JP7198116B2 - Multi-stage compressor - Google Patents

Description

The present invention relates to a multi-stage compressor having multiple compressor bodies.

In recent years, there is a strong demand for energy-saving compressors, and high efficiency and large air volume are becoming more and more important. A multi-stage compressor is one of the methods for achieving this. For example, Patent Literature 1 discloses a two-stage screw compressor.

The multistage compressor is connected between a front compressor body, a rear compressor body that further compresses the gas compressed by the front compressor body, a discharge side of the front compressor body, and a suction side of the rear compressor body. and an intermediate flow path.

JP 2017-166401 A

The set value of the pressure in the intermediate flow path (hereinafter referred to as the intermediate pressure) is the pressure ratio of the multi-stage compressor (more specifically, the ratio of the pressure on the discharge side of the main body of the final stage compressor and the pressure on the suction side of the main body of the first stage compressor). Determined according to the set value of . Structurally, the volume ratio of the main body of each stage compressor (more specifically, the ratio of the volume of the working chamber at the completion of suction to the volume of the working chamber at the start of discharge) is between the set value of the pressure ratio of the multi-stage compressor and the Design based on pressure setting.

By the way, the operating value of the pressure ratio of the multi-stage compressor changes depending on the operating conditions of the multi-stage compressor (more specifically, for example, the control value of the discharge side pressure of the main body of the final stage compressor), and accordingly the operating value of the intermediate pressure changes. In addition, the pressure difference between the main bodies of each stage compressor (more specifically, the difference between the pressure on the discharge side and the pressure on the suction side) changes, and accordingly the volumetric efficiency of the main body of each stage compressor changes. , the operating value of the intermediate pressure changes.

If the operating value of the intermediate pressure is higher than the set value, the pressure in the working chamber during the compression stroke of the pre-compressor main body becomes lower than the operating value of the intermediate pressure, resulting in insufficient compression. Therefore, it is preferable to design the volume ratio of each stage compressor main body so that the set value of the intermediate pressure is relatively high. However, when the intermediate pressure is designed to have a relatively high set value, the operating value of the intermediate pressure tends to be lower than the set value. If the operating value of the intermediate pressure is lower than the set value, the pressure in the working chamber during the compression stroke of the pre-compressor body becomes higher than the operating value of the intermediate pressure, resulting in excessive compression. That is, energy loss occurs and efficiency decreases.

SUMMARY OF THE INVENTION It is an object of the present invention to improve efficiency by adjusting the pressure in the working chamber in the compression stroke of the main body of the pre-compressor in accordance with the change in the intermediate pressure. It is.

In order to solve the above problems, the configurations described in the claims are applied. The present invention includes a plurality of means for solving the above-mentioned problems, and to give an example, a front compressor main body and a rear compressor main body for further compressing the gas compressed by the front compressor main body an intermediate flow path connected between the discharge side of the front-stage compressor body and the suction side of the rear-stage compressor body; and a discharge flow path connected to the discharge side of the rear-stage compressor body . In the multi-stage compressor, a front stage valve hole that communicates the intermediate passage with a working chamber for a compression stroke different from a working chamber for a discharge stroke of the front stage compressor main body; a pressure difference between the pressure in the working chamber in the compression stroke and the pressure in the intermediate flow path ; a post-stage valve hole connected between the flow paths, and a post-stage arranged in the post-stage valve hole and operated by a pressure difference between a pressure in the working chamber during the compression stroke of the post-compressor main body and a pressure in the discharge flow path. a release valve , wherein the pre-stage release valve blocks the pre-stage valve hole when the pressure in the working chamber in the compression stroke of the pre-compressor main body is lower than the pressure in the intermediate flow path, and the pre-stage compressor When the pressure in the compression stroke working chamber of the main body is higher than the pressure in the intermediate flow path, the front stage valve hole is brought into communication, and the rear release valve opens the pressure in the compression stroke working chamber of the rear compressor body. The latter valve hole is closed when the pressure is lower than the pressure in the discharge passage, and the latter valve hole is closed when the pressure in the working chamber of the compression stroke of the latter compressor body is higher than the pressure in the discharge passage. are in communication.

According to the present invention, efficiency can be improved by adjusting the pressure in the working chamber in the compression stroke of the main body of the pre-compressor according to the change in the intermediate pressure.

Problems, configurations, and effects other than those described above will be clarified by the following description.

1 is a vertical sectional view showing a schematic structure of a two-stage screw compressor according to a first embodiment of the present invention; FIG. FIG. 2 is a horizontal cross-sectional view showing the structure of the main body of the pre-compressor in the first embodiment of the present invention; FIG. 3 is a radial cross-sectional view showing the structure of the main body of the pre-compressor in the first embodiment of the present invention; It is a horizontal sectional view showing the structure of the front stage compressor main body in the 1st modification of this invention. FIG. 5 is a vertical cross-sectional view showing a schematic structure of a two-stage screw compressor according to a second embodiment of the present invention; FIG. 5 is a vertical cross-sectional view showing a schematic structure of a two-stage scroll compressor in a second modified example of the present invention; FIG. 5 is a vertical cross-sectional view showing a schematic structure of a two-stage scroll compressor in a third modified example of the invention; FIG. 11 is a cross-sectional view showing the structure of a release valve in a fourth modified example of the invention;

Taking a two-stage screw compressor as an example to which the present invention is applied, a first embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG.

FIG. 1 is a vertical sectional view showing a schematic structure of a two-stage screw compressor in this embodiment. FIG. 2 is a horizontal sectional view showing the structure of the main body of the pre-compressor in this embodiment. FIG. 3 is a radial cross-sectional view showing the structure of the main body of the pre-compressor in this embodiment. In addition, in FIG. 2, for the sake of convenience, illustration of the retainer of the pre-stage release valve is omitted.

The two-stage screw compressor of this embodiment includes a front compressor main body 1, a rear compressor main body 2 for further compressing gas (specifically, air or refrigerant, etc.) compressed by the front compressor main body 1, An intermediate flow path 3 connected between the discharge side of the compressor main body 1 and the suction side of the post-compressor main body 2 and a discharge flow path 4 connected to the discharge side of the post-compressor main body 2 are provided. Although not shown, the intermediate flow path 3 is provided with an intercooler, and the discharge flow path 4 is provided with an aftercooler.

The pre-compressor main body 1 accommodates a male rotor 5A and a female rotor 6A (screw rotors) having parallel rotation axes and meshing with each other, and a male rotor 5A and a female rotor 6A. and a casing 7A forming a female rotor side working chamber.

The male rotor 5A is rotatably supported by a suction side bearing 8A and a discharge side bearing 9A, and the female rotor 6A is rotatably supported by a suction side bearing 8B and a discharge side bearing 9B. One of the male rotor 5A and the female rotor 6A is rotated by a first motor (not shown), and the other is rotated by the meshing of the male rotor 5A and the female rotor 6A. However, gears may be used to synchronously rotate the male rotor 5A and the female rotor 6A.

As the male rotor 5A and the female rotor 6A rotate, the male rotor side working chamber and the female rotor side working chamber move from one axial side (left side in FIGS. 1 and 2) to the other side (right side in FIGS. 1 and 2). ), their volumes change. As a result, a suction stroke, a compression stroke, and a discharge stroke are sequentially performed. More specifically, in the suction stroke, the male rotor side working chamber X1 and the female rotor side working chamber Y1 increase in volume and suck gas from the suction port 10A. The volumes of the male rotor side working chamber X2 and the female rotor side working chamber Y2 in the compression stroke are reduced to compress the gas. The male rotor side working chamber X3 and the female rotor side working chamber Y3 in the discharge stroke discharge the compressed gas from the discharge port 11A.

The post-compressor main body 2 accommodates a male rotor 5B and a female rotor 6B (only 5B is shown) which are meshed with each other and whose rotating shafts are parallel, and the male rotor 5B and the female rotor 6B. It has a casing 7B that forms a working chamber and a female rotor side working chamber.

The male rotor 5B is rotatably supported by a suction side bearing and a discharge side bearing (not shown), and the female rotor 6B is rotatably supported by a suction side bearing and a discharge side bearing (not shown). One of the male rotor 5B and the female rotor 6B is rotated by a second motor (not shown), and the other is rotated by the meshing of the male rotor 5B and the female rotor 6B. However, gears may be used to synchronously rotate the male rotor 5B and the female rotor 6B.

As the male rotor 5B and the female rotor 6B rotate, the male rotor side working chamber and the female rotor side working chamber move from one side (left side in FIG. 1) to the other side (right side in FIG. 1) in the axial direction. Its volume changes. As a result, a suction stroke, a compression stroke, and a discharge stroke are sequentially performed. More specifically, the male rotor side working chamber X4 and the female rotor side working chamber (not shown) in the suction stroke increase in volume and suck gas from the suction port 10B. The volumes of the male rotor side working chamber X5 and the female rotor side working chamber (not shown) in the compression stroke are reduced to compress the gas. The male rotor side working chamber X6 and the female rotor side working chamber (not shown) in the discharge stroke discharge compressed gas from the discharge port 11B.

Here, as one of the features of the present embodiment, the pressure ratio of the two-stage screw compressor (more specifically, the ratio of the pressure on the discharge side of the main body 2 of the post-stage compressor and the pressure on the side of the suction side of the main body 1 of the pre-compressor) is In order to consider changes in the operating value of the pressure in the intermediate flow path 3 (hereinafter referred to as intermediate pressure) accompanying changes in the operating value, the volume ratio of the pre-compressor main body 1 is adjusted so that the set value of the intermediate pressure is relatively high. is set. As a result, insufficient compression of the pre-compressor main body 1 is avoided. The details are described below.

Assuming that there is no pressure loss or gas leakage in the intermediate passage 3, and that the intake air temperature of the post-compressor main body 2 is the same as the intake air temperature of the pre-compressor main body 1, the power is minimized. The pressure ratio Pi/Ps1 of the pre-compressor body 1 is given by the following equation (1). Ps1 is the pressure on the suction side of the main body 1 of the pre-compressor, Pi is the intermediate pressure, and Pd2 is the pressure on the side of the discharge of the main body 2 of the post-compressor.

However, in practice, due to insufficient cooling in the intermediate passage 3, the intake air temperature of the post-compressor main body 2 does not become the same as the intake air temperature of the pre-compressor main body 1. In addition, when the operating value of the pressure ratio of the two-stage screw compressor changes, the pressure difference in the main body of each stage compressor (more specifically, the difference between the discharge side pressure and the suction side pressure) also changes. The volumetric efficiency of the stage compressor body changes. Then, as shown by the following equation (2), the pressure ratio Pi/Ps1 of the front compressor body 1 is the ratio of the stroke volume Vth2 of the rear compressor body 2 and the stroke volume Vth1 of the front compressor body 1, The ratio between the rotation speed N2 of the compressor main body 2 and the rotation speed N1 of the pre-compressor main body 1, the ratio between the volumetric efficiency ηv2 of the post-compressor main body 2 and the volumetric efficiency ηv1 of the pre-compressor main body 1, and the post-compressor main body 2 and the suction side temperature Ts1 of the main body 1 of the pre-compressor. That is, the actual pressure ratio Pi/Ps1 is higher than the ideal value calculated using equation (1).

For example, assume that the operating value of the pressure ratio of a two-stage screw compressor varies in the range of 8-9. Using formula (1), when the pressure ratio of the two-stage screw compressor is Pd2/Ps1=9, the pressure ratio of the pre-compressor main body 1 is Pi/Ps1=3 (that is, the suction of the pre-compressor main body 1 If the side pressure Ps1=0.1 MPa, then the intermediate pressure Pi=0.3 MPa). Although the volume ratio of the pre-compressor main body 1 corresponding to the pressure ratio Pi/Ps1=3 (ideal value) is 2.2, since the actual pressure ratio Pi/Ps1 is higher than the ideal value, the pre-compressor main body The volume ratio of 1 is set to 2.3. As a result, even if the operating value of the intermediate pressure changes with changes in the operating value of the pressure ratio of the two-stage screw compressor, the pressure in the working chamber in the compression stroke of the pre-compressor main body 1 is lower than the operating value of the intermediate pressure. not high. Therefore, under-compression does not occur.

Also, assume that the operating value of the pressure ratio of the two-stage screw compressor varies in the range of 8 to 14, for example. Using formula (1), when the pressure ratio Pd2/Ps1 of the two-stage screw compressor is 14, the pressure ratio Pi/Ps1 of the pre-compressor body 1 is 3.74 (i.e., the pre-compressor body 1 , the intermediate pressure Pi=0.374 MPa). Although the volume ratio of the pre-compressor body 1 corresponding to the pressure ratio Pi/Ps1=3.74 (ideal value) is 2.6, the actual pressure ratio Pi/Ps1 is higher than the ideal value. The volume ratio of the machine body 1 is set to be 2.8. As a result, even if the operating value of the intermediate pressure changes with changes in the operating value of the pressure ratio of the two-stage screw compressor, the pressure in the working chamber in the compression stroke of the pre-compressor main body 1 is lower than the operating value of the intermediate pressure. not high. Therefore, under-compression does not occur. According to the consideration described above, the volume ratio of the pre-compressor main body 1 is 2.3 or more and 2.8 or less.

As described above, the volume ratio of the pre-compressor main body 1 is set so that the set value of the intermediate pressure is relatively high. Then, if the operating value of the pressure ratio of the two-stage screw compressor becomes relatively low, and accordingly the operating value of the intermediate pressure becomes relatively low, the pre-compressor main body 1 is overcompressed (specifically, the compression stroke The pressure in the working chamber of is higher than the intermediate pressure). Therefore, as another feature of the present embodiment, the pre-compressor body 1 includes a pre-stage valve hole 12A communicating between the male rotor side working chamber X2 in the compression stroke and the intermediate flow path 3, and a pre-stage valve hole 12A arranged in the pre-stage valve hole 12A. It has a release valve 13A, a front stage valve hole 12B communicating between the female rotor side working chamber Y2 in the compression stroke and the intermediate flow path 3, and a front stage release valve 13B arranged in the front stage valve hole 12B.

As shown in FIG. 2, the pre-stage valve hole 12A is formed to extend in a direction perpendicular to the axial direction of the male rotor 5A. Similarly, the front stage valve hole 12B is formed to extend in a direction perpendicular to the axial direction of the female rotor 6A.

As shown in FIG. 3, the valve seats (step surfaces) of the front stage valve holes 12A and 12B are formed so as to extend in a direction parallel to a straight line connecting the center of the male rotor 5A and the center of the female rotor 6A. ing. However, in order to reduce the volume on the working chamber side of the seating surfaces of the front stage valve holes 12A and 12B, the valve seats of the front stage valve holes 12A and 12B are positioned so that they You can tilt it.

The pre-stage release valve 13A has a valve body 14A arranged on the valve seat of the pre-stage valve hole 12A, a retainer 15A that holds the valve body 14A, and bolts 16A that fix the valve body 14A and the retainer 15A. When the pressure in the male rotor side working chamber X2 in the compression stroke is lower than the intermediate pressure, the valve body 14A does not deform, so the front stage valve hole 12A is closed. On the other hand, when the pressure in the male rotor side working chamber X2 in the compression stroke is higher than the intermediate pressure, the valve body 14A is deformed, so that the front stage valve hole 12A is brought into the communicating state. As a result, the pressure in the male rotor side working chamber X2 in the compression stroke can be reduced to the intermediate pressure.

Similarly, the pre-stage release valve 13B has a valve body 14B arranged on the valve seat of the pre-stage valve hole 12B, a retainer 15B that restrains the valve body 14B, and bolts 16B that fix the valve body 14B and the retainer 15B. . When the pressure in the female rotor side working chamber Y2 in the compression stroke is lower than the intermediate pressure, the valve body 14B is not deformed, so the front stage valve hole 12B is closed. On the other hand, when the pressure in the female rotor side working chamber Y2 in the compression stroke is higher than the intermediate pressure, the valve body 14B is deformed, so that the front stage valve hole 12B is brought into a communicating state. As a result, the pressure in the female rotor side working chamber Y2 in the compression stroke can be reduced to the intermediate pressure.

Therefore, in this embodiment, it is possible to improve the efficiency by adjusting the pressure in the working chamber in the compression stroke of the precompressor main body 1 according to the change in the intermediate pressure. Further, in the present embodiment, the front release valves 13A and 13B are actuated by the differential pressure between the pressure in the working chamber during the compression stroke of the front compressor main body 1 and the intermediate pressure. Therefore, it is suitable for an oil-free compressor (specifically, no oil is supplied to the working chamber).

In the first embodiment, the front valve hole 12A is formed to extend in a direction perpendicular to the axial direction of the male rotor 5A, and the front valve hole 12B is formed to extend in the axial direction of the female rotor 6A. Although the case where it is formed so as to extend in a vertical direction has been described as an example, it is not limited to this and can be modified without departing from the gist of the present invention. For example, as in the modification shown in FIG. 4, the front valve hole 12A is formed along the extending direction of the tooth spaces of the male rotor 5A, and the front valve hole 12B is formed along the extending direction of the tooth spaces of the female rotor 6A. may be formed along In this modified example, compared to the first embodiment, it is possible to reduce the time during which the adjacent male rotor side working chambers in the compression stroke are communicated with each other via the pre-stage valve hole 12A. In addition, compared to the first embodiment, it is possible to reduce the time during which the adjacent female rotor side working chambers in the compression stroke are communicated with each other via the pre-stage valve hole 12B. Therefore, inhibition of compression operation can be suppressed.

A second embodiment of the present invention will be described with reference to FIG. In addition, in this embodiment, the same code|symbol is attached|subjected to the part equivalent to 1st Embodiment, and description is abbreviate|omitted suitably.

FIG. 5 is a vertical sectional view showing the structure of the two-stage screw compressor in this embodiment.

In this embodiment, the rear compressor main body 2 includes a rear valve hole 17A that communicates the male rotor side working chamber X5 in the compression stroke with the discharge passage 4, a rear release valve 18A that is arranged in the rear valve hole 17A, a compression A post-stage valve hole 17B (not shown) that communicates the female rotor-side working chamber of the stroke with the discharge passage 4, and a post-stage release valve 18B (not shown) arranged in the post-stage valve hole 17B. Since the rear valve holes 17A and 17B have the same structure as the front valve holes 12A and 12B described above, the description thereof will be omitted.

The post-release valve 18A has the same structure as the above-described pre-release valve 13A. That is, it has a valve disc arranged on the valve seat of the rear stage valve hole 17A, a retainer for holding the valve disc, and bolts for fixing the valve disc and the retainer. When the pressure in the male rotor side working chamber X5 in the compression stroke is lower than the pressure in the discharge passage 4, the valve body does not deform, so that the rear stage valve hole 17A is closed. On the other hand, when the pressure in the male rotor side working chamber X5 in the compression stroke is higher than the pressure in the discharge passage 4, the valve body deforms, so that the rear stage valve hole 17A is brought into communication. As a result, the pressure in the male rotor-side working chamber X5 during the compression stroke can be reduced to the pressure in the discharge passage 4 .

Similarly, the post-release valve 18B has the same structure as the pre-release valve 13B described above. That is, it has a valve body arranged on the valve seat of the rear stage valve hole 17B, a retainer for holding the valve body, and bolts for fixing the valve body and the retainer. When the pressure in the working chamber on the female rotor side in the compression stroke is lower than the pressure in the discharge passage 4, the valve body does not deform, so that the rear stage valve hole 17B is closed. On the other hand, when the pressure in the working chamber on the female rotor side in the compression stroke is higher than the pressure in the discharge passage 4, the valve element deforms, so that the rear stage valve hole 17B is brought into communication. As a result, the pressure in the female rotor side working chamber during the compression stroke can be reduced to the pressure in the discharge passage 4 .

Therefore, in this embodiment, in addition to the same effect as the first embodiment, the pressure in the working chamber in the compression stroke of the post-compressor main body 2 is adjusted in accordance with the change in the pressure in the discharge passage 4 to improve the efficiency. You can get the effect of improving.

In the first and second embodiments, the main body of each stage compressor has two screw rotors. is possible. For example, each stage compressor body may have one or three screw rotors.

In addition, in the first and second embodiments, the two-stage screw compressor was described as an example of application of the present invention, but the present invention is not limited to this, and may be a two-stage scroll compressor. Such a modified example will be described with reference to FIG. 6 or FIG. In addition, in this modified example, the same code|symbol is attached|subjected to the part equivalent to 1st or 2nd embodiment, and description is abbreviate|omitted suitably.

In the modification shown in FIG. 6, the pre-compressor main body 1A includes a fixed scroll member 20A having a spiral wrap and an orbiting scroll member having a spiral wrap that meshes with the wrap of the fixed scroll member 20A to form a working chamber. 21A, a crankshaft 22A engaged with the orbiting scroll member 21A, a casing 23A provided below the fixed scroll member 20A and housing the orbiting scroll member 21A, and above (discharge side) the fixed scroll member 20A. and a provided cover 24A.

The orbiting scroll member 21A is rotatably supported by an Oldham ring (not shown) without rotating, and the crankshaft 22A is rotatably supported by bearings (not shown). The crankshaft 22A is rotated by a motor (not shown) to orbit the orbiting scroll member 21A.

As the orbiting scroll member 21A orbits, the volume of the working chamber changes while moving from the outside to the inside in the radial direction. As a result, a suction stroke, a compression stroke, and a discharge stroke are sequentially performed. Specifically, in the suction stroke, the working chamber increases in volume and sucks gas from the suction port 25A. The volume of the working chamber Z1 in the compression stroke is reduced to compress the gas. The working chamber Z2 in the discharge stroke discharges the compressed gas from the discharge port 26A.

The post-compressor main body 2A includes a fixed scroll member 20B having a spiral wrap, an orbiting scroll member 21B having a spiral wrap that meshes with the wrap of the fixed scroll member 20B to form a working chamber, and an orbiting scroll member 21B. It comprises an engaged crankshaft 22B, a casing 23B provided below the fixed scroll member 20B to accommodate the orbiting scroll member 21B, and a cover 24B provided above (discharge side) the fixed scroll member 20B. .

The orbiting scroll member 21B is rotatably supported by an Oldham ring (not shown) without rotating, and the crankshaft 22B is rotatably supported by bearings (not shown). The crankshaft 22B is rotated by a motor (not shown) to orbit the orbiting scroll member 21B.

As the orbiting scroll member 21B orbits, the volume of the working chamber changes while moving from the outside to the inside in the radial direction. As a result, a suction stroke, a compression stroke, and a discharge stroke are sequentially performed. More specifically, the working chamber in the suction stroke increases in volume and sucks gas from the suction port 25B. The volume of the working chamber Z3 in the compression stroke is reduced to compress the gas. The working chamber Z4 in the discharge stroke discharges the compressed gas from the discharge port 26B.

In this modification, as in the first and second embodiments, the volume ratio of the pre-compressor main body 1A is set so that the set value of the intermediate pressure is relatively high. The front-stage compressor body 1A includes a front-stage valve hole 12 that communicates the working chamber Z1 in the compression stroke with the intermediate flow path 3, and a front-stage release valve 13 arranged in the front-stage valve hole 12. Then, when the pressure in the working chamber Z1 in the compression stroke is lower than the intermediate pressure, the front release valve 13 closes the front valve hole 12 . On the other hand, when the pressure in the working chamber Z1 in the compression stroke is higher than the intermediate pressure, the front release valve 13 brings the front valve hole 12 into communication. As a result, the pressure in the working chamber Z1 during the compression stroke can be reduced to the intermediate pressure. Therefore, as in the first and second embodiments, efficiency can be improved by adjusting the pressure in the working chamber in the compression stroke of the front compressor main body 1A according to the change in the intermediate pressure.

In the modification shown in FIG. 7, as in the second embodiment, the rear compressor main body 2A is arranged in the rear valve hole 17 communicating between the working chamber Z3 in the compression stroke and the discharge passage 4, and the rear valve hole 17. and a post-stage release valve 18 . When the pressure in the working chamber Z3 during the compression stroke is lower than the pressure in the discharge passage 4, the rear release valve 18 closes the rear valve hole 17. As shown in FIG. On the other hand, when the pressure in the working chamber Z3 in the compression stroke is higher than the pressure in the discharge passage 4, the rear release valve 18 brings the rear valve hole 17 into communication. As a result, the pressure in the working chamber Z3 during the compression stroke can be reduced to the pressure in the discharge passage 4. FIG. Therefore, as in the second embodiment, the pressure in the working chamber in the compression stroke of the post-compressor main body 2A can be adjusted in accordance with the change in the pressure in the discharge passage 4 to improve the efficiency.

In the embodiments and modifications described above, the front release valve (or the rear release valve) has a valve body that deforms due to the pressure difference between the pressure in the working chamber during the compression stroke and the intermediate pressure (or the pressure in the discharge passage). Although the case has been described as an example, it is not limited to this, and modifications are possible without departing from the gist of the present invention. Such a modified example will be described with reference to FIG. Although FIG. 8 shows the front release valve 13 as a representative, other front release valves or rear release valves may be used.

In this modification, the front release valve (or the rear release valve) includes a valve body 30, a spring 31 that biases the valve body 30 toward the working chamber side (lower side in FIG. 8), and the valve body 30 and the spring 31. It has a retainer 32 as a restraint and bolts 34 for fixing the retainer 32 . When the pressure in the working chamber in the compression stroke is lower than the sum of the intermediate pressure (or the pressure in the discharge passage) and the biasing force of the spring 31, the valve element 30 is positioned on the working chamber side and the front stage valve hole (or the rear stage valve hole) is closed. valve hole) is closed and the pressure in the working chamber in the compression stroke is higher than the sum of the pressure in the intermediate flow path (or the pressure in the discharge flow path) and the biasing force of the spring 31, the valve body 30 is positioned on the side of the intermediate flow path ( or the discharge channel side) to bring the front stage valve hole (or the rear stage valve hole) into a communicating state. Even in such a modified example, the same effect as described above can be obtained.

In the above description, the present invention is applied to a two-stage compressor having two compressor bodies. It's okay. A three-stage compressor, which is one of the specific examples, will be described in detail.

The three-stage compressor includes a first-stage compressor body, a second-stage compressor body that further compresses the gas compressed by the first-stage compressor body, and a second-stage compressor body that further compresses the gas compressed by the second-stage compressor body. a third-stage compressor body to be compressed; a first intermediate flow path connecting the discharge side of the first-stage compressor body and the suction side of the second-stage compressor body; A second intermediate flow path connecting the suction side of the three-stage compressor main body and a discharge flow path connected to the discharge side of the third-stage compressor main body are provided.

A first stage valve hole (previous stage valve hole) that communicates the first intermediate passage with a working chamber for a compression stroke that is different from the working chamber for a discharge stroke of the first stage compressor main body, and is arranged in the first stage valve hole. A first stage release valve (pre-stage release valve) may be provided. In addition, a second stage valve hole (previous stage valve hole) that communicates the second intermediate passage with a working chamber for a compression stroke that is different from the working chamber for a discharge stroke of the second stage compressor main body, and is arranged in the second stage valve hole. A second stage release valve (previous stage release valve) may be provided. Also, a third stage valve hole (rear stage valve hole) that communicates a discharge passage with a working chamber for a compression stroke different from the working chamber for a discharge stroke of the third stage compressor main body, and A third stage release valve (later stage release valve) may be provided.

1, 1A front compressor main body, 2, 2A rear compressor main body, 3 intermediate flow path, 4 discharge flow path, 5A, 5B male rotor (screw rotor), 6A, 6B female rotor (screw rotor) ), 7A, 7B ... casing, 12, 12A, 12B ... front stage valve hole, 13, 13A, 13B ... front stage release valve, 17, 17A, 17B ... rear stage valve hole, 18, 18A, 18B ... rear stage release valve

Claims (3)

a front compressor body, a rear compressor body for further compressing the gas compressed by the front compressor body, and an intermediate connected between the discharge side of the front compressor body and the suction side of the rear compressor body. A multi-stage compressor comprising a flow path and a discharge flow path connected to the discharge side of the post-compressor main body ,
a pre-stage valve hole that communicates the intermediate passage with a working chamber for a compression stroke that is different from a working chamber for a discharge stroke of the pre-stage compressor main body;
a pre-stage release valve disposed in the pre-stage valve hole and operated by a differential pressure between the pressure in the working chamber of the compression stroke of the pre-compressor main body and the pressure in the intermediate passage ;
a post-stage valve hole connected between a compression stroke working chamber different from the discharge stroke working chamber of the post-compressor main body and the discharge passage;
a post-stage release valve disposed in the post-stage valve hole and operated by a differential pressure between a pressure in the working chamber of the compression stroke of the post-compressor main body and a pressure in the discharge passage ;
The pre-stage release valve shuts off the pre-stage valve hole when the pressure in the working chamber during the compression stroke of the pre-compressor main body is lower than the pressure in the intermediate flow passage, and the pre-stage release valve closes the pre-stage valve hole during the compression stroke of the pre-compressor main body. when the pressure in the working chamber is higher than the pressure in the intermediate passage, the pre-stage valve hole is brought into communication ;
The latter release valve shuts off the latter valve hole when the pressure in the working chamber of the latter compressor main body during the compression stroke is lower than the pressure of the discharge flow path, thereby closing the latter compressor main body during the compression stroke. A multi-stage compressor , wherein the rear stage valve hole is brought into communication when the pressure in the working chamber is higher than the pressure in the discharge passage . In the multistage compressor according to claim 1,
The front-stage compressor main body includes a screw rotor and a casing housing the screw rotor and forming a working chamber in a tooth space thereof,
A multi-stage compressor, wherein the pre-stage valve hole is formed along an extending direction of tooth grooves of the screw rotor. In the multistage compressor according to claim 1 or 2 ,
A multi-stage compressor, wherein the volume ratio of the front-stage compressor main body is 2.3 or more and 2.8 or less.

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