Work machine

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]

[0001] The present invention relates to a work machine capable of tightening screws. [Background technology]

[0002] 2. Description of the Related Art Impact drivers and electronic pulse drivers are known as impact tools that fasten bolts or the like by using the impact force generated by impacting a hammer against an anvil.

[0003] The impact driver is equipped with a spring that biases the hammer toward the anvil, and a single operation of the trigger switch rotates the hammer in only one direction. After colliding with the engagement protrusion on the anvil, the hammer moves away from the anvil against the biasing force of the spring, and then rotates past the engagement protrusion, making it ready to collide with the engagement protrusion again.

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

[0005] The following Patent Document 1 discloses an impact tool that has the same structure as a conventional impact driver but operates in an electronic pulse mode. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-827 Summary of the Invention [Problem to be solved by the invention]

[0007] In an impact tool, for example, when the torque applied to the motor is low in the first half of a screw tightening operation, both the hammer and the anvil rotate, and no impact occurs. According to the inventor's findings, during the period when no impact occurs, the engagement between the tool bit and the screw is released, causing the tool bit to spin freely, which is known as cam-out. Cam-out also occurs in work tools such as drill drivers that do not have a rotary impact mechanism such as a hammer or anvil.

[0008] The inventors have found that electronic pulse control, which alternates between forward and reverse rotation of a motor, is effective in suppressing come-out. Meanwhile, the inventors have discovered that if electronic pulse control is performed at a timing not intended by the operator, workability may be adversely affected. Furthermore, the inventors have discovered that a large reverse current is generated when switching from forward to reverse rotation in electronic pulse control, which may cause problems such as battery degradation, exceeding the withstand voltage of the circuit, and overheating of the circuit.

[0009] An object of the present invention is to solve at least one of the following problems 1 to 3. · Issue 1: To provide a work machine that suppresses the occurrence of cam-out. Issue 2: To provide a work machine that prevents electronic pulse control from being performed at a timing not intended by the operator. · Issue 3: To provide a work machine that suppresses reverse current in electronic pulse control. [Means for solving the problem]

[0010] One aspect of the present invention is a work machine capable of screw tightening, A motor; a tool attachment portion that is driven by the driving force of the motor and that can attach a tool; an operation unit capable of switching between driving and stopping the motor; and a control unit that controls the motor in response to an operation of the operation unit. The control unit The motor is capable of performing electronic pulse control to alternately rotate forward and backward, The electronic pulse control can be executed during a low torque period in which the load on the tool bit is low during the period in which the operating unit is operated.

[0011] Another aspect of the present invention is a work machine capable of screw tightening, A motor; a tool attachment portion that is driven by the driving force of the motor and that can attach a tool; an operation unit capable of switching between driving and stopping the motor; and a control unit that controls the motor in response to an operation of the operation unit. The control unit The motor is capable of performing electronic pulse control to alternately rotate forward and backward, The condition necessary for executing the electronic pulse control is that the amount of operation of the operation unit is equal to or greater than a predetermined amount.

[0012] The present invention may be expressed as an "electric working machine," "electric tool," "electrical equipment," etc., and such expressions are also valid as aspects of the present invention. [Effects of the Invention]

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

[0014] [Figure 1] 1 is a side cross-sectional view of a work machine 1 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a circuit block diagram of the work machine 1. [Figure 3] 3 is a control flowchart of the work machine 1. [Figure 4] 4 is a time chart of the operation of the work machine 1, in which the amount of operation of the trigger switch 6 is changed during the operation. [Figure 5] 10 is a time chart of the operation of the work machine 1, in which the hammer 8 starts striking the anvil 10 midway. [Figure 6]4 is a flowchart showing a first example of the electronic pulse control (S9) in FIG. 3. [Figure 7] 1A is a time chart showing the operation of the work implement 1 when the load on the tool bit 14 is small, and FIG. 1B is a time chart showing the operation of the work implement 1 when the load on the tool bit 14 is large. [Figure 8] 10 is a flowchart showing a second example of the electronic pulse control (S9) in FIG. 3. [Figure 9] 10 is a flowchart showing a third example of the electronic pulse control (S9) in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] In the following, identical or equivalent components, members, etc. shown in each drawing are denoted by the same reference numerals, and redundant explanations will be omitted where appropriate. The embodiments are illustrative and do not limit the invention. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0016] Fig. 1 is a side cross-sectional view of a work machine 1 according to an embodiment of the present invention. Fig. 1 defines the front-rear and up-down directions of the work machine 1, which are perpendicular to each other. The front-rear direction is a direction parallel to the motor shaft 3a of the work machine 1. The work machine 1 is a work machine capable of tightening screws, and specifically, is an impact driver.

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

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

[0019] The upper end of the handle portion 2b is connected to a middle portion of the motor housing portion 2a in the front-rear direction and extends downward from the middle portion. The work machine 1 has a trigger switch 6 and a rotation direction changeover switch 13 at the upper end of the handle portion 2b. The trigger switch 6 is an operating part that allows the operator to switch between driving and stopping the motor 3 (the driving state of the motor 3). The trigger switch 6 is an infinitely variable speed switch. The rotation direction changeover switch 13 is a rotation direction changeover part that allows the operator to switch between forward and reverse rotation of the motor 3, i.e., forward and reverse rotation of the anvil 10 described below.

[0020] The battery mounting section 2c is provided at the lower end of the handle section 2b, and a battery pack 7 can be detachably mounted thereon. The work machine 1 operates using power from the battery pack 7. The work machine 1 has an operation panel 20 (switch panel) on the front upper surface of the battery mounting section 2c. The work machine 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 tool attachment portion inside the motor housing portion 2a and the hammer case 11. The reduction mechanism 4, the spindle 5, the hammer 8, and the spring 9 constitute a rotary impact mechanism that converts the driving force (rotational force) of the motor 3 into rotary impact force that acts on the anvil 10.

[0022] The motor 3 is an inner rotor type brushless motor. The reduction mechanism 4 reduces the rotation speed of the motor 3 and transmits it to the spindle 5. The spindle 5 rotates and drives the hammer 8. The hammer 8 is movable back and forth relative to the spindle 5. A spring 9 biases the hammer 8 forward. The hammer 8 rotates or rotary strikes the anvil 10. In other words, the anvil 10 is driven by the driving force of the motor 3. The anvil 10 is rotatably supported by a hammer case 11 and is located in front of the hammer 8. The anvil 10 has a tool attachment hole 10a into which a tool 14 such as a bit can be attached.

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

[0024] 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 microcomputer 95.

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

[0026] The magnetic sensor 84 detects the magnetic field generated by the rotor of the motor 3 and transmits the result to a 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 the result to a microcomputer 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 the result to the microcomputer 95.

[0027] The mode selector switch 87 is provided on the operation panel 20 in Fig. 1. The mode selector switch 87 transmits the drive mode selected by the operator to the microcomputer 95. The drive modes include a pulse mode (first mode) in which electronic pulse control, which will be described later, is performed, and a non-pulse mode (second mode) in which electronic pulse control is not performed.

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

[0029] 1 under the control of the microcomputer 95. The control circuit voltage detection circuit 93 detects the output voltage of the control circuit voltage supply circuit 88 and sends it to the microcomputer 95. The display LED drive circuit 94 supplies a drive current to the display LEDs provided on the operation panel 20.

[0030] The microcomputer 95 is a control unit that controls the drive of the motor 3. The microcomputer 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 the "set rotation direction"), and the operation of the trigger switch 6, to control the drive of the motor 3. The microcomputer 95 can control the effective value of the voltage applied to the motor 3 (hereinafter referred to as the "motor applied voltage") by the duty of the PWM control (hereinafter referred to as the "duty").

[0031] The microcomputer 95 can detect the load on the motor 3 based on the motor current. The microcomputer 95 can distinguish between forward and reverse rotation of the motor 3 based on the signal from the rotor position detection circuit 85, i.e., the signal from the magnetic sensor 84.

[0032] The microcomputer 95 is capable of executing electronic pulse control. The electronic pulse control 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 the pulse mode, the microcomputer 95 executes electronic pulse control during a low torque period in which the load on the tool bit 14 is low while the trigger switch 6 is operated. The low torque period is a period in which the hammer 8 does not strike the anvil 10 (hereinafter referred to as "strike"), i.e., a period in which the hammer 8 and the anvil 10 rotate together.

[0033] According to the inventor's findings, during low torque periods, cam-out, in which the engagement between the tool bit 14 and the screw disengages and the tool bit 14 spins freely, is likely to occur. The inventor has found that executing electronic pulse control during low torque periods as described above is effective in suppressing cam-out. With electronic pulse control during low torque periods, even if the engagement between the tool bit 14 and the screw becomes shallow and cam-out is likely to occur, the reverse rotation control can restore (deepen) the engagement between the tool bit 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 not intended by the operator, workability may be impaired. Generally, in the early stages of screw tightening, the screw is prone to wobbling relative to the mating material, so the trigger operation amount is reduced and tightening is continued until the screw becomes less likely to wobble. If electronic pulse control is performed in such an early stage of screw tightening, it actually makes the system less user-friendly.

[0035] Even when the amount of trigger operation is small, even when not in the early stages of screw tightening, the worker is working carefully, making it less likely for cam-out to occur, and using electronic pulse control would actually make it less convenient to use. Therefore, the microcomputer 95 sets the condition for executing electronic pulse control as being that the amount of operation of the trigger switch 6 (hereinafter referred to as the "trigger operation amount") is equal to or greater than a predetermined amount.

[0036] This allows the operator to switch between executing and not executing electronic pulse control depending on the amount of trigger operation, thereby preventing electronic pulse control from being performed at a time unintended by the operator, i.e., when the amount of trigger operation is small, such as at the beginning of screw tightening or when performing the work carefully, and preventing deterioration of usability.

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

[0038] During one ON operation (motor drive operation) of the trigger switch 6, that is, when the trigger operation amount is changed while the motor 3 is being driven, the microcomputer 95 switches whether or not to execute electronic pulse control according to the changed operation amount. Specifically, when the trigger operation amount is changed from less than a predetermined amount to equal to or greater than the predetermined amount, the microcomputer 95 transitions from normal control to electronic pulse control, and when the trigger operation amount is changed from equal to or greater than the predetermined amount to less than the predetermined amount, the microcomputer 95 transitions from electronic pulse control to normal control.

[0039] The predetermined amount of trigger operation when switching from normal control to electronic pulse control may be set larger than the predetermined amount when switching from electronic pulse control to normal control, thereby preventing frequent switching between normal control and electronic pulse control.

[0040] In pulse mode, the microcomputer 95 requires that the motor 3 is not in a no-load state, where no external load is applied. The reason for this is as follows: Since no come-out occurs in a no-load state, there is no benefit to performing electronic pulse control. On the other hand, if electronic pulse control is performed in a no-load state, unnecessary heat generation occurs due to repeated forward and reverse rotation control. When the microcomputer 95 detects a no-load state while executing electronic pulse control, it either switches to normal control or stops the motor 3.

[0041] The microcomputer 95 considers the non-no-load state to be a necessary condition for continuing electronic pulse control but not a necessary condition for starting electronic pulse control in order to prevent delays in the start of electronic pulse control due to the time required to detect that the non-no-load state is present. If the trigger operation amount is equal to or greater than a predetermined amount, the microcomputer 95 starts electronic pulse control regardless of whether the no-load state is present, thereby enabling electronic pulse control to be started quickly and achieving a rapid come-out suppression effect.

[0042] The microcomputer 95 executes normal control during the high-torque period when the trigger switch 6 is operated and the load on the tool bit 14 is high. The high-torque period is the period when impacts are being performed. In other words, the microcomputer 95 determines that the absence of impacts is a necessary condition for continuing electronic pulse control. Note that normal control during the high-torque period is an example of impact control. In other words, normal control and impact control are the same in the case of an impact driver.

[0043] According to the inventor's findings, come-out is less likely to occur during high torque periods than during low torque periods. On the other hand, if electronic pulse control is performed during high torque periods, the number of impacts per hour decreases, and the tightening speed decreases. By performing normal control during high torque periods as described above, the decrease in tightening speed can be suppressed.

[0044] The microcomputer 95 considers the absence of an impact to be a necessary condition for continuing electronic pulse control but not a necessary condition for starting electronic pulse control in order to prevent delays in the start of electronic pulse control due to the time required to detect that an impact has not occurred. The microcomputer 95 starts electronic pulse control if the trigger operation amount is equal to or greater than a predetermined amount, regardless of whether an impact has occurred, thereby enabling electronic pulse control to be started quickly and achieving a rapid come-out suppression effect.

[0045] The microcomputer 95 can decelerate the motor 3 by brake control. Brake control is control that consumes the rotational energy of the motor 3 without supplying power from an external source to the motor 3, thereby decelerating the motor 3 faster than natural deceleration. Brake control is, for example, control that applies short-circuit braking. Short-circuit braking is, for example, control that turns off the switching elements Q1 to Q3 on the upper arm side and turns on at least one of the switching elements Q4 to Q6 on the lower arm side continuously or intermittently. Note that reverse control performed on the motor 3 that is rotating forward is control that supplies power for reverse rotation from an external source and is not brake control.

[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 starts when the operator turns on the trigger switch 6.

[0047] The microcomputer 95 starts driving the motor 3 by turning on the trigger switch 6 (S1). The microcomputer 95 first performs normal control (S2). If the trigger operation amount is equal to or less than the stop threshold ("Yes" in S3), the microcomputer 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 predetermined time has not elapsed since the detection of the rotation of the motor 3 ("No" in S5), the microcomputer 95 continues normal control (S19). This predetermined time is a mask time immediately after the start of the motor 3, during which electronic pulse control is not performed. By providing a mask time, electronic pulse control is prevented from being initiated during the short period of time during which the trigger switch 6 is turned on. The mask time is, for example, 200 milliseconds.

[0049] If a predetermined time has passed 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 or switches to normal control (S19).

[0050] If the microcomputer 95 does not detect an impact during execution of normal control ("No" in S21), the process returns to S3.

[0051] When the microcomputer 95 detects an impact during execution of normal control ("Yes" in S21), it continues normal control until the trigger operation amount becomes equal to or less than the stop threshold ("No" in S17).

[0052] When the trigger operation amount becomes equal to or less than the stop threshold value (YES in S17), the microcomputer 95 stops the motor 3 (S23).

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

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

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

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

[0057] When the trigger operation amount exceeds the stop threshold at time t1, the microcomputer 95 increases the duty according to the trigger operation amount. This increases the motor rotation speed and the motor current. The temporary sharp increase in motor current immediately after time t1 is due to the starting current (starting current).

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

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

[0060] In electronic pulse control, forward rotation control and reverse rotation control are repeated. However, because reverse rotation control is performed until the microcomputer 95 detects the reverse rotation of the motor 3, the motor rotation speed during reverse rotation is significantly lower than the motor rotation speed during forward rotation. For example, if the motor 3 has a 4-pole, 6-slot configuration and the three magnetic sensors 84 are spaced 60 degrees apart around the circumference of the motor 3, the microcomputer 95 can detect reverse rotation if the motor 3 rotates reverse by 30 degrees or more.

[0061] In electronic pulse control, the microcomputer 95 gradually changes the duty after switching between forward rotation control and reverse rotation control, thereby suppressing the peak current at the time of switching.

[0062] In electronic pulse control, one reverse rotation control followed by one forward rotation control constitutes one cycle. The magnitude of the motor current immediately before the end of the forward rotation control in each cycle varies depending on the load on the tool bit 14, i.e., the load on the motor 3. In the example of Figure 4, the tightening progresses toward the later cycles, and the load on the tool bit 14 increases, so the motor current immediately before the end of the forward rotation control increases toward the later cycles. The microcomputer 95 can detect the 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 amount of trigger operation, and when the amount of trigger operation falls below a predetermined amount X2 (electronic pulse control stop threshold) at time t3, the microcomputer 95 stops electronic pulse control and switches to normal control. When the operator turns off the trigger switch 6 at time t4, the microcomputer 95 sets the duty to 0 and stops the motor 3.

[0064] 5 is a time chart of the operation of the work machine 1, and is a time chart in the case where impact starts midway. Below, the differences from FIG. 4 will be mainly explained.

[0065] When the trigger operation amount exceeds the stop threshold at time t11, the microcomputer 95 increases the duty in accordance with the trigger operation amount. In the period between times t11 and t12, the trigger operation amount becomes equal to or greater than the predetermined amount X1, but at this point in time, the mask time has not yet elapsed since the motor 3 started rotating, so the microcomputer 95 executes normal control.

[0066] At time t12, when the mask time has elapsed from time t11, the microcomputer 95 starts electronic pulse control. In the example of Fig. 5, impacts start during execution of electronic pulse control from time t12 to t13, and fluctuations (fluctuations) in the motor rotation speed occur due to the impacts (part A in Fig. 5).

[0067] At time t13 when the microcomputer 95 detects two fluctuations in the motor rotation speed due to impact, the microcomputer 95 stops the electronic pulse control and shifts to normal control.

[0068] After time t13, impacts are repeated under normal control, the tightening progresses, the load on the tool bit 14 increases, and the motor current increases. To maintain the motor rotation speed, the duty also increases.

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

[0070] Electronic pulse control during low torque periods is effective in suppressing come-out, but the inventors have found that a large reverse current is generated when switching from forward rotation to reverse rotation under electronic pulse control, which can cause problems such as battery degradation, exceeding the withstand voltage of the circuit, heat generation in the circuit, etc. Below, we will explain electronic pulse control that can effectively deal with these problems.

[0071] Figure 6 is a flowchart showing a first example of the electronic pulse control (S9) of Figure 3. The microcomputer 95 initializes various parameters (S31). For example, the microcomputer 95 sets the maximum duty in the electronic pulse control to a predetermined value, here 20% as an example, and sets the execution time of the brake control in the first cycle to a predetermined time, here 30 milliseconds as an example.

[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 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 microcomputer 95 ends the forward rotation control and starts brake control (S33). The brake control is a control to apply a short-circuit brake, and turns off the switching elements Q1 to Q3 on the upper arm side and turns on the switching elements Q4 to Q6 on the lower arm side. The microcomputer 95 continues the brake control until the brake time has elapsed (NO in S35).

[0074] When the brake time has elapsed since the start of the brake control (YES in S35), the microcomputer 95 starts the reverse rotation control (S37). The microcomputer 95 continues the reverse rotation control until the reverse rotation of the motor 3 is detected (NO in S39).

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

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

[0077] When the pulse period time has elapsed since the start of the brake control (YES in S49), the microcomputer 95 sets the brake time in the next period (S51 to S63).

[0078] If the immediately preceding cycle was the first cycle of electronic pulse control (YES in S51), the microcomputer 95 sets the brake time 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] That is, the first cycle in electronic pulse control begins with a higher motor rotation speed than the other cycles because there is a mask time of, for example, 200 milliseconds before it. Therefore, in the first cycle, the braking time is set longer to ensure sufficient deceleration even when the motor rotation speed is high. However, if the braking time is adjusted using feedback control based on this longer braking time, the braking time will remain too long over multiple cycles, and it will take a long time to reach the optimal braking time.

[0080] The processing of S53 described above shortens the time required to reach the optimum braking time by resetting the actual braking time in the first cycle as the reference time rather than using it as is.

[0081] If the immediately preceding cycle is not the first cycle of the electronic pulse control (NO in S51), the microcomputer 95 proceeds to S55 without changing the set value of the braking time from the actual braking time in the immediately preceding cycle.

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

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

[0084] If the reverse rotation time in the immediately preceding cycle is between 3 ms and 5 ms (NO in S55, NO in S59), the microcomputer 95 does not change the set value of the brake time from the current value (S63) and returns to S33.

[0085] The reverse rotation time in the immediately preceding cycle becomes longer as the forward rotation speed of the motor 3 (hereinafter referred to as "forward rotation speed") at the start of reverse rotation control becomes higher. The braking time setting described above aims to make the forward rotation speed at the start of reverse rotation control in each cycle as constant as possible, thereby making the reverse rotation time in each cycle as constant as possible.

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

[0087] FIG. 7(B) is a time chart of the operation of the work machine 1 when a large load is applied to the bit 14. Time T1' indicates the reverse rotation time in a certain cycle. Time T2' indicates the forward rotation time in the same cycle. Time T3' indicates the braking time in the same cycle. Time T4' is the total time of times T1' to T3', and indicates the time of one cycle of electronic pulse control.

[0088] 7(A) and (B), when the load on the tool bit 14 is large, the reaction force from the screw to the tool bit 14 is large compared to when the load on the tool bit 14 is small. Therefore, the motor rotation speed decreases quickly under brake control, and the braking time required to decelerate to a certain forward rotation speed is shortened (T3' <T3)。

[0089] On the other hand, because reverse rotation control starts from a constant forward rotation speed, the reverse rotation time is constant regardless of the load on the tool bit 14 (T1 ≒ T1'). Also, the cycle of electronic pulse control is constant for all cycles (T4 = T4'). Therefore, when the load on the tool bit 14 is large, the forward rotation time is longer than when the load on the tool bit 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 of Figure 6, the braking time in the next cycle is adjusted according to the reverse rotation time in an arbitrary cycle, whereas in the example of Figure 8, the braking force in the next cycle is adjusted according to the reverse rotation time in an arbitrary cycle.

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

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

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

[0094] If the immediately preceding cycle is not the first cycle of the electronic pulse control (NO in S51), the microcomputer 95 proceeds to S69 without changing the set value of the braking force from the actual braking force in the immediately preceding cycle.

[0095] The microcomputer 95 sets the braking force for the next cycle (S69). If the reverse rotation time in the immediately preceding cycle is longer than the reference reverse rotation time, the set value of the braking force is increased relative to the current value. If the reverse rotation time in the immediately preceding cycle is longer than the reference reverse rotation time, the set value of the braking force is decreased relative to the current value. A specific example of calculating the braking force is also shown in FIG. 8.

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

[0097] The microcomputer 95 continues brake control until the motor rotation speed drops to, for example, 500 rpm or less (NO in S36). When the motor rotation speed drops to, for example, 500 rpm or less (YES in S36), the microcomputer 95 starts reverse rotation control (S37). When the microcomputer 95 detects the reverse rotation of the motor 3 (YES in S39), it turns off all of the switching elements Q1 to Q6 (S41). Here, it is not necessary to record the reverse rotation time in FIG. 6 (S43 in FIG. 6).

[0098] When the pause time has elapsed since the switching elements Q1 to Q6 were turned off (YES in S45), the microcomputer 95 starts forward rotation control (S47). When the pulse period time has elapsed since the start of braking control (YES in S49), the microcomputer 95 returns to S33. Here, the setting of the braking time (S51 to S63) in FIG. 6 is not required.

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

[0100] (1) The microcomputer 95 executes electronic pulse control during the low torque period when cam-out is likely to occur and the load on the tool bit 14 is low while the trigger switch 6 is operated. Therefore, even if the engagement between the tool bit 14 and the screw becomes shallow and cam-out is likely to occur, the reverse rotation control can restore the engagement between the tool bit 14 and the screw, thereby preventing cam-out.

[0101] (2) The microcomputer 95 sets the trigger operation amount being equal to or greater than a predetermined amount as a necessary condition for executing electronic pulse control. This allows the operator to switch between executing and not executing electronic pulse control depending on the trigger operation amount. This prevents electronic pulse control from being executed at a time unintended by the operator, i.e., when the trigger operation amount is small, such as at the beginning of screw tightening or when performing the work carefully, thereby preventing deterioration in usability.

[0102] (3) When the trigger operation amount is changed during one ON operation of the trigger switch 6, i.e., while the motor 3 is being driven, the microcomputer 95 switches whether or not to execute electronic pulse control according to the changed operation amount. This eliminates the need for the operator to re-operate the trigger switch 6 to switch whether or not to execute electronic pulse control, making it easy to use.

[0103] (4) The microcomputer 95 determines that a necessary condition for continuing electronic pulse control is that the motor 3 is not in a no-load state where no external load is applied. Therefore, it is possible to prevent unnecessary heat generation due to electronic pulse control in a no-load state where no come-out occurs.

[0104] (5) The microcomputer 95 performs normal control during the high torque period when the trigger switch 6 is operated and the load on the tool bit 14 is high. Therefore, electronic pulse control is performed during the high torque period to reduce the number of impacts per hour, thereby preventing a decrease in the tightening speed.

[0105] (6) The microcomputer 95 starts electronic pulse control if the trigger operation amount is equal to or greater than a predetermined amount, regardless of whether there is no load or whether the load on the tool bit 14 is high. This allows electronic pulse control to be started quickly, and the come-out suppression effect can be achieved quickly.

[0106] (7) In the example shown in Figures 6 to 9, when switching from forward rotation control to reverse rotation control in electronic pulse control, the microcomputer 95 performs brake control after forward rotation control before switching to reverse rotation control. This reduces the reverse current when switching from forward rotation control to reverse rotation control. This prevents problems such as battery degradation, exceeding the circuit's withstand voltage, and circuit heat generation caused by a large reverse current.

[0107] (8) The microcomputer 95 makes the forward rotation time longer than the reverse rotation time in each cycle of the electronic pulse control. This improves the efficiency of screw tightening work compared to when the forward rotation time and reverse rotation time are the same.

[0108] (9) In the example of Fig. 6, the microcomputer 95, in electronic pulse control, changes the brake time in the next cycle according to the reverse rotation time in a given cycle, and controls the reverse rotation time so that it falls within a certain range. Keeping the reverse rotation time within a certain range improves the working feel.

[0109] (10) In the example of Fig. 9, the microcomputer 95 switches to reverse control when the motor rotation speed falls below a predetermined value due to brake control under electronic pulse control. This makes the reverse rotation time roughly constant, improving the working feel.

[0110] (11) In electronic pulse control, the microcomputer 95 continues reverse rotation control until it detects that the motor 3 has rotated in the reverse direction, and then switches to forward rotation control when it detects that the motor 3 has rotated in the reverse direction. This minimizes the reverse rotation time and ensures a long forward rotation time, improving the efficiency of screw tightening. To restore engagement between the tool bit 14 and the screw, it is sufficient to remove the torque acting on the tool bit 14 in the forward direction. Therefore, once it is confirmed that the motor 3 has rotated in the reverse direction, further reverse rotation is not necessary.

[0111] (12) In electronic pulse control, the microcomputer 95 keeps the cycle constant over multiple cycles (preferably all cycles) and varies the forward rotation time, reverse rotation time, and braking time per cycle. This allows for flexible control, such as shortening the braking time and lengthening the forward rotation time when the load on the tool bit 14 is large and a short braking time is sufficient, thereby improving the efficiency of screw tightening operations.

[0112] (13) In electronic pulse control, the microcomputer 95 does not execute brake control when switching from reverse rotation control to forward rotation control. Unlike forward rotation control, reverse rotation control has a lower motor rotation speed, making it less likely to cause problems such as heat generation even without brake control. Therefore, by switching from reverse rotation control to forward rotation control without brake control, the motor 3 can be rotated forward quickly, while minimizing disadvantages such as heat generation.

[0113] (14) In electronic pulse control, the microcomputer 95 stops the brake control and starts the reverse control before the forward rotation of the motor 3 stops. Because the braking force decreases as the motor rotation speed decreases, starting the reverse control before the forward rotation of the motor 3 stops can prevent the brake time from becoming longer and the forward rotation time from becoming shorter.

[0114] While the present invention has been described above using the embodiments as examples, it will be understood by those skilled in the art that various modifications can be made to the components and processes of the embodiments within the scope of the claims. Modifications will be discussed below.

[0115] The working machine of the present invention is not limited to the impact driver exemplified in the embodiment, but may be other types of machine such as an impact wrench, an electronic pulse driver, an oil pulse tool, or a drill driver.

[0116] In the case of an electronic pulse driver, impact control (impact control) when high torque occurs also involves repeating forward and reverse rotation of the motor. However, the impact control of an electronic pulse driver reverses the hammer, and the reverse control takes longer than the electronic pulse control described above. In other words, the impact control of an electronic pulse driver is not intended to suppress come-out, and is clearly different from the electronic pulse control described above.

[0117] The various times, duties, braking forces, etc., given as specific numerical values ​​in the embodiments do not limit the scope of the invention in any way, and can be changed as desired to suit the required specifications. [Explanation of symbols]

[0118] 1...work machine, 2...housing, 2a...motor accommodating section, 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 (tip tool mounting section), 10a...tip tool mounting hole, 11...hammer case, 12...front cap (protective member), 13...rotation direction change switch (rotation direction change section), 14...tip 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 change 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...microcomputer

Claims

1. A work machine capable of screw tightening, A motor; a tool attachment section that is driven by the driving force of the motor and is capable of attaching a tool tip; an operation unit capable of switching between driving and stopping the motor; a control unit that controls the motor in response to an operation of the operation unit, The control unit is The motor is capable of performing electronic pulse control to alternately rotate forward and backward; The electronic pulse control can be executed during a low torque period during which the load on the tool bit is low during the period during which the operating unit is operated. Work machine.

2. The control unit is When the operation amount of the operation unit is equal to or less than a stop threshold, the motor is not driven, When the operation amount of the operation unit exceeds the stop threshold and is less than a predetermined value that is greater than the stop threshold, an effective value of a motor applied voltage to be applied to the motor is controlled in accordance with the operation amount of the operation unit; A necessary condition for executing the electronic pulse control is that the operation amount of the operation unit is equal to or greater than a predetermined value that is greater than the stop threshold value. The work machine according to claim 1.

3. A work machine capable of screw tightening, A motor; a tool attachment section that is driven by the driving force of the motor and is capable of attaching a tool tip; an operation unit capable of switching between driving and stopping the motor; a control unit that controls the motor in response to an operation of the operation unit, The control unit is The motor is capable of performing electronic pulse control to alternately rotate forward and backward; When the operation amount of the operation unit is equal to or less than a stop threshold, the motor is not driven, When the operation amount of the operation unit exceeds the stop threshold and is less than a predetermined value that is greater than the stop threshold, an effective value of a motor applied voltage to be applied to the motor is controlled in accordance with the operation amount of the operation unit; A necessary condition for executing the electronic pulse control is that the operation amount of the operation unit is equal to or greater than a predetermined value that is greater than the stop threshold value. Work machine.

4. The control unit executes normal control to continue rotating the motor in one direction when the operation amount of the operation unit exceeds the stop threshold and is less than a predetermined value that is greater than the stop threshold. A work machine according to claim 2 or 3.

5. The control unit continues the normal control until a predetermined mask time has elapsed since starting the execution of the normal control. A work machine according to claim 4.

6. when the operation amount of the operation unit is changed while the motor is being driven, the control unit switches whether or not to execute the electronic pulse control in accordance with the changed operation amount. A work machine according to claim 4.

7. The control unit determines that a necessary condition for continuing the electronic pulse control is that the motor is not in an unloaded state in which no load is applied from the outside. A work machine according to any one of claims 1 to 3.

8. When the control unit detects the no-load state during execution of the electronic pulse control, the control unit transitions to normal control in which the motor continues to rotate in one direction, or stops the motor. A work machine according to claim 7.

9. The control unit executes normal control to continue rotating the motor in one direction during a high torque period in which a load on the tool bit is high during the period in which the operation unit is operated. A work machine according to any one of claims 1 to 3.

10. A rotary impact mechanism is provided for converting the driving force of the motor into a rotary impact force and transmitting the rotary impact force to the tool attachment portion, The control unit determines that a necessary condition for continuing the electronic pulse control is that the rotary impact mechanism is not impacting the tool attachment unit. A work machine according to any one of claims 1 to 3.

11. When the control unit detects the impact during execution of the electronic pulse control, the control unit transitions to normal control in which the motor continues to rotate in one direction. A work machine according to claim 10.

12. The rotary impact mechanism includes a hammer rotated by the motor and an anvil that is struck by the hammer. A work machine according to claim 10.

13. A tool holder and a rotary impact mechanism that converts the rotational force of the motor into a rotary impact force and applies it to the tool holder, the control unit is capable of executing the pulse control during the low torque period during which the operating unit is operated and during the high torque period during which the rotary impact mechanism performs an impact, and is capable of executing normal control for causing the motor to continue to rotate in one direction; When the control unit detects an impact by the rotary impact mechanism while executing the pulse control, the control unit switches from the pulse control to normal control in which the motor continues to rotate in one direction. The work machine according to claim 1.

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