working machine

Abstract

The present application provides a work machine capable of suppressing temperature rise of a motor. An arithmetic unit 95 continuously performs electronic pulse control even in a no-load state in which no load is applied to a tip tool holding portion, and if the average of the motor current detection value in the forward rotation drive of the motor 3 becomes equal to or greater than a threshold value (if the load applied to the tip tool holding portion increases), the maximum duty ratio when the motor 3 is rotated forward and the rate of increase of the duty ratio are set (updated) to values higher than initial values, so as to set the number of rotations of the motor 3 to be high, or the period of the electronic pulse control is set (updated) to a value smaller than an initial value.

Description

Technical Field

[0001] This invention relates to a machine capable of tightening screws. Background Technology

[0002] An impact screwdriver or similar machine is known to perform tasks such as screw tightening by striking a hammer against an anvil. The impact screwdriver includes a spring that applies force to the hammer against the anvil, causing the hammer to rotate in only one direction during a single trigger operation. After striking the engagement protrusion of the anvil, the hammer overcomes the force applied by the spring and moves away from the anvil, passing over the engagement protrusion and rotating, thus returning to a state where it can strike the engagement protrusion again.

[0003] Patent Document 1 and Patent Document 2 disclose the following: Regarding an impact screwdriver, it includes a control unit capable of performing normal control to make the motor rotate continuously and pulse control (electronic pulse control) to make the motor rotate intermittently.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 5725347

[0007] Patent Document 2: Japanese Patent Application Publication No. 2023-166104 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] Under normal control conditions without load, there is a risk that electronic pulse control may fail to initiate in situations where it is difficult to determine whether there is no load, such as a light load condition at the start of screw tightening, and where electronic pulse control is required. Furthermore, if high-output pulse control is continuously applied under no-load conditions where no external load is applied to the top tool holder, the motor is prone to overheating.

[0010] The first objective of this invention is to provide a working machine that can suppress the risk of pulse control failure during light load conditions at the start of screw tightening. Furthermore, the second objective of this invention is to provide a working machine that can suppress the temperature rise of the motor.

[0011] Technical means to solve the problem

[0012] One embodiment of the present invention is a screw fastening machine. The screw fastening machine is characterized by comprising: a motor; a top tool holder driven by the motor for rotation; a rotation direction switching unit configured to indicate whether to rotate the top tool holder in either a forward or reverse rotation direction; a control unit configured to execute pulse control, the pulse control repeating at a predetermined period the rotation of the motor at a predetermined speed in a predetermined direction, thereby causing the top tool holder to rotate in the predetermined rotation direction indicated by the rotation direction switching unit; and an operation unit configured to indicate the start and stop of the motor, the control unit being configured such that: if the operation unit is operated, the pulse control is executed, and regardless of whether the top tool holder is in an unloaded state without load applied, the pulse control is continuously executed while the top tool holder rotates in the predetermined rotation direction indicated by the rotation direction switching unit.

[0013] This invention can also be described as an "electric work machine" or "electric tool" or "electric equipment", and the content described in this way is also valid as the form of this invention.

[0014] The effects of the invention

[0015] This invention provides a machine tool that can suppress the risk of pulse control failure during light load conditions at the start of screw tightening. Furthermore, this invention provides a machine tool that can suppress motor temperature rise. Attached Figure Description

[0016] [ Figure 1 [1] is a side cross-sectional view of the work machine 1 according to an embodiment of the present invention.

[0017] [ Figure 2 [ ] is the circuit block diagram of machine 1.

[0018] [ Figure 3 [ ] is a flowchart of the pulse mode of machine 1.

[0019] [ Figure 4 [This is a flowchart illustrating the first example of electronic pulse control of machine 1.]

[0020] [ Figure 5 [This is a flowchart illustrating a second example of electronic pulse control for machine 1.]

[0021] [ Figure 6 [This is a graph showing the time changes of the motor 3's rotation speed, current, and PWM control duty cycle in the first or second case of performing electronic pulse control under no-load conditions.]

[0022] [ Figure 7[This is a graph showing the changes in the rotational speed, current, and PWM control duty cycle of motor 3 in the first or second case of electronic pulse control during screw tightening operations.]

[0023] [ Figure 8 [This is a flowchart illustrating the third example of electronic pulse control of the work machine 1.]

[0024] [ Figure 9 [This is a flowchart illustrating the fourth example of electronic pulse control of the work machine 1.]

[0025] [ Figure 10 [This is a graph showing the changes in the rotational speed, current, and duty cycle of motor 3 under the third or fourth case of electronic pulse control in a no-load state.]

[0026] [ Figure 11 [This is a graph showing the time variation of the motor 3's rotation speed, current, and PWM control duty cycle in the third or fourth case of electronic pulse control during screw tightening operations.] Detailed Implementation

[0027] Figure 1 This is a side sectional view of the work machine 1 according to an embodiment of the present invention. Figure 1 Define the mutually orthogonal front-back and up-down directions in machine 1. Machine 1 is a machine capable of tightening screws, specifically an impact screwdriver.

[0028] The work machine 1 includes a housing 2. The housing 2 has a motor housing 2a, a handle 2b, and a battery housing 2c.

[0029] The motor housing 2a is a cylindrical part whose central axis is approximately parallel to the front-rear direction. The housing 2 includes a hammer housing 11, for example made of metal, connected to the front of the motor housing 2a. The front surface of the hammer housing 11 is covered by a front cover 12, which serves as a protective member such as an elastomer.

[0030] The upper end of the handle portion 2b is connected to the middle portion in the front-rear direction of the motor housing portion 2a, and extends downward from the middle portion. The working machine 1 has a trigger switch 6 and a rotation direction switching switch 13 at the upper end of the handle portion 2b. The trigger switch 6 is an operating part (motor drive operation part) that allows the operator to switch the start (drive) and stop (drive state of the motor 3) of the motor 3. The trigger switch 6 is a continuously variable speed switch. The rotation direction switching switch 13 is a rotation direction switching part that allows the operator to switch the forward and reverse rotation of the motor 3, i.e., the forward and reverse rotation of the anvil 10 described later. Forward rotation is an example of rotation in a predetermined direction. Reverse rotation is an example of rotation in the opposite direction to the predetermined direction.

[0031] A battery mounting section 2c is located at the lower end of the handle section 2b, and the battery pack 7 is mounted thereon in a removable manner. The work machine 1 operates by power from the battery pack 7. The work machine 1 has an operation panel 20 (switch panel) on the upper front surface of the battery mounting section 2c. The work machine 1 has a control board 30 inside the battery mounting section 2c.

[0032] The working 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 holding part for the top tool within the motor housing 2a and the hammer housing 11. The reduction mechanism 4, the spindle 5, the hammer 8, and the spring 9 are transmission mechanisms that transmit the rotation of the motor 3 to the anvil 10, and are configured to generate a continuous rotational force or an intermittent rotational force (rotational striking force) on the anvil 10 according to the load (screw fastening load) applied to the anvil 10.

[0033] Motor 3 is an internal rotor type brushless motor with a motor shaft 3a parallel to the front-rear direction. A reduction mechanism 4 slows the rotation of motor 3 and transmits the speed to the main shaft 5. The main shaft 5 drives the hammer 8 to rotate. Hammer 8 can move relative to the main shaft 5 in the front-rear direction. Spring 9 applies a force to hammer 8 forward. Hammer 8 rotates or strikes anvil 10 (generating continuous or intermittent rotational force on anvil 10). That is, anvil 10 is driven to rotate by motor 3. Anvil 10 is rotatably supported on hammer housing 11 and located in front of hammer 8. Anvil 10 has a tool mounting hole 10a for mounting a tool 14 such as a drill bit.

[0034] The work machine 1 has light-emitting diodes (LEDs) 16 around the front of the hammer housing 11 to illuminate the area around the work area. The work machine 1 also has a sensor substrate 15. The sensor substrate 15 is equipped with a sensor for detecting the rotation of the motor 3. Figure 2 The magnetic sensor 84 is shown. The sensor substrate 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.

[0035] Figure 2 This 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 switching switch 87, a control circuit voltage supply circuit 88, a battery voltage detection circuit 89, a motor current detection circuit 91, a lighting LED driver circuit 92, a control circuit voltage detection circuit 93, a display LED driver circuit 94, and an arithmetic unit 95.

[0036] The inverter circuit 82 includes three-phase bridge-connected semiconductor switching elements Q1 to Q6. 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. The control signal output circuit 83, according to the control of the arithmetic unit 95, applies a drive signal, such as a pulse width modulation (PWM) signal, to the gates of each of the switching elements Q1 to Q6.

[0037] The magnetic sensor 84 detects the magnetic field generated by the rotor of the motor 3 and sends the signal to the rotor position detection circuit 85. The rotor position detection circuit 85 detects the rotor position of the motor 3 using the signal from the magnetic sensor 84 and sends the signal to the arithmetic unit 95. The rotational speed detection circuit 86 detects the rotational speed (hereinafter referred to as "motor speed") of the motor 3 using the signal from the rotor position detection circuit 85 and sends the signal to the arithmetic unit 95.

[0038] Mode switch 87 is set Figure 1 On the operation panel 20. The mode switch 87 is a mode switching operation unit for the operator to switch the mode of the calculation unit 95, transmitting the operator's mode switching operation to the calculation unit 95. The modes of the calculation unit 95 will be described later.

[0039] The control circuit voltage supply circuit 88 steps down the output voltage of the battery pack 7 and converts it into a power supply voltage for the arithmetic unit 95, etc., and supplies it to the arithmetic unit 95, etc. The battery voltage detection circuit 89 detects the output voltage of the battery pack 7 and sends it to the arithmetic unit 95. The motor current detection circuit 91 detects the motor current by measuring the voltage of the resistor R set in the current path (hereinafter referred to as "motor current") flowing through the motor 3, and sends it to the arithmetic unit 95.

[0040] The LED driver circuit 92, under the control of the arithmetic unit 95, directs... Figure 1 The lighting LED 16 is supplied with driving current. The control circuit voltage detection circuit 93 detects the output voltage of the control circuit voltage supply circuit 88 and sends it to the arithmetic unit 95. The display LED driving circuit 94 supplies driving current to the display LEDs provided on the operation panel 20.

[0041] The arithmetic unit 95 includes a microcontroller and is a control unit that controls the drive of the motor 3. The arithmetic unit 95 controls the inverter circuit 82 via the control signal output circuit 83, for example, by performing PWM control, based on the mode selected by the mode switching switch 87, the rotation direction set by the rotation direction switching 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.

[0042] The arithmetic unit 95 can control the effective value of the applied voltage (hereinafter referred to as "motor applied voltage") applied to the motor 3 by controlling the duty cycle (DUTY, hereinafter referred to as "duty cycle") of the PWM control. The arithmetic unit 95 can detect the load applied to the motor 3 by detecting the motor current. The arithmetic unit 95 can distinguish and detect the forward and reverse rotation of the motor 3 based on the signal from the rotor position detection circuit 85, that is, based on the signal from the magnetic sensor 84.

[0043] The arithmetic unit 95 can perform normal control, which continuously rotates the motor 3 in a specified direction, and pulse control, which repeatedly rotates the motor 3 in the specified direction and in the opposite direction (hereinafter referred to as "electronic pulse control"). In electronic pulse control, when the arithmetic unit 95 rotates the motor 3 at a specified speed, it sets the duty cycle (sets the effective value of the applied voltage to the motor 3) through open-loop control or closed-loop control. The arithmetic unit 95 has two modes: a pulse mode (first mode) in which electronic pulse control can be performed, and a non-pulse mode (second mode) in which electronic pulse control is not performed. The operator can switch between pulse mode and non-pulse mode using the mode switching switch 87. In non-pulse mode, the arithmetic unit 95 always performs normal control according to the operation of the trigger switch 6. The pulse mode of the arithmetic unit 95 will be described below.

[0044] Figure 3 This is a flowchart of the pulse mode for machine 1. Figure 3 In the middle, the rotation direction is set to forward.

[0045] If trigger switch 6 is operated (if motor drive operation is performed on trigger switch 6), the arithmetic unit 95 performs normal control to continuously rotate motor 3 in the forward direction (S1). If less than 160 ms, a predetermined time, has elapsed since the operation of trigger switch 6, the arithmetic unit 95 continues to perform normal control (S3 "No"). If 160 ms has elapsed since the operation of trigger switch 6 (S3 "Yes"), the arithmetic unit 95 switches from normal control to electronic pulse control to drive motor 3 (S7). 160 ms is the mask time shortly after motor 3 starts, and it is the mask time during which electronic pulse control is not performed. By setting the mask time, electronic pulse control can be suppressed during the short period of trigger switch 6 being on. The arithmetic unit 95 continues to perform electronic pulse control until the operation of trigger switch 6 is released (motor stop operation is performed on trigger switch 6) (S13 "No", S7). If the operation of trigger switch 6 is released (S13 "Yes"), the arithmetic unit 95 stops the motor.

[0046] Figure 4 This is a flowchart illustrating the first example of electronic pulse control of the work machine 1.

[0047] The calculation unit 95 sets the initial value for electronic pulse control (S61). Specifically, the calculation unit 95 sets the maximum duty cycle (hereinafter referred to as "maximum duty cycle during forward rotation") for driving the motor 3 in forward rotation to 15%, and sets the duty cycle rise rate (hereinafter referred to as "duty cycle rise rate during forward rotation") for driving the motor 3 in forward rotation to 0.8% / ms. The number of motor revolutions when driving the motor 3 in forward rotation with a duty cycle of 15% (the initial value of the maximum duty cycle during forward rotation) corresponds to the first rotational speed.

[0048] The arithmetic unit 95 terminates the forward drive of the motor 3 (S63) and performs braking control (S65). Braking control consumes the rotational energy of the motor 3 without supplying power from the outside, thereby decelerating the motor 3 faster than natural deceleration. Braking control is, for example, applying short-circuit braking. Short-circuit braking is, for example, disengaging the upper arm-side switching elements Q1 to Q3 and continuously or intermittently connecting at least one of the lower arm-side switching elements Q4 to Q6. Furthermore, the reverse control of the forward-rotating motor 3 is a control that supplies reverse power from the outside, and is not braking control.

[0049] The arithmetic unit 95 continues to perform braking control until the motor speed drops below a specified speed ("No" in S67). If the motor speed drops below the specified speed ("Yes" in S67), the arithmetic unit 95 ends the braking control (S69).

[0050] The calculation unit 95 updates the setting value of the reverse drive in the electronic pulse control (S71). Specifically, the calculation unit 95 sets the duty cycle when the motor 3 reverses (hereinafter referred to as "reverse duty cycle") in the electronic pulse control to the initial value of 1%, sets the maximum duty cycle when the motor 3 reverses (hereinafter referred to as "maximum duty cycle during reverse") to 20%, and sets the duty cycle rise rate when the motor 3 reverses (hereinafter referred to as "duty cycle rise rate during reverse") to 0.8% / ms.

[0051] The arithmetic unit 95 performs reverse drive of motor 3 (S73). Simultaneously, the arithmetic unit 95 updates the reverse duty cycle (S75) and confirms whether motor 3 is reversed (S77) at predetermined intervals (e.g., 1 ms), while continuing to perform reverse drive of motor 3 until reverse drive of motor 3 is detected (S77 "No"). If reverse drive of motor 3 is detected (S77 "Yes"), the arithmetic unit 95 updates the reverse duty cycle (S79) and confirms the duration from the detection of reverse drive of motor 3 (S81), while continuing to perform reverse drive of motor 3 until the reverse drive duration has elapsed from the detection of reverse drive of motor 3 (S81 "No"). If the reverse drive duration has elapsed from the detection of reverse drive of motor 3 (S81 "Yes"), the arithmetic unit 95 terminates the reverse drive of motor 3 (S83).

[0052] The calculation unit 95 updates the setting value of the forward drive in the electronic pulse control (S85). Specifically, the calculation unit 95 sets the duty cycle (hereinafter referred to as "forward duty cycle") when the motor 3 rotates forward in the electronic pulse control to an initial value of 1%, and sets the time for forward drive of the motor 3 (hereinafter referred to as "set forward time") to a time corresponding to 85 ms, which is the period of the electronic pulse control (hereinafter referred to as "pulse period"), that is, the time required from the end of forward drive of the motor 3 (S63) to the end of reverse drive (S83) from 85 ms.

[0053] The arithmetic unit 95 drives the motor 3 to rotate forward (S87). At regular intervals (e.g., 1 ms), the arithmetic unit 95 stores the motor current detection value (S89), updates the forward rotation duty cycle (S91), and confirms the elapsed time since the start of the forward rotation drive of the motor 3 (S93). The arithmetic unit 95 drives the motor 3 to rotate forward until the set forward rotation time has elapsed since the start of the forward rotation drive of the motor 3 (S93 "No").

[0054] If a set forward rotation time has elapsed since the start of forward rotation of motor 3 (S93 "Yes"), the calculation unit 95 calculates the average value of the motor current detected during the forward rotation of motor 3 (hereinafter referred to as "average current during forward rotation") (S95). When calculating the average current during forward rotation, the calculation unit 95 excludes the starting current of motor 3 during forward rotation, i.e., the temporary large current shortly after the start of forward rotation (e.g., ...). Figure 6 (The current value of part A). For example, the calculation unit 95 does not use the motor current detection value for a predetermined time from the start of the forward drive of motor 3 to calculate the average current value during forward rotation.

[0055] If the average current during forward rotation is above a threshold (e.g., 5.5 A) (S97 "Yes"), the calculation unit 95 sets the maximum duty cycle during forward rotation to +4% relative to the current value and the duty cycle rise rate during forward rotation to +0.15% / ms relative to the current value (S99), and returns to S63. However, in S99, the upper limit of the maximum duty cycle during forward rotation is set to 35%, and the upper limit of the duty cycle rise rate during forward rotation is set to 1.5% / ms. After reaching the upper limit, the maximum duty cycle and the duty cycle rise rate during forward rotation are maintained. The motor revolutions when the motor 3 is driven in forward rotation at duty cycles of 19%, 23%, ..., 35% (maximum duty cycle during forward rotation after rising from the initial value) correspond to the second rotation speed.

[0056] If the average current during forward rotation is not above a threshold (e.g., 5.5 A) ("No" in S97), the arithmetic unit 95 sets the maximum duty cycle during forward rotation to -4% relative to the current value and the duty cycle rise rate during forward rotation to -0.15% / ms relative to the current value (S101), and returns to S63. However, in S101, the lower limit of the maximum duty cycle during forward rotation is set to 15%, and the lower limit of the duty cycle rise rate during forward rotation is set to 0.8% / ms. After reaching the lower limit, the maximum duty cycle and the duty cycle rise rate during forward rotation are maintained.

[0057] The threshold for the average current during forward rotation is set to be greater than the average current during forward rotation under no-load conditions when no load is applied to the anvil 10 from the outside.

[0058] Figure 5 This is a flowchart illustrating a second example of electronic pulse control for machine 1. The second example is from... Figure 4 In the first example shown, S101 is removed, and the system directly returns to S63 from "No" in S97. That is, if the average current during forward rotation is not above a threshold (e.g., 5.5A) ("No" in S97), the arithmetic unit 95 returns to S63 without changing the maximum duty cycle during forward rotation or the duty cycle rise rate during forward rotation. Other aspects of the second example are the same. Figure 4 The first example shown is the same.

[0059] Figure 6 It is a graph showing the time changes of motor speed, motor current, and duty cycle (DUTY) in the first or second case of electronic pulse control under no-load conditions. Figure 7 It is a graph showing the time changes of motor speed, motor current, and duty cycle (DUTY) in the first or second case of electronic pulse control during screw tightening operations.

[0060] exist Figure 6 and Figure 7 In the middle, the trigger switch 6 is turned on around 0.04 s on the horizontal axis, and normal control is performed until around 0.2 s. The following is a graph of electronic pulse control.

[0061] exist Figure 6 In the current-free state, due to the electronic pulse control, the average current during forward rotation will not exceed the threshold (e.g., 5.5 A), and the maximum duty cycle and the rate of increase of the duty cycle during forward rotation will not exceed the threshold. Figure 4 or Figure 5 The initial values ​​set in S61 are 15% and 0.8% / ms, respectively. Therefore, the motor speed, motor current, and duty cycle become approximately the same time waveform in each pulse cycle.

[0062] exist Figure 7During the screw tightening process, the motor current increases with each pulse cycle. In a pulse cycle containing 0.6 s (corresponding to the fifth cycle of the nth cycle), the average current during forward rotation exceeds the threshold. Therefore, in pulse cycles after 0.6 s (corresponding to cycles after the sixth cycle of the (n+1)th cycle), for each pulse cycle, the maximum duty cycle during forward rotation increases by 4%, and the rate of increase of the duty cycle during forward rotation increases by 0.15% / ms. In a pulse cycle shortly after 1 s, the maximum duty cycle during forward rotation becomes the upper limit of 35%, and the rate of increase of the duty cycle during forward rotation becomes the upper limit of 1.5% / ms. The maximum duty cycle and the rate of increase of the duty cycle during forward rotation are maintained in subsequent pulse cycles.

[0063] Figure 8 This is a flowchart illustrating a third example of electronic pulse control for the work machine 1. Figure 4 The first example shown controls the maximum duty cycle and the rate of increase of the duty cycle during forward rotation based on whether the average current during forward rotation is above a threshold. In contrast, in... Figure 8 In the third example shown, the pulse period is changed based on whether the average current during forward rotation is above a threshold. The following is in comparison with... Figure 4 The explanation will focus on the different parts of the first example shown.

[0064] In setting the initial values ​​for electronic pulse control (S61a), the arithmetic unit 95 sets the maximum duty cycle during forward rotation to 35%, the duty cycle rise rate during forward rotation to 1.5% / ms, and the pulse period to 120 ms. 120 ms corresponds to the first cycle. The arithmetic unit 95 and... Figure 4 The first example shown is processed in the same way as S63 to S83.

[0065] In the update of the forward drive setting value in electronic pulse control (S85a), the calculation unit 95 sets the forward duty cycle to the initial value of 1%, and sets the forward drive time to a time corresponding to 120 ms as the pulse period, that is, the time obtained by subtracting the time required from the end of the forward drive of the motor 3 (S113) to the end of the reverse drive (S133) from 120 ms. The calculation unit 95 and... Figure 4 The first example shown is processed in the same way as S87 to S97.

[0066] If the average current during forward rotation is above a threshold (e.g., 5.5 A) (S97 "Yes"), the arithmetic unit 95 sets the pulse period to -10 ms relative to the current value (S99a) and returns to S63. However, in S99a, the lower limit of the pulse period is set to 85 ms, and the pulse period is maintained after the lower limit is reached. If the pulse period is less than 85 ms when the pulse period is set to -10 ms, the pulse period is set to 85 ms. Each of 110 ms, 100 ms, 90 ms, and 85 ms (pulse periods shorter than the initial value) corresponds to the second period. The method of shortening the pulse period is to reduce at least one of the forward rotation time or forward rotation angle of the motor 3, or the reverse rotation time or reverse rotation angle of the motor 3.

[0067] If the average current during forward rotation is not above a threshold (e.g., 5.5 A) ("No" in S97), the arithmetic unit 95 sets the pulse period to +10 ms relative to the current value (S101a) and returns to S63. However, in S101a, the upper limit of the pulse period is set to 120 ms, and the pulse period is maintained after the upper limit is reached.

[0068] Figure 9 This is a flowchart illustrating the fourth example of electronic pulse control for machine 1. The fourth example is from... Figure 8 In the third example shown, S101a is removed, and the system directly returns to S63 from "No" in S97. That is, if the average current during forward rotation is not above a threshold (e.g., 5.5 A) ("No" in S97), the arithmetic unit 95 returns to S63 without changing the pulse period. Other aspects of the fourth example are the same as... Figure 8 The third example shown is the same.

[0069] Figure 10 It is a graph showing the time changes of motor speed, motor current, and duty cycle (DUTY) in the third or fourth case of electronic pulse control under no-load conditions. Figure 11 This is a graph showing the time variations of motor speed, motor current, and duty cycle (DUTY) in the third or fourth case of electronic pulse control during screw tightening operations.

[0070] exist Figure 10 and Figure 11 In the middle, the trigger switch 6 is turned on around 0.04 s on the horizontal axis, and normal control is performed until around 0.2 s. The following is a graph of electronic pulse control.

[0071] exist Figure 10 In the current-free state, during electronic pulse control, the average current during forward rotation will not exceed the threshold (e.g., 5.5 A), and the pulse period will not change from... Figure 8 or Figure 9 The initial value set in S61a, which is 120 ms, changes. Therefore, the motor speed, motor current, and duty cycle become approximately the same time waveform in each pulse cycle.

[0072] exist Figure 11 During the screw tightening process, the motor current increases with each pulse cycle. In a pulse cycle containing 0.3 s, the average current during forward rotation exceeds the threshold. Therefore, in the pulse cycles following 0.3 s, the pulse cycle is shortened by 10 ms for each pulse cycle. In a pulse cycle containing 0.7 s, the pulse cycle reaches its lower limit of 85 ms, and thereafter maintains the pulse cycle.

[0073] This implementation method achieves the following effects.

[0074] (1) After a shielding time has elapsed since the operation of the trigger switch 6, the arithmetic unit 95 does not perform electronic pulse control based on a non-no-load state. Therefore, compared to the case of normal control under no-load conditions, the risk of electronic pulse control failing to start can be suppressed in states where it is difficult to determine a no-load state, such as a light load state at the start of screw tightening, and where electronic pulse control is required. Furthermore, the shielding time can also be omitted.

[0075] (2) In the first and second examples of electronic pulse control, if the average current during forward rotation exceeds a threshold (if the load applied to the anvil 10 increases), the calculation unit 95 sets the motor speed (specified rotational speed) higher by setting (updating) the maximum duty cycle during forward rotation to a value higher than the initial value. Therefore, compared with control that increases the maximum duty cycle during forward rotation from an unloaded state, the motor current in the unloaded state is suppressed. Therefore, the temperature rise of the motor 3 caused by the motor current when the trigger switch 6 is continuously turned on in the unloaded state can be suppressed. For example, when the work machine 1 is housed in the casing or the like for transport, even in the case of accidental operation of the trigger switch 6, the temperature rise of the motor 3 is suppressed because the motor current is suppressed. In addition, by suppressing the output of the motor 3 in the unloaded state, the noise or vibration when the trigger switch 6 is turned on in the unloaded state can be reduced. On the other hand, if the load increases to a certain level due to screw tightening operations, the maximum duty cycle during forward rotation becomes higher and the motor speed increases, thus suppressing the decrease in screw tightening speed.

[0076] (3) In the first and second examples of electronic pulse control, when the average current during forward rotation becomes above a threshold and the maximum duty cycle during forward rotation is increased, the arithmetic unit 95 gradually or periodically increases the maximum duty cycle during forward rotation in each pulse cycle, and gradually or periodically increases the motor speed. Therefore, sudden changes in motor speed can be suppressed, and the deterioration of the working feel can be suppressed.

[0077] (4) In the first and second examples of electronic pulse control, when the average current during forward rotation becomes above the threshold and the maximum duty cycle during forward rotation is increased, the arithmetic unit 95 also increases the rate of increase of the duty cycle during forward rotation. Therefore, when the maximum duty cycle during forward rotation is increased, the time from the start of forward rotation control to the duty cycle reaching the maximum duty cycle during forward rotation can be suppressed, and the deterioration of the working feel can be suppressed.

[0078] (5) In the third and fourth examples of electronic pulse control, if the average current during forward rotation exceeds a threshold (if the load applied to the anvil 10 increases), the calculation unit 95 sets (updates) the pulse period to a value smaller than the initial value. Therefore, compared with control that shortens the pulse period from the no-load state, the number of forward and reverse rotation switching times (switching speed) in the no-load state is suppressed. As a result, the temperature rise of the motor 3 caused by the switching between forward and reverse rotation when the trigger switch 6 is continuously engaged in the no-load state can be suppressed. In addition, by suppressing the number of forward and reverse rotation switching times in the no-load state, the noise or vibration when the trigger switch 6 is engaged in the no-load state can be reduced. On the other hand, if the load increases to a certain level due to screw tightening operations, the pulse period becomes shorter, thus suppressing the decrease in screw tightening speed.

[0079] (6) In the third and fourth examples of electronic pulse control, when the average current during forward rotation becomes above a threshold and the pulse period is shortened, the arithmetic unit 95 gradually or periodically shortens the pulse period in each pulse period and gradually or periodically reduces the number of forward and reverse rotation switching. Therefore, it can suppress sudden changes in the number of forward and reverse rotation switching and suppress the deterioration of the working feel.

[0080] The present invention has been described above using embodiments as examples, but the present invention is not limited to these embodiments. Various modifications can be made to the various matters specifically described in the embodiments within the scope of the claims.

[0081] The first or second example of electronic pulse control can be combined with the third or fourth example. That is, in electronic pulse control, when the average current value during forward rotation becomes above a threshold (when the load applied to the anvil 10 increases), the arithmetic unit 95 can increase the maximum duty cycle and the rate of increase of the duty cycle during forward rotation, and shorten the pulse period.

[0082] When the arithmetic unit 95 rotates the motor 3 at a specified rotational speed in electronic pulse control, it can set the advance angle or energizing angle of the motor 3 through open-loop control or closed-loop control.

[0083] In electronic pulse control, the arithmetic unit 95 can replace the closed-loop control that checks the average current during forward rotation to be above the threshold and adjusts the maximum duty cycle and the rate of increase of the duty cycle during forward rotation, or the pulse cycle, in each pulse cycle, and instead executes the following open-loop control: after checking that the average current during forward rotation is above the threshold once during one operation of the trigger switch 6, the average current during forward rotation is not checked thereafter, but instead the maximum duty cycle and the rate of increase of the duty cycle during forward rotation are increased towards the upper limit in each pulse cycle, or the pulse cycle is shortened towards the lower limit.

[0084] In the first and second examples of electronic pulse control, the method of increasing the motor speed when the average current during forward rotation becomes above the threshold can be replaced by increasing the duty cycle (increasing the effective value of the voltage applied to the motor) or, based on this, increasing the advance angle of the voltage applied to the motor, or increasing the energizing angle of motor 3.

[0085] The conditions for initiating electronic pulse control, besides the shielding time elapsed since the operation of trigger switch 6, can be specified in the same way as in Patent Document 2. For example, the calculation unit 95 can use a predetermined amount of pull on trigger switch 6 as a condition for initiating electronic pulse control. Furthermore, the conditions for continuous electronic pulse control can also be specified in the same way as in Patent Document 2. For example, the calculation unit 95 can use the absence of striking the anvil 10 as a condition for continuous electronic pulse control. The shielding time during which electronic pulse control is not performed shortly after motor 3 starts can also be omitted. That is, the calculation unit 95 can also perform electronic pulse control shortly after motor 3 starts.

[0086] Electronic pulse control is simply a control that causes the motor 3 to rotate intermittently in a specified direction. For example, it can also be a control that alternately and repeatedly causes the motor 3 to rotate forward and a control that stops the motor 3.

[0087] The shielding time, maximum duty cycle during forward rotation, duty cycle rise rate during forward rotation, pulse period and the magnitude of these changes, as well as the initial values ​​of the forward and reverse duty cycles, the maximum duty cycle during reverse rotation, the duty cycle rise rate during reverse rotation, and the threshold value of the average current during forward rotation, etc., which are exemplified as specific values ​​in the embodiments, do not limit the scope of the invention in any way and can be arbitrarily changed according to the required specifications.

[0088] The working machine of the present invention is not limited to the impact screwdriver illustrated in the embodiments, but may also be other types such as impact wrench, hydraulic pulse tool, electronic pulse screwdriver, electric drill screwdriver, etc.

[0089] Explanation of icon numbers

[0090] 1: Work machine

[0091] 2: Shell

[0092] 2a: Motor housing section

[0093] 2b: Handle section

[0094] 2c: Battery Installation Department

[0095] 3: Motor

[0096] 3a: Motor shaft

[0097] 4: Speed ​​reduction mechanism

[0098] 5: Spindle

[0099] 6: Trigger switch (operating unit)

[0100] 7: Battery pack

[0101] 8: Hammer

[0102] 9: Spring

[0103] 10: Anvil (top tool holder)

[0104] 10a: Top tool mounting hole

[0105] 11: Hammer casing

[0106] 12: Front cover (protective component)

[0107] 13: Rotation direction switching switch (rotation direction switching unit)

[0108] 14: Top Tools

[0109] 15: Sensor substrate

[0110] 16: Lighting LED

[0111] 82: Inverter circuit

[0112] 83: Control signal output circuit

[0113] 84: Magnetic sensor

[0114] 85: Rotor position detection circuit

[0115] 86: Rotational speed detection circuit

[0116] 87: Mode Switch

[0117] 88: Control circuit voltage supply circuit

[0118] 89: Battery voltage detection circuit

[0119] 91: Motor current detection circuit

[0120] 92: LED driver circuit for lighting

[0121] 93: Control circuit voltage detection circuit

[0122] 94: Display LED driver circuit

[0123] 95: Computation Department (Control Department)

Claims

1. A machine for tightening screws, The operating machine is characterized by including: motor; The top tool holder is driven to rotate by the motor. The rotation direction switching unit is configured to indicate whether the tip tool holding unit is rotated in either a forward or reverse rotation direction; The control unit is capable of performing pulse control, which repeats the rotation of the motor in a predetermined direction at a predetermined speed at a predetermined cycle, thereby causing the tip tool holding part to rotate in the set rotation direction indicated by the rotation direction switching unit; as well as The operating unit is configured to instruct the motor to start and stop. The control unit is configured such that if the operation unit is operated, the pulse control is executed, and regardless of whether it is in a no-load state where no load is applied to the tip tool holding part, the tip tool holding part is rotated in the set rotation direction indicated by the rotation direction switching unit while the pulse control is continuously executed.

2. The work machine according to claim 1, characterized in that, The control unit is configured such that, when the pulse control is performed in the no-load state, if the load applied to the top tool holding part increases, the predetermined rotation speed is increased or the predetermined cycle is shortened, thereby continuously performing the pulse control.

3. The work machine according to claim 1, characterized in that, The control unit is configured such that, if the operation unit is operated, the predetermined rotation speed and the predetermined period are set to a first rotation speed and a first period, respectively, to execute the pulse control; if the load applied to the top tool holding part increases, the predetermined rotation speed is set to a second rotation speed higher than the first rotation speed, or the predetermined period is set to a second period shorter than the first period, thereby executing the pulse control.

4. The work machine according to claim 1, characterized in that, The control unit is configured such that, in the pulse control, under the no-load state, the specified rotational speed and the specified period are respectively set to the first rotational speed and the first period.

5. The work machine according to claim 1, characterized in that, The control unit is configured such that, in the pulse control, it determines, based on the current when the motor rotates in the predetermined direction, that the load applied to the top tool holding part has increased compared to the no-load state.

6. The work machine according to claim 1, characterized in that, The control unit is configured such that if the operation unit is operated, normal control is performed to continuously rotate the motor in the predetermined direction, and the pulse control is maintained even when the no-load state is in effect after a shielding time has elapsed since the operation of the operation unit.

7. The operating machine according to claim 6, characterized in that, The control unit is configured to apply a first applied voltage to the motor during normal control, and to apply a second applied voltage to the motor that is lower than the first applied voltage during pulse control.

8. The work machine according to claim 3, characterized in that, The control unit is configured such that, when executing the pulse control, in the nth cycle, while the motor is rotating forward with the predetermined rotation speed and the predetermined cycle set to the first rotation speed and the first cycle respectively, if the load applied to the top tool holding part increases, then in the next (n+1)th cycle of the nth cycle, the predetermined rotation speed is set to the second rotation speed, or the predetermined cycle is set to the second cycle, thereby causing the motor to rotate in the predetermined direction.

9. The operating machine according to claim 3, characterized in that, The control unit is configured to: gradually or periodically increase the specified rotation speed when the specified rotation speed is set to a second rotation speed that is higher than the first rotation speed, or gradually or periodically shorten the specified period when the specified period is set to a second period that is shorter than the first period.

10. The work machine according to claim 1, characterized in that, The control unit is configured such that, in the pulse control, after causing the motor to rotate in the predetermined direction, it stops the motor, or causes the motor to rotate in the opposite direction to the predetermined direction.

11. The work machine according to claim 10, characterized in that, The control unit is configured to, when changing the predetermined cycle to a second cycle shorter than the first cycle, reduce at least one of the following: the time or angle for rotating the motor in the predetermined direction, the time for stopping the motor, or the time or angle for rotating the motor in the opposite direction to the predetermined direction.

12. The work machine according to claim 1, characterized in that, The control unit is configured such that, in the pulse control, when the motor is rotated in the specified direction at the specified rotational speed, the applied voltage, advance angle, or energizing angle of the motor is set by open-loop control or closed-loop control.

13. The work machine according to claim 1, characterized in that, The device includes a transmission mechanism that transmits the rotation of the motor to the tip tool holder, and is configured to generate a continuous or intermittent rotational force on the tip tool holder depending on the load applied to it. The control unit is configured to perform pulse control while the continuous rotational force is generated by the transmission mechanism.

14. The work machine according to claim 13, characterized in that, The transmission mechanism includes a hammer, which is driven to rotate by the motor. If the load applied to the anvil, which serves as the holding part of the top tool, increases, the hammer switches from a state of rotating integrally with the anvil to a state of striking the anvil.

15. The work machine according to claim 13, characterized in that, The transmission mechanism includes: a main shaft driven to rotate by the motor; a hammer movable relative to the main shaft in a front-back direction and driven to rotate by the main shaft; a spring that applies a force to the hammer forward; and an anvil that transmits the continuous rotational force or the intermittent rotational force through the hammer.

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