JPS6354917B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention actively raises the oil temperature from the start of operation when the cooling oil and oil tank are cold, when condensation is likely to occur. While minimizing the time in the initial operation region until the tank shifts to a steady operation region where it is sufficiently warm and condensate is less likely to occur, the energy required to actively raise the oil temperature is minimized. This article relates to an oil-cooled compressor.

In an oil-cooled compressor, such as a screw compressor, the compressor body is cooled and lubricated by oil sucked together with the gas to be compressed (usually air). The compressed gas discharged from the compressor body is then removed from oil in an oil tank and then led to a storage tank or directly to equipment that requires compressed gas. Since it is at a high temperature, it is cooled down and used again to cool and lubricate the compressor body.

By the way, compressed gas immediately after being discharged from the compressor main body is high temperature and humid, so especially when the oil and oil tank itself are not sufficiently warm, such as at the start of operation, the compressed gas is cooled in the oil tank and drained. occurs, causing oil deterioration and rusting. In other words, it is preferable that the oil be at a low temperature in order to cool the compressor 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 it is preferable that the pressure of the compressed gas is 8-9 kg/cm ² In this case, it is usually necessary to keep the temperature of the gas to be compressed at room temperature +50°C or higher, that is, 70° to 90°C or higher).

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, in the above-mentioned conventional systems, it takes time for the oil to reach the dew point temperature of the compressed gas at which condensation does not occur from a temperature as low as room temperature at the start of operation. Since the continuous operation time of a motor that starts and stops using a pressure switch is short, it takes a considerable amount of time until the oil temperature rises sufficiently. This phenomenon is particularly noticeable when the storage tank is close to its maximum pressure at the start of operation.

The present invention solves the above-mentioned drawbacks, and the present invention actively raises the oil temperature as quickly as possible by continuing to drive the motor until the steady operating range is reached where condensation is less likely to occur in the oil tank. It is an object of the present invention to provide an oil-cooled compressor in which the energy required for proactively increasing the oil temperature is minimized by preventing an excessive increase in the oil temperature.

As a means to solve the conventional problems, the motor control for driving the compressor body is installed in the system downstream of the compressor body, and the pressure in the system increases above a certain value. A pressure switch is provided in the oil tank that operates to stop the operation of the motor when the relative humidity of the compressed gas in the oil tank is within a preset value within a range where condensation is likely to occur. A humidity switch that operates when the compressor main body is operated, and a circuit that controls the motor so that when the humidity switch is activated while the compressor main body is operated, the motor is kept running even if the pressure switch is activated. be.

According to this configuration, when the pressure on the downstream side of the compressor body exceeds a certain value at the start of operation, the pressure switch is activated, but the pressure switch is set so that the relative humidity of the compressed gas in the oil tank is likely to cause drainage. When the relative humidity is within the set value (for example, 90% to 100%), the humidity switch is activated and the connected circuit continues to operate the motor.
Raise the oil temperature quickly and reduce the occurrence of condensate.

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 suction side of the compressor body 1 via a switching valve 3, and a discharge pipe 5 extending from the discharge side of the compressor body 1 is connected to an oil tank 6.
The opening is above the oil level. The oil tank 6 has an oil separator 7 built-in above its oil surface, and the oil separator 7 and a compressed gas storage tank 8 are connected via a pipe 9. A pressure holding valve 10 and a check valve 11 are connected in this order. Also, 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 1
2, temperature control valves 13 are sequentially installed from the oil tank 6 side;
A bypass pipe 1 to which an oil cooler 14 and an oil filter 15 are connected, and which bypasses the oil cooler 14, is connected between the oil pipe 12 between the elements 14 and 15 and the temperature control valve 13.
6. Furthermore, the oil separator 7 and the suction side of the compressor main body 1 are connected by an oil return pipe 18 provided with a throttle 17.

A discharge valve 19 is connected to the oil tank 6, and is composed of a solenoid valve that is closed during excitation, and substantially constitutes a load reduction device at the time of startup.

20 is a pressure switch, 21 is a humidity switch, and the pressure switch 20 is a normally closed type that opens when the pressure in the storage tank 8 rises to a predetermined pressure. Further, the humidity switch 21 is connected to the oil separator 7.
It detects the relative humidity immediately downstream of the compressed gas after the oil has been almost completely separated.For example, it is a normally open type that closes when the relative humidity is between 90% and 100%. ing.

Both switches 20 and 21 work together to control the operation of the motor 2, and an example of the circuit will be described below. The motor 2 is of a three-phase AC type, and the first line 2a, second line 2b, and third line are
Line 2c is connected to power supply 22, and each line 2a, 2b,
2c is the normally open contact 23a, 23 of the electromagnetic switch 23.
b, 23c are connected. This electromagnetic switch 2
One end of the coil 23d in No. 3 is connected to the third wire 2c on the side closer to the power source 22 than the contact 23c. The other end of the coil 23d is connected via the humidity switch 21 to the second wire 2b on the motor 2 side than the contact 23b, and is connected to the second wire 2b via the pressure switch 20 and main switch 24 which are in series with each other. It is connected to the second line 2b on the side closer to the power supply 22 than 23b. And both contacts 23
On the motor 2 side from a and 23b, the first line 2
The coil 19 of the air release valve 19 is connected between a and the second wire 2b.
a is connected.

Next, the operation of the above configuration will be explained. First, when the main switch 24 is closed when the oil and oil tank 6 are sufficiently cooled to about room temperature and the storage tank 8 is empty, the pressure switch 20 is closed, so the coil 23d is energized. The contacts 23a, 23b, and 23c are closed, and at the same time the motor 2 is energized, the coil 19a is excited and the discharge valve 19 is closed. By energizing the motor 2, the compressor main body 1 is driven, and the compressor main body 1 sucks in air as the compressed gas that has passed through the oil and the suction filter 4 (the switching valve 3 is connected to the oil tank 6).
Since the pressure inside is small, compressor main body 1 is
(The suction side of the oil is communicated with the atmosphere), and the compressed oil is cooled, lubricated, and sealed by the sucked oil. The compressed gas compressed by the compressor main body 1 is discharged onto the oil tank 6 together with the oil heated by the heat of compression, where the oil is roughly separated. Then, when the compressed gas passes through the oil separator 7, the oil content is almost completely removed, and then,
It is stored in the storage tank 8. On the other hand, the separated oil is returned to the compressor main body 1 via the oil pipe 12 and the oil return pipe 18, but since the oil temperature has not yet risen sufficiently, most of the oil that has flowed into the oil pipe 12 What?
It passes through the bypass pipe 16 without passing through the oil cooler 14.

In this way, the oil temperature rises due to the heat of compression, but at the same time, the pressure in both tanks 6 and 8 also rises. When the pressure inside the storage tank 8 reaches a predetermined pressure, the pressure switch 20 is activated and opened.
The switching valve 3 is switched in response to the pressure inside the oil tank 6 when it is opened, and the suction side of the compressor main body 1 is communicated with the inside of the oil tank 6.

Here, when the pressure switch 20 is opened as described above, the motor 2 and the air release valve 19 take different operating modes depending on the operation of the humidity switch 21. That is, when the relative humidity of the compressed gas after oil content is removed is 90 to 100%, which is a value that tends to cause drainage, the humidity switch 21 is closed, and therefore the motor 2 At the same time, the air release valve 19 also remains closed.
Therefore, the compressor main body 1 takes a mode in which the compressed gas in the oil tank 6 is compressed again, and thereby,
While generating less heat of compression than when compressing the atmosphere, the oil temperature is further increased. When the relative humidity of the compressed gas from which the oil has been removed falls below 90% due to this further increase in oil temperature (this state becomes the steady operating range), the humidity switch 21 is opened, and the motor 2 is thereby no longer energized. At the same time as this is cut off and stopped, the release valve 19 opens to release the pressure inside the oil tank 6 (note that the pressure switch 20 has already been opened as described above).

After the motor 2 stops, when the pressure inside the storage tank 8 decreases by consuming the compressed gas, the pressure switch 20 closes and drives the motor 2 again, and after this, the humidity switch 21 closes. Unless this happens, starting and stopping of the motor 2 is controlled only by the pressure switch 20.

By the way, once the motor 2 is stopped, even if the humidity switch 21 is closed, the pressure switch 2
The motor 2 will not be started unless 0 is closed. That is, in the embodiment, the pressure switch 20 exclusively controls starting of the motor 2 and the humidity switch 21 exclusively controls stopping of the motor 2 in the initial operation range. The adoption of this control method is based on the viewpoint that starting the motor 2 is practically required when there is a shortage of compressed gas, and also because the oil tank 6 is vented to reduce the starting load when the motor 2 is stopped. At this time, even if the relative humidity in the oil tank 6 temporarily increases due to adiabatic expansion and the humidity switch 21 is closed, from the viewpoint of preventing the motor 2 from starting,
This is preferable.

Although the embodiments have been described above, the present invention is not limited thereto, and includes, for example, the following cases.

The pressure switch 20 may be one that is activated by pressure at an appropriate location in the system downstream of the compressor main body.

The humidity switch 21 may be one that operates based on the humidity of an element that has a causal relationship with the generation of drain in the oil tank 6, such as immediately downstream of the oil separator 7.

When the motor 2 continues to operate even after the pressure switch 20 is opened, the means for preventing the compressed gas line from becoming overpressured includes, for example,
A release valve for releasing compressed gas into the oil tank 6 (has a different function from the release valve 19,
In the circuit configuration as shown in FIG. 2, appropriate means may be adopted, such as providing a device that releases air under conditions such that the pressure switch 20 is open and the humidity switch 21 is closed.

As is clear from the above description, the present invention has the following features:
It is possible to shorten the time required to reach the steady operation range in which drainage is less likely to occur, that is, the time in the initial operation range, which is preferable in terms of preventing drainage.

Also, since the motor operation is controlled by a humidity switch, compared to the case where the motor operation is controlled by taking into account the temperature difference between the room temperature and the inside of the oil tank, such as when using a temperature switch, for example, It is possible to shorten the operating time of the motor only for raising the oil temperature, which is preferable from the viewpoint of energy saving. In other words, the motor that utilizes the temperature difference determines when to stop the motor so that no condensate is generated at the maximum room temperature of the operating atmosphere, so when the room temperature is sufficiently low, condensate no longer occurs. Despite this, the oil temperature continues to rise (the motor continues to be driven) until a predetermined temperature difference (approximately 50 degrees Celsius) corresponding to the maximum room temperature is reached, resulting in wasted energy.

[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 an electrical circuit diagram showing one embodiment of the present invention. 1... Compressor body, 2... Motor, 6... Oil tank, 8... Storage tank, 12... Oil piping, 20
...Pressure switch, 21...Humidity switch.

Claims (1)

[Scope of Claims] 1. A compressor main body driven by a motor and compressing gas while being cooled by oil, an oil tank removing oil from compressed gas discharged from the compressor main body, and an inside of the oil tank. An oil pipe for supplying oil to the compressor body via an oil cooler and a system line downstream of the compressor body, and when the pressure in the system line increases above a certain value. and a pressure switch that is activated to stop the operation of the motor, the pressure switch being installed in the oil tank and having a relative humidity of the compressed gas in the oil tank in advance in a range where condensation is likely to occur. a humidity switch that operates when the humidity is within a set value; and a circuit that controls the motor to continue operating even if the pressure switch is activated when the humidity switch is activated while the compressor main body is being driven. An oil-cooled compressor characterized by having the following. 2. Claim 1, characterized in that a pressure switch is provided to operate when the pressure in a storage tank provided in a system on the downstream side of the compressor body rises above a certain value. The oil-cooled compressor described.