A screw pump

Abstract

A screw pump provided by the present invention belongs to the technical field of construction machinery, and includes a housing with an accommodation cavity inside; an air inlet is provided on one end face of the housing, and an air outlet is provided on the other side; the first rotor has a first screw rod and first screw teeth; the first screw rod penetrates through the housing; a second rotor, having a second screw rod and second screw teeth; the second screw rod penetrates through the housing; the second screw teeth are meshed and connected with the first screw teeth; there is a first gap between both the first screw teeth and the second screw teeth and the housing, and there is a second gap between two adjacent first screw teeth and second screw teeth. During the working process of the first rotor and the second rotor of this device, considering the thermal expansion effect, and being able to ensure that the gas will not generate a backflow phenomenon due to high pressure, and also ensuring to avoid the jamming phenomenon, so both the first gap and the second gap are set to change first to become smaller and then larger, which can ensure that the gas at the high-pressure end will not generate a backflow and will not jam under the premise of maintaining stable operation.

Description

Technical Field

[0001] The present invention relates to the technical field of construction machinery, and particularly relates to a screw pump. Background Art

[0002] A screw pump is a gas pumping device that uses a pair of screws to rotate synchronously and at high speed in opposite directions in a pump housing to generate suction and exhaust effects, and is mainly applied to high-purity vacuum process.

[0003] At present, domestic screw pump rotors are mainly divided into two types: equal pitch and variable pitch. For the equal pitch rotor screw vacuum pump, the volume of the closed cavity formed by the screw rotor and the housing remains constant all the time, without internal compression, and the gas temperature rise is not obvious, but the efficiency is low; for the variable pitch rotor screw vacuum pump, the volume of the closed cavity formed by the screw rotor and the housing gradually decreases, the compression is stable, and the efficiency is high, but the gas temperature rise is large. Due to the large gas temperature rise, the high-pressure end of the rotor is extremely prone to thermal expansion, resulting in a decrease in the gap between the high-pressure end of the rotor and the housing. If the initial value of the meshing gap between the rotors is designed to be small, there will be a normal gap between the low-pressure end and the housing, while there will be friction or even jamming between the high-pressure end and the housing; if the initial value of the meshing gap between the rotors is designed to be large, the friction and jamming during operation between the high-pressure end and the housing are avoided, but due to the large gap, the gas is extremely easy to flow back from the high-pressure side to the low-pressure side, resulting in the phenomenon that the vacuum degree cannot rise.

[0004] For the variable pitch rotor in the prior art, in order to make the gaps between the high-pressure end and the low-pressure end of the rotor and the housing normal at the same time, the gap between the rotor and the housing is set as an arithmetic difference gap, which gradually decreases from the low-pressure end to the high-pressure end to achieve normal gaps at both the high-pressure end and the low-pressure end.

[0005] However, in the prior art, it is not considered that during the actual operation of the rotor, the temperature of the high-pressure end of the rotor becomes higher after working on the gas, and deformation occurs under the action of thermal expansion, resulting in the phenomenon that the high-pressure end rotor will still be jammed. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that deformation occurs under the action of thermal expansion, resulting in the phenomenon that the high-pressure end rotor will still be jammed. To solve the above technical problem, the present invention provides a screw pump.

[0007] A screw pump includes:

[0008] A housing with an accommodation cavity inside; an air inlet is provided on one end face of the housing; an air outlet is provided on the other end face of the housing;

[0009] A first rotor having a first screw and first screw teeth provided on the first screw; the first screw penetrates through the housing;

[0010] The second rotor, having a second screw and second screw teeth; the second screw penetrates through the housing; the second screw teeth are arranged on the second screw; the second screw teeth are meshed and connected with the first screw teeth;

[0011] There is a first gap between both the first screw teeth and the second screw teeth and the housing; the first gap first becomes smaller and then larger along the direction from the air inlet to the air outlet;

[0012] There is a second gap between two adjacent first screw teeth and second screw teeth; the second gap first becomes smaller and then larger along the direction from the air inlet to the air outlet.

[0013] As a preferred solution, the equation for the size of the first gap is:

[0014] δ = C + (K - Z)C1 (Z < K)

[0015] δ = C + (Z - K)C2 (Z > K)

[0016] δ is the value of the first gap; Z is the distance from a point on the first screw teeth or the second screw teeth to the end face of the air inlet; C is the basic gap, a constant; C1, C2 are the product of the operating temperature of the first rotor and the expansion coefficient, or the product of the operating temperature of the second rotor and the expansion coefficient; K is half of the length of the accommodation cavity.

[0017] As a preferred solution, the equation for the size of the first gap is:

[0018] β = C + (K - Z)C1 (Z < K)

[0019] β = C + (Z - K)C2 (Z > K)

[0020] β is the value of the second gap; Z is the distance from a point on the first screw teeth or the second screw teeth to the end face of the air inlet; C is the basic gap, a constant; C1, C2 are the product of the operating temperature of the first rotor and the expansion coefficient, or the product of the operating temperature of the second rotor and the expansion coefficient; K is half of the length of the accommodation cavity.

[0021] As a preferred solution, there is a third gap between the top of the first screw teeth and the root of the second screw teeth or between the top of the second screw teeth and the root of the first screw teeth.

[0022] As a preferred solution, the equation for the size of the third gap is:

[0023] γ = C3 + (K - Z)C (Z < K)

[0024] γ = C3 + (Z - K)C (Z > K)

[0025] γ is the value of the third clearance; Z is the distance from a point on the first helical tooth (3) or the second helical tooth (5) to the end face of the air inlet; C3 is the basic clearance, a constant; C is the product of the operating temperature and the expansion coefficient of the first rotor, or the product of the operating temperature and the expansion coefficient of the second rotor; K is half of the length of the accommodating cavity.

[0026] As a preferred solution, the axes of the first screw rod and the second screw rod are arranged in parallel.

[0027] As a preferred solution, the thickness of the first helical tooth first decreases and then increases from the air inlet to the air outlet.

[0028] As a preferred solution, the thickness of the second helical tooth first decreases and then increases from the air inlet to the air outlet.

[0029] As a preferred solution, one end of the first screw rod is connected to a servo motor.

[0030] The technical solution of the present invention has the following advantages:

[0031] 1. A screw pump provided by the present invention includes: a housing having an accommodating cavity inside; an air inlet is provided on one end face of the housing; an air outlet is provided on the other end face of the housing; a first rotor having a first screw rod and a first helical tooth provided on the first screw rod; the first screw rod penetrates through the housing; a second rotor having a second screw rod and a second helical tooth; the second screw rod penetrates through the housing; the second helical tooth is provided on the second screw rod; the second helical tooth is meshed and connected with the first helical tooth; there is a first clearance between both the first helical tooth and the second screw rod and the housing; the first clearance first decreases and then increases along the direction from the air inlet to the air outlet; there is a second clearance between adjacent first helical teeth and second helical teeth; the second clearance first decreases and then increases along the direction from the air inlet to the air outlet. During the working process of the first rotor and the second rotor of the present device, the temperature gradually increases from the air inlet of the housing to the air outlet of the housing. Considering the thermal expansion effect, and ensuring that the gas will not generate a backflow phenomenon due to high pressure, and also avoiding the occurrence of jamming phenomenon, so both the first clearance and the second clearance are set to first decrease and then increase, which can ensure that the gas at the high-pressure end will not generate a backflow or jamming phenomenon on the premise of maintaining stable operation.

[0032] 2. A screw pump provided by the present invention is provided with a first rotor and a second rotor, and the axes of the first rotor and the second rotor are arranged in parallel. This arrangement can ensure that the two rotors remain stable during the working process, increasing the practicability of the present device.

[0033] 3. A screw pump provided by the present invention, one end of the first rotor is connected to a servo motor, and the first rotor is driven to move by the servo motor. The servo motor has the advantages of stable output and large torque, which can ensure the stable operation of the first rotor and increase the practicability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0035] Figure 1 It is a schematic diagram of the overall structure of the screw pump of the present invention.

[0036] Description of the reference numerals:

[0037] 1. Housing; 2. First screw; 3. First thread; 4. Second screw; 5. Second thread. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following will clearly and completely describe the technical solutions of the present invention with reference to the drawings. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0039] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0040] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] As Figure 1 shown, a screw pump provided by the present invention includes: a housing 1, a first rotor, and a second rotor; the housing 1 has an accommodation cavity inside; an air inlet is provided on one end face of the housing 1; an air outlet is provided on the other end face of the housing 1; the first rotor has a first screw 2 and a first tooth 3 provided on the first screw 2; the first screw 2 penetrates through the housing 1; the second rotor has a second screw 4 and a second tooth 5; the second screw 4 penetrates through the housing 1; the second tooth 5 is provided on the second screw 4; the second tooth 5 is meshed and connected with the first tooth 3; there is a first gap between both the first tooth 3 and the second tooth 5 and the housing 1; the first gap first becomes smaller and then larger along the direction from the air inlet to the air outlet; there is a second gap between two adjacent first teeth 3 and second teeth 5; the second gap first becomes smaller and then larger along the direction from the air inlet to the air outlet.

[0043] As Figure 1 shown, during the working process of the first rotor and the second rotor of the present device, the temperature gradually increases from the air inlet of the housing 1 to the air outlet of the housing 1. Considering the thermal expansion effect, and ensuring that the gas will not generate a backflow phenomenon due to high pressure, and also avoiding the occurrence of jamming, the first gap and the second gap are both set to first become smaller and then larger, which can ensure that the gas at the high-pressure end will not generate a backflow and will not jam under the premise of stable operation.

[0044] The first rotor in this solution is the driving rotor, and the second rotor is the driven rotor; the first rotor, the second rotor, and the housing 1 are combined together to form a sealed volume chamber, and the sealed volume chamber gradually becomes smaller from the air inlet direction to the air outlet direction.

[0045] One end of the first screw 2 is connected to a servo motor, and a stable driving force is provided to the first rotor through the servo motor. By utilizing the advantages of stable output and large torque of the servo motor, the first rotor can operate stably.

[0046] When the screw pump starts to work, gas enters from the air inlet, and then, as the first rotor and the second rotor rotate, it is pressed into the air outlet step by step. At this time, the sealed volume cavity formed by the first rotor, the second rotor and the housing 1 gradually decreases, the compression is stable and the efficiency is relatively high, but the temperature rise of the gas is relatively large. Due to the large temperature rise of the gas, the high-pressure ends of the first rotor and the second rotor are extremely prone to thermal expansion, resulting in a decrease in the first gap between the high-pressure ends of the first rotor and the second rotor and the housing 1. When the first gap between the first rotor, the second rotor and the housing 1 is too small, jamming will occur during the movement process. However, if the first gap between the first rotor, the second rotor and the housing 1 is set too large, gas reflux will occur, which will also affect the normal use of this device. Therefore, in this solution, the first gap is set to become smaller first and then larger along the direction from the air inlet to the air outlet. The equation for the size of the first gap is:

[0047] δ = C + (K - Z)C1 (Z < K)

[0048] δ = C + (Z - K)C2 (Z > K)

[0049] δ is the value of the first gap; Z is the distance from the point on the first spiral tooth 3 or the second spiral tooth 5 to the end face of the air inlet; C is the basic gap, a constant; C1 and C2 are the products of the operating temperature of the first rotor or the second rotor and the expansion coefficient of the first rotor or the second rotor; K is half of the length of the accommodation cavity.

[0050] When the screw pump starts to work, under the action of thermal expansion, the second gap between the first spiral tooth 3 and the second spiral tooth 5 will also change. Similarly, in order to prevent jamming and reflux phenomena, the second gap is set to become smaller first and then larger along the direction from the air inlet to the air outlet. The equation for the second gap is:

[0051] β = C + (K - Z)C1 (Z < K)

[0052] β = C + (Z - K)C2 (Z > K)

[0053] β is the value of the second gap; Z is the distance from the point on the first spiral tooth 3 or the second spiral tooth 5 to the end face of the air inlet; C is the basic gap, a constant; C1 and C2 are the products of the operating temperature of the first rotor or the second rotor and the expansion coefficient of the first rotor or the second rotor; K is half of the length of the accommodation cavity.

[0054] There is a third gap between the top of the first spiral tooth 3 and the root of the second spiral tooth 5 or between the top of the second spiral tooth 5 and the root of the first spiral tooth 3.

[0055] The equation for the size of the third gap is:

[0056] γ = C3 + (K - Z)C (Z < K)

[0057] γ = C3 + (Z - K)C (Z > K)

[0058] γ is the value of the third clearance; Z is the distance from a point on the first helical tooth 3 or the second helical tooth 5 to the end face of the air inlet; C3 is the basic clearance, a constant; C is the product of the operating temperature and the expansion coefficient of the first rotor, or the product of the operating temperature and the expansion coefficient of the second rotor; K is half of the length of the accommodating cavity.

[0059] In order to meet the value of the second clearance, the thicknesses of the first helical tooth 3 and the second helical tooth 5 in this device can be changed accordingly to meet the value of the second clearance. Since the thickness of the first helical tooth 3 first decreases and then increases due to the second clearance, the thickness of the first helical tooth 3 first decreases and then increases. The thickness of the second helical tooth 5 also changes according to the change of the second clearance, and the movement of the second helical tooth 5 first decreases and then increases.

[0060] To ensure the stability of the operation of this device, the axes of the first screw rod 2 and the second screw rod 4 are arranged in parallel. This arrangement can ensure that the two rotors remain stable during operation, increasing the practicality of this device.

[0061] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A screw pump, characterized in that, Comprising: A housing (1) with an accommodation cavity inside; an air inlet is provided on one end face of the housing (1); an air outlet is provided on the other end face of the housing (1). A first rotor having a first screw rod (2) and first screw teeth (3) provided on the first screw rod (2); the first screw rod (2) penetrates through the housing (1). A second rotor having a second screw rod (4) and second screw teeth (5); the second screw rod (4) penetrates through the housing (1); the second screw teeth (5) are provided on the second screw rod (4); the second screw teeth (5) are meshed and connected with the first screw teeth (3). There is a first gap between both the first screw teeth (3) and the second screw teeth (5) and the housing (1); the first gap first becomes smaller and then larger along the direction from the air inlet to the air outlet. There is a second gap between two adjacent first screw teeth (3) and second screw teeth (5); the second gap first becomes smaller and then larger along the direction from the air inlet to the air outlet. The equation for the size of the first gap is: δ = C1 + (K - Z)C (Z < K) δ = C1 + (Z - K)C (Z > K) δ is the value of the first gap; Z is the distance from a point on the first screw teeth (3) or the second screw teeth (5) to the end face of the air inlet; C1 is the basic gap, a constant; C is the product of the operating temperature of the first rotor and the expansion coefficient, or the product of the operating temperature of the second rotor and the expansion coefficient; K is half of the length of the accommodation cavity. The equation for the size of the second gap is: β = C2 + (K - Z)C (Z < K) β = C2 + (Z - K)C (Z > K) β is the value of the second gap; Z is the distance from a point on the first screw teeth (3) or the second screw teeth (5) to the end face of the air inlet; C2 is the basic gap, a constant; C is the product of the operating temperature of the first rotor and the expansion coefficient, or the product of the operating temperature of the second rotor and the expansion coefficient; K is half of the length of the accommodation cavity. There is a third gap between the top of the first screw teeth (3) and the root of the second screw teeth (5) or between the top of the second screw teeth (5) and the root of the first screw teeth (3). The equation for the size of the third gap is: γ = C3 + (K - Z)C (Z < K) γ = C3 + (Z - K)C (Z > K) γ is the value of the third gap; Z is the distance from a point on the first screw teeth (3) or the second screw teeth (5) to the end face of the air inlet; C3 is the basic gap, a constant; C is the product of the operating temperature of the first rotor and the expansion coefficient, or the product of the operating temperature of the second rotor and the expansion coefficient; K is half of the length of the accommodation cavity. The axes of the first screw rod (2) and the second screw rod (4) are arranged in parallel. The thickness of the first screw teeth (3) first becomes smaller and then larger from the air inlet to the air outlet, and the thickness of the second screw teeth (5) first becomes smaller and then larger from the air inlet to the air outlet. One end of the first screw rod (2) is connected to a servo motor.

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