Optical measuring device and measuring method using the same

Abstract

SOLUTION: In a state in which a movement of contact is limited by a stopper with which an optical measuring device of incremental dimension system measuring at least one of the inside diameters of the device under test and an outside diameter is provided, a linear scale is detected using a leading head. A count number of reading at this time is beforehand memorized as an initial value. Next, a master used as a module is measured and a count number of reading of a linear scale is memorized. Then, an actual device under test is measured.EFFECT: And in measurement of the device under test, the memorizing stopper corrects a measurement result of a device under test using reading in the state in which the reading and master are measured in the state in which the movement was limited. Since the optical measuring device of incremental dimension system of easy composition of having a stopper is prepared even if the relative distance between a linear scale and a detecting element is moving after power cut, the starting point can be set without performing mastering.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an optical measuring instrument for measuring inner diameters, outer diameters, etc., and a measuring method using the same, and more particularly to an optical measuring instrument suitable for including an incremental type optical scale, and a measuring method using the same. [Background technology]

[0002] For example, optical measuring instruments are often used in bore gauges that measure the inside diameter of cylinders because they are capable of high-precision measurements. In such optical measuring instruments, a scale with a large number of light-transmitting and light-opaque areas regularly arranged is provided in the sensor section, and an incremental encoder is constructed by detecting the transmitted or reflected light after irradiating the scale with light. In the case of an incremental encoder, the absolute position is unknown before measurement, so it is necessary to find the origin, which serves as the reference for the absolute position, in some way during measurement.

[0003] In Patent Document 1, in order to detect an origin signal of an optical encoder with a simple configuration, the encoder has a light source, a main scale having an incremental signal generating pattern capable of relative movement in the arrangement direction, a first photodiode array consisting of a plurality of photodiodes that receives a light beam that is transmitted through or reflected by the main scale illuminated by the light source and also serves as an index scale, an incremental scale signal detection unit having a second photodiode array consisting of a plurality of first photodiode arrays, and an incremental signal processing unit that processes an output signal from the second photodiode array. The main scale has an origin signal generating pattern with the same pitch as the plurality of incremental signal generating patterns, and the origin signal processing unit processes an output signal from the origin signal detection unit consisting of a plurality of first photodiode arrays.

[0004] Another method for determining the origin of an optical encoder is described in Patent Document 2. In this publication, in order to determine the origin position in an incremental encoder with a simple configuration without providing a special scale for detecting the origin, the encoder has a reading head having a light-emitting section and a light-receiving section, and a linear scale arranged opposite the reading head and formed with multiple scale patterns. In the linear scale, the widths of the alternating reflective and transmissive sections are substantially the same, and at least one reflective or transmissive section is missing along its entire length, and the missing section is determined as the origin.

[0005] Furthermore, in Patent Document 3, in order to detect the reference point of the contactor in the measurement head, the angular position of the arm at start-up and the angular position of the arm when the contactor is brought into contact with each step of a block having multiple steps are measured at two different locations, and the reference point of the contactor is found from the angular positions obtained. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2013-36945 A [Patent Document 2] JP 2017-142203 A [Patent Document 3] JP 2004-125732 A Summary of the Invention [Problem to be solved by the invention]

[0007] Measuring instruments with incremental scales, such as encoders, may use batteries for portability or because commercial power wiring is an obstacle to measurement. In such cases, the power is turned off except when measurements are being made to avoid unnecessary battery consumption and extend the interval between battery changes. If the power is turned off when the measuring instrument is not in use, the relative positions of the scale and the light receiving part of the measuring instrument may change during the time the power is turned off, or the position information may be cleared and no record may remain in the measuring instrument, making it necessary to perform the work of detecting the origin. Therefore, a reconfirmation work is generally performed using a master whose dimensions are known. If it becomes necessary to detect the origin using the master every time the measuring instrument is turned off, then the origin calibration using the master will be required every time machining is performed, for example, in post-machining inspection, which increases the number of work steps and reduces work efficiency. To avoid this problem, powering the measuring instrument at all times would result in the frequent battery replacement or charging work described above in the case of a battery-powered measuring instrument.

[0008] In the above Patent Document 1, a scale with a special reflective / non-reflective pattern is provided for detecting the origin, so it seems possible to reliably detect the origin, but the addition of an extra scale increases the scale width, making miniaturization difficult. In addition, a standard scale cannot be used, resulting in high costs. In Patent Document 2, the origin position is detected in a similar manner by omitting some of the patterns on the scale, but there is a concern that the accuracy will deteriorate in the areas where the patterns are omitted. In this case, too, the standard scale needs to be processed, resulting in high costs. In addition, in all of these cases, the origin position needs to be set in advance to a position corresponding to the measurement range for each measuring device, and the advance adjustment work requires a lot of time.

[0009] On the other hand, in the case of the device described in Patent Document 3, which uses a stepped block for origin detection, calibration using the stepped block is required every time the origin is detected, which is the same as detection using a master, and reduces work efficiency. In particular, when the power supply of the measuring device is frequently turned off to reduce battery consumption of the measuring device, it is necessary to detect the origin using the block at a frequency similar to the frequency of the power supply being turned off.

[0010] The present invention has been made in consideration of the above-mentioned conventional technology, and has an object to provide a measurement method in which, by preparing an incremental type measuring instrument with a simple configuration, it is possible to omit measurement for setting the origin using a master, even if relative distance information between the scale and the detector is lost after the power is turned off. Another object of the present invention is to provide an incremental type measuring instrument that can easily cope with a power cut. [Means for solving the problem]

[0011] The present invention, which achieves the above object, is configured as follows.

[0012] [1] An incremental type measuring instrument comprising a scale in which reflective and transmissive areas are alternately and regularly arranged, a reading head having a light emitting means and a light receiving means, and a control means, further comprising a stopper for limiting the relative movement of the scale with respect to the reading head, and the control means calculates the output difference between a state in which the movement is limited by the stopper and a state in which a master is measured. [2] The measuring instrument described in [1], wherein the control means calculates the amount of movement of the workpiece from the measured value when the movement is restricted and the output difference stored in advance. [3] The measuring instrument described in [1] further comprises a contactor connected to the scale and contacting a work to move the scale relative to the reading head, wherein the control means calculates the amount of movement due to contact with the work from the measurement value when the movement is restricted and the output difference stored in advance. [4] The measuring device according to any one of [1] to [3], wherein the amount of movement is the number of counts read on the scale. [5] A method for measuring a workpiece using the measuring instrument described in [1], the method comprising the steps of: pre-storing the count number of the scale reading when the movement is restricted by the stopper as an initial value; measuring the master and storing the count number; and measuring the workpiece, wherein the measurement of the workpiece involves using the initial value and the count number measured by measuring the master to correct the count number of the reading obtained by measuring the workpiece to obtain a measurement value.

[0013] Another feature of the present invention is that an optical measuring instrument capable of measuring at least an inner diameter and an outer diameter includes at least two contacts capable of coming into contact with a portion to be measured, a measuring arm that holds the contacts, a pressing means for rotatably pressing the measuring arm, a holding member that rotatably holds the measuring arm and has a stopper formed thereon that limits the rotation of the measuring arm, a sensor unit that detects the amount of movement of the measuring arm, and a control unit that processes and stores the output of the sensor unit, wherein the sensor unit forms an incremental type sensor unit by including a scale attached to one of the measuring arm and the holding member, and having alternating and regular reflective and transmissive portions, and a reading head having a light emitting means and a light receiving means attached to the other of the measuring arm and the holding member, and the control unit has a memory means for storing an output difference between a state in which the movement of the measuring arm is limited by the stopper and a state in which the measuring arm measures a master.

[0014] In this feature, it is preferable that the optical measuring instrument is an optical measuring instrument capable of measuring inner diameters, and that the scale and the light receiving means are arranged so that the output from the sensor unit increases or decreases in the order of a state limited by the stopper, a state where the master is measured, and a state where the contact is retracted within the holding member, and it is desirable to include a battery that supplies power to the sensor unit and the control unit, and a switch means that cuts off the power supply from the battery.

[0015] Another feature of the present invention for achieving the above object is a measurement method for measuring at least one of the inner diameter and outer diameter of an object to be measured using an incremental type optical measuring instrument, the method comprising the steps of: pre-storing as an initial value the count number of the reading of the linear scale of the optical measuring instrument obtained using a reading head when the movement of the contact is restricted by a stopper provided on the optical measuring instrument; then measuring a master that serves as a measurement standard and storing the count number of the reading of the linear scale; and then actually measuring at least one of the inner diameter and outer diameter of the object to be measured, wherein in the measurement step of the object to be measured, the count number of the reading obtained by measuring the object to be measured is corrected using the stored count number of the reading when the movement is restricted by the stopper and the count number of the reading when the master is measured, and the inner diameter or outer diameter is obtained from the corrected count number.

[0016] In this feature, after the step of measuring the master and storing the count number, it is desirable to execute the measurement step of the object to be measured multiple times in succession without executing the step of measuring the master and storing the count number, regardless of whether the optical measuring instrument is powered off or not, and it is further desirable to measure the master and update and store the count number read on the linear scale after the measurement step of measuring the object to be measured has been repeated a predetermined number of times, which is two or more. Effect of the Invention

[0017] According to the present invention, by locating a scale beyond a stopper position that is the measurement limit in an incremental optical measuring instrument, setting a master position that serves as a reference within a measurement range from this stopper position, and providing a means for storing the relationship between the master position and the stopper position, even if the power is turned off, it is possible to set the origin based on the stored position information before the power is turned off without performing actual mastering corresponding to the origin setting. Also, since the origin can be set using the stored master position and stopper position, the incremental optical measuring instrument can easily handle a power cut and can reduce the time required for measurement. [Brief description of the drawings]

[0018] [Figure 1] 1 is a vertical sectional view of an embodiment of an optical inner diameter measuring instrument according to the present invention. [Diagram 2] 1 is a vertical sectional view of an embodiment of an optical outer diameter measuring instrument according to the present invention. [Diagram 3] 3A and 3B are a top view and a side view showing an example of a sensor unit according to the present invention. [Figure 4] 4 is a diagram illustrating the operation of the sensor unit shown in FIG. 3. [Diagram 5] 4 is a diagram showing an example of an output from a sensor unit shown in FIG. 3. [Figure 6] 5A to 5C are schematic diagrams illustrating an origin setting method according to the present invention. [Figure 7] 4 is a flowchart of an origin setting method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, some examples of optical measuring instruments using the incremental type sensor according to the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing an example of an optical measuring instrument 100 using an incremental type optical sensor, which is an example of a bore gauge 100 for measuring inner diameters. Fig. 1(a) is a side cross-sectional view, Fig. 1(b) is a front cross-sectional view, and Fig. 1(c) is a bottom view.

[0020] The bore gauge 100 has a measuring section 60 located at the bottom and a control section 70 located at the top. The measuring section 60 has a cylindrical outer shape, and is protected by a protective cover 42 with a closed bottom surface 43. Inside the protective cover 42, a pair of measuring arms 28 extending vertically are arranged near the protective cover 42. An opening is formed at the upper end of each measuring arm 28, and a shaft 34 attached to an arm holder 40 fits into this opening. The arm holder 40, together with a base member of the bore gauge 100 (not shown), constitutes the stationary side of the bore gauge 100.

[0021] A bearing means 32 is disposed between the shaft 34 and the measuring arm 28, so that the measuring arm 28 can rotate with low friction around the shaft 34. In order to prevent the bore gauge 100 from becoming too large, a sliding bearing such as an oil-retaining bearing is used for the bearing means 32, but in cases where there is no size restriction, a rolling bearing which is expected to provide bearing accuracy can also be used.

[0022] A gauge head 24 is attached to the other end of each measuring arm 28, i.e., near the lower end, facing outward in a direction perpendicular to the longitudinal axis (up-down axis) of the measuring arm 28. The gauge head 24 has a substantially cylindrical base material and a contactor 26 attached to the outer end of the base material. The contactor 26 is the part that abuts against the inner surface of the workpiece to be measured, and is substantially hemispherical. Soft and hard materials are used depending on the object to be measured. For example, if the object to be measured is an aluminum alloy, a relatively soft metal or nonmetal that does not damage the object to be measured can be used, and if the object to be measured is a relatively hard steel, a metal such as stainless steel or a nonmetal such as ruby ​​can be used. A through hole 20 that is slightly larger than the gauge head 24 is formed in the part of the protective cover 42 corresponding to the gauge head 24, and the tip of the gauge head 24 can enter and exit this through hole 20 without resistance in a direction perpendicular to the longitudinal axis of the measuring arm 28.

[0023] A recess is formed in the inner part of the measurement arm 28 on the opposite side to the side where the measurement element 24 is attached, in a portion of the measurement arm 28 above the portion where the measurement element 24 is attached, to which the compression spring 22 is attached. That is, recesses are formed on the opposing surfaces of the pair of measurement arms 28 at the same position on the longitudinal axis of the pair of measurement arms 28, and each end of the compression spring 22 is held in each recess. As a result, the pair of measurement arms 28 are constantly pressed so as to move away from each other toward the outside. Note that in FIG. 1, both ends of one compression spring 22 are held by the pair of measurement arms 28, respectively, but two or more compression springs 22 may be used, one end of which is in contact with the measurement arm 28, and the other end of which is fixed to a base member not shown.

[0024] A protruding stopper 50 is formed on the inner surface of the protective case 42, above the pressure spring 22, at the position where each measuring arm 28 moves. The stopper 50 is intended to limit the outward rotation of each measuring arm 28 around the axis 34. In other words, when the side of the measuring arm 28 abuts against the stopper 50, even if the pressure of the pressure spring 22 is being applied to the measuring arm 28, the rotation of the measuring arm 28 is physically stopped by the stopper 50 and the measuring arm 28 cannot rotate any further. This position of the measuring arm 28 is the initial state when the bore gauge 100 is used.

[0025] Above the stopper 50, a linear scale 4 constituting an incremental type sensor section is attached on the surface of the measuring arm 28. The scale direction of the linear scale 4 is aligned with the moving direction of the gauge head 24. A reading head 1 is disposed facing the linear scale 4. The reading head 1 is held by a reading head holder 30, which is connected to a base member (not shown). The sensor section will be described in detail later with reference to FIG. 3.

[0026] A detection signal from the reading head 1 is sent to a control unit 70 on the upper part of the bore gauge 100 via the reading head holding member 30 etc. The control unit 70 is provided with a control means 82 equipped with a storage means 86, and the result of signal processing of the detection signal from the reading head 1 is stored in the non-volatile memory of the storage means 86. A battery 84, such as a size AA battery, is connected to the control means 82 via a switch 88 as a power source.

[0027] Here, the bore gauge 100 shown in Fig. 1 can be used for product inspection, or so-called inspection, after machining a workpiece in, for example, an NC automatic machine or a machining center, so that if power is supplied to the control means 82 during machining, the battery 84 will be consumed rapidly and will require frequent replacement. To solve this problem, the switch 88 is generally turned off when machining a workpiece, and is turned on to supply power only when necessary for inspection. In this case, if the bore gauge 100 is of the incremental type, calibration for absolute length is required every time the power is turned on again. The present invention simplifies the processing after the power is turned on again, as will be described later.

[0028] Another embodiment of the incremental type measuring instrument according to the present invention is shown in Fig. 2. This measuring instrument 190 is an optical outer diameter measuring instrument equipped with a measuring unit 160 and a control unit 170, and its main configuration is almost the same as that of the bore gauge 100 shown in Fig. 1. This figure shows a state in which a workpiece W is being measured. At the longitudinal intermediate portion of a pair of measuring arms 128 arranged opposite to each other, a shaft 134 and a bearing 132 for rotatably holding the measuring arms 128 are arranged. At the tip side of each measuring arm 128, a measuring element 124 having a contact 126 is attached facing inward so as to face each other. The contact 126 is hemispherical and comes into contact with the outer surface of the workpiece W.

[0029] A linear scale 104 constituting a sensor unit is attached to the other end of the measuring arm 128. Here, in order to improve the resolution of the measuring arm 128, the longitudinal attachment position of the linear scale 104 is set as far away as possible from the axis 134 which is the center of rotation. Although not shown, a reading head is disposed opposite the linear scale, and its detection signal is input to the control means 182 of the control unit 170 as indicated by the dashed line.

[0030] The pressure spring 122 is provided between the shaft 134, which is the rotation center position, and the tip end to which the linear scale 104 is attached so that the pair of measuring arms 128 always rotate in the closing direction. That is, one end of the pressure spring 122, which is fixed to a base member (not shown), abuts against the side of the measuring arm 128 and presses each measuring arm 128 outward at this position. In addition, a protruding stopper 150 is formed on the case 142 corresponding to the outer side of the measuring arm 128, between the shaft 134, which is the rotation center, and the tip end to which the linear scale 104 is attached. The stopper 150 limits the rotation of the measuring arm 128 in the narrowing direction at the measurement position due to the pressing force of the pressure spring 122, and the state in which the measuring arm 128 abuts against the stopper 150 is the initial state of the outer diameter measuring instrument 190.

[0031] In the control section 170, a control means 182 equipped with a storage means 186 is disposed in the case 142, and a battery 184 such as an AA battery is connected to the control means 182 via a switch 188. A detection signal detected by a reading head (not shown) is subjected to processing such as digital conversion in the control means 182 and stored in the storage means 186.

[0032] Next, the details of the linear scale 4 constituting the incremental type sensor section and the reading head 1 arranged opposite the linear scale 4 will be explained with reference to Figures 3 and 4. Figure 3 shows the arrangement of the linear scale 4 and the reading head 1, with Figure 3(a) being a top view and Figure 3(b) being a front view. Figure 4 is a schematic diagram showing how the signal detected by the sensor section is processed by the control means 82 in Figure 1 (or the control means 182 in Figure 2).

[0033] The linear scale 4 has reflective sections 5b formed by depositing a metal with high light reflectance, such as Ag or Al, on a scale 4a made of glass, for example, by vapor deposition, and transmissive sections 5a formed as non-deposited sections (or non-processed sections) between the reflective sections 5b. The reflective sections 5b and the transmissive sections 5a have the same width, for example, 20 μm, and the reflective sections 5b and the transmissive sections 5a form a scale pattern 5. A large number of scale patterns 5 are repeatedly formed in the X direction, which is the moving direction of the measurement arm 28 (128). As described above, the linear scale 4 is attached to the measurement arm 28 and moves in the X direction together with the measurement arm 28.

[0034] Meanwhile, the reading head 1 is disposed parallel to and facing the linear scale 4 with a gap therebetween, and together with the linear scale 4 forms an incremental type optical encoder or sensor unit. The reading head 1 has a light emitting unit 2 and a light receiving unit 3 on a scale substrate 1a. The light emitting unit 2 has a light source made up of an LED array or a laser array. The light receiving unit 3 has a light receiving element made up of a photodiode array, as well as a grating and a light transmitting member.

[0035] In the sensor section thus configured, when the linear scale 4 moves in the X direction in the figure together with the measuring arm 28, incident light 11 emitted from the light-emitting section 2 is incident on multiple scale patterns 5 on the linear scale 4, is reflected by the reflecting section 5b and enters the light-receiving section 3 as reflected light 12, while at the transmitting section 5a it passes through the linear scale 4 as transmitted light 13. The reflected light 12 that enters the light-receiving section 3 is thereafter processed as a detection signal of the amount of movement of the linear scale 4 in the X direction.

[0036] The process after the light emission in the sensor unit will be described with reference to Fig. 4. The reading head 1 arranged on the reading head holder 30 obtains a sine wave detection signal 202 from each diode in the diode array of the light receiving element by the movement of the linear scale 4, as shown in the upper left circle in Fig. 4. These detection signals are combined with the diodes in the diode array and aggregated into an A-phase signal 204 and a B-phase signal 206 that is 90° out of phase with the A-phase, and are sent to a multiplication circuit 230 where they are amplified and then converted into a digital signal via an analog / digital conversion circuit. The digitized A-phase signal 214 and B-phase signal 216 are counted by a counter circuit 232, and a count number according to the amount of movement of the linear scale 4 in the X direction is obtained.

[0037] Here, the optical measuring instruments 100 and 190 used in this embodiment adopt an incremental method, so the difference in the count number between before and after the movement of the linear scale 4 can be converted into a length. However, since it is not an absolute encoder, it is not possible to know from the count number alone how much absolute length the count number before the movement corresponds to, and prior calibration is required for each measurement. In particular, if the power supply of the measuring instrument is cut off before the measurement, the zero point or reference position of the measuring instrument is not retained as information, so calibration is always required. In such a case, conventionally, the measuring instrument is positioned on a master M with a known inner or outer diameter to start the measurement, and the count number of the master at that time is used as the reference point or zero point. Then, in subsequent measurements, the difference between the measured count number of the master M and the measured count number of the work W is added or subtracted from the count number of the work W to obtain the measured value. For this reason, it is necessary to set the master M and the work W at the same measurement position, which takes a lot of time to set. Below, a measurement method of the present invention using the measuring instruments 100 and 190 described with reference to Figs. 1 to 4, which solves this problem, will be described.

[0038] 5 to 7 are diagrams of a measurement method using the measuring instruments 100 and 190 according to the present invention, and FIG. 5 is a diagram showing an example of a detection signal detected by the reading head 1. The state after digitization through a digital conversion circuit is shown, and FIG. 6(a) is an example of an output when the measuring instruments 100 and 190 are used for the first time, and FIG. 6(b) is an example of an output when the measurement is performed for the second or subsequent times. FIG. 6 is a diagram showing only the lower part of the bore gauge 100 shown in FIG. 1, and FIG. 6(a) shows the initial state of the measuring instrument 100, and FIG. 6(b) shows a case where the master M is measured without going through a power cut after measurement in the initial state (state of (a)). FIG. 6(c) is a diagram showing the state of the measuring instrument 100 when the power is turned on again after the measurement is once completed and the power is turned off, and FIG. 6(d) is a diagram showing a state where the workpiece W is measured without turning off the power after FIG. 6(c). FIG. 7 is a flowchart explaining the above series of measurement operations.

[0039] For example, consider a case where the inner diameters of a plurality of parts (workpieces) of the same shape are machined continuously and automatically in a machining center. The machining center is equipped with a bore gauge for measuring the inner diameter, and the bore gauge 100 is used to measure the inner diameter of each workpiece W after machining. Since machining takes a certain time, the power supply for the bore gauge 100 for measurement is turned off during machining. Since the bore gauge 100 is an incremental type, the origin is not stored. Therefore, first, before measuring the first workpiece W, the count number at the maximum diameter (maximum measurement range) of the bore gauge 100 is measured. That is, the count number n0 is measured when the measuring arm 28 of the bore gauge 100 abuts against the stopper 50 of the bore gauge. This corresponds to FIG. 6(a), and in this example, the count number is 50. The position where the measuring arm 28 abuts against the stopper 50 is the reference point P on the bore gauge 100 for subsequent measurements. S Used as.

[0040] Next, the bore gauge 100 is moved to the position of the master M. Alternatively, the master M is moved to the measurement position, and the inner diameter position P on the bore gauge 100 of the master M is M The number of counts corresponding to mAt this time, the contact 26 of the bore gauge 100 abuts against the inner surface of the master M, but the measuring arm 28 is no longer abutting against the stopper 50 and is separated from the stopper 50. This state corresponds to FIG. 6(b), and in this example, the count number is 100. Since the inner diameter of the master M is known, the reference point position P measured in FIG. 6(a) is S is the count number n of master M m and the reference point position P S From the difference N between the count number n0 and the count number n1, the following equation is obtained with reference to FIG.

[0041] φD S =φD M +kN=φD M +k(n m -n0) Here, D S is the distance between the tips of the contacts 26 when the measuring arm 28 abuts against the stopper 50, and φD M is the inner diameter of the master M (known). k is the length per count, which is a value specific to the measuring device. The count number of the master M obtained here and the reference point position P S The difference N between the counts is stored in the storage means 86, which is a non-volatile memory included in the control means 82 of the bore gauge 100. S Now that the number of counts of the measured value and its distance conversion value have been obtained, the inner diameter of the first workpiece W1 is measured without turning off the power to the bore gauge 100.

[0042] The contact 26 of the bore gauge 100 comes into contact with the inner surface of the workpiece W1. This corresponds to FIG. 6(d), and in this example, the count is 212. Even in this state, the measuring arm 28 does not come into contact with the stopper 50 and is separated from the stopper 50. As in the above formula, the measured inner diameter φD of the workpiece W1 is W1 is obtained by the following formula:

[0043] φD W1 =φDs+k(n W1 -n0) where n W1 is the measured count number of workpiece W1.

[0044] After this, the machining center starts machining the next workpiece W2. Therefore, in order to prevent consumption of the battery 84 of the bore gauge 100, the power supply to the bore gauge 100 is temporarily cut off. Then, after machining of the workpiece W2 is completed, measurement of the inner diameter of the workpiece W2 is resumed. While the power supply was cut off in the bore gauge 100, information indicating the relative position between the incremental linear scale 4 and the reading head 1 was lost, or the relative position changed for some reason, and information on the reference position cannot be obtained.

[0045] Therefore, before measuring the workpiece W2, the count number m0 is measured again with the measuring arm 28 in contact with the stopper 50. Since the bore gauge 100 constantly presses the measuring arm 28 toward the stopper 50 with the pressing spring 22, this measurement can be easily performed by simply turning the power back on. The measurement state corresponds to FIG. 6(c), and the count number obtained by measurement in this example is 70. The state of the bore gauge 100 is the same as that before measuring the first workpiece W1, but since the power was turned off, there may be a difference in the count number. Before measuring the first workpiece W1, the relative relationship between the reference position and the master position is known, and is stored in the storage means 86 as the count number N. Therefore, referring to FIG. 5(b), the reference position P where the measuring arm 28 abuts against the stopper 50 is measured. S1 The position where the count number is larger by N counts from the position P on the bore gauge 100 of the master M M1 The position P of the master M is M1 Since the calibration value obtained by the master M is not necessary for the second or subsequent workpieces W, the measurement using the stopper 50 of the bore gauge 100 is used instead of the calibration value using the master M, so that the work efficiency is significantly improved.

[0046] Since the calibration equivalent to the calibration using the master M has been performed using the stopper 50, the calibration of the bore gauge 100 has been completed. Then, as in FIG. 6(d), the contact 26 is brought into contact with the inner surface of the workpiece W2, and the count number n W2 From the obtained count, φD W2 =φDs+k(n W2 -m0) Thus, the inside diameter of the workpiece W2 can be obtained accurately. For the third and subsequent workpieces W, the measurement with the stopper 50 and the measuring arm 28 in contact with each other and the measurement of the inside diameter of the actual workpiece W are repeated.

[0047] As is clear from the above, in the bore gauge 100, which is an optical measuring instrument capable of measuring the inner diameter, the measurement range does not expand beyond the default state in which the measuring arm 28 abuts against the stopper 50, and this state becomes the lower or upper limit of the count number of the linear scale 4 depending on the count direction in which the reading head 1 reads the linear scale 4. The master M is measured inside the linear scale 4 beyond this limit value, and when the contactor 26 is further retracted to the protective cover 42 side, a smaller diameter cannot be measured, so this becomes the upper or lower limit of the measurement. Therefore, the measured inner diameter becomes smaller in the order of the abutment position of the stopper 50 and the measuring arm 28, the master position, and the retraction limit position of the contactor, and the count number becomes smaller or larger in this order depending on the count direction of the reading head 1. In the present invention, a member on which the stopper 50 that rotatably holds the measuring arm 28 and limits the rotation of the measuring arm 28 is formed is called a holding member. In the embodiment shown in FIG. 1, the holding member is a combination of an arm holder 40 and a protective cover 42.

[0048] Next, the above-mentioned measurement method will be explained again with reference to the flow chart of FIG. 7. When the measurement program is started, the power supply of the bore gauge 100 is turned on in step S700 before measuring the first workpiece W1. Normally, in this state, the measurement arm 28 of the bore gauge 100 is pressed against the stopper 50 by the pressing spring 22, so the output of the bore gauge 100 in this state is measured (step S710). Next, the inner diameter of the master M, the inner diameter of which is known, is measured using the bore gauge 100 (step S720). Then, in step S730, the control means 82 calculates the difference between the count number measured in step S710 when the measurement arm 28 abuts against the stopper 50 and the count number of the bore gauge 100 measured in step S720, and stores the difference in the storage means 86. In the case of the first workpiece, the difference reading is omitted, the contact 26 is brought into contact with the inner surface of the workpiece W1 to measure the inner diameter of the workpiece W1, and the control means 82 calculates the inner diameter of the workpiece W1 using the difference in the count number. The calculation result is stored in the storage means 86, or used as feedback for processing (step S740).

[0049] Since the measurement of the first workpiece W1 is completed in step S740, the internal diameter machining of the next workpiece is started. In order to prevent consumption of the battery 84 of the bore gauge 100, the power is turned off in step S750 and the next measurement is awaited. In step S760, it is determined whether there is a next measurement. If there is no measurement, the process ends. If there is a next measurement, the process proceeds to step S770. In step S770, the process waits for the next workpiece W2 that has finished machining, and when the workpiece W2 reaches the measurement position, the power of the bore gauge 100 is turned on again. Then, the measurement arm 28, which is in the normal default state, is abutted against the stopper 50 and the measurement of the bore gauge 100 is performed (step S780).

[0050] Next, in step S790, it is determined whether a predetermined number of measurements have been performed since the previous measurement of the master M. This determination is performed because, for example, when the hardness of the workpiece W to be measured is relatively high and the hardness of the contactor 26 is low, the amount of wear of the contactor 26 becomes significant when the contactor 26 abuts against the inner surface of the workpiece W reaches a predetermined number of times, which may increase the measurement error. Conversely, when the hardness of the workpiece W is low and the hardness of the contactor 26 must be reduced to prevent damage to the workpiece W, the contactor 26 may be worn by abutting against the workpiece W in the same manner. When the number of measurements reaches a number at which wear that may affect the measurement result is a concern, the process returns to step S720 and the master M is measured again. If the number of measurements has not yet reached a number at which the wear of the contactor 26 becomes noticeable, the process returns to step S740, and the difference N between the count number when the initial master M was measured and the count number when the measuring arm 28 abutted against the stopper 50, which is stored in the memory means 86 of the control means 82, is read, and the workpiece W2 is measured. Thereafter, steps S740 to S790 or steps S720 to S790 are repeated as long as there are measurement objects.

[0051] As described above, according to the above embodiment, in an incremental optical measuring instrument for measuring inner or outer diameter, a stopper against which the measuring arm abuts is provided, and therefore the calibration by the master every time the power of the measuring instrument is turned off can be substituted by the detection of the stopper, so that the time required for calibration can be significantly reduced, and the time for optical measurement can be reduced. This reduces the inspection time after machining of the workpiece, and the number of steps for machining the workpiece can be reduced. In the above embodiment, the stopper is provided on the stationary side of the measuring instrument, such as the protective case, but it goes without saying that it may be provided on the movable side, that is, the measuring arm side. The stopper may be in any form as long as it can stop the movement of the movable side. [Explanation of symbols]

[0052] 1...reading head, 2...light source (light emitting portion), 3...photodiode (light receiving portion), 4...linear scale, 5...scale pattern, 5a...transmitting portion, 5b...reflective portion, 11...incident light, 12...reflected light, 13...transmitted light, 20...through hole, 22...pressure spring, 24...measuring element, 26...contact, 28...measuring arm, 30...reading head holding member, 32...bearing means, 34...axis, 40...arm holding device, 42...protective cover, 43...bottom surface, 50...stopper, 60...measuring portion, 70...control portion, 82...control means, 84...battery, 86...storage means, 88...switch, 100...inner diameter measuring instrument (bore gauge), 104...linear scale, 122... Compression spring, 124...measuring element, 126...contact, 128...measuring arm, 132...bearing, 134...shaft, 142...case, 150...stopper, 160...measuring element, 170...control unit, 182...control means, 184...battery, 186...storage means, 188...switch, 190...outer diameter measuring instrument, 202...detection signal, 204...output signal (phase A), 206...output signal (phase B), 214-214b...digitized signal (phase A), 216-216b...digitized signal (phase B), 230...multiplication circuit, 232...counter circuit, C0...display counter, k...coefficient, M...master, m0...count number, N...count number difference, n0...count number (stopper), n m …Count number (master) P S , P s1 …Stopper position (on the linear scale), P M , P M1 …Master position (on the linear scale), W…Workpiece (measured object), X…Probe movement direction

Claims

1. a scale in which reflective portions and transmissive portions are alternately and regularly formed; An incremental measuring instrument comprising: a reading head having a light emitting means and a light receiving means; a control means; a stopper for limiting a relative movement of the scale with respect to the reading head; and a memory means, The measuring instrument according to claim 1, wherein the control means calculates an output difference between a state in which the master is measured and a state in which the movement is restricted by the stopper, which is stored in the memory means, and stores the output difference in the memory means.

2. 2. The measuring instrument according to claim 1, wherein said control means calculates the amount of said movement of the workpiece from a measurement value in a state where said movement is restricted and said output difference stored in advance.

3. connected to the scale; The measuring device further includes a contact that moves the scale relative to the reading head by contacting the workpiece, 2. The measuring instrument according to claim 1, wherein said control means calculates the amount of movement caused by contact with said workpiece from a measurement value in a state in which said movement is restricted and said output difference stored in advance.

4. The measuring device according to any one of claims 1 to 3, wherein the amount of movement is a number of counts reading on the scale.

5. A measurement method for measuring a workpiece using the measuring instrument according to claim 1, comprising: a step of storing in advance, as an initial value, a count number of the reading of the scale in a state in which the movement is restricted by the stopper; measuring the master and storing the count; measuring the workpiece; The measurement of the workpiece is the initial value and the count number obtained by measuring the master are used to correct the count number of the reading obtained by measuring the workpiece, thereby obtaining a measurement value.

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