JP6984742B2 - Electric tool - Google Patents

Description

The present invention relates to a power tool.

As an electric tool for tightening screws, etc., the rotary striking mechanism is driven by a motor, and by applying rotation and striking to the anvil, the rotational striking force is intermittently transmitted to the tip tool to perform work such as screw tightening. Power tools such as tools are known. Impact tools can achieve high tightening torque despite their small size and light weight, but if the target material for tightening the screws is a soft material such as gypsum board, tightening the wood screws will cause the screw heads to sink deeply from the surface of the gypsum board due to overtightening. There is a high risk of screwing, and in the worst case, it may penetrate the gypsum board. If you make such a mistake, you need to reattach the entire gypsum board that you were working on. Gypsum board (or plasterboard) is a building material made from gypsum-based material in the form of a plate and wrapped in special paperboard, and is most often used for indoor walls and ceilings. Gypsum board has excellent fire resistance in addition to its high heat insulating and sound insulating properties. When fixing gypsum board on plywood with wood screws, a dedicated "board driver" is often used as an electric tool for tightening the wood screws. As in Patent Document 1, the board driver arranges a stopper ring around the bit at the tip, and the screw head of the wood screw reaches the tip of the stopper ring, that is, the same position as the surface of the gypsum board. It is possible to always tighten the wood screws to the optimum position by automatically blocking the transmission of power by the motor.

Japanese Unexamined Patent Publication No. 9-174448

When performing screw tightening work on gypsum board in this way, a dedicated "board driver" is used, but if it is troublesome to prepare a "board driver" such as reworking a part of gypsum board, it is convenient. You may want to finish the work with a certain impact driver (impact tool). In such a case, the worker paid attention to the trigger operation of the impact driver and worked not to overtighten the wood screw. Therefore, there has been a demand for easy tightening work on gypsum board while using an impact driver.

The present invention has been made in view of the above background, and an object of the present invention is to facilitate screw tightening work by using a power tool regardless of the hardness of the target material. Another object of the present invention is to provide a power tool in which a mode for tightening a screw to a soft mating material is added to one of the operation modes. Yet another object of the present invention is to provide an electric tool that allows the motor to be stopped before the screw head penetrates the gypsum board. Still another object of the present invention is to provide a power tool with an additional automatic tightening mode for performing additional tightening on a screw in the middle of tightening.

The following is a description of typical features of the invention disclosed in the present application. According to one feature of the present invention, the motor, the trigger for adjusting the start and rotation of the motor, the striking mechanism rotated by the motor, the output shaft connected to the striking mechanism and tightening the screw, and the motor. In an electric tool having a current detection circuit for detecting a flowing current, a motor, a trigger, and a control device connected to the current detection circuit to control the rotation of the motor, the control device detects the motor by the current detection circuit. It is configured to detect the impact by the striking mechanism and the seating of the screw by the change of the current, and when the operator operates the trigger, the motor is rotated, and the screw is used as the mating material in the state where the impact by the striking mechanism is not detected. It was configured to rotate the motor so that it would be tightened to, and stop the rotation of the motor when the screw was seated in a state where the impact by the impact mechanism was not detected. Here, the mating material has a soft first material such as gypsum board and a second material provided as a base for the soft first material and harder than the first material, and the screw is inserted in a state where the striking mechanism does not hit. Even when tightened to the first material and the second material, the rotation of the motor is stopped when the screw is seated. By detecting the seating of the screw and stopping the motor before the striking by the striking mechanism is started, it is possible to prevent the head of the screw from accidentally penetrating a soft mating material such as gypsum board. In the power tool, in addition to the first mode (for example, impact mode) in which the motor rotates when the operator's trigger is operated and the striking mechanism strikes and tightens the screw to the mating material, the motor is operated when the operator operates the trigger. It is configured to provide a second mode (for example, gypsum board mode) in which the screw is tightened to the mating material while rotating and the striking mechanism does not strike, and the rotation of the motor is stopped when the screw is seated. Further, it has a current detection circuit that detects the current flowing through the motor, and in the second mode, the control device triggers when the amount of change in the current detected by the current detection circuit per predetermined time exceeds the seating stop threshold. The rotation of the motor is stopped regardless of the operation.

According to another feature of the present invention, in an electric tool having a striking mechanism rotated by a motor, a control device for controlling the rotation of the motor, and a current detection circuit for detecting the current flowing through the motor, the control device outputs. The current value flowing through the motor immediately after the start of rotation of the shaft is detected for each unit time, the first-order differential value and second-order differential value for the unit time are calculated from the current values of the latest multiple units, and the rotation of the motor is calculated from the current value. The seating stop threshold for stopping the motor is calculated, and when the seating stop threshold calculated using the second-order differential value is exceeded, the rotation of the motor is stopped regardless of the operation of the trigger. The seating stop threshold is set based on the current flowing through the motor detected by the current detection circuit immediately after the start of rotation of the output shaft. Further, the seating stop threshold value is calculated by using a linear equation so that the current value measured from the start of rotation of the output shaft to the seating stop of stopping the rotation of the motor is smaller as it is larger and larger as it is smaller. To. Specifically, THS, which is the seating stop threshold, measures the current value I from the start of rotation of the output shaft, _{and is set for each tightening operation by the formula TH S} = -αI + β (where α is a coefficient and beta is an initial value). Will be done. Further, a memory for recording the latest number of data among the measured current values is provided while the motor is rotating, and the control device calculates the first derivative value (dI / dt) from the stored current values.

According to still another feature of the present invention, the striking mechanism has a hammer rotated by a motor and an anvil impacted by the hammer, and the control device is used when the hammer passes behind the anvil and shifts to a striking motion. When a sudden drop in the current value of is detected, the rotation of the motor is stopped regardless of the pulling operation of the trigger. That is, this function operates as an "impact operation suppression mode" and cuts off the current supply immediately before the striking operation is performed, so that it is possible to suppress the phenomenon that the wood screw is strongly driven into the soft mode following a strong striking. Also, if the trigger is pulled again with the tip tool attached to the output shaft pushed by the screw after the rotation of the motor has stopped, the control device will tighten the trigger for a predetermined time and then pull the trigger. Stops the rotation of the motor regardless of the operation. The tip tool mounted on the output shaft is, for example, a driver bit that occupies a wood screw, and the predetermined time is set to be smaller than the rotation time required for one rotation of the wood screw.

According to still another feature of the present invention, the motor, the trigger for adjusting the start and rotation of the motor, the striking mechanism rotated by the motor, the output shaft connected to the striking mechanism, and the rotation of the motor. In an electric tool having a control device to control, when the operator operates the trigger, the motor rotates to tighten the screw to the mating material, the motor is stopped when the screw is seated, and then the tip tool attached to the output shaft is screwed. When the trigger is pulled again while it is pressed against, the motor is rotated for a predetermined time and then the rotation of the motor is stopped regardless of the pulling operation of the trigger. This screw is, for example, a wood screw, and the predetermined time is set to be smaller than the rotation time required for one rotation of the wood screw, preferably less than or equal to the rotation time required for half a rotation.

According to still another feature of the present invention, the motor, the trigger for adjusting the start and rotation of the motor, the striking mechanism rotated by the motor, the output shaft connected to the striking mechanism, and the rotation of the motor. In a power tool that has a control device to control, when the operator operates the trigger, the motor rotates and tightens the screw to the mating material, and if the motor does not stop even if the screw is seated, the striking mechanism makes the first striking. After that, it was configured to stop the rotation of the motor regardless of the operation of the trigger.

According to the power tool of the present invention, screw tightening work can be easily and reliably performed regardless of the hardness of the mating material. In addition, additional tightening can be automatically performed for screws in the middle of tightening. In this way, the tightening work can be reliably performed using an electric tool regardless of the hardness of the mating material (for example, gypsum board), so when the amount of work is not enough to prepare a dedicated driver (board driver). Can complete the work with just an impact tool. In addition, in order to prevent over-tightening to a soft board, the motor is stopped as soon as the screw is seated, and an automatic catch-up mode is provided to compensate for the insufficient tightening, which is practical. We were able to realize a power tool that is expensive and can prevent the occurrence of tightening mistakes on gypsum board.

It is a perspective view which shows the appearance of the impact tool 1 which concerns on embodiment of this invention. It is a vertical sectional view which shows the whole structure of the impact tool 1 of this Example. It is a figure for demonstrating the procedure of tightening a wood screw to a gypsum board using the impact tool 1 of this Example. (A) to (C) are diagrams for explaining the relationship between the seating state detected by the impact tool 1 of this embodiment and the tightening control, and (D) is overtightened by the conventional impact tool. It is a figure which shows the state. It is a circuit diagram of the drive control system of the motor 3 of the impact tool 1 of this embodiment. It is a figure which shows the relationship between the lapse of tightening time and the motor current by the difference in the hardness of the material to be tightened (gypsum board + plywood). It is a figure which shows the change amount of the motor current waveform with the lapse of the tightening time of the impact tool 1 of this Example, (A) shows the current value I (the same as FIG. 6), (B) is the current value I. (C) shows the second-order differential value of the current value I. It is a flowchart which shows the tightening procedure in the gypsum board mode of the impact tool 1 of this Example (the 1). It is a flowchart which shows the tightening procedure in the gypsum board mode of the impact tool 1 of this Example (the 2). It is a flowchart which shows the tightening procedure in the gypsum board mode of the impact tool 1 of this Example (the 3). It is a figure for demonstrating the method of detecting the presence / absence of a load at the start of tightening of the impact tool 1 of this Example. It is a figure which shows the situation which the hammer 24 hits the anvil 28 at the time of a normal rotation. It is a figure which shows the current waveform of the motor 3 when the hammer 24 is detached from the anvil 28 during the tightening operation of the impact tool 1 of this Example. It is a figure for demonstrating the method of seating determination by the software of the impact tool 1 of this Example. It is a figure for _{demonstrating the method of determining the threshold value TH S} for seating determination in the impact tool 1 of this Example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the front-back, left-right, and up-down directions will be described as the directions shown in the figure. In this embodiment, the impact tool 1 will be described as an example of the power tool.

FIG. 1 is a side view showing the appearance of the impact tool 1 according to the embodiment of the present invention. The impact tool 1 uses a rechargeable pack-type battery 90 as a power source, applies a rotational force and a striking force to the output shaft 10 using a motor as a drive source, and has a driver bit or the like held in the mounting hole 10a by the mounting mechanism 11. Rotational striking force is intermittently transmitted to a tip tool (not shown) to perform operations such as screw tightening and bolt tightening. The housing 2 of the impact tool 1 extends from a substantially cylindrical body portion 2a for accommodating a motor and a power transmission mechanism and a substantially central portion of the body portion 2a in a direction substantially orthogonal to the axis A1. Therefore, the handle portion 2b for the operator to grip with one hand and the lower end portion (anti-body portion side end portion) located on the opposite side of the body portion 2a among the end portions of the handle portion 2b are provided. It is composed of a battery mounting portion 2c. A trigger lever 7a is arranged so as to project forward in the upper part of the handle portion 2b, and a forward / reverse direction for switching the rotation direction of the output shaft 10 in the forward direction or the reverse direction on the rear side of the trigger lever 7a. A switching lever 8 is provided.

The battery mounting portion 2c has substantially the same lateral area as the upper surface of the battery 90, and a battery 90 made of a secondary battery such as a lithium ion battery is mounted inside the battery mounting portion 2c. The battery 90 is removable, and when it is removed from the state shown in FIG. 1, the battery 90 is relatively moved forward with respect to the power tool body while pushing the latch buttons 91 on both the left and right sides. Inside the battery mounting portion 2c, a control circuit board (described later in FIG. 2) arranged substantially horizontally in the front-rear and left-right directions is arranged. The first switch panel 36 is provided on the upper surface portion of the battery mounting portion 2c and in front of the lower end portion of the handle portion 2b. The first switch panel 36 has a light switch for lighting the lighting device 9, a battery remaining amount display switch and a battery remaining amount display lamp for displaying the remaining amount of the battery 90, and a striking strength. The strength indicator lamp is arranged. A second switch panel 37 is also provided on the left side surface of the battery mounting portion 2c, and a strength changeover switch 38 for adjusting the striking strength (tightening strength) is provided. A hook 50 for suspending the impact tool 1 from the operator's waist belt is provided diagonally rearward and downward of the strength changeover switch 38. The hook 50 is removable and can be attached not only to the left side surface of the battery mounting portion 2c as shown in FIG. 1 but also to the right side surface, and may be left removed.

A slit-shaped air intake 17b is formed near the rear end side of the body portion 2a of the housing 2, and an air exhaust port is formed near the outer periphery of the rotor fan 15 (described later in FIG. 2) on the front side thereof. The slit 17c is formed. A hammer case 5 is provided on the front side of the housing 2 which is made of metal and is formed in a cup shape and has a through hole formed at the tip thereof for passing the output shaft 10. A lighting device 9 using an LED is provided on the lower side near the front end of the hammer case 5.

FIG. 2 is a vertical sectional view showing the internal structure of the impact tool 1 of this embodiment. The motor 3 is housed in a tubular body portion 2a of a housing 2 having a substantially T-shaped shape when viewed from the side. The motor 3 is a DC (direct current) motor without a brush (rectifying brush), and is a 4-pole 6-slot brushless DC motor. The motor 3 includes a rotor (rotor) 3a provided with a permanent magnet and a stator (stator) 3b provided with a multi-phase armature winding (stator winding) such as a three-phase winding. The motor 3 uses the output of the position detection element 13 composed of a plurality of Hall ICs for detecting the magnetic force of the permanent magnet of the rotor 3a to detect the rotor position, and uses the output of the position detection element 13 to transmit the DC voltage supplied from the battery or the like to a plurality of semiconductors. It operates by being switched by the switching element 14. The rotating shaft 4 of the motor 3 is arranged concentrically with the axis A1 of the cylindrical body portion 2a, and is pivotally supported by the housing 2 by two bearings 16a and 16b on the front side and the rear side. On the rear side of the stator 3b, a substantially annular inverter circuit board 12 for mounting the three position detection elements 13, the six semiconductor switching elements 14, and the like is arranged. The inverter circuit board 12 is a substantially annular double-sided board having a diameter substantially the same as the outer diameter of the motor 3. Six semiconductor switching elements 14 are provided to form an inverter circuit, and the energization of the stator windings of each phase is switched. As the semiconductor switching element 14, a FET (field effect transistor), an IGBT (insulated gate bipolar transistor), or the like is used. The inverter circuit is controlled by a microcomputer, and the energization timing of the armature winding of each phase is set based on the position detection result of the rotor 3a by the position detection element 13, so that advanced rotation control becomes easy.

The hammer case 5 houses the deceleration mechanism 20 and the impact mechanism 21 inside, and is provided on the front side of the body portion 2a of the housing 2. The hammer case 5 is made of an integral metal product, and a through hole 5a for passing the output shaft 10 is formed in a front portion corresponding to a cup-shaped bottom. On the outside of the hammer case 5, a mounting mechanism 11 for mounting or removing a tip tool (not shown) is provided at the tip portion of the output shaft 10.

A rotor fan 15 is mounted coaxially with the rotating shaft 4 between the rotor 3a and the bearing 16a. The rotor fan 15 is integrally molded by, for example, a plastic mold, and is a so-called centrifugal fan that sucks air from the rear inner peripheral side and discharges it to the radial outer side on the front side. The air flow generated by the rotor fan 15 is taken into the body portion 2a from the air intake inlet 17b (see FIG. 1) formed in the housing portion around the air intake inlet 17a and the inverter circuit board 12, and is mainly a rotor. It flows forward so as to pass between 3a and the stator 3b, and is discharged to the outside of the housing 2 by the rotor fan 15 from a slit 17c (see FIG. 1) described later formed in the housing portion around the rotor fan 15. To.

The rotor 3a forms a magnetic path formed by a permanent magnet. The stator 3b is manufactured by a laminated structure of an annular thin iron plate, and six teeth (not shown) are formed on the inner peripheral side, and an enamel wire is wound around each tooth to form a coil. In this embodiment, the coil is a star connection having three phases of U, V, and W.

A trigger lever 7a is arranged so as to project forward in the upper part of the handle portion 2b extending integrally from the body portion 2a of the housing 2 at a substantially right angle, and a trigger switch 7 is provided behind the trigger lever 7a. The user can adjust the trigger pushing amount (operation amount) and control the rotation speed of the motor 3 by grasping the handle portion 2b with one hand and pulling the trigger lever 7a backward with an index finger or the like. The rotation direction of the motor 3 can be switched by operating the forward / reverse switching lever 8. The lower portion of the handle portion 2b is provided with a battery mounting portion 2c whose diameter is expanded in a direction substantially orthogonal to the axis B1 direction of the handle portion 2b. A battery 90, which is a drive power source for the motor 3, is detachably mounted on the battery mounting portion 2c. A control circuit unit 30 for controlling the inverter circuit board 12 of the motor 3 is provided on the upper portion of the battery 90. The control circuit unit 30 accommodates a control circuit board (not shown) provided so as to extend in the front-rear, left-right directions. A microcomputer 40, which will be described later in FIG. 5, is mounted on the control circuit board. The control circuit board 31 is connected to the inverter circuit board 12 via a signal line. A switch panel for arranging a remaining amount check switch of the battery 90, an LED display device for displaying the remaining amount, and a lighting switch of the lighting device 9 on the upper surface of the battery mounting portion 2c in the vicinity of the control circuit board 31. 36 is provided.

The body portion 2a of the housing 2 is manufactured by integrally molding a synthetic resin material together with the handle portion 2b and the battery mounting portion 2c, and is formed so as to be divided into two left and right on a vertical surface passing through the rotation shaft 4 of the motor 3. At the time of assembly, the left side member and the right side member of the housing 2 are prepared, and the deceleration mechanism 20 and the impact mechanism 21 are incorporated in advance in one housing 2 (for example, the left housing) as shown in the cross-sectional view of FIG. A method is adopted in which the hammer case 5 and the motor 3 and the like are assembled, and then the other housing 2 (for example, the housing on the right side) is overlapped and tightened with a plurality of screws.

The impact mechanism 21 is provided on the output side of the speed reduction mechanism 20 using planetary gears, includes a spindle 22 and a hammer 24, and is rotatably held by a bearing 18b at the rear end and a metal 18a at the front end. The deceleration mechanism 20 and the impact mechanism 21 form a power transmission mechanism for driving the tip tool by the motor 3. When the trigger lever 7a is pulled to start the motor 3, the motor 3 starts rotating in the direction set by the forward / reverse switching lever 8, and the rotational force is decelerated by the deceleration mechanism 20 and transmitted to the spindle 22. The spindle 22 rotates at a predetermined speed. Here, the spindle 22 and the hammer 24 are connected by a cam mechanism, and this cam mechanism is formed on the V-shaped spindle cam groove 23 formed on the outer peripheral surface of the spindle 22 and the inner peripheral surface of the hammer 24. It is composed of a hammer cam groove 25 and two steel balls 26 that engage the cam grooves 23 and 25. The hammer 24 is always urged forward by the hammer spring 27. Hitting claws (hammer claws 24a and 24b, which will be described later in FIG. 12) projecting convexly in the axis A1 direction and hitting claws hit by the hitting claws at two locations on the opposite rotation planes of the hammer 24 and the anvil 28. (Anvil claws 28a and 28b, which will be described later in FIG. 12) are formed in rotational symmetry.

When the spindle 22 is rotationally driven, the rotation is transmitted to the hammer 24 via the cam mechanism, and the striking claw of the hammer 24 engages with the striking claw of the anvil 28 before the hammer 24 rotates half a turn. To rotate. When a relative rotation occurs between the spindle 22 and the hammer 24 due to the engagement reaction force between the hammer 24 and the anvil 28 during rotation, the hammer 24 compresses the hammer spring 27 along the spindle cam groove 23 of the cam mechanism and the motor. Start retreating to the 3rd side. Then, when the striking claw of the hammer 24 gets over the striking claw of the anvil 28 and the engagement between the two is released by the backward movement of the hammer 24, the hammer 24 accumulates in the hammer spring 27 in addition to the rotational force of the spindle 22. While being rapidly accelerated in the direction of rotation and forward by the action of the elastic energy and the cam mechanism, the hammer spring 27 moves forward by the urging force of the hammer spring 27, and the striking claw of the hammer 24 reengages with the striking claw of the anvil 28. Then it starts to rotate together. Since such a strong rotational striking force is applied to the anvil 28, the rotational striking force is transmitted to a tip tool (not shown) mounted in the mounting hole 10a of the output shaft 10 integrally formed with the anvil 28. After that, the same operation is repeated, and the rotational striking force is intermittently and repeatedly transmitted to the tip tool, and for example, a wood screw is screwed into a member to be tightened (not shown) such as wood.

3 (A) to 3 (E) are views for explaining a procedure for tightening a wood screw to a gypsum board as a first material by using the impact tool 1 of this embodiment. The gypsum board 71 is made of gypsum and is molded by covering both sides with gypsum board base paper. It is an interior material for buildings that has features such as fire resistance, sound insulation, dimensional stability, and ease of construction. It is widely used for the walls and ceilings of buildings. Since a soft board such as a gypsum board lacks strength as a wall material when used alone, the gypsum board 71 is often laminated on a plywood which is a second material. FIG. 3A shows a state immediately before tightening a wood screw 73 having a length of 25 mm by superimposing a gypsum board 71 having a plate thickness of 10 mm on a base made of plywood. Here, the operator positions the tip 73d of the wood screw 73 on the gypsum board 71, and fits the tip tool 70 into the cross groove (not shown) of the crown surface 73a of the wood screw 73. The wood screw 73 is formed by a countersunk portion 73b extending in the radial direction and a screw portion 73c having a thread formed on the outer peripheral side. Here, the crown surface 73a, which is the upper surface of the dish portion 73b, has a flat shape except for the cross groove portion. The outer peripheral surface of the dish portion 73b has a shape in which the outer edge of the cross section including the axial direction is narrowed down in a quadratic curve so as to form a funnel shape from the crown surface 73a.

When the operator pulls the trigger lever 7a in the state of FIG. 3A, the motor 3 is started. When the motor 3 starts to rotate, the tip tool 70 rotates, the wood screw 73 fitted with the tip tool 70 rotates, and the tip 73d of the wood screw 73 is screwed into the gypsum board 71. FIG. 3B shows a state in which the tip 73d of the wood screw 73 is located in the gypsum board 71. From FIG. 3B, when the tip tool 70 further rotates and the wood screw 73 rotates, the tip 73d of the wood screw 73 reaches the base 72 such as plywood, and the wood screw 73 is screwed into the base 72. The tightening load required for the tool 70 increases. Since the diameter of the threaded portion 73c of the wood screw 73 of this embodiment is almost constant when viewed in the axial direction except for the threaded portion, the load that increases as the tightening progresses is the load between the gypsum board 71 and the base 72. It gradually increases in proportion to the penetration length.

FIG. 3D shows a state in which the funnel-shaped outer peripheral surface of the dish portion 73b is in contact with the surface of the gypsum board 71. When the funnel-shaped outer peripheral surface of the dish portion 73b abuts on the surface of the gypsum board 71 in this way, the tightening load rapidly increases. Therefore, the microcomputer 40 of the impact tool 1 detects that a part of the outer peripheral surface of the dish portion 73b is in contact with the surface of the gypsum board 71 (seating state), and stops the motor 3. Specific methods for seating detection will be described later with reference to FIGS. 6 and 7. Here, the state of the wood screw 73 in which the seated state is detected and stopped as shown in FIG. 3D is a state in which the crown surface 73a protrudes from the surface of the gypsum board 71 by a height S. Ideally, it is preferable that the microcomputer 40 stops the rotation of the wood screw 73 when S = 0. However, since the tightening load on the material to be tightened (gypsum board 71 and base 72) is not constant, it is difficult to always keep S = 0 unless the relative positions of the surfaces of the tip tool 70 and the gypsum board 71 are detected. On the other hand, it must be absolutely avoided that S <0 due to overtightening of the wood screw 73. This is because if the thickness of the gypsum board 71 is partially less than the specified amount due to overtightening of the wood screws 73, the fixing force of the wood screws 73 will be insufficient. Also, because gypsum board is fragile, if it penetrates the paper on the surface, almost no fixing force is generated. Therefore, in this embodiment, when the axial length of the plate portion 73b and T _S, in a state satisfying 0 ≦ _S <T S, stop microcomputer 40 of the motor 3 in the range approaching the possible S = 0 I controlled it so that it could be done. The microcomputer 40 forcibly stops the motor 3 when the operator is in the seated state and detects a certain tightening state even if the trigger lever 7a is still pulled. That is, before the impact mechanism 21 hits, in other words, the impact mechanism 21 does not hit and tightens the wood screw 73 in a state where the hammer and the anvil are in contact with each other and rotates, and when the wood screw 73 is seated, the motor 3 is stopped. I'm letting you.

When the rotation of the tip tool 70 is stopped in the state of FIG. 3D, the crown surface 73a is in a state of protruding from the surface of the gypsum board 71, so that additional tightening (retightening) is required. Therefore, in the impact tool 1 of this embodiment, a new control for tightening the wood screw 73, that is, "tightening control" is additionally added. The "tightening control" is a control in which the microcomputer 40 rotates the tip tool 70 by a certain amount and then automatically stops it, and is controlled so that the rotation amount in the "tightening control" becomes constant. Here, the rotation amount of the tightening control is defined by the drive time of the motor 3. The microcomputer 40 starts the rotation of the tip tool 70 when the operator pulls the trigger lever 7a, and when the motor 3 is driven for a predetermined minute time, the motor is driven regardless of the pulling state of the operator's trigger lever 7a. Stop the rotation of 3. The amount of rotation at this time is such that the insufficient tightening amount of the wood screw 73 can be completed by tightening 1 to 3 times. In the state of FIGS. 3D to 3E, the trigger lever 7a may be pulled while the tip tool 70 is pressed against the top surface 73a, or the tip tool 70 is once separated from the top face 73a. The operation may be such that the tip tool 70 is pressed against the top surface 73a of the head again and then the trigger lever 7a is pulled again. In order to realize the tightening control shown in FIG. 3D, the microcomputer 40 detects the amount of the initial load immediately after the trigger lever 7a is pulled, and determines whether or not there is a large load. Depending on the presence or absence of a large load, it is determined whether the situation when the trigger lever 7a is pulled corresponds to the state shown in FIG. 3A or whether the trigger lever 7a is pulled again in the state shown in FIG. 3D. The method of this determination will be described later in FIG.

4 (A) to 4 (C) are diagrams for explaining the relationship between the seated state detected by the impact tool 1 of this embodiment and the tightening control. For comparison, FIG. 4D also shows a state in which the conventional impact tool is overtightened. FIG. 4A shows a state in which the seat detected by the impact tool 1 of this embodiment has reached the optimum screw tightening position, and is when tightened by using the impact tool 1 of this embodiment. It is advisable to control the tightening to this state by about 70 to 90%. Here, the surface of the gypsum board 71 and the crown surface 73a of the wood screw 73 are flush with each other.

Left in the state of FIG. 4 (B) shows a state in which the seating position detected by the impact tool 1 is insufficient, the top surface 73a of the wood screw 73 is floating distance S ₁ from the surface of the gypsum board 71 .. After that, the optimum screw tightening position shown on the right side is reached by performing additional tightening only once. Figure 4 left in the state of (C) shows another state in which the seating position detected by the impact tool 1 is insufficient Further, the distance the top surface 73a of the wood screw 73 from the surface of the gypsum board 71 S ₂ ( Only S ₂ > S ₁ ) is floating. In this case, one tightening is not enough, so by performing two tightening, the optimum screw tightening position as shown on the right side is reached. Here, it is undeniable that the operation of pulling the trigger lever 7a while pressing the tip tool 70 against the top surface 73a is required twice, which is troublesome. However, if it is overtightened as shown in FIG. 4D, there is a high possibility that one gypsum board 71 must be re-tightened. Therefore, overtightening occurs rather than the demerit that the operation of pulling the trigger lever 7a again increases. The disadvantages are much greater. In this embodiment, the state of FIG. 4A is about 70 to 90%, the state of (B) is about 20 to 0.5%, the state of (C) is about 10 to 0.5%, and (D). It is preferable that the microcomputer 40 can control the rotation of the motor 3 so that the occurrence of the above situation becomes zero. When the wood screw 73 is seated, the motor 3 is stopped, but the trigger lever 7a can be re-operated to tighten the motor 3. At this time, if the seating of the wood screw 73 cannot be detected and the motor 3 does not stop, the motor 3 may be stopped after the first impact is detected. According to this configuration, the operation up to the overtightening can be executed by the first operation of the trigger lever 7, and the overtightening of the wood screw 73 can be suppressed.

Next, the configuration and operation of the drive control system of the motor 3 will be described with reference to FIG. FIG. 5 is a schematic block diagram of the impact tool 1 of this embodiment. In this embodiment, a battery 90 composed of a secondary battery is used as a power source, and a control circuit unit (control device) 30 includes a microcomputer 40 to control a brushless DC motor, and a plurality of semiconductor switching elements Q1 to Q6 are used. Drives the configured inverter circuit. The motor 3 is a so-called inner rotor type, and has three position detection elements arranged at intervals of 60 ° so as to face the rotor 3a configured by embedding a magnet (permanent magnet) including a pair of N poles and S poles. 13 is provided. The stator 3b includes star-connected three-phase windings U, V, W.

Six switching elements Q1 to Q6 such as FETs connected in a three-phase bridge format are mounted on the inverter circuit board 12. The microcomputer 40 mounted on the control circuit board 31 drives and controls the switching elements Q1 to Q6 via the control signal output circuit 48. Each gate of the six switching elements Q1 to Q6 bridge-connected is connected to the control signal output circuit 48, and each drain or each source of the six switching elements Q1 to Q6 is a star-connected stator winding. Connected to U, V, W. As a result, the six switching elements Q1 to Q6 perform a switching operation by the switching element drive signal (drive signal of H4, H5, H6, etc.) input from the control signal output circuit 48, and the battery applied to the inverter circuit. The DC voltage of 90 is set as three-phase (U-phase, V-phase and W-phase) voltages Vu, Vv and Vw, and power is supplied to the stator windings U, V and W.

Of the switching element drive signals (3-phase signals) that drive each gate of the 6 switching elements Q1 to Q6, the three switching elements Q4, Q5, and Q6 on the negative power supply side are pulse width modulated signals (PWM signals) H4. , H5, H6, and the pulse width (duty ratio) of the PWM signal based on the detection signal of the operation amount (stroke) of the trigger lever 7a of the trigger switch 7 by the microcomputer 40 mounted on the control circuit board 31. By changing the power supply amount to the motor 3, the start / stop and rotation speed of the motor 3 are controlled.

The control circuit unit 30 includes a microcomputer 40, a current detection circuit 41, a switch operation detection circuit 42, an applied voltage setting circuit 43, a rotation direction setting circuit 44, a rotor position detection circuit 45, a rotation number detection circuit 46, and input / output. The unit 49 is mounted. Although not shown, the microcomputer 40 that forms the core of the control circuit unit 30 is for storing a CPU for outputting a drive signal based on a processing program and data, and a program and control data corresponding to a flowchart described later. It includes a ROM, a RAM for temporarily storing data, and a microcomputer having a built-in timer and the like. The current detection circuit 41 is a voltage detecting means for detecting the current flowing through the motor 3 by measuring the voltage across the shunt resistor 32, and the detected current is input to the microcomputer 40. In this embodiment, the shunt resistor 32 is provided between the battery 90 and the inverter circuit to detect the current value flowing through the semiconductor switching elements Q1 to Q6, but the shunt resistor 32 is provided between the inverter circuit and the motor 3. The current value flowing through the motor 3 may be detected.

The switch operation detection circuit 42 detects whether or not the trigger lever 7a is pulled, and if it is pulled even a little, an on signal is output to the microcomputer 40. The applied voltage setting circuit 43 is a circuit for setting the applied voltage of the motor 3, that is, the duty ratio of the PWM signal in response to the moving stroke of the trigger lever 7a. The rotation direction setting circuit 44 is a circuit for detecting the operation of forward rotation or reverse rotation by the forward / reverse switching lever 8 of the motor and setting the rotation direction of the motor 3. The rotor position detection circuit 45 is a circuit for detecting the relational positions between the armature windings U, V, and W of the rotor 3a and the stator 3b based on the output signals of the three position detection elements 13. The rotation speed detection circuit 46 is a circuit that detects the rotation speed of the motor based on the number of detection signals from the rotor position detection circuit 45 counted within a unit time. The control signal output circuit 48 supplies a PWM signal to the switching elements Q1 to Q6 based on the output from the microcomputer 40. The power supplied to each armature winding U, V, W is adjusted by controlling the pulse width of the PWM signal.

A signal from the input / output unit 49 for switching the operation mode is input to the microcomputer 40. The signals input from the input / output unit 49 include input signals from the first switch panel 36 and the second switch panel 37, and input signals of other sensors. Further, the signal output from the microcomputer 40 to the input / output unit 49 is a lighting or extinguishing instruction signal to the drive circuit for driving the lighting device 9 for illuminating the vicinity of the tip tool, and an LED display on the first switch panel 36. Includes lighting signal.

FIG. 6 is a diagram showing the relationship between the passage of tightening time and the motor current due to the difference in hardness of the material to be tightened (gypsum board + plywood). The vertical axis is the current value I (unit: A), and the horizontal axis is the passage of time (unit: milliseconds). Here, a case is shown in which the wood screw 73 is ideally tightened to the state shown in FIG. 3 (E) with only one tightening, and the current value 61 shown by the solid line is applied to the soft base 72 in addition to the gypsum board 71. Shows the tightening status. Further, the current value 62 shown by the dotted line indicates the state of tightening to the hard base 72 in addition to the gypsum board 71. In the case of a soft substrate, when the operator pulls the trigger lever 7a to tighten the wood screw 73 from the state shown in FIG. 3 (A) at time 0, the current value 61 becomes slightly as shown by arrows 61a to 61b as the tightening progresses. Ascend to. Note that the effect of the starting current immediately after the start of the motor 3 is not shown here (the same applies to FIG. 7 described later). When the seating initial state becomes (the boundary position of the pan 73b and the screw portion 73c of the wood screw 73 is a state that has reached the surface of the gypsum board 71) at time t _1, the current rapidly value as indicated by an arrow 61c is increased ..

Microcomputer 40, an appropriate timing after detecting the seated initial state, i.e. at time t ₂ to stop the rotation of the motor 3. Similarly, in the case of a hard substrate, when the operator pulls the trigger lever 7a at time 0, the current value 62 linearly rises as shown by arrows 62a to 62b as the tightening progresses. Then, when the seating state at time t _1, large current as indicated by an arrow 62c is increased. The microcomputer 40 stops the rotation of the motor 3 at the right time, i.e. the time t ₂ after the detection of the seating. In the actual tightening operation, the rotation speed of the output shaft 10 is not always the same in the case of a hard base and a soft base, and the times t ₁ and t ₂ vary. Therefore, the time shown in FIG. 6 is only an example. As can be seen from this waveform diagram, in the case of a soft substrate, the degree of increase in the inclination after sitting shown by the arrow 61c is larger than the small inclination of the current value 61 before sitting as shown by the arrows 61a to 61b. On the other hand, in the case of a hard substrate, the degree of increase in the current value 62 after the initial sitting state shown by the arrows 62c is smaller than the inclination of the current value 62 before the initial sitting state shown by the arrows 62a to 62b. _{In this embodiment, the stop threshold TH S} (described later) for stopping the motor 3 is set while considering the difference in the ratio of the slope of the current value after the initial state of seating to the slope of the current value before the initial state of seating. I tried to set it optimally. As described above, in this embodiment, even if the hardness of the material to be tightened is different, the seating can be reliably detected and the motor 3 can be stopped.

FIG. 7 is a diagram showing the relationship of the motor current with the passage of the tightening time due to the difference in the hardness of the material to be tightened (plasterboard of the first material + plywood of the second material), and is a vertical view of FIG. 7 (A). The axis shows the current value I, the vertical axis of (B) shows the differential value of the current value I, and the vertical axis of (C) shows the second-order differential value of the current value I. FIG. 7A is the same diagram as FIG. FIG. 7B is obtained by differentiating the current values 61 and 62 of FIG. 7A with respect to time, respectively, to calculate the differential values 63 and 64 by dI / dt. dI / dt indicates the magnitude of the slope of the graph in FIG. 7 (A), and the differential value 63 in the case of a soft base shown by a solid line is the state of the arrow 63a before sitting, and in the case of a hard base shown by a dotted line. It is smaller than the arrow 64a of the differential value 64 of. Further, the dI / dt between the arrival at the initial seating position at time t1 and the time when the top surface 73a of the wood screw 73 reaches the same surface as the gypsum board 71 is the rising edge of the differential value 63 in the case of a soft base (arrow). 63b) is clearly larger than the rising edge of the differential value 64 (arrow 64b) in the case of a hard base. The present inventors have <and (64a, relationship arrows 63b and 64b (63b relationship between the arrows 63a and 64a 63a)> attention to the fact that 64b) is reversed, and to set the stop threshold value TH _S. As a result, it has become possible to individually set _{the optimum stop threshold TH S} (described later) according to the difference in hardness of the base material, which is the second material, for each tightening.

FIG. 7C is obtained by further differentiating the differential values 63 and 64 to calculate the slope of the graph of the differential values 63 and 64 in FIG. 7B. That is, it is the second derivative value as seen from FIG. 7A, and the second derivative values 65 and 66 are calculated by ^{d 2} I / dt ^2. As can be understood here, from time 0 to time t ₁ , the second derivative values 65 and 66 are almost 0, and there is no difference between them. On the other hand, from time t ₁ to time t ₂ , the second derivative values 65 and 66 rise sharply. _{The stop threshold TH S} for stopping the motor 3 is changed according to the rising condition. The idea is that when the base material is hard and the tightening load is large, d ² I / dt ² becomes smaller in the range from time t ₁ to t ₂ as in the second derivative value 66, so that the stop threshold TH _S becomes smaller. To set. On the other hand, when the base material is soft and the tightening load is small, d ² I / dt ² becomes large in the range from time t ₁ to t ₂ as in the second derivative value 65, so that the stop threshold TH _S becomes large. Set. As described above, in this embodiment, the stop threshold value TH _S is moved up and down as shown by the arrow 81 according to the magnitude ^{of d 2} I / dt ² after reaching the seating initial position. By this vertical is, since in accordance with the size of the differential value 63 from time 0 to time t ₁ can vary the stop threshold TH _S, reaches the seating initial position after pulling the trigger lever 7a It is possible to change the stop threshold TH _{S in the interval between them.}

8 to 10 are flowcharts showing a tightening procedure in the gypsum board mode of the impact tool 1 of this embodiment. When the battery 90 is attached to the impact tool 1 and the trigger lever 7a is first pulled and the trigger switch 7 is turned on, power is supplied to the microcomputer 40. Therefore, the microcomputer 40 is activated and shown in FIGS. 8 to 10. Perform each step shown in. Each step shown in FIGS. 8 to 10 is executed by software by a program stored in advance in the microcomputer 40. First, the microcomputer 40 detects the set operation mode of the impact tool 1 (step 101). As the operation mode of the impact tool 1 of this embodiment, "gypsum board mode (second mode, operation mode for soft board)" is added in addition to the conventional impact operation mode (first mode). Has been done. In the impact operation mode, the tightening strength can be set in a plurality of stages (for example, 4 stages). The operation mode of the impact tool is not limited to the first mode and the second mode, and other operation modes such as a tex screw tightening mode (third mode) and other operation modes may be provided. The description of the third mode and other operation modes in the above will be omitted. In step 101, the microcomputer 40 determines whether any of these modes is set.

Next, the microcomputer 40 sets the rotation direction of the motor 3 by detecting the setting of the forward / reverse switching lever 8 (step 102). Next, the microcomputer 40 determines whether the operation mode detected in step 101 is the "normal mode (normal impact operation mode)" or the new "gypsum board mode" added by the present embodiment. (Step 103). When the operation mode is the "normal mode", the microcomputer 40 controls steps 104 to 110, which are the same controls as the conventional impact tool. That is, the microcomputer 40 sets the target rotation speed of the motor 3 even according to the tightening strength due to the set impact operation (step 104), and whether or not the trigger lever 7a is pulled and the trigger switch 7 is turned on. Is determined (step 105). If the trigger lever 7a is not pulled in step 105, the process returns to step 101, and if the trigger lever 7a is pulled, the motor 3 is started to be driven (step 106). Next, the microcomputer 40 determines whether or not the trigger switch 7 is turned off while the motor 3 is rotating (step 107), and if it is not turned off, detects the rotation speed of the motor 3 (step 109), and steps. The target rotation speed set in 104 is compared with the detected current rotation speed, a duty ratio in PWM control is set, the inverter circuit is controlled so as to have the duty ratio, and the process returns to step 107 (step 110). .. When the trigger lever 7a is returned in step 107 and the trigger switch 7 is turned off, the driving of the motor 3 is stopped to end the tightening operation (step 108). The above is the normal impact operation mode that has been conventionally performed.

If it is determined in step 103 that the microcomputer 40 is set to the "gypsum board mode", the steps after step 111 are executed. In step 111, the microcomputer 40 determines whether the rotation direction of the motor 3 is set to "reverse". In the case of reversal, the seating detection and the tightening control peculiar to the gypsum board are unnecessary, so the process proceeds to step 104. In step 114, the microcomputer 40 sets a target rotation speed of the motor 3 suitable for tightening the gypsum board (step 112), and determines whether or not the trigger lever 7a is pulled and the trigger switch 7 is turned on (step 112). 113). If the trigger lever 7a is not pulled in step 113, the process returns to step 101, and if the trigger lever 7a is pulled, the motor 3 is started to be driven (step 114). Next, the microcomputer 40 determines whether or not the trigger switch 7 is turned off while the motor 3 is rotating (step 115), and if it is not turned off, detects the rotation speed of the motor 3 (step 117), and steps. The target rotation speed set in 112 is compared with the detected current rotation speed, a duty ratio in PWM control is set, the inverter circuit is controlled so as to have the duty ratio, and the process proceeds to step 121 in FIG. (Step 118). When the trigger lever 7a is returned in step 115 and the trigger switch 7 is turned off, the driving of the motor 3 is stopped (step 116), and the tightening operation is completed.

FIG. 9 is a processing procedure following step 118 of FIG. In the "gypsum board mode", the microcomputer 40 first detects the drive time (step 119). This detection is performed at regular intervals (for example, every 1 millisecond), and the interval is measured using the timer function of the microcomputer 40. Next, the microcomputer 40 measures the current value I flowing through the motor 3 using the current detection circuit 41 (see FIG. 5) (step 120). Next, the microcomputer 40 temporarily stores in an internal memory (not shown) the measured current value I (e.g. the current value I _n of the time t _n) (step 121). Next, the microcomputer 40 determines whether the “initial load determination end flag” in the gypsum board mode is set (= “1”) or unset (= “0”) (step 122). Here, the "initial load determination end flag" is the state before tightening as shown in FIG. 3A or the state after the trigger lever 7a in FIG. 3D after the trigger lever 7a is pulled in the gypsum board mode. It is a flag indicating whether or not a load determination indicating whether or not the tightening control is performed is executed. When "1" of the initial load determination end flag is detected, it indicates that the determination of the state before tightening or the tightening control has been completed. When the initial load determination end flag "1" is not detected, it indicates that the determination of the state before tightening or the tightening control has not been completed. The initial load determination end flag is cleared when the operator releases the trigger lever 7a, and "0" is input.

If the initial load determination has not been completed in step 122, that is, if the initial load determination end flag "1" has not been detected, the time for the microcomputer 40 to detect the initial load state is within the appropriate range (within the determination time area). (Step 126). Here, with reference to FIG. 11, a load detection method of whether or not the tightening control should be executed will be described. FIG. 11 is a diagram for explaining a method of detecting the presence or absence of a load at the start of tightening of the impact tool 1, and is executed every time immediately after the operator pulls the trigger lever 7a in the “gypsum board mode”. The vertical axis of the graph is the current value I (unit A) detected by the current detection circuit 41 (see FIG. 5), and the horizontal axis is the passage of time (unit: millisecond). Here, two waveforms of current values 68 and 69 are shown. The current value 68 is a state in which there is a load for tightening as in the case of tightening in FIG. 3 (E), and the current value 69 is a state in which there is no load for tightening as in FIG. 3 (A). When the operator pulls the trigger lever 7a at time 0, the motor 3 starts and starts rotation. Immediately after starting the motor 3, a large starting current flows as shown by arrows 68a and 68b. Therefore, the current value I measured within this time should not be used for judgment (dead period), and the starting current disappears. current 68 flowing to the motor 3 is stable around the predetermined section (load detection section), i.e., the arrow 68b, the current value 68, 69 of the period from time _t a ~t _b measured as 69b, which It is determined whether or not the value of is exceeding the threshold value TH _l. Here, the threshold value TH _l is a threshold value preset for load detection, and if the threshold value TH _l is exceeded, there is a load, that is, a “catch-up state” from FIGS. 3 (D) to (E). If it is determined that the threshold value is TH _l or less, it is determined that there is no load at the start of tightening the wood screw 73 shown in FIG. 3 (A). Whether exceeds the threshold TH _l, it may be determined by the peak value of the current 68 and 69 leading to the time t _a ~t _b, may be determined by the average value, and a filtering process The determination may be made after removing the noise. Since this load detection section is in _{a section sufficiently before the time t 1} (t ₁ > t _e ) when seating is detected, the microcomputer 40 has a load and no load at the initial stage of tightening each of the wood screws 73. You can judge the state of. Incidentally, after crossing the "Load Yes" a to time t _b, at time t _e after the elapse of a predetermined time, the microcomputer 40 stops the motor 3. Here, the set value of the predetermined time, from the time 0 to the time t _e is about 80 ms, is the extent to rotate the wood screw about 90 degrees. If the answer is "no load", the microcomputer 40 stops the motor 3 at time t ₂ and the seating detection as shown in FIG.

Return to step 126 in FIG. In step 126, the time when the current value is detected, it is determined that it is within the detection time for the initial load detection, when in less than the load detection time, that is, between t _a from the time 0 in FIG. 12 Then, the process returns to step 115 in FIG. In step 126, when the current value is within the detection time, it is determined whether or not the _{detected current value I exceeds the load detection threshold value TH l (step 127).} When the load detection threshold value TH _l is exceeded, the microcomputer 40 determines that the initial load state (with load) has been detected, determines the initial load determination flag as "1 (= with load)", and at the same time, determines. The determination end flag of the initial load is changed to "1 (= determined)" (step 128, 129), and the process returns to step 115 in FIG. If the load detection threshold TH _l is not exceeded in step 127, the microcomputer 40 determines that the initial load state (no load) has been detected, and determines that the initial load determination flag is “0 (= no load)”. (Step 130), the initial load determination end flag is changed to "1 (= determined)" (step 129), and the process returns to step 115 in FIG.

In step 122 of FIG. 9, when the determination end flag of the initial load is “1 (= determined)”, it is determined whether the determined result is with or without load (step 123), and the load is increased. If not, the process proceeds to step 131 of FIG. 10 in order to perform normal tightening that is not a catch-up by the gypsum board mode. When there is a load in step 123, the microcomputer 40 drives the motor 3 for a certain period of time in order to perform tightening, and returns to step 115 of FIG. 8 while the fixed time is not reached. After a certain period of time has elapsed, the microcomputer 40 stops the rotation of the motor and ends the tightening operation in the gypsum board mode. Even when the motor is stopped in step 125, it may be in the center state of FIG. 4 (C). In that case, the operator pulls the trigger lever 7a again to further tighten up.

FIG. 10 is a flowchart showing a subsequent processing procedure in the case of “no load” in step 123 of FIG. Here, the microcomputer 40 detects whether or not the hammer 24 is likely to hit the anvil 28 (step 131). Here, a method of detecting after the actual impact is performed by using an acceleration sensor may be used, but by detecting the current value I of the motor 3, the hammer 24 retracts and the engagement state with the anvil 28 is released. Detects that it has become a detached state. The detection of this detached state will be described with reference to FIGS. 12 and 13.

FIG. 12 is a diagram showing a situation in which the hammer 24 hits the anvil 28 during normal rotation, and is a view of the anvil 28 and the hammer 24 viewed from the front side of the axis A1 (see FIG. 2). Is. In FIG. 12A, the motor 3 rotates and the hammer 24 rotates in the forward rotation direction, and the hammer claws (striking claws) 24a and 24b rotate the anvil claws (struck claws) 28a and 28b of the anvil 28 backward in the rotation direction. The anvil 28 rotates in the same direction as the hammer 24 because it is shaped like a push from. When the load received from the tip tool 70 (see FIG. 3) increases in this state, the hammer 24 retracts for the first time while compressing the hammer spring 27 (see FIG. 2) by the spindle cam mechanism, and finally the hammer claws 24a and 24b and the anvil. The contact length of the claws 28a and 28b in the axis A1 direction becomes 0. As a result, as shown in FIG. 12B, the hammer claws 24a and 24b pass through the rear side of the anvil claws 28a and 28b and rotate in the direction of the arrow indicated by "hammer drive" in the figure. At this time, since the hammer claws 24a and 24b are not in contact with the anvil claws 28a and 28b in the rotational direction, the load of the motor 3 when the hammer 24 is retracted as shown in FIG. The value I also becomes smaller. In FIG. 12C, the hammer claws 24a and 24b pass through the rear side of the anvil claws 28a and 28b and rotate in the direction of the arrow while moving forward by the urging force of the hammer spring 27 (see FIG. 2). In this rotation, since the hammer claws 24a and 24b are in an idling state in which they are not in contact with the anvil claws 28a and 28b, the motor 3 is not subjected to the tightening load, and the current value I is further reduced. FIG. 13 shows the current value I of the motor 3 when reaching FIGS. 12 (A) to 12 (C).

FIG. 13 is a diagram showing a current waveform of the motor 3 when the hammer 24 separates from the anvil 28 during the tightening operation of the impact tool 1 of the present embodiment. The vertical axis represents the current value I (unit A) of the motor 3 detected by the current detection circuit 41 (see FIG. 5), and the horizontal axis represents the passage of time. _{The times t A} and t _{B on the} horizontal axis are the times in the states of FIGS. 12A and 12B. As shown in FIGS. 3A to 3C, when the wood screw 73 (see FIG. 3) is tightened, the current value 69 of the motor 3 gradually increases as shown by the arrow 69c until it is seated. The increase in the current value 69 indicated by the arrow 69c is because the hammer claws 24a and 24b rotate so as to push the anvil claws 28a and 28b from the rear in the rotation direction. In this state, as shown in FIG. 12B, when the hammer claws 24a and 24b are separated to the rear side and the engagement with the anvil claws 28a and 28b is released, the load applied to the hammer 24 is sharply reduced. Therefore, the current value 69 drops sharply as shown by the arrow 69d. If the current supply to the motor 3 is continued at the time of the arrow 69d, the motor 3 accelerates and causes the hammer claws 24a and 24b to vigorously hit the anvil claws 28a and 28b. However, in this embodiment, since the tightening is performed on a soft member called gypsum board 71 (see FIG. 3), the tightening work involving the striking operation of the impact tool 1 is in an overtightened state because the torque is too high (FIG. 4 (4)). There is a high risk of inviting. Therefore, in this embodiment, the microcomputer 40 detects a sudden drop in the current value 69 to detect the state in which the impact is performed in advance, and drives the motor 3 _{before the impact is performed, for example, at time t f.} The current supply was stopped.

Return to FIG. 12 again. As shown in FIG. 12C, even if the microcomputer 40 stops supplying the drive current to the motor 3 while the hammer 24 is idling, the motor 3 continues to rotate due to inertia, so that FIG. 12D is shown. As shown in the above, the hammer claws 24a and 24b hit the anvil claws 28b and 28a. However, since the driving current does not flow through the motor 3 during this striking, the striking force is weakened, and the tightening force applied to the material to be tightened (gypsum board 71 shown in FIG. 4) is also small, so that it is in an overtightened state. Can be effectively prevented. When a hammer back state occurs in which the hammer claws 24a and 24b are controlled as described above and the hammer claws 24a and 24b ride on the anvil claws 28a and 28b and retreat, the microcomputer 40 stops supplying the drive current to the motor 3 and causes a normal impact. Control so that no operation is performed. With this control, it is possible to satisfactorily tighten the screw to a soft member whose tightening torque is too high in the striking operation. As shown in FIG. 13, in this embodiment, the supply of the drive current to the motor 3 is completely stopped when the hammer 24 is retracted, but even if the hammer 24 is not completely stopped, the supply of the drive current is significantly reduced, for example. The rotation may be continued so as to reduce the current value 69 in FIG. 11 to less than 30%.

Return to FIG. In step 132 of FIG. 10, when the microcomputer 40 detects a blow, it stops the supply of the drive current to stop the drive of the motor 3 and end the process (step 139). Since the motor 3 does not stop suddenly but rotates by inertia, the impact is performed only once. However, since the power supply is cut off immediately before the impact, the wood screw 73 is overtightened by the execution of the impact. There is no risk of a condition occurring.

In step 132, when the hitting cannot be detected, that is, when a significant decrease in the current value I cannot be detected as shown by the arrow 69d in FIG. 13, the detected change amount of the current current value I is detected. (Step 133). In the principle of this embodiment shown in FIG. 7, the differential value of the current value I and the second-order differential value are calculated and the judgment is made based on them, but the actual difference judgment by the microcomputer 40 is made in FIG. Do as shown in. FIG. 14 is a diagram for explaining a method of seating determination by software of the impact tool 1 of this embodiment. Here, it is assumed that the current value 60 has increased as shown in FIG. At this time, the microcomputer 40 at predetermined time intervals, wherein the measurement of the current value flowing to the motor 3 for each time T, the measured n-th current value (n is a natural number) and I _n. That I _n is the current value measured is, which current value I _n-1 is measured at time t _n-1 earlier by time T, the current value I _n-2 time 2T only before time It was measured at t _n-2. These _{I n, I n-1,} I n-2 is temporarily stored in the internal memory of the microcomputer 40. After completing the measurement of the current value _{I n} at time _{t n,} the microcomputer 40 _{(I n -I n-1)} - by calculating the value of _{(I n-1 -I n-} 2), the current value 60 Detects the slope per unit time. When this detection result exceeds the threshold value TH _S , the microcomputer 40 determines that the wood screw 73 is seated and stops the driving of the motor 3.

14, compares the current and the current _{I n} step 133, the current _{I n-1} measured immediately before. Next, the current amount of the current value In _{-2 measured immediately before the current In-1} primary stored in the internal memory of the microcomputer 40 is measured is detected (step 134). Next, a variation of the current value of the current measurement interval (I n _{-I n-1),} the amount of change in the current value of the previous measurement period of the current measurement interval, i.e., the change amount of the past current values (I _{The difference between n-1-} I _n-2 ) is calculated (step 135). Next, the microcomputer 40 sets a _{threshold value (stop threshold value TH S} ) for stopping the motor 3 from the amount of change in the current value calculated in step 135. The method of setting the stop threshold value TH _S will be described with reference to FIG.

In FIG. 15, the vertical axis represents _{the magnitude of the threshold value TH S} , and the horizontal axis represents the value of the current value I (unit A). The stop threshold value 80 for stopping the motor 3 when the screw is seated is linearly changed within the range of the _{current I min to} I _max. Here, in the range of _{I min} <I <I _max , the threshold value TH _S is set by _{the formula TH s = αI + β.} α and β are coefficients. As _{the current value I for calculating TH S} , any current value within a predetermined range from time 1 to n can be used, but for example, if the average value of the currents in a plurality of sections is used. good.

Returning to step 136 of FIG. 10, when the stop threshold value 80 of the motor 3 is determined in step 136 using the equation shown in FIG. 15, the difference in the amount of change calculated in step 135 is the set stop threshold value TH _S. (Step 137). If the difference in the amount of change calculated in step 135 _{does not exceed the stop threshold TH S} , the process returns to step 115 of FIG. 8, and if _{the difference exceeds the stop threshold TH S} , the microcomputer 40 stops driving the motor 3. And end the process (step 138). Since the microcomputer 40 _{controls the tightening by using the stop threshold TH S} as described above, the motor 3 can be stopped in a state where the wood screw 73 is seated and the wood screw 73 is not overtightened. Moreover, since the microcomputer 40 automatically stops the motor even when the operator keeps pulling the trigger lever 7a, ideal tightening is performed even for screw tightening to a soft member such as gypsum board 71. It can be carried out. Further, when the tightening is insufficient, the operator can pull the trigger lever 7a again to catch up for a certain number of rotations, so that the ideal tightening state can be reached.

Although the present invention has been described above based on the examples, the present invention is not limited to the above-mentioned examples, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the example of tightening the gypsum board as the tightening mode of the soft board has been described, but the same can be applied to the case of screwing a soft board other than the gypsum board or a soft member. Further, the power tool is not limited to the impact tool using a battery, and may be an impact tool using an AC commercial power source. Further, the striking mechanism (impact mechanism) may be not only a mechanical impact mechanism using a hammer and an anvil, but also an electric tool using an oil pulse mechanism.

1 ... Impact tool, 2 ... Housing, 2a ... Body part, 2b ... Handle part, 2c ... Battery mounting part, 3 ... Motor, 3a ... Rotor, 3b ... Stator, 4 ... Rotating shaft, 5 ... Hammer case, 5a ... Penetration Hole, 7 ... Trigger switch, 7a ... Trigger lever, 8 ... Forward / reverse switching lever, 9 ... Lighting device, 10 ... Output shaft, 10a ... Mounting hole, 11 ... Mounting mechanism, 12 ... Inverter circuit board, 13 ... Position detection element , 14 ... semiconductor switching element, 15 ... rotor fan, 16a, 16b ... bearing, 17a, 17b ... air inlet, 17c ... slit (air outlet), 18a ... metal, 18b ... bearing, 20 ... deceleration mechanism, 21 ... Impact mechanism, 22 ... Spindle, 23 ... Spindle cam groove, 24 ... Hammer, 24a, 24b ... Hammer claw, 25 ... Hammer cam groove, 26 ... Steel ball, 27 ... Hammer spring, 28 ... Anvil, 28a, 28b ... Anvil claw, 30 ... control circuit unit (control device), 31 ... control circuit board, 32 ... shunt resistance, 36 ... switch panel, 37 ... (second) switch panel, 38 ... strength changeover switch, 40 ... microcomputer (calculation unit), 41 ... Current detection circuit, 42 ... Switch operation detection circuit, 43 ... Applied voltage setting circuit, 44 ... Rotation direction setting circuit, 45 ... Rotor position detection circuit, 46 ... Rotation number detection circuit, 48 ... Control signal output circuit, 49 ... Input / output unit, 50 ... Hook, 60, 61, 62 ... Current value, 63, 64 ... (Current) differential value 65, 66 ... (Current) second-order differential value, 68, 69 ... Current value, 70 ... Tip Tool, 71 ... Gypsum board (1st material), 72 ... Base (2nd material), 73 ... Wood screw, 73a ... Top surface, 73b ... Dish part, 73c ... Screw part, 73d ... Tip, 80 ... Stop threshold, 90 ... Battery, 91 ... Latch button TH _{l ... Threshold TH S} ... Stop threshold (for load detection)

Claims (14)

With the motor
A trigger for adjusting the start and rotation of the motor,
The striking mechanism rotated by the motor and
An output shaft that is connected to the striking mechanism and tightens the screw,
A current detection circuit for detecting the current flowing through the motor, and
In a power tool having the motor, the trigger, and a control device connected to the current detection circuit to control the rotation of the motor.
The control device is
By the change in was detected current by said current detecting circuit, and the striking by the striking mechanism, and a seating of the screw, is configured for detect respectively,
When the operator operates the trigger, the motor is rotated and the screw is tightened to the mating material .
When it is detected that the impact is performed by the impact mechanism, the rotation of the motor is stopped regardless of the operation of the trigger due to the detection of the first impact .
When the seating of the screw is detected without the impact by the striking mechanism being detected, the rotation of the motor is stopped regardless of the operation of the trigger due to the detection of the seating of the screw. A power tool featuring. The mating material has a first material and a second material that is harder than the first material.
The first aspect of the present invention, wherein the motor stops rotating when the screw is seated even when the screw is tightened to the first material and the second material, respectively, without the impact mechanism striking. Electric tool. In the first mode, when the operator operates the trigger, the motor rotates, the striking mechanism strikes, and the screw is tightened to the mating material.
It has a second mode in which the motor rotates when the operator operates the trigger, the screw is tightened to the mating material without hitting the striking mechanism, and the rotation of the motor is stopped when the screw is seated. The power tool according to claim 1 or 2, wherein the power tool is characterized by the above. In the second mode, when the amount of change in the current detected by the current detection circuit per predetermined time exceeds the seating stop threshold value, the control device stops the rotation of the motor regardless of the operation of the trigger. The power tool according to claim 3, wherein the power tool is characterized by the above. The control device is
The current value flowing through the motor immediately after the start of rotation of the output shaft is detected for each unit time, and the first-order differential value and the second-order differential value with respect to the unit time are calculated from the current values for the most recent plurality of units.
From the current value, the seating stop threshold value for stopping the rotation of the motor is calculated.
The power tool according to claim 4, wherein when the seating stop threshold value calculated by using the second derivative value is exceeded, the rotation of the motor is stopped regardless of the operation of the trigger. The power tool according to claim 5, wherein the seating stop threshold value is set based on the current flowing through the motor detected by the current detection circuit immediately after the start of rotation of the output shaft. The seating stop threshold is determined by using a linear equation so that the larger the current value measured from the start of rotation of the output shaft to the seating stop at which the rotation of the motor is stopped, the smaller the current value, and the smaller the current value, the larger the current value. The power tool according to claim 6, wherein the power tool is calculated. The seating stop threshold THS measures the current value I from the start of rotation of the output shaft, and measures the current value I.
The power tool according to claim 7, wherein the power tool is set for each tightening operation by the formula of THS = −αI + β (where α is a coefficient and beta is an initial value). A memory for recording the latest number of data of the measured current values during the rotation of the motor is provided.
The power tool according to claim 8, wherein the control device calculates the first derivative value (dI / dt) from the stored current value. The striking mechanism includes a hammer rotated by the motor and
With an anvil that is hit by the hammer,
When the control device detects a sudden drop in the current value when the hammer passes behind the anvil and shifts to a striking operation, the control device stops the rotation of the motor regardless of the pulling operation of the trigger. The power tool according to any one of claims 5 to 9. After the rotation of the motor is stopped, if the trigger is pulled again with the tip tool attached to the output shaft pressed against the screw, the control device performs the tightening for a predetermined time and then the trigger. The power tool according to any one of claims 1 to 10, wherein the rotation of the motor is stopped regardless of the pulling operation. With the motor
A trigger for adjusting the start and rotation of the motor,
The striking mechanism rotated by the motor and
The output shaft connected to the striking mechanism and
In an electric tool having a control device for controlling the rotation of the motor.
The control device is
When the operator operates the trigger, the motor rotates and tightens the screw to the mating material.
When the striking mechanism makes the first striking, the rotation of the motor is stopped regardless of the operation of the trigger.
In a state where the striking mechanism does not make the first striking,
Wherein Once screw is seated, to stop the motor regardless of the operation of the trigger,
After that, when the trigger is pulled again with the tip tool attached to the output shaft pressed against the screw, the motor is rotated for a predetermined time and then the motor is rotated regardless of the pulling operation of the trigger. A power tool characterized by stopping. The screw is a wood screw
The power tool according to claim 11 or 12, wherein the predetermined time is set to be smaller than the rotation time required for the rotation of one round of the wood screw. With the motor
A trigger for adjusting the start and rotation of the motor,
The striking mechanism rotated by the motor and
An output shaft that is connected to the striking mechanism and tightens the screw,
A current detection circuit for detecting the current flowing through the motor, and
In a power tool having the motor, the trigger, and a control device connected to the current detection circuit to control the rotation of the motor.
The control device is
By the change in the current detect by the current detection circuit, and the striking by the striking mechanism, and a seating of the screw, is configured to be detected, respectively,
When the operator operates the trigger, the motor is rotated to rotate the motor.
When the striking mechanism makes the first striking, the rotation of the motor is stopped regardless of the operation of the trigger.
In a state where the striking mechanism does not make the first striking,
When the screw is seated, the rotation of the motor is stopped regardless of the operation of the trigger.
After that, when the trigger is pulled again with the tip tool attached to the output shaft pressed against the screw, the motor is rotated, and after a predetermined time, the rotation of the motor is stopped regardless of the pulling operation of the trigger. A power tool characterized by being configured as such.

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