JP2009047115A - Single-stage root-type vacuum pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact single-stage root-type vacuum pump that improves a cooling efficiency by introducing outside air into a casing, and is capable of a closed operation. <P>SOLUTION: An inlet 14 is provided at a position n exceeding a volume moving angle of 120 degrees from the center of each of rotating shafts 8 and 10 of each of rotors 9 and 11 with respect to a virtual line m connecting the centers of the rotating shafts 8 and 10. An outlet 15 is provided at a position o exceeding the volume moving angle of 120 degrees in the opposite direction of the inlet 14 from the center of each of the rotating shafts 8 and 10 with respect to the virtual line m. In a surrounding wall portion on the side of the outlet 15 from the virtual line m, and in the vicinity of the virtual line m, outside-air introducing holes 16 are formed so as to communicate with inside the casing 1 so that they correspond to the rotors 9 and 11. A motor housing 2 attached to a side portion of the casing 1 is installed with a built-in motor 25 having the rotating shaft 10 serving one of the rotors as its output shaft. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a single-stage roots-type vacuum pump used for a vacuum source such as a moving system that sucks and conveys articles with a suction cup and a water collection tank of a vacuum sewer system.

  A multi-stage roots type vacuum pump as shown in Patent Document 1 is used as a vacuum pump used for a vacuum source such as holding a negative pressure in a tank of the moving system or the vacuum sewer system. When a vacuum pressure difference of −70 kPa or more is generated between the vacuum pump and the discharge port, the temperature of the casing on the discharge port side may be about 150 ° C. In order to prevent troubles caused by the temperature rise, a multi-stage roots vacuum pump has been developed that employs a cooling method in which an outside air or cooling air introduction port is provided in a stage chamber that generates a vacuum action immediately before the final stage chamber. (Patent Document 2).

  However, the conventional multi-stage Roots type vacuum pump has the disadvantages of high manufacturing cost and large installation space.

In addition, in the conventional single-stage roots vacuum pump, the operation with the suction port completely closed, that is, the so-called “deadline operation” cannot be performed.
By the way, if the deadline operation is performed, the temperature of the entire pump becomes high and the bearing supporting the rotor may be damaged, or the clearance between the rotor and the casing may be lost, leading to poor rotation.
Japanese Patent No. 2684526 Japanese Patent No. 3571985

  An object of the present invention is to provide a compact single-stage roots-type vacuum pump that improves cooling efficiency by introducing outside air into a casing and enables a deadline operation.

In order to achieve the above object, according to the first aspect of the present invention, a pair of three-leaf rotors are provided in a casing in which a suction port and a discharge port are formed, and the suction port and the discharge port communicate with each other. A single-stage roots-type vacuum pump that sucks air from the suction port by rotating both rotors so that there is no discharge, and discharges the sucked air from the discharge port,
The suction port is provided at a position n that exceeds a volume movement angle of 120 ° from the center of each rotation axis with respect to an imaginary line m connecting the centers of the rotation shafts of the rotors. Provided at a position o exceeding a volume movement angle of 120 ° in the opposite direction to the suction port from the center of each rotation axis with respect to an imaginary line m connecting the centers of the rotation shafts. It is provided so as to generate two sealed spaces surrounded by the leaf pieces adjacent to each rotor and the inner wall surface of the casing between the discharge port side, the peripheral wall portion on the discharge port side from the virtual line m, and the virtual space In the vicinity of the line m, an outside air introduction hole is provided so as to correspond to each rotor and communicate with the inside of the casing, and a rotating shaft of one rotor is used as an output shaft in a motor housing attached to one side of the casing. It has a built-in motor. It is a sign.

  In order to achieve the same object, the invention described in claim 2 is the single-stage roots-type vacuum pump according to claim 1, characterized in that the outside air introduction hole is provided in a horizontally long slit shape. is there.

(Invention of Claim 1)
According to this single-stage Roots type vacuum pump, a large amount of outside air is introduced into the casing through the outside air introduction hole, thereby enabling operation under a high vacuum of −50 kPa or more. The total volume movement angle of the enclosed space surrounded by the adjacent leaf pieces of each rotor and the inner wall surface of the casing is 240 degrees, and the movement distance of the seal portion between the top of the rotor leaf piece and the inner wall surface of the casing is increased. Leakage was reduced and volumetric efficiency was improved. Furthermore, since the timing at which the air on the discharge port side flows into the sealed space is early, the amount of outside air inflow increases and the temperature rise of the pump body is suppressed, so that the cooling efficiency is improved.

  In addition, the installation space is smaller than that of a multi-stage roots vacuum pump, and the adoption of a built-in motor makes the entire pump compact and enables a deadline operation.

(Invention of Claim 2)
In this single-stage roots-type vacuum pump, the outside air introduction hole is provided in a horizontally long slit shape, so that the effective area of the introduction hole can be increased and the casing can be made compact.

  The best mode of the present invention will be described below with reference to the drawings. FIG. 1 is a front view (a) and a side view (b) of a single-stage roots vacuum pump according to the present invention, FIG. 2 is a longitudinal side view, FIG. 3 is a longitudinal front view of the main part, and FIG. FIG. 5 is an explanatory view showing the rotational action of the rotor and the inflow conditions (a) to (f) of the outside air into the casing.

  In FIG. 2, a single-stage roots vacuum pump P according to the present invention has a motor housing 2 attached to one side of a casing 1 and a gear housing 5 attached to the other side, and a bearing attached to the motor housing 2. 3 and a bearing 6 mounted on the gear housing 5 are provided so as to freely support two parallel rotating shafts 8 and 10, and end portions of the rotating shafts 8 and 10 protruding from the gear housing 5. A pair of timing gears 12 and 12 that mesh with each other are attached. A gear cover 7 is attached to the gear housing 5. Further, the motor housing 2 is provided with a built-in motor 25 whose output shaft is the rotating shaft 10 protruding from the housing 2. 26 is a motor casing attached to the motor housing 2, 27 is a rotor attached to the rotary shaft 10 penetrating through the motor casing 26, and 28 is a fixed provided on the motor casing 26 side so as to correspond to the rotor 27. A child 29 is a cooling fan attached to the tip of the rotating shaft 10 projecting outward from the motor casing 26, and 30 is a fan cover.

As shown in FIG. 3, in the casing 1 in which the suction port 14 and the discharge port 15 are formed, a pair of three-leaf rotors 9 and 11 provided on the rotary shafts 8 and 10 can rotate in opposite directions. The air sucked from the suction port 14 is compressed and discharged from the discharge port 15 by the rotational operation of the rotors 9 and 11.
A well-known minute gap c is provided between the inner wall surface 1a of the casing 1 and the tops of the leaf pieces of the rotors 9 and 11, as is well known.

The suction port 14 has a position n that exceeds a volume movement angle of 120 ° from the center of each rotary shaft 8, 10 with respect to a virtual line m connecting the centers of the rotary shafts 8, 10 of the rotors 9, 11. Is provided with a laterally long mouth portion 14a.

  The discharge port 15 has an angle of 120 ° in the direction opposite to the suction port 14 from the center of each rotation shaft 8, 10 with respect to a virtual line m connecting the centers of the rotation shafts 8, 10 of the rotors 9, 11. A horizontally long mouth portion 15a is provided at a position o beyond the volume movement angle. Further, in the peripheral wall portion of the casing 1 on the discharge port 15 side from the imaginary line m, and in the vicinity of the imaginary line m, the horizontally long slit-shaped outside air introduction holes 16 and 16 correspond to the rotors 9 and 11, respectively. Respectively. Reference symbol s denotes a sealed space surrounded by the adjacent leaf pieces of the rotors 9 and 11 and the inner wall surface 1a of the casing 1.

FIG. 1 shows an external view of a single-stage roots vacuum pump P according to the present invention. In the figure, 31 is a base to which the casing 1 is fixed, 32 is a silencer attached to the suction port 14 of the casing 1, 33 is a silencer attached to the outside air introduction holes 16, 16, and 34 is a silencer attached to the discharge port 15. . These silencers are small in order to reduce the installation space.
Thus, the single-stage roots vacuum pump P according to the present invention is configured.

  Next, the operation of the single-stage roots type vacuum pump P of the present invention will be described. The rotors 9 and 11 are rotated in opposite directions by the operation of the motor 25 to suck air from the suction port 14 and the air is compressed. While being mixed with the outside air sucked from the outside air introduction holes 16, 16, the temperature of the compression heat is lowered and the air is discharged from the discharge port 15. FIG. 5 shows a situation where the outside air flows from the outside air introduction holes 16 and 16 into the sealed space s and moves. In the drawing, the portion represented by the satin pattern shows a place where the outside air from the outside air introduction hole 16 flows into the sealed space s that moves as the rotors 9 and 11 rotate.

(Experiment)
The performance experiment of the single-stage roots type vacuum pump P of the present invention was conducted. The results are shown in Table 1.
However, as for the temperature measurement value, the value after 3 hours of continuous operation is shown at the closing pressure at which the temperature condition is worst.
Suction port diameter: 20mm, motor output: 1.5kW (200v, 2p)

  As a result of the above-mentioned experiment, it was confirmed that the closing operation was possible with the single-stage roots type vacuum pump P, and there was no problem with the influence of the temperature rise.

  As described above, according to this single-stage roots-type vacuum pump, a large amount of outside air can be introduced into the casing from the outside air introduction hole, and operation under a high vacuum of -50 kPa or more is possible. Furthermore, since the temperature rise of the pump body is suppressed, the cooling efficiency is improved.

Front view (a) and side view (b) of single stage roots type vacuum pump of the present invention Same side view Same vertical section front view Side view of casing outlet Explanatory drawing which shows the rotational action of a rotor, and the inflow situation (a)-(f) of the outside air in the casing

Explanation of symbols

P: single-stage roots vacuum pump 1 according to the present invention ... casing 1a ... inner wall surface 2 of casing ... motor housings 8, 10 ... rotating shafts 9, 11 ... rotor 14 ..Suction port 15 ... Discharge port 16, 16 ... Outside air introduction hole 25 ... Built-in motor m ... Virtual line s connecting the centers of the rotation axes of the rotors ... Sealed space

Claims (2)

A pair of three-leaf rotors are provided in the casing in which the suction port and the discharge port are formed, and air is sucked from the suction port by rotating both rotors so that the suction port and the discharge port do not communicate with each other. A single-stage roots-type vacuum pump that inhales and discharges inhaled air from an outlet,
The suction port is provided at a position n that exceeds a volume movement angle of 120 ° from the center of each rotation axis with respect to an imaginary line m connecting the centers of the rotation shafts of the rotors. Provided at a position o exceeding a volume movement angle of 120 ° in the opposite direction to the suction port from the center of each rotation axis with respect to an imaginary line m connecting the centers of the rotation shafts. It is provided so as to generate two sealed spaces surrounded by the leaf pieces adjacent to each rotor and the inner wall surface of the casing between the discharge port side, the peripheral wall portion on the discharge port side from the virtual line m, and the virtual space In the vicinity of the line m, an outside air introduction hole is provided so as to correspond to each rotor and communicate with the inside of the casing, and a rotating shaft of one rotor is used as an output shaft in a motor housing attached to one side of the casing. It has a built-in motor. Single stage roots type vacuum pump.   2. The single-stage roots-type vacuum pump according to claim 1, wherein the outside air introduction hole is provided in a horizontally long slit shape.

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