JPH01257528A - Manufacture of crankshaft - Google Patents

Abstract

PURPOSE:To reduce vibration of each part by a method wherein after a work of grinding a crank pin, correction is made so that center holes previously formed in both end surfaces of a crank shaft coincide with the axis of a journal part, and thereafter the crank shaft is held by means of the center holes to apply a grinding work on a journal part. CONSTITUTION:Subsequently to a work to grind crank pins 12a-12d, correction is made so that the axes of journal parts 10a and 10b at both ends coincide with center holes 36 and 38. Based on the corrected opening parts (center holes) 36 and 38, finish grinding of the journal parts 10a-10d is performed. Thereby, stroke precision of the crank pins 12a-12d of a crank shaft rotationally driven centering around the journal parts 10a-10d is improved, meanwhile, since the journal parts 10a-10d are ground after a work of grinding the crank pins 12a-12d, vibration of each part is also reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for manufacturing a crankshaft, and more particularly to a method for manufacturing a crankshaft in which the stroke accuracy of the crank pin is high.

Conventional technology A crankshaft is connected to a piston through a crank pin and a connecting rod that are eccentrically provided with respect to the journal portion, and is rotated by the reciprocating motion of the piston to extract the shaft output of the engine. Therefore, high strength, rigidity, wear resistance, etc. are required. Therefore, when manufacturing such crankshafts, the mechanical strength of the crankshaft is generally improved by subjecting the crankshaft made of mechanical structural carbon steel or the like that has been forged into a predetermined shape to heat treatment through quenching and tempering. After that, it is normal to remove the distortion caused by the heat treatment, and then grind the journal part, crank pin, etc.

Problems to be Solved by the Invention However, upon detailed inspection by the inventors of the crankshaft manufactured in this manner, it was found that there were problems such as errors and variations in the stroke of the crank pin, and run-out in various parts. was there.

The present invention has been made against the background of the above circumstances, and its purpose is to improve the stroke accuracy of the crank pin and to reduce the runout of various parts.

Means for Solving the Problems In order to achieve the above object, the inventors of the present invention conducted further experiments and research, and found that after grinding the crank pin, the runout of each part became large, and both ends of the crankshaft It has been found that when the journal portion is ground using a center hole previously provided in the surface as a reference, the stroke accuracy of the crank pin is significantly impaired. This is because the surface layer of the crankpin is scraped away during the grinding process, and the residual stress generated on the surface layer during heat treatment is released, causing the crankshaft to deform, causing the axis of the center hole and journal to become misaligned. This is thought to be due to the

The present invention has been made based on this knowledge, and its gist is that after a crankshaft having a journal portion and a crank pin is subjected to a prescribed heat treatment, the journal portion and crank pin are subjected to a grinding process. After grinding the crank pin, the center holes previously provided on both end faces of the crankshaft are corrected to match the axis of the journal portion, and then the corrected center holes are The crankshaft is held in place while the journal portion is ground.

Operation and Effects of the Invention With this method, even if the crankshaft is deformed due to grinding of the crank pin, the center hole can be corrected so that it is aligned with the axis of the journal portion, and the correction can be made easily. Since the journal part is ground while the crankshaft is held in the center hole, the stroke accuracy of the crank pin of the crankshaft which is rotated based on the journal part is improved. By grinding the journal part, the runout of each part is also reduced.

In addition, when correcting the center hole, it is preferable to rotatably support the journal part and perform the correction while rotating the crankshaft, in order to prevent misalignment caused by dimensional errors of the journal part.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

First, FIG. 1 is a diagram showing a machining process according to the manufacturing method of the present invention, and FIG. 2 is a diagram showing an example of a crankshaft manufactured according to the machining process of FIG. 1. This crankshaft is used in a four-cylinder automobile engine, and has five journal parts 10a, 10b, 10c, and 10.
d, 10e and four crank pins 12a, 12b, 1
2c, 12d, and counterweights 14a, 14b, 14c are provided on opposite sides of the crank pins 12a, 12b, 12c, 12d, respectively.

14d (hereinafter, unless otherwise noted, they are simply referred to as journal portion 10. crank pin 1).
2. counterweight 14).

Further, front shafts 16. A rear flange 18 is provided, and a 20° pilot hole 22 is provided in the center of both end faces.
is formed. On the front shaft 16, a pair of pulleys are brought into contact with the thrust surfaces 24 and 26, respectively, and relative rotation is prevented by a rotation locking key fitted in the keyway 28.30. The flywheel is attached to the rear flange 18 by tightening bolts on the thrust surface 32.
The bolts are tightened into the screw holes 34 in a state where they are in close contact with each other, so that they are integrally fixed. Further, a bearing is arranged in the pilot hole 22. Above screw hole 2
0. The openings 36 and 38 of the pilot hole 22 are both tapered and are used as center holes in the processing step or subsequent steps.

When manufacturing such a crankshaft, first, a material such as carbon steel for mechanical structure is shaped into a desired shape, that is, the journal portion 10. Crank pin 12. Counterweight 14. Front axis 16. and a rear flange 18, and then processed according to the processing steps shown in the first section. Hereinafter, this processing step will be explained in detail with reference to FIG. 1.

First, the forged crankshaft is heat treated by induction hardening and tempering to obtain the desired mechanical strength, and then strain is measured and strain removed by the heat treatment.

Then, using the journal parts 10a and 10e at both ends as a reference, that is, by fixing these journal parts 10a and 10e, the above-mentioned is applied to the end face of the crankshaft using a rotary tool installed opposite to the end face of the crankshaft. Neniana 20. A pilot hole 22 is formed.

Further, a screw hole 34 is machined in the rear 7-ray 18.

Next, the screw hole 20 formed above. Pilot I/hole 22
1! -7. After grooving and rolling the journal portion 10 while rotating the shaft, semi-finishing grinding is performed only on the journal portions 10a and 10e at both ends. This semi-finishing grinding process is performed on the crank pin 12 which is subsequently performed.
The journal portions 10a and 10e serve as a reference when such machining is performed.

That is, in the next grinding process of the crank pin 12, the journal parts 10a and 10e are fixed, and the crank pin 12 is ground at a position spaced apart by half the stroke of the crank pin 12 from their axes. In addition, in the subsequent correction of the center hole and finishing of the pilot hole 22, the journal portion 10a.

10e rotatably supports the crankshaft,
While rotating the crankshaft, the openings 36, 38 are modified and the pilot hole 22 is finished by a rotary tool provided opposite the end face. This modification of the openings 36, 38 causes their center lines to coincide with the axes of the journals 10a, 10e. In addition, the modification of the opening 38 and the pilot hole 22
The finishing of the pilot hole 2 is carried out by using a combination tool that is integrally equipped with a tool for grinding the inner circumferential surface of the cylinder and a tool for grinding the taper surface.
Modification of the opening 38 can be carried out continuously following the finishing process of 2.

Here, the center hole is corrected following the grinding of the crank pin 12 because the crankshaft is deformed by the grinding of the crank pin 12 and the previously machined screw hole 20. Center line of pilot hole 22 and journal part 10
Since the axis of the screw hole 20. This is because if post-process processing is performed using the openings 36 and 38 of the pilot hole 22 as a reference, processing errors will occur. According to experiments conducted by the present inventors, the crankshaft is deformed due to the grinding process of the crank pin 12. As shown in FIG. This phenomenon is thought to occur because the residual stress generated in the crank pin 12 is released by removing the surface layer by grinding.

Thereafter, while rotating the crankshaft with reference to the modified opening 36, 38, the front shaft 16
．． Rear flange 18. and central journal part 10c
Grinding is performed on the pair of thrust surfaces 40 that face each other with the two sides in between, finish grinding is performed on all journal parts 10, and further, the rotation of the crankshaft is stopped and the grooves of the keyways 28 and 30 are cut. . Finally, the counterweight 14 is balanced and paper lapping is performed to complete the series of processing. As a result, the crankshaft shown in FIG. 2 is obtained.

As described above, in this embodiment, following the grinding of the crank pin 12, the openings 36 and 38 are modified so that the axes of the journal parts 10a and 10e at both ends coincide with the center hole, and the modified openings are Since the finish grinding of the journal portion 10 is performed using the portions 36 and 38 as a reference, the stroke accuracy of the crank pin 12 of the crankshaft that is rotationally driven with respect to the journal portions 10 is improved, and the crank pin 12 Since the journal part 10 is ground after the grinding process, the runout of each part is also reduced.

In particular, in this embodiment, when correcting the center hole, the journal parts 10a, 10e are rotatably supported and the openings 36, 38 are corrected while rotating the crankshaft. Misalignment between the shaft centers and the center line of the center hole due to dimensional errors or the like is prevented, and the stroke accuracy of the crank pin 12 is further improved.

On the other hand, if the crankshaft whose crank pin 12 has been ground is driven to rotate with reference to the journal portions 10a and 10e at both ends, the deformation of the crankshaft due to the grinding of the crank pin 12 may cause damage to other parts. Runout occurs in the journal portions 10b, 10c, 10d and the front shaft 16. Also,
The center hole of such a crankshaft, that is, the opening 3
If the journal part 10 is ground using these as a reference without correcting 6.38, the grinding allowance will be biased due to misalignment due to the deformation of the crankshaft, and the stroke of the crank pin 12 will change. .

Although one embodiment of the present invention has been described above in detail based on the drawings, the present invention can also be implemented in other embodiments.

For example, in the above embodiment, a case has been described in which the center hole, that is, the opening 36, 38, is corrected while rotating the crankshaft, but it is also possible to correct the center hole while fixing the crankshaft.

Further, in the embodiment described above, the journal portions 10a, 10 at both ends
Although the center hole is corrected using e as a reference, it is also possible to correct the center hole using other journal parts 10 such as the journal parts 10b and 10d as a reference.

Further, in the embodiment described above, semi-finishing grinding is performed on the journal portions 10a and ioe prior to grinding the crank pin 12, but such grinding is not necessarily necessary.

Furthermore, in the embodiment described above, a method for manufacturing a crankshaft used in a four-cylinder automobile engine was explained.
The present invention can be similarly applied to the manufacture of crankshafts used in other multi-cylinder engines such as six-cylinder engines.

In addition, grooving and roller hooking for the crank pin 12 are done by machining and front shaft 16. Grinding of the rear flange 18.degree. and thrust surface 40, keyway cutting of the keyway 28.degree. In short, it is sufficient if the center hole is corrected after the crank pin 12 is ground, and then the journal portion 10 is finished by grinding.

Although other examples are not provided, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the machining process of a crankshaft according to the method of the present invention. FIG. 2 is a partially cutaway front view showing an example of a crankshaft manufactured according to the processing steps shown in FIG. 1. 10a, 10b, 10c, 10d, 10e: Journal portions 12a, 12b, 12c, 12d: Crank pin 36.
38: Opening (center hole) Applicant Toyota Motor Corporation Fujikoshi Figure 1 Heli

Claims (1)

[Scope of Claims] After performing a predetermined heat treatment on a crankshaft having a journal portion and a crank pin, the journal portion and the crank pin are subjected to a grinding process; A center hole provided in advance on both end faces of the shaft is corrected so as to match the axis of the journal portion, and then the journal portion is subjected to a grinding process while the crankshaft is held in the corrected center hole. A method for manufacturing a crankshaft, characterized by: