TWI670418B - Spiral vacuum pump - Google Patents

Abstract

When a spiral vacuum pump having a pair of spiral rotors is formed by one of the curves forming the right-angled cross-sectional shape of the helical teeth, the gap between the helical teeth of the two helical rotors is widened at the center of the rotation center. It narrows toward its outer peripheral side.

In the first curve, when the gap between the tooth surfaces of the two helical teeth (22a, 22b) is zero, the external rotation is created for the point on the second circular arc of the other spiral rotor that constitutes the pair. The coordinates (X _t , Y _t ) in the radial direction of the wheel are corrected by the correction angle (α) calculated based on the coordinate and the following formula (Formula 1), and the corrected coordinates are connected (X=X _t cosα) -Y _t sinα, Y=X _t sinα+Y _t cosα) and the depictor,

Description

Spiral vacuum pump

The present invention relates to a spiral vacuum pump comprising a pair of helical rotors having a twisting direction in a reverse direction and having equally spaced helical teeth, such that the pair of helical rotors are stored in a non-contact manner with each other. The outer casing is sucked from one end of the outer casing by the synchronous rotation of the two spiral rotors and is discharged from the other end.

Such a spiral vacuum pump is known, for example, from Patent Document 1. In this conventional example, the right-angled cross-sectional shape of the helical tooth is created by the first circular arc centering on the rotation center of the spiral rotor constituting the bottom of the tooth, and the spiral rotor constituting the tooth tip portion thereof. a second arc centered on the center of rotation; and a first curve and a second curve connecting the first arc and the second arc, respectively. Further, the first curve is created by an outer-rotary line created at a point on the second circular arc of the other spiral rotor that constitutes the pair, and the second curve is a virtual rack formed by a predetermined curve. Creation.

The spiral vacuum pumping is performed by sealing the gas sucked from the suction port of the outer casing between the spiral rotor and the outer casing and transferring it by compression. Spit out from the spout of the outer casing. At this time, when the spiral teeth do not interfere with each other and the gap between the tooth surfaces of the two helical teeth is increased, the reverse flow rate of the gas flowing back through the gap increases, which causes a decrease in pumping ability. For this reason, considering the thermal expansion and processing accuracy of the use environment of the spiral vacuum pumping, it is necessary to design the gap between the tooth surfaces of the two helical teeth when the pair of spiral rotors are meshed in a non-contact manner. Make the same to the full length and reduce as much as possible (for example, 0.05 mm).

In the above-described conventional example, when the first and second circular arcs are connected to the first and second circular arcs, it is found that the gap between the helical teeth of the two helical rotors is wide at the center of rotation. It narrows toward the outer peripheral side. The reason for this is that the pitch angle (θp) of the helical teeth at an arbitrary distance (R) in the radial direction from the center of rotation of the spiral rotor is different. Therefore, the inventors of the present invention have found that the correction angle (α) is calculated based on the pitch angle (θp) at a distance (R) from the rotation center of the spiral rotor, and the external rotation is corrected accordingly. When the coordinates of the wheel line are used, the gap between the tooth surfaces of the two helical teeth can be made equal to the entire radial length.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Publication No. Hei 8-189485

The present invention has been made by the creator of the above findings, and an object of the invention is to provide a spiral vacuum pump in which the gap between the tooth surfaces of the two helical teeth when the pair of spiral rotors are meshed with each other in a non-contact manner.

In order to solve the above problems, a pair of helical rotors having helical directions in which the twisting directions are reversed and having equal pitches are provided, and the pair of spiral rotors are stored in the outer casing in a non-contact manner, and the two spirals are used. The spiral vacuum pump of the present invention in which the synchronous rotation of the rotor is inhaled from one end of the casing and is discharged from the other end is a right-angled cross-sectional shape of the helical tooth, and is created by the rotation center of the spiral rotor constituting the bottom of the tooth. a first arc having a center; a second arc centering on a rotation center of the spiral rotor constituting the tooth tip portion; and a first curve and a second curve connecting the first arc and the second arc; The two-axis directions in the radial direction orthogonal to each other in the axial right-angle cross section of the spiral rotor are the X-axis and the Y-axis, and the first curve is for the case where the gap between the tooth faces of the two helical teeth is zero. The coordinate in the radial direction of the outer-rotary line created by the point on the second arc of the other pair of spiral rotors (X _t =2Acosθ-r _d cos(2θ), Y _t =2Asinθ-r _d Sin(2θ), between the centers of rotation of the two helical rotors Half of the radius r _d of the second arc-based, from the rotational angle [theta] based), based on the coordinates of each coordinate with the calculated correction angle ([alpha]) for correction, the correction link formula (Equation 1) ( X=X _t cosα-Y _t sinα, Y=X _t sinα+Y _t cosα) and is depicted.

(where P is the distance between the helical teeth, R is the radial distance from the center of the axis of rotation of the helical rotor, and DG is the distance between the tooth faces of the helical teeth)

According to the present invention, the correction angle (α) is calculated in accordance with the pitch angle (θp) at the distance (R) of the rotation center of the spiral rotor, and the coordinates of the outer rotation wheel line are corrected, so that a pair of spiral rotors can be used. The gap between the tooth faces of the two helical teeth when they are in meshing with each other in a non-contact manner is made equal and as small as possible throughout the radial direction.

In the present invention, the second curve is preferably formed by combining a hypocycloid and an involute.

1‧‧‧Shell

2 ₁ , 2 ₂ ‧ ‧ spiral rotor

21a, 21b‧‧‧Rotary axis

22a, 22b‧‧‧ helical teeth

T1‧‧‧1st arc

T2‧‧‧2nd arc

T3‧‧‧1st curve

T4‧‧‧2nd curve

Fig. 1 is a cross-sectional view for explaining a configuration of a spiral vacuum pump according to an embodiment of the present invention.

[Fig. 2] (a) is a view showing a cross-sectional shape of a helical tooth, (b) is a view showing a right-angled cross-sectional shape of the helical tooth, and (c) is a non-contact engagement of the two helical teeth. A right-angled cross-sectional view of the shaft as shown in the state.

[Fig. 3] (a) is a view in which one spiral rotor is cut in an inner diameter of a helical tooth serving as the spiral rotor, and (b) a spiral rotor is formed as a helical tooth of another spiral rotor. The inner diameter is taken as a diagram under cutting.

[Fig. 4] Variation of the mutual gap between the helical teeth of a pair of helical rotors The reason for the description of the graph.

FIG. 5 is a diagram for explaining correction of coordinates of the first curve. FIG.

Referring to Fig. 1, SP is a spiral vacuum pump of an embodiment of the present invention. The spiral vacuum pump SP is provided with a cylindrical outer casing 1. On one side (upper side in FIG. 1) of the outer casing 1, a connecting pipe (not shown) from a device (vacuum chamber or the like) intended to evacuate is provided. A freely connected suction port 11 is provided. On the other side (lower side in Fig. 1) of the outer casing 1, a discharge port 12 for discharging the gas in the outer casing 1 to the outside is provided. Further, in the operating space 1a in the casing 1, a pair of spiral rotors 2 ₁ and 2 ₂ are stored in a state in which the helical teeth 22a and 22b integrally formed on the rotating shafts 21a and 21b are in a non-contact manner. . Hereinafter, a pair of spiral rotors 2 _{1 are} made based on the posture shown in Fig. ₁ . The direction in which the rotating shafts 21a and 21b of the ₂₂ are extended is the up-and-down direction, and the direction orthogonal thereto is the left-right direction, and the term indicating the direction is used.

The upper opening and the lower opening of the outer casing 1 are closed by the intake side cover 13a and the discharge side cover 13b which airtightly hold the operation space 1a inside. Bearings 3a and 3b are attached to the intake side cover 13a and the discharge side cover 13b, respectively, and the upper end portion and the lower end portion of the rotation shafts 21a and 21b of the pair of right and left spiral rotors 2 ₁ and 2 ₂ are supported. Further, the lower end portions of the rotating shafts 21a and 21b are extended below the discharge side cover 13b, and the gears 4a and 4b of the same form that mesh with each other are externally inserted. Further, the lower end of the rotary shaft 2 lines ₁ 21a is provided with a right screw rotor coupling 5a, made 5b is connected to the coupling provided in the drive shaft 61 of the motor 6 so that the power of the drive motor 6 is introduced to the rotary shaft 21a. Thereby, the two spiral rotors 2 ₁ and 2 ₂ rotate in opposite directions in synchronization with each other, and the gas sucked from the intake port 11 of the outer casing 1 is sealed while being sealed between the spiral rotors 2 ₁ and ₂₂ and the outer casing 1 in the spiral. The terminal portions of the teeth 22a and 22b are compressed and discharged from the discharge port 12.

Each of the helical teeth 22a and 22b of the spiral rotors 2 ₁ and 2 ₂ is formed such that the distance between the helical teeth 22a and 22b (the height in the vertical direction), that is, the pitch P (or the lead) is equal and twisted. The direction becomes reverse. The axial cross-sectional shape and the axial right-angle cross-sectional shape of the respective helical teeth 22a and 22b are as shown in Figs. 2(a) to 2(c), and are formed by forming the bottom of the tooth (in Fig. 2(b), a first arc t1 centering on the rotation center tc of the rotation shafts 21a and 21b between the Ta-Tbs, and a spiral rotor 2 ₁ constituting the tooth tip portion (between Tc and Td in Fig. 2(b)) The rotation center of 2 ₂ is the second arc t2 of the center tc; and the first curve t3 (between Tb and Tc in FIG. 2(b)) and the second which respectively connect the first arc t1 and the second arc t2 Curve t4 (between Td-Ta in Fig. 2(b)). The second curve t4 is formed, for example, by combining a hypocycloid and an involute.

When this, each of the helical teeth 22a of the first curve t3 constitute a screw rotors _1, 2 whereby the one point on the second arcuate t2 of the other screw rotor ₂₂ and the record into the epitrochoid and Creation, was found The gap between the spiral teeth 22a and 22b is widened on the side of the rotation center tc of the rotary shafts 21a and 21b as shown in Figs. 3(a) and 3(b), and becomes narrower toward the outer peripheral side thereof. The reason for this is that the pitch angles (θp) of the helical teeth 22a, 22b at any distance (R) in the radial direction from the center of rotation tc are different, that is, as shown in Fig. 4, at an arbitrary distance (R) The length (circumference) of the circular arc of the circle having the radius is, for example, A, B, and C, and the formation angles θp1, θp2, and θp3 when the height is connected to the pitch height are different. For this reason, it is necessary to make the gap between the opposing spiral teeth 22a and 22b constant by a certain angle.

In the present embodiment, the first curve t3 is formed as follows: the second arc t2 of the other spiral rotor 2 ₂ when the gap between the tooth surfaces of the two helical teeth 22a and 22b is zero. The coordinates on the radial direction of the outer rotator line created by the upper point (X _t = 2Acos θ - r _d cos(2θ), Y _t = 2Asin θ - r _d sin (2θ), A-system two-helical rotor 2 ₁ , 2 ₂ The half of the distance between the rotation centers tc, r _d is the radius of the second arc t2, and the θ-system rotation angle is corrected by the correction angle (α) calculated based on the coordinates and the following formula (Expression 1). The coordinates are corrected by linking the corrected coordinates (X=X _t cosα-Y _t sinα, Y=X _t sinα+Y _t cosα).

That is, referring to Fig. 5, when the first curve t3 is the outer-rotary line, a curve shown by a dotted line in Fig. 5 is drawn (X _t = 2Acos θ - r _d cos (2θ), Y _t =2Asin θ - r _d sin (2θ), and the pitch angle (θp) at this time is based on the distance (R) from the rotation center tc of the spiral rotors 2 ₁ and 2 ₂ , and can be expressed by the following equation (Expression 2) Said.

When the distance to be moved from the position where the gap between the tooth surfaces of the two helical teeth 22a and 22b is zero is ij, the Ij system can be expressed by the following formula (Expression 3), and the following formula can be changed ( Equation 4). In this case, P is the distance between the helical teeth 22a and 22b, R is the radial distance from the center of the rotating shafts 21a and 21b, and DG is the distance between the tooth faces of the helical teeth 22a and 22b.

From the above equations (Expression 2) to Equation (Expression 4), the correction angle (α) can be expressed in the above formula (Expression 1), and when it is shown in Fig. 5, it is a line indicated by a chain line. . In addition, FIG. 5 shows a coordinate system when the center of rotation of the spiral rotors 2 ₁ and 2 ₂ is (X, Y)=0, 0, which corresponds to a rotation of 180° as shown in FIG. 2(b). State.

The correction angle (α) is determined as above, and the coordinates (X _t , Y _t ) of the outer rotation wheel in the case where the gap between the tooth surfaces of the two helical teeth 22a and 22b is zero are corrected based on the correction angle (α). In the case of the first curve t3, the connection coordinates (X=X _t cosα-Y _t sinα, Y=X _t sinα+Y _t cosα) indicated by solid lines in Fig. 5 are obtained. According to the above embodiment, the correction angle (α) is calculated from the pitch angle (θp) of the distance (R) of the rotation center tc of the spiral rotors 2 ₁ and 2 ₂ , and the coordinates of the outer rotation wheel line are corrected. The gap between the tooth surfaces of the two helical teeth 22a and 22b when the pair of helical rotors 2 ₁ and 2 _{2 are} in a non-contact manner can be made equal to each other in the radial direction as much as possible.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above. In the above embodiment, the second curve t4 is formed by combining the epicycloid and the involute, but the present invention is not limited thereto, and may be, for example, a sinusoidal curve, a cycloid, or a Crosoe curve. Further, the number of the spiral rotors 2 ₁ and 2 ₂ is not necessarily one, and may be two or more.

Claims (2)

A spiral vacuum pump comprising a pair of helical rotors having a twisting direction in a reverse direction and having equally spaced helical teeth, wherein the pair of spiral rotors are housed in a casing in a non-contact manner with each other, by the pair The synchronous rotation of the spiral rotor is inhaled from one end of the outer casing and is discharged from the other end. The shape of the helical tooth having a right-angled cross section is created by a first circular arc which is the bottom of the tooth constituting the helical tooth. The second arc is centered on the rotation center of the pair of spiral rotors, and the first curve and the first axis are the center of rotation of the pair of spiral rotors; a curve in which the first arc and the second arc are connected to each other, and the two axial directions orthogonal to each other in the axial cross section of the pair of spiral rotors are X-axis and Y-axis. The first curve is drawn by the following method: based on the second circle of the other spiral rotor of the pair of spiral rotors when the gap between the tooth flanks of the two helical teeth is zero An outer-rotary line created by a point on the arc that has different pitch angles of helical teeth of any distance in the radial direction from the center of rotation of the pair of helical rotors, for the radial coordinates of the outer-rotary line (X _t =2Acosθ-r _d cos(2θ), Y _t =2Asinθ-r _d sin(2θ), A is a half of the distance between the centers of rotation of the pair of spiral rotors, and r _d is the radius of the second arc. The θ-system rotation angle is corrected by the correction angle (α) calculated based on the coordinate and the following formula (Expression 1), and the corrected coordinates are connected (X=X _t cosα-Y _t sinα, Y=X _t sinα) +Y _t cosα), (wherein P is the distance between the spiral teeth, R is a radial distance from the center of the rotation axis of the pair of spiral rotors, and DG is a distance between half of the tooth faces of the helical teeth). A spiral vacuum pump according to claim 1, wherein the second curve is formed by combining a hypocycloid and an involute.