Electric tool

Abstract

The present invention improves convenience of an electric tool by achieving size reduction or weight reduction of a speed reduction mechanism. An electric tool 1A according to an embodiment is provided with: a motor 20; a pin wheel 8 connected to the motor 20 via a power transmission path; and a speed reduction part 30 that includes a paradoxical planetary gear mechanism and that is provided in the power transmission path. The speed reduction part 30 includes: a gear case 40; a sun gear 51 to which driving force output from the motor 20 is input; a planetary gear 52 meshing with the sun gear 51; and a fixed internal gear 53 and a movable internal gear 54 meshing with the planetary gear 52. The fixed internal gear 53 cannot rotate relative to the gear case 40, and the movable internal gear 54 can rotate relative to the gear case 40. Further, the number of teeth of the fixed internal gear 53 and the number of teeth of the movable internal gear 54 are different from each other.

Description

Power Tool

[0001] The present invention relates to a power tool.

[0002] Currently, various power tools are manufactured and sold. Patent Document 1 describes a nailing machine which is an example of a power tool. The nailing machine described in Patent Document 1 comprises an electric motor, a gear case, and a speed reduction mechanism accommodated in the gear case. The speed reduction mechanism comprises a plurality of planetary gear mechanisms arranged coaxially.

[0003] International Publication No. 2018 / 100943

[0004] For power tools equipped with a speed reduction mechanism, it is desired to improve convenience by achieving size and weight reduction of the speed reduction mechanism.

[0005] In one embodiment, the power tool comprises a motor, an actuating part connected to the motor via a power transmission path, and a speed reduction part that includes a strange planetary gear mechanism and is provided in the power transmission path. The speed reduction part comprises a gear case, an input gear to which a driving force output from the motor is input, an intermediate gear meshing with the input gear, a fixed gear meshing with the intermediate gear, and an output gear that meshes with the intermediate gear to constitute the strange planetary gear mechanism together with the input gear, the intermediate gear, and the fixed gear. The fixed gear is non-rotatable relative to the gear case, the output gear is rotatable relative to the gear case, and the number of teeth of the fixed gear is different from the number of teeth of the output gear.

[0006] According to the present invention, size and weight reduction of the speed reduction mechanism is achieved, and the convenience of the power tool is further improved.

[0007] This is a front view showing the external appearance of the power tool according to Embodiment 1. This is a side view showing the external appearance of the power tool according to Embodiment 1. This is a partial cross-sectional view showing the structure of the power tool according to Embodiment 1. This is an explanatory diagram showing the external appearance of the reduction gear of Embodiment 1. This is a cross-sectional view showing the structure of the reduction gear of Embodiment 1. This is an enlarged cross-sectional view showing the structure of the reduction gear of Embodiment 1. This is a schematic diagram showing the structure of the reduction gear of Embodiment 1. This is an exploded perspective view showing the structure of the reduction gear of Embodiment 1. This is an explanatory diagram showing the relationship between the rotation (revolution) of the planetary gear and the rotation of the movable internal gear. This is another explanatory diagram showing the relationship between the rotation (revolution) of the planetary gear and the rotation of the movable internal gear. This is an enlarged cross-sectional view showing the support structure of the planetary gear. This is a partially enlarged view showing the meshing state of the planetary gear, fixed internal gear and movable internal gear. This is an enlarged cross-sectional view showing a modified example of the gear case. This is a front view showing the external appearance of the power tool according to Embodiment 2. This is a partial cross-sectional view showing the structure of the power tool according to Embodiment 2. This is a partial cross-sectional view showing the structure of the power tool according to Embodiment 3. This is an enlarged cross-sectional view showing the structure of the reduction gear of according to a modified example of Embodiment 3. This is an enlarged cross-sectional view showing the structure of the deceleration unit according to a modified example of Embodiment 3.

[0008] Embodiments of the present invention will be described below with reference to the drawings. In all drawings used to illustrate the embodiments, the same or substantially identical components and elements will be denoted by the same reference numerals. For convenience, hatching may be omitted even in cross-sections, and hatching may be applied even in non-cross-sections. Components and elements that have already been described will generally not be described again.

[0009] (Embodiment 1) <Overview of the Power Tool> Figure 1 is a front view showing the external appearance of the power tool 1A according to this embodiment. Figure 2 is a side view showing the external appearance of the power tool 1A. Figure 3 is a partial cross-sectional view showing the structure of the power tool 1A. Note that the cross-section shown in Figure 3 is the cross-section along the line A-A in Figure 1.

[0010] The power tool 1A according to this embodiment is suitable for driving fasteners into mating materials such as wood and plasterboard. More specifically, the power tool 1A according to this embodiment is a nail gun for driving nails into mating materials. Therefore, in the following description, the power tool 1A according to this embodiment may be referred to as "nail gun 1A".

[0011] As mainly shown in Figure 2, the nail gun 1A has a nail gun body 2 and a magazine 3. Multiple nails are loaded into the magazine 3. The magazine 3 is equipped with a feeder 3a. The feeder 3a supplies the multiple nails loaded in the magazine 3 one by one to the nail gun body 2.

[0012] The nail gun body 2 has a ejection unit 4, a striking unit 5, and a biasing unit 6. The ejection unit 4 supports the nails supplied from the magazine 3, and the biasing unit 6 biases the striking unit 5 in a predetermined direction. The striking unit 5, biased by the biasing unit 6, strikes the nails supported by the ejection unit 4. The nails struck by the striking unit 5 are ejected from the nail gun body 2 and driven into the target material. The ejection unit 4, striking unit 5, and biasing unit 6 will be explained in more detail later.

[0013] <Housing> The nail gun body 2 has a housing 10 which consists of a main body 11, a handle 12, a motor housing 13, a connecting part 14, etc. One end of the handle 12 and the motor housing 13 in the longitudinal direction is connected to the main body 11, and the other end of the handle 12 and the motor housing 13 in the longitudinal direction is connected to the connecting part 14. In other words, the main body 11, the handle 12, the motor housing 13 and the connecting part 14 are an integrated unit.

[0014] The main body 11 has a roughly rectangular cylindrical shape overall. Here, the longitudinal direction of the main body 11 shown in Figures 1 to 3 is defined as the "up-down direction," and the longitudinal direction of the handle 12 and motor housing 13 is defined as the "front-back direction." Furthermore, a third direction perpendicular to the up-down direction and the front-back direction is defined as the "left-right direction." The right and left sides are distinguished based on the operator's viewpoint when using the nail gun 1A.

[0015] To describe the housing 10 again according to the above definition, the handle portion 12 is located above the motor housing portion 13 and extends rearward from the back of the main body portion 11. On the other hand, the motor housing portion 13 is located below the handle portion 12 and extends rearward from the back of the main body portion 11.

[0016] Magazine 3 is located to the left of the handle 12 and motor housing 13 in normal use. In other words, the handle 12 and motor housing 13 are located to the right of magazine 3 in normal use. In the following description, the side on which magazine 3 is located in the drawings may be referred to as the "magazine side," regardless of whether magazine 3 is shown in the drawings or not. Similarly, the side on which the handle 12 is located in the drawings may be referred to as the "handle side," regardless of whether handle 12 is shown in the drawings or not.

[0017] As mainly shown in Figure 3, a battery mounting section 14a is provided on the back of the connecting section 14, to which a battery pack BP capable of supplying power is detachably attached. A controller CE, which serves as the control unit, is housed inside the connecting section 14. While the rated voltage of the battery pack BP is 18V, the rated voltage can be any value between 7.2V and 36V.

[0018] The housing 10 is composed of two housing members made of synthetic resin such as nylon or polycarbonate. More specifically, the housing 10, which has a main body portion 11, a handle portion 12, a motor housing portion 13, and a connecting portion 14, is formed by two housing members that are butted against each other and fixed together.

[0019] <Injection Section> Refer to Figure 2 again. The injection section 4 extends downward from the lower part (bottom) of the main body 11. The injection section 4 has a blade guide 4a that forms an injection passage through which nails are supplied by the magazine 3 and also serves as a sliding guide for the driver blade 5b. The injection section 4 also has a nose 4b that connects the blade guide 4a and the cylinder 6b to assemble them together and supports the rotation axis of the pinwheel 8. The nails loaded in the magazine 3 are fed into the injection passage by the feeder 3a and held within the injection passage.

[0020] A push lever 7a and an adjuster 7b are provided near the injection section 4. When the push lever 7a comes into contact with the mating material, it moves upward relative to the material against the biasing force of the coil spring. When the push lever 7a is separated from the mating material, it moves downward relative to the material due to the biasing force of the coil spring. The pushing lever 7a rising to a predetermined position is one of the conditions for the nail gun 1A to perform the nailing operation.

[0021] <Striking section, biasing section> The striking section 5 and the biasing section 6 are housed in the main body 11. The striking section 5 has a piston 5a and a driver blade 5b. The biasing section 6 has a pressure accumulator 6a and a cylinder 6b. The pressure accumulator 6a is housed in the upper part of the main body 11. The cylinder 6b has a cylindrical shape extending downward from the pressure accumulator 6a. The pressure accumulator 6a and the cylinder 6b are in communication with each other to form a pressure chamber. The pressure chamber defined by the pressure accumulator 6a and the cylinder 6b is filled with gas. More specifically, the pressure chamber is filled with compressed air.

[0022] The piston 5a is housed within the cylinder 6b so as to be able to move up and down. Therefore, the volume of the pressure chamber increases or decreases as the piston 5a moves (up and down). Specifically, the volume of the pressure chamber is minimum when the piston 5a moves to the top dead center and maximum when the piston 5a moves to the bottom dead center. Note that the piston 5a shown in Figure 2 is located at the bottom dead center.

[0023] When the piston 5a is at top dead center, the compressed air pressure in the pressure chamber is preferably between 0.8 MPa and 1.5 MPa, with 1.162 MPa being an example. When the piston is at bottom dead center, the pressure in the pressure chamber is preferably between 0.4 MPa and 0.8 MPa, with 0.6 MPa being an example. The inner diameter (diameter) of the cylinder 6b is preferably between 37 mm and 70 mm, with 40 mm being an example. In cases where the compressed air pressure in the pressure chamber is high and the rated voltage of the battery pack BP is 18V, conventionally, it was necessary to use a reduction gear with a large number of parts and a large weight in order to generate sufficient torque in the pinwheel 8 (the weight of a conventional reduction gear is, for example, 324 g). On the other hand, in this embodiment, the reduction gear 30 is made lighter by using a unique planetary gear mechanism. The weight of the reduction gear 30 in this embodiment is 147 g, but the weight of the reduction gear 30 may be any value between 100 g and 250 g.

[0024] The driver blade 5b is an elongated metal component that extends vertically. The upper end of the driver blade 5b is connected to the piston 5a. Alternatively, the driver blade 5b extends downward from the piston 5a.

[0025] The driver blade 5b moves up and down in conjunction with the piston 5a. As the piston 5a moves from the top dead center to the bottom dead center, the driver blade 5b, which moves in conjunction with the piston 5a, strikes the head of the nail.

[0026] <Motor> As shown in Figure 3, the nail gun 1A has a motor 20 which is the drive source. The motor 20 is an electric brushless motor and has a drive shaft 21 that extends in the front-rear direction. The drive shaft 21 of the motor 20 is connected to the input element of the reduction unit 30 which will be described later.

[0027] The motor 20 operates using power supplied from the battery pack BP according to the control of the controller CE. When predetermined conditions are met, the controller CE supplies power stored in the battery pack BP to the motor 20 to operate it. When the above predetermined conditions are no longer met, or when other predetermined conditions are met, the controller CE cuts off the power supply from the battery pack BP to the motor 20, thereby stopping the motor 20.

[0028] The motor 20 is connected to the pinwheel 8 via a power transmission path. More specifically, the input element of a reduction unit 30, which is located on the power transmission path, is connected to the motor 20, and the output element of the reduction unit 30 is connected to the rotation axis of the pinwheel 8.

[0029] As a result, the pinwheel 8 is driven by the rotational driving force output from the motor 20 and reduced by the reduction unit 30. In other words, the pinwheel 8 is an operating part connected to the motor 20 via a power transmission path.

[0030] The pin wheel 8 is provided with multiple pins that engage with multiple racks provided on the driver blade 5b. The multiple racks are arranged at predetermined intervals along the longitudinal direction (vertical direction) of the driver blade 5b. On the other hand, the multiple pins are arranged at predetermined intervals along the circumferential direction (rotational direction) of the pin wheel 8.

[0031] As the pinwheel 8 rotates, the pins of the pinwheel 8 and the rack of the driver blade 5b engage sequentially, causing the driver blade 5b to move upward. As a result, the piston 5a moves from the bottom dead center to the top dead center. In other words, the striking section 5 (piston 5a and driver blade 5b) rises. This reduces the volume of the pressure chamber (accumulator 6a and cylinder 6b), and increases the internal pressure of the pressure chamber. In other words, the compressed air filling the pressure chamber is further compressed.

[0032] From another perspective, the pinwheel 8 rotates while engaging with the driver blade 5b, thereby moving the striking part 5 upward against the biasing force of the biasing part 6.

[0033] Subsequently, when the engagement between the pin of the pinwheel 8 and the rack of the driver blade 5b is released, the piston 5a is moved from the top dead center to the bottom dead center by the pressure of the compressed air in the pressure chamber. In other words, the striking section 5 (piston 5a and driver blade 5b) descends.

[0034] As described above, the biasing unit 6 biases the striking unit 5 to one side (downward) in the vertical direction. The pinwheel 8 moves the striking unit 5 to the other side (upward) in the vertical direction, against the biasing force of the biasing unit 6.

[0035] <Reduction Unit> <Gear Case> As shown in Figure 3, the reduction unit 30 has a gear case 40 and a gear set 70 which includes a plurality of gears housed in the gear case 40. As will be described in detail later, the plurality of gears housed in the gear case 40 constitute a mysterious planetary gear mechanism. The gear set 70 consists of an input gear 51, a bearing 71, a plate 72, a washer 73, a fixed gear 53, a rotating shaft 57, a needle bearing 58, a spacer 59, an intermediate gear 52, a planetary carrier 55, a washer 74, an output gear 54, and a washer 75, as shown in Figure 8.

[0036] Figure 4 is an explanatory diagram showing the external appearance of the deceleration unit 30. Figure 5 is a cross-sectional view showing the structure of the deceleration unit 30. Note that the cross-section shown in Figure 5 is the cross-section along the line B-B in Figure 2.

[0037] The gear case 40 is made of resin and has a cylindrical shape. More specifically, the shape of the gear case 40 is cylindrical or substantially cylindrical. The total length (axial length) L of the gear case 40 shown in Figure 4 is 40.8 mm. The outer diameter D of the gear case 40 shown in Figure 5 is 43.0 mm. The weight of the gear case 40 is 27 g, the weight of the gear assembly 70 housed in it is 120 g, and the weight of the reduction unit 30, which includes the gear case 40 and the gear assembly 70, is 147 g.

[0038] Multiple recesses 41 are provided on the side surface of the gear case 40. As shown in Figure 4, each recess 41 extends in the axial direction (front-rear direction) of the gear case 40. As shown in Figure 5, two recesses 41 are provided at positions 180 degrees apart on the outer surface of the gear case 40. The protrusions 15 provided on the inner wall of the motor housing 13 fit into each of the recesses 41.

[0039] The gear case 40 is supported within the housing 10 by the engagement of the recess 41 and the protrusion 15, and rotation relative to the housing 10 is prevented. Alternatively, the protrusion 15 provided on the housing 10 is a projection (rib) that holds the side surface of the gear case 40 and prevents the gear case 40 from rotating.

[0040] As described above, in this embodiment, the side surface of the gear case 40 is held by the housing 10. Alternatively, there are no protrusions or bumps on the front or rear of the gear case 40 that are held by the housing 10. As a result, in this embodiment, the overall length L of the gear case 40 is shortened.

[0041] <Elastic Body> As shown in Figure 5, an elastic body 42 is interposed between the recess 41 and the protrusion 15. The elastic body 42 absorbs at least a portion of the rotational force acting on the gear case 40 through elastic deformation. In other words, the elastic body 42 is a cushioning material interposed between the motor housing portion 13 of the housing 10 and the gear case 40.

[0042] In this embodiment, the load on the gear case 40 is reduced by the elastic body 42. Therefore, in this embodiment, a lightweight and inexpensive resin gear case 40 is used. However, the reduction of the load on the gear case 40 by the elastic body 42 is not an essential condition for making the gear case 40 out of resin.

[0043] <<Mysterious Planetary Gear Mechanism>> Figure 6 is an enlarged cross-sectional view showing the structure of the speed reduction unit 30. Figure 7 is a schematic diagram showing the structure of the speed reduction unit 30. Figure 8 is an exploded perspective view showing the structure of the speed reduction unit 30. As described above, the speed reduction unit 30 includes a mysterious planetary gear mechanism. The mysterious planetary gear mechanism is a type of planetary gear mechanism, which is a gear mechanism (differential gear mechanism) that can achieve a large reduction ratio despite its small size.

[0044] The mysterious planetary gear mechanism is constituted by a plurality of gears accommodated in the gear case 40. The gear case 40 accommodates at least an input gear 51, a plurality of intermediate gears 52, a fixed gear 53, and an output gear 54, and these gears constitute the mysterious planetary gear mechanism.

[0045] In the following description, the input gear 51 may be referred to as a "sun gear 51", and the intermediate gear 52 may be referred to as a "planetary gear 52". Further, the fixed gear 53 may be referred to as a "fixed internal gear 53", and the output gear 54 may be referred to as a "movable internal gear 54".

[0046] The sun gear 51 is a spur gear located at the center of the mysterious planetary gear mechanism. It should be noted that all gears in the present embodiment do not necessarily have to be spur gears, and may be helical gears, for example. A driving force output from the motor 20 is input to the sun gear 51. That is, the sun gear 51 is an input element of the speed reduction unit 30. Specifically, one end of the drive shaft 21 of the motor 20 is press-fitted into the sun gear 51.

[0047] The planetary gears 52 are spur gears arranged around the sun gear 51 and mesh with the sun gear 51. In the present embodiment, three planetary gears 52 are arranged around the sun gear 51. Each planetary gear 52 is independently rotatable and is integrated by a planetary carrier 55.

[0048] The fixed internal gear 53 and the movable internal gear 54 are annular internal gears surrounding the plurality of planetary gears 52, and mesh with each of the planetary gears 52. In other words, both the fixed internal gear 53 and the movable internal gear 54 are ring gears.

[0049] However, the fixed internal gear 53 is not rotatable relative to the gear case 40. On the other hand, the movable internal gear 54 is rotatable relative to the gear case 40. As is most clearly shown in Figure 8, a plurality of engaging protrusions 56 are integrally molded on the outer circumferential surface of the fixed internal gear 53. More specifically, eight engaging protrusions 56 extending in the axial direction are provided at equal intervals on the outer circumferential surface of the fixed internal gear 53.

[0050] On the other hand, an engagement groove 43 into which an engagement projection 56 is inserted is integrally molded on the inner circumferential surface of the gear case 40. The fixed internal gear 53 is prevented from rotating relative to the gear case 40 by the engagement projection 56 being inserted into the engagement groove 43.

[0051] The fixed internal gear 53 and the movable internal gear 54 share a common axis of rotation and are adjacent to each other in the direction of the axis of rotation. The three planetary gears 52 are positioned between the sun gear 51 and the internal gears 53 and 54. Furthermore, each planetary gear 52 meshes with the sun gear 51 and also with the internal gears 53 and 54. However, the number of teeth Z3 of the fixed internal gear 53 and the number of teeth Z4 of the movable internal gear 54 are different (Z3 ≠ Z4).

[0052] As a result, when the planetary gear 52 completes one revolution around the sun gear 51 as the sun gear 51 rotates, the movable internal gear 54 rotates by the difference in the number of teeth between the fixed internal gear 53 and the movable internal gear 54, which is ΔZ. In other words, the movable internal gear 54 rotates by the difference in the number of teeth between the fixed internal gear 53 and the movable internal gear 54, which is ΔZ, when the planetary gear 52 completes one revolution.

[0053] In this embodiment, the fixed internal gear 53 has 39 teeth (Z3), and the movable internal gear 54 has 42 teeth (Z4). In other words, the tooth difference ΔZ in this embodiment is 3. Therefore, in this embodiment, when the planetary gear 52 revolves once, the movable internal gear 54 rotates by the length of 3 gear teeth. As a result, in this embodiment, the movable internal gear 54 rotates at a rotational speed of 1 / 105 of the rotational speed of the sun gear 51. In other words, the reduction ratio of this unique planetary gear mechanism is 105. The movable internal gear 54 is the output element of the reduction unit 30.

[0054] Figures 9 and 10 are explanatory diagrams showing the relationship between the rotation (revolution) of the planetary gear 52 and the rotation of the movable internal gear 54. When the sun gear 51 shown in Figure 9 rotates clockwise, each planetary gear 52 rotates counterclockwise on its own axis while revolving clockwise.

[0055] If the position of the planetary gear 52 shown in Figure 9 is taken as 0 degrees, then the position of the planetary gear 52 shown in Figure 10 is 60 degrees. In other words, the planetary gear 52 shown in Figure 10 revolves 60 degrees relative to the planetary gear 52 shown in Figure 9. Therefore, the movable internal gear 54 shown in Figure 10 rotates clockwise by half a gear tooth relative to the movable internal gear 54 shown in Figure 9.

[0056] Here, the rotation direction of the movable internal gear 54 relative to the rotation direction of the sun gear 51 is determined by the relationship between the number of teeth Z3 of the fixed internal gear 53 and the number of teeth Z4 of the movable internal gear 54. Specifically, when the number of teeth Z4 of the movable internal gear 54 is greater than the number of teeth Z3 of the fixed internal gear 53 (Z3 < Z4), the rotation direction of the sun gear 51 and the rotation direction of the movable internal gear 54 coincide. On the other hand, when the number of teeth Z4 of the movable internal gear 54 is less than the number of teeth Z3 of the fixed internal gear 53 (Z3 > Z4), the rotation direction of the sun gear 51 and the rotation direction of the movable internal gear 54 do not coincide (they are reversed).

[0057] Furthermore, in either case, it is not possible to rotate the input side from the output side. In other words, even if torque is input to the movable internal gear 54, which is the output element, the sun gear 51, which is the input element, will not rotate. As a result, the reduction unit 30, which includes the mysterious planetary gear mechanism, also functions as a one-way clutch provided in the power transmission path. From another perspective, in the nail gun 1A of this embodiment, there is no need to provide a one-way clutch in the power transmission path. As a result, cost reduction, weight reduction, and miniaturization are achieved.

[0058] ≪Support Structure of Planetary Gear≫ Figure 11 is an enlarged cross-sectional view showing the support structure of the planetary gear 52. The planetary gear 52 is required to mesh simultaneously with the fixed internal gear 53 and the movable internal gear 54, which are superimposed in the axial direction. For this reason, the component length (axial length) of the planetary gear 52 becomes longer, and the overall length of the rotation axis 57 of the planetary gear 52 also becomes longer.

[0059] Furthermore, the component length of the planetary gear 52 needs to be changed in accordance with the component lengths of the fixed internal gear 53 and the movable internal gear 54. And if the component length of the planetary gear 52 is changed, the overall length of the rotating shaft 57 will also be changed.

[0060] As shown in Figure 11, the planetary gear 52 is rotatably supported by two bearings (needle bearings 58) located at both ends of the rotating shaft 57. Furthermore, a cylindrical spacer 59 is positioned between the two needle bearings 58.

[0061] As a result, the length of the planetary gear 52 components and the overall length of the rotating shaft 57 can be changed simply by changing the spacer 59. In other words, the length of the planetary gear 52 components is not constrained by the length of the needle bearing 58. Therefore, the design freedom for the planetary gear 52 is increased.

[0062] <Meshing Height> Figure 12 is a partially enlarged view showing the meshing state of the planetary gear 52, the fixed internal gear 53, and the movable internal gear 54. In Figure 12, a dot pattern is added to the fixed internal gear 53 to make it easier to distinguish between the fixed internal gear 53 and the movable internal gear 54.

[0063] As shown in Figure 12, the meshing height T3 of the fixed internal gear 53 with respect to the planetary gear 52 and the meshing height T4 of the movable internal gear 54 with respect to the planetary gear 52 are different.

[0064] Note that "meshing height" refers to the amount of meshing between the gear teeth. For example, the meshing height T3 of the fixed internal gear 53 with respect to the planetary gear 52 is the amount of meshing between the gear teeth of the fixed internal gear 53 and the gear teeth of the planetary gear 52. Similarly, the meshing height T4 of the movable internal gear 54 with respect to the planetary gear 52 is the amount of meshing between the gear teeth of the movable internal gear 54 and the gear teeth of the planetary gear 52.

[0065] By reducing the total tooth height of either internal gear 53 or 54 (making the meshing height T3 and meshing height T4 different), it is expected that efficiency will be improved by reducing friction with the planetary gear 52 due to the reduction in tooth surface area. Therefore, in this embodiment, by reducing the total tooth height of the fixed internal gear 53, the meshing height T3 of the fixed internal gear 53 with respect to the planetary gear 52 is made lower than the meshing height T4 of the movable internal gear 54 (T3 < T4).

[0066] More specifically, the tooth heights of the gear teeth of the fixed internal gear 53 and the movable internal gear 54 are adjusted so that the meshing height T3 of the fixed internal gear 53 is lower than the meshing height T4 of the movable internal gear 54. As a result, in this embodiment, the tip circle diameter of the fixed internal gear 53 is larger than the tip circle diameter of the movable internal gear 54.

[0067] However, improvements in efficiency, such as reduced friction, can also be achieved to some extent by making the meshing height T4 of the movable internal gear 54 lower than the meshing height T3 of the fixed internal gear 53.

[0068] However, in this embodiment, the meshing height T3 of the fixed internal gear 53 is set lower than the meshing height T4 of the movable internal gear 54 for the following reasons.

[0069] Generally, gear teeth with a low meshing height receive a larger surface load than gear teeth with a high meshing height. For this reason, gear teeth with a low meshing height are more prone to breakage than gear teeth with a high meshing height.

[0070] Therefore, when the meshing height T3 of the fixed internal gear 53 is to be lower than the meshing height T4 of the movable internal gear 54, it is desirable to increase the tooth width of the fixed internal gear 53 to increase the strength of the gear teeth. In order to increase the tooth width of the fixed internal gear 53, it is necessary to increase the component length (axial length) of the fixed internal gear 53.

[0071] For similar reasons, when the meshing height T4 of the movable internal gear 54 is to be lower than the meshing height T3 of the fixed internal gear 53, it is desirable to increase the tooth width of the movable internal gear 54 to increase the strength of the gear teeth. And in order to increase the tooth width of the movable internal gear 54, it is necessary to increase the component length (axial length) of the movable internal gear 54.

[0072] Here, the fixed internal gear 53 is prevented from rotating relative to the gear case 40 by an engaging projection 56 provided on its outer circumferential surface. In other words, the rotation prevention structure of the fixed internal gear 53 is realized by the engaging projection 56. Therefore, in order to improve the durability and reliability of the rotation prevention structure, it is desirable to increase the width of the engaging projection 56 and thereby increase its strength. And in order to increase the width of the engaging projection 56, it is necessary to increase the component length (axial length) of the fixed internal gear 53.

[0073] In other words, the fixed internal gear 53 requires an extended component length for reasons other than improving the strength of the gear teeth by increasing the tooth width. Therefore, in this embodiment, by making the meshing height T3 of the fixed internal gear 53 lower than the meshing height T4 of the movable internal gear 54, the overall length of the mysterious planetary gear mechanism (≒ overall length L of the gear case 40) is kept as short as possible while simultaneously satisfying the above-mentioned multiple requirements. From another perspective, this avoids extending the component length of the movable internal gear 54, thereby achieving miniaturization of the reduction unit 30.

[0074] Furthermore, if the width of the engaging projection 56, which engages with the gear case 40 to prevent the rotation of the fixed internal gear 53, is increased, the load on the gear case 40 will be reduced. Therefore, lowering the meshing height T3 of the fixed internal gear 53 to a lower meshing height T4 of the movable internal gear 54 also contributes to reducing the load on the gear case 40.

[0075] In other words, making the meshing height T3 of the fixed internal gear 53 lower than the meshing height T4 of the movable internal gear 54 also contributes to the adoption of a lightweight and inexpensive resin gear case 40.

[0076] ≪Gear Dimensions≫ The dimensions of each part of the planetary gear 52, fixed internal gear 53, and movable internal gear 54 are as shown in Table 1. Note that the dimensions listed in Table 1 include those already mentioned. The unit of the numerical values ​​shown in Table 1 is [mm]. In order to obtain sufficient performance while suppressing an increase in the overall size of the product, it is desirable that the tooth tip diameter of the fixed internal gear 53 and the movable internal gear 54 be between 25.0 mm and 35 mm.

[0077]

[0078] <Modified Gear Case> Figure 13 is an enlarged cross-sectional view showing a modified gear case 40. Protrusions 44a and 44b are integrally molded at one axial end (tip) of the gear case 40 shown in Figure 13. The protrusions 44a and 44b fit into recesses provided in the nose 4b (Figures 3 and 4) via a cushioning material.

[0079] The gear case 40 shown in Figure 13 is supported within the housing 10 by the protrusions 44a and 44b fitting into the recesses of the nose 4b, and rotation relative to the housing 10 is prevented.

[0080] In Figure 4, the gear case 40 is held by its side by the housing 10. In contrast, in Figure 13, the gear case 40 is held by its end face (tip face) by the nose 4b. Therefore, the gear case 40 shown in Figure 13 does not have the recess 41 shown in Figure 4.

[0081] (Embodiment 2) Figure 14 is a front view showing the external appearance of the power tool 1B according to this embodiment. Figure 15 is a partial cross-sectional view showing the structure of the power tool 1B. The cross-section shown in Figure 15 is the cross-section along the line C-C in Figure 14.

[0082] The power tool 1B according to this embodiment is suitable for cutting bar stock. More specifically, the power tool 1B according to this embodiment is a cutting machine mainly for cutting threaded bolts. Therefore, in the following description, the power tool 1B according to this embodiment may be referred to as the "threaded bolt cutter 1B".

[0083] The all-thread cutter 1B has a motor 20 as a drive source. The motor 20 is connected to the cam 60 via a power transmission path. More specifically, the input element (input gear (sun gear) 51) of the reduction unit 30 provided on the power transmission path is connected to the motor 20, and the output element (output gear (movable internal gear) 54) of the reduction unit 30 is connected to the camshaft 61.

[0084] As a result, the cam 60 is driven by the rotational driving force output from the motor 20 and reduced by the reduction unit 30. In other words, the cam 60 is an operating part connected to the motor 20 via a power transmission path.

[0085] When the cam 60 rotates, the cutting mechanism, which consists of the movable arm 62 and other components, is activated. As a result, the movable blade 63 approaches the fixed blade 64 and rotates. This causes the threaded bolt set between the movable blade 63 and the fixed blade 64 to be cut.

[0086] (Embodiment 3) <Overview of the Power Tool> Figure 16 is a partial cross-sectional view showing the structure of the power tool 101 according to this embodiment. Figures 17 and 18 are enlarged cross-sectional views showing the structure of the reduction unit 130 of the power tool 101 according to this embodiment.

[0087] The power tool 101 according to this embodiment is suitable for screw tightening using a screwdriver bit and drilling using a drill bit. In the following description, the power tool 101 according to this embodiment may be referred to as the "driver drill 101". Note that the reduction gear 130 of the power tool 101 according to this embodiment has a different configuration from the reduction gear 30 of Embodiments 1 and 2, and the details will be described later.

[0088] The driver drill 101 has a motor 20 as a drive source. The motor 20 is connected to the spindle 160 via a power transmission path. More specifically, the input element (input gear (sun gear) 151) of a reduction unit 130 provided on the power transmission path is connected to the motor 20, and the output element (output shaft 161) of the reduction unit 130 is connected to the spindle 160. As a result, the spindle 160 is driven by the rotational driving force output from the motor 20 and reduced by the reduction unit 130. In other words, the spindle 160 is an operating part connected to the motor 20 via a power transmission path.

[0089] As the spindle 160 rotates, the drill chuck 162 connected to the spindle 160 also rotates integrally with the spindle 160. The drill chuck 162 can hold cutting tools such as screwdriver bits and drill bits, and by rotating while holding the cutting tool, it performs screw tightening operations, such as rotating screws in the workpiece, and drilling operations, such as drilling holes in the workpiece.

[0090] The reduction gear unit 130 of the "Mysterious Planetary Gear Mechanism" has a gear case 140 and a gear set housed in the gear case 140 that constitutes the mysterious planetary gear mechanism. The mysterious planetary gear mechanism includes an input gear 151, an intermediate gear 152, a fixed gear 153, an output gear 154, and a planetary carrier 155. The configuration of the mysterious planetary gear mechanism is the same as that of Embodiment 1 and Embodiment 2. In other words, when the input gear 151 rotates, the intermediate gear 152 that meshes with the input gear 151 meshes with the fixed gear 153 and the output gear 154 and rotates and revolves. Since the output gear 154 has a different number of teeth than the fixed gear 153, the output gear 154 rotates as the input gear 151 revolves.

[0091] However, the planetary carrier 155 differs from the planetary carrier 55 of Embodiments 1 and 2 in that it has an internal tooth meshing portion 155a on the radially inward side. The meshing portion 155a can mesh with an meshing portion 161d formed on the shaft portion 161a of the output shaft 161, which will be described later.

[0092] ≪Switching Section≫ The power tool 101 according to this embodiment differs from Embodiments 1 and 2 in that the reduction section 130 has an output shaft 161 as a switching section. The output shaft 161 includes a shaft portion 161a, a cylindrical portion 161b, a meshing portion (first meshing portion) 161c, a meshing portion (second meshing portion) 161d, a link connection portion 161e, and a wall portion 161f. The shaft portion 161a is a columnar shape extending in the axial direction of the output shaft 161 and is located at the radial center of the output shaft 161. The cylindrical portion 161b is a cylindrical shape concentric with the shaft portion 161a and is arranged radially outward at a distance from the shaft portion 161a. The wall portion 161f is a plate shape extending radially, with its radially outer side connected to the front end of the cylindrical portion 161b and its radially inner side connected to the shaft portion 161a. The meshing portion 161c is an internal tooth formed on the radially inner surface of the cylindrical portion 161b, and can mesh with the meshing portion 154a, which is an external tooth formed on the output gear 154. The meshing portion 161d is an external tooth formed on the radially outer surface of the shaft portion 161a, and can mesh with the meshing portion 155a, which is an internal tooth formed on the planetary carrier 155. The link connection portion 161e is a groove provided on the radially outer surface of the cylindrical portion 161b and extends in the circumferential direction. The output shaft 161 is formed from two parts that can be separated in the axial direction, and the shaft portion 161a is provided spanning the two parts. An external meshing portion 161g is also formed on the radially outer surface of the front end of the shaft portion 161a, and when this meshes with the spindle 160, the output shaft 161 and the spindle 160 rotate as a single unit.

[0093] The output shaft 161 is movable axially (in the front-rear direction) relative to the spindle 160. However, since the engagement allowance (the length of the meshing portion 161g in the axial direction) between the meshing portion 161g of the output shaft 161 and the spindle 160 is greater than the amount of movement of the output shaft 161, the output shaft 161 maintains its meshing with the spindle 160 even when it moves axially.

[0094] The power tool 101 according to this embodiment has a shift lever 164 and a link 163. The shift lever 164 is an operating part operated by the operator, and specifically moves in the front-rear direction (axial direction) relative to the housing 10 by the operator's operation. The link 163 is connected to the shift lever 164 directly or indirectly via another member, and moves axially relative to the gear case 140 by the operator's operation of the shift lever 164. The radially inner end of the link 163 is inserted into a groove-shaped link connection portion 161e formed on the outer surface of the cylindrical portion 161b of the output shaft 161. Therefore, the output shaft 161 is connected to the link 163 so that it cannot move relative to it in the axial direction, but can rotate relative to it in the circumferential direction. In other words, the output shaft 161 moves relative to the gear case 140 and the spindle 160 integrally with the link 163. That is, the output shaft 161 moves axially by the operator's operation of the shift lever 164.

[0095] ≪Switching between low-speed and high-speed modes≫ The meshing portion 161c of the output shaft 161 can mesh with the meshing portion 154a of the output gear 154, and the meshing portion 161d of the output shaft 161 can mesh with the meshing portion 155a of the planetary carrier 155, but these do not mesh simultaneously. In the state shown in Figure 17, where the output shaft 161 is positioned on the front side (one side in the axial direction), the meshing portion 161d of the output shaft 161 does not mesh with the meshing portion 155a of the planetary carrier 155, but the meshing portion 161c of the output shaft 161 meshes with the meshing portion 154a of the output gear 154. Furthermore, as shown in Figure 18, in the state where the output shaft 161 is positioned on the rear side (the other side in the axial direction) (second state), the meshing portion 161c of the output shaft 161 does not mesh with the meshing portion 154a of the output gear 154, but the meshing portion 161d of the output shaft 161 meshes with the meshing portion 155a of the planetary carrier 155. In other words, when the output shaft 161 is positioned on one side in the axial direction, the output shaft 161 meshes with the output gear 154 but does not mesh with the planetary carrier 155, and when the output shaft 161 is positioned on the other side in the axial direction, the output shaft 161 meshes with the planetary carrier 155 but does not mesh with the output gear 154. In this way, the output shaft 161 changes the meshing partner by moving axially relative to the spindle 160. Furthermore, as mentioned above, even if the output shaft 161 moves in the axial direction, the meshing between the output shaft 161 and the spindle 160 is maintained. Therefore, it can be said that the output shaft 161 does not change all of its meshing partners when it moves in the axial direction, but rather changes only some of the multiple meshing partners.

[0096] In the state shown in Figure 17, where the output shaft 161 is positioned on one side in the axial direction, the output shaft 161 is meshed with the output gear 154. Therefore, when the output gear 154 rotates, the output shaft 161 also rotates integrally with the output gear 154. Since the output gear 154 is the output end of the planetary gear mechanism, it has a large reduction ratio relative to the input gear 151. Specifically, the reduction ratio of the reduction unit 130 in the state where the output shaft 161 is positioned on one side in the axial direction is 65. In the state where the output shaft 161 is positioned on one side in the axial direction, the operating mode of the reduction unit 130 is the low-speed mode. Furthermore, in the state where the output shaft 161 is positioned on one side in the axial direction, the reduction unit 130 can be said to connect the drive shaft 21 of the motor 20 and the spindle 160 via the planetary gear mechanism. The state of the reduction unit 130 with the output shaft 161 positioned on one side in the axial direction, as shown in Figure 17, is an example of the first transmission state.

[0097] As shown in Figure 18, when the output shaft 161 is positioned on the other side in the axial direction, the output shaft 161 is meshed with the planetary carrier 155. Therefore, when the planetary carrier 155 rotates, the output shaft 161 also rotates integrally with the planetary carrier 155. Although the planetary carrier 155 is a component of the mysterious planetary gear mechanism, it is not the output end of the mysterious planetary gear mechanism, so its reduction ratio relative to the input gear 151 is smaller than that of the output gear 154. Specifically, the reduction ratio of the reduction unit 130 when the output shaft 161 is positioned on the other side in the axial direction is 5. When the output shaft 161 is positioned on the other side in the axial direction, the operating mode of the reduction unit 130 is high-speed mode. Furthermore, since the output shaft 161 is meshed with the planetary carrier 155 and not the output gear 154 which is the output end of the mysterious planetary gear mechanism, the reduction unit 130 can be said to connect the drive shaft 21 of the motor 20 and the spindle 160 without going through the mysterious planetary gear mechanism when the output shaft 161 is positioned on the other side in the axial direction. The state of the reduction unit 130, where the output shaft 161 is located on the other side in the axial direction, as shown in Figure 18, is an example of a second transmission state.

[0098] As described above, the power tool 101 according to this embodiment has an output shaft 160 that changes the reduction ratio of the reduction unit 130 by switching the reduction unit 130 between a first transmission state in which the motor 20 and spindle 160 are connected via a mysterious planetary gear mechanism, and a second transmission state in which the motor 20 and spindle 160 are connected without the mysterious planetary gear mechanism. With this configuration, a high reduction ratio of the reduction unit 130 can be achieved while suppressing the increase in size of the power tool 101 by using a mysterious planetary gear mechanism, and the workability of the operator can be improved by making this reduction ratio changeable. In addition, since the reduction ratio is switched by changing the mating part of the output shaft 160, the reduction ratio can be changed with a simple configuration.

[0099] Furthermore, the effect of switching the reduction ratio by changing the mating gear of the output shaft 160 does not depend on whether the reduction unit has a special planetary gear mechanism. In other words, instead of having multiple transmission members such as the input gear 151, intermediate gear 152, fixed gear 153, output gear 154, and planetary carrier 155 as in this embodiment, a configuration may be used in which multiple stages of a normal planetary gear mechanism consisting of an input gear, planetary gear, fixed gear, and planetary carrier are provided as multiple transmission members.

[0100] The output shaft 161 has a shape in which a shaft portion 161a located at the radial center and a cylindrical portion 161b located radially outside the shaft portion 161a are connected by a radially extending wall portion 161f. Since the inner surface of the cylindrical portion 161b and the outer surface of the shaft portion 161a are provided with meshing portions 161c and 161d, respectively, the multiple meshing portions 161c and 161d necessary to change the meshing partner of the output shaft 161 can be compactly laid out. In addition, in order to move the output shaft 161, it is necessary to connect a link 163 that connects the output shaft 161 and the shift lever 164 to the output shaft 161. Here, by providing the link connection portion 161e of the output shaft 161 on the outer circumference of the cylindrical portion 161b rather than the smaller diameter shaft portion 161a, the dimensions of the link 163 can be reduced, improving durability.

[0101] <Modified Version of Embodiment 3> Figures 19 and 20 are enlarged cross-sectional views showing a modified version of Embodiment 3. In this embodiment, the reduction gear 230 includes a second planetary gear (second intermediate gear) 262 and a second planetary carrier (second carrier) 264 connected downstream of the mysterious planetary gear mechanism. The second planetary gear 262 has a meshing portion 262a. The second planetary carrier 264 includes a meshing portion 264a and rotatably supports the second planetary gear 262. The second planetary carrier 264 is also connected to the spindle 260 and rotates integrally with it.

[0102] In this embodiment, the output gear 254 is included in the planetary gear mechanism as an output element and is also a switch that is movable in the axial direction. The output gear 254 includes a meshing portion 254a, a meshing portion 254b, a meshing portion 254c, a meshing portion 254d, and a link connecting portion 254e. The output gear 254 is formed in a cylindrical shape. The meshing portion 254a is an internal tooth provided at the rear of the radial inner surface of the output gear 254 and is capable of meshing with the intermediate gear 152. The meshing portion 254c is an internal tooth provided at the middle of the radial inner surface of the output gear 254 and is capable of meshing with the meshing portion 262a of the second intermediate gear 262. The meshing portion 254b is an internal tooth provided at the front of the radial inner surface of the output gear 254 and is capable of meshing with the meshing portion 264a of the second planetary carrier 264. The meshing portion 254d is an external tooth provided on the outer surface of the output gear 254, and is capable of meshing with the meshing portion 240a provided on the gear case 240. The link connection portion 254e is formed in the shape of a groove on the radial outer surface of the output gear 254, into which the link 163 is inserted. The output gear 254 moves relative to the gear case 240 and the spindle 260 integrally with the link 163, similar to the output shaft 161 in Embodiment 3. In other words, the output gear 254 moves axially due to the operator's operation of the shift lever 164.

[0103] As shown in Figure 19, when the output gear 254 is positioned on the rear side (the other side in the axial direction), the meshing portion 254c of the output gear 254 does not mesh with the meshing portion 262a of the second intermediate gear 262, and the meshing portion 254d does not mesh with the meshing portion 240a of the gear case 240. However, the meshing portion 254a meshes with the intermediate gear 152, and the meshing portion 254b meshes with the meshing portion 264a of the second planetary carrier 264. Therefore, when the input shaft 151 rotates, the intermediate gear 152, which meshes with the input gear 151, meshes with the fixed gear 153 and the output gear 254, causing it to rotate and revolve. Since the output gear 254 has a different number of teeth than the fixed gear 153, the output gear 254 rotates as the input gear 151 revolves. As a result, the second planetary carrier 264 rotates integrally with the output gear 254, and the spindle 260 also rotates integrally with the second planetary carrier 264.

[0104] Thus, in the state shown in Figure 19, where the output gear 254 is located on the rear side (the other side in the axial direction), the input gear 151, intermediate gear 152, fixed gear 153, output gear 254, and planetary carrier 255 function as a mysterious planetary gear mechanism. In other words, the reduction unit 230 connects the drive shaft 21 of the motor 20 and the spindle 260 via the mysterious planetary gear mechanism when the output gear 254 is located on the other side in the axial direction. The reduction ratio of the reduction unit 230 when the output gear 254 is located on the other side in the axial direction is 65, and the operating mode of the reduction unit 230 in this state is the low-speed mode. The state of the reduction unit 230 when the output gear 254 is located on the other side in the axial direction is an example of the first transmission state.

[0105] As shown in Figure 20, when the output gear 254 is positioned on the front side (one side in the axial direction), the meshing portion 254a of the output gear 254 does not mesh with the intermediate gear 152, and the meshing portion 254b does not mesh with the meshing portion 264a of the second planetary carrier 264. However, the meshing portion 254c meshes with the meshing portion 262a of the second intermediate gear 262, and the meshing portion 254d meshes with the meshing portion 240a of the gear case 240. Therefore, when the input shaft 151 rotates, the intermediate gear 152 that meshes with the input gear 151 meshes with the fixed gear 153 and rotates and revolves. As the intermediate gear 152 revolves, the planetary carrier 255 also rotates. When the planetary carrier 255 rotates, the second intermediate gear 262 that meshes with the planetary carrier 255 meshes with the output gear 254 and rotates and revolves. Furthermore, the output gear 254 does not rotate because its meshing portion 254d is engaged with the meshing portion 240a of the gear case 240. As the second intermediate gear 262 revolves, the second planetary carrier 264 also rotates, and the spindle 260 rotates integrally with the second planetary carrier 264.

[0106] Thus, in the state shown in Figure 20, where the output gear 254 is positioned on the front side (one side in the axial direction), the output gear 254 does not rotate, and therefore the input gear 151, intermediate gear 152, fixed gear 153, and planetary carrier 255 do not function as a mysterious planetary gear mechanism. In other words, the reduction unit 230 can be said to connect the drive shaft 21 of the motor 20 and the spindle 260 without going through the mysterious planetary gear mechanism when the output gear 254 is positioned on one side in the axial direction. The reduction ratio of the reduction unit 230 when the output gear 254 is positioned on one side in the axial direction is 17.33, and the operating mode of the reduction unit 230 in this state is the high-speed mode. The state of the reduction unit 230 when the output gear 254 is positioned on one side in the axial direction is an example of the second transmission state.

[0107] As described above, the output gear 254 changes its meshing partner by moving in the axial direction. More specifically, the output gear 254 changes some of its meshing partners by moving in the axial direction, thereby switching the reduction ratio of the reduction unit 230. In other words, the power tool 101 according to this embodiment has an output gear 254 that changes the reduction ratio of the reduction unit 230 by switching the reduction unit 230 between a first transmission state in which the motor 20 and spindle 260 are connected via a mysterious planetary gear mechanism, and a second transmission state in which the motor 20 and spindle 260 are connected without the mysterious planetary gear mechanism. With this configuration, it is possible to achieve a high reduction ratio of the reduction unit 230 while suppressing the increase in size of the power tool 101 by using a mysterious planetary gear mechanism, and by making this reduction ratio changeable, the work efficiency of the operator can be improved. Furthermore, the reduction unit 230 according to this embodiment can also be described as being switchable between a first transmission state in which a driving force is output at a first reduction ratio using a single-stage planetary gear mechanism, and a second transmission state in which a driving force is output at a second reduction ratio smaller than the first reduction ratio using a two-stage planetary gear mechanism.

[0108] The present invention is not limited to the embodiments described above, and can be modified in various ways without departing from its essence. In this embodiment, a nail gun, a threaded rod cutter, and a driver drill were described as examples of power tools in the present invention. However, the present invention can also be applied to various power tools having a reduction gear (for example, fastening and drilling tools other than driver drills that rotate a long-shaft tip tool, and cutting and machining tools such as circular saws, brush cutters, and grinders that rotate a flat-plate tip tool). The reduction ratio of the mysterious planetary gear mechanism provided in the reduction gear 30 can be changed arbitrarily. However, it is preferable to change the reduction ratio of the mysterious planetary gear mechanism within the range of 50 to 150.

[0109] The number of teeth Z3, Z4 and the tooth difference ΔZ are not limited to the above values. However, the number of teeth Z3 and Z4 are preferably in the range of 30 to 60, and the tooth difference ΔZ is preferably in the range of 1 to 3. In addition, the weight of the reduction unit 30 is preferably in the range of 100g to 250g. In this embodiment, the weight of the nail gun 1A is 2100g, and the ratio of the weight of the reduction unit 30 to this is 4.8% to 11.9%. Also, the ratio of the weight of the gear assembly 70 to the weight of the nail gun 1A is 3.5% to 10.6%.

[0110] 1A, 1B, 101... Power tools (nail gun, threaded rod cutter), 2... Nail gun body, 3... Magazine, 3a... Feeder, 4... Discharge unit, 4a... Blade guide, 4b... Nose, 5... Impact unit, 5a... Piston, 5b... Driver blade, 6... Biasing unit, 6a... Pressure container, 6b... Cylinder, 7a... Push lever, 7b... Adjuster, 8... Pin wheel, 10... Housing, 11... Main body, 12... Handle, 13... Motor housing, 14...Connecting part, 14a...Battery mounting part, 15...Protrusion, 20...Motor, 21...Drive shaft, 30, 130, 230...Reduction part, 40, 140, 240...Gear case, 240a...Meshing part, 41...Recess, 42...Elastic body, 43...Engagement groove, 44a, 44b...Protrusion, 51, 151...Input gear (sun gear), 52, 152...Intermediate gear (planetary gear), 53, 153...Fixed gear (fixed internal gear), 54, 154...Output gear (movable internal gear), 15 4a...meshing part, 55, 155, 255...planetary carrier, 56...engaging projection, 57...rotating shaft, 58...needle bearing, 59...spacer, 60...cam, 61...camshaft, 62...movable arm, 63...movable blade, 64...fixed blade, 70...gear assembly, 71...bearing, 72...plate, 73, 74, 75...washer, 160, 260...spindle, 161...output shaft (switching part), 161a...meshing part, 161a...shaft part, 161b... Tube section, 161c...meshing section (first meshing section), 161d...meshing section (second meshing section), 161e...link connection section, 161f...wall section, 162...drill chuck, 163, 263...link, 164...shift lever (operating section), 254...output gear (switching section), 262...second intermediate gear (second planetary gear), 262a...meshing section, 264...second planetary carrier (second carrier), 264a...meshing section, BP...battery pack, CE...controller

Claims

1. An electric power tool comprising: a motor; an operating unit connected to the motor via a power transmission path; and a reduction unit provided in the power transmission path, which includes a mysterious planetary gear mechanism, wherein the reduction unit includes: a gear case; an input gear to which the driving force output from the motor is input; an intermediate gear that meshes with the input gear; a fixed gear that meshes with the intermediate gear; and an output gear that, by meshing with the intermediate gear, constitutes the mysterious planetary gear mechanism together with the input gear, the intermediate gear, and the fixed gear, wherein the fixed gear is not rotatable relative to the gear case; the output gear is rotatable relative to the gear case; and the number of teeth of the fixed gear and the number of teeth of the output gear are different.

2. The power tool according to claim 1, wherein the meshing height of the fixed gear with respect to the intermediate gear and the meshing height of the output gear are different.

3. The power tool according to claim 1, wherein either the fixed gear or the output gear has fewer teeth and a lower meshing height with respect to the intermediate gear than the other of the fixed gear or the output gear.

4. The power tool according to claim 3, wherein the fixed gear has fewer teeth than the output gear and has a lower meshing height with respect to the intermediate gear.

5. The power tool according to claim 4, wherein the gear case is made of resin.

6. The power tool according to claim 1, comprising a housing for housing the gear case, and an elastic body interposed between the gear case and the housing.

7. The electric tool according to claim 1, comprising: an injection part for supporting a fastener; a striking part for striking the fastener supported by the injection part; and a biasing part for biasing the striking part to one side in a first direction, wherein the operating part rotates while engaging with the striking part, thereby moving the striking part to the other side in the first direction against the biasing force of the biasing part.

8. An electric power tool comprising: an injection unit for supporting a fastener; a striking unit for striking the fastener supported by the injection unit; a biasing unit defining a pressure chamber between itself and the striking unit and biasing the striking unit to one side in a first direction by the pressure of compressed air in the pressure chamber; a motor; an operating unit connected to the motor via a power transmission path and rotating while engaging with the striking unit, thereby moving the striking unit to the other side in the first direction against the biasing force of the biasing unit; and a reduction unit provided in the power transmission path, wherein the reduction unit includes: a gear case; an input gear, at least a portion of which is housed in the gear case and to which a driving force output from the motor is input; and an output gear, at least a portion of which is housed in the gear case and rotates in response to the driving force of the input gear, wherein the pressure of the compressed air in the pressure chamber is 0.8 MPa or more and 1.5 MPa or less, and the weight of the reduction unit is 100 g or more and 250 g or less.

9. The power tool according to claim 8, further comprising a battery mounting section into which a battery pack capable of supplying power to the motor, having a rated voltage of 7.2V or more and 36V or less, is detachably mounted.

10. The power tool according to claim 8, wherein the weight of the reduction gear is 4.8% or more and 11.9% or less of the weight of the power tool.

11. The power tool according to claim 1, further comprising a switching unit that changes the reduction ratio of the reduction unit by switching the reduction unit between a first transmission state in which the motor and the operating unit are connected via the mysterious planetary gear mechanism and a second transmission state in which the motor and the operating unit are connected without the mysterious planetary gear mechanism.

12. The power tool according to claim 11, wherein the switching unit is an output shaft capable of meshing with the output gear, and the reduction ratio is switched by changing the meshing partner.

13. The power tool according to claim 12, wherein the reduction unit includes a carrier that rotatably supports the intermediate gear, and the first transmission state is achieved when the output shaft meshes with the output gear, and the second transmission state is achieved when the output shaft meshes with the carrier without meshing with the output gear.

14. The power tool according to claim 13, wherein the output shaft changes the mating object by moving axially relative to the operating part.

15. The power tool according to claim 14, comprising a link that moves axially by operation of an operator, wherein the output shaft includes a shaft portion located at the radial center, a cylindrical portion located radially outside the shaft portion, a first meshing portion formed on the inner surface of the cylindrical portion and capable of meshing with the output gear, a second meshing portion formed on the outer surface of the shaft portion and capable of meshing with the carrier, and a link connecting portion formed on the outer surface of the cylindrical portion and connecting to the link.

16. The power tool according to claim 11, wherein the switching unit is the output gear, and the reduction ratio is changed by changing the mating gear.

17. The reduction gear includes a carrier that rotatably supports the intermediate gear, a second intermediate gear that meshes with the carrier, and a second carrier that rotatably supports the second intermediate gear and is connected to the operating part, wherein the first transmission state is achieved when the output gear meshes with the intermediate gear and the second carrier, and the second transmission state is achieved when the output gear meshes with the second intermediate gear and the gear case without meshing with the intermediate gear and the second carrier, as described in claim 16.

18. The power tool according to claim 17, wherein the output gear changes its meshing partner by moving in the axial direction.

19. An electric power tool comprising: a motor; an operating unit connected to the motor via a power transmission path; and a reduction unit provided in the power transmission path, wherein the reduction unit includes: a gear case; an input gear to which the driving force output from the motor is input; a plurality of transmission members to which the driving force from the input gear is input; and an output shaft capable of selectively meshing with one of the plurality of transmission members, and which switches the reduction ratio of the reduction unit by moving in the axial direction to change the meshing partner.

20. The power tool according to claim 19, comprising a link that moves axially by operation of an operator, wherein the plurality of transmission members include a first transmission member and a second transmission member, and the output shaft includes a shaft portion located at the center in the axial direction, a cylindrical portion located radially outside the shaft portion, a first meshing portion formed on the inner surface of the cylindrical portion and capable of meshing with the first transmission member, a second meshing portion formed on the outer surface of the shaft portion and capable of meshing with the second transmission member, and a link connecting portion formed on the outer surface of the cylindrical portion and connecting to the link.

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