JPH0646032B2 - Positive displacement oil-free gas pressure pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a positive displacement rotary machine, and more particularly to a non-lubricating gas pressure pump suitable for handling corrosive gas. It is used for compressors and vacuum pumps.

[Conventional technology]

For displacement type rotary machines, along with studies on high-speed operation, studies on non-lubrication of working chambers have been made to meet social needs. On the other hand, a vacuum pump applied to a semiconductor manufacturing apparatus or the like is strongly required to have a corrosion resistant structure because of the characteristics of the gas to be exhausted. As a general technique for coping with these, formation of a protective film on the surface of a member is considered to be promising. However, the surface pressure is large without lubrication, and the sliding speed is 1 m.
There is no disclosure example of a coating forming technique capable of high-speed operation at a speed of / s or more for a long time and having corrosion resistance. For example, Japanese Patent Laid-Open No. 52-57505 and US Pat.
No. 3,600,114.

In addition, Japanese Utility Model Publication No. 57-191532 discloses that the outer sliding surface of a core material made of a composition in which a reinforcing filler is mixed with a polyimide resin is a sliding composition mainly composed of the polyimide resin. Coated composite molded articles are disclosed.

[Problems to be Solved by the Invention]

JP-A-52-57505 and USP3600114 show a scroll type fluid machine. However, the forming part is a scroll part and only the part where both scroll members contact and slide. It is carried out, and from the idea of a soft layer, a measure for clearance control between both scroll parts and prevention of seizure without mere lubrication is shown in the expectation of a familiar effect. In addition, it is shown that the formed film is an elastic film such as rubber and that Teflon is applied as a self-lubricating material. However, the material itself is applied at a high PV value (surface pressure x sliding speed). It is difficult. Furthermore, since the applied resin does not have heat resistance during use, it has been disclosed in JP-A-52-57505.
There is also a problem in that the structure of the machine is complicated because a means for cooling the scroll wrap portion to prevent the temperature rise of the coating itself is required as shown in Japanese Patent Laid-Open Publication No. Further, as described above, when viewed from the entire wall surface in contact with the handling gas, no consideration is given to the handling of the corrosive gas because it is a partial treatment, and it is difficult to provide the machine with corrosion resistance. It was a thing. In addition, although patents disclosing the purpose of providing cartilage on the surface have also been applied, these measures are not suitable for operation at a non-lubricating type and a high PV value, judging from the examples, and particularly at high speed. There is a problem in securing trust in driving,
In some cases, consideration is given only to the case of reliability improvement measures under oil lubrication. In the case of the above-mentioned disclosed patent, the sliding speed under non-lubrication is limited to about 1 m / s, and there is almost no consideration for operating at a speed higher than this for a long period of time, for example, 8000 hours without maintenance. .

Further, the one disclosed in Japanese Utility Model Laid-Open No. 57-191532 discloses a reinforcing core material composed of a polyimide resin and a filler, and has an adhesiveness to metal and a breaking strength when applied to a positive displacement machine. However, heat dissipation has not been fully considered.

The object of the present invention is not only to allow the working chamber of the positive displacement gas pump to have lubricating oil, but also to enable high-speed operation for a long time even under unlubricated conditions, and to handle corrosive gases as well. To provide the gas pressure pump.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the positive displacement oil-free gas pressure pump of the present invention sucks and compresses gas by gradually reducing the working chamber formed by the components of the compression mechanism according to the rotational movement of the drive shaft. , In the positive displacement gas pressure pump for discharging, the base material of the parts constituting the compression mechanism is made of metal, and the surface of the member in contact with the handling gas is made of tetrafluoroethylene resin and polyimide resin. A synthetic resin coating film as a main component is formed, and the resin coating film has a thickness of 0.01 mm to 0.2 mm.

[Action]

In order to withstand a high PV value under non-lubricated conditions and to obtain corrosion resistance, it is necessary to form a synthetic resin film containing tetrafluoroethylene resin and polyimide resin as main components. That is, when the surface of the base material is coated with this hybrid resin, first, the enamel-like resin is applied to 250-28.
By performing the heat treatment at 0 ° C., a hard coating film in which the hard polyimide resin serves as a binder and the soft tetrafluoroethylene resin serves as a lubricant is obtained. Since the formed hardness is a hard layer having a pencil hardness of about 3H to 7H, it becomes possible to withstand a high sliding surface pressure, and even at a high sliding speed due to the lubricating effect of the tetrafluoroethylene resin described above. It is possible to obtain a small coefficient of friction, and polyimide resin can be applied as a heat resistant material.
It can be used under high temperature. As a concrete example of the above capabilities, when the ambient temperature is 100 ° C., the surface pressure P is 5
00 kg / cm ² , sliding speed V 5 m / s, maximum PV value 30 kg
/ Cm · m / s is acceptable, and at the same temperature of 200 ° C., the surface pressure P is 500 kg / cm ² , the sliding speed V is 4 m / s,
The maximum PV value is 20 kg / cm · m / s.

In consideration of the above sliding performance, adhesion strength of the coating, breaking strength, and heat dissipation, the thickness of the coating is 0.
It is suitable from 01 mm to 0.2 mm. That is, according to the characteristics of the synthetic resin film, the film thickness is a thickness that can be determined because the adhesive force is superior to the shear (breaking) stress in the film generated by the frictional force acting on the sliding surface. .

〔Example〕

 An embodiment of the present invention will be described below with reference to FIG.

This shows a scroll type gas pressure pump. First of all, the structure is described above. The fixed scroll 1 includes an end plate 1a and a spiral scroll lap 1b.
The scroll trap 1b is provided with a gas suction port 3 at the outer peripheral portion thereof and a discharge port 4 at the central portion thereof. The fixed scroll 1 is fixed to the casing 5 by the connecting means via the sealing means 14. The orbiting scroll 2 is composed of an end plate 2a having a bearing element 8 in the center, and a spiral scroll rap 2b standing upright. And the orbiting scroll 2 is
Since the fixed scroll 1 is engaged with the fixed scroll 1 while maintaining a constant angle, rotation is prevented by a plurality of pin cranks 6 on the outer peripheral portion of the end plate 2a. This pin crank 6
Is locked to the casing 5 on one side. The components described above are referred to as components forming the compression mechanism section. A drive shaft 10 is supported by an upper bearing 12a and a lower bearing 12b fixed to the casing. The drive shaft 10 further has a shaft sealing element 13 and a crankshaft 9 at a tip portion thereof, and the crankshaft 9 is provided with a bearing element 8 to orbit the scroll 2.
Is engaged with. A balance weight 11 is further provided on the drive shaft 10 in order to balance the centrifugal force generated by the orbiting movement of the orbiting scroll 2. Further, in order to ensure a stable movement of the orbiting scroll 2, the outer peripheral portion of the end plate 2a thereof is slidably supported by the fixed scroll 1 and the casing 5. Each of the bearing elements 7, 8 and 12a adopts a rolling bearing, and a perflurpolyether grease is applied to lubricate them. A grease leakage prevention seal member 16 is also provided on the crankshaft 9 portion. Next, regarding the main part of the present invention, that is, at a line 15 drawn thicker in FIG. 1, a synthetic resin material of polyimide resin and Teflon resin, which is resistant to non-lubrication and has corrosion resistance, is applied to the surface of the member. It shows that it is configured. The thickness of this coating is 0.01 mm to 0.2 considering the sliding performance, the adhesion strength of the coating, the breaking strength, and the heat dissipation.
mm is preferred. Also, in order to obtain the adhesion of the coating,
The base material is not suitable for a material such as powder or cast iron whose surface has a fine pinhole shape, and is preferably one having a fine surface roughness. However, it does not have to be a mirror surface such as a Cr-plated surface. Furthermore, before applying the resin, it is important to perform a heat treatment (for example, about 300 ° C.) for removing foreign matters such as oil, water, gas and soap attached to the surface of the base material.

Further, in order to obtain a coating film having a thickness of 0.05 mm or more, it is possible to apply a cutting allowance to the base material, coat it thickly, and then finish it. FIG. 2 shows a partially enlarged view of this configuration. As in this embodiment, the surface treatment is performed over the entire surface of the gas that flows in from the suction port, so that the base metal of the member does not directly touch the gas and any gas can be handled. Further, in practice, it is not necessary to provide the resin of the present invention on the entire surface, and a protective film for corrosion resistance is provided at a site where only contact with gas is performed, and the present invention is provided only at a sliding site. It is possible to provide the resin. Further, when it is provided at the sliding portion, the structure shown in FIG. 3 can be applied. In this, a base material is first provided with a ceramic coating layer, and a synthetic resin coating containing a polyimide resin and a tetrafluoroethylene resin as main components is further provided thereon.

In order to improve wear resistance, if a ceramic film is provided on the base material and the resin is further coated, the hardness of the ceramic is backed up in addition to the pencil hardness of 3H to 7H of the synthetic resin itself. Therefore, the progress of wear can be prevented. Then, this synthetic resin coating is
When applied to Al or Al alloys, it is possible to provide light parts that can withstand hard non-lubricating sliding conditions. In addition, since the tetrafluoroethylene resin, which has excellent corrosion resistance, protects the surface that is in contact with gas from Al and Al alloys, which have weak corrosion resistance, it is a lightweight gas that can handle highly corrosive halogen-based gases without lubrication. A pressure pump can be provided. In addition to this, since the resin coating of the present invention is an enamel-like mixed liquid before heat treatment, it can be applied by brush or spray, so that coatings of any shape can be formed. is there. Therefore, the base material can also be applied as a resin.

Even when the scroll type gas pressure pump having the above resin coating is used as a vacuum pump, there is a great effect. In the scroll type, the suction pressure is as low as 10 ^-3 Torr even if the discharge pressure is atmospheric pressure. by the way,
Although there are materials that have poor wear resistance in vacuum in general non-lubricated sliding materials, in the present invention, the synthetic resin used has problems in physical properties such as sliding characteristics in the applied pressure range. Absent. Moreover, in the case of vacuum evacuation, the halogen gas may be used in the semiconductor manufacturing apparatus, but even at this time, a highly reliable pump can be obtained without being corroded for a long period of time. By the way, the amount of wear of the outer peripheral surface 2a of the orbiting scroll end plate 2a on the thrust receiving surface is about 70 μm, which is a very small calculation predicted value, even after continuous operation for 8,000 hours.

FIG. 4 shows an example of a rotary vane type. And FIG. 5 shows the AOS cross section of FIG. In this case, the synthetic resin coating 15 composed mainly of polyimide resin and tetrafluoroethylene resin is formed on the inner surface of the suction port 21, the inner surface of the casing 23, the outer surface of the rotor 24, the inner surfaces of the side covers 25 and 25 ', and the spout. It is formed on the inner surface of the outlet 21. In the gas pressure pump of this formation, the vane 22 is often made of an inorganic material such as a carbon material, and when it has self-lubricating property, it is not necessary to provide a coating as in the embodiment. Further, when the use condition is that no corrosive gas is used, the inner surface of the casing 23 which is a sliding surface and the rotor 2 are used.
The outer surface of 4 and the inner surfaces of the side covers 25, 25 'are sufficient. Since 26 is a shaft sealing means, the surface coating can be provided up to this position. Further vane 2
When 2 is a metal material, it is possible to provide the surface coating.

As another embodiment, a case of a Scrilleu type gas pressure pump will be described below with reference to FIGS. 6 and 7. FIG. 7 shows a BB cross section of FIG. The screw type pump includes a male rotor 30, a female rotor 31, and a casing 32.
Thereby forming a working chamber. And the male rotor 30
The female rotor 31 which is synchronized by the timing gear 36 rotates with the rotation of, and the gas is pumped. The synthetic resin coating 15 mainly composed of polyimide resin and ethylene tetrafluoride resin is used for the inner surface of the suction port 33 and the inner surface of the suction chamber 34, the surface of the male rotor 30, and the female rotor 3.
1, the inner surface of the casing 32, and the inner surface of the discharge port 35. Even in this case, when the corrosive gas is not handled, the resin is applied to both rotors 30, 3
It is also possible to provide only the surface of 1 and the inner surface (including the end surface) of the casing 32.

In addition to the above embodiment, depending on the sliding condition, in any case, it may be provided on either the rotor side or the stator side (casing side).

Further, in the positive displacement oil-free gas pressure pump as shown in the figure, the thickness of the resin coating is often preferably about 0.1 mm depending on the final processing finish.

Further, it is needless to say that the same means can be applied to the reciprocating gas pressure feed pump, which is not particularly shown, in addition to the above embodiments.

In addition, the resin coating can be applied to the sliding surface of a non-lubricated plain bearing.

[Effects of the Invention] As described above, according to the present invention, a polyimide resin having excellent wear resistance even under non-lubrication sliding, excellent seizure resistance, excellent corrosion resistance, good heat dissipation, rupture strength and strong adhesion. Since 0.01 to 0.2 mm mainly composed of tetrafluoroethylene resin can be formed on the surface of the member that constitutes the working chamber by the hard synthetic resin coating, it can handle any gas and is high speed without lubrication. You can drive. Therefore, the amount of gas handled increases per unit time, and conversely, if the required amount of gas handled is kept constant, the pump can be downsized. In addition, since the sliding surface in the working chamber has good wear resistance, it does not wear out over a long period of time and maintains a dimension close to the initial design dimension, so the airtightness of the working chamber is not compromised. Therefore, high performance can be ensured over a long period of time.
In addition to the hermeticity, the seizure resistance is excellent, so that reliability over a long period can be secured. Further, particularly when it is implemented as a vacuum pump, a great effect can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a scroll type oil-free gas pressure pump according to this embodiment. FIG. 2 is a partial sectional view of FIG. FIG. 3 is a cross-sectional view showing an embodiment of a treatment layer provided on the surface of the base material, FIG. 4 is a rotary vane type oil-free gas pressure feed pump showing another embodiment, and FIG. It is a figure. FIG. 6 shows another example of a screw-type oil-free type gas pressure pump according to the seventh embodiment.
The figure is a sectional view thereof. 1 ... Fixed scroll, 2 ... Orbiting scroll, 3 ...
Intake port, 4 ... Outlet port, 5 ... Casing, 6 ... Pin crank, 9 ... Crank shaft, 10 ... Main shaft, 11 ...
Balance weight, 13 ... Shaft sealing means, 15 ... Corrosion resistance,
Abrasion resistant resin layer, 22 ... Vane, 23 ... Casing, 24 ... Rotor, 30 ... Male rotor, 31 ... Female rotor, 32 ... Casing, 36 ... Timing gear.

Claims (5)

[Claims] 1. A positive displacement gas pressure pump that sucks, compresses, and discharges gas by gradually reducing a working chamber formed by parts constituting the compression mechanism in accordance with the rotational movement of a drive shaft. The base material of the part to be formed is made of metal, and a synthetic resin film containing a tetrafluoroethylene resin and a polyimide resin as main components is formed on at least a part of the surface of the member in contact with the handling gas, and The volumetric oil-free gas pressure pump, wherein the resin coating has a thickness of 0.01 mm to 0.2 mm. 2. The positive-displacement oil-free pressure pump according to claim 1, wherein the positive-displacement oil-free pressure pump is a scroll-type gas pressure pump. 3. A positive displacement oil-free gas pressure pump according to claim 1, wherein the resin coating formed on the surface of the member is provided at least at a portion which may be a sliding surface. 4. A positive displacement oil-free gas pressure pump according to claim 1, wherein the base material is aluminum or an aluminum alloy. 5. The hardness of a resin film formed on the surface of a member through a heat treatment process, wherein the synthetic resin is added to the surface of the member that is in contact with the handling gas in the positive displacement oil-free gas pressure pump according to claim 1. A positive displacement oil-free gas pressure pump having a pencil hardness of 3H to 7H.