Title of Invention

LOW-NOISE LIQUID COOLING TYPE COMPRESSOR

Abstract

According to a low-noise liquid cooling type compressor of the present invention, in a liquid cooling type screw compressor having a pair of male and female screw rotors meshing with each other, a liquid injection hole is provided in an intake flow path for taking in gas supplied to the screw rotors, and liquid is injected from the above liquid injection hole to the intake flow path. By such a configuration, even when rotation speed of the compressor is changed and frequency of generated noise is changed, a noise reducing effect in various operation states can be obtained and mainly amplitude of noise escaped to the exterior through the intake flow path of the compressor, particularly pulsatile amplitude on the intake side of a compressor main body is lowered so as to suppress a noise value.

Full Text

TITLE OF THE INVENTION LOW-NOISE LIQUID COOLING TYPE COMPRESSOR BACKGROUND OF THE INVENTION (FIELD OF THE INVENTION) The present invention relates to a liquid cooling type screw compressor having a pair of male and female screw rotors meshing with each other, and a lownoise liquid cooling type compressor for mainly lowering amplitude of noise escaped to the exterior through an intake flow path of the compressor, particularly pulsatile amplitude on the intake side of a compressor main body so as to suppress a noise value. (DESCRIPTION OF THE RELATED ART) A temperature of a screw rotor (hereinafter, also referred to as a rotor) of a screw compressor is raised as a fluid is compressed. Therefore, a cooling mechanism for cooling the screw rotor is essential. As such a cooling mechanism, in general, an external cooling device is conventionally used for supplying the cooling air and cooling liquid or the like. Firstly, a description will be given to a general cooling mechanism of an oil cooling type screw compressor in which cooling oil (hereinafter, also simply referred to as oil) is used as the cooling liquid with reference to Fig. 8. Fig. 8 is a sectional view of a main body of a conventional and general oil cooling type screw compressor. The above oil cooling type screw compressor 31 is provided with a pair of male and female screw rotors 32 meshing with each other within a rotor casing 30. The above screw rotors 32 are rotatably supported by a bearing portion 33 on the intake side and a bearing portion 34 on the discharge side. Shaft sealing portions 35 and 36 are respectively provided between the above bearing portions 33 and 34 and the screw rotors 32. Oil injection holes 38, 39 and 40 for injecting the oil to oil injection points such as the bearing portions 33 and 34, the shaft sealing portions 35 and 36 and a rotor chamber 37 serving as a gas compression space part within the screw compressor 31 are provided. Then, gas taken in from an intake port 41 of the screw compressor 31 is compressed while receiving oil injection from the oil injection holes 38, 39 and 40 and discharged from a discharge port 42 as the compressed air together with the oil. The discharged compressed gas and the discharged oil are separated from each other in an oil separation and collection vessel (not shown) and the compressed gas is fed to a discharge flow path 43. Here, the oil injected to the rotor chamber 37 works for cooling the gas compression part, sealing and lubricating between the screw rotors 32 and between the screw rotors 32 and an inner wall part of the rotor casing 30. Next, a description will be given to noise measure techniques according to conventional examples of a compressor with reference to Figs. 9 and 10. Fig. 9 is a system diagram showing one example of a two-step oil free compressor according to the conventional example, and Fig. 10 is a sectional view showing one example of a silencer of a compressor according to the conventional example. A noise measure of the compressor according to the conventional example includes, although not shown, a screw compressor with package in which a heavy compressor main body serving as an oscillation source and an electric motor are supported rigidly to a floor surface by a mount and a supporting pillar so as to suppress oscillation amplitude and prevent oscillation propagation to a base plate of the package and a cover (refer to Japanese Patent Laid-Open No. Hei7-20836l). However, the above conventional example is to suppress propagation of oscillation generated by the compressor main body and the electric motor. Therefore, suppression of noise itself generated by the compressor main body is not taken into consideration. Particularly, since the compressor has to take in the outside air, it is difficult to prevent a pulsatile sound from the intake port from easily leaking out to the exterior. Next, in the two-step oil free compressor according to the conventional example, as shown in Fig. 9, since a plurality of discharge pipes are provided over a main part thereof, for example since a discharge pipe of a lower compressor 50 is divided into two discharge pipes 51 and 52, transmission loss is increased and a noise value caused by pulsation of discharge pressure of the compressor is reduced (refer to Japanese Patent Laid-Open No. Hei7-133774). The above compressor exercises an effect of reducing the noise caused by the pulsation of the discharge pressure to a determined frequency component of 2 kHz or more. However, when screw rotation speed is changed, frequency of the generated noise is changed, and it is not possible to obtain the noise reducing effect in all the operation states. In the silencer of the compressor according to another conventional example, as shown in Fig. 10, a first silencer 54 communicating with a discharge hole of the compressor and a second silencer 55 communicating with the first silencer 54 through a connection piping 53 are provided and a chamber 56 is provided in the connection piping 53 so that columnar resonant frequency generated between the silencers in a multiple silencer structure avoids basic frequency of pressure pulsation and hence a decrease in a silencing effect is prevented (Japanese Patent Laid-Open No. Hei6-10875). As well as the above conventional example, the present conventional example exercises an effect of reducing the noise of the pulsation of the discharged pressure in a determined frequency band. However, when the rotation speed of the compressor is changed, the frequency of the generated noise is changed, and it is not possible to obtain the noise reducing effect in all the operation states. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a low-noise liquid cooling type compressor capable of obtaining a noise reducing effect in various operation states even when rotation speed of the compressor is changed and frequency of generated noise is changed, for mainly lowering amplitude of noise escaped to the exterior through an intake flow path of the compressor, particularly pulsatile amplitude on the intake side of a compressor main body so as to suppress a noise value. In order to achieve the above object, a liquid cooling type compressor of the present invention is a screw compressor comprising a pair of male and female screw rotors meshing with each other, wherein a liquid injection hole is provided in an intake flow path for taking in gas supplied to the screw rotors, and liquid is injected from the liquid injection hole to the intake flow path. According to the liquid cooling type compressor of the above configuration, in the liquid cooling type screw compressor having a pair of the male and female screw rotors meshing with each other, the liquid injection hole is provided in the intake flow path for taking in the gas supplied to the screw rotors, and the liquid is injected from the liquid injection hole to the intake flow path. Thereby, the liquid injected to the liquid injection hole works as a heavy object in the intake flow path of the compressor and mainly lowers the amplitude of the noise escaped to the exterior through the intake flow path of the compressor, particularly oscillation amplitude of a pulsatile sound on the intake side of the compressor so as to reduce the noise value. In the above liquid cooling type compressor, the liquid may be capable of being injected to a rotor chamber in which the screw rotors are housed, liquid separation and collection means for separating the liquid from the compressed air and collecting the separated liquid may be provided in a discharge flow path for discharging the compressed gas, and a liquid injection line for injecting the liquid separated and collected by the liquid separation and collection means may be connected to the liquid injection hole. By such a configuration, without requiring different liquid supply means, the cooling liquid used for cooling and lubricating the screw rotors and sealing between the rotors can be utilized as liquid for reducing the noise value. Alternatively, in the above liquid cooling type compressor, sound pressure detection means for detecting a pulsatile sound on the intake side may be provided in the intake flow path, flow rate adjustment means for controlling a flow rate of the liquid may be provided in the liquid injection line, and control means for receiving a sound pressure signal detected by the sound pressure detection means and controlling the flow rate adjustment means on the basis of the sound pressure signal may be provided. By such a configuration, a proper amount of liquid can be supplied for a pulsatile sound in the intake flow path, that is, for rotation speed of the compressor and the most effective noise reducing effect can be realized. Alternatively, in the above liquid cooling type compressor, an inverter may be provided in a drive motor driving the screw rotors, flow rate adjustment means for controlling a flow rate of the liquid may be provided in the liquid injection line, and control means for receiving a frequency signal commanded to the drive motor by the inverter and controlling the flow rate adjustment means on the basis of the frequency signal may be provided. By such a configuration, a proper amount of liquid can be supplied for a pulsatile sound in the intake flow path, that is, for rotation speed of the compressor and the most effective noise reducing effect can be realized. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a system diagram for explaining a low-noise liquid cooling type compressor according to a first embodiment of the present invention; Fig. 2 is a system diagram for explaining a low-noise liquid cooling type compressor according to a second embodiment of the present invention," Fig. 3 is one instance of a pulsatile sound detected by a sound pressure sensor according to a comparative example of the present invention; Fig. 4 is comparative data of a sound pressure level at screw rotation speed of 1000 r/min according to the present example; Fig. 5 is comparative data of a sound pressure level at screw rotation speed of 2500 r/min according to the present example; Fig. 6 is comparative data of a sound pressure level at screw rotation speed of 4000 r/min according to the present example; Fig. 7 is comparative data of a sound pressure level at screw rotation speed of 5410 r/min according to the present example; Fig. 8 is a sectional view of a main body of a conventional and general oil cooling type screw compressor; Fig. 9 is a system diagram showing one example of a two-step oil free compressor according to a conventional example; and Fig. 10 is a sectional view showing one example of a silencer of a compressor according to a conventional example. DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a description will be given to a liquid cooling type screw compressor according to a first embodiment of the present invention with reference to Fig. 1. Fig. 1 is a system diagram for explaining the low-noise liquid cooling type compressor according to the first embodiment of the present invention. With regard to the low-noise liquid cooling type compressor according to the first embodiment of the present invention, a description will be given to a lownoise oil cooling type screw compressor in which cooling oil is used as cooling liquid as an example of the embodiment. The above low-noise oil cooling type screw compressor is provided with a compressor main body 1 in which a pair of male and female screw rotors 2a and 2b meshing with each other are rotatably housed in a rotor chamber 4 formed inside a rotor casing 3. While an intake flow path 5 is connected to an intake port la of the compressor main body 1, the one end side of a discharge flow path 6 is connected to a discharge port lb thereof. Then, only the male rotor 2a which is one of a pair of the male and female screw rotors 2a and 2b forming the compressor main body 1 is connected to a drive shaft 7 of a drive motor M. By rotating the screw rotors 2 a and 2b by the above drive motor M, gas supplied from the intake flow path 5 is taken in from the intake port la of the compressor main body 1, compressed and discharged from the discharge port lb to the discharge flow path 6 as a high pressure fluid. The drive motor M is housed in a motor housing inside a motor casing 8. The above motor casing 8 is integrally combined with the rotor casing 3. Then, the drive motor M is formed by a stator (not shown) fixed to an inner surface of the motor casing 8 and a rotator 7a rotating around the drive shaft 7 and rotation thereof is controlled by a predetermined frequency signal transmitted from control means 21a incorporated in a controller 21 to an inverter 22. The above drive motor M transmits rotation force of the drive shaft 7 axially supported by an intake side bearing 9a and a discharge side bearing 9b to the screw rotors 2a and 2b of the compressor main body 1. Meanwhile, the intake flow path 5 is provided with an intake adjusting valve 5a for adjusting a flow rate of the gas passing through the intake flow path 5. A valve opening degree thereof is controlled by the control means 21a in the controller 21. An oil separation and collection vessel (oil separation and collection means) 10 is interposed on the discharge flow path 6. An oil separation element 10a is provided inside the oil separation and collection vessel 10. Since little oil is mixed in high pressure gas flowing into the above oil separation and collection vessel 10, the above oil is caught by the oil separation element 10a provided inside the oil separation and collection vessel 10. The oil caught by the oil separation element 10a is dribbled by self-weight, and an oil puddle 10b is formed on the lower side inside the oil separation and collection vessel 10. The oil collected in the oil puddle 10b as mentioned above is circulated from the oil separation and collection vessel 10 through an oil circulation path 11 communicating with the compressor main body 1 by an oil pump (not shown). An oil cooler 12 is interposed on the above oil circulation path 11, and the passing oil is cooled down by controlling a temperature by the control means 21a in the controller 21. Then, the oil cooled down by the oil cooler 12 is supplied to points in need of oil supply through oil injection flow paths provided in the rotor casing 3. Such oil injection flow paths are formed by an oil injection flow path to the intake side bearing (and a shaft sealing portion) 9a, an oil injection flow path to the discharge side bearing (and a shaft sealing portion) 9b, and an oil injection flow path to compression space formed by the screw rotors 2a and 2b and the rotor casing 3. Further, an oil injection hole 20 is provided in the intake flow path 5 for taking in the gas supplied to the rotor chamber 4 and formed so as to inject the cooling oil into the above oil injection hole 20. That is, an oil injection line 11a for injecting the oil which is separated and collected by the oil separation and collection vessel 10 and cooled down by the oil cooler 12 nterposed on the oil circulation path 11 is connected to the oil injection hole 10 provided in the intake flow path 5, and formed so as to inject the cooling )il into the intake flow path 5. The oil injection hole 20 is preferably arranged in the intake flow path 5 which is placed between the intake adjusting valve 5a provided in an intake part of the intake flow path 5 and she intake port la of the compressor main body 1. As mentioned above, by injecting the cooling liquid from the oil injection hole 20 to the intake flow path 5, the cooling liquid injected from the oil injection hole 20 works as a heavy object in the intake flow path 5 of the compressor and mainly lowers amplitude of noise escaped to the exterior (for example, the exterior of package (not shown) in which constituent elements of the compressor are housed) through the intake flow path 5 of the compressor, particularly oscillation amplitude of a pulsatile sound on the intake side of the compressor so as to reduce a noise value. A part of the cooling oil (cooling liquid) used for cooling, lubricating, sealing or the like of the screw rotors 2a and 2b can be utilized as liquid for reducing the noise value. Next, a description will be given to a low-noise liquid cooling type compressor according to a second embodiment of the present invention with reference to Fig. 2. Fig. 2 is a system diagram for explaining the low-noise liquid cooling type compressor according to the second embodiment of the present invention. It should be noted that different points of the second embodiment of the present invention from the first embodiment are existence of flow rate adjustment means for controlling a flow rate of the oil and a configuration of the controller, and other points are all the same. Therefore, a description will be given only to the configuration of the flow rate adjustment means and the controller. In the first embodiment of the present invention, the oil injection line Ua for injecting the oil cooled down by the oil cooler 12 is connected to the oil injection hole 20 provided in the intake flow path 5, and formed so as to inject the cooling oil into the intake flow path 5, while the control means 21a for controlling the temperature of the oil cooler 12 and the rotation of the drive motor M is incorporated in the controller 21. Meanwhile, in the second embodiment of the present invention, a flow rate adjusting valve 24 for adjusting an oil injecting amount of the cooling oil is interposed on the oil injection line 11a and a sound pressure sensor (sound pressure detection means) 23 for detecting the pulsatile sound on the intake side is attached to the intake flow path 5. Then, a sound pressure signal detected by the sound pressure sensor 23 is transmitted to the controller 21. On the basis of the above sound pressure signal, a valve opening degree of the flow rate adjusting valve 24 can be controlled by the control means 21a incorporated in the controller 21. That is, memory means 21b and arithmetic means 21c are incorporated in the controller 21 in addition to the control means 21a. Meanwhile, a microphone or the like is preferably used as the sound pressure sensor 23. The pulsatile sound (or a frequency spectrum or a sound pressure level thereof) on the intake side of the compressor detected by such a sound pressure sensor 23 is changed in accordance with a change in rotation speed of the compressor main body 1. In the memory means 21b in the controller 21, reference data of the sound pressure level in a predetermined frequency band in accordance with the change in the rotation speed of the compressor main body 1 (or an integration value in a predetermined frequency band of a power spectrum) is preliminarily stored and reference data of a proper oil injecting amount and a proper opening degree of the flow rate adjusting valve 24 in accordance with the sound pressure level is preliminarily stored. Then, since the sound pressure signal is transmitted from the sound pressure sensor 23, arithmetic processing such as the Fast Fourier Transformation (FFT) is performed by the internal arithmetic means 21c, and the controller 21 calculates data of the frequency spectrum (horizontal axis^ frequency (Hz), vertical axis: sound pressure level (dB)). The sound pressure level (the integration value of the power spectrum) in a predetermined frequency band such as 125 Hz to 4 kHz is calculated by the arithmetic means 21c on the basis of the above data. The above calculated value is compared with the reference data preliminarily stored in the memory means 21b so as to determine the proper opening degree of the flow rate adjusting valve 24. The valve opening degree of the above flow rate adjusting valve 24 is adjusted and controlled by the control means 21a. Instead of the sound pressure signal transmitted from the sound pressure sensor 23, a frequency signal corresponding to rotation speed of the drive motor M or the screw rotors 2 a and 2b may be received from the inverter 22 driving the drive motor M so that the valve opening degree of the flow rate adjusting valve 24 is adjusted and controlled on the basis of the above frequency signal. As mentioned above, in the liquid cooling type screw compressor having' a pair of the male and female screw rotors 2a and 2b meshing with each other, the oil injection hole 20 is provided in the intake flow path 5 for taking in the gas supplied to the above screw rotors 2a and 2b, and the cooling liquid is injected from the above oil injection hole 20 to the intake flow path 5. Thereby, the cooling liquid injected from the oil injection hole 20 works as the heavy object in the intake flow path 5 of the compressor and mainly lowers the amplitude of the noise escaped to the exterior through the intake flow path of the compressor, particularly the oscillation amplitude of the pulsatile sound on the intake side of the compressor so as to reduce the noise value. The sound pressure sensor (sound pressure detection means) 23 for detecting the pulsatile sound on the intake side is provided in the intake flow path 5, or the inverter 22 is provided in the drive motor M driving the screw rotors 2a and 2b, and further the flow rate adjusting valve (flow rate adjustment means) 24 for controlling a flow rate of the cooling liquid is provided in the oil injection line 11a respectively. The control means 21a capable of receiving the sound pressure signal detected by the sound pressure sensor 23 or the frequency signal commanded to the drive motor M by the inverter 22 and controlling the flow rate adjusting valve 24 on the basis of the above sound pressure signal or the above frequency signal is provided. Therefore, a proper amount of the cooling liquid can be supplied for a pulsatile sound in the intake flow path 5, that is, for rotation speed of the compressor and the most effective noise reducing effect can be realized. [Example] Next, a description will be given to the present example in which a conventional oil cooling type screw compressor is modified so as to correspond to the first embodiment of the present invention and the oil is injected from the oil injection hole provided in the intake flow path and a comparative example in which the oil is not injected with reference to Figs. 3, 4 to 7. Fig. 3 is one instance of the pulsatile sound detected by the sound pressure sensor provided in the intake flow path according to the comparative example of the present invention. Fig. 4 is comparative data of a sound pressure level at screw rotation speed of 1000 r/min according to the present example. Fig. 5 is comparative data of a sound pressure level at screw rotation speed of 2500 r/min according to the present example. Fig. 6 is comparative data of a sound pressure level at screw rotation speed of 4000 r/min according to the present example. Fig. 7 is comparative data of a sound pressure level at screw rotation speed of 5410 r/min according to the present example. In the comparative example in which the oil is not injected from the oil injection hole 20 provided in the intake flow path 5, a time waveform of the pulsatile sound in the intake flow path 5 detected by the sound pressure sensor 23 is a waveform in a saw-tooth shape shown in Fig. 3 and a cause of generating pulsation due to a change in volume. With regard to the sound pressure level of such a pulsatile sound, as shown in Figs. 4 to 7, the sound pressure level in the present example in which the oil is injected from the oil injection hole is lower than the comparative example in which the oil is not injected in all the frequency except for a frequency band from 250 to 500 Hz of 1/1 octave frequency at screw rotation speed band from 4000 r/min to 5410 r/min. That is, it is found that by injecting the cooling oil from the oil injection hole 20 provided in the intake flow path 5, the cooling oil injected to the oil injection hole 20 works as the heavy object in the intake flow path 5 of the compressor and lowers the oscillation amplitude of the pulsatile sound on the intake side of the compressor so as to reduce the noise value. It should be noted that in the embodiments of the present invention, the description is given to an instance of the oil cooling type screw compressor in which the cooling oil is used as the cooling liquid. However, the liquid used for injection to the intake flow path of the liquid cooling type screw compressor according to the present invention is not limited to the oil. The present invention can also be applied to a screw compressor in which a refrigerant (in the case of a heat pump and a freezing machine) or cooling water is used. The present invention can also be applied to the heat pump and the freezing machine for example. We claim: 1. A liquid cooling type screw compressor, comprising: a pair of male and female screw rotors meshing with each other, wherein a liquid injection hole is provided in an intake flow path for taking in gas supplied to said screw rotors, and liquid is injected from the liquid injection hole to the intake flow path. 2. The liquid cooling type compressor according to claim 1, wherein the liquid is capable of being injected to a rotor chamber in which said screw rotors are housed, liquid separation and collection means for separating the liquid from compressed gas and collecting the separated liquid is provided in a discharge flow path for discharging the compressed gas, and a liquid injection line for injecting the liquid separated and collected by the liquid separation and collection means is connected to the liquid injection hole. 3. The low-noise liquid cooling type compressor according to claim 1 or 2, wherein sound pressure detection means for detecting a pulsatile sound on the intake side is provided in the intake flow path, flow rate adjustment means for controlling a flow rate of the liquid is provided in the liquid injection line, and control means for receiving a sound pressure signal detected by the sound pressure detection means and controlling the flow rate adjustment means on the basis of the sound pressure signal is provided. 4. The liquid cooling type compressor according to claim 1 or 2, wherein an inverter is provided in a drive motor driving said screw rotors, flow rate adjustment means for controlling a flow rate of the liquid is provided in the liquid injection hne, and control means for receiving a frequency signal commanded to the drive motor by the inverter and controlling the flow rate adjustment means on the basis of the frequency signal is provided.

Documents:

2894-CHE-2008 AMENDED CLAIMS 20-03-2014.pdf

2894-CHE-2008 EXAMINATION REPORT REPLY RECEIVED. 20-03-2014.pdf

2894-CHE-2008 FORM-1 20-03-2014.pdf

2894-CHE-2008 FORM-3 20-03-2014.pdf

2894-CHE-2008 OTHERS 20-03-2014.pdf

2894-che-2008 abstract.pdf

2894-che-2008 claims.pdf

2894-che-2008 correspondance others.pdf

2894-che-2008 correspondence-others.pdf

2894-che-2008 description (complete).pdf

2894-che-2008 drawings.pdf

2894-che-2008 form-1.pdf

2894-che-2008 form-18.pdf

2894-che-2008 form-26.pdf

2894-che-2008 form-3.pdf

2894-che-2008 form-5.pdf

2894-che-2008 others.pdf

2894-CHE-2008-Petition for Annexure.pdf

2894-CHE-2008-Petition for POR.pdf