Abstract:
A rotation sensor of a bearing with a rotation sensor comprises a sensor housing having a sensor and mounted on an outer race, and a sensor target ring having a detector sensed by the sensor and separated from an inner race, in which a setscrew is provided so as to be displaced to a first position between a through-hole formed in the sensor housing and a screw hole formed in the sensor target ring or a second position in which it is held in either one of recesses.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a bearing with a rotation sensor in which an optical or a magnetic rotation sensor is incorporated in a bearing and a method of incorporating the above to a rotating object.  
         [0003]     2. Description of the Background Art  
         [0004]     For example, there is a bearing with a rotation sensor in which a rotation sensor is mounted on a roller bearing to detect a rotation speed or a rotation direction. According to such bearing with the rotation sensor, as disclosed in Japanese Unexamined Patent Publication No. 9-297151, for example, a sensor is arranged at an outer race which is a fixed-side race and a sensor target ring is arranged at an inner race which is a rotation-side race. The sensor target ring comprises a detector at one end face of a flange, which comprises a region in which light is reflected and a region in which light is not reflected which are alternately arranged. A rotation sensor detects the rotation speed or the rotation direction by irradiating the detector with light from the sensor and sensing the reflected light from the detector.  
         [0005]     According to the conventional optical bearing with the rotation sensor, the sensor housing comprising the sensor is mounted on the fixed-side race and the sensor target ring is incorporated in the rotation-side race. Therefore, when an outer peripheral surface of a rotation spindle engages with an inner peripheral surface of the rotation-side race to be fixed, when its engaging force is small, a skid is generated between the rotation spindle and the rotation-side race of the bearing comprising the sensor target ring during rotation. Especially, when the bearing with the rotation sensor is incorporated in an office machine such as a copying machine or a printer, engagement of a bearing could be loose and tolerance of size is increased. Thus, it is highly likely that the skid is generated. As a result, rotation displacement of the rotation spindle is not correctly measured and measurement cannot be taken with high precision.  
         [0006]     As means for solving the above problem, a method in which the sensor target ring and the rotation-side race are separated and the sensor target ring is directly mounted on the rotation spindle is considered. Thus, even when a skid is generated between the rotation-side race and the rotation spindle, since relative displacement in the rotation direction is not generated between the rotation spindle and the sensor target ring, measurement can be taken with high precision without affecting the rotation detection precision of the rotation spindle.  
         [0007]     However, when the sensor target ring and the rotation-side race are separated, it is necessary to handle the bearing and the sensor target ring separately when they are transported before the bearing is mounted on the rotation spindle.  
       SUMMARY OF THE INVENTION  
       [0008]     It is an object of the present invention to provide a bearing with a rotation sensor in which an error in measuring the rotation due to a skid between a rotation-side race and a rotating object is prevented by separating a sensor target ring from the rotation-side race and connecting means for connecting a sensor housing to the sensor target ring, so that handleability is improved.  
         [0009]     According to the present invention, a bearing with a rotation sensor comprises a bearing including a rotation-side race and a fixed-side race, and a rotation sensor detecting rotation of a rotating object on which the rotation-side race is mounted, in which the rotation sensor comprises a sensor housing having a sensor and mounted on the fixed-side race, a sensor target ring having a detector sensed by the sensor and separated from the rotation-side race, and connecting means provided so as to selectively change over a state in which the sensor housing and the sensor target ring are connected and a state in which they are disconnected. Thus, since the sensor housing and the sensor target ring are connected, the sensor target ring can be handled as an integral part with a bearing body when the bearing with the rotation sensor is transported and they are disconnected when the sensor target ring is mounted on the rotating object.  
         [0010]     Preferably, the connecting means may comprise a fixed-side recess formed in the sensor housing, a rotation-side recess formed in the sensor target ring so as to be opposed to the fixed-side recess, and a connecting shaft provided such that it can be displaced to a first position between the fixed-side recess and the rotation-side recess, or a second position in which it is held in either one of the recesses.  
         [0011]     Furthermore, the fixed-side recess may be a through-hole penetrating the sensor housing, the rotation-side recess may be a screw hole, and the connecting shaft may be a setscrew to engage with the screw hole of the sensor target ring.  
         [0012]     Preferably, the screw hole is a through-hole penetrating the sensor target ring, and the setscrew can be used as a setscrew for fixing the sensor target ring to the rotating object. Thus, the rotating object and the sensor target ring can be easily fixed. In addition, since the sensor target ring is directly mounted on the rotating object whose rotation is to be detected, by the setscrew, even when a skid is generated between the rotation-side race and the rotating object, relative displacement between the rotating object and the sensor target ring is not generated in the rotation direction, so that highly precise measurement can be implemented without affecting rotation detection precision of the rotating object.  
         [0013]     Preferably, the fixed-side recess is a screw hole to engage with the setscrew. Thus, the sensor housing and the sensor target ring can be more surely connected.  
         [0014]     Preferably, a length of the setscrew is shorter than a length of the screw hole of the sensor target ring. Thus, when the setscrew is screwed into the screw hole and held in it, the sensor housing and the sensor target ring can be separated.  
         [0015]     Preferably, the sensor target ring is made of a resin. Thus, when the setscrew engages with the screw hole of the sensor target ring, since a screw thread is formed in the screw hole, it is not necessary to previously provide a screw thread in the screw hole in manufacturing steps, so that the number of manufacturing steps can be reduced.  
         [0016]     Another aspect of the present invention provides a method of incorporating a bearing with a rotation sensor into a rotating object. The bearing with the rotation sensor comprises a sensor housing having a sensor and mounted on a fixed-side race of the bearing and a sensor target ring having a detector sensed by the sensor and separated from a rotation-side race of the bearing. The sensor housing and the sensor target ring are connected by connecting means before the bearing with the rotation sensor is incorporated into the rotating object. The sensor target ring is separated from the sensor housing by disconnecting the connecting means and the sensor target ring is fixed to the rotating object when the bearing with the rotation sensor is incorporated into the rotating object.  
         [0017]     Preferably, the connecting means comprises a connecting shaft to connect the sensor target ring to the sensor housing, and the connecting shaft is used as fixing means for fixing the sensor target ring to the rotating object when the bearing is incorporated into the rotating object.  
         [0018]     Preferably, each of the sensor housing and the sensor target ring has a through-hole to which the connecting shaft is inserted, the connecting shaft is positioned at a boundary between the through-hole of the sensor housing and the through-hole of the sensor target ring to connect the sensor housing and the sensor target ring before the bearing with the rotation sensor is incorporated, and the connecting shaft is positioned in the through-hole of the sensor target ring to separate the sensor target ring from the sensor housing and an end of the connecting shaft abuts on a surface of the rotating object to fix the sensor target ring to the rotating object when the bearing with the rotation sensor is incorporated into the rotating object.  
         [0019]     The bearing with the rotation sensor according to the present invention comprises the connecting means provided such that the state in which the sensor target ring to be directly mounted on the rotating object is connected to the sensor housing and a state in which they are disconnected can be selectively changed over. Thus, since the sensor target ring can be handled as an integral part with the bearing body during transportation, the bearing with the rotation sensor can be easily handled. In addition, the sensor target ring can be separated from the sensor housing when they are activated.  
         [0020]     According to the method of incorporating the bearing with the rotation sensor into the rotating object in the present invention, the sensor housing and the sensor target ring can be connected before the bearing with the rotation sensor is incorporated into the rotating object, so that the bearing with the rotation sensor can be easily handled. In addition, when the bearing with the rotation sensor is incorporated into the rotating object, the sensor target ring and the sensor housing are disconnected and the sensor target ring can be fixedly mounted on the rotating object. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  is a schematic sectional view showing a bearing with a rotation sensor according to one embodiment of the present invention, in which a sensor housing and a sensor target ring are connected to each other;  
         [0022]      FIG. 2  is a schematic sectional view showing the bearing with the rotation sensor according to one embodiment of the present invention, in which the sensor housing and the sensor target ring are disconnected and the sensor target ring is fixed to a rotating object;  
         [0023]      FIG. 3  is a schematic sectional view showing a bearing with rotation sensor according to another embodiment of the present invention, in which a sensor housing and a sensor target ring are connected; and  
         [0024]      FIG. 4  is a schematic view in which a sensor and a detector of the sensor target ring are arranged oppositely in a radial direction of a bearing. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]      FIG. 1  is a sectional view showing an embodiment of the present invention, in which a roller bearing  1  comprises an inner race  2  and an outer race  3  and a rolling element  4  arranged between the inner race  2  and the outer race  3 . The rolling element  4  is held by a retainer  6  and equally spaced. One end of a bearing space between the inner race  2  and the outer race  3  is sealed by a seal  5  and a sensor housing  7  is arranged at the other end. Although the inner race  2  constitutes a rotation-side race and the outer race  3  constitutes a fixed-side race in this example, the inner race  2  may be the fixed-side race and the outer race  3  may be the rotation-side race.  
         [0026]     The inner race  2  is mounted on an outer peripheral surface of a rotation spindle  13  as a rotating object and a sensor target ring  8  is also mounted on it separately. The sensor target ring  8  comprises a mount part  8   a  whose inner peripheral surface has contact with the outer peripheral surface of the rotation spindle  13  and a flange  8   b  extending from the outer peripheral surface in a diameter direction. A detector  10  comprising a region in which light is reflected and a region in which light is not reflected is formed on one end surface of the flange  8   b.    
         [0027]     The sensor housing  7  engages with an inner diameter surface of the outer race  3 . A sensor  9  is arranged in the sensor housing  7  so as to be opposed to the detector  10 . A rotation sensor  11  comprises the sensor  9  and the detector  10 .  
         [0028]     A screw hole  8   c  as a rotation-side recess is formed from an outer peripheral surface to an inner peripheral surface of the mount part  8   a  in the sensor target ring  8 . A through-hole  7   a  connected to the screw hole  8   c  of the sensor target ring  8  is provided in the sensor housing  7  as a fixed-side recess.  
         [0029]     Since the sensor target ring  8  does not engage with the inner race  2 , it is separated from the bearing  1  with the rotation sensor before mounted on the rotation spindle  13 . Thus, a setscrew  12  as a connecting shaft is inserted into the screw hole  8   c  and the through-hole  7   a  and held between the sensor housing  7  and the sensor target ring  8 , so that both are connected. Thus, the sensor target ring  8  can be integrated with the bearing  1  with the rotation sensor. As a result, since a screw thread is not formed in the inner peripheral surface of the through-hole  7   a  of the sensor housing  7 , they are not completely fixed. However, since the sensor target ring  8  is not separated from the bearing  1  with the rotation sensor during transportation, they can be easily handled.  
         [0030]      FIG. 2  is a sectional view showing a state after the bearing  1  with the rotation sensor is mounted on the rotation spindle  13 . When the sensor target ring  8  is mounted on the rotation spindle  13 , it is necessary to disconnect the sensor housing  7  and the sensor target ring  8 . In this case, the setscrew  12  which connected the sensor housing  7  to the sensor target ring  8  is screwed into the screw hole  8   c  to be held there.  
         [0031]     Furthermore, when the setscrew  12  is screwed in until it abuts on the rotation spindle  13 , the sensor target ring  8  can be directly fixed to the rotation spindle  13 . Thus, the sensor target ring  8  can be easily fixed to the rotation spindle  13 .  
         [0032]     As described above, since the sensor target ring  8  is directly mounted on the rotation spindle  13  whose rotation is to be detected, by the setscrew  12 , even when a skid is generated between the inner race  2  and the rotation spindle  13 , relative displacement in the rotation direction is not generated between the rotation spindle  13  and the sensor target ring  8 , so that measurement can be implemented with high precision without affecting rotation detection precision of the rotation spindle  13 .  
         [0033]     In addition, a length of the setscrew  12  is made so as to be shorter than a length of the screw hole  8   c . Thus, when the setscrew  12  is screwed into the screw hole  8   c  and held therein, the sensor housing  7  and the sensor target ring  8  can be separated.  
         [0034]      FIG. 3  is a sectional view showing a bearing  1  with a rotation sensor according to another embodiment of the present invention. According to this embodiment, screw threads are formed in an inner peripheral surface of a through-hole  7   a  in a sensor housing  7  and other constitutions are the same as those in  FIG. 1 . When the bearing  1  with the rotation sensor is transported, a setscrew  12  engages with a screw hole  8   c  of a sensor target ring  8  and the through-hole  7   a  in the sensor housing  7 , so that the sensor housing  7  and the sensor target ring  8  can be more surely fixed to each other.  
         [0035]      FIG. 4  is a sectional view showing a bearing with a rotation sensor la according to still another embodiment of the present invention. According to this embodiment, a detector  10  is provided on an outer peripheral surface of a mount part  8   a , and a sensor  9  mounted on a sensor housing  7  and the detector  10  are opposed to each other in a radial direction of a bearing.  
         [0036]     According to the above embodiments, the sensor target ring  8  may be made of a resin. Thus, when the setscrew  12  engages with the sensor target ring  8 , since the screw threads are formed inside the screw hole  8   c  at that time, it is not necessary to previously provide screw threads in the screw hole  8   c  in manufacturing steps and the number of manufacturing steps can be reduced.  
         [0037]     Although only one sensor  9  is provided in the sensor housing  7  in the above embodiments, when the sensors  9  are provided at a plurality of positions, not only the rotation speed but also a rotation direction can be detected and measurement can be implemented with higher precision.  
         [0038]     Although the rotation of the rotation spindle  13  is detected by detecting reflected light of the detector  10  using the sensor  9  in the above embodiments shown in FIGS.  1  to  3 , the rotation of the rotation spindle  13  may be detected by arranging regularly spaced slits (not shown) in the flange  8   b  as a detector, providing a light source opposed to the sensor  9  with respect to the slits and detecting light outputted from the light source through the slits by the sensor  9 .  
         [0039]     In addition, a ball or a roller may be used as the rolling element  4 . Furthermore, the present invention may be applied to not only the roller bearing but also a sliding bearing and an air bearing.  
         [0040]     Still furthermore, although the optical rotation sensor is used in the above embodiments shown in FIGS.  1  to  4 , the present invention is not limited to this and a magnetic sensor may be used.  
         [0041]     In addition, although the through-hole  7   a , the screw hole  8   c  and the setscrew  12  engaging with the screw hole  8   c  serve as both connecting means for connecting the sensor housing  7  and the sensor target ring  8  and fixing means for fixing the sensor target ring  8  to the rotation spindle  13  in the above embodiments, both means may be separately provided.  
         [0042]     In this case, the screw hole  8   c  as the means for connecting the sensor housing  7  and the sensor target ring  8  may not penetrate the inner peripheral surface of the mount part  8   a . In addition, the screw hole  8   c  and the through-hole  7   a  may be oppositely provided in an axial direction of the bearing  1  with the rotation sensor.  
         [0043]     Still furthermore, they may be connected such that the screw hole  8   c has the same diameter as that of the through-hole  7   a  and a connecting shaft is inserted between the screw hole  8   c  and the through-hole  7   a , or such that a stopper to connect the sensor housing  7  and the sensor target ring  8  is provided and the sensor housing  7  and the sensor target ring  8  are connected by the stopper during transportation and they may be disconnected when they are activated.  
         [0044]     In addition, as the fixing means for fixing the sensor target ring  8  to the rotation spindle  13 , the sensor target ring  8  may engage with the rotation spindle  13  or a key groove may be provided in the inner peripheral surface of the mount part  8   a  of the sensor target ring  8  and in the outer peripheral surface of the rotation spindle  13  to engage with each other.  
         [0045]     Although the embodiments of the present invention have been described with reference to the drawings in the above, the present invention is not limited to the above illustrated embodiments. Various kinds of modifications and variations may be added to the illustrated embodiments within the same or equal scope of the present invention.  
         [0046]     The present invention is advantageously applied to the bearing with the rotation sensor to be mounted on the rotating object to detect the rotation of the rotating object.