JPS58107888A - Lubricating device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lubricating device for a screw compressor for a refrigeration system, in particular operating as a heat pump.

In screw compressors with one or two shafts, oil is injected under pressure into the compressor to lubricate the bearings, rotors, shaft seals, and in some cases transmission equipment. It is well known that the seal between the rotor and the hose is used to further disperse some of the compression heat.

The oil is separated from the compressed refrigerant/oil mixture in an oil separator, cooled in a cooler, and repopulated into the compressor.

In the case of conventional screw compressors in refrigeration or heat pump systems, such as low-temperature heating installations, where relatively low condensing temperatures are required, refueling in this manner does not present any particular difficulties.

In these cases, the oil separated in the oil separator maintains an acceptable viscosity, so that a lubricating oil film can be formed well in the compressor.

FIG. 1 shows the construction of this type of refrigeration system, which can also operate as a heat pump under indicated conditions. This device includes a screw compressor 3 driven by an electric motor 1 via a coupling 2;
There is a refrigeration circuit including an oil separator 4, a condenser 5 and an evaporator 6.

For example, ammonia may be used as the refrigerant.

Refrigerant vapor compressed in the compressor 3 and containing oil as a component is introduced into the oil separator 4 .

The oil-refrigerant solution forming in this oil separator is removed from the separator and sent by a pressure increase pump 7 to a cooler 8 and then to branch lines 9, 10a, 10b.

11 into the compression chamber, and is sent to the bearing (not shown) and the shaft seal portion 12. In this case, for example, water may be used as the cooling liquid for the cooler 8 and the condenser 5, and this cooling liquid is first sent to the cooler 8 and then to the condenser 5 in the direction of the arrow. The heating medium of the evaporator 6 may be water, seawater, air, or the like.

However, when using a screw compressor for heat pump equipment, such as high-temperature heating equipment, 65 to 12
A high condensation temperature of around 0°C is required.

Because of the high condensing temperatures in the refrigeration circuit of the device, the compressor must deliver a relatively high final pressure. As a result, the refrigerant is fluorochlorohydrocarbon (e.g. R
12 and R22), hydrocarbons or hydrocarbon mixtures, the refrigerant is considerably concentrated in the lubricating oil at the final pressure in the oil separator. Due to the increased refrigerant content in the oil, the viscosity of the oil-refrigerant solution may become so thick that a lubricant film can no longer be reliably formed within the compressor.

The solubility of refrigerant in oil depends on the type of refrigerant, the type of oil, the final pressure of the compressor, and the refrigerant exiting the compressor.
Depends on the outlet temperature of the oil mixture.

The greater the pressure in the oil separator, the greater the solubility of the refrigerant in the oil, and the higher the temperature, the lower the solubility.

The object of the present invention is to provide an oil supply device for a screw compressor in which the viscosity can be kept under control by reducing the refrigerant content in the oil. This problem can be solved by dividing the oil/refrigerant solution flow path that forms in the oil separator into two tributaries before entering the cooler, and then leaving the first tributary uncooled at at least one point inside the compression chamber. and dissipating the heat of compression from a second branch in the cooler and injecting the cooled branch into at least the compressor bearing.

From Shio NK according to the invention, the cooled tributary used in the bedding ring has a viscosity that ensures that an oil film forms to the required extent, while the oil can be removed by injecting the uncooled tributary directly into the compression chamber. Maintain the outlet temperature at a suitably high temperature to allow a minimum amount of refrigerant to enter.

The compressed refrigerant-oil mixture outlet temperature varies with the compressor compression ratio, which depends on the temperature of the heat transfer medium in the refrigerant circuit evaporator and the temperature created for the heat absorption medium in the condenser.

Oil injected into the compressor due to fluctuations in compression ratio.
The amount of refrigerant solution also varies.

If, for example, we reduce the compression ratio, i.e. the pressure in the evaporator increases and the pressure in the condenser remains constant, or if the pressure in the evaporator remains constant and the pressure in the condenser decreases, the injected oil The amount of refrigerant solution also decreases. In the optimal case with a decreasing compression ratio, the amount of oil/refrigerant solution injected is such that the outlet temperature is constant or fluctuates within a range such that the viscosity of the cooled tributary is not critically affected. reduced to a certain degree.

However, there are operating conditions in which the amount of oil injected changes due to changes in the compression ratio, and the outlet temperature drops to such an extent that the viscosity of the oil/refrigerant solution becomes inappropriate. It is possible that the value increases beyond the value that causes deterioration.

In order to ensure reliable operation of the device even in such cases for screw compressor oiling, according to a feature of the invention a step is included to control the flow rate of at least one tributary stream as a function of the compressor outlet temperature. According to a modified embodiment for influencing the outlet temperature, a sensor for the outlet temperature of the refrigerant-oil mixture is provided to control a three-way valve connected to the two feed lines of the oil-refrigerant solution.

This outlet temperature control can also be used in cases where unacceptable conditions for screw compressor oiling occur during part load operation.

Next, the present invention will be explained in detail below with reference to FIGS. 2 to 4.

In FIG. 2, the oil and refrigerant solution flow path 13 formed in the oil separator is divided into two branches, one after passing through the bong 7°7 and the other before entering the cooler 8. The branch line 10a is cooled by the cooler 8.

It is sent to the bearing (not shown) and the shaft seal portion 12 via 10b and 11. The second uncooled substream is injected into the compression chamber via line 14 containing control valve 15.

A temperature sensor 1 is installed in the discharge line 16 of the compressor 3.
7 is provided to act on the control valve 15 through the final control element.

As mentioned above, the outlet temperature of the compressed refrigerant/oil mixture affects the solubility of the refrigerant in the oil of the oil separator 4 and thus the viscosity of the lubricating oil. On the other hand, this outlet temperature must not exceed the top critical value.

If the outlet temperature deviates from the required value due to changing operating conditions, the temperature sensor 17
The control valve 15 is opened and closed by an appropriate amount in response to a signal sent to the control valve 15.

In the embodiment described above, the outlet temperature is controlled via a flow control device, but in the embodiment shown in FIG. 3, it is controlled by controlling the temperature of the tributary stream injected into the compression chamber. In this case, if the outlet temperature deviates from the set value, the final control element 2
1 influences the three-way pulse f20 connected to two feed lines for oil and refrigerant solution, one line 14 branches off before entering the cooler 8 and the other line 19 After exiting the cooler 8, the outlet line 14a branches off from the joining line 22 and is sent to the compression chamber.

In the embodiment shown in FIG. 4, the outlet temperature is controlled by controlling the flow rate of a portion of the cooling branch, and the amount of uncooled oil/refrigerant solution injected into the compression chamber via line 14 is constant. is kept constant for the operating conditions.

If the outlet temperature deviates from the set value, temperature sensor 1
T passes through the final control element 23 to the two-way pulp 24
The feed line 25 of the valve is connected to the joining line 22, and the outlet line 26 is led to the compression chamber. The three-way loop occupies an intermediate position at the exit temperature required so that a portion of the cooled oil-refrigerant solution is constantly mixed with the uncooled oil-refrigerant solution. As soon as the outlet temperature exceeds the set point, the amount of cooled oil-refrigerant solution injected into the compression chamber increases or the outlet temperature set point causes the medium solution to mix inside the compression chamber.

It must be pointed out that in all of the embodiments the uncooled tributary stream can be injected into the compression chamber at one point.

It is also preferred to send an uncooled oil/refrigerant solution to the shaft seal instead of the cooling solution.

[Brief explanation of the drawing]

Figure 1 is a diagram of an ordinary refrigeration system, and Figure 2 is a flow diagram of the oil supply system for the screw compressor in the refrigeration circuit of a heat pump facility.The outlet temperature is determined by controlling the flow rate of the uncooled tributary. FIG. 6 is a similar diagram of the second embodiment, in which the outlet temperature is controlled by controlling the temperature of the oil/refrigerant solution injected into the compression chamber;
FIG. 4 is a flow diagram of the third embodiment, in which the outlet temperature is controlled by controlling the flow rate of the oil/refrigerant solution injected into the compression chamber. 3: Screw conlusor; 4: Oil separator; 5: Condenser: 6: Evaporator: 8: Cooler: 12: Shaft seal; 10a
, 10b, 11: Branch line: 15: Control pulp; 1F: Temperature sensor; 18: Final control element: 20: Three-way bulge; 24: Two-way 7-guruzo agent Asamura Akigai 4 people 1 Fig, 3F i g, 4

Claims (1)

[Scope of Claims] (1) A lubricating device for a screw compressor, especially for a refrigeration device operated as a heat pump, in which oil is circulated in a closed circuit and separated from a compressed refrigerant-oil mixture in an oil separator, A partial amount of refrigerant from the separated oil is dissolved into the oil due to pressure as well as temperature, the heat of compression absorbed by the oil is then dissipated in the cooler, and the oil-refrigerant solution is injected under pressure into the screw compressor. In the oil supply system described above, the oil/refrigerant solution flow path formed in the oil separator is divided into two tributaries before entering the cooler, and the first tributary is in an uncooled state at least in one location. A refueling system characterized in that the heat of compression is dissipated from a second branch in the cooler, and a small amount of the cooled branch is injected into the compressor bearing. (2. The oil supply device according to claim 1 is characterized in that it is provided with a sensor for the outlet temperature of the refrigerant-oil mixture, and the signal of the sensor controls the flow rate of at least one tributary stream. (3) A refueling device according to claim 1, comprising a sensor for the outlet temperature of the refrigerant-oil mixture, the sensor being connected to two feed lines for the oil-refrigerant solution. A lubrication system that controls a three-way valve connected to the oil feeder, one feed line branches off before entering the cooler, the other feed line leaves the cooler, and the three-way pulp outlet line is sent to the compression chamber. .