Pin bushing and manufacturing method thereof

Abstract

The present disclosure provides a pin bushing and a method for manufacturing the same. The pin bushing includes a first axial section, a second axial section, and a midsection. The first axial section and the second axial section are axially located at opposite ends of the pin bushing. The midsection is disposed between the first axial section and the second axial section. The midsection has a mid-radial outer portion and a mid-radial inner portion. The first axial section, the second axial section, and the mid-radial outer portion have hardness values ​​greater than the hardness value of the mid-radial inner portion.

Description

[Technical Field]

[0001] The present disclosure relates to truck pin bushings used in the construction machinery field, and more particularly to pin bushings and methods of manufacturing the same. [Background technology]

[0002] Construction machinery such as excavators and bulldozers are typically equipped with tracks. A typical track design includes a sprocket for driving the track, a pin, and a pin bushing positioned around the pin. Because the outer surface of the pin bushing must engage with the sprocket and both ends of the inner surface must engage with the pin, the outer surface of the pin bushing is often subject to wear. To extend the service life of pin bushings, they are typically heat-treated during manufacturing to improve their hardness and wear resistance. However, conventional heat treatment processes involve complex steps, consume a lot of energy, and are expensive.

[0003] Therefore, it would be desirable to provide a pin bushing and method of manufacturing the same to at least partially address the above-mentioned problems. Summary of the Invention

[0004] The purpose of this disclosure is to provide a pin bushing and a manufacturing method thereof that can simplify work steps and reduce costs while ensuring the hardness of the pin bushing.

[0005] According to one aspect of the present disclosure, there is provided a pin bushing including a through hole extending through the pin bushing in the axial direction of the pin bushing, a first axial section, a second axial section, and an intermediate section disposed around the through hole. The first axial section and the second axial section are located at both ends of the pin bushing in the axial direction, and the intermediate section is disposed between the first axial section and the second axial section. The intermediate section has an intermediate radially outer portion and an intermediate radially inner portion in the radial direction of the pin bushing, the intermediate radially inner portion having a radially inward surface that surrounds a portion of the through hole. The hardness values ​​of the first axial section, the second axial section, and the intermediate radially outer portion are greater than the hardness value of the intermediate radially inner portion.

[0006] According to another aspect of the present disclosure, there is provided a method of manufacturing the pin bushing described above, the method comprising the steps of: preforming a pin bushing; subjecting the preformed pin bushing to induction heating; moving the induction coil in an axial direction of the pin bushing; adjusting at least one of a supply speed, an output power, and an induction frequency of the induction coil according to a relative position between the induction coil and the pin bushing so that the first axial section and the second axial section are completely heated from the outside to the inside in the radial direction of the pin bushing, the intermediate radially outer portion is heated, and the intermediate radially inner portion is not heated or is heated to a lesser extent than the intermediate radially outer portion; cooling and quenching the first axial section and the second axial section and the intermediate radially outer portion.

[0007] The solution described above achieves high hardness in the pin bushing's middle radially outer section and both ends, while maintaining a relatively low hardness in the middle radially inner section, by performing a single heating operation with an induction heater. This provides excellent wear resistance for both ends and the middle radially outer section, while improving impact resistance and fatigue life for the middle radially inner section, making the pin bushing suitable for use with medium-sized excavators. Furthermore, this solution simplifies the work steps, significantly reduces costs, and saves manpower and material resources. [Brief explanation of the drawings]

[0008] For a better understanding of the above and other objects, features, advantages and functions of the present disclosure, reference can be made to the preferred embodiments illustrated in the drawings. The same reference numerals in the drawings represent the same parts. Those skilled in the art should understand that the drawings are intended to schematically illustrate the preferred embodiments of the present disclosure and are not intended to limit the scope of the present disclosure. All parts in the drawings are not drawn to scale.

[0009] [Figure 1] FIG. 1 shows a cross-sectional view of a pin bushing according to certain preferred embodiments of the present disclosure. [Figure 2] FIG. 2 shows a flow chart of a method for manufacturing a pin bushing according to certain preferred embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, specific embodiments of the present disclosure will be described in detail with reference to the drawings. Only preferred embodiments of the present disclosure are described here. Those skilled in the art can implement other aspects of the present disclosure based on these preferred embodiments, and these aspects also fall within the scope of the present disclosure.

[0011] First, it should be noted that the directional and positional terms in this disclosure should be understood as relative directions and positions, rather than absolute directions and positions.

[0012] FIG. 1 is a cross-sectional view of a pin bushing 100 according to a preferred embodiment of the present disclosure. This pin bushing can be used in the track of a construction machine. Generally, the outer surfaces of both ends of the pin bushing each engage a chain-rail joint, the inner surfaces of both ends of the pin bushing engage a pin shaft, and the outer surface of the center portion of the pin bushing engages a drive sprocket in the track. For example, the construction machine can be either an on-road vehicle (such as a bulldozer or excavator) or an off-road vehicle. The pin bushing according to a preferred embodiment of the present disclosure is particularly suitable for use in a medium-sized excavator.

[0013] As shown in FIG. 1 , the pin bushing 100 is generally hollow cylindrical and includes a through-hole 110 extending therethrough in the axial direction. The through-hole 110 has a substantially uniform inner diameter in the axial direction, meaning that the inner surface of the pin bushing 100 is cylindrical. Preferably, the outer surface of the pin bushing 100 is also generally cylindrical. Furthermore, the pin bushing 100 includes a first axial section 120, a second axial section 130, and a middle section 140 disposed around the through-hole. The first axial section 120 and the second axial section 130 are located at opposite axial ends of the pin bushing 100, and the middle section 140 is disposed between the first axial section 120 and the second axial section 130. The first axial section 120, the second axial section 130, and the middle section 140 each have a specific length in the axial direction of the pin bushing 100 and a specific thickness in the radial direction of the pin bushing 100. Preferably, the pin bushing 100 is a single, integrally molded piece.

[0014] In a preferred embodiment, the pin bushing 100 is made from a carbon steel material. More preferably, the pin bushing 100 may be made from a low alloy medium carbon steel material.

[0015] 1 , the intermediate section 140 has an intermediate radially outer portion 141 and an intermediate radially inner portion 142. In the radial direction of the pin bushing 100, the intermediate radially inner portion 142 is located radially inward of the pin bushing 100 relative to the intermediate radially outer portion 141, and the intermediate radially inner portion 142 is adjacent to the through hole 110. The intermediate radially inner portion 142 has a radially inward surface 142a and a radially outward surface 142b radially opposite the radially inward surface 142a, and the radially inward surface 142a surrounds a portion of the through hole 110. The intermediate radially inner portion 142 has a specific length in the axial direction and a specific depth in the radial direction. Both ends of the intermediate radially inner portion 142 have rounded corners. In a preferred embodiment, the depth D2 of the intermediate radially inner portion 142 is within a range of 60% to 40% of the total wall thickness D of the pin bushing 100, and the depth D1 of the intermediate radially outer portion 141 is within a range of 40% to 60% of the total wall thickness D of the pin bushing 100. For example, the depth D2 of the intermediate radially inner portion 142 may be set to 55% of the total wall thickness D of the pin bushing 100, and the depth D1 of the intermediate radially outer portion 141 may be set to 45% of the total wall thickness D of the pin bushing 100. Alternatively, the intermediate radially outer portion 141 and the intermediate radially inner portion 142 may be set to the same depth. The axial length L1 of the intermediate radially inner portion 142 is preferably within a range of 40% to 60% of the total axial length L of the pin bushing 100. For example, the axial length L1 of the intermediate radially inner portion 142 may be set to 40%, 50%, or 60% of the total axial length L of the pin bushing 100. Those skilled in the art can set the value according to actual needs.

[0016] The intermediate radially outer portion 141 and the intermediate radially inner portion 142 have different hardness values. The hardness value of the intermediate radially outer portion 141 is greater than the hardness value of the intermediate radially inner portion 142, and the hardness values ​​of the first axial section 120 and the second axial section 130 are greater than the hardness value of the intermediate radially inner portion 142. Note that the "hardness values ​​of the first axial section 120 and the second axial section 130" referred to herein refer to the overall hardness of the first axial section 120 and the second axial section 130 from their inner diameter to their outer diameter. That is, the hardness value of the portion of the first axial section 120 from one end of the first axial section 120 to the other end of the first axial section 120 in the axial direction, and the hardness value of the portion of the first axial section 120 from the radially inner to outer side, are all greater than the hardness value of the intermediate radially inner portion 142. The hardness value of the portion of the second axial section 130 from one end of the second axial section 130 in the axial direction to the other end of the second axial section 130, and the hardness value of the portion of the second axial section 130 from the inner side to the outer side in the radial direction are all greater than the hardness value of the intermediate radially inner portion 142.

[0017] Preferably, the hardness values ​​of the first axial section 120 and the second axial section 130 are the same, and the hardness values ​​of the first axial section 120 and the second axial section 130 are the same as the hardness value of the intermediate radially outer portion 141. This solution may simplify the hardening process of the pin bushing 100. Those skilled in the art will understand that the hardness values ​​of the first axial section 120, the second axial section 130, and the intermediate radially outer portion 141 can also be set to different values ​​according to actual needs.

[0018] Preferably, the first axial section 120, the second axial section 130, and the intermediate radially outer portion 141 have a hardness value in the range of HRC 55 to HRC 60, and the intermediate radially inner portion 142 has a hardness value of HRC 35 or less. For example, the hardness values ​​of the first axial section 120, the second axial section 130, and the intermediate radially outer portion 141 can be set to HRC 55, HRC 56, HRC 58, etc. The hardness value of the intermediate radially inner portion 142 can be set to HRC 34, HRC 30, etc. In a preferred embodiment, the first axial section 120, the second axial section 130, and the intermediate radially outer portion 141 have a martensite structure, and the intermediate radially inner portion 142 has a pearlite and ferrite structure.

[0019] With the above configuration, both ends of the pin bushing 100 have a high hardness, and the middle radially outer portion 141 of the pin bushing 100 also has a high hardness, so both ends and the middle radially outer portion of the pin bushing 100 have excellent wear resistance, thereby improving the service life. Because the middle radially inner portion 142 of the pin bushing 100 is relatively soft, it has better impact resistance and fatigue life, making the pin bushing suitable for the use conditions of medium-sized excavators.

[0020] A method for manufacturing the pin bushing 100 according to a preferred embodiment of the present disclosure will now be described with reference to FIG.

[0021] As shown in FIG. 2, in a preferred embodiment, the method of manufacturing the pin bushing 100 includes the following.

[0022] First, the pin bushing 100 is preformed. Here, the preformed pin bushing 100 refers to the pin bushing before the heat treatment process is performed. The preforming process of the pin bushing 100 can be performed according to a method known in the art, and a detailed description will be omitted here. The preformed pin bushing 100 is already formed into a substantially hollow cylindrical shape.

[0023] Next, induction heating is performed on the preformed pin bushing 100. This step includes passing the pin bushing 100 through an induction coil of an induction heating device. The induction heating device may be a medium-frequency induction heating device equipped with a servo motor feeder. Next, the induction coil is moved in the axial direction of the pin bushing 100, and at least one of the induction coil feed speed, output power, and induction frequency is adjusted according to the relative positions of the induction coil and the pin bushing 100 to control the radial hardness distribution of the pin bushing 100. Preferably, the adjustment of the induction coil feed speed and the adjustment of the output power can be performed in combination.

[0024] Preferably, the induction coil feed speed in the first axial section 120 and the second axial section 130 is slower than the induction coil feed speed in the middle section 140, and the output power of the induction coil in the first axial section 120 and the second axial section 130 is greater than the output power of the induction coil in the middle section 140. This allows the first axial section 120 and the second axial section 130 to be completely heated from the outside to the inside in the radial direction of the pin bushing 100, the intermediate radially outer portion 141 to be heated, and the intermediate radially inner portion 142 to be unheated. Although an embodiment in which the intermediate radially inner portion 142 is not heated is a preferred embodiment of the present disclosure, it should be noted that the intermediate radially inner portion 142 may be slightly heated during actual heat treatment. This solution is also within the scope of the present disclosure. With the above solution, after heat treatment, the first axial section 120 and the second axial section 130 of the pin bushing 100 have a completely austenitic structure, and the intermediate radially outer portion 141 also has an austenitic structure. On the other hand, the unheated or slightly heated intermediate radially inner portion 142 has a mixed structure of pearlite and ferrite.

[0025] Preferably, the induction coil supply speed in the intermediate section 140 is 2 to 2.5 times the induction coil supply speed in the first axial section 120 and the second axial section 130, and the induction coil output power in the first axial section 120 and the second axial section 130 is 1.1 to 1.5 times the induction coil output power in the intermediate section 140. More preferably, the induction coil supply speed in the first axial section 120 and the second axial section 130 is 4 to 8 mm / sec, and the output power is 250 to 350 kW. More preferably, the induction coil supply speed in the intermediate section 140 is 12 to 16 mm / sec, and the induction coil output power in the first axial section 120 and the second axial section 130 is 210 to 310 kW.

[0026] In another embodiment, the radial hardness distribution of the pin bushing 100 can also be adjusted by changing the induction frequency of the induction heating device. Preferably, the induction frequency of the induction coil in the first axial section 120 and the second axial section 130 can be lower than the induction frequency of the induction coil in the middle section 140, so that the first axial section 120 and the second axial section 130 can be completely heated from the outside to the inside along the radial direction of the pin bushing 100, the intermediate radially outer section 141 can be heated, and the intermediate radially inner section 142 can be not heated or only slightly heated.

[0027] Preferably, the first axial section 120 and the second axial section 130 of the pin bushing 100 are heated at a temperature in the range of 900°C to 950°C for 5 to 6 seconds for each of the first axial section 120 and the second axial section 130, and the middle section 140 is heated at a temperature in the range of 900°C to 950°C for 8 to 10 seconds.

[0028] The first axial section 120, the second axial section 130, and the intermediate radially outer portion 141 can then be cooled and quenched. As an example, the cooling can be performed by spraying water at high pressure. Alternatively, other cooling media such as oil can be used in the quenching process, or a certain proportion of quenching liquid can be added to the water. Those skilled in the art can set this according to actual needs.

[0029] After cooling and quenching, the structure of the first axial section 120, the second axial section 130, and the intermediate radially outer portion 141 may be transformed to martensite, and the intermediate radially inner portion 142 may maintain the original substrate soft structure, i.e., pearlite and ferrite. [Industrial Applicability]

[0030] In the above arrangement, both ends of the pin bushing 100 have a high hardness, the middle radially outer portion 141 of the pin bushing 100 also has a high hardness, and the middle radially inner portion 142 of the pin bushing 100 is relatively soft. This solution allows the pin bushing 100 to exhibit excellent wear resistance during operation at both ends and the middle radially outer portion 141, improving its service life. The middle radially inner portion also has better impact resistance and fatigue life. A pin bushing with the above solution reduces the frequency of maintenance and repairs, reducing the overall maintenance costs of construction machinery using the pin bushing and improving the user experience.

[0031] Furthermore, according to the above solution, the induction heating device can increase the hardness of the intermediate radially outer portion 141 and both ends of the pin bushing 100 with only one heating operation, and decrease the hardness of the intermediate radially inner portion 142 of the pin bushing 100. This solution can simplify the work steps and reduce costs while ensuring the hardness distribution of the pin bushing.

[0032] The above description of various embodiments of the present disclosure is provided for illustrative purposes to those skilled in the art and is not intended to exclude other embodiments from the disclosure or to limit the disclosure to a single disclosed embodiment. As noted above, various alternatives and modifications of the present disclosure will be apparent to those skilled in the art. Thus, while several alternative embodiments have been described in detail, those skilled in the art will understand or readily develop other embodiments. The present disclosure is intended to include all alternatives, modifications, and variations of the present disclosure described herein, as well as other embodiments that fall within the spirit and scope of the present disclosure described herein.

Claims

1. A pin bushing comprising a through hole penetrating the pin bushing in the axial direction of the pin bushing, a first axial section, a second axial section, and an intermediate section arranged around the through hole, wherein the first axial section and the second axial section are located at both ends of the pin bushing in the axial direction, the intermediate section is located between the first axial section and the second axial section, the intermediate section has an intermediate radially outer portion and an intermediate radially inner portion in the radial direction of the pin bushing, the intermediate radially inner portion has a radially inward surface, the radially inward surface surrounds a portion of the through hole, and the hardness values ​​of the first axial section, the second axial section, and the intermediate radially outer portion are greater than the hardness value of the intermediate radially inner portion.

2. The pin bushing according to claim 1, wherein the pin bushing is made of carbon steel material.

3. The pin bushing according to claim 1, wherein the structure of the first axial section, the second axial section, and the intermediate radially outer portion is martensite, and the structure of the intermediate radially inner portion is pearlite and ferrite.

4. The pin bushing according to claim 1, wherein the shape of the pin bushing satisfies at least one of the following: the outer surface of the pin bushing is cylindrical, and the inner surface of the pin bushing is cylindrical.

5. The pin bushing according to claim 4, wherein the depth of each portion of the intermediate section satisfies at least one of the following: the depth of the intermediate radially outer portion is in the range of 40% to 60% of the total wall thickness of the pin bushing, and the depth of the intermediate radially inner portion is in the range of 60% to 40% of the total wall thickness of the pin bushing.

6. The pin bushing according to claim 5, wherein the axial length of the intermediate radially inner portion is within the range of 40% to 60% of the total axial length of the pin bushing.

7. The pin bushing according to claim 6, wherein the intermediate radially inner portion has rounded corners at both ends in the axial direction.

8. The pin bushing according to any one of claims 1 to 7, wherein the hardness values ​​of the portion of the first axial section in the radial direction are all greater than the hardness values ​​of the intermediate radial inner portion, and the hardness values ​​of the portion of the second axial section in the radial direction are all greater than the hardness values ​​of the intermediate radial inner portion.

9. The pin bushing according to claim 8, wherein the hardness values ​​of the first axial section, the second axial section, and the intermediate radial outer portion are in the range of HRC 55 to HRC 60, and the hardness value of the intermediate radial inner portion is HRC 35 or less.

10. The method is A step of pre-forming the pin bushing, The step of performing induction heating on the pre-formed pin bushing, Moving the induction coil in the axial direction of the pin bushing, Adjusting at least one of the supply speed, output power, and induction frequency of the induction coil according to the relative position between the induction coil and the pin bushing, such that the first axial section and the second axial section are completely heated from the outside to the inside in the radial direction of the pin bushing, the intermediate radial outer portion is heated, and the intermediate radial inner portion is not heated or is heated to a lower degree than the intermediate radial outer portion, A method for manufacturing a pin bushing according to claim 1, further comprising the step of cooling and quenching the first axial section, the second axial section, and the intermediate radially outer portion.

11. The method according to claim 10, wherein the supply speed of the induction coils in the first axial section and the second axial section is slower than the supply speed of the induction coils in the intermediate section.

12. The method according to claim 10 or 11, wherein the output power of the induction coils in the first axial section and the second axial section is greater than the output power of the induction coils in the intermediate section.

13. The method according to claim 10, wherein the induction frequency of the induction coil in the first axial section and the second axial section is lower than the induction frequency of the induction coil in the intermediate section.

14. The method according to claim 11, wherein the supply speed of the induction coil in the intermediate section is 2 to 2.5 times the supply speed of the induction coil in the first axial section and the second axial section.

15. A method in which the output power of the induction coil in the first axial section and the second axial section is 1.1 to 1.5 times the output power of the induction coil in the intermediate section, the method according to claim 12.

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