Work equipment

Abstract

To provide a work machine capable of increasing a brake time after power shutdown.SOLUTION: A control part 20, when a trigger 11 is turned on and a battery pack 5 is mounted, drives a motor 31. The control part 20, when a voltage of a battery temperature detection terminal 28 is 0 V, determines that the battery pack 5 is disengaged, turns switching elements Q1 to Q3 off, turns switching elements Q4 to Q6 on, and applies electric brake to the motor 31. The control part 20, when a lower side gate voltage is reduced to a threshold, turns all of switching element driving signals H1 to H6 off. The control part 20, when the lower side gate voltage is recovered, carries out brake control again.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Working machines driven by commercial power sources or DC power sources are known. Patent Document 1 discloses a working machine driven by a storage battery as a DC power source, specifically an electric lawn mower. When the storage battery falls off during operation in the working machine of Patent Document 1, the control operation unit is operated by the electric charge accumulated in the electrolytic capacitor, the switching element is controlled by the control operation unit, the drive coil is short-circuited, and a brake is applied to the motor to forcibly stop the rotary blade.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration of Patent Document l, the case where the electric charge accumulated in the electrolytic capacitor decreases (the voltage of the electrolytic capacitor decreases) is not considered. Further, in the configuration of Patent Document l, since the fall-off of the storage battery is detected when the voltage of the terminal to which the voltage of the storage battery is input becomes equal to or lower than a predetermined value, a diode is provided so that the regenerative energy of the motor does not flow to the storage battery side and false detection does not occur. With this diode, the control operation unit cannot be operated by the regenerative energy of the motor. On the other hand, if this diode is removed, the fall-off of the storage battery cannot be detected due to the voltage increase caused by the regenerative energy of the motor.

[0005] An object of the present invention is to solve at least one of the following problems 1 to 3. ·Problem 1... To provide a working machine capable of lengthening the braking time after power-off. • Problem 2: To provide a work machine capable of improving the reliability of detecting power outages. • Challenge 3: To provide a work machine capable of applying the optimal brakes according to the situation. [Means for solving the problem]

[0007] One aspect of the present invention is a work machine. This work machine is Motor and, An operating unit operated by an operator to instruct the motor to start and stop, It has multiple switching elements, including multiple upper switching elements connected to the upper arm and multiple lower switching elements connected to the lower arm. A drive unit that drives the motor in response to the operation of the control unit, A control unit that controls the drive unit, The motor power supply The housing has a removable battery pack, A work machine equipped with, The control unit, The first state in which the operating unit is operated and then the operation of the operating unit is released. In this case, the drive unit is controlled to intermittently turn on one of the switching elements, either the upper or lower one, among the plurality of switching elements to produce a first braking force. , A second state in which the battery pack is detached from the housing while the motor is rotating. When , To continuously turn on at least two of the multiple switching elements, one on the upper side and one on the lower side, a second braking force greater than the first braking force is obtained. The drive unit is configured to control the aforementioned drive unit. did, This is a work machine characterized by the following features. .

[0008] Another aspect of the present invention is a work machine. This work machine is A motor powered by electricity supplied from a power source, An operating unit operated by an operator to instruct the motor to start and stop, A drive unit having a switching element and driving the motor in accordance with the operation of the operation unit, A voltage detection unit for detecting the input voltage of the drive unit, A control unit that controls the drive unit, A work machine equipped with, When the voltage detected by the voltage detection unit rises, the control unit is configured to apply a brake to the motor.

[0010] The present invention may be expressed as "electric working machines", "electric tools", "electrical equipment", etc., and those expressed as such are also effective as aspects of the present invention.

Effects of the Invention

[0011] According to the present invention, at least one of the above problems 1 to 3 can be solved.

Brief Description of the Drawings

[0012] [Figure 1] Circuit block diagram of the working machine 1 according to an embodiment of the present invention. [Figure 2] Cross-sectional view of the motor 3 of the working machine 1. [Figure 3] Timing chart when the trigger 11 is turned off during the drive of the motor 31 in the working machine 1. [Figure 4] Timing chart regarding the first control example of the working machine 1. [Figure 5] Timing chart regarding the second control example of the working machine 1. [Figure 6] Flowchart of the third control example of the working machine 1. [Figure 7] Flowchart of the fourth control example of the working machine 1. [Figure 8] Timing chart regarding the third control example of the working machine 1. [Figure 9] Timing chart regarding the fourth control example of the working machine 1. [Figure 10] Diagram showing the time change of the direction of the phase current after the trigger 11 is turned off during the drive of the motor 31 in the working machine 1. [Figure 11] Diagram showing the direction of the phase current in each section of A - F of the timing chart in FIG. 8. [Figure 12] Diagram showing the direction of the phase current in each section of A - F of the timing chart in FIG. 9. [Figure 13] Side view of a portable circular saw as an example of the working machine 1. [Figure 14] A perspective view of a brush cutter, which is an example of a work machine 1. [Modes for carrying out the invention]

[0013] This embodiment relates to a work implement 1. The work implement 1 is, for example, a portable circular saw as shown in Figure 13 or a brush cutter as shown in Figure 14, and has a housing 10 and a trigger 11 as an operating part. A battery pack 5, which serves as the power source, is detachably attached to the housing 10. The mechanical configuration of portable circular saws and brush cutters is well known, so a description will be omitted here. The circuit configuration of the work implement 1 will be described below.

[0014] Figure 1 is a circuit block diagram of the work machine 1. The work machine 1 comprises a motor 31, an inverter circuit 30, and a control unit 20.

[0015] The motor 31 is powered by electricity supplied from the battery pack 5. The motor 31 is a 4-pole, 6-slot inner rotor type three-phase brushless motor as shown in Figure 2, and has a stator 32 and a rotor 33. The stator 32 has U-phase, V-phase, and W-phase stator windings 34 connected in a star configuration (Y-connection). The operator can start and stop the motor 31 by operating the trigger 11.

[0016] The inverter circuit 30 is a drive unit that drives the motor 31 in response to the operation of the trigger 11, under the control of the control unit 20. The inverter circuit 30 converts the DC output of the battery pack 5 into AC and supplies it to each stator winding 34 of the stator 32 to drive the motor 31. An electrolytic capacitor C for surge absorption is provided between the input terminals of the inverter circuit 30. The inverter circuit 30 includes three-phase bridge-connected switching elements Q1 to Q6 such as FETs and IGBTs.

[0017] The sources of switching elements Q1 to Q3 and the drains of switching elements Q4 to Q6 are connected to each other and also to star-connected stator windings U, V, and W. Parasitic diodes D1 to D6 are in parallel between the drains and sources of each of the switching elements Q1 to Q6.

[0018] Switching elements Q1 to Q6 turn on when the input voltage to their gate (control terminal) is high, and turn off when it is low. The on / off state of switching elements Q1 to Q6 is controlled by the control unit 20.

[0019] Each gate of switching elements Q1 to Q6 is connected to the inverter drive unit 25 of the control unit 20. Switching elements Q1 to Q6 perform switching operations in response to switching element drive signals H1 to H6 input from the inverter drive unit 25. As a result, the DC voltage from the battery pack 5 applied to the inverter circuit 30 is supplied as a three-phase AC voltage to the U-phase, V-phase, and W-phase stator windings.

[0020] The energizing method of the inverter circuit 30 is the well-known 120-degree energizing (square wave drive), and the upper (high voltage side) switching elements Q1 to Q3 connected to the upper arm (high voltage line) are turned on sequentially in 120-degree increments out of a 360-degree cycle, and the lower (low voltage side) switching elements Q4 to Q6 connected to the lower arm (low voltage line) are also turned on sequentially in 120-degree increments out of a 360-degree cycle. During the on period, at least one of the upper switching elements Q1 to Q3 and the lower switching elements Q4 to Q6 may be controlled by PWM (Pulse Width Modulation).

[0021] The current detection circuit 12 detects the drive current of the motor 31 by the voltage across a resistor R installed in the path of the motor 31's drive current (the current flowing through each stator winding 34 of the stator 32), and transmits it to the control unit 20.

[0022] The battery voltage detection circuit 13, acting as a voltage detection unit, detects the output voltage of the battery pack 5 (the input voltage of the inverter circuit 30) and transmits it to the control unit 20. When the battery pack 5 is connected, the voltage detected by the battery voltage detection circuit 13 is the output voltage of the battery pack 5 (hereinafter referred to as "battery voltage"). On the other hand, if the battery pack 5 is disconnected while the motor 31 is running (rotating), the voltage detected by the battery voltage detection circuit 13 rises above the battery voltage due to the regenerative energy of the motor 31. Therefore, when the voltage detected by the battery voltage detection circuit 13 rises above the expected battery voltage, the control unit 20 can determine that the battery pack 5 has been disconnected (detect a power outage).

[0023] The temperature detection element 15 is, for example, a thermistor and is provided near the motor 31 or inverter circuit 30. The temperature detection circuit 16 detects the temperature of the motor 31 or inverter circuit 30 based on the output voltage of the temperature detection element 15 and transmits it to the control unit 20.

[0024] Hall IC19 is an example of a magnetic detection element, and as shown in Figure 2, three of them are arranged at 60° intervals in the circumferential direction. INT1-INT3 shown in Figure 2 are the output signals of each Hall IC19, and their waveforms are shown in Figures 8-9 described later. The rotor position detection circuit 17 detects the rotational position of the rotor 33 (hereinafter referred to as "motor rotational position") based on the output signals of the Hall IC19 and transmits it to the control unit 20. The control unit 20 can detect the rotational speed of the motor 31 (hereinafter referred to as "motor rotational speed") based on the signals from the rotor position detection circuit 17.

[0025] The switch mechanism 18 transmits a linked switch operation detection signal to the control unit 20 in response to the operator's operation of the trigger 11. The switch mechanism 18 also includes a contact switch SW located between the positive terminal of the battery pack 5 and the upper input terminal of the inverter circuit 30 and the high-voltage terminal of the electrolytic capacitor C. The contact switch SW switches on and off in conjunction with the operation of the trigger 11.

[0026] A diode D7 is connected in parallel to the contact switch SW. Diode D7 is connected in a direction that allows current to flow from the inverter circuit 30 to the battery pack 5. With diode D7 present, if the battery pack 5 is detached from the housing 10 while the contact switch SW is off, the regenerative energy of the motor 31 can be supplied to the gate voltage generation circuit 22 and the control circuit power generation circuit 24, thereby maintaining the running state of the control unit 20.

[0027] The gate voltage generation circuit 22 generates upper gate voltages to be applied to the gates of switching elements Q1 to Q3 and lower gate voltages to be applied to the gates of switching elements Q4 to Q6 based on the battery voltage, and supplies them to the inverter drive unit 25.

[0028] The control circuit power generation circuit 24 converts the output voltage of the gate voltage generation circuit 22 into a power supply voltage for the control unit 20, etc., and supplies it to the control unit 20, etc. The gate voltage detection circuit 26 detects the output voltage of the gate voltage generation circuit 22 and transmits it to the control unit 20.

[0029] The battery temperature detection circuit 27 detects the temperature of the battery pack 5 based on the voltage at the battery temperature detection terminal 28, i.e., the output signal of the temperature detection element 7 of the battery pack 5, and transmits it to the control unit 20. The battery temperature detection terminal 28 is a temperature terminal to which temperature information of the battery pack 5 is input. When the battery pack 5 is connected, the voltage at the battery temperature detection terminal 28 is around 2.8V, and is a voltage value corresponding to the temperature of the battery pack 5. On the other hand, when the battery pack 5 is not connected, the voltage at the battery temperature detection terminal 28 is 0V. Therefore, the control unit 20 can determine whether the battery pack 5 is connected or not, i.e., whether the power supply has been cut off or not, based on the voltage at the battery temperature detection terminal 28.

[0030] In the work machine 1, the battery temperature detection terminal 28 functions not only for detecting the temperature of the battery pack 5, but also as a battery installation detection terminal that detects whether or not the battery pack 5 is connected, as described above. Furthermore, the battery temperature detection terminal 28 also functions as a communication terminal between the battery pack 5 and the control unit 20. In other words, the work machine 1 is configured to perform both digital and analog communication between the control unit 20 and the battery pack 5, and by switching between digital and analog communication at any time, temperature information can be detected and information can be communicated (digital communication) via the battery temperature detection terminal 28. In order to improve the accuracy of detecting when the battery pack 5 has come loose, the control unit 20 may periodically check the communication status with the battery pack 5 via the battery temperature detection terminal 28 in addition to temperature detection, and may determine that the battery pack 5 has come loose from the housing 10 even if communication is not established.

[0031] The control unit 20 controls the inverter circuit 30 in response to the operation of the trigger 11, thereby controlling the drive of the motor 31. The control unit 20 includes a calculation unit 21 and an inverter drive unit 25 (pre-driver circuit).

[0032] The calculation unit 21 generates gate control signals based on signals from the rotor position detection circuit 17 and outputs them to the inverter drive unit 25. There are six gate control signals, corresponding to the switching elements Q1 to Q6 of the inverter circuit 30, and each of them is a binary signal that is high level when switching elements Q1 to Q6 are turned on and low level when they are turned off.

[0033] The inverter drive unit 25 generates switching element drive signals H1 to H6 based on the output voltage of the gate voltage generation circuit 22, with increased current capability for each gate control signal, and outputs them to the gates (control terminals) of the switching elements Q1 to Q6 of the inverter circuit 30. The switching element drive signals H1 to H6 become high level when the corresponding gate control signal is high level, and low level when the gate control signal is low level.

[0034] Figure 3 is a time chart for when the trigger 11 is turned off while the motor 31 is being driven in the work machine 1. Before time t1, the trigger 11 is on, and the control unit 20 drives the motor 31.

[0035] When the trigger 11 is turned off at time t1, the system enters the first state. The control unit 20 sets the switching element drive signals H1 to H3 applied to the gates of the upper switching elements Q1 to Q3 to a low level, and the switching element drive signals H4 to H6 applied to the gates of the lower switching elements Q4 to Q6 to a high level. As a result, the upper switching elements Q1 to Q3 are turned off, and the lower switching elements Q4 to Q6 are turned on, applying an electric brake to the motor 31. The brake control initiated at time t1 corresponds to the first brake control.

[0036] Figure 4 is a time chart for a first control example of the work machine 1. Before time t2, the trigger 11 is ON, the battery pack 5 is installed, and the control unit 20 drives the motor 31.

[0037] When the battery pack 5 is detached from the housing 10 at time t2, the voltage at the battery temperature detection terminal 28 becomes 0V (a voltage value indicating power cutoff). Even when the battery pack 5 is detached from the housing 10, the gate voltage generation circuit 22 and the control circuit power generation circuit 24 operate using the power stored in the electrolytic capacitor C, and the start state of the control unit 20 is maintained.

[0038] When the control unit 20 detects that the battery pack 5 has detached from the housing 10 at time t2 based on the voltage at the battery temperature detection terminal 28, the control unit 20 sets the switching element drive signals H1 to H3 to a low level and the switching element drive signals H4 to H6 to a high level. As a result, switching elements Q1 to Q3 turn off and switching elements Q4 to Q6 turn on, applying an electric brake to the motor 31.

[0039] From time t2 onward, the energy stored in electrolytic capacitor C gradually decreases. The lower gate voltage is maintained at 15V until time t3, but as the energy stored in electrolytic capacitor C decreases, it gradually drops from 15V from time t3 onward. The lower gate voltage is the voltage of the switching element drive signals H4~H6 when they are at a high level. Therefore, the voltages of the switching element drive signals H4~H6 also decrease in conjunction with the decrease in the lower gate voltage.

[0040] When the lower gate voltage drops to a threshold at time t4, the control unit 20 turns off all switching element drive signals H1 to H6. As a result, the electrolytic capacitor C is charged by the regenerative energy of the motor 31, the input voltages to the gate voltage generation circuit 22 and the control circuit power supply generation circuit 24 are restored, and the lower gate voltage is also restored.

[0041] When the lower gate voltage rises to a predetermined value at time t5, the control unit 20 performs the same brake control as it did at time t2. Thereafter, the same operation as at times t2 to t5 is repeated until the motor 31 stops.

[0042] Figure 5 is a time chart for a second control example of the work machine 1. Compared to the first control example, the second control example differs in the number of switching elements in the inverter circuit 30 that are turned on during brake control after the battery pack 5 has detached from the housing 10. The operation up to time t12 in Figure 5 is the same as the operation up to time t2 in Figure 4.

[0043] When the battery pack 5 detaches from the housing 10 at time t12, the system enters the second state. When the control unit 20 detects that the battery pack 5 has detached from the housing 10 based on the voltage at the battery temperature detection terminal 28, it sets the switching element drive signals H1~H3 and H6 to a low level and the switching element drive signals H4 and H5 to a high level. This turns off the switching elements Q1~Q3 and Q6 and turns on the switching elements Q4 and Q5, applying an electric brake to the motor 31. The brake control started at time t12 (corresponding to the second brake control) has a smaller braking force compared to the brake control started at time t2 in Figure 4, because fewer switching elements are turned on, but it also consumes less energy stored in the electrolytic capacitor C.

[0044] From time t12 onward, the energy stored in electrolytic capacitor C gradually decreases. The lower gate voltage is maintained at 15V until time t13, but as the energy stored in electrolytic capacitor C decreases, it gradually drops from 15V after time t13. The voltage levels of the switching element drive signals H4 and H5 also decrease in conjunction with the decrease in the lower gate voltage. The period from time t12 to t13 is longer than the period from time t2 to t3 in Figure 4. This is due to the difference in energy consumption due to brake control in the two periods.

[0045] When the lower gate voltage drops to a threshold at time t14, the control unit 20 turns off all switching element drive signals H1 to H6. As a result, the electrolytic capacitor C is charged by the regenerative energy of the motor 31, the input voltages to the gate voltage generation circuit 22 and the control circuit power supply generation circuit 24 are restored, and the lower gate voltage is also restored.

[0046] When the lower gate voltage rises to a predetermined value at time t15, the control unit 20 performs the same brake control that was started at time t12. Thereafter, the same operation as at times t12 to t15 is repeated until the motor 31 stops.

[0047] Figure 6 is a flowchart of the third control example of the work machine 1. The control unit 20 drives the motor 31 (S1), and when the trigger 11 is ON (NO in S3) and the voltage at the battery temperature detection terminal 28 drops below a threshold (YES in S5), it determines that the battery pack 5 has detached from the housing 10 and performs brake control (S7). The threshold in S5 is set lower than the voltage range that can be input to the battery temperature detection terminal 28 when the battery pack 5 is connected.

[0048] If the trigger 11 is off in S3 (YES in S3), the control unit 20 performs brake control (S7). The brake control in S7 is the same as the brake control started at time t2 in Figure 4, and applies an electric brake by turning off switching elements Q1 to Q3 and turning on switching elements Q4 to Q6.

[0049] If the motor speed is not below the threshold (NO in S9), the control unit 20 determines that the motor 31 is not stopped and proceeds to S11. If the lower gate voltage is not below the threshold (NO in S11), the control unit 20 determines that the switching elements Q4 to Q6 are not in a half-on state and continues brake control (S7). If the lower gate voltage is below the threshold (YES in S11), the control unit 20 determines that the switching elements Q4 to Q6 are in a half-on state and performs off control from S13 onwards. The half-on state is a state in which the switching element is not fully turned on due to a low lower gate voltage, resulting in high on-resistance.

[0050] The control unit 20 detects the motor rotation position from the combination of output signals from the Hall IC 19 (S13).

[0051] The control unit 20 determines the combination of output signals from the Hall IC 19. U phase (INT1): L, V phase (INT2): H, W phase (INT3):H When this happens (YES in S15), the switching element Q6 is turned off (S17), and the process returns to S11.

[0052] The control unit 20 determines the combination of output signals from the Hall IC 19. U phase (INT1): H, V phase (INT2): H, W phase (INT3): L, When this happens (YES in S19), the switching element Q5 is turned off (S21), and the process returns to S11.

[0053] The control unit 20 determines the combination of output signals from the Hall IC 19. U phase (INT1): H, V phase (INT2): L, W phase (INT3): H, When this happens (YES in S23), the switching element Q4 is turned off (S25), and the process returns to S11.

[0054] Figure 7 is a flowchart of the fourth control example of the work machine 1. The control unit 20 drives the motor 31 (S1), and when the trigger 11 is ON (NO in S3), and the voltage detected by the battery voltage detection circuit 13 exceeds a threshold (YES in S5a), it determines that the battery pack 5 has detached from the housing 10 and performs brake control (S7a). The threshold in S5a is higher than the voltage range expected for the battery voltage, for example, 55V.

[0055] The brake control in S7a is the same as the brake control started at time t12 in Figure 5, which applies the electric brake by turning off switching elements Q1~Q3 and Q6 and turning on switching elements Q4 and Q5.

[0056] If the trigger 11 is off in S3 (YES in S3), the control unit 20 performs brake control (S4) and proceeds to S5a. The brake control in S4 is the same as the brake control in S7 in Figure 6, and applies an electric brake by turning off switching elements Q1 to Q3 and turning on switching elements Q4 to Q6. In the brake control in S4, switching elements Q4 to Q6 may be turned on intermittently (PWM control). If the condition of S5a is met during the brake control in S4 (the battery pack 5 is detached from the housing 10), the control unit 20 proceeds to the brake control in S7a.

[0057] If the motor speed is not below the threshold (NO in S9), the control unit 20 determines that the motor 31 is not stopped and proceeds to S11. If the lower gate voltage is not below the threshold (NO in S11), the control unit 20 determines that the switching elements Q4 and Q5 are not in a half-on state and continues brake control (S7a). If the lower gate voltage is below the threshold (YES in S11), the control unit 20 determines that the switching elements Q4 and Q5 are in a half-on state and performs off control from S13 onwards. Off control is the off control in Figure 6 with the processing related to Q6, which is already off (S15, 17), removed.

[0058] Figure 8 is a time chart for the third control example of the work machine 1. Although not shown in the illustration, in Figure 8 the trigger 11 is always on. Before time t21, the trigger 11 is on and the battery pack 5 is installed, and the control unit 20 drives the motor 31.

[0059] When the battery pack 5 is detached from the housing 10 at time t21, the voltage at the battery temperature detection terminal 28 becomes 0V (a voltage value indicating power cutoff). Even when the battery pack 5 is detached from the housing 10, the gate voltage generation circuit 22 and the control circuit power generation circuit 24 operate using the power stored in the electrolytic capacitor C, and the start state of the control unit 20 is maintained.

[0060] When the control unit 20 detects that the battery pack 5 has detached from the housing 10 at time t21 based on the voltage at the battery temperature detection terminal 28, the control unit 20 sets the switching element drive signals H1 to H3 to a low level and the switching element drive signals H4 to H6 to a high level. As a result, switching elements Q1 to Q3 turn off and switching elements Q4 to Q6 turn on, applying an electric brake to the motor 31.

[0061] When the lower gate voltage drops below the threshold at time t23, the control unit 20 performs off control (corresponding to the processing from S13 onwards in Figure 6) by sequentially turning off the switching elements Q4 to Q6.

[0062] The control unit 20 lowers the switching element drive signal H6 to a low level at the timing (time t25) when the output signal (INT2) of the V-phase Hall IC 19 rises. This turns off the switching element Q6. The current that was flowing through the switching element Q6 now flows through the diode D3 of the switching element Q3.

[0063] The control unit 20 then lowers the switching element drive signal H5 to a low level at the timing (time t27) when the output signal (INT1) of the U-phase Hall IC 19 rises. This turns off the switching element Q5. The current that was flowing through the switching element Q5 now flows through the diode D2 of the switching element Q2.

[0064] The control unit 20 then lowers the switching element drive signal H4 to a low level at the timing (time t29) when the output signal (INT3) of the W-phase Hall IC 19 rises. This turns off the switching element Q4. The current that was flowing through the switching element Q4 now flows through the diode D1 of the switching element Q1.

[0065] The order in which switching elements Q4 to Q6 are turned off depends on the motor rotation position when the lower gate voltage drops below the threshold.

[0066] During the period from time t25 to t27, switching elements Q4 and Q5 are in the ON state (conducting state) for brake control, and during the period from time t27 to t29, switching element Q4 is in the ON state for brake control. Brake control with switching elements Q4 to Q6 in the ON state corresponds to the third brake control, and brake control with switching elements Q4 and Q5 in the ON state and brake control with switching element Q4 in the ON state corresponds to the fourth brake control. Alternatively, brake control with switching elements Q4 to Q6 in the ON state and brake control with switching elements Q4 and Q5 in the ON state corresponds to the third brake control, and brake control with switching element Q4 in the ON state corresponds to the fourth brake control. The fourth brake control has a weaker braking force than the third brake control.

[0067] At time t29, all switching elements Q4 to Q6 are turned off, the electrolytic capacitor C is charged by the regenerative energy of the motor 31, the input voltage to the gate voltage generation circuit 22 and the control circuit power generation circuit 24 is restored, and the lower gate voltage is also restored.

[0068] If the lower gate voltage rises above the threshold at time t31, the control unit 20 performs the same brake control as it did at time t21. Thereafter, the same operation as at times t21 to t31 is repeated until the motor 31 stops.

[0069] Figure 9 is a time chart for the fourth control example of the work machine 1. Before time t41, the trigger 11 is ON, the battery pack 5 is installed, and the control unit 20 drives the motor 31.

[0070] When trigger 11 is turned off at time t41, the first braking section begins, and control unit 20 sets the switching element drive signals H1 to H3 to a low level and intermittently sets the switching element drive signals H4 to H6 to a high level. As a result, switching elements Q1 to Q3 are turned off and switching elements Q4 to Q6 are intermittently turned on, applying an electric brake to motor 31.

[0071] During the first braking section starting at time t41, the battery pack 5 detaches from the housing 10, and the voltage on the input side of the inverter circuit 30 (hereinafter referred to as "inverter input voltage") begins to rise.

[0072] When the inverter input voltage exceeds the threshold of 55V at time t43, the second braking section is entered, and the control unit 20 sets the switching element drive signals H1~H3 and H6 to a low level and the switching element drive signals H4 and H5 to a high level. As a result, switching elements Q1~Q3 and Q6 turn off and switching elements Q4 and Q5 turn on, applying an electric brake to the motor 31.

[0073] When the lower gate voltage drops below the threshold at time t45, the control unit 20 performs off control (corresponding to the processing from S13 onwards in Figure 7) by sequentially turning off the switching elements Q4 and Q5.

[0074] The control unit 20 lowers the switching element drive signal H5 to a low level at the timing (time t47) when the output signal (INT1) of the U-phase Hall IC 19 rises. This turns off the switching element Q5. The current that was flowing through the switching element Q5 now flows through the diode D2 of the switching element Q2.

[0075] The control unit 20 then lowers the switching element drive signal H4 to a low level at the timing (time t49) when the output signal (INT3) of the W-phase Hall IC 19 rises. This turns off the switching element Q4. The current that was flowing through the switching element Q4 now flows through the diode D1 of the switching element Q1.

[0076] The order in which switching elements Q4 and Q5 are turned off depends on the motor rotation position when the lower gate voltage drops below the threshold.

[0077] During the period from time t47 to t49, the brake control is in the ON state with switching element Q4. The brake control with switching elements Q4 and Q5 ON corresponds to the third brake control, and the brake control with switching element Q4 ON ​​corresponds to the fourth brake control. The fourth brake control has a weaker braking force than the third brake control.

[0078] At time t49, both switching elements Q4 and Q5 are turned off, the electrolytic capacitor C is charged by the regenerative energy of the motor 31, the input voltage to the gate voltage generation circuit 22 and the control circuit power generation circuit 24 is restored, and the lower gate voltage is also restored.

[0079] If the lower gate voltage rises above the threshold at time t51, the control unit 20 performs the same brake control as it did at time t43. Thereafter, the same operation as at times t43 to t51 is repeated until the motor 31 stops.

[0080] Figures 10(A) to (F) show the time change in the direction of the phase current (regenerative current) after the trigger 11 is turned off while the motor 31 is being driven in the work machine 1. The direction of the phase current changes sequentially as the motor 31 rotates. The phase current flows in a closed loop between the switching elements Q4 to Q6 and the stator 32.

[0081] Figures 11(A) to (F) show the direction of the phase current (regenerative current) in each section AF of the time chart in Figure 8. Between Figures 11(B) and (C), there is a timing when the direction of the W-phase current changes from flowing out from the stator 32 to flowing into the stator 32, and the switching element Q6 is turned off in accordance with this timing. Also, between Figures 11(D) and (E), there is a timing when the direction of the V-phase current changes from flowing out from the stator 32 to flowing into the stator 32, and the switching element Q5 is turned off in accordance with this timing. Furthermore, after Figure 11(F), there is a timing when the direction of the U-phase current changes from flowing out from the stator 32 to flowing into the stator 32, and the switching element Q4 is turned off in accordance with this timing.

[0082] Figures 12(A) to (F) show the direction of the phase current (regenerative current) in each section AF of the time chart in Figure 9. In Figures 12(A) to (F), the switching element Q6 is off throughout, so no current flows from the drain side to the source side of the switching element Q6. Between Figures 12(D) and (E), there is a timing when the direction of the V-phase current changes from flowing out from the stator 32 side to flowing into the stator 32 side, and the switching element Q5 is turned off in accordance with this timing. Also, after Figure 12(F), there is a timing when the direction of the U-phase current changes from flowing out from the stator 32 side to flowing into the stator 32 side, and the switching element Q4 is turned off in accordance with this timing.

[0083] This embodiment provides the following effects and benefits.

[0084] (1) The work machine 1 has a diode D7 in parallel with the contact switch SW, and when the battery pack 5 is detached from the housing 10 with the contact switch SW in the OFF position, the regenerative energy of the motor 31 is sent to the gate voltage generation circuit 22 and the control circuit power generation circuit 24 via the diode D7, thereby ensuring a longer power supply for the control unit 20 and maintaining the start state of the control unit 20 for a longer period.

[0085] (2) The control unit 20 determines whether the battery pack 5 has detached from the housing 10 based on the voltage at the battery temperature detection terminal 28 or the inverter input voltage. Therefore, unlike a configuration in which the battery pack 5 is determined to have detached from the housing 10 when the voltage at the input terminal of the output voltage of the battery pack 5 falls below a predetermined value, there is no need to provide a diode (such as the diode 51 in Patent Document 1) to prevent false detections caused by regenerative energy from the motor 31 flowing to the battery pack 5. Thus, when the battery pack 5 detaches from the housing 10, the regenerative energy from the motor 31 can be supplied to the gate voltage generation circuit 22 and the control circuit power supply generation circuit 24, and the start state of the control unit 20 can be maintained for a longer period of time.

[0086] (3) In the first to third control examples shown in Figures 4 to 6 and Figure 8, the control unit 20 determines that the battery pack 5 has been removed from the housing 10 when the voltage of the battery temperature detection terminal 28 falls below a threshold, for example, 0V. Therefore, one battery temperature detection terminal 28 can be used for three functions: temperature detection, communication, and battery installation detection. As a result, it is possible to increase functionality without increasing the number of terminals (while maintaining compatibility with conventional devices) and while suppressing an increase in size.

[0087] (4) In the fourth control example shown in Figures 7 and 9, the control unit 20 determines that the battery pack 5 has detached from the housing 10 when the inverter input voltage exceeds a threshold. This reduces the risk of false detection due to looseness in the terminal connection between the battery pack 5 and the main body of the work machine 1. Furthermore, by setting the inverter input voltage threshold to, for example, 55V, it is possible to suit both cases where the rated voltage of the battery pack 5 is 18V and 36V.

[0088] (5) When the lower gate voltage drops below a threshold during brake control after the battery pack 5 has detached from the housing 10, the control unit 20 temporarily turns off all switching elements Q4 to Q6. This suppresses heat generation in the switching elements due to current flow in the half-on state, thereby preventing damage to the switching elements. Furthermore, when the lower gate voltage recovers due to the regenerative energy of the motor 31, the control unit 20 resumes brake control. This ensures a longer total brake control time, thereby increasing the reliability of stopping the motor 31.

[0089] (6) In the third and fourth control examples shown in Figures 6 to 9, when the lower gate voltage drops below the threshold and all switching elements Q4 to Q6 are turned off, the control unit 20 turns off the switching element through which the phase current flows at the timing when the direction of the phase current changes from flowing out from the stator 32 to flowing into the stator 32. This suppresses the voltage rise due to regenerative energy.

[0090] (7) In the second and fourth control examples shown in Figures 5, 7, and 9, the control unit 20 turns off switching elements Q1 to Q3 and Q6 and turns on switching elements Q4 and Q5 during brake control after the battery pack 5 has detached from the housing 10. Therefore, compared to brake control in which switching elements Q1 to Q3 are turned off and switching elements Q4 to Q6 are turned on, the decrease in the lower gate voltage can be suppressed, and the time until the lower gate voltage falls below the threshold, i.e., the duration of one brake control can be extended. As a result, when the lower gate voltage falls below the threshold and all switching elements Q4 to Q6 are turned off, the phase current is sufficiently small, and the voltage rise due to regenerative energy is suppressed. Furthermore, if the trigger 11 is turned off when the battery pack 5 has not detached from the housing 10, the control unit 20 ensures high braking force by performing brake control in which switching elements Q1 to Q3 are turned off and switching elements Q4 to Q6 are turned on. In this way, appropriate brake control can be performed according to the usage conditions of the work machine 1.

[0091] Although the present invention has been described above using embodiments as examples, the present invention is not limited to these embodiments. Various modifications are possible to each of the matters specifically described in the embodiments within the scope of the claims.

[0092] The voltage values, the number of poles and slots of the motor 31, etc., exemplified as specific numerical values ​​in the embodiments do not limit the scope of the invention in any way and can be arbitrarily changed to suit the required specifications. The work machine of the present invention is not limited to portable circular saws or brush cutters, but may be other types such as tabletop circular saws or grinders. [Explanation of symbols]

[0093] 1...Work implement, 5...Battery pack, 7...Temperature detection element, 10...Housing, 11...Trigger (operating unit), 12...Current detection circuit, 13...Battery voltage detection circuit, 15...Temperature detection element, 16...Temperature detection circuit, 17...Rotor position detection circuit, 18...Switch mechanism, 19...Hall IC, 20...Control unit, 21...Calculation unit, 22...Gate voltage generation circuit, 24...Control circuit power generation circuit, 25...Inverter drive unit (pre-driver circuit), 26...Gate voltage detection circuit, 27...Battery temperature detection circuit, 28...Battery temperature detection terminal (temperature terminal), 30...Inverter circuit (drive unit), 31...Motor (brushless motor), 32...Stator, 33...Rotor, 34...Stator winding.

Claims

1. Motor and, An operating unit operated by an operator to instruct the motor to start and stop, A drive unit having multiple switching elements, including multiple upper switching elements connected to an upper arm and multiple lower switching elements connected to a lower arm, drives the motor in accordance with the operation of the operating unit, A control unit that controls the drive unit, A housing on which the battery pack that powers the motor can be attached and detached, A work machine equipped with, The control unit, When the operating unit is operated and then released, in the first state, the drive unit is controlled to intermittently turn on one of the upper and lower switching elements among the plurality of switching elements to produce a first braking force. When the motor is rotating and the battery pack is detached from the housing, the drive unit is configured to continuously turn on at least two of the multiple switching elements, one on the upper side and one on the lower side, to control the drive unit so that a second braking force greater than the first braking force is obtained. A work machine characterized by the following features.

2. A work machine according to claim 1, The battery pack is equipped with a temperature detection terminal for detecting the temperature of the battery pack, The control unit detects that the battery pack has been detached from the housing based on the information input from the temperature detection terminal. A work machine characterized by the following features.

3. A work machine according to claim 1, The battery pack is equipped with a temperature detection terminal for detecting the temperature of the battery pack, The control unit is configured to apply the brakes to the motor when the voltage input from the temperature detection terminal falls below a threshold value while the operation unit is being operated and the motor is rotating. A work machine characterized by the following features.

4. A work machine according to claim 1, The drive unit is equipped with a voltage detection unit that detects the voltage on the input side of the drive unit, The control unit detects that the battery pack has detached from the housing based on the voltage increase detected by the voltage detection unit. A work machine characterized by the following features.

5. A work machine according to claim 1, The drive unit is equipped with a voltage detection unit that detects the voltage on the input side of the drive unit, The control unit is configured to apply the brakes to the motor when the voltage detected by the voltage detection unit rises. A work machine characterized by the following features.

6. A work machine according to claim 5, The control unit is configured to apply the brakes to the motor when the voltage is greater than the voltage of the power supply. A work machine characterized by the following features.

7. A work machine according to claim 1, A switch is provided in the current path between the battery pack and the drive unit, and is switched on or off by the operation of the control unit, The switch and a diode connected in parallel are provided, The diode is connected in a direction that allows current to flow from the drive unit side to the battery pack side. A work machine characterized by the following features.

8. A work machine according to claim 1, The second braking force varies depending on the number of switching elements among the plurality of switching elements that are turned on. A work machine characterized by the following features.

9. A motor powered by electricity supplied from a power source, An operating unit operated by an operator to instruct the motor to start and stop, A drive unit having a switching element and driving the motor in accordance with the operation of the operation unit, A voltage detection unit for detecting the input voltage of the drive unit, A control unit that controls the drive unit, A work machine equipped with, The control unit is configured to apply the brakes to the motor when the voltage detected by the voltage detection unit rises. A work machine characterized by the following features.

10. A work machine according to claim 9, The control unit is configured to detect the interruption of the power supply when the voltage rises. A work machine characterized by the following features.

11. A work machine according to claim 9 or 10, The control unit is configured to apply the brakes to the motor when the voltage is greater than the voltage of the power supply. A work machine characterized by the following features.

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