JPS628384Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a preheating device used for cold starting of a diesel engine.

[Prior art and problems that the invention attempts to solve]

A preheating device for a diesel engine facilitates starting of a diesel engine by energizing each glow plug provided in a combustion chamber such as a precombustion chamber or a main combustion chamber. In a conventional preheating device, the engine is preheated before starting, and the glow plug is energized and heated even when the engine is started (when the starter is driven). However, if the engine is to be restarted immediately after operation and while the engine has not yet been sufficiently cooled, there is no need to perform the above-mentioned preheating. In such cases, conventionally, the key switch contact arrangement is OFF.
A preheating position is provided in the direction of rotation opposite to the starting position, and the engine is started without the preheating device being activated in advance, but even in that case, the glow plug must be heated when the engine is started by cranking. is being carried out, and power is wasted.

Therefore, the present invention solves the above-mentioned drawbacks of the prior art, and the purpose of the present invention is to provide a preheating device for a diesel engine that can automatically stop preheating at engine cranking start based on the engine temperature. In order to further improve the operability of the diesel engine key switch, the key switch arrangement is particularly useful in systems where the preheating position is located next to the off position side of the starting position. The goal is to provide equipment.

[Means for solving problems]

The features of the present invention that achieve the above object include: a key switch having at least a starter starting contact for opening and closing a circuit connecting a power source and a starter; a glow plug for preheating the engine; a preheating timer for controlling preheating of the glow plug, a reset circuit for resetting the preheating timer when the starter is started, a determination circuit for determining whether or not energization of the glow plug is necessary in relation to the engine temperature during starter startup, and the preheating timer. and a glow energization circuit that energizes the glow plug based on the output signal of the discrimination circuit and the output signal of the discrimination circuit.

〔Example〕

The present invention will be explained in detail below using the drawings. FIG. 1 is a circuit diagram of an embodiment of a preheating device according to the present invention. In this figure, 1 is a key switch installed in the driver's cab, and this key switch has a movable contact 1a having a predetermined contact area, a fixed contact for accessories 1b, a fixed contact for preheating 1c, and a starting contact 1d.
Contains. The movable contact 1a is connected to the positive side of the battery 3 via a fuse 2. The accessory fixed contact (hereinafter referred to as ACC contact) 1b is connected to the switch circuit 6 and the switch circuit 7 via the electromagnetic coil 4b of the relay 4 and the electromagnetic coil 5b of the relay 5, respectively. The other end of 7 is grounded. switch circuit 6
is determined by the output of the preheating time setting circuit 8, which will be described later, and the switch circuit 7 is determined by the output of the engine temperature determination circuit 9, which will be described later.
It is configured to be turned on and off by the output of each. An indicator lamp 10 provided in the driver's cab is connected in parallel to both ends of the electromagnetic coil 4b. The ACC contact 1b is further connected to the power input terminal of the preheating time setting circuit 8.

A preheating fixed contact (hereinafter referred to as GL contact) 1c of the key switch 1 is connected to a glow plug 11 provided in each combustion chamber of the engine via a normally open contact 4a of a relay 4 and a resistor, and is further connected to a preheating time setting circuit. It is connected to one signal input terminal of 8. In addition, the starting fixed contact (hereinafter referred to as ST contact) 1d is a momentary mechanism, and is connected to the glow plug 11 via the normally closed contact 5a of the relay 5, and is further connected to the other signal input terminal of the preheating time setting circuit 8. It is connected to the. A temperature sensing circuit 12 attached to the water jacket of the engine and configured to detect the temperature of the cooling water of the engine is connected to yet another signal input terminal of the preheating time setting circuit 8.

A circuit for preheating the engine before starting.
That is, a detailed circuit diagram of the preheating time setting circuit 8, the switch circuit 6, and the temperature sensing circuit 12 is shown in FIG. As shown in this figure, the signal input terminal 8a of the preheating time setting circuit 8 is connected to the ST contact 1 of the key switch 1.
d, and the input terminal 8b is connected to the GL contact 1c. In the preheating time setting circuit 8, these input terminals 8a and 8b are connected to a reset input terminal and a set input terminal of a flip-flop 20, respectively. The output terminal of the flip-flop 20 is connected to the discharge control transistor Tr ₂₁ of the integrating capacitor C ₂₁ of the integrator 21. The integrator 21 consists of an operational amplifier OP ₂₁ , an integrating capacitor C ₂₁ provided in its feedback circuit, and its discharge control transistor.
The input terminal of the integrator ₂₁ is connected to the temperature sensing circuit 12 via the integrating resistor _R21 . The output terminal of the integrator 21 is connected to the comparison input terminal of a comparator 22 composed of an operational amplifier OP ₂₂ and the like, and the output terminal of this comparator 22 is connected to the reset input terminal of the flip-flop 20. . The temperature sensing circuit 12 is also connected to a comparison input terminal of a comparator 23 consisting of an operational amplifier OP ₂₃ , etc.
The output terminal of is connected to the reset input terminal of flip-flop 20. On the other hand, the Q output terminal of the flip-flop 20 is connected to the control input terminal of a switch circuit 6, and is configured to turn on/off the transistor _Tr6 in this circuit 6.

In this embodiment, the temperature sensing circuit 12 is configured such that a thermistor and a resistor are connected in series between the power supplies so that the thermistor is on the positive side, and the output is taken out from the midpoint of these. As a result, a voltage that is positively proportional to the engine temperature value is output.

A detailed circuit diagram of the circuits for performing the heating operation at engine start, which is a feature of the present invention, namely, the temperature sensing circuit 12, the engine temperature determination circuit 9, and the switch circuit 7, is shown in Fig. 3. As shown in this figure, the output terminal of the temperature sensing circuit 12 is connected to an operational amplifier
The output terminal of the engine temperature determination circuit 9 is connected to a comparison input terminal of the engine temperature determination circuit 9 which is composed of a comparator such as an OP _9. The output terminal of the determination circuit 9 is connected to a control input terminal of a switch circuit 7 which is configured to control the on/off switching of a transistor _Tr7 in the switch circuit 7.

Next, the operation of the apparatus of this embodiment will be explained. When the key switch 1 is operated, power is first supplied to the ACC contact 1b, and then to the preheating time setting circuit 8, the engine temperature determination circuit 9, and the like. Next, when the key switch 1 is operated to connect power to both the GL contact 1c and the ACC contact 1b, the flip-flop 20 (second
A trigger signal based on the rise of the applied voltage from the GL contact is applied to the set input terminal shown in FIG. Therefore, the contact 4a closes and the glow plug 11 is energized, and preheating before starting the engine is started.

On the other hand, since the transistor Tr ₂₁ of the integrator 21 is turned off by setting the flip-flop 20,
The integrator 21 starts an integration operation, and its output level is determined by the comparator 22, thereby performing a timed operation. Since the voltage input to the integrator 21 is the output of the temperature sensing circuit 12 corresponding to the temperature of the engine coolant, the preheating time based on the timed operation is a function of the engine temperature. When the preheating time set as described above has elapsed, a trigger signal is applied from the comparator 22 to the reset input terminal of the flip-flop 20, thus turning off the switch circuit 6 and stopping the energization of the glow plug 11 and indicator lamp 10. Ru.

Further, the comparator 23 is used to reset the flip-flop when the temperature of the engine coolant is higher than a set value, so as not to perform the above-mentioned preheating operation before starting the engine.

Now, after the engine operator has confirmed that the indicator lamp 10 in the driver's cab has gone out, he turns on the key switch 1.
When the ST contact 1d is connected to the power supply (in this case, the ACC contact, GL contact, and ST contact are all connected to the power supply), normally the glow plug 11
is connected to the power source via the ST contact 1d and the normally closed contact 5a of the relay 5, and both heating and engine starting are performed. However, in the present invention, the relay 5 is configured to be controlled by a switch circuit 7, and this switch circuit 7 is controlled on/off by an engine temperature determination circuit 9. That is, the voltage according to the engine temperature value from the temperature sensing circuit 12 is applied to the operational amplifier of the discrimination circuit 9 which constitutes a comparator.
When this voltage is applied to the comparison input of OP ₉ and exceeds the reference setting voltage, the relay 5 is driven to turn on the transistor Tr ₇ of the switch circuit 7, and the normally closed contact 5a is opened. Therefore, in this case, the glow plug 11 is not energized at the time of engine cranking start. In this embodiment, the comparator output is set to a high level when the engine coolant temperature reaches 60° C. or higher.

[Effect of idea]

As explained in detail above, according to the device of the present invention, if the temperature of the engine is above a predetermined value when the engine is started by cranking, that is, the temperature at which starting is performed quickly without glow energization, the glow plug is activated. Since it is configured so that it does not energize, there is no wasted power consumption. In particular, since it is necessary to flow a large current through the starter circuit when starting the engine, the present invention is also beneficial in terms of battery capacity and durability. Furthermore, even if the driver performs various engine starting operations at his/her own will via the key switch, glow energization control before starting and glow energization control during engine cranking start are performed independently and automatically. Another advantage of the present invention is that each control can be performed accurately and fool-proof.

[Brief explanation of the drawing]

FIG. 1 is an overall circuit diagram of an embodiment of the present invention, and FIGS. 2 and 3 are circuit diagrams showing a part of FIG. 1 in detail. 1...key switch, 2...fuse, 3...
Battery, 4, 5... Relay, 6, 7... Switch circuit, 8... Preheating time setting circuit, 9... Engine temperature discrimination circuit, 10... Display lamp, 11...
Glow plug, 12...Temperature sensing circuit.

Claims (1)

[Claims for Utility Model Registration] A key switch having at least a starter starting contact for opening and closing a circuit connecting a power source and a starter, a glow plug for preheating an engine, and a glow plug for preheating an engine by the glow plug before starting the starter. A preheating timer to control, a reset circuit to reset the preheating timer when the starter is started, a determination circuit to determine whether or not to energize the glow plug in relation to the engine temperature during starter startup, and an output signal of the preheating timer. and a glow energization circuit that energizes the glow plug based on an output signal of the discrimination circuit.