Impact tool

Abstract

To suppress a come-out phenomenon from occurring.SOLUTION: An impact tool is provided with a motor to which voltages of 18V or more are inputted, a spindle that is rotated by the motor, a spindle groove formed on the spindle, a ball retained on the spindle groove, a hammer supported by the spindle through the ball, a spring that energizes the hammer forward, and an anvil that is hit in a rotating direction by the hammer. Hitting-starting torque showing torque that acts on the anvil when the hammer starts to hit the anvil is 1100 Nmm or less.SELECTED DRAWING: Figure 23

Description

[Technical field]

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

[0002] 2. Description of the Related Art In the technical field related to impact tools, a rotary impact tool such as that disclosed in Patent Document 1 is known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4600562 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to improve the ease of use when using impact tools, there is a demand for technology that can suppress the occurrence of the cam-out phenomenon, in which the tip tool comes out of the cross groove formed in the head of the screw.

[0005] The technology disclosed in this specification aims to suppress the occurrence of the come-out phenomenon. [Means for solving the problem]

[0006] This specification discloses an impact tool. The impact tool includes a motor to which a voltage of 18 V or more is input, a spindle rotated by the motor, a spindle groove formed in the spindle, a ball held in the spindle groove, a hammer supported by the spindle via the ball, a spring that biases the hammer forward, and an anvil that is struck in the rotational direction by the hammer. An impact start torque, which indicates the torque acting on the anvil when the hammer starts striking the anvil, is 1100 N·mm or less. Effect of the Invention

[0007] According to the technique disclosed in this specification, the occurrence of the come-out phenomenon is suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a front perspective view showing an impact tool according to an embodiment. [Diagram 2] FIG. 2 is a side view showing an upper portion of the impact tool according to the embodiment. [Diagram 3] FIG. 3 is a vertical cross-sectional view showing an upper portion of the impact tool according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing an upper portion of the impact tool according to the embodiment. [Diagram 5] FIG. 5 is an exploded perspective view from the front showing a part of the impact mechanism according to the embodiment. [Figure 6] FIG. 6 is an exploded perspective view showing a part of the impact mechanism according to the embodiment, seen from the rear. [Figure 7] FIG. 7 is a side view showing the spindle according to the embodiment. [Figure 8] FIG. 8 is a top view showing the spindle according to the embodiment. [Figure 9] FIG. 9 is a top view showing a part of the spindle according to the embodiment. [Figure 10] FIG. 10 is a perspective view showing a part of the spindle according to the embodiment. [Figure 11] FIG. 11 is a vertical cross-sectional view showing the spindle according to the embodiment. [Figure 12] FIG. 12 is a cross-sectional view showing a spindle according to the embodiment. [Figure 13] FIG. 13 is a side view showing the hammer according to the embodiment. [Figure 14] FIG. 14 is a vertical cross-sectional view showing the hammer according to the embodiment. [Figure 15] FIG. 15 is a cross-sectional view showing the hammer according to the embodiment. [Figure 16] FIG. 16 is a perspective view showing a spindle according to the embodiment. [Figure 17] FIG. 17 is a cross-sectional view for explaining the operation of the impact mechanism according to the embodiment. [Figure 18] FIG. 18 is a cross-sectional view for explaining the operation of the impact mechanism according to the embodiment. [Figure 19] FIG. 19 is a cross-sectional view for explaining the operation of the impact mechanism according to the embodiment. [Figure 20] FIG. 20 is a top view showing a part of a spindle according to a comparative example. [Figure 21] FIG. 21 is a diagram for explaining the relationship between the spindle and the ball according to each of the example and the comparative example. [Figure 22] FIG. 22 is a diagram for explaining the force that the balls according to the example and the comparative example receive from the spindle. [Figure 23] FIG. 23 is a diagram for explaining the impact start torque according to each of the example and the comparative example. [Figure 24] FIG. 24 is a diagram showing the tightening speed, average current, and average voltage for each of the example and the comparative example. [Diagram 25] FIG. 25 is a diagram showing the direction in which the load is transmitted from the ball to the hammer in each of the example and the comparative example. [Figure 26] FIG. 26 is a schematic diagram illustrating the structure of the spring element according to the embodiment. [Figure 27] FIG. 27 is a graph for explaining the changes in torque, rotation amount, and spring load according to the stroke of the hammer. [Figure 28] FIG. 28 is a graph for explaining the changes in torque, rotation amount, and spring load according to the stroke of the hammer when the spring element is a single coil spring. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In one or more embodiments, the impact tool includes a motor receiving an input voltage of 18 V or more, a spindle rotated by the motor, a spindle groove formed in the spindle, a ball held in the spindle groove, a hammer supported on the spindle via the ball, a spring that biases the hammer forward, and an anvil struck in the rotational direction by the hammer. An impact start torque, which indicates the torque acting on the anvil when the hammer starts striking the anvil, is 1100 N·mm or less.

[0010] When a load torque of a predetermined value or more acts on the anvil from the screw during a screw tightening operation, the rotation of the anvil and the hammer stops. Since the spindle continues to rotate by the motor, if the spindle continues to rotate while the rotation of the hammer is stopped, the hammer moves backward relative to the spindle. After the hammer moves backward, the hammer moves forward while rotating due to the biasing force of the spring. As the hammer moves forward while rotating, the anvil is struck by the hammer in the direction of rotation. In the above configuration, the strike start torque is small, so the timing at which the hammer starts striking the anvil is advanced. In other words, the period from when the screw tightening starts to when the hammer strikes the anvil is shortened.

[0011] In a screw tightening operation, the anvil is rotated with the tool attached to it inserted into the cross groove formed in the head of the screw. If the timing of the hammer starting to strike the anvil is delayed, that is, if the period from the start of screw tightening to the time the hammer strikes the anvil is long, there is a high possibility that the tool will come out of the cross groove, causing a cam-out phenomenon. With the above configuration, the timing of the hammer starting to strike the anvil is advanced, thereby suppressing the cam-out phenomenon.

[0012] In one or more embodiments, the impact tool includes a battery mounting portion to which a battery pack is attached, the battery pack having a rated voltage of 18V or more.

[0013] In the above configuration, the rated voltage of the battery pack is 18V or more, which enables the impact tool to have a high output.

[0014] In one or more embodiments, the depth of the spindle groove varies with axial position on the spindle.

[0015] In the above configuration, the occurrence of the come-out phenomenon is suppressed.

[0016] In one or more embodiments, the depth of the rear of the spindle groove is greater than the depth of the front of the spindle groove. The depth of the ends of the spindle groove is greater than the depth of the center of the spindle groove.

[0017] In the above configuration, the center of the ball can be recessed inside the spindle groove, so the rotational component of the force acting between the spindle and the ball becomes large. This increases the rotational speed of the hammer as it moves forward while rotating. Because the rotational speed of the hammer is increased, the hammer can strike the anvil with a large impact force.

[0018] In one or more embodiments, the end of the spindle groove is located rearward of the center of the spindle groove. When the hammer moves rearward relative to the spindle, the ball moves to the end of the spindle groove. At the end of the spindle groove, the center of the ball is located inside the spindle groove.

[0019] When the hammer moves backward relative to the spindle, the ball moves from the center to the end of the spindle groove. When the hammer moves forward relative to the spindle due to the biasing force of the spring, the ball moves from the end to the center of the spindle groove. In the above configuration, the center of the ball is recessed inside the spindle groove at the end of the spindle groove, so the rotational speed of the hammer is increased when the hammer moves forward while rotating. Because the rotational speed of the hammer is increased, the hammer can strike the anvil with a large impact force.

[0020] In one or more embodiments, in the central portion of the spindle groove, the center of the ball is located outside the spindle groove.

[0021] When the hammer strikes the anvil, the ball moves from the end of the spindle groove to the center. In the above configuration, the center of the ball is located outside the spindle groove at the center of the spindle groove, so the rotational speed of the hammer is increased at the moment when the hammer strikes the anvil. Since the rotational speed of the hammer is increased, the hammer can strike the anvil with a large impact force.

[0022] In one or more embodiments, the ball moves in a circular motion such that the center of the ball moves along an imaginary circle defined in an imaginary plane, the center of the imaginary circle being defined at a location offset from the axis of rotation of the spindle.

[0023] In the above configuration, the hammer can strike the anvil with a large striking force.

[0024] In one or more embodiments, the impact tool may include a motor receiving an input voltage of 18V or more, a spindle rotated by the motor, a spindle groove formed in the spindle, a ball held in the spindle groove, a hammer supported by the spindle via the ball, a spring for biasing the hammer forward, and an anvil struck in the rotational direction by the hammer. The impact tool may have a maximum tightening torque of more than 220N·m. An impact start torque, which indicates the torque acting on the anvil when the hammer starts striking the anvil, may be 1300N·mm or less. The maximum tightening torque is the torque when the fastened material is tightened, and generally refers to the torque measured by a re-tightening torque wrench or the like for the fastened material after fastening. It is not a method of measuring by loosening a nut or bolt. Generally, this maximum tightening torque is listed in the catalog of each manufacturer.

[0025] With the above configuration, even if the maximum tightening torque is increased above 220 N·m, the impact start torque can be suppressed to 1300 N·mm or less. Because the impact start torque is low, the timing when the hammer starts to strike the anvil is accelerated. In other words, the amount of screw rotation from when the screw tightening starts until the hammer strikes the anvil is reduced. Because the timing when the hammer starts to strike the anvil is accelerated, the occurrence of the cam-out phenomenon is suppressed.

[0026] In one or more embodiments, the impact tool may include a battery mounting portion to which a battery pack is attached. The battery pack may have a rated voltage of 18V or more.

[0027] In the above configuration, the rated voltage of the battery pack is 18V or more, which enables the impact tool to have a high output.

[0028] In one or more embodiments, the depth of the spindle groove may vary with axial position of the spindle.

[0029] In the above configuration, the occurrence of the come-out phenomenon is suppressed.

[0030] In one or more embodiments, the impact tool may have a maximum tightening torque of 230 N·m or greater.

[0031] With the above configuration, even if the maximum tightening torque is 230 N m, the impact start torque can be reduced to 1300 N mm or less, making it possible to achieve both a high maximum tightening torque and suppress the reduction in cam-out.

[0032] In one or more embodiments, the impact tool may have a maximum tightening torque (N·mm) divided by a striking torque (N·mm) greater than 165.

[0033] Generally, the higher the maximum tightening torque, the higher the impact start torque tends to be, and the higher the impact start torque and the later the timing of the impact start, the more likely the cam-out phenomenon occurs. The value obtained by dividing the maximum tightening torque by the impact start torque becomes larger as the maximum tightening torque increases and becomes larger as the impact start torque decreases, so this is an index that indicates the lowness of the impact start torque relative to the magnitude of the maximum tightening torque (i.e., the degree of suppression of the come-out phenomenon). In the above configuration, the value obtained by dividing the maximum tightening torque by the impact start torque is greater than 165, so the come-out phenomenon can be suppressed more effectively compared to the magnitude of the maximum tightening torque.

[0034] In one or more embodiments, the impact tool may include a motor, a spindle rotated by the motor, a cam element including a spindle groove formed in the spindle and a ball held in the spindle groove, a hammer supported on the spindle via the ball, a spring element for biasing the hammer forward, and an anvil struck in the rotational direction by the advanced hammer. The hammer may move backward while rotating against the biasing force of the spring element due to the rotational torque applied from the motor via the spindle and the cam element at the time of striking, and then may move forward while rotating due to the elastic force of the compressed spring element and the cam element. Each of the cam element and the spring element may have a structure for nonlinearly increasing the required torque so as to suppress an increase in the required torque required to rotate the hammer in a region where the rearward stroke of the hammer is small, and to promote an increase in the required torque in a region where the stroke of the hammer is large.

[0035] In the above configuration, the maximum tightening torque is increased while the impact start torque is reduced, so that it is possible to achieve both a high maximum tightening torque and the suppression of cam-out. That is, in order to increase the maximum tightening torque, the motor output is increased to increase the rotation speed of the hammer. If the rotation speed of the hammer is high, the time it takes for the hammer to reach the angle at which it strikes the anvil is shortened. In order to make the forward movement of the hammer in time for the timing at which it strikes the anvil, the biasing force of the spring element is increased to cause the hammer to advance quickly. If the biasing force of the spring element is increased, the torque required to rotate and retract the hammer increases, so that the impact start torque becomes higher.

[0036] Thus, normally, when the maximum tightening torque is increased, the impact start torque is increased. Therefore, as described above, the cam element and spring element are used to make the change in the required torque according to the stroke nonlinear, suppressing the increase in the required torque when the stroke is small, making it easier to move the hammer backward and reducing the impact start torque. By promoting the increase in the required torque when the stroke is large, the rotational speed of the hammer when moving forward is increased, thereby increasing the maximum tightening torque. As a result, the occurrence of the cam-out phenomenon can be suppressed while increasing the maximum tightening torque.

[0037] In one or more embodiments, a first region is defined as the region from the position where the rearward stroke of the hammer is at its minimum to the position where the hammer and the anvil are not in contact, and a second region is defined as a predetermined region where the stroke is greater than that of the first region and includes the position where the stroke is at its maximum, and the degree of change in the required torque with respect to the stroke in the first region may be smaller than the degree of change in the required torque with respect to the stroke in the second region.

[0038] In the above configuration, the degree of increase in the required torque associated with the stroke is suppressed in the first region, so that the hammer can be moved to a position where the hammer and the anvil are not in contact with each other with a smaller required torque. Therefore, the required torque in the first region is reduced, so that the impact start torque can be lowered. If the degree of increase in the required torque associated with the stroke remains suppressed, the required torque does not increase sufficiently even when the hammer reaches the maximum stroke, and the rotation speed of the hammer cannot be increased. Therefore, by increasing the degree of increase in the required torque associated with the stroke in the second region, a high maximum tightening torque can be achieved.

[0039] In one or more embodiments, the maximum required torque in the first region may be 1300 N·mm or less.

[0040] With the above configuration, the impact start torque can be effectively reduced.

[0041] In one or more embodiments, the impact tool may have a maximum tightening torque of 230 N·m or more and 350 N·m or less.

[0042] With the above configuration, it is possible to realize a high maximum tightening torque while suppressing the impact start torque.

[0043] In one or more embodiments, the depth of the rear of the spindle groove may be greater than the depth of the front of the spindle groove.

[0044] In the above configuration, the ball placed in the spindle groove is away from the rotation axis at the front of the spindle groove and close to the rotation axis at the rear of the spindle groove. Therefore, at the front of the spindle groove, the hammer 47 can be rotated and stroked backward with a lower torque, which contributes to reducing the torque required to start striking. At the rear of the spindle groove, the component in the rotational direction of the force acting between the spindle and the ball becomes relatively large, and the rotational speed of the hammer is increased as it moves forward while rotating. The increased rotational speed of the hammer contributes to an increase in the maximum tightening torque.

[0045] In one or more embodiments, the hammer may have a hammer groove in which at least a portion of the ball is disposed. When a tangent vector is a direction parallel to a tangent of a circle that passes through a contact point between the ball and the hammer groove and is centered on the rotation axis of the spindle, and a load vector is a direction in which a load is transmitted from the ball to the contact point with the hammer, the angle between the tangent vector and the load vector at the rear of the spindle groove may be smaller than the angle between the tangent vector and the load vector at the front of the spindle groove.

[0046] The smaller the angle between the tangent vector and the load vector, the more the force acting from the spindle to the ball acts exclusively in the rotational direction. In the above configuration, the angle is relatively small at the front of the spindle groove, and the axial component of the force acting from the spindle to the ball is relatively large. Therefore, the hammer can be stroked backward with a lower torque, which contributes to reducing the impact start torque. At the rear of the spindle groove, the rotational component of the force acting from the spindle to the ball is relatively large. Therefore, the rotational speed of the hammer is increased when it moves forward while rotating, which contributes to increasing the maximum tightening torque.

[0047] In one or more embodiments, the spring element may include a first coil spring and a second coil spring. The first coil spring may constantly apply a biasing force to the hammer that causes the hammer to move forward. The second coil spring may apply a biasing force to the hammer when the hammer moves rearward.

[0048] In the above configuration, when the stroke of the hammer is small, the hammer is biased only by the first coil spring, making it easier to move the hammer backward and reducing the torque required to start striking. When the stroke of the hammer is large, the hammer is biased by both the first and second coil springs, making it easier to move the hammer forward, so that even if the hammer rotation speed is increased, the hammer can be moved forward quickly and strike the anvil appropriately. This allows the maximum tightening torque to be increased.

[0049] [First 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.

[0050] In the embodiment, the direction parallel to the rotation axis AX of the motor 6 is referred to as the axial direction, the direction circumferential 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.

[0051] The rotation axis AX extends in the front-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 is appropriately referred to as the radially inner side, and a position farther from or away from the rotation axis AX is appropriately referred to as the radially outer side.

[0052] [Impact tools] Fig. 1 is a front perspective view showing an impact tool 1 according to an embodiment. Fig. 2 is a side view showing an upper part of the impact tool 1 according to an embodiment. Fig. 3 is a vertical cross-sectional view showing an upper part of the impact tool 1 according to an embodiment. Fig. 4 is a horizontal cross-sectional view showing an upper part of the impact tool 1 according to an embodiment.

[0053] In the embodiment, the impact tool 1 is an impact driver, which is a type of screw tightening tool. The impact tool 1 includes a housing 2, a rear cover 3, a hammer case 4, a hammer case cover 5, a motor 6, a reduction mechanism 7, a spindle 8, a striking mechanism 9, an anvil 10, a tool holding mechanism 11, a fan 12, a battery mounting section 13, a trigger lever 14, a forward / reverse rotation switching lever 15, an operation display section 16, a mode switching switch 17, and a light assembly 18.

[0054] 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 disposed to the right of the left housing 2L. The left housing 2L and the right housing 2R are fixed together by a plurality of screws 2S. The housing 2 is composed of a pair of half housings.

[0055] The housing 2 has a motor accommodating portion 21, a grip portion 22, and a battery holding portion 23.

[0056] The motor accommodating portion 21 is cylindrical and accommodates the motor 6. The motor accommodating portion 21 accommodates at least a portion of the hammer case 4.

[0057] The grip portion 22 extends downward from the motor housing portion 21. The trigger lever 14 is provided on an upper portion of the grip portion 22. The grip portion 22 is held by an operator.

[0058] The battery holding portion 23 is connected to a lower end portion of the grip portion 22. The outer dimensions of the battery holding portion 23 are larger than the outer dimensions of the grip portion 22 in both the front-rear direction and the left-right direction.

[0059] The rear cover 3 is made of synthetic resin. The rear cover 3 is disposed rearward of the motor accommodating portion 21. The rear cover 3 accommodates at least a portion of the fan 12. The fan 12 is disposed on the inner peripheral side of the rear cover 3. The rear cover 3 is disposed so as to cover an opening at the rear end portion of the motor accommodating portion 21. The rear cover 3 is fixed to the rear end portion of the motor accommodating portion 21 with two screws 3S.

[0060] The motor accommodating portion 21 has an air intake port 19. The rear cover 3 has an air exhaust port 20. Air in the external space of the housing 2 flows into the internal space of the housing 2 through the air intake port 19. Air in the internal space of the housing 2 flows out to the external space of the housing 2 through the air exhaust port 20.

[0061] The hammer case 4 is made of metal. In the embodiment, the hammer case 4 is made of aluminum. The hammer case 4 is cylindrical. The hammer case 4 is connected to the front of the motor accommodating section 21. The bearing box 24 is fixed to the rear of the hammer case 4. A screw thread is formed on the outer periphery of the bearing box 24. A screw groove is formed on the inner periphery of the hammer case 4. The screw thread of the bearing box 24 and the screw groove of the hammer case 4 are coupled to each other, thereby fixing the bearing box 24 and the hammer case 4. The hammer case 4 is sandwiched between the left housing 2L and the right housing 2R. At least a portion of the hammer case 4 is accommodated in the motor accommodating section 21. The bearing box 24 is fixed to each of the motor accommodating section 21 and the hammer case 4.

[0062] The hammer case 4 accommodates at least a portion of the reduction mechanism 7, the spindle 8, the striking mechanism 9, and the anvil 10. At least a portion of the reduction mechanism 7 is disposed inside the bearing box 24. The reduction mechanism 7 includes a plurality of gears.

[0063] The hammer case 4 has a first cylindrical portion 401 and a second cylindrical portion 402. The first cylindrical portion 401 is disposed around the striking mechanism 9. The second cylindrical portion 402 is disposed forward of the first cylindrical portion 401. The outer diameter of the second cylindrical portion 402 is smaller than the outer diameter of the first cylindrical portion 401.

[0064] The hammer case cover 5 covers at least a portion of the surface of the hammer case 4. The hammer case cover 5 protects the hammer case 4. The hammer case cover 5 suppresses contact between the hammer case 4 and objects around the hammer case 4.

[0065] The motor 6 is a power source of 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 accommodating portion 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.

[0066] The stator 26 includes a stator core 28 , a front insulator 29 , a rear insulator 30 , and a coil 31 .

[0067] 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.

[0068] The front insulator 29 is provided at the front of the stator core 28. The rear insulator 30 is provided at the rear 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 disposed so as to cover a portion of the surface of the teeth. The rear insulator 30 is disposed so as to cover a portion of the surface of the teeth.

[0069] 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 multiple coils 31 are connected via fusing terminals 38.

[0070] The rotor 27 rotates about a rotation axis AX. The rotor 27 has a rotor core portion 32, a rotor shaft portion 33, a rotor magnet 34, and a sensor magnet 35.

[0071] The rotor core portion 32 and the rotor shaft portion 33 are each made of steel. The rotor shaft portion 33 protrudes in the front-rear direction from an end face of the rotor core portion 32. The rotor shaft portion 33 includes a front shaft portion 33F that protrudes forward from the front end face of the rotor core portion 32 and a rear shaft portion 33R that protrudes rearward from the rear end face of the rotor core portion 32.

[0072] The rotor magnet 34 is fixed to the rotor core portion 32. The rotor magnet 34 is cylindrical. The rotor magnet 34 is disposed around the rotor core portion 32.

[0073] The sensor magnet 35 is fixed to the rotor core portion 32. The sensor magnet 35 is annular. The sensor magnet 35 is disposed on the front end surface of the rotor core portion 32 and the front end surface of the rotor magnet .

[0074] A sensor board 37 is attached to the front insulator 29. The sensor board 37 is fixed to the front insulator 29 with screws 29S. 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 sensor magnet 35. The rotation detection element detects the position of the sensor magnet 35 of the rotor 27, thereby detecting the position of the rotor 27 in the rotational direction.

[0075] The rotor shaft portion 33 is rotatably supported by a rotor bearing 39. The rotor bearing 39 includes a front rotor bearing 39F that rotatably supports the front shaft portion 33F, and a rear rotor bearing 39R that rotatably supports the rear shaft portion 33R.

[0076] The front rotor bearing 39F is held in the bearing box 24. The bearing box 24 has a recess 24A recessed forward from the rear surface of the bearing box 24. The front rotor bearing 39F is disposed in the recess 24A. The rear rotor bearing 39R is held in the rear cover 3. The front end of the rotor shaft portion 33 is disposed in the internal space of the hammer case 4 through an opening in the bearing box 24.

[0077] A pinion gear 41 is formed on the front end of the rotor shaft portion 33. The pinion gear 41 is connected to at least a part of the reduction mechanism 7. The rotor shaft portion 33 is connected to the reduction mechanism 7 via the pinion gear 41.

[0078] The reduction mechanism 7 is disposed forward of the motor 6. The reduction mechanism 7 connects the rotor shaft portion 33 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 shaft portion 33. The reduction mechanism 7 includes a planetary gear mechanism.

[0079] The reduction mechanism 7 has a plurality of gears. The gears of the reduction mechanism 7 are driven by a rotor 27.

[0080] 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 case 4. Each of the plurality of planetary gears 42 meshes with the pinion gear 41. The planetary gear 42 is rotatably supported by 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 case 4. The internal gear 43 is always non-rotatable with respect to the hammer case 4.

[0081] When the rotor shaft portion 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 portion 33.

[0082] 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. The spindle 8 is rotated by the rotor 27. The spindle 8 rotates by the rotational force of the rotor 27 transmitted by the reduction mechanism 7. The spindle 8 transmits the rotational force of the motor 6 to the anvil 10 via a ball 48 and a hammer 47.

[0083] The spindle 8 has a flange portion 8A and a spindle shaft portion 8B protruding forward from the flange portion 8A. The planetary gear 42 is rotatably supported on the flange portion 8A via a pin 42P. The rotation axis of the spindle 8 and the rotation axis AX of the motor 6 coincide with each other. The spindle 8 rotates about the rotation axis AX. The spindle 8 is rotatably supported by a spindle bearing 44. A convex portion 8C is provided at the rear end of the spindle 8. The convex portion 8C protrudes rearward from the flange portion 8A. The convex portion 8C is disposed so as to surround the spindle bearing 44.

[0084] 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 protrusion 24B that protrudes forward from the front surface of the bearing box 24. The spindle bearing 44 is disposed around the protrusion 24B.

[0085] The striking mechanism 9 is driven by the motor 6. The rotational force of the motor 6 is transmitted to the striking mechanism 9 via the reduction mechanism 7 and the spindle 8. 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 striking mechanism 9 has a hammer 47, a ball 48, a first coil spring 49, a second coil spring 50, a third coil spring 51, a first washer 52, and a second washer 53. The striking mechanism 9 including the hammer 47, the ball 48, the first coil spring 49, the second coil spring 50, the third coil spring 51, the first washer 52, and the second washer 53 is housed in the first cylindrical portion 401 of the hammer case 4.

[0086] The hammer 47 is disposed forward of the reduction mechanism 7. The hammer 47 is disposed around the spindle 8. The hammer 47 is held by the spindle 8. The ball 48 is disposed between the spindle 8 and the hammer 47. The hammer 47 has a cylindrical hammer body 47D and a hammer protrusion 47E provided at the front of the hammer body 47D. A ring-shaped recess 47C is provided on the rear surface of the hammer body 47D. The recess 47C is recessed forward from the rear surface of the hammer body 47D.

[0087] The hammer 47 is disposed around the spindle shaft portion 8B. The hammer 47 has a hole 47A in which the spindle shaft portion 8B is disposed.

[0088] 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.

[0089] The first washer 52 is disposed inside the recess 47C. The first washer 52 is supported by the hammer 47 via a plurality of balls 54. The balls 54 are disposed forward of the first washer 52.

[0090] The second washer 53 is disposed inside the recess 47C and rearward of the first washer 52. The outer diameter of the second washer 53 is smaller than the outer diameter of the first washer 52. The second washer 53 and the hammer 47 are relatively movable in the front-rear direction.

[0091] The first coil spring 49 is disposed around the spindle shaft portion 8B. The rear end of the first coil spring 49 is supported by the flange portion 8A. The front end of the first coil spring 49 is disposed inside the recess 47C and supported by the first washer 52. The first coil spring 49 constantly generates a biasing force (elastic force) that moves the hammer 47 forward.

[0092] The second coil spring 50 is disposed around the spindle shaft portion 8B. The second coil spring 50 is disposed radially inward of the first coil spring 49. The rear end of the second coil spring 50 is supported by the flange portion 8A. The front end of the second coil spring 50 is disposed inside the recess 47C and supported by the second washer 53. The second coil spring 50 generates a biasing force (elastic force) that moves the hammer 47 forward when the hammer 47 moves rearward.

[0093] The third coil spring 51 is disposed around the spindle shaft portion 8B. The third coil spring 51 is disposed radially inward of the first coil spring 49. The third coil spring 51 is disposed inside the recess 47C. The rear end of the third coil spring 51 is supported by the second washer 53. The front end of the third coil spring 51 is supported by the first washer 52. The third coil spring 51 generates a biasing force (elastic force) that moves the second coil spring 50 rearward. The biasing force of the third coil spring 51 presses the rear end of the second coil spring 50 against the flange portion 8A. This prevents the second coil spring 50 from moving freely relative to the flange portion 8A.

[0094] The ball 48 is made of a metal such as steel. The ball 48 is disposed between the spindle shaft portion 8B and the hammer 47. The spindle 8 has a spindle groove 8D in which at least a part of the ball 48 is disposed. The spindle groove 8D is provided in a part of the outer circumferential surface 8S of the spindle shaft portion 8B. The hammer 47 has a hammer groove 47B in which at least a part of the ball 48 is disposed. The hammer groove 47B is provided in a part of the inner surface of the hammer 47. The ball 48 is disposed between the spindle groove 8D and the hammer groove 47B. The ball 48 can roll on the inside of the spindle groove 8D and the inside of the hammer groove 47B. The hammer 47 can move along with the ball 48. 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 47B.

[0095] The anvil 10 is disposed forward of the motor 6. The anvil 10 is an output part of the impact tool 1 that rotates based on the rotational force of the rotor 27. At least a portion of the anvil 10 is disposed forward of the hammer 47. The anvil 10 has a tool hole 10A into which a tool bit is inserted. The tool hole 10A is provided at the front end of the anvil 10. The tool bit is attached to the anvil 10.

[0096] The anvil 10 has an anvil protrusion 10B. The anvil protrusion 10B is provided at the rear end of the anvil 10. The anvil protrusion 10B protrudes rearward from the rear end of the anvil 10. The spindle 8 is disposed rearward of the anvil 10. A spindle recess 8E is provided at the front end of the spindle shaft portion 8B. The anvil protrusion 10B is disposed in the spindle recess 8E.

[0097] The anvil 10 has a rod-shaped anvil shank 101 and an anvil protrusion 102. The tool hole 10A is provided at the front end of the anvil shank 101. A tool tip is attached to the anvil shank 101. The anvil protrusion 102 is provided at the rear end of the anvil 10. The anvil protrusion 102 protrudes radially outward from the rear end of the anvil shank 101.

[0098] The anvil 10 is rotatably supported by the 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 coincident. The anvil 10 rotates around the rotation axis AX. The bearing 46 is disposed around the anvil shaft portion 101. The bearing 46 is disposed inside the second cylindrical portion 402 of the hammer case 4. The bearing 46 is held in the second cylindrical portion 402 of the hammer case 4. The bearing 46 rotatably supports the front portion of the anvil shaft portion 101.

[0099] An O-ring 45 is disposed between the bearing 46 and the anvil shaft portion 101. The O-ring 45 contacts both the outer periphery of the anvil shaft portion 101 and the inner periphery of the bearing 46.

[0100] In the embodiment, two bearings 46 are arranged in the axial direction. The bearings 46 include a bearing 46A and a bearing 46B arranged rearward of the bearing 46A.

[0101] In the embodiment, two O-rings 45 are arranged in the axial direction. The O-rings 45 include an O-ring 45A and an O-ring 45B arranged rearward of the O-ring 45A. The O-ring 45A is arranged between the bearing 46A and the anvil shaft portion 101. The O-ring 45B is arranged between the bearing 46B and the anvil shaft portion 101.

[0102] The bearing 46 is a ball bearing. The bearing 46 has an inner ring, balls, and an outer ring. The inner ring of the bearing 46A contacts the O-ring 45A. The inner ring of the bearing 46B contacts the O-ring 45B. The balls of the bearing 46 are disposed between the inner ring and the outer ring in the radial direction. The balls of the bearing 46 contact each of the inner ring and the outer ring. A plurality of balls of the bearing 46 are disposed in the circumferential direction. The outer ring is disposed radially outward of the inner ring and the balls. The outer ring of the bearing 46A contacts the inner circumferential surface of the second cylindrical portion 402. The outer ring of the bearing 46B contacts the inner circumferential surface of the second cylindrical portion 402.

[0103] At least a portion of the hammer 47 is capable of contacting the anvil projection 102. A hammer projection 47E that projects forward is provided at the front of the hammer 47. The hammer projection 47E and the anvil projection 102 are capable of contacting each other. When the motor 6 is driven while the hammer 47 and the anvil projection 102 are in contact with each other, the anvil 10 rotates together with the hammer 47 and the spindle 8.

[0104] The anvil 10 is struck in the rotation direction by the hammer 47. For example, in a screw tightening operation, when the load acting on the anvil 10 becomes high, a situation may occur in which the anvil 10 cannot be rotated by the load of the first coil spring 49 alone. When the anvil 10 cannot be rotated by the load of the first coil spring 49 alone, the rotation of the anvil 10 and the hammer 47 stops. The spindle 8 and the hammer 47 can move relatively in the axial direction and the circumferential direction via the ball 48. Even if the rotation of the hammer 47 stops, the rotation of the spindle 8 continues by the power generated by the motor 6. When the spindle 8 rotates while the rotation of the hammer 47 is stopped, the ball 48 moves backward while being guided by each of the spindle groove 8D and the hammer groove 47B. The hammer 47 receives a force from the ball 48 and moves backward along with the ball 48. That is, the hammer 47 moves backward by the rotation of the spindle 8 while the rotation of the anvil 10 is stopped. As the hammer 47 moves rearward, the contact between the hammer 47 and the anvil protrusion 102 is released.

[0105] As described above, the first coil spring 49 constantly generates a biasing force that moves the hammer 47 forward. The second coil spring 50 generates a biasing force that moves the hammer 47 forward after the hammer 47 moves rearward from a specified position. The hammer 47 that has moved rearward moves forward due to the biasing forces of the first coil spring 49 and the second coil spring 50. When the hammer 47 moves forward, it receives a force in the rotational direction from the ball 48. That is, the hammer 47 moves forward while rotating. When the hammer 47 moves forward while rotating, the hammer 47 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 47E of the hammer 47. 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.

[0106] The tool holding mechanism 11 is disposed around the front part of the anvil 10. The tool holding mechanism 11 holds a tool bit inserted into a tool hole 10A of the anvil 10. The tool holding mechanism 11 is capable of attaching and detaching the tool bit.

[0107] The tool holding mechanism 11 includes a ball 71 , a leaf spring 72 , a sleeve 73 , a coil spring 74 , and a positioning member 75 .

[0108] The anvil 10 has a support recess 76 that supports the ball 71. The support recess 76 is formed in the outer circumferential surface 8S of the anvil shank 101. In the embodiment, two support recesses 76 are formed in the anvil shank 101.

[0109] The balls 71 are movably supported by the anvil 10. The balls 71 are disposed in the support recesses 76. The balls 71 are disposed in one support recess 76.

[0110] A through hole connecting the inner surface of the support recess 76 and the inner surface of the tool hole 10A is formed in the anvil shaft 101. With the ball 71 supported by the support recess 76, it is disposed inside the tool hole 10A via at least a portion of the ball 71. The ball 71 can fix a tool bit inserted into the tool hole 10A. The ball 71 is movable between an engagement position where the tool bit is fixed and a release position where the fixation of the tool bit is released.

[0111] The leaf spring 72 generates an elastic force that moves the ball 71 to the engagement position. The leaf spring 72 is disposed around the anvil shaft portion 101. The leaf spring 72 generates an elastic force that moves the ball 71 radially inward.

[0112] The sleeve 73 is a cylindrical member. The sleeve 73 is disposed around the anvil shaft 101. The sleeve 73 is axially movable around the anvil shaft 101. The sleeve 73 can prevent the ball 71, which is disposed at the engagement position, from escaping from the engagement position. The sleeve 73 can be moved in the axial direction to change the state of the ball 71 from the engagement position to a release position.

[0113] The sleeve 73 is movable around the anvil shaft portion 101 between a blocking position where the sleeve 73 blocks radially outward movement of the balls 71 and an allowing position where the sleeve 73 allows radially outward movement.

[0114] By disposing the sleeve 73 in the blocking position, the ball 71 disposed in the engagement position is prevented from moving radially outward. In other words, by disposing the sleeve 73 in the blocking position, the ball 71 disposed in the engagement position is prevented from escaping from the engagement position. By disposing the sleeve 73 in the blocking position, the tool bit is maintained in a state where it is fixed by the ball 71.

[0115] By moving the sleeve 73 to the permissible position, the ball 71 disposed at the engagement position is permitted to move radially outward. By moving the sleeve 73 to the permissible position, the ball 71 is changed to a state in which it can be moved from the engagement position to the release position. In other words, by placing the sleeve 73 at the permissible position, the ball 71 disposed at the engagement position is permitted to escape from the engagement position. By placing the sleeve 73 at the permissible position, the state in which the bit is fixed by the ball 71 can be released.

[0116] The coil spring 74 generates an elastic force to move the sleeve 73 to the blocking position. The coil spring 74 is disposed around the anvil shaft 101. The blocking position is set rearward of the allowable position. The coil spring 74 generates an elastic force to move the sleeve 73 rearward.

[0117] The positioning member 75 is a ring-shaped member fixed to the outer circumferential surface 8S of the anvil shaft 101. The positioning member 75 is fixed at a position capable of facing the rear end of the sleeve 73. The positioning member 75 positions the sleeve 73 at the blocking position. The sleeve 73, which is given an elastic force moving rearward by the coil spring 74, comes into contact with the positioning member 75, and is positioned at the blocking position.

[0118] The fan 12 is disposed behind the stator 26 of the motor 6. The fan 12 generates an airflow for cooling the motor 6. The fan 12 is fixed to at least a part of the rotor 27. The fan 12 is fixed to a rear part of the rear shaft part 33R via a bush 12A. The fan 12 is disposed between the rear rotor bearing 39R and the stator 26. The fan 12 rotates by the rotation of the rotor 27. The fan 12 rotates together with the rotor shaft part 33 as the rotor shaft part 33 rotates. As the fan 12 rotates, air in the external space of the housing 2 flows into the internal space of the housing 2 through the 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 through the exhaust port 20 into the external space of the housing 2.

[0119] The battery mounting section 13 is disposed at the lower part of the battery holding section 23. The battery mounting section 13 is connected to the battery pack 25. The battery pack 25 is mounted to the battery mounting section 13. In the embodiment, there is one battery mounting section 13. One battery pack 25 is mounted to the battery mounting section 13. The battery pack 25 is detachable from the battery mounting section 13. The battery pack 25 is mounted to the battery mounting section 13 by being inserted into the battery mounting section 13 from the front of the battery holding section 23. The battery pack 25 is removed from the battery mounting section 13 by being removed forward from the battery mounting section 13. The battery pack 25 includes a secondary battery. In the embodiment, the battery pack 25 includes a rechargeable lithium ion battery. By being mounted to the battery mounting section 13, the battery pack 25 can supply power to the impact tool 1. The motor 6 is driven based on the power supplied from the battery pack 25. The operation and display unit 16 operates using power supplied from a battery pack 25 .

[0120] The rated voltage of the battery pack 25 is equal to or higher than 18 V. The rated voltage of the battery pack 25 may be 18 V, 36 V, or 72 V.

[0121] The trigger lever 14 is provided on the grip portion 22. The trigger lever 14 is operated by an operator to start the motor 6. By operating the trigger lever 14, the motor 6 is switched between being driven and being stopped.

[0122] The forward / reverse switching lever 15 is provided on the upper part of the grip portion 22. 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.

[0123] The operation display unit 16 is provided on the battery holding unit 23. The operation display unit 16 is provided on the upper surface of the battery holding unit 23, further forward than the grip unit 22. The operation display unit 16 has a plurality of operation buttons 16A. When the operator operates the operation buttons 16A, the operation mode of the motor 6 is switched.

[0124] The mode changeover switch 17 is provided on the upper part of the trigger lever 14. The mode changeover switch 17 is operated by an operator to change the operation mode of the motor 6.

[0125] The light assembly 18 emits illumination light. The light assembly 18 illuminates the anvil 10 and the periphery of the anvil 10 with illumination light. The light assembly 18 illuminates the front of the anvil 10 with illumination light. The light assembly 18 also illuminates the tool tip attached to the anvil 10 and the periphery of the tool tip with illumination light. In the embodiment, the light assembly 18 includes a ring-shaped base member 18A and a plurality of light-emitting elements 18B held by the base member 18A. The base member 18A is disposed around the second cylindrical portion 402 of the hammer case 4. The light assembly 18 also has a ring member 18C that prevents the base member 18A from slipping forward from the second cylindrical portion 402.

[0126] In the embodiment, a ring member 61 is disposed between the anvil protrusion 102 and the rear bearing 46B. The ring member 61 is an annular member. The ring member 61 is made of metal. An example of the metal forming the ring member 61 is iron. The front and rear surfaces of the ring member 61 are both flat. At least a portion of the rear surface of the ring member 61 is disposed to face the front surface of the anvil protrusion 102. At least a portion of the front surface of the ring member 61 contacts the rear end surface of the rear bearing 46B.

[0127] In the embodiment, a suppression member 62 is disposed to engage with each of the hammer case 4 and the ring member 61. The suppression member 62 suppresses the ring member 61 from slipping out rearward. Examples of the suppression member 62 include a snap ring or a C-ring. The suppression member 62 is disposed so as to come into contact with the ring member 61.

[0128] The hammer case 4 has a support surface 4A facing at least a part of the front surface of the ring member 61. The support surface 4A of the hammer case 4 and the rear end surface of the rear bearing 46 are arranged substantially in the same plane. At least a part of the ring member 61 is arranged between the front surface of the anvil protrusion 102 and the support surface 4A of the hammer case 4.

[0129] The ring member 61 prevents contact between the hammer case 4 and the anvil protrusion 102 .

[0130] At least a portion of the front surface of the ring member 61 contacts the support surface 4A of the hammer case 4. In addition, at least a portion of the front surface of the ring member 61 contacts the rear end surface of the rear bearing 46B.

[0131] A front outer edge portion indicating the outer edge of the front surface of the ring member 61 contacts the support surface 4A of the hammer case 4. A front inner edge portion indicating the inner edge of the front surface of the ring member 61 can contact the rear end surface of the outer ring of the bearing 46B. The ring member 61 is disposed radially outward from the inner ring of the bearing 46B. There is no contact between the ring member 61 and the inner ring of the bearing 46B.

[0132] The outer edge of the rear surface of the ring member 61 comes into contact with the suppression member 62 .

[0133] A groove 4B into which at least a portion of the suppression member 62 fits is provided on the inner surface of the first cylindrical portion 401 of the hammer case 4. By disposing the suppression member 62 in the groove 4B, fluctuation in the relative position between the hammer case 4 and the suppression member 62 at least in the axial direction is suppressed.

[0134] The ring member 61 and the suppression member 62 prevent the bearing 46 from falling off rearward (to the other axial side).

[0135] The outer front edge of the anvil projection 102 slopes rearwardly toward the outside in the radial direction.

[0136] In the front-rear direction, the restraining member 62 is disposed between the front outer edge of the anvil projection 102 and the rear outer edge of the ring member 61 .

[0137] [Spindle] FIG. 5 is an exploded perspective view from the front showing a part of the impact mechanism 9 according to the embodiment. FIG. 6 is an exploded perspective view from the rear showing a part of the impact mechanism 9 according to the embodiment. FIG. 7 is a side view showing the spindle 8 according to the embodiment. FIG. 8 is a top view showing the spindle 8 according to the embodiment. FIG. 9 is a top view showing a part of the spindle 8 according to the embodiment. FIG. 10 is a perspective view showing a part of the spindle 8 according to the embodiment. FIG. 11 is a vertical cross-sectional view showing the spindle 8 according to the embodiment. FIG. 12 is a cross-sectional view showing the spindle 8 according to the embodiment, which corresponds to the cross-sectional view taken along the line AA in FIG. 11. FIG. 13 is a side view showing the hammer 47 according to the embodiment. FIG. 14 is a vertical cross-sectional view showing the hammer 47 according to the embodiment. FIG. 15 is a cross-sectional view showing the hammer 47 according to the embodiment, which corresponds to the cross-sectional view taken along the line BB in FIG. 14. FIG. 16 is a perspective view showing the spindle 8 according to the embodiment.

[0138] The spindle 8 is disposed forward of the motor 6. The spindle 8 rotates about a rotation axis AX by the motor 6. A spindle groove 8D is formed in the spindle 8. The spindle 8 has a flange portion 8A and a spindle shaft portion 8B that protrudes forward from the flange portion 8A. Two spindle grooves 8D are formed in the spindle shaft portion 8B. The balls 48 are held in the spindle groove 8D. One ball 48 is held in one spindle groove 8D.

[0139] Each spindle groove 8D has a central portion 81 and a pair of end portions 82. The position of the central portion 81 and the positions of the end portions 82 are different in the circumferential direction. One end portion 82 is disposed on one circumferential side of the central portion 81, and the other end portion 82 is disposed on the other circumferential side of the central portion 81. The end portions 82 of the spindle groove 8D are disposed rearward of the central portion 81 of the spindle groove 8D.

[0140] 11, 12, and 16, the ball 48, while held in the spindle groove 8D, performs circular motion on an imaginary plane 91 inclined at a predetermined angle θa from the rotation axis AX of the spindle 8. The spindle groove 8D is formed in an arc shape on the imaginary plane 91. The predetermined angle θa is 45 degrees. Note that the predetermined angle θa does not have to be 45 degrees, and may be any angle between 30 degrees and 60 degrees, for example.

[0141] 14 and 15, the ball 48, while being held in the hammer groove 47B, moves circularly on an imaginary plane 91 inclined at a predetermined angle θb from the rotation axis AX of the hammer 47. The hammer groove 47B is formed in an arc shape on the imaginary plane 91. The predetermined angle θb is 45 degrees.

[0142] That is, on the imaginary plane 91, each of the spindle groove 8D and the hammer groove 47B has an arc shape.

[0143] The spindle groove 8D is formed by a cutting tool 92 such as an end mill. As shown in FIG. 12, the cutting tool 92 performs a circular motion so as to move along a virtual circle 90 defined on a virtual plane 91. As shown in FIG. 12 and other figures, a center 90C of the virtual circle 90 is defined at a position shifted from the rotation axis AX of the spindle 8. The diameter of the virtual circle 90 is smaller than the diameter Da of the spindle shaft portion 8B. The center 92C of the cutting tool 92 moves along the virtual circle 90. The orbit of the center 92C of the cutting tool 92 is within the width of the spindle shaft portion 8B. The orbit of the center 92C of the cutting tool 92 is arc-shaped. At least a part of the orbit of the center 92C of the cutting tool 92 when forming the spindle groove 8D is disposed radially inward from the outer circumferential surface 8S of the spindle shaft portion 8B.

[0144] In at least a portion of the formation of the spindle groove 8D, a center 92C of the cutting tool 92 is positioned radially inward from the outer peripheral surface 8S of the spindle shaft portion 8B. In the formation of the end portion 82 of the spindle groove 8D, the center 92C of the cutting tool 92 is positioned radially inward from the outer peripheral surface 8S of the spindle shaft portion 8B. In the formation of the central portion 81 of the spindle groove 8D, the center 92C of the cutting tool 92 is positioned radially outward from the outer peripheral surface 8S of the spindle shaft portion 8B.

[0145] The ball 48 performs circular motion so as to move along a virtual circle 90 defined on a virtual plane 91. As shown in FIG. 12 etc., a center 90C of the virtual circle 90 is defined at a position shifted from the rotation axis AX of the spindle 8. The center 48C of the ball 48 moves outside the virtual circle 90. The trajectory of the center 48C of the ball 48 is within the width of the spindle shaft portion 8B. The trajectory of the center 48C of the ball 48 is substantially arc-shaped.

[0146] The depth of the spindle groove 8D varies depending on the position in the axial direction (front-rear direction) of the spindle 8. In the embodiment, the depth of the rear portion of the spindle groove 8D is deeper than the depth of the front portion of the spindle groove 8D. That is, the depth of the end portion 82 of the spindle groove 8D is deeper than the depth of the center portion 81 of the spindle groove 8D.

[0147] In at least a portion of the spindle groove 8D, the center 48C of the ball 48 may be disposed inside the spindle groove 8D. In an end portion 82 of the spindle groove 8D, the center 48C of the ball 48 may be disposed inside the spindle groove 8D. In a central portion 81 of the spindle groove 8D, the center 48C of the ball 48 may be disposed outside the spindle groove 8D.

[0148] [Impact tool operation] Next, a description will be given of the operation of the impact tool 1. Figures 17, 18, and 19 are cross-sectional views for explaining the operation of the impact mechanism 9 according to the embodiment.

[0149] When performing a screw tightening operation on a work object, a tool tip (driver bit) used for the screw tightening operation is inserted into the tool hole 10A of the anvil 10. The tool tip inserted into the tool hole 10A is held by the tool holding mechanism 11. After the tool tip is attached to the anvil 10, the operator holds the grip portion 22 with, for example, the right hand and pulls the trigger lever 14. When the trigger lever 14 is pulled, power is supplied from the battery pack 25 to the motor 6, the motor 6 is started, and at the same time, the light assembly 18 is turned on. When the motor 6 is started, the rotor shaft portion 33 of the rotor 27 rotates. When the rotor shaft portion 33 rotates, the rotational force of the rotor shaft portion 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 by the spindle 8 via a pin 42P. The revolution of the planetary gear 42 causes the spindle 8 to rotate at a rotational speed lower than the rotational speed of the rotor shaft portion 33.

[0150] When the spindle 8 rotates 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. The rotation of the anvil 10 progresses the screw tightening operation. The rotational force of the spindle 8 is transmitted to the hammer 47 via the ball 48. When the spindle 8 and the hammer 47 rotate together, the ball 48 is disposed in the center 81 of the spindle groove 8D.

[0151] When a load torque of a predetermined value or more acts on the anvil 10 from the screw as the screw tightening operation progresses, the rotation of the anvil 10 and the hammer 47 stops. In the following description, the load torque when the rotation of the anvil 10 and the hammer 47 stops is appropriately referred to as the stop load torque, and the point in time when the rotation of the anvil 10 and the hammer 47 stops is appropriately referred to as the time when the hammer stops.

[0152] That is, when a stop load torque acts on the anvil 10 from the screw during a screw tightening operation, the rotation of the anvil 10 and the hammer 47 stops. Since the spindle 8 continues to rotate by the motor 6, if the spindle 8 continues to rotate while the rotation of the hammer 47 is stopped, the hammer 47 moves backward relative to the spindle 8.

[0153] As the hammer 47 moves backward relative to the spindle 8, the contact between the hammer 47 and the anvil protrusion 102 is released. In the following description, the point in time when the hammer 47 moves backward relative to the spindle 8 and the contact between the hammer 47 and the anvil protrusion 102 is released is appropriately referred to as the start of impact.

[0154] As shown in FIG. 17, at the start of impact, the ball 48 is located in the center portion 81 of the spindle groove 8D.

[0155] When the contact between the hammer 47 and the anvil protrusion 102 is released and the hammer 47 moves rearward relative to the spindle 8, the ball 48 moves from the center 81 to the end 82 of the spindle groove 8D. Within the axial range of movement of the hammer 47 relative to the spindle 8, the hammer 47 moves to the rearmost position. In the following description, the point in time when the hammer 47 moves to the rearmost position relative to the spindle 8 is appropriately referred to as the maximum stroke.

[0156] As shown in FIG. 18, at the maximum stroke, the ball 48 is disposed at the end 82 of the spindle groove 8D.

[0157] The hammer 47 that has moved rearward moves forward while rotating due to the forward biasing forces of the first coil spring 49 and the second coil spring 50. When the hammer 47 moves forward relative to the spindle 8, the ball 48 moves from the end 82 of the spindle groove 8D to the center 81. In the following description, the point in time immediately before the hammer 47 moves forward while rotating and strikes the anvil 10 is appropriately referred to as the start of striking. Also, the point in time when the hammer 47 is striking the anvil 10 in the rotational direction is appropriately referred to as the time of striking.

[0158] As the hammer 47 moves forward while rotating, the anvil 10 is struck in the rotational direction by the hammer 47. This causes the anvil 10 to rotate about the rotation axis AX with high torque. As a result, the screw is tightened with high torque into the work object.

[0159] FIG. 19 shows the spindle 8, ball 48 and hammer 47 during striking.

[0160] In the following description, the torque acting on the anvil 10 when the hammer 47 starts striking the anvil 10 is referred to as the strike start torque. The strike start torque is equal to the above-mentioned stop load torque. In other words, the strike start torque is equal to the load torque acting on the anvil 10 from the screw when the rotation of the anvil 10 and the hammer 47 stops during the screw tightening operation.

[0161] [effect] The effects of the impact tool 1 according to the embodiment will be described below in comparison with a conventional spindle 800. In the following description, the spindle 8 according to the above-described embodiment will be appropriately referred to as an example, and the spindle 800 according to the conventional example will be appropriately referred to as a comparative example.

[0162] 20 is a top view showing a part of a spindle 800 according to a comparative example. A spindle groove 800D is formed in a spindle shaft portion 800B of the spindle 800 according to the comparative example. The spindle groove 800D is a V-shaped spindle groove that is generally adopted in existing spindles. The depth of the center of the spindle groove 800D is substantially equal to the depth of the end portions.

[0163] FIG. 21 is a diagram for explaining the relationship between the spindle 8,800 and the ball 48 according to each of the example and the comparative example.

[0164] As shown in FIG. 21, in the spindle 8 according to the embodiment, the center 48C of the ball 48 is disposed inside the spindle groove 8D at the end 82 of the spindle groove 8D. The depth of the end 82 of the spindle groove 8D is deeper than the depth of the central portion 81 of the spindle groove 8D. Therefore, when the ball 48 is disposed at the end 82, the ball 48 sinks into the inside of the spindle groove 8D compared to when the ball 48 is disposed at the central portion 81. That is, when the ball 48 is disposed at the end 82 of the spindle groove 8D, the distance between the rotation axis AX and the center 48C in the radial direction is shorter than the distance between the rotation axis AX and the outer peripheral surface 8S of the spindle shaft portion 8B. When the ball 48 is disposed at the end 82 of the spindle groove 8D, the center 48C is disposed radially inward of the outer peripheral surface 8S.

[0165] 21, in the spindle 800 according to the comparative example, the depth of the center of the spindle groove 800D is substantially equal to the depth of the end portion. Therefore, when the ball 48 is disposed at the end portion 820 of the spindle groove 800D, the ball 48 is disposed radially outward compared to when the ball 48 is disposed at the end portion 82 of the spindle groove 800D according to the embodiment.

[0166] FIG. 22 is a diagram for explaining the force that the ball 48 according to each of the example and the comparative example receives from the spindle 8,800.

[0167] As shown in FIG. 22, in the spindle 8 according to the embodiment, when the ball 48 is disposed at the end 82 of the spindle groove 8D, the ball 48 sinks inward in the radial direction, so that the rotational component of the force acting between the spindle 8 and the ball 48 at the maximum stroke is large. That is, as shown by the arrow Ve, the force acting from the spindle 8 to the ball 48 acts exclusively in the rotational direction. As described with reference to FIG. 18, the time when the ball 48 is disposed at the end 82 of the spindle groove 8D is the maximum stroke. At the maximum stroke, the ball 48 receives exclusively the force in the rotational direction, so that the hammer 47 can move forward while rotating at a high rotational speed. Of the force acting from the spindle 8 to the ball 48, the axial component is a wasteful force. Of the force acting from the spindle 8 to the ball 48, the axial component is small and the rotational component is large, so that the hammer 47 can move forward while rotating at a high rotational speed.

[0168] 22, in the spindle 800 according to the comparative example, when the ball 48 is disposed at the end 820 of the spindle groove 800D, the axial component of the force acting from the spindle 800 to the ball 48 is large, as indicated by the arrow Vc. In this case, it is difficult to increase the rotational speed of the hammer 47.

[0169] Fig. 23 is a diagram for explaining the impact start torque for each of the examples and the comparative example. In the graph shown in Fig. 23, the horizontal axis indicates the elapsed time from the start of the screw tightening operation. The vertical axis indicates the impact start torque acting on the anvil 10. As described above, the impact start torque is the torque acting on the anvil 10 when the hammer 47 starts to strike the anvil 10. The impact start torque is equal to the stop load torque acting on the anvil 10 from the screw when the rotation of the anvil 10 and the hammer 47 stops during the screw tightening operation.

[0170] As shown in Fig. 23, in the comparative example, the impact start torque is about 1350 N·mm. In the example, the impact start torque is 1100 N·mm or less. In the example shown in Fig. 23, the impact start torque according to the example is about 1000 N·mm or less.

[0171] When the impact start torque is small, the occurrence of the cam-out phenomenon in which the tip tool (driver bit) comes out of the cross groove in the head of the screw during screw tightening is suppressed. According to the inventor's findings, when the impact start torque is small, the timing at which the anvil 10 starts impacting is advanced. In other words, when the impact start torque is small, the amount of screw rotation from the start of screw tightening to the start of impact is reduced. When the amount of screw rotation from the start of screw tightening to the start of impact is small, the occurrence of the cam-out phenomenon is suppressed.

[0172] FIG. 24 is a diagram showing the tightening speed, average current, and average voltage for each of the examples and the comparative examples. The tightening speed means the work speed for tightening one screw. The larger the value, the higher the tightening speed, meaning that the time required from start to finish of the tightening of one screw is shorter. The average current is the average value of the current consumed by the motor 6 in the tightening of one screw. The average voltage is the average value of the voltage input to the motor 6 in the tightening of one screw. The smaller the average current and average voltage, the less power consumed by the motor 6.

[0173] Using the impact tools according to the example and the comparative example, tightening operations were carried out on a 90 mm long coarse thread screw, a 120 mm long coarse thread screw, and a 150 mm long metal screw.

[0174] As shown in Fig. 24, the tightening speed in the example is higher than the tightening speed in the comparative example. As described with reference to Fig. 21, in the example, the hammer 47 rotates at a high rotational speed, so that the anvil 10 can be struck with a large striking force. Since the anvil 10 is struck with a large striking force, the screw tightening operation can be completed in a short time.

[0175] FIG. 25 is a diagram showing the direction in which the load is transmitted from the ball 48 to the hammer 47 according to each of the embodiment and the comparative example. FIG. 25 shows the state at the time of the maximum stroke, which is the time when the hammer 47 moves to the rearmost position relative to the spindle 8,800. A direction passing through a contact point 47F between the ball 48 and the inner surface of the hammer groove 47B and parallel to the tangent of a circle centered on the rotation axis AX of the spindle 8 is defined as a tangent vector Vr. A direction in which the load is transmitted from the ball 48 to the contact point 47F with the hammer 47 is defined as a load vector Vp. In the embodiment, the angle α between the tangent vector Vr and the load vector Vp at the maximum stroke is 50 degrees or less. The angle α between the tangent vector Vr and the load vector Vp at the maximum stroke in the embodiment shown in FIG. 25 is 45.1 degrees. On the other hand, the angle α between the tangent vector Vr and the load vector Vp at the maximum stroke in the comparative example is 56.3 degrees.

[0176] In the embodiment, the angle α between the tangent vector Vr and the load vector Vp at the start of the impact is 43.1 degrees. In the comparative example, the angle α between the tangent vector Vr and the load vector Vp at the start of the impact is 57.3 degrees.

[0177] In the embodiment, the angle α between the tangent vector Vr and the load vector Vp at the time of impact is 58.6 degrees, whereas in the comparative example, the angle α between the tangent vector Vr and the load vector Vp at the time of impact is 85.7 degrees.

[0178] As described above, the end 82 of the spindle groove 8D is disposed rearward of the central portion 81 of the spindle groove 8D. When the hammer 47 moves rearward relative to the spindle 8, the ball 48 moves to the end 82 of the spindle groove 8D. In the embodiment, the angle α between the tangent vector Vr and the load vector Vp changes based on the position of the ball 48 in the spindle groove 8D (hammer groove 47B). In the embodiment, the angle α between the tangent vector Vr and the load vector Vp becomes smaller as the ball 48 approaches the end of the spindle groove 8D.

[0179] This means that the smaller the angle α between the tangent vector Vr and the load vector Vp, the more the force acting from the spindle 8 to the ball 48 acts mainly in the rotational direction. In this embodiment, the force acting from the spindle 8 to the ball 48 has a small axial component and a large rotational component, so that the hammer 47 can move forward while rotating at a high rotational speed.

[0180] As described above, in the embodiment, the impact tool 1 includes the motor 6, the spindle 8 disposed forward of the motor 6 and rotated by the motor 6, the spindle groove 8D formed in the spindle 8, the ball 48 held in the spindle groove 8D, the hammer 47 supported by the spindle 8 via the ball 48, the first coil spring 49 and the second coil spring 50 which bias the hammer 47 forward, and the anvil 10 which is struck in the rotational direction by the hammer 47. The depth of the spindle groove 8D differs depending on the axial position of the spindle 8.

[0181] As described above, when a stop load torque is applied from the screw to the anvil 10 during a screw tightening operation, the rotation of the anvil 10 and the hammer 47 stops. Since the spindle 8 continues to rotate by the motor 6, if the spindle 8 continues to rotate while the rotation of the hammer 47 is stopped, the hammer 47 moves backward relative to the spindle 8. After the hammer 47 moves backward, the hammer 47 moves forward while rotating due to the biasing forces of the first coil spring 49 and the second coil spring 50. As the hammer 47 moves forward while rotating, the anvil 10 is struck by the hammer 47 in the rotational direction.

[0182] In the above configuration, the depth of the spindle groove 8D varies depending on the axial position of the spindle 8, so the rotational component of the force acting between the spindle 8 and the ball 48 becomes large. This increases the rotational speed of the hammer 47 as it moves forward while rotating. Because the rotational speed of the hammer 47 is increased, the hammer 47 can strike the anvil 10 with a large striking force.

[0183] In addition, since the rotational component of the force acting between the spindle 8 and the ball 48 becomes larger and the axial component becomes smaller, the first coil spring 49 and the second coil spring 50 can urge the hammer 47 forward even if the spring constant of the first coil spring 49 and the second coil spring 50 is small. That is, even if the urging force of the first coil spring 49 and the second coil spring 50 is small, the hammer 47 can move forward while rotating due to the urging force of the first coil spring 49 and the second coil spring 50. By using the first coil spring 49 and the second coil spring 50 with a small urging force, the timing at which the hammer 47 starts to strike the anvil 10 is advanced. That is, the period from the point at which the rotation of the hammer 47 stops to the point at which the hammer 47 strikes the anvil 10 is shortened.

[0184] In a screw tightening operation, the anvil 10 is rotated with the tool attached to the anvil 10 inserted into the cross groove formed in the head of the screw. If the timing at which the hammer 47 starts striking the anvil 10 is delayed, i.e., if the amount of screw rotation from the start of screw tightening to the time the hammer 47 strikes the anvil 10 is large, there is a high possibility that the tool will come out of the cross groove, causing a cam-out phenomenon. With the above configuration, the timing at which the hammer 47 starts striking the anvil 10 is advanced, suppressing the occurrence of the cam-out phenomenon.

[0185] In the embodiment, the end 82 of the spindle groove 8D is disposed rearward of the center portion 81 of the spindle groove 8D. When the hammer 47 moves rearward relative to the spindle 8, the ball 48 moves to the end 82 of the spindle groove 8D. At the end 82 of the spindle groove 8D, the center 48C of the ball 48 is disposed inside the spindle groove 8D.

[0186] When the hammer 47 moves backward relative to the spindle 8, the ball 48 moves from the center 81 to the end 82 of the spindle groove 8D. When the hammer 47 moves forward relative to the spindle 8 due to the biasing forces of the first coil spring 49 and the second coil spring 50, the ball 48 moves from the end 82 of the spindle groove 8D to the center 81. In the above configuration, the center 48C of the ball 48 is immersed inside the spindle groove 8D at the end 82 of the spindle groove 8D, so that the rotational speed of the hammer 47 is increased when the hammer 47 moves forward while rotating. Because the rotational speed of the hammer 47 is increased, the hammer 47 can strike the anvil 10 with a large striking force.

[0187] In the embodiment, in the central portion 81 of the spindle groove 8D, the center 48C of the ball 48 is disposed outside the spindle groove 8D.

[0188] When the hammer 47 strikes the anvil 10, the ball 48 moves from the end 82 of the spindle groove 8D to the central portion 81. In the above configuration, the center 48C of the ball 48 is disposed outside the spindle groove 8D at the central portion 81 of the spindle groove 8D, so that the rotational speed of the hammer 47 is increased at the moment when the hammer 47 strikes the anvil 10. Because the rotational speed of the hammer 47 is increased, the hammer 47 can strike the anvil 10 with a large striking force.

[0189] In the embodiment, the spindle 8 has a flange portion that supports the rear ends of the first coil spring 49 and the second coil spring 50, and a spindle shaft portion 8B that protrudes forward from the flange portion. The spindle groove 8D is formed in the spindle shaft portion 8B. The orbit of the center 48C of the ball 48 is within the width of the spindle shaft portion 8B.

[0190] In the above-described configuration, the range of movement of the ball 48 is small, so that it is possible to prevent the impact tool 1 from becoming large while increasing the rotation speed of the hammer 47.

[0191] In an embodiment, the trajectory is an arc.

[0192] In the above configuration, the ball 48 moves circularly along an imaginary circle with a small radius. Therefore, the hammer 47 can move axially while rotating smoothly. Since the sliding resistance of the hammer 47 is reduced, the rotation speed of the hammer 47 is increased. Therefore, the hammer 47 can strike the anvil 10 with a large striking force.

[0193] In an embodiment, the ball 48 may perform a circular motion in an imaginary plane inclined at a predetermined angle from the rotation axis of the spindle 8 .

[0194] In the above-described configuration, the sliding resistance of the hammer 47 is reduced, and therefore the rotation speed of the hammer 47 is increased. Therefore, the hammer 47 can strike the anvil 10 with a large striking force.

[0195] In this embodiment, the ball 48 performs a circular motion such that a center 48C of the ball 48 moves along an imaginary circle defined on an imaginary plane. A center 90C of the imaginary circle is defined at a position offset from the rotation axis AX of the spindle 8.

[0196] In the above configuration, the hammer 47 can strike the anvil 10 with a large striking force.

[0197] In the embodiment, the spindle 8 has a flange portion that supports the rear ends of the first coil spring 49 and the second coil spring 50, and a spindle shaft portion 8B that protrudes forward from the flange portion. The spindle groove 8D is formed in the spindle shaft portion 8B. The diameter of the imaginary circle is smaller than the diameter of the spindle shaft portion 8B.

[0198] In the above-described configuration, the range of movement of the ball 48 is small, so that it is possible to prevent the impact tool 1 from becoming large while increasing the rotation speed of the hammer 47.

[0199] In the embodiment, the impact start torque, which indicates the torque acting on the anvil 10 when the hammer 47 starts to impact the anvil 10, is 1100 N·mm or less.

[0200] In the above configuration, since the impact start torque is small, the timing at which the hammer 47 starts to strike the anvil 10 is advanced. In other words, the amount of screw rotation from the start of screw fastening to the time when the hammer 47 strikes the anvil 10 is reduced.

[0201] If the timing at which the hammer 47 starts striking the anvil 10 is late, i.e., if the amount of screw rotation from the start of screw tightening to the time the hammer 47 strikes the anvil 10 is large, there is a high possibility that the cam-out phenomenon will occur, in which the tool tip comes out of the cross groove. With the above configuration, the timing at which the hammer 47 starts striking the anvil 10 is advanced, thereby suppressing the occurrence of the cam-out phenomenon.

[0202] In the embodiment, the impact tool 1 includes a battery mounting portion 13 to which a battery pack 25 is attached. The rated voltage of the battery pack 25 is 18 V or higher.

[0203] In the above configuration, since the rated voltage of the battery pack 25 is 18 V or more, the impact tool 1 can have a high output.

[0204] In this embodiment, the depth of the spindle groove 8D varies depending on the axial position of the spindle 8.

[0205] In the above configuration, the occurrence of the come-out phenomenon is suppressed.

[0206] In the embodiment, the depth of the rear portion of the spindle groove 8D is deeper than the depth of the front portion of the spindle groove 8D. The depth of the end portion 82 of the spindle groove 8D is deeper than the depth of the center portion 81 of the spindle groove 8D.

[0207] In the above configuration, the center 48C of the ball 48 can sink into the spindle groove 8D, so the rotational component of the force acting between the spindle 8 and the ball 48 becomes large. This increases the rotational speed of the hammer 47 as it moves forward while rotating. Because the rotational speed of the hammer 47 is increased, the hammer 47 can strike the anvil 10 with a large striking force.

[0208] [Another embodiment] In the above-described embodiment, the width of the end portion 82 of the spindle groove 8D may be greater than the width of the central portion 81 of the spindle groove 8D. When the width of the end portion 82 is greater than the width of the central portion 81, the rotational component of the force acting between the spindle 8 and the ball 48 at the maximum stroke becomes greater.

[0209] In the above-described embodiment, the impact tool 1 is an impact driver. The impact tool 1 may be an impact wrench. In the above-described embodiment, the impact tool 1 may be an angle impact tool.

[0210] In the above-described embodiment, the power source of the impact tool 1 does not have to be the battery pack 25, and may be a commercial power source (AC power source). The commercial power source inputs a voltage of 18 V or more to the motor 6.

[0211] In the above embodiment, a configuration including the first coil spring 49 and the second coil spring 50 has been shown, but the striking mechanism 9 of the impact tool 1 may include a single spring. The single spring may be a linear spring whose spring constant is approximately constant within the stroke range, or may be a non-linear spring whose spring constant changes midway through the stroke.

[0212] [Second embodiment] A second embodiment will be described below. In the following description, the same or equivalent components as those in the above-described embodiment are denoted by the same reference numerals, and the description of those components will be simplified or omitted.

[0213] The impact tool 1 of the second embodiment, similar to the first embodiment described above (see Figures 1 to 4), comprises a motor 6, a spindle 8 rotated by the motor 6, a spindle groove 8D formed in the spindle 8, a ball 48 held in the spindle groove 8D, a cam element including a hammer groove 47B in which at least a portion of the ball 48 is disposed, a hammer 47 supported on the spindle 8 via the ball 48, a spring element (spring) that urges the hammer 47 forward, and an anvil 10 that is struck in the rotational direction by the hammer 47.

[0214] A voltage of 18V or more is input to the motor 6. The impact tool 1 according to the second embodiment includes a battery mounting portion 13 to which a battery pack 25 is mounted, and the rated voltage of the battery pack 25 is 18V or more.

[0215] The impact tool 1 according to the second embodiment has a maximum tightening torque higher than 220 N·m. Specifically, the maximum tightening torque is 230 N·m or more and 350 N·m or less. The impact tool 1 according to the second embodiment has an impact start torque, which indicates the torque acting on the anvil 10 when the hammer 47 starts to strike the anvil 10, of 1300 N·mm or less. At the timing when the hammer 47 starts to strike the anvil 10, the contact between the hammer 47 and the anvil protrusion 102 is released, so that the torque acting on the anvil 10 decreases instantaneously. The torque at the time when the torque acting on the anvil 10 decreases instantaneously is the impact start torque. The impact tool 1 according to the second embodiment has a value obtained by dividing the maximum tightening torque (N·mm) by the impact start torque (N·mm) greater than 165.

[0216] (Explanation of the relationship between maximum tightening torque and impact start torque) Next, the relationship between the maximum tightening torque and the impact start torque will be explained. When the impact start torque is high, the cam-out phenomenon is more likely to occur, so it is desirable to lower the impact start torque in order to suppress the occurrence of the cam-out phenomenon. On the other hand, if one tries to increase the maximum tightening torque, the impact start torque usually also increases. The reason for this is as follows.

[0217] First, in order to increase the maximum tightening torque, the output of the motor 6 is increased to increase the rotation speed of the hammer 47. By increasing the rotation speed of the hammer 47, the kinetic energy given to the anvil 10 at the time of impact is increased, and the maximum tightening torque is increased. However, if the rotation speed of the hammer 47 is high, the time until the hammer 47 reaches the angle at which it strikes the anvil 10 is shortened. If the rotation speed of the hammer 47 is high, the hammer 47 rotates too much before it moves forward and strikes the anvil 10 after moving backward, so that the hammer 47 before striking comes into contact with the rear surface of the anvil 10, resulting in a loss of kinetic energy at the time of impact, and the tightening torque at the time of impact does not increase. In order to make the forward movement of the hammer 47 in time for the timing at which the hammer 47 strikes the anvil 10, the biasing force (elastic force) of the spring element is increased to quickly advance the hammer 47.

[0218] When the biasing force (elastic force) of the spring element becomes large, the hammer 47 can be advanced quickly, while a large biasing force is applied to the hammer 47 when the hammer 47 is retracted. As a result, the torque required to rotate and retract the hammer 47 (hereinafter referred to as the required torque) increases. The impact start torque corresponds to the maximum value of the torque required to retract the hammer 47 to the position where the contact between the hammer 47 and the anvil protrusion 102 is released. Therefore, if the biasing force of the spring element is increased and the required torque increases, the impact start torque increases accordingly.

[0219] In this way, normally, when the maximum tightening torque is increased, the impact start torque also increases. In contrast, in the second embodiment, even when the maximum tightening torque is higher than 220 N m, by setting the impact start torque to 1300 N mm or less, both a high maximum tightening torque and suppression of cam-out (low impact start torque) are achieved.

[0220] (Spring elements and cam elements) Next, a structure for increasing the maximum tightening torque while decreasing the impact start torque will be described. In the second embodiment, the cam element and the spring element each have a structure that suppresses an increase in the torque required to rotate the hammer 47 in a region where the rear stroke of the hammer 47 is small, and increases the required torque nonlinearly so as to promote an increase in the required torque in a region where the stroke of the hammer 47 is large.

[0221] During impact, the hammer 47 rotates backward against the biasing force of the spring element due to the rotational torque applied from the motor 6 via the spindle 8 and the cam element, and then rotates forward due to the elastic force of the compressed spring element and the cam element. At position Q1, which is the forward limit of the hammer 47, the stroke is zero. When the hammer 47 is at its forward limit, the ball 48 is located at a center portion 81, which is the front end portion of the spindle groove 8D. When the hammer 47 is at position Q3 (see FIG. 26), which is the backward limit, the stroke of the hammer 47 is maximum. When the hammer 47 is at its backward limit, the ball 48 is located at an end portion 82, which is the rear end portion of the spindle groove 8D.

[0222] First, the spring element will be described. Fig. 26 is a schematic diagram illustrating the structure of the spring element according to the embodiment.

[0223] The spring element includes a first coil spring 49 and a second coil spring 50. In an embodiment, the spring element further includes a third coil spring 51.

[0224] As described above, the first coil spring 49 is supported by the flange portion 8A and biases the hammer 47 via the first washer 52 and the ball 54. For simplification, the first washer 52 and the ball 54 are omitted in Fig. 26. The first coil spring 49 constantly applies a biasing force (elastic force) that moves the hammer 47 forward. In other words, the first coil spring 49 biases the hammer 47 forward even when the stroke of the hammer 47 is zero.

[0225] The second coil spring 50 is supported by the flange portion 8A, and biases the hammer 47 via a second washer 53, a third coil spring 51, a first washer 52, and a ball 54. The second coil spring 50 applies a biasing force to the hammer 47 when the hammer 47 moves rearward.

[0226] The third coil spring 51 generates a biasing force (elastic force) between the second coil spring 50 and the hammer 47 that moves the second coil spring 50 rearward, thereby suppressing the second coil spring 50 from moving freely relative to the flange portion 8A. The spring constant of the third coil spring 51 is sufficiently small compared with the spring constants of the first coil spring 49 and the second coil spring 50. The biasing force of the third coil spring 51 is small enough to suppress the second coil spring 50 from moving freely, and does not substantially affect the stroke of the hammer 47.

[0227] Therefore, when the stroke of the hammer 47 is zero (when the hammer 47 is at position Q1), the second coil spring 50 is substantially in a natural length state and does not apply a biasing force to the hammer 47. When the hammer 47 retracts to a position where the third coil spring 51 is at its contact length, the second coil spring 50 applies a biasing force to the hammer 47 according to the stroke of the hammer 47. The spring constant of the second coil spring 50 is greater than the spring constant of the first coil spring 49.

[0228] In this embodiment, the first coil spring 49, the second coil spring 50, and the third coil spring 51 are linear springs. The spring constant of the first coil spring 49 is 36.4 N / mm. The spring constant of the second coil spring 50 is 150 N / mm. The spring constant of the third coil spring 51 is 1.6 N / mm.

[0229] As shown in FIG. 26, a first region R1 is defined as a region from position Q1 where the rearward stroke of the hammer 47 is minimum (i.e., stroke is "0") to position Q2 where the hammer 47 and the anvil 10 are not in contact, and a second region R2 is defined as a predetermined region including position Q3 where the stroke is greater than that of the first region R1 and where the stroke is maximum. Since the hammer 47 and the anvil 10 are not in contact at the rear end of the first region R1, position Q2 at the rear end of the first region R1 is the impact start position. Position Q4, which is the start point of the second region R2, is the position where the third coil spring 51 is at the contact length in FIG. 26. Position Q4 and position Q2 may be the same position.

[0230] In the embodiment, the degree of change in the required torque with respect to the stroke in the first region R1 is smaller than the degree of change in the required torque with respect to the stroke in the second region R2. That is, for the spring element, the degree of change in the biasing force (elastic force) with respect to the stroke in the first region R1 is smaller than the degree of change in the biasing force (elastic force) with respect to the stroke in the second region R2.

[0231] When the hammer 47 is in the first region R1, the spring element biases the hammer 47 substantially only by the biasing force of the first coil spring 49. Strictly speaking, the biasing force of the third coil spring 51 acts on the hammer 47, but the biasing force of the third coil spring 51 is negligibly small compared to the biasing force of the first coil spring 49.

[0232] When the hammer 47 is in the second region R2, the spring element biases the hammer 47 with the biasing forces of both the first coil spring 49 and the second coil spring 50. Therefore, the degree of change in the biasing force (elastic force) relative to the stroke is greater when the hammer 47 is in the second region R2 than when the hammer 47 is in the first region R1.

[0233] Next, the cam elements will be described.

[0234] As described above, the cam element includes the spindle groove 8D, the ball 48, and the hammer groove 47B. The depth of the spindle groove 8D varies depending on the axial position of the spindle 8. That is, as shown in FIG. 12, the depth of the rear part of the spindle groove 8D is deeper than the depth of the front part of the spindle groove 8D. The depth of the end part 82 of the spindle groove 8D is deeper than the depth of the central part 81 of the spindle groove 8D. Therefore, when the ball 48 is disposed at the end part 82, the ball 48 sinks into the inside of the spindle groove 8D, compared to when the ball 48 is disposed at the central part 81. When the ball 48 is disposed at the end part 82 of the spindle groove 8D, the distance between the rotation axis AX and the center 48C in the radial direction is shorter than the distance between the rotation axis AX and the outer peripheral surface 8S of the spindle shaft part 8B. When the ball 48 is disposed at the end part 82 of the spindle groove 8D, the center 48C is disposed radially inward of the outer peripheral surface 8S.

[0235] In the first region R1 where the stroke is small, the ball 48 is located at the front of the spindle groove 8D. The front of the spindle groove 8D is shallower than the rear of the spindle groove 8D, so the ball 48 is away from the rotation axis AX. That is, in the first region R1 where the stroke is small, the contact point between the ball 48 and the inner surface of the hammer groove 47B is relatively far from the rotation axis AX, so the torque required to rotate the hammer 47 is reduced. Therefore, in the first region R1, the torque required to rotate and move back the hammer 47 is lower, so the hammer 47 can easily reach the impact start position.

[0236] In the second region R2 where the stroke is large, the ball 48 is located at the rear of the spindle groove 8D. The rear of the spindle groove 8D is deeper than the front of the spindle groove 8D, so the ball 48 moves closer to the rotation axis AX. That is, in the second region R2 where the stroke is large, the contact point between the ball 48 and the inner surface of the hammer groove 47B moves relatively closer to the rotation axis AX, so the torque required to rotate the hammer 47 increases. Therefore, in the second region R2, the required torque can be effectively increased, so that the hammer 47 can start moving forward quickly.

[0237] The angle α (see FIG. 25) between the tangent vector Vr and the load vector Vp at the rear of the spindle groove 8D is smaller than the angle α between the tangent vector Vr and the load vector Vp at the front of the spindle groove 8D. As described above, the angle α at the maximum stroke (i.e., at the rear of the spindle groove 8D) in the embodiment shown in FIG. 25 is 45.1 degrees. The angle α at the time of impact (i.e., at the front of the spindle groove 8D) in the embodiment shown in FIG. 25 is 58.6 degrees. The smaller the angle α between the tangent vector Vr and the load vector Vp, the more the force acting from the spindle 8 to the ball 48 acts exclusively in the rotational direction. When the hammer 47 advances due to the spring element, the axial component of the force acting from the spindle 8 to the ball 48 is smaller and the rotational component is larger, so that the hammer 47 can move forward while rotating at a high rotational speed.

[0238] With this configuration, the cam element makes the degree of change in the required torque relative to the stroke in the first region R1 smaller than the degree of change in the required torque relative to the stroke in the second region R2.

[0239] Fig. 27 is a graph for explaining changes in torque, rotation amount, and spring load according to the stroke of the hammer 47. In Fig. 27, the horizontal axis of the graph represents the stroke of the hammer 47. The vertical axis of the graph represents the torque acting on the spindle 8 (the torque with which the motor 6 attempts to rotate the hammer 47), the hammer rotation amount (degrees), and the spring load.

[0240] 27, the rate of change (slope) of the spring load relative to the stroke in the first region R1 is smaller than the rate of change (slope) of the spring load relative to the stroke in the second region R2. That is, the rate of change (slope) of the required torque relative to the stroke in the first region R1 is based on the spring constant of the first coil spring 49. The rate of change (slope) of the required torque relative to the stroke in the second region R2 is based on the composite spring constant of the first coil spring 49 and the second coil spring 50. Therefore, the spring element suppresses an increase in the required torque in the first region R1 and promotes an increase in the required torque in the second region R2.

[0241] Fig. 28 is a graph for explaining the changes in torque, rotation amount, and spring load according to the stroke of the hammer 47 when the spring element is a single coil spring. In Fig. 28, the horizontal axis of the graph represents the stroke of the hammer 47. The vertical axis of the graph represents the torque acting on the spindle 8, the hammer rotation amount (degrees), and the spring load. The degree of change (slope) of the spring load according to the stroke due to the spring element in Fig. 28 is constant. For this reason, by referring to Fig. 28, the change in the required torque due to the cam element of the embodiment can be understood.

[0242] In the example shown in FIG. 28, the degree of change (slope) of the torque with respect to the stroke in the first region is smaller than the degree of change (slope) of the torque with respect to the stroke behind the impact start position. Furthermore, in the second region R2, the degree of change (slope) of the torque increases as the maximum stroke (i.e., the rear part of the spindle groove 8D) is approached. The degree of change (slope) of the required torque with respect to the stroke in the first region R1 is based on the depth of the front part of the spindle groove 8D. The degree of change (slope) of the required torque with respect to the stroke in the second region R2 is based on the depth of the rear part of the spindle groove 8D. Therefore, the cam element suppresses the increase in the required torque in the first region R1 and promotes the increase in the required torque in the second region R2. Note that in the case of FIG. 28, since there is no position Q4 where the third coil spring 51 becomes the contact length, the start point of the second region R2 shows a position where the stroke is the same as the position Q4 in FIG. 27.

[0243] In this way, both the spring element and the cam element have a structure that suppresses an increase in the required torque in the first region R1 and increases the required torque nonlinearly so as to promote an increase in the required torque in the second region R2. In the embodiment, the synergistic effect of the spring element and the cam element allows the hammer 47 to retreat to the impact start position (position Q2) with a lower torque in the first region R1, so that the impact start torque is reduced. In the second embodiment, the maximum value of the required torque in the first region R1 (i.e., the impact start torque) is 1300 N·mm or less. In the embodiment, the hammer 47 is rotated at high speed with a larger torque in the second region R2 due to the biasing force of the spring element and the shape of the spindle groove 8D. The impact tool 1 achieves a high maximum tightening torque by striking the anvil 10 with the hammer 47 rotated at high speed. In the second embodiment, the impact tool 1 has a maximum tightening torque of 230 N·m or more and 350 N·m or less.

[0244] As described above, in the second embodiment, the impact tool 1 includes the motor 6 to which a voltage of 18 V or more is input, the spindle 8 rotated by the motor 6, the spindle groove 8D formed in the spindle 8, the ball 48 held in the spindle groove 8D, the hammer 47 supported by the spindle 8 via the ball 48, springs (a first coil spring 49 and a second coil spring 50) that bias the hammer 47 forward, and the anvil 10 struck in the rotational direction by the hammer 47. The impact tool 1 has a maximum tightening torque higher than 220 N·m. An impact start torque, which indicates a torque acting on the anvil 10 when the hammer 47 starts striking the anvil 10, is 1300 N·mm or less.

[0245] With the above configuration, even if the maximum tightening torque is increased above 220 N·m, the impact start torque can be suppressed to 1300 N·mm or less. Because the impact start torque is low, the timing at which the hammer 47 starts to strike the anvil 10 is accelerated. In other words, the amount of screw rotation from the start of screw tightening to the time the hammer 47 strikes the anvil 10 is reduced. Because the timing at which the hammer 47 starts to strike the anvil 10 is accelerated, the occurrence of the cam-out phenomenon is suppressed.

[0246] In the second embodiment, the impact tool 1 includes a battery mounting portion 13 to which a battery pack 25 is attached. The rated voltage of the battery pack 25 is 18V or more.

[0247] In the above configuration, since the rated voltage of the battery pack 25 is 18 V or more, the impact tool 1 can have a high output.

[0248] In the second embodiment, the depth of the spindle groove 8D varies depending on the position of the spindle 8 in the axial direction.

[0249] In the above configuration, the occurrence of the come-out phenomenon is suppressed.

[0250] In the second embodiment, the impact tool 1 has a maximum tightening torque of 230 N·m or more.

[0251] With the above configuration, even if the maximum tightening torque is 230 N m or more, the impact start torque can be reduced to 1300 N mm or less, thereby achieving both a high maximum tightening torque and suppressing the reduction in cam-out.

[0252] In the second embodiment, the impact tool 1 has a value obtained by dividing the maximum tightening torque (N·mm) by the impact start torque (N·mm) that is greater than 165.

[0253] Generally, the higher the maximum tightening torque, the higher the impact start torque tends to be, and the higher the impact start torque and the later the timing of the impact start, the more likely the cam-out phenomenon occurs. The value obtained by dividing the maximum tightening torque by the impact start torque becomes larger as the maximum tightening torque becomes higher, and the lower the impact start torque, the larger the value becomes, so it is an index that indicates the smallness of the impact start torque relative to the maximum tightening torque (i.e., the degree of suppression of the come-out phenomenon). In the above configuration, the value obtained by dividing the maximum tightening torque by the impact start torque is greater than 165, so the come-out phenomenon can be suppressed more effectively compared to the magnitude of the maximum tightening torque.

[0254] In the second embodiment, the impact tool 1 includes a motor 6, a spindle 8 rotated by the motor 6, a cam element including a spindle groove 8D formed in the spindle 8 and a ball 48 held in the spindle groove 8D, a hammer 47 supported by the spindle 8 via the ball 48, a spring element for biasing the hammer 47 forward, and an anvil 10 struck in the rotational direction by the advanced hammer 47. The hammer 47 retracts while rotating against the biasing force of the spring element due to the rotational torque applied from the motor 6 via the spindle 8 and the cam element at the time of impact, and then advances while rotating due to the elastic force of the compressed spring element and the cam element. Each of the cam element and the spring element has a structure for suppressing an increase in the torque required to rotate the hammer 47 in a region where the rearward stroke of the hammer 47 is small, and for promoting an increase in the torque required in a nonlinear manner in a region where the stroke of the hammer 47 is large.

[0255] In the above configuration, the maximum tightening torque is increased while the impact start torque is reduced, so that both a high maximum tightening torque and suppression of cam-out can be achieved. That is, in order to increase the maximum tightening torque, the output of the motor 6 is increased to increase the rotation speed of the hammer 47. If the rotation speed of the hammer 47 is high, the time required for the hammer 47 to reach an angle at which it strikes the anvil 10 is shortened. In order to make the forward movement of the hammer 47 in time for the timing at which the hammer 47 strikes the anvil 10, the biasing force of the spring element is increased to cause the hammer 47 to advance quickly. If the biasing force of the spring element is increased, the torque required to rotate and retract the hammer 47 increases, so that the impact start torque becomes higher.

[0256] Thus, normally, when the maximum tightening torque is increased, the impact start torque is increased. Therefore, as described above, the cam element and the spring element are used to nonlinearly change the required torque according to the stroke, and the increase in the required torque when the stroke is small is suppressed, making it easier to move the hammer 47 backward and reducing the impact start torque. By promoting the increase in the required torque when the stroke is large, the hammer 47 can be quickly advanced even if the rotation speed of the hammer 47 is increased, allowing the anvil 10 to be appropriately struck, thereby increasing the maximum tightening torque. As a result, the occurrence of the cam-out phenomenon can be suppressed while increasing the maximum tightening torque.

[0257] In the second embodiment, a first region R1 is defined as a region from the position where the rearward stroke of the hammer 47 is minimum to the position where the hammer 47 and the anvil 10 are not in contact with each other, and a second region R2 is defined as a predetermined region where the stroke is greater than that of the first region R1 and includes a position where the stroke is maximum. The degree of change in the required torque relative to the stroke in the first region R1 is smaller than the degree of change in the required torque relative to the stroke in the second region R2.

[0258] In the above configuration, the degree of increase in the required torque associated with the stroke is suppressed in the first region R1, so that the hammer 47 can be moved to the position Q2 where the hammer 47 and the anvil 10 are not in contact with each other with a smaller required torque. When the hammer 47 and the anvil 10 are not in contact with each other, the hammer 47 becomes rotatable and an impact is initiated. Therefore, the required torque in the first region R1 is reduced, so that the impact start torque can be lowered. If the degree of increase in the required torque associated with the stroke is suppressed, the required torque does not increase sufficiently even when the hammer 47 reaches the maximum stroke, and the maximum tightening torque cannot be increased. Therefore, by increasing the degree of increase in the required torque associated with the stroke in the second region, a high maximum tightening torque can be achieved.

[0259] In the second embodiment, the maximum value of the required torque in the first region R1 is 1300 N·mm or less.

[0260] With the above configuration, the impact start torque can be effectively reduced.

[0261] In the second embodiment, the impact tool 1 has a maximum tightening torque of 230 N·m or more and 350 N·m or less.

[0262] With the above configuration, it is possible to realize a high maximum tightening torque while suppressing the impact start torque.

[0263] In the second embodiment, the depth of the rear portion of the spindle groove 8D is greater than the depth of the front portion of the spindle groove 8D.

[0264] In the above configuration, the rotation radius of the ball 48 arranged in the spindle groove 8D is relatively large at the front of the spindle groove 8D and relatively small at the rear of the spindle groove 8D. At the front of the spindle groove 8D, the rotational component of the force acting between the spindle 8 and the ball 48 is relatively small, and the axial component is relatively large. Therefore, the hammer can be stroked backward with a lower torque, which contributes to reducing the impact start torque. At the rear of the spindle groove 8D, the rotational component of the force acting between the spindle 8 and the ball 48 is relatively large, and the rotational speed of the hammer when moving forward while rotating is increased. Since the rotational speed of the hammer is increased, it contributes to increasing the maximum tightening torque.

[0265] In the second embodiment, the hammer 47 has a hammer groove 47B in which at least a portion of the ball 48 is disposed. A tangent vector Vr is a direction parallel to a tangent of a circle that passes through a contact point 47F between the ball 48 and the hammer groove 47B and is centered on the rotation axis AX of the spindle 8, and a load vector Vp is a direction in which a load is transmitted from the ball 48 to the contact point 47F with the hammer 47. The angle α formed by the tangent vector Vr and the load vector Vp at the rear of the spindle groove 8D is smaller than the angle α formed by the tangent vector Vr and the load vector Vp at the front of the spindle groove 8D.

[0266] In the above configuration, the smaller the angle α between the tangent vector Vr and the load vector Vp, the more the force acting from the spindle 8 to the ball 48 acts exclusively in the rotational direction. At the front of the spindle groove 8D, the angle α becomes relatively small, and the axial component of the force acting from the spindle 8 to the ball 48 becomes relatively large. Therefore, the hammer can be stroked backward with a lower torque, which contributes to reducing the impact start torque. At the rear of the spindle groove 8D, the rotational component of the force acting from the spindle 8 to the ball 48 becomes relatively large. Therefore, the rotational speed of the hammer when moving forward while rotating is increased, which contributes to increasing the maximum tightening torque.

[0267] In the second embodiment, the spring element includes a first coil spring 49 and a second coil spring 50. The first coil spring 49 constantly applies a biasing force to the hammer 47 to move the hammer 47 forward. The second coil spring 50 applies a biasing force to the hammer 47 when the hammer 47 moves rearward.

[0268] In the above configuration, when the stroke of the hammer 47 is small, the hammer 47 is biased only by the first coil spring 49, making it easier to move the hammer 47 backward and reducing the torque required to start striking. When the stroke of the hammer 47 is large, the hammer 47 is biased by both the first coil spring 49 and the second coil spring 50, making it easier to move the hammer 47 forward, so that even if the rotation speed of the hammer 47 is increased, the hammer 47 can be moved forward quickly to appropriately strike the anvil 10. This makes it possible to increase the maximum tightening torque.

[0269] (Example) Next, examples will be described. Test data was measured for Example 1 and Example 2 and Comparative Examples 1 to 7, which are impact tool products, and compared together with the specification values ​​of each example. Example 1 corresponds to the impact tool according to the first embodiment. Example 2 corresponds to the impact tool according to the second embodiment. Example 2 has a higher maximum tightening torque than Example 1. Therefore, Example 1 is compared with Comparative Examples 1 to 3, which are a group of Comparative Examples 1 to 7 with relatively smaller maximum tightening torques. Example 2 is compared with Comparative Examples 4 to 7, which are a group of Comparative Examples 1 to 7 with relatively larger maximum tightening torques.

[0270] Example 1 Table 1 shows Example 1 and Comparative Examples 1 to 3. [Table 1]

[0271] The impact tool according to the first embodiment has a battery rated voltage of 36 V. Therefore, the battery pack 25 of the impact tool according to the first embodiment has a rated voltage of 18 V or more. A voltage of 18 V or more is input to the motor 6 of the impact tool according to the first embodiment.

[0272] "No-load rotation speed" refers to the number of rotations per minute (RPM) of the hammer 47 in a no-load state where no load is applied to the anvil 10. The no-load rotation speed of the impact tool according to Example 1 is 3700 RPM.

[0273] "Impact start torque" indicates the average value of the impact start torque measured in multiple impact tests. The impact start torque is expressed with three significant digits, with the last digit rounded off.

[0274] The impact tool according to Example 1 has an impact start torque of 1000 N·mm (1.00 N·m). Therefore, in the impact tool according to Example 1, the impact start torque, which indicates the torque acting on the anvil 10 when the hammer 47 starts to strike the anvil 10, is 1100 N·mm or less.

[0275] In contrast, in Comparative Examples 1, 2, and 3, the impact start torque is higher than 1100 N·mm.

[0276] The maximum tightening torque of the impact tool according to Example 1 is 220 N·m. Therefore, the maximum tightening torque of the impact tool according to Example 1 is greater than 200 N·m. In contrast, the maximum tightening torque of Comparative Examples 1 to 3 is 200 N·m or less.

[0277] Thus, even in Comparative Example 2, which has the closest maximum tightening torque to Example 1, the impact start torque is 1220 N·mm. In contrast, in Example 1, even when the maximum tightening torque is higher than 200 N·m, the impact start torque can be made 1100 N·mm or less, so that both a high maximum tightening torque and suppression of cam-out (low impact start torque) are achieved among products with the same torque level.

[0278] In the impact tool of Example 1, the value obtained by dividing the maximum tightening torque (N·mm) by the impact start torque (N·mm) is 220. Therefore, in the impact tool of Example 1, the value obtained by dividing the maximum tightening torque by the impact start torque is greater than 165. In contrast, in Comparative Examples 1, 2, and 3, the value obtained by dividing the maximum tightening torque by the impact start torque is less than 165. Therefore, the impact tool of Example 1 achieves both a higher maximum tightening torque and a lower impact start torque.

[0279] "Number of impacts" refers to the number of impacts per minute (IPM) by the hammer 47. The impact tool according to Example 1 has a number of impacts of 4600. The spring constant of the impact tool according to Example 1 is 36.4 (N / mm).

[0280] The "mounting load" refers to the magnitude of the biasing force (elastic force) that the spring element (spring) applies to the hammer 47 when the impact tool is not in operation, i.e., the magnitude of the preload. The mounting load in the impact tool according to Example 1 is 120 (N). Thus, in the impact tool according to Example 1, the mounting load of the spring element that biases the hammer is 150 (N) or less.

[0281] In contrast, the mounting load of the spring element that biases the hammer is greater than 150 (N) in all of Comparative Examples 1, 2, and 3. Therefore, the impact tool according to Example 1 can effectively reduce the impact start torque due to the small mounting load of the spring element.

[0282] "Hammer inertia" refers to the magnitude of the moment of inertia of the hammer 47 of the impact tool. The hammer inertia of the impact tool according to the first embodiment is 32.0 (Kg mm 2 ).

[0283] The "impact start stroke" refers to the stroke of the hammer 47 to the impact start position where the hammer 47 and the anvil 10 are not in contact with each other. In this specification, the stroke of the hammer 47 refers to the amount of rearward displacement from position Q1 (see FIG. 26), which is the forward limit of the hammer 47. The impact start stroke of the impact tool according to the first embodiment is 4.1 (mm).

[0284] The overall product length of the impact tool according to Example 1 is 102.0 (mm). The striking part width of the impact tool according to Example 1 is 58.00 (mm). Note that the "striking part width" refers to the width dimension of the striking mechanism 9.

[0285] The product mass of the impact tool according to Example 1 is 0.85 (kg). The "product mass" refers to the mass of the entire impact tool excluding the battery pack 25. Since the size and mass of the battery pack 25 vary depending on the battery capacity and battery voltage, the product mass is defined as the mass excluding the mass of the battery pack for comparison with the examples and comparative examples.

[0286] In Table 1, "rotation amount at impact" means the rotation amount (rad) of the hammer per impact when the impact tool strikes. In the impact tool of Example 1, Comparative Example 1, and Comparative Example 3, the number of rotations at impact is 1.57. In Comparative Example 2, it is 2.09.

[0287] Example 2 Table 2 shows the specifications of Example 2 and Comparative Examples 4 to 7. [Table 2]

[0288] The impact tool according to the second embodiment has a battery with a rated voltage of 36 V. Therefore, the battery pack 25 of the impact tool according to the second embodiment has a rated voltage of 18 V or more. A voltage of 18 V or more is input to the motor 6 of the impact tool according to the second embodiment.

[0289] The no-load rotation speed of the impact tool according to Example 2 is 3900 RPM.

[0290] The impact tool according to Example 2 has an impact start torque of 1200 N·mm (1.20 N·m). Therefore, in the impact tool according to the example, the impact start torque, which indicates the torque acting on the anvil 10 when the hammer 47 starts to strike the anvil 10, is 1300 N·mm or less.

[0291] The maximum tightening torque of the impact tool according to Example 2 is 230 N·m. Therefore, the impact tool according to the examples has a maximum tightening torque higher than 220 N·m. The impact tool according to the examples has a maximum tightening torque of 230 N·m or more. The impact tool according to the examples has a maximum tightening torque of 230 N·m or more and 350 N·m or less.

[0292] Thus, the impact tool of Example 2 has a maximum tightening torque of more than 220 N·m and an impact start torque of 1300 N·mm or less. On the other hand, in Comparative Examples 4 to 7, the maximum tightening torque is 220 N·m or less, or the impact start torque is more than 1300 N·mm.

[0293] In Comparative Example 7, which has the closest maximum tightening torque to Example 2, the impact start torque is 1730 N·mm. In contrast, according to Example 2, even if the maximum tightening torque is 230 N·m, which is higher than 220 N·m, the impact start torque can be made 1300 N·mm or less, so that both a high maximum tightening torque and suppression of cam-out (low impact start torque) are achieved among products with the same torque level.

[0294] In the impact tool according to Example 2, the value obtained by dividing the maximum tightening torque (N·mm) by the impact start torque (N·mm) is 192. Therefore, in the impact tool according to Example 2, the value obtained by dividing the maximum tightening torque by the impact start torque is greater than 180.

[0295] In contrast, in all of Comparative Examples 4 to 7, the value obtained by dividing the maximum tightening torque by the impact start torque is smaller than 180. Therefore, the impact tool according to Example 2 achieves both a higher maximum tightening torque and a lower impact start torque.

[0296] The impact tool according to Example 2 has a number of impacts of 4700. The spring constant of the impact tool according to Example 2 is 60.4 (N / mm). The mounting load of the impact tool according to Example 2 is 120 (N). Thus, the impact tool according to Example 2 has a mounting load of the spring element that biases the hammer of 150 (N) or less.

[0297] The hammer inertia of the impact tool according to Example 2 is 33.9 (Kg mm 2 The impact start stroke of the impact tool according to Example 2 is 4.1 (mm).

[0298] The overall product length of the impact tool according to Example 2 is 102.0 (mm). The striking portion width of the impact tool according to Example 2 is 58.00 (mm). The product mass of the impact tool according to Example 2 is 0.87 (kg). The amount of rotation during striking is 1.57 (rad) for the impact tool according to Example 2 and Comparative Examples 1 to 4.

[0299] (Performance evaluation index) Next, performance evaluation indexes for the above-mentioned examples and comparative examples will be described. The performance evaluation indexes are index values ​​calculated to evaluate specific performance of the impact tool based on each specification value or measurement value. In this specification, three index values ​​are shown in terms of maximum tightening torque and cam-out suppression.

[0300] The first index value PIa is expressed by the formula (1).

number

[0301] The second index value PIb is expressed by the formula (2).

number

[0302] The third index value PIc is expressed by the formula (3).

number

[0303] Table 3 shows the index values ​​calculated for each of the Examples and Comparative Examples. [Table 3]

[0304] The first index value PIa of the impact tool according to Example 1 is 231.22, and the first index value PIa of the impact tool according to Example 2 is 250.27. The impact tool according to the embodiment has a first index value PIa of 200 or more, preferably 230 or more, and more preferably 240 or more. This makes it possible to effectively improve the maximum tightening torque.

[0305] The second index value PIb of the impact tool according to Example 1 is 0.944, and the second index value PIb of the impact tool according to Example 2 is 1.024. The second index value PIb of the impact tool according to the embodiment is 0.8 or more, preferably 0.9 or more, and more preferably 1.0 or more. This makes it possible to effectively suppress the occurrence of cam-out.

[0306] The third index value PIc is the same as the numerical value of maximum tightening torque / impact start torque shown in Tables 1 and 2, and is 220 for the impact tool according to Example 1 and 192 for the impact tool according to Example 2. The impact tool according to the embodiment has a third index value PIc of 165 or more, preferably 180 or more, and more preferably 200 or more. This makes it possible to increase the cam-out suppression performance relative to the magnitude of the maximum tightening torque. [Explanation of symbols]

[0307] 1...impact tool, 2...housing, 2L...left housing, 2R...right housing, 2S...screw, 3...rear cover, 3S...screw, 4...hammer case, 4A...support surface, 4B...groove, 5...hammer case cover, 6...motor, 7...reduction mechanism, 8...spindle, 8A...flange portion, 8B...spindle shaft portion, 8C...projection portion, 8D...spindle groove (cam element), 8E...spindle recess, 8S...outer periphery, 9...impact mechanism, 10...anvil, 10A...tool hole, 10B...anvil projection, 11...tool holding mechanism, 12...fan, 12A...bush, 13...battery mounting portion, 14...trigger lever bar, 15...forward / reverse switching lever, 16...operation display unit, 16A...operation button, 17...mode switching switch, 18...light assembly, 18A...base member, 18B...light emitting element, 18C...ring member, 19...air intake, 20...air exhaust, 21...motor housing, 22...grip portion, 23...battery holding portion, 24...bearing box, 24A...recess, 24B...projection, 25...battery pack, 26...stator, 27...rotor, 28...stator core, 29...front insulator, 29S...screw, 30...rear insulator, 31...coil, 32...rotor core portion, 33...rotor core portion, 34...rotor core portion, 35...rotor core portion, 36...rotor core portion, 37...rotor core portion, 38...rotor core portion, 39...rotor core portion, 40...rotor core portion, 41...rotor core portion, 42...rotor core portion, 43...rotor core portion, 44...rotor core portion, 45...rotor core portion, 46...rotor core portion, 47...rotor core portion, 48...rotor core portion, 49...rotor core portion, 50...rotor core portion, 51...rotor core portion, 52...rotor core portion, 53...rotor core portion, 54...rotor core portion, 55...rotor core portion, 56...rotor core portion, 57...rotor core portion, 58...rotor core portion, 59...rotor core portion, 60...rotor core portion, 61...rotor core portion, 62...rotor core portion, 63...rotor core portion, 64...rotor core portion, 65...rotor core portion, 6 Shaft portion, 33F...front shaft portion, 33R...rear shaft portion, 34...rotor magnet, 35...sensor magnet, 37...sensor board, 38...fusing terminal, 39...rotor bearing, 39F...front rotor bearing, 39R...rear rotor bearing, 41...pinion gear, 42...planetary gear, 42P...pin, 43...internal gear, 44...spindle bearing, 45...O-ring, 45A...O-ring, 45B...O-ring, 46...bearing, 46A...bearing, 46B...bearing, 47...hammer, 47A...hole, 47B...hammer groove (cam element), 47 C...recess, 47D...hammer body, 47E...hammer protrusion, 47F...contact point, 48...ball (cam element), 48C...center, 49...first coil spring (spring element), 50...second coil spring (spring element), 51...third coil spring (spring element), 52...first washer, 53...second washer, 54...ball, 61...ring member, 62...restraining member, 71...ball, 72...leaf spring, 73...sleeve, 74...coil spring, 75...positioning member, 76...support recess, 81...center, 82...end, 90...virtual circle, 90C...center, 91...virtual plane,92...Cutting tool, 92C...Center, 101...Anvil shaft portion, 102...Anvil protrusion portion, 401...First cylindrical portion, 402...Second cylindrical portion, 800...Spindle, 800B...Spindle shaft portion, 800D...Spindle groove, 820...End portion, AX...Rotation axis, Da...Diameter, Q1...Position, Q2...Position, Q3...Position, Q4...Position, R1...First region, R2...Second region, Vc...Arrow, Ve...Arrow.

Claims

1. A motor to which a voltage of 18V or more is input; a spindle rotated by the motor; A spindle groove formed in the spindle; a ball held in the spindle groove; a hammer supported by the spindle via the ball; A spring that biases the hammer forward; and an anvil that is struck in a rotational direction by the hammer, An impact start torque, which indicates a torque acting on the anvil when the hammer starts to impact the anvil, is 1100 N mm or less. Impact tool.

2. A battery mounting section is provided to which a battery pack is mounted, The rated voltage of the battery pack is 18 V or more.

2. The impact tool according to claim 1.

3. The depth of the spindle groove varies depending on the axial position of the spindle.

2. The impact tool according to claim 1.

4. A motor; a spindle rotated by the motor; A spindle groove formed in the spindle; a ball held in the spindle groove; a hammer having a hammer groove in which at least a portion of the ball is disposed and supported by the spindle via the ball; A spring that biases the hammer forward; and an anvil that is struck in a rotational direction by the hammer, The time when the hammer moves to the rearmost position relative to the spindle is defined as the maximum stroke time. a tangent vector is a direction that passes through a contact point between the ball and the hammer groove and is parallel to a tangent to a circle having a center on the rotation axis of the spindle; If the direction in which the load is transmitted from the ball to the contact point with the hammer is defined as a load vector, The angle between the tangent vector and the load vector is 50 degrees or less. Impact tool.

5. an end portion of the spindle groove is disposed rearward of a center portion of the spindle groove, When the hammer moves rearward relative to the spindle, the ball moves to the end of the spindle groove; the angle becomes smaller as the ball approaches the end of the spindle groove; 5. An impact tool according to claim 4.

6. A motor to which a voltage of 18V or more is input; a spindle rotated by the motor; A spindle groove formed in the spindle; a ball held in the spindle groove; a hammer supported by the spindle via the ball; A spring that biases the hammer forward; and an anvil that is struck in a rotational direction by the hammer, The maximum tightening torque is greater than 220 Nm. An impact start torque, which indicates a torque acting on the anvil when the hammer starts to impact the anvil, is 1300 N mm or less. Impact tool.

7. A battery mounting section is provided to which a battery pack is mounted, The rated voltage of the battery pack is 18 V or more.

7. An impact tool according to claim 6.

8. The depth of the spindle groove varies depending on the axial position of the spindle.

7. An impact tool according to claim 6.

9. The maximum tightening torque is 230 N m or more.

7. An impact tool according to claim 6.

10. The value obtained by dividing the maximum tightening torque (N mm) by the impact start torque (N mm) is greater than 165; 7. An impact tool according to claim 6.

11. A motor; a spindle rotated by the motor; A cam element including a spindle groove formed in the spindle and a ball held in the spindle groove; a hammer supported by the spindle via the ball; A spring element biasing the hammer forward; and an anvil that is struck in a rotational direction by the advanced hammer, When striking, the hammer moves backward while rotating against the biasing force of the spring element due to the rotational torque applied from the motor via the spindle and the cam element, and then moves forward while rotating due to the elastic force of the compressed spring element and the cam element, Each of the cam element and the spring element has a structure that suppresses an increase in the torque required to rotate the hammer in a region where the rear stroke of the hammer is small, and increases the required torque nonlinearly so as to promote the increase in the required torque in a region where the stroke of the hammer is large. Impact tool.

12. When a first region is defined as a region from a position where the rear stroke of the hammer is minimum to a position where the hammer and the anvil are not in contact with each other, and a second region is defined as a predetermined region that is larger than the first region and includes a position where the stroke is maximum, a degree of change in the required torque with respect to the stroke in the first region is smaller than a degree of change in the required torque with respect to the stroke in the second region; An impact tool according to claim 11.

13. The maximum value of the required torque in the first region is 1300 N mm or less.

13. An impact tool according to claim 12.

14. The maximum tightening torque is 230 N.m or more and 350 N.m or less. An impact tool according to claim 11.

15. The depth of the rear portion of the spindle groove is greater than the depth of the front portion of the spindle groove. An impact tool according to claim 11.

16. the hammer has a hammer groove in which at least a portion of the ball is disposed; a tangent vector is a direction that passes through a contact point between the ball and the hammer groove and is parallel to a tangent to a circle having a center on the rotation axis of the spindle; If the direction in which the load is transmitted from the ball to the contact point with the hammer is defined as a load vector, an angle between the tangent vector and the load vector at a rear portion of the spindle groove is smaller than an angle between the tangent vector and the load vector at a front portion of the spindle groove; An impact tool according to claim 11.

17. The spring element includes a first coil spring and a second coil spring. The first coil spring constantly applies a biasing force to the hammer to move the hammer forward, The second coil spring applies the biasing force to the hammer when the hammer moves rearward. An impact tool according to claim 11.

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