JP6447020B2 - Switch circuit and appliance - Google Patents

Description

  The present invention relates to a switch circuit and an electric appliance, and more particularly to a switch circuit whose output changes according to an operation amount of a trigger and an electric appliance including the switch circuit.

  Conventionally, a trigger switch has been used as a switch used in an electric appliance such as an electric tool. In this type of trigger switch, the output changes according to the operation amount when the trigger is pulled.

  FIG. 8 is a schematic diagram showing an electric circuit of a power tool 100 including a trigger switch 101 that is conventionally used. As shown in FIG. 8, the electric circuit of the electric power tool 100 includes a trigger switch 101, a control unit 102, a power source E, a motor M, and an FET (Field-Effect Transistor) 103. As shown in FIG. 9, in the conventional electric power tool 100, the power source E, the motor M, and the FET 103 are directly connected, and the control unit 102 is connected to the gate of the FET 103.

  The control unit 102 includes a terminal 102 a, a terminal 102 b, and a terminal 102 c, and each terminal is electrically connected to the trigger switch 101. The control unit 102 applies a reference voltage between the terminals 102a and 102b. The control unit 102 is connected to the gate of the FET 103.

  FIG. 9 shows an example of a trigger switch 101 conventionally used. FIG. 9A is a schematic diagram of the configuration of the trigger switch 101 when the trigger switch 101 is not operated. As shown in FIG. 9A, the trigger switch 101 includes a substrate 104, a brush 105, and a trigger (not shown).

  A conductive portion 106 and a printed resistance portion 107 are formed on the substrate 104, and a conductive material brush 105 is fixed on the substrate 104 so as to slide in the left and right directions in the direction of the arrow according to the operation amount of the trigger. ing. A terminal 102c is connected to the conductor portion 106, and a terminal 102a and a terminal 102b are connected to both ends of the printed resistor portion 107, respectively.

  FIG. 9B shows a schematic configuration diagram of the trigger switch 101 when the trigger operation amount is the maximum. When the trigger switch 101 is operated, the brush slides in the right direction, and the state shown in FIG. Therefore, the resistance value between the terminal 102b and the terminal 102c decreases according to the operation amount of the trigger, and the voltage input to the terminal 102c decreases. The control unit 102 controls the motor M according to the voltage input to the terminal 102c. Thus, a trigger switch is realized in which the rotational speed (output) of the electric tool changes according to the operation amount of the trigger.

  However, in the above-described trigger switch 101, since the resistance value is changed by sliding the brush 105 with respect to the substrate, the contact between the brush 105 and the substrate 104 is caused by wear of the brush 105 and the like with time. It becomes unstable. In particular, when the resistance value fluctuates in an unstable manner when the trigger is pulled to the maximum, the maximum output of the electric power tool 100 fluctuates, resulting in poor work efficiency.

  In Patent Document 1, in order to solve the above-described problem, an auxiliary switch is provided in a circuit that is input to the control device, and a trigger switch that turns on the auxiliary switch when the operation amount of the trigger becomes maximum is disclosed. It is disclosed. When the auxiliary switch is turned on, the voltage input to the control device becomes constant when the auxiliary switch is turned on. Therefore, when the auxiliary switch is turned on, the output of the motor is constant and the electric tool rotates even at the full speed range. A highly stable trigger switch is realized.

JP 2011-51083 A (published March 17, 2011)

  In the trigger switch described in Patent Document 1, if the operation amount of the trigger is maximized and the auxiliary switch is not turned ON, there is a possibility that a time during which the rotation of the electric power tool is unstable will occur. However, as the operation mechanism of the auxiliary switch wears over time, a difference occurs between the operation amount of the trigger that turns on the auxiliary switch and the full speed range of the electric tool.

  FIG. 10 is a graph in which the horizontal axis represents the amount of operation of the trigger, and the vertical axis represents the ON position of the auxiliary switch, the resistance value of the trigger switch, and the rotational speed of the electric tool.

  FIG. 10A shows an example in which the auxiliary switch is not turned on unless the trigger is further pulled and operated after the resistance value of the trigger switch reaches the maximum. In this way, if the trigger switch must be further pulled after the resistance value of the trigger switch reaches the maximum, the entire rotational speed range of the power tool deviates from the ON position of the auxiliary switch. A region with no effect will be created.

  FIG. 10B shows an example in which the resistance value of the trigger switch does not become maximum unless the auxiliary switch is turned on and the trigger is further pulled. Also in this case, as in the example shown in FIG. 10A, the threshold value of the resistance value of the trigger switch where the rotational speed of the electric tool is in the full speed range and the position where the auxiliary switch is turned on are shifted. An area where the effect of the auxiliary switch is not generated is generated.

  (C) of FIG. 10 shows an example in which the auxiliary switch is turned on when the resistance value of the trigger switch is smaller than the threshold value of the resistance value of the trigger switch in which the rotational speed of the electric tool is in the full speed range. . In such a case, since the rotational speed of the electric tool is in the full speed range at the moment when the auxiliary switch is turned on, the rotational speed immediately before the full speed range varies.

  In addition, since the trigger switch is mounted on a power tool that generates vibrations or shocks, chattering occurs at the contact point of the auxiliary switch due to vibrations or shocks, the resistance value does not change, and the power tool does not rotate. There is also the problem of becoming stable.

  Further, since it is necessary to provide an auxiliary switch separately, there is a problem that a space for mounting the auxiliary switch is required and it is difficult to reduce the size.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a switch circuit and an electric appliance that have high output stability and can be miniaturized.

  In order to solve the above-described problem, the switch circuit according to the present invention, which is interlocked with the trigger of the electric appliance and whose output changes according to the operation amount of the trigger, has an input unit, and inputs to the input unit A control circuit unit that controls the output based on the above, a slider that has two ends, and slides from a first position to a second position in accordance with the operation amount of the trigger, and the slider And a terminal that is electrically connected to the input portion, and one end of the slider is in sliding contact with the resistor, The other end is in contact with the terminal when the slider is in a predetermined position from the first position, and is not in contact with the terminal when the slider is in the second position from the predetermined position. .

  According to the above configuration, the slider is not in contact with the terminal at the second position where the operation amount of the trigger is the maximum. As a result, even if vibration or impact occurs when the slider is in the second position, the output does not change, and a switch circuit with high output stability can be provided. Further, since an auxiliary switch is not required, a switch circuit that can be miniaturized can be provided.

  Further, the switch circuit according to the present invention includes a voltage dividing circuit connected to a power source of the electric appliance, and a transistor inserted in series in the voltage dividing circuit, and the base of the transistor is The terminal may be electrically connected, and a potential at a predetermined point on the voltage dividing circuit may be input to the input unit.

  According to said structure, the voltage input into the base of a transistor changes according to the operation amount of a trigger, and the electric current which flows between the collector-emitter of a transistor changes. Therefore, a switch circuit that can change the potential input to the input part of the control circuit part according to the sliding position of the slider and perform output according to the operation amount of the trigger is realized. Can do.

  Further, the control circuit unit may control the output by a microcomputer.

  According to said structure, even if the control circuit part controls the output with a microcomputer, the switch circuit which can perform the output according to the operation amount of a trigger is realizable.

  Furthermore, the switch circuit according to the present invention may be provided in an electric appliance.

  According to said structure, an electrical appliance provided with the switch circuit which has high output stability and can be reduced in size can be provided.

  The present invention can provide a switch circuit and an electric appliance that have high output stability and can be miniaturized.

1 is a circuit diagram of a power tool according to a first embodiment of the present invention. It is the structure schematic which shows the variable resistance part with which the trigger switch circuit of the electric tool shown in FIG. 1 is equipped. 4 is a graph according to the first embodiment of the present invention, in which a horizontal axis represents an operation amount of a trigger and a vertical axis represents a potential input to a control circuit unit. It is a circuit diagram of an electric tool concerning a 2nd embodiment of the present invention. It is the graph which took the amount of operation of a trigger on the horizontal axis, and took the electric potential inputted into the control circuit part on the vertical axis concerning the 2nd embodiment of the present invention. It is a circuit diagram of the electric tool based on the 3rd Embodiment of this invention. It is a composition schematic diagram showing the variable resistance part concerning the 1st modification. It is a circuit diagram of the electric tool used conventionally. It is the structure schematic which shows the trigger switch with which the electric tool shown in FIG. 8 is equipped. In the trigger switch circuit provided with the conventionally used auxiliary switch, the operation amount of the trigger is shown on the horizontal axis, and the ON position of the auxiliary switch, the resistance value of the trigger switch, and the rotation speed of the electric tool are shown on the vertical axis. .

  A first embodiment according to the present invention will be described.

  The trigger switch circuit according to the present embodiment is provided in electric tools such as an electric drill and household electric appliances such as a dryer. However, the present invention is not limited to this, and can be applied to any electric appliance including a motor and a trigger switch. In the present embodiment, an electric tool will be described as an example of an electric appliance provided with a trigger switch.

  FIG. 1 shows a circuit diagram of a power tool 10 according to the present embodiment. In the power tool 10 of the present embodiment, a trigger switch circuit 11, a power source E, and a motor M are electrically connected. .

  The power source E is a DC power supply source and may be a battery built in the electric power tool 10 or a rectified external commercial AC power source. The motor M is a power source that generates power, and is connected in series with the power source E.

(Configuration of trigger switch circuit)
The trigger switch circuit 11 controls the operation of the motor M by turning it on and off in conjunction with a trigger (not shown). The trigger switch circuit 11 includes a control circuit unit 21, a variable resistor unit 22, resistors R1 to R5, transistors T1 and T2, and a diode D.

  The transistor T2 is an n-type MOSFET (metal-oxide-semiconductor field-effect transistor). The transistor T2 is arranged downstream of the motor M in series between the motor M and the power source E. The transistor T2 has a drain connected to the motor M, a source connected to the negative electrode of the power source E, and a gate connected to the control circuit unit 21. Therefore, the transistor T2 passes a current between the drain and the source when the voltage input to the gate is at the Hi level, and does not flow the current when the voltage input to the gate is at the low level. Thereby, ON / OFF of the motor M is controlled.

  The diode D is arranged in parallel with the motor M and protects the back electromotive force generated in the motor M from flowing to other parts of the circuit.

  In the trigger switch circuit 11, a resistor R2, a transistor T1, a resistor R3, and a resistor R4 are arranged in series in this order so as to be in parallel with the motor M and the transistor T2, and the resistor R2, the resistor R3, and the resistor R4 are A voltage dividing circuit is configured.

  The transistor T1 is an NPN transistor, and has a collector connected to the positive electrode of the power supply E via a resistor R2 and an emitter connected to the negative electrode of the power supply E via a resistor R3 and a resistor R4. The base of the transistor T1 is connected to the variable resistance unit 22 via the resistor R1.

  The control circuit unit 21 includes an input unit 21a and an output unit 21b. The potential between the resistor R3 and the resistor R4 on the voltage dividing circuit is input to the input unit 21a of the control circuit unit 21. Depending on the input potential, the output unit 21b supplies the gate of the transistor T2. The pulse voltage is output. The pulse voltage to be output is PWM (Pulse Width Modulation) in accordance with the potential input to the input unit 21a. The control circuit unit 21 controls the output of the motor M by changing the duty ratio of the output pulse voltage (ratio of the pulse width to one cycle).

  FIG. 2 shows an example of a schematic configuration diagram of the variable resistance unit 22. As shown in FIG. 2, the variable resistance portion 22 includes a resistance VR, a slider 23, and terminals 31 to 33.

  FIG. 2A is a schematic diagram illustrating the resistor VR and the terminals 31 to 33. As shown in FIG. 1, the variable resistor 22 is connected to the circuit through terminals 31 to 33. The terminal 33 is connected to the base of the transistor T1 through the resistor R1. The terminal 31 and the terminal 32 are connected to the positive electrode and the negative electrode of the power supply E, respectively.

  The terminals 31 to 33 are conductive members, and the terminal 31 is connected to one end of the resistor VR, and the terminal 32 is connected to the other end of the resistor VR. Further, the resistor VR is arranged in parallel with the motor M and the transistor T2.

  FIG. 2B is a front view of the slider 23 as viewed from the side, and FIG. 2C is a front view of the slider 23 as viewed from above. The slider 23 is a conductive member that slides in conjunction with the trigger, and includes two end portions 23a and 23b as shown in FIG. The end 23a includes two contacts 23a-1 and 23a-2, and the end 23b similarly includes two contacts 23b-1 and 23ab-2.

  In the slider 23, the contacts 23 a-1 and 23 a-2 are in sliding contact with the terminal 31, the resistor VR, and the terminal 33, and the contacts 23 b-1 and 23 b-2 are in sliding contact with the terminal 33. ing.

When the trigger is not operated, the end portions 23a and 23b of the slider 23 are at the position P ₀ (first position) indicated by a broken line in FIG. And 23b slide in the direction of the arrow shown in FIG. When the amount of operation of the trigger reaches the maximum, the position P ₂ (second position) indicated by the alternate long and short dash line in FIG.

  In the end 23a of the slider 23, the contact 23a-1 and the contact 23a-2 slide from the terminal 31 to the terminal 32 in accordance with the operation amount of the trigger. The end 23b of the slider 23 is connected to another conductive member when the contact 23b-1 and the contact 23b-2 slide on the terminal 33 and the operation amount of the trigger becomes a predetermined value or more. Do not open end.

  The resistor R5 is arranged in parallel with the transistor T1, the resistor R3, and the resistor R4 so that one end is connected between the transistor T1 and the resistor R1 and the other end is connected to the negative electrode of the power source E. .

(Trigger switch circuit operation)
Next, the operation of the trigger switch circuit 11 during the trigger operation will be described with reference to FIG. FIG. 3 is a graph in which the operation amount of the trigger is taken on the horizontal axis and the potential input to the control circuit unit 21 is taken on the vertical axis.

First, when the trigger is not operated, the slider 23 is at the position P ₀ , the end 23 a is connected to the terminal 31, and the end 23 b is connected to the terminal 33. Therefore, as shown in FIG. 3, the current input to the base of the transistor T1 is large enough to turn on the transistor T1, and a high potential is input to the control circuit unit 21.

  When the trigger is pulled by a predetermined amount, the slider 23 slides, and the contact point of the end 23a is switched from the terminal 31 to the variable resistor VR (operation amount α in FIG. 3).

  Thereafter, when the trigger is further pulled, the current input to the base of the transistor T1 gradually decreases according to the operation amount, and the potential input to the control circuit unit 21 also decreases.

When the operation amount of the trigger is a predetermined amount, the end portion 23b of the slider 23 slides to the position P _{1 (predetermined} position), the position P _1, no longer connected to the terminal 33, the slider 23 The connection destination of the end portion 23a changes from the resistance VR to the terminal 32, and the transistor T1 is turned OFF (operation amount β in FIG. 3). Thereby, the potential input to the control circuit unit becomes equal to the potential of the terminal 32.

  Here, as described above, the control circuit unit 21 switches the duty ratio of the pulse voltage to be output according to the potential input to the input unit 21a, and controls the rotation speed of the motor M.

  The control circuit unit 21 performs control so that the motor M is not rotated until the operation amount of the trigger becomes α. When the trigger operation amount is between α and β, the control circuit unit 21 controls the motor M so that the rotation speed of the motor M increases as the trigger operation amount increases. When the operation amount of the trigger exceeds β, the motor M rotates at the maximum speed and becomes the full speed range. When the operation amount of the trigger reaches the maximum value, the slider 23 is in the second position.

  As described above, the trigger switch circuit according to the present embodiment controls the rotation speed of the motor M to be in the full speed range when the operation amount of the trigger reaches a predetermined value (operation amount β), and is integrated with the trigger. Thus, one end 23 b of the sliding element 23 that slides is not connected to the terminal 33.

  As a result, even if chattering due to vibration or impact of the electric tool occurs in the entire speed range, the resistance value of the variable resistance portion 22 changes because the end portion 23b of the slider 23 is not connected to the terminal 33. do not do. Therefore, it is possible to provide a trigger switch circuit with high output stability in all speed ranges.

  Further, unlike the trigger switch described in Patent Document 1, an auxiliary switch mechanism is not provided, so that no extra space is required and the size can be reduced.

In the present embodiment, the position P ₁ is provided between the position P ₀ and the position P ₂ , and at the position P ₁ , the end 23 b of the slider 23 is not connected to the terminal 33, and the slide Although the connection destination of the end 23a of the moving element 23 is changed from the resistance VR to the terminal 32 and the transistor T1 is turned off, the present invention is not limited to this. Position _{P 1} where the end portion 23b is not connected to the terminal 33 of the slider 23 may be any position _{P 2} side of a position of the slider 23 that the transistor T1 is turned OFF.

[Embodiment 2]
Another embodiment of the present invention will be described with reference to FIGS. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

  FIG. 4 shows a circuit diagram of the electric tool 40 according to the present embodiment. The power tool 40 according to the present embodiment includes a trigger switch circuit 41 that is different from the power tool 10 according to the first embodiment. Hereinafter, differences from the trigger switch circuit 11 according to the first embodiment will be described.

  The trigger switch circuit 41 according to the present embodiment does not include the resistor R5 of the trigger switch circuit 11 according to the first embodiment, but includes a resistor R6 instead. One end of the resistor R6 is connected between the resistor R1 and the base of the transistor T1, and the other end is connected between the emitter of the transistor T1 and the resistor R3.

  FIG. 5 is a graph showing the operation of the trigger switch circuit 41 according to the present embodiment, in which the amount of operation of the trigger is plotted on the horizontal axis and the potential input to the control circuit unit 21 is plotted on the vertical axis.

  As shown in FIG. 5, in this modification, when the operation amount of the trigger becomes γ, the gradient of the potential input to the control circuit unit changes. This is because the resistor R6 is provided in parallel with the base-emitter of the transistor T1.

  Specifically, in the interval where the operation amount of the trigger is from α to γ, the transistor T1 is ON, and the resistor R3 and the resistor R4 have two currents, a current passing through the transistor T1 and a current passing through the resistor R6. Flows.

  When the operation amount of the trigger becomes γ, the transistor T1 is turned off, and only the current that has passed through the resistor R6 flows through the resistor R3 and the resistor R4. Thus, when the operation amount exceeds γ, the gradient of the potential input to the control circuit unit changes.

  With the trigger switch circuit 41 having such a configuration, when the operation amount is small (between α and β), the change in rotational speed is small with respect to the operation amount, and when the operation amount is large (from β to γ). In the meantime, the change in the rotation speed can be increased with respect to the operation amount.

  Here, in the power tool, the low speed region where the amount of operation of the trigger is small is frequently used for screw positioning and the like. Therefore, in the low speed region, the change in rotational speed is gradual with respect to the amount of operation of the trigger. By doing so, a low speed range can be provided widely and the convenience of an electric tool improves.

[Embodiment 3]
Still another embodiment of the present invention will be described with reference to FIG. For convenience of explanation, members having the same functions as those described in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 6 shows a circuit diagram of the electric power tool 50 according to the present embodiment. The power tool 50 according to the present embodiment includes a trigger switch circuit 51 different from the power tool 10 according to the first embodiment. Hereinafter, differences from the trigger switch circuit 11 according to the first embodiment will be described.

  The trigger switch circuit 51 according to the present embodiment includes a control circuit unit 61 that is controlled by a microcomputer. Similar to the control circuit unit 21, the control circuit unit 61 outputs a pulse voltage from the output unit 61 b in accordance with the potential input to the input unit 61 a and controls the rotation speed of the motor M.

  Thus, even if it is a structure provided with the control circuit part 61 controlled by a microcomputer, the effect similar to the trigger switch circuit 11 which concerns on 1st Embodiment can be acquired.

[Modification 1]
A modification of the present invention will be described with reference to FIG. For convenience of explanation, members having the same functions as those described in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  This modification differs from the first embodiment in the structure of the variable resistance portion 22. FIG. 7 is a schematic configuration diagram illustrating a variable resistance unit according to this modification. 7A shows the resistance VR and the terminals 31 to 33. FIG. 7B shows a front view of the slider 43 as viewed from the side, and FIG. These show the front view which looked at the slider 43 from the upper direction.

  As shown in FIG. 7, in the variable resistance unit according to this modification, the terminal 31, the variable resistance VR, the terminal 32, and the terminal 33 are arranged on a straight line in this order.

  The slider 43 has a longitudinal direction parallel to the straight line, and includes an end portion 43a and an end portion 43b in the longitudinal direction. Further, a contact 43a-1 and a contact 43a-2 are formed at the end 43a, and a contact 43b-1 and a contact 43b-2 are formed at the end 43b.

Slider 43, like the slider 23 according to the first embodiment, at the time of triggering unoperated, the ends 43a and 43b is in the position P ₁ shown by a broken line in FIG. 7 (a). Further, the slider 43 according to the operation amount of the trigger, the ends 43a and 43b to a position _{P 2} shown by the one-dot chain line in FIG. 7 (a), the terminal 31, the variable resistor VR, the terminal 32 and the terminal 33 It slides in the direction of the arrow, which is the straight line direction.

  Even if the variable resistor 22 has such a configuration, the same effect as the trigger switch circuit 11 according to the first embodiment can be obtained.

[Modification 2]
Still another modification of the present invention will be described. For convenience of explanation, members having the same functions as those described in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the first embodiment described above, the transistor T1 provided in the trigger switch circuit 11 is an NPN transistor. However, the transistor T1 may be a PNP transistor. In the case where the transistor T1 is an NPN transistor, the potential input to the control circuit unit 21 is changed from the Low level to the Hi level in accordance with the operation amount of the trigger, so that the first implementation is performed. The effect similar to the trigger switch circuit 11 which concerns on a form can be acquired.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be used for a shift switch circuit provided in an electric tool or the like.

10 Electric tools (electric appliances)
DESCRIPTION OF SYMBOLS 11 Switch circuit 21 Control circuit part 21a Input part 22 Variable resistance part 23 Slider 23a End part 23b End part 33 Terminal E Power supply VR resistance T1 transistor

Claims (3)

A switch circuit that interlocks with the trigger of the electric appliance, and the output changes according to the operation amount of the trigger,
A control circuit unit that has an input unit and controls the output based on an input to the input unit;
A slider having two ends and sliding from the first position to the second position in accordance with the operation amount of the trigger;
A resistance capable of obtaining a resistance value corresponding to the sliding position of the slider;
A terminal electrically connected to the input unit;
One end of the slider is in sliding contact with the resistance,
The other end of the slider is
When the slider is in a predetermined position from the first position, it is in contact with the terminal,
When the slider is in the second position from the predetermined position , not in contact with the terminal ,
The switch circuit includes a voltage dividing circuit connected to a power source of the electric appliance, and a transistor inserted in series with the voltage dividing circuit,
The base of the transistor is electrically connected to the terminal;
The switch circuit , wherein a potential at a predetermined point on the voltage dividing circuit is input to the input unit .   The switch circuit according to claim 1, wherein the control circuit unit controls the output by a microcomputer. Appliance comprising a switching circuit according to claim 1 or 2.

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