JP2011073116A - Rotary striking tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the rotation of a motor by discriminating between an impact by main striking and an impact based on its other factor, in a rotary striking tool using an oil pulse unit. <P>SOLUTION: This rotary striking tool includes a motor having a rotation position detecting element, the oil pulse unit driven by the motor, an output shaft connected to the oil pulse unit and installing a tip tool, and a detecting means for detecting the size of impact force generated in the oil pulse unit, measures a time interval up to a position signal of the rotation position detecting element appearing thereafter when the impact is detected by the detecting means, determines that the impact is caused by the main striking when the measured time interval is a predetermined time or more, and determines that the impact is a half pulse when the measured time interval is less than the predetermined time. When the impact by the main striking reaches a specified output value, the rotation of the motor is stopped. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rotary impact tool that is rotationally driven by a motor and tightens a fastening member such as a screw or a bolt by using an intermittent impact force.

  As a rotary impact tool (power tool) for tightening screws, bolts, etc., a rotary impact tool for tightening by applying a rotational force or an impact force in the rotational direction is known. As a kind of rotary impact tool, as described in Patent Document 1, the hammer part is rotated in a state in which it is movable in the axial direction using a spring or a cam mechanism, and the hammer rotates once with respect to the anvil part. An impact driver of a method of hitting once or twice, and an oil pulse tool using an oil pulse unit as a hitting mechanism as in Patent Document 2 are known.

  The oil pulse tool has a feature that operation noise is low because there is no collision between metals. A motor is used as power for driving the oil pulse unit, and the output shaft of the motor is directly connected to the oil pulse unit. When a trigger switch for operating the oil pulse tool is pulled, driving power is supplied to the motor, and the motor driving force is changed in proportion to the amount by which the trigger switch is pulled to control the rotation speed of the motor. When pulsed torque is generated in the oil pulse unit, a strong impact torque is transmitted to the tip tool, and the torque sensor detects the peak value of the torque of the output shaft due to each impact. The rotation angle of the output shaft is detected by an angle sensor provided on the output shaft, and the peak torque approaches the target output from the difference between the target peak torque curve from the start to the end of screw tightening and the measured peak torque. Control as follows.

JP 2005-305578 A Japanese Patent Laid-Open No. 06-091552

  In the oil pulse unit exemplified in Patent Document 2, high-pressure air is used as a power source, but in recent years, a rotary impact tool using an electric motor has been used. In the rotary impact tool using an electric motor, the peak torque at each impact is detected, the target torque value at the next impact is set according to the magnitude of the peak torque, and the impact is performed at the target torque value. Performs motor rotation control. Then, when the peak torque at the time of impact exceeds the determination value for completion of tightening, the motor is stopped. When performing this control, it is important to accurately detect the peak torque at the time of impact using a torque sensor, but in the case of an oil pulse unit, not only the peak torque due to the main impact, A pulse due to torque appearing at a point about 180 degrees apart from the main striking position and rotation position (in this specification, the torque pulse at a point separated by 180 degrees is referred to as a “half pulse”). It is important to accurately identify and control the peak torque.

  The present invention has been made in view of the above background, and an object of the present invention is to control the rotation of a motor by accurately discriminating impact caused by main impact and impact based on other factors in a rotary impact tool using an oil pulse unit. It is in providing the rotary impact tool which performs.

  Another object of the present invention is to provide a rotary impact tool that can distinguish an impact based on a main impact and an impact based on other factors by using an output of a position detection element of a brushless motor.

  Still another object of the present invention is to set a threshold value for ignoring the output of the detecting means for detecting the magnitude of impact, and to exclude the use of an output value that does not reach this threshold value for motor rotation control. It is an object of the present invention to provide a rotary impact tool that enables tightening control without the influence of the above.

  Of the inventions disclosed in the present application, typical features will be described as follows.

  According to one aspect of the present invention, a motor having a rotational position detecting element, an oil pulse unit driven by the motor, an output shaft connected to the oil pulse unit and mounted with a tip tool, and an impact in the oil pulse unit In the rotary impact tool having a detecting means for detecting the magnitude of the shock, when the output value of the magnitude of the impact force is detected by the detecting means, the time interval until the position signal of the rotating position detecting element that appears thereafter is measured. If the measured time interval is greater than or equal to a predetermined time, the output value is determined to be due to the main impact, and if the measured time interval is less than the predetermined time, the output value is a half pulse. Judgment was made and tightening control was performed using the output value of the main impact. When the output from the main hit reaches a specified output value, the rotation of the motor is stopped.

  According to another feature of the invention, the motor has a rotor having a permanent magnet and a stator having a winding, and the rotational position detecting element is a plurality of Hall elements provided facing the permanent magnet. The position signal is created from the output signals of a plurality of rotational position detection elements. A Hall element is an element that detects a magnetic field using the Hall effect, and converts a magnetic field generated by a magnet or a magnetic field generated by a current into an electrical signal and outputs the electrical signal. Three Hall elements are arranged at predetermined intervals in the circumferential direction, and the position signal appears every 30 degrees, for example, every 30 degrees.

  According to still another feature of the present invention, a threshold value of the output value detected by the detecting means is provided, and an output value equal to or less than the threshold value is not adopted for measuring the time interval. Further, a control unit is provided to process the detection signal detected from the detection means, and to control the rotation of the motor using the detection signal. The control unit preferably includes a microprocessor, and performs feedback control by comparing the output value of the detection means with the target output value.

  According to the first aspect of the present invention, when the output value is detected by the detecting means, the time interval until the position signal of the rotational position detecting element that appears thereafter is measured, and the measured time interval is equal to or greater than a predetermined time. In this case, since the output value is determined to be due to the main impact, it is possible to realize a rotary impact tool that can perform tightening with high accuracy without being affected by the half pulse detected by the detection means.

  According to the invention of claim 2, the motor has a rotor having a permanent magnet and a stator having a winding, and the rotational position detecting element is a plurality of hall elements provided facing the permanent magnet, Since the position signal is created from the output signals of a plurality of Hall elements, it is not necessary to provide a sensor for detecting the rotation angle on the output shaft on which the tip tool is mounted, and the size of the rotary impact tool can be reduced. Moreover, the manufacturing cost can be reduced.

  According to the third aspect of the present invention, three Hall elements are arranged at predetermined intervals, and the position signal appears every time the rotor rotates by a predetermined angle. Therefore, the rotation angle of the oil pulse unit is determined by the rotational position detection element of the motor. Can be detected.

  According to the invention of claim 4, since the rotation of the motor is stopped when the output value reaches the specified output value, it is possible to finish the work after confirming that the tightening is surely completed by the main impact. it can.

  According to the invention of claim 5, since the threshold value of the output value detected by the detecting means is provided, and the output value below the threshold value is not adopted for measuring the time interval, the output value is small such as when passing through after the main impact. It is possible to prevent an adverse effect on the tightening control due to.

  According to the sixth aspect of the present invention, since the control unit that processes the signal detected from the detection means and controls the rotation of the motor using the detection signal is provided, the rotation control of the motor with high accuracy can be realized.

  According to the invention of claim 7, since the control unit has a microprocessor and performs feedback control by comparing the adopted output value with the target output value, the motor rotation control by the target output value management is highly accurate. Can be realized.

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

It is sectional drawing which shows the whole structure of the impact driver which concerns on the Example of this invention. It is an expanded sectional view of the oil pulse unit 4 of FIG. FIG. 3 is a cross-sectional view taken along the line AA of FIG. 2 and illustrating a movement of one rotation in an operating state of the oil pulse unit 4 in eight stages. It is a block diagram which shows the structure of the drive control system of the motor 3 which concerns on the Example of this invention. It is a figure which shows the relationship between the output waveform of the rotor position detection circuit 43, and the rotation position signal of the motor 3 using the waveform. It is a graph which shows the relationship between the timing of impact in oil pulse unit 4 and time, the relationship of the output signal of an impact sensor related to it, and the rotational speed of a motor. It is a flowchart which shows the control which determines the output peak by the main hit by the Example of this invention. It is a figure which shows another example of the main impact position, a half pulse position, and the appearance position of a position detection pulse.

  Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, description will be made using an impact driver using an oil pulse unit as an example of the rotary impact tool. In the description of the present specification, the up and down and front and rear directions are described as the directions shown in FIG. FIG. 1 is a sectional view showing an entire impact driver according to an embodiment of the present invention.

  The impact driver 1 drives the motor 3 using electric power supplied from the outside by the power cord 2, drives the oil pulse unit 4 by the motor 3, and rotates and hits the main shaft 24 of the oil pulse unit 4. Is applied to a tool bit, hexagon socket, or other tip tool (not shown) for continuous or intermittent transmission to perform tightening operations such as screw tightening, nut tightening, and bolt tightening.

  The power supplied by the power cord 2 is direct current or alternating current such as AC 100V. In the case of alternating current, a rectifier (not shown) is provided in the impact driver 1 and converted to direct current, and then sent to the motor drive circuit. The motor 3 is a brushless DC motor having a rotor 3b having a permanent magnet on the inner peripheral side and a stator 3a having a winding wound around an iron core on the outer peripheral side, and is constituted by two bearings 10a and 10b. The rotation shaft is rotatably fixed and is accommodated in the cylindrical body portion 6 a of the housing 6. The housing 6 is made of a plastic body or the like, with the body portion 6a and the handle portion 6b being integrally formed. A drive circuit board 7 for driving the motor 3 is disposed behind the motor 3, and an inverter circuit composed of a semiconductor element such as an FET and the rotational position of the rotor 3b are detected on the circuit board. Therefore, a rotational position detecting element 42 such as a Hall element or Hall IC is mounted. A cooling fan unit 17 for cooling is provided at the rearmost end inside the body portion 6a of the housing.

  A trigger switch 8 is disposed in the vicinity of the attachment portion of the handle portion 6b of the housing extending downward from the body portion 6a at a substantially right angle, and is proportional to the amount of the trigger switch 8 pulled by the switch circuit board 14 provided immediately below. The signal is transmitted to the motor control board 9a. Below the handle portion 6b, two control boards 9, a motor control board 9a and a rotational position detection board 9b, are provided. The motor control board 9a is provided with an impact sensor 12 for detecting impact of impact in the oil pulse unit 4. The magnitude of the hit made can be detected from the output of the impact sensor 12. Note that the means for detecting the magnitude of impact in the oil pulse unit 4 is not limited to the impact sensor 12 but may be means for detecting the magnitude of impact by the current flowing through the motor.

  In the oil pulse unit 4 built in the body portion 6 a of the housing, the liner plate 23 on the rear side is directly connected to the rotation shaft of the motor 3, and the main shaft 24 on the front side functions as the output shaft of the impact driver 1. When the trigger switch 8 is pulled to start the motor 3, the rotational force of the motor 3 is transmitted to the oil pulse unit 4. When the oil pulse unit 4 is filled with oil and no load is applied to the main shaft 24 or when the load is small, the main shaft 24 is almost rotated only by the resistance of the oil. Rotate synchronously. When a strong load is applied to the main shaft 24, the rotation of the main shaft 24 stops, and only the liner on the outer peripheral side of the oil pulse unit 4 continues to rotate, and the oil pressure suddenly increases at a position where one place of oil is sealed per rotation. The main shaft 24 is rotated by a strong spire-like torque, and a large tightening torque is transmitted to the main shaft 24. Thereafter, the same striking operation is repeated several times, and the fastening target is tightened with the set torque. The main shaft 24 is connected to the body portion 6a of the housing 6 by the bearing 10c. The bearing 10c of the present embodiment is a ball bearing, but other bearings such as a needle bearing can be used.

  FIG. 2 is an enlarged cross-sectional view of the oil pulse unit 4 of FIG. The oil pulse unit 4 is mainly composed of two parts: a drive part that rotates in synchronization with the motor 3 and an output part that rotates in synchronization with the main shaft 24 to which the tip tool is attached. The drive portion that rotates in synchronization with the motor 3 includes a liner plate 23 that is directly connected to the rotation shaft of the motor 3, a liner 21 that has a substantially cylindrical outer diameter that is fixed so as to extend forward on the outer peripheral side, and a lower plate. 22 is included. The output portion that rotates in synchronization with the main shaft 24 includes the main shaft 24 and a blade that is attached to a groove formed 180 degrees apart on the outer peripheral side of the main shaft 24 via a spring.

  The main shaft 24 is penetrated by the lower plate 22 and is held so as to be able to rotate in a closed space formed by the liner 21, the liner plate 23 and the lower plate 22. In this closed space, torque is generated. Oil (hydraulic oil) is filled. An O-ring 30 is provided between the lower plate 22 and the main shaft 24, and an O-ring 29 is provided between the liner 21 and the liner plate 23 to ensure airtightness between them. Although not shown, the liner 21 is provided with a relief valve (not shown) for releasing the oil pressure from the high pressure chamber to the low pressure chamber, and the tightening torque can be adjusted by controlling the maximum pressure of the generated oil.

  FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2, and illustrates a movement of one rotation in the use state of the oil pulse unit 4 in eight stages. Inside the liner 21 is formed a liner chamber having a cross section that forms four regions as shown in FIG. Blades 25 a and 25 b are fitted and inserted into two opposed groove portions on the outer peripheral portion of the main shaft 24 via springs, and attached to the circumferential direction by the springs so that the blades 25 a and 25 b abut against the inner surface of the liner 21. Be forced. On the outer peripheral surface of the main shaft 24 between the blades 25a and 25b, two convex seal surfaces 26a and 26b that are axially extending are provided. Convex seal surfaces 27a and 27b and convex portions 28a and 28b are formed on the inner peripheral surface of the liner 21.

  In the impact driver 1, when the seat surface of the tightening bolt is seated at the time of bolt tightening, a load is applied to the main shaft 24, the main shaft 24 and the blades 25 a and 25 b are almost stopped, and only the liner 21 continues to rotate. As the liner 21 rotates with respect to the main shaft 24, an impact pulse is generated once per rotation. When the impact pulse is generated, the impact driver 1 has a convex formed on the inner peripheral surface of the liner 21. The convex seal surface 27a and the convex seal surface 26a formed on the outer peripheral surface of the main shaft 24 are in contact with each other. At the same time, the convex seal surface 27b and the convex seal surface 26b come into contact with each other. As described above, the pair of convex seal surfaces formed on the inner peripheral surface of the liner 21 and the pair of convex seal surfaces formed on the outer peripheral surface of the main shaft 24 are in contact with each other. It is divided into a chamber and two low-pressure chambers. An instantaneous strong rotational force is generated in the main shaft 24 due to the pressure difference between the high pressure chamber and the low pressure chamber.

  Next, the operation procedure of the oil pulse unit 4 will be described. (1) to (8) in FIG. 3 are views showing a state in which the liner 21 makes one rotation at a relative angle with respect to the main shaft 24. By pulling the trigger 8, the motor 3 rotates, and the liner 21 rotates in synchronization therewith. In this embodiment, the liner plate 23 is directly connected to the rotation shaft of the motor 3 and rotates at the same rotation speed. However, the present invention is not limited to this configuration, and may be connected via a speed reduction mechanism. When no load is applied to the main shaft 24 or when the load is small, the main shaft 24 rotates almost in synchronization with the rotation of the motor 3 only by the resistance of oil. When a heavy load is applied to the tip tool, the rotation of the main shaft 24 stops, and the outer liner 21 continues to rotate. FIG. 3 shows a state in which only the liner 21 continues to rotate.

  (1) in FIG. 3 is a diagram showing a positional relationship when a striking force is generated on the main shaft 24 by an impact pulse. The position shown in (1) is a “position where oil is sealed”, which is located once per rotation. Here, the convex sealing surfaces 27a and 26a, the sealing surface 27b and the sealing surface 26b, the blade 25a and the convex portion 28a, and the blade 25b and the convex portion 28b contact each other in the entire axial direction of the main shaft 24, respectively. As a result, the inner space of the liner 21 is divided into four chambers of two high-pressure chambers and two low-pressure chambers.

  Here, the high pressure and the low pressure are pressures of oil existing inside. Further, when the liner 21 is rotated by the rotation of the motor 3, the volume of the high pressure chamber decreases, so that the oil is compressed and a high pressure is instantaneously generated. This high pressure pushes the blade 25 toward the low pressure chamber. As a result, a strong rotational torque is generated on the main shaft 24 by momentarily applying a rotational force via the upper and lower blades 25a and 25b. By forming this high-pressure chamber, a strong striking force that rotates the blades 25a, 25b in the clockwise direction in the drawing acts. The position shown in FIG. 3A is referred to as “blow position” in this specification.

  FIG. 3 (2) shows a state in which the liner 21 has rotated 45 degrees from the striking position. After passing the striking position shown in (1), the convex seal surfaces 27a and 26a, the convex seal surface 27b and the seal surface 26b, the blade 25a and the convex portion 28a, and the blade 25b and the convex portion 28b are in contact with each other. Is released, the space partitioned into the four chambers inside the liner 21 is released, and oil flows into each other space, so that no rotational torque is generated, and the liner 21 further rotates as the motor 3 rotates. .

  FIG. 3 (3) shows a state in which the liner 21 has rotated 90 degrees from the striking position. In this state, the blades 25a and 25b contact the convex seal surfaces 27a and 27b and retreat radially inward to a position where they do not protrude from the main shaft 24. Therefore, no rotational torque is generated without being affected by the oil pressure. The liner 21 rotates as it is.

  FIG. 3 (4) shows a state in which the liner 21 has rotated 135 degrees from the striking position. In this state, the inner space of the liner 21 communicates and no oil pressure change occurs, so that no rotational torque is generated on the main shaft.

  FIG. 3 (5) shows a state in which the liner 21 has rotated 180 degrees from the striking position. At this position, the convex seal surfaces 27b and 26a and the convex seal surface 27b and the seal surface 26b come close to each other, but do not come into contact with each other. This is because the convex seal surfaces 26a and 26b formed on the main shaft 24 are not in a symmetrical position with respect to the axis of the main shaft. Similarly, the convex sealing surfaces 27a and 27b formed on the inner periphery of the liner 21 are not in a symmetrical position with respect to the axis of the main shaft. Therefore, almost no rotational torque is generated at this position because it is hardly affected by oil. In addition, since the oil with which it is filled is viscous and the convex seal surfaces 27b and 26a or the convex seal surfaces 27a and 26b face each other, a slightly high pressure chamber is formed. ) To (4) and (6) to (8), a slight rotational torque is generated, but this rotational torque has no effect on tightening.

  The states (6) to (8) in FIG. 3 are substantially the same as (2) to (4), and no rotational torque is generated in these states. Further rotation from the state of (8) returns to the state of (1) of FIG. 3, the convex sealing surfaces 27a and 26a, the sealing surface 27b and the sealing surface 26b, the blade 25a and the convex portion 28a, the blade 25b. And the convex portion 28b contact each other in the entire axial direction of the main shaft 24, and thereby the inner space of the liner 21 is partitioned into four chambers of two high-pressure chambers and two low-pressure chambers. Torque is generated.

  Next, the configuration and operation of the drive control system of the motor 3 will be described with reference to FIG. FIG. 4 is a block diagram showing the configuration of the drive control system of the motor 3. In this embodiment, the motor 3 is a three-phase brushless DC motor. This brushless DC motor is an inner rotor type, and includes a rotor (rotor) 3b including a plurality of sets of permanent magnets (magnets) including N poles and S poles, and a star-connected three-phase fixing. In order to detect the rotational position of the stator 3a (stator) composed of the child windings U, V, W and the rotational position of the rotor 3b, three rotational positions are arranged at predetermined intervals in the circumferential direction, for example, every 60 degrees. A detection element 42 is provided. Based on the position detection signals from these rotational position detection elements 42, the energization direction and time to the stator windings U, V, W are controlled, and the motor 3 rotates.

  The inverter circuit 47 includes six switching elements Q1 to Q6 such as FETs connected in a three-phase bridge format. The gates of the six switching elements Q1 to Q6 connected in a bridge are connected to the control signal output circuit 46, and the drains or sources of the six switching elements Q1 to Q6 are star-connected stator windings. Connected to U, V, W. Thus, the six switching elements Q1 to Q6 perform a switching operation by the switching element drive signals (drive signals H1 to H6) input from the control signal output circuit 46, and are applied to the inverter circuit 47. Is supplied to the stator windings U, V, and W as three-phase (U-phase, V-phase, and W-phase) voltages Vu, Vv, and Vw. Note that the DC power source 52 may be constituted by a secondary battery that is detachably provided.

  Of the switching element drive signals (three-phase signals) for driving the gates of the six switching elements Q1 to Q6, the three negative power supply side switching elements Q4, Q5, Q6 are converted into pulse width modulation signals (PWM signals) H4, The operation amount (stroke) of the trigger switch 8 is supplied to the motor 3 by changing the pulse width (duty ratio) of the PWM signal based on the detection signal of the applied voltage setting circuit 49. Is adjusted to control the start / stop and rotation speed of the motor 3.

  Here, the PWM signal is supplied to any one of the positive power supply side switching elements Q1 to Q3 or the negative power supply side switching elements Q4 to Q6 of the inverter circuit 47, and the switching elements Q1 to Q3 or the switching elements Q4 to Q6 are switched at high speed. As a result, the power supplied to each stator winding U, V, W from the DC power source is controlled. In this embodiment, since the PWM signal is supplied to the negative power supply side switching elements Q4 to Q6, the electric power supplied to the stator windings U, V, W by controlling the pulse width of the PWM signal. Can be adjusted to control the rotation speed of the motor 3.

  The impact driver 1 is provided with a forward / reverse switching lever 51 for switching the rotational direction of the motor 3, and the rotational direction setting circuit 50 switches the rotational direction of the motor each time a change in the forward / reverse switching lever 51 is detected. The control signal is transmitted to the calculation unit 41. Although not shown, the calculation unit 41 is a central processing unit (CPU) for outputting a drive signal based on the processing program and data, a ROM for storing the processing program and control data, and for temporarily storing data. RAM, a timer, and the like. The rotation speed detection circuit 44 is a circuit that receives the signal from the rotor position detection circuit 43 and detects the rotation speed of the motor 3, and outputs the detected value to the calculation unit 41. The rotation angle detection circuit 44 is a circuit that outputs a position signal indicating the rotation position of the motor 3 from the signals from the plurality of rotor position detection circuits 43. The impact detection circuit 45 is a circuit that receives the signal of the impact sensor 12 as input, detects the magnitude of impact caused by the impact, and outputs the detected magnitude to the computing unit 41.

  The control unit 41 forms a drive signal for alternately switching predetermined switching elements Q1 to Q6 based on the output signals of the rotation direction setting circuit 50 and the rotor position detection circuit 43, and outputs the drive signal as a control signal. Output to the circuit 46. As a result, the predetermined windings of the stator windings U, V, and W are alternately energized to rotate the rotor 3b in the set rotation direction. In this case, the drive signal applied to the negative power supply side switching elements Q4 to Q6 of the inverter circuit 47 is output as a PWM modulation signal based on the output control signal of the applied voltage setting circuit 49. The current value supplied to the motor 3 is measured by the current detection circuit 48, and the value is fed back to the calculation unit 41 so as to be adjusted to the set driving power. The PWM signal may be applied to the positive power supply side switching elements Q1 to Q3.

  Next, it is a figure which shows the relationship between the output waveform of the rotor position detection circuit 43, and the rotation position signal of the motor 3 using the waveform using FIG. The motor 3 is a three-phase two-pole motor, and is provided with three position detection elements 42 separated by 60 degrees for the U, V, and W phases. A signal obtained by A / D-converting the output signal from the position detection element 42 becomes rectangular waves 61 to 63, and each of the rotation angles of the rotor 3b is changed from High to Low every 90 degrees or from Low. It changes alternately to High. The rectangular waveform 64 is a pulse wave whose polarity is inverted by the rising edge or falling edge of the rectangular waves 61 to 63 for U, V, and W phases, and the rectangular wave 64 having a short interval every time the rotor 3b rotates by 30 degrees. Appears. This rectangular wave is used as a position detection pulse. When the rotor 3b rotates 360 degrees, 12 position detection pulses appear. In FIG. 6, the rectangular wave 64 is in a high state every 30 degrees of rotation from the starting point of the position of the rotor 3b (= rotation angle 0 degree, position signal “12”), and the rotor 3b is in relation to the stator 3a. 12th rectangular pulse appears at the time of 360 ° rotation.

  In the oil pulse unit 4 in this embodiment, since the input portion (liner plate 23) is connected to the rotation shaft of the motor 3, the rotation angle of the rotor 3b and the rotation of the liner 21 are synchronized. The rotation angles match. The rotation of the liner 21 and the main shaft 24 is not completely synchronized as shown in FIG. 3, but when the main shaft 24 is rotated by a certain angle by striking, the liner rotates until reaching the next striking position. The rotation angle 21 (= the rotation angle of the rotor 3b) is (360 degrees + the rotation angle rotated by the impact).

FIG. 6 is a graph showing the relationship between the impact timing of the oil pulse unit 4, the output signal of the impact sensor related to the timing, and the rotational speed of the motor. In FIG. 6, the horizontal axis represents the passage of time, and the horizontal axes of the three graphs are shown on the same scale. FIG. 6A is a graph showing the relationship between the passage of time and the output signal of the impact sensor at the time of impact. The output peak of the impact sensor appears greatly in a pulse shape at the position (main hitting position) of the rotation angle 360 degrees of the liner 21 shown in FIG. 3 (1) (arrows 71 and 73). In addition, the liner 21 slightly reversely rotates after the main hit, and the liner 21 passes the hit position again, so that a slightly small output peak 71a appears. However, the set threshold value N ₁ of the output signal detected by the impact detection circuit 45, so below the threshold of the output peaks are ignored, because not used for processing in the arithmetic unit 41 for the output peak 71a, clamping It does not interfere with control. Similarly, the output peak 73a is also ignored because it is below the threshold.

  On the other hand, an output peak 72 appears at a position rotated approximately 180 degrees from the main hit, that is, at the position shown in FIG. In this embodiment, the output peak 72 is referred to as a “half pulse” in correspondence with the main pulse caused by the main impact. The output peak 72 is originally unnecessary for tightening management and is preferably ignored. However, the output peak 72 often exceeds the threshold, and it is difficult to automatically exclude it from the processing in the calculation unit 41. In addition, because of the presence of the output peak 72, the positions of the output peaks 71 and 73 may be erroneously identified. In the tightening control of the impact driver 1, the positions of the main hit output peaks 71 and 73 are accurately determined. Otherwise, tightening control may not be performed correctly.

  Therefore, in this embodiment, the time interval t1 from a certain output peak (for example, 71) to the next position detection pulse (for example, 74b) is measured, and the output peak is determined when t1 is equal to or longer than a predetermined time. Identified as being due to a major blow. The graph of FIG. 6 (2) shows the time and the appearance timing of the position detection pulse 74. The position detection pulse 74 appears every 30 degrees of the rotation angle of the motor 3 and the liner 21. Strictly speaking, the position detection pulse 74 is a rectangular wave as indicated by 64 in FIG. 5, but is simply indicated by a vertical line in this figure. The graph in FIG. 6 (3) is a graph showing the rotation speed of the motor 3.

What should be noted here is that, after the output peak 71 in the main hit, the motor 3 is greatly reduced in rotation by the hit (arrow 76) and is slightly rotated in reverse (arrow 77). As the reverse rotation 77 occurs in this way, the interval between the position detection pulses from 74a to 74b becomes significantly larger than the interval between the other position detection pulses. On the other hand, at the output peak 72 due to the half pulse, the rotational speed of the motor 3 slightly decreases (arrow 79) due to the occurrence of a small hit (arrow 78). Therefore, the interval (74c to 74d) between the position detection pulses immediately after the appearance of the output peak 72 slightly increases. However, since the interval Tp ₁ is remarkably larger than the interval Tp ₂ , whether the output peak due to the main blow is caused by comparing the sizes of the intervals Tp ₁ and Tp ₂ with a preset reference value Td. It is possible to easily identify whether it is due to a half pulse.

  Next, a procedure for identifying whether the output peak that appears is due to a main hit or a half pulse will be further described with reference to the flowchart of FIG. The flowchart shown in FIG. 7 is realized by software, for example, by a microprocessor included in the calculation unit 41 executing a program.

7, first, set the threshold N _1, sets a waiting time Td to be the output peak or the half pulse or criteria in the main striking (step 81). Next, when the trigger switch is pulled, the motor 3 is started (step 82). Next, the calculation unit 41 detects the output peak by monitoring the output value output from the impact detection circuit 45 and the position signal from the rotation angle detection circuit 44 (step 83). If there here in the detected output peak threshold N ₁ below, and rejected as an output peak to be used for rotation control of the motor, the flow returns to step 83 (step 84, 85). If the detected output peak threshold N ₁ or more (step 84), measures the time interval Tp to the position detection pulse next occurrence from the detection of the output peak (step 86).

  Next, it is determined whether the measured time interval Tp is equal to or less than Td (step 87). As the reference time interval Td, for example, an average value of the time of the position pulses 74a to 74b and the time of the position pulses 74c to 74d in FIG. 7 can be set. When the time interval Tp is less than Td, it means that the drop in the rotation speed of the motor 3 due to the impact at the time of the output peak is small, and it can be determined that it is due to half pulses. Therefore, the output peak is not adopted and the process returns to step 83 (step 88). On the other hand, when the time interval Tp is equal to or greater than Td, it means that the rotational speed of the motor 3 is greatly reduced due to the impact at the time of the output peak, and it can be determined that this is due to the main impact. Therefore, the output peak is adopted (step 89).

  Next, it is determined whether or not the adopted output value exceeds the cut output value (target tightening output value of the fastening material) (step 90). If it exceeds, the motor is stopped as the tightening is completed (step 92). ), And the tightening process is terminated. If not exceeded, feedback control for duty change is performed, and the calculation unit 41 sets the target output at the time of the next hit, controls the rotation of the motor 3 so that the hit is performed at the target output, Returning to step 83 (step 91). Usually, when a hit is made, the rotation of the motor 3 is controlled so that a predetermined target output is generated by the hit. For example, a predetermined initial value is set for the target output Tr1 of the first hit, and an actual hit is performed by control according to the target output Tr1. When the peak output in actual hitting is T, the next target output Tr2 is further calculated with reference to the magnitude of the peak output T, and hitting is performed. In this way, feedback control is performed to reflect the strength of the previous hit to control the next hit. In the feedback control, for example, when the output peak adopted in step 89 is lower than the target output, the duty ratio is increased, and when the output peak adopted in step 89 is higher than the target output, the duty ratio is decreased. To control.

FIG. 8 is a diagram illustrating another example of the main hitting position, the half pulse position, and the position detection pulse appearance position. 6 (1) and 6 (2), the output peak 71 due to the main impact, the output peak 72 due to the half pulse, and the state in which the position detection pulse appears simultaneously have been described. However, in actuality, the main impact position, the half pulse position, and the position detection pulse appearance position are not synchronized, so the main impact position and the position detection pulse appearance position, the half pulse position and the position detection as shown in FIG. The appearance positions of pulses may be shifted from each other. By detecting the position detection pulse 94b appearing in the following this case is a be output peak 71, by which the determination whether a Td less measured time interval Tp _3, the detected output peak It is possible to immediately determine whether is due to a main blow or a half pulse. Similarly, by detecting the position detection pulse 94d appearing next to the output peak 72, since the measured time interval Tp ₄ is Td less, the detected output peak is due to the half pulse Judgment can be made immediately.

As shown in FIG. 8 (3), the next position detection pulse 95b may appear immediately after the output peak 71 due to the main impact appears. In this case, Tp <Td even at the time of the main hit, which may be mistaken for a half pulse. Therefore, a dead time W for detecting the position detection pulse is provided immediately after the appearance of the output peak 71 due to the main blow, and the time interval Tp ₅ from the passage of the dead time to the first detected position detection pulse 95b is measured. You may do it. By setting the dead time W in this manner, it is possible to accurately identify the output peak due to the main hit and the output peak due to the half pulse in any state. Note that the length of the dead time W is preferably set based on the interval between position detection pulses at the set rotational speed of the motor. Similarly, first measuring the time interval Tp ₆ to the detection position detection pulse 95f after a lapse of dead time W also when the output peak 72 due to determine whether there are less than the time interval Td of the reference.

As described above, according to the present embodiment, the output peak of the hit sensor due to each main hit is detected, and the rotational speed of the motor is controlled based on this output peak. As a result, it is possible to immediately identify whether the detected output peak is due to the main impact or due to the half pulse, so that it is possible to perform the tightening control with high accuracy of the rotary impact tool. Moreover, even without to exclude half pulse by According if the setting of the threshold N ₁ of the output peak to the present embodiment, it is possible to accurately determine the occurrence of a peak pulse by the main striking, the rotation control and the tightening accuracy rotary impact tool Reliability can be improved.

  As mentioned above, although demonstrated based on the Example which shows this invention, this invention is not limited to the above-mentioned form, A various change is possible within the range which does not deviate from the meaning. For example, in the present embodiment, an example of an impact driver using an oil pulse unit has been described as an example of a rotary impact tool. However, the present invention is not limited to this example. The present invention can be similarly applied to the rotary impact tool. In the above-described embodiment, the brushless DC motor is used as the drive source for the impact mechanism. However, even a brushed DC motor is a rotary impact tool using another drive source such as an air motor. Can be applied similarly.

1 Impact Driver 2 Power Cord 3 Motor 3a Motor Stator 3b Motor Rotor 4 Oil Pulse Unit 6a Housing Body 6b Housing Handle
7 Drive circuit board 8 Trigger switch 9 Control board
9a Motor control board 9b Rotation position detection board 10a, 10b, 10c Bearing 12 Impact sensor 14 Switch circuit board 16 Metal 17 Cooling fan unit 21 Liner 22 Lower plate 23 Liner plate 24 Main shaft 25a, 25b Blade
26a, 26b Convex seal surface 27a, 27b Convex seal surface 28a, 28b Convex part 29, 30 O-ring 41 Calculation part 42 Rotation position detection element 43 Rotor position detection circuit
44 Rotation angle detection circuit 45 Impact detection circuit 46 Control signal output circuit 47 Inverter circuit 48 Current detection circuit 49 Applied voltage setting circuit 50 Rotation direction setting circuit 51 Forward / reverse switching lever 52 Direct current power supply 61 to 64 Rectangular wave
70 to 73 Output peaks 70 and 72 (due to the main impact pulse) Output peaks 74 and 74a to 74d (due to half pulses) Position detection pulses 94, 94a to 94d Position detection pulses 95, 95a to 95f Position detection pulses

Claims (7)

A motor having a rotational position detecting element, an oil pulse unit driven by the motor, an output shaft connected to the oil pulse unit and mounted with a tip tool, and the magnitude of impact generated in the oil pulse unit In the rotary impact tool having detection means for detecting,
When the output value of the magnitude of impact force is detected by the detection means,
Measure the time interval until the position signal of the rotational position detection element that appears afterwards,
If the measured time interval is greater than or equal to a predetermined time, the output value is determined to be due to a main blow,
Determining that the output value is a half-pulse when the measured time interval is less than a predetermined time;
A rotary impact tool, wherein tightening control is performed using the output value of the main impact. The motor has a rotor having permanent magnets and a stator having windings,
The rotational position detecting element is a plurality of Hall elements provided facing the permanent magnet,
The rotary impact tool according to claim 1, wherein the position signal is created from output signals of the plurality of hall elements.   The rotary hitting tool according to claim 2, wherein three Hall elements are arranged at predetermined intervals, and the position signal appears every time the rotor rotates by a predetermined angle.   The rotary impact tool according to any one of claims 1 to 3, wherein the rotation of the motor is stopped when an output value of the main impact reaches a specified output value.   The rotary impact tool according to claim 4, wherein a threshold value of an output value detected by the detection unit is provided, and an output value equal to or less than the threshold value is not adopted for the measurement of the time interval.   The rotary impact tool according to claim 4, further comprising a control unit that processes a detection signal detected from the detection unit and performs rotation control of the motor using the detection signal. The control unit has a microprocessor;
The rotary impact tool according to claim 6, wherein the rotation control of the motor is performed by performing feedback control by comparing an output value of the detection means and a target output.

Images