Crankshaft drilling method

Abstract

To provide a piercing method for a crank shaft capable of preventing a hardening crack in a hardening process without making formation of a through hole difficult, and the crank shaft to which piercing is applied by using the method.SOLUTION: A piercing method for a crank shaft for forming an oil circulation through hole 20 penetrating from a surface of a journal shaft part 12 to a surface of a pin shaft part 14 includes: a recessed part formation process of forming a recessed part 24 at a through hole formation position on an outer surface of the journal shaft part 12 or the pin shaft part 14 before formation of the through hole 20; a hardening process of applying high-frequency hardening to the surface of the crank shaft 10 after the recessed part formation process; and a through hole formation process of forming the through hole 20 from a portion in which the recessed part 24 is formed after the hardening process. A depth of the recessed part 24 is a depth at which the surface of the recessed part 24 is in an unhardened or incompletely hardened state in the hardening process.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for drilling a crankshaft, law, particularly to a method for drilling a crankshaft for forming a through hole for oil circulation that penetrates between a journal shaft portion and a pin shaft portion. In the law It relates thereto.

Background Art

[0002] In an automobile crankshaft, journal shaft portions and pin shaft portions are alternately arranged in the longitudinal direction of the crankshaft. The journal shaft portions are supported by bearings in a crankcase, and the ends of connecting rods are connected to the pin shaft portions. Therefore, the outer peripheries of the journal shaft portions and the pin shaft portions become sliding portions, and in order to improve the lubrication of these sliding portions, a through hole that penetrates between the journal shaft portion and the pin shaft portion is provided, and lubricating oil is supplied to the journal shaft portion and the pin shaft portion through this through hole (see, for example, Patent Document 1).

[0003] FIG. 4 is an explanatory diagram of a method for drilling a crankshaft disclosed in Patent Document 1. First, through holes 32 and 34 that penetrate between the outer surfaces of the shaft portions are formed in the journal shaft portion 12 and the pin shaft portion 14. These through holes 32 and 34 are formed so as to penetrate substantially through the axial centers of the journal shaft portion 12 and the pin shaft portion 14 and be substantially perpendicular to the outer surface of the shaft portion. Then, from the crank arm portion 36, an inclined hole 20 is formed through an inclined hole forming hole portion 40 so as to communicate with the through holes 32 and 34 and the substantially axial centers of the journal shaft portion 12 and the pin shaft portion 14. After these through holes 32 and 34 and the inclined hole 20 are machined and formed, high-frequency quenching is performed on the surface of the crankshaft 10 using a high-frequency quenching device to form a hardened layer.

[0004] In recent years, due to the need for smaller and more powerful engines, there has been a demand for crankshafts with shorter overall lengths. As the overall length of the crankshaft is shortened, as shown in Figure 5, the web 16 between the journal shaft portion 12 and the pin shaft portion 14 becomes thinner, and the oblique hole 20 and the surface radius portion 18 of the journal shaft portion 12 and the pin shaft portion 14 become closer together.

[0005] After forming the through-hole 32 in the journal shaft portion 12 and the through-hole 34 in the pin shaft portion 14, a through-hole forming hole portion 40 is formed in the web 16 to create the through-hole 20. If high-frequency induction hardening is then performed to ensure strength, the surface radius portion 18 and the through-hole 20 are close together, and overheating due to the hardening of the surface radius portion 18 can induce quench cracks within the through-hole 20. For this reason, the through-hole 20 is formed after high-frequency induction hardening. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2001-271825 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0007] As described above, in the case of a crankshaft 10 with a shortened overall length, if through holes 32 and 34 are formed in the journal shaft portion 12 and the pin shaft portion 14 respectively, and then a through hole 20 is machined to penetrate the journal shaft portion 12 and the pin shaft portion 14, and then high-frequency induction hardening is performed, there is a risk of hardening cracks occurring in the through hole 20. Therefore, until now, the method used has been to form through holes 32 and 34 in the journal shaft portion 12 and the pin shaft portion 14 respectively, then perform high-frequency induction hardening, and then machine the through hole 20.

[0008] However, with this method, machining burrs are generated at the intersection of the through hole 20 and the through holes 32 and 34 formed in the journal shaft portion 12 and the pin shaft portion 14, respectively, requiring deburring work. In addition, in order to close the through hole forming hole portion 40 made in the web 16 to form the through hole 20, it is necessary to insert a separate member into this through hole forming hole portion 40.

[0009] The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a method for drilling holes in a crankshaft that can prevent quench cracking during the hardening process without making it difficult to form through holes. Law The purpose is to provide. [Means for solving the problem]

[0010] To achieve the above objective, the method for drilling holes in a crankshaft according to one embodiment of the present invention is: In a method for drilling holes in a crankshaft to form through-holes for oil circulation that penetrate from the surface of the journal shaft to the surface of the pin shaft, Before the through hole is formed 、 The journal shaft and The pin shaft portion Both A recess formation step in which a recess is formed at the location of the through hole on the outer surface, After the recess formation step, a hardening step is performed on the surface of the crankshaft by high-frequency induction hardening, The process includes a through-hole forming step, which follows the quenching step, in which the through-hole is formed from the location where the recess is formed. The depth of the recess is greater than the depth of the hardened layer formed by high-frequency induction hardening, and is such that the bottom surface of the recess is unhardened or incompletely hardened when the recess is not sealed during the hardening process.

[0011] In this method, before forming the through-holes for oil circulation, a recess is first formed on the outer surface of the journal shaft or pin shaft at the location where the through-holes will be formed. Then, a hardening process is performed before the through-hole formation process, and the through-hole formation process is performed after the high-frequency hardening process. Furthermore, the depth of the recess is set so that it is not hardened even during the hardening process, and the bottom of the recess remains unhardened after the hardening process. Therefore, for example, the through-hole formation process starting from the recess using a drill can be performed in the same way as in the normal pre-hardening state. In this way, since no through-holes are formed during high-frequency hardening, the occurrence of hardening cracks due to the presence of through-holes is also avoided.

[0013] This method creates recesses in both the journal shaft and the pin shaft, so that the starting and ending points of the through hole are not hardened by high-frequency induction hardening. This eliminates the need to process the hardened layer, making the machining of the through hole easier.

[0014] One embodiment of the present invention is the aforementioned In a method for drilling holes in a crankshaft, The recess is characterized in that the angle between the wall surface of the recess and the outer surface of the pin shaft portion and / or the journal shaft portion is perpendicular or obtuse.

[0015] In this method, after forming a recess, high-frequency induction hardening is performed. However, since the angle between the wall surface of the recess and the outer surface of the pin shaft and / or journal shaft is perpendicular or obtuse, and there are no acute angles, there is no risk of cracking due to high-frequency induction hardening.

[0016] One embodiment of the present invention relates to a method for drilling holes in the crankshaft, The through hole extends linearly from the outer surface of the pin shaft portion to the outer surface of the journal shaft portion. It is characterized by the following:

[0017] One embodiment of the present inventionIn the method for drilling holes in the crankshaft, a linear through-hole can be easily formed from the concave portions on the surfaces of the pin shaft portion and / or the journal shaft portion. And, by forming this through-hole extending linearly, the presence of the portions of the through-holes that were conventionally formed in the pin shaft portion and the journal shaft portion, respectively, so as to penetrate substantially through the axis and be substantially perpendicular to the outer surface of the shaft portion, is eliminated. Therefore, the oil circulation becomes better, and the work of closing the holes for forming the conventional through-holes and the work of removing burrs are also unnecessary.

Advantages of the Invention

[0018] In the method for drilling holes in the crankshaft of the present invention In the law since quenching is performed before forming the through-hole for oil circulation, the problem of cracking during quenching is solved. And, after the quenching process, since the through-hole is formed from the concave portions where hardening due to quenching has not occurred, no difficulty in processing occurs. Also, since a linear through-hole is formed, the processing operation is facilitated.

Brief Description of the Drawings

[0019] [Figure 1] It is an explanatory view of a crankshaft to which the method for drilling holes in the crankshaft of the present invention is applied. [Figure 2] It is an explanatory view of the concave portion in FIG. 1. [Figure 3] It is an explanatory view of the concave portion in FIG. 1. [Figure 4] It is an explanatory view of the conventional hole drilling method. [Figure 5] It is an explanatory view of the conventional hole drilling method.

Embodiments for Carrying Out the Invention

[0020] The crankshaft drilling method of the present invention and an embodiment of a crankshaft drilled by this method will be described in detail below with reference to the drawings. The crankshaft of this embodiment has a short overall length and a thin web between the journal portion and the pin shaft portion.

[0021] Figure 1 is an explanatory diagram of a crankshaft with holes drilled in it according to this embodiment. A portion of the crankshaft 10 is shown in a partial cross-section, and a through hole 20 is formed from the outer surface of the pin shaft portion 14 to the outer surface of the journal shaft portion 12. The hardened layers of the pin shaft portion 14 and the journal shaft portion 12 by high-frequency induction hardening are indicated by reference numeral 28 (area with dots).

[0022] The procedure for drilling holes is described below. First, recesses 24 are formed at the through-hole formation positions on the outer surfaces of the journal shaft portion 12 and the pin shaft portion 14 (recess formation step).

[0023] Figure 2 is an explanatory diagram of a recess formed on the outer surface. The recess 24 is round in shape, with a diameter of approximately 5 mm, and the distance from the outer surface 22 to the bottom of the recess 24 is approximately 2.5 mm. These values ​​are just one example and are not limited to these values. The depth was set to approximately 2.5 mm so that, as will be described later, when the crankshaft 10 is subjected to high-frequency induction hardening, the bottom 30 of the recess 24 will be an unhardened (uncured) or incompletely hardened portion.

[0024] Furthermore, the angle between the wall surface 26 of the recess 24 and the outer surface 22 is formed to be perpendicular or obtuse. In this way, even though induction hardening is performed after the recess 24 is formed, the angle between the wall surface 26 of the recess 24 and the outer surface 22 of the pin shaft portion 14 and the journal shaft portion 12 is perpendicular or obtuse, and there are no acute angles, so there is no risk of cracking due to induction hardening.

[0025] In this embodiment, the recesses 24 formed in the journal shaft portion 12 and the pin shaft portion 14 have the same diameter, depth, and shape.

[0026] After forming recesses 24 on the entire surface of the journal shaft portion 12 and the pin shaft portion 14, high-frequency induction hardening is performed (hardening process). High-frequency induction hardening is a well-known method, and in order to set the hardening depth, the frequency, current, etc. are adjusted as appropriate considering the resistance value, magnetic permeability, etc. of the material constituting the crankshaft 10. In this embodiment, as described above, the frequency, current, etc. are adjusted so that the bottom portion 30 of the recess 24 remains an unhardened portion.

[0027] Figure 3 shows the hardening process in the recesses 24 formed on the outer surfaces of the journal shaft portion 12 and the pin shaft portion 14. Figure 3(a) shows the case where the recesses 24 are formed, and Figure 2(b) shows the case where the recesses 24 are not formed.

[0028] When the recess 24 is formed, the high-frequency induction hardening conditions are set so that the bottom 30 of the recess 24 is not hardened, as described above. In this embodiment, as set, the bottom 30 of the recess 24 remains unhardened, as shown in Figure 3(a). The hardened areas (hardened areas) are indicated by reference numeral 28 (with a dot).

[0029] If the recess 24 is not formed, the hardened portion 28 is formed to a substantially uniform depth from the outer surface 22, as shown in Figure 3(b). In this embodiment, when hardening is performed, the hardening depth is approximately 2.0 mm.

[0030] After the surface hardening process of the crankshaft 10 is performed, a through hole 20 is formed from the bottom 30 of the recess 24 (through hole formation process). In this embodiment, since the recess 24 is formed on both the journal shaft portion 12 and the pin shaft portion 14, the starting and ending points where the through hole 20 is formed are not hardened by high-frequency induction hardening. Therefore, there is no need to process the hardened layer, and the processing of the through hole 20 becomes easier. The through hole 20 is formed using a normal drill.

[0031] In other embodiments, the recess 24 is formed only on the outer surface 22 where the formation of the through hole 20 begins. In this other embodiment, when the drill exits the outer surface 22 at the final stage of forming the through hole 20, the outer surface 22 has become harder due to heat treatment, but the tip of the drill does not wobble due to the through hole 20 that has been machined up to that point, so the through hole 20 can be formed without any problems.

[0032] The drilling process for the crankshaft 10 is completed by forming these through holes 20 at all predetermined locations on the crankshaft 10.

[0033] According to the crankshaft drilling method for the crankshaft 10 of this embodiment and the crankshaft drilled by this method, the through hole 20 from the journal shaft portion 12 to the pin shaft portion 14 is formed between recesses 24 formed on the outer surfaces 22 of the journal shaft portion 12 and the pin shaft portion 14, respectively. Since the bottom portion 30 of the recess 24 is not hardened, the through hole 20 can be easily machined.

[0034] Furthermore, in the crankshaft 10 that has undergone this drilling process, only the through-holes 20 that penetrate the pin shaft portion 14 and the journal shaft portion 12 extend in a straight line. As a result, the existence of through-holes that were conventionally formed in the pin shaft portion 14 and the journal shaft portion 12, respectively, which passed almost through the axis and penetrated almost perpendicularly to the outer surface 22 of the shaft portion, is eliminated. Consequently, oil circulation is improved, and the work of sealing the conventional through-hole forming portion 40 and deburring is eliminated. Therefore, a high-performance crankshaft can be provided.

[0035] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. For example, the diameter of the through hole 20 is approximately 1.6 mm, the diameter of the recess 24 is approximately 5 mm, and the depth of the recess 24 is approximately 2.5 mm, but the invention is not limited to these values. Also, although the shape of the recess 24 is round, it may be an inverted trapezoid, an inverted triangle, or a U-shape. [Explanation of Symbols]

[0036] 10 Crankshaft 12 Journal axis 14 Pin shaft 16 Web 18 R section 20 through holes 22 Outer surface 24 recesses 26 Wall surface 28 Hardened section 30 bottom 32 Journal shaft through hole 34 Through-hole in the pin shaft 36 Crank arm section 40 Hole section for forming through holes (angled holes)

Claims

1. In a method for drilling holes in a crankshaft to form through-holes for oil circulation that penetrate from the surface of the journal shaft to the surface of the pin shaft, Before forming the through hole, a recess forming step is performed in which recesses are formed at the through hole formation positions on the outer surfaces of both the journal shaft portion and the pin shaft portion. After the recess formation step, a hardening step is performed on the surface of the crankshaft by high-frequency induction hardening, The process includes a through-hole forming step, which follows the quenching step, in which the through-hole is formed from the location where the recess is formed. A method for drilling holes in a crankshaft, characterized in that the depth of the recess is greater than the depth of the hardened layer by the high-frequency induction hardening, and the depth is such that the bottom surface of the recess is unhardened or incompletely hardened when the recess is not sealed during the hardening process.

2. The method for drilling holes in a crankshaft according to claim 1, characterized in that the angle between the wall surface of the recess and the outer surface of the pin shaft portion and / or the journal shaft portion is perpendicular or obtuse.

3. The method for drilling holes in a crankshaft according to claim 1 or 2, characterized in that the through hole extends linearly from the outer surface of the pin shaft portion to the outer surface of the journal shaft portion.

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