JPH0429115Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an oil-free screw air compressor in which the casing of the compressor body is cooled by a cooling water circulation system.

(Prior art) An oil-free screw air compressor (hereinafter simply referred to as a screw compressor) rotates a pair of male and female screw rotors without contact while maintaining a small distance between them, sealing, lubricating, and It compresses air without injecting cooling oil and discharges clean compressed air that does not contain any oil.
In order to avoid contact between the male and female screw rotors or the casing due to thermal expansion caused by compression heat, a jacket section with a double structure of the casing is provided to limit the temperature (for example,
The casing is cooled by circulating cooling water (in this specification, water or antifreeze) at a temperature of

This type of screw compressor is roughly divided into an air-cooled type and a water-cooled type, depending on the means for cooling the casing and cooling the cooling water that has risen in temperature.

As shown in Fig. 5, an air-cooled screw compressor sucks air into a compressor body 1 through a filter 2, compresses it to a predetermined pressure, cools it with a pre-cooler 3 and an after-cooler 4, and then releases the compressed air. While the cooling water is pumped to the point of use, a cooling water circulation system consisting of a water pump 5, a radiator 6, and a fan 7 cools the casing of the compressor body 1, the precooler 3, and the aftercooler 4. Because it is air-cooled by radiator 6,
There is no need for the user to supply a cooling means such as a radiator. In addition, 8 is the compressor main body 1
This is the main motor that drives the.

On the other hand, in a water-cooled screw compressor, a cooling tower is used instead of the radiator 6. That is, the cooling water that has heated up by cooling the casing of the compressor main body 1, the precooler 3, and the aftercooler 4 is led to the cooling tower, where it is cooled by heat exchange with the air passing through the cooling tower, and then circulated. It drains water and provides new cooling water. This water-cooled screw compressor requires piping work between the screw compressor unit and the cooling tower on the user side, and the installation location is naturally limited, so the air-cooled type is preferable to the water-cooled type. There are many cases where

(Problem to be solved by the invention) However, in the air-cooled screw compressor with the radiator, when the outside temperature is, for example, 40°C, the temperature of the cooling water is only cooled to about 50°C, and the cooling water is not used. Since the temperature limit (for example, 32°C) is exceeded, the compressor cannot sufficiently cool the casing of the compressor, causing the rotor to come into contact with the compressor and making it impossible to operate.

The present invention was devised in view of these problems, and its purpose is to provide a screw compressor whose cooling water temperature is not affected by the outside air temperature and which can be operated even at high outside air temperatures.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides an oil-free screw air compressor equipped with a cooling water circulation system for cooling the compressor body. A heat pump cycle is formed including an expansion valve, an expansion valve, and an evaporator, and the cooling water of the cooling water circulation system is passed through the evaporator immediately before entering the compressor main body, and heat between the cooling water and the refrigerant of the heat pump cycle is formed. A cooling device was provided to cool the cooling water through exchange.

(Example) Next, an example of the present invention will be described with reference to the drawings.

Figure 1 shows the first screw compressor according to the present invention.
The conventional screw compressor shown in FIG. 3 is an embodiment except that a cooling device 11 is provided in place of the radiator 6 in the cooling water circulation system, and a fan 9 is provided to cool the aftercooler 4 and the main motor 8. are substantially the same, and corresponding parts are given the same numbers and their explanation will be omitted.

The cooling water circulation system supplies cooling water for cooling the compressor main body 1 and precooler 3 to a water tank 10 and a water pump 5.
It is configured to be circulated and reusable by a cooling device 11, which will be described later. That is, water pump 5
The cooling water pumped up from the water tank 10 is cooled down to a predetermined temperature (for example, 32°C) or lower in the cooling device 11, the casing is cooled in the first compressor body 1, and the compressed air is further cooled in the precooler 3. After cooling and raising its temperature, it returns to the water tank 10. Here, the reason why the aftercooler 4 is not cooled is to suppress the temperature rise of the cooling water as much as possible to lower the cooling capacity of the cooling device 11 and to reduce costs.

The cooling device 11 consists of a closed loop including a compressor 12, a condenser 13, a fan 14, an expansion valve 15, an evaporator 16, and an accumulator 17,
Forms a heat pump cycle that circulates refrigerant such as Freon. That is, the refrigerant compressed by the compressor 12 is cooled and condensed by the air from the fan 14 in the condenser 13, and is depressurized by the expansion valve 15.
The evaporator 16 absorbs the heat of evaporation from the cooling water just before it enters the compressor main body 1, cools the cooling water, and then returns it to the compressor 12 via the accumulator 17.

The screw compressor configured as described above cools the cooling water using the cooling device 11 that forms a heat pump cycle in the cooling water circulation system, so it is not affected by the outside temperature, and even if the outside temperature reaches 40 degrees Celsius, there is no temperature limit. (for example, 32°C) or lower, and can maintain the temperature at a constant temperature (for example, 20°C).

In the first embodiment, the aftercooler 4 may also be included in the cooling water circulation system. In this case, the cooling device 11 is installed in the conventional screw compressor as shown in FIG. It can be installed as a substitute, reducing costs.

FIG. 2 shows a second embodiment of the present invention, in which the cooling water circulation system is divided into a first cooling water circulation system a that cools the casing of the compressor main body 1, and a precooler 3.
and a second cooling water circulation system b for cooling the aftercooler 4. The first cooling water circulation system a includes a cooling water cooling device 11 comprising a heat pump cycle as in the first embodiment, and the second cooling water circulation system b cools the cooling water using a radiator 18 and a fan 19. It is something. In this embodiment, the second cooling water circulation system b including the radiator 18 is affected by the rise in outside temperature, and the first cooling water circulation system a is not affected by the outside temperature. Therefore,
Even if the outside temperature reaches 40°C and the cooling function of the radiator 18 decreases, the temperature of the compressed air exiting the aftercooler 4 will only rise, and the compressor body 1 will be able to operate without rotor contact. be. Furthermore, since the first cooling water circulation system a only needs to cool the casing of the compressor body 1, the cooling capacity of the cooling device 11 may be lower than that of the first embodiment, further reducing costs.

In the second embodiment, a fan may be used instead of the second cooling water circulation system b to air-cool the main motor 8 as well as the pre-cooler 3 and the after-cooler 4.

In both the first and second embodiments described above, the condenser 13
Although this invention is of an air-cooled type in which the condenser 13 is cooled by a fan 14, the present invention is not limited to this. It includes.

Among these, as shown in FIG. 3, the third embodiment is
The compressor main body 1, filter 2, precooler 3, aftercooler 4, and main motor 8 are provided with the same configuration as the first embodiment. Also, a compressor 12, a condenser 13, a dryer 20, an expansion valve 15, an evaporator 16
The cooling water of the first cooling water circulation system c, which is circulated by the water pump 21 in order to cool the compressor main body 1, is passed through the evaporator 16 of the cooling device 11 forming the heat pump cycle including the heat pump cycle. The cooling water is designed to be cooled by heat exchange with the refrigerant.

Furthermore, in this embodiment, the condenser 13 and the main motor 8 are water-cooled. That is, cooling water is sent from the water tank 10 into the condenser 13 and the main motor 8 by the water pump 5, and this cooling water is sent to the condenser 1.
A second cooling water circulation system d is provided which circulates the cooling water from the main motor 8 to the radiator 6 via the precooler 3, and from the radiator 6 back to the water tank 10. The cooling water coming out of the main motor 8 and the cooling water coming through the condenser 13 and pre-cooler 3 are combined and sent to the radiator 6 by the fan 19.
After being cooled down, the fuel is sent to the condenser 13 and the main motor 8 again to cool them.

In this way, in this embodiment, the condenser 13 is water-cooled and has a large heat transfer coefficient, so it is smaller than an air-cooled one.

Furthermore, while the first and second embodiments require two fans, one for cooling the radiator and the other for cooling the condenser, in this embodiment, only one cooling fan is needed by making the cooling fan a little larger. From this point of view as well, devices are becoming more compact.

Next, as shown in FIG. 4, the fourth embodiment
In the embodiment, cooling water was led directly from the water pump 5 to the main motor 8 and from the condenser 13 to the precooler 3, but instead of being led from the water pump 5 to the condenser 13.
In addition, instead of providing the second cooling water circulation system d of the third embodiment, the cooling water is guided from the water pump 5 through the evaporator 16, the compressor main body 1, and the precooler 3 to the radiator 6. A cooling water circulation system e is provided to guide the cooling water.

With this configuration, a cooling water pump dedicated to the compressor body 1, such as the water pump 21 in FIG. 3, is not required, and all the cooling water is passed through the radiator 18 for cooling. ,
When the outside temperature is low, the compressor 12 can be stopped to save power.

(Effects of the invention) As is clear from the above description, according to the invention, a heat pump cycle including a compressor, a condenser, an expansion valve, and an evaporator is formed, and the cooling water of the cooling water circulation system is transferred to the compressor. A cooling device is provided that cools the cooling water by passing it through the evaporator and exchanging heat with the refrigerant of the heat pump cycle just before entering the main body. For this reason, the most important compressor body is first cooled by the cooling water cooled by the heat pump cycle, and the cooling water can be adjusted to a constant temperature below a predetermined temperature regardless of the outside temperature.As a result, the compressor The discharge temperature of the main body can be kept constant and the amount of thermal expansion can be kept constant, making it possible to operate the screw compressor without contacting the rotor.

In particular, when the condenser and main motor are water-cooled as in the third embodiment, the device can be made smaller and lighter.

Furthermore, as in the fourth embodiment, the condenser and main motor are water-cooled, and the cooling water circulation system for the main motor and condenser is partially shared with the cooling water circulation system for the compressor body, thereby achieving the above effect. Another advantage is that power can be saved.

[Brief explanation of the drawing]

Figures 1 to 4 are cooling water system diagrams of screw compressors according to the first to fourth embodiments of the present invention;
The figure is a cooling water system diagram of a conventional screw compressor. 1...Compressor main body, 11...Cooling device, 12...
... Compressor, 13 ... Condenser, 15 ... Expansion valve, 1
6...Evaporator.

Claims (1)

[Claims for Utility Model Registration] (1) In an oil-free screw air compressor equipped with a cooling water circulation system for cooling the compressor body, a heat pump cycle including a compressor, a condenser, an expansion valve, and an evaporator is used. a cooling device configured to cool the cooling water by passing the cooling water of the cooling water circulation system into the evaporator immediately before entering the compressor body and cooling the cooling water by heat exchange with the refrigerant of the heat pump cycle. An oil-free screw air compressor. (2) The oil-free screw air compressor according to claim 1, wherein the condenser is of an air-cooled type. (3) The oil-free screw air compressor according to claim 1, wherein the condenser is water-cooled together with the drive device for the compressor main body.