JPH06170697A - Method and device for supervising overload of drill - Google Patents

Abstract

PURPOSE:To surely prevent a drill from being damaged by jamming chips in a flute of the drill. CONSTITUTION:In the beginning at the time of drilling by a drill 8, a load current is sampled in a drill driving motor Mp when drilled to a depth where a flute 13 of the drill is not filled with chips, to obtain a mean value of the load current, and further when drilled by the drill 8 by setting a value, for instance, 1.1 times this mean value to serve as the reference value, drilling action is automatically stopped when the load current is increased to the reference value or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill overload monitoring method and apparatus.

[0002]

2. Description of the Related Art When a flute of a drill, that is, a twist groove is clogged with chips, an excessive torque is applied to the drill by a motor and the drill is damaged. Therefore, it is necessary to monitor the overload that acts on the drill and stop the drilling operation when the overload occurs.

A typical prior art technique detects a load current of a motor for driving a drill, and when the load current exceeds a reference value manually set by an operator, the drilling operation is stopped.

[0004]

In such a prior art, the operator sets the reference value of the load current of the motor according to the type of drill. Therefore, each time the type of drill used changes, the reference value must be set again, which is troublesome, and the reference value may be set erroneously. Therefore, the prior art cannot accurately monitor drill overload.

It is an object of the present invention to provide a method and a device for enabling accurate detection of drill overload.

[0006]

DISCLOSURE OF THE INVENTION The present invention is directed to a drill driving motor for drilling a workpiece to a depth such that chips produced by drilling the drill do not clog the flute with the drill. Detecting the load current, setting a reference value larger than the detected load current, and stopping the drilling work when the load current of the motor exceeds the reference value when drilling deeper than the depth. Is a method for monitoring overload of a drill.

The present invention also provides a first motor for driving the drill, a means for detecting a load current of the first motor, a second motor for displacing the drill toward and away from the workpiece, and a second motor for the drill. 2 means for detecting the displacement amount by the motor, and in response to each output of the load current detecting means and the displacement amount detecting means,
Means for setting a predetermined reference value that is equal to or greater than the load current when drilling to a predetermined depth that does not clog the flutes with chips from drilling holes, and respond to each output of the load current detection means and reference value setting means However, at the time of drilling deeper than the predetermined depth, a means for level discriminating that the load current has become a reference value or more and a means for responding to the output of the drill discriminating means and stopping the drilling work are included. It is a featured drill overload monitoring device.

According to the present invention, the reference value setting means sets the load current during the drilling period up to the predetermined depth,
A means for sampling at predetermined time intervals, a calculating means for calculating an average value of the sampled load current values in response to the output of the sampling means, and a reference value larger than the average value calculated by the calculating means. And means for setting.

According to the present invention, the sampling means is
The load current is sampled after at least the outer peripheral corners of the drill have entered the work piece.

Further, the invention is characterized in that the stopping means rotationally drives the second motor in a direction opposite to that at the time of drilling to displace the drill away from the workpiece.

Further, the invention is characterized in that the stopping means stops the first and second motors.

Further, according to the present invention, the displacement amount detecting means and the stopping means are combined into one unit, and the displacement amount detecting means is the sampling start position of the load current at the time of displacement of drilling by the second motor of the drill. Deriving a signal representing the sampling end position, the stopping means stops the drilling work in response to the interrupt signal, and the reference value setting means and the level discriminating means are combined to form another unit, The reference value setting means is a means for calculating an average value of the load current when the drill is displaced from the sampling start position to the sampling end position, and a predetermined reference value equal to or higher than the average value in response to the output from the average value calculation means. The level discriminating means includes a means for setting the load current, and after the signal representing the sampling end position is generated, the load current becomes equal to or higher than the reference value. Derive the interrupt signal when the Tsu characterized in providing stop means.

[0013]

According to the present invention, when drilling a workpiece by a drill, the drill and the workpiece are relatively moved by the second motor while the drill is driven to rotate by the first motor. The workpiece is drilled by moving the drill and the workpiece relative to each other by moving the workpiece closer to and away from the workpiece. At the initial stage of drilling, so that the chips do not clog the flutes, that is, the twist grooves, for example, the tip of the drill enters from the outer peripheral corner of the drill to the shank side by about the drill diameter, for example, 5 to 10 mm. Detect the load current of the first motor for driving the drill during the drilling period,
When a predetermined reference value equal to or higher than the load current, for example, a reference value 1.1 times the load current is set by the setting means and then deeper drilling is performed, the load current of the first motor becomes equal to or higher than the reference value. This is detected by the level discrimination means, and the drilling work is stopped. In this way, it is possible to prevent the drill flute from being clogged with chips and exerting excessive torque on the drill, and to prevent damage to the drill.

Further, according to the present invention, when the hole is drilled up to the predetermined depth, the load current thereof constantly fluctuates minutely, and the reference value is accurately set regardless of such fluctuation. In order to be able to do so, during the period of drilling to the predetermined depth, the load current is set to 100 msec at predetermined time intervals.
For each time, sampling is performed by the sampling means, an average value of the sampled load current values is calculated, and a reference value larger than that is set based on this average value.

In obtaining such an average value,
After at least the outer peripheral corner of the drill has entered the work piece, the load current is sampled, and the shallow hole is cut in the work piece only by the radial part of the cutting edge at the tip of the drill. The load current of the first motor is small, and it is possible to prevent such a small load current from adversely affecting the determination of the average value.

Whether or not the outer peripheral corner of the drill has entered the workpiece can be detected by, for example, displacement amount detecting means.

According to the present invention, when the drilling is driven by the first motor, when the load current exceeds the reference value and the drilling operation is stopped, the second motor is rotationally driven in the direction opposite to that of the drilling. Then, the drill may be displaced away from the work piece, or both the first and second motors may be stopped.

Furthermore, according to the present invention, the displacement amount detecting means and the stopping means are constituted as one unit, and the reference value setting means and the level discriminating means are constituted as another unit. In the one unit of
By connecting said another unit, it is possible to easily carry out the present invention, and thus to carry out the present invention additionally in relation to an existing drilling device comprising said one unit. It will be possible.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a front view of a drilling device 1 using a drill according to an embodiment of the present invention. The table 3 to which the workpiece 2 is fixed can be moved in the horizontal xy plane by the x-axis direction motor Mx and the y-axis direction motor My. A column 4 is erected at the fixed position, and the moving body 5 can be moved up and down by a motor Mz in the vertical z-axis direction. A spindle motor Mp is attached to the moving body 5, and the spindle 6 is rotationally driven around the vertical axis by the motor Mp. A chuck 7 is fixed to the spindle 6, and various chucks 8 are attached by the chuck 7.
Can be replaced and installed. The motor Mz rotationally drives a screw rod having a vertical axis, and a nut screwed to the screw rod is fixed to the moving body 5, and thus the moving body 5 is vertically displaced by the screw drive. As another embodiment of the present invention, the table 3 may be driven to move up and down by the motor Mz, and the vertical positions of the motor Mp and the drill 8 may be fixed.

FIG. 2 is a sectional view showing a state in which the workpiece 2 is drilled by the drill 8. Drill 8
The main cutting edge 10 of the tip portion 9 of the
In the outer peripheral corner 11 which is the outermost portion in the radial direction of 0,
The margin portion 12 is continuous, and the drill 8 is formed with a flute 13 which is a twist groove for discharging chips. The rest position of the drill 8 before the drilling work is set to z0, and the moving body 5, and hence the drill 8 is displaced downward by the motor Mz during the drilling work, and the tip 9 of the drill 8 is attached to the workpiece 2.
Enter, and its outer peripheral corner 11 is the surface 1 of the workpiece 2.
The position of the drill 8 when positioned at 4 is z1. Further, the position when the outer peripheral corner 11 is drilled by a predetermined depth h1 from the surface 14 of the workpiece 2 after finishing the drilling is z2. This depth h1 is for the drill 8
It is a value at which the flutes 13 are not clogged with the chips produced by the drilling, and may be about the drill diameter, for example, 5 to 10 mm. The workpiece 2 is drilled and penetrated by the drill 8, and the lower limit position of the outer peripheral corner 11 of the drill 8 is indicated by z3. As another embodiment of the present invention, the drill 8 is the work piece 2
The workpiece 2 may be processed so as to form a bottomed drill hole by drilling halfway in the thickness direction. Drill 8
2 moves downward in FIG. 2 to perform drilling, the motor Mz is rotationally driven in the forward direction, and when moving from the position z3 after the drilling, the motor Mz is rotationally driven in the reverse direction to raise the drill 8. To do.

FIG. 3 is a diagram showing changes in the load current during drilling of the motor Mz. The tip 9 of the drill 8
From the position z01 where the chisel edge 15 comes into contact with the surface of the workpiece 2 to the position z1 where the outer peripheral corner 11 coincides with the surface 14, the drill 8 is rotationally driven as the drill 8 penetrates from the workpiece 2. The load current of the motor Mp that operates increases. When the drill 8 further penetrates into the work piece 2 for drilling, the load current is substantially constant or gradually increases and changes as indicated by reference numeral 16. When the drill 8 penetrates the workpiece 2, the motor Mp
Load current becomes smaller.

If the flutes 13 of the drill 8 are clogged with chips during the drilling of the work piece 2 by the drill 8, the torque required to rotate the drill 8 increases and therefore the motor Mp The load current increases as indicated by reference numeral 17 in FIG. According to the present invention, when such a load current becomes equal to or greater than a predetermined reference value I0, the motor Mp is driven to rotate as it is, and the motor Mz is driven to rotate in the opposite direction to raise the drill 8. In this way, the drilling work is stopped.

FIG. 4 is a block diagram showing the electrical construction of an embodiment of the present invention. A unit U1 for controlling the motors Mx, My, Mz and the motor Mp, and another unit U2 connected to the processing circuit 18 of the unit U1 via a detachable connector 19 are provided. The unit U2 has a processing circuit 20. The processing circuit 18 as described above is realized by an NC (numerical control) device, and the processing circuit 20 is realized by, for example, a microcomputer and is called a programmable controller. Therefore, the unit U2 according to the present invention is connected to the existing unit U1 by the connector 19,
By slightly changing the configuration of the processing circuit 18 of the unit U1, and therefore the program, it is possible to easily realize the overload monitoring of the drill of the present invention by using the existing drilling device as it is.

FIG. 5 is a flow chart for explaining the operation of the processing circuit 18 of the unit U1. Motor M
After the positions of the table 3 and the work piece 2 in the horizontal plane are determined by x and My, the table 3 is stationary and the process proceeds from step a1 to step a2.
Are driven in the forward direction to lower the moving body 5 from the position z0.
At this time, the motor Mp is also driven to rotate. The position of the drill 8 corresponds to the number of pulses given to the motor Mz, and therefore the positions z0 to z of the outer peripheral corner 11 of the drill 8 are set.
3 can always be detected by the displacement amount detecting means 21 of FIG.

In step a3, it is judged whether or not the position of the drill 8 coincides with the surface 14 of the workpiece 2, and if so, the process moves to the next step a4, in which the load current detection means 22 of the motor Mp detects the load current. The processing circuit 18 outputs a sampling start signal and supplies it from the connector 19 to the processing circuit 20 of the unit U2. In the next step a5,
It is judged whether or not the outer peripheral corner 11 of the drill 8 has come to the position z2, and if so, the process proceeds to the next step a6, and a signal for ending the sampling of the load current by the load current detection signal 22 is outputted and the connector 19 is outputted. It is given to the processing circuit 20. In this way, the load current of the motor Mp is, for example, 10 while the drill 8 moves from the position z1 to the position z2.
It is sampled and detected at time intervals of 0 msec. The distance h1 between the positions z1 and z2 is shallow as described above, and therefore, the flutes 13 of the drill 8 are not clogged with chips, and thus the load of the motor Mp depending on the cutting resistance when the drill 8 is drilled. Current detection will be performed.

At step a7, it is judged whether or not an interrupt signal is given from the processing circuit 20 of the unit U2 to the processing circuit 18 via the connector 19, and when the interrupt signal is given, that is, the load current detecting means 22.
When the load current is detected by, when the load current exceeds the reference value I0, the process proceeds to step a8,
The motor Mz is rotationally driven in the opposite direction to raise the movable body 5, and thus the drill 8, to return to the rest position z0. At this time, the motor Mp is kept rotating. The drill 8 returns to the rest position z0 in step a9.

When the drill 8 continues the drilling work from the above-mentioned position z2, if it does not receive the interrupt signal, it moves from step a7 to step a10, and the displacement amount detecting means 21 determines whether or not it has reached the lower limit position z3. After reaching the lower limit position z3, the drilling operation is stopped, and a series of operations is completed in step a11.

As another embodiment of the present invention, step a8
In, the rotations of both the motors Mz and Mp may be stopped.

FIG. 6 shows the processing circuit 2 of the unit U2 of FIG.
6 is a flowchart for explaining the operation of 0. At the time of drilling with the drill 8, the process moves from step b1 to step b2, and it is judged whether or not a sampling start signal from the processing circuit 18 of the unit U1 is received, and when the sampling start signal is received, that is, the outer peripheral corner of the drill 8. When 11 coincides with the surface 14 of the workpiece 2, the process proceeds to the next step b3, and every 100 msec,
The load current of the motor Mp detected by the load current detection means 22 is sampled and stored in the memory 23, and the sampling number n is incremented and stored in the memory 24 of the processing circuit 20.

In step b4, it is judged whether the sampling end signal from the processing circuit 18 is received, that is, whether the outer peripheral corner 11 of the drill 8 has reached the position z2 in FIG. 2, and the sampling end signal is received. Occasionally, the process moves to step b5, and each sampling time j
The average value I1 of the detected load currents Ij for each
Calculate and calculate by.

[0031]

[Equation 1]

The rotational speed of the motor Mz during drilling is constant, and therefore the descending displacement speed of the drill 8 is constant.

At step b6, the reference value I0 is calculated by the equation (2).

I0 = a · I1 (2) Here, a is a value set in advance by programming in the processing circuit 20, and is 1.1 or 1.05, for example.
It may be a value such as.

When the drill 8 further drills the workpiece 2 beyond the position z2, in step b7, the load current detection means 22 continuously, that is, a time shorter than the sampling time interval 100 msec described above. In step b8, it is determined whether or not the detected value is equal to or larger than the reference value I0 set by the reference value setting means 25. The reference value setting means 25 is realized by, for example, a memory, and stores the reference value I0 obtained by the above-mentioned formula 2.

In step b8, when the load current I of the motor Mp detected by the load current detecting means 22 becomes equal to or greater than the reference value I0, the process moves to the next step b9 and the processing circuit 20 sends an interrupt signal. It is generated and given from the connector 19 to the processing circuit 18, and a series of operations is ended in step b10. Interrupt signal is processing circuit 1
8, the drilling operation by the drill 8 is stopped in the next step a8, as described in relation to the step a7 in FIG. In this way, when the load current I becomes equal to or greater than the reference value I0, the drilling work is stopped to prevent the drill 8 from being damaged in order to prevent the drill 8 from being further overloaded.

The present invention can be carried out particularly preferably in a so-called deep hole drill in which the load current of the motor Mp is almost constant regardless of the depth of the hole when the drill 8 is drilled. The present invention can be widely practiced in connection with various drills.

[0038]

As described above, according to the present invention, when the workpiece is drilled, the load current of the drill driving motor is detected when the drill flute is drilled to a depth where chips are not clogged. Then, based on the load current, a reference value is set, and then, when further drilling work is performed, if the load current of the motor exceeds the reference value, the drilling work is stopped. It is not necessary for the operator to manually set the reference value for overload prevention for each type of drill, as in the above, and this makes it possible to accurately achieve overload monitoring of the drill and It is possible to prevent damage to the drill caused by setting the value to a large value by mistake.

Further, according to the present invention, at the predetermined depth, the load current is sampled at predetermined time intervals, an average value of the sampled load current values is calculated, and a reference value is calculated based on the average value. Since the value is set, even if the load current changes to a large or small value due to noise or vibration of the drill during the drilling period up to the predetermined depth, it is possible to prevent the setting of the reference value from being greatly incorrect. Be done.

Further, according to the present invention, the displacement amount detecting means and the stopping means are constituted as one unit, and the reference value setting means and the level discriminating means are constituted as another unit, and such two units are constituted. Since the drill is overloaded for monitoring, the present invention can be easily realized by connecting another unit according to the present invention to the existing drilling device provided with the one unit. It is possible to

[Brief description of drawings]

FIG. 1 is a front view of a hole punching device 1 according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state when drilling a workpiece 2 with a drill 8.

FIG. 3 is a diagram showing a load current during a drilling operation of a motor Mp that rotationally drives a drill 8.

FIG. 4 is a block diagram showing an electrical configuration of an embodiment of the present invention.

FIG. 5 is a flowchart for explaining the operation of the processing circuit 18 of the unit U1.

FIG. 6 is a flowchart for explaining an operation of a processing circuit 20 of another unit U2.

[Explanation of symbols]

 1 Drilling Device 2 Workpiece 3 Table 5 Moving Object 8 Drill 9 Tip of Drill 8 11 Outer Corner Corner 13 Flute 18, 20 Processing Circuit 19 Connector 21 Displacement Detecting Means 22 Load Current Detecting Means 23 Memory 25 Reference Value Setting Means 24 Counter Mx, My, Mz Motor Mp Drill 8 drive motor

Claims (7)

[Claims] 1. A drill is used to drill a hole in a workpiece to a depth such that chips produced by drilling the drill do not clog the flute, and the load current of a drill driving motor at the time of drilling to the depth is detected. Set a reference value larger than the load current, when drilling deeper than the depth, when the load current of the motor is more than the reference value, the overload of the drill, characterized by stopping the drilling work Monitoring method. 2. A first motor for driving a drill, a means for detecting a load current of the first motor, a second motor for displacing the drill toward and away from a workpiece, and a second motor for the drill. Responsive to the output of the means for detecting the amount of displacement and the load current detecting means and the amount of displacement detecting means, the flutes will not be clogged with chips due to the drilling of the drill. Means for setting a predetermined reference value, in response to each output of the load current detection means and the reference value setting means, at the time of drilling deeper than the predetermined depth,
An overload monitoring device for a drill, comprising: a means for discriminating a level when a load current exceeds a reference value; and a means for responding to an output of the drill discriminating means to stop a drilling operation. 3. The reference value setting means samples the load current during the drilling period up to the predetermined depth at predetermined time intervals, and responds to the output of the sampling means to detect the sampled load current. 3. An overload monitoring device for a drill according to claim 2, further comprising: a calculating means for calculating an average value of the values and a means for setting a reference value larger than the average value calculated by the calculating means. 4. The overload monitoring device for a drill according to claim 3, wherein the sampling means samples the load current after at least the outer peripheral corner of the drill has entered the workpiece. 5. The overload monitoring of the drill according to claim 2, wherein the stopping means rotationally drives the second motor in a direction opposite to that at the time of drilling to displace the drill away from the workpiece. apparatus. 6. The overload monitoring device for a drill according to claim 2, wherein the stopping means stops the first and second motors. 7. The displacement amount detecting means and the stopping means are combined to form one unit, and the displacement amount detecting means is a sampling start position and sampling end position of the load current at the time of displacement of drilling by the second motor of the drill. The stop means stops the drilling work in response to the interrupt signal, the reference value setting means and the level discriminating means are combined to form another unit, and the reference value setting is performed. Means calculates the average value of the load current when the drill is displaced from the sampling start position to the sampling end position, and sets a predetermined reference value above the average value in response to the output from the average value calculation means. The level discriminating means includes a means for detecting that the load current exceeds the reference value after the signal indicating the sampling end position is generated. Overload monitoring apparatus of the drill according to claim 2, wherein derive the interrupt signal characterized in providing stop means.