JP2014050906A - Boosting type power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boosting type power tool capable of further improving convenience for a user.SOLUTION: A boosting type power tool includes a boosting power supply section 3 boosting power supply voltage Vb supplied from a battery pack 2 to generate prescribed voltage and outputting power having the generated prescribed voltage, and a motor 10 to be driven by the power output by the boosting power supply section 3. The boosting type power tool further includes a battery voltage detection section of a characteristic detection circuit 46 detecting the power supply voltage Vb before boosting. The boosting power supply section 3 adjusts the size of power to be output according to detection voltage detected by the battery voltage detection section.

Description

  The present invention relates to a step-up power tool that uses a battery as a power source.

  Such power tools often employ lithium-ion secondary batteries that have a large battery capacity and can be miniaturized as batteries that serve as power sources. The lithium ion secondary battery can maintain a good state for a long time by appropriately controlling charging and discharging so as to avoid overdischarge and overcharge. For example, Patent Literature 1 describes an example of such an electric tool.

  The electric tool described in Patent Literature 1 includes a battery pack made of a lithium ion secondary battery, a switching element that switches a current flowing through the motor, and a drive voltage generation unit that generates a drive voltage of the switching element. Then, the drive voltage generation means generates a drive voltage that is boosted to a voltage that can reliably drive the switching element when the voltage of the battery pack is low. Thereby, even when the voltage of the battery pack is low, the switching element is reliably driven by the drive voltage. That is, in the electric tool, current is passed from the battery to the motor when no overdischarge or overcurrent is detected, while supply of current from the battery to the motor is stopped when overdischarge or the like is detected.

JP 2011-161545 A

  The electric tool described in Patent Literature 1 can appropriately protect the battery from overdischarge and overcurrent. However, even if the operation is for protecting the battery, if the user does not know the remaining capacity of the battery, the user may feel that the power tool has suddenly stopped. In particular, power tools that increase power supply voltage and adjust power in recent years, so-called boost power tools, can stably supply output power, while lowering power supply voltage is recognized by users. It's getting harder.

  For example, as shown in FIG. 8, in the step-up power tool, the supply voltage Vs applied to the motor is kept constant regardless of fluctuations in the power supply voltage Vb. That is, the influence of the fluctuation of the power supply voltage Vb on the driving force of the motor is small. On the other hand, when it is detected that the power supply voltage Vb has decreased to the overdischarge detection level Vod at time tf, the boosting power tool is stopped, and the drive of the tool suddenly stops at this time tf.

  Further, as shown in FIG. 9, in the step-up power tool, it may be detected at time tf that the power supply voltage Vb is temporarily lowered to the overdischarge detection level Vod due to overload or the like. At this time, regardless of whether or not the power supply voltage Vb recovers in a short time, the boosting power tool stops boosting at time tf, so that the user has the impression that the driving of the tool suddenly stops, even temporarily. Will receive.

  This invention is made | formed in view of such a situation, The objective is to provide the pressure | voltage rise type electric tool which can improve a user's convenience more.

  The boost power tool of the present invention boosts a power supply voltage supplied from a power supply to generate a predetermined voltage, and outputs a power having the generated predetermined voltage, and the power supply outputs A step-up electric tool including a motor driven by electric power, and a detection unit that detects a power supply voltage before the boosting, wherein the power supply unit is in accordance with a detection voltage detected by the detection unit. , Adjusting the magnitude of the output power.

  In this step-up power tool, it is preferable that the power supply unit limits a current input from the power supply according to the detected voltage and adjusts the magnitude of the output power according to the limited current. .

-In this pressure | voltage rise type electric tool, it is preferable that the said power supply part adjusts the magnitude | size of the electric power to output by adjusting the voltage to output based on the detected voltage.
In this step-up power tool, the power supply unit is set with the power supply voltage that should reduce the output power as a regulation voltage, and the power supply unit has the detection voltage lower than the regulation voltage. It is preferable to reduce the output power.

  -In this pressure | voltage rise type electric tool, the said power supply voltage which should stop the said output electric power is set to the said power supply part as a stop voltage, and the said detection voltage is lower than the said stop voltage in the said power supply part When, it is preferable to stop the output of power.

  -In this pressure | voltage rise type electric tool, it is preferable that the said power supply part estimates the remaining capacity of the said power supply from the said detection voltage, and notifies this estimated remaining capacity to a user.

  According to the step-up electric tool of the present invention, an effect of improving user convenience can be obtained.

The circuit diagram which shows schematic structure of the circuit of the electric tool in 1st Embodiment which actualized the pressure | voltage rise type electric tool of this invention. The block diagram which shows schematic structure in the same embodiment. 4 is a graph showing an example of changes in power supply voltage and power supply current in the embodiment. 4 is a graph showing an example of changes in power supply voltage and supply voltage in the embodiment. In the same embodiment, the graph which shows in detail an example of the change of a supply voltage when a power supply current becomes a discharge regulation current value. In the same embodiment, the graph which shows in detail an example of the change of a supply voltage when a power supply current becomes a discharge regulation current value. The graph which shows an example of the change of a power supply voltage and a supply voltage about the electric tool in 2nd Embodiment which actualized the pressure | voltage rise type electric tool of this invention. The graph which shows typically the relationship between the power supply voltage and supply voltage by the conventional pressure | voltage rise type electric tool. The graph which shows typically the relationship between the power supply voltage and supply voltage by the conventional pressure | voltage rise type electric tool.

(First embodiment)
Hereinafter, a first embodiment of a power tool that embodies a step-up power tool according to the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the power tool includes a power tool main body 1 and a battery pack 2 that can be attached to and detached from the power tool main body 1. The electric power tool main body 1 includes a boost power source unit 3 that boosts a voltage applied from the battery pack 2 and a motor 10 that is supplied with electric power from the boost power source unit 3. The motor 10 is a direct current motor, and the switching element 50 (FET) connected in series to the boosting power source unit 3 controls the on / off of the power supplied from the boosting power source unit 3 to adjust the flowing current. The

  The battery pack 2 includes a secondary battery composed of one or a plurality of battery cells (for example, lithium ion batteries). The battery pack 2 includes first and second power terminals 21 and 22 that are electrically connected to the power tool body 1. In the present embodiment, the first power supply terminal 21 is a positive terminal and the second power supply terminal 22 is a negative terminal. Note that the power supply voltage of the battery pack 2 decreases due to a decrease in the remaining capacity. Further, since the remaining capacity of the battery pack 2 is approximately proportional to the output voltage (power supply voltage Vb) of the battery, the remaining capacity can be estimated from the power supply voltage Vb.

  The electric tool body 1 includes first and second input terminals 31 and 32 for electrically connecting the battery pack 2. In the present embodiment, the first input terminal 31 is a positive terminal and the second input terminal 32 is a negative terminal. That is, in the power tool body 1, the first power supply terminal 21 of the battery pack 2 is connected to the first input terminal 31, and the second power supply terminal 22 of the battery pack 2 is connected to the second input terminal 32. .

  The boost power supply unit 3 boosts the power supply voltage Vb applied from the battery pack 2 to a supply voltage Vs necessary for driving the motor 10, and supplies the motor 10 with supply power having the boosted supply voltage Vs. The step-up power supply unit 3 includes a series circuit including a coil 41 connected to the first input terminal 31 and a capacitor 44 connected to the second input terminal 32. Further, the boosting power supply unit 3 includes a diode 42 between the coil 41 and the capacitor 44 in order to prevent a backflow of current from the capacitor 44 to the coil 41. Further, the boosting power supply unit 3 includes a switching element 43 (FET) parallel to a series circuit composed of a diode 42 and a capacitor 44, and a control circuit 45 electrically connected to a control terminal of the switching element 43. Yes. The motor 10 is electrically connected between both terminals of the capacitor 44. That is, the boosting power supply unit 3 outputs the supply power of the supply voltage Vs from between both terminals of the capacitor 44 and supplies this supply power to the motor 10.

  The step-up power supply unit 3 includes a characteristic detection circuit 46 that measures the power supply current Ib (discharge current) and the power supply voltage Vb from the battery pack 2 and the supply current Is and the supply voltage Vs output to the motor 10. .

  As shown in FIG. 2, the characteristic detection circuit 46 includes a voltage detection unit 51 that detects a voltage and a current detection unit 54 that detects a current. The voltage detection unit 51 is connected between both terminals of the battery voltage detection unit 53 connected to the first and second input terminals 31 and 32 to detect the power supply voltage Vb and the capacitor 44 of the boost power supply unit 3 and supplied. And a load voltage detection unit 52 that measures the voltage Vs. The current detection unit 54 detects a power supply current Ib from a resistor (not shown) arranged between the battery pack 2 and the boost power supply unit 3 and supplies a current from a resistor (not shown) arranged between the boost power supply unit 3 and the motor 10. Is is detected.

  The characteristic detection circuit 46 is electrically connected to the control circuit 45. The characteristic detection circuit 46 outputs a signal corresponding to the power supply voltage Vb as a detection voltage detected by the battery voltage detection unit 53 and a signal corresponding to the supply voltage Vs detected by the load voltage detection unit 52 to the control circuit 45, respectively. . The characteristic detection circuit 46 outputs a signal corresponding to the power supply current Ib and the supply current Is detected by the current detection unit 54 to the control circuit 45.

  The control circuit 45 is electrically connected to the characteristic detection circuit 46, the control terminal of the switching element 43, and the control terminal of the switching element 50. That is, the control circuit 45 receives the power supply voltage Vb, the power supply current Ib, the supply voltage Vs, and the supply current Is value from the characteristic detection circuit 46.

  The control circuit 45 is configured as a microcomputer including an arithmetic processing unit, a storage device of ROM and RAM, and the like. The control circuit 45 stores a program used for various processes, various parameters necessary for the program process, and the like in a nonvolatile storage device (for example, ROM).

  In the present embodiment, the program includes a drive control program that controls driving of the motor 10 and a boost control program that generates supply power. The drive control program controls the drive of the motor 10 by adjusting the current flowing through the motor 10 in accordance with a user instruction. The boost control program performs PWM control (on / off control) of the switching element 43 in order to boost the power supply voltage Vb. The boost control program also controls the power supply current Ib that is discharged from the battery pack 2 in the PWM control.

  The various parameters include first to third overdischarge detection voltage values Vod1 to Vod3 as regulation voltages used for processing by the boost control program, and first to third discharge regulation current values Ic1 to Ic3. Yes.

  As shown in FIG. 3, the first to third overdischarge detection voltage values Vod1 to Vod3 are voltage values for determining overdischarge of the battery pack 2, and when the power supply voltage Vb is lower, the battery pack 2 is determined to be overdischarge. In the present embodiment, the magnitudes of the first to third overdischarge detection voltage values Vod1 to Vod3 are set such that Vod3> Vod2> Vod1. Then, the first overdischarge detection voltage value Vod1 as the stop voltage is a level at which the discharge of the battery pack 2 is stopped, and the second overdischarge detection voltage value Vod2 must immediately stop the discharge of the battery pack 2. It is a necessary level. Further, the third overdischarge detection voltage value Vod3 is a level at which the discharge of the battery pack 2 needs to be reduced.

  The first to third discharge regulation current values Ic1 to Ic3 are current values used for determining whether or not the power supply current Ib of the battery pack 2 is regulated. When the power supply current Ib is larger, the battery pack 2 It is determined that the power supply current Ib needs to be regulated. In the present embodiment, the magnitudes of the first to third discharge regulation current values Ic1 to Ic3 are set in a relationship of Ic1> Ic2> Ic3. The first discharge regulation current value Ic1 is the maximum current value that may be discharged from the battery pack 2, and the second discharge regulation current value Ic2 is discharged from the battery pack 2 at the initial stage of the voltage drop. It may be a current value. The third discharge regulation current value Ic3 is a current value that may be discharged from the battery pack 2 when the voltage drop has progressed.

  The control circuit 45 includes a voltage / current control unit 61 that converts the power supply voltage Vb into the supply voltage Vs by executing a boost control program. The voltage / current control unit 61 converts the power supply voltage Vb into the supply voltage Vs by performing PWM control of the switching element 43 based on a predetermined condition. More specifically, the control circuit 45 turns on the switching element 43 to store predetermined electromagnetic energy in the coil 41, and then turns off the switching element 43 to release electromagnetic energy from the coil 41. The voltage generated between the terminals of the capacitor 44 is boosted by the released electromagnetic energy, and the boosted voltage becomes the supply voltage Vs. That is, the control circuit 45 appropriately adjusts the ON / OFF timing of the switching element 43 and the duty ratio of the ON period / OFF period by PWM control. The control circuit 45 adjusts the power supply voltage Vb, the power supply current Ib, the supply voltage Vs, and the supply current Is to the predetermined voltage and current determined for the power tool.

  That is, the boost power supply unit 3 converts the power input from the battery pack 2 into the power supplied to the motor 10 based on the PWM control by the voltage / current control unit 61 of the control circuit 45. At this time, if sufficient power can be supplied to the motor 10 from the boosting power supply unit 3, the motor 10 can generate a rotational driving force (or rotational speed) corresponding to the user's operation. On the other hand, if sufficient power cannot be supplied from the boost power supply unit 3 to the motor 10, that is, if the power is insufficient, the motor 10 cannot generate the rotational driving force (or rotational speed) corresponding to the user's operation. .

  When the boost control program is executed, the control circuit 45 causes the power supply current Ib from the battery pack 2 to exceed the level set from any one of the first to third discharge regulation current values Ic1 to Ic3. Do not. The control circuit 45 compares the power supply current Ib detected by the characteristic detection circuit 46 with the set discharge regulation current value so that the power supply current Ib does not exceed the set discharge regulation current value. To do.

  As shown in FIGS. 3 and 4, the power tool of the present embodiment has a power supply before the time t1 (left side of the time t1 in the figure) if the power supply voltage Vb of the battery pack 2 is equal to or higher than a predetermined level. The current Ib does not reach the first discharge regulation current value Ic1. That is, when the power supply current Ib does not reach the first discharge regulation current value Ic1, the control circuit 45 can obtain necessary power from the battery pack 2. As a result, the control circuit 45 can cause the coil 41 to store predetermined electromagnetic energy required for boosting and boost the power supply voltage Vb to the supply voltage Vs.

  On the other hand, in the power tool of the present embodiment, when the voltage drop of the power supply voltage Vb of the battery pack 2 proceeds after time t1 (right side of time t1 in the figure), the power supply current Ib increases and the first discharge regulation current is increased. The level of value Ic1 is reached. That is, when the battery pack 2 is discharged, the control circuit 45 is required to boost the voltage from the battery pack 2 in order to control the duty ratio of the PWM control so as to suppress the power supply current Ib to the level of the first discharge regulation current value. Power cannot be obtained. Therefore, the control circuit 45 cannot store sufficient electromagnetic energy in the coil 41, and cannot increase the power supply voltage Vb to the supply voltage level Vo.

  In the present embodiment, the control circuit 45 sets the first to third discharge regulation current values Ic1 to Ic3 according to the power supply voltage Vb. The control circuit 45 sets the first discharge regulation current value Ic1 when the power supply voltage Vb is equal to or higher than the third overdischarge detection voltage value Vod3. The control circuit 45 sets the second discharge regulation current value Ic2 when the power supply voltage Vb is less than the third overdischarge detection voltage value Vod3 and equal to or greater than the second overdischarge detection voltage value Vod2. Furthermore, the control circuit 45 sets the third discharge regulation current value Ic3 when the power supply voltage Vb is less than the second overdischarge detection voltage value Vod2 and equal to or more than the first overdischarge detection voltage value Vod1. The control circuit 45 sets the power supply current Ib to “0” when the power supply voltage Vb is less than the first overdischarge detection voltage value Vod1.

  The control circuit 45 includes a switch unit 62 having a trigger switch that is a switch that can be operated by a user with a finger or the like. The trigger switch of the switch unit 62 includes ON / OFF for starting and stopping the motor 10, and the resistance value of the volume resistor changes according to the operation amount (trigger pull-in amount). The control circuit 45 detects a change in the operation amount of the trigger switch of the switch unit 62 and controls the current flowing through the motor 10 by controlling the switching element 50 based on the detected operation amount. For example, when the control circuit 45 detects that the operation amount of the trigger switch is small, the control circuit 45 performs control so that the current flowing through the switching element 50 becomes small. When the control circuit 45 detects that the operation amount of the trigger switch is large, the control circuit 45 flows through the switching element 50. Control to increase the current.

  That is, the boost power supply unit 3 adjusts the power supplied to the motor 10 by controlling the current that the control circuit 45 passes to the motor 10 according to the user's operation on the switch unit 62. The adjustment of power by the control circuit 45 includes starting and stopping of the motor 10 and adjustment of the rotation speed during operation.

  A tip tool (bit) (not shown) is attached to the rotating shaft of the motor 10 via a power transmission unit (not shown). Therefore, the electric tool is configured to rotate when the rotational driving force of the motor 10 is transmitted via the power transmission unit. As a result, the electric power tool can perform various types of processing on the workpiece, such as a screwdriver screwed into a screw or a drill as a tip tool forming a hole.

  Note that the electric tool receives a reaction force from the workpiece to be processed into the tip tool to be rotationally driven, and this reaction force is felt by a user who holds the electric tool. The reaction force received by the electric tool varies depending on the material of the workpiece, the type of the tip tool, the output of the motor, and the like. For this reason, the reaction force received by the electric power tool changes in accordance with the output of the motor when a specific workpiece is processed using a specific tip tool. For this reason, the user can estimate the output of the motor according to the reaction force transmitted (feeled) from the gripped power tool. Then, the user operates the trigger switch according to the reaction force felt by the hand and adjusts the output of the motor, thereby appropriately processing the workpiece with the electric tool. At this time, when the user feels that the reaction force received from the power tool is reduced even though the operation of reducing the output of the motor is not performed, it is assumed that the power supply has weakened, that is, the output power of the battery pack has decreased. To do. The user can also estimate the motor output reduction from the motor rotation speed and sound, the display and sound for notifying the output reduction, and the like.

Next, the operation of the step-up power supply unit 3 will be described in detail with reference to FIGS.
As shown in FIG. 3, as the battery pack 2 continues to be used, the power supply voltage Vb gradually decreases with time. On the other hand, the boosting power supply unit 3 requests the battery pack 2 for power necessary for storing electromagnetic energy in the coil 41 regardless of the decrease in the power supply voltage Vb. That is, when the boosting power supply unit 3 tries to obtain power from the battery pack 2, the power supply current Ib is increased in inverse proportion to the decrease in the power supply voltage Vb. That is, in the battery pack 2, the power supply current Ib increases as the power supply voltage Vb drops.

  As shown in FIGS. 3 to 5, the control circuit 45 performs control so that the power supply current Ib does not exceed the first discharge regulation current value Ic <b> 1 in order to maintain a good state of the battery pack 2 for a long time. That is, when the power supply current Ib reaches the level of the first discharge regulation current value Ic1 (time t1), the control circuit 45 maintains the power supply current Ib at the first discharge regulation current value Ic1 (time t1 to time t2). ).

  After time t1, the power supply voltage Vb continues to drop as the supply current Is (load current) accumulates, and the power supply current Ib is regulated to the first discharge regulation current value Ic1. Energy is reduced. For this reason, the supply voltage Vs falls below the supply voltage level Vo (time t1 to time t2).

  That is, after time t1, the motor 10 is supplied with the supply voltage Vs that is lower than the supply voltage level Vo, so that the driving force (or the rotational speed) of the motor 10 decreases. Such a decrease in driving force (or rotational speed) is felt as a change in response to the user holding the electric power tool main body 1, and the so-called battery in which the remaining capacity of the battery pack 2 is reduced by the user is weak. It can be recognized that it has become. For example, when the user recognizes that the battery has become weak, he / she uses the electric tool in consideration of the remaining battery level.

  As shown in FIGS. 3, 4 and 6, when time t2 is reached, the control circuit 45 detects that the power supply voltage Vb has dropped to the level of the third overdischarge detection voltage value Vod3, and the power supply current Ib Is maintained at the second discharge regulation current value Ic2 (time t2 to time t3).

  After time t2, the power supply voltage Vb continues to drop as the supply current Is (load current) accumulates, and the power supply current Ib is regulated to the second discharge regulation current value Ic2. Energy is reduced more. Therefore, the supply voltage Vs further decreases from the level at time t2 (time t2 to time t3).

  That is, after time t2, the motor 10 is supplied with the supply voltage Vs that is lower than the supply voltage level Vo, so that the driving force (or the rotational speed) of the motor 10 is further reduced. Such a decrease in driving force (or rotational speed) is perceived as a change in response to the user, and it can be recognized that the so-called battery has become weaker because the remaining capacity of the battery pack 2 has become smaller. For example, when the user recognizes that the battery has become weaker, the user uses the electric tool in consideration of the time to replace the battery.

  As shown in FIGS. 3 and 4, when time t3 is reached, the control circuit 45 detects that the power supply voltage Vb has dropped to the level of the second overdischarge detection voltage value Vod2, and supplies the power supply current Ib to the third power supply current Ib. The discharge regulation current value Ic3 is maintained (time t3 to time t4).

  After time t3, the power supply voltage Vb continues to drop as the supply current Is (load current) accumulates, and the power supply current Ib is regulated to the third discharge regulation current value Ic3. Energy is further reduced. For this reason, the supply voltage Vs further decreases from the level at time t3 (time t3 to time t4).

  That is, after time t3, the motor 10 is supplied with the supply voltage Vs that is further lower than the supply voltage level Vo, so that the driving force (or the rotational speed) of the motor 10 further decreases. Such a decrease in driving force (or rotation speed) is felt as a change in response to the user, and it can be recognized that there is almost no so-called battery in which the remaining capacity of power of the battery pack 2 is extremely small. For example, when the user recognizes that there is almost no battery, the user can stop using the power tool and quickly replace the battery.

  As shown in FIGS. 3 and 4, when time t4 is reached, the control circuit 45 detects that the power supply voltage Vb has dropped to the level of the first overdischarge detection voltage value Vod1, and stops the boosting operation. That is, the power supply current Ib is maintained at “0” (after time t4). Since the boosting power supply unit 3 stops the boosting operation, the supply voltage Vs becomes “0” (after time t4).

  That is, the step-up power tool cannot be used at time t4 because no electric power is supplied to the motor 10. As a user, if the electric tool stops suddenly during work, the user may feel that the tool has stopped suddenly or be in trouble. However, by notifying the remaining capacity of the battery pack 2 in stages, the user is less likely to receive the impression that the tool suddenly stops, and can schedule a battery replacement time according to the convenience of work. It becomes like this.

  Further, since the boost power supply unit 3 decreases the supply voltage Vs stepwise or gradually until the boost operation is stopped, a temporary decrease in the power supply voltage Vb due to a temporary overload is immediately boosted. The possibility of stopping the operation is also reduced. That is, since the voltage drop of the power supply voltage Vb is suppressed by reducing the power supply current Ib, the possibility that the power supply voltage Vb is lowered to the stop voltage (the first overdischarge detection voltage value Vod1) at once is reduced. Is done. Therefore, the possibility that the motor 10 is stopped due to the temporary decrease in the power supply voltage Vb is reduced, and the motor 10 is driven even if the output is low, so that convenience is improved.

As described above, according to the step-up electric tool of the present embodiment, the effects listed below can be obtained.
(1) When the power supply voltage Vb decreases due to a decrease in the remaining capacity of the battery pack 2 or the like, the supply power output from the boost power supply unit 3 decreases according to the decrease in the power supply voltage Vb. For example, the output of the motor 10 also decreases as the power output from the boost power supply unit 3 is adjusted to be small. The decrease in the output of the motor 10 changes the response to the user. The user can detect a decrease in the driving force (or the number of rotations) of the step-up power tool from the change in response, and can estimate that the remaining capacity of the battery pack 2 is decreasing. As a result, the user can use the step-up electric tool in consideration of the remaining capacity of the battery pack 2, and thus the user is less likely to receive the impression that the tool suddenly stops. Thus, since the user can recognize that the remaining capacity of the battery pack 2 has decreased, the convenience of the user who uses the step-up power tool is improved.

  (2) As the power supply current Ib is limited, the power output from the boost power supply unit 3 naturally decreases. As a result, power corresponding to the remaining capacity of the battery pack 2 is output.

(3) Since the supply power to be output when the power supply voltage Vb is lower than the first to third overdischarge detection voltage values Vod1 to Vod3 is reduced, the output power can be easily adjusted.
(4) Since overdischarge of the battery pack 2 is prevented based on the first overdischarge detection voltage value Vod1, it is easy to prevent overdischarge and overcurrent of the battery pack 2 of the electric tool.

(Second Embodiment)
Next, a second embodiment of the step-up electric tool according to the present invention will be described with reference to FIG.

  The present embodiment is different from the first embodiment in that the boost power supply unit 3 changes the level of the supply voltage Vs based on the overdischarge detection voltage value. The same reference numerals are assigned to the same components, and the detailed description is omitted for convenience of description.

  As shown in FIG. 7, the control circuit 45 sets the first to third limit voltage values Vc1 to Vc3 as the regulation values of the supply voltage Vs according to the power supply voltage Vb. The magnitudes of the first to third limit voltage values Vc1 to Vc3 are set to have a relationship of Vc1> Vc2> Vc3. The first limit voltage value Vc1 is the same value as the supply voltage level Vo. The control circuit 45 sets the first limit voltage value Vc1 when the power supply voltage Vb is equal to or higher than the third overdischarge detection voltage value Vod3. The control circuit 45 sets the second limit voltage value Vc2 when the power supply voltage Vb is less than the third overdischarge detection voltage value Vod3 and is equal to or greater than the second overdischarge detection voltage value Vod2. Furthermore, the control circuit 45 sets the third limit voltage value Vc3 when the power supply voltage Vb is less than the second overdischarge detection voltage value Vod2 and equal to or greater than the first overdischarge detection voltage value Vod1. The control circuit 45 sets the supply voltage Vs to “0” when the power supply voltage Vb is less than the first overdischarge detection voltage value Vod1.

That is, the control circuit 45 performs PWM control so that the supply voltage Vs becomes a set limit voltage value.
Next, the operation of the boost power supply unit 3 will be described.

The control circuit 45 sets the supply voltage Vs to the first limit voltage value Vc1 when the power supply voltage Vb is equal to or higher than the third overdischarge detection voltage value Vod3.
When the control circuit 45 detects that the power supply voltage Vb becomes less than the third overdischarge detection voltage value Vod3 at time t11, the control circuit 45 sets the supply voltage Vs to the second limit voltage value Vc2. As a result, an increase in the power supply current Ib is suppressed.

  When the control circuit 45 detects that the power supply voltage Vb becomes less than the second overdischarge detection voltage value Vod2 at time t12, the control circuit 45 sets the supply voltage Vs to the third limit voltage value Vc3. As a result, an increase in the power supply current Ib is suppressed.

  When the control circuit 45 detects that the power supply voltage Vb becomes less than the third overdischarge detection voltage value Vod1 at time t13, the control circuit 45 sets the supply voltage Vs to “0”. This prevents overdischarge of the battery pack 2.

  Thus, the supply voltage Vs is reduced based on the first to third overdischarge detection voltage values Vod1 to Vod3, so that an increase in the power supply current Ib from the battery pack 2 is suppressed. As a result, overdischarge of the battery pack 2 can be prevented, and overdischarge can be regulated in stages.

  Further, as the supply voltage Vs decreases, the supply power also decreases, so the driving force (or rotation speed) of the motor 10 also decreases. As a result, the driving force (or rotational speed) of the motor 10 can be reduced stepwise. That is, the user can feel a decrease in the remaining capacity of the battery pack 2 from the driving force of the motor 10 or the like (reaction force of the electric power tool body).

  As described above, according to the step-up electric tool of the present embodiment, in addition to the effects (1), (3), (4) described in the first embodiment, the effects listed below. Can be obtained.

  (5) Based on the decrease in the power supply voltage Vb, the supply voltage Vs of the power output from the boost power supply unit 3 is decreased. That is, the magnitude of the power output from the boost power supply unit 3 is reduced. As a result, power corresponding to the remaining capacity of the battery pack 2 is output.

(Other embodiments)
In addition, each said embodiment can also be implemented with the following aspects.
In each of the above embodiments, the case where the remaining capacity of the battery pack 2 is notified by the driving force of the motor 10 or the like is illustrated. However, in addition to this, the remaining capacity of the battery pack may be notified visually, audibly, or a combination thereof. For this notification, the calculation result in the control circuit in each of the above embodiments may be used, or the value of the remaining capacity of the battery pack calculated from the power supply voltage may be used. For visual transmission, for example, display of characters and graphics on the display device, LED for notification of low remaining capacity, a level meter, and the like may be used. For auditory transmission, for example, sound or voice may be output from a speaker.

  Thereby, the user can confirm the decrease in the remaining capacity of the battery pack by such notification. As a result, the user can more reliably recognize the remaining capacity of the battery pack 2. That is, user convenience is further improved.

  In each of the above embodiments, the case where a trigger switch that changes the resistance value of the volume resistance is provided in the switch unit 62 is illustrated. However, the present invention is not limited to this, and a known structure other than the volume resistor can be applied to the switch unit as long as the switch unit can detect a user operation. Thereby, the improvement of the design freedom of a pressure | voltage rise type electric tool is achieved.

  In each of the above embodiments, the case where voltage or current is measured has been exemplified. However, if the voltage or current can be measured, a known method may be applied as a voltage or current measurement method. Can do. Thereby, the improvement of the design freedom of a pressure | voltage rise type electric tool is achieved.

  In each of the above embodiments, the case where three first to third overdischarge detection voltage values Vod1 to Vod3 are set is illustrated. However, the present invention is not limited to this, and any overdischarge detection voltage value may be used as long as the number of overdischarge detection voltage values is two or more because it is only necessary to detect overdischarge stepwise. Thereby, the improvement of the design freedom of a pressure | voltage rise type electric tool is achieved. Moreover, since the adjustment precision of the power supply performed according to overdischarge (remaining capacity) goes up, a user's convenience can also be improved.

  In the first embodiment, the case where three first to third discharge regulation current values Ic1 to Ic3 are set is illustrated. However, the present invention is not limited to this, and it is only necessary to be able to regulate the discharge current in a stepwise manner. Thereby, the improvement of the design freedom of a pressure | voltage rise type electric tool is achieved. Moreover, since the adjustment precision of the power supply performed according to remaining capacity increases, a user's convenience can also be improved.

  In each of the above embodiments, the case where the battery pack 2 is detachable from the power tool main body 1 is illustrated. However, the present invention is not limited to this, and the battery pack is not limited to a detachable configuration as long as power can be supplied to the power tool body, and even if an external battery pack is connected by an electric wire or non-contact power supply or the like, power is supplied. Good. In addition, the battery pack may be fixed to the power tool main body and not attachable / detachable. In this case, the battery pack may be charged by connecting the power tool body to a charger. Further, an external power source may be connected to the power tool main body to drive the power tool and to charge the battery pack.

As a result, the application range of the step-up power tool and the degree of freedom in design can be increased.
In each of the above embodiments, the case where the battery pack 2 is composed of a lithium ion battery is exemplified. However, the present invention is not limited to this, and the battery pack may be a secondary battery other than a lithium ion battery, such as a nickel cadmium battery or a nickel metal hydride battery. Thereby, the improvement of the design freedom of a rechargeable electric tool is achieved.

  In each of the above embodiments, the case where the battery pack 2 is a secondary battery has been illustrated, but the present invention is not limited thereto, and may be a primary battery. Thereby, the improvement of the design freedom of a rechargeable electric tool is achieved.

  DESCRIPTION OF SYMBOLS 1 ... Electric tool main body, 2 ... Battery pack, 3 ... Boosting power supply part, 10 ... Motor, 21 ... 1st power supply terminal, 22 ... 2nd power supply terminal, 31 ... 1st input terminal, 32 ... 2nd Input terminal 41 ... Coil 42 ... Diode 43 ... Switching element 44 ... Capacitor 45 ... Control circuit 46 ... Characteristic detection circuit 50 ... Switching element 51 ... Voltage detection unit 52 ... Load voltage detection unit 53 Battery voltage detection unit 54 Current detection unit 61 Voltage current control unit 62 Switch unit Ib Power supply current Is Supply current Vb Power supply voltage Vo Supply voltage level Vs Supply voltage Vod: Overdischarge detection level, Ic1 to Ic3: First to third discharge regulation current values, Vc1 to Ic3: First to third limit voltage values, Vod1 to Vod3: First to third overdischarge detection voltages value.

Claims (6)

A power supply unit configured to boost a power supply voltage supplied from a power supply to generate a predetermined voltage, output power having the generated predetermined voltage, and a motor driven by the power output from the power supply unit. A step-up power tool,
A detection unit for detecting a power supply voltage before boosting;
The power supply unit adjusts the magnitude of the output power in accordance with a detection voltage detected by the detection unit. The boost power tool according to claim 1, wherein the power supply unit limits a current input from the power supply according to the detected voltage, and adjusts the magnitude of the output power according to the limited current. The step-up electric tool according to claim 1, wherein the power supply unit adjusts the output voltage based on the detected voltage to adjust the magnitude of the output power. In the power supply unit, the power supply voltage that should reduce the output power is set as a regulation voltage, and the power supply unit reduces the output power when the detection voltage is lower than the regulation voltage. The pressure | voltage rise type electric tool as described in any one of Claims 1-3. The power supply unit is configured such that the power supply voltage to stop the output power is set as a stop voltage, and the power supply unit stops outputting power when the detection voltage is lower than the stop voltage. Item 5. The step-up electric tool according to any one of Items 1 to 4. The boost power tool according to any one of claims 1 to 5, wherein the power supply unit estimates a remaining capacity of the power supply from the detected voltage and notifies the user of the estimated remaining capacity.

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