WO2019097783A1

WO2019097783A1 - Aluminum alloy turbine shaft nut

Info

Publication number: WO2019097783A1
Application number: PCT/JP2018/030167
Authority: WO
Inventors: 彰太郎中村
Original assignee: 株式会社中村製作所
Priority date: 2017-11-20
Filing date: 2018-08-12
Publication date: 2019-05-23
Also published as: JP2019094525A; CN110073016A; JP6294557B1

Abstract

The present invention is an aluminum alloy nut that is to be used for fixing an impeller to a turbine shaft of an exhaust-turbine-type turbocharger. The material used for the aluminum alloy nut is an aluminum alloy that contains, by weight ratio, 10.0%–11.5% of silicon, no more than 0.50% of iron, 2.0%–3.0% of copper, no more than 0.10% of manganese, 0.20%–0.50% of magnesium, no more than 0.10% of zinc, no more than 0.10% of titanium, and, of other elements, no more than 0.10% of each and no more than 0.15% total, the remainder being aluminum. By using said aluminum alloy, the aluminum alloy nut is not only lighter weight but also achieves needed mechanical properties, even at high temperatures. In particular, the aluminum alloy nut does not loosen due to temperature change and, when combined with other members, improves response and reduces noise and vibration.

Description

Aluminum alloy turbine shaft nut

The present invention relates to a material technology of a nut, and more specifically, a reduction in turbo lag, improvement of response, noise, and vibration by using a lightweight aluminum alloy material as a nut for a turbine shaft in an exhaust turbine turbocharger for automobiles. Relates to the technology of suppressing nuts.

Automotive exhaust turbine turbochargers are used in automotive internal combustion engines, from aircraft technology that enables high-altitude flight with low oxygen concentration by densifying the air and sending more oxygen to the combustion chamber. It is a technology diverted as Exhaust gas turbine turbochargers for automobiles have undergone many changes since the beginning of development, and the initial objective is to improve output. In 1973, BMW introduced BMW's first exhaust gas turbine turbocharger to vehicles. The 2002 Turbo appeared to achieve about 30% power improvement, and in Japan, after that, further increase in power by intercooler, ceramicizing of turbine blades, adopting ball bearings for turbine shaft etc. There is a time background that was unfolded.

Turbocharger is an indispensable means for achieving high output, and is also effective in improving thermal efficiency and reducing emissions. In particular, because high acceleration performance is required for passenger cars, titanium aluminum alloy (Ti-Al based alloy) and magnesium based alloy (Mg alloy), and resin impellers etc. have also appeared for high response. And high strength material technology is proposed.

As described above, although technology related to exhaust turbine turbochargers has been enhanced, needs in recent years are focused on avoiding exhaustion of fossil fuels, the impact of exhaust gases on the environment, and environmental load reduction. There is an urgent need to develop exhaust turbocharged turbochargers that can be supercharged from a low speed range suitable for small diesel engines mainly in Europe and small displacement gasoline engines being promoted in Japan.

Usually, in an exhaust turbine turbocharger, high-temperature combustion gas exceeding 800 ° C. comes into contact with the exhaust side impeller, and its heat is heated through the turbine shaft to a nut provided on the end opposite to the exhaust side If the nut looses and falls off, damage to the impeller and the possibility of discarding the turbocharger itself may occur. Therefore, it is essential for the nut used at the end of such a turbine shaft that the heat resistance is excellent and the mechanical characteristics are unlikely to deteriorate even under conditions such as high temperature heating. In addition, it is desirable to reduce the weight of the nut as much as possible because the nut greatly affects the performance if the dynamic balance in the high rotation range is disturbed. However, with regard to the nut, it can be said that the development is delayed among the members constituting the exhaust turbine.

In view of such problems, if it can be made of stainless alloy conventionally used for exhaust turbine type turbocharger as a material of nut, or aluminum alloy smaller than the specific gravity of chromium based steel, the above-mentioned weight reduction It is thought that it can solve the problem. However, heat resistance is a problem of aluminum. The melting point of aluminum is as low as 660 ° C, the recrystallization temperature is around 200 ° C, and when it is creeping, it is mechanically around 180 ° C, and by heat alloying, mechanical at these high temperature ranges It is necessary to improve the nature. With regard to technological development of aluminum by alloying, many researches have already been made on tensile strength, hardness and the like, and products comparable to high carbon steel such as spring steel have been developed. However, the screws are fastened by holding the elastic force between the male and female screws, and if the volume expansion coefficient differs depending on the temperature change, it does not function as a screw, so the hardness and strength should simply be high. Rather, the function of the nut as a screwing member does not decrease in the temperature range to be used, and the development of a material of the nut having the property of being hard to loosen is still delayed.

Conventionally, various technical proposals have been made from other than the present inventor in order to solve the above-mentioned problems. For example, there is disclosed a technology in which the title of the invention is "12% chromium-based steel nut material excellent in seizure resistance" (see Patent Document 1). Specifically, in order to realize a nut material having excellent creep and creep rupture strength and excellent seizure resistance, the proportion of each metal element is specified by weight ratio, and a conventional 12% Cr-based steel nut material is used. In the same manner as in the above, it is a technology called "a material having excellent creep and creep rupture strength and having excellent anti-seizure characteristics equivalent to that of 5% Cr-based steel of a current nut material. However, the technology described in Patent Document 1 does not solve the problem of achieving weight reduction by using a material made of an aluminum alloy, which is the problem of the present invention.

Moreover, the technique which makes the title of invention a "supercharger" is disclosed (refer patent document 2). Specifically, the object is to “provide a supercharger which can improve the reliability of a fastening structure between a turbine impeller and a shaft and can be manufactured inexpensively”, and the means is “a turbine impeller on the turbine side of a shaft And a thrust surface for axially positioning a turbine impeller supported by the shaft end, the turbine impeller having a shaft center portion of a hub having a plurality of blades. A central hole passing in the center direction is formed, and a cylindrical recessed hole is provided in the axial direction and recessed from the outer end face of the hub, and one end of the central hole is opened at the center of the bottom of this recessed hole The nut inserted into the inside of the recessed hole is screwed and fixed to the male screw portion of the shaft end protruding from the central hole by inserting one axial end of the shaft into the central hole. It is. However, the technology described in Patent Document 2 is intended to reduce the influence of heat by preventing the combustion gas from directly hitting the nut, and to achieve weight reduction by using an aluminum alloy material. It does not solve the problem.

Also, a technology is disclosed in which the title of the invention is referred to as "turbocharger" (see Patent Document 3). Specifically, it is an object of the present invention to provide a turbocharger capable of reducing whirl vibration, and the means includes a shaft connecting a turbine and a compressor, and a bearing portion rotatably supporting the shaft. And a sliding bearing interposed between the shaft and the bearing portion, wherein the bearing portion is formed of an aluminum-based material, and the shaft is made of a steel material. And the slide bearing is formed of a copper-based material. However, the technology described in Patent Document 3 is a material related to an aluminum alloy of a bearing used for a high rotation turbine shaft, and the conditions are different from those of a nut for a turbine shaft as in the present invention. It does not lead to the solution.

As described above, the techniques described in Patent Documents 1 to 3 disclose effective techniques related to turbochargers, but if it is possible to use an aluminum alloy for these techniques, individual techniques can be used. It is clear that further improvement in performance can be expected by weight reduction as well as the functions possessed, and technical proposals that use such an aluminum alloy material for weight reduction of a nut can be said to be urgently needed.

Japanese Patent Application Laid-Open No. 7-25289 JP 2012-92815 A JP 2013-209934 Patent No. 5477930

The present invention uses an aluminum alloy having a small specific gravity to achieve weight reduction while avoiding the phenomenon that a nut is loosened due to a change in mechanical characteristics necessary even at high temperatures, and other members. It is an object of the present invention to provide a high response, low noise, low vibration and highly effective nut technology.

The present invention is an aluminum alloy nut used to fix an impeller to a turbine shaft of an exhaust turbine turbocharger, and the material is silicon (Si) in a weight ratio of 9.5 to 11.5%. Iron (Fe): 0.50% or less, Copper (Cu): 4.0 to 5.0%, Manganese (Mn) 0.3% or less, Magnesium (Mg) 0.40 to 0.80%, Zinc Aluminum composed of (Zn) 0.5% or less, titanium (Ti) 0.2% or less, each other 0.10% or less, and the other total being 0.15% or less, with the balance being aluminum (Al) Adopt a configuration that is made of alloy.

Further, the present invention is a nut made of an aluminum alloy used to fix an impeller to a turbine shaft of an exhaust turbine turbocharger, and the material is silicon (Si) in a ratio by weight: 10.0 to 11. 5%, iron (Fe): 0.50% or less, copper (Cu): 2.0 to 3.0%, manganese (Mn): 0.10% or less, magnesium (Mg): 0.20 to 0.. 50%, zinc (Zn): 0.10% or less, titanium (Ti): 0.10% or less, each other 0.10% or less, the other total being 0.15% or less, the balance being aluminum (Al It is also possible to adopt a configuration made of an aluminum alloy composed of

Further, according to the present invention, it is also possible to adopt a configuration in which the outer peripheral portion of the aluminum alloy turbine shaft nut is formed to have unevenness.

Further, according to the present invention, it is also possible to adopt a configuration in which a screwing portion that enables tightening and removal by a screwing fastener is provided on one end surface of the aluminum alloy turbine shaft nut.

Moreover, this invention can also employ | adopt the structure which has an unevenness | corrugation in an inner peripheral part and is provided with the hole shape corresponding to the external shape of the said screwing fastener penetrated from one end surface.

Further, according to the present invention, in a state in which the tool insertion depth by the hole shape corresponding to the outer shape of the screwing fastener is screwed to the turbine shaft, the male screw portion of the turbine shaft protrudes from the nut It is also possible to adopt a configuration in which the exhaust turbine is configured in a non-overlapping relationship.

According to the nut for an aluminum alloy turbine shaft according to the present invention, by using aluminum alloys AA1 and AA2 as raw materials, specific gravity is smaller than conventional steel materials, stainless steel alloys, chromium alloys and the like, For example, compared with steel 7.8, aluminum is 2.6 and about 1/3, and weight reduction can be realized, reducing the inertial force around the rotation axis, improving response and reducing turbo lag, and It exhibits excellent effects that make it possible to reduce vibration and noise.

In addition, although the nut for an aluminum alloy turbine shaft according to the present invention has only a small size when viewed from the ratio of the whole constituting an exhaust turbine, the weight is reduced to improve the rotation performance, and at the time of deceleration Even if the throttle valve is closed, supercharging of the excess air can be prevented, and the waste due to the release of the exhaust energy from the waste gate valve can be reduced.

In addition, according to the nut for an aluminum alloy turbine shaft according to the present invention, other compositions added to the base aluminum can easily obtain silicon, iron, copper, manganese, etc., and the economic burden can be suppressed. In this respect, the present invention has advantageous effects as compared with the prior art.

In addition, according to the nut for an aluminum alloy turbine shaft according to the present invention, the response is improved more than before due to the synergistic effect by combining with the technology (see Patent Document 4) already obtained by the inventor of the present invention. Exerts extremely effective effects in that it is possible to dramatically reduce vibration and noise

It is structure explanatory drawing which shows the basic composition of the nut for aluminum alloy turbine shafts which concerns on this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is structure explanatory drawing explaining the structure of the exhaust gas turbine using the nut for aluminum alloy turbine shafts which concerns on this invention. It is use condition explanatory drawing explaining the use condition of the nut for aluminum alloy turbine shafts which concerns on this invention.

The present invention is intended to reduce the weight by utilizing an aluminum alloy having a small specific gravity for the nut 2 used at the end of the turbine shaft 31 for the exhaust turbine turbocharger 10, and to improve the rotational response of the exhaust turbine 30. , The reduction of the turbo lag, and the suppression of the vibration are the most characterized. Hereinafter, it demonstrates based on drawing. However, the present invention is not limited to the shapes and configurations described in the drawings and tables, and can be changed within the range in which the effects exhibited as the creation of the technical idea of the present invention can be obtained.

FIG. 1 shows the entire configuration of an aluminum alloy turbine shaft nut 1 according to the present invention. The nut 1 for an aluminum alloy turbine shaft according to the present invention is a nut 2 used for an end portion of a bearing of a turbine shaft 31, and the shape thereof is a normal hexagonal nut 2 as shown in FIG. Alternatively, a hexagonal socket nut 2 as shown in FIG. 1 (b) may be used. Further, it may be a wave shaped nut 2 as shown in FIG. 1 (c) or a wave type holed nut 2 as shown in FIG. 1 (d). Further, as shown in FIG. 1 (e), the outer shape is cylindrical and has no unevenness on the surface, and a tool insertion hole H for inserting a tool into the inner diameter is provided with a hole in the thick portion between the inner diameter and the outer diameter. The nut 2 may be used. That is, it is desirable to reduce the generation of noise by eliminating the projecting shape as much as possible and making it a shape with less air resistance.

As in the embodiment shown in FIGS. 1 (a) and 1 (c), in the case where the concavo-convex shape is provided from the outer periphery toward the outside and this is tightened with a tool, Although noise may be generated, since the thickness T of the nut 2 in the width direction can be reduced, there is an advantage that weight reduction can be achieved. Note that the above-mentioned outer peripheral uneven shape is changed from the hexagonal shape in FIG. 1A to a polygonal shape (for example, 9 angles or 12 angles), or as shown in FIGS. 1C and 1D. It is also effective to reduce the amount of protrusion change due to unevenness one by one by increasing the number of undulations.

On the other hand, as in the embodiment shown in FIG. 1 (b) and FIG. 1 (d), in the case where the concavo-convex shape is provided in the direction from the inner circumferential surface toward the center and this is tightened by a tool, Since the tool insertion depth K is required, the thickness T of the nut 2 is increased, which may increase the weight as a whole. But,
Since the uneven portion can be eliminated on the outer periphery, there is an advantage that the cause of noise can be removed. That is, in the shape from FIG. 1 (a) to FIG.1 (b), both reduction of a noise and weight reduction can not be achieved.

Therefore, as shown in FIG. 1 (e), a plurality of insertion holes are provided equiangularly from the center on the same pitch circle between the inner diameter and the outer diameter while reducing the thickness T of the nut. For example, the female screw portion S necessary for screwing the tool insertion depth K and the male screw portion of the turbine shaft 31 can be configured to have the same thickness, and the above-mentioned unevenness is unnecessary on the surface The noise generated from the shape can also be prevented. When such a configuration is adopted, although not shown in the drawings, a screwing fastener 70 of a dedicated tool is required. However, if a dedicated attachment is prepared for a socket wrench or torque wrench, it can be coped with using an existing tool. The shape of the aluminum alloy turbine shaft nut 1 according to the present invention is not limited to the shape shown in FIG. 1 as long as the outer periphery and the end face have no unevenness or decrease in size. .

The nut 1 for a turbine shaft of an aluminum alloy according to the present invention has the technical features by the above-described shape and the technical features specifying the raw materials as the aluminum alloys AA1 and AA2 shown below. The greatest feature of the technology is that the aluminum alloy which can not be used in the high temperature environment of the exhaust turbine 30 is made available. And, it is important to prevent the loosening of the nut 2 due to the change of the mechanical characteristics in the heating state. Therefore, first, the composition of the aluminum alloys AA1 and AA2 and the mechanical characteristics in the case of being used for raising the temperature will be described with reference to Tables 1 to 5.

Conventionally, as a material of the nut 2 of the turbine shaft 31 in the exhaust turbine turbocharger 10, an alloy (Cr-Ni based) obtained by adding nickel and chromium to a steel base, a chromium based alloy (Cr steel) or a stainless steel based A variety of alloys have come to be used, such as alloys (Ni-Cr) and titanium alloys (Ti-based), and alloys with extremely excellent mechanical properties have been developed, for example, WASPALOY (registered trademark) and Materials such as Inconel (registered trademark) which are excellent in high temperature characteristics such as corrosion resistance, heat resistance, oxidation resistance, and creep resistance have been proposed. In addition, expensive materials such as Haynes alloy, nickel cobalt-based alloy, Cu-Ni-based alloy and the like that are used in aircraft etc. are also nuts for the turbine shaft 31 of the exhaust turbine turbocharger 10 in part. It is also considered possible to use as (2).

However, since these alloys are based on nickel, chromium or the like having a large specific gravity, it can be said that the materials are difficult to be reduced in weight, and they are expensive and solve the problem of the present invention to reduce the cost. It can be said that it is an unsuitable material. In addition, titanium has a specific gravity of twice that of aluminum 4.5, but it can be made thin because of its high specific strength, so it is possible to reduce the weight as an absolute weight, and it has heat resistance and strength. Some are used also for the nut 2 and the turbine shaft 31 of a special exhaust turbine type turbocharger 10 such as a competition vehicle. However, since titanium is also expensive, the cost problem becomes greater. Therefore, in the present invention, an aluminum alloy with a small burden in cost is used, and the composition thereof will be described as follows.

FIG. 2 is a configuration explanatory view for explaining the configuration of an exhaust turbine 30 using the aluminum alloy turbine shaft nut 1 according to the present invention. As shown in FIG. 2, the exhaust turbine 30 is shown to be configured by an exhaust side impeller 32, an intake side impeller 33, a turbine shaft 31, and an integrated floating metal bearing 20.

The exhaust turbine 30 is a rotating body on which the exhaust side impeller 32 and the intake side impeller 33 are disposed and fixed at both ends of the turbine shaft 31.

The exhaust side impeller 32 is an impeller for absorbing the energy of the exhaust gas as rotational motion, and transmits the energy to the intake side impeller 33 provided at the opposite end through the turbine shaft 31. In order to efficiently absorb the working fluid from the exhaust gas and convert it into rotational motion, the plurality of blades are formed into a shape suitable for supercharging, and in a gasoline engine, the temperature of the exhaust gas exceeds 1000 ° C. In some cases, materials that can withstand such temperatures are required. Although ceramic materials and titanium alloys are conventionally used in some racing vehicles, etc., although ceramics are excellent in heat resistance, they are easily cracked etc., and titanium alloys are expensive and have problems in cost. doing. Therefore, in the present invention, by using an aluminum alloy also for the nut 2, the purpose is to improve the response of supercharging due to the inertial force of the rotating body, so the exhaust side impeller 32 rotates on the same axial core. It is effective to reduce the weight as much as possible.

The intake side impeller 33 is a member that rotates by utilizing the pressure and the flow rate of natural air flowing in from the atmosphere by the driving force transmitted from the exhaust side impeller 32 through the turbine shaft 31 and is an internal cylinder. It is an impeller for pushing air into. In addition, since the turbine reaches nearly 200,000 rotations, the peripheral speed may exceed the speed of sound in the vicinity of the blade tip of the impeller, and heat resistance against being heated by air resistance and mechanical strength against resistance It is necessary to have sheath strength in the temperature range used.

FIG. 3 shows a state in which the aluminum alloy turbine shaft nut 1 according to the present invention has been used for the exhaust turbine turbocharger 10 before it rotates. Although FIG. 3 shows a state in which the present invention is applied to a general exhaust type supercharging device, the present invention is not particularly limited to such description, and in the entire exhaust turbine turbocharger 10. The position, the ratio, etc. are illustrated. Hereinafter, members of respective portions constituting the whole of a general exhaust turbine turbocharger 10 used for the aluminum alloy turbine shaft nut 1 according to the present invention will be described.

The floating metal 20 is a cylindrical sliding bearing, maintaining the clearance between the inner and outer shafts and the bearing housing 40, and is a rotatable floating bearing. Further, the oil film on the inner and outer peripheries has a high damping effect and a low relative speed, which is suitable for high-speed bearings.

The turbine housing 50 is a component that encloses the exhaust side impeller 32 and is configured of an introduction portion and an exhaust portion of the exhaust gas, and plays a role of accelerating the exhaust gas from the engine and guiding it to the determined exhaust side impeller 32. It is. Such a turbine housing 50 is always exposed to high temperature in order to direct exhaust gas directly, and is generally made of cast iron having characteristics such as heat resistance, heat dissipation, and thermal expansion resistance.

The bearing housing 40 is located at the center of the turbine housing 50 and the compressor housing 60, includes a bearing of the turbine shaft 31, and has a function of connecting and supporting the two housings. The configuration of the aluminum alloy turbine shaft nut 1 according to the present invention exemplifies the case where a bearing housing 40 is used to support one floating metal bearing 20 in which the intake side and the exhaust side are integrated. .

The compressor housing 60 wraps the intake side impeller 33 and is constituted of an air intake portion and an air discharge portion to guide the air and has a function of converting dynamic pressure given by the intake side impeller 33 into static pressure. .

White metals conventionally used for bearings are excellent in seizure resistance and adaptability, etc., and were said to be optimum materials, but they have the problem that the limits of the materials for bearings become low when exposed to high temperatures. Copper-lead alloys or lead-bronze alloys have been developed as alternatives to the above, and there have also appeared materials with extremely small reduction in mechanical properties at high temperatures. However, such an alloy needs to be plated, and the problem of increasing the number of manufacturing processes and increasing costs has to be solved. In the process of researching and developing aluminum alloys as the material of such bearings, The inventors of the present invention have found an aluminum alloy that exhibits a characteristic that is not easily loosened even at high temperatures, from the relationship of the elongation as a screwing member at high temperatures, the coefficient of linear expansion and the like. The composition is described below.

Silicon (Si) suppresses expansion due to heat by containing to improve wear resistance, and the content is within the range of 9.5 Wt% to 11.5 Wt%, more preferably 10 It is desirable to be within the range of 0. 0 Wt% to 11.5 Wt%.

Iron (Fe) is contained to prevent seizure. However, increasing the iron content will lower the strength. The content is desirably 0.5 wt% or less.

Copper (Cu) is contained to improve the strength, and by further adding nickel, the strength can be further improved. The content is preferably in the range of 2.0 Wt% to 5.0 Wt%, preferably in the range of 2.0 Wt% to 3.0 Wt%, or 4.0 Wt% to 5.0 Wt%. .

Manganese (Mn) can improve the strength while maintaining the corrosion resistance of aluminum as it is, and further improves the strength by containing magnesium (Mg). It is desirable that the content is within the range of 0.3 wt% or less, and more preferably 0.1 wt% or less.

By containing magnesium (Mg), strength and corrosion resistance can be improved. However, if it is cold-worked, stabilization processing is performed because its strength decreases with age. In particular, in the exhaust turbine turbocharger 10 used at high temperature, there is a problem of stress corrosion cracking, so the right side of the soft material is required. Furthermore, the inclusion of magnesium (Mg) and silicon (Si) at a constant content ratio contributes to age hardening by heat treatment. The content is within the range of 0.2 Wt% to 0.8 Wt%, preferably within the range of 0.2 Wt% to 0.5 Wt% or 0.4 Wt% to 0.8 Wt%. desirable.

Zinc (Zn), together with magnesium (Mg), is heat treated to be the highest strength alloy among aluminum alloys. The content is desirably 0.5 Wt% or less, more preferably 0.1 Wt% or less.

Titanium (Ti) can be used for grain refinement, mechanical property improvement, or prevention of shrinkage cracking with an Al—Cu-based alloy or the like. However, when the content is excessive, there arises a problem that the viscosity of the molten metal increases. The content is within the range of 0.2 Wt% or less, more preferably 0.1 Wt% or less.

By blending each of the above-mentioned metals, if an aluminum alloy having a small specific gravity can be used also for the nut 2 under high temperature, a lightweight exhaust turbine 30 can be configured, and many problems such as the following problem and heat conduction It can be said that the problem can be solved.

However, the melting point of aluminum (Al) is about 660 ° C, the recrystallization temperature is as low as about 200 ° C, and a creep reaction may occur at 180 ° C. It is thought that an aluminum alloy can not be used as the nut 2 fixed to the bearing housing 40 after the impeller is mounted on the turbine shaft 31 of a certain exhaust turbine type turbocharger 10. However, the exhaust turbine type turbocharger 10 of recent years is equipped with an intercooler, an independent lubrication mechanism, or a cooling device, etc., and the high temperature side of the temperature range is lowered, and the turbine shaft 31 also improves the lubricating oil performance. The temperature does not rise so much, and is at most about 150 ° C, does not rise to a temperature at which the nut 2 creeps, and even aluminum alloys in which mechanical properties such as strength and hardness are easily affected by heat It is possible to respond as long as it has the required mechanical properties around 200 ° C.

Therefore, the inventor of the present invention studies a material of a nut 1 for an aluminum alloy turbine shaft that solves all the above-mentioned problems, and mechanical characteristics as the nut 2 even at around 200 ° C. In addition to solving the problems, the aluminum alloys AA1 and AA2 according to the present invention are completed as highly durable materials that do not age-deteriorate due to hardness and elongation.

The composition of the composition of the alloy used for the material of the aluminum alloy turbine shaft nut 1 according to the present invention will be described with reference to Tables 1 and 2. Table 1 which concerns is shown about the compounding relationship of the other alloying element mix | blended with aluminum, and Table 2 shows what was especially excellent in heat resistance among the stainless steel alloys conventionally used for comparison. Furthermore, since the weight of stainless steel is increased, the composition of a typical brass as a lightweight material is also shown for comparison.

Table 1 shows the proportions of various metals blended in the base metal, and the invention according to

claim

1 or 2 according to the present invention is shown as aluminum alloys AA1 and AA2 in order from the top, and below that, It is made to be able to compare with the material conventionally used for the turbine shaft 31. Table 2 shows three representative types from conventional stainless steels and one representative from brass types. Table 1 concerned and Table 2 concerned are compared, and a difference of composition and combination is clarified.

The mechanical properties of the aluminum alloys AA1 and AA2 according to the present invention will be described with reference to Tables 3 and 4. Table 3 investigates the material characteristics of the aluminum alloy according to the present invention, and Table 4 investigates the mechanical characteristics in the case of using stainless steel and brass materials. The materials to be investigated are those after tempering (T6 treatment) of the extruded material at room temperature. The survey items are tensile strength (MPa), 0.2% proof stress (MPa), elongation (%), and hardness (HRB), and the results of the survey are shown.

The fastening nut 2 for the turbine shaft 31 used under high temperature is subject to thermal expansion due to heating and metal fatigue due to repeated cooling after the engine is stopped. High mechanical properties such as properties and corrosion resistance are required. In particular, the principle of fastening of the male and female screws is not to simply show high values of tensile strength and hardness, since they are not loosened by extension or expansion to the yield point.

As a material of the nut 2 for the exhaust turbine type turbocharger 10 used under high temperature, there is Inconel (registered trademark) or the like which is said to be a high heat resistant material superior to a stainless steel alloy. However, as described above, there is a problem that the cost is high and the cost burden is large to use. Moreover, titanium is also a material excellent in heat resistance, but it is as expensive as the above-mentioned Inconel, and even though it is a metal that breaks rapidly due to the fact that the yield point is unstable due to temperature and there is little elongation. Even if it can be used as an additive for improving the heat resistance performance, it can not be said that it is suitable for the fastening nut 2 for the turbine shaft 31 as it is. Under such current conditions, there is a current condition that stainless steels such as SUS304 and SUS316, which are excellent in heat resistance and corrosion resistance, are used as a hand.

SUS304 is one of the most widely spread types of heat-resistant steel among stainless steels called aka 18Cr-8Ni or 18-chromium stainless steel, and is known for its good mechanical properties such as corrosion resistance and weldability. It is done. In addition, SUS316L is a steel material that is slightly softened by reducing the amount of carbon to a particularly corrosion resistant SUS316 among austenitic stainless steels and has improved machinability, both of which are used for heat resistant bolts and heat resistant nuts 2 It is done. However, the specific gravity is 7.8, which is approximately three times heavier than aluminum.

However, stainless steels have a high coefficient of thermal expansion, and there is a problem that when they are heated, they tend to loosen due to expansion. In addition, as the cause of the screw loosening at high temperature, the reduction of the bolt axial force and the reduction of the screw surface friction are considered as the main factors. Generally, when expansion and contraction are repeated by temperature cycles etc., microscopic expansion and stress relaxation (Surface roughness level) occurs, axial force tends to decrease, and there is a possibility that loosening may occur in an environment under high temperature, and there is a current situation that chemical products such as locking agents are also used.

In addition, depending on the combination of materials, adhesion may occur and the friction on the screw surface may become strong. Therefore, the material of the nut 2 should be selected according to the diameter and length of the turbine shaft 31 and the material. Is important, and it is common to make the material of the external thread and the internal thread the same.

The mechanical properties of the aluminum alloys AA1 and AA2 according to the present invention in the heated state are shown in Table 5.

In Table 5, after investigating the mechanical properties as shown in Table 2, the alloys composed of the aluminum alloys AA1 and AA2 shown in Table 1 are subjected to high heat exceeding the working temperature range from normal temperature by the following procedure It is the result of investigating the change of the mechanical property after predetermined time progress, the range up to. Specifically, after solution treatment, artificially age-hardened ones are not actively cold-worked, heat-treated (T6 (JIS standard)), and then heated at 150 ° C. or 200 ° C. for 100 hours, and then The sample was left standing at room temperature, processed into tensile test pieces, heated again to 150 ° C. or 200 ° C. by a heater of a tensile tester, and subjected to a tensile test and the like.

From the above measurement results of mechanical properties, Table 5 shows that the nuts 2 of the turbine shaft 31 of the exhaust turbine turbocharger 10 use the aluminum alloys AA1 and AA2 according to the present invention even in the heating condition of 150 ° C. and 200 ° C. It shows that it is possible. That is, when using aluminum alloys AA1 and AA2 whose specific gravity is about one third of that of the conventional stainless steel-based alloy, weight reduction, response improvement, reduction of turbo lag, suppression of generation of self-excited signal, and noise generation Exerts the effect of preventing

In aluminum alloys AA1, mechanical properties at a state heated to 200 ° C. after T6 heat treated, the tensile strength, from 426N / mm ² to 219N / mm ^2, to 0.99 ° C. In 359N / mm ^2, in the hardness test Although the Brinell hardness decreases from 79 (HRB) to 60 (HRB) (200 ° C.), the mechanical properties of brass (C3604) at room temperature due to the increase in elongation from 11% to 16% The tensile strength is 420 N / mm ² , the elongation is 25%, the linear expansion coefficient is 20.5 × 10 ^−6, and mechanical properties as a screw are provided.

In aluminum alloy AA2, mechanical properties at a state heated to 200 ° C. after T6 heat treated, the tensile strength, from 458N / mm ² to 259n / mm ^2, to 0.99 ° C. In 393N / mm ^2, in the hardness test Little change in Brinell hardness from 85 (HRB) to 71 (HRB) (200 ° C), 86 (150 ° C), elongation increased from 8% to 15% (200 ° C), elongation changed at 150 ° C It showed 15%. Therefore, the aluminum alloy AA2 is similar to the mechanical properties at normal temperature of brass (C3604) which has been conventionally used as a typical material in comparison with aluminum alloy AA1, and the brass (C3604) The aluminum alloy according to the present invention has a characteristic that the tensile strength does not show a large change such as 314 N / mm ^{2 at} 100 ° C. heating and 310 N / mm ² at 200 ° C., but falls sharply to 196 N / mm ^{2 at} 400 ° C. It can be said that the characteristics are very similar to those of AA2.

Refining is performed on the assumption that the product is used at 150 ° C. and 200 ° C. for 100 hours, and hardness and tensile strength are measured after T6 treatment. Note that such T6 treatment is a heat treatment combining treatment for artificially carrying out precipitation aging in order to improve the mechanical properties, strength, hardness and machinability of the aluminum alloy. Hardening and tempering are performed.

The linear expansion coefficient is a characteristic of the material necessary for the design of the nut 2 and indicates an expansion ratio which expands and contracts in a specific direction, and unlike the thermal expansion coefficient which expands with a change in volume, the coefficient changes depending on the shape . In the present invention, expansion in the screwing direction, which is the fastening relationship between the male screw and the female screw, is a problem, but the aluminum alloys AA1 and AA2 have linear expansion coefficients of 22.2 × 10 ⁻⁶ / ° C. and 20.8, respectively. Since it is × 10 ^-6 / ° C, and it shows a linear expansion coefficient similar to that of a typical brass (C3604) nut 2 of the conventional product, the loosening of the nut 2 due to heat is caused by the conventional brass nut It shows that it becomes the same as 2. However, such numerical values take into consideration the expansion characteristics corresponding to the turbine shaft 31 which is the counterpart of the conventionally used brass or other nut 2, and if the material of the turbine shaft 31 changes, the material The aluminum alloy AA1 and the aluminum alloy AA2 may be used properly depending on the situation.

The hardness is said to be less likely to be loosened if there is a difference in the frictional resistance at the contact surface of the male screw and the female screw to prevent loosening, and the aluminum alloy corresponding to the hardness of the male screw of the turbine shaft 31 AA1 and aluminum alloy AA1 may be used properly. In the present invention, the aluminum alloy AA1 is 79 HRB, the aluminum alloy AA2 is 85 HRB, and although a slight decrease in hardness is observed at 200 ° C., the hardness is 70 HRB for AA1 and 71 HRB for AA2, and stainless steel at normal temperature It can be seen that sufficient performance is maintained even in comparison to and brass.

In addition, it tested also about loosening of the nut by temperature rise. After tightening with a torque wrench at a specified torque, the temperature was raised, and after a certain time, in order to grasp the loosened state of the nut 2, measurement was performed with the torque wrench. Basically, there is almost no change in the test, and although not described, the test was not loosened at 200 ° C. or less with the impeller held by the turbine shaft 31.

While the present inventors are reviewing various processing conditions such as surface roughness and roundness, even if the high-accuracy roundness characteristics and surface roughness characteristics are improved, the generation of noise from the turbine is quite difficult. That is, it may be possible to suppress the generation of the vibration by slightly changing the roundness on the inner surface of the bearing hole 26 to a polygonal position because it is difficult to suppress the generation of the vibration causing the noise. Based on the idea of changing the roundness variously, repeat the experiment on the presence or absence of vibration and noise generation, technology to reduce the generation of vibration "low vibration type floating metal bearing" (see Patent Document 4) (below, Low vibration sliding using the aluminum alloy AA1 and AA2 materials of the nut 1 for the aluminum alloy turbine shaft according to the present invention. By the receiving, it is possible to synergistically effective resulting from mutual technology.

That is, although the invention according to the low vibration slide bearing can obtain a high centering effect and an effect of suppressing the occurrence of noise from the low rotation region to the high rotation region, the effect of the invention relates to the generation from the start of rotation. As a result, the weight reduction of the entire exhaust turbine 30 can be achieved by reducing the weight of the nut 2, which is one of the parts constituting the rotating body, and suppression of turbo lag, improvement of response, self-excited vibration and noise And the like can be suppressed.

Therefore, the surface of the bearing hole 26 of the aluminum alloy turbine shaft nut 1 according to the present invention is provided with a plurality of regions having different fluid lubrication conditions equidistantly equidistant from the shaft center, and the clearance slightly changes on the surface of the bearing hole 26 It is desirable to adopt a configuration that causes a change in hydraulic pressure by forming a substantially convex narrow membrane-like flow path in the axial direction in the oil flow path.

Furthermore, the clearance is changed so that the regions having different fluid lubrication conditions gently connect the substantially convex narrow membranous flow channel toward the axial center and the substantially concave wide membranous flow channel toward the outer peripheral direction. It is also effective to

The centering property (self-centering function), which is an effect of the configuration, is rotated as in the distribution of pressure generated from the Reynolds equation, when a portion having a slightly different roundness is disposed at the same circular peripheral edge of the equiangular position. Because the pressure changes that occur are always of the same magnitude and occur at equal intervals on the same circumference, the pressure difference generates a force toward the center of the turbine shaft 31 at all times, and the centering effect is rotation even if the rotational speed is low. Occurs almost simultaneously with Therefore, if the weight of the turbine and the rotating bearing can be reduced, the problems of the present invention are solved, and the response is improved, the turbo lag is reduced, the self-excited vibration is suppressed, and the generation of noise due to the vibration is reduced. It is possible to provide the exhaust turbine turbocharger 10.

According to the nut for an aluminum alloy turbine shaft according to the present invention, the increase of the rotational speed of the exhaust turbine 30 in the exhaust turbine type turbocharger is quickened, as a result, the turbo lag can be reduced and the response can be improved. The reduction of moment enables suppression of self-excited vibration and reduction of noise generation, and in particular, it is easy to adapt to small exhaust turbine type turbochargers that are becoming smaller in size, and the industrial applicability is high in Japan's automobile industry in the future It is considered to be.

DESCRIPTION OF SYMBOLS 1 Aluminum alloy nut for a turbine shaft 2 Nut 10 Exhaust turbine type turbocharger 20 Floating metal bearing 26 Bearing hole 30 Exhaust turbine 31 Turbine shaft 32 Exhaust side impeller 33 Intake side impeller 40 Bearing housing 50 Turbine housing 60 Compressor housing 70 Screwing fastening Tool AA1 Aluminum alloy AA2 Aluminum alloy H Tool insertion hole K Tool insertion depth S Female thread T Thickness of nut

Claims

An aluminum alloy nut (2) used to secure an impeller to a turbine shaft (31) of an exhaust turbine turbocharger (10), comprising:
The material is in weight ratio,
Silicon (Si): 9.5 to 11.5%,
Iron (Fe): 0.50% or less,
Copper (Cu): 4.0 to 5.0%,
Manganese (Mn) 0.3% or less,
Magnesium (Mg) 0.40 to 0.80%,
Zinc (Zn) 0.5% or less,
Titanium (Ti) 0.2% or less,
Others are each 0.10% or less, and the other total is 0.15% or less,
The balance is aluminum (Al)
An aluminum alloy turbine shaft nut (1), characterized in that it is made of an aluminum alloy (AA2) composed of
An aluminum alloy nut (2) used to secure an impeller to a turbine shaft (31) of an exhaust turbine turbocharger (10), comprising:
The material is in weight ratio,
Silicon (Si): 10.0 to 11.5%,
Iron (Fe): 0.50% or less,
Copper (Cu): 2.0 to 3.0%,
Manganese (Mn): 0.10% or less,
Magnesium (Mg): 0.20 to 0.50%,
Zinc (Zn): 0.10% or less,
Titanium (Ti): 0.10% or less,
Others are each 0.10% or less, and the other total is 0.15% or less,
The balance is aluminum (Al)
An aluminum alloy turbine shaft nut (1), characterized in that it is made of an aluminum alloy (AA1) composed of
The outer peripheral portion of the aluminum alloy turbine shaft nut (1),
The nut (1) for an aluminum alloy turbine shaft according to claim 1 or 2, wherein the nut (1) is formed with irregularities.
One end face of the aluminum alloy turbine shaft nut (1),
The nut (1) for an aluminum alloy turbine shaft according to claim 1 or 2, further comprising a screwing portion that enables tightening and removal by the screwing fastener (70).
Has irregularities on the inner circumference,
The nut for an aluminum alloy turbine shaft according to claim 3 or 4, wherein a hole shape corresponding to the outer shape of the screw fastener (70) inserted from one end face is provided. 1).
The tool insertion depth (K) by the hole shape corresponding to the outer shape of the screwing fastener (70) is
In a state in which the nut (2) is screwed to the turbine shaft (31),
6. The exhaust turbine (30) according to any one of claims 3 to 5, characterized in that the external threaded portion of the turbine shaft (31) does not protrude from the nut (2) to constitute an exhaust turbine (30). Nut for aluminum alloy turbine shaft (1).