KR100922776B1 - Combination Structure Of Light Weight Cam Shaft Using Thermal Expansion Coefficient - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight camshaft coupling structure using thermal expansion characteristics. The cam unit is arranged in the same number as the number of valves to open and close the intake / exhaust valve of the engine, and the shaft unit is mounted to the cam unit. It is made of a cam shaft consisting of a), wherein the cam part is made separately of the cam pieces of iron material, and the aluminum alloy or heat-resistant aluminum alloy or heat-resistant light metal molten through the casting method after inserting the separately produced cam pieces in the mold In the lightweight camshaft in which the campieces and the shaft portion (journal portion) are integrally formed by injecting a magnesium alloy, the combination according to the difference in thermal expansion coefficient (aka, shrinkage) of the steel campiece and the lightweight metal shaft portion Shrinkage reinforcement is formed on the cam piece to prevent weakening of the binding force due to shrinkage at the site, and serves as the shrinkage reinforcement. When the lightweight metal is injected into the sharp portion to form the reinforcing fastening portion is characterized in that the cam piece and the shaft portion is integrally coupled, through which the present invention is due to the difference in thermal expansion coefficient according to the material difference of the cam piece and shaft portion There is an effect that can prevent the weakening of the binding force.

Camshaft, campiece, shaft, joint, lightweight metal, shrinkage reinforcement, thermal expansion coefficient

Description

Combination Structure Of Light Weight Cam Shaft Using Thermal Expansion Coefficient

The present invention relates to a lightweight camshaft coupling structure for a vehicle engine, and more particularly, a shaft portion (journal portion) formed of a separately produced iron campiece and an aluminum alloy or heat-resistant magnesium alloy material, which is a lightweight metal. In the process of manufacturing a lightweight camshaft for a vehicle by insert-inserting in a mold by a casting method, the coupling force may be prevented from being weakened due to the difference in thermal expansion coefficient (aka, shrinkage) according to the material difference between the campiece and the shaft part. It relates to a lightweight camshaft coupling structure using thermal expansion characteristics in which the shape structure of the coupling portion of the cam piece and the shaft portion is changed and improved.

As is well known, the Cam Shaft, the main part of the engine dynamometer, is sequentially powered by rocker arms, tappets, and push rods that open and close the intake and exhaust valves through repetitive rotational movements. It is made to open and close the valve.

In particular, the camshaft of the automobile engine is a component that controls the opening and closing timing of the intake and exhaust valves of the combustion chamber by receiving the rotational force of the crankshaft, and the high rotation (750-4,500 RPM) in the low temperature and high temperature range (-15 to 120 ° C) and This part is used in bad condition such as rotation bending fatigue and lubrication wear.

Typically, the camshaft is installed between the cylinder block and the cylinder head, which are components of the vehicle engine, and the number of valve cams equal to the number of valves is arranged to open and close the valves. In other words, the valve cam holding the cam nose in the same number as the intake valve and exhaust valve of the engine is arranged at the right position and angle so as to be supported by a bearing on the side or the top of the crankcase in parallel with the crankshaft. The same camshaft is also equipped with an eccentric cam for driving a fuel pump and a helical gear for driving a distributor or oil pump.

And even if the curve of the surface of the valve cam including the cam nose is slightly changed, the opening and closing times of each valve and the lift are different, which greatly affects the performance of the engine. It is desirable to.

Such a cam shaft is coaxially installed with a timing sprocket so as to be connected to the crank shaft of the engine as a timing belt so that the rotational force of the crank shaft can be transmitted to the cam shaft, and the locker in close contact with the valve cam according to the rotation of the cam shaft. It allows the arm to open and close multiple intake and exhaust valves, as well as to operate each device associated with it.

On the other hand, existing camshafts used for internal combustion engines have been made of chilled cast iron, but these cast iron camshafts can no longer satisfy the requirements of continuously pursuing higher engine performance and lighter weight. It became. That is, the conventional camshaft is formed of an integral rod shape by using both the cam and the shaft as the same material, and in this case, a cast iron casting is applied by special steel forging.

In the case of the camshaft manufactured by the small method of cast iron casting, it is necessary to harden the nose surface of the valve cam which is strongly rubbed with the rocker arm or the tappet, so that the high frequency quenching of the casting, remelting casting, and nodular graphite casting is performed. There is a problem that must be subjected to heat treatment through a variety of methods, such as Osten wave treatment.

And the cast iron cast camshaft is heavy in the situation where fuel efficiency improvement and high speed and high output are required. Therefore, it is necessary to increase the vehicle fuel consumption and increase the number of valves for high speed and high output.In this case, the gap between the cam and the cam is narrow. There are many defects in casting defects, the wear resistance of the cam surface is poor, and the corrosion resistance is poor. In addition, cast iron casting camshaft is a representative 3D industry due to the manufacturing method of the manufacturing method, the defect rate is high, and automation is difficult, which has the disadvantage of low productivity.

Therefore, the necessity of developing the camshaft through the new construction method that can compensate for the shortcomings of the existing integrated cast iron casting camshaft and cope with the multi-valve according to the optimization of the engine performance and the light weight of the engine, and excellent wear resistance. .

Meanwhile, a method for manufacturing a cam shaft by a prefabricated method has been proposed. Prefabricated methods include a diffusion bonded hollow camshaft manufacturing method or a mechanically assembled camshaft manufacturing method.

First, the method of manufacturing the diffusion bonded hollow camshaft, in the camshaft component, the valve cam is formed of metal powder, and then preliminary presintering is performed at about 1,000 ° C. The sintering cam is diffusion bonded, and the journal dam, front piece, rear piece, etc. is a metal joining method of copper bonding. Next, the method of manufacturing a mechanically assembled camshaft includes a method of press-fitting and fixing a camshaft component to a hollow tube by mechanical friction or a manufacturing method of manufacturing a camshaft component by assembling plastic injection between components.

The hollow camshaft has the advantage of being about 30% lighter than the cast iron cast camshaft, but the manufacturing process is complicated and there are many variables in the manufacturing conditions, causing problems in always producing a large quantity of a constant product. In other words, Toring-Ton of the United States and Presta of Europe are producing some camshafts using a prefabricated method, and Nippon Piston Ring (NPR) of Japan is also a prefabricated camshaft. Produces.

However, Toring-Ton of the United States applies the expansion method, and in Europe, Presta adopts the press-in method, which results in the detachment of the cam due to the low coupling force and the deterioration of wear characteristics significantly depending on the heat treatment conditions. In addition, the camrose has a variety of problems, such as the production is possible only when the thickness of 5mm or more.

In particular, the prefabricated camshafts produced by Nippon Piston Ring (NPR) of Japan are steel tubes with light weight in sintered valve cams with improved wear characteristics in order to meet the requirements that conventional cast iron camshafts could not satisfy. Hollow sintered camshaft combined.

In other words, the prefabricated camshaft using the sintering agent cam by using the powder metal (Power Metal) is hollow by the steel pipe shaft, and can be applied to a narrow cam, which is difficult to be small by the casting method or the forging method. In addition to the reduction in width, the design freedom of the component shape and the material selection freedom are large, and the cam can be freely spaced between the cams.

In addition, PFC1, PFC2, PFC4, etc., which are widely used as sintering cam material of hollow sintered camshaft, have high hardness carbide of chromium (Cr) homogeneously dispersed in bainite matrix structure, resulting in excellent pitch and wear resistance under high surface pressure. Is showing. Therefore, the hollow sintered camshaft has the advantages of low investment cost and environment-friendly, and the process is simplified to reduce the defect rate and cost. In addition, it is possible to ensure high durability by forming a composite carbide, and because it is a hollow type, there is an advantage that it can be reduced by more than 30% compared to cast iron.

As such, hollow sintered camshafts have the advantage of greater design freedom in addition to the advantages of being lighter in weight, and as the multi-valve or miniaturization of the engine progresses in recent years, adoption of the cam sintering has been strongly anticipated. However, the above hollow sintered camshaft has been accompanied with various difficulties in its assembly because the cam must be assembled in phase when the cam is coupled to the shaft.

In addition, in the case of the camshaft currently used, the shaft serves not only as a structural member for supporting the cam and transmitting rotational force but also as a channel for delivering engine oil to the journal part, but since it uses an extruded steel tube, There was a limit to reducing the size of the inner diameter of the. For example, when the diameter of the outer diameter is 26 mm, it is almost impossible to pull out the diameter of the inner diameter to 13 mm or less, and in this case, the weight reduction effect is lost.

Therefore, during cold start, the oil supply is delayed from the oil pan located at the bottom of the engine to the camshaft, thus lubrication-free wear is in progress, and this wear has the greatest influence on the life of the camshaft.

On the other hand, in order to achieve high output efficiency of the engine, efforts have been made to increase power by lightening the driving parts of the engine and reducing the moment of inertia to realize high RPM, which has been mainstream until the early 90s. As described above in the steel camshaft, the development of the hollow sintered camshaft using the powder cam and the steel tube may be the same as the background. As a result, in the future, it is required to develop a high-performance camshaft that is lighter in weight and can overcome wear at cold start and has a competitive price.

In this regard, a technology related to "lightweight aluminum camshaft and its manufacturing method" has been recently researched and filed by the applicant (Application No. 10-2004-0071282). In other words, in the cam shaft manufacturing method comprising a cam portion arranged in the same number as the number of valves to open and close the intake and exhaust valves of the engine and a shaft portion (Journal portion) for mounting the cam portion, The cam part is separately manufactured by the cam pieces, and the separately manufactured cam pieces are inserted into the mold, and then the molten aluminum alloy is injected into the mold by the aluminum casting method, so that these cam pieces and the shaft part (journal part) are inserted. By integrally molding, a lightweight aluminum camshaft was constructed.

The lightweight aluminum camshaft composed of this manufacturing method provides a lighter camshaft than the hollow sintered camshaft, and improves the durability of the engine and reduces the camshaft by minimizing lubrication-free wear that occurs during cold start in the existing engine. By reducing the moment of inertia by the high RPM of the engine, the engine power improvement and low fuel consumption can be realized.

However, the lightweight aluminum camshaft of such a manufacturing method has a problem in that the coupling portion between the shaft portion and the campiece is weak when the campiece is inserted into the aluminum shaft and inserted through the casting method. That is, in the process of joining the iron cam piece and the aluminum shaft part by the insert method through the casting method, there is a problem in that the bonding force is weakened due to the difference in thermal expansion coefficient (aka, shrinkage rate) according to the material difference between the cam piece and the shaft part. .

Accordingly, the present invention is to meet the development needs of the new high-performance camshaft as described above, and to provide a camshaft lighter than the hollow sintered camshaft, a cam piece made of a separately produced iron (Fe) material cam Piece) and the shaft part (journal part) formed of aluminum (Al) alloy or heat-resistant magnesium (Mg) alloy material, which is a lightweight metal, are inserted into a mold by a casting method in the process of manufacturing a lightweight camshaft for a vehicle. In order to prevent the coupling force from weakening due to the difference in thermal expansion coefficient (aka, shrinkage rate) according to the material difference between the cam piece and the shaft part, the thermal expansion characteristic can be improved by changing the shape structure of the coupling part of the cam piece and the shaft part. The purpose is to provide a lightweight aluminum camshaft coupling structure used.

Lightweight camshaft coupling structure using the thermal expansion characteristics of the present invention for realizing the above object, the cam portion arranged in the same number as the number of valves for opening and closing the intake and exhaust valves of the engine, and the cam portion It consists of a cam shaft made of a shaft (Shaft; journal portion), the cam portion is made of steel campieces separately, the light weight melted through a casting method after inserting the separately produced campieces into a mold In constructing a lightweight camshaft in which the campieces and the shaft portion (journal portion) are integrally formed by injecting metal, the thermal expansion coefficient of the iron campiece and the shaft portion made of aluminum alloy or heat-resistant magnesium alloy, which is a lightweight metal, Shrink reinforcement part is formed on the cam piece in order to prevent the weakening of the binding force due to the shrinkage at the joining site according to the difference. It is characterized in that the technical relationship between the cam piece and the shaft portion is integrally coupled as the reinforcing fastening portion is formed by the injection of lightweight metal melted into the shrinkage reinforcement portion.

Particularly, when the cam pieces and the shaft part are integrally formed in the mold, the cam pieces and the shaft part are formed to be larger than the diameter of the shaft part for increasing the bonding strength at the joint part of the cam pieces and the shaft part. The joint of the reinforcing rib form is molded to have.

In addition, the reinforcing reinforcement portion on the cam piece has a circular hole shape formed in plurality in close proximity to the shaft hole formed in the center portion of the cam piece, the reinforcing fastening portion of the shaft portion is a lightweight metal melted with respect to the reinforcing reinforcement portion of the through hole shape The injection molding is integrally formed to form a structurally improved coupling structure due to shrinkage characteristics due to the difference in thermal expansion coefficient between the campfire and the shaft portion.

In addition, the contraction reinforcement portion on the campiece has a long hole shape formed by grooves extending toward the inner wall of the campiece in the shaft hole formed in the center portion of the campiece, and the reinforcing fastening portion of the shaft portion is a lightweight metal melted with respect to the contraction reinforcement portion of the long hole shape. It is injected and integrally molded. That is, the reinforcing fastening portion of the cam piece and the reinforcing fastening portion of the shaft portion have a shape structure corresponding to each other, and the shape of the reinforcing reinforcing portion and the reinforcing fastening portion of the cam piece is made of aluminum alloy or heat-resistant magnesium alloy, which is a lightweight metal, and a lightweight metal. Any shape may be used as long as it has a shape structure that can compensate for the difference in shrinkage at the joint according to the difference in thermal expansion coefficient (aka, shrinkage) of the shaft.

In particular, a lightweight camshaft using different physical properties of the thermal expansion coefficient of the present invention inserts a cam piece of iron material into a mold, and injects an aluminum alloy or a heat-resistant magnesium alloy, which is a molten lightweight metal, into the campiece and the lightweight alloy. In order to join the shaft portion of the material, it is preferable to use any one of a casting method such as a die casting method, a squeeze casting method, and a semi-solid casting method.

As described above, according to the lightweight camshaft coupling structure using the thermal expansion characteristics of the present invention, the cam-shaft of the cam shaft and the shaft portion made of aluminum alloy or heat-resistant magnesium alloy of lightweight metal alloy By integrally forming through, it has the advantage that can be reduced by at least 30% compared to the conventional hollow sintered camshaft, can be provided at a low price while having high durability and rigidity.

In particular, the cam piece has a reinforcing reinforcing part on the cam piece so as to prevent the coupling force from weakening due to the difference in thermal expansion coefficient (aka, shrinkage rate) according to the material difference between the cam piece and the shaft part. There is an effect that can greatly improve the bonding force by changing the shape structure of the coupling portion of the piece and the shaft portion. Furthermore, an advantage of realizing various effects that can be achieved through the manufacturing method of the lightweight aluminum camshaft described in the application No. 10-2004-71282 filed by the present applicant can be provided.

In addition, when the lightweight camshaft of the coupling structure using the thermal expansion coefficient difference characteristics between the components according to the present invention is used, the durability of the engine is improved by minimizing the lubrication-free wear occurring during cold start in the engine and the inertia by reducing the camshaft Moment reduction, as well as high engine RPM (RPM) of the resulting engine is expected to provide an effect that can be implemented to improve the engine output and low fuel consumption.

Hereinafter, with reference to the accompanying drawings of the preferred embodiment of the configuration principle for a lightweight camshaft coupling structure using the thermal expansion characteristics of the present invention will be described in detail.

First of all, in describing the camshaft coupling structure of the present invention, the camshaft coupling structure of the present invention can increase the coupling force between components made of different materials while reducing weight by using different thermal expansion characteristics between the shaft portion and the cam portion constituting the camshaft. As the present invention adopts the manufacturing method of the light camshaft previously filed as it is to be described with the description.

First, as shown in Figs. 1 and 2, the lightweight camshaft 1 according to the present invention is similar to the conventional cast iron cast camshaft or hollow sintered camshaft, such as the number of valves to open and close the intake and exhaust valves of the engine. It consists of the cam part 2 arrange | positioned by the number and the shaft part 3 (shaft, what is called a journal part) which mounts the said cam part 2. However, in the present invention, the shaft portion 3 constituting the camshaft 1 is made of aluminum alloy or heat-resistant magnesium alloy, especially among lightweight metals, so as to achieve relatively lighter weight than the conventional hollow sintered camshaft. .

That is, the lightweight camshaft coupling structure of the present invention using different coefficients of thermal expansion between components, the cam portion (2a) is separated separately by the production method of the sintering agent powder cam using a metal powder commonly known as The cam pieces 2a, which are separately manufactured, are inserted into the mold 4, and then integrally formed with the shaft part 3 made of aluminum alloy or heat-resistant magnesium alloy, which is a lightweight metal melted through a casting method.

At this time, since the cam piece 2a forming the cam part 2 is manufactured separately in the form of a sintering agent powder cam or a forged cam, which has been previously introduced, the cam piece 2a has characteristics to be already provided as the cam shaft 1 in the wear and corrosion resistance part. It was confirmed to have enough. In particular, the shaft portion 3 of the lightweight camshaft 1 of the present invention is based on an aluminum alloy of lightweight metal, but heat-resistant magnesium which can increase the bonding strength between the cam portion 2 and the thermal expansion characteristics of iron material It may be optionally applied as long as it is a lightweight metal material including an alloy.

As such, the cam piece 2a of the lightweight camshaft 1 of the present invention is preferably manufactured by a powder cam manufacturing method using powder metal, which is known to be more preferable in terms of wear resistance and corrosion resistance, but is not limited thereto. In addition to the powder cam manufacturing method can be produced in the form of forging cam by forging commonly known.

The lightweight camshaft 1 according to the present invention is made of a lightweight metal alloy material melted on the campiece 2a made of iron in the process of manufacturing the campiece 2a, as shown in FIGS. 6A to 6C. In the process of injecting the shaft part 3 to each other, the shrinkage rate is different at the coupling part due to the difference in the coefficient of thermal expansion, thereby changing the shape of the existing campiece already introduced in advance to prevent the mutual coupling force from dropping. It has its features. That is, the shape structure of the coupling portion is changed so that the shape of the portion where the cam piece 2a of the iron material and the shaft portion 3 of the alloy of the lightweight metal are coupled in consideration of the shrinkage difference is mutually complemented.

In more detail, as shown in the first embodiment of FIG. 4 and the second embodiment of FIG. 5, the coefficient of thermal expansion of the cam piece 2a made of iron and the shaft part 3 made of a light metal material is known. Shrinkage reinforcement parts 7a and 7b are formed on the cam piece 2a to prevent weakening of the bonding force due to shrinkage at the coupling part according to the shrinkage rate difference, and melt into the shrinkage reinforcement parts 7a and 7b. As the lightweight metal is injected and the reinforcing fastening portions 8a and 8b are formed in the shaft portion 3, the cam piece 2a and the shaft portion 3 are integrally coupled to each other.

In particular, in the first embodiment of Fig. 4, the contraction reinforcing portion 7a on the cam piece 2a is moved toward the inner wall of the cam piece 2a from the circular shaft hole 9a formed at the center of the cam piece 2a. It forms an extended recessed long hole shape, and the reinforcing fastening part 8a of the shaft part 3 has a coupling structure in which molten lightweight metal is injected into the long hole-shaped shrinkage reinforcing part 7a and integrally molded. At this time, the reinforcing reinforcement portion 7a of the long hole shape is preferably arranged in at least one form at a predetermined interval in the shaft hole (9a).

According to such a coupling structure, the reinforcing fastening of the shaft portion 3 which is melt-injected with aluminum alloy or heat-resistant magnesium material, which is a lightweight metal, in the shrinkage reinforcing portion 7a formed in the groove wall of the iron cam piece 2a in the form of a long hole. The part 8a is coupled to the bar 8a, even though the shaft part 3 of the light-weight metal solidified by being injected into the shaft hole 9a of the cam piece 2a contracts with the cam piece 2a by contraction. Since the contraction reinforcement portion 7a of the long hole shape and the reinforcement fastening portion 8a fused and melted thereto are firmly coupled to each other regardless of the shrinkage rate, the coupling force is structurally prevented from weakening.

In the second embodiment of FIG. 5, unlike the first embodiment of FIG. 4 described above, the contraction reinforcing portion 7b on the cam piece 2a has a small circular hole shape instead of a long hole shape. That is, it has a contraction reinforcement portion 7b in the form of a hole penetrating relatively smaller than the shaft hole 9b around the circular shaft hole 9b formed in the center portion of the cam piece 2a. The reinforcing fastening part 8b is also injected into the shrinkage reinforcing part 7b of the cam piece 2a in the shape of a hole as in the first embodiment, and is integrally molded while holding each other with the difference in the coefficient of thermal expansion. It can be firmly integrated together while giving.

According to the coupling structure due to the difference in the coefficient of thermal expansion between the components, the cam piece because the reinforcing fastening portion (8b) of the lightweight metal is injected into the shrinkage reinforcing portion (7b) of the hole shape of the metal (iron) material is coupled to the cam piece Even if the coupling portion of the lightweight metal shaft portion 3 injected into the shaft hole 9b of (2a) solidifies and contracts with the cam piece 2a by contraction, these contraction reinforcing portions 7b and reinforcing fastening portions 8b. In order to be firmly coupled to hold each other regardless of the shrinkage ratio, it is possible to prevent the weakening of the coupling force in advance, as well as to achieve a more robust coupling structure than the shape structure of the first embodiment. At this time, the cam piece (2a) is formed in the inner wall of the reinforcing reinforcement portion (7b) formed in a number is preferably wrapped around the shaft hole (9b) in the center and is arranged round.

Furthermore, as shown in the first and second embodiments, the reinforcing reinforcement portions 7a and 7b formed on the cam piece 2a made of iron and the shaft portion 3 made of aluminum (or heat-resistant magnesium) alloy material, which is light metal, are used. The reinforcing fastening portions 8a and 8b to be formed have a shape structure corresponding to each other, and the shape of these shrinkage reinforcing reinforcing portions 7a and 7b and the reinforcing fastening portions 8a and 8b are different from the cam piece 2a made of iron. Any shape may be used as long as it is a shape structure that can compensate for the difference in shrinkage on the joint according to the difference in thermal expansion coefficient (aka, shrinkage) of the shaft portion 3 of the lightweight metal.

On the other hand, when the campieces 2a and the shaft portion 3 are integrally molded in the mold 4, the shaft portion for increasing the bonding strength at the junction of the campieces 2a and the shaft portion 3 It is preferable to form a joining portion 3a in the form of a reinforcing rib having a structure surrounding the sides of the respective cam pieces 2a while being formed larger than the diameter of (3).

That is, the joining portion 3a has a structure surrounding the side of the cam piece 2a, so that the reinforcing fastening portions 7a and 7b of the cam piece 2a and the reinforcing fastening portions 8a and 8b of the shaft portion 3 are formed. ) Serves to prevent exposure to the outside, as well as to prevent the front and rear movement of the cam piece (2a) in the shaft portion (3) serves to increase the binding force as a result.

The present invention is to design the cam piece (2a) to have the shape of the coupling structure as described above in the joining method of the cam portion 2 and the shaft portion 3, the hollow steel tube shaft and the small through a conventional sintering furnace Compared to the sintering process of diffusion bonding sintering powder cams, the manufacturing process is simplified by the present applicant using a casting method such as a die casting method, which is relatively easy and precise. Can be.

For reference, a method of manufacturing a light camshaft for achieving a light camshaft coupling structure for a vehicle using a difference in coefficient of thermal expansion according to the present invention will be described with reference to specific features of the light camshaft manufactured through the manufacturing method. It mainly consists of material preparation process, casting process, oil hole processing process and finishing process.

<1> Material Preparation Process

First, the material preparation process is a step before preparing inserts into the mold 4 shown in FIG. 6A by preparing and separately preparing the cam pieces 2a corresponding to the cam portions 2 of the cam shaft 1. At this time, the separately produced cam pieces (2a) is to use the sintered by molding in the form of a powder cam using a powder metal using a method of manufacturing a cam of the hollow sintered camshaft of the conventional prefabricated camshaft manufacturing method.

In particular, since only the cam piece 2a is separately sintered and manufactured in the sintering furnace according to the present invention, the powder cam and the steel tube are charged together in the sintering furnace when the conventional hollow sintered camshaft is manufactured. Since the amount can be increased, there is an advantage to improve the charging efficiency of the sintering furnace. Of course, in addition to the powder cam can also be used in the form of forging cam produced by forging.

In this case, it is preferable that the cam pieces manufactured separately use a metal and an alloy capable of cold forming or heat treatment. That is, the chemical composition, mechanical properties, and the like with respect to the material of the cam piece are illustrated in Tables 1 and 2.

TABLE 1

Material name (symbol) Chemical composition (wt%) C Si Mn P Ni Cr Mo S Etc 4% Cr 1.4-2.8 0.5-1.5 1.0 ↓ 0.3 ~ 0.8 0.5-2.5 2.5 ~ 5.5 0.5-2.0 - 1.0 ↓ 8% Cr 2.3 ~ 3.0 0.5-1.5 1.0 ↓ 0.2-0.7 1.8 ~ 2.4 1.0-3.0 1.0-3.0 - 1.0 ↓ 12% Cr 1.5 ~ 3.0 0.5 ~ 1.2 1.0 ↓ 0.3 ~ 0.8 0.5-2.0 0.5-2.0 0.5-2.0 - 1.0 ↓ S50 ~ 58C 0.47-0.61 0.15-0.35 0.60-0.90 0.03 ↓ - - - 0.035 ↓ 0.03 ↓ SCM440 0.38-0.43 0.15-0.35 0.6-0.85 0.03 ↓ - 0.9-1.2 0.15-0.3 0.03 ↓ 0.03 ↓ SUJ2 0.95-1.1 0.4-0.7 0.9-1.15 0.03 ↓ 0.25 ↑ 0.9-1.2 0.1-0.25 0.03 ↓ 0.03 ↓

TABLE 2

Material name (symbol) Mechanical properties Manufacture process Hardness (HRC) Density (g / cm 3) 4% Cr 52-63 7.45 ↑ Powder / sinter 8% Cr 52-63 7.45 ↑ Powder / sinter 12% Cr 52-63 7.45 ↑ Powder / sinter S50 ~ 58C 50-60 7.50 ↑ minor SCM440 50-60 7.50 ↑ minor SUJ2 50-60 7.50 ↑ minor

<2> casting process

First, the cam pieces 2a prepared through the material preparation process are inserted into the mold 4 designed and manufactured according to the camshaft structure, as shown in FIG. 6B. At this time, the cam pieces 2a are sequentially inserted into the position to be formed by the shaft portion 3 in the mold 4 according to the position set according to the arrangement of the cam portion 2.

When the cam pieces 2a are inserted into the mold 4, the aluminum alloy or the heat-resistant magnesium alloy, which is a lightweight metal, is injected in a molten state according to the casting method. At this time, as a casting method, it is preferable to use a casting method using a cold chamber diecasting type die casting equipment, and it is preferable to use atmospheric and vacuum or horizontal and vertical die casting equipment according to the shape and required characteristics. Do.

In particular, the casting pressure (Casting Pressure, usually referred to as "injection pressure") of the die casting according to the die casting method is preferably in the range of 60 ~ 1300kgf / ㎠, die casting casting speed (Injection Velocity, usually "injection speed" It is preferable to carry out within 0.5-3.0 kPa range. In addition, the melt temperature of die casting is preferably 600 ~ 800 ℃.

Of course, as a casting method of the light alloy, in addition to the above-described general die casting method, a gravity mold casting method, a squeeze casting method, and a semisolid casting method may be used. At this time, in the case of the gravity mold casting method, it is preferable to maintain the molten metal temperature of about 600 ~ 800 ℃.

In addition, the injection pressure in the squeegee casting method corresponding to the pressure casting is 200 ~ 1600kgf / ㎠, the injection speed is 0.5 ~ 2.0㎧, the melt temperature is preferably about 600 ~ 800 ℃, the injection pressure in the semi-solid casting method 50-500 kgf / cm <2> of silver, the injection speed of 0.5-2.0 Pa, semi-solid (semi-melting) temperature of 450-650 degreeC are preferable.

The molten aluminum alloy (or heat-resistant magnesium alloy) is injected into the mold 4 under the above conditions, and the campieces 2a and the shaft portion 3 are integrally formed so that casting is completed. The shaft 1 is taken out in the mold 4 as shown in FIG. 6C to complete the casting process.

At this time, as a result of examining the mechanical properties of the prototype of the lightweight camshaft (1) taken out in the same manner as described above, the tensile strength of the product reaches 200 ~ 350MPa, the product strength (0.2%) 180 ~ 300MPa The elongation of the product reached 1-15%.

In particular, when the cam pieces 2a and the shaft portion 3 are joined to each other by being cast and molded by an aluminum (or heat-resistant magnesium) alloy in the mold 4, these cam pieces 2a and the shaft portion 3 In order to improve the strength of the joint at the joint between the (3), a structure in which the joint 3a extending from the side of each cam piece 2a and having a diameter larger than the diameter of the shaft 3 can be formed. Equipped. That is, when a lightweight camshaft in which the campieces 2a and the shaft portion 3 are joined to each other through a casting process is cast and molded, the side surfaces of the campieces 2a are larger than the diameter of the shaft portion 3. The joint 3a having a large diameter is provided.

The joining portion 3a is a structure that cannot be formed by a hollow sintered camshaft manufacturing method for sintering a powder cam to a conventional steel tube, and the manufacturing method according to the molding of lightweight metal using the thermal expansion coefficient difference of the present invention. It is a structure that can be represented by characteristics. That is, since the joint portion 3a can be sufficiently implemented to have a structure surrounding the side of the cam piece 2a on the mold 4, the cam pieces 2a and the shaft portion 3 in the lightweight cam shaft to which the present invention is applied. It will have a structural feature to increase the bonding strength of.

<3> Oil Hole Process

Subsequently, when the lightweight camshaft 1 is cast through the die casting method, the front piercing and the oil hole 5 required for the structure of the camshaft 1 are processed. In particular, the lightweight camshaft 1 taken out through the casting process has a solid camshaft structure, and the oil is drilled through the center of the shaft portion 3 of the camshaft 1 in the oil hole process. Forming the hollow 6 together with the processing of the grooves 5 makes it possible to change the solid camshaft into the shape of the hollow camshaft, which makes it possible to provide a lighter camshaft 1.

Of course, the oil groove 5 inserts a core (not shown) in the form of an oil groove 5 when injecting the molten lightweight metal into the shaft portion 3 on the mold 4 through the core method in addition to the drill processing method. After that, the oil groove 5 may be formed by removing the core.

On the other hand, when using a steel tube in the conventional hollow sintered camshaft as described above, due to the characteristics of the steel tube produced through the drawing process, the hollow diameter can not be processed to a predetermined size or less, the oil filling time (Oil Filling Time) of During cold start due to the problem, the oil supply from the oil pan located at the bottom of the engine to the camshaft may be delayed and oil-free wear may proceed. To solve this problem, the oil pump capacity has to be increased, but according to the present invention, In the case of the lightweight camshaft (1), the oil groove (5) and the hollow (6) are processed through a separate drill or core method, so that the size of the hollow (6) diameter is satisfied while the light supply condition is satisfied. It will have the advantage that it can be processed to the size with the optimum conditions necessary for the oil filling time.

<4> finishing process

After the oil hole 5 or the like is processed in the cast-molded lightweight camshaft 1, the cam part 2 is also roughed and ground through a common technique commonly known in the journal for a more precise finish. Grinding gives a more precise finish.

Through such roughing and grinding finishing process, the final product of the lightweight aluminum camshaft will be released. Of course, a separate heat treatment may be performed to improve characteristics such as better durability in the finishing process and to modify the surface of the cam part.

1 and 2 are a perspective view and a cross-sectional view of the coupling state for a lightweight aluminum camshaft.

Figure 3 is a perspective view of the coupling state showing the camshaft main portion of the lightweight metal coupled to the campiece and the shaft portion different thermal expansion coefficient in accordance with the present invention.

Figure 4 and Figure 5 is an exploded perspective view showing a coupling form of the cam piece and the shaft portion as the first and second embodiments of the present invention, respectively.

6A to 6C are views sequentially showing a manufacturing process in which a lightweight aluminum camshaft is configured, FIG. 6A is a state before inserting the campieces into a mold, and FIG. 6B is a state where the campieces are inserted into the mold. 6c is a manufacturing process drawing showing the state where the aluminum camshaft was taken out after the aluminum casting process.

Explanation of symbols on the main parts of the drawings

1: Camshaft 2: Cam part

2a: campiece 3: shaft portion

3a: junction 4: mold

5: oil groove 6: hollow

7a, 7b: Shrink reinforcement part 8a, 8b: Reinforcement part

9a, 9b: shaft hole

Claims (5)

The cam pieces 2a of the cam part 2 are separately manufactured, and the cam pieces 2a manufactured separately are inserted into the mold 4, and then molten lightweight metal is injected through a casting method. In constructing a lightweight camshaft for integrally forming these campieces 2a and the shaft portion 3, Prevents the weakening of the coupling force due to the shrinkage at the coupling site due to the difference in thermal expansion coefficient (aka, shrinkage rate) of the cam piece 2a of the iron material and the shaft portion 3 of the aluminum alloy or the heat-resistant magnesium alloy, which is a lightweight metal. Shrinkage reinforcement portions 7a and 7b are formed on the cam piece 2a so that lightweight metal melted into the shrinkage reinforcement portions 7a and 7b is injected to reinforce the fastening portion 8a to the shaft portion 3. , 8b) lightweight camshaft coupling structure using the thermal expansion characteristics, characterized in that integrally configured as formed. The method according to claim 1, When the campieces 2a and the shaft portion 3 are integrally molded in the mold 4, the shaft for increasing the bonding strength at the junction of these campieces 2a and the shaft portion 3 Formed larger than the diameter of the portion 3, lightweight camshaft coupling using a thermal expansion characteristics characterized in that the joint portion 3a of the reinforcing rib form having a structure surrounding the sides of each of the cam pieces (2a) is molded rescue. The method according to claim 1 or 2, The reinforcing reinforcement portion 7a on the cam piece 2a has a circular hole shape formed through the inner wall of the shaft portion 9a close to the shaft hole 9a formed in the center portion of the cam piece. Reinforcing fastening portion (8a) is a lightweight camshaft coupling structure using a thermal expansion characteristics, characterized in that the molten lightweight metal is injected into the shrinkage reinforcing portion (7a) of the hole shape integrally molded. The method according to claim 1 or 2, The reinforcing reinforcement portion 7a on the cam piece 2a extends toward the inner wall of the cam piece 2a in the shaft hole 9b formed at the center of the cam piece to form a long hole shape. Reinforcing fastening portion (8a) is a lightweight camshaft coupling structure using the thermal expansion characteristics, characterized in that the injection of the lightweight metal to the reinforcing reinforcement portion (7a) of the long hole shape. The method according to claim 1, Insert the cam piece 2a made of iron into the mold 4, and inject the molten lightweight metal aluminum alloy or the heat-resistant magnesium alloy into the cam piece 2a and the shaft 3 made of the light metal material. Lightweight camshaft coupling structure using thermal expansion characteristics, characterized in that any one of the casting method, such as die casting method, squeeze casting method, semi-solid casting method to apply.

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