JP2020165442A - Spindle device and electric tool - Google Patents

Abstract

To provide a spindle device that is excellent in high-speed rotation and vibration accuracy of a rotational shaft although a bearing for supporting the rotational shaft for tool connection is made compact.SOLUTION: Bearings 3, 4 that support a rotational shaft 2 are ball bearings, and inward raceway grooves 2b, 2c are formed on the surface of the rotational shaft 2, so that a pitch circle diameter of a ball 5 is reduced to make the bearings 3 and 4 lightweight and compact while increasing a ball diameter to increase a load capacity. It is advisable to further suppress the radial vibration of the rotational shaft 2 by forming the two bearings 3 and 4 into a rear combination angular contact ball bearing and applying a preload.SELECTED DRAWING: Figure 1

Description

The present invention relates to a spindle device capable of connecting a tool to a hole of a rotating shaft, and an electric tool including the spindle device.

Power tools such as impact drivers and impact wrenches are widely used for tightening and loosening bolts and screws at high speed.

Generally, a power tool has a bearing for supporting a rotating shaft (so-called anvil), an electric motor, a transmission mechanism from the electric motor to the rotating shaft, etc. built in the housing, and the rotating shaft can be bolted or screwed according to the work. It has a structure with holes for inserting and connecting a tool (so-called bit). The tool connected to the hole is prevented from coming off by a holder such as a chuck. The rotation of the electric motor is transmitted to the rotating shaft by the transmission mechanism, and the rotating shaft and the tool are rotated integrally. The housing is provided with a hand grip. The user of the power tool can carry the handgrip by holding it in his / her hand and operate the necessary switch with his / her finger to proceed with the work.

Torque, impact, etc. act on the rotating shaft that holds the tool when tightening bolts and the like. Therefore, the bearing that supports the rotating shaft needs to receive vibration and load generated during tightening. Conventionally, as the bearing, a slide bearing, a needle bearing, and a ball bearing have been used. For example, in the power tool of Patent Document 1, a slide bearing is adopted as a bearing for supporting the rotating shaft.

Japanese Patent No. 6027946

Since a power tool is a handy type that can be carried around, it is generally required to be compact and lightweight. Further, when the rotation speed of the tool is low or the tip of the tool swings greatly, the workability of turning the bolt or the like is lowered. Therefore, it is also required to have excellent high-speed rotation and runout accuracy of the rotating shaft. That is, the bearing that supports the rotating shaft is required to have high-speed rotation, runout accuracy, and compactness.

Plain bearings and needle bearings have a small bearing cross-sectional height, which is advantageous for making power tools compact, but are inferior to ball bearings in terms of high-speed rotation and runout accuracy. On the other hand, standard ball bearings are inferior in load capacity and are disadvantageous in compactness.

In view of the above background, the problem to be solved by the present invention is to make a spindle device excellent in high-speed rotation and runout accuracy of the rotating shaft while the bearing supporting the rotating shaft for connecting tools is compact. is there.

In order to achieve the above object, the present invention relates to a spindle device including a rotating shaft having a hole for connecting a tool and a bearing that rotatably supports the rotating shaft, wherein the bearing is an outer ring and the outer ring. The inner raceway groove is composed of a ball bearing having a ball bearing having an inner raceway groove located inside the above ring and a plurality of balls arranged between the outer ring and the inner raceway groove, and the inner raceway groove is the rotation. The structure formed on the surface of the shaft was adopted.

According to the above configuration, since a ball bearing is used as a bearing for supporting the rotating shaft, the high-speed rotation and runout accuracy of the rotating shaft are excellent as compared with a needle bearing or the like. Further, since the bearing has a structure having an inner raceway groove formed on the surface of the rotating shaft, the ball diameter can be increased and the load capacity can be increased as compared with a standard ball bearing having an inner ring. it can. Therefore, it is possible to make a spindle device having excellent high-speed rotation and runout accuracy of the rotating shaft while the bearing is compact.

Preferably, the two bearings are provided, and the two bearings are configured as a rear combination angular contact ball bearing in which the back surfaces of the outer rings are joined to each other, and a preload is applied to the two bearings. .. In this way, the rotating shaft can be supported by a bearing arrangement that has relatively high rigidity and is suitable for supporting moment loads, and the radial runout of the bearing can be reduced. Therefore, the radial runout of the rotating shaft is particularly suppressed. be able to.

More specifically, it is preferable to provide an elastic body interposed between the back surfaces of the outer rings. In this way, preload can be applied to both bearings even if the two bearings do not have an inner ring.

Further, the rotating shaft is formed of a steel material, the inner raceway groove of the two bearings is formed of a hardened surface portion, and the hole portion is the hardened portion of the rotating shaft. Of the two bearings, the ball diameter of the bearing located on the side closer to the hole is preferably smaller than the ball diameter of the bearing located on the far side. When the rotating shaft is made of steel, the inner raceway groove can be made to have an appropriate hardness by quenching. On the other hand, if the hole is deepened, the tool can be inserted deeply into the hole and the radial runout of the tool can be suppressed, but it is not easy to form the hole in the hardened portion by quenching. If the ball diameter of the bearing located on the side closer to the hole is reduced, the inner raceway groove can be formed at a position farther from one end in the axial direction of the rotation axis, so that the portion to be hardened can be formed. It can be kept away from the formation site of the hole. That is, while making the two inner raceway grooves formed on the surface of the rotating shaft made of steel material have appropriate hardness, a hole is formed deeply from one end in the axial direction of the rotating shaft to suppress radial runout of the tool. Can be done.

The electric tool including the spindle device according to the present invention, the electric motor serving as the drive source of the rotating shaft, and the housing in which the electric motor and the bearing are built has the tool runout due to the adoption of the spindle device described above. It can be suppressed, and it is lightweight and compact near the bearing, so that workability can be improved.

As described above, by adopting the above configuration, the present invention can make a spindle device excellent in high-speed rotation and runout accuracy of the rotating shaft while the bearing supporting the rotating shaft for connecting tools is compact. ..

Longitudinal front view showing the spindle device according to the first embodiment of the present invention. Front view showing the appearance of the power tool provided with the spindle device of FIG. Longitudinal front view showing a spindle device according to a second embodiment of the present invention.

The spindle device and the power tool according to the first embodiment as an example of the present invention will be described with reference to FIGS. 1 and 2 of the accompanying drawings.

The spindle device 1 shown in FIG. 1 is for an electric tool including a rotating shaft 2 and two bearings 3 and 4 that rotatably support the rotating shaft 2 with respect to the housing 10.

The rotating shaft 2 has a hole 2a for connecting a tool. The hole portion 2a includes a hexagonal hole portion extending concentrically with the rotating shaft 2 from one end in the axial direction of the rotating shaft 2.

Here, the axial direction refers to a direction along the rotation center line of the rotation axis. Hereinafter, the radial direction refers to a direction perpendicular to the rotation center line, and the circumferential direction refers to a circumferential direction around the rotation center line.

Of the two bearings 3 and 4, the first bearing 3 located on the side farther from the hole 2a has an outer ring 3a, an inner raceway groove 2b located inside the outer ring 3a, and an outer ring 3a and the inner side. It is composed of a ball bearing having a plurality of balls 5 arranged between the track groove 2b and the track groove 2b. The second bearing 4 located on the side closer to the hole 2a is arranged between the outer ring 4a, the inner raceway groove 2c located inside the outer ring 4a, and the outer ring 4a and the inner raceway groove 2c. It is composed of a ball bearing having a plurality of balls 5 formed therein. The two bearings 3 and 4 each include a cage (not shown) that keeps the distance between the balls 5 in the circumferential direction.

The two outer rings 3a and 4a are each composed of an annular bearing component having a raceway groove on the inner peripheral side. The two inner raceway grooves 2b and 2c are formed on the outer peripheral portion of the surface of the rotating shaft 2.

The rotating shaft 2 is composed of a single member including a hole 2a and two inner raceway grooves 2b and 2c on the surface, and the entire rotating shaft 2 is made of a seamless steel material.

Considering that the ball 5 rolls directly on the inner track grooves 2b and 2c, the surface hardness of each inner track groove 2b and 2c is set to Rockwell hardness HRC58 or more and 62 or less, and the inner track groove 2b, The calculated average roughness Ra of 2c is preferably 0.02 or less. The Rockwell hardness HRC is defined in Japanese Industrial Standards JIS-Z2245: 2016 "Rockwell hardness test? Test method". The arithmetic mean roughness Ra is defined in JIS-B0601: 2013 "Product Geometric Specification (GPS) -Surface Material: Contour Curve Method-Terms, Definitions and Surface Material Parameters".

Of the outer peripheral portion of the rotating shaft 2, a predetermined range in the axial direction including the two inner raceway grooves 2b and 2c is a hardened surface portion. Therefore, each inner track groove 2b, 2c is composed of a hardened surface portion. By the quenching, the orbital grooves 2b and 2c on the inner side are hardened to the Rockwell hardness range of HRC58 to 62.

The quenching method for adjusting the inner track grooves 2b and 2c to the Rockwell hardness HRC58 to 62 is not particularly limited, but in the illustrated example, induction hardening is adopted. In the case of induction hardening, it is possible to prevent the hardened portion from staying near the outer periphery of the rotating shaft 2 and not reaching the vicinity of the hole portion 2a.

The hole 2a is formed after quenching in order to avoid distortion due to quenching. The hole depth D from one end of the rotating shaft 2 in the axial direction to the bottom of the hole 2a is set shorter than the axial distance from one end of the rotating shaft 2 in the axial direction to the second inner raceway groove 2c. This is to avoid forming the hole 2a in the hardened portion, facilitate the processing of the hole 2a, and facilitate the connection with the tool.

The two bearings 3 and 4 are configured as back-combined angular contact ball bearings in which the back surfaces of the outer rings 3a and 4a are joined to each other.

The front surface of the first outer ring 3a is axially abutted against the shoulder portion 11 provided on the inner circumference of the housing 10. The lid 12 of the housing 10 is axially abutted against the front surface of the second outer ring 4a. The two outer rings 3a and 4a are axially positioned by the shoulder portion 11 and the lid 12.

That is, the first outer ring 3a and the second outer ring 4a are abutted against each other in the axial direction. An elastic body 6 is interposed between the back surfaces of both outer rings 3a and 4a. The elastic body 6 is arranged in a compressed state between the recesses formed on the back surfaces of the two outer rings 3a and 4a. The recesses of both outer rings 3a and 4a hold the elastic body 6 in a predetermined posture. The elastic body 6 presses the two outer rings 3a and 4a in a direction away from each other in the axial direction. The elastic body 6 is made of, for example, a coil spring, and is arranged at a plurality of locations evenly distributed in the circumferential direction. Preload is applied to the two bearings 3 and 4 by the spring force of the elastic body 6. This preload corresponds to a so-called constant pressure preload method, whereby the rotational runout (radial runout, etc.) of each of the bearings 3 and 4 can be suppressed to be small.

In addition, in order to adjust the preload amount, the distance between the two outer rings 3a and 4a may be finely adjusted with a shim or the like. The preload amount is preferably 20 N or more and 490 N or less, although it depends on the usage conditions. If the preload amount exceeds 490N, there is a concern that excessive preload may lead to heat generation of the power tool. Further, when the preload amount is less than 20 N, the preload amount may not be sufficient for the usage conditions, and the runout accuracy of the rotating shaft 2 may not be suppressed to be small.

The bearings 3 and 4 are grease-lubricated. The grease to be sealed is not particularly limited. When power tools are used in cold regions, greases that can be used even at low temperatures, such as Martemp PS2 (registered trademark, made by Kyodo Yushi), Beacon 325 (registered trademark, made by Esso Petroleum), Isoflex Super LDS18 (registered) Trademark (manufactured by NOK Kluber) may be used.

The spindle device 1 is used as a component of a portable power tool as shown in FIG. The electric tool shown in FIG. 2 includes a spindle device 1, a housing 10, an electric motor 20, a transmission mechanism 30, a switch circuit 40, a tool 50 attached to and detached from the rotating shaft 2, and a battery 60.

The housing 10 is a casing containing two bearings 3 and 4 of the spindle device 1, an electric motor 20, a transmission mechanism 30, and a switch circuit 40. The lower part of the housing 10 is a hand grip 13.

The electric motor 20 serves as a drive source for the rotating shaft 2. The transmission mechanism 30 decelerates the output rotation of the electric motor 20 and transmits the output rotation to the rotation shaft 2, and also gives an impact in the rotation direction to the rotation shaft 2. The structure of the transmission mechanism 30 is not particularly limited, and for example, the one disclosed in Patent Document 1 may be adopted.

The battery 60 is removable from the lower end of the hand grip 13. The switch circuit 40 supplies the electric power of the battery 60 to the electric motor 20 and controls the drive of the electric motor 20 in response to the operation of the switch 41 arranged in the vicinity of the handgrip 13.

The tool 50 has a hexagonal columnar base end that can be inserted and removed from the hole 2a of the rotary shaft 2 shown in FIG. 1, and a tip for various operations such as a screwdriver, a wrench, and a drill. The tool 50 shown in FIG. 2 is fixed to the rotating shaft 2 by a holder such as a chuck.

As described above, the spindle device 1 and the power tool shown in FIGS. 1 and 2 employ ball bearings as the bearings 3 and 4 that support the rotating shaft 2, so that the rotating shaft 2 has high-speed rotation and runout accuracy. Is excellent. Since the bearings 3 and 4 have a structure having inner raceway grooves 2b and 2c formed on the surface of the rotating shaft 2, if it is a standard ball bearing, the ball can be utilized by utilizing the cross-sectional area where the inner ring is arranged. It is possible to increase the load capacity of the bearings 3 and 4 by increasing the ball diameter of the ball 5 and to make the outer diameters of the bearings 3 and 4 compact by reducing the pitch circle diameter of the plurality of balls 5. .. As described above, in the spindle device 1, the bearings 3 and 4 that support the rotary shaft 2 for connecting tools are compact, but the load capacity and rigidity of the bearings 3 and 4 are increased, and the rotary shaft 2 has high-speed rotation and runout. It can be made excellent in accuracy.

Therefore, since the spindle device 1 and the power tool provided with the spindle device 1 suppress the runout of the tool 50 when the rotating shaft 2 rotates, the workability when using the power tool can be improved, and the runout of the tool 50 can be improved. It is also possible to improve the machining accuracy of the workpiece by improving the accuracy.

Further, the spindle device 1 and the power tool provided with the spindle device 1 have reduced the weight of the bearings 3 and 4 by omitting the inner ring, and the bearings of the housing 10 have been made more compact as the outer diameters of the bearings 3 and 4 have been reduced. Can be planned. This also contributes to the improvement of workability when using the power tool.

Further, the spindle device 1 is configured as a rear combination angular contact ball bearing in which two bearings 3 and 4 supporting the rotating shaft 2 are joined to each other on the back surfaces of the outer rings 3a and 4a, and the two bearings 3 and 4 are formed. Since preload is applied, the rotating shaft 2 is supported by the rear combination angular contact ball bearings 3 and 4, which are relatively high in rigidity and are suitable for supporting moment loads, and the rigidity of each of the bearings 3 and 4 is increased. Is improved, so that the radial runout of each of the bearings 3 and 4 is reduced. Therefore, the spindle device 1 and the electric tool can particularly suppress the radial runout of the rotating shaft 2, and thus further suppress the radial runout of the tool 50.

Further, since the spindle device 1 includes an elastic body 6 interposed between the back surfaces of the outer rings 3a and 4a, preload is applied to both bearings 3 and 4 even if the two bearings 3 and 4 do not have an inner ring. be able to.

Although FIG. 1 shows an example in which the ball diameters of the two bearings 3 and 4 are the same, the ball diameters of the first bearing 3 and the ball diameters of the second bearing 4 may be different. A second embodiment as an example thereof is shown in FIG. In the following, only the differences from the first embodiment will be described, and the same reference numerals will be used for common components.

Of the two bearings 3 and 4 according to the second embodiment, the ball diameter of the second bearing 4 located on the side closer to the hole 2a is smaller than the ball diameter of the first bearing 3 located on the far side. .. As the ball diameter of the second bearing 4 is reduced, the inner diameter and width of the second outer ring 4a are reduced.

Further, since the ball diameter of the second bearing 4 is smaller than that of the first embodiment, the width of the inner raceway groove 2c is smaller than that of the first embodiment, and the inner raceway groove 2c is also smaller. The position of is changed to a position far from one end in the axial direction of the rotating shaft 2 as compared with the first embodiment, and the portion of the rotating shaft 2 that has been induction hardened is also changed accordingly.

The depth D of the hole 2a is enlarged as compared with the first embodiment, but the hole 2a does not reach the induction hardened portion. That is, the hole portion 2a is located at a position outside the hardened portion of the rotating shaft 2.

As described above, in the spindle device 1 according to the second embodiment, the ball diameter of the second bearing 4 located on the side closer to the hole 2a is reduced, and the inner raceway groove 2c is formed on the rotating shaft 2 by that amount. It can be formed at a position far from one end in the axial direction, and the portion hardened by quenching can be kept away from the formed portion of the hole 2a. That is, the spindle device 1 makes the two inner raceway grooves 2b and 2c formed on the surface of the rotating shaft 2 made of steel material have appropriate hardness, and deepens the hole 2a from one end in the axial direction of the rotating shaft 2. It can be formed to suppress the radial runout of the tool 50 (see FIG. 2).

It should be considered that each embodiment disclosed this time is exemplary in all respects and not restrictive. Therefore, the scope of the present invention is indicated by the scope of claims and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Spindle device 2 Rotating shaft 2a Holes 2b, 2c Inner raceway grooves 3, 4 Bearings 3a, 4a Outer ring 5 Balls 6 Elastic body 10 Housing 20 Electric motor 50 Tools

Claims (5)

In a spindle device including a rotary shaft having a hole for connecting a tool and a bearing that rotatably supports the rotary shaft.
The bearing comprises a ball bearing having an outer ring, an inner raceway groove located inside the outer ring, and a plurality of balls arranged between the outer ring and the inner raceway groove.
A spindle device characterized in that the inner raceway groove is formed on the surface of the rotating shaft. The first aspect of the present invention, wherein the two bearings are provided, and the two bearings are formed as a rear combination angular contact ball bearing in which the back surfaces of the outer rings are joined to each other, and a preload is applied to the two bearings. Spindle device. The spindle device according to claim 2, further comprising an elastic body interposed between the back surfaces of the outer rings. The rotating shaft is made of steel,
The inner raceway grooves of the two bearings consist of a hardened surface.
The hole is located at a position off the hardened portion of the rotating shaft.
The spindle device according to claim 2 or 3, wherein the ball diameter of the bearing located on the side closer to the hole of the two bearings is smaller than the ball diameter of the bearing located on the far side. An electric tool comprising the spindle device according to any one of claims 1 to 4, an electric motor serving as a drive source for the rotating shaft, and a housing containing the electric motor and the bearing.

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