JP4677315B2 - Grinding fluid thickness measuring apparatus and grinding machine using the apparatus - Google Patents

Description

  The present invention relates to a thickness measuring device for a grinding fluid supplied between a cylindrical grinding wheel and a reference member, and a grinding machine controlled based on the thickness of the grinding fluid obtained by the thickness measuring device.

  When grinding a workpiece with a grinding wheel, the grinding fluid is supplied to the grinding point between the workpiece and the grinding wheel and cooled and lubricated to prevent grinding burn, thermal distortion, etc. of the workpiece due to grinding heat. .

  In recent years, a grinding fluid supply method as described in Patent Document 1 has been developed so that a workpiece and a grinding wheel can be sufficiently cooled and lubricated with a small amount of grinding fluid. As disclosed in Patent Document 1, the grinding fluid supply method described in Patent Document 1 is a grinding wheel simultaneously with the start of the supply of grinding fluid from an air jet at a position upstream of the grinding point in the direction of grinding wheel rotation. Grinding the grinding wheel with a small amount of grinding fluid by spraying along the grinding surface of the grinding wheel from one side to the other side and blocking the air layer associated with the grinding wheel by the air jet. It adheres well to the surface so that it can be sufficiently supplied to the grinding point.

  However, even if the grinding stone associated air layer is blocked and a small amount of grinding fluid can be supplied to the grinding point as in Patent Document 1, the flow rate of the grinding fluid supplied from the supply source is insufficient. Cannot prevent grinding burn, thermal distortion, etc. of the workpiece. For this reason, conventionally, grinding burn, thermal distortion, and the like are prevented from occurring by supplying a larger amount of grinding liquid than originally required. Even if a sufficient amount of grinding fluid is supplied, the operator must visually determine whether the grinding fluid has a predetermined thickness (film thickness) on the grinding wheel and is attached to the grinding wheel. In recent years, a technique for accurately measuring the thickness of the grinding fluid has been required.

FIG. 10 shows an example of an apparatus for measuring the thickness of the grinding fluid, which includes a grinding wheel G that rotates about the rotation axis O, and in which the workpiece W is ground in the feed direction of the workpiece W indicated by an arrow in the figure. A pair of electrodes 1 and 2 are embedded so as to be exposed to each other, and a voltage source E and an ammeter 4 are connected to the pair of electrodes 1 and 2 to constitute an electric circuit. Then, the grinding liquid is supplied from the grinding liquid nozzle 6 toward the gap between the grinding wheel G and the workpiece, and the workpiece W is ground. The current flowing through the grinding fluid when the workpiece W is ground by the grinding wheel G is measured by the ammeter 4 and integrated and recorded by the recorder 7. By analyzing the electrical resistance value of the grinding fluid from the accumulated current value, the film thickness of the grinding fluid in the interference region between the grinding wheel G and the workpiece W is estimated.
JP 2004-17265A (paragraph number [0019] from the fifth page to paragraph number [0021] from the sixth page, FIG. 6)

  However, in the apparatus shown in FIG. 10, the electrodes 1 and 2 are moved in a direction perpendicular to the rotational axis O of the grinding wheel G as the workpiece W is fed, and the film thickness between the moved electrodes is measured. The film thickness of the grinding liquid is the thickest immediately below the grinding liquid nozzle 6, while it is the thinnest in the interference region between the grinding wheel G and the workpiece W. For this reason, the current measured by the ammeter 4 becomes the average film thickness of the grinding fluid staying between the grinding fluid nozzle 6 and the area between the grinding wheel G and the workpiece W. It was difficult to evaluate the relationship between the thickness of the grinding fluid and the current (electrical resistance). Further, in the interference region between the grinding wheel G and the workpiece W, the amount of the supplied grinding fluid is small, and the grinding fluid film formed between the electrodes may be in an intermittent state. When such a state occurs between the electrodes, no current flows between the electrodes, and a state where the electrical resistance value is infinite is recorded intermittently. For this reason, it is difficult to accurately estimate the film thickness of the grinding fluid even if the accumulated current values are simply accumulated.

  The object of the present invention is therefore to provide an instantaneous amount of grinding fluid at the grinding wheel and workpiece interference area, for example the grinding point, i.e. the thickness of the fluid film of the grinding fluid flow formed between the grinding surface and the workpiece. An object of the present invention is to provide an apparatus capable of accurately measuring (hereinafter referred to as the thickness of the grinding fluid).

  The feature of claim 1 for solving the above-described problem is that a grinding wheel rotated around a rotation axis, a reference member disposed opposite to a grinding surface of the grinding wheel, and the grinding wheel and the reference member A voltage is applied between the grinding fluid supply means for supplying the grinding fluid therebetween, the plurality of electrodes provided on the reference member and insulated from each other, and the adjacent electrodes of the plurality of electrodes, via the grinding fluid. Measuring an electric resistance value of a grinding fluid passing through a gap between the grinding wheel and a reference member by measuring current flowing between the plurality of electrodes, and measuring the electric resistance value In a grinding fluid thickness measuring device comprising a thickness computing means for computing the thickness of the grinding fluid passing through the gap between the grinding wheel and a reference member based on the electrical resistance value measured by the device, the plurality of electrodes are Parallel to the axis of rotation of the grinding wheel Disposed reference member, is that the fixed resistance between the wiring for applying a mutually voltage between adjacent electrodes of the plurality of electrodes are connected in parallel.

  According to a second aspect of the present invention, there is provided a grinding wheel that rotates about a rotation axis, and a workpiece support device that supports a workpiece, and supplies a grinding fluid to a grinding point with the workpiece of the grinding wheel. In the grinding machine which grinds the workpiece by moving the grinding wheel and the workpiece support device relative to each other, the thickness of the grinding fluid thickness measuring device according to claim 1 and the thickness of the grinding fluid of the grinding fluid thickness measuring device. And an approach detection means for detecting that the grinding wheel has approached the reference member based on a detection signal.

  According to a third aspect of the present invention, there is provided a grinding wheel that rotates about a rotation axis, and a workpiece support device that supports a workpiece, and supplies a grinding fluid to a grinding point with the workpiece of the grinding wheel. In the grinding machine which grinds the workpiece by relatively moving the grinding wheel and the workpiece support device, the grinding fluid thickness measuring device according to claim 1 and the grinding fluid from the grinding fluid thickness measuring device And a grinding fluid judgment means for judging whether the grinding fluid is abnormal or normal based on the thickness signal.

  According to a fourth aspect of the present invention, there is provided a grinding wheel that rotates about a rotation axis, and a workpiece support device that supports a workpiece, and supplies a grinding liquid to a grinding point with the workpiece of the grinding wheel. In the grinding machine which grinds the workpiece by moving the grinding wheel and the workpiece support device relative to each other, the grinding fluid thickness measuring device according to claim 1 and the grinding fluid thickness measurement on the front surface of the grinding wheel base. And a grinding fluid thickness-electric resistance value calibration device including a reference plate provided so as to be able to face the reference member of the device.

  In the invention according to claim 1 configured as described above, by arranging the pair of electrodes on the reference member in parallel with the rotation axis of the grinding wheel, the parallel line formed by the pair of electrodes and the rotation axis of the grinding wheel Measure the instantaneous amount of grinding fluid that passes through the surface to be formed. The film thickness of the grinding fluid that passes through the grinding surface is different because the heights of the abrasive tips that are the individual cutting edges are uneven and the height of the binder surface for fixing and supporting the abrasive grains is uneven. It is not constant in the width direction of the grinding wheel. However, in the present invention, by measuring the electrical resistance in the minute volume of the grinding fluid passing through the grinding surface, the minute height fluctuations on these grinding wheel working surfaces are averaged, so that the grinding wheel and the reference member can be averaged. The film thickness of the grinding fluid passing through can be measured accurately.

  In addition, measurement noise can be reduced by configuring a plurality of electric circuits including a pair of electrodes in parallel.

  Furthermore, the fixed resistance is connected in parallel with the wiring for applying a voltage between the adjacent electrodes, so that even when there is no grinding fluid flowing between the grinding wheel and the reference member, the voltage applied to the fixed resistance A finite electric resistance value generated by the flowing current is measured by the electric resistance measuring device. Therefore, since the calculated electrical resistance value does not become infinite, the thickness of the grinding fluid can be easily measured without the calculated electrical resistance value of the grinding fluid being intermittent.

  According to the configuration of the second aspect of the invention, in the grinding machine, the grinding wheel and the reference member are brought close to each other while the grinding fluid is supplied between the grinding wheel and the reference member by the grinding fluid supply means. When the grinding fluid thickness measuring device detects that the thickness of the grinding fluid between the grinding wheel and the reference member has become equal to or less than a predetermined value, the approach detection means indicates that the reference member and the grinding wheel have approached. Detect that. Therefore, it is possible to provide a grinding machine in which the thickness measuring device can be used instead of the proximity switch.

  According to the third aspect of the present invention, the grinding wheel and the reference member are brought close to each other while the grinding fluid is supplied between the grinding wheel and the reference member by the grinding fluid supply means. When the grinding fluid determination means does not determine that the clearance between the grinding wheel and the reference member is larger than the predetermined value even though the grinding wheel and the reference member are closer than the predetermined value. Can provide a grinding machine capable of determining whether or not the grinding fluid is supplied, such as determining that the grinding fluid is not normally supplied.

  According to the configuration of the fourth aspect of the present invention, the reference plate and the reference member provided on the front surface of the grindstone table are brought close to each other so that the relationship between the grinding fluid thickness and the electrical resistance value can be accurately and easily on the actual machine. Can be calibrated.

  A grinding machine provided with a grinding fluid thickness measuring apparatus according to an embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, a grindstone table 11 is slidably mounted on the bed 10, and moves forward and backward in the X-axis direction approaching and separating from the workpiece W via a ball screw mechanism (not shown) by a servo motor 12. Is done. The amount of rotation of the servo motor 12 is detected by an encoder 12a attached to the rear end of the servo motor 12. A grinding wheel shaft 13 having a grinding wheel G attached to one end is rotatably supported on the grinding wheel base 11 and is rotated by an electric motor 29. The grinding wheel G is configured by adhering a plurality of grinding wheel chips to the outer peripheral surface of a disk-shaped base formed of a metal such as iron or aluminum. The outer peripheral surfaces of the plurality of grindstone chips are shaped into a grinding surface Ga.

  In addition, although the present Example demonstrated by the example of the segment grindstone which adhere | attached the several grindstone chip | tip on the outer peripheral surface of a base | substrate as a grindstone wheel, it is not limited to this. For example, a known vitrified bond grindstone may be used.

  A grinding wheel guard 19 that covers the grinding wheel G is fixed to the grinding wheel base 11. A grinding fluid nozzle 21 is attached to the upper surface of the grinding wheel guard 19, and the grinding fluid is supplied from the grinding fluid nozzle 21 toward the grinding point P where the grinding wheel G grinds the workpiece W. The grinding fluid nozzle 21 is connected by a grinding fluid supply pipe 33 to a grinding fluid tank 32 that stores the grinding fluid. A pump 34 of the grinding liquid supply device 20 is attached in the middle of the grinding liquid supply pipe 33. The pump 34 is rotated by a motor 35, draws up the grinding fluid from the grinding fluid tank 32, and supplies a grinding fluid flow 22 having a predetermined flow rate to the grinding fluid nozzle 21.

  A table 14 is slidably mounted on the bed 10 and is moved by a servo motor 15 through a ball screw mechanism 16 in the Z-axis direction perpendicular to the X-axis. The rotation amount of the servo motor 15 is detected by an encoder 15a attached to the servo motor 15, as shown in FIG. A headstock (not shown) and a tailstock 18 constituting the workpiece support device 17 are mounted on the table 14, and the workpiece W is sandwiched between the centers of the spindle stock and the tailstock 18 and rotated. Is done.

  A reference member 55 constituting the grinding fluid thickness measuring device 50 shown in FIG. 2 for measuring the thickness of the grinding fluid is attached to the side surface of the tailstock 18 on the grinding wheel G side.

  As shown in FIG. 2, a digital servo control device 40 a is connected to the servo motor 12. This digital servo control device 40a is connected to a CNC device 41 that controls the entire machine, and controls the rotation of the servo motor 12 based on the deviation between the feed command from the CNC device 41 and the position feedback signal of the grinder base 11 from the encoder 12a. Then, the feed speed and movement position of the grinding wheel platform 11 are controlled. The servomotor 15 is connected to a digital servo control device 40b, and this digital servo control device 40b is connected to a CNC device 41. The digital servo control device 40b controls the rotation of the servo motor 15 based on the deviation between the feed command from the CNC device 41 and the position feedback signal of the table 14 from the encoder 15a, and controls the feed speed and moving position of the table 14. .

  In addition to the digital servo control devices 40a and 40b, the CNC device 41 includes a sequence controller (hereinafter referred to as “PLC”) that opens and closes the electromagnetic on-off valve 24 and controls the grinding fluid supply device 20 based on commands from the CNC device 41. ) 42 and an input / output device 43 for inputting / outputting various information.

  The grinding fluid supply device 20 includes a pump 34, a motor 35, and an inverter circuit 36 that controls the rotation of the motor 35. The inverter circuit 36 is connected to the PLC 42, and controls the rotation of the motor 35 based on the rotation start and rotation stop command and the rotation speed of the pump 34 commanded from the CNC device via the PLC 42. Then, a grinding fluid having a flow rate corresponding to the rotational speed of the pump 34 is supplied.

  The CNC device 41 includes a CPU 44, a ROM 45, and a RAM 46 for storing input data and the like. The ROM 45 stores a grinding cycle as an NC program.

  Next, a detailed configuration of the grinding fluid thickness measuring apparatus 50 that measures the thickness of the grinding fluid will be described. As shown in FIG. 3, the thickness measurement device 50 mainly includes a measurement unit 51, an electrical resistance value measurement device 52, and a thickness calculation device 53. The measurement unit 51 includes the reference member 55, and the reference member 55 has a rectangular block shape made of an insulating material such as a resin material. As shown in FIG. 4, a plurality (five in the embodiment) of electrode rods 56 a to 56 e arranged in a straight line on a straight line A parallel to the rotational axis O of the grinding wheel G are disposed on the reference member 55. Yes. The electrode rods 56a to 56e have a cylindrical shape having the same cross-sectional area as the cross-sectional area, are separated by a predetermined arrangement distance L1 to L4, and are embedded in the reference member 55 so that one end face is exposed on the surface of the reference block. It is. As shown in FIG. 3, the electrode rods 56 a to 56 e are connected to the plus-side wiring 57 and the minus-side wiring 58 whose adjacent electrodes are different from each other. That is, if the electrode rod 56a is connected to the plus side wiring 57, the electrode rod 56b adjacent to the electrode rod 56a is connected to the minus side wiring 58, and similarly the electrode rod 56c adjacent to the electrode rod 56b is connected to the plus side wiring 58. 57. As a result, the electrode rods 56a, 56c and 56e are connected to the plus side wiring 57, the electrode rods 56b and 56d are connected to the minus side wiring 58, and the electrode rods 56a to 56e are the plus side wiring 57 where the adjacent electrodes are different from each other. And the negative side wiring 58 is alternately wired. A pair of electrode rods by the adjacent electrode rods 56a to 56e is constituted by, for example, electrode rods 56a and 56b and electrode rods 56b and 56c. The measurement unit 51 is further provided with a fixed resistance r for connecting the plus side wiring 57 and the minus side wiring 58, and this fixed resistance r has a known electric resistance value R0 in advance, and the adjacent electrode rods 56a to 56e. As shown in FIG. 3, an electric circuit is formed in parallel with the pair of electrode bars formed by the above.

  An electrical resistance measurement device 52 is connected to the measurement unit 51. The electrical resistance value measuring device 52 includes a direct current stabilized power source 59, which is connected to the plus side wiring 57 and the minus side wire 58 of the measuring unit 51, and that measures a voltage of a predetermined value V. 51. In addition, the electric resistance value measuring device 52 calculates an electric resistance value Rs in the measuring unit 51 from the ammeter 60, the current value I of the ammeter 60 and the voltage value V of the DC stabilized power supply 59, and outputs the resistance value Rs. A vessel 61 is provided.

  A thickness calculator 53 is connected to the resistance calculator 61. The thickness calculation device 53 is a device that calculates the thickness T of the grinding fluid based on the electrical resistance value Rs output from the resistance value calculator 61, and includes a storage unit 62 and a CPU 63. The storage unit 62 stores relationship data between the electrical resistance value Rcal measured in advance and the thickness T of the grinding fluid, and the CPU 63 calculates the thickness T of the grinding fluid at the electrical resistance value Rs output from the resistance value calculator 61. Calculation is performed based on the relational data between the electrical resistance value Rs of the storage unit 62 and the thickness T of the grinding fluid. The thickness calculation device 53 is connected to the CNC device 41.

  Here, the operation of the grinding fluid thickness measuring apparatus 50 will be described. When the grinding fluid is not supplied, there is a space between the electrode rods 56a, 56c, 56e connected to the plus side wiring 57 and the electrode rods 56b, 56d connected to the minus side wiring wire 58. The electrode rods 56a, 56c, 56e and the electrode rods 56b, 56d are electrically open. At this time, only an electric current flows through the electric resistance value measuring device 52 via the fixed resistance r. In this state, when the grinding fluid adheres between the electrode rods 56a, 56c, 56e and the electrode rods 56b, 56d, the electrode rods 56a, 56c, 56e and the electrode rods 56b, 56d are electrically connected via the grinding fluid. As shown in FIG. 3, the electrode rods 56a, 56c, 56e and the electrode rods 56b, 56d are energized by the electric resistances Ra to Rd. Here, the electrical resistance values of the electrical resistances Ra to Rd are determined by the thickness T of the grinding fluid. As a result, an electrical resistance value obtained by combining the electrical resistance values of the electrical resistances Ra to Rd determined by the thickness T of the grinding fluid and the electrical resistance value of the fixed resistance r is output from the resistance value calculator 61 as Rs. become. The relationship between the electrical resistance value Rs and the grinding fluid thickness T is obtained, for example, by a grinding fluid thickness-electrical resistance calibration device shown in FIG. In FIG. 5, reference numeral 70 denotes a lifting stage. An elevating table 71 is provided on the elevating stage 70. By operating an elevating dial 72 provided on a side surface of the elevating stage 70, the elevating table 71 is moved up and down by an unillustrated lifting mechanism. A petri dish 73 filled with a grinding fluid is placed on the lifting table 71. In the petri dish 73, the reference member 55 is buried in a grinding fluid. On the opening surface side of the petri dish 73, an insulating plate 74 is fixed at a predetermined position by a support rod 75 and is disposed to face the reference member 55. For this reason, when the raising / lowering table 71 moves up and down by operation of the raising / lowering dial 72, the insulating plate 74 and the reference member 55 of the measurement part 51 can be contacted / separated. As a result, when the insulating plate 74 and the reference member 55 are separated from each other, the grinding fluid flows into the gap d between the insulating plate 74 and the reference member 55, the value of the gap d is measured, and the gap d and the electrode rods 56a to 56e are measured. Based on the current flowing between them, the relationship between the grinding fluid thickness T equal to the gap d and the electrical resistance value Rs can be measured as shown in FIG. At this time, the sensitivity is adjusted by adjusting the electric resistance value of the fixed resistor r.

  An embodiment of another grinding fluid thickness-electric resistance value calibration apparatus for obtaining the relationship between the electrical resistance value Rs and the grinding fluid thickness T shown in FIG. 6 will be described with reference to FIG. An insulating plate 74 is fixed to the front surface of the grindstone base 11 as a reference plate. The table 14 is moved in the Z-axis direction by the servo motor 15 so that the insulating plate 74 is opposed to the reference member 55, and the grindstone base 11 is moved by the servo motor 12 to bring the insulating plate 74 and the reference member 55 close to the measurement start position. Let The grinding fluid supply device 20 is activated with the opening of the grinding nozzle 21 facing the insulating plate 74, and the grinding fluid flow 22 is supplied from the grinding fluid nozzle 21 toward the insulating plate 74. In this state, by bringing the grindstone table 11 closer to the insulating plate 74 based on a command from the CNC device 41, the insulating plate 74 and the reference member 55 can be brought closer to the known gap d. Based on each gap d at this time and the current flowing between the electrode rods 56a to 56e, the relationship between the thickness T of the grinding fluid equal to the gap d and the electrical resistance value Rs can be measured as shown in FIG. it can.

  Next, the operation at the start of grinding of the grinding machine configured as described above will be described based on the flowchart of FIG. The flowchart of FIG. 7 shows the operation of the NC program stored in the ROM 45 of the CNC device 41, and is executed when a machining start is instructed from the input / output device 43 to the CNC device 41. When the program is started, first, in step 100, a rotation command is issued to the electric motor 29, and the grindstone G starts rotating. Further, a rotation command for the workpiece W is issued, the workpiece W is sandwiched and rotated between both centers of the headstock and the tailstock 18, and the grindstone platform 11 is advanced by the servo motor 12. In step 110, a grinding fluid supply command is output from the CNC device 41 to the grinding fluid supply device 20 via the PLC 42. When the grinding fluid supply command is output, the grinding fluid supply device 20 supplies the grinding fluid flow 22 from the grinding fluid nozzle 21 toward the grinding wheel G.

  In step 120, the table 14 is moved by the servo motor 15 and moved to a position where the grinding surface Ga of the grinding wheel G and the reference member 55 face each other. Thereafter, in step 130, the grinding wheel base 11 is advanced by a small amount by the servo motor 12, and the process proceeds to step 140. In step 140, a grinding fluid thickness T signal is input from the grinding fluid thickness measuring device 50, and in step 150, it is determined whether or not the grinding fluid thickness T 0 is stored in advance in the RAM 46. If the grinding liquid stored in the RAM 46 has a predetermined thickness T0, it is assumed that the grinding surface Ga of the grinding wheel G has advanced to a predetermined position. In step 160, the grinding wheel diameter of the grinding wheel G is corrected, and then in step 170. The start of the grinding cycle is commanded and the process is terminated. If the signal of the grinding fluid thickness T input from the measuring device main body in step 150 is larger than the predetermined grinding fluid thickness T0 stored in the RAM 46 in advance, the processing returns to step 130 and is input from the grinding fluid thickness measuring device 50. The grinding wheel base 11 is advanced by a small amount until the signal T of the grinding fluid thickness T reaches the predetermined grinding fluid thickness T0 stored in the RAM 46. Thus, by measuring the thickness T of the grinding fluid supplied from the grinding fluid nozzle 21 to the grinding surface Ga of the grinding wheel G, and detecting that the thickness T of this grinding fluid has reached a predetermined thickness T0, The approach between the grinding surface Ga of the grinding wheel G and the reference member 55 can be detected.

  Steps 140 and 150 constitute an approach detection means for detecting that the grinding wheel G has approached the reference member 55 based on the grinding fluid thickness detection signal of the grinding fluid thickness measuring device 50.

  Next, a second embodiment of the grinding machine will be described. In the second embodiment, it is determined whether or not the grinding fluid is normally supplied. FIG. 8 is a flowchart for explaining the operation of the CNC device 41. The apparatus configuration of the second embodiment is the same as that of the first embodiment, and only the operation of the apparatus is different. Therefore, the description of the apparatus configuration is omitted, and only the operation is based on FIG. explain.

  When the program of FIG. 8 is started, first, in step 200, a rotation command is issued to the electric motor 29, and the grindstone G starts rotating. Further, a rotation command for the workpiece W is issued, the workpiece W is sandwiched and rotated between both centers of the headstock and the tailstock 18, and the grindstone platform 11 is advanced by the servo motor 12. In step 210, a grinding fluid supply command is output from the CNC device 41 to the grinding fluid supply device 20 via the PLC 42. When the grinding fluid supply command is output, the grinding fluid supply device 20 supplies the grinding fluid flow 22 from the grinding fluid nozzle 21 toward the grindstone G.

  In step 220, the table 14 is moved by the servo motor 15 and moved to a position where the grinding surface Ga of the grinding wheel G and the reference member 55 face each other. In step 230, a predetermined position X0 where the grinding fluid is supplied to the reference member 55. The grindstone base 11 is advanced by the servo motor 12 until the time. Then, the grinding fluid thickness T when the grindstone base 11 is at the predetermined position X0 is inputted from the grinding fluid thickness measuring device 50 in step 240, and the grinding fluid thickness T inputted from the thickness measuring device 50 is previously determined as the CNC device. It is determined whether or not the grinding fluid is normally supplied by determining whether or not the value is equal to or greater than a predetermined value T1 stored in the RAM 46 (step 250). When it is determined from the determination in step 250 that the measured thickness T of the grinding fluid is equal to or greater than the predetermined value T1, the process proceeds to step 260. When the measured thickness T of the grinding fluid is smaller than the predetermined value T1, the grinding fluid flow 22 is reached. In step 270, the CNC device 41 retracts the grindstone table 11 without starting the grinding cycle, and after stopping the electric motor 29, the CNC device 41 displays an abnormality on the input / output device 43 in step 280. Let If it is determined in step 250 that the measured thickness T of the grinding fluid is equal to or greater than the predetermined value T1, the start of the grinding cycle is commanded in step 260, and the process is terminated.

Steps 240 and 250 constitute grinding fluid determination means for determining whether the grinding fluid is abnormal or normal based on the grinding fluid thickness signal from the grinding fluid thickness measuring device 50.

The side view which shows the grinding machine to which the thickness measuring apparatus which concerns on this invention is applied. The block diagram of the digital servo control apparatus in the grinding machine which concerns on FIG. The block diagram of a thickness measuring apparatus. The figure which shows electrode arrangement | positioning in the reference | standard member of a thickness measuring apparatus. The figure which shows the calibration apparatus for calibrating the relationship between the thickness of a grinding fluid, and an electrical resistance value. Data showing the relationship between grinding fluid thickness and electrical resistance. 3 is a flowchart showing the operation of the grinding machine according to the first embodiment. The flowchart which shows operation | movement of the grinding machine which concerns on 2nd Embodiment. The figure which shows the other calibration apparatus for calibrating the relationship between the thickness of a grinding fluid, and an electrical resistance value. The figure which shows an example of the conventional apparatus which measures the thickness of a grinding fluid.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Bed, 11 ... Grinding wheel base, 12 ... Servo motor, 12a ... Encoder, 13 ... Grinding wheel shaft, 14 ... Table, 15 ... Servo motor, 15a ... Encoder, 16 ... Ball screw mechanism, 17 ... Workpiece support device, 18 ... Tailstock, 19 ... Grinding wheel guard, 20 ... Grinding fluid supply device, 21 ... Grinding fluid nozzle, 22 ... Grinding fluid flow, 24 ... Electromagnetic on-off valve, 29 ... Electric motor, 32 ... Grinding fluid tank, 33 ... Grinding fluid supply Pipe 34, pump 35, motor 36, inverter circuit 40 a digital servo control device 40 b digital servo control device 41 CNC device 42 sequence controller (PLC) 43 input / output device 44 CPU, 45... ROM, 46... RAM, 50... Grinding fluid thickness measurement device, 51. 5 ... reference member, 56a to 56e ... electrode rod, 57 ... positive side wiring, 58 ... negative side wiring, 59 ... direct current stabilized power supply, 60 ... ammeter, 61 ... resistance value calculator, 62 ... storage unit, 63 ... CPU, 70 ... Elevating stage, 71 ... Elevating table, 72 ... Elevating dial, 73 ... Petri dish, 74 ... Insulating plate, 75 ... Support bar, G ... Grinding wheel, Ga ... Grinding surface, W ... Workpiece, P ... Grinding point , O: rotation axis of the grinding wheel, A: straight line parallel to the rotation axis of the grinding wheel, L1 to L4: arrangement distance of the electrode rod, r: fixed resistance, Ro: previously known electric resistance value, I: current value, V: Voltage value, T: Grinding fluid thickness, T0: Predetermined grinding fluid thickness, T1: Predetermined grinding fluid thickness, Ra to Rd: Electrical resistance between electrode rods, Rcal: Premeasured electrical resistance, Rs ... Electrical resistance.

Claims (4)

A grinding wheel that rotates about the axis of rotation;
A reference member disposed to face the grinding surface of the grinding wheel;
Grinding fluid supply means for supplying a grinding fluid between the grinding wheel and a reference member;
A plurality of electrodes provided on the reference member and insulated from each other;
A voltage is applied between adjacent electrodes of the plurality of electrodes, and a current flowing between the plurality of electrodes is measured via a grinding fluid, thereby passing through a gap between the grinding wheel and a reference member. An electrical resistance measuring device for measuring the electrical resistance of the grinding fluid;
In a grinding fluid thickness measuring device comprising a thickness computing means for computing the thickness of the grinding fluid passing through the gap between the grinding wheel and a reference member based on the electrical resistance value measured by the electrical resistance value measuring device,
The plurality of electrodes are arranged on the reference member in parallel with the rotation axis of the grinding wheel,
A grinding fluid thickness measuring apparatus, wherein a fixed resistor is connected in parallel between wirings for applying a voltage between adjacent electrodes of the plurality of electrodes. A grinding wheel that rotates about the axis of rotation;
A workpiece support device for supporting the workpiece,
In a grinding machine for grinding the workpiece by relatively moving the grinding wheel and the workpiece support device while supplying a grinding liquid to a grinding point with the workpiece of the grinding wheel,
The grinding fluid thickness measuring device according to claim 1,
An approach detection means for detecting that the grinding wheel has approached the reference member based on a grinding fluid thickness detection signal of the grinding fluid thickness measuring device;
A grinding machine characterized by comprising: A grinding wheel that rotates about the axis of rotation;
A workpiece support device for supporting the workpiece,
In a grinding machine for grinding the workpiece by relatively moving the grinding wheel and the workpiece support device while supplying a grinding liquid to a grinding point with the workpiece of the grinding wheel,
The grinding fluid thickness measuring device according to claim 1,
Based on the grinding fluid thickness signal from the grinding fluid thickness measuring device, grinding fluid judgment means for judging whether the grinding fluid is abnormal or normal,
A grinding machine characterized by comprising: A grinding wheel that rotates about the axis of rotation;
A workpiece support device for supporting the workpiece,
In a grinding machine for grinding the workpiece by relatively moving the grinding wheel and the workpiece support device while supplying a grinding liquid to a grinding point with the workpiece of the grinding wheel,
The grinding fluid thickness measuring device according to claim 1,
Grinding fluid thickness-electric resistance calibration device including a reference plate provided on the front surface of the grindstone table so as to be able to face the reference member of the grinding fluid thickness measuring device;
A grinding machine characterized by comprising:

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