JPH0811372B2 - Hammer drill - Google Patents

Description

Detailed Description of the Invention 【Technical field】

TECHNICAL FIELD The present invention relates to a hammer drill which not only rotates a drill bit but also gives an impact impact in the axial direction.

[Background Art]

There is a drilling tool for concrete called a hammer drill. As shown in FIG. 12, this is provided with a piston 4 which is reciprocally driven in the axial direction and a hammer 41 which is also slidable in the axial direction, and an air spring is interposed between the piston 4 and the piston 4. The movement is transmitted to the hammer 41 via an air spring, and the hammer 41 further applies a striking impact to the drill bit 8. By the way, in this type of hammer drill, as a motion converting member that converts the rotation of the motor into the reciprocating motion of the piston, a normal crank structure is used as shown in FIG. 12, and the motor is also operated at a constant speed. Since it is supposed to rotate, when the time axis is taken, the movement of the piston 4 is a sine movement as shown by PC in the figure. Hammer 41
Since the piston 4 follows the movement of the piston 4 via the air spring, the movement thereof is as shown by HC in the figure, and the drill bit 8
The hit position HP is the one that goes to the hit position HP
The speed is higher than that in the backward moving backward path, and the striking force is higher than when the drill bit 8 is directly hit by the piston 4. However, if the striking force is further increased to enable the drilling of a large-diameter hole, the piston 4 will have to be set no matter how the spring constant of the air spring is set.
Since there is only sinusoidal motion, there is a limit. Even if the output of the motor is increased, the one using a battery as a power source has a limitation from this point, and the output of the motor cannot be increased indefinitely.

[Object of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hammer drill that exhibits high drilling ability even when the motor output is low.

DISCLOSURE OF THE INVENTION

Accordingly, the present invention is directed to a motor, a spindle which is rotationally driven by the motor and holds a drill bit, and a motor which is connected to the motor through a motion converting member to reciprocate and through the air spring and the hammer. In a hammer drill equipped with a piston for applying a striking impact to a drill bit, it is characterized in that it is provided with a non-uniform speed-increasing means for making the forward travel speed of the piston faster than the homeward travel speed. By making the speed higher than the speed of the return path, the striking force by the hammer is further increased. Hereinafter, the present invention will be described in detail based on illustrated embodiments. First, the overall structure will be described. As shown in FIG. 2, the main body housing 1 has a chuck portion 13 to which a drill bit 8 is attached at a front end thereof, and a handle portion 16 extends from a rear end portion thereof. The storage battery pack 9 is detachably arranged in the lower central portion, and the auxiliary storage battery pack 60 is detachably mounted in the upper rear portion. In the figure, 14 is a switch handle, 15 is a rotation direction switching handle, and 29 is a switch box. The auxiliary storage battery pack 60 is housed in a case 61 having a lid 62, and a hook 65 provided on the main body housing 1.
It is attached to the main body housing 1 by locking one end of the case 61 to the screw hole 66 of the main body housing 1 through the other end of the case 61, and at this time, it is arranged on the surface of the case 61. Battery terminal 6
4, 64 are connected to the connection terminals 67, 67 arranged on the upper surface of the rear end portion of the main body housing 1. The auxiliary battery pack 60 and the storage battery pack 9 are connected in parallel in the switch box 29 as shown in FIG. When working in a small space or when the amount of work is small, work is performed only with the storage battery pack 9, and when the amount of work is large, the auxiliary battery pack 60 is also installed to increase the power supply capacity, thereby eliminating the trouble of replacing the battery pack 9. It is what The motor 2 is housed in the main body housing 1 with its axial direction in the front-rear direction, and a pinion 21 is fixed to the output shaft 20 thereof. This pinion 21 is press-fitted and fixed to one end of an intermediate shaft 23 whose both ends are rotatably supported by bearings 22 and 22 by a housing 11 and a motor mount 12 and whose axial direction is parallel to the axial direction of the motor 2. Gear 24
Is meshing with. The motion converting member 5 is attached to one end of the intermediate shaft 23, and the pinion is attached to the other end.
25 is stuck. On the other hand, in the front end portion of the main body housing 1, a spindle 31 rotatably supported by a bearing 30 is installed. A gear 32 that meshes with the pinion 25 is provided on the outer peripheral surface of the rear end.
This spindle 31 to which is fixed is a striker 33
Has a key 39 that engages with the chuck handle 38 and the long groove 80 of the drill bit 8 at the tip.
At the same time, the chuck 13 that holds the drill bit 8 so that it can slide freely within a predetermined range is configured. The striker 33 has an axial sliding range defined by a locking body 34 fixed inside the spindle 31. Behind striker 33, piston 4 and hammer 41
Is installed. The piston 4 is mounted on the intermediate shaft 23 and the spindle 31 by the motor mount 12 on which the motor 2 is mounted.
The piston 4 is slidably held in a direction parallel to the axial direction of the piston and is connected to the motion converting member 5 and has a bottomed cylindrical shape with a closed rear end. The hammer 41 is slidably accommodated. The motion converting member 5 shown in the present embodiment converts a rotary motion into a reciprocating motion, and also serves as a non-uniform speed-increasing means 6 for making the forward path speed in the reciprocating motion of the piston 4 faster than the return path speed. The cylindrical rotor 55 fixed to the intermediate shaft 23, the endless cam groove 56 cut on the outer peripheral surface of the rotor 55, and the shaft projecting from the outer peripheral surface of the piston 4. And a roller 57 that is supported by and runs in the cam groove 56. When the intermediate shaft 23 and the rotating body 55 rotate, the roller 57 slidingly engaged with the cam groove 56 drives the piston 4 in its axial direction to cause the piston 4 to reciprocate. With this hammer drill, however, the tip of the drill bit 8 is brought into contact with the surface to be drilled so that the rear end of the drill bit 8 abuts the striker 33.
When the motor 2 is operated by operating 14, the rotation of the motor 2 is transmitted from the intermediate shaft 23 to the drill bit 8 via the spindle 31 and the key 39. Further, the piston 4 is reciprocated through the motion converting member 5, and the hammer 41 follows the reciprocal movement of the piston 4 via the air spring in the air chamber 42 in the piston 4, and the hammer 41 causes the striker 33 to move. The striking impact when striking is transmitted to the drill bit 8 through the striker 33. Here, the cam groove 56 in the motion converting member 5
When the axis of rotation of the rotor 55 is the y-axis and the rotation angle is the x-axis, the cam groove 56 has a sawtooth curve instead of a sine curve as shown in FIG. The movement of the piston 4, which is reciprocally driven in the axial direction in accordance with the change in the y-axis direction, is as shown by PC in FIG.
The forward path moving to the hitting position HP side is faster than the returning path, and accordingly, the hammer 41 also strikes the drill bit 8 via the striker 33 as shown by HC in the figure. The speed of the outbound route increases. Since the strength of the impact shock when the hammer 41 strikes the striker 33 is determined by the mass of the hammer 41 and the sled, the impact shock is increased by increasing the speed. Another embodiment is shown in FIGS. 6 and 7. This is a spherical body 50 attached to the intermediate shaft 23 as the motion converting member 5.
A ring 52 rotatably attached to the outer peripheral surface of the spherical body 50 via a large number of balls 51, a shaft 53 protruding from the ring 52, and slidable with respect to the shaft 53. The slider 54 has one end connected to the piston 4 by the pin 44, and the rotation center axis of the ring 52 is inclined with respect to the axial direction of the intermediate shaft 23. The shaft 53 protruding from the ring 52 swings when the spherical body 50 rotates by transmitting the rotation of the motor 2 by spline connection with the intermediate shaft 23 or connection with the reduction gear 24. Yes, as a result, the reciprocating drive of the piston 4 is performed. Then, here, the pinion 21 and the gear 24, which transmit power between the output shaft 20 and the intermediate shaft 23 of the motor 2, are a pair of non-circular gears or an eccentric gear, as shown in FIG. This constitutes the non-uniform velocity conversion means 6. The rotation of the intermediate shaft 23 is made to rotate at a non-constant speed, whereby the forward speed of the piston 4 is made faster than the backward speed. 8 to 11 show still another embodiment. This is different from the above-mentioned two embodiments in that the non-uniform speed-increasing means 6 is not constructed as a mechanical one but is constituted by a motor 2 for performing non-uniform speed rotation. That is, a pulse motor is used as the motor 2, and as shown in FIG. 8, a sensor S for detecting the position of the piston 4 is provided on the motor mount 12 and is connected to a control circuit CPU composed of a microprocessor. As shown in FIG. 9, the pulse generator OSC for driving the motor 2 and the sensor S are connected to the I / O port P, and the I / O port P is connected to the motor 2 via the power driver D. Connected. The I / O port P is an input / output circuit having a register for storing the data output from the control circuit CPU, and the power driver D is a current amplification circuit for switching the coil current according to the signal from the I / O port P. . The control circuit CPU changes the rotation speed of the motor 2 during one rotation by supplying the motor 2 with pulses P _{1 to} P _{N having} a pulse width according to the data held by the control circuit CPU. The output of the sensor S is used for synchronization at the initial stage of driving the motor 2. FIG. 10 shows a flow chart of this control, and FIG. 11 shows a time chart. At first, a pulse P ₀ having a relatively wide pulse width is sent to the motor 2 to start the motor 2, and the position data Sn of the piston 4 is cyclically fetched from the sensor S and compared with the position data Sn ₋₁ one cycle before. Then, if it is found that the piston 4 has come to the last retracted position and moved forward, after setting the flag Su, the pulse P having the same pulse width as the above until the piston 4 reaches the maximum forward position and starts retreating. _Continue sending ₀ to rotate at a constant speed. After that, the number of pulses P _{1 to} P _N set according to the number of poles _N of the motor 2 is sequentially applied to the motor 2.
To be repeatedly supplied. At this time, during the backward movement of the piston 4, that is, for the pulses P _{0 to} P _i corresponding to the return period, the pulse width is widened to rotate at a low speed, and the pulse corresponding to the forward movement of the piston 4 during the forward period. P _{i + 1 to} P _N are rotated at high speed by narrowing the pulse width. The values of the position data S _{0 to} Sn are set to be smallest when the piston 4 is in the most forward position and largest when the piston 4 is in the last retracted position. Although the hammer 41 is slidable in the piston 4 in each of the above-described embodiments, the piston 4 and the hammer 41 slide in the same cylinder as in the conventional example. Of course, it may be configured to move.

【The invention's effect】

As described above, in the present invention, since the forward stroke speed of the piston is increased, a strong striking force can be obtained without using a large output motor, and even in a battery-powered one. Therefore, it is possible to obtain a tool capable of piercing a large-diameter hole.

[Brief description of drawings]

1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a longitudinal sectional view showing the entire structure of the same, FIG. 3 is a cam diagram of the same, and FIG.
FIG. 5 is a characteristic diagram showing the same operation, FIG. 5 is a power supply circuit diagram of the same as above, FIG. 6 is a vertical sectional view of another embodiment, FIG. 7 is a partial perspective view of the same as above, and FIG. FIG. 9 is a longitudinal sectional view of the embodiment, FIG. 9 is a block circuit diagram of the same as above, FIG. 10 is a flowchart of the same as above, FIG. 11 is a time chart showing the operation of the same, and FIG. 12 is a characteristic diagram showing the operation of the conventional example. Yes, 4 is a piston,
Reference numeral 5 is a motion conversion member, 6 is a non-uniform speed control means, 8 is a drill bit, and 41 is a hammer.

Claims (4)

[Claims] 1. A drill comprising a motor, a spindle which is rotationally driven by the motor and holds a drill bit, and a motor which is connected to the motor through a motion converting member to reciprocate and through an air spring and a hammer. A hammer drill equipped with a piston for applying a striking impact to a bit, characterized in that the hammer drill is provided with non-uniform speed-increasing means for making the forward speed of the piston faster than the backward speed. 2. The hammer drill according to claim 1, wherein the non-constant speed-changing means is a positive-moving cam provided as a motion converting member. 3. The hammer according to claim 1, wherein the non-uniform velocity means is a pair of non-circular or eccentric gears provided in the power transmission system from the motor to the piston. Drill. 4. The hammer drill according to claim 1, wherein the non-uniform speed-increasing means is a variable speed motor composed of a pulse motor.