JPS6237232B2 - - Google Patents

Description

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

[Prior Art] When a glow plug is used to preheat the combustion chamber of an engine to assist in starting, the preheating temperature of the glow plug required for smooth engine starting and the temperature of the engine before starting are closely related. When the cooling water temperature is 10°C, the glow plug only needs to be heated to 400 to 500°C, and for a cold start when the air temperature is -20°C, it is necessary to raise the temperature to 800°C or higher. However, in the past, the temperature of the glow plug was not controlled according to the engine temperature, so when the temperature was high, power was wasted and the glow plug overheated, reducing its durability, and when the temperature was low, preheating was insufficient, resulting in a smooth start. I couldn't help it.

In order to solve this drawback, conventionally, for example, in Japanese Utility Model Application Publication No. 54-15138, the energization time of the glow plug is set depending on the engine cooling water temperature, and the glow plug is preheated during the energization time. A preheating device is disclosed that includes a water temperature timer that stops energizing the glow plug if the cooling water temperature reaches a set temperature or higher during the energization time.

[Problems to be solved by the invention] However, this preheating device controls the glow plug temperature by the energization time and does not detect the glow plug temperature, so it is difficult to raise the glow plug temperature to a temperature sufficient for starting. The preheating temperature tends to fluctuate, and there are cases where a sufficient preheating effect cannot be obtained at low temperatures.

Furthermore, this preheating device stops energizing the glow plug after it reaches the set temperature during a cold start, so if the temperature suddenly drops to a temperature insufficient for starting the engine, In some cases, the engine could not be started by manually changing the switch until the temperature rose to a temperature sufficient to start the engine.

The present invention makes it possible to control the temperature of the glow plug in accordance with the engine temperature, thereby preventing wasted power consumption and deterioration of durability due to overheating of the glow plug at high temperatures, as well as providing a sufficient preheating effect even at low temperatures. The purpose of this invention is to provide a temperature control device for glow plugs.

[Means for Solving the Problems] The glow plug temperature control device of the present invention is a temperature control device that changes the preheating temperature range of the glow plug according to the water temperature of the engine. a comparator that measures the change in resistance value of the water temperature sensor of the engine and produces a high output when the measurement result meets a predetermined condition; and a circuit that energizes the glow plug when the high output of the comparator is input. and a pulse oscillator that starts operating when the comparator has a low output and causes the relay to periodically open and close the contact, and the glow plug is at the preheating temperature. After the temperature rises within the preheating temperature range, the temperature of the glow plug is raised and lowered to maintain it within the preheating temperature range.

[Function] The glow plug temperature control device of the present invention has the following function.

(When preheating the glow plug) In the glow plug temperature control device of the present invention, the pulse oscillator first starts operating, activates the relay, closes the contact provided in the energizing circuit to the glow plug, and energizes the glow plug. do. Then, the comparator measures the change in resistance value due to temperature change of the glow plug and the change in resistance value of the engine's water temperature sensor.
When certain conditions are met, a high output is generated and the relay acts to close the contacts.

That is, when the water temperature of the engine is low, the glow plug is energized for a long time and the preheating temperature is also high, so that a sufficient preheating effect can be obtained. Further, when the water temperature of the engine is high, the time for energizing the glow plug is short and the preheating temperature is low.

When the temperature of the glow plug reaches the preheating temperature, the comparator switches from high output to low output and activates the relay to stop energizing the glow plug.

(After preheating the glow plug) The glow plug is de-energized, stops rising in temperature, and begins to cool down due to heat radiation. The pulse oscillator oscillates due to the reversal of the output of the comparator, activating the relay periodically, and the comparator outputs a high output when the temperature of the glow plug falls below the preheating temperature range, activating the relay to energize the glow plug. . Low output occurs when the temperature is within the preheating temperature range. In this way, the glow plug repeatedly raises and lowers its temperature, and is maintained within the preheating temperature range depending on the engine temperature. If the starter motor is rotated in this state, the engine will start reliably.

This prevents wasteful power consumption and reduces durability due to overheating of the glow plug.
It also extends the life of glow plugs. Therefore, it is possible to control the temperature of the glow plug according to the engine temperature.

[Example] Next, the present invention will be specifically described based on an example shown in the drawings.

Reference numeral 1 designates a glow plug installed in a diesel engine, which uses a pure nickel wire with a high coefficient of temperature resistance as a heating element, and has a characteristic that its resistance value changes greatly as the temperature changes, as shown in FIG. 2 is a resistor connected in series with glow plug 1, which has a small temperature resistance coefficient and a resistance value of 1/10 or less of the glow plug; 3 is a water temperature sensor that detects the temperature of the engine cooling water; In the example a thermistor is used. 4 is a resistor connected in series with the water temperature sensor 3, and the glow plug 1, the resistor 2, the water temperature sensor 3, and the resistor 4 form a bridge circuit.

5 is the voltage at the junction point P between the glow plug 1 and the resistor 2, which is one output terminal of the bridge circuit, and the voltage at the junction point Q, which is the other output terminal of the bridge circuit, between the water temperature sensor 3 and the resistor 4. A comparator 6 inputted via a voltage dividing circuit to be described later is a relay that uses the output of the comparator 5 to open and close a contact 6a provided on the power supply side of the glow plug.

B is a battery, S is a switch, 11 is an energization control circuit, A is an OR circuit, C is an amplifier, and T is a pulse oscillator. 7 and 8 are resistors that form a voltage divider circuit for the voltage at point P, and 9 and 10 are resistors that divide the voltage at point Q at the same ratio as the voltage divider circuit composed of resistor 7 and resistor 8. 7, 8, 9,
10 uses a resistor having a resistance about 100 times that of resistors 2 and 4.

The glow plug temperature control device operates as follows.

When switch 8 for starting the diesel engine is closed, relay 6 is forcibly operated for a short time by the action of pulse oscillator T, and contact 6a is closed. The glow plug 1 has a small resistance value when the temperature is low, and the glow plug 1 is set so that the voltage at point P is lower than the voltage at point Q.
The resistance values of resistor 2, water temperature sensor 3, and resistor 4 are set, and the junction point M of resistors 7 and 8, where the voltage at point P and the voltage at point Q are divided at the same ratio, is the junction point of resistors 9 and 10. N means that the voltage at point M is lower than the voltage at point N. At this time, the comparator 5 generates a high level output, the relay 6 operates and closes the contact 6a, and the glow plug 1 is heated to the preheating temperature by being energized. The resistance value of the glow plug 1 increases as the temperature increases, and the voltage at point P also increases, eventually becoming higher than the voltage at point Q. As a result, the voltage at point M becomes higher than the voltage at point N, so the output of comparator 5 is reversed to low level, relay 6 is reset, contact 6a is opened, and glow plug 1 is de-energized, temperature rise stops, and heat is dissipated. The temperature begins to drop. This inversion of the output of the comparator 5 causes the pulse oscillator T to oscillate, which causes the relay 6 to act periodically and inputs the voltages at points P and Q to the comparator 5 via the voltage dividing circuit. When the voltage at point P is higher than the voltage at point Q, the relay 6 is reset, but when the glow plug 1 becomes cold and its resistance value decreases, and the voltage at point P becomes lower than the voltage at point Q, the comparator The output is reversed and becomes a high level, the contact 6a remains closed, and the glow plug 1 is energized again and the temperature rises again. Glow plug 1 rises in temperature and the voltage at point P becomes Q
When the voltage becomes higher than the voltage at the point, the output of the comparator 5 is again inverted to the low level, and the temperature of the glow plug 1 starts to decrease due to the stop of energization. In this way, the glow plug 1 is kept within the preheating temperature range by repeatedly increasing and decreasing the temperature. If the starter motor is rotated in this state, the engine will start.

The energization and de-energization of the glow plug 1 is determined by the voltage at point P, which changes as the resistance value of the glow plug 1 changes, as shown in FIG. 6, which changes as the resistance value of the water temperature sensor 3 changes as shown in FIG. It is determined by whether it is low or high based on the voltage at the point.

When the water temperature of the engine is low, as at t1 shown in Figures 5 and 6, the reference voltage V1 at point Q becomes high;
The energization time to the glow plug 1 is T1 shown in Fig. 7.
The preheating temperature range is long as shown in A' in FIG. 7, and the preheating temperature range is high as shown in A' in FIG. 7, making it possible to start the engine smoothly.

Further, when the water temperature t2 is high as shown in FIGS. 5 and 6, the reference voltage V2 at point Q is low, the energization time to the glow plug 1 is short as shown in FIG. 7, and the preheating temperature range is It becomes low as shown by B' in Figure 7. This prevents wasteful power consumption and extends the life of the glow plug.

Note that the voltage dividing circuit consisting of the resistor 7 and the resistor 8 and the voltage dividing circuit consisting of the resistor 9 and the resistor 10 in this embodiment are not essential components of the present invention, but
By increasing the resistance value, resistor 2 or resistor 3 →
The current flows in the order of comparator 5 → ground, and the current that does not contribute to the rise in temperature of the glow plug can be significantly reduced, and wasteful power consumption in resistor 2 or 3 can be reduced.

In this example, a pure nickel wire is used as the heating element in order to obtain a change in resistance value with respect to temperature changes in the glow plug, but an element having a large change in resistance value with respect to temperature change may be incorporated into the glow plug in addition to the heating element. good. Further, even if the pulse oscillator T starts oscillating at the same time as the switch S is closed, the same operation can be obtained since the OR circuit A is provided.

FIG. 1A shows an example of the circuit of this embodiment.

R is a resistor, Co is a capacitor, Tr is a transistor, and Di is a diode.

FIG. 2 shows another embodiment of the invention.

In this embodiment, a resistor R is connected in parallel with the water temperature sensor 3.
2. A resistor R1 is connected in series with these, and the change in resistance value of the water temperature sensor 3 is adjusted in accordance with the starting characteristics of the engine to obtain a voltage change at point Q.

FIG. 3 shows yet another embodiment of the invention.

A circuit consisting of bimetal switches B1 and B2 and resistors R3, R4, and R5 is used as a water temperature sensor. The resistance value of the water temperature sensor in this example is the 8th
The voltage changes as shown in the figure, and accordingly, the voltage at the Q point also changes stepwise as shown in FIG. Also, the glow plug temperature rise and preheating temperature range is A' or A' in Figure 10.
As shown in B', the temperature of the glow plug can be controlled according to the engine temperature.

[Effects of the Invention] The glow plug temperature control device of the present invention has the following effects.

A. When the engine water temperature is low, the glow plug will be energized for a long time and the preheating temperature range will be high.
A sufficient preheating effect can be obtained and the engine can be started smoothly.

(a) When the engine water temperature is high, the energization time to the glow plug is short and the preheating temperature range is low.
As a result, wasteful power consumption can be prevented, and a decrease in durability due to overheating of the glow plug can be prevented, and the life of the glow plug can be extended.

C) Due to the above a) and b), the preheating temperature range is changed according to the engine temperature, so it is possible to reliably control the temperature of the glow plug.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a glow plug temperature control device showing one embodiment of the present invention, Fig. 1A is its circuit diagram, Fig. 2 is a circuit diagram of the water temperature sensor portion of another embodiment, and Fig. 3 4 is a graph showing the resistance and temperature characteristics of the glow plug, FIG. 5 is a characteristic graph of the water temperature sensor, and FIG. 6 is a water temperature sensor output signal. The graph shown in FIG. 7 is a graph showing the temperature increase characteristics of the glow plug. FIG. 8 is a characteristic graph of another water temperature sensor, FIG. 9 is a graph showing the output signal of the water temperature sensor, and FIG. 10 is a graph showing the temperature increase characteristic of the glow plug. In the figure, 1... glow plug, 2, 4, 7, 8,
9, 10...Resistance, 3...Water temperature sensor, 5...Comparator,
6... Relay, 6a... Contact, 11... Energization control circuit,
B...Battery, T...Pulse oscillator.

Claims (1)

[Claims] 1. A temperature control device that changes the preheating temperature range of a glow plug according to the water temperature of an engine, which measures a change in resistance value due to a change in temperature of the glow plug and a change in resistance value of a water temperature sensor of the engine. a comparator that produces a high output when the measurement result meets a predetermined condition; a relay that closes a contact provided in the energizing circuit to the glow plug when the high output of the comparator is input; and a pulse oscillator that starts operating when an output is generated and causes the relay to operate so as to periodically open and close the contacts, and after the glow plug is heated to the preheating temperature range, the temperature of the glow plug is increased or decreased. and maintaining the temperature within the preheating temperature range.