JPS59134381A - Control system of glow plug for diesel engine - Google Patents

Abstract

PURPOSE:To improve the response of control in a control system using a digital processor by setting the period of control pulse signals of a power amplifier short at the former period and long at the latter period for calculating frequently at the former period when the temperature is changed greatly. CONSTITUTION:Decision is made whether a calculation flag Fs of a connected time S of a power amplifier is equal to one or not. When Fs=1, a step 92 is taken, and when Fs=0, a step 100 is selected. At the step 110, a disconnected time Sb is replaced with (20-S)msec, and at the step 111, with (60-S)msec. Thereby, the period of a control pulse signal is kept at 20msec up to a time t4, and at 60msec after the time t4. This construction permits to calculate the duty ratio frequently at the former period when the temperature of a glow plug is changed greatly for improving the response of control.

Description

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

In a diesel engine, a glow plug is provided in the pre-combustion chamber, and glow (preheating) is performed at the time of starting, so that the air-fuel mixture can be ignited smoothly at the time of starting. However, in conventional control devices for controlling the temperature of glow plugs, the signals are processed by analog circuits, and relays,
Hardware elements such as timers are used, which complicates the control circuit and increases costs, and the temperature of the glow plug is precisely controlled by a circuit.

Therefore, in a previous application, the present applicant disclosed a control device that controls the temperature of a glow plug using a digital processor.

In other words, in the control device of this prior application, a power amplifier is connected in series with the glow plug that heats the pre-combustion chamber, and the temperature of the glow plug is detected from the terminal voltage of the glow plug.
The digital processor calculates the duty ratio of the control pulse signal of the power amplifier by comparing the actual temperature of the glow plug with the target temperature, and flows a current related to this duty ratio to the glow plug.

In the control device of this prior application, the duty ratio calculation period was constant over the entire glow plaque control period. With glow plugs, the temperature change is large in the first half of the control period, and the temperature change is small in the second half, so if the calculation cycle is constant as in the case of the previous 0M device, the control responsiveness deteriorates in the first half, and the power decreases in the second half. Because the amplifier is turned on and off more frequently than necessary, the lifespan (durability) of the power amplifier decreases, and there is a problem in that there is less time available for other calculation processes.

An object of the present invention is to provide a control device for a glow plug for a diesel engine that can ensure control responsiveness in the early stage and avoid problems such as frequent turning on and off of the power booster in the latter stage. be.

In order to achieve this object, according to the present invention, the period of the control pulse signal of the power booster is set to be short in the first half of the control period of the glow plug, and long in the second half of the control period of the glow plug. In this way, the duty ratio is calculated frequently during the first period when the temperature change of the glow plug is large, and the energizing current of the glow plug is changed according to the sudden temperature change of the glow plug, improving control responsiveness. . Furthermore, in the later stages when the temperature change of the glow plug is small, the interval between calculations of the duty ratio increases, thus extending the life of the power amplifier and increasing the time available for calculation processing other than glow control.

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. 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. The electronic control unit 11 is a CPU as a digital processor.
12, ROM, 13, RAM 14, A/D (analog/digital converter) 15, and input/output board 1
6, and these elements 12 to 16 are connected to each other by an address data bus 17. Voltage V1 added to the connection point 19 of voltage dividing resistors 5 and 6 and the connecting point of voltage dividing resistors 7 and 8
91 V2O is sent to A/D15. Connection point 19.2
The values of the voltage dividing resistors 5 to 8 are selected such that the maximum voltage of 0 does not exceed the maximum allowable input voltage of the A/D 15.

The water temperature sensor 22 detects the temperature of the cooling water and sends the 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 (on) during a period when the control pulse signal is at a low level voltage, and is non-conductive (off) 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 24 indicating that the engine switch is in the on position and the start position.
and the start signal 25 is sent to the input/output boat 16. When the engine switch is in the on position, the injection pump is in a drivable state, and when the engine switch is in the start position, the starter is in an operating state. The engine rotation speed sensor 26 is connected to the crankshaft 27
The output voltage of the pickup 29 is sent to the input/output port 16 via a waveform shaping circuit 30.

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 period of the target temperature Co in each control pattern is t==0-t,1, t1''-t2,
It is divided into three parts, t2 to t3. The glow continues until t=t3. In the control period of 0<1≦tl, the target temperature Co
is set to C1, and during the control period when tl<t≦t2, the target temperature CO rises at a slope a with respect to the passage of unit time, and then is maintained at C2, and during the control period when t2<t≦t3, the target temperature CO The temperature Co decreases at a slope b with respect to the passage of unit time and is then maintained at C3. If the claw plug 1 is energized when the glow plug l is cold, the glow plug l
Although the glow plug temperature detected from the terminal voltage is below the allowable value, it may locally exceed the allowable value and shorten the life of the glow plug. To avoid this, CI is lower than C2. set to the value.

However, just before cranking, the target temperature Cθ is set to 02 so that the glow plug l reaches its original heating temperature. After the start is completed, the target temperature CO is lowered to 03 to reduce the load on the storage battery and extend the life of the glow plug l.

Note that tl is set to a constant value regardless of the control pattern.

3 to 9 are CI, C2+C3, t2°t3. a+
It shows the relationship between b and cooling water temperature. The slope a+b is 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. C21C3, t2. t3.
Regarding b, it is set so that the lower the cooling water temperature, the higher the Co value and the longer the glow.

Figure 1O shows the initial settings (
This is the initialization routine. 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. Step 37
Now, 61 is calculated from the temperature of the cooling 7 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 and i' are calculated from the cooling water temperature based on the map shown in the graph of FIG. In step 40, 12 is calculated from the cooling water temperature based on the map shown in FIG. In step 41, b is divided from the cooling water temperature based on the map according to the graph of FIG. In step 42, C3 is calculated from the cooling water temperature based on the map shown in FIG. In step 43, the elapsed time measurement timer Tm is cleared, that is, the timer value T
Set c to zero. In step 44, the conduction time S of the power amplifier 3 in one period of the control pulse signal is set to 20 m5ec.
(When the control pulse signal is 50H7) is substituted.

In step 45, t4 is calculated. t4 will be explained later in FIG. 15 and FIG. 16.

FIG. 11 shows a time interrupt routine for calculating the target temperature Co. In step 49, the glow control execution flag Fg=
], and only if Fg21, step 5
Proceed to 0 and beyond. In step 50, the elapsed time Tc is increased by a predetermined amount (increment). In step 51, Tc
Determine whether ≦tl, and if Tc≦t1, step 5
The process proceeds to step 2, and if Tc>tl, the process proceeds to step 55. In step 52, CI is substituted into the target temperature Co. In step 55, it is determined whether Tc≦t2, and if Tc≦t2, the process proceeds to step 56, and if Tc>t2, the process proceeds to step 62. In step 56, Co, +a is assigned to Co. In step 57, it is determined whether Co > C2 or not. If CO > C2, step 58 is executed and Co is set to 0.
Substitute 2. In step 62, it is determined whether Tc≦t3 or apricot, and if Tc<t3, the process proceeds to step 63, and Tc>
If it is t3, the process advances to step 66. In step 63, c
Assign o-su to Co. In step 64, Co<03
If C'o<(:3, step 65
Execute and substitute C3 for Co. In step 66, the claw control execution flag Fg is reset.

FIG. 12 shows a time interrupt routine for calculating the conduction time S1 of the power amplifier 3, that is, the duty ratio of the control pulse signal when the frequency of the control pulse signal sent to the power amplifier 3 is 50 Hz. If the actual temperature Cr of the glow plug 1 is higher than the target temperature Co, 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 20m5ec and 8m, respectively.
m5ec (if the frequency of the control pulse signal is +00
In the case of 0/60 Hy, the upper and lower limits of the conduction time are set to 6.0 m5et and 24 m5ec, respectively. ), the amount of change ΔS in S increases as ΔC (=ICr−Col) increases. Actual temperature Cr of glow plug 1
is the voltage V19 at the connection point 19°20 in Fig. 1,
It is determined from the ratio of A/D converted values of V2O. The resistance values of glow plug 1 and current detection resistor 2 are R
If g + Rc, Rg is the temperature C of the claw plug l.
Rc varies with respect to r, while Rc
The relation to the temperature Cr is constant. As a result, Rg/
(Rg + Rc), therefore, the voltage V at the connection points 19 and 20]9°V The ratio of the A/D conversion value of 20 is not related to the change in 10B, but is related to the change in Cr, and this ratio Cr can be accurately detected from. In step 70, it is determined whether the glow control execution flag Fg = 1 or An, and Fg = 1.
Only if so, the process proceeds to step 71 and subsequent steps. Step 71
Then, compare the target temperature CO of the claw plug l with the actual temperature Cr, and if CO≧Cr, proceed to step 72 and 1.
If Co<Cr, the process advances to step 79. In step 72, Co - Cr is substituted into ΔC. Step 73
Then, ΔS is subtracted from ΔC according to the graph in 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. Step 7
In step 4, S+ΔS is substituted for S. In step 75, S
>20m5ec or not, S>20m5ec
If so, execute step 76 and set it as S-205-2O. In step 79, Cr - Co is substituted into ΔC.

In step 80, ΔS is calculated from 8C according to the graph of FIG. 13 or 14.

In step 81, S-ΔS is substituted for S. Step 8
2, it is determined whether S < 8 m5ec, and S <
If it is 8 m5ec, execute step 83 and S=:
8 m5ec.

FIG. 15 is a flowchart of a time interrupt routine for switching the power amplifier 3 on and off.

As can be seen from steps 102.103.109 to I11, the period of the control pulse signal of the power amplifier is set to 20 m5ec from the start of glow control until time t4, that is, in the first half of the glow control period, and after time t4, that is, during glow control In the latter half of the period, the period is set to 60 m5ec. Step 92 is actually performed 5m5ec before the time when the power amplifier 3 is switched from off to on.
Steps 93 to 95 are processing for executing step 101 at the next time interrupt, in which step 101 switches the power amplifier 3 from off to on, and steps 104 and 105 execute step 101 at the next time interrupt. This is a process for executing step 108 in step 108.
Now switch power amplifier 3 from on to off, step 1
12 and 113 are processes for executing step 92 at the next time interrupt.

To explain each step in detail, in step 90, the value Tf of the free running counter is read. Tf represents the current time, and the value Rc of the output comparison register is Tf
The time interrupt routine shown in FIG. 15 is executed when this matches. In step 91, the tl' calculation flag F of the conduction time S
Determine whether s = 1 or not. 1. If Fs = 1, proceed to step 92; if Fs = O, proceed to step 10
Go to 0. In step 92, the conduction time S of the power amplifier 3
Divide. The details of step 92 are as explained in FIG. In step 93, the value R of the output comparison register is
Substitute Tf + 5 m5ec for c. Step 94
Then, the subtraction flag Fs of the conduction time S is reset. In step 95, a conduction time set flag Ft is set.

In step 100, it is determined whether the conduction time set flag Ft is 21 or 1, and if Ft=1, the process proceeds to step 101.
If Ft = O, proceed to step +08. In step +01, the claw control output port of input/output port 16 (
=Duty Baud 1~ Set). This turns on the power amplifier 3. In step +02, the value Tc of the elapsed time measurement timer Tm defined in step 43 and t4
If Tc<t4, proceed to step 104; if Tc>t4, proceed to step 103 and proceed to step 1.
Proceed to 04. FIG. 16 shows the relationship between t4 and cooling water temperature. The lower the cooling water temperature, the longer it takes for the glow plug I to reach the target temperature Co, and the longer the time for the rapid temperature change of the glow plug 1.
4 increases. In step 103, SX3 is connected for a conduction time S
Assign to . In step 104, Tf + S m5ec is assigned to the value Rc of the output comparison register. step +
At step 05, the conduction time set flag Ft is reset. In step 108, the glow control output port is reset. As a result, power amplifier 3 is turned off. Step] 0
9, similarly to step +02, the elapsed time measurement timer Tm
The value Tc and t4 are compared, and if Tc is less than t4, the process proceeds to step 110, and if Tc > t4, the process proceeds to step 111. In step 110, the non-conduction time sb is set to (
20-5) Substitute m5ec, and in step 111 substitute (li O5) msec for the non-conduction time sb. In step 112, the value Rc of the output comparison register is set to Tf +
Substitute Sb -5. In step 113, the conduction time S is divided. Fig. 1 is a control circuit diagram of a glow plug for a diesel engine, Fig. 2 is a diagram showing a change in target temperature of a glow plug over time, and Figs. CL C2+ C3+ t2. t:La.

Graph showing the relationship between b and cooling water temperature, 10th is a flowchart of the initial setting routine, 11th is a flowchart of eye temperature calculation routine, 1512 is a flowchart of duty force meter Et routine, 13th Figures 14 and 14 are graphs showing the relationship between the required amount ΔS of the conduction time S and the deviation ΔC, m! Figure 1.5 is a flowchart of the routine for switching the power J'f1 width switch on and off.
FIG. 6 is a graph showing the relationship between the cooling water temperature and the time t4 at which the cycle of the It power amplifier control pulse signal is switched.

1...Glow plug, 3...Power amplifier, 11...
・Electronic control device.

L Figure 3 Figure 4 Figure 5 G Koaki q profit return Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] A power amplifier is connected in series to the glow plug that heats the pre-combustion chamber, the temperature of the glow plug is detected from the terminal voltage of the glow plug, and the electric power is calculated by comparing the actual temperature of the glow plug with the target temperature using a digital processor. In a control device for a diesel engine glow plug that calculates the duty ratio of the control pulse signal of an amplifier and causes a current related to this duty ratio to flow through the glow plug, the period of the control pulse signal in the first half of the glow plug control period is changed to A control device for a claw plug for a diesel engine, which is characterized by making the period shorter than the period.