaporator heat exchanger inlet 58 through the expansion means 57 to the one or plurality of condenser heat exchangers 52, 54, and to connect an evaporator heat exchanger outlet 58 to compressor 51. The evaporator heat exchanger 58 and the expansion means 57 can be arranged inside a hold 50 used for the transport of refrigerated goods. One or both of the evaporator heat exchanger 58 and the expansion means 57 may also be arranged in a separate insulating chamber or compartment 70 as described below with reference to Fig. 6. The hold 50 may, for example, be comprised in a tractor trailer or be made up from a tractor trailer of a refrigerated cargo truck 300.

[0076] Alternatively, and as shown in Fig. 6, the evaporator heat exchanger 58 can be arranged close to the hold 50 in a separate insulating chamber 70, the insulating walls of which are connected to a connecting (external) wall of the hold. In this case, an opening 72 is provided in the connecting wall of the hold 50 which leads to the insulating chamber 70 for guiding the medium (in particular air) blown through the evaporator heat exchanger 58 by an evaporator fan or the like into the hold 50. The expansion means 57 can be arranged i) inside the insulating chamber 70 or ii) near the evaporator heat exchanger 58 inside the compartment 50 or ii) outside both, the hold 50, and the insulation chamber 70, but preferably close to the evaporator heat exchanger 58. The compressor 51 and one or more condenser heat exchangers 52, 54 are arranged outside both the hold 50 and the insulating chamber 70.

[0077] To control the flow of refrigerant from the one or a plurality of condenser heat exchangers 52, 54 to the expansion means 57 and then to (the inlet of) the evaporator heat exchanger 58, the inlet flow control valve 28 is arranged in the refrigerant flow (in other words, the refrigerant piping) between one or a plurality of condenser heat exchangers 52, 54 and the expansion means 57. Similarly, the outlet flow control valve 29 is arranged in the refrigerant flow (in other words, the refrigerant piping) between (the outlet of) the evaporator heat exchanger 58 and the compressor 51 to control the refrigerant flow from evaporator heat exchanger 58 to compressor 51. Both the inlet flow control valve 28 and the outlet flow control valve 29 are positioned outside the interior of the hold 50.

[0078] Preferably, the inlet flow control valve 28 and / or the outlet flow control valve 29 are arranged close to the evaporator heat exchanger 58 in or on a connecting / external wall of the hold 50. If the evaporator heat exchanger 58 is arranged in a separate insulating chamber 70, the inlet flow control valve 28 and the outlet flow control valve 29 are preferably arranged in or on an insulating wall of the insulating chamber. The inlet flow control valve 28 and the outlet flow control valve 29 can be arranged on the same or different insulating walls of the insulating chamber 70. The inlet flow control valve 28 and / or the outlet flow control valve 29, described above in detail, are so-called mechanical valves, that is, not electrically actuated like the impact sensor 8.

[0079] Optionally, a refrigerant-to-refrigerant heat exchanger 55 (also called internal heat exchanger or IHX) may be arranged within the hold 50 between the outlet of the evaporator heat exchanger 58 and the outlet flow control valve 29 to increase the sub-cooling of the refrigerant. Alternatively, the refrigerant-to-refrigerant heat exchanger 55 can be arranged in the insulation chamber 70 shown in Fig. 6. The refrigerant-to-refrigerant heat exchanger 55 can ensure economical operation and increased efficiency. An intake valve 60, in particular an intake modulation valve, can be arranged upstream of the compressor 51 and downstream of the outlet flow control valve 29. Furthermore, a compressor expansion valve 61 may be arranged between the inlet of the compressor 51 and an outlet of the condenser heat exchangers 52, 54. The compressor expansion valve 61 opens and closes in response to the discharge temperature 154 of the refrigerant leaving the compressor 51 and serves to prevent overheating of the compressor 51.

[0080] The transport refrigeration system 200 may comprise the impact sensor 8 of the invention as described above in connection with Fig. 1 to Fig. 3. The transport refrigeration system 200 may moreover comprise an access door sensor (not shown), for example, a door switch located at or in proximity to a compartment access door 64, configured to detect whether the compartment access door 64 is open or not.

[0081] The transport refrigeration system 200 may moreover comprise a gas sensor 65 arranged within the compartment 50 to detect a concentration of gas 165 within the compartment 50, in particular a concentration of flammable and / or toxic gas such as inflammable and / or toxic refrigerant vapor. The transport refrigeration system 200 preferably also comprises a temperature sensor 67 arranged inside the hold 50 to detect the temperature 167 of the hold.

[0082] The transport refrigeration system 200 may comprise a control unit 68 preferably arranged outside the hold 50. The control unit 68 may comprise an integrated circuit with a microprocessor or the like, with ports and interfaces to interact communicatively with the various components of the transport refrigeration system 200. The control unit 68 is configured to control the compressor 51 by means of corresponding activation signals and a signal for turning the compressor 51 on or off. The control unit 68 may moreover be configured to control the expansion means 57, the suction valve 60 and / or the compressor expansion valve 61 by means of corresponding control signals 157, 160, 161, and / or to send a communication signal 171, in particular an alarm signal, by means of a communication network to a remote server in certain situations described below.

[0083] The control unit 68 may moreover be configured to receive the following signals as inputs: an output signal of the safety switch of the compressor 151 , a suction temperature 152 of the refrigerant on the suction side of the compressor 51, a suction pressure 153 on the suction side of compressor 51, a discharge temperature 154 of the refrigerant on the discharge side of compressor 51, a discharge pressure 155 on the discharge side of compressor 51, a temperature of the refrigerant evaporator 162 downstream of the evaporator heat exchanger 58, a pressure of the refrigerant evaporator 163, an output signal of an access door sensor 164 (for example, a door switch), an output signal of the gas sensor 65 (that is, the concentration of gas inside the compartment 165), a possible signal 166 which indicates whether the impact sensor 8 is in the deactivated state (the output signal 166 is received by the control unit 68) or activated state (no output signal 166 is received), and / or a temperature of the compartment 167 detected by the temperature sensor of the compartment 67.

[0084] For example, when the temperature 167 of the hold measured by the temperature sensor 67 has increased above a set temperature, the control unit 68 orders the start of operation of the compressor 51, thus starting a refrigeration cycle.

[0085] During the refrigeration cycle, the control unit 68 preferably controls the expansion means 57 based on the temperature of the refrigerant evaporator 112 and the pressure of the refrigerant evaporator 113, both measured downstream of the evaporator heat exchanger 58 (and upstream of a possible refrigerant-to- refrigerant heat exchanger 55) using suitable temperature and pressure sensors. The expansion means 57 are controlled in such a way that the evaporator heat exchanger 58 is supplied with the appropriate amount of refrigerant to achieve the set temperature of the compartment. The control unit 68 converts the evaporator pressure 113 measured downstream of the evaporator heat exchanger 58, for example, by means of a table stored in the control unit 68, into a refrigerant temperature calculated downstream of the evaporator heat exchanger 58. The control unit 68 then calculates the difference between the measured evaporator temperature 112 and the calculated temperature of the refrigerant, the difference being the overheating of the refrigerant. The overheating indicates whether the gaseous refrigerant is above its saturation or boiling point when it leaves the evaporator heat exchanger 58. If the overheating is too high, this may entail poor refrigeration results. On the other hand, if the overheating is too low, an excessive amount of refrigerant may be fed into the evaporator heat exchanger 58, which may cause damage to the compressor 51 due to fluid backflow. The control unit 68 preferably controls the expansion means 57 through its corresponding control signal 157 in such a way that the amount of refrigerant introduced into the evaporator heat exchanger 58 gives rise to adequate overheating.

[0086] The control unit 68 may moreover be configured to control the suction valve 60 of the compressor 51 based on the suction pressure 153 and suction temperature 152 measured / detected on the suction side of the compressor 51.

[0087] The control unit 68 may moreover be configured to control the expansion valve of the compressor 61 on the basis of the discharge temperature 154 and the discharge pressure 155 measured / detected on the discharge side of the compressor 51 such that the overheating of the compressor 51 can be advantageously avoided.

[0088] When the hold temperature 167 is equal to or lower than the set temperature of the compartment, the refrigeration cycle may be interrupted. In the event that a flammable refrigerant is used, safety is increased by having as little refrigerant as possible within those parts of the transport refrigeration system that are located in compartment 50 (in other words, the parts of the hold of the refrigeration circuit of the transport refrigeration system 200). Therefore, if the control unit 68 determines that the hold temperature 167 measured by the temperature sensor of the compartment 67 is equal to or lower than the set temperature, the control unit 68 turns off the compressor 51.

[0089] When a crash or similar high-impact horizontal acceleration produces activation of the impact sensor 8, a signal may be sent to the control unit 68, informing the control unit 68 of the activated state of the impact sensor 8. Since a crash may have caused damage to the refrigerant piping or other components of the refrigerant circuit within the hold 50, the control unit 68 preferably insulates the compartmentalized parts of the refrigerant circuit from the noncompartmentalized parts. Since an impact may lead to the rupture, for example, of the refrigerant piping and thus to the leakage of flammable and / or toxic refrigerant, the control unit 68 switches off the compressor 51. Since flammable gas may have already escaped and the compressor 51 represents a source of ignition, the compressor 51 is preferably turned off as soon as possible instead of first emptying the hold 50 of the refrigerant. Likewise, additional potential ignition sources in the hold 50 such as an evaporator fan, lighting, batteries, and other electrical appliances and electronic circuits are deactivated by the control unit 68. Preferably, the entire hold 68 is switched over to have no power by the control unit 68 for safety reasons. Similarly, if the compressor safety switch detects overpressure on the compressor 51 and switches off the compressor 51 for safety reasons, with the consequent equilibrium of pressures acting on the shutters 4 and 10 of the valves 28, 29. The output signal 151 of the safety switch represents an input signal of the control unit 68. The same applies if an overtemperature is detected on the compressor 51, i.e. a compressor temperature that exceeds a predefined temperature threshold.

[0090] The control unit 68 also receives as an input signal the gas concentration measured by the gas sensor 65 inside the hold. The control unit 68 compares the measured gas concentration with a predefined gas concentration threshold. If the measured gas concentration exceeds the predefined gas concentration threshold, which could indicate a leak of flammable and / or toxic refrigerant, the control unit 68 shuts down the compressor 51 for safety reasons. The control unit 68 preferably switches the entire compartment 50 to have no power to extinguish all potential ignition sources.

[0091] The control unit 68 is preferably configured to send, wirelessly, a communication signal 171 , in particular an alarm signal, by means of a communication terminal and a communication network to a remote server, when the control unit 68 carries out the insulation of the hold 50. The communication signal I the alarm signal 171 is sent in particular if an accident is detected by the impact sensor 1 and / or a gas leak is detected. The communication signal / alarm signal 171 serves to inform a transport manager, a fleet owner or a central service point that a dangerous situation has occurred involving the leak of flammable gas, which could endanger the cargo. For example, the repair of the refrigeration system 200 can be requested through the communication signal

Claims

CLAIMS1. Valve unit (2) comprising: an input flow regulation valve (28) and an output flow regulation valve (29), wherein each of the input flow regulation valve (28) and the output flow regulation valve (29) includes: a shutter (4, 10) displaceable by means of a fluid pressure from a closed position to an open position, and a movable rod (39, 9) along which said shutter (4, 10) slides axially between a first stop (30, 33) of the movable rod (39, 9) corresponding to said closing position and a second stop (31, 34) of the movable rod (39, 9) corresponding to said open position, the valve unit (2) further comprising an impact sensor (8), said impact sensor (8) comprising:- an inner slide (6) cooperating with one end (5) of each movable rod (39, 9) and moveable transversally thereto, the inner slide (6) being displaceable between a first position in which it prevents the displacement of the movable rod (39, 9) and a second position in which the displacement of the movable rod (39, 9) is permitted in order to cause said second stop (31, 34) to move forward so as to bring said shutter (4, 10) from the open position to the closed position, the first position corresponding to a set-back position and the second position corresponding to a forward position,- an activation element (7) of the inner slide (6), movable between a non- operational position and an operational position in order to move the inner slide (6) from the set-back position to the forward position,- an inertial body (12) cooperating with the activation element (7) to permit, in the event of an impact, the displacement of said activation element (7) from the non-operational position to the operational position and the consequent displacement of the inner slide (6) from the set-back position to the forward position.

2. Valve unit according to claim 1, characterized in that the inertial body of the impact sensor (8) comprises a movable ball (12) in a travel space of the impact sensor (8), the travel space comprising a rigid seat (32) with a conical surface tilted upwards, the ball in the resting position being arranged on the deepest part of the conical surface of the rigid seat (32), and in that said activation element (7)of said inner slide (6) rests normally against the ball (12) in order to maintain the activation element (7) in the non-operational position, the activation element (7) disengaging from the ball (12) when the ball (12) moves from the resting position allowing displacement of the activation element (7) into its operational position.

3. Valve unit according to claim 1 or claim 2, characterized in that the inner slide (6) is formed with at least one tilted plane (27) on which the respective ends (5) of said movable rods (39, 9) slide when the inner slide (6) moves from the first position to the second position.

4. Valve unit according to claim 3, characterized in that the respective ends (5) of the movable rods (39, 9) are in rolling contact with said inner slide (6).

5. Valve unit according to one of the preceding claims, characterized in that the respective shutters (4, 10) of the inlet flow control valve (28) and of the outlet flow control valve (29) are slidingly arranged on the respective movable rods (39, 9) that cooperate with said inner slide (6), such that the closing of the respective shutters (4, 10) of said inlet flow control valve (39) and of said outlet flow control valve (9), operated by means of said inertial body (12), occurs simultaneously.

6. Refrigeration system, in particular a transport refrigeration system, to control the temperature of a hold (50), the refrigeration system (200) including a refrigeration circuit comprising:- a compressor (51) configured to compress a refrigerant;- a condenser heat exchanger (52, 54) operationally coupled to the compressor (51);- an evaporator heat exchanger (58) operationally coupled to the compressor (51);- expansion means (57) for reducing the refrigerant pressure, the expansion means (57) being arranged between the condenser heat exchanger (52, 54) and the evaporator heat exchanger (58);- a valve unit (2) of one of the preceding claims, wherein:- the inlet flow control valve (28) of the valve unit (2) is arranged between the condenser heat exchanger (52, 54) and the expansion means (57) and configured to control the flow of refrigerant from the condenser heat exchanger (52, 54) to the evaporator heat exchanger (58); and- the outlet flow control valve (29) of the valve unit (2) is arranged between the evaporator heat exchanger (58) and the compressor (51) and configured to control the flow of refrigerant from the evaporator heat exchanger (58) to thecompressor (51); and,- a control unit (68) configured to control the compressor (51).

7. Refrigeration system according to claim 6, wherein the control unit (68) is configured to perform an insulation of the hold (50) by switching off the compressor (51), if at least one of the following is detected: a compartment temperature (167) is equal to or lower than the set temperature of the compartment; an access door (64) to the hold (50) is open; the compressor pressure exceeds a predefined pressure threshold; the compressor temperature exceeds a predefined temperature threshold; a gas concentration inside the hold (50) exceeds a predefined gas concentration threshold; or a leakage in the refrigeration circuit is detected.

8. Refrigeration system according to claim 6 or 7, wherein the control unit (68) is configured to perform the insulation of the hold (50) if the impact sensor (8) is in an activated state.

9. Method for controlling a refrigeration system (200) of a hold (50) according to one of claims 6 to 8, characterized in that said impact sensor (8) operates the simultaneous closure of said valves controlling the inlet flow and the outlet flow (28, 29).

10. Method according to claim 9, wherein the insulation of the hold (50) is carried out by switching off the compressor (51), if at least one of the following conditions is detected: a compartment temperature (167) is equal to or lower than the set temperature of the compartment; an access door (64) to the compartment (50) is open; the compressor pressure exceeds a predefined pressure threshold; the compressor temperature exceeds a predefined temperature threshold; a gas concentration inside the hold (50) exceeds a predefined gas concentration threshold; a leakage in the refrigeration circuit is detected.

11. Method according to any one of claims 9 to 10, wherein the control unit (68) performs the insulation of the hold (50) if the impact sensor (8) is in an activated state.

12. Method according to any one of claims 9 to 11, wherein the control unit(68) wirelessly sends, by means of a communication terminal, a communication signal (171) to a remote server, when the insulation of the hold (50) is carried out.

Images