ULTRASONIC PROBE FOR MEDICAL DIAGNOSTIC EXAMINATION

Abstract: An ultrasonic probe which scans an ultrasonic beam in a sector area by a mechanical means are disclosed. The ultra­ sonic probe essentially comprises a driving motor, a rotary shaft rotatably supported in a direction perpendicular to the direction of driving shah of the driving motor, a rotor shaft rotatably supported in a direction parallel to the direction of the rotary shaft, a rotor mounted on the rotor shaft for mount­ ing ultrasonic transducers, screw gear means for trans­ mitting rotation of the motor to the rotary shaft, and means for transmitting rotation of the rotary shaft to the rotor. An embodiment of the transmitting means is also dis­ closed.

Description: BACKGROUND OF THE INVENTION The present invention relates to ultrasonic probes particularly for medical diagnostic purposes, and more particularly to ultrasonic probes which scan an ultrasonic beam by a mechanical means. Fig. 1 shows a conventional mechanical sector-scanning type ultrasonic probe (hereafter referred to as "MSP"). A sub-rotary shaft 106 is rotatably supported at its ends to a frame 101. The sub-rotary shaft 106 is rotated by a motor 102 through motor shaft 103, and bevel gears 104, 105. The rotation of the sub-rotary shaft 106 is transmitted to a rotor shaft 108 through spur gears 107 and 109. The rotor shaft 108 rotates a rotor 110 having ultrasonic transducers 111 for mechanically scanning. The rotation number of the motor 102 is detected by a rotary encoder 112 which controls a driving circuit 113 of the motor 102. Reference numeral 114 designates an oil seal. In the conventional MSP, the interlocking between the bevel gears 104 and 105 is poor, so that the rotation of the motor 102 cannot be transmitted smoothly to the rotor 110, thereby deteriorates picture quality of an object. Furthermore, the bevel gears 104, 105 generate high driving noise when interlocked therebetween. In addition to this, the bevel gears 104, 105 are expensive. In the meantime, the rotation of the sub-rotary shaft 10-5 cannot be transmitted smoothly to the rotor 110, because of eccentricity of the spur gears 107, 109. The spur gears 107, 109 also generate high driving noise when interlocked therebetween. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an ultrasonic probe which has a mechanism to transmit the rotation of the motor smoothly to the rotor on which ultrasonic transducer are mounted. It is another object of the present invention to reduce the manufacturing cost of ultrasonic probes. It is a further object of the present invention to facilitate assembly the sub-rotary axis and the rotor axis. It is a further object of the present invention to provide an ultrasonic probe with low driving noise. The present invention provides an ultrasonic probe comprising a driving motor, a rotary shaft rotatably supported in a direction perpendicular to the direction of a driving shaft of said driving motor, a rotor shaft rotatably supported in a direction parallel to the direction of the rotary shaft, a rotor mounted on said rotor shaft for mounting ultrasonic transducers, first means for transmitting rotation of said driving motor to said rotary shaft, and second means for transmitting rotation of said rotary shaft to said rotor shaft, characterised in that said first means comprises first screw gear attached to a driving shaft of said driving motor and second screw gear attached to said rotary shaft, said first and second screw gears are engageably located, and in that said second means comprises first pulley attached to said rotary shaft, a second pulley attached to said rotor shaft, and a timing belt stretched across said first and second pulleys. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described in further detail with reference to the accompanying drawings, in which: Fig. 1 is longitudinal a cross-sectional view of a conventional ultrasonic probes; Fig. 2 is a longitudinal cross-sectional view of an embodiment of the ultrasonic probe in accordance with the present invention; Fig. 3 is a side view of the ultrasonic probe of Fig. 2 without casing; Fig. 4 is a longitudinal cross-sectional view of another embodiment of the ultrasonic probe in accordance with the present invention; Fig. 5 is a side view of the ultrasonic probe of Fig. 4 without casing; Fig. 6A is a longitudinal cross-sectional view of third embodiment of the ultrasonic probe in accordance with the present invention; Fig. 6B is a sectional view taken along the line 6B-6B of Fig. 6A; Fig. 7A is a sectional view taken along the line 7A-7A of Fig. 6B; Fig. 7B is a side view of a part of Fig. 7A; Fig. 8 is a longitudinal cross-sectional view of fourth embodiment of the ultrasonic probe in accordance with the present invention; Fig. 9 is a cross-sectional view of a part of ultrasonic probe of Fig. 8; Fig. 10A is a longitudinal cross-sectional view of fifth embodiment of the ultrasonic probe in accordance with the present invention; Fig. 10B is a sectional view taken along the line 10B-10B of Fig. 10A; Fig. 10C is a sectional view taken along the line 10C-10C of Fig. 10A; Fig. 11A is a sectional view taken along the line 11A-11A of Fig. 10A; Fig. 11B is a side view of a part of Fig. 11A; Fig. 12 is a longitudinal cross-sectional view of sixth embodiment of the ultrasonic probe in accordance with the present invention; Fig. 13 is a sectional view taken along the line 13-13 of Fig. 12; Fig. 14 is a front view of a part of the ultrasonic probe of Fig. 12; Fig. 15 is a side view of the part of Fig. 14; Fig. 16 is a front view of another part of the ultrasonic probe of Fig. 12; Fig. 17 is a side view of the part of Fig. 16; and Fig. 18 is a longitudinal cross -sectional front view of seventh embodiment of a part of the ultrasonic probe in accordance with the present invention. The same or corresponding elements and parts are designated at like reference numerals throughout the drawings. DETAILED DESCRIPTION OF THE INVENTION Referring now to Figs. 2 and 3, a driving motor 2 is supported at bottom plate 1C of a metal frame 1 by bolts 3a, 3b. The metal frame 1 has a pair of supporting frames 1a, 1b. A sub-rotary shaft 5 is supported at lower portion of the supporting frames 1a, 1b in perpendicular direction to the direction of a driving shaft 4 of the driving motor 2. The driving shaft 4 has a screw gear 9 at its top end. The sub-rotary shaft 5 has a screw gear 10 which is interlockable to the screw gear 9 of the driving shaft. The supporting frames 1a and 1b also supports a rotor shaft 7, parallel to the sub-rotary shaft 5, at upper portion. The rotor shaft 7 supports a rotor 6 on which ultrasonic transduces 8 are mounted. The sub-rotary shaft 5 and rotor shaft 7 are mechanically coupled through spur gears 11 and 12, each is mounted at one end of each of the sub-rotary shaft 5 and rotor shaft 7. The driving motor 2 is coupled to a rotary encoder 13 for detecting rotation of the rotor 6 or ultrasonic transducer 8. A front casing 15 made of plastics is screwed to a block casing 16 of plastics. In the front casing 15, is filled with acoustic energy propagating liquid. The liquid 17 is sealed by O-ring 18 between the bottom plate 1C and the front casing 15, and by oil sealing means 19 between the driving shaft 4 and the bottom plastic 1C. When the driving motor 2 is activated by a control circuit 14, the rotation of the driving shaft 4 of the driving-motor 2 is transmited to the sub-rotary shaft 5 through screw gears 9 and 10 to rotate the sub-rotary shaft 5. The rotation of the sub-rotary shaft 5 is similarly transmitted to the rotor shaft 7 through spur gears 11 and 12 to rotate rotor shaft 7. As a result, rotor 6 is rotated and scanning of the ultrasonic transducer is performed. The screw gears 9 and 10 are always interlocked with plural gear teeth with each other, so that the rotation of the motor shaft 4 is smoothly transmitted to the rotor shaft 7, whereby superior picture quality is obtained, and driving noise of the screw gears is very low. In addition, the serew gears 9 and 10 are easy to process the teeth in comparison with bevel gears, which reduces manufacturing cost of the gears. Referring now to Figs. 4 and 5, a timing pulley 21 is provided at one end portion of the sub-rotary shaft 5. In the same maner, a timing pulley 22 is provided at one end of the rotor shaft 7. The timing pulleys 21 and 22 are coupled with a timing belt 23. The sub-rotary shaft 5 is rotated by the driving motor 2 through screw gears 9 and 10. The rotation of the sub-rotary shaft 5 is transmitted to the rotor shaft 7 through the timing pulleys 21 and 22, and the timing belt 23. The rotor shaft 7 rotates the rotor 6 to perform scanning of ultrasonic beam from the ultrasonic transducer 8. As described above, the transmission of the rotation from the sub-rotary shaft to the rotor shaft 7 is achieved indirectly by the flexible timing belt 23. Therefore, an error of distance between the sub-rotary shaft 5 and the rotor shaft 7, which is occured in manufacturing them, is absorbed in the timing belt 23, so that irregularity of the rotor 6 based on the error of distance between the sub-rotary shaft 5 and the rotor 7, or an eccentricity of the spur gears 107, 109 (see Fig. 1) is avoided. Furthermore, the flexible timing belt 23 reduces driving noise occurring between the timing pulleys 21, 22 and the timing belt 23, and makes the rotor axis 7 rotate smoothly for obtaining stable ultrasonic picture information. Referring now to Figs. 6A, 6B, 7A and 7B, a third embodiment of the present invention will be described. A sub-frame 20 is provided near the supporting frame 1b between the supporting frames 1a and 1b. The sub-rotary shaft 5 is rotatably supported between the supporting frame 1a and the sub-frame 20. At the top portion of the frames supporting 1a and 1b, a U-shape notch 25, and screw holes 26, 27 are provided as shown in Figs. 7A and 7B. The rotor 6 having ultrasonic transducers is rotatably mounted arround the rotor shaft 7 through bearings 28. Both ends of the rotor shaft 7 are detachably mounted into the U-shaped notches 25 by screws 29 inserted into the screw holes 26 and 27. At one end of the sub-rotary shaft 5, a pulley 21 without brim is furnished between the supporting frame 1b and sub-frame 20. The pulley 21 is coupled with a pulley 22 having brim arround the rotor shaft 7 through the timing belt 23. The supporting frame 1b has an aperture 30 having diameter larger than that of the pulley 21. The embodiment makes it possible to take the timing belt 23 off the pulleys 21 and 22 and put it back on, because the rotor axis 7 is detachable from the supporting frames 1a and 1b by screwing off the screw 29, and the aperture 30, through which putting on and off the timing belt 23 is performed, is provided. It is also easy to take the timing belt 23 off the pulley 21 and put it back on because the latter has no brim. Fig. 8 illustrates fourth embodiment of the present invention. In Fig. 8, same parts and elements as those of Fig. 6 are labelled with same reference numerals. The embodiment is different from that of Fig. 6 in attaching portion of pulley 21 to the sub-rotary shaft 5. In Fig. 8, the pulley 21 is attached to the sub-rotary axis 5 by an attaching member 31 adjustable in the rotary direction. The attaching member 31 will be explained detail with Fig. 9. One end portion of the sub-rotary shaft 5 is supported by the sub-frame 20 at the top end of the sub-rotary shaft, a flange member 33, a supporting portion 32, and a screw hole 34 are provided. The pulley 21 is mounted arround the supporting portion 32, and fixed between the flange member 33 and a washer 35 which is clamped by a screw bolt 36 inserted into the screw hole 34 of the sub-rotary shaft 5. The timing belt 23 is put on between the pulley 21 and the pulley 22 around the rotor shaft 7. The aperture 30 having diameter larger than that of the pulley 21 is provided through the supporting frame 1b at the position corresponding to the pulley 21. Reference numeral 37 designates a seal member provided between the motor driving shaft 4 and the bottom plate 1C of the frame 1. The emission direction 38 of the ultrasonic beam from the ultrasonic transducer 8 is given by a detectable signal from the rotary encoder 13. Therefore, the attachment angle of the pulley 21 to the sub rotary shaft 5 may be adjustable as follows. When assembly of the ultrasonic probe is complete, the screw bolt 36 is loosened through the aperture 30, and driving motor 2 is rotated. When the rotary encoder 13 generates predetermined signal, the driving motor 2 is stopped, and the pulley 21 is rotated by hand to a certain position where the emission direction of the ultrasonic beam 38 is coincident to the predetermined direction, holding the sub-rotary shaft 5 in fixed state. When adjusted in this way, the pulley 21 is fixed to the sub-rotary shaft 5 by screwing down the screw bolt 36. As descibed above, it is possible to manufacture and adjust the emission direction of the ultrasonic beam in short time without skill. Figs. 10A to 11B illustrates fifth embodiment showing in particular a bearing portion of the sub-rotary shaft. The same parts and elements as those of Fig. 6 are labelled with the same reference numerals. The sub-rotary shaft 5 is rotatably supported on the supporting frame 1a and the sub-frame 20 with radial bearings 43 and 44. The sub-rotary shaft 5 is inserted into the inner wall of the radial bearing 43 and 44 at stepped end portions 5a and 5b. A brim 44a of the radial bearing 44 is engaged with inner surface of the sub-frame 20 to regulate one-directional thrusting of the sub-rotary shaft 5. A supporting member 45 is slidably mounted to the supporting frame 1a at top end side of the stepped portion 5a of the sub-rotary shaft 5. The supporting member 45 is composed of a circular plate 46, ring portion 47 and a projection 48 on the circular plate 46. A leaf spring 49 is attached to the supporting frame 1a with a screw 50. The leaf spring 49 pushes the projection 48 of the supporting member 45 to regulate the position of the radial bearing 43. When the motor 2 is driven, the sub-rotary shaft 5 undergoes bi-directional thrusting load along its axial direction which is liable to oscillate the sub-rotary shaft 5. However, the brim 44 and the leaf spring 49 prevent the oscillation of the sub-rotary shaft 5 to lower the vibration and driving noise of the ultrasonic probe. The leaf spring 49 also operates as a safety device for shock. The height of the ring portion 47 of the supporting member can be made low so that the supporting frame 1a can be made thin. As a result, the radius r₁ of the front casing 15 can be made small to realise a slender ultrasonic probe. The slender ultrasonic probe can widen the observation area in a human body when the probe is held between ribs of the human body. Figs. 12 to 17 illustrates sixth embodiment of a part of the bearing portion of the rotor shaft according to the present invention. The same parts and elements as those of Fig. 2 are labelled with same reference numerals. At the top end portion of the supporting frame 1b, a supporting plate 51 is adjustably mounted with a screw 54 through an oblong holes 53 as shown in Fig. 15. In the same manner, a supporting plate 52 is adjustably mounted to the supporting frame 1a with a screw 54 through an oblong holes 53 as shown in Fig. 17. Each of the supporting plates 51 and 52 is made of stainless steel leaf spring member, and apertures 55, 56 are provided at top portion thereof. The periphery of the aperture 55 has a V-shaped portion 55a, 55b and a straight portion 55c which is arranged to make equal angle with each periphery of the V-shaped portion 55a, 55b as shown in Fig. 15. One side of the aperture 55 is cut out to make an opening portion 57. A cut portion 58 is provided at outside of one periphery 55b of the V-shaped portion 55a, 55b. The rotor shaft 7 has a groove 59 having straight bottom at one end portion thereof. The width of the groove 59 is same as the thickness of the supporting plate 51. This end of the rotor shaft 7 is inserted into the aperture 55 in such a manner that the groove 59 engages with the straight portion 55C of the aperture 55. The V-shaped portion 55a, 55b contacts to the outer periphery of the rotor shaft 7 at points a₁ and b₁, and the straight portion 55C contacts to the straight bottom of the groove 59. The contacted straight portion C₁ pushes the rotor shaft 7 to the contacted points a₁ and b₁ by a spring tension of the opening portion 57. As a result, the rotor shaft 7 is supported in locked state. The spring tension is adjustable by providing the cut portion 58. In the mean time, as shown in Fig. 17, the periphery of the aperture 56 has a V-shaped portion 56a, 56b, which is almost same as the V-shaped portion 55a, 55b mentioned above, and a straight portion 56C arranged to make equal angle with each periphery of the V-shaped portion 56a, 56b. An opening portion 60 and a cut portion 61 are also provided as same as the supporting plates 51 of Fig. 15. Another end of the rotor shaft 7 is inserted into the aperture 56 in such a manner that the V-shaped portion 56a,55b and the straight portion 56C contacts to the outer pheriphery of the rotor shaft 7 at points a₂, b₂ and c₂ respectively. The contacted point c₂ pushes the rotor shaft 7 to the contacted points a₂ and b₂ by a spring tension of the opening portion 60 to support the rotor shaft 7 in a locked state. The spring tension is also adjustable by the cut portion 61. This supporting means can absorb thermal expansion of the rotor shaft 7 in axial direction. The supporting plates 51 and 52 are small in thickness. Therefore, diameter D₁ of the front casing 15, inner radius r₁ of the front casing 15, and distance L₁ between the rotor 6 and inner top surface of the front casing 15 can be made small. This produces a wide observation area as with the embodiment of Figs. 10A to 11B. Referring now to Fig. 18, another embodiment of the bearing portion of the rotor shaft will be described. On outer surface of a rotor shaft 71, a groove 73 is provided in which an elastic ring having cut portion is inlaid An outer ring 72a of a bearing 72 is sandwiched between a stepped portion 75c of a transholder 75 and a calkin 75a of the transholder 75. An inner ring 72b of the bearing 72 is sandwiched between a stepped portion 71a of the rotor shaft 71 and the elastic ring 74. Thus the bearing 72 is fixed. A bearing holder 77 is inserted into inner side of the transholder 75 in such a manner that the bearing holder 77 is sandwiched between a calkin 75b of the transholder 75 and outer core 78. A bearing 79 is disposed between the bearing hold 77 and a rotor shaft 76. An outer ring 79a of the bearing holder 79 is held to a projected portion 77a of the bearing holder 77, and movable to axial direction against the rotor shaft 76 and the bearing holder 77. Therefore, the bearing 79 is movable along inner surface of the bearing holder 77. As a result, no thrusting load is imposed on the bearings 72 and 79, so that the rotor 6 can rotate smoothly, and the bearings 72 and 79 are made long in life.

Claims: An ultrasonic probe comprising a driving motor (2), a rotary shaft (5) rotatably supported in a direction perpendicular to the direction of a driving shaft (4) of said driving motor, a rotor shaft (7, 71) rotatably supported in a direction parallel to the direction of the rotary shaft, a rotor (6) mounted on said rotor shaft (7, 71) for mounting ultrasonic transducers (8), first means (9, 10) for transmitting rotation of said driving motor to said rotary shaft, and second means (21, 22, 23) for transmitting rotation of said rotary shaft to said rotor shaft, characterised in that said first means comprises first screw gear (9) attached to a driving shaft of said driving motor and second screw gear (10) attached to said rotary shaft, said first and second screw gears are engageably located, and in that said second means comprises first pulley (21) attached to said rotary shaft (5), a second pulley (22) attached to said rotor shaft (7), and a timing belt (23) stretched across said first and second pulleys (21,22). An ultrasonic probe as claimed in claim 1, wherein said rotary shaft (5) and rotor shaft (7) are supported by a pair of supporting frames (1a, 1b). An ultrasonic probe as claimed in claim 1 or 2, further comprising first (1a) and second (1b) supporting frames, and third frame (20) located inner side of said second frame (1b), said rotor shaft (7) is supported by said first (1a) and second (1b) supporting frames, and said rotary shaft (5) is supported by said first (1a) and third (20) frames. An ultrasonic probe as claimed in claim 3, wherein said rotor shaft (7) is detachably supported by inserting into notches (25) provided on said first (1a) and second (1b) frames. An ultrasonic probe as claimed in claim 3, wherein said rotary shaft (5) is supported by first (43) and second (44) bearing means, said first bearing means (43) is provided on said first supporting frame (1a) and regulated in position with a supporting member (45) and a leaf spring (49) for thrusting said supporting member (45) and said second bearing means ((44) is provided on said third supporting frame (20) under regulation of thrusting of one direction. An ultrasonic probe as claimed in claim 3, wherein said rotor shaft (7) is supported by supporting plates (51, 52) made of leaf spring fixed on each of said first (1a) and second (1b) supporting frames in such a manner that said rotor shaft (7) is inserted into an aperture (55, 56) bored on each of said supporting plates (51,52). An ultrasonic probe as claimed in claim 6, wherein each of said aperture (55,56) contacts to said rotor shaft (7) at three positions (a₂ b₂ c₂) of outer surface of said rotor shaft (7). An ultrasonic probe as claimed in claim 6, wherein a part (33c) of peripheral of one of said apertures (55) is inserted in a groove (59) provided on one end portion of said rotor shaft (7). An ultrasonic probe as claimed in claim 1, wherein said rotor shaft (7,71) is supported by first and second bearing means (72) is disposed in a transholder (75) located in said rotor, and fixed to said rotor shaft (71) with an elastic ring (74) inlayed in a groove (73) provided on outer surface of said rotor shaft (71), said second bearing means (79) is supported by a bearing holder (77) which is fixed to inner portion of said transholder (75) by a calkin (75a) of said transholder (75). An ultrasonic probe as claimed in claim 3, wherein said first (21) and second (22) pulleys and timing belt (23) are disposed between said second (1b) and third (20) supporting frames. An ultrasonic probe as claimed in claim 1, wherein said first pulley (21) has no brim. An ultrasonic probe as claimed in claim 3, wherein said second supporting frame (1b) is disposed outside of said first pulley (21), and has an aperture (30) of diameter larger than that of said first pulley. An ultrasonic probe as claimed in claim 1, further comprising means (31-36) for adjusting rotational position of said first pulley (21) to said rotary shaft (5). An ultrasonic probe as claimed in claim 3, wherein said means (31-36) comprises a supporting rod (32) coaxially disposed at one end of said rotary shaft, a flange member (33) disposed inside of said supporting rod (32), a washer plate ((35) for putting said first pulley (21) between said flange member (33) and said washer plate (35), and a screw (36) for fixing said washer plate (35) to said first pulley (21). An ultrasonic probe according to claim 1 , characterised in that the rotor (6) has ultrasonic transducers disposed on surfaces thereof a transholder (75) disposed in said rotor (6), a rotor shaft (7,71) for supporting said rotor (6) and said transholder (75), first bearing member (72) disposed in said transholder (75) for supporting one end of said rotor shaft (71), a ring means (74) inlayed in a groove (73) provided on a surface of said rotor shaft (71) for fixing said first bearing member (72) to said rotary shaft (5), second bearing member (79) disposed on the other side of said rotary shaft (5) and a bearing holder (77) fixed in said transholder (75) with a calkin (75a) of said transholder (75) for holding said second bearing member (79).

Inventors: KIKUCHI,KOH, MORITA,YASUYUKI, SUGIYAMA,YOSHIYUKI
Applicants: MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1987
Main classification: G10K11
IPC codes: G10K11