Two-stage compression high-vacuum small dry vacuum pump

Abstract

The invention discloses a two-stage compression high-vacuum small-size dry vacuum pump which comprises a vacuum pump body, the vacuum pump body comprises two stages of compression cylinders connected in series, engaged female and male rotors are rotatably installed in the compression cylinders, and motors used for driving the female and male rotors are installed on the compression cylinders; the multi-transmission frequency converter is simultaneously connected to the motor of the two-stage compression cylinder; the collecting assembly comprises a first sensor used for collecting actual exhaust pressure in real time and a second sensor used for collecting actual inter-stage pressure in real time; and the controller is connected to the transmission frequency converter and the acquisition assembly, and the controller comprises a first sub-control module and a second sub-control module. The problems that an existing high-vacuum-degree small dry vacuum pump does not conduct synchronous control on two-stage compression, and the risk hidden danger of inter-stage rotating speed unbalance exists are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vacuum pumps, in particular to a two-stage compression high vacuum small dry vacuum pump. BACKGROUND

[0002] The small dry vacuum pump generally adopts multi-stage compression to realize high efficiency, high vacuum degree and stable operation, aiming to improve the ultimate vacuum degree. Because the compression ratio of single-stage compression vacuum pump is limited, the multi-stage series compression vacuum pump can improve the final vacuum degree, and the multi-stage compression vacuum pump matches the gas flow through the volume change between different stages to avoid the efficiency loss caused by gas back leakage at low gas pressure in single-stage compression. Single-stage high compression ratio will cause the gas temperature to rise sharply, which may damage the sealing material, while multi-stage compression can reduce the gas temperature step by step, reduce the influence of thermal stress on the pump body, and reduce the energy consumption by 20-30% compared with single-stage adiabatic compression, also avoiding the high instantaneous power of single-stage motor, prolonging the service life of bearings and transmission components.

[0003] In summary, the core goal of multi-stage compression of high vacuum degree small dry vacuum pump is to balance the vacuum degree, efficiency and reliability, and its essence is to break through the physical limit of single stage through multi-stage compression, while reducing the thermal load and energy consumption. On the premise of meeting the requirements, the fewer the number of stages is, the better, and two-stage compression is usually used.

[0004] The electrical system of high vacuum degree small dry vacuum pump generally includes a control system, a driving system and an execution system. The standard controller of the control system integrates control process logic and pre-alarm protection measures, and monitors the running state of the vacuum pump in real time to control the driving system to control the operation of the motor of the execution system. The control system of the two-stage compression high vacuum small dry vacuum pump currently uses a standard controller, the driving system uses two frequency converters, and the execution system uses two permanent magnet synchronous motors. Although it seems simple and practical, it actually has some shortcomings: The permanent magnet synchronous motor of the execution system is relatively large in size, which makes the vacuum pump that should be compact in structure slightly bulky, and the metal material of the motor shell is used for heat conduction, which makes the heat dissipation efficiency relatively low, causing easy overheating during high load operation; The driving system directly uses two sets of frequency converters, which is simple and convenient, but lacks integration; The control system adds a frequency converter to control the motor of the two-stage compression based on the single-stage compression standard controller, and the two sets of frequency converters also use the start-stop control mode, which basically meets the working requirements of the whole machine, but does not synchronize the control of the two-stage compression, making the control scheme not perfect and having the risk of imbalance between stages. SUMMARY

[0005] In order to overcome the defects of the prior art, a two-stage compression high vacuum small dry vacuum pump is provided to solve the problem that the existing high vacuum small dry vacuum pump does not synchronously control the two-stage compression and has the risk of imbalance between stages.

[0006] In order to achieve the above-mentioned purpose, a two-stage compression high vacuum small dry vacuum pump is provided, comprising: The vacuum pump body comprises two-stage compression cylinders connected in series, the male and female rotors are rotatably installed in the compression cylinders, and the compression cylinders are provided with motors for driving the male and female rotors; The multi-drive frequency converter is connected to the motors of the two-stage compression cylinders at the same time; The acquisition assembly comprises a first sensor for acquiring the actual exhaust pressure in real time and a second sensor for acquiring the actual inter-stage pressure in real time; The controller is connected to the drive frequency converter and the acquisition assembly, and the controller comprises a first sub-control module and a second sub-control module, based on the first pressure difference between the target exhaust pressure and the actual exhaust pressure and the first pressure difference being non-zero, the first sub-module increases the first shaft frequency of the multi-drive frequency converter to increase the motor speed of the primary compression cylinder driven by the first shaft of the multi-drive frequency converter, so that the actual exhaust pressure rises, after the first pressure difference decreases, the first sub-module reduces the first shaft frequency by a given increase amplitude to reduce the increase amplitude of the motor speed of the primary compression cylinder, so that the increase amplitude of the actual exhaust pressure is slowed down, and this is repeated, so that the first pressure difference returns to zero, and based on the second pressure difference between the target inter-stage pressure and the actual inter-stage pressure and the second pressure difference being non-zero, the second sub-control module increases the second shaft frequency of the multi-drive frequency converter to increase the motor speed of the secondary compression cylinder driven by the second shaft of the multi-drive frequency converter, thereby adjusting the actual inter-stage pressure to assist the first pressure difference to return to zero.

[0007] Further, the motor is a parallel-shaft double-rotor motor, and the double rotors of the parallel-shaft double-rotor motor are coaxially arranged with the male and female rotors.

[0008] Further, the motor is attached with a heat sink through heat-conducting adhesive.

[0009] Further, the heat sink is an extruded heat sink.

[0010] The controller of the two-stage compression high vacuum small dry vacuum pump of the present application increases the sub-modules (first sub-control module and second sub-control module) for synchronous control of the two-stage compression to synchronously control the rotational speed of the two-stage compression cylinders, and the rotational speed between the two-stage compression is balanced through PID control, so that the two-stage compression high vacuum small dry vacuum pump of the present application runs efficiently and stably under high load, and is suitable for high-precision vacuum application scenarios such as laboratories. Attached Figure Description

[0011] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the structure of a two-stage compression high-vacuum small dry vacuum pump according to an embodiment of the present invention.

[0012] Figure 2 This is a schematic diagram of the structure of the vacuum pump body according to an embodiment of the present invention.

[0013] Figure 3 This is a schematic diagram of the internal structure of the vacuum pump body according to an embodiment of the present invention.

[0014] Figure 4 This is a schematic diagram of the internal structure of the compression cylinder according to an embodiment of the present invention.

[0015] Figure label: Vacuum pump body 1, compression cylinder 11, primary compression cylinder 11a, secondary compression cylinder 11b, male and female rotors 12, motor 13, radiator 14; Multi-drive frequency converter 2; Data acquisition component 3, first sensor 31, second sensor 32; Controller 4, first sub-control module 41, second sub-control module 42. Detailed Implementation

[0016] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] Reference Figures 1 to 4 As shown, the present invention provides a two-stage compression high vacuum small dry vacuum pump, including: a vacuum pump body 1, a multi-drive frequency converter 2, a data acquisition component 3, and a controller 4.

[0019] See Figure 3 As shown, the vacuum pump body 1 includes two-stage compression cylinders 11. The two-stage compression cylinders 11 are connected in series. Specifically, the two-stage compression cylinders 11 include a primary compression cylinder 11a and a secondary compression cylinder 11b. Air from outside the vacuum pump body is drawn in through the air inlet of the primary compression cylinder, undergoes primary compression in the primary compression cylinder, and then undergoes secondary compression in the secondary compression cylinder to generate compressed air.

[0020] The compression cylinder 11 is rotatably mounted with the engaged male and female rotors 12. The compression cylinder 11 is mounted with the motor 13. The motor 13 is used to drive the male and female rotors 12.

[0021] The multi-drive frequency converter 2 is simultaneously connected to the motors 13 of the two-stage compression cylinder 11.

[0022] The acquisition assembly 3 includes a first sensor 31 and a second sensor 32. The first sensor 31 is used to acquire the actual exhaust pressure in real time. The second sensor 32 is used to acquire the actual inter-stage pressure in real time.

[0023] The controller 4 is connected to the drive frequency converter and the acquisition assembly 3.

[0024] The controller 4 includes a first sub-control module 41 and a second sub-control module 42.

[0025] After the first sub-control module 41 and the second sub-control module 42 of the controller acquire the actual exhaust pressure and the actual inter-stage pressure, based on the first pressure difference between the target exhaust pressure and the actual exhaust pressure and the first pressure difference being non-zero, the first sub-module increases the first shaft frequency of the multi-drive frequency converter 2 to increase the rotation speed of the motor 13 of the first-stage compression cylinder 11a driven by the first shaft of the multi-drive frequency converter 2, so that the actual exhaust pressure rises. After the first pressure difference decreases, the first sub-module decreases the first shaft frequency by a given increase amplitude to reduce the increase amplitude of the rotation speed of the motor 13 of the first-stage compression cylinder 11a, so that the increase amplitude of the actual exhaust pressure is slowed down. This is repeated to make the first pressure difference zero. At the same time, based on the second pressure difference between the target inter-stage pressure and the actual inter-stage pressure and the second pressure difference being non-zero, the second sub-control module 42 increases the second shaft frequency of the multi-drive frequency converter 2 to increase the rotation speed of the motor 13 of the second-stage compression cylinder 11b driven by the second shaft of the multi-drive frequency converter 2, so as to adjust the actual inter-stage pressure to assist in making the first pressure difference zero.

[0026] In the embodiment, the motor 13 is a parallel-shaft double-rotor motor 13. The double rotors of the parallel-shaft double-rotor motor 13 are coaxially arranged with the male and female rotors 12.

[0027] In the embodiment, the motor 13 is adhesively connected with the heat sink 14 through a heat-conducting adhesive.

[0028] Both the parallel-shaft double-rotor motor body and the heat sink are modular and detachable. The double rotors of the motor are coaxial with the male and female rotors of the vacuum pump body, which embodies the compact structure and improves the transmission efficiency. Meanwhile, the extruded heat sink is attached to the motor stator through heat-conducting potting adhesive, which ensures the compact structure of the vacuum pump and effectively reduces the temperature rise of the motor.

[0029] The multi-drive frequency converter of the two-stage compression high-vacuum small dry vacuum pump is composed of a set of rectifier modules and a set of double-shaft inverter modules, and the combination mode is more in line with integration.

[0030] The controller of the two-stage compression high-vacuum small dry vacuum pump increases a two-stage compression synchronous control submodule (a first sub-control module and a second sub-control module). The drive system of the two-stage compression high-vacuum small dry vacuum pump adopts a multi-drive frequency converter. For the frequency converter, it is composed of a rectifier and an inverter. The difference lies in that the rectifier module and the inverter module of the standard frequency converter are fixed and cannot be separated, while the multi-drive frequency converter is composed of the rectifier module and the inverter module, and the inverter module can be divided into a single-shaft inverter module and a double-shaft inverter module according to the number of control motors. The multi-drive frequency converter of the two-stage compression high-vacuum small dry vacuum pump is composed of the rectifier module and the double-shaft inverter module, and receives the command of the controller to control the execution system. The execution system of the two-stage compression high-vacuum small dry vacuum pump is a parallel-shaft double-rotor motor. The parallel-shaft double-rotor motor and the radiator both adopt a modularized detachable design. The double rotors of the parallel-shaft double-rotor motor are coaxial with the male and female rotors of the vacuum pump body. The extruded radiator is attached to the motor through heat-conducting pouring sealant, which ensures that the motor is small in size and meets the compact structure of the vacuum pump while effectively reducing the motor temperature rise. The two-stage compression high-vacuum small dry vacuum pump of the application runs efficiently and stably under high load, and is suitable for high-precision vacuum application scenarios such as laboratories.

[0031] The controller of the two-stage compression high-vacuum small dry vacuum pump adopts PID (Proportional-Integral-Derivative) control. PID control is a classic automatic control algorithm. It adjusts the control quantity in real time according to the system error through the combination operation of the proportional (P), integral (I) and differential (D) links, so as to realize that the controlled object quickly, accurately and smoothly tracks the target value.

[0032] The real-time monitored exhaust pressure is the actual exhaust pressure, and the exhaust pressure set by the user is the target exhaust pressure. The pressure difference (the first pressure difference) between the two is used as the input of the first sub-control module, and the adjustment control quantity of the first sub-control module is used as the first shaft frequency given value of the double-shaft inverter module, which is used to adjust the motor speed driven by the first shaft in real time, so as to adjust the exhaust pressure.

[0033] When the first pressure difference is non-zero, the first shaft frequency given value will increase, so that the motor speed driven by the first shaft increases, and the exhaust pressure rises. After the first pressure difference decreases, the increase amplitude of the first shaft frequency given value decreases, so that the increase amplitude of the motor speed driven by the first shaft decreases, and the increase amplitude of the exhaust pressure slows down. The first pressure difference further decreases, and the process is repeated, and finally the first pressure difference input returns to zero.

[0034] The inter-stage pressure monitored in real time is the actual inter-stage pressure, the theoretical inter-stage pressure is the target inter-stage pressure, and the pressure difference (second pressure difference) between the two is taken as the input of the second sub-control module, and the adjustment control amount of the second sub-control module is taken as the second shaft frequency given of the dual-shaft inverter module, so as to adjust the motor speed driven by the second shaft, thereby adjusting the inter-stage pressure; and finally the first pressure difference input is returned to zero, so as to realize the speed balance between the two stages of compression.

[0035] The above description is only the preferred embodiment of the present application and the explanation of the applied technical principles. It should be understood by those skilled in the art that the scope of the application involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or equivalent features without departing from the inventive concept. For example, the technical solutions formed by the mutual replacement of the above features and the technical features disclosed in the present application (but not limited to) having similar functions.

Claims

1. A two-stage compression high vacuum small dry vacuum pump characterized by, The application relates to a vacuum pump body, a multi-transmission frequency converter, a collection component and a controller. The vacuum pump body comprises two-stage compression cylinders connected in series, the compression cylinders are rotatably installed with meshed male and female rotors, and the compression cylinders are installed with motors for driving the male and female rotors. The multi-transmission frequency converter is simultaneously connected to the motors of the two-stage compression cylinders. The collection component comprises a first sensor for collecting an actual exhaust pressure in real time and a second sensor for collecting an actual inter-stage pressure in real time. The controller is connected to the transmission frequency converter and the collection component, and the controller comprises a first sub-control module and a second sub-control module.

2. The two-stage compression high vacuum small dry vacuum pump according to claim 1, characterized in that, When a first pressure difference between a target exhaust pressure and the actual exhaust pressure is not zero, the first sub-control module increases a first shaft frequency of the multi-transmission frequency converter to increase a motor rotating speed of a first-stage compression cylinder driven by a first shaft of the multi-transmission frequency converter, so that the actual exhaust pressure rises.

3. The two-stage compression high vacuum small dry vacuum pump according to claim 1, characterized in that, When the first pressure difference decreases, the first sub-control module decreases the first shaft frequency by a given increasing amplitude to reduce the increasing amplitude of the motor rotating speed of the first-stage compression cylinder, so that the rising amplitude of the actual exhaust pressure is reduced.

4. The two-stage compression high vacuum small dry vacuum pump according to claim 3, characterized in that, The first sub-control module is repeatedly used to make the first pressure difference zero. When a second pressure difference between a target inter-stage pressure and the actual inter-stage pressure is not zero, the second sub-control module increases a second shaft frequency of the multi-transmission frequency converter to increase a motor rotating speed of a second-stage compression cylinder driven by a second shaft of the multi-transmission frequency converter, so that the actual inter-stage pressure is adjusted to assist the first pressure difference to be zero. The motor is a parallel-shaft double-rotor motor, and the double rotors of the parallel-shaft double-rotor motor are coaxially arranged with the male and female rotors. The motor is bonded with a radiator through heat-conducting glue. The radiator is an extruded radiator.

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