JPS6044511B2 - Diesel engine preheating control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a starting assist device for a diesel engine equipped with a preheating plug.

(Prior Art and Its Disadvantages) In order to improve the startability of a diesel engine, it is known to arrange a preheating plug in the combustion chamber and to make the preheating plug red hot when the diesel engine is started.

By the way, conventional starting aid devices are constructed so that when the key switch is placed in the engine start position, current flows through the preheating plug, causing it to become red hot.

Starting time can be shortened by passing a large current through the preheating plug to make it rapidly red hot, but this cannot be put to practical use because there is a risk that the heating element of the preheating plug may melt due to the large current. It takes 20 to 30 minutes to complete the process, that is, until the preheating plug becomes red-hot to a temperature of about 900 DEG C., which has the drawback of extremely poor starting performance of the diesel engine. In addition, as described in West German Patent Publication No. 1426713, spark plugs using a heating element whose resistance value increases as the temperature rises (
Prepare a preheating plug (preheating plug) and insert it into the Wheatstone bridge circuit as a resistor, and when current flows through the spark plug, the unbalanced state at the diagonal end of the Wheatstone bridge causes the current to flow through the control transistor. a device for energizing or demagnetizing a power switch control relay, thereby passing or short-circuiting a control resistor leading to the spark plug to maintain the temperature of the spark plug at a constant state; There are devices that maintain the temperature of the spark plug in a constant state by directly turning it on and off using a switching element, and these devices are used, for example, to ignite the heating mechanisms of internal combustion engines, buses that use liquid materials, jet propulsion machines, etc. Used in spark plugs and devices such as those used for

Since the spark plug of the spark plug device needs to maintain a constant temperature over a long period of time, the resistance value of the heating element remains unchanged even if the rated voltage is continuously applied to the spark plug. is such that it will not melt. In other words, when this is used as a starting aid for a diesel engine, the key switch can be used as a starting aid for a diesel engine.
It is inevitable that it will take 20 to 308 hours from setting the spark plug to the starting position to starting the engine, and even if this is used, there is no benefit other than accurately maintaining the red-hot temperature of the spark plug. OBJECTS OF THE INVENTION Therefore, it is an object of the present invention to provide a novel device which makes it possible to start a diesel engine immediately when the key switch is placed in the engine start position, and to To provide a new device that can reliably start an engine by another means when a starting device fails.

(Summary of the Invention) In the present invention, when the heating element reaches a set temperature, the rapid heating circuit is cut off via the current control element to maintain the heating element at a predetermined temperature by the bridge circuit output including the heating element of the preheating plug. It has a first control circuit and a second control circuit that connects a stabilizing circuit in series with the heating element, and operates by switching between the first control circuit and the second control circuit when starting the starter. a manual preheating switch that manually activates the second control circuit when the first control circuit fails; and a manual preheating switch that manually activates the second control circuit when the first control circuit fails; There is provided a preheating control device for a diesel engine, characterized in that it has means for determining the direction of passing current to prevent malfunction of the engine.

(Example) Next, an example of the present invention will be explained in detail using drawings! explain.

In FIG. 1, 1 is a power source consisting of a battery, and 2 is a key switch.

The key switch 2 has two fixed contacts 21 and 22, and further has a movable contact 23 rotated by a key 2K. This movable contact 23 contacts the fixed contact 21 at the first step position, and even if you release your finger from the key 2K, the movable contact 23 remains in this first step position.
Do not move from the step position. When the key 2K is further rotated with the finger, the movable contact 23 further rotates and contacts both the fixed contacts 21 and 22 to reach the second step position, but when the finger is released from the key 2K, the movable contact 23 rotates further and reaches the second step position (not shown). The spring causes the key 2K and the movable contact 23 to return to the first step position. Reference numeral 3 designates a set temperature reaching indicator lamp that indicates that a preheating plug, which will be described later, has reached a predetermined temperature, and 4 a control circuit.

A well-known comparison circuit and switching circuit are provided inside this, and the detailed structure will be described later. 6 is a preheating plug provided for each cylinder of the diesel engine, and 51 is a heating element.

This heating element has a positive temperature coefficient, so its resistance value changes with temperature changes near the preheating set temperature, and the degree to which it will melt due to temperature rise when the rated voltage is continuously applied is small. It has a resistance value. 6 is a detection microresistance having a preset resistance value r1, and 8 and 9 are resistors having resistance values R2 and R3 set to configure the heating element 51, the detection microresistance 6, and the bridge circuit 10. It is the body.

Normally, a plurality of detection microresistors 6 and preheating plugs 5 are used depending on the number of cylinders, but for the sake of simplicity,
In FIG. 1, only one address is shown. 71, 72
11a is a conductor connecting intermediate points Ml, m2 of the bridge circuit 10 to the control circuit 4; 11a is a relay for the rapid heating circuit;
b is the relay for the stabilization circuit, 12 is the contact of the relay on the fast heating circuit side, 13 is the contact of the relay on the stabilization circuit side, 14 and 15
is an excitation coil that closes both the contacts 12 and 13 when excited.

16 is a heating circuit connected to the contact 12 side of the relay 11a, 17 is connected to the contact 13 side of the relay 11b,
This is a stabilizing circuit having a stabilizing resistor 17a.

Reference numeral 18 is a starter relay, and the contact 18 is activated when the excitation coil 18a connected to the fixed contact 22 of the key switch 2 is energized.
b is configured to be a closed circuit.

19 is a starter that operates when contact 18b of starter relay 18 is closed.

Reference numeral 30 denotes a water temperature detection switch that detects the temperature of the cooling water near the cylinder, and it closes when a detection part 30a disposed in the cooling water reaches, for example, 50°C, and the set temperature attainment indicator lamp 3 also serves as the display. .

Reference numeral 31 denotes a manual preheating switch, which is used in an emergency, for example, when the control circuit 4 breaks down and it becomes impossible to apply voltage to the preheating plug.

However, when the manual preheating switch is used, it takes a long time to start the engine as in the conventional case. A diode 32 is provided to prevent the starter 19 from operating unnecessarily when the key switch 2 is rotated to the first step position, and constitutes means for determining the direction of the passing current.

In the control circuit 4, there is a comparison. A circuit 41, a relay 42 which is normally closed and opens the circuit when a drive signal is applied, and a relay 44 which is normally open and closes the circuit when a drive signal is applied.
Rh having the inverter 43 has a high resistance on the order of megohms. Incidentally, F is a news, and 24 is a circuit for energizing various accessory parts. The control circuit male bridge circuit 10 and the relay 11a also constitute a first control circuit, and the bridge circuit 10 and the relay 1 also constitute a first control circuit.
1b1 stabilizing circuit 17 constitutes a second control circuit. Next, the operation of the starting assist device shown in FIG. 1 will be explained using an example of a cold automatic mode. In a cold region, when the engine cooling water temperature is below 50° C., the water temperature detection switch 30 is turned off.

Therefore, the relay 42 is in an operable state. Next, in order to start the engine, the operator rotates the key 2K of the key switch 2 with his/her finger and brings the movable contact 23 into contact with the fixed contact 21 at the first step position. is in the on state, the excitation coil 14 of the relay 11a is energized, and its contact 12 is turned on, so that the power source 1 generates heat in the preheating plug 5 disposed for each cylinder via the rapid heating circuit 16. A large current flows to the body 51, and the heating element 5
1 is heated rapidly. As the temperature of the heating element 51 rises, its resistance value also increases. As long as the resistance value R is smaller than the set temperature equivalent resistance value Rs,
Since the intermediate point M2 of the bridge circuit 10 has a higher potential than the intermediate point m1, the output voltage of the comparator circuit 41 is "O". Therefore, the relay 42 continues to be in the on state, and the contacts of the relay 11a 12 is also kept in the on state, and the heating element 51 of the preheating plug 5 is heated continuously.When the temperature of the heating element 51 reaches the set temperature, its resistance value also becomes the resistance corresponding to the set temperature described above. If the resistance value of the heating element 51 exceeds Rs even slightly, the potential at the intermediate point M2 of the bridge circuit 10 will be lower than that at the intermediate point me. The output changes from "0" to "1", the relay 42 is energized and this contact is turned off, so the excitation coil 14 of the relay 11a is also deenergized and the contact 12 is turned off. Therefore, since the power supply to the heating element 51 is cut off, its temperature also decreases. The output of the comparator circuit 4 is also sent to the relay 44, and the relay 44 is turned on only while this output is ゜゜1゛, and the set temperature attainment indicator lamp 3 lights up. On the other hand, when the contact 12 of the relay 11a is turned off, the power supply to the bridge circuit 10 is also cut off, and the output of the comparator circuit 41 becomes "0" again, so the relay 42 is turned on, and the relay 11a is also turned on, causing the bridge circuit 10 to be cut off. 10, the temperature of the heating element 51 rises as described above, the output of the comparator 41 becomes ゜゛1゛ again, and the supply of voltage to the bridge circuit 10 is cut off. This intermittent operation is repeated. .

During this time, the set temperature attainment indicator lamp 3 will be in a blinking state.
All preheat valves will display an indication that the set temperature has been reached.
Note that the intermittent repetition time of the preheating plug 5 is determined by the relay 11a.
This is mostly determined by the operation delay time from when the excitation coil 14 is energized until the contact 12 is turned on, but if it is desired to make the intermittent repetition time a little longer, for example, the relay 42 may be provided with a delay operation. Next, when the operator rotates the key 2K of the key switch 2 with his/her finger and brings the movable contact 23 into contact with the fixed contacts 21 and 22 at the second step position, the starter relay 18 activates the excitation coil 18a. Since the circuit is closed, the contact 13 of the relay -11b is turned on by the action of the excitation coil 15 at the same time as the starter 19 starts, so the current flows from the power supply 1 to the heating element 51 of the preheating plug 5 via the stabilizing circuit 17. As a result, a voltage drop occurs due to the stabilizing resistor 17a, and even if a voltage is continuously applied to the preheating plug 5, the heating element 51 of the preheating plug 5 does not melt and becomes red hot.

Then, fuel is injected into the red-hot preheating plug 5, and the diesel engine is started. Note that when the key 2K is placed in the second step position, the control voltage is applied from the fixed contact 23 to the relay 42 of the control circuit 4 through the line 45, so the relay 42 is in an open state during this time, and the relay 11
a is in an open state and the fast heating circuit is in a rest state. Once the diesel engine has started, the operator releases the key 2K, and the key 2K automatically returns to the first step position.

At this time, the relay 11a is energized as described above and the rapid heating circuit is activated, but since the diesel engine has started and the temperature inside the cylinder is 900°C, the relay 42 is closed. As a result, the rapid heating circuit becomes inoperable. Although FIG. 1 shows a circuit with only one preheating plug 5, if it is applied to a four-cylinder diesel engine, for example, four preheating plugs 5 will be required. As shown in FIG. 2, each preheating plug 5a to
5d are provided with comparison circuits 41a to 41d, their outputs are input to an OR circuit 47, and the OR circuit 47 operates the relay 42.

Furthermore, in order to simplify the circuit, a plurality of preheating plugs may be connected in parallel to the preheating plug 5 shown in the first diagram. (Effects of the Invention) As explained in detail above, the heating element of the preheating plug according to the present invention has such a low resistance that it will melt immediately if a predetermined voltage is continuously applied.
When voltage is applied to the preheating valve with the key switch in the position one step before the engine starting position, a large amount of power can be immediately supplied, and the heating element of the preheating valve is raised to the preheating set temperature at a speed incomparable to conventional methods. can.

Moreover, since the heating element of the preheating plug is configured to immediately cut off power supply to the heating element using the control circuit when the heating element reaches the preheating set temperature, the heating element of the preheating plug will not melt. In addition, after the key switch is placed one step before the engine starting position, the rapid heating circuit is operated to perform preheating operation, and at the same time the starter is started, the preheating valve is continuously lit at a constant temperature. Diesel engines operate immediately even when they are completely cold in cold regions, and the operator perceives the time from when the key switch is turned to the engine start position to when the engine starts as the starting time, so it is difficult to operate the engine. It has many effects, such as feeling as if the engine has started instantly. Furthermore, since the present invention is equipped with a manual preheating switch, the engine can be reliably started even if the rapid heating circuit fails, thereby providing a more reliable, reliable, and energy-saving preheating control device. can do.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a preheating plug and part of a control circuit. 1: Power supply, 2: Key switch, 4: Control circuit, 5: Preheating plug, 251: Heating element, 10: Bridge circuit, 11a, 1
1b: Relay, 16: Fast heating circuit, 17: Stabilization circuit, 1
8: Starter relay, 19: Starter, 30: Water temperature detection switch, 31: Manual preheating switch.

Claims (1)

[Claims] 1. A first control circuit that interrupts the rapid heating circuit via a current control element to maintain the heating element at a predetermined temperature when the heating element reaches a set temperature by the output of a bridge circuit including the heating element of the preheating plug; a changeover key switch having a second control circuit connecting a stabilizing circuit in series with the heating element, and switching between the first control circuit and the second control circuit when starting the starter; It is characterized by having a manual preheating switch that manually activates a second control circuit when the first control circuit malfunctions, and a passing current direction determining means that prevents malfunction of the starter when the second control circuit is activated. Diesel engine preheating control device.