JPH0423111B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rapid heating control method and apparatus for a preheating plug, which is a starting assist device for a diesel engine.

[Prior Art] In order to improve the startability of a diesel engine, it is known to use a preheating plug installed in the cylinder head of the engine so as to project a heating part into the combustion chamber.

With conventional preheating plugs, it takes 15 to 30 seconds to preheat a portion of the combustion chamber to reach the preheating set temperature, for example, approximately 900°C. However, waiting for this 15 to 30 second preheating time before driving is unbearable for drivers who are accustomed to gasoline-fueled engines, and there has been a desire to shorten the preheating time.

The following are examples of devices that meet these demands.

For example, in JP-A No. 55-5475, the resistance value of the heating element 31 below (in parentheses indicates the symbol used in the above publication) is set when voltage is continued to be applied. saturated at temperature and heating element 31
A Wheatstone bridge type control circuit 7 is constituted by a plurality of resistors 4, 5, and 6 including the heating element 31 of the preheating plug 3, and is made of a metal resistor having a unique resistance value corresponding to the set temperature of the starter switch 2. A comparator 8 is connected to a power source (battery; ₁ ) via _a power source (battery; It is equipped with a relay contact actuating device 9 that operates in response to the output signal of the comparator 8, and the switching is controlled by the relay contact actuating device 9 between the starter switch 2 and the input side of the Wheatstone bridge type control circuit 7. Relay contact 10
and a resistor 11 which is connected in parallel to the relay contact 10 and whose resistance value increases as the temperature rises, and when the preheating plug 3 reaches a predetermined temperature by the Wheatstone bridge type control circuit 7. This is detected and outputted from the comparator 8, which activates the starter 14 via the starter relay 13 via the amplifier 12, opens the relay contact 10 via the relay contact actuator 9, and turns off the preheating valve after reaching a predetermined temperature. This is intended to reduce the amount of current flowing to the preheating plug 3 by switching the current flowing through the preheating plug 3 so that it passes through the resistor 11.

Additionally, the one shown in Japanese Patent Publication No. 53-26262 is a preheating valve that is turned on before the starter motor [2] - the numbers in parentheses hereafter indicate the codes used in the above publication - is turned on. A rotation speed detection circuit [3] that turns off the circuit of the starter motor [2] when the signal from the engine rotation speed sensor [1] reaches a predetermined rotation speed;
A circuit 4 is provided that automatically operates in connection with the circuit [3] and generates a signal to turn off the preheating plug circuit when the engine speed rises to the level of self-powered rotation, and ] to start the engine, stop the cell motor [2] at the same time as the engine starts (first explosion), start the timer clock from the time of stop, and when a predetermined period of time has elapsed (when the engine has almost reached self-operation). This stops the power supply to the preheating plug.

[Problems to be Solved by the Invention] However, all of the above-mentioned examples rapidly heat the combustion chamber of the engine to a predetermined temperature required for starting in cold weather, for example, 900°C. If you simply increase the heating speed and perform rapid heating, the preheating plug will be rapidly heated from a low temperature (outside temperature) to a high temperature (for example, 900℃), and as a result, the heating element of the preheating plug will be at a high temperature, while the outer periphery of the preheating plug will remain at a low temperature. In other words, a large thermal gradient occurs between the heating coil and the outer circumferential portion, and this causes thermal stress, which may lead to problems such as cracks or disconnections in various parts of the heating element.

The present invention was invented in view of the above-mentioned conventional device, and when starting an engine, the temperature difference between the inside and outside of the preheating plug is adjusted from the time when the preheating plug starts to be preheated to the first set temperature, which is a temperature sufficient for starting the engine, and a low temperature. Ultra-rapid heating is performed until the second set temperature, which can be lowered, is reached, and after reaching the second set temperature, the heating speed is slowed down to perform rapid heating. Compared to the case where the preheating plug is heated all at once to the first set temperature, the temperature difference between the inside and outside when heating the preheating plug is reduced, the thermal stress caused by the temperature difference is reduced, and the cracking and disconnection of the preheating plug due to thermal stress is prevented. , and by performing ultra-rapid heating up to the second set temperature T _M , we provide a method that can shorten the preheating time compared to conventional preheating devices, and also incorporate a timer, which allows By automatically stopping the power supply to the preheating plug, the energization time is minimized, extending the life of the preheating plug, and the timer starts counting when the set temperature is reached, making it more reliable. It is an object of the present invention to provide a heating control device for a preheating plug that can prevent the preheating plug from cracking or disconnection by minimizing the energization time required.

[Means for Solving the Problems] In order to achieve the above object, the preheating plug rapid heating control method and device of the present invention heat the heating coil 1a of the preheating plug 1 at a temperature sufficient for starting the engine. Heating is performed at ultra-rapid heating speed a until the second set temperature T _M , which is lower than the first set temperature T _S , is reached.
After the set temperature T _M is exceeded, the first heating is performed at rapid heating speed b, which is slower than ultra-rapid heating speed a.
A rapid heating control method for a preheating plug that reduces the temperature difference between the inside and outside when heating the preheating plug 1 by heating it until it reaches a set temperature T _S , and a heating coil 1a of the preheating plug 1 connected to a power source _E0 . a bridge circuit 20 including a bridge circuit 20, and a comparison output when a second set temperature T _M lower than the first set temperature T _S , which is a temperature sufficient for starting the engine in the heating coil 1a of the preheating plug 1 connected to the bridge circuit 20, is reached. a relay drive circuit 5 connected to the comparator C and actuated by the output of the comparator C; and a first relay coil connected to the relay drive circuit 5 and actuated by the output of the circuit 5. RL ₁ and the second relay coil RL ₂ , and the second set temperature is provided between the relay drive circuit 5 and the second relay coil RL ₂ .
A timer 6 turns on when T _M is reached and energizes the second relay coil RL ₂ until a predetermined time after reaching the first set temperature T _S , and a first relay coil RL provided between the power source E ₀ and the bridge circuit 20. a normally closed contact RL ₁ that opens when the second relay coil RL ₁ is activated; a normally open contact RL ₂ that is provided in parallel with the normally closed contact RL ₁ and closes when the second relay coil RL ₂ is activated; rl ₂ and a voltage drop resistor R ₃ connected in series, and the ultra-rapid heating speed a is maintained until the second set temperature T _M is reached.
When heating the preheating plug ₁ , the temperature is increased by heating the _preheating plug 1 at and a rapid heating control device for the preheating plug to reduce the difference in temperature between the inside and outside of the preheating plug.

[Function] The function of the preheating plug rapid heating control device according to the present invention is as follows.

The heating current from the power source E ₀ flows through the normally closed contact rl ₁ , the current detection resistor Re of the bridge circuit 20, and the preheating plug 1, and ultra-rapid heating of the preheating plug 1 is started. As the preheating plug 1 is heated, the resistance of the heating coil 1a gradually increases, and the potential at the intermediate point a of the bridge circuit 20 rises. When the potential at intermediate point a increases,
The balance of the bridge circuit 20 is broken, and the voltage between intermediate points a and b gradually increases. The temperature of the preheating plug 1 is lower than the first set temperature T _S of the heating coil 1a of the preheating plug 1, and the temperature that can reduce the temperature difference between the inside and outside when heating the preheating plug 1, that is, specifically, the first setting. The second set temperature of the switching point is set to approximately 1/2 of the temperature T _S
When T _M is reached, comparator C is activated and provides an output signal. This output signal activates the relay drive circuit 5 and energizes the first relay coil RL ₁ . When the first relay coil RL ₁ is energized, the relay drive circuit 5 also sends an output signal to the timer 6, and the timer 6 causes the timer 6 to reach the first set temperature and further to warm up the engine for a predetermined period of time. 2nd relay coil
Energize RL ₂ . When the second relay coil RL ₂ is energized, it closes its normally open contact RL ₂ . Thereby, the voltage drop resistor _R3 is inserted in series with the heating coil 1a of the preheating plug 1. Therefore, the current flowing through the preheating plug 1 will be reduced. The resistance of this voltage drop resistor R ₃ changes with temperature, similar to the preheating plug 1, so as the temperature of the preheating plug 1 rises, the resistance value of the voltage drop resistor R ₃ also increases.
The current flowing through the preheating plug 1 is reduced. As a result, the heating rate changes from ultra-rapid heating to rapid heating,
While gradually raising the temperature, the first set low speed T _S is reached.

Therefore, the heating coil 1a of the preheating plug 1 is heated at a temperature lower than the first set temperature T _S , which is sufficient for starting the engine, until it reaches the second set temperature T _M that can reduce the temperature difference between the inside and outside of the preheating plug. is heated at ultra-rapid heating speed a, and after exceeding the second set temperature T _M ,
Heating can be performed at rapid heating speed b until the first set temperature T _S is reached.

[Example] Next, an example of the rapid heating control device for a preheating plug according to the present invention will be described in detail with reference to the drawings.

In FIG. 3 showing a control circuit in the rapid heating control device for a preheating plug according to the present invention, E ₀ is a power source;
It consists of the vehicle's battery, etc., and 2 is the key switch. 1 is the preheating plug, Rg is the resistance of the heating coil 1a of the preheating plug 1, and Re is the current detection resistance of the preheating plug 1, which has a value of 1/10 or less of the room temperature resistance of the preheating plug 1. It is connected in series to the heating coil 1a. rl ₁ and rl ₂ are relay contacts installed in parallel,
rl ₁ is a normally closed contact of the first relay coil RL ₁ , and rl ₂ is a normally open contact of the second relay coil Rl ₂ . Each of the contacts rl ₁ and rl ₂ has one end in common and is connected to a bridge circuit 20 having a current detection resistor Re, and the other relay contact rl ₁ is connected to a power source Eo via a key switch 2. Also, relay contact RL ₂
The other is the relay contact rl ₁ through the voltage drop resistor R ₃
is connected to the key switch 2 together with the other end of the . Here, the voltage drop resistor _R3 is constituted by a heating element having a resistance temperature coefficient similar to that of the heating coil 1a of the preheating plug 1, as will be described later. The heating coil 1a of the preheating plug 1 includes a power source Eo → key switch 2 → relay contact rl ₁ or a voltage drop resistor R ₃ and a relay contact.
The heating current will flow through the circuit rl ₂ → current detection resistor Re → preheating plug 1 → power supply Eo. _R1 , _R2
is the resistance, the current detection resistance Re and the resistance of the preheating plug 1
A bridge circuit 20 is configured with Rg. C is a comparator connected between intermediate points a and b of the bridge circuit 20. A relay drive circuit 5 is connected to the output terminal of the comparator C. RL ₁ is a first relay coil, one end of which is connected to the output terminal of the relay drive circuit 5, and the other end of which is grounded. 6 is turned on when the preheating plug 1 reaches the second set temperature T _M , and the second relay coil RL ₂ is turned on.
The timer is connected to the output terminal of the relay drive circuit 5 and is turned off after a predetermined time period sufficient for warming up the engine has passed since the first set temperature T _S is reached.

RL ₂ is a second relay coil, one end of which is connected to the output terminal of the timer 6, and the other end connected to the power source Eo.

Further, the specific structure of the voltage drop resistor R ₃ is as shown in FIG. are connected at the connecting portion 14 to form a heating element 21 having the same temperature coefficient of resistance as the heating coil 1a of the preheating plug 1. It has a structure in which a heat insulating material 15 is inserted between the heating element made of nickel wire 13 and nichrome wire 12 and the main body 11, and is attached to a part of the engine cylinder block with a mounting screw 16 to prevent temperature changes in the cylinder block. Since the temperature changes at the same time, the resistance value of the heating element 21 also changes.

Next, the operation of the preheating plug rapid heating control device having the above configuration will be explained.

First, when key switch 2 is turned on, the power supply Eo is connected to the normally closed contact rl ₁ of the first relay, and the current detection resistor.
A heating current flows through Re, the preheating plug 1, and the power source E ₀ , and ultra-rapid heating of the preheating plug 1 begins. As the preheating plug 1 is heated, the resistance Rg of the heating coil 1a also gradually increases, and the potential at the intermediate point a of the bridge circuit 20 rises. When the potential at intermediate point a increases, the balance of bridge circuit 20 is broken, and the voltage between intermediate points a and b gradually increases. The temperature of the preheating plug 1 is lower than the first set temperature T _S of the heating coil 1a of the preheating plug 1,
The switching point g is set to a temperature that can reduce the temperature difference between the inside and outside when heating the preheating plug 1, that is, more specifically, to approximately 1/2 of the first set temperature T _S of the heating coil 1a of the preheating plug 1. 2 When the set temperature T _M is reached, comparator C operates and outputs an output signal. This output signal activates the relay drive circuit 5, and the first relay coil
RL ₁ energizes. When the first relay coil RL ₁ is energized, it opens its normally closed contact rl ₁ . Furthermore, the relay drive circuit 5 also sends an output signal to the timer 6, and the timer 6 causes the second
After reaching the set temperature T _M , the second relay coil RL 2 is turned on, and after reaching the first set temperature T _S , the second relay coil RL ₂ is energized until it is turned off after a predetermined time period sufficient for warming up has elapsed. When the second relay coil RL ₂ is energized, it closes its normally open contact RL ₂ . Thereby, the voltage drop resistor _R3 is inserted in series with the heating coil 1a of the preheating plug 1. Therefore, the current flowing through the preheating plug 1 is reduced. The resistance of this voltage drop resistor R ₃ changes with temperature, similar to the preheating plug 1, so as the temperature of the preheating plug 1 rises, the resistance value of the voltage drop resistor R 3 also increases, and the resistance of the voltage drop resistor R ₃ increases as the temperature of the preheating plug
This reduces the current flowing to the

As shown in Fig. 1, heating of the preheating plug 1 is stopped at the same heating speed from the start of preheating to the first set temperature T _S for preheating, and the preheating plug 1 is heated at a temperature lower than the first set temperature. Heating is performed at ultra-rapid heating speed a until the second set temperature T _M , which can reduce the temperature difference between the inside and outside during heating, is reached, and after the second set temperature T _M is exceeded, the heating coil 1a is heated. The heating is performed by switching to the corresponding rapid heating speed b. In other words, as shown in Fig. 2, heating is performed with a large initial current e from the preheating start point to the switching point g, that is, the point where the temperature reaches the second set temperature T _M in Fig. 1, and beyond the switching point g. After that, the heating current is decreased in inverse proportion to the preheating time, as shown in FIG. Therefore, the difference between the temperature of the heating coil 1a of the preheating plug 1 and the temperature of the outer circumferential portion is smaller than d when ultra-rapid heating is performed all at once from the start of preheating, as shown by the curve c in FIG. 1.

Figure 5 shows the voltage drop resistance R ₃ as shown in Figure 4.
is installed on the engine cylinder block and connected in series to the heating coil 1a of the preheating plug at the switching set temperature T _M as shown in the circuit of Figure ₃ . It is a figure showing the temperature characteristic of a stopper. Point c in the diagram is the set temperature
At the switching point of T _M , curve a shows the case where the temperature of the voltage drop resistor R ₃ is low, and curve b shows the case where the temperature of the voltage drop resistor R ₃ is high. Curve d is the case where ultra-rapid heating is continued.

[Effects of the Invention] As described in detail above, the method and device for rapidly heating a preheating plug according to the present invention heats the heating coil 1a of the preheating plug 1 to the first set temperature, which is a temperature sufficient for starting the engine. Second set temperature T _M lower than T _S
Heat at ultra-rapid heating speed a until reaching .
After the second set temperature T _M is exceeded, heating is performed at a rapid heating speed b that is slower than the ultra-rapid heating speed a until the first set temperature T _S is reached. Rapid heating control method of preheating plug to reduce the difference and power supply
A bridge circuit 20 connected to E ₀ and including the heating coil 1a of the preheating plug 1, and a first set temperature which is a temperature sufficient for starting the engine in the heating coil 1a of the preheating plug 1 connected to the bridge circuit 20.
A comparator C that outputs an output when a second set temperature T _M lower than T _S is reached, and a comparator C that is connected to the comparator C and
a relay drive circuit 5 operated by the output of the
A first relay coil RL ₁ and a second relay coil RL ₂ connected to the relay drive circuit 5 and operated by the output of the circuit 5;
It is provided between the relay coil RL ₂ and turns on when the second set temperature T _M is reached, and the first set temperature
A timer 6 that energizes the second relay coil RL ₂ until a predetermined time after reaching T _s , a power supply E ₀ and a bridge circuit 2
0 and a normally closed contact rl ₁ that opens when the first relay coil RL ₁ is activated, and the normally closed contact rl ₁
It consists of a normally open contact rl ₂ which is provided in parallel with the second relay coil RL ₂ and closes when the second relay coil RL ₂ is activated, and a voltage drop resistor R ₃ connected in series with the normally open contact rl 2. Heating is performed at ultra-rapid heating speed a until reaching _M , and after exceeding the second set temperature T _M ,
A rapid heating control device for a preheating plug that reduces the temperature difference between the inside and outside when heating the preheating plug 1 by heating the preheating plug 1 at a rapid heating speed b that is slower than the ultra-rapid heating speed a until a first set temperature _{T S} is reached. Therefore, when starting the engine, the temperature is lower than the first set temperature which is sufficient for starting the engine from the time the preheating plug starts preheating, and is a temperature that can reduce the difference in temperature between the inside and outside when heating the preheating plug, that is, a specific temperature. , ultra-rapid heating is performed until the temperature of the preheating plug reaches the second set temperature, which is set to approximately 1/2 of the first set temperature, and after reaching the third set temperature T _M , Since the heating rate is relaxed, the difference in temperature between the inside and outside when heating the preheating plug 1 is reduced compared to the case where ultra-rapid heating heats the preheating plug 1 from the start of preheating to the first set temperature T _S at once. The thermal stress applied to the preheating plug 1 caused by this is reduced, the preheating plug is prevented from cracking or disconnecting due to thermal stress, and ultra-rapid heating is performed up to the second set temperature _TM , compared to conventional preheating devices. This has the effect of shortening the preheating time.

In addition, since the timer 6 automatically stops energizing the preheating plug after preheating is completed, the energization time becomes the minimum necessary and the life of the preheating plug can be extended. Since timing starts when the set temperature is reached, cracks and disconnections of the preheating plug can be more reliably prevented.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the preheating plug temperature, the temperature difference between the inside and outside of the preheating plug, and the heating time in the preheating plug control device according to the present invention, and FIG. 2 is a diagram showing the relationship between the current flowing through the preheating plug and the heating time. Diagrams showing the relationship, Figure 3 is a preheating plug control circuit diagram, Figure 4 is a sectional view of voltage drop resistor R ₃ ,
FIG. 5 is a diagram showing the temperature characteristics of the preheating plug depending on the temperature level of the voltage drop resistor _R3 . Eo...Power source, 1...Preheating plug, 1a...Heating coil, 2...Key switch, 5...Relay drive circuit, 6...Timer, C...Comparator, RL ₁ , RL ₂
...First and second relay coils, rl ₁ , rl ₂ ... Relay contacts, Re ... Current detection resistor, R ₁ , R ₂ ... Resistor, R ₃ ... Voltage drop resistance, 11 ... Resistor body ,
12... Nichrome wire, 13... Nickel wire, 20
... Bridge circuit.

Claims (1)

[Claims] 1. The heating coil 1a of the preheating plug 1 is set to a first set temperature that is sufficient for starting the engine.
Heating is performed at the ultra-rapid heating speed a until the second set temperature T _M , which is lower than T _S , is reached, and after the second set temperature T _M is exceeded, the rapid heating speed b is slower than the ultra-rapid heating speed a.
A rapid heating control method for a preheating plug, characterized in that the temperature difference between the inside and outside of the preheating plug 1 is reduced when the preheating plug 1 is heated by heating the preheating plug 1 until it reaches a first set temperature T _S . 2 The second set temperature T _M is the first set temperature
The rapid heating control method for a preheating plug according to claim 1, characterized in that the temperature is set to approximately 1/2 of T _S. 3. A bridge circuit 20 connected to the power source E ₀ and including the heating coil 1a of the preheating plug 1; and a first set temperature that is a temperature sufficient for starting the engine in the heating coil 1a of the preheating plug 1 connected to the bridge circuit 20. A comparator C that outputs an output when a second set temperature T _M lower than T _S is reached; a relay drive circuit 5 connected to the comparator C and activated by the output of the comparator C; A first relay coil RL ₁ and a second relay coil RL ₂ are connected to each other and are operated by the output of the circuit 5, and are provided between the relay drive circuit 5 and the second relay coil RL ₂ , and are provided between the second relay coil RL 2 and the second set temperature. Timer 6 turns on when T _M is reached and energizes the second relay coil RL ₂ until a predetermined time after reaching the first set temperature T _S
, a normally closed contact RL ₁ provided between the power source E ₀ and the bridge circuit 20 and opened when the first relay coil RL ₁ is activated, and a second relay provided in parallel with the normally closed contact RL ₁ . a normally open contact rl ₂ that closes when coil RL ₂ is actuated;
It consists of the normally open contact rl ₂ and a voltage drop resistor R ₃ connected in series, and heats at an ultra-rapid heating speed a until the second set temperature T _M is reached, and once the second set temperature T _M is exceeded. The present invention is characterized in that the temperature difference between the inside and outside of the preheating plug 1 is reduced when heating the preheating plug 1 by heating at a rapid heating speed b that is slower than the ultra-rapid heating speed a until the first set temperature T _S is reached. A rapid heating control device for preheating plugs. 4 The second set temperature T _M is the first set temperature
4. The rapid heating control device for a preheating plug according to claim 3, wherein the temperature is set to approximately 1/2 of T _S.