JPS59108877A - Glow plug control device for diesel engine - Google Patents

Abstract

PURPOSE:To increase the life of glow plugs and reduce the load on a battery by controlling an output so that the target temperature is lowered relating to the lapse of time after starting operation. CONSTITUTION:The voltage at nodes 19, 20 for a current detecting resistor 2 is transmitted to an A/D 15, and a power amplifier 3 receives control pulse signals from the duty port section of an input-output port 16 through a drive circuit 23. On a control circuit, during the period 0<=t<=t1, the temperature is maintained at C1, during the period t1<=t<=t2, it is maintained at C2 after rising at an inclination (a) and, during the period t2<=t<=t3, it is maintained at C3 after falling at an inclination (b). Thereby, since the target temperature of a glow plug 1 is lowered relating to the lapse of time with the rise in temperature due to the combustion of fuel after starting operation, the high-temperature period of glow plugs 1 is reduced, increasing the life of the glow plugs 1 while reducing the load on a battery.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a glow plug for a diesel engine.

In a diesel engine, a glow plug is installed in the pre-combustion chamber, and glows (preheats) during starting (cranking) to ensure smooth ignition of the air-fuel mixture during starting. In conventional temperature control devices, the target temperature of the glow plug is maintained during the glow period at the same value after startup as before startup. However, since the combustion chamber temperature gradually rises after startup, it is not necessary to maintain the glow plug temperature as high as it is at the beginning of startup. ) and increase the load on the storage battery (battery).

An object of the present invention is to provide a control device for a glow plug for a diesel engine that can improve the life of the glow plug and reduce the load on the storage battery.

To achieve this object, the invention provides a glow plug for heating a pre-combustion chamber, a target temperature setting means for setting a target temperature of this glow plug, and a glow plug that In a control device for a diesel engine glow plug, which is equipped with an energizing current control means for controlling the energizing current of a diesel engine, the output control device controls the output of the target temperature setting means so that the target temperature decreases over time after starting. have the means.

In this way, after startup, the target temperature of the glow plug is reduced over time as the temperature rises due to the combustion of fuel in the combustion chamber, so the high temperature period of the glow plug is reduced and the life of the glow plug is extended. At the same time, the load on the storage battery can be reduced.

The present invention will be described in detail with reference to the drawings.

FIG. 1 shows an overview of the control circuit. Glow plugs 1 provided in each precombustion chamber of a four-cylinder diesel engine are connected in parallel to each other, and are connected to a power supply terminal 4 of a predetermined voltage element B of a DC power source via a current detection resistor 2 and a power amplifier 3. has been done. The current detection resistor 2 is connected in series to the glow plug 1. Voltage dividing resistor 5
, 6 are connected to each other in series and are provided between the power supply terminal of the glow plug 1 and the ground. Other voltage dividing resistors 7 and 8 are connected in series with each other and are provided between the power supply terminal of the current detection resistor 2 and the ground. The electronic control device 11 includes a CPU 12 as a digital processor.
, ROM 13, RAM 14, A/D (analog/digital converter) 15, and input/output port 16,
These elements 12-16 are connected to each other by an address data bus 17. Connection point 19 of voltage dividing resistor 5゜6
and the voltage at the connection point 20 of the voltage dividing resistors 7 and 8 is A/D]5
sent to. The maximum voltage at connection points 19 and 20 is A/D1
The voltage dividing resistor 5 must be connected so as not to exceed the maximum allowable input voltage of 5.
A value of ~8 is selected. The water temperature sensor 22 detects the temperature of the cooling water and sends a detection signal to the A/D 15. The power amplifier 3 receives a control pulse signal from the duty port section of the input/output port 16 via the drive circuit 23. The PNP type power amplifier 3 is conductive during a period when the control pulse signal is at a low level voltage.]-1 is non-conductive during a period when the control pulse signal is at a high level voltage. The engine switch provided in the driver's seat has an on position and a start position in addition to an off position (or lock position), and an on signal 2 indicating that the engine switch is in the on position and the start position.
4 and start signal 25 are sent to input/output port 16. When the engine switch is in the on position, the injection pump is not ready to be driven, and when the engine switch is in the start position, the starter is in operation.

The engine rotation speed sensor 26 includes a pickup 29 that changes the output voltage as it passes through teeth 28 provided at equal angular intervals on the outer circumference of the crankshaft 27. The output voltage of the pickup 29 is outputted through a waveform shaping circuit 30. It is sent to the input/output port 16.

FIG. 2 shows the relationship between the target temperature Co of the glow plug 1 and the elapsed time t. 1=0 is the start time of the glow, ie, when the engine switch is turned on from the off or accessory position, or from the on position to the start position. FIG. 2 illustrates three control patterns, and the control periods of the target/target temperature CO in each control pattern are t=Q~tl, tl~t2. It is divided into three parts, t2 to t3. Glowing is performed until t=t3. In the control period of 0xLl, the target temperature Co is set to C1, and in the control period of tl(t2), the target temperature Co is set to C1.
is maintained at C2 after increasing at a slope a from 1 to 1 with respect to the passage of unit time, and during the control period of t2<t<t3, the target temperature Co
starts to fall at a slope b with respect to the passage of unit time, and then is maintained at C3. If glow plug 1 is energized when it is cold, the glow plug temperature detected from the terminal voltage of glow plug 1 may locally exceed the allowable value even though it is below the allowable value. This may shorten the life of the glow plug, and to avoid this, C1
is set to a value lower than C2. However, just before cranking, the target temperature co is set to C2 so that the glow plug 1 reaches its original heating temperature.

After completion of starting, the target temperature CO is lowered to C3 to reduce the load on the storage battery and extend the life of the glow plug 1. Note that tl is set to a constant value regardless of the control pattern.

3 to 9 are CI, C2,03,t2. t3.
a.

It shows the relationship between b and cooling water temperature. The slopes a and b are expressed as the amount of rise and fall of the target temperature per unit time. The cooler the glow plug 1 is, the greater the risk of local heating of the glow plug 1 at the start of glow, so C1 is set to a smaller value as the cooling water temperature is lower. C2, C3, t2. t3
．． a.

Regarding b, it is set so that the lower the cooling water temperature, the higher the CO and the longer the glow.

FIG. 10 shows an initialization routine performed when the engine switch is turned off or moved from the accessory position to the on position. In step 35, a glow control execution flag Fg is set. In step 36, t3 as one hour of heating is calculated from the cooling water temperature based on the map according to the graph of FIG. In step 37, C1 is calculated from the cooling water temperature based on the map according to the graph of FIG. In step 38, a is calculated from the cooling water temperature based on the map according to the graph of FIG. In step 39, C2 is calculated from the cooling water temperature based on the map shown in the graph of FIG. In step 4o, t2 is calculated from the cooling water temperature based on the map shown in FIG.
Calculate. In step 41, b is calculated from the cooling water temperature based on the map shown in the graph of FIG. In step 42, 03 is calculated from the cooling water temperature based on the map shown in FIG. In step 43, the elapsed time measuring timer Tm is cleared, that is, the timer value Tc is set to zero.

FIG. 11 shows a time interrupt routine for calculating the target temperature Co. In step 49, the glow control execution flag Fg=
1 or not, and only if Fg-1, step 5
Proceed to 0 and beyond. In step 50, the elapsed time Tc is increased by a predetermined amount (increment). In step 51, T
It is determined whether c<tl, and if Tc<tl, the process proceeds to step 52; if Tc)tl, the process proceeds to step 55. In step 52, C1 is substituted for the target temperature Co.

In step 55, it is determined whether Tc<t2, and Tc
If <t2, the process proceeds to step 56; if Tc>t2, the process proceeds to step 62. In step 56, co-1-
Assign a to C0. In step 57, it is determined whether or not Co>C2. If Co)C2, step 58 is executed and C2 is substituted for CO. In step 62, Tc<t3
It is determined whether or not, and if TC<t3, the process proceeds to step 63, and if TC>t3, the process proceeds to step 66. In step 63, C0-b is assigned to CO.

In step 64, it is determined whether c, o<C3, and CO<
If it is 03, step 65 is executed and C3 is substituted for CO. In step 66, the glow control execution flag Fg is reset.

FIG. 12 shows a time interrupt routine for calculating the conduction time S of the power amplifier 3, that is, the duty ratio of the control pulse signal. The actual temperature Cr of the glow plug 1 is the target temperature c
If it is higher than o, the conduction time S is decreased, that is, the duty ratio is decreased, and if it is lower, the conduction time S is increased, that is, the duty ratio is increased. The upper and lower limits of S are 5Qmsec and 20m5ec, respectively, and S
The amount of change ΔS becomes thicker when ΔC (=ICr−C01) is large. The actual temperature Cr of the glow plug 1 is determined by the voltage VI9. at the connection points 19 and 20 in FIG. V20 to A/
It is determined from the ratio of the D-converted values. If the resistance values of the glow plug 1 and the current detection resistor 2 are Rg and Re, respectively, Rg changes in relation to the temperature Cr of the glow plug 1, whereas Re is constant regardless of the temperature Cr of the glow plug 1. It is. As a result, Rg/(Rg+Rc),
l, Therefore, the ratio of the A/D conversion values of the voltages at the connection points 19 and 20 is not related to the change in 10B, but is related to the change in Cr,
Cr can be accurately detected from this ratio. In step 70, it is determined whether the glow control execution flag Fg=1 or not, and only when Fg=1, the process proceeds to step 71 and subsequent steps.

In step 71, the target temperature co of the glow plug 1 is compared with the actual temperature Cr, and if CO>Cr, step 7
The process proceeds to step 2, and if CO<Cr, the process proceeds to step 79. In step 72, Co-Cr is substituted into ΔC. In step 73, Δ
Calculate ΔS from C. In FIG. 13, there is a dead zone in the control of the duty ratio, and in FIG. 14, there is no dead zone. In step 74, S+ΔS is substituted for S.

In step 75, it is determined whether or not S ) 50 m sec, and if S > 50 m sec, step 76
Execute and set S=5Q m see. Step 7
9, assign (::r-Co to ΔC. Step 80
Then, ΔS is calculated from ΔC according to the graph in FIG. 13 or 14. In step 81, S-ΔS is substituted for S.

In step 82, it is determined whether S (20 m sec), and if S < 20 m sec, step 83 is executed to set S = 20 m sec.

FIG. 15 shows a time interrupt routine that is executed after the time interrupt routine of FIG. 12 in order to set the duty ratio for S and L. In step 85, data corresponding to S is input/output. It is set in the duty port section of port 16. In this way, the power amplifier 3 is controlled with a duty ratio corresponding to S, and the time per cycle is S.
conducts only.

FIG. 16 is a functional block diagram of the present invention. The target temperature setting means 90 sets the target temperature Co based on the engine coolant temperature sent from the water temperature sensor 22. The output control means 91 controls the timing after the ON signal 24 or the start signal 25 is generated, that is, at the time t= when the glow starts.
A predetermined time has elapsed from 0 to target temperature C from time t=t2.
The target temperature setting means 90 is controlled so that o decreases from the target temperature C2 during cranking to the lower limit C3 as time passes. The passage of time is carried out by counting clock pulses from clock 9, with t2 being a function of engine coolant temperature (FIG. 6). The actual temperature Cr of the glow plug 1 is detected from the power supply terminal voltage of the glow plug 1, and the duty ratio calculation/output means 92 controls the power amplifier 3 based on the deviation Co-Cr between the target temperature Co and the actual temperature Cr. The duty ratio of the pulse signal is calculated, and the power amplifier 30, which serves as a current control means for the glow plug 1, is turned on and off. In this way, the high temperature period of the glow plug 1 is shortened, thereby extending the life of the glow plug and reducing the load on the storage battery.

[Brief explanation of the drawing]

Fig. 1 is a control circuit diagram of a glow plug for a diesel engine, Fig. 2 is a diagram showing changes in the target temperature of the glow plug over time, and Figs. 1 to 9 (not Fig. 3) are shown in Fig. 2.
, C2, C3, t2. t3. a. Figure 10 is a flowchart of the initial setting routine, Figure 11 is a flowchart of the target temperature calculation routine, Figure 12 is a flowchart of the duty ratio calculation routine, and Figure 13 is a graph showing the relationship between b and cooling water temperature. 14 and 14 are graphs showing the relationship between the variation ΔS of the conduction time S and the deviation ΔC, FIG. 15 is a flowchart of a duty ratio setting routine, and FIG. 16 is a functional block diagram of the present invention. 1... Ri I: l -7' lag, 3... Power amplifier,
24...On signal, 25...Start signal, 9o.
...Target temperature setting means, 91...Output control means. 0 Bellow ° to 1 Height Qcna Cutting δ Figure 5 Cooling water temperature D Figure 6 Figure 7 Figure 8 Figure 9 Cooling water temperature D Cooling water temperature 10
Figure Dead zone Figure 14 Derivative deviation △C (=lCo-Crl)

Claims (1)

[Claims] A glow plug for heating a pre-combustion chamber, a target temperature setting means for setting a target temperature of the glow plug, and an energizing current control means for controlling the current flowing through the glow plug in relation to the output of the target temperature setting means. A control device for a glow plug for a diesel engine, comprising an output control means for controlling the output of the target temperature setting means so that the target temperature decreases over time after starting. control device for glow plugs.