JP2758719B2 - Liquid injection screw compressor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid injection type screw compressor, and particularly to a structure of a male rotor.

BACKGROUND ART As shown in FIG. 11, this type of conventional liquid injection screw compressor has a casing 12,
In the figure, a suction port is provided with one end face in the longitudinal direction as a suction side, and a discharge port 11 is provided with the other end face as a discharge side. Also,
The casing 12 has a structure in which a pair of rotors 13 and 14 that rotate while meshing with helical teeth are incorporated.

The compressed gas is supplied to the casing 12 in the suction process.
Is sucked into the rotor tooth space 15 from the suction port, and is compressed by the reduction of the volume of the rotor tooth space 15 as the rotors 13 and 14 rotate as a compression step, and is discharged from the discharge port 11 of the casing 12 as the discharge step. It is designed to be ejected.

In the compressed gas discharge process, the rotor tooth space 15 communicates with the discharge port 11 of the casing 12, and the volume of the rotor tooth space 15 decreases to zero with the rotation of each of the rotors 13 and 14 until the internal space becomes zero. This is a step of sending the compressed gas to the discharge port 11, and this discharge step is performed by the rotor tooth space 15 and the discharge port 11.
11 to FIG. 13 depending on the form of the discharge path communicating with.

First, in the first step, as shown in FIG. 11, the discharge direction of the compressed gas from the rotor tooth space 15 is in the radial direction and the axial direction of the rotor tooth space 15.

Next, in the second step, as shown in FIG. 12, the discharge direction of the compressed gas from the rotor tooth space 15 is in the axial direction of the rotor tooth space 15 only, It is in a semi-confined state.

Further, the third step is a completely closed state in a so-called discharge step in a state where there is no discharge path connecting the rotor tooth space 15 and the discharge port 11 as shown in FIG.

Further, the tooth surfaces of the rotors 13, 14 are sufficiently lubricated by a liquid such as oil injected into the casing 12,
Heat generated during compression of the compressed gas is absorbed, and leakage of the compressed gas from the compression side to the suction side is reduced to enhance the sealing effect.

In the structure of the conventional liquid injection type screw compressor, in the third step of the compressed gas discharging step, there is no discharge path that connects the rotor tooth space 15 and the discharge port 11, but even in this state, As the volume of the rotor groove space 15 decreases, the liquid lubricating the tooth surfaces of the rotors 13 and 14 is confined in the rotor groove space 15 and compressed, causing a rapid pressure increase. That is, a so-called liquid compression phenomenon occurs.

The sudden increase in the pressure of the liquid due to the liquid compression phenomenon becomes a pulse-like load and acts on the respective bearings of the rotors 13 and 14, so that the life of the bearings of the rotors 13 and 14 is shortened. Or cause vibration during operation of the compressor.

Further, when the rotation speed of the rotors 13 and 14 increases, the discharge resistance of the liquid to the tooth surface increases, so that the liquid compression phenomenon occurs even in the semi-closed state which is the second step in the discharge step. There is. In particular, when the compressed gas is a light gas such as hydrogen or helium, the liquid is easily trapped in the rotor tooth space in the semi-closed state or the completely closed state in the discharge process.

In order to reduce the liquid compression phenomenon, various improvements such as the shape of the discharge port 11 of the casing 12 and the end faces of the rotors 13 and 14 facing the discharge port 11 have been made. Sufficient results were not obtained, such as significant leakage of compressed gas from the air to the suction side, or significant reduction in compression efficiency.

Therefore, as shown in FIG. 14, a dropout portion 16 is formed at the discharge end of the male rotor 13 by cutting out the discharge end of the male rotor 13 on a plane parallel to the rotor axis, and a step is formed on the rotor tooth surface. When trying to eliminate the liquid pressure phenomenon by a method that sticks, in order to completely eliminate the liquid compression, it is necessary to release the liquid and gas before the liquid compression occurs, and there is a problem that the efficiency is reduced .

That is, when the closing portion 17 between the rotors 13 and 14 is viewed from above with the female rotor 14 removed, as shown in FIG. 14, the closing start shape has a shape in which the width closer to the valley becomes smaller. For this reason, if the escape passage is not formed before the start of the closing with a stepped dropping structure in which the rotor discharge end is cut out on two planes, a plane 18 parallel to the rotor axis and a plane 19 crossing the rotor axis, the closing The corner will fall inside the start line. In this case, the rotation slightly advances from the start of the closing, and the binding line is changed to a dashed line a as shown in FIG.
The escape passage of the liquid at the position of is the hatched portion b, and the escape of the liquid immediately after the start of the binding is hardly secured. In addition, the escape of the liquid in the circumferential direction is smooth, but the escape of the liquid in the axial direction is performed as shown in FIG.
It was not performed smoothly because 16a was formed. For this reason, the liquid compression was not completely eliminated, and an increase in pressure occurred at the early stage of binding.

Further, in order to completely eliminate the liquid compression, it is necessary to cut off the liquid larger than the binding start line, which results in an excessive leakage of the compressed gas. In particular, as shown in FIG. 17 and FIG. 18, when the tip speed (peripheral speed) of the rotor increases, the liquid on the case surface loses the trapped liquid that tries to escape in the circumferential direction. Since the fluid flows in the direction d relatively opposite to the escape direction c, the resistance of the liquid to escape in the circumferential direction increases, and there is a problem that the liquid must be cut off considerably larger than the binding start line in order to completely eliminate the liquid compression. .

The present invention has been made in view of the above problems, and can prevent a sudden increase in pressure of a liquid due to a liquid compression phenomenon in a semi-closed state and a completely closed state in a compressed gas discharge process while maintaining compression efficiency. It is an object of the present invention to provide a liquid injection type screw compressor having a structure.

DISCLOSURE OF THE INVENTION The liquid injection type screw compressor of the present invention has a casing in which one end in the longitudinal direction is on the suction side and the other end is on the discharge side, and is incorporated into the casing by being engaged with each other.
It has a pair of male and female rotors.

The male rotor has a helical convex tooth shape having an outer radius R and a number of Z teeth.

Then, a chamfer is applied to a corner portion of an end face of the tooth mold facing the discharge side of the casing, and the range of the chamfer is convex with the rotation direction being the center of the rotation axis of the male rotor. from the point P of the corner angle [psi _S than the addendum shaped for tooth die is positioned at the angle [psi _S to be -10 ° ≦ ψ _S ≦ 35 °, the angle [psi _E is ψ _{S <ψ E} ≦ 160 ° / Z up to a point Q at the corner located at an angle ψ _E ,
Chamfering amount D _S of chamfering amount Dr and axial radial direction of the chamfer is obtained by the 0.007R ≦ Dr ≦ (1.2 / Z ) R 0.007R ≦ D S ≦ (1.2 / Z) R .

According to this configuration, since the corner of the end face of the male rotor facing the discharge side is chamfered, the male rotor and the female rotor are in a semi-closed state or a completely closed state in the compressed gas discharging step. When the liquid confined in the rotor groove space surrounded by the rotor starts to be compressed due to the reduction in the volume of the rotor groove space, the corner of the male rotor is chamfered to form the rotor groove space into a casing. The liquid is extruded into the rotor tooth space in the suction step by communicating with the rotor tooth space in the suction step, so that the pressure of the liquid sealed in the rotor tooth space can be prevented from rising, and A liquid injection type screw compressor that can prevent a load due to an increase in pressure from acting on bearings of the male rotor and the female rotor.

Further, in the present invention, the chamfer of the male rotor is formed by one curved surface or flat surface.

With this configuration, the confinement start line substantially coincides with the confinement start line, no step is formed in any direction, the escape of the compressed gas is small, and the liquid compression can be further reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a discharge side of a casing showing one embodiment of a preferred liquid injection type screw compressor of the present invention, FIG. 2 is a side view of a part of the discharge side of the male rotor, 3 is a front view of a part of the male rotor on the discharge side, FIG. 4 is a cross-sectional view taken along the line AA of FIG. 3, and FIG. 5 is a front view of a part of the male rotor chamfered in a plane. FIG. 6 is a perspective view of a part of the above,
7 is a cross-sectional view taken along the line AA of FIG. 6, FIG. 8 is a front view of a part of a male rotor chamfered into a curved surface, FIG. 9 is a side view of a part of the male rotor, and FIG. FIG. 11 is a front view showing a state in which the discharge direction of the compressed gas of the conventional liquid injection screw compressor from the rotor tooth space is the radial direction and the axial direction of the rotor tooth space, and FIG. Fig. 13 is a front view showing a state in which the discharge direction of the compressed gas from the rotor groove space is in the axial direction of the rotor groove space. Fig. 13 is a discharge passage that connects the rotor groove space to the discharge port. FIG. 14 is a side view of a part of the discharge side of the male rotor in which the discharge end has been cut off from the rotor tooth space and the discharge port, and FIG. FIG. 16 is a cross-sectional view taken along line AA of FIG. 15, and FIG. 17 is a perspective view of the same. FIG. 18 is a cross-sectional view of line B-B of FIG. 17.

BEST MODE FOR CARRYING OUT THE INVENTION A liquid injection type screw compressor according to an embodiment of the present invention is a first type.
Explanation will be made based on FIG. 2 and FIG.

In FIG. 1, reference numeral 1 denotes a casing. Inside the casing 1, a pair of male rotors 2 having helical teeth is provided.
And the female rotor 3 are engaged with each other and incorporated. The male rotor 2 and the female rotor 3 are supported in parallel by bearings provided at both ends of the casing 1 and rotate in the casing 1. Furthermore, one end of the casing 1 is provided with a suction port on the suction side, and the other end is provided on the discharge side with a discharge port.
Is provided.

The male rotor 2 is a convex toothed rotor having the number of teeth Z and having an outer radius R, and a chamfer provided at a corner of an end face 5 of the casing 1 facing the suction side. A part 6 is formed. As shown in FIGS. 3 and 4, the chamfered surface of the chamfered portion 6 is flat, and the connecting portion between the chamfered surface of the chamfered portion and the tooth surface of the male rotor 2 is 400 / R. Avoid the steps above.

And the confinement start line and the chamfer line of this chamfer 6
21 matches. In the figure, reference numeral 22 denotes a confinement line in which the compressed gas is compressed.

The scope of the chamfer portion 6, Examples about the rotation axis of the male rotor 2 rotating direction of the male rotor 2 (in the arrow direction), than the angle [psi _S is addendum A convex tooth type, - from point P corners located 10 ° ≦ ψ _S ≦ 35 ° ... (1) and a angle [psi _S, the angle [psi _E
There, [psi _{S <be} until point Q corners located [psi _E ≦ 160 ° / Z ...... becomes (2) angle [psi _E.

Further, the chamfering unit 6, as shown in FIGS. 1 and 2, the beveled amount of radial male rotor 2 Dr, if the chamfering amount of axial and D _S, respectively 0.007R ≦ Dr ≦ (1.2 / Z) R ...... (3) 0.007R ≦ D S ≦ (1.2 / Z) R ...... (4) to become the chamfer amount Dr, the range _{D S (1), (2} ) It is formed more notched.

Further, the shape of the chamfered portion 6 may be an appropriate shape such as a shape in which the point P and the point Q are linearly notched, or a shape in which an arc-shaped curved surface is cut along a corner.

The female rotor 3 is a concave toothed rotor,
As the male rotor 2 rotates, the male rotor 2 comes into contact with the male rotor 2 at a pitch circle and rotates.

Then, a liquid such as cooling oil is injected into the casing 1 to lubricate the tooth surfaces of the male rotor 2 and the female rotor 3 so that leakage of compressed gas from the discharge side to the suction side is reduced. Has become.

 Next, the operation of the present embodiment will be described.

When the liquid injection screw compressor is operated, the male rotor 2 and the female rotor 3 rotate while meshing with each other while the tooth surfaces are lubricated with the liquid inside the casing 1. And
The compressed gas is supplied to the casing 1 as the rotors 2 and 3 rotate.
Is sucked into the rotor tooth space 7 surrounded by the rotors 2 and 3 and the casing 1, compressed and discharged from the outlet 4 of the casing 1.

The discharge direction of the compressed gas from the rotor tooth space 7 during the discharge process of the compressed gas is only in the axial direction of the rotor tooth space 7 in a semi-closed state, or the rotor tooth space 7 and the discharge port 4 In a completely closed state in which there is no communicating discharge path, when the liquid sealed in the rotor tooth space 7 starts to be compressed due to the decrease in the volume of the rotor tooth space 7, the rotor tooth space 7 The corner portion chamfered portion 6 communicates with the rotor tooth space 8 during the suction process of the casing 1. For this reason, the liquid is pushed out into the rotor tooth space 8 during the suction process, so that a sudden increase in pressure due to the liquid compression phenomenon can be prevented. Accordingly, no load is applied to the bearings of the rotors 2 and 3 due to the rapid increase in the pressure of the liquid, so that the life of the bearings can be prevented from being shortened.

In addition, the chamfered portion 6 of the male rotor 2 is provided in the above (1),
(2) The amount of chamfer in the radial direction while being applied within the range of expression
Dr and axial chamfer amount D _S is the (3), (4) the minimum value is the case 0.007R smaller than can not reduce the liquid compression phenomenon. Further, chamfering amount D _S of chamfering amount Dr and the axial direction of the radial direction, the (3), (4)
If the value is larger than the maximum value (1.2 / Z) R in the equation, a large amount of compressed gas leaks from the discharge side of the casing 1 to the suction side, and the compression efficiency is reduced.

Therefore, for example, the male rotor 2 has four teeth,
Outside radius of 102 mm, the range of beveled of the male rotor 2 (1), (2) based on the equation, and to [psi _{E =} 35 ° than [psi _{S =} 5 °, on the basis of the equation (3) Radial chamfer amount Dr = 4m
m, when the axial chamfer amount D _S = 4 mm based on the equation (4), if the male rotor 2 is rotated at 4000 rpm, leakage of the compressed gas from the discharge side to the suction side may occur. In addition, it is possible to prevent a sudden increase in pressure of the liquid due to the liquid compression phenomenon in the discharge process. Since the power required for compressing the liquid is reduced, the compression efficiency is increased by 3%.

Then, the chamfered surface of the chamfered portion 6 is changed as shown in FIGS.
As shown in the figure, the angle of the male rotor 2 can be reduced along the closing start line 20 so that the closing start line 20 and the chamfer line coincide with each other. Since no step is formed in any direction, the liquid can escape. Therefore, compared with the case where a step is formed on the tooth surface of the male rotor 2, the escape of the compressed gas is small,
In addition, liquid compression can be sufficiently reduced.

Also, as shown in FIGS. 5 to 7, when the chamfered portion 6 in which the discharge end of the male rotor 6 is chamfered in one plane is formed, the male rotor 2 and the casing 1 are formed as shown in FIG. Is formed with a chamfered surface 23 having a degree of taper in the rotational direction. On the chamfered surface 23 of the tapered surface, a thrust force 24 is generated in the axial direction due to the wedge effect of the liquid lubrication, and acts to prevent the end face of the male rotor 2 from contacting the end face of the casing 1. Also, the thrust force is increased when the gap between the end face of the male rotor 2 and the inner face of the casing 1 is reduced. Avoiding contact with In particular, in the case of a screw compressor, the discharge end faces of the rotors 2 and 3 and the casing 1
The gap between the inner surface of the compressor is one of the major factors that affect the performance of the compressor. If the gap can be reduced, the amount of gas leaking through this portion can be reduced, so that the efficiency can be improved. Can be.

Therefore, if the discharge end of the male rotor 2 is chamfered so as to form a chamfered surface 23 in the rotational direction as shown in FIG. 5, the rotor discharge end and the inner surface of the casing 1 can be reduced, and Efficiency can be improved.

Further, as shown in FIGS. 8 to 10, when the chamfered portion 6 of the end face facing the discharge side of the male rotor 2 is formed into one curved surface, the gap between the inner surface of the casing 1 and the rotors 2, 3 is reduced. The small area increases, the wedge effect increases, and
Even if the gap between the rotors 2 and 3 is reduced, contact can be avoided, so that the efficiency is improved. The thrust force due to this wedge effect is
It does not become a pulse-like force such as a liquid compression force due to the confinement, and has almost no adverse effect on bearings and seals, and is a force that can be used effectively.

INDUSTRIAL APPLICABILITY The liquid injection type screw compressor according to the present invention is effective as a compressor for a refrigeration apparatus and a gas pumping apparatus.

Claims (2)

(57) [Claims] 1. A casing in which one end in a longitudinal direction is on the suction side and the other end is on the discharge side, and a pair of a male rotor and a female rotor which are incorporated in the casing so as to be engaged with each other. A helical convex tooth shape having an outer radius R and a number of teeth having Z teeth, and a chamfered portion of an end surface of the tooth shape facing the discharge side of the casing is chamfered; , the corners Examples forward direction of rotation about the rotation axis of the male rollers, the angle [psi _S than the addendum of the convex tooth type is positioned at an angle [psi _S to be -10 ° ≦ ψ _S ≦ 35 ° from point P corners, angles [psi _E is up to point Q of the corner portion positioned at an angle [psi _E as a ψ _{S <ψ E} ≦ 160 ° / Z, beveled amount of radial direction of the chamfer Dr and chamfering amount D _S in the axial direction, especially that it has the 0.007R ≦ Dr ≦ (1.2 / Z ) R 0.007R ≦ D S ≦ (1.2 / Z) R Injection type screw compressor. 2. A liquid injection type screw compressor according to claim 1, wherein the chamfer of the male rotor is formed by one surface.