JPS644078B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an oil-cooled compressor that increases the temperature of oil as quickly as possible to prevent the generation of condensate.

(Prior art) In an oil-cooled compressor, such as a screw compressor, the compressor body is cooled and lubricated by the oil sucked in together with the gas to be compressed (usually air). The compressed gas discharged from the tank is led to a compressed gas storage tank (hereinafter referred to as a storage tank) after oil is removed from it in an oil tank, while the separated oil is cooled because it is at a high temperature due to the heat of compression. After that, it is used again to cool and lubricate the compressor body. 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 main body, 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 is connected between the oil tank and the oil cooler system, and the temperature adjustment valve and the suction port of the compressor body are connected by a bypass pipe that bypasses 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.

However, with this conventional system, it takes time for the oil to reach the dew point temperature of compressed gas from which no condensation occurs from a temperature as low as room temperature at the start of operation.
Since the continuous operation time of those that are stopped 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.

For this reason, recently, as seen in Japanese Unexamined Patent Publication No. 12093/1983, a switching valve has been installed on the gas suction side of the compressor body to selectively communicate the suction side of the compressor body with the atmosphere or the oil tank. When the pressure inside the oil tank becomes higher than the set pressure, the switching valve is switched by that pressure to connect the suction side of the compressor main body and the oil tank to perform unloader operation. There is a configuration with .

With this type, when the temperature is low, if the pressure inside the oil tank becomes higher than the set value, the unloader is operated, and even if the pressure switch is activated due to the pressure increase in the storage tank, the motor is stopped. It is possible to quickly raise the oil temperature without causing the oil temperature to rise.

(Problem to be Solved by the Invention) Incidentally, in the oil-fed compressor described above, a check valve is provided in the pipe that communicates the oil tank and the storage tank, and normally this check valve is operated by the biasing force of a spring. Since the valve is opened against the pressure, the pressure inside the oil tank becomes higher than the pressure in the storage tank. Therefore, in order to make the pressure inside the storage tank the highest, the pressure inside the oil tank needs to be higher than that.

In addition, the pressure switch has an error in switching, and may switch when the pressure inside the storage tank becomes higher than the set maximum pressure.

Therefore, if the pressure at which the switching valve is switched and the unloader operation is started is set to the pressure at which the pressure switch is switched, the unloader operation will start before the pressure in the storage tank reaches the maximum pressure, causing the storage A predetermined pressure may not be stored in the tank, or the rise in oil temperature may be delayed, and furthermore, there is a risk that unnecessary unloader operation may be performed during normal operation.

Therefore, in order to prevent these, the pressure at which the switching valve is switched and the unloader operation is performed is set to a pressure _P2 that is higher by a certain value than the pressure _P1 at which the pressure switch operates, taking the above conditions into consideration.

However, if the pressure of the oil tank used to perform unloader operation is set higher than the operating pressure of the pressure switch, extra power will be required to increase the pressure {(P ₂ ) - (P ₁ )}. Moreover, as the pressure increases, drainage becomes more likely to occur. Furthermore, each member must be designed to withstand the higher pressure P ₂ set for unloader operation than the pressure P ₁ under normal operating conditions, which is extremely disadvantageous in terms of cost. .

(Means for Solving the Problems) As a means to solve the above drawbacks, we have developed a compressor body that is driven by a motor and compresses gas while being cooled by oil, and a compressor body that compresses gas while being cooled by oil. an oil tank for removing oil; an oil pipe for supplying the oil in the oil tank to the compressor body via an oil cooler; and an oil pipe connected to the oil tank for storing the compressed gas from which the oil has been removed. and an electromagnetic valve mechanism connected to the gas suction side of the compressor body to close the suction side and communicate the oil tank and the suction side to perform an unloader operation. , a pressure switch that operates when the pressure in the storage tank rises above a certain value; a temperature switch that operates when the oil temperature in the oil tank rises above a set value; and a pressure switch that operates when the oil temperature in the oil tank rises above a set value. a connection circuit that causes the electromagnetic valve mechanism to perform the unloading operation when the oil temperature in the oil tank is lower than a set value, and causes the pressure switch to control the motor when the oil temperature is higher than the set value; It is characterized by having the following.

(Function) According to this configuration, when the oil temperature is low, even if the pressure in the storage tank increases and the pressure switch is activated, the motor continues to be driven by the connection circuit. On the other hand, the electromagnetic valve mechanism is electrically switched by the operation of the pressure switch, and an unloader operation is performed in which the suction side of the compressor body is closed and the pressure in the oil tank is returned to the suction side of the compressor body.

This causes the oil temperature to rise, and when the oil temperature reaches the set temperature, the motor is stopped, and from then on, the motor is controlled only by the pressure switch.

In this way, the unloader operation is performed without increasing the pressure much above the operating pressure of the pressure switch, and the oil temperature is quickly raised to a temperature at which condensation is difficult to occur. Note that the pressure inside the oil tank will increase by the amount of the check valve installed, but
Since it is not set high considering various conditions as in the past, it has almost no effect.

(Example) Examples of the present invention will be described below based on 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 cooperates with a solenoid valve 20 to be described later to constitute an electromagnetic valve mechanism. A discharge pipe 5 extending from the discharge side of the oil tank 6 is opened above the oil surface of the oil tank 6. 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. 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 includes a temperature control valve 13, an oil cooler 14, an oil cooler 14, An oil filter 15 is connected, and a bypass pipe 16 that bypasses the oil cooler 14 connects the oil pipe 12 between the elements and the temperature control valve 13. Furthermore, the oil separator 7 and the oil pipe 12 between the elements are
It is connected by an oil return pipe 18 provided with 7.

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 normally closed and closes at a pressure below a predetermined minimum pressure. It returns and opens at a predetermined maximum pressure (P ₂ > P ₁ ). Also, oil tank 6
is equipped with a solenoid valve 20, a temperature switch 21 that operates according to the temperature of the oil, and a release valve 22 for releasing compressed gas.
The release valve 22 is a normally closed type that opens when activated at a temperature of T ₁ or higher, and the release valve 22 is a normally open type electromagnetic release valve that closes when energized.
0 is of a normally open type that is opened during demagnetization, and when this is open, the pressure within the oil tank 6 is supplied to the unloader valve 3 to close it.

The pressure switch 19 and temperature switch 21 are
They cooperate to control the motor 2 and control the release valve 22 according to the operating status of the motor 2.
The pressure switch 19 also controls the solenoid valve 20, ie, the unloader valve 3.

The connection circuit of each of the above-mentioned elements 2, 19, 20, 21, 22 is shown in FIG. , the second wire 2b, and the third wire 2c are connected to the power supply 23, and each wire 2a, 2b, 2c has 24 normally open contacts 24a, 24b, 24c of an electromagnetic switch.
is connected. Further, the main switch 25, the temperature switch 21, and the self-holding contact 24d of the electromagnetic switch 24 are connected in series, and the electromagnetic switch 24
The coil 24e, one terminal 19a of the two-terminal pressure switch 19, and the main switch 25 are connected in series. The other terminal 19b of the pressure switch 19 and the coil 20a of the electromagnetic valve 20 are connected in series. In addition, 22a in the figure is a coil of the release valve 22.

Next, the operation of the above structure will be explained based on FIG. 3, which shows this in general.
Incidentally, in FIG. 3, the α line indicates the pressure change, and the β line indicates the oil temperature change.

First, when the oil is sufficiently cooled to about room temperature and the storage tank 8 is empty, when the main switch 25 is manually closed as shown in FIG. 2, the terminal 19a of the pressure switch 19 is closed. Therefore, the coil 24e of the electromagnetic on-off valve 24 is excited and its contacts 24e to 24d are closed, the motor 2 is energized, and the coil 22a is energized.
is excited and the release valve 22 is closed. By energizing the motor 2, the compressor main body 1 is driven.
Furthermore, since the terminal 19b of the pressure switch 19 is also closed, the solenoid valve 20 is closed and the unloader valve 3 is opened. This means that a sufficient amount of air (atmospheric air) is sucked in and a compression effect is performed. The compressed gas compressed by this compressor main body 1 is discharged onto an oil tank 6 together with oil heated by the heat of compression, 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 and is compressed. It is supplied to the machine 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 by the time the oil temperature reaches _T1 .
When this pressure reaches P ₂ , the pressure switch 19 operates and opens, but the coil 24 of the electromagnetic switch 24
Since the temperature switch 21 connected to e is closed, the motor 2 continues to be energized and therefore the compressor body 1 continues to be driven. However, at this time, since the pressure switch 19 is open, the solenoid valve 20 is demagnetized and opened, and as a result, the pressure in the oil tank 6 acts on the unloader valve 3, closing it. Therefore, although the compressor main body 1 continues to be driven, it does not suck in new gas and perform compression, but instead enters an unloader operation. Even during this unloader operation, the oil continues to be heated, albeit more slowly than during compression. When the oil temperature further rises due to this oil heating operation and reaches temperature _T1 , the temperature switch 21 is opened and the motor 2 is stopped.

After the temperature of the oil reaches T1 or _above , the motor 2 enters a normal operating state in which starting and stopping are controlled only by the pressure switch 19. That is, the temperature switch 21 stops the motor 2, but has no involvement in starting it.

Note that in area A in Figure 3, the pressure inside the storage tank 8 is
The initial operation range until P ₂ is reached, the B area is the unloader operation area, and the D area is the pressure opening/closing operation area.
This shows a transition region where region C transitions from region B to region D.

FIG. 4 shows another embodiment of the invention. In this embodiment, an electromagnetic switching valve 26 is used instead of the unloader valve 3 and the electromagnetic valve 20, and during heating operation (region B in FIG. 3), the gas in the oil tank 6 is throttled 26.
The air is sucked into the compressor main body 1 via a.

Although the release valve 22 opens only when the motor 2 stops to reduce the load upon restart, the release valve 22 may not be provided.

(Effects of the Invention) As is clear from the above, the present invention has the following advantages:
In order to quickly raise the oil temperature to a level at which no condensation occurs, the pressure switch is activated and the solenoid valve mechanism is electrically switched in the connected circuit to perform unloader operation. The pressure is not much higher than when the switch is activated, which reduces unnecessary load operation and reduces the amount of condensate generated. Furthermore, since the unloader operation is started by a pressure switch, there is no difference in pressure within the compressed gas storage tank between the unloader operation and normal operation, so that a stable supply of compressed gas can be achieved.

In addition, the pressure in the path from the compressor main body to the compressed gas storage tank does not become much higher than the pressure when the pressure switch is activated, and unlike conventional methods, special pressure resistance has been taken into consideration for each component. You don't have to.

Furthermore, conventional systems have two control systems: control of the switching valve using the pressure in the oil tank and control of the motor using a pressure switch, but with the present invention, the switching valve and motor can be controlled using only the pressure switch. Therefore, the control system has a simple configuration. In particular, in the conventional type, the switching valve is switched by pressure, which makes it difficult to route and seal the piping, but in the present invention, connections are made by wiring, so such problems do not occur.

[Brief explanation of drawings]

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 electric circuit diagram, FIG. 3 is a diagram showing the overall operation, and FIG. 4 is a system diagram of main parts showing another embodiment of the present invention. 1... Compressor body, 2... Motor, 3... Unloader valve (electromagnetic valve mechanism), 20... Solenoid valve (electromagnetic valve mechanism), 6... Oil tank, 8... Compressed gas storage tank, 11... Check valve, 19... Pressure switch, 21... Temperature switch, 24... Electromagnetic 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-cooled type comprising: an oil pipe for supplying oil to the compressor body via an oil cooler; and a compressed gas storage tank connected to the oil tank and storing compressed gas from which oil has been removed. In the compressor, an electromagnetic valve mechanism connected to the gas suction side of the compressor body to close the suction side and communicate the oil tank and the suction side to perform an unloader operation; and a pressure in the compressed gas storage tank. a pressure switch that operates when the temperature of the oil in the oil tank rises above a set value; a temperature switch that operates when the oil temperature in the oil tank rises above a set value; A connection circuit that causes the electromagnetic valve mechanism to perform the unloading operation when the oil temperature is lower than the set value, and causes the pressure switch to control the motor when the oil temperature is higher than the set value. oil-cooled compressor. 2. The oil-cooled compressor according to claim 1, wherein the electromagnetic valve mechanism includes an electromagnetic valve and an unloader valve that closes the suction side by opening the electromagnetic valve to perform an unloader operation. 3. The oil-cooled compressor according to claim 1, wherein the electromagnetic valve mechanism is a two-position electromagnetic switching valve.