JP2808470B2 - Vacuum pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vacuum pump.

(Prior Art) A conventional vacuum pump will be described with reference to FIG.
Is a rotor, (2) is a housing, (A) is an intake port provided at the upper part of the housing (2), (E) is an exhaust port provided at an upper and lower middle part of the housing (2), (7) (7) ) Is a ball bearing rotatably supporting the rotor (1), and (10) is a rotor (1) and the housing (2).
(11a) and (12a) are rotor blades of each pump compression stage provided in upper and lower stages above the rotor (1), and (11b) and (12b) are rotor blades of each pump compression stage ( 11
a) Stators provided in the upper and lower stages in the housing (2) around (12a), (D) is a gas inlet provided in the upper and lower middle part of the housing (2), and (18) is an inlet ( A gas introduction path for introducing a gas different from the gas inhaled from A) from the gas introduction port (D) to the pump compression stage in the housing (2).
By rotating the rotor (1) having the impellers (11a) and (12a) after the compression of each pump, the gas is sucked into the housing (2) from the suction port (A) while a gas different from the same gas is sucked. From the gas inlet (D) to the pump compression stage in the housing (2) via the gas inlet (18), and the sucked gas is discharged from the outlet (F) to the atmosphere outside the housing (2). It exhausts directly.

(Problems to be Solved by the Invention) In the conventional vacuum pump shown in FIG. 3, when the molecular weight of the gas sucked into the housing (2) from the suction port (A) is small, the gas having a large molecular weight is converted into one gas. The gas introduction port (D), which is the gas introduction system, is introduced into the pump compression stage in the housing (2) via the gas introduction passage (18). As is clear from the figure, the exhaust performance depends on the molecular weight of the gas,
Viscosity coefficient, pressure of each compression stage, gas temperature (heat transfer coefficient, heat transfer coefficient), and pump type (centrifugal stage, vortex stage, etc.)
Greatly influenced by Focusing only on the molecular weight of the gas, and with only one gas introduction path, it is not possible to perform an optimal pumping action in each pump compression stage not only in a steady state but also in a transient state when the pressure changes.

In addition, some gases have the property of deteriorating general metal materials and oils, such as corrosiveness and radiation,
Although solidification occurs below 0 ° C, as shown in FIG. 3, a metallic rotor (1) and a metallic stator (11
b) In a vacuum pump in which (12b) has a metal ball bearing (7), the material strength is reduced early and the vacuum pump is broken. In addition, there has been a problem that the rotation performance is reduced due to the deterioration of the bearing characteristics, and from this point, the vacuum pump does not operate.

The present invention has been proposed in view of the above problems, and its object is to include those having a property of deteriorating general metal materials and oils such as corrosiveness and radiation in a gas. However, an object of the present invention is to provide a vacuum pump that can maintain the durability of the vacuum pump and can perform an optimal pumping operation in each pump compression stage even in a transitional period when the pressure changes.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a housing having an intake port and an exhaust port, a ceramic rotor disposed in the housing along the axis thereof, and A plurality of stators arranged in the upper and lower stages in the housing around the rotor, a gas bearing rotatably supporting the rotor, and a gas turbine driving the rotor; In the vacuum pump for directly exhausting the gas sucked into the exhaust port to the atmosphere from the exhaust port, the gas sucked from the inlet port has a molecular weight, a viscosity coefficient, a specific heat ratio,
A plurality of gas inlets for introducing a plurality of types of gases having different heat transfer coefficients into the pump compression stage in the housing are provided in the housing downstream of the suction port in correspondence with the respective pump compression stages. The controller has a controller for controlling the mixing ratio and mass flow rate of the mixed gas according to the pressure conditions of each pump compression stage.

(Function) The rotor is made of ceramics, and non-contact gas bearings are used for the bearings of the rotor to make it oil-free, degrading general metal materials and oils such as corrosive and radioactive gases. , The durability of the vacuum pump is maintained. Also, the mixing ratio and mass flow rate of the mixed gas composed of various gases are controlled in accordance with the pressure conditions of each pump compression stage, and the pressure ratio of each pump compression stage is increased so that the pressure at the intake port is sufficiently reduced. Therefore, the optimum pumping action is performed in each pump compression stage even in the transition of pressure change.

(Embodiment) Next, the vacuum pump of the present invention will be described with reference to an embodiment shown in FIG. 1. (1) is a ceramic rotor, (2) is a housing, and the housing (2) is an intermediate portion (2a). And an upper part (2b) and a lower part (2c).

(A) is an intake port provided at the upper part (2b) of the housing (2), (E) is an exhaust port provided at an intermediate part (2a) of the housing (2), (7a) (7b) (7c) Is a gas bearing that rotatably supports the rotor (1), (10) is a gas turbine provided on the rotor, (12) is a ceramic stator, and the ceramic stator (12) is the rotor (1). The upper and lower stages are provided in a housing (2) (upper portion (2b)) around each of the pump compression stage rotors provided in the upper stage (2b).

(B) A plurality of types of gases different from the types of gases that (C) and (D) inhale through the intake port are provided in the housing (2).
And a plurality of gas inlets (B), (C), and (D) for introducing gas to the intermediate pump stage in the housing (2).
Are formed in the middle part (2a) and the upper part (2b).

 (3a) and (3b) are cooling water flow paths.

Next, the operation of the vacuum pump shown in FIG. 1 will be specifically described.

A gas turbine (10) rotates a rotor (1) having centrifugal stage rotors to suck gas from a suction port (A) into a housing (2), while a gas of a different type from the gas is sucked into the housing (2). It is sucked into each pump compression stage in the housing (2) through the inlets (B), (C) and (D), and these sucked gases are directly exhausted from the outlet (E) to the atmosphere outside the housing (2). I do.

At this time, inside each pump compression stage, the suction port (A)
The gas sucked in from the air and the gas flowing backward from the exhaust port (E) due to the pressure difference are mixed, and the mass flow rate of the gas becomes smaller and the gas closer to the intake port (A) becomes closer to the exhaust port (E). As compared with, the volume flow rate is small, and the gas flow state in each pump compression stage is different.

Therefore, gas inlet (B) for each pump compression stage
(C) and (D) are provided to change the characteristics and mass flow rate of the gas introduced independently of the flow state of the gas to optimally control the exhaust characteristics.

In the vicinity of the intake port (A), the gas flow state is a molecular flow or an intermediate flow. In the region of the molecular flow or the intermediate flow, a mixed gas having a high molecular weight is introduced to improve the exhaust characteristics.

On the other hand, near the exhaust port (E), the flow state of the gas is a slip flow and a viscous flow.
A gas with a large viscosity coefficient is introduced to improve the exhaust characteristics.

In a vacuum pump, heat generation due to windage is large.
By introducing a gas mixture with a large heat conduction coefficient and heat transfer coefficient,
The cooling effect is enhanced and the thermal deformation is reduced, thereby increasing the assembly tolerance.

In addition, the rotor (1) and the stator (12) are made of a ceramic material so that a gas that degrades the properties of the material and oil can be used as a mixed gas, and the gas bearing (7a)
(7b) The rotor (1) is rotatably supported by (7c) to achieve oil-free operation.

In order to control the mixing ratio and mass flow rate of the mixed gas composed of various gases in accordance with the pressure conditions of each pump compression stage, the following means may be employed. Inlet (A)
The type and flow rate of the gas sucked from the inlet and the type of the gas sucked from the suction port are different, and the type of each gas mixed and introduced into each pump compression stage is set as an input value of the control device. The control device uses a table and an arithmetic expression that are input in advance to determine the type and flow rate of the gas to be sucked, that is, each pump pressure stage suitable for the pressure condition of each pump compression stage determined from the condition of the suction gas. Calculate the type and flow rate of gas to be introduced into The result of the operation is converted into a voltage which is an analog signal, and the voltage is applied to a valve for adjusting the flow rate provided for each of the gas inlets (B), (C) and (D), so that each pump compression stage Control the mixing ratio and mass flow rate of the gas introduced into

(Effect of the Invention) As described above, the vacuum pump of the present invention has a rotor made of ceramics and uses a non-contact gas bearing for the rotor bearing to make it oil-free, so that the gas contains no corrosive or radioactive gas. The durability of the vacuum pump can be maintained even if a material having the property of deteriorating general metal materials and oils is included.

In addition, the mixing ratio and mass flow rate of the mixed gas composed of various gases are controlled according to the pressure conditions of each pump compression stage.
Since the pressure ratio of each pump compression stage is increased and the pressure at the intake port is sufficiently reduced, an optimal pumping operation can be performed in each pump compression stage even during a transition period when the pressure changes.

[Brief description of the drawings]

FIG. 1 is a longitudinal side view showing an embodiment of a vacuum pump according to the present invention, FIG. 2 is an explanatory view showing an exhaust performance analysis result for various gases of the vacuum pump, and FIG. 3 is a longitudinal section showing a conventional vacuum pump. It is a side view. (1) Ceramic rotor, (2) Housing, (2a) Middle part of housing (2), (2b)
Upper part of housing (2), (2c) ... housing (2)
Lower part of (7a) (7b) (7c) ... gas bearing, (10) ...
Gas turbine, (12) ... Ceramics stator,
(A) ... intake port, (B) (C) (D) ... gas introduction port, (E) ... exhaust port.

Continuing from the front page Examiner Tsuyoshi Kumakura (56) References JP-A-63-75387 (JP, A) Fully open 1983-67999 (JP, U) Really open 1984-85397 (JP, U) Field (Int.Cl. ⁶ , DB name) F04D 19/04

Claims (1)

(57) [Claims] A housing having an inlet and an outlet;
A ceramic rotor disposed in the housing along the axis thereof, a plurality of stators disposed in upper and lower stages in the housing around the rotor, a gas bearing rotatably supporting the rotor, and the rotor And a gas turbine that drives the pump, and a vacuum pump that directly exhausts the gas sucked into the housing from the suction port to the atmosphere from the exhaust port, wherein the gas sucked from the suction port has a molecular weight, a viscosity coefficient, and a specific heat. Ratio, a plurality of gas inlets for introducing a plurality of types of gases having different heat transfer coefficients to the pump compression stage in the housing are provided in the housing downstream of the suction port in correspondence with each pump compression stage, It has a controller that controls the mixing ratio and mass flow rate of the mixed gas composed of various gases according to the pressure conditions after each pump is compressed. Empty pump.