CN115921994A

CN115921994A - Gear machining method

Info

Publication number: CN115921994A
Application number: CN202210937022.5A
Authority: CN
Inventors: 若松刚; 桑原隆将; 秋月启作
Original assignee: Nachi Fujikoshi Corp
Current assignee: Nachi Fujikoshi Corp
Priority date: 2021-10-05
Filing date: 2022-08-05
Publication date: 2023-04-07
Also published as: JP2023055021A

Abstract

The invention provides a gear machining method capable of reducing the interference of tooth root and improving the machining precision of tooth surface when cutting tooth surface in post machining. A gear machining method for machining a gear by cutting, characterized in that the center of a tooth profile (104) is cut shallow so as to satisfy the minimum allowable error of OBD or BBD, and tooth surfaces (108, 110) are cut so as to have the central value of the allowable error of OBD or BBD without changing the amount of cut after the center of the tooth profile (104) is cut.

Description

Gear machining method

Technical Field

The present invention relates to a gear machining method for machining a gear by cutting.

Background

As machining methods for cutting gears, gear shaving, gear hobbing, and gear shaping are known.

The shaving process is performed in a state where the rotation of a rotary blade as a cutting tool and the rotation of a workpiece as a processing object are synchronized and the rotation axis (arbor) of the rotary blade is inclined with respect to the rotation axis (workpiece axis) of the workpiece. When a normal spur gear is machined by the gear shaving process, the rotary shaver is moved in parallel to the tooth width direction of the workpiece to perform gear cutting while keeping a shaft intersection angle of the cutter shaft with respect to the workpiece shaft constant. As a result, in the gear shaving process, a difference occurs between the rotation direction of the workpiece and the rotation direction of the rotary scraper, and "slippage" occurs when the rotary scraper interferes with the workpiece. The interference portion is cut off from the workpiece by this slippage, and a tooth groove (tooth profile) or the like is machined in the workpiece.

In shaving, for example, a shaving cutter as a cutting tool is pressed against a rotating workpiece while reciprocating up and down to cut, thereby forming a tooth profile or the like in the workpiece.

In the gear machining method of patent document 1, the helical blade is moved not only in the tooth width direction of the workpiece but also in the circumferential direction to cut the teeth, thereby machining a skew tooth profile in which the tooth tip position changes in the tooth width direction.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2020-19096

Disclosure of Invention

Problems to be solved by the invention

In some cases, the gear is further cut after the shape of the gear is temporarily created, as in finish machining or finish machining after heat treatment. In the following description, this will be referred to as "post-processing". The post-processing can be performed by shaving as shown in patent document 1, or shaving, hobbing, or shaping.

However, when the cutting edge of the knife is used to cut the tooth surface (tooth side surface), the cutting load is suddenly increased due to the meshing fluctuation when the cutting edge of the knife is used to cut the vicinity of the tooth root, and therefore, the workpiece and the knife are vibrated or the rotational speed is varied. This also causes a problem that the shape of the tooth surface is disturbed, which deteriorates the machining accuracy.

The present invention has been made in view of the above problems, and an object thereof is to provide a gear machining method capable of reducing the amount of interference at the tooth root and improving the machining accuracy of the tooth surface when cutting the tooth surface in post-machining.

Means for solving the problems

In order to solve the above problems, a typical configuration of a gear machining method according to the present invention is a gear machining method for machining a gear by cutting, characterized in that a tooth profile center is cut shallow so as to satisfy a minimum allowable error of OBD (Over Ball Diameter) or BBD (Between Ball Diameter), and after a required tooth profile length is cut, a tooth surface is cut so as to have a center value of the allowable error of OBD or BBD without changing a cutting amount.

"cutting shallow to satisfy the minimum of the allowable error" means that the upper limit value of OBD is targeted in the case of the external gear, and the lower limit value of BBD is targeted in the case of the internal gear. Then, the tooth slot is widened by cutting the tooth surface, and thus, the OBD or BBD goes toward the center value. In this case, since the cutting depth is not changed, the length of the tooth profile required for cutting is not increased, and the amount of interference in the vicinity of the tooth root is reduced, so that the meshing variation is less likely to occur. Therefore, the cutting resistance does not vary, and the machining accuracy of the tooth surface can be improved.

The gear cutting process may be performed by a gear shaving process, a hobbing process, or a gear shaping process. In the post-processing of the tooth surface by these processes, the processing accuracy can be improved.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a gear machining method capable of reducing the amount of interference at the tooth root and improving the machining accuracy of the tooth surface when cutting the tooth surface in post-machining.

Drawings

Fig. 1 is a diagram illustrating a gear machining method according to an embodiment of the present invention.

Fig. 2 is a flowchart illustrating the gear machining method of fig. 1.

Fig. 3 is a schematic diagram illustrating a cutting range.

Description of the reference numerals

100. A workpiece; 102. rotating the scraper; 104. tooth profile; 106. a tooth bottom; 108. a left tooth flank; 110. the right flank.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Dimensions, materials, other specific numerical values, and the like shown in the embodiment are merely examples for facilitating understanding of the present invention, and do not limit the present invention unless otherwise specified. In the present specification and the drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and overlapping description is omitted, and elements not directly related to the present invention are omitted from illustration.

Fig. 1 is a diagram illustrating a gear machining method according to an embodiment of the present invention. Fig. 2 is a flowchart illustrating the gear processing method of fig. 1.

The gear machining method is a method of machining a gear by cutting machining, and is applied to "post-machining" such as finishing in which after a shape of the gear is temporarily created (i.e., after "pre-machining"), heat treatment is performed and further cutting is performed. The post-machining can be performed by so-called gear shaving, hobbing, or gear shaping. Hereinafter, post-processing by the shaving processing will be described.

In the gear machining method, first, a workpiece 100 in which a shape (tooth profile) of a gear is temporarily created by pre-machining is prepared, and post-machining is started by synchronizing the phase of rotation of the workpiece 100 and the phase of rotation of the doctor blade 102 shown in fig. 1 (a).

Specifically, as shown in fig. 1 (a), the length of the tooth profile 104 of the workpiece 100 required for the tooth profile is cut so shallow as to satisfy the minimum allowable error of OBD (Over Ball Diameter: outer Diameter of steel Ball), and in the case of OBD, cutting is performed with the upper limit value as a target (step S100). Here, in step S100, the center B of the spiral blade 102 indicated by a chain line in the drawing is made to coincide with the center a of the tooth profile 104 also indicated by a chain line, thereby cutting the center of the tooth profile. In addition, the upper limit of OBD is targeted in the case of the external gear, and the lower limit of BBD is targeted in the case of the internal gear.

Next, as shown in fig. 1 (b), the phase of the doctor blade 102 is changed to the left with respect to the workpiece 100. Thereby, the center B of the spiral blade 102 is located on the left side of the center a of the tooth form 104, and only the left tooth surface 108 of the tooth form 104 is cut (step S102).

Next, as shown in fig. 1 (c), the phase of the doctor blade 102 is changed to the right with respect to the workpiece 100. Thereby, the center B of the spiral blade 102 is located on the right side of the center a of the tooth form 104, and only the right tooth face 110 of the tooth form 104 is cut (step S104).

When the left and

right tooth surfaces

108 and 110 are cut, the tooth grooves are widened, and thus OBD becomes small (BBD becomes large in the case of an internal gear). As shown in fig. 1 (a), 1 (b), and 1 (c), the depth of the cut (depth of the spiral blade 102) is not changed, but the OBD is reduced when the left and

right tooth surfaces

108 and 110 are cut. Then, the left and

right tooth surfaces

108 and 110 are cut so as to be the center value of the allowable error of the OBD or BBD.

Fig. 3 is a schematic diagram illustrating a cutting range. In fig. 3, the shape and the size ratio are greatly exaggerated for convenience of explanation. The shape indicated by the broken line P shows a conventional example, and shows an example of the center of the cutting tooth profile 104 up to the center value of the allowable error of the OBD or BBD. That is, the dotted line P indicates that the left tooth surface 108 and the right tooth surface 110 are cut simultaneously.

In contrast, in the present invention, first, the length of the required tooth profile of the tooth profile 104 is cut as indicated by the broken line N1. Then, the phase is changed without changing the plunge (without changing the depth), and the left tooth surface 108 is cut as indicated by a broken line N2, and the right tooth surface 110 is cut as indicated by a broken line N3 (the left and right order is different). Thus, it is appreciated that to create identical left and

right flanks

108, 110, the dashed lines N1-N3 of the present invention are farther from the root 106 (cut shallower) than the prior art dashed line P.

According to the above gear machining method, since the cutting depth is not changed when the left tooth surface 108 and the right tooth surface 110 are cut compared with when the tooth profile center is cut, the amount of interference at the tooth root can be reduced, and the meshing fluctuation is less likely to occur, so that the machining accuracy of the tooth surface can be improved. In addition, in the post-processing of the tooth surface by the shaving processing, the processing accuracy can be improved.

In the above-described gear machining method, the right tooth surface 110 is cut after the left tooth surface 108 is cut, but the present invention is not limited thereto, and the left tooth surface 108 may be cut after the right tooth surface 110 is cut. In addition, only one of the left tooth surface 108 and the right tooth surface 110 may be cut.

In the gear machining method, the tolerance of OBD (Over Ball Diameter: outer Diameter of steel Ball) is applied to each cutting process, but the method is not limited thereto. That is, when the gear temporarily created by the preceding machining is an internal gear, machining accuracy can be improved in the post-machining of the tooth surface by the skiving machining by performing each cutting machining by applying an allowable error of BBD (Between Ball Diameter). In the case of OBD of the external gear, the vicinity of the upper limit value is targeted, and in the case of BBD of the internal gear, the vicinity of the lower limit value is targeted.

In the above-described gear processing method, the post-processing is performed by the shaving processing, but the present invention is not limited thereto, and the post-processing may be performed by the shaving processing, the hobbing processing, or the gear shaping processing. In this case, the shaving blade is pressed against the rotating workpiece 100 to cut in place of the rotary blade 102, and the above-described cutting processes are performed, whereby the processing accuracy can be improved in the post-processing of the tooth surface by the shaving process.

While preferred embodiments of the present invention have been described above with reference to the drawings, it is needless to say that the present invention is not limited to these examples. It is obvious that those skilled in the art can conceive various modifications and alterations within the scope of the claims, and these modifications also fall within the technical scope of the present invention.

Industrial applicability

The present invention can be used as a gear machining method for machining a gear by cutting.

Claims

1. A gear machining method for machining a gear by cutting, characterized in that,

the center of the tooth profile is cut shallowly so as to satisfy the minimum tolerance of OBD or BBD,

after the tooth profile center is cut, the tooth surface is cut so as to be a central value of an allowable error of the OBD or BBD without changing the cutting depth.

2. The gear processing method according to claim 1,

the cutting process of the gear is performed by a shaving process, a hobbing process, or a gear shaping process.