CN211924462U - Screw compressor - Google Patents

Abstract

The utility model provides a screw compressor, include: the compression device comprises a shell, a compression mechanism and a compression mechanism, wherein a low-pressure cavity, a compression cavity and a high-pressure cavity are defined in the shell, and a fluid to be compressed enters the compression cavity from the low-pressure cavity and is then discharged from the high-pressure cavity; a pair of screws relatively rotatable, having a pair of helical tooth sections engaged with each other, located in the compression chamber, the compression chamber communicating with the low pressure chamber through at least a suction end of the pair of helical tooth sections and communicating with the high pressure chamber through at least a discharge end of the pair of helical tooth sections; and a capacity adjustment mechanism including a slider located in the compression chamber and movable in a direction parallel to the axis of the screw, wherein the length of the slider is greater than the length of the helical tooth section, and the slider has at least two different full load positions that completely cover the entire length of the helical tooth section. In the first full-load position, the slide block extends out of the low-pressure cavity by a first distance relative to the spiral tooth section, and in the second full-load position, the slide block extends out of the low-pressure cavity by a second distance which is smaller than the first distance and is larger than or equal to 0 relative to the spiral tooth section.

Description

Screw compressor

Technical Field

The utility model relates to a compressor, especially a screw compressor with hold accent mechanism.

Background

Screw compressors have found widespread use in refrigeration systems. The working principle of the existing screw compressor is that a pair of mutually meshed male and female screws are driven by a motor to rotate relatively, so that the volume defined between teeth on the screws and the wall of a compressor shell is changed, and four processes of suction, closing, compression and discharge of fluid (such as gas) are realized. When the compressor is fully operated, the ratio between the interdental volume V0 when suction is fully completed (i.e., compression is just started) and the interdental volume V1 when discharge is started is referred to as the built-in volume ratio VI of the compressor, VI being V0/V1. During compression, the distance that the fluid travels between the pair of screw flights meshing with each other is referred to as the axial compression distance.

Capacity adjustment mechanisms are commonly provided in existing screw compressors to adjust the load level of the compressor during start-up and/or operation of the compressor. Fig. 1 shows a schematic diagram of a conventional screw compressor with a four-stage capacity-regulating mechanism. As shown in fig. 1, a low pressure chamber C1, a compression chamber C2, and a high pressure chamber C3 are defined in the casing of the compressor 10. A pair of relatively rotatable screws 11 are disposed in the compression chamber C2 and have male and female screw tooth sections engaged with each other, respectively. The compression chamber C2 communicates with the low pressure chamber C1 at least through the suction end of the pair of helical tooth segments and communicates with the high pressure chamber C3 at least through the discharge end of the pair of helical tooth segments. A four-stage capacity-adjusting mechanism is arranged in the compressor 10, and comprises a slide block 12, a piston mechanism and an oil circuit system. The oil system consists of 4 pipelines, namely an oil delivery pipe 7, a 25% load pipe 3, a 50% load pipe 8 and a 75% load pipe 9. The pipeline can be an external pipe or a hole in the casing casting. The oil delivery pipe 7 is provided with a flow limiting plug 1 for realizing flow limiting, or the flow can be limited by a capillary tube. One end of the oil delivery pipe 7 is communicated with an oil storage tank positioned in the high-pressure cavity, and the other end is communicated with an oil cavity 13 of the piston mechanism. One end of the 25% load pipe 3 is connected with the oil delivery pipe 7, and the other end is communicated with the low-pressure cavity and is provided with a control valve. One end of the 50% load tube 8 communicates with the oil chamber 13, and the other end communicates with the low pressure chamber, and is provided with a control valve. One end of the 75% load adjusting pipe 9 communicates with the oil chamber 13, and the other end communicates with the low pressure chamber, and is provided with a control valve. The compressor utilizes the pressure difference between the high-pressure cavity and the low-pressure cavity to realize automatic oil supply. The slider 12 can be driven to move by opening/closing the control valves on the different load lines, thereby adjusting the load of the compressor in the fourth gear of 25%, 50%, 75% and 100%. When any one control valve on the 25% load pipe 3, the 50% load pipe 8 and the 75% load pipe 9 is opened, the sliding block moves, so that a part of the length of the spiral tooth section in the compression cavity, which is close to the suction end, is bypassed to the low-pressure cavity, the flow of the compressed fluid is reduced, and the partial load function is achieved.

Fig. 2 shows a schematic diagram of a conventional screw compressor with a stepless capacity control mechanism. The compressor 10' is similar in construction to the compressor 10 of fig. 1. Except that the oil passage system in the compressor 10' is composed of an oil supply pipe 15 and a bypass pipe 14. An oil supply valve 16 is installed in the oil supply pipe 15, and one end of the oil supply pipe 15 communicates with the oil reservoir of the high pressure chamber and the other end communicates with the oil chamber 13. A bypass valve 17 is mounted on the bypass pipe 14, and one end of the bypass pipe 14 communicates with the oil chamber 13 and the other end communicates with the low-pressure chamber. By opening/closing the oil supply valve and the bypass valve, the movement of the slider 12 can be arbitrarily controlled, so that the load of the compressor 10' can be arbitrarily adjusted between 25% and 100% full load. When the load of the compressor is adjusted to be not full load, namely less than 100%, the sliding block moves, so that a part of length of the spiral tooth section close to the suction end is bypassed to the low-pressure cavity, the flow of the compressed fluid is reduced, and the function of partial load is achieved.

While the prior art screw compressors are capable of load modulation, the built-in volume ratio at full compressor loading is fixed and not adjustable. In a specific application, the external volume ratio of the compressor may be changed frequently, for example, depending on the kind of refrigerant or the working environment. For example, for a compressor with an internal volume ratio of 2.2, when the client application operating condition is 2/36 ℃, the external volume ratio is 2.2, and the working efficiency of the compressor is the highest when the external volume ratio is matched with the internal volume ratio. When the client application working condition is 2/45 ℃, the external volume ratio is 2.7; when the client application working condition is 2/50 ℃, the built-out volume ratio is 3.03 and is not matched with the built-in volume ratio of 2.2, so that the compressor is under-compressed, the power consumption of the compressor is increased, and the efficiency of the whole machine is poor. Therefore, the existing screw type refrigeration compressor cannot meet the requirements of customers for applying the compressor to different working conditions.

SUMMERY OF THE UTILITY MODEL

It is an object of the present invention to provide a screw compressor to solve one or more of the above-mentioned problems of the prior art.

In order to achieve the above object, the present invention provides a screw compressor, which is characterized by comprising: a housing defining therein a low pressure chamber, a compression chamber and a high pressure chamber, a fluid to be compressed entering the compression chamber from the low pressure chamber and then being discharged from the high pressure chamber; a pair of screws relatively rotatable with each other, having a pair of helical tooth sections engaged with each other, the pair of helical tooth sections being located in the compression chamber, the compression chamber communicating with the low pressure chamber at least through a suction end of the pair of helical tooth sections and communicating with the high pressure chamber at least through a discharge end of the pair of helical tooth sections; and a capacity adjustment mechanism including a slider located in the compression chamber and movable in a direction parallel to axes of the pair of screw rods, wherein a length of the slider is greater than a length of the pair of helical tooth sections, and the slider has at least two different full-load positions completely covering an entire length of the pair of helical tooth sections, a first full-load position in which a low-pressure-side end portion of the slider projects toward the low-pressure chamber with respect to the suction end of the pair of helical tooth sections by a first distance, and a second full-load position in which the low-pressure-side end portion of the slider projects toward the low-pressure chamber with respect to the suction end of the pair of helical tooth sections by a second distance that is less than the first distance and equal to or greater than 0.

When the slide block is in the full-load position, the compression cavity is communicated with the low-pressure cavity only through the suction ends of the pair of spiral tooth sections.

The slider also includes at least one partial load position in which the slider covers only a portion of the length of the pair of helical tooth segments, and the portion of the length of the pair of helical tooth segments not covered by the slider communicates with the low pressure chamber.

The capacity adjusting mechanism further comprises: a spigot seat for locating said low pressure side end of said slide when said slide is in said first full load position.

When the slider is in the second full-load position, the low-pressure-side end portion of the slider is flush with end surfaces of the suction ends of the pair of helical tooth segments.

The high-pressure side end of the slider has a concave bird's beak structure disposed facing the pair of helical tooth segments, and the discharge ends of the pair of helical tooth segments are located at the corresponding positions of the bird's beak structure when the slider is at the first full-load position.

The capacity adjusting mechanism further comprises: the piston mechanism comprises an oil cylinder and a piston arranged in the oil cylinder, the piston divides the oil cylinder into a first chamber and a second chamber, and the first chamber and the second chamber are connected with the sliding block through a connecting rod; the oil way system is communicated with the first cavity of the oil cylinder; and a spring disposed within the second chamber of the cylinder biasing the piston toward a minimum part load position.

The oil path system includes: the first oil pipe is connected between the first cavity of the oil cylinder and the oil storage tank in the high-pressure cavity; the second oil pipe is connected between the first oil pipe and the low-pressure cavity, and a first valve is arranged on the second oil pipe; and at least one third oil pipe connected between a predetermined position of the first chamber of the oil cylinder and the low pressure chamber, each third oil pipe being provided with a second valve, wherein the first valve and the second valve are solenoid valves.

When the first valve and the second valve are both closed, the slide is in the first full load position; said slide being in said second fully loaded position when said first valve is closed and one of said second valves is open; and/or the slider covers only a portion of the length of the pair of helical tooth segments when the first valve is open, in the partially loaded position.

The oil path system includes: the oil supply pipe is connected between the first cavity of the oil cylinder and the oil storage tank in the high-pressure cavity, and an oil supply valve is arranged on the oil supply pipe; and a bypass pipe connected between the oil supply pipe and the low pressure chamber, the bypass pipe being provided with a bypass valve, wherein the oil supply valve and the bypass valve are solenoid valves.

According to the utility model discloses, length through with the slider sets up to be greater than the length of spiral tooth section for the slider can have two at least full load positions. According to the utility model discloses a screw compressor has realized the regulation to compressor built-in volume ratio from this.

Drawings

The invention will be described in detail with reference to the following drawings and detailed description, in which:

FIG. 1 is a schematic diagram of a prior art screw compressor having a four-stage capacity modulation mechanism;

FIG. 2 is a schematic diagram of a prior art screw compressor having a stepless capacity modulation mechanism

FIG. 3 is a schematic cross-sectional view of a screw compressor according to an embodiment of the present invention;

FIG. 3A is a schematic perspective view along the slider of FIG. 3 showing a bird's beak configuration;

FIG. 4 is a schematic end view taken along line A-A of FIG. 3;

FIG. 5 is a partial schematic cross-sectional view taken along line B-B of FIG. 4 illustrating the capacitance adjustment mechanism;

fig. 6A-6C are schematic diagrams of a capacitance-adjustment mechanism according to an embodiment of the present invention, showing a first fully-loaded position, a second fully-loaded position, and a partially-loaded position, respectively; and

fig. 7A-7C are schematic diagrams of a capacitance-adjustment mechanism according to another embodiment of the present invention, showing a first fully loaded position, a second fully loaded position, and a partial loaded position, respectively.

Detailed Description

The present invention is specifically described below by way of exemplary embodiments. It should be understood, however, that elements, structures and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

FIG. 3 is a schematic cross-sectional view of a screw compressor according to an embodiment of the present invention; FIG. 4 is a schematic end view taken along line A-A of FIG. 3; FIG. 5 is a partial schematic sectional view taken along line B-B in FIG. 4; fig. 6A-6C are schematic diagrams of a capacity adjustment mechanism according to an embodiment of the present invention, respectively showing a first fully loaded position, a second fully loaded position, and a partial loaded position.

As shown in fig. 3-5 and 6A-6C, a screw compressor 100 according to an embodiment of the present invention includes a housing 110 defining a low pressure chamber 101, a compression chamber 102, and a high pressure chamber 103 therein. The housing 100 may be separate or integral, and these are not intended to limit the present application. Fluid to be compressed (e.g., refrigerant) may enter low pressure chamber 101 from inlet port 104 in housing 110 and then enter compression chamber 102 for compression. The compressed fluid is discharged to the high pressure chamber 103 and out the discharge port 105 in the housing. The compressor 100 includes a pair of screws 121, 122 (fig. 4) that are relatively rotatable. The compressor 100 may further include a motor 106 for driving the pair of screws 121, 122 to rotate. The screws 121, 122 have a pair of male and female screw tooth segments 123, 124 that mesh with each other. The pair of helical tooth segments are located within the compression chamber 102 and fluid entering the compression chamber 102 is compressed between the male and female helical tooth segments 123, 124. Compression chamber 102 communicates with low pressure chamber 101 through at least suction end 125 of the pair of helical tooth segments 123, 124, and communicates with high pressure chamber 103 through at least discharge end 126 of the pair of helical tooth segments 123, 124. The compressor 100 further includes a capacity adjustment mechanism 130, and the capacity adjustment mechanism 130 includes a slider 132. The slider 132 is located in the compression chamber 102 and is movable in a direction parallel to the axes of the pair of screws 121, 122. Here, the length Ls of the slider 132 is set to be greater than the length Lt of the helical tooth segments 123, 124, so that the slider 132 can have at least two different full load positions that completely cover the entire length of the helical tooth segments 123, 124. In the first full load position, the low-pressure side end 135 of the slider 132 projects toward the low-pressure chamber 101 by a first distance L1 with respect to the suction end 125 of the pair of helical tooth segments 123, 124. In the second full load position, the low-pressure side end 135 of the slider 132 projects toward the low-pressure chamber 101 relative to the suction ends 125 of the pair of helical tooth segments 123, 124 by a second distance L2, wherein the second distance is less than the first distance and equal to or greater than 0. When the slider 132 is located at the second full-load position where the second distance is equal to 0, the low-pressure side end 135 of the slider 132 is flush with the end surface of the suction end 125 of the helical tooth segments 123, 124.

Therefore, according to the utility model discloses, set up the length through with the slider to be greater than the length of helical tooth section for the slider can have at least two full load positions, namely, covers the position of the whole length of helical tooth section completely. When the slider position is biased toward the low pressure chamber (i.e., the extended distance is longer relative to the suction end of the helical tooth segment), the effective compression length of the fluid in the compression chamber is shorter and the compressed fluid is discharged earlier, so the compressor now has a relatively smaller built-in volume ratio; when the slider position is biased toward the high pressure chamber (i.e., the distance of protrusion is shorter relative to the suction end of the helical tooth segment), the effective compression length of the fluid in the compression chamber is longer and the compressed fluid is discharged later, so that the compressor now has a relatively large built-in volume ratio. Therefore, the utility model discloses a regulation to compressor built-in volume ratio.

According to an example of the present invention, the capacitance-adjusting mechanism 130 may further include a socket 112 for the slider 132 for limiting the low-pressure side end 135 of the slider 132 when the slider 132 is in the first full-load position, so as to limit the slider 132 from continuing to move in the direction of the low-pressure chamber 101. The stop seat 112 may, for example, protrude from the wall between the low pressure chamber 101 and the compression chamber 102 or may be formed directly by this wall. Thus, in the other full load positions of the slide than the first full load position, the low pressure side end 135 of the slide 132 is spaced from the spigot seat 112. Furthermore, the socket 112 may also be disposed on the low-pressure side end 135 of the slider 132 or the high-pressure side end 136 of the slider 132 to limit the slider 132 from moving further toward the low-pressure chamber 101. It will be appreciated that in either fully loaded position, the slider 132 completely covers the entire length of the pair of helical tooth segments 123, 124, and therefore the compressor is at 100% load even though the slider 132 is not abutting the stop block 112. Here, the built-in volume ratio of the compressor when the slider 132 is in the second full load position is greater than the built-in volume ratio of the compressor when the slider 132 is in the first full load position. Because the slide 132 is closer to the high pressure chamber 103 in the second full load position than in the first full load position, the effective compression length of fluid within the compression chamber 102 is longer.

According to the utility model discloses, slider 132 can have more than two full load positions to make the built-in volume ratio that can adjust the compressor adapt to more operating modes. When the slide block 132 is in any full load position, the compression chamber 102 communicates with the low pressure chamber 101 only through the suction end 125 of a pair of helical tooth segments, without the low pressure chamber 101 being bypassed for any length of the helical tooth segment. Thus, compressor 100 is now operating at 100% load. This is the essential difference between the present invention built-in volume ratio regulation and the prior art load regulation. In prior art load regulation, the slider has only one position that is sufficient for the compressor 100 to operate at 100% load.

According to the present invention, the slider 132 further comprises at least one partial load position in which the slider 132 may cover only a portion of the length of a pair of helical tooth segments 123, 124, while the portion of the length of the helical tooth segments 123, 124 not covered by the slider 132 communicates with the low pressure chamber 101. Thus, the compressor 100 according to the present invention can operate under partial load as the prior art compressor. This is particularly advantageous for start-up or standby of the compressor, etc.

In one example, referring to fig. 3A, the high pressure side end 136 of the slider 132 is provided with a bird's beak structure 133, the bird's beak structure 133 being recessed facing the helical tooth sections 123, 124 to facilitate the discharge of the compressed fluid. When the slide is in the first full load position described above, discharge end 126 of the helical tooth segment is in correspondence with beak formation 133.

The capacity adjustment mechanism 130 according to the present invention further includes a piston mechanism 140, an oil system, and a spring 137. The piston mechanism 140 includes a cylinder 141 and a piston 145 disposed in the cylinder, and the piston 145 divides the cylinder 141 into a first chamber 142 and a second chamber 143 and is connected to the slider 132 by a connecting rod 146. The oil passage system communicates with the first chamber 142 of the cylinder 141, and the piston 145 is driven to move when hydraulic oil enters the first chamber 142 by a high-low pressure difference between the high pressure chamber 103 and the low pressure chamber 101. A spring 137 is disposed within the second chamber 143 of the cylinder 141 to bias the piston 145 toward a minimum part-load position.

According to the utility model discloses an oil piping system who holds adjustment mechanism can be similar with the oil piping system who holds adjustment mechanism among the prior art, perhaps can utilize the oil piping system who has now held adjustment mechanism to reform transform and form. The following is a detailed description.

As shown in fig. 6A to 6C, an oil passage system 150 according to an example of the present invention includes: a first oil pipe 151, a second oil pipe 152, and at least one third oil pipe 153. The first oil pipe 151 is connected between the oil reservoir 107 (fig. 3) in the high pressure chamber 103 of the housing 110 and the first chamber 142 of the cylinder 141 for supplying the first chamber 142 with hydraulic oil. The second oil pipe 152 is connected between the first oil pipe 151 and the low pressure chamber 101, and is provided with a first valve 152a thereon. The third oil pipe 153 is connected between a predetermined position P of the first chamber 142 of the cylinder and the low pressure chamber 101, and the second valve 153a is provided on the third oil pipe 153. When the compressor is operated, oil is supplied by a pressure difference between the high pressure chamber 103 and the low pressure chamber 101. When both the first valve 152a and the second valve 153a are closed, the piston 145 is pushed to the rightmost side of the cylinder 141 in fig. 6A, and may be disposed such that the low-pressure side end 135 of the slider 132 projects toward the low-pressure chamber 101 by a first distance L1 with respect to the suction end 125 of the pair of helical tooth segments 123, 124 at this time, and the slider 132 is in the first full-load position, as shown in fig. 6A. Similarly, it may be provided that when the first valve 152a is closed and the second valve 153a is open, the low-pressure side end 135 of the slider 132 projects toward the low-pressure chamber 101 by a second distance L2 with respect to the suction end 125 of the pair of helical tooth segments 123, 124, with the slider 132 in the second full-load position, as shown in fig. 6B. Wherein L2 is equal to or less than L1, in one example L2 is equal to 0. Alternatively or additionally, the slider 132 covers only a portion of the length of the pair of helical tooth segments 123, 124 when the first valve 152a is open, in a partially loaded position, as shown in fig. 6C. Here, each valve may be a solenoid valve.

In one example, the oil passage system 150 may include another third oil pipe 154 connected between another predetermined position Q of the first chamber 142 of the cylinder and the low pressure chamber 101, and another second valve 154a is provided on the third oil pipe 154. The further predetermined position Q may be set further away from the low pressure chamber 101 than the predetermined position P, see fig. 6A, and it may be set that the slider 132 is in a part-load position or in a further full-load position when the first valve 152a is closed and the further second valve 154a is open. Alternatively, the other predetermined position Q may be set closer to the low pressure chamber 101 than the predetermined position P, when the first valve 152a and the second valve 153a are closed and the other second valve 154a is opened, and the slider 132 is at the other full-load position.

The oil circuit system 150 of the present invention can be implemented by using the existing four-stage capacity adjusting mechanism. For example, the oil delivery pipe, the 25% load pipe, the 50% load pipe, and the 75% load pipe in the existing four-stage capacity-adjusting mechanism can be respectively used as the first oil pipe 151, the second oil pipe 152, the third oil pipe 154, and the third oil pipe 153 in the oil circuit system 150 of the present invention. In a specific example, the deviation Δ L of the axial compression distance is, for example, 13mm for the case of VI 2.2 and VI 2.7. The distance between the positions of the piston of the conventional four-stage capacity-adjusting mechanism at 75% load and 100% full load may be set to Δ L, and the length Ls of the slider in the conventional four-stage capacity-adjusting mechanism may be set to be longer than the length Lt of the helical tooth segment by Δ L, where Ls is Lt + Δ L. After the transformation, the 100% load position with the VI of 2.2 in the original four-stage capacity adjusting mechanism is still the 100% load position with the VI of 2.2, the original 75% load position is the 100% load position with the VI of 2.7, and the original 50% load position and the original 25% load position are still partial load positions. The specific part load value depends on the setting of the cylinder. In one example, the length of the ram can be adjusted appropriately to still achieve the 50% load position and the 25% load position. The setting and adjustment of the partial load position is the same as in the prior art and will not be described in detail here.

In another specific example, the distance between the positions of the piston at 50% load and 100% full load of the existing four-stage capacity-regulating mechanism can be set to Δ L, and the length Ls of the slider can be set to be longer than the length Lt of the helical tooth stage by Δ L, i.e., Ls ═ Lt + Δ L. After the transformation, the 100% load position with VI of 2.2 in the original four-stage capacity adjustment mechanism is still the 100% load position with VI of 2.2, the original 50% load position is the 100% load position with VI of 2.7, the original 75% load position is the 100% load position with VI corresponding to a value between 2.2 and 2.7, and the original 25% load position is still the partial load position. As described above, by properly adjusting the length of the cylinder, the 25% load position can still be achieved.

As shown in fig. 7A-7C, an oil system 160 according to another alternative embodiment of the present invention may include an oil supply line 161 and a bypass line 162. The oil supply pipe 161 is connected between an oil reservoir (not shown) in the high pressure chamber 103 and the first chamber 142 of the oil cylinder 141 for supplying pressurized hydraulic oil to the first chamber 142. The oil supply pipe 161 is provided with an oil supply valve 161 a. The bypass pipe 162 is connected between the oil supply pipe 161 and the low pressure chamber 101, and a bypass valve 162a is provided in the bypass pipe 162. Both the supply valve 161a and the bypass valve 162a may be solenoid valves. By controlling the opening and closing of the oil supply valve 161a and the bypass valve 162a, respectively, the piston 132 can be moved to an arbitrary position in the cylinder 141.

In one example, when the piston 145 is pushed toward the rightmost side of the cylinder 141, as shown in fig. 7A, the low-pressure side end 135 of the slider 132 protrudes toward the low-pressure chamber 101 by a first distance L1 with respect to the suction end 125 of the pair of helical tooth segments 123, 124, and the slider 132 is in the first full-load position. When the piston 145 slides in the forward direction, the slider 132 is moved leftward together. When the low-pressure side end 135 of the slider 132 projects a second distance L2 toward the low-pressure chamber 101 relative to the suction ends 125 of the pair of helical tooth segments 123, 124, as shown in fig. 7B, the slider 132 is in a second full-load position, as shown in fig. 7B. Wherein L2 is equal to or less than L1, in one example L2 is equal to 0. Alternatively or additionally, when the slider 132 covers only a portion of the length of a pair of helical tooth segments 123, 124, as shown in fig. 7C, the slider 132 is in a partial load position.

According to the utility model discloses an oil piping system 160 can utilize the current stepless oil piping system who holds the accent mechanism to realize. In a specific example, the deviation Δ L of the axial compression distance is, for example, 13mm for the case of VI 2.2 and VI 2.7. It is possible to set the position of the piston of the conventional stepless capacity-adjusting mechanism at, for example, 75% load (at P75 in fig. 7A) and the position interval at 100% full load to Δ L, and set the length Ls of the slider in the conventional stepless capacity-adjusting mechanism to be longer than the length Lt of the helical tooth segment by Δ L, that is, Ls ═ Lt + Δ L. After the transformation, the 100% load position with VI of 2.2 in the original stepless capacity adjustment mechanism is still the 100% load position with VI of 2.2, and the original 75% load position is the 100% load position with VI of 2.7. Any partial load position of the original load between 75% and 100% becomes a 100% load position of a corresponding value of VI between 2.2 and 2.7. The partial load position with the original load less than 75 percent is still the partial load position, and the stepless regulation of the load can still be realized. In this example, both a stepless adjustment of the internal volume ratio VI in the variable range of 2.2 to 2.7 and a stepless adjustment of the partial load are achieved. The setting and adjustment of the partial load position is the same as in the prior art and will not be described in detail here.

In another specific example, the deviation Δ L of the axial compression distance is, for example, 38mm for the case of VI 2.2 and VI 4.8. The distance between the 25% load position and the 100% full load position of the piston of the conventional stepless capacity adjustment mechanism may be set to be greater than Δ L, and the slider length Ls of the conventional stepless capacity adjustment mechanism may be set to be longer than the length Lt of the helical tooth segment by Δ L, that is, Ls is Lt + Δ L. After such modification, the 100% load position with VI of 2.2 in the conventional stepless variable capacity mechanism is still the 100% load position with VI of 2.2, and the predetermined position at a distance Δ L from the 100% full load position is the 100% load position with VI of 4.8. A wider range of stepless adjustment of VI between 2.2 and 4.8 can be achieved when the piston is between this predetermined position and the 100% load position. When the piston is between the predetermined position and the original 25% load position, a part load stepless adjustment can be achieved.

In the above, specific VI values (e.g. 2.2, 2.7, 4.8) and specific load positions (e.g. 25% load position, 50% load position, 75% load position and 100% load position) are taken as examples, and a plurality of specific embodiments for adjusting the internal volume ratio by using the volume adjustment mechanism of the present invention are described. It should be understood, however, that the compressor according to the present invention may be adapted to other VI values and may have other load positions depending on the actual situation, which are not intended as limitations of the present invention.

It should be noted that, although the present invention has been described by the above embodiments, the present invention may have other various embodiments. Various modifications and changes may be made by those skilled in the art without departing from the spirit and scope of the invention, and it is intended that all such modifications and changes fall within the scope of the appended claims and their equivalents.

Claims (10)

1. A screw compressor, comprising:

a housing defining therein a low pressure chamber, a compression chamber and a high pressure chamber, a fluid to be compressed entering the compression chamber from the low pressure chamber and then being discharged from the high pressure chamber;

a pair of screws relatively rotatable with each other, having a pair of helical tooth sections engaged with each other, the pair of helical tooth sections being located in the compression chamber, the compression chamber communicating with the low pressure chamber at least through a suction end of the pair of helical tooth sections and communicating with the high pressure chamber at least through a discharge end of the pair of helical tooth sections; and

a capacity adjustment mechanism including a slider located in the compression chamber and movable in a direction parallel to axes of the pair of screw rods, wherein a length of the slider is greater than a length of the pair of helical tooth segments, and the slider has at least two different full-load positions completely covering the entire length of the pair of helical tooth segments, a first full-load position in which a low-pressure-side end of the slider projects toward the low-pressure chamber with respect to the suction ends of the pair of helical tooth segments by a first distance, and a second full-load position in which the low-pressure-side end of the slider projects toward the low-pressure chamber with respect to the suction ends of the pair of helical tooth segments by a second distance that is less than the first distance and equal to or greater than 0.

2. The screw compressor of claim 1, wherein said compression chamber communicates with said low pressure chamber only through a suction end of said pair of helical tooth segments when said slide block is in said full load position.

3. The screw compressor of claim 1, wherein the slide block further comprises at least one partial load position in which the slide block covers only a portion of the length of the pair of helical tooth segments and the portion of the length of the pair of helical tooth segments not covered by the slide block communicates with the low pressure chamber.

4. The screw compressor of claim 1, wherein the capacity adjustment mechanism further comprises: a spigot seat for locating said low pressure side end of said slide when said slide is in said first full load position.

5. The screw compressor of claim 1, wherein when said slide block is in said second full load position, said low pressure side end of said slide block is flush with an end face of said suction end of said pair of helical tooth segments.

6. The screw compressor of claim 1, wherein a high pressure side end of said slide has a concave bird's beak configuration disposed facing said pair of helical tooth segments, a discharge end of said pair of helical tooth segments being at a corresponding location of said bird's beak configuration when said slide is in said first full load position.

7. The screw compressor of claim 3, wherein the capacity adjustment mechanism further comprises:

the piston mechanism comprises an oil cylinder and a piston arranged in the oil cylinder, the piston divides the oil cylinder into a first chamber and a second chamber, and the first chamber and the second chamber are connected with the sliding block through a connecting rod;

the oil way system is communicated with the first cavity of the oil cylinder; and

a spring disposed within the second chamber of the cylinder biasing the piston toward a minimum part load position.

8. The screw compressor of claim 7, wherein the oil system comprises:

the first oil pipe is connected between the first cavity of the oil cylinder and the oil storage tank in the high-pressure cavity;

the second oil pipe is connected between the first oil pipe and the low-pressure cavity, and a first valve is arranged on the second oil pipe; and

at least one third oil pipe connected between a predetermined position of the first chamber of the cylinder and the low pressure chamber, each third oil pipe being provided with a second valve,

wherein the first valve and the second valve are solenoid valves.

9. The screw compressor of claim 8,

when the first valve and the second valve are both closed, the slide is in the first full load position;

said slide being in said second fully loaded position when said first valve is closed and one of said second valves is open; and/or

The slider covers only a portion of the length of the pair of helical tooth segments when the first valve is open, in the partially loaded position.

10. The screw compressor of claim 7, wherein the oil system comprises:

the oil supply pipe is connected between the first cavity of the oil cylinder and the oil storage tank in the high-pressure cavity, and an oil supply valve is arranged on the oil supply pipe; and

a bypass pipe connected between the oil supply pipe and the low pressure chamber, the bypass pipe being provided with a bypass valve,

wherein the supply valve and the bypass valve are solenoid valves.

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