JPH09155755A - Rotational striking tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive rotational striking tool which fastens a fastener such as a bolt and a nut by applying rotational striking force to an anvil with a hammer driven by a motor and the like and which can easily adjust the fastening torque. SOLUTION: This tool is formed to fasten a fastener by applying rotational striking force to an anvil with a hammer 4 driven by a motor 1. In this case, an acceleration sensor 10 constituting a strike impact detecting sensor which detects rotational striking force of tightening is installed within a tool main body, and an output of the strike impact detecting sensor 10 shuts off the motor 1 so as to control fastening torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary impact tool used for tightening fasteners such as bolts and nuts.

[0002]

2. Description of the Related Art In a conventional tool of this type, when a worker hears a hitting sound and empirically determines that it is sufficient, the driving source is manually stopped to perform a tightening operation. Therefore, proper torque management was difficult. To solve this problem,
The torque of the output shaft is measured by a strain gauge attached to the output shaft, or the number of hits due to the back and forth movement of the hammer is counted and the motor is automatically stopped and tightened as described in JP-A-5-162086. A rotary impact tool that controls torque is used.

[0003]

In the rotary impact tool, a large tightening torque can be obtained by the rotary impact mechanism, but when tightening small screws, the tightening torque becomes excessive and the screw is blunted or broken. Sometimes. Also,
Particularly in a battery driven rotary impact tool, battery exhaustion becomes a problem, and it is desired to work efficiently. Therefore, it is desired to stop the motor promptly when the predetermined tightening torque is reached. For this reason, conventionally, the torque of the output shaft is measured by a strain gauge attached to the output shaft, or the number of hits due to the back and forth movement of the hammer is counted,
The motor is stopped when the predetermined tightening torque is reached.

In order to measure torque with a strain gauge, a sensor must be attached to the output shaft, and a slip ring or the like needs to be interposed in order to take out a signal from the strain sensor, which makes the structure complicated and large in size. was there. When monitoring the front-back movement of the hammer, a sensor such as a limit switch must be installed near the hammer, and the housing needs to be changed to install the sensor. Further, in both cases, it is difficult to install the sensor and the control unit in the same place, and there is a problem that it takes time and cost to assemble the wiring and the like to the control unit. SUMMARY OF THE INVENTION An object of the present invention is to provide a rotary impact tool which is easy to use and can be tightened without licking or breaking small screws, and which enables efficient work.

Another object of the present invention is to install a percussion impact sensor for detecting percussion impact on a control circuit board inside the tool so that the impact impact sensor can be manufactured inexpensively and without changing the structure of the rotary percussion tool. An object of the present invention is to provide a rotary impact tool in which the impact detection axis of the sensor is oriented in a direction in which two components of impact impact are combined to efficiently detect impact impact and accurately control screw tightening torque.

[0006]

SUMMARY OF THE INVENTION The above-described object is to provide a rotary impact tool for imparting a rotational impact force to an anvil by a hammer driven by a motor to tighten a fastener such as a bolt or a nut, and a rotation at the time of tightening. This is achieved by installing a striking impact detection sensor that detects a striking force in the main body, and stopping the motor by the detection output of the striking impact detection sensor.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. In FIG. 1, the rotary impact tool includes a reduction mechanism 2 for reducing the rotation of the motor 1, a hammer 4 for transmitting the output from the reduction mechanism 2 to the anvil 3 as a rotary impact force, and a bit 12 attached to the anvil 3 via a socket 13. Etc. The handle portion of the housing 5 has a motor 1
A speed change switch 6 for controlling the start and rotation speed of the motor 1, a reverse switch 7 for switching the rotation direction of the motor 1, a rechargeable battery 8 as a power source of the motor 1 are built in, and a dial 11 for setting a tightening condition is provided on the upper surface of the housing 5. Is provided. A control circuit board 9 is installed behind the motor 1, and the acceleration sensor 1 constituting the impact sensor of the present invention is mounted on the control circuit board 9.
0 is implemented.

The acceleration sensor 10 detects an impact in the direction of the impact detection shaft 21 shown in FIG. In FIG. 2, the impact detection axis 21 is set to be tilted, for example, by 45 ° from the Y axis on the bottom surface of the acceleration sensor 10 in the Z axis direction perpendicular to the bottom surface.
By arranging the impact detection shaft 21 so as to be tilted in this manner, it is possible to detect impacts in a direction parallel to the bottom surface of the acceleration sensor 10 and in a direction perpendicular to the bottom surface of the acceleration sensor 10.
Due to the structure of the rotary impact tool, impact impact occurs in the output shaft direction and the output shaft rotation direction. As shown in FIG. 3, the impact shock in the rotation direction of the output shaft is the smallest on the center of the output shaft and increases as the distance increases. The impact shock in the output shaft direction is
It is constant even if it deviates from the output shaft axis. Acceleration sensor 10
An example of installation of is shown in FIG. The acceleration sensor 10 is displaced from the output shaft axis center 41, and the impact detection shaft 21 is moved in the output shaft rotation direction 42.
On the other hand, it is installed so as to be inclined at 45 ° in the output shaft direction 43 (Z axis). By installing the acceleration sensor 10 in this manner, impact shocks in the output shaft rotation direction 42 and the output shaft direction 43 can be efficiently detected simultaneously by one acceleration sensor 10.

FIG. 5 shows an example in which the control circuit board 9 is rotated by 90 degrees in the output shaft direction with respect to the installation method shown in FIG. In the acceleration sensor 10, by directing the Z axis in FIG. 2 in the output axis rotation direction 51 and the Y axis in the output axis direction 52,
Impact impacts in the output shaft rotation direction 51 and the output shaft rotation direction 52 can be detected.

FIG. 6 shows an example in which a control circuit is installed on the side surface of the housing 5 by using a flexible control circuit board 9. In this case, the acceleration sensor 10 uses a sensor in which the impact detection shaft 21 has directivity in only one direction set in the Y-axis direction shown in FIG.
The impact impacts in the output shaft direction 43 and the output shaft rotation direction 44 are detected by installing at an angle. In any installation method, since the acceleration sensor 10 can be installed on the control circuit board 9, it is not necessary to change the structure of the housing 5 or the rotation striking mechanism to install the acceleration sensor 10.

FIG. 7 is a flow chart showing the control procedure of the present invention. The operation of the control circuit shown in FIG. 8 will be described below in accordance with the procedure of FIG. The start in FIG. 7 corresponds to a procedure in which the operator pulls the trigger lever 14 of the transmission switch 6. First, forward rotation and reverse rotation are discriminated (step 70
1) In the case of normal rotation, for example, the set value set by the torque setting means 85 composed of a variable resistance interlocked with the dial 11 is read (step 702). As the fastener is tightened and the output shaft torque exceeds a certain value as shown in FIG. 9, the rotary impact operation starts at time A. At this time, a large impact impact peak B occurs for each rotational impact, and the impact impact detection circuit 83 detects this change in acceleration (step 703). When a hit impact is detected, the timer 84 starts operating (step 704), the output of the timer 84 is compared with the set value by the comparator 86 (step 705), and if both match, the comparator 86 causes the switching control means 87. Output a stop signal to. At the time of C in FIG. 9, the switching control means 87 cuts off the motor 1 from the rechargeable battery 8 by the semiconductor control element 88 and stops the motor 1 (step 7).
06). Finally, the operator releases the trigger lever 14 to complete the tightening operation. At the time of reverse rotation, no control is performed until the operator releases the trigger lever 14 and the operation waits (step 707).

In the torque control based on the number of hits, the timer 84 in FIG. 8 is replaced with a counter for counting the number of hits, step 704 in FIG. 7 is started for the counter for counting the number of hits, and step 705 is used to determine the number of hits. It can be realized by replacing the operation. The broken line portion 89 in FIG. 8 can be replaced by a microcomputer, and in this case, the flowchart of FIG. 7 is controlled by software.

[0013]

According to the present invention, the impact shock detection sensor such as the acceleration sensor is installed in the main body, and the motor is stopped when the predetermined tightening torque is reached by the detection output of the detection sensor. An inexpensive rotary impact tool can be provided without changing the structure of the rotary impact tool.
Further, since the hitting impact detection sensor is installed on the control circuit board, there is no need to circulate the lead wire and the like, and there is an effect that it can be provided at low cost and at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a rotary impact tool of the present invention.

FIG. 2 is an explanatory perspective view showing a structural diagram of an acceleration sensor.

FIG. 3 is a graph showing a strength distribution of impact in a rotating direction.

FIG. 4 is a side view showing an installation example of an acceleration sensor which constitutes the rotary impact tool of the present invention.

FIG. 5 is a side view showing another example of installation of the acceleration sensor.

FIG. 6 is a side view showing still another example of installation of the acceleration sensor.

FIG. 7 is a flowchart showing an embodiment of a control procedure of the rotary impact tool of the present invention.

FIG. 8 is a block circuit diagram showing an embodiment of a control circuit of the rotary impact tool of the present invention.

FIG. 9 is a graph showing the relationship between impact impact and output shaft torque.

[Explanation of symbols]

1 is a motor, 3 is a hammer, 4 is an anvil, 9 is a control circuit board, and 10 is an acceleration sensor.

Claims (7)

[Claims] 1. A rotary impact tool for applying a rotary impact force to a anvil by a hammer driven by a motor to tighten a fastener such as a bolt or a nut, wherein the impact impact detects a rotary impact force at the time of tightening. A rotary impact tool characterized in that a detection sensor is installed in the tool body, and the output of the impact shock detection sensor stops the motor to control the tightening torque. 2. The rotary impact tool according to claim 1, wherein the impact impact detection sensor is an acceleration sensor. 3. The rotary impact tool according to claim 1, wherein the impact impact detection sensor is installed on a control circuit board. 4. The rotary impact tool according to claim 1, wherein the impact impact detection sensor is installed so as to be displaced from the axis of the output shaft so as to detect the impact in the rotation direction. 5. The rotary impact tool according to claim 1, wherein the impact impact detection sensor is installed so as to be displaced from the axis of the output shaft to detect an impact in the output shaft direction. 6. The impact impact detection sensor is installed so as to be displaced from the axis of the output shaft, and the impact detection axis of the impact impact detection sensor is directed toward the combined direction of the output axis direction and the output axis rotation direction to output the output axis direction. The rotary impact tool according to claim 1, wherein the impact in the rotation direction of the output shaft is detected as a vector sum. 7. The rotary impact tool according to claim 3, wherein the front control circuit board is provided behind the tool body.