JPS6130151B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling preheating time by a glow plug type preheating device installed in a diesel engine.

In conventional glow plug type preheating devices, the driver determines the preheating time by the glow plug and the time for energizing the glow plug based on the red-hot state of an indicator using a heating wire. However, with this kind of equipment, you have to rely on judgment based on experience regarding differences in ambient temperature and engine warm-up state.
This was a difficult point for ordinary drivers. For this reason, recently there have been models that detect the engine cooling water temperature and control the energization time to the glow plugs (such as Japanese Patent Application Laid-Open No. 1983-1924), but this Since the level of the terminal voltage is not controlled, it is still inconvenient.

For example, Japanese Unexamined Patent Publication No. 1942-1989 discloses a configuration in which the energization time is varied depending on the temperature of the cooling water, but does not disclose a configuration in which the energization time is varied depending on the level of the terminal voltage of the glow plug. The water temperature detection switch used here is configured so that the temperature rises when energized. For example, when the battery voltage is high, the temperature rises quickly and the energization time is shortened, but when the voltage is applied directly to the glow plug, Therefore, precise control is not possible. That is, since the glow plug current is a large current, the voltage drop caused by the wiring from the battery to the glow plug cannot be ignored. Of course, if it is compatible with one vehicle model, the voltage drop due to the wiring is almost the same, but even in this case, the voltage drop due to relay contacts etc. varies widely and cannot be said to be perfect. Furthermore, since the voltage drop may vary greatly depending on the type of vehicle, it may be necessary to change the performance of the water temperature detection switch, etc.

In view of these circumstances, the present invention provides a preheating time control device that can always obtain the optimum preheating time and is not affected by changes in the length of the wiring from the battery to the glow plug. In order to achieve this, the temperature of the engine's cooling water is detected by a temperature sensing element, and the terminal voltage of the glow plug is detected by comparing it with a constant voltage circuit, and the preheating time is determined depending on both. . More specifically, the comparison means compares the charging voltage of the capacitor charged with the terminal voltage of the glow plug and the voltage determined by the temperature sensing element sensitive to the engine coolant temperature based on the voltage of the constant voltage circuit. The present invention is characterized in that the preheating time is controlled by comparing the preheating time by opening and closing a switching contact inserted between the battery and the glow plug based on the output of the comparing means.

An embodiment of the present invention will be described below with reference to the drawings.

In Fig. 1, 1 is the battery, 2 is the main switch (the switch that turns on when the key switch is in the on position and the start position), 3 is the starter switch (the switch that is turned on when the key switch is in the start position), 4 is the glow plug, and 5 is the starter switch. is a pilot lamp.

Reference numeral 6 denotes a preheating time control circuit, which has four input terminals, to which wiring 8 for inputting terminal voltages of the main switch 2, starter switch 3, thermistor 7 for detecting engine coolant temperature, and glow plug 4 are connected respectively. A relay 9 is connected to the output terminal. Contact 10 of this relay 9 is battery 1
The glow plug 4 is inserted into the wiring between the glow plug 4 and the glow plug 4. R ₁ to R ₁₅ are resistors, D ₁ to _{D 7} are diodes, D _Z
is a Zener diode that constitutes a constant voltage circuit, C
is a capacitor, A ₁ and A ₂ are comparators, T ₁ and T ₂
is a transistor.

In the figure, V ₀ is the battery voltage, V _Z is the voltage of the constant voltage circuit, V _T is the voltage determined by thermistor 7, V _A is the reference constant voltage, V _C is the charging voltage of capacitor C, and V _G is the glow The terminal voltage (applied voltage) of the plug 4 is shown. Here, V ₀ > V _G > V _Z >
It is V _A.

Next, the operation will be explained. However, in the explanation, the voltage between the base and emitter of the transistor, the forward voltage drop of the diode, etc. will be ignored.

To start the engine, turn on main switch 2.
When turned on, since V _C = 0 at the moment of turning on, V _A
>V _C , and the output of comparator A ₁ becomes H level, approximately V ₁ . Also, since V _T >V _C ,
The output of comparator _A2 is almost 0 at L level.
(V). If the output of comparator A ₂ is at L level, transistor T ₂ turns on, which excites relay 9 and turns on its contact 10, which energizes glow plug 4 and lights pilot lamp 5 at the same time. Notify the driver that preheating is in progress.

In this state, the output of the comparator _A1 is at H level, so the current _I13 flowing through the diode _D4 and the resistor _R13 , the diode _D1 , the resistor _R6 , and the transistor
The current I ₆ (I ₆ ≪ I ₁₃ ) flowing through T ₁ plus the current I ₁₃ +
Charge capacitor C with _I6 .

V _C increases with time, and when V _C > V _A ,
Since the output of the comparator _A1 is inverted and becomes L level, _I13 =0, and the capacitor C is charged only with _I6 .

Then, when V _C >V _T , the comparator A ₂
is reversed and its output becomes H level, transistor T ₂ is turned OFF, which demagnetizes relay 9 and turns OFF its contact 10, so that the glow plug 4 is de-energized and the pilot lamp 5 is also turned off. The light turns off to notify the driver that preheating is complete. In this state, I ₆ = 0, but since the output of comparator A ₂ is at H level, I ₁₃ flows again through diode D ₅ and resistor R ₁₃ , which charges V _C until it reaches V _Z and reheats it. is prevented.

The changes over time after the main switch of V _C is turned on are shown in the second section for when V _G is V _G1 and when V _G2 is V G2.
As shown in the figure. The solid line is for V _G = V _G1 and the broken line is for V _G = V _G2 , where both V _G1 and V _G2 are constant values, and V _G1 <
V _G2 . Note that everything is shown as a straight line here, and in the case of only I ₆ it is a straight line because it is a constant current as shown below, but in the case of I ₁₃ it is not actually a straight line. However, since this poses no problem for explanation purposes, it was approximated by a straight line.

As can be understood from Figure 2, when the glow plug terminal voltage V _G is V _G1 , the energization time is t ₆ , but when the voltage V _G2 is higher than V _{G 1} , the energization time is shortened to t ₅ . Ru. That is, when the voltage V _G is high, the charging current to the capacitor C increases and the charging voltage V _C of the capacitor C increases quickly, and when the voltage V _G is low, the rate of increase of the voltage V _C becomes slow. If wiring 8 from glow plug 4 and diode D ₁ are removed in Figure 1 and wired as shown by wiring 8', there will be a voltage drop due to wiring resistance from battery 1 to glow plug 4. ,
If installed in a different car model, the length of the wire from the battery 1 to the glow plug 4 may change, resulting in a different voltage drop, so in order to accurately control the temperature of the glow plug 4, the preheating control circuit 6 must be installed for each car model. circuit constants must be set. However,
In the present invention, since the capacitor C is charged by the glow plug terminal voltage V _G , the battery 1
Since the voltage drop caused by the wiring from the glow plug 4 to the glow plug 4 can be ignored, the same preheating control circuit 6 can be used even if the vehicle model is different.

Further, V _T can be expressed as follows.

V _T =R ₃ +R _T /R ₂ +R ₃ +R _T ·V _Z However, R _T is the resistance value of the thermistor 7, and can be expressed as a function of the cooling water temperature T as shown below.

R _T1 : Resistance value at temperature T ₁ (K) R _T2 : Resistance value at temperature T ₂ (K) B: Positive constant, so V _T decreases as the cooling water temperature rises. As a result, the time period during which the glow plug 4 is energized is controlled as shown in FIG. 3 in accordance with the cooling water temperature.

The region higher than the temperature Ta at the bending point in the figure is V _T
<V _A , and the temperature Ta is set by resistor R ₄
Alternatively, this can be done freely by changing V _A by changing _R5 , and the setting of the energization time ta at that time can also be done freely by changing the resistor _R13 . Further, the slope in a region lower than the temperature Ta is a change in the resistance R ₆ , and the slope in a region higher than the temperature Ta is a change in the resistance R ₃ , which can be set freely. Also, the energization time tb ₁ when the temperature is Tb
(The ratio between V _G =V _G1 and tb ₂ (V _G =V _G2 ) can be arbitrarily set by changing V _Z using the Zener diode D _Z.

After preheating is completed, the driver confirms this by turning off the pilot lamp 5 and turning off the starter switch 3.
Just turn it on and drive the starter motor (not shown) to start the engine. Starter switch 3
When it is ON, the relay 9 is energized through the diode _D7 , so its contact 10 is turned ON and the glow plug 4 is energized again, making it easier to start the engine.

Here, the functions of diode D ₂ and resistor R ₁₁ will be explained. In FIG. 2, for example, V _G =V _G1
In this case, the time to energize the glow plug 4 is t ₆ , but if you turn on the starter switch 3 and start the engine even though it is preheating at t ₂ , the engine will start at t ₄ . If it is turned off because the engine has started, it will preheat even after starting from t ₄ to t ₆ . Therefore, in order to prevent this, when the starter switch 3 is turned on, the capacitor C is rapidly charged through the diode D ₂ and the resistor R ₁₁ , and at the time t ₃ , the output of the comparator A ₂ is inverted and the transistor T ₂ is turned on. Turn off. transistor
Even if _T2 is OFF, if the starter switch 3 is ON, the relay 9 is excited through the diode _D7 , so that the glow plug 4 is energized. but,
If the starter switch 3 is turned off at time _t4 , the transistor _T2 is turned off, so that the glow plug 4 is not energized after _t4 , and the above-mentioned disadvantage is eliminated. This case is shown in FIG. 2 by a dashed line.

In this embodiment, the starter switch 3 is
If it is ON, the pilot lamp 5 will always light up, so it is easy to confirm whether the pilot lamp 5 is disconnected. This is because during preheating, if the cooling water temperature is high, the energization time to the glow plug 4 and the lighting time of the pilot lamp 5 will be short, and although it may not be possible to confirm that the pilot lamp 5 is disconnected, the starter switch 3 may not be turned on. In this case, the pilot lamp 5 must be turned on, so that it can be confirmed whether the pilot lamp 5 is disconnected or not.

Furthermore, if a manually operable switch 11 is added as shown in FIG. If the pilot lamp 5 lights up during operation due to a malfunction, preheating can be canceled by switching the switch 11 to the #2 position, which is safe even in the unlikely event of a malfunction.

In addition, if the bending point in Figure 3 is not necessary and the slope of the glow plug energization time with respect to the cooling water temperature is gentler than a certain level, the comparator
_A1 is not necessary. That is, if the change in resistance value of the thermistor 7 with respect to temperature is large (the above-mentioned constant B is large), the comparator _A1 is not necessary. However, current thermistors have limitations, and comparators
There are many cases where A ₁ must be used.

As explained above, according to the present invention, the preheating time by the glow plug can be controlled by the engine cooling water temperature and the terminal voltage of the glow plug.
Optimal preheating time can always be obtained, making it extremely easy to start the engine, and since the capacitor is charged by the terminal voltage of the glow plug, the voltage drop caused by the wiring from the battery to the glow plug is ignored. Therefore, even if the length of the wiring changes due to different types of vehicles, the preheating time can be optimally controlled using the same device.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the device of the present invention;
Figure 2 is a diagram mainly showing the change in charging voltage of capacitor C over time, Figure 3 is a diagram mainly showing the relationship between engine coolant temperature and glow plug energization time, and Figure 4 is a diagram mainly showing the relationship between engine coolant temperature and glow plug energization time.
The figure is a diagram showing a modification of the above embodiment. 1...Battery, 2...Main switch, 3...
...Starter switch, 4...Glow plug, 7...
...Thermistor, 9...Relay.

Claims (1)

[Claims] 1. A comparison means is provided to compare the charging voltage of the capacitor charged by the terminal voltage of the glow plug and the voltage determined by the temperature sensing element that is sensitive to the engine cooling water temperature based on the voltage of the constant voltage circuit. 1. A glow plug preheating time control device, characterized in that the output of the means opens and closes a switching contact inserted between a battery and a glow plug.