JP2001264004A - Actuator displacement detector of electromagnetic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a displacement of a machine element by using electromagnet driving the machine element. SOLUTION: This displacement detector of electromagnetic actuator is provided with a displaceable machine element, two or more electromagnets, a running driver applying a drive current to the first of those electromagnets to displace the machine element, a sensing driver applying detecting signal to the second, which is not the same as the first, electromagnet, and a detection circuit detecting the impedance change of the electromagnet to which the detection signal is applied. Thus a separate sensor for detecting the displacement is dispensed with, and the displacement of the machine elements can be detected, without having to limit the degree of design freedom of an electromagnetic actuator. It is also possible to mount a switching means for switching the connection of the running driver and the sensing driver toward electromagnets, and to detect the displacement successively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting displacement of a mechanical element in an electromagnetic actuator, and more specifically, to an apparatus for detecting the displacement of a mechanical element by using an electromagnet used to drive the mechanical element. The present invention relates to a displacement detection device that detects displacement.

[0002]

2. Description of the Related Art In general, in an actuator for driving a mechanical element, in addition to driving the mechanical element by mechanical driving by connecting a cam, a lot or the like, electromagnetic driving is performed. Driving by an electromagnetic actuator excites an electromagnet by an electric signal and drives a mechanical element by an attractive force of the generated electromagnet. Electromagnetic actuators are capable of finely controlling the drive timing and drive force by controlling electrical signals, and are therefore widely used in fields where precise timing control and variable control are desired.

[0003] Electromagnetic actuators are also used in various places in vehicles, such as in opening and closing control of engine idle control valves, fuel injection valves, EGR control valves, and the like. In particular, as a future possibility, it is desired to apply an electromagnetic actuator to an engine intake / exhaust valve. For example, Japanese Patent Application Laid-Open No. 7-83012 describes an electromagnetically driven valve in which power consumption is reduced by providing a spring with a spring whose spring constant increases as the displacement amount of the mover of the valve increases. .
As described above, when the intake and exhaust valves are driven by the electromagnetic actuator, the valve timing can be controlled in various ways as compared with the mechanical drive, and the output characteristics and fuel efficiency of the engine can be improved.

In order to precisely control the opening and closing of the intake and exhaust valves of the engine in the vehicle by electromagnetic driving, the displacement of the valve is measured, and the current supplied to the electromagnet is controlled in accordance with the displacement. Is required to be realized. Various methods for detecting displacement have been proposed. For example, Japanese Patent Publication No. 05-501597 describes a valve lift sensor using a Hall element or the like. In addition, by using a search coil,
A method of detecting displacement by detecting overcurrent or by using a differential transformer has been proposed.

[0005]

Generally, a sensor for detecting the displacement of a mechanical element driven by an electromagnetic actuator, such as a Hall element or a search coil disclosed in Japanese Patent Application Laid-Open No. 5-501597, is a mechanical device. It is implemented separately from the electromagnet that is excited to drive the element. Therefore, when mounting the sensor, it is necessary to devise a space layout (arrangement), which may limit the degree of freedom in designing the electromagnetic actuator. In addition, there is another problem that a harness for the sensor is separately required, which increases the cost.

Accordingly, the present invention has been made to solve the above problems, and has as its object to use an electromagnet excited to drive a mechanical element as a sensor for detecting displacement of the mechanical element. An object of the present invention is to provide an electromagnetic actuator capable of measuring a displacement of a mechanical element without providing a separate sensor.

[0007]

According to a first aspect of the present invention, there is provided a displacement detecting device for an electromagnetic actuator, comprising: a mechanical element capable of being displaced;
Two electromagnets, a drive driver that excites a first electromagnet of the electromagnets to displace the mechanical element,
A sensing driver for applying a detection signal to a second electromagnet different from the electromagnet; and a detection circuit for detecting a change in impedance of the electromagnet to which the detection signal has been applied, and the mechanical element based on the change in the impedance. The structure of detecting the displacement of is adopted.

According to the first aspect of the present invention, since the electromagnet for driving the mechanical element is used for detecting the displacement of the mechanical element, there is no need to provide a separate sensor for detecting the displacement, and the design of the electromagnetic actuator can be reduced. The displacement of the machine element can be detected without limiting the degree of freedom.

According to a second aspect of the present invention, in the displacement detecting device of the first aspect, the drive driver excites the first electromagnet by alternately switching the first and second electromagnets, and the drive driver excites the first electromagnet. When connecting a sensing driver to the second electromagnet, and connecting the sensing driver to the electromagnet so as to connect the sensing driver to the first electromagnet when the drive driver excites the second electromagnet. A configuration is provided in which switching means for switching is provided.

According to the second aspect of the present invention, the electromagnets for applying the detection signal are alternately switched in response to the electromagnets excited to drive the mechanical elements being alternately switched. Can be detected.

According to a third aspect of the present invention, in the displacement detecting device of the first or second aspect, the sensing driver is connected to the electromagnet via a resistor, and detects a change in impedance based on a change in voltage of the resistor. Take the configuration.

According to the third aspect of the present invention, the displacement of the mechanical element can be detected based on the change in the voltage of the resistance, so that the displacement can be detected with a simple circuit configuration.

According to a fourth aspect of the present invention, in the displacement detecting device of the third aspect, the sensing driver includes an oscillation circuit for outputting an AC signal, and the oscillation circuit is connected to an electromagnet via the resistor and the capacitor. In this configuration, the frequency of the AC signal matches the resonance frequency of the electric circuit including the connected resistor, capacitor, and electromagnet.

According to the fourth aspect of the present invention, since the resonance system is configured to detect the impedance change of the electromagnet with the maximum sensitivity, the displacement of the mechanical element can be detected with the maximum sensitivity.

According to a fifth aspect of the present invention, there is provided the first to fourth aspects.
In any one of the displacement detection devices, the detection circuit corrects a signal representing the displacement of the mechanical element detected based on the change in the impedance based on a drive signal for exciting the electromagnet from the drive driver. A configuration is provided in which multiplying correction means is provided.

According to the fifth aspect of the invention, the influence of the electromagnet excited when the mechanical element is driven can be compensated, so that the displacement of the mechanical element can be detected more accurately.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to the drawings, taking an electromagnetic actuator for driving a valve of an engine as an example. However, the present invention is not limited to an electromagnetic actuator for driving a valve of an engine, but can be widely applied to a device for electromagnetically driving a mechanical element.

FIG. 1 is a block diagram showing the overall configuration of an electromagnetic actuator 60 on which a displacement detecting device 70 according to the present invention is mounted, and its drive driver 12 and control device 50. The control device 50 includes a microcomputer and a circuit element attached thereto, and includes a central processing unit 51 (hereinafter, referred to as a “CPU”), a ROM 52 (a read-only memory) for storing programs and data to be executed, A RAM 53 (random access memory) for providing an area and storing calculation results and the like, an input / output interface 54 for receiving signals from various sensors and transmitting control signals to various parts of the engine are provided.

Input / output interface 5 of control device 50
4 includes an engine speed (Ne) and an engine coolant temperature (T
w), intake air temperature (Ta), battery voltage (VB), signal from various sensors representing ignition switch (IGSW) 7
9 is input, and the desired torque detected by the required load detection means 78 is input. Based on these inputs, the control device 50 determines parameters such as the timing of power supply, the magnitude of the voltage to be supplied, and the time for supplying the voltage in accordance with a control program stored in the ROM 52 in advance. Is output to the drive driver 12 via the input / output interface 54. The required load detection means 78
For example, it can be realized by an accelerator pedal sensor that detects the depression amount of the accelerator pedal.

The drive driver 12 switches the voltage (for example, 12 V) supplied from the constant voltage source 75 to a predetermined current in accordance with a control signal from the control device 50, and the current is provided to the electromagnetic actuator 60. To the electromagnets 5 and 6. For example, drive driver 12 may generate a pulse width modulation (PWM) signal and apply it to electromagnets 5 and 6.

The electromagnetic actuator 60 opens and closes the valve 4 based on a voltage applied to the electromagnet 5 or 6 from the drive driver 12 and / or other control signals. The valve 4 is provided in an intake passage or an exhaust passage (hereinafter, referred to as an intake / exhaust passage) of the internal combustion engine, and opens and closes the intake / exhaust passage (not shown). When the valve 4 is driven upward by the electromagnetic actuator 60, the valve 4 comes into close contact with a valve seat provided in the intake / exhaust passage of the engine and stops, closing the intake / exhaust passage. When the valve 4 is driven downward by the electromagnetic actuator 60, the valve 4 leaves the valve seat, descends to a position separated by a predetermined distance from the valve seat, and opens the intake / exhaust passage.

A valve shaft 7 is connected to the valve 4 upward, and the valve shaft 7 is supported so as to be movable in the axial direction. The armature 2 is provided on the valve shaft 7, and the armature 2 is formed of a disk-shaped magnetic metal, and is configured to be vertically displaced by the magnetic attraction of the electromagnets 5 and 6. The armature 2 is biased by a spring 3 so as to balance at an intermediate position between the electromagnets 5 and 6 when the electromagnets 5 and 6 are not driven. The electromagnets 5 and 6 are of a solenoid type and are arranged vertically above and below the magnetic yokes 1A and 1B, respectively.

When a current is supplied from the drive driver 12 to the electromagnet 5, the magnetic yoke 1A and the armature 2 are magnetized and attract each other, and the armature 2 is attracted upward. As a result, the valve 4 is driven upward by the valve shaft 7, comes into close contact with the valve seat, stops, and is closed. Stop the current supply to the electromagnet 5,
When an electric current is applied to the electromagnet 6, the magnetic yoke 1B and the armature 2 are magnetized, and a force for attracting the armature 2 downward acts, and the armature 2 is driven downward in combination with the action of gravity to contact the magnetic yoke 1B. Stop in state. As a result, the valve 4 is driven downward by the valve shaft 7, and the valve 4 is opened. As described above, since the current applied to the electromagnets 5 and 6 is controlled by the control device 50 and the drive driver 12, the electromagnetic force to the armature 2 can be finely controlled and optimized. As a result, it is possible to improve fuel efficiency, reduce emissions and improve horsepower of the internal combustion engine.

The displacement detection circuit 70 includes a sensor circuit 10A.
And 10B, and switches 8A and 8B connected to each of the sensor circuits. Further, the sensor circuits 10A and 10B are provided with a sensing driver 9A.
9B, and detection circuits 11A and 11B, respectively.

The sensing drivers 9A and 9B output an AC signal having a constant voltage amplitude, and supply a sensing current to the electromagnets 5 and 6 when connected to the electromagnets 5 and 6, respectively. When a sensing current is applied to the electromagnet 5, the detection circuit 11A detects a change in impedance of the electromagnet 5. Similarly, when a sensing current is applied to the electromagnet 6, the detection circuit 11B
The change in the impedance is detected. Since the impedance change changes according to the displacement of the armature 2, the displacement of the armature 2 can be detected by detecting the impedance change.

The switch 8A switches whether or not the sensing driver 9A is connected to the electromagnet 5 in response to a drive signal from the drive driver 12. Similarly, the switch 8B performs switching in response to a drive signal from the drive driver 12 to connect or not connect the sensing driver 9B to the electromagnet 6. The electromagnet 5 is the drive driver 1
2, the electromagnet 6 is connected to the sensing driver 9B by the switch 8B. Conversely,
When the electromagnet 6 is driven by the drive driver 12, the electromagnet 5 is turned on by the switch 8A.
A is connected.

Thus, when the electromagnet 5 is excited and the armature 2 is attracted upward, the electromagnet 6 becomes a sensing coil for detecting the displacement of the armature 2, and a sensing current for detecting the displacement is supplied by the sensing driver 9B. The detection circuit 11B is applied to the electromagnet 6
Detects a change in impedance of the electromagnet 6. Similarly, when the electromagnet 6 is excited and the armature 2 is attracted downward, the electromagnet 5 becomes a sensing coil for detecting the displacement of the armature 2 and the sensing driver 9A
As a result, a sensing current is applied to the electromagnet 5, and the detection circuit 11A detects a change in impedance of the electromagnet 5. As described above, since the sensing coil is alternately switched in response to the drive driver 12 alternately exciting the pair of electromagnets, the displacement of the armature 2, that is, the valve 4 can be continuously detected.

FIG. 2 shows the driving driver 1 shown in FIG.
2, an example of a specific configuration of the displacement detection circuit 70 and the electromagnetic actuator 60 will be described. In this example, the sensor circuits 10A and 10B shown in FIG.

The drive driver 12 is connected to the electromagnet 5 via the terminal 40, and energizes the electromagnet 5 by supplying a drive current. The drive driver 12 is connected to the electromagnet 6 via the terminal 41, and excites the electromagnet 6 by supplying a drive current.

Further, the drive driver 12 is connected to the sensor circuit and the switch 8A via the switching signal terminal 18, and to the switch 8B via the inverter 17. Switches 8A and 8B are, for example, FE
It can be realized by using a transistor such as T. Thus, the opening and closing of the switches 8A and 8B are controlled by the switching signal output from the switching signal terminal 18 by the drive driver 12. For example, when the switching signal is at the HIGH level, the switches 8A and 8B are open, and when the switching signal is at the LOW level, the switches are closed. Since the inverter 17 is provided, the switches 8A and 8B
Are opposite to each other.

The switching signal output from the switching signal terminal 18 is transmitted from the drive driver 12 to the control device 50 (FIG. 1).
Is output when the electromagnet to be excited is switched in response to a control signal from the controller. When the drive driver 12 supplies a drive current to the electromagnet 5, a HI signal is output from the switching signal terminal 18.
When the GH level signal is output, the switch 8A is opened to cut off the sensor circuit 10 from the electromagnet 5 so that the drive current does not flow through the sensor circuit 10. at the same time,
The HIGH level switching signal is set to the LOW level by the inverter 17, the switch 8B is closed, the sensor circuit 10 is connected to the electromagnet 6, and a sensing current is supplied to the electromagnet 6 to detect a change in impedance of the electromagnet 6.

Conversely, when the drive driver 12 excites the electromagnet 6, a LOW level signal is output from the switching signal terminal 18, the switch 8A is closed, and a sensing current is supplied to the electromagnet 5 to turn on the electromagnet 5. Detect changes in impedance. At the same time, the switching signal becomes HIGH level by the inverter 17, and the switch 8B
Is opened to cut off the sensor circuit 10 from the electromagnet 6.

A power controller 26 is connected to the output terminal 20 of the sensor circuit 10.
Receives the current control signal based on the impedance change of the electromagnets 5 and 6 output from the output terminal 20, and inputs the current control signal to the drive driver 12 via the terminal 25. The drive driver 12 passes this current control signal to the control device 50 (FIG. 1), and the control device 50 controls the drive current for exciting the electromagnets 5 and 6 based on the received current control signal.

Next, the operation of the configuration shown in FIG. 2 will be described. The drive driver 12 is connected to the electromagnet 5 via the terminal 40.
When a current of 1 to 10 (A) is applied to the
The switching signal output through the switch 8 causes the switch 8
A is opened, the sensor circuit 10 is cut off from the electromagnet 5, and the switch 8B is closed, so that the sensor circuit 1 is closed.
0 is connected to the electromagnet 6. Thus, the electromagnet 5 is excited, and the armature 2 coupled to the valve 4 is moved to the electromagnet 5
, And move upward. At the same time, sensor circuit 1
Generated at 0, eg 1 with a predetermined amplitude
The sensing current of about 0 to 200 kHz is applied to the terminal 23,
It flows to the terminal 24 through the switch 8B and the electromagnet 6.

When the drive current is applied to the electromagnet 5 and the armature 2 is displaced upward, the impedance of the electromagnet 6 facing the electromagnet 5 changes, and the phase and amplitude of the sensing current change based on this impedance change. This change in the sensing current is detected by the sensor circuit 10, and a current control signal is output from the output terminal 20 as a signal representing the displacement of the armature 2.

Conversely, when the drive driver 12 energizes the electromagnet 6 via the terminal 41, the switch 8B is opened by the switching control signal output via the terminal 18, and the sensor circuit 10 The switch 8A is closed, and the sensor circuit 10 is connected to the electromagnet 5. Thus, the electromagnet 6 is excited, and the armature 2 coupled to the valve 4 is attracted by the electromagnet 6 and moves downward. At the same time, the sensing current generated by the sensor circuit 10 flows to the terminal 22 through the terminal 21, the switch 8A, and the electromagnet 5.

When the drive current is applied to the electromagnet 6 and the armature 2 is displaced downward, the impedance of the electromagnet 5 facing the electromagnet 6 changes, and the phase and amplitude of the sensing current change based on this impedance change. This change in the sensing current is detected by the sensor circuit 10, and a current control signal is output from the output terminal 20 as a signal representing the displacement of the armature 2.

In another embodiment, the switching means can be realized without using a switch. For example,
A sensing driver is connected to each of the electromagnets, and each sensing driver supplies a sensing current to the corresponding electromagnet in response to a permission signal from the control device 50. As the drive driver switches the electromagnet for supplying the drive current, a permission signal is sent to a sensing driver connected to an electromagnet different from the electromagnet to be excited by the drive driver. In this manner, the signals of the driving driver and the sensing driver applied to the electromagnet can be switched.

FIG. 3 shows the principle of displacement detection of the armature 2, which is compatible with FIGS. Armature 2
Is at an intermediate position between the electromagnets 5 and 6, and when the displacement is zero, the reactance of the electromagnet 5 is represented by X, the AC resistance is represented by R, and the inductance is represented by L.

As shown in FIG. 2, a sensor circuit 10 is connected to the electromagnet 5, and FIG. 3 shows only main elements of the sensor circuit 10. The electromagnet 5 has capacitors 21 and 22 connected in series, and the capacitor 22 has a resistor 29 connected in series. The capacitance of each of the capacitors 21 and 22 is represented by C,
The resistance value of the resistor 29 is represented by r.

Changes in the reactance X and the inductance L when the displacement of the armature 2 changes by ΔU are represented by ΔX and ΔL, respectively. The armature 2 is displaced, and the AC resistance based on the eddy current loss of the armature changes by ΔR, so that the potential difference between both ends of the resistor 29 becomes ΔV
Let's say it has changed. When the armature 2 is located closer to the electromagnet 5 from the intermediate position, the change ΔR of the AC resistance is Δ
R> 0, and ΔR <0 when located closer to the electromagnet 6 from the intermediate position.

An oscillation circuit (not shown) for outputting a sensing current i provided in the sensor circuit 10 has a voltage amplitude of V
Where ω is the angular frequency, a change ΔV in the voltage across the resistor 29 is expressed by the following equation (1). Here, j represents an imaginary number.

[0043]

ΔV = V · r / (R + ΔR + j (X + ΔX) + r + (2 / (jωC))) − V · r / (R + jX + r + (2 / (jωC))) Equation (1)

X = ωL, ΔX = ωΔL, and | (Δ
R + jωΔL) | << | (R + jωL + r + (2 / (j
ωC))) |, Equation (1) can be approximated as Equation (2) below.

[0045]

ΔV ≒ −V · r (ΔR + jωΔL) / (R + r + jωL + (2 / (jωC))) ² Equation (2)

As is clear from the equation (2), the voltage change ΔV of the resistor 29 is the impedance change (ΔR
+ JωΔL). Here, the sensitivity coefficient K is determined as follows as the impedance change per unit displacement.

[0047]

K３ (ΔR + jωΔL) / ΔU Equation (3) Therefore, the above equation (2) is expressed by the following equation (4).

[0048]

[Number 4] ΔV = -V · r · K · ΔU / (R + r + jωL + (2 / (jωC))) 2 Equation (4)

At a particular frequency ω, K can be considered to be constant, so that the displacement ΔU is proportional to the voltage change ΔV of the resistor 29, as is apparent from equation (4). Therefore, displacement of the armature 2 can be detected by detecting a potential difference between both ends of the resistor 29.

Next, in order to configure the detection circuit so as to maximize the sensitivity, a condition for maximizing the absolute value of ΔV is determined. In order to maximize the absolute value of ΔV in equation (4), the denominator may be minimized, and thus the following equation (5) is derived.

[0051]

Equation 5 jωL + (2 / (jωC)) = 0 Equation (5)

Since L represents the inductance of the coil when the displacement is zero, if a capacitance C is selected so as to be in a resonance state when the displacement is zero as shown in equation (5),
It can be seen that the sensitivity of the detection circuit is maximized. That is,
If a resonance state that satisfies the condition of Expression (5) is incorporated into a circuit, a detection circuit with optimized sensitivity can be configured. In this manner, the voltage change of the resistor can be detected with the maximum sensitivity, so that the displacement of the armature can be detected with higher accuracy. In this example, the resonance state is realized using two capacitors, but the resonance state may be realized using different numbers of capacitors. Also, the resonance state can be realized by using a parallel connection.

FIG. 4 shows the sensor circuit 10 shown in FIG.
FIG. 3 is a circuit diagram showing details of the embodiment. This circuit has a pair of symmetrical circuit structures A and B substantially at a line connecting the terminals 14 and 35. In the A system, the terminals 21 and 22 are connected to the electromagnet 5, and constitute a circuit for applying a sensing current to the electromagnet 5 and detecting a change in impedance of the electromagnet 5. In the B system, the terminals 23 and 24 are connected to the electromagnet 6, and constitute a circuit that applies a sensing current to the electromagnet 6 and detects a change in impedance of the electromagnet 6. Therefore, the following description will focus on the system A, but the operation of the system B can be similarly considered.

The terminal 14 of the sensor circuit 10 is connected to the drive driver 12 (FIG. 2), and a switching signal is input via the terminal 14. By the switching signal, switch 4
3 is controlled to operate the system A to measure the impedance change of the electromagnet 5, the switch 43 is connected to the terminal 45A.
Is connected to the terminal 45B when the impedance change of the electromagnet 6 is measured by operating the system B.

The sensor circuit 10 includes an oscillating circuit 27, and outputs an AC signal output from the oscillating circuit 27 to a resistor 2
9 and the electromagnet 5 via the resonance control capacitor 28A.
Is applied. The oscillation circuit 27 includes, for example, an RC oscillation circuit,
It can be realized by an LC oscillation circuit, a crystal oscillation circuit, or the like. The AC signal applied to the electromagnet 5 flows through the terminal 22 to the ground (ground).

After the potential difference between both ends of the resistor 29 is amplified by the differential amplifier circuit 40A, it is rectified in the detection circuit 41A using the reference potential V ₀ and synchronously detected using the oscillation signal. After that, the synchronously detected signal is
The AC signal is removed by the smoothing circuit 42A, and the DC signal is output via the terminal 20 as a DC signal.

When the B-system operates, the potential difference between both ends of the resistor 31 is amplified and detected similarly to the operation of the A-system except that the oscillation signal is inverted by the inverter 47 and used in the detection circuit 41B. And smoothed, terminal 2
0 is output.

The magnetic flux density B caused by the drive current I from the drive driver 12 to the electromagnet causes a change in the magnetic field of the sensing coil, and the sensing output output to the terminal 20 may change. It is preferable to provide some compensation mechanism. In this embodiment, a monitor signal based on the drive current, which is output via a terminal 19 (FIG. 2) of the drive driver 12, passes from a terminal 15 through a band-pass filter (BPF) 36 to the A and B systems. (At terminal 46) to compensate for the sensing output. For details of this compensation circuit, see FIGS.
It will be described later with reference to FIG.

FIG. 5 shows the sensor circuit 10 shown in FIG.
3 shows voltage waveforms at each terminal. The horizontal axis of the waveform shown in FIG. 5 indicates time. The waveform 82 is an AC signal output from the oscillation circuit 27 and having a constant amplitude.

As shown by the waveform 81, when the switching signal 18 is set to the LOW level at time t0,
The drive driver 12 energizes the electromagnet 6, and the sensor circuit 1
0 is connected to the electromagnet 5. Thus, as shown by the waveform 80, the electromagnet 6 is excited by the drive driver 12 during the time t0 to t1, and the armature 2 is accordingly driven.
Move from the vicinity of the electromagnet 5 toward the electromagnet 6. A system of the sensor circuit 10 shown in FIG. 4 operates, a sensing current flows through the electromagnet 5, and a change in impedance of the electromagnet 5 is measured. As the armature 2 moves downward, the AC resistance transitions from a large state to a small state, so that the amplitude of the voltage applied to the resistor 29 gradually increases as shown in a waveform 83.

A waveform 83 indicates a voltage waveform at the terminal 32 after rectification and synchronous detection by the detection circuit 41A. A signal reduced by an amount corresponding to the voltage amplitude of the resistor 29 appears as a waveform. A waveform 85 indicates a change in voltage at the terminal 33 after the synchronous detection of the signal 84 is performed by the smoothing circuit 42A. Waveform 8
As shown in FIG. 5, a signal corresponding to the impedance change of the electromagnet 5 is output as a DC signal. Time t
Comparing the waveforms 80 and 85 at 0 to t1, it is clear that the two waveforms are in a proportional relationship.

At time t1, the switching signal becomes HIGH.
When the level changes to the level, the connection of the electromagnet is switched, and the drive driver 12 energizes the electromagnet 5 and the sensor circuit 10
Is connected to the electromagnet 6. Thus, as shown in the waveform 80, the electromagnet 5 is excited by the drive driver 12 during the time t1 to t2, and the armature 2 is accordingly
It moves from the vicinity of the electromagnet 6 toward the electromagnet 5. A sensing current is applied to the electromagnet 6, and a change in impedance of the electromagnet 6 is measured. As the armature 2 moves upward, the AC resistance transitions from a large state to a small state, so that the amplitude of the voltage applied to the resistance 31 gradually increases as shown in a waveform 83.

A waveform 87 indicates a voltage waveform at the terminal 34 after being rectified by the detection circuit 41B at the reference potential V1 and synchronously detected by the oscillation signal. The signal increased by the signal amount corresponding to the potential amplitude of the resistor 31 appears as a waveform. Compared to the waveform 84, the polarity of the increase / decrease is inverted because the polarity of the reference potential V1 is opposite to the polarity of the reference potential V0 in the A system, and as shown in FIG. Is input in the B system in an inverted manner. The waveform 88 is the synchronously detected signal 8
7 is smoothed by the smoothing circuit 42B, and the terminal 37
5 shows the change in voltage at. As shown by the waveform 88, a signal corresponding to the impedance change of the electromagnet 6 is output as a DC signal. As can be seen by comparing waveforms 80 and 88 at times t1 to t2,
The two waveforms are in a proportional relationship.

The waveform 89 indicates the waveform of the voltage output from the output terminal 20 of the sensor circuit 10. The waveform 89 corresponds to the waveform 85 at the time t0 to t1 due to the switching signal 18.
And at time t1 to t2, the waveform 89 is selected. It is clear that waveform 89 changes in proportion to the displacement of valve 4 shown in waveform 80. Thus, the displacement of the valve 4 can be detected by detecting the output of the sensor circuit 10.

As described above with reference to FIG. 4, it is preferable to compensate the influence of the magnetic flux density B on the sensing output by the driven electromagnet. Since the magnetic flux density B changes according to the drive current I, monitoring the drive current I can compensate for the sensing output. FIG. 6 shows an example of this compensation circuit. Here, a description will be given of compensation when the drive driver 12 applies a drive current I to the electromagnet 6 and uses the electromagnet 5 as a sensing coil. However, the same applies when the electromagnet 5 is an excitation coil and the electromagnet 6 is a sensing coil. Can be considered.

The drive driver 12 has a current detecting means 47 such as a current sensor, for example.
Thus, the driving current I is detected, and a voltage signal (referred to as a monitor signal) proportional to the driving current I is output from the output terminal 19. The terminal 19 is the input terminal 15 of the sensor circuit 10.
Connected to. The monitor signal is processed through an appropriate band pass filter (BPF) 36 and output as a compensation signal. On the other hand, as described with reference to FIG. 5, the sensing signal processed by the A system for detecting the impedance change of the electromagnet 5 is output to the output terminal 35. Thus, at the terminal 46, a compensation signal is applied to the sensing signal processed by the A system, and the compensated sensing output is output via the output terminal 20 as a displacement signal representing a change in impedance of the electromagnet 5, that is, displacement of the valve. Is output.

FIG. 7 shows the waveform of each part shown in FIG. A waveform 91 indicates a waveform of the drive current I that flows through the electromagnet 6, and a waveform 92 indicates a monitor signal that is a voltage signal proportional to the drive current I. A waveform 93 indicates a voltage signal after filtering the voltage signal of the waveform 92 by the BPF 36, that is, a compensation signal. Waveform 94 shows the voltage signal, ie, the sensing signal, before being compensated and after being processed by the A system shown in FIG. As is apparent from the figure, the waveform 94 has a distortion in a part of the waveform under the influence of the drive current I. A waveform 95 indicates a voltage signal as a sensing output after the compensation signal of the waveform 93 is applied to the sensing signal of the waveform 94, and the distortion of the waveform of the waveform 94 is compensated by the compensation signal of the waveform 93. You can see that. By providing the compensation circuit in this manner, the sensing output affected by the drive current is compensated, and a displacement signal that represents the displacement of the valve more accurately can be obtained.

[0068]

According to the first aspect of the present invention, since the electromagnet for driving the mechanical element is used for detecting the displacement of the mechanical element, it is not necessary to separately provide a sensor for detecting the displacement, and the electromagnetic actuator is not required. Displacement of a machine element can be detected without limiting the degree of freedom of design.

According to the second aspect of the present invention, the electromagnets for applying the detection signal are alternately switched in response to the electromagnets which are excited to drive the mechanical elements being alternately switched. Can be detected.

According to the third aspect of the present invention, the displacement of the mechanical element can be detected based on the change in the voltage of the resistance, so that the displacement can be detected with a simple circuit configuration.

According to the fourth aspect of the present invention, since the resonance system is configured to detect the impedance change of the electromagnet with the maximum sensitivity, the displacement of the mechanical element can be detected with the maximum sensitivity.

According to the fifth aspect of the present invention, the influence of the electromagnet excited when driving the mechanical element can be compensated, so that the displacement of the mechanical element can be detected more accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the entirety of an electromagnetic actuator, a displacement detection device, and a control device thereof according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic circuit of an electromagnetic actuator and a displacement detection device according to one embodiment of the present invention.

FIG. 3 is a diagram for explaining the principle of displacement detection according to the present invention.

FIG. 4 is a diagram showing details of a sensor circuit in one embodiment of the present invention.

FIG. 5 is a diagram showing waveforms at various parts of a sensor circuit according to one embodiment of the present invention.

FIG. 6 is a diagram showing a compensation circuit for sensing output in one embodiment of the present invention.

FIG. 7 is a diagram showing waveforms at various parts of the compensation circuit shown in FIG. 6 in one embodiment of the present invention.

[Explanation of symbols]

2 Armature 4 Valve 5, 6 Electromagnet 8A, 8B Switch 9A, 9B Sensing driver 10, 10A, 1
0B Sensor circuit 11A, 11B Detection circuit 12 Drive driver 50 Control device 60 Electromagnetic actuator

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01D 5/18 G01D 5/18 C 5/20 5/20 J H01F 7/18 H01F 7/18 Z (72 ) Inventor Minoru Nakamura 1-4-1 Chuo, Wako-shi, Saitama Pref. Inside Honda R & D Co., Ltd. (72) Inventor Toshihiro Yamaki 1-4-1 Chuo Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (Reference) 2F063 AA02 BA06 CA40 DA05 DD03 GA03 GA29 GA33 GA36 KA01 LA05 2F077 AA43 CC02 FF03 FF39 VV01 3G018 AB09 BA38 CA12 DA45 DA66 GA18 3H106 DA08 DA22 DB32 DC02 EE03 FA01 FA07 FB04 FB08 KK18 KK19

Claims (5)

[Claims] 1. A displacement detecting device for an electromagnetic actuator, comprising: a mechanical element capable of being displaced; at least two electromagnets; and a drive current applied to a first electromagnet among the electromagnets to displace the mechanical element. A driving driver for causing the first electromagnet to apply a detection signal to a second electromagnet different from the first electromagnet; and a detection circuit for detecting a change in impedance of the electromagnet to which the detection signal is applied; A displacement detecting device for detecting a displacement of the mechanical element based on a change of the mechanical element. 2. The driving driver according to claim 1, wherein the driving driver comprises:
When the drive driver applies a drive current to the first electromagnet, the sensing driver is connected to the second electromagnet, and the drive driver is connected to the second electromagnet. The displacement detection device according to claim 1, further comprising a switching unit configured to switch connection of the sensing driver to an electromagnet so that the sensing driver is connected to the first electromagnet when a drive current is applied. 3. The displacement detecting device according to claim 1, wherein the sensing driver is connected to an electromagnet via a resistor, and detects a change in the impedance based on a voltage change in the resistor. 4. The sensing driver includes an oscillating circuit that outputs an AC signal. The oscillating circuit is connected to an electromagnet via the resistor and the capacitor, and the frequency of the AC signal is connected to the electromagnet. The displacement detection device according to claim 3, wherein the displacement detection device matches a resonance frequency of an electric circuit including the capacitor and the electromagnet. 5. The apparatus according to claim 1, wherein said detection circuit includes a correction means for correcting a signal representing a displacement of the mechanical element detected based on the change in the impedance based on a drive current from the drive driver. The displacement detection device according to any one of claims 1 to 4.