JP5884390B2 - Heating device - Google Patents

Description

  The present invention relates to a heating device having a heating element that generates heat by energization and whose resistance value changes with a positive correlation according to its own heating temperature, and an energization control module that controls energization from the power source to the heating element, Stable energization control and quick deterioration abnormality detection are realized with a simple configuration. In particular, a glow plug provided for each cylinder of a diesel combustion engine is used as a heating element, and the heating element and the energization control module are substantially cylindrical housings. It is suitable for a control unit integrated glow plug that is integrally accommodated therein.

  Conventionally, as an abnormality detection device for detecting an abnormal disconnection or an overcurrent abnormality of a glow plug that assists ignition of a diesel combustion engine, a current sensor or a shunt resistor is connected between the glow plug and a switch means for controlling energization to the glow plug. There is known an apparatus for detecting a deterioration of a glow plug or a disconnection abnormality by calculating a resistance value of the glow plug from a current flowing through the glow plug and a voltage applied to the glow plug by providing a current detection means such as the above.

  Japanese Patent Laid-Open No. 2004-260688 discloses detection means for detecting a detection value corresponding to the resistance of the glow plug by energizing the glow plug for preheating the internal combustion engine, and energizing the glow plug immediately after the operation of the internal combustion engine is stopped. There is disclosed a glow plug deterioration determination device including determination means for determining deterioration of the glow plug based on the detection value detected by the detection means.

  In Patent Document 2, first voltage output means for converting a current flowing through a heater into a voltage and outputting a first voltage value, and a second voltage value connected to a power source and corresponding to the voltage of the power source are output. By comparing the first voltage value output from the second voltage output means, the first voltage output means and the second voltage output means respectively with the second voltage value, it is determined whether or not the heater has deteriorated. A heater deterioration detection apparatus including a comparison determination unit is disclosed.

  In Patent Document 3, for a heater having a heating resistor that generates heat when energized and its resistance value changes with a positive correlation according to its own temperature change, the resistance value of the heating resistor becomes a target resistance value. A heater energization control device that controls energization of the heating resistor by a resistance value control system that controls energization so as to coincide with each other, and the heat generation when the drive of the internal combustion engine to which the heater is attached is stopped First acquisition means for energizing the resistor to acquire the first resistance value of the heating resistor, and information on environmental temperature according to the environment in which the heater is used when acquiring the first resistance value The environmental information acquisition means to be acquired, the calculation means for calculating the target resistance value based on the information on the first resistance value and the environmental temperature, and the calculation means when the internal combustion engine is driven. Calculated the to match the target resistance value, the energization control apparatus of the heater, characterized in that a current supply control means for controlling the energization of the heating resistor is disclosed.

In conventional degradation determination devices such as those disclosed in Patent Documents 1 and 2, current detection means for detecting the current flowing through the glow plug, and a shunt resistor or the like is used as a reference for providing a threshold value for determining degradation. ing.
In addition, there is an individual difference in the resistance value of the glow plug. Therefore, the resistance value calculated from the plug current flowing through the glow plug detected using the shunt resistor having a constant resistance value and the voltage applied to the glow plug, and the reference resistance having the constant resistance value If the deterioration state is determined as a threshold by comparison, the individual difference is ignored.
For example, in the case of a glow plug with a high initial resistance, when the resistance value slightly increases with use, it is detected in a state where it can reach the target temperature and is not actually deteriorated. If the resistance value exceeds a certain threshold value, it may be erroneously determined as being deteriorated. Conversely, in the case of a glow plug with a low initial resistance value, the target temperature cannot be reached. Despite deterioration, the original initial resistance is low, so even if the resistance value increases with use, if it does not exceed a certain threshold, it may be erroneously determined as normal. there were.

Further, in the conventional glow plug energization control device, energization to a plurality of glow plugs provided for each cylinder of the internal combustion engine is controlled by one energization control device. In such a configuration, there is an individual difference in the resistance value of each glow plug, so in order to avoid overheating, the average supplied by PWM control with the glow plug having the lowest resistance value within the rating as a reference The voltage V _AVG is determined, and power determined by V _AVG ² / R _GP is supplied.
For this reason, even if it is possible to avoid overheating of the glow plug having a low resistance value among the plurality of glow plugs, there is a possibility that the ultimate temperature and the temperature rising rate of the glow plug having a high resistance value may be reduced.

Furthermore, the glow plug energization control device as disclosed in Patent Document 3 uses environmental information such as engine water temperature, so the control method is complicated, requires a CPU with high arithmetic processing capacity, an interrupt timer, etc. Therefore, the size of the apparatus is inevitably increased, and it may be difficult to mount various electronic control apparatuses in a highly integrated engine room.
In addition, in the conventional glow plug energization control device, the plug current applied to the flow plug or the plug applied to the glow plug is used to control the heat generation temperature of the glow plug more accurately or to detect an abnormality of the glow plug. The voltage is A / D converted and transmitted to the ECU side, and calculation processing is performed on the ECU side for use in stopping the glow plug energization control device and for temperature correction. It is exchanged between the glow plug energization control device and the ECU. Since the amount of data to be processed is enormous, a high-performance CPU is required, and high-speed data communication means such as CAN is required, which inevitably increases manufacturing costs.
Further, when a constant target power is applied by a method as described in Patent Document 3, there is a big problem that the actual heat generation temperature falls below the target temperature due to the influence of swirl.

  Therefore, in view of such circumstances, the present invention has an extremely simple configuration and excellent mountability, and in addition, when a plurality of heating elements are used at the same time, the accuracy depends on individual differences of individual heating elements that are unavoidably present. It is an object of the present invention to provide a control unit-integrated heat generating device capable of determining the presence or absence of deterioration and controlling the temperature of each heat generating element independently and accurately.

According to the first aspect of the present invention, a heating element that generates heat when energized and its resistance value changes with a positive correlation in accordance with its own temperature change, and a power source so that the resistance value of the heating element matches a reference resistance value. A heating control device for controlling the power supply to the heating element from above, wherein the heating element and the control module are integrally housed in a housing, and the power supply control module measures in advance a reference resistance value storing means for storing a resistance value of the heating body at a predetermined target temperature as the reference resistance value, as a threshold the reference resistance value, the resistance value of the heating body at the time of energization is below the reference resistance value When the resistance value of the heating element exceeds the reference resistance value, the energization is stopped and the change in resistance value accompanying the temperature change of the heating element is reflected in the energization control. And the resistance value change reflecting means,
The effective power P _ACT by the energization control, the advance in the measured predetermined target temperature to an initial reference power value P _INT applied to the heating body, the degradation threshold power Ru is calculated by multiplying a predetermined ratio P _REF below if it becomes comprises a determining deterioration determining unit deterioration.

According to a second aspect of the present invention, the reference resistance value is provided as a resistor that can be adjusted by electrical trimming.

According to a third aspect of the present invention, the electrical trimming is performed by digital trimming using a zener zap or a polysilicon fuse.

According to a fourth aspect of the present invention, the heating element is a glow plug provided for each cylinder of the internal combustion engine.

In the invention of claim 5, the deterioration determination is performed either before cranking the internal combustion engine, immediately after the internal combustion engine is stopped, or at an idle stop.

According to the first aspect of the present invention, the heating element and the energization control module are integrated, and even if there is an individual difference in the resistance value of the heating element in the manufacturing stage, the heating element is provided for each heating device according to the individual difference. The reference resistance value can be set, and when the resistance value change reflecting means reflects the change in the resistance value due to the temperature change to the energization control, the accuracy is independently determined without depending on the state of other heat generating devices. Temperature control is possible.
In addition, as in the past, since temperature control is possible in a self-contained manner without using external information such as engine water temperature, the structure can be greatly simplified, and the manufacturing cost can be reduced. In addition to being able to mount, it also has excellent mountability.

In addition , when the temperature control is performed so that the resistance value of the heating element matches the reference resistance value by the temperature change reflecting means, if the resistance value of the heating element increases due to long-term use, the effective power P _ACT is reduced, as the actual heating temperature is lowered by the deterioration determination means, the effective power P _ACT becomes less than the degradation threshold power P _REF, is a possibility that the heat generation temperature becomes less critical temperatures available It can be determined that it has deteriorated at some point, using external environment information, etc. as before, exchanging a lot of information with an external processing unit, etc. In a simple configuration, it is possible to detect the presence or absence of deterioration in a self-contained manner and promptly take measures against the deterioration abnormality.

According to the invention of claim 2 , it is possible to form a desired reference resistance value by using a part of the elements constituting the energization control module, and without increasing the size of the energization control module, the high A control unit-integrated heating device that can accurately control the temperature and can determine whether there is a deterioration abnormality with a simple configuration can be realized.

According to the invention of claim 3, the reference resistance value corresponding to the individual difference of the heating elements can be easily and accurately adjusted by digital trimming.

According to the invention of claim 4 , even if there are individual differences among the plurality of glow plugs, it is possible to control the temperature independently and accurately without being influenced by each other, and to quickly determine whether there is any deterioration. Since it can be determined, a highly reliable control unit integrated glow plug can be realized with an extremely simple configuration.

According to the fifth aspect of the present invention, it is possible to determine the deterioration of the glow plug with high accuracy without being affected by the operating state of the internal combustion engine.

(A) is a block diagram which shows the outline | summary of the heat generating apparatus in the 1st Embodiment of this invention, (b) controls each electricity supply to the several glow plug provided in every cylinder of the internal combustion engine independently, respectively. The block diagram which shows the whole outline | summary of the control part integrated glow plug to do. 1 shows the structure of the control unit integrated glow plug shown in FIG. 1, wherein (a) is a longitudinal sectional view, (b) is a transverse sectional view taken along line A-A in FIG. FIG. 2 is a longitudinal sectional view showing an outline of a so-called metal heater used as a glow plug to which the present invention can be applied; FIG. 4D is a longitudinal sectional view showing an outline of a so-called ceramic heater used as a glow plug to which the present invention can be applied. Figure. FIG. 4 is a characteristic diagram showing the correlation between the temperature of a glow plug to which the present invention is applied and the plug resistance value, where R _INT indicates the resistance temperature characteristic in the initial state, and R _ACT indicates the resistance in the state after use for a certain period of time. A temperature characteristic is shown, and R _WRN indicates a resistance temperature characteristic in a deteriorated state. The flowchart which shows the initial temperature rising control method used for the heat generating apparatus of this invention. The flowchart which shows the steady control method used for the heat generating apparatus of this invention. It is a time chart of the heat generating device to which this invention is applied, (a) shows a drive signal, (b) shows change of plug resistance, (c) shows the determination result of a temperature change reflection means. (D) shows the operating state of the semiconductor switching element when the temperature change is fed back, (e) shows the change in energization current, (f) shows the change in average power, (g) Indicates changes in the exothermic temperature. In the steady control mode of the heat generating device to which the present invention is applied, it is a time chart in which the time from the initial state to the deteriorated state is arranged in time series, where (a) shows the drive signal and (b) shows the plug (C) shows the determination result of the temperature change reflecting means, (d) shows the operating state of the semiconductor switching element when the temperature change is fed back, and (e) shows the conduction current. (F) shows a change in average power, and (g) shows a change in heat generation temperature. The flowchart which shows the afterglow control method used for the heat generating apparatus of this invention. The effect of this invention is shown, (a) is a characteristic diagram which shows the temperature control state in the steady control mode, (b) is a characteristic diagram which shows the temperature control state in the preheating control mode, (c) is the afterglow control mode The characteristic view which shows the temperature control state in. The flowchart for determining the necessity of deterioration determination.

As a heating device in the first embodiment of the present invention, a heating element 10 provided for each cylinder of an internal combustion engine (not shown) is used as a heating element, and an energization control module 20 that controls energization from the power source 6 to the heating element 10 is housed. The control unit-integrated glow plug 1 that is integrally accommodated in the 30 will be described.
In the control unit-integrated glow plug 1 in the present embodiment, the heating element 10 that generates heat when energized and whose resistance value changes with a positive correlation in accordance with its own temperature change, and its resistance value R _GP is the target resistance value. The energization control module 20 that controls energization from the power source 7 to the heating element 10 so as to match _RTRG and the heating element 10 are integrally housed in a substantially cylindrical housing 30, and the energization control module 20 The reference resistance value storage means 232 for storing the resistance value of the heating element 10 at a predetermined target temperature _TTRG measured in advance as the reference resistance value _RC , and the reference resistance value _RC as a threshold value. when the resistance value R _GP is below the reference resistance value R _C maintaining energization, the resistance value varying with a change in temperature of the heating element 10 by stopping the energization when exceeding the reference resistance value R _C It is provided with a resistance value change reflecting unit 233 to be reflected in current control. The target resistance value _RTRG is a resistance value at the target temperature _TTRG and is substantially the same as the reference resistance value _RC .
Further, the energization control module 20 is calculated by multiplying the initial reference power value P _INT applied to the heating element 10 in a steady state at a predetermined temperature measured in advance by a predetermined ratio, and a predetermined deterioration limit temperature T _WRN. the degradation time of the power value _{P WRN} that is supposed to be applied to the heating element 10, and and a deterioration determining deterioration determining unit 234 as the deterioration threshold power P _REF is at.

Deterioration determining unit 234 in the present embodiment, in the case where the resistance value _{R GP} of the heating element 10 to feedback control so as to coincide with the reference resistance value _{R C,} with respect to the target power _{P TRG} as a reference of objectives the temperature _{T TRG} The effective power P _ACT calculated from the value of the plug current I _GP that actually flows through the heating element 10 and the plug voltage V _GP applied to the heating element 10 is less than the predetermined degradation power value P _WRN. And a self-diagnosis means for outputting a self-diagnosis signal DI is provided as an initial reference power required to realize a target temperature T _TRG at the time of manufacture as a specific power value P _WRN at the time of deterioration. for the value _{P INT,} a certain percentage (e.g., 90%) using a value obtained by multiplying, can be Rukoto and degradation threshold power _{P REF.}

Referring to FIG. 1, as a heating device in the first embodiment of the present invention, a heating element 10 _{(1 to n)} provided for each cylinder of an internal combustion engine 8 _{(not shown)} and generating heat by energization, and an engine control device (ECU) ) 7 outputs a drive signal SI for determining the target temperature _TTRG corresponding to the operating condition of the engine 8, and in synchronization with the drive signal SI, energization from the power source 6 to the heating element 10 _(1-n) The energization control module 20 _(1-n) for controlling the reference resistance _RC by comparing the reference resistance _RC with the actually detected plug resistance R _GP is housed in the integrated housing portion 30 _(1-n) . The control unit-integrated glow plug 1 connected to the ECU 7 through the connector terminals (41, 42, 43) accommodated in the connector unit 40 _(1-n) will be described.
The control unit module 20 _{(1 to n)} includes at least a semiconductor switching element 21, a drive circuit unit 22, and a heating element control IC 23 in a mold package 200, and includes a power input terminal 201, a drive signal input terminal 202, The self-diagnosis signal output terminal 203, the output terminal 204, and the ground terminal 205 are drawn out.

In the present embodiment, an N-channel power MOSFET is used for the semiconductor switching element 21 (hereinafter referred to as MOS 21 as appropriate).
The MOS 21 has a plurality of control MOSs 210 (hereinafter referred to as main MOSs 210) for controlling opening and closing of a large current flowing through the heating element 10, and a part of the MOS 21 is for detecting the current flowing through the heating element 10. The current MOS is used as a current detection MOS 211 (hereinafter referred to as a sense MOS 211). The main MOS 210 and the sense MOS 211 form a current mirror circuit, and a current detection resistor 212 is formed by being connected to the sense MOS 211. .
The current detection resistor 212 is connected to the deterioration determination means 23 which is a main part of the present invention via the sense terminal SEN.

In the present embodiment, the drive circuit unit (DRV) 22 includes a boosting unit such as a charge pump, for example, and, for example, a duty ratio T for causing the ECU 7 to generate a target temperature _TTRG according to the operating state of the engine 8. in synchronization with the fall of the driving signal output SI to determine the _{oN / T,} to drive the MOS 21, and outputs a voltage boosted to a predetermined drive voltage V _GG.
In the time chart described later, as shown in FIGS. 6 and 7, an example is shown in which energization is started in synchronization with the fall of the drive signal SI. In the present invention, Hi, Lo of the drive signal SI is shown. The side on which the MOS 21 is driven can be changed as appropriate.

The charge pump is composed of, for example, an operational amplifier 220, a charge capacitor 222, an output capacitor 224, and diodes 223 and 225. By switching the operational amplifier 220, charging and discharging of the power supply voltage V _B to the charge capacitor 222 are repeated. by discharging by superimposing the energy stored in 224, applying a gate voltage V _GG boosted to twice the voltage or the like of the power supply voltage V _B as the drive voltage V _GG between the gate and source of the current-controlled semiconductor device 21 To do.
Further, FIG. 1 shows a charge pump composed of an operational amplifier 220, diodes 221 and 223, and capacitors 222 and 224 as boosting means. However, in the present invention, the boosting method is not limited. A so-called chopper type DC-DC converter combining a choke coil, a capacitor, a diode, or the like, a flyback type DC-DC converter including a step-up transformer, or the like may be used.

The heating element control IC 23, which is a main part of the present invention, includes a resistance value calculation unit 230, a reference resistance storage unit (reference resistance forming unit) 231, a reference resistance adjustment unit (zener zap circuit) 232, and a resistance value change reflection. A means (F / B means) 233, an initial power reference resistance R _CINT , an initial power reference resistance adjusting means (Zener zap circuit) 235, and a deterioration determining means 234 are configured.
The resistance value calculating means 230 includes the plug current I _GP detected by the current detection resistor 212 and the plug voltage V _GP applied from the semiconductor switching element 21 to the heating element 10 (the source voltage V _{SS of the} semiconductor switching element 21). The plug resistance value R _GP of the heating element 10 is calculated from the above.

Further, in the present embodiment, an example is shown in which the current I _GP when calculating the resistance value R _GP is detected by the sense MOS 211, but the current detection method is not limited in the present invention.
For example, detecting the plug voltage V _GP generated when a constant current is applied to the heating element 10 with a relatively low value of several tens mA to several hundred mA from the heating element control IC 23 side with the MOS 21 turned off. Thus, the resistance value R _GP of the heating element 10 can be detected with higher accuracy.

The plug resistance value R _GP of the heating element 10 is determined by the inherent resistance temperature characteristic of the heating element 10, and there is a certain correlation between the heating temperature of the heating element 10 and the plug resistance R _GP .
Therefore, when the control unit integrated glow plug 1 is manufactured, that is, after the heating element 10 and the control unit module 20 are connected, the heating element 10 is energized to increase the temperature to a predetermined target temperature (T ₁ ). The resistance value is measured by an external measuring instrument, and this is stored as a reference resistance value _RC in a reference resistance storage unit (reference resistance forming unit) 231 (hereinafter referred to as MEM 231) by an external signal.
Note that the resistance value may be measured alone when the heating element 10 is manufactured, and the value may be stored in the MEM 231 of the control module 20.

Resistance change reflecting unit (F / B means) 233, a reference resistance value R _C stored in MEM231, compared with the plug resistance R _GP detected when it is actually used, the results driving circuit Feedback to the unit 22.
Since the heating temperature of the heating element 10 is controlled by opening and closing the semiconductor switching element 21 so as to maintain the reference resistance value _RC based on the reference resistance value _RC corresponding to each resistance temperature characteristic, Compared to the case where energization control is performed on a plurality of glow plugs under uniform conditions, it is possible to control to a desired heat generation temperature with higher accuracy.

However, when the heating element 10 is used for a long time, a phenomenon such as migration in which the metal used for the electrode diffuses into the insulator or the conductive component moves between the heating element and the insulator. Or the contact resistance increases due to electrode peeling / oxidation, etc., and the plug resistance _RGP increases.

Therefore, it is determined that the temperature has deteriorated when the heat generation temperature has decreased from a target temperature T _TRG (for example, 1250 ° C.) to a deterioration limit temperature T _WRN (for example, 1150 ° C.) that has decreased by a certain value ΔT (for example, 100 ° C.) or more.
However, the controller-integrated glow plug 1 of the present invention controls the temperature by controlling the energization so that the plug resistance value R _GP matches the reference resistance value _RC without measuring the actual heat generation temperature. Therefore, the presence or absence of deterioration cannot be detected by the actual heat generation temperature.

Further, since the current value I _GP changes depending on the battery voltage (power supply voltage) + B, it is not possible to ensure the accuracy of determining the deterioration based on the average current.
Therefore, the change of the effective power _{P ACT} when being controlled to plug resistance _{R GP} so that the target temperature _{T TRG} matches the reference resistance value _{R C,} for example, the initial reference in the initial target temperature _{T TRG} The power value P _INT is stored as an initial power reference resistance value R _PINT by electrical trimming, and is determined to be deteriorated when it changes from that value to a certain value and becomes equal to or less than a predetermined deterioration threshold power P _REF .

The feature of the present invention is that the resistance value R _GP of the heating element 10 is not calculated and the deterioration is determined by determining the threshold value as in the conventional case, but the deterioration determination is not performed, but the resistance value R _GP of the heating element 10 is constant. By performing energization control so as to coincide with the value _RC , when the heat generation temperature is kept constant, the resistance value R _GP with respect to a predetermined temperature increases with the deterioration of the heating element 10, and the effective power P _The deterioration is detected by detecting that the _ACT decreases.
By using a memory element such as a resistor or a memory that can be trimmed in order to store the initial reference power value P _INT that serves as a reference for deterioration determination at this time, it is possible to perform deterioration determination with high accuracy according to individual differences. It has become.

Specifically, the initial reference resistance value R _PINT is provided as a resistor that can be adjusted by electrical trimming using the reference resistance adjusting means 232.
More specifically, the electrical trimming is performed by digital trimming using a zener zap or a polysilicon fuse.
Further, the reference resistance value _RC may be given using a memory. However, in this case, it should be noted that a microcomputer is required, and the circuit scale is greatly increased.

With reference to FIG. 2, the structural features of the control unit-integrated glow plug 1 in the first embodiment of the heat generating device of the present invention will be described.
The control unit-integrated glow plug 1 includes a housing 30 formed in a substantially cylindrical shape, a heating element 10 provided on the distal end side thereof, an energization control module 20 accommodated in the housing, and a connector portion for connecting to the outside. 40 is a structure assembled integrally with 40.
In the present invention, the heating element 10 may be a so-called metal heater 10 as shown in FIG. 4D or a so-called ceramic heater 10a as shown in FIG.

  In the metal heater 10, a heating coil 102 made of a metal resistance wire coil and a control coil 104 are connected in series inside a substantially bottomed cylindrical metal protective tube 103 that is open at the proximal end and closed at the distal end. The grounding part 101 housed together with the insulating material 100 such as powder and provided on the distal end side of the heating coil 102 is electrically connected to the metal protective tube 103, and on the proximal end side of the control coil 103, An input terminal 106 is connected to achieve conduction. The heating coil 102 and the control coil 103 are formed to have a predetermined specific resistance using, for example, a known resistance material such as an Fe—Cr—Al alloy, an Fe—Cr alloy, or an Ni—Cr alloy.

The ceramic heater 10a includes a ceramic resistor 102a formed in a substantially U shape, a pair of lead portions 103a and 104a for conducting the ceramic resistor 102a and the outside, and an insulator 100a formed in a substantially column shape covering these. One end of a lead portion 103a connected to one end portion of the ceramic resistor 102a is drawn out in the side surface direction of the insulator 100a to form a ground terminal 101a, and the other end portion of the ceramic resistor 102a The leading end of the lead 104a connected to the lead is pulled out to the base end of the insulator 100a to form an input terminal 105a. The input terminal 105a is connected to the energization control module 20 through the input terminal fitting 106a. It has been.
For the ceramic resistor 102a, for example, a conductive ceramic material made of a mixed sintered body of silicon nitride and tungsten carbide is used.
The lead portions 103a and 104a are made of a heat resistant metal material such as tungsten.
An insulating ceramic material such as silicon nitride is used for the insulator 100a.

The metal heater 10 or the ceramic heater 10 a is held and fixed by a substantially cylindrical heating element holding member 31.
The heating element holding member 31 is made of, for example, a metal material such as SUS and is formed in a substantially cylindrical shape. The heating element holding member 31 holds and fixes the metal heater 10 or the ceramic heater 10a inside the metal protection tube 103 or a ground. Electrically connected to the terminal 101a, one end of the heating element 10 is grounded to the engine via the housing 30.
In the case of the metal heater 10, the metal protective tube 103 and the heating element holding member 31 are fixed to each other by a known method such as laser welding, brazing or screw tightening.
In the case of the ceramic heater 10a, the insulator 100a and the heating element holding member 31 are fixed by a known method such as fitting and brazing.

The housing 30 includes a housing base 300 formed in a substantially cylindrical shape.
A distal end side cylindrical portion 302 for holding the heating element holding member 31 is formed on the distal end side of the housing 30, and a proximal end side cylinder upper portion 311 of the heating element holding member 31 is inserted and fixed by welding or the like. ing.
A screw portion 303 is formed on the outer periphery of the housing 30 to be screwed and fixed to the combustion chamber of the engine.
A connector portion 30 that houses the energization control module 20 inside and that is connected to the outside is fixed to the base end portion 301 of the housing 30.
A hexagonal portion 304 for screwing the screw portion 303 is formed on the outer periphery on the proximal end side of the housing 30.

The connector portion 40 is fixed to the proximal end side of the housing 30 so as to be covered with a substantially cylindrical collar 320.
The connector part 40 is constituted by a resin molded part 400 formed in a substantially cylindrical shape using a thermoplastic resin or the like and connector terminals 41, 42, 43 fixed to the inside thereof for connection to the outside. .
On the proximal end side of the connector portion 40, a fitting portion 401 is formed which is formed in a substantially cylindrical shape and fits with a mating connector for connection to the outside.
A terminal fixing portion 402 in which connector terminals 41, 42, and 43 for connection to the outside are insert-molded is formed in the middle of the connector portion 40.
The connector terminals 41, 42, and 43 for connection to the outside are the power input terminal 41, the drive signal input terminal 42, and the self-diagnosis signal output terminal 43, respectively, but the number of connector terminals is increased or decreased as necessary. it can.
For example, it may be provided zener connector terminal for achieving the connection between the zener zap input terminal T _ZP1, T _ZP2 and external case of adjusting the resistance value of the reference resistance value R _C the zener zap trimming.
In order to reduce the number of terminals, these zener zap connector terminals may be shared with the drive signal input terminal 42, the self-diagnosis signal output terminal 43, or the power input terminal 41.
On the distal end side of the connector portion 40, a distal end side partition portion 402 that partitions a control module accommodation space 404 for accommodating the energization control module 20 is formed. And

As shown in FIG. 5A, the power input connector terminal 41, the drive signal input connector terminal 42, and the self-diagnosis signal output connector terminal 43 are respectively connected to the power input terminal 201 and the drive signal input of the energization control module 20. The terminal 202 and the self-diagnosis signal output terminal 203 are connected.
Further, the output terminal 204 (source terminal V _SS ) of the energization control module 20 is connected to the heating elements 10 and 10 a via the energizing middle shaft 24, and the GND terminal 205 is connected to the housing 30 via the grounding terminal 250. In addition, the engine is grounded via the housing 30.

In this embodiment, the MOS 21, DRV 22, JDG 23, etc. of the energization control module 20 having a circuit configuration as shown in FIG. 1 are integrally accommodated in the resin molding part 200 by epoxy resin or the like and placed outside the package. The lead frame is pulled out to form a power input terminal 41 (BAT), a drive signal input terminal 42 (SI), a self-diagnosis signal output terminal 43 (DI), an output terminal 204 (V _SS ), and a ground terminal 205 (GND). It is.
In the drawing, the energization control module 20 is represented by a so-called DIP type package. However, in the present invention, the package structure of the energization control module 20 is not limited, and a so-called SIP type or other known IC is used. The structure used for the package can be adopted as appropriate.
Specifically, for mounting in the glow plug housing 30, a small discrete semiconductor element package capable of mounting both a power MOSFET and a control IC, for example, a thin resin of about 10 mm × 17 mm × 4.5 mm A so-called TO-220 type package in which terminals arranged in the order of input terminal, ground, and output terminal are drawn out from one of the mold packages is desirable.

Here, the temperature characteristics of the heating element 10 used in the control unit integrated glow plug 1 of the present invention will be described with reference to FIG.
This figure shows the relationship between the heater temperature and the resistance value of the heating element in the steady state, i.e., when the heater temperature and the resistance value are saturated after a certain period of time when power is applied to the heating element. Initial state resistance temperature characteristic R _INT to be confirmed is indicated by a one-dot chain line, resistance temperature characteristic R _ACT after use for a certain period of time is indicated by a broken line, and resistance temperature characteristic R _WRN at the time of deterioration in a deteriorated state after long-term use is indicated by a solid line Yes.
As shown in the figure, the slope of the resistance temperature characteristic does not change between the initial state and the deteriorated state, and the parallel movement is performed so that the resistance value with respect to the same temperature becomes high.
For this reason, when the resistance value with respect to the target temperature _TTRG in the initial state is set to the reference resistance value _RC , if the energization control is performed so as to maintain the reference resistance value _RC , the heat generation temperature decreases, and the allowable limit temperature It is necessary to determine that the state that has decreased to T _WRN is a deteriorated state and perform processing such as an abnormality warning.

With reference to FIG. 4 and FIG. 5, the energization control method and the deterioration determination method of the control unit integrated glow plug 1 of the present invention will be described.
FIG. 4 shows a flowchart in the initial temperature raising mode (M _INT ).
When the key switch SW is turned on, the initial temperature increase mode (M _INT ) in step S100 is started, and when the input of the drive signal SI output from the ECU 30 is detected in the drive signal input confirmation process in step S110, the step Proceeding to the heating element energization process of S120, energization of the heating element 10 is started.
Next, in the current / voltage detection process in step S130, the plug current I _GP and the plug voltage V _GP flowing in the heating element 10 are detected.
Next, in the plug resistance value calculation process in step S140, the plug resistance value R _GP is calculated from the plug current I _GP and the plug voltage V _GP .

Next, in the mode switching determination process in step S150, the plug resistance value R _GP is compared with the reference resistance value _RC with respect to the target temperature in the initial state, and whether or not the reference resistance _RC has been reached, that is, the heating element 10 It is determined whether or not the heat generation temperature has reached the target temperature.
If the plug resistance value R _GP is less than or equal to the reference resistance value _RC , the determination is No, and the process returns to step S110 to maintain the initial temperature increase mode (M _INT ).

If the plug resistance value R _GP is greater than the reference resistance value _RC , the determination is Yes, the initial temperature rise mode (M _INT ) is terminated, and the routine proceeds to the steady control mode in step S200.
In the heating element energization process in step S120, a preheating control mode ( _MPRE ) in steps S121, S122, and S123 may be performed in order to prevent overheating.
Specifically, the reference resistance value slightly lower resistance than R _C (preheating target temperature, for example, a value corresponding to 1000 ° C.) was used as a preheat control mode switching reference resistance value R _CH, preheat control mode switching determination in step S121 fever in stroke, compared with the plug resistance R _GP preheating control mode changeover reference resistance value R _CH, when the plug resistance R _GP is below the preheating control mode switching reference resistance value R _CH is determined No, early In order to raise the temperature of the body 10 to the preheating target temperature, the process proceeds to an initial temperature raising mode maintenance process in step S123, and power exceeding the rating is applied with a duty of approximately 100%.

In the preheating control mode switching determination process in step S121, when the plug resistance _{R GP} exceeds preheat control mode switching reference resistance value _{R CH} proceeds to decision Yes, and preheat control mode in step S122 _{(M PRE),} the preheating control With the mode switching reference resistance value R _CH as a threshold value, the preheating control mode (M _PRE ) control is performed by on / off control so that the constant temperature is lower than the target temperature, for example, for about 1 second.
Specifically, for example, the preheating control mode M _PRE can be implemented by performing the processing according to the flow of steps S1221 to S1225.
In the time-up determination process in step S1221, it is determined whether or not a predetermined time _{tref has} elapsed since the start of the preheating control mode.
If the predetermined time has not elapsed (t <t _ref ), the determination becomes Yes, and the process proceeds to the energization necessity determination process in step S1222, and the necessity of energization is determined by comparing R _GP and R _CH .
If R _GP > R _CH in step S1222, the determination is yes, and the process proceeds to step S1223, where energization is turned off. If R _GP ≤R _CH , the determination is no, the process proceeds to step S1224, and energization is turned on. Further, the process proceeds to a resistance value calculation process in step S1225, R _GP is calculated again, and the process returns to step S1221 to repeat the loop.
When a predetermined time elapses from the start of the preheating control mode, the preheating mode is terminated and the process proceeds to the main routine.
In the preheating control mode (M _PRE ) in step S122, the temperature is maintained at a target temperature, for example, about 250 ° C. lower than 1250 ° C. for a period of time, so that the temperature rise process (transition increase) to the steady control mode (M _CST ) thereafter. _{Overtemperature} increase in (temperature mode) (M _TRN ) is suppressed.
Further, in the initial temperature raising mode (M _INT ), the plug resistance value R _GP changes every moment as the temperature rises, so the deterioration determination is not performed.

Note that the preheating control mode (M _PRE ) is not _limited to a single temperature. For example, a plurality of preheating control modes may be provided such that the first preheating target temperature is 1000 ° C. and the second preheating target temperature is 1100 ° C. good.
In this case, it is possible to switch between the first preheating target temperature and the second preheating target temperature by changing the duty ratio of the driving signal SI. Information on the plug resistance R _GP needs to be transmitted, and the amount of information increases, resulting in the same problem as in the prior art.
Therefore, in the present invention, even when such a plurality of preheating control modes are provided, the first preheating reference resistance and the second preheating resistance corresponding to each target temperature are processed so that they can be processed independently in the control module 20. Are prepared in the control module 20.
As in the case of one preheating target temperature in the preheating mode, whether or not energization is necessary is determined by comparing the plug resistance R _GP with these reference resistance values in the same manner as in step S121 or step S150 described above, and the plug resistance R _GP If the MOS 21 is opened and closed so as to match the respective reference resistance values and the energization control is performed, the control module 20 side can perform the process in a self-contained manner without depending on the process on the ECU 7 side.

Furthermore, in the present invention, it is not necessary when a sufficient capacity can be secured for the power source, but when energization to the plurality of heating elements 10 _{(1 to n)} is started at the same time, a large inrush current overlaps and the power source 6 There is a possibility that the temperature rise rate becomes slow.
Therefore, as in the heat generating device of the present invention, the control unit-integrated glow plugs 1 ₍ 1 to _n) provided for the respective cylinders are provided with independent energization control modules 20, and each of the glow plugs 1 ₍ 1 to _n). In the case where the heating elements 10 _{(1 to n)} are independently energized, self-cylinder position determining means for detecting the own cylinder position and drive delay means for shifting the energization start timing according to the cylinder position are provided. It is desirable to provide it.

FIG. 5 shows a flowchart in the steady control mode.
In the steady control mode of step S200, energization control is performed according to the drive signal SI, energization control is performed according to the reference resistance value _RC of each heating element 10, and a deterioration state is determined to warn of an abnormality. be able to.
When the steady control mode of step S200 is started, the input of the drive signal SI is detected in the drive signal input confirmation process of step S210, the process proceeds to the heating element energization process of step S220, and the heating element 10 is energized.

In the current / voltage detection process in step S220, the plug current I _GP and the plug voltage V _GP flowing in the heating element 10 are detected.
Then the effective power plug resistance value calculation process of step S230, the effective power value _{P ACT} and the plug resistance _{R GP} is calculated from the plug current _{I GP} and the plug voltage _{V GP.}

Next, in the deterioration process of step 240, the presence or absence of deterioration is determined as a threshold value by comparing the effective power _PACT and the deterioration threshold power _PREF .
Note that the degradation threshold power P _REF is a degradation power value P _WRN that has decreased to a certain value , for example, 90%, relative to the initial reference power value P _INT in the initial state.
If the effective power P _ACT is higher than the deterioration threshold power P _REF in the deterioration determination step in step S240, it is determined that the battery has not deteriorated and the determination is Yes, and the resistance value change reflecting means (F / F) in step S250 is determined. Proceed to step B).

In the deterioration determination process in step S240, when the effective power _PACT is lower than the deterioration threshold power _PREF (for example, when it is 90% or less of the initial reference power value _PINT ), it is determined that the power is deteriorated. Thus, the determination is No, and the process proceeds to an abnormality diagnosis signal output process in step S260.
In the resistance value change reflecting means (F / B process) in step S250, the plug resistance value R _GP is compared with the reference resistance value _RC in order to feed back the change in the plug resistance value, and the plug resistance value R _GP is used as the reference resistance value. If it exceeds _RC , the determination becomes Yes, and the process proceeds to an energization stop process of Step 270. If the plug resistance value R _GP is equal to or less than the reference resistance value _RC , the determination is No, and the process proceeds to the energization maintenance process of Step 280.

In the energization stop process of step S270, energization is stopped assuming that the heat generation temperature of the heating element 10 has reached the target value, and the process returns to step S210.
In the energization maintaining step of step S280, energization is maintained assuming that the heat generation temperature of the heating element 10 has not reached the target value.
By repeating step S210 to step S280, energization is controlled, and the plug resistance value R _GP close to the individual reference resistance value _RC of each glow plug 1 (1 to n) is maintained.

  In the abnormality diagnosis signal output process in step S260, a self-diagnosis signal DI indicating a deterioration abnormality is output. For example, a warning lamp is lit to notify the driver of the deterioration abnormality, prompt replacement, or energize the heating element 10. A treatment according to necessity such as stopping is performed.

Here, the operation of the control unit integrated glow plug 1 of the present invention will be described with reference to FIG. In addition, in this figure, the control result when not implementing preheating mode is shown.
The drive signal SI determines the duty ratio for determining the target temperature _TTRG according to the driving situation, and rises according to the determination result of the necessity of energization detected by the resistance value change reflecting means 233 as described above. Switching between opening and closing of the MOS 21 in synchronization with the edge or the falling edge When the drive signal SI is input from the ECU as shown in FIG. As shown in b), energization of the heating element 10 is started and the heat generation temperature rises.

As described above, when the plug resistance exceeds Rc, the determination result in step S250 is Yes. At this time, the output of the resistance value change reflecting means 233 is set to 0 as shown in FIG. Do not energize the.
However, instead of immediately shutting off the energization to the heating element 10, the energization is performed at a duty according to SI (for example, 90% duty) until the end of energization of one pulse, and at the rise of the next drive signal SI, When the MOS 21 is opened to cut off the power supply to the heating element 10 and the plug resistance decreases to Rc or less, the determination result in step S250 becomes No, and the resistance value change is reflected so that the power supply to the heating element 10 is resumed. The output of the means 233 is set to 1, and the MOS 21 is closed in synchronization with the fall of the next drive signal SI to energize the heating element 10.

As described above, in the present invention, the reference resistor _RC is used as a reference for switching between stopping and executing the energization of the heating element 10 as shown in FIG. This is because, when the determination result (JDG) shown in FIG. 4C is in an off state, if the drive signal SI rises, the MOS 21 is turned off in synchronization with this, and the determination result (JDG) is on. If the drive signal SI falls in the state, the MOS 21 is turned on in synchronization therewith.
Therefore, as shown in this figure (d), since it is performed in synchronization with the rising or falling edge of the drive signal SI, the temperature change at that time, as shown in this figure (e), the plug resistance R _GP In the control module 20, the F / B control is performed so as to make the plug resistance R _GP coincide with the reference resistance _RC in a conventional manner. The temperature of the heating element 10 can be matched with the target temperature _TTRG without using the engine water temperature or other temperature information.

Here, with reference to FIG. 7, the degradation determination method used for the heat generating device of the present invention will be described.
FIG. 7 shows a time chart in which the state from the initial state to the deteriorated state is arranged in time series in the steady control mode of the heat generating device to which the present invention is applied.
As shown in the figure (a), regardless of the deteriorated state of the heating element 10, from the ECU 7, the set driving signal SI corresponding to the target temperature T _TRG is output.
As shown in FIG. 3, the heating element 10 gradually deteriorates with long-term use, and the resistance value R _GP with respect to a constant heating temperature gradually increases.
When the resistance value R _GP of the heating element 10 increases with the progress of deterioration, as shown in FIGS. 5B and 5C, the reference resistor RC is set after energization is started in synchronization with the fall of the drive signal SI. The timing of exceeding becomes gradually earlier, and the maximum value of the resistance value R _GP that rises in one cycle when energized at a constant duty ratio also increases.
For this reason, in the deteriorated state, the time during which the plug resistance R _GP is higher than the reference resistance _RC becomes longer, and the number of times the MOS 21 is turned off increases as shown in FIG.
Therefore, the plug current I _GP is lowered as shown in FIG. 5E, and the effective power P _ACT is gradually lowered as shown in FIG.
At this time, the effective power _PACT is determined to be deteriorated when it changes in a certain amount or more with respect to the initial reference power value _PINT for the predetermined temperature in the initial state measured in advance and becomes equal to or less than the deterioration threshold power _PREF .
As shown in FIG. 4E, in the initial state, the heat generation temperature T is maintained at the target temperature _TTRG , and as the deterioration progresses, the heat generation temperature T decreases by ΔT or more and eventually becomes the deterioration limit temperature T _WRN or less. As described above, the self-diagnosis signal DI indicating the deterioration abnormality is output.
The reference resistance value _RC and the initial reference power value P _INT of each heating element 10 are stored in the MEM 232 at the time of manufacture, and based on these, the energization control and the deterioration abnormality determination are made, so the deterioration state of other glow plugs The temperature is accurately maintained without being affected by the deterioration, and a deterioration abnormality is warned at an appropriate time.

With reference to FIG. 8, the energization control method in the afterglow control mode will be described.
In the above-described embodiment, the deterioration determination is performed in the steady control mode when performing so-called pre-glow control in which the control unit-integrated glow plug 1 is energized to assist ignition of the internal combustion engine. Even in the afterglow control mode for the purpose of reduction, the deterioration determination of the control unit integrated glow plug of the present invention can be performed.
In this case, the deterioration can be determined according to a flow almost similar to that in the steady control mode. However, in the deterioration determination process in step S340, the second deterioration current I _WRN2 is used as a threshold for comparison with the plug current I _GP. The resistance value change reflecting means (F / B process) in step S350 performs threshold determination by comparing with the second reference resistance value _RC2 calculated from the plug resistance value _RGP and the reference resistance value _RC .
After the glow control mode, since the target temperature is lower than the stationary control mode, the second degradation time of the power P _WRN2 and also low second reference resistance value R _C2 in proportion thereto is used.
In the conventional deterioration determination apparatus, the deterioration determination of the glow plug is performed within a limited time immediately after the energization is stopped. However, in the control unit integrated type glow plug 1 of the present invention, the steady control mode and the after glow control mode are used. Since it is always performed during this period, it is possible to quickly detect and respond to deterioration abnormality.

FIG. 9A is a characteristic diagram showing a temperature control state when the preheating control mode of the control unit integrated glow plug 1 of the present invention is not performed, and FIG. 9B is a case where the preheating control mode is performed. FIG. 9C is a characteristic diagram showing the temperature control state in the afterglow control mode.
As shown in FIG. 6A, in the initial temperature increase mode (M _INT ), the temperature is increased quickly by approximately 100% duty or overpower supply, and further, the mode is lower than the first target temperature T _1. At the switching temperature T _CH , switching from the early temperature increase control to the temperature increase suppression control is performed, so that the excessive temperature increase of the glow plug is suppressed, and after reaching the first target temperature, in the steady control mode, Because the energization control that is fed back to the drive signal is performed using the reference resistance _RC according to the resistance temperature characteristic of the threshold as a threshold, the temperature is accurately maintained, the deterioration is always judged during the steady control mode period, and the deterioration abnormality is detected at an early stage In addition, in the afterglow control mode, the temperature can be accurately maintained at the second target temperature, and the deterioration abnormality is always determined during the afterglow control period. It is possible to perform the early deterioration anomaly detection in the.
As described above, when the preheating control mode M _PRE is executed, as shown in FIG. 4B, the temperature is kept lower than the target temperature for a certain period of time, so that overheating is reliably prevented. , then, via a transition mode _{M TRN,} shifts to the steady control mode _{M CST,} is maintained at the target temperature. In this case, the deterioration determination is performed in a state where the temperature of either the preheating control mode M _PRE or the steady control mode _MCST is stable.

With reference to FIG. 10, a description will be given of a desirable time for performing deterioration detection and a determination method thereof.
In the above-described embodiment, the method of performing the deterioration determination simultaneously with the energization control in the steady control mode and the afterglow control mode has been described. However, in this embodiment, disturbance due to the driving situation is excluded, and the presence or absence of deterioration is more accurately detected. As a deterioration determination method for detection, a method is shown in which the deterioration determination is performed either before cranking, immediately after the internal combustion engine is stopped, or at an idle stop.
For example, at the time of cranking, a large inrush current flows through the starter motor, and the battery voltage fluctuates. For this reason, since the current I _GP flowing through the heating element 10 changes greatly due to the fluctuation of the battery voltage + B, it is difficult to accurately detect the plug resistance R _GP . In addition, even when the engine is operating, there is a possibility that the battery voltage fluctuates, making it difficult to detect the plug resistance R _GP with high accuracy.
Therefore, it is desirable that the deterioration determination of the present invention be performed either before cranking the internal combustion engine 8, immediately after the internal combustion engine is stopped, or at an idle stop.
As shown in FIG. 10, in the operation status confirmation process in step S400, for example, information indicating the operation status such as the engine speed NE is read, and in the deterioration determination availability determination process in step S410, the operation read in step S400. Based on the information indicating the situation, it is determined whether it is before cranking, immediately after the internal combustion engine is stopped, or at the time of idling stop.
If it is either before cranking, immediately after the internal combustion engine is stopped, or at the time of idling stop, the determination becomes Yes, and the process proceeds to the deterioration determination step in step S430, or before cranking, immediately after the internal combustion engine is stopped, or If it is not during idle stop, the determination is No, and the process returns to step S400 without performing deterioration determination.
The deterioration determination process of step S430, as in the above embodiment, the plug current _{I GP} flowing through the heating element 10, and a plug voltage _{V GP} applied to the heating element 10, the effective power P _ACT is calculated, predetermined this The degradation threshold power _PREF is compared and determined.
Note that the deterioration determination may be performed on the glow plug side at all times, and the engine operating state may be determined on the ECU side and used selectively.

In the present embodiment, an example in which an N-channel power MOSFET is disposed upstream of a load and is driven to open and close by a high-side driver has been shown. However, in the present invention, the semiconductor switching element 21 is an N-channel power MOSFET. However, the present invention is not limited to this, and a configuration in which a P-channel power MOSFET is provided on the high side may be used.
In general, it is known that the P-channel power MOSFET has a larger on-resistance than the N-channel MOSFET, but the drive circuit 22 does not need a gate voltage boosting means such as a charge pump.
Further, an N-channel power MOSFET may be provided on the downstream side of the load and driven to open and close by a low side driver. In this case, there is a problem that a voltage is applied to the glow plug other than during the operation, but it is not necessary to provide a boosting means such as a charge pump in the drive circuit unit 22, and the circuit can be simplified.

1 Control unit integrated glow plug (heat generating device)
10 Glow plug (heating element)
20 Control module 200 Mold package 201 Power input terminal 202 Drive signal input terminal 203 Self-diagnosis signal output terminal 204 Output terminal 205 Ground terminal 21 Semiconductor switching element 210 Control cell 211 Current detection cell (mirror circuit section)
212 Resistance for current detection (Zener zap resistor)
22 Driving circuit 220 Operational amplifier 221, 223 Diode 222, 224 Capacitor 23 Heating element control IC
230 Resistance value calculation means (current / voltage detector)
231 Reference resistance storage unit (reference resistance forming unit)
232 Reference resistance adjustment means (Zener zap circuit)
233 Resistance value change reflecting means (F / B means)
234 Deterioration determining means 30 Housing portion 40 Connector portion 41 Power input connector terminal 42 Drive signal input connector terminal 43 Self-diagnosis signal output connector terminal 6 Power source 7 Engine control device 8 Internal combustion engine SI Drive signal P _ACT Effective power P _INT Initial reference power P _WRN degradation power threshold R _C reference resistance R _CH mode switching resistance threshold T _ZP 1, T _ZP 2 reference resistance trimming terminal M _INT initial heating mode M _PRE preheating control mode M _TRN transition mode M _CST steady control mode

JP 2009-36092 A JP 2009-191842 A JP 2010-127487 A

Claims (5)

A heating element that generates heat when energized and its resistance value changes with a positive correlation according to its own temperature change, and energization from the power source to the heating element so that the resistance value of the heating element matches the reference resistance value A heating device having an energization control module for controlling
While housing the heating element and the control module integrally in a housing,
The energization control module is
A reference resistance value storing means for storing a resistance value of the heating element as the reference resistance value in advance the measured predetermined target temperature,
With the reference resistance value as a threshold, energization is maintained when the resistance value of the heating element during energization falls below the reference resistance value, and energization is stopped when the resistance value of the heating element exceeds the reference resistance value. A resistance value change reflecting means for reflecting a change in resistance value accompanying a temperature change of the heating element in the energization control;
The effective power P _ACT by the energization control is equal to or less than the deterioration threshold power P _REF calculated by multiplying the initial reference power value P _INT applied to the heating element at a predetermined target temperature measured in advance by a predetermined ratio. A heat generation apparatus comprising: a deterioration determination unit that determines that deterioration has occurred . The heating device according to claim 1, wherein the reference resistance value is provided as a resistor that can be adjusted by electrical trimming . The heat generating device according to claim 2 , wherein the electrical trimming is performed by digital trimming using a zener zap or a polysilicon fuse . The heating device according to any one of claims 1 to 3, wherein the heating element is a glow plug provided for each cylinder of the internal combustion engine . The heat generating device according to claim 4 , wherein the deterioration determination is performed before cranking of the internal combustion engine, immediately after the internal combustion engine is stopped, or at an idle stop .