JPH08338350A - Ignition device for internal combustion engine - Google Patents

Abstract

PURPOSE: To automatically shut off electricity, and thereby protect transistors when heat is abnormally generated by integrating a thermal shut off circuit forcibly stopping primary current, into one chip when a temperature detected by a temperature detection circuit exceeds a temperature set in advance. CONSTITUTION: A IGBT 14 functionally provides/shuts off primary current flowing into the primary coil of an ignition coil, and a current detection circuit 15 functionally detects the primary current. A current limiting circuit 16 controls the gate voltage of the IGBT 14 so as to limit the primary current to a set value based on current detected by the current detection circuit 15, a temperature detection circuit and a thermal shut-off circuit 17 detect the temperature of an IC chip 18 by the temperature detection circuit, and the primary current is forcibly shut off by the thermal shut-off circuit 17 based on a temperature detected by the temperature detection circuit. By this constitution, the ignition device can be obtained, which is composed of one chip IC provided with a protective function.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for an internal combustion engine, and more particularly to an ignition device for an internal combustion engine which is configured as a one-chip for forcibly shutting off energization when the ignition device abnormally generates heat.

[0002]

2. Description of the Related Art An ignition device for an internal combustion engine that has been generally used in the past is connected to an electronic control device for an internal combustion engine (hereinafter referred to as "ECU") 1 and an ECU 1 as shown in FIG. An ignition device 2 connected via an end 13, an ignition coil 3 connected to the ignition device 2 to which a current is input from the ignition device 2 to the primary side, and an output current from the secondary side of the ignition coil 3 The spark plug 4 is supplied. EU
The output stage of C1 includes a PNP transistor 9, an NPN transistor 10, a collector of the PNP transistor 9, and an N
It consists of a resistor 11 connected between the collector of the PN transistor 10 and a resistor 12 arranged between the collector of the NPN transistor 10 and the connection end 13 of the ignition device 2. The transistors 9 and 10 are turned on and off in response to the instruction output of, and HIGH and LOW pulses are output to the ignition device 2 side.

The ignition device 2 includes a power transistor 5 and
A hybrid IC 6 having a current detection load 7 and a current control circuit 8 mounted therein. When the output signal of the ECU 1 input from the connection end 13 changes from LOW to HIGH, the transistor 5 starts energization and changes from HIGH to LOW. A high voltage of 300 to 400 V is generated in the collector part of the transistor 5 by shutting off the energization, and this high voltage current is guided to the primary side of the ignition coil 3 and becomes higher in the secondary side coil. Is supplied to the ignition coil 4 and is discharged by the ignition coil 4.

As an ignition device for an internal combustion engine, for example, the invention described in Japanese Patent Laid-Open No. 64-45963 is known. The present invention operates in accordance with an ignition coil, a current limiting period detection circuit that outputs a pulse signal during a period in which the primary current of the ignition coil is controlled to a predetermined value, and an output signal of the current limiting period detection circuit. And applying an output signal of the timer circuit to the current limiting circuit, the first circuit is provided after a predetermined time determined by the timer circuit from the time when the current limiting of the primary current of the ignition coil is started. The current limiting period detection circuit is configured to output the same output signal as when the primary current is limited, even when the secondary current is cut off.

[0005]

By the way, in the former general ignition coil, the instruction output from the ECU 1 is input to the ignition device 2 side, and the ignition coil 4 is ignited in accordance with the instruction output. However, in this circuit, safety measures such as a safety device when an abnormality occurs are not particularly considered. Therefore, even if the ignition time becomes long and the temperature rises, nothing can be done on the ignition device side.

The latter prior art has a self-shut-off function for detecting an abnormality from the duration of the primary current and forcibly shutting it off.
The set time is counted by a timer, and the primary current is cut off when the condition exceeds the set time. Since an abnormality is detected from the duration of the primary current, a timer circuit is required. Becomes complicated. In addition, a large capacitor is required to set the time constant, which makes it difficult to form a single chip. Furthermore, with the conventional configuration, the transistor may be destroyed due to abrupt heat generation due to a dump surge that occurs when the battery line is abnormal, and it is difficult to effectively deal with a breakdown accident due to this type of heat generation, and it is not always reliable. It wasn't expensive.

The present invention has been made in view of the circumstances of the prior art as described above, and an object thereof is to provide a one-chip protection circuit for automatically shutting off power supply to protect a transistor when abnormal heat is generated. It is an object of the present invention to provide an ignition device for an internal combustion engine, which can be integrated in the interior and can be downsized.

[0008]

In order to achieve the above object, the present invention provides a semiconductor with a primary current flowing through a primary side of an ignition coil in response to an ignition control signal output from an electronic control unit for an internal combustion engine. Energized by the switching circuit used,
In an ignition device for an internal combustion engine that performs a cutoff control to generate a high voltage on a secondary side, based on the switching circuit, a current detection circuit that detects the primary current, and a current detected by the current detection circuit. A current limiting circuit that controls the gate voltage to limit the primary current to a preset value, a temperature detection circuit that detects the temperature, and a temperature detected by the temperature detection circuit that is not less than the preset temperature. In that case, the thermal shutoff circuit for forcibly shutting off the primary current is integrated into one chip. That is, in the present invention, the thermal shutoff circuit that detects the temperature of the chip and forcibly shuts off the primary current supplied to the ignition coil when the sensed temperature becomes equal to or higher than the set temperature is provided with a thermal shutoff circuit. The configuration is integrated in one chip together with a switching circuit for energizing, a current detection circuit for detecting the primary current to the ignition coil, and a current limiting circuit for limiting the primary current to a set value.

In this case, it is desirable that the preset temperature is set to about 200 ° C., and the thermal shut-off circuit has a hysteresis of 50 ° C. or more at the time of restoration, and after the forced shutoff, the temperature is set to the above temperature. That is, do not return until the temperature drops by 50 ° C or more.
Generally, the time is several tens of seconds to several minutes. Further, the temperature detecting circuit for detecting the temperature can be configured to include a diode or a resistor built in one chip.

[0010]

According to the above means, the primary current supplied to the switching circuit is monitored by the current detection circuit, and the current limiting circuit controls the gate voltage of the semiconductor of the switching circuit based on the current detected by the current detection circuit. Then 1
Limit the secondary current. On the other hand, the temperature of the one-chip IC including the switching circuit is monitored by the temperature detection circuit, and when the temperature of the chip exceeds the set temperature due to continuous energization or dump surge, for example, the thermal shutoff circuit detects this and Next current is forcibly cut off. Thus, in addition to the large current switching function and the current limiting function, a circuit having a semiconductor (power transistor) protection function against energization and dump surge can be configured in one chip.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

The ignition device 2 in this embodiment has an insulated gate bipolar transistor (hereinafter abbreviated as "IGBT") 14 as shown in the internal equivalent circuit of FIG.
The current detecting circuit 15, the current limiting circuit 16, the temperature detecting circuit and the thermal shutoff circuit 17 are integrated on one chip and configured by a one-chip IC 18 mounted. The IGBT 14 has a function of energizing and interrupting the primary current flowing through the primary coil of the ignition coil 3, and the current detection circuit 15 has a function of detecting the primary current. The current limiting circuit 16 is the current detection circuit 15
The gate voltage of the IGBT 14 is controlled on the basis of the current detected by to limit the primary current to the set value, and the temperature detection circuit and the thermal shutoff circuit 17 detect the temperature of the IC chip 18 by the temperature detection circuit, The shut-off circuit 17 forcibly shuts off the primary current based on the temperature detected by the temperature detection circuit,
It also functions to restore.

FIG. 2 shows a specific configuration of each of the above circuits. Integrated as above. In the one-chip IC18, IG
BT14 is an enhancement type n-channel MOS
The gate 19 and the PNP bipolar transistor 20 are combined with each other, and parasitic Zener diodes 21a and 21b for flowing a flywheel current are provided between the collector and the drain and between the drain and the source.

A load element 22 for current detection as the current detection circuit 15 is provided between the collector of the IGBT 19 and GND. The current detection load element 22 may be an impedance element capable of setting a current as well as a resistance. The current limiting circuit 16 is composed of a differential circuit including transistors (FETs) 23 and 24 and resistors 25 and 26.
To the base of the transistor 24, an output terminal on the power source side, which is divided by resistors 27 and 28, is connected. Since the base voltage of the transistor 23 operates so as to have the same potential as the base voltage of the transistor 24, by setting the temperature coefficient of the resistors 27 and 28 of the voltage dividing power supply to zero, the load element 22 for current detection is controlled. The voltage drop is always constant and current detection without temperature counting is possible.

The thermal shutoff circuit 17 is provided to prevent thermal destruction of the power transistor due to continuous energization as described above, and the transistor 29 and the signal line 3 are provided.
Diode 32, 33 connected in the forward direction from 1 to GND, its pull-up element 34, transistor 3
5 and 36 and resistors 37, 38 and 39, and a differential circuit and resistors 40 and 41 which form a voltage dividing power source. The output of this differential circuit is the transistor 35.
From the drain of the transistor 2 through the resistor 30
To the gate of the transistor 9 and via the resistor 43
6 gates, respectively. The diodes 32 and 33 and the pull-up element 34 form a temperature detection circuit.

FIG. 3 shows the relationship between time, primary current, collector-emitter voltage, and power consumption. Generally, the heat generation of the transistor is determined by the power consumption, so the heat generation state of the transistor can be obtained by integrating the primary current and the collector-emitter voltage. Therefore, assuming that the current-restricted range of the IGBT 14 is t ₁ and the current-restricted range is t ₂ , the value of the primary current in the current-restricted range t ₁ is 0 A to 8 A normally.
N, OFF, collector-emitter voltage is 1-2V
_Therefore , the power consumption P is obtained by P = {V _ce (I _cmax / 2) t ₁ } / cycle (1)

For example, when t ₁ = 4 ms and the period is 6 ms, the power consumption is 4 W and the heat generation is small. However, when continuous energization occurs, the power consumption in the current limiting range t ₂ is in a mode that lasts for a long time. The value of the primary current in the range of the current limiting range t ₂ is constant at 8 A as can be seen from FIG. 4A, and the collector-emitter voltage V _ce is about 8 V as seen from FIG. 4B. The power consumption P is P = 8 [A] × 8 [V] = 64 [W] (2) Therefore, the amount of heat generated is large in the current limit range t ₂ , and the power transistor (IGBT 1
4) will lead to destruction. Further, when a problem occurs in the battery line during current limitation and a dump surge is applied to the line, the amount of heat generated further increases, resulting in destruction in a short time.

The thermal shut-off means a function of detecting the temperature of the transistor or the chip and forcibly shutting off the energization signal before the temperature reaches the breakdown temperature. The operating principle of the thermal shutoff circuit 17 will be described below with reference to FIG. In FIG. 4, a control signal for driving the ignition coil 4 is shown, and a primary current of the ignition coil 4 which is turned on and off by the control signal is shown. Further, the range indicated by the symbol a is a range of continuous energization, the position indicated by the symbol b is a point where the thermal shutoff is activated, and the position indicated by the symbol c is a point where the thermal shutoff state is restored. Is a gate voltage of the transistor 36, and is set so that a voltage of about 1.0 V is applied to the gate of the transistor 36 of the differential circuit by the voltage division of the resistors 40 and 41. Is the gate voltage of the transistor 35. Since the gate of the transistor 35 is connected to the anodes of the diodes 32 and 33 that are stacked in two stages, the gate has a voltage that is twice the forward voltage of the diode.
That is, at normal temperature, 0.7 [V] × 2 = 1.4 [V] (3) is applied, and in a normal state, the output of the differential circuit is LO.
It becomes W, and the transistor 29 is OFF. Since the forward voltage of the diode generally has a temperature coefficient of −2 mV / ° C., when the temperature rises, the voltage drops accordingly. For example, when an abnormality such as continuous energization occurs and the temperature of the transistor rises to 200 ° C., a voltage drop of −0.002 [V] × 200 = −0.4 [V] (4) Become. Therefore, the voltage applied to the transistor 35 is 1.4 [V] -0.4 [V] = 1.0 [V] (5), and the output of the differential circuit is HIGH as shown by Then, the transistor 29 is turned on, the gate voltage of the IGBT 14 is dropped to GND, and the primary current is forcibly cut off.
Further, the output of this differential circuit is returned to the gate of the transistor 36 via the resistor 43, and the return threshold value'has a hysteresis of 0.1 V or more. Therefore, the temperature of the IGBT 14 is 50 ° C. or more higher than the shutoff temperature. Re-energization is prohibited until the temperature drops. That is, the hysteresis of the above voltage becomes the operating temperature hysteresis, and self-recovers according to the temperature drop based on the operating temperature hysteresis. The shutoff temperature is higher than the junction temperature of the IGBT 14 (operation guarantee), and
The temperature of the BT 14 is set so as not to cause thermal destruction.

Although the diodes 32 and 33 are used as the temperature detecting elements in the above embodiment, elements such as resistors having a temperature coefficient may be used instead of the diodes.

In the circuit configuration of the above embodiment,
The HIGH voltage of the input signal, which is a constant voltage for driving the IGBT 14, is used as the power supply of the current limiting circuit and the thermal shutoff circuit. However, as in the above-mentioned differential circuit, the resistor 26 is provided between the input and the gate of the IGBT 14. Provided,
The circuit power supply is taken from the input side, and the current limit and thermal shutoff outputs are connected to the gate of the IGBT 14 so that the circuit power supply can be secured even if the gate of the IGBT 14 is controlled. This enables output from three terminals.

FIG. 5 is a circuit diagram showing another embodiment of the circuit of FIG. 2 in which an input signal is not used as a circuit power source and a separate power source is taken in from the outside. In the figure, the resistor 44
The Zener diode 45 serves to make the voltage taken in from the external power supply 46 a constant voltage, and the other parts, which are not particularly described, are configured similarly to the embodiment shown in FIG.

[0022]

As is apparent from the above description, according to the present invention configured as described above, when abnormal heat generation occurs, the thermal shutoff circuit is activated based on the temperature detected by the temperature detection circuit. Since the primary current is forcibly cut off, it is possible to provide an ignition device including a one-chip IC having a protection function that does not damage the semiconductor element of the switching circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing an internal equivalent circuit of an ignition device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a circuit integrated into one chip of the ignition device according to the embodiment.

FIG. 3 is a characteristic diagram showing a relationship between transistor time, primary current, collector-emitter voltage, and power consumption.

FIG. 4 is a timing chart showing the operation of the ignition device according to the embodiment.

FIG. 5 is a circuit diagram of a circuit integrated into one chip of an ignition device according to another embodiment.

FIG. 6 is a circuit diagram showing a configuration of an entire ignition device according to a conventional example.

[Explanation of symbols]

 1 ECU 2 Ignition device 3 Ignition coil 4 Spark plug 5 Transistor 14 IGBT 15 Current detection circuit 16 Current limiting circuit 17 Thermal shutoff circuit 18 One-chip IC 32, 33 Diode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuaki Fukatsu 2477 Kashima Yatsu, Hitachi Takanaka, Ibaraki Pref. 3 In Hitachi Automotive Engineering Ring Co., Ltd. (72) Inventor Noboru Sugiura 2520, Takataka, Hitachinaka, Ibaraki Hitachi, Ltd. Automotive Equipment Division

Claims (5)

[Claims] 1. A switching circuit using a semiconductor supplies a primary current flowing through a primary side of an ignition coil in accordance with an ignition control signal output from an electronic control unit for an internal combustion engine,
In an ignition device for an internal combustion engine that performs a cutoff control to generate a high voltage on a secondary side, based on the switching circuit, a current detection circuit that detects the primary current, and a current detected by the current detection circuit. A current limiting circuit that controls the gate voltage to limit the primary current to a preset value, a temperature detection circuit that detects the temperature, and a temperature detected by the temperature detection circuit that is not less than the preset temperature. Then, a thermal shutoff circuit for forcibly shutting off the primary current is integrated into a single chip. 2. The ignition device for an internal combustion engine according to claim 1, wherein the preset temperature is approximately 200 ° C. 3. The thermal shutoff circuit is provided with a hysteresis of 50 ° C. or more at the time of restoration, and after the forced shutoff,
3. The ignition device for an internal combustion engine according to claim 1, wherein the ignition device is not returned until the temperature drops by the temperature or more. 4. The ignition device for an internal combustion engine according to claim 1, wherein the temperature detection circuit includes a diode built in one chip. 5. The ignition device for an internal combustion engine according to claim 1, wherein the temperature detection circuit includes a resistor built in one chip.