WO2024075275A1

WO2024075275A1 - Screw compressor

Info

Publication number: WO2024075275A1
Application number: PCT/JP2022/037604
Authority: WO
Inventors: 駿岡田; 雅章上川; 雅浩神田
Original assignee: 三菱電機株式会社
Priority date: 2022-10-07
Filing date: 2022-10-07
Publication date: 2024-04-11

Abstract

This screw compressor comprises a casing, a screw shaft, a screw rotor, a gate rotor, a slide valve, and a bearing housing. The slide valve has a valve body part that faces the screw rotor, and a guide part that has a sliding surface that faces the outer circumferential surface of the bearing housing. A groove section is formed along the sliding direction on one among the sliding surface of the guide part and the outer circumferential surface of the bearing housing, and a protruding section that fits into the groove section is formed on the other. The slide valve is configured to be able to slide in the direction of the rotation axis of the screw rotor while the protruding section is fitted into the groove section.

Description

Screw Compressor

This disclosure relates to a screw compressor.

As disclosed in Patent Document 1, a screw compressor is known as one type of positive displacement compressor, and is used as a component of a refrigerant circuit built into a refrigerator or the like. One known screw compressor is a single screw compressor in which, for example, one screw rotor with a spiral tooth groove and two gate rotors with multiple gate rotor teeth that fit into the tooth grooves of the screw rotor are housed inside a casing. In a single screw compressor, multiple compression chambers are formed by mutually meshing and engaging the tooth grooves of the screw rotor and the gate rotor teeth of the gate rotor. One end of the screw rotor in the rotation axis direction is the refrigerant intake side, and the other end is the refrigerant discharge side. The inside of the casing is partitioned into a low pressure space provided on the suction side of the compression chamber, and a high pressure space provided on the discharge side of the compression chamber.

The screw rotor is fixed to a screw shaft that is rotated by a drive unit provided inside the casing. Both ends of the screw shaft are rotatably supported by bearing housings having bearings inside. The screw shaft is also connected to the drive unit on the refrigerant suction side. When the screw rotor is rotated via the screw shaft that is rotated by the drive unit, the refrigerant in the low pressure space is sucked into the compression chamber and compressed, and the refrigerant compressed in the compression chamber is discharged into the high pressure space.

Some screw compressors are equipped with a pair of slide valves that are arranged in slide grooves formed on the inner cylindrical surface of the casing and are slidably movable in the direction of the rotation axis of the screw rotor. The slide valves slide in the direction of the rotation axis of the screw rotor to change the discharge start position of the high-pressure gas refrigerant compressed in the compression chamber, thereby changing the discharge opening timing and changing the internal volume ratio. This slide valve has a valve body portion that faces the screw rotor, and a guide portion that forms a sliding surface facing the outer circumferential surface of the bearing housing. A gap is provided between the sliding surface of the guide portion and the outer circumferential surface of the bearing housing to drive the slide valve in the direction of the rotation axis of the screw rotor. Also, a gap is provided between the valve body portion of the slide valve and the outer circumferential surface of the screw rotor to allow the screw rotor to be driven to rotate.

However, in a screw compressor, when the screw rotor and slide valve thermally expand due to an increase in the temperature of the refrigerant gas compressed in the compression chamber, the gap between the guide part of the slide valve and the outer peripheral surface of the bearing housing, and the gap between the valve body part of the slide valve and the outer peripheral surface of the screw rotor may decrease. In addition, in a screw compressor, the screw rotor may rotate in the reverse direction due to the high and low pressure difference inside the casing after operation is stopped. When the screw rotor rotates in the reverse direction, the valve body part of the slide valve may rotate circumferentially due to the influence of changes in the internal pressure of the compression chamber, etc., and the slide valve may come into contact with the screw rotor, resulting in seizure, etc. Furthermore, in a screw compressor, the valve body part of the slide valve may rotate circumferentially due to changes in pressure acting from the compression chamber even during normal operation.

In view of this, in Patent Document 1, a protrusion is provided on the guide portion of the slide valve that protrudes relatively further in the circumferential direction than the valve body portion, and when the slide valve rotates in the circumferential direction, the protrusion comes into contact with the bearing holder, thus preventing contact between the slide valve and the screw rotor.

JP 2013-60877 A

However, in Patent Document 1, the protrusions on the guide portion of the slide valve are provided on the surface facing the bearing holder, so the gap between the slide valve and the bearing holder required to drive the slide valve in the axial direction is small. In this case, there is a concern that the gap between the slide valve and the bearing holder may be further reduced due to thermal expansion of the slide valve or the bearing holder, causing the slide valve to come into contact with the bearing holder, deteriorating the drivability of the slide valve in the axial direction.

This disclosure has been made to solve the above problems, and aims to provide a screw compressor that can prevent contact between the slide valve and the screw rotor.

The screw compressor according to the present disclosure includes a casing forming an outer shell, a screw shaft disposed within the casing and driven to rotate, a screw rotor having a spiral tooth groove on its outer circumferential surface and fixed to the screw shaft, a gate rotor having a plurality of gate rotor teeth that fit into the tooth grooves of the screw rotor and forming a compression chamber together with the casing and the screw rotor, a slide valve configured to slide freely in the direction of the rotation axis of the screw rotor, and a bearing housing having a bearing therein that rotatably supports an end of the screw shaft, the slide valve having a valve body portion facing the screw rotor and a guide portion having a sliding surface facing the outer circumferential surface of the bearing housing, one of the sliding surface of the guide portion and the outer circumferential surface of the bearing housing has a groove portion formed along the sliding direction, and the other has a protrusion portion that fits into the groove portion, and the slide valve is configured to slide freely in the direction of the rotation axis of the screw rotor with the protrusion portion fitted into the groove portion.

According to the present disclosure, a groove formed on one of the guide portion of the slide valve and the outer circumferential surface of the bearing housing fits into a protrusion formed on the other, thereby restricting circumferential rotation of the slide valve. Therefore, even if the pressure acting on the valve body portion of the slide valve facing the outer circumferential surface of the screw rotor fluctuates, the slide valve will not rotate circumferentially, and contact between the slide valve and the screw rotor can be suppressed.

1 is a vertical cross-sectional view showing an internal structure of a screw compressor according to a first embodiment. 2 is an enlarged cross-sectional view showing a main part taken along line AA in FIG. 1. 2 is an enlarged cross-sectional view showing a main part taken along line BB in FIG. 1. FIG. 2 is a perspective view showing a slide valve of the screw compressor according to the first embodiment. 3 is a side view showing a guide portion of a slide valve of the screw compressor according to the first embodiment. FIG. 6 is a cross-sectional view taken along the line CC shown in FIG. 5. FIG. 2 is a perspective view showing a bearing housing of the screw compressor according to the first embodiment. 4 is an enlarged cross-sectional view showing a main part of a first modified example of the screw compressor according to the first embodiment. FIG. FIG. 11 is a perspective view showing a bearing housing of a second modified example of the screw compressor according to the first embodiment. 4 is an enlarged cross-sectional view showing a main part of a second modified example of the screw compressor according to the first embodiment. FIG. FIG. 4 is an explanatory diagram showing the operation of the compression section of the screw compressor according to the first embodiment, illustrating a suction stroke. FIG. 4 is an explanatory diagram showing the operation of the compression section of the screw compressor according to the first embodiment, illustrating a compression process. FIG. 4 is an explanatory diagram showing the operation of the compression section of the screw compressor according to the first embodiment, illustrating a discharge process. FIG. 11 is a perspective view showing a bearing housing of a screw compressor according to a second embodiment. FIG. 11 is a perspective view showing a modified example of the bearing housing of the screw compressor according to the second embodiment.

Below, an embodiment of the present disclosure will be described with reference to the drawings. Note that in each drawing, the same or corresponding parts are given the same reference numerals, and their description will be omitted or simplified as appropriate. Furthermore, the shape, size, arrangement, etc. of the configurations shown in each drawing may be changed as appropriate.

Embodiment 1.
FIG 1 is a vertical cross-sectional view showing an internal structure of a screw compressor 100 according to a first embodiment. FIG 2 is an enlarged cross-sectional view showing a main part along the line A-A shown in FIG 1. FIG 3 is an enlarged cross-sectional view showing a main part along the line B-B shown in FIG 1. FIG 4 is a perspective view showing a slide valve 7 of the screw compressor 100 according to the first embodiment. FIG 5 is a side view showing a guide portion 71 of the slide valve 7 of the screw compressor 100 according to the first embodiment. FIG 6 is a cross-sectional view along the line C-C shown in FIG 5. FIG 7 is a perspective view showing a bearing housing 8 of the screw compressor 100 according to the first embodiment.

In the screw compressor 100 according to the first embodiment, a single-stage single-screw compressor will be described as an example. As shown in FIG. 1, the screw compressor 100 has a cylindrical casing 1 that forms the outer shell, and a compression section 2 and a drive section 3 that are provided inside the casing 1. The inside of the casing 1 is partitioned into a low-pressure space 10 and a high-pressure space 11.

As shown in FIG. 1, the compression section 2 includes a screw shaft 4, a screw rotor 5, a pair of gate rotors 6, a gate rotor support (not shown), a pair of slide valves 7, and a bearing housing 8.

The screw shaft 4 is disposed within the casing 1 and is driven to rotate by the drive unit 3. The screw shaft 4 extends in the axial direction of the casing 1, with one shaft end rotatably supported by a bearing 8a disposed opposite the discharge side of the screw rotor 5, and the other shaft end rotatably supported by a bearing (not shown) disposed on the suction side of the refrigerant. The screw shaft 4 is also connected to the drive unit 3 on the suction side of the refrigerant.

As shown in Figures 1 and 2, the screw rotor 5 has a plurality of helical tooth grooves 5a on the outer circumferential surface of a cylinder. The screw rotor 5 is fixed to the screw shaft 4 and rotates together with the screw shaft 4 which is rotated by the drive unit 3. As shown in Figure 1, the low pressure space 10 side of the screw rotor 5 in the direction of the rotation shaft is the refrigerant intake side, and the high pressure space 11 side is the refrigerant discharge side. In addition, a predetermined gap 75 is formed between the screw rotor 5 and the slide valve 7. This is to prevent contact when assembling the screw compressor 100, for example, or to prevent contact between the slide valve 7 and the screw rotor 5 during operation of the screw compressor 100, which may cause seizure or the like.

The gate rotor 6 has a number of gate rotor teeth 6a formed on its outer periphery that fit into the tooth grooves 5a of the screw rotor 5, and is arranged to radially sandwich the screw rotor 5 as shown in FIG. 1. The compression section 2 has a compression chamber 20 formed by the tooth grooves 5a of the screw rotor 5 and the gate rotor teeth 6a of the gate rotor 6 meshing with each other. The screw compressor 100 has a configuration in which two gate rotors 6 are arranged facing one screw rotor 5 with a 180 degree shift. Therefore, two compression chambers 20 are formed on the upper side of the screw shaft 4 and the lower side of the screw shaft 4. The gate rotor support (not shown) has a number of gate rotor support teeth that are arranged facing the number of gate rotor teeth 6a, and supports the gate rotor 6.

As shown in FIG. 1, the slide valve 7 is provided in a slide groove formed on the inner cylindrical surface of the casing 1, and is configured to be freely slidable in the direction of the rotation axis of the screw rotor 5. One example of the slide valve 7 is an internal volume ratio adjustment valve. As shown in FIG. 1 and FIG. 4, the slide valve 7 includes a valve body portion 70 facing the screw rotor 5, a guide portion 71 having a sliding surface 710 facing the outer peripheral surface of the bearing housing 8, and a guide rod 77 supported by the slide groove end portion 12.

The guide portion 71 is provided on one end side of the valve body portion 70 in the direction of the rotation axis of the screw rotor 5, and is connected to the valve body portion 70 by a connecting portion 72. As shown in FIG. 2, a predetermined gap 75 is formed between the valve body portion 70 and the screw rotor 5. Also, as shown in FIG. 3, a gap 76 is formed between the sliding surface 710 of the guide portion 71 and the outer peripheral surface of the bearing housing 8 to drive the slide valve 7 in the direction of the rotation axis of the screw rotor 5. Also, as shown in FIG. 1, a discharge port 7a for the refrigerant compressed in the compression chamber 20 is provided between the valve body portion 70 and the guide portion 71. The refrigerant discharged from the discharge port 7a is discharged into the high-pressure space 11.

The slide valve 7 is connected to the slide valve drive device 74 via a rod 73 fixed to the end face of the guide portion 71. In other words, the slide valve 7 moves along the direction of the rotation axis of the screw rotor 5 by the rod 73 which moves axially when driven by the slide valve drive device 74. The slide valve drive device 74 is, for example, configured to be driven by gas pressure, hydraulic pressure, or a motor.

The guide rod 77 is provided on the other end side of the valve body portion 70 in the direction of the rotation axis of the screw rotor 5. The guide rod 77 is inserted into a hole 12a formed in the slide groove end portion 12 so as to be freely slidable. The slide groove end portion 12 is a portion formed to protrude inward from the inner wall surface of the casing 1 toward the screw shaft 4 and face the slide valve 7. The guide rod 77 is inserted in the hole 12a of the slide groove end portion 12 without coming out even when the slide valve 7 slides, and is provided to prevent the axial displacement of the slide valve 7. The outer surface of the guide rod 77 may be circular or semicircular, or may be polygonal, for example, to prevent the slide valve 7 from rotating.

In the screw compressor 100, the valve body portion 70 of the slide valve 7 moves along the direction of the rotational axis of the screw rotor 5, thereby adjusting the discharge timing of the refrigerant sucked into the compression chamber 20. Specifically, the slide valve 7 can be positioned on the suction side to advance the opening of the discharge port 7a, thereby advancing the discharge timing, and can be moved to the discharge side to delay the opening of the discharge port 7a, thereby delaying the discharge timing. In other words, the screw compressor 100 operates with a low internal volume ratio when the discharge timing is advanced, and operates with a high internal volume ratio when the discharge timing is delayed.

As shown in FIG. 1, the bearing housing 8 is provided close to the discharge end of the screw rotor 5. The bearing housing 8 has a bearing 8a therein that rotatably supports the end of the screw shaft 4. The outer diameter of the bearing housing 8 is larger than the outer diameter of the screw rotor 5. The outer diameter of the bearing housing 8 may be smaller than the outer diameter of the screw rotor 5, but it is preferable that it is larger than the outer diameter of the screw rotor 5.

The drive unit 3 is composed of an electric motor 30. The electric motor 30 is composed of a stator 31, which is fixed in contact with the inside of the casing 1 and has a radial gap, and a motor rotor 32, which is rotatably arranged inside the stator 31. The motor rotor 32 is connected to the refrigerant suction side of the screw shaft 4 and is arranged on the same axis as the screw rotor 5. The screw compressor 100 rotates the screw rotor 5 by the electric motor 30 driving the screw shaft 4. The electric motor 30 is driven at a variable rotation speed by an inverter (not shown), and is operated by accelerating and decelerating the rotation speed of the screw shaft 4.

In the screw compressor 100, when the screw rotor 5 and the slide valve 7 thermally expand due to an increase in the temperature of the refrigerant gas compressed in the compression chamber 20, the gap 76 between the sliding surface 710 of the guide portion 71 of the slide valve 7 and the outer peripheral surface of the bearing housing 8, and the gap 75 between the valve body portion 70 of the slide valve 7 and the outer peripheral surface of the screw rotor 5 may decrease. In addition, after the screw compressor 100 is stopped, the screw rotor 5 may rotate in the reverse direction due to the high and low pressure difference in the casing. When the screw rotor 5 rotates in the reverse direction, the slide valve 7 may rotate in the circumferential direction due to the influence of the change in the internal pressure of the compression chamber 20, and the valve body portion 70 may come into contact with the screw rotor 5, which may cause seizure, etc. Furthermore, even during normal operation, the screw compressor 100 may rotate the slide valve 7 in the circumferential direction due to the change in pressure acting from the compression chamber 20, and the valve body portion 70 may come into contact with the screw rotor 5, which may cause seizure, etc.

In the screw compressor 100 according to the first embodiment, as shown in Figs. 3 to 6, a groove 71a is formed along the sliding direction on the sliding surface 710 of the guide portion 71 of the slide valve 7, and as shown in Figs. 3 and 7, a cylindrical protrusion 80 is provided on the outer peripheral surface of the bearing housing 8 to fit into the groove 71a. The slide valve 7 is configured to be able to slide freely in the rotation axis direction of the screw rotor 5 with the protrusion 80 fitted into the groove 71a. In other words, the slide valve 7 is restricted from rotating in the circumferential direction by fitting the protrusion 80 into the groove 71a, while maintaining a gap 76 between the sliding surface 710 of the guide portion 71 and the outer peripheral surface of the bearing housing 8. In addition, as shown in Fig. 3, a gap S is formed between the bottom surface of the groove 71a and the tip surface of the protrusion 80 in order to improve the drivability of the slide valve 7. A small gap is also formed between the side wall surface of the groove 71a and the side surface of the protrusion 80 in order to improve the drivability of the slide valve 7.

The groove portion 71a may be formed in a range that takes into account the amount of movement of the slide valve 7, and may be formed from one end of the guide portion 71 to the other end along the sliding direction of the slide valve 7 as shown in FIG. 6, or may be formed only in a partial range. In addition, the groove portion 71a is not limited to a rectangular shape as shown in FIG. 5, and may be another shape.

The protrusion 80 is provided in the range of the outer circumferential surface of the bearing housing 8 where the guide portion 71 of the slide valve 7 slides (the range indicated by the dotted line in FIG. 7), and is located within the groove portion 71a even when the slide valve 7 slides. As an example, the protrusion 80 is provided in the center of the range of the outer circumferential surface of the bearing housing 8 where the guide portion 71 slides, but it may be provided in any other position within the range where the guide portion 71 slides.

The protrusion 80 is provided by forming a cylindrical through hole or groove on the outer surface of the bearing housing 8 and joining a cylindrical pin by pressing or shrink fitting into the through hole or groove. By making the protrusion 80 cylindrical, the side wall surface of the groove 71a and the side surface of the protrusion 80 are in line contact. In other words, by making the protrusion 80 cylindrical, even if the slide valve 7 rotates and the side surface of the protrusion 80 comes into contact with the side wall surface of the groove 71a, the contact area between the groove 71a and the protrusion 80 can be reduced, so that frictional resistance can be suppressed and the drivability of the slide valve 7 can be improved. In addition, by shortening the protruding length of the protrusion 80, the range of line contact between the side wall surface of the groove 71a and the side surface of the protrusion 80 can be reduced.

Note that the protrusion 80 is not limited to the cylindrical shape shown in the figure, but may be rectangular or have other shapes. The protrusion 80 may also be integrally formed by machining a part of the bearing housing 8.

Furthermore, it is preferable that the protrusion 80 is formed from a material with a smaller linear expansion coefficient than the material of the slide valve 7 and the bearing housing 8. In the screw compressor 100, depending on the operating conditions, the parts around the screw rotor 5 may become hot, causing the slide valve 7, the bearing housing 8, and the protrusion 80 to thermally expand. Even in such a case, a small gap can be secured between the groove 71a and the protrusion 80, so deterioration of the drivability of the slide valve 7 can be suppressed.

FIG. 8 is an enlarged cross-sectional view of a main part of the first modified example of the screw compressor 100 according to the first embodiment. In the screw compressor 100 according to the first embodiment, as shown in FIG. 8, a groove 81 may be formed on the outer peripheral surface of the bearing housing 8 along the sliding direction of the slide valve 7, and a protrusion 71b that fits into the groove 81 may be formed on the sliding surface 710 of the guide portion 71 of the slide valve 7. The slide valve 7 is configured to be freely slidable in the direction of the rotation axis of the screw rotor 5 with the protrusion 71b fitted into the groove 81. The protrusion 71b may be formed integrally with the guide portion 71 of the slide valve 7, or may be provided by forming a groove in the guide portion 71 of the slide valve 7 and pressing a cylindrical pin into the groove or joining it by shrink fitting or the like.

FIG. 9 is a perspective view showing the bearing housing 8 in a second modified example of the screw compressor 100 according to the first embodiment. FIG. 10 is a cross-sectional view showing an enlarged view of the main parts of the second modified example of the screw compressor 100 according to the first embodiment. In the second modified example of the screw compressor 100 shown in FIGS. 9 and 10, the tip surface 80a of the cylindrical protrusion 80 is configured to be hemispherical. For example, even if the slide valve 7 and the bearing housing 8 thermally expand and the tip surface 80a of the protrusion 80 comes into contact with the bottom surface of the groove 71a of the guide portion 71, the tip surface 80a of the protrusion 80 and the bottom surface of the groove 71a can be brought into point contact. This reduces the contact area between the protrusion 80 and the groove 71a, thereby suppressing deterioration of the drivability of the slide valve 7. Although not shown in the figures, the tip surface 80a of the protrusion 80 is not limited to being hemispherical, but may be, for example, curved, other than flat, or may have a tip portion tapered toward the bottom surface of the groove 71a.

Next, the operation of the screw compressor 100 according to the first embodiment will be described with reference to Figures 11 to 13. Figure 11 is an explanatory diagram showing the operation of the compression section 2 of the screw compressor 100 according to the first embodiment, illustrating the suction process. Figure 12 is an explanatory diagram showing the operation of the compression section 2 of the screw compressor 100 according to the first embodiment, illustrating the compression process. Figure 13 is an explanatory diagram showing the operation of the compression section 2 of the screw compressor 100 according to the first embodiment, illustrating the discharge process. Note that in Figures 11 to 13, each process will be described with a focus on the compression chamber 20 indicated by dotted hatching.

As shown in Figures 11 to 13, in the screw compressor 100, the screw rotor 5 is rotated by the electric motor 30 via the screw shaft 4, causing the gate rotor teeth 6a of the gate rotor 6 to move relatively within the tooth grooves 5a that form the compression chamber 20. As a result, within the compression chamber 20, a cycle consisting of a suction process (Figure 11), a compression process (Figure 12), and a discharge process (Figure 13) is repeated.

Figure 11 shows the state of the compression chamber 20 during the suction stroke. The screw rotor 5 is driven by the electric motor 30 and rotates in the direction of the solid arrow. This causes the volume of the compression chamber 20 to decrease, as shown in Figure 12.

As the screw rotor 5 continues to rotate, the compression chamber 20 is connected to the discharge port 7a as shown in FIG. 13. This causes the high-pressure refrigerant gas compressed in the compression chamber 20 to be discharged to the outside through the discharge port 7a. The same compression then occurs again on the back surface of the screw rotor 5.

Here, the conventional circumferential rotation prevention structure of the slide valve will be described. Conventional rotation prevention structures of the slide valve include, for example, a structure in which a key groove is formed in the valve body of the slide valve and the high and low pressure partitions of the casing, and a common key is inserted into the key groove. There is also a structure in which a key groove is formed in one of the valve body of the slide valve and the high and low pressure partitions of the casing, and a protrusion that fits into the key groove is formed in the other. These rotation prevention structures of the slide valve are provided between the high and low pressure partitions of the casing 1 and the valve body of the slide valve 7, so it is necessary to maintain airtightness so that high-pressure refrigerant gas does not leak into the low-pressure space. In order to maintain airtightness, it is necessary to make contact between the key groove and the key formed on the outer surface of the slide valve, and to maintain this contact state over a certain dimension along the sliding direction of the slide valve. This makes it possible to prevent the circumferential rotation of the slide valve 7, but it causes a problem of deterioration in the drivability of the slide valve 7.

Furthermore, the conventional anti-rotation structure is provided on the outer surface of the valve body 70 that faces the high and low pressure partitions of the casing 1. Therefore, when the pressure compressing the refrigerant by the screw rotor 5 acts on the valve body, the valve body 70 is pressed against the casing 1, which increases the airtightness of the anti-rotation structure, but may deteriorate the drivability of the slide valve 7.

In contrast, in the screw compressor 100 according to the first embodiment, as a circumferential rotation prevention structure, a groove 71a is formed along the sliding direction on one of the sliding surface 710 of the guide portion 71 and the outer peripheral surface of the bearing housing 8, and a protrusion 80 that fits into the groove 71a is formed on the other. In other words, in the screw compressor 100 according to the first embodiment, since the rotation prevention structure is provided in the high pressure space 11, high pressure refrigerant gas does not leak into the low pressure space 10. Therefore, for example, a gap S can be formed between the groove bottom surface of the groove 71a and the tip surface of the protrusion 80, thereby reducing contact between the protrusion 80 and the groove 71a. Therefore, in the screw compressor 100 according to the first embodiment, it is possible to prevent circumferential rotation while improving the drivability of the slide valve 7.

In addition, in the screw compressor 100 according to the first embodiment, when the pressure compressing the refrigerant by the screw rotor 5 acts on the valve body 70 and the valve body 70 is pressed against the inner wall surface of the casing 1, the airtightness of the groove 71a and the protrusion 80 decreases, improving the drivability of the slide valve 7.

Incidentally, in the above-mentioned Patent Document 1, a protrusion is provided on the guide portion of the slide valve, so the gap between the guide portion of the slide valve and the outer peripheral surface of the bearing housing is small. Therefore, when the slide valve and the bearing housing thermally expand due to an increase in temperature of the refrigerant gas compressed in the compression chamber, the protrusion provided on the guide portion comes into contact with the outer peripheral surface of the bearing housing, which may deteriorate the drivability of the slide valve.

As described above, the screw compressor 100 according to the first embodiment includes a casing 1 forming an outer shell, a screw shaft 4 arranged in the casing 1 and driven to rotate, a screw rotor 5 having a spiral tooth groove 5a on its outer circumferential surface and fixed to the screw shaft 4, a gate rotor 6 having a plurality of gate rotor teeth 6a that fit into the tooth grooves 5a of the screw rotor 5 and forming a compression chamber 20 together with the casing 1 and the screw rotor 5, a slide valve 7 configured to slide freely in the rotation axis direction of the screw rotor 5, and a bearing housing 8 having a bearing 8a therein that rotatably supports the end of the screw shaft 4. The slide valve 7 has a valve body portion 70 facing the screw rotor 5, and a guide portion 71 having a sliding surface 710 facing the outer circumferential surface of the bearing housing 8. A groove portion 71a is formed along the sliding direction on one of the sliding surface 710 of the guide portion 71 and the outer circumferential surface of the bearing housing 8, and a protrusion portion 80 that fits into the groove portion 71a is provided on the other. The slide valve 7 is configured to be freely slidable in the direction of the rotation axis of the screw rotor 5 with the protrusion 80 fitted into the groove 71a.

Therefore, in the screw compressor 100 according to embodiment 1, the projection 80 fits into the groove 71a, so that the circumferential rotation of the slide valve 7 can be restricted. Therefore, even if the pressure acting on the valve body 70 that faces the outer circumferential surface of the screw rotor 5 fluctuates, the slide valve 7 will not rotate in the circumferential direction, and contact between the slide valve 7 and the screw rotor 5 can be suppressed. In addition, the gap 76 between the sliding surface 710 of the guide portion 71 and the outer circumferential surface of the bearing housing 8 can be maintained, so deterioration of the drivability of the slide valve can be suppressed.

The protrusion 80 is cylindrical. This allows the side wall surface of the groove 71a and the side surface of the protrusion 80 to be in line contact. This reduces the contact area between the groove 71a and the protrusion 80, suppressing frictional resistance and improving the drivability of the slide valve 7.

In addition, the tip surface 80a of the protrusion 80 that fits into the groove 71a is semispherical or curved. Therefore, even if the slide valve 7 and the bearing housing 8 thermally expand and the tip surface 80a of the protrusion 80 comes into contact with the bottom surface of the groove 71a of the guide part 71, the tip surface 80a of the protrusion 80 and the bottom surface of the groove 71a can be in point contact. This reduces the contact area between the protrusion 80 and the groove 71a, thereby preventing deterioration of the drivability of the slide valve 7.

In addition, a gap S is formed between the bottom surface of the groove 71a and the tip surface 80a of the protrusion 80, improving the drivability of the slide valve 7.

Embodiment 2.
Next, a screw compressor 100 according to a second embodiment will be described based on Fig. 14 and Fig. 15 while referring to Figs. 1 to 13. Fig. 14 is a perspective view showing a bearing housing 8 of the screw compressor 100 according to the second embodiment. Note that the same components as those of the screw compressor 100 described in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

In the screw compressor 100 according to the second embodiment, as shown in Figs. 4 to 6, a groove 71a is formed along the sliding direction on the sliding surface 710 of the guide portion 71 of the slide valve 7. As shown in Fig. 14, a protrusion 82 that fits into the groove 71a is formed on the outer circumferential surface of the bearing housing 8. The protrusion 82 of the screw compressor 100 according to the second embodiment is configured as a rod extending along the sliding direction of the slide valve 7. With the protrusion 82 fitted into the groove 71a, the slide valve 7 is configured to be freely slidable in the direction of the rotation axis of the screw rotor 5. In other words, the slide valve 7 is restricted from rotating in the circumferential direction by the protrusion 82 fitting into the groove 71a. In addition, a gap is formed between the bottom surface of the groove 71a and the tip surface of the protrusion 82 in order to improve the drivability of the slide valve 7. A small gap is also formed between the side wall surface of the groove 71a and the side surface of the protrusion 82 in order to improve the drivability of the slide valve 7.

The protrusion 82 is provided on the outer circumferential surface of the bearing housing 8 in the range where the guide portion 71 of the slide valve 7 slides (the range indicated by the dotted line in FIG. 14). As an example, the protrusion 82 is provided by forming a groove on the outer surface of the bearing housing 8 along the sliding direction of the slide valve 7 and pressing a rod-shaped key into the groove or joining a rod-shaped key by shrink fitting or the like. The protrusion 82 only needs to be provided in a range that takes into account the amount of movement of the slide valve 7, and may be formed from one end to the other end along the axial direction of the bearing housing 8, or may be provided only in a partial range. The protrusion 82 may also be provided by forming a through hole on the outer surface of the bearing housing 8 and pressing a rod-shaped key into the through hole or joining it by shrink fitting or the like.

In the screw compressor 100 according to the second embodiment, the protrusion 82 is configured as a rod extending along the sliding direction of the slide valve 7, so that the rotation of the slide valve 7 in the circumferential direction can be more effectively restricted.

It is preferable that the protrusion 82 is made of a material with a smaller linear expansion coefficient than the materials of the slide valve 7 and the bearing housing 8. Depending on the operating conditions of the screw compressor 100, the parts around the screw rotor 5 may become hot, causing the slide valve 7, the bearing housing 8, and the protrusion 82 to thermally expand. Even in such a case, a small gap can be secured between the groove 71a and the protrusion 82, thereby preventing deterioration of the drivability of the slide valve 7.

Also, in the screw compressor 100 according to the second embodiment, as shown in FIG. 8, a groove may be formed on the outer peripheral surface of the bearing housing 8 along the sliding direction, and a protrusion that fits into the groove may be formed on the sliding surface 710 of the guide portion 71 of the slide valve 7. With the protrusion fitted into the groove, the slide valve 7 is configured to be able to slide freely in the direction of the rotation axis of the screw rotor 5. The protrusion may be formed integrally with the guide portion 71 of the slide valve 7, or may be provided by forming a groove in the guide portion 71 of the slide valve 7 and pressing a rod-shaped key into the groove or joining it by shrink fitting, etc.

15 is a perspective view showing a modified example of the bearing housing 8 of the screw compressor 100 according to the second embodiment. In the modified example of the screw compressor 100 shown in FIG. 15, the tip surface 82a of the protrusion 82 is configured to have a curved shape, which is a surface other than a flat surface. For example, even if the slide valve 7 and the bearing housing 8 thermally expand and the tip surface 82a of the protrusion 82 comes into contact with the bottom surface of the groove 71a of the guide portion 71, the tip surface 82a of the protrusion 82 and the bottom surface of the groove 71a can be in line contact. This reduces the contact area between the protrusion 82 and the groove 71a, thereby suppressing deterioration of the drivability of the slide valve 7. Although not shown in the figure, the protrusion 82 is not limited to having the tip surface 82a in a curved shape, and the tip portion may be configured to have a tapered shape toward the bottom surface of the groove 71a.

The screw compressor 100 has been described above based on the embodiment, but the screw compressor 100 is not limited to the configuration of the above-mentioned embodiment. The above-mentioned configuration of the screw compressor 100 is an example, and some of the components may be omitted or other components may be included. Although the screw compressor 100 has been described using a single-stage single screw compressor as an example, it may be, for example, a two-stage single screw compressor. The slide valve 7 is not limited to an internal volume ratio adjustment valve, and may be configured to adjust the compression capacity, for example. The gate rotor 6 is not limited to the two-piece configuration shown in the figure, and may be one. In short, the screw compressor 100 includes the range of design changes and application variations that are normally made by a person skilled in the art, within the scope of the technical concept.

1 casing, 2 compression section, 3 drive section, 4 screw shaft, 5 screw rotor, 5a tooth groove, 6 gate rotor, 6a gate rotor tooth section, 7 slide valve, 7a discharge port, 8 bearing housing, 8a bearing, 10 low pressure space, 11 high pressure space, 12 slide groove end, 12a hole, 20 compression chamber, 30 electric motor, 31 stator, 32 motor rotor, 70 valve body section, 71 guide section, 71a groove section, 71b protrusion section, 72 connection section, 73 rod, 74 slide valve drive device, 75 gap, 76 gap, 77 guide rod, 80 protrusion section, 80a tip surface, 81 groove section, 82 protrusion section, 82a tip surface, 100 screw compressor, 710 sliding surface, S gap.

Claims

A casing that forms an outer shell;
a screw shaft disposed within the casing and rotatably driven;
a screw rotor having a spiral tooth groove on an outer circumferential surface and fixed to the screw shaft;
a gate rotor having a plurality of gate rotor teeth that fit into tooth grooves of the screw rotor and that forms a compression chamber together with the casing and the screw rotor;
a slide valve configured to be slidable in the direction of the rotation axis of the screw rotor;
a bearing housing having a bearing therein for rotatably supporting an end of the screw shaft,
the slide valve has a valve body portion facing the screw rotor and a guide portion having a sliding surface facing an outer circumferential surface of the bearing housing,
a groove portion is formed along a sliding direction on one of the sliding surface of the guide portion and the outer peripheral surface of the bearing housing, and a protrusion portion that fits into the groove portion is provided on the other of the sliding surface of the guide portion and the outer peripheral surface of the bearing housing,
the slide valve is configured to be slidably movable in the direction of the rotation axis of the screw rotor with the protrusion fitted in the groove.
The screw compressor according to claim 1, wherein the protrusion is cylindrical.
The screw compressor according to claim 1 or 2, wherein the tip surface of the protrusion that fits into the groove has a curved shape.
The screw compressor according to any one of claims 1 to 3, wherein the tip surface of the protrusion that fits into the groove is hemispherical.
The screw compressor according to claim 1, wherein the protrusion is formed in a rod shape extending along the sliding direction of the slide valve.
The screw compressor according to claim 5, wherein the tip surface of the protrusion that fits into the groove is curved.
The screw compressor according to any one of claims 1 to 6, wherein a gap is formed between the groove bottom surface of the groove portion and the tip surface of the protrusion portion.