Work equipment

Abstract

To provide a work machine suppressing generation of coming-out.SOLUTION: A micro computer 95 in a work machine 1 can execute electronic pulse control which alternately repeats normal rotation control for normally rotating a motor 3, reverse rotation control for reversely rotating the motor 3. The micro computer 95 executes the electronic pulse control in a low-torque period in which a load applied on a tip end tool 14 is low, of a period operating a trigger switch 6. The micro computer 95 makes it a necessary condition for executing the electronic pulse control that an amount of operation of the trigger switch 6 is a predetermined amount or more.SELECTED DRAWING: Figure 2

Description

Technical Field

[0007] ,

[0001] The present invention relates to a working machine capable of screwing.

Background Art

[0002] As an impact tool that performs fastening work such as bolts by the impact force of colliding a hammer against an anvil, an impact driver and an electronic pulse driver are known.

[0003] The impact driver includes a spring that biases the hammer toward the anvil, and rotates the hammer in only one direction in one operation of the trigger switch. After the hammer collides with the engaging projection of the anvil, the hammer moves in a direction away from the anvil against the biasing force of the spring, and rotates over the engaging projection to be in a state where it can collide with the engaging projection again.

[0004] In the electronic pulse driver, after the hammer collides with the engaging projection of the anvil, the hammer is reversed so that the hammer can collide with the engaging projection again.

[0005] The following Patent Document 1 discloses an impact tool having the same structure as a conventional impact driver but realizing the operation of an electronic pulse mode.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In impact tools, for example, when the torque applied to the motor is low during the initial stages of screw tightening, the hammer and anvil rotate together, and no impact occurs. According to the inventor's findings, during periods when no impact occurs, cam-out is likely to occur, where the engagement between the tool tip and the screw disengages, causing the tool tip to spin freely. Cam-out can also occur in work tools such as drill drivers that do not have a rotating impact mechanism such as a hammer or anvil.

[0008] The inventors have found that electronic pulse control, which alternately rotates the motor in the forward and reverse directions, is effective in suppressing cam-out. On the other hand, the inventors have also found that if electronic pulse control is performed at a timing unintended by the operator, work efficiency may be reduced. Furthermore, the inventors have found that when switching from forward to reverse rotation in electronic pulse control, a large reverse current is generated, which may cause problems such as battery degradation, circuit voltage overload, and circuit overheating.

[0009] The objective of the present invention is to solve at least one of the following problems 1 to 3. • Problem 1: To provide a work machine that suppresses the occurrence of cam-out. • Problem 2: To provide a work machine that suppresses the occurrence of electronic pulse control at times unintended by the operator. • Problem 3: To provide a work machine that suppresses reverse current in electronic pulse control. [Means for solving the problem]

[0011] One aspect of the present invention is A work machine capable of tightening screws, Motor and, A tip tool mounting section, which is driven by the driving force of the aforementioned motor and to which a tip tool can be attached, An operating unit that can switch the motor on and off, The system includes a control unit that controls the motor in accordance with the operation of the control unit, The control unit, The aforementioned motor can perform electronic pulse control, which alternately repeats forward and reverse rotation. When the amount of operation of the control unit is less than or equal to the stop threshold, the motor is not driven. When the amount of operation of the control unit exceeds the stop threshold but is less than a predetermined value greater than the stop threshold, the effective value of the motor voltage applied to the motor is controlled according to the amount of operation of the control unit. The condition for executing the electronic pulse control is that the amount of operation of the control unit is greater than or equal to a predetermined value that is greater than the stop threshold. It is a work machine. One aspect of the present invention is A work machine capable of tightening screws, Motor and, A tip tool mounting section, which is driven by the driving force of the aforementioned motor and to which a tip tool can be attached, An operating unit that can switch the motor on and off, The system includes a control unit that controls the motor in accordance with the operation of the control unit, The control unit, The aforementioned motor can perform electronic pulse control, which alternately repeats forward and reverse rotation. During the period in which the operating unit is being operated, the electronic pulse control can be executed during the low-torque period when the load on the tip tool is low. The condition for the continuation of the electronic pulse control is that the motor is not in an unloaded state where no external load is applied. It is a work machine. One aspect of the present invention is A work machine capable of tightening screws, Motor and, A tip tool mounting section, which is driven by the driving force of the aforementioned motor and to which a tip tool can be attached, An operating unit that can switch the motor on and off, The system includes a control unit that controls the motor in accordance with the operation of the control unit, The control unit, The aforementioned motor can perform electronic pulse control, which alternately repeats forward and reverse rotation. During the period in which the operating unit is being operated, the electronic pulse control can be executed during the low-torque period when the load on the tip tool is low. When a no-load state where no external load is applied to the motor is detected during the execution of the electronic pulse control, a transition is made to normal control in which the motor continues to rotate in one direction, or the motor is stopped. It is a working machine. One aspect of the present invention is A working machine capable of screwing, A motor, A tip tool mounting portion that is driven by the driving force of the motor and to which a tip tool can be mounted, A rotary impact mechanism that converts the driving force of the motor into rotational impact force and transmits it to the tip tool mounting section, An operation unit capable of switching between driving and stopping of the motor, A control unit that controls the motor according to an operation of the operation unit, and includes: The control unit is Capable of executing electronic pulse control that alternately repeats forward and reverse rotations of the motor, During a period in which the operation unit is being operated, electronic pulse control can be executed during a low torque period in which the load applied to the tip tool is low, During the execution of the electronic pulse control, when Rotary impact mechanism of the tip tool mounting part A strike is detected, a transition is made to normal control in which the motor continues to rotate in one direction, It is a working machine.

[0012] The present invention may be expressed as "electric working machine", "electric tool", "electric device", etc., and those expressed as such are also effective as aspects of the present invention.

Effect of the Invention

[0013] According to the present invention, at least one of the above problems 1 to 3 can be solved.

Brief Description of the Drawings

[0014] [Figure 1] A side cross-sectional view of a working machine 1 according to an embodiment of the present invention. [Figure 2] A circuit block diagram of the working machine 1. [Figure 3] A control flowchart of the working machine 1. [Figure 4]This is a time chart of the operation of work machine 1, showing the time when the amount of operation of trigger switch 6 is changed during operation. [Figure 5] This is a time chart of the operation of work machine 1, including the case where hammer 8 starts striking anvil 10 midway through the operation. [Figure 6] A flowchart showing the first example of electronic pulse control (S9) in Figure 3. [Figure 7] (A) is a time chart of the operation of the work implement 1 when the load on the tip tool 14 is small. (B) is a time chart of the operation of the work implement 1 when the load on the tip tool 14 is large. [Figure 8] A flowchart showing a second example of electronic pulse control (S9) in Figure 3. [Figure 9] A flowchart showing a third example of electronic pulse control (S9) in Figure 3. [Modes for carrying out the invention]

[0015] In the following, identical or equivalent components, parts, etc., shown in each drawing will be denoted by the same reference numeral, and redundant descriptions will be omitted as appropriate. The embodiments are illustrative and not limiting to the invention. Not all features or combinations thereof described in the embodiments are necessarily essential to the invention.

[0016] Figure 1 is a side cross-sectional view of a work implement 1 according to an embodiment of the present invention. Figure 1 defines the mutually orthogonal front-rear and up-down directions in the work implement 1. The front-rear direction is parallel to the motor shaft 3a of the work implement 1. The work implement 1 is a work implement capable of tightening screws, and specifically, it is an impact driver.

[0017] The work machine 1 has a housing 2. The housing 2 has a motor housing section 2a, a handle section 2b, and a battery mounting section 2c.

[0018] The motor housing 2a is a cylindrical portion with its central axis substantially parallel to the front-rear direction. The housing 2 includes a hammer case 11, for example, made of metal, which is connected to the front of the motor housing 2a. The front surface of the hammer case 11 is covered with a front cap 12, which is a protective member such as an elastomer.

[0019] The handle portion 2b has its upper end connected to the intermediate portion in the front-to-back direction of the motor housing portion 2a and extends downward from the intermediate portion. The work machine 1 has a trigger switch 6 and a rotation direction change switch 13 at the upper end of the handle portion 2b. The trigger switch 6 is an operating unit that allows the operator to switch the motor 3 on and off (the driving state of the motor 3). The trigger switch 6 is a stepless speed control switch. The rotation direction change switch 13 is a rotation direction change unit that allows the operator to switch the forward and reverse rotation of the motor 3, that is, the forward and reverse rotation of the anvil 10 described later.

[0020] The battery mounting section 2c is located at the lower end of the handle section 2b, and the battery pack 7 can be detachably attached to it. The work implement 1 operates on the power of the battery pack 7. The work implement 1 has an operation panel 20 (switch panel) on the front upper surface of the battery mounting section 2c. The work implement 1 has a control board 30 inside the battery mounting section 2c.

[0021] The work machine 1 has a motor 3, a reduction mechanism 4, a spindle 5, a hammer 8, a spring 9, and an anvil 10 as a tip tool mounting part, all housed in a motor housing 2a and a hammer case 11. The reduction mechanism 4, spindle 5, hammer 8, and spring 9 constitute a rotary impact mechanism that converts the driving force (rotational force) of the motor 3 into rotational impact force and applies it to the anvil 10.

[0022] Motor 3 is an inner rotor type brushless motor. The reduction mechanism 4 reduces the rotation of motor 3 and transmits it to spindle 5. Spindle 5 rotates the hammer 8. The hammer 8 is movable in the front-rear direction relative to spindle 5. Spring 9 biases the hammer 8 forward. The hammer 8 rotates or rotates-impacts the anvil 10. That is, the anvil 10 is driven by the driving force of motor 3. The anvil 10 is rotatably supported in the hammer case 11 and is located in front of the hammer 8. The anvil 10 has a tip tool mounting hole 10a on which a tip tool 14 such as a bit can be attached.

[0023] The work implement 1 has lighting LEDs 16 around the front of the hammer case 11 to illuminate the area around the work site. The work implement 1 has a sensor board 15. The sensor board 15 is equipped with a magnetic sensor 84 shown in Figure 2 to detect the rotation of the motor 3. The sensor board 15 is supported in front of the main body of the motor 3 (the part of the motor 3 excluding the motor shaft 3a) in a position approximately perpendicular to the motor shaft 3a.

[0024] Figure 2 is a circuit block diagram of the work machine 1. The work machine 1 includes an inverter circuit 82, a control signal output circuit 83, a magnetic sensor 84, a rotor position detection circuit 85, a rotation speed detection circuit 86, a mode selector switch 87, a control circuit voltage supply circuit 88, a battery voltage detection circuit 89, a motor current detection circuit 91, an illumination LED drive circuit 92, a control circuit voltage detection circuit 93, a display LED drive circuit 94, and a microcontroller 95.

[0025] The inverter circuit 82 includes three-phase bridge-connected semiconductor switching elements Q1 to Q6. The inverter circuit 82 converts the DC power output by the battery pack 7 into AC power for driving the motor 3 and supplies it to the motor 3. The control signal output circuit 83 applies a drive signal, such as a PWM (Pulse Width Modulation) signal, to each gate of the switching elements Q1 to Q6 according to the control of the microcontroller 95.

[0026] The magnetic sensor 84 detects the magnetic field generated by the rotor of the motor 3 and transmits it to the rotor position detection circuit 85. The rotor position detection circuit 85 detects the rotor position of the motor 3 based on the signal from the magnetic sensor 84 and transmits it to the microcontroller 95. The rotation speed detection circuit 86 detects the rotation speed of the motor 3 (hereinafter referred to as "motor rotation speed") based on the signal from the rotor position detection circuit 85 and transmits it to the microcontroller 95.

[0027] The mode selector switch 87 is located on the operation panel 20 shown in Figure 1. The mode selector switch 87 transmits the drive mode selected by the operator to the microcontroller 95. The drive modes include a pulse mode (first mode) which performs electronic pulse control as described later, and a non-pulse mode (second mode) which does not perform electronic pulse control.

[0028] The control circuit voltage supply circuit 88 steps down the output voltage of the battery pack 7 to convert it into a power supply voltage for the microcontroller 95, etc., and supplies it to the microcontroller 95, etc. The battery voltage detection circuit 89 detects the output voltage of the battery pack 7 and transmits it to the microcontroller 95. The motor current detection circuit 91 detects the motor current (hereinafter referred to as "motor current") by the voltage across the resistor R provided in the path of the current flowing through the motor 3 and transmits it to the microcontroller 95.

[0029] The lighting LED drive circuit 92 supplies drive current to the lighting LED 16 in Figure 1, according to the control of the microcontroller 95. The control circuit voltage detection circuit 93 detects the output voltage of the control circuit voltage supply circuit 88 and transmits it to the microcontroller 95. The display LED drive circuit 94 supplies drive current to the display LEDs provided on the operation panel 20.

[0030] The microcontroller 95 is a control unit that controls the drive of the motor 3. The microcontroller 95 controls the inverter circuit 82 via the control signal output circuit 83, for example, by PWM control, in accordance with the drive mode selected by the mode selector switch 87, the rotation direction set by the rotation direction selector switch 13 (hereinafter referred to as "set rotation direction"), and the operation of the trigger switch 6, thereby controlling the drive of the motor 3. The microcontroller 95 can control the effective value of the applied voltage applied to the motor 3 (hereinafter referred to as "motor applied voltage") by the duty cycle of the PWM control (hereinafter referred to as "duty cycle").

[0031] The microcontroller 95 can detect the load on motor 3 based on the motor current. The microcontroller 95 can distinguish and detect forward and reverse rotation of motor 3 based on the signal from rotor position detection circuit 85, that is, in response to the signal from magnetic sensor 84.

[0032] The microcontroller 95 is capable of performing electronic pulse control. Electronic pulse control is a control method that alternately repeats forward rotation control, which rotates the motor 3 in the forward direction, and reverse rotation control, which rotates the motor 3 in the reverse direction. In pulse mode, the microcontroller 95 performs electronic pulse control during the low-torque period when the load on the tip tool 14 is low, while the trigger switch 6 is being operated. The low-torque period is the period when the hammer 8 does not strike the anvil 10 (hereinafter referred to as "striking"), that is, the period when the hammer 8 and the anvil 10 rotate together.

[0033] According to the inventors' findings, during low-torque periods, cam-out is likely to occur, where the engagement between the tool tip 14 and the screw disengages, causing the tool tip 14 to spin freely. The inventors have found that performing electronic pulse control during low-torque periods is effective in suppressing cam-out. With electronic pulse control during low-torque periods, even if the engagement between the tool tip 14 and the screw becomes shallow and a cam-out is likely to occur, reverse control can restore (deepen) the engagement between the tool tip 14 and the screw, thereby suppressing cam-out.

[0034] On the other hand, the inventors have found that if electronic pulse control is performed at a timing unintended by the operator, work efficiency may be reduced. Generally, in the initial stages of screw tightening, the screw tends to wobble relative to the workpiece, so the trigger operation is kept small and tightening is continued until the screw no longer wobbles. If electronic pulse control is performed during this initial stage of screw tightening, it can actually make the tool less convenient to use.

[0035] Even outside of the initial stages of screw tightening, when the trigger operation amount is small, the operator is working carefully, making cam-out less likely, and electronic pulse control would actually make it less user-friendly. Therefore, the microcontroller 95 makes it a condition for executing electronic pulse control that the amount of operation of the trigger switch 6 (hereinafter referred to as "trigger operation amount") is equal to or greater than a predetermined amount.

[0036] According to this, the operator can switch whether or not to execute electronic pulse control depending on the trigger operation amount. Therefore, it is possible to suppress the activation of electronic pulse control at unintended times, i.e., when the trigger operation amount is small, such as at the beginning of screw tightening or when working carefully, thereby preventing deterioration in usability.

[0037] In pulse mode, the microcontroller 95 performs control that keeps motor 3 rotating in one direction (hereinafter referred to as "normal control") when the trigger operation amount is less than a predetermined amount. In non-pulse mode, the microcontroller 95 performs normal control regardless of whether the trigger operation amount is greater than or equal to a predetermined amount.

[0038] When the trigger operation amount is changed during a single ON operation of the trigger switch 6 (motor drive operation), i.e., while the motor 3 is being driven, the microcontroller 95 switches whether or not to execute electronic pulse control according to the changed operation amount. Specifically, when the trigger operation amount changes from less than a predetermined amount to more than a predetermined amount, the microcontroller 95 switches from normal control to electronic pulse control, and when the trigger operation amount changes from more than a predetermined amount to less than a predetermined amount, it switches from electronic pulse control to normal control.

[0039] Regarding the trigger operation amount, the predetermined amount when transitioning from normal control to electronic pulse control may be larger than the predetermined amount when transitioning from electronic pulse control to normal control. This makes it possible to suppress frequent back-and-forth control between normal control and electronic pulse control.

[0040] The microcontroller 95 requires that motor 3 not be in an unloaded state (where no external load is applied) in pulse mode to continue electronic pulse control. The reason for this is as follows: In an unloaded state, cam-out does not occur, so there is no benefit to performing electronic pulse control. On the other hand, performing electronic pulse control in an unloaded state would unnecessarily increase heat generation due to the repeated switching between forward and reverse rotation. If the microcontroller 95 detects an unloaded state while electronic pulse control is being performed, it will switch to normal control or stop motor 3.

[0041] The reason why the microcontroller 95 requires the absence of a no-load state to continue electronic pulse control, but not to start it, is to prevent delays in starting electronic pulse control caused by the time required to detect the absence of a no-load state. The microcontroller 95 starts electronic pulse control regardless of whether there is a no-load state or not, as long as the trigger operation amount is above a predetermined amount, thereby enabling a rapid start to electronic pulse control and quickly achieving a cam-out suppression effect.

[0042] The microcontroller 95 performs normal control during the high-torque period when the load on the tool tip 14 is high while the trigger switch 6 is operated. The high-torque period is the period during which impact occurs. In other words, the microcontroller 95 considers the absence of impact as a necessary condition for the continuation of electronic pulse control. Note that the normal control during the high-torque period is an example of impact control. In other words, in the case of an impact driver, normal control and impact control are the same.

[0043] According to the inventor's findings, cam-out is less likely to occur during high-torque periods compared to low-torque periods. On the other hand, if electronic pulse control is applied during high-torque periods, the number of impacts per unit time decreases, and the tightening speed decreases. As described above, by using normal control during high-torque periods, the decrease in tightening speed can be suppressed.

[0044] The reason why the microcontroller 95 requires the absence of impact to be a necessary condition for continuing electronic pulse control, but not a necessary condition for starting electronic pulse control, is to prevent delays in starting electronic pulse control due to the time required to detect that no impact is occurring. By starting electronic pulse control regardless of whether an impact is occurring or not, as long as the trigger operation amount is above a predetermined amount, the microcontroller 95 can quickly start electronic pulse control and quickly achieve a cam-out suppression effect.

[0045] The microcontroller 95 can decelerate motor 3 through brake control. Brake control is a control method that decelerates motor 3 faster than natural deceleration by consuming the motor 3's rotational energy without supplying it with external power. Brake control is, for example, a control that applies a short-circuit brake. Short-circuit brake is a control method that, for example, turns off switching elements Q1 to Q3 on the upper arm side and continuously or intermittently turns on at least one of switching elements Q4 to Q6 on the lower arm side. Note that reverse rotation control performed on a motor 3 that is rotating in the forward direction is not brake control, as it involves supplying power for reverse rotation from an external source.

[0046] Figure 3 is a control flowchart for the work machine 1. In Figure 3, "electronic pulse control" is an abbreviation for "electronic pulse control." The flowchart in Figure 3 is started when the operator turns on the trigger switch 6.

[0047] The microcontroller 95 starts driving the motor 3 when the trigger switch 6 is turned on (S1). The microcontroller 95 first performs normal control (S2). If the trigger operation amount is less than or equal to the stop threshold (yes in S3), the microcontroller 95 stops the motor 3 (S23). The operation amount at the stop threshold is what is known as "play," and the motor 3 will not drive at this operation amount.

[0048] If the microcontroller 95 has not yet detected the rotation of the motor 3 (no in S5), it continues normal control (S19). This predetermined time is a mask time immediately after the motor 3 is started, during which electronic pulse control is not performed. By setting a mask time, the activation of electronic pulse control during the short ON operation of the trigger switch 6 is suppressed. The mask time is, for example, 200 milliseconds.

[0049] If a predetermined time has elapsed since the rotation of the motor 3 was detected (Yes in S5), and the trigger operation amount is less than a predetermined amount (No in S7), the microcontroller 95 continues normal control or switches to normal control (S19).

[0050] If the microcontroller 95 does not detect a blow during normal control execution (S21 "No"), it returns to S3.

[0051] If the microcontroller 95 detects a blow during normal control (S21 "Yes"), it continues normal control until the trigger operation amount falls below the stop threshold (S17 "No").

[0052] When the trigger operation amount falls below the stop threshold (S17 "Yes"), the microcontroller 95 stops motor 3 (S23).

[0053] If a predetermined time has elapsed since the rotation of the motor 3 was detected (S5 "Yes"), and the trigger operation amount is greater than or equal to a predetermined amount (S7 "Yes"), the microcontroller 95 continues or switches to electronic pulse control (S9).

[0054] If the microcontroller 95 does not detect a no-load state ("No" in S11) and does not detect a blow ("No" in S13) during the execution of electronic pulse control, it returns to S3.

[0055] If the microcontroller 95 detects a no-load state (S11 "Yes") or an impact (S13 "Yes") while electronic pulse control is being performed, it switches to normal control (S15) and continues normal control until the trigger operation amount falls below the stop threshold (S17 "No").

[0056] Figure 4 is a time chart of the operation of the work implement 1, and shows the time chart when the amount of operation of the trigger switch 6 is changed during operation. In Figure 4, the duty cycle in reverse control is shown as a negative value. The same applies to Figure 5.

[0057] When the trigger operation amount exceeds the stop threshold at time t1, the microcontroller 95 increases its duty cycle in accordance with the trigger operation amount. This increases the motor speed and motor current. The sudden sharp increase in motor current immediately after time t1 is due to the starting current.

[0058] Before time t2, the trigger operation amount is less than a predetermined amount X1 (electronic pulse control start threshold), and the microcontroller 95 performs normal control. In normal control, the microcontroller 95 controls the duty cycle to keep motor 3 rotating in the forward direction so that the motor rotation speed corresponds to the trigger operation amount.

[0059] Around time t2, the operator increases the trigger operation amount, and when the trigger operation amount reaches a predetermined amount X1 or more at time t2, the microcontroller 95 starts electronic pulse control.

[0060] In electronic pulse control, forward and reverse rotation are repeated. However, since the reverse rotation control is only performed until the microcontroller 95 detects the reverse rotation of the motor 3, the motor speed during reverse rotation is significantly smaller than the motor speed during forward rotation. For example, if the motor 3 has a 4-pole, 6-slot configuration and the spacing between the three magnetic sensors 84 is 60 degrees in the circumferential direction of the motor 3, the microcontroller 95 can detect the reverse rotation if the motor 3 rotates 30 degrees or more in reverse.

[0061] The microcontroller 95 suppresses the peak current during switching by gradually changing the duty cycle after switching between forward and reverse rotation in electronic pulse control.

[0062] In electronic pulse control, one cycle consists of one reverse rotation control followed by one forward rotation control. The motor current immediately before the end of the forward rotation control in each cycle differs in magnitude depending on the load on the tool tip 14, i.e., the load on the motor 3. In the example in Figure 4, as the cycle progresses, the tightening progresses and the load on the tool tip 14 increases, and the motor current immediately before the end of the forward rotation control increases as the cycle progresses. The microcontroller 95 can detect a no-load state when the motor current immediately before the end of the forward rotation control is smaller than the no-load detection threshold.

[0063] Around time t3, the operator reduces the trigger operation amount. When the trigger operation amount falls below a predetermined amount X2 (electronic pulse control stop threshold) at time t3, the microcontroller 95 stops electronic pulse control and switches to normal control. At time t4, when the operator turns off the trigger switch 6, the microcontroller 95 sets the duty cycle to 0 and stops the motor 3.

[0064] Figure 5 is a time chart of the operation of the work machine 1, specifically the time chart when impact is started midway through the operation. The following explanation will focus on the differences from Figure 4.

[0065] If the trigger operation amount exceeds the stop threshold at time t11, the microcontroller 95 increases its duty cycle according to the trigger operation amount. During the period between times t11 and t12, the trigger operation amount becomes greater than or equal to a predetermined amount X1, but since the mask time has not elapsed since motor 3 started rotating at this point, the microcontroller 95 performs normal control.

[0066] At time t12, after the mask time has elapsed from time t11, the microcontroller 95 starts electronic pulse control. In the example in Figure 5, striking begins during the execution of electronic pulse control from time t12 to t13, causing fluctuations (wobble) in the motor rotation speed due to the striking (part A in Figure 5).

[0067] The microcontroller 95 stops electronic pulse control and switches to normal control at time t13, when it detects two fluctuations in motor rotation speed due to impact.

[0068] From time t13 onward, under normal control, impacts are repeated, tightening progresses, the load on the tip tool 14 increases, and the motor current rises. In order to maintain the motor speed, the duty cycle also increases.

[0069] When the operator turns off the trigger switch 6 at time t14, the microcontroller 95 sets the duty cycle to 0 and stops the motor 3.

[0070] While electronic pulse control during low torque periods is effective in suppressing cam-out, the inventors have found that a large reverse current is generated when switching from forward to reverse rotation in electronic pulse control, which can cause problems such as battery degradation, circuit voltage overload, and circuit overheating. Below, we will describe an electronic pulse control that can suitably address these problems.

[0071] Figure 6 is a flowchart showing the first example of electronic pulse control (S9) in Figure 3. The microcontroller 95 performs initial settings for various parameters (S31). For example, the microcontroller 95 sets the maximum duty cycle in electronic pulse control to a predetermined value, in this case 20%, and sets the execution time of brake control in the first cycle to a predetermined time, in this case 30 milliseconds.

[0072] One cycle of electronic pulse control consists of brake control, reverse control, and forward control. Hereinafter, the execution time of brake control in each cycle will also be referred to as "brake time," the execution time of forward control as "forward time," and the execution time of reverse control as "reverse time."

[0073] The microcontroller 95 terminates forward rotation control and starts brake control (S33). Brake control is a short-circuit brake control, which turns off switching elements Q1~Q3 on the upper arm side and turns on switching elements Q4~Q6 on the lower arm side. The microcontroller 95 continues brake control until the brake time has elapsed (NO in S35).

[0074] When the braking time elapses from the start of brake control (YES in S35), the microcontroller 95 starts reverse control (S37). The microcontroller 95 continues reverse control until reverse rotation of motor 3 is detected (NO in S39).

[0075] When the microcontroller 95 detects the motor 3 reversing direction based on the output signal from the magnetic sensor 84 (YES in S39), it turns off all switching elements Q1 to Q6 (S41) and records the reversal time (S43). The microcontroller 95 keeps all switching elements Q1 to Q6 off until a pause time of, for example, 2 milliseconds has elapsed (NO in S45).

[0076] The microcontroller 95 starts forward rotation control (S47) after a pause time has elapsed since turning off switching elements Q1 to Q6 (YES in S45). The microcontroller 95 continues forward rotation control from the start of brake control until the time of one cycle of electronic pulse control (hereinafter referred to as "pulse cycle time") has elapsed (NO in S49). The pulse cycle time is, for example, 80 milliseconds.

[0077] When the pulse cycle time has elapsed since the start of brake control (YES in S49), the microcontroller 95 sets the brake time for the next cycle (S51-S63).

[0078] If the previous cycle was the first cycle of the electronic pulse control (YES in S51), the microcontroller 95 sets the brake time setting to 15 milliseconds, even though the actual brake time was 30 milliseconds, and proceeds to S55 (S53). The reason for setting the brake time to 15 milliseconds is as follows:

[0079] In other words, in electronic pulse control, the first cycle starts with a higher motor speed compared to other cycles, due to a mask time of, for example, 200 milliseconds prior to it. Therefore, in the first cycle, the braking time is set longer to allow for sufficient deceleration even at high motor speeds. On the other hand, if the braking time is adjusted using feedback control based on this longer braking time, the state of excessively long braking time will continue for multiple cycles, and the time required to reach the optimal braking time will be prolonged.

[0080] The S53 process described above shortens the time required to achieve the optimal braking time by resetting the brake time to an appropriate time, rather than using the actual braking time in the first cycle as the reference.

[0081] If the previous cycle is not the first cycle of the electronic pulse control (NO in S51), the microcontroller 95 proceeds to S55 without changing the brake time setting from the actual brake time in the previous cycle.

[0082] If the reversal time in the previous cycle was less than 3 milliseconds (YES in S55), the microcontroller 95 shortens the brake time setting by 1 millisecond from the current setting (hereinafter referred to as "current value") (S57) and returns to S33.

[0083] If the reversal time in the previous cycle exceeds the second threshold of 5 milliseconds (NO in S55, YES in S59), the microcontroller 95 increases the brake time setting by 1 millisecond from the current value (S61) and returns to S33.

[0084] If the reversal time in the previous cycle is between 3 milliseconds and 5 milliseconds (NO in S55, NO in S59), the microcontroller 95 does not change the brake time setting from its current value (S63) and returns to S33.

[0085] The reversal time in the immediately preceding cycle increases as the forward rotation speed of motor 3 at the start of reverse control (hereinafter referred to as "forward rotation speed") increases. The above brake time setting aims to keep the forward rotation speed at the start of reverse control in each cycle as close to constant as possible, thereby keeping the reversal time in each cycle as close to constant as possible.

[0086] Figure 7(A) is a time chart of the operation of the work machine 1 when the load on the tip tool 14 is small. Time T1 indicates the reversal time in a certain period. Time T2 indicates the forward rotation time in the same period. Time T3 indicates the braking time in the same period. Time T4 is the sum of times T1 to T3, and represents the time of one period of electronic pulse control.

[0087] Figure 7(B) is a time chart of the operation of the work machine 1 when the load on the tip tool 14 is large. Time T1' indicates the reversal time in a certain period. Time T2' indicates the forward rotation time in the same period. Time T3' indicates the braking time in the same period. Time T4' is the sum of times T1' to T3', and represents the time of one period of electronic pulse control.

[0088] Comparing Figures 7(A) and (B), when the load on the tip tool 14 is large, the reaction force from the screw to the tip tool 14 is larger compared to when the load on the tip tool 14 is small. As a result, the motor speed decreases faster in brake control, and the braking time required to decelerate to a certain positive rotation speed is shortened (T3'). <T3)。

[0089] On the other hand, since reverse control is initiated from a certain forward rotation speed, the reverse rotation time is constant regardless of the load on the tip tool 14 (T1 ≈ T1'). Also, the period of the electronic pulse control is constant throughout all periods (T4 = T4'). Therefore, when the load on the tip tool 14 is large, the forward rotation time is longer compared to when the load on the tip tool 14 is small (T2' > T2).

[0090] Figure 8 is a flowchart showing a second example of the electronic pulse control (S9) in Figure 3. In the example in Figure 6, the braking time in the next cycle was adjusted according to the reversal time in an arbitrary cycle, whereas in the example in Figure 8, the braking force in the next cycle is adjusted according to the reversal time in an arbitrary cycle.

[0091] The microcontroller 95 can change the braking force by changing the ratio of the on period (duty cycle in brake control) in a short-circuit brake that intermittently turns on the switching elements Q4 to Q6 on the lower arm side.

[0092] The process up to S49 in Figure 8 is the same as the process up to S49 in Figure 6. However, in the initial setup at S31 in Figure 8, the microcontroller 95 sets the braking force in the first cycle to its maximum value (100%).

[0093] If the previous cycle was the first cycle of the electronic pulse control (YES in S51), the microcontroller 95 sets the brake force setting value to its initial value (e.g., 50%), even though the brake force was actually at its maximum value, and proceeds to S69 (S67).

[0094] If the previous cycle is not the first cycle of the electronic pulse control (NO in S51), the microcontroller 95 proceeds to S69 without changing the brake force setting value from the actual brake force in the previous cycle.

[0095] The microcontroller 95 sets the braking force for the next cycle (S69). If the reversal time in the previous cycle is longer than the reference reversal time, the brake force setting is increased relative to the current value; if the reversal time in the previous cycle is longer than the reference reversal time, the brake force setting is decreased relative to the current value. A specific example of brake force calculation is shown in Figure 8.

[0096] Figure 9 is a flowchart showing a third example of the electronic pulse control (S9) in Figure 3. In the example in Figure 6, the braking time was set in advance, whereas in the example in Figure 9, the braking time is not predetermined, and braking control is performed until the motor speed falls below a predetermined speed (for example, below 500 rpm). For this reason, the braking time is not set in the initial settings of S31 in Figure 9. The following explanation will focus on the differences from Figure 6.

[0097] The microcontroller 95 continues brake control until the motor speed drops to, for example, 500 rpm or less (NO in S36). When the motor speed drops to, for example, 500 rpm or less (YES in S36), the microcontroller 95 starts reverse control (S37). When the microcontroller 95 detects the reverse rotation of motor 3 (YES in S39), it turns off all switching elements Q1 to Q6 (S41). In this case, recording the reverse rotation time in Figure 6 (S43 in Figure 6) is unnecessary.

[0098] When the microcontroller 95 turns off switching elements Q1 to Q6 and a pause time has elapsed (YES in S45), it starts forward rotation control (S47). When the pulse period time has elapsed since the start of brake control (YES in S49), the microcontroller 95 returns to S33. Here, the brake time setting in Figure 6 (S51 to S63) is not necessary.

[0099] According to this embodiment, the following effects can be achieved.

[0100] (1) The microcontroller 95 performs electronic pulse control during the period when the trigger switch 6 is operated, specifically during the low-torque period when cam-out is likely to occur and the load on the tip tool 14 is low. Therefore, even if the engagement between the tip tool 14 and the screw becomes shallow and a cam-out is likely to occur, the engagement between the tip tool 14 and the screw can be restored by reverse control, thereby suppressing cam-out.

[0101] (2) The microcontroller 95 requires that the trigger operation amount be above a predetermined amount as a condition for executing electronic pulse control. Therefore, the operator can switch whether or not to execute electronic pulse control depending on the trigger operation amount. Thus, it is possible to suppress the execution of electronic pulse control at times unintended by the operator, i.e., when the trigger operation amount is small, such as at the beginning of screw tightening or when working carefully, thereby suppressing deterioration of usability.

[0102] (3) When the trigger operation amount is changed during a single ON operation of the trigger switch 6, i.e., while the motor 3 is being driven, the microcontroller 95 switches whether or not to execute electronic pulse control according to the changed operation amount. Therefore, the operator does not need to operate the trigger switch 6 again to switch whether or not to execute electronic pulse control, making it easy to use.

[0103] (4) The microcontroller 95 requires that the motor 3 not be in an unloaded state where no external load is applied, as a condition for continuing electronic pulse control. Therefore, it is possible to suppress the unnecessary increase in heat generated by electronic pulse control in an unloaded state where cam-out does not occur.

[0104] (5) The microcontroller 95 performs normal control during the high-torque period when the load on the tip tool 14 is high while the trigger switch 6 is operated. Therefore, it is possible to suppress the decrease in the number of impacts per unit time and the decrease in tightening speed by performing electronic pulse control during the high-torque period.

[0105] (6) Regardless of whether there is no load or not, and whether the load on the tip tool 14 is high or not, the microcontroller 95 starts electronic pulse control if the trigger operation amount is greater than or equal to a predetermined amount. As a result, electronic pulse control can be started quickly, and the cam-out suppression effect can be obtained quickly.

[0106] (7) In the examples shown in Figures 6 to 9, the microcontroller 95, in electronic pulse control, performs brake control after forward rotation control before switching to reverse rotation control. Therefore, the reverse current when switching from forward rotation control to reverse rotation control can be suppressed. Thus, problems such as battery degradation, circuit voltage exceeding, and circuit overheating caused by large reverse currents can be suppressed.

[0107] (8) The microcontroller 95 makes the forward rotation time longer than the reverse rotation time in each cycle of the electronic pulse control. As a result, the efficiency of screw tightening work is improved compared to when the forward rotation time and reverse rotation time are the same.

[0108] (9) In the example in Figure 6, the microcontroller 95 changes the braking time in the next cycle according to the reverse time in an arbitrary cycle in electronic pulse control, and controls the reverse time so that it is within a certain range. By keeping the reverse time within a certain range, the working feel is improved.

[0109] (10) In the example shown in Figure 9, the microcontroller 95 switches to reverse control when the motor speed falls below a predetermined speed due to brake control in electronic pulse control. As a result, the reverse time becomes approximately constant, improving the working feel.

[0110] (11) In electronic pulse control, the microcontroller 95 continues reverse control until it detects that the motor 3 has reversed direction, and then switches to forward control. This minimizes the reverse time and maximizes the forward time, thereby improving the efficiency of screw tightening. To restore the engagement between the cutting tool 14 and the screw, it is sufficient for the forward torque applied to the cutting tool 14 to disappear, so once the reverse direction of the motor 3 is confirmed, further reverse rotation is unnecessary.

[0111] (12) In electronic pulse control, the microcontroller 95 keeps the period constant over multiple cycles (preferably the entire cycle), and makes the forward rotation time, reverse rotation time, and braking time per cycle variable. Therefore, flexible control is possible, for example, by shortening the braking time and lengthening the forward rotation time when the load on the tip tool 14 is large and a short braking time is sufficient, thereby improving the efficiency of screw tightening work.

[0112] (13) In electronic pulse control, the microcontroller 95 does not perform brake control when transitioning from reverse control to forward control. Unlike forward control, reverse control results in a lower motor rotation speed, and problems such as overheating are less likely to occur even without brake control. Therefore, by switching from reverse control to forward control without brake control, the motor 3 can be rotated in the forward direction quickly, while the disadvantages such as overheating are suppressed.

[0113] (14) In electronic pulse control, the microcontroller 95 stops the brake control and starts reverse control before the motor 3 stops rotating in the forward direction. As the motor rotation speed decreases, the braking force decreases, so by starting reverse control before the motor 3 stops rotating in the forward direction, it is possible to suppress the increase in braking time and decrease in forward rotation time.

[0114] The present invention has been described above using embodiments as examples, but it will be understood by those skilled in the art that various modifications are possible to each component and each processing step of the embodiments within the scope of the claims. Modifications will be discussed below.

[0115] The work machine of the present invention is not limited to the impact driver exemplified in the embodiments, but may be other types such as impact wrenches, electronic pulse drivers, oil pulse tools, drill drivers, etc.

[0116] In the case of an electronic pulse driver, the impact control (striking control) when high torque is applied also involves repeatedly switching the motor's forward and reverse rotation. However, the impact control of an electronic pulse driver reverses the hammer, resulting in a longer reverse control period than the electronic pulse control described above. In other words, the impact control of an electronic pulse driver is not intended to suppress cam-out and is clearly different from the electronic pulse control described above.

[0117] The various values ​​such as time, duty cycle, and braking force exemplified as specific numerical values ​​in the embodiments do not limit the scope of the invention in any way and can be arbitrarily changed to suit the required specifications. [Explanation of symbols]

[0118] 1...Work implement, 2...Housing, 2a...Motor housing, 2b...Handle section, 2c...Battery mounting section, 3...Motor, 3a...Motor shaft, 4...Reduction mechanism, 5...Spindle, 6...Trigger switch (operating section), 7...Battery pack, 8...Hammer, 9...Spring, 10...Anvil (attachment tool mounting section), 10a...Attachment tool mounting hole, 11...Hammer case, 12...Front cap (protective member), 13...Rotation direction switching switch (rotation direction switching section), 14...Attachment tool, 15...Sensor board, 16...Illumination LED, 82...Inverter circuit, 83...Control signal output circuit, 84...Magnetic sensor, 85...Rotor position detection circuit, 86...Rotation speed detection circuit, 87...Mode switching switch, 88...Control circuit voltage supply circuit, 89...Battery voltage detection circuit, 90..., 91...Motor current detection circuit, 92...Illumination LED drive circuit, 93...Control circuit voltage detection circuit, 94...Display LED drive circuit, 95...Microcontroller.

Claims

1. A work machine capable of tightening screws, Motor and, A tip tool mounting section, which is driven by the driving force of the aforementioned motor and to which a tip tool can be attached, An operating unit that can switch the motor on and off, The system includes a control unit that controls the motor in accordance with the operation of the control unit, The control unit, The aforementioned motor can perform electronic pulse control, which alternately repeats forward and reverse rotation. When the amount of operation of the control unit is less than or equal to the stop threshold, the motor is not driven. When the amount of operation of the control unit exceeds the stop threshold but is less than a predetermined value greater than the stop threshold, the effective value of the motor voltage applied to the motor is controlled according to the amount of operation of the control unit. The condition for executing the electronic pulse control is that the amount of operation of the control unit is greater than or equal to a predetermined value that is greater than the stop threshold. Work equipment.

2. The control unit performs normal control, which keeps the motor rotating in one direction, when the amount of operation of the operating unit exceeds the stop threshold but is less than a predetermined value greater than the stop threshold. The work machine according to claim 1.

3. The control unit continues the normal control until a predetermined mask time has elapsed since detecting the rotation of the motor. The work machine according to claim 2.

4. The control unit, when the amount of operation of the operating unit is changed while the motor is being driven, switches whether or not to execute the electronic pulse control according to the changed amount of operation. The work machine according to claim 2.

5. A work machine capable of tightening screws, Motor and, A tip tool mounting section, which is driven by the driving force of the aforementioned motor and to which a tip tool can be attached, An operating unit that can switch the motor on and off, The system includes a control unit that controls the motor in accordance with the operation of the control unit, The control unit, The aforementioned motor can perform electronic pulse control, which alternately repeats forward and reverse rotation. During the period in which the operating unit is being operated, the electronic pulse control can be executed during the low-torque period when the load on the tip tool is low. The condition for the continuation of the electronic pulse control is that the motor is not in an unloaded state where no external load is applied. Work equipment.

6. When the control unit detects the no-load state during the execution of the electronic pulse control, it switches to normal control, which continues to rotate the motor in one direction, or stops the motor. The work machine according to claim 5.

7. A work machine capable of tightening screws, Motor and, A tip tool mounting section, which is driven by the driving force of the aforementioned motor and to which a tip tool can be attached, An operating unit that can switch the motor on and off, The system includes a control unit that controls the motor in accordance with the operation of the control unit, The control unit, The aforementioned motor can perform electronic pulse control, which alternately repeats forward and reverse rotation. During the period in which the operating unit is being operated, the electronic pulse control can be executed during the low-torque period when the load on the tip tool is low. If a no-load state is detected during the execution of the electronic pulse control, where no external load is applied to the motor, the system will switch to normal control, which continues to rotate the motor in one direction, or it will stop the motor. Work equipment.

8. The control unit, During the period in which the operating unit is being operated, the electronic pulse control can be executed during the low-torque period when the load on the tip tool is low. During the period in which the operating unit is being operated, if the load on the tip tool is high, normal control is performed to keep the motor rotating in one direction. The work machine according to claim 1.

9. The system includes a rotary impact mechanism that converts the driving force of the motor into rotational impact force and transmits it to the tip tool mounting section. The control unit considers the fact that the rotary impact mechanism is not striking the tip tool mounting portion as a condition necessary for the continuation of the electronic pulse control. The work machine according to claim 1.

10. A work machine capable of tightening screws, Motor and, A tip tool mounting section, which is driven by the driving force of the aforementioned motor and to which a tip tool can be attached, A rotary impact mechanism that converts the driving force of the motor into rotational impact force and transmits it to the tip tool mounting section, An operating unit that can switch the motor on and off, The system includes a control unit that controls the motor in accordance with the operation of the control unit, The control unit, The aforementioned motor can perform electronic pulse control, which alternately repeats forward and reverse rotation. During the period in which the operating unit is being operated, the electronic pulse control can be executed during the low-torque period when the load on the tip tool is low. If, during the execution of the aforementioned electronic pulse control, the system detects an impact on the tip tool mounting portion by the rotary impact mechanism, it switches to normal control, in which the motor continues to rotate in one direction. Work equipment.

11. The rotary striking mechanism comprises a hammer rotated by the motor and an anvil struck by the hammer. The work machine according to claim 9.

12. The motor has a rotational impact mechanism that converts the rotational force of the motor into rotational impact force and applies it to the tip tool mounting section. The control unit is capable of performing the electronic pulse control during the low-torque period, which is the period during which the rotary striking mechanism does not perform striking, and is capable of performing the normal control, which keeps the motor rotating in one direction, during the high-torque period, which is the period during which the rotary striking mechanism performs striking. The work machine according to claim 5 or 8.

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