JPS6154952B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a starting device for a diesel engine, and particularly to control of a glow plug during cold starting.

Conventionally, when cold starting a diesel engine, the glow plug is first preheated before cranking, and after the glow plug becomes red hot, the key switch is set to the starter position to energize the starter and glow plug, and the fuel is turned off manually or automatically. Activate the fuel increase device to increase the amount of fuel supplied. When the engine completely explodes, the key switch is returned from the starter position to the on position, but at the same time, the power to the glow plug is cut off, so when the engine temperature is low, the combustion of the air-fuel mixture in the cylinder becomes incomplete, and self-sustaining operation becomes impossible. It becomes possible, and the engine stops.

In order to improve the above points, we developed a system in which the glow plug is energized by operating a manual switch even after the key switch is returned from the starter position to the on position after the engine has completely exploded, and the engine cooling water temperature or atmospheric temperature is A method has been proposed in which a timer circuit is provided that detects the low temperature and operates the glow plug and fuel increase device for a predetermined period of time.

However, the former method is not only cumbersome as it requires manual operation, but also, if the glow plug is energized for a long time, when the engine reaches high speeds (e.g. over 2000 rpm), the glow plug itself will be affected by the combustion heat of the air-fuel mixture in the cylinder and the energization. The glow plug may become abnormally high in temperature due to the heat generated by it, and there is a risk of melting. Contrary to the above, if the power to the glow plug is cut off too early (before the engine reaches idling speed), the fuel injected into the combustion chamber of the engine will not be sufficiently atomized, making it impossible to start and sustain operation. This has the disadvantage that a large amount of unburned air-fuel mixture is released.

Furthermore, since the latter method does not directly detect the temperature inside the cylinder, there is a risk that the glow plug will continue to be energized and the amount of fuel will continue to increase even if the engine rotates at high speeds and the cylinder temperature becomes high. There is a risk that the glow plug will be abnormally heated and melted due to the combustion of excess fuel and the heat generated by energization.

The present invention was made in view of the above problem, and even after the key switch is returned from the starter position to the on position after the engine has completely exploded, until the engine rotational speed reaches a predetermined value (a value near the idling rotational speed), To provide a starting device for a diesel engine that can prevent burnout of a glow plug, ensure continuous starting operation, and shorten warm-up time by automatically energizing the glow plug.

The present invention will be explained in detail below based on the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention.

In FIG. 1, 1 is a key switch, which has an off position 1A, an on position 1B, and a starter position 1C.
has. 2 is a battery, 3 is a fuse, 4 is an alternator, and 4A is a neutral point. 5 is a temperature sensor that detects engine cooling water temperature or exhaust temperature, etc., and the temperature is a set value (for example, engine cooling water temperature 30°C)
When this happens, the contact turns on. Further, 6 is a control circuit (details will be described later), which inputs the output signal of the neutral point of the alternator 4 and the signal of the temperature sensor 5, and continues to output an output signal when at least one of both signals exceeds a set value. It has a holding circuit. Further, 7 is a relay, which has a coil 7A, a normally closed contact 7B, and a normally open contact 7C. 8 is an actuator for increasing the amount of starting fuel, and when energized, a fuel control lever (not shown) operates in the direction of increasing the amount of starting fuel. Also, 9 is the coil 9
A and a normally open contact 9B, 10 is a lamp, 11 is a glow plug, 12 is a timer circuit, and when the temperature sensor 13 is off, for example, 30 seconds after the power is turned on, and when it is on, for example, for 15 seconds. If it operates, and a signal from relay 7 (output when contact 7C is on) is given, it will not operate at all.
In addition, 13 indicates that the temperature is the set value (for example, the engine cooling water temperature is
14 is a coil 14A and a normally open contact 14B.
15 is a thyristor, 16 is a resistor, and 17 is a starter relay.

Next, the operation will be explained.

First, when the key switch 1 is placed in the on position 1B during a cold start of the engine, current flows through the control circuit 6 and the timer circuit 12. At this time, since the engine is stopped, the rotation speed is below the set value (for example, 800 rpm), and the engine cooling water temperature is below the set value (for example, 30 rpm).
Since the temperature sensor 5 is off at temperatures below 0.degree. C.), the control circuit 6 does not send out an output, and therefore the relay 7 is not energized, so the normally closed contact 7B is on. Therefore, the actuator 8 is actuated to move a fuel control lever (not shown) in the fuel increasing direction.

Additionally, the timer circuit 12 operates at the same time as the power is turned on, and when the temperature sensor 13 is off (for example, when the cooling water temperature is below 20°C), the timer circuit 12 operates for 30 seconds, and when the temperature sensor 13 is on (for example, 20
℃ or higher), the relay 14 is energized for 15 seconds. Therefore, contact 14B turns on, and relay 9
The contact 9B is turned on, and as a result, current flows from the battery 2 of the glow plug 11 and the glow plug 11 is preheated for a predetermined period of time (30 seconds or 15 seconds as described above). During this preheating time, the lamp 10 is lit to indicate that preheating is in progress.

Next, when the timer time has passed, contact 1 of relay 14
4B is turned off, resulting in contact 9B of relay 9
Since the glow plug 11 is also turned off, the preheating of the glow plug 11 is completed, and at the same time, the lamp 10 is turned off to indicate that the preheating has been completed.

After heating up, turn key switch 1 to starter position 1.
When the engine is turned on (both 1B and 1C are on at this time), current flows to the starter relay 17, the starter motor is activated, and the engine is cranked. At the same time, thyristor 1 is connected via resistor 16.
Since a trigger signal is given to the gate of 5, the thyristor 15 is turned on, and therefore the relay 9 is energized, the contact 9B is turned on, and the glow plug 11 is turned on.
A current flows through it and it heats up. Note that at this time, since the actuator 8 is operating as described above, the amount of fuel is increased.

Next, when the engine completely explodes, the key switch 1 is returned from the starter position 1C to the ON 1B position, but the thyristor 15 has a self-holding function and remains in the ON state, so the glow plug continues to be heated and the amount of fuel continues to increase. has been done.

In this state, when the engine warms up and the rotation speed reaches the set value (e.g. 800 rpm), the control circuit 6 sends out an output, the relay 7 is energized, and the normally closed contact 7
B is off and normally open contact 7C is on. Therefore, the operation of the actuator 8 is stopped, the fuel increase is completed, and the thyristor 15 is turned off, so that the heating of the glow plug 11 is also completed. Furthermore, the control circuit 6
has a holding circuit, and once the rotational speed exceeds a set value, it continues to output output. The control circuit 6 also sends out an output when the temperature sensor 5 is turned on, but since the rate of increase in engine cooling water temperature is slower than the rate of increase in rotational speed, the rotational speed is higher during cold starting. Reach the set value first.

As mentioned above, during a cold start, the amount of fuel is increased and the glow plug is heated until the engine speed reaches the set value, which ensures continuous starting operation and prevents burnout of the glow plug. .

Next, the warm start time will be explained.

First, when the engine cooling water temperature at the time of starting is equal to or higher than the set value of the temperature sensor 13 (for example, 20° C.), the preheating time is shortened to 15 seconds as described above.

When the engine cooling water temperature is higher than the set value of the temperature sensor 5 (for example, 30°C), the temperature sensor 5
is on, the control circuit 6 sends out an output at the same time as the key switch 1 is turned on, the relay 7 is energized, and the normally closed contact 7B is turned off.
Normally open contact 7C is turned on. Therefore, normally open contact 7
A signal is sent to the timer circuit 12 via C, and since the timer circuit 12 is inactive, the relay 14 is not energized and the glow plug is not preheated.
Further, since the normally closed contact 7B of the relay 7 is turned off, the actuator 8 does not operate, and the fuel amount is not increased.

In other words, during a warm start (the engine temperature is sufficiently high,
When there is no need to preheat or increase the amount of fuel, neither the amount of fuel is increased nor the glow plug is heated, so problems such as burnout of the glow plug will not occur.

In the embodiment shown in FIG. 1, the glow plug and fuel increase are controlled in common, but only the glow plug may be controlled.

Next, FIG. 2 is a diagram showing one embodiment of the control circuit 6, which is composed of a waveform shaping circuit 6A, a switching circuit 6B, and a holding circuit 6C. In addition, the same reference numerals as in FIG. 1 indicate the same parts.

In FIG. 2, the neutral point 4A of the alternator 4
A signal outputted from the engine rotation speed that changes in synchronization with the engine rotation speed is converted by the waveform shaping circuit 6A into a pulse signal (square wave) having a repetition period corresponding to the engine rotation speed. Next, in the switching circuit 6B, while the above pulse signal is at a high level, the transistor Q ₁ is turned on and the capacitor C ₁ is turned on.
is charged and the transistor is at a low level.
When Q ₁ is turned off, the charge on capacitor C ₁ is transferred to resistor R ₁
is discharged through. Therefore, as the repetition period of the pulse signal becomes shorter (the rotational speed increases), the potential at the ground terminal of capacitor C ₁ (base terminal of transistor Q ₂ ) decreases, and when the value falls below a predetermined value, transistor Q ₂ is turned on. Therefore, the transistor Q ₃ is also turned on, and a trigger signal is applied to the gate electrode G of the thyristor Q ₄ of the holding circuit 6C, so the thyristor Q ₄ is turned on, and current flows through the coil 7A of the relay 7 to excite it. Note that since the thyristor Q has a self-holding function, once a trigger signal is applied, it remains on as long as the power supply voltage _Vcc is applied even if the trigger signal is no longer applied.

Furthermore, since the capacitor _C1 is immediately charged when the temperature sensor 5 is turned on, the transistors _Q2 and _Q3 are turned on and the thyristor _Q4 is triggered regardless of the repetition period of the pulse signal.

Next, FIG. 3 is a diagram showing another embodiment of a sensor for detecting the rotational speed of an engine.

First, FIG. 3A uses a magnet 18 that rotates in synchronization with the rotation of the engine and a reed switch 19, and the reed switch 19 is turned on each time the convex portion of the magnet 18 approaches.

In addition, Fig. 3(b) uses a magnet 20 and a coil 21 that rotate in synchronization with the engine rotation.
The voltage generated in the coil 21 in response to the rotation of the coil 21 is used as a signal.

3C is equipped with a switch mechanism that detects the engine lubricating oil pressure and turns off when the oil pressure corresponding to the set rotational speed is reached.

In FIG. 3C, 22 is a diaphragm that divides an atmospheric chamber 23 (23A is a pore) and a hydraulic chamber 24. 25 is a threaded portion that is screwed into an engine oil pressure passage (not shown), and 25A is a screw portion that connects the engine oil pressure to the oil pressure chamber 2.
4, 26 and 27 are stoppers that sandwich the diaphragm 22, and 28 is a passage that leads to the diaphragm 2.
A rod 31 that slides on the guide 29 is moved up and down via a spring 30.

When the engine lubricating oil pressure reaches the oil pressure corresponding to the set rotational speed, the rod 31 moves upward against the spring 32 to push up the contact piece 33 and cut off the conduction between the contacts 34 and 35.

Note that if a sensor like the one shown in FIG. 3C is used, when the contacts 34 and 35 are off, the thyristor in FIG.
Since it is only necessary to configure _Q4 to trigger, the configuration of the control circuit 6 becomes extremely simple.

As explained above, according to the present invention, during a cold start when the engine temperature is below the set value, even after the key switch is returned from the starter position to the on position after the engine has completely exploded, the engine rotation speed will not reach the set rotation speed until the engine rotation speed reaches the set rotation speed. By continuing to energize the glow plug, starting and sustained operation can be reliably performed and burnout of the glow plug can be prevented. If the above set rotational speed is set to a value close to the idling rotational speed, for example around 400 to 1500rpm, it will be possible to start and sustain operation in practice, and the high temperature combustion gas will glow at high rotational speeds (about 2000rpm or higher). There is no risk of contact with the plug.

In addition, during a warm start when the engine temperature is higher than the set value,
Since the glow plug is not energized regardless of the engine speed, battery discharge can be prevented as much as possible, and the capacity of the battery can be reduced, reducing vehicle weight and cost, as well as increasing the durability of the glow plug. There are effects such as being able to improve

[Brief explanation of the drawing]

FIG. 1 is an embodiment of the present invention, FIG. 2 is an embodiment of a control circuit, and FIG. 3 is an embodiment of a sensor for detecting rotational speed. Explanation of symbols, 1...Key switch, 1A...Off position, 1B...On position, 1C...Starter position, 2...Battery, 3...Fuse, 4...Alternator, 4A...Neutral point, 5 ... Temperature sensor, 6 ... Control circuit, 7 ... Relay, 8 ... Actuator, 9 ... Relay, 10 ... Lamp, 1
1... Glow plug, 12... Timer circuit, 13
...Temperature sensor, 14...Relay, 15...Thyristor, 16...Resistor, 17...Starter relay.

Claims (1)

[Claims] 1. A sensor that detects engine rotation speed, a sensor that detects engine temperature, a glow plug that is heated by electricity, and a timer circuit that outputs a signal to preheat the glow plug for a predetermined period of time. , when the engine temperature is above a predetermined set value, the timer circuit is deactivated, and even after cranking starts, the engine rotational speed reaches a predetermined set rotation speed or more or the engine temperature reaches a predetermined set value or more. A starting device for a diesel engine, comprising a circuit for controlling energization of a glow plug until 2. The diesel engine starting device according to claim 1, wherein the timer circuit changes the length of the predetermined time stepwise or continuously depending on the engine temperature. 3 Set rotation speed above 400rpm to 1500rpm
A starting device for a diesel engine according to claim 1, characterized in that the starting device is set to a certain value below.