JP2000033507A - Striking force adjusting mechanism of hammer drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a striking force adjusting mechanism of a hammer drill capable of obtaining a striking force suitable for work stably by opening and closing an air adjusting hole securely and switching to either of hammer mode and hammer drill mode easily in the interlocking relationship with the opening and closing operations of the air adjusting hole. SOLUTION: A cylinder 6 of a hammer drill can rotate in the peripheral direction by an electric motor M. A piston 12 and a striking piece 13 are arranged in the cylinder 6 so as to reciprocate and slide by forming an air chamber 14 therebetween. At least one pneumatic pressure adjusting hole 6a communicating the inside with the outside of the cylinder 6 is provided in the cylinder 6, and the pneumatic pressure adjusting hole 6a is opened and closed by an opening and closing means to adjust impact energy by means of the striking piece 13. The opening and closing means is constituted by a cylindrical member 16 fitted in an outer peripheral face of the cylinder 6 so as to slide. The cylindrical member 15 intermittently continues the transmission of power to the cylinder 6 from the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a striking force adjusting mechanism for a hammer drill.

[0002]

2. Description of the Related Art In general, a hammer drill is used for hanging and drilling operations. A piston and a striker are reciprocally slidable in a cylinder so as to form an air chamber therebetween. The piston is reciprocally slid by an electric motor, while the air chamber is used as an air spring, whereby the striker is resiliently and intermittently moved, and the energy of the striker is attached to an attachment such as a drill bit. To the work to be imparted with a striking force.

[0003] When a drilling operation is performed using such a hammer drill, if the striking force is too large, it is difficult to drill a hole with high accuracy due to large striking vibration. Further, in the case where a hole is made in a material softer than concrete such as a brick, if the impact force is too large, chipping or cracking may occur.

In view of such circumstances, Japanese Patent Application Laid-Open No. 62-24 / 1987
No. 977 discloses a technique for adjusting the pressure in an air chamber by providing a cylinder of a hammer drill with an air pressure adjusting hole communicating with an air chamber between a piston and a striker, and opening and closing the air pressure adjusting hole by opening / closing means. (Hereinafter referred to as “prior art”).

According to the prior art, the impact force of the hammer drill can be adjusted by adjusting the pressure in the air chamber as described above. It is possible to secure a strong impact force suitable for the hanging operation, and at the same time, to reduce the pressure in the air chamber during the drilling operation to secure a weak impact force suitable for the drilling operation.

[0006]

However, in the prior art, the opening / closing means for opening / closing the air pressure adjusting hole includes a disk-shaped adjusting plate having an adjusting hole and an adjusting knob connected to the adjusting plate so as to rotate the adjusting plate. It is composed of That is, on the outer peripheral surface of the cylinder, a circular seating surface is formed around the air pressure adjusting hole, and the adjusting plate is rotatably housed in the seating surface. On the other hand, in the casing of the hammer drill, an adjusting knob is rotatably mounted at a position corresponding to the air pressure adjusting hole of the cylinder, and the above-described adjusting plate is connected to the adjusting knob.

In the prior art, it is essential that the cylinder be held non-rotatably with respect to the casing of the hammer drill due to the use of the opening and closing means having such a structure. Therefore, although the hitting force adjusting mechanism according to the prior art can be applied to a hammer drill in which a cylinder is held so as not to rotate with respect to a casing,
It is not applicable to hammer drills where the cylinder is held rotatably with respect to the casing.

Further, in the prior art, the adjustment plate is rotated improperly due to the vibration during the operation using the hammer drill, and the opening area of the air adjustment hole is changed in an unstable manner. Difficult to do.

An object of the present invention is to reliably open and close the air adjusting hole, to stably obtain a striking force suitable for work, and to operate the hammer mode in conjunction with the opening and closing operation of the air adjusting hole. Another object of the present invention is to provide a hammer drill striking force adjusting mechanism capable of easily switching to any one of a hammer drill mode and a hammer drill mode.

[0010]

In order to solve the above-mentioned problem, according to the present invention, a piston (12) and a striker (13) form an air chamber (14) between them. Motor (M)
The cylinder (6) rotatable in the circumferential direction is provided with at least one air pressure adjusting hole (6a) that communicates the inside and the outside thereof, and the air pressure adjusting hole (6a) is opened and closed by opening and closing means. In a striking force adjusting mechanism of a hammer drill for adjusting impact energy by a striker (13), the opening / closing means is a cylindrical member (1) slidably fitted to an outer peripheral surface of the cylinder (6).
6), wherein the cylindrical member (16) interrupts transmission of power from the electric motor (M) to the cylinder (6).

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a hammer drill adjusting mechanism according to an embodiment of the present invention will be described in detail with reference to the drawings. Prior to the description, the basic structure of the hammer drill itself will be described below. Will be described.

The hammer drill includes an electric motor M and a gear train G.
, Crankshaft 3, cylinder 6, piston 1
2, a connecting rod 5, a striker 13, and a meson 15, which are housed in casings C 1, C 2, C 3.

The electric motor M is housed in a casing C1 connected to a leg Hb below the handle H such that its output shaft is arranged substantially parallel to the grip Ha of the handle H of the hammer drill.

The gear train G includes a handle H of a hammer drill.
A motor shaft gear 1 built in an upper end of an output shaft of the electric motor M, a crank gear 2 meshed with the motor shaft gear 1, and a motor shaft The bevel gear 8 includes an intermediate gear 7 that meshes with the gear 1 and a bevel gear 8 that rotates integrally with the intermediate gear 7. Power transmitted to the bevel gear 8 is transmitted through a connecting sleeve 9 described below.
It can be transmitted to the cylinder 6.

The crankshaft 3 also has a casing C connected to the upper leg Hc of the handle H of the hammer drill.
2 and is connected to the crank gear 2 so as to rotate integrally with the crank gear 2 of the gear train G described above.

The cylinder 6 is disposed in a casing C3 formed by extending the side of the casing C2 opposite to the handle H in the lateral direction, and is provided with a bearing 1
0, rotatably supported via a bearing 11. The cylinder 6 has a partition 6f on the inner peripheral surface at a substantially central position.

The piston 12 is slidably disposed in the cylinder 6 at a position behind the partition 6f (see FIGS. 1 and 2).

The connecting rod 5 transmits the power of the crankshaft 3 to the piston 12. That is, one end of the connecting rod 5 is rotatably connected to the crankshaft 3 via the eccentric pin 4, and the other end is rotatably connected to the piston 12 via the piston pin 12a. Accordingly, the power of the electric motor M is transmitted to the piston 12 through the motor shaft gear 1, the crank gear 2, the crankshaft 3, and the connecting rod 5, and the piston 12 reciprocates in the cylinder 6 by the driving of the electric motor M. I do.

The striker 13 has a first air chamber 14 formed with the piston 12 described above, and further has a second air chamber 25 formed with the partition 6 f of the cylinder 6 in the cylinder 6. It is arranged to be able to slide back and forth.

A cylindrical spindle 23 is fitted inside the distal end of the cylinder 6 and is fixed thereto. The rear portion of the spindle 23 forms a meson accommodating chamber 22 in cooperation with the partition 6f of the cylinder 6.

The meson 15 is provided with the above-described meson storage chamber 22.
Are slidably arranged in the axial direction. The rear end of the meson 15 can penetrate the partition 6 f of the cylinder 6 and contact the tip of the striker 13.

Further, the bit 20 is mounted on the spindle 23 so as to be slidable in the axial direction. That is, the engagement of the long groove 20 a provided in the outer peripheral surface of the rear end portion of the bit 20 in the axial direction with the roller 26 held by the spindle 23 causes the
Is allowed to slide freely within a predetermined range, and the bit 20 rotates together with the spindle 23. The rear end of the bit 20 can contact the front end of the meson 15 described above.

As shown in FIG. 2, in the cylinder 6, a position slightly closer to the rear than the partition 6f,
Air holes 6b, 6c, and 6d are formed at a position corresponding to the rear part and near the piston 12 located at the top dead center, respectively.

Here, when the bit 20 is separated from the object to be processed, the bit 20, the meson 15 and the striker 13 as a whole move to the left in FIG. 1, and as a result, the air hole 6c becomes the first hole. It communicates with the air chamber 14. Thereby, even if the piston 12 slides back and forth, the slide of the striker 13 is avoided. As described above, the air hole 6c has an action of preventing an empty shot during non-operation.

On the other hand, when the bit 20 is pressed against the workpiece, the bit 20, the meson 15, and the striking element 1
3 moves to the right in FIG. 1 as a whole, and as a result, the air hole 6c is closed. Here, the striking element 13 also reciprocates following the reciprocating sliding of the piston 12. At this time, the air pressure in the first air chamber 14 and the second air chamber 25 is adjusted by the air holes 6d and 6b, respectively. Done. As described above, the air holes 6d and 6b are used for the first operation.
By adjusting the air pressure in the air chamber 14 and the second air chamber 25,
This has the effect of ensuring efficient reciprocating sliding of the striker 13. In particular, the air hole 6b has an action of adjusting an air spring that exerts a braking action on the advancement of the striker 13.

In the cylinder 6, between the air hole 6b and the air hole 6c, an air pressure adjusting hole 6a for allowing the air in the second air chamber 25 to escape to the outside is spaced apart in the circumferential direction of the cylinder 6. A plurality are formed. This air pressure adjusting hole 6
“a” communicates the inside and the outside of the cylinder 6 similarly to the air holes 6b, 6c, and 6d described above.

In order to apply the striking force adjusting mechanism of the present invention to the hammer drill having the above-described structure, the following components are added:

The connecting sleeve 9 is arranged between the cylinder 6 and the bearing 10. At the rear end, a cylindrical member 16 as an opening / closing means for opening / closing the air pressure adjusting hole 6a, which can be engaged with the front end of the coupling sleeve 9, is fitted to the outside of the cylinder 6. In a state where the cylindrical member 16 is slid forward,
A lock sleeve 17 for locking this to the casing C3 is provided. An operating means 21 for sliding the cylindrical member 16 in the axial direction is provided on the casing C3.

The connecting sleeve 9 is disposed between the cylinder 6 and the bearing 10 as shown in FIGS. The coupling sleeve 9 is rotatably supported by the casing C3 via the bearing 10 and is also rotatable with respect to the cylinder 6. The connecting sleeve 9 has a bevel gear 9a at the rear end.
Are engaged with the above-described bevel gear 8 (see FIG. 1). Accordingly, the power of the electric motor M is transmitted to the motor gear 1, the intermediate gear 7, the bevel gear 8, and the connecting sleeve 9,
As a result, the connection sleeve 9 is driven by the electric motor M,
It is rotatable around the cylinder 6 in the circumferential direction. Further, the connecting sleeve 9 described above has a tooth portion 9b at the front end thereof, which can mesh with a tooth portion 16b of a cylindrical member 16 described later.

The cylindrical member 16 as opening / closing means is provided with a cylinder 6 so that the above-mentioned air pressure adjusting hole 6a can be closed.
Are arranged so as to be slidable in the axial direction with respect to the cylinder 6 and non-rotatable in the circumferential direction while being in close contact with the outer peripheral surface of the cylinder 6. That is, as shown in FIG. 7, key grooves 16 d,
On the other hand, on the outer peripheral surface of the cylinder 6, there are formed keys (not shown) which can be engaged with the key grooves 16d. Thus, the key of the cylinder 6 is connected to the key grooves 16d, 1d of the cylindrical member 16.
By engaging the cylindrical member 16 with the outer periphery of the cylinder 6 so as to engage with the cylinder 6d, the cylindrical member 16 is slidable in the axial direction and non-rotatable in the circumferential direction with respect to the cylinder 6. .

The above-described cylindrical member 16 has a plurality of through-holes 1 that match the plurality of air pressure adjusting holes 6 a of the cylinder 6.
6a (see FIGS. 6 and 7). Further, at the rear end of the cylindrical member 16, the tooth portion 9b of the connection sleeve 9 described above is provided.
Is formed with a tooth portion 16b (see FIG. 6). Further, the cylindrical member 16 has an outwardly facing flange 16c.
Are integrally formed, and on the outer peripheral surface of the flange 16c, a tooth portion 16e that can mesh with a tooth portion 17a of a lock sleeve 17 described later is formed.

The cylindrical member 16 is provided with a spring 18 so that its teeth 16b mesh with the teeth 9b of the connecting sleeve 9.
Is always energized by Thus, the cylindrical member 1
When the teeth 16b of the cylinder 6 engage with the teeth 9b of the connecting sleeve 9, the air pressure adjusting holes 6a of the cylinder 6
The cylindrical member 16 is closed without being aligned with the through hole 16 a of the cylindrical member 16.

The lock sleeve 17 has, at its rear end, a tooth portion 17a which can be engaged with the tooth portion 16e of the cylindrical member 16 described above.
have. The lock sleeve 17 is attached to the inner peripheral surface of the casing C3 so as to be slidable in the axial direction and non-rotatably outside the cylindrical member 16 described above. As an example of such attachment means, a casing C
A key groove extending in the axial direction may be formed on the inner peripheral surface of the lock sleeve 17, and a key engageable with the key groove may be formed on the outer peripheral surface of the lock sleeve 17. The lock sleeve 17 is constantly pressed toward the connection sleeve 9 by a spring 19.

As shown in FIGS. 1 to 5, the operating means 21 has a columnar boss 21a.
An operation pin 21b is embedded at a position deviated from the center of the end face a. The boss 2 of this operating means 21
1a is the operation pin 21b is the flange 1 of the cylindrical member 16.
6c is rotatably fitted in a mounting hole 24 formed in the casing C3 so as to be able to come into contact with 6c. Therefore, by rotating the operating means 21 from outside the casing C3, the position of the operating pin 21b changes, and the sliding position of the cylindrical member 16 is determined according to the position of the operating pin 21b.

That is, when the operating pin 21b is located on the right side in the mounting hole 24 of the casing C3 as shown in FIG. 3, the cylindrical member 16 is moved by the action of the spring 18 to the right side in FIG. , The teeth 16b of the cylindrical member 16 mesh with the teeth 9b of the coupling sleeve 9. In this state, the air pressure adjusting hole 6 a of the cylinder 6 is closed by the cylindrical member 16. This state is hereinafter referred to as “hammer drill mode”.

When the operating pin 21b is located at the center in the mounting hole 24 of the casing C3 as shown in FIG. 4, the cylindrical member 16 is opposed to the spring 18 and is located on the left side in FIG. By slightly moving, the teeth 16 of the cylindrical member 16 are moved.
b is disengaged from the teeth 9b of the coupling sleeve 9,
Moreover, the teeth 16e of the flange 16c of the cylindrical member 16
There is no engagement between the lock sleeve 17 and the teeth 17a of the lock sleeve 17. Also in this state, the air pressure adjusting hole 6 a of the cylinder 6 is closed by the cylindrical member 16. This state is hereinafter referred to as “first hammer mode”.

When the operating pin 21b is located on the left side in the mounting hole 24 of the casing C3 as shown in FIG. 5, the cylindrical member 16 is opposed to the spring 18 and is located on the left side in FIG. Further moving, the flange 1 of the cylindrical member 16 is moved.
The teeth 16e of 6c mesh with the teeth 17a of the lock sleeve 17. In this state, the air pressure adjusting hole 6a of the cylinder 6 matches the through hole 16a of the cylindrical member 16, and the air pressure adjusting hole 6a is opened. This state is hereinafter referred to as “second
"Hammer mode".

The operating means 21 preferably has a switching and holding mechanism (not shown) for holding the operating means in any one of the hammer drill mode, the first hammer mode and the second hammer mode. This switching holding mechanism is, for example,
A ball disposed in a ball chamber formed in the casing C3 so as to communicate with the mounting hole 24, and a spring disposed in the ball chamber so as to push the ball toward the mounting hole 24; A click mechanism including a recess formed in the operation means 21 is configured to receive the pushed ball.

Next, a method of using the hammer drill impact force adjusting mechanism of the present invention will be described below.

First, when the bit 20 is reciprocated resiliently and intermittently while rotating, the operating means 21
Rotate to keep in hammer drill mode. In the state where the hammer drill mode is maintained, the operation pin 21b is located on the right side in the mounting hole 24 of the casing C3 as shown in FIG. As a result, the tooth portion 16b of the cylindrical member 16 moves to the right in FIG.
Meshes with the tooth portion 9b. In this state, the air pressure adjusting hole 6 a of the cylinder 6 is closed by the cylindrical member 16.

In this state, when the electric motor M is driven, the power of the electric motor M is transmitted to the piston 12 via the motor shaft gear 1, the crank gear 2, the crank shaft 3, and the connecting rod 5, and as a result, the piston 12 The cylinder slides back and forth in the cylinder 6. Energy generated by the reciprocating sliding of the piston 12 is transmitted to the striker 13 via the first air chamber 14, and the striker 13 also reciprocates in the cylinder 6. That is, when the piston 12 retreats, the striker 13 also retreats due to the action of the air pressure in the first air chamber 14. When the piston 12 reaches the retreat limit and starts to move forward,
The first air chamber 14 is compressed, and the air pressure therein rises. When the pressure reaches a certain value, the striker 13 moves forward vigorously by air pressure and collides with the meson 15.

On the other hand, the meson 15 is
, Reciprocally slides in the axial direction while receiving intermittent impact energy from the striker 13. Therefore, the impact energy given to the striker 13 is transmitted to the bit 20.

Apart from the above-described transmission path for the power of the motor M, the power of the motor M is transmitted to the coupling sleeve 9 via the motor shaft gear 1, the intermediate gear 7, and the bevel gear 8.

Here, the teeth 9 b of the connecting sleeve 9 mesh with the teeth 16 b of the cylindrical member 16, and the cylindrical member 16 cannot rotate in the circumferential direction with respect to the cylinder 6. Therefore, the power of the electric motor M transmitted to the coupling sleeve is further transmitted to the cylinder 6 via the cylindrical member 16, and as a result, the cylinder 6 rotates in the circumferential direction. Therefore, the bit 20 attached to the spindle 23 via the roller 26 also rotates in the circumferential direction.

As described above, the bit 20 reciprocates resiliently and intermittently while rotating, and its impact energy is given to the workpiece. In the hammer drill mode, the air pressure adjusting hole 6 a of the cylinder 6 is closed by the cylindrical member 16. Therefore, the striker 13
During the forward movement, the air in the second air chamber 25 flows out of the cylinder 6 only through the air holes 6b, and thus the amount of air flowing out of the cylinder 6 is significantly limited. As a result, the outflow of the air in the second air chamber 25 to the outside is delayed with respect to the advance of the striker 13, and the moving speed of the striker 13 is reduced by the action of the air spring by the second air chamber 25. The energy when the striker 13 collides with the meson 15 is reduced, and the impact force is weakened.

When the bit 20 is reciprocated resiliently and intermittently in a freely rotatable state, the operating means 21
Is rotated to maintain the first hammer mode. In the state where the first hammer mode is held, the operation pin 2
1b is located centrally in the mounting hole 24 of the casing C3, as shown in FIG.
6 slightly moves to the left in the figure against the spring 18 to disengage the teeth 16b of the cylindrical member 16 and the teeth 9b of the coupling sleeve 9 from each other.
6, the tooth portion 16e of the flange 16c and the lock sleeve 17
Does not mesh with the teeth 17a. Even in this state, the air pressure adjusting hole 6a of the cylinder 6 is
6 closed.

In this state, when the electric motor M is driven, the power of the electric motor M is transmitted to the piston 12 via the motor shaft gear 1, the crank gear 2, the crank shaft 3, and the connecting rod 5, and as a result, the piston 12 The cylinder slides back and forth in the cylinder 6. The energy generated by the reciprocating sliding of the piston 12 is transmitted to the striker 13, the meson 15 and the bit 20, as in the above-mentioned hammer drill mode.

On the other hand, separately from the above-described transmission path of the power of the motor M, the power of the motor M is supplied to the motor shaft gear 1,
The transmission is transmitted to the connection sleeve 9 via the intermediate gear 7 and the bevel gear 8, but in the first hammer mode, the meshing between the teeth 16b of the cylindrical member 16 and the teeth 9b of the connection sleeve 9 is released. . Accordingly, the connecting sleeve 9 idles around the outer circumference of the cylinder 6, and the power transmitted to the connecting sleeve 9 is not transmitted to the cylinder 6.

Further, in the first hammer mode, there is no engagement between the teeth 16e of the flange 16c of the cylindrical member 16 and the teeth 17a of the lock sleeve 17, and as a result, free rotation of the cylinder 6 is allowed. Is done. Therefore,
The bit 20 reciprocates resiliently and intermittently in a freely rotatable state.

In the first hammer mode, as in the hammer drill mode, the air pressure adjusting hole 6a of the cylinder 6 is closed by the cylindrical member 16, so that the striker 13 collides with the meson 15. The energy of the time is reduced, and the impact power is weakened.

When the bit 20 is reciprocated spontaneously and intermittently in a state where the bit 20 cannot rotate freely, the operating means 21
Is further rotated to maintain the second hammer mode. In the state where the second hammer mode is held, the operation pin 21b is located on the left side in the mounting hole 24 of the casing C3 as shown in FIG. The tooth 16e of the flange 16c of the cylindrical member 16 meshes with the tooth 17a of the lock sleeve 17 by moving further to the left in FIG. In this state, the air pressure adjusting hole 6a of the cylinder 6 matches the through hole 16a of the cylindrical member 16, and the air pressure adjusting hole 6a is opened.

When the motor M is driven in this state, the power of the motor M is transmitted to the piston 12 via the motor shaft gear 1, the crank gear 2, the crank shaft 3, and the connecting rod 5, and as a result, the piston 12 The cylinder slides back and forth in the cylinder 6. The energy generated by the reciprocating sliding of the piston 12 is transmitted to the striker 13, the meson 15 and the bit 20, as in the above-mentioned hammer drill mode and first hammer mode.

On the other hand, separately from the above-described transmission path of the power of the motor M, the power of the motor M is supplied to the motor shaft gear 1,
Although transmitted to the connection sleeve 9 via the intermediate gear 7 and the bevel gear 8, in the second hammer mode, the meshing between the teeth 16b of the cylindrical member 16 and the teeth 9b of the connection sleeve 9 is released. . Accordingly, the connecting sleeve 9 idles around the outer circumference of the cylinder 6, and the power transmitted to the connecting sleeve 9 is not transmitted to the cylinder 6.

Further, in the second hammer mode,
The teeth 16 e of the flange 16 c of the cylindrical member 16 mesh with the teeth 17 a of the lock sleeve 17. The lock sleeve 17 cannot rotate with respect to the casing C3. As a result, the rotation of the cylinder 6 in the circumferential direction is restricted. Therefore, the bit 20 reciprocates elastically and intermittently in a non-rotatable state.

Further, in the second hammer mode, the air pressure adjusting hole 6a of the cylinder 6 matches the through hole 16a of the cylindrical member 16, and the air pressure adjusting hole 6a is opened. Therefore, when the striker 13 advances, the air in the second air chamber 25 flows out of the cylinder 6 not only through the air hole 6b but also through the air pressure adjusting hole 6a. As a result, the air in the second air chamber 25 flows out to the outside quickly with respect to the advance of the striker 13, and the moving speed of the striker 13 is reduced to the second air chamber 2.
5 without substantially receiving the action of the air spring by 5, whereby a large energy can be secured when the striker 13 collides with the meson 15, and a large impact force can be obtained.

The number of air pressure adjusting holes 6a in the above-described striking force adjusting mechanism of the present invention is arbitrary. Also, cylindrical member 1
6 has been described as having a through hole 16a that matches the air pressure adjusting hole 6a, but it is sufficient that the cylindrical member 16 has a function of opening and closing the air pressure adjusting hole 6a.
a may be omitted.

Although the above-described striking force adjusting mechanism of the present invention has been described as being configured so that the cylindrical member 16 slides by rotating the operating means 21, the structure of the operating means is not limited to this. However, it can be changed as appropriate, and for example, includes power transmission means such as appropriate gears and / or links, and can reliably switch and hold the rearward and forward sliding limit positions of the cylindrical member 16. It is also possible to employ other possible forms of operating means.

The cylindrical member 16 has been described as being slid by the operating means 21 described above.
If the rear end 6 and the front end 6 are configured so as to be reliably switched and held, the cylindrical member 16 may be slid directly without providing the above-mentioned operation means.

Further, the hitting force adjusting mechanism of the present invention has been described as being capable of realizing three types of modes, a hammer drill mode, a first hammer mode, and a second hammer mode. It may be possible to realize two types of modes, a mode and a second hammer mode.

[0060]

According to the present invention described in detail above, claim 1
As described in the above, the piston and the striker are respectively arranged so as to be reciprocally slidable so as to form an air chamber therebetween, and communicate the inside and the outside with a cylinder rotatable in a circumferential direction by an electric motor. A striking force adjusting mechanism of a hammer drill for adjusting impact energy by the striker by providing at least one air pressure adjusting hole and opening and closing the air pressure adjusting hole by an opening / closing means. It is constituted by a cylindrical member slidably fitted to the surface, wherein the cylindrical member is
Since the transmission of the power from the electric motor to the cylinder is intermittently performed, the opening and closing of the air adjustment hole can be reliably performed, and a striking force suitable for work can be stably obtained. In conjunction with the opening / closing operation of the adjustment hole, it is possible to easily switch to any one of the hammer mode and the hammer drill mode.

Further, since the striking force is adjusted at the same time as the mode is switched, the operation as a hammer drill is performed.
Cracking of the material due to excessive hanging force can be effectively prevented. In addition, since the cylindrical member has not only the opening and closing of the air adjusting hole but also a mode switching function, it is possible to add a striking force adjusting function without adding new parts.

[Brief description of the drawings]

FIG. 1 is a partially sectional front view showing a hammer drill to which a striking force adjusting mechanism of the present invention is applied.

FIG. 2 is a partially enlarged sectional view of the hammer drill of FIG.

FIG. 3 is an enlarged sectional view of a main part showing a striking force adjusting mechanism held in a hammer drill mode.

FIG. 4 is an enlarged sectional view of a main part showing a striking force adjusting mechanism held in a first hammer mode.

FIG. 5 is an enlarged sectional view of a main part showing a striking force adjusting mechanism held in a second hammer mode.

FIG. 6 is a front view showing a cylindrical member in the striking force adjusting mechanism of the present invention.

FIG. 7 is a sectional view taken along line VII-VII of FIG. 6;

[Explanation of symbols]

 M motor 6 cylinder 6a air pressure adjusting hole 12 piston 13 striker 14 air chamber 16 cylindrical member

Claims (1)

[Claims] A piston and a striker are reciprocally slidably arranged to form an air chamber therebetween.
A cylinder rotatable in a circumferential direction by an electric motor is provided with at least one air pressure adjusting hole communicating the inside and the outside thereof, and the impact energy by the striker is adjusted by opening and closing the air pressure adjusting hole by opening and closing means. In the hitting force adjusting mechanism for a hammer drill, the opening / closing means is configured by a cylindrical member slidably fitted to an outer peripheral surface of the cylinder, and the cylindrical member is configured to transmit power from the electric motor to the cylinder. A hammer drill striking force adjustment mechanism characterized by intermittent transmission.