JP5428850B2 - Hammer drill - Google Patents

Description

  The present invention relates to an electric tool such as a hammer drill, and more particularly to an electric tool that automatically stops an electric motor when a tip tool reaches a target depth.

  Electric tools that automatically stop drilling when a target drilling depth is reached are known. Such an electric tool is provided with a sensing system for calculating a drilling depth based on a distance from a sensor arranged on the power tool to the surface of the work material, and when the drilling is performed to the target depth, the drive current circuit is cut off. Thus, the perforation is automatically stopped (for example, Patent Document 1).

However, in a normal work material, since the friction of scrap of the cut work material is large, it is difficult to extract the tip tool after the automatic stop. Therefore, a method of pulling out while rotating the tip tool by restarting the electric motor is effective.
German Patent No. 2838968

  However, because the friction of the cut work material is large, if the electric motor is suddenly restarted, the tip tool is locked and the electric tool body is swung around, which is dangerous.

  An object of the present invention is to provide an electric tool capable of automatically stopping an electric motor when reaching a target depth, and capable of restarting the electric motor without locking the tip tool when the tip tool is extracted. It is to be.

In order to solve the above problems, an electric tool of the present invention includes an electric motor that outputs a rotational force, a rotation transmission mechanism that can transmit the rotational force of the electric motor to a tip tool, and the rotational force of the electric motor. A striking mechanism that can be converted into striking force and transmitted to the tip tool, a distance sensor that measures the distance to the work material, and a memory that stores the distance from the distance sensor to the tip of the tip tool as a reference distance comprising means, it can be calculated as a distance drilling depth from the measured measured distance based-out work material surface by said distance sensor to the tip of the tool bit, the target depth the drilling depth is set and a control unit for automatically stopping said electric motor to reach a is, the control unit, the time of the to restart the electric motor after the electric motor is automatically stopped, the measured distance by the distance sensor before When the reference distance small, while driving the electric motor at a low driving force than normal, if the measured distance is greater than the reference distance, characterized in that for driving the electric motor in the normal driving force And

According to such a configuration, when the control unit restarts the electric motor after automatically stopping the electric motor, the control unit lowers the electric motor based on the measurement distance from the distance sensor. Since it can be driven by the driving force, it is possible to prevent the tip tool from being locked in the work material due to a sudden restart, and the tip tool can be easily removed. According to such a configuration, when the electric motor is restarted after the electric motor is automatically stopped, if the tip tool remains in the work material, the electric motor is operated with a low driving force. By driving, the tip tool is prevented from locking in the work material, while when the tip tool has already been extracted from the work material, the electric motor is driven with the normal driving force to Drilling can be started.

  Moreover, when the said control part is driving the said electric motor with the driving force lower than usual, when a predetermined condition is satisfy | filled, it is preferable to stop the said electric motor automatically. According to such a configuration, operability can be improved.

  Moreover, it is preferable that the said control part stops the said electric motor automatically as predetermined conditions, when the said front-end tool reaches the position of zero depth. According to such a configuration, the driving of the electric motor can be automatically stopped when the tip tool comes out of the work material.

  Further, in the case where the electric motor is driven with a driving force lower than usual, the control unit turns the electric motor when the depth of the tip tool from the surface of the work material becomes deeper than the target depth. It is preferable to stop automatically. According to such a configuration, when an operator tries to remove the tip tool but accidentally pushes it in the drilling direction, it is possible to prevent drilling deeper than the intended depth.

  The electric motor is preferably a brushless motor. According to such a configuration, a larger rotational force can be output.

    According to the electric tool of the present invention, when the electric motor is restarted after the electric motor is automatically stopped, the electric motor can be driven with a driving force lower than usual based on the measurement distance from the distance sensor. It is possible to prevent the tool body from being swung by the tip tool being locked in the work material due to a sudden restart.

  An embodiment in which the electric power tool of the present invention is applied to a hammer drill will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing the entire hammer drill 1, and a handle part 10 and a housing 20 constitute a casing. The housing 20 is provided with a tool holding unit 30 for holding the tip tool 60 in a detachable manner.

  A trigger switch 12 that can be operated by an operator is attached to the handle portion 10. The trigger switch 12 protrudes from the handle portion 10 while being biased by a spring (not shown). By pushing the trigger switch 12 against the spring force in the handle portion 10 inward, an electric motor 21 to be described later can be started, and the rotation speed of the electric motor 21 is controlled by adjusting the trigger pushing amount. be able to.

  In the housing 20, an electric motor 21, an impact mechanism portion 3, a rotation transmission mechanism portion 5, a control circuit portion 7 (FIG. 2), and an inverter circuit portion 9 (FIG. 2) are accommodated. The electric motor 21 includes an output shaft portion 22 that is a drive shaft, and outputs a rotational driving force.

  The striking mechanism unit 3 converts the rotational force of the electric motor 21 into a striking force and transmits it to the tip tool 60, and the rotation transmission mechanism unit 5 transmits the rotational force of the electric motor 21 to the tip tool 60. It is. The striking mechanism unit 3 and the rotation transmission mechanism unit 5 have known configurations. In the striking mechanism unit 3, when the cam unit 31 converts the rotational motion of the electric motor 21 into reciprocating motion and reciprocates the piston 33. The striking element 34 disposed in the air chamber 32 of the piston 33 is reciprocated by the pressure of the air in the air chamber 32 and strikes the intermediate element 35. The striking force is applied to the tip tool 60 via the intermediate element 35. In the rotation transmission mechanism unit 5, the rotational force of the electric motor 21 is transmitted to the tip tool 60 through the gears 51 and 52, the intermediate shaft unit 53, the gears 54 and 55, and the cylinder 56.

  The housing 20 is provided with a non-contact distance sensor 6, a controller panel 8, and a forward / reverse switching lever 13 (FIG. 2). The distance sensor 6 measures the distance from the distance sensor 6 to the object. The operator operates the controller panel 8 to switch on / off an automatic stop function, which will be described later, and designates a target depth Ld.

  Next, the circuit configuration of the hammer drill 1 will be described with reference to FIG. Electric motor 21 in the present embodiment is a three-phase brushless DC motor. The electric motor 21 is an inner rotor type, and detects a rotational position of a rotor (magnet rotor) 21a configured by embedding a permanent magnet (magnet) including a pair of N poles and S poles. And three rotational position detecting elements (Hall ICs) 21b, 21c, 21d arranged every 60 °, and a current of 120 ° electrical angle based on position detection signals from the rotational position detecting elements 21b, 21c, 21d. It is composed of an armature winding 21f composed of three-phase windings U, V, and W of a star-connected stator 21e controlled in a section.

  The inverter circuit unit (power converter) 9 includes six FETs (hereinafter referred to as “transistors”) Q1 to Q6 connected in a three-phase bridge format and flywheel diodes (not shown). The gates of the six transistors Q1 to Q6 connected in a bridge are connected to the control signal output circuit 77, and the sources or drains of the six transistors Q1 to Q6 are star-connected armature windings U, V and Connected to W. As a result, the six transistors Q1 to Q6 perform a switching operation in accordance with the switching element drive signal input from the control signal output circuit 77, and the DC voltage applied to the inverter circuit unit 9 is changed to the armature windings U and V. , Supplied to W.

The control circuit unit 7 includes a control unit 71, a current detection circuit 72, an applied voltage setting circuit 73, a rotation direction setting circuit 74, a rotation position detection circuit 75, a rotation number detection circuit 76, and a control signal output circuit 77. . The control unit 71 includes a microcomputer and includes a CPU 71A, a ROM 71B, a RAM 71C, and the like. A control program is stored in the ROM 71B. The RAM 71C has a reference distance storage area 71d for storing the reference distance L0 and a target depth storage area 71e for storing the target depth Ld.
The current detection circuit 72 is a circuit for detecting a motor current flowing in the electric motor 21, and the detected current is input to the control unit 71.

  The applied voltage setting circuit 73 is a circuit for setting the applied voltage of the electric motor 21 in response to the pressing amount of the trigger switch 12. The rotation direction setting circuit 74 is a circuit for setting a rotation direction of the electric motor 21 by detecting a forward rotation or reverse rotation operation by the forward / reverse switching lever 13 of the electric motor 21. The rotational position detection circuit 75 detects the relative position between the rotor 21a and the armature windings U, V, and W of the stator 21e based on the output signals of the three rotational position detection elements 21b, 21c, and 21d. Circuit. The rotation speed detection circuit 76 is a circuit that detects the motor rotation speed based on the number of detection signals from the rotor position detection circuit 75 counted within a unit time.

The control signal output circuit 77 supplies a PWM signal to the power supply side transistors Q1 to Q6 based on the output from the control unit 71. By controlling the pulse width of the PWM signal, the number of revolutions of the electric motor 21 in the rotational direction set by adjusting the power supplied to each armature winding U, V, W can be controlled.
Various signals from the distance sensor 6 and the controller panel 8 are input to the control unit 71.

  Next, the control process in the present embodiment will be described with reference to the flowcharts of FIGS. 3 (a) and 3 (b). The control process shown in FIGS. 3A and 3B is executed by the CPU 71A based on the control program stored in the ROM 71B, and is started when the power supply of the hammer drill 1 is turned on.

  In the control process of FIG. 3, first, it is detected whether or not the automatic stop function is turned on (S1). If it is not turned on (S1: No), the process returns to S1 and the process is repeated. On the other hand, if it is turned on (S1: Yes), it is detected whether or not the reference distance L0 is set by the operator (S3). As shown in FIG. 1, the reference distance L0 is a distance from the distance sensor 6 to the tip of the tip tool 60. For example, the distance sensor 6 when the tip of the tip tool 60 is brought into contact with the surface of the work material. Is set as a reference distance L0.

  If the reference distance L0 is not set (S3: No), it waits until it is set. On the other hand, when the reference distance L0 is set (S3: Yes), this is stored in the reference distance storage area 71d of the RAM 71C (S5). Next, it is detected whether or not the target depth Ld is designated by the worker (S7). If the target depth Ld is not specified (S7: No), it waits until it is specified. On the other hand, when the target depth Ld is designated (S7: Yes), this is stored in the target depth storage area 71e of the RAM 71C (S9).

  Next, it is detected whether or not the trigger switch 12 is turned on by the operator (S11). If it is not turned on (S11: No), it waits until it is turned on. On the other hand, when the trigger switch 12 is turned on (S11: Yes), the CPU 71A drives the electric motor 21 at a predetermined rotational speed corresponding to the pushing amount of the trigger switch 12, and starts drilling (S13).

  Next, it is detected whether or not the drilling depth Lx has reached the target depth Ld (S15). The drilling depth Lx is obtained by subtracting the current detection distance L1 by the distance sensor 6 from the reference distance L0 stored in the reference distance storage area 71d (Lx = L0−L1). When the target depth Ld has been reached (S15: Yes), since the drilling has been performed up to the target depth, the current supply to the electric motor 21 is interrupted to end the drilling (S25), and the process proceeds to S27. To do.

  On the other hand, when the target depth Ld has not been reached (S15: No), it is detected whether or not the trigger switch 12 has been turned off by the operator (S17). If not turned off (S17: No), the process returns to S15. On the other hand, if it is turned off (S17: YES), it is detected whether or not there has been an instruction to change the target depth Ld from the operator (S19). An instruction to change the target depth Ld can be made by operating the control panel 8. When there is a change instruction (S19: Yes), the process returns to S9, and the changed target depth Ld is stored in the target depth storage area 71e of the RAM 71C. On the other hand, when there is no change instruction (S19: No), it is detected whether or not the trigger switch 12 is turned on (S21). If it is turned on (S21: Yes), the process returns to S13. If it is not turned on (S21: No), the process returns to S19.

  In S27, it is detected whether or not the trigger switch 12 is turned on. If it is not turned on (S27: No), it is detected whether or not the reference distance L0 stored in the reference distance storage area 71d is equal to or smaller than the current detection distance L1 by the distance sensor 6 (S29). If the reference distance L0 is equal to or smaller than the current detection distance L1 (S29: Yes), the CPU 71A determines that the tip tool 60 has come out of the work material, and returns to the process of S11. That is, after the drilling is finished, the tip tool 60 may be easily removed from the work material by lifting the hammer drill 1. In such a case, without waiting for the next drilling start state without performing the processing after S31. Become.

  On the other hand, if the reference distance L0 is larger than the current detection distance L1 (S29: No), the tip tool 60 has not yet come out of the work material, and the process returns to S27.

  On the other hand, in the case where the scrap of the cut work material is caught and the tip tool 60 cannot be easily removed, a method of extracting the tip tool 60 while rotating the tip tool 60 is effective. However, sudden restart is dangerous because the tool 60 is locked and the tool body is swung. Therefore, when the trigger switch 12 is turned on again by the operator (S27: Yes), the CPU 71A restarts the electric motor 21 at 50% of the predetermined rotation speed (S31). In this case, the amount of decrease in the rotational speed is not limited to 50%, and is preferably set to an appropriate value according to the torque of the electric motor 21 and the type of the tip tool 60. The rotation direction of the electric motor 21 may be either the forward direction or the reverse direction.

  Next, it is detected whether or not the reference distance L0 stored in the reference distance storage area 71d is equal to or less than the current detection distance L1 by the distance sensor 6 (S33). If the reference distance L0 is equal to or less than the current detection distance L1 (S33: Yes), the CPU 71A determines that the tip tool 60 has come off the work material, stops driving the electric motor 21 (S35), and starts the next drilling. It will be in a waiting state.

  On the other hand, if the reference distance L0 is greater than the current detection distance L1 (S33: No), it is detected whether the drilling depth Lx is greater than the target depth Ld (S37). For example, if the operator tries to remove the tip tool 60 but accidentally pushes it in the direction of drilling, if the electric motor 21 continues to be driven as it is, the drill will be deeper than the target depth Ld. In such a case, the result of S37 is Yes (S37: Yes), the current supply to the electric motor 21 is immediately interrupted to stop drilling (S39), and the process returns to S27.

  If strict accuracy is not required for the drilling depth, the current supply may not be interrupted immediately in S39, and it may be automatically stopped after being continuously driven for a predetermined time (for example, 2 seconds).

  The power tool according to the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the gist of the invention described in the claims. For example, in the above embodiment, when it is detected in S33 of FIG. 3 that the tip tool 60 has been removed from the work material (detection distance L1 ≧ reference distance L0), the driving of the electric motor 21 is automatically stopped. However, the driving of the electric motor 21 may be automatically stopped when other conditions are satisfied. For example, the load on the electric motor 21 may be monitored, and it may be determined that the tip tool 60 has been removed when the load is reduced, and the drive of the electric motor 21 may be automatically stopped, or may be driven for a predetermined time after restarting. It may be automatically stopped later. The load on the electric motor 21 can be monitored based on the motor rotational speed detected by the rotational speed detection circuit 76.

Sectional drawing which shows the whole structure of the electric tool which concerns on embodiment by this invention. The block diagram which shows the drive control staff of the motor in the electric tool which concerns on embodiment of this invention. The flowchart which shows the drive process by embodiment of this invention. The flowchart which shows the drive process by embodiment of this invention.

1: hammer drill, 3: striking mechanism, 5: rotation transmission mechanism, 6: distance sensor, 7: control circuit, 8: controller panel, 9: inverter circuit, 10: handle, 12: trigger switch, 20 : Housing, 21: Electric motor, 60: Tip tool, 71: Control unit, 71A: CPU, 71B: ROM, 71C: RAM, 71d: Base 1 quasi-distance storage area, 71e: Target depth storage area, 77: Control Output circuit, L0: Reference distance, Ld: Target depth, Lx: Drilling depth, L1: Current detection distance

Claims (5)

An electric motor that outputs rotational force;
A rotation transmission mechanism capable of transmitting the rotational force of the electric motor to a tip tool;
A striking mechanism that can convert the rotational force of the electric motor into striking force and transmit it to the tip tool ;
A distance sensor that measures the distance to the work material ;
Storage means for storing the distance from the distance sensor to the tip of the tip tool as a reference distance;
And can be calculated as a distance drilling depth from the measured measured distance based-out work material surface by said distance sensor to the tip of the tool bit reaches the target depth of the drilling depth is set A control unit for automatically stopping the electric motor,
When the measurement distance by the distance sensor is smaller than the reference distance when the electric motor is restarted after automatically stopping the electric motor, the control unit controls the electric motor with a driving force lower than usual. On the other hand, when the measured distance is larger than the reference distance, the electric motor is driven with a normal driving force . The control unit automatically stops the electric motor when a predetermined condition is satisfied when the electric motor is driven with a driving force lower than normal after the electric motor is automatically stopped. The power tool according to claim 1.   The electric power tool according to claim 2, wherein the control unit automatically stops the electric motor when the tip tool reaches a position of zero depth as a predetermined condition. In the case where the control unit drives the electric motor with a driving force lower than usual after automatically stopping the electric motor, the depth of the tip tool from the surface of the work material is larger than the target depth. The electric tool according to any one of claims 1 to 3, wherein when the depth is increased, the electric motor is automatically stopped. The electric tool according to any one of claims 1 to 4, wherein the electric motor is a brushless motor.

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