JP2002168184A - Oil-free screw compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a smaller and lighter oilless screw compressor in a simple structure in spite that an adequate oil pump for high-speed rotation is built therein. SOLUTION: The oil pump 6 for supplying oil both to bearings 7, 8 for supporting a pair of male rotor 2 and female rotor 3 and to synchronous gears 9, 10 for transmitting the rotation of the female rotor 3 connected to a motor shaft 23 to the male rotor 2 is provided at the end of a driving-side shaft 41 of the male rotor 2 of the pair of male rotor 2 and female rotor 3 on the opposite side to the synchronous gears 9, 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oilless screw compressor, and more particularly to an oilless screw compressor incorporating an oil pump suitable for high-speed rotation.

[0002]

2. Description of the Related Art Many conventional oilless screw compressors are driven by a general-purpose induction motor, and the rotation speed of the general-purpose induction motor depends on the power supply frequency.
It rotates around 3000 or 3600 rotations. On the other hand, the rotation speed of the oilless screw compressor is
There is a need for a rotation that is three to eight times the rotation of a general purpose induction motor. Therefore, in order to increase the rotation speed, the screw rotor of the compressor is driven to increase the speed of the rotation of the general-purpose induction motor via a speed increaser configured by gears or the like.

[0003] Therefore, the oilless screw compressor is provided with bearings and synchronous gears, and is supplied with oil for the purpose of lubricating and cooling them. An oil pump of a trochoid type or the like is installed as a supply means. The oil pump is
A gearbox mounted type added to the input (low speed) axis of the gearbox,
Alternatively, there is a separate type attached to the compressor as a separate type pump.

For example, an oilless screw compressor disclosed in Japanese Patent Application Laid-Open No. 2000-97186 is directly driven by a high-speed motor without using a gearbox, but an oil pump is provided separately from the compressor body. Is provided. In the screw compressor disclosed in Japanese Patent Application Laid-Open No. 4-8889, a screw groove or a spiral groove is formed on a shaft of a screw rotor or an end face of a screw tooth to function as an oil pump.

[0005]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open
Oil-free screw compressor disclosed in 00-97186 publication,
Since an oil pump and a motor for driving the oil pump are separately required, the size of the entire compressor becomes large, and it is difficult to reduce the size and weight. In addition, a separately installed motor and bearings for various parts of the pump are required, and power loss increases.

Further, the male and female rotors of an oilless screw compressor driven by a high-speed motor have a maximum rotational speed of 20 / min.
Since it may exceed 000 rotations, it is not possible in principle to drive directly at the same rotation speed with a positive displacement pump such as a normal gear pump from the viewpoint of vibration noise and reliability.
Also, if a speed reducer or the like is installed for driving the pump, the size and weight will be reduced.

[0007] Further, in the oilless screw compressor, since the discharge temperature is extremely high, thermal deformation of the rotor is large. The rotor and the rotor shaft expand and contract due to thermal deformation in the axial direction. Furthermore, since it is a high-speed rotating body, there is also axial vibration. Therefore, in order to use a part of the rotor shaft as the shaft of the oil pump, the oil pump needs to be able to absorb such thermal deformation and vibration displacement.

The oil pump for a screw compressor disclosed in Japanese Patent Application Laid-Open No. 4-8889 is provided for the purpose of supplying oil to a gap at the end face of a screw rotor and reducing internal leakage of gas passing through the gap. . Therefore, the lubrication means does not have a shaft seal, and the lubrication path runs along the shaft surface,
It only goes to the end face gap, and it is impossible to lubricate bearings and synchronous gears.

The installation position is limited between the screw teeth of the rotor and the high pressure side bearing. Therefore, the degree of freedom in the arrangement of the entire compressor is small.

An object of the present invention is to provide a small and lightweight oilless screw compressor which has a simple structure despite having a built-in oil pump suitable for high-speed rotation.

[0011]

In order to achieve the above object, an oilless screw compressor according to the present invention is characterized in that a bearing portion for supporting a pair of male and female rotors and one of the bearing portions connected to a motor shaft are provided. An oil pump for supplying oil to a gear unit that transmits the rotation of the rotor to the other rotor is provided at a shaft end of the other rotor opposite to the gear unit with respect to the pair of male and female rotors.

Specifically, the present invention provides the following compressors.

The present invention provides a motor, a pair of male and female rotors connected to and rotating with the motor, and the motor of the male and female pair of rotors disposed opposite to the motor with respect to the pair of male and female rotors. A gear unit for transmitting rotation of one rotor connected to the motor shaft to the other rotor, an oil pump for supplying oil to the gear unit and a bearing unit supporting both rotors, the pair of male and female rotors, and a gear A non-lubricating screw compressor having a part, a bearing part, and a casing for housing an oil pump, wherein the oil pump is provided with a shaft end of the other rotor opposite to the gear part with respect to the pair of male and female rotors. And a non-lubricating screw compressor.

Preferably, the oil pump includes a non-contact type visco pump for increasing the pressure of the oil by rotation of the rotor shaft of the other rotor, and a non-contact type shaft sealing device for sealing the increased pressure of the oil.

[0015] Preferably, the non-contact type visco pump is a visco pump having a thread groove.

Preferably, the non-contact type shaft sealing device is a floating type sleeve seal or a Visco seal having a thread groove in which the torsion direction of the groove is formed opposite to the torsion direction of the thread groove of the Visco pump. .

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An oilless screw compressor according to an embodiment of the present invention will be described below with reference to the drawings.

A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a configuration of an oilless screw compressor according to a first embodiment of the present invention, and shows a horizontal cross section of an oilless screw compressor that incorporates an oil pump and is driven by a high-speed motor. . FIG. 2 shows a vertical cross section of an oil pump incorporated in the oilless screw compressor of FIG. 1, FIG. 3 is an explanatory diagram of flow rate / differential pressure characteristics of the oil pump of FIG. 2, and FIG. FIG. 4 is a diagram illustrating flow rate / differential pressure characteristics of the oil pump in FIG. 3.

As shown in FIG. 1, a compressor main body 1 accommodates a male rotor 2 and a female rotor 3 which rotate while meshing with each other about two parallel axes, and tooth space portions of both rotors. And casing 4 having a high pressure port (both not shown)
And a low-pressure casing 5 containing the drive shafts of both rotors.
It is composed of

In FIG. 1, the left direction is referred to as a low pressure side and the right direction is referred to as a high pressure side with reference to the tooth portions of both rotors. The shaft portions of the male rotor 2 and the female rotor 3 are rotatably supported by a low-pressure bearing 7 and a high-pressure bearing 8. Although the gas compressed by the oilless screw compressor of the present invention is intended for general gas, the following description is based on the assumption that air is most widely used as an application example.

A pair of synchronous gears 9 and 10 are fixed to the high pressure side shaft ends of the male rotor 2 and the female rotor 3, and rotate the two rotors synchronously. Although the teeth of the two rotors are in mesh, a small clearance is secured between them, and strictly, they are in a non-contact state. Therefore, the driving torque is transmitted from one rotor, that is, the female rotor 3 to the other rotor, that is, the male rotor 2 via the meshing of the synchronous gears 9 and 10.

It is necessary to lubricate bearings and gears for lubrication and cooling. On the other hand, the oilless compressor has a duty to supply clean compressed air free of oil, and oil is not allowed to enter the compression chamber formed in the tooth space of the clew teeth. Therefore, a non-contact type shaft sealing device is provided between the low pressure side bearing 7 and the tooth grooves of the male rotor 2 and the female rotor 3 and between the high pressure side bearing 8 and the tooth grooves of the male rotor 2 and the female rotor 3. Provided. These non-contact type shaft sealing devices include a compressed gas seal 11 and an oil drain 12.

Thus, intrusion of oil into the compression chamber can be prevented, and conversely, inflow of gas from the compression chamber to the oil pump 6 can be prevented.

Fins 13 are provided on the outer periphery of the casing 4 for the purpose of promoting cooling.

The high-speed motor 21 has a motor shaft 23 to which the rotor core 22 is fixed, and a load-side bearing 24 provided on a motor casing 27 and a counter-load provided on a cover 28 for rotatably supporting the motor shaft 23. And a side bearing 25.

Lubricating oil is forcibly supplied to these bearings.
A non-contact type oil drain 29 is provided between the load-side bearing 24, the non-load-side bearing 25, and the rotor core 22. Also,
The stator core 26 is fixed to the motor casing 27 at a position facing the rotor core 22, and the motor casing 27
Is provided with a cooling jacket 30 for supplying cooling water or coolant liquid.

A shaft spline and a hole spline are provided at the shaft ends of the female rotor 3 and the motor shaft 23, and mesh with each other to form a spline coupling 31.

In the space formed on the low pressure side of the drive side shaft 41 of the male rotor 2, an oil pump 6 as an oil supply means is provided on the drive side shaft 41. The oil pump 6 has a function of increasing the pressure of the lubricating oil by the rotation of the drive side shaft 41.

The oil pump 6 includes a drive shaft 41 of the male rotor 2.
It has the ability to absorb thermal deformation and vibration displacement, prevent oil from entering the compression chamber, and ensure a sufficient amount of oil supply to the bearings and the synchronous gears 9 and 10.

FIG. 2 shows the structure of the oil pump 6. A sleeve 42 is fixed to the drive shaft 41 of the male rotor 2, and fixes the inner ring of the cylindrical roller bearing 7 in the axial direction. The pump casing 43 is fixed to the low-pressure side casing 5 forming a part of the casing by bolts (not shown), and presses the outer ring of the cylindrical roller bearing 7 in the axial direction.

The pump casing 43 has a sleeve 42
The pump cover 44 is fitted concentrically with the pump casing 4 by bolts (not shown).
By tightening to 3, it is fixed in the axial direction.

An O-ring 47 is provided to prevent the oil pressurized by the visco pump 44 from leaking through the fitting portion.

The oil shaft pressurized by the visco pump 44 is a floating type sleeve seal 5.
4, and a spring device 55.

Floating type sleeve seal 5
4 is axially pressed against the end face 56 of the pump casing 43 by a spring device 55, and the sleeve seal 5
4 is opposed to the sleeve 42 via a narrow gap.

An oil suction pipe 49 is screwed into the pump cover 46, and the pressurized oil collected by the lantern ring portion 50 of the visco pump 44 is guided from the oil discharge pipe 51 to a cooler (not shown). From there, it is supplied to each bearing, the synchronous gears 9, 10 and each part of the spline coupling 31 to lubricate them.

The oil suction pipe 49 is connected to an oil sump 61 provided below the oil pump 6 via a suction oil strainer (not shown).

The visco pump 44 is provided with a rectangular screw on the inner periphery thereof in the direction shown by the broken line,
It faces the outer periphery of 2 via a narrow gap to form a thread groove pump. Further, the pump casing 43 is provided with an oil discharge chamber 52 and an oil discharge passage 53, and the oil discharged from the bearing 7 is quickly discharged through the oil discharge chamber 52 and the oil discharge passage 53.

Next, the operation of this embodiment will be described.

After the high-speed motor 21 is started, the speed of the high-speed motor 21 is quickly increased to a predetermined rotation speed in order to expel air in the suction pipe 49 of the oil pump 6 and the pump, and is provided in a discharge passage of the oil pump 6. After the detected oil pressure sensor (not shown) confirms the pressure increase, the rotation speed is controlled to a predetermined value. When the control of the high-speed motor 21 thereafter is desired to keep the discharge air pressure of the compressor constant, the rotation speed is controlled in accordance with the output of the discharge air pressure sensor, and the discharge air pressure and the discharge air volume are controlled. If it is desired to control both in association with each other, the rotation speed control is performed while changing the target discharge pressure in accordance with the relationship between the rotation speed and the discharge air pressure which is set in advance and stored in a microcomputer or the like.

The flow rate / differential pressure characteristics of the oil pump 6 will be described with reference to FIGS. In FIG. 3, the distance from the center of the pump to the oil level 62 of the oil sump 61 is H, and the oil level 62
The pressure of the oil in the oil discharge chamber 52 is Pa (almost atmospheric pressure), the pressure of the suction chamber 63 of the visco pump 44 is Ps, the discharge pressure of the pump is Pd, and the oil flow rate flowing through the visco pump 44 is Q.
Assuming that p is the oil flow rate flowing through the sleeve seal 54 and Q is the discharge oil flow rate, Q = Qp + Qs.

If ΔP in FIG. 4 is Pd-Pa and γ is the specific gravity of oil, the ΔP to Qp characteristic of the visco pump 44 can be represented by a straight line AC. Point A is the point of the maximum flow rate Qpm, and point C is the point of the pressure obtained by subtracting γH from the sealing pressure ΔPpm of the pump. The ΔP to Qs characteristic of the sleeve seal 54 is represented by a straight line OD. The bold line AE indicates the ΔP to Q characteristics of the oil pump 6, and the discharge oil flow rate of the pump is obtained by subtracting the amount of leakage from the sleeve seal 54 from the discharge oil flow rate of the Visco pump 44.
At this point, the discharge oil flow rate of the pump becomes zero.

When the rotation speed of the drive side shaft 41 decreases, the characteristic shown in FIG. 4 is reduced toward the origin O in proportion to the ratio of the rotation speed. When the oil temperature increases and the viscosity decreases, the characteristic becomes substantially proportional to the viscosity. Thus, the characteristics are reduced in the vertical direction in FIG.

In this embodiment, since the oil pump 6 uses the visco pump 44 having a screw groove and the floating type sleeve seal 54 as the non-contact shaft seal, the displacement is absorbed by each member, Even if the rotor 2 has an axial vibration and an axial thermal deformation, it is possible to realize an oil pump in which the influence is eliminated. The floating type sleeve seal 54 has an effect that the clearance between the sleeve seal 54 and the drive side shaft 41 can be reduced and oil leakage from the sleeve seal 54 can be reduced.

Further, since the suction port of the thread groove pump is provided on the shaft end side, air does not leak during operation, and a stable pumping operation can be performed.

Next, a second embodiment of the present invention will be described with reference to FIGS. The description of items common to the first embodiment will be omitted. FIG. 5 shows a vertical cross section of an oil pump incorporated in an oilless screw compressor according to a second embodiment of the present invention, and FIG. 6 shows the flow rate / differential pressure characteristics of the oil pump of FIG. FIG.

In FIG. 5, the same parts as those in FIG. 2 are denoted by the same reference numerals. A Visco seal 4 is used instead of the floating type sleeve seal in the first embodiment.
5 is a feature of the present embodiment.

An O-ring 48 for sealing the back surface of the visco-seal 45 is provided. In addition, the torsion direction of the screw groove provided in the Visco seal 45 is opposite to the torsion direction of the screw groove of the Visco pump 44. Sleeve 42 for both thread grooves
Opposes the outer periphery of the shaft through a narrow gap, and forms a thread groove pump and a thread groove seal.

The flow rate / differential pressure characteristics of the oil pump 6 will be described with reference to FIG. The same symbols are used as in FIG.
The ΔP to Qp characteristics of the Visco pump 44 can be almost represented by a straight line AC,
The ΔP to Qs characteristics of the visco seal 45 can be represented by a polygonal line OFG.
Point F is the point of the sealing pressure ΔPsm of the Visco seal 45, and OF
The interval is Qs = 0. Straight line GF is the maximum flow rate of Visco Seal 45
This is an extension of a straight line connecting the points K and F representing Qsm. Thick line AHJ
Indicates the ΔP to Q characteristics of the oil pump 6, and since there is no leakage from the visco seal 45 during AH, the discharge oil flow rate of the pump is equal to the oil flow rate of the visco pump 44. Leakage from the visco-seal 45 occurs between HJ and at point J, the discharge oil flow rate of the pump becomes zero.

When the rotation speed of the drive side shaft 41 decreases, the characteristic shown in FIG. 6 is reduced toward the origin O in proportion to the ratio of the rotation speed. When the oil temperature increases and the viscosity decreases, the characteristic becomes substantially proportional to the viscosity. Thus, the characteristics are reduced in the vertical direction in FIG. Regarding the optimization of the rectangular thread portion of the Visco pump 44, see the literature (ASME Journal of Tribology, Vol. 112, April 199).
0, p409-414).

In the present embodiment, the Visco seal 45 is used as a non-contact shaft seal, and there is an effect that oil does not leak up to the sealing pressure.

In this embodiment of the present invention, the oil pump is provided at the shaft end on the drive side of the male rotor. However, in the oilless screw compressor, the shaft of either the male rotor or the female rotor is provided. There is a vacant space near the end, so it may be installed there.

Although a high-frequency motor is used as the high-speed motor, any type of motor, such as a permanent magnet type synchronous motor used in electric vehicles or the like, may be used.

[0053]

According to the present invention, the oil pump can be arranged in a space formed near the shaft end of either the male rotor or the female rotor, and can be provided at the shaft end of the rotor.
As a result, the space factor of the entire compressor is improved,
In addition, the structure is simplified, and the oilless screw compressor can be reduced in weight and size.

Further, since the oil pump can be provided directly connected to the rotor shaft, power loss can be reduced.

[Brief description of the drawings]

FIG. 1 is a horizontal sectional view of an oilless screw compressor according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional view of an oil pump built in the oilless screw compressor of FIG.

FIG. 3 is an explanatory diagram of a flow rate / differential pressure characteristic of the oil pump of FIG. 2;

FIG. 4 is a view showing a flow rate / differential pressure characteristic of the oil pump of FIG. 3;

FIG. 5 is a vertical sectional view of an oil pump incorporated in an oilless screw compressor according to a second embodiment of the present invention.

FIG. 6 is a view showing a flow rate / differential pressure characteristic of the oil pump of FIG.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 compressor body 2 male rotor 3 female rotor 4 casing 5 low-pressure casing 6 oil pump 9
10: synchronous gear, 21: high-speed motor, 41: drive side shaft,
42 ... Sleeve, 43 ... Pump casing, 44 ... Visco pump, 45 ... Visco seal, 46 ... Pump cover,
49: oil suction pipe, 51: oil discharge pipe, 54: sleeve seal

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akira Suzuki 390 Muramatsu, Shimizu-shi, Shizuoka F-term in Industrial Machinery Group, Hitachi, Ltd. (Reference) 3H029 AA03 AA15 AA24 AB03 BB06 BB32 CC16 CC36 CC58

Claims (4)

[Claims] A motor, a pair of male and female rotors connected to and rotating with the motor, and a motor of the motor of the pair of male and female rotors disposed on a side opposite to the motor with respect to the pair of male and female rotors. A gear portion that transmits the rotation of one rotor connected to the shaft to the other rotor, an oil pump that supplies oil to a bearing portion that supports the gear portion and the two rotors, and the pair of male and female rotors, a gear portion, In an oilless screw compressor having a bearing portion and a casing containing an oil pump, the oil pump is provided at a shaft end of the other rotor opposite to the gear portion with respect to the pair of male and female rotors. Oil-free screw compressor characterized by the above-mentioned. 2. A non-contact type visco pump according to claim 1, wherein said oil pump pressurizes said oil by rotation of a rotor shaft of said other rotor, and a non-contact type shaft sealing device for sealing said pressurized oil. And a non-lubricating screw compressor. 3. The oilless screw compressor according to claim 2, wherein said non-contact type visco pump is a visco pump having a thread groove. 4. The non-contact type shaft sealing device according to claim 2, wherein the non-contact type shaft sealing device has a floating type sleeve seal or a screw groove formed in a direction in which the groove is twisted in a direction opposite to that of the screw groove of the Visco pump. An oilless screw compressor characterized by being a Visco Seal.