JPS6130153B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a starting assist device for a diesel engine using a glow plug, and more particularly, to supplying power to the glow plug through a power changeover switch device and controlling the changeover switch device to switch between two positions. In particular, the present invention relates to a starting aid device which maintains the glow plug within a set temperature after rapidly raising the temperature of the glow plug.

This type of starting aid device is equipped with a safety device to prevent such a burnout accident because if the control operation by the changeover switch device is not performed reliably, the glow plug will overheat and cause a burnout accident. It is desirable to The inventors have found that in the case where the changeover switch device includes at least a relay contact and operates the changeover switch by opening and closing the relay contact, prevention of accidents due to welding of the relay contact is a dominant requirement for preventing overheating accidents of glow plugs. This invention was developed with this in mind.

SUMMARY OF THE INVENTION An object of the present invention is to provide a starting assist device of this type using a relay contact capable of reliable large current control at relatively low cost, which advantageously improves safety.

That is, the diesel engine starting assist device of the present invention supplies power to the glow plug through a two-position power switching switch device that includes at least a relay contact, and quickly turns on and off the glow plug by controlling the relay contact on and off. In a diesel engine starting aid device that raises the temperature to a certain level and keeps it within the set temperature,
An auxiliary relay contact is provided in series with the switch device or its relay contact, and as a circuit for detecting welding of the relay contact of the switch device, the glow plug side terminal voltage of the relay contact and the signal voltage for excitation control of the solenoid coil of the relay contact are used. The present invention is characterized in that a logic circuit is provided which takes as two input signals, and the output of the logic circuit opens the auxiliary relay contact and issues a warning. explain.

1-1 and 1-2, 1,
1...... is a glow plug that is a heating element made of a metal material whose resistance changes depending on the temperature; 2 is a Wheatstone bridge that includes the glow plug and is essentially made up of four resistors together with resistors 3, 4, and 5; 6; 7 is a power source for supplying power to the Wheatstone bridge 2, and 7 is a power amount two-position switching device that includes at least a relay contact and is interposed between the power source 6 and the Wheatstone bridge 2; contact
It is said that it consists only of RE1-1. RE2
-1 is the relay contact RE1- of the above switch device 7
An auxiliary relay contact 8 is installed in series with 1, and inputs the voltage at intermediate points 9 and 10 of Wheatstone bridge 2, so as to keep the temperature of glow plugs 1, 1, etc. within the set temperature. Relay contact RE1-
11 is a solenoid excitation control circuit for controlling the excitation state of the solenoid coil of relay contact RE1-1 in response to the output signal of the control circuit;
RE1-2 is the solenoid coil of the relay contact RE1-1, and 12 is a welding detection circuit of the relay contact.
This is a logic circuit in which the excitation control signal 1-2, that is, the output signal RO of the control circuit 8 in this case, is used as two input signals, and one signal is used as a gate signal for the other signal. More specifically, this welding detection circuit 12 basically detects a resistance 1 by a signal voltage A.
Capacitor 15 charged via 3 and 14
and diode 1 connected in parallel with capacitor 15.
6 and a switching transistor 18 forming a discharge circuit via a resistor 17, signal voltage A becomes the power supply voltage, and signal voltage B serves as a signal to de-energize the solenoid coil RE1-2 (relay contact signal that turns off RE1-1)
In other words, when the voltage reaches zero, the capacitor 15
Charging is started, and the charging voltage whose voltage is adjusted by the voltage adjusting resistors 19 and 20 is applied to the base of the transistor 21, turning on the transistor 21 so that an output signal can be taken out from its emitter terminal. ing. RE2-2 is the solenoid coil of the auxiliary relay contact RE2-1, RE3-1 is the relay contact of the solenoid coil RE3-2, and the normally closed contact is connected in series to the solenoid coil RE2-2 of the auxiliary relay contact, and the relay The normally open contact of contact RE3-1 is a solenoid coil.
It is connected in series with RE3-2 to form a self-holding circuit. 22 is a switching transistor connected in parallel to the relay contact RE3-1, and its base current is controlled in response to the output signal of the weld detection circuit 12. L is solenoid coil
This is a warning lamp connected in parallel with RE3-2. 23 is the main switch of the starting assist device, and 24 is an emergency glow plug energization means that operates separately from the operation of the power supply circuit to the glow plug via the switch device 7. Here, the power limiting resistor 2
a normally open relay contact RE4-1 for supplying power directly to the glow plug via 5 and a contact RE4-1 energized by a pushbutton switch 26;
It consists of a solenoid coil RE4-2.

Here, the control circuit 8 will be explained in more detail. 801 is a voltage comparator circuit that stably maintains zero output when the voltage applied to the Wheatstone bridge becomes zero;
2 is a resistor for positive feedback of the output of the voltage comparison circuit 801 to the input side, 803 is an OR circuit consisting of two diodes, and 804 is a reference voltage setting resistor 80.
A voltage comparator circuit 808 which takes the intermediate point of 5,806 and the charging voltage of the capacitor 807 as two inputs, a positive feedback resistor 809, a diode 810 and a resistor 8
11 and a switching transistor 8 to form a circuit for charging the capacitor 807 with the output voltage of the voltage comparison circuit 808 and a discharging circuit for the capacitor 807 via the resistor 812.
13, and the output of the voltage comparison circuit is the OR circuit 80.
When the output of the transistor 813 is a zero voltage signal, as long as the input of the other OR circuit (output of the voltage comparison circuit 801) is a zero voltage signal, the output of the transistor 813 is a feedback circuit 814 which provides a conduction signal of the transistor to the base terminal and provides an off signal to the transistor 813 when the output of the OR circuit 803 is a plus 1 signal;
It is an oscillating circuit.

Next, to explain the operation of the starting assist device of this embodiment, when the main switch 23 is turned on, the solenoid coil RE2-2 of the auxiliary relay is energized, the contacts of the auxiliary relay are closed, and the solenoid excitation control The power supply voltage is also applied to the circuit 11 and the control circuit 8, and the transistor 8 is applied via the feedback circuit 814.
13 is made conductive, the capacitor 807, if charged, will be discharged and the voltage comparator circuit 808 will soon output a plus 1 signal. When this plus 1 signal is output, the reference potential at the midpoint between resistors 805 and 806 is switched to a higher level by positive feedback resistor 809, and charging of capacitor 807 via resistor 811 is started. At this time, the plus one signal is processed through the OR circuit 803, and the transistor 813 is turned off by a low voltage signal from the circuit 814. In addition, the solenoid excitation control circuit 11
An excitation signal is applied to the solenoid coil RE1-2, the relay contact RE1-1 is closed, and the voltage of the power source 6 is applied to the Wheatstone bridge 2. Since the glow plug is cold and its resistance is low, the voltage comparator circuit 801 continues to emit a plus one signal, but in the meantime, the charging voltage of the capacitor 807 reaches the higher reference voltage, so the voltage comparator circuit 808 changes to a zero signal. At that time, the reference voltage is also changed to a lower reference voltage due to the positive feedback resistor 804, but on the other hand, since the plus 1 signal voltage from the voltage comparator circuit 801 is maintained in the transistor 813, the feedback circuit 814 The off state is maintained via the capacitor 807, and the capacitor 807 waits in the fully charged state. When the glow plug reaches the set temperature, the output signal of the voltage comparison circuit 801 reliably changes to a zero signal, turns off the relay contact RE1-1 via the solenoid excitation control circuit 11, and maintains the zero signal. On the other hand, the voltage comparison circuit 801
At the same time as the zero signal is generated, the transistor 813 is made conductive via the feedback circuit 814, and the capacitor 807 is discharged via the resistor 812 to the lower reference voltage generated at the midpoint between the resistors 805 and 806. The voltage comparator circuit 808 maintains the zero signal and then changes to a plus 1 signal, and at this time, the plus 1 signal is output to the solenoid coil excitation control circuit 11 via the OR circuit 803, turning on the relay contact RE1-1. In turn, power is supplied to the glow plug again and it returns to its original state. In this way, the supply power is controlled on and off so that the glow plug reaches the set temperature, but during this time, for example, with the help of a pilot lamp that displays the appropriate time, the starter switch of the diesel engine (not shown) is turned on and the engine is turned on. is started. Now, when relay contact RE1-1 is welded, signal voltage A is the terminal voltage on the glow plug side of the contact, and signal voltage B is solenoid excitation control circuit 1.
Although the contact RE1-1 is generating an excitation signal to turn off the contact, that is, a zero signal, the contact RE1-1 continues to generate a contact closing signal, that is, a power supply voltage signal, so that the welding detection circuit 1
2 immediately outputs a signal to turn off the solenoid coil RE2-2, and the auxiliary relay contact RE
2-2 is opened to prevent the glow plug from overheating. Also, since the warning lamp L lights up, the driver should use the emergency glow plug energizing means 2.
4, it is sufficient to perform an emergency start without using this starting assist device.

In addition, in this invention, the power amount second position changeover switch device 7 has a relay contact RE as shown in FIG.
1-1 and a bypass resistor 71 connected in parallel may be used. In that case, although there is a power loss due to the resistor 71, the durability of the relay contact RE1-1 is extended. In addition, the way to connect the glow plugs in Wheatstone Bridge 2 is as shown in Figure 3.
The series resistor 3 may be connected only to the terminal.

This invention has the advantage that, especially when using a switch device 7 consisting only of relay contacts, the required life of the auxiliary relay contacts can be much lower, and therefore a starting auxiliary device with an extremely high sense of security can be obtained at low cost. Effective.

[Brief explanation of the drawing]

1-1 and 1-2 are circuit diagrams of one embodiment of the diesel engine starting aid device of the present invention, and FIGS. 2 and 3 are circuit diagrams of other embodiments of the present invention, respectively. It is. 1...Glow plug, 7...Switch device for switching power amount to two positions, 12...Welding detection circuit, RE
1-1...Relay contact of power amount 2-position switching device, RE2-1...Auxiliary relay contact, RE2
-2...Solenoid coil of auxiliary relay contact.

Claims (1)

[Scope of Claims] 1. Electric power is supplied to the glow plug via a two-position electric power switching device including at least a relay contact, and the temperature of the glow plug is rapidly raised by controlling the relay contact on and off. In a starting aid device for a diesel engine that is designed to keep the temperature within a set temperature, an auxiliary relay contact is provided in series with the switch device or its relay contact, and the relay contact is used as a welding detection circuit for the relay contact of the switch device. A logic circuit is provided which takes as two input signals the glow plug side terminal voltage and the excitation control signal voltage of the solenoid coil of the relay contact, and the output of the logic circuit opens the auxiliary relay contact and also issues a warning. A starting aid device for a diesel engine, which is characterized by the following features: 2. The switch device consists only of relay contacts.
The starting assist device for a diesel engine according to claim 1.