JP5578059B2 - Glow plug abnormality detection device - Google Patents

Description

  The present invention relates to an abnormality detection device for a glow plug that heats fuel to assist ignition in an internal combustion engine and to clean combustion exhaust.

  Conventionally, as a failure diagnosis device for a glow plug that heats fuel in order to assist ignition of an internal combustion engine and to clean combustion exhaust gas, a change in the resistance value of the glow plug from a current flowing through the glow plug and a voltage applied to the glow plug Various investigations have been made on glow plug abnormality detection devices for detecting the presence or absence of failure.

  For example, Patent Document 1 discloses a current detection circuit that detects a current flowing through a glow plug, a signal latch circuit that temporarily holds a state of a current signal output from the current detection circuit, and a voltage applied to the glow plug. A voltage detection circuit for detecting the voltage, a voltage signal output from the voltage detection circuit and a current signal output from the signal latch circuit when the energization to the glow plug is in an on state, and the voltage signal and the current signal are monitored. There is disclosed a glow plug failure diagnosis device including a diagnosis processing circuit that executes at least a diagnosis signal processing relating to the presence or absence of a failure based on the state of the above.

  Japanese Patent Laid-Open No. 2004-228688 discloses a glow plug failure diagnosis apparatus for diagnosing the presence / absence of abnormality of a glow plug provided for each cylinder of an engine, and a driving means capable of individually energizing / cutting off the glow plug of each cylinder. Current detection means for detecting the current value of the parallel connection of the glow plugs of each cylinder, and the current value detected by the current detection means by sequentially energizing the glow plugs of each cylinder through the driving means while shifting in time. There is disclosed a glow plug failure diagnosing device comprising: a diagnostic means for diagnosing the presence or absence of an abnormality of the glow plug based on the increase state of the glow plug and identifying the abnormal glow plug.

  Further, in Patent Document 3, a plurality of switch means provided on a plurality of power supply lines for supplying power from a battery to a plurality of glow plugs, respectively, for switching between energization and non-energization of the glow plug, and the plurality of switch means Among these, in the state where the timing control by the control means is possible, and the control means capable of timing control to turn on the other one or a plurality of switch means while turning on one of the switch means, An energization state detection unit that detects an energization state of the glow plug from the battery, and an abnormality determination that determines an energization abnormality of a part of the plurality of glow plugs based on a detection result by the energization state detection unit And an abnormality detection apparatus characterized by comprising the means.

In the conventional glow plug fault diagnosis devices as disclosed in Patent Documents 1, 2, 3, etc., any abnormality is detected by providing a current detection means and detecting the current flowing through the glow plug.
On the other hand, ceramic glow plugs have been used in recent years because of their good warmth, but ceramic glow plugs have a large change in resistance due to temperature rise due to energization, and the current flowing through the glow plug changes greatly. In the conventional method using current as a standard, a plurality of current detection means having different detection ranges are provided in order to correspond to a wide detection range, or not only the current flowing through the glow plug but also the voltage applied to the glow plug. It is necessary to detect and calculate the resistance value at the same time, the amount of information for detecting an abnormality is enormous, and a computing element with high processing capacity is required, or much information is sent between the ECU and the glow plug energization control device. It has been difficult to easily diagnose the presence or absence of a failure, for example, requiring high-speed communication means for transmitting and receiving data.

  In glow plug energization control devices, disconnection detection is an indispensable legal requirement. In particular, ceramic glow plugs may be damaged by overpower and damage the engine, and detection of abnormalities is as quick as possible. Need to be done.

  Therefore, in view of such a situation, the present invention has an object to provide a glow plug abnormality detection device that can quickly detect an abnormality and specify the type of the abnormality with a simple configuration without requiring current detection. To do.

According to the first aspect of the present invention, it occurs in a glow plug that is attached to each cylinder of the internal combustion engine and generates heat by energization, and a glow plug energization control device that controls the energization of the glow plug to adjust the heat generation temperature of the glow plug. In the glow plug abnormality detection device for detecting an abnormality, a first power source that opens and closes energization from the driving power source to the glow plug in accordance with a drive signal transmitted to the glow plug energization control device in accordance with an operation state of the internal combustion engine. An open / close switch, a first current limiting means for limiting the drive current of the first open / close switch and slowly opening and closing the first open / close switch over a period of 50 μs to 300 μs , an abnormality determination power supply, foreign as well as connected to the normally determining power supply provided in parallel with the first on-off switch, immediately at the time of up to 10μs according to the above drive signal A second opening / closing switch for opening / closing, a second current limiting means for limiting a current flowing from the abnormality determining power source to the glow plug via the second opening / closing switch, and a rise or fall of the drive signal. An abnormality determining means for determining an abnormality by comparing a voltage applied to the glow plug from the driving power source or the abnormality determining power source with a predetermined threshold voltage at a predetermined abnormality determining time;

  Specifically, as in the invention of claim 2, the abnormality determining means determines that the abnormality is present when the input voltage is higher than the threshold voltage.

According to a third aspect of the present invention, the predetermined abnormality determination time is shorter than half of the time from the start of rising of the first open / close switch to completion, and from the start of rising of the second open / close switch. The disconnection determination time is a time longer than half of the time until completion, and it is determined that the disconnection is abnormal when the input voltage at the disconnection determination time is higher than the threshold voltage.

  In the invention of claim 4, the energization control device performs control to energize by shifting the energization start timing to each cylinder in order to smooth the current to the glow plug, and as the predetermined abnormality determination timing, A period in which the first open / close switch and the second open / close switch are open is defined as an inter-terminal short-circuit determination period, and an inter-terminal short-circuit abnormality occurs when the input voltage in the inter-terminal short-circuit determination period is higher than the threshold voltage. Is determined.

  According to a fifth aspect of the present invention, when the drive signal is not transmitted at all to the glow plugs provided in all the cylinders, the first voltage is detected when the input voltage of the abnormality determination means is higher than the threshold voltage. It is determined that the on / off switch or the second on / off switch has failed.

According to the present invention, at the rise of the drive signal, the load power is small at normal time, and the voltage of the drive power supply is gradually increased via the first open / close switch that is slowly closed. When it is determined that the glow plug is normal by comparing it with the threshold voltage at the abnormality determination time, and the disconnection abnormality occurs in the glow plug, the load resistance is large, and the second open / close switch is quickly closed. The voltage of the abnormality determination power supply that is input is immediately applied as an input voltage, and it can be determined as a disconnection abnormality by comparing with the threshold voltage at a predetermined abnormality determination timing.
Further, when the control for shifting the energization timing is performed by the cylinder in order to smooth the current to the glow plug, the control signal is inputted to the abnormality determination means in a normal state during the period when the drive signal is off. When the input voltage decreases and can be determined to be normal by comparison with the above threshold voltage, and when a short-circuit abnormality between terminals occurs across multiple glow plugs, a short-circuit between terminals is passed at a predetermined abnormality determination time. Since the voltage to be applied from the driving power supply to the other glow plug is detected as the input voltage, it can be determined that the short circuit between terminals is abnormal by comparing with the threshold voltage.
According to the present invention, since the abnormality of the glow plug and the energization control device can be detected by detecting only the voltage applied to the glow plug without requiring current detection as in the prior art, the configuration of the device becomes extremely simple. In addition, it is possible to specify the type of abnormality as well as the presence or absence of abnormality.
In addition, since the presence or absence of an abnormality is determined at an extremely early stage during the rise or fall of the drive signal, an abnormality is detected before a large current flows through the glow plug, and a response is quickly made when an abnormality is detected. Since it is possible to take measures, it is possible to reliably avoid serious troubles such as damage to the glow plug due to overpower.
Furthermore, according to the invention of each claim, a more specific type of abnormality can be specified.

The block diagram which shows the outline | summary of the glow plug abnormality detection apparatus in embodiment of this invention. The operation and effect of the glow plug abnormality detection device in the embodiment of the present invention are shown, (a) is a time chart showing the relationship between the drive signal and the terminal voltage, (b) is an equivalent circuit at the drive start-up at normal time FIG. 5C is a characteristic diagram showing a change in terminal voltage, and FIG. 6C is a characteristic diagram showing an equivalent circuit diagram and a change in terminal voltage at a drive rise when a disconnection abnormality occurs. The method for detecting the short circuit abnormality between terminals of the glow plug abnormality detection device in the embodiment of the present invention is shown, (a) is a characteristic diagram showing the change of the terminal voltage at the fall at the normal time, (b) is a short circuit between the terminals. (C) is a characteristic diagram showing a change in the terminal voltage at the falling edge. The flowchart which shows the disconnection abnormality detection method of the glow plug abnormality detection apparatus in embodiment of this invention. The flowchart which shows the short circuit detection method between terminals of the glow plug abnormality detection apparatus in embodiment of this invention.

With reference to FIG. 1, the outline | summary of the glow plug abnormality detection apparatus 1 in embodiment of this invention is demonstrated.
The glow plug abnormality detection device 1 is attached to each cylinder of an internal combustion engine _{(not shown)} and is driven according to a glow plug 10 _{(1 to n)} that generates heat by energization and a control signal SI from an engine control unit (ECU) 40. The glow plugs 10 _{(1 to n)} are controlled to be energized from the first power supply 30 provided as a power source to maintain the glow plugs 10 _{(1 to n)} at a desired heat generation temperature _{. n)} and a glow plug energization control unit (GCU) 20 that detects an abnormality in the energization path and transmits it to the ECU 40 as a self-diagnosis signal DI.

The GCU 20 includes a first open / close switch SW1 ₍ 1- _n) provided as the drive open / close switch 21 ₍ 1- _n) and a first current limit means I1 _{(1 )} provided as the drive current limiting means 22 _{(1-n). ~n),} the abnormality judgment means opening and closing means _{23 (second} closing provided as _{1 to n)} switch _{SW 2 (1 to n),} a second provided as abnormality determining means current limiting means _{24 (1 to n)} The current limiting means I2 _(1-n) , drive control means (DRV) 25, abnormality determination means 26 _(1-n) , and self-diagnosis unit (DIU) 27 are included.

In the ECU 40, a target temperature of the glow plug 10 _{(1 to n)} corresponding to the operating condition of the period is calculated, and a control signal SI for realizing the temperature is transmitted to the GCU 20.
In general, in order to maintain the glow plug at a predetermined temperature, PWM (pulse width modulation) control in which the duty ratio is adjusted is performed, and the drive signal SI is a pulse signal that is turned on / off in accordance with the duty ratio.

In the DRV 25 of the GCU 20, a drive signal GI ₁ for driving the first opening / closing switch SW1 ₍ 1 to _n) that controls energization to each glow plug 10 ₍ 1 to _n) in synchronization with the SI transmitted from the ECU 40. _˜n is a predetermined timing t _INT (for example, in a four-cylinder engine, when one cycle of the drive signal SI is T, the cycle is shifted by approximately a quarter cycle and t _INT = ¼T). Then, SW1 _(1-n) is opened and closed according to the drive signals _GI1-n . In this way, the current flowing through the glow plugs 10 _{(1 to n)} is smoothed by performing the control of energizing the glow plugs 10 _{(1 to n)} provided in each cylinder by shifting the energization start timing. be able to.
At this _{time, SW1} driving current _{I1 (1 to n)} for opening and closing the inputted _{SW1 (1 to n)} to the gate of _{(1 to n),} because they are limited by the drive current limiting means _{22 (1 to n),} When the drive signals _GI1-n are high, SW1 _(1-n) is closed slowly, and when the drive signals G1- _n are low, SW1 _(1-n) is slowly And opened.
On the other hand, the second opening / closing switch (SW2 _(1-n) ) provided as the abnormality determination means opening / closing means 23 _(1-n) is immediately closed in synchronization with the rising of the driving signals G1- _n , and the driving signal GI. _It is opened immediately in synchronization with the fall of 1 to _n .
SW2 _(1-n) is provided with a second current limiting means 24 _(1-n) such as a constant current source or high resistance, and the second limited current I2 _(1-n) has a normal load. In this case, the current is limited to a very low value (for example, 10 mA or less) with respect to the current (several A to several tens A) flowing through SW2 _{(1 to n)} .
SW1 _(1-n) and SW2 _(1-n) are connected in parallel, and the output side is connected to the input of the abnormality determination means 26 _(1-n) .

For example, a comparator is used as the abnormality determination unit 26 _{(1 to} n), and the terminal voltage VG 1 to _n or the second power supply voltage VB ₂ applied to the glow plug 10 (1 to n) is the input voltage V _IN. As a comparison voltage, a predetermined threshold voltage V _REF is input, the input voltage _VIN is compared with the threshold voltage V _REF, and when the input voltage _VIN is higher than the threshold voltage V _REF , a high output is obtained. When _VIN is lower than the threshold voltage _VREF , the output is low.
The threshold voltage V _REF is adjusted to be approximately _{one half} of the second power supply voltage VB ₁ by providing a voltage dividing resistor with the second power supply 31 provided as a power supply for abnormality determination. .
In the present embodiment, the first power source 30 and the second power source 31 are configured as separate power sources. However, the first power source 30 and the second power source 31 are configured as a common power source. Also good.

Each of the abnormality determination means 26 _{(1 to n)} compares the input voltage _VIN read in the predetermined timing (t _1REF ) and the period (t _2REF ) as the abnormality determination timing with the threshold voltage V _REF , in the disconnection determination time _{t 1ref,} when it becomes the V _{iN> V REF} determines the disconnection abnormality, the inter-terminal short judging period _{t 2ref,} when it becomes the V _{iN> V REF} is a short circuit between the terminals judge.
In addition, as the abnormality determination time, it is longer than the time (for example, 10 μs) from the start of the second open / close switch SW2 _{(1 to n)} to the completion, and is the time from the start of the first open / close switch to the completion. A time shorter than half of (for example, 50 μs to 300 μs) is set as a disconnection determination time t _1REF .
A period from the completion of the first fall until the start of the first rise is determined as an inter-terminal short-circuit decision period _t2REF .
A section in which the gate voltage G _{(1 to n)} is low is _{defined as} a determination time (t _2REF ) of the short circuit between terminals, and if a voltage exceeding a predetermined threshold is detected in the section, it is determined that there is an abnormality.

The self-diagnosis circuit (DIU) 27 transmits a self-diagnosis signal DI to the ECU 40 based on the output of the abnormality determination means 26 _(1-n) .
Since the self-diagnosis signal DI is binary information of only the determination result, the communication load is small.
In addition, when an abnormality is detected by a conventional current, an arithmetic process may be performed on the ECU side in order to process a large amount of data. According to the present invention, however, the abnormality determination unit 26 provided in the GCU 20 has an analog glow. Since the abnormality is promptly determined by the jig and only the result is transmitted to the ECU 40, the calculation load on the ECU 40 can be reduced.
In the glow plug abnormality detection device 1 of the present invention, only the voltage VGL applied to the glow plug 10 _{(1 to n)} is used as input information for determining abnormality, and detection of disconnection abnormality and detection of short circuit abnormality between terminals. Since both can be performed using one abnormality determination means 26 _{(1 to n)} , the configuration is extremely simple and an abnormality can be detected promptly.

In detecting the disconnection abnormality, the switching time of SW1 _{(1 to n)} and SW2 _{(1 to n)} are set so that the rise time of the terminal voltage VGL _{(1 to n)} can be reliably differentiated depending on whether or not there is a load resistance. to provide a difference between the switching times _of), the _{SW1 (1 to n),} a first driving current limiting means _{22 (1 to n) provided} on the _{SW2 (1 to n),} a second current limit Since the means 24 _{(1 to n)} is provided, the disconnection abnormality can be prevented from being erroneously detected by determining the threshold value of the terminal voltage VGL _{(1 to n)} at a certain moment.
On the other hand, the short circuit between the _terminals, instead of determining the moment of the fall of _{VGL (1~n), VGL (1~n} ) monitors the duration should be off.
For this reason, in order to prevent erroneous detection, there is a possibility that the voltage does not surely become low during the transition of falling and rising, so a time during which a certain section is not monitored is provided.

With reference to FIG. 2, the effect with respect to the disconnection detection of this invention is demonstrated.
As shown in this figure (a), in DRV25, according to the drive signal SI transmitted from ECU40, the separate drive signal GI1- _n which controls opening / closing from the power supply 30 to each glow plug 10 _(1-n) . Are transmitted with a predetermined timing t _INT (for example, 1 / 4T).
In the abnormality detection device 1 of the present invention, as shown in a flow described later, abnormality determination is performed in synchronization with the rise or fall of the drive signal.
The normal disconnection detection determination will be described with reference to FIG. The left side of this figure (b) is an equivalent circuit diagram showing the input / output of the abnormality determination means 26 in the normal state, and the right side shows the input signal and the determination method of the abnormality determination means 26 in the normal state. FIG. 6 is a characteristic diagram of an input voltage _VIN at the time of rising of a drive signal.
As shown in the figure (b), in the normal state, the first impedance Z ₁ resulting from the first opening and closing switch SW1 and the first current limiting means, be regarded as a variable resistor to decrease gradually can, a second opening and closing switch SW2 the second impedance Z ₂ due to the second current limiting means, much larger than the resistance value R of the glow plug 10, the power supply voltage VB ₁ gradually increases by the application of the terminal voltage VG which asymptotically approaches, compared to the current IG flowing through the glow plug 10, the second limit current I2 flowing through the second opening and closing switch SW ₂ is negligible much smaller.
For this reason, the input voltage _VIN of the abnormality determining means 26 is equal to the terminal voltage VGL applied to the glow plug 10, and slowly rises over a period of 50 μs to 300 μs as shown on the right side of the figure. , it reaches the first power supply voltage VB _1.
In a predetermined disconnection determination time t1 _REF (for example, 20 μs to 100 μs), the terminal voltage VG is lower than the threshold voltage V _REF , and the output of the abnormality determination unit 26 is low, and is determined to be normal.
On the other hand, when the glow plug 10 is broken, as shown in the figure (c) left, no current flows to the glow plug 10, quickly by closed SW _2, the diagram (c) the right As shown, the second power supply voltage VB _{2 that} has rapidly increased in a short time of about 10 μs is input to the abnormality determination means 26 as the input voltage _VIN .
For this reason, in a predetermined disconnection determination time t _1REF (for example, 20 μs to 100 μs), the input voltage _VIN is the second power supply voltage VB ₂ that is higher than the threshold voltage V _REF . The output becomes high and it is determined that the disconnection is abnormal.

With reference to FIG. 3, the effect with respect to the short circuit abnormality between terminals of this invention is demonstrated.
For the short circuit between terminals, the time when VGL should be off is monitored instead of determining the moment when VGL falls.
Therefore, in order to prevent erroneous detection, there is a possibility that the voltage does not surely become low during the transition of falling and rising, and a time during which a certain section is not monitored is provided.
In synchronization with the fall of the drive signal Gn, in order to ensure that the first opening / closing switch SW1 is fully opened, reading of the terminal voltage VGL is waited until a predetermined time TL has elapsed, and the next drive is performed. The terminal voltage VGL is read only during the inter-terminal short-circuit determination period _t2REF until the signal Gn rises.
At this time, as shown in FIG. 5A, since the first opening / closing switch SW1 is in a fully open state under normal conditions, the glow plug 10 is not energized, and the abnormality determination means The output of No. 26 becomes low and is determined to be normal.
On the other hand, when a short-circuit abnormality occurs between the terminals, as shown in FIG. 5B, the drive signal G1 becomes low and the first opening / closing switch SW1 _{(1 )} connected to _one glow plug 10 _{(1). )} Is open and bypassed by the closed first terminal open / close switch SW1 ₍₂₎ connected to the other glow plug 10 ₍₂₎ by a short circuit between the terminals, and one glow plug 10 ₍₁₎ Energization to is maintained.
For this reason, as shown in FIG. _4C , the input voltage _VIN becomes higher than V _REF even in a predetermined inter-terminal short-circuit determination period t _2REF when the output is to be low. The output of the determination means 26 becomes high, and it is determined that the short circuit between terminals is abnormal.
The first opening / closing switch SW1 ₍₁₎ for controlling energization to _one glow plug 10 ₍₁₎ and the first opening / closing switch SW1 ₍₂₎ for controlling energization to the other glow plug 10 _(2). Even if a short circuit abnormality between the terminals occurs between the first open / close switches SW1 ₍₁₎ and SW1 ₍₂₎ , the short circuit determination period between terminals is t. _Even during the period of _2REF , the output of the abnormality determination means 26 is low and can be determined to be normal, but since any switch is in an open state, the glow plug 10 ₍₁₎ is not energized, causing actual harm. Does not reach.

A disconnection abnormality detection flow will be described with reference to FIG.
In the drive signal rise detection process in step S100, drive opening / closing means (first operation ₎ for controlling energization of each glow plug 10 _(1-n) oscillated at each glow plug at a predetermined timing in synchronization with the rise of the drive signal SI. 1 of the opening and closing switch _{SW 1} a _{(1 to n))} for detecting the rise of the drive signal _{G 1 to n} to be driven.
First as a closing switch loose閉行step S110, in synchronization with the rising of the driving signal _{GI 1 to n,} a first driving current _{I1 (1 to n,} which is limited by the drive current limiting means _{22 (1 to n) )} is input to the gate G of the first on-off switch _{SW1 (1 to n),} the first on-off switch _{SW1 (1 to n)} is closed slowly, terminal applied to the glow plug _{10 (1 to n)} The voltages VG 1 to _n increase gradually.
Second as the opening and closing switch speed閉行step S120, in synchronization with the rising of the driving signal _{GI 1 to n,} immediately the second opening and closing switch _{SW2 (1 to n)} it is closed.
At this time, the current flowing through the second opening / closing switch SW2 _{(1 to n)} is the second current so as not to affect the voltage rise when the glow plug 10 _{(1 to n)} is normally connected. It is limited to the second limited current I2 _{(1 to n)} by the limiting means 24 _{(1 to n)} .
In the disconnection determination time measurement process in step S130, counting of the disconnection determination time t is started in synchronization with the rise of the drive signals G1 to _n .
The decision time determination process of step S140, step up whether a predetermined decision time t ₁ has elapsed is determined, disconnection determination time t ₁ is a predetermined disconnection determination time t _{1ref (first} determination time) The loop of S140 is repeated.
Note that the predetermined disconnection determination time t _1REF is set to a time (for example, 20 μs to 100 μs) that is less than half of the operation time (for example, 50 μs to 300 μs) until the _first opening / closing switch SW ₁ is completely closed. .
When the disconnection determination time t ₁ reaches a predetermined disconnection determination time t _1REF , the process proceeds to a terminal voltage reading process in step 150.
In the terminal voltage reading process in step S150, the voltage VG _{(1 to n)} applied to the glow plug 10 _{(1 to n)} is read into the abnormality determination means 26 as the input voltage _VIN .
At this time, since the first open / close switch SW1 ₍ 1 to _n) is slowly closed, the voltage VG ₍ 1 to _n) applied to the glow plug 10 ₍₁ to _{10 )} is the first drive voltage VB. Ascending to ₁ gradually.
On the other hand, the second open / close switch SW2 _(1-n) is already closed, but is limited to the second limited current I2 _(1-n) by the second current limiting means 24 _(1-n) . , since the second power supply current flowing from VB _{2 I2 (1 to n)} is much smaller than the current IG flowing through the glow plug _{10 (1 to n),} it does not increase almost _{VGL (1 to n)} voltage, The input voltage _VIN of the abnormality determination means 26 becomes voltages VGL 1 to _n applied while slowly rising to the glow plug 10 _{(1 to n)} via the first opening / closing switch SW1 ₍ 1 to _n) .
The on / off switch SW2 _{(1 to n)} is already closed, but is limited to the second limited current I2 _{(1 to n)} by the second current limiting means 24 _{(1 to n)} . Even if it flows into the glow plug of the resistor, very little voltage is generated.
In other words, since (voltage) = (current) × (resistance), for example, assuming that I = 10 mA and R = 2Ω, the generated voltage is very small at 20 mV when the load is normal.
On the other hand, since the resistance becomes infinite when the load is open, _VIN is stuck to VB ₂ at the moment when SW ₂ is closed.
The terminal voltage threshold determination process of step S160, the abnormal voltage read to the determining means 26 _{V IN} and a predetermined threshold voltage _{V REF} (e.g., 1 / 2VB ₂₎ comparing the determination with is performed.
At this time, if there is no abnormality in the glow plug 10, the load resistance is small, but a current flows to the glow plug 10 at a predetermined disconnection determination time t _1ref, but the second opening and closing switch SW ₂ is already closed impedance Since the voltage drop due to the second current limiting means 24 having a large value is large and the first open / close switch SW1 is not completely closed, the terminal voltage VG is lower than the threshold voltage _VREF .
Therefore, it becomes determination No and progresses to the normal determination process of step S180.
On the other hand, if the disconnection abnormality in the glow plug 10 _{(1 to n)} is generated, no current flows through the glow plug 10 _{(1 to n),} the load resistance is large, a second opening which is quickly closed a second voltage of the drive power supply VB ₂ applied by the switch _{SW2 (1 to n)} is the input voltage _{V iN} next abnormality determination unit 26, are higher than the threshold voltage _{V REF.} Therefore, it becomes determination Yes and progresses to the disconnection determination process of step S170.
In the disconnection determination process of step S170, the self-diagnosis signal DI becomes high and is transmitted to the ECU 40.
In the normal determination process of step S180, the self-diagnosis signal DI becomes low and is transmitted to the ECU 40.
Thus, the disconnection abnormality detection process is completed.

With reference to FIG. 5, a flow of detecting a short circuit abnormality between terminals will be described.
The drive signal falling edge detection process in step S200, the energization of the respective glow plugs _{10 (1 to n)} to be oscillated at a predetermined timing in synchronization with the falling of the drive signal SI to the glow plugs _{10 (1 to n)} The driving opening / closing means for controlling (the falling of the driving signals G1 to _n for driving the first opening / closing switches SW1 ₍ 1 to _n) is detected.
In the first opening / closing switch slow opening process of step S210, the driving current I1 ₍ 1- _n) limited by the driving current limiting means 22 _(1-n) is synchronized with the falling of the driving signals G1- _n. The first open / close switch SW1 ₍ 1 to _n) is opened slowly, and the terminal voltages VG 1 to _n applied to the glow plugs 10 _{(1 to n)} gradually decrease.
In the second opening / closing switch speed opening process of step S220, the second opening / closing switch SW2 _(1-n) is quickly opened in synchronization with the falling of the drive signals G1- _n .
In the inter-terminal short judging time measurement process of step S230, the synchronization with the rising of the drive signal G _{1 to n,} the measurement of the inter-terminal short circuit determination start time t ₂ is started.
In the terminal short-circuit determination start determination process in step S240, it is determined whether or not the first opening / closing switch SW1 ₍ 1 to _n) is completely opened and the terminal voltage VGL has reached a time TL that should be low. This loop is repeated until the time TL elapses.
In the process for determining the short circuit between terminals in step S240, when a predetermined time TL has elapsed, the determination becomes Yes, and the process proceeds to the terminal voltage reading process in step S250.
In the terminal voltage reading process in step S250, the terminal voltage VGL of the glow plug 10 is read into the abnormality determining means 26.
The terminal voltage threshold determination process of step S260, the abnormality judgment means input voltage read in 26 _{V IN} and a predetermined threshold voltage _{V REF} (e.g., approximately 1 / 2VB ₂₎ comparison determination that is performed.
At this time, if there is no abnormality in the glow plug 10 at a predetermined inter-terminal short judging period _{t 2ref,} the input voltage _{V IN} is equal to or less than about 1/2 of the drive power supply voltage VB _1, the threshold voltage _{V REF} Is also a low value.
Therefore, it becomes determination No and progresses to the normal determination process of step S180.
On the other hand, when a short circuit abnormality between the terminals occurs in the glow plug 10 _{(1 to n)} , for example, a short circuit between the first open / close switch SW1 ₍₁₎ and the first open / close switch SW1 _(2). When the first open / close switch SW1 ₍₁₎ is open, the drive power supply 30 and the glow plug 10 ₍₁₎ are conducted by bypassing the other first open / close switch SW1 _(2). A drive power supply voltage VB1 is applied to the glow plug 10 ₍₁₎ to become the input voltage _VIN of the abnormality determining means 26, which is higher than the threshold voltage _VREF .
Therefore, it becomes determination Yes and progresses to the short circuit determination process between terminals of step S270.
In the inter-terminal short-circuit determination process in step S270, the self-diagnosis signal DI becomes high and is transmitted to the ECU 40.
In the normal determination process of step S280, the self-diagnosis signal DI becomes low and is transmitted to the ECU 40.
In the terminal short-circuit determination end determination process in step S290, the presence or absence of the rising of the drive signal Gn is detected, and determination No is made until the next rising of the drive signal Gn is detected, and the loop from step S250 to step S290 is repeated. The terminal voltage VGL is continuously monitored during the predetermined inter-terminal short-circuit abnormality detection period t2REF.
If the rising of the next drive signal Gn is detected in step S290, the determination becomes Yes, and the inter-terminal short-circuit abnormality detection process is terminated.

In the above embodiment, a plurality of SW ₁ 21 ( _{1 to} n) and drive current limiting means 22 _{(1 to 1} ) are provided in order to realize control and abnormality detection of the plurality of glow plugs 10 (1 to n) by one GCU 20 _{. Although n)} , SW ₂ 23 _{(1 to n)} and second current limiting means 24 _{(1 to n)} abnormality determination means 26 ₍ 1 to _n) are arranged in one GCU 20, an example is shown. The present invention is not limited to the above-described embodiment, and is first driven to open and close slowly by the drive current I1 limited by the first current limiting means 22 while following the drive signal GI for driving the glow plug 10. An opening / closing switch 21, a second opening / closing switch 23 that is driven to open / close quickly according to the drive signal GI, a second current limiting means 24 that limits the current I 2 flowing through the second opening / closing switch 23, 1 closing switch 21 and the second opening and closing switch 23 is connected in parallel, a second power supply voltage input through the output voltage VG and the second current limiting means 24 of the first on-off switch 21 VB ₂ an input voltage V _iN bets, the drive signal at the rising and falling in measured synchronously the predetermined disconnection determination time t1 _REF and a predetermined short circuit between the terminals determination period t _2ref of GI, the input voltage V _iN and the threshold voltage V These means (21, 22, 23, 24, 25, 26, 27) can be used for each glow plug 10 as long as it detects the presence or absence of disconnection and the presence or absence of short circuit between terminals by comparing with _REF. It may be arranged in the GCU 20 provided independently.

Furthermore, in the said embodiment, although the example which provided the abnormality determination means 26 _(1-n) each independently with respect _to several glow plug 10 _(1-n) was shown, one abnormality determination means 26 is shown. _Is shared by a plurality of glow plugs 10 _{(1 to n)} , and the cylinders that determine disconnection abnormality are sequentially switched in synchronization with the rise and fall of the drive signals GI 1 to _n to determine the abnormality. You may make it implement.
However, in the above-described embodiment, the configuration in which both the disconnection and the short circuit between the terminals are continuously detected is shown. However, the case where only the disconnection detection is performed and the case where only the short circuit between the terminals is performed is switched. Instead of switching each time the drive signal rises and falls, the short-circuit abnormality between terminals is caused by a predetermined period t from the fall of one drive signal to the rise of the next drive signal. _2REF may be continuously monitored and determined.

Further, the terminal voltages VG 1 to _n applied to the glow plugs 10 _{(1 to n)} are detected and compared with a predetermined threshold voltage V _REF when the first open / close switch 21 ₍ 1 to _n) is in an off state. Accordingly, it is possible to detect the presence or absence of a short circuit between terminals with other glow plugs 10 _{(1 to n)} and the presence or absence of a failure of the switching element. The threshold voltage V _REF in such a case, not only the predetermined threshold voltage V _REF in the above embodiment, previously prepared a plurality of voltage levels, it is possible to improve the detection accuracy by comparing.

Further, in the state where the drive signal SI is not transmitted at all, by detecting the terminal voltages VGL 1 to _n applied to the glow plugs 10 _{(1 to n)} , the switching element failure and the short circuit between the terminals are detected. it can.

1 Glow Plug Abnormality Detection Device 10 _(1-n) Glow Plug 20 Glow Plug Energization Control Device (GCU)
21 _(1-n) Drive opening / closing means (first opening / closing switch SW1)
22 _(1-n) Abnormality determining means opening / closing means (second opening / closing switch SW2)
23 _(1-n) Drive switching current limiting means (first current limiting means)
24 _(1-n) Abnormality determining means Current limiting means (second current limiting means)
25 Drive control circuit (DRV)
26 Abnormality determination means (OP)
27 Self-diagnosis circuit (DIU)
30 Drive power supply (first power supply)
31 Abnormality determination power supply (second power supply)
40 Engine control unit (ECU)
SI drive signal G _{(1 to n)} individual drive signal DI abnormality diagnosis signal V _IN input voltage V _REF threshold voltage VGL terminal voltage IG glow plug current VB ₁ drive power supply voltage VB ₂ abnormality determination means power supply voltage

JP 2010-180812 A JP 2008-297925 A JP 2008-31979 A

Claims (5)

Glow plug abnormality that detects an abnormality that occurs in a glow plug that is attached to each cylinder of an internal combustion engine and generates heat by energization, and a glow plug energization control device that controls energization to the glow plug to adjust the heat generation temperature of the glow plug In the detection device,
A first open / close switch that opens and closes energization from the drive power supply to the glow plug in accordance with a drive signal transmitted to the glow plug energization control device in accordance with an operating state of the internal combustion engine;
First current limiting means for limiting the drive current of the first open / close switch and slowly opening / closing the first open / close switch over a period of 50 μs to 300 μs ;
Power supply for abnormality determination;
A second open / close switch connected to the power source for abnormality determination and provided in parallel with the first open / close switch, and rapidly opening / closing in 10 μs or less according to the drive signal;
Second current limiting means for limiting a current flowing from the abnormality determination power source to the glow plug via a second open / close switch;
An abnormality determination for determining an abnormality by comparing a voltage applied to the glow plug from the driving power supply or the abnormality determination power supply with a predetermined threshold voltage at a predetermined abnormality determination timing from the rise or fall of the drive signal. And a glow plug abnormality detecting device.   The glow plug abnormality detection device according to claim 1, wherein the abnormality determination unit determines that an abnormality occurs when the input voltage is higher than the threshold voltage. The predetermined abnormality determination time is a time shorter than one half of the time from the start of the rise of the first open / close switch to the completion, and 2 of the time from the start of the rise of the second open / close switch to completion. The glow plug abnormality detection device according to claim 1, wherein a disconnection determination time is determined as a disconnection determination time that is longer than a half, and a disconnection abnormality is determined when an input voltage at the disconnection determination time is higher than the threshold voltage. In order to smooth the current to the glow plug, the energization control device performs control to energize each cylinder by shifting the energization start timing,
As the predetermined abnormality determination time, a period in which the first open / close switch and the second open / close switch are opened is an inter-terminal short-circuit determination period,
The glow plug abnormality detection device according to any one of claims 1 to 3, wherein when the input voltage in the inter-terminal short-circuit determination period is higher than the threshold voltage, an inter-terminal short-circuit abnormality is determined.   In a state where the drive signal is not transmitted at all to the glow plugs provided in all the cylinders, when the input voltage of the abnormality determination means is higher than the threshold voltage, the first open / close switch or the second switch The glow plug abnormality detection device according to any one of claims 1 to 4, wherein it is determined that a failure of the open / close switch.

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