JP2009072888A - Impact tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an impact tool such as an impact driver and an impact wrench. <P>SOLUTION: The impact driver 100 includes: a motor 1; a spindle 11 rotated by the motor 1; a rotary impact mechanism section 10 generating striking power applied to the axial direction of the spindle to strike an end tool and transmitting the rotational force of the spindle 11 and striking power to the end tool; a current detection circuit 32 detecting a current value flowing into the motor 1; and a control signal output circuit 37 controlling the current value flowing into the motor 1. When the current detection circuit 32 detects a current value exceeding a predetermined value, the control signal output circuit 37 lowers the current value flowing into the motor 1 over a first predetermined period before and after generating the striking power by the rotary impact mechanism section 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an impact tool such as an impact driver or an impact wrench.

Impact tools use a battery pack as a power source, drive a rotary impact mechanism using a motor as a drive source, and apply rotation and impact to the anvil to intermittently transmit the rotary impact force to the tip tool to perform operations such as screw tightening Is to do. (For example, refer to Patent Document 1). Conventionally, as a motor used as a drive source, a DC motor provided with a brush and a commutator has been widely used. However, an attempt has been made to use a brushless DC motor instead. A brushless DC motor is excellent in torque characteristics as compared with a DC motor with a brush, and can tighten a screw, a bolt, or the like on a workpiece by a stronger force.
JP 2002-46078 A

  However, in the tightening work for hard members such as bolts and nuts, the hammer and the anvil impact reaction force is large, and the driving force of the brushless DC motor is applied, and the hammer is greatly retracted. . If the amount of retraction of the hammer is excessive, there is a problem that the impact force due to the collision with the mechanism portion facing the hammer increases and the mechanism portion is damaged.

  In view of such circumstances, the present invention is intended to provide an impact tool that enables a tightening operation with a large torque and that does not cause damage to a mechanism portion facing a hammer when a rotational impact force is generated. .

  In order to achieve the above object, an impact tool of the present invention generates an impact force that strikes a tip tool by acting in an axial direction of the electric motor, a spindle rotated by the electric motor, and an axial direction of the spindle, A rotary impact mechanism that transmits the rotational force and impact force of the spindle to the tip tool, current detection means for detecting the current value flowing through the electric motor, and current control means for controlling the current value flowing through the electric motor. And when the current detection means detects a current value exceeding a predetermined value, the current control means is applied to the electric motor over a first predetermined period before and after the rotational impact mechanism portion generates a striking force. It is characterized by lowering the value of flowing current.

  According to such a configuration, when the current detection unit detects a current value exceeding a predetermined value, the current control unit is the electric motor over the first predetermined period before and after the rotation impact mechanism unit generates the striking force. Since the value of the current flowing through the coil is lowered, it is possible to prevent an excessive striking force from being generated, thereby preventing the spindle from retreating excessively and colliding with the barrier to be damaged.

  Further, it further comprises a rotation speed detection means for detecting the rotation speed of the electric motor, and a minimum rotation speed detection means for detecting a minimum rotation speed from the rotation speed of the electric motor detected by the rotation speed detection means, When the minimum rotation speed detecting means detects the minimum rotation speed, it is preferable that the first predetermined period starts after a second predetermined period has elapsed since the detection of the minimum rotation speed.

  According to such a configuration, it is possible to reliably detect the time until the hitting force is generated by detecting the minimum rotation speed.

  Further, when the current detection unit detects a current value exceeding the predetermined value a predetermined number of times, it is preferable that the current control unit lowers a current value flowing through the electric motor.

  According to such a configuration, it is possible to reliably detect that an excessive striking force is generated.

  The electric motor is preferably a brushless DC motor.

  According to such a structure, a screw, a volt | bolt, etc. can be fastened to a to-be-processed member with stronger force.

  In addition, an impact tool according to another aspect of the present invention generates an impact force that hits a tip tool by acting in an axial direction of the electric motor, a spindle rotated by the electric motor, and an axial direction of the spindle. A rotary impact mechanism for transmitting a rotational force and a striking force to the tip tool, a current detecting means for detecting a current value flowing through the electric motor, a current control means for controlling a current value flowing through the electric motor, and the electric motor Time measuring means for measuring the time during which current is flowing, and when the current detecting means detects a current value exceeding a predetermined value during a first predetermined period timed by the time measuring means, Performing a current value reduction process for reducing the value of the current flowing through the electric motor by the current control means over a first predetermined period before and after the rotational impact mechanism portion generates a striking force; When the current value reduction process is not executed during the first predetermined period timed by the time measuring means, the current value reduction process is not executed after the first predetermined period has elapsed. Yes.

  According to such a configuration, when the current value reduction process is not executed during the first predetermined period timed by the time measuring means, the current value reduction process is not executed after the first predetermined period has elapsed. For example, in the case of driving a screw into a wood or the like for which current value reduction processing is not desirable, the screw can be reliably driven into the wood or the like.

  Further, it further comprises a rotation speed detection means for detecting the rotation speed of the electric motor, and a minimum rotation speed detection means for detecting a minimum rotation speed from the rotation speed of the electric motor detected by the rotation speed detection means, When the minimum rotation speed detecting means detects the minimum rotation speed, it is preferable that the first predetermined period starts after a second predetermined period has elapsed since the detection of the minimum rotation speed.

  According to such a configuration, it is possible to reliably detect the time until the hitting force is generated by detecting the minimum rotation speed.

  Further, when the current detection unit detects a current value exceeding the predetermined value a predetermined number of times, it is preferable that the current control unit lowers a current value flowing through the electric motor.

  According to such a configuration, it is possible to reliably detect that an excessive striking force is generated.

  The electric motor is preferably a brushless DC motor.

  According to such a structure, a screw, a volt | bolt, etc. can be fastened to a to-be-processed member with stronger force.

  In addition, an impact tool according to another aspect of the present invention generates an impact force that hits a tip tool by acting in an axial direction of the electric motor, a spindle rotated by the electric motor, and an axial direction of the spindle. A rotary impact mechanism for transmitting a rotational force and a striking force to the tip tool, a current detecting means for detecting a current value flowing through the electric motor, a current control means for controlling a current value flowing through the electric motor, and the electric motor A rotation speed detecting means for detecting the rotation speed of the rotary tool, and a hitting interval detecting means for detecting a hitting interval at which the rotary impact mechanism hits the tip tool. When a current value exceeding the value is detected, the current control means flows to the electric motor over a period before and after the rotational impact mechanism generates a striking force. Run the current reduction process of reducing the current value, in response to said strike distance detecting means striking interval detected by, is characterized in that to change the length of time before and after the rotating impact mechanism to generate a striking force.

  According to such a configuration, since the period before and after the rotary impact mechanism unit generates the striking force is changed according to the striking interval detected by the striking interval detecting means, it seems that the non-uniform striking force is generated. In some cases, they can be rectified, thereby preventing the spindle from being excessively retracted and colliding with the barrier and causing damage.

  Further, when the hit interval detected by the hit interval detecting means is longer than the reference interval, the period before and after the rotary impact mechanism portion generates the hitting force is made longer than the reference time, and conversely, the hit interval detecting means Is shorter than the reference interval, it is preferable that the period before and after the rotational impact mechanism portion generates the impact force be shorter than the reference time.

  According to such a configuration, the non-uniform hitting force can be corrected more easily.

  The striking interval detection means includes a minimum rotation speed detection means for detecting a minimum rotation speed from the rotation speed of the electric motor detected by the rotation speed detection means, and the electric motor detected by the rotation speed detection means. A maximum rotation number detecting means for detecting a maximum rotation number from the rotation number of the rotation impact mechanism unit according to the time from the timing at which the maximum rotation number is detected to the timing at which the minimum rotation number is detected It is preferable to change the period before and after generating the striking force.

  According to such a configuration, it is possible to reliably detect the hitting interval by detecting the time from the timing at which the maximum rotational speed is detected to the timing at which the minimum rotational speed is detected.

  Further, when the current detection unit detects a current value exceeding the predetermined value a predetermined number of times, it is preferable that the current control unit lowers a current value flowing through the electric motor.

  According to such a configuration, it is possible to reliably detect that an excessive striking force is generated.

  The electric motor is preferably a brushless DC motor.

  According to such a structure, a screw, a volt | bolt, etc. can be fastened to a to-be-processed member with stronger force.

  According to the impact tool of the present invention, it is possible to prevent the spindle from retreating excessively and colliding with the barrier to be damaged.

  Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a structural diagram showing the entire electric tool when the present invention is applied to a cordless type impact driver, FIG. 2 is an operation explanatory view of a rotary impact mechanism, and FIG. 3 is a motor of an electric tool constituted by a brushless DC motor. It is a block diagram without closing the composition of a drive part.

  First, the configuration of the impact driver 100 according to the embodiment of the present invention will be described with reference to FIG. The impact driver 100 has one end (right end in the drawing) to the other end (drawing) along the same direction (horizontal axis direction) as the rotation axis of a brushless DC motor 1 (hereinafter referred to as “motor 1”) described later. A tool body including a body housing portion 6 extending to the left end portion of the body housing portion 6 and a handle housing portion 7 depending from the body housing portion 6, and a tip tool holder disposed at the other end portion of the body housing portion 6. Although not shown in the figure, a driver bit (tip tool) for receiving a rotational impact force from the tool body and tightening a screw on the workpiece is detachably attached to the portion 8. Instead of a driver bit, a bolt tightening bit can be mounted as a tip tool.

  A motor 1 serving as a driving source is attached to one end of the body housing portion 6, and a tip tool (not shown) is attached to and detached from a tip tool holding portion 8 that outputs rotational impact force to the other end portion of the body housing portion 6. Can be installed freely.

  A circuit board on which the inverter unit 2 for driving the motor 1 is mounted is mounted on one end side of the body housing unit 6. In the middle part of the body housing part 6, there are a power transmission mechanism part (deceleration mechanism part) 9 for transmitting rotational force in the direction of the rotational axis of the motor 1, a rotational impact mechanism part 10 for giving the rotational impact force, and the rotational impact mechanism part. An anvil 13 that transmits 10 rotational impact forces to the tip tool is mounted.

  A battery pack case 4 accommodating a battery pack 4a serving as a driving power source for the motor 1 is detachably attached to the lower end portion of the handle housing portion 7. A circuit board on which a control circuit unit 3 for controlling the inverter unit 2 of the motor 1 is mounted is provided on the upper part of the battery pack case 4 so as to extend in a direction crossing the paper surface. On the other hand, a trigger switch 15 is disposed at the upper end portion of the handle housing portion 7. The trigger switch 15 protrudes from the handle housing portion 7 while being biased by a spring. As will be described later, the motor 1 can be started by pushing the trigger switch 15 inward in the handle housing portion 7 against the spring force, and the rotation speed of the motor 1 is controlled by adjusting the trigger pushing amount. can do.

  The battery pack 4 a is electrically connected so as to supply drive power to the trigger switch 15 and the control circuit unit (circuit board) 3 and to supply drive power to the inverter unit 2.

  The rotational force of the rotational output shaft of the motor 1 is transmitted through a power transmission mechanism (deceleration mechanism) 9 engaged with the gear teeth of the rotational output shaft 9 to form a spindle 11 constituting a part of the rotational impact mechanism 10. Is transmitted to. The power transmission mechanism (deceleration mechanism) 9 includes a pinion gear (sun gear) 9a and two planetary gears 9b meshing with the pinion gear 9a, which are provided in an inner cover (not shown) in the fuselage housing portion 6. It has been incorporated. The spindle 11 is given a rotational force that is decelerated relative to the rotation of the brushless DC motor 1 by the power transmission mechanism (deceleration mechanism) 9.

  The rotary impact mechanism unit 10 is attached to the spindle 11 to which a rotational force is applied via a power transmission mechanism unit (deceleration mechanism unit) 9 and is engaged with the spindle 11 so as to be movable in the direction of the rotation axis of the spindle 11. A hammer 12 that gives a striking force, and an anvil 13 that rotates with a rotating striking force by the hammer 12 and has a tip tool holding portion 8 are provided. The hammer 12 and the anvil 13 each have two hammer convex portions (striking portions) 12a and two anvil convex portions 13a that are symmetrically arranged at two locations on the plane of rotation, and the hammer convex portion 12a and the anvil. The convex portions 13a are in positions where they mesh with each other in the rotational direction.

  The rotational impact force is transmitted by the engagement of the convex portions 12a and 13a. The hammer 12 is slidable in the axial direction with respect to the spindle 11 in a ring region surrounding the spindle 11, and is urged forward in the axial direction by a spring 14. An inverted V-shaped (substantially triangular) cam groove 12 b is provided on the inner peripheral surface of the hammer 12. On the other hand, a V-shaped cam groove 11 a is provided on the outer peripheral surface of the spindle 11 in the axial direction, and a ball (steel ball) 17 inserted between the cam groove 11 a and the inner peripheral cam groove 12 b of the hammer 12. The hammer 12 rotates through the.

  2A and 2B are diagrams showing the relation between the operation schematic diagram of the rotary impact mechanism 10 and the motor rotation speed. FIG. 2A shows a state in which the hammer 12 is retracted and separated from the convex portion 13a of the anvil 13, and FIG. The state in which the spring 12 is urged by a spring (not shown) while rotating from the retracted state and is moving toward the convex portion 13 a of the anvil 12, (C) is the convex portion of the anvil 13 by the urging force of the spring. It is the figure which showed the state which gave the rotational impact force to 13a and the convex part 12a of the hammer 12 and the convex part 13a of the anvil 13 were engaged.

  When the torque acting between the workpiece and the fastening tool such as a screw is small in the rotary impact mechanism unit 10, the rotational force of the spindle 11 applied from the motor 1 causes the cam of the spindle 11 to clamp the ball 17. It is transmitted to the hammer 12 via the groove 11a and the cam groove 12b of the hammer 12, and the spindle 11 and the hammer 12 begin to rotate together. The spindle 11 and the hammer 12 are relatively twisted, and the hammer 12 is retracted while being compressed while twisting the spring 14 along the cam groove 11a of the spindle (indicated by the arrow shown in FIG. 2A). Direction), when the hammer 12 gets over the height of the anvil projection 13a from the time when the hammer projection 12a is separated from the coupling with the anvil projection 13a, the meshing with the anvil 13 is released (see FIG. 2A). State shown). At this time, the motor rotational speed shows the minimum value. Further, the hammer 12 receives the urging force by the spring 14 and the guide by the cam groove 11a, and advances while rotating (the state shown in FIG. 2B). An impact torque is applied to the anvil projection 13a of the anvil 13 (the state shown in FIG. 2C). As will be described later, this impact torque is transmitted to the driver bit attached to the tip tool holding portion 8 of the anvil 13, and further, the rotational impact torque is transmitted from the driver bit to the fastener screw and screwed into the workpiece. Or tighten. Since the hammer convex portion 12a and the anvil convex portion 13a are again engaged with each other, the hammer 12 starts to move backward again, and the above-described striking operation is repeated.

  Next, the inverter circuit unit 2 and the control circuit unit 3 of the motor 1 will be described with reference to FIG.

  In the present embodiment, the motor 1 is a three-phase brushless DC motor. The motor 1 is an inner rotor type, and a rotor (magnet rotor) 1b configured by embedding a permanent magnet (magnet) including a pair of N poles and S poles, and a rotational position of the magnet rotor 1b are detected. Three rotation position detection elements (Hall ICs) 5a, 5b, 5c arranged every 60 °, and an energization section of a current having an electrical angle of 120 ° based on position detection signals from the rotation position detection elements 5a, 5b, 5c And the armature winding 1d composed of the three-phase windings U, V and W of the star-connected stator 1c controlled by the above. In the present embodiment, the position detection of the rotor 1b of the motor 1 is performed electromagnetically using a Hall IC. However, the induced electromotive voltage (counterelectromotive force) of the stator winding 1d is filtered. It is also possible to adopt a sensorless system that detects the rotor position by taking it out as a logic signal.

  The inverter circuit unit (power converter) 2 is composed of six FETs (hereinafter referred to as “transistors”) Q1 to Q6 connected in a three-phase bridge format and flywheel diodes (not shown). The gates of six bridged transistors Q1 to Q6 are connected to a control signal output circuit 37, and the sources or drains of the six transistors Q1 to Q6 are star-connected armature windings U, V and Connected to W. As a result, the six transistors Q1 to Q6 perform a switching operation according to the switching element drive signal input from the control signal output circuit 37, and the DC voltage of the battery pack 4a applied to the inverter unit 2 is changed to three phases (U Power is supplied to the armature windings U, V, and W as voltages Vu, Vv, and Vw.

  The control circuit unit 3 includes a calculation unit 31, a current detection circuit 32, an applied voltage setting circuit 33, a rotation direction setting circuit 34, a rotation position detection circuit 35, a rotation number detection circuit 36, and a control signal output circuit 37. . Although not shown, the calculation unit 31 is a CPU for outputting a drive signal based on a processing program and data, a ROM for storing programs and control data corresponding to flowcharts to be described later, and for temporarily storing data. The microcomputer includes a RAM, a timer, and the like. The current detection circuit 32 is a circuit for detecting the motor current flowing through the motor 1, and the detected current is input to the calculation unit 31.

  The applied voltage setting circuit 33 is a circuit for setting the applied voltage of the motor 1, that is, the duty ratio of the PWM signal, in response to the pressing amount of the trigger switch 15. The rotation direction setting circuit 11 is a circuit for setting the rotation direction of the motor 1 by detecting an operation of forward rotation or reverse rotation by the forward / reverse switching lever 16 of the motor. The rotational position detection circuit 12 detects the relative position between the rotor 1b and the armature windings U, V, and W of the stator 1c based on the output signals of the three rotational position detection elements 5a, 5b, and 5c. Circuit. The rotation speed detection circuit 36 is a circuit that detects the motor rotation speed based on the number of detection signals from the rotor position detection circuit 35 counted within a unit time.

  The control signal output circuit 37 supplies a PWM signal to the power supply side transistors Q1 to Q6 based on the output from the calculation unit 31. By controlling the pulse width of the PWM signal, the number of revolutions of the motor 1 in the rotational direction set by adjusting the power supplied to each armature winding U, V, W can be controlled.

  Next, control of the impact driver 100 according to the first embodiment will be described with reference to FIGS. 4, 5A, and 5B. FIG. 4 is a time chart showing the relationship between the striking torque T, the motor current I, and the motor rotation speed N. FIGS. 5A and 5B show the motor 1 before and after striking with the hammer 12. It is a flowchart of the control which decreases the rotation speed.

  First, the relationship between the impact torque, the motor current, and the motor rotation speed will be described with reference to FIGS. FIG. 4 is a time chart showing the relationship between the impact torque T, the motor current I, and the motor rotational speed N.

  When the hammer 12 is engaged with the anvil convex portion 13a of the anvil 13, the load applied to the motor 1 is maximized. Therefore, as shown in FIG. 4, the rotational speed N of the motor 1 is minimized ((A)). On the other hand, when the load on the motor 1 is maximized, the motor current I is maximized ((B)). Thereafter, when the hammer 12 rides on the anvil projection 13a of the anvil 13, the load in the rotational direction of the motor 1 decreases, and when the hammer 12 gets over the anvil projection 13a of the anvil 13 and the engagement between the two is released (FIG. 2 ( A) to (C)), the load applied to the motor 1 is minimized, and the rotational speed N of the motor 1 is maximized ((C)). On the other hand, when the load applied to the motor 1 is minimized, the motor current I is minimized ((D)). The hammer 12 is struck at the timing when the rotational speed N of the motor 1 becomes maximum and the motor current I becomes minimum ((E)).

  Here, as in the present embodiment, when a motor having a large driving force such as a brushless motor is used, the hammer hits excessively, so that the hammer rides over the convex part of the anvil. It may retreat and hit the opposite barrier as it is, breaking the barrier. Therefore, in the present embodiment, the rotational speed of the motor 1 is decreased before and after the hammer 12 is hit.

  In the flowcharts of FIGS. 5A and 5B, first, it is determined whether the PWM duty of the motor control is 100% (S501). This is because the excessive retraction of the hammer 12 as described above is a phenomenon that usually occurs when the trigger switch 15 is pulled to the maximum, that is, when the PWM duty is 100%.

  If the PWM duty is not 100% (S501: NO), it continues to determine whether the PWM duty is 100%. When the PWM duty is 100% (S501: YES), it is subsequently determined whether or not the motor current I is 35 A or more (S502). In the present embodiment, the threshold value is set to 35 A as a current value that may cause excessive retraction of the hammer 12, but other values may be used.

  When the motor current I is smaller than 35A (S502: NO), it is continuously determined whether or not the motor current I is 35A or more. When the motor current I is 35 A or more (S502: YES), a timer for time Ta (10 msec) is started (S503) (see FIG. 4), and it is determined again whether the motor current I is 35 A or more ( S504).

  When the motor current I is 35 A or more (S504: YES), CNT1 is counted up (S505), and then it is determined whether or not time Ta (10 msec) has elapsed (S506). If the motor current I is smaller than 35 A (S504: NO), it is determined whether the time Ta (10 msec) has elapsed without counting up the CNT1 (S506). In this way, the number of times that the motor current I detected within a predetermined time (10 msec in the present embodiment) is equal to or greater than the threshold 35A is counted.

  When the time Ta (10 msec) has not elapsed (S506: NO), after the elapse of the 1 msec interval (S507), the process returns to S504 to determine again whether or not the motor current I is 35 A or more. If the time Ta (10 msec) has elapsed (S506: YES), it is determined whether CNT1 is greater than 5 (S508).

  When CNT1 is 5 or less (S508: NO), the process returns to S502, and it is determined again whether or not the motor current I is 35A or more. If CNT1 is greater than 5 (S508: YES), CNT2 is counted up (S509), and then it is determined whether CNT2 is greater than 5 (S510). When CNT2 is 5 or less (S510: NO), the process returns to S502, and it is determined again whether or not the motor current I is 35 A or more. As described above, after the determination that the motor current I detected in S503 to S507 was more than 5 times and the threshold value 35A or more (S508) is performed 5 times, the rotational speed of the motor 1 described below is decreased. Start control.

  If CNT2 is greater than 5 (S510: YES), then the maximum value Nmax of the motor rotation speed N is determined (S511) (see FIG. 4). In the present embodiment, the motor rotation speed N is detected every 1 msec. When the detection result is larger than the previous detection result, the maximum value is updated, and the updated value after four detections is set as the maximum value Nmax. decide. Thereby, the timing of hitting by the hammer 12 is detected.

  Subsequently, the minimum value Nmin of the motor rotation speed N is determined (S512) (see FIG. 4). In the present embodiment, the motor rotation speed N is detected every 1 msec. When the detection result is smaller than the previous detection result, the minimum value is updated, and the minimum value after four detections is set as the minimum value Nmin. decide. Thereby, the timing at which the hammer 12 engages with the anvil projection 13a, that is, the timing immediately before the hammer 12 rides on the anvil projection 13a is detected.

  Subsequently, a timer at time Tb (7 msec) is started (S513), and it is determined whether time Tb (7 msec) has elapsed (S514) (see FIG. 4). If the time Tb (7 msec) has not elapsed (S514: NO), it is subsequently determined whether or not the time Tb (7 msec) has elapsed. Here, the time Tb (7 msec) is not limited to 7 msec as long as it is shorter than the period from the timing at which the hammer 12 is engaged with the anvil projection 13a to the timing at which the hammer 12 is hit. Thus, the motor 1 is driven at a PWM duty of 100% until slightly before the timing when the hammer 12 is hit.

  If Tb (7 msec) has elapsed (S514: YES), a timer for time Tc (6 msec) is started (S515), and then the PWM duty is reduced to 70% (S516) (see FIG. 4). ). Here, the time Tc (6 msec) is not limited to 6 msec as long as it includes the timing at which the hammer 12 is hit. As a result, the motor 1 is driven with a PWM duty of 70% before and after the timing at which the hammer 12 strikes.

  Thereafter, it is determined whether or not the time Tc (6 msec) has elapsed (S517) (see FIG. 4). If the time Tc (6 msec) has not elapsed (S517: NO), it is subsequently determined whether or not the time Tc (6 msec) has elapsed, and if the time Tc (6 msec) has elapsed ( (S517: YES), the PWM duty is returned to 100% (S518).

  With such a configuration, the PWM duty of the motor control is reduced before and after the timing at which the hammer 12 strikes, that is, the number of revolutions of the motor 1 is reduced, so that excessive hammering by the hammer 12 is prevented. 12 is prevented from excessively retracting and colliding with the barrier to be damaged.

  Next, control of the impact driver 100 according to the second embodiment of the present invention will be described with reference to FIGS. 6, 7A and 7B. FIG. 6 is a time chart showing the relationship between the striking torque T, the motor current I, and the motor rotational speed N. FIGS. 7A and 7B show the motor 1 before and after striking with the hammer 12. It is a flowchart of the control which decreases the rotation speed. In FIGS. 7A and 7B, the same steps as those in the flowcharts of FIGS. 5A and 5B are denoted by the same reference numerals, and only different portions will be described.

  In the second embodiment, after determining that the PWM duty is 100% in S501 of FIG. 7A, the timer of time Tz (300 msec) is started (S701) (see FIG. 6). Thereafter, it is determined whether or not the time Tz (300 msec) has elapsed (S702). If the time Tz (300 msec) has not elapsed (S702: NO), the process proceeds to S502, and FIG. The control described in 5 (b) is performed. If it is determined in S510 that CNT2 is 5 or less, the process returns to S702 again to determine whether or not the time Tz (300 msec) has elapsed. On the other hand, when it is determined that the time Tz (300 msec) has elapsed (S702: YES), it is determined whether or not the time Tz (300 msec) has elapsed. And the control of the content demonstrated in FIG.5 (b) is not performed.

  As described above, in the second embodiment, when the control for reducing the rotation speed of the motor 1 is not started within a predetermined period (300 msec in the present embodiment), the rotation speed of the motor 1 is subsequently increased. Do not control to decrease. For example, when the tip tool is a driver, a screw is driven into wood or the like, and therefore, the driving may be incomplete if the rotation speed of the motor 1 is reduced. However, in the second embodiment, if the control for reducing the rotational speed of the motor 1 is not started within a predetermined period, the control for reducing the rotational speed of the motor 1 is not performed thereafter, so that it is ensured. Screws can be driven into wood.

  Next, control of the impact driver 100 according to the third embodiment of the present invention will be described with reference to FIGS. 8 and 9A to 9C. FIG. 8 is a time chart showing the relationship between the striking torque T, the motor current I, and the motor rotation speed N. FIGS. 9A to 9C show the motor 1 before and after striking with the hammer 12. It is a flowchart of the control which decreases the rotation speed. 9A to 9C, the same steps as those in the flowcharts of FIGS. 7A and 7B are denoted by the same reference numerals, and only different portions will be described.

  In the third embodiment, after determining that CNT2 is larger than 5 in S510 of FIG. 9A, it is determined whether or not the Tc flag is 0 (S901). If the Tc flag is 0 (S901: YES), it is determined whether Td_old4 <Td_old3, Td_old3> Td_old2, Td_old2 <Td_old1, and Td_old1 <Td (S902). Here, Td_old4, Td_old3, Td_old2, and Td_old1 are Td four times before, three times before, two times before, and one time before, respectively. Td will be described later.

  When Td_old4 <Td_old3, Td_old3> Td_old2, Td_old2 <Td_old1, and Td_old1 <Td (S902: YES), after setting the Tc flag to 1 (S904), the motor speed N is set to S511. The maximum value Nmax is determined. In the case of NO in S901 or S902, the process proceeds to S511 as it is, and the maximum value Nmax of the motor rotation speed N is determined.

  That is, the Tc flag is set to 1 only when the original Tc flag is 0, Td_old4 <Td_old3, Td_old3> Td_old2, Td_old2 <Td_old1, and Td_old1 <Td.

  After determining the maximum value Nmax of the motor rotation speed N in S511, the timer is started (S904), and then the minimum value Nmin of the motor rotation speed N is determined (S512). Simultaneously with the determination of the minimum value Nmin of the motor rotation speed N, the timer count is stopped and the count value Td is stored (S905). That is, the count value Td is the time from the maximum value Nmax to the minimum value Nmin of the motor rotation speed N, and the Td stored here is used in the determination of S902. Therefore, “Td_old4 <Td_old3, Td_old3> Td_old2, and Td_old2 <Td_old1, and Td_old1 <T” in S902, the interval between hits by the hammer 12 increases or decreases alternately as shown in the section A of FIG. Means that

  Subsequently, when it is determined in S513 and S514 that the time Tb (7 msec) has elapsed, it is determined whether or not the Tc flag is 1 (S906). If the Tc flag is 1 (S906: YES), it is determined whether or not the previous value of the time Tc is 4 msec (S907). When the previous value of the time Tc is 4 msec (S907: YES), the time Tc is set to 9 msec (S908), and the timer is started (S911). On the other hand, when the previous value of the time Tc is not 4 msec (S907: NO), the time Tc is set to 4 msec (S909), and the timer is started (S911).

  If the Tc flag is not 1 (S906: NO), the time Tc is set to 6 msec (S910), and the timer is started (S911). Simultaneously with the start of the timer in S911, the PWM duty is reduced to 70% (S912), and then it is determined whether or not the time Tc has passed (S913).

  If the time Tc has not elapsed (S913: NO), it is subsequently determined whether or not the time Tc has elapsed. If the time Tc has elapsed (S913: YES), the PWM duty is set to 100. Return to% (S914). Thereafter, it is determined whether or not the time Tx has elapsed (S915). If the time Tx has not elapsed (S915: NO), the process returns to S901 to determine again whether the Tc flag is 0 or not. If the time Tx has elapsed (S915: YES), the Tc flag is set to 0 (S916), and the process returns to S901.

  As described above, in the present embodiment, the subsequent Td is predicted from the increase / decrease pattern of the past Td (battering interval), and the subsequent Td is controlled to be uniform. Therefore, even when the hammer 12 strikes at non-uniform intervals, they can be corrected, and excessive hammering by the hammer 12 can be prevented, whereby the hammer 12 is excessively retracted and becomes a barrier. It prevents it from colliding with and damaging it.

  It should be noted that the impact tool of the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the gist of the present invention.

  The impact tool of the present invention is used for tightening screws such as bolts at work sites.

1 is an overall structural diagram of a power tool according to an embodiment of the present invention. It is the figure which showed the operation | movement schematic of the rotation impact mechanism part in the electric tool shown in FIG. 1, and the figure which showed the relationship between motor rotation speed, (A) is the state which the hammer retracted | separated and removed from the anvil, (B) the hammer retracted The state in which the hammer is urged by a spring (not shown) while rotating and is moving toward the anvil while rotating is shown, and (C) shows the state in which the hammer is engaged by applying a rotational striking force to the anvil by the urging force of the spring. Figure. The functional block diagram which shows the drive control system of the motor in the electric tool shown in FIG. It is a time chart which showed various characteristics at the time of performing drive control by a 1st embodiment of the present invention, (A) is an impact torque characteristic, (B) is a motor current characteristic, (C) is a motor rotation speed. It is a characteristic. The flowchart explaining the drive control by the 1st Embodiment of this invention. The flowchart of the part following the flowchart shown to Fig.5 (a). It is a time chart which showed various characteristics at the time of performing drive control by a 2nd embodiment of the present invention, (A) is an impact torque characteristic, (B) is a motor current characteristic, (C) is a motor rotation speed. It is a characteristic. The flowchart explaining the drive control by the 2nd Embodiment of this invention. The flowchart of the part following the flowchart shown to Fig.7 (a). It is a time chart which showed various characteristics at the time of performing drive control by a 3rd embodiment of the present invention, (A) is an impact torque characteristic, (B) is a motor current characteristic, (C) is a motor rotation speed. It is a characteristic. The flowchart explaining the drive control by the 3rd Embodiment of this invention. The flowchart of the part following the flowchart shown to Fig.9 (a). FIG. 10 is a flowchart of a portion following the flowchart shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Impact driver 1 Brushless DC motor 2 Inverter part 3 Control circuit part 31 Calculation part 32 Current detection circuit 33 Applied voltage setting circuit 34 Rotation direction setting circuit 35 Rotation position detection circuit 36 Rotation number detection circuit 37 Control signal output circuit 4 Battery pack case 4a Battery pack 5a, 5b, 5c Rotation position detection element (Hall IC)
6 Body housing part 7 Handle housing part 8 Tip tool holding part 9 Power transmission mechanism part (deceleration mechanism part)
DESCRIPTION OF SYMBOLS 10 Rotation impact mechanism part 11 Spindle 12 Hammer 13 Anvil 14 Spring 15 Trigger switch 16 Forward / reverse switching lever 17 Ball (steel ball)

Claims (13)

An electric motor;
A spindle rotated by the electric motor;
A rotational impact mechanism that acts in the axial direction of the spindle to generate a striking force that strikes the tip tool, and transmits the rotational force and striking force of the spindle to the tip tool;
Current detection means for detecting a current value flowing through the electric motor;
Current control means for controlling a current value flowing through the electric motor,
When the current detection means detects a current value exceeding a predetermined value, the current value that the current control means flows through the electric motor over a first predetermined period before and after the rotational impact mechanism portion generates a striking force. Impact tool characterized by lowering.   A rotation number detection means for detecting the rotation number of the electric motor; and a minimum rotation number detection means for detecting a minimum rotation number from the rotation number of the electric motor detected by the rotation number detection means. 2. The first predetermined period starts after a second predetermined period has elapsed since the detection of the minimum rotational speed by the rotational speed detection means. Impact tool.   3. The impact according to claim 1, wherein, when the current detection unit detects a current value exceeding the predetermined value a predetermined number of times, the current control unit decreases a current value flowing through the electric motor. tool.   The impact tool according to claim 1, wherein the electric motor is a brushless DC motor. An electric motor;
A spindle rotated by the electric motor;
A rotational impact mechanism that acts in the axial direction of the spindle to generate a striking force that strikes the tip tool, and transmits the rotational force and striking force of the spindle to the tip tool;
Current detection means for detecting a current value flowing through the electric motor;
Current control means for controlling a current value flowing through the electric motor;
Time measuring means for measuring the time during which current flows in the electric motor,
When the current detecting means detects a current value exceeding a predetermined value during the first predetermined period timed by the time measuring means, during the first predetermined period before and after the rotational impact mechanism portion generates a striking force. When the current control means executes a current value reduction process for reducing the current value flowing through the electric motor, and the current value reduction process is not executed during the first predetermined period timed by the time measuring means. The impact tool is characterized in that the current value reduction process is not executed after the first predetermined period has elapsed.   A rotation number detection means for detecting the rotation number of the electric motor; and a minimum rotation number detection means for detecting a minimum rotation number from the rotation number of the electric motor detected by the rotation number detection means. 6. The first predetermined period starts after a second predetermined period elapses after the minimum rotational speed is detected by the rotational speed detection means. Impact tool.   7. The impact according to claim 5, wherein when the current detection unit detects a current value exceeding the predetermined value a predetermined number of times, the current control unit decreases the value of the current flowing through the electric motor. tool.   The impact tool according to claim 5, wherein the electric motor is a brushless DC motor. An electric motor;
A spindle rotated by the electric motor;
A rotational impact mechanism that acts in the axial direction of the spindle to generate a striking force that strikes the tip tool, and transmits the rotational force and striking force of the spindle to the tip tool;
Current detection means for detecting a current value flowing through the electric motor;
Current control means for controlling a current value flowing through the electric motor;
A rotational speed detection means for detecting the rotational speed of the electric motor;
An impact interval detection means for detecting an impact interval at which the rotary impact mechanism hits the tip tool; and
When the current detection means detects a current value exceeding a predetermined value during a predetermined period, the current control means supplies a current that flows to the electric motor over a period before and after the rotational impact mechanism portion generates a striking force. A current value reduction process for lowering the value is executed, and a period before and after the rotary impact mechanism unit generates a striking force is changed according to the striking interval detected by the striking interval detecting means. Impact tool.   When the hitting interval detected by the hitting interval detecting means is longer than the reference interval, the period before and after the rotary impact mechanism generates the hitting force is made longer than the reference time, and conversely, the hitting interval detecting means detects The impact tool according to claim 9, wherein when the hitting interval is shorter than a reference interval, a period before and after the rotary impact mechanism generates the hitting force is shorter than a reference time.   The hitting interval detection means includes a minimum rotation speed detection means for detecting a minimum rotation speed from the rotation speed of the electric motor detected by the rotation speed detection means, and a rotation of the electric motor detected by the rotation speed detection means. A maximum rotation number detecting means for detecting a maximum rotation number from the number, and the impact of the rotation impact mechanism unit hits according to the time from the timing when the maximum rotation number is detected to the timing when the minimum rotation number is detected The impact tool according to claim 9 or 10, wherein a period before and after generating the force is changed.   12. The current control unit according to claim 9, wherein when the current detection unit detects a current value exceeding the predetermined value a predetermined number of times, the current control unit decreases a current value flowing through the electric motor. Impact tool as described in   The impact tool according to claim 9, wherein the electric motor is a brushless DC motor.

Images