JPH0342156Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a downhole motor used primarily for underground excavation, such as a turbo drill, and particularly to a pressure bushing that reduces the pressure difference acting on the lower seal. It is.

BACKGROUND ART As shown in FIG. 5, a turbine 2 is provided at one end of a cylindrical main body 1, and a bit 5 is attached to a rotor 4 at the tip of a shaft 3 connected to the turbine 2.
Turbine 2 is rotated by mud water sent from a mud pump (not shown) on the ground, thereby rotating shaft 3, rotor 4, and beat 5, and hole 6 (pile well) is bored in the bedrock with bit 5. The muddy water that rotates the turbine 2 is ejected from the rotor 4 to the bit 5 through the hole 7 of the shaft 3, and the excavated chips are turned into muddy water and forced to the ground through the hole 6 and the annular space (annulus) 8 of the main body 1. Hall motors are known.

In such a downhole motor, a large load acts on the shaft 3, so a radial bearing 9 that supports the shaft 3 and a thrust bearing 10 that supports the thrust force due to the fluid pressure difference are installed between the shaft 3 and the main body 1. In addition to providing
An upper seal 11 consisting of a mechanical seal and a lower seal 12 consisting of a mechanical seal are provided between the shaft 3 and the main body 1 in order to shield the lubricating oil of the radial bearing 9 and the thrust bearing 10 from external fluid (the muddy water mentioned above). and.

The lower seal 12 is a fixed structure, and the upper seal 11 is a floating structure that slides in the axial direction and floats between the muddy water and the sealing lubricating oil _{. T} ) flows into the annulus 8 and acts on the upper seal 11, and the muddy water (pressure P _O
-P _T -P _N ) is discharged to the annulus 8.

For this purpose, the lower seal 12 has a bit aperture 13.
In addition to being constantly exposed to the differential pressure P _N generated at
Since the differential pressure P _N requires a certain level of high pressure in order to effectively remove chips, the lower seal 12 needs to be an expensive one that can withstand high pressure, which is difficult in terms of cost and durability. There's a problem.

Therefore, as shown in FIG. 6, the applicant first
Above the bearing part of the shaft 3, there is a gap 15 between the outer cylinder 13' on the main body side and the inner cylinder 14 on the shaft side.
A vacuum bushing 16 having a
The application was filed for a downhole motor that is installed between the bearing and the bearing to reduce the pressure of muddy water acting on the shaft bearing.

Problems that the invention aims to solve The previously applied pressure reduction bushing wears out when muddy water containing dirt particles passes through the gap 15, so in order to ensure durability, it is necessary to use a hard material with excellent wear resistance. Outer cylinder 1 is made of material such as cemented carbide or ceramics.
3' and the inner cylinder 14 need to be manufactured.

However, when the outer cylinder 13' and the inner cylinder 14 are made of a hard material with excellent wear resistance such as cemented carbide or ceramics, the following problem arises.

It is weak against impact loads, may chip or crack when the outer cylinder 13' and the inner cylinder 14 collide during rotation, and generally has a high Young's modulus (2
(~3 times), the conformability of the contact portion is poor, and if the shaft 3 becomes unsteady, it will cause uneven contact and a high surface pressure will occur in extremely localized areas, resulting in thermal cracks or pits.

Therefore, the previously applied vacuum bushing has a problem of poor durability.

Means and action for solving the problem At least one of the inner cylinder and the outer cylinder constituting the pressure reducing bushing is attached via an elastic material, and the elastic material can absorb impact force and prevent uneven contact due to shaft stiffness. It is designed to prevent

Embodiment FIG. 3 is a bottom sectional view of a downhole motor, and a vacuum throttle 20 is provided between the shaft 3 and the main body 1 above the upper seal 11, and this vacuum throttle 20 is shown in FIG. like shaft 3
An inner cylinder 23 made of a carbide material such as WC that fits around the outer periphery of the cylinder and is pressed and fixed to the stepped part 22 with a nut 21.
and an outer cylinder 26 made of a carbide material such as WC attached to the inner periphery of a holding cylinder 24 made of a rope material fitted and fixed to the inner periphery of the shaft 1 via a pair of viscoelastic bodies, for example, rubber 25. (P _O −
The muddy water having a pressure of P _T ) is depressurized when passing through the gap 27 and has a pressure of P _A .

Because of this, the pressure acting on the upper seal 11 is significantly lower than the mud water pressure (P _O - P _T ),
In addition, the pressure of the muddy water passing through the bit throttle 13 is also approximately equal to the pressure of the annulus 8, so the pressure of the bit throttle differential is not applied to the lower seal 12, so the lower seal 12 is not subjected to too high a pressure. There is no need to withstand it, making it an inexpensive and durable bottom seal.

Further, when abnormal pressure occurs for some reason, the abnormal pressure is absorbed when passing through the gap 27 and does not act directly on the upper seal 11, so the lower seal 12 can be protected from the abnormal pressure.

In addition, the outer cylinder 26 can attenuate and absorb impact loads such as collisions from the support with the rubber 25, which is a viscoelastic body, and will not chip or crack.
The inner cylinder 23 absorbs the axial stiffness of the shaft 3.
This prevents uneven contact between the outer cylinder 26 and equalizes the load pressure.

In addition, since a pair of rubbers 25 are provided in the axial direction, the radial spring constant is reduced by about half compared to when supported by the same volume of rubber, and the amount of swinging displacement of the shaft 3 is easily absorbed, and the surface The drop in pressure can be measured.

In addition, a recess 28 is formed on the inner peripheral surface of the rubber 25 where it joins with the outer cylinder 26, and the joint between the outer cylinder 26 and the rubber 25 has an uneven shape. It is possible to maintain shear strength sufficient to withstand the torque generated by the friction between the two.

FIG. 4 shows a second embodiment, in which the outer cylinder 26 is divided into two parts, and between the shaft 3 and the main body 1,
A journal bearing 32 is provided, which has an inner sleeve 29 made of a carbide material such as WC, and an outer sleeve 31 made of a carbide material such as WC fixed to a support sleeve 30 made of a rope material to maintain a constant distance between the two. Thus, the gap 27 between the inner cylinder 23 and the outer cylinder 26 is maintained constant.

In this case, the muddy water flows through the holes 33 of the support sleeve 30.
It is discharged through the gap 27.

In the above embodiment, the rubber 25 was attached to the outer cylinder 26, but it may be attached to the inner cylinder 23 side, or the rubber 25 may be attached to the inner cylinder 23 side.
It may be attached to both the outer cylinder 26 and the rubber 25, or the rubber 25 may be integrated without being divided.

Effects of the invention: The pressure of the muddy water can be reduced while flowing through the gap 27 between the inner cylinder 23 and the outer cylinder 26 of the pressure reducing bushing 20, so the bit throttling differential pressure will not act on the lower seal, so the lower seal will not be under high pressure. A lower seal that is less expensive and more durable can be used.

Furthermore, since at least either the inner cylinder 23 or the outer cylinder 26 is attached via an elastic material, the impact load at the time of a collision can be attenuated and absorbed, and the shaft will not chip or crack. 3
absorbing the axial stiffness of the inner cylinder 23 and outer cylinder 2.
6 can be prevented from hitting unevenly, and the load pressure can always be equalized.

[Brief explanation of drawings]

1 to 4 show embodiments of the present invention, and the first
The figure is a cross-sectional view of the pressure reducing bushing part, Figure 2 is a cross-sectional view of the pressure reducing bushing, Figure 3 is a schematic cross-sectional view of the entire body, and Figure 4 is a cross-sectional view of the pressure reducing bushing.
The figure is a sectional view of a pressure reducing bushing part showing another embodiment, FIG. 5 is an overall sectional view of the downhole motor, and FIG. 6 is a schematic sectional view of the previously applied one. 1 is the main body, 3 is the shaft, 20 is the pressure reducing bushing, 23 is the inner cylinder, 26 is the outer cylinder, and 27 is the gap.

Claims (1)

[Scope of utility model registration request] Shaft 3 between main body 1 and shaft 3
The pressure reducing bushing 20 has an axial gap 27 between the inner cylinder 23 and the outer cylinder 26 above the bearing part of the pressure reducing bushing 20.
A downhole motor characterized in that at least one of the inner cylinder 23 and the outer cylinder 26 is provided with an elastic material interposed therebetween.