JPS5915681A - Glow-plug controller for diesel-engine - Google Patents

Abstract

PURPOSE:To permit a glow plug to be always supplied with a constant electric power, even if a battery voltage fluctuates, by controlling an interrupting switch according to the output signal from a comparator for comparing output signals from a smoothing circuit and a calculation circuit with each other, in a glow- plug controller. CONSTITUTION:One terminal of a starting switch 2 is connected to the input terminal 301 of a glow-plug controller 3, and the other terminal is connected to the input terminal 302 of the apparatus 3, and the output terminal 303 of the apparatus 3 is connected to one edge of a glow plug 4, and an interrupting switching element 304 is connected to the input terminal 301. A smoothing circuit 306 smoothes the output pulse of the interrupting switching element 304 and converts said pulse into analog voltage V1, and a calculation circuit 307 calculates 1/V from the voltage V of a battery 1, and outputs an analog voltage V2. The output voltages of the both circuits described in the above V1 and V2 are compared in a comparator 308, and if V2>=V1, said output generates a high-level signal, and if V2<V1, a low-level signal is generated, in order to control the interrupting switch 304, and a constant electric power is always supplied to the glow plug 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glow plug control device for a diesel engine. ´ In general diesel engines, the current value applied to the glow plug during starting and after starting is different.

After starting, a small current value is sufficient. Conventionally, in order to reduce the current value, fixed resistors are connected in series for control, but this causes a lot of power loss. In addition, the glow plug's resistor has a temperature coefficient and the resistance value of the resistor is detected.
temperature control.

Glow plugs with a high temperature coefficient have a problem in that they are not durable because a large current flows instantaneously at the start of energization.

In view of the above-mentioned problems, an object of the present invention is to reduce power loss, increase the durability of the elements used, and reduce the temperature of the glow plug based on the idea of eliminating the fixed resistance by using a glow plug without a temperature coefficient. The purpose is to carry out appropriate control of

In the present invention, a smoothing circuit smoothes the output pulse of the intermittent switching element to convert it into an analog signal, an arithmetic circuit that calculates the reciprocal of the storage battery voltage, and a comparator that compares the output signals of the smoothing circuit and the arithmetic circuit. , and the intermittent switching element that is controlled according to the output signal of the comparator and intermittents power to the glow plug.

A glow plug control device for a diesel engine as an embodiment of the present invention is shown in FIG. Reference numeral 1 denotes a battery, the negative electrode of which is grounded, and the positive electrode connected to one terminal of the key switch 2 and an input terminal 301 of the glow plug control device 3. The other end of the start switch 2 is connected to an input terminal 302 of the glow plug control device 3. Glow plug control device 3
The output terminal 303 of is connected to the = end of the glow plug 4.

Power transistor 3 as an intermittent switching element
04 is a PNP type, and its emitter is connected to the input terminal 301. The collector is connected to the smoothing circuit 306 and the output terminal 303 . The pace is connected to the output of drive circuit 310. A first input terminal of the timer 305 is connected to the input terminal 302, and a second input terminal of the timer 305 is connected to the input terminal 301. The output of timer 305 is connected to one input of OR gate 309. The input of the smoothing circuit 306 is output terminal 3
03, and its output is connected to the inverting input of comparator 308.

The input of the arithmetic circuit 307 is connected to the input terminal 301, and the output is connected to the non-inverting input of the comparator 308.

The output of the comparator 308 is connected to the other input of the oak gate 309. The output of the oak gate 309 is connected to the input of the drive circuit 310. The other end of the glow plug 4 is grounded.

FIG. 1 explains the operation of the device. When the start switch 2 is turned on, the timer 305 outputs a high level signal for a certain period of time corresponding to the voltage V of the battery 1. In this case, when the voltage V is high, the time is short, and when the voltage V is low, the time is long. When the output of the timer 305 is high level, the oracle 30
The output of the glow plug 4 becomes high level, and the drive circuit 310 amplifies the power, turns on the power transistor 304, and turns on the glow plug 4.
The battery 1 is energized at a voltage approximately equal to the voltage V of the battery 1.

After a certain period of time has elapsed, the output of timer 305 becomes low level.

If the power transistor 304 is on for a long time, the output of the comparator 308 will be at a low level, as will be described later, and the drive circuit 310 will be turned off. power transistor 304 (
'i is turned off and power supply to the glow plug 4 is stopped. This fixed time TS is the time from when the glow plug 4 starts to be energized until it reaches about 900°C. Of course battery 1
This constant time T8 changes depending on the voltage .

Next, when the power transistor 304 is turned off, the smoothing circuit 3
Since the output of 06 becomes zero, the output of comparator 308 becomes high level and power transistor 304 is turned on. As the on-time becomes longer, the output of the smoothing circuit 306 (paper pressure v1) becomes higher. When v1≧v2, the output of the comparator 308 becomes low level and f) the power transistor 304 is turned off. Therefore, when the voltage V of the battery 1 is constant, self-oscillation occurs at a pulse period of a constant date (FIG. 2).

A smoothing circuit 306 smoothes the duty pulse shown in FIG. 2 and converts it into an analog voltage v1. The arithmetic circuit 307 calculates 1/V(B) from the voltage V(B) of the battery 1 and outputs an analog voltage 2. For example, an IC product number 8013 manufactured by Intern is used for this calculation.

A comparator 308 compares the output voltage v1 of the smoothing circuit 306 with the output voltage v2 of the arithmetic circuit 307, and outputs a high level signal when v2≧v1, and outputs a low level signal when Vz<V+.

In FIG. 2, if the pulse width is T1 and the period is T2, the smoothed voltage v1 is TIXV(B)÷T2. - The output voltage v2 of the force calculation circuit 307 is 1/V(B).

If the system is self-oscillating at a constant period, the comparator 308
The input is v2 in v1. Therefore, T1×v(B
) ÷ T2 = 1 ÷ V (B) The power transistor 304 (7) 11:l/''/l' becomes the equation (1) from (B), and the duty ratio R between the width T1 and the period T2 is the voltage V of the battery 1. It can be seen that it is inversely proportional to the square of (B). Therefore, the data
The tee ratio R will be inversely proportional to the supplied power. Therefore, the duty ratio for changes in battery 1 voltage V(B) is
Since the ratio RFi changes by the square root, the power supplied to the glow plug 4 remains constant.

Here, if the period T2 is controlled to be constant, the pulse width T1 will be the square root of the change in the voltage V(B) of the battery 1.
changes. If the pulse width T1 is controlled to be constant, the period T2 changes by the reciprocal of the square root with respect to a change in the voltage V(B)j). In other words, the frequency will change.

FIG. 3 shows the circuit configuration of the smoothing circuit 306. This is a generally known CR circuit, and one end of the resistor 306a is connected to the output terminal 303, and the other end is connected to one end of the capacitor 306b and the inverting input of the comparator 308. The other end of the capacitor 306111 is grounded.

The operation of the circuit of FIG. 3 will be explained with reference to FIG. Fourth
In figure (1), vll is the voltage V(B) of Nonoteri 1
When is low, V12 is the resistance R and capacitor 3 when it is high.
06b connection point, that is, the output voltage.

V(Hl) is the threshold voltage of the comparator 308 when the output of the smoothing circuit 306 is VH. The comparator has hysteresis so that the output is at low level at 5 V(l(1) and V(
This is the threshold voltage that becomes high level at Ll) and the comparator 30
The output of 8 has the waveform shown in FIG. 4 (2).

Similarly, V12 is the threshold voltage of the comparator 308 when the output of the smoothing circuit 306 is V12; V(U2) is a low level output, and V(L2) is a high level threshold voltage. The output of the comparator 308 has the waveform shown in FIG. 4(3).

When the power supply voltage increases, the comparator 30
The voltage of the non-inverting input 8 becomes low as shown in V12 in FIG. 4(1). Therefore, the charging voltage of the capacitor 306b of the smoothing circuit 306 in FIG.
flows through the glow plug 4, but the discharge gradient b2 in that case is smaller than the gradient b1 when the charging voltage is high. Therefore, the discharge time becomes longer.

On the other hand, when V(B) is large, the charging gradient a2 of the capacitor 306b becomes larger than the charging gradient a1 when V(B) is small. However, for changes in V(B), the comparator 308
The self-excited oscillation period is almost determined by the voltage at the non-inverting input of V(B), that is, the slope of discharging due to the charging voltage of the capacitor 306b, and FIG. 4 (2) shows the period when V(B) is low and (3) when V(B) is high. FIG. 4(4) shows the output waveform of the output freezing control circuit 3 of the power transistor 304 when V(B) is low, and FIG. 4(5) shows the output waveform when V(B) is high.

When the timer 305 is at a low level, the OR gate 309 directly applies the signal from the comparator 308 to the drive circuit 310 . The drive circuit 310 is composed of a power amplifier circuit, and when the input is at a high level, the transistor 304 is completely saturated and turned on, and when the input is at a low level, it is completely turned off. Note that although a power transistor was used to control the power supplied to the glow plug 4, it is obvious that any switch capable of supplying a large current, such as a relay, may be used.

The upper limit of the self-oscillation frequency is determined by the response delay of electronic components such as the power transistor 304 or the comparator 308, and the lower limit is determined by the response speed of the glow plug 4, so it is approximately 50.
~1000 Hz is appropriate for the device shown in Figure 1, which includes an intermittent switch that cuts off the power to the glow plug, an output of the on/off switch, a smoothing circuit that smooths the 9 pulses into an analog signal, and the reciprocal of the battery voltage. An arithmetic circuit that calculates the equation, a comparator that compares the output signals of the smoothing circuit and the arithmetic circuit, and a comparator that controls the on/off switch according to the output signal of the comparator, so that the power is always constant even when the battery voltage fluctuates. can be supplied to the glow plug.

According to the present invention, it is possible to reduce power loss, increase the durability of the elements used, and appropriately control the glow plug temperature.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a glow plug control device for a diesel engine as an embodiment of the present invention, Fig. 2 is a waveform diagram showing output/glucose waveforms of the glow plug control device, and Fig. 3 is a diagram showing the device shown in Fig. 1. FIG. 4 is a waveform diagram illustrating the operation of the circuit shown in FIG. 3. (Explanation of symbols) 1... Battery, 2... Key switch, 3... Glow plug control device, 301, 302, 303... Terminal, 304... War transistor, 305...
Timer, 306... Smoothing circuit, 307... Arithmetic circuit, 308... Comparator, 309... Or dirt, 3
10... Drive circuit, 4... Glow plug. Figure 1 Figure 2 Figure 3 96

Claims (1)

[Claims] 1. A smoothing circuit that smoothes the output pulses of the intermittent switching element into an analog signal, an arithmetic circuit that calculates the reciprocal of the storage battery voltage, a comparator that compares the output signals of the smoothing circuit and the arithmetic circuit, and the comparator. 1. A glow plug control device for a diesel engine, comprising: an intermittent switching element that is controlled in accordance with an output signal of the glow plug, and intermittents power to the glow plug.