JP3084331B2 - Impact force control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a striking force control device for measuring a striking force when a struck object is struck and controlling the struck force to a constant striking force.

[0002]

2. Description of the Related Art An air hammer device for hitting a casting product in order to remove molding sand from the casting product is disclosed in, for example, Japanese Utility Model Application Laid-Open No. H10-31087.
No. 36357. In such an air hammer device, when hitting a work, it is necessary to measure the hitting force of the hammer device and apply an appropriate hitting force to the work. In order to apply this proper impact force to the work, the impact force is measured and controlled, and in the conventional measurement of the impact force, the air hammer device is temporarily stopped,
A load cell is placed on the hitting surface instead of the work, and the measurement is performed using the value output from the load cell by hitting the load cell.

[0003]

The above-described conventional impact force measurement using a load cell is not an accurate measurement because the measurement is not performed by hitting the workpiece during actual machining. Further, since no measurement is performed during machining, preventive processing, that is, a change in the impact force is fed back to always maintain an appropriate impact force.

In particular, in recent years, the thickness of aluminum castings has been reduced,
When an excessive impact force is applied to the work, dents and cracks are generated on the work and the work becomes defective. For this reason, the impact force must be quantitatively measured and the workpiece must be impacted with the optimal impact force.

It is an object of the present invention to provide a striking force control device which measures a striking force during machining and feeds back a change in the striking force so as to always maintain a proper striking force.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is characterized in that a chisel urged backward by a spring, an air cylinder formed behind the chisel, An air control proportional valve that controls the air pressure supplied to the air cylinder, a hammer that is fitted in the air cylinder so as to be able to move forward and backward, and that strikes the chisel, and that the chisel hits an object to be hit. A striking force sensor for detecting a striking force, and a controller for inputting a striking force detection signal from the striking force sensor and controlling the air control proportional valve so that the striking force is constant by comparing the signal with a set value. It was done.

[0007]

With the above arrangement, the impact force sensor measures the impact force during machining, processes the impact force detection signal of the impact force sensor with, for example, an FFT analyzer, compares the signal with a set value, and determines the impact force from the result. The air control proportional valve is controlled so that the air pressure becomes constant, the air pressure supplied to the air cylinder is changed, and an appropriate striking force is always maintained.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a striking device. The striking device 1 is axially movable on a housing 2 and has a spring 4
A chisel 3 urged in a retreating direction, an air cylinder 5 integrally coupled to the housing 2 behind the chisel 3, and fitted in the air cylinder 5 so as to be able to advance and retreat, And a hammer 6 for hitting the end.

The air cylinder 5 is provided at its rear end with an air supply port 5a. The air supply port 5a is connected to the air supply device 7 via an air control proportional valve 8 for controlling the supply air pressure. Piping is connected. An air discharge port 5b is provided at the front end. The position of the air discharge port 5b is normally closed by the side wall of the hammer 6 as shown by the solid line in FIG. 1, but the hammer 6 moves to the forward end as shown by the dotted line in FIG. When you open,
The air in the air cylinder 5 is set to be released to the atmosphere.

The hitting device 1 has a chisel 3 with a work W
A striking force sensor for detecting a striking force when striking the (hit object) is provided. As a specific structure, as shown in FIG. 1, a mounting member 9 is fixed to the tip of the chisel 3, and an acceleration sensor 10 is mounted on the mounting member 9.

As another example of a design change, as shown in FIG. 2, a magnetized portion 18 is provided at the rear end of the chisel 3, and the displacement sensor 1 is attached to the air cylinder 5 at a position corresponding to the magnetized portion 18.
9 may be fixed facing the magnetized portion 18. The case of FIG. 2 is effective when the impact force of the chisel 3 is very strong. Further, as shown in FIG. 3, a strain measuring sensor 21 having a built-in strain gauge 20 may be attached to the tip of the chisel 3. In the following description, the acceleration sensor 10, the displacement sensor 19, and the striking force sensor of the strain measuring sensor 21
This will be described with reference to the acceleration sensor 10 indicated by.

The acceleration sensor 10 includes a controller 11
It is connected to the. The controller 11 includes a sensor amplifier 13 connected to the acceleration sensor 10 and an FFT connected to the sensor amplifier 13 via a filter 14.
It comprises an analyzer 15, a central processing unit (CPU) 12 connected to the FFT analyzer 15, and an interface (IF) 16 connected to the central processing unit 12.

The air control proportional valve 8 is connected to an interface (IF) 16, and a display device 17 is also connected to the interface (IF).

The operation of the hitting device 1 causes the hammer 6 to move forward by supplying air whose air pressure is controlled by the air control proportional valve 8 to the air supply port 5a of the air cylinder 5. As a result, the chisel 3 is hit, the chisel 3 compresses the spring 4 and moves forward, and the tip of the chisel 3 hits the workpiece W.

When the hammer 6 operates at the forward end, the air discharge port 5b is opened, and the air in the air cylinder 5 is discharged to the atmosphere. When the air in the air cylinder 5 is released to the atmosphere, the pressing force of the hammer 6 disappears,
The chisel 3 is moved backward by the spring 4 and returns to the original position. Therefore, by repeating the supply of air, the above operation is repeated and the workpiece W is continuously hit.

In the above-described striking operation, the acceleration sensor 10 detects a striking force, and outputs an output (a striking force detection signal) of the acceleration sensor 10 to the controller 11. The data from the acceleration sensor 10 has the frequency shown in FIG. 4, and the arrow A indicates the time of impact.

The acceleration sensor 10 based on the frequency shown in FIG.
Is amplified by the sensor amplifier 13, filtered by the filter 14, and input to the FFT analyzer 15. This FF
In the T analyzer 15, the output of the acceleration sensor 10 at the frequency shown in FIG.
(Referred to as “processing”) to obtain data of the frequency shown in FIG. B in the data of FIG. 5 is the first order term of the acceleration (hitting force), and C is the second order term.

In the present invention, the impact force is kept constant by observing the change in the frequency of the first order term of the acceleration (impact force) subjected to the FFT processing. That is, the impact force changes due to air leakage from the sliding surface of the chisel 3 and wear of the tip of the chisel 3. As a result, the acceleration becomes H as shown in FIG.
Is a normal value, but in the abnormal case, the normal frequency H is displaced E in the D direction and becomes an abnormal frequency I. In FIG. 6, P is a peak value at the frequency H of the normal value.

By measuring the displacement E and controlling the air control proportional valve 8 in accordance with the displacement to change the air pressure supplied to the air cylinder 5, the frequency I of the abnormal value can be changed in the direction opposite to the direction D. To the normal value frequency H.

As shown in FIG. 7, most of the causes of the change in the acceleration (hitting force) are the clearance 22 on the sliding surface of the chisel 3.
Is increased, and the air leaks from the clearance 22. As a result of this air leakage, as shown by the abnormal value frequency I in FIG. 8, which is the same as FIG. 6, the peak acceleration J decreases, and at the same time, the striking frequency K decreases.

Therefore, the peak value P or the normal frequency H
If the air pressure supplied to the air cylinder 5 is increased so as to eliminate the amount of displacement based on either of the above, the lowered peak value and the frequency I of the abnormal value return to normal.

As described above, the acceleration (hitting force) also changes due to wear of the tip of the chisel 3. As shown in FIG. 9, the tip 23 of the chisel 3 is abnormally worn on one side 23 of the tip of the chisel 3. This is a special case of extreme wear of the chisel 3, but in such a case, the FFT-processed acceleration (hitting force) data, as shown in FIG.
The striking frequency is the same as the normal value frequency H and the abnormal value frequency I, and the peak value, that is, the peak acceleration J decreases.

In this case, normally, the air pressure supplied to the air cylinder 5 is raised on the basis of only the change in the peak value to return to the waveform of the frequency H of the normal value. If the frequency does not return, the change in the frequency is also measured. If the frequency does not change, it can be determined that the chisel 3 is abnormally worn.

As shown in FIG. 11, a lower limit L of the set value K of the peak value of the normal frequency H and a lower limit S of the set value R of the normal frequency H are set, and the judgment is made based on these. .

These data are, as described above, FFT
Analyzed by the analyzer 15, the central processing unit 12 controls the proportional valve 8 for air control to change the air pressure supplied to the air cylinder 5 so that the striking force becomes constant, and constantly applies a constant striking force in-line. Things.

FIG. 12 shows the impact force control operation of the apparatus of the present invention.
This will be described with reference to the flowchart of FIG. At start 30, air pressure is supplied to the air cylinder 5 and the air hammer 6
Is pressed down and the chisel 3 is beaten. As a result, the chisel 3 descends against the force of the spring 4 and hits the workpiece W. At this time, it is desirable that the initial value of the air pressure for striking the work W be an empirically obtained optimum value for striking the work W. However, since a set value to be described later is determined based on this optimum value, even if there is some error in the initial value, the air pressure is corrected to an appropriate value by the operation of the impact force control.

When the impact of the work W is started, acceleration data is measured by the acceleration sensor 10 attached to the chisel 3 (step 31), and the acceleration data is sent to the FF of the controller 11.
The analysis is performed by the T analyzer 15 (step 32). Here, it is determined whether or not the amplitude of the primary impact frequency, that is, the peak value is within a set value (step 33). The striking operation is continuously performed with a constant striking force within the value.

If the peak value of the primary impact frequency is out of the set value in step 33, the central processing unit 12 controls the air control proportional valve 8 in proportion to the amount of change from the set value. Is changed (step 34). Then, in step 35, it is determined whether or not the current input air pressure exceeds the upper limit. If not, the process returns to step 31 and repeats the steps after step 31. That is, until the input air pressure exceeds the upper limit in step 35, the input air pressure is changed in accordance with the deviation between the peak value and the set value. If it is determined in step 35 that the input air pressure exceeds the upper limit and the input air pressure cannot be further increased, the process proceeds to step 36.

In step 36, it is determined whether the current frequency is smaller than the lower limit S of the set value. If it is smaller than the lower limit S, the peak value and the frequency are displaced as described above. Therefore, it can be determined that the clearance of the sliding surface of the chisel 3 is large. A warning is displayed on the display device 17 to replace the main body or replace the chisel 3 with an appropriate clearance.
To be displayed.

If the current frequency is larger than the lower limit S of the set value in step 36, it can be determined that the frequency has not been displaced, and it can be determined that the tip of the chisel 3 has been abnormally worn. In step 39, a warning is displayed on the display device 17 to replace the chisel 3.

As described above, the striking force control device of the present embodiment processes the detection value from the acceleration sensor 10 by the FFT analyzer 15, compares the peak value and the frequency with the set value, and sets the air control proportional valve 8 By controlling the air pressure by adjusting the pressure, the impact force of the impact device 1 can be kept constant.

Further, when the striking force cannot be returned to the normal state even if the input air pressure exceeds the set value, it is possible to warn of the replacement of the striking device 1 or the chisel 3 from the frequency state. The worker can perform appropriate maintenance work to quickly bring the state of the impact device 1 to a normal state.

[0033]

As described above, according to the present invention, the signal (output) detected by a striking force sensor, which is the striking force of a chisel striking a work which has been struck by an air hammer, is compared with a set value, and the striking force is kept constant. The input air pressure supplied to the air cylinder of the air hammer is controlled by an air control proportional valve so that the impact force is measured during the impact force processing, and an appropriate constant impact force is obtained. The striking force can be controlled so as to be maintained.

Thus, the quality of the work to be subjected to the impact processing can be improved. In particular, an appropriate impact force corresponding to the work can be applied to a work having a small thickness, so that the work can be cracked. To prevent. In addition, by adjusting the input air pressure supplied to the air cylinder of the air hammer to an appropriate impact force for the workpiece, etc., it is possible to prevent the excessive impact force from being applied unnecessarily and improve the chisel life. it can.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a device of the present invention showing a controller and an air control circuit together.

FIG. 2 is a cross-sectional view showing another embodiment of the impact force sensor in the device of the present invention.

FIG. 3 is a sectional view showing another embodiment of the impact force sensor in the device of the present invention.

FIG. 4 is a waveform chart showing output data from an acceleration sensor in the device of the present invention.

FIG. 5 is a waveform chart showing data after FFT processing in the device of the present invention.

FIG. 6 is a waveform chart showing amplitudes of a normal value frequency and an abnormal value frequency.

FIG. 7 is a sectional view showing a cause of a change in acceleration (hitting force) due to air leakage.

FIG. 8 is a waveform chart showing data after FFT processing in the case of a change in acceleration (hitting force) due to air leakage.

FIG. 9 Acceleration (hitting force) due to abnormal wear of the chisel tip
Sectional view showing the cause of change

FIG. 10 is a waveform diagram showing data after FFT processing in the case of a change in acceleration (hitting force) due to air leakage.

FIG. 11 is a diagram showing a lower limit of a set value of a normal frequency peak value and a lower limit of a set value of a normal frequency.

FIG. 12 is a flowchart showing the operation of the apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Impact device 2 Housing 3 Chisel 4 Spring 5 Air cylinder 6 Hammer 7 Air supply device 8 Proportional valve for air control 10 Acceleration sensor 11 Controller 12 Central processing unit 15 FFT analyzer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuya Sakai 1-1-1, Asahi-cho, Kariya-shi, Aichi Prefecture Inside Toyota Koki Co., Ltd. (72) Inventor Takeo Furuya 1, Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Motor Vehicle Stock In-house (72) Inventor Mikiya Nozaki 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Tomohiko Nishiyama 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-62-104666 (JP, A) JP-A-53-1639 (JP, A) JP-A-3-81254 (JP, U) JP-A-3-36357 (JP, U) JP-A-56-105374 (JP, U) Japanese Utility Model Showa 55-111671 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 29/00 G01L 5/00

Claims (1)

(57) [Claims] 1. A chisel urged in a backward direction by a spring, an air cylinder formed behind the chisel, an air control proportional valve for controlling air pressure supplied to the air cylinder, and the air cylinder A hammer, which is fitted so as to be capable of moving forward and backward, and hits the chisel, a hitting force sensor which detects a hitting force when the chisel hits an object to be hit, and a hitting force detection signal of the hitting force sensor. And a controller that controls the air control proportional valve so that the impact force becomes constant by comparing the set value with the set value.