An adaptive regulating Roots pump bypass device

Abstract

The invention discloses an adaptive regulating Roots pump bypass device. The invention adopts an electromagnetic regulating valve as the gas path regulating unit of the inlet and outlet bypass device of the Roots pump, utilizes the first Wheatstone bridge, the second Wheatstone bridge and the automatic regulating circuit to form the circuit system of the bypass device, and serves as the center of power supply, signal processing and signal execution of the bypass device, and uses the hot wire resistors of the first Wheatstone bridge and the second Wheatstone bridge as the measuring unit of the inlet and outlet temperature of the Roots pump. The balance of the Wheatstone bridge is utilized to adjust the opening of the electromagnetic valve in real time, and the differential pressure at the inlet and outlet of the Roots pump is accurately controlled within a reasonable range, so as to effectively reduce the increase in energy consumption caused by the extensive exhaust of the mechanical overflow valve.

Description

Technical Field

[0001] The invention relates to the field of vacuum technology, and in particular to a self-adaptive regulating Roots pump bypass device. Background Art

[0002] Roots pump is a double-rotor positive displacement vacuum pump. In the pump chamber, there are two "8"-shaped rotors installed perpendicularly on a pair of parallel shafts. Since the rotors in the pump chamber of the Roots pump are non-contact transmission and frictionless, the rotors can run at a high speed of 3000r / min, and there is no need to use oil lubrication in the chamber, so the oil-free clean pumping process can be achieved. In the low and medium vacuum range, the single pump pumping speed can exceed 1500m 3 / h, which can only be achieved by Roots pumps. Therefore, if a suitable combination of backing pump and Roots pump is selected, even a backing pump with a low pumping speed can achieve the extraction of a large amount of gas, and compared with a single backing pump with the same pumping speed, the energy consumption is greatly reduced.

[0003] When the pumping speed of the previous mechanical pump is not enough or the starting pressure of the Roots pump is too high, the gas at the outlet of the Roots pump cannot be discharged in time, resulting in too high outlet pressure of the Roots pump. At this time, the resistance of the rotor increases, the friction heat is high, and the rotor expands under the temperature effect, so that the gaps between the rotors and even the gaps between the rotors and the Roots pump cavity are offset, and then collisions occur, causing irreparable damage to the Roots pump. Therefore, when the outlet pressure of the Roots pump exceeds the maximum allowable pressure difference, in order to avoid the temperature rise effect of the Roots pump under a large pressure difference, it is necessary to set a bypass device to allow the high-pressure gas to flow back to the inlet of the Roots pump. In addition, in order to start the Roots pump at a higher pressure and further reduce the pumping time, it is also necessary to set a bypass protection device in the Roots pump to reduce the pressure at the outlet of the Roots pump in time and reduce the load on the rotor.

[0004] At present, the common bypass devices of Roots pumps are mechanical, such as flap valve type and counterweight valve type. Although the structure of mechanical bypass devices is relatively simple, the springs of such bypass devices will fatigue during long-term operation, resulting in changes in the elastic coefficient, causing the bypass valve to open prematurely. During long-term operation, the bypass device cannot be opened and closed smoothly due to rust and oil and gas pollution. In addition, mechanical bypass devices are all extensive exhaust with poor controllability, causing a large amount of gas at the outlet of the Roots pump to instantly re-enter the vacuum system, requiring re-evacuation, which in turn increases energy consumption. In addition, a single bypass valve is only suitable for a specific Roots pump and has poor versatility. Summary of the invention

[0005] In view of this, the present invention provides an adaptively adjustable Roots pump bypass device, in which a Wheatstone bridge is installed at the inlet and outlet of the Roots pump respectively, and the opening of the electromagnetic regulating valve is further adjusted by measuring the difference in the output of the two bridges under different pressures, so as to achieve timely and accurate adjustment when the Roots pump exceeds the maximum allowable pressure difference.

[0006] The invention discloses an adaptive regulating Roots pump bypass device, comprising: a first Wheatstone bridge, a second Wheatstone bridge, an automatic regulating circuit and an electromagnetic regulating valve; wherein the electromagnetic regulating valve is arranged on the gas path between the inlet and the outlet of the Roots pump; one arm of each of the first Wheatstone bridge and the second Wheatstone bridge is a hot wire resistor, and the two hot wire resistors are respectively arranged at the inlet and the outlet of the Roots pump; the automatic regulating circuit (3) compares the difference between the output voltages of the first Wheatstone bridge and the second Wheatstone bridge, and adjusts the opening of the electromagnetic regulating valve according to the difference.

[0007] Preferably, the heating wire resistor adopts a cylindrical spiral platinum wire.

[0008] Preferably, a thin quartz layer is laid on the surface of the heating wire resistor.

[0009] Preferably, the hot wire resistor is fastened to the threaded vacuum electrode, and then fastened to the inlet and outlet of the Roots pump through the vacuum electrode threaded interface.

[0010] Preferably, the solenoid control valve adopts the FK interface.

[0011] Preferably, the first Wheatstone bridge, the second Wheatstone bridge and the automatic regulating circuit adopt an integrated circuit design, and the hot wire and the electromagnetic regulating valve are respectively connected through leads.

[0012] Preferably, when equation (1) is satisfied, the electromagnetic regulating valve starts to adjust the opening under the drive of the automatic regulating circuit:

[0013]

[0014] Wherein, ΔP is the maximum allowable pressure difference of the Roots pump; k1 and k2 are calibration coefficients reflecting the relationship between the output voltage of the first Wheatstone bridge and the second Wheatstone bridge and the pressure of the Roots pump, and the values ​​of k1 and k2 are determined by experiments; U1 and U2 are the voltages output by the first Wheatstone bridge installed at the inlet of the Roots pump and the second Wheatstone bridge installed at the outlet of the Roots pump due to the imbalance of the bridges; U 10 , U 20 are the initial output voltages of the first Wheatstone bridge and the second Wheatstone bridge respectively.

[0015] Preferably, the opening K of the electromagnetic regulating valve is calculated according to formula (2):

[0016]

[0017] Wherein, k3 is a coefficient related to the characteristics of the bypass device and is determined through experiments.

[0018] Beneficial effects:

[0019] The present invention adopts an electromagnetic regulating valve as an air path regulating unit of an inlet and outlet bypass device of a Roots pump, utilizes a first Wheatstone bridge, a second Wheatstone bridge and an automatic regulating circuit to form a circuit system of the bypass device, and serves as a hub for power supply, signal processing and signal execution of the bypass device, uses the hot wire resistors of the first Wheatstone bridge and the second Wheatstone bridge as measuring units for the inlet and outlet temperatures of the Roots pump, utilizes the balance of the Wheatstone bridge to adjust the opening of the electromagnetic valve in real time, and accurately controls the differential pressure at the inlet and outlet of the Roots pump within a reasonable range, thereby effectively reducing the increase in energy consumption caused by the extensive exhaust of a mechanical overflow valve.

[0020] By adopting the Wheatstone bridge, the regulating resistance of the Wheatstone bridge can be utilized to realize the automatic zero adjustment function; by adopting the electromagnetic regulating valve, it also has the advantage of continuous opening adjustment.

[0021] In addition, the bypass device of the present invention has good matching performance for Roots pumps of different flow specifications. When the hardware configuration remains unchanged, the bypass device can be easily used in Roots pumps of different specifications by adjusting the adjustment coefficient between the opening of the solenoid valve and the output voltage of the bridge. The bypass device is easy to install and has strong operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic structural diagram of a bypass device of a self-adaptive regulating Roots pump according to the present invention;

[0023] Figure 2 The figure is a schematic diagram of assembling the bypass device of the self-adaptive regulating Roots pump and the Roots pump of the present invention.

[0024] Among them, 1-the first Wheatstone bridge, 2-the second Wheatstone bridge, 3-the automatic adjustment circuit, 4-the electromagnetic control valve, and 5-the Roots pump. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0026] The invention provides a self-adaptive regulating Roots pump bypass device. An electromagnetic regulating valve is arranged on a gas path between an inlet and an outlet of the Roots pump. The balance of a Wheatstone bridge is utilized. Two Wheatstone bridges are used to respectively measure the temperatures of the inlet and outlet of the Roots pump. Then, according to the outputs of the two Wheatstone bridges, the opening of the electromagnetic regulating valve is automatically adjusted so that the high-pressure gas at the outlet of the Roots pump flows back to the inlet of the Roots pump, and the pressure at the outlet of the Roots pump is timely reduced so that the Wheatstone bridge is restored to balance.

[0027] The self-adaptive regulating Roots pump bypass device of the present invention is as follows Figure 1 and Figure 2 As shown, it includes: a first Wheatstone bridge 1, a second Wheatstone bridge 2, an automatic regulating circuit 3 and an electromagnetic regulating valve 4; wherein, one arm of each of the first Wheatstone bridge 1 and the second Wheatstone bridge 2 is a hot wire resistor, and the two hot wire resistors are respectively connected to the inlet and outlet of the Roots pump to sense the temperature of the inlet and outlet of the Roots pump; the automatic regulating circuit 3 adjusts the opening of the electromagnetic regulating valve 4 according to the difference in output voltage between the first Wheatstone bridge 1 and the second Wheatstone bridge 2, so that the high-pressure gas at the outlet of the Roots pump flows back to the inlet of the Roots pump.

[0028] Specifically, the first Wheatstone bridge 1 includes a hot wire resistor R1, an adjustable resistor R 1V , Fixed resistor R 11 and fixed resistor R 12 The second Wheatstone bridge 2 includes a hot wire resistor R2 and an adjustable resistor R 2V , Fixed resistor R 21 and fixed resistor R 22 The hot wire resistor R1 of the first Wheatstone bridge 1 is connected to the inlet of the Roots pump 5, and the hot wire resistor R2 of the second Wheatstone bridge 2 is connected to the outlet of the Roots pump 5. When the Roots pump 5 is started, the pressure at the inlet and outlet of the Roots pump 5 changes, causing the first Wheatstone bridge 1 and the second Wheatstone bridge 2 to lose balance; the automatic adjustment circuit collects the output of the first Wheatstone bridge and the second Wheatstone bridge as feedback signals, converts them into corresponding pressure differences according to the set calibration coefficient, and automatically adjusts the opening of the electromagnetic regulating valve 4 by comparing them with the set maximum allowable pressure difference; the high-pressure gas at the outlet of the Roots pump 5 flows back to the inlet of the Roots pump 5 through the electromagnetic regulating valve 4, and finally the temperature of the hot wire resistor R1 and the hot wire resistor R2 returns to the equilibrium temperature, completing the bypass adjustment of the Roots pump.

[0029] The pressure difference between the inlet and outlet of the Roots pump 5 can be expressed as a functional relationship between the output voltage difference between the first Wheatstone bridge 1 and the second Wheatstone bridge 2. By modifying the set calibration coefficient, the bypass device of the present invention can be applied to various types of Roots pumps, and has good versatility. At the same time, the first Wheatstone bridge 1, the second Wheatstone bridge 2, and the automatic adjustment circuit 3 can be designed as an integrated circuit, and the hot wire and the electromagnetic regulating valve are respectively connected by leads, which is easy to install. In addition, when the bypass device is in standby mode, the first Wheatstone bridge 1 and the second Wheatstone bridge 2 will automatically adjust the zero adjustment resistance (adjustable resistance R 1V , R 2V ), realize bridge balance, realize automatic zero adjustment function, and eliminate zero drift caused by long-term use and circuit noise.

[0030] The hot wire is preferably a cylindrical spiral platinum wire. The platinum wire has a high temperature coefficient. The spiral shape allows a longer platinum wire to be laid in a smaller space, so that the initial resistance of the platinum wire is comparable to the resistance of the other three resistors on the bridge. A thin layer of quartz can also be laid on the surface of the hot wire to increase the strength of the hot wire. When installing the hot wire, first fasten the hot wire to the threaded vacuum electrode, and then fasten it to the inlet and outlet of the Roots pump through the vacuum electrode threaded interface.

[0031] The electromagnetic regulating valve 4 preferably has an FK interface, which is convenient for disassembly and has a function of continuous opening adjustment.

[0032] When the above bypass device is used to adjust the Roots pump:

[0033] First, use KF ferrules to fasten the inlet and outlet of the electromagnetic regulating valve to the inlet and outlet of the Roots pump 5 respectively, and introduce the hot wire resistors R1 and R2 into the corresponding inlet and outlet of the Roots pump 5 through the threaded vacuum electrodes, enter the standby state, and start the vacuum unit equipped with the Roots pump 5.

[0034] The maximum allowable pressure difference of the Roots pump 5 is set to ΔP. The bypass device is connected to the bypass channel of the Roots pump 5. As the Roots pump 5 runs, the temperature and pressure at the inlet and outlet of the Roots pump 5 begin to change. The resistance of the hot wire installed at the inlet and outlet of the Roots pump 5 changes due to the temperature change, resulting in an unbalanced corresponding Wheatstone bridge. Assuming that the voltage output of the first Wheatstone bridge 1 installed at the inlet of the Roots pump 5 due to the bridge imbalance is U1, and the voltage output of the second Wheatstone bridge 2 installed at the outlet of the Roots pump 5 due to the bridge imbalance is U2, when formula (1) is satisfied, the electromagnetic regulating valve 4 starts to adjust under the drive of the automatic regulating circuit 3:

[0035]

[0036] Wherein, k1 and k2 are calibration coefficients reflecting the relationship between the output voltage of the first Wheatstone bridge 1 and the second Wheatstone bridge 2 and the pressure of the Roots pump, respectively, and are determined by experiments; U 10 , U 20 are the initial output voltages of the first Wheatstone bridge 1 and the second Wheatstone bridge 2 respectively;

[0037] The adjustment amount of the automatic adjustment circuit 3, that is, the opening degree K of the electromagnetic control valve 4 is calculated according to formula (2):

[0038]

[0039] Where k3 is a coefficient related to the characteristics of the bypass device and is determined through experiments.

[0040] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An adaptive regulating Roots pump bypass device, characterized in that: include: A first Wheatstone bridge (1), a second Wheatstone bridge (2), an automatic regulating circuit (3) and an electromagnetic regulating valve (4); wherein the electromagnetic regulating valve (4) is arranged on a gas path between an inlet and an outlet of a Roots pump (5); one arm of each of the first Wheatstone bridge (1) and the second Wheatstone bridge (2) is a hot wire resistor, and the two hot wire resistors are respectively arranged at the inlet and the outlet of the Roots pump (5); the automatic regulating circuit (3) compares the difference between the output voltages of the first Wheatstone bridge (1) and the second Wheatstone bridge (2), and adjusts the opening of the electromagnetic regulating valve (4) according to the difference; When equation (1) is satisfied, the electromagnetic regulating valve (4) starts to adjust the opening degree under the drive of the automatic regulating circuit (3): Wherein, ΔP is the maximum allowable pressure difference of the Roots pump (5); k1 and k2 are calibration coefficients reflecting the relationship between the output voltage of the first Wheatstone bridge (1) and the second Wheatstone bridge (2) and the pressure of the Roots pump, and the values ​​of k1 and k2 are determined through experiments; U1 and U2 are the voltages output by the first Wheatstone bridge (1) installed at the inlet of the Roots pump (5) and the second Wheatstone bridge (2) installed at the outlet of the Roots pump (5) due to the imbalance of the bridges; U 10 , U 20 are respectively the initial output voltages of the first Wheatstone bridge (1) and the second Wheatstone bridge (2); The opening degree K of the electromagnetic regulating valve (4) is calculated according to formula (2): Wherein, k3 is a coefficient related to the characteristics of the bypass device and is determined through experiments.

2. The self-adaptive regulating Roots pump bypass device according to claim 1, characterized in that: The hot wire resistor uses a cylindrical spiral platinum wire.

3. The self-adaptive regulating Roots pump bypass device according to claim 1 or 2, characterized in that: A thin layer of quartz is laid on the surface of the hot wire resistor.

4. The self-adaptive regulating Roots pump bypass device according to claim 1, characterized in that: The hot wire resistor is fastened to the threaded vacuum electrode, and then fastened to the inlet and outlet of the Roots pump through the vacuum electrode threaded interface.

5. The self-adaptive regulating Roots pump bypass device according to claim 1, characterized in that: The electromagnetic regulating valve (4) adopts an FK interface.

6. The self-adaptive regulating Roots pump bypass device according to claim 1, characterized in that: The first Wheatstone bridge (1), the second Wheatstone bridge (2) and the automatic regulating circuit (3) adopt an integrated circuit design and are respectively connected to the hot wire and the electromagnetic regulating valve through lead wires.

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