Impact tool

Abstract

To suppress occurrence of abnormal impact.SOLUTION: An impact tool includes: a motor; a hammer rotated by the motor; an anvil stuck by the hammer in the rotating direction; two or more springs which energize the hammer forward toward the anvil and are arranged in parallel; a cam mechanism which retreats the hammer while compressing the springs by the driving force of the motor, and advances the hammer by elastic force of the compressed springs; and a hammer storage part for storing the hammer. The springs energize the hammer at a predetermined attachment load when the hammer is at an advance limit position. A value obtained by dividing a synthetic spring constant (N / mm) of the springs by a synthetic attachment load (N) is greater than 0.3.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The technology disclosed herein relates to impact tools. [Background technology]

[0002] In the technical field related to impact tools, an impact tool such as that disclosed in Patent Document 1 is known. The impact tool includes an anvil that is struck in the rotational direction by a hammer. The driving force of a motor is converted into a force in the retracting direction of the hammer by a cam mechanism, and the hammer is retracted while compressing a spring. When the retracting hammer overcomes the anvil, the elastic energy of the spring is released, and the hammer moves forward while rotating, striking the anvil in the rotational direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-187700 A Summary of the Invention [Problem to be solved by the invention]

[0004] When the hammer strikes the anvil, a reaction force acts on the hammer from the fastening member (such as a bolt or screw) in a direction that causes the hammer to retract. The magnitude of the reaction force to the strike varies depending on the size of the fastening member. If the reaction force is too large, the hammer may retract too far and collide with a rear member, or the spring may reach its full length and suddenly stop. If the reaction force is too small, the hammer may retract too little, and as it moves forward, it may collide axially with the anvil. In this specification, such an impact state that occurs when the hammer retracts too far or too little is referred to as an "abnormal impact," as it differs from the intended, proper impact. When an abnormal impact occurs, vibrations in the impact tool are generated in the direction of the hammer's movement, or the hammer's impact force decreases, resulting in a poor usability of the impact tool.

[0005] The technology disclosed in this specification aims to suppress the occurrence of abnormal impacts. [Means for solving the problem]

[0006] This specification discloses an impact tool. The impact tool may include a motor, a hammer rotated by the motor, an anvil struck by the hammer in the rotational direction, two or more springs arranged in parallel that urge the hammer forward toward the anvil, a cam mechanism that compresses the spring with the driving force of the motor to move the hammer backward and advances the hammer using the elastic force of the compressed spring, and a hammer housing that houses the hammer. The spring may urge the hammer with a predetermined mounting load when the hammer is at its forward limit position. The value obtained by dividing the composite spring constant (N / mm) of the spring by the composite mounting load (N) may be greater than 0.3. [Effects of the Invention]

[0007] According to the technology disclosed in this specification, the occurrence of abnormal impacts can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of an impact tool according to an embodiment, seen from the front right. [Figure 2] FIG. 2 is a side view showing the impact tool according to the embodiment. [Figure 3] FIG. 3 is a vertical cross-sectional view showing the impact tool according to the embodiment. [Figure 4] FIG. 4 is a vertical cross-sectional view showing an upper portion of the impact tool according to the embodiment. [Figure 5] FIG. 5 is a cross-sectional view showing the upper part of the impact tool according to the embodiment. [Figure 6] FIG. 6 is a perspective view showing the striking mechanism and the anvil according to the embodiment, seen from the front right. [Figure 7]FIG. 7 is a cross-sectional view showing the hammer in the disengaged position. [Figure 8] FIG. 8 is a perspective view showing the inner surface of the housing according to the embodiment. [Figure 9] FIG. 9 is a cross-sectional view taken along a line passing through the rear insulator according to the embodiment, as viewed from the rear. [Figure 10] FIG. 10 is a perspective view showing the motor according to the embodiment, seen from the right rear. [Figure 11] FIG. 11 is a vertical cross-sectional view showing a column portion according to the embodiment. [Figure 12] FIG. 12 is a cross-sectional view taken along a line passing through the front insulator according to the embodiment, as viewed from the front. [Figure 13] FIG. 13 is an explanatory diagram for explaining the operation of the hammer according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] In one or more embodiments, the impact tool may include a motor, a hammer rotated by the motor, an anvil struck by the hammer in the rotational direction, two or more springs arranged in parallel that urge the hammer forward toward the anvil, a cam mechanism that compresses the spring with the driving force of the motor to move the hammer backward and advances the hammer using the elastic force of the compressed spring, and a hammer housing that houses the hammer. The spring may urge the hammer with a predetermined mounting load when the hammer is at its forward limit position. The value obtained by dividing the composite spring constant (N / mm) of the spring by the composite mounting load (N) may be greater than 0.3. Hereinafter, the value obtained by dividing the composite spring constant of the spring by the composite mounting load will be referred to as the "ratio Rm."

[0010] The attached load is the magnitude of the elastic force of the spring when the hammer is at its forward limit position. Note that the attached load is not the load required for assembly. The attached load corresponds to the elastic force of the spring in its initial state when attached to the impact tool. The attached load corresponds to the spring force of the spring when it is compressed by the difference between the spring's natural length and its length when attached (attached length). The combined attached load is the magnitude of the total elastic force of two or more springs when the hammer is at its forward limit position. In other words, the combined attached load is the attached load when two or more springs are considered as a single virtual spring. The combined spring constant is the spring constant when two or more springs are considered as a single virtual spring.

[0011] In the above configuration, the smaller the composite mounting load and the larger the spring constant of the spring, the larger the ratio Rm (combined composite spring constant divided by the composite mounting load). Because the composite mounting load is relatively small, the hammer recoils significantly even when the reaction force from the fastening member (e.g., bolt or screw) during impact is small. Therefore, even when the reaction force is small, the hammer can be prevented from colliding axially with the anvil due to insufficient recoil. On the other hand, because the composite spring constant is relatively large, the spring's elastic force increases significantly when the hammer recoils and the spring is compressed, effectively counteracting the reaction force from the fastening member. Therefore, even when the reaction force is large, the hammer does not recoil excessively, preventing the hammer from colliding with a rear member or the spring from reaching its full length. By increasing the ratio Rm to greater than 0.3, abnormal impacts can be prevented even when large or small reaction forces are applied. This prevents abnormal impacts even when the impact tool is used to tighten fastening members of various sizes.

[0012] In one or more embodiments, the spring may include a first spring and a second spring. The inner diameter of the first spring may be larger than the inner diameter of the second spring. The spring constant of the first spring may be at least twice the spring constant of the second spring.

[0013] With the above configuration, the spring constant of the second spring can be made relatively small. This prevents the wire diameter of the second spring, which has a small inner diameter, from becoming larger and the number of turns from becoming smaller. As a result, it is possible to prevent the solid length of the second spring from becoming excessively large and the lifespan of the second spring from becoming relatively shorter.

[0014] In one or more embodiments, the installed length, which is the length of the spring when the hammer is in its forward limit position, may be 90% or more of the free length of the spring.

[0015] In the above configuration, the spring load can be effectively reduced by increasing the spring length, i.e., by reducing the amount of deflection during installation. As a result, even when the reaction force from the fastening member is small, the hammer can be retracted to the distance necessary to avoid axial collision between the hammer and the anvil.

[0016] In one or more embodiments, the cam mechanism may cause the retracting hammer to come out of contact with the anvil when it reaches the disengagement position, and the distance from the forward limit of the hammer to the disengagement position may be 50% or less of the distance from the forward limit of the hammer to the retraction limit.

[0017] In the above configuration, the short distance from the forward limit to the release position makes it easier for the hammer to pass the release position even when the reaction force from the fastening member is small and the amount of retraction of the hammer is small, thereby reducing the risk of the hammer and the anvil colliding in the axial direction. The relatively long distance from the release position to the retraction limit makes it possible to reduce the risk of the hammer reaching the retraction limit and colliding with other members even when the reaction force from the fastening member is large.

[0018] In one or more embodiments, the spring may have a constant spring constant from the forward limit of the hammer to just before the retraction limit of the hammer. Having a constant spring constant in the range up to just before the retraction limit of the hammer means that when the spring approaches its full length near the retraction limit of the hammer, the spring constant may change near the full length. In other words, the spring can be considered a substantially linear spring in this range, and is not a nonlinear spring whose spring constant actively changes depending on the amount of deflection.

[0019] The above configuration can suppress the occurrence of abnormal impacts without using a special nonlinear spring. In addition, since the spring constant does not change depending on the position of the hammer, the hammer can move smoothly forward and backward.

[0020] In one or more embodiments, the impact tool may have a maximum tightening torque of 1300 N·m or more and 3000 N·m or less.

[0021] With the above configuration, even when tightening large or small fastening members using an impact tool with a large hammer impact force, the occurrence of abnormal impacts can be suppressed, and a decrease in the usability of the impact tool due to abnormal impacts can be avoided.

[0022] In one or more embodiments, the combined mounting load of the springs may be greater than 0 (N).

[0023] The above configuration prevents play (gaps between the spring and other components) from forming at the spring attachment point due to dimensional tolerances, thereby preventing the spring from moving when the impact tool is not in use.

[0024] In one or more embodiments, the impact tool may include a motor, a hammer rotated by the motor, an anvil struck by the hammer in the rotational direction, a spring urging the hammer forward toward the anvil, a cam mechanism that compresses the spring with the driving force of the motor to move the hammer backward and advances the hammer using the elastic force of the compressed spring, and a hammer housing that houses the hammer. The spring may urge the hammer with a predetermined release load at a release position where the retracted hammer is out of contact with the anvil due to the cam mechanism. The value obtained by dividing the spring constant (N / mm) of the spring by the release load (N) may be greater than 0.09. Hereinafter, the value obtained by dividing the spring constant by the release load will be referred to as the "ratio Rd."

[0025] In the above configuration, the smaller the breakaway load and the larger the spring constant of the spring, the larger the ratio Rd (the spring constant divided by the breakaway load). Because the breakaway load is relatively small, the hammer retracts a large distance even when the reaction force from the fastening member (such as a bolt or screw) during impact is small. Therefore, even when the reaction force is small, the hammer can be prevented from colliding axially with the anvil due to insufficient retraction. On the other hand, because the spring constant is relatively large, the spring's elastic force increases significantly when the hammer retracts and compresses the spring, effectively counteracting the reaction force from the fastening member. Therefore, even when the reaction force is large, the hammer does not retract excessively, preventing the hammer from colliding with a rear member or the spring from reaching its full length. By increasing the ratio Rd to greater than 0.09, abnormal impacts can be prevented even when large or small reaction forces are applied. This prevents abnormal impacts even when the impact tool is used to tighten fastening members of various sizes.

[0026] In one or more embodiments, the spring may include a first spring and a second spring disposed in parallel with the hammer, and the sum of the spring constants of the first spring and the second spring divided by the sum of the breakaway loads of the first spring and the second spring may be greater than 0.09.

[0027] In the above configuration, by arranging the first and second springs in parallel, the ratio Rd of the entire spring can be easily made greater than 0.09. Furthermore, compared to the case of a single spring, the wire diameter of each of the first and second springs can be made smaller, and the solid length can be shortened, which alleviates constraints on the spring design.

[0028] In one or more embodiments, the spring may include a first spring and a second spring arranged in parallel with the hammer. The value obtained by dividing the spring constant of the first spring by the breakaway load of the first spring may be greater than 0.10. The value obtained by dividing the spring constant of the second spring by the breakaway load of the second spring may be greater than 0.09. Hereinafter, the value obtained by dividing the spring constant of the first spring by the breakaway load will be referred to as the "ratio RdA," and the value obtained by dividing the spring constant of the second spring by the breakaway load will be referred to as the "ratio RdB."

[0029] In the above configuration, the hammer is biased by multiple springs (first spring, second spring), and by making the spring ratios RdA and RdB greater than 0.10 and 0.09, respectively, it is possible to alleviate the design constraints of the springs while suppressing the occurrence of abnormal impacts.

[0030] In one or more embodiments, the inner diameter of the first spring may be larger than the inner diameter of the second spring. The spring constant of the first spring may be at least twice the spring constant of the second spring.

[0031] With the above configuration, the spring constant of the second spring can be made relatively small. This prevents the wire diameter of the second spring, which has a small inner diameter, from becoming larger and the number of turns from becoming smaller. As a result, it is possible to prevent the solid length of the second spring from becoming excessively large and the lifespan of the second spring from becoming relatively shorter.

[0032] In one or more embodiments, the release length, which is the length of the spring when the hammer is in the release position, may be 75% or more of the free length of the spring.

[0033] In the above configuration, the spring release length is increased, i.e., the amount of deflection at the release position is reduced, thereby effectively reducing the spring release load. As a result, even when the reaction force from the fastening member is small, the amount of retraction required to avoid axial collision between the hammer and the anvil can be easily generated.

[0034] In one or more embodiments, the distance from the forward limit of the hammer to the disengagement position may be 50% or less of the distance from the forward limit of the hammer to the retraction limit.

[0035] In the above configuration, since the distance to the release position is short, even when the reaction force from the fastening member is small and the amount of retraction of the hammer is small, the hammer can easily pass through the release position, thereby reducing the occurrence of axial collision between the hammer and the anvil. Since the distance from the release position to the retract limit is relatively long, even when the reaction force from the fastening member is large, the hammer can be prevented from reaching the retract limit and colliding with other members.

[0036] In one or more embodiments, the spring may have a constant spring constant from the forward limit of the hammer to just before the retraction limit of the hammer.

[0037] The above configuration can suppress the occurrence of abnormal impacts without using a special nonlinear spring. In addition, since the spring constant does not change depending on the position of the hammer, the hammer can move smoothly forward and backward.

[0038] In one or more embodiments, the impact tool may have a maximum tightening torque of 1300 (N·m) or more and 3000 (N·m) or less.

[0039] With the above configuration, even when tightening large or small fastening members using an impact tool with a large hammer impact force, the occurrence of abnormal impacts can be suppressed, and a decrease in the usability of the impact tool due to abnormal impacts can be avoided.

[0040] In one or more embodiments, the springs may have a combined load of greater than 0 (N) when the hammer is at its forward limit position, preferably greater than 0 (N).

[0041] The above-described configuration can prevent play from being formed at the attachment point of the spring due to dimensional tolerances, thereby preventing the spring from moving when the impact tool is not in use.

[0042] In one or more embodiments, the impact tool may further include a speed reduction mechanism that reduces the rotational speed of the motor and transmits the reduced speed to the hammer. The speed reduction mechanism may have a reduction ratio of 1 / 15 or more and 1 / 100 or less.

[0043] In the above configuration, a high tightening torque can be generated by the reduction mechanism.

[0044] In one or more embodiments, the impact tool may include a motor, a hammer rotated by the motor, an anvil struck by the hammer in the rotational direction, a spring urging the hammer forward toward the anvil, a cam mechanism that compresses the spring with the driving force of the motor to move the hammer backward and advances the hammer using the elastic force of the compressed spring, and a hammer housing that houses the hammer. The spring may urge the hammer with a predetermined mounting load when the hammer is at its forward limit position. The spring constant (N / mm) of the spring divided by the mounting load (N) may be greater than 0.3. The impact tool 1 may have a maximum tightening torque of 1300 (N·m) or greater.

[0045] In the above configuration, the smaller the mounting load and the larger the spring constant of the spring, the larger the ratio Rm (the spring constant divided by the mounting load). Because the mounting load is relatively small, the hammer retracts a large distance even when the reaction force from the fastening member (such as a bolt or screw) during impact is small. Therefore, even when the reaction force is small, the hammer can be prevented from colliding axially with the anvil due to insufficient retraction. On the other hand, because the spring constant is relatively large, the spring's elastic force increases significantly when the hammer retracts and compresses the spring, effectively counteracting the reaction force from the fastening member. Therefore, even when the reaction force is large, the hammer does not retract excessively, preventing the hammer from colliding with a rear member or the spring from reaching its full length. By increasing the ratio Rm to greater than 0.3, abnormal impacts can be prevented even when large or small reaction forces are applied. This prevents abnormal impacts even when the impact tool is used to tighten fastening members of various sizes.

[0046] [Embodiment] Hereinafter, an embodiment will be described with reference to the drawings. In the embodiment, the positional relationship of each part will be described using the terms left, right, front, rear, top, and bottom. These terms indicate relative positions or directions based on the center of the impact tool 1. The impact tool 1 has a motor 6 as a power source.

[0047] In the embodiment, the direction parallel to the rotation axis AX of the motor 6 is referred to as the axial direction, the direction circumferentially around the rotation axis AX is referred to as the circumferential direction or rotation direction, and the radial direction of the rotation axis AX is referred to as the radial direction.

[0048] The rotation axis AX extends in the front-to-rear direction. One axial side is the front, and the other axial side is the rear. In addition, in the radial direction, a position closer to or approaching the rotation axis AX will be referred to as the radially inner side, and a position farther from or away from the rotation axis AX will be referred to as the radially outer side.

[0049] <Impact tool> FIG. 1 is a perspective view of the impact tool 1 according to the embodiment, seen from the front right. FIG. 2 is a side view of the impact tool 1 according to the embodiment. FIG. 3 is a vertical cross-sectional view of the impact tool 1 according to the embodiment. FIG. 4 is a vertical cross-sectional view of the upper part of the impact tool 1 according to the embodiment. FIG. 5 is a horizontal cross-sectional view of the upper part of the impact tool 1 according to the embodiment. FIG. 6 is a perspective view of the striking mechanism 9 and the anvil 10 according to the embodiment, seen from the front right.

[0050] In this embodiment, the impact tool 1 is an impact wrench and includes a housing 2, a hammer housing 4, a cover 3, a motor 6, a speed reducer 7, a spindle 8, a striking mechanism 9, an anvil 10, a fan 12, a battery mounting section 13, a trigger lever 14, a forward / reverse rotation switch lever 15, an operation display 16, and a light 17.

[0051] The housing 2 is made of synthetic resin. In this embodiment, the housing 2 is made of nylon. The housing 2 includes a left housing 2L and a right housing 2R located to the right of the left housing 2L. The left housing 2L and the right housing 2R are fixed together with a plurality of screws 2S. The housing 2 is made up of a pair of split housing halves.

[0052] The housing 2 has a motor accommodating portion 21, a grip portion 22, and a battery holding portion 23.

[0053] The motor housing portion 21 houses the motor 6. The motor housing portion 21 and the hammer housing portion 4 are fixed together by a plurality of screws 2T.

[0054] The grip portion 22 is held by an operator and extends downward from the motor housing portion 21. The trigger lever 14 is provided on the upper portion of the grip portion 22.

[0055] The battery holding portion 23 holds the battery pack 25 via the battery attachment portion 13. The battery holding portion 23 is connected to the lower end of the grip portion 22. The external dimensions of the battery holding portion 23 are larger than the external dimensions of the grip portion 22 in both the front-rear and left-right directions.

[0056] The motor accommodating section 21 has an intake port 19 and an exhaust port 20. The exhaust port 20 is provided forward of the intake port 19. Air in the external space of the housing 2 flows into the internal space of the housing 2 through the intake port 19. Air in the internal space of the housing 2 flows out to the external space of the housing 2 through the exhaust port 20.

[0057] The hammer housing 4 houses at least a portion of the speed reduction mechanism 7, the spindle 8, the striking mechanism 9, and the anvil 10. At least a portion of the speed reduction mechanism 7 is disposed inside the bearing box 24. The speed reduction mechanism 7 includes a plurality of gears.

[0058] The hammer accommodating portion 4 is made of metal. In this embodiment, the hammer accommodating portion 4 is made of aluminum. The hammer accommodating portion 4 is cylindrical. The hammer accommodating portion 4 is connected to the front part of the motor accommodating portion 21. A bearing box 24 is fixed to the rear part of the hammer accommodating portion 4. The front part of the bearing box 24 is fitted into the rear part of the hammer accommodating portion 4, thereby fixing the bearing box 24 and the hammer accommodating portion 4 together.

[0059] The cover 3 is arranged to cover at least a part of the outer surface of the hammer housing portion 4 .

[0060] The motor 6 is a power source for the impact tool 1. The motor 6 is an inner rotor type brushless motor. The motor 6 has a stator 26 and a rotor 27. The stator 26 is supported by the motor housing 21. At least a portion of the rotor 27 is disposed inside the stator 26. The rotor 27 rotates relative to the stator 26. The rotor 27 rotates about a rotation axis AX extending in the front-rear direction.

[0061] The reduction mechanism 7 connects the rotor 27 and the spindle 8. The reduction mechanism 7 transmits the rotation of the rotor 27 to the spindle 8. The reduction mechanism 7 rotates the spindle 8 at a rotational speed lower than the rotational speed of the rotor 27. The rotation of the spindle 8 is transmitted to the hammer 47 via a cam mechanism 48. As a result, the reduction mechanism 7 reduces the rotation of the motor 6 and transmits it to the hammer 47. The reduction mechanism 7 is disposed forward of the motor 6. The reduction mechanism 7 includes a planetary gear mechanism. The reduction mechanism 7 has multiple gears. The gears of the reduction mechanism 7 are driven by the rotor 27. The reduction ratio of the reduction mechanism 7 is, for example, 1 / 15 or more. The reduction ratio of the reduction mechanism 7 is, for example, 1 / 100 or less.

[0062] The spindle 8 rotates by the rotational force of the rotor 27 transmitted by the reduction mechanism 7. The spindle 8 is disposed forward of at least a portion of the motor 6. The spindle 8 is disposed forward of the stator 26. At least a portion of the spindle 8 is disposed forward of the rotor 27. At least a portion of the spindle 8 is disposed forward of the reduction mechanism 7. The spindle 8 is disposed rearward of the anvil 10.

[0063] The striking mechanism 9 strikes the anvil 10 in the rotational direction based on the rotational force of the spindle 8 rotated by the motor 6. The rotational force of the motor 6 is transmitted to the striking mechanism 9 via the speed reducer 7 and the spindle 8.

[0064] The anvil 10 is the output shaft of the impact tool 1 that rotates based on the rotational force of the rotor 27. The anvil 10 is struck in the rotational direction by the striking mechanism 9. The anvil 10 is disposed forward of the motor 6. A socket, which is a type of tip tool, is attached to the front end of the anvil 10. The front end of the anvil 10 has a rectangular prism shape. The anvil 10 is disposed forward of at least a portion of the spindle 8.

[0065] The fan 12 generates an airflow for cooling the motor 6. The fan 12 is disposed forward of the stator 26 of the motor 6. The fan 12 is fixed to at least a portion of the rotor 27. As the fan 12 rotates, air from the external space of the housing 2 flows into the internal space of the housing 2 through the air intake port 19. The air that has flowed into the internal space of the housing 2 cools the motor 6 by circulating through the internal space of the housing 2. As the fan 12 rotates, the air that has circulated through the internal space of the housing 2 flows out into the external space of the housing 2 through the air exhaust port 20.

[0066] The battery attachment section 13 is connected to the battery pack 25. The battery pack 25 is attached to the battery attachment section 13. The battery pack 25 is detachable from the battery attachment section 13. The battery attachment section 13 is disposed below the battery holding section 23. The battery pack 25 is attached to the battery attachment section 13 by being inserted into the battery attachment section 13 from the front of the battery holding section 23. The battery pack 25 is removed from the battery attachment section 13 by being pulled forward from the battery attachment section 13. The battery pack 25 includes a secondary battery. In the embodiment, the battery pack 25 includes a rechargeable lithium-ion battery. When attached to the battery attachment section 13, the battery pack 25 can supply power to the impact tool 1. The motor 6 is driven by the power supplied from the battery pack 25.

[0067] The trigger lever 14 is operated by an operator to start the motor 6. Operating the trigger lever 14 switches between driving and stopping the motor 6. The trigger lever 14 is provided on the grip portion 22.

[0068] The forward / reverse switching lever 15 is operated by an operator. By operating the forward / reverse switching lever 15, the rotation direction of the motor 6 is switched from one of the forward direction and the reverse direction to the other. By switching the rotation direction of the motor 6, the rotation direction of the spindle 8 is switched. The forward / reverse switching lever 15 is provided on the upper part of the grip portion 22.

[0069] The operation display unit 16 has a plurality of operation buttons 16A and an indicator display 16B. The operation mode of the motor 6 is switched when the operator operates the operation button 16A. The indicator display 16B has a plurality of light-emitting elements. The indicator display 16B displays the operation mode of the motor 6 by changing the lighting pattern of the plurality of light-emitting elements. The operation display unit 16 is provided in the battery holding unit 23. The operation display unit 16 is provided on the top surface of the battery holding unit 23, further forward than the grip unit 22.

[0070] The light 17 emits illumination light. The light 17 illuminates the anvil 10 and the area around the anvil 10 with the illumination light. The light 17 illuminates the area in front of the anvil 10 with the illumination light. The light 17 also illuminates the tool attachment attached to the anvil 10 and the area around the tool attachment with the illumination light. The light 17 is disposed above the trigger lever 14.

[0071] The hammer accommodating section 4 has a first cylindrical section 401, a second cylindrical section 402, and a connecting section 403. The first cylindrical section 401 is arranged around the striking mechanism section 9. The second cylindrical section 402 is arranged forward of the first cylindrical section 401. The outer diameter of the second cylindrical section 402 is smaller than the outer diameter of the first cylindrical section 401. The connecting section 403 is arranged to connect the front section of the first cylindrical section 401 and the rear section of the second cylindrical section 402. The inner diameter of the second cylindrical section 402 is smaller than the inner diameter of the first cylindrical section 401.

[0072] The motor 6 has a stator 26 and a rotor 27. The stator 26 has a stator core 28, a front insulator 29, a rear insulator 30, and a coil 31. The rotor 27 rotates about a rotation axis AX. The rotor 27 has a rotor core 32, a rotor shaft 33, and a rotor magnet 34.

[0073] The stator core 28 is disposed radially outward of the rotor 27. The stator core 28 includes a plurality of stacked steel plates. The steel plates are metal plates whose main component is iron. The stator core 28 is cylindrical. The stator core 28 has a plurality of teeth that support the coils 31.

[0074] The front insulator 29 is provided in the front portion of the stator core 28. The rear insulator 30 is provided in the rear portion of the stator core 28. The front insulator 29 and the rear insulator 30 are each an electrical insulating member made of synthetic resin. The front insulator 29 is arranged so as to cover part of the surface of the teeth. The rear insulator 30 is arranged so as to cover part of the surface of the teeth.

[0075] The coil 31 is attached to the stator core 28 via the front insulator 29 and the rear insulator 30. A plurality of coils 31 are arranged. The coils 31 are arranged around the teeth of the stator core 28 via the front insulator 29 and the rear insulator 30. The coils 31 and the stator core 28 are electrically insulated by the front insulator 29 and the rear insulator 30. The plurality of coils 31 are connected via a bus bar unit 38.

[0076] The rotor core 32 and the rotor shaft 33 are both made of steel. The rotor shaft 33 is disposed inside the rotor core 32. The rotor core 32 and the rotor shaft 33 are fixed together. The front end of the rotor shaft 33 protrudes forward from the front end surface of the rotor core 32, and the rear end of the rotor shaft 33 protrudes rearward from the rear end surface of the rotor core 32.

[0077] The rotor magnet 34 is fixed to the rotor core 32. The rotor magnet 34 is disposed inside the rotor core 32.

[0078] A sensor board 37 is attached to the rear insulator 30. The sensor board 37 has a disk-shaped circuit board with a hole in the center and a rotation detection element supported by the circuit board. At least a portion of the sensor board 37 faces the rotor magnet 34. The rotation detection element detects the position of the rotor magnet 34 of the rotor 27, thereby detecting the position of the rotor 27 in the rotational direction.

[0079] The rotor shaft 33 is rotatably supported by rotor bearings 39. The rotor bearings 39 include a front rotor bearing 39F that rotatably supports the front end of the rotor shaft 33, and a rear rotor bearing 39R that rotatably supports the rear end of the rotor shaft 33.

[0080] The front rotor bearing 39F is held in the bearing box 24. The bearing box 24 has a recess 241 recessed forward from the rear surface of the bearing box 24. The front rotor bearing 39F is disposed in the recess 241. The rear rotor bearing 39R is held in the rear surface portion 21B of the motor housing portion 21. The front end portion of the rotor shaft 33 is disposed in the internal space of the hammer housing portion 4 through an opening in the bearing box 24.

[0081] The fan 12 is fixed to the front of the rotor shaft 33. The fan 12 is disposed between the front rotor bearing 39F and the stator 26. The fan 12 rotates due to the rotation of the rotor shaft 33. As the rotor shaft 33 rotates, the fan 12 rotates together with the rotor shaft 33.

[0082] A pinion gear 41 is formed on the front end of the rotor shaft 33. The pinion gear 41 is connected to at least a part of the speed reduction mechanism 7. The rotor shaft 33 is connected to the speed reduction mechanism 7 via the pinion gear 41.

[0083] The reduction mechanism 7 has a plurality of planetary gears 42 arranged around the pinion gear 41, and an internal gear 43 arranged around the plurality of planetary gears 42. The pinion gear 41, the planetary gear 42, and the internal gear 43 are each housed in the hammer housing 4. Each of the plurality of planetary gears 42 meshes with the pinion gear 41. The planetary gear 42 is rotatably supported on the spindle 8 via a pin 42P. The spindle 8 is rotated by the planetary gear 42. The internal gear 43 has internal teeth that mesh with the planetary gear 42. The internal gear 43 is fixed to the hammer housing 4. The internal gear 43 is always non-rotatable relative to the hammer housing 4.

[0084] When the rotor shaft 33 is rotated by the drive of the motor 6, the pinion gear 41 rotates, and the planetary gear 42 revolves around the pinion gear 41. The planetary gear 42 revolves while meshing with the internal teeth of the internal gear 43. Due to the revolution of the planetary gear 42, the spindle 8 connected to the planetary gear 42 via the pin 42P rotates at a rotational speed lower than the rotational speed of the rotor shaft 33.

[0085] The spindle 8 rotates due to the torque of the motor 6. The spindle 8 transmits the torque of the motor 6 to the anvil 10 via the impact mechanism 9. The impact mechanism 9 rotates due to the torque of the rotor 27. The spindle 8 has a spindle shaft 8A and a flange 8B provided at the rear of the spindle shaft 8A. The planetary gear 42 is rotatably supported on the flange 8B via a pin 42P. The rotation axis of the spindle 8 coincides with the rotation axis AX of the motor 6. The spindle 8 rotates around the rotation axis AX. The spindle 8 is rotatably supported by a spindle bearing 44. A protrusion 8C is provided at the rear end of the spindle 8. The protrusion 8C protrudes rearward from the flange 8B. The spindle bearing 44 is arranged to surround the protrusion 8C.

[0086] The bearing box 24 is disposed around at least a portion of the periphery of the spindle 8. The spindle bearing 44 is held in the bearing box 24. The bearing box 24 has a recess 242 recessed from the front surface of the bearing box 24 to the rear. The spindle bearing 44 is disposed in the recess 242.

[0087] The striking mechanism 9 has a hammer 47, a cam mechanism 48, and a spring 50. The striking mechanism 9 including the hammer 47, the cam mechanism 48, and the spring 50 is housed in a first cylindrical portion 401 of the hammer housing 4. The first cylindrical portion 401 is disposed around the hammer 47.

[0088] The hammer 47 is disposed forward of the speed reduction mechanism 7. The hammer 47 is disposed around the spindle shaft 8A. The hammer 47 is supported by the spindle shaft 8A. The anvil 10 is disposed forward of the hammer 47.

[0089] The hammer 47 is rotated by the motor 6. The rotational force of the motor 6 is transmitted to the hammer 47 via the reduction mechanism 7 and the spindle 8. The hammer 47 can rotate together with the spindle 8 based on the rotational force of the spindle 8 rotated by the motor 6. The rotation axis of the hammer 47, the rotation axis of the spindle 8, and the rotation axis AX of the motor 6 coincide with each other. The hammer 47 rotates around the rotation axis AX.

[0090] The hammer 47 has a base portion 471 , a rear ring portion 473 , a support ring portion 474 , and a hammer protrusion portion 475 .

[0091] The base portion 471 is disposed around the spindle shaft portion 8A. The base portion 471 is annular. The spindle shaft portion 8A is disposed inside the base portion 471.

[0092] The rear ring portion 473 protrudes rearward from the outer periphery of the base portion 471. The rear ring portion 473 is cylindrical. A rear end portion of the rear ring portion 473 is disposed rearward of a rear end portion of the support ring portion 474.

[0093] The support ring portion 474 protrudes rearward from the inner periphery of the base portion 471. The support ring portion 474 is cylindrical. The support ring portion 474 is disposed around the spindle shaft portion 8A. The support ring portion 474 is supported by the spindle shaft portion 8A via the cam mechanism 48.

[0094] The hammer protrusion 475 protrudes forward from the front surface of the base portion 471. The front surface of the hammer protrusion 475 is disposed forward of the front surface of the base portion 471. Two hammer protrusions 475 are disposed in the circumferential direction. The two hammer protrusions 475 are positioned 180 degrees apart in the circumferential direction.

[0095] A recess 476 is formed by the rear surface of the base portion 471, the inner peripheral surface of the rear ring portion 473, and the outer peripheral surface of the support ring portion 474. The recess 476 is provided in the rear portion of the hammer 47. The recess 476 is formed so as to be recessed forward from the rear surface of the hammer 47.

[0096] The cam mechanism 48 converts the driving force of the motor 6 in the rotational direction into driving force in the front-to-rear direction of the hammer 47. The cam mechanism 48 moves the hammer 47 backward while compressing the spring 50 using the driving force of the motor 6. The cam mechanism 48 moves the hammer 47 forward while rotating using the elastic force of the compressed spring 50. The cam mechanism 48 includes a hammer ball 49, a spindle groove 8D, and a hammer groove 477.

[0097] The hammer ball 49 is made of a metal such as steel. The hammer ball 49 is disposed between the spindle shaft portion 8A and the hammer 47. The hammer ball 49 is disposed between the outer peripheral surface of the spindle shaft portion 8A and the inner peripheral surface of the hammer 47. The hammer ball 49 engages with the spindle 8 and the hammer 47. The hammer ball 49 transmits the driving force of the motor 6 to the hammer 47 via the spindle 8.

[0098] The spindle groove 8D is provided on a portion of the outer peripheral surface of the spindle shaft portion 8A. At least a portion of the hammer ball 49 is disposed in the spindle groove 8D. The spindle groove 8D is a recessed portion provided on a portion of the outer peripheral surface of the spindle shaft portion 8A. The spindle groove 8D extends obliquely in the axial and circumferential directions. The hammer groove 477 is provided on a portion of the inner peripheral surface of the hammer 47. At least a portion of the hammer ball 49 is disposed in the hammer groove 477. The hammer groove 477 is a recessed portion provided on a portion of the inner peripheral surface of the support ring portion 474. The hammer ball 49 is disposed between the spindle groove 8D and the hammer groove 477. The hammer ball 49 can roll inside the spindle groove 8D and inside the hammer groove 477. The hammer 47 can move along with the hammer ball 49. The spindle 8 and the hammer 47 can move relative to each other in the axial direction and the rotational direction within a movable range defined by the spindle groove 8D and the hammer groove 477.

[0099] The spring 50 is disposed around the spindle shaft portion 8A. The spring 50 biases the hammer 47 forward toward the anvil 10. The spring 50 is a compression coil spring. Two or more springs 50 are provided and are disposed in parallel with the hammer 47. In this embodiment, the springs 50 include two springs: a first spring 50A and a second spring 50B. The first spring 50A and the second spring 50B are compression coil springs. The first spring 50A and the second spring 50B are disposed around the spindle shaft portion 8A so that the spindle shaft portion 8A passes through them. The first spring 50A and the second spring 50B are disposed concentrically around the spindle shaft portion 8A. The inner diameter D1 of the first spring 50A is larger than the inner diameter D2 of the second spring 50B. The inner diameter D1 of the first spring 50A is larger than the outer diameter of the second spring 50B. The second spring 50B is disposed radially inward of the first spring 50A. That is, the second spring 50B is disposed in parallel to the inner diameter side of the first spring 50A. The front end portions of the first spring 50A and the second spring 50B are disposed inside the recess 476 of the hammer 47.

[0100] The rear end portions of the first springs 50A and the second springs 50B are supported by the front surface of the flange portion 8B and contact the front surface of the flange portion 8B.

[0101] A washer 61 is disposed inside the recess 476 of the hammer 47. The front end portion of the first spring 50A and the front end portion of the second spring 50B are supported by the washer 61. The washer 61 is a ring-shaped member.

[0102] The washer 61 is disposed rearward of the base portion 471. The washer 61 supports the front end portions of the first spring 50A and the second spring 50B. In the radial direction, the washer 61 is disposed between the rear ring portion 473 and the support ring portion 474. The washer 61 is disposed inside the recess 476. The washer 61 is supported by the hammer 47 via a plurality of support balls 54. When the hammer 47 is disposed at the frontmost position within the movable range of the hammer 47 in the front-rear direction, the support balls 54 are disposed forward of the rear end portions of the hammer balls 49.

[0103] The support ball 54 is disposed in a support groove 478 provided in the hammer 47 inside the recess 476. In this embodiment, the support groove 478 is provided on the rear surface of the base portion 471. The support groove 478 is provided in a ring shape so as to surround the rotation axis AX. A plurality of support balls 54 are disposed in the support groove 478 along the rotation direction. The support balls 54 support the washer 61.

[0104] The washer 61 is sandwiched between the spring 50 and the support ball 54 in the front-rear direction. The washer 61 is spaced apart from the hammer 47 and the spindle 8.

[0105] The springs 50 (first spring 50A and second spring 50B) are attached to the striking mechanism 9 in a state in which they are pre-compressed relative to their natural length. The springs 50 bias the hammer 47 with a predetermined attachment load when the hammer 47 is at position P1 (see Figure 13), which is its forward limit. The forward limit position P1 is the position of the hammer 47 when the hammer ball 49 is positioned at the front end of the spindle groove 8D. Figures 4, 5, and 6 show the state in which the hammer 47 is at position P1, which is its forward limit. The first spring 50A and the second spring 50B each constantly generate an elastic force that moves the hammer 47 forward.

[0106] The anvil 10 is struck in the rotational direction by the hammer 47. The anvil 10 has an anvil shaft portion 101, an anvil protrusion portion 102, and a recessed portion 103.

[0107] The anvil shaft portion 101 extends in the axial direction (front-to-back direction). The anvil shaft portion 101 has a rotation axis AX. The anvil shaft portion 101 is positioned forward of the spindle 8 and the hammer 47. At least a portion of the anvil shaft portion 101 is positioned in an opening provided at the front end of the hammer accommodating portion 4. The anvil shaft portion 101 passes through the second cylindrical portion 402. The front end of the anvil shaft portion 101 protrudes forward from the opening of the hammer accommodating portion 4. A socket, which is a type of tip tool, is attached to the front end of the anvil shaft portion 101.

[0108] The anvil protrusion 102 protrudes radially outward from the rear end of the anvil shaft portion 101. Two anvil protrusions 102 are arranged circumferentially. The two anvil protrusions 102 are circumferentially spaced 180 degrees apart. When the hammer 47 is at its forward limit position P1, the anvil protrusion 102 and the hammer protrusion 475 overlap in the front-to-rear direction. In other words, the anvil protrusion 102 and the hammer protrusion 475 are aligned in the rotational direction. The anvil protrusion 102 is struck by the hammer protrusion 475 in the rotational direction. A washer 53 is arranged between the front surface of the anvil protrusion 102 and the rear surface 402R of the second cylindrical portion 402. The washer 53 prevents contact between the anvil protrusion 102 and the second cylindrical portion 402. The rear end of the second cylindrical portion 402 receives the load of the anvil protrusion 102 via the washer 53.

[0109] The recess 103 is provided so as to recess forward from the center of the rear surface of the anvil 10. The front end of the spindle 8 is disposed in the recess 103.

[0110] The base portion 471 is disposed rearward of the anvil protrusion 102. The rear surface of the anvil protrusion 102 and the front surface of the base portion 471 are spaced apart.

[0111] The anvil 10 is rotatably supported by the anvil bearing 46. The rotation axis of the anvil 10, the rotation axis of the hammer 47, the rotation axis of the spindle 8, and the rotation axis AX of the motor 6 are all coincident. The anvil 10 rotates around the rotation axis AX. The anvil bearing 46 is arranged around the anvil shaft portion 101. A portion of the anvil bearing 46 is arranged inside the second cylindrical portion 402 of the hammer accommodating portion 4. The anvil bearing 46 is held in the second cylindrical portion 402 of the hammer accommodating portion 4. The anvil bearing 46 is press-fitted into the second cylindrical portion 402. The anvil bearing 46 is fixed to the hammer accommodating portion 4 inside the hammer accommodating portion 4. The anvil bearing 46 rotatably supports the anvil shaft portion 101.

[0112] As shown in FIG. 5, the anvil bearing 46 has a recess 46A recessed radially outward between the front and rear ends of its inner circumferential surface. The recess 46A is formed in an annular shape along the circumferential direction of the anvil bearing 46. The recess 46A faces a groove 104 formed in the outer circumferential surface of the anvil shaft portion 101. A lubricant is disposed in the space formed by the recess 46A and the groove 104. An annular seal member 65 is provided at the front end of the inner circumferential surface of the anvil bearing 46.

[0113] The radially outer outer edge of the front surface of the washer 53 faces the rear surface of the second cylindrical portion 402. The radially inner inner edge of the front surface of the washer 53 is positioned on a step portion 46B formed on the outer periphery of the rear surface of the anvil bearing 46.

[0114] The hammer protrusion 475 can come into contact with the anvil protrusion 102. When the motor 6 is driven while the hammer 47 and the anvil protrusion 102 are in contact with each other, the anvil 10 rotates together with the hammer 47 and the spindle 8. When the load acting on the anvil 10 is small during a bolt tightening operation, the driving force of the motor 6 causes the anvil 10 to rotate together with the hammer 47 and the spindle 8.

[0115] The anvil 10 is struck in the rotational direction by the hammer 47. For example, during a bolt tightening operation, if the load acting on the anvil 10 becomes too high, a situation may occur in which the anvil 10 cannot be rotated by the driving force of the motor 6. When the anvil 10 cannot be rotated, the rotation of the anvil 10 and the hammer 47 stops. The spindle 8 and the hammer 47 can move relative to each other in the axial and circumferential directions via the hammer ball 49. Even when the rotation of the hammer 47 stops, the rotation of the spindle 8 continues due to the power generated by the motor 6. The driving force of the motor 6 causes the cam mechanism 48 to compress the spring 50 and move the hammer 47 backward. Therefore, when the spindle 8 rotates while the rotation of the hammer 47 is stopped, the hammer ball 49 moves backward while being guided by the spindle groove 8D and the hammer groove 477. The hammer 47 receives a backward force from the hammer ball 49 and moves backward along with the hammer ball 49. That is, the hammer 47 moves rearward by rotating the spindle 8 while the rotation of the anvil 10 is stopped. When the hammer 47 moves rearward, the contact between the hammer 47 and the anvil protrusion 102 is released.

[0116] Specifically, when the hammer 47 retracts until the tip of the hammer protrusion 475 passes the rear end position of the anvil protrusion 102, the hammer protrusion 475 and the anvil protrusion 102 are no longer in contact with each other in the rotational direction. In this specification, the position at which the hammer 47, retracted by the cam mechanism 48, is no longer in contact with the anvil 10 is referred to as the disengagement position P2. FIG. 7 is a cross-sectional view showing the hammer 47 in the disengagement position P2. When the load acting on the anvil 10 is high, the hammer 47 is prevented from rotating by the anvil 10 from the forward limit to the disengagement position P2. At the disengagement position P2 and behind the disengagement position P2, the hammer protrusion 475 is positioned behind the anvil protrusion 102, and therefore the hammer 47 can rotate without being engaged with the anvil 10.

[0117] When the hammer 47 moves rearward, the hammer 47 rotates relative to the spindle shaft portion 8A. The washer 61 is spaced apart from the hammer 47 and the spindle 8. Therefore, the rotation of the hammer 47 is not impeded by the washer 61. Furthermore, the rotation of the support ball 54 between the washer 61 and the hammer 47 allows the hammer 47 to rotate smoothly.

[0118] The hammer 47, which has moved rearward, moves forward due to the elastic force of the spring 50. As the hammer 47 moves forward, the hammer ball 49 moves forward while being guided by the spindle groove 8D and the hammer groove 477. As the hammer 47 moves forward, it receives a rotational force from the hammer ball 49. That is, the hammer 47 moves forward while rotating. As the hammer 47 moves forward while rotating, the hammer protrusion 475 comes into contact with the anvil protrusion 102 while rotating. As a result, the anvil protrusion 102 is struck in the rotational direction by the hammer protrusion 475. Both the power of the motor 6 and the inertial force of the hammer 47 act on the anvil 10. Therefore, the anvil 10 can rotate around the rotation axis AX with high torque.

[0119] Note that, when focusing on each hammer protrusion 475, when the hammer 47 retracts, the hammer protrusion 475 comes into contact with one of the anvil protrusions 102. After retracting, when the hammer 47 moves forward while rotating, the hammer protrusion 475 passes behind one of the anvil protrusions 102 in the rotational direction and collides with the other anvil protrusion 102 in the rotational direction. Therefore, the hammer 47 rotates approximately 180 degrees in one striking operation from when the hammer 47 starts to retract, stops its retraction, moves forward, and collides with the anvil 10. Two striking operations are performed while the hammer 47 makes one rotation.

[0120] <Housing and stator support structure> In the impact tool 1, an impact is generated when the hammer 47 strikes the tool. The impact is also transmitted to the motor 6 via the spindle 8 and the speed reduction mechanism 7. In this embodiment, the housing 2 and the motor 6 have a structure that fixes the stator 26 in the axial and rotational directions.

[0121] Fig. 8 is a perspective view showing the inner surface of a housing according to the embodiment. Fig. 8 shows the inner surface of the left housing 2L. Fig. 9 is a cross-sectional view taken from the rear, passing through the rear insulator 30 according to the embodiment. Fig. 10 is a perspective view taken from the right rear, showing the motor 6 according to the embodiment. Fig. 11 is a vertical cross-sectional view showing a pillar portion 73 according to the embodiment. Fig. 12 is a cross-sectional view taken from the front, passing through the front insulator 29 according to the embodiment.

[0122] The housing 2 has support walls 71 and 72 that fit along the outer peripheral surface of the stator 26. The support walls 71 and 72 are provided in the motor accommodating section 21. The motor accommodating section 21 has a peripheral surface 21A that surrounds the periphery of the motor 6 and a rear surface 21B that covers the rear of the motor 6. The support walls 71 and 72 protrude inward from the peripheral surface 21A of the motor accommodating section 21 toward the outer peripheral surface of the stator core 28. The outer peripheral surface of the stator core 28 is circular. The tip surfaces of the support walls 71 and 72 (the end surfaces on the stator 26 side) are curved surfaces that are curved in an arc along the outer peripheral surface of the stator core 28. The tip surfaces of the support walls 71 and 72 are in surface contact with the outer peripheral surface of the stator core 28. The support walls 71 and 72 are arranged at positions spaced apart in the front-to-rear direction. The support walls 71 and 72 respectively support the front and rear portions of the outer peripheral surface of the stator core 28. Each of the support walls 71 and 72 is formed by a left half and a right half of the left housing 2L and the right housing 2R, and the left housing 2L and the right housing 2R are combined to sandwich the stator core 28.

[0123] The housing 2 has pillar portions 73 that face the rear surface of the stator 26. The pillar portions 73 are provided in the motor accommodating portion 21. The pillar portions 73 protrude inward in the left-right direction from the peripheral surface portion 21A of the motor accommodating portion 21. The pillar portions 73 are formed on each of the left housing 2L and the right housing 2R. The pillar portion 73 of the left housing 2L protrudes to the right from the inner surface of the left housing 2L. The pillar portion 73 of the right housing 2R protrudes to the left from the inner surface of the right housing 2R. One pillar portion 73 is provided at the top and bottom of the motor accommodating portion 21 in the left housing 2L. One pillar portion 73 is provided at the top and bottom of the motor accommodating portion 21 in the right housing 2R. A total of four pillar portions 73 are provided.

[0124] The pillar portion 73 extends rearward. The pillar portion 73 is connected to the rear surface portion 21B of the motor accommodating portion 21. Therefore, the pillar portion 73 is connected to the peripheral surface portion 21A and rear surface portion 21B of the motor accommodating portion 21. The pillar portion 73 has a first support surface 73A that faces the rear surface of the stator core 28 in the axial direction. The pillar portion 73 has a second support surface 73B that faces the rear insulator 30 fixed to the stator core 28 in the rotational direction. The first support surface 73A is the surface of the pillar portion 73 that faces forward. The second support surface 73B is composed of two surfaces: the left-right end surfaces of the pillar portion 73, and a surface that faces the center of the motor accommodating portion 21 in the up-down direction.

[0125] As shown in Fig. 10, a rear insulator 30 is disposed on the rear surface of the stator core 28. An outer peripheral portion 30A of the rear insulator 30 is formed to have a generally circular shape along the outer periphery of the stator core 28. The rear insulator 30 covers most of the rear surface of the stator core 28. An engagement recess 30B that engages with the pillar portion 73 is provided on the outer peripheral portion 30A of the rear insulator 30. The engagement recess 30B is formed at four locations on the outer peripheral portion 30A of the rear insulator 30, corresponding to the four pillar portions 73: the upper left, lower left, upper right, and lower right.

[0126] The engagement recess 30B has a notch shape recessed radially inward from the outer circumferential portion 30A of the rear insulator 30. By recessing radially inward, the engagement recess 30B exposes the rear surface of the stator core 28. The pillar portion 73 of the housing 2 is provided to fit into the notch-shaped engagement recess 30B. As a result, as shown in FIG. 11 , the pillar portion 73 disposed in the engagement recess 30B faces the rear surface of the stator core 28 in the axial direction. A first support surface 73A of the pillar portion 73 faces the rear surface of the stator core 28 in the axial direction. As a result, the pillar portion 73 supports the rear surface of the stator core 28 in the axial direction. The first support surface 73A of the pillar portion 73 comes into contact with the rear surface of the stator core 28, thereby preventing the stator 26 from shifting axially rearward.

[0127] The pillar portions 73 extend to the rear surface 21B of the motor accommodating portion 21, and thus can transmit axial forces from the rear surface of the stator core 28 to the rear surface 21B. This improves the axial rigidity of the pillar portions 73 compared to when the pillar portions 73 are not connected to the rear surface 21B. This allows the pillar portions 73 to effectively support the axial impact load acting on the stator 26 in conjunction with the striking operation.

[0128] The engagement recess 30B has a V-shaped notch shape. The V-shaped inner surface of the engagement recess 30B is an engagement surface 30C that engages with the pillar portion 73 in the rotational direction. As shown in FIG. 9 , the pillar portion 73 disposed in the engagement recess 30B faces the V-shaped inner surface of the engagement recess 30B in the rotational direction. The second support surfaces 73B of the pillar portion 73 face the V-shaped engagement surfaces 30C on both one side and the other side of the rotational direction. This allows the pillar portion 73 to support the rear insulator 30 in the rotational direction. The pillar portion 73 prevents misalignment of the stator 26 in the rotational direction by contacting the second support surfaces 73B with the engagement surfaces 30C of the engagement recess 30B of the rear insulator 30.

[0129] 11, the pillar portion 73 extends to the rear surface 21B of the motor accommodating portion 21, thereby engaging with the engagement surface 30C of the rear insulator 30 in the rotational direction within a range of width W. Since the contact area (engagement area) with the engagement surface 30C of the rear insulator 30 can be increased, the impact load in the rotational direction acting on the stator 26 due to the striking operation can be effectively supported.

[0130] As shown in FIG. 10 , the front insulator 29 is disposed on the front surface of the stator core 28. An outer peripheral portion 29A of the front insulator 29 is provided with an engagement surface portion 29B that engages with the support rib 74. The front insulator 29 is formed to have a generally circular shape along the outer periphery of the stator core 28. The engagement surface portion 29B is provided on the upper and lower portions of the outer peripheral portion 29A of the front insulator 29. The engagement surface portion 29B is a linear flat surface formed by linearly removing the upper and lower portions of the outer peripheral portion 29A of the front insulator 29 in the left-right direction. The engagement surface portion 29B is formed on each of the left and right sides in a range that straddles the center (rotation axis AX) of the stator 26 in the left-right direction. The front surface of the stator core 28 is exposed where the engagement surface portion 29B is formed.

[0131] As shown in FIG. 8, the housing 2 has a support rib 74 that faces the front surface of the stator 26. The support rib 74 is provided in the motor accommodating portion 21. The support rib 74 protrudes inward in the left-right direction from the peripheral surface portion 21A of the motor accommodating portion 21. One support rib 74 is provided at the top and one at the bottom of the motor accommodating portion 21. The support rib 74 is formed on each of the left housing 2L and the right housing 2R, and when the left housing 2L and the right housing 2R are assembled, a linear rib extends from one end to the other end of the motor accommodating portion 21 in the left-right direction.

[0132] The support rib 74 has a first support surface 74A that faces axially the front surface of the stator core 28. The first support surface 74A is the surface of the support rib 74 that faces rearward. The support rib 74 has a second support surface 74B that faces the engagement surface portion 29B of the front insulator 29 in the rotational direction. The second support surface 74B is a surface that faces toward the center of the motor accommodating portion 21 in the up-down direction. The second support surface 74B is the downward-facing surface (lower surface) of the upper support rib 74, and is the upward-facing surface (upper surface) of the lower support rib 74.

[0133] The first support surface 74A of the support rib 74 faces the front surface of the stator core 28 in the axial direction. As a result, the support rib 74 axially supports the front surface of the stator core 28. The first support surface 74A comes into contact with the front surface of the stator core 28, so that the support rib 74 prevents the stator 26 from shifting forward in the axial direction.

[0134] As shown in FIG. 12 , the second support surface 74B of the support rib 74 faces the engagement surface portion 29B of the front insulator 29 in the rotational direction. When the stator 26 rotates around the rotation axis AX, the engagement surface portion 29B comes into contact with the second support surface 74B, thereby supporting the front insulator 29 in the rotational direction. As a result, the support rib 74 supports the stator 26 in the rotational direction via the front insulator 29. The second support surface 74B and the engagement surface portion 29B face each other at both the left and right sides across the center (rotation axis AX) of the stator 26 in the left-right direction. Therefore, the support rib 74 supports the rotation of the stator 26 in both the forward and reverse directions.

[0135] The second support surface 74B of the support rib 74 and the engagement surface 29B of the front insulator 29 face each other with a small gap therebetween, taking into consideration dimensional tolerances. The gap between the second support surface 74B and the engagement surface 29B is larger than the gap between the second support surface 73B of the pillar portion 73 and the engagement surface 30C of the rear insulator 30. Therefore, support in the rotational direction of the stator 26 is achieved by the pillar portion 73, and when a large torque that cannot be supported by the pillar portion 73 acts on the stator 26, the support in the rotational direction by the support rib 74 functions.

[0136] <Spring design> Next, the design of the spring 50 according to the embodiment will be described. First, the behavior of the hammer 47 when striking will be described.

[0137] Figure 13 is a schematic diagram showing the step-by-step behavior of the hammer 47 when striking. Figure 13(A) shows a state in which the hammer 47 is at position P1, which is the forward limit. Figure 13(B) shows a state in which the hammer 47 is at position P2, which is the release position. Figure 13(C) shows a state in which the hammer 47 is at position P3, which is the backward limit. The position of the hammer 47 is based on the front end face of the hammer 47, i.e., the position of the front end face of the hammer protrusion 475.

[0138] As described above, the impact by the hammer 47 begins when the anvil 10 cannot be rotated by the driving force of the motor 6 alone due to the progress of tightening of fastening members (not shown), such as bolts. With the anvil 10 fixed by the fastening members, the hammer 47 retreats from position P1, which is the forward limit, as shown in FIG. 13(A). As shown in FIG. 13(B), when the hammer 47 retreats past a release position P2, where the hammer protrusion 475 and the anvil protrusion 102 are no longer in contact, the hammer 47 begins to rotate. When the hammer protrusion 475 passes the anvil protrusion 102 with which it was in contact in the rotational direction, the hammer 47 can advance toward the forward limit (position P1). The retreat of the hammer 47 releases the elastic energy of the compressed spring 50, causing the hammer 47 to advance while rotating. As a result, the hammer protrusion 475 collides (strikes) against the next anvil protrusion 102 in the rotational direction.

[0139] When the hammer 47 strikes, a reaction force from the fastening member acts on the hammer 47 via the anvil 10. The reaction force acts in a direction that rotates the hammer 47 in the opposite direction to the striking direction, and is converted by the cam mechanism 48 into a driving force that moves the hammer 47 backward. Immediately after striking, the hammer 47 begins to recoil backward due to the action of the reaction force from the fastening member. In this way, the recoil of the hammer 47 is generated by the action of the reaction force from the fastening member in addition to the driving force of the motor 6. The amount of recoil of the hammer 47 (the distance it recoils from position P1, which is the forward limit) is affected by the magnitude of the reaction force from the fastening member. The greater the reaction force from the fastening member, the greater the amount of recoil of the hammer 47.

[0140] As shown in FIG. 13C, when the hammer 47 reaches position P3, which is the retraction limit, the hammer 47 stops retracting due to contact with another component, not the elastic force of the spring 50. Position P3, which is the retraction limit, is either the position where the hammer 47 contacts another component or the position where the spring 50 reaches its full length. In FIG. 13C, the rear end of the support ring portion 474 of the hammer 47 contacts the flange portion 8B of the spindle 8, stopping the retraction of the hammer 47. If the spring 50 is compressed to its full length before the hammer 47 contacts another component, the retraction of the hammer 47 is stopped because the spring 50 can no longer be compressed. In either case, when the hammer 47 reaches its retraction limit, an axial impact occurs as the hammer 47 stops, causing unnecessary vibrations in the impact tool 1.

[0141] When the reaction force from the fastening member is small, the amount of retraction of the hammer 47 is small. For example, if the amount of retraction of the hammer 47 is small and the hammer 47 only retracts to the vicinity of the release position P2, the distance from when the hammer 47 starts advancing to when it reaches the release position P2 is short. Therefore, the hammer protrusion 475 cannot pass the anvil protrusion 102 in the rotational direction before the hammer 47 reaches the release position P2, and the front surface of the hammer protrusion 475 axially collides with the rear surface of the anvil protrusion 102. After the collision, when the hammer protrusion 475 passes over the anvil protrusion 102 in the rotational direction, the forward movement of the hammer 47 resumes, and the hammer protrusion 475 collides with the next anvil protrusion 102 in the rotational direction. In this case, the hammer protrusion 475 axially collides with the anvil protrusion 102, causing unnecessary vibrations in the impact tool 1. Furthermore, the axial collision between the hammer 47 and the anvil 10 does not contribute to the impact force in the rotational direction, but results in a loss of elastic energy in the spring 50, resulting in a decrease in the fastening force.

[0142] From the viewpoint of suppressing the occurrence of these abnormal impacts, it is undesirable for the amount of recoil of the hammer 47 due to the reaction force from the fastening member to be too large or too small. The reaction force from the fastening member depends on the size of the fastening member. When the size of the fastening member is large and the energy that the fastening member can accept is large, the reaction force on the hammer 47 is small. When the size of the fastening member is small and the energy that the fastening member can accept is small, the reaction force on the hammer 47 is large. Therefore, in this embodiment, the configuration of the spring 50 suppresses the occurrence of abnormal impacts for a wider range of reaction forces, i.e., for a wider size range of fastening members.

[0143] <Relationship between spring constant and mounting load> Specifically, in this embodiment, the value (ratio Rm) obtained by dividing the composite spring constant (N / mm) of the spring 50 by the composite mounting load F0 (N) is greater than 0.3. The composite mounting load F0 is the elastic force of the entire spring 50 when the hammer 47 is at position P1, which is the forward limit. If the composite spring constant of the spring 50 is K, then equation (1) holds. Rm=K / F0>0.3 (1)

[0144] As described above, the spring 50 includes a first spring 50A and a second spring 50B. The first spring 50A and the second spring 50B are arranged in parallel with the hammer 47. In this case, the overall composite spring constant K of the spring 50 is calculated as the sum of the spring constants of the first spring 50A and the second spring 50B. If the spring constant of the first spring 50A is KA and the spring constant of the second spring 50B is KB, then K = KA + KB. Furthermore, the overall composite mounting load F0 of the spring 50 is calculated as the sum of the mounting loads of the first spring 50A and the second spring 50B. If the mounting load of the first spring 50A is FA0 and the mounting load of the second spring 50B is FB0, then F0 = FA0 + FB0. In this embodiment, the value (ratio Rm) obtained by dividing the sum of the spring constants of the first spring 50A and the second spring 50B by the sum of the mounting loads of the first spring 50A and the second spring 50B is greater than 0.3. That is, equation (2) holds true. Rm=(KA+KB) / (FA0+FB0)>0.3 ···(2) More preferably, the ratio Rm is greater than 0.45.

[0145] In addition, in this embodiment, the value of the ratio Rm for each spring also satisfies the condition that it is greater than 0.3. That is, the value obtained by dividing the spring constant KA of the first spring 50A by the mounting load FA0 of the first spring 50A (hereinafter referred to as the ratio RmA) is greater than 0.3. The value obtained by dividing the spring constant KB of the second spring 50B by the mounting load FB0 of the second spring 50B (hereinafter referred to as the ratio RmB) is greater than 0.3. That is, the formulas (3) and (4) hold true. RmA=KA / FA0>0.3 (3) RmB=KB / FB0>0.3 (4)

[0146] The spring 50 has a constant composite spring constant in the range from the forward limit (position P1) of the hammer 47 to just before the retraction limit (position P3) of the hammer 47. The first spring 50A and the second spring 50B each have a constant spring constant in the range from the forward limit (position P1) of the hammer 47 to just before the retraction limit (position P3) of the hammer 47. The range up to just before the retraction limit (position P3) excludes positions where the spring constants inevitably change as the springs approach their full length. In this embodiment, the spring constant KA of the first spring 50A is greater than the spring constant KB of the second spring 50B. The wire diameter of the first spring 50A is greater than the wire diameter of the second spring 50B. The spring constant KA of the first spring 50A is at least twice the spring constant KB of the second spring 50B. More preferably, the spring constant KA of the first spring 50A is 2.3 times or more the spring constant KB of the second spring 50B.

[0147] The value of the ratio Rm increases as the composite spring constant K increases. The value of the ratio Rm increases as the composite mounting load F0 decreases. The spring constant depends on the wire diameter and the spring diameter, etc. Therefore, the range of the spring constant is limited by structural constraints, such as accommodating the spring 50 within the recess 476.

[0148] In the embodiment, the combined mounting load F0 is greater than 0 (N). The mounting loads FA0 and FB0 of the first spring 50A and the second spring 50B are each greater than 0 (N). The mounting load is determined by the difference between the natural length and the mounting length of the spring 50, assuming a given spring constant. The natural length is the length of the spring 50 when it is not extended or contracted. The mounting length is the length of the spring when the hammer 47 is at position P1, which is the forward limit. In the embodiment, the mounting length of the spring 50 is 90% or more of the free length of the spring 50. The mounting length of the first spring 50A is 95% or more of the free length of the first spring 50A. The mounting length of the second spring 50B is 93% or more of the free length of the second spring 50B. This allows the mounting load to be reduced, thereby increasing the value of the ratio Rm.

[0149] In the embodiment, the upper limit of the ratio Rm is not particularly limited, as it is determined depending on the structure and specifications of the impact tool 1. The ratio Rm is, for example, smaller than 1.

[0150] <Relationship between spring constant and breakaway load> In the embodiment, the value (ratio Rd) obtained by dividing the spring constant (N / mm) of the spring 50 by the release load (N) is greater than 0.09. The release load is the elastic force of the spring 50 when the hammer 47 is at the release position P2. In other words, the spring 50 biases the hammer 47 with a predetermined release load at the release position P2 where the hammer 47, which is moved backward by the cam mechanism 48, is out of contact with the anvil 10. In the embodiment, since the spring 50 includes a first spring 50A and a second spring 50B, the value (ratio Rd) obtained by dividing the composite spring constant K (N / mm) of the spring 50 by the composite release load F1 (N) is greater than 0.09. Equation (5) holds for the composite spring constant K of the spring 50. Rd=K / F1>0.09 (5) More preferably, the ratio Rd is greater than 0.15.

[0151] The overall combined breakaway load F1 of the spring 50 is calculated as the sum of the breakaway loads of the first spring 50A and the second spring 50B. If the breakaway load of the first spring 50A is FA1 and the breakaway load of the second spring 50B is FB1, then F1 = FA1 + FB1. In this embodiment, the value obtained by dividing the sum of the spring constants of the first spring 50A and the second spring 50B by the sum of the breakaway loads of the first spring 50A and the second spring 50B is greater than 0.09. That is, equation (6) holds true. Rd=(KA+KB) / (FA1+FB1)>0.09 ···(6)

[0152] In addition, in this embodiment, the value of the ratio Rd for each spring is also greater than 0.09. That is, the value obtained by dividing the spring constant KA of the first spring 50A by the breakaway load FA1 of the first spring 50A (ratio RdA) is greater than 0.10. The value obtained by dividing the spring constant KB of the second spring 50B by the breakaway load FB1 of the second spring 50B (ratio RdB) is greater than 0.09. Therefore, equations (7) and (8) hold true. RdA=KA / FA1>0.10 (7) RdB=KB / FB1>0.09 (8)

[0153] The smaller the composite breakaway load F1, the larger the value of the ratio Rd. The breakaway load is determined by the amount of deflection of the spring 50 at the breakaway position P2, given the spring constant. In other words, the smaller the distance L11 (i.e., the amount of deflection from the mounting length) from the position P1, which is the forward limit of the hammer 47, to the breakaway position P2, the smaller the breakaway load.

[0154] In this embodiment, the release length, which is the length of the spring 50 when the hammer 47 is in the release position P2, is 75% or more of the free length of the spring 50. The release length of the first spring 50A is 79% or more of the free length of the first spring 50A. The release length of the second spring 50B is 80% or more of the free length of the second spring 50B. This allows the combined release load F1 to be reduced, thereby increasing the value of the ratio Rd. Naturally, the combined release load F1, release loads FA1 and FB1 are greater than 0 (N).

[0155] In the embodiment, there is no particular upper limit to the ratio Rd, as it is determined depending on the structure and specifications of the impact tool 1. The ratio Rd is, for example, smaller than 0.5.

[0156] In the embodiment, the distance L11 from the forward limit (position P1) of the hammer 47 to the release position P2 is 50% or less of the distance L10 from the forward limit (position P1) to the retraction limit (position P3) of the hammer 47. This relatively increases the margin from when the hammer 47, which bounces back due to the reaction force from the fastening member, reaches the release position P2 until it reaches the retraction limit (position P3). This prevents the hammer 47 from reaching the retraction limit when it is retracted.

[0157] The maximum tightening torque of the impact tool 1 is not particularly limited. In the embodiment, the impact tool 1 has a maximum tightening torque of 1300 (N·m) or more. In the embodiment, the impact tool 1 has a maximum tightening torque of 3000 (N·m) or less. For impact tools 1 with a maximum tightening torque of 1300 (N·m) or more and 3000 (N·m) or less, there is a strong need to expand the size range of both the upper and lower limits of the fasteners that can be tightened. Therefore, by applying the impact tool 1 of the embodiment to a torque range with a maximum tightening torque of 1300 (N·m) or more and 3000 (N·m) or less, the size range of fasteners that can be tightened without generating abnormal impacts can be effectively expanded. The maximum tightening torque is the torque when tightening a fastener, and generally refers to the torque measured by the retightening torque method for fasteners after tightening. The retightening torque method is a method in which torque is applied to a fastener after tightening and the torque is measured when the fastener starts to turn again. Note that this is not a method of measuring by loosening nuts or bolts. Generally, this maximum tightening torque is listed in the catalogue of each manufacturer.

[0158] <Operation of impact tool> Next, the operation of the impact tool 1 will be described. For example, when performing a bolt tightening operation on a work object, the worker holds the grip portion 22 with, for example, the right hand and pulls the trigger lever 14 with the index finger of the right hand. When the trigger lever 14 is pulled, power is supplied from the battery pack 25 to the motor 6, the motor 6 starts, and the light 17 turns on. When the motor 6 starts, the rotor shaft 33 rotates. When the rotor shaft 33 rotates, the rotational force of the rotor shaft 33 is transmitted to the planetary gear 42 via the pinion gear 41. The planetary gear 42 revolves around the pinion gear 41 while rotating on its own axis while meshing with the internal teeth of the internal gear 43. The planetary gear 42 is rotatably supported on the spindle 8 via the pin 42P. The revolution of the planetary gear 42 rotates the spindle 8 at a rotational speed lower than that of the rotor shaft 33.

[0159] When the spindle 8 rotates while the hammer protrusion 475 and the anvil protrusion 102 are in contact with each other, the anvil 10 rotates together with the hammer 47 and the spindle 8. As the anvil 10 rotates, the bolt tightening operation progresses.

[0160] As the bolt tightening operation progresses, if a load equal to or greater than a predetermined value acts on the anvil 10, the rotation of the anvil 10 and the hammer 47 stops. If the spindle 8 rotates while the rotation of the hammer 47 is stopped, the hammer 47 moves rearward. As the hammer 47 moves rearward, the contact between the hammer protrusion 475 and the anvil protrusion 102 is released.

[0161] When the hammer 47 moves rearward, the hammer 47 rotates relative to the spindle shaft portion 8A. The washer 61 is spaced apart from the hammer 47 and the spindle 8. Therefore, the rotation of the hammer 47 is not hindered by the washer 61. In addition, the support ball 54 is disposed between the washer 61 and the hammer 47. The rotation of the support ball 54 allows the hammer 47 to rotate smoothly.

[0162] The hammer 47, which has moved rearward, moves forward while rotating due to the elastic force of the first spring 50A and the second spring 50B. As the hammer 47 moves forward while rotating, the anvil protrusion 102 is struck in the rotational direction by the hammer protrusion 475. This causes the anvil 10 to rotate about the rotation axis AX with high torque. As a result, the screw is tightened into the workpiece with high torque.

[0163] <Effects> The effects of the impact tool 1 according to the embodiment will be described below in comparison with an impact tool provided with a conventional spring.

[0164] Table 1 is a list showing design values related to the springs of an example which is one configuration example of the impact tool 1 according to the embodiment, and comparative examples 1 and 2 which are impact tools equipped with springs according to conventional examples. In Table 1, the normal length is the maximum distance the hammer can be retracted by the cam mechanism. The normal length in Table 1 is different from the normal length of a spring as a general technical term. The normal load is the elastic force of each spring when the hammer is in the position of the normal length. [Table 1]

[0165] The first spring 50A of the embodiment had a spring constant KA of 53.2 [N / mm], an attachment load FA0 of 101.1 [N], and a breakaway load FA1 of 526.7 [N]. The second spring 50B of the embodiment had a spring constant KB of 22.2 [N / mm], an attachment load FB0 of 59.9 [N], and a breakaway load FB1 of 237.3 [N]. The total spring constant of the first spring 50A and the second spring 50B (i.e., the composite spring constant K) was 75.4 [N / mm], the total attachment load of the first spring 50A and the second spring 50B (i.e., the composite attachment load F0) was 161.0 [N], and the total breakaway load of the first spring 50A and the second spring 50B (i.e., the composite breakaway load F1) was 764.0 [N].

[0166] From these, in the impact tool according to the embodiment, the ratio Rm of the entire spring 50 was calculated as Rm = 0.47 from equation (2). Furthermore, the ratio RmA of the first spring 50A was calculated as RmA = 0.53 from equation (3). The ratio RmB of the second spring 50B was calculated as RmB = 0.37 from equation (4). In the embodiment, the ratios Rm, RmA, and RmB are all greater than 0.3.

[0167] Furthermore, the ratio Rd of the entire spring 50 is calculated as Rd = 0.099 from equation (6). The ratio RdA of the first spring 50A is calculated as RdA = 0.101 from equation (7). The ratio RdB of the second spring 50B is calculated as RdB = 0.093 from equation (8). In the example, the ratios Rd, RdA, and RdB are all greater than 0.09. Furthermore, the ratio RdA is greater than 0.10. The impact tool 1 according to the example has a maximum tightening torque of 1700 [N·m].

[0168] In this embodiment, the inner diameter of the first spring 50A (45.5 mm) is larger than the inner diameter of the second spring 50B (34.4 mm). The spring constant KA of the first spring 50A is approximately 2.40 times the spring constant KB of the second spring 50B. The attached length of the first spring 50A (38.8 mm) is approximately 95% of the free length of the first spring 50A (40.7 mm). The attached length of the second spring 50B (37.0 mm) is approximately 93% of the free length of the second spring 50B (39.7 mm). The release length of the first spring 50A (30.8 mm) is approximately 76% of the free length of the first spring 50A (40.7 mm). The release length (29 mm) of the second spring 50B is approximately 73% of the free length (39.7 mm) of the second spring 50B. The distance L11 from the forward limit of the hammer 47 to the release position P2 is approximately 55% of the distance L10 from the forward limit to the retract limit of the hammer 47.

[0169] In this embodiment, the reduction ratio of the reduction mechanism 7 is 1 / 15.67.

[0170] Comparative Examples 1 and 2 are impact tools having a single spring.

[0171] The spring of Comparative Example 1 had a spring constant of 99.5 [N / mm], an attachment load of 826.3 [N], and a release load of 1622.6 [N]. In Comparative Example 1, the spring ratio Rm was calculated as Rm = 0.12 from equation (1). In Comparative Example 1, the spring ratio Rd was calculated as Rd = 0.061 from equation (5). In Comparative Example 1, the maximum tightening torque was 1700 [N m].

[0172] The spring of Comparative Example 2 had a spring constant of 33.5 [N / mm], an attachment load of 375.3 [N], and a release load of 643.4 [N]. In Comparative Example 2, the spring ratio Rm was calculated as Rm = 0.09 from equation (1). In Comparative Example 2, the spring ratio Rd was calculated as Rd = 0.052 from equation (5). In Comparative Example 2, the maximum tightening torque was 1700 [N m].

[0173] As described above, in both Comparative Example 1 and Comparative Example 2, the ratio Rm is smaller than 0.3. In both Comparative Example 1 and Comparative Example 2, the ratio Rd is smaller than 0.09. In Comparative Example 1, the spring constant is large, but the mounting load and removal load are large, so the ratio Rm and ratio Rd are smaller than those of the Examples. In Comparative Example 2, the mounting load and removal load are relatively small, but the spring constant is small, so the ratio Rm and ratio Rd are smaller than those of the Examples.

[0174] In Comparative Examples 1 and 2, the reduction ratio of the reduction mechanism is 1 / 15.67, which is the same as that of the example.

[0175] <Hammer operation test> A hammering operation test was carried out on each of the impact tool 1 according to the example, the impact tool according to the comparative example 1, and the impact tool according to the comparative example 2.

[0176] In the hammer operation test, impact operations were performed under multiple conditions with different spring specifications when tightening the fastening member, and it was investigated whether or not abnormal impacts occurred.

[0177] In the example (when the composite spring constant was 75.4 [N / mm], the composite mounting load was 161.0 [N], the composite removal load was 764.0 [N], Rm = 0.47, and Rd = 0.099), no abnormal impacts occurred in the axial direction of the anvil 10 or in the direction of the hammer 47 colliding with the retraction limit, within the range of high-strength friction bolts with nominal diameters of M20 to M30.

[0178] In Comparative Example 1 (composite spring constant 99.5 [N / mm], composite mounting load 826.3 [N], composite removal load 1622.6 [N], Rm = 0.12, Rd = 0.061), tests were conducted with high-strength friction fastening bolts in the range of nominal diameters M20 to M30, and no abnormal impact occurred in which the hammer collided with the retraction limit. With nominal diameters less than M30, no abnormal impact occurred in which the hammer collided with the anvil in the axial direction, but with a nominal diameter of M30, abnormal impact in which the hammer collided with the anvil in the axial direction occurred.

[0179] In Comparative Example 2 (spring constant 33.5 [N / mm], installation load 375.3 [N], removal load 643.4 [N], Rm = 0.09, Rd = 0.052), tests were conducted with high-strength friction-fitting bolts with nominal diameters of M20 to M30, and no abnormal impacts occurred in which the hammer collided with the anvil in the axial direction. No abnormal impacts occurred in which the hammer collided with the retraction limit when the nominal diameter was over M20, but abnormal impacts occurred in which the hammer collided with the retraction limit when the nominal diameter was M20.

[0180] These results indicate that abnormal impacts, where the hammer collides with the retraction limit, do not occur when the spring constant is larger, and abnormal impacts, where the hammer collides with the anvil in the axial direction, do not occur when the installation load and release load are smaller. However, abnormal impacts, where the hammer collides with the anvil in the axial direction, occur when the installation load and release load are larger, and abnormal impacts, where the hammer collides with the anvil in the axial direction, occur when the bolt has a nominal diameter of M30. In other words, when the installation load, release load, and spring constant ratios, Rm and Rd, are in the ranges of Rm > 0.30 and Rd > 0.090, respectively, neither of the two types of abnormal impacts occurs for high-strength friction-fastening bolts with nominal diameters of M20 to M30. These results confirm that the impact tool 1 according to the embodiment can suppress abnormal impacts over a wider range of reaction forces.

[0181] As described above, in this embodiment, the impact tool 1 includes the motor 6, the hammer 47 rotated by the motor 6, the anvil 10 struck by the hammer 47 in the rotational direction, two or more springs 50 (first spring 50A, second spring 50B) arranged in parallel and biasing the hammer 47 forward toward the anvil 10, a cam mechanism 48 that compresses the spring 50 with the driving force of the motor 6 to move the hammer 47 backward and advances the hammer 47 using the elastic force of the compressed spring 50, and a hammer housing 4 that accommodates the hammer 47. The spring 50 biases the hammer 47 with a predetermined mounting load when the hammer 47 is at position P1, which is the forward limit. The value (ratio Rm) obtained by dividing the composite spring constant (N / mm) of the spring 50 by the composite mounting load F0 (N) is greater than 0.3.

[0182] In the above configuration, the smaller the composite mounting load F0 and the larger the composite spring constant of the spring 50, the larger the value obtained by dividing the composite spring constant by the composite mounting load F0 (ratio Rm). Because the composite mounting load F0 is relatively small, the retraction amount of the hammer 47 is large even when the reaction force from the fastening member (such as a bolt or screw) during impact is small. Therefore, even when the reaction force is small, the hammer 47 can be prevented from colliding axially with the anvil 10 due to insufficient retraction amount. On the other hand, because the composite spring constant is relatively large, when the hammer 47 retracts and the spring 50 is compressed, the elastic force of the spring 50 increases significantly, effectively counteracting the reaction force from the fastening member. Therefore, even when the reaction force is large, the hammer 47 does not retract excessively, preventing the hammer 47 from colliding with a rear member or the spring 50 from reaching its full length. As described above, by making the ratio Rm greater than 0.3, the occurrence of abnormal impact can be prevented even when a large or small reaction force is applied. This makes it possible to prevent abnormal impacts from occurring even when the impact tool 1 is used to tighten fastening members of various sizes.

[0183] In the embodiment, the spring 50 includes a first spring 50A and a second spring 50B that are arranged in parallel with the hammer 47. The value obtained by dividing the spring constant of the first spring 50A by the mounting load FA0 of the first spring 50A (ratio RmA) is greater than 0.3. The value obtained by dividing the spring constant of the second spring 50B by the mounting load FB0 of the second spring 50B (ratio RmB) is greater than 0.3.

[0184] In the above configuration, the hammer 47 is biased by multiple springs 50 (first spring 50A, second spring 50B), and by making the ratios RmA and RmB of each spring greater than 0.3, it is possible to alleviate design constraints on the springs 50 while suppressing the occurrence of abnormal impacts.

[0185] In this embodiment, the spring 50 includes a first spring 50A and a second spring 50B. The inner diameter D1 of the first spring 50A is larger than the inner diameter D2 of the second spring 50B. The spring constant of the first spring 50A is at least twice the spring constant of the second spring 50B.

[0186] With the above configuration, the spring constant of the second spring 50B can be made relatively small. This prevents the wire diameter of the second spring 50B, which has a small inner diameter, from becoming larger and the number of turns from becoming smaller. As a result, it is possible to prevent the contact length of the second spring 50B from becoming excessively large and the lifespan of the second spring 50B from becoming relatively shorter.

[0187] In this embodiment, the attached length L0, which is the length of the spring 50 when the hammer 47 is at the forward limit position P1, is 90% or more of the free length of the spring 50.

[0188] In the above configuration, the mounting length L0 of the spring 50 is increased, i.e., the amount of deflection during mounting is reduced, thereby effectively reducing the mounting load of the spring 50. As a result, even if the reaction force from the fastening member is small, the hammer 47 can be retracted to the distance necessary to avoid axial collision between the hammer 47 and the anvil 10.

[0189] In this embodiment, when the hammer 47, which is moved backward by the cam mechanism 48, reaches the release position P2, it is out of contact with the anvil 10. A distance L11 from the forward limit of the hammer 47 to the release position P2 is 50% or less of a distance L10 from the forward limit of the hammer 47 to the retraction limit.

[0190] In the above configuration, because the distance L11 to the release position P2 is small, even when the reaction force from the fastening member is small and the amount of retraction of the hammer 47 is small, the hammer 47 can easily pass through the release position P2, thereby preventing the hammer 47 from colliding with another member in the axial direction with the anvil 10. Because the distance from the release position P2 to the retraction limit is relatively large, even when the reaction force from the fastening member is large, the hammer 47 can be prevented from reaching the retraction limit and colliding with another member.

[0191] In this embodiment, the spring 50 has a constant spring constant in the range from the forward limit (position P1) of the hammer 47 to a predetermined position just before the retraction limit (position P3) of the hammer 47.

[0192] With the above configuration, the occurrence of abnormal impacts can be suppressed without using a special nonlinear spring for the spring 50. Furthermore, since the spring constant does not change depending on the position of the hammer 47, the operation of the hammer 47 can be made smoother when the hammer 47 moves forward and backward.

[0193] In the embodiment, the impact tool 1 has a maximum tightening torque of 1300 (N·m) or more and 3000 (N·m) or less.

[0194] With the above configuration, even when tightening large or small fastening members using an impact tool 1 with a large impact force from the hammer 47, the occurrence of abnormal impacts can be suppressed, and a decrease in the usability of the impact tool 1 due to abnormal impacts can be avoided.

[0195] In the embodiment, the combined mounting load F0 of the spring 50 is greater than 0 (N).

[0196] The above configuration can prevent play from being formed at the attachment point of the spring 50 due to dimensional tolerances, and therefore, can prevent the spring 50 from moving when the impact tool 1 is not in use.

[0197] In an embodiment, the impact tool includes a motor 6, a hammer 47 rotated by the motor 6, an anvil 10 struck by the hammer 47 in the rotational direction, a spring 50 that urges the hammer 47 forward toward the anvil 10, a cam mechanism 48 that retracts the hammer 47 while compressing the spring 50 with the driving force of the motor 6 and advances the hammer 47 with the elastic force of the compressed spring 50, and a hammer housing 4 that houses the hammer 47. The spring 50 urges the hammer 47 with a predetermined release load at a release position P2 where the retracted hammer 47 is out of contact with the anvil 10 due to the cam mechanism 48. The value (ratio Rd) obtained by dividing the composite spring constant (N / mm) of the spring 50 by the composite release load F1 (N) is greater than 0.09.

[0198] In the above configuration, the smaller the composite breakaway load F1 and the larger the composite spring constant of the spring 50, the larger the ratio Rd (combined composite spring constant divided by the composite breakaway load F1). Because the composite breakaway load F1 is relatively small, the retraction amount of the hammer 47 is large even when the reaction force from the fastening member (such as a bolt or screw) during impact is small. Therefore, even when the reaction force is small, the hammer 47 can be prevented from colliding axially with the anvil 10 due to insufficient retraction amount. On the other hand, because the composite spring constant is relatively large, when the hammer 47 retracts and the spring 50 is compressed, the elastic force of the spring 50 increases significantly, effectively counteracting the reaction force from the fastening member. Therefore, even when the reaction force is large, the hammer 47 does not retract excessively, preventing the hammer 47 from colliding with a rear member or the spring 50 from reaching its full length. As described above, by making the ratio Rd greater than 0.09, the occurrence of abnormal impact can be prevented even when a large or small reaction force is applied. This makes it possible to prevent abnormal impacts from occurring even when the impact tool 1 is used to tighten fastening members of various sizes.

[0199] In the embodiment, the spring 50 includes a first spring 50A and a second spring 50B that are arranged in parallel with the hammer 47. The sum of the spring constants of the first spring 50A and the second spring 50B divided by the sum of the breakaway loads of the first spring 50A and the second spring 50B is greater than 0.09.

[0200] In the above configuration, by arranging the first spring 50A and the second spring 50B in parallel, it is possible to easily make the ratio Rd greater than 0.09 for the entire spring 50. Furthermore, compared to the case of a single spring, the individual wire diameters of the first spring 50A and the second spring 50B can be made smaller, and the contact length can be shortened, thereby easing design constraints on the spring 50.

[0201] In this embodiment, the spring 50 includes a first spring 50A and a second spring 50B that are arranged in parallel with the hammer 47. The value obtained by dividing the spring constant KA of the first spring 50A by the breakaway load FA1 of the first spring 50A (ratio RdA) is greater than 0.10. The value obtained by dividing the spring constant KB of the second spring 50B by the breakaway load FB1 of the second spring 50B (ratio RdB) is greater than 0.09.

[0202] In the above configuration, the hammer 47 is biased by multiple springs 50 (first spring 50A, second spring 50B), and by making the spring ratios RdA and RdB greater than 0.10 and 0.09, respectively, it is possible to alleviate the design constraints of the springs 50 while suppressing the occurrence of abnormal impacts.

[0203] In this embodiment, the release length L1, which is the length of the spring 50 when the hammer 47 is at the release position P2, is 75% or more of the free length of the spring 50.

[0204] In the above configuration, the release load of the spring 50 can be effectively reduced by increasing the release length L1 of the spring 50, i.e., by reducing the amount of deflection at the release position P2. As a result, even if the reaction force from the fastening member is small, the amount of retraction required to avoid axial collision between the hammer 47 and the anvil 10 can be easily generated.

[0205] In the embodiment, the impact tool 1 includes a speed reduction mechanism 7 that reduces the rotation speed of the motor 6 and transmits the reduced speed to the hammer 47. The reduction ratio of the speed reduction mechanism 7 is 1 / 15 or more and 1 / 100 or less.

[0206] In the above configuration, the reduction mechanism 7 can generate a high tightening torque.

[0207] In this embodiment, the impact tool 1 includes a motor 6, a hammer 47 rotated by the motor 6, an anvil 10 struck by the hammer 47 in the rotational direction, a spring 50 urging the hammer 47 forward toward the anvil 10, a cam mechanism 48 that compresses the spring 50 with the driving force of the motor 6 to move the hammer 47 backward and advances the hammer 47 with the elastic force of the compressed spring 50, and a hammer housing 4 that houses the hammer 47. The spring 50 urges the hammer 47 with a predetermined mounting load when the hammer 47 is at position P1, which is its forward limit. The value (ratio Rm) of the spring 50 divided by the mounting load (N) is greater than 0.3. The impact tool 1 has a maximum tightening torque of 1300 (N·m) or greater.

[0208] In the above configuration, the smaller the mounting load and the larger the spring constant of the spring 50, the larger the value obtained by dividing the spring constant by the mounting load (ratio Rm). Because the mounting load is relatively small, the retraction amount of the hammer 47 is large even when the reaction force from the fastening member (such as a bolt or screw) during impact is small. Therefore, even when the reaction force is small, the hammer 47 can be prevented from colliding axially with the anvil 10 due to insufficient retraction amount. On the other hand, because the spring constant is relatively large, the elastic force of the spring 50 increases significantly when the hammer 47 retracts and compresses the spring 50, effectively counteracting the reaction force from the fastening member. Therefore, even when the reaction force is large, the hammer 47 does not retract excessively, preventing the hammer 47 from colliding with a rear member or the spring 50 from reaching its full length. By setting the ratio Rm to be greater than 0.3, abnormal impacts can be prevented even when a large or small reaction force is applied. This prevents abnormal impacts from occurring even when the impact tool is used to tighten fastening members of various sizes.

[0209] [Other embodiments] In the above-described embodiment, the impact tool 1 is an impact wrench. The impact tool 1 may be an impact driver. In this case, the impact tool 1 includes an anvil 10 having an attachment hole formed therein for attaching a driver bit as an end tool.

[0210] In the above-described embodiment, the spring 50 includes the first spring 50A and the second spring 50B. The spring 50 may be a single spring, or may include three or more springs.

[0211] In the above-described embodiment, the spring 50 has a constant spring constant. However, the spring 50 may be a nonlinear spring whose spring constant changes depending on the position of the hammer 47. When the spring 50 is a nonlinear spring whose spring constant changes depending on the position of the hammer 47, the spring constant used in calculating the ratios Rm, RmA, RmB, Rd, RdA, and RdB is the spring constant when the hammer 47 is at the release position P2. The spring constant when the hammer 47 is at the forward limit position P1 may be smaller than the spring constant when the hammer 47 is at the release position P2. The spring constant when the hammer 47 is at the backward limit position P3 may be larger than the spring constant when the hammer 47 is at the release position P2.

[0212] In the above-described embodiment, the power source for the impact tool 1 does not have to be the battery pack 25, and may be a commercial power source (AC power source). [Explanation of symbols]

[0213] 1...Impact tool, 2...Housing, 2R...Right housing, 2L...Left housing, 3...Cover, 4...Hammer housing, 6...Motor, 7...Reduction mechanism, 8...Spindle, 8A...Spindle shaft, 8B...Flange, 8C...Convex, 8D...Spindle groove, 9...Impact mechanism, 10...Anvil, 12...Fan, 13...Battery mounting section, 14...Trigger lever, 15...Forward / reverse switching lever, 16B...Indicator display, 16A...Operation button, 16...Operation display, 17...Light, 19...Intake port, 20...Exhaust port, 21...Motor housing, 21B...Rear portion, 21A...periphery portion, 22...grip portion, 23...battery holding portion, 24...bearing box, 25...battery pack, 26...stator, 27...rotor, 28...stator core, 29...front insulator, 29A...outer periphery portion, 29B...engagement surface portion, 30...rear insulator, 30A...outer periphery portion, 30B...engagement recess, 30C...engagement surface, 31...coil, 32...rotor core, 33...rotor shaft, 34...rotor magnet, 37...sensor board, 38...busbar unit, 39...rotor bearing, 39R...rear rotor bearing, 39F...front rotor bearing Ring, 41... pinion gear, 42P... pin, 42... planetary gear, 43... internal gear, 44... spindle bearing, 46... anvil bearing, 46A... recess, 47... hammer, 48... cam mechanism, 49... hammer ball, 50... spring, 50A... first spring, 50B... second spring, 53... washer, 54... support ball, 61... washer, 71... support wall portion, 73... column portion, 73A... first support surface, 73B... second support surface, 74... support rib, 74A... first support surface, 74B... second support surface, 101... anvil shaft portion, 102 ...anvil protrusion, 103...recess, 104...groove, 241...recess, 242...recess, 401...first cylindrical portion, 402...second cylindrical portion, 402R...rear surface, 403...connection portion, 471...base portion, 473...rear ring portion, 474...support ring portion, 475...hammer protrusion, 476...recess, 477...hammer groove, 478...support groove, AX...rotating axis, D1...inner diameter, D2...inner diameter, F0...composite mounting load, F1...composite removal load, L0...mounting length, L1...removal length, L10...distance, L11...distance, P1...forward limit position, P2...removal position, P3...rear limit position, W...width.

Claims

1. A motor; a hammer rotated by the motor; an anvil that is struck in a rotational direction by the hammer; two or more springs arranged in parallel to bias the hammer forward toward the anvil; a cam mechanism that moves the hammer backward while compressing the spring by the driving force of the motor and moves the hammer forward by the elastic force of the compressed spring; a hammer accommodating portion that accommodates the hammer, the spring biases the hammer with a predetermined mounting load when the hammer is at its forward limit position; The value obtained by dividing the combined spring constant (N / mm) of the spring by the combined mounting load (N) is greater than 0.3; Impact tool.

2. The spring includes a first spring and a second spring, The inner diameter of the first spring is larger than the inner diameter of the second spring, The spring constant of the first spring is at least twice the spring constant of the second spring. The impact tool according to claim 1 .

3. The attached length of the spring when the hammer is at its forward limit position is 90% or more of the free length of the spring. The impact tool according to claim 1 .

4. When the hammer, which is retracted by the cam mechanism, reaches a release position, it is no longer in contact with the anvil. The distance from the forward limit of the hammer to the release position is 50% or less of the distance from the forward limit to the retract limit of the hammer. The impact tool according to claim 1 .

5. The spring has a constant spring constant in a range from the forward limit of the hammer to just before the backward limit of the hammer. The impact tool according to claim 1 .

6. The maximum tightening torque is 1300 (N·m) or more and 3000 (N·m) or less. The impact tool according to claim 1 .

7. The combined mounting load of the spring is greater than 0 (N), The impact tool according to claim 1 .

8. A motor; a hammer rotated by the motor; an anvil that is struck in a rotational direction by the hammer; a spring that biases the hammer forward toward the anvil; a cam mechanism that moves the hammer backward while compressing the spring by the driving force of the motor and moves the hammer forward by the elastic force of the compressed spring; a hammer accommodating portion that accommodates the hammer, The spring biases the hammer with a predetermined release load at a release position where the hammer, which is retracted by the cam mechanism, is out of contact with the anvil; The value obtained by dividing the spring constant (N / mm) of the spring by the breakaway load (N) is greater than 0.

09. Impact tool.

9. The spring includes a first spring and a second spring provided in parallel with the hammer, a value obtained by dividing the sum of the spring constants of the first spring and the second spring by the sum of the breakaway loads of the first spring and the second spring is greater than 0.09; 9. The impact tool according to claim 8.

10. The spring includes a first spring and a second spring provided in parallel with the hammer, a value obtained by dividing the spring constant of the first spring by the breakaway load of the first spring is greater than 0.10; a value obtained by dividing the spring constant of the second spring by the breakaway load of the second spring is greater than 0.09; 9. The impact tool according to claim 8.

11. The inner diameter of the first spring is larger than the inner diameter of the second spring, The spring constant of the first spring is at least twice the spring constant of the second spring. An impact tool according to claim 9 or 10.

12. a release length, which is the length of the spring when the hammer is in the release position, is 75% or more of the free length of the spring; 9. The impact tool according to claim 8.

13. The distance from the forward limit of the hammer to the release position is 50% or less of the distance from the forward limit to the retract limit of the hammer.

9. The impact tool according to claim 8.

14. The spring has a constant spring constant in a range from the forward limit of the hammer to just before the backward limit of the hammer.

9. The impact tool according to claim 8.

15. The maximum tightening torque is 1300 (N·m) or more and 3000 (N·m) or less.

9. The impact tool according to claim 8.

16. The spring has a combined mounting load greater than 0 (N) when the hammer is at its forward limit position.

9. The impact tool according to claim 8.

17. a speed reduction mechanism that reduces the rotation speed of the motor and transmits the reduced speed to the hammer; The reduction ratio of the reduction mechanism is 1 / 15 or more and 1 / 100 or less.

9. An impact tool according to claim 1 or 8.

18. A motor; a hammer rotated by the motor; an anvil that is struck in a rotational direction by the hammer; a spring that biases the hammer forward toward the anvil; a cam mechanism that moves the hammer backward while compressing the spring by the driving force of the motor and moves the hammer forward by the elastic force of the compressed spring; a hammer accommodating portion that accommodates the hammer, the spring biases the hammer with a predetermined mounting load when the hammer is at its forward limit position; The spring constant (N / mm) of the spring divided by the mounting load (N) is greater than 0.3, The maximum tightening torque is 1300 (N m) or more. Impact tool.

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