JP2003314477A - Rotary pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability by eliminating problems of causing wear and seizure of sliding surfaces of a side housing and a rotor in the case of performing side sealing of a rotor by reducing a side clearance without using a sealing member in a rotary pump wherein either one of the rotor and side housing is formed of an aluminum alloy. <P>SOLUTION: The surface of the member formed of an aluminum alloy, out of the rotor 4 and the side housing (a housing 1 and an end frame 2) is provided with an anodized aluminum film 19 sealed with molybdenum disulfide, and the other member is provided with a coating film 18 of tungsten carbide to enhance the close contact properties of surfaces on which side sealing is performed using these films as sliding surfaces. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary pump in which a rotor or a side housing is made of an aluminum alloy to reduce its weight, and more specifically, it is possible to secure performance in dry operation, simplify it, and improve its durability. This is related to a well-known rotary pump.

[0002]

2. Description of the Related Art For example, as a rotary vacuum pump,
Wankle type, scroll type, rolling piston type, and vane type are known.

These pumps have a casing whose both ends are closed by side housings, and a rotor which is housed in an eccentric arrangement in the casing. The inner surface of the casing and the rotor are rotated or revolved or rotationally accompanied by revolution. Intake and exhaust are performed by causing a volume change in a chamber formed between the chamber and the outer peripheral surface.

In this rotary type pump, when a rotor made of resin or aluminum is used for weight reduction, the side clearance (gap between the rotor and side casing) of the rotor changes due to the difference in thermal expansion from the iron casing. When the side clearance becomes large, gas in the chamber leaks from the chamber and pump performance deteriorates. On the contrary, when the side clearance becomes small, the friction of the sliding surface hinders the rotation of the rotor.

Further, there is an aluminum alloy having a thermal expansion coefficient close to that of an iron casing. However, if a rotor of a Wankel pump is formed from this, the gear integrally formed inside the rotor will be worn and cannot be put to practical use. Become.

As a countermeasure against this, if a method is adopted in which the gear portion is made of a different material and is joined to the rotor, the area for the side seal of the rotor must be secured at a place other than the gear portion, and the rotor size becomes large. Become. In addition, since the two parts are manufactured and combined, the product becomes expensive.

Therefore, it is considered to form the rotor with an iron material and the side housing with an aluminum alloy.

On the other hand, since it is possible to reduce the driving force and the vibration noise by reducing the weight of the rotor, it has been considered to form the rotor with an aluminum alloy and the side housing with an iron material.

[0009]

Aluminum is a metal that is easily worn and welded. Therefore, in a rotary pump in which either the rotor or the side housing is made of an aluminum alloy, it is difficult to perform the side seal of the rotor (seal with the side housing) by a method of reducing the side clearance.

The side seal of the rotor can be carried out by attaching a side seal member to the side surface of the rotor as in the Wankel type rotary engine. However, unlike the engine, the pump does not involve high compression, so the side clearance is small. The required performance can be ensured by a method of reducing gas leakage, and this method can simplify the structure by omitting the side seal member. However, when the side clearance is reduced, the rotor and the side housing come into close contact with each other, causing problems such as wear and seizure of the sliding surface.

There is also a method of protecting the sliding surface by using a lubricant, but this method requires a mechanism and means for supplying and enclosing the lubricant, which complicates the structure of the pump.

Further, if the sliding surface is coated with a fluorine-based resin, which is generally used as a non-lubricating sliding agent, the resin coating wears quickly and the side clearance increases,
The amount of gas leakage increases and it becomes difficult to secure pump performance. In addition to this, the resin has a large coefficient of thermal expansion, and the side clearance fluctuates due to temperature changes. Therefore, it is difficult to reduce the sliding resistance with the resin.

Therefore, an object of the present invention is to prevent wear and seizure on the sliding surface so that the side seal of the rotor can be performed by a method of keeping the side clearance small.

[0014]

In order to solve the above-mentioned problems, according to the present invention, an alumite in which the surface of a member formed of an aluminum alloy among the rotor and the side housing is sealed with molybdenum disulfide is used. At least one kind of coating film selected from tungsten carbide, tungsten, and amorphous carbon is provided on the surface of the other member, and these films are slid to form a side clearance between the rotor and the side housing. It was done by the method of reducing.

Tungsten carbide, tungsten,
At least one type of coating film selected from amorphous carbon and the alumite coating film sealed with molybdenum disulfide need only be present on at least the sliding surface of the rotor and the side housing.

Further, it is preferable that the rotor and the casing that houses the rotor have substantially the same linear expansion coefficient by selecting the same material.

The pump to which the present invention is applied may be a vacuum pump or a compression pump.

[0018]

Function: Tungsten carbide, tungsten and amorphous carbon have seizure resistance and wear resistance. Alumite also has wear resistance. Further, the coefficient of friction of the alumite coating that has been subjected to the sealing treatment with molybdenum disulfide is low. The inventor has found that among a wide variety of membranes, these membranes have good compatibility and are most suitable as a combination.

By providing these membranes on the rotor and the side housing and sliding them, abrasion and seizure of the sliding surface are effectively prevented, so that the side clearance can be kept small and the pump performance can be improved. You can prevent the decline. Further, the rotor side seal can be performed by a method of reducing the side clearance without using a lubricant or a side seal member, and the structure of the pump can be simplified.

[0020]

1 and 2 show an embodiment of the present invention. The illustrated pump is a Wankel type vacuum pump, in which a casing 3 is sandwiched between a housing 1 and an end frame 2 (these two are side housings), and the three are connected by bolts B.

A triangular rotor 4 is housed in the casing 3, and an internal gear 5 provided on the rotor 4 meshes with a pinion 6 fixed to the housing 1. The rotor 4 of the illustrated pump is made of iron alloy, and the housing 1 and the end frame 2 are made of aluminum alloy.

A crankshaft 8 supported by the housing 1 and the end frame 2 is passed through a bearing 7 inside the rotor 4, and the eccentric shaft 8a of the crankshaft is arranged concentrically with the internal gear 5. Are fitted to the bearing 9 incorporated in the rotor 4.

The crankshaft 8 is connected to the output shaft of the motor 10. When the crankshaft 8 is rotated by the motor 10, the rotor 4 meshed with the pinion 6 revolves around the pinion 6 while rotating. Reference numeral 11 denotes a weight balancer attached to the crankshaft 8 for the purpose of reducing the vibration generated by the eccentric movement of the rotor 4.

The inner surface of the casing 3 has a bilobal shape which is slightly larger than the movement trajectory of the apex of the rotor 4, and the chamber 1 formed between the inner surface and the outer peripheral surface between the apexes of the rotor.
The rotational movement of the rotor 4 accompanied by the revolution of the rotor 4 causes a volume change, and intake and exhaust are repeated.

The housing 1 has an intake hole 13 and an exhaust hole 1
The gas in the chamber 12 which has been provided with two 4 each and has moved to the compression stroke is transferred from the exhaust hole 14 to the check valve 15 provided in each exhaust hole.
Exhausted through. The exhaust gas passes through the inside of the motor 10 in the illustrated pump and goes out through the drain pipe 16.

An apex seal 17 is slidably installed in each apex of the rotor 4 in the radial direction, and the apex seal 17 is pressed against the inner surface of the casing 3 by the centrifugal force generated by the rotation of the rotor to form the outer circumference of the rotor and the inner surface of the casing. The seal between them is made.

The seal between the rotor 4 and the housing 1 and between the end frame 2 is made by the side clearance of the rotor.

The thickness of the casing 3 is made slightly thicker than the thickness of the rotor 4 so that a clearance C for rotating the rotor is generated between the rotor 4 and the housing 1 and the end frame 2, respectively. The side seal of the rotor is made as small as possible.

Further, when trying to secure the pump performance in this way, there arises a problem of abrasion and seizure of the sliding surface having improved adhesion. As a solution to the problem, the surface of the rotor 4 shown in FIG. The tungsten carbide coating film 18 shown in FIG. 1 is provided on the surfaces of the housing 1 and the end frame 2 with an alumite film 19 sealed with molybdenum disulfide, and these are abraded.

The tungsten carbide coating film 18 can be formed by the PVD method (vapor phase synthesis method) or the like. An intermediate layer of chromium or the like which enhances adhesiveness may be interposed between the coating film 18 and the base material (rotor 4). Further, the coating film 18 may be replaced with a film of tungsten or amorphous carbon, or a film in which any two or three of tungsten carbide, tungsten, and amorphous carbon are mixed.

FIG. 4 is an enlarged view of the structure of the alumite film 19. The alumite coating 19 formed on the surface of the base material has fine pores, and the fine pores are molybdenum disulfide 20.
It is sealed by. The molybdenum disulfide 20 can be deposited in the fine pores by performing a secondary electrolysis treatment of an aqueous solution of ammonium tetrathiomolybdate.

The surface layer portion of the rotor 4 coated with tungsten carbide has extremely high hardness and has seizure resistance and wear resistance, but the mating sliding members, that is, the housing 1 and the end frame 2 are aluminum alloys. However, the hardness is low, and there is a problem that even a slight inclination of the rotor cuts aluminum. Further, if the hardness of the aluminum alloy is increased as a measure to avoid the problem, the coefficient of friction is increased, which is disadvantageous in terms of downsizing of the motor.

The alumite coating 19 sealed with molybdenum disulfide has a low coefficient of friction and excellent wear resistance. By combining this with a coating film of tungsten carbide, wear and seizure on the sliding surface can be prevented. Reduction can be realized by downsizing the motor. The coating film 18 formed of tungsten or amorphous carbon can also obtain similar effects, although not to the same degree as tungsten carbide.

If the side clearance of the rotor becomes large due to the temperature change, the sealing performance of the side seal deteriorates. In order to suppress the deterioration of the sealing performance due to the temperature change, it is preferable that the rotor 4 and the casing 3 are made of the same material so that their linear expansion coefficients are substantially the same.

Next, the results of the effect confirmation test will be shown. A vacuum pump having the structure shown in FIGS. 1 and 2 in which the housing 1 and the end frame 2 (side housing) are made of an aluminum alloy and the rotor 4 is made of an iron-based alloy is used. Is represented). The rotation speed of the pump was 4200 rpm.

The alumite provided in the housing of sample 1 (comparative product) was not subjected to sealing treatment with molybdenum disulfide. The housing of sample 2 (comparative product) is provided with Ni plating, and the housing of sample 3 (invention product) is provided with an alumite coating which has been subjected to a sealing treatment with molybdenum disulfide. In addition, a coating film of tungsten carbide (WC) was provided on the rotors of Samples 1, 2, and 3. The test results are also shown in Table 1.

An experiment was also carried out on a film provided with a DLC (diamond-like carbon) film and a fluorine resin film, which are known to have good sliding characteristics, but the DLC film had poor adhesion to the base material and peeling occurred. It was Further, the amount of wear of the fluorine resin film was large.

[0038]

[Table 1]

In the embodiment, the rotor is made of iron alloy and the side housing (housing 1 and end frame) is made of aluminum alloy. However, the rotor is made of aluminum alloy and the side housing is made of iron material. The same effect can be obtained by providing the rotor with an alumite film sealed with molybdenum disulfide and the side housing with a coating film of tungsten carbide or the like.

The Wankel type vacuum pump shown in the drawing is used for connecting the intake hole 13 to, for example, a vacuum booster of a vehicle and sucking the air in the vacuum booster to make the inside of the booster a negative pressure. The scope of application of the present invention extends to scroll type, rolling type, vane type vacuum pumps and compression pumps of various types.

[0041]

As described above, according to the present invention, an alumite film sealed with molybdenum disulfide and a coating film made of at least one of tungsten carbide, tungsten and amorphous carbon are provided corresponding to the rotor and the side housing. Since these films are slid to prevent wear and seizure on the sliding surface, the rotor side seal is made by a method with a small side clearance to allow dry operation with a simple structure. In addition, it is possible to maintain the performance of the pump and improve its durability.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a pump according to an embodiment.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is an enlarged sectional view showing a sliding portion between a rotor and a side housing.

[Fig. 4] Structure chart of alumite film subjected to sealing treatment with molybdenum disulfide

[Explanation of symbols]

1 housing 2 end frame 3 casing 4 rotor 5 Internal gear 6 pinion 7, 9 bearing 8 crankshaft 10 motors 12 chambers 15 Check valve 17 Apex Seal 18 Tungsten Carbide Coating Film 19 Anodized film 20 Molybdenum disulfide

Claims (4)

[Claims] 1. A rotor housed in a casing and a side housing that closes both ends of the casing are made of an aluminum alloy, and the rotor and the revolution or revolution of the rotor cause rotation between the rotor and the casing inner surface. In a rotary pump for performing volume change in a chamber formed in a chamber for intake and exhaust, in the rotor and the side housing, a surface of a member formed of an aluminum alloy is sealed with molybdenum disulfide for sealing. A rotary pump, wherein a coating is provided on the surface of the other member, and at least one coating selected from tungsten carbide, tungsten, and amorphous carbon is provided. 2. The rotary pump according to claim 1, wherein the linear expansion coefficient of the rotor is substantially the same as that of the casing. 3. A rotary vacuum pump adopting the structure according to claim 1. 4. A rotary type compression pump adopting the structure according to claim 1.