JP2011074809A - Glow plug current-carrying control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further effectively and simply suppress the adhesion of deposit to a glow plug having a function of detecting the inner pressure of a cylinder of an internal combustion engine. <P>SOLUTION: A glow plug current-carrying control device executes start time control which is glow current-carrying for improving the starting stability of an engine when the engine starts. When the engine becomes a finish timing t1 in the start time control, deposit suppressing control which is a glow current-carrying for suppressing the adhesion of deposit to the glow plug is continuously executed. At that time, a heater current-carrying amount is set so as to make the heater temperature of the glow plug lower than that of the start time control. Thereby, the temperature of the glow plug is raised to suppress the adhesion of deposit by a heat migration phenomenon. As the heater temperature is low, the deposit suppressing control can be executed for a long time. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a glow plug energization control device that performs glow energization on a glow plug having a function of detecting an in-cylinder pressure of an internal combustion engine.

  In a diesel vehicle or the like equipped with a diesel engine, a glow plug is often provided so as to protrude into the cylinder in order to assist the engine start. According to this, when the engine is started, the glow plug energization control device energizes the heater built in the glow plug, so that the in-cylinder temperature rises or the temperature of the fuel that collides with the heater being high is instantaneously increased. By doing so, it is possible to improve the ignition stability of the fuel and improve the starting stability of the engine.

  On the other hand, an in-cylinder pressure sensor (CPS: Cylinder Pressure Sensor) that detects in-cylinder pressure is provided in order to grasp and feed back the combustion state in the cylinder and control the combustion in the cylinder. Conventionally, a glow plug having a function of detecting in-cylinder pressure in which the glow plug and the in-cylinder pressure sensor are integrated is known (for example, see Patent Document 1).

  Here, FIG. 2 is a schematic view showing a state in which this type of glow plug 5 is attached to the engine head 10. In the following, for convenience of explanation, the upper side in FIG. 2 is defined as the base end side, and the lower side is defined as the front end side. As shown in FIG. 2, the glow plug 5 has a hollow body 52, a heater 53, a sensor element 54, and a middle shaft 55. The heater 53 has a rod-like shape, and the tip side protrudes from the body 52 and protrudes into the cylinder 20. Further, the base end side of the heater 53 is fixed to the middle shaft 55 inside the body 52. The heater 53 is electrically connected to the ECU 7 and the glow controller 51 as a glow plug energization control device via a middle shaft 55. When the engine is started, in order to improve the ignitability of fuel, the glow controller 51 is energized to the heater 53 to raise the surface temperature of the heater 53.

  On the other hand, the heater 53 and the middle shaft 55 are movable in the axial direction (vertical direction in FIG. 2) in order to detect the in-cylinder pressure. That is, the heater 53 receives the in-cylinder pressure, and the heater 53 and the intermediate shaft 55 are moved in the direction toward the proximal end of the body 52 by an amount corresponding to the in-cylinder pressure. A sensor element 54 (for example, a piezoelectric element or a strain gauge) that detects the amount of displacement of the heater 53 and the central shaft 55 is connected to the proximal end side of the central shaft 55. The displacement detected by the sensor element 54 corresponds to the in-cylinder pressure, and the voltage corresponding to the in-cylinder pressure is transmitted to the ECU 7. The ECU 7 controls combustion based on information obtained from a voltage corresponding to the in-cylinder pressure. Thus, the glow plug 5 has a function of detecting the in-cylinder pressure.

  By the way, when the fuel is burned in the cylinder 20, particulate matter (particulates) such as soot may be discharged or unburned fuel (HC) may be discharged. In particular, in a combustion mode that extremely reduces the generation of NOx, such as PCCI combustion (premixed combustion), a large amount of unburned fuel tends to be discharged as a contradiction. Since the glow plug 5 protrudes into the cylinder 20, deposits resulting from these particulate substances and unburned fuel may adhere inside the body 52 of the glow plug 5 as shown in FIG. 7. . If deposits are deposited and deposited on the clearance between the body 52 and the movable parts 53 and 55 of the glow plug 5 or inside the body 52, the movability of the heater 53 and the central shaft 55 is deteriorated. As a result, the signal output of the in-cylinder pressure detected by the sensor element 54 decreases. Here, FIG. 8 is a diagram showing the in-cylinder pressure detected by the sensor element 54 at each crank angle, and shows the in-cylinder pressure before deposit deposition and the in-cylinder pressure after deposit deposition. As shown in FIG. 8, it can be seen that when the deposit accumulates, the detected in-cylinder pressure decreases. Therefore, conventionally, a technique for suppressing deposit accumulation has been proposed (see, for example, Patent Document 2).

  Patent Document 2 describes a technique in which a deposit heating removal heater is provided in an in-cylinder pressure sensor, and the deposited deposit is thermally decomposed by heating the heater.

JP 2009-58156 A JP 2008-19827 A

  However, when the technique of Patent Document 2 is applied to the glow plug, it is necessary to newly provide a heater for removing deposit heat in the glow plug, so that the existing glow plug cannot be used as it is, and the configuration becomes complicated. . In the technique of Patent Document 2, the deposit is thermally decomposed and removed, and thus a large heater energization amount that is sufficient for thermal decomposition is required. For this reason, there are problems that the life of the heater is reduced and that it is difficult to operate the heater for a long time from the viewpoint of reliability.

  The present invention has been made in view of the above problems, and an object thereof is to more effectively and easily suppress deposit adhesion to a glow plug having a function of detecting the in-cylinder pressure of an internal combustion engine.

In order to solve the above-mentioned problems, the present invention provides a glow plug having a function of detecting the in-cylinder pressure of an internal combustion engine with a startup control that is glow energization for the purpose of improving the start stability of the internal combustion engine. In the glow plug energization control device to be executed,
Separately from the start-up control, deposit suppression control, which is glow energization for the purpose of suppressing deposit adhesion to the glow plug, is executed, and the glow plug is heated to suppress deposit adhesion by thermophoresis. It is characterized by that.

  According to this, the glow plug energization control device of the present invention suppresses deposit adhesion by executing deposit suppression control that is glow energization for the purpose of suppressing deposit adhesion to the glow plug. Therefore, it is not necessary to add a new configuration such as a dedicated heater, and the existing glow plug can be used as it is, and deposit adhesion can be easily suppressed. Further, since the deposit suppression control is glow energization that suppresses deposit adhesion due to thermophoresis, a smaller heater energization is sufficient than when deposits are thermally decomposed and removed. Therefore, the deposit suppression control can be executed for a long time, and deposit adhesion can be effectively suppressed. As a result, it is possible to prevent a decrease in detection accuracy of the in-cylinder pressure.

  In the glow plug energization control device of the present invention, the deposit suppression control is glow energization in which the heater energization amount is set so that the heater temperature of the glow plug is lower than that at the time of starting control.

  As described above, since the deposit suppression control is glow energization that suppresses deposit adhesion due to thermophoresis, an effect of suppressing deposit adhesion is expected if the temperature of the glow plug is higher than the ambient temperature. Therefore, in deposit suppression control, the purpose is to create a temperature gradient with the surroundings, so the heater temperature of the glow plug is higher than in the case where the in-cylinder temperature rises or the fuel is ignited directly as in the case of control at start-up. The heater energization amount is set so as to be low, and thus deposit suppression control can be executed for a long time.

  In the glow plug energization control device of the present invention, the deposit suppression control is glow energization in which the heater energization amount is set so as to have a low heater temperature that does not affect the life of the glow plug.

  Thereby, even if the deposit suppression control is executed for a long time, it is possible to reduce the situation where the lifetime of the glow plug is reached and it becomes unusable.

  The lower heater temperature is a temperature whose upper limit temperature is included in the range of 700 ° C. to 900 ° C. and lower than the upper limit temperature. Thus, by setting the upper limit temperature of the low heater temperature in the range of 700 ° C. to 900 ° C., the temperature that does not affect the life of the glow plug differs depending on the type of heater such as a ceramic heater or a metal heater. A low heater temperature can be defined.

Further, in the glow plug energization control device according to the present invention, the glow plug energization control device includes an acquisition unit that acquires an operating condition of the internal combustion engine that affects deposit adhesion to the glow plug,
The deposit suppression control is executed so that the heater temperature according to the operating condition of the internal combustion engine acquired by the acquisition means is obtained.

  According to this, under operating conditions where the amount of particulate matter such as soot is increased, the heater temperature is increased to increase the temperature gradient, and the thermophoresis phenomenon is greatly exerted to effectively suppress deposit adhesion. it can. On the other hand, when the operating conditions are such that the amount of particulate matter such as soot discharged is small, deposit adhesion can be suppressed without increasing the heater temperature so much. In this way, since the deposit suppression control is executed so that the heater temperature corresponds to the operating condition of the internal combustion engine that affects the deposit adhesion to the glow plug, the heater energization as a whole rather than when the temperature is always controlled to the same temperature. The amount can be suppressed, and fuel consumption can be improved and CO2 can be reduced.

  Further, the fuel injection amount can be acquired as the operating condition of the internal combustion engine. According to this, it is considered that as the fuel injection amount increases, the amount of particulate matter such as soot discharged increases, and accordingly, the deposit adhesion amount to the glow plug also increases. That is, the amount of particulate matter such as soot discharged can be estimated by acquiring the fuel injection amount.

  Further, it is desirable that the deposit suppression control is continuously executed during operation of the internal combustion engine. As a result, deposit adhesion can be effectively suppressed during operation of the internal combustion engine, so that it is possible to prevent a decrease in in-cylinder pressure detection accuracy during operation of the internal combustion engine.

  Further, the deposit suppression control may be stopped under the operating conditions of the internal combustion engine in which the deposit on the glow plug is small. Under the operating conditions of the internal combustion engine in which the deposit adhesion to the glow plug is small, it is considered that the detection accuracy of the in-cylinder pressure is not greatly reduced even if the deposit suppression control is not performed. Therefore, in this case, by stopping the execution of the deposit suppression control, the heater power can be suppressed, and fuel consumption can be improved and CO2 emissions can be reduced.

It is the figure which showed schematic structure of the engine control system. 1 is a schematic diagram showing a state in which a glow plug 5 is attached to an engine head 10. FIG. It is the figure which showed the time change of the heater temperature and engine water temperature in glow energization. 2 is an enlarged view of a heater 53 and an engine head 10. FIG. 6 is a diagram showing a relationship between a heater temperature T and a life N of the heater 53. FIG. It is the figure which showed the relationship between the generation amount of microparticles | fine-particles, the fuel injection amount Q, and engine speed NE. It is a figure for demonstrating that a deposit adheres inside the body 52 etc. of the glow plug 5. FIG. It is the figure which showed the relationship between the cylinder pressure detected by the sensor element 54, and a crank angle.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The system of the present embodiment is an engine control system that controls a diesel engine equipped with a common rail fuel injection device.

  First, a schematic configuration of the engine control system of the present embodiment will be described. FIG. 1 is a diagram showing a schematic configuration of the engine control system of the present embodiment. As the engine 1 to be controlled by this system, a multi-cylinder (for example, in-line four-cylinder) engine mounted on a four-wheeled vehicle (for example, an AT vehicle) is assumed. However, in FIG. 1, only one cylinder 11 is shown for convenience of explanation. Here, paying attention to one cylinder 11, the system will be described.

  As shown in FIG. 1, this system uses an engine 1 that rotates a crankshaft (not shown) that is an output shaft by torque generated through combustion in a cylinder 11 as a control target, and controls various types of the engine 1. It is constructed with a sensor, ECU 7 and the like. Hereinafter, each element constituting this system including the engine 1 to be controlled will be described in detail.

  In the engine 1 (diesel engine), a cylinder (cylinder) 11 is basically formed by a cylinder block 14 and an engine head 10. The cylinder block 14 is provided with a cooling water passage (water jacket, not shown) for circulating the cooling water in the engine 1 and a water temperature sensor 79 for detecting the temperature of the cooling water (cooling water temperature) in the cooling water passage. It has been. And the engine 1, especially the cylinder block 14, and the engine head 10 are cooled with the cooling water.

  A piston 16 is accommodated in the cylinder 11, and a reciprocating motion of the piston 16 rotates a crankshaft (not shown) that is an output shaft of the engine 1. The crankshaft is provided with a pulsar 42 that rotates together with the crankshaft. A plurality of teeth are formed on the outer periphery of the pulsar 42. A crank angle sensor 71 (for example, an electromagnetic pickup) that outputs a crank angle signal indicating the crank angle CA by detecting teeth formed on the pulsar 42 is provided on the outer peripheral side of the pulsar 42.

  On the other hand, in the fuel supply system of this system, the in-cylinder injection method is adopted as the fuel supply method. That is, in the cylinder 11, high-pressure fuel sent from a high-pressure pump (not shown) is stored in the common rail 12 (pressure accumulation pipe) in the cylinder 20 (combustion chamber), and high-pressure fuel (for example, pressure “1000 atm” supplied from the high-pressure fuel is stored. An injector 13 serving as an electromagnetically driven fuel injection valve for directly injecting the above-mentioned light oil) into the cylinder 20 is fixed to the engine head 10. In the engine 1, a required amount of fuel is injected and supplied to each cylinder 11 as needed by such valve opening drive of the injector 13.

  The engine head 10 is provided with a glow plug 5 that protrudes into the cylinder 20 to assist in starting the engine. That is, when the engine is started, the glow plug 5 is energized by a heater built in the glow plug 5 to raise the in-cylinder temperature, or the heater surface temperature is raised to instantaneously raise the colliding fuel. In order to improve the ignitability of the fuel. Further, the glow plug 5 has a function of detecting an in-cylinder pressure that is a pressure in the cylinder 20. Here, FIG. 2 is a schematic view showing a state in which the glow plug 5 is attached to the engine head 10. In the following, for convenience of explanation, the upper side in FIG. 2 is defined as the base end side, and the lower side is defined as the front end side. As shown in FIG. 2, the glow plug 5 has a hollow body 52, a heater 53, a sensor element 54, and a middle shaft 55.

  As the heater 53, a metal or ceramic heater is used. When the heater 53 is energized, the heater 53 generates heat at a heater temperature corresponding to the energization amount. The heater 53 has a rod-like shape, and the tip side protrudes from the body 52 and protrudes into the cylinder 20. Further, the base end side of the heater 53 is fixed to the middle shaft 55 inside the body 52. Further, the heater 53 is electrically connected to the ECU 7 and the glow controller 51 as the glow plug energization control device via the middle shaft 55, and generates heat by energization from the ECU 7 and the glow controller 51.

  On the other hand, the heater 53 and the intermediate shaft 55 are movable in the axial direction (vertical direction in FIG. 2) in order to detect the in-cylinder pressure. That is, the heater 53 receives the in-cylinder pressure, and the heater 53 and the intermediate shaft 55 are moved in the direction toward the proximal end of the body 52 by an amount corresponding to the in-cylinder pressure. A sensor element 54 that detects the amount of displacement of the heater 53 and the middle shaft 55 is connected to the proximal end side of the middle shaft 55. The sensor element 54 is a sensor that detects the displacement amount of the heater 53 and the central shaft 55. For example, a piezoelectric element that generates electricity according to the displacement amount or a strain gauge that has a strain amount according to the displacement amount is used. The displacement detected by the sensor element 54 corresponds to the in-cylinder pressure, and the voltage corresponding to the in-cylinder pressure is transmitted to the ECU 7. The ECU 7 then grasps the combustion state in the cylinder 20 based on information obtained from the voltage corresponding to the in-cylinder pressure, that is, estimates the ignition timing and combustion temperature, further detects knocking, detects the peak position of the in-cylinder pressure, misfires Detection is possible. Thus, the glow plug 5 has a function of detecting the in-cylinder pressure.

  Returning to the description of FIG. 1, the glow controller 51 is electrically connected to the heater 53 (see FIG. 2) of the glow plug 5. The glow controller 51 is also electrically connected to the ECU 7 and energizes the heater 53 with a heater energization amount corresponding to an ON-OFF drive signal or a pulse width modulation signal (PWM signal) generated from the ECU 7. .

  Further, a vehicle (not shown) (for example, a four-wheel passenger car or a truck) that travels by using the engine 1 as power is provided with various sensors for vehicle control in addition to the above sensors. For example, an accelerator sensor 85 that outputs an electric signal corresponding to the state (displacement amount) of the pedal is provided on an accelerator pedal corresponding to a driving operation unit for notifying the vehicle side of the torque required by the driver. It is provided to detect the operation amount (depression amount). Further, an ignition switch 83 for instructing supply / stop of electric power to the electric system of the vehicle and a starter switch 84 for instructing start / stop of the engine 1 are provided. As these switches 83 and 84, for example, switches that are switched on / off in conjunction with the rotational position of a key inserted in a key cylinder (not shown) are used. Moreover, the structure which can switch an ON / OFF state by operation of a push button type switch called what is called a push switch may be sufficient. The switches 83 and 84 and the accelerator sensor 85 are connected to the ECU 7.

  The ECU 7 has a microcomputer, a RAM, and a ROM (not shown) inside, and the microcomputer operates the various actuators such as the injector 13 while using the RAM and ROM, so that the engine can be optimized in accordance with the situation at that time. 1 is performed.

  The ECU 7 also executes processing for controlling energization (glow energization) to the glow plug 5. Specifically, at the time of engine start, the start-up control for energizing the glow 53 to the heater 53 of the glow plug 5 is executed via the glow controller 51 to raise the temperature of the heater 53. That is, by executing the start-up control and raising the temperature of the heater 53, the temperature in the cylinder is raised, or the fuel that collides with the heater 53 being raised to a high temperature is instantaneously raised, thereby igniting the fuel. To improve engine starting stability.

  By the way, when the fuel is burned in the cylinder 20, particulate matter (particulates) such as soot may be discharged or unburned fuel (HC) may be discharged. Since the glow plug 5 protrudes into the cylinder 20, deposits resulting from these particulate substances and unburned fuel may adhere to the glow plug 5. If deposits adhere to and accumulate on the glow plug 5, the movability of the heater 53 and the central shaft 55 deteriorates. As a result, the signal output of the in-cylinder pressure detected by the sensor element 54 decreases. Therefore, the ECU 7 executes deposit suppression control that is glow energization for the purpose of suppressing deposit adhesion to the glow plug 5 separately from the startup control. The ECU 7 and the glow controller 51 correspond to the “glow plug energization control device” of the present invention.

  Hereinafter, deposit suppression control, which is a feature of the present invention, will be described. At that time, in order to clarify the difference from the start-time control that is executed when the engine is started, the start-time control will be described first.

<Control at start-up>
When the engine is started, the engine water temperature, which is the temperature of the cooling water, is low, so that the in-cylinder temperature is low, and even if the air in the cylinder 20 is compressed, the fuel ignition temperature may not be reached. In this case, the engine 1 cannot be started quickly. In order to avoid this, the start-time control is executed.

  The starting control is started at timing t = 0 when the ignition switch 83 (see FIG. 1) is turned on. That is, when the ignition switch 83 is turned on, the ECU 7 outputs a PWM signal corresponding to a desired heater energization amount to the glow controller 51, and the glow controller 51 supplies the heater energization amount corresponding to the PWM signal to the heater 53. Energize the glow. As a result, the heater 53 generates heat, and the heater temperature rises by an amount corresponding to the heater energization amount. When the heater temperature rises, the in-cylinder temperature rises or the fuel that has collided is instantaneously increased in temperature, so that the ignitability of the fuel is improved. In this state, when the starter switch 84 (see FIG. 1) is turned on, the ECU 7 drives the starter motor (not shown) to start the engine 1. At this time, since the ignitability of the fuel is improved by the startup control, the engine 1 can be started quickly.

  Thereafter, the start-time control is terminated at a timing when the engine water temperature rises and the engine 1 can operate stably. Specifically, in the present embodiment, the starting control is terminated at timing t1 when the engine water temperature reaches a predetermined temperature. That is, the ECU 7 monitors the engine water temperature detected by the water temperature sensor 79 (see FIG. 1) when executing the start-up control, and starts the glow controller 51 at the timing t1 when the engine water temperature reaches a predetermined temperature. Stops PWM signal output as time control.

  Here, FIG. 3A is a diagram showing a time change of the heater temperature (heater energization amount) of the heater 53 of the glow plug 5, and FIG. 3B is a diagram showing a time change of the engine water temperature. is there. In FIGS. 3A and 3B, the time axis of the horizontal axis is common.

  In FIG. 3, the start time control is executed from time t = 0 to t = t1. And the heater energization amount in the meantime is controlled so that the heater temperature becomes higher as the engine water temperature becomes lower. That is, as shown in FIG. 3B, the engine water temperature is the lowest immediately after the start-time control is started and gradually increases with the passage of time, as shown in FIG. The heater energization amount is controlled so that the heater temperature becomes the maximum value immediately after the start-up control is started and gradually decreases with the passage of time. As described above, the start-up control is terminated at the timing t1 when the engine water temperature reaches the predetermined temperature.

  In this embodiment, the heater energization amount in the start-up control is changed according to the engine water temperature, but the heater energization amount may be constant regardless of the engine water temperature. In the present embodiment, the start-up control is terminated at the timing t1 when the engine water temperature reaches a predetermined temperature, but may be terminated at a predetermined timing regardless of the engine water temperature. Conventionally, in order to improve the combustion stability of the engine after the engine is started, after-glow control is performed in which the glow plug is continuously energized after the engine is started to keep the in-cylinder temperature at a high temperature. Therefore, the ECU 7 may execute afterglow control for a predetermined period following the start-up control.

  As described above, when the start-up control is completed at the timing t1 (when the afterglow control is executed, after the afterglow control is finished), as shown in FIG. Decreased to fulfill the role of the glow plug 5. On the other hand, in the present invention, following the start-up control, deposit suppression control that is glow energization for the purpose of suppressing deposit adhesion to the glow plug 5 is executed.

<Deposit control>
That is, the deposit suppression control is started at the end timing t1 of the startup control. Therefore, the ECU 7 continues to energize the heater 53 via the glow controller 51 even after the start-up control is terminated. Here, FIG. 4 is an enlarged view of the heater 53 and the engine head 10, and is a diagram for explaining that deposits are suppressed by deposit suppression control. As shown in FIG. 4, when the deposit suppression control is executed, the heater 53 is heated. On the other hand, since the engine head 10 is cooled by the cooling water, a temperature gradient is generated between the heater 53 and the engine head 10. Therefore, a thermophoretic force acts between the heater 53 and the engine head 10 in the direction from the high temperature side heater 53 to the low temperature side engine head 10. Therefore, as shown in FIG. 4, most of the fine particles 99 such as soot and unburned fuel generated in the combustion chamber 20 adhere to the engine head 10 without adhering to the heater 53. As a result, deposit adhesion to the glow plug 5 is suppressed, and a decrease in in-cylinder pressure detection accuracy can be prevented.

  Next, the heater energization amount in the deposit suppression control will be described. Here, FIG. 5 is a diagram for explaining the heater energization amount in the deposit suppression control, and shows the relationship between the heater temperature T (horizontal axis) of the heater 53 and the life N (vertical axis) of the heater 53. It is. As shown in FIG. 5, the heater 53 has a lifetime N, and the lifetime N becomes shorter as the heater 53 is used at a higher temperature. For example, if the heater 53 is continuously used at the heater temperature T1, the heater 53 becomes unusable with the life N1 (the number of energization cycles or the total energization time). Therefore, since the energization at the high heater temperature T1 is assumed at the time of starting, it is not preferable to continue using the heater 53 at that temperature. Therefore, in the deposit suppression control, the heater energization amount is set so as to have a low heater temperature that does not affect the life N of the heater 53.

  Specifically, as shown in FIG. 5, the heater 53 has a longer life N as the heater temperature T becomes lower, but hardly affects the life N at a temperature lower than a certain lower limit temperature. Therefore, the lower limit temperature is set as the upper limit temperature T2max, and the predetermined temperature T2 equal to or lower than the upper limit temperature T2max is set as the low heater temperature. In the deposit suppression control, the heater energization amount is set so as to be the low heater temperature T2. 5 differs depending on the type of the heater 53. That is, the value of the upper limit temperature T2max varies depending on the type of the heater 53 (ceramic heater, metal heater, etc.), and specifically, the upper limit temperature T2max is in the range of 700 ° C. to 900 ° C. depending on the type of the heater 53. It will change. Therefore, depending on the type of the heater 53, the temperature included in the range of 700 ° C. to 900 ° C. is set as the upper limit temperature T2max, and the temperature below the upper limit temperature T2max is set as the low heater temperature T2.

  In the starting control, in order to improve the ignitability of the fuel, it is necessary to increase the in-cylinder temperature or to instantaneously increase the temperature of the collided fuel. Therefore, it is necessary to increase the heater temperature of the heater 53 to some extent. is there. Therefore, generally, the heater energization amount is set so that the heater temperature is equal to or higher than the temperature T2max.

  The deposit suppression control is continuously executed while the engine 1 is operating. Thereby, deposit adhesion can be effectively suppressed while the engine 1 is in operation, so that it is possible to prevent the detection accuracy of the in-cylinder pressure from being lowered while the engine 1 is in operation. Thereafter, the deposit suppression control is terminated at the timing when the operation of the engine 1 is stopped. The stop of the engine 1 may be determined based on a signal from the starter switch 84 (see FIG. 1).

  As described above, in the present embodiment, deposit suppression control is executed as glow energization separately from start-up control, so deposit adhesion to the glow plug 5 can be suppressed. Further, since the heater energization amount is set so that the heater temperature in the deposit suppression control is lower than that in the start-up control and does not affect the life of the glow plug 5, Suppression control can be executed.

(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to the drawings. In the first embodiment, the heater energization amount in the deposit suppression control is set to be a constant low heater temperature T2, but in the second embodiment, the heater energization amount is set according to the operating condition of the engine 1. This is an embodiment in which Other configurations and processes other than the heater energization amount are the same as those in the first embodiment. Hereinafter, the second embodiment will be described with a focus on differences from the first embodiment.

  As described above, in the present invention, for the purpose of suppressing deposit adherence to the glow plug 5, deposit suppression control for energizing the heater 53 of the glow plug 5 is performed. In the deposit suppression control, deposit adhesion is suppressed by a thermophoresis phenomenon by setting the heater temperature of the heater 53 to be higher than the ambient temperature of the engine head 10 or the like. The thermophoresis phenomenon becomes more significant as the temperature gradient becomes larger. Therefore, as the temperature gradient between the heater temperature of the heater 53 and the engine head 10 becomes larger, deposit adhesion to the glow plug 5 is further suppressed. it can. However, if the heater energization amount is large, the power generation amount of the alternator increases, leading to deterioration in fuel consumption and increase in CO2 emissions. On the other hand, the amount of soot and unburned fuel generated in the cylinder 20 varies depending on the operating conditions of the engine 1, so the deposit amount varies depending on the operating conditions of the engine 1. Therefore, in the present embodiment, when the operating conditions of the engine 1 in which the amount of particulate matter such as soot is large are discharged, the particulate matter such as soot is discharged while the heater temperature is raised and the deposit suppression control is executed. When the operating condition of the engine 1 is small, the heater temperature is lowered and the deposit suppression control is executed.

  Here, FIG. 6 is a graph showing the relationship between the amount of particulates such as soot and unburned fuel generated in the cylinder 20 that is the source of deposit, the fuel injection amount Q, and the engine speed NE. In FIG. 6, curves 95a to 95c indicate the relationship between the fuel injection amount Q and the engine speed NE, respectively, in the case of different fine particle generation amounts (the fine particle generation amount is “95c> 95b> 95a”). . That is, when the operating condition of the engine 1 determined by the fuel injection amount Q and the engine speed NE is on the curve 95a, for example, an amount of fine particles determined by the curve 95a is generated. Further, the generation amount of the fine particles between the curves 95a to 95c has the relationship that the curve 95c is the largest, the curve 95b is the next largest, and the curve 95a has the smallest generation amount of the fine particles.

  As shown in FIG. 6, in the case of the same engine speed NE, the larger the fuel injection amount Q, the more fine particles are generated. This is because when the engine speed NE is the same, the richer the fuel injection amount Q, the richer the air-fuel ratio. And when many microparticles | fine-particles generate | occur | produce, the adhesion amount of the deposit to the glow plug 5 will also increase by that much. Therefore, in the present embodiment, the amount of deposit adhesion is estimated based on the fuel injection amount Q.

  Next, details of the deposit suppression control of the present embodiment will be described. The deposit suppression control of the present embodiment is started at the end timing t1 (see FIG. 3) of the start-time control, as in the first embodiment. Then, during the operation of the engine 1, the deposit suppression control is continuously executed, and the operation is terminated at the timing when the operation of the engine 1 is stopped.

  The heater energization amount in the deposit suppression control is set according to the operating condition of the engine 1, that is, the fuel injection amount Q as described above. Specifically, the ECU 7 always acquires the fuel injection amount Q while the engine 1 is operating. The fuel injection amount Q may be a command value determined based on the operation amount of the accelerator pedal by the driver detected by the accelerator sensor 85 (see FIG. 1), the engine speed NE, and the like. The ECU 7 that acquires the fuel injection amount Q corresponds to “acquisition means” of the present invention.

  Then, the ECU 7 determines the heater energization amount according to the acquired fuel injection amount Q. Specifically, for example, a map showing the relationship between the fuel injection amount Q and the heater energization amount, such that the heater energization amount increases as the fuel injection amount Q increases, is stored in advance in a ROM or the like. The heater energization amount may be determined with reference to FIG. However, since the life N of the heater 53 is shortened when the heater energization amount is too large, the heater energization amount is determined within a low heater temperature range (up to the upper limit temperature T2max) that does not affect the life N of the heater 53 shown in FIG. Then, the ECU 7 performs glow energization with the determined heater energization amount.

  In this way, the deposit suppression control is executed with the heater energization amount corresponding to the fuel injection amount Q. During the operation of the engine 1, the fuel injection amount Q varies depending on the situation. The energization amount also varies.

  As described above, in the present embodiment, the deposit adhesion can be effectively suppressed by increasing the heater temperature and causing the thermophoresis phenomenon to act greatly under the operating conditions in which the deposit adhesion is increased. In addition, the amount of energization of the heater can be suppressed as compared with the case where the temperature is always controlled to the same temperature, and fuel consumption can be improved and CO2 can be reduced.

  The glow plug energization control device of the present invention is not limited to the above-described embodiment, and can be variously modified without departing from the scope of the claims. For example, in the above-described embodiment, the deposit suppression control is continuously executed while the engine 1 is operating. However, when the operating condition of the engine 1 is a condition in which the deposit is less attached, the deposit suppression control is executed. May be canceled. This is because it is considered that under such operating conditions, the detection accuracy of the in-cylinder pressure is not greatly reduced even if the deposit suppression control is not performed. For example, the operating condition with less deposit adhesion may be when the engine 1 is idling or when the fuel injection amount Q is equal to or less than a predetermined value. As a result, heater power can be suppressed, and fuel consumption can be improved and CO2 emissions can be reduced.

1 engine (internal combustion engine)
5 Glow plug 7 ECU (Acquisition means)
10 Engine head 11 Cylinder 20 In-cylinder 51 Glow controller 52 Body 53 Heater 54 Sensor element 55 Center shaft

Claims (8)

In a glow plug energization control device for performing start-up control that is glow energization for the purpose of improving the start stability of an internal combustion engine for a glow plug having a function of detecting an in-cylinder pressure of the internal combustion engine,
Separately from the start-up control, deposit suppression control, which is glow energization for the purpose of suppressing deposit adhesion to the glow plug, is executed, and the glow plug is heated to suppress deposit adhesion by thermophoresis. A glow plug energization control device characterized by that.   2. The glow plug energization according to claim 1, wherein the deposit suppression control is a glow energization in which a heater energization amount is set so that a heater temperature of the glow plug is lower than that in the start-up control. Control device.   The glow plug energization control device according to claim 2, wherein the deposit suppression control is glow energization in which a heater energization amount is set so as to be a low heater temperature that does not affect a life of the glow plug.   The glow plug energization control device according to claim 3, wherein the low heater temperature has an upper limit temperature in a range of 700 ° C to 900 ° C and is equal to or lower than the upper limit temperature. Obtaining means for obtaining operating conditions of the internal combustion engine that affect deposit adhesion to the glow plug;
The glow plug energization control according to any one of claims 1 to 4, wherein the deposit suppression control is executed so that a heater temperature corresponding to an operating condition of the internal combustion engine acquired by the acquiring means is obtained. apparatus.   The glow plug energization control device according to claim 5, wherein the acquisition unit acquires a fuel injection amount as an operation condition of the internal combustion engine.   The glow plug energization control device according to any one of claims 1 to 6, wherein the deposit suppression control is continuously executed during operation of the internal combustion engine.   The glow plug energization control device according to any one of claims 1 to 7, wherein execution of the deposit suppression control is stopped under an operation condition of the internal combustion engine in which deposit adhesion to the glow plug is small.

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