JP3320257B2 - Ignition device for internal combustion engine - Google Patents

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 having a one-chip structure for forcibly shutting off current when the ignition device generates abnormal heat.

[0002]

2. Description of the Related Art As shown in FIG. 6, an ignition device for an internal combustion engine, which has been generally used, is connected to an electronic control unit (hereinafter, referred to as an "ECU") 1 for the internal combustion engine. An ignition device 2 connected through the 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 And a supplied spark plug 4. EU
The output stage of C1 includes a PNP transistor 9, an NPN transistor 10, a collector of the PNP transistor 9, and N
It comprises a resistor 11 connected between the collector of the PN transistor 10 and a resistor 12 disposed 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, and HIGH and LOW pulses are output to the ignition device 2 side.

[0003] The ignition device 2 comprises a power transistor 5,
When the output signal of the ECU 1 input from the connection terminal 13 changes from LOW to HIGH, the transistor 5 starts energizing and changes from HIGH to LOW. A high voltage of 300 to 400 V is generated at the collector of the transistor 5 by cutting off the current, and this high voltage current is guided to the primary side of the ignition coil 3 and further increased by the secondary side coil. And supplied to the ignition coil 4 and discharged by the ignition coil 4.

[0004] As an ignition device for an internal combustion engine, for example, the invention described in Japanese Patent Application Laid-Open No. 64-45963 is known. The present invention relates to an ignition coil, a current limit period detection circuit for outputting a pulse signal during a period in which the primary current of the ignition coil is controlled to a predetermined value, and an operation in response to an output signal of the current limit period detection circuit. A timer circuit that applies a signal output from the timer circuit to the current limiting circuit, thereby starting the current limiting of the primary current of the ignition coil after a predetermined time determined by the timer circuit. In addition to interrupting the secondary current, the current limiting period detection circuit is configured to output the same output signal as when the primary current is limited, even in the interrupted state.

[0005]

By the way, in the former general ignition coil, an instruction output from the ECU 1 is input to the ignition device 2 side, and the ignition coil 4 is ignited according to the instruction output. 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.

Further, the latter prior art has a self-shut-off function of detecting an abnormality from the duration of the primary current and forcibly shutting off the current.
The set time is counted by a timer, and when the condition exceeds the set time, the primary current is cut off. 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 for setting the time constant, which makes it difficult to form a single chip. Furthermore, with the conventional configuration, the transistor may be destroyed by sudden heat generated by a dump surge that occurs when an abnormality occurs in the battery line, and it is difficult to effectively cope with a destruction accident caused by this type of heat. It was not expensive.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances of the prior art, and has as its object to provide a one-chip protection circuit for automatically shutting off current when abnormal heat generation occurs to protect a transistor. It is an object of the present invention to provide an ignition device for an internal combustion engine which can be centralized in the apparatus and can be downsized.

[0008]

In order to achieve the above object, the present invention relates to a semiconductor device for transmitting a primary current flowing through a primary side of an ignition coil to a semiconductor 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 the ignition device for an internal combustion engine that generates a high voltage on the secondary side by performing cutoff control, 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 a gate voltage to limit the primary current to a predetermined value; a temperature detecting circuit that detects a temperature; and a first temperature detecting circuit that detects a temperature detected by the temperature detecting circuit . When the temperature becomes equal to or higher than the
Maintain state and reduce to a preset second temperature
It is characterized in that a thermal shut-off circuit for recovering from shutdown is integrated into one chip. That is, according to the present invention, a thermal shut-off circuit that detects the temperature of the chip and forcibly cuts off the primary current supplied to the ignition coil when the detected temperature becomes equal to or higher than the set temperature is provided by cutting off the current to the ignition coil, A switching circuit for supplying current, a current detection circuit for detecting a primary current to the ignition coil, and a current limiting circuit for limiting the primary current to a set value are integrated on a single chip.

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 return, and after the forcible shut-off, sets the temperature. That is, do not return until the temperature drops by 50 ° C. or more.
Generally, it takes several tens of seconds to several minutes. Further, the temperature detection circuit for detecting the temperature can be configured to include a diode or a resistor built on one chip.

[0010]

According to the above means, the primary current supplied to the switching circuit is monitored by the current detecting circuit, and the current limiting circuit controls the semiconductor gate voltage of the switching circuit based on the current detected by the current detecting 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 becomes equal to or higher than the set temperature due to, for example, continuous energization or dump surge, the thermal shut-off circuit detects the temperature and detects the temperature. Forcibly cut off the secondary current. In this manner, a circuit having a semiconductor (power transistor) protection function against energization and dump surges in addition to a large current switching function and a current limiting function can be formed on a single chip.

[0011]

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

The ignition device 2 of 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 shut-off circuit 17 are integrated on one chip, and are configured by a one-chip IC 18 mounted. The IGBT 14 has a function of supplying and interrupting a 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 a current detecting circuit 15
The primary current is limited to a set value by controlling the gate voltage of the IGBT 14 based on the current detected by the IGBT 14, and the temperature detection circuit and the thermal shut-off circuit 17 detect the temperature of the IC chip 18 by the temperature detection circuit. Forcibly shutting off the primary current based on the temperature detected by the temperature detection circuit by the shut-off circuit 17,
It also functions to return.

FIG. 2 shows a specific configuration of each of the above circuits. Integrated as described above. In the one-chip IC 18, IG
BT14 is an enhancement type n-channel MOS
Parasitic Zener diodes 21a and 21b are provided in combination with the gate 19 and the PNP bipolar transistor 20, and allow a flywheel current to flow between the collector and the drain and between the drain and the source.

The current detecting load element 22 as the current detecting circuit 15 is provided between the collector of the IGBT 19 and GND. The current detecting load element 22 may be an impedance element that can set a current as well as a resistance. The current limiting circuit 16 is configured by a differential circuit including transistors (FETs) 23 and 24 and resistors 25 and 26.
An output terminal on the power supply side divided by resistors 27 and 28 is connected to the base of the transistor 24. Since the base voltage of the transistor 23 operates so as to have the same potential as the base voltage of the transistor 24, the current detection load element 22 is set by setting the temperature coefficients of the resistors 27 and 28 of the divided power supply to zero. The voltage drop is always constant, and current detection without a temperature count becomes possible.

The thermal shut-off circuit 17 is provided for preventing thermal destruction of the power transistor due to continuous energization or the like as described above.
1. Diodes 32 and 33, their pull-up elements 34, and transistors 3
5 and 36 and resistors 37, 38, and 39, and resistors 40, 41, etc., which constitute a divided power supply. The output of this differential circuit is a transistor 35
Of the transistor 2 through the resistor 30
9 and the transistor 3 via the resistor 43.
6 are connected to the respective gates. The diodes 32 and 33 and the pull-up element 34 constitute a temperature detection circuit.

FIG. 3 shows the relationship among time, primary current, collector-emitter voltage, and power consumption. Generally, the heat generation of a transistor is determined by the power consumption, and the heat generation state of the transistor can be obtained by integrating the primary current and the collector-emitter voltage. Therefore, assuming that the range of the IGBT 14 not subject to the current limitation is t ₁ and the range of the current limitation is t ₂ , the value of the primary current in the range t ₁ not subject to the current limitation is 0 A to 8 A, and
N, OFF, collector-emitter voltage is 1-2V
_Therefore , the power consumption P is obtained by P = {V _ce (I _cmax / 2) t ₁ } / period (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 the continuous current occurs, the power consumption of the current restriction range t ₂ becomes long continue mode. Since the value of the primary current in the range of the current restriction range t ₂ is constant at 8A as seen from FIG. 3 (a), the collector-emitter voltage V _ce is about 8V As seen from FIG. 3 (b), The power consumption P is as follows: P = 8 [A] × 8 [V] = 64 [W] (2) Therefore, a large amount of heat is generated in the current limit range t ₂ , and the power transistor (IGBT 1
4) will lead to destruction. Further, when a failure occurs in the battery line during the current limitation and a dump surge rides on the line, the calorific value further increases, leading to destruction in a short time.

The term "thermal shut-off" refers to a function of detecting the temperature of a transistor or a chip and forcibly interrupting an energization signal before the temperature reaches a breakdown temperature. Hereinafter, referring to FIG.
7 will be described. 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 energized and cut off by the control signal is shown. The range indicated by the symbol a is the range of continuous energization,
The position indicated by the symbol b is the point where the thermal shut-off has acted, and the position indicated by the symbol c is the point where the device returns from the thermal shut-off state. Is a gate voltage of the transistor 36, and a voltage of about 1.0 V is set to the gate of the transistor 36 of the differential circuit by a 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 which are stacked in two stages, the gate has a voltage twice as high as the forward direction of the diodes, that is, 0.7 [V] × 2 = 1.4 [V] (3) is applied, and in a normal state, the output of the differential circuit is LO
W, and the transistor 29 is turned off. Since the forward voltage of a diode generally has a temperature coefficient of −2 mV / ° C., when the temperature rises, the voltage falls accordingly. For example, when an abnormality such as continuous energization occurs and the temperature of the transistor rises to 200 ° C., the 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 in FIG. 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 returns to the gate of the transistor 36 via the resistor 43, and the return threshold 'has a hysteresis of 0.1 V or more, so that the temperature of the IGBT 14 is 50 ° C. or more higher than the shut-off temperature. Re-energization is prohibited until it drops. That is, the hysteresis of the voltage becomes the operating temperature hysteresis, and self-recovery is performed in response to a temperature drop based on the operating temperature hysteresis. The shut-off temperature is higher than the junction temperature of the IGBT 14 (operation guarantee) and the IGBT 14
The temperature is set so that the BT 14 does not 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 can be used instead of the diodes.

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

FIG. 5 is a circuit diagram showing another embodiment in which an input signal is not used as a circuit power source and another power source is taken in from the outside of the circuit of FIG. In FIG.
The zener diode 45 is used to make the voltage taken from the external power supply 46 a constant voltage, and other components that are not particularly described have the same configuration as the embodiment shown in FIG.

[0022]

As is apparent from the above description, according to the present invention having the above-described structure, when abnormal heat generation occurs, the thermal shut-off circuit is activated based on the temperature detected by the temperature detection circuit. Forcibly shut off primary current
To maintain the state and shut off when the temperature drops to the specified temperature.
Since the recovery from, it is possible to provide an ignition device consisting of one-chip IC never semiconductor element Suinngu circuit may be broken.

[Brief description of the 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 among a transistor time, a primary current, a 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]

 DESCRIPTION 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 shut-off circuit 18 One-chip IC 32, 33 Diode

Continued on the front page (72) Inventor Katsuaki Fukatsu 2477, Kashima-Yatsu, Oaza-Koji, Hitachinaka-shi, Ibaraki Prefecture Inside (72) Inventor Noboru Sugiura 2520, Oaza-Kiba, Hitachinaka-shi, Ibaraki Hitachi, Ltd. Manufacturing Equipment Division (56) References JP-A-57-204629 (JP, A) JP-A-51-72839 (JP, A) JP-A-64-357 (JP, A) JP-A-5-332234 ( JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02P 3/00-3/05

Claims (5)

(57) [Claims] 1. A secondary circuit comprising: a primary circuit that flows 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; An ignition device for an internal combustion engine that generates a high voltage at a current, a current detection circuit that detects the primary current, and a gate voltage that is controlled based on the current detected by the current detection circuit to set the primary current in advance. A current limiting circuit for limiting the temperature to a predetermined value, a temperature detecting circuit for detecting a temperature, and forcibly cutting off the primary current when a temperature detected by the temperature detecting circuit becomes equal to or higher than a first temperature set in advance. and maintaining its state, the detected temperature is pre
A thermal shut-off circuit for recovering from shut-off when the temperature drops to a predetermined second temperature lower than the first temperature , the current detection circuit, the current limiting circuit, the temperature detection circuit, and the like.
The thermal shut-off circuit is connected to the switching circuit.
An ignition device for an internal combustion engine, which is integrated into a road and a single chip. 2. The ignition device for an internal combustion engine according to claim 1, wherein said first temperature is approximately 200 ° C. 3. The ignition device for an internal combustion engine according to claim 1, wherein said thermal shut-off circuit has a hysteresis of 50 ° C. or more at the time of recovery. 4. The ignition device for an internal combustion engine according to claim 1, wherein said temperature detection circuit includes a diode built on one chip. 5. The ignition device for an internal combustion engine according to claim 1, wherein said temperature detection circuit includes a resistor built on one chip.