KR100957074B1 - Crank-shaft for an air compressor and method of manufacturing the same - Google Patents

Abstract

It is a technical problem of the present invention to provide a crank shaft for an air compressor which can renew the shape of the crank and improve the dynamic stability together with the hollow shaft. To this end, the crankshaft for the air compressor of the present invention includes a hollow shaft and a disc-shaped crank formed with an insertion hole fixed to the outer circumferential surface of the shaft, the connecting rod being connected to the outer circumferential surface thereof, and Is formed in the crank, but is formed at a portion spaced from the center of the crank by a predetermined interval so that the crank rotates eccentrically when the shaft is rotated.

Air, Compressor, Crank, Shaft, Disc Shape

Description

Crankshaft for air compressor and manufacturing method therefor {CRANK-SHAFT FOR AN AIR COMPRESSOR AND METHOD OF MANUFACTURING THE SAME}

The present invention relates to a crankshaft for an air compressor, and more particularly, to a crankshaft for an air compressor and a method for manufacturing the same, which can improve the dynamic stability by reducing the weight and simplify the manufacturing process.

Generally, air compressors are used in diesel engine vehicles such as buses, trucks, special vehicles, and industrial vehicles, and various devices requiring compressed air, such as brake brakes, air suspensions, and doors, which are shock absorbers. To provide compressed air.

Specifically, as shown in FIG. 1, the air compressor includes a solid shape rotatably supported by the body 10 and the body 10 and including a crank pin 23 and a crank arm 24. A solid crank shaft 20, a connecting rod 30 rotatably connected to the crank pin 23, a piston 40 hinged to the connecting rod 30, The cylinder 10 includes a cylinder 50 which surrounds the piston 40 and a compressed air reservoir 60 provided on the upper end of the cylinder 50.

Therefore, when the crankshaft 20 receives the rotational force by the external force, the piston 40 through the crank pin 23 and the connecting rod 30 is up and down reciprocating motion. As such, the air in the cylinder 50 flows into the compressed air reservoir 60 and the air in the compressed air reservoir 60 is compressed through the reciprocating motion of the piston 40. As a result, the compressed air of the compressed air reservoir 60 needs this and is sent to various devices (not shown).

Hereinafter, the crankshaft 20 is demonstrated concretely.

The crankshaft 20 includes a shaft 21 having a solid shape and a crank 22. The crank 22 also includes a crank pin 23 located eccentrically on the shaft 21 and a crank arm 24 connecting the shaft 21 and the crank pin 23. In particular, the crankshaft 20 is made of a steel material, and is manufactured through hot forging. In addition, the forged crankshaft 20 is turned and ground to have a desired shape.

However, as the shaft 21 is manufactured in a solid shape, the amount of inertia increases due to its own weight, so that the dynamic stability may decrease. In addition, the durability of the air compressor may be degraded due to the decrease in dynamic stability, and the efficiency of the device may be reduced because a large amount of fuel is required to rotate the crankshaft 20 due to the weight of the crankshaft 20. .

Therefore, research to reduce the weight of such a crankshaft 20 has been made continuously.

In particular, in order to reduce the weight of the shaft 21, Korean Patent Laid-Open Publication No. 2003-0045479 (hereinafter referred to as "prior art") is known a technique for making the shaft 21 into a hollow shape.

However, as shown in FIG. 2, this prior art only manufactures the shaft 1 in a hollow shape to reduce the weight, and does not include a technique for reducing the weight of the crank 2. That is, in the prior art, a crank pin 2a for connecting to a connecting rod (see “30” in FIG. 1) is formed to protrude from the crank 2, similarly to the existing crank 22. A counterweight 2b is formed on the outer surface. Therefore, the prior art will be limited in reducing the weight of the crankshaft (3).

In addition, according to the prior art, since the carbon constituting the crank 2 is contained in 0.5% by weight or less based on the weight ratio of the total composition, it was found through experiments that the hardness was not high because sufficient carbide was not formed after sintering. .

In addition, according to the prior art, after welding the shaft (1) and the crank (2) to form a separate oxide film in order to improve the corrosion resistance and abrasion resistance it may take a lot of time and manufacturing cost.

In addition, according to the prior art, as the sintering and welding separately proceed, the manufacturing time and manufacturing cost may be high.

The present invention is to solve the problems of the prior art, the technical problem of the present invention is to provide a crank shaft for an air compressor that can improve the dynamic stability with a hollow shaft by renewing the shape of the crank.

Another technical problem of the present invention is to provide a method of manufacturing a crankshaft for an air compressor that can reduce the production time and manufacturing cost by performing sintering and bonding at the same time.

In order to achieve the above object, the crankshaft for an air compressor according to an embodiment of the present invention is formed of a hollow shaft, and the insertion hole is fixed to the outer peripheral surface of the shaft is formed, the connecting rod is connected to the outer peripheral surface A crank in shape, and the insertion hole is formed in the crank, and is formed at a portion spaced from a center of the crank so that the crank rotates eccentrically when the shaft is rotated.

In addition, in order to reduce the weight of the crank, grooves or holes may be further formed in the portion of the crank except the insertion hole.

The shaft may be made of carbon steel, the crank may be made of an iron-based sintered alloy, and the shaft and the crank may be diffusion-bonded to each other through heat treatment.

For example, the iron-based sintered alloy forming the crank is composed of a ternary alloy of iron (Fe) -carbon (C) -phosphorus (P), and the iron (Fe) -carbon (C) -phosphorus (P) 3 To the base alloy, 1.0 to 3.5% by weight of carbon, 0.3 to 2.5% by weight of phosphorus, and the remaining iron may be added based on the weight ratio of the entire composition.

As another example, the cranked iron-based sintered alloy is composed of a quaternary alloy of iron (Fe) -carbon (C) -chromium (Cr) -phosphorus (P), and the iron (Fe) -carbon (C)- In the quaternary alloy which is chromium (Cr) -phosphorus (P), 1.0-3.5 weight% carbon, 10.0-23.0 weight% chromium, 0.3-2.0 weight% phosphorus, respectively, based on the weight ratio of the whole composition, respectively. Molybdenum (Mo), silicon (Si) and manganese (Mn) of 0.02 to 1.0% by weight and the remaining iron may be added.

On the other hand, the method for manufacturing a crank shaft for an air compressor according to an embodiment of the present invention includes a shaft manufacturing step of manufacturing a hollow shaft, a crank molding step of forming a crank molded body into a disc shape using a metal mixed powder, An assembling step of assembling the shaft and the crank molded body, and assembling the shaft and the crank molded body, and sintering the crank molded body into a crank in a sintering furnace and simultaneously sintering the crank molded body between the shaft and the metal. And a heat treatment step of heat treating the shaft and the crank after the sintering bonding, and a machining step of grinding the outer circumferential surface of the crank after the heat treatment.

In addition, in the crank forming step, the molding density of the metal mixed powder may be 6.0 ~ 7.0 g / cm 3.

In addition, in the crank forming step, a recess or a hole may be formed in the crank to reduce the weight of the crank.

Further, in the sintering bonding step, the sintering bonding atmosphere is a vacuum or non-oxidizing atmosphere, and the sintering bonding temperature may be in the range of 1000 to 1200 ℃.

For example, when the sintering furnace is a vacuum sintering furnace in which vacuum is maintained, in the heat treatment step, nitriding gas may be injected into the vacuum sintering furnace to cool the crankshaft.

As another example, when the sintering furnace is a general sintering furnace in which vacuum is not maintained, in the heat treatment step, the sintering furnace may be heat treated by quenching, carburizing or high frequency.

According to the crankshaft for an air compressor according to an embodiment of the present invention, the crank is formed in a disc shape and has a structure in which a connecting rod is directly connected to the outer circumferential surface of the disc-shaped crank without using a crank pin, and reduces its weight. At the same time as the insertion hole is formed in the crank so that the shaft is fitted, it is possible to significantly reduce the overall weight of the crank shaft with the hollow shaft. Ultimately, the dynamic stability of the shaft can be improved, and the durability of the device can be improved as the dynamic stability is improved. In addition, since the weight of the crankshaft is reduced, less fuel is used to rotate the shaft than in the prior art, so the efficiency of the device can be improved.

In addition, according to the crankshaft for the air compressor according to an embodiment of the present invention, as the groove or hole is formed in the crank, it is possible to further reduce the weight of the crankshaft.

In addition, according to the crankshaft for the air compressor according to an embodiment of the present invention, as the amount of each component of the alloy element constituting the crank is set optimally, wear resistance and friction characteristics can be improved. Ultimately, it is not necessary to form a separate oxide film as in the prior art to improve wear resistance, thereby simplifying the process.

In addition, according to the manufacturing method of the crankshaft for the air compressor according to an embodiment of the present invention, by sintering the crank molded body and at the same time by joining the crank molded body and the shaft can significantly reduce the manufacturing time and manufacturing cost.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

Figure 3 is a cross-sectional view showing a crank shaft according to an embodiment of the present invention, Figure 4 is a side view showing a crank in the crank shaft according to an embodiment of the present invention, and Figure 5 is a V-V cross-sectional view of FIG.

Crankshaft for an air compressor according to an embodiment of the present invention, as shown in Figures 2 and 3, a hollow shaft 110, and a disc shaped crank 120.

First, the shaft 110 will be described in detail with reference to FIG. 3.

The shaft 110 has a hollow shape. Therefore, since the weight of the shaft 110 itself can be significantly reduced, the dynamic stability of the shaft 110 can be improved, and the durability of the device can be improved as the dynamic stability is improved. In addition, since the weight of the shaft 110 itself is reduced, fuel for rotating the shaft 110 is less used than in the related art, and thus the efficiency of the device may be improved. In addition, the shaft 110 may be made of carbon steel. In particular, when the shaft 110 is made of carbon steel, the strength and rigidity of the shaft 110 with respect to the external force (rotation force generated in the engine) can be secured, and the hardenability can be improved during the high frequency heat treatment. The hollow shaft 110 may be manufactured by drawing or the like.

In addition, the carbon steel constituting the shaft 110 may include a carbon component of 0.35 to 0.6% by weight based on the total weight ratio. If the carbon component is less than 0.35% by weight, strength and rigidity are not secured, and if the carbon component is greater than 0.6% by weight, brittleness becomes large, and thus the role of the shaft 110 may not be performed. In particular, when the shaft 110 contains 0.35 to 0.6% by weight of carbon components based on the total weight ratio, intermetallic diffusion bonding with the crank 120 made of the iron-based sintered alloy to be described later may be smoothly performed.

Hereinafter, the crank 120 will be described in detail with reference to FIGS. 3 to 5.

The crank 120 includes an insertion hole 121 that is inserted into and fixed to the outer circumferential surface of the shaft 110 and has a disc shape. The connecting rod 30 is rotatably connected to the outer circumferential surface of the disc-shaped crank 120. In particular, since the connecting rod 30 is directly connected to the outer circumferential surface of the disc-shaped crank 120, a crank pin (see "2a" in FIG. 2) and a crank arm ("2b in FIG. 2") as in the prior art. Are not required separately). Furthermore. The insertion hole 121 of the crank 120 allows the crank 120 to rotate eccentrically when the shaft 110 is rotated, that is, the piston (see "40" in FIG. 6) reciprocates through the connecting rod 30. In order to be able to do so, it is formed in a portion spaced apart from the set interval from the center of the crank 120. In particular, when the shaft is inserted into the insertion hole 121, the weight of the crank 120 can be further reduced due to the insertion hole 121.

Therefore, since the weight of the crank 120 itself can be significantly reduced, the dynamic stability of the crankshaft 100 can be improved, and the durability of the device can be improved as the dynamic stability is improved. In addition, since the weight of the crank 120 itself is reduced, less fuel is used to rotate the crankshaft 100 than in the related art, and thus the efficiency of the device may be improved.

In addition, in order to reduce the weight of the crank 120, a groove 122 or a hole (not shown) may be further formed in a portion of the crank 120 except for the insertion hole 121. In detail, the recess 122 or the hole (not shown) may be formed in a half moon shape concave round toward the insertion hole 121. Particularly, the reason for forming the half moon shape is that the crank 120 has a disc shape and the insertion hole 121 is formed in the eccentric portion, so as to reduce the weight of the crank 120 as much as possible, avoiding the insertion hole 121. to be. Alternatively, the hole (not shown) may have a circular shape as another example.

In addition, the crank 120 may be made of an iron-based sintered alloy for intermetallic diffusion bonding with the shaft 110. In particular, the crank 120 may be required to be more wear-resistant to withstand external forces (rotational force generated in the engine), and may be required to further reduce the friction with the connecting rod 30.

According to this requirement, the crank 120 may be made of an iron (Fe) -carbon (C) -phosphorus (P) ternary alloy, for example, as shown in Examples 1 to 5 of Table 1, and other For example, as shown in Examples 6 to 18 of Table 1, it may be made of iron (Fe) -chromium (Cr) -carbon (C) -phosphorus (P) quaternary alloy. In particular, the big difference between the ternary alloy and the quaternary alloy is in the presence of chromium, depending on the material of the connecting rod 30 rotatably connected to the outer circumferential surface of the crank 120, the ternary alloy is also used or ternary alloy This would be used too. If the material of the connecting rod 30 is of low hardness (for example, aluminum), it is not necessary to include expensive chromium. If the material of the connecting rod 30 is of high hardness (for example, steel), expensive chrome It would be desirable to include.

Crank Chemical Composition division C Cr P Mo Si Mn Fe condition Example 1 2.0 - 1.5 - - - Remainder Good Example 2 2.5 - 1.0 - - - Remainder Good Example 3 3.0 - 0.8 - - - Remainder Good Example 4 1.0 - 0.3 - - - Remainder Good Example 5 3.5 - 2.5 - - - Remainder Good Example 6 1.0 8.8 0.3 0.9 0.4 0.3 Remainder Good Example 7 1.0 10.0 0.5 0.9 0.4 0.3 Remainder Good Example 8 1.5 10.0 0.5 0.9 0.4 0.3 Remainder Good Example 9 2.5 10.0 0.5 0.9 0.4 0.3 Remainder Good Example 10 2.5 10.0 1.0 0.9 0.4 0.3 Remainder Good Example 11 3.5 10.0 2.0 0.9 0.4 0.3 Remainder Good Example 12 1.0 25.0 0.3 0.9 0.4 0.3 Remainder Bad Example 13 1.0 23.0 0.5 0.9 0.4 0.3 Remainder Good Example 14 1.5 23.0 0.5 0.9 0.4 0.3 Remainder Good Example 15 2.5 23.0 0.5 0.9 0.4 0.3 Remainder Good Example 16 2.5 23.0 1.0 0.9 0.4 0.3 Remainder Good Example 17 3.0 23.0 2.0 0.9 0.4 0.3 Remainder Good Example 18 3.5 25.0 2.5 0.9 0.4 0.3 Remainder Bad

First, with reference to Examples 1-5 of Table 1, the characteristic and required value of each component with respect to an iron (Fe) -carbon (C) -phosphorus (P) ternary alloy are demonstrated concretely.

Carbon (C) has a property of improving the wear resistance by forming carbide (carbide, carbide) with other elements and strengthening properties, and is preferably added at 1.0 to 3.5% by weight based on the weight ratio of the entire composition. The critical significance is that when the amount of carbon is less than 1.0% by weight, sufficient carbides are not formed and hardness is not high, and when it is larger than 3.5% by weight, excessive carbide forms, causing brittleness and the final grinding. It was found through experiments that the processing was difficult. In addition, carbon plays a role of lowering the junction temperature by performing a peritectic reaction with phosphorus (P), which is another element constituting the crank 120, which is to be described later. It has been shown through experiments that the shrinkage of the crank molded body during sintering is very large and the deformation amount is large, requiring further processing.

Phosphorus (P) reacts with iron (Fe) and carbon (C) to produce a three-way, three-way reaction reaction liquid phase with a low melting point, and as a result, the shrinkage of the crank molded body increases when the crank molded body is sintered. Has properties that facilitate interdiffusion bonding. It is preferable to add 0.3 to 2.5 weight% based on the weight ratio of the whole composition. The critical significance is that when the phosphorus component is less than 0.3% by weight, the amount of liquid phase appearance is relatively small, and the experiment shows that diffusion bonding between metals with the shaft 110 is inferior, and when the phosphorus component is larger than 2.5% by weight. Due to the large amount of liquid phase appearance, the dimensional precision was reduced and required for further processing, and it was shown through experiments.

Iron (Fe) forms the base of the crank 120, and occupies the rest except chromium and phosphorus.

Hereinafter, with reference to Examples 6-18 of Table 1, the characteristic and required value of each component with respect to an iron (Fe)-chromium (Cr) -carbon (C) -phosphorus (P) quaternary alloy are demonstrated concretely.

Carbon (C) has a property of improving the wear resistance by forming carbide (carbide, carbide) with other elements and strengthening properties, and is preferably added at 1.0 to 3.5% by weight based on the weight ratio of the entire composition. The critical significance is that when the amount of carbon is less than 1.0% by weight, sufficient carbides are not formed and hardness is not high, and when it is larger than 3.5% by weight, excessive carbide forms, causing brittleness and the final grinding. It was found through experiments that the processing was difficult. In addition, carbon plays a role of lowering the junction temperature by performing a peritectic reaction with phosphorus (P), which is another element constituting the crank 120 to be described later, and when larger than 3.5% by weight, the crank molded body due to the excessive liquid phase appearance. It has been shown through experiments that the shrinkage of the crank molded body during sintering is very large and the deformation amount is large, requiring further processing.

Phosphorus (P) reacts with iron (Fe) and carbon (C) to produce a three-way, three-way reaction reaction liquid phase with a low melting point, and as a result, the shrinkage of the crank molded body increases when the crank molded body is sintered. Has properties that facilitate interdiffusion bonding. It is preferable to add 0.3 to 2.0 weight% based on the weight ratio of the whole composition. The critical significance is that when the phosphorus component is less than 0.3% by weight, the amount of liquid phase appearance is relatively small, and the experiment shows that diffusion bonding between the metals and the shaft 110 is inferior, and when the phosphorus component is larger than 2.0% by weight. Due to the large amount of liquid phase appearance, the dimensional precision was reduced and required for further processing, and it was shown through experiments.

Chromium (Cr) has a property of improving the abrasion resistance of the crank 120, it is preferably added in 10.0 ~ 23.0% by weight based on the weight ratio of the entire composition. As a critical significance, when the chromium component is less than 10.0% by weight, the wear resistance is lowered to less than or equal to the minimum required hardness of the crank 120, HRC45, through experiments, and when the chromium component is greater than 23% by weight, It was found through experiments that machining is difficult due to the formation of carbides, and the brittleness increases, and it has been shown through experiments that the wear life of the connecting rod 30 made of aluminum is reduced to reduce the overall life. In particular, Examples 12 and 18 in Table 1 has a chromium component of more than 23.0% by weight and was found to be poor.

As other components, as shown in Examples 6 to 18 of Table 1, molybdenum (Mo), silicon (Si), and manganese (Mn) are added to the crank 120 of the quaternary alloy to improve the hardenability. In particular, molybdenum, silicon and manganese are preferably added at 0.02 to 1.0% by weight, respectively, based on the weight ratio of the total composition. The critical significance, when less than 0.02% by weight did not appear to contribute to the improvement of the hardenability through experiments, and when greater than 1.0% by weight it was shown through the experiments that the improvement of the hardenability compared to the cost.

Iron (Fe) forms the base of the crank 120, and occupies the rest except for carbon, chromium, phosphorus and other components.

Hereinafter, a method of manufacturing the crankshaft 100 for an air compressor according to an embodiment of the present invention will be described in detail with reference to FIG. 7.

7 is a flowchart illustrating a method of manufacturing a crankshaft for an air compressor according to an embodiment of the present invention.

First, a hollow shaft 110 and a disc shaped crank 120 are manufactured (see S10 and S20). The hollow shaft 110 may be manufactured by drawing, and the disc shaped crank 120 is formed of a metal mixed powder. Hereinafter, a process of molding the disc-shaped crank 120 will be described in detail.

Specifically, a molding press (not shown) is used to make the metal mixed powder into the desired crank 120 shape. In addition, the insertion hole 121 is formed in the molded body of the crank 120 so that the molded body of the crank 120 is fitted to the outer circumferential surface of the shaft 110 during the molding process. In addition, in order to reduce the weight of the crank 120 in the molding process, it is possible to form half-moon grooves 122 on both sides of the molded body of the crank 120, another example of the circular shape in the molded body of the crank 120 Holes (not shown) may be formed.

Moreover, it is preferable that the shaping density of the crank 120 is set to 6.0-7.0 g / cm <3>. In a critical sense, if the molding density is less than 6.0 g / cm 3, the molded body of the crank 120 may break when the molded body of the crank 120 is moved for bonding with the shaft 110, and the sintering furnace ( At the same time, when the molded body of the crank 120 is sintered and the crank 120 is bonded to the shaft 110, the sintered density may be lowered to lower the hardness of the crank 120, and the molding density may be 7.0 g. If larger than / cm 3, excessive mold pressure can damage the mold of the molding press.

Thereafter, the molded body of the shaft 110 and the crank 120 is assembled (see S30). Specifically, insert the insertion hole 121 formed in the molded body of the crank 120 on the outer peripheral surface of the shaft 110. In particular, in view of the shrinkage of the molded body of the crank 120 during the sintering bonding process to be described later, as shown in Table 2, the assembly tolerance between the outer diameter of the shaft 110 and the inner diameter (insertion hole) of the molded body of the crank 120 It is preferable to put.

division Example 1 Example 2 Example 3 Example 4 Example 5 crank Outer diameter 75.4 75.4 75.4 75.4 75.4 Molded body Bore 42.5 42.5 42.5 42.5 42.5 Hollow Outer diameter 42.48 42.45 42.4 42.3 42.2 shaft Bore 28.5 28.5 28.5 28.5 28.5 Assembly clearance 0.02 0.05 0.1 0.2 0.3 Junction Good Good Good Good Bad

(Note. Assembly clearance = crank molding inner diameter-hollow shaft outer diameter)

An assembly gap between the inner diameter of the crank 120 molded body and the outer diameter of the shaft 110 is appropriate for the loose fitting amount defined in the general processing, and as shown in Examples 1 to 5 of Table 2, the outer diameter of the shaft 110 is In the case of approximately Φ42 to Φ42.5mm, it has been shown through experiments that it is desirable to have an assembly clearance of 0.02 to 0.2mm. However, although not shown in Table 2, when the outer diameter of the shaft 110 is approximately Φ 50 to 500 mm, which is a large diameter, the assembly gap is relatively increased to have an assembly gap of 0.3 to 1.0 mm.

Thereafter, the assembled shaft 110 and the crank 120 molded body are intermetallic diffusion-bonded in a sintering furnace (not shown) (see S40). At this time, the molded body of the crank 120 is sintered into the crank 120 in a sintering furnace (not shown). Hereinafter, the sintering bonding process will be described in detail.

The atmosphere of the sintering furnace (not shown) may be a non-oxidizing vacuum or reducing atmosphere, the sintering bonding temperature is preferably carried out within the range of 1000 ~ 1200 ℃, this sintering bonding temperature is the formation of the pore liquid phase of Fe-CP Temperature. In particular, the critical significance, when less than 1000 ℃ sintering of the molded body of the crank 120 does not occur sufficiently, the mechanical properties are low and the bonding with the shaft 110 is shown through experiments, and than 1200 ℃ When it is high, it was confirmed that the equipment and operating cost to maintain this temperature is high, and the experiment showed that the dimensional precision is low due to the appearance of liquid phase.

The time required for sintering bonding is related to the size of the product, and if the cross-sectional thickness of the crank 120 molding is approximately 12-25 mm, typically 30 to 90 minutes is suitable, and the cross-sectional thickness of the crank 120 molding is increased. It will be required to lengthen the time required for sintering and bonding. In particular, since the bonding is performed at the same time as the sintering, a separate bonding process is not required, thereby significantly reducing manufacturing time and manufacturing cost. Furthermore, when the crank 120 and the shaft 110 are joined through sintering, the joint has a near-net-shape, so that no later turning operations are required, so that the manufacturing time and manufacturing cost are eliminated. Can be further reduced.

When the sintering and bonding is completed in this way, the shaft 110 and the crank 120 is heat-treated (see S50). Hereinafter, the heat treatment process will be described in detail.

For example, when sintering and bonding are performed in a vacuum sintering furnace (not shown) having a vacuum inside thereof, after the sintering bonding time is completed, the crank 120 sintered by injecting nitrogen gas into the vacuum sintering furnace (not shown). It is preferable to carry out nitrogen cooling so that the surface hardness of) may be HRC45 or more.

As another example, when sintering and joining are performed in a continuous non-vacuum sintering furnace (not shown) with another apparatus, since nitrogen cooling is not possible, to improve the overall strength of the shaft 110 and the crank 120 after sintering joining. It is preferable to carry out heat treatment such as quenching or carburizing. In addition, when a local heat treatment is required, a part of the crank 120 or the shaft 110 may be locally heat treated using a high frequency wave. Particularly, for the high frequency heat treatment, the shaft 110 may preferably include 0.35 to 0.6 wt% of carbon based on the total weight ratio.

After that, when the heat treatment is completed, the outer peripheral surface of the crank 120 is ground (see S60). In particular, since the outer circumferential surface of the crank 120 is a portion that is rotatably connected with the connecting rod 30, the outer surface of the crank 120 is ground to reduce friction with the connecting rod 30.

On the other hand, the crankshaft 100 made in this way can be applied to the air compressor, as shown in FIG.

6 is a longitudinal sectional view showing a state in which a crankshaft for an air compressor according to an embodiment of the present invention is applied to an air compressor.

As described above, the crankshaft for the air compressor and the manufacturing method thereof according to an embodiment of the present invention may have the following effects.

According to the crankshaft 100 for an air compressor according to an embodiment of the present invention, the crank 120 is formed into a disc shape and has a disc shape without using a crank pin (see "2a" in FIG. 2) as in the prior art. The connecting rod 30 is directly connected to the outer circumferential surface of the crank 120, and as the insertion hole is formed in the crank 121 so as to reduce the weight and the shaft 110 is fitted, The overall weight of the crankshaft 100 together with the shaft 110 can be significantly reduced. Ultimately, the dynamic stability of the crankshaft 100 may be improved, and the durability of the device may be improved as the dynamic stability is improved. In addition, since the weight of the crankshaft 100 is reduced, less fuel is used to rotate the crankshaft 100 compared to the prior art, and thus the efficiency of the device can be improved.

In addition, according to the crank shaft 100 for an air compressor according to an embodiment of the present invention, as the groove 122 or the hole (not shown) is formed in the crank 120, the weight of the crank shaft 100 further Can be reduced.

In addition, according to the crankshaft 100 for an air compressor according to an embodiment of the present invention, as the amount of each component of the alloy element constituting the crank 120 is set optimally, wear resistance and friction characteristics can be improved. Ultimately, the process may be simplified since it does not form a separate oxide film as in the prior art for improving wear resistance.

In addition, according to the manufacturing method of the crankshaft 100 for an air compressor according to an embodiment of the present invention, by sintering the crank (120) molded body and at the same time by joining the crank (120) molded body and the shaft (110) Time and manufacturing costs can be significantly reduced.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a longitudinal sectional view showing a general air compressor.

2 is a cross-sectional view showing a crankshaft according to the prior art.

3 is a cross-sectional view showing a crank shaft according to an embodiment of the present invention.

Figure 4 is a side view showing the crank in the crankshaft according to an embodiment of the present invention.

5 is a cross-sectional view taken along line V-V of FIG.

6 is a longitudinal sectional view showing a state in which a crankshaft for an air compressor according to an embodiment of the present invention is applied to an air compressor.

7 is a flowchart illustrating a method of manufacturing a crankshaft for an air compressor according to an embodiment of the present invention.

Explanation of symbols for main parts of the drawings

100: crankshaft 110: shaft

120: crank 121: insertion hole

122: groove 30: connecting rod

Claims (11)

delete delete In the crankshaft for the air compressor, Hollow shaft, and An insertion hole fixed to the outer circumferential surface of the shaft and formed therein, the connecting rod having a circular inner circumferential surface comprising a disc-shaped crank having a circular outer circumferential surface so as to be rotatably connected to the outer circumferential surface, and The insertion hole is formed in the inside of the crank, and is formed in a portion spaced from the center of the crank so that the crank rotates eccentrically when the shaft is rotated, In order to reduce the weight of the crank, grooves or holes are further formed in a portion of the crank except the insertion hole, The shaft is made of carbon steel, The crank is made of an iron-based sintered alloy, and The crank shaft for the air compressor is the crank is sintered at the same time as the shaft and the crank is diffusion-bonded to each other in a sintering furnace. 4. The method of claim 3, The iron-based sintered alloy forming the crank Consisting of a ternary alloy that is iron (Fe) -carbon (C) -phosphorus (P), To the ternary alloy of iron (Fe) -carbon (C) -phosphorus (P), 1.0 to 3.5% by weight of carbon, 0.3 to 2.5% by weight of phosphorus, and the remaining iron are added, based on the weight ratio of the entire composition. Crankshaft for air compressors. 4. The method of claim 3, The iron-based sintered alloy forming the crank Consists of a quaternary alloy that is iron (Fe) -carbon (C) -chromium (Cr) -phosphorus (P), In the quaternary alloy of iron (Fe) -carbon (C) -chromium (Cr) -phosphorus (P), 1.0 to 3.5% by weight of carbon and 10.0 to 23.0% by weight of chromium are based on the weight ratio of the entire composition. And 0.3 to 2.0% by weight of phosphorus, 0.02 to 1.0% by weight of molybdenum (Mo), silicon (Si) and manganese (Mn), and the remaining iron is added to the crankshaft for the air compressor. In the manufacturing method of the crankshaft for air compressors of Claim 3, A shaft manufacturing step of manufacturing a hollow shaft, A crank forming step of forming a crank molded body into a disc shape using a metal mixed powder; An assembling step of assembling the shaft and the crank molded body, Sintering step of assembling the shaft and the crank molded body and then sintering the crank molded body into a crank in a sintering furnace and simultaneously diffusing and joining the crank molded body between the shaft and the metal; A heat treatment step of heat-treating the shaft and the crank after the sintering bonding, and And a processing step of grinding the outer circumferential surface of the crank after the heat treatment. In claim 6, In the crank forming step, the forming density of the metal mixed powder is 6.0 ~ 7.0 g / cm 3 manufacturing method of the crank shaft for the air compressor. In claim 7, In the crank forming step, to form a groove or a hole in the crank to reduce the weight of the crank manufacturing method of the crank shaft for the air compressor. In claim 6, In the sintering bonding step, The sintered bonding atmosphere is a vacuum or non-oxidizing atmosphere, and Process for producing a crankshaft for an air compressor, the sintering junction temperature is in the range of 1000 to 1200 ℃. In claim 6, If the sintering furnace is a vacuum sintering furnace in which vacuum is maintained, In the heat treatment step, injecting a nitriding gas into the vacuum sintering furnace for producing a crank shaft for an air compressor for nitriding cooling. In claim 6, If the sintering furnace is a normal sintering furnace in which vacuum is not maintained, In the heat treatment step, a method of manufacturing a crank shaft for an air compressor which is heat-treated by any one of quenching, carburizing or high frequency.

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