Work machine

Abstract

Provided is a work machine in which it is possible to suppress a rise in the temperature of a motor. A calculating unit 95 continues to execute electronic pulse control even in an unloaded state in which no load is applied to a tip tool holding portion, and when the average detected value of the motor current of a motor 3 during forward drive becomes equal to or greater than a threshold (when the load applied to the tip tool holding portion increases), the calculating unit 95 sets (updates) a maximum duty and a duty increase rate for when the motor 3 is rotates in the forward direction to a value higher than an initial value, thereby setting the rotation speed of the motor 3 to be higher, or sets (updates) the cycle of the electronic pulse control to a value smaller than an initial value.

Description

Work equipment

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

[0002] There are known working machines such as impact drivers that perform tasks such as screw tightening by striking a hammer against an anvil. The impact driver includes a spring that biases the hammer toward the anvil, and a single operation of a 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 over the engagement protrusion, making it ready to collide with the engagement protrusion again.

[0003] Patent Documents 1 and 2 disclose an impact driver that is equipped with a control unit that can execute normal control, which rotates the motor continuously, and pulse control (electronic pulse control), which rotates the motor intermittently.

[0004] Patent No. 5725347 JP 2023-166104 A

[0005] If normal control is used under no-load conditions, there is a risk that electronic pulse control will not start in conditions where it is difficult to distinguish from a no-load condition and electronic pulse control is required, such as a light load condition when starting to tighten a screw.In addition, if high-output pulse control continues under no-load conditions where no external load is applied to the tool holder, the motor is likely to become hot.

[0006] A first object of the present invention is to provide a work machine that can reduce the risk of pulse control not being executed when a screw is first tightened under a light load, and a second object of the present invention is to provide a work machine that can reduce the temperature rise of the motor.

[0007] One aspect of the present invention is a work machine capable of tightening screws, comprising: a motor; a tool holder rotated by the motor; a rotation direction switch configured to specify whether the tool holder is to rotate in a set rotation direction (forward or reverse); a control unit capable of executing pulse control to rotate the motor in a set direction at a set rotation speed ...

[0008] 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.

[0009] According to the present invention, it is possible to provide a work machine that can reduce the risk of pulse control not being executed when a screw is first tightened under a light load condition, and also to provide a work machine that can reduce the temperature rise of the motor.

[0010] 1 is a side cross-sectional view of a work machine 1 according to an embodiment of the present invention. A circuit block diagram of the work machine 1. A flowchart of pulse modes of the work machine 1. A flowchart showing a first example of electronic pulse control of the work machine 1. A flowchart showing a second example of electronic pulse control of the work machine 1. A graph showing changes over time in the rotation speed, current, and PWM control duty of the motor 3 when the first or second example of electronic pulse control is executed in an unloaded state. A graph showing changes over time in the rotation speed, current, and PWM control duty of the motor 3 when the first or second example of electronic pulse control is executed during screw tightening work. A flowchart showing a third example of electronic pulse control of the work machine 1. A flowchart showing a fourth example of electronic pulse control of the work machine 1. A graph showing changes over time in the rotation speed, current, and PWM control duty of the motor 3 when the third or fourth example of electronic pulse control is executed in an unloaded state. A graph showing changes over time in the rotation speed, current, and PWM control duty of the motor 3 when the third or fourth example of electronic pulse control is executed during screw tightening work.

[0011] 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 mutually perpendicular front-rear and up-down directions of the work machine 1. The work machine 1 is a work machine capable of tightening screws, and specifically, is an impact driver.

[0012] 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.

[0013] The motor housing 2a is a cylindrical portion whose central axis is substantially 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 housing 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.

[0014] The handle portion 2b has an upper end 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 selector switch 13 at the upper end of the handle portion 2b. The trigger switch 6 is an operation unit (motor drive operation unit) that allows an operator to switch between starting (driving) and stopping (driving state of the motor 3) the motor 3. The trigger switch 6 is an infinitely variable speed switch. The rotation direction selector switch 13 is a rotation direction selector that allows an operator to switch between forward and reverse rotation of the motor 3, i.e., forward and reverse rotation of the anvil 10 described below. Forward rotation is an example of rotation in a predetermined direction. Reverse rotation is an example of rotation in a direction opposite to the predetermined direction.

[0015] 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.

[0016] 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 holder, housed within a motor housing 2a and a hammer case 11. The reduction mechanism 4, spindle 5, hammer 8, and spring 9 constitute a transmission mechanism that transmits the rotation of the motor 3 to the anvil 10, and is a transmission mechanism (rotary impact mechanism) configured to generate a continuous rotational force or an intermittent rotational force (rotary impact force) on the anvil 10 in response to a load (screw tightening load) applied to the anvil 10.

[0017] The motor 3 is an inner rotor type brushless motor and has a motor shaft 3a parallel to the front-to-rear direction. The reduction mechanism 4 reduces the rotation 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 in the front-to-rear direction relative to the spindle 5. A spring 9 biases the hammer 8 forward. The hammer 8 rotates or rotary strikes the anvil 10 (generating a continuous or intermittent rotational force on the anvil 10). In other words, the anvil 10 is rotationally driven by 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.

[0018] 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 also 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.

[0019] 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 calculation unit 95.

[0020] 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. 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 under the control of the calculation unit 95.

[0021] 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 calculation unit 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 calculation unit 95.

[0022] The mode changeover switch 87 is provided on the operation panel 20 in Fig. 1. The mode changeover switch 87 is a mode changeover operation unit that allows the operator to change the mode of the calculation unit 95, and transmits the operator's mode changeover operation to the calculation unit 95. The modes of the calculation unit 95 will be described later.

[0023] 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 calculation unit 95, etc., and supplies it to the calculation unit 95, etc. The battery voltage detection circuit 89 detects the output voltage of the battery pack 7 and sends it to the calculation unit 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 calculation unit 95.

[0024] 1 under the control of the calculation unit 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 calculation unit 95. The display LED drive circuit 94 supplies a drive current to the display LEDs provided on the operation panel 20.

[0025] The calculation unit 95 is a control unit that includes a microcontroller or the like and controls the driving of the motor 3. The calculation unit 95 controls the inverter circuit 82 via the control signal output circuit 83, for example, by PWM control, in accordance with the 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, thereby controlling the driving of the motor 3.

[0026] The calculation unit 95 can control the effective value of the voltage applied to the motor 3 (hereinafter referred to as "motor applied voltage") by the duty of PWM control (hereinafter referred to as "duty"). The calculation unit 95 can detect the load on the motor 3 by the motor current. The calculation unit 95 can distinguish between forward and reverse rotation of the motor 3 by the signal from the rotor position detection circuit 85, i.e., in accordance with the signal from the magnetic sensor 84.

[0027] The calculation unit 95 can perform normal control, which continuously rotates the motor 3 in a predetermined direction, and pulse control (hereinafter referred to as "electronic pulse control"), which alternates between rotating the motor 3 in the predetermined direction and rotating the motor 3 in the opposite direction. When rotating the motor 3 at a predetermined rotation speed under electronic pulse control, the calculation unit 95 sets the duty (sets the effective value of the voltage applied to the motor 3) using open-loop control or closed-loop control. The calculation unit 95 operates in two modes: a pulse mode (first mode) in which electronic pulse control is possible, and a non-pulse mode (second mode) in which electronic pulse control is not possible. The operator can switch between the pulse mode and the non-pulse mode using the mode selector switch 87. In the non-pulse mode, the calculation unit 95 always performs normal control in response to the operation of the trigger switch 6. The pulse mode of the calculation unit 95 is described below.

[0028] Fig. 3 is a flowchart of the pulse mode of the work machine 1. In Fig. 3, the set rotation direction is forward rotation.

[0029] When the trigger switch 6 is operated (when the trigger switch 6 is operated to drive the motor), the calculation unit 95 executes normal control, which continuously rotates the motor 3 in the forward direction (S1). The calculation unit 95 continues normal control unless a predetermined time of 160 ms has elapsed since the trigger switch 6 was operated ("No" in S3). When 160 ms has elapsed since the trigger switch 6 was operated ("Yes" in S3), the calculation unit 95 switches from normal control to electronic pulse control and drives the motor 3 (S7). The 160 ms is a mask time immediately after the start of the motor 3, during which electronic pulse control is not performed. By providing this 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 calculation unit 95 continues electronic pulse control until the trigger switch 6 is released (when the trigger switch 6 is operated to stop the motor) ("No" in S13, S7). When the trigger switch 6 is released ("Yes" in S13), the calculation unit 95 stops the motor.

[0030] FIG. 4 is a flowchart showing a first example of electronic pulse control of the work machine 1.

[0031] The calculation unit 95 sets initial values ​​for electronic pulse control (S61). Specifically, the calculation unit 95 sets the maximum duty when rotating the motor 3 in the forward direction (hereinafter referred to as the "maximum duty during forward rotation") to 15% and the duty increase rate when rotating the motor 3 in the forward direction (hereinafter referred to as the "duty increase rate during forward rotation") to 0.8% / ms in the electronic pulse control. The motor rotation speed when the motor 3 is driven in the forward direction at a duty of 15% (initial value of the maximum duty during forward rotation) corresponds to the first rotation speed.

[0032] The calculation unit 95 ends the forward rotation of the motor 3 (S63) and performs brake control (S65). Brake control is control in which the rotational energy of the motor 3 is consumed 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 in which short-circuit braking is applied. Short-circuit braking is, for example, control in which the switching elements Q1 to Q3 on the upper arm side are turned off and at least one of the switching elements Q4 to Q6 on the lower arm side is continuously or intermittently turned on. Note that reverse control performed on the motor 3 that is rotating forward is control in which power for reverse rotation is supplied from an external source and is not brake control.

[0033] The calculation unit 95 continues the brake control until the motor rotation speed falls below the predetermined rotation speed ("No" in S67). When the motor rotation speed falls below the predetermined rotation speed ("Yes" in S67), the calculation unit 95 ends the brake control (S69).

[0034] The calculation unit 95 updates the set values ​​for reverse drive in the electronic pulse control (S71). Specifically, the calculation unit 95 sets the duty when rotating the motor 3 in the reverse direction (hereinafter referred to as the "reverse duty") to an initial value of 1%, the maximum duty when rotating the motor 3 in the reverse direction (hereinafter referred to as the "maximum reverse duty") to 20%, and the increase rate of the duty when rotating the motor 3 in the reverse direction (hereinafter referred to as the "reverse duty increase rate") to 0.8% / ms.

[0035] The calculation unit 95 drives the motor 3 in the reverse direction (S73). The calculation unit 95 updates the reverse rotation duty (S75) and checks whether the motor 3 has rotated in the reverse direction (S77) at predetermined time intervals (e.g., 1 ms), and drives the motor 3 in the reverse direction until it detects that the motor 3 has rotated in the reverse direction (No in S77). When the calculation unit 95 detects that the motor 3 has rotated in the reverse direction (Yes in S77), it updates the reverse rotation duty (S79) and checks the duration since the detection of the reverse rotation of the motor 3 (S81), and drives the motor 3 in the reverse direction until the reverse rotation duration has elapsed since the detection of the reverse rotation of the motor 3 (No in S81). When the reverse rotation duration has elapsed since the detection of the reverse rotation of the motor 3 (Yes in S81), the calculation unit 95 stops the reverse rotation of the motor 3 (S83).

[0036] The calculation unit 95 updates the set value for forward rotation drive in the electronic pulse control (S85). Specifically, the calculation unit 95 sets the duty for rotating the motor 3 in the forward direction in the electronic pulse control (hereinafter referred to as the "forward rotation duty") to an initial value of 1%, and sets the time for driving the motor 3 in the forward direction (hereinafter referred to as the "set forward rotation time") to a time corresponding to the period of the electronic pulse control (hereinafter referred to as the "pulse period") of 85 ms, i.e., the time obtained by subtracting from 85 ms the time required from the end of the forward rotation drive of the motor 3 (S63) to the end of the reverse rotation drive (S83) described above.

[0037] The calculation unit 95 drives the motor 3 in the forward direction (S87). The calculation unit 95 stores the detected value of the motor current (S89), updates the forward rotation duty (S91), and checks the elapsed time from the start of forward rotation of the motor 3 (S93) at predetermined time intervals (e.g., 1 ms), and drives the motor 3 in the forward direction until the set forward rotation time has elapsed from the start of forward rotation of the motor 3 ("No" in S93).

[0038] When the set forward rotation time has elapsed since the start of forward rotation of the motor 3 ("Yes" in S93), the calculation unit 95 calculates the average of the detected values ​​of the motor current during forward rotation of the motor 3 (hereinafter "average forward rotation current") (S95). When calculating the average forward rotation current value, the calculation unit 95 excludes the startup current during forward rotation of the motor 3, i.e., the temporary large current immediately after the start of forward rotation (e.g., the current value at part A in FIG. 6). For example, the calculation unit 95 does not use the detected value of the motor current for a predetermined time after the start of forward rotation of the motor 3 in calculating the average forward rotation current value.

[0039] If the average forward rotation current is equal to or greater than a threshold value (e.g., 5.5 A) ("Yes" in S97), the calculation unit 95 increases the forward rotation maximum duty by 4% relative to the current value and increases the forward rotation duty increase rate by 0.15% / ms relative to the current value (S99), and then returns to S63. However, in S99, the upper limits of the forward rotation maximum duty and the forward rotation duty increase rate are set to 35% and 1.5% / ms, respectively, and after the upper limits are reached, the forward rotation maximum duty and the forward rotation duty increase rate are maintained. The motor rotation speed when the motor 3 is driven in the forward rotation at each of the duties of 19%, 23%, ..., 35% (maximum forward rotation duty increased from the initial value) corresponds to the second rotation speed.

[0040] If the average current value during forward rotation is not equal to or greater than the threshold value (for example, 5.5 A) ("No" in S97), the calculation unit 95 sets the maximum forward rotation duty to -4% of the current value and the forward rotation duty increase rate to -0.15% / ms of the current value (S101), and returns to S63. However, in S101, the lower limits of the maximum forward rotation duty and the forward rotation duty increase rate are set to 15% and 0.8% / ms, respectively, and after the lower limits are reached, the maximum forward rotation duty and the forward rotation duty increase rate are maintained.

[0041] The threshold value of the average current value during normal rotation is set to be larger than the average current value during normal rotation in a no-load state where no load is applied to the anvil 10 from the outside.

[0042] Figure 5 is a flowchart showing a second example of electronic pulse control of the work machine 1. In the second example, S101 is eliminated from the first example shown in Figure 4, and the process returns directly to S63 from "No" in S97. That is, if the average current value during forward rotation is not equal to or greater than a threshold value (e.g., 5.5 A) ("No" in S97), the calculation unit 95 returns to S63 without changing the forward rotation maximum duty and the forward rotation duty increase rate. Other aspects of the second example are the same as those of the first example shown in Figure 4.

[0043] Fig. 6 is a graph showing the changes over time in motor rotation speed, motor current, and duty when the first or second example of electronic pulse control is executed under no load. Fig. 7 is a graph showing the changes over time in motor rotation speed, motor current, and duty when the first or second example of electronic pulse control is executed during screw tightening work.

[0044] 6 and 7, the trigger switch 6 is turned on at approximately 0.04 seconds on the horizontal axis, normal control is performed up to approximately 0.2 seconds, and the graphs thereafter show electronic pulse control.

[0045] In Figure 6, because of the no-load condition, the average current value during forward rotation does not exceed a threshold value (e.g., 5.5 A) in electronic pulse control, and the maximum duty during forward rotation and the forward rotation duty increase rate do not change from the initial values ​​of 15% and 0.8% / ms, respectively, set in S61 in Figure 4 or Figure 5. For this reason, the motor rotation speed, motor current, and duty have approximately the same time waveforms in each pulse period.

[0046] 7 , the motor current increases with each pulse period as the screw tightening operation progresses, and the average forward rotation current exceeds the threshold value in the pulse period including 0.6 s (the fifth period corresponding to the nth period). Therefore, in pulse periods after 0.6 s (periods from the sixth period onward corresponding to the n+1th period), the forward rotation maximum duty increases by 4% and the forward rotation duty increase rate increases by 0.15% / ms. In the pulse period immediately after 1 s, the forward rotation maximum duty reaches its upper limit of 35%, and the forward rotation duty increase rate is also upper limit of 1.5% / ms. In subsequent pulse periods, the forward rotation maximum duty and the forward rotation duty increase rate are maintained.

[0047] Figure 8 is a flowchart showing a third example of electronic pulse control of the work machine 1. While the first example shown in Figure 4 described above is a control in which the maximum duty during forward rotation and the duty increase rate during forward rotation are changed depending on whether the average current value during forward rotation is equal to or greater than a threshold value, the third example shown in Figure 8 changes the pulse period depending on whether the average current value during forward rotation is equal to or greater than a threshold value. The following description will focus on the differences from the first example shown in Figure 4.

[0048] In setting the initial values ​​of the electronic pulse control (S61a), the calculation unit 95 sets the maximum duty during forward rotation to 35%, the duty increase rate during forward rotation to 1.5% / ms, and the pulse period to 120 ms. 120 ms corresponds to the first period. The calculation unit 95 performs the processes of S63 to S83 in the same manner as in the first example shown in FIG. 4.

[0049] In updating the set value for forward rotation drive in electronic pulse control (S85a), the calculation unit 95 sets the forward rotation duty to an initial value of 1% and the set forward rotation time to a time corresponding to the pulse period of 120 ms, that is, the time obtained by subtracting from 120 ms the time required from the end of forward rotation drive (S113) to the end of reverse rotation drive (S133) of the motor 3. The calculation unit 95 performs the processes of S87 to S97 in the same manner as in the first example shown in FIG.

[0050] If the average current value during forward rotation is equal to or greater than a threshold value (e.g., 5.5 A) ("Yes" in S97), the calculation unit 95 reduces the pulse period by 10 ms from 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 reaching the lower limit. If the pulse period falls below 85 ms when 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 pulse period can be shortened by reducing 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.

[0051] If the average current value during forward rotation is not equal to or greater than the threshold value (e.g., 5.5 A) ("No" in S97), the calculation unit 95 adds 10 ms to the current value of the pulse period (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.

[0052] Figure 9 is a flowchart showing a fourth example of electronic pulse control of the work machine 1. In the fourth example, S101a is eliminated from the third example shown in Figure 8, and control returns directly to S63 from "No" in S97. That is, if the average current value during forward rotation is not equal to or greater than a threshold value (e.g., 5.5 A) ("No" in S97), the calculation unit 95 returns to S63 without changing the pulse period. Other aspects of the fourth example are the same as those of the third example shown in Figure 8.

[0053] Fig. 10 is a graph showing the changes over time in motor rotation speed, motor current, and duty when the third or fourth example of electronic pulse control is executed under no load. Fig. 11 is a graph showing the changes over time in motor rotation speed, motor current, and duty when the third or fourth example of electronic pulse control is executed during screw tightening work.

[0054] 10 and 11, the trigger switch 6 is turned on at approximately 0.04 seconds on the horizontal axis, normal control is performed up to approximately 0.2 seconds, and the graphs thereafter show electronic pulse control.

[0055] In Figure 10, because there is no load, the average current value during forward rotation does not exceed a threshold value (e.g., 5.5 A) in electronic pulse control, and the pulse period is not changed from the initial value of 120 ms set in S61a in Figure 8 or Figure 9. Therefore, the motor rotation speed, motor current, and duty have approximately the same time waveforms in each pulse period.

[0056] 11, the motor current increases with each pulse period as the screw tightening operation progresses, and the average current during forward rotation exceeds the threshold value for pulse periods including 0.3 s. Therefore, for pulse periods after 0.3 s, the pulse period shortens by 10 ms for each pulse period. For pulse periods including 0.7 s, the pulse period reaches the lower limit of 85 ms, and is maintained thereafter.

[0057] This embodiment has the following advantages.

[0058] (1) After the mask time has elapsed since the operation of the trigger switch 6, the calculation unit 95 performs electronic pulse control without the condition that the load is not on. Therefore, compared to when normal control is performed in the no-load state, the risk of electronic pulse control not starting is reduced in a state where it is difficult to distinguish from the no-load state and electronic pulse control is required, such as a light load state at the start of tightening a screw. The mask time may be omitted.

[0059] (2) In the first and second examples of electronic pulse control, when the average current value during forward rotation exceeds the threshold value (when the load on the anvil 10 increases), the calculation unit 95 sets (updates) the maximum forward rotation duty to a value higher than the initial value, thereby increasing the motor rotation speed (predetermined rotation speed). This reduces the motor current in the no-load state compared to control that increases the maximum forward rotation duty from the no-load state. This reduces the temperature rise of the motor 3 due to the motor current when the trigger switch 6 remains turned on in the no-load state. For example, even if the trigger switch 6 is accidentally left turned on when the work machine 1 is stored in a case or the like and transported, the motor current is reduced, thereby reducing the temperature rise of the motor 3. Furthermore, reducing the output of the motor 3 in the no-load state reduces noise and vibration when the trigger switch 6 is turned on in the no-load state. On the other hand, when the load increases above a certain level due to a screw tightening operation, the maximum forward rotation duty increases, increasing the motor rotation speed, thereby preventing a decrease in the screw tightening speed.

[0060] (3) In the first and second examples of electronic pulse control, when the average current during forward rotation exceeds the threshold value and the maximum duty during forward rotation is increased, the calculation unit 95 gradually or stepwise increases the maximum duty during forward rotation for each pulse period, thereby gradually or stepwise increasing the motor rotation speed. This prevents sudden changes in the motor rotation speed and prevents deterioration of the working feel.

[0061] (4) In the first and second examples of electronic pulse control, when the average forward rotation current value becomes equal to or exceeds the threshold value and the forward rotation maximum duty is increased, the calculation unit 95 also increases the forward rotation duty increase rate. As a result, when the forward rotation maximum duty is increased, the time from the start of forward rotation control until the duty reaches the forward rotation maximum duty is prevented from becoming long, and a deterioration in the working feel is prevented.

[0062] (5) In the third and fourth examples of electronic pulse control, when the average current value during forward rotation exceeds the threshold value (when the load on the anvil 10 increases), the calculation unit 95 sets (updates) the pulse period to a value smaller than the initial value. Therefore, compared to control that shortens the pulse period from the no-load state, the number of times (switching speed) the motor switches between forward and reverse rotation in the no-load state is reduced. This reduces the temperature rise of the motor 3 caused by switching between forward and reverse rotation when the trigger switch 6 remains on in the no-load state. Furthermore, reducing the number of times the motor switches between forward and reverse rotation in the no-load state reduces noise and vibration when the trigger switch 6 is turned on in the no-load state. Meanwhile, when the load increases above a certain level during a screw tightening operation, the pulse period shortens, thereby preventing a decrease in the screw tightening speed.

[0063] (6) In the third and fourth examples of electronic pulse control, when the average current value during forward rotation exceeds the threshold value and the pulse period is shortened, the calculation unit 95 gradually or stepwise shortens the pulse period for each pulse period, thereby gradually or stepwise reducing the number of times the forward rotation and reverse rotation are switched. This prevents a sudden change in the number of times the forward rotation and reverse rotation are switched, and prevents a deterioration in the working feel.

[0064] Although the present invention has been described above using the embodiments as examples, the present invention is not limited to the embodiments. Various modifications can be made to the details specifically described in the embodiments within the scope of the claims.

[0065] The first or second example of the electronic pulse control may be combined with the third or fourth example. That is, when the average current value during forward rotation in the electronic pulse control becomes equal to or greater than a threshold value (when the load on the anvil 10 increases), the calculation unit 95 may increase the maximum duty during forward rotation and the forward rotation duty increase rate, and may also shorten the pulse period.

[0066] When rotating the motor 3 at a predetermined rotation speed under electronic pulse control, the calculation unit 95 may set the advance angle or conduction angle of the motor 3 by open-loop control or closed-loop control.

[0067] In electronic pulse control, instead of closed-loop control that checks whether the average current value during forward rotation is equal to or greater than a threshold value for each pulse period and adjusts the maximum duty during forward rotation and the duty increase rate during forward rotation, or the pulse period, the calculation unit 95 may execute open-loop control that, once it has checked once that the average current value during forward rotation has become equal to or greater than a threshold value during one operation of the trigger switch 6, increases the maximum duty during forward rotation and the duty increase rate during forward rotation toward an upper limit for each pulse period, or shortens the pulse period toward a lower limit, without checking the average current value during forward rotation.

[0068] In the first and second examples of electronic pulse control, when the average current value during forward rotation exceeds a threshold value and the motor rotation speed is increased, the method may be to increase the advance angle of the voltage applied to the motor or to increase the conduction angle of the motor 3, instead of or in addition to increasing the duty (increasing the effective value of the voltage applied to the motor).

[0069] The condition for starting electronic pulse control may be determined similarly to Patent Document 2, in addition to the elapse of the mask time from the operation of the trigger switch 6. The calculation unit 95 may determine, for example, that the pulling amount of the trigger switch 6 is equal to or greater than a predetermined amount as a condition for starting electronic pulse control. The condition for continuing electronic pulse control may also be determined similarly to Patent Document 2. The calculation unit 95 may determine, for example, that no impact is being made on the anvil 10 as a necessary condition for continuing electronic pulse control. The mask time during which electronic pulse control is not performed immediately after starting the motor 3 may be omitted. In other words, the calculation unit 95 may execute electronic pulse control immediately after starting the motor 3.

[0070] The electronic pulse control may be any control that causes the motor 3 to rotate intermittently in a predetermined direction, and may be, for example, a control that alternately repeats forward rotation control that causes the motor 3 to rotate forward and stop control that stops the motor 3.

[0071] The mask time, maximum duty during forward rotation, duty increase rate during forward rotation, pulse period, and the range of change when changing these, as well as the initial values ​​of forward rotation duty and reverse rotation duty, maximum duty during reverse rotation, duty increase rate during reverse rotation, threshold value of average current during forward rotation, etc., which are given as examples of specific numerical values ​​in the embodiments, do not in any way limit the scope of the invention and can be changed as desired to suit the required specifications.

[0072] 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 oil pulse tool, an electronic pulse driver, or a drill driver.

[0073] 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 holding 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, 91...motor current detection circuit, 92...illumination LED drive circuit, 93...control circuit voltage detection circuit, 94...display LED drive circuit, 95...calculation section (control section).

Claims

1. A working machine capable of being screwed, comprising a motor, a tip tool holder rotatably driven by the motor, a rotation direction switching unit configured to instruct whether to rotate the tip tool holder in a forward rotation or a reverse rotation setting rotation direction, a control unit capable of executing pulse control to repeat the rotation of the motor in a predetermined direction at a predetermined rotation speed at a predetermined cycle and rotate the tip tool holder in the set rotation direction instructed by the rotation direction switching unit, and an operation unit configured to instruct the start and stop of the motor. When the operation unit is operated, the control unit executes the pulse control and rotates the tip tool holder in the set rotation direction instructed by the rotation direction switching unit while continuing to execute the pulse control regardless of whether it is a no-load state where no load is applied to the tip tool holder. A working machine characterized by this.

2. The working machine according to claim 1, wherein when the load applied to the tip tool holder increases while the control unit is executing the pulse control in the no-load state, the control unit is configured to increase the predetermined rotation speed or shorten the predetermined cycle to continue executing the pulse control. A working machine characterized by this.

3. The working machine according to claim 1, wherein when the operation unit is operated, the control unit sets the predetermined rotation speed and the predetermined cycle to a first rotation speed and a first cycle, respectively, and executes the pulse control. When the load applied to the tip tool holder increases, the control unit is configured to set the predetermined rotation speed to a second rotation speed higher than the first rotation speed or set the predetermined cycle to a second cycle shorter than the first cycle and execute the pulse control. A working machine characterized by this.

4. The working machine according to claim 1, wherein in the pulse control, the control unit is configured to maintain the state in which the predetermined rotation speed and the predetermined cycle are set to the first rotation speed and the first cycle, respectively, in the no-load state. A working machine characterized by this.

5. The working machine according to claim 1, wherein in the pulse control, the control unit is configured to determine that the load applied to the tip tool holder has increased from the no-load state based on the current when the motor rotates in the predetermined direction. A working machine characterized by this.

6. The working machine according to claim 1, wherein when the operation unit is operated, the control unit executes normal control to continuously rotate the motor in the predetermined direction, and after a mask time has elapsed from the operation of the operation unit, even in the no-load state, the control unit is configured to maintain the execution of the pulse control. A working machine characterized by this.

7. The working machine according to claim 6, wherein the control unit is configured to apply a first applied voltage to the motor in the normal control and apply a second applied voltage lower than the first applied voltage to the motor in the pulse control. A working machine characterized by this.

8. The working machine according to claim 3, wherein when the control unit is executing the pulse control, in the nth cycle, in a state where the motor is rotating forward with the predetermined rotational speed and the predetermined period set as the first rotational speed and the first period respectively, when the load applied to the tip tool holding unit increases, in the (n + 1)th cycle following the nth cycle, the control unit is configured to set the predetermined rotational speed to the second rotational speed or set the predetermined period to the second period and rotate the motor in the predetermined direction. A working machine characterized by this.

9. The working machine according to claim 3, wherein when the control unit sets the predetermined rotational speed to the second rotational speed higher than the first rotational speed, the control unit gradually or stepwise increases the predetermined rotational speed, or when the control unit sets the predetermined period to the second period shorter than the first period, the control unit gradually or stepwise shortens the predetermined period. A working machine characterized by this.

10. The working machine according to claim 1, wherein in the pulse control, the control unit is configured to stop the motor or rotate the motor in a direction opposite to the predetermined direction after rotating the motor in the predetermined direction. A working machine characterized by this.

11. The working machine according to claim 10, wherein when the control unit changes the predetermined period to the second period shorter than the first period, at least one of the time or rotation angle for rotating the motor in the predetermined direction, the time for stopping the motor, or the time or rotation angle for rotating the motor in a direction opposite to the predetermined direction is reduced. A working machine characterized by this.

12. The working machine according to claim 1, wherein in the pulse control, when rotating the motor in the predetermined direction at the predetermined rotational speed, the control unit is configured to set the applied voltage, advance angle, or energization angle of the motor by open-loop control or closed-loop control. This is a characteristic of the working machine.

13. The working machine according to claim 1, comprising a transmission mechanism that transmits the rotation of the motor to the tip tool holding portion, the transmission mechanism being configured to generate a continuous rotational force or an intermittent rotational force on the tip tool holding portion according to the load applied to the tip tool holding portion. The control unit is configured to execute the pulse control in a state where the continuous rotational force is generated by the transmission mechanism. This is a characteristic of the working machine.

14. The working machine according to claim 13, wherein the transmission mechanism includes a hammer that is rotationally driven by the motor and switches from a state of rotating integrally with the anvil to a state of striking the anvil when the load applied to the anvil as the tip tool holding portion increases. This is a characteristic of the working machine.

15. The working machine according to claim 13, wherein the transmission mechanism includes a spindle that is rotationally driven by the motor, a hammer that is movable in the front-rear direction with respect to the spindle and is rotationally driven by the spindle, a spring that biases the hammer forward, and an anvil to which the continuous rotational force or the intermittent rotational force is transmitted by the hammer. This is a characteristic of the working machine.

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