JPH0237175A - Preheating residual time display for diesel engine - Google Patents

Abstract

PURPOSE:To make both displays for preheating completion and preheating residual time performable with the same indicator lamp by generating a lamp driving signal in a specified period with duty ratio conformed to an output differential between a difference circuit and a function generator circuit. CONSTITUTION:A difference between output of an integrating circuit 4 in a power source Vcc and output of a cooling water temperature detector 2 connected to a water temperature sensor 1 is securable with a difference circuit 8. Here output of this difference circuit 8 shows a length of residual time up to preheating completion with a DC level. In addition, a specified period of output from a function generator 9 is compared with the output of the difference circuit 8 by a comparator 3. Consequently, output of this comparator 3 comes to such a lamp driving signal as having a duty, the ampler in residual time, the more in the ratio of an ON level. When the output of this comparator 3 is inputted into a buffer 5, a current flows in an indicator lamp 6 from a battery power source, so that the residual time can be displayed by a variation in luminance between lighting and unlighting.

Description

[Detailed Description of the Invention] [Summary] The remaining time until the completion of preheating of a diesel engine that requires preheating at startup is displayed by changing the brightness of an indicator lamp.

(Industrial Application Field) The present invention relates to a remaining preheating time display device for a diesel engine.

Diesel engines require preheating when starting, so an indicator that indicates when preheating is complete is essential.

[Conventional technology]

FIG. 4 shows an example of a conventional preheating completion display device, in which reference numeral 1 denotes a water temperature sensor (for example, a thermistor) whose resistance value changes depending on the cooling water temperature of a diesel engine. 2 is the resistance R,,R
A cooling water temperature detection circuit using a cooling water temperature sensor 2 converts the current flowing from the stabilized power supply Vcc to the water temperature sensor 1 into a voltage ◎. As shown in Figure 5+8), this voltage ◎ decreases as the cooling water temperature rises (because the resistance value of water temperature sensor 1 decreases).
. 3 is a comparator that compares the voltage ◎ with the output ■ of the integrating circuit 4.

Since the voltage ◎ corresponds to the cooling water temperature, it is considered that it does not change during the preheating time of about 10 seconds at the most.

On the other hand, the integrating circuit 4 consisting of the capacitor C1, its charging resistor R3, its discharging resistor R4, etc., increases the integral voltage (2) with a predetermined time constant R3cm when the power supply Vcc rises, as shown in FIG. Therefore, comparator 3 is the sixth
As shown in the figure, the output ■ is inverted after a period of time T has elapsed since the rise of Vcc. The time of this reversal is the time when preheating is completed, and the time up to that point is the remaining preheating time. This preheating remaining time decreases sequentially with T1 being the maximum.

The output of comparator 3 is connected to transistor Ql.

When input to the buffer 5 consisting of Q2, current limiting resistor R5, etc., when ■ = L (low), the inverter transistor Q,
is off, the oven collector type output transistor Q2 is turned on, and current flows from the power source (battery) 10B to the indicator lamp 6.

This current becomes -H (high) and is cut off when the transistor Q1 is turned on and the transistor Q2 is turned off, so the lamp 6 is lit for the time Tl from the rise of Vcc until the time when ■=■.

Note that resistors R6 and R7 constitute an OR circuit 7 for driving the lamp 6 with other inputs.

[Problem to be solved by the invention]

The above-mentioned time T1 is a value that differs depending on the value of the voltage ◎, and therefore the value of the cooling water temperature, but since the conventional driving method is that the lamp 6 is turned on from the start of preheating to the completion of preheating, and is turned off when the preheating is completed, the remaining preheating time The disadvantage is that the driver cannot determine how much

The present invention is a driving method in which the brightness gradually decreases as preheating progresses, and turns off when preheating is completed, and is intended to display not only the completion of preheating but also changes in the remaining time during that time.

[Means to solve the problem]

FIG. 1 is a block diagram of the present invention, and 1 to 6 are the same circuits as in FIG. 4. However, the difference ■ between the output ■ of the integrating circuit 4 and the output ◎ of the cooling water temperature detection circuit 2 is obtained by the differential circuit (differential amplifier) 8, and the difference between the output ■ of the differential circuit 8 and the function generating circuit 9 Compare the output ■ with comparator 3 and get the difference output ■
Constant cycle lamp drive signal with duty according to ■
This is different from FIG. 4 in that it is made to occur.

[Effect]

The signal (■) of the differential circuit 8 indicates how much the integral signal (■) must rise to reach the cooling water temperature detection output (◎), or in other words, the length of remaining time until the preheating is completed when the output becomes (◎-■), as a DC level.

The function generator 69 generates, for example, a triangular wave (2) with a constant period, and the comparator 3 compares this triangular wave (2) with the remaining time output (2). Therefore, the output (2) becomes a lamp drive signal having a duty in which the ratio of ON level increases as the remaining time increases.

Figure 2 shows four typical cases, from the left: the lighting state immediately after preheating starts, the right one is a slightly darker brightness state with more remaining time, the next is a much darker brightness state with less remaining time, and The last one is the light-off state when preheating is completed.

The remaining time can be displayed by providing a state in which the brightness changes between turning on and off, but the timer function for this can be realized by using the existing Vcc integration circuit 4, so we will need an additional configuration. 8.9 may be less.

〔Example〕

FIG. 3 is a block diagram showing one embodiment of the present invention, and the whole shows a preheating device for a diesel engine.

The area within the one-dot chain line frame is the □ preheating 11- device, and the area within the broken line frame is the preheating remaining time display device of the present invention. A battery 21 is provided externally, and when the key switch 22 is turned on, a constant voltage circuit 31 supplies a stabilized power supply Vcc into the control device. Reference numeral 23 denotes a glow plug for preheating, to which a rapid preheating current at the time of starting is supplied through the main relay 24, and an afterglow current after starting is supplied through the sub-relay 25 and glow register 26. 27 is a charge lamp.

The main relay 34 is turned on only while the output of the OR gate G1 is L. This is the case when all four outputs of the AND circuits 03 to G5 and the second timer 32 are at L. The output of the starter signal detection circuit 35 indicates that the key switch 22 is in the starter position S.
When it reaches T, it becomes H, but until then it is L, so all the analogues G3-G5 are open with the output of inverter 3.

The input of the AND gate G3 is the output of the third timer 33, which remains high only for a time T3 from the rise of Vcc, and thereafter becomes H. This time T3 is shortened as the terminal voltage of the glow plug 23 (detected by the detection circuit 34) increases. The input to the AND gate G4 is the status output of the voltage regulator 36 (O after engine start, 11 before start), and the input to the AND gate G5 is a specific water temperature (for example, 40 O).
The second timer 32 is activated when Vcc rises and when the starter signal is detected, and changes the output from L to H after a certain period of time I2. to be reversed. This time T2 is switched by the timer switching circuit 38 in two ways, about 20 seconds and about 140 seconds. 20s is when the output of the regulator 36 is O, and 140S is when the output is l.

The sub-relay 25 is turned on only while the output of the OR gate G2 is L. The input of this OR gate G2 is the second timer 3
2's output and Antogame) G5's output.

Note that Il and I2 are inverters that invert the outputs of the OR gate cm and G2.

The configuration and operation from the water temperature sensor 1 to the indicator lamp 6 are the same as in FIG. 1 except for the OR circuit 7.

〔Effect of the invention〕

As described above, according to the present invention, there is an advantage that the completion of preheating of the diesel engine and the remaining preheating time can be displayed using the same indicator lamp.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the present invention, Fig. 2 is an operating waveform diagram of the present invention, Fig. 3 is a block diagram of an embodiment of the present invention, Fig. 4 is a circuit diagram of a conventional preheating completion display device, and Fig. 5 4 is an output characteristic diagram of each circuit in FIG. 4, and FIG. 6 is an operation waveform diagram of FIG. 4. Applicant: Minoru Aoyagi, Patent Attorney, Fujitsu Ten Limited

Claims (1)

[Claims] 1. Circuit for detecting cooling water temperature of diesel engine (2)
), a timer (4, 8) that measures the remaining time until the required preheating is completed based on the cooling water temperature detected by the detection circuit (2), and a duty that changes in the direction of decreasing the brightness as the remaining time decreases. A circuit (3,
8); and an indicator lamp (6) that is dynamically driven by the lamp drive signal.