JP2002370163A - Cutting-in starting point positioning method for grinding wheel to work and grinding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting-in starting point automatic detecting mechanism of a grinding wheel by a noncontact method. SOLUTION: While supplying a grinding liquid to a work surface toward a machining point of a work 2 placed on a table 4 movable in the horizontal direction from a nozzle 30 arranged in the vicinity of a grinding wheel head of a grinding device 1, a grinding wheel rotating to a work surface is lowered to the work surface, a sound pressure signal received by an underground microphone 300 contacting with the grinding liquid passing through into the nozzle for supplying the grinding liquid is passed through a band-pass filter 307 for passing a prescribed frequency band, a basic frequency is extracted from the sound pressure signal passed through this band-pass filter, and time (Pi =P0 ) when a value Pi of the sound pressure signal in the basic frequency reaches a value P0 of the sound pressure signal in the preset basic frequency is determined as a cutting-in starting point of the grinding wheel to the work.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the starting point of cutting of a grindstone with respect to a work in a grinding apparatus without bringing the grindstone into contact with the work, and a grinding apparatus for implementing the method.

[0002]

2. Description of the Related Art A vertical grinding apparatus for grinding a disc-shaped grinding wheel rotated by an electric motor to a desired cutting amount from above a work (workpiece) has a cutting starting point. In order to determine the position, the operator turns the wheel while turning the handle connected to the manual pulse generator or pressing the jog button while watching the distance of the gap between the wheel and the work.
Then, the worker works the whetstone at a speed lower than the descent speed of the whetstone in the above-described process while rotating the handle or pressing the jog button while watching the distance of the gap between the whetstone and the work. The cutting is performed by recognizing the position where a slight spark has flew or the position where the cutting water has changed as the cutting start point.

[0003] This operation is performed not only by a general-purpose machine but also by an NC machine. For NC machines, do this once
Once the cutting start point position of the grindstone with respect to the tool is determined, it can be performed automatically thereafter. However, the work of recognizing the starting point must be performed based on the intuition and experience of the operator, and the conditions vary depending on the work shape and the material of the work. Cost.

[0004] In addition, this work requires a long time for grinding when a grindstone is gently approached to the work and a fine cut is started starting from a place where the distance between the grindstone and the work is far. Conversely, if you approach the whetstone with a very fast speed, the whetstone will collide violently with the work, and the whetstone will be damaged.
The work may be damaged which cannot be removed by grinding. Therefore, the work of determining the starting point of the grinding wheel cutting is the work that the operator dislikes most.

[0005] It has been proposed to carry out a mechanized operation for determining the starting point of the grinding wheel cutting. For example, Japanese Utility Model Laid-Open No. 63-1103
No. 71 discloses a surface grinding apparatus in which a distance sensor for measuring the distance between the upper surface of a work mounted on a table and a processing surface of a rotating grindstone in a non-contact manner is provided on a safety protection cover of the grindstone. In Japanese Patent Application Laid-Open No. Hei 2-198768, an air discharge unit is provided near a magnet table on a table, and air from an air micrometer is discharged from an air outlet of the air discharge unit. A method for detecting a cutting start point non-contacting method of a grinding wheel in which the position of the grinding surface of the grinding wheel with respect to the air discharge portion is detected by a change in the supply air pressure in an air micrometer is approached. However, these non-contact detection methods of the cutting start point of the grinding wheel do not directly detect the distance between the grinding surface of the grinding wheel and the surface to be ground of the work.

[0006] Japanese Patent Application Laid-Open No. 2000-263436 discloses that a liquid is supplied to a surface of a work located on a horizontally movable table to form a liquid thin film on the surface of the work.
While irradiating the surface of the liquid thin film with light from the light source of the color identification sensor, and condensing the reflected light on an optical fiber to recognize the color component of the light, the value E is calculated by the arithmetic unit of the CPU. The liquid formed on the work surface as the rotating whetstone approaches the work is lowered by moving the whetstone, which can be raised and lowered, provided in the direction perpendicular to the work surface to the work surface. The air is entrained in the thin film, and fine bubbles are generated inside the liquid thin film, and the value E of the color component of the light is previously stored in the storage unit of the CPU. A method is provided in which the position of the grindstone with respect to the work when the color component value Eo becomes the starting point of the cutting of the grindstone is provided.

The method using the color identification sensor is an excellent method for determining the starting point of cutting of a grinding wheel because it is not affected by the change in the thickness of the grinding fluid having water bubbles on the work. Depending on the size of the work, the mounting position of the color identification sensor is restricted, and if the work size is too small or too large, it is not suitable.

[0008]

SUMMARY OF THE INVENTION The present invention is a non-contact method, which can directly detect the distance between the grinding surface of a grindstone and the surface to be ground of a work, and is limited to the size of the work. It is an object of the present invention to provide a method for determining a starting point of cutting of a grinding wheel without the need for grinding and a grinding device capable of implementing the non-contact detection method.

[0009]

According to a first aspect of the present invention, a grinding fluid is directed from a nozzle provided near a grinding wheel head of a grinding device to a working point of a work placed on a table. The grinding wheel which is rotated with respect to the work surface is lowered to the work surface while being supplied to the work surface, and the underwater microphone installed in the nozzle for supplying the grinding liquid receives the wave. The sound pressure signal of the liquid is passed through a band-pass filter that passes through a predetermined frequency band, a fundamental frequency is extracted from the sound pressure signal that has passed through the band-pass filter, and the value (P _i ) of the sound pressure signal at the fundamental frequency Has reached the value (P ₀ ) of the sound pressure signal at the preset fundamental frequency (P _i = P ₀ )
It is intended to provide a method for determining a time as a starting point of cutting of a grindstone with respect to a work.

The value (P ₀ ) of the sound pressure signal at the fundamental frequency of the underwater microphone at the cutting start position of the grindstone with respect to the work is measured in advance, and this is measured by the control unit (CP).
U), the starting point of the cutting of the grinding wheel for the second and subsequent times is determined by the time when the rotating grinding wheel is lowered with respect to the work, and transmitted from the underwater microphone over time. When the value (P _i ) of the sound pressure signal at the fundamental frequency of the received sound pressure signal reaches the value (P ₀ ) of the sound pressure signal at the fundamental frequency (P _i = P ₀ ), the whetstone of the grinding wheel with respect to the work is used. The cutting start point is automatically determined and the descent of the grinding wheel can be stopped.

According to a second aspect of the present invention, there is provided a table on which a work is placed, driving means for reciprocating or rotating the table in a horizontal direction, and a table perpendicular to the surface of the table. A grindstone shaft provided so as to be able to move up and down, means for raising and lowering the grindstone shaft,
A grindstone rotatably provided on the grindstone shaft, a nozzle capable of ascending and descending together with the grindstone, and supplying a grinding fluid to a processing point of a work placed on the table; Underwater microphone that comes into contact with the grinding fluid passing therethrough, a bandpass filter that receives a sound pressure signal received by the underwater microphone and passes through a predetermined frequency band, and an extraction that extracts a fundamental frequency from the sound pressure signal that has passed through the bandpass filter A control device having a circuit, a storage unit, a recording unit, and a comparison unit, wherein the recording unit receives a sound pressure signal (P _i ) at the fundamental frequency extracted by the extraction circuit over time, and obtains the value (P
_i) a pre acoustic pressure signal at the fundamental frequency stored in the storage unit and a value of (P ₀₎ in comparison the comparison unit, from the control device when P _i has reached _{P 0 (P i = P 0} ) A control device for outputting a signal to stop the descent to the grinding wheel shaft elevating means.

There is provided a surface grinding apparatus capable of performing the above-described method of detecting the starting point of cutting of a grinding stone.

According to a third aspect of the present invention, the value of the sound pressure signal (P _i ) at the fundamental frequency extracted by the extraction circuit is changed to the value of the sound pressure signal (P ₀ ) at the fundamental frequency stored in the storage unit in advance. When it reaches (P _i = P ₀ ), a storage unit for storing the position of the grindstone with respect to the work as the grindstone starting point position, an on / off switch for detecting the starting point position of the grindstone, and when the switch is On The function of the grinding wheel jog button or manual pulse generator is invalid and the raising and lowering of the grinding wheel is disabled.When the switch is off, the function of the grinding wheel jog button or the manual pulse generator is enabled and the raising and lowering of the grinding wheel becomes possible. It is characterized in that it is provided with a grinding wheel upper and lower cutting manual pulse generator or a button switch in which the work is cut by the grinding stone.

[0014] On-Of detection of starting point position of cutting of grinding wheel
When the f-switch is On, the function of the grinding wheel jog button or the manual pulse generator is invalid, so that the operator may accidentally rotate the handle provided with the manual pulse generator,
Alternatively, even if the grinding wheel jog button is pressed, the grinding wheel remains stopped, or the steering wheel idles, and no cutting is performed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a partially cutaway plan view showing the relationship between a work, a grinding wheel, and a grinding wheel incision starting point detecting mechanism, FIG. 2 is a perspective view of a surface grinding device, and FIG. FIG. 4 is a partial sectional view of the underwater microphone, FIG. 5 is a block diagram showing an embodiment of the present invention, and FIG. 6 is a correlation diagram between the sound pressure at the fundamental frequency and the grindstone / work. It is.

1, 2 and 3, 1 is a surface grinding device, 2 is a work, 3 is a grindstone, 4 is a table capable of reciprocating in the horizontal direction (X-axis direction), and 5 is work. A base unit, 6 is an electromagnetic chuck, 7 is a saddle that can reciprocate in the front-rear direction (Z-axis direction), 8 is an operation panel, 8a is an on-off switch for detecting the starting point of cutting of a grinding wheel, and 8b is a manual pulse of grinding wheel vertical cutting. A generator button, 9 is a column, 10 is a grindstone head, 11 is a grindstone shaft, 12 is lifting means for moving the grindstone 3 in the vertical direction (Y-axis direction), 13 is a motor, 14 is a screw body, and 15 is a screw body. A screw shaft, 16 is a bearing, 17 is a security cover, 316 is a control device (CPU), 30 is a grinding fluid supply nozzle, and 300 is a submersible microphone.

The rotating grinding wheel 3 in the form of a disk is turned on the surface of the work 2 by turning a hand handle (not shown) provided on the front surface of the grinding device or by pressing a grinding wheel raising / lowering button 8b of the operation panel 8. To a position about 1 mm from
00m / min). Then, the approach speed of the grindstone 3 is set to 0.1 to 0.01 m by pressing the grindstone up / down button.
/ Sec, and lowered from the surface of the work 2 to a position of about 0.01 to 1 mm. When the ball screw 15 is moved up and down by driving the motor 13 of the elevating means 12, the nozzle 30 provided on the outside or inside of the rotating grinding wheel safety protection cover 17 causes the nozzle 30 provided with the descent of the grinding stone. The structure approaches the work and moves away from the work as the grindstone rises. The nozzle 30 sprays a grinding liquid on the surface of the work 2 fixed to the electromagnetic chuck 6 on the table 4. Grinding liquid spray angle of the nozzle 30 is the processing point (grinding surface) of the grindstone 3
3a is provided so that the grinding fluid can reach it.

The grinding fluid sprayed from the nozzle 30 forms a thin film on the work 2, and the distance between the work and the grindstone is about 1-2 m.
The color does not change up to m, but the rotating whetstone 3
Begins to contain fine bubbles in the thin film as it approaches the work 2, and further forms a white band-like grinding fluid stream containing fine bubbles of approximately the same width as the grindstone as the grindstone approaches the work. The amount of the bubbles increases as the grindstone approaches the work.

The underwater microphone 300 has a pressure sensor for a piezoelectric transducer (for example, a piezo-electric ceramic transducer element) 301 inside, and its surroundings are protected by a waterproof cover 303 to supply the grinding fluid. The underwater microphone is installed on the nozzle wall by using the bore 302 at a position where the underwater microphone comes into contact with the grinding fluid passing through the inside of the nozzle 30.
The sound pressure received by the pressure sensor 301 is converted into an electric signal, pre-amplified by a preamplifier 304 incorporated in the underwater microphone so as to give an output sensitivity of 0.1 or 1 V / Unit, and a lead line 305. Using amplifier 30
6 is output.

The sound pressure signal amplified by the amplifier 306 passes through a predetermined frequency band.
(For example, 6 to 8K)
Hz). Bandpass filter 3
The sound pressure signal which passed through 07 is sent to the oscilloscope 308 as an AC signal, and the sound pressure signal with the passage of time is analog-displayed on an oscilloscope display. The sound pressure signal passed through the bandpass filter 307 is converted into a DC signal and sent to the amplifier 306, and the sound pressure signal over time is digitally displayed on a display.

Further, the sound pressure signal passed through the band pass filter 307 is output to the extraction circuit 311 of the output device 310, and the fundamental frequency (for example, 7KH) is obtained from the output sound pressure signal.
z) The sound pressure signal is extracted. In the extraction circuit 311, a high frequency portion is extracted from each frequency by the fundamental frequency extraction circuit 312, and a noise portion is removed from the result to extract a basic frequency.

In the line extracting circuit 313, after obtaining the true peak of the signal level of the fundamental frequency, tracking is performed in the time direction to extract a line, and the line is extracted to the recording unit of the control unit 316 via the cable 314. And outputs a sound pressure signal (see FIG. 6).

The control device (CPU) 316 has OK data.
(P₀) Storage unit (ROM), data rewriting latch times
It has a path recording unit (RAM) and a counting circuit (comparator). Record
The recording unit (RAM) stores the basic data extracted by the extraction circuit 311.
Sound pressure signal at frequency (P _i) Over time, this
Value (P_i) And the basic frequency stored in the storage unit (ROM) in advance.
Sound pressure signal at wavenumber (P₀) Value in the comparison section
Then P_iIs P₀Reached (P_i= P₀Sometimes a control device
The descent stop signal is output to the grinding wheel shaft elevating means 12. Abrasive
The motor 13 of the stone shaft elevating means receives the stop signal and receives the stop signal.
When the driving of the grinding wheel is stopped, the descent of the grinding wheel axis stops, and the grinding wheel
It will be located at the cutting start point for the cut.

As described above, the value of the sound pressure signal (P ₀ ) at the fundamental frequency stored in the storage unit (ROM), which is used to indicate the cutting start point, depends on the diameter, width, Since it depends on the material, work material, grinding fluid composition, etc., the actual work grinding conditions (grinding fluid supply amount,
Is lowered to click two surfaces, the grinding wheel outer peripheral bottom and word - - grindstone rotation speed, the grinding wheel 3 which rotates the wheel spindle descending speed) word the distance between click on the horizontal axis, the sound pressure signal at the fundamental frequency (P _I ) Is plotted on the vertical axis by experimentation in advance, and from this correlation diagram, the grinding wheel outer peripheral bottom and the wedge are defined as the grinding wheel cutting start point.
The distance between the click (e.g., 0.1 mm) the value of the sound pressure signal at the fundamental frequency in defined as P _0.

The unit of the output sound pressure signal of the underwater microphone is decibel (dB), and the sensitivity is −15 per 1 μPa / V.
A frequency from 0 dB to -210 dB is selected. The underwater microphone is supplied by Bruel Kjaer of Denmark or its distributor Matsushita Interchange.
Hydrophone 8103, 810 from Techno
Available as Type 4 (trade name).

In the block diagram showing an embodiment of the present invention shown in FIG. 5, reference numeral 300 denotes an underwater microphone, 302 denotes a coupler, 305 denotes a cable, 306 denotes an amplifier, 307 denotes a band-pass filter, and 308 denotes an oscilloscope. , 311
Is an extraction circuit, 312 is a fundamental frequency extraction circuit, 313 is a line extraction circuit, 314 is a cable, 316 is a control device,
317 is an I / O port, 318 is an external device such as a sequencer, and 319 is a cable.

Detection of Starting Point of Grinding Wheel Cut: In the method of detecting the starting point of grinding stone cutting according to the present invention, a method of setting the starting point of grinding stone cutting at a position of about 0.02 mm from the work surface will be described below as an example. First, detection of the starting position of the cutting point of the grinding wheel on the operation panel 8 O
The n-Off switch 8a is turned off, and while the grinding liquid is sprayed from the nozzle to the work surface (15 to 25 liters / minute), a continuous thin film is formed on the work surface while the hand handle (feeding of one rotation) is performed. 5 mm) to quickly move the grindstone to a distance of about 2 mm above the work surface.

Next, the grinding fluid is placed on the table from the nozzle at the processing point of the work (before the grinding is started, the work is not processed. The rotating grindstone is manually lowered to a distance of about 0.02 mm from the work surface while supplying the work to the work surface (to the bottom of the outer peripheral edge). The sound pressure is received by the pressure sensor 301 of the underwater microphone 300 through the grinding fluid supplied from the nozzle, preamplified by the preamplifier 304, output as a sound pressure signal, and further amplified by the amplifier 306. The signal is passed through a band-pass filter 307 that passes a predetermined frequency band, a fundamental frequency is extracted from the sound pressure signal that has passed through the band-pass filter, and the value (P _i ) of the sound pressure signal at the fundamental frequency is recorded. .

[0029] The outer peripheral bottom of the rotating grindstone is 0.
When the distance reaches 02 mm, the value (P _i ) of the sound pressure signal at the fundamental frequency is read, and the value at this time is the value (P ₀ ) of the sound pressure signal at the fundamental frequency corresponding to the grinding wheel cutting start point position. Decide. This value is stored in the CPU 316
Is stored in the OK data storage unit (ROM). In the grinding of the work after the second time, when the value (P _i ) of the sound pressure signal at the fundamental frequency reaches P ₀ (P _i = P ₀ ), the starting point of cutting of the grindstone with respect to the work is defined as: P _i = P ₀
And the calculation circuit (comparing unit) calculates the
Then, a signal for stopping the driving of the motor 13 of the grinding wheel shaft elevating means 12 is transmitted to stop the lowering of the grinding wheel.

That is, the grindstone is retracted from the work surface, and the cutting start point position detection O of the grindstone on the operation panel 8 is performed again.
The n-Off switch 8a is turned off, the value of the sound pressure signal (P _i ) at the fundamental frequency is read via the pressure sensor 301 of the underwater microphone 300 while the grindstone is lowered, and transmitted to the latch circuit (RAM). The value P ₀ of the sound pressure signal at the fundamental frequency input to the ROM is compared with the value (P _i ) of the sound pressure signal at the fundamental frequency sequentially transmitted to the RAM. When the value (P _i ) reaches P ₀ (P _i = P ₀ ), the sequencer 318 is used as the starting point for cutting the grinding wheel with respect to the work.
The position of the cutting start point of the grindstone on the operation panel 8 of the grinding device 1 is transmitted to the on-off switch 8a.
Is changed from green to red to notify the worker that the start point has been reached, and the switch 8a is switched to On.

Next, the setting of the cutting speed (processing speed of the grindstone) is switched, the on-off switch 8a for detecting the starting point of the cutting of the grindstone is turned off, and the handle is rotated to start the cutting of the work. Press the jog button 8b to start cutting the work.

[0032]

According to the present invention, since the cutting start point of the grinding wheel can be set in a non-contact manner, the work is easy and the chance of breaking the grinding wheel is reduced. Also, since the sound wave passing through the grinding fluid is detected by the underwater microphone, the machine that picks up noise is reduced compared to the conventional method of picking up the sound wave in the air, so the grinding wheel cutting start point is determined with higher reliability. be able to.

[Brief description of the drawings]

FIG. 1 is a partially cutaway plan view showing a relationship between a work, a grinding wheel, and a grinding wheel cutting start point detecting mechanism.

FIG. 2 is a perspective view of a surface grinding device.

FIG. 3 is a side view in which a part of the surface grinding device is cut away.

FIG. 4 is a partial sectional view of an underwater microphone.

FIG. 5 is a block diagram illustrating an embodiment of the present invention.

FIG. 6 is a correlation diagram between a sound pressure at a fundamental frequency and a grindstone / work.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Surface grinding device 2 Work 3 Grinding stone 30 Grinding fluid supply nozzle 300 Underwater microphone 316 Control device

Continued on the front page F term (reference) 3C029 AA24 3C034 AA20 BB92 CA11 CA24 DD14 3C043 BA12 CC03

Claims (3)

[Claims] A grinding liquid is supplied to a work surface of a work placed on a table from a nozzle provided in the vicinity of a grindstone head of the grinding apparatus while the grinding fluid is being supplied to the work surface. The grindstone rotating with respect to the work surface is lowered to the work surface, and the underwater microphone installed in the nozzle for supplying the grinding fluid receives a sound pressure signal of the grinding fluid received in a predetermined frequency band. Pass through a band-pass filter to pass, extract the fundamental frequency from the sound pressure signal that has passed through this band-pass filter,
When the value (P _i ) of the sound pressure signal at the fundamental frequency reaches the value (P ₀ ) of the sound pressure signal at the preset fundamental frequency (P _i = P ₀ ), the cutting of the grindstone with respect to the work is performed. How to determine the starting point. 2. A table on which a work is placed, a driving means for reciprocating or rotating the table in a horizontal direction, and a table which is vertically movable with respect to the surface of the table. A grindstone shaft, means for raising and lowering the grindstone shaft, a grindstone rotatably provided on the grindstone shaft, and a work point which can be raised and lowered together with the grindstone and which is mounted on the table. A nozzle for supplying a grinding fluid, an underwater microphone that comes into contact with the grinding fluid passing through the nozzle, a bandpass filter that receives a sound pressure signal received by the underwater microphone, and passes a predetermined frequency band, and a bandpass filter. An extraction circuit for extracting a fundamental frequency from a sound pressure signal, and a control device having a storage unit, a recording unit, and a comparison unit, wherein the sound pressure signal at the fundamental frequency (P
_i ) is received by the recording unit over time, and the value (P _i ) and the sound pressure signal (P ₀ ) at the fundamental frequency stored in the storage unit in advance are received.
Is compared by the comparison unit, and P _i reaches P ₀ (P _i =
A control device which outputs a signal to stop the descent to the grinding wheel shaft elevating means at the time of P ₀ ). 3. The grinding device according to claim 1, wherein the value of the sound pressure signal (P _i ) at the fundamental frequency extracted by the extraction circuit is changed to a value of the sound pressure signal (P ₀ ) at the fundamental frequency stored in the storage unit in advance. When it reaches (P _i = P ₀ ), a storage unit for storing the position of the grindstone with respect to the work as the grindstone starting point position, an on / off switch for detecting the starting point position of the grindstone, and when the switch is On The function of the grinding wheel jog button or manual pulse generator is invalid and the raising and lowering of the grinding wheel is disabled.When the switch is off, the function of the grinding wheel jog button or the manual pulse generator is enabled and the raising and lowering of the grinding wheel becomes possible. 3. The grinding apparatus according to claim 2, further comprising a hand wheel generator or a button switch for vertically cutting the grinding wheel, wherein the workpiece is cut by the grinding wheel.