JP3384225B2 - Oil-cooled screw compressor and operating method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refueling screw compressor that uses oil for cooling compressed air and a method of operating the same.

[0002]

2. Description of the Related Art In a conventional refueling screw compressor, as described in JP-A-5-141383, even a compressor having an automatic start / stop function causes a motor to be frequently started. In order to prevent the heating of the motor, a method of limiting the number of stoppages within a predetermined time, a method of not stopping the motor for a predetermined time after starting, and the like have been used.

[0003]

SUMMARY OF THE INVENTION In the above-mentioned prior art, in a compressor having an automatic start / stop function, a sufficient amount of drainage is prevented from occurring in the oil separator tank before the temperature at start-up stabilizes. Was not considered. That is, when the start and stop are repeated at short time intervals under the high temperature and high humidity condition, it is unavoidable that drainage occurs in the oil separator tank.

By the way, the air sucked in during operation of the compressor contains water, and when this is compressed,
It becomes drain and collects in the oil separator tank. If left unattended, the deterioration of oil will be accelerated, causing problems such as rusting and corrosion inside the equipment and also affecting the life of the bearing. For this reason, it is important to create an operating condition in which no drain is generated in the oil separator tank. A general method for preventing the occurrence of drainage is to maintain the oil temperature above the temperature at which drainage occurs by means of a temperature control valve.
However, in a compressor having an automatic start / stop function, a low load operation may be performed and the compressor may stop before the oil temperature rises to a temperature at which drainage does not occur. If such an operation pattern is repeated, drain may be generated and accumulated in the oil separator tank. If the operation is continued for a long time in this state, there is a high possibility that the bearing of the compressor body will be damaged or the lubricating oil will be deteriorated.

An object of the present invention is to provide a structure having a structure having an automatic start / stop function, a structure, and an operation control system for preventing generation and retention of drain in an oil separator tank.

[0006]

In order to achieve the above object , the first feature of the present invention is to provide a male drive driven by a drive means.
A screw compressor body having both female rotors and this screw
Liu The pressure of the gas discharged from the compressor body is detected.
Discharge pressure detection means and suction of the screw compressor
The suction flow rate control means disposed on the only side, and the screw
-Oil separating means arranged on the downstream side of the compressor body,
Communication means for releasing the pressure in the oil separation means to the atmosphere
And a start-stop control for controlling the start and stop of the drive means.
Control means and a check valve provided on the downstream side of the oil separation means
And pressure detection for detecting the pressure on the downstream side of this check valve
In an oil-cooled screw compressor equipped with
To detect the temperature and humidity of the fluid drawn into the compressor body
And the discharge temperature of the fluid discharged from the compressor body.
Temperature detecting means for detecting the temperature, and the temperature of the suction fluid
And humidity and suction from the means for detecting the humidity and humidity
Drain generation limit temperature based on the discharge pressure from the pressure detection means
Detected by the discharge pressure detecting means and the discharge pressure detecting means.
Change the flow rate of the suction flow rate control means according to the discharge pressure
Control (U type operation), pressure on the downstream side of the check valve is
When the set pressure PH of 1 is reached, the suction flow control hand
No load operation by closing the stage and opening the communication means
After this no-load operation, the pressure on the downstream side of the check valve becomes
When the set pressure PL of 2 is reached, the suction flow rate control means
Control for opening and closing the communication means (I-type operation
And whether the unloaded operation continues for a specified time or longer.
Or when the load factor is within a predetermined range, stop the drive means.
Control (P-type operation), and these U-type, I-type and P-type
Capacity control means for combined operation control
The capacity control means, when the compressor is started, or
At least when the above-mentioned
The temperature inside the oil separation means reaches the drain generation limit temperature.
The above-mentioned type I operation is not performed until
To do.

And preferably, the temperature of the inhaled fluid and
Means for detecting humidity, the discharge pressure detection means, and the discharge
Output to the oil separation means based on the output from the output temperature detection means.
The operating time required to evaporate the amount of condensed water produced
And the condensed water is collected in the oil separation means based on the calculation result.
The compressor is controlled by the capacity control means so that it does not accumulate
Good to do.

In order to achieve the above object, a second aspect of the present invention is provided.
The feature is the start and stop of the screw compressor according to the load.
The operating method of the oil-cooled screw compressor that controls the
Oil separating means provided on the discharge side of the screw compressor body
The suction side of the screw compressor body depending on the side pressure
U-type operation step for controlling the suction flow rate control means provided in the
And a check valve provided on the downstream side of the oil separating means.
Before the pressure on the further downstream side of reaches the first set pressure PH
The oil separation means is provided while closing the suction flow rate control means.
Side pressure is released to the atmosphere for no load operation,
After turning, the pressure on the downstream side of the check valve becomes the second set pressure PL.
When it reaches, the suction flow rate control means is opened and the oil content is
Control to close the line that opens the inside of the separating means to the atmosphere
I-type operation step and nothing in this I-type operation step
When the load operation continues for more than the specified time or the load factor
When the screw compressor body falls below a certain range,
And a P-type operation step for stopping the driving source to be driven
Well, at the time of start-up, it is started by the U-type operation step,
Of the fluid sucked into the screw compressor body
On the discharge side of the screw compressor body based on temperature and humidity
Calculate the drain generation limit temperature TL in the oil separation means
After the temperature of exceeds the drain generation limit temperature TL
To shift from the formula operation step to the I operation step
There is something I did.

And, preferably, the I-type operation
Increase from the second set pressure PL to the first set pressure PH
When the time t1 reaches the set value t, the P-type operation is started.
It is good to do.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below with reference to the drawings. 1 is a diagram showing a first embodiment of the present invention and is a system diagram of an oil-cooled screw compressor. The air sucked from the suction filter 1 passes through the suction throttle valve 2, is compressed between the male and female rotors 3 of the screw compressor, and is discharged from the discharge port 4. Lubricating oil is injected into the rotor 3 portion of the screw compressor 12 in order to cool the compression heat generated by the compression of air and also as a lubricant and a seal. The compressed air discharged together with the lubricating oil from the discharge port 4 flows into the oil separator tank 5,
The oil is separated from the lubricating oil in the oil separator element 6, and sequentially flows from the discharge pipe 7 through the check valve 8 and the pressure regulating valve 9 into the aftercooler 10, cooled by the aftercooler 10, and then discharged to an external device (not shown).

On the other hand, the lubricating oil is the oil separator tank 5
It is separated from the compressed air inside and is guided to the oil cooler 11 from the bottom of the oil separator tank 5. Lubricating oil cooled by the oil cooler 11 and uncooled lubricating oil that does not pass through the oil cooler are mixed in the temperature control valve 13 section, and the mixed lubricating oil lubricates the screw compressor body 12. The temperature control valve 13 adjusts the oil supply temperature so that drainage does not occur at the outlet of the compressor body. That is, the mixing ratio of the lubricating oil cooled by the oil cooler 11 and the uncooled lubricating oil not passing through the oil cooler 11 is automatically adjusted.

Here, the capacity of the compressor is adjusted using the following three methods. (1) The valve plate 14 of the suction throttle valve 2 attached to the suction port side of the compressor body 12 is moved in the axial direction according to the pressure detected by the pressure sensor 30 provided downstream of the oil separator element 6. That is, when the pressure of the oil separator element 6 rises, the pressure adjusting valve 15 is opened to introduce control air into the suction throttle valve 2 to adjust the opening degree of the valve plate 14 to adjust the suction air amount of the compressor ( Hereinafter referred to as U-type operation).

(2) The pressure downstream of the check valve 8 is detected by the pressure detector 16, and when the detected pressure reaches the set upper limit pressure, the valve plate 14 of the suction throttle valve 2 is closed. At the same time, the oil separator element 6 is provided on the upstream side of the check valve 8.
It is released to the atmosphere via a solenoid valve 17 and a suction throttle valve 2 provided downstream of the. As a result, the pressure in the oil separator tank 5 is reduced and the loadless operation is performed. After that, when the pressure downstream of the check valve 8 drops to the set lower limit pressure, full load operation is restored (hereinafter referred to as I-type operation).

In the I-type operation described in (3) and (2), when no-load operation continues for a long time, or when the load factor is smaller than a predetermined range, the motor 18 is stopped because the amount of air used is small. . After that, when the air is consumed again and the pressure downstream of the check valve 8 decreases, the motor 18 is restarted (hereinafter referred to as P-type operation). Here, the load factor L
_R is the time t _PR for the pressure detected by the pressure detector 16 to rise to the set value P _H and the time t for the pressure to fall to the set value P _L.
It is the ratio of _PL . That is, L _R = t _PR / (t _PR +
t _PL ), which is usually set to about 0.1.

Here, in the present embodiment, when the compressor enters the automatic start-stop operation mode in the P-type operation, the temperature of the air in the oil separator tank 5 detected by the temperature sensor 31 is kept in the pressurized state. Do not perform the I-type operation until the temperature reaches a level at which drainage does not occur, and forcefully enter the U-type operation mode.

The reason for this will be described below. Generally, in the U-type operation, since the same pressure as that at full load is applied to the discharge side of the compressor, the power can be reduced only to 65 to 75% of that at full load. On the other hand, in the I-type operation, since the pressure on the discharge side of the compressor is released to the atmosphere, the power can be reduced to 30 to 35% of the full load. Therefore, even if the temperature control valve 13 used in the compressor system has a function of keeping the oil supply temperature constant, the compressor main body 12 discharges when the state close to no load continues in the I-type operation mode. The temperature of the air may rise significantly slower. It is rare that the compressor will be completely operated with no load immediately after startup under actual usage conditions of the compressor, but in the case of parallel operation of multiple compressors, it is possible to start it under conditions close to no load. . In the I-type operation, when it is considered that there is no load, the intake amount of air is only the control air of the capacity control mechanism. In this case, the pressure inside the oil separator tank 5 is reduced, and drainage does not occur. However, under operating conditions close to no load, full load operation is performed for a very short period of time during complete no load operation. Therefore, the drain is most likely to be generated. This situation will be further described with reference to FIG.

FIG. 2 is a diagram showing a rising pattern of the discharge temperature of the compressor body 12 depending on the load state immediately after starting. In the figure, the line A indicates the rising speed of the discharge temperature of the compressor body 12 at the time of full load operation, the line B at the time of 0% load in the I type operation, and the lines C and D at the time of 5% and 10% load, respectively. Shows. On the other hand, in the U-type operation, the power consumption is almost double that in the I-type operation even when the engine is started with no load.
As indicated by the line, the temperature _TL at which drainage does not occur reaches a temperature close to the temperature increase at full load. Similarly, the F and G lines show the rising speed of the discharge temperature of the compressor body at 5% and 10% load in the U-type operation, respectively. Compared to the I-type operation under the same load conditions, drainage occurs. It takes about 1/3 to reach the temperature that does not occur. Therefore, no load immediately after startup,
Alternatively, even if the load is light, the amount of drainage that may be accumulated in the oil separator tank is 1/3 or less of that in the case of the I-type operation. That is, since it is difficult to drain the drain manually when the P-type operation is used, it is optimal to use the U-type operation when starting the compressor by the automatic operation.

However, if the U-type operation is left as it is, the power consumption is large under no load or light load, and the effect of energy saving is small. Therefore, when the air temperature in the oil separator tank reaches the temperature _TL at which drainage does not occur, the U-type operation is changed to the I-type operation. In order to detect this temperature, instead of the temperature sensor 31, a sensor having a temperature proportional output such as a thermocouple or thermistor provided at the discharge port of the compressor body 12 of the oil-cooled screw compressor is usually used as the discharge temperature sensor 19. Therefore, there is no need to install a new sensor.

When the no-load operation continues, the motor is stopped by shifting to the P-type operation to prevent wasteful power consumption. FIG. 3 shows the flow of the operation pattern of this embodiment when the operation of the compressor is controlled in this way.

Next, a second embodiment of the present invention will be described with reference to FIGS. 4 and 5. In the second embodiment, the compressor is automatically started by the U-type operation as in the first embodiment, and the discharge temperature of the compressor body 12 is raised to the temperature _TL at which the drain is not generated. After that, the mode I operation is switched to. And, the load operation time during I-type operation,
That is, the pressure downstream of the oil separator element 6 is
The time t ₁ from the setting load return pressure P _L to the setting upper limit pressure P _H is integrated (see FIG. 4). When the accumulated load time reaches the preset time t, the P-type operation mode is entered. The compressor is not stopped even if the load is low until the preset time t is reached. FIG. 5 shows a flow of the operation pattern of this embodiment in which the compressor is controlled in this way.

FIG. 6 shows a discharge temperature region A in which drainage occurs and a discharge temperature region B in which accumulated drainage evaporates, assuming that the intake air temperature is 30 ° C., the relative humidity is 80%, and the discharge pressure is 0.69 MPa. Show. Then, FIG. 7 shows how the drain amount Q _d in the oil separator tank 5 changes in the state of FIG. 6. Under this condition, the generation of drain is stopped in about 2 minutes, the drain accumulated at startup is evaporated in about 4 minutes, and all the drain is carried away to the discharge line. The above is the case where full load operation is always performed. When the unloading operation is performed after entering the draining operation temperature range B, the evaporation amount is significantly reduced as compared with that under full load. That is, the most effective means for evaporating the drain once generated in the oil separator tank 5 again and taking it out from the tank is to carry out the load operation at the discharge temperature or higher at which the drain is not generated, and therefore in the present embodiment, The example is further advanced and a stop time limit is set. Since the stop time limit is obtained by integrating only the load time t ₁ , it is possible to surely evaporate the drain that is expected to be accumulated in the oil separator tank 5.

Next, a third embodiment of the present invention will be described. ◆ Under constant suction temperature and humidity conditions,
The limit temperature TL at which drainage occurs increases as the discharge pressure increases. Therefore, if the discharge pressure to be operated is different, the temperature at which the U-type operation in the above-mentioned first and second embodiments is switched to the I-type operation should be changed. Because, under the conditions of suction air temperature of 30 ° C, relative humidity of 80%, and discharge pressure of 0.69 MPa, the drain generation limit temperature is about 70 ° C, while the discharge pressure rises to 0.84 MPa even under the same suction condition. Then, the drain generation limit temperature is about 78 ° C. Therefore, if the switching temperature from the U-type operation to the I-type operation is kept at 70 ° C, the accumulation of the drain evaporation operation time will start earlier, and the accumulated drain may not be completely evaporated. To do. On the contrary, when the engine is operated at a pressure lower than the set value, the time longer than the actually required time is set as the stop time limit, and the energy saving effect is impaired.

Therefore, in the present embodiment, the control pressure for the I-type operation is detected by the pressure sensor 16, and the upper limit pressure P _H and the lower limit pressure P _L are set by key-in input to the control microcomputer. The switching temperature of the I-type operation from U-type operation, calculated from the set value of the input upper limit pressure P _H with microcomputer according automatically to the upper limit pressure PH in the case of setting pressure is changed To raise or lower the switching temperature. Thereby, even when the operating pressure is changed, the operation of the compressor can be appropriately controlled.

Further, a fourth embodiment of the present invention will be described below. In this embodiment, a sensor for detecting the temperature and humidity of the air sucked by the compressor is provided on the suction side of the compressor,
The drain generation limit temperature is calculated from the suction temperature and humidity of the compressor detected by this sensor and the discharge pressure detected by the pressure sensor. Then, the amount of drain generated in the oil separator tank is calculated from the operating time until the temperature is reached, and the load operating time required to evaporate the drain is obtained based on the amount of drain. The subsequent procedure is similar to that of the second embodiment. In the above-described embodiment, the amount of drainage accumulated in the oil separator tank is determined by assuming the worst condition of the specification value (for example, 30 ° C. relative humidity 90%) for both the suction temperature and the suction humidity, and the stop limit is determined from the drainage amount. Although the time was set, according to the present embodiment, the drain amount is calculated based on the condition closer to the actual operating condition, so when the suction condition is dry than the worst condition of the specification value, The stop time limit can be shortened.

[0025]

According to the present invention, the screw compressor
Intake fluid temperature and humidity, as well as from the screw compressor
Calculate the drain generation limit temperature based on the discharge pressure and
When the compressor is started, or when
Temperature, the temperature inside the oil separation means is
U-type operation is compulsory until the temperature reaches
Control for changing the flow rate of the suction flow rate control means).
Since it has been set so that drain will not collect in the oil separation means etc.
It can be suppressed, and even if drainage accumulates, it can be evaporated and spit out.
Oil can be separated because it can be carried out of the machine together with the discharged air.
Rust of equipment due to the accumulation of drain in the means,
And failure due to it, trouble due to poor lubrication of the bearing
It can be prevented. In addition, draining work that is troublesome for users
The labor of work can be saved. Also, the actual operating conditions
Is it possible to calculate the drain amount based on similar conditions?
The drainage according to the amount of water in the intake air.
The operating time for
Even if you can achieve optimal drain prevention and energy saving
It

[0026]

[Brief description of drawings]

FIG. 1 is a system diagram of a first embodiment of an oil-cooled screw compressor according to the present invention.

FIG. 2 is a graph illustrating a change in discharge temperature at the time of startup due to a difference in operation method.

FIG. 3 is a flow chart of an operation method according to the first embodiment of the present invention.

FIG. 4 is a graph of an operating pressure pattern according to the second embodiment of the present invention.

FIG. 5 is a flow chart of an operation method according to a second embodiment of the present invention.

FIG. 6 is a graph illustrating a change in discharge temperature at startup.

FIG. 7 is a graph illustrating changes in the drain amount in the oil separator tank.

[Explanation of symbols]

1 ... Suction filter, 2 ... Suction throttle valve, 3 ... Rotor, 4 ... Discharge port, 5 ... Oil separator tank,
6 ... Oil separator element, 7 ... Discharge pipe,
8 ... Check valve, 9 ... Adjusting compressor valve, 10 ... After cooler, 11 ... Oil cooler, 12 ... Compressor body, 1
3 ... Temperature control valve, 14 ... Suction throttle valve valve plate, 15 ... Pressure adjustment valve, 16 ... Pressure detector, 17 ... Solenoid valve, 18 ...
... motor, 19 ... discharge temperature sensor, 20 ... cooling fan motor, 21 ... cooling fan, 22 ... exhaust valve,
23 ... Belt, 24 ... Oil filter, 25 ... Orifice.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F04C 29/02 331 F04C 29/02 331Z 341 341Z 351 351D G05B 19/02 G05B 19/02 D (56) Reference Japanese Patent Laid-Open No. 4 -136498 (JP, A) JP-A-2-223694 (JP, A) JP-A-6-249190 (JP, A) JP-A-7-332248 (JP, A) JP-A-8-319982 (JP, A) ) JP-A-50-15113 (JP, A) JP-A-52-155405 (JP, A) JP-A-58-220996 (JP, A) JP-A-63-208697 (JP, A) JP-A-56- 580 (JP, A) JP-B 64-4078 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F04C 18/16 F04C 29/00-29/10 F04B 49/00- 49/10 G05B 19/02

Claims (4)

(57) [Claims] Claim: What is claimed is: 1. A screw compressor body driven by a driving means and having both male and female rotors, a discharge pressure detecting means for detecting a gas pressure discharged from the screw compressor body, and a suction of the screw compressor. Side, a suction flow rate control means, an oil separating means arranged downstream of the screw compressor body, a communicating means for releasing the pressure in the oil separating means to the atmosphere, and the drive Start-stop control means for controlling the start and stop of the means, and the oil
Check valve provided on the downstream side of the separating means, and
In an oil-cooled screw compressor equipped with a pressure detector for detecting the pressure on the flow side, the temperature and humidity of the fluid sucked into the compressor body are detected.
Means for detecting the discharge temperature of the fluid discharged from the compressor body.
Suction from the discharge temperature detecting means and the means for detecting the temperature and humidity of the suction fluid
Based on the temperature and humidity and the discharge pressure from the discharge pressure detection means.
Means for calculating a drain occurrence threshold temperature can control said discharge pressure detecting means to vary the flow rate of the suction flow amount control means in accordance with the discharge pressure detected (U Shikiun
Rolling), the suction flow rate control means together <br/> said opening the communication means is no-load operation when closing the when the pressure of the check valve downstream reaches a first set pressure PH, the free control the pressure of the check valve downstream after load operation is closed together the communicating <br/> means open the reaches Then the suction flow rate control means to a second set pressure PL (I type operation), and the Mu control load operation or the load factor for predetermined time or longer stops the drive unit when the following predetermined range (P-type operation)
Prepared to operate by combining these U-type, I-type and P-type operations
And a capacity control means for controlling the capacity control means , the capacity control means at the time of starting or stopping the compressor.
When the state is changed to the starting state, at least the oil
Until the temperature in the separation means reaches the drain generation limit temperature.
Then, the U-type operation is forcibly performed without performing the I-type operation.
Cormorant oil-cooled screw compressor, characterized in that. 2. The temperature of the suction fluid according to claim 1,
Means for detecting humidity, the discharge pressure detection means, and the discharge
Output to the oil separation means based on the output from the output temperature detection means.
The operating time required to evaporate the amount of condensed water produced
And the condensed water is collected in the oil separation means based on the calculation result.
The compressor is controlled by the capacity control means so that it does not accumulate
An oil-cooled screw compressor characterized in that. 3. Starting of a screw compressor according to load and
For operating method of oil-cooled screw compressor that controls stop
Of the oil separation means provided on the discharge side of the screw compressor body.
Installed on the suction side of the screw compressor body depending on the pressure.
U-type operation step for controlling the digitized suction flow rate control means
And a check valve provided downstream of the oil separating means.
When the pressure on the downstream side reaches the first set pressure PH, the suction is performed.
The flow rate control means is closed and the pressure on the oil separation means side is reduced.
After releasing the power to the atmosphere and performing no-load operation, after this no-load operation
The pressure on the downstream side of the check valve reaches the second set pressure PL.
And opening said suction flow rate control means and said oil separation means
I-type operation that controls to close the line that opens the inside to the atmosphere
In the I step and the no load operation for a predetermined time
When the above continues or the load factor falls below the specified range
Stop the drive source that drives the screw compressor body
A P-type operating step for causing the fluid to be started by the U-type operating step at the time of startup and at least sucked into the screw compressor body.
The discharge side of the screw compressor body based on the temperature and humidity
The drain generation limit temperature TL is calculated, and the temperature in the oil separation means exceeds the drain generation limit temperature TL.
After that, move from the U-type operation step to the I-type operation step.
The operation of an oil-cooled screw compressor characterized by
How to turn. 4. The I-type operation according to claim 3,
Increase from the second set pressure PL to the first set pressure PH
When the time t1 reaches the set value t, the P-type operation is started.
Operation side of the oil-cooled screw compressor which is characterized that you
Law .