JPH0636312Y2 - Two-stage screw compressor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial field of application) The present invention relates to a two-stage screw compressor, and particularly to a lubricating oil that has been lubricated and cooled for bearings of an oil injection type screw compressor. The position of the oil return hole, the seal in the rotor casing, and the position of the oil injection hole of the lubricating oil for cooling.

(Prior Art) In an oil-injection type screw compressor, the lubricating oil that has lubricated and cooled the bearing and the like is introduced from the oil return hole into the rotor casing and used for internal lubrication, as well as for sealing. On the other hand, the lubricating oil injected from the oil injection hole into the rotor casing has an internal sealing action and a cooling action. In this way, the lubricating oil respectively introduced from the oil return hole and the oil injection hole is compressed together with the gas and sent out from the discharge hole and flows into the oil separator, where the lubricating oil is separated from the compressed gas and is again separated. It flows into the lubricating oil circuit.
The internal structure of the rotor casing 13 of the conventional oil injection type screw compressor having such a structure will be described with reference to FIGS. FIG. 1 is viewed in the vertical direction, and includes a female rotor 1, a male rotor 2, a gas suction chamber 3, a cylinder inner wall 4 forming a closed tooth space, and a discharge port 5. The inlet edges 6 and 7 are male and female rotors.
It is formed along the tooth traces 1 and 2 so that when the tooth space of both rotors is maximized, the tooth space is closed by the cylinder inner wall 4. FIG. 2 is a view of the rotor casing 13 as viewed in the horizontal direction on the inner surface of the female rotor 1 side. As can be seen from this figure, the oil return hole 8 is conventionally provided near the edge 6 of the inlet of the rotor casing 13 on the female rotor 1 side. At such an installed position of the oil return hole 8, as shown in FIG. 3, the rotor tooth tip I passes through the oil return hole 8 by the rotation of the female rotor 1, and the next tooth tip II is still at the edge of the suction port. At a position that does not reach 6, the compression space of the tooth space formed by the rotor tooth tip I and the rotor tooth tip II communicates with both the oil return hole 8 and the gas suction chamber 3.

Next, although the compressed gas may be considerably dissolved in the lubricating oil of the oil injection type screw compressor, the dissolution rate of the two will be described by taking the case of a refrigerator using R-22 as a refrigerant as an example. To do. Fig. 4 shows 15 when the refrigerant condensing temperature Tc = 35 ° C.
0SUS (150 Saybolt universal second, 150sabolt unive
rsal second · Unit of viscosity of oil) It shows the relationship between the amount of Freon-22 dissolved in oil and the oil temperature and pressure.The characteristic of the oil injection type screw compressor is that the discharge pressure is 14 kg / cm. R of about 20% by weight in the operation of about ² abs
It will be lubricated with a solution of lubricating oil in which -22 is dissolved and a refrigerant R-22.

By the way, since the conventional oil return hole 8 communicates with the gas suction chamber 3 side as described above, the returning lubricating oil flows into the low pressure portion, which has the following drawbacks.

(A) The refrigerant dissolved in the lubricating oil is gasified in the low pressure portion, and the amount of gas sucked from the compressor is reduced.

(B) The wet gas in the low-temperature intake gas comes into contact with the warm-returning lubricating oil, is overheated, and re-expands to reduce the actual intake gas amount.

Fig. 5 shows the applicant's two-stage screw compressor 1612.
C (3,000r / m, displacement low side = 619m ³ / h, high side = 19
6m ³ / h compound two-stage screw compressor) shows the ratio of the amount of gas sucked in (Gc) kg / h and the amount of gas that is dissolved and supplied to the compressor together with oil (Go) kg / h. Therefore, when the refrigerant evaporation temperature Te is -60 ° C, it is about the theoretical intake gas amount (Gc).
Gas (Go) equivalent to 54% is contained in the lubricating oil and supplied to the compressor. Therefore, if this oil flows into the low pressure portion, it will be gasified as in the above (a) and (b), and the amount of intake gas will be significantly reduced.

In order to eliminate this drawback, there is a method of extracting air from the lubricating oil to be supplied in advance, but the installation becomes complicated due to the installation of a pressure container for extraction and the arrangement of the oil supply pipes and the like related thereto.

Therefore, in order to eliminate the above-mentioned various drawbacks, the oil return hole is provided in the male rotor and the female rotor immediately after the intake gas in each tooth groove of the male and female rotor is completely closed and in the vicinity of the meshing of both teeth. A device has been developed which is provided so as to open at corresponding positions (Japanese Utility Model Publication No. 55-28714). However, this example is a case of single-stage compression, and in the case of two-stage compression, the advantage is not sufficiently utilized only by providing the position of the oil return hole in this way.

In the first place, in the oil injection type screw compressor, in order to prevent gas leakage from the gap of the rotor part and to improve the efficiency, the lubricating oil is injected into the rotor tooth space to perform the gas sealing action. The injected lubricating oil must be agitated by the rotor rotating at high speed and carried to the discharge port, and power is consumed to agitate this oil. Therefore, the contradictory phenomenon that the lubricating oil being injected in order to improve the performance causes power loss on the contrary is inherent, but in the above-mentioned conventional technology, the operating conditions (the refrigerant In the actual situation, the optimum amount of oil supply is not always distributed for the evaporation temperature).

Further, even in the case of the two-stage type in the oil injection type screw compressor, the oil injection holes are intentionally provided not only in the low pressure stage but also in the high pressure stage, and the lubricating oil is injected into each of the high pressure and low pressure stages. However, the fact is that the optimum amount of oil is not supplied according to operating conditions. The above-mentioned two-stage type is an example of compound type two-stage compression, but the same applies to the case of two-stage compression in which the low stage and the high stage are separated.

(Problems to be Solved by the Invention) The present invention solves the above problems of the prior art by changing and selecting the positions of the oil return hole and the oil injection hole of the lubricating oil and by partially changing the lubricating oil circuit. The object is to obtain a two-stage screw compression device that can be resolved.

[Constitution of device]

(Means for Solving Problems) The two-stage screw compression device of the present invention has the following constitution in order to solve the above problems.

The low-stage compressor is provided with a lubricating oil circuit and an oil return hole for returning lubricating oil that has lubricated and cooled a part of the bearing of the low-stage compressor to the low-stage compressor, A lubricating oil circuit and an oil return hole for returning the lubricating oil that has lubricated and cooled the rest of the bearing portion and the lubricating oil that has lubricated and cooled the bearing portion of the high-stage compressor to the high-stage compressor are provided. The oil return holes provided in the compressor, and provided in the low-stage compressor and the high-stage compressor, the discharge side is equal to or more than one pitch of the tip of the rotor than the end edge forming the closing line of the cylinder inner wall of the rotor casing. In the inside of the cylinder, and the oil injection hole is provided only in the low-stage compressor, and the oil injection hole is located on the higher pressure side than the oil return hole.

(Operation) Since the oil return holes of the low-stage compressor and the high-stage compressor are both provided inside the cylinder where they do not communicate with the low pressure side, the refrigerant dissolved in the lubricating oil may become gasified in the low pressure part. Therefore, the intake gas amount of the compressor is not reduced. In addition, since "a part of the lubricating oil" that lubricates and cools the bearings of the low-stage compressor is introduced through the oil return hole of the high-stage compressor, both high and low levels are better than those introduced through the oil return hole of the low-stage compressor. The total amount of oil flowing through the stage compressor decreases (the amount of lubricating oil flowing into the rotor casing of each of the low stage compressor and the high stage compressor from the oil return hole depends on the amount between the oil header and the oil return hole). Although it depends on the pressure difference, the cylinder internal pressure at the oil return hole position of the high-stage compressor is naturally higher than the cylinder internal pressure at the oil return hole position of the low-stage compressor. Therefore, the pressure difference between and is smaller than that in the case of the low-stage compressor. Therefore, by introducing "a part of the lubricating oil" toward the oil return hole of the high-stage compressor, the amount of inflowing oil is reduced. And this decrease in total oil quantity is high and low It reduces the oil agitation power by the rotor of the high-stage compressor, and because the oil injection holes are provided only in the low-stage compressor, compared to the conventional technology in which the oil injection holes are provided in the high-stage compressor as well. The power consumed for stirring the lubricating oil can also be saved.

(Example) An example of the implementation of the present invention will be described. FIG. 6 shows a lubricating oil circulation circuit of a two-stage screw compressor for a refrigerator. The male and female rotors 1 and 2 are on the low stage side, and the male and female rotors 11 and 12 are on the high stage side. The male rotor 2 and the male rotor 12 are integrally connected to each other and are driven by a prime mover to drive the female rotor 1
Male rotor 2 and male rotor 11 mesh with each other
Driven by 12.

The male rotor 2 on the low stage side has its one end supported by a main bearing 28 and a thrust bearing 29, and the other end supported by a side bearing 35. The female rotor 1 on the low stage side has one end of its rotary shaft supported by a main bearing 28 'and a thrust bearing 29', and the other end of its rotary shaft supported by a side bearing 35 '. 30 is a seal.

On the other hand, the male rotor 12 on the high stage side has one end of its rotary shaft supported by the main bearing 36 and the thrust bearing 37, and the other end of its rotary shaft supported by the side bearing 38. Further, the female rotor 11 on the high-stage side has one end of its rotary shaft at a main bearing 36 'and a thrust bearing 37'.
The side bearing 3 on the other end of the rotary shaft.
Each supported by 8 '. 39 is a balance piston.

The gas is sucked into the low-stage side from the path 21 communicating with the evaporator,
After compression, it is sucked to the high-stage side through the intermediate pressure path 22, 23, 24,
After compression, it is discharged from the path 25 and flows into the condenser via an oil separator (not shown). The lubricating oil is separated from the oil separator connected to the path 25, flows into the oil header 27 via the path 26, is divided into a plurality of paths from here, and is supplied to each part of the compressor.

Lubricating oil from the path 31 is split into the flow of the main bearings 28, 28 '→ the flow of the thrust bearings 29, 29' and the flow of the seal 30, and then merges to the low-pressure side compressor from the oil return hole 8 of the female rotor 1. Inflow forms a “lubricating oil circuit”. The lubricating oil from the path 32 is directly injected into the compressor on the low stage side from the oil injection hole 14 on the higher pressure side than the oil return hole 8. The main bearing that splits the lubricating oil from the path 33 to the side bearings 35 and 35 ', and then diverts it from the path 34 without flowing into the low-stage compressor.
36, 36 '→ Part of the flow of lubricating oil diverted from the passage 34 while flowing into the compressor on the high stage side from the oil return hole 18 of the female rotor 11 by joining with the flow of the thrust bearings 37, 37' Flows through the side bearings 38, 38 'and then the oil return hole 1
It flows from 8 to the high-stage compressor to form a “lubricating oil circuit”. In the prior art, the lubricating oil shunted to the side bearings 35, 35 'was also intentionally introduced into the low-stage compressor, so power was needed to stir this oil by rotating the rotor. By doing so, this power can be saved. The other part of the branched flow of the lubricating oil from the path 34 acts on one side of the balance piston 39, and the other side of the balance piston 39 communicates with the path to the oil return hole 8 of the low-stage compressor. , "Leakage" from the labyrinth seal portion of the balance piston 39 is caused to flow into the compressor.

The entire amount of the lubricating oil that has flowed in from the oil return hole 8 and the oil injection hole 14 of the compressor on the low stage side is discharged from the discharge port of the compressor together with the refrigerant to the route 22 and passes through the routes 23 and 24 to the high stage side. Enter the compressor.

The oil return holes 8 and 18 are configured as follows. In FIG. 7, the tip of the rotor with the larger number of teeth on the lower stage side
When II reaches the edge 6 of the suction port, that is, the tip I and the tip
After the tooth space I is formed by II and the cylinder inner wall 4, the oil return hole 8 is directed from the end edge 6 of the suction port toward the projecting end face 10 so that the tooth tip I passes through the oil return hole 8. It is provided at a position separated by at least one pitch of the tip of the rotor having the larger number of teeth. The above mutual relationship is more apparent from FIG. That is, in the prior art, since the oil return hole 8'is provided at a position close to the edge 6, when the tooth tip I'of the female rotor passes through the oil return hole 8 ', the tooth tip II' is still at the edge. 6 is not reached, and the oil return hole 8'opens to communicate with the low pressure side. On the other hand, in the embodiment of the present invention, the oil return hole 8
Since the tooth tip II reaches the end edge 6, the tooth tip I is still immediately in front of the oil return hole 8.
A closed tooth space is formed by the tooth tip II and the cylinder inner wall 4, and the oil return hole 8 does not open to the low pressure portion. The oil return hole 18 on the high pressure side is also provided at the same position.

By providing the oil return holes 8 and 18 at the positions as described above,
The oil return holes 8 and 18 do not directly communicate with the gas suction chamber as in the prior art, and the refrigerant dissolved in the lubricating oil is not gasified in the low pressure portion. On the low-stage side, the low-temperature, wet intake gas flowing from the evaporator does not come into contact with the warm-returning oil and is re-expanded by overheating, so that the intake gas amount to the compressor does not decrease.

The oil return holes 8 and 18 are bored on the rotor side having a large number of teeth, but in this embodiment, there are four male rotors and six female rotors, so they are bored on the female rotor side. If the oil return holes are provided on the side of the rotor having a large number of teeth, they can be provided closer to the closing line and the re-expansion of the refrigerant can be further reduced.

Further, in the prior art, even in the case of two-stage compression, the lubricating oil was injected aimlessly in the high-stage compressor to inject the lubricating oil, so an excess amount of oil was introduced, and this was agitated by the rotor and the discharge port was agitated. Power was required to stir this oil in order to carry it to. In the present invention, the oil supply to the high-stage compressor is the sum of the lubricating oil introduced from the low-stage compressor via the path 24 and the lubricating oil introduced through the oil return hole 18 flowing through the bearings on the high-stage side. It has been found that the amount of oil is sufficient, and that the amount of oil is sufficient for the sealing, cooling, and lubricating actions in the rotor casing, and there is no hindrance in the performance of the high-stage compressor. Based on this discovery, the present invention abolished the oil injection hole of the high-stage compressor, and the power could be saved.

Refrigerating machine oil is used as the lubricating oil, but synthetic oil or liquid mixed with a lubricant may be used. Next, FIG. 9 shows the relationship between the amount of oil supply and the adiabatic efficiency based on changes in the operating conditions of the refrigerator. This is the two-stage screw compressor (16
12C type) with refrigerant R-22, refrigerant condensing temperature Tc = 35 ° C, rotation speed N = 3000r.pm, and how the amount of refueling affects the adiabatic efficiency when the refrigerant evaporation temperature is changed. It can be seen that there is an optimum amount of oil. That is, it can be seen that the optimum amount of oil supply that maximizes the adiabatic efficiency decreases as the refrigerant evaporation temperature decreases. In the embodiment of the present invention, the passages 31, 32, 33, 34, etc. branched from the oil header 27 of FIG. 6 are provided with throttles so that the optimum oil supply amount is obtained according to the operating conditions (refrigerant evaporation temperature) of the refrigerator. Adjust the amount of oil supplied.

Next, when the two-stage screw compressor is operated under the same conditions as above, that is, the refrigerant R-22, the refrigerant condensing temperature Tc = 35 ° C., and the rotation speed N = 3000 rpm, and the refrigerant evaporation temperature is different. The effects of the embodiment of the present invention will be described with reference to FIG.

The △ mark is a curve showing the relationship between the evaporation temperature and the adiabatic efficiency according to the conventional technology, but the curve after providing a throttle to obtain the optimum oil supply amount becomes like the ◇ mark, and measures for the optimum oil supply amount The curve after the adjustment of the oil return hole and the position of the oil return hole is shown as a circle. According to this, the refrigerant evaporation temperature Tc = 35 ° C,
When the optimum oil supply amount and oil return position are adjusted at the refrigerant condensing temperature Te = -60 ° C, the adiabatic efficiency is approximately 25%.
I see that it improves.

[Effect of device]

In the two-stage screw compression device, since the oil return holes of the low-stage side and high-stage side oil injection type screw compressors are provided at cylinder internal positions that do not communicate with the low pressure side,
There is no possibility that the refrigerant dissolved in the lubricating oil will be gasified in the low pressure part. Therefore, the amount of gas sucked into the compressor is not reduced.

Also, "a part of the lubricating oil" that lubricates and cools the bearings of the low-stage compressor is introduced from the oil return hole of the high-stage compressor by the lubricating oil circuit, so that it is introduced from the oil return hole of the low-stage compressor. Compared with the case where it is introduced, the total amount of oil flowing through the low-stage compressor and the high-stage compressor is reduced. Therefore, this reduction in the total amount of oil can reduce the power consumed by the rotor for stirring the oil.

Furthermore, in the prior art, even in the case of two-stage compression, the high-stage compressor was purposely provided with oil injection holes to inject the lubricating oil, but on the high-stage compressor side, along with the compressed gas from the discharge port of the low-stage compressor. Since there is lubricating oil that is sent, it is sufficient to have the lubricating oil that is introduced from the oil return hole outside that, and the lubricating oil from the oil injection hole is used for sealing, cooling, and lubricating inside the rotor casing. Turned out to be unnecessary. For this reason, in the present invention, the oil injection hole is provided only in the low-stage compressor, so that it is necessary to stir extra lubricating oil as compared with the prior art in which the oil injection hole is provided in the high-stage compressor as well. The power that was used can also be saved.

[Brief description of drawings]

FIG. 1 is a plan view of a conventional oil injection type screw compressor as seen from the suction port side, FIG. 2 is an explanatory diagram of the suction port as seen in the horizontal direction from the female rotor side, and FIG. 3 is from the female rotor side. FIG. 4 is an explanatory view of the positional relationship among the edge forming the closing line of the suction port, the oil return hole, and the thread line of the female rotor as seen, FIG. 4 is a graph of the amount of CFC-22 dissolved in oil, and FIG. Fig. 6 is a graph showing the relationship between evaporation temperature and Go / Gc, Fig. 6 is a diagram of the oil supply system of the embodiment of the present invention, and Fig. 7 is a confinement line of the intake port seen from the female rotor side in the embodiment of the present invention. 8 is an explanatory view of the positional relationship between the edge, the oil return hole, and the screw thread line of the female rotor, and FIG. 8 is an explanatory view of the positional relationship between the edge, the oil return hole, and the addendum of the female rotor in the above embodiment, FIG. 9 is a graph showing the relationship between oil supply amount and adiabatic efficiency in an oil injection type screw compressor, and FIG. Is a graph showing the Nerugi effect. DESCRIPTION OF SYMBOLS 1 ... Female rotor as a rotor, 2 ... Male rotor as a rotor, 4 ... Cylinder inner wall, 6, 7 ... Suction port edge, 8 ... Oil return hole, 10 ... Discharge end face, 11 ... Female rotor as a rotor,
12 ... Male rotor as rotor, 13 ... Rotor casing,
14 ... Oil injection hole, 18 ... Oil return hole.

Claims (3)

[Scope of utility model registration request] 1. A low-stage compressor is provided with a lubricating oil circuit and an oil return hole for returning a lubricating oil, which is obtained by lubricating and cooling a part of a bearing of the low-stage compressor, to the low-stage compressor, Lubricating oil circuit and oil return for lubricating the rest of the bearing of the low-stage compressor and lubricating the cooled lubricant and for lubricating the bearing of the high-stage compressor and returning the cooled lubricant to the high-stage compressor. A hole is provided in the high-stage compressor, and the oil return hole provided in each of the low-stage compressor and the high-stage compressor has a tip 1 of the rotor more than an end edge of the cylinder inner wall of the rotor casing that forms a closing line. Two-stage screw compression, which is provided at each cylinder internal position on the discharge side corresponding to the pitch or more, and has an oil injection hole only in the low-stage compressor, and the oil injection hole is located on the higher pressure side than the oil return hole. apparatus. 2. A utility model registration request wherein each passage for supplying oil to the oil return hole and the oil injection hole is provided with a throttle for adjusting the amount of oil supply so that the adiabatic efficiency becomes maximum with respect to the refrigerant evaporation temperature. A two-stage screw compression device according to claim 1. 3. The two-stage screw compressor according to claim 1 or 2, wherein the oil return hole is provided at a position inside the cylinder on the rotor side having the larger number of teeth.