JP2005010019A - Measuring head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high accuracy measuring head wherein products are equalized by reducing scattering of individual differential coil parts in a plurality of measuring heads, and the drift of output value of the differential transformer due to temperature characteristic of whole measuring head is reduced. <P>SOLUTION: The differential coil part 16 of the differential transformer 15 detecting the displacement of a contactor is fixed by split clamp fixing to an attaching hole 21A by way of a ring 23 having slitting, fixed by split clamp in a narrow range, and the assembling position of the attaching hole 32A of the ring 23 in an axial direction is set to a position reducing the drift of the output value of the differential transformer 15 due to temperature characteristics of the whole measuring head. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a measuring head, and is used in particular for a machine control gauge or a surface roughness profile measuring machine incorporated in a grinding machine or the like, and reduces a drift of an output value of a detector caused by temperature characteristics. It is about.
[0002]
[Prior art]
Conventionally, machine control gauges (automatic sizing devices) and surface roughness contour shape measuring machines incorporated in grinding machines, etc. have a contact at the tip and are supported rotatably with a fulcrum member as a fulcrum. A detector that detects the displacement of the contactor by detecting the displacement of the seesaw member, the biasing member that urges the seesaw member in one direction, and the contact member across the fulcrum member. A measuring head provided with is used.
[0003]
In this detector, a linear so-called LVDT (Linear Voltage Differential Transducer) composed of a differential coil portion fixed to a measurement head body and a core attached to a seesaw member and inserted into the differential coil portion. A voltage differential transformer (commonly called a differential transformer) is used. The amount of movement of the contact is detected as a voltage change by LVDT, and the detected value of LVDT is processed by the control unit to be obtained as the amount of movement.
[0004]
The machine control gauge is composed of a single seesaw member, an L-shaped measuring head that measures displacement at one location with a single contactor, and two opposing seesaw members that are incorporated as a pair. A sandwich-type measuring head or the like that sandwiches the object to be measured with the contact and measures the outer diameter of the object to be measured is used (for example, see Patent Document 1).
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-181502
[Problems to be solved by the invention]
In the measurement head used in the conventional machine control gauge described in the above-mentioned Patent Document 1, the surface roughness profile measuring machine, etc., the differential coil of the LVDT is provided in a mounting hole with a slit formed in the measurement head body. In general, it is inserted and fixed by cleaving over the entire outer periphery.
[0007]
However, in the case of fixing by split tightening, it seems that it is fixed in a large area, but in reality, the surface roughness of the inner peripheral surface of the mounting hole with a slot and the surface roughness of the outer peripheral surface of the differential coil section. As a result, the differential coil section is held only at a limited number of random points, and the actual position of the hold point varies from product to product.
[0008]
As described above, since the reference for mounting the differential coil portion is not constant, the temperature characteristics due to thermal deformation of the core of the LVDT and the differential coil portion vary greatly from product to product. Further, there was no means for reducing the drift of the LVDT zero point due to the temperature characteristics of the entire measuring head, and the measurement error was large.
[0009]
The present invention has been made in view of such circumstances, and by clarifying the mounting reference of the differential coil portion of the differential transformer, the variation in fixing of the individual differential coil portions in a plurality of measurement heads is reduced. It is an object of the present invention to provide a highly accurate measuring head that can equalize products and can reduce the drift of the output value of the differential transformer due to the temperature characteristics of the entire measuring head.
[0010]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the invention according to claim 1 is a seesaw member having a contact at the tip and supported rotatably about a fulcrum member, and the seesaw member in one direction. An urging member that urges the contact member, and a detector that is provided on the opposite side of the contact member with the fulcrum member interposed therebetween, and detects the displacement amount of the contact member by detecting the displacement amount of the seesaw member. In the measuring head, the detector includes a differential coil portion that is inserted into a slotted attachment hole formed in the measurement head body and is fixed by split tightening, and the differential coil portion that is attached to the seesaw member. And a differential transformer composed of a core inserted into the part, wherein the differential coil part is fixed to the attachment hole by a tightening through a ring having a slit.
[0011]
According to the first aspect of the present invention, the differential coil portion of the differential transformer for detecting the displacement amount of the contact is fixed and fixed to the mounting hole via the ring having a slit, so that it is split in a narrow range. It can be fixed and the mounting standard becomes clear. For this reason, in the plurality of measurement heads, variation in fixing of the differential coil portion for each measurement head is reduced, and the quality is stabilized. Further, the attachment position can be easily adjusted by adjusting the interposition position of the ring.
[0012]
According to a second aspect of the present invention, in the first aspect of the invention, the mounting position of the ring in the axial direction of the mounting hole is a drift of the output value of the differential transformer caused by the temperature characteristics of the entire measuring head. It is characterized by being set to a position to be reduced.
[0013]
According to the second aspect of the present invention, the drift of the output value of the differential transformer caused by the temperature characteristics of the entire measurement head can be easily reduced, and the quality variation among the individual measurement heads in the plurality of measurement heads. Can be easily reduced.
[0014]
According to a third aspect of the present invention, there is provided a seesaw member having a contact at the tip and supported rotatably about the fulcrum member, an urging member for urging the seesaw member in one direction, and the fulcrum A detector that is provided on the opposite side of the contact across the member and detects the displacement of the contact by detecting the displacement of the seesaw member. A differential coil part inserted into a slotted attachment hole formed in the measurement head body and fixed by split fastening, and a core attached to the seesaw member and inserted into the differential coil part. A differential transformer is characterized in that a concave portion is formed on the inner peripheral surface of the mounting hole, leaving only a portion with a predetermined width that contacts the outer peripheral surface of the differential coil portion.
[0015]
According to the third aspect of the invention, the differential coil portion of the differential transformer that detects the displacement amount of the contact is abutted against the inner peripheral surface of the mounting hole with a predetermined width and is fixed by being tightened. It can be fixed and fixed within the range, and the mounting standard becomes clear. For this reason, in the plurality of measurement heads, variation in fixing of the differential coil portion for each measurement head is reduced, and the quality is stabilized.
[0016]
According to a fourth aspect of the present invention, in the third aspect of the present invention, the position in the axial direction of the mounting hole of the portion of the inner peripheral surface of the mounting hole that is in contact with the outer peripheral surface of the differential coil portion is the entire measuring head. It is characterized in that it is set at a position where the drift of the output value of the differential transformer due to temperature characteristics is reduced.
[0017]
According to the fourth aspect of the present invention, the drift of the output value of the differential transformer due to the temperature characteristics of the entire measurement head is reduced, and the quality variation among the individual measurement heads in the plurality of measurement heads is reduced.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a measuring head according to the present invention will be described in detail with reference to the accompanying drawings. In each figure, the same number or symbol is attached to the same member.
[0019]
FIG. 1 is a side sectional view showing a configuration of a measuring head according to the present invention. As shown in FIG. 1, the measuring head 10 is a pinch type for measuring the outer diameter of the workpiece W, and has a pair of seesaw mechanisms and has a vertical target structure.
[0020]
The measuring head 10 includes a measuring head main body 21, a fulcrum member 11, a seesaw member 12 including an arm 12A and a finger 13, a contact 14, an LVDT (differential transformer) 15 as a detector, a biasing member 17, a damper 18, The boot 19 is composed of a case 22 and the like.
[0021]
The fulcrum member 11 is supported by the holder 20 and attached to the measurement head main body 21. The arm 12 </ b> A is held by a fulcrum member 11 so that the seesaw can be rotated around the fulcrum member 11. A finger 13 is screwed to one end of the arm 12 </ b> A, and a contact 14 that contacts the workpiece W is attached to the tip of the finger 13. On the other hand, the core 15A of the LVDT 15 is attached to the other end of the arm 12A. Further, the differential coil portion 16 of the LVDT 15 is fixed to the measuring head main body 21 by split tightening.
[0022]
The arm 12A is provided with a biasing member 17 that presses the contact toward the workpiece W. A compression spring is used for the urging member 17, but various members such as a tension spring and other elastic members can be applied as long as they can generate a rotational force on the arm 12A. Further, a damper 18 is provided on the arm 12A to suppress jumping and vibration of the contact 14.
[0023]
The other members excluding the tip of the arm 12A, the finger 13 and the contact 14 are covered with a case 22. The case 22 has an opening, and the tip of the arm 12A protrudes from the opening. In addition, a boot 19 is provided in the opening to prevent dust and mist from entering the case 22.
[0024]
Next, the operation of the measuring head 10 configured as described above will be described. First, the measuring head 10 is set with respect to the workpiece W. Since the contact 14 is pressed against the work W by the urging member 17, the contact 14 is rotationally displaced about the fulcrum member 11 according to the dimension of the work W. When the contactor 14 is rotationally displaced, the core 15A of the LVDT 15 attached to the arm 12A is also rotationally displaced. The amount of displacement of the core 15A is detected by the differential coil section 16 of the LVDT 15, the detection signal is processed by the A / D conversion section 30, and sent to the control section 40 to determine the dimension of the workpiece W.
[0025]
At this time, since the damper 18 is provided on the arm 12A, jumping and vibration of the contact 14 are prevented. Further, since the boot 19 is attached to the opening of the case 22, the processing liquid, mist, and other dusts do not enter the case 22.
[0026]
Next, each part will be described in more detail. First, the main body structure of the measuring head 10 is such that all the main components are attached to the measuring head main body 21 and are attached to the case 22 after forming a single unit.
[0027]
As the fulcrum member 11, a cross spring fulcrum as shown in FIG. The cross spring fulcrum has a configuration in which two leaf springs as shown in the left diagram of FIG. 2A are arranged in a cross, but in this embodiment, a wire as shown in the right diagram of FIG. It is integrated by cutting out by cutting. This integrated cruciform spring fulcrum is suitable for a high-precision fulcrum because it is high in processing cost but has rigidity and good repeatability.
[0028]
In addition to the above, the fulcrum member 11 can use an L-shaped spring fulcrum shown in FIG. 2B, an elastic fulcrum shown in FIG. 2C, a bearing, a pivot fulcrum, and the like. The L-shaped spring fulcrum is less expensive than the cross spring, but is inexpensive and generally used. However, although there is a drawback that the center of the fulcrum moves with the turning motion, it is a level that does not cause a problem when LVDT is used for the detector.
[0029]
The elastic fulcrum is highly accurate but can only take a small turning angle, so it can be used inexpensively when the measurement range is narrow. The bearing fulcrum is not limited in turning angle, but it must be replaced periodically because the accuracy is reduced due to wear.
[0030]
As shown in FIG. 1, the finger 13 is separate from the arm 12A and is fixed to the arm 12A with a screw so that it can be exchanged according to the shape of the work. However, the finger 13 is integrated with the arm 12A. It doesn't matter. Moreover, although the material of the finger 13 is stainless steel, it is also possible to use iron with rust-proof plating or ceramics.
[0031]
The cross-sectional shape of the finger 13 is a circular cross section in order to reduce the influence of the pressure of the coolant on the measurement because the coolant is also applied to the finger 13 when measuring the workpiece W to be processed while applying the coolant. However, the shape is not limited to a circle, and a square cross section, an elliptic cross section, or the like may be used.
[0032]
As shown in FIG. 1, the contact 14 uses a screw-type contact 14 so that fine adjustment in the height direction can be performed. The contact 14 may be directly embedded in the finger 13 and the height adjustment may be performed at the finger mounting portion.
[0033]
Super steel or diamond is embedded in the tip portion of the contact 14 that contacts the workpiece W. The tip portion needs to be resistant to wear, and super steel, diamond, ruby or the like is generally used, but it can be used depending on the material of the workpiece W.
[0034]
In the case of measuring a hard material such as iron or stainless steel, an inexpensive super steel is used, but in the case of measuring a rotating workpiece W, diamond that is more resistant to wear is used. In addition, when measuring soft materials such as aluminum, copper, and soft glass, diamonds with good slipping are used, and scratches and dents are generated by reducing the measuring force and slowing the fall speed from the retracted state. Is prevented.
[0035]
The tip shape of the contactor 14 is usually an R shape. Various sizes of R are used, but particularly when measuring the workpiece W being processed in-process, a tip shape having a small R of about R0.5 to R1.5 mm is used so as not to bite chips.
[0036]
Further, when the measurement surface is rough, the value may vary by picking up a fine roughness, so that a tip shape having a large R is used in terms of averaging. In such a case, about R3 to R6 mm is the tip R that is used as a standard. Also in the case of the soft workpiece W, R3 mm or more is used in order to reduce the dent of the workpiece W at the time of contact, and about R3 to R6 mm is normally used.
[0037]
In the case of measuring a discontinuous surface such as a gear, R is sized to straddle the groove, R in a direction parallel to the groove is set to about R1.5, and a ship-shaped contact 14 is used as a whole.
[0038]
When measuring the outer diameter of the rotating gear, the small contact 14 has a large amount of depression and jumping, and the measured value varies. Further, even if the structure straddles the groove, the falling and jumping up cannot be completely suppressed, and when the rotation speeds up, the rattling becomes large or the jumping up state is almost in contact. Therefore, it is necessary to strengthen the effect of the damper 18 and regulate the peripheral speed, contact, and non-contact time of the workpiece W. For the measurement, a method is used in which the workpiece W is rotated one or more times and the maximum value is stored.
[0039]
In addition, a cylindrical super steel contact 14 may be used. In this case, the contact insertion hole of the finger 13 is split and fixed by split tightening. Further, if the contact portion with the workpiece W is worn, it is rotated and fixed again, and the life is extended by using an unused surface. However, since this cylindrical contact 14 is difficult to be parallel to the workpiece W, it is used under special conditions such as when it is too narrow to use an R-type contact.
[0040]
3 and 4 are partially enlarged views for explaining the mounting structure of the differential coil portion 16 of the LVDT 15 to the measuring head body 21 and the mounting structure of the core 15A to the arm 12A. FIG. 3 is a side sectional view. FIG. 4 is a plan view.
[0041]
The core 15A is attached to the core holder 15B, and is fixed to the slot with a slot in the arm 12A via the core holder 15B. As the material of the core 15A, permalloy having good magnetic properties is used.
[0042]
As shown in FIG. 3, the differential coil portion 16 has a coil 16B wound around three stages on a resin bobbin 16A, and a bobbin case 16C is fitted on the outside thereof. The bobbin case 16C is an end portion of the bobbin 16A. It is fixed with the nut 16D using the screw part formed in the. The bobbin case 16C is made of permalloy for magnetic shielding from the outside. The lead wire 16E of the coil 16B is drawn out from the notch of the bobbin case 16C.
[0043]
The measurement head main body 21 for fixing the differential coil portion 16 is provided with an attachment hole 21A, and a slit 21B as shown in FIG. 4 is formed in the attachment hole 21A. A ring 23 is interposed between the outer peripheral surface of the differential coil portion 16 inserted into the mounting hole 21A and the inner peripheral surface of the mounting hole 21A.
[0044]
The differential coil section 16 is tightened to the measuring head main body 21 by tightening the screw 24 with the ring 23 interposed, and is fixed in a narrow area because the height of the ring 23 is low.
[0045]
FIG. 5 is a perspective view showing the ring 23. As shown in FIG. 5, the ring 23 has a thin ring shape and is formed with a slit 23 </ b> A, and has a shape that is easy to bend when the differential coil portion 16 is split to the measuring head body 21. The height of the ring 23 is preferably as low as possible without causing the wobbling of the differential coil section 16, and in this embodiment, a ring having a height of about 2.5 mm to 3 mm is used.
[0046]
Since the measuring head 10 is composed of a combination of members having various complicated shapes, the measuring head 10 exhibits complicated temperature characteristics with respect to the environmental temperature. Due to this temperature characteristic, the output of the LVD Т15 drifts, causing a decrease in detection accuracy. For this reason, the differential coil section 16 is fixed at a position where the output drift of the LVD 15 due to this temperature characteristic is minimized. That is, the ring 23 is disposed at a position where the output drift in the axial direction of the mounting hole 21A is minimized. The mounting position of the ring 23 is set by experimentally finding the best position for each type of measuring head 10.
[0047]
FIG. 6 shows another embodiment of the present invention, and shows a structure in which the differential coil portion 16 is attached to the measurement head main body 21 without using the ring 23. As shown in FIG. 6, the inner peripheral surface of the mounting hole 21 </ b> A provided in the measurement head main body 21 is vertically dented portions 21 </ b> C and 21 </ b> C with a predetermined width portion in contact with the outer peripheral surface of the differential coil portion 16. Is formed. The differential coil portion 16 is fixed by being clamped by the narrow inner peripheral surface of the mounting hole 21A.
[0048]
The relief portions 21C and 21C are formed so that the width of the portion of the inner peripheral surface of the mounting hole 21A that contacts the outer peripheral surface of the differential coil portion 16 is about 2.5 mm to 3 mm. Also, the position where the inner peripheral surface of the mounting hole 21A is in contact with the outer peripheral surface of the differential coil portion 16 is experimentally set at a position where the output drift of the LVD Т15 caused by the temperature characteristics of the measuring head 10 is minimized. Looking for. Further, minute position adjustment can be performed by moving the differential coil section 16 and the core 15A.
[0049]
[Comparative example]
The temperature at which the position of the ring 23 was experimentally determined via the conventional measuring head in which the mounting structure of the differential coil portion 16 of the LVD 15 is split and fixed over the entire inner peripheral surface of the mounting hole 21A and the ring 23 of the present invention. A temperature characteristic comparison experiment was performed using the measuring head 10 which was fixed at the position where the characteristic compensation effect was high.
[0050]
The experiment was performed on two experimental samples (gauge 1 and gauge 2) for each of the conventional measuring head and the measuring head 10 of the present invention. First, set the LVDТ15 output to zero at an ambient temperature of 20 ° C, increase the ambient temperature to 50 ° C in 5 ° C increments, and then decrease the ambient temperature to 20 ° C in 5 ° C increments at each ambient temperature. The output of LVDТ15 was recorded.
[0051]
7 and 8 are graphs showing the experimental results. FIG. 7 shows the temperature characteristics of a conventional measuring head, and FIG. 8 shows the temperature characteristics of the measuring head 10 of the present invention. As shown in FIG. 7, the conventional measuring head had a maximum drift of -1.23 [mu] m for gauge 1, a maximum drift of -2.38 [mu] m for gauge 2, and a maximum variation of 1.15 [mu] m between samples.
[0052]
On the other hand, as shown in FIG. 8, the measuring head 10 of the present invention has a maximum drift of 0.09 μm for the gauge 1 and a maximum drift of −0.51 μm for the gauge 2, and a maximum variation of 0.6 μm between samples. Met.
[0053]
As described above, the measurement head 10 of the present invention has a maximum drift that is reduced in the range of 4/10 to 4/100, and the variation between samples is also reduced to ½, as compared with the conventional measurement head. .
[0054]
Thus, the measuring head of the present invention fixes the differential coil section 16 with a narrow width, so that the fixed reference position becomes clear and becomes substantially constant between products. For this reason, variations in temperature characteristic values between products are reduced. Also, the drift of the output of the LVD 15 due to the ambient temperature change is not considered to be caused by the expansion and contraction of only the core 15A and the differential coil section 16, but is assumed to be caused by the temperature characteristics of the entire measuring head 10, and the differential coil Since the fixed position of the part 16 is determined by obtaining an optimal position from experimental values, drift can be minimized.
[0055]
【The invention's effect】
As described above, according to the measuring head of the present invention, the differential coil portion of the differential transformer that detects the displacement amount of the contact is fixed and fixed in the mounting hole via the ring having the slit. It can be fixed in a narrow range, and the mounting standard becomes clear. For this reason, in the plurality of measurement heads, the variation in fixing of the differential coil portion for each measurement head is reduced, the variation in temperature characteristic value between products is reduced, and the quality is stabilized. Further, the attachment position can be easily adjusted by adjusting the interposition position of the ring.
[0056]
Also, by adjusting the intervening position of the ring, it is possible to easily reduce the drift of the output value of the differential transformer due to the temperature characteristics of the entire measuring head, and for each measuring head in a plurality of measuring heads. Variations in quality can be easily reduced.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing a measurement head according to an embodiment of the invention. FIG. 2 is a perspective view showing various fulcrum members. FIG. 3 is a partially enlarged view of the measurement head according to an embodiment of the invention. 4 is a partially enlarged plan view of a measuring head according to an embodiment of the present invention. FIG. 5 is a perspective view showing a ring. FIG. 6 is a partially enlarged view of a measuring head according to another embodiment of the present invention. FIG. 8 is a graph showing temperature characteristics of a conventional measuring head. FIG. 8 is a graph showing temperature characteristics of the measuring head of the present invention.
DESCRIPTION OF SYMBOLS 10 ... Measuring head, 11 ... Supporting member, 12 ... Seesaw member, 12A ... Arm, 13 ... Finger, 14 ... Contact, 15 ... LVDТ (differential transformer) (detector), 15A ... Core, 16 ... Differential coil , 17 ... Biasing member, 21 ... Measurement head body, 21A ... Mounting hole, 21B ... Slit, 21C ... Nigger part, 23 ... Ring

Claims (4)

A seesaw member that has a contact at the tip and is rotatably supported with the fulcrum member as a fulcrum, an urging member that urges the seesaw member in one direction, and opposite the contact across the fulcrum member In a measuring head having a detector provided on a side and detecting a displacement amount of the contact by detecting a displacement amount of the seesaw member,
The detector is inserted into a mounting hole with a slit formed in the measurement head body and fixed by split fastening, and the detector is attached to the seesaw member and inserted into the differential coil part. A differential transformer composed of a core and
The measurement head according to claim 1, wherein the differential coil portion is fixed to the mounting hole through a ring having a slit. The assembly position in the axial direction of the mounting hole of the ring is set to a position that reduces a drift of an output value of the differential transformer caused by a temperature characteristic of the entire measurement head. 2. The measuring head according to 1. A seesaw member that has a contact at the tip and is rotatably supported with the fulcrum member as a fulcrum, an urging member that urges the seesaw member in one direction, and opposite the contact across the fulcrum member In a measuring head having a detector provided on a side and detecting a displacement amount of the contact by detecting a displacement amount of the seesaw member,
The detector is inserted into a mounting hole with a slit formed in the measurement head body and fixed by split fastening, and the detector is attached to the seesaw member and inserted into the differential coil part. A differential transformer composed of a core and
The measuring head according to claim 1, wherein a concave portion is formed on the inner peripheral surface of the mounting hole, leaving only a portion having a predetermined width contacting the outer peripheral surface of the differential coil portion. The position in the axial direction of the mounting hole in the part of the mounting hole that contacts the outer peripheral surface of the differential coil portion reduces the drift of the output value of the differential transformer due to the temperature characteristics of the entire measuring head. The measuring head according to claim 3, wherein the measuring head is set at a position where

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