JP4546322B2 - Oil-cooled compressor - Google Patents

Description

  The present invention relates to an oil-cooled compressor provided with an air-cooled oil cooler.

Conventionally, an oil-cooled compressor provided with an air-cooled oil cooler is known (see, for example, Patent Documents 1 and 2).
JP-A-6-213186 JP 2003-206864 A

  In Patent Document 1, the oil temperature at the outlet of the air-cooled oil cooler (oil cooler) is detected, and based on this detected temperature, the air volume for cooling the air-cooled oil cooler is controlled, An oil-cooled compressor is disclosed in which condensation of moisture (drain) in oil is suppressed by keeping the temperature of oil entering at a set temperature.

  In Patent Document 2, the rotation speed of a motor that is a driving unit of a cooling fan of an air-cooled oil cooler is controlled based on the detected discharge temperature, and the discharge temperature is a temperature at which moisture in the discharge gas is condensed and deposited. An oil-cooled compressor that maintains a higher oil temperature is disclosed.

  The performance of the oil-cooled compressor improves as the oil supply temperature to the gas compression space decreases. However, if the oil supply temperature becomes too low, the discharge temperature of the compressed gas decreases too much, causing moisture in the gas to condense and deposit. The problem arises.

  The moisture in the gas is condensed and precipitated in the compressor on the discharge side where the gas is in a compressed state. In the case of the oil-cooled compressor described in Patent Document 1, the oil on the outlet side of the air-cooled oil cooler Even if the temperature is kept at the set temperature, the temperature cannot be controlled on the discharge side, and therefore there is a problem that the condensation and precipitation of moisture cannot be prevented. Furthermore, the amount of moisture condensed in the gas is a function of the pressure and temperature of the gas. The higher the pressure and the lower the temperature, the easier it is for the moisture to condense. Therefore, if it is intended to prevent moisture condensation only by temperature control, it is necessary to control the temperature assuming the discharge pressure, which is the highest gas pressure, and as a result, the oil supply temperature cannot be lowered. . In other words, it is important to maintain the discharge temperature appropriately. According to the control of the oil supply temperature alone, even if the oil supply temperature is less than the discharge temperature and the oil supply temperature is low enough to cause condensation of the water, the discharge temperature is The oil supply temperature is set to a temperature that can prevent condensation of water in the discharge gas, even though the discharge temperature may be more appropriate than the condensation temperature of the water in the discharge gas. As a result, there arises a problem that the compressor performance is lowered.

  In the invention described in Patent Document 2, the discharge temperature is appropriately set to avoid condensation of moisture in the discharge gas as compared with the oil-cooled compressor in which the motor rotation speed of the cooling fan of the air-cooled oil cooler is constant. Although there are effects such as management and energy saving, further energy saving is demanded.

  The present invention has been made to solve the above-mentioned problems and to meet the above-mentioned demands, and provides an oil-cooled compressor that prevents condensation and precipitation of moisture in the discharge gas and enables energy saving. It is something to try.

In order to solve the above problems, the first invention is:
Air-cooled air that is blown by a cooling fan from the oil reservoir of the oil separator / collector that separates and recovers the oil supplied to the gas compression space in the compressor body from the oil reservoir to a temperature control valve that has a variable flow diversion function. After passing through the oil cooler, or after passing through the bypass flow path without going through the air-cooled oil cooler, the oil flow path leading to the gas compression space;
A discharge temperature detector for detecting the gas discharge temperature;
A controller for controlling the motor of the cooling fan and the temperature control valve based on the discharge temperature detected by the discharge temperature detector, and adjusting the rotational speed of the motor and the bi-directional diversion ratio at the temperature control valve; ,
Optimum discharge temperature when the amount of moisture Ws contained in the gas sucked into the compressor main body and the amount of water Wd accompanying the gas discharged from the compressor main body in the saturated state become the same value in the controller T _do is set,
The controller
When the discharge temperature T _d is higher than the optimum discharge temperature T _do , the amount of oil passing through the air-cooled oil cooler to the gas compression space is increased and the temperature control valve is turned on. All of the oil that leads to the gas compression space through the air-cooled oil cooler,
When the discharge temperature T _d is lower than the optimum discharge temperature T _do , the amount of oil passing through the bypass flow path to the gas compression space is increased, and the discharge temperature T and the optimum discharge temperature T do. The larger the difference in the discharge temperature T _do, the greater the amount of oil that passes through the bypass flow path to the gas compression space.
It adjusts the two-way diversion ratio in the temperature control valve,
If the discharge temperature T _d is lower than the value higher than the optimum discharge temperature T _do by a temperature ΔT, the rotation speed of the motor is kept constant,
In addition higher than higher by the value above the discharge temperature T _d temperature than the optimum discharge temperature T _do [Delta] T, so that the discharge temperature T _d is higher by a value temperature [Delta] T from the optimum discharge temperature T _do, the rotation speed of the motor Is to adjust.

In the second aspect of the invention, in addition to the configuration of the first aspect of the invention, if the controller has a temperature higher than the optimum discharge temperature T _do if the discharge temperature T _d is higher than a value higher than the optimum discharge temperature T _do by a temperature ΔT. The rotational speed of the motor is adjusted by PID calculation using a value higher by ΔT as a target value of the discharge temperature T.

In the third aspect of the invention, in addition to the structure of the first or second aspect of the invention , the temperature ΔT is a constant introduced to prevent the chattering phenomenon from occurring in the controller.

  The oil-cooled compressor according to the present invention has effects such as prevention of moisture condensation and precipitation in the discharge gas, energy saving and noise suppression.

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows an oil-cooled compressor 1 according to the present invention. A compressor main body 11 of the oil-cooled compressor 1 is connected to a suction flow path 13 and a discharge flow path 14 with a motor 12 as a drive unit. Yes.

The suction flow path 13 is provided with a suction temperature detector 15 for detecting the temperature of the suction gas and a suction humidity detector 16 for detecting the humidity of the suction gas. The discharge flow path 14 is provided with an oil separation and recovery device 19 and Is provided. An oil separation element 21 is provided in the upper part of the oil separator / collector 19, and an oil reservoir 22 is provided in the lower part of the oil separator / collector 19.
A discharge temperature detector 17 that detects the temperature of the discharge gas and a discharge pressure detector 18 that detects the pressure of the discharge gas in the space between the oil separation element 21 and the oil reservoir 22 in the oil separation and recovery device 19 are provided. Is provided. In FIG. 1, the discharge temperature detector 17 and the discharge pressure detector 18 are disposed in a space portion between the oil separation element 21 and the oil reservoir 22 in the oil separation and recovery device 19. It may be arranged in a portion of the discharge flow path 14 other than the above.

  From the oil reservoir 22, the gas compression space in the compressor body 11 passes through the oil filter 23, the temperature control valve 24 and the air-cooled oil cooler 25, or passes through the oil filter 23, the temperature control valve 24 and the bypass passage 26. An oil passage 27 leading to an oil supply location such as a bearing / shaft seal extends. The temperature control valve 24 has a two-way variable diversion function. That is, the temperature control valve 24 passes through the air-cooled oil cooler 25 and communicates with the gas compression space in the compressor body 11 and the amount of oil communicated with the gas compression space through the bypass passage 26. Each of which can be adjusted by an arbitrary diversion ratio. The air-cooled oil cooler 25 includes a cooling fan 29 that is driven by a separate motor 28 independent of the motor 12.

  The suction temperature detector 15, the suction humidity detector 16, the discharge temperature detector 17 and the discharge pressure detector 18 are connected to the controller 31, and the suction temperature indicating the suction temperature, the suction humidity, the discharge temperature and the discharge pressure detected thereby. A signal, a suction humidity signal, a discharge temperature signal, and a discharge pressure signal are input to the controller 31. Further, the controller 31 is connected to the temperature control valve 24 and the motor 28, and the temperature of oil injected into the gas compression space is controlled based on the input suction temperature signal, suction humidity signal, discharge temperature signal and discharge pressure signal. The temperature control valve 24 and the motor 28 are controlled by the controller 31 so that the temperature is appropriate. That is, the two-way diversion ratio in the temperature control valve 24 is adjusted, and the rotation speed of the motor 28 is adjusted.

Next, an operation method of the oil-cooled compressor 1 having the above configuration will be described.
In the oil-cooled compressor 1 having the above-described configuration, the gas sucked into the compressor main body 11 from the suction flow path 13 is compressed in the gas compression space while receiving oil injection from the oil flow path 27, and is increased in pressure and temperature. Then, the oil is discharged into the discharge flow path 14 with the oil and guided to the oil separator / collector 19. In the oil separator / collector 19, the compressed gas and the oil are separated, and the compressed gas is sent out to the portion of the discharge passage 14 extending from the upper part of the oil separator / collector 19, and the oil is temporarily stored in the oil reservoir 22. The oil in the oil reservoir 22 flows into the oil flow path 27, passes through the oil filter 23, and is divided into the air-cooled oil cooler 25 side and the bypass flow path 26 side by the temperature control valve 24. The gas is then sent to the gas compression space, and then returned from the discharge flow path 14 to the oil separator / collector 19 and repeatedly circulated.

  By the way, in the oil separator / recovery unit 19, in order to prevent condensation of moisture from the compressed gas, it is necessary to maintain the compressed gas at a temperature at which the moisture is in a gas state, that is, water vapor.

When the suction gas of the compressor body 11 is air, for example, if the suction temperature is T _s (° C.) and the suction humidity is D _s (%), the moisture content W _s (kg) in the suction gas per 1 m ^3. / m ³ ) is expressed by the following equation.

Next, if the pressure of compressed air, that is, the discharge pressure is P _d (kg / cm ² G), and the temperature of the compressed air, that is, the discharge temperature is T _d (° C.), it is accompanied by saturated compressed air per 1 m ^3. The carried-out water amount W _d (kg / m ³ ) flowing out is expressed by the following equation.

The discharge temperature T _d when the suction gas is the atmosphere, the suction pressure P _s is 760 mmHg, the suction temperature T _s is 40 ° C., the suction humidity D _s is 75%, and the discharge pressure P _d is 7 kg / cm ² G. The calculation results regarding the relationship between (° C.) and the contained water content W _s (kg / m ³ ) and the carried-out water content W _d (kg / m ³ ) are as shown in FIG. The water content W _s and the curve II correspond to the carried water content W _d , respectively.

In order to prevent precipitation of condensed water from the compressed air in the discharge flow path 14 including the oil separator / recovery unit 19, the water content W _s ≦ the water content W _{d taken out} may be set. It can be seen that when the temperature is about 80 ° C. or higher, the magnitude relationship is reached, and condensed water from the compressed air does not precipitate in the discharge flow path 14.

In the oil-cooled compressor 1, in order to minimize energy consumption and suppress noise as much as possible, it is necessary to reduce the discharge temperature as much as possible while maintaining the relationship of the content water content W _s ≦ the export water content W _d. desirable. Therefore, the moisture content W _s = the moisture content W _{d taken} out, and the suction temperature T _s and the suction humidity indicated by the input signals to the controller 31 from the suction temperature detector 15, the suction humidity detector 16 and the discharge pressure detector 18, respectively. in the controller 31 on the basis of the D _s and the discharge pressure _{P d,} the optimum discharge temperature _{T do} is calculated. Incidentally, the suction gas is a atmosphere, 760 mmHg suction pressure P _s, 40 ° C. The inlet temperature T _s, the suction humidity D _s 75%, when the discharge pressure P _d was 7 kg / cm ² G, the above As shown in FIG. 2, the optimum discharge temperature T _do is about 80 ° C.

Subsequently, based on the difference between the optimum discharge temperature T _do and the detected discharge temperature T _d indicated by the temperature signal from the discharge temperature detector 17 to the controller 31, the controller 31 controls the motor 28 of the temperature control valve 24 and the cooling fan 29. Is controlled as follows.

When the optimum discharge temperature T _do + ΔT> the detected discharge temperature T _d , the motor 28 of the cooling fan 29 is kept at “a constant rotational speed”. At the same time, when the detected discharge temperature T _d is higher than the optimum discharge temperature T _do , the temperature adjustment valve 24 is controlled so that the amount of oil to the air-cooled oil cooler 25 side is increased as compared to the case where it is not. . If Kere lower than the detected discharge temperature T _d is the optimum discharge temperature T _do the contrary, the temperature regulating valve 24 is controlled so that the oil amount to the bypass passage 26 side increases than would otherwise be the case. That is, for example, if the detected discharge temperature T _d is higher than the optimum discharge temperature T _do , the temperature control valve 24 allows all of the oil that passes through the gas compression space via the temperature control valve 24 to pass through the air-cooled oil cooler 25. Is controlled. Then, if lower than the optimum discharge temperature T _do is detected discharge temperature T _d, the more difference between the detected discharge temperature T _d and the optimal discharge temperature T _do is large, the amount of oil communicating with said gas compression space through the bypass passage 26 The temperature control valve 24 is controlled to increase.

ΔT is a constant introduced to prevent the chattering phenomenon from occurring in the controller 31. For example, when the optimum discharge temperature T _do is about 80 ° C., ΔT is about 2 ° C.

The above "constant rotational speed" is a motor cooling air volume Q _{m_min} per unit time necessary for air-cooling the motor 12 so that the temperature of the coil in the motor 12 is maintained below the allowable maximum temperature in a constant case. In a fixed case, it is necessary for air-cooling the oil-cooled oil cooler 25 so that the discharge gas supplied from the discharge channel 14 on the secondary side of the oil separator / collector 19 is maintained below the maximum allowable temperature. This means the number of rotations of the motor 28 of the cooling fan 29 that can generate a larger air volume _out of the air volume Q _{a_min} for cooling the oil cooler per unit time.

Further, specifically, the above-mentioned fixed case of the air volume Q _{m_min} for cooling the motor is the minimum number of rotations allowed for the motor 12 due to the characteristics of the motor 12 as the drive unit of the oil-cooled compressor 1. And the case where the ambient temperature of the motor 12 is the highest temperature that the motor 12 can tolerate. The above-mentioned fixed case of the air flow rate Q _{a_min} for cooling the oil cooler is the minimum rotational speed allowed for the motor 12 due to the characteristics of the motor 12 as the drive unit of the oil-cooled compressor 1, and the motor 12 Is the maximum temperature that the motor 12 can tolerate, and the entire amount is led to the air-cooled oil cooler 25 side through the temperature control valve 24.

On the other hand, when the optimum discharge temperature T _do + ΔT ≦ the detected discharge temperature T _d , the rotational speed of the motor 28 of the cooling fan 29 is controlled so that the detected discharge temperature T _d becomes the optimum discharge temperature T _do + ΔT. The temperature control valve 24 is controlled so that the entire amount of oil from the oil reservoir 22 is guided to the air-cooled oil cooler 25.

In this case, the number of rotations of the motor 28 of the cooling fan 29 is equal to or higher than the “constant number of rotations”. Specifically, based on the difference between the optimum discharge temperature T _do and the discharge temperature T _d detected by the discharge temperature detector 17 provided in the oil separator / collector 19, the controller 31 performs PID calculation, and the motor 28 , And the motor 28 is controlled based on the calculation result.

For example, a PID arithmetic expression for calculating the rotation speed of the motor 28 is expressed as follows.

However, for use in the practice operation, the target value of the discharge temperature T _d is the optimum discharge temperature T _do not itself, because that is the optimum discharge temperature T _{do +} [Delta] T, the following equation in place of Equation (3) is Used for PID calculation.

As described above, in the oil-cooled compressor 1, even when the optimum discharge temperature T _do + ΔT> the detected discharge temperature T _d , the power of the cooling fan 29 can be maintained in the minimum necessary state, and the discharge temperature can be appropriately maintained. On the other hand, energy can be saved in avoiding condensation and precipitation of moisture, and noise can be suppressed.

Further, a description will be given based on FIG. FIG. 3 is a correlation diagram (line (A) and line (A)) between the detected discharge temperature _Td and the number of rotations of the motor 28 of the cooling fan 29. Further, the detected discharge temperature _Td and the oil filter 23 are air-cooled. It is a correlation diagram (line (c) and line (d)) with the opening degree of the valve port of the temperature control valve 24 connected to the oil cooler 25.

The vertical axis on the left side of FIG. 3 indicates the opening degree of the valve port of the temperature control valve 24 connected from the oil filter 23 to the air-cooled oil cooler 25. Where 100% is indicated on the shaft, the opening degree of the valve port is the maximum, that is, all of the oil communicating with the gas compression space of the compressor body 11 via the temperature control valve 24 is air-cooled. It shows that the oil cooler 25 has been passed. In other words, this FIG. 3 can also be said to be a correlation diagram between the detected discharge temperature _Td and the two-way diversion ratio in the temperature control valve 24. The vertical axis on the right side of FIG. 3 indicates the number of rotations of the motor 28 of the cooling fan 29 in units of percent, assuming that the highest number of rotations is 100%.

As described above, when the detected discharge temperature T _d is above the optimum discharge temperature T _{do +} [Delta] T, as detected discharge temperature T _d is optimum discharge temperature T _{do +} [Delta] T, speed control of the motor 28 of the cooling fan 29 Is done. As can be understood from the line (a) in FIG. 3, here, when the detected discharge temperature T _d is equal to or higher than the optimum discharge temperature T _do + ΔT, it is approximately proportional to the detected discharge temperature T _d . The motor 28 of the cooling fan 29 is increased or decreased. Further, as can be understood well from the line (A) in FIG. 3, if the detected discharge temperature _Td is lower than the optimum discharge temperature _Tdo + ΔT, the rotation speed of the motor 28 is fixed at a constant value of the lowest rotation speed. Rotational speed ”.

On the other hand, is higher than the optimum discharge temperature T _do is detected discharge temperature T _d, as can be seen better from the line of FIG. 3 (c), the valve port of the temperature control valve 24 leading from the oil filter 23 to the air-cooled cooler 25 The opening becomes 100%, and all of the oil that passes through the temperature adjustment valve 24 to the gas compression space of the compressor body 11 passes through the air-cooled oil cooler 25. Also, as can be understood better from the line of FIG. 3 (d), when the detected discharge temperature T _d is lower than the optimum discharge temperature T _do is enough difference between the detected discharge temperature T _d and the optimal discharge temperature T _do is greater The amount of oil that passes through the bypass passage 26 and the gas compression space of the compressor body 11 increases. That is, the lower the detected discharge temperature _{Td, the} greater the amount of oil that passes through the bypass passage 26 and the gas compression space of the compressor body 11 than through the air-cooled oil cooler 25. At the time of the detected discharge temperature Tmin in FIG. 3, the opening degree of the valve port of the temperature control valve 24 connected from the oil filter 23 to the air-cooled cooler 25 becomes 0%, and the compressor body 11 is connected via the temperature control valve 24. All of the oil communicating with the gas compression space passes through the bypass passage 26.

In the above example, the temperature control valve 24 and the motor 28 of the cooling fan 29 are controlled based on the detected discharge temperature _Td detected by the discharge temperature detector 17, but the controller 21 has the PID as described above. In the case of an arithmetic function, the above control may be performed based on the output Pa of the PID calculation (horizontal axis (e) in FIG. 3). When the time constant of the system is large or when the gain is small, it is better to give ΔT no width, and when the time constant is short and the gain is large, ΔT is wide. Better stability.

  In the present invention, the discharge temperature must be detected and the discharge temperature detector 17 is necessary, but the other suction temperature detector 15, the suction humidity detector 16, and the discharge pressure detector 18 are not necessarily required. Absent.

  For example, when the oil-cooled compressor 1 is operated assuming that the intake gas is the atmosphere and the humidity of the atmosphere is 100% of the maximum, the suction humidity detector 16 on the suction side of the compressor body 11 is not necessary. . In this case, the maximum atmospheric temperature is assumed to be 40 ° C, for example, and as long as the operation is performed under the suction condition of 40 ° C or less, the amount of moisture in the atmosphere is less than that at 40 ° C. Since precipitation of condensed water in the compressed air can be prevented, the suction temperature detector 15 on the suction side is also unnecessary. Further, if the intake pressure can be regarded as being constant as in the case where the intake gas is the atmosphere, the discharge pressure is uniquely determined by the specifications of the compressor body 11, and the discharge pressure detector 18 is not required.

It is a figure which shows the whole structure of the oil-cooled compressor which concerns on this invention. It is a figure which shows the relationship between the discharge temperature in the oil-cooled compressor shown in FIG. 1, each content amount of discharge gas, and each discharge gas. Detection discharge temperature T _d and the rotation speed of the motor of the cooling fan is a correlation diagram between the opening degree of the valve port of the temperature control valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Oil-cooled compressor 11 Compressor main body 12 Motor 13 Suction flow path 14 Discharge flow path 15 Suction temperature detector 16 Suction humidity detector 17 Discharge temperature detector 18 Discharge pressure detector 19 Oil separation recovery device 21 Oil separation element 22 Oil reservoir 23 Oil filter 24 Temperature control valve 25 Air-cooled oil cooler 26 Bypass passage 27 Oil passage 28 Motor 29 Cooling fan 31 Controller

Claims (3)

Air-cooled air that is blown by a cooling fan from the oil reservoir of the oil separator / collector that separates and recovers the oil supplied to the gas compression space in the compressor body from the oil reservoir to a temperature control valve that has a variable flow diversion function. After passing through the oil cooler, or after passing through the bypass flow path without going through the air-cooled oil cooler, the oil flow path leading to the gas compression space;
A discharge temperature detector for detecting the gas discharge temperature;
A controller for controlling the motor of the cooling fan and the temperature control valve based on the discharge temperature detected by the discharge temperature detector, and adjusting the rotational speed of the motor and the bi-directional diversion ratio at the temperature control valve; ,
Optimum discharge temperature when the amount of water Ws contained in the gas sucked by the compressor main body and the amount of water Wd accompanying the gas discharged from the compressor main body in a saturated state are equal to the controller. T _do is set,
The controller
When the discharge temperature T _d is higher than the optimum discharge temperature T _do , the amount of oil passing through the air-cooled oil cooler to the gas compression space is increased and the temperature control valve is turned on. All of the oil that leads to the gas compression space through the air-cooled oil cooler,
When the discharge temperature T _d is lower than the optimum discharge temperature T _do , the amount of oil passing through the bypass flow path to the gas compression space is increased, and the discharge temperature T and the optimum discharge temperature T do. The larger the difference in the discharge temperature T _do, the greater the amount of oil that passes through the bypass flow path to the gas compression space.
It adjusts the two-way diversion ratio in the temperature control valve,
If the discharge temperature T _d is lower than the value higher than the optimum discharge temperature T _do by a temperature ΔT, the rotation speed of the motor is kept constant,
In addition higher than higher by the value above the discharge temperature T _d is the temperature than the optimum discharge temperature T _do [Delta] T, so that the discharge temperature T _d is higher by a value temperature [Delta] T from the optimum discharge temperature T _do, the rotation speed of the motor An oil-cooled compressor characterized by adjusting the pressure. The controller
In addition higher than higher by the value above the discharge temperature T _d is the temperature ΔT than the optimum discharge temperature T _do, the at PID calculation a target value of the discharge temperature T as high a value temperature ΔT than the optimum discharge temperature T _do The oil-cooled compressor according to claim 1 , wherein the number of rotations of the motor is adjusted. 3. The oil-cooled compressor according to claim 1, wherein the temperature ΔT is a constant introduced to prevent a chattering phenomenon from occurring in the controller. 4.

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