JP2006025894A - Contact detecting device and x-ray ct apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contact detecting device which judges output signals from two or more touch sensors by a single judgment circuit and an X-ray CT apparatus equipped with such the contact detecting device. <P>SOLUTION: The contact detecting apparatus 6 includes a voltage dividing circuit (400) in which the voltage dividing resistance (R2) is connected in series to a series circuit of the two or more touch sensors (402) having the resistance short-circuited by the contact with a substance and a judgment circuit (500) which judges a level of the output voltage of the voltage dividing circuit on the basis of two threshold values. The output voltage is the voltage drop of the voltage dividing resistance (R1). One threshold value of the two threshold values is larger than 0 and smaller than the output voltage when none of the two or more touch sensors touch the substance, and the other threshold value is larger than the one threshold value and smaller than the output voltage when at least one of the two or more touch sensors touches the substance. The two threshold values are given by Zener voltage of Zener diodes (ZD1 and ZD2). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a contact detection apparatus and an X-ray CT (computed tomography) apparatus, and more particularly to an apparatus for detecting contact with an object and an X-ray CT apparatus provided with such a contact detection apparatus.

In an X-ray CT apparatus, for example, a touch sensor is attached to a movable part that is driven by power, such as a gantry with a variable inclination angle, and something touches the touch sensor during the movement of the movable part. Sometimes the moving parts are stopped immediately. In order to enable such control, a determination circuit that monitors the output signal of the touch sensor and determines the presence or absence of contact is used (see, for example, Patent Document 1).
JP 2000-325333 A (page 2-3, FIG. 1-4)

  Since a determination circuit is provided for each touch sensor, when a plurality of touch sensors are provided for the same zone so as to cope with various assumed contacts, a plurality of determination circuits must be provided. However, there is a problem that the number of parts increases.

  Accordingly, an object of the present invention is to realize a contact detection device that determines output signals of a plurality of touch sensors with a single determination circuit, and an X-ray CT apparatus including such a contact detection device.

  (1) According to one aspect of the invention for solving the above-described problem, a voltage dividing resistor is connected in series to a series circuit of a plurality of touch sensors having a resistance that is short-circuited in contact with an object. A contact detection device comprising: a pressure circuit; and a determination circuit that determines a level of an output voltage of the voltage dividing circuit based on two threshold values.

  (2) According to another aspect of the invention for solving the above problems, a movable part that moves by power, a contact detection device that detects contact between the movable part and an object, and contact detection by the contact detection apparatus An X-ray CT apparatus having a stop device that stops the movement of a movable part, wherein the contact detection device has a voltage dividing resistance in a series circuit of a plurality of touch sensors having a resistance that is short-circuited in contact with an object. An X-ray CT apparatus comprising: a voltage dividing circuit connected in series; and a determination circuit that determines a level of an output voltage of the voltage dividing circuit based on two threshold values.

It is preferable that the output voltage is a voltage drop of the voltage dividing resistor in terms of appropriately detecting the presence or absence of contact.
The two threshold values are values that are lower than the output voltage when one threshold value is greater than 0 and no object touches any of the plurality of touch sensors, the other threshold value is greater than one threshold value, and Based on the magnitude relationship between the output signal and the two threshold values, a value that is lower than the output voltage when an object contacts at least one of the plurality of touch sensors is determined based on the magnitude relationship between the output signal and the two threshold values. This is preferable in that each failure is distinguished and detected.

  It is preferable that the two threshold values are each given by a Zener voltage of the Zener diode in order to stabilize the threshold values.

  In the invention in each aspect described above, the contact detection device includes a voltage dividing circuit in which a voltage dividing resistor is connected in series to a series circuit of a plurality of touch sensors having a resistance that is short-circuited in contact with an object. A contact detection device that determines the output signals of a plurality of touch sensors with a single determination circuit, and such a contact. An X-ray CT apparatus provided with a detection apparatus can be realized.

  The best mode for carrying out the invention will be described below with reference to the drawings. Note that the present invention is not limited to the best mode for carrying out the invention. FIG. 1 shows the configuration of the X-ray CT apparatus. This apparatus is an example of the best mode for carrying out the present invention. An example of the best mode for carrying out the present invention relating to an X-ray CT apparatus is shown by the configuration of the apparatus.

  As shown in the figure, the apparatus includes a gantry 100, a table 200, and an operator console 300. The gantry 100 scans the subject 10 carried by the table 200 with an X-ray beam (beam), collects scan data, and inputs the scan data to the operator console 300. The operator console 300 performs image reconstruction based on data input from the gantry 100, and displays the reconstructed image on a display 302.

  The operator console 300 also controls the operation of the gantry 100 and the table 200. Under the control of the operator console 300, the gantry 100 performs scanning under a predetermined scanning condition, and the table 200 positions the subject 10 in the imaging space so that a predetermined part is scanned.

  Positioning is performed by adjusting the height of the top plate 202 and the horizontal movement distance of the cradle 204 thereon by a built-in position adjustment mechanism. The height of the top plate 202 is adjusted by swinging the support column 206 around the attachment portion to the base 208. The top plate 202 is displaced vertically and horizontally by the swing of the support column 206. The cradle 204 is displaced horizontally on the top plate 202. Depending on the scanning conditions, scanning is performed with the gantry 100 tilted. The gantry 100 is tilted by a built-in tilt mechanism.

  Thus, since the gantry 100 and the table 200 become a movable part having power, the movable part is stopped when the movable part comes into contact with any object for the safety of the patient or the user.

  In order to detect contact with an object, a touch sensor is provided on the movable part. The touch sensor is provided at a place where a patient or a user is likely to be pinched, for example, on the lower surface of the top plate 202 or near the opening end of the gantry 100 as indicated by a broken line.

  An example of the arrangement of the touch sensors on the lower surface of the top plate 202 is shown in FIG. As shown in the figure, three touch sensors 402 are arranged so as to draw a U shape along the edge of the lower surface of the top plate 202. The outer shape of the touch sensor 402 is generally a tape shape, for example, a width of about 10 mm and a length of about 200 mm.

  As shown in FIG. 3, the touch sensor 402 includes a pair of conductors 412 and 414 and a resistor 416 that terminates between these conductors. The pair of conductors 412 and 414 are supported in parallel within a small interval in an insulating flexible sheath 410.

  With such a configuration, the resistance value between the conductors 412 and 414 shows the same value as the resistance 416 when the object is not in contact, but when the object is in contact, the resistance 416 is due to the contact between the conductor 412 and the conductor 414. Is short-circuited to become almost zero resistance. That is, the touch sensor represents the presence or absence of contact with the magnitude of resistance.

  FIG. 4 is a block diagram showing the configuration of the present apparatus from the viewpoint of contact safety measures. As shown in the figure, the present apparatus is configured such that the driving unit 2, the movable unit 4 driven by the driving unit 2, the contact detection device 6 that detects contact of the movable unit 4, and the contact detection device 6 detects contact. A stop device 8 for stopping the drive by the drive unit 2 is provided.

  The movable part 4 is an example of the movable part in the present invention. The contact detection device 6 is an example of a contact detection device in the present invention. Stop device 8 and drive device 2 are examples of a stop device in the present invention.

  The gantry 100 and the table 200 correspond to the movable part 4. A drive mechanism corresponding to the drive unit 2 is a drive mechanism built in each of the gantry 100 and the table 200. Combinations of the contact detection device 6 and the stop device 8 are also built in the gantry 100 and the table 200, respectively.

  An electrical configuration of the contact detection device 6 is shown in FIG. This apparatus is an example of the best mode for carrying out the present invention. An example of the best mode for carrying out the present invention relating to a contact detection device is shown by the configuration of the present device.

  As shown in the figure, the contact detection device 6 includes a voltage dividing circuit 400 and a determination circuit 500. The voltage dividing circuit 400 is configured by connecting resistors R1 and R2 in series to both ends of a series circuit of a plurality of touch sensors 402, respectively. Here, an example in which the number of touch sensors 402 is three is shown, but the present invention is not limited to this, and an appropriate plural number may be used.

  The voltage dividing circuit 400 is an example of a voltage dividing circuit in the present invention. The touch sensor 402 is an example of the touch sensor in the present invention. The resistor R2 is an example of a voltage dividing resistor in the present invention.

  A DC voltage with the resistor R2 side being common is applied to the voltage dividing circuit. The value of the voltage is 24V, for example. A voltage drop in the resistor R2 is output to the determination circuit 500 through a voltage follower 420.

  Since the gain of the voltage follower 420 is +1, the same voltage as the voltage drop in the resistor R2 is output to the determination circuit 500. The voltage follower 420 also reduces the output impedance of the voltage dividing circuit 400.

  The output voltage of the voltage dividing circuit 400, that is, the voltage drop across the resistor R2, becomes the minimum value E1 when none of the three touch sensors 402 senses contact. This is because the resistors R of the three touch sensors 402 are all in series with the resistor R1, and the voltage dividing ratio is minimized.

  On the other hand, when any one of the three touch sensors 402 senses contact, the output voltage of the voltage dividing circuit 400 becomes a voltage E2 larger than the minimum value E1. This is because the resistance R of the touch sensor 402 that sensed the contact becomes almost zero, and accordingly, the resistance in series with the resistance R1 decreases and the voltage dividing ratio increases.

  Note that the output voltage of the voltage dividing circuit 400 is 0 V, that is, common when the touch sensor 402 has a failure such as disconnection or disconnection, because the current does not flow through the resistor R2 and the voltage drop disappears. It becomes a potential.

  The determination circuit 500 includes a pair of transistor circuits. The output signals of the voltage follower 420 are commonly input to these transistor circuits. The determination circuit 500 is an example of a determination circuit in the present invention.

  One of the pair of transistor circuits is connected between the transistor Q1, a series circuit of a Zener diode ZD1 and a resistor R11 connected in series to the base of the transistor Q1, and a base emitter. And a resistor R13 connected in series to a collector. This transistor circuit outputs the collector potential of the transistor Q1 as a failure signal.

  The other transistor circuit includes a transistor Q2, a series circuit of a Zener diode ZD2 and a resistor R21 connected in series to the base thereof, a resistor R22 connected between the base and the emitter, and a resistor R23 connected in series to the collector. It consists of. This transistor circuit outputs the collector potential of the transistor Q2 as a contact signal.

  In the circuit of the transistor Q1, a Zener diode ZD1 having a Zener voltage of, for example, 4.3 V is used. This Zener voltage is about 1.5 V lower than the output voltage value E1 of the voltage dividing circuit 400.

  For this reason, when the output voltage of the voltage dividing circuit 400 is E1 or E2, the Zener diode ZD1 becomes conductive and current flows to the base of the transistor Q1, thereby turning on the transistor Q1 and turning on the collector potential. It becomes a low potential (L).

  On the other hand, when the output voltage of the voltage dividing circuit 400 is 0V, the Zener diode ZD1 does not conduct, so that no current flows to the base of the transistor Q1, so that the transistor Q1 is turned off and the collector is turned off. The potential becomes a high potential (H).

  That is, this transistor circuit becomes L when any of the three touch sensors 402 is in a non-contact state or when any one of them is in a contact state, and a failure such as disconnection of the touch sensor 402 has occurred. A fault signal that sometimes becomes H is generated.

  In the circuit of the transistor Q2, a Zener diode ZD2 having a Zener voltage of, for example, 6.8 V is used. This Zener voltage is larger than the output voltage value E1 of the voltage dividing circuit 400 and about 1.5V lower than the output voltage value E2.

  For this reason, when the output voltage of the voltage dividing circuit 400 is E2, the Zener diode ZD2 becomes conductive and current flows to the base of the transistor Q2, thereby turning on the transistor Q2 and reducing the collector potential to a low potential (L). It becomes.

  When the output voltage of the voltage dividing circuit 400 is E1, since the Zener diode ZD2 is not conducted, current does not flow to the base of the transistor Q2, the transistor Q2 is turned off, and the collector potential becomes high potential (H).

  Even when the output voltage of the voltage dividing circuit 400 is 0V, since the Zener diode ZD2 is not conducted, current does not flow to the base of the transistor Q2, so that the transistor Q2 is turned off and the collector potential becomes high (H). Become.

  That is, this transistor circuit becomes L when any one of the three touch sensors 402 is in a contact state, and becomes H when all the three touch sensors 402 are in a non-contact state, and the touch sensor 402 fails. A fault signal that becomes H when the error occurs.

  In this way, the determination circuit generates a failure signal and a contact signal whose levels change according to the state of a plurality of touch sensors, so that even if there are a plurality of touch sensors, only one determination circuit can be used.

Further, since the voltage drop of the voltage dividing resistor is used as the output voltage of the voltage dividing circuit, it is possible to appropriately detect the presence or absence of contact with the plurality of touch sensors.
The two threshold values for determining the output voltage of the voltage dividing circuit are values that are lower than the output voltage when one of the threshold values is greater than 0 and the object does not touch any of the plurality of touch sensors, Is a value that is lower than the output voltage when the object is in contact with at least one of the plurality of touch sensors and the threshold value of one of the plurality of touch sensors. Contact, contact and touch sensor failure can be detected separately.

Further, since the two threshold values are respectively given by the Zener voltage of the Zener diode, the threshold values can be stabilized.
FIG. 6 shows combinations of failure signal and contact signal levels corresponding to non-contact, contact, and failure states. As shown in the figure, in the non-contact state, the combination of the contact signal and the failure signal is (H, L), in the contact state, the combination of the contact signal and the failure signal is (L, L), and in the failure state, the contact is made. The combination of the signal and the failure signal is (H, H).

  The stop device 8 controls the operation of the drive unit 2 based on such a contact signal and a failure signal. That is, when the combination of the contact signal and the failure signal is (H, L), the drive is not stopped due to the non-contact state, and the drive is performed when the combination of the contact signal and the failure signal is (L, L). Stop. Also, when the combination of both signals becomes (H, H), the driving is also stopped from the viewpoint of risk prevention.

It is a figure which shows the structure of the X-ray CT apparatus of an example of the best form for implementing this invention. It is a figure which shows arrangement | positioning of a touch sensor. It is a figure which shows the structure of a touch sensor. It is a figure which shows the structure from a viewpoint of the contact safety countermeasure of the X-ray CT apparatus of an example of the best form for implementing this invention. It is a figure which shows the structure of the contact detection apparatus of an example of the best form for implementing this invention. It is a figure which shows the combination of the level of a failure signal and a contact signal in each state of non-contact, a contact, and a failure.

Explanation of symbols

2 Drive unit 4 Movable unit 6 Contact detection device 8 Stop device 100 Gantry 200 Table 300 Operator console 400 Voltage dividing circuit 500 Determination circuit 402 Touch sensor

Claims (8)

A voltage dividing circuit in which a voltage dividing resistor is connected in series to a series circuit of a plurality of touch sensors having a resistance that is short-circuited in accordance with contact with an object;
A determination circuit for determining the level of the output voltage of the voltage dividing circuit based on two threshold values;
The contact detection apparatus characterized by comprising. The output voltage is a voltage drop of the voltage dividing resistor;
The contact detection apparatus according to claim 1. The two threshold values are values that are lower than the output voltage when one threshold value is greater than 0 and no object touches any of the plurality of touch sensors, the other threshold value is greater than one threshold value, and A value that falls below the output voltage when an object contacts at least one of the plurality of touch sensors;
The contact detection apparatus according to claim 2. The two thresholds are each given by the Zener voltage of the Zener diode.
The contact detection device according to claim 1, wherein the contact detection device is a touch detection device. An X-ray CT apparatus having a movable part that moves by power, a contact detection device that detects contact between the movable part and an object, and a stop device that stops the movement of the movable part in response to contact detection by the contact detection device,
The contact detection device includes:
A voltage dividing circuit in which a voltage dividing resistor is connected in series to a series circuit of a plurality of touch sensors having a resistance that is short-circuited with contact with an object;
A determination circuit for determining the level of the output voltage of the voltage dividing circuit based on two threshold values;
An X-ray CT apparatus comprising: The output voltage is a voltage drop of the voltage dividing resistor;
The X-ray CT apparatus according to claim 5. The two threshold values are values that are lower than the output voltage when one threshold value is greater than 0 and no object touches any of the plurality of touch sensors, the other threshold value is greater than one threshold value, and A value that falls below the output voltage when an object contacts at least one of the plurality of touch sensors;
The X-ray CT apparatus according to claim 6. The two thresholds are each given by the Zener voltage of the Zener diode.
The X-ray CT apparatus according to claim 5, wherein the X-ray CT apparatus is any one of claims 5 to 7.

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