JPH07132449A - Groove machining method - Google Patents

Abstract

PURPOSE:To provide an ultrasonic machining method enabling the machining of a groove of several mum in depth with accuracy requested like a spiral groove provided at the rotary ring of a compressor. CONSTITUTION:An ultrasonic machining tool 24 is provided with a hollow dummy tool 33 besides a machining tool 31, and a mandrel 35 having hard material 36 such as diamond at the tip is inserted into the through hole 34 of the dummy tool 33. Spring force toward the tip is imparted to the mandrel 35 by a spring 41, and a sensor 42 for detecting the moving quantity is fitted to the mandrel 35. The tip consumed quantity of the machining tool 31 associated with the progress of machining is detected by the sensor 42 by the displacement of the mandrel 35, and machining is performed while knowing the depth of a groove from this displacement and the feed quantity of the tool 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a groove processing method, and is applied to, for example, processing of a seal groove.

[0002]

2. Description of the Related Art A bearing seal mechanism for a compressor is required to ensure a reliable seal under a variable pressure. However, the dry gas seal method has the following features, so that the conventional oil film seal method is used. It is considered to be more promising than the mechanical seal method.

Since the dry gas seal is a non-contact seal in which a gas intervenes, the mechanical loss is extremely small.
A seal oil pump is not required, a drive source from the outside is not required, size reduction and energy saving can be achieved, and initial cost, running cost, maintenance cost and installation space can be reduced. Supports high peripheral speeds and high pressures. Since it is a non-contact seal, it has no wear, is highly reliable, and has a long life.

FIG. 4 shows a compressor having a basic structure of a dry gas seal. The rotary ring 1 and the stationary ring 2 constitute a seal portion, and seal between the inside of the high pressure machine and the side of the low pressure atmosphere. The rotary ring 1 is fixed to the rotary shaft 3 via a pair of sleeves 4 and 5. On the other hand, the stationary ring 2 is held by a seal case 6 attached to a housing that surrounds the rotating shaft 3, and is pressed toward the rotating ring 1 side by a spring 7. In the figure, 8 is a tolerance ring and 9 is an O-ring.

As shown in FIG. 5, which is an enlarged view of the seal portion indicated by reference numeral "A" in FIG. 4, a circumferential groove 10 is provided on the shaft sealing surface of the stationary ring 2, and this circumferential groove is provided. A plurality of seal gas supply holes 11 for communicating 10 with the inside of the machine are provided in the circumferential direction of the stationary ring 2. Further, as shown in FIG. 5 and FIG. 6 showing a three-dimensional structure of a part of the rotary ring 1, the shaft sealing surface of the rotary ring 1 partially overlaps with a portion facing the circumferential groove 10 and spirals in the outer peripheral direction. A plurality of grooves 12 are provided.
The inner portions of the rotary ring 1 and the stationary ring 2 inside the circumferential groove 10 are the sliding seal surfaces 13 and 14.

7 and 8 show the sealing action in such a sealing structure. When stationary, as shown in FIG. 7, the force acting on the stationary ring 2 acts in the direction to close the space between the rotating ring 1 and the stationary ring 2, so that the sealing surface 1 of the rotating ring 1 and the stationary ring 2 is closed.
3, 14 make contact and the gas is sealed. When driving,
As shown in FIG. 8, the seal gas from the seal gas supply hole 11 is supplied to the circumferential groove 10, and the seal gas is pushed from the circumferential groove 10 toward the outer periphery of the spiral groove 12 as the stationary ring 2 is rotated. A dynamic pressure is generated to levitate. In the seal portion, the seal gas leaks to the low pressure side from the gap 15 created by this dynamic pressure, but since the gap 15 is as small as several μm, the leak amount of the seal gas is extremely small.

[0007]

By the way, the spiral groove 12 arranged on the shaft sealing surface of the rotary ring 1 constituting one of the above-mentioned sealing structures is three-dimensionally highly accurate and complicated. In particular, the depth d of the spiral groove 12 is a factor that most governs the sealing function, usually d = 3 to 8 μm,
It is necessary to finish the variation to about ± 1 μm. As the material, carbides such as tungsten carbide (WC) and silicon carbide (SiC), powder alloys in which these high hardness substances are dispersed and strengthened, and cermets are used.

Photochemical etching has hitherto been used as a method for producing such a rotary ring, but this method has the following problems. Since the base material of the rotary ring has high etching resistance, it takes a long time to etch. In other words, productivity was low. It is necessary to change the type of the etching solution every time the type of the base material is changed, it is difficult to secure the stability of the groove depth accuracy, and the production control is complicated. Since the base material has high etching resistance, the resist film coated on the surface of the base material is also easily damaged, the accuracy of the spiral groove is reduced, the yield is poor, the cost is high, and the stability of the sealing performance is also affected.

[0009]

The structure of the present invention for solving the above-mentioned problems is accompanied by the progress of processing of a mandrel which is inserted into the hollow portion of an ultrasonic machining tool for machining a groove and has a hard portion at its tip. The ultrasonic processing is performed while detecting the displacement with respect to the tool.

The tool may be one for machining the groove itself to be machined, or one for machining a dummy groove different from the groove to be machined.

[0011]

According to the groove machining method of the present invention, the tool tip wears with ultrasonic machining, but the mandrel hardly wears. Therefore, the wear amount of the tool tip can be known from the difference between the two.
The groove depth can be calculated from the feed amount of the tool and the wear amount of the tool tip, enabling highly accurate groove processing.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of an ultrasonic machining apparatus for carrying out an embodiment method according to the present invention, FIG. 2 shows a tool used in the embodiment method, and FIG. 3 shows a machining state. It is shown. In addition, this embodiment is applied to the processing of the spiral groove of the compressor rotating ring.

In FIG. 1, reference numeral 21 is a vibrator case, on which the first horn 22 is supported. A second horn 23 is supported on the tip of the first horn 22, and an ultrasonic machining tool (hereinafter, referred to as a tool) 24 that is an electrode is attached to the tip of the second horn 23. On the other hand, a magnetostrictive conversion element 25 is attached to the rear end of the first horn 22, and an oscillator 26 is attached to the magnetostrictive conversion element 25.
Are connected.

That is, the magnetostriction conversion element 2 is controlled by the oscillator 26.
The ultrasonic vibration is generated through the first horn 2
2, it is given to the tool 24 via the second horn 23. The amplitude distribution of the device is also shown in FIG.

As shown in FIG. 2, the tool 24 has a structure in which a plurality of processing tools 32 are arranged on the same circumference at the base end 31 and a dummy tool 33 is arranged at the center thereof. The cross-sectional shape of each processing tool 32 is substantially the same as the spiral groove to be processed. Strictly speaking, it has a size obtained by subtracting a numerical value about twice the diameter of the processed abrasive grain from the shape of the spiral groove to be processed. The machining tools 32 are provided in the same number as the spiral grooves formed in the circumferential direction of the rotary ring.
All spiral grooves may be machined at one time, but in accordance with the capabilities of the ultrasonic machining equipment, some number of machining tools of all spiral grooves should be provided, and 1/2, 1 / of all spiral grooves Processing may be performed while rotating the rotary ring in increments of 3 ... 1 / n.

The central dummy tool 33 has a cylindrical shape,
As shown in FIG. 3, a through hole 34 is formed in the center thereof, and a mandrel 35 is slidably inserted therein. A hard material 36 such as diamond or sapphire is attached to the tip of the mandrel 35. Mandrel 35
A flange-shaped protrusion 38 having a notch 37 is formed on the other end side of the. When the tool 24 is attached to the second horn 23, a spring 41 is provided between the protrusion 38 of the mandrel 35 and the second horn 23. Therefore, the mandrel 35 is always given a spring force directed toward the tip side. A sensor 42 of a displacement strain plate is attached to the notch 37 of the protrusion 38. The sensor 42 is connected to an amplifier (not shown).

Next, a method of processing a spiral groove using the above apparatus, that is, an embodiment of the present invention will be described with reference to FIGS. The tool 24 supported by the ultrasonic processing device is lightly pressed against the surface of the rotary ring 1 with a constant pressing force, and a machining liquid in which the abrasive grains 43 are dispersed in water is supplied between the tool 24 and the rotary ring 1. The oscillator 26 applies ultrasonic vibration to the tool 24 via the horns 22 and 23. The abrasive grains 43 collide with the surface of the rotary ring 1 to finely break the surface, and the spiral groove 12 having the same shape as the machining tool 32 is formed. Since the size of the tool 24 is determined in relation to the abrasive grains 43, the spiral groove 12 having the groove width as designed can be processed.

As the machining progresses, the tip of the machining tool 32 wears, and the tip of the dummy tool 33 at the center of the tool 24 also wears at the same speed as the other machining tools 32. However, the mandrel 35 in the dummy tool 33 is hardly worn because the hard material 36 is attached to the tip thereof, and the mandrel 35 is pressed downward by the spring 41.
The tip of 3 and the tip of the mandrel 35 are flush with each other. Therefore, the wear amount of the tip of the processing tool 32 can be grasped from the difference between the two. This is a sensor 42 provided in the notch 37 of the protrusion 38.
Is obtained as the detection result (potential) of. The detection result can be amplified and read. In the figure, 44 is a dummy tool 33.
It is a groove processed by.

On the other hand, the feed amount of the tool 24 (the feed amount in the Z-axis direction) is numerically controlled. Therefore, from the difference between the feed amount and the consumption amount of the machining tool 32, the groove 1 being machined is processed.
A depth h of 2 is required. Therefore, the depth is 3-8 μm
The spiral groove 12 with an allowable variation of ± 1 μm
Can be processed. The portion processed by the dummy tool 33 is a hole that will be processed later and fitted into the sleeve.

In the above embodiment, the hollow dummy tool 33 is separately provided and the mandrel 35 is inserted into the hollow dummy tool 33. However, the machining tool 32 itself may be provided with a through hole to allow the mandrel 35 to pass therethrough. Good.

Next, an example of actual processing by the method according to the present invention will be shown. Diameter 170mm, thickness 12m
On the surface of the rotary ring material made of m tungsten carbide,
Twenty-four spiral grooves having a depth of 5 μm (+1.5 μm, −0.5 μm), an outer edge radius Ro = 72 mm, and an inner edge radius Ri = 66 mm (see FIG. 6) were processed at a pitch of 15 °.
The tool used was a material of SKH51 and the number of divisions was 4, and the abrasive was 6000 mesh silicon carbide. As processing conditions, the output was 750 W and the processing speed (Z-axis feed) was 0.02 mm / min.

Under the above conditions, when the tool is brought into contact with the surface of the rotary ring material, the zero point of the groove depth measuring instrument is cleared,
Processing has started. 95 seconds after the start of processing, the processing depth was 5 μm, so the ultrasonic oscillation was stopped. The obtained spiral groove had a depth of 5 μm (+1.5 μm, −0.5 μm).

Although the above-mentioned embodiment applies the present invention to the processing of the spiral groove of the rotary ring of the compressor, the present invention can be generally applied to the processing of the groove with high accuracy. Further, by changing the cross-sectional shape of the processing tool, it can be applied to the processing of grooves having complicated shapes other than the blade shape.

[0024]

According to the groove machining method of the present invention, the displacement of the mandrel which is inserted into the hollow portion of the ultrasonic machining tool for machining the groove and which has the hard portion at the tip with respect to the tool progresses as the machining progresses. Since the ultrasonic machining is performed while detecting, the machining depth can be known from this displacement and the feed amount of the tool, and the groove can be machined with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic view of an ultrasonic processing apparatus used for carrying out an embodiment method of the present invention.

FIG. 2 is a diagram showing a side surface and a front surface of an example of a tool together.

FIG. 3 is a cross-sectional view showing a processed state.

FIG. 4 is a partial cross-sectional view of an example of a compressor.

5 is an enlarged view of a portion A in FIG.

FIG. 6 is a diagram showing a three-dimensional structure of a rotary ring and a spiral groove.

FIG. 7 is an explanatory diagram of sealing when the compressor is stationary.

FIG. 8 is an explanatory diagram of sealing during operation of the compressor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotating ring 2 stationary ring 3 rotating shaft 4, 5 sleeve 6 seal case 7 spring 10 circumferential groove 11 seal gas supply hole 12 spiral groove 21 transducer case 22 first horn 23 second horn 24 ultrasonic processing tool 26 oscillator 31 Processing tool 33 Dummy tool 34 Through hole 35 Mandrel 36 Hard material 38 Protrusion 41 Spring 42 Sensor

Claims (1)

[Claims] 1. An ultrasonic machining is performed while detecting a displacement of a mandrel which is inserted into a hollow portion of an ultrasonic machining tool for machining a groove and has a hard portion at a tip thereof with respect to the tool as the machining progresses. Characteristic groove processing method.