JP2002317782A - Oil free screw compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil free screw compressor for supplying the oil at an appropriate pressure to a balance piston and an appropriate quantity of the oil to a bearing and a seal parts without increasing a capacity of an oil pump. SOLUTION: This oil free screw compressor 1 is provided with the balance piston 18 provided inside a columnar space part 17 formed in a suction side rotor shaft end integrally with the rotor shaft end freely to be slid, a counter- thrust force generating oil flow passage 23A extended from a branch point 24 in an oil flow passage 23, which is extended from an oil tank 21 through an oil pump 22, to the columnar space 17 to supply the pressure oil for generating the back pressure in the direction from the suction side to the discharge side of the balance piston 18 to the columnar space 17, and a lubricating and sealing oil flow passage 23B divided in the downstream of the branch point 24 in the oil flow passage 23 and communicated with a bearing and a shaft seal part 16S and 16D through an orifice 25. A flow control means 2 is provided between the branch point 24 and the branch point of the lubricating and sealing oil flow passage 23B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil-free screw compressor having a balance piston for applying a force to a screw rotor in a direction from a suction side to a discharge side.

[0002]

2. Description of the Related Art Conventionally, an oil-free screw compressor 10 shown in FIG. 2 is known. The casing 11 of the oil-free screw compressor 10 has a suction port 12 on one side and a discharge port 13 on the other side.
A pair of male and female screw rotors 14 rotatably meshed with each other
(In the drawing, only one of the female side and the male side appears, and the other does not.) Screw rotor 14
The rotor shafts 15S and 15D extend on both sides of the shaft, and are supported by bearings 16S and 16D, respectively. Also,
A columnar space 17 is formed at the end of the rotor shaft on the suction side, and a balance piston 18 is provided in the columnar space 17 so as to be integral with and slidable with the rotor shaft end. In addition, at each of the female and male bearings 16S, 16D, a shaft sealing means (not shown) is disposed adjacent to these.

On the other hand, an oil passage 23 extends from an oil tank 21 via an oil pump 22, and a branch passage extends from the oil passage 23 on the secondary side of the oil pump 22. That is, the anti-thrust which supplies the columnar space 17 with a pressure oil which flows from the secondary side branch point 24 to the columnar space 17 and generates back pressure in the direction from the suction side to the discharge side with respect to the balance piston 18. The oil channel 23A for force generation extends. Further, on the downstream side of the branch point 24, the oil flow path 23 is provided with four lubrication / seals which communicate with the female and male bearings 16S and 16D in the casing 11 and the shaft sealing means via the orifice 25. It branches into a use oil flow path 23B. However, only one of the female side and male side appears in the drawing,
Only the sealing oil flow path 23B is shown. Bearing 16
The oil supplied to S and the oil leaked from the columnar space portion 17 are returned to the oil tank 21 by the oil return flow path 26A, and the oil supplied to the bearing 16D is returned to the oil tank 21 by the oil return flow path 26B.

During operation of the compressor, a thrust force in the direction from the high-pressure discharge side to the low-pressure suction side acts on the screw rotor 14 as shown by an arrow X, and this thrust force is further applied to the rotor shaft 15S. , 15D via bearing 1D
Acts on 6S, 16D. If there is no countermeasure against the thrust force, the bearings 16S and 16D are subjected to an excessive load due to the thrust force, and their durability is impaired. For this reason, pressure oil is sent from the oil pump 22 to the columnar space 17 via the anti-thrust force generating oil flow path 23 </ b> A, and a back pressure is applied to the balance piston 18. As a result, an anti-thrust force in the direction from the suction side to the discharge side acts on the rotor shaft 16S as shown by the arrow Y, and the thrust force acting on the bearings 16S, 16D is canceled, thereby reducing the load on the bearings 16S, 16D. Is done.

In the oil-free screw compressor 10 described above, the bearings 16S and 16D and the columnar space 17
Is supplied from the oil pump 22 at the same pressure,
When the bearings 16 </ b> S and 16 </ b> D are rolling bearings, the amount of oil required for lubrication may be smaller than the amount of oil sent to the columnar space 17. As a method of reducing the amount of oil supplied from the oil flow path 23, there are a method of providing a flow control means in the oil flow path 23 and a method of lowering the oil pressure. About oil in
In order to apply a back pressure to the balance piston 18, it is necessary to secure a pressure equal to or higher than a certain value. Therefore, the bearing 1
An orifice 25 is provided at a position before 6S, 16D to reduce the amount of oil from the lubrication / seal oil flow path 23B to the bearings 16S, 16D.

[0006]

In the conventional oil-free screw compressor 10 described above, the balance piston 1
8 pressure and bearing 16S that must be reserved for the action of back pressure, the pressure difference between the pressure supplied to 16D and P _B, when the diameter of the orifice 25 is D, bearing 16S, 1
The oil amount Q supplied to 6D is represented by the following equation. Q = CD (P _B ) ^1/2 (1) C: Flow coefficient (value determined by actually measuring the orifice 25) The differential pressure P _B is determined by the bearing life, and the oil amount Q is required for the bearings 16S and 16D. Since this value is determined by oil, the orifice diameter D is obtained from the equation (1).

However, if the orifice diameter D calculated by the equation (1) is small, the orifice 24 is clogged by dust or the like, so that the orifice diameter D is usually set to 1.2 mm or more from experience. Therefore, when a large differential pressure P _B, the oil amount Q required oil amount or more. As a result, the required capacity of the oil pump 22 also increases, and there arises a problem that the performance decreases with an increase in the required power. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described conventional problem, and it is possible to supply an appropriate amount of oil to a bearing / seal portion while supplying oil at a necessary pressure to a balance piston without increasing the capacity of an oil pump. It is an object of the present invention to provide an oil-free screw compressor capable of supplying oil.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a pair of male and female mating female members rotatably housed in a casing having a suction port on one side and a discharge port on the other. A balance piston integrally and slidably provided with the rotor shaft end in a columnar space formed at the rotor shaft end on the suction side of the screw rotor, and an oil flow extending from an oil tank via an oil pump. A pressure oil that extends from a branch point on the secondary side of the oil pump in the path and communicates with the columnar space and generates a back pressure in a direction from the suction side to the discharge side with respect to the balance piston is supplied to the columnar space. Anti-thrust force generating oil flow path portion, and a lubrication / seal that branches off downstream of the branch point of the oil flow path and communicates through a flow control means to each of the bearing and shaft sealing portion in the casing. Oil passage section In yl-free screw compressor, it is formed with intervening flow control means between the branch point and the branch point of the lubricating-sealing oil flow passage portion of the oil flow passage.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an oil-free screw compressor 1 according to the present invention. Portions common to the oil-free screw compressor 10 shown in FIG. In the oil-free screw compressor 1, an example of the flow control means is provided at a portion between the secondary branch point 24 of the oil pump 22 in the oil flow path 23 and the branch point of the lubrication / seal oil flow path portion 23A. An orifice 2 is interposed, and oil is guided to each of the lubricating and sealing oil flow passages 23B via the orifice 2.

Normally, the oil pressure required for the back pressure of the balance piston 18 is about 0.3 MPa, and the oil amount required for each of the four bearings 16S and 16D on the female and male sides is 0.1 MPa.
It is about 5 L / min. When the oil pressure is 0.3 MPa and the oil amount is 0.5 L / min, the orifice diameter D that is compatible with both is 0.8 mm. However, if the orifice diameter D is 0.8 mm, clogging due to dust or the like is likely to occur, and as described above, the orifice diameter D needs to be at least 1.2 mm. Therefore, the orifice diameter D is set to 1.
If it is 2 mm, the oil pressure is 0.3 MPa, the oil amount to each of the above four places is 1.2 L / min, and a total of four oil supply parts for the four bearing rotors of the pair of male and female screw rotors 14 are provided. The oil amount becomes 0.8 L / min. However, the total amount of oil required for the four bearing lubrication units is 2.0 L / min, so an oil pump with an unnecessarily large capacity is required, and the motor power for operating these oil pumps also increases. Will do.

On the other hand, when the oil amount is 0.5 L / min and the orifice diameter D is the minimum required of 1.2 mm, the oil pressure is 0.06 MPa, and the oil-free screw compression according to the present invention is considered. In the machine 1, while the oil pressure at the outlet of the oil pump 22 is set to 0.3 MPa required for the balance piston 18, the oil amount flowing through the orifice 25 is 2.0 L / min.
(= 0.5 L / min × 4) and if the oil pressure at the outlet of the orifice 25 is 0.06 MPa, the orifice 2
5 has a diameter D of 2.6 mm. In other words, orifice 2
Assuming that the diameter D of the bearing 5 is 2.6 mm, the required oil pressure of 0.3 MPa is secured for the balance piston 18 and the appropriate oil amount is 0.5 L / min for the four bearing lubrication parts. Will be maintained. As described above, in the oil-free screw compressor 1, the oil at the necessary pressure is supplied to the balance piston without increasing the capacity of the oil pump 22.
An appropriate amount of oil is supplied to the bearings and seals.

The orifice 25 may be of a variable throttle type.
Instead, a flow control valve for controlling the pressure on the upstream side (primary side) may be adopted, and the amount of lubricating oil in the bearing may be slightly increased to secure an appropriate back pressure for the balance piston 18.
The present invention includes any of these. If the back pressure acting on the balance piston 18 is weak, that is, if the anti-thrust force is weak, the thrust force acting on the bearings 16S and 16D is increased, the bearing life is shortened, and conversely, if the anti-thrust force is strong. In addition, the thrust force acting on the bearings 16S and 16D is weakened, which causes the bearings 16S and 16D to wobble, which also shortens the life of the bearing. However, in the case of the oil-free screw compressor 1, such a problem is solved.

[0013]

As is apparent from the above description, according to the present invention, a pair of male and female screws which are rotatably housed in a casing having a suction port on one side and a discharge port on the other side. A balance piston provided integrally and slidably with the rotor shaft end in a columnar space formed at the rotor shaft end on the suction side of the rotor, and an oil flow passage extending from an oil tank via an oil pump The oil pump extends from the branch point on the secondary side of the oil pump, communicates with the columnar space portion, and supplies back pressure to the columnar space portion that generates a back pressure in the direction from the suction side to the discharge side with respect to the balance piston. For an anti-thrust force generating oil flow path portion, and for lubrication and sealing, which branches off at a downstream side of the branch point of the oil flow path and flows through a flow control means to each of a bearing and a shaft sealing portion in the casing. Oil with oil flow path In free screw compressor, it is formed by interposing a flow control means between the branch point and the branch point of the lubricating-sealing oil flow passage portion of the oil flow passage.

For this reason, it is possible to supply an appropriate amount of oil to the bearing / seal portion while supplying oil at a necessary pressure to the balance piston without increasing the capacity of the oil pump, thereby reducing the performance. There are effects such as no inviting.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of an oil-free screw compressor according to the present invention.

FIG. 2 is a diagram showing an overall configuration of a conventional oil-free screw compressor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 oil-free screw compressor 11 casing 12 suction port 13 discharge port 14 screw rotor 15S, 15D rotor shaft 16S, 16D bearing 17 columnar space 18 balance piston 21 oil tank 22 oil pump 23 oil flow path 23A anti-thrust force generating oil Flow path section 23B Oil flow path section for lubrication / seal 24 Branch point 25 Orifices 26A, 26B Oil return flow path

Claims (1)

[Claims] 1. A columnar space formed at a rotor shaft end on a suction side of a pair of male and female screw rotors rotatably housed in a casing having a suction port on one side and a discharge port on the other side. A portion extending integrally with the end of the rotor shaft and slidably provided from a branch point on a secondary side of the oil pump in an oil flow path extending from an oil tank through the oil pump; An anti-thrust force generating oil flow path for supplying pressure oil, which communicates with the columnar space and generates back pressure in a direction from the suction side to the discharge side with respect to the balance piston, to the columnar space; In the oil-free screw compressor having a lubrication / seal oil passage portion which branches off on the downstream side of the branch point and communicates through the flow control means to each of the bearings and shaft seal portions in the casing, The above oil flow path An oil-free screw compressor, wherein a flow control means is formed between a branch point and a branch point of the lubrication / seal oil flow path.