AUTOMATIC MEASURING APPARATUS

There is provided an automatic measuring apparatus that automates an inexpensive and easy-to-use contact-type measuring device. An automatic measuring apparatus includes a measuring device including a movable element that is displaceable with respect to a fixed element and moves forward and backward to be brought into contact with or away from a workpiece, and a displacement detection part that detects a displacement or position of the movable element, and an automatic operation part that automates the forward/backward movement of the movable element by power. When the movable element is brought into contact with the workpiece, vibration is applied directly or indirectly to at least one of the workpiece and the measuring device in such a manner that contacting surfaces of the workpiece and the measuring device are in close contact with each other by changing a relative position and posture between the workpiece and the measuring device.

INCORPORATION BY REFERENCE

This application is based upon and claims the benefit of priority from JP patent application No. 2023-141875, filed on Aug. 31, 2023 (DAS code 0D23), the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automatic measuring apparatus that automatically measures a workpiece using a small-sized measuring device for measuring a dimension of the workpiece.

2. Description of Related Art

Micrometers, calipers, Hall tests, cylinder gauges, and Borematic (registered trademark) are known as measuring devices (measuring tools) that measure the dimensions of workpieces. Such contact-type measuring devices (measuring tools) are widely used because of their ease of use, measurement stability, relatively low cost, and other advantages. However, it is required for a workpiece and a movable element (a spindle, a measuring jaw, or a contact point) to be in proper close contact and for the same measurement pressure to be constantly applied, which inevitably results in manual measurement. Therefore, measurement with such a contact-type measuring machine is time-consuming and labor intensive.

As an alternative to manual measurement, non-contact measurement devices such as air micrometers and laser scan micrometers have been proposed for use at production sites (JP H08-14871 A). However, air micrometers and laser scan micrometers are themselves extremely expensive and relatively difficult to maintain.Patent Literature 1: JP H10-89903 APatent Literature 2: JP 2019-100904 APatent Literature 3: JP H08-14871 A

SUMMARY OF THE INVENTION

Although various proposals have been made to automate contact measurement, such as those using motor power, there have been no cases of successful practical applications that have been widely used by the general public (JP H10-089903 A). In addition, it is possible to automate contact measurement by using a coordinate measuring machine (CMM) or the like (JP 2019-100904 A), but it requires an investment of tens to hundreds of millions of yen, which is not appropriate to use a CMM as a substitute for measurement using a micrometer or caliper.

A purpose of the present invention is to provide an automatic measuring apparatus that automates an inexpensive and easy-to-use contact-type measuring device.

An automatic measuring apparatus according to an exemplary embodiment of the present invention includes:a measuring device that measures a dimension of a workpiece, the measuring device including a movable element that is displaceable with respect to a fixed element and moves forward and backward to be brought into contact with or away from the workpiece, and a displacement detection part that detects a displacement or position of the movable element;an automatic operation part that automates the forward/backward movement of the movable element by power; anda vibration actuator that directly or indirectly applies vibration, when the movable element is brought into contact with the workpiece, to at least one of the workpiece and the measuring device to facilitate a change in a relative position and posture between the workpiece and the measuring device in such a manner that contacting surfaces of the workpiece and the movable element are in close contact with each other by changing the relative position and posture between the workpiece and the measuring device at a pressure lower than a predetermined measurement pressure set in advance in the measuring device, in whichthe automatic measuring apparatus automatically measures the workpiece using the measuring device.

In an exemplary embodiment of the present invention, it is preferable that the automatic measuring apparatus further includes:a moving means for relatively moving the workpiece and the measuring device to place the workpiece within a measurement range of the measuring device; anda floating joint part interposed between the moving means and the measuring device to allow relative translation and rotation of the measuring device with respect to the moving means, in whichthe vibration actuator is attached to the measuring device.

In an exemplary embodiment of the present invention, it is preferable that the automatic measuring apparatus further includes:a workpiece holding part that holds the workpiece, in whichthe workpiece holding part holds the workpiece in such a manner that a position and posture of the workpiece is changed at a pressure lower than the predetermined measurement pressure set in advance in the measuring device when the movable element is brought into contact with the workpiece, andthe vibration actuator is attached to the workpiece holding part.

In an exemplary embodiment of the present invention, it is preferable that the automatic operation part moves the movable element forward to bring the movable element into contact with the workpiece, then moves the movable element backward by a predetermined amount, and finally moves the movable element forward again to generate the predetermined measurement pressure between the workpiece and the movable element, andthe vibration actuator is driven, when the movable element is moved forward again to generate the predetermined measurement pressure between the workpiece and the movable element.

In an exemplary embodiment of the present invention, it is preferable that the displacement detection part acquires the displacement or position of the movable element as a measurement value after the automatic operation part stops the forward re-movement of the movable element and the vibration actuator stops driving.

An automatic measuring apparatus according to an exemplary embodiment of the present invention includes;a measuring device that measures a dimension of a workpiece, the measuring device including a movable element that is displaceable with respect to a fixed element and moves forward and backward to be brought into contact with or away from the workpiece, and a displacement detection part that detects a displacement or position of the movable element;an automatic operation part that automates the forward/backward movement of the movable element by power; anda workpiece holding part that holds the workpiece in such a manner that a position and posture of the workpiece is changed at a pressure lower than a predetermined measurement pressure set in advance in the measuring device when the movable element is brought into contact with the workpiece.

In an exemplary embodiment of the present invention, it is preferable that the workpiece holding part includes:a base part;a workpiece installation stage on which the workpiece is to be placed or installed; anda floating joint part interposed between the base part and the workpiece installation stage to allow relative displacement of the workpiece installation stage with respect to the base part.

In an exemplary embodiment of the present invention, it is preferable that the floating joint part includes:a translation-allowing mechanism part that allows translational displacement of the workpiece installation stage with respect to the base part; anda rotation-allowing mechanism part that allows rotation of the workpiece installation stage with respect to the base part, and
the base part, the translation-allowing mechanism part, the rotation-allowing mechanism part, and the workpiece installation stage are provided in this order from a lower side.

In an exemplary embodiment of the present invention, it is preferable that the translation-allowing mechanism part includes a translation body that allows translation of the workpiece installation stage with respect to the base part, andthe rotation-allowing mechanism part includes a flexible body that is deformable to allow displacement of the workpiece installation stage in an inclination direction with respect to the base part.

In an exemplary embodiment of the present invention, it is preferable that the workpiece holding part includes a restriction means for regulate displacement of the workpiece installation stage, andthe restriction means regulates the displacement of the workpiece installation stage when the movable element is away from the workpiece, and allows the displacement of the workpiece installation stage when the movable element and the workpiece are in contact with each other and the measurement pressure is applied to the workpiece from the movable element.

In an exemplary embodiment of the present invention, it is preferable that the workpiece holding part includes a vibration actuator that directly or indirectly applies vibration to the workpiece to facilitate a change in a relative position and posture between the workpiece and the measuring device.

In an exemplary embodiment of the present invention, it is preferable that the workpiece holding part includes:a restriction means for regulating displacement of the workpiece installation stage; anda vibration actuator that directly or indirectly applies vibration to the workpiece to facilitate a change in the relative position and posture between the workpiece and the measuring device,
the automatic operation part moves the movable element forward to bring the movable element into contact with the workpiece, then moves the movable element backward by a predetermined amount, and finally moves the movable element forward again to generate the predetermined measurement pressure between the workpiece and the movable element, and
the restriction means releases the workpiece installation stage to allow the displacement of the workpiece installation stage and the vibration actuator is driven, when the movable element is moved forward again to generate the predetermined measurement pressure between the workpiece and the movable element.

DETAILED DESCRIPTION

Embodiments of the present invention are illustrated and described with reference to the reference signs assigned to the elements in the drawings.

Note that, each embodiment may be implemented independently, or two or more embodiments may be implemented in combination, and examples of modification added in each embodiment are applicable to other embodiments.

First Exemplary Embodiment

In the following, a first exemplary embodiment of the present invention is described.

FIG.1is an overall configuration diagram showing an automatic measuring apparatus100.

The automatic measuring apparatus100includes a measuring-apparatus main body120and a control unit800.

The measuring-apparatus main body120includes a robot arm part130as a moving means, and an automatic measuring unit200.

The moving means will be described using an articulated arm robot as an example, but a simpler moving mechanism combining one or two axes of rotation or straight lines may be used. Since the moving means is only required to relatively move a workpiece W and a measuring device, the moving means can transfer the workpiece W or the moving means can move the measuring device, but the moving means that transfers the workpiece W will be described as an example in the first exemplary embodiment. For example, a workpiece W (for example, a part) machined by a machine tool (for example, a numeric control (NC) lathe) is conveyed by a conveyor belt111.

The workpiece W is transferred to a stocker112for pretreatment. As pretreatment, deoiling and dust removal by air blow may be performed. The pretreated workpiece W is transferred by a robot arm part130, which is the moving means, into a measurement area of the automatic measuring unit200.

The robot arm part130is an articulated robot arm part130and includes a robot hand140for grasping the workpiece W at its tip and a camera150for image recognition. The robot arm part130recognizes the workpiece W by image recognition, grasps the workpiece W with the robot hand140, and transfers the workpiece W to the measurement area of the automatic measuring unit200. Here, the robot hand140is assumed to place the workpiece W in a preset orientation (posture) in the measurement area and release the workpiece W once.

For a simpler system, a person may manually pick up and transfer the workpiece W.

The workpiece W transferred to the measurement area in this manner is measured for its dimension by the automatic measuring unit200.

Automatic Measuring Unit200

The automatic measuring unit200brings a contact point (movable element) into contact with a workpiece W to measure a dimension of the workpiece W. Although it is possible to measure either the inside dimension (inside diameter) or the outside dimension (outside diameter) as the dimension of the workpiece W, the outside dimension (outside diameter) is measured as an example in the first exemplary embodiment.

The automatic measuring unit200is an automated micrometer300as a small-sized measuring device (small-sized measuring tool). The automatic measuring unit200in the first exemplary embodiment is referred to as an automatic micrometer device200.

FIG.2is an external view of the automatic micrometer device200.

The automatic micrometer device200includes a micrometer (measuring device)300, a measuring-device support frame part400, an automatic operation part500, a workpiece holding base part (workpiece holding part)460, and a vibration motor (vibration actuator)600.

The micrometer300is originally a small-sized, manually operated measuring device, and a commercially available micrometer300can be used as the micrometer300in the present exemplary embodiment.

The configuration of the micrometer300is briefly described below.

The micrometer300includes a U-shaped frame (fixed element)310, a spindle (movable element)330, a thimble part340, and a displacement detection part350.

The U-shaped frame310includes an anvil320inside one end of the U-shape.

The spindle330is provided at the other end of the U-shaped frame310and is axially movable forward and backward with respect to the anvil320. The spindle330is provided with a measuring surface on one end face of the spindle330to be brought into contact with the workpiece W. Similarly, the anvil320is provided with a measuring surface on the other end face of the anvil320to be brought into contact with the workpiece W. The measuring surfaces are machined into flat surfaces and formed of cemented carbide material or ceramic.

Note that the U-shaped frame310may be, for example, a micrometer head that does not include the anvil320. The anvil320, which is paired with the spindle330to sandwich the workpiece W, may be installed on the measurement axis as a separate body from the micrometer300.

The spindle330is fed and moved forward and backward in an axial direction by the rotary operation of the thimble part340. There are two types of methods for feeding the spindle330: a rotary feed type in which the spindle330itself rotates, and a linear feed type in which the spindle330itself does not rotate. In the rotary feed type, the spindle330is provided with a male thread, and the U-shaped frame310is provided with a female thread. The thimble part340and the spindle330are engaged to rotate together, and the spindle330is rotated by the rotary operation of the thimble part340. Then, the spindle330is moved forward or backward by the screw feed. In the linear feed type, a feed screw is provided inside the thimble part340, and the spindle330is provided with a pin that engages with the feed screw. When the thimble part340is rotated while the spindle330is locked, the spindle330is fed by the engagement between the pin and the feed screw. The type of the micrometer300to be employed in the present exemplary embodiment can be either the rotary feed type or the linear feed type.

The thimble part340is disposed at the other end of the spindle330at the other end of the U-shaped frame310. The thimble part340is an operation part that moves the spindle330forward and backward by rotary operation.

The micrometer300to be employed in the present exemplary embodiment preferably includes a constant pressure mechanism between the thimble part340and the spindle330. The constant pressure mechanism disengages the thimble part340and the spindle330when a preset load is applied to the spindle330, thereby causing the thimble part340to idle against the spindle330. By constantly activating the constant pressure mechanism in the same proper manner during measurement, a measurement pressure during measurement can be kept constant, and the measurement accuracy (repeatability) can be kept high. The constant pressure mechanism is incorporated in a commercially available micrometer300and is disclosed in JP 3115555 B, JP 3724995 B, JP 5426459 B, and JP 5270223 B. The constant pressure mechanism can be constituted by a ratchet mechanism that allows slippage to occur when a force above a predetermined load is applied between the thimble part340and the spindle330, or a plate spring interposed between an outer sleeve and an inner sleeve of the thimble part340to allow slippage to occur above a predetermined load.

The micrometer300to be employed in the present exemplary embodiment preferably includes a measurement-pressure detection mechanism that detects the load applied to the spindle330. For example, such a measurement-pressure detection mechanism is disclosed in JP 3751540 B, JP 4806545 B, and JP 2019-190916 A. The measurement-pressure detection mechanism may directly or indirectly detect the load applied to the spindle330with a strain gauge or the like, or may detect that the load applied to the spindle330has reached a predetermined value based on the activation of the constant pressure mechanism. The measurement-pressure detection mechanism outputs a signal (measurement pressure signal) when detecting a predetermined measurement pressure. For example, the displacement detection part350performs sampling (latching) of a measurement value (displacement) in response to the detection of the predetermined measurement pressure by the measurement-pressure detection mechanism.

The displacement detection part350detects the displacement (or position) of the spindle330. The displacement detection part350is constituted by a rotary encoder or linear encoder.

The displacement detection part350may be an analog type (scale type) instead of an encoder. In this case, for automation, the scale may be read by the digital camera150or the like, and the measurement value may be read by image analysis (image recognition). In this case, the displacement detection part350may be constituted by an analog-type scale, the digital camera150, and an image recognition unit (image analysis unit).

In addition, the U-shaped frame310includes a display panel311for displaying a measurement value and switches for operation on its front face. The U-shaped frame310further has a measurement value output function for outputting the measurement value externally via wired or wireless communication as a function of a built-in electric circuit.

Next, the measuring-device support frame part400is described. The measuring-device support frame part400includes a base frame410and a measuring-device holding part420.

The base frame410is a rectangular frame as a whole. For the sake of explanation, mutually orthogonal XYZ coordinate axes are taken as shown inFIG.2. Of the four sides constituting the base frame410, the two sides parallel to the X axis direction are a first long side part411and a second long side part412, and the two sides parallel to the Y axis direction are a first short side part413and a second short side part414.

The first long side part411, the second long side part412, the first short side part413, and the second short side part414are desirably stretchable to adjust their lengths. This allows the size of the base frame410to be adjusted according to the size of the micrometer300or the workpiece W.

The measuring-device holding part420is installed on the first long side part411, the automatic operation part500is installed on the second short side part414, and the workpiece holding base part460is installed on the second long side part412. The first long side part411has a rail to allow the installation position of the measuring-device holding part420to be adjusted along the X-axis direction. Similarly, the second short side part414has a rail to allow the installation position of the automatic operation part500to be adjusted along the Y-axis direction. The second long side part412has a rail to allow the installation position of the workpiece holding base part460to be adjusted along the X-axis direction.

The measuring-device holding part420is fixedly attached to the first long side part411. The measuring-device holding part420sandwiches the micrometer300between upper and lower clamping pieces to attach the micrometer300to the base frame410(first long side part411).FIG.3is a cross-sectional view of the measuring-device holding part420.

The measuring-device holding part420includes a first clamping piece421and a second clamping piece422, and the first clamping piece421and the second clamping piece422each have an elastic rubber sheet423as a cushioning material on the surfaces facing each other. In addition to elastic rubber, the cushioning material may be a foam resin, a spring, or an air-sealed bag (for example, an air cap). The cushioning material has enough cushioning to not inhibit vibration when vibration is applied to the micrometer300by the vibration motor600, which will be described later. Alternatively, the clamping pieces421and422may be thin plates, and the clamping pieces421and422themselves may have elasticity to hold the measuring device (micrometer300). The U-shaped frame (fixed element)310of the micrometer (measuring device)300is clamped between the first clamping piece421and the second clamping piece422. The orientation of the micrometer300is as follows: the forward/backward movement direction (axial direction) of the spindle330is parallel to the X axis, the one end side (anvil320side) of the U-shaped frame310faces the first short side part413, and the other end side (thimble side) of the U-shaped frame310faces the second short side part414.

The automatic operation part500automates the forward/backward movement of the spindle (movable element)330by the power of a motor520.

The automatic operation part500includes a motor housing510, a motor520, and a power transmission part530.

The motor housing510houses the motor520and a motor controller. The motor housing510is disposed on an extension of the centerline of the spindle330(or the thimble part340) of the micrometer300. In other words, the automatic operation part500is installed in such a manner that the rotation axis of the rotor of the motor520is on the same line as the center axis of the spindle330(or the thimble part340). If necessary, the position of the motor housing510may be adjusted by moving the motor housing510along the rail of the second short side part414.

The motor520may be a normal electric motor that extracts the rotation of the rotor to the output shaft. However, the motor520is preferably capable of controlling the rotation angle (the number of revolutions) of forward and reverse rotation to some extent by control pulses. In addition, the motor520preferably has a torque detection function. (Various methods are known for detecting the torque of the motor520, such as determining the torque from the increase or decrease in the applied current (applied voltage).) A stepping motor can be used as the motor520. (Needless to say, a servo motor or a synchronous motor is also applicable, and the structure and drive system of the motor520are not particularly limited.)

The power transmission part530includes a fastening ring531that fits onto the thimble part340, a rotating plate532provided to rotate in synchronization with the rotation axis of the rotor of the motor520, and a transmission link rod533that connects the fastening ring531and the rotating plate532. One end of the transmission link rod533is fixed to the fastening ring531and the other end is fixed to the rotating plate532. The transmission link rod533is parallel to the center axis of the spindle330. When the rotating plate532is rotated by the motor520, the rotation is transmitted to the fastening ring531through the transmission link rod533, and the fastening ring531is rotated in synchronization with the rotating plate532.

The workpiece holding base part460holds the workpiece W to be measured in the measurement area of the micrometer (measuring device)300. The workpiece holding base part460includes a supporting column461and a workpiece placing plate462. The supporting column461is attached to the first long side part411. The workpiece placing plate462is an L-shaped plate having a plane parallel to the XY plane, and is fixed to the supporting column461. The position of the supporting column461is adjusted along the second long side part412in order for the workpiece W held by the workpiece holding base part460to be in the measurement area of the micrometer (measuring device)300, and the height (position in the Z-axis direction) of the workpiece placing plate462is adjusted in order for a part to be measured of the workpiece W to be sandwiched between the anvil320and the spindle330.

The surface of the workpiece placing plate462on which the workpiece W is placed is flat, and the workpiece W placed on and held by this placing surface easily changes its position and posture when pushed by the spindle330. In other words, when the spindle330comes into contact with the workpiece W, the workpiece W is pushed toward the anvil320and slides on the placing surface until the workpiece W comes into contact with the anvil320. Then, when the workpiece W comes into contact with the anvil320, the movement of the workpiece W is restricted, and the workpiece W is sandwiched between the anvil320and the spindle330. At this time, the workpiece W changes its posture, causing the measuring surface of the anvil320and the contact surface of the workpiece W to be in close contact and the measuring surface of the spindle330and the contact surface of the workpiece W to be in close contact. In this manner, the workpiece W is not fixed and is allowed to move to some extent on the placing surface, which allows the part to be measured of the workpiece W to be sandwiched between the anvil320and the spindle330without any gap.

If the friction of the placing surface of the workpiece placing plate462is too small, the workpiece W can slip and fall down when placed by the robot hand140or a human hand, or deviate from the orientation or posture in which it was placed, and the placing surface of the workpiece placing plate462is desirably unevenly machined to generate some friction with the workpiece W. The placing surface is desirably machined to allow the workpiece W to change its position and posture when a force less than a set measurement pressure (about 1 N to 5 N) is applied to the workpiece W while the workpiece is on the placing surface.

The vibration motor (vibration actuator)600is attached to the micrometer300. Here, the vibration motor600is attached to one end surface of the U-shaped frame310of the micrometer300, but the vibration motor600can be attached to any position of the micrometer300(measuring device), and may be attached to the spindle side frame of the micrometer300. In the exemplary embodiment, the vibration motor600is attached to the outer surface of the micrometer300(measuring device) because the commercially available micrometer300is to be used in the automatic measuring apparatus100in its original form, but the vibration motor600may be embedded in an electronic unit or frame part. The vibration actuator is only required to generate vibration, and may be a what is called an eccentric motor, a piezoelectric actuator, a rotary vibration actuator, or a linear vibration actuator. The vibration motor600may incorporate a dedicated small battery, or may be powered by the micrometer300. The vibration motor600is connected to the control unit800via a wireless or wired connection and is driven by control signals from the control unit800.

The control unit800includes an arithmetic unit and a memory device that are constituted by a computer including a central processing unit (CPU), a read-only memory (ROM), and a random access memory (RAM), and a motor drive circuit that generates drive signals (voltage signals or current signals) and applies them to the motor520. The control unit800controls the rotational drive of the motor520to control the forward/backward movement of the spindle330. The control unit800further drives the vibration motor600at an appropriate timing to facilitate a change in the posture of the workpiece W. In addition, the control unit800also samples measurement values from the micrometer300(displacement detection part350) at an appropriate timing. The control operation of the control unit800will be described later with reference to a flowchart.

Explanation of Operation

The operation of the automatic micrometer device200is described below.

FIGS.4and5are flowcharts for explaining the measurement operation of the automatic micrometer device200.

When detecting that the workpiece W is set on the workpiece placing plate462by the robot arm part130(ST110: YES), the control unit800performs preset (programmed) motor drive control. The control unit800rotates the motor520forward at a relatively high speed to move the spindle330forward toward the anvil320(ST120). The rotational speed of the motor520at this time is, for example, 180 rpm (or about 100 rpm to 200 rpm).FIG.6shows an example of the spindle330moving forward.

In ST120, it is desirable to increase the rotational speed as high as possible in terms of reducing a measurement time. However, if the rotational speed is too high, the workpiece W can be damaged when the spindle330comes into contact with the workpiece W. In addition, if the rotational speed is too high, the centrifugal force generated in the power transmission part530becomes high, and which makes the motor torque large. Then, due to the configuration of detecting the contact between the spindle330(anvil320) and the workpiece W by the magnitude of the torque, the torque detection function can erroneously detect the contact between the spindle330(anvil320) and the workpiece W. Therefore, it is desirable to first set a torque threshold for detecting the contact between the spindle330and the workpiece W, and then rotate the motor520at a speed that does not exceed this torque threshold.

As the spindle330moves forward toward the anvil320, the spindle330comes into contact with the workpiece W. Since the workpiece W is not fixed on the workpiece placing plate462, the workpiece W is pushed by the spindle330and brought into contact with the anvil320.

FIG.7is a view showing an example of the workpiece W sandwiched between the anvil320and the spindle330. At the moment when the workpiece W is sandwiched between the anvil320and the spindle330, the motor torque increases, and the motor controller detects, through the torque detection function, that the spindle330has come into contact with the workpiece W, in other words, that the anvil320and the spindle330have come into contact with the workpiece W (ST130: YES).

When detecting that the spindle330has come into contact with the workpiece W, the control unit800immediately rotates the motor520in reverse for a predetermined number of revolutions at a relatively high speed to move the spindle330backward (ST140). The number of the reverse rotation revolutions is, for example, 180 rpm. The number of the reverse rotation revolutions is, for example, 0.5 rpm. This rotational speed (180 rpm) is an example, and the rotational speed during the forward movement (ST120) may be the same as or different from the rotational speed during the reverse rotation (ST140).

Here, the spindle330is not “stopped” or “slowed down”, but is desirably moved backward once with a relatively high reverse rotation. The first reason is to ensure that the spindle330does not dig into the workpiece W. Transmitting a control signal to move the spindle330backward once rather than simply stopping the spindle330ensures that the spindle330does not dig into the workpiece W. Although the constant pressure mechanism is activated when the measurement pressure is generated, it is necessary to secure the operating distance of the spindle330in order to activate the constant pressure mechanism while the spindle330is constantly moved forward at the same speed. For this reason, it is desirable to move the spindle330backward once to ensure the same operation of applying the measurement pressure to the workpiece W at all times.

Then, the spindle330is moved forward again to bring the spindle330in close contact with the workpiece W at the predetermined measurement pressure (ST150, ST160). At this time, the vibration motor600is driven in conjunction with the forward re-movement of the spindle330(ST141). In other words, after the first high-speed backward movement step (ST140) and before the start of the low-speed forward movement step (ST150), the control unit800starts the drive of the vibration motor600(ST141).

The motor520is rotated forward at a relatively low speed to move the spindle330forward toward the anvil320(ST150, ST160). As the low-speed forward movement step (ST150), the motor520is rotated forward at a relatively low speed. The number of revolutions is the same as that in the previous backward movement (ST140).

Here, 0.5 revolutions at 9 rpm are used, for example. The workpiece W is slowly pushed to ensure the contact between the workpiece W and the anvil320and between the workpiece W and the spindle330. At this time, the vibration of the vibration motor600is transmitted to the micrometer300, causing the spindle330and the anvil320to vibrate slightly. This reduces the friction at the interface between the workpiece W and the spindle330and between the workpiece W and the anvil320, and facilitates a change in the posture of the workpiece W.

Then, as a measuring-surface contact step (ST160), the motor520is rotated forward at a relatively low speed (ST160). The number of revolutions is assumed to be, for example, equivalent to the number of revolutions of the thimble part340(the number of revolutions of the spindle330) corresponding to the time from when the workpiece W comes into contact with the anvil320and the spindle330until the constant pressure mechanism is activated. Here, 0.5 revolutions at 9 rpm are used. (This is the same as ST150, but the rotational speed and the number of revolutions may be appropriately changed.) Here, the constant pressure mechanism is slowly activated once to ensure that the contact surfaces between the workpiece W and the anvil320, and the contact surfaces between the workpiece W and the spindle330are securely fitted with each other (brought into close contact with each other).

Now, the workpiece W is firmly sandwiched between the anvil320and the spindle330in this state. The drive of the vibration motor600is stopped (ST161).

As a measurement-pressure application step (ST170), the motor520is rotated forward at a relatively high speed. For example, 3 revolutions at 180 rpm are used. At this time, the constant pressure mechanism is activated again, and the predetermined measurement pressure is applied.

Note that, the motor rotational speed in this step (ST170) may be higher (for example, 150 rpm to 250 rpm). Since the contact surfaces between the workpiece W and the spindle330have been fitted in the previous step (ST160), the contact surfaces between the spindle330(anvil320) and the workpiece W are now firmly fitted. Therefore, it is unlikely that the spindle330(anvil320) digs into the workpiece W. In addition, since the spindle330(anvil320) and the workpiece W are already in contact with each other, there is no such limitation that will cause the torque detection function to erroneously detect the contact between the spindle330(anvil320) and the workpiece W. The number of revolutions in this step (ST170) is the number of revolutions required to activate the constant pressure mechanism, which is about 1.5 to 3.5 revolutions and depends on the specifications of the micrometer300(constant pressure mechanism) to be used.

At the moment when the constant pressure mechanism is activated in the measurement-pressure application step (ST170), the micrometer300samples a measurement value (ST180). The sampled measurement value (measurement data) is output externally via wired or wireless communication, and the measurement data is collected and processed by an external personal computer (PC) or a data processing device via the control unit800.

Up to this point, one measurement value has been acquired, the control unit800rotates the motor520in reverse at a relatively high speed to move the spindle330backward. This measurement operation is continued while the workpiece W is replaced.

With the automatic measuring apparatus100according to the present exemplary embodiment, it is possible to almost automate the measurement operation for the workpiece W. The automatic micrometer device200according to the present exemplary embodiment automates the micrometer300, which is a small-sized measuring device (small-sized measuring tool). Since it is expected that a typical factory already owns the micrometer300, automation of the micrometer300can be achieved simply by preparing the measuring-device support frame part400, the workpiece holding base part460, the automatic operation part500, and the vibration motor600. In other words, the cost required to introduce automatic measurement can be kept extremely low, which contributes greatly to reducing labor shortages.

The micrometer300is a contact type and has extremely high measurement stability. In addition, the micrometer300has a long history and is widely used in the world, making it the most familiar measuring device for measurement operators. Therefore, operators are fully familiar with the necessary handling of the micrometer300, such as calibration work, and there is almost no need to learn or train difficult work procedures.

Various automatic measuring apparatuses have been proposed in the past, but most of them used non-contact measuring tools. For example, many of them used air micrometers, laser scan micrometers, or the like. However, such non-contact measurement devices are extremely expensive and somewhat difficult to maintain. In this respect, the automatic micrometer device200according to the present exemplary embodiment that can automate the micrometer300has the advantage of being inexpensive and easy to handle.

One of the reasons why it has been difficult to automate the micrometer300, which is a representative of small-sized measuring devices (small-sized measuring tools), is that it was difficult to properly sandwich the workpiece W from both sides and fit the contact surfaces (measuring surfaces). In this respect, the relative position between the workpiece W and the micrometer300is not fixed in the present exemplary embodiment, and the position and posture can be changed by a force lower than the measurement pressure. In addition, the constant pressure mechanism in the micrometer300and the torque detection mechanism in the motor520are comprehensively used to move the spindle330forward and backward in several steps. In particular, the step of firmly fitting (being in close contact between) the measurement surfaces (contact surfaces) (ST160) and the step of applying the predetermined measurement pressure (ST170) are performed. Furthermore, the vibration motor600is driven at an appropriate timing to facilitate a change in the posture of the workpiece W, which ensures the close contact between the workpiece W and the spindle330and between the workpiece W and the anvil320. Normally, when a thimble is manually rotated, a measurement is performed by rotating the thimble at a constant speed and applying a constant pressure at the same constant rotation, but not by moving the thimble backward or by operating the constant pressure mechanism in two slow and fast stages. However, through repeated experiments under different conditions, control steps different from the manual operation have been devised, and it is possible to acquire stable measurement values even in automatic measurement. This makes it possible to automate the micrometer300. In addition, the workpiece W can always be measured with the same operation by the motor control, and this eliminates a problem of differences in measurement values caused by the skill level or movement habits of each operator.

Although the contact between the workpiece W and the spindle330is detected by torque detection, the contact between the spindle330(movable element) and the workpiece W can also be detected by the displacement detection part350from a detection value. For example, by contrasting the number of times drive pulses are transmitted to the motor520with the displacement of the spindle330, it may be determined that the spindle330comes into contact with the workpiece W when the spindle330stops without moving forward as expected for a predetermined number of consecutive times.

Although the vibration motor600installed on the measuring device (micrometer) is described as an example, the vibration motor may be installed on the workpiece holding base part to provide vibration to the workpiece W. Alternatively, the vibration motor may be installed on both the measuring device and the workpiece holding base part.

Second Exemplary Embodiment

A second exemplary embodiment of the present invention is described below.

The present exemplary embodiment describes an automatic inside-diameter measuring apparatus2100that automates measurement of the inside diameter (hole diameter) of a hole to be measured.

FIG.8is an overall external view of the automatic inside-diameter measuring apparatus2100.

The automatic inside-diameter measuring apparatus2100includes a measuring-apparatus main body2110and a control unit2140that controls the overall operation.

Measuring-apparatus Main Body

The measuring-apparatus main body2110includes an electric inside-diameter measuring unit2120that measures the diameter of a hole to be measured and an articulated robot arm part2130as a moving means to move the electric inside-diameter measuring unit2120.

The electric inside-diameter measuring unit2120is attached to and held by a hand part2131, which is the tip of the robot arm part2130. The electric inside-diameter measuring unit2120is inserted into the inside of a hole to be measured to acquire a measurement value of the inside diameter. The electric inside-diameter measuring unit2120further has a function for autonomously adjusting its own position and posture to accurately measure the hole to be measured.

The configuration of the electric inside-diameter measuring unit2120is described.

FIG.9is an external perspective view of the electric inside-diameter measuring unit2120from a slightly front side.

FIG.10is an external perspective view of the side of the electric inside-diameter measuring unit2120from a slightly rear side.

FIG.11is a front view of the electric inside-diameter measuring unit2120.

The electric inside-diameter measuring unit2120includes an electric inside-diameter measuring device2200, a measuring-device support frame part2300, a floating joint part (floating joint mechanism part)2400, a restriction means2500, a collision detection part2600, a force sensor part2132, and a vibration motor (vibration actuator)2700.

The electric inside-diameter measuring device2200is an existing manual inside-diameter measuring device (for example, Hole test) whose rod feed is motorized.

FIG.12is a cross-sectional view of the internal structure of the electric inside-diameter measuring device2200.

The electric inside-diameter measuring device2200includes a cylinder case part (fixed element)2210, a rod2230, a thimble part2240, a contact point (movable element)2250, a displacement detection part2260, an outer case part2270, a display unit2273, and an electric drive unit (automatic operation part)2280.

The cylinder case part2210is a case having a cylindrical shape as a whole.

The rod2230moves axially forward and backward inside the cylinder case part2210. The cylinder case part2210includes an upper cylinder case part2211constituting an upper part, a middle cylinder case part2213constituting a middle part, a lower cylinder case part2214constituting a lower part, and a head cylinder part2215constituting a measuring head part2220. The middle cylinder case part2213is attached to the lower end of the upper cylinder case part2211, the lower cylinder case part2214is attached to the lower end of the middle cylinder case part2213, and the head cylinder part2215is attached to the lower end of the lower cylinder case part2214.

The rod2230is a longitudinal rod-shaped body as a whole. The rod2230includes an upper rod2231and a lower rod2233. The upper rod2231is a spindle and has a feed screw (male thread) on the outer surface of its base end (upper end side). The upper cylinder case part2211has a female thread, and the feed screw is screwed with the female thread.

The thimble part2240is provided at the base end (upper end side) of the upper rod2231. The thimble part2240includes a thimble sleeve2241, a ratchet sleeve2242, and a coil spring2243. The thimble sleeve2241is fitted externally to the base end of the upper rod2231(rod2230) by the fit of a tapered surface2251and is adhered to the base end of the upper rod2231(rod2230). The ratchet sleeve2242is a cylindrical body provided above the thimble sleeve2241, and the coil spring2243is interposed between the thimble sleeve2241and the ratchet sleeve2242. A push screw is screwed onto the base end face of the upper rod2231, and the ratchet sleeve2242is pushed by the head flange of the push screw. At this time, the coil spring2243is sandwiched between the ratchet sleeve2242and the thimble sleeve2241.

Between the ratchet sleeve2242and the thimble sleeve2241, a ratchet mechanism (not shown) is provided. Here, the rotation direction of the ratchet sleeve2242, the thimble sleeve2241, or the rod2230in the direction of feeding the rod2230downward (in the direction of protruding the contact point2250) is a positive rotation direction. In contrast, the rotation direction of the ratchet sleeve2242, the thimble sleeve2241, or the rod2230in the direction of feeding the rod2230upward (the direction in which the contact point2250is moved backward) is a negative rotation direction. The ratchet mechanism allows the ratchet sleeve2242to idle against the thimble sleeve2241in the positive rotation direction, and does not allow the ratchet sleeve2242to idle in the negative rotation direction.

When the ratchet sleeve2242is subjected to (positive) rotary operation, the rotation of the ratchet sleeve2242is transmitted to the rod2230via the coil spring2243and the thimble sleeve2241. There is an upper limit to the force (rotational force) transmitted from the ratchet sleeve2242to the rod2230. That is, if an attempt is made to rotate the rod2230with a force exceeding the frictional force (static frictional force) acting between the ratchet sleeve2242, the coil spring (load regulating elastic body)2243, and the thimble sleeve2241, the ratchet mechanism causes the ratchet sleeve2242to idle against the thimble sleeve2241. The thimble part2240constitutes a constant pressure mechanism that regulates the upper limit of the force (measuring force) acting between an object to be measured and the contact point2250. Conversely, a predetermined force (measuring force), which can be defined by the indentation amount of the push screw, is generated between the object to be measured and the contact point2250, and when the contact point2250applies the predetermined force (measuring force) to the object to be measured, the reaction force is applied to the contact point2250, that is, the electric inside-diameter measuring device2200.

The lower rod2233is provided inside the head cylinder part2215.

The upper end of the lower rod2233is in contact with the lower end of the upper rod2231. The lower end of the lower rod2233is conical.

The contact point2250is provided in the head cylinder part2215to move forward and backward in a direction perpendicular to the axial direction of the rod2230. Three contact points2250are provided at 120° intervals in the head cylinder part2215. Each contact point2250has a thin round shaft tip2252made of carbide at its outer end. When each contact point2250moves forward in the protruding direction, the round shaft tip2252is brought into contact with the inner wall of the object to be measured.

The inner end side of each contact point2250is formed with a tapered surface2251, and the tapered surface2251is brought into contact with the conical surface of the lower rod2233. The conical surface of the lower rod2233and the tapered surface2251of each contact point2250constitute a displacement direction conversion means for changing the direction of force and displacement to a right angle.

Inside the head cylinder part2215, a spring (for example, plate spring)2216corresponding to each contact point2250is provided, one end of the plate spring2216is fixed to the inner wall of the head cylinder part2215, and the other end of the plate spring2216is fixed to the contact point2250. Each plate spring2216biases the corresponding contact point2250in the direction of being moved into the head cylinder part2215. When the rod2230is pulled upward by an external force, the force of each plate spring2216causes the contact point2250to follow the rod2230and to move in the direction of entering the head cylinder part2215.

The part of the head cylinder part2215(the tip end part of the inside-diameter measuring device) where the contact point2250is protruded and retracted is also referred to as the measuring head part2220.

The displacement detection part2260is provided inside the middle cylinder case part2213to detect displacement of the upper rod2231. The displacement detection part2260is what is called a rotary encoder including a rotor2261provided to rotate integrally with the upper rod2231, a stator2262that counts the revolutions of the rotor2261, and a signal processing calculation unit (not shown). The detection method of the displacement detection part2260is not particularly limited, and examples of the displacement detection part2260include a photoelectric encoder, a capacitive encoder, an electromagnetic induction encoder, a magnetic encoder, and the like.

The outer case part2270is an outer cylinder part that covers the outside of the cylinder case part2210. The outer case part2270is provided to cover the electric inside-diameter measuring device2200above the middle of the lower cylinder case part2214. The outer case part2270is constituted by two parts of an outer case body part2271that accommodates the middle part thereinside and an outer case upper part2272that accommodates the upper part thereinside. The outer case body part2271is a cylindrical body that covers the entire middle cylinder case part2213corresponding to the middle part of the electric inside-diameter measuring device2200, as well as the upper end side of the lower cylinder case part2214and the lower end side of the upper cylinder case part2211.

The outer case upper part2272is a cylindrical body connected to the upper end of the outer case body part2271and covers the upper cylinder case part2211constituting the upper part of the electric inside-diameter measuring device2200.

The display unit2273includes a display part2274and is attached to the side openings of the middle cylinder case part2213and the outer case body part2271to close the openings. The display part2274is the digital display part2274(for example, a liquid crystal display panel or an organic EL display panel) fitted into the central area of the display unit2273. The display part2274shows the measurement value calculated by the signal processing calculation unit (not shown) and the like.

The display unit2273is provided with a connector, and the measurement value calculated by the signal processing calculation unit (not shown) is output externally.

The electric drive unit2280is a drive unit that rotates the ratchet sleeve2242of the thimble part2240. The electric drive unit2280is attached above the outer case upper part2272. The electric drive unit2280is, for example, a motor, and the rotational output of the motor is transmitted to the ratchet sleeve2242via a power transmission mechanism (a gear train, a coupling belt, a coupling shaft, a coupling link, or the like).

The operation of the electric inside-diameter measuring device2200is basically the same as that of an existing manual inside-diameter measuring device, except that the rod is fed by the electric drive unit2280.

When the rod2230is moved forward and backward by electric power, the contact points2250are protruded from and retracted in the head cylinder part2215in accordance with the movement of the lower rod2233. By detecting the displacement (position) of the rod2230when the three contact points2250are in even contact with the inner wall of a hole to be measured, the inside diameter of the hole to be measured is acquired as the measurement value.

The measuring-device support frame part2300is an L-shaped member in side view and includes a support column part2310and a support base part2320. The support base part2320is attached at right angles to the lower end of the vertical support column part2310.

The support column part2310is adjacent and parallel to the electric inside-diameter measuring device2200. The restriction means2500is provided on the front face of the support column part2310, and the restriction means2500switches between holding and releasing of the electric inside-diameter measuring device2200. This point is described later.

The support base part2320is provided so as to be bent in an L-shape from the lower end of the support column part2310toward the electric inside-diameter measuring device2200. The support base part2320includes a first insertion hole2321through which the head cylinder part2215of the electric inside-diameter measuring device2200is inserted. The electric inside-diameter measuring device2200is attached in such a manner that the upper part above the lower cylinder case part2214is placed on the support base part2320via the floating joint part2400while the head cylinder part2215is inserted in the first insertion hole2321.

Floating Joint Part2400

The floating joint part2400is described below.

FIG.13is an exploded view of the floating joint part2400.

FIG.14is a cross-sectional view of the floating joint part2400.

The floating joint part2400is a joint (or coupling mechanism) that allows rotation of the electric inside-diameter measuring device2200with respect to the support frame part2300and also allows horizontal translation of the electric inside-diameter measuring device2200with respect to the support frame part2300.

If there is an axial misalignment (inclination and distortion) between the electric inside-diameter measuring device2200and the hole to be measured, the floating joint part2400allowing rotation and translation allows the electric inside-diameter measuring device2200to autonomously adjust its own position and posture.

The floating joint part2400includes a rotation-allowing mechanism part2410and a translation-allowing mechanism part2420.

The rotation-allowing mechanism part2410includes a first spring holder2411, a coil spring (flexible body or elastic body)2412, and a second spring holder2413. The first spring holder2411and the second spring holder2413are roughly ring-shaped, with a flange extending radially outward from each ring.

As shown in the cross-sectional view inFIG.14, the first spring holder2411is fitted externally to the outer surface of the lower cylinder case part2214at the upper side of the lower cylinder case part2214, and the first spring holder2411is thereby fixedly attached to the electric inside-diameter measuring device2200. Here, the lower end face of the outer case body part2271and the first spring holder2411are continuously integrated, and the position where the first spring holder2411is attached to the electric inside-diameter measuring device2200is fixedly regulated.

As an exemplary embodiment, the first spring holder2411may be installed in such a manner that the height (position) of the first spring holder2411corresponds to the height (position) of the center of gravity of the electric inside-diameter measuring device2200. For example, the first spring holder2411is installed in such a manner that the height (position) of the first spring holder2411is approximately the same as the height (position) of the center of gravity of the electric inside-diameter measuring device2200. Alternatively, the first spring holder2411may be installed in such a manner that the height (position) of the first spring holder2411is within 20%, 15%, 10%, or 5% (of the length of the electric inside-diameter measuring device2200in the vertical direction) above or below the height (position) of the center of gravity of the electric inside-diameter measuring device2200.

The upper end of the coil spring2412is received by the first spring holder2411with the coil spring2412receiving the lower cylinder case part2214(electric inside-diameter measuring device2200) thereinside. The lower end of the coil spring2412is received by the second spring holder2413.

As an exemplary embodiment, instead of one coil spring2412, a plurality of elastic bodies or springs may be provided to surround the electric inside-diameter measuring device2200(at equal angular intervals).

Although it is better for the spring to have a larger diameter (for the distance between the spring and the center axis of the electric inside-diameter measuring device2200to be larger) to support the electric inside-diameter measuring device2200, if the diameter of the spring is too large (the distance between the spring and the center axis of the electric inside-diameter measuring device2200is too large), the measurement pressure of the inside-diameter measuring device alone cannot autonomously adjust the inclination of the electric inside-diameter measuring device2200to align with the axis of the hole. If the diameter of the spring is to be increased (the distance between the spring and the center axis of the electric inside-diameter measuring device2200is to be increased), the spring constant (modulus of elasticity) should be decreased.

If the diameter of the spring is to be reduced (the distance between the spring and the center axis of the electric inside-diameter measuring device2200is to be reduced), the spring constant (modulus of elasticity) may be slightly increased. Although the elastic spring is described in the exemplary embodiment, the member coupling the first spring holder2411and the second spring holder2413may be a flexible member without elasticity instead of the coil spring2412, as long as the posture adjustment in the rotational direction of the electric inside-diameter measuring device2200can be allowed.

The second spring holder2413is coupled to the translation-allowing mechanism part2420. As shown in the cross-sectional view inFIG.14, a ring hole2414of the second spring holder2413has a slight length (height) in the axial direction, and the diameter of the ring hole2414is slightly larger than the cylinder case part2210(lower cylinder case part2214) of the electric inside-diameter measuring device2200to the extent that it allows the inclination of the electric inside-diameter measuring device2200. The ring hole2414may be a tapered hole in which the diameter of the ring hole increases toward the upper side or lower side.

The translation-allowing mechanism part2420includes a horizontal plate (translation body)2421and a ball roller2423.

The horizontal plate2421is a plate provided above the support base part2320. The horizontal plate2421includes a second insertion hole2422through which the electric inside-diameter measuring device2200(lower cylinder case part2214) is inserted. The second spring holder2413is fitted into the second insertion hole2422from above.

That is, the rotation-allowing mechanism part2410is on the horizontal plate2421, and the electric inside-diameter measuring device2200is supported by the rotation-allowing mechanism part2410. In other words, the electric inside-diameter measuring device2200is supported on the horizontal plate2421with the rotation-allowing mechanism part2410therebetween.

The ball roller2423is disposed on the upper face of the support base part2320. Here, four ball rollers2423are installed at 90-degree intervals around the first insertion hole2321and the second insertion hole2422, and the horizontal plate2421is placed on the ball rollers2423.

The horizontal plate2421placed on the ball rollers2423can move horizontally with very little force, almost without friction. On the other hand, in order to deform the coil spring2412(elastic body) as the rotation-allowing mechanism part2410, a force is required to resist the elastic force. Therefore, in the present exemplary embodiment, when a force (rotational or translational force) acts on the electric inside-diameter measuring device2200, the translation-allowing mechanism part2420has relative priority in displacement.

The operation of adjusting the position and posture of the electric inside-diameter measuring device2200by the effects of the floating joint part2400is described with reference toFIGS.15to19. For example,FIG.15shows a case assuming that a hole to be measured has been machined with a deviation from the design value and that the hole that should have been drilled vertically has an inclination and slightly deviates from the position of the design value to the right in the drawing. The electric inside-diameter measuring unit2120is moved to the hole by the robot arm part2130, and the measuring head part2220is inserted into the hole. Even if the drive of the robot arm part2130is accurately controlled, there is a position and angle deviation between the axis of the electric inside-diameter measuring device2200and the axis of the hole to be measured, because the hole to be measured deviates from the design value.

Now, in order to accurately measure the inside diameter of the hole to be measured, all the three contact points2250need to be brought into even contact with the inside wall of the hole to be measured. First, the electric drive unit2280drives the rod2230to move the rod2230downward. Then, the tip (cone) of the lower rod2233protrudes the contact points2250, and one of the three contact points2250closer to the inner wall of the hole to be measured is brought into contact with the inner wall of the hole to be measured. As the lower rod2233continues to protrude the contact points2250, a reaction force is applied to the contact points2250from the inside wall of the hole. This reaction force causes the electric inside-diameter measuring device2200to be pushed in the opposite direction. The reaction force pushes near the lower end of the lower rod2233from the contact points2250, but the displacement of the horizontal plate2421occurs first before the deformation of the coil spring2412of the rotation-allowing mechanism part2410. Thus, as shown inFIGS.16and17, the displacement of the horizontal plate2421first absorbs the axial misalignment between the electric inside-diameter measuring device2200and the hole to be measured. The first insertion hole2321of the support base part2320has a diameter large enough to allow horizontal movement of the electric inside-diameter measuring device2200.

At the time ofFIG.16(FIG.17), the axal inclination is still misaligned between the electric inside-diameter measuring device2200and the hole to be measured. When the lower rod2233continues to protrude the contact points2250from the state shown inFIG.16(FIG.17), the tips (round shafts) of the contact points2250are brought into contact with the inner wall of the hole, and at this time (due to the length of the three round shafts), the reaction force applied to the electric inside-diameter measuring device2200from the inner wall of the hole to be measured has a moment of rotation. At this time, the reaction force from the inner wall of the hole deforms the coil spring2412of the rotation-allowing mechanism part2410as shown inFIGS.18and19, and the inclination of the electric inside-diameter measuring device2200is adjusted to align the axis of the electric inside-diameter measuring device2200with the axis of the hole to be measured. The ring hole2414of the second spring holder2413allows the inclination of the electric inside-diameter measuring device2200.

Eventually, when the three contact points2250push against the inner wall of the hole to be measured with the predetermined measurement pressure, the floating joint part2400(the rotation-allowing mechanism part2410and the translation-allowing mechanism part2420) allows the electric inside-diameter measuring device2200to autonomously adjust its own position and posture to accurately measure the inside diameter of the hole to be measured. In other words, once the robot arm part2130is able to insert the measuring head part2220of the electric inside-diameter measuring device2200into the hole to be measured, the inside diameter of the hole can be accurately measured through automatic posture adjustment without the need for manual sensory adjustment or advanced feedback control.

The restriction means2500is provided to the support frame part2300to hold and support the electric inside-diameter measuring device2200. The restriction means2500includes two clamping pieces2510that clamp the electric inside-diameter measuring device2200from a direction perpendicular to the axis as shown, for example, inFIGS.9and10. Here, the clamping pieces2510clamp the outer case body part2271from both sides. The clamping pieces2510are movable, and the restriction means2500can switch between a hold state of the electric inside-diameter measuring device2200and a release state in which the holding is released.

Even though the clamping pieces2510are opened to release the electric inside-diameter measuring device2200, the gap between each clamping piece2510and the electric inside-diameter measuring device2200is preferably limited to a predetermined upper limit (about 5 mm or 10 mm) to regulate any large displacement (translation or inclination) of the electric inside-diameter measuring device2200beyond the limit.

The electric inside-diameter measuring device2200is placed on the support base part2320via the floating joint part2400. In order for the electric inside-diameter measuring device2200to be able to autonomously adjust its posture according to the hole to be measured with its own measurement pressure, the floating joint part2400needs to be soft (softness or flexibility). Therefore, if the electric inside-diameter measuring device2200is simply placed on the floating joint part2400, the electric inside-diameter measuring device2200can swing unsteadily, be inclined greatly, or fall down, depending on the rigidity (softness) of the floating joint part2400. From a safety point of view, it is undesirable that the electric inside-diameter measuring device2200swings or falls down. In addition, if the posture of the electric inside-diameter measuring device2200is not fixed, the position of the measuring head part2220is unstable, and the robot arm part2130cannot be able to insert the measuring head part2220of the electric inside-diameter measuring device2200into the hole to be measured.

For these reasons, when the electric inside-diameter measuring device2200is not inserted in a hole to be measured, the restriction means2500clamps and holds the electric inside-diameter measuring device2200. Then, when the measuring head part2220of the electric inside-diameter measuring device2200is inserted in a hole to be measured, the restriction means2500releases the electric inside-diameter measuring device2200in order for the electric inside-diameter measuring device2200to be able to autonomously change and adjust its posture (to perform autonomous adjustment) by the floating joint part2400.

The collision detection part2600detects that the electric inside-diameter measuring device2200has collided with something with a force greater than a predetermined force.

FIG.20is an exploded view of the collision detection part2600.

FIG.21is a perspective view of the collision detection part2600when viewed from a slightly rear side.

The collision detection part2600is provided between the rear side of the support column part2310and the hand part2131of the robot arm part2130. Here, the collision detection part2600detects that a large force is applied to the electric inside-diameter measuring device2200in the direction of being pushed upward from below in the Z direction (vertical direction) when the electric inside-diameter measuring device2200approaches an object (for example, the workpiece W) from above the object and collides with the workpiece W. That is, the collision detection direction of the collision detection part2600is almost parallel to the direction when the electric inside-diameter measuring device2200approaches a hole to be measured.

The collision detection part2600includes a fixed plate2601, a mounting plate2602, a linear guide2610, a biasing means2620, and a contact sensor2630.

The fixed plate2601is attached directly or indirectly to the hand part2131of the robot and is fixedly provided to the hand part2131. Here, the force sensor part2132is provided between the hand part2131of the robot and the collision detection part2600. Therefore, the collision detection part2600is attached to the hand part2131of the robot arm part2130via the force sensor part2132.

The mounting plate2602is attached directly or indirectly to the rear face of the support column part2310and is fixedly provided to the support column part2310(support frame part2300). The linear guide2610is disposed between the fixed plate2601and the mounting plate2602and guides the moving direction of the mounting plate2602with respect to the fixed plate2601in the vertical direction. The linear guide2610includes a groove frame body2611having a groove in the vertical direction and a slide body2612that slides in the groove of the groove frame body2611in the vertical direction. Here, the groove frame body2611is attached to the fixed plate2601, and the slide body2612is attached to the mounting plate2602.

The biasing means620is two coil springs2620.

One end of each coil spring2620is fastened to the fixed plate2601, and the other end of the coil spring2620is fastened to the mounting plate2602. Each coil spring2620constantly biases the mounting plate2602in the direction of pulling down the mounting plate2602with respect to the fixed plate2601. That is, the position of the mounting plate2602when the mounting plate2602is lowered vertically downward with respect to the fixed plate2601by its own weight, the weight of the electric inside-diameter measuring device2200, and the biasing force of the coil spring2620is a reference position.

The contact sensor2630includes a contact detection block2631disposed on the fixed plate2601, and a ball plunger2632provided to the mounting plate2602. As shown inFIG.21, when the mounting plate2602is at the reference position with respect to the fixed plate2601, the ball plunger2632on the mounting plate2602is in contact with (fitting into) the contact detection block2631.

Here, it is assumed that, for example, the position of a hole machined in a workpiece W deviates significantly from the design value. In this state, when the robot arm part2130attempts to insert the electric inside-diameter measuring device2200into the hole to be measured from above, the measuring head part2220of the electric inside-diameter measuring device2200collides with the workpiece W. The electric inside-diameter measuring device2200(measuring head part2220) deviates from the hole and collides with the workpiece W, and the electric inside-diameter measuring device2200(measuring head part2220) is pushed further into the workpiece W. Then, when a force exceeding the gravitational force of the electric inside-diameter measuring device2200and the biasing force of the biasing means (coil springs)2620are applied to the collision detection part2600, the mounting plate2602slides upward and the ball plunger2632of the mounting plate2602is removed from the contact detection block2631. The contact sensor2630transmits a signal (collision detection signal) when the contact detection block2631detects the separation of the ball plunger2632(or when the contact detection block2631can no longer detect the contact of the ball plunger2632).

When the collision detection part2600detects that the electric inside-diameter measuring device2200has collided with something, the control unit2140immediately stops the operation of the robot arm part2130.

Force Sensor Part2132

The force sensor part2132is, for example, a 6-axis (forces in three orthogonal axial directions and rotational forces around the axes) force sensor. While the collision detection part2600is specialized to detect a force pushing up from below in the vertical direction (Z-direction), the force sensor part2132detects forces applied to the electric inside-diameter measuring device2200in all directions.

The articulated robot arm part2130is what is called a robot arm and moves the hand part2131, which is the tip of the robot arm part2130, three-dimensionally with the vertical and horizontal rotational drive axes. The hand part2131of the robot arm part2130is coupled to the support frame part2300via the force sensor part2132and the collision detection part2600. The force sensor part2132detects that the electric inside-diameter measuring device2200has collided with an object with an unexpected force exceeding a predetermined force in directions where the collision detection part2600does not detect collisions (that is, in directions other than the vertical direction (Z direction)). When the force sensor part2132detects an unexpected collision of the electric inside-diameter measuring device2200, the control unit2140immediately stops the operation of the robot arm part2130. This further ensures safety.

The vibration motor (vibration actuator)2700is attached to the electric inside-diameter measuring device2200. A mounting support2710is attached to the housing of the electric drive unit2280, and the vibration motor2700is installed above the electric drive unit2280by the mounting support2710. Here, the vibration motor2700is installed on the center axis of the electric inside-diameter measuring device2200and on the side away from the contact points2250. The vibration motor2700is installed on the central axis because it is convenient for balancing the overall weight, but the vibration motor2700may be installed off the central axis. In this case, it is preferable to attach a counterbalance so that the center of gravity of the inside-diameter measuring device does not deviate from the central axis line.

Here, the vibration motor2700is installed on the side away from the contact points2250because it is advantageous in terms of moment and it is considered that even a small vibration motor2700can provide sufficiently effective vibration to the contact points2250. The vibration motor2700may be installed as close to the contact point2250as possible. In this case, the vibration of the vibration motor2700is directly transmitted to the contact points2250. This is suitable, for example, when the vibration of the contact point2250needs to be finely controlled according to the material of the workpiece W.

FIG.22is a functional block diagram showing the control unit2140. The control unit2140includes a measurement operation control unit2150, a robot arm drive control unit2160, and a central control unit2170.

The measurement operation control unit2150controls the measurement operation of the electric inside-diameter measuring device2200.

The measurement operation control unit2150includes a restriction control unit2151, a motor drive control unit2152, and a measurement value acquisition unit2153.

The restriction control unit2151controls the opening and closing operation of the clamping pieces2510of the restriction means2500to control the timing of holding and releasing the electric inside-diameter measuring device2200. The motor drive control unit2152controls the drive of the electric drive unit2280and the vibration motor2700. The measurement value acquisition unit2153acquires a measurement value from the electric inside-diameter measuring device2200. That is, the measurement value acquisition unit2153receives a sensor value of the displacement detection part2260to acquire the measurement value of the inside diameter of a hole to be measured based on the displacement (position) of the rod2230.

The robot arm drive control unit2160controls the operation of the robot arm part2130. The central control unit2170integrally controls the measurement operation control unit2150and the robot arm drive control unit2160.

Control Operation of Automatic Inside-diameter Measuring Apparatus2100

The following describes a series of operations in which the measuring-apparatus main body2110(the electric inside-diameter measuring unit2120and the robot arm part2130) automatically measures the inside diameter of a hole to be measured under the control of the control unit2140.

FIG.23is a flowchart of the overall operation of automatic inside-diameter measurement (automatic inside-diameter measurement operation).

The workpiece W (object to be measured) having a hole (hole to be measured) is transferred by a conveyor belt or rail in a production line and brought to a predetermined position in front of the measuring-apparatus main body2110(the electric inside-diameter measuring unit2120and the robot arm part2130). The automatic inside-diameter measuring apparatus2100automatically and sequentially performs inside-diameter measurement on the inside diameters of holes that are designated (set) as objects to be measured among the workpieces W (objects to be measured) to be transferred. The position (coordinates) of a hole to be measured of each designated workpiece W (objects to be measured) has been set (stored) as part of a measuring part program in the central control unit2170. Alternatively, the inside-diameter measurement may be performed automatically and sequentially while searching for a hole to be measured by image recognition using the camera150or the like.

Here, it is assumed that the hole to be measured is a hole drilled to have an opening on the top face in the vertical direction, and that the electric inside-diameter measuring device2200is inserted into the hole from above while maintaining a roughly vertical orientation.

The automatic inside-diameter measurement operation has a hole insertion step (approaching step) (ST2100), a measurement step (ST2200), and a hole retraction step (retraction step) (ST2300).

The hole insertion step (ST2100) is a step of moving the electric inside-diameter measuring unit2120by the robot arm part2130and inserting the measuring head part2220of the electric inside-diameter measuring device2200into the hole to be measured (in other words, a step of approaching the workpiece W from above the workpiece W).

FIG.24is a flowchart showing an operating procedure of the hole insertion step (ST2100).

In the hole insertion step (ST2100), first, the destination (target coordinates) of the electric inside-diameter measuring device2200to be moved by the robot arm part2130is set to the hole to be measured (ST2110). Then, it is confirmed that the electric inside-diameter measuring device2200is restricted by the restriction means2500(ST2120). In the present exemplary embodiment, the state in which the restriction means2500restricts (holds) the electric inside-diameter measuring device2200is a default state (which may be paraphrased as a standard state or a reference state). However, since the holding by the restriction means2500can be released after the electric inside-diameter measuring device2200is maintained or replaced, the hold state needs to be confirmed. Then, when the electric inside-diameter measuring device2200is not held (ST2120: NO), the restriction control unit2151transmits a signal to perform a holding step (ST2130) by the restriction means2500. By restricting (holding) the electric inside-diameter measuring device2200while the robot arm part2130moves the electric inside-diameter measuring unit2120, the robot arm part2130can stably and safely move the electric inside-diameter measuring device2200.

The drive of the robot arm part2130is started (ST2140) to move the electric inside-diameter measuring unit2120, and the measuring head part2220of the electric inside-diameter measuring device2200is inserted into the hole to be measured.

At this time, for example, if the machining position of the hole to be measured has deviated from the design value, the electric inside-diameter measuring device2200(measuring head part2220) can unexpectedly collide with the workpiece W. In this regard, the robot arm drive control unit2160monitors signals from the collision detection part2600and the force sensor part2132(ST2150). If a collision between the electric inside-diameter measuring device2200(measuring head part2200) and the workpiece W is detected (ST2150: YES), the drive of the robot arm part2130is immediately stopped (emergency stop) (ST2180). Thereafter, the central control unit2170may report the abnormality to an operator.

When the measuring head part2220of the electric inside-diameter measuring device2200is inserted into the hole to be measured and reaches the target coordinates, the drive of the robot arm part2130is temporarily stopped (ST2170).

Next, the procedure proceeds to the measurement step (ST2200).

FIG.25is a flowchart showing an operating procedure of the measurement step (ST2200). In the measurement step (ST2200), first, the holding by the restriction means2500is released (ST2210) to put the electric inside-diameter measuring device2200in a release state. Thus, the electric inside-diameter measuring device2200is in a state of being supported by the support frame part2300via the floating joint part2400, which allows the electric inside-diameter measuring device2200to autonomously adjust its position and posture.

Then, the motor drive control unit2152transmits a drive signal to drive the electric drive unit2280. First, a first forward movement step (ST2220) is performed. The first forward movement step (ST2220) is a step of moving the contact points2250forward until the contact points2250are brought into first contact with the inner wall of the hole to be measured. The electric drive unit2280(for example, a motor) is driven to move the rod2230forward (in this case, downward) to move the contact points2250forward toward the inner wall of the hole. In the first forward movement step (ST2220), the motor is driven at high speed to move the rod2230and the contact points2250as fast as possible to improve measurement efficiency. (For example, if the rod2230is a screw feed, the rotational speed of the rod2230is 100 rpm to 200 rpm. In terms of the speed at which the rod2230or the contact points2250move, the speed may be 10 μm/s to 20 μm/s.)

As the contact points2250move forward toward the inner wall of the hole, the contact points2250are brought into contact with the inner wall of the hole.

Here, in the present exemplary embodiment, the number of contact points2250is three. If the axis of the electric inside-diameter measuring device2200and the axis of the hole to be measured are perfectly aligned, the three contact points2250can be brought into contact with the inner wall of the hole at the same time, but the axis of the electric inside-diameter measuring device2200and the axis of the hole to be measured are misaligned because of the driving error of the robot arm part2130and the machining error of the workpiece W. In this case, any one of the three contact points2250is brought into first contact with the inner wall of the hole. When any one of the three contact points2250has been brought into contact with the inner wall of the hole (ST2230: YES), the first forward movement step (ST2220) is immediately stopped, and the procedure proceeds to a first backward movement step (ST2240). The fact that the contact points2250have been brought into contact with the inner wall of the hole may be confirmed, for example, by calculating the motor torque from the applied current (applied voltage) of the motor to determine that (one of) the contact points (has) have been brought into contact with the inner wall of the hole when the torque exceeds a predetermined value.

In the first backward movement step (ST2240), the rod2230and the contact points2250are moved backward slightly in the opposite direction. This avoids the contact points2250from digging into the inner wall of the hole due to its momentum after the contact points2250have been brought into contact with the inner wall of the hole in the first forward movement step (ST2220). The distance for moving the contact points2250backward in the first backward movement step (ST2240) is very small, for example, 0.001 mm to 0.01 mm.

The speed of backward movement of the contact points2250in the first backward movement step (ST2240) may be as fast as possible. For example, if the rod2230is a screw feed, the rotational speed of the rod2230is 100 rpm to 200 rpm. In terms of the speed at which the rod2230or the contact points2250move, the speed may be 10 μm/s to 20 μm/s.

After the contact points2250are moved backward slightly in the first backward movement step (ST2240), the motor drive control unit2152start the drive of the vibration motor2700(ST2241). In other words, after the first backward-movement step (ST2240) and before the start of a second forward-movement step (ST2250), the motor drive control unit2152starts the drive of the vibration motor2700(ST2241).

In the second forward movement step (ST2250), the contact points2250are moved forward again. In the second forward movement step (ST2250), the contact points2250are moved forward slowly (at a low speed with fine movement).

The feed speed of the contact points2250in the second forward movement step (ST2250) is preferably slow (fine movement). For example, if the rod2230is a screw feed, the rotational speed of the rod2230is 10 rpm to 20 rpm. In terms of the speed at which the rod2230or the contact points2250move, the speed may be 1 μm/s to 2 μm/s.

The position and inclination of the electric inside-diameter measuring device2200are autonomously adjusted by the reaction force of the contact points2250pushing against the inner wall of the hole. The effects of the autonomous adjustment of the position and inclination of the electric inside-diameter measuring device2200by the floating joint part2400allowing translation and rotation are as described above. In addition, the vibration of the vibration motor2700is transmitted to the contact points2250(round shaft tips2252) at this time to cause the contact points2250(round shaft tips2252) to vibrate slightly. This reduces the friction at the interface between the contact points2250(round shaft tips2252) and the workpiece W (inner wall of the hole), and facilitates a change in the posture of the electric inside-diameter measuring device2200.

When the three contact points2250are in even contact with the inner wall of the hole with the predetermined measurement pressure, the autonomous adjustment of the position and inclination of the electric inside-diameter measuring device2200is completed. When the three contact points2250are in contact with the inner wall of the hole with the predetermined measurement pressure, the ratchet mechanism (constant pressure mechanism) is activated. That is, the electric drive unit2280rotates and drives the thimble part2240(ratchet sleeve2242) until the ratchet mechanism (constant pressure mechanism) is activated, which causes the contact points2250to be in even contact with the inner wall of the hole with the predetermined measurement pressure.

The second forward movement step (ST2250) can be rephrased as an autonomous adjustment step.

At this point, the motor drive control unit2152stops the drive of the vibration motor2700(ST2251).

In this state, the displacement detection part2260detects the displacement (position) of the rod2230. In acquiring the measurement value, the displacement (position) of the rod2230may be detected by the displacement detection part2260immediately after the drive of the vibration motor2700is stopped, or by performing the measurement-pressure application step again to driving the electric drive unit2280at a relatively high speed and activate the ratchet mechanism (constant pressure mechanism), the measurement value may be sampled when the constant pressure is applied. The measurement value acquisition unit2153acquires the inside diameter of the hole based on the displacement (position) of the rod2230(ST260).

After the measurement value is acquired, the contact points2250are moved backward in a second backward movement step (ST2270) to separate the contact points2250from the inner wall of the hole.

After the measurement step (ST2200), the electric inside-diameter measuring device2200is retracted from the hole to be measured in the hole retraction step (ST2300).FIG.26is a flowchart showing an operation procedure of the hole retraction step (ST2300). In the hole retraction step (ST2300), first, the electric inside-diameter measuring device2200is restricted (held) by the restriction means2500(ST2320), and then the robot arm part2130moves the electric inside-diameter measuring unit2120to be retracted from the hole (ST2330).

This completes the measurement of the inside diameter of one hole. Until measurement of all the holes to be measured is completed, ST2100to ST2300are repeated (ST2400).

In this manner, according to the present exemplary embodiment, the inside diameter of a hole can be automatically measured by the electric inside-diameter measuring unit2120(the electric inside-diameter measuring device2200and the robot arm part2130) without the need for a person to hold and operate the inside-diameter measuring device. In the case of inside diameter measurement, the three contact points2250need to be properly in close contact with the inner wall of the hole. However, due to the weight of the inside-diameter measuring device and the surface texture (roughness) of the workpiece W, the posture of the inside-diameter measuring device cannot be changed properly by the contact points2250(round shaft tip2252) sliding on the inner wall of the hole. In this respect, the vibration motor2700is driven at an appropriate timing in the present exemplary embodiment to reduce the friction between the contact point2250(round shaft tip2252) and the workpiece W (inner wall of the hole) and facilitate a change in the posture of the inside-diameter measuring device. This makes it possible to acquire stable measurement values even in automatic measurement.

In the above embodiment, the releasing step (ST2210) is performed before the first forward movement step (ST2220). The releasing step (ST2210) may be suspended until the contact between the contact point2250and the inner wall of the hole is detected (ST2230: Yes), and after the contact between the contact point2250and the inner wall of the hole is detected in the first forward movement step (ST2220), the releasing step (ST2210) may be performed before the first backward movement step (ST2240). Alternatively, the releasing step (ST2210) may be performed after the contact between the contact point2250and the inner wall of the hole is detected (ST2230: Yes) and the first backward movement step (ST2240) is performed. However, the start of the drive of the vibration motor2700is performed after the releasing step and before the second forward movement step (ST2250).

Third Exemplary Embodiment

A third exemplary embodiment of the present invention is described below.

In the second exemplary embodiment, the floating joint part2400, the restriction means2500, and the vibration motor2700are provided in the electric inside-diameter measuring unit2120. In the third exemplary embodiment, a floating joint part3400, a restriction means3500, and a vibration motor3700are provided in a workpiece holding part.

FIG.27is a diagram schematically showing the third exemplary embodiment.

In the third exemplary embodiment, the electric inside-diameter measuring device2200is directly attached to the measuring-device support frame part2300. The hand part2131of the robot arm part2130is coupled to the support frame part2300via the force sensor part2132and the collision detection part2600, which may be common to the second exemplary embodiment. Therefore, it is not assumed that the hand part2131of the robot arm part2130and the electric inside-diameter measuring device2200change their relative position or relative posture.

In the third exemplary embodiment, a workpiece holding base part (workpiece holding part)3000is provided.

The workpiece holding base part3000includes a base part3100, a workpiece installation stage3200, a floating joint part3400, a restriction means3500, and a vibration motor3700.

The workpiece W is placed on the workpiece installation stage3200. It is assumed that the workpiece W is transferred by a moving means (robot) for transferring workpieces, but a person may replace the workpiece W by hand. Here, it is assumed that the workpiece W does not slide and move on the surface of the workpiece installation stage3200. For example, if the surface of the workpiece installation stage3200has a non-slip finish and the workpiece W has some weight, the workpiece W does not easily move on the workpiece installation stage3200. Alternatively, the surface of the workpiece installation stage3200may have a recessed portion (recess) to receive the workpiece W, or a plurality of pins (protrusions) to restrict the movement of the workpiece W.

The configuration of the floating joint part3400is basically the same as that in the second exemplary embodiment. That is, the floating joint part3400including a translation-allowing mechanism part3420that allows translation of the workpiece installation stage3200with respect to the base part3100and a rotation-allowing mechanism part3410that allows rotation of the workpiece installation stage3200with respect to the base part3100. Between the base part3100and the workpiece installation stage3200, the translation-allowing mechanism part3420and the rotation-allowing mechanism part3410are provided in this order from a lower side.

A first spring holder3411is provided on the rear face of the workpiece installation stage3200, a second spring holder3413is provided on the upper face of a horizontal plate (translation body)3421, and a coil spring3412is interposed between the first spring holder3411and the second spring holder3413. A ball roller3423is disposed on the upper face of the base part3100, and the horizontal plate (translator)3421is provided on the ball roller3423. The floating joint part3400is interposed between the base part3100and the workpiece installation stage3200to allow translational movement of the workpiece installation stage3200and rotational displacement of the workpiece installation stage3200. In other words, the workpiece holding base part3000can allow translation and rotation of the workpiece W placed on the workpiece installation stage3200.

The restriction means3500restricts the displacement of the workpiece installation stage3200and clamps the workpiece installation stage3200from both sides by two clamping pieces3510having a configuration almost similar to that of the restriction means2500in the second exemplary embodiment. By closing or opening the movable clamping pieces3510, the restriction means3500can switch between a hold state of the workpiece installation stage3200and a release state in which the holding is released.

The vibration motor3700is installed on the workpiece installation stage3200. The vibration motor3700is preferably provided, but may not be provided. Since the workpiece holding base part (workpiece holding part)3000in the third exemplary embodiment allows displacement of the workpiece installation stage3200by the floating joint part3400, the workpiece W can be pushed and displaced by the contact points of the measuring device without the vibration motor3700. However, if the workpiece W is a heavy object, the vibration motor3700is desirably provided to cause the workpiece W to be displaced.

The third exemplary embodiment is different from the second exemplary embodiment in that an object to be held/released by the restriction means3500is the workpiece installation stage3200and that an object to be vibrated by the vibration motor3700is the workpiece W via the workpiece installation stage3200. The steps of automatic inside-diameter measurement operation are similar to those in the second exemplary embodiment. As the effects of the workpiece holding base part3000in the third exemplary embodiment, the workpiece installation stage3200is translated and inclined (rotated) in such a manner that the inner wall of the workpiece W and the contact points2250(round shaft tips2252) of the electric inside-diameter measuring device2200are in close contact. For example, as shown inFIG.28, if the centerline of the workpiece deviates from the center of the hole, the workpiece installation stage3200is translated to adjust the position of the workpiece in such a manner that all the contact points2250(round shaft tips2252) are in close contact with the inner wall of the workpiece. Alternatively, as shown inFIG.29, if the centerline of the workpiece is inclined with respect to the bottom of the workpiece, the workpiece installation stage3200is inclined (rotated) to adjust the position of the workpiece in such a manner that all the contact points2250(round shaft tips2252) are in close contact with the inner wall of the workpiece. In addition, by applying vibration to the workpiece W from the vibration motor3700through the workpiece installation stage3200, the friction at the interface between the contact points2250(round shaft tips2252) and the workpiece W (inner wall of the hole) can be reduced to facilitate a change in the posture of the workpiece W on the workpiece installation stage3200.

In the third exemplary embodiment, the electric inside-diameter measuring device2200is not supported by the floating joint part3400, and the posture of the electric inside-diameter measuring device2200can be controlled almost as intended by the hand (hand part2131) of the robot (moving means) to maintain a vertical posture, for example. The electric inside-diameter measuring device2200is to be connected to a power feed cable and a transmission cable for control signals or measurement data, and this applies forces due to the rigidity and the weight of the cables to the electric inside-diameter measuring device2200. As in the second exemplary embodiment, if the electric inside-diameter measuring device2200is supported by a displacement-allowing mechanism such as the floating joint part3400, the posture may be affected by external disturbances. In this regard, the electric inside-diameter measuring device2200is not supported by the floating joint part3400in the third exemplary embodiment, and is not easily affected by external disturbances such as cables. Although the workpiece installation stage3200supporting the workpiece W is supported by the floating joint part3400, there is no need to connect a thick cable to the workpiece installation stage3200, which eliminates the workpiece installation stage3200being affected by cables or other disturbances. This enables stable dimensional measurement of the workpiece.

In the above embodiment, the base part3100and the workpiece installation stage3200are connected by the floating joint part3400, and the floating joint part3400includes the rotation-allowing mechanism part3410and the translation-allowing mechanism part3420. Since the workpiece installation stage3200is only required to be translated and rotated (inclined) to some extent with respect to the base part3100, the floating joint part3400may be, for example, elastic rubber, foam resin, a spring, or an air-sealed bag such as an air cap.

The restriction means3500includes the clamping pieces3510that clamp the workpiece installation stage3200from both sides, but it can be any means that can regulate displacement of the workpiece installation stage3200. For example, as shown inFIG.30, a hole3210may be provided in the lower face of the workpiece installation stage3200, a pin3110may be provided from the lower side of the workpiece holding base part3000to move upward and downward in order to switch between the hold state and the release state of the workpiece installation stage3200by inserting or removing the pin3110in the hole3210. Similarly, a pin may be provided in the lower face of the workpiece installation stage3200and a cylinder may be provided from the lower side of the workpiece holding base part3000to move upward and downward in order to switch between the hold state and the release state of the workpiece installation stage3200by inserting or removing the cylinder into the pin.

The present invention is not limited to the above exemplary embodiments, and can be appropriately modified without departing from the gist.

In the above embodiments, the floating joint par is provided on either the measuring device or the workpiece holding part, but each of the measuring device and the workpiece holding part may include the floating joint part.

Similarly, in the above exemplary embodiments, the vibration motor is provided on either the measuring device or the workpiece holding part, but each of the measuring device and the workpiece holding part may include the vibration motor.

Reference Signs