JP5447025B2 - Impact tools - Google Patents

Description

  The present invention relates to an impact tool that is driven by a motor and realizes a new striking mechanism, and more particularly to an impact tool that adjusts the striking strength during impact operation according to the magnitude of the tightening load.

  The impact tool drives the rotary impact mechanism using a motor as a drive source, and intermittently transmits the rotary impact force to the tip tool by applying rotational force and impact force to the anvil to perform operations such as screw tightening. is there. In recent years, brushless DC motors have been widely used as drive sources. The brushless DC motor is, for example, a DC (direct current) motor without a brush (rectifying brush), and uses a coil (winding) on the stator (stator) side and a magnet (permanent magnet) on the rotor (rotor) side. The rotor is rotated by sequentially energizing the predetermined coil with the electric power driven by the inverter circuit. The inverter circuit is configured using a large-capacity output transistor such as an FET (Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor), and is driven with a large current. A brushless DC motor is excellent in torque characteristics as compared with a brushed DC motor, and can tighten a screw, a bolt, or the like on a workpiece by a stronger force.

  As an example of an impact tool using a brushless DC motor, for example, the technique of Patent Document 1 is known. In Patent Document 1, a hammer that has a continuously rotating impact mechanism portion and engages movably in the direction of the rotation axis of the spindle when a rotational force is applied to the spindle via a power transmission mechanism portion (deceleration mechanism portion). Rotates and rotates the anvil that contacts the hammer. The hammer and the anvil each have two hammer protrusions (striking parts) arranged symmetrically with each other at two locations on the plane of rotation, and these protrusions are in positions that mesh with each other in the rotation direction. Rotating impact force is transmitted by the meshing. The hammer is slidable in the axial direction with respect to the spindle in a ring region surrounding the spindle, and an inverted V-shaped (substantially triangular) cam groove is provided on the inner peripheral surface of the hammer. A V-shaped cam groove is provided in the axial direction on the outer peripheral surface of the spindle, and the hammer rotates via a ball (steel ball) inserted between the cam groove and the inner peripheral cam groove of the hammer. To do.

JP 2009-72888 A

  In the conventional power transmission mechanism, the spindle and the hammer are held via a ball disposed in the cam groove, and the hammer can be moved backward in the axial direction with respect to the spindle by a spring disposed at the rear end. It is configured. Therefore, the hammer is indirectly driven by the motor via the cam mechanism, which increases the number of parts in the power transmission portion from the spindle to the hammer, increasing the manufacturing cost, and reducing the size of the tool body. was difficult.

  Also, in the conventional impact tool, when performing the tightening work while performing impact with the impact mechanism, the impact is performed so that a constant tightening torque (set maximum torque) is generated every time. Even when the torque is small, hitting was performed at the set maximum torque.

  The present invention has been made in view of the above background, and an object thereof is to provide an impact tool that realizes an impact mechanism with a simple mechanism hammer and anvil and can be tightened accurately with a predetermined tightening torque. is there.

  Another object of the present invention is to provide an impact tool that performs impact efficiently while adjusting the impact strength during impact operation according to the magnitude of the tightening load.

  Still another object of the present invention is to provide an impact tool that realizes power saving by flowing an optimum drive current to the motor for hitting.

  The characteristics of representative ones of the inventions disclosed in the present application will be described as follows.

According to one feature of the present invention, a hammer connected to the motor, a impact tool having, an anvil is struck by Ha comma, motor by being driven alternately in the forward rotation and reverse rotation When the anvil is struck with a hammer and the motor is driven in the forward or reverse rotation, a pause interval is provided, and the length of the pause interval between the reverse rotation of the motor and the forward rotation is determined according to the detected load. Change the length, change the reverse rotation angle of the hammer, or change the reverse rotation angle of the hammer. The reverse rotation angle of the hammer can be adjusted by adjusting the length of the rest period after driving reverse rotation, or by changing the applied voltage during reverse rotation of the motor.

According to another feature of the present invention, the magnitude of the load due to impact is detected, and the magnitude of the drive current to the motor is changed according to the magnitude of the load. The drive current can be changed, for example, by changing the applied voltage supplied to the motor. The motor is a brushless DC motor, has an inverter circuit for driving the motor, and changes the applied voltage by changing the duty ratio of PWM control in the inverter circuit .

According to still another aspect of the present invention, there is provided an impact tool having a motor, a hammer connected to the motor, and an anvil hit by the hammer by alternately driving the motor in forward and reverse rotations. Then, the magnitude of the load caused by the impact is detected, and the reverse rotation angle of the motor is controlled according to the magnitude of the load . In this case, when the small size of the required load is small reverse rotation angle, when the magnitude of the required load is controlled so as to increase the reverse rotation angle.

According to the first aspect of the present invention, the hammer is hit against the anvil by alternately driving the motor in the forward direction and the reverse direction, and when the motor is driven in the forward direction or the reverse direction, the pause section is provided and detected. Since the length of the resting section between reverse rotation and forward rotation of the motor is changed according to the load size, the hammer inversion distance (running distance before hitting) can be adjusted simply by adjusting the length of the resting section. Can be adjusted, and the strength of the impact can be easily adjusted.
According to the second aspect of the present invention, the magnitude of the load caused by the impact is detected, and the magnitude of the drive current to the motor is changed according to the magnitude of the load. The optimum drive current can be supplied to the motor, and it is possible to prevent tightening with a tightening torque higher than necessary at light loads.

According to the invention of claim 3 , since the change of the drive current changes the applied voltage supplied to the motor, the drive current can be adjusted by simple control.

According to the invention of claim 4 , the motor is a brushless DC motor, has an inverter circuit for driving the motor, and changes the applied voltage by changing the duty ratio of PWM control in the inverter circuit. The applied voltage can be accurately controlled by the control unit.

According to the invention of claim 5, since the reverse rotation angle of the hammer is changed according to the detected magnitude of the load , the strength of impact can be easily adjusted.

According to the invention of claim 6, the reverse rotation angle of the hammer is increased as the detected load increases, so that the strength of the impact can be gradually increased, and the optimum tightening torque is obtained. Thus, the tightening operation can be performed efficiently.

  According to the seventh aspect of the present invention, the reverse rotation angle of the hammer is adjusted by the length of the pause section after the reverse rotation is driven. Therefore, the reverse rotation angle of the hammer is adjusted only by adjusting the length of the pause section. Can be easily adjusted.

  According to the invention of claim 8, since the reverse rotation angle of the hammer is changed by changing the applied voltage at the time of reverse rotation of the motor, it is possible to easily increase the impact strength simply by changing the control in the inverter circuit. Can be adjusted.

According to the ninth aspect of the present invention, in the impact tool that hits the hammer against the anvil by alternately driving the motor forward and backward, the reverse rotation angle of the motor is controlled according to the detected load. Therefore, optimal motor control can be performed according to the magnitude of the tightening load.

According to the invention of claim 10, when the load size is small, the reverse rotation angle is reduced, and when the load size is large, the reverse rotation angle is increased. Tightening with torque can be prevented, and efficient tightening work can be performed.

  The above and other objects and novel features of the present invention will become apparent from the following description and drawings.

It is a longitudinal section showing the whole structure of impact tool 1 concerning the example of the present invention. It is a perspective view which shows the external appearance of the impact tool 1 which concerns on the Example of this invention. It is an expanded sectional view of the vicinity of the striking mechanism 40 of FIG. It is a perspective view which shows the shape of the hammer 41 and the anvil 46 of FIG. It is a perspective view from another angle which shows the shape of the hammer 41 and the anvil 46 of FIG. It is a functional block diagram which shows the drive control system of the motor 3 of the impact tool which concerns on the Example of this invention. FIG. 4 is a cross-sectional view taken along a line AA in FIG. 3 and is a view for explaining drive control of the hammer 41 in “continuous drive mode”. FIG. 4 is a cross-sectional view taken along a line AA in FIG. 3 and is a view for explaining drive control of the hammer 41 in “intermittent drive mode”. It is a figure which shows the trigger signal at the time of operation | movement of the impact tool 1, the drive signal to an inverter circuit, the rotational speed of the motor 3, and the hammering situation of the hammer 41 and the anvil 46. It is a figure which shows the relationship between the drive signal to the inverter circuit in the intermittent drive mode (2) of FIG. 9, the operating current which flows into a motor, and the rotational speed of a motor. It is a flowchart which shows the control procedure in the intermittent drive mode (2) of the impact tool 1 which concerns on the Example of this invention. It is a flowchart which shows the control procedure in the intermittent drive mode (2) of the impact tool 1 which concerns on 2nd Example of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the front and rear, front and rear, and left and right directions will be described as the directions shown in FIGS.

  FIG. 1 is a longitudinal sectional view showing the overall structure of an impact tool according to the present invention. The impact tool 1 uses a rechargeable battery pack 30 as a power source, drives the striking mechanism 40 using the motor 3 as a driving source, and applies rotation and striking to the anvil 46 as an output shaft, thereby providing a tip tool (not shown) such as a driver bit. Transmitting continuous rotational force and intermittent striking force to the screw and tightening bolts.

  The motor 3 is a brushless DC motor and is accommodated in a cylindrical body portion 6a of a housing 6 (see FIG. 2) having a substantially T-shape when viewed from the side. The housing 6 can be divided into two substantially right and left members having a substantially symmetrical shape, and these members are fixed by a plurality of screws. Therefore, a plurality of screw bosses 20 are formed in one of the divided housings 6 (left housing in the present embodiment), and a plurality of screw holes (not shown) are formed in the other (right housing). The rotating shaft 19 of the motor 3 is rotatably held by a bearing 17b on the rear end side of the body portion 6a and a bearing 17a provided near the center portion. A substrate 7 on which six switching elements 10 are mounted is provided behind the motor 3, and the motor 3 is rotated by performing inverter control with these switching elements 10. A rotational position detection element 58 such as a Hall element or Hall IC is mounted on the front side of the substrate 7 in order to detect the position of the rotor 3a.

  A trigger switch 8 and a forward / reverse switching lever 14 are provided in an upper portion of a grip portion 6b that integrally extends substantially perpendicularly from the body portion 6a of the housing 6, and the trigger switch 8 is biased by a spring (not shown) to be gripped by the grip portion 6b. A trigger operation portion 8a protruding from the center is provided. A control circuit board 9 having a function of controlling the speed of the motor 3 by the trigger operation portion 8a is accommodated below the grip portion 6b. A battery pack 30 in which a plurality of battery cells such as nickel metal hydride and lithium ions are accommodated is detachably attached to the battery holding portion 6 c formed below the grip portion 6 b of the housing 6.

  A cooling fan 18 that is attached to the rotary shaft 19 and rotates in synchronization with the motor 3 is provided in front of the motor 3. The cooling fan 18 sucks air from the air intakes 26a and 26b provided at the rear of the body portion 6a. The sucked air is discharged to the outside of the housing 6 through a plurality of slits 26c (see FIG. 2) formed in the body portion 6a of the housing 6 and in the vicinity of the outer peripheral side of the cooling fan 18 in the radial direction.

  The striking mechanism 40 is composed of two parts, an anvil 46 and a hammer 41, and the hammer 41 is fixed so as to connect the rotation shafts of a plurality of planetary gears of the planetary gear reduction mechanism 21. Unlike a known impact mechanism that is widely used at present, the hammer 41 does not have a cam mechanism having a spindle, a spring, a cam groove, a ball, and the like. The anvil 46 and the hammer 41 are connected so that only a relative rotation of less than one rotation can be performed by a fitting shaft and a fitting hole formed near the rotation center. The anvil 46 is formed integrally with an output shaft portion on which a tip tool (not shown) is mounted, and a mounting hole 46a having a hexagonal cross section in the axial direction and the vertical plane is formed at the front end. The rear side of the anvil 46 is connected to the fitting shaft of the hammer 41 and is held rotatably with respect to the case 5 by the metal bearing 16a near the center in the axial direction.

  The case 5 is manufactured by metal integral molding for housing the striking mechanism 40 and the planetary gear speed reduction mechanism 21, and is attached to the front side of the housing 6. Further, the outer peripheral side of the case 5 is covered with a resin cover 11 in order to prevent heat transfer and achieve an impact absorbing effect and the like. A tip tool holding means for holding the tip tool is formed at the tip of the anvil 46, and the tip tool is attached and detached by moving the sleeve 15 in the front-rear direction.

  In the impact tool 1, when the trigger operation unit 8 a is pulled and the motor 3 is activated, the rotation of the motor 3 is decelerated by the planetary gear reduction mechanism 21, and the rotation speed is a predetermined ratio with respect to the rotation speed of the motor 3. The hammer 41 is driven directly. When the hammer 41 rotates, the rotational force is transmitted to the anvil 46, and the anvil 46 starts rotating at the same speed as the hammer 41.

  FIG. 2 is a perspective view showing an appearance of the impact tool 1 of FIG. The housing 6 is composed of three parts (6a, 6b, 6c), and a cooling air discharge slit 26c is formed in the body portion 6a in the vicinity of the outer peripheral side of the cooling fan 18 in the radial direction. A control panel 31 is provided on the upper surface of the battery holding portion 6c. Various operation buttons, display lamps, and the like are arranged on the control panel 31. For example, a switch for turning on / off the LED light 12 and a button for checking the remaining amount of the battery pack are arranged. Further, a button switch 32 for switching the drive mode (drill mode, impact mode) of the motor 3 is provided on the side surface of the battery holding portion 6c. When the operator pushes the button switch 32 in the right direction, the drill mode and the impact mode are alternately switched.

  The battery pack 30 is provided with a release button 30a, and the battery pack 30 can be removed from the battery holding portion 6c by moving the battery pack 30 forward while pressing the release buttons 30a located on the left and right sides. A detachable metal belt hook 33 is provided on the left and right sides of the battery holding portion 6c. In FIG. 2, it is attached to the left side of the impact tool 1, but it is also possible to remove the belt hook 33 and attach it to the right side of the impact tool 1. A strap 34 is attached near the rear end of the battery holding portion 6c.

  FIG. 3 is an enlarged cross-sectional view of the vicinity of the striking mechanism 40 of FIG. The planetary gear speed reduction mechanism 21 is a planetary type, and a sun gear 21a connected to the tip of the rotating shaft 19 of the motor 3 serves as a drive shaft (input shaft), and a plurality of outer gears 21d fixed to the body portion 6a. Planetary gear 21b rotates. The plurality of rotating shafts 21c of the planetary gear 21b are held by a hammer 41 having a planetary carrier function. The hammer 41 rotates as a driven shaft (output shaft) of the planetary gear speed reduction mechanism 21 at a predetermined reduction ratio in the same direction as the motor 3. The reduction ratio should be set appropriately based on factors such as the main tightening target (screw or bolt), the output of the motor 3, and the required tightening torque. In the example, the reduction ratio is set so that the rotation speed of the hammer 41 is about 1/8 to 1/15 with respect to the rotation speed of the motor 3.

  An inner cover 22 is provided on the inner peripheral side of the two screw bosses 20 inside the body portion 6a. The inner cover 22 is a member manufactured by integral molding of synthetic resin such as plastic. A cylindrical portion is formed on the rear side, and a bearing 17a that rotatably fixes the rotating shaft 19 of the motor 3 at the cylindrical portion. Hold. In addition, a cylindrical step portion having two different diameters is provided on the front side of the inner cover 22, and a ball type bearing 16b is provided on the smaller step portion, and the larger cylindrical step portion is provided. Part of the outer gear 21d is inserted into the part from the front side. The outer gear 21d is non-rotatably attached to the inner cover 22, and the inner cover 22 is non-rotatably attached to the body portion 6a of the housing 6. Therefore, the outer gear 21d is fixed in a non-rotating state. Further, a flange portion having a large outer diameter is provided on the outer peripheral portion of the outer gear 21 d, and an O-ring 23 is provided between the flange portion and the inner cover 22. Grease (not shown) is applied to the rotating portions of the hammer 41 and the anvil 46, and the O-ring 23 seals the grease so that it does not leak to the inner cover 22 side.

  A characteristic feature of this embodiment is that the hammer 41 has the function of a planet carrier that holds the plurality of rotating shafts 21c of the planetary gear 21b. Therefore, the rear end portion of the hammer 41 extends to the inner peripheral side of the inner ring of the bearing 16b. Further, the inner peripheral portion on the rear side of the hammer 41 is disposed in a cylindrical internal space that houses a sun gear 21 a attached to the rotating shaft 19 of the motor 3. In the vicinity of the front central axis of the hammer 41, a fitting shaft 45 serving as a shaft portion protruding forward in the axial direction is formed, and the fitting shaft 45 is a cylindrical fitting formed near the rear central axis of the anvil 46. Fits into the hole 46f. The fitting shaft 45 and the fitting hole 46f are pivotally supported so that both can rotate relatively.

  Next, the detailed structure of the striking mechanism 40 shown in FIGS. 1 and 2 will be described with reference to FIGS. FIG. 4 is a perspective view showing the shapes of the hammer 41 and the anvil 46 according to the first embodiment of the present invention. The hammer 41 is seen from an oblique front and the anvil 46 is seen from an oblique rear. FIG. 5 is a perspective view showing the shapes of the hammer 41 and the anvil 46. The hammer 41 is a view seen obliquely from the rear, and the anvil 46 is a partial view seen obliquely from the front. The hammer 41 is formed with two blade portions 41c and 41d protruding in a radial direction from the cylindrical main body portion 41b. The blade portions 41d and 41c are each formed with a protruding portion that protrudes in the axial direction, and a pair of striking portions and weight portions are formed on each of the blade portions 41c and 41d.

  On the blade portion 41c side, the outer peripheral portion is formed in a fan shape, and a protruding portion 42 that protrudes forward in the axial direction from the outer peripheral portion is formed. The fan-shaped portion and the projecting portion 42 function as a striking portion (striking claw) and simultaneously function as a weight portion. The striking surfaces 42a and 42b are formed on both sides of the protrusion 42 in the circumferential direction. The striking surfaces 42a and 42b are both formed in a flat surface, and are appropriately angled so as to make good surface contact with the striking surface to be described later of the anvil 46. On the other hand, the blade part 41d is formed so that the outer peripheral part spreads in a fan shape, and the shape of the fan part increases the mass of the part and acts as a weight part. In addition, a protruding portion 43 that protrudes forward in the axial direction from the radial center of the blade portion 41d is formed. The protrusion 43 acts as a striking portion (striking claw), and striking surfaces 43a and 43b are formed on both sides in the circumferential direction. The striking surfaces 43a and 43b are both formed in a flat shape, and are given an appropriate angle in the circumferential direction so as to satisfactorily come into surface contact with the striking surface to be described later of the anvil 46.

  A fitting shaft 41a that is fitted into the fitting hole 46f of the anvil 46 is formed in the vicinity of the axial center of the main body portion 41b and on the front side. On the rear side of the main body portion 41b, two disk portions 44a and 44b and a connection portion 44c for connecting them at two locations in the circumferential direction are formed so as to function as a planet carrier. Through holes 44d are formed at two locations in the circumferential direction of the disk portions 44a and 44b, two planetary gears 21b (see FIG. 3) are disposed between the disk portions 44a and 44b, and the planetary gear 21b. The rotating shaft 21c (see FIG. 3) is mounted in the through hole 44d. A cylindrical portion 44e extending in a cylindrical shape is formed on the rear side of the disk portion 44b. The outer peripheral side of the cylindrical portion 44e is held by the inner ring of the bearing 16b. The sun gear 21a (see FIG. 3) is disposed in the space 44f inside the cylindrical portion 44e. The hammer 41 and the anvil 46 shown in FIGS. 4 and 5 are preferable in terms of strength and weight when manufactured in a metal integrated structure.

  The anvil 46 is formed with two blade portions 46c and 46d that protrude in the radial direction from the cylindrical main body portion 46b. A protruding portion 47 that protrudes rearward in the axial direction is formed near the outer periphery of the blade portion 46c. The hitting surfaces 47 a and 47 b are formed on both sides in the circumferential direction of the protrusion 47. On the other hand, a protruding portion 48 protruding rearward in the axial direction is formed in the vicinity of the radial center of the blade portion 46d. The hitting surfaces 48 a and 48 b are formed on both sides in the circumferential direction of the protrusion 48. When the hammer 41 rotates in the forward direction (rotating direction in which a screw or the like is tightened), the striking surface 42a comes into contact with the hit surface 47a, and at the same time, the hit surface 43a comes into contact with the hit surface 48a. Further, when the hammer 41 rotates in the reverse direction (rotating direction for loosening a screw or the like), the striking surface 42b comes into contact with the hit surface 47b, and at the same time, the hit surface 43b comes into contact with the hit surface 48b. The shapes of the protrusions 42, 43, 47, and 48 are determined so that the abutment occurs simultaneously.

  As described above, according to the hammer 41 and the anvil 46 shown in FIGS. 4 and 5, the impact tool 1 is well balanced at the time of impact since the impact is performed at two symmetrical positions with respect to the rotating shaft center. Can be configured to be difficult to shake. Further, since the striking surfaces are provided on both sides in the circumferential direction of the projecting portion, the impact operation can be performed not only in the normal rotation but also in the reverse rotation, so that an easy-to-use impact tool can be realized. Further, the hammer 41 hits the anvil 46 only in the circumferential direction, and does not strike the anvil 46 in the axial direction or forward, so that the tool is pressed more than necessary with the tip tool in the impact mode. This is advantageous when tightening wood screws or the like into wood.

  Next, the configuration and operation of the drive control system of the motor 3 will be described with reference to FIG. FIG. 6 is a block diagram showing the configuration of the drive control system of the motor 3. In this embodiment, the motor 3 is a three-phase brushless DC motor. This brushless DC motor is a so-called inner rotor type, and includes a rotor (rotor) 3a including a plurality of sets (two sets in this embodiment) of permanent magnets (magnets) including N poles and S poles. A stator (stator) 3b composed of three-phase stator windings U, V, and W connected in a star connection, and a predetermined interval in the circumferential direction to detect the rotational position of the rotor 3a, for example, an angle of 60 ° Three rotational position detecting elements (Hall elements) 58 are provided for each. Based on the position detection signals from these rotational position detecting elements 58, the energization direction and time to the stator windings U, V, W are controlled to rotate the motor 3. The rotational position detection element 58 is provided at a position facing the permanent magnet 3 c of the rotor 3 a on the substrate 7.

  The electronic elements mounted on the substrate 7 include an inverter circuit 52 including six switching elements Q1 to Q6 such as FETs connected in a three-phase bridge format. The gates of the six switching elements Q1 to Q6 that are bridge-connected are connected to a control signal output circuit 53 mounted on the control circuit board 9, and the drains or sources of the six switching elements Q1 to Q6 are It is connected to the stator windings U, V, W that are star-connected. As a result, the six switching elements Q1 to Q6 perform a switching operation by the switching element drive signals (drive signals such as H4, H5, and H6) input from the control signal output circuit 53 and are applied to the inverter circuit 52. Electric power is supplied to the stator windings U, V, and W using the DC voltage of the battery pack 30 as three-phase (U-phase, V-phase, and W-phase) voltages Vu, Vv, and Vw.

  Of the switching element drive signals (three-phase signals) for driving the gates of the six switching elements Q1 to Q6, the three negative power supply side switching elements Q4, Q5, Q6 are converted into pulse width modulation signals (PWM signals) H4, The pulse width (duty ratio) of the PWM signal is supplied as H5 and H6 and based on the detection signal of the operation amount (stroke) of the trigger operation unit 8a of the trigger switch 8 by the calculation unit 51 mounted on the control circuit board 9. The amount of electric power supplied to the motor 3 is adjusted by changing, and the start / stop of the motor 3 and the rotation speed are controlled.

  Here, the PWM signal is supplied to any one of the positive power supply side switching elements Q1 to Q3 or the negative power supply side switching elements Q4 to Q6 of the inverter circuit 52, and the switching elements Q1 to Q3 or the switching elements Q4 to Q6 are switched at high speed. As a result, the power supplied to the stator windings U, V, W from the DC voltage of the battery pack 30 is controlled. In this embodiment, since the PWM signal is supplied to the negative power supply side switching elements Q4 to Q6, the power supplied to each stator winding U, V, W is adjusted by controlling the pulse width of the PWM signal. Thus, the rotation speed of the motor 3 can be controlled.

  The impact tool 1 is provided with a forward / reverse switching lever 14 for switching the rotational direction of the motor 3, and the rotational direction setting circuit 62 switches the rotational direction of the motor each time a change in the forward / reverse switching lever 14 is detected. The control signal is transmitted to the calculation unit 51. Although not shown, the arithmetic unit 51 is a central processing unit (CPU) for outputting a drive signal based on the processing program and data, a ROM for storing the processing program and control data, and for temporarily storing data. RAM, a timer, and the like.

  The control signal output circuit 53 forms a drive signal for alternately switching predetermined switching elements Q1 to Q6 based on the output signals of the rotation direction setting circuit 62 and the rotor position detection circuit 54, and controls the drive signal. The signal is output to the signal output circuit 53. As a result, the predetermined windings of the stator windings U, V, and W are alternately energized to rotate the rotor 3a in the set rotation direction. In this case, the drive signal applied to the negative power supply side switching elements Q4 to Q6 is output as a PWM modulation signal based on the output control signal of the applied voltage setting circuit 61. The current value supplied to the motor 3 is measured by the current detection circuit 59, and the value is fed back to the calculation unit 51 to be adjusted to the set driving power. The PWM signal may be applied to the positive power supply side switching elements Q1 to Q3.

  The rotation speed detection circuit 55 is a circuit that receives signals from the plurality of rotor position detection circuits 54, detects the rotation speed of the motor 3, and outputs it to the calculation unit 51. The impact detection sensor 56 detects the magnitude of impact generated on the anvil 46, and its output is input to the computing unit 51 via the impact impact detection circuit 57. The impact sensor 56 can be realized by, for example, an acceleration sensor attached to the control circuit board 9, and the motor 3 is automatically stopped when tightening is completed with a specified torque using the output of the impact sensor 56. Anyway.

  The impact tool 1 according to the present embodiment can be driven in the “continuous drive mode” and the “intermittent drive mode”. The “continuous drive mode” is a simple control mode in which the hammer is continuously driven and the anvil is continuously rotated in one direction. The “intermittent drive mode” is a control mode in which a strong tightening torque is generated on the anvil by striking the hammer against the anvil while rotating and stopping the hammer in a forward or reverse direction. In the “intermittent drive mode”, since the hammer 41 needs to be rotated forward and backward in order to hit the anvil 46, the motor 3 is specially controlled. The control in the intermittent drive mode is a unique control method that can be realized by the hammer 41 and the anvil 46 according to the present embodiment. In the intermittent drive mode, the hammering operation by the hammer 41 is performed, so that the tightening angle per time is smaller than that in the continuous drive mode. Therefore, when tightening by impact operation, the initial required torque of the tightening operation is driven in the continuous drive mode during the period where the required torque is small, and the reaction force from the tightening target becomes stronger and the required tightening torque becomes larger. If the mode is switched to the intermittent drive mode, the total time required for tightening in the impact mode can be shortened.

  Here, the rotation operation of the hammer 41 and the anvil 46 will be described with reference to FIGS. FIG. 7 is a cross-sectional view taken along the line AA in FIG. 3 and is a diagram for explaining basic drive control of the hammer 41 in the “continuous drive mode” described above. From these sectional views, the positional relationship between the protruding portions 42 and 43 protruding in the axial direction from the hammer 41 and the protruding portions 47 and 48 protruding in the axial direction from the anvil 46 will be understood. The direction of rotation of the anvil 46 during the tightening operation (forward rotation) is counterclockwise in this figure, and the hammer 41 is driven as shown in FIGS. 7 (1) → (2) → (3) → (4). Rotate in order. At this time, the hammer 41 continuously rotates in the directions of arrows 71, 72, 73, 74 by driving the motor 3, so that the anvil 46 is pushed from the rear from the hammer 41 so that the striking surface 42 a of the hammer 41. , 43a is in contact with the hit surfaces 47a, 48a of the anvil 46, and the anvil 46 rotates in synchronization with the arrow direction.

  In the “continuous drive mode” shown in FIG. 7, the tightening is performed in a state where the rotational torque of the motor 3 that drives the hammer 41 is larger than the reaction force received from the material to be tightened, and the load at the time of tightening is Under small circumstances, the anvil 46 can be rotated in synchronism simply by rotating the hammer 41 with the motor 3, so that tightening can be performed at high speed by using the “continuous drive mode” in the initial stage of tightening in the impact mode. Can do.

  FIG. 8 is a cross-sectional view taken along the line AA in FIG. 3 and is a view for explaining basic drive control of the hammer 41 in the “intermittent drive mode” of the impact tool 1 described above. In the “intermittent drive mode”, the hammer 41 is hit against the anvil 46 by moving the hammer 41 forward and backward by driving the motor 3 in a unique manner, rather than rotating the hammer 41 in only one direction. Is. FIG. 8A is a diagram showing an initial state, and this state shows a state immediately after switching from another drive mode such as “continuous drive mode” to “intermittent drive mode”. In this state, by starting the reverse rotation of the motor 3, the hammer 41 is rotated in the direction of the arrow 81 (the direction opposite to the rotation direction of the anvil 46).

  The hammer 41 and the anvil 46 can be rotated by a relative angle of less than 360 degrees, and only the hammer 41 can be reversely rotated from the state (1). When the motor 3 is reversely rotated to near the state of (2), the reverse rotation drive of the motor 3 is stopped, but the hammer 41 continues to rotate in the direction of the arrow 82 due to inertia and reversely rotates to the position of (3). Immediately before the position shown in FIG. 8 (3), the motor 3 is caused to rotate forward by passing a drive current in the normal direction, so that the rotation of the hammer 41 in the direction of the arrow 83 stops and the rotation in the direction of the arrow 84 (normal Rotation in the direction). Here, the position at which the hammer 41 performs reversal is referred to as “reversal position”. In this embodiment, the rotation angle from the reversal start of the hammer 41 to the reversal position is about 240 degrees. In order to reverse the hammer 41 by about 240 degrees, the motor 3 needs to be reversed at this angle by the reciprocal of the reduction ratio of the planetary gear reduction mechanism 21. The reversal angle may be arbitrarily set within the maximum reversal angle, but is preferably set according to a required value of the magnitude of the tightening torque obtained by the impact.

When the hammer 41 is reversed, it rotates again in the forward rotation direction. However, as shown in FIG. 8 (4), the projecting portion 42 again passes the outer periphery of the projecting portion 48, and at the same time, the projecting portion 43 Continue to rotate in the direction of arrow 85 while accelerating. In this way, in order to allow both to pass, the inner diameter R _H2 of the protruding portion 42 is configured to be larger than the outer diameter R _A1 of the protruding portion 48 so that they do not collide. Similarly, the outer diameter R _H1 of the protruding portion 43 is configured to be smaller than the inner diameter R _A2 of the protruding portion 47 so that they do not collide. By configuring in this positional relationship, the relative rotation angle between the hammer 41 and the anvil 46 can be configured to be greater than 180 degrees, and a sufficient amount of inversion angle of the hammer 41 can be secured with respect to the anvil 46. The reversal angle can be an acceleration zone before hitting the hammer 41 against the anvil 46.

  Next, when the hammer 41 is accelerated and rotated in the direction of the arrow 86 to the state of FIG. 8 (5), the striking surface 42 a of the protruding portion 42 collides with the hit surface 47 a of the protruding portion 47. At the same time, the striking surface 43 a of the protrusion 43 collides with the striking surface 48 a of the protrusion 48. Thus, a well-balanced blow can be performed on the anvil 46 by colliding at two locations on the opposite side of the rotation axis.

As a result of this striking, as shown in FIG. 8 (6), the anvil 46 is struck by the hammer 41 from the rear and rotates in the direction of the arrow 87, and the tightening material is tightened by the rotation accompanying this striking. Done. The hammer 41 has a protruding portion 42 that is the only protrusion at the concentric position in the radial direction (position of _RH2 or more and _RH3 or less), and the third unique point in the concentric position (position of _RH1 or less). It has the protrusion part 43 which is protrusion. The anvil 46 has a protrusion 47 that is the only protrusion at the radial concentric position (position of R _A2 or more and R _A3 or less), and is the only protrusion at the concentric position (position of R _A1 or less). A protrusion 48 is provided. As described above, in the “intermittent drive mode”, the hammer 3 is alternately rotated in the forward direction and the reverse direction by alternately rotating the motor 3 in the forward direction and the reverse direction, and the batting operation is performed on the anvil 46. .

  Next, a driving method of the impact tool 1 according to the present embodiment will be described with reference to FIG. In the impact tool 1 according to the present embodiment, the anvil 46 and the hammer 41 are formed so as to be relatively rotatable at a rotation angle of less than 360 degrees. Therefore, since the hammer 41 cannot be rotated relative to the anvil 46 by more than one rotation, its rotation control is also unique. FIG. 9 is a diagram illustrating a trigger signal, an inverter circuit drive signal, a rotation speed of the motor 3, and a hammering state of the hammer 41 and the anvil 46 when the impact tool 1 is operated. In each graph, the horizontal axis is time, and the horizontal axis is shown together so that the timing of each graph can be compared.

In the impact tool 1 according to the present embodiment, in the tightening work in the impact mode, the motor 3 is first fastened in the continuous drive mode, and when the required tightening torque value becomes large, the intermittent drive mode (1 To the intermittent drive mode (2) of the motor 3 and tightening is performed. In the continuous drive mode in T ₂ from the time T ₁ of the FIG. 9, the arithmetic unit 51 performs control based on the motor 3 to the target speed. For this reason, the calculating part 51 accelerates the motor 3 until it reaches | attains the target rotation speed shown by the arrow 85a after starting. The rotation of the anvil 46 in the continuous drive mode rotates while being pushed by the hammer 41. Here, the hammer 41 is continuously rotated in synchronization with the continuous rotation of the rotor 3a. The ratio between the rotational speed of the rotor 3a and the rotational speed of the hammer 41 may be 1: 1, but it is preferable to have a predetermined reduction ratio. Thereafter, when the tightening reaction force from the tip tool attached to the anvil 46 increases, the reaction force transmitted from the anvil 46 to the hammer 41 increases, so that the rotation speed of the motor 3 gradually decreases as indicated by an arrow 85b. . Therefore, by detecting a current value supplied to the drop in the rotational speed of the motor 3 is switched to the intermittent drive mode of the motor 3 (1) at time T _2.

The intermittent drive mode (1) is a mode in which the motor 3 is driven intermittently rather than continuously, and is driven in pulses so that “pause → forward rotation drive” is repeated a plurality of times. Here, “driving in a pulsed manner” means that the drive current supplied to the motor 3 is pulsated by pulsating the gate signal applied to the inverter circuit 52, thereby pulsating the rotation speed or output torque of the motor 3. It is to drive control so that. This pulsation is from time _{T 2,} to _{T 21} is the drive current OFF supplied to the motor (pause), from time _{T 21} to _{T 3} and the driving current ON of the motor (drive), from time _{T 3} to _{T 31} the drive current to OFF (pause), from time _{T 31} to time _{T 4} repeats oN-OFF of the drive current such that the drive current oN, a large period (e.g., several tens Hz~ hundred and several tens Hz) Is generated by Note that PWM control is performed to control the rotational speed of the motor 3 when the drive current is ON, but the pulsation cycle is sufficiently small compared to the duty ratio control cycle (usually several kilohertz).

In the example of FIG. 9, to suspend the supply of the drive current from T ₂ to a certain time the motor 3, after the rotation speed of the motor 3 is lowered in the arrow 86a, the arithmetic unit 51 (see FIG. 5) is the drive signal 83a Is sent to the control signal output circuit 53 to supply a pulsed drive current (drive pulse) to the motor 3 to accelerate the motor 3. This acceleration control does not necessarily mean driving at a duty ratio of 100%, but may be controlled at a duty ratio of less than 100%. Next, when the hammer 41 strongly collides with the anvil 46 at the point of the arrow 86b, a striking force is given as shown by the arrow 88a. When the striking force is applied, the supply of the driving electric current to the motor 3 is again stopped for a predetermined period, and after the rotational speed of the motor has dropped as indicated by the arrow 86c, the calculation unit 51 sends the driving signal 83b to the control signal output circuit. The motor 3 is accelerated by sending it to 53. Then, the hammer 41 strongly collides with the anvil 46 at the point indicated by the arrow 86d, so that a striking force is given as indicated by the arrow 88b. In the intermittent drive mode (1), the intermittent drive that repeats the “pause → forward rotation drive” of the motor 3 described above is repeated once or a plurality of times. If a higher tightening torque is required, the state is detected. Then, the mode is switched to the rotational drive mode in the intermittent drive mode (2). Whether or not a high tightening torque is required can be determined using, for example, the number of rotations of the motor 3 (before and after the arrow 86d) when the striking force indicated by the arrow 88b is applied.

  The intermittent drive mode (2) is a mode in which the motor 3 is intermittently driven and the motor 3 is driven in a pulse form as in the intermittent drive mode (1), but “pause → reverse drive → pause → forward rotation”. Drive to repeat “drive” multiple times. In other words, in the intermittent drive mode (2), not only the forward rotation drive of the motor 3 but also the reverse rotation drive is applied, so that the hammer 41 is rotated backward by a sufficient relative angle with respect to the anvil 46 as shown in FIG. Then, the hammer 41 is accelerated in the forward rotation direction and vigorously collides with the anvil 46. In this manner, the hammer 41 is alternately driven in both the forward and reverse directions to generate a strong tightening torque on the anvil 46.

9, when at time T ₄ switched to the intermittent driving mode (2), the driving of the motor 3 by pause, then the motor 3 by sending a negative direction of the drive signal 84a to the control signal output circuit 53 Reverse rotation. The forward rotation and reverse rotation are realized by switching the signal pattern of each drive signal (on / off signal) output from the control signal output circuit 53 to each of the switching elements Q1 to Q6. When the motor 3 rotates backward by a predetermined rotation angle (arrow 87a), the driving of the motor 3 is temporarily stopped. When the driving of the motor 3 is stopped, the driving voltage is not supplied to the motor 3, so that the motor 3 rotates by inertia. Thereafter, in order to start forward rotation driving (arrow 87 b), a driving signal 84 b in the positive direction is sent to the control signal output circuit 53. In the rotational drive using the inverter circuit 52, the drive signal is not switched to the plus side or the minus side. However, in FIG. -Schematically divided into directions.

  In the vicinity of the rotation speed of the motor 3 reaching the maximum speed, the hammer 41 collides with the anvil 46 (arrow 87c). This collision generates a tightening torque (arrow 89a) that is much larger than the tightening torque (88a, 88b) generated in the intermittent drive mode (1). When the collision occurs in this way, the rotation speed of the motor 3 decreases so as to reach the arrows 87c to 87d. In the present embodiment, the drive signal to the motor 3 is continuously supplied for a predetermined time after the collision is performed. However, it may be controlled to stop the drive signal to the motor 3 at the moment when the collision indicated by the arrow 89a is detected. In this case, when the tightening target is a bolt or nut, it is transmitted to the operator's hand after hitting. Less recoil. As shown in this embodiment, the reaction force to the worker is smaller than that in the continuous drive mode by causing the drive current to flow through the motor 3 even after a collision, which is suitable for work in an intermediate load state. In addition, the fastening speed is fast and the power consumption can be reduced as compared with the pulse strong mode.

Thereafter, the drive of the motor 3 is temporarily stopped, and then the motor 3 is reversely rotated by sending a drive signal 84c in the negative direction to the control signal output circuit 53. Similarly, “pause → reverse rotation drive → pause → normal rotation driving "tightening of a strong fastening torque by repeating a predetermined number of times is performed, the motor 3 is stopped by the operator releases the trigger operation at time T _9, fastening operation is completed. The completion of the work may be controlled not only to release the trigger operation by the operator but also to stop the driving of the motor 3 when the calculation unit 51 determines that the fastening with the set fastening torque is completed. A method of detecting the tightening torque will be described later.

FIG. 10 shows the control of the continuous drive mode (2) portion of FIG. 9, and is a diagram showing the relationship among the drive signal to the inverter circuit, the operating current flowing through the motor, and the rotational speed of the motor. At time T _4, the switching control of the continuous drive mode (1) to the continuous driving mode (2), the arithmetic unit 51 by pause the driving of the motor 3, thereafter, controls the negative direction of the drive signals 84a By sending the signal to the signal output circuit 53, the motor 3 is rotated in the reverse direction. The calculation unit 51 causes the drive signal 84a in the negative direction to flow for a predetermined time, and the rotation speed of the motor 3 reaches a predetermined reverse rotation speed indicated by an arrow 87a. Next, the arithmetic unit 51 to pause the driving of the motor 3 by the time P _1. During this time, the motor 3 rotates while maintaining the rotation speed in the reverse direction due to inertia. After lapse of the rest time _{P 1,} computing unit 51 starts forward rotation drive of the motor 3 (arrow 87b). The forward rotation driving is performed only for the forward rotation driving time D _1, and the hammer 41 collides with the anvil 46 immediately before this D ₁ elapses (time T ₅ ), so that the anvil 46 is hit. A strong tightening torque is generated due to impact. Here, it is preferable to set default values in advance for the time P ₁ and the forward rotation drive time D ₁ immediately after the transition to the continuous drive mode (2). After the elapsed time t _a after striking is performed, the arithmetic unit 51 measures the drive current value I _{1 (peak} magnitude of the arrows 90a) to the motor 3.

By our experiments, the magnitude of peak current I _m immediately after the hit of the m-th from the transition to continuous driving mode (2) was found to substantially proportional to the tightening torque by the striking. The tightening torque value TR _m at the m-th hit in the intermittent drive mode (2) is
TR _m = k · ΔI _m (where k is a proportional constant, m = 1, 2,..., N)
It can be expressed as The torque value TR _m serves as a reference for setting the rest time P _{m + 1} after the next reverse current and the forward rotation drive time D _{m + 1} to apply the forward current, and based on the obtained torque value TRm. The pause time P _{m + 1} and the forward rotation drive time D _{m + 1} are set. This setting method may be calculated by a predetermined calculation formula, but a storage device (not shown) in the calculation unit 51 uses the relationship between the torque value TR _m , the pause time P _{m + 1} , and the normal rotation drive time D _{m + 1} as a data table in advance. It is good to store in.

Next, after measuring the obtained peak current I ₁ , the rest time t _b is set, and then the calculation unit 51 supplies the drive signal 84c in the negative direction so that the motor 3 has a predetermined reverse rotation speed, for example − Control is performed to reach 3000 rpm, and when the predetermined reverse rotation speed indicated by the arrow 87e is reached, the supply of the drive signal 84c is stopped. The dwell time P ₂ of the case, determined by the torque value TR ₁ clamped obtained during the first blow. Here, the m-th pause time P _m is preferably increased as the tightening torque value TR _m−1 is increased. That downtime to increase the P _m means that the range extending from FIG. 8 (2) (3), a period in which the hammer 41 is reversely rotated by inertia becomes longer, as a result, the inversion angle of the hammer 41 Becomes larger and the reverse position is on the rear side. An increase in the angle of reversal of the hammer 41 increases the run distance of the next hit, and therefore the rotational speed in the positive direction when the hammer 41 hits the anvil 46 increases, and a larger tightening torque value TR _m is generated. Can be made.

Motor 3 is accelerated in the positive direction from the point of the arrow 87f, the point of the arrow 87 g, the rotational speed or at time T ₆ strikes the anvil 46 as well as reach the peak. The After the strike is performed, similarly to the time of the first strike, after a lapse of time t _a, the arithmetic unit 51 measures the drive current value I _{2 (peak} magnitude of the arrow 90b), the above-described formula calculating a torque value TR ₂ fastened with. Thereafter, only pause the driving of the motor 3 time t _b. Hereinafter, repeating the same operation, the third strike at time T _7, the fourth striking at time T ₈ are performed. In addition, a tightening torque value TR _m is calculated at the time of each hit, and a pause time P _{m + 1} is determined. Then, the motor 3 is stopped when the worker releases the trigger operation at time T9.

Thus, we were able to establish a method of detecting the torque value TR _m tightened with the magnitude of the peak current I _m of the driving current. As a result, it was possible to control the impact tool so as to perform an optimal impact according to the size of the tightening load, thereby suppressing wasteful energy consumption and saving power.

Next, the control procedure in the intermittent drive mode (2) of the impact tool 1 according to the embodiment of the present invention will be described using the flowchart of FIG. First, when driving in the intermittent drive mode (1) shown in FIG. 9 is completed, the mode is shifted to the intermittent drive mode (2) (step 111). In the intermittent drive mode (2), as shown in FIG. 10, the current is passed in the order of rest → reverse current → pause → forward current to cause the hammer 41 to collide with the anvil 46. In the forward rotation current, the motor 3 is driven at a predetermined current, for example, 50 A by constant current control, the hammer 41 is accelerated in the forward rotation direction from the initial position, and the hammer 41 collides with the anvil 46. In this collision, not only the inertia of the hammer 41 but also the inertia of the rotor 3a can be used, so that even a relatively lightweight hammer 41 can generate a strong striking force. Upon first blow in the intermittent driving mode (2), dwell time P ₁ and normal rotation drive time D ₁ is the default value is used which is set in advance. Next, it is detected whether or not an impact has been detected. If not, the system waits until it is detected (step 112). This hit detection is performed by the hit impact detection sensor 56 (see FIG. 6). If a hit is detected, the process waits until _a predetermined time ta has elapsed (step 113). When the predetermined time t _a has passed, to detect the peak current I _m by measuring the driving current of the motor 3 (step 114). This measurement is performed using the current detection circuit 59 (see FIG. 6).

Then, to calculate the torque value TR _m tightened based on the peak current _{I m} obtained (step 115). Next, it is determined whether the tightening torque value TR _m has reached the set predetermined tightening torque, or whether the operator has turned off the trigger switch 8 (step 116). When the switch 8 is turned off, the rotation of the motor 3 is stopped (step 121), and the tightening operation is finished.

If none of the above results in step 116, it is further determined whether the pause time t _b has elapsed (that is, whether time t _a + t _b has elapsed since the hit was detected). (Step 117). If the pause time t _b has elapsed, it supplies the reverse current to the motor 3, thereby reversely rotating the motor 3 (step 118). Constant current control is also performed for the reverse current. Next, it is detected whether or not the rotational speed of the motor 3 has reached a predetermined reverse rotational speed (for example, −3000 rpm), and if not, it waits while continuing constant current control until it reaches (step 119). . If it has reached, the supply of the reverse current of the motor 3 is stopped, and from the tightening torque value TR _m obtained in step 115, the pause time P _{m + 1} , the normal rotation drive time D _{m + 1} , and the next normal rotation drive The constant current control value is calculated, and the process returns to step 111 (step 120). Here, the constant current control value in the next forward rotation drive is increased when the tightening torque value TR _m is large, and is decreased when the tightening torque value TR _m is small. Relationship torque value TR _m and tightening the constant current control value, may be stored in the data table form or in a storage unit (not shown) which in advance in the arithmetic unit 51 in functional form.

As described above, in this embodiment, since the magnitude of the tightening torque due to the anvil is calculated based on the magnitude of the drive current flowing in the motor 3 immediately after hitting, without using a separate torque detection device such as a strain sensor. A torque detecting means can be realized, the tightening load can be detected for each impact and reflected in the control of the motor, and the tightening operation can be performed with high accuracy. Although it configured to provide a reverse rotation current to the motor 3 after a predetermined dwell time t _b has elapsed in step 117, the motor 3 Once this rotational speed of the motor 3 is reduced to a predetermined rotational speed (e.g. 5000 rpm) Alternatively, a reverse current may be supplied.

Next, a control procedure in the intermittent drive mode (2) of the impact tool 1 according to the second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, the control method of the first embodiment and the motor 3 are the same, of detecting the tightening torque value TR _m using a peak current I _m is supplied to the motor 3 after impact is However, the detection is made by using the degree of decrease in the rotational speed of the motor 3 after the impact. 10, after the lapse time t _a after striking is performed at the time of the arrow 87c, the arithmetic unit 51 to pause the driving of the motor 3 by the time t _b. At this time, the arithmetic unit 51 monitors the drop in the rotational speed of the motor 3 during the time course of this t _b, calculates an inclination .DELTA.N ₁ rotational speed curve.

This slope ΔN ₁ indicates that the drive current continues to flow for a short time after the impact, and indicates the degree of decrease in the rotational speed of the motor 3 immediately after the drive current is stopped. A large slope ΔN ₁ means a large tightening torque due to impact. Means that. The inventors' experiments have shown that the tightening torque value TR _m is almost inversely proportional to the slope ΔN _m, and the tightening torque value TR _m at the m-th hit in the intermittent drive mode (2) is
TR _m = −α · ΔN _m (where α is a proportional constant, m = 1, 2,..., N)
It can be expressed as The torque value TR _m serves as a reference for setting the rest time P _{m + 1} after the next reverse current and the forward drive time D _{m + 1} to apply the forward current. The torque value TR _m is based on the obtained torque value TR _m . In addition, a pause time P _{m + 1} and a normal rotation drive time D _{m + 1} are set. This setting method may be calculated by a predetermined calculation formula, but a storage device (not shown) in the calculation unit 51 uses the relationship between the torque value TR _m , the pause time P _{m + 1} , and the normal rotation drive time D _{m + 1} as a data table in advance. It is good to store in.

Next, immediately after measuring the obtained slope ΔN ₁ (arrow 87d), the calculation unit 51 supplies the negative drive signal 84c so as to reach a predetermined reverse rotation speed, for example, −3000 rpm. Then, the rotation speed of the motor 3 reaches a predetermined reverse rotation speed indicated by an arrow 87e, and then the supply of the drive signal 84c is stopped. The dwell time P ₂ of the case, determined by the torque value TR ₁ clamped obtained during the first blow. Here, the m-th pause time P _m is preferably increased as the tightening torque value TR _m−1 is increased. That downtime to increase the P _m means that the range extending from FIG. 8 (2) (3), a period in which the hammer 41 is reversely rotated by inertia becomes longer, as a result, the inversion angle of the hammer 41 Becomes larger and the reverse position is on the rear side. An increase in the angle of reversal of the hammer 41 increases the run distance of the next hit, and therefore the rotational speed in the positive direction when the hammer 41 hits the anvil 46 increases, and a larger tightening torque value TR _m is generated. Can be made.

Motor 3 is accelerated in the positive direction from the point of the arrow 87f, the point of the arrow 87 g, the rotational speed or at time T ₆ strikes the anvil 46 as well as reach the peak. This after striking is performed, similarly to the time of the first strike, after a lapse of time t _a, the arithmetic unit 51 to pause the driving of the motor 3 by the time t _b. At this time, the arithmetic unit 51, a drop degree of the rotational speed of the motor 3 in this t _b time monitoring, calculates an inclination .DELTA.N ₂ rotational speed curve. Hereinafter, repeating the same operation, the third strike at time T _7, the fourth striking at time T ₈ are performed. In addition, a tightening torque value TR _m is calculated at the time of each hit, and a pause time P _{m + 1} is determined. Then, the motor 3 is stopped when the worker releases the trigger operation at time T9.

Next, the control procedure in the intermittent drive mode (2) of the impact tool 1 according to the second embodiment of the present invention will be described using the flowchart of FIG. First, when driving in the intermittent drive mode (1) shown in FIG. 9 is completed, the mode is shifted to the intermittent drive mode (2) (step 131). In the intermittent drive mode (2), as shown in FIG. 10, the current is passed in the order of rest → reverse current → pause → forward current to cause the hammer 41 to collide with the anvil 46. Next, it is detected whether or not a hit has been detected. If not, the process returns to step 131. If a hit is detected, the process waits until _a predetermined time ta has elapsed (step 133). When the predetermined time t _a has passed, stopping the supply of the forward current to the motor 3 starts detecting the rotation angle Δθ of the motor 3 (step 134). The rotation angle Δθ can be detected by the rotor position detection circuit 54 using a rotation position detection element 58 (see FIG. 6) provided in the motor 3.

Next, stop the supply of the forward rotation current to the motor 3 until the time t _b elapses, by detecting the rotation angle of the motor 3, to obtain the rotational angle [Delta] [theta], fall degree of the rotation speed of the motor 3 calculating a .DELTA.N _m indicating the. As described above, the tightening torque value can be calculated from this ΔN _m . Next, in step 136, it is determined whether the set tightening torque has been reached or whether the operator has turned off the trigger switch 8 (step 136). If the tightening torque has been reached, or the trigger switch 8 is turned off. If it is determined that the motor 3 has stopped, the rotation of the motor 3 is stopped (step 141), and the tightening operation is terminated.

If none of the above applies in step 136, the process proceeds to step 137, and it is further determined whether or not the pause time t _b has elapsed (that is, time t _a + t _b has elapsed since the hit was detected). Then, it waits (step 137). If rest time t _b has elapsed, it supplies the reverse current to the motor 3, thereby reversely rotating the motor 3 (step 138). Constant current control is also performed for the reverse current. Next, it is detected whether or not the rotation speed of the motor 3 has reached a predetermined reverse rotation speed (for example, −3000 rpm). If not, the process waits until it reaches (step 139). When it has been reached, from the tightening torque value TR _m obtained in step 135, the rest time P _{m + 1} , the normal rotation drive time D _{m + 1} , and the constant current control value in the next normal rotation drive are calculated, and the process returns to step 131. (Step 140). Here, the constant current control value in the next forward rotation is increased when the obtained ΔN _m is large, and is decreased when it is small. The relationship between the constant current control value and the rotation angle ΔN _m is stored in a data table format in advance in a storage device (not shown) in the calculation unit 51, or
Constant current control value = k · Δθ (where k is a proportional constant)
You may make it calculate by.

  As described above, according to the second embodiment, since the decrease in the rotational speed of the motor immediately after the impact is detected and the magnitude of the tightening torque due to the impact is calculated from the decrease rate, a separate torque detection device such as a strain sensor is provided. The torque detecting means can be realized without using it, the tightening load can be detected for each impact and reflected in the control of the motor, and the tightening operation can be performed with high accuracy. The magnitude of the tightening torque may be configured not only to detect a decrease in the rotational speed of the motor but also to detect the magnitude of the tightening torque due to the anvil based on the amount of the rotational angle of the motor.

  As mentioned above, although this invention was demonstrated based on the Example, this invention is not limited to the above-mentioned Example, A various change is possible within the range which does not deviate from the meaning.

1 Impact tool 3 Motor 3a (Motor) rotor 3b (Motor) stator
3c (Motor) Permanent Magnet 3d Insulating Member 3e (Motor) Coil 5 Case 6 Housing 6a (Housing) Body 6b (Housing) Grip 6c (Housing) Battery Holding Unit 7 Substrate 8 Trigger Switch 8a Trigger Operation Part 9 Control circuit board 10 Switching element 11 Cover 12 LED light 14 Forward / reverse switching lever 15 Sleeve 16a Metal bearing 16b Bearings 17a and 17b Bearing 18 Cooling fan
19 (motor) rotating shaft 20 screw boss 21 planetary gear reduction mechanism 21a sun gear 21b planetary gear 21c rotating shaft 21d outer gear 22 inner cover 23 O-ring 26a, 26b air intake 26c slit 30 battery pack 30a release button 31 control panel 32 Button switch (pulse mode / drill mode switch)
33 Belt hook 34 Strap 40 Impact mechanism 41 Hammer 41a Fitting shaft 41b Main body portion 41c, 41d Blade portion 42 Projection portion 42a, 42b Impact surface 43 Projection portion 43a, 43b Impact surface 44a, 44b Disc portion 44c Connection portion 44d Through hole 44e Cylindrical part 44f Space 45 Fitting shaft 46 Anvil 46a Mounting hole 46b Body part 46c, 46d Blade part 46f Fitting hole 47 Projection part 47a, 47b Impact surface 48 Projection part 48a, 48b Impact surface 50 Control part 51 Calculation part 52 Inverter circuit 53 Control signal output circuit 54 Rotor position detection circuit 55 Rotation speed detection circuit 56 Impact impact detection sensor 57 Impact impact detection circuit 58 Rotation position detection element 59 Current detection circuit 60 Switch operation detection circuit 61 Applied voltage setting circuit 62 Rotation direction Setting circuit

Claims (10)

An impact tool having a motor, a hammer connected to the motor, and an anvil hit by the hammer,
By hitting the hammer against the anvil by driving the motor alternately forward and reverse,
Detecting the magnitude of the load caused by the impact,
When driving the motor forward or reverse, a pause section is provided,
An impact tool characterized by changing a length of a resting section between reverse rotation and forward rotation of the motor according to the detected magnitude of the load . 2. The impact tool according to claim 1, wherein the magnitude of the drive current to the motor is changed according to the magnitude of the load . The impact tool according to claim 2 , wherein the drive current is changed by changing an applied voltage supplied to the motor. The motor is a brushless DC motor;
Having an inverter circuit for driving the motor;
The impact tool according to claim 3 , wherein the applied voltage is changed by changing a duty ratio of PWM control in the inverter circuit.   The impact tool according to claim 3 or 4, wherein a reverse rotation angle of the hammer is changed according to the detected magnitude of the load.   6. The impact tool according to claim 5, wherein the reverse rotation angle of the hammer is increased as the detected magnitude of the load increases.   The impact tool according to claim 6, wherein the reverse rotation angle of the hammer is adjusted according to a length of a pause section after the reverse rotation is driven.   The impact tool according to claim 6, wherein a reverse rotation angle of the hammer is changed by changing an applied voltage during reverse rotation of the motor. An impact tool comprising: a motor; a hammer connected to the motor; and an anvil that is struck by the hammer by alternately driving the motor forward and backward.
Detecting the magnitude of the load caused by the impact,
An impact tool, wherein a reverse rotation angle of the motor is controlled in accordance with a magnitude of the load. When the load is small, reduce the reverse rotation angle,
The impact tool according to claim 9, wherein the reverse rotation angle is increased when the load is large.

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