JP2012246798A - Ion current detecting device - Google Patents

Abstract

An ion current detection device capable of realizing cost reduction is provided.
An ignition coil configured to receive a DC voltage from a DC power source, a switching element that controls ON / OFF of a primary coil current, and a secondary coil L2 are induced in the primary coil L1 and the secondary coil L2. An ignition plug PG that discharges in a direction toward the DC power source based on the high voltage generated, a DC power source side terminal of the primary coil L1, and a DC power source side terminal of the secondary coil L2 Operates in response to a diode D1 that regulates the discharge direction of the plug, voltage dividing resistors R1 and R2 that are connected to both ends of the diode D1 and receive a DC voltage of the DC power supply, and a signal voltage at a connection point of the voltage dividing resistors R1 and R2. And an ionic current flowing through the spark plug based on the DC voltage of the DC power supply is detected as an output of the amplifier circuit 3.
[Selection] Figure 1

Description

  The present invention relates to an ion current detection device capable of detecting an ion current generated by combustion of an internal combustion engine with a simple and low-cost circuit configuration.

  In an internal combustion engine such as an automobile engine, energy is generated by burning an air-fuel mixture introduced into a combustion chamber by ignition discharge of a spark plug. In such an internal combustion engine, molecules in the combustion chamber are ionized at the time of combustion. Therefore, if a bias voltage is applied to the spark plug at an appropriate timing, an ionic current can be acquired.

  And it becomes possible to grasp | ascertain the presence or absence of the occurrence of knocking based on whether or not a knock signal is superimposed on the acquired ion current (for example, Patent Documents 1 to 2). In addition, on the basis of the acquired ion current, engine control such as OBD (On-board diagnostics) correspondence, exhaust gas reduction, and fuel consumption reduction is performed.

  FIG. 2 illustrates the circuit configuration described in Patent Document 1. In this ion current detection device, when the switching element Q is turned OFF, a high voltage in the direction shown in the figure is generated in the secondary coil L2 of the ignition coil. Then, the spark plug PG performs ignition discharge in the negative direction (minus discharge). Further, at the time of this OFF transition, the discharge current of the spark plug PG flows through the path of the secondary coil L2 → zener diode ZD11 and capacitor C11 → diode D22, and the capacitor C11 is charged. After the ignition discharge current converges, the ion current i flows in the direction of the solid line using the voltage across the capacitor C11 as a bias power source, and the detection signal Rf * i corresponding to the ion current i is output from the OP amplifier 30. .

  On the other hand, a circuit configuration as shown in FIG. 3 that realizes positive discharge instead of negative discharge is also known (see Patent Document 2). In the circuit shown in FIG. 3, when the switching element Q is turned off, a high voltage in the direction shown in the figure is generated in the secondary coil L2 of the ignition coil, and the spark plug PG is ignited in the positive direction.

  At the time of this OFF transition, the capacitor C11 is charged through the path of the primary coil L1, the diode D11, the Zener diode ZD11, and the capacitor C11 → the diode D22. After that, when the voltage across the spark plug PG drops, the ion current i flows in the direction of the solid line using the voltage across the capacitor C11 as a bias power supply, and the detection signal Rf * i is output from the OP amplifier 30.

JP 2006-077763 A JP 2002-180949 A

  However, in the circuit configuration as shown in FIGS. 2 and 3, the capacitor C11 and the Zener diode ZD11 are required as a bias circuit for detecting the ionic current, and the circuit configuration is somewhat complicated, and the cost of these components is high. There was a problem. That is, it is necessary to ensure the desired operation of these parts at a high temperature (for example, 160 ° C.) and a high pressure (for example, 250 V to 350 V), and it is difficult to reduce the cost.

  This invention is made | formed in view of said problem, Comprising: It aims at providing the ion current detection apparatus which can implement | achieve further cost reduction.

  In order to solve the above problems, an ion current detection device according to the present invention includes an ignition coil configured such that a primary coil and a secondary coil are electromagnetically coupled, and both the primary coil and the secondary coil receive a DC voltage from a DC power source. Based on the switching element that receives a DC voltage from the DC power source through the primary coil and controls the primary coil current ON / OFF, and the high voltage that is induced in the secondary coil when the switching element is OFF. Connected between the spark plug that discharges in the direction toward the DC power source, the DC power source side terminal of the primary coil, and the DC power source side terminal of the secondary coil to restrict the discharge direction of the spark plug in one direction Distributing by the first and second resistance elements connected between the current regulation element, the DC power supply side terminal of the current regulation element, and the DC power supply side terminal of the secondary coil. A circuit and an amplifier circuit that operates in response to a signal voltage at a connection point of the first resistor element and the second resistor element, and outputs an ionic current flowing through the spark plug based on the DC voltage of the DC power supply to the output of the amplifier circuit Is configured to be detectable.

  In the present invention, since the ionic current is detected based on the DC voltage of the DC power supply, a circuit element that requires a desired operation at a high temperature and a high pressure becomes unnecessary, and a reduction in cost can be realized.

  “Receiving a DC voltage via a primary coil” is not limited to a mode in which the primary coil is connected to the collector terminal of the switching element as in the embodiment. For example, the primary coil is connected to the emitter terminal of the switching element. It is a concept that includes a mode in which are connected.

  In the present invention, the signal voltage at the connection point of the first resistance element and the second resistance element is preferably supplied to the input terminal of the amplifier circuit via the protective resistance element. Similarly, it is preferable that a protective element that restricts the current direction in one direction is disposed between the input terminal of the amplifier circuit and the ground.

  The amplifier circuit includes a signal voltage received at a non-inverting input terminal and an OP amplifier in which a third resistance element is disposed between the inverting input terminal and the output terminal. Between the inverting input terminal and the ground, A fourth resistance element is typically arranged. Moreover, it is preferable that the primary coil and the secondary coil are configured by winding coil windings in opposite phases.

  According to the ion current detection device of the present invention described above, since a heat-resistant circuit component that ensures a desired operation under a high pressure is not required, the circuit configuration is simple and cost reduction is realized. Can do.

It is a circuit diagram explaining the ion current detection apparatus which concerns on an Example. It is a circuit diagram explaining a prior art. It is a circuit diagram explaining another prior art.

  Hereinafter, an ion current detection apparatus according to an embodiment will be described with reference to the circuit diagram of FIG. As shown in the figure, this ion current detection device includes an ignition coil 1 in which a primary coil L1 and a secondary coil L2 are electromagnetically coupled, a switching element 2 that controls ON / OFF of a current in the primary coil L1, and an OP amplifier AMP. Current detector 3, spark plug PG connected in series to secondary coil L 2, battery power supply VB for supplying DC voltage to primary coil L 1 and current detector 3, and ON only at the time of ignition discharge of spark plug PG It is mainly composed of an operating diode D1.

  Although not particularly limited, the OP amplifier AMP is configured to operate with a single power supply Vcc generated from the battery power supply VB. Moreover, the switching element 2 is specifically configured by, for example, an IGBT (Insulated Gate Bipolar Transistor).

  The ignition pulse SG is supplied to the gate terminal of the IGBT, the collector terminal is connected to the battery power supply VB via the primary coil L1, and the emitter terminal is connected to the ground. Further, a cathode terminal and an anode terminal of a Zener diode (not shown) are connected to the collector terminal and the emitter terminal of the IGBT.

  The primary coil L1 and the secondary coil L2 constituting the ignition coil 1 are wound in the secondary coil L2 when the coil winding is wound in the opposite phase and the switching element 2 is turned OFF to interrupt the current of the primary coil L1. The high voltage in the direction shown in the drawing is generated. As a result, the spark plug PG realizes negative discharge that performs ignition discharge from the ground toward the battery power source VB (see FIG. 1B). And the diode D1 is connected to the battery side terminal of the primary coil L1 and the secondary coil L2 in the direction which implement | achieves the electric path of a minus discharge.

  The current detection unit 3 includes an OP amplifier AMP, a feedback resistor R3 connected between the inverting terminal (−) and the output terminal of the OP amplifier AMP, and a ground connected between the inverting terminal (−) of the OP amplifier AMP and the ground. Connected to both ends of the resistor R4, a Zener diode ZD connected between the non-inverting terminal (+) of the OP amplifier AMP and the ground, a protective resistor r connected to the inverting terminal (+) of the OP amplifier AMP, and the diode D1. The divided voltage resistors R1 and R2 are configured.

  As illustrated, the connection point of the voltage dividing resistors R1 and R2 is connected to the non-inverting terminal (+) of the OP amplifier AMP through the protective resistor r. The OP amplifier AMP operates as a non-inverting amplifier circuit and amplifies the input voltage Vi of the non-inverting input terminal by (1 + R3 / R4) times. That is, the output voltage Vo of the OP amplifier AMP is Vo = (1 + R3 / R4) × Vi.

  The protective resistor r is a protective element for the OP amplifier AMP and may be omitted. The Zener diode ZD is a circuit element for protecting the OP amplifier AMP, and it is not necessary to use an expensive circuit element.

  Next, the circuit operation of the ion current detection device having the above circuit configuration will be described.

<At ignition discharge>
When the ignition pulse SG that turns on the switching element 2 by rising at the timing t0 falls at the timing t1, the ignition plug PG ignites and discharges based on the induced voltage of the secondary coil L2, and the discharge current is The secondary coil L2 → the diode D1 → the battery power source VB → the spark plug PG flows through the path (see the broken line arrow in FIG. 1B).

  Note that, during this ignition discharge, the voltage across the voltage dividing resistors R1 and R2 matches the forward voltage drop Vf of the diode D1, so the potential at the connection point of the voltage dividing resistors R1 and R2 is the voltage Vb of the battery power supply VB. Vb−Vf × R1 / (R1 + R2) ≈Vb. Therefore, the output voltage Vo of the OP amplifier AMP is saturated in the positive direction and becomes the power supply voltage level.

<When ion current is detected>
In the above ignition discharge operation, when the discharge energy thereafter converges, the diode D1 in the ON state transitions to the OFF state. Then, thereafter, the ion current io flows through the path of the battery power source VB → the voltage dividing resistor R1 → the voltage dividing resistor R2 → the secondary coil L2 → the spark plug PG. Here, if the resistance value of the path of the voltage dividing resistor R2 → secondary coil L2 → ignition plug PG is R, the input voltage Vi to the OP amplifier AMP is:
Since Vi = io × R, the output voltage Vo of the OP amplifier AMP is
Vo = (1 + R3 / R4) × R × io
Thus, the detection voltage Vo corresponding to the ion current io can be obtained.

  As described above, according to this embodiment, a dedicated bias circuit is not required, and the detection voltage Vo corresponding to the ion current can be acquired based on the battery power supply VB. Therefore, the circuit configuration can be simplified and the entire apparatus can be reduced. Cost reduction can be realized. That is, a desired operation can be realized without using an expensive Zener diode ZD11 or capacitor C11 as shown in FIGS.

  As mentioned above, although the Example of this invention was described in detail, specific circuit structure does not limit this invention at all. For example, although the OP amplifier AMP has been illustrated, it is needless to say that a circuit element that functions in the same manner may be used.

L1 Primary coil L2 Secondary coil 1 Ignition coil 2 Switching element 3 Amplifier circuit D1 Current regulating element R1 First resistance element R2 Second resistance element

Claims (5)

An ignition coil configured such that a primary coil and a secondary coil are electromagnetically coupled, and both the primary coil and the secondary coil receive a DC voltage from a DC power source;
A switching element that receives a DC voltage from a DC power source via a primary coil and controls ON / OFF of the primary coil current;
A spark plug that discharges in the direction from the ground toward the DC power source based on the high voltage induced in the secondary coil during the OFF operation of the switching element;
A current regulating element connected between the DC power supply side terminal of the primary coil and the DC power supply side terminal of the secondary coil to regulate the discharge direction of the spark plug in one direction;
A voltage dividing circuit including a first resistance element and a second resistance element connected between a DC power supply side terminal of the current regulating element and a DC power supply side terminal of the secondary coil;
An amplification circuit that operates in response to a signal voltage at a connection point between the first resistance element and the second resistance element;
An ion current detection device configured to detect an ion current flowing in a spark plug based on a DC voltage of a DC power source as an output of an amplifier circuit.   The ion current detection device according to claim 1, wherein the signal voltage at the connection point between the first resistance element and the second resistance element is supplied to the input terminal of the amplifier circuit via the protective resistance element.   The ion current detection device according to claim 1, wherein a protection element that restricts a current direction to one direction is disposed between the input terminal of the amplifier circuit and the ground. The amplifier circuit is configured by an OP amplifier that receives a signal voltage at a non-inverting input terminal and arranges a third resistance element between the inverting input terminal and the output terminal,
The ion current detection device according to claim 1, wherein a fourth resistance element is disposed between the inverting input terminal and the ground.   The ionic current detection apparatus according to claim 1, wherein the primary coil and the secondary coil are configured by winding coil windings in opposite phases.

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