JPS6133676B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric impact tool that operates a hammer using an electromagnetic attraction force generated by an electromagnetic solenoid as a driving source.

This type of electric impact tool generally has an electromagnetic solenoid with a hammer inserted inside the housing.
The hammer is actuated by the electromagnetic attraction force generated by the electromagnetic solenoid by energizing the electromagnetic solenoid for a short period of time with a half cycle of a commercial AC power supply or a direct current obtained from the AC power supply via a rectifier. These electric impact tools are ideal as portable impact tools because they are smaller and lighter overall than impact tools that use compressed air from a compressor as a driving source. The drawback is that it is not possible to obtain a sufficiently large striking force with force. The electromagnetic attraction force generated by an electromagnetic solenoid increases in proportion to the number of turns of the solenoid and the drive current flowing through the solenoid. Conventionally, there have been proposed means for increasing the striking force by driving a capacitor, which causes a large discharge current obtained by discharging a solenoid to flow through a solenoid.

By the way, when it comes to impact tools, if you want to obtain impact force by supplying the same electrical energy to the electromagnetic solenoid, it is better to instantaneously flow a large current through the solenoid like the capacitor drive described above, and gradually increase the current over time. It is possible to obtain a larger impact force than by letting the hammer flow, and similarly, a greater impact force can be generated by making the impact energy applied to the hammer more pointed. However, even if the capacitor is driven as described above, the capacitor will exhibit discharge characteristics that depend on the time constant determined by the capacitor's capacitance and the solenoid's impedance.
In reality, the drive current flows through the solenoid for the time determined by the above-mentioned time constant, and the striking energy applied to the hammer cannot be made very sharp.

SUMMARY OF THE INVENTION The present invention provides an electromagnetic solenoid housed in a housing, a movable iron core in which at least the magnetic resistance of the end portion is smaller than that of the central portion with respect to the magnetic field generated by the electromagnetic solenoid, and the movable iron core. The movable iron core is movably disposed in the center hole of the electromagnetic solenoid and is configured to be attracted and moved by the magnetic field generated by the electromagnetic solenoid. To provide an electric impact tool with a novel structure that aims to improve driving force by applying sharp impact energy to a large impact force to obtain a large impact force.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to drawings showing one embodiment.

FIG. 1 is a partially cutaway sectional view showing an embodiment of an electric nailer 1 constructed according to the present invention. In this embodiment, an electric nailer 1 includes a housing 3 in which an electromagnetic solenoid 2 as a driving source is housed.
, a grip 4 protruding from the side wall of the housing 3, a magazine 4 for storing connecting nails attached to the lower part of the housing 3, and a power supply control for supplying driving power to the electromagnetic solenoid 2. The electromagnetic attraction force generated in the electromagnetic solenoid 2 by supplying driving power from the power supply control device 5 to the electromagnetic solenoid 2 by operating the switch mechanism 6 provided on the grip 4. Activate the hammer 7 to insert one nail sent out from the magazine 4 into the nose portion 3A of the housing 3.
It is configured to drive the hammer one by one by reciprocating the hammer 7.

The electromagnetic solenoid 2 has a through hole 2 in the center part.
It consists of a solenoid coil 2A wound to form a solenoid coil 2A and a bottomed cylindrical yoke 2B that fits the solenoid coil 2A. It is fixed. Note that openings 2b ₁ and 2b ₂ are formed at each bottom of the yoke 2B, corresponding to the central through hole 2a formed by the solenoid coil 2A.

Further, the hammer 7 for driving the nail sent out from the magazine 4 into the nose portion 3A of the housing 3 is
It is connected to a movable iron core 9 which is disposed so as to be freely inserted into the central through hole 2a of the electromagnetic solenoid 2. When the movable core 9 is inserted into the central through hole 2a of the electromagnetic solenoid 2, flanges 9a and 9b are provided at both ends to correspond to the openings 2b ₁ and 2b ₂ of the yoke 2B. The hammer 7 is connected to the flange portion 9a at one end, and a flange plate 11 to which one end of a coil spring 10 is fixed is attached to the flange portion 9b at the other end. This coil spring 10 consists of a mounting ring 8 fixing the electromagnetic solenoid 2 and a flange plate 11 provided on the other end flange portion 9b of the movable iron core 9.
The elastic force of the movable iron core 9 holds the movable core 9 in the stopped position as shown by the imaginary line in FIG.

Further, the power supply control device 5 includes, for example, a large-capacity capacitor that is charged by a DC voltage obtained by rectifying a commercial AC power supply in a rectifier circuit (not shown), and is connected to the It is connected between a power source and the main body of the electric nail gun 1, and when a switch mechanism 6 provided on the grip 4 is operated, the charged energy of the capacitor is released and instantaneously applied to the electromagnetic solenoid 2 as a driving current. It is configured to supply

In the embodiment configured as described above, the movable core 9 is inserted into the central through hole 2a of the electromagnetic solenoid 2.
Since each flange portion 9a, 9b provided at both ends exhibits a smaller magnetic resistance characteristic than the central portion with respect to the magnetic field generated by the electromagnetic solenoid 2, the magnetic flux density in each of the flange portions 9a, 9b is increased, Moreover, each opening 2b ₁ , 2 of the yoke 2B of the electromagnetic solenoid 2 effectively acts as a striking force.
b The electromagnetic attraction force due to the magnetic field in _{the second} part acts on each flange part 9a, 9b of the movable iron core 9, and the striking force due to the electromagnetic attraction force by the electromagnetic solenoid 2 is applied with a large peak energy. Become. Therefore, the hammer 7 connected to the flange portion 9a at one end of the movable iron core 9 can drive a nail sharply and with large impact energy. Note that the movable core 9 is connected to the electromagnetic solenoid 2.
When the electromagnetic attraction force disappears, the elastic force of the coil spring 10 automatically returns to the predetermined stopped position. Further, in the housing 3 in which the movable core 9 is reciprocated in this manner, damper members 12a and 12b are disposed at the portions where the flange portions 9a and 9b of the movable core 9 come into contact. The damper members 12a and 12b absorb the impact caused by the inertial force during the reciprocating operation of the movable core 9.

Here, the characteristic curve of the driving force obtained when a general cylindrical movable iron core is inserted into the central through hole 2a of the electromagnetic solenoid 2, and the characteristic curve of the driving force obtained in the above embodiment according to the present invention. The curve and
Shown in Figure 2. In FIG. 2, the solid line shows the characteristic curve of the sharp driving force obtained by the embodiment of the present invention, and the broken line shows the characteristic curve of the driving force when a general movable iron core is used. .

In the above embodiment, the magnetic resistance at both ends of the movable core 9 was reduced by providing flanges 9a and 9b at both ends of the movable core 9, but as shown in FIG. Both end portions 19a, 19b are formed of a high magnetic permeability material having higher magnetic permeability than the central portion 19c, and both end portions 19a, 1
Movable iron core 19 designed to increase the magnetic flux density of 9b
Alternatively, as shown in FIG. 4, a movable iron core 29 may be used in which the central portion 29c is fitted with a low magnetic permeability material 29d to increase the magnetic flux density at both ends 29a and 29b. However, the nail can be driven with a sharp point and a large impact energy as in the above-described embodiment.

As is clear from the description of the above embodiments, according to the present invention, the magnetic field generated by the electromagnetic solenoid acts intensively on both ends of the movable core, and the electromagnetic attractive force due to the generated magnetic field is sharply and Since large impact energy can be applied to the hammer, an electric impact tool with a large driving capacity can be provided.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway sectional view showing an embodiment of an electric nail gun constructed to which the present invention is applied. FIG. 2 is a characteristic diagram showing a characteristic curve of driving force obtained by the above embodiment. FIG. 3 is a schematic sectional view showing another example of the movable core applied to the above embodiment. FIG. 4 is a schematic cross-sectional view showing still another example of the movable core that is similarly applied to the above embodiment. 1...Electric nailer, 2...Electromagnetic solenoid, 2
A...Solenoid coil, 2B...Yoke, 2a
...Through hole of electromagnetic solenoid, 3...Housing, 4...Grip, 5...Power control device, 6...
...Switch mechanism, 7... Hammer, 9, 19, 29...
...Movable iron core, 9a, 9b...Flange part, 19
a, 19b...Both ends of the movable core made of high magnetic permeability material, 29d...low magnetic permeability material.

Claims (1)

[Scope of Claims] 1. An electromagnetic solenoid housed in a housing; a movable iron core having magnetic resistance characteristics at least at the ends smaller than those in the central portion with respect to the magnetic field generated by the electromagnetic solenoid; An electric hammer connected to an iron core, the movable iron core being movably disposed in a center hole of the electromagnetic solenoid and being attracted and moved by a magnetic field generated by the electromagnetic solenoid. 2. The electric hammer according to claim 1, wherein the movable iron core has flanges formed at both ends so that the magnetic resistance characteristics of the both ends are smaller than the magnetic resistance characteristics of the central portion. tool. 3. The electric hammer according to claim 1, wherein the movable iron core has a central portion covered with a low magnetic permeability material so that the magnetic resistance characteristics at both ends are smaller than the magnetic resistance characteristics at the central portion. tool. 4. The electric motor according to claim 1, wherein the movable iron core has both ends made of a high magnetic permeability material so that the magnetic resistance characteristics of the both ends are smaller than the magnetic resistance characteristics of the central portion. Percussion tools.