JP3808415B2 - Ultrasonic probe - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to an ultrasonic probe attached to an ultrasonic diagnostic apparatus that renders an ultrasonic diagnostic image by electrically or mechanically scanning an ultrasonic wave.
[0002]
[Prior art]
Conventionally, the technology described in FIG. 1 of Patent Document 1 below is known for this type of ultrasonic probe. Hereinafter, a conventional ultrasonic probe will be described. An element (transducer) that transmits and receives an ultrasonic signal is fixed to a rotor, and ultrasonic scanning is realized by transmitting and receiving an ultrasonic wave while rotating the element using a motor as a drive source. Specifically, the position of the rotor, that is, the position of the element is detected by a position information detector using a magnetic pattern drum of about 300 per rotation attached to the side surface of the rotor and an MR sensor facing it. In order to depict this ultrasonic tomographic image, the rotational position of the rotor is detected, and information on the rotational position is fed back to the ultrasonic diagnostic apparatus body (not shown), and the ultrasonic signal from the element and the rotational position of the rotor Based on the information, an ultrasonic tomogram is drawn on the ultrasonic diagnostic apparatus body. In the prior art, an MR (magnetoresistive) sensor, a GMR (giant magnetoresistive) sensor, or the like is used as a sensor element having a magnetoresistive effect facing the magnetic drum as a position detecting means.
[0003]
That is, FIG. 7 is a simplified illustration of a conventional ultrasonic probe. In the figure, a magnetic drum 1 is attached to a side surface of a rotor 11 to which an element (not shown) for transmitting and receiving ultrasonic waves is fixed. The window 5 seals the acoustic coupling liquid 3 for transmitting the transmission / reception signal of the ultrasonic element to the living body without attenuation. The MR sensor 2 is composed of a magnetoresistive element, and a pattern is generally formed on the MR sensor substrate 15 made of glass by a vapor deposition technique. The MR sensor 2 formed on the MR sensor substrate 15 is arranged to face the magnetic drum 1, is fixed to the frame 5, and the magnetic flux intersects the MR sensor 2 by the magnetization pattern formed on the magnetic drum 1. The resistance value changes due to the change of.
[0004]
FIG. 5 is a drawing showing the positional relationship between the magnetic drum and the MR sensor 2 pattern, and shows that the magnetic flux generated at the N pole and S pole of the magnetic drum intersects the MR sensor 2 pattern. . In general, the MR sensor 2 takes out the midpoint of two MR sensor patterns as shown in FIG. 6, and uses the fact that the resistance value changes due to the magnetic flux intersected by the two MR sensors, thereby adjusting the position of the magnetic drum. Detected. FIG. 6 shows an MR sensor pattern equivalently replaced with a resistor. A1 and A4 in FIG. 6 are arranged such that when A1 is at the center of the S pole with respect to the pattern pitch of the N pole and the S pole of the magnetic drum, A4 is positioned between the N pole and the S pole. Thus, when the magnetic flux crossing A1 is minimum, the magnetic flux crossing A4 is maximized. One of A1 is connected to the power source, and the other of A4 is connected to the ground.
[0005]
In the MR sensor connected as described above, the magnetic flux crossing A4 is the maximum in the positional relationship of FIG. 5, and the magnetic flux crossing A1 is the minimum, thereby minimizing the resistance value of A4. The midpoint potential of the two MR sensor patterns changes. In the case of taking a large output in the case of position detection using the MR sensor, the A phase signal output from the midpoint of A1 and A4 and the A bar that is 180 degrees out of phase with the A phase signal, that is, inverted. A signal is obtained, and the two output signals are amplified by a differential amplifier. In order to detect the rotation direction, a B signal having a phase difference of 90 degrees is obtained on the same principle as the A signal, and the rotation direction is detected from the A phase and B phase signals.
[0006]
FIG. 5 shows the positional relationship between the MR sensor pattern for obtaining the A and A bars and the B and B bars and the N pole and S pole patterns of the magnetic drum.
[0007]
The actual magnetic drum 1 has a cylindrical shape as shown in FIG. 7, and the gap between the MR sensor and the magnetic drum is minimized from the rotation center position to the frame, and the gap increases on both sides of the perpendicular line. Yes. Therefore, the flow velocity of the acoustic coupling liquid existing in the gap shown in FIG. 7 is inversely proportional to the size of the gap.
[0008]
The MR sensor 2 shown in FIG. 7 is a magnetoresistive element, and a current always flows as shown in the equivalent circuit of FIG. 6, and the MR sensor pattern generates heat according to Ohm's law. Heat generated from the MR sensor pattern is radiated to the acoustic coupling liquid 3 and the MR sensor substrate that are in contact with each other.
[0009]
If the heat transfer to the acoustic coupling liquid is dominant here, the cooling effect is large if the flow velocity of the acoustic coupling liquid flowing through the gap between the magnetic drum and the MR sensor is fast, and the cooling effect is small if the flow velocity is slow, The temperature of the MR sensor pattern itself varies depending on the gap with the magnetic drum, that is, the relative positional relationship with the magnetic drum. It is a well-known fact that the resistance of a solid changes with temperature. Originally, the resistance value of an MR sensor pattern that should be changed only by the magnetic flux generated by the pattern of the magnetic drum becomes a different value depending on the temperature change. As is clear from FIG. 5, the intermediate position on the arrangement of A and A bar is different from the intermediate position of B and B bar, and it is physically impossible to arrange the two on a perpendicular line with the rotation axis as the center. The flow rate of the acoustic coupling liquid is always unbalanced. That is, the position detecting means using the MR sensor is in the acoustic coupling liquid, and the acoustic coupling liquid exists between the magnetic drum and the MR sensor. The acoustic coupling liquid flows through the gap between the magnetic drum and the MR sensor by the rotation of the magnetic drum. Since the gap between the cylindrical drum and the planar MR sensor is not uniform, the flow rate of the acoustic coupling liquid is not uniform.
[0010]
[Patent Document 1]
Japanese Patent No. 2876510 [0011]
[Problems to be solved by the invention]
However, in the above conventional ultrasonic probe, the MR sensor is generally formed by vapor-depositing a magnetoresistive element as a ferromagnetic material on a glass substrate. It was found that the MR sensor pattern, which is a resistor formed on a glass substrate with low thermal conductivity, has non-uniform heat dissipation. When the temperature of the MR sensor pattern becomes non-uniform, the resistance value of the MR sensor changes, and as a result, the output signal of the MR sensor changes depending on the rotational speed and direction of the rotor, and accurate position information cannot be obtained. Had.
[0012]
The present invention solves the above-mentioned conventional problems, makes the heat dissipation of the MR sensor pattern uniform, reduces the change in MR sensor output due to the rotational speed and direction of the magnetic drum that rotates integrally with the rotor, and is accurate. The first object is to provide an ultrasonic probe for detecting accurate position information.
[0013]
The second object of the present invention is to reduce the non-uniformity of heat dissipation caused by the non-uniform liquid flow velocity, reduce the change in output of the MR sensor due to the rotational speed and direction of the magnetic drum, and detect accurate position information. It is to be.
[0014]
[Means for Solving the Problems]
To achieve the above object, an ultrasonic probe of the present invention includes a piezoelectric element that transmits and receives ultrasonic waves, a rotor that rotatably holds the piezoelectric element, a liquid sealing chamber that houses the rotor, An acoustic coupling liquid filled in the liquid sealing chamber; a sensor element having a magnetoresistive effect provided in the liquid sealing chamber for detecting the position of the rotor; and a magnetic drum attached to the rotor; The sensor element includes an A phase and a B phase, and each of the phases is composed of two or more magnetoresistive elements and outputs a midpoint potential thereof, and the two or more magnetoresistive elements An ultrasonic probe is arranged at an intermediate position of the element at different positions in the A phase and the B phase, and a substrate on which a pattern of the sensor element is formed is silicon nitride.
[0015]
Thereby, the heat radiation of the MR sensor pattern is made uniform, the change in the MR sensor output due to the rotational speed and direction of the magnetic drum rotating integrally with the rotor is reduced, and accurate position information can be detected. In particular, silicon nitride has a thermal conductivity of 150 W / m · K or more, makes the heat dissipation of the MR sensor pattern uniform, and changes the MR sensor output according to the rotational speed and direction of the magnetic drum that rotates integrally with the rotor. Reduced and accurate position information can be detected.
[0016]
Next, another ultrasonic probe of the present invention includes a piezoelectric element that transmits and receives ultrasonic waves, a rotor that rotatably holds the piezoelectric element, a liquid sealing chamber that houses the rotor, and the liquid sealing An acoustic coupling liquid filled in a chamber; a sensor element having a magnetoresistive effect provided in the liquid sealing chamber for detecting the position of the rotor; and a magnetic drum attached to the rotor; The sensor element includes an A phase and a B phase, and each phase is composed of two or more magnetoresistive elements and outputs a midpoint potential thereof. The ultrasonic probe is arranged at an intermediate position at a different position between the A phase and the B phase, and the sensor element has a thermal conductivity of 0.01 W / m · K to 5 W / m on the upper surface thereof. · K coated with at which material less sensor element Characterized in that there.
[0017]
Thereby, the heat radiation of the MR sensor pattern is made uniform, the change in the MR sensor output due to the rotational speed and direction of the magnetic drum rotating integrally with the rotor is reduced, and accurate position information can be detected.
[0018]
The material having a low thermal conductivity is preferably an epoxy resin. Further, the material having low thermal conductivity is preferably a glass wool coating film and an epoxy resin coating film thereon. Moreover, it is preferable that the film thickness of the said coating film is the range of 5-30 micrometers.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
4 to 7 described in the conventional example is the same as the present invention except for the following.
[0021]
(First embodiment)
FIG. 1 is a cross-sectional view of the ultrasonic probe in the first embodiment of the present invention, and the MR sensor substrate 4 is a silicon substrate made of silicon nitride. Since other reference numerals are common to the conventional example of FIG.
[0022]
2A and 2B are diagrams in which portions of the MR sensor substrate 4 and the MR sensor 2 in FIG. 1 are extracted, FIG. 2A is a schematic perspective view of the MR sensor 2, and FIG. 2 is a schematic sectional view of an MR sensor 2. FIG. The wiring in the cross-sectional view of FIG. 2B schematically represents the MR sensor pattern 2a.
[0023]
Conventionally, glass was used for the MR sensor substrate, but the thermal conductivity of optical glass is as small as 0.55 to 1.13 W / m · k. When the substrate on which the MR sensor pattern 2a is deposited is glass, the heat generated by the MR sensor pattern 2a is difficult to transfer through the glass, and most of the heat is radiated to the acoustic coupling liquid on the upper surface of the MR sensor pattern 2a.
[0024]
In the first embodiment of the present invention, a material having a large thermal conductivity of 150 to 200 W / m · k is used for the MR sensor substrate 4, and the heat generated by the MR sensor pattern 2 a is transmitted through the silicon substrate made of silicon nitride. As a result, the temperature difference of each pattern of the MR sensor is extremely reduced, and the temperature difference due to the difference in the flow velocity of the acoustic coupling liquid on the upper surface of the MR sensor pattern can be reduced. Therefore, it is possible to reduce the influence of the MR sensor output signal due to the rotation speed and rotation direction of the rotor 11 to which the magnetic drum, ie, the element is fixed. In the above, the thickness of the silicon substrate was 0.8 mm, and the size of the MR sensor 2 including the silicon substrate was 3.3 mm in length and 7.1 mm in width.
[0025]
According to the present embodiment, the heat radiation of the MR sensor pattern becomes uniform, and an accurate element position can be detected with little change due to the rotational speed and direction of the magnetic drum, that is, the rotor.
[0026]
(Second embodiment)
FIG. 3 shows a second embodiment. Even if the MR sensor substrate is a glass substrate 8, an epoxy resin 7 having a low thermal conductivity of 0.19 W / m · k is formed on the surface of the MR sensor 2 with a thickness of 30 μm. By coating, heat generated from the MR sensor pattern is less likely to be transferred to the acoustic coupling liquid side, and as a result, changes in the flow rate of the acoustic coupling liquid, that is, sensor output signals depending on the rotational speed and rotational direction of the rotor 11 to which the acoustic element is fixed. Can reduce the effects of
[0027]
In addition, even if the substrate on which the MR sensor is formed is a glass having low thermal conductivity, the MR sensor surface is contacted with the MR sensor surface by coating the surface of the MR sensor with a material having low thermal conductivity, such as epoxy or glass wool. The heat radiation to the acoustic coupling liquid is reduced. As a result, there is little change in the heat radiation amount due to the position of the MR sensor pattern, and the temperature of the MR sensor pattern can be made uniform. It is possible to detect an accurate position with little change due to the rotation speed and the rotation direction.
[0028]
(Third embodiment)
FIG. 4 shows a third embodiment, which further enhances the effect of the second embodiment. That is, the MR sensor 2 on the surface of the MR sensor substrate made of the glass substrate 8 is coated with glass wool 10 and the epoxy resin 7 is coated thereon.
[0029]
The thermal conductivity of the glass wool 10 is 0.03 to 0.05 W / m · k, which is a value lower than the thermal conductivity of the epoxy resin. The glass wool 10 contains air having a low thermal conductivity in the material, and the thermal conductivity of the glass wool 10 containing air increases due to the penetration of the acoustic coupling liquid. Epoxy coatings are applied. The thickness of glass wool was 30 μm, and the thickness of the epoxy resin was 10 μm.
[0030]
As described above, the three embodiments are listed. However, the effect can be further enhanced by combining the second embodiment or the third embodiment in addition to the first embodiment.
[0031]
According to the above embodiment, even if the position detection means using the MR sensor is provided in the liquid, the position of the rotor 11 to which the element is fixed can be reliably detected with little error due to the rotation speed and the rotation direction. Is possible.
[0032]
【The invention's effect】
As described above, by using a material having high thermal conductivity for the substrate of the MR sensor, it is possible to detect an accurate position with little change due to the rotation speed and the rotation direction. The same effect can be obtained by coating the surface of the MR sensor with a material having low thermal conductivity.
[0033]
Although the MR sensor is used as the position detecting means of the present invention, a GMR sensor may be used.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an ultrasonic probe in a first embodiment of the present invention.
2A is a schematic perspective view of an MR sensor according to a first embodiment of the present invention, and FIG. 2B is a schematic cross-sectional view of the MR sensor.
FIG. 3 is a cross-sectional view of an MR sensor according to a second embodiment of the present invention.
FIG. 4 is a cross-sectional view of an MR sensor according to a third embodiment of the present invention.
FIG. 5 is a diagram for explaining a relative positional relationship with an MR sensor by developing a conventional cylindrical magnetic drum.
FIG. 6 is a diagram illustrating an equivalent circuit of the MR sensor.
FIG. 7 is a cross-sectional view of a conventional ultrasonic probe.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Magnetic drum 2 MR sensor 3 Acoustic coupling liquid 4 MR sensor board 5 Frame 6 Liquid flow velocity 7 Epoxy resin 8 Glass substrate 9 Silicon substrate 10 Glass wool 11 Rotor

Claims (5)

Piezoelectric element that transmits and receives ultrasonic waves, a rotor that rotatably holds the piezoelectric element, a liquid sealing chamber that houses the rotor, an acoustic coupling liquid that is filled in the liquid sealing chamber, and a position of the rotor A sensor element having a magnetoresistive effect provided in the liquid sealed chamber for detecting the magnetic field, and a magnetic drum attached to the rotor,
The sensor element includes an A phase and a B phase, and each phase is composed of two or more magnetoresistive elements and outputs a midpoint potential thereof.
An ultrasonic probe in which an intermediate position between the two or more magnetoresistive elements is arranged at different positions in the A phase and the B phase,
An ultrasonic probe, wherein a substrate on which the sensor element pattern is formed is silicon nitride. Piezoelectric element that transmits and receives ultrasonic waves, a rotor that rotatably holds the piezoelectric element, a liquid sealing chamber that houses the rotor, an acoustic coupling liquid that is filled in the liquid sealing chamber, and a position of the rotor A sensor element having a magnetoresistive effect provided in the liquid sealed chamber for detecting the magnetic field, and a magnetic drum attached to the rotor,
The sensor element includes an A phase and a B phase, and each phase is composed of two or more magnetoresistive elements and outputs a midpoint potential thereof.
An ultrasonic probe in which an intermediate position between the two or more magnetoresistive elements is arranged at different positions in the A phase and the B phase,
Ultrasound probe, wherein the sensor element is a sensor element and the upper surface thermal conductivity coated with the material is below 0.01 W / m · K or higher 5W / m · K. The ultrasonic probe according to claim 2 , wherein the coating material is an epoxy resin. The ultrasonic probe according to claim 3, wherein the coating material further includes glass wool, and a glass wool coating film is formed under the epoxy resin coating film. The ultrasonic probe according to claim 2, wherein a film thickness of the coating film coated on the sensor element is 1 to 500 μm.

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