JP5084067B2 - Servo type sensor - Google Patents

Description

  The present invention relates to a servo-type sensor that detects physical quantities such as acceleration, speed, and displacement.

  Conventionally, a servo-type sensor is known as a sensor that detects physical quantities such as acceleration, speed, and displacement (see, for example, Patent Document 1). For example, in a servo type sensor that detects acceleration, as shown in FIG. 16, one end (base end portion 1a) of a pendulum 1 made of a rod-shaped member is connected to the substrate 3 of the servo type sensor via an elastic body such as a spring 2. On the other hand, the other end (free end 1b) of the pendulum 1 is configured to be movable. The force applied to the pendulum 1 is detected to obtain the acceleration. Specifically, in the case of a servo sensor that detects the acceleration by driving the pendulum 1 using electromagnetic force, a wound coil 4 is attached to the free end 1b of the pendulum 1, and the free end 1b. And a magnet 5 are arranged at a predetermined distance from each other. The servo type sensor includes a displacement amount detection unit 6 that detects the force applied to the pendulum 1 from the displacement amount, receives a displacement amount detected by the displacement amount detection unit 6, and causes a current to flow through the coil 4 to generate a magnet 5. A servo amplifier 7 is provided to cancel the force applied to the pendulum 1 by the electromagnetic force generated between the two and the pendulum 1 and position the pendulum 1 at the equilibrium point.

  Incidentally, the displacement amount detection unit 6 includes a light emitting unit such as a light emitting diode having a certain luminance, and a light receiving unit such as a photodiode that receives light emitted from the light emitting unit and converts it into an electric signal, although not particularly illustrated. When the sensor is not accelerated and the pendulum is positioned at a predetermined equilibrium point, the light receiving unit receives the maximum amount of light received and the light receiving unit moves as the pendulum moves from the equilibrium point. A slit for reducing the amount of received light is provided.

  The servo sensor configured in this way is provided with a detection unit 8 that detects the magnitude of the current that the servo amplifier 7 flows into the coil 4, and the physical quantity applied to the pendulum 1 by the detection signal output from the detection unit 8, For example, the magnitude of acceleration can be detected. Incidentally, whether or not this type of servo type sensor is functioning normally may be determined by providing a diagnostic function to the servo type sensor.

  This diagnostic function includes, for example, a diagnostic coil 10 different from the above-described coil 4 at the free end 1b of the pendulum 1, and a power supply unit (diagnostic current generating unit) 11 for supplying current to the diagnostic coil 10. Configured as a thing. The diagnostic coil 10 generates magnetic flux when current flows from the power supply unit (diagnostic current generating unit) 11 during diagnosis. This magnetic flux acts on the magnet 5 disposed in the vicinity of the free end 1b of the pendulum 1, and drives the free end 1b of the pendulum 1. Then, the displacement amount detection unit 6 detects the displacement of the pendulum 1 and gives a detection signal to the servo amplifier 7. The servo amplifier 7 receives this detection signal, cancels the displacement generated in the pendulum 1, and controls the current supplied to the coil 4 so as to be positioned at the equilibrium point. That is, the current that the servo amplifier 7 applies to the coil 4 has a correlation with the current that the power supply unit 11 flows into the diagnostic coil 10. Therefore, the detection unit 8 detects a current change of the servo amplifier 7, and it is possible to diagnose the quality of the sensor by examining the relationship between the detected value and the current value that the power source unit 11 has flowed into the diagnostic coil 10. .

JP-A-8-170970

  However, in the above-described conventional servo type sensor, even if the diagnostic current generator sends a current to the diagnostic coil and applies a force to the pendulum to deviate from the equilibrium point, the pendulum is not connected to the servo amplifier. It is positioned at the original equilibrium point by control. For this reason, the conventional servo-type sensor has a problem that it cannot detect defects such as deterioration of the spring that holds the pendulum, deterioration of the displacement detection unit, and deterioration of the magnet.

  The present invention has been made in response to such a conventional situation, and an object of the present invention is to provide a servo-type sensor capable of performing failure diagnosis with a simple configuration.

  In order to achieve the above-described object, a servo type sensor according to the present invention has a pendulum with one end locked so as to be displaced in a predetermined uniaxial direction, and the other end is a movable free end. A displacement amount detection unit for detecting a magnitude of an external force applied to the pendulum as a displacement amount from a predetermined equilibrium point in the pendulum; a coil attached to the free end portion of the pendulum; and the free end portion of the pendulum; A magnet disposed with a predetermined gap, and a servo that positions the pendulum at the equilibrium point by passing a current that cancels the external force applied to the pendulum in response to the displacement detected by the displacement detector. An amplifier, a resistor interposed between the coil and the ground electrode, an acceleration detection unit for detecting acceleration acting on the pendulum from a value of a voltage drop generated in the resistor, and the displacement amount detection unit, Instead of the detected displacement A switch circuit for supplying a preset test voltage to the servo amplifier, and a preset reference value and a voltage drop generated in the resistor in a state where the preset test voltage is applied to the servo amplifier. A determination unit that compares the value with each other to determine whether the resistor is abnormal.

  Alternatively, the servo-type sensor according to the present invention includes a pair of fixed electrodes that are opposed to each other with an outer edge fixed to a predetermined casing, and a movable electrode that is sandwiched between the pair of fixed electrodes and has an outer edge fixed to the casing. A weight which is fixed at a predetermined position of the movable electrode and receives an external force to bend the movable electrode, and a capacitance change in a capacitor formed by the external force received by the weight by the fixed electrode and the movable electrode A capacitance detecting unit that detects the amount, and an electrostatic force acting between the fixed electrode and the movable electrode in response to the amount of change in capacitance detected by the capacitance detecting unit, and a predetermined equilibrium point An electrode driving unit for positioning the movable electrode, a resistor connected in parallel to the capacitor, an acceleration detecting unit for detecting an acceleration acting on the movable electrode from a value of a voltage drop generated in the resistor, and the static Capacitance detector In place of the detected amount of change in capacitance, a switch circuit that applies a preset test voltage to the electrode driver, and a preset test voltage that is preset to the electrode driver And a determination unit that determines whether the resistor has an abnormality by comparing the reference value thus generated with a value of a voltage drop generated in the resistor.

  As described above, according to the servo sensor according to the present invention, instead of the driving force that cancels the external force applied to the detection body by the driving unit, another driving force is applied to the detection body, and a preset reference value is set. By comparing the value of the voltage drop generated in the resistor with the value of the resistor, the presence or absence of abnormality of the resistor can be easily determined.

It is a schematic block diagram which shows the servo type sensor which concerns on this invention. FIG. 2 is a circuit diagram showing an example of a servo amplifier peripheral circuit in the servo type sensor shown in FIG. 1. It is a circuit diagram which shows an example of the servo amplifier peripheral circuit in the servo type sensor which concerns on another embodiment of this invention. FIG. 4 is a circuit diagram showing a periphery of a servo amplifier, which is a modification of the servo type sensor shown in FIG. 1. It is a modification of the servo type sensor shown in FIG. 1 and is a circuit diagram showing the periphery of a displacement amount detection unit. FIG. 6 is a modification of FIG. 5, and is a circuit diagram showing the periphery of a displacement amount detection unit. It is the schematic which shows the structure of the detection part using a piezoelectric element. It is the schematic which shows the structure of the detection part using a Hall element. It is the schematic which shows the structure of the detection part using a sound wave. It is the schematic which shows the structure of the detection part using a high frequency oscillator. It is the schematic which shows the structure of the detection part using the electrostatic capacitance change of a capacitor | condenser. It is a block diagram which shows the structure of the detection circuit which confirms the sensitivity of the detection part shown in FIG. It is a servo type sensor which concerns on another embodiment of this invention, Comprising: It is a figure which shows the structure of a 3-axis micromachining electrostatic capacitance sensor. It is sectional drawing which looked at the triaxial micromachining sensor shown in FIG. 13 from the side. It is a figure which shows the displacement when acceleration is added to the -x-axis and z-axis directions of the 3-axis micromachining sensor shown in FIG. It is a schematic block diagram which shows the conventional servo type sensor.

  Hereinafter, a servo sensor according to an embodiment of the present invention will be described with reference to the drawings. In the following description, parts having the same functions as those of the conventional servo type sensor are denoted by the same reference numerals and the description thereof is briefly described.

  FIG. 1 is a schematic block diagram showing a servo type sensor according to the present invention. In this figure, it is assumed that gravity acts on the servo type sensor in the downward direction of the drawing. FIG. 1 shows a part of the embodiment of the present invention, and the scope of the present invention is not limited by FIG.

  Here, the servo type sensor according to the present invention is different from the conventional servo type sensor in that the current output from the power supply unit 11 is servoed in place of the point that the diagnostic coil 10 is excluded and the detection signal of the displacement detection unit 6. It is in the point given to the amplifier 7. That is, the servo-type sensor according to the present invention provides the balance of the pendulum 1 by applying the current output from the power supply unit 11 instead of the detection signal (detection current) output from the displacement detection unit 6 as the input of the servo amplifier 7. The pendulum 1 is displaced from the point.

  Incidentally, the displacement amount detection unit 6 includes a light emitting unit such as a light emitting diode having a certain luminance, and a light receiving unit such as a photodiode that receives light emitted from the light emitting unit and converts it into an electric signal, although not particularly illustrated. Provided with a slit that maximizes the amount of light received by the light receiving unit when the pendulum is positioned at a predetermined equilibrium point, and reduces the amount of light received by the light receiving unit as the pendulum moves from the equilibrium point. It has become. Specifically, this equilibrium point is the position of the pendulum 1 when the acceleration applied in the detection direction is [0 Gal (cm / s2)], and is also referred to as a zero equilibrium point.

  The pendulum 1 is locked to the substrate 3 of the servo sensor with one end (base end portion 1a) of the pendulum 1 as an axis (running shaft) so as to be displaced in a predetermined uniaxial direction. In other words, the pendulum 1 is configured to be displaced by swinging only in the left-right direction in this figure, and not swinging in the front-rear direction or the vertical direction.

  When the displacement amount detection unit 6 detects that the pendulum 1 has deviated from the equilibrium point, the displacement amount detection unit 6 gives a current [I3] of a detection signal corresponding to the amount of displacement as an input to the servo amplifier 7. Then, the servo amplifier 7 controls the pendulum 1 to be an equilibrium point by passing a current [I1] corresponding to the current [I3] of the detection signal to the coil 4 attached to the pendulum 1 in order to correct this deviation (see FIG. Feedback control).

  When the current [I2] output from the power supply unit 11 is input to the servo amplifier 7 instead of the detection signal from the displacement amount detection unit 6, the servo amplifier 7 disconnected from the feedback control system is connected to the power supply unit 11. Outputs a current corresponding to the current [I2] output from the current to the coil 4. Then, the pendulum 1 moves to a position shifted from the original equilibrium point and is stabilized. The displacement amount of the pendulum 1 at this time is detected by the detection unit 8. Therefore, in the servo type sensor according to the present invention, it is only necessary to determine whether the servo type sensor functions correctly based on the detection value of the detection unit 8 by the determination unit 12 described later.

  Schematically, the servo type sensor that is diagnosed as described above will be described with reference to a specific circuit shown in FIG. Incidentally, in the servo type sensor shown in FIG. 1, both of the input signal inputted to the servo amplifier 7 and the output signal outputted from the servo amplifier 7 are signals of current level, but the servo type sensor shown in FIG. In this case, the detection signal output by the displacement detection unit 6 after detecting the displacement and the signal output from the power supply unit 11 and applied to the servo amplifier 7 are used as voltage level signals. That is, the servo amplifier 7 performs voltage / current conversion, and plays a role of controlling an output current flowing through the coil 4 in accordance with a voltage value input to the servo amplifier 7.

  In the circuit diagram shown in FIG. 2, the portion surrounded by the broken line indicates the servo amplifier 7 described above. The input terminal of the servo amplifier 7 has a displacement amount detection unit 6 that detects the displacement of the pendulum 1 and outputs the displacement amount as a voltage level signal, and the servo amplifier 7 for diagnosis to perform diagnosis of the servo type sensor. Is connected to a power supply unit 11 for supplying a signal having a voltage level of. On the other hand, the output of the servo amplifier 7 is connected from the coil 4 attached to the free end 1b of the pendulum 1 to the ground electrode via a resistor R1 connected in series to the coil 4.

  Specifically, the servo amplifier 7 includes an operational amplifier 7a that amplifies and outputs an input signal, a feedback resistor R2 that feeds back an output signal of the operational amplifier 7a to the negative input terminal of the operational amplifier 7a, a displacement detection unit 6, and a power supply unit. 11 and resistors R3 and R4 inserted between the negative input terminal of the operational amplifier 7a. Incidentally, the operational amplifier 7a operates as a negative feedback amplifier with its positive input terminal grounded.

  On the other hand, the resistor R1 inserted between the coil 4 and the grounding pole causes a voltage drop proportional to the current output from the servo amplifier 7. And the voltage drop which arose in this resistor R1 is given to the detection part 8 via switch S1. The detection unit 8 measures the voltage drop of the resistor R1 that varies depending on the output current of the servo amplifier 7, and the signal output from the servo amplifier 7 according to the detected voltage drop, that is, the balance of the pendulum 1 is measured. The servo amplifier 7 detects the current that flows through the coil 4 in order to correct the deviation from the point. That is, the detector 8 plays a role of detecting an external force applied to the pendulum 1, that is, an acceleration by measuring a voltage drop generated in the resistor R <b> 1. The signal detected by the detection unit 8 is given to the determination unit 12 that compares the voltage value output from the power supply unit 11 to determine whether the servo type sensor is good or bad.

  Specifically, the current output from the servo amplifier 7 increases in proportion to the voltage output from the power supply unit 11 and flows through the coil 4. Then, the magnetic flux generated in the coil 4 increases in proportion to the current flowing into the coil 4. This magnetic flux acts on the magnet 5 disposed in the vicinity of the coil 4 and appears as a driving force for moving the pendulum 1 from the equilibrium point.

  That is, the force for moving the pendulum 1 from the equilibrium point increases in proportion to the voltage output from the power supply unit 11. Therefore, the pendulum 1 is displaced from the equilibrium point in proportion to the voltage output from the power supply unit 11. Therefore, if the determination unit 12 holds in advance the voltage value output from the power supply unit 11 and the amount of displacement of the pendulum 1 corresponding to this voltage value as the determination reference of the determination unit 12, the quality of the servo sensor is determined. can do.

  Incidentally, although the details of the circuit shown in FIG. 2 will be described later, a normal acceleration detection mode, a diagnostic mode, and a resistor R1 can be obtained by switching a switch S2 of two circuits and three contacts and a switch S2, S3 and S7 of one circuit and two contacts, respectively. The inspection mode and the inspection mode of the servo amplifier 7 can be switched.

  Specifically, the switch S1 is configured such that the contacts of the two circuits are switched in conjunction with each other, the contacts C1 and C3 of one circuit are connected to a circuit connecting the coil 4 and the resistor R1, and the contact C2 is displaced. It is connected to the output of the quantity detector 6. The contacts C5 and C6 of the other circuit of the switch S1 are open (not connected), and the contact C7 is grounded. Incidentally, the switch S1 is configured such that the contact C1 and the contact C5, the contact C2 and the contact C6, the contact C3 and the contact C7 are switched in pairs. The common contact C4 (connected to any one of the contacts C1 to C3) of one circuit in the switch S1 switched in this way is provided to the detection unit 8, while the common contact C8 (contact C5) of the other circuit of the switch S1. Are connected to the output of the displacement detector 6, that is, the contact C2 of the switch S1.

  The contact C9 of the switch S2 is connected to the output of the power supply unit 11, while the contact C10 of the switch S2 is open (not connected). The common contact C11 of the switch S2 is connected to the negative input terminal of the operational amplifier 7a via the resistor R4.

  The contact C12 of the switch S3 is connected to the output terminal of the operational amplifier 7a, while the contact C13 of the switch S3 is connected to the output of the power supply unit 11. The common contact C14 of the switch S3 is connected to the coil 4.

  The contact C101 of the switch S7 is connected to the output of the displacement amount detection unit, while the contact C102 of the switch S7 is grounded. The common contact C100 of the switch S7 is connected to the negative input terminal of the operational amplifier 7a via the resistor R3.

  In the servo type sensor configured as described above, the settings of the switches S1, S2, S3, and S7 are switched for each operation mode shown below.

(1) Normal acceleration detection mode In this mode, the switch S1 is switched so that the common contact C4 and the contact C1, and the common contact C8 and the contact C5 are respectively connected. That is, the switch S1 switches so that the detection unit 8 detects the value of the voltage drop generated in the resistor R1. On the other hand, the switch S2 switches so that the common contact C11 and the contact C10 are connected. That is, the voltage of the power supply unit 11 is not applied to the negative input terminal of the operational amplifier 7a. The switch S3 switches so that the common contact C14 and the contact C12 are connected. That is, the output current of the operational amplifier 7a is given to the coil 4. The switch S7 switches so that the common contact C100 and the contact 101 are connected and the output signal of the displacement amount detection unit 6 is applied to the negative input terminal of the operational amplifier 7a via the resistor R3.

  By setting each switch in this way, the displacement detection unit 6 can detect the displacement of the pendulum 1 from the equilibrium point caused by the force applied to the pendulum 1. The displacement detected by the displacement detector 6 is given to the operational amplifier 7a via the resistor R3. The operational amplifier 7a receives this input signal, amplifies it to a predetermined level, and outputs it to the coil 4 via the switch S3. Then, the magnetic flux is generated in the coil 4 by the current output from the operational amplifier 7a. This magnetic flux appears as an electromagnetic force with the magnet 5. Then, the pendulum 1 tries to return to the original equilibrium point by the generated electromagnetic force. At this time, the current output from the operational amplifier 7a, that is, the current flowing through the coil 4, appears as a voltage drop across the resistor R1. This voltage drop is proportional to the magnitude of the current flowing to move the pendulum 1 to its original equilibrium point. That is, as the acceleration applied to the pendulum 1 increases, the pendulum 1 tends to be displaced from the equilibrium point, so that the current output from the operational amplifier 7a increases and the voltage drop generated in the resistor R1 increases. The detection unit 8 can obtain the acceleration received by the pendulum 1 by detecting the voltage value across the resistor R1.

(2) Diagnostic mode Even in the normal acceleration detection mode described above, for example, if it is ensured that no external force is applied to the pendulum 1, a predetermined voltage is applied from the power supply unit 11 to the servo amplifier 7 in this state. By detecting the voltage drop across the resistor R1, it is possible to detect the presence or absence of an abnormality in the servo sensor. However, in the normal acceleration detection mode, since the change in the current flowing through the coil 4 is small, the servo type sensor according to the present invention is provided with a diagnosis mode in order to more reliably determine the quality of the servo type sensor.

  Specifically, the diagnosis mode is switched so that the common contact C4 and the contact C2 and the common contact C8 and the contact C6 of the switch S1 are respectively connected. That is, the switch S <b> 1 switches so that the detection unit 8 detects the voltage value output from the displacement amount detection unit 6. On the other hand, the switch S2 switches so that the common contact C11 and the contact C9 are connected. That is, the voltage output from the power supply unit 11 is applied to the negative input terminal of the operational amplifier 7a. The switch S3 switches so that the common contact C14 and the contact C12 are connected. That is, the output current of the operational amplifier 7a is given to the coil 4. The switch S7 switches so that the common contact C100 and the contact 102 are connected and grounded. That is, the displacement amount detection unit 6 and the servo amplifier 7 are disconnected from each other so that the displacement amount detection signal output from the displacement amount detection unit 6 is not given to the servo amplifier 7.

  After setting each switch in this way, a voltage is applied from the power supply unit 11 to the negative input terminal of the operational amplifier 7a via the switch S2 and the resistor R4. Then, the operational amplifier 7 a outputs a current proportional to the voltage applied to the negative input terminal from the output terminal of the operational amplifier 7 a and gives it to the coil 4. The coil 4 generates magnetic flux by the current supplied from the operational amplifier 7a. Then, an electromagnetic force is generated between the coil 4 and the magnet 5. Due to this electromagnetic force, the pendulum 1 moves from the equilibrium point and stops when the electromagnetic force balances with the weight of the pendulum and the restoring force of the spring 2. At this time, the displacement amount detection unit 6 outputs the displacement amount of the pendulum 1 displaced from the original equilibrium point as a detection signal. This detection signal, that is, the displacement amount, can be detected by the detection unit 8 via the switch S1.

  In the diagnostic mode, as described above, the switch S7 is switched so that the signal output from the displacement detection unit 6 is not applied to the servo amplifier 7, so that the power supply unit 11 is proportional to the magnitude of the voltage applied to the operational amplifier 7a. As a result, the displacement amount of the pendulum 1 changes. At this time, the correspondence between the voltage output from the power supply unit 11 and the detection signal output from the displacement detection unit 6 at that time may be stored in the determination unit 12 in advance as a reference value. When the level of the detection signal detected by the displacement amount detection unit 6 becomes a value different from the reference value stored in the determination unit 12, it can be determined that there is an abnormality in the servo sensor.

  Incidentally, in this diagnostic mode, as described above, the switch S7 is switched so that the signal output from the displacement detector 6 is not given to the servo amplifier 7. Therefore, the displacement detected by the displacement detector 6 The voltage drop value generated at both ends of the resistor R1 detected by the detector 8 via the contacts C2 and C4 of the switch S1 without being affected by the current can be increased. For this reason, it is possible to improve detection accuracy.

  Thus, as described above, the displacement amount of the pendulum 1 when the power supply unit 11 applies the test voltage to the operational amplifier 7a is detected as the displacement of the displacement amount detection unit 6, and the test voltage stored in the determination unit 12 in advance is detected. By using the relationship with the displacement amount, the quality of the servo type sensor can be determined. Specifically, since the pendulum 1 is actually displaced in addition to the operational amplifier 7a, the deterioration of the coil 4, and the abnormality of the displacement detection unit 6, the spring that locks the pendulum 1 will be described in detail later. 2. Sensitivity deterioration of the displacement amount detection unit 6 and deterioration of the magnet 5 can also be detected.

(3) Inspection mode of resistor R1 By the way, in the normal acceleration detection mode, the change in the current flowing through the coil 4 is small, and therefore the voltage drop generated across the resistor R1 is also small. Therefore, the servo-type sensor according to the present invention has an inspection mode of the resistor R1 that more reliably checks the quality of the resistor R1. The switch S7 switches so that the common contact C100 and the contact 101 are connected and the output signal of the displacement amount detection unit 6 is applied to the negative input terminal of the operational amplifier 7a via the resistor R3.

  Specifically, the switch S1 switches so that the common contact C4 and the contact C3, and the common contact C8 and the contact C7 are connected. By switching the switch S1 in this way, the detection unit 8 can detect the value of the voltage drop generated in the resistor R1. The output of the displacement detector 6 is grounded so that it does not become an input signal of the operational amplifier 7a. On the other hand, the switch S2 switches so that the common contact C11 and the contact C9 are connected. That is, the voltage of the power supply unit 11 is applied to the negative input terminal of the operational amplifier 7a. The switch S3 switches so that the common contact C14 and the contact C12 are connected. When the switch S3 is thus switched, the output current of the operational amplifier 7a is supplied to the coil 4.

  By setting each switch in this way, the signal output from the displacement detector 6 is not given to the operational amplifier 7a. That is, the input to the operational amplifier 7 a is only the output voltage of the power supply unit 11. Therefore, a current proportional to the output voltage of the power supply unit 11 is output from the operational amplifier 7a and flows through the coil 4 and the resistor R1. At this time, the voltage drop generated in the resistor R1 can be detected by the detector 8. Then, the relationship between the voltage value output from the power supply unit 11 and the value of the voltage drop generated in the resistor R1 is held in the determination unit 12 in advance as a reference value. Thus, when the relationship between the voltage value output from the power supply unit 11 and the voltage drop generated in the resistor R1 is different from the reference value held in the determination unit 12, it can be determined that the resistor R1 is abnormal. .

  Incidentally, the output of the displacement detector 6 is grounded so as not to be given to the negative input terminal of the operational amplifier 7a. For this reason, the determination unit 12 compares the reference value previously stored in the determination unit 12 without being affected by the output signal (disturbance) of the displacement amount detection unit 6, so that the deterioration of the resistor R1 can be detected with high sensitivity. it can.

(4) Inspection mode of servo amplifier 7 In this mode, the switch S1 switches so that the common contact C4 and the contact C3, and the common contact C8 and the contact C7 are connected. That is, the switch S1 is switched so that the detection unit 8 detects the value of the voltage drop generated in the resistor R1, and the output of the displacement detection unit 6 is grounded. The switch S2 switches so that the common contact C11 and the contact C9 are connected, and applies the voltage of the power supply unit 11 to the negative input terminal of the operational amplifier 7a. The switch S3 switches so that the common contact C14 and the contact C12 are connected, and gives the output current of the operational amplifier 7a of the servo amplifier 7 to the coil 4. The switch S7 switches so that the common contact C100 and the contact 101 are connected and the output signal of the displacement amount detection unit 6 is applied to the negative input terminal of the operational amplifier 7a via the resistor R3.

  After setting each switch in this way, the power supply unit 11 applies a predetermined voltage to the negative input terminal of the operational amplifier 7a. And the determination part 12 hold | maintains the value [V1] of the voltage drop which arose in resistor R1 which the detection part 8 detected at this time.

  Next, the switches S1 and S2 are left as they are. On the other hand, the switch S3 switches so that the common contact C14 and the contact C13 are connected. That is, the switch S3 switches so that the output current of the power supply unit 11 is supplied to the coil 4. After setting each switch in this way, the power supply unit 11 applies a predetermined voltage to the negative input terminal of the operational amplifier 7a. At this time, the determination unit 12 holds the value [V2] of the voltage drop generated in the resistor R1 detected by the detection unit 8. Then, the determination unit calculates [V1 ÷ V2] to obtain the amplification degree of the servo amplifier 7. Next, the determination unit 12 compares the amplification degree of the servo amplifier 7 held in advance with the amplification degree of the servo amplifier 7 obtained as described above. When they are different, it is determined that the servo amplifier 7 has an abnormality.

  The above-described inspection method is exemplified by applying the output voltage of the power supply unit 11 to the negative input terminal of the operational amplifier 7a. For example, as shown in FIG. 4, the ground connected to the positive input terminal of the operational amplifier 7a is connected. Instead of this, a switch S4 for applying a voltage output from the power supply unit 11 to the positive input terminal may be provided. Incidentally, FIG. 4 shows only the servo amplifier 7, the displacement detection unit 6 and the power supply unit 11 of FIG. 3 described above, and other components are omitted.

  In this case, the polarity of the voltage output from the power supply unit 11 is calculated and amplified in the operational amplifier 7a by setting the polarity opposite to the voltage output from the power supply unit 11 during the above-described inspection method. This is equivalent to applying the output voltage of the power supply unit 11 to the negative input terminal of the operational amplifier 7a. Therefore, the current output from the servo amplifier 7 changes according to the voltage value output from the power supply unit 11. For this reason, if the detection unit 8 detects the value of the voltage drop generated across the resistor R1 as described above and the determination unit 12 determines, the quality of the servo sensor can be determined.

  Alternatively, in addition to the inspection method described above, the inspection may be performed by adding the output of the power supply unit to the input of the displacement amount detection unit 6. For example, FIG. 5 shows a more detailed circuit configuration of the displacement amount detection unit 6 described above. As shown in this figure, the displacement detection unit 6 is provided with a photodiode 40 that receives light emitted from a light emitting unit (not shown in FIG. 5) and converts it into an electrical signal. The photodiode 40 is connected to the power source on the cathode side, and the anode side is grounded via a current limiting resistor R5 that limits a current flowing through the photodiode 40.

  The current flowing through the photodiode 40 changes according to the level of light received by the photodiode 40. Therefore, the voltage drop level of the current limiting resistor R5 varies depending on the light receiving level of the photodiode 40. In order to amplify and detect this voltage change, the negative input terminal of the operational amplifier 6a is connected to the connection point between the anode of the photodiode 40 and the current limiting resistor R5 via the resistor R6. The operational amplifier 6a grounds the positive input terminal of the operational amplifier 6a and connects the output terminal and the negative input terminal of the operational amplifier 6a via the feedback resistor R7 to generate the current limiting resistor R5 with a predetermined amplification factor. Amplifies the voltage value of the voltage drop. The output of the operational amplifier 6a is given as an input signal of the servo amplifier 7 at the next stage. That is, the operational amplifier 6a operates as a negative feedback amplifier.

  In the displacement amount detection unit 6 configured as described above, a voltage having a polarity opposite to the voltage drop generated in the current limiting resistor R5 is applied from the power supply unit 11 to the negative input terminal of the operational amplifier 6a via the switch S5 and the resistor R8. To do. Then, the voltage value of the negative input terminal of the operational amplifier 6a of the displacement amount detection unit 6 decreases. By doing so, the current flowing through the photodiode 40 is reduced, which is equivalent to a reduction in the voltage across the current limiting resistor R5. That is, the operational amplifier 6a gives the amplified signal to the servo amplifier 7 at the next stage so as to position the pendulum 1 at the original equilibrium point.

  At this time, the current output from the servo amplifier 7 changes according to the voltage value output from the power supply unit 11. Therefore, if the detection unit 8 detects the value of the voltage drop that occurs across the resistor R1 as described above and the determination unit 12 determines, the quality of the servo sensor can be determined.

  Alternatively, in addition to the above-described method, the switch S6 is applied to the positive input terminal so that the voltage output from the power supply unit 11 is applied instead of the ground to which the positive input terminal of the operational amplifier 6a is connected as shown in FIG. It may be provided. Incidentally, circuit elements having the same reference numerals as those in FIG. 5 have the same role as the above-described functions.

  In this case, the polarity of the voltage output from the power supply unit 11 is set to the same polarity as the voltage drop generated in the current limiting resistor R5. Then, it is equivalent to applying a voltage having a polarity opposite to that of the current limiting resistor R5 to the negative input terminal of the operational amplifier 6a as described above after being amplified in the operational amplifier 6a. Therefore, since the current output from the servo amplifier 7 changes according to the voltage value output from the power supply unit 11, the detection unit 8 detects the value of the voltage drop that occurs across the resistor R1, as described above. If the determination unit 12 determines the detection value, it is possible to determine whether the servo type sensor is good or bad.

  Thus, as described above, the servo-type sensor according to the present invention controls the servo amplifier 7 to adjust the current flowing through the coil 4 attached to the free end 1b of the pendulum 1. Then, after the pendulum 1 is positioned at a predetermined equilibrium point by the magnetic force generated in the coil 4 and the electromagnetic force generated between the free end 1b and the magnet 5 provided with a predetermined gap, the servo amplifier is further moved. The current flowing from 7 to the coil 4 is varied. For this reason, the pendulum 1 is displaced according to the magnitude of the current flowing into the coil 4. Since the displacement amount of the pendulum 1 changes in accordance with the current value flowing into the coil 4, if the determination unit 12 holds the displacement amount of the pendulum 1 with respect to the current flowing into the coil 4 as a reference value in advance, the servo sensor Can be determined.

  Further, since the servo type sensor according to the present invention is diagnosed by displacing the pendulum 1, the details will be described later. In addition to the deterioration of the servo amplifier 7, the coil 4, the abnormality of the displacement detection unit 6, It is also possible to detect deterioration of the spring 2 that is locked, deterioration of the detection sensitivity of the displacement amount detection unit 6, deterioration of the magnet 5, and the like.

In the above-described embodiment, a coil is provided at the free end 1b of the pendulum 1 and a servo sensor using an electromagnetic force generated between the pendulum 1 and the magnet 5 disposed in the vicinity thereof. For example, as shown in FIG. 3, it may be a servo type sensor driven by an electrostatic force acting between the plates of the capacitor C. This embodiment differs from the above-described embodiment in that a pole plate is provided at the free end 1b of the pendulum 1 instead of the coil 4, and a different gap is provided between the pole plate and the pole plate with a predetermined gap. The capacitor C is formed by facing the electrode plates. The servo-type sensor taking such a form is suitable as a sensor applied to, for example, a micromachine. In this case, the output of the operational amplifier 7a of the servo amplifier 7 is connected to the electrode plate on the free end 1b side of the pendulum 1, and the other electrode plate is grounded. That is, this servo type sensor drives the pendulum 1 using the electrostatic force generated between the plates of the capacitor C by the voltage output from the operational amplifier 7a.

  Even in the servo-type sensor configured as described above, the pendulum 1 is displaced from a predetermined equilibrium point by applying the voltage of the power supply unit 11 as an input of the operational amplifier 7a as in the above-described embodiment. The displacement amount detection unit 6 detects the displacement amount, and the determination unit 12 may determine whether the detected displacement amount is a value corresponding to the voltage value output from the power supply unit 11.

  In the servo type sensor using the driving force generated in the capacitor C, the change of the driving signal becomes large, so that R1 can be inspected using the normal acceleration detection mode. Therefore, the circuit can be simplified without using the R1 inspection mode.

  Thus, the servo type sensor according to the present invention can be applied regardless of the driving means of the pendulum 1. Further, since a separate driving means for diagnosis such as a diagnostic coil is not required, it is suitable for a servo-type sensor applied to a micro device such as a micromachine.

  In the servo-type sensor described above, the displacement amount detection unit 6 includes a light emitting unit such as a light emitting diode having a constant luminance, and a light receiving unit such as a photodiode that receives light emitted from the light emitting unit and converts it into an electrical signal. When the pendulum is located at a predetermined equilibrium point, the light receiving unit receives a maximum amount of light received, and a slit is provided that reduces the amount of light received by the light receiving unit as the pendulum moves from the equilibrium point. The optical method is illustrated. In this case, it is preferable that the pendulum 1 is used for a servo-type sensor having a large shape because assembly adjustment is easy.

  Of course, the amount of displacement of the pendulum 1 may be detected using other detection components without using this optical method. Specifically, as shown in FIG. 7, the detection component includes a piezo element 50 that detects a stress applied to a spring 2 (plate spring) that locks the base end portion 1a of the pendulum 1 to the substrate 3 from a change in resistance value. Use it. Then, the displacement amount of the spring 2, that is, the change in the resistance value of the piezo element 50 may be detected by a displacement amount detection unit (not shown in FIG. 7), and a detection signal may be output as a signal indicating the displacement amount. If this piezo element 50 is used as a detection element, a servo type sensor suitable for a micromachine can be constructed, which is effective.

  Alternatively, as shown in FIG. 8, a position detection magnet 20 attached to a predetermined position of the pendulum 1 and a position detection magnet 20 provided near the position detection magnet 20 so as to face the position detection magnet 20. A Hall element 21 whose resistance value changes due to a change in the magnetic force of the magnet 20, and a displacement amount detection circuit 22 that detects a change in the resistance value of the Hall element 21, that is, a displacement amount where the pendulum 1 is displaced from a predetermined equilibrium point. It is good also as the displacement amount detection part 6 provided and comprised. In this case, the Hall element 21 can also be configured using the driving magnet 5, and the servo type sensor according to the present invention can be configured more simply.

  Alternatively, as shown in FIG. 9, a sound generator 23 that generates a sound wave (for example, an ultrasonic wave) having a predetermined frequency, and a sound wave generated by the sound generator 23 that is positioned with a predetermined gap from the pendulum 1 are applied to the pendulum 1. Output from the speaker 24, a microphone 25 that receives the sound wave output from the speaker 24 and reflected by the pendulum 1, an acoustic input unit 26 that amplifies the sound wave received by the microphone 25, and an output from the sound generation unit 23 Displacement amount of the sound wave detection system configured to include a control calculation unit 27 that controls the sound wave to be output and detects the displacement amount from the equilibrium point of the pendulum 1 from the time delay of the sound wave output from the speaker 24 and received by the microphone 25 The detection unit 6 may be used.

  Alternatively, as shown in FIG. 10, a metal plate 28 or the like attached at a predetermined position of the pendulum 1, an inductance L provided so as to face the vicinity of the metal plate 28, and the inductance L are connected in parallel. The displacement detection unit 6 may be a high-frequency proximity circuit including an oscillator 29 including a capacitor C that forms a resonance circuit (tank circuit). The tank circuit of the displacement detection unit 6 changes its Q value when the gap between the metal plate 28 attached to the pendulum 1 and the inductance L changes. The change in the Q value is detected by the next-stage detector 30 as a change in the amplitude of the oscillator 29. The detection signal (analog signal) of the detector 30 is converted into a digital signal by the A / D converter 31, and the displacement of the pendulum 1 deviating from the equilibrium point is detected by the signal processing calculation unit 32 in the next stage. Configured as

  Alternatively, as shown in FIG. 11, a metal plate 33 attached to a predetermined position of the pendulum 1 and another metal plate 34 is provided in the vicinity of the metal plate 33 so as to face the metal plate 33 on the substrate 3, for example. Thus, the capacitor Cx is formed by the metal plates 33 and 34. A displacement change detecting circuit 35 is provided for detecting the displacement of the pendulum 1 between the metal plates 33 and 34 (between electrode plates), that is, a change in the capacitance of the capacitor Cx. The displacement amount detection unit 6 configured to output the displacement amount of the pendulum 1 displaced from the equilibrium point as a detection signal of the capacitance change detection circuit 35 may be used. If the displacement of the pendulum 1 is detected from the change in the capacitance of the capacitor Cx as described above, it is preferable that the servo type sensor described above can be configured in a micromachine as described later.

  In addition, in the servo-type sensor according to the present invention, the displacement amount detection unit 6 is not limited to the above-described detection method as long as it can detect that the pendulum 1 is displaced from a predetermined equilibrium point.

  Further, the servo type sensor described above has been described on the assumption that gravity is applied downward to the sensor as shown in FIG. 1. However, even if the sensor is installed at an angle with respect to the direction of gravity, the output is used for diagnosis. On the other hand, if the output value of the servo type sensor in the normal mode is small and within the range of detection accuracy, it is possible to diagnose the servo type sensor as described above. Specifically, in a servo-type sensor that is basically installed with respect to the direction of gravity, when the servo-type sensor is installed at an angle of θ with respect to the direction of gravity, 980 sin θ [Gal (Cm / s2)] acceleration (gravity) occurs, but if this value is used as an initial value for diagnosis when this value is measured in the installed state, the above-described diagnostic method is applied. Thus, it is possible to diagnose the soundness of the servo-type sensor. That is, the servo type sensor of the present invention can diagnose the soundness of the servo type sensor without being limited by the installation state (posture).

  Of course, when a servo type sensor is used for an earthquake sensor or the like, it is generally required that the servo type sensor be installed at a horizontal position (within ± 3 degrees) perpendicular to the direction of gravity. In this case, it is also possible to determine that the sensor is not correctly installed at the horizontal position by the detection signal (displacement output signal from the equilibrium point) output from the servo type sensor without using the above-described diagnostic method. It is.

  The present invention is not limited to the embodiment described above. For example, in a three-axis micromachining sensor applied to a micromachine, as shown in FIG. 13, two disk-shaped conductor plates having a predetermined area are arranged so as to face each other, and the outer periphery thereof is placed on a casing or the like (not shown). Fixed electrodes 70 and 74 that are fixed, and a movable electrode (diaphragm) 71 that is a disc-shaped conductor plate that is disposed so as to be sandwiched between these fixed electrodes 70 and 74 and has an outer periphery fixed to a housing or the like (not shown). It is configured with. As will be described in detail later, the movable electrode 71 has a weight 72 attached to the lower surface of the center thereof, and is bent by receiving an external force applied to the weight 72. Further, by applying a voltage between the movable electrode 71 and the fixed electrodes 70 and 74, the movable electrode 71 can be bent using an electrostatic force acting between these electrodes, and can be positioned at an arbitrary part. ing.

  Incidentally, in this figure, the lower direction of the paper is drawn in the direction of gravity, and each electrode 70, 71, 74 is drawn so as to be orthogonal to this direction of gravity. It is possible to take an attachment mode.

  Here, as indicated by a broken line in FIG. 13, the x-axis in the horizontal direction perpendicular to the gravity direction from the center O of the movable electrode 71 is the y-axis, and the horizontal direction perpendicular to the x-axis and passing through the center O is the y-axis. Let us consider an orthogonal coordinate consisting of a z-axis penetrating through x and an x-axis and a y-axis and parallel to the direction of gravity. Then, the surfaces of the fixed electrodes 70 and 74 and the movable electrode 71 are separated from each other in the z-axis direction, and the electrode surfaces are coaxially arranged in a direction orthogonal to the z-axis, that is, in the horizontal direction. Incidentally, the orthogonal coordinates are positioned so that the central portion of the arc on the outer periphery of the movable electrode 71 divided into four and the axis of the x axis or the y axis coincide.

  The movable electrode 71 is formed with three electrode portions that are concentrically divided by an insulator 73 around the z-axis passing through the movable electrode 71. These three electrode portions are composed of a circular inner electrode 71a, an annular middle electrode 71b, and an outermost annular outer electrode 71c from the center O of the movable electrode 71 toward the radial direction. These electrodes 71a, 71b, 71c are electrically insulated by an insulator 73.

  The outer electrode 71 c located on the outermost side of the movable electrode 71 further forms four conductor portions divided into four by an insulator 73 in the radial direction of the movable electrode 71. Four capacitors formed by the outer electrode 71c of the movable electrode 71 divided into four parts and the disk-shaped upper fixed electrode 70 located above the movable electrode 71 are defined as follows.

  A capacitor formed by an outer electrode 71c of the movable electrode 71 divided into four divided in the positive direction of the x-axis and an outer electrode 71c of the upper fixed electrode 70 described later is [Cxp], and 4 is positioned in the negative direction of the x-axis. The capacitor formed by the outer electrode 71c and the fixed electrode 70 of the divided movable electrode 71 is [Cxm], and the outer electrode 71c and the fixed electrode 70 of the four-divided movable electrode 71 positioned in the positive direction of the y-axis are used. The capacitor formed is [Cyp], and the capacitor formed by the outer electrode 71c of the movable electrode 71 divided into four and positioned in the negative direction of the y-axis and the fixed electrode 70 is [Cym].

  A capacitor formed by the inner fixed electrode 70 facing the inner electrode 71a of the movable electrode 71 is represented by [Cz]. A weight 72 having a predetermined weight is fixed to the inner electrode 71a of the movable electrode 71.

  On the other hand, the disc-shaped upper fixed electrode 70 positioned above the movable electrode 71 is formed with three electrode portions that are concentrically divided by an insulator 73 around the z-axis passing through the upper fixed electrode 70. ing. The three electrode portions are formed from a circular inner electrode 70a, an annular middle electrode 70b, and an outermost annular outer electrode 70c from the z axis passing through the center of the upper fixed electrode 70 toward the radial direction. Become. These electrodes 70a, 70b, and 70c are electrically insulated from each other by an insulator 73.

  Among these, the inner electrode 70a forms a capacitor with the inner electrode 71a of the movable electrode 71 facing the inner electrode 70a. Incidentally, this capacitor is [Cz] as described above. The outermost outer electrode 70c of the upper fixed electrode 70 is opposed to the outermost electrode of the movable electrode 71 divided into four to form four capacitors. These four capacitors are [Cxp, Cxm, Cyp, Cym] as described above.

  The capacitances of these capacitors [Cz, Cxp, Cxm, Cyp, Cym] are measured by a capacitance detection unit (not shown). Although details will be described later, the external force applied to the weight 72, that is, the acceleration applied to the weight 72 is detected by detecting the amount of change in the capacitance of these capacitors by the capacitance detection unit.

  The annular middle electrode 70b sandwiched between the inner electrode 70a and the outer electrode 70c of the upper fixed electrode 70 is further divided into four in the radial direction by the insulator 73, and the central portion of each arc is the x axis, Or it is divided so as to coincide with the axis of the y-axis.

  Here, four capacitors formed by the middle electrode 70b divided into four parts and the middle electrode 71b facing the movable electrode 71 are defined as follows. [Cxpv1] is a capacitor formed by the middle electrode 71b divided into four in the positive direction of the x axis and the middle electrode 71b of the movable electrode 71 facing the four divided middle electrodes 70b in the negative direction of the x axis. A capacitor formed by the middle electrode 71b of the movable electrode 71 facing the middle electrode 70b is [Cxmv1], and the inside of the movable electrode 71 facing the four-divided middle electrode 70b positioned in the positive direction of the y-axis. The capacitor formed by the side electrode 71b is [Cypv1], and the capacitor formed by the middle electrode 71b divided into four in the negative y-axis direction and the middle electrode 71b facing the movable electrode 71 is [Cymv1]. ].

  The four capacitors formed by the middle electrode 70b of the upper divided fixed electrode 70 divided into four and the middle electrode 71b of the movable electrode 71 facing each other are electrostatic charges generated when a DC voltage is applied by a DC power source (not shown). It plays the role of the electrode drive part which attracts the movable electrode 71 to the upper fixed electrode 70 side by the attractive force.

  On the other hand, the disc-shaped lower fixed electrode 74 positioned below the movable electrode 71 has three electrode portions that are concentrically divided by an insulator 73 around the z-axis passing through the lower fixed electrode 74. Is formed. The three electrode portions are formed by forming a circular inner electrode 74a, an annular middle electrode 74b, and an outermost annular outer electrode 74c from the z axis passing through the center of the lower fixed electrode 74 in the radial direction. Consists of. These electrodes 74a, 74b, and 74c are electrically insulated by an insulator 73, respectively.

  Among these, the annular middle electrode 74b sandwiched between the innermost inner electrode 74a and the outermost outer electrode 74c is further divided into four in the radial direction by the insulator 73, and the central portion of each arc is formed. It is divided so as to coincide with the axis of the x axis or the y axis.

  Here, four capacitors formed by the middle electrode 74b of the lower fixed electrode divided into four parts and the middle electrode 71b of the movable electrode 71 facing each other are defined as follows. [Cxpv2] is a capacitor formed by four middle electrodes 74b divided in the positive direction of the x-axis and the middle electrode 71b facing the movable electrode 71, and divided into four in the negative direction of the x-axis. A capacitor formed by the middle electrode 71b of the movable electrode 71 facing the middle electrode 74b is [Cxmv2], and the inside of the movable electrode 71 facing the four-divided middle electrode 74b positioned in the positive direction of the y-axis. [Cypv2] is a capacitor formed with the side electrode 71b, and [Cymv2] is a capacitor formed with the middle electrode 71b that is divided into four in the negative direction of the y-axis and the movable electrode 71 that is opposed to the movable electrode 71. ].

  The four capacitors formed by the middle electrode 74b of the lower fixed electrode 74 divided into four and the middle electrode 71b of the movable electrode 71 facing each other are static generated when a DC voltage is applied by a DC power source (not shown). It plays the role of the electrode drive part which attracts the movable electrode 71 to the lower fixed electrode 74 side by the electrosuction force.

  In the three-axis micromachining sensor configured as described above, it is assumed that the device to which the sensor is attached moves in the positive direction of the x axis. Then, acceleration is applied to the weight 72 attached to the sensor in the negative direction of the x-axis. At this time, the movable electrode 71 receives the acceleration applied to the weight 72 and bends as shown in FIG. 15A, for example, so that the distance between the electrode located on the negative side of the x-axis and the upper fixed electrode 70 is shortened. On the other hand, the distance between the movable electrode 71 located on the positive side of the X axis and the upper fixed electrode 70 is increased. For this reason, among the capacitors formed between the movable electrode 71 and the upper fixed electrode 70, the capacitance of the capacitor [Cxm] located in the negative x-axis direction is increased while being located in the positive x-axis direction. The capacitance of the capacitor [Cxp] decreases.

  On the other hand, the average distance between the movable electrode 71 divided into four in the positive and negative directions of the y-axis and the upper fixed electrode 70, that is, between the electrode plates of the middle electrode 71 b and the upper fixed electrode 70 of the movable electrode 71. The average distance does not change. Accordingly, the capacitances of the capacitors [Cyp], [Cym], and [Cz] formed in the y-axis direction and the z-axis direction do not change. A capacitor [Cxpv1] formed between the middle electrode 71b of the movable electrode 71 and the middle electrode 70b of the upper fixed electrode 70 located in the positive direction of the x axis, and the middle electrode 71b of the movable electrode 71, A DC voltage is applied to each of the capacitors [Cxmv2] formed between the lower fixed electrode 74 and the middle electrode 74b positioned in the negative direction of the x axis. Then, an electrostatic attractive force is generated between the capacitors [Cxpv1, Cxmv2] and the fixed electrodes 70, 74, and no external force (acceleration) is applied to the weight 72, that is, as shown in FIG. To the horizontal equilibrium point.

  At this time, the voltage applied to the capacitors [Cxpv1, Cxmv2] by the electrode driving unit is the capacitance of the capacitor changed by the external force (acceleration) being applied to the weight 72, that is, the capacitor located in the negative direction of the x axis [ Cxm] and the capacitances of the capacitors [Cxp] located in the positive direction of the x-axis may be controlled so as to be the capacitances in the original equilibrium state. Incidentally, the three-axis micromachining sensor detects the acceleration applied in the negative direction of the x-axis by the voltage value applied to the capacitors [Cxpv1, Cxmv2] at this time.

  Next, when acceleration is applied in the negative direction of the z axis in the triaxial micromachining sensor, the weight 72 receives an external force (acceleration) in the positive direction of the z axis. Therefore, the central portion of the movable electrode 71 is bent upward as shown in FIG. 15B, and the electrode plate distance between the movable electrode 71 and the upper fixed electrode 70 is shortened. The amount of change in the electrode plate distance at this time is greatest for the innermost inner electrode 71 a of the movable electrode 71. Therefore, in the capacitor formed between the movable electrode 71 and the upper fixed electrode 70, the electrostatic capacitance of the capacitor [Cz] formed between the inner electrode 71 a of the movable electrode 71 and the inner electrode 70 a of the fixed electrode 70. The amount of change in capacity is the largest.

  Further, the electrode plate distances of the four capacitors [Cxp, Cxm, Cyp, Cym] formed between the outer electrode 71c outside the movable electrode 71 and the electrode 70c outside the upper fixed electrode 70 are in the z-axis direction. Although the displacement changes, the average distance between the plates of the outer electrode 71c and the upper fixed electrode 70 in each capacitor changes equally and becomes shorter. For this reason, the capacitance in the capacitors [Cxp, Cxm, Cyp, Cym] formed by the electrode plates arranged in the x-axis direction and the y-axis direction of the movable electrode 71 changes equally.

  At this time, the electrode driver (not shown) is connected to four capacitors [Cxpv2, Cxmv2, Cypv2, Cymv2] formed between the middle electrode 74b of the lower electrode 74 and the middle electrode 71b of the variable electrode 71. By applying an equal voltage to each other and applying an electrostatic attraction force that cancels the external force (acceleration) applied to the weight 72, the movable electrode 71 is positioned at a predetermined equilibrium point. At this time, the voltage applied to the four capacitors [Cxpv2, Cxmv2, Cypv2, Cymv2] is set to a voltage that only cancels the displacement amount in the z-axis direction that has been changed by applying an external force (acceleration) to the weight 72. Specifically, this voltage is the capacitance of each of the four capacitors [Cxp, Cxm, Cyp, Cym] formed between the outer electrode 71 c outside the movable electrode 71 and the electrode 70 c outside the upper fixed electrode 70. However, what is necessary is just to control so that the movable electrode 71 may become the electrostatic capacitance when it was in the original equilibrium state. At this time, the acceleration applied in the positive direction of the z-axis can be detected based on the voltage values applied to the capacitors [Cxpv2, Cxmv2, Cypv2, Cymv2] by the electrode driver.

  As described above, the three-axis micromachining sensor uses the displacement amount of the movable electrode 71 displaced by the external force (acceleration) applied to the weight 72 as the capacitance of the capacitor formed between the movable electrode 71 and the upper fixed electrode 70. While detecting the change, the acceleration can be detected by a voltage value that provides an electrostatic attraction force between the fixed electrodes 70 and 74 and the movable electrode 73 to cancel out the displacement.

  Even in the three-axis micromachining sensor based on such an operation principle, a predetermined force is applied to the weight 72 to cause the movable electrode 71 to bend, and the capacitance between the fixed electrodes 70 and 74 is displaced. If comprised in this way, it is possible to detect abnormality of a sensor similarly to embodiment mentioned above. For example, a capacitor [Cxpv1] formed between the middle electrode 70b of the upper fixed electrode 70 and the middle electrode 71b of the movable electrode 71 after the weight 72 fixed to the movable electrode 71 is positioned at a predetermined equilibrium point. , Cxmv1, Cypv1, Cymv1], or any capacitor [Cxpv2, Cxmv2, Cypv2, Cymv2] formed between the middle electrode 74 of the lower fixed electrode 74 and the middle electrode 71b of the movable electrode 71 Apply voltage to. At this time, the electrostatic attractive force between the capacitors to which the voltage is applied increases. This electrostatic attraction force changes by changing the voltage applied to the capacitor. For this reason, the weight 72 is displaced from a predetermined position (equilibrium point). Therefore, this displacement amount is used to change the capacitance of the four capacitors [Cxp, Cxm, Cyp, Cym] formed between the outer electrode 71 c outside the movable electrode 71 and the electrode 70 c outside the upper fixed electrode 70. The capacitance detection unit detects the amount, and the determination unit 12 may determine whether the detected change amount of the capacitance is a change amount corresponding to the voltage value applied to the capacitor. .

  Next, detection means for detecting deterioration of components constituting the servo sensor according to the present invention will be described.

  An optical method including a light-emitting unit composed of a light source such as a light-emitting diode (LED) having a predetermined luminance and a light-receiving unit such as a phototransistor that receives light emitted from the light-emitting unit and converts it into an electrical signal is used. In order to confirm the soundness of the optical system formed by the light emitting unit and the light receiving unit in the displacement amount detecting unit 6, for example, when the current flowing through the LED is changed, the change in the amount of light emitted by the variable LED is changed by the light receiving unit. What is necessary is just to make it detectable. More specifically, a plurality of current values to be passed through the LEDs can be set, and at that time, the level of the electric signal received by the light receiving unit and converted into an electric signal is held in advance. Then, in order to confirm the soundness of the light receiving system, a current to be supplied to the light source of the light emitting unit is set based on a preset setting value. At this time, the level of the electrical signal received by the light receiving unit and converted into an electrical signal is compared with the level held in advance, and if it is within a predetermined allowable range, it can be determined that the optical system is healthy. .

  Next, as described above, a metal plate 33 attached to a predetermined position of the pendulum 1 shown in FIG. 11 and another metal plate 34 attached to the vicinity of the metal plate 33 so as to face the metal plate 33, respectively. A method of inspecting the sensitivity of the displacement detection unit 6 that detects the displacement of the pendulum 1 from the capacitance change of the capacitor Cx formed with the metal plates 33 and 34 is described. To do.

  As shown in FIG. 12, in the displacement amount detection unit 6, one end of the capacitor Cx is grounded, and the other end receives a pulse signal (for example, a rectangular wave) output from the pulse signal generation unit 60 via the resistor R. It is done. Then, the output voltage of the integrating circuit formed by the resistor R and the capacitor Cx is shaped through a low-pass filter (LPF) 61 and supplied to the servo amplifier 7. That is, the displacement detection unit 6 outputs a change in the capacitance of the capacitor Cx as a change in voltage.

  In the displacement amount detection unit 6 configured in this way, the signal waveform output from the pulse signal generation unit 60 is detected by the detection unit 8 when, for example, its output voltage value, frequency, duty, etc. are varied. The signal is held in the determination unit 12 in advance. When the displacement amount detection unit 6 is inspected, it is possible to detect sensitivity deterioration of the displacement amount detection unit 6 by comparing with a detection signal held in advance by the determination unit 12.

  Next, as shown in FIG. 8, a position detection magnet 20 attached to a predetermined position of the pendulum 1 and a position detection magnet 20 provided near the position detection magnet 20 so as to face the position detection magnet 20. A Hall element 21 that detects a change in the magnetic force of the magnet 20 and changes its resistance value, and a displacement amount detection that detects a change in the resistance value of the Hall element 21, that is, a displacement amount that the pendulum 1 is displaced from a predetermined equilibrium point. A method for detecting the displacement amount detection unit 6 constituted by the circuit 22 will be described.

  In this case, the output value changes in proportion to the current by varying the current that the displacement detection circuit 22 passes through the Hall element 21. Therefore, when the current flowing through the Hall element 21 is varied, the value of the detection signal detected by the detection unit 8 may be held in the determination unit 12 in advance. When the displacement amount detection unit 6 is inspected, it is possible to detect the sensitivity deterioration of the displacement amount detection unit 6 by comparing with the value of the detection signal previously held in the determination unit 12.

  Next, a method for detecting the deterioration of the spring 2 will be described. Here, a method of determining the deterioration of the spring 2 using the diagnosis mode in the servo type sensor shown in FIG. In this case, the setting of each switch is the same as in the above-described diagnosis mode, and will be omitted.

  In this detection method, a plurality of different sine wave AC signals set in advance are output from the power supply unit 11 and given to the servo amplifier 7, and the value of the detection signal detected by the detection unit 8 at this time is held in the determination unit 12 in advance. Keep it. Then, when diagnosing the deterioration of the spring 2, a plurality of different sine wave AC signals set in advance from the power supply unit 11 are output and compared with the value of the detection signal held in advance in the determination unit 12. Incidentally, the value of the detection signal previously held in the determination unit 12 is an effective value, an integral value, a peak value, or the like of the detection signal detected by the detection unit 8.

  As a result of the comparison by the determination unit 12, when it is determined that the detection signal is different from the detection signal detected by the detection unit 8 held in advance, it can be determined that the spring 2 has deteriorated. According to this detection method, since signals having different frequencies are given to the spring 2, it is possible to diagnose deterioration of the frequency characteristics of the spring 2.

  Alternatively, a signal including various frequencies such as white noise and pink noise and a step wave (unit step wave) may be applied to the servo amplifier 7 from the power supply unit 11. Although not shown in FIG. 3, the detection signal detected by the detection unit 8 is confirmed by the FFT (Fast Fourier Transform) analysis to confirm the resonance frequency or to be compared with the power of the resonance frequency in the initial state, thereby resonating the spring 2. Degradation can be determined.

  Further, in the case of a servo sensor that detects the acceleration by driving the pendulum 1 using electromagnetic force as shown in FIG. 1, the wound coil 4 is attached to the free end 1b of the pendulum 1 as described above. A magnet 5 is disposed at a predetermined distance from the free end 1b. In order to detect the deterioration of the magnet 5, a magnetoresistive element (Hall element) whose electrical resistance value changes in proportion to the magnetic force generated from the magnet 5 may be provided in the vicinity of the magnet 5. In this case, the magnetic force detected by the magnetoresistive element is held in advance as a resistance value in the storage unit of the servo sensor. When determining the soundness of the magnet 5, the resistance value detected by the magnetoresistive element is compared with the value of the magnetic resistance previously stored in the storage unit, and if the magnet 5 is within a predetermined common range, the magnet 5 is healthy. It can be determined that there is.

Thus, as described above, the displacement amount of the pendulum 1 when the power supply unit 11 applies the test voltage to the operational amplifier 7a is detected as the displacement of the displacement amount detection unit 6, and the test voltage stored in the determination unit 12 in advance is detected. By using the relationship with the displacement amount, the quality of the servo type sensor can be determined. Furthermore, since the pendulum 1 is actually displaced in addition to the operational amplifier 7a, the deterioration of the coil 4, and the abnormality of the displacement amount detection unit 6, the spring 2 that locks the pendulum 1, the displacement amount detection unit 6 It is possible to detect the deterioration of sensitivity and the deterioration of the magnet 5.
The servo type sensor described above has been described with respect to a servo type sensor that detects acceleration. However, it can be applied to a servo type sensor that detects physical quantities such as displacement and pressure. is there.

DESCRIPTION OF SYMBOLS 1 Pendulum 2 Spring 3 Board | substrate 4 Coil 5 Magnet 6 Displacement amount detection part 7 Servo amplifier 8 Detection part 10 Diagnosis coil 11 Power supply part 12 Determination part

Claims (2)

A pendulum with one end locked to displace in a predetermined uniaxial direction and the other end movable freely; and
A displacement amount detection unit for detecting the magnitude of an external force applied to the pendulum as a displacement amount from a predetermined equilibrium point in the pendulum;
A coil attached to the free end of the pendulum;
A magnet disposed with a predetermined gap from the free end of the pendulum;
A servo amplifier that receives the amount of displacement detected by the displacement amount detector and applies a current to the coil to cancel the external force applied to the pendulum and positions the pendulum at the equilibrium point;
A resistor interposed between the coil and the ground electrode;
An acceleration detecting unit for detecting an acceleration acting on the pendulum from a value of a voltage drop generated in the resistor;
Instead of the displacement detected by the displacement detector, a switch circuit that applies a preset test voltage to the servo amplifier;
Judgment of judging whether the resistor is abnormal by comparing a preset reference value with a voltage drop value generated in the resistor in a state where a preset test voltage is applied to the servo amplifier. A servo-type sensor. A pair of fixed electrodes that are opposed to each other with their outer edges fixed to a predetermined housing;
A movable electrode sandwiched between the pair of fixed electrodes and having an outer edge fixed to the housing;
A weight that is fixed at a predetermined position of the movable electrode and receives an external force to bend the movable electrode;
A capacitance detecting unit that detects an external force received by the weight as a change in capacitance in a capacitor formed by the fixed electrode and the movable electrode;
An electrode driving unit that receives an amount of change in capacitance detected by the capacitance detection unit and applies an electrostatic force between the fixed electrode and the movable electrode to position the movable electrode at a predetermined equilibrium point;
A resistor connected in parallel to the capacitor;
An acceleration detector for detecting an acceleration acting on the movable electrode from a value of a voltage drop generated in the resistor;
Instead of the amount of change in capacitance detected by the capacitance detection unit, a switch circuit that applies a preset test voltage to the electrode driving unit,
In a state where a preset test voltage is applied to the electrode driving unit, the presence / absence of abnormality of the resistor is determined by comparing a preset reference value with a voltage drop value generated in the resistor. A servo type sensor comprising: a determination unit;

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