Abstract:
A shape measuring machine  100  which measures the shape of an object to be measured by bringing the surface of a probe  124  into direct contact with the object to be measured  102  has a photocatalyst film  124   b  on the tip end surface of the probe  124.  The shape measuring machine  100  may be provided with a light source for activating the photocatalyst film  124   b.  The photocatalyst film  124   b  may have a metal oxide. The photocatalyst film  124   b  may contain at least one of carbon and nitrogen. Thereby, organic contamination can be removed by subjecting the surface to self cleaning due to decomposition of organic substances and such dirt that requires cleaning can also be easily removed by controlling the hydrophilic property.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The disclosure of Japanese Patent Application No. 2007-220205 filed on Aug. 27, 2007 including specifications, drawings and claims is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a shape measuring machine and a contact-type probe thereof (simply referred to as a probe) and, in particular, to a shape measuring machine equipped with a probe which is preferably used in a shape measuring machine that measures the shape of an object to be measured by bringing the probe into direct contact with the object to be measured and makes it possible to decompose and remove contamination when the probe is contaminated and to the probe thereof. 
         [0004]    2. Description of the Related Art 
         [0005]    In a measuring machine which measures a shape of an object to be measured, during measurement of the object to be measured, contamination including dust or oil is gradually adhered to the tip end of a probe. Then measurement accuracy deteriorates due to a change in contact sensitivity or in the tip end shape of the probe. 
         [0006]    In order to maintain measurement accuracy, it is necessary to remove a probe and clean the probe. Alternatively, as shown in Japanese Published Unexamined Patent Application No. 2000-35325 (Patent Document 1), it has been proposed that, the tip end of the probe is appropriately cleaned by blowing air in place of removal of the probe. 
         [0007]    However, in particular, a micro probe (the tip end diameter of the probe is 100 μm or smaller) and an easily breakable probe are easily damaged by being broken or bent when handled in attaching or detaching for cleaning, thus making it difficult to clean the probes. 
         [0008]    Also, as shown in Patent Document 1, even when a probe is cleaned by blowing air without removing the probe, there may be a case where the probe is not sufficiently cleaned, depending on the extent or type of contamination (also referred to as dirt). 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention has been made in order to solve the above-described problems and, an object thereof is to provide a shape measuring machine equipped with a probe in which organic contamination (dirt caused by adhered organic substances) is removed by subjecting the surface to self cleaning due to decomposition of the organic substances and such dirt that requires cleaning is also easily removed by controlling the hydrophilic property and also to provide the probe. 
         [0010]    A first aspect of the present invention is a shape measuring machine which measures the shape of an object to be measured by bringing the surface of the probe into direct contact with the object to be measured and the probe is provided with a photocatalyst film at the tip end surface, thereby solving the above problems. 
         [0011]    A second aspect of the present invention is the shape measuring machine which is provided with a light source for activating the photocatalyst film. 
         [0012]    Further, a third aspect of the present invention is the shape measuring machine in which the light source is lit in a state where an object to be measured is not measured for the shape. 
         [0013]    Further, a fourth aspect of the present invention is the shape measuring machine in which a state where the object to be measured is not measured for the shape is at night. 
         [0014]    Further, a fifth aspect of the present invention is the shape measuring machine in which the probe is cleaned when an abnormal shape measurement value is detected. 
         [0015]    Further, a sixth aspect of the present invention is the shape measuring machine in which light is to be irradiated after cleaning. 
         [0016]    Still further, a seventh aspect of the present invention is the shape measuring machine in which light is constantly irradiated to the probe. 
         [0017]    Further, an eighth aspect of the present invention is the shape measuring machine in which the photocatalyst film contains a metal oxide. 
         [0018]    Further, a ninth aspect of the present invention is the shape measuring machine in which the photocatalyst film contains at least one of carbon and nitrogen. 
         [0019]    A tenth aspect of the present invention is to provide a probe of a shape measuring machine which measures a shape of an object to be measured by bringing a surface of the probe into direct contact with the object to be measured, wherein a photocatalyst film is formed on the surface thereof. 
         [0020]    According to the present invention, organic contamination can be decomposed, and inorganic contamination (dirt caused by adhered inorganic substances) and contamination that is not completely decomposed and requires cleaning (hereinafter referred to as inorganic contamination and the like) can also be easily removed by cleaning, thus making it possible to keep the surface of the probe clean. In other words, a decrease in performance and measurement errors resulting from the influence of contamination can be reduced, thereby making it possible to maintain a favorable measurement accuracy. 
         [0021]    Further, it is possible to decrease the number of times of attaching and detaching a probe for cleaning the probe, thereby improving workability. Then, it is also possible to decrease or prevent damage of the probe due to attachment or detachment. 
         [0022]    These and other novel features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The preferred embodiments will be described with reference to the drawings, wherein like elements have been denoted throughout the figures with like reference numerals, and wherein; 
           [0024]      FIG. 1  is a constitutional schematic diagram of a shape measuring machine main body according to a first embodiment of the present invention. 
           [0025]      FIG. 2  is a pattern diagram showing a relationship between light sources and a probe mounted on the shape measuring machine according to the first embodiment of the present invention. 
           [0026]      FIG. 3  is an entire block diagram showing the shape measuring machine according to the first embodiment of the present invention. 
           [0027]      FIG. 4  is a pattern diagram showing a relationship between light sources and a probe according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    Hereinafter, a detailed description is given for embodiments of the present invention with reference to the drawings. 
         [0029]    The first embodiment of the present invention will be explained with reference to  FIG. 1  to  FIG. 3 .  FIG. 1  is a construction schematic diagram of a shape measuring machine main body of the present embodiment.  FIG. 2  is a pattern diagram showing a relationship between light sources and a probe mounted on the shape measuring machine.  FIG. 3  is an entire block diagram of the shape measuring machine. 
         [0030]    As shown in  FIG. 3 , a shape measuring machine  100  is substantially divided into a shape measuring machine main body  110  and a control device  150 . First, a description is given for the shape measuring machine main body  110  with reference to  FIG. 1 . 
         [0031]    The shape measuring machine main body  110  is, for example, a main body of a three-dimensional coordinate measuring machine, includes a press platen  114  on a base  112 , and has a head  120  on a gate-shaped frame on the press platen. On the head  120 , a detector  122  is provided, and to its tip end, a probe  124  is attached. The gate-shaped frame is made up of a pair of columns  116  rising from the press platen  114  and a beam  118  laid across the pair of columns  116 . The columns  116  support the beam  118 , and the head  120  is movable in the left and right direction (X direction) along the beam  118 . The detector  122  attached to the head  120  is movable in the up and down direction (Z direction) in the drawing. The columns  116  are movable in the front and rear direction (Y direction) on the press platen  114 , so that the head  120  is also movable in the Y-axis direction. The detector  122  is able to detect pressure and deformation via the probe  124  in the X, Y, and Z directions. As shown in  FIG. 3 , for these movements, XYZ motors  126  are used, and moving distances in the respective directions are measured by linear encoders  128 . 
         [0032]    As shown in  FIG. 2 , the probe  124  is, for example, provided with a probe sphere  124   a  at the tip end. Then, a photocatalyst film  124   b  is uniformly formed on the surface of the probe sphere  124   a.  It is noted that a photocatalyst is a substance which facilitates chemical reactions on exposure to light without changing (to be described later). In the present embodiment, for example, titanium oxide (TiO 2 ), which is a metal oxide, can be mainly used as a photocatalyst. Among CVD (chemical vapor deposition) (including atmospheric pressure CVD, plasma CVD and photo-excited CVD) better in coating property than other methods such as sputtering and vapor deposition, plasma CVD is, in particular, used in order to form a uniform film. This is because plasma CVD is an effective method by which a film is easily formed without heating a substrate and no thermal damage is given to the probe  124 . 
         [0033]    As shown in  FIG. 1 , light sources  132  can be disposed, for example, on one corner  130  on the press platen  114 . Since the tip end of the probe  124  is spherical, for example, two ultraviolet lamps can be disposed as the light sources  132 . Further, as shown in  FIG. 2 , when the probe  124  moves and halts at a predetermined position, the probe sphere  124   a  is located exactly in the middle of these two light sources  132  and constituted so that an ultraviolet ray is irradiated uniformly to the probe sphere  124   a  at the tip end thereof. 
         [0034]    Next, a description is given for a control device  150  with reference to  FIG. 3 . The control device  150  is provided with a storage  152 , a controller  154 , a display unit  156  and an operating unit  158 . 
         [0035]    The storage  152  is connected to the controller  154 , and set values and programs necessary for controlling the shape measuring machine main body  110  are read therein. Programs and others for controlling the light sources  132  are also read therein. 
         [0036]    The controller  154  is connected to the detector  122 , the XYZ motors  126 , the linear encoders  128  and the light sources  132 . When measuring an object to be measured  102 , for example, the XYZ motors  126  are driven so that the pressure or displacement applied to the detector  122  via the probe  124  is made constant, and the shape of the object to be measured  102  can be obtained from the values of the linear encoders  128  at this time. 
         [0037]    The display unit  156  is connected to the controller  154  and provided with a monitor screen and a speaker, and necessary information is transmitted to an operator with images and voice whenever necessary. 
         [0038]    The operating unit  158  is provided with input devices such as a keyboard and a mouse and connected to the controller  154 . Instructions are input by an operator whenever necessary. 
         [0039]    Next, a description is given for functions of the photocatalyst film  124   b.    
         [0040]    Since the photocatalyst film  124   b  of the present embodiment contains titanium oxide, light is irradiated to activate photocatalyst functions, thus producing a potent oxidative power. As a result, organic contamination adhered to the surface of the photocatalyst film  124   b  is oxidized to decompose into water and carbon dioxide. Accordingly, the organic contamination is decomposed, thus making it possible to keep the surface of the photocatalyst film  124   b  clean. 
         [0041]    When light is irradiated, the surface of the titanium oxide-containing photocatalyst film  124   b  is given an excellent hydrophilic property. For this reason, wettability is improved, and water easily comes into a space between the surface and organic contamination or inorganic contamination adhered to the surface, thus making it possible to easily wash away the organic contamination, the inorganic contamination or the like by using water or a drug solution in which water is used as a solvent. Further, the hydrophilic property is provided to exert such effects that dirt is less likely to adhere thereto. 
         [0042]    It is noted that in order to activate titanium oxide, light energy corresponding to band gap energy between the conduction band of titanium oxide and the valence band is required, and the energy is light at an ultraviolet ray region (400 nm or less). Then, titanium oxide is characterized in that it keeps photocatalyst effects for a long time after activation (from the above description, it has a potent oxidative power and an excellent hydrophilic property). On activation, it is possible to impart the hydrophilic property to the photocatalyst film  124   b  at a light quantity smaller than that imparting a potent oxidative power. 
         [0043]    Next, a description is given for actions of the present embodiment. 
         [0044]    In a state where the object to be measured  102  is not measured for the shape, for example, during a predetermined period of time at night or the like, the probe  124  is allowed to move to one corner  130  on the press platen  114 , and in a position shown in  FIG. 2 , the light source  132  is lit. If the time during which light is irradiated to the photocatalyst film  124   b  (activation time) is, for example, several dozen minutes, it is sufficient for keeping the photocatalyst effects over one day or longer. In other words, even when the object to be measured  102  is measured for the shape for a whole day, dust is less likely to adhere due to the presence of the photocatalyst film  124   b,  and when organic contamination is generated, the organic contamination is decomposed, thus making it possible to keep the surface of the probe  124  clean. As a result, it is possible to minimize shape errors resulting from dirt. 
         [0045]    Further, in the case of inorganic contamination or the like, the hydrophilic property is exhibited to improve wettability of the photocatalyst film  124   b  on cleaning with water or a drug solution, thereby making it possible to enhance the cleaning effects and easily wash away the inorganic contamination and others. Therefore, at a stage where shape measurement values are found abnormal, it is necessary to carry out measurements again after cleaning and quickly verify the shape measurement values. It is noted that after measurement of the shape, light is again irradiated to the photocatalyst film  124   b,  by which wettability of the drug solution can be further improved to increase the cleaning effects and shorten the cleaning time. 
         [0046]    As described so far, since the organic contamination can be decomposed and the inorganic contamination or the like can also be removed easily by means of cleaning, it is possible to keep the probe  124  constantly clean. In other words, a decrease in performance and measurement errors resulting from contamination can be reduced, thereby making it possible to maintain favorable measurement accuracy. 
         [0047]    Further, the photocatalyst film  124   b  can be activated without removing the probe  124  and the probe  124  can be attached or detached for cleaning at a smaller number of times, resulting in an improved workability. Then, it is also possible to decrease or prevent damage of the probe  124  due to attachment or detachment. 
         [0048]    More specifically, a micro probe (the tip diameter of the probe is 100 μm or smaller) and an easily breakable probe can omit cleaning with a drug solution due to the decomposing and cleaning (self-cleaning) function on the surface with regard to organic contamination thereof. In other words, the probe  124  can be attached or detached for cleaning at a smaller number of times, thus making it possible to reduce damage to the probe  124  on handling of the probe  124 . Further, when cleaning with a drug solution, the hydrophilic property is controlled, thereby the probe can be prevented from damage such as breakage or bending when the surface tension of the drug solution is made problematic in soaking the probe  124  in the drug solution. Still further, due to photocatalyst effects, cleaning power more satisfactory than cleaning by air can be obtained. In addition, cleaning with a drug solution may be conducted in combination with cleaning by air. 
         [0049]    The light sources  132  are provided on the press platen  114 . Since provision of the light sources  132  causes no change in the shape of the probe  124  and the detector  122 , the object to be measured  102  can be measured for the shape at a degree of freedom similar to that of the conventional shape measuring machine. 
         [0050]    Further, since the photocatalyst film  124   b  is formed by plasma CVD, a uniform film is formed on a probe sphere  124   a  to give no thermal damage to the probe  124 , thereby shape accuracy of the probe sphere  124   a  is not impaired due to the influence of the photocatalyst film, and shape measurement errors can be minimized. 
         [0051]    In the first embodiment, although the activation time is set to several dozen minutes, the present invention is not limited thereto, and the activation time can be set to several hours. In this case, the photocatalyst effects can be provided so as to last for several days. 
         [0052]    Further, in the first embodiment, the photocatalyst film  124   b  is activated in a state where no measurement is made for the shape, however, the present invention is not limited thereto. As shown by disposing a light source  132   a  according to the second embodiment of the present invention given in  FIG. 4 , the light source  132   a  may be mounted on the detector  122  so that light can be constantly irradiated even on measurement. In this case, it is not necessary to provide the light source  132  on the one corner  130  on the press platen  114  shown in the first embodiment. Therefore, it is possible to obtain a greater degree of freedom on the position and size of the object to be measured  102 . Still further, the photocatalyst film  124   b  is kept activated constantly and exhibits greater photocatalyst effects, thus making it possible to keep the probe  124  cleaner as compared with the first embodiment. 
         [0053]    Further, the light sources  132  are not limited to an ultraviolet lamp. LEDs may be usable as long as they are a light source for an ultraviolet ray. Still further, the number of light sources  132  is not limited to two, and one or more of them may be acceptable. The light sources  132  are mounted on the press platen  114 , however, the present invention is not limited thereto. A tubular body to enclose the probe  124  is provided on the head  120  so as to also serve as a cover for protecting the probe  124  when the shape measurement is halted, thereby the probe  124  may be housed manually or automatically to light an ultraviolet lamp provided on the tubular body. 
         [0054]    Further, the present invention is not limited to only a case where the light sources  132  are necessarily provided on the shape measuring machine  100 . For example, the light sources  132  are provided outside the shape measuring machine  100 , and the probe  124  is removed from the shape measuring machine  100 , whenever necessary, thus the light sources  132  may be brought downward to irradiate light. In this instance, a conventional shape measuring machine excluding the probe  124  may be used as it is. Therefore, only the light sources  132  and the probe  124  are provided, by which the present invention can be realized quickly, easily and at an extremely low cost. 
         [0055]    Further, light irradiated from light sources is not limited to an ultraviolet ray. Visible light may also be used as long as it is light having energy for exhibiting the photocatalyst effects of the photocatalyst film. 
         [0056]    Further, the photocatalyst film is not manufactured only by a method described in the present embodiment. Another method includes a film forming method based on monomolecular film-forming technology using a liquid (LB method and the like). According to this film forming method, one layer is about several nanometers in thickness, and it is necessary to repeat coating procedures several times in order to obtain a uniform target film thickness of the present invention. However, soaking in a liquid makes it possible to form a uniform photocatalyst film, and also the film thickness distribution can be controlled at the monomolecular layer level, thereby the shape of film thickness can be controlled more properly. 
         [0057]    Still further, the photocatalyst film is not limited to a film containing titanium oxide. It may contain other metal oxides such as tin oxide, zinc oxide, and tungsten oxide. Therefore, the compositions of the photocatalyst film are not limited to titanium oxide, tin oxide, zinc oxide and tungsten oxide, and nitrogen and carbon may be added thereto in a small quantity. For example, during formation of titanium oxide by CVD, a small quantity of nitrogen or carbon is simultaneously introduced, thereby titanium oxide is partially changed into titanium nitride or titanium carbon. Therefore, the photocatalyst film is increased in hardness, making it possible to improve the durability of the probe  124  and make the service life longer. 
         [0058]    In addition, the photocatalyst film can be controlled for hydrophilic property. It can also be actively controlled for hydrophilic property and water repellency. For example, where a repellent binder (such as fluorinated resin) and a photocatalytic substance are used to form a film, the water repellency of the binder can be made predominant by suppressing the activation of the photocatalyst film. Alternatively, where the photocatalytic substance is also water repellent, it is possible to utilize both the hydrophilic property and water repellency, depending on activation conditions. 
         [0059]    It should be apparent to those skilled in the art that the above-described embodiments are merely illustrative which represent the application of the principles of the present invention. Numerous and varied other arrangements can be readily devised by those skilled in the art without departing from the spirit and the scope of the invention.