JPH064063Y2 - Glow plug preheating controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a device for controlling preheating of a glow plug of a diesel engine.

(Prior Art) In a diesel engine, the glow plug is started in a state where the cylinder chamber is warmed, but the glow plug is rapidly preheated in order to shorten the preheating time. One of the control devices for rapid preheating of glow plugs is one that uses a timer circuit having a capacitor and a comparator.
That is, one input terminal of the comparator is supplied with a constant reference voltage made by a Zener diode, and the other input terminal is supplied with the voltage of the capacitor.
The capacitor is charged when the ignition key switch is closed. Then, when the charging voltage of this capacitor exceeds the reference voltage, the output level of the comparator changes and activates the switch means such as a transistor to stop the rapid preheating of the glow plug and an indicator for displaying the rapid preheating state. The lamp is off. The driver confirms that the glow plug has been preheated sufficiently by turning off the indicator lamp, and then turns the starter motor.

However, in the above control device, the driver tries to rotate the starter motor after confirming that the indicator lamp has been turned off, that is, after the temperature of the glow plug has passed the peak. was there.

Further, in the above control device, the preheating completion temperature of the glow plug becomes substantially constant regardless of the temperature of the engine itself. Therefore, when the temperature of the engine itself is high, the preheating temperature of the glow plug is low, but the preheating is performed for an unnecessarily long time, which wastes power and requires a waiting time for the driver. There was a drawback of making it longer than that. Further, when the temperature of the engine itself is low, there is a drawback in that preheating is insufficient although it is necessary to raise the preheating temperature of the glow plug.

Therefore, a glow plug preheating control device described in JP-B-60-53798 has been developed. With this device,
It has a reference voltage generating circuit composed of three resistors, a first resistor, a second resistor and a third resistor, and a voltage between the first resistor and the second resistor is the first reference voltage. The voltage between them is the second reference voltage. The second reference voltage is higher than the first reference voltage by the voltage drop of the second resistor.

The device of this publication has two comparators, a first comparator and a second comparator. The first reference voltage is input to one input terminal of the first comparator, and the voltage of the capacitor of the timer circuit is input to the other input terminal. Switch means for opening and closing the power supply circuit of the indicator lamp is connected to the output terminal of the first comparator.
When the charging voltage of the capacitor exceeds the first reference voltage and the output level of the first comparator changes, the indicator lamp is turned off. The second reference voltage is input to one input terminal of the second comparator, and the voltage of the capacitor is input to the other input terminal. To the output terminal of the second comparator, switch means for opening and closing the power supply circuit for rapid preheating of the glow plug is connected, and the switch means is such that the voltage of the capacitor exceeds the second reference voltage. Two
The rapid preheating of the glow plug is stopped when the output level of the comparator changes.

In the device of the above publication, the first reference voltage is lower than the second reference voltage, so that the indicator lamp is turned off earlier than the rapid preheating stop of the glow plug by a fixed time. Therefore, when the driver turns the starter motor after confirming that the indicator lamp is off, the temperature of the glow plug has almost reached the maximum value, and the starter motor can be turned at the optimum timing. Start is performed.

Further, in the device of the above publication, a water temperature sensor consisting of a negative characteristic thermistor whose resistance value changes in response to the engine cooling water temperature is connected in parallel with the first resistance, and when the engine temperature is low, the indicator lamp lights up. Both the time and the rapid preheating time of the glow plug are lengthened to preheat the glow plug to a required temperature, and when the engine temperature is high, the preheating time is shortened to prevent wasteful preheating.

(Problems to be Solved by the Invention) In the control device of the above publication, the change in the first and second reference voltages based on the change in the resistance value of the water temperature sensor becomes too high when the engine cooling water temperature is equal to or lower than a predetermined temperature. And
There is a drawback that the rapid preheating time of the glow plug becomes longer than necessary and the life of the glow plug is shortened.

Incidentally, JP-A-60-101280 and JP-A-61-1
In the control device of JP-A-207879, the reference voltage used for controlling the indicator lamp is limited by the limiter means composed of a transistor.
More specifically, the voltage between two resistors connected in series is used as a reference voltage, a transistor is connected in parallel with one resistor, and the voltage of the water temperature sensor is supplied to the base of this transistor to control the current of the transistor. By doing
The reference voltage is changed according to the engine cooling water temperature. Then, in the comparator, when the charging voltage of the capacitor exceeds the reference voltage, the switch means is operated to turn off the indicator lamp. In this configuration, when the engine cooling water temperature decreases to a predetermined temperature, the voltage of the water temperature sensor increases and the transistor is turned off. Therefore, the reference voltage is limited with the voltage divided by the above two resistors as the upper limit value. . Therefore, even if the engine coolant temperature is lower than the predetermined temperature, the lighting time of the indicator lamp will not be lengthened accordingly, and the starter motor operation will be accelerated accordingly, and the glow plug preheating time will be substantially reduced. It can be shortened.

However, in these publications, the preheating of the glow plug is controlled based on the change in the resistance value of the glow plug, and since this control circuit and the control circuit for the above-described indicator lamp are independent, the correspondence relationship is It had the drawback of becoming unstable. Further, since the limiter circuit uses a transistor, there is a drawback that the indicator lamp lighting time varies due to the influence of temperature change.

(Means for Solving Problems) The present invention has been made to solve the above problems.
The gist of the invention is to include (a) a detection voltage generation circuit that outputs a voltage at one end of a water temperature sensor whose resistance value changes in response to the temperature of engine cooling water as a detection voltage, and (b) an operational amplifier and a diode. By connecting the anode side of the diode to the inverting input terminal of the operational amplifier and the cathode side to the output terminal of the operational amplifier, the operational amplifier is negatively feedback-connected through the diode and connected to the non-inverting input terminal of this operational amplifier. A limiter circuit for inputting the detection voltage and (c) first, second, and third resistors are connected in series in order, and a voltage between the first resistor and the second resistor is output as a first reference voltage, A voltage between the second resistor and the third resistor is output as a second reference voltage, and the limiter circuit is connected to one of the first and second resistors and between the second and third resistors. Die A reference voltage generating circuit connected to the anode of the battery, (d) a timer circuit that is formed by connecting a resistor and a capacitor in series, and starts charging or discharging when the ignition key switch is closed; 1
A reference voltage is input to one input terminal, a voltage of the capacitor of the timer circuit is input to the other input terminal, and a first comparator for comparing the two and (f) the second reference voltage is input to one. A second comparator for inputting the voltage of the capacitor of the timer circuit to the other input terminal for comparing the two, and (g) the output level of the first comparator and the second comparator. Responding to the output of the comparator that changes faster, closing the indicator lamp power supply circuit when the ignition key switch is closed, and opening the power supply circuit when the output level of the comparator changes, indicator lamp control switch means, (H) In response to the output of one of the first and second comparators whose output level changes slowly, when the ignition key switch is closed, the glow plug is quickly predicted. Close the use feeder circuit is in the glow plug preheating control device being characterized in that a glow plug control switch means for opening the feed circuit when the output level change of the comparator.

(Operation) Since the reference voltage generation circuit sends the first and second reference voltages to the first and second comparators, and the timer circuit sends the capacitor voltage to the first and second comparators, For the preheating control of the glow plug and the indicator lamp control, the reference voltage generating circuit and the timer circuit can be used in common, and the circuit configuration can be simplified. Further, a stable correspondence relationship can be secured for the control between the glow plug and the indicator lamp, and the indicator lamp can be turned off and the rapid preheating stop of the glow plug can be executed after a certain period of time, and a reliable start can be performed.

Since the first and second reference voltages change in response to the terminal side voltage of the water temperature sensor that detects the engine cooling water temperature,
It is possible to optimally control the rapid preheating time of the glow plug and the lighting time of the indicator lamp according to the engine coolant temperature. Moreover, the limiter circuit allows the first,
Since the second reference voltage is controlled, it is possible to prevent the glow plug from being preheated longer than necessary when the temperature of the cooling water of the engine is lower than the predetermined temperature, and it is possible to extend the life of the glow plug. Further, since the limiter circuit is used for both the rapid preheating control of the glow plug and the lighting control of the indicator lamp, the circuit configuration is simplified and the stable correspondence between the two controls is not impaired. .

The limiter circuit is composed of an operational amplifier and a diode. When the diode is on, the operational amplifier acts as a voltage follower, and due to its imaginary short circuit,
The detection voltage can be made equal to the first reference voltage or the second reference voltage without being affected by the voltage drop across the diode. Therefore, even if the voltage drop of the diode fluctuates due to the temperature change, the situation such that the first and second reference voltages fluctuate does not occur, and consequently the fluctuation K of the preheating time of the glow plug or the lighting time of the indicator lamp K. Never invite.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings from FIG. 1 to FIG. In FIG. 1, reference numeral 1 is a battery as a power source, and a glow plug 3 ...
A power supply circuit 2 for rapid preheating is connected. The power supply circuit 2 is provided with a normally open contact 80a of a relay 80 which will be described later. A power source side control bus 5 is connected to the positive electrode of the battery 1 via an ignition key switch 4, and a ground side control bus 6 is connected to the negative electrode.

One end of a water temperature sensor 11 composed of a negative characteristic thermistor whose resistance value changes according to the engine cooling water temperature is connected to the grounding side control bus 6. The other end of the water temperature sensor 11 has resistors 12 and 13 connected thereto. It is connected to the power supply side control bus 5 via. Further, a resistor 14 is interposed between the resistance point P ₀ between the resistors 12 and 13 and the ground side control bus 6. The water temperature sensor 11 and the resistors 12 to 14 form a detection voltage generation circuit 10. The detection voltage generation circuit 10 outputs the voltage at the connection point P ₀ as the detection voltage V ₀ . The resistors 12 to 14 play a role of adjusting the correspondence between the engine coolant temperature and the detected voltage V ₀ .

The detection voltage V ₀ from the detection voltage generation circuit 10 is input to the non-inverting input terminal of the operational amplifier 21. The output terminal and the inverting input terminal of the operational amplifier 21 are negatively feedback-connected via the diode 22. The diode 22 has a cathode connected to the output terminal of the operational amplifier 21 and an anode connected to the inverting input terminal of the operational amplifier 21. The operational amplifier 21 and the diode 22 form a limiter circuit 20.

Between the control buses 5 and 6, there is interposed a reference voltage generation circuit 30 in which first, second and third resistors 31, 32 and 33 are connected in series in order from the ground side. The anode of the diode 22 is connected between the first resistor 31 and the second resistor 32. The voltage V _{1 at the} connection point P ₁ becomes a first reference voltage described later. In addition, the second resistor 32
As for the voltage of the connection point P ₂ between the third resistor 33 and the third resistor 33, V ₂ becomes the second reference voltage described later.

The first reference voltage V ₁ is input to the non-inverting input terminal of the first comparator 41, and the second reference voltage V ₂ is input to the non-inverting input terminal of the second comparator 42. The voltage Vc from the timer circuit 50 is input to each inverting input terminal of the first comparator 41 and the second comparator 42.

The timer circuit 50 is formed by connecting a resistor 51 and a capacitor 52 in series, the resistor 51 is connected to the power supply side control bus 5 and the capacitor 52 is connected to the ground side control bus 6. Then, the voltage Vc of the capacitor 52 becomes equal to that of the comparator 4
1, 42 are input.

The output terminal of the first comparator 41 is connected to the base of the first transistor 61 via the resistor 63. The first transistor 61 is a switch means for opening and closing the power supply circuit 71 of the indicator lamp 70, the collector of which is connected to the power source side control bus 5 through the resistor 72 and the indicator lamp 70, and the emitter of which is for grounding. It is connected to the control bus 6.

The output terminal of the second comparator 42 is connected to the base of the second transistor 62 via the resistor 64. Between the collector of the second transistor 62 and the power source side control bus 5, the relay 80 for actuating the normally open contact 80a is interposed. The emitter of the second transistor 62 is connected to the ground side control bus 6. Therefore, the second transistor 62 plays a role as a switch means for opening and closing the power supply circuit 2 for rapid heating of the glow plug 3.

In the above configuration, turn the ignition key switch 4 to O
When set to N, the detection voltage V ₀ is generated in the detection voltage generation circuit 10. By the way, the resistance value of the water temperature sensor 11 becomes higher as the engine cooling water temperature becomes lower and becomes lower as the engine cooling water temperature becomes higher, as shown in FIG. Therefore, the detection voltage V
₀ represents a continuous curve consisting of a solid line and a broken line in FIG. 3 corresponding to the engine cooling water temperature.

As shown in FIG. 3, in the region where the engine cooling water is higher than the predetermined temperature T ₀ , the diode 22 is in the conducting state, the operational amplifier 21 functions as a voltage follower, and the imaginary short circuit causes the first comparator 41 to receive the first voltage. 1 The reference voltage V ₁ is made equal to the detection voltage V ₀ . Therefore, even if the drop voltage of the diode 22 changes due to the change of the ambient temperature,
This change in voltage drop without affecting the first reference voltages V _1, the first reference voltage V ₁ was stable to ambient temperature.

On the other hand, the second reference voltage V ₂ to the second comparator 42 is obtained by the following equation.

V ₂ = (R ₃₂ · Vb + R ₃₃ · V ₁ ) / (R ₃₂ + R ₃₃ ) ...
(1) However, in the above formula (1), Vb is the voltage of the battery 1, and R ₃₂ and R ₃₃ are the resistance values of the resistors 32 and 33. The second reference voltage V ₂ higher than the first reference voltage V _1, shows a change corresponding to the first reference voltage V _1. This second reference voltage V ₂ is also stable with respect to the ambient temperature.

When the engine cooling water is below the predetermined temperature T ₀ , the detected voltage V ₀ becomes higher than the voltage V ₁ max of the following equation, and the diode 2
Since 2 is in the non-conducting state, the first reference voltage V ₁ does not follow the detection voltage V ₀ and is limited to V ₁ max.

V ₁ max = Vb · R ₃₁ / (R ₃₁ + R ₃₂ + R ₃₃ ) ... (2) However, in the above formula (2), R ₃₁ is the resistance value of the first resistor 31. Similarly, when the engine cooling water temperature is T ₀ or lower as described above, the second reference voltage V ₂ is limited to V ₂ max represented by the following equation.

V ₂ max = (R ₃₂ · Vb + R ₃₃ · V ₁ max) / (R ₃₂ +
R ₃₃ ) = Vb · (R ₃₁ + R ₃₂ ) / (R ₃₁ + R ₃₂ + R ₃₃ )
(3) On the other hand, when the ignition key switch 4 is turned on, the charging of the capacitor 52 is started, and this charging voltage Vc is input to the inverting input terminals of the comparators 41 and 42, and the comparators 41 and 42 use the above-described reference voltage. The voltages are compared with V ₁ and V ₂ .

In the charging process, the charging voltage Vc is the first reference voltage V
When less than _1, the indicator lamp 70 from the output of the first comparator 41 is turned ON first transistor 61 has the H level is illuminated. Then, when the charging voltage Vc exceeds the first reference voltage V ₁ , the first comparator 41
Output goes low and the first transistor 61 turns off.
It becomes F, and the indicator lamp 70 is turned off. The driver turns the starter motor after confirming that the light is off.

Similarly, when the charging voltage Vc is lower than the second reference voltage V ₂ , the output of the second comparator 42 is at the H level and the second transistor 62 is turned on, so that the relay 80 is excited and its normal state is maintained. The open contact 80a is closed, and the glow plugs 3 are energized. As a result, the glow plugs 3 are rapidly preheated. Then, when the charging voltage Vc exceeds the second reference voltage V ₂ , in other words, when the glow plugs 3 reach the desired temperature, the output of the second comparator 42 becomes the L level and the second transistor 62. Is turned off, the power supply circuit 2 for rapid preheating of the glow plugs 3 ... Is opened, and the rapid preheating is stopped.

As described above, since the first reference voltage V ₁ is lower than the second reference voltage V ₂ , turning off the indicator lamp 70 is earlier than stopping the energization of the glow plugs 3. This time difference Δt is constant. That is, O of the ignition key switch 4
Assuming that the time from the turning on of the indicator lamp 70 by N to the turning off thereof is t ₁ and the rapid preheating time of the glow plugs 3 is t ₂ , these t ₁ and t ₂ are expressed by the following equation.

_{t 1 = - (R 51 ×} C 52) × 1n (1-V 1 / Vb) ...
_{(4) t 2 = - (} R 51 × C 52) × 1n (1-V 2 / Vb) ...
(5) However, in the above equations (4) and (5), R ₅₁ and C ₅₂ are the resistance value of the resistor 51 and the capacitance of the capacitor 52, respectively. Therefore, the time difference Δt can be expressed by the following equation.

Δt = t ₂ −t ₁ = (R ₅₁ × C ₅₂ ) × 1 nR ₃₃ / (R ₃₂ + R ₃₃ ) ...
(6) As is apparent from the equation (6), the time difference Δt is a constant R ₅₁ ,
Since it is determined only by C ₅₂ , R ₃₃ , R ₃₂ , and R ₃₃ ,
It is constant. In this way, the indicator lamp 70
In order to allow the driver to turn off the light early after allowing for the delay time from when the driver confirms that the light has been turned off until the starter is activated, the glow plugs 3 ...
When the maximum temperature is reached, the starter motor can be turned. Moreover, since the time difference Δt is always constant, stable starting can be performed.

When the engine cooling water temperature is equal to or higher than the predetermined temperature T ₀ , the first reference voltage V ₁ and the second reference voltage V ₂ are the detection voltage V _0.
Therefore, the glow plugs 3 can be rapidly preheated and the indicator lamp 70 can be turned on for an optimum time in accordance with the engine cooling water temperature.

Further, the second reference voltage V ₂ is limited to a constant voltage V ₂ max when the engine cooling water temperature is lower than T ₀ .
It is possible to limit the energizing time to the glow plug 3 ...
As a result, it is possible to prevent the glow plugs 3 ... from entering the rapid preheating state for an unnecessarily long time, and it is possible to extend the life of the glow plugs 3. At this time, the first reference voltage V ₁
Is also limited to a constant voltage V ₁ max, the time difference between turning off the indicator lamp 70 and stopping the rapid preheating of the glow plugs 3 can be kept constant.

Furthermore, since the first reference voltage V ₁ and the second reference voltage V ₂ can be stable with respect to the ambient temperature, the rapid preheating time of the glow plugs 3 ... And the lighting time of the indicator lamp 70 are also stable with respect to the ambient temperature.

In the detection voltage generation circuit 10, when the resistance 12 is very small or omitted, the resistance value of the water temperature sensor 11 becomes very small when the engine cooling water temperature is very high, and the detection voltage V ₀ becomes It can approach zero. In this case, the imaginary short circuit is not established, and the first reference voltage V ₁ becomes higher than the detection voltage V ₀ by the voltage drop of the diode 22. As a result, since the indicator lamp 70 lights up for a short time, it is possible to confirm whether the indicator lamp 70 is disconnected or whether the entire control device is operating normally. .

The present invention is not limited to the above-mentioned embodiment and various modes are possible. For example, the anode of the diode 22 of the limiter circuit 20 is connected to the connection point P ₂ in FIG. 1, and when the engine cooling water temperature is equal to or lower than the predetermined temperature T ₀ , the second reference voltage V ₂ becomes equal to the detection voltage V _0. You may.

Also, the timer circuit turns on the ignition key switch.
The capacitor may start discharging when N is reached. In this case, since the output level of the second comparator changes faster than that of the first comparator, the second comparator is used for indicator lamp control, and the first comparator is used for rapid preheat control of the glow plug. To use.

In the above embodiment, the power supply circuit for rapid preheating of the glow plug and the circuit for controlling the opening / closing of the glow plug are shown.However, the glow plug power supply circuit for keeping warm, pre-glow, rotation of the starter motor, etc. Needless to say, a circuit for is added if necessary.

(Effect of the Invention) As described above, in the present invention, the reference voltage generating circuit,
The timer circuit, the limiter circuit, and the detection voltage generating circuit are commonly used for the rapid preheating control of the glow plug and the indicator lamp control, so that the circuit configuration can be simplified.

A stable correspondence can be secured between both controls, and the indicator lamp can be turned off and the rapid preheating of the glow plug can be stopped after a certain period of time, and a reliable start can be performed.

The glow plug can be rapidly preheated and the indicator lamp can be turned on for an optimum time period in accordance with the engine cooling water temperature.

When the engine cooling water is below a predetermined temperature, the preheat time can be limited to extend the life of the glow plug.

Since the operational amplifier and the diode are used in the limiter circuit, the rapid preheating time of the glow plug and the lighting time of the indicator lamp can be stabilized against the ambient temperature.

[Brief description of drawings]

FIGS. 1 to 4 show an embodiment of the present invention. FIG. 1 is a circuit diagram of a glow plug preheating control device, FIG. 2 is a diagram showing temperature characteristics of a water temperature sensor, and FIG. FIG. 3 is a diagram showing the relationship between the detection voltage, the first reference voltage, the second reference voltage and the engine cooling water temperature, and FIG. 4 is a diagram showing the lighting time of the indicator lamp, the rapid preheating time of the glow plug and the engine cooling water temperature. It is a figure which shows a relationship. 1 ... Power source (battery), 2 ... Power supply circuit for rapid preheating, 3 ...
Glow plug, 4 ... Ignition key switch, 10
... detection voltage generation circuit, 11 ... water temperature sensor, 20 ... limiter circuit, 21 ... operational amplifier, 22 ... diode, 30 ...
Reference voltage generating circuit, 31 ... First resistance, 32 ... Second resistance,
33 ... Third resistance, 41 ... First comparator, 42 ... Second comparator, 50 ... Timer circuit, 52 ... Capacitor, 61 ... Indicator lamp control switch means (transistor), 62 ... Glow plug control switch means ( Transistor), 70 ... Indicator lamp.

Claims (1)

[Scope of utility model registration request] 1. A detection voltage generating circuit for outputting as a detection voltage a voltage at one end of a water temperature sensor whose resistance value changes in response to the temperature of cooling water for an engine; and (b) an operational amplifier and a diode. By connecting the anode side of the diode to the inverting input terminal of the operational amplifier and the cathode side to the output terminal of the operational amplifier, the operational amplifier is negatively feedback-connected through the diode. A limiter circuit for inputting the above detection voltage to (1), and (c) first, second, and third resistors are connected in series in order, and the first
The voltage between the resistor and the second resistor is output as the first reference voltage, the voltage between the second resistor and the third resistor is output as the second reference voltage, and the voltage between the first and second resistors and Second, third
The reference voltage generating circuit that connects the anode of the diode of the limiter circuit to either one of the resistors of (1) and (d) the resistor and the capacitor are connected in series, and when the ignition key switch is closed, charging or A timer circuit that starts discharging, and (e) a first comparator that inputs the first reference voltage to one input terminal and the voltage of the capacitor of the timer circuit to the other input terminal and compares the two. And (f) a second comparator that inputs the second reference voltage to one input terminal and the voltage of the capacitor of the timer circuit to the other input terminal, and compares the two, and (g) the above The indicator lamp power supply circuit is closed when the ignition key switch is closed in response to the output of the one of the first comparator and the second comparator whose output level changes faster. The indicator lamp control switch means for opening this power supply circuit when the output level of the comparator changes, and (h) the output of the one of the first and second comparators whose output level changes slowly. In response, the glow plug control switch means for closing the power supply circuit for rapid preheating of the glow plug when the ignition key switch is closed and for opening the power supply circuit when the output level of the comparator changes. Plug preheat control device.