JP5155964B2 - Glow plug energization control device and heat generation system - Google Patents

Description

  The present invention relates to an energization control device for a glow plug used for preheating a diesel engine and the like, and a heat generation system including the energization control device.

  2. Description of the Related Art Conventionally, glow plugs that generate heat when energized have been used to assist in starting an engine of a car or the like and for stable driving. The glow plug includes, for example, a heating resistor (such as a heating coil and a ceramic heater), a control coil, a lead portion (medium shaft), a metal shell, and the like serving as a path for power supplied to the heating resistor. As a control method for energizing such a glow plug, a constant power control method and a resistance value control method are known.

  In the constant power control method, the supplied power is calculated from the voltage applied to the glow plug and the flowed current, and is further integrated to energize the glow plug so that the integrated power amount obtained by the integration becomes a predetermined power amount. Control method. According to this control method, the glow plug generates heat in accordance with the amount of electric power that has been input. Therefore, if the predetermined amount of electric power is input, the glow plug can be set to a predetermined temperature.

  However, when the glow plug is affected by the external temperature, such as when the glow plug's heating resistor is cooled due to disturbance due to changes in engine speed, load (throttle opening), water temperature, etc. It is difficult to keep the temperature constant. Here, in order to maintain the temperature constant, it is necessary to obtain information such as the engine speed and load from the ECU, for example, and to control the effective voltage to be applied based on the information (for example, Patent Document 1) reference).

  However, when performing energization control, calculating the effective voltage to be applied according to changes in various parameters such as engine speed, load, and water temperature may increase the processing load. In realizing these, it is inevitable to increase the cost such as manufacturing an energization control device using a microcomputer with high processing capability. On the other hand, in order to reduce the processing load, it is conceivable to create a map that can uniquely determine the effective voltage to be applied from the various parameters and the target temperature, and to control energization based on the map. . However, when creating a map, it is necessary to perform complicated processing in consideration of the various parameters described above, and as a result, an increase in processing load cannot be avoided. Alternatively, an increase in the number of manufacturing steps of the product is unavoidable, such as an increase in the work period required to create this map.

  On the other hand, the resistance value control method is a method of controlling energization to the glow plug so that the resistance value of the glow plug approaches the target resistance value corresponding to the target temperature. According to this control method, even if the glow plug is affected by a temperature change due to a disturbance, the effective voltage to be applied may be changed in accordance with the fluctuation of the glow plug resistance value caused by the disturbance. Therefore, it is said that the glow plug can be maintained at a constant temperature relatively easily without causing an increase in processing load as compared with the above method.

JP 2004-278513 A

  However, today, with increasing environmental awareness on a global scale, there is a concern that the conventional resistance value control method may result in insufficient temperature control of the glow plug against the above disturbance. That is, in the conventional resistance value control method, the resistance value of the heat generating resistor is assumed on the assumption that all fluctuations in the resistance value of the glow plug occur only in the heat generating resistor which is the main part of heat generation of the glow plug. The target resistance value is set so as to change the energization amount corresponding to the fluctuation, and the glow plug is energized so as to have the target resistance value. However, the value measured as the resistance value of the glow plug (hereinafter also referred to as “the resistance value of the entire glow plug”) includes not only the resistance value of the heating resistor but also the resistance value of the heating resistor. This is a value obtained by adding the resistance value of the power supply harness connected to the section and the glow plug, and the resistance value of the metal shell. For this reason, for example, when the heat generating resistor of the glow plug is partially cooled by a disturbance such as a swirl generated in the combustion chamber after driving the engine (starting cranking), As the temperature decreases, the resistance value of the heating resistor decreases, but the resistance value of the entire glow plug does not decrease so much. Therefore, even if the input power (effective voltage) is increased by an amount corresponding to the decrease in the resistance value, the increased input power is used for heat generation of the control coil, etc., and the temperature of the heating resistor is set to swirl, etc. As a result, it cannot be raised as much as it is lowered, and as a result, it may be difficult to maintain the temperature of the glow plug at the target temperature. Conventionally, sufficient study has not been made on the influence of disturbance generated in the combustion chamber on the glow plug, and temperature control with higher accuracy has not been performed.

  In order to help understanding this phenomenon, numerical values will be exemplified and described. First, a situation is assumed in which the resistance value of the entire glow plug is maintained at 1.2Ω and constant heat generation is performed. It can be confirmed that the resistance value of the entire glow plug is maintained at 1.2Ω by being calculated and measured by the energization control device. Here, of the resistance value of the entire glow plug, if the resistance value of the resistance heating element is 1.0Ω, the resistance value of the remaining portion such as the control coil and the lead portion is 0.2Ω. For this situation, it is assumed that a situation occurs in which the heating resistor is locally cooled by disturbance. Then, the resistance value of the heating resistor decreases to, for example, 0.9Ω. Accordingly, the resistance value of the entire glow plug is 1.1Ω. This is because the resistance value of the remaining portion is unchanged from 0.2Ω because it is a local cooling of only the heating resistor.

  Here, in the conventional resistance value control system, in order to return the resistance value of the entire glow plug to 1.2Ω, which is defined as the target resistance value, in order to maintain the heat generation temperature of the glow plug, increase. Thus, it is realized that the resistance value of the entire glow plug to be measured is 1.2Ω. However, it is not guaranteed that all of the increase in input power is used in the heating resistor, and it is conceivable that the increase in input power is used in each of the heating resistor and the remaining portion. That is, while the main heating is performed by the heating resistor, a slight heat is generated in the remaining part. As a result, the resistance value of the heating resistor is, for example, 0.9Ω to 0.95Ω, and the resistance value of the remaining portion is 0.25Ω.

  Since the resistance value of the entire glow plug is 1.2Ω in this way, even if it seems that the same heat generation as before the disturbance occurs, the temperature generated by the heating resistor is actually the disturbance. Compared to before the occurrence, it has decreased after the disturbance. In addition, the numerical value used here is illustrated for convenience and there is no problem that it is different from the actual numerical value.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to control energization to the glow plug by a resistance value control system that controls energization so that the resistance value of the glow plug matches the target resistance value. It is an energization control device for a glow plug, and an object is to provide an energization control device and a heat generation system for a glow plug that can suppress a temperature drop due to disturbance such as swirl and can stably maintain a target temperature. .

  Hereinafter, each configuration suitable for solving the above-described object will be described in terms of items. In addition, the effect specific to the corresponding structure is added as needed.

Configuration 1 . The glow plug energization control device of this configuration generates heat by energization, and the glow plug resistance value matches a predetermined target resistance value for a glow plug whose own resistance value changes according to its own temperature change. A glow plug energization control device for controlling an applied voltage to the glow plug by a resistance value control system for controlling energization as follows:
First acquisition means for acquiring a first resistance value of the glow plug by energizing the glow plug when driving of the internal combustion engine to which the glow plug is attached is stopped;
Intermediate value setting means for setting an intermediate value of the target resistance value based on at least the first resistance value;
Using the first relational expression showing the relationship between the voltage applied to the glow plug and the temperature of the glow plug when the drive of the internal combustion engine is stopped, the glow plug is applied to reach the target temperature. A reference effective voltage setting means for setting a reference effective voltage which is a power voltage;
Using the second relational expression showing the relationship between the resistance value of the glow plug and the temperature of the glow plug when the driving of the internal combustion engine is stopped, the glow plug corresponding to the target temperature of the glow plug is used. A reference resistance value setting means for setting a reference resistance value which is a resistance value;
The resistance of the glow plug corresponding to the voltage applied to the glow plug, obtained based on the relationship between the voltage applied to the glow plug and the resistance value of the glow plug when the internal combustion engine is driven. A correction value setting means for setting a disturbance correction value from the resistance correction value using a third relational expression indicating a relationship between a resistance correction value based on a difference between the value and the reference resistance value;
A target resistance value setting means for setting the target resistance value using an intermediate value of the target resistance value and the disturbance correction value after the start of driving of the internal combustion engine;
And an effective voltage determining means for determining an effective voltage to be applied to the glow plug based on the reference effective voltage and the target resistance value.

  The first relational expression is the relationship between the effective voltage applied to the glow plug and the temperature of the glow plug when the effective voltage is applied when the driving of the internal combustion engine is stopped (no disturbance). For example, it can be expressed as an equation having a predetermined first-order correlation as shown in FIG.

  Further, the second relational expression is that when the drive of the internal combustion engine is stopped (without disturbance), an amount of electric power necessary to bring the glow plug to a predetermined temperature is input, and the resistance of the glow plug at that time It can be derived by measuring the value, and can be expressed as a predetermined linear expression as shown in FIG. 10, for example.

  Further, the third relational expression can be obtained by changing the effective voltage, the engine speed and the load (throttle opening), for example, with the water temperature kept constant in a state where the internal combustion engine is driven (a state where there is a disturbance). The relational expression between the resistance value of the glow plug and the effective voltage and the relational expression between the resistance value of the glow plug and the effective voltage in a state where the driving of the internal combustion engine is stopped can be obtained. For example, as shown in FIG. 12, the third relational expression shows the difference (effective voltage difference) between the effective voltage during driving and the effective voltage during non-driving (reference effective voltage, etc.), the resistance value during driving, and the non-driving time The resistance correction value based on the difference between the resistance values can be expressed as having a predetermined correlation.

  In addition, “when the drive of the internal combustion engine is stopped” means that when the operation of the internal combustion engine is stopped, for example, when the internal combustion engine is in an idle state, the disturbance is stable. Including when you are.

According to this configuration 1, the target resistance value is set in consideration of the influence of heat generation or the like in the resistance portion such as the control coil. Therefore, even if the heating resistor is partially cooled due to the influence of swirl or the like, for example, by increasing the input power by the amount of power consumed in the resistance part, the heating resistor is The electric power to be input to maintain the target temperature can be more reliably input to the heating resistor. Thereby, about a glow plug (heat generating resistor), the temperature fall by a swirl etc. can be suppressed and target temperature can be maintained stably.
If this configuration is described using numerical values in the same manner as described above, the target resistance value is not set (returned) to 1.2Ω before the disturbance occurs, but is set to 1.3Ω, for example. As a result, the resistance value of the heating resistor is 1.0Ω, and the resistance value of the remaining portion is 0.3Ω. Although the resistance value of the entire glow plug differs by 0.1Ω before and after the occurrence of the disturbance, the resistance value of the heating resistor that mainly contributes to the heating of the combustion chamber does not change before and after the occurrence of the disturbance and maintains the temperature. It becomes possible.
In addition to this, it is not necessary to provide sophisticated communication means required when using the constant power control method, and the manufacturing cost can be reduced.

Further, according to the configuration 1 , after the driving of the internal combustion engine is started, the target resistance value is set using the disturbance correction value obtained using the third relational expression. Here, as described above, the third relational expression is taken into consideration when the internal combustion engine is driven (that is, when a swirl or the like is generated), and corresponds to the voltage applied to the glow plug. The resistance correction value based on the difference between the resistance value of the glow plug and the reference resistance value (resistance value when no disturbance occurs) is shown. Therefore, using the disturbance correction value obtained from the resistance correction value, an intermediate target resistance value based on the reference resistance value obtained when the internal combustion engine is not driven (that is, no swirl or the like is generated). By correcting the value, it is possible to set an appropriate target resistance value considering the influence of swirl and the like. As a result, temperature drop due to swirl or the like can be prevented more reliably, and the temperature of the glow plug can be stably maintained at the target temperature.

  Note that the reference effective voltage of each glow plug may vary. For this reason, when a plurality of glow plugs are controlled by commonly using the third relational expression obtained based on the reference effective voltage of a certain glow plug, the resistance correction value (disturbance correction value) varies for each glow plug. The target resistance value may not be set appropriately. Thus, each glow plug may be controlled using a third relational expression that is different for each glow plug. Further, as the effective voltage difference in the third relational expression, a difference between the voltage applied to the glow plug and the standard effective voltage that is a standard reference effective voltage set for each glow plug product number may be used. Since the standard effective voltage is close to the reference effective voltage of each glow plug, an appropriate target resistance value can be set for each glow plug even when the common third relational expression is used. .

Configuration 2 . In the glow plug energization control device according to the present configuration, in the configuration 1 , the correction value setting means is configured to adjust the resistance value of the glow plug as the temperature rises until the temperature of the glow plug is saturated after the internal combustion engine is driven. The disturbance correction value is varied corresponding to the increase.

  Before the predetermined time elapses from the start of driving (cranking) of the internal combustion engine, there is a possibility that the portion other than the heating resistor in the glow plug is not sufficiently heated. For this reason, the resistance value of the entire glow plug may not be sufficiently saturated. If the resistance correction value obtained from the third relational expression is used as a disturbance correction value as it is, an excessive temperature rise of the glow plug is caused. There is a risk that.

In this respect, according to the configuration 2 , since the resistance value of the glow plug can be increased with the temperature rise until the temperature of the glow plug is saturated after the internal combustion engine is driven, the disturbance correction value is adjusted in accordance with the increase. (For example, the initial disturbance correction value is set to a low value, and the disturbance correction value is gradually increased in response to the increase in the resistance value of the glow plug as the glow plug is energized.) ). Therefore, it is possible to more reliably prevent excessive temperature rise of the glow plug while effectively suppressing the temperature drop due to the influence of swirl or the like.

  It should be noted that the time required for the temperature of the glow plug to be saturated (substantially constant) is determined in advance, and the resistance correction value may be varied from the start of driving the internal combustion engine until the time elapses. .

Configuration 3 . The energization control device for the glow plug of this configuration obtains information on the environmental temperature according to the environment in which the glow plug is used in the above configuration 1 or 2 ,
The intermediate value setting means sets an intermediate value of the target resistance value based on the environmental temperature information.

  “Environmental temperature” refers to the water temperature or the outside air temperature of the internal combustion engine.

According to the configuration 3 , when setting the intermediate value of the target resistance value, environmental information indicating a change in the water temperature and the like is taken into consideration in addition to the reference resistance value. Therefore, the target resistance value that is the control target can be set more appropriately, and the temperature of the glow plug can be more stably maintained at the target temperature.

Configuration 4 . A glow plug energization control device according to any one of the above configurations 1 to 3 , and a heat generation system including the glow plug.

As in the configuration 4 , the above technical idea may be embodied in a heat generation system including a glow plug. In this case, basically the same effects as those of the above-described configuration 1 and the like are exhibited.

It is a block diagram which shows the structure of the system which controls electricity supply to a glow plug by GCU. It is a flowchart of the main routine of the electricity supply control program performed in GCU. It is a flowchart of the electricity supply process called from the main routine of an electricity supply control program. It is a flowchart which shows the process at the time of exchange check interruption. It is a flowchart which shows the process at the time of performing heat insulation energization. It is a flowchart which shows the process at the time of performing an adjustment correction value setting process. It is a flowchart which shows the process at the time of performing a swirl correction process. It is a graph which shows transition of the temperature of a glow plug, and target resistance value. It is a graph which shows the example of a voltage temperature relational expression. It is a graph which shows the example of resistance temperature relational expression. It is a graph which shows the example of a water temperature correction formula. It is a graph which shows the example of a correction formula. It is a graph which shows the fluctuation | variation of the target resistance value correction coefficient with respect to energization time. (A) is the partially broken front view of the glow plug of this embodiment, (b) is the elements on larger scale of the glow plug front-end | tip part. It is a graph which shows the temperature of the glow plug at the time of using the GCU which concerns on this invention, and the temperature of the glow plug at the time of using the GCU which concerns on a prior art example when various engine operation states are changed.

  Hereinafter, an embodiment will be described with reference to the drawings. A glow control unit (GCU) 21 as an energization control unit controls energization of a glow plug 1 that is used for assisting start-up of a diesel engine (hereinafter referred to as “engine”) EN of the automobile and for improving driving stability. Is.

  First, prior to the description of the GCU 21, a schematic configuration of the glow plug 1 controlled by the GCU 21 will be described.

  As shown in FIGS. 14A and 14B, the glow plug 1 includes a cylindrical metal shell 2 and a sheath heater 3 attached to the metal shell 2.

  The metal shell 2 has a shaft hole 4 penetrating in the direction of the axis CL1, and the outer peripheral surface thereof has a hexagonal cross section for engaging a screw portion 5 for mounting to the engine EN and a tool such as a torque wrench. The tool engaging portion 6 is formed.

  The sheath heater 3 is configured by integrating a tube 7 and a middle shaft 8 in the direction of the axis CL1.

  The tube 7 is a cylindrical tube whose front end portion is mainly composed of iron (Fe) or nickel (Ni), and the rear end of the tube 7 is sealed with an annular rubber 16 between the inner shaft 8 and the tube 7. ing. In addition, on the inner side of the tube 7, a heating coil 9 (corresponding to a “heating resistor” in the present invention) joined to the tip of the tube 7 and a control coil connected in series to the rear end of the heating coil 9. 10 and an insulating powder 11 such as magnesium oxide (MgO) powder are enclosed.

  The heating coil 9 is constituted by a resistance heating wire made of, for example, an Fe-chromium (Cr) -aluminum (Al) alloy. On the other hand, the control coil 10 is composed of a resistance heating wire mainly composed of Ni, for example.

  In addition, the tube 7 is formed with a small-diameter portion 7a that accommodates the heating coil 9 and the like at the distal end thereof by swaging or the like, and a large-diameter portion 7b having a larger diameter than the small-diameter portion 7a on the rear end side Is formed. The large diameter portion 7 b is press-fitted and joined to the small diameter portion 4 a formed in the shaft hole 4 of the metal shell 2, so that the tube 7 is held in a state of protruding from the tip of the metal shell 2.

  The middle shaft 8 has its tip inserted into the tube 7, is electrically connected to the rear end of the control coil 10, and is inserted through the shaft hole 4 of the metal shell 2. The rear end of the middle shaft 8 protrudes from the rear end of the metal shell 2. At the rear end of the metal shell 2, the rubber-made O-ring 12, the resin-made insulating bush 13, and the insulating bush 13 are removed. A pressing ring 14 for preventing and a nut 15 for connecting a current-carrying cable are fitted into the middle shaft 8 in this order from the tip side.

  Next, the glow control unit (GCU) 21 that is a feature of the present invention will be described.

  FIG. 1 is a block diagram showing a schematic configuration of a system that controls energization to the glow plug 1 by the GCU 21. Although only one glow plug 1 is shown in FIG. 1, the actual engine EN is provided with a plurality of cylinders, and a glow plug 1 and a switch 37 described later are provided for each cylinder. . The energization control by the GCU 21 is performed independently for each glow plug 1, but the control method is the same. Therefore, energization control performed by the GCU 21 for any one glow plug 1 will be described below.

  The GCU 21 operates by power supplied from the battery VA, and includes a microcomputer 31 having a CPU 32, a ROM 33, a RAM 34, and the like.

  The microcomputer 31 has a normal mode that operates with an operation clock having a high oscillation frequency and a power saving mode that operates with an operation clock having an oscillation frequency lower than that of the normal mode, and the drive of the engine EN is stopped ( When the engine key EK is off), the power saving mode is entered. In the power saving mode, the microcomputer 31 stops execution of various programs and waits for input of an interrupt signal. When an interrupt signal is input, the microcomputer 31 returns to the normal mode and executes various programs. In general, initialization (for example, so-called initialization processing such as clearing of internal registers and RAM 34, setting of initial values to various flags and counters) is performed when the CPU 32 is activated. The microcomputer 31 according to the present embodiment can reduce power consumption during standby when the driving of the internal combustion engine is stopped by mounting such a power saving mode.

  Further, the microcomputer 31 has a built-in interrupt timer 35, and a signal generated periodically (for example, every 60 seconds) from the interrupt timer 35 is input to the CPU 32 as an interrupt signal. Further, the microcomputer 31 is configured to receive a signal notifying that the engine key EK is on or off, and this signal also functions as an interrupt signal in the power saving mode.

  In addition, the GCU 21 is provided with a switch 37. Here, energization control to the glow plug 1 by the GCU 21 is performed by PWM control, and the switch 37 switches on / off of energization to the glow plug 1 in accordance with an instruction from the microcomputer 31. In the present embodiment, in order to measure the resistance value of the glow plug 1, the switch 37 is configured to operate an FET (field effect transistor) having a current detection function via an NPN transistor or the like. .

  The switch 37 may be a relatively inexpensive FET that does not have a current detection function. In this case, for example, a resistance value of the glow plug 1 may be measured by providing a shunt resistance between the switch 37 and the glow plug 1 and measuring a current flowing through the shunt resistance. In addition, a resistance for current detection is provided in parallel with the switch 37, a predetermined current is supplied when the energization to the glow plug 1 is off, and the resistance value of the glow plug 1 is calculated based on the obtained partial pressure. It is good to do.

  The GCU 21 is connected to an automobile electronic control unit (ECU) 41 via a predetermined communication means (for example, CAN). A measured value of a water temperature sensor SE that measures the coolant temperature of the engine EN is input to the ECU 41, and the GCU 21 acquires the coolant temperature (water temperature information) from the ECU 41 as environmental temperature information. Note that the GCU 21 may directly acquire the water temperature information from the water temperature sensor SE without acquiring the water temperature information from the ECU 41.

  Further, a microcomputer 31 is connected to the terminal for power supply of the glow plug 1 through voltage dividing resistors 38 and 39, and a voltage (GCU21) applied to the glow plug 1 is connected to the microcomputer 31. The voltage obtained by dividing the voltage output from (1) is input. The microcomputer 31 can calculate the applied voltage to the glow plug 1 based on the input voltage, and can also calculate the glow voltage from the applied voltage and the current flowing through the glow plug 1 measured by the FET of the switch 37. The resistance value of the plug 1 can be obtained.

  The value measured as “the resistance value of the glow plug 1” is strictly the resistance value of the glow plug 1 (that is, the resistance of the heating coil 9, the control coil 10 and the central shaft 8 connected in series). Not only the value) but also the resistance value of a harness or the like connecting the switch 37 and the glow plug 1 is included. That is, the “resistance value of the glow plug 1” in this embodiment is the resistance value of the heating coil 9 and the power supply path to the heating coil 9 including the control coil 10, the central shaft 8, and the harness (in the present invention). This is based on the sum of the resistance value (corresponding to “resistance portion”) and the resistance value of the metal shell 2 and the like. Therefore, in this embodiment, “the resistance value of the glow plug 1” is also referred to as “the resistance value of the entire glow plug”.

  Further, in the GCU 21 configured as described above, calibration (correction / adjustment) is performed on the correlation between the temperature of the glow plug 1 and the resistance value when controlling the energization of the glow plug 1. The resistance value before correction for the glow plug 1 (corresponding to the “first resistance value”) is obtained.

  Here, the calibration is performed as follows. That is, the resistance value of each glow plug varies depending on various factors, and even if the product number is the same, the relationship between temperature and resistance value is affected by the variation. And the amount of generated heat are due to the material of the heat generating resistor (heat generating coil 9) of the glow plug, and the variation is relatively small. Accordingly, the heating resistor serving as a reference is energized and energized so that the temperature rise is saturated at the control target temperature (target temperature), and the integrated amount (integrated power amount) of the input power at that time is obtained. Then, if this integrated electric energy is input to the glow plug to be calibrated, the temperature of the glow plug becomes the target temperature. In other words, the resistance value of the heating resistor at this time (when the integrated electric energy is applied) is obtained as a resistance value before correction for each glow plug 1, and each glow plug 1 is determined based on the resistance value before correction. When the resistance value control is performed, correction, that is, calibration is realized so that there is no variation between the solids of the plurality of glow plugs 1. In the present embodiment, the resistance value thus obtained is used as the resistance value before correction. However, in the present invention, the calibration method is not limited to this method.

  In the GCU 21, the calibration for the glow plug 1 as described above is performed for the newly attached glow plug 1 when it is detected that the glow plug 1 has been replaced. Then, the pre-correction resistance value obtained by calibration is applied to the glow plug 1 every time the engine EN is driven (every time the glow plug 1 is used). In other words, the glow plug 1 is not calibrated every time the engine EN is driven. In order to detect replacement of the glow plug 1, the GCU 21 in the present embodiment not only performs energization control for the glow plug 1, but also performs replacement confirmation of the glow plug 1 described later.

  Next, a specific example of energization control performed by the GCU 21 on the glow plug 1 will be described with reference to the flowcharts of FIGS. FIG. 2 is a flowchart of the main routine of the energization control program performed in the GCU 21. FIG. 3 is a flowchart of energization processing called from the main routine of the energization control program. FIG. 4 is a flowchart showing processing when an exchange check interrupt is performed. FIG. 5 is a flowchart showing a process when performing heat insulation energization. FIG. 6 is a flowchart showing an adjustment correction value setting process called when performing heat insulation energization, and FIG. 7 is a flowchart showing a swirl correction process called when performing heat insulation energization.

  First, before explaining energization control, various variables and flags used in the energization control program will be described (however, various variables and flags used in the heat insulation energization process will be described later). Each flag and variable is stored in the RAM 34, but the value is held unless the CPU 32 is initialized regardless of the driving mode of the microcomputer 31.

  The “check flag” is a flag that is set when the replacement confirmation (replacement check) of the glow plug 1 is performed. Specifically, the check flag is set when an interrupt signal from the interrupt timer 35 is issued. In the energization control program, when it is confirmed that the check flag is established, a series of processes for confirming replacement of the glow plug 1 is performed.

  The “initial flag” is used to turn on the engine key EK by executing a specific processing portion (S23 to S28 described later) in a series of processes repeatedly executed when the engine key EK is turned on in the energization control program. This flag is used for the determination condition to be executed only at the first time. The initial flag is established when the engine key EK is turned on and a specific processing portion is executed, and is not established when the engine key EK is turned off.

  The “exchange flag” is a flag that is set when it is detected that the glow plug 1 has been exchanged in a series of processing for confirming the exchange of the glow plug 1. In the energization control program, calibration for the glow plug 1 is performed when an exchange flag is established.

  The “correction flag” is a flag used for determination when performing calibration. As described above, the calibration is performed when the replacement of the glow plug 1 is confirmed. However, the calibration is also performed when the pre-correction resistance value obtained by the calibration is in a clear state (that is, 0). Although the resistance value before correction is stored in the RAM 34, for example, when a situation where the RAM 34 is cleared occurs, for example, when the battery VA is replaced or at the time of initial shipment, a new resistance value before correction is obtained by performing calibration. A correction flag is established as required.

The “pre-correction resistance value” is a resistance value acquired by calibration, and represents a resistance value (target resistance value) of the glow plug 1 corresponding to a temperature (target temperature) that is a target for maintaining (warming) the glow plug 1. In the calculation, it refers to the resistance value of the glow plug 1 as a source. In the initial state (when the RAM 34 is cleared and the value is 0, such as at the time of initial shipment or when the battery VA is replaced), a predetermined initial value is set.
[Operation during normal operation]
Next, details of energization control for the glow plug 1 will be described. First, energization control performed on the glow plug 1 during normal operation (a state in which the glow plug 1 is not replaced or the like) will be described. In this state, the values of the check flag, initial flag, replacement flag, and correction flag are all 0.

  First, in a state where the driving of the engine EN is stopped (the engine key EK is off), the microcomputer 31 is shifted to the power saving mode, and the interrupt timer 35 waits for an interrupt signal to be input. .

  In this state, when the engine key EK is turned on, an interrupt signal notifying the microcomputer 31 of the on state is input. Then, the operation clock of the microcomputer 31 is switched to one having a high oscillation frequency, and the transition from the power saving mode to the normal mode is performed. With the transition to the normal mode, execution of the energization control program shown in FIG. 2 is started, and various settings necessary for performing energization control of the glow plug 1 in the normal mode are performed (S11). Further, the interrupt prohibition process is performed (S12), and thereafter the interrupt signal input to the microcomputer 31 is ignored until the interrupt prohibition process is canceled (S19).

  Next, the check flag is referred to (S13). In addition, since the replacement confirmation of the glow plug 1 is not performed during normal operation, the check flag is not established. Therefore, the process proceeds to S18, and the energization processing subroutine shown in FIG. 3 is called. As shown in FIG. 3, in the energization process, first, it is confirmed from the terminal voltage of the microcomputer 31 connected to the engine key EK whether or not the engine key EK is on (S21). At this time, when the engine key EK is turned on, the process proceeds to S22. While the engine key EK is on, the energization of the glow plug 1 is controlled so as to perform rapid temperature increase energization and heat insulation energization described later.

  When the first energization process is executed after returning to the normal mode, the initial flag is set to 0 in the initial state as in the case of the check flag. As described above, the initial flag is a flag for performing S22 to S28 only once after returning to the normal mode. Accordingly, the initial flag is set to 1 in S23 so that the process can be skipped and proceed to S29 in the subsequent S22.

  Next, the resistance value before correction is read (reference value) (S24). Here, if the resistance value before correction is not 0, it means that calibration has already been performed. Thereafter, the exchange flag is referred to (S27). As described above, the replacement flag is set when it is detected that the glow plug 1 has been replaced (the processing when the glow plug 1 is replaced will be described later). The exchange flag is 0. Therefore, it will progress to S29.

  In S29 to S36, power is actually applied to the glow plug 1. That is, from the start of energization to the glow plug 1 until the temperature of the glow plug 1 is set to the predetermined temperature increase target temperature (S29; No), the temperature of the glow plug 1 is set as shown in FIG. Energization (rapid temperature rise energization) is performed for rapid increase (S30).

  In this rapid temperature increase energization, the curve indicating the relationship between the electric power supplied to the glow plug 1 and the elapsed time is matched with a reference curve prepared in advance, so that the glow plug 1 is independent of the characteristics of the glow plug 1. Is rapidly raised (for example, about 2 seconds) to the target temperature. Specifically, using a relational expression or a table indicating a predetermined reference curve, the power to be input at each time point corresponding to the elapsed time from the start of energization is obtained. The voltage to be applied to the glow plug 1 is obtained from the relationship between the current flowing through the glow plug 1 and the value of power to be applied at that time, and the voltage applied to the glow plug 1 is controlled by PWM control. As a result, the power is input so as to draw the same curve as the reference curve, and the glow plug 1 generates heat according to the integrated amount of power input up to each point in the temperature raising process. Accordingly, when the power supply along the reference curve is completed, the glow plug 1 reaches the temperature increase target temperature in the time corresponding to the reference curve.

  Thereafter, the process returns to S21, and the process of S30 is repeated until the rapid temperature increase energization is completed, and the rapid temperature increase energization of the glow plug 1 is continued. Since the initial flag is established in S23, in S22, the process proceeds to S29 without performing the processes in S23 to S28.

  In the present embodiment, the end timing of the rapid temperature increase energization in S29 is a case where one of the following three conditions is satisfied. The first is a case where the elapsed time from the start of rapid temperature increase energization reaches a predetermined time (for example, 3.3 seconds). The second case is a case where the integrated power amount supplied to the glow plug 1 becomes a predetermined power amount (for example, about 214 J). In these cases, since it is considered that the temperature of the glow plug 1 has reached the temperature increase target temperature, the rapid temperature increase energization is terminated. The third is a case where the resistance value R of the glow plug 1 measured by the microcomputer 31 becomes a predetermined resistance value (for example, 780 mΩ). That is, when the temperature of the glow plug 1 is already high to some extent at the time when the power supply to the glow plug 1 is started (for example, after the previous energization stop, the energization is performed again without being sufficiently cooled) Etc.), the power supply is stopped when the resistance value R of the glow plug reaches a predetermined resistance value. Thereby, the excessive temperature rise of the glow plug 1 can be prevented.

  When it is determined that any of the above-described termination conditions is satisfied and the rapid temperature increase energization is completed while S29 to S30 are repeated and the rapid temperature increase energization is continued (S29; Yes), to the glow plug 1 Is immediately stopped (S31). Here, in the present embodiment, heat retention energization (so-called afterglow energization) is performed after rapid temperature increase energization, and the temperature of the glow plug 1 is maintained at the target temperature, thereby improving the drive stability after the engine EN is started. Yes. The operation at the time of heat conduction will be described in detail later.

  When it is determined that the heat insulation energization is completed after S32 to S35 are repeated and the heat insulation energization is continued (S32; Yes), the power supply to the glow plug 1 is stopped (S36). Thereafter, while the engine key EK is on, the glow plug 1 is not energized. The condition for terminating the heat insulation energization process may be, for example, when a predetermined time (for example, 180 s) has elapsed since the start of the heat insulation energization.

  When the engine key EK is turned off and the driving of the engine EN is stopped (S21; No), the initial flag is reset so that the processing such as S23 is performed at the next driving of the engine EN (S41). . Here, when the engine key EK is turned off and the rapid heating energization or heat insulation energization is being performed on the glow plug 1 (S42; Yes), the energization is stopped (S43). If not, the process proceeds to S44 as it is. In S44, when the correction flag is referred to and calibration is being performed, the correction flag is not established, and the process directly returns to the main routine. On the other hand, when the correction flag is established, calibration is performed (the operation at the time of calibration will be described later).

Returning to FIG. 2, when the correction flag is not established (S44; No), the energization process of S18 is terminated, and interruption is permitted (S19). As a result, an interrupt signal input to the microcomputer 31 can be received again. After various settings necessary for shifting to the power saving mode are performed (S20), the operation clock of the microcomputer 31 is switched to one having a low oscillation frequency. Thereby, the transition from the normal mode to the power saving mode is performed, and the energization control program is stopped.
[Operation when confirming replacement]
Next, a series of processing when confirmation of replacement of the glow plug 1 is performed will be described. The replacement confirmation of the glow plug 1 is periodically performed when the engine EN is not driven, that is, when the microcomputer 31 is in the power saving mode. In this embodiment, the replacement of the glow plug 1 is confirmed every 60 seconds, and this time interval is set to be shorter than the time required from the removal of the glow plug 1 to the engine EN to the installation. Yes. That is, the time interval is set so that the replacement of the glow plug 1 is confirmed while the glow plug 1 is removed from the engine EN.

  When the microcomputer 31 is in the power saving mode, if the interrupt signal generated at each time interval is input from the interrupt timer 35 to the CPU 32, the interrupt signal is accepted, and the microcomputer 31 is in the normal mode. Migrate to When an interrupt signal is input from the interrupt timer 35, the replacement check interrupt processing program shown in FIG. 4 is executed and a check flag is established (S51). Thus, when the energization control program shown in FIG. 2 is executed, the establishment of the check flag is confirmed in S13 (S13; Yes), and a series of processing (S14 to S17) for confirming replacement of the glow plug 1 is performed. To be implemented.

First, energization is performed for a short time (for example, 25 ms) to the glow plug 1 side, and the resistance value (energization resistance value) on the glow plug 1 side is obtained from the voltage applied at that time and the applied current. (S14). Then, after resetting the check flag (S15), it is compared whether or not the energization resistance value is larger than a predetermined threshold value (replacement determination value). When the glow plug 1 is removed from the engine EN, no current flows because the glow plug 1 does not exist, and as a result, the energization resistance value becomes very large. Therefore, if the energization resistance value is larger than the replacement determination value, it is determined that the glow plug 1 has been removed, that is, the glow plug 1 has been replaced (S16; Yes), and the replacement flag is established (S17). . On the other hand, when the energization resistance value is less than or equal to the replacement determination value (S16; No), it is determined that the glow plug 1 has not been replaced. Thereafter, the processing after S19 described above is performed, and the process shifts to the power saving mode.
[Operation during calibration]
Next, an operation when performing calibration for the glow plug 1 will be described. As described above, the calibration of the glow plug 1 is performed when the replacement of the glow plug 1 is detected (that is, when the replacement flag is established) or when the resistance value before correction is clear. For example, this is performed when the engine EN is not driven in order to avoid the influence of disturbance such as swirl or fuel cooling. Further, in the calibration, the glow plug 1 is heated to the same level as the temperature at the start of the engine EN, so that power consumption is large. Therefore, calibration is performed when the engine EN is driven and then stopped, that is, when the battery VA is expected to be charged.

  When the engine key EK is turned on and the engine EN is driven, after returning to the normal mode, the normal energization control of the glow plug 1 is performed as shown in FIG. 3 (S21 to S36). Similarly to the above, when the processing of S21 to S36 is performed for the first time after the engine key EK is turned on, the initial flag is 0 (S22; No), so S23 to S28 are executed. At this time, if the replacement flag is established (S27; Yes), or if the pre-correction resistance value is in a clear state (S25; Yes), the correction flag is established and the replacement flag is reset ( S26). Further, since the pre-correction resistance value stored in the RAM 34 at this time can be that of the glow plug 1 before replacement, the pre-correction resistance value is set to an initial value (S28), and then the above-described glow plug is set. 1 is performed (S29 to S36).

  The initial value of the resistance value before correction is set as follows. That is, even when the resistance value control of other glow plugs having different characteristics is performed using the target resistance value calculated from the initial value, none of the glow plugs is overheated.

  As described above, the engine key EK is turned on for the first time after the replacement of the glow plug 1 or the pre-correction resistance value is cleared (for example, when the vehicle is shipped for the first time or when the battery VA is replaced), and the engine EN is driven. In such a case, the energization control of the glow plug 1 is performed as usual. When the engine key EK is turned off (S21; No), since the correction flag is established this time, the process proceeds to S45 in S44 and calibration is performed (S44; Yes).

  As described above, in the calibration, an integrated electric energy that obtains the target temperature is input to the glow plug 1, the temperature rise of the glow plug 1 is saturated, and the resistance value when the temperature is stabilized at the target temperature is obtained. The resistance value before correction is acquired. In this embodiment, when the time from the start of calibration reaches a predetermined time (for example, 60 seconds), it is considered that the temperature increase of the glow plug 1 is saturated. Accordingly, a timer (not shown) is started at the start of calibration and until the time required for saturation elapses (S45; No), the final input power amount becomes a predetermined integrated power amount for the glow plug 1. In such a manner, correction energization is performed in which constant power is applied per hour (S46). Thereafter, the process returns to S21 and the correction energization is continued.

  If a predetermined time has elapsed from the start of the correction energization, the process proceeds to S47. At this time, since the temperature of the glow plug 1 has reached the target temperature, the resistance value of the glow plug 1 at that time is obtained and stored in the RAM 34 as a resistance value before correction (S47). Furthermore, the water temperature information of the water temperature sensor SE is acquired from the ECU 41, and the water temperature information is stored in the RAM 34 together with the resistance value before correction (S48). Then, the correction flag is reset assuming that the calibration is completed (S49), the energization to the glow plug 1 is stopped, the correction energization is terminated (S50), and the process returns to the main routine of FIG. The CPU 32 that acquires the pre-correction resistance value (first resistance value) corresponds to the “first acquisition means” in the present invention.

When returning to the main routine, interrupts are permitted (S19) and various settings are made (S20). Then, the transition to the power saving mode is performed, and the energization control program is stopped. If the engine key EK is turned on during calibration, rapid temperature increase energization and heat insulation energization are performed. However, since the calibration is not completed, the pre-correction resistance value is not acquired, the initial value is set as the pre-correction resistance value, and the energization control of the glow plug 1 is performed. Accordingly, calibration is performed again when the engine key EK is turned off.
[Operation during thermal insulation]
Next, energization control during heat insulation energization, which is a feature of the present invention, will be described. First, various variables and flags used in the heat insulation energization program will be described.

  The “initial calculation end flag” is used when setting various values used in the heat insulation energization to initial values. The initial calculation end flag is established when the various values are set to initial values, and is not established before the initial values are set.

  The “initial target temperature” is a temperature that is initially set as the target temperature of the glow plug 1 during heat insulation energization.

The “reference effective voltage V ₀ ” is set from a relational expression (voltage-temperature relational expression) between the temperature of the glow plug 1 in a state without disturbance and the effective voltage to be applied to the glow plug 1 to reach the temperature. It is acquired based on the set target temperature. In this embodiment, the voltage-temperature relational expression is prepared in advance, and as shown in FIG. 9, the glow plug temperature and the reference effective voltage V ₀ have a substantially first-order correlation. The voltage-temperature relational expression corresponds to the “first relational expression” in the present invention.

The “control effective voltage V ₁ ” is an effective voltage that is actually applied to the glow plug 1.

The “average effective voltage V ₂ ” is an average value of the control effective voltage V ₁ within a predetermined time.

The “standard effective voltage V ₃ ” is a value set for each type (product number) of the glow plug as an effective voltage to be applied when setting the glow plug to the target temperature. In the present embodiment, a value corresponding to the type of glow plug 1 is set in advance as the standard effective voltage V ₃ .

The “reference resistance value R ₀ ” is set from a relational expression (resistance temperature relational expression) indicating a relation between the temperature of the glow plug 1 and the resistance value of the glow plug 1 at the temperature in a state where there is no disturbance. It is acquired based on the target temperature. In this embodiment, the resistance temperature relational expression is prepared in advance. For example, as shown in FIG. 10, the temperature of the glow plug and the resistance value have a predetermined first-order correlation. The relationship between the resistance value and the temperature varies greatly from plug to plug as described above, but the variation rate (slope) of the resistance value with respect to the temperature is relatively small for each plug. Therefore, there is no need to calculate the relationship between the resistance value and the temperature for each plug and derive the resistance temperature relational expression. As the resistance temperature relational expression, for example, the target temperature when the above-described calibration is performed, and the calibration An equation having a predetermined inclination passing through the coordinates of the pre-correction resistance value obtained in the process can be used. The resistance temperature relational expression corresponds to the “second relational expression” in the present invention.

The “adjustment correction value R ₁ ” is added to the reference resistance value R _{0 in} order to correct the reference resistance value R ₀ when calculating a target resistance value R _TAR (target resistance value intermediate value R ₄ ) described later. And are sequentially updated by an adjustment value setting process described later. In the present embodiment, the initial value of the adjustment correction value R ₁ is set in advance to a predetermined numerical value (for example, 0 mΩ).

The “target temperature change correction value R ₂ ” is a value calculated based on the target temperature set at the present time based on the relational expression (resistance temperature relational expression) between the temperature and the resistance value described above. More specifically, the difference between the resistance value at the initial target temperature derived from the resistance temperature relational expression and the resistance value at the currently set target temperature derived from the resistance temperature relational expression, and the target temperature has been changed. In this case, it is used to correct the target resistance value R _TAR (standard resistance value intermediate value R ₄ ).

The “water temperature change correction value R ₃ ” is stored at the time of calibration with the water temperature measured by the water temperature sensor SE based on a preset correction equation (water temperature correction equation) indicating the relationship between the water temperature and the correction value. It is derived from the difference from the water temperature. The water temperature correction equation can be specified for each type of engine (in other words, it does not change depending on the type of plug). For example, as shown in FIG. 11, the water temperature and the correction value are predetermined. Can be derived as having a first order correlation.

The “target resistance value intermediate value R ₄ ” is calculated as a result of correcting the reference resistance value R ₀ by the adjustment correction value R ₁ , the target temperature change correction value R ₂ , and the water temperature change correction value R _3. Is.

The “swirl correction value R ₅ ” corresponds to the “disturbance correction value” in the present invention, and takes into account the influence of the swirl and the like after the engine is started, and the target resistance intermediate value R ₄ after the engine is started. Are added.

The “target resistance value correction coefficient α” is a numerical value used when deriving the swirl correction value R ₅ . In the present embodiment, the swirl correction value R ₅ is represented by an expression “(V ₂ −V ₃ ) / α”.

The “target resistance value R _TAR ” is calculated based on the target resistance value intermediate value R ₄ and the swirl correction value R ₅ , and is a resistance value that is a target of resistance value control when the glow plug 1 is set to the target temperature. Note that the target resistance value R _TAR is updated as needed through a process described later.

  Next, details of energization control during heat insulation energization will be described. First, as shown in FIG. 5, the initial calculation end flag is checked (S61), and it is confirmed whether or not resistance value control (ie, heat insulation energization) has been performed. When this has not been performed, initial setting processing (S62 to S65) is performed. On the other hand, when the warming energization has been performed, the process proceeds to an adjustment correction value setting process (S66) described later.

In the initial setting process, first, a reference resistance value R ₀ is set based on the initial target temperature and the resistance value before correction (S62). Specifically, a value obtained by subtracting a predetermined resistance value (for example, 180 mΩ) from the resistance value at the initial target temperature obtained by referring to the above resistance temperature relational expression is set as the reference resistance value R ₀ . The CPU 32 for setting the reference resistance value R ₀ corresponds to “reference resistance value setting means” in the present invention.

Further, referring to the voltage temperature relational expression, the effective voltage at the initial target temperature is set as the reference effective voltage V ₀ (S63). In addition, the target resistance value correction coefficient α is set to a predetermined initial value (S64), and the initial calculation is performed so as not to branch to the initial setting process (S62 to S65) in S61 during the subsequent heat insulation energization process. An end flag is established (S65).

On the other hand, if the first calculation completion flag is established; The (S61 No), the adjustment correction value setting process (S66), adjusting the correction value R ₁ is determined.

More specifically, as shown in FIG. 6 and FIG. 8, a predetermined reference time T ₁ (for example, 2.5 s) elapses from the start of the heat insulation energization (S661; No). A predetermined adjustment value R _n (eg, 1 mΩ) is added to the initial value of the adjustment correction value R ₁ every first time interval (eg, 50 ms) (S663). Also, every second predetermined time interval (for example, 80 ms) from the first reference time T ₁ until a preset second reference time T ₂ (for example, 6.4 s) elapses (S662; No). The adjustment value R _n is added to the adjustment correction value R ₁ (S665). Furthermore, during a period from the second reference time T ₂ until a preset third reference time T ₃ (eg, 6.4 s) has elapsed (S664; No), a preset third time interval (eg, , 500 ms), the adjustment value is added to the adjustment correction value R ₁ (S666).

Next, returning to FIG. 5, the target resistance value intermediate value R ₄ is set based on the reference resistance value R _{0 and the} like (S67). Specifically, a value obtained by adding the reference resistance value R ₀ , the adjustment correction value R _1, and the water temperature change correction value R ₃ is set as the target resistance value intermediate value R ₄ . However, when a target temperature different from the initial target temperature is set, the target temperature change correction value R ₂ is further added to the target resistance value intermediate value R ₄ . That is, the target resistance value intermediate value R ₄ is “R ₄ = R ₀ (reference resistance value) + R ₁ (adjustment correction value) + R ₂ (target temperature change correction value) + R ₃ (water temperature change correction value)”. Determined based on the formula. Therefore, as described above, the increase amount per unit time of the adjustment correction value R ₁ changes in three stages. Therefore, when the target temperature change correction value R ₂ and the water temperature change correction value R ₃ are not considered. As shown in FIG. 8, the target resistance value intermediate value R ₄ gradually increases while gradually reducing the slope. The CPU 32 that calculates and sets the target resistance value intermediate value R ₄ corresponds to the “intermediate value setting means” in the present invention.

Incidentally, by gradually adding the adjustment correction value R ₁ with respect to the reference resistance R _0, eventually, decrease the reference resistance value R ₀ set in S62 is complemented. In other words, the increase rate of the adjustment correction value R ₁ is set so that the decrease of the reference resistance value R ₀ can be finally supplemented.

By the way, the reason why the reference resistance value R ₀ is corrected using the adjustment correction value R ₁ that gradually increases as described above is as follows. That is, as described above, the resistance value of the glow plug 1 is measured not only in the resistance value of the heat generating portion (heat generating coil 9) but also in the harness that electrically connects the GCU 21 and the heat generating portion (heat generating coil 9). And the resistance value of the entire glow plug including the resistance value of the control coil 10 and the like. However, immediately after the start of the heat insulation energization, the temperature of the heat generating portion (heat generating coil 9) of the glow plug 1 is relatively high and the resistance value is relatively large, while the other portions (control coil 10 and the like) generate heat. The temperature from the portion is not sufficiently transmitted, and the resistance value is relatively low (that is, the resistance value of the glow plug 1 is not saturated).

Therefore, in the present embodiment, the reference resistance value R ₀ is set to a lower value in consideration of the relatively low resistance value of the control coil 10 and the like for a while from immediately after the start of the heat insulation energization. The target resistance value intermediate value R _{4 as} a basis for deriving the target resistance value R _TAR is set to a relatively low value. On the other hand, when heating progresses and the resistance value of the control coil 10 and the like increases, the adjustment correction value R ₁ is added to the reference resistance value R ₀ , so that the target resistance value intermediate value R ₄ ( As a result, the target resistance value R _TAR ) increases in response to the fluctuation of the resistance value of the glow plug 1.

Returning to the description of the heat insulation energization control, after setting the target resistance value intermediate value R ₄ (S67), the reference effective voltage V ₀ is set from the target temperature set at the present time based on the voltage-temperature relational expression (S68). . The CPU 32 for setting the reference effective voltage V ₀ corresponds to “reference effective voltage setting means” in the present invention.

Next, cranking before whether (before the engine start) is confirmed (S69), before and after cranking, the PI control to be described later (S74), used when calculated control effective voltages V ₁ The proportional term coefficient K and integral term coefficient T _I in the control equation [V ₁ = V ₀ + K × {(R _TAR −R) + (T _S / T _I ) × Σ (R _TAR −R)}] are changed. Be made. [T _S is a sampling time, and in this embodiment, a predetermined time (for example, 25 ms) is preset as T _S. ]
Before cranking (S69; Yes), there is little change in the engine state. Therefore, in order to prevent overshoot (overheating) immediately after rapid temperature increase, the coefficients K and T _I are set to predetermined values so that the speed of bringing the resistance value of the glow plug 1 to the target resistance value can be relatively lowered. (For example, K = 20V / Ω, T _I = 5 s) is set (S70). On the other hand, after cranking, the resistance value of the glow plug 1 is changed to the target resistance value in order to make the temperature of the glow plug 1 follow the target temperature more easily in response to fluctuations in the engine speed. The coefficients K and T _I are set to predetermined numerical values (for example, K = 80 V / Ω, T _I = 1.25 s) in order to relatively increase the speed (S71).

If it is determined that the pre-cranking; The (S69 Yes), followed by the coefficient K, T _I setting (S70), as the target resistance R _TAR, the target resistance intermediate value R ₄ is set as (S72). The CPU 32 that sets the target resistance value R _TAR corresponds to the “target resistance value setting means” in the present invention.

On the other hand, if it is determined that the after the cranking; The (S69 No), followed by the coefficient K, T _I setting (S71), swirl correction process (S73) is performed. The swirl correction process will be described in detail later.

After the target resistance value R _TAR is set in S72, the control effective voltage V ₁ to be applied to the glow plug ₁ is calculated using the target resistance value R _TAR and the measured resistance value R of the glow plug 1. (S74). That is, the control effective voltage V ₁ is set based on the expression “V ₁ = V ₀ + K × {(R _TAR −R) + (T _S / T _I ) × Σ (R _TAR −R)}”. . The CPU 32 for setting the control effective voltage V ₁ corresponds to the “effective voltage determining means” in the present invention.

Further, the average effective voltage V ₂ is calculated based on the control effective voltage V ₁ set so far (S75). In the present embodiment, since the control effective voltage V ₁ is calculated once every predetermined time (for example, 25 ms) corresponding to the operation clock of the CPU 32, the average effective voltage V ₂ is An average value of the control effective voltage V ₁ within a time sufficiently longer than the predetermined time (for example, 250 ms) is calculated.

Thereafter, the duty ratio is calculated based on the control effective voltage V ₁ and the output voltage (controller output voltage) from the GCU 21 to the glow plug 1 (S76), and the energization to the glow plug 1 is controlled based on the duty ratio. Is done. Thereafter, the processing from S61 to S76 is repeatedly performed until the termination condition of the heat insulation energization processing is satisfied (that is, S32 becomes “Yes”). Note that the duty ratio may be calculated using the supply voltage of the battery VA instead of the output voltage from the GCU 21.

  Next, in describing the swirl correction process (S73), first, a correction formula as a third relational expression used in the swirl correction process will be described.

In the present embodiment, in the desktop test, the standard effective voltage V ₂ that is the average value of the control effective voltage V ₁ obtained by driving the engine alone with various changes in the engine speed, load, water temperature, etc. The difference obtained by subtracting the effective voltage V ₃ (effective voltage difference) and the resistance correction value corresponding to the difference (the difference between the resistance value R of the glow plug when the engine is driven and the reference resistance value R ₀ when the engine is not driven) (Refer to FIG. 12) is preset as the correction formula. In particular, in the present embodiment, the resistance correction is performed when the average effective voltage V ₂ is equal to the standard effective voltage V ₃ in view of the fact that the effective voltage difference and the resistance correction value are empirically recognized to have a first order correlation. Using a point where the value is 0 as a reference point, a linear equation is derived using the coordinates of several points indicating the relationship between the effective voltage difference and resistance correction value obtained by changing the engine speed, load, etc. The primary equation is used as a correction equation. The correction equation indicates a resistance value to be added to the target resistance value R in order to increase the amount of power to be input in consideration of the influence of heat generation in the resistance portion such as the control coil 10. Further, the correction formula is used in common when performing energization control of each glow plug 1.

Returning to the description of the swirl correction process, as shown in FIG. 7, the swirl correction value R is divided from the resistance correction value described above according to whether or not a predetermined time (for example, 20 s) has elapsed since the start of cranking (S731). ₅ is set.

That is, before the predetermined time has elapsed from the start of cranking (S731; No), the resistance value of the glow plug 1 is not sufficiently increased in the temperature of the glow plug 1 other than the heat generation portion. May not be sufficiently saturated. Therefore, if the resistance correction value obtained from the above correction equation is used as it is, there is a risk of overheating. Therefore, from the viewpoint of preventing excessive temperature rise, in the present embodiment, the swirl correction value R ₅ is set to be low until a predetermined time elapses from the start of cranking described above. It gradually increases. Specifically, the swirl correction value R ₅ can be expressed as “(V ₂ −V ₃ ) / α” in consideration of the above correction formula, and the target resistance value correction coefficient α is set every predetermined time (for example, 1 second). The resistance correction value and swirl correction value R ₅ derived from the correction formula are finally reduced (ie, after a predetermined time has elapsed from the start of cranking) by decreasing by a predetermined amount (for example, 1) (S732). Are set so that the initial value of the target resistance value correction coefficient α and the reduction rate per unit time of the target resistance value correction coefficient α are set.

On the other hand, when the predetermined time has elapsed from the start of cranking (S731; Yes), it is considered that the resistance value of the glow plug 1 is in a saturated state. Therefore, as a swirl correction value R _5, a relatively large value corresponding to the resistance correction value derived from the correction equation is set. The CPU 32 for setting the swirl correction value R ₅ corresponds to “correction value setting means” in the present invention.

  In this embodiment, at a predetermined target temperature (eg, 1200 ° C.), as shown in FIG. 13, the reciprocal (1 / α) of the target resistance value correction coefficient α is set within a predetermined time (eg, 20 s). The initial value and change rate of the target resistance correction coefficient α so as to increase from a predetermined first set value (for example, 8.8 mΩ / V) to a predetermined second set value (for example, 13.5 mΩ / V). Is set.

Following the setting of the swirl correction value, it is determined whether or not the average effective voltage V ₂ is equal to or higher than the standard effective voltage V ₃ (S733). Here, when the average effective voltage V ₂ is equal to or higher than the standard effective voltage V ₃ (S733; Yes), it is considered that the engine is in a state after the engine start, and thus it is necessary to correct the swirl. Therefore, a value obtained by adding the swirl correction value R ₅ to the target resistance value intermediate value R ₄ is set as the target resistance value R _TAR (S734).

On the other hand, when the average effective voltage V ₂ is less than the standard effective voltage V ₃ (S733; No), it is considered that the engine has not been started, and therefore it is not necessary to correct the swirl. Therefore, the value of the target resistance value intermediate value R ₄ is set as the target resistance value R _TAR as it is (S735).

Thereafter, until the heat insulation energization end condition is satisfied, the heat insulation energization control of S61 to S76 is performed based on the target resistance value R _TAR set (updated) as needed.

As described above in detail, according to the present embodiment, after the cranking, the correction formula is used for the target resistance value intermediate value R ₄ in consideration of the influence of heat generation in the resistance portion such as the control coil 10. A value obtained by adding the swirl correction value R ₅ obtained in this way is set as the target resistance value R _TAR . Here, the correction formula is based on the time when the engine is driven (that is, when the swirl is generated), and the resistance value of the glow plug corresponding to the voltage applied to the glow plug 1 A resistance correction value based on a difference from a reference resistance value R ₀ (resistance value when no disturbance occurs) is shown. Accordingly, using the swirl correction value R ₅ obtained from the resistance correction value, the reference resistance value R ₀ (target resistance value) obtained in a state where the engine EN is not driven (that is, no swirl is generated). By correcting the intermediate value R ₄ ), it is possible to set an appropriate target resistance value R _TAR considering the influence of swirl. As a result, temperature drop due to swirl can be more reliably prevented, and the temperature of the glow plug 1 can be stably maintained at the target temperature.

Further, since the resistance value of the glow plug 1 increases as the temperature rises after the engine EN is driven until the temperature of the glow plug 1 is saturated, the swirl correction value R ₅ is changed in accordance with the increase. That is, in the present embodiment, the initial swirl correction value R ₅ is set low, and the swirl correction value R ₅ is gradually increased in accordance with the energization time to the glow plug 1. Accordingly, it is possible to more reliably prevent an excessive temperature rise of the glow plug 1 while sufficiently suppressing a temperature drop due to swirl.

In addition, when setting the target resistance value intermediate value R ₄ , environmental information (water temperature change correction value R ₃ ) indicating a change in the water temperature and the like is taken into consideration in addition to the reference resistance value R ₀ . Therefore, the target resistance value R _TAR as a control target can be set more appropriately, and the temperature of the glow plug 1 can be stably maintained at the target temperature.

The swirl correction value R ₅ is derived using the standard effective voltage V ₃ . Here, for example, it is conceivable to use the reference effective voltage V ₀ of one glow plug instead of the standard effective voltage V _{3. In} this case, the reference effective voltage V ₀ and the reference effective voltage of other plugs are used. Since V ₀ is different from each other, there is a possibility that an appropriate swirl correction value R ₅ cannot be set for each glow plug. In this respect, in the present embodiment, the standard effective voltage V ₃ which is a relatively close value to the reference effective voltage V ₀ of each glow plug is used, and therefore common to the energization control of each glow plug. Even if the correction formula is used, it is possible to accurately control the energization of each glow plug.

Furthermore, by setting the resistance correction value based on the difference from the average effective voltage V ₂ that is the average value of the control effective voltage V ₁ , it is possible to prevent the fluctuation of the resistance correction value from becoming extremely large. As a result, the temperature fluctuation of the glow plug 1 can be more reliably prevented from becoming extremely large.

  Next, in order to confirm the effects achieved by the present invention, the GCU according to the embodiment (the one that performs the swirl correction process) and the GCU according to the comparative example (the conventional example) (the one that does not perform the swirl correction process) The state of the engine was changed variously using each of the above, and the temperature (plug temperature) of the glow plug controlled by each GCU was measured. The engine state is a total of five states of engine start (stop state), idling, rotation speed 2000 rpm, 3000 rpm, 4000 rpm as an example on the low load side including no load, and rotation speed 4000 rpm as an example on the high load side. Comparisons are made in six states. FIG. 15 shows the results of the test. The target temperature of the glow plug was 1250 ° C. Further, in FIG. 15, the temperature of the glow plug controlled using the GCU according to the example is plotted with a black square (■), and the temperature of the glow plug controlled using the GCU according to the comparative example is indicated by a cross (× ).

  As shown in FIG. 15, the temperature of the glow plug controlled by the GCU according to the comparative example increases as the engine speed increases (in other words, as the influence of disturbance such as swirl increases). It was found that the target temperature was difficult to maintain due to a decrease (in this test, the maximum temperature decreased by 84 ° C. before starting).

  On the other hand, when the glow plug is controlled by the GCU according to the embodiment, the difference between the maximum temperature and the minimum temperature is extremely small even if the engine speed increases or the degree of load changes. It was found that the glow plug can be maintained at the target temperature in the state (in this test, 12 ° C.) (that is, stably). This is to maintain the heating resistor at the target temperature by performing the swirl correction process even when the heating resistor is partially cooled by the influence of the swirl after the engine is started. This is thought to be because the power to be supplied to the heating resistor could be supplied more reliably to the heating resistor.

  As described above, in order to stably maintain the glow plug at the target temperature in consideration of the results of the above test, for example, by adding power to the glow plug such as adding a swirl correction value based on the correction formula to the target resistance value. It can be said that it is desirable to set the target resistance value in consideration of the influence of the resistance region such as the control coil when the operation is performed.

  In addition, it is not limited to the description content of the said embodiment, For example, you may implement as follows. Of course, other application examples and modification examples not illustrated below are also possible.

(A) In the above embodiment, the GCU 21 acquires the coolant temperature (water temperature information) from the ECU 41 as the environmental temperature information, and uses the environmental temperature information to obtain the target resistance intermediate value R ₄ (target resistance value). R _TAR ) has been calculated. On the other hand, the target resistance value intermediate value R ₄ (target resistance value R _TAR ) may be calculated without using the environmental temperature information. In this case, it is not necessary to provide a communication means between the GCU 21 and the ECU 41 or the water temperature sensor SE, and the manufacturing cost can be suppressed.

  (B) In the above embodiment, the GCU 21 is configured to control the energization of the glow plug 1 (metal glow plug) having the heat generating coil 9, but the control target by the GCU 21 is limited to this. is not. For example, the dimensions of each member, the composition of the coil, and the like can be appropriately changed to those that can be easily controlled by the GCU 21. Further, the glow plug is not limited to the metal glow plug. Therefore, the GCU 21 may be configured to control energization of the ceramic glow plug having the ceramic heater.

(C) In the above embodiment, the target resistance intermediate value R ₄ (target resistance value R _TAR ) is adjusted by adding the adjustment correction value R ₁ until the temperature of the control coil 10 etc. is sufficiently increased. and in which is (S66, S67) is, without going by adding the adjustment correction value R _1, set the resistance value at the target temperature obtained from resistance temperature relationship described above as the reference resistance value R ₀ as it is the The target resistance value intermediate value R ₄ may be calculated from the reference resistance value R ₀ . That is, immediately after the start of cranking, the energization control may be performed assuming that the resistance value of the glow plug 1 is already saturated.

(D) In the above embodiment, by decreasing the target resistance correction coefficient alpha, although swirl correction value R ₅ are increased gradually with the lapse of energization time, the swirl correction value R ₅ energization time The swirl correction value R ₅ may not be changed with the lapse of time [however, the swirl correction value R ₅ does not change, and the swirl correction value R ₅ is different from the effective voltage difference (average effective voltage V ₂ and standard effective voltage). It varies depending on the difference from the voltage V ₃ ].

  (E) Although not specifically described in the above embodiment, the temperature changes in the combustion chamber in which the glow plug 1 is disposed, such as the control information of the opening timing of the intake and exhaust valves, the flow rate of the air flow sensor, and the change in the fuel injection amount. The target resistance value may be set in consideration of the influence of the disturbance that gives the resistance to the resistance parts other than the heating coil 9. In this case, the heat generation temperature can be maintained in a more stable state.

  DESCRIPTION OF SYMBOLS 1 ... Glow plug, 9 ... Heat generating coil (heat generating resistor), 21 ... Glow control device (GCU) as an electricity supply control device, EN ... Engine (internal combustion engine).

Claims (4)

For a glow plug that generates heat when energized and changes its own resistance value according to its own temperature change, a resistance value control system that controls energization so that the resistance value of the glow plug matches a predetermined target resistance value A glow plug energization control device for controlling a voltage applied to the glow plug,
First acquisition means for acquiring a first resistance value of the glow plug by energizing the glow plug when driving of the internal combustion engine to which the glow plug is attached is stopped;
Intermediate value setting means for setting an intermediate value of the target resistance value based on at least the first resistance value;
Using the first relational expression showing the relationship between the voltage applied to the glow plug and the temperature of the glow plug when the drive of the internal combustion engine is stopped, the glow plug is applied to reach the target temperature. A reference effective voltage setting means for setting a reference effective voltage which is a power voltage;
Using the second relational expression showing the relationship between the resistance value of the glow plug and the temperature of the glow plug when the driving of the internal combustion engine is stopped, the glow plug corresponding to the target temperature of the glow plug is used. A reference resistance value setting means for setting a reference resistance value which is a resistance value;
The resistance of the glow plug corresponding to the voltage applied to the glow plug, obtained based on the relationship between the voltage applied to the glow plug and the resistance value of the glow plug when the internal combustion engine is driven. A correction value setting means for setting a disturbance correction value from the resistance correction value using a third relational expression indicating a relationship between a resistance correction value based on a difference between the value and the reference resistance value;
A target resistance value setting means for setting the target resistance value using an intermediate value of the target resistance value and the disturbance correction value after the start of driving of the internal combustion engine;
A glow plug energization control device comprising: effective voltage determination means for determining an effective voltage to be applied to the glow plug based on the reference effective voltage and the target resistance value. The correction value setting means varies the disturbance correction value in response to an increase in the resistance value of the glow plug as the temperature rises after the internal combustion engine is driven until the temperature of the glow plug is saturated. The glow plug energization control device according to claim 1 . While acquiring information of the environmental temperature according to the environment where the glow plug is used,
The glow plug energization control device according to claim 1 or 2 , wherein the intermediate value setting means sets an intermediate value of the target resistance value based on the environmental temperature information.   A heat generation system including the glow plug energization control device according to any one of claims 1 to 3 and the glow plug.

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