JPH0329993B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oil-cooled compressor that prevents the generation of condensate.

Oil-cooled compressors For example, in screw compressors, the compressor body is cooled and lubricated by the oil sucked in together with the gas to be compressed (usually air), and the compressor body discharged from the compressor body cools and lubricates the compressor body. After the oil is removed from the oil tank, the gas is led to the storage tank via a check valve.The separated oil is at a high temperature due to the heat of compression, so it is cooled and then returned to the compressor body. Used for cooling and lubrication. When the inside of the storage tank reaches a predetermined maximum pressure, the pressure switch that detects this opens and stops the motor that drives the compressor, and the air inside the storage tank is consumed and the inside reaches the specified maximum pressure. When the minimum pressure is reached, the pressure switch is closed and the motor is driven.

By the way, the compressed gas immediately discharged from the compressor body is high temperature and humid, so if the oil and oil tank itself are not sufficiently warm, such as at the start of operation, the compressed gas will be cooled in the oil tank and drained. This causes oil deterioration and rusting. In other words, it is preferable that the oil be at a low temperature in order to cool the compressor main body, but in order to prevent the generation of condensate, the oil should be at a certain high temperature (this is determined by the dew point temperature of the compressed gas, but the pressure of the compressed gas is 8 to 9 kg/cm ² Normal room temperature +50℃
above). For this reason, conventionally, a temperature adjustment valve was connected between the oil tank and the oil cooler system, and the temperature adjustment valve and the suction port of the compressor body were connected by a bypass pipe that bypassed the oil cooler. The ratio of the flow rate flowing through the oil cooler and the bypass pipe is controlled according to the temperature of the oil cooler.

However, while this conventional method is relatively effective when the oil temperature has reached a temperature at which no condensate occurs, it is effective when the oil temperature has not risen to a temperature at which condensate no longer occurs. , it became impossible to expect any kind of prevention of drain generation. In other words, if compressed air is repeatedly used and stopped within a short period of time from a state where the pressure inside the storage tank is almost at its maximum, the motor will also be started and stopped frequently. However, for this reason, it is difficult to obtain sufficient compression heat to raise the oil temperature, and the oil remains at a low temperature due to natural heat radiation when the motor is stopped, resulting in drainage. Become.

In particular, in order to reduce the load when restarting, the compressed gas in the oil tank is released (air vented) to the atmosphere when the motor is stopped. This is not particularly desirable in terms of preventing drain generation.

The present invention has been made in view of the above circumstances, and includes an oil heater that heats the oil when the motor stops to compensate for heat radiation due to natural heat radiation or adiabatic expansion. It is characterized by being able to maintain the oil at a temperature at which no drainage occurs.

Embodiments of the present invention will be described below with reference to the drawings. In Fig. 1, 1 is a compressor main body, and 2 is a motor that drives the compressor main body.The compressor main body 1 may be, for example, a screw type or a vane type with male and female rotors that mesh with each other. used. A suction filter 4 is connected to the compressed gas suction side of the compressor main body 1 via an unloader valve 3 that constitutes a suction throttling mechanism in cooperation with an electromagnetic on-off valve 20 to be described later. A discharge pipe 5 extending from the discharge side of the oil tank 6 is opened into the oil tank 6. An oil separator 7 is built into the oil tank 6.
The oil separator 7 and a compressed gas storage tank 8 are connected via a pipe 9, and a pressure holding valve 10 and a check valve 11 are connected to the pipe 9 in this order from the oil separator 7 side.

Further, an oil pipe 12 extending from the oil in the oil tank 6 is connected to the suction side of the compressor main body 1, and the oil pipe 12 is connected to a temperature regulating valve 1 sequentially from the oil tank 6 side.
3. The oil cooler 14 and oil filter 15 are connected,
Oil pipe 12 and temperature control valve 13 between elements 14 and 15
are connected by a bypass pipe 16 that bypasses the oil cooler 14. Furthermore, the oil pipe 12 between the oil separator 7 and the elements 14 and 15 is connected to the throttle 17.
It is connected by an oil return pipe 18 equipped with.

A pressure switch 19 is connected to the storage tank 8, which operates according to the magnitude of the internal pressure, and the pressure switch 19 is of a two-terminal type in the embodiment, and is set to a predetermined minimum pressure P. ₁ (in the example, 6.5Kg/cm ² ) or less, the valve returns to closed, and at a predetermined maximum pressure P ₂ (in the example, 8.5Kg/cm ² ), it opens.

The oil tank 6 is equipped with a temperature switch 21 that operates according to the internal oil temperature, a release valve 22 for releasing compressed gas, and an oil heater 23. The temperature switch 21 returns to close at a temperature below a predetermined minimum temperature T ₁ (78° C. in the example) at which no drainage occurs, and opens at a predetermined maximum temperature T ₂ (85° C. in the example). The release valve 22 is of an electromagnetic type, and is closed when energized and opened when demagnetized.

The unloader valve 3 is configured to close upon receiving the pressure within the oil tank 6 via a pressure transmission pipe 24, and the electromagnetic on-off valve 20 is connected to the pressure transmission pipe 24. This electromagnetic on-off valve 20 is
Closed when energized and open when demagnetized.

The pressure switch 19 and temperature switch 21 work together to control starting and stopping of the motor 2, and also control the operation (ON, OFF) of the oil heater 23. The electrical connections are shown in FIG. In this figure 2,
25 is a power source; 26 is a manually operated start switch for the power switch; 27 is a stop switch for the power switch; 28 is a relay for the power switch;
8a, 28b, 8c are the relay contacts. Moreover, 29 is a relay of an electromagnetic switch, and 29a~
29e is its relay contact. Furthermore, 30 is a temperature relay as a safety device, and an oil tank 6
When the oil temperature inside rises abnormally (110 in the example)
It opens when the temperature reaches ℃). In addition, 19a, 1
Reference numeral 9b indicates each contact point of the pressure switch 19, which is a two-terminal type, and the oil heater 23 is shown as an electric heater.

Next, the operation of the above structure will be explained with reference to FIG. 3, which generally shows this.

First, when the oil is cool enough to about room temperature and the storage tank 8 is empty, when the starting switch 26 is manually operated and closed as shown in FIG. 2, the relay 28 is energized. Each contact point 2
8a to 28c are closed. Each of these contacts 28a~
28c maintains this closed state because 28a causes the starter switch 26 to self-retain. By closing the contact 28b, the relay 29 is energized (one terminal 19a of the pressure switch 19 is
Since the storage tank 8 is empty, it is closed), and the contacts 29a to 29d are closed, while only the contact 29e is open. As a result, motor 2,
The electromagnetic on-off valve 20 and the release valve 22 are energized (the other terminal 19b of the pressure switch 19 is also closed like the one terminal 19a for the reason mentioned above), and the motor 2 drives the compressor main body 1. The electromagnetic on-off valve 20 is closed, the unloader valve 3 is opened, and the air release valve 22 is closed.

Therefore, the compressor main body 1 sufficiently sucks in gas (usually the atmosphere) together with oil through the filter 4.
This results in a compression effect. The compressed gas compressed by the compressor main body 1 is discharged together with oil heated by the heat of compression into an oil tank 6, where the oil is separated. Then, when the compressed gas passes through the oil separator 7, oil is completely removed, and then the compressed gas is stored in the storage tank 8. On the other hand, the separated oil is used again to cool and lubricate the compressor body 1 via the oil pipe 12, but since the oil temperature has not yet risen sufficiently, most of it passes through the bypass pipe 16. It is then supplied to the compressor main body 1.

In this way, the oil temperature rises due to the heat of compression, but since the pressure rise is larger than the oil temperature rise, the pressure rises to _P2 before the oil temperature reaches _T1 . When this pressure reaches _P2 , both contacts 19a and 19b of the pressure switch 19 are opened, and the electromagnetic on-off valve 2
0 is demagnetized, but since the temperature switch 21 remains closed, the relay 29 continues to be energized.
Therefore, although the compressor main body 1 continues to be driven,
Gas is not newly sucked in and compressed, and the system operates as an unloader. Even during this unloader operation, the oil continues to be heated, albeit more slowly than during compression. When the oil temperature further increases due to this oil heating operation and reaches temperature _T2 , the temperature switch 21 is opened, the relay 29 is demagnetized, the motor 2 is stopped, and the air release valve 22 is opened.

By stopping the motor 2, the oil tank 6 (the oil inside) is caused to expand due to natural heat radiation and adiabatic expansion due to the release of compressed gas to the atmosphere via the air release valve 22.
Temperature drops. However, at this time, as the relay 29 is demagnetized, its contact 29e is closed, so that the oil heater 23 is energized and the temperature drop is prevented.

After this, when the pressure in the storage tank 8 becomes less than P ₁ due to the consumption of compressed gas, the pressure switch 1 is activated.
9 contacts 19a and 19b are closed, the motor 2 is energized again, and normal compression operation is performed. That is, the temperature switch 21 is configured to stop the motor 2, but is not involved in starting the motor 2 in any way. In this way, if the motor 2 is started only by the pressure switch 19, it is possible to prevent the motor 2 from repeatedly starting and stopping within an extremely short period of time due to oil temperature changes (prevention of so-called hunting operation). ).

As is clear from the above description, the present invention
When the oil temperature is low and condensation is likely to occur,
Even if the pressure switch is activated, the motor will not stop.
Perform unloader operation to quickly raise the oil temperature, and when the oil temperature reaches a temperature at which no condensation occurs, the pressure switch controls the start and stop of the motor, and when the motor stops, the air release valve is activated. Even if the compressed gas in the oil tank is activated and the oil temperature attempts to drop due to adiabatic expansion, the oil heater is activated and the oil temperature can be maintained at a temperature where no condensation occurs. Become.

Therefore, in an oil-cooled compressor provided with a release valve, it is possible to reliably prevent the occurrence of drainage due to a drop in oil temperature caused by adiabatic expansion when compressed gas in an oil tank is released.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing one embodiment of the present invention, Figure 2 is a system diagram showing an embodiment of the present invention.
The figure is a diagram showing an example of an electric circuit used in the present invention, and FIG. 3 is a diagram showing the operation of the present invention. 1... Compressor body, 2... Motor, 3... Unloader valve, 6... Oil tank, 8... Compressed gas storage tank, 11... Check valve, 19... Pressure switch, 21... Temperature switch , 23...oil heater,
25...Power supply, 26, 27...Power switch, 2
9...Relay.

Claims (1)

[Claims] 1. A compressor body that is driven by a motor and compresses gas while being cooled by oil; an oil tank that removes oil from the compressed gas discharged from the compressor body; A compressed gas storage tank that is connected via a check valve and stores compressed gas from which oil has been removed, and a release valve that releases the compressed gas in the oil tank to the atmosphere when the motor is stopped. In the refrigerated compressor, an oil heater for heating oil in the oil tank; a pressure switch that closes when the pressure in the compressed gas storage tank is below a predetermined minimum pressure and opens when the pressure is above a predetermined maximum pressure; an unloader valve that is provided on the suction side of the compressor body and closes when the pressure switch is open to operate the compressor body as an unloader, and the temperature of the oil in the oil tank is such that no drainage occurs. When at least one of the pressure switch and the temperature switch is closed and energized, an electric signal is input to energize the motor and cut off energization to the oil heater, thereby reducing the pressure. When both the switch and the temperature switch are open, no electrical signal is input, and a relay is provided that cuts off power to the motor and also powers the oil heater, and when an electrical signal is input to the relay, An oil-cooled compressor characterized in that an electric circuit is provided in which a contact that closes and opens when no input is applied is disposed in series with the temperature switch.