JPS6028635B2 - Sizing device with temperature compensation function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sizing device that measures the outer diameter of a workpiece during machining, detects that the workpiece has reached a predetermined size, and outputs a sizing signal. The purpose of this is to correct the sizing operating point by the elongation in the axial direction of the workpiece that occurs in response to the thermal expansion of the workpiece due to processing heat, etc., and to improve the sizing accuracy of the workpiece, which is not affected by temperature changes. The aim is to ensure high accuracy without any problems.

In general, a sizing device used in a grinding machine uses a measuring head to measure the outer dimension of the workpiece being processed, and then outputs a measurement signal in advance from the measuring head according to the outer dimension of the workpiece. When compared with the set voltage, a sizing signal is output when the measurement signal falls below the set voltage.

By the way, the workpiece thermally expands due to processing heat generated during grinding, etc., so if you measure the outer dimensions of the workpiece and perform processing in this state, the actual outer dimensions of the machined workpiece will be The diameter of the workpiece becomes smaller due to thermal expansion, making it impossible to secure the outer diameter of the workpiece with high accuracy. Therefore, in order to deal with such defects, a temperature detector is installed on the measuring head to measure the temperature of the outer peripheral surface of the workpiece, and the measurement signal output from the measuring head is corrected by the output of this temperature detector. Therefore, it has been proposed to shift the sizing operating point.
In this system, the measurement signal is corrected based on the temperature of the outer peripheral surface of the workpiece, so if the coefficient of thermal expansion changes due to a change in the material of the workpiece, and the amount of dimensional increase due to thermal expansion changes, accurate correction may not be possible. However, since the temperature sensor is installed in a position that is in contact with the outer circumferential surface of the workpiece, the temperature sensor is prone to wear and temperature measurement errors are likely to occur due to splashing of coolant.

The present invention has been made in view of these points, and is configured so that the tailstock center can be retracted by thermal expansion of the workpiece, and the amount of retraction of the tailstock center can be applied to the rear end of the tailstock. This feature is characterized in that detection is performed by a displacement detection device provided.

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, a table 10' is guided on a bed (not shown), and a headstock 11 is positioned at the left end of the table 10. and. A spindle [3] having a spindle center 12 mounted thereon is mounted on the headstock 11, and is rotatably driven by a motor 14. Also,
A drive pin 15 that engages with the end of the workpiece W is protruded from the tip end surface of the main shaft 13 . On the other hand, the L tailstock 16 is listed on the right end of the table army Q, and this tailstock 1
6, a center sleeve wing 8 to which a tailstock center tortoise 7 is attached is suspended, and a key 19 fixed to the tailstock 16 and a keyway 20 formed in the center sleeve 181 allow the center sleeve 181 to rotate in all directions. Only exercise is allowed.

A spring 21 constituting a pushing means is installed between the center sleeve 18 and the tailstock 16, and the tailstock center 7 is pressed toward the workpiece W side. As a result, the workpiece W is held and rotated by the drive pin 15. In this state, the grinding wheel 22 is fed by a predetermined amount toward the workpiece W and is traversed within a predetermined range in the direction of the ratchet line of the workpiece W, thereby grinding the outer circumferential surface of the workpiece W. Furthermore, a differential transformer 23 is fixed to the rear of the tailstock 16 as a displacement detection device, and the differential transformer 23 detects displacement by a change in the position of a movable core 23a, which is a movable part. The core 23a is connected via the connecting arm 18a to the rear end of the center sleeve, the right end in FIG. sleeve turtle 8
The differential transformer 23 detects the movement of the tailstock center 17 in all axial directions. Further, a measuring head 2 is guided to a position facing the grinding wheel 22 across the workpiece W on the table 10 so as to be movable in a direction perpendicular to the bag line of the workpiece W. It is designed to measure the outer diameter dimension of.

The measuring head 24 is provided with four coils forming a bridge circuit whose inductance changes depending on the displacement of the measuring head 25, for example, and the measuring head 24 is moved toward the workpiece W by a hydraulic cylinder (not shown). When the measuring head 25 of the measuring head 24 is positioned on the rattan line of the workpiece W, the measuring head 24 outputs a measurement signal according to the external dimension of the workpiece W. 26 is a measurement head 24 and a differential transformer 23
This sizing control device 26 also constitutes the sizing device according to the present invention, and this sizing control device 26 corrects the measurement signal outputted from the measuring head 24 by the amount of elongation of the workpiece W in the tracking line direction. The corrected measurement signal is compared with the set voltage and the sizing signals AS1 and AS2 are output.
By the sizing signal output from this sizing control device 26,
Switching from rough grinding to coarse grinding, completion of grinding, etc. are controlled.

FIG. 2 is a block diagram showing a specific configuration of the sizing control device 26, which mainly includes a displacement amount detection section 27 which forms a displacement detection device together with the cover transformer 23, a dimension side measurement section 28, and an operating point. It is composed of a correction circuit 29 and comparison circuits 40 and 41. In this figure, 31 is an oscillation circuit that applies an alternating current voltage to the coil of the measurement head 23; 31 is an amplifier circuit that amplifies a minute level measurement signal corresponding to the outer diameter of the workpiece W output from the measurement head 24; 32 is the amplifier circuit 3
A synchronous rectifier circuit that rectifies the AC measurement signal output from 1 in synchronization with the AC voltage generated from the oscillation circuit 30,
This synchronous rectifier circuit 32 outputs a DC measurement voltage according to the outer dimensions of the workpiece W. This DC measurement voltage is amplified to a predetermined level by an amplifier circuit 33 and applied to one input terminal of an arithmetic circuit 34 constituting the operating point correction circuit 29. Further, G 35 applies an AC voltage to the differential transformer 23 that detects the axial movement of the tailstock center 7 in all directions. The AC measurement voltage depending on the position is amplified by an amplifier circuit 36 similar to the amplifier circuit 31, and synchronously rectified by a synchronous rectifier circuit 37.

As a result, "from the synchronous rectifier circuit 37 to the tailstock center 17
A DC signal corresponding to the position will be output. 3
8 indicates that even if the position of the tailstock center 17 varies due to variations in the center hole provided in the workpiece W, the centering due to thermal expansion of the workpiece W is not affected by the variation in the position of the tailstock center 17. This is an arithmetic circuit for measuring the amount of axial movement of the tailstock center 17. This arithmetic circuit 38 uses a DC voltage representing the initial position of the tailstock center 17 charged in a capacitor CI via a gate GI, and a synchronous rectifier. circuit 37
A DC voltage representing the current position of the tailstock center 17 given to the gate GI is inputted from the input terminal GI, and the deviation between the two is outputted as a signal representing the elongation of the workpiece W in all axial directions.

This signal is then applied to the variable amplification circuit 39 of the operating point correction circuit 29 via the gate G2. The variable amplifier circuit 39 converts the signal representing the elongation of the workpiece W in the axial direction output from the arithmetic circuit 38 into a signal representing the elongation of the workpiece W in the diametrical direction, and sets this converted signal to a predetermined level. For example, the workpiece W
The amplification factor is changed by setting the variable resistor VRI according to the ratio of the diameter and length of the
A signal representing the diametrical elongation of the workpiece W output from the variable amplifier circuit 39 is applied to the other input of the arithmetic circuit 34. This arithmetic circuit 34 uses the measurement signal representing the outer diameter dimension of the workpiece W outputted from the amplifier circuit 33 to calculate
This subtracts the signal representing the elongation of the workpiece W in the diametrical direction outputted from the variable amplifier circuit 39, and the arithmetic circuit 34 outputs a measurement signal that has been corrected for the increase in external dimension due to thermal expansion of the workpiece W. is output.

This corrected measurement signal is then applied to the comparator circuit 40, and when the measurement signal falls below the set voltage VSI set in the variable resistor VR2, the comparator circuit 40 sends it to the gate G3.
The first sizing signal ASI is output via the variable resistor V
When the voltage falls below the set voltage VS2 set in R3, the comparator circuit 4
1 outputs a second sizing signal AS2 via gate G4. Note that 42 controls the operation timing of the entire sizing control device 26, and as shown in FIG. Only s is output, and after this,
A signal to open gate G2 is now output.

Then, after a certain period of time has elapsed after the gate G2 was opened, a signal to open the gates G3 and G4 is output. The time is set to be enough time for the DC voltage output from the synchronous rectifier circuit 37 to charge the capacitor CI, and the time is set to the variable amplifier circuit 39 and the arithmetic circuit 34.
, the time required for the operations of the comparison circuits 40 and 41 to become stable is set. Next, the operation of the sizing device having the above configuration will be explained.

Now, suppose that machining is started with the workpiece W being held by the spindle center 12 and the tailstock center 17, and the measuring head 24 is moved toward the workpiece using a hydraulic cylinder (not shown). A sizing start signal START is given to the sizing control device 26 from a strong electric control device (not shown). This results in
At the same time as the sizing control device 26 starts operating, the control circuit 42 outputs a signal to open the gate GI.
I is only open for a certain amount of time.

Then, the DC voltage output from the synchronous rectifier circuit 37 is charged to the capacitor CI via the gate GI, and the voltage representing the initial position of the tailstock center 17 is stored and held in the capacitor CI. Gate GI when time $ passes
The sending of the signal to open the gate is stopped, and instead the gate G
A signal to open 2 is now output.

When the gate G2 is opened, the variable amplifier circuit 39 is given a voltage corresponding to the deviation between the voltage stored in the capacitor CI and the voltage output from the synchronous rectifier circuit 37. However, at the start of measurement, the synchronous rectifier circuit 37 Since the voltage output from is equal to the voltage stored in capacitor CI,
The deviation becomes zero. Therefore, no signal is output from the variable amplifier circuit 39, and only the measurement signal output from the amplifier circuit 33 is given to the arithmetic circuit 34. At this time, the amplifier circuit 33 outputs a measurement signal corresponding to the outer diameter of the workpiece W, and the arithmetic circuit 34 outputs the measurement signal output from the amplifier circuit 33 as it is without being corrected. . As the machining progresses and the outer diameter of the workpiece W decreases, the measurement signal output from the amplifier circuit 33 decreases accordingly.

Additionally, as the workpiece W is heated by grinding resistance or the like as machining progresses, the workpiece W will develop a thermal arm tension. A higher value will be output. On the other hand, when the workpiece W undergoes thermal expansion, the workpiece W expands in the direction of the track line according to the degree of thermal expansion, and the tailstock center column 7 moves backward against the pressing force of the spring 2 turtle. will be moved.

Then, the movable core 238 of the cluster transformer 23 is moved.
The signal output from the differential transformer 23 changes. As a result, the DC voltage output from the synchronous rectifier circuit 37 increases by an amount corresponding to the amount of elongation of the workpiece W in the rut direction, and a deviation occurs between the voltage stored in the capacitor C and the capacitor Ci. When a deviation occurs between the voltage of the synchronous rectifier circuit 37 and the output voltage of the synchronous rectifier circuit 37, even if this deviation is calculated by the calculation circuit 38', the calculation circuit 32 outputs a signal corresponding to the elongation of the workpiece W in the vertical direction. Then, the signal corresponding to the elongation of the workpiece W in the koji direction is transmitted to the variable amplifier circuit 3.
g' is thereby converted into a signal representing the elongation of the workpiece in the diametrical direction and applied to the other input terminal of the arithmetic circuit 3.
As a result, the measurement signal outputted from the amplifier circuit 33 accompanied by thermal expansion is corrected by the signal outputted from the variable amplifier circuit 3g. A measurement signal representing the outer diameter dimension of the workpiece W at room temperature will be output.
When the workpiece W is ground until it has a diameter larger than the predetermined precision grinding start dimension by the amount due to thermal expansion, the measurement signal output from the calculation circuit 3 becomes lower than the set voltage VS, so the comparator circuit A first sizing signal is output from 48.

As a result, the grinding of the workpiece W is started.The machining of the workpiece W further progresses until the external dimensions of the workpiece W become larger than the predetermined grinding completion dimensions by the amount of thermal expansion. Then, since the measurement signal outputted from the arithmetic circuit 34 falls below the set voltage VS2, the second sizing signal AS2 is outputted from the comparator circuit 41 and machining of the L workpiece W is stopped.

The workpiece W machined in this way will shrink when the machining is completed and the workpiece W returns to room temperature, and the outer dimensions will become the predetermined dimensions at the completion of grinding. However, if the ratio of the outer diameter to the length changes, the variable resistor VR blade of the variable amplifier circuit 3g may be adjusted according to this ratio.Also, only the material of the workpiece W has to be changed. In this case, there is no need to perform the above adjustment.In this case, the sizing device of the present invention detects the elongation of the workpiece W in all axial directions and corrects the external strain dimension, and the thermal expansion coefficient This is because when the increase in the external dimension is high, there is also a large elongation in the axial direction, and accordingly, the external dimension has to be corrected a lot. The sizing operation point was shifted by detecting the elongation and correcting the measurement signal according to the detected elongation. Alternatively, the amplification degree of the amplifier circuits 339 to 31 may be corrected to shift the sizing operating point.

In addition, other detectors such as a linear magnetic scale may be used to move the tailstock center dimension in the direction of the ball.

Furthermore, although the above embodiment does not take into account the expansion of the workpiece W due to changes in room temperature, it is possible to detect the ambient temperature and correct the sizing operating point by taking into account the change in ambient temperature. , more precise sizing operation can be expected. As described above, in the sizing device of the present invention, the elongation in the axial direction due to thermal expansion of the workpiece is detected by the movement of the tailstock center in all the axial directions, and the elongation in the axial direction of the workpiece is detected. Since the sizing operating point is corrected according to the amount, it is possible to perform highly accurate temperature correction regardless of the material of the workpiece, which has the advantage of maintaining high sizing accuracy.

In addition, in the present invention, the tailstock center is configured to move backward according to the thermal expansion of the L workpiece, and the displacement of the tailstock center is detected by attaching it to the rear end of the tailstock. Since the displacement detection device is detected by the device, it is possible to move the displacement detection device away from the workpiece, which prevents the displacement detection device from being heated due to machining heat and causing measurement errors. This has the advantage that reliability can be improved without scattering onto the equipment.

Furthermore, since the tip of the tailstock is in contact with the workpiece, the relative sliding speed between the tailstock center and the workpiece caused by the rotation of the workpiece can be reduced, reducing wear. This has the advantage of not only improving durability but also reducing heat generation caused by slippage and reducing measurement errors caused by temperature rises.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a state in which the outer dimensions of a workpiece are being measured by the sizing device of the present invention, and FIG. 2 is a block diagram showing a specific configuration of the sizing control device 26 in FIG. 1. FIG. 3 is a timing chart showing control signals output from the control circuit 42 in FIG. 11... Headstock, 12... Spindle center, 1
3... Main spindle, 16... Tailstock, 17...
...Tailstock center, 18... Center sleeve, 23...
...Differential transformer, 24...Measuring head, 26...
Sizing control device, 27...Displacement amount detection section, 28.
...Measurement section, 29...Operating point correction circuit, 30,3
5...Oscillation circuit, 31, 33, 36...
・Amplifier circuit, 32, 37...Synchronous rectifier circuit, 3
4, 38... Arithmetic circuit, 39... Variable amplifier circuit, 40, 41... Comparison circuit, AS1, AS
2...Sizing signal, C1...Capacitor, GI~
G4...Gate, VRI~VR3...Variable resistor, VS1, VS2...Setting voltage, W...
...workpiece. Figure 3 Figure 2 Figure 3

Claims (1)

[Claims] 1. The outer diameter of the workpiece being machined while being held between the spindle center and the tailstock center is measured by the measuring head during processing, and the measured voltage output from the measuring head is compared with the set voltage. In a sizing device that outputs a sizing signal by determining when a workpiece has reached a predetermined size, a center sleeve with a tailstock center fitted at the tip is movably mounted on the tailstock. A displacement detection device is provided with a pushing means for pushing the center sleeve toward the spindle center side, has a movable part that is movable in a direction parallel to the spindle axis, and detects displacement by a change in the position of the movable part. is attached to the rear end of the tailstock opposite to the center attachment side, the movable part of this displacement detection device is connected to the center sleeve, and the workpiece detected by the displacement detection device is An operation of correcting the measurement voltage output from the measurement head or the set voltage according to the elongation, and shifting the operating point at which the sizing signal is output by the amount of the diameter dimension thermally expanded due to the temperature rise of the workpiece. A sizing device having a temperature correction function, characterized in that it is provided with a point correction circuit.