JP4915569B2 - Electric tool drive control circuit, electric tool - Google Patents

Description

  The present invention relates to an electric tool powered by a motor.

  Conventionally, a hand-held electric tool as disclosed in, for example, Japanese Patent Laid-Open No. 2005-137134 is widely known, and a circuit shown in FIG. 15 is used as a drive control circuit for a motor mounted on such an electric tool. is there.

  The drive control circuit 6 ′ shown in FIG. 15 includes a power source E ′ that supplies electric power to the motor M ′ and a flywheel that regenerates the counter electromotive voltage to the motor M ′ when the counter electromotive voltage is generated in the motor M ′. A diode D ′, a trigger switch SW 1 ′ that is turned on when operation of an operation button (not shown) is started, a volume switch SW 2 ′ that outputs a voltage signal corresponding to the operation amount of the operation button, and power supply to the motor M ′ The switching element SW3 ′ for switching on and off is compared with the power supply voltage and the back electromotive voltage generated in the motor M ′, and an H (high) or L (low) digital signal is output according to the comparison result. PWM control of the switching operation of the comparator CMP ′ and the switching element SW3 ′, and the output signal of the comparator CMP ′ and the volume switch SW And a 'in response to the output signal of the control unit 7 for changing the duty of the PWM signal'.

In this circuit, when the back electromotive voltage generated in the motor M ′ by the load exceeds the reference voltage, an H (high) digital signal (comparison signal) is output from the comparator CMP ′, and the control unit 7 ′ Increase.
JP 2005-137134 A

  By the way, when this drive control circuit is configured to increase the on-duty of the PWM signal without limitation while the H (high) digital signal is acquired from the comparator CMP ′, the following problems can be considered. .

  In other words, when the decomposition width of the control unit 7 ′ is large (the processing capability of the control unit 7 ′ is low), compared with the case where the control unit 7 ′ having a small decomposition width (high processing capability) is employed, The adjustment pitch of the duty is rough, and when the duty is changed, a step is likely to occur in the rotation operation of the motor M ′. Further, in the low-speed rotation region, since the ratio of the amount of change of the duty with respect to the current duty is relatively large, especially when the control unit 7 ′ having a large decomposition width is employed, coupled with the roughness of the duty adjustment pitch, Due to the change of the duty, the rotational operation of the motor M ′ varies stepwise relatively in a short time. Such a change in duty appears as an unstable behavior of the motor M ′, which may give a user a sense of discomfort.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a drive control circuit and an electric tool that can perform rotation control of a motor that does not give the user a sense of incongruity.

According to the first aspect of the present invention, when a counter electromotive voltage is generated in the motor in the drive control circuit of the electric tool for controlling the driving of the motor of the electric tool, the counter electromotive voltage and a predetermined reference voltage are A comparison unit that outputs a comparison signal according to the comparison result, a switching element for switching on / off of power supply from a power source to the motor, and an output of the motor are set in a desired state A volume switch that outputs a signal of a level corresponding to an operation amount of an input operation unit for performing an input, and a PWM whose duty is changed according to a comparison signal output from the comparison unit and an output signal of the volume switch A control unit that outputs a signal and controls a switching operation of the switching element, and a restriction on a change in duty of the PWM signal by the control unit Change but are set for each of a plurality of signal levels in accordance with the output signal of the volume switch, wherein, within limits defined by the limit value, the duty of the PWM signal to be output to the switching element It is something to be made.

According to the present invention, a limit value related to a change in duty of the PWM signal by the control unit is set for each of a plurality of signal levels according to the output signal of the volume switch, and within a limit range determined by the limit value. Since the duty of the PWM signal output to the switching element is changed, it is possible to prevent or suppress the duty from changing greatly. Therefore, in the low-speed rotation region, it is possible to prevent or suppress the rotation operation of the motor M from being relatively stepped and fluctuating in a short time due to a change in duty.

According to a second aspect of the present invention, in the drive control circuit for the electric power tool according to the first aspect, the duty of the PWM signal output to the switching element as a limit value related to a change in the duty of the PWM signal by the control unit. An upper limit value is set for each of a plurality of signal levels according to the output signal of the volume switch.

  According to the present invention, for each output signal level of the volume switch, the duty of the PWM signal output to the switching element increases only to a certain upper limit value. Therefore, it is possible to prevent or suppress the duty from changing greatly in the low speed rotation region.

Invention according to claim 3, in the drive control circuit of the power tool according to claim 2, in infinitesimal range the intensity of the output signal is predetermined from 0 of the volume switch, the switching element The amount of increase in the duty of the PWM signal to be output to is set to 0.

In infinitesimal of a predetermined range from the output intensity of the signal is 0 the volume switch, even those duty change in the PWM signal is small, a large proportion of the change to the current duty is relatively In some cases, the rotational operation of the motor changes drastically and gives a sense of incongruity to the user.

Therefore, as in the present invention, the infinitesimal range the intensity of the output signal is predetermined from 0 of the volume switch, an increase of the duty of the PWM signal output to the switching element is set to 0 it is, it is possible to prevent or inhibit the rotation of the motor changes abruptly increases in infinitesimal range the intensity of the output signal is predetermined from 0 of the volume switch.

According to a fourth aspect of the present invention, in the drive control circuit for the electric power tool according to the first aspect, the duty of the PWM signal output to the switching element is set as a limit value related to a change in the duty of the PWM signal by the control unit. An upper limit value for the increase rate is set for each of a plurality of signal levels according to the output signal of the volume switch.

  According to the present invention, for each output signal level of the volume switch, the increasing rate of the duty of the PWM signal output to the switching element increases only to a certain increasing rate. Therefore, it is possible to prevent or suppress the duty from changing (abruptly) at a large increase rate in the low-speed rotation region.

The invention according to claim 5, in the drive control circuit of the power tool according to claim 4, in infinitesimal range the intensity of the output signal is predetermined from 0 of the volume switch, the switching element The increase rate of the duty of the PWM signal to be output is set to 0.

According to the present invention, the infinitesimal range the intensity of the output signal is predetermined from 0 of the volume switch, the duty rate of increase of the PWM signal output to the switching element by setting to zero Similarly to the third aspect of the invention, it is possible to prevent the rotational operation of the motor from changing drastically in the range.

  The invention according to claim 6 is an electric tool comprising a motor and a drive control circuit for controlling driving of the motor, wherein the drive control circuit is the drive control circuit according to any one of claims 1 to 5. It is a power tool.

  According to the present invention, in the electric power tool, the operation according to any one of claims 1 to 5 can be obtained.

  According to the present invention, it is possible to prevent or suppress a drastic change in duty. Thereby, it is possible to prevent or reduce the occurrence of unstable behavior of the motor that gives the user a sense of incongruity in the low-speed rotation range.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted. FIG. 1 is an external perspective view showing an example of a configuration of an embodiment according to the present invention.

As shown in FIG. 1, the electric tool 1 includes, for example, a tool part 2 constituting an impact driver and a battery pack 3 attached to the tool part 2. The tool part 2 includes a rotating part 4 to which a tool such as a driver or a drill (not shown) is attached, and an operation button 5. The actuating button 5, by being pushed by the user, the main power switch for supplying an output supply voltage V _E from the battery E in the battery pack 3 (see FIG. 2) to the control unit 7 and the motor M (see FIG. 2) It is. The actuating button 5 is for turning on the trigger switch SW1 (see FIG. 2) when the push is started and starting the supply of power from the battery E to the motor M, and changing the supply power according to the push amount.

  FIG. 2 is a diagram showing a power supply circuit 6 mounted on the electric tool 1. As shown in FIG. 2, the power supply circuit 6 includes a battery E, a motor M, a flywheel diode D, a trigger switch SW1, a volume switch SW2, a switching element SW3, a comparator CMP, and a control unit 7. Have

  The battery E is a power source of the motor M mounted on the battery pack 3. The motor M is connected in series to the battery E via the trigger switch SW1. The flywheel diode D is connected in parallel to the motor M with respect to the battery E so that the anode (anode) is connected to a terminal on the battery E side of the motor M.

The trigger switch SW1 is a switch that is turned on when the operation button 5 is pushed. The volume switch SW2 includes a resistance element R1 and a terminal T connected to the control unit 7, and the position where the terminal T is connected to the resistance element R1 changes according to the amount of pressing of the operation button 5, output voltage to the control unit 7 for generating by using the power supply voltage V _E (hereinafter, referred to as volume voltage) is a switch that is configured to vary.

  The switching element SW3 is composed of, for example, an FET, the control terminal is connected to the control unit 7, the input terminal is connected to the motor M, and the output terminal is connected to the negative electrode of the battery E. The control unit 7 turns on and off the PWM (Pulse Width Modulation) is controlled. When the on-duty of the PWM signal output from the control unit 7 changes, the on-time of the switching element 3 per cycle changes, and thereby the amount of power supplied to the motor M is controlled.

In the comparator CMP, the terminal on the battery E side of the motor M is connected to the inverting input terminal (−), the anode of the flywheel diode D is connected to the non-inverting input terminal (+), and the non-inverting input terminal (+). and the counter electromotive voltage of the motor M to be input, depending on the magnitude of the supply voltage V _E as an example of the reference voltage, and outputs a digital signal of H (high) or L (low).

That is, when the switching element SW3 is switched from on to off, a counter electromotive voltage is generated in the motor M. The counter electromotive voltage increases momentarily and then gradually decreases. On the other hand, the comparator CMP, the counter electromotive voltage is at greater than the supply voltage V _E, and outputs a digital signal of H (high) to the control unit 7. Here, in one cycle of comparison operation of the comparator CMP, at no load, as shown in FIG. 3, shorter than the time period that the counter electromotive voltage exceeds the power supply voltage V _E is below the power source voltage V _E, in the present embodiment, the comparison operation timing by the comparator CMP, so that delaying at least the time that the counter electromotive voltage exceeds the power supply voltage V _E. Therefore, when there is no load, as shown in FIG. 4, an L (low) digital signal is always output from the comparator CMP at a constant period.

On the other hand, if there is a load, as shown in FIG. 5, no load as opposed to the said counter electromotive voltage power supply voltage times beyond V _E significantly longer than the time below the power supply voltage V _E. Therefore, as shown in FIG. 6, when the comparator CMP performs the comparison operation at the above-described comparison operation timing, an H (high) digital signal is output from the comparator CMP at a constant period.

  The control unit 7 is composed of, for example, a microcomputer incorporating a ROM for storing a control program, a RAM for temporarily storing data, and the like, and functionally includes a table storage unit 8 and a PWM signal output unit 9.

  The table storage unit 8 stores in advance a correspondence relationship between the volume voltage at no load and the on-duty in the PWM signal in a table format. As shown in FIG. 7, the on-duty of the PWM signal is set to increase as the volume voltage increases, and the table storage unit 8 stores this relationship in a table format in advance.

  The PWM signal output unit 9 generates a PWM signal having a duty corresponding to the volume voltage output from the volume switch SW2 and the comparison signal output from the comparator CMP, and outputs the PWM signal to the switching element SW3. It is.

  That is, as described above, the PWM signal output unit 9 does not output an H (high) digital signal from the comparator CMP when there is no load, and thus corresponds to the volume voltage corresponding to the amount of pressing of the operation button 5. The on-duty is derived with reference to the table in the table storage unit 8, and the derived on-duty PWM signal is output to the switching element SW3.

  On the other hand, when there is a load, the PWM signal output unit 9 generates a PWM signal with the duty corresponding to the current volume voltage stored in the table of the table storage unit 8 as an initial value, and outputs H (high) from the comparator CMP. In response to this digital signal, the on-duty of the PWM signal output to the switching element SW3 is increased.

  Here, if the on-duty of the PWM signal is increased without limitation while an H (high) digital signal is acquired from the comparator CMP, the duty is applied to the load as shown by the solid line in FIG. 7B. Although the fluctuation varies within the corresponding fluctuation range, especially when the disassembly width of the control unit 7 is large (the processing capability of the control unit 7 is low), the fluctuation range of the duty becomes very large.

  In other words, when the disassembly width of the control unit 7 is small (the processing capability of the control unit 7 is high), the on-duty from 0 (%) to 100 (%) is controlled in, for example, 1024 steps. When the disassembly width of the unit 7 is large, the on-duty from 0 (%) to 100 (%) is controlled in, for example, 256 levels. When the disassembly width of the control unit 7 is large, the disassembly width of the control unit 7 is The amount of change in duty per stage is larger than when it is small. As a result, when the disassembly width of the control unit 7 is large, the duty cannot be increased or decreased more finely as the disassembly width of the control unit 7 is small. Therefore, when the duty is changed, the rotational operation of the motor M is stepped. This is likely to occur, and the duty fluctuation range becomes larger than when the disassembly width of the control unit 7 is small.

  Even in the case where the disassembly width of the control unit 7 is small, in the high-speed rotation range of the motor M, the ratio of the duty change amount to the current duty is relatively small. Therefore, when the duty is changed, even if the amount of change (absolute amount) of the duty is relatively large, the change in the duty appears as a change in the operation of the motor M that makes the user feel uncomfortable. It is thought that there are few.

  However, in the low-speed rotation range of the motor M, the ratio of the duty change amount to the current duty is relatively large. Therefore, when the duty is changed, even if the amount of change (absolute amount) of the duty is small, the change of the duty appears as a change in the operation of the motor M that makes the user feel uncomfortable. Cheap.

  Furthermore, in order to prevent erroneous control of the motor M, the control unit 7 is designed to perform control to increase the duty only when, for example, a comparison signal for increasing the duty is continuously received from the comparator CMP a predetermined number of times. If the content of the comparison signal changes, the control unit 7 does not change the duty promptly (immediately after the change) by the control unit 7, and the control unit 7 controls the duty. There may be a delay with respect to the content change of the comparison signal (switching of the comparison result). In particular, when the disassembly width of the control unit 7 is large, the duty control cycle is longer than when the disassembly width of the control unit 7 is small. Therefore, the PWM signal is smaller than when the disassembly width of the control unit 7 is small. When the duty is changed, there is a high possibility that this will appear as a change in the operation of the motor M that gives the user of the electric tool 1 a sense of discomfort.

  In this way, particularly when the controller 7 having a large disassembly width is used, when the duty is changed without limitation, it is possible to give a sense of incongruity to the user of the electric tool 1 particularly in the low-speed rotation range of the motor M. In this embodiment, the upper limit value of the on-duty is set according to the volume voltage. In particular, in the low-speed rotation range, the upper limit value of the on-duty (variation range) is smaller than that in the high-speed rotation range. It is set.

  For example, as shown in FIGS. 8 and 9, the volume voltage that can be output from the volume switch SW2 is divided into five stages, and when no load is applied, the first and second stages are turned on from the lowest volume voltage. Assume that the duty “10” is set to the on-duty “20” for the third and fourth stages, and the on-duty “30” for the fifth stage. Note that “1” to “5” in the volume voltage column shown in FIG. 8 indicate the number of steps of the volume voltage.

  In this case, in the present embodiment, “20” is set for the first stage and the second stage from the smaller volume voltage, and “40” is set for the third stage to the fifth stage as the upper limit of the increase amount of the on-duty. Is set. That is, when the volume voltage is in the first stage, the on-duty can be increased or decreased in a range from 10% to 30 (= 10 + 20)%. When the volume voltage is in the third stage, the on-duty is increased from 20% to 40 (= 20 + 20)%. It means that it can be increased or decreased within the range. The upper limit value of the on-duty set according to the volume voltage is stored in the table storage unit 8.

  As described above, by limiting the increase / decrease range of the on-duty in the PWM signal, it is possible to suppress the occurrence of a situation in which the sudden duty change occurs and the rotational speed of the rotating unit 4 changes suddenly. . Particularly, by setting the upper limit value of the on-duty smaller in the low-speed rotation range than in the high-speed rotation range (ΔD1 <ΔD2 shown in FIG. 9), the rotation speed of the rotating unit 4 changes abruptly in the low-speed rotation range. Can be prevented from occurring. As a result, it is possible to prevent or suppress the user of the electric tool 1 from feeling uncomfortable.

FIG. 10 is a flowchart showing the operation of each unit in the power supply circuit 6. As shown in FIG. 10, the load on the motor M is applied (step # 1), the counter electromotive voltage generated in the motor M is changed (step # 2), when the back electromotive voltage exceeds the power supply voltage V _E ( Step # 3) An H (high) digital signal is output from the comparator CMP (step # 4). The control unit 7 receives this digital signal (step # 5), and the control unit 7 changes the duty within a range up to a preset upper limit value (step # 6).

  As described above, by setting the upper limit value of the on-duty according to the volume voltage and limiting the increase / decrease range of the on-duty in the PWM signal, it is possible to suppress the occurrence of a sudden change in the operation of the motor M. As a result, it is possible to prevent or suppress an uncomfortable feeling to the user of the electric tool, particularly in the low-speed rotation range of the motor M, particularly when the controller 7 having a large disassembly width is used.

  In this case, in addition to or in place of the above-described embodiment, the following modifications may be employed.

  (1) In the first embodiment, the upper limit value of the increase amount of the duty according to the volume voltage is set, and the duty is changed within the range up to the upper limit value. An upper limit value of the duty increase rate may be set.

  FIG. 12 is a graph showing the upper limit value of the duty increase rate when there is no load, and FIGS. 13 and 14 are graphs and diagrams showing the upper limit value of the duty increase rate when there is a load.

  As shown in FIG. 12, the upper limit value of the duty increase rate is constant when there is no load. Therefore, the PWM signal output unit 9 changes the duty in the range up to the upper limit value of the increase rate for each control cycle by the control unit 7 regardless of the volume voltage when there is no load.

  On the other hand, as shown in FIGS. 13 and 14, when there is a load, the upper limit value of the duty increase rate is set according to the volume voltage. For example, if the preset volume voltage is divided into 5 stages and the duty at each stage of the volume voltage is set in the same manner as in FIG. The upper limit value of the on-duty increase rate is set to “2” for the first and second stages, and “4” for the third to fifth stages. That is, when the volume voltage is in the first stage, the on-duty can be increased in a range of up to 2% per control cycle by the control unit 7, and when the volume voltage is in the third stage, up to 4% per the control cycle. It means that it can be increased in the range of. The upper limit value of the on-duty increase rate set according to the volume voltage is stored in the table storage unit 8.

  Thus, by setting the upper limit value of the duty increase rate, it is possible to suppress the occurrence of a situation in which a sudden change in the duty occurs and the rotation speed of the rotating unit 4 changes abruptly. . In particular, by setting the upper limit value of the on-duty increase rate smaller in the low-speed rotation range than in the high-speed rotation range (Δd1 <Δd2 shown in FIG. 13), the rotation speed of the rotating unit 4 is rapidly increased in the low-speed rotation range. Can be prevented from occurring. As a result, it is possible to prevent or suppress the user of the electric tool 1 from feeling uncomfortable.

  (2) A minute range from 0 (V) to a predetermined minute level is a large change in operation of the motor M that can give the user a sense of discomfort even if the duty of the PWM signal changes minutely. Probability is high. That is, in the minute range, the rate of change with respect to the current duty becomes very large, and the rotational operation of the motor may change drastically and give the user a sense of discomfort. Therefore, for the minute range, by setting the increase amount from the initial value of the duty in the PWM signal to 0, or the increase rate from the initial value to 0, the motor that can give the user a sense of incongruity in the minute range It is possible to prevent or suppress the occurrence of a large operation change of M.

It is an external view which shows an example of a structure of the electric tool which concerns on one Embodiment of this invention. It is a figure which shows the electric power supply circuit mounted in an electric tool. It is a figure which shows the magnitude relationship between the back electromotive force voltage at the time of no load, and a power supply voltage. It is a figure which shows the waveform of the output signal of the comparator at the time of no load. It is a figure which shows the magnitude relationship between the back electromotive force voltage and power supply voltage when there exists load. It is a figure which shows the waveform of the output signal of a comparator when there exists load. (A) is a graph which shows the relationship between the volume voltage at the time of no load, and on-duty, (b) is a figure showing the fluctuation | variation of on-duty when there exists load. It is explanatory drawing of the characteristic part of this case. It is a figure which shows the characteristic part of this case. It is a flowchart which shows operation | movement of an electric power supply circuit. It is a figure which shows the characteristic part of this case. It is a figure showing the upper limit of the increase rate of the duty at the time of no load. It is a figure which shows the characteristic part of this case. It is explanatory drawing of the characteristic part of this case. It is explanatory drawing of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric tool 7 Control part 8 Table memory | storage part 9 PWM signal output part M Motor CMP Comparator SW2 Volume switch SW3 Switching element

Claims (6)

In the drive control circuit of the electric tool that controls the drive of the electric tool motor,
When a counter electromotive voltage is generated in the motor, the comparator compares the magnitude of the counter electromotive voltage with a predetermined reference voltage, and outputs a comparison signal according to the comparison result;
A switching element for switching on and off power supply from a power source to the motor;
A volume switch that outputs a signal of a level corresponding to an operation amount of an input operation unit for performing an input for setting the output of the motor to a desired state;
A control unit that outputs a PWM signal with a duty changed according to a comparison signal output from the comparison unit and an output signal of the volume switch, and controls a switching operation of the switching element;
A limit value related to a change in duty of the PWM signal by the control unit is set for each of a plurality of signal levels according to the output signal of the volume switch,
The control unit is a drive control circuit for an electric tool that changes a duty of a PWM signal output to the switching element within a limit range determined by the limit value. The upper limit value of the duty of the PWM signal output to the switching element is set for each of a plurality of signal levels corresponding to the output signal of the volume switch as a limit value related to the change in duty of the PWM signal by the control unit. The drive control circuit of the electric tool according to claim 1. The infinitesimal range the intensity of the output signal is predetermined from 0 of the volume switch, claims, characterized in that the increased amount of the duty of the PWM signal output to the switching element is set to 0 Item 3. A drive control circuit for an electric tool according to Item 2. As a limit value regarding the change in duty of the PWM signal by the control unit, an upper limit value for the increase rate of the duty of the PWM signal output to the switching element is set for each of a plurality of signal levels corresponding to the output signal of the volume switch. The drive control circuit of the electric tool according to claim 1, wherein the drive control circuit is set. The infinitesimal range the intensity of the output signal is predetermined from 0 of the volume switch, wherein, wherein the duty rate of increase of the PWM signal to be output to the switching element is set to 0 Item 5. A drive control circuit for an electric tool according to Item 4. A motor,
In an electric tool comprising a drive control circuit for controlling the drive of the motor,
The power control circuit according to claim 1, wherein the drive control circuit is a drive control circuit according to claim 1.

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