WO2001002731A1

WO2001002731A1 - Delivery valve for scroll-type compressor

Info

Publication number: WO2001002731A1
Application number: PCT/IB2000/000874
Authority: WO
Inventors: Denis Violette; Jean De Bernardi
Original assignee: Danfoss Maneurop S.A.
Priority date: 1999-07-01
Filing date: 2000-06-29
Publication date: 2001-01-11
Also published as: AU5242200A; FR2795781A1; FR2795781B1

Abstract

This valve comprises a tubular body (23), of which the opposite end to the pipe (16) that brings in gas to the delivery chamber is closed, this body comprising a cavity which has a first portion (25) for guiding the shut-off leaf (32) and a second portion (26) in permanent communication with the delivery chamber. The body comprises, in the first portion (25), radial openings (28) which open into the delivery chamber.

Description

DELIVERY VALVE FOR SCROLL-TYPE COMPRESSOR The present invention relates to a delivery valve for a scroll-type compressor.

A scroll-type compressor is depicted in Figure 1 of the appended diagrammatic drawing. This compressor comprises a hermetic housing 2 inside which are formed an intake chamber 3 with an inlet 4 for the gas, and a delivery chamber or pressure chamber 5 with an outlet 6 for the gas. The intake chamber 3 and delivery chamber 5 are separated by a dividing wall 7. Mounted inside the intake chamber 3 is an electric motor, the stator 8 and rotor 9 of which are depicted diagrammatically in the drawing. The rotor 9 is associated with a shaft 10 guided in rotation in a lower bearing 12 and an upper bearing 13. The pump intended to raise the pressure of the gas consists of two scrolls, one scroll 14 belonging to the dividing wall 7, and a moving scroll 15 driven by the drive shaft 10 and which is off-centred with respect to this shaft so that, during an orbital movement, it delimits pockets of varying and increasingly small size in which the gas is compressed before escaping through an outlet orifice 16 towards the delivery chamber 5. A valve system denoted by the overall reference 17 is mounted on the outlet 16, so as to allow the gas to pass towards the pressure chamber and prevent gas from passing from this same chamber towards the intake chamber.

Known valves have various structures. In a first instance, the valve is a free valve mounted so that it can slide, or articulated. A drawback with this type of valve is that as the oil inside the compressor is diffused in the form of an aerosol onto the various components, a film of oil is formed and causes the valve to * stick" open, which means that when the compressor is stopped, pressurized gas contained in the high-pressure chamber can pass into the intake chamber where the pressure is lower and cause the rotating parts of the machine to run backwards. Aside from the fact that closure is uncertain, there sometimes occur phenomena of flutter which disrupt the operation of the compressor, impairing its efficiency and generating noise which is unpleasant for those around it.

There are also known reed valves, such a reed consisting of a spring leaf which opens for each compression spike, and whose elasticity causes it to close between two spikes. This technique can be justified in the field of refrigeration, given an improvement in performance, but cannot be justified in the field of air-conditioning. This technique generates significant noise as a result of the flapping of the reed each time it moves . US-A-5, 94, 422 shows a scroll type compressor equipped with a delivery valve comprising : a tubular body, fixed to the face of the dividing wall between the intake chamber and the delivery chamber or to a plate attached to this wall, one end of this body being open and in communication with the outlet pipe from the compression stage,

- a shut-off leaf which has an area at least equal to that of the opening in the outlet pipe from the compression stage and can be displaced parallel to itself between a closed position in which it shuts off this pipe and an open position in which it rests against a seat formed in the tubular body,

- at least one radial opening formed in the body between the part that forms the seat for the leaf, in the open position, and the wall delimiting the opening of the outlet pipe from the compression stage.

When the pressure of the delivered fluid decreases, the shut-off leaf should normally be released from its seat, to switch into its closure position, since the pressure in the delivery chamber is then higher than the pressure in the tubular body. However, this only happens in theory, because a balancing of pressures occurs virtually instantaneously between the tubular body and the delivery chamber. Therefore, in reality, the leaf is not subjected to a pressure difference which would ensure its movement back to the closure position.

The object of the invention is to provide a delivery valve for a scroll-type compressor, which provides immediate closure of the communication between the intake chamber and the delivery chamber when the compressor is stopped, which has excellent stability when flow is irregular, including if the compression ratio exceeds the geometric compression ratio, and which generates reduced noise.

To this end, the delivery valve of the above- mentioned type, to which the invention relates, comprises: a chamber which, formed in the body on the side thereof that lies between the part that forms the seat for the leaf in the open position and a bottom end of the body, has a cross section that is smaller than that of the shut-off leaf and communicates with the delivery chamber via at least one orifice formed in the bottom end of the chamber, the cross section of this orifice being small in comparison with the cross section of the bottom end of the chamber. In practice, when the compressor is operating, the pressure of the gas coming from the compression stage causes the shut-off leaf to move and come to rest against the seat formed in the tubular body. The leaf remains held against this seat by virtue of the presence of a film of oil, and this avoids the phenomena of flapping that result from instantaneous closures at each compression spike. The gas escapes radially through the openings formed in the body, this arrangement substantially improving the sound deadening compared with the known device. Furthermore, in the chamber that lies between the bottom end of the body and the shut-off leaf, when the valve is in the open position, there is a pressure equal to the pressure inside the delivery chamber. However, given that this pressure is exerted only on an area which is smaller than the total area of the leaf, there is no risk that it will cause this leaf to move into the valve-closed position. However, as soon as the compressor stops, that is to say as soon as the pressure at the compression stage drops, since the pressure in the chamber of the valve body in communication with the delivery chamber is appreciably higher than the pressure on the other side of the shut-off leaf, this leaf is immediately moved into the valve-closed position. The pressure in the body chamber decreases less sharply than the pressure inside the delivery chamber, in consideration of the small cross-section of the orifices allowing for communication between these two chambers.

Advantageously, the diameter of each orifice formed in the bottom end of the tubular body is smaller than or equal to 2 mm, whereas the diameter of the chamber is approximately 25 to 30 mm, for example. Furthermore, the cross section of flow of the radial openings which allow for communication between the inside of the tubular body and the delivery chamber decreases from the chamber of the tubular body towards the delivery chamber, one of the inherent dimensions delimiting this cross section being small.

Preferably, the value of the inherent dimensions of the cross section can be comprised between 0 and 1 mm.

According to a first embodiment of this valve, the shut-off leaf consists of a circular disc, while the tubular body has an internal cavity of circular cross section exhibiting two successive portions of different diameters, that is to say, on its open-end side, a portion the diameter of which is essentially equal to the diameter of the shut-off leaf, extended by a portion of smaller diameter, these two portions being connected by a shoulder that forms a seat for the leaf, when the valve is in the open position, radial openings being formed in the body between the shoulder and the open end of the body.

The radial openings formed in the body may consist of holes or cutouts opening into the edge of the body resting against the wall of the compressor separating the intake chamber and the delivery chamber.

According to an advantageous feature of the invention, the body comprises, on the outside of the tubular part in which at least one radial opening is formed, a peripheral skirt which, with the tubular part, delimits an annular chamber, the cross section of which decreases from the tubular part radially outwards, and communicates with the delivery chamber via a slit formed between the skirt and the dividing wall between the intake chamber and the delivery chamber, or a plate fixed to this wall .

This annular chamber, the cross section of which decreases from the inside outwards, produces a great amount of sound deadening, making the operation of the compressor particularly quiet.

According to another feature, holes providing communication with the delivery chamber open into that part of the body that forms the seat for the leaf when the valve is in the open position. Advantageously, the cross section of the holes that open into the seat increases towards the delivery chamber. This arrangement, when the compressor is stopped, and because of the pressure in the chamber at the closed-end side of the body, allows the shut-off leaf to detach from its seat and the movement of the shut-off leaf towards its closed position to be accelerated, allowing a large volume of gas to pass through these holes.

According to another embodiment of this valve, the outlet orifice from the compression stage is annular in shape or consists of a number of holes arranged in a ring, the shut-off leaf has a corresponding annular shape, and the body has an annular cavity, the cross section of which decreases radially outwards, the outermost edge of the body delimiting a slit or openings with the dividing wall between the intake chamber and the delivery chamber, or a plate fixed to this wall, the annular cavity having, on its closed-end side, a bearing surface that forms a seat for the shut-off leaf when the valve is in the open position, and into which there opens an annular cavity of smaller cross section communicating with the delivery chamber via at least one orifice.

In this case, the valve may be fixed centrally to the dividing plate. In this case too, perfect sound deadening is achieved by reducing the cross section of the annular cavity of the body in the direction in which the gas flows.

In any case, the invention will be well understood from the description which follows, with reference to the appended diagrammatic drawing which, by way of non-limiting examples, depicts a number of embodiments of this delivery valve for a scroll-type compressor:

Figure 1 is a skeleton diagram of a scroll-type compressor, in longitudinal section;

Figure 2 is a view in exploded perspective of a first valve and of the dividing plate between the intake chamber and the delivery chamber;

Figure 3 is a view in section on a diametral plane of the device of Figure 2;

Figure 4 is a view in diametral section on a larger scale of the valve of Figure 2;

Figures 5 and 6 are two views, in exploded perspective and in section on a diametral plane, respectively, of a second valve;

Figure 7 is a perspective view of the inside of the body of the valve of Figures 5 and 6; Figure 8 is a view of this same valve m diametral section and on a larger scale;

Figures 9 and 10 are two views, m perspective and in section on a diametral plane, respectively, of a third valve.

Figure 2 depicts a first valve comprising, mounted on a plate 22 fixed to the dividing wall 7 between the intake chamber and the delivery chamber, a body 23 screw-fastened by a peripheral flange 24. The body 23 has an internal cavity which has two successive portions 25 and 26 of circular cross section which are connected by a shoulder 27, the portion 26 having a smaller cross section than the portion 25. The portion 25 is located at the open-end side equipped with the flange 24, while the portion 26 is located at the closed-end side of the cavity. Formed m the peripheral wall of the body and between the shoulder 27 and the open end, are uniformly spaced openings 28 placing the interior cavity of the body in communication with the delivery chamber. Formed in the bottom end 29 of the body 23 is an orifice 30 for placing the bottom end of the cavity m communication with the delivery chamber. The cavity acts as a housing for a shut-off leaf 32 m the form of a disc, the cross section of which is at least equal to the orifice that is to be shut off, and the diameter of which corresponds to that of that portion 25 of the cavity that has the larger cross section.

The way m which this valve works is as follows: when the compressor is m operation, the pressure of gas moves the valve 32 from its position in which it rests against the plate 22, m which it shuts off the pipe 16, into a position in which it rests against the shoulder 27 that forms a seat. It is kept against this shoulder during variations in pressure that result from compression spikes by the "sticking" effect of the present oil film. The gas can pass from the compression stage towards the delivery chamber through the openings 28. The bottom end of the cavity of the body, corresponding to the portion 26, is therefore in communication with the delivery chamber 30. However, given the equilibrium of the pressures on each side of the shut-off leaf 32, the latter remains pressed remains pressed against its seat. When the compressor is stopped, the pressure underneath the shut-off leaf 32 drops abruptly, and the pressure in the cavity portion 26, equal to the pressure in the delivery chamber, causes the shut-off leaf to move immediately into its position of resting against the plate 22, shutting off the pipe 16, that is to say the valve-closed position.

Figures 5 to 8 depict an alternative form of this valve, in which the same elements are denoted by the same references as before.

In this embodiment, the body comprises, on the outside of the tubular part in which the radial openings are formed, a peripheral skirt 33 which, with the tubular part, delimits an annular chamber 34, the cross section of which decreases from the tubular part radially outwards and communicates outwards with the delivery chamber via a slit 35 formed between the skirt and the plate 22. It should be noted that the radial openings opening into the first portion 25 are not holes but cutouts 36 opening into the lower edge of the tubular part.

In this case, attachment to the plate is achieved by screwing using screws 31 through holes 37 formed in the skirt-shaped part 33. In this valve, holes 38 opening into the shoulder 24 forming the seat provide communication with the delivery chamber. These holes 38 widen on the delivery chamber side. The way in which this valve works is similar to the way in which the valve described earlier with reference to Figures 2 to 4 works. The essential difference is the result of the fact that the annular chamber 34, the cross section of which decreases in the direction in which the gas flows, provides deadening of the running noises of the compressor. Furthermore, when the compressor is stopped, after the shut-off leaf 32 has detached from the seat under the action of the pressure in the portion 26 of the cavity of the body, the passage of pressurized gas through the holes 38 accelerates the movement of the shut-off leaf towards its closed position.

Figures 9 and 10 depict another alternative form of this valve, in which the same elements are denoted by the same references as before. In this case, gas can leave the compression stage through three elongate slots 39 arranged in a ring. The shut-off leaf 40 has a corresponding annular shape and the body 42 of the valve has an annular cavity 43 the cross section of which decreases radially outwards, the outermost edge 44 of the body delimiting a slit 45 with the plate 22 fixed to the dividing wall. On the same side as its closed end, the annular cavity 43 has a bearing surface 46 forming a seat 27, 46 for the shut-off leaf 40, when the valve is in the open position. Opening into this bearing surface 46 is an annular cavity 47 of smaller cross section communicating via an orifice 48 with the delivery chamber. The central part 49 of the body of the valve serves to attach this valve to the plate 22 using a screw-nut system 50.

This valve works in the same way as the valves described earlier. When the compressor is stopped, the shut-off leaf 40 shuts off the openings 39. When the compressor is in operation, the pressure moves the shut-off leaf 40 to press it against the seat 27, 46 formed at the closed end of the cavity. Gas can therefore flow through the cavity 43, and pass from this cavity into the delivery chamber through the slit 45. When the compressor is stopped, the pressure in the annular chamber 47 allows the shut-off leaf to detach and makes it move into its closed position. Just as in the previous embodiment described, the reduction in cross section of the annular chamber 43 through which the gas passes considerably reduces the running noise of the compressor.

As is clear from the foregoing, the invention provides a great improvement to the prior art by supplying a delivery valve for a scroll-type compressor which has excellent stability in operating periods, ensures immediate closure when the compressor is stopped, and affords a substantial reduction in the running noise of the compressor. As goes without saying, the invention is not restricted simply to the embodiments of this delivery valve which have been described hereinabove by way of non-limiting examples; on the contrary, it encompasses all alternative forms thereof. Thus, in particular, the plate 22 could be omitted, its structure being built into the dividing plate between the intake chamber and the delivery chamber, or alternatively the size of the body could differ and have more the shape of a plate, or finally, the number and/or shape of the slits and openings could differ, without in any way departing from the scope of the invention.

Claims

1. Delivery valve for a scroll-type compressor, intended to be mounted at the downstream end of an outlet pipe from the compression stage which consists of a stationary scroll and of a moving scroll, driven in an orbital movement, and located at the inlet to the high-pressure chamber or delivery chamber of the compressor, comprising: - a tubular body (23, 42), fixed to the face of the dividing wall (7) between the intake chamber (3) and the delivery chamber (5) or to a plate (22) attached to this wall, one end of this body being open and in communication with the outlet pipe (16) from the compression stage,

- a shut-off leaf (32, 40) which has an area at least equal to that of the opening in the outlet pipe (16) from the compression stage and can be displaced parallel to itself between a closed position in which it shuts off this pipe and an open position in which it rests against a seat (27, 46) formed in the tubular body,

- at least one radial opening (28, 35, 36, 45) formed in the body between the part (27, 46) that forms the seat for the leaf, in the open position, and the wall delimiting the opening of the outlet pipe from the compression stage, characterized in that it comprises a chamber (26, 47) which, formed in the body (23, 42) on the side thereof that lies between the part (27, 46) that forms the seat for the leaf (32, 40) in the open position and a bottom end (29) of the body, has a cross section that is smaller than that of the shut-off leaf and communicates with the delivery chamber via at least one orifice (30, 48) formed in the bottom end of the chamber, the cross section of this orifice being small in comparison with the cross section of the bottom end of the chamber.

2. Valve according to Claim 1, characterized in that the diameter of each orifice (30, 48) formed in the bottom end of the tubular body is smaller than or equal to 2 mm.

3. Valve according to one of Claims 1 and 2, characterized in that the cross section of flow of the radial openings which allow for communication between the inside of the tubular body (23, 42) and the delivery chamber decreases from the chamber of the tubular body towards the delivery chamber, one of the inherent dimensions delimiting this cross section being small.

4. Valve according to one of Claims 1 to 3, characterized in that the shut-off leaf consists of a circular disc (32), while the tubular body (23) has an internal cavity of circular cross section exhibiting two successive portions of different diameters, that is to say, on its open-end side, a portion (25) the diameter of which is essentially equal to the diameter of the shut-off leaf (32), extended by a portion (26) of smaller diameter, these two portions (25, 26) being connected by a shoulder (27) that forms a seat for the leaf (32), when the valve is in the open position, radial openings (28, 36) being formed in the body (23) between the shoulder (27) and the open end of the body.

5. Valve according to either one of Claims 1 and

2, characterized in that the body (23) comprises, on the outside of the tubular part (25) in which at least one radial opening (36) is formed, a peripheral skirt (33) which, with the tubular part, delimits an annular chamber (34), the cross section of which decreases from the tubular part (25) radially outwards, and communicates with the outside via a slit (35) formed between the skirt (33) and the dividing wall between the intake chamber and the delivery chamber, or a plate (22) fixed to this wall.

6. Valve according to one of ^■ Claims 1 to 3, characterized in that the outlet orifice from the compression stage is annular in shape or consists of a number of holes (39) arranged in a ring, the shut-off leaf (40) has a corresponding annular shape, and the body has an annular cavity (43), the cross section of which decreases radially outwards, the outermost edge (44) of the body delimiting a slit (45) or openings with the dividing wall between the intake chamber and the delivery chamber, or a plate (22) fixed to this wall (7), the annular cavity (43) having, on its closed-end side, a bearing surface (46) that forms a seat for the shut-off leaf (40) when the valve is in the open position, and into which there opens an annular cavity (43) of smaller cross section communicating with the delivery chamber via at least one orifice (48).

7. Valve according to one of Claims 1 to 6, characterized in that holes (38) providing communication with the delivery chamber open into that part of the body

(27) that forms the seat for the leaf when the valve is in the open position.

8. Valve according to Claim 7, characterized in that the cross section of the holes (38) that open into the seat (27) increases towards the delivery chamber.