JPS6155626B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention mainly relates to a device for controlling the temperature of a glow plug installed in a sub-combustion chamber of a diesel engine.

[Prior Art] Diesel engines are equipped with glow plugs for smooth starting, but the reality is that they are generally used only when starting the engine and are not used after the engine has started.

[Problems to be Solved by the Invention] However, in operating conditions where the combustion temperature is low, such as during idling immediately after starting, diesel engines produce large combustion noise and vibrations, and suffer from irregular combustion with a large amount of carbon in the exhaust. Easy to occur.

In order to improve this irregular combustion, a temperature control device has been proposed that incorporates a temperature sensor into the glow plug and starts energizing when the glow plug becomes low temperature and stops when the glow plug becomes high temperature.
The structure of the glow plug is complicated, which makes it prone to failure and increases costs.

As described above, the present invention provides temperature control for glow plugs that can effectively prevent irregular combustion, which causes large combustion noise and vibrations and contains a large amount of carbon in the exhaust gas, without complicating the structure of the glow plug. purpose.

[Means for Solving the Problems] In order to solve the above problems, the glow plug temperature control device of the present invention includes a glow plug equipped with a heating element whose resistance value changes according to temperature changes, A bridge circuit is formed by connecting a relay contact provided in the energizing circuit of the glow plug, a detection resistor whose resistance value change is smaller than that of the heating element, and the glow plug in series, and the voltage applied to the glow plug is A comparator that receives A and reference voltage B and opens and closes the contact, a timer that opens and closes the contact in periodic operation, and a circuit that detects a low level at a terminal of a regulator or a low rotational speed of the engine. and an AND circuit inputting the output of the circuit and the outputs of the comparator and timer, and the AND circuit receives the output of the circuit and the output of the comparator and timer, and when the output of the circuit and the output of the comparator and timer are input, When the voltage A is lower than a reference voltage B, the contact is closed to energize the glow plug, and when the voltage A is higher than the reference voltage B, the contact is opened to de-energize the glow plug. .

[Function and Effects of the Invention] With the above configuration, the temperature control device for a glow plug of the present invention detects a change in the resistance value of the heating element of the glow plug using a comparator, The glow plug is energized even when the combustion temperature is low, such as when the diesel engine is idling immediately after starting, and when the combustion temperature is low.
Without complicating the structure of the glow plug, irregular combustion that causes large combustion noise and vibration and contains a large amount of carbon in the exhaust gas can be effectively prevented.

[Example] Next, the glow plug temperature control device of the present invention will be specifically described based on an example shown in the drawings.

1 is a glow plug installed in a sub-combustion chamber of a diesel engine, and its heating element is made of a material having a large positive temperature coefficient of resistance, such as nickel (Ni). 2 is a detection resistor connected in series with the glow plug 1, which has a temperature coefficient of resistance sufficiently smaller than the temperature coefficient of resistance of the heating element of the glow plug 1, and has a resistance of 1/10 or less of the resistance value of the glow plug 1. has value.

3 is a battery, S is a switch, 4a is a contact of relay 4 provided in the power circuit, R1 and R2
is a reference resistor connected in series, and forms a bridge circuit with the glow plug 1 and the detection resistor 2.

5 is a comparator that compares the voltage at point A applied to glow plug 1 with the reference voltage at point B determined by resistors R1 and R2; for example, when comparator 2 has a high output, relay 4 operates; The relay 4 is controlled to return when the output is low. 6 is a timer connected to the output terminal of the comparator 5;
While the contact 4a of the relay 4 is open due to the output of , the temperature of the glow plug 1 is detected by periodically operating the relay 4 for a short time.

7 is an OR circuit connected to the output side of the comparator 5 and the output side of the timer 6. 8 is an inverter, which is a circuit that is connected to the terminal of regulator RG and outputs an output when it detects a low level of regulator RG. 9 is a circuit that converts the engine speed into an electrical signal and outputs when it detects a low engine speed. Inverter, 10 is an OR circuit with inputs of inverters 8 and 9, 11 is an OR circuit 7 and 1
The output of the AND circuit 11 is connected to the input terminal of the relay 4 via the amplifier AMP. The timer 6 has the function of generating an output that operates the relay 4 for a short time (about 0.2 seconds) when the switch S is turned on.

Next, the operation when the control temperature of the glow plug 1 is set to 1000° C. in this glow plug temperature control device will be explained.

Before starting (generally the temperature of glow plug 1 is 1000℃)
When the switch S is closed, the timer 6 operates the relay 4 for a short time. This causes contact 4
a is closed, and the voltage at point A and the reference voltage at point B are compared by comparator 5, but since the voltage at point A is lower than the reference voltage at point B, comparator 5 connects a high output. Therefore, relay 4 continues to operate, and glow plug 1
The glow plug continues to be energized, and the temperature of the glow plug increases.
When the temperature of the glow plug increases to 1000° C. or higher, the voltage at point A becomes higher than the reference voltage at point B, so comparator 5 reverses from high output to low output, and relay 4 returns to normal. The diesel engine is started by detecting the reversal of the output of the comparator 5 by means of an indicator (not shown) such as a separately provided indicator light or buzzer, and operating the starter motor. Also, if you turn on switch S, the temperature of glow plug 1 will be 1000.
If the temperature is above .degree. C., the output of the comparator 5 is inverted, and the relay 4 is immediately reset, thereby preventing the glow plug 1 from further rising in temperature.

When the diesel engine is operated at high speed and the combustion chamber is high temperature, relay 4 is in the reset state and relay contact 4a
is open, but when the engine is operated at low speed and the engine speed is low or the terminal of regulator RG is at a low level, the output from the periodic operation of timer 6 and the output from inverter 8 or 9 are The circuit 11 operates and operates the relay 4 via the amplifier. When relay contact 4a closes,
When the temperature of the glow plug 1 in the auxiliary combustion chamber is higher than the set temperature of 1000°C, the resistance value of the heating element of the glow plug 1 is large and the voltage at point A is higher than the reference voltage at point B. The output of 5 is reversed, and when timer 6 returns, relay 4 also returns.
Open contact 4a.

When the relay contact 4a closes, if the temperature of the glow plug 1 in the auxiliary combustion chamber is lower than the above set temperature, the voltage at point A will be lower than the reference voltage at point B, and the output of comparator 5 will not be inverted, but will flow through OR circuit 7. The AND circuit continues to operate. Therefore, even when the timer 6 returns, the relay 4 continues to operate, and the glow plug 1 is energized and generates heat, increasing its temperature, thereby preventing irregular combustion in the diesel engine. Glow plug 1 has a set temperature of 1000℃
When the temperature rises above this level, the output of comparator 5 is reversed.
Since the AND circuit 11 is reset, the relay 4 is reset and the contact 4a is opened to stop the supply of electricity to the glow plug 1.

If there are multiple glow plugs, the comparator 5 measures the resistance change of only one glow plug 1a as shown in FIG.
The energization to the glow plugs 1c and 1d may be controlled, and as shown in FIG.
Comparators 5a, 5b, 5c,
5d may be provided, and the output of this comparator may be configured as an OR circuit using the glow plug with the largest temperature change as a reference to control the energization to all the glow plugs.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of a temperature control device for glow plugs according to the present invention, Fig. 2 is a partial diagram of the device having a plurality of glow plugs, and Fig. 3 is a partial diagram of the device having a plurality of other glow plugs. It is. In the figure, 1... glow plug, 2... detection resistor,
4... Relay, 4a... Contact, 5... Comparator, 6
...Timer, 7,10...OR circuit, 11...
AND circuit.

Claims (1)

[Scope of Claims] 1. A glow plug including a heating element whose resistance value changes in accordance with temperature changes; a relay contact provided in an energizing circuit of the glow plug; and a glow plug whose resistance value changes less than that of the heating element. a comparator that connects a detection resistor and the glow plug in series to form a bridge circuit, receives voltage A applied to the glow plug and reference voltage B as input, and opens and closes the contact; a timer that opens and closes the contact in operation; a circuit that detects a low level at a terminal of the regulator or a low rotational speed of the engine; and an AND circuit that inputs the output of the circuit and the output of the comparator and the timer. The AND circuit, when inputting the output of the circuit and the output of the comparator and timer, closes the contact so as to energize the glow plug if the voltage A is lower than the reference voltage B; A temperature control device for a glow plug, characterized in that when voltage A is higher than reference voltage B, the contact is opened so as to de-energize the glow plug.