JPH0825179A - Power drill - Google Patents

Abstract

PURPOSE:To provide a power drill, facilitating positioning a drill point end to accurately and safely perform drilling work further to eliminate apprehension of damaging the drill, in the drilling work. CONSTITUTION:In this constitution, a drill 6 is mounted through a chuck part 4 and a jaw part 5 on a shaft 7 of an electric motor 20, to arrange a sensor part 10, formed of a pressure responsive resistance element, through a bearing 9 in a rear part of the shaft 7, so as to detect pressing force applied to the drill 6 in the sensor part 10, and based on this detection signal, so as to accelerate the electric motor 20 in proportion to the detected pressing force to the maximum rotational speed, a power supply current is controlled by a drive control circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric drill, and more particularly, to an electric drill which automatically adjusts the rotational speed of the drill according to the amount of pressing force applied in the thrust direction of the drill.

[0002]

2. Description of the Related Art In general, an electric drill has an electric motor housed in a main body casing and a switch attached to the main body casing is turned on / off so that a tip and a jaw of the main body casing are inserted through a chuck and a chin. Rotate the connected drill.

Such a conventional electric drill can usually be operated only by turning on or off the switch for supplying a drive current to the electric motor, and in the former case, the type of electric motor is also changed. However, if it is a single-phase series motor that is commonly used in this type of electric drill, the rotation speed will usually decrease slightly when a load is applied, but it still rotates at a considerably high speed. Stay in the state. On the other hand, in the latter case, needless to say, the rotation of the drill is stopped.

[0004]

Therefore, in the conventional electric drill, when the drill is driven, the rotation speed of the hole is controlled rather than the appropriate rotation speed regardless of the change in the pressing force applied to the tip of the drill. When the drilling operation is already in the high-speed rotation state, the drilling operation progresses, the load increases and the rotation speed decreases, and if the hole penetrates like a through hole, At the same time, the behavior of returning to the high rotation speed under no load is shown. Then
In such a conventional electric drill, it is difficult to position the drill, or the rotation speed during operation is improper, so the drill deteriorates sharply and its life decreases,
There was a problem of lacking safety when drilling a hole and protection of the drill.

More specifically, in the case of drilling a through hole, the electric drill, unless the switch is turned off at the start of the drilling work, during the work and when there is a through hole,
Since it is always rotating at a high rotation speed, positioning is difficult at the beginning of work, and it is difficult to make a hole at an appropriate position. There was a problem in safety, protection of the drill, and proper drilling work because the shape of the through hole was changed due to strong contact with the inner peripheral wall, breakage of the drill occurred. Such a problem is particularly inconvenient when an amateur is working.

In addition, in the conventional electric drill, the rotation speed could not be properly controlled regardless of the size of the hole to be drilled, so that the rotation speed was higher than the drill diameter. There was also a problem in that the blade was overheated and overheated, causing deterioration.

Therefore, the present invention has been made in view of the above various problems, and by changing the rotation speed of the drill based on the pressing force applied to the drill, even an amateur can easily Moreover, it is a problem to be solved to provide an electric drill capable of easily and appropriately performing an appropriate machining operation safely.

[0008]

SUMMARY OF THE INVENTION An object of one aspect of the present invention is to provide an electric drill in which a drill attached to a tip portion of a main body is rotationally driven by an electric motor provided in the main body. An electric drill having drive control means for controlling the rotation speed of the electric motor so as to increase the pressing force according to the size thereof based on the pressing force applied to the tip of the drill, whereby the above problems can be solved. .

The drive control means is based on the function, that is, the pressing force applied to the tip of the drill, according to its size, for example, in proportion to the size, or not necessarily in an exact proportional relationship. In general, the configuration is not limited to a specific configuration as long as the rotation speed of the electric motor can be controlled so that the rotation speed increases as the pressing force increases. As the drive control means, for example, a detection means for detecting a pressing force applied to the tip of the drill and outputting a detection signal, and a detection signal from the detection means are proportional to the magnitude thereof. Thus, a configuration including a rotation speed control unit that controls the rotation speed of the electric motor can be employed.

More specifically, as the detecting means, a resistance element that changes its resistance value according to the pressing force applied to the drill can be adopted, and as the rotating speed control means, , A triac that turns on the power supply current supplied to the electric motor in every half cycle in a phase in which a trigger current is made to flow from the gate circuit to the gate electrode, and a current that flows in the resistance element every half cycle of the power supply current. A gate circuit that charges and discharges a capacitor to a capacitor, and a trigger diode to which the charge and discharge voltage is applied causes a trigger current to flow to the gate electrode at the timing when the voltage exceeds the breakdown voltage to turn on the triac. can do.

The gist of the second configuration of the present invention is as follows.
In an electric drill in which a drill attached to the tip of the main body is driven to rotate by an electric motor provided in the main body, the constant pressing force applied to the tip of the drill is the change rate of the rotation speed of the electric motor. Change rate setting means for setting a change rate of the rotation speed that changes for each, and based on the pressing force applied to the tip of the drill, while changing the rotation speed of the electric motor to increase according to the magnitude, The electric drill comprises drive control means for changing the rotation speed of the electric motor at a change rate corresponding to the setting state of the change rate setting means, and the above-mentioned problems can also be solved by this.

As the drive control means, various configurations that match the purpose thereof are adopted. For example, the pressing force applied to the tip of the drill is detected to correspond to the setting state of the change rate setting means. It is possible to employ a configuration including a detection unit that outputs a detection signal and a rotation speed control unit that controls the rotation speed of the electric motor based on the detection signal from the detection unit.

Further, as the detecting means, there is adopted a constitution comprising a plurality of resistance elements for changing the resistance values thereof at different ratios in accordance with the pressing force applied to the tip of the drill, and as the change ratio setting means. A switch for selecting a plurality of resistance elements of the detection means can be adopted.

Further, as the rotation speed control means, the power supply current supplied to the electric motor is changed every half cycle.
A triac that turns on in a phase in which a trigger current is made to flow from the gate circuit to the gate electrode, and a trigger diode to which the current flowing through the resistance element is charged / discharged to / from a capacitor every half cycle of the power supply current and the charge / discharge voltage is applied Therefore, it is possible to adopt a configuration including a gate circuit that turns on the triac by causing a trigger current to flow through the gate electrode at a timing when the charge / discharge voltage exceeds the breakdown voltage. Needless to say, other configurations can be adopted as long as they have similar functions.

[0015]

Therefore, according to one aspect of the present invention, the drill attached to the tip portion of the main body is driven to rotate by the electric motor provided in the main body. At this time, the drive control means determines the pressure based on the pressing force applied to the drill. Then, the rotation speed of the electric motor is controlled so as to increase according to the size.

Therefore, the rotational speed of the drill of the electric drill can be adjusted in accordance with the pressing force applied to the drill. For example, at the start of drilling work, before the tip of the drill comes into contact with the target site. , The drill is kept in a rotation stopped state or an extremely low speed rotation, and at the time of the initial contact, the low speed rotation corresponding to a small pressing force at the time of positioning is held, so that the drill can be positioned safely and easily. Then, the rotation speed is increased corresponding to the correspondingly increased pressing force, and the appropriate drilling work can be performed.

Further, in the work of drilling a through hole, the pressing force naturally disappears when the hole penetrates, so the rotation speed of the drill is reduced to an extremely low speed or stopped according to the setting. Later, the rotating drill can avoid problems such as cutting the inner peripheral wall of the through hole to widen its diameter, deforming it, breaking the drill, etc.
Even if an amateur performs this drilling work, the safety of work and protection of the drill can be established, and appropriate drilling work can be easily performed.

In this case, as described above, the drive control means detects the pressing force applied to the tip of the drill,
When the detecting means for outputting the detecting signal and the rotating speed controlling means for controlling the rotating speed of the electric motor on the basis of the detecting signal from the detecting means are used, they are added to the drill with a simple structure. The rotation speed of the drill can be easily controlled based on the pressing force.

Further, as described above, the detecting means is
A resistance element that changes its resistance value in accordance with the pressing force applied to the drill, and the rotation speed control means controls the power supply current supplied to the electric motor every half cycle by a gate circuit to be described later. Triac that turns on at the phase where the trigger current is applied to the electrode, and every half cycle of the power supply current, charges and discharges the current flowing through the resistance element to the capacitor, and the voltage is applied by the trigger diode to which the charge and discharge voltage is applied. When configured with a gate circuit that turns on the triac by flowing a trigger current to the gate electrode at a timing exceeding the breakdown voltage, a simpler and cheaper configuration detects the pressing force applied to the drill, The rotation speed of the drill can be controlled.

According to the second aspect of the present invention, the drill attached to the tip of the main body is driven to rotate by the electric motor provided in the main body. At this time, the drive control means adjusts the pressing force applied to the drill. Based on this, while controlling the rotation speed of the electric motor to increase according to its size,
The rotation speed of the electric motor is changed according to the change rate of the rotation speed set by the change rate setting means. Needless to say, the rate of change in the rotational speed is the rate of change in the rotational speed that changes with each constant pressing force applied to the tip of the drill.

Therefore, according to the change rate setting means, depending on the type of work, for example, the diameter of the hole to be drilled,
By setting the rate of change of the rotation speed that changes at each constant pressing force applied to the tip of the drill, in the work, that is, in the work of drilling large diameter holes and the work of small diameter holes, the drilling work is started. Sometimes the pressing force applied to the drill is detected before the tip of the drill touches the target site, at the time of positioning at the time of initial contact, during the work, and at the time of penetrating the through hole. The rotation speed of the drill can be adjusted more finely so that it rotates at a rotation speed that is suitable for the machine, which further improves the safety of work and also makes it easier to protect the drill and perform appropriate drilling work. It can be carried out.

In this case, as described above, for example, the drive control means detects the pressing force applied to the tip of the drill and outputs a detection signal corresponding to the setting state of the change ratio setting means. And a rotation speed control means for controlling the rotation speed of the electric motor based on a detection signal from the detection means, the configuration is simple and can be easily performed based on the pressing force applied to the drill. The rotation speed of the drill can be controlled more appropriately.

Further, as described above, the detecting means is
According to the pressing force applied to the tip of the drill, the resistance value is composed of a plurality of resistance elements that change at different rates, and the change rate setting means is a switch that selects a plurality of resistance elements of the detection means. The rotation speed control means, the triac for turning on the power supply current supplied to the electric motor every half cycle in a phase in which a trigger current is supplied to the gate electrode from the gate circuit described later, and a half cycle of the power supply current. Each time, the current flowing through the resistance element is charged / discharged to / from the capacitor, and the trigger diode to which the charging / discharging voltage is applied causes the trigger current to flow to the gate electrode at the timing when the voltage exceeds the breakdown voltage to turn on the triac. If it is configured with a gate circuit, it will be added to the drill due to the simpler and cheaper configuration. By detecting the pressing force can be controlled more finely the rotational speed of the drill.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The examples described below are preferred specific examples of the present invention, so various technically preferable limitations are attached, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these modes.

1 to 5 are views showing an embodiment of the electric drill of the present invention. FIG. 1 is a schematic side view of the electric drill, and FIG. 2 is a chuck part and a part of the inside of the electric drill. Fig. 3 is a cutaway plan view, Fig. 3 is an enlarged front view of the slide switch, Fig. 4 is a characteristic curve diagram showing a characteristic curve showing the relationship between the pressing force applied to the drill and the rotation speed, and Fig. 5 is its drive control circuit. It is a circuit diagram of. The characteristic curve of FIG. 4 is obtained by an electric drill using a single-phase series-wound electric motor, but only the pressing force and the change in the rotational speed due to this are accurately obtained without including the decrease in the rotational speed due to the load. Therefore, the measurement was performed while pressing the tip of the drill against the rotatable pressing force measuring plate. Therefore, this graph does not include the effect of load.

Although this is an embodiment of the second aspect of the present invention, the first aspect of the present invention is to provide a change rate setting means for setting a change rate of the rotational speed which changes at every constant pressing force applied to the tip of the drill. Only the difference is that it does not have two,
Since it is included in the second aspect of the present invention, the description of the second example of the present invention will also serve as the explanation of the first example of the present invention.

In FIG. 1, the electric drill 1 has a substantially L-shaped casing 2, and the casing 2 has a body portion 2a and a grip portion 2b.
And have. A trigger-shaped power switch 3 is attached to the inside of the L-shaped corner of the housing 2, and the power of the electric drill 1 can be turned on / off by turning the power switch 3 on / off. it can.

A chuck portion 4 and a jaw portion 5 are formed at the tip of the body portion 2a of the housing 2. By operating the chuck portion 4, the jaw portion 5 is opened and closed, and the drill 6 can be attached and detached. Can be attached to.

The chuck portion 4 is, as shown in FIG.
It is connected to the shaft 7 of the electric motor 20. The shaft 7 also extends to the rear of the electric motor 20 and is rotatably supported by the housing 2 via bearings 8 and 9. As the electric motor 20, a single-layer series-wound motor is used in this embodiment. It is possible to use other types of electric motors, but in that case, it will be necessary to replace the drive control circuit and the like described later with corresponding ones. The bearing 9 on the housing 2 side simultaneously supports the thrust direction and the radial direction, and is composed of an inner ring 9 a and an outer ring 9 b, and the inner ring 9 a is connected to the shaft 7. The outer ring 9b is fixed to the end support 11 via the sensor unit 10. The end support 11 is fixed to the housing 2.

The sensor unit 10 is interposed between the shaft 7 and the end support 11 via the bearing 9 as described above, and is drilled via the bearing 9 and the shaft 7 as will be described later. A plurality of resistance elements (three in this embodiment) whose resistance value changes in response to the pressing force applied to the thrust direction 6 in the thrust direction are incorporated in a stacked manner. The resistance value used is inversely proportional to the magnitude of the pressing force, and becomes smaller as the pressing force increases. The three resistance elements have different rates of change in resistance value with respect to the pressing force per unit.

As shown in FIG. 1, a slide switch (change ratio setting means) is provided on the side surface of the body 2a of the housing 2.
12 is provided, and the slide switch 12 is a switch for selecting the change rate of the rotation speed of the electric motor 20 according to the pressing force applied to the drill 6, as described later.

The slide switch 12 is slid along a slide groove 2c formed on the side surface of the body portion 2a. Further, as shown in FIG. 3, the slide switch 12 extends in the longitudinal direction of the slide groove 2c. Along the "OFF" and "OF"
Switch position graduations 12a to 12d are formed, which are indicated by "○" marks that increase with distance from the "F" position. Note that "OFF" here means that the rotational speed of the drill 6 corresponding to the pressing force is not controlled.

The "OFF" switch position scale 12a is
As shown by the characteristic curve A in FIG. 4, the switch position does not change the rotation speed of the electric motor 20, and the smallest switch position scale 12b marked with a circle is the push position as shown by the characteristic curve B in FIG. When there is no pressure, it has a reasonably small rotation speed (150 rpm in this example), and the rotation speed increases with a steep characteristic curve, that is, at a large change rate with respect to the increase change of the pressing force per unit. Switch position.

As shown by the characteristic curve C in FIG. 4, the switch position scale 12c of the intermediate size "○" shows the same moderately small rotation speed as the characteristic curve B when there is no pressing force. Switch position 12b with the smallest "○" mark
It is a characteristic curve with a gentler slope, that is, the switch position where the rotation speed increases at a slightly gradual change rate with respect to the increase change of the pressing force per unit, and the largest "○".
As shown by the characteristic curve D in FIG. 4, the switch position scale 12d marked with the mark has a moderately small rotation speed similar to the characteristic curve B when there is no pressing force, and the switch position 12c marked with the middle mark "○". The switch position is such that the rotational speed increases with a characteristic curve having a more gradual slope, that is, at a more gradual change rate with respect to an increase change in the pressing force per unit.

As shown in FIG. 5, an electric motor 20 and a drive control circuit (drive control means) 21 are incorporated in the housing 2, and the drive control circuit 21 includes the triac 2
2, a diac 23, a fixed resistor R1, a capacitor C1 and the sensor unit 10 are provided.

The sensor unit 10 is composed of three pressure response resistance elements VR1, VR2, VR3, and each pressure response resistance element VR1, VR2, VR3 changes depending on the applied pressing force per unit. The ratio of resistance is different. As described above, the resistance value decreases in inverse proportion to the increase in the pressing force as described above, but the decreasing rate of the resistance value, that is, the proportional constant is different. That is, the resistance value of the pressure response resistance element VR1 greatly changes with respect to the applied pressure, and the resistance value of the pressure response resistance element VR3 changes gently with respect to the applied pressure. Reduce the resistance value. The resistance value of the pressure response resistance element VR2 changes at an intermediate ratio between the pressure response resistance element VR1 and the pressure response resistance element VR3 with respect to the applied pressure, and the resistance value decreases.

It is assumed that the fixed resistor R1 has a resistance value that matches the resistance value when a pressing force greater than the corresponding maximum value is applied to each of the pressure response resistance elements VR1, VR2, VR3.

By the way, the fixed resistance R1 and each pressure response resistance element VR1, VR2, VR3 of the sensor section 10 are described.
One end of the slide switch 12
Are connected to terminals corresponding to the switch position scales 12a to 12d, and the other ends thereof are commonly connected and connected to the capacitor C1 and one electrode of the diac 23.

AC power is supplied to the electric motor 20 through the power switch 3, and the triac 22 is inserted in the power line of the electric motor 20.

The gate electrode of the triac 22 is
The other electrode of the diac 23 is connected to the fixed resistance R1 or the pressure response resistance elements VR1, VR2, VR.
The capacitor C1 is charged through any one of
When the voltage across both ends of the diac exceeds the breakdown voltage of the diac 23, its discharge current flows through the diac 23,
The triac 22 is turned on. Phase control in which the triac 22 is turned on in a phase determined by the charging time until the charging voltage of the capacitor C1 charged through any of the fixed resistance R1 or the pressure response resistance elements VR1, VR2, VR3 exceeds the breakdown voltage of the diac 23. Is.

Further, the triac 22 and the electric motor 2
A common terminal of the slide switch 12 is connected to a connection point with 0. The other electrode of the capacitor C1 is connected to the other electrode side of the triac 22.

Therefore, when the slide switch 12 is set to the switch position scale 12a and is connected to the fixed resistor R1, the drive control circuit 21 fixes the fixed resistor R1.
When the capacitor C1 is charged by the charging current flowing through the capacitor C1 and its voltage exceeds the breakdown voltage of the diac 23, a discharging current flows through the diac 23, which serves as a trigger current flowing through the gate electrode of the triac 22 and causes the triac 22 to operate. Turn on. This is repeated cyclically, and a constant average current is applied to the electric motor 2
0, the electric motor 20 is rotationally driven at a constant rotational speed as shown by a characteristic curve A in FIG. In the case of this embodiment, it is 3000 rpm.

As described above, the resistance value of the fixed resistor R1 is made to coincide with the resistance value of the pressure responsive resistance elements VR1, VR2, VR3 when a pressing force exceeding the maximum value is applied to each of them. The characteristic curve A of No. 1 is the same as the maximum rotation speed (3000 rpm) of the latter characteristic curves B, C and D regardless of the pressing force. However, this is the case where there is no load due to the nature of the single-phase series-wound electric motor used as the electric motor 20, and if a load is applied, the rotation speed will decrease depending on the size,
It drops to about 0 rpm.

When the slide switch 12 is set on the switch position scale 12b and is connected to the pressure response resistance element VR1, the drive control circuit 21 causes the capacitor C1 to operate with the charging current flowing through the pressure response resistance element VR1. When the battery is charged and its voltage exceeds the breakdown voltage of the diac 23, a discharge current flows through the diac 23, which becomes a trigger current flowing through the gate electrode of the triac 22, and turns on the triac 22. This is repeated, and the average current is the electric motor 20.
And drives the electric motor 20 to rotate.

However, the pressure response resistance element VR1
Has its resistance value drastically reduced in accordance with the magnitude of the pressing force applied to the drill 6, so that the time until the charging voltage of the capacitor C1 exceeds the breakdown voltage of the DIAC 23 becomes short, and the drive control circuit 21 becomes As shown by the characteristic curve B in FIG. 4, the rotation speed of the electric motor 20 is rapidly increased in accordance with the increase in the pressing force applied to the drill 6. When the value of the maximum pressing force (about 10 kg) is exceeded, the resistance value of the pressure response resistance element VR1 becomes the same as the fixed resistance R1,
It will rotate at the same speed. Note that the influence of the load is also omitted here to explain only the relationship with the pressing force.
When a load is applied, the slope of the characteristic curve B shown in FIG. 4 becomes slightly gentle, and if the load is the same as in the OFF state, the maximum rotation speed will be 2500 rpm.
Since this point is the same as this point, the description thereof will be omitted.

Further, when the slide switch 12 is set to the switch position scale 12d and is connected to the pressure response resistance element VR3, the drive control circuit 21 is the same as when it is connected to the pressure response resistance element VR1. In addition, when the capacitor C1 is charged by the charging current flowing through the pressure response resistance element VR3 and the voltage exceeds the breakdown voltage of the diac 23, a discharging current flows through the diac 23, which triggers to flow to the gate electrode of the triac 22. It becomes a current and turns on the triac 22. This is repeated, and the average current is 2
0, and the electric motor 20 is rotationally driven.

However, the pressure response resistance element VR3
Has a resistance value that gradually decreases in accordance with the magnitude of the pressing force applied to the drill 6, so that the time until the charging voltage of the capacitor C1 exceeds the breakdown voltage of the DIAC 23 becomes long, and the drive control circuit 21 As shown by the characteristic curve D in FIG. 4, the rotational speed of the electric motor 20 is gradually increased in accordance with the increase in the pressing force applied to the tip of the drill 6 in the thrust direction. And the value of the maximum pressing force (about 23
If it exceeds Kg), the resistance value of the pressure response resistance element VR3 becomes
It becomes the same as the fixed resistor R1 and rotates at the same speed.

When the slide switch 12 is set to the switch position scale 12c and connected to the pressure responsive resistance element VR2, the drive control circuit 21 is connected to the pressure responsive resistance elements VR1 and VR3. Similarly, when the capacitor C1 is charged by the charging current flowing through the pressure responsive resistance element VR2 and its voltage exceeds the breakdown voltage of the diac 23, a discharging current flows through the diac 23, which is applied to the gate electrode of the triac 22. It becomes a flowing trigger current, and the triac 2
Turn 2 on. This is repeated, the average current flows through the electric motor 20, and the electric motor 20 is rotationally driven.

However, the pressure response resistance element VR2
The resistance value of the drill 6 decreases at an intermediate change rate between the pressure response resistance elements VR1 and VR3 according to the magnitude of the thrust force applied to the drill 6, so that the charging voltage of the capacitor C1 is reduced to the diac 23. The time until the breakdown voltage of the drill 6 exceeds the intermediate value is also an intermediate length, and the drive control circuit 21 drives the motor 6 according to the increase in the pressing force applied to the drill 6 as shown by the characteristic curve C in FIG. The rotation speed of the motor 20 is increased at an intermediate change rate. When the value of the maximum pressing force (about 16 kg) is exceeded, the pressure response resistance element V
The resistance value of R2 is the same as that of the fixed resistor R1, and the resistors rotate at the same speed.

Therefore, the drive control circuit 21 always supplies a constant drive current to the electric motor 20 in accordance with the state of the slide switch 12, regardless of the change in the pressing force.
If the load is constant, the drill 6 is rotated at a constant rotation speed, or the drive current supplied to the electric motor 20 is changed according to the thrust force applied to the drill 6 to change the rotation speed to various values. Change at the rate of change.

Since this embodiment is constructed as described above, it operates as follows. When performing the drilling work, first, the slide switch 12 is set to any of the switch position scales 12b to 12d corresponding to the diameter of the hole to be drilled. The setting to any one of the switch position scales 12b to 1 attached to the upper side of the slide groove 2c of the slide switch 12
The slide switch 12 is moved in accordance with the large and small diameter "○" marks corresponding to 2d. When the rotational speed of the drill 6 is changed according to the thrust force applied to the drill 6 in order to increase the rotational speed, the above settings are made. If it is not necessary to change the rotation speed according to the pressing force applied to the drill 6, the switch position scale 12a, that is, OFF is selected.

When the setting of the slide switch 12 is completed in this way, next, the drill 6 of the electric drill 1 is brought close to the drilling position of the processing object, and the power switch 3 is turned on. At this time, as can be seen from FIG. 4, when the slide switch 12 is set to the switch position scale 12a, that is, OFF, at a constant high rotation speed (3000 rp).
m) the drill 6 is rotating and slide switch 12
Is a switch position scale 12b to 12d, that is, a small diameter ◯ to
If it is set to any of the maximum diameter ○,
The drill 6 is rotating at an extremely low rotation speed (150 rpm).

Therefore, when the slide switch 12 is set to the switch position scales 12b to 12d, the drill 6 is rotating at an extremely low rotation speed, and therefore the electric drill 1 is operating normally. Can be confirmed, and by rotating at a low speed, the drill 6 at the start of work is much easier than when stopped.
Positioning work of the tip of can be performed.

In the above case, the pressure responsive resistance elements VR1, VR2, V depend on which of the switch position scales 12b-12d the slide switch 12 has selected.
When any one of R3 is selected and the drill 6 of the electric drill 1 is strongly pressed against the object as the drilling work progresses, the corresponding pressure response resistance element VR1, according to the thrust force applied to the drill 6, VR2, VR3
However, the resistance value is changed at each unique change rate. Therefore, the phase in which the drive control circuit 21 turns on the triac 22 changes depending on the pressing force applied to the drill 6 and which one the slide switch 12 selects.

Therefore, depending on the contents of the drilling work,
As described above, by appropriately setting the slide switch 12 to the appropriate switch position scales 12a to 12d, the average current supplied to the electric drill 6 is changed according to the thrust force applied to the drill 6. The rotation speed can be changed at various change rates.

For example, when the slide switch 12 is set to the switch position scale 12b, that is, the position of the smallest "○" mark, the rotation speed of the drill 6 can be rapidly increased according to the pressing force, and the small hole Appropriate work can be done when opening. Further, when the slide switch 12 is set to the switch position scale 12d, that is, the position of the largest "○" mark, the rotation speed of the drill 6 can be gradually increased according to the pressing force, and when a large hole is to be drilled. You can do the right work. Further, the slide switch 12 is provided with a switch position scale 12c,
That is, when set to the position of the middle size "○" mark,
Depending on the pressing force, the rotation speed of the drill 6 can be increased at an intermediate change rate between when the switch position scale 12b is set and when the switch position scale 12d is set, and a hole of an intermediate size is opened. Appropriate work can be done when opening.

Then, in the work of opening the through hole, when the through hole penetrates, the pressing force applied to the drill 6 suddenly disappears. At this time, as can be seen from FIG. 4, the drill 6 is extremely small. Since it returns to rotation at the rotation speed (150 rpm), even if the drill 6 makes strong contact with the inner wall of the through hole,
It is possible to avoid the problem that the size of the through hole changes and the drill breaks due to cutting of the peripheral side wall, and safety and protection of the drill and appropriate drilling work can be easily performed.

When the slide switch 12 is set to the switch position scale 12a, the drill 6 can be rotated at a constant speed if the load is constant regardless of the thrust force applied to the drill 6. You can
If necessary, it is possible to perform work using this.

As described above, according to this embodiment, the drill 6 is rotationally driven by the electric motor 20. At this time,
Since the rotation speed of the electric motor 20 is controlled based on the thrust force applied to the drill 6, the rotation speed of the drill 6 of the electric drill 1 is adjusted according to the pressure force applied to the drill 6. Even when an amateur is working, for example, at the start of drilling work, a small pressing force is used to perform appropriate positioning in a low-speed rotation state, and during the work, an increasing pressing force is applied. Accordingly, the rotation speed is increased, and proper drilling work can be performed.

In the work of drilling the through hole, when the through hole penetrates, the pressing force naturally disappears, and the rotation speed of the drill 6 of the electric drill 1 decreases, so the rotating drill. Can avoid the problem of changing the size of the through hole and breaking the drill 6 by contacting the wall surface of the through hole, and safety and protection of the drill and appropriate drilling work can be easily performed. it can.

Further, according to this embodiment, the pressing force applied to the drill 6 in the thrust direction is detected by the sensor unit 10,
Based on the detection result of the sensor unit 10, the electric motor 20
Since the rotation speed of the drill 6 is controlled, the rotation speed of the drill 6 can be easily controlled based on the pressing force applied to the drill 6 with a simple configuration.

Further, in this embodiment, the sensor unit 10 is
It is composed of pressure response resistance elements VR1, VR2, VR3 whose resistance value changes according to the pressure applied to the drill 6, and the drive control circuit 21 is composed of a triac 22, a diac 23, a fixed resistance R1, and a capacitor C1. Therefore, the rotational speed of the drill 6 can be controlled by detecting the pressing force applied to the drill 6 with a simpler and cheaper configuration.

Further, according to this embodiment, since the slide switch (change rate setting means) 12 can set the change rate of the rotation speed according to the type of work, the set change rate and the drill can be set. By adjusting the pressing force applied to the drill 6, the rotation speed of the drill 6 of the electric drill 1 can be adjusted more finely, the work safety is further improved, and the drill 6 can be protected and properly protected. Hole drilling work can be performed more easily.

Further, according to this embodiment, a plurality of pressure response resistance elements VR1, VR2, VR3 are selected by the slide switch 12 so that the change rate of the rotation speed of the drill 6 can be selected. With a simpler and cheaper structure, an appropriate change rate is selected according to the hole diameter to be drilled, the pressing force applied to the drill 6 is detected, and the rotation speed of the drill 6 is further refined. Can be controlled.

In the above embodiment, three types of pressure response resistance elements VR1, VR2 and VR3 are provided.
The number of pressure drills is not limited to three, and by appropriately increasing or decreasing the number of pressure response resistance elements, it is possible to provide an appropriate electric drill 1 according to the price and the purpose of use.

Further, in the above embodiment, the drill 6
Thrust force in the thrust direction to the pressure response resistance element VR
1, VR2, VR3 is detected, and the rotation speed of the drill 6 is adjusted by adjusting the power supply current supplied to the electric motor 20 by the detection result, that is, the resistance change, but this is not the only option. Not by other means, drill 6
The pressing force applied to the electric motor 20 may be detected, and the power supply current supplied to the electric motor 20 may be controlled based on the detection result.

Further, the mounting structure of the pressure responsive resistance element is not limited to that of the above embodiment, and for example,
As shown in FIG. 6, an iron plate 32 is arranged at the rear end of the shaft 7 of the electric motor 20, and a pressure response resistance element 31 is sandwiched between the iron plate 32 and the end support 30. The pressure responsive resistance element 31 may detect the thrust force applied to the drill 6 in the thrust direction.

[0068]

According to the electric drill of the present invention, the drill attached to the tip of the main body is rotationally driven by the electric motor provided in the main body. At this time, the drill is driven by the drive control means. The rotation speed of the electric motor is controlled based on the pressing force applied to the electric motor. Therefore, the rotational speed of the electric drill is adjusted according to the thrust force applied to the drill, and even when an amateur is working,
For example, when the pressing force at the time of starting the drilling work is low, the rotation speed is low, so that proper positioning can be performed. In the middle of the work, the rotation speed increases as the pressing force increases, and the appropriate drilling work is performed. be able to.

Further, in the work of drilling a through hole, when the through hole penetrates, the pressing force naturally disappears and the rotation speed of the drill decreases, so that the rotating drill is It is possible to avoid problems such as cutting operation by making strong contact with the peripheral wall, expanding and deforming the through hole, and causing breakage of the drill, and safety and protection of the drill and proper drilling work are facilitated. It can be carried out.

In this case, the drive control means detects the pressing force applied to the drill and outputs a detection signal, and the rotation speed of the electric motor is determined based on the detection signal from the detection means. If the rotation speed control means for controlling is provided, the rotation speed of the drill can be easily controlled with a simple configuration based on the thrust force applied to the drill.

Further, the detecting means is composed of a resistance element that changes its resistance value in accordance with the pressing force applied to the drill, and the rotation speed control means controls the power supply current supplied to the electric motor by half. Triac that turns on at the phase where the trigger current flows from the gate circuit from the gate circuit described later every cycle, and the current flowing through the resistance element is charged and discharged to the capacitor every half cycle of the power supply current, and the charge and discharge voltage is applied. The trigger diode is configured to be a gate circuit that turns on the triac by flowing a trigger current to the gate electrode at a timing when the voltage exceeds the breakdown voltage, and the pressing force applied to the drill is simpler and less expensive. Can be detected to control the rotational speed of the drill.

According to the second electric drill of the present invention, the drill attached to the tip of the main body is driven to rotate by the electric motor provided in the main body. At this time, the pressing force applied to the drill by the drive control means. The rotation speed of the electric motor is changed based on the change ratio of the rotation speed with respect to the pressing force per unit set by the change ratio setting means.

Therefore, the change rate setting means sets the change rate of the rotational speed in accordance with the type of work, for example, the size of the diameter of the hole to be drilled, so that the set change rate and the pushing force applied to the drill are set. By adjusting the pressure, the rotation speed of the drill can be adjusted more finely, the work safety is further improved, and the protection of the drill and proper drilling work are made easier. You can

In this case, the drive control means detects the pressing force applied to the drill and outputs a detection signal corresponding to the setting state of the change rate setting means, and a detection signal from the detection means. Based on the above, a rotation speed control means for controlling the rotation speed of the electric motor is provided, and the rotation speed of the drill can be more appropriately adjusted with a simple configuration based on the pressing force applied to the drill. Can be controlled.

Further, the detecting means is composed of a plurality of resistance elements that change their resistance values at different rates according to the pressing force applied to the tip of the drill, and the change rate setting means is the detecting means. A switch for selecting a plurality of resistance elements, the rotation speed control means, the power supply current supplied to the electric motor, for each half cycle, in a phase in which a trigger current is made to flow from the gate circuit to the gate electrode to be described later. The triac that turns on and the current flowing through the resistance element is charged / discharged to / from the capacitor every half cycle of the power supply current, and the trigger current is applied from the trigger diode to which the charge / discharge voltage is applied, at the timing when the voltage exceeds the breakdown voltage. If it is configured with a gate circuit that turns on the triac by flowing it to the gate electrode, it is simpler and cheaper. Formed by, by detecting the pressing force applied to the drill, the rotational speed of the drill and more can be controlled more finely.

[Brief description of drawings]

FIG. 1 is a schematic side view of an electric drill according to an embodiment.

FIG. 2 is a partially cutaway plan view of the chuck portion and the inside of the electric drill of one embodiment.

FIG. 3 is an enlarged front view of a slide switch according to an embodiment.

FIG. 4 is a characteristic curve diagram showing the relationship between the thrust direction pressing force applied to the drill and the rotational speed of the drill of the electric drill according to the embodiment.

FIG. 5 is a circuit diagram of a drive control circuit of an electric drill according to an embodiment.

FIG. 6 is a partially cutaway plan view of another embodiment regarding the disposition position of the pressure response resistance element.

[Explanation of symbols]

 1 Electric Drill 2 Housing 2a Body 2b Grip 2c Slide Groove 3 Power Switch 4 Chuck 5 Chin 6 Drill 7 Shaft 8 Bearing 9 Bearing 9a Inner Ring 9b Outer Ring 10 Sensor 11 End Support 12 Slide Switch 12a-12d Switch position scale 20 Electric motor 21 Drive control circuit 22 Triac 23 Diac R1 Fixed resistance VR1 to VR3 Pressure response resistance element C1 Capacitor

Claims (6)

[Claims] 1. An electric drill in which a drill attached to the tip of a main body is driven to rotate by an electric motor provided in the main body, the size of which is determined according to the pressing force applied to the tip of the drill. An electric drill having drive control means for controlling the rotation speed of the electric motor so as to increase the electric power. 2. The drive control means detects the pressing force applied to the tip of the drill and outputs a detection signal, and the rotation speed of the electric motor based on the detection signal from the detection means. The electric drill according to claim 1, wherein the electric drill comprises: 3. The detection means is composed of a resistance element that changes its resistance value according to the pressing force applied to the drill, and the rotation speed control means controls the power supply current supplied to the electric motor. Every half cycle, a triac that turns on in a phase in which a trigger current flows from the gate circuit to the gate electrode described later, and a current flowing through the resistance element is charged / discharged to / from the capacitor every half cycle of the power supply current, and the charging / discharging voltage is changed. The electric drill according to claim 2, further comprising: a gate circuit that applies a trigger current to the gate electrode and turns on the triac at a timing when a voltage of the applied trigger diode exceeds a breakdown voltage. 4. An electric drill in which a drill attached to a tip portion of a main body is rotationally driven by an electric motor provided in the main body, wherein a change rate of a rotation speed of the electric motor is a tip of the drill. Change rate setting means for setting a change rate of the rotational speed that changes for each constant pressing force applied to the electric motor, and based on the pressing force applied to the tip of the drill, the rotational speed of the electric motor is increased in accordance with the magnitude. An electric drill comprising: drive control means for changing the rotational speed of the electric motor at a change rate corresponding to the setting state of the change rate setting means. 5. The drive control means detects the pressing force applied to the tip of the drill and outputs a detection signal corresponding to the setting state of the change rate setting means, and the detection from the detection means. The electric drill according to claim 4, further comprising: a rotational speed control unit that controls a rotational speed of the electric motor based on a signal. 6. The detection means is composed of a plurality of resistance elements that change their resistance values at different rates according to the pressing force applied to the tip of the drill, and the change rate setting means includes the detection means. A switch for selecting a plurality of resistance elements of, the rotation speed control means, the power supply current to be supplied to the electric motor, for each half cycle, in a phase in which a trigger current flows from the gate circuit to the gate electrode described later. The triac that turns on and the current flowing through the resistance element is charged / discharged to / from the capacitor every half cycle of the power supply current, and the trigger current is applied at the timing when the voltage exceeds the breakdown voltage from the trigger diode to which the charge / discharge voltage is applied. A gate circuit which flows into the gate electrode to turn on the triac, the electric drill according to claim 5.