JP3373622B2 - Impact wrench - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an impact wrench used for tightening and loosening bolts, nuts and screws.

[0002]

2. Description of the Related Art Today, impact wrenches are often used for tightening bolts and nuts. However, if the tightening work using an impact wrench is carried out based on the experience and intuition of the operator, the tightening force of the bolts and nuts will vary, and over-tightening and under-tightening will easily occur. Was difficult.

In order to eliminate this problem, many impact wrenches have been developed which control the tightening force. For example,
The type that controls the number of rotations of the motor does not generate more than the set impact force. Further, the type that controls the number of hits or the hit time limits the amount of hitting force applied.

[0004]

However, all such prior arts only limit the output generated from the impact wrench. Therefore, depending on the environmental conditions such as the state of screws and the presence or absence of washers, the bolts and nuts that have already been tightened with the prescribed tightening force may be further impacted, or the impact force may not be sufficient for things that are not yet tightened, etc. I have a problem.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an impact wrench capable of controlling the tightening torque with high accuracy while monitoring the tightening condition. It is in.

[0006]

In order to achieve the above object, an impact wrench of the present invention comprises an anvil 2 provided on an output shaft 1 and a hammer 4 rotated by a motor 3.
In the impact wrench in which the cam is mechanically engaged by the cam mechanism, and the impact rotational force tightens and tightens the bolts, nuts, screws, etc. , the load applied to the output shaft 1 increases.
Hammer provided on the hammer 4 toward the first strike
After the claw 19 and the anvil 2 are disengaged, the hammer
The engagement is disengaged from the time when the claw 19 and the anvil 2 are engaged.
Means for detecting the engagement time up to the time point, means for calculating the engagement time of the means for detecting the engagement time to the torque applied to the output shaft 1, and the torque by the calculation means to the set value. It is characterized in that it comprises means for stopping the rotation of the motor 3 when it reaches.

It is also preferable that the display device 5 for displaying the torque value obtained by the calculating means is provided. Further, the means for detecting the engagement time is a hammer 4
It is also preferable to detect the energization time of the current flowing in the anvil 2.

[0008]

With the above structure , the load applied to the output shaft 1 is large.
I installed it on the hammer 4 for the first first hit
After the hammer claw 19 and the anvil 2 are disengaged,
Engage from the time when the hammer claw 19 and the anvil 2 engage
The torque applied to the output shaft 1 is calculated by detecting the engagement time until the time when the motor 3 is disengaged, and the rotation of the motor 3 is calculated when the torque applied to the output shaft 1 reaches a predetermined torque. Stop and complete tightening. As a result, the tightening torque can be controlled with high accuracy, and even if the tightening conditions (screw condition, presence or absence of washer, etc.) are changed, it is possible to obtain accurate tightening torque.

Further, in the device provided with the display device 5 for displaying the torque value obtained by the calculating means, the tightening torque can be visually confirmed and the tightening torque can be easily controlled. Further, when the means for detecting the engagement time detects the energization time of the current flowing through the hammer 4 and the anvil 2, the engagement time between the hammer 4 and the anvil 2 can be detected easily and accurately.

[0010]

EXAMPLE A housing 6 of an impact wrench is made of a material such as a synthetic resin. As shown in FIG. 1, a battery pack 8 is detachably attached to the lower end of a handle 7 at the bottom of the housing 6. There is. An operation switch 10 is provided at an inner corner between the main body housing portion 9 and the handle portion 7 on the upper portion of the housing 6. A motor 3 is housed inside a rear portion of the main body housing portion 9, and a drive shaft 11 is rotatably attached to the center of the main body housing portion 9 so as to connect the motor shaft 12 and the drive shaft 11 of the motor 3. A deceleration mechanism 13 such as a planetary gear deceleration mechanism is interposed therebetween so that the rotation from the motor 3 can be decelerated and given to the drive shaft 11. A hammer 4 is rotatably attached to the outer periphery of the drive shaft 11, a hammer cam 14 is formed on the inner periphery of the hammer 4, and the drive shaft cam 1 is attached to the outer periphery of the drive shaft 11.
5, the hammer cam 14 and the drive shaft cam 15 are formed.
A steel ball 16 is interposed between and, and the drive shaft 11 and the hammer 4 are connected so as to interlock with each other. Hammer 4 and reduction mechanism 1
A spring 17 is interposed between the spring 3 and the spring 3, and the hammer 4 is biased in the Y direction by the spring 17. The output shaft 1 is rotatably attached to the tip of the main body housing portion 9, and a bit attachment that can be fitted with a bolt, a nut, or a screw is detachably attached to the output shaft 1. . An anvil 2 is provided at the rear end of the output shaft 1, and a hammer claw 19 is provided at the front end of the hammer 4, so that the hammer claw 19 and the anvil 2 can be engaged with each other. When the hammer 4 retracts against the spring 17, the engagement between the hammer claw 19 and the anvil 2 is disengaged, and when the hammer 4 advances by the force of the spring 17, the hammer claw 19 and the anvil 2 are disengaged.
And are to be engaged.

The operation of the impact wrench having the above structure will be described. The rotation of the drive shaft 11 is driven by the drive shaft cam 15 and the steel ball 1.
6, transmitted to the hammer 4 via the hammer cam 14. And the hammer claw 1 of the hammer 4 urged by the spring 17
The rotation is transmitted to the output shaft 1 by the engagement between the anvil 2 and the anvil 2. When the load applied to the output shaft 1 increases, the hammer 4 and the drive shaft 11 rotate relative to each other, the hammer 4 retracts in the X direction along the lead of the drive shaft cam 15, and compresses the spring 17.
When the hammer 4 moves backward in the X direction, the hammer claw 19 and the anvil 2 are disengaged, and the hammer claw 19 is moved to the anvil 2 side.
When the vehicle goes over the point, the hammer 4 advances in the Y direction along the lead of the drive shaft cam 15 due to the restoring force of the spring 17, the hammer claw 19 again shock-engages with the anvil 2, and the rotational force is applied to the output shaft 1. give. In this way, the hammer 4 is adapted to repeat the reciprocating motion in the axial direction as well as the rotating motion.

Next, the detector for detecting the engagement time between the hammer claw 19 and the anvil 2 will be described. A brush 21 is mounted in a groove 20 provided on the inner circumference of the main body housing portion 9, the brush 21 is biased by a spring 22, and the brush 21 is elastically contacted with the outer surface of the hammer 4. The lead wire 23 is extended from the brush 21 and connected to the engagement time detection circuit 24. In addition, the lead wire 26 from the bearing 25 of the anvil 2
Is also connected to the engagement time detection circuit 24 so that the energization of the anvil 2 and the hammer 4 can be detected. Since the drive shaft 1 and the anvil 2 are interposed by a bearing 27 made of an insulator, the hammer 4 and the anvil 2 are normally not electrically connected.

FIG. 4 shows a circuit diagram having an engagement time detection circuit. The hammer 4 is connected to the engagement time detection circuit 24 via the brush 21, and is grounded at the engagement time detection circuit 24. The anvil 2 is connected to the DC power source Vcc via the resistor R _3.
Is also connected to the negative side of the comparator 28. The DC power supply Vcc is connected to the + side of the comparator 28 via voltage dividing resistors R ₁ and R ₂ for setting a reference voltage. The comparator 28 is a microcomputer 29.
The microcomputer 29 is connected to the DC power supply Vcc. Reference numeral 30 is a volume, and 5 is a display device for displaying the torque value obtained by the calculation of the microcomputer 29. The drive circuit of the motor 3 is connected to the battery 31, and the drive circuit is provided with the FET 32 which can be switched under the control of the microcomputer 29.

When the anvil 2 and the hammer 4 come into contact with each other,
The input signal of the comparator 28 drops from high to low, and the output of the comparator 28 becomes as shown in FIG. With the impact wrench, the anvil 2 and the hammer 4 are in contact and rotating until the first hit. And when a load is applied, the impact starts. Anvil 2 under load
Slips off the hammer 4 and separates. Therefore, the non-contact time is generated, and thereafter, the detection of the engagement time ΔT ₁ of the first impact is started. That is, the microcomputer 29 starts observing the engagement time (striking time) from the first low off time. The microcomputer 29 detects the engagement time ΔT between the anvil 2 and the hammer 4 by detecting the pulse width shown in FIG. Then, the microcomputer 29 calculates the impact torque. That is, F = Iω / ΔT T = RF, where I is the impact of the hammer inertia moment (initial setting constant), ω is the hammer angular velocity (initial setting constant), and R is the anvil arm length (initial setting constant). Calculate the torque. If this torque value becomes larger than the set torque T ₀ , the motor 3 is set to FET 32.
Stop at. The calculated torque value is displayed on the display device 5.

Next, the operation will be described with reference to the flow chart shown in FIG. When started, microcomputer 2
9 reads the volume voltage V _F which is set by the volume 30, sets the set torque T ₀ to stop the motor 3 by volume voltage V _F. And to measure the engagement time ΔT by measuring the high time of the pulse is. By measuring the engagement time ΔT, the impact torque is calculated by F = Iω / ΔT and T = RF. Then, this is repeated until the impact torque T reaches the set torque T ₀ . The impact torque calculated at this time is displayed on the display device 5. When the impact torque T becomes equal to or larger than the set torque T ₀ , the microcomputer 29 sends a signal to the FET 32 to stop the motor 3 and stop the tightening work.

In the above embodiment, the engagement time was detected by detecting the energization time flowing between the anvil 2 and the hammer 4. However, when the output shaft 1 is provided with a piezoelectric element or a strain gauge, it is generated when a shock is applied. You may make it detect the occurrence time.

[0017]

According to the present invention a negative according to the output shaft as narrative
When the load becomes large, install it on the hammer toward the first hit.
After disengaging the hammer hammer claw from the anvil,
Engagement is disengaged from the point when the nummer claw and anvil engage
Means for detecting the engagement time up to the point in time , means for calculating the engagement time of the means for detecting the engagement time to the torque applied to the output shaft, and torque by the calculation means reaching a set value Since the means for stopping the rotation of the motor is provided, the hammer claw and the anvil are disengaged.
Later, from the time when the hammer claw and the anvil are engaged
The torque applied to the output shaft is calculated by detecting the engagement time up to the point when the torque is released, and the motor rotation is stopped when the torque applied to the output shaft reaches the predetermined torque. Tightening is completed, and it is possible to control the tightening torque of bolts, nuts, and screws with high accuracy, and also to ensure accurate tightening torque even if the tightening conditions (screw condition, presence of washers, etc.) change. Is.

Further, in the invention according to claim 2 of the present invention, since the display device for displaying the torque value obtained by the calculating means is provided, the tightening torque can be visually confirmed and the tightening torque is managed. It's easy. Further, in the invention according to claim 3 of the present invention, the means for detecting the engagement time is for detecting the energization time of the current flowing through the hammer and the anvil. It can be accurately detected.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view of an embodiment of the present invention.

FIG. 2 is a partially omitted cross-sectional view showing an enlarged main part of the same.

FIG. 3 is an exploded perspective view of a main part of the above.

FIG. 4 is a circuit diagram of a main part of the above.

FIG. 5 is an explanatory diagram showing an output of the above comparator.

FIG. 6 is a flowchart of the same operation.

[Explanation of symbols]

1 output shaft 2 anvil 3 motor 4 hammer

Claims (3)

(57) [Claims] 1. An impact wrench that shock-engages a hammer, which is rotated by a motor, with a cam mechanism on an anvil provided on an output shaft, and relaxes bolts, nuts, screws, and the like by the impact rotational force. Out
The load on the force axis becomes large
The engagement between the hammer claw provided on the hammer and the anvil
The hammer claw and the anvil are engaged after
Means for detecting the engagement time from the time when the engagement is disengaged, a means for calculating the engagement time of the means for detecting the engagement time to the torque applied to the output shaft, and the torque by the calculation means. The impact wrench is provided with means for stopping the rotation of the motor when reaches a set value. 2. The impact wrench according to claim 1, further comprising a display device for displaying the torque value obtained by the calculation means. 3. The impact wrench according to claim 1, wherein the engagement time detecting means detects an energization time of a current flowing through the hammer and the anvil.