JP2533769B2 - Hammer drill - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hammer drill that imparts not only rotation but also axial impact vibration to a drill bit.

(Background Art) As a tool for drilling concrete, there is one called a hammer drill. This has a piston that is reciprocally driven in the axial direction and a striking body that is also slidable in the axial direction,
The movement of the piston is transmitted to the striking body via an air spring interposed between the piston and the striking body, and the striking body applies striking vibration to the drill bit. In addition, electronically control the number of rotations of this hammer drill to prevent step deviation of the drilling position, and depending on the material of the material to be drilled, for example, concrete is rotated at high speed and the hardness of mortar, foamed concrete, etc. If the material is relatively low, there is one that allows the drilling speed to be adjusted, such as low speed rotation.

By the way, the hammering vibration of the hammer drill is generated by the air spring and the hammering body, and there is a disadvantage that a resonance phenomenon occurs in a low rotation range. FIG. 6 shows how the resonance phenomenon occurs. As the input amount of the motor rotation speed control means increases, the rotation speed of the drill bit increases linearly. On the other hand, if the number of impacts of the drill bit falls within the resonance region, a resonance phenomenon occurs and the impact vibration becomes unstable. However, as the input amount further increases, the resonance disappears and the impact becomes stable. When this resonance phenomenon occurs during work, an abnormal sound is generated, the strength of striking changes discontinuously, the striking interval changes, and the drilling ability decreases. Also, it becomes difficult to make a clean hole with good roundness.

(Object of the Invention) The present invention has been proposed in view of the above points, and an object of the present invention is to provide a hammer drill having a motor rotation speed control means in which a resonance phenomenon does not occur.

DISCLOSURE OF THE INVENTION In order to achieve the above object, the present invention provides a rotation transmission means for imparting rotation to a drill bit held by a spindle,
In a hammer drill including an impact transmission means having an air spring for impacting the drill bit and an impact body, and a motor rotation speed control means for variably controlling the rotation speed of a motor driving the transmission means, the motor rotation The speed control means is provided with an interlocking volume on an operation handle whose operation amount is variable, and in a predetermined operation range of the operation handle, the output of the motor for driving the striking means is constant,
Further, the gist of the invention is a hammer drill, which is characterized in that when a predetermined operation range is exceeded, an output obtained by adding a predetermined amount of output is supplied to a motor.

Hereinafter, embodiments of the hammer drill of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of the hammer drill of the first embodiment, FIG. 2 is a circuit diagram of its motor rotation speed control means, and FIG. 3 is a view showing changes in the number of rotations of a drill bit and the number of impacts.

First, the overall structure of the first embodiment will be described.
As shown in FIG. 1, the main body has a chuck portion 3 to which a drill bit 2 is attached at a front end, a handle portion 4 is provided at a rear end, and a storage battery pack 5 is provided at a central portion of the main body. It is detachably attached. In the figure, 6 is a switch handle, 7 is a rotation direction switching handle, 8 is a motor mount, 9 is an air hammer base, and 10 is a housing that also serves as a motor case. The motors 11 and 12 are housed in the lower part of the motor mount 8 in such a manner that their axial directions are parallel to each other and are orthogonal to the drill bit. The output shaft 13 thereof has a bevel gear 15 and the output shaft 14 thereof has a pinion. 16
Are fixed respectively. The pinion 16 is a reduction gear 18 fixed to one end of a crank 17 that converts rotation into reciprocating motion.
Is meshing with. The crank 17 is rotatably held by a bearing 19 and attached to the motor mount 8 and the air hammer base 9. Crank 17 connecting rod
20 is arranged to reciprocate the piston 21. On the other hand, a spindle 24 rotatably supported by bearings 22 and 23 is arranged in the front end portion of the housing 10. The spindle 24 has a bevel gear 25 that meshes with the bevel gear 15 fixedly attached to the outer peripheral surface of the rear end thereof, and has a striker 26 slidably mounted therein in the axial direction. The chuck portion 3 is configured to hold so that it can be freely moved. The striker 26 has its axial sliding range regulated by a locking body 27 fixed inside the spindle 24.

On the other hand, a piston 21 and a striking body 28 are installed behind the striker 26. The piston 21 is slidably held by the air hammer base 9 in the direction parallel to the axial direction of the spindle 24. The bottomed cylindrical piston 21 connected to the crank 17 has a closed rear end. The hitting body 28 is slidably housed inside.

The crank 17 converts a rotary motion into a reciprocating motion.

Further, the electric power supplied from the storage battery pack 5 is distributed to the motors 11 and 12 via the switch module 29.

Due to this configuration, the rotation of the motor 12 is
The crank 17 is rotated via the pinion 16 and the reduction gear 18, and the rotation of the crank 17 is converted into a linear movement to reciprocate the piston 21. The reciprocating motion of this piston 21
The striking body 28 is reciprocally driven by interposing air sealed in a space 30 formed in a gap between the piston 21 and the striking body 28 as an air spring. Next, the reciprocating motion of the impacting body 28 is caused by the striker 26.
Impact vibration is applied to the drill bit 2 via.

Similarly, the rotation of the motor 11 is transmitted to the spindle 24 via the bevel gears 15 and 25, and rotates the drill bit 2 via the chuck portion 3.

Next, the control of the rotation of the motors 11 and 12 will be described with reference to FIG.

In the figure, reference numeral 40 is a variable resistor built in the switch handle 6, and the resistance value changes by changing the operation amount of the switch handle 6. The change in the resistance value of the variable resistor 40 is passed through the feedback circuit 41 and the output circuit 42 to the transistor 43.
The rotation speed of the motor 11 can be continuously changed from zero by controlling.

On the other hand, when the rotation speed of the motor 11 increases, the voltage of the feedback circuit 41 rises, and when it becomes higher than the reference voltage 44 set in advance, an output signal is output from the comparator 45 to turn on the transistor 46 to turn on the motor. Rotate 12 to generate a blow to the drill bit. Further, the reference voltage 44 can be arbitrarily adjusted by the user by a volume (not shown), and can be freely changed according to the number of hits that resonate. In the figure, 47 is the storage battery pack 5.
Reference numeral 48 denotes a rotation detector that detects the number of rotations of the motor 11 and inputs it to the feedback circuit 41.

Variable resistance that is the input amount of the motor rotation speed control means when the rotation of the hammer drill is controlled by the above circuit
FIG. 3 shows the relationship between the resistance value of 40 and the number of rotations and the number of impacts of the drill bit. That is, in the low-speed resonance region, since the motor 12 is not driven, the impact vibration is not applied, the drill bit only rotates, and the resonance phenomenon does not occur. This makes it possible to easily and accurately set the drilling position when starting the drilling work, which has been troublesome in the past.

Although the first embodiment described above is a hammer drill equipped with two motors, the hammer drill of the second embodiment in which rotation and striking vibration are applied by one motor will be described below. FIG. 4 is a circuit diagram of the motor rotation speed control means of the second embodiment, and FIG. 5 is a diagram showing changes in the number of rotations of the drill bit and the number of impacts.

In the second embodiment, so to speak, an area where the rotation number of the drill bit is invariable is provided corresponding to the area where the impact number of the drill bit is invariable. That is, in FIG. 4, when the sliding contact 51 of the variable resistor 50 incorporated in the switch handle or the like (not shown) moves from point A to point D on the variable resistor by the operation of the switch handle or the like, The resistance value of the resistor 50 increases linearly from point A to point B,
A constant value is maintained from the point to the point before the point C, and at the point C, the resistance increases sharply by the resistance of the resistor R1 provided by bypassing between the points B and C, and thereafter linearly increases. Show. This variable resistor 50 with a discontinuous resistance value allows the output circuit 52
Controls transistor 53 and drives motor 54. In the figure, 47 is a power source housed in a storage battery pack or the like (not shown).

When the rotation of the hammer drill is controlled by the above circuit, the relationship between the input amount of the motor rotation speed control means, that is, the movement amount of the sliding contact 51 of the variable resistor 50, and the rotation speed and the number of hits of the drill bit is shown. Fig. 5 shows As is apparent from the figure, this second embodiment allows a harmful resonance region to instantaneously pass by changing the resistance value of the variable resistor 50 discontinuously. Even with a hammer drill equipped with, the resonance phenomenon could be prevented with a simple circuit configuration.

(Effect of the Invention) In the present invention, the rotation speed of the motor for driving the striking means is adjusted by the volume (operation handle), but in order to avoid the resonance region as shown in FIG. As shown in Fig. 5, the output of the motor is constant in the operation range of the volume (operation handle) so as to avoid the hitting area where the resonance phenomenon occurs, and when the output exceeds the predetermined range, the output of the predetermined amount is output. Supply the output to the motor. As a result, the resonance region in the impact vibration can be avoided and the occurrence of the resonance phenomenon can be prevented, so that a stable impact can always be obtained and the perforation can be smoothly performed.

[Brief description of drawings]

FIG. 1 is a sectional view of the hammer drill of the first embodiment, and FIG.
FIG. 4 is a circuit diagram of the motor rotation speed control means, FIG. 3 is a view showing changes in the number of rotations of the drill bit and the number of hits, and FIG. 4 is a circuit diagram of the motor rotation speed control means of the second embodiment. 5
FIG. 6 is a diagram showing changes in the number of rotations of the drill bit and the number of impacts, and FIG. 6 is a diagram showing a conventional example. 2 is a drill bit, 3 is a chuck part, 4 is a handle part,
5 is a storage battery pack, 6 is a switch handle, 7 is a rotation direction switching handle, 8 is a motor mount, 9 is an air hammer base, 10 is a housing, 11 and 12 are motors, 13 and 14
Is an output shaft, 15 is a bevel gear, 16 is a pinion, 17 is a crank, 18 is a reduction gear, 19 is a bearing, 20 is a connecting rod,
21 is a piston, 22 and 23 are bearings, 24 is a spindle, 25 is a bevel gear, 26 is a striker, 27 is a locking body, 28 is a striking body,
29 is a switch module, 30 is an air spring space, 40
Is a variable resistor, 41 is a feedback circuit, 42 is an output circuit,
43 is a transistor, 44 is a reference voltage, 45 is a comparator, 46 is a transistor, 47 is a power supply, 48 is a rotation detector, 50 is a variable resistor, 51 is a sliding contactor, 52 is an output circuit, 53 is a transistor, 54 Is a motor.

Claims (1)

(57) [Claims] 1. A rotation transmission means for giving rotation to a drill bit held by a spindle, an impact transmission means having an impacting body with an air spring for giving impact to the drill bit, and a rotation speed of a motor for driving the transmission means. In a hammer drill having a motor rotation speed control means for variably controlling the number of strokes, the motor rotation speed control means includes an operating volume variable operation handle and an interlocking volume, and in a predetermined operating range of the operation handle, A hammer drill, characterized in that the output of a motor for driving the means is constant, and when the output exceeds the predetermined operation range, an output added with a predetermined amount of output is supplied to the motor.