JPH10306790A - Molecular pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate adhesion of a product generated by sublimation of exhaust gas by keeping rotor temperature within a specified range in a high vacuum area and a low vacuum area. SOLUTION: A first heater 30 and a water jacket 39 are fitted to the intake side of a housing 21, and a second heater 40 is fitted to the exhaust side. A temperature sensor 41 is fitted to the lower side of a rotor 27 in the housing 21. A control part 42 controls the action of a second heating control part 44 according to the difference between exhaust gas temperature from the temperature sensor and target temperature so as to keep the exhaust side temperature of the casing 21 within a specified range, and controls the action of a flow control part 46 or a first heating control part 48 according to the value of difference between the input current value I of a high frequency motor 37 and the reference value I0 so as to keep the temperature of the rotor 27 within a specified range not exceeding the heat resisting temperature 12 deg.C of aluminum. The temperature of the rotor 27 is thus kept within the specified range of 100 deg.C-110 deg.C to prevent adhesion of a product generated by sublimation of exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an improvement of a molecular pump.

[0002]

2. Description of the Related Art There is a turbo molecular pump as a molecular pump for making a high vacuum in a chamber. As shown in FIG. 4, the turbo molecular pump includes a cylindrical casing 1, a base 2 supporting the casing 1, a motor housing 3 provided in the casing 1 on the base 2, Bearings 4 and 5 provided in motor housing 3
And a rotor 7 fixed to the rotating shaft 6. On the outer periphery of the rotor 7, rotor blades 8 are provided in multiple stages. Further, stator blades 9 are provided in multiple stages on the inner peripheral surface of the casing 1 and are arranged between the rotor blades 8, 8,.

The flange 13 of the casing 1
The gas sucked through a suction port 14 from a chamber (not shown) connected to the
And forced exhaust is performed toward the exhaust port 15. Reference numeral 16 denotes an oil tank provided in the bottom of the base 2. Reference numeral 17 denotes a high frequency motor.

When the process gas in the chamber is exhausted, the gas sucked from the intake port 14 may be sublimated to be a product and deposited in the turbo molecular pump. Such products are likely to accumulate on the exhaust side of the rotor 7 on the high pressure side, and a failure occurs due to clogging or the like by the accumulated products. Therefore, a heating means is provided, and the exhaust side is heated by the heat from the heating means to heat the exhaust gas, thereby preventing sublimation.

[0005]

However, the above-mentioned conventional turbo-molecular pump has the following problems.
FIG. 5 shows the relationship between the suction gas pressure and the temperatures of the casing 1 and the rotor 7 in the turbo-molecular pump shown in FIG. In FIG. 5, in a low vacuum region where the suction gas pressure is 10 ² Pa or more, the casing 1 and the rotor 7 radiate heat mainly by radiation and convection, so that the temperature difference between the casing 1 and the rotor 7 is small. However, the suction gas pressure is 10 ^-8 Pa ~
In the high vacuum area to the middle vacuum area of 1 Pa, the environment around the rotor 7 is close to a vacuum, so that the rotor 7 radiates heat only by radiation. On the other hand, the casing 1 radiates heat mainly by radiation and convection. Therefore, the casing 1
The temperature tends to decrease as compared with the rotor 7, and the temperature difference between the casing 1 and the rotor 7 increases, so that the temperature of the casing 1 falls about 50 ° C. below the temperature of the rotor 7.

[0006] From the above, by the heating means,
If the temperature of the casing 1 or the rotor 7 is kept constant over the entire gas pressure range in which the turbo molecular pump is used, the following problems occur.

FIG. 6 shows a state in which a heater 18 as the heating means is attached to the outer periphery of the casing 1 of the turbo molecular pump as shown in FIG.
The figure shows the temperature of the rotor 7 when the heating amount of the heater 18 is controlled so that the temperature of the casing 1 detected by the temperature sensor 19 installed in the vicinity keeps a constant temperature of 100 ° C. In this case, in a high vacuum region, the temperature of the rotor 7 is about 50 ° C. higher than the temperature of the casing 1, so that the temperature of the rotor 7 is about 150 ° C., which exceeds the heat-resistant temperature of aluminum, which is the material of the rotor 7, of 120 ° C. Therefore, there is a problem that driving becomes impossible.

Further, FIG. 7 shows that, as shown in FIG. 7 (b), a heater 18 as the heating means is attached to the outer periphery of the casing 1 of the turbo molecular pump, and the temperature of the rotor 7 is set to a heat resistant temperature of aluminum of 120 ° C. The following constant temperature 100 ℃
3 shows the temperature of the casing 1 when the heating amount of the heater 18 is controlled so as to maintain the temperature. Here, the rotor 7 is tens of thousands.
Since high-speed rotation at rpm is performed, a temperature sensor cannot be directly installed on the rotor 7. Therefore, a pressure sensor 20 is installed at the intake port 14 of the casing 1 and the pressure sensor 2
Inhalation gas pressure by 0 (that is, the degree of vacuum in the chamber)
Thus, the temperature of the rotor 7 is estimated from FIG. In this case, since the temperature of the casing 1 is lower than the temperature of the rotor 7 by about 50 ° C. in the high vacuum area to the medium vacuum area, the temperature of the casing 1 becomes about 50 ° C. There is a problem of sticking to the exhaust part.

SUMMARY OF THE INVENTION An object of the present invention is to provide a molecular pump capable of maintaining the rotor temperature within a fixed range in a high vacuum range to a low vacuum range and eliminating product adhesion due to sublimation of exhaust gas.

[0010]

According to a first aspect of the present invention, there is provided a molecular pump having a casing and a rotor fitted in the casing. Adjusting means, exhaust side heating means provided on the exhaust side of the casing,
The rotor load detecting means for detecting the load of the rotor, the temperature detecting means for detecting the exhaust gas temperature, and the temperature on the exhaust side of the casing based on the detected value of the temperature detecting means are set within a certain range. A first control unit for controlling the exhaust-side heating unit, and a second control unit for controlling the temperature adjustment unit based on a detection value of the rotor load detection unit so that the temperature of the rotor falls within a predetermined range. It is characterized by having.

According to the above configuration, the first control means controls the exhaust-side heating means based on the detected value of the exhaust gas temperature by the temperature detection means, so that the temperature on the exhaust side of the casing is kept within a constant range. It is. Further, the temperature control means is controlled by the second control means based on the detection value of the rotor load detection means, and the temperature of the rotor is kept within a fixed range. Thus, even if the rotor load detected by the rotor load detecting means changes, that is, if the suction gas pressure changes, the temperature of the rotor is lower than the heat resistant temperature of aluminum and the exhaust gas does not sublime. Kept within range. Therefore, there is no adhesion of products due to the sublimation of the exhaust gas over a wide gas pressure range in which the present molecular pump is used.

Further, according to a second aspect of the present invention, in the molecular pump according to the first aspect of the present invention, the temperature control means may include:
It is characterized by including intake side heating means and intake side cooling means.

According to the above configuration, the second control means controls the intake-side heating means and the intake-side cooling means as the temperature adjusting means, so that the temperature of the rotor can be easily maintained within the fixed range. It is.

According to a third aspect of the present invention, in the molecular pump according to the second aspect, the second control means includes:
When the detected value of the rotor load detecting means is equal to or less than a reference value, the intake side cooling means is operated, and when the detected value of the rotor load detecting means is larger than the reference value, the intake side heating means is activated. It is characterized by being operated.

According to the above configuration, when the value detected by the rotor load detecting means is equal to or less than the reference value, that is, when the suction gas pressure is low to medium pressure (high vacuum to medium vacuum),
The intake side cooling means is operated by the second control means to radiatively cool the rotor. On the other hand, when the detected value of the rotor load is larger than the reference value, that is, when the exhaust gas pressure is high pressure (low vacuum), the intake side heating means is operated by the second control means and the rotor is operated. Radiant heating. In this way, the temperature of the rotor is reliably kept within the fixed range over a wide gas pressure range in which the present molecular pump is used.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a schematic sectional view of the molecular pump according to the present embodiment. The molecular pump according to the present embodiment is a screw pump.

The base 22, motor housing 23, bearings 24, 25, rotating shaft 26, flange 33, intake port 34,
Exhaust port 35, oil tank 36 and high frequency motor 37
Has the same basic configuration as the base 2, the motor housing 3, the bearings 4, 5, the rotating shaft 6, the flange 13, the intake port 14, the exhaust port 15, the oil tank 16 and the high frequency motor 17 in the turbo molecular pump shown in FIG. And work similarly.

No stator blade is provided on the inner peripheral surface of the casing 21. And on the outer periphery of the rotor 27,
A helical screw 28 extending from the intake port 34 to the exhaust port 35 is formed. Then, with the rotation of the rotor 27,
Gas sucked through a suction port 34 from a chamber (not shown) connected to the flange 33 is compressed by a screw groove 29 formed between the screws 28 of the rotor 27, and is compressed toward a discharge port 35. Forcibly exhaust.

A first heater 38 as the heating means on the intake side and a water jacket 39 as the cooling means on the intake side are mounted on the outer periphery of the intake side of the housing 21. Further, a second heater 40 as the exhaust-side heating means is attached to the outer periphery of the exhaust side of the housing 21. further,
A temperature sensor 41 is mounted below the rotor 27 in the housing 21. Then, a signal representing the exhaust gas temperature detected by the temperature sensor 41 is transmitted to the control unit 42.
Is input to Further, a signal representing the current value I supplied to the high-frequency motor 37 detected by the current detection unit 43 is input to the control unit 42.

The control section 42 is provided with a second heater for maintaining the temperature on the exhaust side of the casing 21 at the target temperature in accordance with the difference between the exhaust gas temperature based on the signal input from the temperature sensor 41 and the target temperature. The heating amount of 40 is calculated. Then, the current value of the second heater 40 based on this heating amount is
It is sent to the heating control unit 44. Then, the second heating control unit 44 resets the output current of the built-in amplifier to the above current value. Thus, the heating amount of the second heater 40 is controlled such that the exhaust-side temperature of the casing 21 becomes the target temperature.

Further, based on the input current value I of the high-frequency motor 37 based on the signal from the current detection unit 43 and the reference value I ₀ , the control unit 42 determines the rotor if I−I ₀ ≦ 0. As shown in FIG. 6 (a), the rotor 27 is made of a heat-resistant material such as aluminum because the load on the shaft 27 is small and the inside of a chamber (not shown) connected to the flange 33 is in a high vacuum to medium vacuum. It is determined that the possibility that the temperature exceeds 120 ° C. is high. Then, as shown in FIG. 2, a casing 2 for keeping the temperature of the rotor 27 within a certain range according to the value of the difference (I-I ₀ ) between the current value I and the reference value I _0.
1 is obtained. On the other hand, when I−I ₀ > 0, the load on the rotor 27 is large and the inside of the chamber is in a low vacuum, so that the difference (I−I) between the current value I and the reference value I ₀ as shown in FIG. _The amount of heating of the casing 21 for keeping the temperature of the rotor 27 within a fixed range is determined according to the value of ₀ ). That is, in the present embodiment, the rotor load detecting means is constituted by the current detecting unit 43.

The amount of cooling or heating is determined, for example, as follows. That is, the value of the difference (I-I ₀ ) between the input current value I of the high-frequency motor 37 and its reference value I ₀ and the temperature of the rotor 27 are kept within a certain range not exceeding the heat-resistant temperature of aluminum of 120 ° C. The relationship between the amount of cooling and the amount of heating of the casing 21 (see FIG. 2) is written in a table in the memory 45, and the table is obtained by drawing the table. The cooling amount or the heating amount of the casing 21 may be calculated by using the relational expression between the difference (I−I ₀ ) and the cooling amount and the heating amount of the casing 21 without using the table. .

The control unit 42 determines that (I−I ₀ ) ≦
In the case of 0, the casing 21 determined as described above is used.
Then, the flow rate of the water in the water jacket 39 is calculated based on the cooling amount, and the opening degree of the valve 47 based on the calculated flow rate value is output to the flow control unit 46. Then, the flow control unit 46
Resets the opening of the valve 47 to the indicated opening. Thus, the intake side of the casing 21 is cooled and the rotor 2
The temperature of No. 7 is kept within a certain range not exceeding the heat-resistant temperature of aluminum of 120 ° C.

On the other hand, when (I−I ₀ )> 0, the current value of the first heater 38 is calculated based on the heating amount of the casing 21 obtained as described above, and the calculated current value is calculated. It is sent to the first heating control unit 48. Then, the first heating control unit 48 resets the output current of the built-in amplifier to the above current value. Thus, the intake side of the casing 21 is heated, and the temperature of the rotor 27 is kept within the above-mentioned fixed range by the radiant heat.

That is, in the present embodiment, the control section 42 and the second heating control section 44 constitute the first control means, and the control section 42, the flow rate control section 46, the valve 47 and the first heating control section 48 constitutes the second control means.

FIG. 3 shows the relationship between the suction gas pressure and the temperatures of the casing 21 and the rotor 27 when the heating amounts of the first and second heaters 38 and 40 and the cooling amount of the water jacket 39 are controlled as described above. Is shown. 3, as a result of the control of the heating amount of the second heater 40 by the control unit 42, the lower end of the casing 21 is maintained at about 130 ° C., the middle part of the casing 21 is maintained at about 70 ° C. It can be seen that the upper end is kept at about 20 ° C.
In addition, simply controlling the temperature of the casing 21 in this manner causes the temperature of the rotor 27 to exceed the heat-resistant temperature of aluminum of 120 ° C. in the high vacuum region as shown by the curve A. As a result of controlling the amount of cooling of the water jacket 39 or the amount of heating of the first heater 38, as shown by the line B, the temperature is maintained at about 100 ° C. which does not exceed the heat-resistant temperature of aluminum of 120 ° C. in the high vacuum range to the low vacuum range. You can see that it is.

Therefore, in a wide gas pressure region in which the screw pump is used, the temperature on the exhaust side of the casing 21 and the rotor 27 is, for example, 100 ° C. to 110 ° C.
, And the exhaust gas is sublimated so that the product does not adhere to the exhaust part. The controller 42 monitors the temperature of the exhaust gas detected by the temperature sensor 41, so that the first heater 38, the second heater 38,
It is possible to detect a failure of the water jacket 40 and a water cut of the water jacket 39. Therefore, by configuring the control unit 42 to output an alarm when the output value of the temperature sensor 41 deviates from the predetermined value range, safety and reliability of the screw pump can be improved.

As described above, in the present embodiment, the first heater 38 and the water jacket 39 are attached to the outer periphery of the housing 21 on the intake side. Further, a second heater 40 is attached to the outer periphery of the housing 21 on the exhaust side. further,
A temperature sensor 41 is mounted below the rotor 27 in the housing 21.

The operation of the second heating control unit 44 is controlled by the control unit 42 in accordance with the difference between the exhaust gas temperature from the temperature sensor 41 and the target temperature.
The heating amount of the second heater 40 is controlled so that the temperature on the exhaust side of the second heater 40 is kept within a fixed range. Further, when the difference between the input current value I of the high-frequency motor 37 and the reference value I ₀ satisfies (I−I ₀ ) ≦ 0, the control unit 42 controls the flow rate control unit 46 according to the value of the difference. The operation is controlled to control the flow rate of the water jacket 39. On the other hand, when (I−I ₀ )> 0, the operation of the first heating control unit 48 is controlled according to the value of the difference to control the amount of heating of the first heater 38. In this way, the temperature of the rotor 27 is maintained within a certain range that does not exceed the heat-resistant temperature of aluminum of 120 ° C. Therefore, in a wide gas pressure range in which the screw pump is used, the temperature of the rotor 27 is kept within a constant range of, for example, 100 ° C. to 110 ° C. The adhesion of products due to sublimation can be prevented.

In the above embodiment, the temperature of the rotor 27 is estimated based on the difference between the input current value I of the high-frequency motor 37 and the reference value I _0.
Temperature sensor 4 at the upper end of the motor housing 23 close to
9 may be provided, and the temperature of the rotor 27 may be estimated by adding the temperature detected by the temperature sensor 49 to the value of the difference between the current value I and the reference value I ₀ . By doing so, the temperature control of the rotor 27 can be performed more accurately. Although the input current value I to the high-frequency motor 37 is used as the rotor load, an input power value may be used.

In the above embodiment, the cooling means of the casing 21 is constituted by the water jacket 39, while the second control means is controlled by the control section 42 and the flow rate control section 46.
It consists of. The amount of cooling of the casing 21 is controlled by the second control means. However, the present invention is not limited to this, and the second control means may be configured by the control unit 42 and the water temperature control unit to control the temperature of the water supplied to the water jacket 39. Absent. Alternatively, while the cooling means is constituted by an air cooling device, the second control means is controlled by the control unit 42.
And an air volume control unit or an air temperature control unit to control the air volume and the air temperature of the air cooling device.

In the above embodiment, a screw pump is described as an example of a molecular pump. However, a turbo molecular pump or a compound pump may be used to increase the rotor temperature by, for example, 100 ° C. to 110 ° C. Can be kept within a certain range. Further, in the above-described embodiment, the molecular pump provided with the oil lubricated bearing having the oil tank 16 has been described as an example. However, the same effect can be obtained by a similar configuration in a molecular pump provided with a magnetic bearing. Obtainable. Further, in the above-described embodiment, both the first heater 38 and the water jacket 39 are provided as the temperature adjusting means. However, depending on the range of the gas pressure to be used, the first heater 38 or the water jacket 39 may be used. Only one of them may be provided.

[0033]

As apparent from the above description, the molecular pump according to the first aspect of the present invention is provided on the exhaust side of the casing by the first control means based on the detected value of the exhaust gas temperature by the temperature detection means. The exhaust-side heating means is controlled to maintain the temperature on the exhaust side of the casing within a fixed range, and the second control means controls the exhaust-side heating means based on the detection value of the rotor load detection means.
Since the temperature of the rotor is kept within a certain range by controlling the temperature adjusting means provided on the intake side of the casing, the range of the rotor load detected by the rotor load detecting means is controlled.
The temperature of the rotor is kept within the constant range over the range of the suction gas pressure. Therefore, if the fixed range in which the temperature of the rotor is maintained is set to a temperature range that is equal to or lower than the heat-resistant temperature of aluminum and the exhaust gas does not sublimate, the present molecular pump is stable over a wide gas pressure range. As a result, it is possible to prevent adhesion of products due to the sublimation of the exhaust gas.

Further, in the molecular pump according to the second aspect of the present invention, since the temperature adjusting means includes the intake-side heating means and the intake-side cooling means, the temperature of the rotor can be easily maintained within the fixed range. be able to.

Further, in the molecular pump according to the third aspect of the present invention, the second control means operates the intake side cooling means when the detection value of the rotor load detection means is equal to or less than a reference value. When the value detected by the rotor load detecting means is larger than the reference value, the intake side heating means is operated. Therefore, when the exhaust gas pressure is low to medium pressure (high vacuum to medium vacuum), the rotor is radiated. On the other hand, when the exhaust gas pressure is high (low vacuum) while cooling, the rotor is radiantly heated. Therefore, according to the present invention,
Over the wide gas pressure range in which the molecular pump is used,
The temperature of the rotor can be reliably kept within the fixed range.

[Brief description of the drawings]

FIG. 1 is a sectional view of a screw pump as a molecular pump of the present invention.

FIG. 2 is an explanatory diagram of calculation of a cooling amount or a heating amount of a casing based on an input current value of a high-frequency motor and a reference value in FIG.

FIG. 3 is a diagram showing a relationship between intake gas pressure and temperatures of a casing and a rotor in the screw pump shown in FIG.

FIG. 4 is a cross-sectional view of a conventional turbo-molecular pump.

FIG. 5 is a diagram showing temperatures of a casing and a rotor in FIG. 4;

FIG. 6 is a diagram showing the temperature of the rotor when the temperature of the casing in FIG. 4 is kept at 100 ° C.

FIG. 7 is a diagram showing the temperature of the casing when the temperature of the rotor in FIG. 4 is kept at 100 ° C.

[Explanation of symbols]

21 ... casing, 27 ... rotor,
29: screw groove, 34: intake port,
35 ... exhaust port, 38 ... first heater, 39 ... water jacket, 40 ... second
Heaters, 41, 49 ... temperature sensors, 42 ...
Control unit, 43 ... Current detection unit, 44 ...
2nd heating control part, 46 ... Flow control part,
48: First heating control unit.

Claims (3)

[Claims] 1. A casing (21), said casing
In a molecular pump having a rotor (27) fitted inside (21), a temperature control means (38, 39) provided on an intake side of the casing (21), and a temperature control means (38, 39) provided on an exhaust side of the casing (21). Exhaust side heating means (40), and rotor load detecting means for detecting the load on the rotor (27).
(43), a temperature detecting means (41) for detecting an exhaust gas temperature, and a temperature on the exhaust side of the casing (21) based on a detection value of the temperature detecting means (41) within a fixed range. First control means (42, 42) for controlling the exhaust side heating means (40).
44) and second control means for controlling the temperature adjusting means (38, 39) based on the detection value of the rotor load detecting means (43) so that the temperature of the rotor (27) falls within a certain range. (42,4
6, 47, 48). 2. The molecular pump according to claim 1, wherein said temperature control means includes an intake-side heating means (38) and an intake-side cooling means (39). 3. The molecular pump according to claim 2, wherein said second control means (42, 46, 47, 48) is adapted to operate when said detection value of said rotor load detection means (43) is equal to or less than a reference value. Operates the intake side cooling means (39), and operates the intake side heating means (38) when the value detected by the rotor load detecting means (43) is larger than the reference value. A molecular pump characterized in that: