JP2005113875A - Control device for diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress generation of deposits by effectively using a glow plug when exhaust gas recirculation control is performed after completion of warming-up of an engine. <P>SOLUTION: This control device for the diesel engine is equipped with exhaust gas recirculation devices (6, 11) for recirculating part of exhaust gas, which is inert gas, from an exhaust system to an intake system, and actuates the exhaust gas recirculation devices (6, 11) under a predetermined condition. The control device for the diesel engine is provided with the glow plug (21) for superheating intake air and glow plug control means (22, 31, 32, 33, 35) for actuating the glow plug (21) in the condition that temperature of combustion gas becomes low during operation of the exhaust gas recirculation devices (6, 11) after completion of warming-up of the engine. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control device for a diesel engine, and particularly to a device equipped with a glow plug.

  In order to reduce NOx contained in the exhaust of a diesel engine, an exhaust gas recirculation device that recirculates part of the exhaust gas, which is an inert gas, from the exhaust system to the intake system and suppresses the maximum temperature during combustion has been conventionally used. Known from. In this system, an exhaust gas recirculation control valve using, for example, a step motor is interposed in an exhaust gas recirculation passage from the exhaust system to the intake system, and the exhaust gas recirculation amount is controlled by opening control by the step motor.

In this case, the exhaust gas recirculation device is deactivated and the glow plug is energized in order to promote the exhaust temperature rise while the catalyst is warming up soon after starting, and then the cooling water temperature reaches the predetermined temperature Caton. Then, there is one that stops energization of the glow plug and operates the exhaust gas recirculation device again (see Patent Document 1).
JP 2003-65121 A

  By the way, the exhaust gas recirculation gas contains various components such as fuel and engine oil oxides, or unoxidized fuel and engine oil. A part of these components in the exhaust gas recirculation gas adheres to each part of the flow path from the position where the exhaust gas recirculation control valve is provided to the intake port, forming a so-called deposit. When the components of this deposit are analyzed, it is considered that not only the adhesive component but also the non-adhesive component and the soot-like substance are mixed and these form a deposit. For example, when such deposit adheres and hardens between the valve body of the exhaust gas recirculation control valve and the valve seat, the cross-sectional area of the EGR gas flowing through the exhaust gas recirculation control valve becomes small and the target exhaust gas recirculation gas flow rate cannot flow. It is also conceivable that the exhaust gas recirculation control valve is not fully opened due to the deposit. Further, in an engine having an exhaust gas recirculation device that has an intake throttle valve in the intake passage separately from the exhaust gas recirculation control valve and closes the intake throttle valve to a predetermined opening when performing exhaust gas recirculation, the exhaust gas recirculation gas is Since the intake throttle valve position is reached, it is conceivable that the cross-sectional area of the intake flow path is reduced due to the generation of deposits, or the intake throttle valve does not open with the valve fully closed.

  Therefore, in order to prevent deposits from being formed, it is necessary to run at high speed with a vehicle equipped with a diesel engine, but in reality, it is not always possible to run at high speed, but the vehicle is used in urban areas and traffic jams In most cases, operation at a low load and a low rotational speed is almost impossible, and it is inevitable that a deposit is formed.

  Accordingly, an object of the present invention is to suppress the generation of deposits by effectively using a glow plug when exhaust gas recirculation control is performed after completion of engine warm-up.

  On the other hand, the technique described in the above-mentioned Patent Document 1 only uses a glow plug to promote exhaust temperature rise during the warming up of the catalyst, and the glow plug is exhausted at the time of exhaust gas recirculation control after completion of engine warming up. The technical idea is different from that of the present invention, which is used to promote temperature rise and suppress the formation of deposits.

  The present invention includes an exhaust gas recirculation device that recirculates a part of exhaust gas, which is an inert gas, from an exhaust system to an intake system, and in a diesel engine control device that operates the exhaust gas recirculation device under a predetermined condition. When the exhaust gas recirculation device is in operation after completion and when the temperature of the combustion gas is low, the glow plug for overheating the intake air is operated.

  According to the present invention, the glow plug is operated when the exhaust gas recirculation device is in operation after the warm-up of the engine is completed and the temperature of the combustion gas is low. It can prevent that combustion gas temperature falls and can suppress the production | generation of a deposit.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, and FIG. 2 is an electric circuit diagram of a glow plug 21. In FIG. 1, reference numeral 1 denotes a diesel engine. The engine 1 mainly includes a fuel tank, a supply pump, a common rail (pressure accumulation chamber), and a common rail type fuel injection device (not shown) including an injection nozzle 8 provided for each cylinder. After the fuel pressurized by the supply pump is once stored in the pressure accumulating chamber, the high pressure fuel in the pressure accumulating chamber is distributed to the injection nozzles 8 corresponding to the number of cylinders and receives a signal from the engine controller 31 as an operating condition. Accordingly, when the fuel injection amount set accordingly reaches a predetermined fuel injection timing, it is directly supplied into the combustion chamber 7.

  The combustion chamber 7 is provided with a glow plug 21 for heating the intake air. As shown in FIG. 2, the glow plug 21 is connected to the positive terminal of the battery 24 via the glow relay 22 and the fuse 23, and the switch means (not shown) in the engine controller 31 is disconnected. Since the contact 22a of the glow relay 22 is opened, the current from the battery 24 does not flow to the glow plug 21, but when the switch means in the engine controller 31 is connected, the coil 22b of the glow relay 22 is connected to the coil 22b from the battery 24. A current flows, the contact 22a is closed, and a current from the battery 24 flows to the glow plug 21 of each cylinder (in the case of a four-cylinder engine in the figure).

  The EGR passage 4 connecting the exhaust passage 2 and the collector portion 3a of the intake passage 3 is provided with an exhaust gas recirculation control valve 6 that can be variably controlled by a step motor (in a strict sense, in a number of steps). ing. The intake throttle valve 11 provided in the intake passage 3 upstream from the collector portion 3a also constitutes a part of the exhaust gas recirculation device, and restricts the intake passage area during exhaust gas recirculation. The intake throttle valve 11 has a negative pressure actuator (not shown), and is closed when the negative pressure VAC is introduced by switching the electromagnetic valve 12 and is opened when the electromagnetic valve 12 is opened to the atmosphere. In the present embodiment, the exhaust gas recirculation device is constituted by the exhaust gas recirculation control valve 6 and the intake throttle valve 11, but the intake throttle valve 11 may not be provided.

  In the engine controller 31 to which signals of the accelerator pedal depression amount from the accelerator opening sensor 32, the engine rotational speed from the rotational speed sensor 33, and the water temperature from the water temperature sensor 34 are input, the exhaust gas recirculation is based on these signals. The exhaust gas recirculation amount is controlled via the control valve 6 and the intake throttle valve 11. FIG. 9 shows the characteristics of the target exhaust gas recirculation rate. The exhaust gas recirculation rate becomes maximum when the engine speed is low and the load is low, and the exhaust gas recirculation rate decreases as the rotational speed Ne increases or the target injection amount Q as the load increases. The exhaust gas recirculation rate becomes zero% (that is, the exhaust gas recirculation control device is in a non-operating state) in the load region and the high rotation speed region. FIG. 10 shows an example of the opening / closing control of the intake throttle valve 11. In the exhaust recirculation region (the region where the exhaust gas recirculation rate is not zero%), the intake air throttling is partially performed at a part of the low rotational speed and low load side where the exhaust gas recirculation rate is high. The valve 11 is closed to increase the differential pressure across the exhaust gas recirculation control valve 6 so that the exhaust gas recirculation amount increases. That is, the intake throttle valve 11 is opened and closed according to FIG. 10, and the step motor for the exhaust gas recirculation control valve 6 is controlled so as to obtain the target exhaust gas recirculation rate shown in FIG.

  On the other hand, in order to ensure the start, the engine controller 31 energizes the glow plug 21 at the start to warm the intake air.

  In the present invention on the premise of an engine having such a glow plug 21 and an exhaust gas recirculation device, special glow control is newly performed using the glow plug 21 when the exhaust gas recirculation device is operated after the after glow (after the engine is warmed up). Do. Here, the special glow control is a control for operating the glow plug 21 of each cylinder when the exhaust gas recirculation device is in operation after the warm-up of the engine is completed and the temperature of the combustion gas is low.

  This special glow control will be further described with reference to FIG. 3. This figure shows how the glow plug 21 is energized when the engine is continuously operated in the idling state (low load low rotation speed range) from the start. It shows whether or not energization is performed. At the time t1, the ignition key switch is turned on and the glow plug 21 is energized at the same time. This is called pre-glow.

  Even after the engine is started at time t2 and the engine rotational speed has increased to reach the complete explosion rotational speed, energization of the glow plug 21 is continued until the engine warm-up is completed in order to improve combustion stability at low temperatures. . This energization is called afterglow, and in this embodiment, it is simply determined that the warm-up has been completed based on the elapsed time after the engine is started. Until it has passed. At time t3 when the after glow ends, the energization to the glow plug 21 is once stopped, and the special glow control is started.

  In the special glow control from time t3, it is first checked whether or not a special glow control condition is satisfied. The establishment of the special glow control condition is to satisfy all of the following conditions.

  (1) The operating condition is in the low load and low rotation speed range.

  (2) The fuel temperature is lower than a predetermined value.

  These conditions (1) and (2) are for estimating when the temperature of the combustion gas after completion of warming up of the engine is low. However, it is assumed that the exhaust gas recirculation device is always operated in the low load low rotation speed region.

  If the above two conditions (1) and (2), that is, the special glow control condition, are satisfied at time t4, the glow plug 21 is not immediately activated at time t4, but (1), (1 Whether or not the state where the two conditions (2) are satisfied continues for a predetermined operation delay time Δt2 (for example, about several minutes), the state where the two conditions (1) and (2) are satisfied The glow plug 21 is operated for the first time at time t5 when the operation delay time Δt2 continues. As described above, the operation of the glow plug 21 is delayed until the operation delay time Δt2 elapses. If the operation delay time Δt2 does not exist, the glow plug 21 is frequently operated due to a short change in operating conditions. This is to avoid this because power consumption increases.

  From time t5, the glow plug 21 is continuously energized for a predetermined time Δt3 (for example, about 3 minutes) and the glow plug 21 is continuously energized for a predetermined time Δt4 (for example, about 5 minutes). In this way, instead of continuously energizing the glow plug 21, the energization period and the non-energization period are repeated at a constant cycle, because the temperature of the combustion gas is suppressed while suppressing the power consumption of the battery 24. It is for raising.

  However, it is conceivable that the glow relay 22 deteriorates due to repeated energization and de-energization of the glow plug 21 every predetermined period, so that the function as a relay can no longer be performed. When the total time of energizing 21 (or the number of times the glow plug 21 is energized continuously) exceeds a predetermined specified value (upper limit value), the glow plug 21 is operated until the engine 1 is stopped thereafter. Is prohibited. Originally, the deterioration of the glow relay 22 should be determined based on the operation of the glow plug 21 after the manufacture, not every trip, but the engine controller is used in this embodiment. No. 31 is for dealing with a case where a function for storing the total time of continuous energization of the glow plug 21 and the number of times of energization of the glow plug 21 after the ignition key switch is OFF is not provided. If the engine controller 31 has a function of storing the total time that the glow plug 21 is continuously energized and the number of times that the glow plug 21 is continuously energized even after the ignition key switch is turned off, the engine controller 31 stores this. What is necessary is just to comprise so that total time and frequency | count may be compared with a predetermined specified value (upper limit value).

  The above-mentioned one trip is a period from the start of the engine to the stop of the engine.

  The glow control executed by the engine controller 31 will be described in detail with reference to a flowchart.

  FIG. 4 is for performing normal glow control, and is executed at regular intervals (for example, every 10 ms). Before the flow of FIG. 4 starts, the glow plug 21 is turned on when the ignition key switch is turned on to prepare for subsequent engine start.

  Step 1 looks at the complete explosion flag (initially set to zero). When the complete explosion flag = 0, the process proceeds to step 2 and the starter switch (abbreviated as “ST SW” in the figure) is viewed. When the starter switch is ON, the process proceeds to step 3 and energization of the glow plug 21 is continued. In step 4, the engine speed Ne is compared with the complete explosion speed. When the engine rotational speed Ne is less than the complete explosion rotational speed, the current process is terminated.

  When the engine rotational speed Ne becomes equal to or higher than the complete explosion rotational speed, the routine proceeds to step 5 where the complete explosion flag = 1 and the timer is started at step 6. This timer is for measuring the elapsed time from the complete explosion.

  Since the complete explosion flag = 1 in step 5, next time, the process proceeds from step 1 to step 7, and the timer value is compared with the specified time Δt1. The specified time Δt1 determines the afterglow time. If the timer value is equal to or less than the specified time Δt1, the process proceeds to step 8 and energization of the glow plug 21 is continued.

  When the timer value exceeds the specified time Δt1, the process proceeds from step 7 to step 9 to stop energizing the glow plug 21 and at step 10 the special glow control start flag (initially set to zero) = 1.

  FIG. 5 is for setting a special glow permission flag, which is executed at regular intervals (for example, every 10 ms).

  In step 11, the special glow control start flag is viewed. When the special glow control start flag = 0, the current process is terminated.

  When the special glow control start flag = 1, the process proceeds to step 12 to see the special glow control permission flag. Since the special glow control permission flag is initially set to zero, the process proceeds to steps 13, 14, 15, and 16 to determine whether or not the special glow control permission condition is satisfied. That is, in steps 13 to 16, whether or not the load is in a low load range, whether or not the rotation speed is in a low rotation speed range, whether or not the fuel temperature is below a predetermined value, and further, the load is in a low load range. It is checked whether or not a predetermined operation delay time Δt2 has elapsed with the condition that the engine speed is in the low rotation speed range and the fuel temperature is equal to or lower than a predetermined value. The load is in a low load range (the target injection amount Q is not more than a predetermined value), the rotation speed is in a low rotation speed range, or the fuel temperature is not more than a predetermined condition. Even if the condition that the load is in the low load range, the rotation speed is in the low rotation speed range, and the fuel temperature is equal to or lower than the predetermined value is satisfied, the predetermined operation delay time Δt2 has not elapsed. Sometimes it is determined that the special glow control permission condition is not satisfied, and the current process is terminated.

  On the other hand, if the predetermined operation delay time Δt2 elapses with the condition that the load is in the low load range, the rotation speed is in the low rotation speed range, and the fuel temperature is equal to or lower than the predetermined value, a special operation is performed. It is determined that the glow control permission condition is satisfied, and the process proceeds to step 17 to set the special glow control permission flag = 1. As described above, when the load is in the low load range and the rotation speed is in the low rotation speed range, the exhaust gas recirculation device is operating. Further, since the combustion gas temperature decreases in such a low load low rotation speed region, the temperature of the exhaust gas recirculation gas also decreases, and deposits are generated downstream including the exhaust gas recirculation control valve 6 and the intake throttle valve 11. Therefore, the special glow control permission flag = 1 is set in order to perform the special glow control.

  Here, the target injection amount Q may be used as a parameter for determining whether or not it is in the low load range. Therefore, if the operating condition determined from the target injection amount Q and the engine rotational speed Ne is in the low load low rotational speed region shown in FIG. 6, it is determined that the load is in the low load region and the rotational speed is in the low rotational speed region. . The target injection amount Q is basically determined in accordance with the accelerator pedal depression amount detected by the accelerator opening sensor 32 and the engine rotational speed detected by the rotational speed sensor 33. Since the fuel temperature sensor 35 is attached to the supply pump, the fuel temperature detected by the fuel temperature sensor 35 may be used. The intake air temperature can be substituted for the fuel temperature.

  When the special glow control permission flag is set to 1 in step 17, the process proceeds to steps 18 to 22 from steps 11 and 12 next time. Steps 18 to 22 are portions for checking whether or not the special glow control permission condition is not satisfied during the special glow control. That is, during the special glow control (special glow control permission flag = 1), the load becomes large and does not fall in the low load range, or the rotational speed becomes high and the low revolution speed range disappears, or the fuel temperature rises to a predetermined value. If not, the process proceeds from Steps 18 to 20 to Steps 21 and 22 where the special glow control permission flag = 0 and the glow energization flag = 0 to stop energization of the glow plug 21.

  FIG. 7 is for performing special glow control, and is executed at regular intervals (for example, every 10 ms). In FIG. 7, first, a description will be given of a case where the operation condition does not change and the special glow control permission flag = 1 is continuously maintained.

  In steps 31 and 32, the special glow control prohibition flag and the special glow control permission flag are observed. Here, since the special glow control prohibition flag is initially set to zero, when the special glow control prohibition flag = 0 and the special glow control permission flag = 1, the process proceeds to step 33, where the special glow control permission flag = 1. See if there was.

  When the special glow control permission flag was 0 in the previous time, that is, when the special glow control permission flag was 0 in the previous time, the process proceeds to steps 34 to 35 in order to operate the glow plug 21 when it is switched to 1 this time. The timer value tON = 0, the timer value tOFF = 0, and the glow energization flag = 1.

  Here, the glow energization flag = 1 is an instruction for energizing the glow plug 21, and the glow energization flag = 0 is a flag for instructing the non-energization of the glow plug 21. For this reason, energization of the glow plug 21 is started in step 36.

  Since the glow energization flag = 1 in step 35, the process proceeds to step 37 and subsequent steps from steps 32 and 33 next time. Steps 37 to 49 are parts for repeating energization and non-energization to the glow plug 21 every certain period Δt3 and Δt4 during the special glow control permission.

  In step 37, the glow energization flag is viewed. Since the glow energization flag is set to 1 in step 35, the process proceeds to step 38 to energize the glow plug 21.

  In step 39, the timer value tON is incremented by a predetermined time Δt, and the timer value tON is compared with the glow energization time Δt3 (constant value) in step 40. When the timer value tON is less than the glow energization time Δt3, the current process is terminated.

  If the timer value tON is accumulated while energizing the glow plug 21 in steps 38 and 39 from the next time, the timer value tON eventually becomes equal to or longer than the glow energization time Δt3 in step 40, so the process proceeds to step 41 at this time. The glow energization flag = 0.

  In step 42, the glow energization time is integrated by adding the timer value tON to the energization integration time SUMON, and in step 43, the timer value tON = 0 is set in preparation for the next energization.

  In step 44, the energization integration time SUMON is compared with a specified value (upper limit value). Here, at the beginning of the special glow control, since the energization integration time SUMON is equal to or less than the specified value, the current process is terminated.

  Since the glow energization flag = 0 in step 41, the process proceeds to step 45 and subsequent steps from steps 32, 33 and 37 next time. In step 45, the energization of the glow plug 21 is stopped. In step 46, the timer value tOFF is incremented by a predetermined time Δt, and the timer value tOFF is compared with the glow non-energization time Δt4 (constant value) in step 47. When the timer value tOFF is less than the glow non-energization time Δt4, the current process is terminated.

  If the timer value tOFF is integrated while deenergizing the glow plug 21 in the next steps 45 and 46, the timer value tOFF will eventually be equal to or longer than the glow deenergization time Δt4 in step 47. Then, the glow energization flag = 1 is set, the timer value tOFF = 0 is set in preparation for the next non-energization, and the current process is terminated. With this glow energization flag = 1, the process proceeds from step 32, 33, 37 to step 38 and subsequent steps.

  In steps 38 to 44, energization of the glow plug 21 is performed for the period of the glow energization time Δt3, and in steps 45 to 49, deenergization of the glow plug 21 is performed for the period of the glow deenergization time Δt4. In this way, when the energization and non-energization of the glow plug 21 are repeated several times for each of the fixed periods Δt3 and Δt4, the energization integration time SUMON in step 42 increases. When the energization integration time SUMON eventually exceeds the specified value, the routine proceeds from step 44 to step 50, where the special glow control prohibition flag = 1 is set.

  By the way, in the flow of FIG. 5 and FIG. 7, the special glow control permission condition is established by, for example, leaving the operation in the low load low rotation speed region before the energization integration time SUMON reaches the specified value once the special glow control is entered. This also corresponds to the case where the engine shifts (and therefore does not become the special glow control prohibition flag = 1), and then shifts to the special glow control by operating again in the low load low rotation speed region. That is, when the operation in the low load low rotation speed region is canceled due to a change in the operating conditions before the energization integration time SUMON reaches the specified value after entering the special glow control, the steps 11, 12, and 18 in FIG. , 22 and the special glow control permission flag = 0 and the glow energization flag = 0. Due to this special glow control permission flag = 0, it is not possible to proceed from step 32 to step 33 onward in FIG. In addition, energization to the glow plug 21 is stopped by the glow energization flag = 0. Further, the amount of time until the timing at which the operation in the low load low rotation speed region is released is held as the energization integration time SUMON.

  When the operation delay time elapses due to the change in the operating condition after that and the operation delay time has elapsed, the process proceeds from step 11 to step 17 in FIG. 5 and the special glow control permission flag = 1. Become. With this special glow control permission flag = 1, the process proceeds from step 31 and 32 to step 33 onward in FIG. 7, and the special glow control that repeats energization and non-energization of the glow plug 21 every predetermined period Δt3 and Δt4 is resumed. Then, after the resumption of the special glow control, the energization integration time SUMON at step 42 increases from the held value. When the energization integration time SUMON in step 42 eventually exceeds the specified value, the process proceeds from step 44 to step 50 and the special glow control prohibition flag = 1.

  When the special glow control prohibit flag is set to 1 in this way, it is not possible to proceed from step 31 to step 32 onward in FIG. In other words, the special glow control is performed only once during the period from engine start to engine stop (one trip).

  Although not shown, the energization integration time SUMON is reset to zero when one trip is completed and the ignition key switch is turned OFF (meaning that this has no memory function).

  Here, the progress of the deterioration of the glow relay 22 is affected by the ambient temperature of the glow relay 22, and the higher the ambient temperature is, the faster the glow relay 22 is degraded. In accordance with this influence, the specified value to be compared with the energization integration time SUMON is set shorter as the atmospheric temperature of the glow relay 22 is higher in accordance with the atmospheric temperature of the glow relay 22. The ambient temperature of the glow relay 22 may be detected by an intake air temperature sensor.

  Here, the operation of the present embodiment will be described.

  FIG. 8 shows the state after the after glow (after completion of warming up of the engine) as in this embodiment when the engine is operated for a certain period of time while keeping the load and the rotation speed constant in the low load and low rotation speed region from the start of the engine. The deposit is made when the glow plug 21 is operated when the exhaust gas recirculation device is operated, and when the glow plug 21 is not operated when the exhaust gas recirculation device is operated after the after glow (after completion of engine warm-up) (conventional device). It is the experimental result which measured what happens to the amount of unburned oxide in the exhaust which is connected. As shown in the figure, according to the experimental results, the glow plug 21 is operated when the glow plug 21 is operated during the operation of the exhaust gas recirculation device after the afterglow (after completion of engine warm-up) as in the present embodiment. It can be seen that the amount of unburned oxide in the exhaust gas is smaller than when not.

  As described above, according to the present embodiment, when the exhaust gas recirculation device after the afterglow (after completion of engine warm-up) is operated, the condition is that the fuel is in the low load low rotation speed region and the fuel temperature is equal to or lower than the predetermined value, that is, the combustion Since the glow plug 21 is positively operated when the temperature of the gas is low (the invention according to claim 1), the temperature of the combustion gas is decreased even under the operating condition where the temperature of the combustion gas is low. It was possible to prevent the generation of deposits.

  In addition, if the conditions for lowering the temperature of the combustion gas are satisfied, the glow plug 21 is immediately activated. Therefore, the glow plug 21 is frequently activated due to a change in operating conditions in a short time, and the battery 24 Although power consumption increases, according to the present embodiment, the operation of the glow plug 21 is delayed until a predetermined operation delay time Δt2 elapses after the condition for reducing the temperature of the combustion gas is satisfied. (Invention of Claim 2), frequent operation of the glow plug 21 accompanying a change in operating conditions for a short time can be avoided, and power consumption of the battery 24 can be suppressed.

  According to this embodiment, the operation of the glow plug 21 is to repeatedly energize the glow plug 21 for a predetermined time Δt3 and to not energize the glow plug 21 for a predetermined time Δt4 ( (Invention of Claim 5) The temperature of combustion gas can be raised, suppressing the power consumption of the battery 24. FIG.

  According to the present embodiment, when the cumulative energization time SUMON of the glow plug 21 in one trip (the total time during which the glow plug is continuously energized) exceeds a predetermined specified value (upper limit value), it is longer than that. Since the operation of the glow plug 21 is prohibited (the invention according to claim 7), even when the engine controller 31 does not have a function of storing the energization integration time SUMON even after the ignition key switch is turned off, the glow relay 22 Can be prevented.

  The progress of the degradation of the glow relay 22 is affected by the ambient temperature of the glow relay 22, and the higher the ambient temperature of the glow relay 22 is, the faster the degradation of the glow relay 22 is. According to the present embodiment, according to this embodiment, the specified value (upper limit value) to be compared with the energization integration time SUMON is set to be shorter as the atmospheric temperature of the glow relay 22 is higher according to the atmospheric temperature of the glow relay 22. Therefore, the degree of deterioration of the glow relay 22 can be accurately estimated.

  In the embodiment, the case has been described where the operation of the glow plug is prohibited when the total time during which the glow plug 21 is continuously energized exceeds a predetermined upper limit value. The operation of the glow plug 21 can be prohibited when a predetermined upper limit value is exceeded.

  The function of the glow plug control means described in claim 1 is performed by steps 32 to 34, 36 to 42, 44, and 46 to 50 in FIG.

The schematic block diagram which shows one Embodiment of this invention. Electrical circuit diagram of glow plug. The wave form diagram for demonstrating special glow control. The flowchart for demonstrating normal glow control. The flowchart for demonstrating the setting of a special glow permission flag. Operation region diagram. The flowchart for demonstrating special glow control. The characteristic view of the amount of unburned oxide in exhaust_gas | exhaustion for demonstrating the effect | action of this embodiment. The characteristic view of a target EGR rate. The control area figure of an intake throttle valve.

Explanation of symbols

1 Engine 6 Exhaust gas recirculation control valve (exhaust gas recirculation device)
11 Intake throttle valve (exhaust gas recirculation device)
21 Glow plug 22 Glow relay 31 Engine controller 32 Accelerator opening sensor 33 Engine speed sensor 35 Fuel temperature sensor

Claims (8)

An exhaust gas recirculation device that recirculates part of the exhaust gas, which is an inert gas, from the exhaust system to the intake system,
In a diesel engine control device that operates the exhaust gas recirculation device under predetermined conditions,
A glow plug that overheats the intake air,
A diesel engine control device comprising: a glow plug control means for operating the glow plug when the exhaust gas recirculation device is in operation after completion of warming up of the engine and the temperature of the combustion gas is low. .   2. The diesel engine control device according to claim 1, wherein the operation of the glow plug is delayed until a predetermined delay time elapses after a condition for lowering the temperature of the combustion gas is satisfied.   The diesel engine control device according to claim 1 or 2, wherein the condition for reducing the temperature of the combustion gas is a low load region of the engine.   3. The diesel engine control device according to claim 1, wherein the condition for lowering the temperature of the combustion gas is when the fuel temperature or the intake air temperature is low. 4.   The operation of the glow plug is to repeatedly energize the glow plug for a predetermined time and not to energize the glow plug for a predetermined time. The control apparatus of the diesel engine as described in any one. A glow relay that can switch between energization and non-energization of the glow plug,
6. The diesel engine according to claim 5, wherein the operation of the glow plug is prohibited when the total time of continuous energization of the glow plug or the number of times of continuous energization exceeds a predetermined upper limit value. Control device. A glow relay that can switch between energization and non-energization of the glow plug,
6. The operation of the glow plug is prohibited when the total time of continuous energization of the glow plug during one trip or the number of continuous energizations exceeds a predetermined upper limit value. Diesel engine control device.   The diesel engine control device according to claim 7, wherein the upper limit value is set according to an ambient temperature in the vicinity of the glow relay.

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