JPH07154010A - Turboblower for laser - Google Patents

Abstract

PURPOSE:To provide a turboblower for forcibly circulating a laser gas being used in a gas laser in which heating of shaft is retarded. CONSTITUTION:A shaft 2 is threaded 19 in the axial direction. Cooling gas flowing into a blower enters into the air gap of the thread 19 and fed sequentially in the axial direction, as shown by an arrow 90, as the shaft 2 rotates before being discharged through vacuum couplings 16, 18. Consequently, the shaft 2 is cooled directly including the hottest part, i.e., the fitting part of the rotor 3 and the shaft 2. This structure enhances the cooling effect of the shaft 2 significantly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser turbo blower for forcibly circulating a laser gas used in a gas laser device, and more particularly to a laser turbo blower for improving a cooling effect of a shaft portion.

[0002]

2. Description of the Related Art Recent carbon dioxide gas laser devices are compact and have a high output and good laser beam quality, and are widely used for laser processing such as cutting metal or non-metal materials and welding metal materials. Is coming. In particular,
As a CNC laser processing machine combined with a CNC (numerical control device), it is rapidly developing in the field of cutting complex shapes at high speed and with high accuracy.

Among these carbon dioxide laser devices, a high-speed axial flow type uses a laser turbo blower for forcibly circulating the laser gas. This is because the laser gas, which has become hot in the discharge tube, is sent to the cooler for forced cooling.

FIG. 6 shows a conventional turbo blower 100 for a laser.
It is a block diagram of A. In the figure, a turbo blade 1 made of aluminum, iron or the like and a shaft 2A for supporting the rotation of the turbo blade 1 are mechanically coupled by a nut 7. The shaft 2A is formed of carbon steel, which is a magnetic material. A rotor 3 is fixed to the shaft 2A along its outer periphery by shrink fitting, press fitting, bonding, or the like. The rotor 3
On the outside of the, there is a stator 4 fixed to a housing 12 made of a metal such as aluminum or stainless steel by shrink fitting, press fitting, adhesion or screwing, and constitutes a motor 3M with the rotor 3. . As the motor 3M, an induction cage motor is adopted because of its high speed, high load, and mass productivity such as aluminum casting method (die casting method).

The turbo blade 1 is rotated by this motor at a high speed of 1 to 100,000 rpm. Therefore, the volume is smaller in inverse proportion to the number of revolutions compared to the low speed rotation roots blower.

Further, in order to support the shaft 2A, a pair of rolling bearings 5 and 6 are used on both sides of the motor 3M. For lubrication of the rolling bearings 5 and 6, low vapor pressure grease or oil is used in order to suppress contamination of optical components as much as possible. A coil spring 11 for applying a preload in the thrust direction toward the turbo blade 1 on the rolling bearing 6 side.
There is. Radiating fins 13 and 14 for cooling the bearings are fixed to the shaft 2A between the motor 3M and the roller bearings 5 and 6 by shrink fitting or press fitting.

With this structure, the laser gas is sucked in as shown by an arrow 9 in FIG. 6 and discharged in the centrifugal direction as shown by an arrow 10. Also, the gas for cooling the bearing is vacuum joint 1
5 and 16 flow into the blower, and the radiation fins 13,
14 and flows out of the blower from the vacuum joints 17 and 18.

[0008]

Since the conventional turbo turbo blower for laser 100A rotates at a high speed of 1 to 100,000 rpm, it is necessary to secure the rigidity against the centrifugal force due to the transmission torque and the unbalance and to avoid the resonance vibration. Therefore, the diameter of the shaft 2A must be increased. Further, the rotor 3 must have a small outer shape in order to reduce the centrifugal force due to its own weight. As a result, the shaft 2A becomes thicker and the rotor 3 becomes thinner than in low-speed rotation, so that the magnetic flux due to the rotating magnetic field passes through not only the rotor 3 but also the shaft 2A, causing iron loss in the shaft 2A. . The occurrence of iron loss will be described with reference to FIGS.

FIG. 7 is a motor sectional view for explaining the flow of magnetic flux at low speed rotation. Due to the rotating magnetic field of the stator 4, the magnetic flux 33 enters the rotor 3 from the teeth 40 of the stator 4 via the gap between the rotor 3 and the stator 4. here,
Since the magnetic permeability of the rotor 3 is higher than that of the shaft 2, and the yoke length L between the slot 32 of the rotor 3 and the inner surface of the rotor 3 is sufficient, the magnetic flux 33 entering the rotor 3
Passes by the shaft 2A and, in the case of two poles, passes through the teeth 41 of the stator 4 opposed by 180 degrees.

FIG. 8 is a motor sectional view for explaining the flow of magnetic flux at high speed rotation. In the case of high-speed rotation, as described above, the rotor 3 becomes thin to reduce the centrifugal force, and the shaft 2A becomes thick to ensure rigidity. For this reason, the yoke length L1 between the slot 32 of the rotor 3 and the inner surface of the rotor 3 is shortened, so that part of the magnetic flux 33 is
As shown in the figure, it will pass through the shaft 2A.

Iron loss includes hysteresis loss and eddy current loss.
The material of the shaft 2A is S45C (carbon steel for machine structural use), SCM (chromium molybdenum steel), SNC (nickel chrome steel), S, etc. defined by JIS because of its workability and strength.
Carbon steel such as Cr (chrome steel) is used. However, these carbon steels have a larger iron loss than the electromagnetic steel plate (silicon steel plate) used for the rotor 3. For example, the iron loss of a general electromagnetic steel sheet is 6 W / kg or less at a magnetizing force of 1.5 T and 50 Hz, while it is about 12 W / kg for carbon steel.

Moreover, the electromagnetic steel sheet used in the rotor 3 is a lamination of thin plates of about 0.3 to 0.5 mm to prevent eddy current loss, but the shaft 2 cannot take the same measure in terms of strength.
Therefore, the iron loss component of the shaft 2A becomes significantly larger than that of the rotor 3.

Further, there is a leakage magnetic flux from the stator coil 42, and this leakage magnetic flux not only enters the rotor 3 inside the stator coil 42, but also enters the shaft 2A when the shaft 2A is thick and passes therethrough. Will be done.

Further, because of the high speed rotation, the current waveform of the drive current supplied from the inverter to the laser turbo blower 100A is not a sine wave but a distorted waveform. The harmonic components of the distorted waveform also cause iron loss.

FIG. 9 shows the waveform of the drive current from the inverter when rotating at 60,000 rpm. The horizontal axis represents time t, and the vertical axis represents drive current I. The drive current I when the laser turbo blower 100 rotates at high speed obviously has a distorted waveform 101 in which the sine wave is distorted.

FIG. 10 is a diagram showing the result of frequency analysis of the waveform of FIG. This is the result of frequency analysis of the distorted waveform 101 using FFT (Fast Fourier Transform), the horizontal axis is the frequency component f, and the vertical axis is the intensity at that time expressed in voltage value dBV. 1 kHz synchronized with rotation
Appears most strongly, but in addition to this 1 kHz, 5 kHz, 7
A large number of harmonics of odd multiples, such as kHz, that are multiples of 3 are generated. As described above, these harmonic components also cause the iron loss to increase, and as a result, the heat generated in the shaft 2 also increases.

On the other hand, regarding cooling, since only a laser gas of about 0.1 atm exists inside the laser turbo blower 100A, an air cooling effect by natural convection cannot be expected. Further, the forced cooling by the radiation fins 13 and 14 is not sufficient.

Therefore, in the experiment, the temperature of the rotor 3 was about 2
The temperature of each inner ring of the rolling bearings 5 and 6 reached 140 ° C or higher. At this time, the outer ring temperature is 4
It was 0 ° C. When the difference between the temperature of the inner ring and the temperature of the outer ring of the rolling bearing is 100 ° C. or more, depending on the shape and size of the rolling bearing, the inner ring is thermally expanded and the gap disappears, causing galling.

Further, the lubricant such as grease or oil used for the rolling bearings 5 and 6 is accelerated to deteriorate at a high temperature, and generally the service life becomes about 1/2 when the temperature rises by 10 ° C. Therefore, if you drive in this state,
Failure of the rolling bearings 5 and 6 due to premature galling occurs, or short-term replacement or replenishment of the lubricant is required. Therefore, a great deal of labor is spent on maintenance.

Further, the temperature rise of the rolling bearings 5 and 6 promotes the evaporation of grease and oil, and the vaporized lubricant is mixed in the laser gas to contaminate the optical parts of the gas laser device, which lowers the laser output and reduces the beam. This caused problems such as poor processing characteristics due to mode deformation.

The present invention has been made in view of the above points, and an object thereof is to provide a turbo turbo blower capable of suppressing heat generation in a shaft to a low level.

[0022]

In order to solve the above problems, the present invention provides a shaft having a turbo blade at its tip, a pair of bearings for supporting the shaft, and a rotor fixed along the outer circumference of the shaft. There is provided a laser turbo blower including a motor including a stator fixed to a housing side, wherein the shaft is provided with a thread groove along an axial direction.

[0023]

Function: A thread groove is provided on the shaft along the axial direction. The cooling gas enters the gap of the thread groove and flows so as to be sequentially fed in the axial direction according to the rotation of the shaft.
Therefore, the shaft is directly cooled, including the fitting portion between the rotor and the shaft, which has the highest temperature.

Further, since the screw groove reduces the contact area between the rotor and the shaft, the total amount of heat transferred from the rotor to the shaft is reduced. Further, since the magnetic flux flowing from the rotor to the shaft is reduced by the thread groove, iron loss is suppressed.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a laser turbo blower of the present invention. In the figure, the same components as those already described in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted. In the laser turbo blower 100 of the present invention, a thread groove 19 is provided on the shaft 2 along the axial direction.

By thus providing the shaft 2 with the thread groove 19, the cooling gas flows as shown by the arrow 90, that is, the cooling gas flowing from the vacuum couplings 15 and 17 into the blower has the thread groove. Enter the 19 voids,
According to the rotation of the shaft 2, it flows so as to be sequentially fed in the axial direction and flows out from the vacuum joints 16 and 18. Therefore, the rotor 3 and the shaft 2 having the highest temperature
The shaft 2 is directly cooled including the fitting portion with.
Therefore, the cooling effect of the shaft 2 can be significantly improved.

As shown in FIG. 2, which is a cross-sectional view of the rotor 3, the screw groove 19 reduces the contact area between the rotor 3 and the shaft 2 by about half, so that the heat transmitted from the rotor 3 to the shaft 2 is reduced. The total amount is reduced. Therefore, heat generation of the shaft 2 can be suppressed.

Further, as shown in FIG. 2, since a gap is formed between the rotor 3 and the shaft 2 by the thread groove 19, the magnetic flux 33 flowing into the shaft 2 from the rotor 3 is blocked, and as a result, the shaft 2 is cut off. The magnetic flux 33 passing through is reduced. Therefore, iron loss such as hysteresis loss and eddy current loss can be suppressed, and heat generation of the shaft 2 can be suppressed also from this point.

As described above, in the present embodiment, by providing the thread groove 19 on the shaft 2, the shaft 2 can be directly cooled and the heat generation of the shaft 2 itself can be suppressed. Therefore, the temperatures of the rolling bearings 5 and 6 are set to 80
The rolling bearings 5 and 6 can be reduced to below ° C.
The life (reliability) of is also improved. Further, since the lubricant used in the rolling bearings 5 and 6 can be prevented from deteriorating, maintenance such as regular replacement or replenishment of the lubricant becomes unnecessary. Moreover, since the evaporation of the lubricant is also reduced,
The optical components used in the gas laser device can be prevented from being contaminated, and the reliability and maintainability of the entire gas laser device can be improved.

FIG. 3 is a diagram showing a second embodiment of the present invention. In the turbo turbo blower 101 in this embodiment, the heat dissipating fins 20 and 21 are also provided with screw grooves 20a and 21.
a is provided.

A gas passage for cooling gas is formed in the mold 22 from the heat radiation fins 20 and 21 having the thread groove shape to the thread groove 19 of the shaft 2. The mold 22 is formed so as to mainly fill the gap around the stator 4. Here, as the material of the mold 22, silicon or an epoxy agent having good heat conductivity, ceramic such as alumina or titanium oxide, or a mixture thereof is used.

As described above, the cooling fins 20 and 21 are provided with the thread grooves 20a and 21a, and the mold 22 is provided with the gas passage for the cooling gas guide. , Radiation fin 2
0 to the thread groove 19 of the shaft 2 and the thread groove 21a of the heat radiation fin 21 are improved,
The flow will be faster. Therefore, the shaft 2
The cooling effect of can be further improved. In addition, since the air volume of the cooling gas also increases, the shaft 2
The cooling effect of can be enhanced.

Further, a mold 22 is formed around the stator 4.
By forming the, the heat from the stator coil 42 (FIG. 2) flows through the mold 22 to the housing 12 side more quickly. Therefore, the motor 3M can be cooled more effectively.

FIG. 4 shows a third embodiment of the present invention. In the laser turbo blower 102 according to this embodiment, the thread groove 19 is provided in the entire axial direction of the shaft 2. The reason why the radiation fins are not provided is that the shaft 2 can be sufficiently cooled by the thread groove 19 of the shaft 2. By removing the heat radiation fins, the laser turbo blower 102 can be made compact and lightweight.

FIG. 5 is a diagram showing the overall configuration of a CO ₂ gas laser device to which the laser turbo blower of the present invention is applied. In the figure, an output coupling mirror 72 is provided at both ends of the discharge tube 71.
And an optical resonator including a total reflection mirror 73.
Metal electrodes 74 and 75 are mounted on the outer circumference of the discharge tube 71. The metal electrode 74 is grounded and the metal electrode 75 is connected to a high frequency power supply 76. Metal electrodes 74 and 7
A high-frequency voltage is applied from the high-frequency power supply 76 during the period 5. As a result, high frequency glow discharge is generated in the discharge tube 71 and laser excitation is performed. The laser beam optical axis in the discharge tube 71 is indicated by 53, and the laser beam optical axis taken out from the output bonding mirror 72 is indicated by 54.

When activating such a gas laser oscillator, the gas inside the entire device is always exhausted by the vacuum pump 52 first. Then, the valve 51 is opened and a predetermined flow rate of the laser gas is introduced from the gas cylinder 50, whereby the gas pressure in the apparatus reaches a specified value. After that, exhaustion of the vacuum pump 52 and introduction of replenishment gas for the valve 51 continue,
A part of the laser gas is continuously replaced with fresh gas while the gas pressure inside the device is kept at a specified value. This prevents gas contamination in the device.

Further, in FIG. 5, laser gas is circulated in the apparatus by a turbo turbo blower 100 (101, 102) which is a blower. The purpose is to cool the laser gas. In a carbon dioxide (CO ₂ ) gas laser, about 20% of the injected electric energy is converted into laser light, and the other is consumed for gas heating. However, theoretically, the laser oscillation gain is proportional to the absolute temperature T to the power of − (3/2), so that the laser gas must be forcibly cooled in order to increase the oscillation efficiency.

In this device, the laser gas is about 200 m / s.
It passes through the discharge tube 71 at a flow rate of ec or more, flows in the direction indicated by the arrow, and is guided to the cooler 78. The cooler 78 removes heating energy mainly from the discharge from the laser gas. Then, the laser turbo blower 100 compresses the cooled laser gas. The compressed laser gas is guided to the discharge tube 71 via the cooler 77. This is because the heat of compression is removed by the cooler 77 before the laser gas compressed by the laser turbo blower 100 (101, 102) is guided again to the discharge tube 71. These coolers 7
Since 7 and 78 are well known, detailed description will be omitted.

Laser turbo blower 100 (101, 1
02) is driven by the inverter 60. The rotation speed of the laser turbo blower 100 (101, 102) is 10,000 to
Since the rotation speed is as high as 100,000 rpm, a high frequency inverter having a frequency of 167 to 1667 Hz is used as the inverter 60.

In the above description, the turbo blade 1 is constructed as a centrifugal blade, but it may be a mixed flow blade or an axial flow blade. Also, rolling bearings were used for the bearings,
Other types of bearings, such as slide bearings, may be used.

[0041]

As described above, in the present invention, the shaft is provided with the thread groove along the axial direction. The cooling gas enters the gap of the thread groove and flows so as to be sequentially fed in the axial direction according to the rotation of the shaft. Therefore, including the fitting part between the rotor and the shaft, which has the highest temperature,
Since the shaft is directly cooled, the cooling effect can be improved.

Further, since the contact area between the rotor and the shaft is reduced by the thread groove, the total amount of heat transferred from the rotor to the shaft is reduced, and heat generation of the shaft can be suppressed.

Further, since the magnetic flux flowing from the rotor to the shaft is reduced by the thread groove, iron loss can be suppressed and heat generation of the shaft can be suppressed also from this point. In this way, the shaft can be directly cooled and the heat generation of the shaft itself can be suppressed, so that the temperature of the bearing can be reduced and the life (reliability) of the bearing can be improved.

Further, since the lubricant used in the bearing can be prevented from deteriorating, maintenance such as regular replacement or replenishment of the lubricant can be eliminated. Moreover, since the evaporation of the lubricant is also reduced, it is possible to prevent the contamination of the optical components used in the gas laser device, and to improve the reliability and maintainability of the entire gas laser device.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of a laser turbo blower of the present invention.

FIG. 2 is a rotor cross-sectional view.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a third embodiment of the present invention.

FIG. 5 is a C to which the laser turbo blower of the present invention is applied.
It is a diagram illustrating the overall configuration of the O ₂ gas laser apparatus.

FIG. 6 is a configuration diagram of a conventional laser turbo blower.

FIG. 7 is a motor cross-sectional view for explaining the flow of magnetic flux at low speed rotation.

FIG. 8 is a motor cross-sectional view for explaining the flow of magnetic flux at high speed rotation.

FIG. 9 is a waveform of a drive current from the inverter when rotating at 60,000 rpm.

FIG. 10 is a diagram showing a result of frequency analysis of the waveform of FIG.

[Explanation of symbols]

 1 Turbo Blade 2 Shaft 3 Rotor 4 Stator 5,6 Rolling Bearing 7 Nut 8 Scroll 9,10 Gas Flow 11 Spring 12 Housing 13,14 Radiating Fin 15-18 Vacuum Joint 19 Magnetic Field Blocking Layer 33 Magnetic Flux 50 Gas Cylinder 51 Valve 52 Vacuum Pump 53 Intra-cavity laser beam optical axis 54 Out-of-cavity laser beam optical axis 60 Inverter 71 Discharge tube 72 Output coupling mirror 73 Total reflection mirror 74,75 Electrode 76 High frequency power supply 77,78 Cooler 100 Laser turbo blower

Claims (4)

[Claims] 1. A motor having a shaft having a turbo blade at its tip, a pair of bearings for supporting the shaft, and a rotor fixed along the outer periphery of the shaft and a stator fixed to the housing side. A laser turbo blower, wherein the shaft is provided with a thread groove along the axial direction. 2. The turbo blower for a laser according to claim 1, wherein screw-shaped heat radiation fins are provided on both sides of the shaft. 3. A turbo blower for a laser according to claim 2, wherein a gas passage for the cooling gas is formed by molding from the heat radiation fin having the thread groove shape to the thread groove of the shaft. 4. The laser turbo blower according to claim 1, wherein a thread groove is provided in the entire axial direction of the shaft.