WO2012088573A1

WO2012088573A1 - Suction valve, method for damping the opening of a suction valve, system for damping the opening of a suction valve, compressor and refrigerator

Info

Publication number: WO2012088573A1
Application number: PCT/BR2011/000500
Authority: WO
Inventors: Marcos Guilherme Schwarz
Original assignee: Whirpool S.A.
Priority date: 2010-12-30
Filing date: 2011-12-28
Publication date: 2012-07-05
Also published as: BRPI1005068A2

Abstract

The present invention refers to a valve system for compressors, preferably used in refrigeration, which comprise a piston with an alternating movement and valves such as flexible pallet. The suction valve comprises a double flexible pallet (21), formed by at least two overlapped and flexible blades (11) and (12), preferably of similar geometry, fastened by the basis, so that the movable end, which is over the orifice for fluid suction (4), does not have mechanical link, allowing the flexible blades (11, 12) to freely slide. The overlapping of these flexible blades (11,12) is used so that, during the movement for opening the valve, there is relative sliding of the up- per blade (31), inverse in relation to the relative sliding of the lower blade (32), and the friction of this sliding causes effect of damping of the valve movement. This friction between the flexible blades (11,12) which constitute the double flexible pallet (21) results from the coefficient of friction among the materials of the flexible blades (11,12), as well as, in a preferred embodiment, by the lubricating oil film that is housed between the flexible blades (11, 12) and by the relative pressure between the blades due to the bending movement. This effect of damping of the movement of the suction valve allows it to be projected so that it has little elastic force and is easily opened, improving the flow of the refrigerant fluid that fills up the cylinder, without the negative effects from excessive opening and from the oscillations of the double flexible pallet (21), thus improving the efficiency and capacity of the compressor, apart from reducing the generation of acoustic waves and noise.

Description

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Specification of Patent of Invention for "SUCTION VALVE, METHOD FOR DAMPING THE OPENING OF A SUCTION VALVE, SYSTEM FOR DAMPING THE OPENING OF A SUCTION VALVE, COMPRESSOR AND REFRIGERATOR."

This invention refers to a system and arrangement for valve system. More specifically, the invention refers to a construction of valves that are used in compressors, generally used for refrigeration.

BACKGROUND OF THE INVENTION

Hermetic compressors, as those used for refrigeration, comprise a piston with an alternating movement and have valve systems for controlling the flow of a refrigerant fluid, generally gas or liquid, which is moved by the compressor when compressed and released by the piston. This valve system is generally formed by a valve plate having an orifice for the flow of refrigerant fluid and, generally, by a thin blade of flexible metal, commonly called pallet, settled over the orifice for the flow of refrigerant fluid. Therefore, the valve allows the refrigerant fluid to flow only in the direction that moves the pallet to far from the valve plate, whereas it prevents such flow from going to a different direction.

The physical construction of this valve system is configured in such a way that the geometry of the pallets ensures the orifice will be closed and, when a difference in pressure among the compartments separated by the orifice for the flow of refrigerant fluid that wins the pallet's elastic force to the opposite direction of the support of the system's wall, that is, when there is sufficient pressure in the opening direction, the pallet moves towards the flow and, this way, allows the refrigerant fluid to flow. On the contrary, if pressure occurs towards the support of the system's wall, that is, if pressure occurs in the closing direction, the pallet remains settled over the orifice, ensuring the sealing of the flow in this direction.

However, generally when this type of valve system is applied to compressors, while the compressor is working there are periods in which the pressure in the opening direction is sufficient to move the pallet, but not sufficient to keep the pallet constantly opened. Thus, the pallet keeps oscillating, usually from a very open position - generally in which the pallet position can move up to 200% beyond the position necessary so that the refrigerant fluid flow rate fully occurs - and a practically closed position, generally around 10% of its course of movement necessary for the full flow rate of the refrige- rant fluid, or, in certain cases, up to a totally closed position. This occurs due to the resonant features formed by the mass and elasticity of the pallet, as well as its interaction with the refrigerant fluid.

Thus, oscillation can have great amplitude and several cycles along a period of aspiration of the refrigerant fluid, or, in other words, of movement of the refrigerant fluid, possibly causing difficulties for the passage of the flow, once every time the valve seeks to complete a cycle of its natural oscillation, that is, when the valve is directed to the undesired closing after a desired opening, a constriction in the flow of the refrigerant fluid occurs until another impulse of opening from the pallet, by the force caused by the pres- sure difference.

According to the current state of the art, the movement of valve oscillation must be minimized to avoid the intense bending of the pallet and, therefore, avoid that the blade reaches the region of plastic deformation when it is bent. The minimization of the movement also aims at reducing the amplitude of oscillation to prevent the pallet from strongly colliding with (at high speed) the valve plate, thus affecting the reliability and the noise of the system. Furthermore, the amplitude of oscillation must be minimized to avoid the constriction of the refrigerant fluid during the compressor's cycle of aspiration, which causes several problems, for instance, the reduction of filling in the cylinder and losses due to turbulence that reduce the compressor's efficiency.

One of the solutions of the current arts is to control the amplitude of oscillation by limiting the course in which the pallet can move, generally using devices such as bumpers. However, these techniques are difficult to implement in the compressor's suction valve, once it is located in the inner region of the cylinder which, apart from making it difficult the production of the components necessary for such limitations, is also located in the space reserved for the piston movement.

Other techniques limit the amplitude of oscillation when increasing the toughness of the blades, using thicker blades to form the blade and, thus, increasing the mass and elasticity of the pallet. However, these tech- niques make it difficult to open the valve and, therefore, restrict the flow of the refrigerant fluid, causing loss of efficiency.

Moreover, another technique to limit the pallets' amplitude of movement is to adjust the project of the suction chamber so that it interacts with the valve. This suction chamber consists of an additional element coupled to the valve plate, built so as to restrict the flow of the refrigerant fluid and, for this reason, to restrict the oscillation movement of the pallet. Such configuration is achieved by a solution in which, where all the refrigerant fluid heading to the orifice of suction of the refrigerant fluid passes, the path is usually built of plastic, performing the role of thermally insulating the refrige- rant fluid that enters the cylinder, and acoustically filtering the noise which is generated by the movement of the suction valve. This chamber is built so as to restrict, to a certain extent, the refrigerant fluid flow, which helps restrict the valve's amplitude of movement, and it also has its geometry projected so that the acoustic response of this chamber is adjusted in order to interact with the movement of the valve, restricting the amplitude of its movement. However, this technique has the disadvantage of restricting the flow of the refrigerant fluid through the chamber, impairing, again, the compressor's efficiency. PURPOSES OF THE INVENTION

Thus, one goal of this invention is to supply a valve system to improve the compressor's efficiency.

Another goal of the present invention is to enable a better flow of the refrigerant fluid and, therefore, increase the compressor's capacity.

An additional goal of this invention is to reduce the efforts and the bending of the pallet, thus avoiding the deformation of the blade and in- creasing its reliability.

One last goal of this invention is to supply a valve system that generates less acoustic noise. SUMMARY AND BRIEF DESCRIPTION OF THE INVENTION

The ways to solve the state of the art problems include a valve system built so that the pallet of the suction valve is formed by at least two overlapped and disconnected blades in an end, capable of freely sliding one in relation to the other, and in a preferred embodiment, existing between them only one oil film formed and retained naturally, conferring a viscous friction effect upon the blades which has a force of opposition to the relative sliding movement which increases as the sliding speed increases between them. The friction between the blades which form the suction valve is, therefore, due to the coefficient of friction among the materials of the blades, by the oil film housed between the blades and by the relative pressure between the blades due to the bending movement of the material.

This system confers a dynamic damping effect for the oscillation movement of the valve, significantly decreasing its amplitude of oscillation. The damping effect allows the blades to be projected so as to show little stiffness and little mass; that is, little elastic force, thus allowing the valve to easily open in the beginning of the period of aspiration of the refrigerant flow and additionally avoid excessive opening during the period of aspiration, remaining open at an amplitude of opening that does not make it difficult the pas- sage of the refrigerant fluid all over the period, improving the flow of the refrigerant fluid that fills up the cylinder, without the negative effects from the valve's excessive opening and from the oscillations, improving the cooling capacity and increasing energy efficiency, apart from reducing the production of acoustic waves.

Therefore, the present invention refers to a valve system for refrigeration compressors such as for displacement, having a piston with alternating movement and valves such as flexible pallet ones, whereas the suction valve is formed by at least two overlapped blades, preferably of similar geometry, fixed by the basis to one of the ends so that the other movable end is located over the suction orifice and does not have mechanical link between the blades, allowing free sliding between the blades. Thus, these blades are overlapped in a way that the during the valve's opening movement, a small relative sliding between the blades occurs, whereas the friction of this sliding causes a damping effect on the pallet's movement.

Other forms of construction that solve the state of the art problems use a suction valve for use in compressors, comprising at least a valve plate and a fluid suction orifice that further has at least two overlapped flexible blades over the fluid suction orifice and supported over the valve plate.

The present invention also presents a method for damping the opening of a suction valve which comprises the overlapping of two or more flexible blades.

There is also a compressor for refrigeration which uses a suction valve according to the proposed solutions, as well as a refrigerator which uses such compressor.

Finally, there is the description of a compressor for refrigeration - such as for displacement - containing a piston, a piston driving mechanism with alternating movement, a cylinder, a valve plate with a fluid suction orifice comprising at least a suction valve - such as flexible pallet - which is formed by at least two overlapped flexible blades, sliding between each other, fixed by their basis to the end opposite to the fluid suction orifice and disconnected in the end that moves and one valve for use in a refrigeration compressor which is formed by at least two overlapped flexible blades, sliding between each other, fixed by their basis to the end opposite to the fluid suction orifice and disconnected in the end that moves.

SUMMARIZED DESCRIPTION OF THE DRAWINGS

The present invention will be more detailed next and described based on figures:

Figure 1 - Illustrates an exploded view of the set valve plate and pallet, according to the current arts;

Figure 2 - Shows an exploded view of the set valve plate and pallet, according to this invention;

Figure 3 - Illustrates a sectional view of the suction valve, showing the positions of closed (a) and open (b) valve according to this invention;

Figure 4 - Shows a graph of the opening position of the pallet over time, according to the prior arts (40) and the invention herein (50).

DETAILED DESCRIPTION OF THE FIGURES

Figure 1 illustrates the state of the art in compressors, preferably used in refrigeration, which comprise valves having a flexible pallet to block or release the flow of a refrigerant fluid, generally a refrigerant fluid or refrigeration liquid. Therefore, the valve having the flexible pallet blocks the flow of the refrigerant fluid in the direction of the flexible pallet 1 to a sustaining plate, commonly called valve plate 3, once the flexible pallet 1 hangs on the valve plate 3 and, thus, blocks the fluid suction orifice 4. On the contrary, the flexi- ble pallet 1 bends to get far from the fluid suction orifice 4 when the refrigerant fluid moves towards the valve plate 3 to the flexible pallet 1 and, thus, releases the flow of the refrigerant fluid. As mentioned in the state of the art description, the problem of such configuration is the oscillation of the flexible pallet 1 from an extremely open position and a practically or totally closed position.

Thus, figure 1 represents a valve system according to the current art, formed by a valve plate 3 which has an orifice for refrigerant fluid suction 4 and a flexible pallet 1 , elements which, therefore, comprise the suction valve. The mass and elasticity of the flexible pallet 1 form a spring-mass re- sonant system, which has a natural frequency of oscillation that will happen in each cycle of aspiration of the refrigerant fluid. This oscillation impairs the flow and stresses the flexible pallet 1 , due to the oscillatory movement, which can cause the deformation of the flexible pallet .

This invention comprises a valve system for compressors that contains at least two flexible blades 11 ,12, preferably of geometry similar to the original flexible pallet 1 ; however, several other geometrical constructions in which the flexible blades 11 ,12 have more or less friction due to specific configurations that make them different can be presented, such as the reduced thickness in one of the flexible blades 11 ,12. These flexible blades 11 ,12 are overlapped and fastened by the basis, as presented by figure 2, forming a double flexible pallet 21.

In this construction, the movable ends of the flexible blades 11 ,12, which are located over the orifice for fluid suction 4, do not have mechanical link between the blades, allowing the flexible blades 11 ,12 to freely slide in this end. It is worth highlighting that, in the preferred embodiment, the profile of the flexible blades 11 ,12 in the movable ends of the flexible blades 11 ,12 may vary, whereas the damping effect varies proportionally according to the length of the blade and to the size of the common area in contact between the two flexible blades 11 , 12. The damping effect will be increased or reduced proportionally in view of the area in the movable ends of the flexible blades 11 ,12. It is also worth recalling that, in general, the higher capacity of the compressor, the larger the orifice for fluid suction 4 and, proportionally, the higher the thickness necessary for the flexible blades 11 ,12 to support the pressure efforts. Therefore, the stiffness of the flexible blades 11 ,12 increases, also increasing the oscillation frequency. Therefore, this invention consists of installing a set - in the preferred embodiment - of two flexible blades 11 , 12 which can be referred to as a double flexible pallet 21. Although the use of two flexible blades 11 ,12 for the valve optimization is preferred, the use of two or more flexible blades 11 ,12 only depends on the calculation of a preferential mass-spring constant, generally calculated in view of the compressor used.

These flexible blades 1 1 ,12 are overlapped, so that, during the opening movement of the valve, a small relative sliding between the movable ends of the flexible blades 11 ,12 occurs, as it can be seen in the detail of figure 3. The friction of this sliding causes an effect of damping of the movement of the flexible blades 11 ,12, which occurs due to the coefficient of fric- tion among the materials of the flexible blades 11 ,12. Additionally, in a preferred embodiment, the coefficient of friction also comprises the friction of a lubricating oil film that is housed between the flexible blades11 ,12 and the relative pressure between the flexible blades 11 ,12 due to the bending movement of the double flexible pallet 21 according to the refrigerant fluid flow. Finally, it is worth highlighting that the friction of this sliding also varies according to the system's temperature, which modifies the oil's viscosity and dilates or constricts the flexible blades 11 ,12. Therefore, there is a relative sliding of the upper flexible blade 31 , inverse in relation to the relative sliding of the lower flexible blade 32, causing the damping of the oscillation of the double flexible pallet 21. This effect of damping of the movement of the double flexible pallet 21 of the suc- tion valve allows the flexible blades 1 ,12 to be projected so as to show the little elastic force and, consequently, facilitates the opening of the double flexible pallet 21. Preferably, the measurement of the flexible blades 11 ,12 is performed by means of specific adjustment calculations and experiments. Thus, the flow of refrigerant fluid that fills up the cylinder is improved, without the existence of negative effects from the excessive opening of the flexible double pallet 21 and its oscillations. Additionally, the compressor's efficiency and capacity are increased and, similarly, the generation of acoustic waves and noises is reduced.

Figure 3 further highlights the behavior of the flexible blades 11 ,12 which form the double flexible pallet 21 , in the originally closed position in which the flexible blades 11 ,12 are found over the orifice for fluid suction 4. Likewise, figure 3 further presents the flexible blades 11 ,12 when they are found in their open position b, in which the cycle of refrigerant fluid aspiration occurs. It is observed that the flexible blades 11 ,12 in the open position have a relative sliding of the lower flexible blade 32 in relation to the relative sliding of the upper flexible blade 31 , due to the curvature of the flexible blades 11 ,12 as well as to the fact that they are mechanically linked in the end 15 opposite to the orifice for fluid suction 4.

This relative sliding 31 ,32 is the movement which offers resis- tance to the oscillation of the flexible bladesl 1 ,12, due to the friction between the flexible blades 11 ,12 as well as, in a preferred embodiment, the presence of lubricating oil at the place. This friction will be a mixed effect between the viscous friction, due to the oil that remains between the flexible blades 11 ,12, and the friction of the surfaces of the flexible blades 11 ,12 which have con- tact.

Finally, figure 4 illustrates the opening movement of the flexible pallet 1 and of the double flexible pallet 21 over time, which shows the movement curve of the flexible pallet 40 and the movement curve of the double flexible pallet 50, wherein it is observed a significant difference in the valve's opening amplitude, whereas the amplitude in the case of the double flexible pallet 21 has damping, caused by the friction between the blades which is lower than that of the state of the art, however sufficient to achieve the opening point for full passage of fluid A2, which allows the flow of the refrigerant fluid without restrictions. Due to the reduction of big amplitude oscillations, the flow of fluid passage will be higher and more constant over the aspiration cycle.

It is possible to observe, still in figure 4, that the minimum opening amplitude A1 which is achieved by the movement curve of the flexible pallet 40 is very small and restrictive to the passage of the refrigerant fluid, which causes, therefore, the constriction of the flow over the aspiration cycle. It is also possible to note that practically half of the valve's opening time is wasted, once the oscillation of the flexible pallet 1 keeps the curve below the point of full passage of fluid A2 which allows the passage of the refrigerant fluid without restrictions; that is, when the elasticity of the flexible pallet 1 is measured so that there is no restriction to the passage of the refrigerant fluid in 100% of the area of the orifice for fluid suction 4. Still in relation to figure 4, it is clear that the high amplitude A3, which is achieved by the movement curve of the flexible pallet 40, is way beyond the full passage of the fluid A2 and, therefore, causes unnecessary mechanical tensions over the flexible pallet 1.

Figure 4 also illustrates that the cycle of aspiration of the refrige- rant fluid starts, preferentially, a little after an angle of rotation from the compressor shaft measuring 180 degrees, at which moment the refrigerant fluid inside the cylinder reaches a pressure lower than the refrigerant fluid which is immediately on the other side of the suction valve, thus causing its opening. This cycle, on the contrary, finishes when the piston no longer moves and the valve searches its position for closing defined by the constructive characteristics of its mass-spring constant.

According to the technique proposed in this invention, the movement of the overlapped flexible blades 11 ,12 can be observed by the movement curve of the double flexible pallet 50, in figure 4. Due to the relative movement between the flexible blades 11 ,12 and the friction that exists opposing to this movement, there is a damping of the oscillation of the double flexible pallet 21. This occurs due to the friction that ends up absorbing the energy accumulated in the mass-spring system of the flexible blades 11 ,12 and, therefore, the overlapping of the flexible blades 11 ,12 causes an opening of the double flexible pallet 21 at a an amplitude close to that of the full passage of fluid A2, avoiding the existence of exaggerated openings and re- strictions to the passage of the refrigerant flow. Therefore, the total efficiency of the compressor increases, once there is lower restriction to the flow over the aspiration cycle.

After describing an example of a preferred embodiment, it shall be understood that the scope of the present invention encompasses other possible variations, being limited only by the contents of the attached claims, where the possible equivalents are included.

Claims

1. Compressor for refrigeration such as for displacement, comprising:

a piston positioned inside a cylinder that compress a refrigerant fluid;

a piston driving mechanism with alternating movement; and a valve plate (3) with an orifice for fluid suction (4), the valve plate comprising at least a suction valve such as flexible pallet;

the compressor being characterized in that the suction valve comprises a double flexible pallet (21) formed by at least two flexible blades

(11 ,12) overlapped in a sliding manner.

2. Compressor according to claim 1 , characterized in that the flexible blades (11 ,12) are fastened by the basis in an end opposite (15) to the orifice for fluid suction (4) and disconnected in the end that moves over the orifice for fluid suction (4).

3. Compressor for refrigeration according to claim 15, characterized in that the flexible blades (11 ,12) have similar geometries.

4. Compressor for refrigeration according to claim 15, characterized in that the double flexible pallet (21) comprises an upper flexible blade (11) and a lower flexible blade (12), the lower flexible blade (12) being positioned in direct contact with the valve plate (3), the upper flexible pallet (11) having reduced thickness in comparison to the thickness of the lower flexible pallet (12).

5. Compressor for refrigeration according to claim 15, characte- rized in that the flexible pallets (11 ,12) are overlapped so as to allow a lubricating oil film of the compressor to be present between both.

6. Suction valve comprising at least a valve plate (3) and an orifice for fluid suction (4), characterized in that it comprises a double flexible pallet (21) formed by at least two flexible blades (11 ,12) overlapped over the orifice for fluid suction (4) and supported on the valve plate (3).

7. Suction valve de according to claim 1 , characterized in that the flexible pallets (11 ,12) are mechanically linked in the end opposite (15) to the orifice for fluid suction (4).

8. Suction valve de according to claim 1 or 2, characterized in that the flexible pallets (1 1 , 12) are overlapped so as to allow a lubricating oil film of the compressor be present between both.

9. Suction valve de according to claim 1 , 2 or 3, characterized in that the flexible pallets (1 1 ,12) have similar geometric embodiments.

10. Suction valve de according to claim 1 , 2 or 3, characterized in that the flexible pallets (1 1 ,12) have different geometric embodiments.

1 1. Suction valve de according to claim 5, characterized in that the upper flexible pallet (1 1 ) has reduced thickness in comparison to that of the lower flexible pallet (12).

12. Suction valve de according to claim 5, characterized in that the lower flexible pallet (12) has reduced thickness in comparison to that of the upper flexible pallet (1 1 ).

13. Suction valve de according to claim 1 , 2 or 3, characterized in that it allows a refrigerant fluid to flow only towards one direction.

14. Suction valve de according to claim 8, characterized in that it allows a refrigerant fluid to flow only towards the direction of the valves (3) to the double flexible pallet (21).

15. Method for damping the opening of a suction valve which comprises:

- a piston that moves inside a cylinder;

- a suction valve having at least a valve plate (3) and an orifice for fluid suction (4);

the system characterized in that the suction valve has at least two overlapped flexible blades (1 1 , 12) over the orifice for fluid suction (4) and supported on the valve plate (3), thus allowing the fluid to flow only in one direction of the piston movement inside the cylinder.

16. Method for damping the opening of a suction valve according to claim 15, characterized in that it comprises the overlapping of at least two flexible blades (1 1 , 12).

17. Method for damping the opening of a suction valve characte- rized in that it comprises a lubricating oil film of the compressor which is present between the flexible blades (11 ,12).

18. Compressor for refrigeration that uses a suction valve according to one of claims 6 to 14, a system according to claim 15 or a method according to claim 16 or 17.

19. Refrigerator that uses a compressor according to claim 18.

20. Valve for use in a refrigeration compressor, characterized in that it is formed by at least two overlapped flexible blades (11 ,12), which slide and are fastened by the basis in the end opposite (15) to the orifice for fluid suction (4) and disconnected in the end that moves.