JPH04203381A - Oil feeding device for scroll compressor for helium - Google Patents

Abstract

PURPOSE:To reduce a pressure pulsation in an oil feeding line and further reduce vibration of a compressor and noise by a method wherein the oil feeding line is provided with a flow rate control of controlling an oil feeding amount in proportion to the number of rotation of the compressor. CONSTITUTION:An oil extracting pipe 30 and an oil feeding pipe 31 are connected by an oil feeding line 36. The oil feeding line is provided with an oil cooler 33 and a flow rate control mechanism 35. If an operating frequency is changed by an inverter 38, the number of rotation of a rotary shaft 14 can be varied and a flow rate of helium gas discharged from the compressor can be easily varied in response to a load. An amount of feeding oil is controlled in proportion to an operating frequency by the flow rate control mechanism 35, an amount of feeding oil can be reduced in the case that the operating frequency is low, so that an amount of oil accumulated in a compression chamber communicating with the oil feeding part can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oil injection mechanism for an oil-filled scroll compressor used in a helium refrigeration system, particularly a refrigeration system for helium liquefaction.

[Conventional technology]

Oil is injected into the compressed gas for cooling the compressed gas. The so-called oil injection method is adopted, for example, in JP-A-61-1.1279.
As disclosed in Publication No. 4, in a closed scroll compressor that maintains the inside of a closed container at a high pressure state, high pressure oil stored at the bottom of the closed container is used as injection oil. Also,
In the example disclosed in Japanese Utility Model Application Publication No. 56-85087, high-pressure oil separated by an oil separator provided in a discharge line is used as injection oil. In these examples, oil injection is performed using the differential pressure between the high pressure and the oil injection part.

Conventionally, compressors used in helium refrigeration systems operate continuously at the rated operating frequency (50 Hz or 60 Hz).
When the refrigeration load decreased, a portion of the discharged gas was bypassed from the discharge side (high pressure side) to the suction side (low pressure side). On the other hand, energy saving can be achieved by controlling the compressor operating frequency using an inverter depending on the refrigeration load. By the way, in a helium liquefaction refrigeration system, a buffer tank is provided to adjust the amount of gas filled in the refrigeration cycle so that the low pressure and high pressure during operation are controlled to be approximately constant. Therefore, the pressure in the oil injection part is also constant, and since oil is injected using the differential pressure between the high pressure and the oil injection part, the amount of oil injection remains almost constant even if the operating frequency is changed.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, since oil is injected using the differential pressure between the high pressure and the oil injection part, the amount of oil injected is kept constant even if the operating frequency is changed. Therefore, the lower the operating frequency, the greater the volumetric flow rate ratio of oil to helium gas. After the operation is stopped, the high pressure gradually decreases and the low pressure gradually increases until they reach the same pressure and are balanced, but until the balance is reached, oil continues to be injected into the oil injection part, so the lower the operating frequency, the more oil The amount of oil that accumulates in the compression chamber leading to the injection part increases. For this reason, the lower the operating frequency is, the more likely an oil compression phenomenon will occur in the compression chamber when restarting after stopping, posing a problem in terms of scroll wrap strength.

An object of the present invention is to provide a highly reliable oil injection mechanism for a helium scroll compressor that does not cause an oil compression phenomenon in the compression chamber when restarting after stopping when the operating frequency is low.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an oil injection line with a flow rate control means for controlling the amount of oil injection in proportion to the rotation speed of the compressor.

[Effect]

Since the oil injection line is provided with a flow rate control means that controls the amount of oil injected in proportion to the rotational speed of the compressor, the amount of oil injected can be reduced when the operating frequency is low. Therefore, after the operation is stopped, the amount of oil injected into the oil injection part can be reduced until the high pressure and low pressure are balanced and the same pressure is reached, so the amount of oil that accumulates in the compression chamber leading to the oil injection part can be reduced. It is possible to provide an oil injection mechanism for a scroll compressor for helium that is highly reliable and does not cause an oil compression phenomenon upon restart.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a longitudinal cross-sectional view and an oil supply system diagram of an oil-lubricated hermetic scroll compressor according to the present invention, and shows a case in which oil is supplied to a compression chamber during compression.

In the figure, a scroll compressor section 2 is housed in the upper part of a closed container 1, and an electric motor part 3 is housed in the lower part. The inside of the closed container 1 is divided into an upper chamber 1a and a motor chamber 1b. The scroll compressor section 2 has a fixed scroll member 5 and an orbiting scroll member 6 that are engaged with each other to form a compression chamber (sealed space).

The fixed scroll member 5 consists of a disc-shaped end plate 5a and a wrap 5b standing upright on the end plate and formed into an impregnated curve or a curve similar to this. Equipped with a suction lower. The orbiting scroll member 6 includes a disk-shaped mirror plate 6a, and a wrap 6b that stands upright thereon and is formed in the same shape as the wrap of the fixed scroll.
and a boss portion 6C formed on the opposite lap surface of the end plate 5. The frame 11 has a bearing portion formed in the center.

A rotating shaft 14 is supported by this bearing portion, and an eccentric shaft 14a at the tip of the rotating shaft is inserted into the boss 6c so as to be able to rotate. Further, a fixed scroll member 5 is fixed to the frame 11 with a plurality of bolts, an orbiting scroll member 6 is supported on the frame 11 by an Oldham mechanism 12 consisting of an Oldham ring and an Oldham key, and the orbiting scroll member 6 is fixed to the fixed scroll member 5. On the other hand, it is formed so that it can rotate without rotating.

A motor shaft 14b is integrally connected to the rotating shaft 14 at the lower part thereof,
It is directly connected to the electric motor section 3. A vertical suction pipe 17 is provided at the suction lower part of the fixed scroll member 5 and extends through the closed container 1.
The upper chamber 1a, to which the discharge port 10 is connected, communicates with the motor chamber 1b via passages 18a and 18b. The motor chamber 1b communicates with a discharge pipe 19 passing through the closed container 1. Further, the upper and lower parts of the motor chamber 1b communicate with each other via a gap 20 between the motor stator 3a and the side wall of the closed container 1 and a gap between the stator 3a and the rotor 3b.

Further, a space 23 (hereinafter referred to as a back pressure chamber) surrounded by a frame 11 is formed on the back side of the end plate of the orbiting scroll member 6, and this back pressure chamber has a 6 m pore hole drilled in the end plate of the orbiting scroll. A pressure between the suction pressure and the discharge pressure is introduced through the orbiting scroll member 6 to the fixed scroll member 5.
It applies an applied force in the axial direction that presses against the

Lubricating oil 24 is stored at the bottom of the sealed container 1, and this oil is sucked up from the oil suction pipe 14d due to the pressure difference between the high pressure inside the sealed container and the intermediate pressure in the back pressure chamber, and then rotates once. axis 1
The suction hole 14c in the swivel bearing 25. The main bearing 26 and the auxiliary bearing 27 are supplied with oil. The oil supplied to each bearing portion passes through the back pressure chamber 23, mixes with the compressed gas injected into the compression chamber of the scroll wrap, and is then discharged together with the discharge gas into the upper chamber 1a. Note that 28 indicates a homing prevention plate disposed on the oil surface of the oil 24.

An oil extraction pipe 30 is opened at the bottom of the closed container 1 to take out the oil 24 at the bottom to the outside of the container. Furthermore, an oil injection pipe 31 is provided in the upper part of the closed container 1 for injecting oil into the compression chamber 2a of the scroll compressor section 2 during compression. This oil injection pipe 31 communicates with the compression chamber 2a via a boat 32 bored in the end plate 5a of the fixed scroll member 5.

The oil extraction pipe 30 and the oil injection pipe 31 are connected by an oil injection line 36, and this oil injection line is provided with an oil cooler 33 and a flow rate control mechanism 35.

Next, the operation of this embodiment will be explained. electric motor rotor 3
When the rotating shaft 14 b directly connected to the rotation shaft 14 b rotates and the eccentric shaft 14 a rotates eccentrically, the orbiting scroll member 6 performs an orbiting motion via the orbiting bearing 25 . This rotational movement causes the compression chamber 2
a gradually moves toward the center and the volume decreases. The working gas enters the suction chamber 2C from the suction pipe 17 via the suction lower, and the oil that has lubricated the bearing flows into the suction chamber 2c from the outer peripheral gap of the orbiting scroll member 6 and mixes with the working gas.

The working gas containing oil is compressed in the compression chamber and discharged from the discharge port 10 to the upper chamber 1a, and then to the passage 18a.

18b and flows into the motor room 1b. Solid arrows indicate the flow of working gas, and dashed arrows indicate the flow of oil. The working gas flowing from the narrow passages 18a, 1.8b = 7- into the wide space of the motor room 1b decreases in flow velocity and changes its flow direction, so that most of the oil contained in the gas is lost. The working gas flows into the discharge pipe 19, and the oil flows into the gap 20 on the outer periphery of the motor rotor.
It flows down through the air and accumulates at the bottom of the sealed container 1. Airtight container 1
The oil 24 stored at the bottom of the container flows into the oil injection line 36 from the oil extraction pipe 3o due to the differential pressure between the pressure inside the closed container 1 (discharge pressure) and the pressure in the compression chamber 2a (pressure below the discharge pressure). The oil reaches the oil cooler 33, where it is appropriately cooled, and then passes through the flow rate control mechanism 35 and the oil injection line 36. The oil is injected into the compression chamber 2a through the oil injection pipe 31 and boat 32.

The oil injected into the compression chamber 2a serves to cool the working gas within the compression chamber and to lubricate sliding parts such as the tip of the scroll wrap. After this oil is compressed together with the working gas, it is discharged from the discharge port 10 into the upper chamber 1a, separated from the working gas in the motor chamber 1b, and collected at the bottom of the closed container 1, as described above. In addition, oil is supplied to each bearing 25° 26.27 by the pressure difference between the pressure inside the closed container 1 and the pressure inside the back pressure chamber 23 (intermediate pressure). This is done through the oil supply hole 14c.

The compressor power outlet 37 is electrically connected to an inverter 38, and if the operating frequency is changed by the inverter 38,
The rotation speed of the rotating shaft 14 can be changed, and the flow rate of helium gas discharged from the compressor can be easily changed depending on the load.

FIG. 2 is a lubrication system diagram shown in FIG. 1, and shows the amount of oil occupied in helium gas when the oil injection amount Q in is controlled in proportion to the operating frequency by the flow rate control mechanism 35 provided in the oil injection line 36. The volumetric flow rate ratio X is shown.

FIG. 3 is the oil injection system diagram of FIG. 1, and shows the oil injection amount Q + n and the oil volumetric flow rate ratio when the oil injection line 36 is not provided with a flow rate control mechanism.

As can be seen by comparing FIG. 2 and FIG. 3, by controlling the oil injection amount QIn in proportion to the operating frequency by the flow rate control mechanism 35 as shown in FIG. After stopping operation,
The amount of oil injected into the oil injection part can be reduced until the high pressure and low pressure are balanced and the same pressure is reached, and the amount of oil accumulated in the compression chamber (2a in Figure 1) leading to the oil injection part can be reduced. It can be reduced. Therefore, it is possible to provide an oil injection mechanism for a helium scroll compressor that does not cause an oil compression phenomenon when restarted.

Furthermore, since the oil injection amount QIn can be reduced when the operating frequency is low, pressure pulsations in the oil injection line can be reduced, and vibrations and noise of the compressor can be reduced.

FIG. 4 shows another embodiment of the present invention, which differs from FIG. 2 in that a stepwise control flow rate control mechanism is provided as the flow rate control mechanism in FIG. 1. FIG. 4 shows a case where the oil injection amount Q In is controlled in three stages. In this case as well, as is clear compared to the case without the flow rate control mechanism shown in Figure 2, the amount of oil injected can be reduced when the operating frequency is low, so after the operation is stopped, high and low pressures are balanced and the same level of pressure is maintained. The amount of oil injected into the oil injection part can be reduced until the pressure reaches , and the amount of oil that accumulates in the compression chamber communicating with the oil injection part can be reduced. Therefore, it is possible to provide an oil injection mechanism for a helium scroll compressor that does not cause an oil compression phenomenon when restarted. Furthermore, since the amount of oil injection can be reduced when the operating frequency is low, pressure pulsations in the oil injection line can be reduced, and vibrations and noise of the compressor can be reduced. Further, the stepwise control flow rate control mechanism can be lower in price than the stepless control flow rate control mechanism shown in FIGS. 1 and 2.

FIG. 5 shows another embodiment of the present invention, which differs from FIG. 1 in that the flow control mechanism includes an on-off valve such as a solenoid valve.
9 and a pressure reducing device 4o such as a capillary in series are connected in parallel to the oil injection line 36, and in FIG. 5, three lines are provided. In this case, when the frequency becomes low, one on-off valve 39 is closed, and when the frequency becomes even lower, two on-off valves 39 are closed. In this case, changes in the oil volumetric flow rate ratio X and the oil injection amount QIn with respect to the frequency are similar to those in the case where the stepwise control flow rate control mechanism shown in FIG. 4 is used. Therefore, in this case as well, it is possible to provide an oil injection mechanism for a helium scroll compressor that does not cause the oil compression phenomenon at the time of restart, improving reliability and reducing vibration and noise of the compressor. can be reduced. Furthermore, the cost can be reduced compared to when using a stepwise flow rate control mechanism.

Incidentally, in all of the embodiments described above, the effects when oil is injected into the compression chamber 2a are described, but even when oil is injected into the suction pipe 17, the same effects as described above can be achieved by the present invention.

Furthermore, in each of the above-mentioned embodiments, the oil injection pipe 3 is
Although the case has been described in which oil is injected into the compression chamber through a plurality of oil injection pipes, similar effects can be achieved by the present invention even when oil is injected into the compression chamber through a plurality of oil injection pipes.

In addition, in the above-mentioned embodiments, high-pressure oil stored at the bottom of a closed container was used as the injection oil, but it is also possible to use high-pressure oil separated by an oil separator installed in the discharge line as the injection oil. A similar effect can be achieved by the invention.

〔Effect of the invention〕

According to the present invention, by controlling the amount of oil injection in proportion to the operating frequency using a flow rate control mechanism provided in the oil injection line, the amount of oil injection can be reduced when the operating frequency is low. It is possible to provide an oil injection mechanism for a helium scroll compressor that does not cause an oil compression phenomenon when restarting.

Furthermore, since the amount of oil injection can be reduced when the operating frequency is low, pressure pulsations in the oil injection line can be reduced, and vibrations and noise of the compressor can be reduced.

[Brief explanation of the drawing]

Fig. 1 is an oil supply system diagram of a scroll compressor according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the oil volumetric flow rate and oil injection amount with respect to the operating frequency in the embodiment of Fig. 1, and Fig. 3 4 is an explanatory diagram showing the oil volume flow rate ratio and oil injection amount with respect to the operating frequency in the case where there is no flow rate control mechanism, and FIG. The explanatory diagram shown in FIG. 5 is a lubrication system diagram of a scroll compressor according to another embodiment of the present invention.

Claims (1)

[Claims] 1. In a scroll compressor for helium, which is controlled to have a variable rotation speed by an inverter and injects oil from the high-pressure section through an oil cooler into the suction pipe or into the compression chamber during compression, there is an oil injection line in the oil injection line that is proportional to the rotation speed of the compressor. An oil injection mechanism for a helium scroll compressor, characterized in that it is provided with a flow rate control means for controlling the amount of oil injection.