Patent Publication Number: US-2023143463-A1

Title: Sensor device for high speed rotating machine

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefits of Taiwan application Serial No. 110141519, filed on Nov. 8, 2021, the disclosures of which are incorporated by references herein in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates in general to a sensor device for high speed rotating machine. 
     BACKGROUND 
     Generally, sensors used in high-speed rotating machinery can be divided into an eddy current type and an inductive type. In particular, for multi-purpose sensing, the inductive type is more suitable. 
     In the application of the maglev centrifugal compressor, non-contact suspension provided by a high-power and high-speed motor and maglev bearings would enhance the performance of the centrifuge to achieve higher efficiency and better energy saving. However, no rotating shaft can be produced with 100% concentricity or perfectly symmetrical /homogeneous axis. Though oscillation of the rotating shaft caused by unbalanced forcing may be reduced by dynamic balancing thereof, yet the oscillations of the rotating shaft at higher speeds can only be controlled by the magnetic bearings. Therefore, in order to suppress the unexpected shaking caused by the eccentricity under high-speed operations, a satisfied maglev control collaborated with eccentric force algorithm with magnetron technology at the magnetic bearings can be better achieved through well knowledge in rotational speed signals of the rotating shaft. Generally, the configuration of the sensor probe, the routing of the sensing signal wiring and the design of the sensing signal circuit are too complicated to achieve lower cost and less manufacturing time. Therefore, how to improve or provide a sensor device able to resolve the above-mentioned problems will be an issue to be solved to the skill in the art. 
     SUMMARY 
     An object of the present disclosure is to provide a sensor device for high speed rotating machine that can provide versatile combinations of rotational speed sensors and radial displacement sensors to maintain detection stability of the rotational speed and reduce the complexity in designing related circuits. In addition, the space for mounting the rotating body can be substantially enlarged, and applicability to the critical situation having excessive spacing between the rotating body and the sensor can be much more feasible. 
     In one embodiment of this disclosure, a sensor device for high speed rotating machine includes a rotating body and a sensor assembly. The rotating body includes a magnetic permeable ring and at least one positioning structure. The magnetic permeable ring further includes a radial displacement sensing area and a rotational speed sensing area. The at least one positioning structure is disposed in the rotational speed sensing area. A top surface of the at least one positioning structure is different to a top surface of the magnetic permeable ring. The sensor assembly includes four radial displacement sensors and two rotational speed sensors. The four radial displacement sensors, disposed separately around the rotating body, are separately disposed in correspondence to the radial displacement sensing area, and each of the radial displacement sensors is separated from the magnetic permeable ring by a radial air-gap spacing. Each of the four radial displacement sensors is a double-probe type sensor. The two rotational speed sensors are disposed separately around the rotating body. Each of the two rotational speed sensors is disposed next to one of the four radial displacement sensors in correspondence to the rotational speed sensing area. Each of the two rotational speed sensors is the double-probe type sensor or a four-probe type sensor. 
     As stated, in the sensor device for high speed rotating machine of the present disclosure, output signals of the two rotational speed sensors are used to generate pulse waves through a differential circuit, and the rotational speed and turning direction of the rotating body can be calculated by measuring the frequency of the pulse waves. Also, different arrangements of the rotational speed sensors and the radial displacement sensors can be provided. Thus, the stability in detecting the rotational speed can be maintained, and the complexity in designing the circuit can be reduced. In addition, in the limited spacing around the rotating body, different spacing between the rotating body and the sensors can be arranged to meet different applications. 
     Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present disclosure and wherein: 
         FIG.  1    is a schematic perspective view of an embodiment of the sensor device for high speed rotating machine in accordance with this disclosure; 
         FIG.  2    is a schematic front view of  FIG.  1   ; 
         FIG.  3    is a schematic perspective view of the double-probe type sensor of  FIG.  1   ; 
         FIG.  4    is a schematic view of the rotational-speed displacement sensor and the magnetic permeable ring of  FIG.  1   ; 
         FIG.  5    demonstrates schematically a framework for signal generation of the sensor device for high speed rotating machine of  FIG.  1   ; 
         FIG.  6    demonstrates schematically the radial displacement sensors and the rotational speed sensors of  FIG.  1    assembled at the non-magnetic base; 
         FIG.  7    shows schematically that the sensor device for high speed rotating machine of this disclosure is equipped with a magnetic permeable ring made of another material; 
         FIG.  8    is a schematic perspective view of another embodiment of the sensor device for high speed rotating machine in accordance with this disclosure; 
         FIG.  9    is a schematic front view of  FIG.  8   ; 
         FIG.  10    demonstrates schematically a framework for signal generation of the sensor device for high speed rotating machine of  FIG.  8   ; 
         FIG.  11    demonstrates schematically the radial displacement sensors and the rotational speed sensors of  FIG.  8    assembled at the non-magnetic base; 
         FIG.  12    is a schematic perspective view of a further embodiment of the sensor device for high speed rotating machine in accordance with this disclosure; 
         FIG.  13    is a schematic front view of  FIG.  12   ; 
         FIG.  14 A  is a schematic perspective view of the four-probe type sensor of  FIG.  12   ; 
         FIG.  14 B  is a schematic exploded view of  FIG.  14 A ; 
         FIG.  15 A  is another exemplary example of the four-probe type sensor in accordance with this disclosure; 
         FIG.  15 B  is a further exemplary example of the four-probe type sensor in accordance with this disclosure; 
         FIG.  16    demonstrates schematically a framework for signal generation of the sensor device for high speed rotating machine of  FIG.  12   ; 
         FIG.  17    demonstrates schematically the radial displacement sensors and the rotational speed sensors of  FIG.  12    assembled at the non-magnetic base; 
         FIG.  18    is a schematic perspective view of one more embodiment of the sensor device for high speed rotating machine in accordance with this disclosure; 
         FIG.  19    is a schematic front view of  FIG.  18   ; 
         FIG.  20    demonstrates schematically a framework for signal generation of the sensor device for high speed rotating machine of  FIG.  18   ; and 
         FIG.  21    demonstrates schematically the radial displacement sensors and the rotational speed sensors of  FIG.  18    assembled at the non-magnetic base. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, specific embodiments of the present disclosure will be further described in conjunction with the accompanying drawings and examples, and the following examples are only used to further and clearly illustrate technical solutions of the present disclosure, not to limit the scope of the present disclosure. 
     It should be noted that, in the following embodiments, the so-called “first” and “second” are used to describe different elements, not for limiting thereto. In addition, for convenience and clarity, the thickness or size of each element in the drawings is shown in an exaggerated, omitted or rough manner for the understanding and reading of those skilled in the art. Also, the size of each element in any of the drawings is not to demonstrate the actual size of the elem, thus is not used to limit the conditions for the implementation of the present disclosure, and therefore has no technical substantive significance. Any modification of the structure, change of the proportional relationship or adjustment of the size will not affect the effect and achievement of the present disclosure. For the purposes of this disclosure, they should still fall within the scope of the technical content disclosed in this disclosure. 
       FIG.  1    is a schematic perspective view of an embodiment of the sensor device for high speed rotating machine in accordance with this disclosure, and  FIG.  2    is a schematic front view of  FIG.  1   . Referring now to  FIG.  1    and  FIG.  2   , in this embodiment of the sensor device for high speed rotating machine  100 , the high speed rotating machine is a maglev centrifugal machine. 
     In particular, the high speed rotating machine herein can be a high efficiency centrifugal chiller, a centrifugal compressor or any the like. The high speed rotating machine is equipped with a high speed spindle with magnetic bearings, and high speed spindle with magnetic bearings includes at least a high speed motor, a front radial bearing, a rear radial bearing, a front axial bearing and a rear axial bearing. Upon such an arrangement of the high speed spindle with magnetic bearings, a non-contact self-rotation can be performed. 
     In this embodiment, the sensor device for high speed rotating machine  100  includes a rotating body  110  and a sensor assembly. The sensor assembly includes four radial displacement sensors “a” and two rotational speed sensors  a   1 ,  a   2 . The rotating body  110  includes a magnetic permeable ring  112  and at least one positioning structure  114 . The rotating body  110  is defined with an axial direction AX and a radial direction RA, in which the radial direction RA can be one of diameter directions which are all perpendicular to the axial direction AX. The magnetic permeable ring  112 , disposed on a surface of the rotating body  110 , includes a radial displacement sensing area G 1  (in particular, the outer surface of the ring) and a rotational speed sensing area G 2 . For a concise explanation, in  FIG.  1   , the radial displacement sensing area G 1  and the rotational speed sensors G 2  are separated by a dashed line. The radial displacement sensing area G 1  is adjacent and also connected to the rotational speed sensing area G 2 . The positioning structure  114 , disposed in the rotational speed sensing area G 2 , has a particular surface different to the surface of the magnetic permeable ring  112 , by which air-gap spacing would be changed while the rotating body  110  is rotating. For example, as shown in  FIG.  1   , the positioning structure  114  is structured to be a cutout surface from the surface of the magnetic permeable ring  112 . This cutout surface can be a groove, a plane, a tooth or any relevant structure. 
     In this embodiment, these four radial displacement sensors a are arranged to surround the rotating body  110 , and all the radial displacement sensors a are disposed separately in the radial displacement sensing area G 1 . As shown in  FIG.  1    and  FIG.  2   , these four radial displacement sensors a are distributed in an equal-spacing arrangement on the magnetic permeable ring  112  by keeping relevant radial air-gap spacing to the magnetic permeable ring  112 . Preferably, two of these four radial displacement sensors a are oppositely arranged on the rotating body  110  in a radial direction RA and connected to form a first direction X, while another two thereof are also oppositely arranged on the rotating body  110  in another radial direction RA and connected to form a second direction Y perpendicular to the first direction X. Namely, any two in the same pair of the radial displacement sensors a are disposed oppositely along the same diameter of the magnetic permeable ring  112 . In other words, the radial displacement sensors a in the first direction X and the second direction Y (i.e., two radial directions RA) are purposely to be differentially arranged. Thereupon, the differential detection theory for generating voltage differences between any two of the radial displacement sensors a is applied to generate differential signals by differentiated positions of the radial displacement sensors a around the magnetic permeable ring  112 . 
     In this embodiment, the radial displacement sensors a double-probe type sensor  120 , as shown in  FIG.  3   . The double-probe type sensor  120  includes a magnetic metal block  122 , two coils  124 A,  124 B and two probes  126 A,  126 B. The magnetic metal block  122  is furnished with two locking holes  122 A for engaging the non-magnetic base  50  as shown in  FIG.  6   . The probes  126 A,  126 B are individually connected with the magnetic metal block  122 . The two coils  124 A,  124 B winding around two respective legs (not labeled on the figure) of the magnetic metal block  122  protrude the corresponding probes  126 A,  126 B from corresponding ends of the two respective coils  124 A,  124 B. It shall be explained that, in this disclosure, the double-probe type sensor  120  is not a simple sheet structure of ring-type Si steel in the art, but a monomer adopted from a sheet of the ring-type Si steel is modified to be the magnetic metal block  122 . As such, the required number of components can be reduced, and a magnetic path between the magnetic metal block  122  and the rotating body  110  would be formed right after the coils  124 A,  124 B are energized. 
     As shown in  FIG.  1   , in this embodiment, the two rotational speed sensors  a   1 ,  a   2  are separately disposed on the outer surface of the rotating body  110 , at positions different to those mounting the radial displacement sensors a. In particular, the rotational speed sensors  a   1 ,  a   2  are individually adjacent to these radial displacement sensors a. In this embodiment, the assembly direction L 1  of the magnetic heads (for example, the probes  126 A,  126 B in  FIG.  3   ) of the rotational speed sensors  a   1 ,  a   2  is coincided with one radial direction RA of the rotating body  110 , and the assembly direction L 2  of the magnetic heads (for example, the probes  126 A,  126 B in  FIG.  3   ) of the radial displacement sensors a is coincided with another radial direction RA of the rotating body  110 . In addition, the assembly direction L 1  of any of the rotational speed sensors  a   1 ,  a   2  is parallel to the assembly direction L 2  of any of the radial displacement sensors a; i.e., both perpendicular to the axial direction AX. The rotational speed sensors  a   1 ,  a   2  are disposed in correspondence to the rotational speed sensing area G 2 . 
     In detail, the rotational speed sensors  a   1 ,  a   2  of this embodiment are all double-probe type sensors  120 , and the rotational speed sensors  a   1 ,  a   2  are disposed among the radial displacement sensors a (for example, in  FIG.  1   , between the lower two radial displacement sensors a). In particular, the rotational speed sensors  a   1 ,  a   2  can pair individually the radial displacement sensors a in the axial direction AX (for example, the two top radial displacement sensors a in  FIG.  1   ). In addition, the assembly direction of the rotational speed sensors  a   1 ,  a   2  is parallel to that of the radial displacement sensors a. Thereupon, it can be realized that, while in assembling the rotational speed sensors  a   1 ,  a   2  and the radial displacement sensors a of this embodiment, a common assembly space can be achieved to simplify structurally the entire sensor mechanism. Thus, the manufacturing cost and time can be substantially reduced. 
     In this embodiment, the rotational speed sensors  a   1 ,  a   2  are spaced from the magnetic permeable ring  112  so as to obtain radial air-gap spacing. Referring to  FIG.  4   , the rotational speed sensors and the magnetic permeable ring are schematically shown. It shall be noted that, in  FIG.  4   , the assembly direction of the rotational speed sensors is not limited thereto, but only sketched to explain the positioning structures and the air-gap spacing. For example, all the probes of the corresponding rotational speed sensors are disposed on the same rotational speed sensing area G 2 . For another example, in the cross-area sensing, the two probes of the same sensor would be located to the radial displacement sensing area G 1  and the rotational speed sensing area G 2 , respectively. Certainly, for the four-probe type sensor, the four probes would be distributed to the radial displacement sensing area G 1  and the rotational speed sensing area G 2 . In one embodiment, in the rotational speed sensor  a   1  or  a   2  (i.e., the double-probe type sensor  120  herein), a first distance  d   1  is defined to the space measured from a bottom end of the probe  126 A or  126 B to an upper top surface S 1  of the magnetic permeable ring  112 . The positioning structure  114  is formed to have a cutout surface from the magnetic permeable ring  112  (the positioning structure  114  can be seen as a recess on the magnetic permeable ring  112 ). The rotational speed sensor  a   1  or  a   2  (the double-probe type sensor  120  in this embodiment) is spaced from a base surface of the positioning structure  114  by a second distance  d   2 . The second distance  d   2  is greater than the first distance  d   1  by a distance difference d. As shown, the distance difference d is the distance from a lower top surface S 1  of the positioning structure  114  to an upper top surface S 2  of the and magnetic permeable ring  112 . With this distance difference d, a differential circuit (i.e., a differential amplifier) would be applied to generate a differential signal and a corresponding voltage pulse. Further, a period of the voltage pulse would be calculated to derive the equivalent speed or rotational speed. In this disclosure, this distance difference d can be adjusted according to the practical magnetic arrangement. The magnetic permeable ring  112  would be integrated with the rotational speed sensor  a   1  or  a   2  (the double-probe type sensor  120  in this embodiment) to form a closed magnetic loop, and the positioning structure  114  and the rotational speed sensor  a   1  or  a   2  would be paired to form an additional air-gap spacing over the radial air-gap spacing upon when the rotating body  110  is rotated. 
       FIG.  5    demonstrates schematically a framework for signal generation of the sensor device for high speed rotating machine of  FIG.  1   . In this embodiment, two separate radial displacement sensors a on the first direction X among many radial directions would generate different voltages corresponding to these two radial displacement sensors a, through the differential amplifier of the sensor circuit, and further generate differential signals corresponding to the voltages. Namely, differential signals can be produced by these two radial displacement sensors a so as to obtain an X-directional displacement signal POS X. Similarly, differential signals can be produced by another two radial displacement sensors a so as to obtain a Y-directional displacement signal POS Y. On the other hand, regarding the rotational speed signals, pairs of sensors may utilize the differential amplifier to generate corresponding signals. A significant difference is that the magnification of the rotational speed signal is much larger than that of the radial signal. The rotational speed sensor  a   1  can integrate the radial displacement sensor a to generate differential signals, and further to obtain a first pulse signal PUL A. Also, the rotational speed sensor  a   2  can be integrated with the radial displacement sensor a to produce corresponding differential signal, and further to obtain a second pulse signal PUL B. The first pulse signal PUL A and the second pulse signal PUL B stand for the rotational speed signals in different directions. After calculation, a difference between two electric fields E+, E- can be obtained. Thereupon, stability in detecting the rotational speed can be maintained, and the complexity in circuit design can be reduced. In another embodiment, the rotational speed sensors  a   1  and the rotational speed sensors  a   2  can be directly applied to form the differential signal so as further to obtain the corresponding rotational speed signals. In this embodiment, the rotating body  112  has two positioning structures  114 . When the rotating body  112  rotates, the rotational speed sensor  a   1  at the first positioning structure  114  would generate the first pulse signal PUL A, and the rotational speed sensor  a   2  at the second positioning structure  114  can be used to generate the second pulse signal PUL B. With the first pulse signal PUL A and the second pulse signal PUL B, a time difference can be derived to be determined as the rotations of the rotating body  112 . 
     Upon the aforesaid arrangement, the sensor device for high speed rotating machine  100  can utilize output signals of the two rotational speed sensors  a   1 ,  a   2  and the pulses generated by the differential circuit (i.e., the differential amplifier that can amplify a difference between two voltage inputs by a predetermined gain) to measure a corresponding pulse frequency. Thus, the rotational speed and the turning direction of the rotating body  110  can be determined and derived from the measured pulse frequency, such that the stability in detecting the rotational speed can be maintained. The complexity in circuit design can be reduced. In addition, the rotational speed sensors  a   1 ,  a   2  and the radial displacement sensors a can be installed and operated together in the limited space around the rotating body  110 . 
     In addition, as shown in  FIG.  6   , the radial displacement sensors and the rotational speed sensors of  FIG.  1    assembled at the non-magnetic base are demonstrated schematically. In this embodiment, the sensor device for high speed rotating machine  100  further includes a non-magnetic base  50  disposed out of the rotating body  110  of  FIG.  1   . The radial displacement sensors a and the rotational speed sensors  a   1 ,  a   2  are separately disposed to the non-magnetic base  50 . In one embodiment, the non-magnetic base  50  can be a base made of aluminum. The non-magnetic base  50  can include a plurality of first assembly cavities  52 A. The exact quantity, dimensions and configurations of the first assembly cavities  52 A are determined according to practical requirements of the radial displacement sensors a and the rotational speed sensors  a   1 ,  a   2 . For example, in this embodiment, the radial displacement sensors a and the rotational speed sensors  a   1 ,  a   2  are individually mounted into the corresponding first assembly cavities  52 A, and the dimensions of the first assembly cavities  52 A are adjusted to accommodate the respective radial displacement sensors a and the rotational speed sensors  a   1 ,  a   2 . In the same first assembly cavity  52 A, the radial displacement sensor a may be disposed at an upper position of the first assembly cavity  52 A having a width H 1 , while the rotational speed sensor  a   1  or  a   2  is disposed at a lower position thereof having a width H 2 . In particular, the width H 1  is equal to the width H 2 . Then, fasteners  60  can be applied to fix the radial displacement sensors a and the rotational speed sensors  a   1 ,  a   2 , so as to lock the sensors to the non-magnetic base  50 . For example, the fastener  60  can be applied to the locking hole  122 A of the magnetic metal block  122  shown in  FIG.  3   , such that the respective sensor can be firmly fixed to the base  50 . 
     Referring back to  FIG.  1   , the magnetic permeable ring  112  can be made of a magnetic material or a conductive metal material. Further, in order to increase the sensitivity of the radial displacement sensors a upon the air gaps in the radial displacement sensing area G 1 , the radial displacement sensing area G 1  shall be made of a magnetic material (such as a silicon steel sheet or an iron), and the rotational speed sensing area G 2  corresponding to the rotational speed sensors  a   1 ,  a   2  shall be made of a magnetic material or as a metal ring. Thus, both the radial displacement sensing area G 1  and the rotational speed sensing area G 2  can be made of the same material (for example, the same magnetic material) so as to make the magnetic permeable ring  112  to be a magnetic metal ring. Namely, the rotating body  110  can be integrally formed to utilize the same magnetic permeable ring. 
     In another embodiment shown in  FIG.  7   , the radial displacement sensing area G 11  and the rotational speed sensing area G 12  of the magnetic permeable ring  112 A are made of different materials. For example, the radial displacement sensing area G 11  is made of a magnetic material so as to form a magnetic metal ring, while the rotational speed sensing area G 12  is made of a non-magnetic metal so as to form a non-magnetic metal ring. Namely, in this embodiment, the radial displacement sensing area G 11  and the rotational speed sensing area G 12  are connected in a hetero junction manner. 
       FIG.  8    is a schematic perspective view of another embodiment of the sensor device for high speed rotating machine in accordance with this disclosure, and  FIG.  9    is a schematic front view of  FIG.  8   . As shown, a difference between this embodiment and the previous embodiment shown in  FIG.  1    through  FIG.  7    is that, in this embodiment, a different arrangement is applied to the rotational speed sensors  a   1 ,  a   2 . The assembly direction L 3  of the magnetic heads (the probes  126 A,  126 B in  FIG.  3   ) of the rotational speed sensors  a   1 ,  a   2  is parallel to the axial direction AX, and the rotational speed sensors  a   1 ,  a   2  are mounted to cross the radial displacement sensing area G 1  and the rotational speed sensing area G 2 . After the magnetic-head coils of the rotational speed sensors  a   1 ,  a   2  are energized, a closed magnetic loop including the magnetic permeable ring  112  would be formed to provide a magnetic path parallel to the axial direction AX but perpendicular to the radial direction RA. On the other hand, the assembly direction L 4  of the magnetic heads (the probes  126 A,  126 B in  FIG.  3   ) of the radial displacement sensors a is parallel to the radial direction RA of the rotating body  110 . 
       FIG.  10    demonstrates schematically a framework for signal generation of the sensor device for high speed rotating machine of  FIG.  8   . In the framework of this embodiment, the two separate radial displacement sensors a in the first direction X among many radial directions would generate different signals so as to obtain an X-directional displacement signal POS X, while the two separate radial displacement sensors a in the second direction Y among many radial directions would generate different signals so as to obtain a Y-directional displacement signal POS Y. Regarding the rotational speed signals, different to  FIG.  5   , in this embodiment, after the two rotational speed sensors  a   1 ,  a   2  form the differential signal and the coils of the rotational speed sensors  a   1 ,  a   2  are energized, a magnetic path would be established to cross the radial displacement sensing area G 1  and the rotational speed sensing area G 2 . As soon as the magnetic path touches the positioning structure  114 , the rotational speed sensor  a   1  would immediately detect the existence of the positioning structure  114  due to an abrupt increase upon the first distance  d   1  by a distance difference d. Simultaneously, the first distance  d   1  to the rotational speed sensor  a   2  is maintained. Thereupon, the differential circuit would generate a first pulse signal PUL A, accordingly. In addition, the second pulse signal PUL B can be generated according to a similar method. The first pulse signal PUL A and the second pulse signal PUL B can be obtained. Thereupon, beside the structuring can be simplified, the stability in detecting the rotational speed can be maintained, and also the complexity in circuit design can be reduced. 
     In addition,  FIG.  11    demonstrates schematically the radial displacement sensors and the rotational speed sensors of  FIG.  8    assembled at the non-magnetic base. As shown in  FIG.  8   ,  FIG.  9    and  FIG.  11   , the assembly direction of the rotational speed sensors  a   1 ,  a   2  is perpendicular to the assembly direction of the radial displacement sensors a. In addition, the magnetic heads (such as the probes  126 A,  126 B of  FIG.  3   ) of the rotational speed sensors  a   1 ,  a   2  are parallel to the axial direction AX, and the magnetic heads (such as the probes  126 A,  126 B of  FIG.  3   ) of the radial displacement sensors a are parallel to the radial direction RA. Nevertheless, all the sensors are disposed at the same circumference. The non-magnetic base  50  includes the aforesaid first assembly cavities  52 A and also second assembly cavities  52 B configured differently to the first assembly cavities  52 A for mounting the rotational speed sensors  a   1 ,  a   2 . In particular, the width H 1  of the first assembly cavity  52 A is greater than the width H 4  of the second assembly cavity  52 B. Except that the radial displacement sensor a is locked by the fasteners  60  resembled to that shown in  FIG.  6   , the rotational speed sensors  a   1 ,  a   2  of this embodiment can be planted into the corresponding second assembly cavities  52 B by dispensing. In other words, the rotational speed sensors  a   1 ,  a   2  and the radial displacement sensors a of this embodiment can be fixed by different methods such as locking or dispensing. 
       FIG.  12    is a schematic perspective view of a further embodiment of the sensor device for high speed rotating machine in accordance with this disclosure, and  FIG.  13    is a schematic front view of  FIG.  12   . A difference between this embodiment and that shown from  FIG.  8    to  FIG.  11    is that, in this embodiment of the sensor device for high speed rotating machine  300 , the rotational speed sensor  b   1  or  b   2  is a four-probe type sensor  130  disposed between two of the radial displacement sensors a. 
       FIG.  14 A  is a schematic perspective view of the four-probe type sensor of  FIG.  12   , and  FIG.  14 B  is a schematic exploded view of  FIG.  14 A . Referring to  FIG.  12    through  FIG.  14 B , the four-probe type sensor  130  includes magnetic metal blocks  132 ,  134 ,  136 , coils  136 A,  136 B,  136 C,  136 D, and probes  138 A,  138 B,  138 C,  138 D. In particular, the magnetic metal block  132 , the coils  136 A,  136 B and the probes  138 A,  138 B are integrated together to form a double-probe type sensor (similar to the double-probe type sensor  120  of  FIG.  3    or  FIG.  12   ), and the magnetic metal block  134 , the coils  136 C,  136 D and the probes  138 C,  138 D are integrated together to form another double-probe type sensor. The magnetic metal block  136  is disposed between another two magnetic metal blocks  132 ,  134  individually connected with the corresponding double-probe sensors, in which the magnetic metal block  136  doesn’t have any probe. After the coils  136 A,  136 B,  136 C,  136 D are energized, a plurality of magnetic paths would be formed between any of the magnetic metal blocks  132 ,  134 ,  136  and the rotating body  110 , between the two coils  136 A,  136 B or  136 C,  136 D, and between any two of the magnetic metal blocks  132 ,  134 ,  136  of the double-probe type sensor. The four-probe sensor  130  may have two to four coils. In particular, the four-probe sensor  130  can have four coils  136 A,  136 B,  136 C,  136 D to individually generate corresponding magnetomotive forcing. For example, as shown in  FIG.  15 A , the four-probe sensor  130 A is equipped with two coils  136 B,  136 D. For a further example shown in  FIG.  15 B , the four-probe sensor  130 B is equipped with three coils  136 A,  136 B,  136 D. With different numbers of coils to connect in series, a plurality of closed-loop magnetic paths and different inductance ranges would be formed. Namely, with the four-probe type sensors  130 ,  130 A,  130 B, various combinations of probes can be formed to contribute different inductance. Thereupon, convenience in assembly can be obtained, and appropriate circuit arrangements for desired harmonic points within limited space and framework for the rotating body  110  with different materials can be feasible. 
       FIG.  16    demonstrates schematically a framework for signal generation of the sensor device for high speed rotating machine of  FIG.  12   . In this example, the two separate radial displacement sensors a in the first direction X among many radial directions would generate different signals so as to obtain an X-directional displacement signal POS X, while the two separate radial displacement sensors a in the second direction Y among many radial directions would generate different signals so as to obtain a Y-directional displacement signal POS Y. Regarding the rotational speed signals, different to  FIG.  10   , in this embodiment, with the two rotational speed sensors  b   1 ,  b   2  to form the four-probe sensor  130 , magnetic paths simultaneously across the radial displacement sensing area G 1  and the rotational speed sensing area G 2  would be generated. While crossing the positioning structure  114  in the rotational speed sensing area G 2 , the rotational speed sensors  b   1 ,  b   2  of the four-probe sensor  130  would associate the radial displacement sensing area G 1  and the rotational speed sensing area G 2  together to generate an electromagnetic induction signal for further forming corresponding differential signal, and thus the first pulse signal PUL A and the second pulse signal PUL B can be obtained. 
     In addition,  FIG.  17    demonstrates schematically the radial displacement sensors and the rotational speed sensors of  FIG.  12    assembled at the non-magnetic base. As shown in  FIG.  12   ,  FIG.  13    and  FIG.  17   , in comparison to the assembly of  FIG.  11   , the difference is that the four-probe sensor  130  having the rotational speed sensors  b   1 ,  b   2  in this embodiment can be planted into the third assembly cavity  52 C and fixed by dispensing. In other words, the rotational speed sensors  b   1 ,  b   2  and the radial displacement sensors a of this embodiment can be fixed by different methods such as locking or dispensing, according to the present mounting. In addition, the magnetic heads (such as the probes  126 A,  126 B of  FIG.  3   ) of the rotational speed sensors  b   1 ,  b   2  are parallel to the radial direction RA, and the magnetic heads (such as the probes  126 A,  126 B of  FIG.  3   ) of the radial displacement sensors a are parallel to the radial direction RA. Further, all the sensors are disposed on the same circumference, and the width H 1  of the first assembly cavity  52 A is equal to the width H 3  of the third assembly cavity  52 C. 
       FIG.  18    is a schematic perspective view of one more embodiment of the sensor device for high speed rotating machine in accordance with this disclosure, and  FIG.  19    is a schematic front view of  FIG.  18   . A difference between this embodiment and the embodiment of  FIG.  12    through  FIG.  17    is that, in this sensor device for high speed rotating machine  400 , the assembly direction of the rotational speed sensors  b   1 ,  b   2  is parallel to the assembly direction of the radial displacement sensors a. In particular, the magnetic heads (such as the probes  138 A,  138 B,  138 C,  138 D of  FIG.  14   ) of the rotational speed sensors  b   1 ,  b   2  are arranged in the radial direction RA of the rotating body  110 , and the magnetic heads (such as the probes  126 A,  126 B of  FIG.  3   ) of the radial displacement sensors a are arranged in the radial direction RA of the rotating body  110 . Namely, the assembly directions of the magnetic heads of the rotational speed sensors  b   1 ,  b   2  and the radial displacement sensors a are perpendicular to the axial direction AX. In addition, all the sensors are disposed on the same circumference. Thus, the calculations for the framework of  FIG.  20    is resembled to that of  FIG.  16   . However, in  FIG.  21   , different to the aforesaid  FIG.  17   , the rotational speed sensors  b   1 ,  b   2  of this embodiment are located into the corresponding first assembly cavities  52 A by locking. 
     In summary, according to the aforesaid embodiments of the present disclosure, the output signals of the two rotational speed sensors are used to generate pulse waves through the differential circuit, and the rotational speed and turning direction of the rotating body can be calculated by measuring the frequency of the pulse waves (in the present disclosure, two rotational speed sensors can generate two sets of pulse waves in sequence, and, by comparing the sequence of the pulse waves, the turning direction can be judged, and the rotational speed can be calculated by evaluating the frequency of the pulse waves). Also, different arrangements of the rotational speed sensors and the radial displacement sensors are provided. Thus, the stability in detecting the rotational speed can be maintained, and the complexity in designing the circuit can be reduced. In addition, in the limited spacing around the rotating body, different spacing between the rotating body and the sensors can be arranged to meet different applications. 
     Furthermore, in the aforesaid embodiments of the present disclosure, by connecting different numbers of coils in series, a plurality of closed-loop magnetic paths and different inductance ranges can be formed, and the four-probe sensors can be equipped with probes to provide different combinations of inductances. Thus, convenience for assembly can be obtained. For the application of the rotating body with different materials, in the limited spacing and structuring, an appropriate circuit to allocate suitable resonance points can be then feasible. 
     With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the disclosure, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present disclosure.