JP5559718B2 - Electric tool - Google Patents

Description

  The present invention relates to a power tool, and more particularly to a power tool provided with a speed change means.

  When screw tightening or drilling work with an electric tool that can switch the reduction ratio according to the work load, first start the work with a reduced speed ratio, that is, low torque and high speed rotation, and then set the reduction ratio. It is efficient to increase the speed and shift the speed toward the high torque low speed rotation side. However, if the gear ratio is switched manually, the reduction speed ratio must be set at the start of work, and an operation to switch to the high reduction ratio side must be added during work, increasing the burden on the operator. End up.

  For this reason, Japanese Patent Application Laid-Open No. H10-228561 proposes a method in which a change in load torque is detected directly or indirectly and a shift is automatically performed in accordance with the change.

  However, in the conventional automatic transmission, the reduction ratio at the start of work is fixed to the reduction speed ratio, and also when the motor is reversely rotated, the reduction ratio is also fixed.

  For this reason, in the case of the screw loosening work performed by reversing the motor, not the screw tightening work performed by rotating the motor forward, the speed ratio is reduced although high torque is required at the initial stage. In other words, the work is started at a low torque and a high rotation, which places a heavy burden on the motor and the like. If the screw loosening operation is started after manually setting to a high reduction ratio, the burden on the motor or the like is reduced, but this cannot take advantage of the automatic transmission.

JP 2009-78349 A

  The present invention has been made in view of the above points, and for each of the work performed by rotating the motor forward and the work performed by rotating the motor reversely, the work is started at an appropriate reduction ratio. It is an object of the present invention to provide an electric tool that can be automatically shifted.

The present invention provides an increase in work load in an electric tool in which a transmission that switches a reduction ratio is arranged between a motor that can rotate forward and backward as a rotational power source and an output unit that is rotationally driven by the motor. The control means for switching the transmission to a high reduction ratio, switching the transmission to a reduction speed ratio when the work load decreases, and changing the initial setting state of the reduction ratio of the transmission at the start of work according to the rotation direction of the motor It is characterized by having.

  The reduction ratio in the initial setting of the reduction ratio when the motor rotation direction is reverse is larger than the reduction ratio in the initial setting of the reduction ratio when the motor rotation direction is normal. If the reduction ratio in the initial setting of the reduction ratio when the motor rotation direction is reverse than the reduction ratio in the initial setting of the reduction ratio in the case of rotation, or if the rotation direction of the motor is normal The speed reduction ratio initial setting state is the non-reduction speed ratio side, and the speed reduction ratio initial setting state when the motor rotation direction is reverse is also the non-reduction speed ratio side.

  It is good also as what was provided with the work start time transmission setting means for a user to change the reduction ratio initial setting of the transmission at the time of work start.

  A transmission that can switch the reduction ratio to three or more stages may be used as the transmission.

  It is also preferable to provide display means for displaying the reduction ratio initial setting state to the user.

  In the present invention, not only the work performed by rotating the motor forward, but also the work performed by rotating the motor in reverse, the work can be started at an appropriate reduction ratio, and the burden on the tool is reduced for this purpose. In addition, the efficiency of the work itself can be improved, and a comfortable work can be performed.

It is a flowchart which shows operation | movement of an example of embodiment of this invention. It is a block diagram same as the above. It is explanatory drawing of the torque change about screw fastening (screw loosening), (a) has shown the time of motor forward rotation, (b) has shown the time of motor reverse rotation. It is a flowchart of another example. It is explanatory drawing of the torque change about the screw fastening (screw loosening) with respect to a reverse screw, (a) has shown the time of motor forward rotation, (b) has shown the time of motor reverse rotation. It is a flowchart of other examples. (a) (b) is explanatory drawing of the torque change about each operation | work. It is a block diagram of another example. It is a flowchart same as the above. It is a flowchart of another example. It is explanatory drawing of the torque change of a drilling operation | work. It is a block diagram of another example. It is a top view same as the above.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiment. The electric tool shown in FIG. 2 is an electric drill driver that uses a motor 10 that can freely rotate in the forward and reverse directions, and the rotational output of the motor 10 has a reduction ratio. Is output to the output unit 12 via a transmission 11 having a speed change function. In the figure, 18 is a battery pack.

 The transmission 11 can switch a reduction ratio by an electromagnetic member such as a solenoid, and the switching operation of the reduction ratio is performed under the control of the control circuit 13.

  The control circuit 13 also controls the rotation of the motor 10 in accordance with the operation of the trigger switch 14. The control circuit 13 that drives the motor 10 through the motor drive circuit 15 has a rotation speed N of the motor 10. Is connected to the current detection means 17 for detecting the motor drive current I. When the reduction ratio switching operation is automatically performed in accordance with the work load, both the detection means described above are used. The control circuit 13 instructs the transmission 11 to switch the reduction ratio in the transmission 11 in accordance with the detection output of the driving state detection means 16, 17.

  If the output load is small when the motor 10 is started up, the motor drive current I increases and the increase rate of the motor rotation speed N also increases. When the output load is large, the motor drive current I increases in the same manner, but the increase rate of the motor rotation speed N is small or zero.

  For this purpose, the control circuit 13 composed of a one-chip microcomputer or the like in this electric power tool is set to the side where the reduction ratio is small (the reduction ratio 1 in FIG. 1) by default, and the motor drive current I ≧ I1 ( When the two conditions A) and the motor rotation speed increase rate ≦ α1 are satisfied, the automatic transmission is shifted to the side where the reduction ratio becomes large (the reduction ratio 2 in FIG. 1).

  Therefore, when performing a work in which the load at the start is small and the work load gradually increases as the work continues, the motor drive current I gradually increases and the motor rotation speed N decreases, but the motor drive current I ≧ I1. When the condition of (A) and the increase rate of the motor rotation speed N ≦ α1 is satisfied, the control circuit 13 automatically shifts the transmission 11 to the side where the reduction ratio becomes larger. In addition, the increase rate of the motor rotation speed N may be a negative value.

  In order to perform automatic gear shifting under the above conditions, there is an inrush current at the start of the motor 10 and an inrush current that occurs when the operator repeats the operation of turning on the trigger switch 14 in the no-load state and returning it to the level just before the off However, if the value of α1 is set to an increase rate that can be determined, automatic automatic shift switching is not performed.

  On the other hand, when the load is reduced as the work is performed, the gear is shifted in the direction of decreasing the reduction ratio. When the work load decreases, the motor drive current I decreases and the motor rotation speed N increases. Accordingly, when the conditions of the motor drive current I ≦ I3 (A) and the motor rotation speed N ≧ N3 are satisfied, the automatic transmission is automatically shifted to the reduction speed ratio (high speed side).

  By the way, in an electric tool such as an electric drill driver, the motor 10 is often rotated forward and used for screw tightening. In this case, the load is initially small and the load increases as the screw tightening proceeds. For this reason, when performing the automatic shift as described above, as described above, it is preferable to set the reduction speed ratio (low torque high speed rotation) in the initial state, and if the work load increases, the high reduction ratio ( When the operation is automatically completed and the trigger switch 14 is turned off, it is preferable to return to the reduction speed ratio which is the initial state.

  However, considering the work performed by reversing the motor 10, the typical work is the work of loosening the tightened screw. At this time, as shown in FIG. It will be big. At this time, if the initial setting is the reduction speed ratio, a large load is applied to the motor 10 at the start of work, and the actual screw loosening work starts after switching to the high reduction ratio. Loss will occur. Moreover, there is a possibility that the motor lock occurs at the start of work. When disassembling instead of assembling, work is mainly performed in the reverse direction, and there are many problems if the initial reduction ratio is set in accordance with the forward rotation.

  For this reason, in this electric power tool, the initial reduction ratio is set to the reduction speed ratio at the time of forward rotation and the initial reduction ratio at the time of reverse rotation in accordance with the setting of the rotation direction by the rotation direction switching means 19 for switching the rotation direction of the motor 10. It is set to a high reduction ratio. For this purpose, the reduction ratio is preferably switched when the rotation direction of the motor 10 is switched by the rotation direction switching means 19.

  Since the initial reduction ratio is switched in accordance with the rotation direction of the motor 10, in this electric tool, when the motor 10 is rotated forward, the operation is started in the state of the reduction speed ratio as described above, and the load becomes large. The transmission 11 is controlled by the control circuit 13 so as to return to the reduced speed ratio by automatically switching to the high speed reduction ratio and finishing the work and turning off the trigger switch 14.

  If the rotation direction of the motor 10 is set to the reverse rotation direction by the rotation direction switching means 19, the transmission 11 is switched to the high reduction ratio state at this point, and the high torque / low speed rotation state is established when the trigger switch 14 is turned on. Work can be started. Then, when the work load is gradually reduced and the above condition is reached, automatic shifting is performed to the reduction speed ratio side. When the work is finished and the trigger switch 14 is turned off, the transmission 11 automatically returns to the high reduction ratio side.

  There is no need to separately perform a changeover operation of the reduction ratio of the transmission 11 when performing screw tightening work or screw loosening work, and the speed reduction ratio at the start of work is a deceleration suitable for each work. Because of the ratio, it is extremely convenient.

  However, some screws are referred to as reverse screws, and when the reverse screws are tightened, the motor 10 is reversed. The work of loosening the reverse screw is performed by rotating the motor 10 forward. Therefore, when working with a reverse screw, contrary to the above embodiment, the initial reduction ratio is set to a high reduction ratio at the time of forward rotation and the initial deceleration at the time of reverse rotation in accordance with the rotation direction set by the rotation direction switching means 19. The ratio may be set to a reduction speed ratio. FIG. 4 shows a flowchart in this case. FIG. 5 (a) shows the torque change when the reverse screw is loosened by forward rotation of the motor, and FIG. 5 (b) shows the torque change when the reverse screw is tightened by reverse rotation of the motor.

  In this case, when the motor 10 is rotated forward, it is set to a high reduction ratio, and when the trigger switch 14 is turned on, the operation can be started in a high torque / low speed rotation state. When the work load gradually decreases and reaches a preset condition, automatic shift is performed to the reduction speed ratio side. When the work is finished and the trigger switch 14 is turned off, the transmission 11 automatically returns to the high reduction ratio side.

  If the rotation direction of the motor 10 is set to the reverse rotation direction by the rotation direction switching means 19, the transmission 11 is switched to the reduced speed ratio state at this point, and the trigger switch 14 is turned on to operate in the reduced speed ratio state. When the load increases, automatic switching to the high reduction ratio is performed, and when the operation is completed and the trigger switch 14 is turned off, the reduction speed ratio is restored.

  For this reason, in the case of this embodiment, it can be used for reverse screw tightening work and the like which are completely opposite to the normal screw tightening work.

  In addition, there is a change in the tightening torque depending on the type of work in forward rotation work. The tightening of the small-diameter screw is a torque change as shown in FIG. 7 (a), and it is efficient to start work at a low speed and high speed rotation on the reduced speed side. However, in the case of a large-diameter screw (for example, a coach screw), the torque changes as shown in FIG. 7B, and when the work is started on the reduction speed ratio side, it is locked immediately after the work is started.

  For such work that requires a high tightening torque immediately after the start of work, work can be performed efficiently by starting work with a high reduction ratio, and the burden on the tool due to motor lock or the like can be reduced. . In addition, when loosening a screw that is fastened, since the beginning of the loosening is a high torque operation, a high torque low speed rotation with a high reduction ratio is also suitable at the start of the operation. For this reason, when high torque is required in both the forward and reverse rotation directions at the start of work, as shown in FIG. 6, the one in which the high reduction ratio is in the initial state can be suitably used.

  Considering that the preferred initial reduction ratio varies depending on the type of work, it is preferable that the user can set the initial reduction ratio. FIG. 8 shows a device provided with a work start speed setting means 20 for the user to set the initial speed reduction ratio, and the control circuit 13 has the speed reduction ratio set by the work start speed setting means 20 set. The control circuit 13 stores the initial reduction ratio and controls the transmission 11. FIG. 9 shows a flowchart.

  For example, when a push switch is used as the work start speed setting means 20, if the push switch is operated when the tool is stopped and the forward direction is set by the rotation direction switching means 19, the forward start state of the work is started. When the push switch is operated when the tool is stopped and set to reverse rotation, the initial reduction ratio at the start of work in the reverse rotation state is switched. The initial reduction ratio is sequentially switched by repeatedly turning on the push switch. Of course, it is not necessary to use a push switch, but as described above, if the initial reduction ratio in the rotational direction set by the rotational direction switching means 19 is changed, The setting operation of the initial reduction ratio and the initial reduction ratio at the time of reverse rotation can be performed with a small number of members, and the user-friendliness is also improved.

  In addition, in order to perform the same work continuously, the operator can perform the work continuously in that state once the initial reduction ratio is set according to the work content. In addition, the use efficiency of one power tool can be increased.

  Of course, the present invention can also be applied to the transmission 11 in which the reduction ratio can be switched in three stages, and FIG. 10 shows a flowchart in this case.

  When the speed reduction ratio is in the smallest state, when the conditions of motor drive current I ≧ I1 (A) and motor rotation speed N increase rate ≦ α1 are satisfied, the speed reduction ratio is switched to a medium speed reduction ratio that is one step higher. When the two conditions of the motor drive current I ≧ I2 (A) and the motor rotation speed N ≦ α2 are satisfied in the state, the automatic transmission is shifted to the side with the largest reduction ratio.

  On the other hand, when the speed reduction ratio is the largest, the speed is automatically changed to the medium speed reduction ratio when the conditions of the motor drive current I ≦ I4 (A) and the motor rotation speed N ≧ N4 are satisfied. In this state, when the conditions of the motor drive current I ≦ I3 (A) and the motor rotational speed N ≧ N3 are satisfied, the automatic transmission is shifted to the high speed side.

  Thus, in the case of the three-speed shift, the initial reduction ratio is preferably set to the medium reduction ratio (medium torque / medium speed rotation) at the time of forward rotation and reverse rotation. In the woodwork drilling operation, drilling with various hole diameters of φ10 mm to φ30 mm is performed. Further, as shown in FIG. 11, the working torque characteristics of the woodworking drilling operation are such that the torque increases at the start of drilling, gradually decreases to a stable torque, and finally penetrates to become zero. For this reason, when the work is started at the reduced speed ratio, the gear shifts to the medium deceleration side immediately after the start of drilling, and the work is completed in the middle deceleration state. Shifting to a high reduction ratio completes the work. That is, in the woodwork drilling work, the work at the reduced speed ratio is almost unnecessary. Therefore, by starting the work from the medium reduction ratio, the work can be efficiently performed without performing an extra shift, and the burden on the operator can be reduced.

  Considering that the present invention is also applicable to the above-described screw tightening operation, it is needless to say that it is preferable to provide the operation start speed setting means 20 so that the user can change the initial reduction ratio.

  FIGS. 12 and 13 show a display unit 21 that notifies the user of the initially set reduction ratio. As the display means 21, for example, a tool provided with three light emitting diodes of a reduction speed ratio (H), a medium reduction ratio (M), and a high reduction ratio (L) on the upper part of the tool can be suitably used. The user is notified of the initial reduction ratio in the current motor rotation direction by turning on the light emitting diode corresponding to the initial reduction ratio at the start of work in the rotation direction determined by the direction switching means 19.

  A total of 6 LEDs of 3 × 2 for forward rotation and reverse rotation may be provided. Since the user can easily recognize the initial reduction ratio set in advance or the initial reduction ratio set by the user himself / herself, it is possible to prevent work failure due to working with an incorrect initial reduction ratio. .

DESCRIPTION OF SYMBOLS 10 Motor 11 Transmission 12 Output part 13 Control circuit 14 Trigger switch 15 Motor drive circuit 16 Motor rotation speed detection means 17 Motor current detection means 18 Battery pack 19 Rotation direction switching means 20 Work start time shift setting means 21 Display means

Claims (7)

In an electric tool in which a transmission that switches a reduction ratio is arranged between a motor that can rotate forward and backward as a rotational power source and an output unit that is rotationally driven by the motor,
When the work load increases, the transmission is switched to a high reduction ratio, and when the work load decreases, the transmission is switched to a reduction speed ratio, and the initial setting state of the transmission reduction ratio at the start of work depends on the rotation direction of the motor. An electric tool comprising a control means for changing.   The reduction ratio in the initial setting of the reduction ratio when the motor rotation direction is reverse is larger than the reduction ratio in the initial setting of the reduction ratio when the motor rotation direction is normal. The electric tool described.   The reduction ratio in the initial setting of the reduction ratio when the motor rotation direction is reverse is smaller than the reduction ratio in the initial setting of the reduction ratio when the motor rotation direction is normal. The electric tool described.   The reduction ratio initial setting state when the motor rotation direction is forward rotation is the non-reduction speed ratio side, and the reduction ratio initial setting state when the motor rotation direction is reverse rotation is also the non-reduction speed ratio side. The electric tool according to claim 1.   The power tool according to any one of claims 1 to 4, further comprising: a work start speed setting unit for a user to change an initial reduction ratio setting of the transmission at the start of the work.   The power tool according to any one of claims 1 to 5, wherein the transmission is capable of switching a reduction ratio to three or more stages.   The power tool according to any one of claims 1 to 6, further comprising display means for displaying a reduction ratio initial setting state to a user.

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