JPS59108875A - Glow plug control device for diesel engine - Google Patents

Abstract

PURPOSE:To enable appropriate glowing even with a failure of a sensor by judging whether input signals from a combustion chamber temp. sensor are normal or not and determining the glowing time using these sensor signals when they are normal while using engine temp. signals when they are not normal. CONSTITUTION:The voltage at a node 20 for a current detecting resistor is transmitted to an A/D 15, and a water temp. sensor 22 detects the temperature of engine cooling water and transmit its value to the A/D 15. A power amplifier 3 receives control pulses from the duty port section of an input-output port 16 through a drive circuit 23. A sensor abnormality judging routine judges whether the signals from a sensor 21 are higher than 1,500 deg.C and whether they are lower than -50 deg.C, judges them to be abnormal when they ar beyond these limits, and determines the glowing time based on the signals from the water temp. sensor 22, while determining the time related to the combustion chamber temp. when they are normal. Thereby an appropriate glowing time can be obtained even when the combustion chamber temp. sensor is in failure.

Description

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

In a diesel engine, glow plugs are installed in the pre-combustion chambers in order to smoothly ignite the air-fuel mixture during startup, and the glow (preheating) by the glow plugs continues even after startup until the four combustion chambers reach a predetermined temperature. There is. However, if the combustion chamber temperature sensor that detects the precombustion chamber temperature malfunctions, no glow will occur at all, or the glow will continue even if the precombustion chamber temperature exceeds a predetermined value, causing white smoke and glow. This may cause a reduction in the life of the plug.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for a glow plug for a diesel engine that can perform glow for an appropriate period of time even if a combustion chamber temperature sensor fails.

To achieve this object, the control device for a diesel engine glow plug according to the present invention includes a glow plug that heats a precombustion chamber, an engine temperature sensor that detects engine temperature, a combustion chamber temperature sensor that detects precombustion chamber temperature, Judgment means for determining whether the input signal from the combustion chamber temperature sensor is normal or abnormal, and if the input signal from the combustion chamber temperature sensor is normal, it is related to the pre-combustion chamber temperature, and the combustion chamber temperature If the input signal from the sensor is abnormal, it is related to the engine temperature]7.

Therefore, when the input signal from the combustion chamber temperature sensor is abnormal, glow is performed for a period determined in relation to the engine temperature, so even when the input signal is abnormal, appropriate glow is performed. It is possible to prevent harmful effects such as the generation of smoke.

In a preferred embodiment, the determining means determines that the input signal from the combustion chamber temperature sensor is abnormal when the input signal is outside a predetermined range set in advance.

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. The current detection resistor 2 is connected in series with the glow plug 1.The voltage dividing resistors 5 and 6 are connected in series with each other, and the power supply terminal of the glow plug 1 is connected to the ground. Further, other voltage dividing resistors 7 and 8 are connected in series with each other and are provided between the power supply side terminal of the current detection resistor 2 and the ground.Electronic control device 11 is CPU1 as a digital processor
2, 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/D15
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 combustion chamber temperature sensor 21 detects the temperature Cp of the pre-combustion chamber, and the water temperature sensor 22 detects the engine cooling water temperature, which is related to the engine temperature. The outputs of these sensors 21 and 22 are sent to A/D 1.5.

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. P.N.
The P-type power amplifier 3 is conductive during the period when the control pulse signal is at a low level voltage, and is non-conductive during the period when the control pulse signal is at a high level voltage. The engine switch located in the driver's seat is in the off or locked position)
In addition, the engine switch has an on position and a start position, and an on signal 24 and a start signal 25 indicating that the engine switch is in the on position and start position are input/output ports]
Sent to 6. When the engine switch is in the on position, the injection pump is ready to drive.
When the engine switch is in the start position, the starter is activated. The engine rotation speed sensor 26 includes teeth 2 provided at equal angular intervals on the outer periphery of the crankshaft 27.
Pickup 29 that changes the output voltage as 8 passes through the pickup 29
The output voltage of the pickup 29 is output to the waveform shaping circuit 3.
0 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, i.e. when the engine switch is turned off or turned on from the accessory position.1. Or when it goes from the on position to the start position. FIG. 2 illustrates three control patterns, and the control period of the target temperature Co in each control pattern is 1=0 to t1. t1-t2. 3 of t2-t3
It can be divided into Glowing is performed until t=t3. In the control period of 0 x t x tl, the target temperature Co is set to C1, and in the control period of tl < t x t2, the target temperature CO increases at a slope a with respect to the passage of unit time, and then is maintained at C2, and is maintained at C2. In the control period of <t>t3, the target temperature Co decreases at a slope b at a rate l~ with respect to the passage of unit time, and is then 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, CI is set to a value lower than C2. However, just before cranking, the target temperature Co is set to 02 so that the glow plug 1 reaches its original heating temperature.

After starting, lower the target temperature CO by 03''!

To reduce the load on a storage battery and extend the life of a glow plug 1. Note that tl is set to a constant value regardless of the control pattern.

3 to 9 are CLC2+CL t2. t3. a,
It shows the relationship between b and cooling water temperature. Slope a.

b is expressed by -E increase amount and decrease amount of target temperature per unit time, and 1-. Since the cooler the glow plug 1 is, the greater the risk of local heating of the glow plug 1 at the start of glow, C1 is set to a smaller value as the cooling water temperature is lower. C2, C3, t2
．． t3. Regarding a and b, settings are made such 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 turned from the accessory position to the on position. In step 35, a glow control execution flag Fg is set. In step 36, t3 at 1 hour and 1~ is calculated from the cooling water temperature based on the map shown in the graph of FIG. Step 37
Now, 01 is calculated from the cooling water temperature based on the map shown in 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, 02 is calculated from the cooling water temperature based on the map according to the graph of FIG. Step 40
Now, based on the map shown in Figure 6, calculate t from the cooling water temperature.
Calculate 2. In step 41, b is calculated from the cooling water temperature based on a map according to 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. In step 44, the combustion chamber temperature sensor abnormality flag FC is reset.

FIG. 11 is a time interrupt routine for calculating the target temperature CO. In step 49, the glow control execution flag Fg
It is determined whether or not Fg = 1, and only if Fg = 1, the process proceeds to step 50 and subsequent steps. In step 50, the elapsed time TC
is increased by a predetermined amount (increment). Step 51
Then, it is determined whether TC<tl, and if Tc<:tl, the process proceeds to step 52, and if Tc>tl, step 55
Proceed to. In step 52, C1 is substituted for the target temperature Co. In step 55, it is determined whether TC<t2 or not.
['ct2, proceed to step 56, Tc)t2
If so, proceed to step 59. In step 56, co-
Substitute 1-a into CO. In step 57, CO>C2
If CO>02, step 58 is executed and C2 is substituted for CO. In step 59, it is determined whether the combustion chamber temperature sensor abnormality flag Fc=O or not, and Fc=
If it is O, the process proceeds to step 60, and if FC=1, the process proceeds to step 62. The combustion chamber temperature sensor abnormality flag FC is reset in step 44 in the initial setting routine of FIG. 10, and is set in step 92 when it is determined to be abnormal in the combustion chamber temperature sensor abnormality determination routine of FIG. 16, which will be described later. . In step 60, the pre-combustion chamber temperature Cp detected by the combustion chamber temperature sensor 21 is compared with a predetermined value Ca, and if Cp<Ca, step 63
If Cp>Ca, the process advances to step 66. In step 62, it is determined whether Tc<t3, and 'l'c(t
If it is 3, the process proceeds to step 63; if 'l'c)t3, the process proceeds to step 66. In this way, when the combustion chamber temperature sensor abnormality flag FCXI: 0, that is, the input signal from the combustion chamber temperature sensor 21 is normal, glow is performed until the pre-combustion chamber temperature Cp exceeds the predetermined value Ca, and the combustion When the room temperature sensor abnormality flag FC=1, that is, the input signal from the combustion chamber temperature sensor 21 is abnormal, a predetermined time t3 elapses in relation to the cooling water temperature in step 36 of the initial setting routine in FIG. Glow is performed until In step 63, Co-b is substituted into CO. In step 64, it is determined whether Co<03, and Co
If <03, step 65 is executed and 03 is assigned to 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 Tutey ratio is decreased, and if it is lower, the conduction time S is increased, that is, the Tutey ratio is increased. The upper and lower limits of S are 5Qmsec and 20m5ec, respectively, and S
The amount of change ΔS is larger when ΔC (=ICr−CoI) is larger. The actual temperature Cr of the glow plug 1 is determined by the voltage V19. at the connection points 19 and 20 in FIG. V20 to A/
It is determined from the ratio of the D-converted values. The resistance values of glow plug 1 and current detection resistor 2 are Rg and Re, respectively.
Then, 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. As a result, Rg/(Rg+R
e), therefore the voltage A/ of the connection point 1.9, 20
The ratio of the D conversion values is not related to the change in 10B, but is related to the change in Cr, and Cr can be accurately detected from this ratio. In step 70, it is determined whether the glow control execution flag is Fg-1, and only if Fg = 1, step 71 is performed.
Proceed to the following. In step 71, the target temperature CO of the glow plug 1 is compared with the actual temperature Cr (-1Co). If Cr, the process proceeds to step 72; if CO<Cr, the process proceeds to step 79. In step 72, Co - Cr is substituted into ΔC. In step 73, ΔS is calculated from ΔC according to the graph of FIG. 13 or 14. In FIG. 13, there is a dead zone in the duty ratio control, 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
is executed to set S=50 msec. Step 7
In step 9, Cr-Co is substituted into ΔCK. In step 80, ΔC is changed to Δ according to the graph of FIG. 13 or 14.
Calculate S. 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 msec.

FIG. 15 is a time interrupt routine that is executed subsequent to the time interrupt routine of FIG. It is set in the utility port section. In this way, the power amplifier 3 is controlled with a duty ratio corresponding to S, and the time S per cycle is S.
conducts only.

FIG. 16 is a flowchart of a combustion chamber temperature sensor abnormality determination routine for determining whether the input signal from the combustion chamber temperature sensor 21 is normal or abnormal. In step 90, it is determined whether the pre-combustion chamber temperature Cp indicated by the input signal from the combustion chamber temperature sensor 21 is higher than 1500°C, and C1)>
If it is 1500°C, proceed to step 92 and Cp<150
If the temperature is 0°C, the process advances to step 91. In step 91, it is determined whether Cp is lower than 150°C 1-1Cp<-
Step 92 is executed only if the temperature is 5Q°C. In step 92, a combustion chamber temperature sensor abnormality flag FC is set.

It is actually possible for the precombustion chamber temperature Cp to be higher than 1500°C or lower than 150°C, C
p > 1500”Ch Louis lti Cp<-50°
If Cf6, cp is abnormal, and in such a case, a combustion chamber temperature sensor abnormality flag FC is set.

FIG. 17 is a functional block diagram of the present invention. Judgment means 9
5 determines whether the input signal from the combustion chamber temperature sensor 21 is normal or not, and the determination result is sent to the glow time setting means 96. The glow temporary opening setting means 96 detects whether the input signal from the combustion chamber temperature sensor 21 is normal based on the input from the determination means 95, and if it is normal, it determines whether the input signal is normal or not in relation to the combustion chamber temperature Cp.
If there is an abnormality, the coolant time is set in relation to the cooling water temperature D (D corresponds to the engine temperature) from the water temperature sensor 22. The glow plug 1 has a glow time setting means 96.
Glows for one hour set by . In this way, when the combustion chamber temperature sensor 21 is out of order, an appropriate glow time is set.

[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 target temperature of the glow plug over time, Figs. 3 to 9 are CI 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, Figures 13 and 12 are graphs showing the relationship between b and cooling water temperature. 1
Figure 4 is a graph showing the relationship between the amount of change ΔS in the conduction time S and the deviation ΔC, Figure 15 is a flowchart of the duty ratio setting routine, Figure 16 is a flowchart of the combustion chamber temperature abnormality determination routine, and Figure 17 is a graph showing the relationship between the variation ΔS of the conduction time S and the deviation ΔC. FIG. 2 is a functional block diagram of the invention. 1... Glow plug, 21... Combustion chamber temperature sensor,
22... Water temperature sensor, 95... Judgment means, 96...
- Time setting means. Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Cooling water temperature D Cooling water temperature D Cooling water temperature O Fig. 1O

Claims (1)

[Claims] 1. A glow plug that heats the pre-combustion chamber, an engine temperature sensor that detects the engine temperature, a combustion chamber temperature sensor that detects the pre-combustion chamber temperature, and an input signal from the combustion chamber temperature sensor that is normal. Judgment means for determining whether there is an abnormality, and if the input signal from the combustion chamber temperature sensor is normal, it is related to the pre-combustion chamber temperature, and if the input signal from the combustion chamber temperature sensor is abnormal, the engine 1. A control device for a glow plug for a diesel engine, comprising a glow time setting means for setting a glow time in relation to temperature. 2. The control device according to claim 1, wherein the determining means determines that the input signal from the combustion chamber temperature sensor is abnormal when the input signal is outside a predetermined range.