Electric work machine

Abstract

To provide an electric working machine configured so as to suppress a motor from generating heat.SOLUTION: An electric working machine 1 comprises a motor 6, an operating part 31, a working part 8, and a control part 10. The working part is driven by the motor to work on an object to be worked. The operating part is operated by a worker. When receiving an operation signal showing an operation amount to the operating part, the control part controls maximum electricity that can be inputted to the motor to first electricity. When a rotating speed of the motor becomes less than a first threshold due to loads on the working part, the electric working machine performs first switching control of switching the maximum electricity to second electricity smaller than the first electricity. When a first period of time elapses after the first switching control is performed, the electric working machine performs second switching control of switching the maximum electricity to third electricity larger than the second electricity. When the rotating speed of the motor becomes a second threshold or more after the second switching control is performed, the electric working machine performs third switching control of switching the maximum electricity to the first electricity.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electric power tool. [Background technology]

[0002] Patent Document 1 discloses a technique in which, when a management device transmits a motor prohibition signal to an electric work machine, a control unit of the electric work machine stops the supply of power from a battery pack to the motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-87359 Summary of the Invention [Problem to be solved by the invention]

[0004] When the load increases while using an electric work machine, the motor generates more heat, and if the work continues under this condition, the heat can cause parts to break down.

[0005] In view of the above circumstances, the present invention aims to suppress heat generation from the motor. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided an electric work machine. The electric work machine includes a motor, an operating unit, a working unit, and a control unit. The working unit is driven by the motor and acts on a work target. The operating unit is operated by a worker. When the control unit receives an operation signal indicating the amount of operation on the operating unit, it controls the maximum power that can be input to the motor to a first power. When the load on the working unit causes the motor's rotation speed to fall below a first threshold, it performs first switching control to switch the maximum power to a second power that is lower than the first power. When a first period has elapsed since the first switching control, it performs second switching control to switch the maximum power to a third power that is higher than the second power. When the motor's rotation speed becomes equal to or higher than the second threshold after performing the second switching control, it performs third switching control to switch the maximum power to the first power.

[0007] According to this aspect, heat generation from the motor can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram showing the hardware configuration of a chainsaw 1. FIG. [Figure 2] FIG. 1 is a diagram showing the appearance of a chain saw 1. [Figure 3] 10 is a flowchart illustrating an example of a control process. [Figure 4] 1 is a graph showing an example of the relationship between the rotation speed of an electric motor 6 and input power. [Figure 5] 10 is a graph showing another example of the relationship between the rotation speed of the electric motor 6 and the input power. [Figure 6] FIG. 3 is a diagram showing an example of a first table. [Figure 7] FIG. 10 is a diagram showing an example of a second table. [Figure 8] FIG. 10 is a diagram showing an example of a third table. [Figure 9] FIG. 10 is a diagram showing an example of a fourth table. [Figure 10] 10 is a graph showing an example of a change in input power to an electric motor 6. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The various features shown in the following embodiments can be combined with each other. In this embodiment, a chainsaw for cutting trees, boards, etc. will be described as an example of an electric work machine according to the present invention.

[0010] Incidentally, the program for realizing the software appearing in this embodiment may be provided as a non-transitory computer-readable medium, or may be provided so that it can be downloaded from an external server, or may be provided so that the program is started on an external computer and its functions are realized on a client terminal (so-called cloud computing).

[0011] In this embodiment, the term "unit" may also include, for example, a combination of hardware resources implemented by a circuit in the broad sense and software information processing that can be specifically realized by these hardware resources. In addition, this embodiment handles various types of information, which may be represented by, for example, physical values ​​of signal values ​​representing voltages and currents, high and low signal values ​​as a binary bit set consisting of 0 or 1, or quantum superposition (so-called quantum bits), and communication and calculations may be performed on a circuit in the broad sense.

[0012] In addition, a circuit in the broad sense is a circuit realized by at least appropriately combining a circuit, circuitry, a processor, a memory, etc. That is, it includes an application specific integrated circuit (ASIC), a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)), etc.

[0013] 1. Hardware Configuration In this section, the hardware configuration of the chainsaw 1 according to this embodiment will be described.

[0014] FIG. 1 is a block diagram showing the hardware configuration of a chainsaw 1. The chainsaw 1 includes a main body 2, a trigger 3, a battery 4, an electric motor 6, an output shaft 7, a cutting tool 8, a blower fan 9, and a control unit 10. The main body 2 has a housing made of resin or the like, and is a part that holds the other parts. The main body 2 holds the trigger 3 and the cutting tool 8 exposed to the outside, and holds the battery 4 in a detachable manner. The main body 2 holds the other parts inside the housing.

[0015] The trigger 3 is a part that is operated by an operator when working with the chainsaw 1. The trigger 3 has a lever 31 and a signal generating unit 32. The lever 31 is an example of an operating unit that is operated by an operator when operating the chainsaw 1. The signal generating unit 32 generates an operating signal that indicates the amount of operation of the lever 31 by the operator. The battery 4 supplies DC power to each of the other components. The inverter 5 converts the DC power supplied by the battery 4 into predetermined AC power. The electric motor 6 is a motor that operates using the AC power converted by the inverter 5.

[0016] The output shaft 7 transmits the driving force generated by the electric motor 6 to the cutting tool 8. The cutting tool 8 rotates by the driving force transmitted by the output shaft 7 and cuts the work object. In this embodiment, the work object is a tree, a board, or the like. In this way, the cutting tool 8 is an example of a working unit that is driven by a motor (electric motor 6 in this embodiment) and acts on the work object. The blower fan 9 rotates by the driving force generated by the electric motor 6 and blows cooling air into the housing.

[0017] The control unit 10 is an example of a control unit that controls the operation of the electric motor 6. The control unit 10 includes an inverter 5, and controls the operation of the electric motor 6 based on an operation signal transmitted from a signal generating unit 32 when an operator grips a lever 31. The control unit 10 includes a control board on which are provided IC circuits (Integrated Circuits) such as a memory 11, a rotation speed detecting unit 12, and a motor control unit 13, and these IC circuits generate and transmit control signals. The control unit 10 includes the memory 11, the rotation speed detecting unit 12, and the motor control unit 13.

[0018] The memory 11 stores various information. The memory 11 may be implemented as a storage device such as a flash memory or a solid state drive (SSD) that stores various programs related to the chainsaw 1 executed by the control unit 10, or as a memory such as a random access memory (RAM) that stores temporarily required information (arguments, arrays, etc.) related to program calculations. The memory 11 stores various programs, variables, etc. related to the chainsaw 1 executed by the control unit 10.

[0019] The rotational speed detection unit 12 has an electromagnetic or photoelectric rotational speed sensor, and detects the rotational speed per unit time of the electric motor 6. The motor control unit 13 controls the power input to the electric motor 6 (hereinafter referred to as "input power") by sending a control signal to the inverter 5 to cause it to perform a switching operation. The motor control unit 13 controls the input power to the electric motor 6 based on parameters stored in the memory 11 and the rotational speed detected by the rotational speed detection unit 12. The rotational speed detection unit 12 may also calculate the rotational speed per unit time of the electric motor 6 from the waveform output from the electric motor 6.

[0020] Fig. 2 is a diagram showing the appearance of the chainsaw 1. Fig. 2 shows the chainsaw 1 as seen from the left. As shown in Fig. 1, the chainsaw 1 has defined up-down, front-rear, and left-right directions. In this embodiment, the up-down direction of the chainsaw 1 is defined as the vertical direction when the chainsaw 1 is placed on a flat, horizontal installation surface. The front-rear direction is defined as the direction perpendicular to the up-down direction, and the left-right direction is defined as the direction perpendicular to the up-down and front-rear directions.

[0021] FIG. 2 shows the main body 2, the battery 4, the cutting tool 8, and the lever 31. The main body 2 has a front handle 21, a rear handle 22, an intake section 23, and an exhaust section 24. The front handle 21 is provided on the front side of the main body 2 and is the section that an operator grips when performing electric work. The rear handle 22 is provided on the rear side of the main body 2 and is the section that an operator grips when performing electric work. The intake section 23 has an intake port and forms a passage for sending cooling air taken in through the intake port into the main body 2. The exhaust section 24 has an exhaust port and discharges the cooling air taken in through the intake section 23 and used to cool heat-generating components such as a motor arranged inside the main body 2 to the outside space.

[0022] 3. Information Processing In this section, information processing in this embodiment will be described. In the chainsaw 1, the motor control unit 13 of the control unit 10 executes control processing to control the power of the current input from the inverter 5 to the electric motor 6 (hereinafter referred to as "input power").

[0023] Fig. 3 is a flowchart showing an example of the control process. After an operator performs a safety operation such as pressing a power button (not shown), the operator grips the lever 31 shown in Fig. 1, causing the signal generating unit 32 to transmit an operation signal to the control unit 10. The control unit 10 starts the control process when it receives the operation signal. Furthermore, the control unit 10 ends the control process when the operator performs an operation to end the operation of the chainsaw 1, such as releasing the lever 31 from its grip. This control process includes looping processes, which are repeatedly executed at predetermined time intervals (e.g., every 0.1 seconds).

[0024] When the motor control unit 13 receives an operation to start the electric motor 6, it first sets the maximum inputtable power stored in the memory 11 to the first power A1 in A11. The maximum inputtable power means the maximum power that can be input to the electric motor 6. The motor control unit 13 controls the input power to the electric motor 6 based on the amount of operation of the lever 31 so that it is equal to or less than the first power A1, which is the set maximum inputtable power.

[0025] Furthermore, the motor control unit 13 converts the rotation speed detected by the rotation speed detection unit 12 at a predetermined timing into a rotation speed per unit time (one minute in this embodiment), and detects this value as the rotation speed of the electric motor 6. The first power A1 will be described with reference to FIG. Fig. 4 is a graph showing an example of the relationship between the rotation speed and input power of the electric motor 6. Fig. 4 shows a line graph in which the horizontal axis is the time axis and the vertical axis indicates the rotation speed (unit: rotations per minute: r / min) and input power (unit: watts: W).

[0026] The graph shown in Fig. 4 shows the changes in rotation speed and input power from time t0 when the lever 31 is operated and the electric motor 6 starts to rotate. In the example of Fig. 4, it is assumed that at the start of operation, the operator grips the lever 31 to the maximum extent, the cutting tool 8 is not in contact with the work object, and no load from the work object is applied to the cutting tool 8. The electric motor 6 rotates at a rotation speed B1 (10,000 r / min in the example of Fig. 4) when the input power is a first power A1 and there is no load on the cutting tool 8.

[0027] When the cutting tool 8 comes into contact with the work object and begins to act (cutting the work object in this embodiment), a load is applied to the cutting tool 8, the rotational speed of the cutting tool 8 decreases, and the rotational speed of the electric motor 6 connected to the cutting tool 8 via the output shaft 7 also decreases. In the example of FIG. 4, cutting begins at time t1, and as the force with which the worker presses the cutting tool 8 against the work object increases, the load on the cutting tool 8 gradually increases, and at the same time, the rotational speed of the electric motor 6 gradually decreases.

[0028] If the motor control unit 13 determines in A12 that the rotation speed of the electric motor 6 has changed from high rotation to a rotation speed less than the first threshold value Th1 (YES), the motor control unit 13 performs first switching control in A13 to switch the maximum input allowable power from the first power A1 to the second power A2. The second power A2 is lower than the first power A1. In other words, the motor control unit 13 performs first switching control when the rotation speed of the electric motor 6 has changed from high rotation to a rotation speed less than the first threshold value Th1 due to the load on the cutting tool 8. Furthermore, if the motor control unit 13 determines in A12 that the rotation speed of the electric motor 6 is equal to or greater than the first threshold value Th1 (NO), the motor control unit 13 controls the electric motor 6 while maintaining the maximum input allowable power to the electric motor 6 at the first power A1.

[0029] In the example of Fig. 4, at time t3, the first switching control causes the maximum inputtable power to the electric motor 6 to become the second power A2, and as a result, the rotation speed of the electric motor 6 drops to 0 r / min. In other words, even if the operator holds the trigger 3 at its maximum operating amount at time t3, if the cutting tool 8 is pressed against the work object, the rotation of the cutting tool 8 will also stop, allowing the operator to recognize that the electric motor 6 is about to stop.

[0030] Next, at A14, the motor control unit 13 performs control to maintain the maximum input allowable power at the second power A2 during the first period T1. Then, at A15, the motor control unit 13 performs second switching control to switch the maximum input allowable power from the second power A2 to the third power A3. That is, the motor control unit 13 performs the second switching control when the first period T1 has elapsed since performing the first switching control. The third power A3 is a power greater than the second power A2. Furthermore, in this embodiment, the third power A3 is a power smaller than the first power A1.

[0031] 4, at time t4, when a first period T1 has elapsed since time t2, the control unit 10 performs second switching control to set the maximum allowable power input to the electric motor 6 to the third power A3. Here, the first period T1 is set to a time period required for the operator to become aware of the driving status. For example, when the operator is pressing the cutting tool 8 against the cutting target, the first switching control causes an extreme decrease in the rotational force of the cutting tool 8, so the first period T1 is set to a time period required for the operator to become aware of the decrease in rotational force or a longer time period.

[0032] Next, in A16, the motor control unit 13 determines whether the second period T2 has elapsed since performing the second switching control. If the motor control unit 13 determines that the second period T2 has elapsed (YES), then in A17, the motor control unit 13 determines whether the rotation speed of the electric motor 6 has changed from a low rotation speed to equal to or greater than the second threshold value Th2. If the motor control unit 13 determines in A17 that the rotation speed of the electric motor 6 has changed from a low rotation speed to equal to or greater than the second threshold value Th2 (YES), then the motor control unit 13 returns to A11 and performs third switching control to switch the maximum inputtable power from the third power A3 to the first power A1. In other words, the motor control unit 13 performs the third switching control if the rotation speed of the electric motor 6 has changed from a low rotation speed to equal to or greater than the second threshold value Th2 after performing the second switching control.

[0033] Furthermore, if the motor control unit 13 determines in A17 that the rotation speed of the electric motor 6 has not increased from low rotation to above the second threshold value Th2 (NO), then in A18 it stops the electric motor 6 by stopping the supply of power to the electric motor 6 (stopping the input of power).

[0034] If the motor control unit 13 determines in A16 that the second period T2 has not elapsed (NO), it controls the electric motor 6 while keeping the maximum inputtable power to the electric motor 6 at the third power A3. Here, the second period T2 is set to a time that is considered to be required for the rotation speed of the electric motor 6 to reach or exceed the second threshold value Th2 after the operator reduces the force with which the cutting tool 8 is pressed against the work target, or a time that is longer than this.

[0035] 4, the motor control unit 13 performs the third switching control by setting the second threshold value Th2 to the same threshold value as the first threshold value Th1. As a result of the third switching control changing the input power to the first power A1, at time t6, the rotation speed of the electric motor 6 increases to the rotation speed B1 (10,000 r / min) at the time of startup.

[0036] Fig. 5 is a graph showing another example of the relationship between the rotation speed and input power of electric motor 6. In the example of Fig. 5, the rotation speed of electric motor 6 changes in the same way as in the example of Fig. 4 until time t4, but at time t5, when the second period T2 has elapsed since the second switching control, the rotation speed is less than second threshold value Th2. In this case, motor control unit 13 stops the input of power to electric motor 6 from time t6 (sets the input power to 0 W) and controls the rotation speed of electric motor 6 to 0 r / min.

[0037] Thus, in this embodiment, the motor control unit 13 stops the input of power to the electric motor 6 if the second period T2 has elapsed since the second switching control was performed before the rotation speed of the electric motor 6 became equal to or greater than the second threshold value Th2.

[0038] When the load on the cutting tool 8 increases, the rotational speed of the cutting tool 8 slows down, and accordingly, the rotational speed of the electric motor 6 also slows down. On the other hand, if the input power remains the same, the energy that would be converted into rotational force is converted into heat, causing excessive heat generation, and the operation of the electric motor 6 is stopped to prevent the excessive heat generation. Therefore, in the chainsaw 1, when the load on the cutting tool 8 increases, second and third switching controls are performed to intentionally reduce the maximum input power that can be input to the electric motor 6 before the operation of the electric motor 6 is stopped, thereby reducing the rotational speed of the electric motor 6.

[0039] This makes it easier for the worker to realize that the electric motor 6 is about to stop before it actually stops due to excessive heat generation. Then, when the worker realizes that the electric motor 6 is about to stop, he or she can resume work without stopping the electric motor 6 by releasing the force pressing the cutting tool 8 against the work target.

[0040] Furthermore, by stopping the electric motor 6 when the rotation speed does not increase after the second switching control as described above, when the load on the cutting tool 8 increases and the heat of the electric motor 6 increases, excessive heat generation can be prevented even if the load on the cutting tool 8 is not relieved.

[0041] Furthermore, during the first period T1, the rotation speed of the electric motor 6 decreases, and the rotation speed of the blower fan 9 also decreases. In this embodiment, the stagnation of the cooling air due to the reduced rotation speed of the blower fan 9 has a greater impact than the suppression of temperature rise due to the reduced rotation speed of the electric motor 6, and the temperature inside the housing increases during the first period T1. Then, when the first period T1 ends and the second switching control is performed, the rotation speed of the electric motor 6 increases, and the rotation speed of the blower fan 9 also increases, and the cooling air begins to blow again.

[0042] After the first switching control is performed, the earlier the operator realizes that the electric motor 6 is about to stop and reduces the force pressing the cutting tool 8 against the work object, the faster the rotation speed of the electric motor 6 increases and the faster the cooling air becomes stronger, thereby suppressing the temperature rise inside the housing. In this way, by performing the first switching control, it is possible to make the operator realize that the electric motor 6 is about to stop before the operation of the electric motor 6 actually stops due to excessive heat, compared to when the first switching control is not performed.

[0043] Furthermore, by performing the second switching control, the blower fan 9 is restored while suppressing heat generation from the electric motor 6 compared to when the second switching control is not performed, thereby preventing the electric motor 6 from stopping due to excessive heat generation. Furthermore, since the operation of the electric motor 6 is controlled as described above while the operator continues to operate the lever 31, the operator does not need to re-grrip the lever 31 and can concentrate on adjusting the force with which the cutting tool 8 is pressed against the work target.

[0044] Furthermore, by increasing the input power to the third power A3 through the second switching control, a driving force is applied to the cutting tool 8, giving the operator a sense of resistance from the chainsaw 1 and allowing the operator to recognize that the electric motor 6 has not yet stopped. In this case, by making the third power A3 smaller than the first power A1, when the cutting tool 8 that was stopped during the first period T1 resumes rotation, a phenomenon such as kickback caused by sudden rotation with strong force is suppressed compared to when the third power A3 is larger than the first power A1, and work can be continued safely.

[0045] <Other embodiments> (1) Electric work equipment In the embodiment, a chainsaw has been described as an example of an electric work machine, but this is not limiting. For example, a hedge trimmer, an engine cutter, etc. may also be used. In short, any electric work machine may be used as long as it has a working unit that operates on power supplied from a detachable battery in the main body. Furthermore, although the motor control unit 13 performs control by setting the second threshold value Th2 to the same threshold value as the first threshold value Th1, the second threshold value Th2 may also be set to a threshold value different from the first threshold value Th1.

[0046] (2) Temperature condition As described above, the electric motor 6 generates excessive heat when the load on the cutting tool 8 increases, and the higher the temperature of the electric motor 6 itself or the surrounding area, the more likely the temperature due to excessive heat will increase. Therefore, the motor control unit 13 may acquire temperature information indicating the temperature state of the electric motor 6 and change a first parameter used to control the rotation speed of the electric motor 6 based on the acquired temperature information. The first parameter includes, for example, a first threshold value Th1, a second threshold value Th2, a first period T1, a second period T2, a second power A2, or a third power A3.

[0047] The temperature information is, for example, information that indicates the temperature of the electric motor 6 itself. In this case, the chainsaw 1 is equipped with, for example, a temperature sensor that detects the temperature of the electric motor 6. The temperature sensor may be of a contact type or a non-contact type, and supplies temperature information that indicates the measured temperature of the electric motor 6 to the motor control unit 13. Note that the temperature information is not limited to information that directly indicates the temperature of the electric motor 6. For example, information that indicates the temperature of the control board of the control unit 10 or the temperature of the inner surface of the housing of the main body 2 may also be used as the temperature information. This is because the control board and the inner surface of the housing are in close proximity to the electric motor 6, and therefore their temperatures fluctuate in the same way as the electric motor 6.

[0048] The motor control unit 13 changes the first parameter using a first table that associates the temperature information of the electric motor 6 with each first parameter. FIG. 6 is a diagram showing an example of the first table. In the example of FIG. 6, temperature information C such as "less than C1", "C1 or more and less than C2", and "C2 or more" is shown. As the temperature information C indicates a higher temperature state, the temperature of the electric motor 6 when the load on the cutting tool 8 increases tends to be higher.

[0049] The temperature information C is associated with a first threshold Th1 such as "Th1-1", "Th1-2", and "Th1-3", and a second threshold Th2 such as "Th2-1", "Th2-2", and "Th2-3". Also, the temperature information C is associated with a second period T2 such as "T2-1", "T2-2", and "T2-3". Further, the temperature information C is associated with a second power A2 such as "A2-1", "A2-2", and "A2-3", and a third power A3 such as "A3-1", "A3-2", and "A3-3".

[0050] For example, the first threshold Th1 is defined such that Th1-1 < Th1-2 < Th1-3. Thereby, as the situation where the temperature of the electric motor 6 tends to be higher, the first threshold Th1 becomes larger, so the timing for performing the first switching control is advanced, and the rotational speed can be decreased before the electric motor 6 overheats, or the state where the electric motor 6 overheats can be ended earlier. Also, the second threshold Th2 is defined such that Th2-1 < Th2-2 < Th2-3. Thereby, as the situation where the temperature of the electric motor 6 tends to be higher, the second threshold Th2 becomes larger, and the timing for performing the third switching control and returning to the third power A3 is delayed, so the time for cooling the electric motor 6 can be lengthened.

[0051] The second power A2 is set so that A2-1 > A2-2 > A2-3. As a result, the input power (second power A2) during the first period T1 decreases as the temperature of the electric motor 6 increases, making it easier for the electric motor 6 to cool down during the first period T1. The third power A3 is set so that A3-1 > A3-2 > A3-3. As a result, it is possible to achieve a balance between preventing an excessive increase in the temperature of the electric motor 6 and making it easy to recognize that the chainsaw 1 is continuing to operate.

[0052] The second period T2 is set so that T2-1 > T2-2 > T2-3. As a result, the second period T2 becomes shorter as the temperature of the electric motor 6 becomes more likely to rise, which makes it more likely that the input power to the electric motor 6 will be stopped and slows down the work pace of the electric work machine, making it less likely that the electric motor 6 will break down due to excessive heat generation.

[0053] In terms of work, the greater the driving force of the electric motor 6, the better, but when the rotation speed drops due to the load on the cutting tool 8, this can cause excessive heat generation. Therefore, as described above, by changing the first parameter based on the temperature information, it is possible to increase the driving force as much as possible, while suppressing the driving force and suppressing heat generation in situations where the temperature is likely to become too high. In other words, it is possible to achieve a balance between suppressing heat generation by the electric motor 6 and the driving force generated by the electric motor 6.

[0054] (3) Remaining battery power The electric motor 6 operates using power supplied from the battery 4. The motor control unit 13 may change a second parameter used to control the rotation speed of the electric motor 6 according to the remaining charge (state of charge) of the battery 4. The remaining charge of the battery is represented, for example, by the remaining capacity or charging rate of the battery. The second parameter includes, for example, a first threshold value Th1, a second threshold value Th2, a first period T1, a second period T2, a second power A2, or a third power A3.

[0055] The motor control unit 13 acquires remaining amount information indicating the remaining amount of the battery 4 from the battery 4. The remaining amount information is information indicating the remaining amount of the battery 4 by a numerical value from, for example, 0% to 100%. The motor control unit 13 changes the second parameter using a second table in which the remaining amount information of the battery 4 is associated with each second parameter.

[0056] FIG. 7 is a diagram showing an example of the second table. In the example of FIG. 7, remaining amount information D such as "less than D1", "greater than or equal to D1 and less than D2", and "greater than or equal to D2" is shown. The same values as the first threshold Th1, the second threshold Th2, the second period T2, the second power A2, or the third power A3 shown in FIG. 6 are respectively associated with the remaining amount information D.

[0057] For example, the first threshold Th1 is defined such that Th1-1 > Th1-2 > Th1-3. As a result, the smaller the remaining amount of the battery 4, the larger the first threshold Th1 becomes, so the timing at which the first switching control is performed is advanced, the power consumption is reduced, and the operating time of the electric motor 6 can be extended. Also, the second threshold Th2 is defined such that Th2-1 > Th2-2 > Th2-3. As a result, the smaller the remaining amount of the battery 4, the larger the second threshold Th2 becomes, and the timing at which the third switching control is performed and the return to the third power A3 is delayed, so the remaining amount of the battery 4 can be conserved.

[0058] Also, the second period T2 is defined such that T2-1 < T2-2 < T2-3. As a result, the smaller the remaining amount of the battery 4, the easier it is for the input power to be stopped, and it is possible to make it less likely that the electric motor 6 suddenly stops due to power failure during use.

[0059] Also, the second power A2 is defined such that A2-1 < A2-2 < A2-3. As a result, as the remaining amount of the battery 4 decreases, the input power (the second power A2) in the first period T1 becomes smaller, so the power consumption in the first period T1 can be suppressed. Also, the third power A3 is defined such that A3-1 < A3-2 < A3-3. Thereby, it is possible to balance the suppression of the power consumption of the electric motor 6 and the ease of recognizing the continuation of the operation of the chainsaw 1.

[0060] In terms of work, the greater the driving force by the electric motor 6, the better. However, in a situation where the remaining amount of the battery 4 is small, it causes the operating time to be shorter. Therefore, as described above, by changing the second parameter based on the remaining amount information D, it is possible to reduce the power consumption by suppressing the driving force while increasing the driving force as much as possible in a situation where the remaining amount of the battery 4 is small. In other words, it is possible to balance the driving force and the operating time of the electric motor 6.

[0061] (4) Hardness of the work object The harder the work object, the more likely the load on the cutting tool 8 will increase. And the greater the load on the cutting tool 8, the lower the rotational speeds of the cutting tool 8 and the electric motor 6 will be, and the more likely the electric motor 6 will generate heat. Therefore, the motor control unit 13 may determine the hardness of the work object and change the third parameter used for controlling the rotational speed of the motor based on the determined hardness.

[0062] The motor control unit 13 determines the hardness of the work object based on, for example, the history of the time (hereinafter referred to as "control interval time") from when the second switching control is performed until the third switching control is performed. The control interval time is the time required for the rotational speed that has once been decreased to increase again to be equal to or higher than the second threshold value Th2, and it becomes shorter as the load on the cutting tool 8 becomes smaller. Since the greater the hardness of the work object, the greater the load on the cutting tool 8, the longer the control interval time indicates that the work object is harder, and the shorter the control interval time indicates that the work object is softer. The motor control unit 13 uses this relationship to determine the hardness of the work object.

[0063] The third parameter includes a first threshold value Th1, a second threshold value Th2, a second power A2, or a third power A3. The motor control unit 13 changes the third parameter using a third table in which the control interval time, the hardness of the work object, and each third parameter are associated with each other.

[0064] FIG. 8 is a diagram showing an example of the third table. In the example of FIG. 8, the hardness of the work object, namely "soft", "medium", and "hard", is shown in association with the control interval time E of "less than E1", "equal to or greater than E1 and less than E2", and "equal to or greater than E2". The same values as the first threshold value Th1, the second threshold value Th2, the second period T2, the second power A2, or the third power A3 shown in FIG. 6 are respectively associated with the hardness of the work object.

[0065] As described above, when the work object is harder and the load on the cutting tool 8 increases, the temperature of the electric motor 6 tends to rise. Therefore, in the third table, each third parameter may be determined so as to show the same magnitude relationship as the first table shown in FIG. 6. For example, in the case of the first threshold value Th1, it may be determined such that Th1-1 < Th1-2 < Th1-3. Thereby, similar to the example of FIG. 6, it is possible to balance the suppression of excessive temperature rise of the electric motor 6 and the ease of recognizing the continuation of the operation of the chainsaw 1.

[0066] (5) Number of stops For example, if the operator tends to strongly press the cutting tool 8 against the work object, the rotational speed does not reach the second threshold value Th2 or higher in the second period T2, and the operation A18 shown in FIG. 3 (stopping the power input to the electric motor 6) is performed, making the cutting tool 8 likely to stop. Therefore, the motor control unit 13 may change the fourth parameter used for controlling the rotational speed of the electric motor 6 based on the number of times the cutting tool 8 has stopped. The fourth parameter includes the first threshold value Th1, the second threshold value Th2, the second power A2, or the third power A3.

[0067] The motor control unit 13 stores the number of stops of the cutting tool 8, and each time the operation of A18 is performed, it performs a process of adding 1 to the stored number of stops. The motor control unit 13 changes the fourth parameter using a fourth table in which the stored number of stops of the cutting tool 8 is associated with each fourth parameter.

[0068] FIG. 9 is a diagram showing an example of the fourth table. In the example of FIG. 9, the number of stops F such as "less than F1", "F1 or more and less than F2", and "F2 or more" is shown. The same values as the first threshold Th1, the second threshold Th2, the second period T2, the second power A2, or the third power A3 shown in FIG. 6 are respectively associated with the number of stops F.

[0069] As the number of stops F of the cutting tool 8 increases, the load on the cutting tool 8 during operation tends to be high, so the temperature of the electric motor 6 also tends to be high. Therefore, in the fifth table, each fifth parameter may be determined so as to show the same magnitude relationship as the first table shown in FIG. 6. For example, in the case of the first threshold Th1, it may be determined such that Th1 - 1 < Th1 - 2 < Th1 - 3. Thereby, similar to the example of FIG. 6, it is possible to balance the suppression of excessive increase in the temperature of the electric motor 6 and the ease of recognizing the continuation of the operation of the chainsaw 1.

[0070] (6) Power saving mode The chainsaw 1 may be provided with a power saving mode. In that case, the motor control unit 13 controls the electric motor 6 by a first mode in which the cutting tool 8 is driven with normal power consumption and a second mode in which the cutting tool 8 is driven with less power consumption than the first mode. And in the case of the second mode, the motor control unit 13 reduces the third power A3 compared to the case of the first mode.

[0071] FIG. 10 is a graph showing an example of changes in input power to the electric motor 6. In the example of FIG. 10, the changes in input power shown in FIG. 4 are shown by a polygonal line A101 connecting the black circles. This polygonal line A101 represents changes in input power in the first mode. In FIG. 10, a polygonal line A102 represents changes in input power in the second mode.

[0072] In the first mode, as described in the embodiment, the input power during the second period T2 is set to the third power A3, thereby providing a driving force to the cutting tool 8 and allowing the operator to recognize that the electric motor 6 has not yet stopped.

[0073] Here, if the second mode is switched to the third power A3, which is the same as the first mode, by the second switching control, the worker will experience the same feel as when working in the first mode, which can lead to confusion as to whether to return to the first mode or the second mode. In the example of FIG. 10, the third power A3 is lower in the second mode than in the first mode, so the feel after the second switching control is different between the first mode and the second mode. As a result, the worker will be less likely to be confused as to which mode they are currently working in.

[0074] <Additional Notes> Furthermore, it may be provided in the following aspects.

[0075] (1) An electric work machine comprising a motor, an operating unit, a working unit, and a control unit, wherein the working unit is driven by the motor and acts on a work object, the operating unit is operated by a worker, and when the control unit receives an operation signal indicating the amount of operation to the operating unit, it controls the maximum power that can be input to the motor to a first power, and when the load on the working unit causes the rotational speed of the motor to fall below a first threshold, it performs first switching control to switch the maximum power to a second power that is smaller than the first power, when a first period has elapsed since the first switching control, it performs second switching control to switch the maximum power to a third power that is larger than the second power, and when the rotational speed of the motor becomes equal to or greater than a second threshold after performing the second switching control, it performs third switching control to switch the maximum power to the first power.

[0076] According to this aspect, heat generation from the motor can be suppressed.

[0077] (2) In the electric operating machine described in (1) above, the third electric power is smaller than the first electric power.

[0078] According to this aspect, work can be continued safely.

[0079] (3) In the electric work machine described in (1) or (2) above, the control unit stops the input of power to the motor if a second period has elapsed since the second switching control before the rotation speed of the motor becomes equal to or greater than a second threshold.

[0080] According to this aspect, excessive heat generation can be prevented even if the load on the working part is not relieved.

[0081] (4) In the electric work machine described in any one of (1) to (3) above, the control unit acquires temperature information indicating the temperature state of the motor, and changes a first parameter used to control the rotational speed of the motor based on the acquired temperature information, and the first parameter includes the first threshold value, the second threshold value, the second power, or the third power.

[0082] According to this embodiment, it is possible to achieve a balance between suppressing heat generation in the motor and driving force.

[0083] (5) In the electric working machine described in any one of (1) to (4) above, the motor operates on power supplied from a battery, and the control unit changes a second parameter used to control the rotational speed of the motor based on the remaining charge of the battery, and the second parameter includes the first threshold value, the second threshold value, the second power, or the third power.

[0084] According to this embodiment, it is possible to achieve a balance between the driving force and the operating time of the motor.

[0085] (6) In the electric work machine described in any one of (1) to (5) above, the control unit determines the hardness of the work object based on the history of the time from when the second switching control is performed to when the third switching control is performed, and changes a third parameter used to control the rotational speed of the motor based on the determined hardness, and the third parameter includes the first threshold value, the second threshold value, the second power, or the third power.

[0086] According to this embodiment, it is possible to achieve a balance between suppressing heat generation in the motor and driving force.

[0087] (7) In the electric working machine described in any one of (1) to (6) above, the control unit changes a fourth parameter used to control the rotational speed of the motor based on the number of times the working unit stops, and the fourth parameter includes the first threshold value, the second threshold value, the second power, or the third power.

[0088] According to this embodiment, it is possible to achieve a balance between suppressing heat generation in the motor and driving force.

[0089] (8) In the electric working machine described in any one of (1) to (7) above, the control unit controls the motor in a first mode in which the working unit is driven with normal power consumption and a second mode in which the working unit is driven with less power consumption than in the first mode, and in the second mode, the third power is less than in the first mode.

[0090] According to this aspect, it is possible to make it difficult to be confused about the current mode during work. Of course, this is not the case. Furthermore, the above-described embodiments and modifications may be combined in any desired manner.

[0091] Finally, while various embodiments of the present invention have been described, these are presented by way of example only and are not intended to limit the scope of the invention. The novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. The embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as defined in the appended claims. [Explanation of symbols]

[0092] 1: Chainsaw 2: Main body 3: Trigger 4: Battery 5: Inverter 6: Electric motor 7: Output shaft 8: Cutting tool 9: Blower fan 10: Control unit 11: Memory 12: Rotation speed detection section 13: Motor control unit 21: Front handle 22: Rear handle 23: Intake section 24: Exhaust section 31: Lever 32: Signal generation unit

Claims

1. An electric work machine, It comprises a motor, an operating unit, a working unit and a control unit, the working unit is driven by the motor to act on a work target, The operation unit is operated by an operator, The control unit When an operation signal indicating an operation amount to the operation unit is received, the maximum power that can be input to the motor is controlled to a first power; When a load on the working unit causes a rotation speed of the motor to become less than a first threshold value representing an overload state, a first switching control is performed to switch the maximum power to a second power that is smaller than the first power; When a first period has elapsed since the first switching control, a second switching control is performed to switch the maximum power to a third power that is greater than the second power and less than the first power; When the rotation speed of the motor becomes equal to or greater than a second threshold value after the second switching control is performed, a third switching control is performed to switch the maximum power to the first power.

2. The electric operating machine according to claim 1, The third power is less than the first power.

3. The electric operating machine according to claim 1, The control unit stops the input of power to the motor if a second period has elapsed since the second switching control before the rotational speed of the motor becomes equal to or greater than a second threshold.

4. The electric operating machine according to claim 1, The control unit acquires temperature information indicating the temperature state of the motor, and changes a first parameter used to control the rotation speed of the motor based on the acquired temperature information, and the first parameter includes the first threshold value, the second threshold value, the second power, or the third power.

5. The electric operating machine according to claim 1, The motor operates on power supplied from a battery, The control unit changes a second parameter used to control the rotational speed of the motor based on the remaining capacity of the battery, and the second parameter includes the first threshold, the second threshold, the second power, or the third power.

6. The electric operating machine according to claim 1, The control unit determines the hardness of the work object based on the history of the time from when the second switching control is performed to when the third switching control is performed, and changes a third parameter used to control the rotation speed of the motor based on the determined hardness, and the third parameter includes the first threshold value, the second threshold value, the second power, or the third power.

7. The electric operating machine according to claim 3, The control unit changes a fourth parameter used to control the rotational speed of the motor based on the number of times the working unit has stopped, and the fourth parameter includes the first threshold value, the second threshold value, the second power, or the third power.

8. The electric operating machine according to claim 1, The control unit controls the motor in a first mode in which the working unit is driven with normal power consumption and a second mode in which the working unit is driven with less power consumption than in the first mode, and in the second mode, the third power is less than in the first mode.

Images