ES2274722B1 - MECHANISM OF YUGO ESCOCES, ESPECIALLY FOR GAS COMPRESSORS. - Google Patents

Abstract

Scottish yoke mechanism, especially for gas compressors. It comprises a cylindrical slide (2) that rotates in the eccentric (3) of a crankshaft (4.4 '') in the opposite direction to it, a guide (5) substantially perpendicular to the axes of rotation of the slide (2) and the eccentric (3) that transforms the rotating movement of the crankshaft (4.4 '') into a linear alternative movement, and a piston (6.6 '') of considerably small diameter integral with said guide (5), said said piston (6.6 '') associated with a cylinder (7.7 '') of a compression chamber (8). It is characterized by the fact that it comprises a rod (9.9 '') integral to the opposite part of the piston (6.6 '') and movable in a guide (10.10 ''). The efforts corresponding to the reaction torque of the conventional Scottish yoke mechanism are reduced, and the force exerted on the rear of the cylinder is eliminated.

Description

Scottish yoke mechanism, especially for gas compressors

The present invention relates to a mechanism of Scottish yoke, especially for gas compressors.

Background of the invention

It is known that the new challenges of respect for environment and, in particular, the requirements of the Protocol of Kyoto regarding climate change forcing a notable decrease in the emission of greenhouse gases by the industrialized countries, face the industry of the refrigeration with the need to find alternatives to current refrigerants of the HFC type (hydrofluorocarbons) that have a high value of GWP (global warming potential).

In this context, CO2 is presented as a compound with very good chances of being accepted as refrigerant in compression refrigeration cycles of steam. Among the important features of CO_ {2} are they find their high working pressures, their high discharge temperatures and high volumetric capacity. These features make low suction pressure systems cooled by ambient air becomes practically necessary work with two stages of compression with cooling intermediate.

In the case of two-stage compression, the high volumetric capacity of CO2 leads, for small powers of commercial refrigeration, ie no domestic, at very low displacements in the second stage that give place to constructive difficulties in the compressors Alternative

The mechanism of the alternative compressors of piston is usually of the crank-crank type. This mechanism requires a joint (bolt) in the area center of the piston through which the connecting rod transmits energy to it necessary to overcome the pressure forces on the head of the piston. This joint does not allow to build a cylinder with smaller diameters of certain values which leads to races ridiculous for very small displacements. A relationship Stroke / small diameter also involves performance Highly variable volumetric with working pressures.

Possible solutions to this problem based on the crank-crank mechanism (double piston diameter) lead to short cranks and lateral forces important. It is therefore necessary to look for alternatives that allow the construction of small displacements with relationships adequate stroke / diameter.

The Scottish yoke mechanism, formed by piston, guide, slide and crankshaft, eliminates the joint in the piston allowing to manufacture it with the desired diameter by small to be. This mechanism has been previously used in compressors for refrigeration although it was falling into disuse by have significant friction, especially due to the pair of reaction that appears between the piston head and the part rear of the cylinder.

In this Scottish yoke mechanism the slide (cylindrical) rotates in the eccentric of the crankshaft in direction contrary to it so that your generatrix remains permanently parallel to itself. This allows a movement linear alternative in a piston integral guide. This guide it has, in a direction perpendicular to its axis, a movement of forward and reverse such that it allows you to keep your axis crossing permanently to the axis of the crankshaft eccentric (which coincides with the rotation of the slide). This move forward and recoil is the one that the guide transmits to the piston, integral with it and fixed axis.

When the eccentric shaft does not cross with the one of the piston appears a pair of forces (crankshaft effort on the guide and force of the pressure in the piston head) that tends to rotate the piston guide assembly over the eccentric This pair is compensated by some efforts of reaction that appear on the piston head and the back of the cylinder. These efforts are the main drawback of This mechanism

Description of the invention

The goal of the Scottish yoke mechanism, in Special for gas compressors of the present invention is solve the problems presented by known mechanisms in the art, providing a number of advantages that will describe below.

The Scottish yoke mechanism, especially for Gas compressors of the present invention, is of the type that it comprises a cylindrical slide that rotates in the eccentric of a crankshaft in the opposite direction to it, a guide noticeably perpendicular to the axes of rotation of the slide and the eccentric which transforms the rotating movement of the crankshaft into a linear alternative movement, and a piston in diameter considerably small solidarity of said guide, said being piston associated with a cylinder of a compression chamber, and it characterized by the fact that it comprises a rod integral with the  opposite part of the piston and movable in a guide.

In this way, thanks to the incorporation of cited guided rod, it is possible to reduce the reaction force in the piston head and eliminate the force on the back of the cylinder. The reaction force in the rod guide replaces the force of the back of the cylinder and constitutes with the force of the piston head the reaction torque inherent in the Scottish yoke mechanism. Being the distance between efforts greater than the one between the piston head and the end rear of the cylinder, the efforts are remarkably less.

Preferably, the diameter of the piston is smaller  than 11 mm As mentioned, the mechanism of the invention It is especially applied in pistons of diameter considerably small.

According to another aspect, the invention also refers to a gas compressor comprising a mechanism of Scottish yoke of the type defined above.

According to another embodiment of the invention, the Gas compressor comprises a Scottish yoke mechanism of the type defined above, and a mechanism of connecting rod-crank associated with a second piston cylinder, operated by a single crankshaft, defining a compressor for two-cylinder refrigeration adapted to gas compression in two stages.

Advantageously, the axles of both cylinders they can be oriented in the same direction, or in the sense opposite each other.

Preferably, the displacement ratio optimal, to reduce the compression work from the conditions from inlet to the first cylinder until the discharge pressure of the second cylinder, is 3 with a tolerance of 20%. This variability can be high due to the volumetric performance of the second piston as it depends on its diameter and the system of Valves that suit you.

Preferably, the gas used is CO2. As previously mentioned, CO_ {2} provides high working pressures, high discharge temperatures and a high volumetric capacity It also meets the requirements of the Kyoto Protocol by contributing to the reduction of the effect greenhouse.

According to another aspect of the invention, the Scottish yoke cylinder comprises means for the lubrication of the piston.

Advantageously, the means for lubrication of the piston comprise an oil accumulator recess made in the cylinder housing and a grease hole communicating said recess with the piston through hole.

In this way, the oil that comes from the exit of the oil hole of the crankshaft wrist arrives in part to the cylinder wall and falls on the accumulator recess, from which through the grease hole it reaches the piston, allowing proper lubrication. The tray mode recess allows the oil to accumulate and therefore guarantees the sufficient and constant supply of oil to the piston.

Brief description of the drawings

In order to facilitate the description of how much  It has been exposed above are attached some drawings in which, schematically and only by way of non-limiting example, they represent two practical cases of realizations of the mechanism of Scottish yoke, especially for gas compressors of the invention, in which:

Figure 1 is a schematic view of the Scottish yoke mechanism with reinforcing rod according to the invention;

Figure 2 is a sectional view schematized of a single-stage refrigeration compressor that incorporates the Scottish yoke mechanism with reinforcing rod according to a first embodiment of the invention;

Figure 3 is a schematic view of a elementary refrigeration circuit in a single-stage system with the refrigeration compressor of figure 2;

Figure 4 is a sectional view schematized of a two stage refrigeration compressor, with a first stage with the crank-crank mechanism conventional and a second stage with the Scottish yoke mechanism with reinforcing rod according to a second embodiment of the invention;

Figure 5 is a schematic view of a refrigeration circuit with two refrigeration compressor stages of figure 4;

Figure 6 is a perspective view of the cylinder associated with the Scottish yoke showing the means of piston lubrication; Y

Figure 7 is a longitudinal section view  of the cylinder of figure 6.

Description of preferred embodiments

As can be seen in figures 1 and 2,  the Scottish yoke mechanism 1 of the invention comprises a cylindrical slide 2 that rotates in the eccentric 3 of a crankshaft 4 contrary to it, a guide 5 noticeably perpendicular to the axes of rotation of the slide 2 and the eccentric 3 that transforms the rotating movement of crankshaft 4 into a linear reciprocating motion, a piston 6 in diameter considerably small, preferably less than 11 mm, integral with said guide 5, said piston 6 being associated with a cylinder 7 of a compression chamber 8, and a rod 9 integral to the opposite part of the piston 6 and movable in a guide 10.

The incorporation of said guided rod 9 allows to reduce the reaction force in the piston head 6 and remove the force on the back of the cylinder 7.

According to a first embodiment of the invention, a single-stage refrigeration compressor 11 is shown in figure 2 which incorporates the mechanism of Scottish yoke 1 with stem of reinforcement of the invention.

A circuit can be seen in figure 3 elementary schematic refrigerator in a single-stage system with the refrigeration compressor 11 of figure 2. From the port of discharge 12 the gas is taken to a cooler 13 of which follows a exchanger 14 with suction line 15 and then to a expansion device 16. Once expanded the gas is carried to an evaporator 17 from which it follows the exchanger 14 and hence to the suction port 18 of the compressor 11.

According to a second embodiment of the invention, a refrigeration compressor 21 of two is shown in figure 4 stages, with a first stage with a mechanism of Conventional connecting rod-crank 22 and a second stage with the 1 'Scottish yoke mechanism with 9' reinforcing rod the invention. The axles of both cylinders are oriented in opposite direction to each other, although they may also be oriented in The same sense.

The incoming gas through the suction port 23 meets the perforated partition 24 where the oil precipitates circulating with the refrigerant. The oil is emptied to volume internal general of the tank 25 by means of the communication drill 26. The mechanism is a standard mechanism of connecting rod-crank 22 with arrangement of a plate valves 27, incorporating both the suction and the ones discharge at cylinder head 28. Gas is discharged through of discharge port 29.

The second stage consists of a 6 'piston that  moves in the cylinder 7 'by means of the mechanism of Scottish yoke 1' with reinforcing rod 9 'according to the invention. The gas coming from the first stage penetrates through the suction port 30 and is download through download port 31.

In figure 5 a circuit can be seen schematic refrigerator with two refrigeration compressor 21 stages of figure 4. This circuit only differs from the one indicated in Figure 3 in which a heat exchanger is arranged additional 32 between discharge 29 of the first stage and the aspiration 30 of the second stage.

Preferably, the gas used is CO2 already which provides high working pressures, high temperatures discharge and high volumetric capacity. It also complies with the requirements of the Kyoto Protocol by contributing to the decrease of the greenhouse effect.

On the other hand, the 7, 7 'cylinder of the yoke 1, 1 'scotch of the invention comprises means for lubrication of the piston. As can be seen in figures 6 and 7, said lubrication means comprise a recess 33 oil accumulator made in the cylinder housing 7 and a grease hole 34 which communicates said recess 33 with the hole 35 of the piston 6. In this way, the oil that comes from the outlet of the hole greasing the crankshaft wrist 4 partly reaches the wall of cylinder 7 and falls on accumulator recess 33, from which to through the grease hole 34 it reaches the piston 6, allowing Proper lubrication The recess 33 as a tray allows that the oil accumulates and therefore guarantees the supply sufficient and constant oil towards the piston 6.

Claims (10)

1. Scottish yoke mechanism (1, 1 '), especially for gas compressors (11, 21), of the type comprising a cylindrical slide (2) that rotates in the eccentric (3) of a crankshaft (4, 4 ') in the opposite direction to it, a guide (5) substantially perpendicular to the axes of rotation of the slide (2) and the eccentric (3) that transforms the crankshaft rotating movement (4, 4') into an alternative movement linear, and a piston (6, 6 ') of considerably small diameter integral with said guide (5), said piston (6, 6') being associated with a cylinder (7, 7 ') of a compression chamber (8) , characterized by the fact that it comprises a rod (9, 9 ') integral with the opposite part of the piston (6, 6') and movable in a guide (10, 10 '). 2. Scottish yoke mechanism (1, 1 ') according to claim 1, characterized in that the diameter of the piston (6, 6') is smaller than
11 mm 3. Gas compressor (11), characterized in that it comprises a Scottish yoke mechanism (1) of the type defined according to claim 1 or 2. 4. Gas compressor (21), characterized in that it comprises a Scottish yoke mechanism (1 ') of the type defined according to claim 1 or 2, and a crank-crank mechanism (22) associated with a second cylinder -piston, driven by a single crankshaft (4 '), defining a two-cylinder refrigeration compressor adapted to gas compression in two stages. 5. Gas compressor (21) according to claim 4, characterized in that the axes of both cylinders (7 ', 28) are oriented in the same direction. 6. Gas compressor (21) according to claim 4, characterized in that the axes of both cylinders (7 ', 28) are oriented in opposite directions to each other. 7. Gas compressor (21) according to claims 4 to 6, characterized in that the optimum displacement ratio, to reduce the compression work from the conditions of entry to the first cylinder (28) to the discharge pressure of the second cylinder (7 '), it is 3 with a tolerance of 20%. 8. Gas compressor (11, 21) according to any of the preceding claims, characterized in that the gas is CO2. 9. Gas compressor (11, 21) according to any of the preceding claims, characterized in that the cylinder (7, 7 ') of the Scottish yoke (1, 1') comprises means (33, 34, 35) for piston lubrication. 10. Gas compressor (11, 21) according to claim 9, characterized in that the means for the lubrication of the piston (6, 6 ') comprise an oil accumulator recess (33) made in the cylinder housing (7, 7 ') and a grease hole (34) communicating said recess (33) with the hole (35) of the piston passage (6, 6').