JPS5943508Y2 - Diesel engine preheating control device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a preheating control device for controlling preheating at the time of starting a diesel engine.

Diesel engines are equipped with glow plugs to facilitate starting, and the pre-combustion chamber is preheated before starting, but it is desirable that the preheating time be as short as possible.

However, in order to start a diesel engine smoothly, it is necessary to raise the temperature of the glow plug to 800°C or higher, but conventionally, the glow plug's heating element, the glow plug's energizing circuit, or the glow plug's center electrode were heated. If a positive resistance-temperature characteristic is provided, the required preheating temperature soo'c
It took about 15 seconds to reach 1.

However, in order to shorten this preheating time, it is not impossible to increase the initial current of the glow plug to 5 seconds or less, but if the time when the glow plug is energized is even slightly too long, the temperature will rise too much. However, there was a drawback that the heating element would melt and the wire would break.

This invention reduces preheating time, prevents wire breakage due to overheating of the glow plug's heating element, and maintains the temperature of the glow plug at a constant value when the engine is completely warmed up. The purpose is to provide a device.

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 is an electrical wiring diagram showing the overall configuration, and 1 is an electric motor control circuit whose output current changes depending on the power supply vehicle.

A charging/discharging circuit 2 charges and discharges the charging/discharging capacitor 2C at a predetermined time constant, and the charging resistor 2a determines the charging time constant, and the discharging resistor 2b determines the discharging time constant.

Reference numeral 3 denotes a reference voltage generation circuit, which generates a constant value of reference voltage that is not affected by fluctuations in the power source of the vehicle.

4I/'i electric current comparison circuit comparison The reference electric current and the output type electric current of the charging/discharging circuit 2 are compared, and when the reference electric current of the upper level is exceeded, the charging/discharging circuit 2 is switched from the charging state to the discharging state. When the lower level of the hysteresis width is reached, the charging state is switched again.

Reference numeral 5 denotes an amplifier circuit, which amplifies the comparative output of the electromotive comparator circuit 4, controls the relay 7 on and off, and intermittently applies the power source from the power supply circuit 6 to the glow plugs 14, 15, 16, and 17. There is.

The 8/I'i display circuit displays the output signal of the amplifier circuit 5 in synchronization with the energization of the globe lags 14, 15, 16, and 17.

9 is a start detector that closes when the diesel engine starts and generates a start detection signal; 10 is a timer circuit that generates a timer signal when a certain period of time has elapsed from the time it received the start detection signal; (integrated circuit) 10a.

11/ri A water temperature sensor that closes when the cooling water temperature of the diesel engine exceeds a certain temperature, and a water temperature detection circuit 12 generates a detection signal whose phase is inverted.

13 is a logic circuit which generates a logic output when either the timer signal from the timer circuit 10 or the detection signal from the water temperature detection circuit 12 is generated; this logic output is added to the amplifier circuit 5; The relay 7 is turned off, and the power supply to the glow plugs 14, 15, 16, and 17 is stopped.

Then, a comparison circuit is constituted by the electric comparison circuit 4, and
The amplifier circuit 5 and the relay 7 constitute a drive circuit.

Next, the operation of the above configuration will be explained.

Now, when a preheating start signal is issued from the power supply circuit 6 when the key switch is turned on at the time of starting, charging in the charging/discharging circuit 2 starts, and the charging electric current starts to charge the reference electric current in the reference electric heating generation circuit 3. When the voltage exceeds the voltage, the comparison output of the electric comparison circuit 4 is inverted and amplified by the amplifier circuit 5 to turn off the relay 7.
At 17, the current that was being applied in the past disappears, and the temperature begins to drop from point P shown in the characteristic diagram of FIG.

At this time, at the same time as the relay 7 is turned off, the display on the display circuit 8 also disappears, and the charging/discharging circuit 2 starts discharging.

When the charging/discharging circuit 2 is discharged at the set lower limit value of the electronic comparator circuit 4 with hysteresis, the output of the electronic comparator circuit 4 is inverted, turning on the relay 7, and displaying it on the display circuit 8. Glow plug 1 lowered at Q point in Figure 2
The temperature from 4 to 11 starts to rise again.

Thereafter, the temperature of the glow plugs 14 to 17 is maintained within the preheating permissible range by repeating the above operation.

At this time, the time constant of the charging/discharging circuit 2 is the glow plug 14
It is determined in accordance with the heat capacity of ~17.

In response to fluctuations in the power supply room voltage, the electric power control circuit 1V corrects the charge amount and controls the preheating time.

In addition, the timer circuit 10 starts operating in response to a signal from the start detection circuit 9, and after a certain period of time has elapsed since the diesel engine started, or when the water temperature reaches a certain temperature or higher according to the water temperature sensor 11, the water temperature detection circuit 12 starts operating. , the output of the timer circuit 10 and the output of this water temperature detection circuit 12 are connected to a logic circuit 1.
3 and the output of the logic circuit 13 cuts off the relay 7 through the amplifier circuit 5 and cuts off the power to the glow plugs 14 to 17, so the temperature of the glow plugs 14 to 17 decreases as shown in Figure 2. start.

In this way, when starting a diesel engine, glow plug 1
4 to 17 to improve the startability,
Further, the temperature of the glow plugs 14 to 17 is maintained at a high temperature after a certain period of time has elapsed after the diesel engine has started, or when the water temperature has risen to a predetermined value (1), thereby reducing the engine operating noise at the initial stage of operation of the diesel engine.

Next, FIG. 3 is an electrical wiring diagram showing the main parts of another embodiment of the present invention, in which the number of intermittent circuits of the relay 7 is reduced compared to the embodiment of FIG. 1, and its durability is improved. It is something.

That is, a second relay 7A and a current limiting resistor 7B are connected in parallel with the relay 7, and the second relay 7A is in the closed state when the key switch to start preheating is turned on, and as shown in FIG. It is switched to an open state upon generation of a logic output from the logic circuit 13.

Therefore, when the relay 7 is turned off during preheating, the glow plug 1 is
Approximately half of the current is supplied to 4 to 17, and the slope of the temperature drop in the characteristic diagram in Figure 2 becomes gentler.
The time from A to the QA case is extended, and the intermittent cycle of the relay 7 can be lengthened.

In this case, the resistance value of the discharging resistor 2b is selected so as to set the discharging time constant of the charging/discharging circuit 2 to a larger value in accordance with the fi and gender correction by the current limiting resistor 7]3.

As described above, in the present invention, when preheating a diesel engine, the power supply to the glow plug is controlled intermittently to maintain its temperature within the permissible preheating range. At the same time, the indicator lamp turns on and off in synchronization with the energization of the glow plug, so the indicator lamp is turned on only when the key switch is turned on and the glow plug reaches its maximum temperature for the first time. Even if cranking is performed some time after the key switch is turned on, the optimum cranking time can be displayed since the temperature is always highest immediately after the indicator lamp goes out.

This has an excellent effect.

[Brief explanation of the drawing]

Fig. 1 is an electrical wiring diagram showing one embodiment of the present invention, Fig. 2 is a percentage diagram showing the temperature control characteristics of the glow plug, and Fig. 3 is an electrical wiring diagram showing the main parts of another embodiment of the invention. It is a diagram. 2...Charging/discharging circuit, 3...Reference voltage generation circuit for determining the upper level, 4...Electric voltage comparison circuit forming a comparison circuit.
5.7... Amplifier circuit and relay forming the drive circuit, 8...
・Display circuit, 14, 15, 16, 17... glow plug.

Claims (1)

[Scope of claim for utility model registration] A glow plug that is attached to a diesel engine and preheats the engine at startup by generating heat in response to energization, and a charger that charges and discharges at a time constant determined by the heat capacity of the glow plug. a discharging circuit; a comparator circuit that switches the charging/discharging circuit to a discharging state when the output signal of the charging/discharging circuit reaches an upper level; and a comparator circuit that switches the charging/discharging circuit to a charging state when the output signal reaches a lower level; A preheating control device for a diesel engine, comprising a drive circuit that repeatedly turns on and off electricity to the glow plug, and a display circuit that repeatedly flashes on and off continuously when the drive circuit is turned on and off.