JPS60135670A - Glow plug control device - Google Patents

Abstract

PURPOSE:To protect the glow plug by a method wherein signals are received from a glow plug temperature signal generating means and an engine starting signal generating means to stop the conduction of the glow plug upon a specified condition. CONSTITUTION:The glow plugs 7-10 are conducted through a stable preheating resistor 5 after the engine is started. When the engine is started and a detecting switch 13 is opened, a transistor 132 is put ON and the transistor 131 is put OFF. The signals S1, S6 of a voltage comparing circuit 16 and a logical integration circuit 133 become high level when the temperature of the glow plug is higher than an upper limit temperature (900 deg.C). Accordingly, the transistor 120 is put ON and the transistors 121, 122 are put OFF to disenergize a relay coil 4a. According to this method, the temperature of the glow plug may be prevented from becoming higher than the upper limit temperature (900 deg.C) and the glow plug may be protected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine preheating control device using a glow plug for a diesel engine or the like.

〔background〕

Published Patent Publication No. 1297, 1983, which the present applicant previously applied for.
In No. 62, after the engine starts, the glow plug is kept at a high temperature only by a sub-relay that supplies power from the power supply to the glow plug via a stable preheating resistor, so it receives heat from the engine until it is shut off due to engine water temperature or a timer. Since power is supplied to the glow plug, there is a problem in that the glow plug deteriorates significantly.

[Purpose of the invention]

The present invention aims to solve the above problems.

〔Example〕

The present invention will be described below according to embodiments shown in the accompanying drawings.

In FIG. 1, 1 is an engine key switch, which has an ignition contact 1a and a starter contact 1b. 2 is an on-vehicle DC power supply, 3.4 is a relay contact, and 3a and 4a are their relay coils. 5 is a stable preheating resistor connected in series with the relay contact 4. Reference numeral 6 denotes a detection resistor having a minute resistance value, which causes a voltage drop proportional to the passing current. 7.8
．． 9.10 is a glow plug consisting of a heating element having a positive and substantially constant temperature coefficient of resistance, and is installed in the sub-combustion chamber of a diesel engine. When the relay coil 3a is energized, the relay contact 3 closes and the glow plugs 7 to 10 are directly energized from the power source 2 via the detection resistor 6. This energization is called a first energization state. Conversely, when only the relay coil 4a is energized without the relay coil 3a being energized, only the relay contact 4 is closed and the glow plugs 7 to IO are energized via the stable preheating resistor 5 and the detection resistor 6. This energized state is referred to as a second energized state. Note that in the first energized state, whether or not the second energized state is established is irrelevant.

11 is a lamp 1.12 indicating permission to start cranking
13 is a temperature detector consisting of a thermistor attached to the engine cooling water jacket, and 13 is a known device that opens when the neutral point voltage of the three-phase alternating current generator for charging the on-board DC power supply 2 rises to a predetermined level when the engine starts. This is the start detection switch.

Reference numeral 14 denotes a control circuit, which is composed of each circuit described below. 15 is a differential amplifier circuit that amplifies the voltage drop across the detection resistor 6, and 16 is a voltage comparison circuit that compares the amplified voltage with a reference voltage. These circuits generate a control signal S which becomes a low level when the voltage drop occurring across the detection resistor 6 is greater than the upper limit determined by the comparison reference voltage of the voltage comparison circuit 16 and the hysteresis, and becomes a high level when it is smaller than the lower limit.

Reference numeral 18 denotes a start response circuit, which generates a control signal S2 which is at a high level when the start detection switch 13 is opened due to engine start, and becomes a closed frontage level (open level) before starting.

Reference numeral 19 denotes a time limit circuit consisting of an RC time constant circuit and a voltage comparator circuit.
A control signal S3 is generated which remains at the frontage level until a predetermined time period determined by the resistance value of the thermistor (thermistor) has elapsed, and which becomes high level after that time elapses. The time limit for this control signal to reverse from the low level to the high level is determined by the temperature sensor 1.
The smaller the resistance value of 2 (higher the temperature), the shorter it will be.

2O is a voltage comparison circuit, which includes a comparison element 11 made of an integrated circuit.
7, and includes one comparator of the temperature sensor 12 (
When the resistance value of the thermistor is smaller than a value corresponding to a set temperature, for example, 40° C., a control signal S4 is generated which becomes a high level and becomes a low level (open level) when it is larger.

21 and 22 are power amplifier circuits each including several transistors, and each front stage transistor receives the above-mentioned control signals s, -.
s3 is input, and the relay coils 3a and 4a are energized by the last stage transistor.

23 is a time circuit, which includes the other comparator of the comparator element 117 made of an integrated circuit, and when the resistance value of the temperature detector 12 is a small value indicating a temperature higher than 40° C., it will wait for several hundred milliseconds. If the value is larger than that, the control signal S5 which becomes low level for only a few seconds is sent to the key switch 1.
This occurs after the ignition contact 1a is turned on. 24
is a power amplification circuit that amplifies the power of this control signal S5 to turn on and off the display lamp 11.

30 is a stop control circuit, and 132 is a transistor that is turned on when the start detection switch 13 is opened when the engine is started and the control signal s2 is at a high level.

Reference numeral 133 is an AND circuit which generates a control signal S6 which is at a high level only when the start detection signal s2 is at a high level and the output signal S1 of the voltage comparison circuit 16 is at a high level, and which is at a low level at other times.

The details of the circuit configuration will be explained below along with the operation of the device. First, the engine is not warmed up enough and the coolant temperature is 40 degrees Celsius.
In the following cases, when the key switch 1 is turned on to the ignition contact 1a, the output of the differential amplifier 111 is at a low potential in the differential amplifier circuit 15, and the voltage is divided by the resistors 109 and 110 in the voltage comparator circuit 16. Since it is lower than the input voltage of the comparator 112, the output of the comparator 112, that is, the control signal St, is at a low level. Also,
Since the engine has not yet been started, the control signals S2 and S3 are at low level. Therefore, in the amplifier circuit 21, the transistor 114 is turned off and the transistors 115 and 116 are turned on.
The relay coil 3a is energized, the relay contact 3 is closed, and the above-mentioned first energized state is realized. Note that since the control signals s3 and s6 are at low level at this time, the transistor 120 is turned off in the amplifier circuit 22, and the transistor 121 is turned off.
．． 122 is turned on, the relay coil 4a is also energized and the relay contact 4 is closed. However, the current to the glow plugs 7-10 flows exclusively through the relay contacts 3 and substantially the first
Valid only when energized.

As a result, the glow plugs 7 to 1O are rapidly energized by the large current, their own resistance increases, and the current passing through the detection resistor 6 decreases. Then, set the resistance value of the detection resistor to R
s, the resistance value of one glow plug 7~1° is R,,
Resistors 101, 102, 103 in the differential amplifier circuit 15
．． The resistance values of 104 are R101%RI02 and R1, respectively.
03, RI04, if the temperature of the glow plug increases beyond the bridge equilibrium point of Rs/ (Ro/4) = RIo +/R+ 02 (RS % RQ < lΩ), the value of RQ will increase. differential amplifier 111
The output is the resistance value R103 of resistor 103, 104, RI0
Comparator circuit 1 is amplified by the resistance ratio RI04/RI03 of 4.
6 and is compared with a reference voltage divided by a resistor 1.9 and a resistor 110. When the reference voltage is reached, the output of the comparator 112, that is, the control signal S- is inverted to high level, and simultaneously the two transistors 131 are turned on. A resistor 130 is connected to provide hysteresis. Then, one of the control signals for the transistor 114 becomes high level, so it is turned on, the subsequent transistors 115 and 116 are turned off, and the main relay 3 is opened.

When the main relay 3 opens, the detection resistor 6 and the glow plugs 7 to 10 are energized at a low voltage via the stable preheating resistor 5 (second energized state), and the temperature of the glow plugs 7 to 1O decreases. Therefore, the resistance value Ro of the glow plug decreases, and the output of the differential amplifier 111 decreases, and when it reaches the hysteresis set point of the comparator 112, the output of the differential amplifier 111 decreases.
The output of 12 is inverted to a low level, and the main relay 3 is energized again. Thereafter, the temperature control is repeated as described above, and the temperature of the glow plug is set at an upper limit of 900°C and a lower limit of 700°C.
Controlled at °C. This temperature control is continued after the key switch 1 is turned on until the end of cranking.

By the way, after turning on the key switch 1, as mentioned above, the control
Since the signal S4 is at low level (open level),
In the time limit circuit 23, the time limit capacitor 123 has a resistor 1
24. Then, the control signal S5 is at a low level immediately after the key switch 1 is turned on, the comparison input voltage (terminal 7) of the comparator (comparison element 117) gradually rises, and the transistor 126 is turned off for about 3.5 seconds. The transistor 127 is turned on and the display lamp 11 is turned on. This lighting time is set to coincide with the time during which the glow plugs 7 to 10 are heated to 700°C to 900°C by the temperature control described above when the automobile is operated at a general environmental temperature. If the indicator lamp 11 goes out after this time has elapsed, this means that the glow plug is generating heat before cranking is possible.

When the driver turns on the key switch 1 to the starter contact 1b, a starter motor (not shown) is energized and starts cranking. During this cranking, the glow plug is maintained at a high temperature by the temperature control described above to help start the engine. Eventually, the engine starts, and when the neutral point voltage of a three-phase AC generator (not shown) rises, the start detection switch 13 opens. Start response circuit 18 responds to this. That is, the diode 129 is biased in the forward direction via the resistor 128, and the control signal S2 changes to high level. Therefore, transistor 114 is turned on regardless of the other control signals S I % S 2, thereby turning off transistors 115, 116 and deenergizing relay coil 3a. That is, when the engine starts,
The relay coil 3a is deenergized and its relay contact 3 is opened, and the glow plugs 7 to 10 are energized via the stable preheating resistor 5.

This second energized state continues until the control signal S3 or S6 becomes high level. That is, when the engine is started and the detection switch 13 is opened, the control signal S3 of the time limit circuit 19 becomes high level after a period of time determined by the engine coolant temperature has passed, turning on the transistor 120 and turning off the transistors 121 and 122. Relay coil 4a is deenergized. Thus, after the engine is started, the glow plug is energized via the stable preheating resistor 5 for a period of several tens of seconds depending on the coolant temperature, and is maintained at a temperature of several hundred degrees determined by the power supply voltage.

By the way, when the engine starts and the detection switch 13 is opened, the control signal S2 becomes high level, and the transistor 1
32 is turned on, and in the voltage comparator circuit 16, the resistor 109.
Reference voltage specified by 110.130 (glow plug temperature 9
Transistor 1 that provides hysteresis (equivalent to 00°C)
31 to prevent hysteresis from being applied, even in the second energized state, when the temperature is above the upper limit temperature (900° C.), the signal S! becomes high level, and the output S6 of the AND circuit 133 becomes high level. Therefore, transistor 120 turns on, and transistor 121
．． 122 is turned off and the relay coil 4a is deenergized. In this way, after the engine starts, the glow plug is energized via the stable preheating resistor 5 for a period of several tens of seconds depending on the cooling water temperature, but the additional circuit 30 prevents the glow plug from receiving heat from the engine or due to an abnormal rise in the power supply voltage. (900°C), the current supply is stopped.

〔Effect of the invention〕

In the present invention, even after the engine starts, which is energization through a stable preheating resistor, if the glow plug temperature reaches the upper limit temperature (900°C), the energization is stopped, so heat is received from the engine and abnormal rise in battery voltage occurs. It is possible to prevent the temperature of the glow plug from exceeding the upper limit temperature (900° C.) due to disconnection of wires other than all the wires, and exhibits an excellent effect of protecting the glow plug.

[Brief explanation of the drawing]

The accompanying drawing is an electrical wiring diagram showing one embodiment of the device of the present invention. 1...Key switch, 2...DC power supply, 3.5...
・Relay contact and stable preheating resistor that form the current supply means. 6...Detection resistor, 7,8.9.10...Glow plug. 13...Start detection switch (start signal generation means). 14... Control circuit, 15... A differential amplifier circuit (current-voltage conversion circuit) which forms temperature signal generation means with the detection resistor 6. 16... Voltage comparison circuit, 21.22... Amplification circuit. Representative Patent Attorney Takashi Okabe

Claims (1)

[Claims] (1,1 includes a glow plug attached to the engine,
In the glow plug control device, the glow plug is energized via a predetermined current supply means after the engine is started, comprising: a temperature signal generating means correlated with the temperature of the glow plug; and a starting signal generating means for the engine. ,
Receiving signals from the temperature signal generating means and the starting signal generating means, when the glow plug temperature is equal to or higher than a predetermined value and the engine is started, supplying the current to the glow plug via the current supply means. A glow plug control device comprising: a control means for stopping energization; (2) The glow plug control device according to claim 1, wherein the current supply means is a stable preheating resistor. (3) The temperature signal generating means comprises a current-voltage conversion circuit that generates a signal voltage according to the magnitude of the current flowing through the glow plug, and the control means comprises a comparison circuit that compares the signal voltage with a predetermined reference voltage. 2. The glow plug control device according to claim 1, wherein the comparison circuit also serves as means for controlling energization of the glow plug before starting the engine.