JP4669566B2 - Contact probe - Google Patents

Description

  The present invention relates to a contact probe used when measuring the surface shape of an optical element such as a lens or a mirror precisely.

  A three-dimensional measuring apparatus that precisely measures the surface shape of an optical element such as a lens or a mirror is divided into two parts: a probe that traces the shape of the object to be measured and a coordinate measuring means that measures the position of the probe. Can think. At this time, what is important for the probe is to pass the surface position of the object to be measured to a member capable of measuring coordinates. An error when the probe traces the surface of the object to be measured is called a trace error. Conventionally, as a configuration of this probe, a probe shaft that can be moved up and down by using an air bearing is disclosed in p. The structure which supports the dead weight of a spring with a spring is proposed.

  When a shape is traced using this type of probe, the aforementioned trace error occurs. It is necessary to use a sufficiently weak spring, that is, a spring having a sufficiently small spring constant so as not to cause a probe pressing force error even if there is a trace error. This is because the amount obtained by multiplying the trace error by the spring constant is an error in the pressing force.

  As another conventional example, as disclosed in Patent Document 1, the tip portion can be easily replaced by separating the tip portion from the stylus body and screwing the tip portion to the stylus body. There is an example devised.

  The probe is often called a stylus, a stylus, or a feeler, but in this specification, the probe is unified.

JP-A-11-132757

  However, the above-described prior art has the following problems.

(1) The size of the spring is increased in order to reduce the pressing force.
The force generated by the spring is a force obtained by applying a pressing force to the weight of the probe. This pressing force is very small, but the weight is not so. Therefore, the force generated by the spring is relatively large.

  However, since the influence of the trace error needs to be reduced as described above, the spring constant has to be reduced. Therefore, the amount of spring deflection, that is, the amount obtained by dividing the generated force of the spring by the spring constant becomes very large.

For example, if the mass of the probe is 10 g and the pressing force is 0.1 mN, the force generated by the spring is F = 9.8 × 10 + 0.1 = 98.1 mN, assuming that the acceleration of gravity is 9.8 m / s ^2. . Further, if the allowable pressing force error is 10%, that is, 0.1 × 10/100 = 0.01 mN, and the trace error is 10 μm, the spring constant K is K = 0.01 / 10 = 0. 001 mN / μm.

  Therefore, the deflection of the spring is F / K = 98.1 mm, and a deflection of about 100 mm is necessary. The size of the spring at this time should be much larger because the length of the spring when no force is applied is added to this.

  Therefore, when the spring is arranged as in the conventional example, it is necessary to lengthen the spring or increase the size in order to lower the spring constant, which increases the size of the probe. When the size is increased, it is difficult to keep the ambient temperature uniform, the shape measurement accuracy is deteriorated, and the size of the measurement axis for scanning the probe is inevitably increased due to the increase in size, which increases the cost of the apparatus.

  Furthermore, if the pressing force is to be lowered, a weaker spring is required, so that the spring portion of the probe becomes very large, which is practically impossible with the conventional method.

(2) The probe pressing force is likely to change.
It is conceivable that the spring expands or contracts due to the influence of ambient temperature change or the like. In the conventional example, the force generated by the spring is large because it includes the weight of the probe. Therefore, if the generated force of the spring changes due to the expansion and contraction of the spring, the influence on the probe pressing force is great.

  For example, in the example described above, the force of the spring is F = 9.8 × 10 + 0.1 = 98.1 mN. Therefore, even a change of only 0.1% results in a change of 0.0981 mN, which is a very large error with respect to the probe pressing force of 0.1 mN. For this reason, precise shape measurement is difficult.

(3) It is difficult to replace the sphere attached to the probe tip.
In the measurement using the contact type probe, no matter how low the pressing force is, it is inevitable that the ball attached to the tip is damaged due to the interaction between the object to be measured and the probe. Therefore, it is necessary to replace the tip sphere. However, in the structure of the probe integrated with the tip sphere as in the conventional example, it is impossible to replace only the tip sphere. Therefore, since it is necessary to completely replace the tip portion integrated with the tip sphere, the efficiency is poor. This is because not only is it time-consuming to exchange, but it is also necessary to prepare a large number of tip portions to which balls are attached. Such effort leads to an increase in measurement cost, which is uneconomical in terms of optical element production.

(4) Fine adjustment of the pressing force is difficult.
Although it is conceivable that the weight of the probe changes due to the exchange of the probe tip or the like, the contact force also changes when the weight of the probe changes. In the conventional example, since the position of the spring cannot be adjusted, it is difficult to finely adjust the error of the pressing force.

  Since the error in the pressing force changes the deformation amount of the object to be measured or the probe, highly accurate shape measurement cannot be performed.

(5) Contact determination is difficult.
When measuring the shape using the probe of the conventional example, it is always necessary to bring the probe close to the object to be measured and stop when it comes into contact. At this time, since the member supporting the probe needs to be moved, the probe itself naturally moves. When the probe moves, disturbance vibration is applied to the probe by the vibration at that time. However, a probe supported by a very weak spring as in the conventional example is greatly shaken under the influence of a slight disturbance vibration.

  It is difficult to detect whether a probe that is greatly shaken has contacted the object to be measured. This is because it takes time to determine whether the displacement of the probe is caused by shaking or contact.

  In the numerical example described above, since the probe mass M = 10 g and the spring constant K = 0.001 mN / μm, the natural frequency of the probe portion is sqrt (K / M) /2π=1.6 Hz. Low. In order to determine this fluctuation, at least one period of time is required, and therefore it can be determined only every 1 / 1.6 = 0.6 seconds. Therefore, contact determination cannot be made unless the approach is very slow.

  This time extends the time required for measurement. This leads to an increase in measurement costs and is uneconomical from the viewpoint of optical element production.

  Therefore, the present invention has been made in view of the above-mentioned unsolved problems of the prior art, and in a contact probe used for measuring the shape of a free-form surface optical element or the like, the contact force is reduced by compensating for its own weight. It is an object of the present invention to provide a contact-type probe that can be reduced in size and improved in measurement accuracy and can be easily replaced with a tip sphere.

In order to achieve the above object, the contact type probe of the present invention is a contact type that measures the shape of the object to be measured by scanning the probe tip while contacting the object to be measured and measuring the coordinate position of the probe. In the probe, a movable member that can be moved three-dimensionally, a probe that is movable in the direction of gravity with respect to the movable member, a balance or a pulley having a fulcrum attached to the movable member, and a movable member A magnetic circuit comprising a fixed yoke, a permanent magnet, a coil that can be energized, or an adjustment screw whose gap between the yoke is variable, and a probe suspended from one end of the balance or pulley, and the other end In the magnetic circuit, the permanent magnet and the coil or the adjusting screw are connected to the balance weight via the yoke. Have been arranged in parallel for, and the balance weight is sandwiched with a gap by the magnetic circuit of the yoke, it is characterized.

  As described above, according to the present invention, a magnetic circuit composed of a yoke, a permanent magnet, and a coil is provided in the probe, and the magnetic force generated by the magnetic circuit varies depending on the constant force for canceling the weight of the probe and the displacement of the probe. By generating the force of the spring element, it is not necessary to provide a large weak spring as in the conventional example, and the probe can be miniaturized. Furthermore, since a mechanical spring is not used, there is no fear that the spring is deformed due to a change in environmental temperature or the like and the pressing force changes, and the measurement accuracy can be improved. Also, since the magnetic force changes by changing the current applied to the coil, it is possible to precisely adjust the pressing force. Even if the probe's own weight changes due to replacement of the probe tip sphere, etc., it is necessary to adjust it again. Therefore, the influence can be reduced and the measurement accuracy can be increased. Furthermore, it is possible to make adjustments by remote operation, and the operation becomes easy, so that an efficient measurement apparatus can be operated.

  Further, according to another contact type probe of the present invention, the probe is suspended from one end of a balance or pulley having a fulcrum fixed to the moving member, and a balance weight is connected to the other end so that the gravity applied to the probe can be reduced. Most of the force can be canceled by the balance weight, and by connecting a spring element that receives a part of the remaining force to the probe or balance weight, the force that the spring bears can be made very small, and a weak spring is used. However, the problem that the spring extends long and the size of the entire probe increases can be avoided. Further, even if the spring is deformed due to a temperature change or the like, since the generated force of the spring is originally small, the influence on the probe pressing force error is small and the measurement accuracy can be improved.

  Furthermore, by attaching a spring connected to the probe or balance weight to a lever having an adjustment mechanism, the length of the spring can be adjusted by the adjustment mechanism, thereby enabling precise adjustment of the contact force of the probe, and the probe tip. Even if the weight of the probe changes due to exchange of a sphere or the like, the influence can be reduced by adjusting it again, so that the measurement accuracy can be increased.

  Also, by using a magnetic circuit consisting of a yoke and a permanent magnet instead of a spring, the force to support the weight of the probe can be generated using the magnetic force of the permanent magnet, and the mass of the balance weight can be reduced. Since the inertia can be reduced, the follow-up performance with respect to minute irregularities of the object to be measured is improved, leading to improvement in measurement accuracy. Furthermore, since the magnetic circuit also has an action of a spring element, it does not require a spring and can be miniaturized.

  Further, by using a magnetic circuit composed of a yoke, a permanent magnet, and a coil, in addition to the effects that can be achieved when using a magnetic circuit composed of a yoke and a permanent magnet, by changing the current supplied to the coil, The force generated by the magnetic circuit can be finely adjusted, and the contact force of the probe can be precisely adjusted. Even if the probe's own weight changes due to replacement of the probe tip ball, etc. Measurement accuracy can be increased. Furthermore, remote control is possible, work efficiency can be improved, and measurement costs can be reduced.

  Furthermore, according to the contact type probe of the present invention, by supporting the probe and balance weight via the air bearing, the probe and the balance weight can be moved without friction, and the error of the pressing force of the probe is eliminated. A highly accurate probe pressing force can be realized, and measurement accuracy can be improved.

  Also, by providing a vacuum path in the probe shaft and vacuum-adsorbing the sphere at the probe tip, the probe tip sphere can be replaced easily, and only the tip sphere needs to be replaced. Since there are few exchange parts, they can be exchanged in a very short time, and the measurement cost can be reduced. Furthermore, since the tip sphere can be easily replaced, a new sphere can be used for all measurements, and the problem of tip sphere wear can be reduced, and measurement reliability and measurement accuracy can be improved.

  In addition, by connecting a vacuum gauge to the vacuum path in the probe shaft, the vacuum gauge can check the presence or absence of the probe tip sphere, avoiding the risk of measuring the shape without adsorbing the probe tip sphere. By checking the degree of vacuum, it is possible to judge whether the tip sphere is attracted or not, and if the tip sphere is stuck, the measurement can be interrupted, reducing the measurement failure rate and improving the measurement reliability. be able to.

  Also, by providing a force sensor in the movable area of the probe, the force sensor can be used to automatically calibrate the probe pressing force immediately before measurement, improving work efficiency and reducing measurement costs. be able to. Furthermore, even if the pressing force changes slightly due to the influence of ambient temperature change or the like, the influence can be eliminated, so that highly accurate measurement is possible. In addition, it is possible to eliminate the possibility of adjusting the probe pressing force due to human factors, thereby improving the measurement reliability.

  The probe or balance weight is provided with a stopper that regulates the movement of the probe or balance weight, and the probe or balance weight can be moved by blowing air or sucking air to the probe or balance weight before measurement. Since the probe can be fixed to the moving member by abutting against the stopper, the vibration of the probe is suppressed, and the contact determination when the probe is brought into contact with the object to be measured can be performed easily and in a short time. Time can be shortened and measurement cost can be reduced.

It is a block diagram which shows the shape measuring apparatus incorporating the contact-type probe of the 1st reference example of this invention partially fractured | ruptured. (A) is the schematic which shows the relationship between a probe and a yoke, a permanent magnet, and a coil, (b) is the schematic which arrange | positioned the magnetoresistive adjustment screw and the gap adjustment screw in the yoke. It is a figure for demonstrating the contact-type probe of the 1st reference example of this invention, (a) is a schematic diagram of the contact-type probe of this reference example, (b) shows the magnetic circuit, c) A schematic view for explaining a conventional contact probe. It is a flowchart explaining the measurement operation | movement of the shape measuring apparatus of this invention. It is a block diagram which shows the shape measuring apparatus incorporating the contact type probe of the 2nd reference example of this invention partially fractured | ruptured. (A) thru | or (c) is a schematic diagram for demonstrating the contact-type probe of the 2nd reference example of this invention, respectively. It is a lineblock diagram showing a shape measuring device incorporating a contact type probe of a 1st embodiment of the present invention partially fractured. It is a figure for demonstrating the contact type probe of the 1st Embodiment of this invention, Comprising: (a) is a schematic diagram of the contact type probe of this embodiment, (b) shows the magnetic circuit. It is a block diagram which shows the shape measuring apparatus incorporating the contact type probe of the 2nd Embodiment of this invention partially fractured | ruptured. It is a schematic diagram for demonstrating the contact type probe of the 2nd Embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings.

(First reference example)
FIG. 1 is a block diagram showing a partially broken shape measuring apparatus incorporating a contact probe according to a first reference example of the present invention. FIG. 2 (a) shows a probe, a yoke, a permanent magnet, It is the schematic which shows the relationship with a coil, The same figure (b) is the schematic which arrange | positioned the magnetoresistive adjustment screw and the gap adjustment screw in the yoke, FIG. 3 is the contact of the 1st reference example of this invention. It is a figure for demonstrating a type | formula probe, Comprising: (a) is a schematic diagram of the contact type probe of this reference example, (b) shows the magnetic circuit, (c) demonstrates the conventional contact type probe. It is a schematic diagram for doing.

  First, a contact probe according to a first reference example of the present invention will be described with reference to FIG.

  FIG. 3C schematically shows a conventional contact probe, and a probe 102 is arranged to be movable in one direction at the tip of a moving member 103 such as a measurement shaft that can be moved three-dimensionally. The probe 102 has a ball 101 at its tip, and is suspended from the moving member 103 by a spring 104. As described above, the spring 104 needs to be a very weak spring, but has to support the weight of the probe 102. Therefore, since the spring 104 is very stretched, the entire size of the probe 102 is also increased. It was a problem.

  On the other hand, in the contact type probe in this reference example, as shown in FIG. 3A, a member 105 made of a ferromagnetic material is attached to the probe 102, and a yoke 106, a permanent magnet 107, and a coil 108 are included. A magnetic circuit is provided on the probe 102. As will be described later, the magnetic force acting between the yoke 106 and the probe 102 (ferromagnetic member 105) is a constant force that cancels the force in the gravitational direction of the probe 102 and the force of the spring element that changes according to the displacement of the probe 102. There is.

The operation of the magnetic circuit in FIG. 3A will be described. This magnetic circuit can be schematically drawn as shown in FIG. The permanent magnet 107 is represented as a simple model by a magnetomotive force M and an internal resistance R ₀ , and a magnetic flux generated from the permanent magnet 107 is Φ. Further, the gap between the probe 102 and the (ferromagnetic member 105) the yoke 106 and [delta], the magnetic resistance of the gap [delta] between _{R 1.} In the coil 108 model, the magnetomotive force is M ′, the generated magnetic flux is Φ ′, and the internal resistance of the yoke or the like is R ₀ ′.

  As shown in FIG. 3A, the overlapping portion of the yoke 106 and the probe 102 (ferromagnetic member 105) is z, the thickness perpendicular to the paper surface is b, the gap (gap) is δ, and the magnetic permeability is If μ, the gap magnetoresistance is

ｚ方向のずり力（磁力）Ｆは次の式から計算できる。

The shear force (magnetic force) F in the z direction can be calculated from the following equation.

これではわかりにくいので、ｚ＝０のまわりで１次までテーラー展開すると、

This is difficult to understand, so if you develop a tailor around z = 0 to the first order,

  The first term in equation (3) is a term that generates a force that supports the weight of the probe 102 by a constant. It can be seen that there is a magnetomotive force M ′ of the coil 108 in the term, and this force can be finely adjusted by adjusting this. The second term includes the amount of movement z of the probe 102, and indicates that the force decreases as z increases. Since the generated force changes as the probe 102 is displaced, it corresponds to a mechanical spring.

That is, the magnetic circuit shown in FIG. 3A functions as a spring element in addition to the same action as the counter balance mass that supports the weight of the probe 102. Further, the magnetic resistance R ₀ and the like can be adjusted by changing the material and shape of the magnet 107 and the yoke 106.

  As described above, by applying these magnetic forces to the probe 102, it is not necessary to use a weak spring having a large size as in the conventional example, and a small probe can be realized. In addition, unlike the conventional example, the spring is deformed due to a change in environmental temperature or the like, and the pressing force does not change, so that the stability of the pressing force is improved.

  Further, since the magnetic force is changed by changing the current supplied to the coil 108, the pressing force can be precisely adjusted. Even if the weight of the probe changes due to the exchange of the sphere 101 at the tip of the probe or the like, the influence can be reduced and the measurement accuracy can be increased by adjusting again. Furthermore, since the pressing force can be adjusted only by controlling the electric current, it is possible to adjust the pressing force by remote operation, and the operation becomes easy, so that an efficient measurement apparatus can be operated.

  As a method for supporting the probe 102, a rolling guide is used in the schematic diagram of FIG. 3A, but it may be supported by a parallel leaf spring or may be supported by an air bearing.

  Next, a shape measuring apparatus incorporating the contact probe of this reference example configured as described above will be described with reference to FIGS. 1 and 2.

  In FIG. 1, a probe tip 2 having a conical tip for attaching a sphere 1 and penetrating a small hole in the center is placed below a probe shaft 4 having a small hole in the center with a spacer 3 interposed therebetween. Secure with screws. The mirror 6 is bonded and fixed to a mirror fixing piece 5 made of a ferromagnetic material, and the mirror fixing piece 5 is screwed and fixed to the upper side of the probe shaft 4. A vacuum pipe 7 communicating with a small hole is fixed at the center of the probe shaft 4, and the vacuum pipe 7 is connected to a vacuum gauge 9 and further connected to a vacuum source (not shown) via an air valve 8. Yes. At this time, the air valve 8 is one that can select whether the vacuum pipe 7 is connected to a vacuum source or released to the atmosphere.

  In this way, by providing a vacuum path in the probe so that the sphere 1 can be vacuum-adsorbed to the conical tip of the probe tip 2, the sphere 1 can be easily obtained by setting the pressure in the vacuum path to atmospheric pressure. It can be removed and the tip 1 can be easily replaced. Since it is not necessary to manufacture and assemble a part to which a tip sphere is attached as in the prior art, the cost and time required for replacement can be reduced. Further, with this configuration, it is possible to economically replace the tip sphere 1 frequently. For example, when a steel ball is used for the tip sphere, the price of the sphere is about 1 to 3 yen, and the effect is great. In addition, since the operation for fixing the probe tip, for example, screw tightening, is not required as in the conventional example, the time required for replacement can be remarkably shortened. As a result, it is possible to always replace and measure with a new sphere, considering the replacement cost, measurement time, etc., and always measuring with a new sphere will damage the tip sphere pointed out in the problem. Even if it occurs, the range of influence can be minimized, that is, only the measurement. Therefore, measurement reliability is improved.

  In addition, dust may be caught when the sphere 1 is vacuum-adsorbed to the tip of the probe tip 2, and in this case, the measurement error becomes very large, so that the measurement reliability deteriorates. However, if the tip sphere 1 sandwiches dust, there is a gap, so air leaks and the degree of vacuum deteriorates. Therefore, it is possible to determine whether the tip sphere is attracted or not by monitoring the degree of vacuum with the vacuum gauge 9 disposed in the vacuum path. If the tip sphere adsorption state is bad, the measurement reliability can be improved by providing a step of interrupting the measurement.

  The probe shaft 4 is supported so as to be movable in the vertical direction with respect to the housing 10 via a so-called air bearing 11 that supports the probe shaft 4 in a non-contact manner through a thin air film. A compressed air hole 12 is formed to guide the compressed air. These compressed air holes 12 can be freely drawn around the inside of the housing 10 by drilling from one side with a drill and closing the surface portion of the hole with screws or an adhesive as necessary. The compressed air hole 12 is connected to a compressed air pipe 13 and further connected to a compressed air source (not shown). With this configuration, the probe shaft 4 can freely move in the vertical direction without friction.

  The housing 10 is provided with a protruding lower stopper 10 b on the lower surface thereof, and restricts excessive movement of the probe shaft 4 in the upward direction by colliding with the spacer 3. Similarly, a projection-like upper stopper 10a is provided on the upper surface portion of the housing 10 so as to abut against the mirror fixing piece 5 of the probe for excessive downward movement. For example, a damper such as a thin rubber sheet is bonded and fixed to these stoppers 10a and 10b in order to reduce the impact. The housing 10 is fixed and supported by a second housing 16 fixed to the measurement shaft 15.

  A yoke 17 constituting a magnetic circuit is fixed to the second housing 16, and a top view of this part is shown in FIG. 2A, and a permanent magnet 18 and a coil 19 are attached to the yoke 17. The magnetic circuit of the probe is configured, and the coil 19 is connected to the current source 20 through wiring. It is assumed that the gap (gap) between the yoke 17 and the mirror fixing piece 5 made of a ferromagnetic material is δ, and the vertical length of the overlapping portion is z. An overlapping portion of the yoke 17 and the mirror fixing piece 5 seen from above is denoted by b.

  The force generated by the magnetic circuit of the probe shown in FIG. 1 and FIG. 2A configured as described above is a constant force that supports the weight of the probe, as will be described based on the aforementioned equation (3). In addition to the action of generating, the action of a spring element whose force changes according to the displacement is also served.

  As for the magnetic circuit of the probe, as shown in FIG. 2B, the yoke 17 is provided with a magnetic resistance adjusting screw 17a for adjusting the magnetic resistance, and the gap δ between the yoke 17 and the mirror fixing piece 5 is provided. A gap adjusting screw 17b may be provided to adjust the angle.

When the magnetic resistance adjusting screw 17a is inserted or removed, the magnetic resistance when the magnetic flux passes through the magnetic resistance increases or decreases, and the magnetic resistances R ₀ and R ₀ ′ in the equation (3) can be adjusted. It is possible to adjust the force and the force corresponding to the spring element. Further, the gap δ can be adjusted by inserting and removing the gap adjusting screw 17b, and the magnetic force generated by the magnetic circuit is changed by changing the gap δ. According to this configuration, it is possible to adjust the ratio of two types of forces generated by the magnetic circuit, that is, a constant force and a force proportional to the displacement, so that the manufacturing accuracy of the parts can be relaxed.

  The second housing 16 is provided with a nozzle 21 that blows air in a direction to push down the probe. A pipe 22 connected to the nozzle 21 is connected to a compressed air source (not shown) via an air valve 23. ing. The air valve 23 is automatically controlled by a controller (not shown), and a measurement operation is performed according to the flowchart shown in FIG. FIG. 4 will be described later.

  The measurement shaft 15 is supported by an XY table 26 so as to be movable using a guide 24 in the same direction as the probe shaft 4, that is, in the vertical direction (Z direction), and is driven by a ball screw 25 and a servo motor 27. The XY table 26 is guided so as to be movable in the X and Y directions with respect to a surface plate (not shown), and is positioned by a servo motor (not shown). A servo motor 27 that drives the measuring shaft 15 is connected to a servo amplifier 29, and the servo amplifier 29 is connected to a control system switching device 31. An encoder 33 is connected to the rotation shaft of the servo motor 27, and its output is connected to the position control compensation circuit 30. When the control system switching device 31 is connected to the position control system, the position of the measurement shaft 15 can be controlled. The control system switching device 31 is automatically controlled by a controller (not shown), and a measurement operation is performed according to the flowchart shown in FIG.

  Further, the interferometer 34 and the quarter-wave plate 35 are fixed to the measurement axis 15, a mirror 36 is disposed above the measurement axis 15, and the mirror 36 is fixed to the frame 37. With this configuration, the interferometer 34 can measure the distance between the mirror 6 and the mirror 34. A mounting table (not shown) for an object to be measured is provided in a lower portion of the frame 37, and the object to be measured 38 is fixed to the mounting table.

  The position adjustment of the probe in the Z direction is performed by measuring the position of the probe shaft 4 in the Z direction with a position sensor 47 disposed at a position facing the convex spherical mirror 46 fixed to the probe shaft 4. That is, light is incident on the optical fiber 42 from a light source (not shown), and a light beam is emitted from the optical fiber fixing piece 43. The optical fiber fixing piece 43 is fixed to the second housing 16 by a fixing member 44. The lens 45 is provided fixed to the fixing member 44, and the light beam is condensed. The condensed light is reflected by a convex spherical mirror 46 fixed to the probe shaft 4 and focused on the position sensor 27. Here, the center of the spherical surface of the convex spherical mirror 46 is arranged on the center axis of the probe shaft 4. The position sensor 47 is fixed on a fine movement table 48 fixed to the measurement shaft 15 and can be fixed by adjusting the position in the Z direction.

  The position sensor 47 is connected to the sensor amplifier 49 and converts the light spot position into an electrical signal. The sensor amplifier 49 is connected to the needle pressure control compensation circuit 32 and further connected to the control system switching device 31. When the control system switching device 31 is connected to the needle pressure control system, the servo motor is controlled so that the output of the sensor amplifier 49 becomes constant.

  In addition, a force sensor 39 for measuring the probe pressing force is installed within the movable range of the probe.

  Next, the measurement operation performed using the shape measuring apparatus configured as described above will be described with reference to the flowchart of FIG.

  First, the probe is prepared before measurement. First, the probe is fixed to the lower end (step S01). That is, the air valve 23 is opened to blow the compressed air from the nozzle 21 to move the probe downward. Then, the mirror fixing piece 5 comes into contact with the upper stopper 10a, and the probe is fixed to the lower end.

  Next, the tip sphere 1 is set as follows (step S02). With the air valve 55 opened and the pressure in the hole inside the probe tip 2 lowered, the tip ball 1 is vacuum-adsorbed to the probe tip 2. When the sphere 1 is vacuum-adsorbed, the pressure inside the pipe decreases, and the measured value of the vacuum gauge 9 approaches a vacuum. Therefore, the presence or absence of the probe tip sphere can be detected by monitoring the measurement value of the vacuum gauge 9 (step S03). If the pressure is abnormal, the process is interrupted because of some failure (step S20). If the pressure is normal, the process proceeds to the next process (after step S04).

  The control system switching device 31 is set as a position control system, that is, a feedback control system is selected so that the position of the measurement axis 15 is constant, and the safe position, that is, the direction in which the probe is farthest from the object to be measured 38. The measuring shaft 15 is retracted (step S04). Next, the XY table 26 is moved so that the probe is placed on the force sensor 39 (step S05), and the measurement shaft 15 is lowered to bring the probe into contact with the force sensor 39 (step S06).

  Here, when the ball 1 at the tip comes into contact with an object to be measured, a force sensor or the like and receives a reaction force, the probe shaft 4 is pushed up, and its displacement can be illuminated and read by a displacement meter using this principle. . The operation of this displacement meter portion will now be described.

  The light beam emitted from the optical fiber fixing piece 43 is incident on the lens 45 while gradually spreading, and is reflected by the convex spherical mirror 46 fixed to the probe shaft 4 while focusing, and is focused on the position sensor 47. The fine movement table 48 is adjusted and fixed in advance so that the focal position is at the center position of the position sensor 47. When the probe shaft 4 moves, the amount of movement in the direction perpendicular to the intermediate direction between the light beam incident on the convex spherical mirror 46 and the reflected light beam, that is, the direction indicated by the arrow A in FIG. The focal position on the position sensor 47 moves. Since the probe shaft 4 is supported so as to be movable only in the vertical direction, the direction indicated by the arrow A is considered to be substantially the direction of movement of the probe shaft 4. When the angle difference between the probe moving direction and the displacement measuring direction is θ, cos θ of the probe moving amount is measured. The position change is converted into an electric signal by the sensor amplifier 49.

  When the probe shaft 4 is pushed up, the overlapping length z between the yoke 17 and the mirror fixing piece 5 increases to the plus side. Then, since the force generated by the magnetic circuit is weakened from the above-described equation (3), the force with which the tip sphere 1 of the probe presses the object to be measured and the like gradually increases. This is the same effect as the spring element is there. Therefore, the output of the sensor amplifier 49 represents the pressing force of the probe. The output of the sensor amplifier 49 is not affected by the inclination around the center of the convex spherical mirror 46. This is because the center of the spherical surface of the convex spherical mirror 46 coincides with the center axis of the probe shaft 4.

  Whether or not the tip sphere of the probe is in contact with the object to be measured can be determined by monitoring the displacement measurement signal of the probe, that is, the signal of the sensor amplifier 49. Since the probe is in contact with the mirror fixing piece 5 and the protruding stopper 10a of the housing 10, the probe does not move even if the measurement shaft 15 moves and there is disturbance vibration. Therefore, the signal of the sensor amplifier 49 is not shaken by disturbance vibration, and contact determination can be easily performed. That is, since it is only necessary to monitor whether or not a predetermined signal level is reached, the presence or absence of contact can be determined at a very high speed, for example, 1 ms.

  Next, the air valve 23 is closed, the blowing of compressed air from the nozzle 21 is stopped, and the movement of the probe is made free (step S07). The measuring shaft 15 is moved until the value of the displacement sensor reaches a predetermined value, for example, 0 volts. Then, the control system switching device 31 is switched to the needle pressure control system (step S08). That is, the measuring shaft 15 is controlled so that the output of the sensor amplifier 49 is constant.

  Next, the pressing force of the probe is measured using the force sensor 39 (step S09). It is determined whether or not the value of the pressing force at this time is a predetermined value (step S10). At this time, whether the pressing force is good or bad is set, for example, as ± 10% of the set value. If not, the probe pressing force is adjusted (step S21). The pressing force can be adjusted by changing the current flowing through the coil 19. Therefore, the current of the current source 20 is adjusted so that the probe pressing force measured by the force sensor 39 becomes a predetermined value.

  If the determination of the probe pressing force (step S10) is good, the control system switching device 31 is switched to the position control system again, the measuring shaft 15 is retracted to the safe position (step S11), and the air valve 23 is opened again. The probe is fixed to the lower end (step S12).

  Thus, the preparation of the probe is completed, and then the process of measuring the shape of the object to be measured starts.

  First, the XY table 26 is moved to the first measurement position (step S13). Then, in the same procedure as before, the measurement shaft 15 is lowered and the tip sphere 1 of the probe is brought into contact with the object to be measured 21 (step S14).

  Next, the air valve 23 is closed, the spraying of compressed air from the nozzle 21 is stopped, and the movement of the probe is made free (step S15).

  Then, the control system switching device 31 is switched to the needle pressure control system (step S16), and the measurement area of the object to be measured is scanned (traced) using the XY table 26, and at the same time, the position of the measurement axis is not shown. (Step S17). Further, the vertical direction of the probe is directly measured by an interferometer 34 that measures the distance between the reference mirror 6 and the reference mirror 36.

  When the entire measurement area is scanned, the control system switching device 31 is switched to the position control system again, the measurement axis is retracted to the safe position (step S18), and the air valve 23 is opened again to fix the probe to the lower end (step S19). .

  As described above, according to this reference example, the gravity applied to the tip sphere 1, the probe tip 2, the spacer 3, the probe shaft 4, the mirror fixing piece 5, the mirror 6, the pipe 7, and the like is shown in FIG. Cancel by the magnetic force generated. Therefore, it is not necessary to use a weak and large spring as in the conventional example. For this reason, a small probe is realizable.

  In addition, since a spring whose generated force changes with respect to environmental changes such as temperature changes is not used, the accuracy of the probe pressing force is improved, and as a result, the measurement accuracy is improved.

  Also, the probe tip sphere can be easily attached and detached, and the probe tip sphere can be frequently replaced. As a result, it becomes possible to reduce the risk of measuring the shape with the damaged tip sphere, and the measurement reliability is improved.

  Further, although the control of the measuring shaft 15 is constituted by a servo motor and a ball screw in this reference example, other driving means such as a linear motor can be used.

  In this reference example, the adjustment of the pressing force has been described with reference to the flowchart of FIG. 4 as preparation of the probe. However, this adjustment is not always necessary for each measurement. That is, the adjustment of the pressing force may be omitted.

( Second reference example )
FIG. 5 is a block diagram showing a partially broken shape measuring apparatus incorporating a contact type probe according to a second reference example of the present invention. FIGS. 6 (a) to 6 (c) respectively show the present invention. It is a schematic diagram for demonstrating the contact-type probe of the 2nd reference example . In this reference example , elements and members similar to those in the first reference example described above will be described with the same reference numerals.

The contact-type probe in this reference example compensates the weight of the probe using a balance and a balance weight, and will be described first with reference to FIG.

  6A, a balance 111 that can swing around a fulcrum 110 is provided on a moving member 103 such as a measurement shaft that can be moved three-dimensionally, and a suspension thread 112 is connected to one end of the balance 111. The probe 102 is connected, the balance weight 114 is suspended from the other end of the balance 111 via a suspension thread 113, one end of a weak fine adjustment spring 115 is connected to the balance weight 114, and the other end of the spring 115 is moved. A fulcrum formed on the member 103 is connected to a rotatable lever 116. An adjustment screw 117 is provided at the other end of the lever 116.

  In this way, by providing the balance weight 114 via the balance 111, the balance weight 114 receives most of the gravity applied to the probe 102, so the force that the spring 115 has is the conventional example (eg, see FIG. 3C). ) Very much. Therefore, even if a weak spring is employed, the problem that the spring extends long and the size of the entire probe increases can be avoided. Furthermore, the length of the spring 115 can be adjusted by adjusting the adjustment screw 117 by connecting one end of the spring 115 to the lever 116 provided with the adjustment screw 117, and the length of the spring 115 can be changed. Therefore, it is possible to precisely adjust the spring force, and thus the contact force of the probe 102 can be precisely adjusted. Further, even if the weight of the probe 102 changes due to exchange of the ball 101 of the probe 102 or the like, the influence can be reduced by adjusting the adjustment screw 117 again, so that the measurement accuracy can be increased.

  Further, even if the spring 115 is deformed due to a temperature change or the like, since the generated force of the spring 115 is originally small, the influence on the probe pressing force error is small. Since the error of the probe pressing force is reduced, the measurement accuracy can be improved.

  FIG. 6B is a schematic diagram of a contact probe in which the adjustment function by the adjustment screw 117 is omitted in the contact probe shown in FIG. That is, the other end of the fine adjustment spring 115 connected under the balance weight 114 is connected to the moving member 103. Even in such a structure, since the balance weight 114 via the balance 111 receives most of the gravity applied to the probe 102, the force that the spring 115 has is very small compared to the conventional example, and even if a weak spring is adopted, It is possible to avoid the problem that the spring extends long and the entire size of the probe increases. Even if the spring 115 is deformed due to temperature change or the like, the generated force of the spring 115 is originally small. There is little influence. Since the error of the probe pressing force is reduced, the measurement accuracy can be improved.

  In addition, as shown in FIG. 6C, a pulley 118 can be used instead of the balance 111. That is, a pulley 118 that is rotatable around a fulcrum 110 is disposed on the moving member 103, the probe 102 is connected to one end of a suspension thread 119 hung around the pulley 118, and a balance weight 114 is connected to the other end. Then, one end of a fine adjustment spring 115 is connected under the balance weight 114, and the other end of the spring 115 is connected to the moving member 103. Even with such a configuration, the same effects as the contact probe shown in FIG. 6B can be obtained.

  Note that the fine adjustment spring 115 is connected to the balance weight 114 in FIGS. 6A to 6C, but it is the same when connected to the probe 102 side. The probe 102 is supported by a rolling guide in FIGS. 6A to 6C. However, the probe 102 may be supported by a parallel leaf spring or by an air bearing.

Next, a shape measuring apparatus incorporating the contact probe of the present reference example configured as shown in FIG. 6A will be described with reference to FIG.

  In FIG. 5, a probe tip 2 having a conical tip for attaching a sphere 1 and penetrating a small hole in the center is placed below the probe shaft 4 having a small hole in the center with a spacer 3 in between. Secure with screws. A mirror 6 having a hole in the center is bonded and fixed to the mirror fixing piece 5, and this mirror fixing piece 5 is screwed and fixed to the upper side of the probe shaft 4. A vacuum pipe 7 communicating with a small hole is fixed at the center of the probe shaft 4, and the vacuum pipe 7 is connected to a vacuum gauge 9 and further connected to a vacuum source (not shown) via an air valve 8. Yes. At this time, the air valve 8 is one that can select whether the vacuum pipe 7 is connected to a vacuum source or released to the atmosphere. Thereby, the sphere 1 can be vacuum-sucked to the conical tip of the probe tip 2, and the tip sphere can be easily replaced. Furthermore, by monitoring the degree of vacuum with the vacuum gauge 9, it is possible to determine whether the tip sphere is in an attracting state and to improve measurement reliability.

  The probe shaft 4 is supported so as to be movable in the vertical direction with respect to the housing 10 via a so-called air bearing 11 that supports the probe shaft 4 in a non-contact manner through a thin air film. Compressed air holes 12 are provided for guiding. These compressed air holes 12 can be freely drawn around the inside of the housing 10 by drilling from one side with a drill and closing the surface portion of the hole with screws or an adhesive as necessary. The compressed air hole 12 is connected to a compressed air pipe 13 and further connected to a compressed air source (not shown). With this configuration, the probe shaft 4 can freely move in the vertical direction without friction.

  The housing 10 is provided with a protruding lower stopper 10b on the lower surface thereof, and restricts excessive movement of the probe shaft 4 in the upward direction by colliding with the spacer 3. Similarly, a projection-like upper stopper 10a is provided on the upper surface portion of the housing 10 so as to abut against the mirror fixing piece 5 of the probe for excessive downward movement. In order to reduce the impact, a damper such as a thin rubber sheet is bonded and fixed to these stoppers. The housing 10 is fixed and supported by a second housing 16 fixed to the measurement shaft 15.

  The second housing 16 is provided with a balance 51 that can swing around a fixed pin 50, and the mirror fixing piece 5 is suspended from one end of the balance 51 via a suspension thread 52. A balance weight 54 is connected to the other end via a suspension thread 53. The balance weight 54 is supported so as to be movable in the vertical direction with respect to the second housing 16 via a so-called air bearing 55 that supports the balance weight 54 in a non-contact manner through a thin air film. It can move freely without friction. The mass of the balance weight 54 is set smaller than the mass on the probe shaft side. The second housing 16 is provided with a compressed air hole 56 for guiding compressed air to the air bearing 55. The compressed air hole 56 is connected to a compressed air pipe 57, and further connected to a compressed air source (not shown). Yes.

  The second housing 16 is provided with a nozzle 21 in a direction in which the balance weight 54 is blown upward. A pipe 22 is connected to the nozzle 21, and the pipe 22 is compressed air (not shown) via an air valve 23. Connected to the source. The air valve 23 is automatically controlled by a controller (not shown).

  One end of a weak fine adjustment spring 58 is connected below the balance weight 54, and the other end of the spring 58 is connected to a lever 59 having an adjustment screw 60. As shown in FIG. 5, the lever 59 can be configured integrally with a part of the second housing 16 as a hinge. In this case, since the position of the hinge serves as a fulcrum, adjustment of the spring adjusting screw 60 can reduce the movement of the screw 60 and change the length of the spring, so that precise adjustment of the spring force is possible. It becomes.

  The measurement shaft 15 is supported by the XY table 26 so as to be movable in the same direction as the probe shaft 4, that is, in the vertical direction (Z direction), and is driven by a ball screw 25 and a servo motor 27. The XY table 26 is guided so as to be movable in the X and Y directions with respect to a surface plate (not shown), and is positioned by a servo motor (not shown). A servo motor 27 that drives the measuring shaft 15 is connected to a servo amplifier 29, and the servo amplifier 29 is connected to a control system switching device 31. An encoder 33 is connected to the rotating shaft of the servo motor 15, and its output is connected to the position control compensation circuit 30. When the control system switching device 31 is connected to the position control system, the position of the measurement shaft 15 can be controlled. The control system switching device 31 is automatically controlled by a controller (not shown).

  The interferometer 34 and the quarter-wave plate 35 are fixed to the measurement axis 15, a mirror 36 is provided above the measurement shaft 15, and the mirror 36 is fixed to the frame 37. With this configuration, the interferometer 34 can measure the distance between the mirror 6 and the mirror 34. A mounting table (not shown) for an object to be measured is provided in a lower portion of the frame 37, and the object to be measured 38 is fixed to the mounting table.

  The position of the probe shaft 4 in the Z direction is adjusted by measuring the position of the probe shaft 4 in the Z direction with a position sensor 47 disposed at a position facing the convex spherical mirror 46 fixed to the probe shaft 4. That is, light is incident on the optical fiber 42 from a light source (not shown), and a light beam is emitted from the optical fiber fixing piece 43. The optical fiber fixing piece 43 is fixed to the second housing 16 by a fixing member 44. The lens 45 is provided fixed to the fixing member 44, and the light beam is condensed. The condensed light is reflected by a convex spherical mirror 46 fixed to the probe shaft 4 and focused on the position sensor 27. Here, the center of the spherical surface of the convex spherical mirror 46 is arranged on the center axis of the probe shaft 4. The position sensor 47 is fixed on a fine movement table 48 fixed to the measurement shaft 15 and can be fixed by adjusting the position in the Z direction.

  The position sensor 47 is connected to the sensor amplifier 49 and converts the light spot position into an electrical signal. The sensor amplifier 49 is connected to the needle pressure control compensation circuit 32 and further connected to the control system switching device 31. When the control system switching device 31 is connected to the needle pressure control system, the servo motor is controlled so that the output of the sensor amplifier 49 becomes constant.

  Further, a force sensor 39 for measuring the probe pressing force is installed within the probe movable range.

  Next, a measurement operation performed using the shape measuring apparatus configured as described above will be described with reference to the flowchart of FIG. 4 described above.

  First, the probe is prepared before measurement. First, the probe is fixed to the lower end (step S01). That is, the air valve 23 is opened to blow compressed air from the nozzle 21, and the balance weight 54 is lifted upward. Then, the balance 51 is tilted, the probe moves downward, and the mirror fixing piece 5 comes into contact with the upper stopper 10a, and the probe is fixed to the lower end.

  Next, the tip sphere 1 is set as follows (step S02). With the air valve 55 opened and the pressure in the hole inside the probe tip 2 lowered, the tip ball 1 is vacuum-adsorbed to the probe tip 2. When the probe is vacuum-sucked, the pressure inside the pipe decreases, and the measured value of the vacuum gauge 9 approaches a vacuum. Therefore, the presence or absence of the probe tip sphere can be detected by monitoring the measured value of the vacuum gauge 9 (step S03). If the pressure is abnormal, the process is interrupted because of some failure (step S20). If the pressure is normal, the process proceeds to the next process (after step S04).

  The control system switching device 31 is set as a position control system, that is, a feedback control system is selected so that the position of the measurement axis 15 is constant, and the safe position, that is, the direction in which the probe is farthest from the object to be measured 38. The measuring shaft 15 is retracted (step S04). Next, the XY table 26 is moved so that the probe is placed on the force sensor 39 (step S05), and the measurement shaft 15 is lowered to bring the probe into contact with the force sensor 39 (step S06).

  Here, when the sphere 1 at the tip comes into contact with the object to be measured, a force sensor or the like and receives a reaction force, the probe shaft 4 is pushed up, and the displacement can be lit and read with a displacement meter using this principle. it can. The operation of this displacement meter portion will now be described.

  The light beam emitted from the optical fiber fixing piece 43 is incident on the lens 45 while gradually spreading, and is reflected by the spherical mirror 46 fixed to the probe shaft 4 while focusing, and is focused on the position sensor 47. The fine movement table 48 is adjusted and fixed in advance so that the focal position is at the center position of the position sensor 47. When the probe shaft 4 moves, the amount of movement in the direction perpendicular to the intermediate direction between the light beam incident on the convex spherical mirror 46 and the reflected light beam, that is, the direction indicated by the arrow A in FIG. The focal position on the position sensor 47 moves. Since the probe shaft 4 is supported so as to be movable only in the vertical direction, the direction indicated by the arrow A is considered to be substantially the moving direction of the probe shaft 4. When the angle difference between the probe moving direction and the displacement measuring direction is θ, cos θ of the probe moving amount is measured. The position change is converted into an electric signal by the sensor amplifier 49.

  When the probe shaft 4 is pushed up, the balance 51 tilts and the spring 58 contracts. A force obtained by multiplying the change length by the spring constant of the spring 58 is generated as a reaction force. The force becomes a pressing force between the ball 1 and the object to be measured. That is, the pressing force is proportional to the amount of movement of the probe shaft. Therefore, the output of the sensor amplifier 49 represents the pressing force of the probe. The output of the sensor amplifier 49 is not affected by the inclination around the center of the convex spherical mirror 46. This is because the center of the spherical surface of the convex spherical mirror 46 coincides with the center axis of the probe shaft 4.

  Whether the probe is in contact with the object to be measured can be determined by monitoring the displacement measurement signal of the probe, that is, the signal of the sensor amplifier 49. Since the probe is in contact with the mirror fixing piece 5 and the stopper 10a of the housing 10, the probe does not move even if the measurement shaft 15 moves and there is disturbance vibration. Therefore, the signal of the sensor amplifier 49 is not shaken by disturbance vibration, and contact determination can be easily performed. That is, since it is only necessary to monitor whether or not a predetermined signal level is reached, the presence or absence of contact can be determined at a very high speed, for example, 1 ms.

  Next, the air valve 23 is closed to stop blowing compressed air from the nozzle 21, and the movement of the probe is made free (step S07). The measuring shaft 15 is moved until the value of the displacement sensor reaches a predetermined value, for example, 0 volts. Then, the control system switching device 31 is switched to the needle pressure control system (step S08). That is, the measuring shaft 15 is controlled so that the output of the sensor amplifier 49 is constant.

  Next, the pressing force of the probe is measured using the force sensor 39 (step S09). It is determined whether or not the value of the pressing force at this time is a predetermined value (step S10). At this time, whether the pressing force is good or bad is set, for example, as ± 10% of the set value. If not, the probe pressing force is adjusted (step S21). In order to set the probe pressing force to a predetermined value, the adjusting screw 60 is turned. Then, the inclination angle of the lever 59 changes, and the position of the lower end of the weak spring 58 changes. On the other hand, since the probe is in contact with the force sensor 39, the position does not change. Accordingly, since the position of the balance weight 54 does not change, the length of the weak spring 58 eventually changes. Then, the force generated by the spring changes, and as a result, the pressing force of the probe changes. Thus, the rotation angle of the adjusting screw 60 is adjusted until the probe pressing force reaches a predetermined value.

  If the determination of the probe pressing force (step S10) is good, the control system switching device 31 is switched to the position control system again, the measurement axis is retracted to the safe position (step S11), and the air valve 23 is opened again. The probe is fixed (step S12).

  Thus, the preparation of the probe is completed, and then the process of measuring the shape of the object to be measured starts.

  First, the XY table 26 is moved to the first measurement position (step S13). Then, in the same procedure as before, the measurement shaft 15 is lowered and the tip sphere 1 of the probe is brought into contact with the object to be measured 21 (step S14).

  Next, the air valve 23 is closed to stop blowing compressed air from the nozzle 21, and the probe moves freely (step S15).

  Then, the control system switching device 31 is switched to the needle pressure control system (step S16), and the measurement area of the object to be measured is scanned (traced) using the XY table 26, and at the same time, the position of the measurement axis is not shown. (Step S17). Further, the vertical direction of the probe is directly measured by an interferometer 34 that measures the distance between the reference mirror 6 and the reference mirror 36.

  When the entire measurement area is scanned, the control system switching device 31 is switched to the position control system again, the measurement axis is retracted to the safe position (step S18), and the air valve 23 is opened again to fix the probe (step S19).

As described above, according to this reference example , the gravity of the tip sphere 1, the probe tip 2, the spacer 3, the probe shaft 4, the mirror fixing piece 5, the mirror 6, the pipe 7, the suspension threads 52 and 53, etc. Since a part of the balance weight 54 takes charge, the force generated by the spring 58 can be greatly reduced as compared with the conventional example. Therefore, even if a weak spring is employed, the extension of the spring does not increase, and the structure can be made relatively small as shown in FIG.

  In addition, since the force generated by the spring is originally small, even if the generated force of the spring slightly changes with respect to environmental changes such as temperature changes, the influence is small. Therefore, the accuracy of the probe contact force is improved, and as a result, the measurement accuracy is improved.

  Also, the probe tip sphere can be easily attached and detached, and the probe tip sphere can be frequently replaced. As a result, it becomes possible to reduce the risk of measuring the shape with the damaged tip sphere, and the measurement reliability is improved.

Further, although the control of the measuring shaft 15 is constituted by a servo motor and a ball screw in this reference example , other driving means such as a linear motor can be used.

In this reference example, the adjustment of the pressing force has been described as a preparation of the probe using the flowchart, but this adjustment is not always necessary in each measurement. That is, the adjustment of the pressing force may be omitted.

Further, in this reference example , the weak spring 58 is disposed below the balance weight 54, but the same applies to a configuration in which the weak spring 58 is pulled upward.

( First embodiment )
Figure 7 is a block diagram showing a first shape measuring apparatus incorporating a contact probe embodiment of the present invention partially broken, 8, contact probe of the first embodiment of the present invention (A) is a schematic diagram of the contact-type probe of this embodiment, and (b) shows its magnetic circuit.

This embodiment is different from the second reference example described above in that a force generation mechanism using magnetic force is provided on the balance weight side, and in order to fix the probe, compressed air is not blown out, but air suction is performed. Since the other parts are the same as those in the first embodiment , their detailed description is omitted. In the present embodiment, the same elements and members as those in the first reference example and the second reference example described above will be described with the same reference numerals.

  First, the contact type probe in this embodiment will be described with reference to FIG. 8A, a balance 111 swingable around a fulcrum 110 is disposed on a moving member 103 such as a measurement shaft that can be moved three-dimensionally, and a suspension thread 112 is connected to one end of the balance 111. A probe 102 having a ball 101 at the tip is connected, a balance weight 114 is suspended from the other end of the balance 111 via a suspension thread 113, and a pair of yokes 121 and 122 are disposed so as to sandwich the balance weight 114. A permanent magnet 123 is attached between the yokes 121 and 122 to constitute a magnetic circuit, and these are fixed to the moving member 103. Further, in order to adjust the strength of the magnetic flux flowing to the balance weight 114 side, an adjustment screw 124 is provided on the lower side of the permanent magnet 123 to bypass the magnetic flux generated by the permanent magnet 123. If the area where the balance weight 114 and the yokes 121 and 122 overlap is different, a so-called magnetic shear force acts, and the balance weight 114 is pulled into the central portion of the yokes 121 and 122. Because of this force, the mass of the balance weight 114 can be reduced.

The operation of the magnetic circuit of FIG. 8A will be described. This magnetic circuit can be schematically drawn as shown in FIG. 8B. The permanent magnet 123 is represented as a simple model by the magnetomotive force M and the internal resistance R ₀ , and the magnetic flux generated from the permanent magnet 123 is Φ. Further, the magnetic resistance of balance weight 114 side is _{R 1,} the magnetic resistance of the adjustment screw 124 ₁ side is _{R 2.} Further, when the overlapping portion on the balance weight 114 side is z, the thickness is b, the gap is δ, and the magnetic permeability is μ, the magnetic resistance is

また、調節ネジ１２４側のギャップをｈ、断面積をＳとすると

If the gap on the adjustment screw 124 side is h and the cross-sectional area is S,

また、ＭとΦには、図８の（ｂ）より次の関係が成り立つ。

Further, the following relationship is established between M and Φ from FIG. 8B.

ｚ方向のずり力はＦは、

The shear force in the z direction is F

これではわかりにくいので、ｚ＝０のまわりで１次までテーラー展開すると、

This is difficult to understand, so if you develop a tailor around z = 0 to the first order,

The first term in Equation (8) is a term that generates a force that supports the weight of the probe with a constant value. Since there is a gap h between the adjusting screw 124 and the yoke 122 in the term, it can be seen that this force can be adjusted by changing the gap h by protruding or retracting the adjusting screw 124. The second term includes the amount of movement z of the probe, and indicates that the force decreases as z increases. Since the generated force changes with displacement, it corresponds to a mechanical spring. That is, the magnetic circuit of FIG. 8A has the same action as the counter balance mass that supports the weight of the probe, and also acts as a spring element. Further, the magnetic resistance R ₀ can be adjusted by changing the material and shape of the magnet 123 and the yokes 121 and 122.

  As described above, in the present embodiment, since the force for supporting the weight of the probe is generated using the magnetic force of the permanent magnet, the mass of the balance weight can be reduced. As the mass of the movable part of the probe becomes lighter, its inertia decreases, so that the follow-up speed for minute irregularities of the object to be measured is improved. An increase in the accuracy of following the object to be measured leads to an improvement in measurement accuracy.

  Next, a shape measuring apparatus incorporating the contact probe of the present embodiment configured as described above will be described with reference to FIG.

  In FIG. 7, the second housing 16 is provided with a nozzle 21a configured to suck the balance weight 54 upward. A pipe 22a is connected to the nozzle 21a, and the pipe 22a has an air valve 23a. Via a vacuum source (not shown).

  A pair of yokes 62, 62 formed with the magnet 63 sandwiched therebetween is fixed to the second housing 16 so that the upper part sandwiches the balance weight 54 with a gap, and the lower part is on the balance weight 54 side. An adjusting screw 64 for adjusting the strength of the flowing magnetic flux is provided. Therefore, a part of the magnetic flux generated from the magnet 63 flows to the balance weight 54 side and the rest flows to the adjustment screw 64 side. Therefore, by rotating the adjustment screw 64 and adjusting the gap between the adjustment screw 64 and the yoke 62, the amount of magnetic flux flowing to the balance weight 54 side can be adjusted. In the present embodiment, the force generated by the magnet 63 has a constant part and a part proportional to the displacement of the probe, as described based on the above-described equation (8), and the constant part cancels the weight of the probe. The part that is proportional to the displacement of the probe acts as a spring element.

  In the shape measuring apparatus configured as described above, the measuring operation is the same as the method described in the flowchart of FIG. However, the probe is fixed by opening the air valve 23a and drawing air from the nozzle 21a to pull up the balance weight 54 and press the probe against the stopper. Further, the method for adjusting the needle pressure is performed by adjusting the adjusting screw 64.

In the present embodiment, the following effects are further obtained with respect to the first embodiment described above.
(1) Since the probe's own weight is supported using magnetic force, the balance weight can be reduced. Accordingly, the inertia of the probe is reduced, and the response and followability of the probe to the surface of the object to be measured can be improved.
(2) Since the magnetic circuit also serves as a spring element, it is not necessary to provide a spring, and the size can be reduced.

In addition, an embodiment having both the pressing force adjusting mechanism using the spring described in the second reference example and the pressing force adjusting mechanism using the magnetic force described in the present embodiment is also conceivable. The effect is the same. In this case, both the spring and magnet mechanisms are required, but the degree of freedom in selecting the range of generated force for each is increased. For example, an embodiment is conceivable in which the magnet is mainly responsible for the probe's own weight and the spring is responsible for the precise force relating to the remaining pressing force. That is, the magnet takes charge of rough adjustment, and the spring takes charge of precise adjustment.

( Second Embodiment )
Figure 9 is a block diagram showing a shape measuring apparatus incorporating a contact probe in the second embodiment of the present invention partially broken, FIG. 10, contact probe of the second embodiment of the present invention It is a schematic diagram for demonstrating.

The present embodiment is characterized in that a force generation mechanism using a permanent magnet and a coil is provided on the balance weight side with respect to the first embodiment described above, and other parts are the same as those of the first embodiment. Detailed description thereof will be omitted. In the present embodiment, the same reference numerals are used for the same elements and members as those in the second reference example or the first embodiment described above.

First, the contact type probe in this embodiment is demonstrated with reference to FIG. A balance 111 swingable around a fulcrum 110 is disposed on a moving member 103 such as a measurement shaft that can be moved three-dimensionally, and a probe 102 having a ball 101 at the tip thereof via a suspension thread 112 at one end of the balance 111. , A balance weight 114 is suspended from the other end of the balance 111 via a suspension thread 113, a yoke 125 is disposed so as to sandwich the balance weight 114, and a magnetic circuit comprising the yoke 125, the permanent magnet 126, and the coil 127. Configure. This magnetic circuit can be drawn as shown in FIG. Such a magnetic circuit has been described in the first reference example, and the details are omitted. When only the conclusion is cited, the magnetic circuit in this embodiment also has the same action as the mass of the counter balance that supports the weight of the probe. It also acts as a spring element. That is, by changing the current flowing through the coil 127, the generated force of the magnetic circuit changes, so that the contact force can be precisely adjusted. Even if the weight of the probe changes due to replacement of the probe tip or the like, the influence can be reduced by re-adjustment, so that the measurement accuracy can be increased. Compared to the second embodiment described above, the configuration is somewhat complicated, but it is only necessary to control the current, so that remote operation is possible, and the operation is facilitated, so that an efficient measurement apparatus can be operated.

  Next, a shape measuring apparatus incorporating the contact probe of the present embodiment configured as described above will be described with reference to FIG.

  In FIG. 9, a magnetic circuit composed of a yoke 65, a magnet 66, and a coil 67 is fixed to the second housing 16, and is arranged so that a balance weight 54 is sandwiched between upper portions of the yoke 65. The coil 67 is connected to a current source 68. The force that the magnetic force generated by the magnet 66 and the coil 67 acts on the balance weight 54 is explained below based on the equation (3). The force generated by the magnetic circuit depends on the constant portion and the probe displacement. There is a proportional part, the constant part acts to cancel the weight of the probe, and the part proportional to the probe displacement acts as a spring element.

In the shape measuring apparatus configured as described above, the measuring operation is the same as the method described in the flowchart of FIG. However, the adjustment of the probe pressing force is simpler than the method described in the first embodiment because the current source 68 is adjusted and the magnetic force generated by the coil 67 is adjusted.

This embodiment has the following advantages in addition to the first embodiment described above.
(1) The adjustment of the probe pressing force can be automated. Since the probe pressing force changes only by controlling the current to the coil, the probe pressing force can be automatically adjusted. Therefore, the measurement preparation time can be shortened, and the measurement cost can be reduced.
(2) The accuracy of adjusting the probe pressing force can be improved. Since the current to the coil can be controlled precisely, it is highly accurate for methods that involve machine movement, such as springs and magnetic adjustment screws. Since the setting accuracy of the pressing force increases, the measurement accuracy can be improved.

DESCRIPTION OF SYMBOLS 1 Sphere 2 Probe tip 3 Spacer 4 Probe shaft 5 Mirror fixing piece 6 Mirror 7 Vacuum piping 8 Air valve 9 Vacuum gauge 10 Housing 10a, 10b Stopper 11 Air bearing 12 Compressed air hole 13 Compressed piping 15 Measuring shaft 16 Second housing 17 Yoke 17a Magnetoresistive adjusting screw 17b Gap adjusting screw 18 Permanent magnet 19 Coil 20 Current source 21, 21a Nozzle 22, 22a Piping 23, 23a Air valve 24 Guide 25 Ball screw 26 XY table 27 Servo motor 29 Servo amplifier 30 Position control compensation circuit 31 Control System Switching Device 32 Needle Pressure Control Compensation Circuit 33 Encoder 34 Interferometer 35 Quarter Wave Plate 36 Mirror 37 Frame 38 Object 39 Force Sensor 42 Optical Fiber 43 Optical Fiber Fixed piece 44 Fixed member 45 Lens 46 Convex spherical mirror 47 Position sensor 48 Fine movement table 49 Sensor amplifier 50 Pin 51 Balance 52, 53 Suspension thread 54 Balance weight 55 Air bearing 56 Compressed air hole 57 Compressed pipe 58 Spring 59 Lever 60 Adjusting screw 62 Yoke 63 Magnet 64 Adjustment screw 65 Yoke 66 Magnet 67 Coil 68 Current source 101 Sphere 102 Probe 103 Moving member 104 Spring 105 Ferromagnetic member 106 Yoke 107 Permanent magnet 108 Coil 110 Support point 111 Balance 112, 113 Hanging thread 114 Balance weight 115 Spring 116 Lever 117 Adjustment screw 118 Pulley 119 Suspension thread 121, 122 Yoke 123 Permanent magnet 124 Adjustment screw 125 Yoke 126 Permanent magnet 127 Coil

Claims (3)

In the contact type probe for measuring the shape of the object to be measured by scanning the probe tip in contact with the object to be measured and measuring the coordinate position of the probe,
A movable member movable in three dimensions;
A probe provided to be movable in the direction of gravity with respect to the moving member;
A balance or pulley having a fulcrum attached to the moving member;
A magnetic circuit composed of a yoke, a permanent magnet, a coil that can be energized, or an adjustment screw whose gap between the yoke and the yoke is variable.
A probe is suspended from one end of the balance or pulley, and a balance weight made of a ferromagnetic material is connected to the other end. The magnetic circuit includes the permanent magnet and the coil or the adjusting screw. The contact type probe is arranged in parallel with the balance weight via a gap, and the balance weight is sandwiched between the yokes of the magnetic circuit.   The contact probe according to claim 1, wherein the probe and / or the balance weight is supported by the moving member via an air bearing. A force sensor is further provided within the movable range of the probe, the probe is brought into contact with the force sensor, and the current of the coil is changed so that the value of the force sensor becomes a predetermined value , or the adjustment screw is rotated. The contact type probe according to claim 1 , wherein the pressing force is adjusted.

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