JP2013202716A - Electric power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power tool capable of performing control hardly causing variation in striking force for each product as compared to uniform current value control.SOLUTION: A first calculation unit 81 calculates a movement amount x in a thrust direction of a hammer 24 from detection signals of Hall elements H1 to H4 on a sensor substrate 40, calculates an average value xby performing moving average processing on the movement amount x based on a plurality of times of striking, compares the average value xwith a target set value x, and when the average value xexceeds a tolerance upper limit (x+Δx), assumes an angular velocity target value ωas a value (ω-Δω) obtained by subtracting a correction amount Δω from a present target angular velocity ω. When the average value xis less than a tolerance lower limit (x-Δx), the first calculation unit 81 assumes the angular velocity target value ωas a value (ω+Δω) obtained by adding the correction amount Δω to the present target angular velocity ω. If the average value xis within the tolerance (x±Δx), the first calculation unit 81 assumes the angular velocity target value ωas the present target angular velocity ω.

Description

  The present invention relates to an electric power tool such as an impact driver that performs operations such as screw tightening using a rotating impact force.

  Impact tools such as impact drivers use a motor as a drive source, apply rotational force to the hammer via the speed reduction mechanism, and intermittently transmit rotational impact force to the tip tool by colliding the hammer with the anvil to tighten the screws. (See, for example, Patent Document 1).

  When a bolt is tightened to a hard member with an impact tool, the bolt begins to tighten the mating member several times and a strong frictional force is generated between the mating material and the bolt nut. And the anvil will hardly rotate. Therefore, the hammer's striking force is mostly stored by the tip tool and anvil torsion, and then returned to the hammer as a repulsive force. The greater the amount of repulsion applied to the hammer, the more the hammer moves backward and compresses the hammer spring, and the accumulated compression energy increases. Therefore, the hammer angular velocity immediately before hitting increases accordingly, and the hitting force further increases.

  However, if the amount of repulsion applied to the hammer is too large, the hammer collides with the stopper to generate an impact force, which propagates to the speed reduction mechanism portion and its periphery. If the same operation is performed for a long time, the mechanical parts may be worn out or damaged, resulting in a decrease in the product life. In addition, when the hammer collides with the stopper, the hammer suddenly shifts from backward to forward, so the timing of impact changes, and the hammer collides with the anvil where it originally does not collide, resulting in decreased impact force, increased vibration, and impact. This will cause damage to the parts.

JP 2002-46078 A JP 2009-72889 A

  With respect to the above problem, Patent Document 2 discloses a method of controlling the motor current so as to decrease when the motor driving current exceeds a predetermined value. As a result, the hammer's striking force is suppressed, so that it is possible to prevent the hammer's repulsion amount from becoming too large and damaging the speed reduction mechanism. However, since the angular velocity of the motor with respect to the current value varies for each product due to individual differences, when uniform current value control is performed, the angular velocity of the motor is reduced more than necessary, and a product with a reduced impact force is generated. These problems are not limited to impact tools that repeatedly strike in the rotational direction, but also apply to hammers and hammer drills that repeatedly strike in the axial direction.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide an electric tool capable of executing control that is less likely to cause variation in impact force for each product as compared with conventional uniform current value control. It is to provide.

One embodiment of the present invention is a power tool. This electric tool
A motor,
A motor control unit for driving and controlling the motor;
A hammer for obtaining a driving force from the motor;
An output unit that is driven by a striking force from the hammer;
Hammer movement amount detection means for detecting the movement amount of the hammer when the hammer strikes the output unit and leaves the output unit;
The motor control unit controls power supplied to the motor according to a movement amount of the hammer.

  The motor control unit may reduce the power supplied to the motor when the amount of movement of the hammer or the average of the number of movements exceeds a predetermined value.

  The motor control unit may reduce the power supplied to the motor when the hammer hitting speed or the average of the hitting speeds for the output part exceeds a predetermined value.

  When the motor control unit detects that the movement amount of the hammer in the thrust direction or the average of a plurality of times of the movement amount exceeds a predetermined value based on the detection signal of the hammer movement amount detection means, The hammer control unit calculates a hammering speed of the hammer for the output unit based on a detection signal of the hammer movement amount detection means, and reduces the calculated hitting speed or a plurality of times of the hitting speed. When the average exceeds a predetermined value, the second control for reducing the power supplied to the motor can be executed, and either control may be executed preferentially according to a predetermined condition.

  A hammer case for accommodating the hammer, wherein the hammer movement amount detection means includes at least one magnetic detection element provided in the hammer case, and a magnetic flux generation means for applying a magnetic field to the magnetic detection element; The magnetic field applied to the magnetic detection element may change as the hammer moves in the thrust direction.

  A plurality of the magnetic detection elements may be provided so that positions in the thrust direction are different.

A speed reduction mechanism for reducing the rotation of the motor;
A spindle interposed between the speed reduction mechanism and the hammer, transmitted from the speed reduction mechanism, and coupled to the hammer by a cam mechanism;
Urging means for urging the hammer toward the output unit,
The cam mechanism includes a spindle cam groove formed in the spindle, a hammer cam groove formed in the hammer, and a ball that commonly engages with the spindle cam groove and the hammer cam groove. The hammer may be moved backward with respect to the output portion against the biasing force of the biasing means when the portion is hit in the rotation direction.

  It should be noted that any combination of the above-described constituent elements, and those obtained by converting the expression of the present invention between methods and systems are also effective as aspects of the present invention.

  According to the present invention, there is provided hammer movement amount detection means for detecting the movement amount of the hammer when the hammer hits the output portion and leaves the output portion, and supplies the motor to the motor according to the movement amount of the hammer. Due to the configuration for controlling the electric power, it is possible to execute the control in which the variation in the striking force for each product is less likely to occur as compared with the conventional uniform current value control.

Sectional drawing which shows the internal structure of the impact driver 1 which concerns on embodiment of this invention. Explanatory drawing of the position detection of the hammer 24 in the impact driver 1 shown in FIG. The functional block diagram which shows the control system of the impact driver 1 shown in FIG. The flowchart of the 1st control of the impact driver 1 shown in FIG. The flowchart of the 2nd control of the impact driver 1 shown in FIG. The flowchart of selection of the 1st control and the 2nd control in the impact driver 1 shown in FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, process, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  FIG. 1 is a cross-sectional view showing an internal structure of an impact driver 1 as an electric power tool according to an embodiment of the present invention. In the figure, the front, rear, and top and bottom directions are defined.

  The impact driver 1 uses a rechargeable battery 39 as a power source, drives the rotary impact mechanism 21 using the motor 3 as a drive source, applies rotational force and impact force to an anvil 30 (an example of an output portion) that is an output shaft, and a sleeve The rotary impact force is intermittently transmitted to a tip tool (not shown) such as a driver bit held in the mounting hole 30a covered with 31 to perform operations such as screw tightening and bolt tightening.

  The brushless DC motor 3 is accommodated in a cylindrical body portion 2a of the housing 2 having a substantially T-shape when viewed from the side. The motor 3 includes a rotor 3a, a stator core 3b fixed to the housing 2, a coil 3c, a magnet 3d (rotor magnet), and a rotating shaft 3e that rotates integrally with the rotor 3a. The insulators 14 and 15 are provided to insulate the stator core 3b and the coil 3c. A rotation shaft 3e of the motor 3 is rotatably held by a bearing 19a and a bearing 19b on the rear end side provided near the center portion of the body portion 2a of the housing 2, and coaxially with the rotation shaft 3e at the front of the motor 3. A rotor fan 13 that is attached and rotates in synchronization with the motor 3 is provided. An inverter circuit board 4 for driving the motor 3 is disposed behind the motor 3. A current is supplied from the battery 39 to the coil 3 c of the motor 3 through the inverter circuit board 4. The air flow generated by the rotor fan 13 is taken into the body portion 2a from an air intake port (not shown) formed in a housing portion around the air intake hole 17 and the inverter circuit board 4, and mainly the rotor 3a and the stator core. 3b, is sucked from the rear of the rotor fan 13 and flows in the radial direction of the rotor fan 13, from the air discharge port (not shown) formed in the housing portion around the rotor fan 13 to the outside of the housing 2 To be discharged.

  The inverter circuit board 4 is an annular multilayer board having substantially the same diameter as the outer shape of the motor 3, and a plurality of switching elements 5 such as FETs (Field Effect Transistors) and position detection elements (such as Hall ICs) on the board. And other electronic elements are mounted. A plastic spacer 35 is provided between the rotor 3a and the bearing 19b. The shape of the spacer 35 is substantially cylindrical, and is arranged in order to keep the distance between the bearing 19b and the rotor 3a constant. The inverter circuit board 4 is connected to the battery 39 via the lead wire 11.

  A trigger switch 6 is disposed in an upper portion of the handle portion 2b extending integrally at a substantially right angle from the body portion 2a of the housing 2, and a switch substrate 7 is provided below the trigger switch 6. A control circuit board 8 having a function of controlling the speed of the motor 3 by the pulling operation of the trigger 6 a is accommodated in the lower part in the handle portion 2 b, and this control circuit board 8 is electrically connected to the battery 39 and the trigger switch 6. Connected. The control circuit board 8 is connected to the inverter circuit board 4 via the signal line 12. A battery 39 composed of a nickel-cadmium battery, a lithium ion battery, or the like is detachably attached to the battery attachment portion 2c below the handle portion 2b.

  The rotary striking mechanism 21 is accommodated in a hammer case 16 that is fitted and fixed to the front side of the housing 2, for example, and includes a planetary gear reduction mechanism 22, a spindle 27, and a hammer 24. The rear end is a bearing 20, and the front end is a metal bearing. 29. When the trigger switch 6 is pulled and the motor 3 is started, the motor 3 starts to rotate in the direction set by the forward / reverse switching lever 10, and the rotational force is decelerated by the planetary gear reduction mechanism 22 and transmitted to the spindle 27. The spindle 27 is driven to rotate at a predetermined speed. Here, the spindle 27 and the hammer 24 are connected by a cam mechanism, and this cam mechanism is formed on the V-shaped spindle cam groove 25 formed on the outer peripheral surface of the spindle 27 and the inner peripheral surface of the hammer 24. The hammer cam groove 28 and a ball 26 (for example, a metal ball such as a steel ball) engaged with the cam grooves 25 and 28 are configured.

  The hammer 24 is always urged forward by the hammer spring 23, and when stationary, the hammer 26 is engaged with the cam grooves 25 and 28 so as to be spaced from the end face of the anvil 30. And the convex part which is not shown in figure is formed symmetrically at two places on the rotation plane where the hammer 24 and the anvil 30 face each other.

  When the spindle 27 is driven to rotate, the rotation is transmitted to the hammer 24 via the cam mechanism, and the convex portion of the hammer 24 engages with the convex portion of the anvil 30 before the hammer 24 rotates halfway. When relative rotation occurs between the spindle 27 and the hammer 24 due to the reaction force at that time, the hammer 24 compresses the hammer spring 23 along the spindle cam groove 25 of the cam mechanism, and the motor 3 side. Start retreating.

  When the protrusion of the hammer 24 moves over the protrusion of the anvil 30 due to the backward movement of the hammer 24 and the engagement between the two is released, the hammer 24 is accumulated in the hammer spring 23 in addition to the rotational force of the spindle 27. While being accelerated rapidly in the rotational direction and forward by the action of the elastic energy and the cam mechanism that has been moved, it moves forward by the urging force of the hammer spring 23, and its convex part is re-engaged with the convex part of the anvil 30 to be integrated. Start spinning. At this time, since a strong rotational impact force is applied to the anvil 30, the rotational impact force is transmitted to the screw via a tip tool (not shown) attached to the mounting hole 30a of the anvil 30. Thereafter, the same operation is repeated, and the rotational impact force is intermittently and repeatedly transmitted from the tip tool to the screw. For example, the screw is screwed into a material to be tightened such as wood.

  Next, a method for detecting the position and speed of the hammer 24 will be described. A cylindrical magnet 41 as a magnetic flux generating means is attached to the outer periphery of the rear end of the hammer 24. The magnet 41 is formed by combining a first magnet 41a whose outer peripheral surface is an N pole surface and a second magnet 41b whose outer peripheral surface is an S pole surface. A sensor substrate 40 is disposed on the hammer case 16. A Hall element is mounted on the sensor substrate 40 as will be described later, and is electrically connected to the control circuit substrate 8.

FIG. 2 is an explanatory diagram of the position detection of the hammer 24 in the impact driver 1 shown in FIG. Four Hall elements (H1 to H4), which are examples of magnetic detection elements, are arranged on the sensor substrate 40 in the front-rear direction and fixed by, for example, soldering. Along with the retraction of the hammer 24 at the time of hitting, the magnetic flux change is detected in order from the Hall elements H1 to H2, H3, and H4. Further, as the hammer 24 advances following the retreat, the magnetic flux change is detected in order from the Hall elements H4 to H3, H2, and H1. The horizontal axis of the output signal shown in FIG. 2 for each Hall element indicates the rear end position of the hammer 24. The position of the hammer 24 (P0 to P9) can be specified by obtaining, for example, a peak value or a point of magnetic flux 0 from the detection signals of the Hall elements H1 to H4. Moreover, the moving speed of the hammer 24 can also be calculated by simultaneously recording the detection times (T0 to T9) at which the hammer 24 has been detected at each position. Assuming that the movable limit of the hammer 24 is x _LIM , the retreat amount 24a reaches the movable limit x _LIM and damages the speed reduction mechanism 22 during heavy load work such as bolt tightening. Therefore, by setting the target value x _SET of the reverse amount 24a to be equal to or less than x _LIM and controlling the motor 3, the reverse amount of the hammer 24 can be optimized.

FIG. 3 is a functional block diagram showing a control system of the impact driver 1 shown in FIG. The microcomputer 80 as a motor control unit is mounted on the control circuit board 8 shown in FIG. The microcomputer 80 includes a first calculation unit 81, a second calculation unit 82, a motor control circuit 83, and memories 84 and 85. Each block of the microcomputer 80 is appropriately realized by hardware, software, and a combination thereof. The memories 84 and 85 may be built-in memories of the microcomputer 80 or may be external memories different from the microcomputer 80. The memory 84 stores a target set value x _SET for the retraction amount 24 a of the hammer 24. The memory 85 stores the rotational energy target set value E _SET of the hammer 24 immediately before hitting.

Motor 3 is PWM controlled in accordance with the target angular velocity omega _iT by the motor control circuit 83, (rotating at an angular velocity omega _i) to generate an angular velocity omega _i. The speed reduction mechanism 22 reduces the angular speed ω _{i of the} motor 3 to an angular speed ω _o (= ω _i / ε) with a speed reduction ratio ε and transmits it to the spindle 27. Hammer 24 is an angular velocity omega _H accelerating the spindle 27 by the elastic energy of the hammer spring 23 at the time of hitting, the angular velocity immediately before the strike the anvil 30 reaches _{ω F (= ω o + ω} H). Hall elements H1 to H4 on the sensor substrate 40 detect magnetic flux that changes as the hammer 24 moves in the thrust direction (axial direction). The first calculation unit 81 and the second calculation unit 82 can calculate the movement amount x and the movement speed v of the hammer 24 in the thrust direction by signal processing based on the output signals of the Hall elements H1 to H4. Then, the first calculation unit 81 and the second calculation unit 82 determine the angular velocity target values ω _iT1 and ω _iT2 by comparing the movement amount x and the movement speed v in the thrust direction of the hammer 24 with target values as will be described later. . The motor control circuit 83 performs PWM control of the motor according to the angular velocity target values ω _iT1 and ω _iT2 determined by the first calculation unit 81 and the second calculation unit 82 and the operation amount of the trigger switch 6 (the pulling amount of the trigger 6a) by the user. Take control.

FIG. 4 is a flowchart of the first control (calculation processing of the first computation unit 81) of the impact driver 1 shown in FIG. The first calculation unit 81 calculates a movement amount x in the thrust direction of the hammer 24 from the detection signals of the Hall elements H1 to H4 on the sensor substrate 40 (S11), and performs a moving average process on the movement amount x due to the multiple hits. The average value x _AVE is calculated (S12), the average value x _AVE is compared with the target set value x _SET (S13), and the average value x _AVE exceeds the allowable range upper limit (x _SET + Δx) (N in S13) ) Is _transferred to the motor control circuit 83 as a value (ω _iT −Δω) obtained by subtracting the correction amount Δω from the current target angular velocity ω _{iT from the} angular velocity target value ω _iT1 (S14). On the other hand, when the average value x _AVE is less than the allowable lower limit (x _SET −Δx) (Y in S13, N in S15), the first calculation unit 81 determines the angular velocity target value ω _iT1 as the current target angular velocity ω _iT. Is supplied to the motor control circuit 83 as a value (ω _iT + Δω) obtained by adding the correction amount Δω to (S16). If the average value x _AVE is within the allowable range (x _SET ± Δx) (Y in S13, Y in S15), the first calculation unit 81 sets the angular velocity target value ω _iT1 as the current target angular velocity ω _iT. It is handed over to 83 (S17).

FIG. 5 is a flowchart of the second control (calculation processing of the second computation unit 82) of the impact driver 1 shown in FIG. The second calculation unit 82 calculates the moving speed v in the thrust direction (forward direction) of the hammer 24 from the detection signals of the Hall elements H1 to H4 on the sensor substrate 40 (S21), and converts the moving speed v into an angular speed (ω _H = 2v / d · tanθ) and (S22), further subjected to striking velocity calculation _{(ω F = ω o + ω} H) (S23), performs rotational energy calculated at the time of hitting ^{_{(E H = Iω F 2/}} 2) ( S24), the rotational energy E _H resulting from multiple hits is subjected to moving average processing to calculate an average value E _AVE (S25), the average value E _AVE is compared with the target set value E _SET (S26), and the average value E _AVE Exceeds the allowable upper limit (E _SET + ΔE) (N in S26), the motor control circuit uses the angular velocity target value ω _iT2 as a value (ω _iT −Δω) obtained by subtracting the correction amount Δω from the current target angular velocity ω _iT. It is handed over to 83 (S27). On the other hand, when the average value E _AVE is less than the allowable range lower limit (E _SET −ΔE) (Y in S26, N in S28), the second calculation unit 82 uses the angular velocity target value ω _iT2 as the current target angular velocity ω _iT. Is supplied to the motor control circuit 83 as a value (ω _iT + Δω) obtained by adding the correction amount Δω to (S29). If the average value E _AVE is within the allowable range (E _SET ± ΔE) (Y in S26, Y in S28), the second calculation unit 82 sets the angular velocity target value ω _iT2 as the current target angular velocity ω _iT and the motor control circuit. It is handed over to 83 (S30). The target set value E _SET can be changed by the operation unit on the upper surface of the control circuit board 8, and the user can change the setting according to the work.

FIG. 6 is a flowchart of selection of the first control and the second control in the impact driver 1 shown in FIG. Based on this flowchart, the motor control circuit 83 determines the priority of the calculation results of the first calculation unit 81 and the second calculation unit 82. First, the setting state of the energy control mode of the operation unit on the upper surface of the control circuit board 8 is confirmed (S51). When not set (N in S51), the movement amount control (ω _iT = ω _iT1 ) of the hammer 24 is always performed according to the calculation result of the first calculation unit 81 (S52), and when set (Y in S51), It is determined whether or not the angular velocity target value ω _iT1 of the 1 calculating unit 81 _{exceeds the} previous target value ω _iT (current target angular velocity) (S53). If the previous target value ω _iT has been exceeded (Y in S53), the movement amount x of the hammer 24 is less than the set value x _SET , so that the energy control (ω _iT = ω _iT2 ) is _performed according to the result of the second calculation unit 82. Perform (S54). When the angular velocity target value ω _iT1 is less than the previous target value ω _iT (N in S53, N in S55), the movement amount x of the hammer 24 is equal to or larger than the set value x _SET , and accordingly, the hammer 24 according to the result of the first calculation unit 81. _Is controlled (ω _iT = ω _iT1 ) (S52). _Only when the angular velocity target value ω _iT1 is equal to the previous target value ω _iT (Y in S55), and when the result of the second calculation unit 82 (angular velocity target value ω _iT2 ) is less than the previous target value ω _iT (Y in S56). Energy control (ω _iT = ω _iT2 ) is performed according to the result of the second calculation unit 82 (S54). Otherwise (N in S56), the movement amount control (ω _iT = ω _iT1 ) of the hammer 24 is performed according to the result of the first calculation unit 81 (S52). By determining the priority, the movement amount of the hammer 24 does not reach the limit value x _LIM , so that the speed reduction mechanism 22 can be protected.

  According to the present embodiment, the following effects can be achieved.

(1) When the hammer 24 strikes the anvil 30 in the rotational direction and moves backward with respect to the anvil 30, the amount of movement of the hammer 24 in the thrust direction is detected and used for driving control of the motor 3 (the amount of repulsion is controlled). ) Due to the configuration, the speed reduction mechanism 22 is damaged due to excessive retraction of the hammer 24, the hammer 24 collides with the stopper, and the hammer 24 and the anvil 30 collide with each other due to abrupt transition from retreat to advance. Compared to the conventional case where uniform current value control is performed to prevent collisions at unsuccessful locations, resulting in reduced impact force, increased vibration, and damage to the impacted part. Thus, it is possible to execute control that is less likely to cause variation. That is, since the amount of repulsion of the hammer 24 can be optimally controlled for each impact driver 1 body, the hammer 24 can be prevented from colliding with the stopper due to excessive retreat, and the impact force can be controlled individually as in the case of uniform current value control. Without being lowered due to the difference, damage to the speed reduction mechanism 22 and the like can be prevented, and the life of the impact driver 1 can be extended.

(2) By controlling the impact energy of the hammer 24 by detecting the movement speed of the hammer 24 in the thrust direction when the hammer 24 moves forward with respect to the anvil 30, the impact force is stabilized and the minimum output is required. It is possible to further improve the life of the impact driver 1 main body. That is, since the rotational energy of the hammer 24 immediately before hitting can be optimally controlled, by setting the minimum value necessary for the work to be performed, the load on the speed reduction mechanism 22 and the like is suppressed, and the impact driver 1 main body has a longer life. Can be In addition, since the impact force of each impact can be made uniform, a stable torque can always be obtained without individual differences, and by making the set value variable, the user can easily obtain the target tightening torque. .

(3) The speed reduction mechanism 22 can be reliably protected by executing the relationship with the movement amount control as described in FIG. 6 while having the function of controlling the hammering energy of the hammer 24.

(4) Since the movement amount of the hammer 24 in the thrust direction can be detected in a non-contact manner by the Hall elements H1 to H4, the risk of damage to the sensor is small. In addition, the position detection is more reliable than the case of using an optical sensor, and the position detection is highly reliable.

  The present invention has been described above by taking the embodiment as an example. However, it is understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiment within the scope of the claims. By the way. Hereinafter, modifications will be described.

  The magnet 41 may be fixed to the hammer case 16 side (such as behind the sensor substrate 40). The arrangement of the magnet 41 is not limited as long as the magnetic flux that changes with the movement of the hammer 24 in the thrust direction can be applied to the Hall elements H1 to H4.

  The number of Hall elements H1 to H4 is arbitrary, and a magnetic detection element other than the Hall element may be used.

  The power tool is not limited to the impact tool such as the impact driver 1 that repeatedly strikes in the rotation direction as described in the embodiment, but may be a hammer or a hammer drill that repeatedly strikes in the axial direction.

1 impact driver 2 housing, 2a body part, 2b handle part, 2c battery mounting part 3 motor, 3a rotor, 3b stator core, 3c coil, 3d magnet,
3e Rotating shaft 4 Inverter circuit board, 5 Switching element, 6 Trigger switch, 6a Trigger, 7 Switch board, 8 Control circuit board, 10 Forward / reverse switching lever, 11 Lead wire,
12 signal lines, 13 rotor fans, 14 insulators, 15 insulators,
17 Air intake hole, 19a, 19b, 20 Bearing,
21 hammering mechanism, 22 planetary gear reduction mechanism, 23 hammer spring, 24 hammer 24a hammer retraction, 25 spindle cam groove, 26 balls, 27 spindle, 28 hammer cam groove, 29 metal bearing, 30 anvil, 30a mounting hole, 31 sleeve , 35 Spacer, 39 Battery, 40 Sensor board, 41 Magnet, 41a Magnet (N pole side), 41b Magnet (S pole side)

Claims (7)

A motor,
A motor control unit for driving and controlling the motor;
A hammer for obtaining a driving force from the motor;
An output unit that is driven by a striking force from the hammer;
Hammer movement amount detection means for detecting the movement amount of the hammer when the hammer strikes the output unit and leaves the output unit;
The electric motor according to claim 1, wherein the motor control unit controls electric power supplied to the motor in accordance with a movement amount of the hammer.   2. The electric tool according to claim 1, wherein the motor control unit reduces power supplied to the motor when a movement amount of the hammer or an average of a plurality of times of the movement amount exceeds a predetermined value.   3. The electric tool according to claim 1, wherein the motor control unit reduces power supplied to the motor when an average of a plurality of hitting speeds or hitting speeds of the hammer with respect to the output unit exceeds a predetermined value. .   When the motor control unit detects that the movement amount of the hammer in the thrust direction or the average of a plurality of times of the movement amount exceeds a predetermined value based on the detection signal of the hammer movement amount detection means, The hammer control unit calculates a hammering speed of the hammer for the output unit based on a detection signal of the hammer movement amount detection means, and reduces the calculated hitting speed or a plurality of times of the hitting speed. 2. The second control for reducing the power supplied to the motor when the average exceeds a predetermined value is executable, and one of the controls is preferentially executed according to a predetermined condition. Electric tool.   A hammer case for accommodating the hammer, wherein the hammer movement amount detection means includes at least one magnetic detection element provided in the hammer case, and a magnetic flux generation means for applying a magnetic field to the magnetic detection element; The electric tool according to any one of claims 1 to 4, wherein a magnetic field applied to the magnetic detection element changes as the hammer moves in a thrust direction.   The power tool according to claim 5, wherein a plurality of the magnetic detection elements are provided so that positions in the thrust direction are different. A speed reduction mechanism for reducing the rotation of the motor;
A spindle interposed between the speed reduction mechanism and the hammer, transmitted from the speed reduction mechanism, and coupled to the hammer by a cam mechanism;
Urging means for urging the hammer toward the output unit,
The cam mechanism includes a spindle cam groove formed in the spindle, a hammer cam groove formed in the hammer, and a ball that commonly engages with the spindle cam groove and the hammer cam groove. The electric tool according to any one of claims 1 to 6, wherein when the part is hit in the rotation direction, the hammer is moved backward with respect to the output part against the urging force of the urging means.