JP2784541B2 - Air motor torque control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air motor torque control device for controlling a tightening torque of an air motor.

(Prior art) In a conventional torque control device in a so-called nut runner using a nut tightening tool as a tool for an air motor,
Two types of techniques described below are known. First,
According to the prior art, a torque transducer is built in a tool, a tightening torque generated by the tool is directly detected, and the operation of the air motor is stopped at a set torque value. In the second prior art, since the rotation speed of the air motor and the tightening torque correspond one to one, an encoder for detecting the rotation speed is built in the tool, and the operation of the air motor is performed when the rotation speed reaches the set rotation speed. It is a method of stopping.

(Problems to be Solved by the Invention) However, in the above-described conventional technology, it is necessary to incorporate a torque transducer or an encoder as a sensor in the tool, so that the tool becomes expensive, and when the tool is damaged, the sensor is also included. Must be replaced. In addition, it is necessary to connect a sensor cable to the air motor in addition to the air hose, which causes a problem that workability is deteriorated. Further, there is a problem that maintenance of the tool is difficult.

An object of the present invention is to provide a torque control device for an air motor capable of controlling a tightening torque without incorporating a sensor in a tool.

(Means for Solving the Problems) A torque control device for an air motor according to the present invention is a torque control device for an air motor in a tightening tool such as a nut runner that uses the air motor as a drive source, and an air passage from the air source to the air motor. An opening / closing valve mechanism and a flow sensor for measuring an air flow rate are further provided, and a controller for closing and controlling the opening / closing valve mechanism based on a value detected by the flow sensor is provided.The controller corresponds to a set torque. A reference flow rate setting unit for setting a reference flow rate determined by the control unit, comparing the flow rate detected by the flow rate sensor with the reference flow rate, and closing the on-off valve mechanism when the detected flow rate becomes equal to or less than the reference flow rate. And a comparator for outputting a signal for performing the operation.

(Operation) In the air motor torque control device having the above configuration,
As shown in FIG. 2, there is a one-to-one correspondence between the torque of the air motor and the number of revolutions, as shown in the TN characteristic. It can be seen that there is a one-to-one correspondence as shown in the -N characteristic. Therefore, the air consumption, that is, the air flow rate of the air passage is measured by the flow sensor, and based on the measurement value of the flow sensor, when the air flow rate of the ventilation passage reaches the air flow rate corresponding to the predetermined set torque value, the tightening torque is determined. Is determined to have reached the set torque value, and the controller controls the opening and closing valve mechanism to close to prevent the flow of air, thereby controlling the tightening torque to a predetermined set value.

(Embodiment) Next, a specific embodiment of a torque control device for an air motor according to the present invention will be described in detail with reference to the drawings.

In FIG. 1 showing an embodiment of the present invention, reference numeral 1 denotes an air source to which high-pressure air compressed by, for example, a compressor (not shown) is supplied.
An air hose 2 (air passage) communicates with the air source 1,
An air motor 3 is connected to a distal end of the air hose 2. A pressure reducing valve 4, a solenoid on-off valve 5 (valve mechanism), and a flow sensor 6 are sequentially provided in the air hose 2 from the air source 1 side. A flow signal 10 of the flow sensor 6 is input to a controller 11, and the controller 11 The electromagnetic shut-off valve 5 is controlled to be closed by the air stop signal 12 described above, that is, the supply of air to the air motor 3 is stopped. Although a differential pressure type pressure transducer (semiconductor gauge, strain gauge, or the like) can be employed as the flow sensor 6, the differential pressure type pressure transducer is advantageous in that it can respond at high speed.

On the other hand, as shown in FIG. 2, there is a one-to-one correspondence between the torque T of the air motor 3 and the rotation speed N as shown in the TN characteristic, and at the same time, the rotation speed N and the air consumption Q Has a one-to-one correspondence as shown in the QN characteristic.
In the apparatus shown in FIG. 1 based on this characteristic, the flow rate sensor 6 measures the air flow rate to the air motor 3, that is, the air consumption, inputs a flow rate signal 10 to a controller 11, and the controller 11 determines that the flow rate signal 10 is a predetermined value. If it is determined that the torque has reached the level corresponding to the set torque, the air stop signal
12 is output to the solenoid valve 5 to close the solenoid valve 5 to stop the air supply to the air motor 3 so that no further tightening torque is generated. In the characteristics of the air motor 3 described above, since the inclination angle of the QN characteristic becomes large in the normal operation range from the stall torque range to the middle speed range of the air motor 3, the torque T is particularly within this range.
It is easy to control precisely.

As shown in FIG. 3, which is a circuit block diagram of the controller 11, the controller 11 includes an amplification circuit 13, a solenoid valve control circuit 14, a comparison circuit 15, a fastening failure detection circuit 16, and a power supply circuit.
It consists of 17 magnitudes. First, the flow signal 10 from the flow sensor 6 is input to the amplifier circuit 13, and the amplifier circuit 13 has a function of amplifying the flow signal 10 to a level at which signal processing in each circuit of the controller 11 is possible. Then, the amplified flow signal 20 from the amplifier circuit 13 is
And the fastening failure detection circuit 16. First, the comparison circuit 15 compares the set air flow rate corresponding to the set torque value set by the tightening torque setting volume 21 with the amplified flow rate signal 20, and the amplified flow rate signal 20 is set by the tightening torque setting volume 21. If it is smaller than the air flow rate, the solenoid valve control circuit 14 outputs the solenoid valve shutoff signal 22 to the solenoid valve control circuit 14.
Outputs the air stop signal 12 for closing the solenoid valve 5 from the air. In addition, the above tightening failure detection circuit 16
Has a function of determining that the tightening is defective, for example, when the double tightening is detected or when the diagonal insertion is detected, and outputs a solenoid valve shutoff signal 23 and an NG output 24. The double tightening refers to retightening a nut that has already been tightened, and detects that the air flow rate suddenly decreases within a set time and determines that the tightening is defective, and The above-mentioned oblique insertion refers to a state in which the nut is obliquely arranged on the bolt and cannot be tightened even when the tool is rotationally driven, and it is determined that a decrease in the air flow rate within the set time is not recognized as a tightening failure. is there.

On the other hand, a start signal 26 from a start switch 25 is input to the solenoid valve control circuit 14, and the start signal 26
Is input to open the electromagnetic on-off valve 5. In addition, whether or not the tightening operation is normal can be displayed based on the OK output 30 or the NG output 24. Incidentally, the power supply circuit 17 has a function of supplying power necessary for the operation of each of the circuits to each of the circuits.

Next, the operating state of the above-described embodiment will be described. When the nut is tightened by the air motor 3 shown in FIG. 1, since the solenoid valve 5 is normally open, air is supplied from the air source 1 through the air hose 2 to drive the air motor 3. If this tightening operation is continued, the air flow rate of the air hose 2 will decrease as the tightening torque increases. Then, the air flow rate of the air hose 2 is measured by the flow rate sensor 6, and the flow rate signal 10 of the flow rate sensor 6 is input to the controller 11,
The above-described processing is performed in each circuit of the controller 11 as shown in FIG. 3, and when the air flow rate decreases to a value corresponding to a predetermined set torque value, an air stop signal 12 is output and the solenoid valve is output. 5 is closed, and the air supply to the air motor 3 is stopped. Therefore, the tightening torque generated by the air motor 3 is controlled to a preset tightening torque value.

In the apparatus of the embodiment described above, since it is not necessary to incorporate various sensors into the tool of the air motor 3 as in the related art, the conventional problems caused by incorporating the sensors in the tool are eliminated.

Although the specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments,
Various modifications can be made within the scope of the present invention. For example, in the above embodiment, the flow sensor 6 is provided on the air hose 2 between the solenoid valve 5 and the air motor 3, but the flow sensor 6 is provided on the air hose 2 between the solenoid valve 5 and the air source 1. It can also be set up. In place of the tightening torque setting volume 21 in FIG. 3, a storage means for storing in advance the correlation between the air consumption and the torque for each type of tool can be used. Further, the opening / closing valve mechanism is not limited to the electromagnetic valve 5, and an opening / closing valve that is opened / closed by an air cylinder or the like may be used.

The tightening torque setting volume 21 or the storage means constitutes a reference flow rate setting section, and the comparison circuit 15 constitutes a comparison section.

(Effect of the Invention) As described above, in the torque control device for an air motor according to the present invention, when the air flow rate is reduced to the air flow rate corresponding to the predetermined set torque value based on the value measured by the flow rate sensor, the tightening is performed. When it is determined that the applied torque has reached the set torque value, the opening and closing valve mechanism is closed to prevent the flow of air, and the tightening torque can be controlled to a predetermined set value. Therefore, since it is not necessary to incorporate various sensors into the tool of the air motor as in the related art, it is possible to solve the conventional problems caused by incorporating the sensors into the tool.

[Brief description of the drawings]

FIG. 1 is a piping system diagram of an embodiment of the present invention, FIG. 2 is a graph showing the relationship between torque and air consumption with respect to rotation speed, and FIG. 3 is a block diagram showing the structure of a controller. 1 ... air source, 2 ... air hose (air passage), 3 ...
Air motor, 5 ... solenoid on-off valve (open / close valve mechanism), 6 ...
Flow rate sensor, 11 Controller, 15 Comparison circuit (comparison section), 21 Tightening torque setting volume (reference flow rate setting section).

Claims (1)

(57) [Claims] 1. A torque control device for an air motor in a tightening tool such as a nut runner driven by an air motor, wherein an open / close valve mechanism and a flow sensor for measuring an air flow rate are provided in an air passage from the air source to the air motor. A controller that closes the on-off valve mechanism based on a value detected by the flow sensor, the controller comprising: a reference flow setting unit for setting a reference flow determined according to a set torque; And comparing the detected flow rate with the flow rate sensor with the reference flow rate, and outputting a signal for controlling the closing of the on-off valve mechanism when the detected flow rate becomes equal to or less than the reference flow rate. Characteristic air motor torque control device.