JPS6155628B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a starting assist device that controls the temperature of a glow plug installed in a diesel engine to prevent overheating during afterglow during normal use of the glow plug.

Conventionally, diesel engines are equipped with a glow plug as a preheating device to ensure smooth starting. Preheating usually takes about 30 seconds, and when the plug reaches a predetermined temperature of about 900°C, power is stopped to the glow plug, the starter is closed, and the engine is started. In climates and regions with high temperatures, there are few problems as the engine can easily go into full condition and smoothly operate after starting, but in cold weather, especially in areas where it gets extremely cold,
Even if the engine is started after the plug has been preheated to a certain temperature, even if the engine explodes completely when idling immediately after starting, the coolant temperature is low and the combustion chamber temperature is low, so the viscosity of the oil is high and the gas cannot be compressed. Leakage inevitably delays combustion, resulting in incomplete combustion, producing white or black smoke, and furthermore, causing unfavorable environmental pollution, such as louder explosions, noise, and increased vibrations. For this reason, afterglow has been proposed in which the glow plug is heated even after the engine has been started. However, this type of glow plug uses a plug designed to reach a predetermined temperature in a predetermined time when energized without combustion, so as the combustion temperature increases and the rotation increases, the battery voltage increases and overvoltage is supplied. However, there was a problem of overheating and decreasing durability.
In addition, to prevent burnout of glow plugs, JP-A-Sho
No. 55-1463 is known, but it is not yet fully satisfactory in improving durability.

SUMMARY OF THE INVENTION Therefore, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a starting assist device that suppresses temperature with the main purpose of preventing a glow plug from becoming overheated. In other words, a circuit that energizes the glow plug intermittently depending on the battery voltage and a comparator timer circuit that is related to the engine temperature represented by the cooling water temperature are provided. The plug is controlled by a signal generated when the rotation speed reaches a constant speed, thereby suppressing excessive heating and improving the durability of the plug.

Next, embodiments of the present invention will be described based on the drawings. First, in FIG. 1 showing the outline, the input terminal of the preheating switch 12 and the relay 1 are connected to the anode of the battery 11.
The input end of No. 3 a contact 13a is connected. a
The output end of the contact 13a is connected to glow plug group 1, which is provided for each combustion chamber of an engine (not shown) and connected in parallel.
4, and a lamp 15 that indicates preheating of the glow plug.
The other end of each element is connected to ground. The relay 13 is connected to the output terminal of the preheating switch 12 and a switch element 16 consisting of transistors Q ₁ and Q ₂ . A preheating time setting timer circuit that energizes the glow plug for a certain period of time using a sensor signal that depends on the water temperature, and a multivibrator that energizes the glow plug by changing the charging current depending on the power battery voltage and changing the on/off time ratio. The output of the oscillation circuit made up of circuit a and gate circuit b is input to the OR circuit as an OR input.
When any of these inputs is received, the switch element 16 closes, activating the relay 13 and heating the glow plug group 14. Further, a timer circuit controls the gate circuit b so that afterglow occurs through the output of the oscillation circuit for a certain period of time based on the voltage of the sensor determined depending on the water temperature. In addition, the output of an AND circuit which receives as AND inputs the signal from the engine speed increase detection circuit 20 and the off-level signal resulting from the completion of manual operation of the starter switch 18 is used to start the operation of the timer circuit. It becomes a signal. Further, the on-level signal of the starter switch 18 that manually operates the starter motor 19 according to the display of the preheating indicator lamp 15 turns on the switch element 16 as another OR input of the OR circuit 17, and during this time the glow plug is continuously heated. It is something to do.

Next, each circuit will be explained in detail. The preheating time setting timer circuit is a resistor _R1 connected between the battery anode side, that is, the output terminal of the preheating switch 12, and ground.
The charging time is determined by the time constant of the capacitor C ₁ and the capacitor potential of the charging circuit is calculated using the amplifier A ₁
The output terminal of the amplifier is positively fed back to the + terminal of the operational amplifier via a resistor _R4 , and is input to one end of a comparator circuit. Also, the voltage division point P ₁ of the voltage setting circuit between the resistor R ₂ connected in series and the water temperature sensor R ₃ consisting of a thermistor that depends on the temperature of the engine cooling water.
Input the set voltage to the + terminal of the above operational amplifier.
Then, the output terminal of the operational amplifier _A1 is connected to the switch element 1 via the resistor _R5 and diode _D2 of the OR circuit 17.
6 is connected to the base of transistor _Q1 .
A diode _D1 is provided which discharges the charge of the capacitor _C1 when the preheating switch 12 is turned off.

The oscillation circuit includes a multivibrator circuit a and a gate circuit b. The multivibrator circuit has resistors R ₁₅ and R ₁₆ connected in series between the anode side of the power supply battery, that is, the output terminal of the preheating switch 12, and ground, and a water temperature sensor R ₂₂ consisting of a thermistor that depends on the temperature of the cooling water. It is connected to the point P ₂ and inputs the set voltage depending on the cooling water temperature to the + terminal of the operational amplifier A ₂ . The output terminal of the operational amplifier A ₂ is connected to the above-mentioned point P ₂ through a resistor R ₁₈ , and a Zener diode D ₄ and a resistor R ₁₇ are connected to the charging circuit of the capacitor C ₅ . Insert into one end of Widget _A2 . Also arithmetic amplifier
The output terminal of _A2 is connected to the switch element ₁₆ and the base of the transistor _Q1 via the resistor R19 of the gate circuit b, the transistor _Q4 , and the diode _D3 of the OR circuit 17. Gate circuit b blocks the output of the multivibrator circuit by transistor _Q4 controlled by a timer circuit to be described later.

The timer circuit has a resistor _R11 between the anode side of the power supply battery, that is, the output terminal of the preheating switch 12, and the ground.
and _R12 are connected in series, and the set voltage at the voltage division point _P3 is input to one end of the operational amplifier _A3 . Furthermore, the charging voltage of a charging circuit having a resistor R ₁₀ and a capacitor C ₃ connected in series is superimposed on the dividing point P ₃ via a diode D ₇ and is input to one end. In addition, at the + end of the arithmetic circuit amplifier A ₃ , there is a signal P ₁ determined in relation to the resistance value of the water temperature sensor R ₃ of the preheating time setting timer circuit.
The set voltage of the point is input. and operational amplifier
The output terminal of _A3 is positively fed back via diode _D9 and resistor _R23 to form a voltage comparator. Further, the output terminal of the operational amplifier _A3 is connected to the base of the transistor _Q4 of the gate circuit b via resistors _R13 and _R14 . Transistor Q ₄ is connected to the resistor R ₁₉
and diode _D3 are connected to the connection point _P4 to appropriately block the oscillation output of the oscillation circuit in connection with the operation of the timer circuit. Also, the output point _P5 of the timer circuit, which is the connection point between resistors _R13 and _R14 , is a diode.
It is connected to the output point (ie, the input point of the timer circuit) _P6 of an AND circuit consisting of a diode _D5 and a transistor _Q3 via D8 _, thereby forming a gate circuit b. When this point _P6 is at the "L" level, the output of the operational amplifier _A3 is blocked. Note that this circuit b is not necessarily necessary. Further, a resistor _R20 and a diode _D6 are provided to discharge the charge of the capacitor _C3 when the preheating switch 12 is turned off.

The AND circuit connects the transistor _Q3 to the connection point _P6 .
is connected, and the L terminal of the regulator is connected via diode _D5 . Further, the base of the transistor _Q3 is connected to the voltage dividing point _P7 of a voltage setting circuit of resistors _R7 and _R8 connected in series between the output terminal of the starter switch 18, that is, the anode of the battery, and the ground. On the other hand, the output end of the starter switch 18 is connected to a relay 21 that controls the starter motor 19.
It is also connected to the base of the transistor Q ₁ via the resistor R ₂₁ and the diode D ₁₀ of the OR circuit 17.

The operation of the control circuit having such a configuration will be explained with reference to FIG. When the preheating switch 12 is closed, the preheating time setting timer circuit
Capacitor C ₁ is charged with the time constant of R ₁ and capacitor C ₁ . The comparator outputs "H" level until the charging voltage exceeds the voltage set by resistors _R2 and _R3 . Therefore, during this time, the switch element 1 is connected via the resistor _R5 and the diode _D2 of the OR circuit 17.
6 transistors Q ₁ and Q ₂ are driven, the output is amplified, and the relay 13 is activated. This closes the a contact 13a, heating the glow plug group 14 and lighting the lamp 15 to indicate that heating is in progress.
The charging voltage of capacitor C ₁ gradually increases and resistor R ₂
When the voltage exceeds the voltage set by the water temperature sensor _R3 , whose resistance value changes depending on the temperature of the cooling water (in this case, the resistance value is high when it is low), the output of the comparator changes to the "L" level. As a result transistor
Q ₁ and Q ₂ become inactive, the relay 13 is opened, the glow plug group 14 is de-energized, and the lamp 15 is extinguished. During this period, the oscillation circuit is operating, but its output is blocked by gate circuit b controlled by the timer circuit. When the starter switch 18 is manually closed when preheating is completed, the transistors Q ₁ and Q ₂ are driven through the resistor R ₂₁ and the diode D ₁₀ , and the glow plug group 14 and the lamp 15 are similarly energized. On the other hand, when the starter switch 18 is closed, the relay 21 is activated and the starter motor 19 is rotated. However, before a complete explosion, the engine rotation is low, and even after a complete explosion, if the set rotation speed has not been reached, the rotation increase detection circuit 20
The terminal outputs "L" level. Also, while the starter switch 18 is closed, the transistor
The base current of _Q3 flows through _Q3 , and the _P6 point is grounded, so it is at the "L" level regardless of the output of the L terminal. Therefore, the resistance R ₁₄ and diode D ₈ at the base of transistor Q ₄ in gate circuit b
When the "L" level output of gate circuit b consisting of the following is added, current flows and conducts, so that the _P4 point is grounded. Therefore, during this time, the output of multivibrator circuit a is blocked. By the way, the rotation increase detection circuit 20 (in this case, the L terminal of the engine charging device) operates and outputs an output, and in this state, the starter switch is opened, so the transistor _Q3 becomes non-conductive, and the point _P6 becomes " Changes to H” level. Therefore, transistor _Q4 of gate circuit b is controlled not by the AND circuit but by the timer circuit. In other words, the output of the multivibrator circuit a is also controlled by the timer circuit. When the _P6 point becomes “H” level, the transistor
The base current of Q ₄ stops flowing and Q ₄ becomes non-conductive, opening gate circuit b. In addition, a calculation is made to amplify the amount of comparison between the _{voltage obtained by superimposing the charging voltage of resistor R 10 and} capacitor C ₃ on the set voltage of resistors R 11 and R ₁₂ , and the voltage determined depending on the water temperature of R ₂ and water temperature sensor R ₃ . amplifier
_A3 outputs an “H” level output when the voltage at point _P1 is higher than the added voltage at point _P3 , and the transistor
Q ₄ is non-conducting (P ₁ when the water temperature is high enough
The voltage at point P3 becomes lower than the voltage at point _P3 , resulting in an "L" level output, the output of the oscillation circuit is cut off, and the glow plug is no longer subjected to afterglow. ) Therefore, from this point on, the transistor _Q1 is driven by the intermittent output of the oscillation circuit. However, the resistance R ₁₀
Since the charging circuit for the capacitor _C3 starts charging at the same time as the _P6 point becomes "H" level, the charging voltage of the capacitor _C3 gradually increases. If this voltage is lower than the set voltage of resistors _R11 and _R12 , the resistor
It is charged with a time constant determined by _R10 and capacitor _C3 , but when it becomes higher than the set voltage, part of the charge is discharged through diode _D7 and resistor _R12 , and the charge voltage rises slowly. Therefore, the resistance R _{is 10}・
By appropriately selecting R ₁₁ and R ₁₂ , the timer time can be changed at any time. and resistance R ₂
When the voltage becomes higher than the voltage determined by the temperature sensor _R3 and the water temperature sensor R3 which depends on the cooling water temperature, the output of the operational amplifier _A3 changes to the "L" level output. As a result, the transistor _Q4 becomes conductive, the resistor _R19 is grounded, and the gate circuit b is closed, thereby blocking the output of the oscillation circuit.
The time until this inhibition can be increased depending on the cooling water temperature, and afterglow will occur. During this time, the glow plug is further controlled by the oscillator circuit so that it does not overheat. In the multivibrator circuit a, the operational amplifier
When A ₂ becomes “L” level, capacitor C ₅
The charge is discharged through resistor _R17 and Zener diode _D4 . And resistance R ₁₅ /R ₁₆ water temperature sensor
When the voltage drops below the first set voltage determined by R ₂₂ and R ₁₈ , the output terminal of the operational amplifier A ₂ changes to the “H” level, and at the same time, the discharge stops and the voltage reaches the “H” level via R ₁₈ . Since the output is fed back, a second set voltage higher than the first set voltage is generated. The capacitor _C5 is then charged again via the Zener diode _D4 and the resistor _R17 . When the charging voltage becomes equal to or higher than the second set voltage, the output of the operational amplifier _A2 changes to the "L" level after discharging, and the capacitor _C5 turns to discharging, and the set voltage becomes the first set voltage. becomes.
This operation is repeated to produce oscillation and intermittent output. Now, if the voltage of the battery is V ₁ (V), its charging current will be IC = (V ₁ - V _z )/R ₁₇ (however, V _z is the Zener voltage), and the charging current will be V since V _z・R ₁₇ is constant. It depends heavily on ₁ . Therefore, when the battery voltage decreases, the charging current decreases significantly, so the charging time becomes longer and the "H" level time becomes longer. On the other hand, as the battery voltage increases, the charging current increases and the charging time becomes shorter, so the "H" level time becomes shorter. Therefore, the output of the circuit also depends on the battery voltage. The discharge current is id=(V ₁ −V _rf )/R ₁₇ (where V _rf
is the forward voltage drop of the Zener diode _D4 ) _V1
≫V _rf , so it hardly changes depending on the voltage. In this way, the heating time is adjusted in relation to the battery voltage, and also by the set voltage determined by the water temperature sensor depending on the water temperature.

As described in detail above, a means is provided to control the energization of the plug in relation to the constant independent rotation speed of the engine, and even after the internal combustion engine has started, the temperature of the cooling water is detected and the energization control is performed depending on this temperature. In addition, we have also taken into account energization control that depends on the battery voltage, so the glow plug does not overheat in the afterglow.
Since it is possible to maintain a constant temperature, it allows reliable and effective startup preparation with simple operations. Therefore, it is possible to improve the durability and reliability of the plug, and also to prevent the generation of black smoke, white smoke, etc. when the combustion condition is unstable immediately after starting, making it an effective means for pollution control. It is something that you have.

[Brief explanation of the drawing]

FIG. 1 is a temperature control block diagram of a glow plug according to the present invention, FIG. 2 is a specific circuit diagram of the control, and FIG. 3 is an explanatory diagram of the operating state of each part. 11...Battery, 12...Preheating switch, 14...
... Glow plug group, 18 ... Starter switch, A ₁ , A ₂ , A ₃ ... Arithmetic amplifier, R ₃ , R ₂₂ ... Water temperature sensor.

Claims (1)

[Claims] 1. A glow plug 14, a power battery 11, switch means 13, 16 for connecting the glow plug 14 and the power battery 11, a preheating indicator 15 for indicating preheating of the glow plug 14, and a starter motor. In a starting assist device for a diesel engine that includes an actuation switch 18 and performs a no-load preparatory operation before starting load operation, the sensor is dependent on water temperature.
A preheating time setting timer 1 that preheats the glow plug 14 for a certain period of time using the _R3 signal and controls the preheating indicator 15, and a preheating time setting timer 1 that controls the preheating indicator 15 and a charging current that changes the on/off time ratio depending on the power supply battery voltage. None An oscillation circuit consisting of a multivibrator circuit a that energizes the glow plug and a gate circuit b provided on the output side thereof, and the output of the preheating time setting timer and the output of the oscillation circuit are input. When said switch means 13,
16, a rotation increase detection circuit 20 consisting of an L terminal, and the rotation increase detection circuit 20.
The rotation increase level signal of the starter motor operating switch 18 and the off level signal of the starter motor operation switch 18 are input to two AND circuits, the output of which controls the gate circuit b, and the operation is started by the output of the AND circuit and depends on the water temperature. and a timer circuit that controls the gate circuit b with a cut level signal to intermittently afterglow for a predetermined time in order to block the output of the oscillation circuit after a predetermined time has elapsed based on the voltage of the sensor _R3 determined by the voltage. , a starting assist device for a diesel engine, characterized in that the glow plug is automatically energized for a predetermined period of time even during preparatory operation of the engine. 2. A series circuit of a water temperature sensor and a resistor for obtaining a water temperature-dependent reference voltage that should be input to one of the voltage comparators and the above-mentioned comparator in the time-limited timer circuit, and a resistor for obtaining the voltage that should be input to the other of the above-mentioned comparators. and an RC charging circuit in which the charging voltage of the capacitor is applied to the series connection point of the series circuit of the resistors through a diode, and when the other input voltage is equal to or higher than the reference voltage value, the comparator The starting assist device for a diesel engine according to claim 1, wherein the output level of the diesel engine is inverted.