US-12617067-B2 - Impact tool, spindle, and spindle manufacturing method

US12617067B2US 12617067 B2US12617067 B2US 12617067B2US-12617067-B2

Abstract

An impact tool includes: a motor; a sun gear rotated by the motor; and at least three planet gears, which mesh with the sun gear; an internal gear, which meshes with the planet gears. A spindle includes a flange portion having a hole in an axial direction for the insertion of the sun gear, and slit portions in at least a side surface thereof for mounting the planet gears, and a shaft portion extending forward from the flange portion in the axial direction. The flange portion is shaped by forging. A hammer is held on the spindle; an anvil is impacted by the hammer in a rotational direction. A hammer case houses the hammer and holds the anvil in a rotatable manner; a tool-accessory retaining part is formed on the anvil; and a coil spring biases the hammer toward the anvil.

Inventors

Shinichi Urano
Tomoyuki Kurata

Assignees

MAKITA CORPORATION

Dates

Publication Date: 20260505
Application Date: 20241001
Priority Date: 20231003

Claims (20)

1 . An impact tool comprising: a motor; a sun gear rotated by the motor; at least three planet gears, which mesh with the sun gear; an internal gear, which meshes with the planet gears; a spindle, which includes a flange portion—having a hole in an axial direction in which the sun gear is inserted, and slit portions in at least a side surface thereof in which the planet gears are mounted—and a shaft portion extending forward from the flange portion in the axial direction, at least a portion of the flange portion having been shaped by forging; a hammer, which is held on the spindle; an anvil configured to be impacted by the hammer in a rotational direction; a hammer case, which houses the hammer and holds the anvil in a rotatable manner; a tool-accessory retaining part, which is provided on the anvil; and a coil spring, which biases the hammer toward the anvil; wherein grain flows in the flange portion of the spindle are formed by the forging to extend outward from the center of the radial direction.
2 . The impact tool according to claim 1 , wherein the flange portion has a cut surface on at least a portion of a surface.
3 . The impact tool according to claim 1 , further comprising: a ball disposed between the spindle and the hammer; wherein the spindle has, in the shaft portion, a spindle groove in which at least a portion of the ball is disposed.
4 . The impact tool according to claim 1 , wherein the spindle is formed using a steel that contains 0.13-1.00 mass % carbon and at least 0.90 mass % chromium.
5 . The impact tool according to claim 1 , wherein the spindle has: a first flange connected to the shaft portion; a second flange disposed opposing the first flange and rearward of the first flange; and at least one coupling portion, which connects the first flange and the second flange to each other in the axial direction.
6 . The impact tool according to claim 5 , wherein: a plurality of the coupling portions is arranged in the circumferential direction and connects the first flange and the second flange to each other in the axial direction; and each of the planet gears is disposed respectively between mutually adjacent coupling portions at a location sandwiched between the first flange and the second flange.
7 . The impact tool according to claim 5 , wherein portions of the spindle that face openings surrounded by the first flange, the second flange, and the plurality of coupling portions are non-cut portions.
8 . A spindle used in a power tool, comprising: a flange portion having a hole in an axial direction for the insertion of a sun gear, and slit portions in at least a side surface thereof for mounting planet gears; and a shaft portion extending forward from the flange portion; wherein the flange portion has been shaped by forging.
9 . The spindle according to claim 8 , wherein the flange portion has a cut surface on at least a portion of a surface.
10 . The spindle according to claim 8 , wherein the shaft portion has a spindle groove in which at least a portion of a ball is disposed.
11 . The spindle according to claim 8 , wherein the spindle is formed using a steel that contains 0.13-1.00 mass % carbon and at least 0.90 mass % chromium.
12 . The spindle according to claim 8 , wherein grain flows in the flange portion are formed by the forging to extend outward from the center of the radial direction.
13 . The spindle according to claim 8 , wherein the flange portion has: a first flange connected to the shaft portion; a second flange disposed opposing the first flange and rearward of the first flange; and a coupling portion, which couples the first flange and the second flange to each other in the axial direction.
14 . The spindle according to claim 13 , wherein: a plurality of the coupling portions is disposed in a circumferential direction; and each of the planet gears is disposed respectively between mutually adjacent coupling portions at a location sandwiched between the first flange and the second flange.
15 . The spindle according to claim 13 , wherein portion of the flange that face openings surrounded by the first flange, the second flange, and the plurality of coupling portions are non-cut portions.
16 . A method of manufacturing a spindle comprising a flange portion—having a hole in an axial direction for the insertion of a sun gear, and a slit portion in at least a side surface thereof for mounting a planet gear—and a shaft portion extending forward from the flange portion, the spindle being used in a power tool, the manufacturing method comprising: providing a slug, which has a flange-corresponding portion and a shaft-corresponding portion that correspond to the flange portion and the shaft portion, respectively; disposing, with respect to the flange-corresponding portion of the slug, a die in which a slit-corresponding part, which corresponds to the slit portion, is formed; and forming the slit portion by forging, in which, in the state in which the die is disposed, a rear-end portion of the flange-corresponding portion is struck in the axial direction to cause plastic deformation of the flange-corresponding portion along the slit-corresponding part of the die.
17 . The method according to claim 16 , further comprising: forming the hole by cutting the flange-corresponding portion after the plastic deformation of the flange-corresponding portion.
18 . The method according to claim 16 , wherein: the slug is formed by forging in the state in which the temperature of the material is −20° C. or higher and 40° C. or lower, 300° C. or higher and 850° C. or lower, or 1,000° C. or higher and 1,250° C. or lower; and the spindle is formed by forging in which the temperature of the formed slug is −20° C. or higher and 40° C. or lower.
19 . The method according to claim 16 , further comprising: heat treating the spindle after formation by forging until the surface hardness of the spindle becomes 300 HV or more.
20 . The impact tool according to claim 5 , wherein both the first flange and the second flange have been shaped by forging such that grain flows in the first flange and the second flange extend outward from the center of the radial direction.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Japanese patent application no. 2023-171993 filed on Oct. 3, 2023, the contents of which are fully incorporated herein by reference. TECHNICAL FIELD The techniques disclosed in the present specification relate to an impact tool, a spindle, and a method of manufacturing the spindle. BACKGROUND ART An impact tool related to the present teachings is disclosed in Japanese Laid-open Patent Publication No. 2021-037561. SUMMARY OF THE INVENTION It is one non-limiting object of the present teachings to disclose techniques for reducing the time required to manufacture the spindle for an impact tool. In one non-limiting aspect of the present teachings, an impact tool may preferably comprise: a motor; a sun gear rotated by the motor; at least three planet gears, which mesh with the sun gear; an internal gear, which meshes with the planet gears; a spindle, which includes a flange portion—having a hole in an axial direction for the insertion of the sun gear, and slit portions in at least a side surface thereof for mounting the planet gears—and a shaft portion extending forward from the flange portion in the axial direction, at least a portion of the flange portion having been shaped (formed) by forging; a hammer, which is held on the spindle; an anvil, which is impacted by the hammer in a rotational direction; a hammer case, which houses the hammer and holds the anvil in a rotatable manner; a tool-accessory retaining part, which is provided on the anvil; and a coil spring, which biases the hammer toward the anvil side. By utilizing the spindle forging techniques disclosed in the present specification, an impact tool, a spindle, and a method of manufacturing method a spindle are provided in which the time required for manufacturing can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an oblique view, viewed from the front, showing an impact tool according to an embodiment of the present teachings. FIG. 2 is a side view showing an upper portion of the impact tool according to the embodiment. FIG. 3 is a longitudinal, cross-sectional view showing the upper portion of the impact tool according to the embodiment. FIG. 4 is a transverse, cross-sectional view showing the upper portion of the impact tool according to the embodiment. FIG. 5 is an exploded, oblique view showing a spindle and associated parts of of the impact tool according to the embodiment. FIG. 6 is a bottom view showing a spindle according to the embodiment. FIG. 7A schematically shows one example of grain flows in a solid portion of the spindle according to a first forging variation of the embodiment. FIG. 7B schematically shows another example of grain flows in the solid portion of the spindle according to a second forging variation of the embodiment. FIG. 8 is a side view of the spindle according to the embodiment. FIG. 9 is a flow chart showing one example of a method of manufacturing the spindle according to the embodiment. FIG. 10 shows one example of a slug (semi-finished product) according to the embodiment. FIG. 11 shows one example of a forging die according to the embodiment. FIG. 12 shows one example of a die-arranging step according to the embodiment. FIG. 13A shows one example of a first type of forging step according to the embodiment. FIG. 13B shows one example of a second type of forging step according to the embodiment. FIG. 14A shows one example of a first type of cutting step according to the embodiment. FIG. 14B shows one example of a second type of cutting step according to the embodiment. FIG. 14C schematically shows one example of grain flows in the solid portion of the spindle according to the embodiment. FIG. 14D schematically shows another example of grain flows in the solid portion of the spindle according to the second forging variation of the embodiment. FIG. 15A showing an example of a forging step according to the first forging variation of the embodiment. FIG. 15B shows another example of a forging step according to the second forging variation of the embodiment. FIG. 16A shows an example of a cutting step according to the embodiment. FIG. 16B shows another example of a cutting step according to the embodiment. FIG. 16C schematically shows another example of grain flows in the solid portion of the spindle according to the second forging variation of the embodiment. FIG. 16D schematically shows another example of the grain flows in the solid portion of the spindle according to the second forging variation of the embodiment. DETAILED DESCRIPTION As was mentioned above, an impact tool according to one aspect of the present teachings preferably comprises: a motor; a sun gear rotated by the motor; at least three planet gears, which mesh with the sun gear; an internal gear, which meshes with the planet gears; a spindle, which includes a flange portion—having a hole in an axial direction for the insertion of the sun gear, and slit portions in at least a