JPH03260330A - Rotor of turbocharger - Google Patents

Abstract

PURPOSE:To improve joint strength in axial and rotating directions by penetrating a stress member which extends integrally from a shaft through a center hole of a turbine wheel, and fixing the stress member by the use of escape- preventing and locking means while charging molten metal. CONSTITUTION:In a rotor 21, an impeller 23 for a compressor is fixed to one end of a hollow shaft 22 by the use of internal chill, while a turbine wheel 27 is connected to the other end through a joint 26 connected by laser beam welding 25. A small diameter part of the joint 26, that is, a stress member 30 is penetrated through a center hole 33 of the turbine wheel 27, and a gap therebetween is blocked by a screw part 31. A molten metal 42 is charged into a rectangular hole 35 for internal chill of the screw part 31. The joint 26 is prevented from escaping and locked. The above-mentioned joint part is thus pressed in axial and rotating directions with a strong force by the use of pretension and pretorsion of the stress member 30, and joint strength is improved.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a rotor for a turbocharger that supercharges an internal combustion engine, and particularly relates to a rotor manufactured by combining a separate turbine wheel and a shaft. It is something.

[Conventional technology]

In the rotor for a turbocharger, the turbine wheel and the compressor impeller must be integrally connected via a shaft, but since the turbine wheel is exposed to the high temperature of the exhaust gas of the internal combustion engine, it is necessary to have heat resistance and corrosion resistance. Fine ceramic materials (for example, Sl
, ~4+ SI[>, titanium material or titanium alloy material (
For example, Ti-6Aβ-4V), heat-resistant steel (for example, Fe
; N+ Cr Mo series) etc. are used, whereas compressor impellers do not require heat resistance and are made of light alloys whose main component is aluminum due to requirements such as light weight, formability, workability, and cost. Since they have completely different properties such as Generally, the wheel and shaft are manufactured as one piece, or even if they are manufactured separately, they are later integrated by a method such as welding, and a light alloy compressor impeller is connected to the other end of the shaft with screws, etc. It is true.

However, the turbine wheel and shaft are integrated,
Of course, manufacturing with the same material means titanium, titanium alloy materials,
When using heat-resistant alloy materials, the cost increases due to the use of large amounts of expensive materials, and due to the properties of the materials, molding,
It is difficult to process, which is doubled if it is made in one piece, so it is not a good idea to manufacture something that requires high precision, such as a turbine rotor.Furthermore, fine ceramic materials have excellent heat resistance and corrosion resistance. Although it is relatively cheap,
There are problems with integrally molding the shaft part with ceramics, such as low mechanical strength, distortion during firing, difficulty in high-precision machining, and difficult bearings. Integrally molded wheel and shaft,
There are many disadvantages to processing.

Therefore, if the turbine wheel and shaft are molded separately and then joined together later, the material suitable for the turbine wheel and the material suitable for the shaft are not the same. When heat-resistant steel is used, it cannot be directly welded, so there is a risk that the joint will become a weak point, causing loosening or play, and reliability problems may arise when used in high-speed turbochargers. I can't say no.

In order to deal with this problem, the present inventor previously disclosed an invention described in Japanese Patent Laid-Open No. 168658/1983. In FIGS. 6 and 7 showing this invention, 1
is a rotor of a turbocharger, 2 is a shaft made of titanium-based material, 3 is a compressor impeller made of a light alloy casting that is connected to one end of the shaft 2 by a nut 4, and 5 is a turbine wheel made of fine ceramic material. A connecting protrusion 810 having a large diameter part 7, a small diameter 'B8, a slit 9, etc. provided at the other end of the shaft 2 is inserted into the bottomed circular hole 6 on one side, and an opening is opened in the center of the turbine wheel 5. In the through hole 11, the bonding metal 12 that connects the end of the shaft 2 and the turbine wheel 5 in the bottomed circular hole 6 flows in a molten state to the other side of the turbine wheel 5 to form the head 13, and the bonding metal After cooling and solidifying the turbine wheel 12, tensile residual stress (britension) is generated due to contraction, and the turbine wheel 5 is tightened from both sides to be strongly integrated with the shaft 2.

[Problem to be solved by the invention]

The conventional technology described in the above-mentioned publication was developed to join items that cannot be directly integrated by a joining method such as welding, such as the turbine wheel 5 made of fine ceramics and the shaft 2 made of titanium-based material. However, tensile residual stress (britension) is acting on the cooled and solidified joint metal 12, and although the turbine wheel 5 is tightened in the axial direction to prevent loosening, tensile stress is applied in the rotational direction. Since the frictional force obtained by multiplying the axial force due to residual stress by the friction coefficient opposes the torque transmitted from the turbine wheel 5 to the shaft 2, it is not necessarily true that the coupling in the rotational direction is strong and perfect. I can't say that.

The torque mentioned above is not very large in the case of a turbocharger, so it is not normally a problem, but if the turbocharger is exposed to abnormal operating conditions, such as a sudden change in rotational speed or a sudden rise in temperature, for a long time. , or when the turbine wheel 5 and the shaft 2 are frequently placed or subjected to vibrations in the rotational direction, it is thought that a deviation in the rotational direction may occur between the turbine wheel 5 and the shaft 2.

An object of the present invention is to provide a turbocharger rotor in which a turbine wheel and a shaft are strongly coupled not only in the axial direction but also in the rotational direction.

It is characterized by:

[Means to solve the problem]

A turbocharger rotor according to the present invention includes a turbine wheel, a shaft connecting the turbine wheel and an impeller of a compressor, and a stress member integrally formed as an extension of the shaft and inserted into a center hole of the turbine wheel. a slip-off prevention means integrally formed with the shaft at one end of the stress member; and a rotation prevention means also provided between the shaft and one side of the turbine wheel at the one end of the stress member. The one end of the stress member is engaged with the one side of the turbine wheel by the wave stopper and the rotation stopper, and the other end of the stress member is engaged with the one side of the turbine wheel. The molten metal is injected into the other side of the turbine wheel while applying a rotational force in the opposite direction to the rotational direction of the turbine wheel and a tensile force in the axial direction.
Fixed in both the axial and rotational directions by solidification [action] In the rotor of the turbocharger according to the present invention, one end of the stress member is substantially fixed to one side of the turbine wheel, and the other end of the stress member is fixed to one side of the turbine wheel. During the manufacturing process, it is twisted by applying a rotational force in the opposite direction to the rotational direction of the turbine wheel, and is also stretched in the axial direction by other means, and is stretched against the other side of the turbine wheel. , bonded by pouring and solidifying molten metal. In this way, a combined stress of a predetermined magnitude of burritosion and britortion is generated in the stress member.

Therefore, the retaining means formed integrally with the shaft is always strongly pressed against one side of the turbine wheel by the axial tensile force due to the britension stress stored in the stress member, and the retaining means is constantly pressed against one side of the turbine wheel. The rotational force due to the stress of the burriton stored in the stress member causes the turbine wheel to be strongly engaged (i.e., in the detent means, the turbine wheel is strongly pressed against the shaft in its rotational direction, and They are biased and connected in such a way that there is no risk of loosening or rattling.

As a result, the coupling between the turbine wheel and the shaft in the axial and rotational directions in the retaining means and the rotation preventing means will not be broken due to external forces or vibrations to a degree that is normally considered, and the two are essentially integral from the beginning. will have a similar function.

〔Example〕

1 to 4 show a rotor of a turbocharger according to a first embodiment, a portion thereof, and a method of manufacturing the same. The rotor 21 of the turbocharger has a hollow shaft 22 made of, for example, pure metal titanium, which is made by cutting out the center part to reduce weight and save materials, and a threaded part at the left end (low-left may be used) in Fig. 1. A compressor impeller 23 (24 indicates its blades) made of a light alloy guicast mainly made of aluminum is fixed in place, and is the same as the shaft 22, which is joined to the other end of the shaft 22 by laser beam welding 25. It consists of a joint 26 made of a material, and a turbine wheel 27 made of, for example, fine ceramics or titanium alloy, which is connected to the joint 26 by special means according to the present invention.

In this way, the rotor of the present invention is assembled by joining together many relatively small parts, and each part can use the appropriate amount of material most suitable for its respective operating conditions without wasting it. .

Moreover, compared to manufacturing many parts as one piece, it has the advantage that it is easier to mold and process, has less distortion and irregularities, and can be finished with high precision.

In addition, since the shaft 22 and the joint 26 are integrated by laser beam welding 25, even if titanium, which has excellent heat resistance, is used for the joint 26, a cheaper material may be used for the shaft 22. It is possible.

The joint 26 of the shaft is clearly shown in FIG. 2, which is a partial view, and FIG. A partially circular flange 2B (the notch is shown as 29), and a narrow diameter part (stress member) that extends long and thin at the tip.
30, a threaded portion 31 formed near the tip thereof, and further includes a tongue piece (means for applying rotational force) 32, which is formed following the threaded portion 31 and is later mostly cut off.

The turbine wheel 27 coupled to the shaft joint 26 has a center hole 33 having a much larger diameter than the narrow diameter portion 30 of the joint 26.
, a projection (
34, a hexagonal or other rectangular hole 35 for accommodating the screw portion 31, and a blade 3.
It is equipped with 6th class.

Next, a method of manufacturing a rotor by coupling the shaft 22 and the turbine wheel 27 will be described. As shown in FIG. 3, the turbine wheel 27 is mounted on a fixed base 37 with bolts 3.
It is attached by means such as 8. The narrow diameter part (stress member) 30 of the joint 26 attached to the tip of the shaft 22 is inserted into the center hole 33 from below and positioned at the center, and the shaft 22 itself is also strongly pushed to the center axis by means not shown. is maintained.

An annular leak stopper 39 is screwed into the threaded portion 31.
A gap 40 between the narrow diameter part 30 and the center hole 33 is covered, and a gap formed between the square hole 35 and the threaded part 31 is bottomed.

A hopper 41 shown by a chain line is attached to the upper opening of the square hole 35, and a molten metal 42 for bonding is injected so as to surround the threaded portion 31 in the square hole 35. As the molten metal, Fe;NiCrMo-based high-grade steel, which is often used as a material for turbine wheels, is suitable. Fitting 26 at the tip of shaft 22 prior to injection
In particular, the narrow diameter portion (stress member) 30 is strongly heated in advance to a high temperature (sufficiently expanded), and the turbine wheel 27 is also heated to some extent. Furthermore, before the molten metal 42 solidifies in the rectangular hole 35, a rotational force T is applied to the tongue piece 32 at the tip of the narrow diameter portion 30, which is a stress member, by means such as a wrench 43. A predetermined amount of twist is generated.

The direction of the rotational force T is opposite to the direction in which the rotor 21 rotates after completion. In this case, the direction of the threaded portion 31 is selected so that it will tighten easily when the turbine wheel 27 rotates the shaft 22. Incidentally, instead of twisting the narrow diameter portion (stress member) 30 and causing it to expand due to heat, a wrench 43 that grips the tongue piece 32 is used to apply a mechanical tensile force in the axial direction along with the twist, so that it is not only twisted but also expanded at the same time. It may also be configured such that the In short, a feature of the present invention is that the combined stress of axial burtension and rotational burritoon is set to act on the small diameter portion (stress member) 30 that is a part of the shaft 22. It is.

In the case of the first embodiment, the britension and pretortion are formed by solidifying the molten metal 42 with the missing circular flange 28, which serves as a retaining and rotation preventing means, and the threaded portion 31 (see Fig. 4 of the exploded drawing). , the rotational force due to pretortion acts between the notch 2 of the circular flange 28 and the square block 44 ) cast in the shape of the square hole 35 .
9 is locked by the projection 34, while the square block 44 integrated with the threaded portion 31 is locked in the square hole 35, so that the projection 34 is connected to the notch 2 of the circular flange.
9, the shaft 22 and the turbine wheel 27 are strongly pressed in the rotational direction, thereby preventing play between the shaft 22 and the turbine wheel 27 in the rotational direction.

Therefore, combined with the action of britension acting in the axial direction, there is no play between the shaft 22 and the turbine wheel 27, and the shaft 22 and the turbine wheel 27 are strongly integrated.
Although the structure is assembled from small parts, it has the same sturdiness and natural frequency characteristics as if it were a single piece. In addition, the gap 40 between the small diameter part (stress member) 30, which is made small in diameter to impart torsion, and the relatively large center hole 33 of the turbine wheel also has a beneficial effect as a heat insulating space, and This is effective in preventing heat from the wheel 27 from being transmitted to the shaft 22. Therefore, the heat resistance of the shaft 22 may be relatively low.

After the molten metal 42 has solidified, the excess tip of the protruding tongue piece 32 is cut off by machining. It goes without saying that the solidified rectangular block 44 may be appropriately ground to maintain its balance as a rotating body.

Next, a second embodiment of the present invention shown in FIG. 5 will be described. In this case, the square hole 35 employed in the first embodiment is not used, and instead, the upper end of the turbine wheel 45 in the drawing is a square end 46 such as a hexagon. The hopper 47 is placed on the turbine wheel 45 while being attached to the fixed base 37, and a sand mold 48 is placed inside the hopper 47.
is formed. Applying a rotational force to the tongue piece 32 at the tip of the narrow diameter portion (stress member) 30, which is an extension of the shaft 22, with the wrench 43, or strongly heating the narrow diameter portion 30 in advance to expand it, or The process of injecting the molten metal 42 while applying a tensile force to the molten metal 42 is the same as in the first embodiment.

In this case, the threaded part 49 formed at the tip of the narrow diameter part (stress member) 30 is connected to the square end 46 of the turbine wheel 45.
However, when the molten metal 42 is injected into the cavity 50 formed by the sand mold 48 and solidified, the threaded part 49 and the square end 46 of the turbine wheel become cast together and are completely integrated. Note that 51 indicates a ring for preventing leakage of molten metal.

A feature of the second embodiment is also found in the lower end of the turbine wheel 45 in FIG. The joint 52, which is integrated with the shaft 22 by laser beam welding 25, includes a narrow diameter portion (stress member) 30 having the aforementioned tongue piece (means for applying rotational force) and a tapered inner surface 53. It has a flange 54 as a slip-off prevention means. A tapered outer surface 55 is formed at the lower end of the turbine wheel 45 so as to fit into the tapered inner surface 53 .

Further, a notch (not shown) provided in the flange 54 engages with a protrusion 56 of the turbine wheel 45, thereby forming a rotation preventing means for preventing relative rotation between the shaft 22 and the turbine wheel 45.

When a tensile force is applied to the narrow diameter portion (stress member) 30, the tapered outer surface 55 of the lower end of the turbine wheel 45 fits into the tapered inner surface of the flange 54, and the protrusion 56 engages with the notch to prevent it from coming off at the same time. By being prevented from rotating, the lower end of the turbine wheel 45 in FIG.
It is integrated with 2.

The upper end of the turbine wheel 45 is the threaded portion 49 of the narrow diameter portion 30
The small diameter 8 (stress member) 3G, on which the combined stress of britension and burritoon is applied, biases the retaining means and the rotation preventing means so that there is no looseness. As in the first embodiment, the flange portion 54 of the shaft 22 and the lower end of the turbine wheel 45 are integrated in this state. Particularly in the case of the second embodiment, since the narrow diameter portion (stress member) 30 can be made long, the allowable amount of elastic deformation due to britension and burritortion can be increased.

This means that the required amount of elastic deformation in the axial and rotational directions can be obtained without making the narrow diameter portion 30 too thin, so the safety factor also increases as the diameter increases.

〔Effect of the invention〕

According to the present invention, the joint portion between the turbine wheel and the shaft is not only strongly pressed in the axial direction by the burritoon of the stress member, but also strongly pressed in the rotational direction by the burritoon of the same stress member, so that it appears as if they were one piece. It becomes a strong bond. Therefore, even if a normally large external force or vibration is applied,
There will be no loosening, rattling, or misalignment in the joints.

In addition, since it is possible to separate the shaft and the turbine wheel and assemble parts of them separately, it becomes easier to form and process them, and it is possible to improve accuracy without any deviations, and moreover, it is possible to assemble parts of them separately. This makes it possible to use the most suitable materials in the minimum amount necessary, and it is possible to achieve high performance while reducing costs.

[Brief explanation of drawings]

FIG. 1(a) is a longitudinal sectional front view showing the overall structure of a rotor of a turbocharger according to a first embodiment of the present invention, and FIG.
) is a side view of a part of the rotor, FIG. 2 is a perspective view showing the shape and structure of the shaft used in the first embodiment, and FIG. 3(a) is a summary of the process for manufacturing the rotor of the first embodiment. 3(b) is a top view of the part, FIG. 4 is an exploded perspective view of the rotor of the first embodiment, and FIG. 5 is a partially cutaway front view of the rotor of the first embodiment. FIG. 6 is a partially longitudinal front view showing the main part of the rotor of a turbocharger according to an embodiment and the main part of the process for manufacturing the rotor; FIG. 6 is a longitudinal front view showing the structure of the rotor of a turbocharger according to the prior art; The figure is a perspective view showing the shape and structure of the main parts. 1...Turbocharger rotor, 2...Shaft, 3...Impeller, 4...
...Nut, 5...Turbine wheel (conventional), 6...Bottomed circular hole, 7...Large diameter part, 8...
・Small diameter part, 9...Slit, 10...Joining protrusion, 11...Through hole, 12...Joining metal, 13...Head, 21...Turbocharger rotor, 22... ... (Hollow) shaft, 23.
... Impeller, 24... Blade, 25... Laser beam welding, 26... Joint, 27... Turbine wheel (first embodiment), 28...
- Notched circular flange, 29... Notch, 30... Small diameter part (stress member) 31... Threaded part, 33... Center hole, 35... Square hole, 37... Fixing Stand, 39... Leak prevention, 41... Hopper 43... Wrench, 45... Turbine wheel 46... Square end, 48... Sand mold, 50... Hollow space, 52...・Joint, 54...flange, 56...protrusion. 32... Tongue piece, 34... Protrusion, 36... Blade, 38... Bolt, 40... Gap, 42... Molten metal, 44... Square block, (Second example) ), 47... Hopper 49... Threaded portion, 51... Leak prevention, 53... Tapered inner surface, 55... Tapered outer surface, Fig. 1 22... Hollow shaft 26... Joint 27... Turbine wheel 28... Missing circular flange 30... Small diameter B (stress member) 32... Tongue piece 34... Protrusion 35... Square hole 44... Square block number 2 Fig. 30...Small diameter part (stress member) 31...Threaded part 32...Language piece 39...Leak stopper 22...Hollow shaft 25...Laser beam welding 26...Joint 28 ...Cut-off circular flange 29...Notch Fig. 4 7...Turbine wheel 8...Cut-off circular flange 9...Notch 0...Small diameter fl! (Stress member) 31... Threaded portion 32... Tongue piece 35... Square hole 39... Leak stopper 5th (stress member) 4 0... Small diameter portion 7... Fixing base 2 ... Molten metal 3 ... Wrench 4 ... Square block 5 ... Turbine wheel 6 ... Square end 8 ... Sand mold 9 ... Thread part 4 ... Flange 5 ... Taper shape external surface

Claims (1)

[Claims] 1. A turbine wheel, a shaft connecting the turbine wheel and an impeller of a compressor, a stress member integrally formed as an extension of the shaft and inserted into a center hole of the turbine wheel, and one end of the stress member a slip-off prevention means integrally formed with the shaft; and a rotation prevention means provided between the shaft and one side of the turbine wheel at the one end of the stress member; The one end of the member is engaged with the one side of the turbine wheel by the slip-off prevention means and the rotation prevention means, and the other end of the stress member is engaged with the one side of the turbine wheel, and the other end of the stress member is engaged with the one side of the turbine wheel. A turbocharger characterized in that the turbocharger is fixed in both the axial and rotational directions by pouring and solidifying molten metal to the other side of the turbine wheel while applying a rotational force and an axial tensile force. rotor.