JPH0531113A - Ultrasonic diagnostic system - Google Patents

Abstract

PURPOSE:To enable effective protection of a motor for driving an ultrasonic vibrator from excessive current free from any burning loss with a simple and inexpensive construction without the use of a fuse for protecting the excessive current, hence eliminating complicated fuse changing work. CONSTITUTION:An ultrasonic diagnostic system having a mechanical scan type probe is provided with a current detecting means 16 in which sensitivity varies with a duration time of a current to detect a drive current of a motor 7 for driving ultrasonic vibrators, a current cutting means 15 to cut the drive current of the motor 7 and a control means 17 to control the current cutting means 15 based on an output of the current detecting means 16. When an abnormal current is detected by the current detecting means 16, the current cutting means 15 is driven through the control means 17 to cut the drive current of the motor 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus having a mechanical scanning type probe for scanning an object by mechanically rotating or linearly moving an ultrasonic transducer by a motor.

[0002]

2. Description of the Related Art In an ultrasonic diagnostic apparatus having a mechanical scanning type probe, a power supply circuit for driving a motor for rotating or linearly moving an ultrasonic vibrator provided in the probe has an ultrasonic signal as its power supply voltage. In many cases, it is different from the power supply voltage of another electric circuit such as a processing circuit, and is generally provided independently of the power supply circuit of the other electric circuit for reasons of noise suppression to the other electric circuit. Further, since such a motor generally controls the rotation speed by servo control, there is no big problem even if the power supply voltage includes some fluctuation.

From the above, the power supply circuit for driving the motor in the conventional ultrasonic diagnostic apparatus is constructed by a simple circuit in which an AC voltage is dropped by a transformer, rectified by a diode, and then a ripple is removed by a capacitor. Was
The overcurrent protection circuit for the motor load is also composed of a simple circuit in which a fuse is connected in series to the drive current path of the motor.

[0004]

However, as described above, in the configuration in which the fuse is simply connected to the drive current path of the motor to protect the motor from overcurrent, the drive of the motor is hindered by the failure of the probe. If the fuse for the overcurrent protection blows due to the increased load caused by the overcurrent protection, the fuse must be replaced when the probe is replaced with a normal one and the diagnosis is restarted. There is the problem of becoming annoying.

Further, since it is necessary to instantaneously flow a large current at the time of starting the motor, it is necessary to determine the rating of the fuse according to the starting current. For this reason, the fuse rating becomes large and it will not operate unless a considerably large current flows, and if the motor drive is interrupted and a large current flows for a long time, the motor will burn before the fuse blows. There is also.

The present invention has been made by paying attention to such a conventional problem, and does not use a fuse for overcurrent protection, and therefore does not perform a troublesome fuse replacement work, and has a simple and inexpensive structure. An object of the present invention is to provide an ultrasonic diagnostic apparatus appropriately configured so that a motor for driving an ultrasonic transducer can be effectively protected from an overcurrent without being burned.

[0007]

In order to achieve the above object, the present invention comprises a mechanical scanning probe for scanning an object by mechanically rotating or linearly moving an ultrasonic transducer by a motor. In ultrasonic diagnostic equipment,
A current detection unit whose sensitivity changes according to the duration of the current for detecting the drive current of the motor, a current cutoff unit for cutting off the drive current of the motor, and the current cutoff unit based on the output of the current detection unit. And a control unit for controlling the motor, and when the abnormal current is detected by the current detection unit, the current cutoff unit is driven via the control unit to cut off the drive current of the motor.

[0008]

FIG. 1 shows a first embodiment of the present invention.
It is applied to an ultrasonic endoscope. Ultrasound endoscope 1
Is detachably connected to the diagnostic apparatus main body 3 via the connector 2. The ultrasonic endoscope 1 is provided with an ultrasonic transducer 5 at the tip of an insertion portion 4 to be inserted into a body cavity, and is driven to rotate by a motor 7 provided in an operation portion 6 via a flexible shaft 8. In addition, the rotation angle of the ultrasonic transducer 5 is detected by the encoder 10 via the rotation transmission mechanism 9. In this embodiment, the diagnostic device main body 3 is provided with a motor drive power supply circuit 11, a pulse width modulation (PWM) control circuit 12 and an overcurrent protection circuit 13, and the motor drive voltage from the motor drive power supply circuit 11 is PWM controlled. In the circuit 12, pulse width modulation is performed based on the output from the encoder 10, and the output is supplied to the motor 7 via the overcurrent protection circuit 13 so that the rotation speed thereof is PWM controlled.

As shown in the block diagram of FIG. 2, the overcurrent protection circuit 13 comprises a current control means 15, a current detection means 16 and a current interruption control means 17, and the current detection means 16 detects the current flowing through the motor 7. The current control means based on the output
The drive current is controlled by 15 and the drive current of the motor 7 is forcibly shut off by the current control means 15 when the output of the current detection means 16 reaches a predetermined value. ..

The current detecting means 16 is constructed so that the sensitivity changes depending on the duration of the current flowing through the motor 7. That is, the PWM control circuit 12 controls the motor drive voltage.
When the PWM control is performed, the drive voltage waveform becomes as shown in FIG. 3A, and the current as shown in FIG. 3B flows through the motor 7. Therefore, in this embodiment, the sensitivity of the current detection means 16 is made dull for the instantaneous peak of the motor drive current,
The current control means 15 does not limit the amount of current flowing through the motor 7, and current cutoff control is performed when a large current can flow through the motor 7 for a long time such as when the rotation of the motor 7 is interrupted and stopped. The means 17 causes the current control means 15 to forcibly cut off the drive current of the motor 7.

FIG. 4 shows an example of a specific circuit configuration of the above-mentioned overcurrent protection circuit 13. In this example, the + 24V output line 21 of the PWM control circuit 12 is connected to the return line 22 via the collector-emitter path of the current controlling transistor Q ₁ , the resistor R ₁ for detecting the current and the motor 7. The collector of the transistor Q ₁ is, one end of resistor R ₂ connected, with the other end is connected to the resistor R ₂ to the base of the transistor Q _1, the collector of the transistor Q ₂ for current detection - through the emitter path resistance Connect to the connection point between R ₁ and motor 7. Further, the emitter of the transistor Q ₁ is connected to the base of the transistor Q ₂ , and the resistor R ₁ is connected in parallel with the capacitor C ₁ for reducing the sensitivity of current detection.

Further, the collector of the transistor Q ₁ passes through the Zener diode D ₁ and the resistor R ₃ and is connected to the transistor Q ₃
The base of the transistor Q ₃ is connected to the base of the transistor Q ₁ and the collector of the transistor Q ₂ and to the return line 22 through the collector-emitter path of the transistor Q ₄ to enhance the collector. Connect to the base of transistor Q ₄ via the drain-source path of FET Q ₅ . The collector of the transistor Q ₁ is connected to the return line 22 via the resistor R ₄ , the resistor R ₅ and the electric field capacitor C ₂ , and the resistor R ₄
Return line 22 and the connection point of the resistors R ₅ via a resistor R ₆
Then, connect the connection point of the resistor R ₅ and the electric field capacitor C ₂ to the gate of the enhancement type FET Q ₅ , respectively.

The operation of the overcurrent protection circuit 13 will be described below. In the normal state where the motor 7 is rotating normally, the current control transistor Q ₁ is almost saturated, current is normally supplied to the motor 7, and the motor is connected to both ends of the resistor R ₁ for current detection. A voltage drop occurs due to the current flowing through 7. Also, in this normal state, the transistors Q ₂ , Q ₃ and Q ₄ are off, and the enhancement type FET Q ₅ is on. The current supplied to the motor 7 is obtained by pulse-modulating the motor driving voltage as shown in FIG. 3A, so that the current is instantaneously generated at the rising edge of the pulse-modulated voltage as shown in FIG. 3B. However, for the current with this peak,
Since the capacitor C ₁ is connected in parallel to the resistor R ₁ and the current detection sensitivity is low, current limiting is not performed.

The current flowing through the motor 7 increases and the resistance R ₁
When the voltage drop generated reaches 0.7V, the base of the transistor Q ₂ to which has a normally off - the transistor Q ₂ is turned on and the emitter is forward biased. When the transistor Q ₂ is turned on, a current flows through the resistor R ₂ and the collector-emitter path of the transistor Q ₂ , which causes the base potential of the transistor Q ₁ to drop, and no more current flows to the motor 7, The amount is constant. In this way, the current flowing through the motor 7 is limited. Further, the transistors Q ₃ and Q ₄ in the normal OFF state constitute a thyristor circuit, a transistor by turning on the transistor Q ₂
Each becomes saturated when the base potential of Q ₁ is to some extent drops, transistor Q ₄ the base potential of the transistor Q ₁
Via, the transistor Q ₁ is turned off by forcing a short circuit to the return line 22.

That is, normally transistors Q ₃ and Q ₄
Is off and does not affect the operation of the transistors Q ₁ and Q ₂ , but the voltage drop across the resistor R ₂ is the Zener voltage of the Zener diode D ₁ (+ 0.7V; the emitter-base voltage of the transistor Q ₃ ) Then, the emitter-base of the transistor Q ₃ is forward biased and the transistor Q ₃ turns on, which enhances the enhancement type FET.
Drain of Q ₅ - transistor Q ₄ is turned on flows current to the base of the transistor Q ₄ through the source passage. Therefore, since the transistor Q ₄ are current flows through the resistor R _2, the base potential of the transistor Q ₁ is forced to be shorted to the return line 22, thereby the transistor Q ₁ is turned off. Thus, transistors Q ₃ and Q ₄ are
Acts as a forced shutoff control means.

On the other hand, the enhancement type FET Q ₅ has a large starting current flowing into the motor 7 when the power is turned on.
It serves to prevent transistors Q ₃ and Q ₄ from turning on. That is, when the power is turned on, the enhancement type FE
The gate potential of TQ ₅ is at the same potential as the return line 22 of the motor 7 and its drain-source resistance is large, so the thyristor circuit composed of the transistors Q ₃ and Q ₄ does not operate. Thus, the transistor Q ₁ in the influence of the starting current of the motor 7 at the time of power-on is prevented from being forcibly turned off, the motor 7 begins to rotate stably.

After that, the electric field capacitor C ₂ is charged through the resistor R ₄ and the resistor R ₅ , the gate potential of the enhancement type FET Q ₅ rises, the resistance between the drain and the source becomes close to zero ohm, and the transistor Q The thyristor circuit of ₃ and Q ₄ is established, and the standby state is set. Therefore,
Under use of the ultrasonic endoscope 1, for example for chewing a strong force patients the insertion portion 4, stops the rotation of the flexible shaft 8, the excessive current flows to motor 7, immediately resistor R ₁ is current Is detected, the transistor Q ₁ is turned off in accordance with the above-mentioned operation, and the current flowing through the motor 7 is cut off.

As described above, in this embodiment, the means for forcibly cutting off the current flowing through the motor 7 is provided, so that the current control means (transistor Q ₁ ) and the current detection means (resistor R ₁ , transistor) are simply used. Compared with the case where Q ₂ ) is provided, heat generation in the transistor Q ₁ due to an increase in motor current when the probe is abnormal can be effectively prevented, and therefore, it is not necessary to provide a large heat sink, so the device can be downsized. Also, the circuit configuration can be relatively simple, so that the cost can be reduced.

FIG. 5 shows the structure of the essential parts of the second embodiment of the present invention. This embodiment is applied to a direct-view type ultrasonic endoscope 31 in which an ultrasonic beam is radiated in a fan shape toward the distal end direction of the insertion axis of the endoscope. As shown in FIG. 5A, a forceps port 36 for inserting and removing the objective lens 32, the illumination lenses 33, 34 and a treatment instrument 35 such as a puncture needle is provided on the distal end surface of the ultrasonic endoscope 31. An ultrasonic transducer 37 is rotatably provided so as to radiate the ultrasonic beam in a fan shape toward the tip of the insertion axis of the endoscope.

As shown in FIG. 5B, the ultrasonic transducer 37 has the same overcurrent as that of the first embodiment through the flexible shaft 39 bent by the roller 38 on the tip surface of the ultrasonic endoscope 31. It is connected to a motor (not shown) whose drive is controlled via a protection circuit. Further, as shown in FIG. 5C, a raising mechanism 40 for displacing the treatment tool 35 within the scanning plane by ultrasonic waves is provided near the insertion tip of the forceps port 36. The raising mechanism 40 is operated by a hand operation knob (not shown) of the ultrasonic endoscope 31, and the treatment instrument 35 thereby.
The movement amount (angle) of the monitor is measured by a sensor such as a counter provided in the ultrasonic endoscope 31, and based on the movement amount, a monitor connected to the diagnostic apparatus main body 41 as shown in FIG. 5D.
The progress line 43 of the treatment instrument 35 is displayed on 42.

As described above, in the ultrasonic endoscope 31 in which the ultrasonic transducer 37 is rotated through the bent flexible shaft 39, the load applied to the motor becomes larger than that in the first embodiment, and the treatment is performed. Since the fluctuation of the load due to the insertion / removal of the tool 35 also becomes large, if the motor for rotating the ultrasonic transducer 37 is drive-controlled through the same overcurrent protection circuit as in the first embodiment, the motor burnout is more effective. Can be prevented and this can be effectively protected from overcurrent.

FIG. 6 shows a third embodiment of the present invention. In this embodiment, the output of a motor driving power supply circuit (not shown) is supplied to an ultrasonic transducer scanning motor 54 via a motor current interruption means 51, a current detection means 52 and a servo circuit 53 to drive the motor 54. At the same time, the rotation speed of the motor 54 is controlled by the servo circuit 53 based on the output pulse of a rotary encoder (not shown) that rotates in conjunction with the motor 54. The current detecting means 52 is the same as in the first embodiment.
The sensitivity is configured to change depending on the duration of the drive current flowing through the motor 54, and the current detected by the current detecting means 52 is supplied to the freeze means 55. Further, the freezing means 55 is also supplied with key input information from the operation panel 56, and the freezing means 55 supplies the motor current cutoff means 51 based on the detected current in the current detecting means 52 and the key input information from the operation panel 56. To shut off the motor drive current.

In this embodiment, in the normal freeze operation, the freeze means 55 is operated by the key input information from the operation panel 56 to stop the screen update in the digital scan converter (not shown) and the motor current cutoff means. Drive 51 to shut off the motor drive current. Further, in the state where the freeze by the key input is released, based on the current detected by the current detecting means 52, when it exceeds a predetermined value, that is, the rotation of the motor 54 is hindered by the failure of the probe or the like, the motor is driven. When the current increases to the extent that it impairs the safety of the device and the patient, the freeze current means 55 drives the motor current interruption means 51 to interrupt the motor drive current. With this configuration, safety can be secured when the motor drive current abnormally increases with a relatively simple configuration.

FIG. 7 shows a fourth embodiment of the present invention. In this embodiment, the current detecting means 61 is constituted by a hall element to output a voltage signal corresponding to the motor drive current, and the voltage signal is supplied to a low pass filter (LPF) 62 to extract a low frequency component, and this LPF is extracted. Based on the output of 62, when it continuously increases abnormally, the control circuit 63 drives the motor current cutoff means 64 to cut off the motor drive current. Indicates that they have the same effect.

According to this embodiment, since the current detecting means 61 is composed of the Hall element, the voltage drop here can be eliminated. Therefore, the output voltage of the motor driving power supply circuit (not shown) can be applied to the motor 54 without waste, and the motor 54 can be stably driven and controlled.
In addition, the detection signal of the motor drive current in the current detection means 61
Since the low frequency component is supplied to the LPF 62 and the motor current cut-off means 64 is controlled by this through the control circuit 63, the motor 54 and the servo circuit 53 are activated at the same time as in the first embodiment. Thus, it is possible to effectively prevent undesired interruption of the motor drive current due to the instantaneous peak of the motor drive current when the motor 54 is PWM controlled.

FIG. 8 shows a fifth embodiment of the present invention. In this embodiment, the current detection means 71 is configured by a transistor circuit, and the motor current cutoff means 72 is configured by a relay circuit, and when the current detected by the current detection means 71 continues to increase abnormally, the current is increased. Detection means
The motor current cut-off means 72 is driven by the output of 71 to open the relay contact to cut off the motor drive current, and the same reference numerals as those in the third embodiment indicate the same functions.

The current detecting means 71 includes a resistor R ₁ for detecting current.
Is provided, one end of which is connected to, for example, the + 24V output line 73 of the motor driving power supply circuit (not shown), the other end of which is connected to the servo circuit 53 through the relay contact of the motor current interruption means 72, and the resistance R ₁ In parallel with the capacitor C ₁ to reduce the detection sensitivity to pulsed current with a narrow pulse width.
Connect. Further, one end of the resistor R ₁ is connected to the resistor R ₂ , the emitter-collector passage of the transistor Q ₁ , and the enhancement type.
It is connected to the return line 74 of the motor drive power supply circuit via the drain-source path of the FET Q ₂ and the resistor R _3, and is also connected to the return line 74 via the resistor R ₄ and the electrolytic capacitor C ₂ and these resistors R ₄ and Connect the gate of FET Q ₂ to the connection point of electrolytic capacitor C ₂ .

Further, the other end of the resistor R ₁ is connected to the return line 74 through the resistor R ₅ , the collector-emitter path of the transistor Q ₃ and the relay coil of the motor current cutoff means 72, and the resistor R ₅ and the transistor Q ₃ are connected. The connection point with the collector of ₃ is connected to the base of the transistor Q ₁ , and the base of the transistor Q ₃ is connected to the source of the FET Q ₂ . The motor current cutoff means 72 is configured such that the relay contact opens when the relay coil is energized and closes when the relay coil is deenergized, and the backflow prevention diode D is connected in parallel to the relay coil. Connecting.

The operation of this embodiment will be described below. When the motor 54 is rotating normally, the resistance is
The voltage drop across R ₁ is small and transistors Q ₁ and Q ₃ are off. Therefore, no current flows in the relay coil, the relay contact remains closed, and the motor 54 is drive-controlled by the servo circuit 53. In contrast, the current flowing through the motor 54 increases, the voltage drop across the resistor R ₁ reaches 0.7 V, the emitter of the transistor Q ₁ which is a normally off - between the base is forward biased Transistor Q ₁ turns on. Here, the transistors Q ₁ and Q _{3 form} a thyristor circuit, and when the transistor Q ₁ is turned on, the transistor Q ₃ is also turned on, and the relay coil passes through the resistor R ₅ and the collector-emitter path of the transistor Q _3. A current flows, which opens the relay contact and interrupts the motor drive current. This state is maintained until the main switch of the device is turned off.

The motor 54 is driven by the servo circuit 53 to PW.
In the case of M control, the motor drive current momentarily peaks at the rise of the pulse-modulated voltage applied to the motor 54, but for the current with this peak, the resistor R ₁ and the capacitor C ₁ Transistors Q ₁ and Q ₃ are connected in parallel, which reduces current sensing sensitivity.
Never turn on. Also, enhancement type FET
As in the case of the first embodiment, Q ₂ is caused by the large starting current flowing into the motor 54 when the power is turned on and the transistor Q ₁ and
Prevent Q ₃ from turning on. That is, when the power is turned on,
The gate potential of the FET Q ₂ is in the return line 74 to the same potential of the motor 54, the drain - for source resistance is large, the thyristor circuit constituted by transistors Q ₁ and Q ₃ are not operated. Therefore, the relay contacts are not forcibly turned off due to the influence of the starting current of the motor 54 when the power is turned on, and the motor 7 starts to rotate stably.

After that, the electric field capacitor C ₂ is connected through the resistor R _4.
Are charged, the gate potential of FET Q ₂ rises, and the resistance between its drain and source becomes close to zero ohms.
The thyristor circuit of Q ₁ and Q ₃ is established, and the standby state is set. Therefore, as in the first embodiment, when the ultrasonic endoscope is used, for example, when the patient bites the insertion portion with a strong force and an excessive current continuously flows to the motor 54, the resistance R is immediately increased. ₁ detects the current and the transistors Q ₁ and Q ₃ are turned on according to the above-mentioned operation, whereby the current flows through the relay coil, the relay contact is opened, and the current flowing through the motor 54 is cut off. As described above, according to this embodiment, it is possible to realize safety measures when the motor drive current abnormally increases with a relatively simple and inexpensive circuit configuration.

9 and 10 show a sixth embodiment of the present invention. In this embodiment, the current detecting means 81 is composed of a Hall element, and its detection signal (voltage signal) is
It is supplied to one input terminal of the comparator 83 via the LPF 82. Here, when the motor 54 is PWM-controlled by the servo circuit 53, the detection signal in the current detection means 81 has a waveform shown in FIG. 10a, and when this voltage signal is passed through the LPF 82, its output, that is, one input terminal of the comparator 83. Will be supplied with the signal having the waveform shown in FIG. 10b. A reference voltage V _ref is applied from the voltage source 84 to the other input terminal of the comparator 83 and compared with the output of the LPF 82, thereby obtaining an output signal as shown in FIG. 10c. The output of this comparator 83 is
It is supplied to the flip-flop (FF) 85 and also supplied to the FF 85 via the timer 86.

The timer 86 is composed of, for example, a one-shot multivibrator, and is triggered by the rising edge of the output of the comparator 83 to output a high level (H) signal for a certain period as shown in FIG. 10d. In this embodiment, the output of the comparator 83 is latched at the fall of the output of the timer 86 in the FF85 to obtain a signal as shown in FIG. 10e, which is supplied as the freeze signal to the freeze means shown in the third embodiment. In the same manner as in the third embodiment, the motor drive current is cut off by the current cutoff means (not shown).
Therefore, the waveforms a, b, and c in FIG. 10 are actually zero after the rising in FIG. 10e.

According to this embodiment, the motor stop function is not activated by a simple sudden overcurrent, for example, a sudden overcurrent generated at the moment when the load of the motor is slightly increased, and the overcurrent continues for a certain period. Alternatively, the motor drive current can be cut off when it occurs multiple times within a certain period. Therefore, the reliability and operability of the ultrasonic diagnostic apparatus can be effectively improved.

It should be noted that the present invention is not limited to the above-described embodiments, but many variations and modifications are possible. For example, the current detection means, the current interruption means, and their control means are not limited to the diagnostic apparatus main body side, but may be provided on the ultrasonic transducer side of the ultrasonic endoscope or the like. It can also be provided as an adapter between and. Further, the drive control of the motor is not limited to PWM control, and other control methods can be applied.

[0036]

As described above, according to the present invention, the drive current of the motor is detected by the current detection means whose sensitivity changes according to the duration of the current, and the current cut-off means by the control means based on the output thereof. Since the motor drive current is forcibly cut off by controlling the motor, the motor can be effectively protected from overcurrent without burning, and the circuit configuration is relatively simple and low cost. You can Further, since it is not necessary to use a fuse for overcurrent protection, it is possible to reduce heat generation, therefore, it is not necessary to provide a large heat sink, the device can be downsized, and cumbersome fuse replacement work is unnecessary.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an overcurrent protection circuit shown in FIG.

3 is a diagram showing drive voltage waveforms and drive current waveforms supplied to the motor shown in FIG. 1. FIG.

4 is a diagram showing an example of a specific circuit configuration of the overcurrent protection circuit shown in FIG.

FIG. 5 is a diagram showing a configuration of a main part of a second embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a main part of a third embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a main part of a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a main part of a fifth embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a main part of a sixth embodiment of the present invention.

FIG. 10 is a diagram showing signal waveforms of various parts for explaining the operation of FIG. 9;

[Explanation of symbols]

 1 Ultrasonic Endoscope 2 Connector 3 Diagnostic Device Main Body 4 Insertion Section 5 Ultrasonic Transducer 6 Operation Section 7 Motor 8 Flexible Shaft 9 Rotation Transmission Mechanism 10 Encoder 11 Motor Drive Power Circuit 12 Pulse Width Modulation (PWM) Control Circuit 13 Overcurrent protection circuit 15 Current control means 16 Current detection means 17 Current interruption control means 21 Output line 22 Return line 31 Ultrasonic endoscope 32 Objective lens 33,34 Illumination lens 35 Treatment tool 36 Forceps mouth 37 Ultrasonic transducer 38 Roller 39 Flexible shaft 40 Raising mechanism 41 Diagnostic device main body 42 Monitor 43 Progress line 51 Motor current cutoff means 52 Current detection means 53 Servo circuit 54 Motor 55 Freeze means 56 Operation panel 61 Current detection means 62 Low pass filter (LPF) 63 Control circuit 64 Motor current interruption means 71 Current detection means 72 Motor current interruption means 73 Output line 74 Return line 81 Current detection means 82 LP F 83 Comparator 84 Voltage source 85 Flip-flop (FF) 86 Timer

Claims (1)

Claim: What is claimed is: 1. An ultrasonic diagnostic apparatus, comprising: a mechanical scanning probe for scanning an object by mechanically rotating or linearly moving an ultrasonic transducer by a motor, wherein a drive current of the motor. Current detecting means whose sensitivity changes according to the duration of the current for detecting the current, current interrupting means for interrupting the drive current of the motor, and control means for controlling the current interrupting means based on the output of the current detecting means. An ultrasonic diagnostic apparatus comprising: